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An investigation of MoP catalysts for alcohol synthesis Zaman, Sharif Fakhruz 2010

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An Investigation of MoP Catalysts for Alcohol Synthesis  by SHARIF FAKHRUZ ZAMAN B.Sc., Bangladesh University of Engineering & Technology, 1999 M.S., King Fahd University of Petroleum & Minerals, 2004  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Chemical and Biological Engineering)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  March 2010  © Sharif Fakhruz Zaman, 2010  Abstract Molecular simulation and experimental methods have been used to assess the catalytic behavior of MoP in the conversion of synthesis gas (CO, CO2, H2) to oxygenated hydrocarbons.  The potential energy surface of synthesis gas conversion to methane and methanol was investigated on a Mo6P3 cluster model of the MoP catalyst. The potential energy surface (PES) for CH4 formation was determined to be: COad → CHOad → CH2Oad → CH2OHad → CH2.ad+H2Oad → CH3.ad+H2Oad → CH4+H2O and for CH3OH : COad → CHOad → CH2Oad → CH2OHad → CH3OHad. The hydroxymethyl (CH2OH) species was a common reaction intermediate for both CH4 and CH3OH formation and the simulation predicted selective formation of CH4 rather than CH3OH from syngas over MoP. The cluster model was modified to investigate the effect of a SiO2 support and a K promoter. Both SiO2 and K decreased the activation energy for methanol formation. However, the activation energy for methanol formation remained higher than the activation energy for C-O bond cleavage. The high adsorption energy of methanol and the formation of geminal dicarbonyl species on the K-Mo6P3-Si3O9 cluster suggested the possibility of the formation of higher oxygenates.  The conversion of syngas to alcohols was also investigated on 5, 10, and 15 wt% MoP supported on silica, with 0, 1, and 5 wt% K added as a promoter The major products were acetaldehyde, acetone and ethanol. Low selectivities to methanol (<5 C atom %) and ii  methane (< 10 C atom%) were observed on the 5%K-10%MoP-SiO2 catalyst. The product distribution obtained over the K-MoP/SiO2 catalyst was distinct from that reported in the literature over other Mo-based catalysts. Addition of Rh to the K-MoP/SiO2 catalyst improved the stability of the catalyst. However, the Rh increased the selectivity to hydrocarbon products, especially CH4, while only increasing the selectivity to ethanol marginally. The reaction kinetics of the major products were described by a simple empirical power law. The activation energies of ethanol and acetaldehyde were very similar, suggesting that both originated from the same surface intermediate.  iii  Table of contents Abstract ..................................................................................................................................... ii Table of contents ...................................................................................................................... iv List of tables ............................................................................................................................. ix List of figures ........................................................................................................................... xi Nomenclature ...........................................................................................................................xv Acknowledgements ................................................................................................................ xxi Dedication ............................................................................................................................. xxii Co-authorship statement ...................................................................................................... xxiii Chapter 1  Introduction ........................................................................................................1  1.1  Introduction ....................................................................................................................2  1.2  Objective and approach of this thesis ............................................................................5  1.3  Biomass ..........................................................................................................................7  1.4  Syngas ............................................................................................................................7  1.5  Ethanol as an alternative transportation fuel ..................................................................8  1.6  Ethanol production processes ......................................................................................12  1.7  Thermodynamics of ethanol production from syngas .................................................13  1.8  Review of ethanol synthesis catalysts ..........................................................................16  1.8.1  Modified methanol synthesis catalyst ..................................................................16  1.8.2  Modified FTS catalyst..........................................................................................19  1.8.3  Rh based catalyst..................................................................................................22  1.8.4  Mo catalyst ...........................................................................................................24  1.9  Role of alkali promoters...............................................................................................28  1.10  Effect of CO2 in the feed ..............................................................................................28  1.11  Summary ......................................................................................................................29  1.12  Molecular modeling in heterogeneous catalysis ..........................................................30  1.13  Types of molecular simulation.....................................................................................31  1.14  Catalyst design by molecular modeling .......................................................................35 iv  1.15  Important property calculations using DFT method ....................................................37  1.16  Transition state searching ............................................................................................38  1.17  Outline of the dissertation ............................................................................................39  1.18  References ....................................................................................................................42  Chapter 2  Synthesis gas conversion over MoP catalysts………………………………..49  2.1  Introduction ..................................................................................................................50  2.2  Experimental ................................................................................................................51  2.3  Results and discussion .................................................................................................53  2.4  Conclusions ..................................................................................................................56  2.5  Acknowledgements ......................................................................................................57  2.6  References ....................................................................................................................64  Chapter 3  A study of synthesis gas conversion to methane and methanol over an Mo6P3 cluster using density functional theory ……..…………..…...66  3.1  Introduction ..................................................................................................................67  3.2  Methods........................................................................................................................69  3.2.1  Calculation procedure ..........................................................................................69  3.2.2  Modeling approach ..............................................................................................70  3.3  Results and discussion .................................................................................................71  3.3.1  An Mo6P3 cluster model of MoP .........................................................................71  3.3.2  CO adsorption on the Mo6P3 cluster ....................................................................71  3.3.3  Determining the potential energy surface for CH4 formation ..............................72  3.3.3.1  Formyl (CHO) and hydroxymethylidyne (COH) ............................................73  3.3.3.2  Formaldehyde (CH2O) and hydroxymethylene (CHOH) ................................74  3.3.3.3  Hydroxymethyl (CH2OH) ................................................................................75  3.3.3.4  C-O bond scission and the formation of CH4 ..................................................75  3.3.3.5  Carbon formation on the surface......................................................................77  3.3.4  Determining the potential energy surface for CH3OH formation ........................78 v  3.3.4.1 3.3.5  Methoxy (CH3O) and methanol (CH3OH).......................................................79 Hydrogen dissociation energy..............................................................................80  3.4  Conclusions ..................................................................................................................81  3.5  Acknowledgements ......................................................................................................81  3.6  References ....................................................................................................................98  Chapter 4  A DFT study of the effect of K and SiO2 on syngas conversion to methane and methanol over an Mo6P3 cluster……...…………….………...102  4.1  Introduction ................................................................................................................103  4.2  Methods......................................................................................................................105  4.3  Results ........................................................................................................................106  4.3.1  Building the Mo6P3 clusters ...............................................................................106  4.3.2  Reactions on the Mo6P3 clusters ........................................................................108  4.3.2.1  C-O bond cleavage .........................................................................................108  4.3.2.2  Methanol formation .......................................................................................110  4.3.3  Discussion ..........................................................................................................112  4.4  Conclusions ................................................................................................................114  4.5  Acknowledgements ....................................................................................................114  4.6  References ..................................................................................................................125  Chapter 5  A study of K promoted MoP-SiO2 catalysts for synthesis gas conversion ....128  5.1  Introduction ................................................................................................................129  5.2  Experimental ..............................................................................................................132  5.3  Results ........................................................................................................................136  5.4  Discussion ..................................................................................................................141  5.4.1  CO2 formation via the water-gas-shift reaction: ................................................145  5.4.2  Characterization of used catalysts:.....................................................................145  5.5  Conclusions ................................................................................................................146  5.6  Acknowledgements ....................................................................................................146 vi  5.7  References ..................................................................................................................161 Syngas conversion over a Rh-K-MoP/SiO2 catalyst ....................................166  Chapter 6 6.1  Introduction ................................................................................................................167  6.2  Experimental ..............................................................................................................170  6.2.1  Catalyst preparation: ..........................................................................................170  6.2.2  Catalyst characterization ....................................................................................171  6.2.3  Catalyst assessment:...........................................................................................172  6.3  Results ........................................................................................................................174  6.3.1  Catalyst characterization: ...................................................................................174  6.3.2  Comparison of catalysts: ....................................................................................177  6.3.3  Activity and selectivity of Rh-K-MoP/SiO2 catalyst: ........................................179  6.3.4  Reaction kinetics ................................................................................................180  6.4  Discussion ..................................................................................................................181  6.5  Conclusions ................................................................................................................186  6.6  Acknowledgements ....................................................................................................186  6.7  References ..................................................................................................................203  Chapter 7  Conclusions and recommendations ................................................................207  7.1  Conclusions ................................................................................................................208  7.2  Recommendations ......................................................................................................211  7.3  References ..................................................................................................................213  Appendix I  Quantum chemistry ..................................................................................215  Appendix II.(a)  Tabulation of experimental data set-I: Evaluation of MoP catalyst activity ........................................................................................219  Appendix II.(b)  Tabulation of experimental data set- II : Kinetic rate law experiment Results, catalyst:1wt%Rh 5wt%K 10wt%MoP/SiO2 ..............................238  Appendix II.(c)  XPS data fitting fresh and spent catalyst .................................................265 vii  Appendix III  Miscellaneous .......................................................................................272  Appendix III.1  Catalyst activity evaluation procedure ..................................................273  Appendix III.2  TCD temperature programming............................................................277  Appendix III.3  FID temperature programming .............................................................277  Appendix III.4  GC switch design ..................................................................................278  Appendix III.5  Retention function of measured components by TCD and FID ...........280  Appendix III.6  Antoine equation for chemicals ............................................................281  Appendix III.7  Numerical calculation of heat and mass transfer limitation..................282  Appendix III.7.(a) Calculation of parameters .....................................................................282 Appendix III.7.(b) Mass transfer controlling reaction criteria ............................................285 Appendix III.7.(c) Criteria for isothermal operation ...........................................................286 Appendix III.7.(d) Criteria for plug flow reactor ................................................................288 Appendix III.8.(a) Deactivation treatment of data ..............................................................289 Appendix III.8.(b) Standard deviation calculation for fraction CO conversion ..................291 Appendix III.9  Repeatability analysis of the experimental data....................................292  Appendix III.10  Statistical analysis and error calculation ...............................................295  Appendix III.11  Statistical analysis : Confidence interval calculation............................301  Appendix III.12  Kinetic modeling of major components of syngas conversion over Rh-K-MoP/SiO2 catalyst ............................................304  Appendix III.13  Matlab program for kinetic analysis of syngas gas conversion over MoP catalyst ...............................................................306  viii  List of tables Table 1.1  Performance of ethanol and mixed alcohol producing catalysts ..........................3  Table 1.2  Comparison of fuel characteristics of gasoline and biomass-derived ethanol… .............................................................................................................11  Table 1.3  Thermodynamics of different reactions relevant in the ethanol synthesis process .................................................................................................15  Table 1.4  Performance of some ethanol synthesis catalysts ...............................................17  Table 2.1  Properties of MoP catalysts supported on SiO2 before and after reaction in synthesis gas......................................................................................58  Table 2.2  XPS peak analysis of MoP catalysts supported on SiO2.....................................59  Table 2.3  Results of synthesis gas conversion on MoP catalysts compared to literature data ......................................................................................................60  Table 3.1  Comparison between Mo6P3 cluster and MoP (001) slab dimensions after geometric optimization ..............................................................................82  Table 3.2  Adsorption energy of CO and CH3OH on transition metals ...............................83  Table 3.3  Properties of surface adsorbed species on Mo6P3 cluster from DFT calculations: angle to the surface, distance between atoms, total energy and adsorption energy of stable surface species relevant to methane and methanol formation from syngas ...................................................84  Table 3.4  Properties of surface adsorbed species on Mo6P3 cluster from DFT calculations: angle to the surface, distance between atoms, total energy and adsorption energy of stable surface species relevant to methane and methanol formation from syngas ...................................................85  Table 3.5  Properties of transition state for reactions shown: structure, angle with the surface, and distance between atoms, energy of reaction and activation energy for methane and methanol formation from syngas.................86  ix  Table 4.1  Threefold SiO2 cluster model structure.............................................................115  Table 4.2  Atomic charge distribution on the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 cluster ................................................................................................................116  Table 4.3  Reactant and product bond length, bond angle and adsorption energy for C-O bond scission step .............................................................................................117  Table 4.4  Transition state for the reaction steps, C-O bond scission and methanol formation from CH2OHad ..................................................................118  Table 4.5  Reactant and product bond length, bond angle and adsorption energy for methanol formation .....................................................................................119  Table 5.1  Properties of the reduced and passivated K-MoP-SiO2 catalysts as a function of MoP and K loading ........................................................................147  Table 5.2  Summary of XPS peak analysis of fresh K-MoP-SiO2 catalysts .....................148  Table 5.3  Results of synthesis gas conversion to oxygenates on K-MoP-SiO2 catalysts compared to literature data. Reaction conditions of K-MoPSiO2 catalyst tests were: Temperature 548 K, Pressure 8.27 MPa, H2:CO 1:1 and GHSV 3960 h-1.........................................................................149  Table 5.4  Comparison of product selectivities from synthesis gas conversion over Mo-based catalysts. ...................................................................................150  Table 6.1  Composition of MoP catalysts after reduction and passivation ........................187  Table 6.2  BET area and surface composition of catalysts as determined by XPS ...........188  Table 6.3  Effect of promoters on synthesis gas conversion over MoP/SiO2 catalysts .....189  Table 6.5  Product selectivity of syngas conversion over some reported ethanol synthesis catalyst ...............................................................................................190  Table 6.4  Product selectivity of syngas conversion over 1%Rh-5%K10%MoP/SiO2 catalyst......................................................................................191  Table6.6  Experimental rate of major product components ..............................................192  Table 6.7  Power law rate parameters for major products and F test statistical analysis ...193  x  List of figures Figure 1.1  Opportunities for catalytic conversion of syngas to fuels and chemicals: WGS = water-gas shift; MTG = methanol-to-gasoline; MTO = methanol-to-olefin; DME = dimethyl ether; HPA = heteropoly acid .................10  Figure 1.2  Synthesis of ethanol from various carbon-containing feed-stocks .....................11  Figure 1.3  Ethanol formation mechanism over Cu based catalyst .......................................18  Figure 1.4  Ethanol formation mechanism over modified FT synthesis catalyst ..................21  Figure 1.5  A simplified sequence for ethanol formation by CO hydrogenation on Rh based catalyst. Individual reaction steps are indicated by boxed number ................................................................................................................23  Figure 1.6  Reaction pathway for CO hydrogenation over transition metal modified ADM catalyst (M denotes Fe, Co or Ni).............................................................26  Figure 1.7  The tentative reaction pathway of CO hydrogenation over transition metal modified Mo2C based catalyst (M denotes as Fe, Co or Ni) ....................27  Figure 2.1  X-ray diffractogram of 1 % K-10 % MoP-SiO2 catalyst compared to bulk MoP and 15 wt % MoP-SiO2 ......................................................................61  Figure 2.2  XPS analysis of 5%K-10% MoP-SiO2 catalyst (a) Mo3d – fresh (b) P2p – fresh (c) Mo3d – used (after reaction) (d) P2p – used (after reaction) .....................................................................................................62  Figure 2.3  CO conversion with time-on-stream over various MoP catalysts. Reaction conditions: pressure = 8.2 MPa, temperature = 548 K, CO:H2 = 1 and GHSV=3960 h-1 ........................................................................................63  Figure 3.1  Comparison between MoP slab (100) face and the Mo6P3 cluster model of the present study .............................................................................................87  Figure 3.2a Density of states (s-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster ..................................................................................88 Figure 3.2b Density of states (p-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster ..................................................................................89 xi  Figure 3.2c Density of states (d-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster ..................................................................................90 Figure 3.3 Reaction network and activation energies for syngas conversion to methanol and methane over the Mo6P3 cluster ...................................................91 Figure 3.4  Methane and methanol formation reaction steps on Mo6P3 cluster ....................92  Figure 3.5  Methane formation reaction steps on Mo6P3 cluster ...........................................93  Figure 3.6  Methanol formation reaction steps on Mo6P3 cluster .........................................94  Figure 3.7  Carbon formation on the Mo6P3 cluster ..............................................................95  Figure 3.8  Kinetic pathway of methane formation over Mo6P3 cluster ...............................96  Figure 3.9  Kinetic pathway of methanol formation over Mo6P3 cluster ..............................97  Figure 4.1  Cluster models of Mo6P3, Mo6P3Si3O9 and K-Mo6P3Si3O9 ..............................120  Figure 4.2  (a) C-O dissociation of CH2OHad species over Mo6P3 cluster, (b) Methanol formation from CH2OHad species over Mo6P3cluster .................121  Figure 4.3  (a) C-O dissociation of CH2OHad species over Mo6P3Si3O9 cluster, (b) Methanol formation from CH2OHad species over Mo6P3Si3O9 cluster .......122  Figure 4.4  C-O dissociation of CH2OHad species over K-Mo6P3Si3O9 cluster, (a)O atom adsorbed on Mo atom close to K atom (b) C atom adsorbed on Mo atom close to K atom ...........................................123  Figure 4.5  Methanol formation from CH2OHad species over K-Mo6P3Si3O9 cluster, (a) O atom adsorbed on Mo atom close to K atom (b) C atom adsorbed on Mo atom close to K atom ...........................................124  Figure 5.1  Experimental setup for syngas conversion to oxygenates ................................151  Figure 5.2  TPR profiles of 10% MoP-SiO2, 1% K-10%MoP-SiO2 and 5%K-10%MoP-SiO2 catalysts ..................................................................152  Figure 5.3  XPS analysis of reduced MoP catalysts after passivation: (A) Mo 3d of 5%K-15%MoP-SiO2; (B) Mo 3d of 15%MoP-SiO2; (C) P2p of 5%K-15%MoP-SiO2 ;(D) P2p of 15%MoP-SiO2; (E) K 2p and C 1s of 5%K-15%MoP-SiO2 catalyst. ..................................................................153  xii  Figure 5.4  Syngas conversion with time-on-stream over MoP-SiO2 catalysts: (a) 5 wt% MoP (b) 10 wt% MoP (c) 15 wt% MoP. Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. .............................................................................................154  Figure 5.5  Average CO conversion over K-MoP-SiO2 catalysts as a function of MoP and K content (wt %). Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1 ...............................................................................................155  Figure 5.6  Selectivity (C atom %) of major products of syngas conversion over K-MoP-SiO2 catalysts; (a) methane (b) acetaldehyde (c) ethanol (d) acetone. Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. ..................................................................156  Figure 5.7  Space-time-yield (STY) of major products of syngas conversion over K-MoP-SiO2 catalysts; (a) total oxygenates (b) acetaldehyde (c) ethanol (d) acetone. Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. ...............................................157  Figure 5.8  Averaged CO conversion as a function Mo/Si and K/Mo ratio as measured by XPS. . • - 0 wt % K; ● - 1wt % K; ▲ - 5 wt% K. Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO 1:1 and GHSV - 3960 h-1. .................................................................................158  Figure 5.9  Methane and C2+ oxygenate selectivity over MoP catalyst as a function of K:Mo surface atom ratio. ■ - 5 wt % MoP; ● – 10 wt % MoP; ▲ - 15 wt% MoP. Reaction conditions: temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. ................................159  Figure 5.10 XPS analysis of carbon C1s over different loadings of MoP catalyst after ~60 h reaction at temperature - 548 K, pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. .........................................................160  xiii  Figure 6.1  TPR profile of MoP/SiO2, K-MoP/SiO2 and Rh-K-MoP/SiO2 catalyst. ..........194  Figure 6.2  XPS plots for fresh Rh-K-MoP/SiO2 catalyst ...................................................195  Figure 6.3  Comparison between K-MoP and Rh-K-MoP catalyst activity for syngas conversion with time at syngas ration H2:CO =1 and pressure 8.27 MPa ......................................................................................196  Figure 6.4  Space-time-yield of oxygenates over Rh-K-MoP catalyst as a function of H2/CO ratio reported for 275 °C (▼), 300°C (▲) 325 °C (●) and 340 °C (■) ................................................................................197  Figure 6.5  Arrhenius plot for methane (♦), acetaldehyde (▲), ethanol (●) and acetone (■) .................................................................................................198  Figure 6.6a Parity plot for methane......................................................................................199 Figure 6.6b Parity plot for acetaldehyde ..............................................................................200 Figure 6.6c Parity plot for ethanol .......................................................................................201 Figure 6.6d Parity plot for acetone .......................................................................................202  xiv  Nomenclature  Å  =  Angstrom (1x10-10 m)  A  =  Pre exponential factor ((mol)1-n.(L)n-1.(s)-1) ), n = order of reaction  AcCHO  =  Acetaldehyde  AcCOOH  =  Acetic ccid  ad (subscript) =  Adsorbed species  ADM  =  Alkali doped molybdenum sulfide  ANOVA  =  Analysis of variance  BE  =  Binding energy (kcal/mol)  BET  =  Brunauer Emmett Teller surface area analysis  BTL  =  Biomass to liquid  BuOH  =  Butanol  C2+ oxy  =  Sum of liquid oxygenates containing two C atoms or greater  C2H5OH  =  Ethanol  C2oxy  =  Sum of liquid oxygenates containing two C atoms ( i.e. ethanol, acetaldehyde and acetic acid)  C3+oxy  =  Sum of liquid oxygenates containing three C atoms or greater  CASTEP  =  Cambridge serial total energy package, DFT simulation software  CG  =  Conjugate gradient  CH2  =  Methylene  CH2O  =  Formaldehyde  CH2OH  =  Hydroxymethyl  xv  CH3  =  Methyl  CH3COCH3  =  Acetone  CH3O  =  Methoxy  CH3OH  =  Methanol  CH4  =  Methane  CHO  =  Formyl  CHOH  =  Hydroxymethylene  CHx  =  Alkyl / carbene species  CI  =  Configuration interaction  CO  =  Carbon monoxide  CO2  =  Carbon dioxide  COH  =  Hydroxymethylidyne  CTL  =  Coal to liquid  DFT  =  Density functional theory  DIIS  =  Direct inversion in an iterative subspace  DME  =  Dimethyl ether  DMol3  =  A unique density functional theory (DFT) quantum mechanical code  DND  =  Double numeric plus d-function  DOF  =  Degrees of freedom  E  =  Activation energy (kJ/mol)  EC(ρ)  =  Correlation energy  Ecl(ρ)  =  Columbic interaction energy  EDX  =  Energy dispersive X-ray  xvi  EtOH  =  Ethanol  EX(ρ)  =  Exchange energy  EXC(ρ)  =  Exchange correlation energy  ∆E  =  Activation energy (kcal/mol)  ∆Ea  =  Activation energy (kcal/mol)  ∆Er  =  Energy of reaction (kcal/mol)  FID  =  Flame ionization detector  Fin  =  Flow rate of reactants in to the reactor (cc/min)  Fout  =  Flow rate of the products out of the reactor (cc/min)  Fstat.  =  A value resulting from a standard statistical test used in ANOVA and regression analysis to determine if the variances between the means of two populations are significantly different  FTS  =  Fischer tropsch synthesis  ௢ ∆‫ܩ‬ଶହԨ  =  Standard Gibbs energy of reaction (kJ/mol)  GC  =  Gas chromatograph  GC/MS  =  Gas chromatograph with mass spectrometer  GGA  =  Generalized gradient approximation  GHG  =  Greenhouse gases  GHSV  =  Gas hourly space velocity (hr-1)  GTL  =  Gas to liquid  H2  ෡ H  =  Hydrogen  =  Hamiltonian operator of the total energy for the system  ∆H  =  Heat of reaction (kcal/mol)  xvii  ௢ ∆‫ܪ‬ଶହԨ  =  Standard heat of reaction (kJ/mol)  Ha  =  Atomic energy unit (1 Hartree= 627.5 kcal/mol)  HAS  =  Higher alcohol synthesis  HC  =  Hydrocarbons  HDN  =  Hydrodenitrogenation  HDS  =  Hydrodesulfurization  HF  =  Hartree fock  HFSCF  =  Hartree fock self consistent field  HOMO  =  Highest occupied molecular orbital  HPA  =  Heteropoly acid  K  =  Kelvin (unit of temperature)  k  =  Reaction rate constant ((mol)1-n.(L)n-1.(s)-1), n = order of reaction  KH  =  Kohn hohenberg  LDA  =  Local density approximation  LoF  =  Lack of fit  LST  =  Linear synchronous transit  LUMO  =  Lowest unoccupied molecular orbital  m  =  Power of PCO in power law model  MeOH  =  Methanol  MM  =  Molecular mechanics  MO  =  Molecular orbital  MPa  =  Mega pascal (Pascal = 1 Newton/square meter)  MSW  =  Municipal solid waste  xviii  MTBE  =  Methyl tertiary butyl ether  MTG  =  Methanol to gasoline  MTO  =  Methanol to olefin  n  =  Power of PH2 in power law model  NEB  =  Nudge elastic band  PCO  =  Partial pressure of CO  PES  =  Potential energy surface  PH2  =  Partial pressure of H2  PrCOOH  =  Propionic acid  PrOH  =  Propanol  Psi  =  Pound per square inch  Psig  =  Pound per square inch gauge  PW91  =  Perdew Wang approximation  QM  =  Quantum mechanics  QST  =  Quadratic synchronous transit  r  =  Radial coordinate of electron  RAB  =  Distance between nuclei A and B  REST  =  Higher carboxylic acid, higher esters, higher aldehydes, higher hydrocarbons (taking carbon number =4)  rexp  =  Experimental rate (µmol. g cat-1.h-1)  rij  =  Distance between electron i and j  rmod  =  Predicted reaction rate (µmol. g cat-1.h-1)  SCF  =  Self consistent field  xix  ܵ஼ைమ  =  Selectivity of CO2  SD  =  Slater determinant  SEM  =  Scanning electron microscopy  STY  =  Space time yield (mg/gm catalyst/hr)  Syngas  =  Mixture of CO, CO2, H2  T  =  Temperature (oC or K)  TCD  =  Thermal conductivity detector  TE  =  Total energy (kcal/mol)  Te[ρ]  =  Kinetic energy of electrons  TPR  =  Temperature programmed reduction  Ucl(r)  =  Columbic interaction potential  Uee[ρ]  =  Electrostatic repulsion between electrons.  Vext[ρ]  =  External potential (electrostatic potential coming from nuclei)  WGS  =  Water gas shift reaction  XCO  =  CO conversion (C atom %)  XPS  =  X-ray photoelectron spectroscopy  XRD  =  X-ray diffraction  Zα  =  Charge of the nuclei  φ୏ୗ ୧  =  Kohn Sham orbital  ‫׏‬ଶ  =  Laplacian operator  ρ(r)  =  Electronic density  Ψ  =  Wave function  xx  Acknowledgements  I wish to express my profound gratitude to Dr. Kevin J. Smith, my advisor for his relentless support and guidance throughout the course of this research work. He was always ready to offer timely suggestions and share his ideas and I have learnt a lot from him.  I wish to thank Dr. Xiaotao Bi, Dr. David Wilkinson and Dr. Olivera Kesler for being part of my examination committee. My appreciation goes to the Chemical & Biological Engineering Department at UBC for giving me the opportunity to pursue this research on a subject of contemporary importance, and NSERC for providing financial support for my research. I would also like to thank everybody who has contributed in one way or another to my experience at UBC: CHBE faculty members, Dr Smith’s group members, fellow graduate students, CHBE workshop technicians Doug, Charles, Graham, Alex and David and CHBE store personnel Horace and Richard. I am also thankful to Mary Fletcher in the Materials Engineering Department for assisting me with XRD, EDX and TEM equipment and Kin Chung Wong at AMPEL for helping me with XPS analysis.  I would like to thank my parents Shariff Nurul Anwar and Bilkis Anwar for their prayers and encouragement and also my wife Tania Tasmin and my daughter Maymunah Zaman Sharif, for their support, love and patience.  Above all, I give thanks to Allah, for the gift of life, with a bit of knowledge and understanding and mercy.  xxi  Dedication  To my loving parents  xxii  Co-authorship statement  This thesis work consists of five different manuscripts which correspond to chapter two to six. The authors are Sharif F. Zaman and Kevin J. Smith. Professor Kevin J. Smith is my PhD supervisor in the Chemical & Biological Engineering Department at the University of British Columbia. The literature review, experimental design and data analysis for this thesis work were done by Sharif F. Zaman under the supervision of Professor Kevin J. Smith. Sharif F. Zaman did the final preparation for each manuscript after careful revision and approval by Professor Kevin J. Smith.  xxiii  Chapter 1  Introduction  1  1.1  Introduction  An increasing concern about global climate change, depletion of fossil fuel resources and rising food prices have increased interest in alternative energy sources [1]. Biomass, one of the most promising renewable energy sources, can be converted into a wide range of liquid fuels referred to as biofuels, including bioethanol, biodiesel, liquid alkenes, furfurals and their derivatives. Among these fuels, bioethanol has been studied extensively in recent years because it is viewed as a clean, sustainable and transportable fuel alternative [1]. About 80% of the world’s ethanol is produced from biomass (starch, corn, sugarcane, etc.) via fermentation processes [2]. Ethanol can also be produced from syngas by an alternative heterogeneous catalytic route. Thermochemical conversion of biomass (i.e. biomass gasification) [2] to syngas is followed by syngas conversion to alcohols. This approach to ethanol production can reduce dependence on food grains and make the process approximately carbon neutral [3].  Although several studies on catalytic conversion of syngas to ethanol have been reported, no commercial catalyst is yet available to produce ethanol from syngas with high selectivity. To date, Rh based catalysts show the highest selectivity to ethanol, but the high cost and limited availability of Rh are the main barriers to commercialization of this synthesis process. Scientists are now looking for alternative, inexpensive, catalysts for ethanol synthesis. Four different processes have been developed, based on the use of non-precious metal catalysts, for ethanol or higher mixed alcohols synthesis from syngas [4]. These are MoS2 catalysts (Sygmol process) developed by DOW chemical, Co-Cu catalysts developed by the French  2  Petroleum Institute (IFP), Cu-Zn-Al catalysts (Octamix process) developed by Lugri and ZnCr-K catalysts (MAS technology) developed by Snamprogetti [1,5]. Performance data of ethanol and mixed alcohol producing catalysts under different operating conditions are provided in Table 1.1. Among the processes using catalysts other than Rh, the IFP and Sygmol processes have the highest C2+ alcohol selectivity and the best commercial prospects, while MSA and Octamix have higher alcohol productivity. However, syngas conversion to C2+ oxygenates (i.e. ethanol) is often limited by the formation of methane and methanol. Table 1.1: Performance of ethanol and mixed alcohol producing catalysts: [5]  Company  Catalyst  % CO conversion  T(oC)  P(MPa)  H2/CO ratio  Products  Hoechst  Rh  NA  275  10.0  NA  EtOH Selectivity = 74.5%  Sagami Research Center  Rh  14  200300  5.1  1.4  Sygmol Process (DOW)  MoS2  10-40  200300  3.4-20.6  1.1-1.2  IFP-Idemitsu ( French Petroleum Institute)  Cu-Co  12-18  260320  5.9-10.0  1-2  17  260420  18.026.4  0.5-3  20-40 wt% MeOH, Alcohol selectivity =85%  20-60  250420  5.0-10.0  1-1.2  53.5 wt% MeOH, 41.9 wt% C2-C4.  Zn-Cr-K MSA [Modified Technology MeOH (Snamprogetti) catalyst] Cu-Zn-Al Octamix [Modified process MeOH ( Lugri) catalyst]  EtOH Selectivity =61%, Alcohol selectivity=90%. 30-70 wt% MeOH Alcohol selectivity = 85% 30-50 wt% C2C4, Alcohol selectivity = 7075%  3  Understanding the underlying reaction mechanisms along with the selection of catalyst and operating conditions is important for the development of new ethanol synthesis catalysts. The mechanism of ethanol formation over different catalysts will be discussed in later sections. The general mechanism of C2 oxygenate formation over Rh based catalysts from syngas has been extensively studied and the main steps are believed to be: (a) dissociative adsorption of CO and H2, (b) formation of surface carbene (CHx)ads and hydroxyl (OH)ads species and (c) CO insertion to form C–C bonds [6]. Ethanol formation is favored by a catalyst that selectively promotes the CO insertion reaction instead of the hydrogenation of the (CHx)ads surface species [2]. Consequently, research is focused on catalysts that have the ability for both dissociative and non-dissociative adsorption of CO and that will give high selectivity to ethanol.  A detailed understanding of the catalytic mechanisms and surface chemistry are critical to catalytic processes. Electronic structure theory based on quantum mechanics is one of the most fundamental tools for molecular and material modeling. The mechanisms are typically controlled by the structural, electronic and thermo-chemical properties of the catalytic materials and the interaction of molecules with these materials [7]. Quantum mechanics enables scientists to calculate the structure, energy and properties of a molecule or an assembly of molecules. Using this energy, one can determine the structure of the reactant and the products as well as the transition state structure that connects the reactant to the products in the chemical reaction [8].  4  The use of computational chemistry in heterogeneous catalyst research and development has increased recently due to improved computational power and accuracy. Density Functional Theory (DFT) can be employed to calculate the formation energy of molecules and solids with high accuracy [9]. Computational chemistry can be used as a tool for a new catalyst search and design, by calculating the catalyst’s suitability for a particular reaction without experimentation and there are several examples of the success and usefulness of this approach in the literature [9-11].  1.2  Objective and approach of this thesis  The objective of this thesis was to investigate a new catalyst (MoP) for synthesis gas conversion with an emphasis on increasing the C2 oxygenates (ethanol) selectivity. The approach to reach the objective was a combination of both theoretical and experimental methods. DFT was used to develop an understanding of the mechanism of the reaction of CO and H2 over MoP catalysts and the role of alkali promoters on the reaction. The experimental work was aimed at improving selectivity to ethanol by modifying the catalyst composition and properties, and the operating conditions.  A cluster model of MoP was developed from the (100) face of an MoP crystal. The Mo6P3 cluster model was in good agreement with the crystal model according to the atomic distances and bond angles. The cluster model was used to investigate the potential energy surface of CH4 and CH3OH formation from CO and H2. Use of the cluster model significantly reduced the computational time required for the calculations, compared to the  5  use of a MoP (100) slab model. The cluster model was extended to investigate the effect of the SiO2 support and K promoter. The Mo6P3-Si3O9 and K-Mo6P3-Si3O9 cluster models were developed for this purpose. To determine the potential energy surface for the formation of CH4 and CH3OH from syngas on the Mo6P3 cluster, CO was first adsorbed on a Mo atom of the cluster via the C atom. Then stepwise addition of a H atom in several possible arrangements to the C and O atom to form the final products CH4 and CH3OH, was investigated. A transition state search was accomplished between two stable surface intermediates. Investigation of the effect of SiO2 support and K promoter was focused on two reaction steps: one was the breaking of the C-O bond of hydroxymethyl species and the second was the formation of CH3OH from hydroxymethyl species. In the experimental study, the MoP catalyst was prepared by impregnation of a silica support with different loadings of MoP (5, 10 and 15 wt %) and K (0, 1 and 5 wt %). The temperature programmed reduction technique was used to reduce the oxide precursor to MoP. Prepared catalysts were analyzed using several characterization techniques, including BET, TPR, CO chemisorptions, XPS, EDX and XRD. A laboratory microreactor was used to evaluate the activity of the MoP catalysts for syngas conversion. Finally, 1 wt% Rh was added to the catalyst with the best performance (5 wt% K 10 wt% MoP/SiO2) to increase the stability and hydrogenation capability of the catalyst. Power law kinetic models were developed for the major products, i.e. methane, acetaldehyde, ethanol and acetone on the RhK-MoP/SiO2 catalyst.  6  1.3  Biomass  Biomass is the term used to describe living matter that is found on the earth’s surface. In terms of energy sources it refers to plants (e.g. wood, crops), animal waste (e.g. dung) and municipal solid waste (MSW) that can be used as a fuel to extract useful energy [12]. Prior to the discovery of inexpensive fossil fuels, our society was dependent on plant biomass (e.g wood), to meet its energy demand [3]. Plant biomass is the only current sustainable source of organic carbon and liquid fuels. Biofuels generate significantly less greenhouse gases (GHG) than fossil fuels and they can be greenhouse gas neutral [2,3]. Reduction of GHG emissions of 19-52% for corn ethanol and up to 86% for cellulosic ethanol have been claimed [13]. Worldwide renewable energy resources (including biomass) account for about 19% of the total world energy usage [14] and they have the potential to supply 50% of the world energy demand in the next century [2].  1.4  Syngas  Syngas is a mixture of carbon monoxide, hydrogen and carbon dioxide. Syngas can be produced by coal gasification, natural gas reforming and biomass gasification. Biomass gasification technology, like coal gasification, is an old technology, but operates at a lower temperature than coal gasification [1]. Gasification is a thermochemical process in which biomass reacts with air or oxygen and steam to produce syngas. A wide range of biomass (forest residue, wood chips, corn stover, animal waste, MSW) can be converted into syngas of consistent composition [2]. These are renewable resources and the products are carbon  7  neutral and thus have less environmental impact than fossil fuels. The produced syngas may contain impurities such as NH3, H2S, and tars and typically needs multistage cleanup before being injected into a catalytic reactor. Syngas can be converted into various fuels and chemicals, as illustrated in Figure 1.1, including gasoline, diesel, and waxes by the Fischer– Tropsch (FT) synthesis using Fe-based and Co-based catalysts, and to methanol using a Cu– ZnO/Al2O3 or Cu–ZnO/Cr2O3 catalysts. These are well established syngas conversion technologies [3,5,15,16]. Methanol obtained from syngas can serve as a building block for the synthesis of a variety of other fuels and chemicals (Figure 1.1), including dimethyl ether (DME), gasoline, olefins, acetic acid, and formaldehyde [17,18]. The technologies for the conversion of natural gas to liquid products, coal to liquid products and biomass to liquid products, all via gasification to syngas followed by FT-type catalytic conversions, are referred to as Gas-to-Liquid (GTL), Coal-to-Liquid (CTL) and Biomass-to-Liquid (BTL) technologies, respectively [1].  1.5  Ethanol as an alternative transportation fuel  Ethanol has the chemical formula C2H5OH and is the same alcohol found in alcoholic beverages. Ethanol can also be used as an effective transportation fuel, termed a biofuel, if it is generated from a renewable resource, i.e. biomass. Most of the ethanol made for fuel is blended with gasoline at concentrations of 5-10 vol% in the USA and the European Union. E10 (10 percent ethanol) is now commonly blended in gasoline as a fuel additive as an alternative to methyl tertiary butyl ether (MTBE), an anti-knocking agent. The use of MTBE has become obsolete due to the carcinogenic properties of the chemical. Although ethanol  8  has a lower volumetric energy content than gasoline (1.53 liters of ethanol have the energy content of 1 liter of gasoline), it can be used as a transportation fuel in suitably modified internal combustion engines. As of today, some motor engines have been developed to run with E85 (85% ethanol and 15% gasoline). Ethanol can also be blended with diesel fuel; this is known as ‘E-Diesel’. About one third more ethanol is needed to travel the same distance as with gasoline, but other ethanol fuel characteristics, including a high octane rating, result in increased engine efficiency and performance, as shown in Table 1.2. In addition, bioethanol can be used as a feedstock for the synthesis of a variety of chemicals, fuels and polymers [1]. Bioethanol is also considered a potential candidate for the production of renewable hydrogen in fuel cell applications via steam reforming or partial oxidation [1,2].  9  NH3  H2  WGS  Syngas  H2O  CO+H2  si s he t yn os h x O ,R Co  Acetaldehyde Alcohols  CuZnO CuCo MoS2  Rh ,R  rb o ny la t i  DME CH3OCH3  on ,  Ethanol  Rh  Acetic Acid  HPA Zeolite  Hydrolysis  ite  e  Hydrogenation  Ca  Alumina Zeolite HPA  Zeo l  Co ,F  Homologation With CO+H2 CuCo MoS2  )  Gasoline Olefins  Figure 1.1:  u,  CuZnO  Methanol  TO M e , t TG eoli M ( Z  Mixed Alcohol  Methyl acetate  Opportunities for catalytic conversion of syngas to fuels and chemicals: WGS = water-gas shift; MTG = methanol-to-gasoline; MTO = methanol-toolefin; DME = dimethyl ether; HPA = heteropoly acid [1].  10  Table 1.2: Comparison of fuel characteristics of gasoline and biomass-derived ethanol [19]  Gasoline Bioethanol *. for ethanol from corn grain  Refinery stream  Solid acid catalysis  Catalytic Hydration  Ethylene  26,456  Greenhouse gas emissions, Octane number g/mile 468 87-93  18,983  344-355*  Fossil fuel (i.e. Coal, Natural gas, Petroleum coke, Petroleum residue)  116  Biomass (i.e. Wood, Wood residue, Agricultural residue Corn, MSW etc)  Gasification  Gas cleanup/ Conditioning  Syngas CO+H2 Catalytic  Hydrolysis  Sugars  Fermentation/ Enzymatic  Fuel  Chemical energy, kJ/L  Ethanol C2 H5 OH  Figure 1.2:  Synthesis of ethanol from various carbon-containing feed-stocks [1].  11  1.6  Ethanol production processes  Currently 80% of the world’s ethanol production is by fermentation. A small portion of industrial grade ethanol is produced by hydration of petroleum based ethylene. Conversion of syngas to ethanol is also of interest, but this approach is not economical with current catalytic technology. The production of ethanol, following different pathways, is depicted in Figure 1.2. (1) Fermentation: Fermentation of sugars derived from corn or sugarcane (6 carbon chain hexo-sugar) is a biological process that converts the starch and suger into beverage grade alcohol containing 14% ethanol. Production of fuel grade alcohol (92.1 vol%) by this process is expensive because of the energy intensive distillation process needed to achieve fuel grade ethanol [20]. (2) Hydration of petroleum-based ethylene: The hydration of ethylene over a solid acid catalyst is used for the production of industrial-grade pure ethanol [21]. The ethylene hydration route is unattractive for large scale production due to the increasing fossil fuel price and the environmental impact of fossil fuels. (3) Enzyme process: Presently, the enzyme process is the most attractive for ethanol production. This new fermentation process (not in commercial practice yet) can convert both 5- and 6-carbon sugars into ethanol. The fermentation of syngas (a mixture of CO and H2) obtained from gasification of unconverted biomass (from enzyme process) to ethanol is also being developed [5,22] using this process.  12  (4) Heterogeneous catalytic processes: This process converts syngas (CO+CO2+H2) into mixed alcohol with high selectivity towards ethanol using a suitable heterogeneous catalyst.  Although fermentation processes are more selective to end products, the reaction rates in thermo chemical processes are orders of magnitude higher and can be used to convert a wide range of feedstock (forest residue, animal waste etc.) to produce a syngas mixture of reasonably consistent composition. This can be a significant advantage in making these processes economically competitive [2]. However, a suitable catalyst for ethanol synthesis from syngas is yet to be identified.  1.7  Thermodynamics of ethanol production from syngas  Syngas as a building block can be converted into ethanol and higher alcohols, either directly or via methanol as an intermediate product. The reaction network consists of a complex set of numerous reactions, with multiple pathways leading to a variety of products that are impacted by kinetic and thermodynamic constraints [1]. In order to understand the synthesis of ethanol or higher oxygenates from biomass derived syngas, it is informative to examine the thermodynamics of the individual reactions leading to ethanol from the compounds present in the syngas. A great deal of literature has been published on the hydrogenation of CO and CO2 to C2+ products [2]. Side reactions to these compounds such as the water gas shift reaction and the methanation reaction also occur.  13  The overall formation of higher alcohols from syngas can be described by the following equations  nCO + 2nH 2 ↔ Cn H 2n +1OH + (n − 1) H 2O ; (n = 1,2,3..)  (1.1)  Hydrocarbons are produced unavoidably by the Fischer-Tropsch reaction.  nCO + (2n + 1)H 2 ↔ Cn H 2n + 2 + nH2O ; (n = 1,2,3..)  (1.2)  Water gas shift reaction CO + H 2O ↔ CO2 + H 2  (1.3)  ௢ ௢ ∆‫ܪ‬ଶହ బ ஼ = -41.1 kJ/mol; ∆‫ܩ‬ଶହబ ஼ = -28.6 kJ/mol;  Methanation reaction  CO + 3H2 ↔ CH4 + H2O  (1.4)  ௢ ௢ ∆‫ܪ‬ଶହ బ ஼ = -205.9 kJ/mol; ∆‫ܩ‬ଶହబ ஼ = -141.9 kJ/mol;  Thermodynamic analysis of the syngas conversion to ethanol and the effect of pressure and temperature on the reactions have been reported by several researchers [1,2]. Thermodynamic parameters for ethanol synthesis are reported in Table 1.3. Methanation is the most thermodynamically favorable reaction and therefore, methane production must be controlled kinetically. An appropriate catalyst surface will impose a kinetic barrier to methane formation whereas it may favor higher alcohol formation. Formation of ethanol is thermodynamically favorable via the route of direct hydrogenation or methanol homologation. Thus it may be inferred from the thermodynamic results, that the formation of ethanol is thermodynamically favorable but needs to be controlled kinetically. All these reactions are highly exothermic. Controlling the heat of reaction is a task for the reactor design engineer to obtain the optimum conversion and protect the life of the catalyst. 14  Oxygenates and hydrocarbons are always accompanied by the production of water, most of which appears to be converted to CO2 through the water gas shift reaction. The reverse water gas shift reaction is the partial reduction of CO2 to CO, which is suggested to be an elementary step in the synthesis of ethanol from CO2 hydrogenation [1].  Table 1.3: Thermodynamics of different reactions relevant in the ethanol synthesis process ∆Go25ºC  ∆Ho25ºC  [kJ/mol]  [kJ/mol]  2CO+4H2 ↔ C2H5OH + H2O  -122.69  -256.09  CH3OH+CO+2H2 ↔ C2H5OH + H2O  -96.96  -165.04  (i) CO+2H2 ↔ CH3OH  -25.06  -90.47  (ii) CH3OH+CO ↔ CH3COOH  -76.95  -123.28  (iii) CH3COOH + 2H2↔ C2H5OH + H2O  -19.87  -41.68  Condensation / Coupling  2CH3OH ↔ C2H5OH + H2O  -71.64  -74.61  Methanation reaction  CO+3H2 ↔ CH4 + H2O  -141.85  -205.84  Water gas shift reaction  CO+H2O ↔ CO2 + H2  -28.58  -41.09  Hydrogenation of CO2  2CO2+ 6H2 ↔ C2H5OH + 3H2O  -65.69  -173.82  Boudouard reaction  2CO ↔ CO2 +C  -120.02  -172.00  Process Direct Hydrogenation of CO to ethanol Methanol homologation  ENSOL process  Reaction  [The values of heats of formation, Gibbs’ free energy of formation, heats of reaction and Gibbs’ free energy of reaction for main reaction products are tabulated in Table AIII-3 and Table AIII-4 in Appendix AIII-7.(c)].  15  1.8  Review of ethanol synthesis catalysts  Heterogeneous catalysts employed for the synthesis of ethanol and higher alcohols can be classified into four categories. (1) Modified methanol synthesis catalyst, (a) High temperature, Zn-Cr based catalyst (b) Low temperature, Cu-Zn based catalyst. (2) Modified FTS based catalyst (3) Rhodium based catalyst (4) Molybdenum based catalyst In Table 1.4 the most promising ethanol synthesis catalysts’ activity and selectivity data are reported.  1.8.1  Modified methanol synthesis catalyst  Both linear alcohols and branched alcohols are produced from syngas over alkali doped methanol synthesis catalysts [23]. The high temperature methanol synthesis catalyst was first studied on alkali promoted ZnO/Cr2O3 [24-28]. The products were methanol and 2-methyl 1propanol with high yield. This catalyst operates at high temperature (> 400 oC) and pressure (30-40 MPa).  Low temperature copper based (Cu/ZnO) methanol synthesis catalysts, promoted with K or Cs, were investigated by several researchers [29-33] in the temperature and pressure range  16  Table 1.4 : Performance of some ethanol synthesis catalysts  HC  C1OH  C2OH  C3+OH  STY alcohol (mg/gm cat./h)  40.5  48.1  1.9  44.5  NR  NR  [44]  1.0  2.0  31.5  15.4  50.8  NR  NR  [6]  300  1.7  NR  50.9  3.0  45.0  NR  NR  [42]  1,740  8,000  2.0  NR  NR  NR  NR  NR  729  [38]  220  305  2,000  2.0  2.2  34.0  8.7  37.0  NA  NR  [40]  300  1,160  2,000  1.0  36.7  61.4  11.3  13.9  24  341  [62]  300  870  10,000  2.0  37.5  51.5  23.4  12.1  13.0  624  [52]  295  1,050  1,300  1.0  29.2  14.5  22.7  40.7  17.4  NR  [53]  327  1,450  14,400  2.0  5.5  17.0  26.0  28.0  28.0  389  [57]  330  725  4,800  2.0  11.7  58.1  18.7  13.2  8.0  150  [78]  320  2,000  4,000  1.1  28.7  31.3  10.8  30.3  22.0  NR  [58]  315  1,377  6,000  2.0  17.8  18.2  37.4  26.9  12.6  NR  [59]  Catalyst  Temp (oC)  Press (psig)  GHSV (h-1)  H2:CO  XCO (%)  6% Rh 1.5% Mn/SiO2  300  783  3,750  2.0  1%Rh/ZrO2  220  14.7  NR  RhCe/SiO2  350  14.7  CuCoCr0.8K0.09 +Cement  250  CoRuSr/SiO2 K-Co-β-Mo2C 1% K-CoMo4 ultrafine MoS2 (Dow chemical) K-RhMoS2/Al2O3 KCoMoS2/C (Mo/Co=4) Cs2CO3Co MoS2/clay Ni/Mn/K/MoS2  *  NR = Not reported in the literature  Selectivity (C atom %)  Ref  17  275-325 oC and 5-11 MPa, respectively. The catalysts produced a mixture of linear and branched alcohols ranging from C1-C6 together with a small amount of other oxygenates and hydrocarbons. Beretta et al. [34] reported that a Cs-Cu-ZnO-Cr2O3 (3/30/45/25 mol%) catalyst, operated at 325 oC and 7.6 MPa and H2:CO = 0.75 showed a methanol space time yield (STY) of 1200 mg.g cat.-1h-1, ethanol STY of 68 mg.g cat.-1h-1 and a total alcohol STY of 1547 mg.g cat-1.h-1.  The high temperature methanol synthesis catalyst, ZnO/Cr2O3, was investigated in the range 350-450 oC and 20-40 atm pressure. This type of catalyst produced isobutanol, the bulky end product of CO hydrogenation. Isobutanol was used as a raw material to produce MTBE (methyl tertiary butyl ether), which was used as a fuel additive and anti-knocking agent. The major products were a mixture of methanol and isobutanol [34]. The STY of methanol was 173.4 mg.g cat.-1h-1 and the total alcohol STY was 288.1 mg.g cat.-1h-1 at 405 oC and 7.6 MPa with H2/CO =0.75. Only a small amount of ethanol was produced. The rate of isobutanol production increased with increasing alkali (K and Cs) [35].  CO/H2  Slow CHO O  H  -C + Cs  Fast - 2H2 2CH3OH CsOH - H2 O  H  +  C H  O  CH2 O  -  Cs+ H2 H2 H2 O  - H2 O - CsOH  CH3CH2OH  Figure 1.3: Ethanol formation mechanism over Cu based catalyst [36].  18  A generalized mechanism of the formation of ethanol on Cu based catalysts is shown in Figure 1.3. An adsorbed formyl species is formed on the surface from CO and H2. Hydrogenation of formyl species to formaldehyde, followed by a subsequent hydrogenation, produces methanol. The adsorbed formyl species can react with another adsorbed formyl species, formed from syngas or from methanol, to produce adsorbed acetyl species. The acetyl intermediate can further react with another formyl species to form propanol or with another acetyl species to form butanol by an aldol type condensation reaction over the basic catalyst surface [36].  In conclusion, it is clear that on modified methanol synthesis catalysts, branched or C2+ alcohols predominate. For ethanol synthesis, these types of catalysts do not show good selectivity, but rather show higher selectivity to C2+ alcohols.  1.8.2  Modified FTS catalyst  These catalysts include Fischer-Tropsch catalysts containing Co, Fe, Ni or Ru supported on Al2O3 or SiO2, with promoters such as Cu and K . Most of these catalytic systems produce hydrocarbons, including CH4 as the predominant product, with a hydrocarbon to alcohol selectivity ratio of one or higher. Among the transition metals, Co is known to be very active for FTS while Cu tends to form alcohols. This leads to the assumption that Co-Cu mixed oxides with a definite structure, such as perovskite or spinel, could be a promising catalyst for syngas conversion to alcohols and hydrocarbons [1]. Takeuchi et al. [37] reported a Co/SiO2 catalyst modified with Re and Sr for the synthesis of ethanol from syngas. At 220  19  o  C, 2.1 MPa and H2:CO:Ar = 6:3:1, Co-Re-Sr/SiO2 (5:5:5:100 wt ratio) showed high  selectivity (24 C atom %) to ethanol.  The IFP (French Petroleum Institute) patented a Co-Cu based catalyst modified by Cr, Mn, Fe, La and K [38]. The catalyst showed the ability to produce ethanol with high selectivity within the liquid products. Typical operating conditions for these catalysts ranged from 5-15 MPa and 220-350 oC using wide range of H2:CO ratios. The yield of ethanol was 100-350 mg. g cat.-1h-1 [38]. The ethanol yield on the IFP CuCo based catalyst was higher than that of methanol and C3+ alcohols. Cu1Co1Cr0.8K0.09+Cement catalyst had a methanol yield of 208 mg.g cat.-1h-1 and an ethanol yield of 341 mg.g cat.-1h-1 with a total alcohol yield of 729 mg.g cat.-1h-1 at the reaction conditions of 250 oC, 12 MPa and H2/(CO+CO2) = 2.  The mechanism of alcohol and hydrocarbon synthesis over the modified FT alcohol synthesis catalysts is shown in Figure 1.4. The main steps are the hydrogenation of the adsorbed formyl species formed by the adsorbed CO and H2 on the surface. Upon hydrogenation, the formyl produces surface alkyl (CHx) species. CO insertion into the metal-alkyl bond forms an acyl intermediate, which upon hydrogenation, produces ethanol. Methane and higher hydrocarbons can be formed by the hydrogenation reaction with another adsorbed alkyl species [39].  20  H  M CO H  M  H2  C  H  1  H C  2  O  H  H  O  M  3  H  O H  CH3OH H H  C  4  H2  M  H  5  OH  H  H  C  M  CO M  H2  11  H3C  9  C  H3C  H  C  M  M  H3C  10  OH H  - H2 O  13  H3C  CH2  M  H  H  C  M  H  H2  C  M  OH  O  H  H  - H 2O  OH H  H  H3 C  +  6  7  8  C  M  CO M  14  β Abstraction 15 H 2C  12  CH3CH2OH  +  CH2  +  H-M  H-M  Figure 1.4: Ethanol formation mechanism over modified FT synthesis catalyst [39].  21  1.8.3  Rh based catalyst  Supported Rh catalysts have been shown to produce C2+ oxygenates such as ethanol, acetaldehyde and acetic acid selectively from syngas [40]. Rh occupies a very interesting position in the periodic table, because it lies between metals that easily dissociate CO to form higher  hydrocarbons  (i.e.  Fe,  Co)  and  those  which  do  not  dissociate  CO  (i.e. Pd, Pt, Ir) [40,41]. Rh based catalysts also produce CH4, an undesired product, with high selectivity. In 1975, Union Carbide reported on a Rh catalyst supported on SiO2 promoted by different metal ions (i.e. Fe, Mn, W, Th, U) [42]. The best performance was obtained for 2.5 wt % Rh supported on SiO2, promoted with 0.05 wt % Fe. At 300 oC and 7.1 MPa using H2/CO=1, the catalyst produced 49% methane, 2.8% methanol, 31.4% ethanol and 9.1% acetic acid [43]. Later, researchers investigated a wider range of supports and promoters to increase the C2 oxygenate (ethanol, acetic acid, acetaldehyde) selectivity and decrease the methanol selectivity. Recently, Hu et al. [44], employed a micro channel reactor containing a 6% Rh 1.5% Mn on SiO2 catalyst for the conversion of biomass derived syngas to alcohols and C2 oxygenate. The reaction was performed in the range of temperature 265-300 oC and pressure 3.8-5.5 MPa. Using a H2/CO = 2 and GHSV = 3750 h-1, methane (38.1% C atom selective) and ethanol (56 % C atom selective) were the main products. The authors noted that reaction temperature rather than reaction pressure had a strong influence on the product selectivity. Recently Fan et al. [45] reported that a carbon nanotube supported Rh based catalyst had the highest overall activity and yield of C2 oxygenates compared to other carbon supported (i.e. graphitic carbon black, very high surface area CMK-3, activated carbon) catalysts. The Rh based catalyst was also promoted by multi component additives (Mn, Li, and Fe). The product distribution was 52.5 C atom % C2+ oxygenate and 14.6 C atom %  22  methane for the Rh-Li-Mn-Fe/Carbon Nanotube catalyst. Although rhodium can form methane, alcohols and other oxygenates by CO hydrogenation, depending on the support, promoter and reaction conditions [2,46-48], the scarcity and price of Rh imposes the main barrier for the adoption of this catalyst. The mechanism of ethanol and higher oxygenate synthesis over Rh is depicted in Figure 1.5. Initially, CO and H2 are adsorbed on the catalyst surface. The adsorbed H and the nondissociatively adsorbed CO then react to form methanol or the CO dissociates to form surface carbon and oxygen species. Adsorbed carbon can then react with adsorbed H to form surface CHx(x = 2, 3) species [6,49]. This surface adsorbed carbene species reacts with nondissociated CO to form adsorbed enol (CH2-CH-OH) species. The enol species is the precursor to C2 oxygenate or C2+ oxygenate formation. Enol can react with adsorbed CO and H to form higher oxygenates or it can react with H to form ethanol [2]. H2  2Had CH3OH  CO O || C ||  4Had  C |  O |  x/2H2  CHx  +(4-x)Had CH4  -H2O +CO +(4-x)Had OH H2 C C2+ Oxygenate  Figure 1.5:  -H2O +COad, Had  CH  +2Had CH3CH2OH  A simplified sequence for ethanol formation by CO hydrogenation on Rh based catalyst [2].  23  1.8.4  Mo catalyst  Mo based catalysts appear to be the most promising for alcohol synthesis from syngas because of the following characteristics [1]: 1.  Mo catalysts are sulfur resistant  2. Catalyst deactivation due to coke deposition is relatively low 3. Catalyst favors the formation of linear alcohols 4. The catalysts are less sensitive to CO2 in the syngas stream.  Mo and MoO3 catalyst: Unsulfided Mo based catalysts promoted by base metals, alkali and noble metals mainly produce mixed linear alcohols from syngas. Tatsumi et al. [50,51] reported 50.3 C atom % selectivity towards alcohol and 20.7 C atom % selectivity towards ethanol on 10 wt% Mo-K/SiO2 catalyst (K/Mo=0.4) at 300 oC, 1.6 MPa pressure and H2:CO = 1. Zhang et al. [52] reported that a K-MoO3 catalyst had 15.3 C atom % selectivity to alcohols and 3.7 C atom % selectivity to ethanol at 300 oC, 6 MPa pressure and H2:CO = 2. Addition of Co (Co/Mo=1/7) increased the alcohol (48.5 C atom %) and higher alcohol (41 C atom %) selectivity. Overall, Mo and MoO3 based catalysts produce mainly hydrocarbons (selectivity~>50 C atom%).  MoS2 catalyst: MoS2 is well known in petroleum industries as a hydrodesulfurization and hydrodenitrogenation catalyst. MoS2 based catalysts display CO hydrogenation to higher alcohol capabilities when doped with alkali metals and thus are known as ADM (alkali doped molybdenum sulfide) catalysts. Dow Chemical Company [53-55] and Union Carbide  24  Corporation [56] independently demonstrated that either supported or unsupported alkali doped MoS2 could produce alcohols from syngas with alcohol selectivity ranging from 75 to 90%. For ethanol, the Dow patent [53] claimed 40% selectivity on a CO2 free basis from syngas, but others reported 10-30% selectivity to ethanol on MoS2 based catalysts depending upon the type of promoters and reaction conditions. Addition of transition metals Rh, Co, and Ni [57-59] as promoters, increased the activity of the catalyst and the selectivity and yield towards higher alcohols, especially ethanol. A 17.8% CO conversion and 81.7% alcohol selectivity were reported at 320 oC, 9.5 MPa and a space velocity of 6000 h-1 with a syngas containing a H2:CO ratio of 2 on Ni/Mn/K/MoS2 catalyst [59]. PowerEnerCat Inc. recently patented nanosized MoS2 (100 nm) catalysts for HAS by the Ecalene process [60]. The process operated at 280 oC and 13.79 MPa produced mixed alcohols with a space time yield higher than 400 mg alcohol. g cat.-1h-1.  Figure 1.6 outlines the formation of alcohols and hydrocarbons on MoS2 [61] based catalysts. The mechanism follows FT synthesis. CO is dissociated readily to form surface CHx on separate MSx (M = Fe, Co or Ni) site and the formation of methane takes place by direct hydrogenation of surface CH species. The non-dissociatively adsorbed CO on the mixed MK-MoS phase then inserts into a metal–methyl carbon bond to produce an alcohol precursor, which is further hydrogenated or dehydrated to form alcohols and hydrocarbons. This route comprises the chain growth via hydrogenated intermediates and chain growth via oxygenated intermediates. The concentration of the surface bound C1 intermediates influence on the formation of methanol and branched alcohols. The linear chain growth via  25  C1 intermediate insertion at the end of the chain resulted in linear primary alcohols, while the addition via C2 intermediate resulted in branched alcohols [61].  CH3OH  CH4  H*  CH* MSx  C2H xO*  CH*x CO*  H*  C3H7OH  C2H6; C2H4 H*  H*  H*  CHxO*  H2+CO  C2H5OH  H*  C2H* x  H* CO*  C3H xO*  H2O  M-KMoSx  O* CO2  Figure 1.6:  Reaction pathway for CO hydrogenation over transition metal modified ADM catalyst (M denotes Fe, Co or Ni) [61].  β-Mo2C Catalyst: Recently, K promoted Co or Ni doped β-Mo2C catalysts have been reported for the conversion of syngas to higher alcohols. The undoped β-Mo2C exhibited a CO conversion of 58% with CO2 and hydrocarbons as major products [62,62-64]. The catalysts were evaluated at the operating conditions of 300oC, 8.0 MPa pressure, syngas ratio of 1, and a space velocity of 2000 h-1. Addition of K decreased the CO conversion and increased the selectivity to alcohols, with 40% ethanol distribution among the alcohols. Both the alcohol selectivity and CO conversion increased upon doping Ni onto K modified βMo2C. Thus, the Ni-K-β-Mo2C exhibited a CO conversion of about 73% with an alcohol  26  selectivity of about 23 C atom%. Doping with Co increased the selectivity to hydrocarbons [64].  CO  H2  Alkane  CO  Alcohol  CO*  CxHyO*  CH*2 C* O * + Mosite#1  H*  CH*x  CxH* y  +  Mosite#2  CO2  Figure 1.7:  The tentative reaction pathway of CO hydrogenation over transition metal modified Mo2C based catalyst (M denotes as Fe, Co or Ni) [61].  The tentatively proposed reaction pathway for CO hydrogenation over Mo2C catalyst follows a dual-site mechanism, similar to that reported by Muramatsu et al.[51]. There are two kinds of Mo carbide species located on the surface of the catalysts, namely the low valent molybdenum (MoI, I = 0–2) carbides and the high valent molybdenum (MoII, II = 4) carbides [61]. The dissociatively adsorbed CO and H2 on MoI carbide sites form CHX species. Chain growth of the alkyl group is propagated by a CH2 insertion process. The alkyl group can migrate to the MoII carbide sites, where CO is adsorbed non-dissociatively. CO is inserted to alkyl groups to form surface acyl species. Finally, the hydrogenation of alkyl groups and acyl species over different Mo carbide sites leads to hydrocarbons and mixed alcohols.  27  1.9  Role of alkali promoters  Alkali promoters such as Na, K, Cs, Sr, have been widely employed in various catalytic systems. They play a significant role in determining the activity, selectivity and life of the catalyst. Alkali metals introduce a site for undissociated CO adsorption on the surface which directly hydrogenates to alcohols. On Cu based catalysts, higher alcohol production has been found to increase in the order Li < Na < K < Cs < Rb, in the same order as their basicity [32]. Calverley and Smith [65] reported an optimum surface concentration of K for the maximum yield of higher alcohols on Cu/ZnO catalyst, with a small improvement in ethanol selectivity. Similar behavior was observed for ZnO-Cr2O3 based high temperature methanol synthesis catalysts. In contrast to the methanol synthesis catalyst, on Co based FT synthesis catalysts [37] and MoS2 catalysts [54] an increase in yield and selectivity to higher alcohols and ethanol is observed with an increase in alkali loading. An optimum alkali loading is required to achieve a maximum selectivity for ethanol and higher alcohols. The promoting effect of alkali (on MoS2) for alcohol formation was found to increase in the order Li > Na > Cs > Rb > K, suggesting that moderate basic promotion is desired [66].  1.10 Effect of CO2 in the feed Limited information is available on the effect of CO2 on higher alcohol synthesis catalyst. Calverley and Smith [65] reported that higher alcohol yield passed through a maximum around 4% CO2 over a Cu/ZnO catalyst. Also, the CoCu based IFP catalyst activity was reported for a syngas mixture containing 13% CO2 [38]. Although the effect of CO2 is not well understood on this type of catalyst, the catalyst exhibits relatively high yield to ethanol  28  and C3+ alcohols compared to other ethanol synthesis catalysts. The MoS2 based catalysts are less sensitive to CO2 than other HAS catalysts though no quantitative data are available to understand the effect of CO2 on ethanol productivity. Gang et al. [67] reported a decrease in C2+ alcohol productivity with increasing CO2 (up to 6.1 mole % in the feed) concentration in the feed. Formation of CO2 over the MoS2 surface was suppressed. However, the presence of CO2 in the feed can cause an increase in the amount of water formed via the reversed water gas shift reaction.  1.11 Summary  From the above literature discussion we can conclude that Rh based catalysts show high selectivity to ethanol formation from syngas. Cost and availability of Rh are the main barriers to the adaptation of this catalyst for commercial operation. Among the alternative higher alcohol synthesis catalysts, modified methanol synthesis catalysts selectively produce mainly methanol and isobutanol, with low selectivity to ethanol. CuCo based catalysts show high yield to ethanol and higher alcohols, but they produce considerable amounts of hydrocarbons. Among the molybdenum based catalysts, MoS2 shows the best selectivity to total alcohols (> 80 C atom %) and ethanol (10-40 C atom%) among the non Rh based ethanol synthesis catalysts. Hence investigation of other Mo based catalysts, i.e. MoP, Mo2N, MoB, for the syngas conversion has drawn interest from researchers. MoS2 catalysts are well known for their hydro desulfurization (HDS) characteristics. Recently, MoP catalysts were reported to possess better activity towards HDS reactions compared to MoS2 catalysts. Consequently, MoP as a new catalyst for syngas conversion is the focus of the present study.  29  1.12 Molecular modeling in heterogeneous catalysis  Recent advances in first principles calculations with the aid of advanced computing facilities allow the calculation of formation energies of molecules and solids, the structure of adsorbed reaction intermediates and their binding energies and reaction pathways (micro kinetics analysis) with high accuracy. These methods are therefore emerging as a potential design tools for catalysis. First principle technique: The fundamental equation upon which first principle calculations are based is the timeindependent Schrödinger equation, ) Η Ψk (r1, r2, r3, ......rn ) = Ε k Ψk (r1, r2, r3, ......rn )  (1.5)  The Hamiltonian for a system (Ĥ, the operator of the total energy for the system) consisting of M nuclei and N electrons is given as follows, N M Z N N 1 M M Z Z ) 1 N 1 M Η = − ∑ ∇ i2 − ∑ ∇ 2A − ∑ ∑ A + ∑ ∑ +∑ ∑ A B 2 i =1 2 A =1 i =1A =1 riA i =1 j > i rij A =1 B > A R AB  (1.6)  Here, A and B run over M nuclei while i and j denote N electrons in the system. The first two terms describe the kinetic energy of the electrons and nuclei. The other three terms represent the attractive electrostatic interaction between the nuclei and electrons and repulsive potential due to the electron-electron and nucleus-nucleus interactions. The derivation of the Hamiltonian operator for an electronic system is shown in Appendix I. The solution to Eq. (1.5) yields the wave function, Ψ, a function of space, which is thought to contain all known information about the system. Solution of Eq. (1.5) yields fundamental information about the  30  system, including probability distributions for all particles in the system and energetic information about particle configurations.  Most of the phenomena in catalysis and surface science rely on electronic effects rather than the nuclear contributions and as the time scale associated with the motion of electrons and atomic nuclei are significantly different, the nuclear and electronic components may be decoupled (Born-Oppenheimer approximation) and the electronic problem may be solved to obtain the electronic energy for a given nuclear configuration. Mapping the potential energy surface (PES) by calculating electronic energy for different nuclear positions can ultimately give the ground state structure and the energy, which are of specific importance for chemical reactions. Analytical solution of Equation (1.5) is not possible for most systems of practical interest and hence approximation and simplifying assumptions are needed. Accordingly various methodologies such as Configuration Interaction (CI), Hartree Fock Self-Consistent Field (HFSCF) approach and Quantum Monte Carlo methods are used for solving the Schrödinger equation [8].  1.13 Types of molecular simulation  In broad terms, quantum mechanical simulation can be divided into three approaches [8]. (1) Ab initio (2) Semi-empirical (3) Density functional theory  31  (1) Ab initio : In the ab initio molecular orbital (MO) methods the Schrödinger equation is solved “from the beginning”. They usually express the molecular orbital as a linear combination of a finite number of basis functions. The basis set can start as a minimal and can be improved systematically, eventually approaching the complete set. The total electronic wave function is expressed as a linear combination of Slater determinants (SDs). The simplest form of the total wave function is a single SD, which is called the Hartree Fock (HF) approximation. To include “electron correlation”, one has to use more than one SD.  Ab initio methods are the ultimate theoretical methods for electronic structure calculations applicable to any atoms and molecules in both ground and excited states. The approximation can be improved by better basis sets and better wave functions. The disadvantage of ab initio methods is their cost and high computational time compared to DFT, semi-empirical and molecular mechanics method.  (2) Semi-empirical : Semi empirical MO methods neglect most of the two electron integral in solving the Schrödinger equation and use experimental results to adjust integrals to obtain good results at very low cost. They are much faster than ab initio methods and also provide explicit information on bond breaking and electronic effects. Important shortcomings of semi-empirical methods are low reliability and a lack of reliable parameters for transition metals. Therefore, they are not applicable to most homogeneous and heterogeneous catalysis modeling.  32  (3) Density functional theory: Hohenberg and Kohn (1964) [68] first provided the basic framework for modern density functional theory proving the fact that the ground state properties are a function of electron density ρ(r). “The total ground state energy of an electron system can be written as a function of electron density, as this energy is at minimum if the density is an exact density for ground state”[68]. In the DFT calculations exact form of the energy functional is unknown and we need to use approximations regarding parts of the functional dealing with kinetic energy and exchange and correlation energies of the system of electrons. The total ground state energy is given by  E[ρ ] = Te [ρ ] + Vext [ρ ] + Uee [ρ ]  (1.7)  Te[ρ] = kinetic energy of electrons Vext[ρ] = the external potential (electrostatic potential coming from nuclei) Uee[ρ] = electrostatic repulsion between electrons. Additionally HK (Hohenberg and Kohn) energy is grouped together with all functionals which are secondary to the Vext[ρ]. ) E [ρ ] = ∫ ρ (r )Vext (r ) dr + FKH [ρ ]  (1.8)  The FHK functional operates only on the density of the universe. In HK theory, the expression relating kinetic energy to density is not known with satisfactory accuracy. Kinetic energy can be calculated from the wave function, provided it is known and need to find the exact energy functional to solve the energy of the system. Kohn and Sham (1965) [65] proposed another method of marrying wave function and density. The total energy becomes ) ) E [ρ ] = To [ρ ] + ∫ Vext (r ) + U cl (r ) ρ (r )dr + E xc [ρ ]  [  ]  (1.9)  33  where To [ρ ] =  1 N KS 2 KS ∑ φi ∇i φi , is the kinetic energy of electrons in a system that has the 2 i =1  same density ρ as the real system and in which there is no electron-electron interaction. It is ) ρ (r ') calculated from the corresponding orbital ( φiKS is the Kohn Sham orbital). U cl (r ) = ∫ dr ' r '− r  is a pure columbic interaction between electrons, which includes electron self interaction. The corresponding energy is given by Ecl (ρ ) = ∫ ∫  ρ (r )ρ (r ') r '− r  ) − Zα is the drdr ' . Vext = ∑ α Rα − r  external potential, the potential coming from nuclei, where Zα is the charge of the α nuclei. Exc(ρ) is the exchange correlation energy, that includes all the energy which is not accounted for by previous terms. The exchange correlation energy is partitioned into two parts, the exchange energy and the correlation energy ( Exc [ρ ] = Ex [ρ ] + Ec [ρ ] ). The most important type of approximation is the local density approximation (LDA) for which the exchange energy is given by E  LDA x  2 [ρ ] = − 3q  3  4 π   1  3  ∫d  3  4  rρ (r ) 3 . The correlation energy is not known  properly and is based on applying perturbation theory in the LDA approximation. LDA has been applied to solid state physics (i.e. band structure of solids), but failed to provide results in quantum chemistry (i.e. information about chemical bonds in molecules, ‘chemical accuracy’). Only GGA [69] (generalized gradient approximation) provides notable improvements by expanding Exc[ρ]. Its general form, E GGA [ρ ] = ∫ d 3 rε xcGGA (ρ (r ), ∇ ρ (r )) . xc  ε xcGGA , is an analytical function with parameters that are fitted to experiment or determined by exact sum rules. GGA gives reliable results for all main types of chemical bonds. Most frequently used local potentials are B88 (Becke, 1988) [70], PW91 (Perdew et al. 1992) [71] for exchange energy and P86 (Perdew, 1986), LYP(Lee-Yang-Parr) [72] for correlation 34  energy. Further improvements of exchange correlation functionals are expected to diminish the remaining gap separating accurate experimental binding energies from DFT predictions.  1.14 Catalyst design by molecular modeling  There are three different ways to model the heterogeneous catalyst system in computational chemistry simulations [73]: (1) Cluster model (2) Embedded cluster model (3) Periodic quantum mechanical calculation  Cluster model: A discrete number of atoms are used to form a cluster structure to model the active site for a catalytic reaction. The catalytic surface reaction steps, i.e. chemisorption and reactivity are local phenomena and are primarily affected by the nearby surface structure. Therefore, rigorous quantum mechanical calculation can be used to elucidate the extent of orbital overlap and electron correlation of the adsorbate/surface ensemble to predict the adsorption geometry, adsorption energies and surface reactivities using the cluster model. An explicit description of the interaction between local molecular orbitals of the adsorbate and the surface is the major advantage of the cluster approach. An incomplete representation of the electronic system provided by its small size and discrete nature of the cluster employed is the major limitation of the cluster approach [73].  35  Embedded cluster approach: The embedded cluster model is simply an extension of the cluster approach that attempts to treat the problems associated with the abrupt cluster termination. A rigorous quantum mechanical (QM) approach is used to model the local region about the active site. The primary cluster is then embedded in a much larger system in order to simulate the external electronic environment. The difficulties with this approach involve accurately matching the electronic structure at the interface between the inner cluster and external model. But this method can simulate the core region with DFT and the outer shell with molecular mechanics and can be carried out on tens of thousands of atoms with less computational cost [73].  Periodic quantum mechanical approach: The extended electronic structure and external field effect for well defined surfaces can be modeled by using periodic infinite slab calculations. In the periodic system a unit cell is defined to represent the system. This unit cell is then subsequently repeated in one, two and three directions, thus providing the electronic structure for linear slab and bulk materials. A complete electronic structure of the catalytic reaction system can be modeled using this periodic approach but in lieu of high computational cost [73].  In this thesis cluster models of Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9 have been used to represent the catalytic system (K-MoP/SiO2) and to carry out the DFT computation to investigate different properties of the catalyst in syngas reaction.  36  1.15 Important property calculations using DFT method  Energies: An accurate knowledge of reaction energies is vital in the determination of favorable reaction pathways, leading to the desired products at low energy. To understand the complex mechanism involved, it is vital to have an accurate knowledge of the reaction pathway, the structure involved and the reaction energies [7].  Binding energy and heat of reaction: DFT calculations provide an efficient way to calculate the total electronic energy (TE) of a system, which may be used to calculate the heat of reaction, ∆H. The adsorption of a species on a surface, ∆H is approximated by the binding energy of the species. Knowledge of the total energies of the adsorbed configuration, the clean slab/cluster representing the catalytic surface and the isolated gas phase species can be used to calculate the BE as : BE = TE( adsorbed configuration) – TE(clean slab/cluster) – TE ( isolated gas phase species). The binding energy thus calculated can be used for determining ∆H as follows: ∆‫ ܪ‬ൌ ∑௡௜ୀଵ ‫ ܧܤ‬ሺܲ‫ݏݐܿݑ݀݋ݎ‬ሻ െ ∑௠ ௜ୀଵ ‫ ܧܤ‬ሺܴ݁ܽܿ‫ݏݐ݊ܽݐ‬ሻ ൅ ∆‫ܪ‬௚௔௦ Where n and m are the number of product and reactant species and ∆Hgas is the heat of reaction in the gas phase.  Activation energies (∆Ea): The thermodynamic properties of surface reaction intermediates can give insights into the possible reaction mechanisms. However, to build a robust kinetic model, a good estimate of the activation energies, ∆Ea, is necessary. It is possible to directly calculate the activation barrier using DFT. The activation energy calculation is embedded within the transition state (TS) search calculation.  37  1.16 Transition state searching  “The transition state search algorithm implemented in CASTEP and DMol3 is a generalized scheme based on the traditional linear and quadratic synchronous transit (LST/ QST) method [74] coupled with previously proposed conjugate gradient (CG) refinement ideas [75]”. The energies of suitable reactant and product structures are first calculated. This is followed by a search for the LST maximum using essentially the method of Halgren and Lipscomb [74]. The maximum energy structure provides an upper bound for the transition state. A conjugate gradient (CG) [76] refinement is initiated for further refinement of the estimated transition state, searching in the direction conjugate to the vector connecting reactants to products. CG method makes intelligent use of gradient information, thereby requiring no explicit hessian to be calculated. The calculation is considered converged if all the residual forces on the structure fall below a certain threshold. If this is not achieved before the number of conjugate directions have been explored, a QST maximum search is performed using the reactant, product and latest CG geometry. A new CG refinement cycle is started following the QST maximum search. This is continued until the required convergence is attained. A frequency analysis is required until convergence is attained. A frequency analysis on the required converged structure should yield exactly one negative Eigen mode, corresponding to the direction in which the system would evolve away from the saddle point.  In this study we used DMol3, a unique density functional theory (DFT) quantum mechanical code that allows users to study problems in chemical (i.e. study of catalyst) and pharmaceutical industry as well as in material science, with high accuracy and reliability.  38  DMol3 can be employed to find transition states using the linear and quadratic synchronous transit (LST/QST) algorithm, transition structure optimization from starting and end structure, with subsequent conjugate gradient method. It also contains powerful transition state confirmation method, Nudge Elastic Band (NEB), which verifies the transition state obtained by the LST/QST technique [75-77].  1.17 Outline of the dissertation  This thesis is arranged in the following order, described chapter-wise below.  Chapter 1: Provides an introduction to the subject area and describes heterogeneous catalysis and computational chemistry modeling of heterogeneous catalytic systems for higher alcohol synthesis from syngas. A brief review of syngas conversion to higher alcohols and the application of computational chemistry in heterogeneous catalysis are described here as well.  Chapters 2-6 are written in the journal style. Each chapter is written in such a way that it can be sent for publication with little or no further editing. Each journal chapter has its own introduction, results and discussion, followed by references. This means that there is some duplication across the chapters in the subsections that focus on the introduction and experimental methods used.  Chapter 2: Preliminary results of syngas conversion to hydrocarbon and liquid oxygenates on 10 wt % MoP catalyst promoted with 1 and 5 wt % K, supported on SiO2, are reported in this  39  chapter. Results show that alkali promoted MoP produces liquid oxygenates selectively compared to hydrocarbons at 275 oC and 8.3 MPa and syngas with a H2:CO =1. The promoted MoP is identified as a potential catalyst.  Chapter 3: Reports on the molecular modeling of syngas conversion over MoP. The building of the cluster model of the MoP catalyst is described this chapter. Electronic properties of the Mo6P3 cluster and the potential energy surface for syngas conversion to methane and methanol over the Mo6P3 cluster are investigated in this chapter.  Chapter 4: In this chapter, the computational chemistry model of the Mo6P3 cluster is extended to a Mo6P3-Si3O9 and a K-Mo6P3-Si3O9 cluster, to investigate the electronic effects of the SiO2 support and the K promoter on the C-O bond breaking and methanol formation step of syngas conversion to methane and methanol. The activation energy of methanol formation is greatly reduced on the K doped cluster model, suggesting that K will be an effective promoter for syngas conversion to higher alcohols.  Chapter 5: A systematic study of the MoP catalyst for syngas conversion to higher oxygenates is reported here. Findings of the investigation of catalysts with 5, 10 and 15 wt % of MoP promoted with 0, 1 and 5 wt% K on SiO2 have been placed in this chapter. The 10 wt% MoP with 5wt% K showed the highest selectivity towards C2+ oxygenates, i.e. ethanol, acetaldehyde and acetone compared to the other catalysts.  40  Chapter 6 : Comparison of performance of the 5 wt % K 10 wt% MoP/SiO2 catalyst with that of a 1 wt % Rh promoted K-MoP/SiO2 catalyst for syngas conversion to higher oxygenates is described in this chapter. An increase in CO conversion and stability was observed for the CO hydrogenation reaction. A power law kinetic model had also been developed to describe the syngas conversion over the stable Rh-K-MoP/SiO2 catalyst.  Chapter 7 : Summarizes the conclusions drawn in chapters 2 – 6 and offers recommendations for future work.  41  1.18 References [1]  Velu S., Santosh K. 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The production of CH3OH using Cu/ZnO catalysts is practiced commercially [1], as is the production of gasoline and diesel fuels via the Fischer-Tropsch synthesis using Fe or Co catalysts [2, 3]. Currently, there is renewed interest in the selective conversion of synthesis gas to C2+ oxygenates, especially ethanol, for use as a fuel or fuel additive [4, 5]. Previous studies have shown that on alkali promoted Cu/ZnO catalysts, C2+ oxygenates are produced by an aldol condensation mechanism that results in mostly isobutanol and a low selectivity to ethanol [1]. Rh catalysts, promoted with Mn or Li, have high selectivity to ethanol (45 C atom %) [6] but the selectivity to methane is also high (> 40 C atom %). Several Mo compounds have also been investigated for synthesis gas conversion. MoS2 [7, 8], Mo2O3 [9] and Mo2C [10, 11] show high selectivity towards liquid oxygenates, especially ethanol when doped with alkali earth metals. However, in most of these cases the selectivity to hydrocarbons is high (> 20 C atom %).  Recently, MoP supported on metal oxides (Al2O3, SiO2) has been investigated as an alternative to MoS2 catalysts for hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) reactions [12, 13]. It has been suggested that metal phosphides may also have good activity in other hydrogenation reactions, such as synthesis gas conversion to hydrocarbons and alcohols [14], but to our knowledge, there are no reports on the use of MoP as a catalyst for synthesis gas conversion to alcohols or hydrocarbons.  In the present study, the  50  conversion of synthesis gas to oxygenates on MoP supported on SiO2 and doped with K is reported.  2.2  Experimental  The silica supported MoP catalysts were prepared by temperature-programmed reduction (TPR) following the procedure established by Phillips et al. [16] for MoP-SiO2 catalysts. For example, to prepare the 10 wt. % MoP-SiO2 catalyst, stoichiometric amounts (Mo/P = 1) of ammonium heptamolybdate (1.39 grams of (NH4)6Mo7O24·4H2O, BDH Chemicals, 99 %) and diammonium hydrogen phosphate (1.04 grams of (NH4)2HPO4, Sigma-Aldrich, 99 %) were dissolved in 15.7 ml of de-ionized water and impregnated drop-wise onto 10 grams of the SiO2 support (Sigma-Aldrich, Grade 62, 60-200 mesh, BET area = 330 m2/g, pore volume = 1.2 cm3/g) with continuous stirring. The impregnated support was held at room temperature for 12 h before being dried at 373 K for 12 h and calcined at 773 K for 5 h. The calcined catalyst precursor was subjected to TPR in a H2 (Praxair, 99.99 %) flow of 120 cm3(STP).min-1.g cat.-1, at a temperature ramp of 1 K/min to a final temperature of 923 K. The final temperature was held for 2 h. After reduction, the catalyst was cooled to room temperature in He and prior to removal from the reactor, the catalyst was passivated in 2 vol. % O2 in He for 2 h at room temperature. Preparation of the 1 wt. % and 5 wt. % K promoted catalysts was achieved by first impregnating 10 grams of the SiO2 support with a solution of potassium nitrate (KNO3, BDH Chemicals, 99.97 %) containing the required amount of KNO3 (0.35 and 1.77 grams, respectively) dissolved in 12 ml of de-ionized water for incipient wetness impregnation. After aging at room temperature for 12 h, the impregnated  51  SiO2 was dried at 373 K for 12 h followed by calcination at 773 K for 5 h. Subsequently, the K-SiO2 support was impreganted with (NH4)6Mo7O24·4H2O and (NH4)2HPO4, dried, calcined and reduced as before.  Single point BET surface areas were measured using a Micromeritics FlowSorbII 2300 analyser. About 0.1 g of the catalyst was degassed at 473 K for 2 h and the measurement was made using 30 % N2 and 70 % He. EDX analysis was performed using a Hitachi S-3000N electron microscope operated with a 20 kV electron beam acceleration voltage. The average composition from at least 10 points was determined for each catalyst sample.  X-ray  Diffraction (XRD) patterns of the prepared catalysts were obtained with a Rigaku Multiflex diffractometer using Cu Kα radiation (λ=1.5406 Å), a scan range of 2θ from 20o to 80o with a step size of 0.04o. A Leybold Max200 X-ray photoelectron spectrometer with an Al Kα photon source was used for the XPS analysis. After reduction and reaction the catalyst was cooled to room temperature in He and prior to removal from the reactor, the catalyst was passivated in 2 vol. % O2 in He for 2 h at room temperature. Exposure of the samples to ambient atmosphere was minimized by transferring the samples either in vacuum or under N2. All XPS spectra were corrected to the C1s peak at 285.0 eV.  Catalyst activities were measured in a laboratory fixed-bed microreactor (o.d. = 9.53 mm and i.d. = 6.35 mm, copper lined stainless steel tube). For all experiments, synthesis gas (H2:CO = 1) was reacted at 548 K, a pressure of 8.27 MPa and a GHSV = 3960 h-1. A high temperature back pressure regulator was used to control the reactor pressure. The reaction products were analyzed using an in-line gas chromatograph (GC). Light gases (CO, CO2 and  52  C1-C4 hydrocarbons) were separated using a 5 m temperature-programmed Porapak Q 80/100 packed column and quantified with a thermal conductivity detector. The alcohols, aldehydes, ketones, carboxylic acids and C5+ hydrocarbons were separated using a 30 m temperatureprogrammed ECTM-wax capillary column (i.d. = 0.53 mm and film thickness 1.20 µm) and quantified using a flame ionization detector. GC/MS analysis was also completed periodically to confirm the identity of the reactor products. All the catalysts were evaluated for a period of at least 50 h of continuous operation and selected experiments were repeated. Analysis of several repeat experiments showed the conversion and selectivity data to be within ±10 % of the reported values.  2.3  Results and discussion  Table 2.1 reports catalyst characterization data for the 10 wt. % MoP-SiO2 and the K promoted MoP-SiO2 catalysts. The BET areas of the reduced MoP catalysts were significantly below that of the corresponding SiO2 (330 m2/g), 1 % K-SiO2 (310 m2/g) or 5 % K-SiO2 (264 m2/g) supports, and the decrease was most significant for the 5% K-SiO2 support. Identification of an MoP phase on silica supported catalysts is difficult at loadings below 15 wt. % MoP [16] and XRD analysis of the 10 wt. % MoP-SiO2 catalyst had no features other than a broad peak at low angles due to SiO2 (see Figure 2.1). However, a 15 wt. % MoP-SiO2 catalyst prepared by the same method as the 10 wt. % MoP-SiO2 showed characteristic peaks of MoP, as shown in Figure 2.1. Results from EDX suggest a bulk catalyst composition that was slightly enriched in P, whereas the XPS data suggest a Mo enriched surface. XPS narrow scan analysis of the passivated 5 wt. % K-10 wt. % MoP-SiO2  53  is shown in Figure 2.2, and a summary of the analysis of both the 10 wt. % MoP-SiO2 and the 5 wt. % K-10wt. % MoP-SiO2 is provided in Table 2.2. The Mo3d spectra of Figure 2.2 (a,c) were de-convoluted using spin orbit splitting of 3.2 eV and three distinct Mo3d5/2 binding energies (BEs). The low BE peak (227.3 – 228.2 eV) was assigned to MoP [15, 16] whereas the higher BEs correspond to Mo+5 and Mo+6 species that result from the passivation of the catalyst [16]. The P2p spectra of Figure 2.2 (b,d) were de-convoluted into two peaks with BE 132.7 – 134.2 eV assigned to phosphate species, and BE 126.3 – 127.2 eV assigned to phosphide species [16]. As expected, the BE of both Mo and P were shifted to lower values when K was present in the catalysts, due to the electron donation associated with this basic promoter. The XPS data confirm the presence of MoP and a strong interaction between the MoP and the K promoter for these catalysts. The fact that no XRD peaks were observed at a loading of 10 wt. % suggests that the MoP is well dispersed on the SiO2, and the XPS data showing the low surface Mo/Si atom ratio (< 0.05 in all cases, Table 2.1), support this assertion.  The conversion of CO with time-on-stream is shown in Figure 2.3 for the 10 wt. % MoPSiO2 catalyst and the same catalyst doped with 1 wt. % and 5 wt. % K. Initially, high conversions were observed for all three catalysts but the activity decreased significantly in the first 20 h of operation. The rate of deactivation slowed significantly after about 20 h time-on-stream.  The XPS data show that the catalyst surface composition remained  relatively P rich after 50 h reaction (Table 2.1). The increased C/Si ratio of the catalysts after reaction and the corresponding decrease in surface area, especially for the K promoted  54  catalysts, suggest that carbon deposition was the likely cause of the decline in CO conversion.  The catalyst activities and selectivities, averaged over a period of up to 50 h after the initial 20 h deactivation, are reported in Table 2.3, with the C atom % selectivities reported on a CO2-free basis. The 10 wt. % MoP-SiO2 catalyst had an activity of 1.81x10-3 mol CO. g cat-1. h-1 and a oxygenate space-time-yield (STY) of 16.2 g.kgcat-1.h-1 at 548 K. A high selectivity to hydrocarbons, with a 35 C atom % selectivity toward CH4, was also observed. The major oxygenated products were acetaldehyde, acetone and ethanol, with a methanol selectivity of 0.6 % and an ethanol selectivity of 4.0 %. The high selectivity to methane rather than methanol over MoP was predicted previously [17].  With the addition of K to the MoP-SiO2 catalyst, a significant change in activity and selectivity was observed. With 1 wt. % K and 5 wt. % K added to the 10 wt. % MoP-SiO2, the activity increased to 4.68x10-3 mol CO.g cat-1.h-1 and 6.87x10-3 mol CO.g cat-1.h-1, respectively, with a corresponding increase in oxygenate STY to 45.8 g.kg cat-1.h-1 and 89.1 g.kgcat-1.h-1, respectively at 548 K. The selectivity to ethanol and acetone also increased significantly compared to the 10 wt. % MoP-SiO2 catalyst, whereas the selectivity to hydrocarbons, especially methane, and the selectivity to acetaldehyde decreased, as shown by the data of Table 2.3. A very small amount of methanol was found in the product from all the MoP catalysts tested. The low methanol selectivity compared to that of C2 oxygenates (acetaldehyde and ethanol) is unique to the MoP catalyst and has not been reported previously for other Mo-based catalysts (see Table 2.3). Mo2C [11] and MoS2 [8] catalysts  55  have high methanol and ethanol selectivity within the alcohol product distribution. The highest ethanol selectivity has been reported on Rh-based catalysts that also show high selectivity to acetaldehyde at low CO conversions, suggesting that the acetaldehyde is a precursor to ethanol [19]. From the results of the present study, the selectivity to acetaldehyde and acetone suggest that the MoP-SiO2 and K-promoted MoP-SiO2 do not have sufficient hydrogenation capability to reduce the acetaldehyde to ethanol or the acetone to isopropyl alcohol.  CO2 was produced in significant amounts over all MoP catalysts reported herein. Selectivities to CO2 were 24.8, 36.7, 36.5 C atom % for the MoP-SiO2, the 1 wt. % K-MoPSiO2 and the 5 wt. % K-MoP-SiO2 catalysts, respectively. Mo-based catalysts are known for their high water-gas shift activity [7, 11], thus promoting CO2 formation from synthesis gas.  2.4  Conclusions  Methane dominated the products of synthesis gas conversion when 10 % MoP-SiO2 was used as catalyst, but a high selectivity (79 C atom %) to liquid oxygenates was obtained by doping the catalyst with K. The major oxygenated products were acetaldehyde, acetone and ethanol and significantly, a very low selectivity to methanol and methane was observed.  56  2.5  Acknowledgements  Financial support from the Natural Science and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.  57  Table 2.1:  Properties of MoP catalysts supported on SiO2 before and after reaction in synthesis gas  EDX Analysis  BET  XPS analysis  Surface Area  Mo:P  C:Si  Mo:Si  P:Si  m2/g  atom ratio  atom ratio  atom ratio  atom ratio  Catalyst  (i)  (ii)  (i)  (ii)  (i)  (ii)  (i)  (ii)  (i)  (ii)  10% MoP-SiO2  263  181  0.71  0.58  0  0.21  0.027  0.020  0.024  0.025  1%K-10 %MoP-SiO2  235  60  0.71  0.71  0  0.33  -  -  -  -  5%K-10% MoP-SiO2  64  6  0.73  0.68  0  0.63  0.018  0.050  0.014  0.062  (i)  – reduced catalyst before reaction  (ii)  – after 50 h reaction at 548 K, 8.2 MPa,CO:H2 = 1 and GHSV = 3960 h-1.  58  Table 2.2:  XPS peak analysis of MoP catalysts supported on SiO2  Catalyst  10%MoP-SiO2  5%K-10%MoP-SiO2  Mo 3d5/2 BE (eV)  P 2p BE (eV)  (i)  (ii)  (i)  (ii)  228.2  228.1  127.2  126.3  230.4  230.7  134.2  133.6  233.0  233.6  227.3  228.0  126.4  127.2  229.8  230.3  132.7  133.0  233.0  232.5  (i) – reduced catalyst before reaction (ii) – after 50 h reaction at 548 K, 8.2 MPa,CO:H2 = 1 and GHSV = 3960 h-1.  59  Table 2.3:  Results of synthesis gas conversion on MoP catalysts compared to literature data  XCO  Selectivitye (C atom %)  SCO2  Catalyst  Oxygenate STY  Ref.  ∑C2oxy  C+3 oxy  (g.kg cat-1.h-1)  4.03  29.6  9.6  16.2  2.2  10.5  34.7  11.9  45.8  13.5  0.3  17.2  33.8  15.4  89.1  NA  NA  13.5  23.1  †  23.1  21.6  NA  [8]  NA  NA  NA  11.3  13.9  †  13.9  24.0  134.4  [11]  NA  NA  NA  1.9  44.5  †  44.5  NA  NA  [6]  (C atom %)  HC  CH4  AcH  Acetone Methanol Ethanol  10%MoP-SiO2 a  2.1  24.8  56.4  35.2  24.5  4.3  0.6  1%K-10%MoP-SiO2 a  4.7  36.7  41.0  22.1  22.5  10.3  5%K-10%MoP-SiO2 a  6.9  36.5  21.1  9.0  14.3  K2CO3-CoMoS2/Clayb  31.9  NA  36.0  NA  K-Co-βMo2Cc  36.7  NA  61.4  6%Rh-1.5%Mn/SiO2 d  40.5  3.4  48.5  This work  Experimental conditions: a : Pressure = 8.2 MPa, temperature = 548 K, CO:H2 = 1 and GHSV = 3960 h-1. b : Pressure = 13.6 MPa, temperature = 593 K, CO:H2 = 1.1 and GHSV = 4000 h-1. c : Pressure = 7.9 MPa, temperature = 573 K, CO:H2 = 1 and GHSV = 2000 h-1. d : Pressure = 53.3 MPa, temperature = 573 K, CO:H2 = 2 and GHSV = 3750 h-1 in a micro channel reactor. e : C atom selectivity on a CO2 free basis † = Only the value of ethanol is reported as in the literature. SCO2 = Selectivity to CO2; HC = all hydrocarbons; AcH = Acetaldehyde; ΣC2 oxy = Sum of acetaldehyde, ethanol and acetic acid; C3+oxy = Propanol, Butanol, Acetic acid, Propionic acid, Methyl acetate, Ethyl acetate; NA = data not available; STY = space time yield.  60  Intensity, a.u.  1%K/10%MoP/SiO2  15%MoP/SiO2  Bulk MoP 20  30  40  50  60  2 THETA  Figure 2.1:  X-ray diffractogram of 1 % K-10 % MoP-SiO2 catalyst compared to bulk MoP and 15 wt. % MoP-SiO2.  61  28000  18000  Intensity, au  26000 25000 24000  17500 Intensity, au  (a) Fresh 10%MoP5%K Mo3d peaks  27000  23000  16500  (b) Fresh 10%MoP5%K P2p peaks  16000  22000 21000  17000  15500 240 238 236 234 232 230 228 226 224  138  136  134  B.E. (eV)  7600  Intensity, au  7200 7000 6800 6600 6400 6200  128  126  (d) Spent 10%MoP5%K P2p peaks  4600 4400 4200 4000  6000 5800 240 238 236 234 232 230 228 226 224  3800 138  136  B.E.(eV)  Figure 2.2:  130  4800  Intensity, au  (c) Spent 10%MoP5%K Mo3d peaks  7400  132  B.E. (eV)  XPS analysis of 5%K-10% MoP-SiO2 catalyst (a) Mo3d – fresh (b) P2p –fresh (d) P2p – used (after reaction).  134  132  130  128  126  B.E. (eV)  (c) Mo3d – used (after reaction)  62  0.2 0.18 0.16  Fractional CO conversion  0.14 10% MoP 5% K SiO2  0.12 0.1  10% MoP 1% K SiO2  0.08 0.06  10% MoP SiO2  0.04 0.02 0 0  10  20  30  40  50  Time [hr]  Figure 2.3:  CO conversion with time-on-stream over various MoP catalysts. Reaction conditions: pressure = 8.2 MPa, temperature = 548 K, CO:H2 = 1 and GHSV=3960 h-1.  63  2.6  References  [1]  Herman R. G., Advances in catalytic synthesis and utilization of higher alcohols, Catalysis Today, 2000, 55(3), 233-45.  [2]  Anderson R. B., The Fischer-Tropsh synthesis, Academic Press, New York, 1984.  [3]  Iglesia E., Design, synthesis, and use of cobalt-based Fischer-Tropsch synthesis catalysts, Applied Catalysis A: General, 1997, 161(1-2), 59-78.  [4]  Spivey J. J., Egbebi A., Heterogeneous catalytic synthesis of ethanol from biomass derived syngas, Chemical Society Review, 2007, (36), 1514-28.  [5]  Velu S., Santosh K. G., A Review of Recent Literature to Search for an Efficient Catalytic Process for the Conversion of Syngas to Ethano,. Energy Fuels, 2008, 22(2), 841-39.  [6]  Hu J., Wang Y., Cao C., Elliott D. C., Stevens D. J., White J. F., Conversion of biomass-derived syngas to alcohols and C2 oxygenates using supported Rh catalysts in a microchannel reactor, Catalysis Today, 2007, 120(1), 90-5.  [7]  Li D., Yang C., Qi H., Zhang H., Li W., Sun Y., et al., Higher alcohol synthesis over a La promoted Ni/K2CO3/MoS2 catalyst, Catalysis Communication, 2004, 5(10), 6059.  [8]  Iranmahboob J., Toghiani H., Hill D. O., Dispersion of alkali on the surface of CoMoS2/clay catalyst: a comparison of K and Cs as a promoter for synthesis of alcohol, Applied Catalysis A: General, 2003, 247(2), 207-18.  [9]  Bian G., Fan L., Fu Y., Fujimoto K., High temperature calcined K–MoO3/γ-Al2O3 catalysts for mixed alcohols synthesis from syngas: Effects of Mo loadings, Applied Catalysis A: General, 1998, 170(2), 255-68.  [10]  Xiang M., Li D., Xiao H., Zhang J., Li W., Zhong B., et al., K/Ni/β-Mo2C: A highly active and selective catalyst for higher alcohols synthesis from CO hydrogenation, Catalysis Today, 2008, 131(1-4), 489-95.  [11]  Xiang M., Li D., Li W., Zhong B., Sun Y., Potassium and nickel doped β-Mo2C catalysts for mixed alcohols synthesis via syngas, Catalysis Communications, 2007, 8(3), 513-8.  [12]  Zuzaniuk V., Prins R., Synthesis and characterization of silica-supported transitionmetal phosphides as HDN catalysts, Journal of Catalysis, 2003, 219(1), 85-96. 64  [13]  Clark P.A., Oyama S.T., Alumina-supported molybdenum phosphide hydroprocessing catalysts, Journal of Catalysis, 2003, 218(1), 78-87.  [14]  Oyama S.T., Novel catalysts for advanced hydroprocessing: transition metal phosphides, Journal of Catalysis, 2003, 216(1-2), 343-52.  [15]  Abu I. I., Smith K. J., HDN and HDS of model compounds and light gas oil derived from Athabasca bitumen using supported metal phosphide catalysts, Applied Catalysis A: General, 2007, 328(1), 58-67.  [16]  Phillips D. C., Sawhill S. J., Self R., Bussell M. E., Synthesis, characterization, and hydrodesulfurization properties of silica-supported molybdenum phosphide cCatalysts, Journal of Catalysis, 2002, 207(2), 266-73.  [17]  Zaman S. F., Smith K. J., A study of synthesis gas conversion to methane and methanol over a Mo6P3 cluster using density functional theory, Molecular Simulation. 2008, 34(10),1073-84.  [18]  Iranmahboob J., Hill D. O., Toghiani H., K2CO3/Co-MoS2/clay catalyst for synthesis of alcohol: influence of potassium and cobalt, Applied Catalysis A: General 2002, 231(1-2), 99-108.  [19]  Egbebi A., Spivey J. J., Effect of H2/CO ratio and temperature on methane selectivity in the synthesis of ethanol on Rh-based catalysts, Catalysis Communication, 2008, 9(14), 2308-11.  65  Chapter 3  A study of synthesis gas conversion to methane and methanol over a Mo6P3 cluster using density functional theory  A version of this chapter has been published. Zaman S. F., Smith K. J. (2008) A study of synthesis gas conversion to methane and methanol over a Mo6P3 cluster using density functional theory. Molecular Simulation, 34, pp. 1073-1084.  66  3.1  Introduction  The conversion of synthesis gas (CO + H2) to alcohols and hydrocarbons using heterogeneous catalysts is well known. The production of CH3OH using Cu/ZnO catalysts is practiced commercially [1], as is the production of gasoline and diesel fuels via the FischerTropsch synthesis using Fe or Co catalysts [2, 3]. The selective conversion of synthesis gas to liquid fuels provides a route to renewable fuels that is almost CO2 neutral if the synthesis gas is produced from biomass. Our interest is in the selective conversion of synthesis gas to ethanol for use as a fuel or fuel additive. Several catalysts, based on metals such as Cu, Co, Pd and Fe, have been investigated for the higher alcohol synthesis [4] but few reports on the synthesis of ethanol from synthesis gas are available. Rhodium-based catalysts are able to produce oxygenates from synthesis gas [4,5]. The addition of appropriate promoters such as Mn enhances the rate of formation of these oxygenates, especially in the case of ethanol [510]. Mo-based catalysts also have high selectivity towards higher alcohols when Mo is doped with alkali metals [11]. Mo2O3 has also been used for the syngas conversion reaction [11], although high ethanol selectivity was not achieved. The highest selectivity for ethanol has been reported on MoS2 catalysts [12]. Interestingly, MoP supported on metal oxides (Al2O3, SiO2), has been investigated as an alternative to MoS2 catalysts for hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) reactions [14, 15] and although there are no reports on the use of MoP for synthesis gas conversion to alcohols or hydrocarbons, previous researchers have suggested that metal phosphides may have good activity in other hydrogenation reactions, such as synthesis gas conversion to hydrocarbons and alcohols [16]. The use of computational chemistry in heterogeneous catalyst research and development has increased recently because of improved computational power and accuracy. Density  67  functional theory (DFT) can be employed to calculate the formation energy of molecules and solids with high accuracy [17]. Information related to the surface reaction, such as heat of reaction, the reaction energy barrier and transition state structure, can also be determined. Computational chemistry can be used as a tool for catalyst design by calculating the catalyst’s suitability for a particular reaction, without experimentation. Thus, a computational approach towards screening potential catalysts for a particular reaction is available and this principle has been reported in the literature [18]. Kubo et al. [17] used DFT to identify new catalyst formulations for methanol and Fischer-Tropsch synthesis based on the adsorption and formation energies of surface stable species on potential catalysts. Greeley and Mavrikakis [19] investigated the competitive methanol decomposition pathway on Pt(111) considering all combinations of stable surface species. Alcala et al. [20] used DFT to generate the reaction energy diagram for ethanol decomposition on Pt(111). Similarly, a kinetic model of methanol decomposition on Pt(111) using DFT has been investigated by Gokhale et al. [21] and Kandoi et al. [22], who also reported the potential energy surface for this reaction.  As a first step in assessing MoP as a catalyst for synthesis gas conversion, especially to ethanol, we report herein on the reaction pathway for CH3OH and CH4 synthesis from CO and H2 over an Mo6P3 cluster, determining the potential energy surface (PES) of the reactions. Due to limited experimental evidence of stable surface species over MoP, we investigated several likely stable surface species in each step of the reaction network and used the results of these calculations to determine the PES.  68  3.2  Methods  3.2.1  Calculation procedure  The DMol3 module of Material Studio (version 4.0) from Accelrys Inc. was used to complete the DFT calculations [23]. Accordingly, the electronic wave functions are expanded in numerical atomic basis sets defined on an atomic-centered spherical-polar mesh. The doublenumerical plus d-function (DND) all electron basis set was used for all the calculations. The DND basis set includes one numerical function for each occupied atomic orbital and a second set of functions for valence atomic orbitals, plus a polarization d function on all atoms. The Becke exchange [24] plus Perdew-Wang approximation [25] non-local functional (GGAPW91) was used in all the calculations. Each basis function was restricted to a cutoff radius of 4.5 Å, allowing for efficient calculations without loss of accuracy. The Kohn–Sham equations [26] were solved by a self-consistent field (SCF) procedure. The techniques of direct inversion in an iterative subspace (DIIS) [27] with a size value of 6 and thermal smearing of 0.005 Ha [28] were applied to accelerate convergence. The optimization convergence thresholds for energy change, maximum force, and maximum displacement between the optimization cycles were 0.00002 Ha, 0.004 Ha/Å, and 0.005 Å, respectively. The k-point set of (1×1×1) was used for all calculations. The activation energy between two surface species was identified by complete linear synchronous transit (LST) and quadratic synchronous transit (QST) search methods [29, 30], followed by transition state confirmation through the nudge elastic band (NEB) method [31]. Spin polarization and symmetry were imposed in all the calculations.  69  3.2.2  Modeling approach  The Mo6P3 cluster model and the reactant and product species were created using the Material Studio Visualizer. The Cartesian positions of the atoms of the Mo6P3 cluster were fixed in a vacuum after performing geometry optimization. The reactants and products were placed on the cluster in several different configurations, based on probable surface structures reported in the literature for CH4 and CH3OH synthesis. Geometric optimization of each structure was then done with the atoms of the Mo6P3 cluster fixed and no constraints placed on the reactants and products. The DFT simulation generates a field around the atoms placed in the vacuum to perform the calculations. For the DMol3 electrostatic potential calculation the xyz dimensions of the field were 10x12x12 Å. For the DMol3 LUMO calculation the xyz dimensions of the field were 9.8x12.14x11.8 Å. Reaction pathway modeling was approached by calculating the adsorption energies of all probable surface species. The adsorption energy was calculated by subtracting the energies of the gas phase species and the cluster from the energy of the adsorbed species according to the equation: Ead = E(adsorbate/cluster) – (Eadsorbate + Ecluster). With this definition, a negative Ead corresponds to a stable surface species. The activation energy was calculated by using the transition state search (TS search) tool in DMol3, applied to the reactant, a stable surface species plus an adsorbed H atom (Had) on the Mo6P3 cluster, and the product.  70  3.3  Results and discussion  3.3.1  An Mo6P3 cluster model of MoP  MoP has a hexagonal crystal structure, belonging to the P6 m 2 space group with lattice parameters a = 3.22 Å and c = 3.19 Å [16, 33]. In the present study, an MoP crystal was built using the above information from which the (100) face was cleaved and a 4 atom –layer was taken as the cluster model, after geometric optimization. Note that the cluster building unit resembles the (100) crystal face of MoP, as shown in Figure 3.1. The distances and angles between atoms for the cluster are tabulated in Table 3.1, and these values compared favorably (within ±95%) to those of the MoP (100) slab. Mulliken population analysis showed a positive charge density (0.048e) on the Mo atoms and a negative charge density (0.128e) on the P atoms of the cluster. Liu and Rodriguez [33] reported Mulliken charge densities of the MoP (001) crystal plane as 0.045e for Mo and –0.077e for P. Although the electron charge on Mo is similar for the cluster and the (001) plane of MoP, the P atoms have higher electronegativity in the cluster compared to the MoP (001) plane. The difference is due to the metal rich stoichiometry of the Mo6P3 cluster.  3.3.2  CO adsorption on the Mo6P3 cluster  The adsorption energy of CO on the Mo6P3 cluster was calculated as –50.73 kcal/mol, in very good agreement with values of –50.5 kcal/mol [32] and -45.66 kcal/mol [33] reported for CO adsorption on the (001) plane of MoP. The CO adsorption energies on Cu(111), Pd(111), Pt(111) and Ni(111), as reported in the literature, are summarized in Table 3.2. These data  71  show that CO is adsorbed more strongly on MoP than on any of these metals. For CO, the highest energy occupied molecular orbital (HOMO) is 5σ, a lone pair orbital, localized on the C atom. The lowest unoccupied molecular orbital (LUMO) is the 2π* orbital, a C-O π antibonding orbital also localized on the C atom. Hence CO adsorbs on the Mo atom through the C atom. The LUMO energy of CO adsorbed on Mo6P3 is –75.18kcal/mol, the HOMO energy is –76.56 kcal/mol and the Fermi level has energy –76.33 kcal/mol. The HOMO energy is lower than the Fermi energy level and the LUMO is above the Fermi energy level, typical for surface chemisorbed species, and hence CO is strongly adsorbed on the Mo6P3 cluster. The density of states (DOS) of the Mo6P3 cluster compared to the DOS of the CO-Mo6P3 system shows that all the s (Figure 3.2.a), p (Figure 3.2.b), and d (Figure 3.2.c) orbitals are altered. The d-orbital energy distribution, being the most affected, implies that the d-orbital of Mo is the main contributor to the adsorption process. 3.3.3  Determining the potential energy surface for CH4 formation  The search for the potential energy surface of CH4 formation from H2 + CO on the Mo6P3 cluster was accomplished by evaluating the adsorption energy of several possible surface intermediates and calculating the activation energy between two successive species. The reaction pathway for CH4 (and CH3OH) formation is depicted in Figure 3.3, where the surface reaction propagates by addition of Had to each stable adsorbed surface species. We have considered all combinations of Had attachment with the C and O atoms of CO. Bond angle, bond length and adsorption energies of adsorbed surface species and transition state structures, heats of reaction and heats of adsorption are reported in Tables 3.3 – 3.5. The structure of the reactants, products and transition states are shown in Figures 3.4 – 3.6.  72  3.3.3.1 Formyl (CHO) and hydroxymethylidyne (COH)  The addition of Had to the C of COad on Mo, yields CHOad species with the C and O attached to two nearby Mo atoms in a bridged structure (Figure 3.4-I). The adsorption energy of this species was calculated as -94.32 kcal/mol (Table 3.3). The addition of Had to the C atom of adsorbed CO species decreases the Mo-C bond strength, as indicated by an increase in bond length (1.99 Å) with respect to COad on-top adsorption (1.97 Å). The Mo-O bond length is 2.10 Å. The hydroxymethylidyne (COHad) species is formed by addition of Had to the O atom of adsorbed COad (Figure 3.4-II). The C atom is bound to a Mo atom (on-top adsorption) and the Mo-C bond length decreases to 1.82 Å, indicating a more tightly bound surface species with higher adsorption energy (-111.62 kcal/mol) compared to CHOad. A higher adsorption energy for COHad, compared to CHOad, has also been observed on Cu(111) [19], Pd(111) [35] and Pt(111) [22] surfaces. The C-O bond length for CHOad is 1.31 Å versus 1.34 Å for the COHad species, whereas for COad, it is 1.18 Å (Table 3.3). Increasing the C-O bond length increases the C and O reactivity, as electrons are being accumulated on the atoms rather than being shared, and the Had added to COad also weakens the C-O covalent bond strength. The activation energy associated with CHOad formation from COad + Had is 41.37 kcal/mol, whereas for COHad, a value of 50.00 kcal/mol was obtained (Table 3.5). Formation of the CHOad is thermodynamically more favorable than the formation of COHad, and both reactions are endothermic, with a heat of formation of 10.13 kcal/mol for CHOad species and 49.50 kcal/mol for COHad species. Nunan et al. [36] reported CHOad as a precursor for alcohol production on copper based catalysts. The results presented herein suggest that CHOad is also the energetically favored precursor for CH4 and CH3OH formation on the Mo6P3 cluster.  73  3.3.3.2 Formaldehyde (CH2O) and hydroxymethylene (CHOH)  Addition of Had to the C atom of the formyl species forms CH2Oad (Figure 3.4-IV), with an adsorption energy of –67.80 kcal/mol. The Mo-C bond length is 2.22 Å and the Mo-O bond length is 1.96 Å. Compared to the CHOad species, the Mo-C bond length is increased, whereas the Mo-O bond length is decreased, CH2Oad is tightly bound through the Mo-O and electrons are withdrawn from the substrate by the O atom. The C-O bond length (1.41 Å) increases compared to CHOad (Table 3.3). The molecular orbital of the CH2Oad species weakens the C-O bond strength. The π electron interaction between CH2 (π bonding and antibonding orbitals) and O (π type loan pair electron) gives rise to a new molecular orbital. Since the energies of these interacting orbitals are similar, the new orbital is C-O antibonding and C-H bonding. If an H atom adds to the O atom of adsorbed CHOad species, CHOHad is formed (Figure 3.4-V) with an adsorption energy of -96.63 kcal/mol. The Mo-C bond length (1.95 Å) decreases and the Mo-O bond length (2.33 Å) increases compared to the adsorbed CHOad species. The C-O bond length for CH2Oad species (1.41 Å) is higher than that of CHOad but lower than that of CHOHad (Table 3.3).  The activation energy for CH2Oad formation is 56.24 kcal/mol compared to 69.53 kcal/mol for CHOHad (Table 3.5). Formation of CH2Oad is thermodynamically more favorable; formation of CH2Oad is exothermic (∆Er = -3.25 kcal/mol), whereas formation of CHOHad is endothermic (∆Er = 2.58 kcal/mol). CHOHad can also be formed by the addition of Had to COHad (Figure 3.4-III) with a lower activation energy (13.22 kcal/mol) and formation energy of 2.59 kcal/mol (Table 3.5) compared to Had addition to CHOad. This route is important for the decomposition of CH4 and CH3OH to CO and H2.  74  3.3.3.3 Hydroxymethyl (CH2OH)  CH2OHad species can evolve either by addition of Had to the C atom of CHOHad species or by the addition of Had to the O atom of adsorbed CH2Oad (Figure 3.4.VI and 3.4.VII). The calculated adsorption energy of CH2OHad on the Mo6P3 cluster was –77.02 kcal/mol. The bond lengths are Mo-C 2.22 Å, Mo-O 1.96 Å and C-O 1.41 Å. These lengths are close to those calculated for the CH2Oad species, whereas compared to CHOHad, the Mo-C bond length is increased and the Mo-O and the C-O bond-lengths are decreased. The activation and reaction energies for CH2Oad+Had→CH2OHad are 59.12 kcal/mol and 34.56 kcal/mol, respectively, and for the CHOHad+Had→CH2OHad they are 25.67 kcal/mol and 0.49 kcal/mol, respectively.  3.3.3.4 C-O bond scission and the formation of CH4  Three intermediates are relevant for C-O bond scission: COHad, CHOHad and CH2OHad. Bond scission from COHad is described in a later section that discusses carbon formation on the catalyst surface. Adding Had to CHOHad yields CHad (carbene) species and H2Oad, whereas adding Had to CH2OHad forms CH2.ad (methylene) and H2Oad. These steps are shown in Figure 3.5-VIII and 3.5-IX, respectively. The adsorption energies of CHad+H2Oad and CH2.ad+H2Oad are –173.42 kcal/mol and –145.98 kcal/mol, respectively. The Mo-C bond length is 1.82 Å for CHad species and 1.96 Å for CH2.ad species. CHad species are more strongly adsorbed on the surface than CH2.ad species. With two H atoms attached to the O atom, the octet condition for O, the most stable condition, is satisfied. The H2Oad molecule subsequently desorbs from the catalyst surface. The activation energy for C-O bond scission 75  via the CHOHad route is 42.16 kcal/mol, whereas, via the CH2OHad route it is 27.88 kcal/mol (Table 3.5). Bond breakage results in heat generation with CHOHad+Had→CHad+H2Oad yielding ∆Er = -5.87 kcal/mol and CH2OHad+ Had → CH2.ad + H2Oad yielding –6.19 kcal/mol.  Addition of Had to CHad species yields CH2.ad species (Figure 3.5-X) with an adsorption energy -106.08 kcal/mol. The H2Oad molecule produced by the C-O bond scission is adsorbed on a Mo atom and the total adsorption energy of CH2.ad+H2Oad is -145.98 kcal/mol with an adsorption energy of H2Oad on the cluster of -32.52 kcal/mol. Separate calculations for the CHad, CH2.ad and CH3ad species on the cluster yielded adsorption energies of –116.23 kcal/mol, -106.08 kcal/mol and -80.94 kcal/mol, respectively. The total adsorption energy for CH2.ad+H2Oad is marginally lower than the sum of the energies of the separately adsorbed species in the system, likely due to interaction effects between the adsorbed species. The activation energy for this reaction step is 60.94 kcal/mol with an exothermic reaction energy ∆Er = -5.45 kcal/mol.  Addition of Had to CH2.ad yields adsorbed CH3.ad species. The Mo-C bond length associated with the CH3.ad intermediate increased to 2.16 Å and the adsorption energy decreased to – 66.42 kcal/mol compared to the adsorbed CH2.ad species. The activation energy for the process is 18.67 kcal/mol with an exothermic heat of reaction ∆Er = -6.01 kcal/mol. The reaction step is depicted in Figure 3.5-XI.  Adding another Had to the C atom of CH3.ad species forms CH4. Both the CH4 molecule and the H2Oad molecule are desorbed from the surface. CH4 has a positive adsorption energy  76  (46.35 kcal/mol), indicating that CH4 is not adsorbed on the surface at the simulation temperature (273 K). Consequently, once CH4 is formed it will not engage in further reaction and will emerge as a product. The activation energy of this step is 12.16 kcal/mol. The reaction is endothermic and the reaction energy is 8.7 kcal/mol. Figure 3.5-XII shows this reaction step.  3.3.3.5 Carbon formation on the surface  Addition of Had to the O atom of CO, rather than to the C atom, yields hydroxymethylidyne (COHad) species. COHad has the C atom attached to Mo, (CO on-top adsorption), whereas the O is not bonded to the catalyst surface. The adsorption energy for COHad is –111.62 kcal/mol, making it more stable than CHOad species on the Mo6P3 cluster. COHad proceeds in the reaction by adding another H atom to C, forming hydroxymethylene species. The COHad route is not energetically favored (∆E = 50.00 kcal/mol) compared to the CHOad route. If Had adds to the O atom of COHad, the C-O bond breaks and H2Oad and surface adsorbed carbon are produced. Carbon is strongly bound to the surface between two molybdenum atoms and a phosphorus atom. This carbon atom is very difficult to remove from the surface and will eventually deactivate the catalyst (Figure 3.7).  Based on the above analysis of the reaction intermediates, the PES for CH4 formation is constructed and depicted in Figure 3.8, in which the thermochemical data and activation energies of the elementary reaction steps are also shown. Accordingly, the favorable PES pathway for the formation of CH4 may be summarized as (Had addition of each step is  77  assumed but not shown): COad [CH3.ad + H2Oad]  3.3.4  CHOad  CH2Oad  CH2OHad  [CH2.ad + H2Oad]  [CH4 + H2O].  Determining the potential energy surface for CH3OH formation  Methanol formation occurs via two precursors, CH2OHad and CH2Oad, which are common to CH4 formation as well. Methanol can be generated from the bridge-bonded CH2OHad species by adding Had to the C atom (Figure 3.6-XIII). The Mo-C bond breaks and the C-O bond length is 1.45 Å and the Mo-O bond length is 2.32 Å. The CH3OHad adsorption energy is 33.21 kcal/mol, relatively high compared to adsorption energies on other metals as shown in Table 3.2. CH3OHad is attached to a Mo atom through the O atom. The DOS for the CH3OHMo6P3 system (Figure 3.2) shows that the d-orbital (which belongs to Mo) distribution is not altered to a great extent, suggesting that the d-orbital does not have strong overlap with the O atom. Similar behavior has been observed with other transition metals [39, 40]. The main interaction occurs between the p-orbital and the s-orbital. The p-orbital interaction comes mostly from the P atom of the Mo6P3 cluster and the oxygen atom. Hence the adsorption energy of CH3OHad on the Mo6P3 cluster is higher than other transition metals, i.e. Pt(111), Pd(111), Cu(111), Ni(111), (Table 3.2) that do not have p orbitals available. Most of the transition metals show low adsorption energy of CH3OH due to a small p-orbital contribution to the bond with the O atom. The HOMO energy of CH3OH-Mo6P3 system is –2.48 kcal/mol and the LUMO is –2.246 kcal/mol, whereas the Fermi energy is -2.25 kcal/mol. The high adsorption energy of CH3OHad on the Mo6P3 cluster suggests that it may be available for further reaction to form ethanol and other higher carbon-number products. The activation and  78  formation energies for CH3OHad via the CH2OHad route are 100.91 kcal/mol and 8.45 kcal/mol, respectively.  3.3.4.1 Methoxy (CH3O) and methanol (CH3OH)  Addition of Had to bridge-bonded CH2Oad yields CH3Oad species (Figure 3.6.XIV), with the carbon atom detached from the metal surface. The C-O bond length is 1.41 Å and the Mo-O bond length is 1.92 Å. The CH3Oad adsorption energy is –109.08 kcal/mol and the activation energy of this step is 71.13 kcal/mol. Addition of another Had to the O atom of CH3Oad yields CH3OHad (Figure 3.6-XV) with an activation energy of 71.54 kcal/mol and energy of reaction of 36.65 kcal/mol.  The PES pathway for CH3OHad formation (Figure 3.9) follows the route (Had addition of each step is assumed but not shown) COad  CHOad  CH2Oad  CH2OHad  CH3OHad.  This route has the lowest energy surface species up to CH2OHad. However, the final step has the largest energy barrier, 100.86 kcal/mol, compared to all other reaction steps. Hence, we conclude that adsorbed COad and Had will form hydroxymethyl but the C-O bond will then break, as the energy barrier is too high to form methanol, resulting in the formation of CH2.ad and water species. This pathway explains the higher selectivity to CH4 than CH3OH when synthesis gas is reacted over MoP catalysts [41]. Blocking the CH4 production path would enhance alcohol production and this may be possible by hindering the approach of a H atom towards the O atom to prevent cleavage of the C-O bond and inhibit water formation. Alkali metals like K should promote this kind of reaction since K provides additional electrons to  79  the nearby O atom and hence can hinder the formation of H2O and enhance alcohol production.  Note that the reverse order of the reactions i.e. the decomposition of methanol and methane over MoP catalysts can also be examined from the data presented herein. Formation of H2 and CO from CH3OH follows the decomposition path [CH3OHad CH2Oad + Had [CH4+H2O  CHOad + Had  CH3.ad+H2Oad  CH3Oad +Had  COad + Had] and from CH4 + H2O the path is  CH2.ad+H2Oad  CH2OHad  CHOHad  COHad  COad].  The same CH3OH decomposition path is observed on Pt(111) [19] and Ni(111) [37].  3.3.5  Hydrogen dissociation energy  Both reaction pathways to CH4 and CH3OH(ad) formation show that most of the intermediate reaction steps are endothermic. However, both CH4 and CH3OH(ad) formation from CO + H2 are exothermic. Heat evolution occurs from adsorption and bond dissociation, whereas bond formation and desorption are endothermic. Bond dissociation can occur between the C-O bond (CH4 formation), and the H-H bond. The exothermic nature of the reactions is mainly attributed to the dissociation of the hydrogen molecule, which was not included in the energy calculations reported herein. The simulation was accomplished taking a H atom adsorbed on a Mo atom with a stable surface carbon bearing species. The hydrogen molecule adsorbs on Mo, and dissociates into atoms and adsorbs on two different Mo atoms. The energy released by H-H bond dissociation is –20.56 kcal/mol and the activation energy is 89.34 kcal/mol.  80  3.4  Conclusions  A DFT study of CH4 and CH3OH formation over an Mo6P3 cluster model is described. The Mo6P3 cluster was representative of the (100) face of MoP and had similar adsorption energies to MoP. Hydroxymethyl (CH2OH) is a common intermediate for both CH4 and CH3OH formation. However, the energy barrier for CH3OH formation from CH2OH was significantly higher than for the formation of methylene and water that leads to CH4. Thus the simulation predicts the formation of CH4 rather than CH3OH over MoP.  3.5  Acknowledgements  Financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.  81  Table 3.1:  Comparison between Mo6P3 cluster and MoP (001) slab dimensions after geometric optimization  Slab  Cluster*  Å  Å  Mo(1)-Mo(2)  3.19  3.19  Mo(1)-P(1)  2.45  2.45  Mo(3)-P(1)  2.45  2.45  Mo(3)-P(2)  2.51  2.45  Mo(1)-P(2)  4.18  4.05  deg  deg  θMo(1)-P(1)-Mo(3)  82.18  82.04  θMo(3)-P(2)-Mo(5)  79.74  82.18  θMo(1)-P(3)-Mo(2)  81.39  81.26  θMo(3)-P(2)-Mo(4)  78.85  81.26  Distances:  Angles:  * see Figure 3.1 for atom locations  82  Table 3.2: Adsorption energy of CO and CH3OH on transition metals  CO Adsorption  CH3OH Adsorption  energy  energy  kcal/mol  kcal/mol  Cu(1 1 1)  -16.14  -4.38  [19,38]  Pd(1 1 1)  -33.90  -6.46  [35]  Pt(1 1 1)  -41.97  -7.61  [22]  Ni(1 1 1)  -35.98  -0.46  [37]  Metal  Reference  83  Table 3.3: Properties of surface adsorbed species on Mo6P3 cluster from DFT calculations: angle to the surface, distance between atoms, total energy and adsorption energy of stable surface species relevant to methane and methanol formation from syngas  Species  θ C-Mo-Mo  θ O-Mo-Mo  dC-Mo  dO-Mo  dC-O  E element  Ead  deg  deg  Å  Å  Å  au  kcal/mol  -  78.28  -  1.97  -  1.18  -113.345  -50.73  CHOad  3.4 - I.c  57.68  66.22  1.99  2.10  1.31  -113.857  -94.32  COHad  3.4 - II.c  77.27  -  1.82  -  1.34  -113.782  -111.62  CHOHad  3.4 - III.c  68.15  63.22  1.95  2.33  1.44  -114.403  -96.63  CH2Oad  3.4 - IV.c  59.70  70.43  2.22  1.96  1.41  -114.504  -67.79  CH2OHad  3.4 - VI.c  67.50  67.95  2.22  1.96  1.41  -115.052  -77.02  CH3Oad  3.6 - XIV.c  -  119.32  -  1.92  1.41  -115.047  -109.08  CH3OHad  3.6 - XIII.c  -  110.03  -  2.32  1.45  -115.711  -33.21  CHad+H2Oad  3.5 - VIII.c  97.67  78.86  1.82  2.29  3.02  -38.457  -173.42  CH2.ad+H2Oad  3.5 - IX.c+ X.c  97.60  79.28  1.96  2.30  3.05  -39.130  -145.97  CH3.ad+H2Oad  3.5 - XI.c  123.65  85.80  2.16  2.36  4.26  -39.814  -66.42  CH3.ad+H2Ofree  -  122.60  Free  2.16  2.37  4.21  -39.814  -66.42  3.5 - XII.c  Free  Free  2.65  2.39  -  -40.492  46.35  COad  CH4+H2Ofree  Figure  Energy of free H2O = -76.422778au.; Adsorption energy of hydrogen atom = -0.58213 au. [au = atomic unit]  84  Table 3.4: Properties of surface adsorbed species on Mo6P3 cluster from DFT calculations: angle to the surface, distance between atoms, total energy and adsorption energy of stable surface species relevant to methane and methanol formation from syngas  Species  Figure  θ C-Mo-Mo  θ O-Mo-Mo  dC-Mo  dO-Mo  dC-O  E element  Ead  deg  deg  Å  Å  Å  au  kcal/mol  COad+Had  3.4 - I.a  78.23  -  1.98  -  1.18  -113.345  -62.03  COad+Had  3.4 - II.a  78.89  -  1.99  -  1.18  -113.345  -61.11  CHOad+Had  3.4 - IV.a  52.98  66.41  1.99  2.10  1.30  -113.857  -106.31  CHOad+Had  3.4 - V.a  57.47  66.31  1.99  2.10  1.30  -113.857  -106.31  COHad+Had  3.4 - III.a  78.40  -  1.82  -  1.33  -113.782  -123.61  CHOHad+Had  3.4 - VI.a  67.89  63.57  1.97  2.23  1.44  -114.403  -117.84  CHOHad+Had  3.5 - VIII.a  68.53  63.26  1.94  2.29  1.47  -114.403  -85.09  CH2OHad+Had  3.5 - IX.a  69.17  66.46  2.20  2.28  1.49  -115.052  -54.88  CH2OHad+Had  3.6 - XIII.a  67.70  67.03  2.21  2.23  1.48  -115.052  -86.94  CH2Oad+Had  3.4 - VII.a  58.21  71.71  2.23  1.96  1.41  -114.504  -81.86  CH3Oad+Had  3.6 - XV.a  -  128.83  -  1.92  1.41  -115.047  -120.61  3.5 - X.a  96.02  78.83  1.81  2.27  2.98  -38.457  -192.56  CH2.ad+H2Oad+Had 3.5 - XI.a  96.08  78.89  1.97  2.29  2.97  -39.130  -103.31  CH3.ad+H2Oad+Had 3.5 - XII.a  123.18  -  2.16  2.36  4.23  -39.814  -81.64  CHad+H2Oad+Had  85  Table 3.5: Properties of transition state for reactions shown: structure, angle with the surface, distance between atoms, energy of reaction and activation energy for methane and methanol formation from syngas  θC-Mo-Mo  θO-Mo-Mo  dC-Mo  dO-Mo  dC-O  ∆Er  ∆E  deg  deg  Å  Å  Å  kcal/mol  kcal/mol  Common: (see figure 3.4) COad+Had→CHOad  70.99  -  1.98  -  1.18  10.13  41.37  COad+Had→COHad  82.83  -  1.92  -  1.24  49.50  50.00  CHOad+Had→CHOHad  65.08  62.87  1.98  2.32  1.32  32.95  69.53  COHad+Had→CHOHad  40.40  -  2.07  -  1.36  2.59  13.22  CHOad+Had→CH2Oad  56.09  67.76  2.01  2.11  1.30  -3.25  56.24  CHOHad+Had→CH2OHad  68.23  63.29  1.96  2.23  1.47  0.49  25.67  CH2Oad+Had→CH2OHad  70.21  62.48  2.22  2.15  1.45  34.56  59.12  CHOHad+Had→CHad+H2Oad  96.09  82.61  1.80  1.98  3.16  -5.87  42.16  CHad+Had+H2Oad→CH2.ad+H2Oad  93.83  79.96  1.83  2.23  2.94  -5.45  60.94  CH2OHad+Had→CH2.ad+H2Oad  94.31  76.84  1.80  1.99  2.88  -6.19  27.88  CH2.ad+Had+H2Oad→CH3.ad+H2Oad  110.36  82.63  1.97  2.35  3.62  -6.01  18.67  CH3.ad+Had+H2Oad→CH4.ad+H2Oad  118.95  -  2.11  2.36  4.39  8.70  12.16  63.04  83.21  2.38  2.13  1.33  -6.22  71.13  -  112.98  4.74  2.03  1.42  36.65  71.54  62.62  73.94  2.30  2.28  1.52  8.45  100.91  Reactions  Methane synthesis: (see figure 3.5)  Methanol synthesis: (see figure 3.6) CH2Oad+Had→CH3Oad CH3Oad+Had→CH3OHad CH2OHad+Had→CH3OHad  86  Mo1  Mo2  P3  P1  Slab model Mo5  Mo6  Mo3  Mo4  P2  Mo1  Mo2  P3  P1  Cluster Model Mo5  Mo6  Mo3  Mo4  P2  Figure 3.1:  Comparison between MoP slab (100) face and the Mo6P3 cluster model of the present study.  87  200  Density of States (Electrons/Ha)  150 100  CH3OH on Mo6P3 Cluster  50 0 200-1.0 150 100  -0.8  -0.6  -0.4  -0.2  0.0  0.2  -0.4  -0.2  0.0  0.2  -0.4  -0.2  0.0  0.2  CO on Mo6P3 Cluster  50 0 200-1.0  -0.8  -0.6  150 100  Mo6P3 Cluster  50 0 -1.0  -0.8  -0.6  Energy (Ha)  Figure 3.2 (a). Density of states (s-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster.  88  375 300  Density of states (Electrons/Ha)  225 150  CH3OH on Mo6P3 Cluster  75 0 375  -0.8  -0.6  -0.4  -0.2  0.0  0.2  -0.4  -0.2  0.0  0.2  300 225 150  CO on Mo6P3 Cluster  75 0 375  -0.8  -0.6  300 225 150  Mo6P3 Cluster  75 0 -0.8  -0.6  -0.4  -0.2  0.0  0.2  Energy (Ha)  Figure 3.2(b). Density of states (p-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster.  89  Density of States (Electrons/Ha)  600 500 400 300 200 100 0  CH 3OH on Mo 6P 3 Cluster  -0.5 600 500 400 300 200 100 0 -0.5 600 500 400 300 200 100 0 -0.5  -0.4  -0.3  -0.2  -0.1  0.0  0.1  0.2  -0.1  0.0  0.1  0.2  -0.1  0.0  0.1  0.2  CO on Mo 6P 3 Cluster  -0.4  -0.3  -0.2  Mo 6P 3 Cluster -0.4  -0.3  -0.2  Energy (Ha)  Figure 3.2(c). Density of states (d-orbital) of Mo6P3 cluster and CO and CH3OH adsorbed on Mo6P3 cluster.  90  CHad + H2Oad  COHad  + Had 13.22 kcal/mol  COad  + Had  + Had CHOHad 26 kcal/mol  + Had + Had + Had CH2OHad CH2 ad+ H2Oad CH3 ad+ H2Oad 19 kcal/mol 27 kcal/mol 12 kcal/mol  CH4 free + H2Ofree  CHOad  41 kcal/mol  CH2Oad  + Had 36 kcal/mol  Figure 3.3:  CH3Oad  + Had  CH3OHad  72 kcal/mol  Reaction network and activation energies for syngas conversion to methanol and methane over the Mo6P3 cluster.  91  Reactant (a)  Transition state (b)  Product (c)  I  II  III  IV  V  VI  VII  {Molybdenum [ Figure 3.4 :  ], Phosphorus [  ], Carbon [  ], Oxygen [  ], Hydrogen [  ]}  Methane and methanol formation reaction steps on Mo6P3 cluster.  92  Reactant (a)  Transition state (b)  Product (c)  VIII  IX  X  XI  XII  {Molybdenum [ Figure 3.5 :  ], Phosphorus [  ], Carbon [  ], Oxygen [  ], Hydrogen [  ]}  Methane formation reaction steps on Mo6P3 cluster.  93  Reactant (a)  Transition state (b)  Product (c)  XIII  XIV  XV  {Molybdenum [  Figure 3.6 :  ], Phosphorus [  ], Carbon [  ], Oxygen [  ], Hydrogen [  ]}  Methanol formation reaction steps on Mo6P3 cluster.  94  { Molybdenum [ Figure 3.7:  ], Phosphorus [  ], Carbon [  ], Oxygen [  ], Hydrogen [  ]}  Carbon formation on the Mo6P3 cluster.  95  Figure 3.8:  Kinetic pathway of methane formation over Mo6P3 cluster.  96  Figure 3.9:  Kinetic pathway of methanol formation over Mo6P3 cluster.  97  3.6  References  [1]  Gotti A. and Prins R., Basic metal oxides as cocatalysts for Cu/SiO2 catalysts in the conversion of synthesis gas to methanol, Journal of Catalysis, 1998, 178 (2), 511– 519.  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[31]  Henkelman G. and Jonsson H., Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points, Journal of Chemical Physics, 2000, 113 (22), 9978–85.  [32]  Feng Z., Liang C., Wu W., Wu Z., Santen A. R., Li C., Carbon monoxide adsorption on molybdenum phosphides: Fourier transform infrared spectroscopic and density functional theory studies, Journal of Physical Chemistry B, 2003, 107 (49), 13698–702.  [33]  Liu P. and Rodriguez J. A., Catalytic properties of molybdenum carbide, nitride and phosphide: a theoretical study, Catalysis Letters, 2003, 91 (3-4), 247–52.  [34]  Neurock M., First-principles analysis of the hydrogenationof carbon monoxide over palladium, Topics in Catalysis,1999, 9 (3-4), 135–52.  [35]  Nunan J. G., Bogdan C. E., Klier K., Smith K. J., Young C., Herman R.G., Higher alcohol and oxygenate synthesis over cesium-doped Cu/ZnO catalysts, Journal of Catalysis, 1989, 116, 195–221.  [36]  Remediakis I. N., Abild-Pedersen F., Norskov J. K., DFT study of formaldehyde and methanol synthesis from CO and H2 on Ni(111), Journal of Physical Chemistry B, 2004, 108 (38), 14535–40.  100  [37]  Greeley J., Gokhale A. A., Kreuser J., Dumesic J. A., Topsoe H., Topsoe N. Y., Mavrikakis M., CO vibrational frequencies on methanol synthesis catalysts: a DFT Study, Journal of Catalysis, 2003, 213 (1), 63–72.  [38]  Hoffmann R., A chemical and theoretical way to look at bonding on surfaces, Reviews of Modern Physics, 1988, 60 (3), 601–28.  [39]  Zeroka D. and Hoffmann R., Adsorption of methoxy on Cu(100), Langmuir, 1986, 2 (5), 553–8.  [40]  Zaman S. F. and Smith K. J., Synthesis gas conversion to alcohols on MoP catalysts, Book of abstracts, 19th Canadian Symposium on Catalysis, 2006, p. 32.  101  Chapter 4  A DFT study of the effect of K and SiO2 on syngas conversion to methane and methanol over an Mo6P3 cluster  A version of this chapter has been accepted for publication. Sharif F. Zaman and Kevin J. Smith (2010) A DFT study of the effect of K over MoP-SiO2 cluster for syngas conversion. Molecular Simulation, 36, pp. 118-126. 102  4.1  Introduction  Modern theoretical chemistry can be used to understand chemical reactivity and mechanisms of heterogeneous catalytic reactions [1-4]. Density functional theory (DFT) can be employed to calculate the formation energy of molecules and solids with high accuracy and information related to the surface reaction can also be determined. Computational chemistry can be used as a tool for catalyst design by calculating the catalyst’s suitability for a particular reaction, without experimentation. Thus, a computational approach towards understanding the role of different catalyst components in a particular reaction is available and this principle has been reported in the literature [5,6]. Promoters also play a key role in heterogeneous catalysis, their use being necessary in many successful industrial catalysts. A simple tool for modifying the surface properties of catalytic materials, widely exploited in heterogeneous catalysis, consists of alkali metal doping [7], the alkali metal acting as an electronic promoter. The dopant enhances the catalytic properties of the active phase, due to its ability to modify the chemisorption properties of the catalyst surface and to affect the chemisorptive bond strength of reactants and reaction intermediates. The most pronounced electronic promotion has been found in the case of K, Rb, and Cs. Many of the promotional effects of K are characteristic of the other alkali metals [8].  Researchers have used computational chemistry to investigate the influence of alkali metal (K) on transition metals (Pt, Ru, Rh, Fe) to understand the dissociative adsorption of CO and N2 relevant in the Fischer-Tropsch and ammonia synthesis, respectively [8,9]. Liu and Hu  103  [10] also used DFT to investigate surface structural effects on C-O bond dissociation, and reported that surface kinks facilitate bond scission.  For the methanol synthesis, CO must adsorb non-dissociatively [11-14] on the active site before being hydrogenated to produce the stable formyl (CHO) surface species [15] that leads to the formation of methanol or higher alcohols. Rh based catalysts are known to be effective for syngas conversion to alcohols [16,17] and they give high selectivity to ethanol (44.5 C atom%) when promoted with Mn [18]. Recent research has focused on Mo-based catalysts [i.e. MoS2, Mo2C, Mo2N and MoP], as they have the characteristics of precious metals (Pt, Rh) [19]. Recently Pistonesi et al. [20] reported methanol adsorption and dissociation to methoxy on a Mo2C surface. No reports on the use of DFT to study the effect of alkali promoter on syngas conversion over Mo catalysts are available, although Kotarba et al. [21] have reported on the modification of the surface electronic properties of Mo2C as a function of K loading.  The microkinetic network of syngas (CO+H2) conversion to methane and methanol over an Mo6P3 cluster, used to simulate an MoP catalyst, was reported previously [22]. An adsorbed hydroxymethyl (CH2OHad) species was shown to be a common intermediate for both CH4 and CH3OH formation. In the present paper, cluster models of Mo6P3-Si3O9 and K-Mo6P3Si3O9 were built and used to investigate the hydrogenation of the CH2OHad species to yield methanol, as well as the C-O bond scission of CH2OHad to yield surface CH2.ad and H2Oad species. Results from this study provide insight into the effects of K on MoP catalyst selectivity in syngas conversion reactions.  104  4.2  Methods  The DMol3 module of Material Studio (version 4.0) from Accelrys Inc. was used to complete the DFT calculations [23]. Accordingly, the electronic wave functions are expanded in numerical atomic basis sets defined on an atomic-centered spherical-polar mesh. The doublenumerical plus d-function (DND) all electron basis set was used for all the calculations. The DND basis set includes one numerical function for each occupied atomic orbital and a second set of functions for valence atomic orbitals, plus a polarization d-function on all non hydrogen atoms. The Becke exchange [24] plus Perdew-Wang approximation [25] non-local functional (GGA-PW91) was used in all the calculations. Each basis function was restricted to a cutoff radius of 4.7 Å, allowing for efficient calculations without loss of accuracy. The Kohn–Sham equations [26] were solved by a self-consistent field (SCF) procedure. The techniques of direct inversion in an iterative subspace (DIIS) [27] with a size value of 6 and thermal smearing of 0.005 Ha [28] were applied to accelerate convergence. The optimization convergence thresholds for energy change, maximum force, and maximum displacement between the optimization cycles were 0.00002 Ha, 0.004 Ha/ Å, and 0.005 Å, respectively. The activation energy between two surface species was identified by complete linear synchronous transit (LST) and quadratic synchronous transit (QST) search methods [29], followed by transition state confirmation through the nudge elastic band (NEB) method [30]. Spin polarization and symmetry were imposed in all the calculations.  In the present work, a cluster model of the MoP catalyst surface has been used. A cluster model is an incomplete representation of the electronic properties of a catalyst surface  105  because of its small size and discrete nature. But it enables rigorous quantum mechanical calculation to elucidate the extent of orbital overlap and electron co-relation of the adsorbate surface ensemble. This allows one to predict the adsorption geometry, adsorption energy and surface reactivity with less expense in computational power compared to a complete surface model. In the present study we have investigated the reaction steps on three cluster models.  The MoP cluster models and the reactant and product species were created using the Material Studio Visualizer. The adsorption energy was calculated by subtracting the energies of the gas phase species and the cluster from the energy of the adsorbed species according to the equation: Ead = E(adsorbate/cluster) – (Eadsorbate + Ecluster). With this definition, a negative Ead corresponds to a stable surface species. The activation energy was calculated by using the transition state search (TS search) tool in DMol3, applied to the reactant, a stable surface species plus an adsorbed H atom (Had) on the clusters, and the product.  4.3  Results  4.3.1  Building the Mo6P3 clusters  The procedure for building a cluster model of MoP was described in detail elsewhere [22]. Accordingly we have built the same Mo6P3 cluster as a model of the (100) surface of MoP in this study, as illustrated in Figure 4.1.  A cluster model of SiO2 was incorporated into the Mo6P3 cluster to simulate the effect of support properties on MoP/SiO2 catalysts. The SiO2 support can be modeled in different  106  molecular arrangements, described by the number of Si atoms in the SiO2 ring. Molecules with 3, 5, 7, and 9 Si atoms have been proposed [31], and in the present work, a 3 Si atom ring cluster with 3 oxygen atoms in the ring and another 6 oxygen atoms attached to Si atoms as dangling bonds, was used. The angles and bond lengths between Si and O in the cluster ring are given in Table 4.1. The SiO2 cluster model is in good agreement with that described by the West and Hench [31] model.  The procedure used to construct the cluster of the present study is depicted in Figure 4.1. The Mo6P3 cluster was placed on the Si3O9 cluster and the total arrangement was geometrically optimized to determine the Mo6P3-Si3O9 cluster structure. Since the Mo6P3 cluster has three different faces, three different arrangements of the Mo6P3 on the Si3O9 cluster were investigated and the minimum energy configuration was used in further analysis. A K atom was then introduced on one side of the Mo6P3-Si3O9 cluster, and two different sites of Mo were investigated on this cluster. Site I, designated as MoI, had the Mo atom closest to the K atom. The influence of K would be expected to be significant at this site, whereas on the Mo atom far from the K - Site II, designated as MoII, the influence would be small. The adsorption of the reaction intermediates on each of the Mo sites, bound through the C and O atoms of the intermediates, were each investigated separately as part of the study.  The electronic charge on the Mo and the K for the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 clusters are listed in Table 4.2. Introduction of the K atom imposed a negative charge (-0.263 e) on the MoI atom, whereas MoII contained a positive charge of 0.118 e. In comparison, on the  107  Mo6P3-Si3O9 cluster, both the MoI and MoII atoms possessed a positive charge of 0.160 e, and 0.145 e, respectively.  4.3.2  Reactions on the Mo6P3 clusters  4.3.2.1 C-O bond cleavage  The C-O bond cleavage of CH2OHad was initiated with a hydroxymethyl species and a hydrogen atom adsorbed on the cluster. The products were adsorbed methyl (CH2.ad) and water species. A comparison of this reaction step on the three different clusters is depicted in Figure 4.2(a), 4.3(a) and 4.4 (a,b). Relevant structural data are summarized in Table 4.3.  Figure 4.2(a) shows that the hydroxymethyl species was adsorbed on the Mo6P3 cluster through a bridge bond, with the C atom bound to one Mo atom, and the O atom bound to the other Mo atom. For Mo6P3 (Figure 4.2(a)) and K-Mo6P3-Si3O9 site II (Figure 4.4(b)), the H atom was adsorbed on the Mo atom where the O atom of the CH2OH.ad species was bound. On the Mo6P3-Si3O9 (Figure 4.3(a)) and the K-Mo6P3-Si3O9 Site I (Figure 4.4(a)), the H was bound on a different Mo atom. The molecular arrangement of the reactants facilitates the CO bond-breaking step on the cluster. The results (Table 4.3) show that the C-Mo and O-Mo bond lengths decreased with the addition of SiO2 and K, to the Mo6P3 cluster, implying that the CH2OHad species was more tightly bound on the clusters with Si3O9 and K, and this observation was supported by the increased adsorption energy of the hydroxymethyl species on the Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I and Site II, compared to the Mo6P3 cluster (Table 4.3).  108  After breaking the C-O bond of the CH2OHads species, the surface species CH2.ad + H2Oad were generated on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I clusters, and CH2.ad+HOad+Had species were formed on Site II of the K-Mo6P3-Si3O9 cluster. The adsorption energy of CH2.ad+ H2Oad on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I clusters was -145.97, -145.51 and -154.27 kcal/mol, respectively. On Site II of the K-Mo6P3Si3O9 cluster, CH2.ad + OHad + Had species had an adsorption energy of –156.35 kcal/mol. The adsorption energies increased on the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 clusters compared to Mo6P3. The highest adsorption energy was observed on the K doped cluster, implying greater stability of the adsorbed species on the K doped cluster than the un-doped Mo3P6Si3O9 cluster. C-Mo bond lengths on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I and Site II were 1.96, 1.92, 2.17 and 2.12 Å, respectively. Compared to Mo6P3, the C-Mo bond length decreased on the Mo6P3-Si3O9, but increased on the K doped Mo6P3-Si3O9 cluster. On both the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 clusters the CH2.ad species formed a geminal structure (the carbon atom was attached to two different Mo atoms as shown in Figure 4.4(a)), and this resulted in an increase in adsorption energy compared to the other two structures. The geminal carbon of the CH2.ad species and the strong binding energies on the K doped catalysts may promote either the insertion of COad species to produce higher oxygenates or the homologation of CH2.ad species to produce higher hydrocarbons.  The O-Mo atomic distance for H2Oad species on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9 (Site I) species was 2.23, 2.31, 3.35 Å, respectively. The distance increased with Si3O9 and K addition to the Mo6P3, indicating that H2O will form readily on the K doped MoP. For the OH species adsorbed on Site II of the K-Mo6P3-Si3O9 cluster, the O-Mo distance was 2.93 Å.  109  The transition state structure information for the hydroxymethyl reaction step over the Mo6P3, Mo6P3-Si3O9 and the K-Mo6P3-Si3O9-Site I and Site II clusters is reported in Table 4.4. Enthalpies of reaction were calculated as -6.19, -23.44, -28.98, and -23.44 kcal/mol for the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I and Site II clusters, respectively. As the bond breaking reaction is highly exothermic, very high negative values for the heat of reaction were observed for this step. Comparing the activation energies, the value calculated on the Mo6P3 cluster (27.88 kcal/mol) decreased to 2.61 kcal/mol on the Mo6P3-Si3O9 cluster, whereas on the K-Mo6P3-Si3O9 cluster the values were 9.85 and 9.08 kcal/mol for Site I and Site II, respectively.  4.3.2.2 Methanol formation  Methanol formation was modeled by Had attached to different Mo sites close to the C atom of the CH2OHad species as reactant, with the formation of CH3OHad as the product. The CH3OHad species was adsorbed via the O atom on a Mo site of the clusters. The reaction step for the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I and Site II is depicted in Figure 4.2(b), 4.3(b), 4.5(a,b) and the bond information of each surface species is reported in Table 4.5.  Data for the reactant structure, reported in Table 4.5, show that the adsorption energy decreased on the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 (O atom adsorbed at Site I) clusters, but increased on the K-Mo6P3-Si3O9 cluster (O atom adsorbed at Site II), compared to the Mo6P3 cluster. The O-Mo bond length decreased with the addition of K and the same trend was  110  observed for the C-Mo bond length. The distances between C-O were similar on all the clusters.  The CH3OHad species was adsorbed on all the clusters via the O atom. The O-Mo distances and the C-O bond lengths are reported in Table 4.5. The adsorption energy of CH3OHad on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9-Site I and Site II clusters was -33.21, -23.75, 20.75 and -35.74 kcal/mol, respectively. The lowest adsorption energy was observed on the K-Mo6P3-Si3O9 cluster at Site I (O adsorbed close to the K atom), but the adsorption energy was much higher than that reported on other methanol producing catalysts such as Cu(111) 4.38 kcal/mol [32], Pd(111) -6.46 kcal/mol [33], Pt(111) -7.61 kcal/mol [34], and Ni(111) 0.46 kcal/mol [35]. Recently, Pistonesi et al. [20] reported an adsorption energy of -8.97 kcal/mol for methanol on a Mo2C cluster. Since the Mo6P3 clusters of the present study show much higher adsorption energy for methanol than these metals, there is the likelihood that on MoP catalysts, strongly adsorbed CH3OH may be available for further reaction and Caddition to yield C2+ products.  Figure 4.2(b), 4.3(b), 4.5(a,b) depict the CH2OHad + Had  CH3OHad reaction step over the  Mo6P3, Mo6P3-Si3O9 and the K-Mo6P3-Si3O9-Site I and Site II clusters. The transition state structure information is summarized in Table 4.4. Activation energies for this reaction step were 100.91, 60.96, 12.07 and 113.95 kcal/mol and the enthalpies of the reaction were 8.45, 4.00, -4.24, and 10.97 kcal/mol on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9 Site I and Site II clusters, respectively. The lowest activation energy was for Site I of the K-Mo6P3Si3O9 cluster. The activation energy decreased by a factor of five compared to the Mo6P3-  111  Si3O9 cluster and by a factor of eight compared to the Mo6P3 cluster. Enthalpies of reaction were positive (endothermic) except for the configuration where the O atom was adsorbed on Site I of the K-Mo6P3-Si3O9 cluster, which had a transition state configuration that gave rise to an exothermic value.  4.3.3  Discussion  The charge distribution on the C and O atoms of the CH3OHad and CH2OHad+Had species, adsorbed on the Mo6P3, Mo6P3-Si3O9 and K-Mo6P3-Si3O9 clusters, is reported in Table 4.2. The C atom of the free CH3OH had a positive charge of 0.062e and the O atom had a negative charge of -0.502 e. However, the adsorbed C and O atoms had negative charges for all the cases investigated herein. For the Mo6P3 and Mo6P3-Si3O9 clusters, the O had a more negative charge than the C and the magnitude of the charges on the atoms didn’t vary significantly over each of the two clusters. For the K-Mo6P3-Si3O9 cluster, the C atom showed a more negative charge than the O atom. In this case, electron donation from K to the MoI followed by electron transfer to the O occurred. Hence charge was shifted to the C atom to compensate for the surface bond between MoI and O. The negative charge on the MoI atom of the K-Mo6P3-Si3O9 site I cluster decreased the adsorption energy of CH3OH (20.75 kcal/mol) compared to the Mo6P3, Mo6P3-Si3O9 clusters because of the repulsion of negative charges.  A decrease in the activation energy of the methanol formation step was observed on the Mo6P3-Si3O9 cluster compared to the Mo6P3 cluster. The activation energy was 100.91  112  kcal/mol for the Mo6P3 cluster and 60.96 kcal/mol or the Mo6P3-Si3O9 cluster. Similarly, the activation energy of the C-O scission reaction step decreased from 27.88 kcal/mol to 2.61 kcal/mol. With the addition of K, the activation energy for CH3OHad formation was significantly decreased to 12.07 kcal/mol on Site I of the K-Mo6P3-Si3O9 cluster. For Site II a higher activation energy of 113.95 kcal/mol was observed. On the other hand for the C-O bond breaking step, the activation energy increased to 9.85 kcal/mol and 9.08 kcal/mol for the K-Mo6P3-Si3O9-Site I and Site II, respectively. Clearly these results show that the C-O bond scission of the CH2OHad species is favored over CH3OHad species formation over all of the Mo6P3 clusters investigated.  The authors recently reported on the activity of 10 wt % MoP on SiO2 catalysts, promoted with 1 and 5 wt % K [36]. The catalyst activity was determined in a laboratory fixed bed microreactor under reaction conditions of 275oC, 8.2 MPa and a WHSV of 3600 h-1. The catalysts were operated at these conditions for an average of at least 50 h time-on-stream. For the 10 wt % MoP on SiO2 catalyst, a high selectivity to methane (35.2 C atom %) was measured. With increased K doping, selectivity to CH4 decreased to 22.1 and 9.0 C atom % over the 1 and 5 wt % K doped MoP-SiO2 catalyst, respectively. Methanol selectivity was low in all cases with values of 0.6, 2.2 and 0.3 C atom % measured over the MoP-SiO2 catalysts, the 1 wt % K/ MoP-SiO2 and the 5 wt % K/ MoP-SiO2, respectively. For the 1 wt % K doped catalysts an increase in methanol selectivity and a decrease in methane selectivity was observed whereas for the 5 wt % K doped catalyst, both the selectivity to methanol and methane decreased, relative to the MoP catalyst. High selectivity towards C2+ oxygenates, especially ethanol, acetaldehyde and acetone, was also observed with increased K loading.  113  Low selectivity to methanol over the 5 wt % K doped catalyst suggested the conversion of methanol to other products, i.e. ethanol and acetone. The DFT model presented herein is in agreement with these experimental findings. Both the model and the experimental data show that methane is produced selectively over MoP and increased methanol selectivity was observed for the K doped cluster and catalyst. The high adsorption energy of methanol over MoP clusters suggests that methanol will undergo further surface reaction to produce higher alcohols and/or other oxygenates, as observed on the K promoted MoP catalysts.  4.4  Conclusions  The DFT calculations on model Mo6P3 clusters showed that the addition of K decreased the activation energy for the formation of methanol on Site I of the K-Mo6P3-Si3O9 cluster to 12.07 kcal/mol, whereas the activation energy for the C-O bond cleavage reaction was lower (9.88 kcal/mol). Hence the model calculations predicted that addition of K would enhance methanol production on MoP catalysts, although CH4 would dominate the product compared to methanol, in agreement with experimental data reported over K doped MoP catalysts supported on SiO2.  4.5  Acknowledgements  Financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.  114  Table 4.1:  Three fold SiO2 cluster model structure  rSi-O  rO-O  rSi-Si  ӨO-Si-O  ӨSi-O-Si  Ref.  1.62  2.52  2.96  102.00  132.00  7  1.65  2.65  3.02  107.12  132.85  This work  115  Table 4.2:  Atomic charge distribution on the Mo6P3-Si3O9 and K-Mo6P3-Si3O9 cluster  Mo(1)  Mo(2)  Mo(3)  Mo(4)  K  O  C  Mo6P3-Si3O9 Cluster Empty cluster  0.16  0.145  0.627  x  x  x  x  CH2OHad+Had  0.335  0.225  0.604  x  x  -0.674  -0.489  CH3OHad  0.208  0.13  x  x  x  -0.713  -0.395  K-Mo6P3-Si3O9 Cluster Empty Cluster 1  CH2OHad+Had 1  1  CH3OH.ad  -0.263  0.118  0.626  0.102  0.894  x  x  -0.77  0.276  0.61  0.087  0.932  -0.532  -0.645  -0.172  0.081  0.616  0.099  0.859  -0.409  -0.667  O atom adsorbed on site I of K-Mo6P3-Si3O9 Cluster.  116  Table 4.3:  Reactant and product bond length, bond angle and adsorption energy for C-O bond scission step Bond Length  Cluster Model  Bond angle (deg)  (deg)  Adsorption energy ∆E [kcal/mol]  69.17  66.46  x  -54.88  1.49  68.523  66.675  111.64  -68.49  2.15  1.51  65.96  68.62  113.74  -70.56  2.14  1.48  63.724  69.94  105.27  -92.47  O-Mo1 [Å]  C-Mo2 [Å]  C-O [Å]  ∠C − Mo 2 − Mo1  Mo6P3  2.28  2.20  1.49  Mo6P3-Si3O9  2.255  2.18  2.20 2.18  Site#1 KMo6P3-Si3O9 Site#2 KMo6P3-Si3O9 [1]  (deg) CH2OH.ad + H.ad  ∠O − Mo1 − Mo 2  ∠C − O − Mo1  CH2.ad + H2Oad Mo6P3  2.23  1.96  x  97.60  79.28  x  -145.97  Mo6P3-Si3O9  2.31  1.92  x  91.313  125.315  x  -145.51  2.35  2.17  x  43.62  135.90  x  -154.27  2.93  2.12  x  43.47  144.70  x  -156.35  Site#1 KMo6P3-Si3O9 Site #2 KMo6P3-Si3O9  117  Table 4.4:  Transition state for the reaction steps, C-O bond scission and methanol formation from CH2OHad  Cluster Models  O-Mo1 [Å]  C-Mo2 [Å]  C-O [Å]  CH2OHad+Had  (deg)  Ea (kcal/ mol)  Er (kcal/ mol)  ∠C − Mo 2 − Mo1  ∠O − Mo1 − Mo 2  ∠C − O − Mo1  (deg)  (deg)  CH2.ad+H2Oad  Mo6P3  1.80  1.99  x  94.31  76.84  x  27.88  -6.19  Mo6P3-Si3O9  1.961  1.973  x  67.82  107.53  x  2.61  -23.44  Site#1 K-Mo6P3-Si3O9  2.21  1.93  x  65.83  101.71  x  9.86  -28.98  Site #2 K-Mo6P3-Si3O9  2.02  2.11  x  62.248  75.65  x  9.08  -23.44  CH2OHad+Had  CH3OHad  Mo6P3  2.30  2.28  1.52  x  73.94  x  100.91  8.45  Mo6P3-Si3O9  2.217  x  1.412  x  103.82  111.73  60.96  4.00  Site#1 K-Mo6P3-Si3O9  2.11  x  1.44  x  76.98  x  12.07  -4.24  Site #2 K-Mo6P3-Si3O9  2.20  x  1.47  x  92.48  118.29  113.95  10.97  118  Table 4.5:  Reactant and product bond length, bond angle and adsorption energy for methanol formation  Cluster Model  Bond distance C-O O-Mo1 C-Mo2 [Å] [Å] [Å]  Bond Angle ∠C − Mo 2 − Mo1  (deg) CH2OH.ad + H.ad  ∠O − Mo1 − Mo 2  ∠C − O − Mo1  (deg)  (deg)  Adsorption energy, ∆E [kcal/mol]  Mo6P3  2.23  2.21  1.48  67.70  67.03  x  -86.94  Mo6P3-Si3O9  2.237  2.189  1.49  66.079  69.168  113.845  -78.86  2.20  2.15  1.51  65.96  68.62  113.74  -78.86  2.19  2.16  1.48  62.31  71.013  102.58  -88.32  Site#1 KMo6P3-Si3O9 Site #2 KMo6P3-Si3O9 [1]  CH3OH.ad Mo6P3  2.32  x  1.45  x  110.03  x  -33.21  Mo6P3-Si3O9  2.244  x  1.46  x  146.029  125.69  -23.75  2.28  x  1.459  x  113.155  119.705  -20.75  2.23  x  1.459  x  105.07  128.838  -35.74  Site#1 KMo6P3-Si3O9 Site #2 KMo6P3-Si3O9 [1]  119  Five Atomic Layer Slab Model of MoP(100) plane  Mo6P3Si3O9  Mo6P3 Cluster Site #2  95% agreement with Slab model.  Site#1 K  Mo6P3 Cluster Model  Silica cluster 6 atom ring cluster K-Mo6P3Si3O9  Geometrically optimized Mo6P3 Cluster  Figure 4.1:  Cluster models of Mo6P3, Mo6P3Si3O9 and K-Mo6P3Si3O9.  Geometrically Optimized Mo6P3Si3O9 Structure Minimum Energy Configuration Arrangement.  120  (a)  (b)  TS  TS  Ea =27.88kcal/mol  Ea = 100.91kcal/mol  Methanol Ead=-1.44eV  Hydroxymethyl & Hydrogen atom Ead= -3.77eV  Er=8.45 kcal/mol  Er=-6.19kcal/mol  CH2.ad+H2Oad Ead=-6.33eV Figure 4.2:  Hydroxymethyl & Hydrogen atom Ead= -2.38eV  (a) C-O dissociation of CH2OHad species over Mo6P3 cluster, (b) Methanol formation from CH2OHad species over Mo6P3cluster.  121  (a)  (b)  TS  Ea = 2.61kcal/mol  TS  Ea= 60.96kcal/mol Methanol Ead=-1.03eV  Hydroxymethyl & Hydrogen atom Ead= -2.97eV  Er=4.0kcal/mol  Er=-23.44kcal/mol  CH2+OH+H Ead=-6.31eV Figure 4.3:  Hydroxymethyl & Hydrogen atom Ead= -3.42eV  (a) C-O dissociation of CH2OHad species over Mo6P3Si3O9 cluster, (b) Methanol formation from CH2OHad species over Mo6P3Si3O9 cluster.  122  TS  (a)  (b)  TS  Exothermic Reaction  Ea = 5.28 kcal/mol  Ea = 9.08kcal/mol  Geminal carbon Species Hydroxymethyl & Hydrogen atom Ead= -4.01eV Er= -23.44kcal/mol 23.44kcal/mol  Hydroxymethyl & Hydrogen atom Ead= -3.06eV Er= -25.56 kcal/mol CH2.ad+H2Oad Ead=-6.69eV Site# 1 Oxygen atom close to K atom Figure 4.4:  CH2.ad+OHad+Had Ead=-6.78eV Site #2 Oxygen atom away from K atom  C-O dissociation of CH2OHad species over K-Mo6P3Si3O9 cluster, (a) O atom adsorbed on Mo atom close to K atom (b) C atom adsorbed on Mo atom close to K atom atom.  123  TS  TS  Ea =12.10 kcal/mol  (a)  (b)  Ea =113.95 kcal/mol  Methanol Ead=-1.55eV Er=10.97 kcal/mol Hydroxymethyl & Hydrogen atom Ead= -3.42eV  Er=-1.52 1.52 kcal/mol Methanol Ead=-0.90eV  Site# 1 Oxygen atom close to K atom Figure 4.5:  Hydroxymethyl & Hydrogen atom Ead= -3.83eV Site# 2 Oxygen atom away from K atom  Methanol formation from CH2OHad species over K-Mo6P3Si3O9 cluster, (a) O atom adsorbed on Mo atom close to K atom (b) C atom adsorbed on Mo atom close to K atom.  124  4.6  References  [1]  Bagus P. 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[30]  Henkelman G., Jonsson H., Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points, Journal of Chemical Physics, 2000, 113 (22), 9978-85.  [31]  West J. K., Hench L. L., Molecular orbital of silica rings and their vibrational spectra, Journal of American Ceramic Society, 1995, 74, 1093-6.  [32]  Greeley J., Mavrikakis M., Methanol Decomposition on Cu(111): A DFT Study, Journal of Catalysis, 2002, 208 (2), 291-300.  [33]  Neurock M., First-principles analysis of the hydrogenation of carbon monoxide over palladium, Topics in Catalysis, 1999, 9 (3-4), 135-52.  [34]  Kandoi S., Greeley J., Sanchez-Castillo A.M., Evans S.T., Gokhale A.A., Dumesic J.A., Mavrikakis M., Prediction of experimental methanol decomposition rates on platinum from first principles, Topics in. Catalysis,2006 37 (12), 17-28.  [35]  Remediakis I. N., Abild-Pedersen F., Norskov J.K., DFT study of formaldehyde and methanol synthesis from CO and H2 on Ni(111), Journal of Physical Chemistry, B, 2004, 108 (38), 14535-40.  [36]  Zaman S. F., Smith K. J., Synthesis gas conversion over MoP catalysts, Catalysis Communication, 2009, 10 (5), 468-71.  correlation  127  Chapter 5  A study of K promoted MoP-SiO2 catalysts for synthesis gas conversion  A version of this chapter has been published. Sharif F. Zaman and Kevin J. Smith (2010) Effect of MoP and K loading on SiO2 for syngas conversion to alcohols. Applied Catalysis A: General, 378, pp. 59-68. 128  5.1  Introduction  Concerns about global climate change and the depletion of fossil fuels have increased interest in alternative fuels development, especially in the area of biomass conversion [1]. Biomass can be converted into a wide range of liquid fuels, such as bio-ethanol and bio-butanol. Ethanol is the focus of attention because it can be produced from agricultural feedstock (e.g. corn, sugarcane) by fermentation [2], or by converting lignocellulose (e.g. corn stove, switch grass, wood waste) to ethanol by an enzymatic process [3]. A third, more flexible approach is biomass gasification to syngas (CO, CO2 and H2) followed by catalytic conversion of the syngas to ethanol and other oxygenated products.  Most known catalysts for the conversion of syngas to oxygenated hydrocarbon products suffer from poor selectivity. Rh and Mn-promoted Rh catalysts have been reported to show high selectivity towards C2+ oxygenates (the sum of oxygenates with 2 or more carbon atoms, including ethanol, acetaldehyde and acetic acid) from syngas [4-10], but in nearly all cases the total hydrocarbon selectivity is > 40 C atom %. High selectivity towards ethanol (34.8 C atom %) was reported on Li/Na containing Mn-promoted Rh/SiO2 catalysts [6]. More recently Hu et al. [7] reported 44.5 % selectivity to ethanol over a 6%Rh-1.5%Mn-SiO2 catalyst, but the hydrocarbon selectivity was 48.5%. Egbebi and Spivey [10] reported high selectivity for acetaldehyde on a Rh-Li-Mn/TiO2 catalyst, explaining that ethanol and acetaldehyde share a common surface intermediate resulting in an increase in ethanol selectivity and a decrease in acetaldehyde selectivity with an increase in the feed gas CO/H2 ratio. However, the high selectivity to hydrocarbons, especially CH4, and cost and supply  129  issues associated with Rh, mean that there is significant interest in developing alternative catalysts for selective ethanol synthesis from syngas. Modified methanol synthesis (Cu-ZnO) catalysts, modified Fischer-Tropsch (Fe, Ru, Co) catalysts and Mo-based catalysts have all been investigated for syngas conversion. Mo-based catalysts generate mainly linear alcohols with relatively high selectivity towards ethanol [2], whereas Cu-ZnO based catalysts produce mostly branched alcohols [11]. MoS2 has been claimed to give high selectivity (40 C atom %) towards ethanol [12]. Subsequently, Li et al. [13], Iranmahboob et al. [14] and Li et al. [15] worked with alkali doped MoS2 that was also promoted with Rh, Co and Ni. Ethanol selectivity varied from 10 to 30 % on a CO2-free basis. Li et al. [16] reported 15 - 30 % ethanol selectivity on a K-MoS2/C catalyst operated at 598 K, 5.1 MPa and a H2:CO ratio of 1:1. Zhang et al. [17] investigated a K-Co-MoS2 catalyst and obtained 12 % ethanol selectivity at 573 K, 6 MPa and a H2:CO ratio of 2:1. Recently, Xiang et al. [18, 19] reported on a K doped β-Mo2C modified with Ni, Co and Fe for alcohol synthesis from syngas. High selectivity toward hydrocarbons was observed and ethanol selectivity of 9 - 14 C atom % was reported on these catalysts at 573 K, 8 MPa and a H2:CO ratio of 1:1.  The oxygenated products are produced from syngas through a series of step-wise C-C bond forming reactions. Ethanol selectivity is generally low because of the slow kinetics of the first C-C bond formation step and the rapid chain growth of C2 intermediates [11, 20, 21] .On alkali promoted Cu-ZnO catalysts, the chain growth occurs via a base-catalysed aldol condensation reaction [21] that propagates the chain to form mostly iso-butanol, whereas, on metal catalysts such as Rh, chain growth occurs via CO insertion into surface CHx fragments generated by the dissociative adsorption of CO [22]. Similar mechanisms have been ascribed  130  to Mo catalysts, although more recent DFT studies have shown that CO does not dissociate on MoS2 [23, 24].  Recently, MoP catalysts supported on SiO2 and Al2O3 were investigated for hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) reactions [25, 26]. Oyama [27] suggested that metal phosphides may also have good activity in other hydrogenation reactions, such as synthesis gas conversion to hydrocarbons and alcohols. However, a DFT study of syngas conversion to CH4 and CH3OH over an Mo6P3 cluster model of an MoP catalyst, demonstrated the tendency to selectively produce CH4 from CO+H2 rather than CH3OH [28]. A high adsorption energy of CH3OH on the cluster suggested that it may assist in the production of higher alcohols [28]. Similar results have also been obtained on MoS2, showing that although CO does not dissociate on MoS2, CH4 is preferentially formed via breaking of the C-O bond of a hydroxymethyl surface intermediate [23]. However, it is well known that alkali promoters decrease selectivity to hydrocarbons [12, 16] and increase the selectivity to oxygenated products on MoS2 [16], Rh [8] and Cu-ZnO [11, 20] catalysts. Recently, Zaman and Smith [29] reported the first results of syngas conversion over an MoPSiO2 catalyst, showing that K-promotion was effective in reducing selectivity to hydrocarbons (CH4) and increasing selectivity to oxygenated products on this catalyst as well. In the present work, the MoP catalysts have been investigated further, with a focus on determining the effect of MoP and K promoter loading on product selectivity. Results of syngas conversion over 5, 10 and 15 wt % MoP, with 0, 1 and 5 wt % K on SiO2 for syngas conversion to alcohols are reported.  131  5.2  Experimental  The silica supported MoP catalysts were prepared by temperature-programmed reduction (TPR) following the procedure established by Phillips et al. [30] for MoP–SiO2 catalysts. To prepare the 5, 10 and 15 wt % MoP–SiO2 catalyst, stoichiometric amounts (Mo/P = 1) of ammonium heptamolybdate (0.69, 1.39 and 2.09 g of (NH4)6Mo7O24 · 4H2O, BDH Chemicals, 99%, respectively) and diammonium hydrogen phosphate (0.52, 1.04 and 1.56 g of (NH4)2HPO4, Sigma–Aldrich, 99%, respectively) were dissolved in 15.7 ml of de-ionized water and impregnated drop-wise onto 10 g of the SiO2 support (Sigma–Aldrich, Grade 62, 60–200 mesh, BET area = 330 m2.g-1, pore volume = 1.2 cm3.g-1) with continuous stirring. The impregnated support was aged at room temperature for 12 h before being dried at 373 K for 12 h and calcined at 773 K for 5 h. The calcined catalyst precursor was subjected to TPR in a H2 (Praxair, 99.99%) flow of 120 cm3 (STP).min−1.g−1, at a temperature ramp of 1 K.min-1 to a final temperature of 923 K. The final temperature was held for 2 h. After reduction, the catalyst was cooled to room temperature in He and prior to removal from the reactor, the catalyst was passivated in a flow of 2 vol % O2 in He for 2 h at room temperature. Preparation of the 1 wt % and 5 wt % K promoted catalyst was achieved by first impregnating 10 g of the SiO2 support with a solution of potassium nitrate (KNO3, BDH Chemicals, 99.97%), prepared by dissolving the required amount of KNO3 (0.26 g and 1.29 g, respectively) in 12 ml of de-ionized water for incipient wetness impregnation. After aging at room temperature for 12 h, the impregnated SiO2 was dried at 373 K for 12 h followed by calcination at 773 K for 5 h. Subsequently, the K-SiO2 support was impregnated 132  with (NH4)6Mo7O24·4H2O and (NH4)2HPO4, dried, calcined and reduced as before. The composition of a selected number of the catalysts was confirmed by ICP-AES analysis conducted by Cantest Laboratories, Vancouver, Canada. The catalyst BET surface areas were measured using a Micromeritics FlowSorb II 2300 analyser. About 0.1 g of the catalyst was degassed at 473 K for 2 h and the measurement was made using 30 % N2 and 70 % He. Temperature-programmed reduction (TPR) experiments were carried out using a Micromeritics AutoChem 2920 apparatus. The sample (160-180 mg) was placed in a quartz U-tube and reduced in a 50 cm3(STP).min−1 flow of 9.5 % H2 in Ar gas mixture. The temperature was increased at a ramp rate of 5 K.min−1 to a final temperature of 1023 K, which was maintained for 4 h. Prior to the analyses, the temperature-programmed reduction of a reference material (silver oxide) was done at the same conditions to calibrate the TPR peak area to the volume of H2 consumed.  The CO uptake was measured by pulsed chemisorption also using a Micromeritics Autochem II 2920 unit. The passivated catalyst was pretreated to remove the passivation layer by passing 50 ml(STP)/min of 10 % H2/Ar while heating from 313 to 923 K at a rate of 5 K/min, and maintaining the final temperature for 1 h. The 10 % H2/Ar flow was then switched to He (50 ml(STP)/min) at 923 K for 1 h in order to remove the adsorbed species. The reactor was subsequently cooled to 298 K, and 0.5 ml pulses of CO were injected into a flow of He (50 ml(STP)/min) and the CO uptake was measured using a TCD. CO pulses were repeatedly injected until no further CO uptake was observed after consecutive injections.  133  Energy dispersive x-ray analysis (EDX) was performed using a Hitachi S-3000N electron microscope operated with a 20 kV electron beam acceleration voltage. Samples were mounted on carbon planchettes with carbon paste. Gold was sputtered onto the catalyst to ensure sufficient conductivity. At least 10 different particles of the catalyst were analysed by EDX and the average of these are reported herein. A Leybold Max200 X-ray photoelectron spectrometer with an Al Kα photon source was used for the XPS analysis of the reduced catalysts after passivation. Exposure of the samples to ambient atmosphere was minimized by transferring the samples from the reactor to the spectrometer either in vacuum or under N2. No further treatment of the catalysts was done in the XPS chamber. All XPS spectra were corrected to the C1s peak with a binding energy (BE) of 284.6 eV.  Catalyst activities were measured in a laboratory fixed-bed microreactor (o.d. = 9.53 mm and i.d. = 6.35 mm, copper lined stainless steel tube). The catalyst particles (average diameter = 150 µm) were placed on a packed bed of quartz wool inside the reactor and held in place by a bed of quartz beads. The catalyst bed depth was 5-7 cm and calculation showed that this configuration ensured plug-flow through the reactor (Appendix AIII-7.(d)). The experimental setup is shown in Figure 5.1. For all experiments, synthesis gas (H2:CO = 1) was reacted at 548 K, a pressure of 8.27 MPa and a gas-hourly space velocity (GHSV) = 3960 h-1. A high temperature back pressure regulator was used to control the reactor pressure. The reactor was operated at a low CO conversion (1-13 % CO) to ensure isothermal operation. Calculation of the internal and external heat and mass transfer rates, and application of the Mears and Weisz-Prater criteria (Appendix AIII-7.(c)), confirmed that at the conditions of the experiments, the reactor operated free of significant heat and mass transfer resistances. The  134  reaction products were analyzed using an in-line gas chromatograph (GC). Light gases (CO, CO2 and C1-C4 hydrocarbons) were separated using a 5 m temperature-programmed Porapak Q 80/100 packed column and quantified with a thermal conductivity detector. The alcohols, aldehydes, ketones, carboxylic acids and C5+ hydrocarbons were separated using a 30 m temperature-programmed ECTM-wax capillary column (i.d. = 0.53 mm and film thickness 1.20 µm) and quantified using a flame ionization detector.  GC/MS analysis was also  completed periodically on the liquid product collected at the reactor exit to confirm the identity of the reactor products. All the catalysts were evaluated over a period of at least 60 h of continuous reaction. The syngas conversion, product selectivity, activity of the catalysts and space time yield (STY) of the products were calculated according to the following equations  % Conversion =  % Selectivity =  Activity =  STY =  Fout × ∑ ni Ci product Fin × Cin  × 100%  ni Ci product ×100% ∑ ni Ci  CO Conversion × Inlet molar flow of CO Wt . of catalyst  Activity × Selectivity of product i × Molecular wt . product i Carbon number product i  where ni is the carbon number of component i and Ci is the mole fraction of component i.  135  5.3  Results  After calcination of the catalyst precursors, it was assumed that the Mo and P species were completely oxidized and present on the support as Mo6+ and P5+, respectively. The TPR profiles for the 10 wt % MoP-SiO2 and the 1 and 5 wt % K-10 wt % MoP-SiO2 catalyst precursors are shown in Figure 5.2. The TPR profile of the 10 wt % MoP-SiO2 catalyst precursor was very similar to that reported by Zuzaniuk et al. [25] with two peak maxima at 727 and 938 K and a characteristic low temperature shoulder at about 700 K. The low temperature peaks were assigned to the reduction of Mo6+ species to Mo4+ [31], while the large peak at 938 K was assumed to result from the overlapping of several peaks, corresponding to the reduction of Mo4+ to Mo0 and of P5+ to P0. For the 1 wt % K-10 wt % MoP catalyst, the lower peak shifts to a higher value (797 K), whereas the higher temperature peak remains unchanged. For the 5 wt % K-10 wt % MoP-SiO2 catalyst, the peaks also shifted to higher temperature compared to the 10 wt % MoP, with peak maxima at 773 and 976 K. The increase in the reduction temperature peak maxima suggests some interaction between the K and the MoP, that is clearly more pronounced at the higher K loading.  The reduction stoichiometry of the calcined precursors may be written as: 2MoO3.P2O5 + 11H2  2MoP + 11H2O  Accordingly, the degree of reduction calculated from Figure 5.2 for each of the catalyst precursors was 78, 72 and 73 % for the 10 wt % MoP-SiO2 and the 1 wt% and 5 wt % K - 10 wt % MoP-SiO2 precursors, respectively. However, as noted in several previous studies of supported metal phosphide catalysts [32-34], the stoichiometry of the reduction reaction is  136  somewhat uncertain. The catalyst precursors may include polyphosphate chains [32, 34] and species such as HxPO4(x-3) and P3+. In addition, during calcination and reduction, some loss of P may occur through volatile phosphorous species that leave the catalyst surface during the reduction or calcination process, all of which may contribute to a higher actual degree of reduction than that calculated from the data of Figure 5.2 [34].  Table 5.1 summarizes the catalyst characterization data for the MoP-SiO2 and the K promoted MoP-SiO2 catalysts as a function of the mass loading of MoP and K. The BET areas of the reduced catalysts were significantly below that of the corresponding SiO2 (330 m2/g), 1 wt % K-SiO2 (310 m2/g) and the 5 wt % K-SiO2 (264 m2/g) supports. In nearly all cases, the BET area decreased with increased loading of MoP and K, and the same trends were observed for the used catalysts.  The EDX data are reported in Table 5.1 as the Mo:Si atomic ratio for both the fresh and used catalysts. Because of interactions with the Si peak, the P content of the catalysts was over estimated by EDX analysis and is not reported.  However, chemical analysis showed  excellent agreement between the nominal and actual compositions of the used catalysts, with an average Mo:P atom ratio of 1.05 ± 0.04 for the catalysts of Table 5.1. The Mo:Si ratio increased with an increase in MoP loading and the K loading did not change this ratio significantly.  The XPS data of Table 5.1 suggest a Mo enriched surface for the reduced catalysts with the Mo:P ratio > 1 in all cases. The K:Mo ratio as measured by XPS was also greater than the  137  nominal K:Mo ratio, indicating that the K was preferentially located near the surface of the catalyst. However, because the K was added to the SiO2 before the MoP, the K:Mo ratio decreased as the MoP loading increased. The XPS narrow scan analysis of the 15 wt % MoPSiO2 reduced catalysts is compared to that of the 5 wt % K-15 wt % MoP-SiO2 in Figure 5.3, and a summary of the analysis of all the reduced catalysts is provided in Table 5.2. The Mo3d spectra were de-convoluted using three distinct Mo3d BEs at 228, 230 and 233 eV (± .5eV) and a spin orbit splitting of 3.2 eV. The low BE peak (227.3 – 228.0 eV) was assigned to MoP [35] whereas the higher BE peaks corresponded to Mo4+ and Mo6+ species. The P2p spectra of Figure 5.3 (C, D) were de-convoluted into two peaks with BE 132.8 – 133.9 eV assigned to phosphate species, and BE 127.2 – 128.5 eV assigned to phosphide species [30]. The curve fit showed that for the catalysts without K, the Mo 3d BE assigned to MoP was 227.9 – 228.2 eV, whereas for the catalysts with K the BE was 227.3 - 227.4 eV, a decrease of more than 0.5 eV (see Table 5.2). These BE shifts are likely a consequence of an interaction between the Mo and K, with an expected electron transfer from the K to the Mo. The K 2p peak was de-convoluted with a 2p BE of 292.8 – 293.1 eV and a spin orbit splitting of 2.6 eV [35, 36]. On Mo2C, the K 2p BE was reported to be 292.5 eV [35] and for K2CO3 added to a Co-MoS2 catalyst a BE of 293.3 eV was reported [37], whereas for K2CO3, Mills [36] reported the K 2p BE as 292.4 eV with a spin orbit split of 2.8 eV.  The CO conversion with time-on-stream for each of the catalysts, measured at 548 K and 8.27 MPa with a H2:CO = 1:1 feed gas at a GHSV = 3960 h-1, is plotted in Figure 5.4 (a-c). Initially, relatively high CO conversions were observed but the conversion declined significantly within the first 20 h and then stabilized. Among the catalysts examined, the 5 wt  138  % K-15 wt % MoP-SiO2 had the highest initial activity. The catalyst activities and selectivities were averaged over a period of up to 60 h after the initial 20 h stabilization period (Appendix AIII.8.(a and b). The average CO conversions over the MoP catalysts are presented in Figure 5.5 and show a general trend of increased conversion with increased MoP and K loading, with the 5 % K - 15 % MoP-SiO2 catalyst having the highest average conversion.  The average catalyst selectivities (C atom %), reported on a CO2-free basis, are summarized in Table 5.3 and Figure 5.6. The data of Table 5.3 show that the MoP-SiO2 catalysts produced mostly CH4 and other hydrocarbons, and as the MoP loading increased the CH4 selectivity decreased, whereas the higher hydrocarbon selectivity increased. DFT studies of syngas conversion over an Mo6P3 cluster model of the MoP catalyst predicted the preferential formation of CH4 versus methanol from syngas [28, 29], as observed for the un-promoted MoP-SiO2 catalysts reported in Table 5.3. The selectivity to oxygenated products, especially acetaldehyde and ethanol, decreased as the MoP loading increased.  With the addition of K to the MoP-SiO2 catalysts, the selectivity to CO2 increased, whereas the selectivity to CH4 (Figure 5.6 (a)) and other hydrocarbons was suppressed.  The  selectivity to C2 oxygenated products (Table 5.3) also increased as K was added to the MoPSiO2, except for the 5 wt % MoP-SiO2 catalyst. In this case, however, the CO conversion was low (< 1 %) compared to that obtained with the K-promoted 5 wt % MoP-SiO2 catalysts and selectivity to oxygenated products is expected to increase at lower conversions. The 5 wt % K-10 wt % MoP-SiO2 catalyst showed the highest selectivity towards C2 oxygenates (39.2  139  C atom %) and the lowest selectivity to C1-C4 hydrocarbons (23.4 C atom %) with a CH4 selectivity of only 9.7 C atom %.  The major oxygenated products obtained over all the catalysts were ethanol, acetaldehyde and acetone. For each level of MoP loading, Figure 5.6(c) shows that addition of K generally increased the ethanol selectivity. In the case of acetaldehyde (Figure 5.6(b)) and acetone (Figure 5.6(d)), however, the selectivity trend was more complex such that for the 10 and 15 wt % MoP-SiO2 catalysts, the addition of K only had a small impact on selectivity to these compounds.  The average space time yield (STY) of the oxygenated products is plotted in Figure 5.7. These data also show a general trend of increased STY with increased MoP loading, as well as with increased K loading at each level of MoP. The highest total oxygenate STY (147.2 mg.g cat-1.h-1) was obtained for the 5 wt % K-15 wt % MoP-SiO2 catalyst. The C2 oxygenate STY (sum of acetaldehyde, ethanol and acetic acid) for the 5, 10 and 15 wt% MoP-SiO2 catalysts promoted with 5 wt % K, was 14.2, 60.7 and 81.3 mg.g cat-1.h-1, respectively at 548 K.  140  5.4  Discussion  The catalyst characterization data showed that the catalyst BET area decreased with increased MoP and K loading on the SiO2 support, presumably due to pore blockage by the MoP and the K. The XPS data confirmed the presence of an MoP phase on the K-SiO2 support that was also confirmed by XRD data reported previously [29]. The TPR data provide some indication of an interaction between the MoP and the K, reflected in the TPR peak temperature shifts to higher temperature when K was present. The nature of the K-Mo interaction is shown by the XPS data, with a shift in the Mo 3d BE associated with MoP to lower values by at least 0.5 eV upon addition of K to the MoP-SiO2 catalyst. The shift in BE is a reflection of an interaction between the MoP and the K, and the decrease in BE is a consequence of the electron donating capability of the K promoter. Previous studies have shown that K addition to a Mo2C catalyst decreased the MoII 3d5/2 BE by 0.4 eV [35], whereas a decrease of 0.6 eV was observed with K addition to a Co-MoS2 catalyst [37]. In the latter case, the reduction in BE was observed for Mo3d5/2, S 2p3/2 and Co 2p3/2. Contrary to these results, Martin-Aranda et al. [38] reported no change in the Mo 3d BE of a NiMoO4 catalyst upon addition of KNO3 and after calcination at 873 K. The K 2p BE of 297.3 eV was consistent with the presence of K2O that would be obtained after calcination at this temperature [38]. In the present work, the Mo 3d BE associated with Mo4+ and Mo6+ species were not shifted by the addition of K, consistent with the results of Martin-Aranda et al. [38], although the K 2p BE (292.8 – 293.1 eV) was consistent with the lower calcination temperature of the present study (773 K) that would likely yield KOH rather than K2O [39]. The Mo:P atom ratio as determined by XPS was > 1 for all catalysts of Table 5.1, suggesting  141  some Mo enrichment on the surface of the catalyst compared to the bulk composition. The Mo enrichment is likely because of some P loss to the support during calcination and reduction [26], since the bulk chemical analysis showed that the amount of P was within ±5% of the nominal catalyst composition.  Nonetheless, the XPS data showed that for the un-promoted MoP-SiO2 catalysts, increased MoP loading increased the surface Mo:Si and P:Si ratio. Furthermore, because the K was added to the SiO2 before the addition of the MoP, the K loading did not have a significant impact on the surface Mo:Si and P:Si ratios measured on the K promoted MoP-SiO2 catalysts. The Mo:Si and P:Si ratios as determined by XPS, are a measure of the MoP dispersion on the catalyst. CO chemisorption performed on the 15 wt % MoP-SiO2 catalyst showed the MoP dispersion to be 3.4 %, close to the XPS Mo:Si ratio of 2.9 % (Table 5.1). The XPS data therefore suggest that increased MoP loading increased MoP dispersion, whereas the K did not significantly affect the dispersion of the MoP on the SiO2. Consequently, as the MoP loading on the un-promoted MoP-SiO2 catalysts increased, an increase in CO conversion was observed (Table 5.3), despite a decrease in total surface area. For the K-promoted MoP-SiO2 catalysts, however, the CO conversion was influenced by the MoP dispersion and the surface K/Mo ratio. Figure 5.8 shows the CO conversion as a function of both the K/Mo and Mo/Si ratio as determined by XPS. The response surface shown was obtained using a Kriging correlation to interpolate between the measured data points. The surface plot shows an increase in CO conversion with increased MoP dispersion (Mo:Si ratio) and a maximum in CO conversion at a K/Mo ratio of approximately 2, for all levels of Mo/Si investigated. The maximum in CO conversion as a function of surface K/Mo  142  ratio is a consequence of increased C2+ oxygenate selectivity (see Figure 5.9 discussed below) and the corresponding increase in produced water that results in an increase in CO conversion through the water-gas-shift reaction.  Although the CO conversion was mainly dependant on the MoP dispersion of the catalysts, the C2+ oxygenate product selectivity was dependent on the K/Mo ratio as determined by XPS, and shown in Figure 5.9. The decreased CH4 selectivity with increased K/Mo ratio, observed at each level of MoP loading (Figure 5.9), is well known in syngas conversion, and is due to the introduction of sites that favor non-dissociative adsorption of CO and C-C chain growth, which enhance the production of higher hydrocarbons and liquid oxygenates [40, 41]. Figure 5.9 suggests an optimum K/Mo ratio for maximum C2+ oxygenate selectivity. Above a K/Mo ratio of about 3, the C2+ oxygenate selectivity decreased, most likely a consequence of the fact that both basic sites (K) and metal sites (MoP) are required for C2+ oxygenate synthesis and an optimum number of each is required at the surface for maximum selectivity to C2+ oxygenates.  The MoP catalysts showed several distinct characteristics in product selectivity compared to MoS2 [12, 14, 42], β-Mo2C [18, 35, 47], Mo2O3 [43] and Mo [44] alcohol synthesis catalysts. Table 5.4 compares the results of synthesis gas conversion over the 5 wt % K – 10 wt % MoP-SiO2 catalyst of the present study, and Mo catalysts reported in the literature. The major liquid oxygenated products obtained on the catalysts of Table 5.4 were linear alcohols, although Muramatsu et al. [45] reported small amounts of acetaldehyde and acetone over the K-Mo/SiO2 catalysts. Furthermore, in most cases, methanol was produced with selectivity >  143  10 C atom % and ethanol had the highest or second highest selectivity among the higher alcohols. The alcohol distribution followed the Anderson-Schulz-Flory chain growth distribution. For MoP, however, a very low selectivity (0.5 - 4.9 C atom %) to methanol was observed for all the catalysts studied. DFT studies have shown that CH3OH adsorbs more strongly on MoP than MoS2, Mo2C or Cu [28, 46] and consequently, on MoP the CH3OH is likely available for further reaction and C-addition to yield C2+ products.  The major  oxygenated products of the reaction were acetaldehyde, ethanol and acetone, suggesting that the hydrogenation kinetics of oxygenated intermediates on the MoP surface was slower than that which occured on MoS2 and Mo2C. The product distribution over the MoP catalysts is similar to that reported on Rh catalysts, where high selectivities to ethanol, acetaldehyde and acetic acid have also been observed [4,7].  Although the reaction conditions, in particular the H2/CO ratio and temperature, vary among the different studies, the data of Table 5.4 are reported at similar levels of CO conversion at the optimized conditions of each study. Under these conditions, the K-MoP catalysts had the lowest selectivity to hydrocarbons among K-Mo [44], K-αMo2C [47], K-β-Mo2C [48], KMoS2 [49] and K-Co-MoS2 [14], although the former catalyst was examined with a H2:CO ratio of 2:1. Importantly, the K-MoP catalyst also had the highest C2+ oxygenate selectivity among all of the Mo-based catalysts.  Comparing the nine catalysts of the present study, the 5 wt % K-10 wt % MoP showed the highest selectivity for liquid oxygenates (76.5 C atom %), especially towards C2 oxygenates (39.2 C atom % for the sum of acetaldehyde, ethanol and acetic acid). Although this catalyst  144  had moderate selectivity towards ethanol (15.3 C atom %), it also showed very low selectivity towards CH4 (< 10 C atom%), which is typically not the case for other Mo-based catalysts such as MoS2 and Mo2C [14, 15, 18, 35, 42].  5.4.1 CO2 formation via the water-gas-shift reaction:  CO2 was formed with high selectivity in all cases over the MoP catalysts due to the fact that Mo is an active catalyst for the water-gas-shift (WGS) reaction. CO2 selectivity was lower on the un-promoted catalysts (Table 5.3) compared to those doped with K. The increased CO2 selectivity was most likely a consequence of the increase in liquid oxygenated products and the corresponding increase in produced water that was rapidly converted to CO2 over the Kdoped MoP catalysts. Although CO2 was produced at the expense of CO, this would reduce the cost of water removal from the oxygenated products.  5.4.2 Characterization of used catalysts:  The properties of the catalysts measured after 60 h reaction at 548 K, 8.27 MPa with a H2:CO = 1:1 synthesis gas feed and a GHSV of 3960 h-1 are presented in Table 5.1 and 5.2. The data of Table 5.1 show that the surface area of the used catalysts decreased significantly compared to the reduced catalysts. The change in BET area as a function of MoP and K loading followed the same trends noted for the reduced catalysts. The C:Si ratio of the used catalysts, determined by EDX analysis, showed evidence of significant carbon deposition as the likely cause of the decreased catalyst surface areas and reduced CO conversion observed in the  145  initial 20 h of operation shown in Figure 5.4. The EDX data also show that there was an increase in carbon deposition with increased K content of the catalysts. Analysis of the C 1s peak of the used catalysts did not show any evidence of K2CO3 (C 1s BE 288.4 eV [36]) present on the catalyst (Figure 5.10), suggesting that the carbon deposit arose from the heavier products or carbon generated by the Boudouard reaction.  5.5  Conclusions  Results presented herein show that MoP catalysts have a distinct product distribution compared to other Mo-based catalysts for syngas conversion. Methane dominated the products from synthesis gas conversion over MoP-SiO2 catalysts. Addition of K increased selectivity towards liquid oxygenates and decreased methane selectivity. The maximum liquid oxygenate selectivity (76.5 C atom %) was obtained over the 5 wt% K-10wt% MoPSiO2 catalyst. The major liquid oxygenated products were acetaldehyde, acetone and ethanol with a low selectivity to methanol.  5.6  Acknowledgements  Financial support from the Natural Science and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.  146  Table 5.1:  Properties of the reduced and passivated K-MoP-SiO2 catalysts as a function of MoP and K loading EDX Analysis  BET Surface Area m2.g-1  XPS analysis  (i)  (ii)  (i)  (ii)  (ii)  (i)  Mo:Si atom ratio (i)  5% MoP  259  234  0.018  0.013  1.2  1.09  0.013  0.012  -  10% MoP  263  181  0.040  0.029  1.4  1.11  0.027  0.024  -  15% MoP  184  123  0.058  0.047  2.0  1.24  0.029  0.024  -  1%K 5% MoP  255  110  0.018  0.019  1.8  1.31  0.015  0.012  1.17  1%K 10% MoP  235  60  0.034  0.044  2.5  1.37  0.025  0.018  0.42  1%K 15% MoP  171  51  0.057  0.052  1.9  1.27  0.031  0.024  0.31  5%K 5% MoP  75  21  0.021  0.02  1.1  1.64  0.017  0.011  5.83  5%K 10% MoP  64  6  0.047  0.047  5.6  1.29  0.028  0.022  3.27  5%K 15% MoP  48  11  0.078  0.046  10.3  1.26  0.029  0.023  1.95  Catalyst  Mo:Si  C:Si  Mo:P  atom ratio  atom ratio  atom ratio  (i)  - reduced catalyst before reaction  (ii)  - after 60 h reaction at 548 K, 8.27 MPa,CO:H2 = 1 and GHSV = 3960 h-1.  P:Si atom ratio (i)  K:Mo atom ratio (i)  147  Table 5.2:  Summary of XPS peak analysis of reduced and passivated K-MoP-SiO2 catalysts  Catalyst  5%MoP  Mo 3d BE  P 2p BE  K 2p BE  eV  eV  eV  228.0  -  229.4  133.9  232.0  5%K-5%MoP  227.4  127.5  229.9  132.9  293.1  233.0  10 % MoP  227.9  127.2  229.9  133.4  233.0  5%K-10%MoP  227.3  127.6  229.8  132.8  292.8  233.0  15% MoP  227.9  127.4  230.0  133.5  233.2  5%K-15%MoP  227.4  128.5  230.1  133.0  292.8  233.0  148  Table 5.3: Results of synthesis gas conversion to oxygenates on K-MoP-SiO2 catalysts Reaction conditions: Temperature 548 K, Pressure 8.27 MPa, H2:CO 1:1 and GHSV 3960 h-1. C atom selectivity (%)  Total Oxygenate STY (g.kg cat-1.h-1)  Catalyst  XCO (Catom%)  SCO2 (Catom%)  HC  CH4  AcH  Acetone  Methanol  Ethanol  C2 oxy  C3+ oxy  5% MoP  0.85  24.4  54.9  40.0  24.7  3.3  1.7  7.8  33.5  9.9  6.8  10%MoP  2.8  24.1  57.3  32.5  19.1  13.8  0.5  4.4  24.0  18.3  20.4  15% MoP  4.4  20.3  59.7  28.9  17.3  11.5  4.9  3.3  20.9  14.5  31.5  1%K- 5%MoP  3.2  42.0  45.2  21.1  17.7  17.7  1.0  7.6  26.3  27.4  29.3  1%K- 10%MoP  6.3  36.0  48.9  21.7  21.2  12.6  1.9  9.8  28.6  20.7  55.9  1%K- 15%MoP  5.7  40.0  45.8  23.3  21.5  13.8  3.3  8.6  30.7  20.2  53.9  5%K- 5%MoP  2.8  45.4  45.3  14.6  14.1  14.3  0.0  11.6  27.3  27.4  26.5  5%K- 10%MoP  8.4  44.9  23.4  9.7  20.5  14.1  4.1  15.3  39.2  33.3  112.9  5%K- 15%MoP  12.4  46.4  31.1  13.0  19.8  15.7  1.1  14.8  36.1  31.6  147.2  SCO2 = Selectivity of CO2; AcH = Acetaldehyde; C2 oxy is the sum of acetaldehyde, ethanol and acetic acid; C3+oxy is the sum of propanol (< 8 C atom%), butanol (<3 C atom%), acetone, acetic acid, propionic acid (< 2 C atom%), Rest (< 8 C atom %,lump of higher carboxylic acids, aldehydes, and esters); NA = data not available; STY = space time yield. † = Only the value of ethanol is reported as in the literature.  149  Table 5.4:  Comparison of product selectivities from synthesis gas conversion over Mo-based catalysts Temperature  Pressure  H2/CO  K  MPa  5%K- 10%MoP  548  K-10%Mo-SiO2  C atom selectivity (%)  Ref.  Ratio  XCO (Catom%)  SCO2 (Catom%)  HC  CH4  Methanol  Ethanol  C2+ oxy  8.3  1  8.4  44.9  23.4  9.7  4.1  15.3  73  573  1.6  1  12.9  4.9  49.5  22.0  17.0  21.0  30  This work [44]  K-β-Mo2C  573  8.0  1  23.4  NA  47.4  NA  18.8  22.0  34  [48]  K-αMo2C  573  7.9  1  14.4  NA  53.4  NA  21.4  15.0  25  [47]  K2CO3-MoS2  573  8.2  1  29.4  27.4  32.8  31.2  47.1  16.5  20  [49]  K-Co-MoS2/C  603  5.0  2  11.7  NA  58.1  NA  18.7  13.2  23  [50]  Catalyst  SCO2 = Selectivity of CO2; C2+  oxy  is the sum of all oxygenates with carbon number 2 or greater; NA = data not available; STY = space time yield.  150  TI  Thermocouple  Sampling valves  PI  Catalyst Bed GAS CHROMATOGRAPH  TCD  FID  Integrator PR  PR  PR  Mass flow Controller  Reactor  To Vent  BPR  Liquid sample collection Heating box  Figure 5.1:  Experimental setup for syngas conversion to oxygenates.  151  H2 consumption, au  10%MoP  1%K-10%MoP  5%K-10%MoP  400  600  800  1000  Temperature, K  Figure 5.2: TPR profiles of 10% MoP-SiO2, 1% K-10%MoP-SiO2 and 5%K-10%MoP-SiO2 catalysts.  152  B  Intensity, au  Intensity,au  A  242 240 238 236 234 232 230 228 226 224 222  242 240 238 236 234 232 230 228 226 224 222  BE, eV  BE, eV  D Intensity, au  Intensity, au  C  138  136  134  132  130  128  126  124  138  BE, eV  136  134  132  130  128  126  124  BE, eV  E  Intensity, au  K2p  C1s  305  300  295  290  285  280  275  BE, eV  Figure 5.3:  XPS analysis of reduced MoP catalysts after passivation: (A) Mo 3d of 5%K-15%MoP-SiO2; (B) Mo 3d of 15%MoP-SiO2; (C) P2p of 5%K-15%MoP-SiO2; (D) P2p of 15%MoP-SiO2; (E) K 2p and C 1S of 5%K-15%MoP-SiO2 catalyst.  153  (a)  Fractional CO conversion  0.10  5% MoP 1% K 0.05  5% MoP 5% K  5% MoP  0.00 0  10  20  30  40  50  60  50  60  (b)  Fractional CO Conversion  0.15  10% MoP 5% K  0.10  10% MoP 1% K  0.05  10% MoP (a)  0.00 0  10  20  30  40  (c)  Fractional CO Conversion  0.20  15% MoP 5% K  0.15  0.10  1% K 15% MoP 0.05  15% MoP 0.00 0  Figure 5.4 :  10  20  30 Time (h)  40  50  60  Syngas conversion with time-on-stream over MoP-SiO2 catalysts: (a) 5 wt% MoP (b) 10 wt% MoP (c) 15 wt% MoP. Reaction conditions: Temperature 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1. 154  14  0% K  1% K  5% K  12.4  12  8.4 % CO Conversion  10 6.3  8  5.69 6  3.15  2.84 4.35  4  2.8 2  5% K  0.85  1% K  0 5% MoP  Figure 5.5 :  0% K 10% MoP  15% MoP  Average CO conversion over K-MoP-SiO2 catalysts as a function of MoP and K content (wt %). Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1.  155  40 0% K  1% K  5% K  30  30 (b) 0% K Acetaldehyde Selectivity  Methane Selectivity  (a)  20  10  0  20  10  10% MoP 15% MoP  20 0% K  1% K  5% K  15  5% MoP 20 (d)  Acetone Selectivity  Ethanol Selectivity  5% K  0 5% MoP  (c)  1% K  10  5  10% MoP  0% K  1% K  15% MoP 5% K  15  10  5  0  0 5% MoP  10% MoP 15% MoP  5% MoP  10% MoP 15% MoP  Figure 5.6: Selectivity (C atom %) of major products of syngas conversion over K-MoPSiO2 catalysts; (a) methane (b) acetaldehyde (c) ethanol (d) acetone. Reaction conditions: Temperature - 548 K, Pressure - 8.3 MPa, H2:CO - 1:1 and GHSV 3960 h-1.  156  0% K  140  1% K  (a)  120  5% K  112.9  100 80 55.9  60 40 20  29.3 26.5  50  147.2  53.9 31.5  20.4  6.8  0% K  Acetaldehyde STY [mg/gm catal/hr]  Total Oxygenate STY [mg/gm catal//hr]  160  0  40  23.5  21.5  20 13.3 9.8  10 3.7  7.1  9.4  0 5% MoP  5% K 33.7  (c) 23.6  20 15 10 4.4  6.1  7.8  9.0 2.6  1.2  2.2  5% MoP  10% MoP 15% MoP  0  0% K  Acetone STY [mg/gm catal/hr]  Ethanol STY [mg/gm catal/hr]  1% K  25  5  30.3  10% MoP  15% MoP  35 0% K  35 30  43.2  5% K  (b)  30  5% MoP 10% MoP 15% MoP 40  1% K  1% K  5% K  30.1  30 (d)  25  18.3  20 15  12.3 8.6  10  6.3 6.0  12.1 7.7  5 0.4 0 5% MoP  10% MoP 15% MoP  Figure 5.7: Space-time-yield (STY) of major products of syngas conversion over K-MoPSiO2 catalysts; (a) total oxygenates (b) acetaldehyde (c) ethanol (d) acetone. Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1.  157  O convers Fractional C  ion  0.12 0.10 0.08 0.06 0.04 0.02 0.00 0.010 0.015  Mo 0.020 /S 0.025 i ra tio  6 4 2 0.030 0  o rati o K/M  Figure 5.8: Averaged CO conversion as a function Mo/Si and K/Mo ratio as measured by XPS. . ♦ - 0 wt % K; ● - 1wt % K; ▲ - 5 wt% K. Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1.  158  50  Methane  40  Selectivity, C atom %  30 20 10 0  C2+ Oxygenates  80 70 60 50 40 30 20 0  1  2  3  4  5  6  K/Mo ratio by XPS  Figure 5.9: Methane and C2+ oxygenate selectivity over MoP catalyst as a function of K:Mo surface atom ratio. ■, □ - 5 wt % MoP; ●,o – 10 wt % MoP; ▲,∆ - 15 wt% MoP. Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1.  159  Intensity, au  5K-15 MoP  15 MoP  10 MoP  5 MoP  292  290  288  286  284  282  280  278  276  Binding Energy (eV)  Figure 5.10:  XPS analysis of carbon C1s over different loadings of MoP catalyst after ~60  h reaction at Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1.  160  5.7  References  [1]  Franco C, Pinto F, Gulyurtlu I, Cabrita I., The study of reactions influencing the biomass steam gasification process, Fuel, 2003, 82(7), 835-42.  [2]  Velu S., Santosh K. G., A Review of recent literature to search for an efficient catalytic process for the conversion of syngas to ethanol, Energy Fuels, 2008, 22(2),841-39.  [3]  George W. H., Sara I., Avelino C., Synthesis of transportation fuels from biomass: Chemistry, Catalysis, and Engineering, Chemical Review, ChemInform 2006.  [4]  Bhasin M. M., Bartley W. J., Ellgen P. C., Wilson T. 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[45]  Muramatsu A., Tatsumi T., Tominaga H., Mixed Alcohol Synthesis from CO–H2 by Use of KCl-Promoted Mo/SiO2 Catalysts, Bulletin of the Chemical Society of Japan, 1987, 60(9), 3157-3161.  [46]  Zaman S. F.,Smith K. J., A DFT study of the effect of K over MoP-SiO2 cluster for syngas conversion, Molecular Simulation, Accepted Manuscript, doi: 10.1080/ 08927020903124585, 2009  [47]  Xiang M., Li D., Li W., Zhong B., Sun Y., Performances of mixed alcohols synthesis over potassium promoted molybdenum carbides, Fuel, 2006, 85(17-18), 2662-2665.  [48]  Xiang M., Li D., Qi H., Li W., Zhong B., Sun Y., Mixed alcohols synthesis from carbon monoxide hydrogenation over potassium promoted β-Mo2C catalysts, Fuel, 2007, 86(9), 1298-1303.  [49]  Woo H. C., Nam I. S., Lee J. S., Chung J. S. and Kim Y. G., Structure and distribution of alkali promoter in K/MoS2 catalysts and their effects on alcohol synthesis from syngas, Journal of Catalysis,1993, 142(2), 672-690.  164  [50]  Li Z., Fu Y., Jiang M., Hu T., Liu T., Xie Y., Active carbon supported Mo–K catalysts used for alcohol synthesis, Journal of Catalysis, 2001, 199(2), 155-161.  165  Chapter 6  Synthesis gas conversion over a Rh-K-MoP/SiO2 catalyst  A version of this chapter will be submitted for publication. Sharif F. Zaman and Kevin J. Smith. Synthesis gas conversion over a Rh-K-MoP/SiO2 catalyst. 166  6.1. Introduction  Interest in the development of new technologies that convert renewable resources to alternative transportation fuels, and thereby address issues of air quality, CO2 emissions and energy security, are increasing. Biomass, especially agricultural and forest residue, has potential as a renewable energy resource and is expected to play an important role in the synthesis of clean and sustainable fuels [1,2]. Biomass can be converted into a wide range of liquid fuels, such as bio-ethanol and bio-butanol. Currently, more than 80% of the world’s ethanol is produced by fermentation of cellulose derived from agricultural feedstocks (corn and sugarcane). Another route to clean fuels from biomass is through the thermocatalytic conversion of synthesis gas (CO+CO2+H2) that is produced from biomass gasification. The synthesis of alcohols from synthesis gas (syngas) has been known since the 1920’s [3,4] and the production of methanol is practiced industrially using Cu/ZnO catalysts [5]. Higher alcohols, especially iso-butanol, are produced when methanol catalysts are promoted with alkali metals. The modified methanol synthesis catalysts, both high temperature Zn/Cr and low temperature Cu/ZnO catalysts, produce C1-C6 linear and branched alcohols [6,7] primarily via an aldol condensation or methanol homologation reaction mechanism [1,8]. However, alkali-promoted methanol catalysts have very low selectivity toward ethanol because of the fast C-C chain growth of the C2 surface intermediate [8]. Many other catalysts for the synthesis of ethanol or mixed alcohols have been reported in the literature, and these can be categorized as (i) modified Fischer-Tropsch (FT) catalysts (ii) Rh-based catalysts and (iii) Mo-based catalysts. Alkali-doped FT catalysts produce mainly hydrocarbons from syngas, 167  with a ratio of hydrocarbon to alcohol equal to one or more [9], and among the alcohols C2+ alcohols predominate. A high yield of alcohols has also been reported on Cu-Co catalysts, but these catalysts produce significant amounts of hydrocarbons, which have a negative effect on the overall process feasibility, especially if the CH4 selectivity is above about 10 % [1]. Rh-based catalysts have the highest reported ethanol selectivity among the various synthesis gas catalysts investigated to date [10]. Lui et al. reported 44.5 C atom % selectivity to ethanol with a considerable amount of CH4 (48 C atom %) in the product [11] when synthesis gas was reacted over a Rh catalyst, promoted with Li and Mn, at 573 K, 3 MPa and a syngas H2:CO ratio of 2. Recently, Rh supported on carbon nanotubes was reported to have good selectivity (52.4 C atom %) towards C2+ oxygenates [12]. The kinetics of ethanol synthesis on Rh catalysts promoted with Mn have also been reported by several researchers [13-16], with values of 90-140 kJ/mol reported for the activation energy of methane formation and 40-70 kJ/mol for ethanol formation. The high hydrocarbon selectivity reported on Rh-based catalysts, especially toward CH4, means that these catalysts would be difficult to implement in a commercial process. Furthermore, because of cost and supply issues associated with Rh, there is significant interest in less expensive synthesis gas conversion catalysts with high alcohol selectivity. Several researchers have reported that Mo sulphides, phosphides, nitrides and carbides show characteristics of precious metal catalysts such as Pt and Rh [17], and that they are highly resistive to sulphur poisoning [1]. These two characteristics have led to several studies of Mo-based catalysts for syngas conversion to alcohols. Synthesis gas conversion at 295 °C, 7.2 MPa and a H2:CO ratio of 1 was reported with high selectivity to ethanol (40 C atom %) over MoS2 [18,19], but later researchers only achieved 10-30 C atom% ethanol selectivity on 168  MoS2 catalysts promoted with Co, Ni, and Mn [20-23]. Recently, syngas conversion over βMo2C at 300 °C and 8 MPa was reported to produce hydrocarbons and alcohols, and among the liquid products, ethanol predominated [24,25]. On alkali doped Mo catalysts (both Mo2C and MoS2), the higher alcohol synthesis followed the Anderson-Schulz-Flory distribution for the C2+ products, with a low selectivity to methanol. Addition of FT metals (Ni, Co, Rh) increased the selectivity of ethanol and enhanced the performance of MoS2 and Mo2C catalysts [20-23,25]. Kinetic models for higher alcohol synthesis over MoS2 catalyst have also been developed by several researchers [26-28] and it is now well established that the alcohol chain growth occurs via a CO insertion mechanism on MoS2 catalysts, although recent theoretical studies have shown that CO does not dissociate on MoS2 [29]. There is very limited information on the kinetics of synthesis gas conversion over Mo2C catalysts, Xiang et al. [25] reported the activation energies for linear alcohols (C1-C5) over several alkali-promoted Mo2C catalysts. Recently, the present authors reported on the product distribution obtained from synthesis gas conversion over a new series of K-MoP catalysts supported on SiO2 [30,31]. Within the investigated range of compositions, a 5 wt% K-10 wt% MoP supported on SiO2 catalyst showed the highest selectivity towards liquid oxygenates and C2 oxygenates, i.e. ethanol (16 C atom %) and acetaldehyde (18 C atom %). Although the MoP catalysts showed promising selectivity to oxygenates and ethanol, the catalysts deactivated during the first 20 hours of operation before stabilizing at a lower level of conversion. In the present study, we demonstrate that addition of 1 wt % Rh to the 5 wt% K- 10 wt% MoP-SiO2 catalyst stabilizes the CO conversion. Furthermore, the addition of Rh increases the C2 oxygenate selectivity and activity. The space-time-yield data for the Rh-K-MoP-SiO2 catalyst, measured at similar 169  CO conversions (10-15%), have been used to develop simplified power law kinetic models of the synthesis of the oxygenated compounds.  6.2  Experimental  6.2.1  Catalyst preparation:  The silica supported Rh-K-MoP catalysts were prepared by stepwise impregnation of the SiO2, followed by calcination and temperature-programmed reduction (TPR). Approximately 10 g of the SiO2 (Sigma–Aldrich, Grade 62, 60–200 mesh, BET area = 330 m2/g, pore volume = 1.2 cm3/g) support was impregnated with a solution of potassium nitrate (1.77 gm KNO3, BDH Chemicals, 99.97% dissolved in 15 ml of de-ionized water). After aging at room temperature for 12 h, the impregnated SiO2 was dried at 373 K for 12 h followed by calcination at 773 K for 5 h. Stoichiometric amounts (Mo:P = 1) of ammonium heptamolybdate (1.39 g of (NH4)6Mo7O24 · 4H2O, BDH Chemicals, 99%) and di-ammonium hydrogen phosphate (1.04 g of (NH4)2HPO4, Sigma–Aldrich, 99%) were dissolved in 15.7 ml of de-ionized water and impregnated drop-wise onto 10 g of the K-SiO2 with continuous mixing. The impregnated support was held at room temperature for 12 h before being dried at 373 K for 12 h and calcined at 773 K for 5 h. To add the 1 wt % Rh, 0.215 g of Rhodium (III) acetate (Sigma–Aldrich, 99%) was dissolved in 15 ml of de-ionized water. A few drops of HNO3 were added to make a translucent solution (light brown-yellow in color). The Rh solution was then added to the calcined K-MoP-SiO2, aged for 12 hrs at room temperature and dried at 373 K for 12 hrs. A final calcination was conducted at 773 K for 5 hrs. The 170  calcined catalyst precursor was subjected to TPR in a H2 (Praxair, 99.99%) flow of 120 cm3 (STP) min−1 g −1, at a temperature ramp of 1 K/min to a final temperature of 923 K. The final temperature was maintained for 2 h. After reduction, the catalyst was cooled to room temperature in He and prior to removal from the reactor, the catalyst was passivated in 2 vol % O2 in He for 2 h at room temperature. Details of the preparation of the MoP/SiO2 and KMoP/SiO2 catalysts used herein for comparison have been reported previously [30].  6.2.2  Catalyst characterization  The chemical composition of the prepared catalysts was done by CANTEST Laboratories (Burnaby, BC) using ICP-AES. Prior to analysis about 0.1 g of catalyst was mixed with 0.7 g of LiBO2 and fused at 1273 K before being dissolved in 100 mL of 4 % nitric acid. The catalyst single point BET surface areas were measured using a Micromeritics FlowSorbII 2300 analyser. About 0.1 g of the catalyst was degassed at 473 K for 2 h and the measurement was made using 30% N2 and 70% He. Temperature-programmed reduction experiments were carried out using a Micromeritics AutoChem 2920 apparatus. The calcined catalyst precursor (160-180 mg) was placed in a quartz U-shaped tube and reduced in a flow of a 9.5% H2/Ar mixture (50 mL.min−1). The temperature was increased at a ramp rate of 5 K min−1 up to 1023 K, the final temperature being maintained for 4 h. Prior to the analyses, the temperature-programmed reduction of a reference material (silver oxide) was carried out using the same procedure. The peak area of the reference material was correlated to the known volume of consumed H2 and these data were used to calculate H2 consumption during the reduction of the phosphide precursors.  171  EDX analysis was performed using a Hitachi S-3000N electron microscope operated with a 20 kV electron beam acceleration voltage. The average composition, from at least 10 data points, was determined for each catalyst sample. A Leybold Max200 X-ray photoelectron spectrometer with an Al Kα photon source was used for the XPS analysis. After reduction and reaction the catalyst was cooled to room temperature in He and prior to removal from the reactor, the catalyst was passivated in 2 vol% O2 in He for 2 h at room temperature. Exposure of the samples to ambient atmosphere was minimized by transferring the samples from the reactor to the spectrometer either in vacuum or under N2. No further treatment of the catalysts was done in the XPS chamber. All XPS spectra were corrected to the C1s peak with a binding energy (BE) of 284.6 eV.  6.2.3  Catalyst assessment:  Catalyst activities were measured in a laboratory fixed-bed micro-reactor (copper lined stainless steel tube with o.d. = 9.53 mm and i.d. = 6.35 mm), operated at low conversion to investigate the kinetics of the reaction. This was achieved at each reaction temperature by adjusting the gas hourly space velocity (GHSV). Hence, at each temperature the amount of catalyst in the reactor varied so that the GHSV increased with reaction temperature. Accordingly, at 573 K, 598 K and 613 K, the GHSV was set at 3960, 7920 and 15840 h-1, by using 1, 0.5 and 0.25 g catalyst, respectively. The catalyst particles (average diameter = 150 µm) were placed on a packed bed of quartz wool inside the reactor and held in place by a bed of quartz beads. The catalyst bed depth was 2-7 cm and calculation showed that this configuration ensured plug-flow through the reactor (Appendix AIII.7.(d)). A high temperature back pressure regulator was used to control the reactor pressure and a mass flow  172  controller was used to control the flow of pre-mixed gas to the reactor. Various H2:CO gas mixtures were investigated. The reaction products were analyzed using an in-line gas chromatograph (GC). Light gases (CO, CO2 and C1–C4 hydrocarbons) were separated using a 5 m temperature-programmed Porapak Q 80/100 packed column and quantified with a thermal conductivity detector. The alcohols, aldehydes, ketones, carboxylic acids and C5+ hydrocarbons were separated using a 30 m temperature-programmed EC™-wax capillary column (i.d. = 0.53 mm and film thickness 1.20 µm) and quantified using a flame ionization detector. GC/MS analysis was also carried out periodically to confirm the identity of the reactor products. The activities of the catalysts were measured at different temperatures and GHSVs and at each condition the catalysts were evaluated for a period of at least 40 h of continuous operation. Some experiments were repeated to quantify the experimental error and analysis showed the conversion and selectivity data to be within ±10% of the reported values (Appendix AIII.9). Calculation of the internal and external heat and mass transfer rates, and application of the Mears and Weisz-Prater criteria (Appendix AIII.7(c)), confirmed that at the conditions of the experiments, the reactor operated free of significant heat and mass transfer resistances.  173  6.3  Results  6.3.1  Catalyst characterization:  Table 6.1 reports the product compositions of the MoP/SiO2, the K-MoP/SiO2 and the Rh-KMoP/SiO2 catalysts used in the present study. Chemical analysis (ICP-AES) of the used catalysts was in good agreement with the nominal catalyst compositions. After use, the MoP was marginally enriched in Mo, likely a consequence of some P loss during temperature programmed reduction of the calcined catalyst precursors [31]. Table 6.1 also shows that the catalyst compositions, as determined by EDX, were in reasonable agreement with the ICPAES chemical analysis, except that the P content was over estimated by EDX (Mo:P ratio < 1 in all cases) because of poor resolution of the Si and P peaks.  The TPR profile of the calcined Rh-K-MoP/SiO2 catalyst precursor is compared to that obtained for the MoP/SiO2 and K-MoP/SiO2 catalyst precursors in Figure 6.1. After calcination, it was assumed that the Mo and P of the catalyst precursors were completely oxidized and present on the support as Mo6+ and P5+, respectively. The TPR profile of the 10 wt % MoP-SiO2 catalyst was in agreement with that reported by Zuzaniuk et al. [32] with two peak maxima at 727 and 938 K and a characteristic low temperature shoulder at about 700 K. The low temperature peaks were assigned to the reduction of Mo6+ species to Mo4+ [33], while the large peak at 938 K was assumed to result from the overlapping of several peaks, corresponding to the reduction of Mo4+ to Mo0 and of P5+ to P0. For the 5 wt % K-10 wt % MoP/SiO2 catalyst, the peaks shifted to higher temperatures compared to the 10 wt % MoP, with peak maxima at 773 and 976 K, and these peak maxima were also present in the 1 wt % 174  Rh – 5 wt % K – 10 wt % MoP/SiO2 catalyst. The Rh-K-MoP/SiO2 catalyst also showed a new reduction peak at about 505 K that was not present in the TPR profiles of the KMoP/SiO2 and MoP/SiO2 catalysts, and was assigned to the reduction of Rh2O3 [15,34,35]. From the TPR analysis there was no clear indication of a strong interaction between the Rh and the MoP. The reduction of Rh2O3 was assumed to follow the reaction stoichiometry Rh2O3 + 3H2  2Rh + H2O and the stoichiometric H2 consumption required to reduce the Rh  present on the 1 wt % Rh – 5 wt % K – 10 wt % MoP - SiO2 catalyst precursor was 145.7 µmol H2/g. The difference between the total H2 consumed for the K-MoP-SiO2 and the RhK-MoP-SiO2 catalyst precursors showed that 100 % of the Rh2O3 was reduced to Rh. The reduction of Mo and P species from their high oxidation state, Mo6+ and P5+ present after calcination, was assumed to follow the reaction 2MoO3.P2O5 + 11 H2  2MoP + 11 H2O.  Accordingly, the degrees of reduction calculated from Figure 6.1 were 78, 73% and 66 % for the 10 wt % MoP/SiO2 catalyst, the 5 wt % K - 10 wt % MoP/SiO2 catalyst and the 1wt% Rh–5 wt % K–10wt% MoP/SiO2, respectively. However, as noted in several previous studies of supported metal phosphide catalysts [36-39], the stoichiometry of the reduction reaction is somewhat uncertain because of the possible presence of polyphosphate chains [36,37] and species such as HxPO4(x-3) and P3+ in the calcined precursors. In addition, during calcination and reduction, some loss of P may occur through volatile phosphorous species that leave the catalyst surface during the reduction or calcination process, all of which may contribute to a higher actual degree of reduction than that calculated from the data of Figure 6.1 [38]. Table 6.2 reports the fresh and used catalyst BET surface areas as well as the catalyst surface composition as determined by XPS analysis of the reduced, passivated catalysts. The BET data show that addition of the K and Rh decreased the surface area of the catalysts compared 175  to the MoP/SiO2 catalyst. The Rh-K-MoP/SiO2 catalyst BET area was 56 m2/g whereas that of K-MoP-SiO2 catalyst was 64 m2/g. However the most significant decrease in area occurred with the addition of K to the MoP/SiO2 catalyst. The used catalysts all showed a decrease in surface area after reaction, mainly due to carbon deposition [30]. Previous work on the K-MoP-SiO2 catalysts has shown that the Mo:Si ratio, as determined by XPS, is a measure of the Mo dispersion [30], and this is not affected significantly by the addition of K to SiO2 prior to the loading of MoP onto the support. The surface composition data of Table 6.2 show, however, that with the addition of Rh, there appears to be a loss in MoP dispersion. For K-MoP/SiO2 catalyst the MoP dispersion was 2.8 % whereas for the RhK-MoP/SiO2 catalyst it was 1.9 %. The surface of the catalysts was also apparently enriched in Mo (Mo:P > 1, Table 6.2), consistent with the bulk chemical analysis, and this loss is ascribed to the loss of surface P during thermal treatment of the catalysts. XPS narrow scan analysis of the reduced and passivated Rh-K-MoP-SiO2 catalyst is shown in Figure 6.2. The Mo3d spectrum of Figure 6.2a was de-convoluted using spin orbit splitting of 3.2 eV and three distinct Mo3d5/2 binding energies (BEs). The low BE peak (228 eV) was assigned to MoP [38,40] whereas the higher BEs correspond to Mo+5 and Mo+6 species that result from the passivation of the catalyst [40]. The P2p spectrum of Figure 6.2b was deconvoluted into two peaks with BE 133 eV assigned to phosphate species and BE 126.6 eV assigned to phosphide species [41]. Although the Rh narrow scan XPS profile had a relatively high signal-to-noise ratio, a Rh peak at 307.6 eV, corresponding to Rh0 species, and a peak at 313.2 eV, corresponding to Rh3+, were identified [41].  176  6.3.2  Comparison of catalysts:  Figure 6.3 compares the CO conversion measured at 548 K, 8.3 MPa and a H2:CO ratio of 1 over the 5 wt % K-10 wt % MoP/SiO2 and the 1 wt % Rh-5 wt % K-10 wt % MoP/SiO2 catalyst. A sharp decrease in activity was observed for the K-MoP-SiO2 catalyst at the beginning of the experiment, and similar behavior was reported previously for a series of catalysts with a range of MoP and K loadings on SiO2 [30]. However, with the addition of Rh, the activity of the catalysts stabilized, and the same catalyst stability was observed at 573 K and a correspondingly higher CO conversion.  Activity and selectivity data were averaged over the 20 - 60 h run time period following the initial 20 h stabilization period for MoP/SiO2 and K-MoP/SiO2 catalysts, and the 10-60 h run time period for the Rh-K-MoP/SiO2 catalyst, and these results are summarized in Table 6.3, comparing the MoP/SiO2 catalyst product distribution obtained from synthesis gas reacted at 548 K and 8.27 MPa to that from the 5 wt% K-10wt% MoP/SiO2 and the 1 wt% Rh-5 wt% K-10wt% MoP/SiO2 catalyst. Although there was a significant increase in CO2 selectivity with K addition to the MoP/SiO2 catalyst, addition of Rh to the K-MoP/SiO2 only increased the CO2 selectivity marginally, and this was in accord with an increase in selectivity to hydrocarbons that results in increased H2O as a by-product. The H2O reacts with CO via the water-gas-shift reaction to produce CO2 and H2. The addition of K to the MoP/SiO2 catalyst suppressed the selectivity to CH4 and increased selectivity to C2 oxygenates. The 5 wt % K10 wt % MoP/SiO2 catalyst, operated at 548 K and 8.27 MPa, had a CH4 selectivity of only 9.7 C atom % and a C2 oxygenate selectivity of 39.2 C atom %. A significant C3+ oxygenate selectivity (33.3 C atom %) was also obtained with a high selectivity towards acetone (14.1 C 177  atom %). In previous work, the 5 wt % K- 10 wt % MoP/SiO2 catalyst was shown to give the lowest CH4 and highest C2 oxygenate selectivity among a series of K-MoP/SiO2 catalysts [30]. At the same operating conditions, the present work shows that addition of 1 wt% Rh to the K-MoP/SiO2 catalyst increased the CO conversion from 8.4 to 9.7%. The selectivity to the undesired products, methane and other hydrocarbons, also increased (Table 6.3). A small decrease in the C2 oxygenate selectivity, increase in ethanol selectivity and decrease in acetaldehyde selectivity, and a decrease in the C3+ oxygenate selectivity, especially acetone, were also observed. The space-time yield (STY) of the C2 oxygenates also increased. With the Rh-K-MoP/SiO2 catalyst, the STY for C2 oxygenate was 66.6 mg.g cat.-1.h-1 compared to 60.7 mg.g cat.-1.h-1 for the 5 wt% K-10 wt% MoP/SiO2 catalyst [30]. By comparison the STY for ethanol on a supported MoS2 catalyst was 43 mg.g cat.-1.h-1 at 538 K, 10.5 MPa and H2:CO = 1.2 [18]. The product selectivity of different ethanol synthesis catalysts is reported in Table 6.4. Among the Mo based catalysts, MoS2 shows the highest selectivity to ethanol (23-40 C atom %) whereas the Rh-K-MoP/SiO2 had higher ethanol selectivity than the Mo2C catalyst. The Rh based catalysts show the highest selectivity toward ethanol but also produce considerable amounts of methane (> 20 C atom%) as a byproduct.  Overall, the present data show that addition of Rh to the K-MoP/SiO2 catalyst improved the stability of the catalyst compared to the K-MoP/SiO2 catalyst. However, the Rh increased the selectivity to hydrocarbon products, especially CH4, while only increasing the selectivity to ethanol marginally. The addition of Rh did not appear to completely hydrogenate the acetaldehyde to ethanol.  178  6.3.3  Activity and selectivity of Rh-K-MoP/SiO2 catalyst:  The Rh-K-MoP/SiO2 catalyst was evaluated at different reaction temperatures, in the range of 548 – 613 K, and with different H2:CO feed gas ratios of 1, 1.5 and 2. At each set of operating conditions, the catalyst weight in the reactor was adjusted so as to maintain approximately the same level of conversion at each set of conditions. This experimental procedure was followed so that the micro-reactor was operated at low conversion to ensure isothermal operation and to ensure that the observed kinetics were free of mass and heat transfer resistances.  The effect of temperature and H2:CO ratio on the product selectivity obtained over the Rh-KMoP-SiO2 catalyst is presented in Table 6.5, and these data show that for all conditions, the CO conversion was in the range of 10 - 25 %. With increased temperature, the methane and total hydrocarbon selectivity increased, whereas the acetone and C3+ oxygenate selectivity decreased. The variations in ethanol and acetaldehyde selectivity were limited because the data were collected over a narrow range of CO conversions. The acetaldehyde selectivity was in the range of 18.8 to 23.2 C atom % and the ethanol selectivity was in the range of 16.2 to 19.7 C atom %. Methanol selectivity increased with increase in temperature although in all the cases the methanol selectivity was below 2 C atom %. Low methanol selectivity is a unique characteristic of the MoP-based catalysts, as reported previously [30]. The CO2 selectivity (Table 6.4) showed a decreasing trend with increased temperature and increased H2/CO ratio. The trend was most pronounced at 325 oC. The WGS reaction [CO+H2O ↔ CO2 +H2, ∆Hr = -41.1 kJ/mol] shifted to the left as H2 partial pressure and/or temperature increased, leading to a decrease in CO2 selectivity. 179  Figure 6.4 shows the effect of temperature and H2:CO ratio on the STY of the C2 oxygenates and C2+ oxygenates. In all cases, the STY increased with an increase in temperature. At 275 and 300 oC there was a small increase in the C2 oxygenate and C2+ oxygenate STY with increased H2:CO ratio. At 325 and 340 oC, however, the reverse trend was observed. Both the C2 oxygenate and C2+ oxygenate STY decreased with increased H2:CO ratio. 6.3.4  Reaction kinetics  The space-time yield data of the various products generated in the present study represent the average rate of formation of each component in the reactor. However, since the conversion levels were kept low as the temperature and H2:CO ratio varied, and the H2 and CO partial pressures were relatively constant throughout the reactor bed (the maximum variation was ±5% in both cases), the space-time-yield data can be taken as an approximation of the intrinsic rate of formation of each of these compounds at the chosen reaction conditions. Hence, reaction kinetic parameters have been estimated from the STY data, reported in Table m 6.6, using simple power law kinetic models, r = kPCO PHn2 , where k is the reaction rate  constant and PCO and PH 2 are the partial pressure of CO and H2 raised to a power m and n respectively. The power law equation was applied to each of the major components: methane, ethanol, acetaldehyde and acetone. The unknown parameters m and n, were evaluated by fitting the model equation to the experimental rate data measured at 325oC, where the maximum number of data points (repeated experiments) was measured. The Marquardt-Levenberg optimization procedure was used to evaluate the parameters by N  minimizing the objective function S = ∑ (rexp − rmod )2 where rexp is the measured STY of the i =1  180  components of interest and rmod is the STY calculated from the power law model. The estimated m and n values were then held constant to determine the value of k at the other reaction temperatures. The activation energy E and frequency factor A were determined by −E fitting the rate constants to the Arrhenius equation, k = A exp   , by plotting ln k vs 1/T  RT   (Figure 6.5). The slope of the fitted line gave the activation energy and the intercept gave the frequency factor. The kinetic parameters for the four major products are reported in Table 6.7. A statistical analysis (F test) (Appendix AIII.10) was performed to confirm that the power law reaction rate models were statistically significant. Parity plots for methane, acetaldehyde, ethanol and acetone, shown in Fig 6.6 (a-d) confirmed the good fit between the experimental observations and the model calculations.  6.4  Discussion  The catalyst characterization data show that addition of Rh to the K-MoP/SiO2 catalyst decreased the catalyst total surface area and MoP dispersion. This suggests that the Rh was likely dispersed over the support as well as the MoP. The Rh:Si atom ratio as measured by XPS was 0.0026, compared to a nominal value of 0.0069, suggesting that the Rh was well dispersed.  However, the TPR and XPS data show that there was minimal chemical  interaction between the MoP and the Rh. The TPR profile of the MoP precursors was not affected by the addition of Rh and the TPR data showed that 100 % of the Rh precursor was reduced to Rh metal. In addition, the BEs of the Mo and P species on the Rh-K-MoP/SiO2 catalyst were similar (within the BE resolution capability of the instrument), to those reported previously for K-MoP/SiO2 catalysts [30]. Hence the catalyst characterization data suggest 181  that the Rh was well dispersed over the catalyst and that the interaction between Rh and the MoP was minimal. In previous work, it was shown that on K-MoP/SiO2 catalysts, both acetaldehyde and ethanol were the major C2 oxygenates in the product. The addition of Rh to the K-MoP/SiO2 catalyst was expected to enhance ethanol selectivity by hydrogenating the acetaldehyde to ethanol. However, the data of Table 6.3 showed that this did not occur to any great extent. Addition of Rh increased the selectivity to CH4 and other hydrocarbons and, to a much lesser extent, increased the selectivity to ethanol although a small decrease in C2 oxygenate was observed.  On MoP catalysts, CO is adsorbed non-dissociatively, similar to that which occurs on MoS2 [29]. DFT studies on an Mo6P3 cluster model of MoP [42] suggested that the reaction path for methane synthesis on MoP catalyst is: H2  CO →  H2  CHO  →  H2  CH 2 O →  and for methanol synthesis it is  H2  CH 2 OH  →  H2  CO →  H2  CH H2  CHO  →  2  + H 2O →  CH  3  H2  CH 2 O →  + H 2O  H2  →  CH  CH 3 OH  .  H2  CH 2 OH  →  4  + H 2O  The most  stable surface species are COad, CHOad, CH2Oad and CH2OHad. The C-O bond breaks at the hydrogenation step when Had is added to the O of the hydroxymethyl (CH2OHad) species, forming CH2.ad and H2O.ad on the surface. The DFT study also showed that addition of alkali promoter, i.e. K, decreases the activation energy required for C-O bond dissociation and leads to the formation of geminal-carbon (-CH2-) species on the surface [43], which are very active surface species that participate in CO insertion reactions or other C-C bond forming reactions with other surface species. The increase in hydrocarbon selectivity observed upon Rh addition to the K-MoP/SiO2 catalyst suggests that the Rh hydrogenates adsorbed (-CH2-)n species to produce methane or higher hydrocarbons and these species likely reside on Rh but  182  may also migrate to the Rh from the MoP. However, the low selectivity to hydrocarbons obtained over K-MoP/SiO2 catalysts suggests that there are relatively few of these species on the MoP catalyst. On the other hand, the fact that the acetaldehyde and ethanol selectvities increased only marginally with addition of Rh to the K-MoP/SiO2 catalysts is indicative of oxygenated surface species, mostly on the K-MoP catalyst that do not migrate to Rh, and hence do not undergo hydrogenation.  The product selectivity from CO hydrogenation reported over other Rh and Mo catalysts is compared in Table 6.4. The MoP catalyst of the present work showed higher selectivity to ethanol compared to Mo2C and MoP gave higher C2 oxygenate selectivity than the Mo and Co based catalysts. However, Rh catalysts are superior to all others in terms of ethanol selectivity, but have significant selectivity to hydrocarbons, especially methane. The MoP catalysts of the present work are promising for syngas to oxygenate conversion in view of their relatively low hydrocarbon selectivity. Finally, in most other alcohol synthesis catalysts, (MoS2, Mo2C, Cs-Cu-ZnO, modified FT catalysts) methanol is the major or second major liquid product [1, 2]; whereas on the MoP catalyst, methanol selectivity was the lowest among the C1 – C3 oxygenated products. A low selectivity to methanol also occurs on Rh based catalysts [10,12,14,15,33,44,45].  The kinetic parameters obtained for the Rh-K-MoP/SiO2 catalyst showed very similar kinetic parameters for the formation of ethanol and acetaldehyde, suggesting that a common intermediate is involved in the kinetic steps leading to these products. Based on DFT results and previous publications [15,16,42,43], C2 oxygenate formation can be postulated to occur  183  by the following mechanism where a common enol surface reaction intermediate is formed via CH2 insertion to stable surface species, CO, CHO, CH2O, CH2OH:  CH 2 + CO →  H2 CH 2CO → CH 2CHOH (enol)  CH 2 + CHO →  CH2 + CH2O → CH2 + CH2OH →  H2 CH 2CHO → CH 2CHOH (enol)  CH2CH2O (enolate) CH2CH2OH  The enol species can be further hydrogenated to ethanol or acetaldehyde. Most kinetic models for Rh based ethanol synthesis catalysts favour a mechanism in which ethanol is produced by the secondary hydrogenation of acetaldehyde, and assume that ethanol and acetaldehyde are formed through a common pathway. For the present catalyst, a different mechanism of reaction appears to be operating. Acetaldehyde was not hydrogenated to ethanol as the H2:CO ratio increased and both acetaldehyde and ethanol were significant products over the Rh-K-MoP/SiO2 catalyst. The MoP does not show the hydrogenation ability to convert acetaldehyde to ethanol that is apparent on Rh catalysts.  The activation energy for methane formation reported on a Rh-CeO2/SiO2 [14] catalyst is 92.5 kJ/mol, for a 1%Rh/SiO2 catalyst [14] a value of 94.6 kJ/mol has been reported and on 1%Rh/ZrO2 [44,45] catalyst the value is 134.6 kJ/mol. The Rh-K-MoP/SiO2 catalyst of the present study has an activation energy of 100.8 kJ/mol for the formation of methane. The relatively similar values of the activation energies for methane formation suggest that on the Rh-K-MoP/SiO2 catalyst, methane forms mainly on the Rh surface. For ethanol formation the activation energy is 49.4 kJ/mol on Rh-CeO2/SiO2, 66.5 kJ/mol on 1%Rh/ZrO2, 70.12 kJ/mol 184  on Mo2C [25] and 24.9 kJ/mol on MoS2 [27] catalyst. On the Rh-K-MoP/SiO2 catalyst the activation energy is significantly higher at 87.8 kJ/mol, suggesting that ethanol and other oxygenates are mainly formed on the K-MoP species of this catalyst than on the Rh species.  The point selectivity (ratio of the rate of desired product to the rate of undesired product) for ethanol and acetaldehyde compared to the undesired product methane can be expressed by equation (i) and (ii). Hence, an increase in CO partial pressure will increase the ethanol and acetaldehyde selectivity marginally, whereas increased H2 partial pressure will reduce both the ethanol and acetaldehyde selectivity.  S=  S=  rEtOH 0.13 −0.60 = kPCO PH2 rCH4  rCH3CHO rCH4  0.08 −0.57 = kPCO PH2  (i)  (ii)  Note also that the methane selectivity increased significantly with increased temperature since Table 6.5 shows that the apparent activation energy for methane formation is greater than that of ethanol and acetaldehyde. A negative effect of hydrogen partial pressure on C2 oxygenate selectivity compared to methane was also reported for Rh/SiO2-CeO2 [14] and Rh/ZrO2 [45,46] catalysts.  185  6.5  Conclusions  The MoP catalysts showed a distinct product distribution compared to other Mo-based catalysts for syngas conversion. Low selectivity to methanol and moderate selectivity to a mixture of C2 oxygenates (acetaldehyde, ethanol and acetic acid) were achieved on the KMoP-SiO2 and the Rh-K-MoP/SiO2 catalysts. Addition of Rh to the K-MoP/SiO2 catalyst improved the stability of the catalyst compared to the K-MoP/SiO2 catalyst. However, the Rh increased the selectivity to hydrocarbon products, especially CH4, while only increasing the selectivity to ethanol marginally. The oxygenated products are mainly produced on K-MoP surface. Power law kinetic models were developed to describe the dependence of STY on temperature and H2 and CO partial pressure for methane, acetaldehyde, ethanol and acetone. The kinetic study suggested a common reaction intermediate for ethanol and acetaldehyde. Hydrogenation of acetaldehyde to ethanol did not occur even in the presence of the Rh. The kinetic data also suggested that formation of oxygenated products would increase at a syngas ratio less than one.  6.6  Acknowledgements  Financial support from the Natural Science and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.  186  Table 6.1:  Composition of MoP catalysts after reduction and passivation  Nominal  Measured - ICP-MS  Measured - EDX  wt %  wt %  wt %  - MoP  10  8.3*  7.8*  - SiO2  90  91.7  92.7  - Mo:P  1.00  1.02  0.70  - K2O  5  5.5  5.8  - MoP  10  10.6*  8.5*  - SiO2  85  83.9  85.6  - Mo:P  1.00  1.10  0.72  - Rh  1  0.85  1.28  - K2O  5  5.0  6.1  - MoP  10  9.4*  9.6*  - SiO2  84  84.8  83.0  - Mo:P  1.00  1.04  0.75  MoP/SiO2  K-MoP/SiO2  Rh-K-MoP/SiO2  * - based on the Mo analysis  187  Table 6.2:  BET area and surface composition of catalysts as determined by XPS  Catalyst  MoP/SiO2  K-MoP/SiO2  Rh-K-MoP/SiO2  BET area, m2/g  263  64  56  BET area after reaction, m2/g  181  6  24  Rh:Si  -  -  0.0026  K:Si  -  0.099  0.084  Mo:Si  0.027  0.028  0.019  P:Si  0.024  0.022  0.016  Mo:P  1.13  1.29  1.20  Surface composition, mole ratio  188  Table 6.3:  Effect of promoters on synthesis gas conversion over MoP/SiO2 catalysts  Catalyst  10%MoP/SiO2 5%K-10%MoP/SiO2 1%Rh-5%K-10%MoP/SiO2  Temperature, °C  275  275  275  GHSV, h-1  3960  3960  3960  H2:CO  1.0  1.0  1.0  CO conversion, %  2.8  8.4  9.7  12.1  60.7  66.7  20.4  112.9  115.1  24.1  44.9  45.0  HC  57.3  23.4  34.9  CH4  32.5  9.7  11.7  Methanol  0.5  4.1  0.7  Acetaldehyde  19.1  20.5  18.8  Ethanol  4.4  15.3  16.2  Acetone  13.8  14.1  5.3  Total C2 oxygenate  24.0  39.2  37.0  Total C3+ oxygenate  18.3  33.3  27.3  STY C2oxygenates, g/(kg cat.h) STY total oxygenates, g/(kg cat.h) SCO2 Selectivity, C atom %  189  Table 6.4:  Product selectivity of syngas conversion over some reported ethanol synthesis catalysts  Catalyst  Temp [Co]  H2:CO  Pressure GHSV % CO Conversion [MPa] [h-1]  Rh-KMoP/SiO2  325  1.0  8.3  15840  13.9  MoS2  295  1.0  7.2  1300  K-RhMoS2/Al2O3  327  2.0  10.0  315  2.0  320  SCO2  Selectivity (C atom %)  Ref.  HC  CH4  MeOH  EtOH  ∑C2Oxy  ∑C2+Oxy  46.0  38.7  16.8  1.5  19.7  43.9  16.0  This work  29.2  NA  14.4  -  22.7  40.7  40.7†  17.4  [18]  14400  5.5  NA  17.0  -  26.0  28.0  28.0†  28.0  [23]  9.7  6000  17.8  NA  18.2  NA  45.8  32.9  32.9†  29.4  [21]  1.1  13.0  4000  31.9  NA  36.0  -  13.5  23.1  23.1†  21.6  [20]  300  1.0  11.6  2000  36.7  NA  63.4  -  11.3  13.9  13.9†  24.0  [46]  1%Rh/ZrO2  220  1.0  0.1  NA  2.0  2.3  31.5  -  15.4  50.8  50.8†  NA  [44]  Rh-Mn-SiO2  280  2.0  5.4  3750  24.6  0.0  38.4  38.4  3.9  56.1  56.1†  1.6  [11]  Ni/K/Mn/ MoS2 K-CoMoS2/Clay K-CoβMo2C  SCO2 = Carbon atom % selectivity to carbon dioxide. AcH = Acetaldehyde; ΣC2 oxy = Sum of acetaldehyde, ethanol and acetic acid; C2+oxy = Acetone, Propanol, Butanol, Propionic acid, Methyl acetate, Ethyl acetate; NA = data not available; STY = space time yield. † = Only selectivity of ethanol is reported  190  Table 6.5:  Temp, °C  Product selectivity of syngas conversion over 1%Rh-5%K-10%MoP/SiO2 catalyst  H2:CO  Selectivity (C atom %)  % CO Conv.  SCO2  HC  CH4 MeOH AcH EtOH Acetone C2Oxy C3+Oxy  ∑C2Oxy STY [g/kg cat/h]  Total Oxy. STY [g/kg cat/h]  275 [GHSV = 3,960 h-1]  1.0  9.7  45.0  34.9  11.7  0.7  18.8  16.2  5.3  37.0  27.3  66.6  115.1  2.0  18.0  44.3  31.8  14.0  0.8  20.4  18.9  9.6  40.9  26.4  88.26  144.3  300 [GHSV=7,9 20 h-1]  1.0  13.6  46.6  33.9  13.3  1.2  19.8  19.4  8.9  40.7  24.1  201.9  321.3  1.5  15.6  45.3  35.4  14.9  1.2  20.8  18.3  10.1  40.7  22.6  202.9  314.5  2.0  22.2  43.2  33.8  14.6  1.3  19.5  17.0  11.2  38.4  26.5  204.9  344.9  1.0  13.9  46.0  38.7  16.8  1.5  23.3  19.7  4.7  43.9  16.0  466.7  650.8  1.5  16.9  44.3  38.5  17.6  1.2  20.0  17.6  8.3  39.4  20.8  426.5  635.2  2.0  21.3  43.0  38.3  18.8  1.2  21.0  17.7  7.7  40.1  20.4  409.6  617.9  325 [GHSV=15, 840 h-1]  340 1.0 19.7 45.2 39.6 18.0 1.8 22.2 19.8 4.9 42.8 15.9 608.9 856.0 [GHSV=15, 2.0 25.0 42.0 42.4 21.1 1.9 23.3 18.7 3.3 42.8 13.0 506.7 683.9 840 h-1] SCO2 = Carbon atom % selectivity to carbon dioxide. AcH = Acetaldehyde; ΣC2 oxy = Sum of acetaldehyde, ethanol and acetic acid; C2+oxy = Acetone, Propanol, Butanol, Propionic acid, Methyl acetate, Ethyl acetate; NA = data not available; STY = space time yield.  191  Table 6.6:  Experimental rate of major product components  Temperature [oC] 275 oC  300 oC  325 oC  340 oC  H2:CO  Reaction rate (µmole.g cat-1.h-1) CH4  CH3CHO  EtOH  Acetone  1.0  901  722  621  136  2.0  1330  971  895  302  1.0  2890  2150  2110  638  1.5  3260  2270  2000  736  2.0  3410  2280  1990  872  1.0  7900  5480  4630  735  1.5  8410  4760  4360  1350  2  8470  4710  3970  559  1.0  11300  6980  6220  1030  2.0  11100  6110  4900  570  192  Table 6.7:  Power law rate parameters for major products and F test statistical analysis ா  ௠ ௡ Power law rate expression, ‫ ݎ‬ൌ ‫ ݌ݔ݁ ܣ‬ቀെ ቁ ܲ஼ை ܲுమ ோ்  Major Products  Power law exponents  Activation energy, E  Preexponential factor, A  Statistical analysis Variance  DOF  Fstat  m  n  kJ/mol  [(mol)1-m-n(L)m+n1 .(s)-1]  Exp.  Power Model  Exp  Power Model  Calc.  CH4  0.56  1.03  100.8  1.85 x 102  4.57 x10-7  3.53 x10-7  4  6  0.32  CH3CHO  0.64  0.46  89.45  2.75 x 102  1.72 x10-5  8.44 x10-8  4  6  1.98  EtOH  0.68  0.43  87.78  1.69 x 102  2.26 x10-5  8.77 x10-8  4  6  1.99  Acetone  -0.27  0.99  97.92  2.98 x 103  6.72 x10-5  1.26 x10-8  4  6  2.00  Table  6.94  193  1100 1000 900 800 700 5%K-10%MoP/SiO2  600 500 1%Rh-5%K-10%MoP/SiO2  0  50  100  150  200  400 300 250  Time (min)  Figure 6.1:  TPR profile of MoP/SiO2, K-MoP/SiO2 and Rh-K-MoP/SiO2 catalyst.  194  Temperature, K  H2 consumption, au  10%MoP/SiO2  15500  15000  Intensity, au  Intensity, au  22000  20000  14500  14000  13500  18000 242  240  238  236  234  232  230  228  226  13000 138  224  136  134  132  130  128  126  124  122  B.E.(eV)  B.E.(eV)  (b) P 2p convolution  (a) Mo 3d convolution 21200 21000  Intensity, au  20800 20600 20400 20200 20000 19800 318  316  314  312  310  308  306  304  302  300  B.E. (eV)  (c) Rh 3d convolution Figure 6.2:  XPS plots for fresh Rh-K-MoP catalyst.  195  0.15 Rh-K-MoP at 573 K  Fractional CO Conversion  0.14 0.13 0.12 0.11  Rh-K-MoP at 548 K  0.10 0.09 0.08  K-MoP at 548 K  0.07 0.06 0  10  20  30  40  50  60  Time [h]  Figure 6.3 :  Comparison between K-MoP and Rh-K-MoP catalyst activity for syngas conversion with time at syngas ratio H2:CO =1 and pressure 8.27 MPa.  196  900  C + Oxygenates  800  C2 Oxygenates  2  STY, g/(kg cat.h)  700 600 500 400 300 200 100 1.0  1.5  H2/CO Ratio  Figure 6.4:  2.0  1.0  1.5  2.0  H2/CO Ratio  Space-time-yield of oxygenates over Rh-K-MoP catalyst as a function of H2/CO ratio reported for 275 °C (▼), 300°C (▲) 325 °C (●) and 340 °C (■).  197  Acetaldehyde 1.E-05  89.5 kJ/mol  Reaction rate constant, k  Acetone  1.E-06  97.9 kJ/mol  Ethanol 87.8 kJ/mol  1.E-07  Methane 100.8 kJ/mol  1.E-08 1.60E-03 1.65E-03 1.70E-03 1.75E-03 1.80E-03 1.85E-03  1/T (K-1) Figure 6.5: Arrhenius plot for methane (♦), acetaldehyde (▲), ethanol (●) and acetone (■).  198  Calculated Rate [mol CH4/g cat./h]  0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 0  0.002  0.004 0.006 0.008 0.01 0.012 Experimental Rate [mol CH4/g cat./h]  0.014  Figure 6.6a.: Parity plot for methane.  199  -3  Calculated Rate[mol CH CHO/g cat./h] 3  8  x 10  7 6 5 4 3 2 1 0 0  1  2 3 4 5 6 7 8 -3 Experimental Rate[mol CH3CHO/g cat./h] x 10  Figure 6.6b.: Parity plot for acetaldehyde.  200  -3  x 10 7  Calculated Rate [mol EtOH/g cat./h]  6  5  4  3  2  1  0 0  1  2 3 4 5 Experimental Rate [mol EtOH/g cat./h]  6  7 -3  x 10  Figure 6.6c.: Parity plot for ethanol.  201  -3  Calculated Rate [mol CH3COCH3/g cat./h]  1.6  x 10  1.4 1.2 1 0.8 0.6 0.4 0.2 0 0  0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Experimental Rate [mol CH3COCH3/g cat./h] x 10-3  Figure 6.6d.: Parity plot for acetone.  202  6.7  References  [1]  Velu S., Santosh K. 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Higher alcohol synthesis over a La promoted Ni/K2CO3/MoS2 catalyst, Catalysis Communication, 2004, 5(10), 605609.  [23]  Li Z., Fu Y., Jiang M., Structures and performance of Rh–Mo–K/Al2O3 catalysts used for mixed alcohol synthesis from synthesis gas, Applied Catalysis A: General, 1999, 187(2), 187-198.  [24]  Xiang M., Li D., Li W., Zhong B., Sun Y., Performances of mixed alcohols synthesis over potassium promoted molybdenum carbides, Fuel, 2006, 85(17-18), 2662-2665.  [25]  Xiang M., Li D., Xiao H., Zhang J., Qi H., Li W., et al., Synthesis of higher alcohols from syngas over Fischer–Tropsch elements modified K/β-Mo2C catalysts, Fuel 2008, 87(4-5), 599-603.  204  [26]  Smith K. J., Herman R. G., Klier K., Kinetic modelling of higher alcohol synthesis over alkali-promoted Cu/ZnO and MoS2 catalysts, Chemical Engineering Science, 1990, 45(8), 2639-2646.  [27]  Gunturu A., K., Kugler, L. E., Cropley, J. B., Dadyburjor, B. D., A kinetic model for the synthesis of high molecular weight alcohols over a sulfided Co-K-Mo/C catalyst. Industrial Engineering and Chemistry Research, 1998, 37, 2107-2115.  [28]  Park T. Y., Nam I. S., Kim Y. G., Kinetic Analysis of Mixed Alcohol Synthesis from Syngas over K/MoS2 Catalyst, Industrial Engineering and Chemistry Research, 1997, 36(12), 5246-5257.  [29]  Shi X., Jiao H., Hermann K., Wang J., CO hydrogenation reaction on sulfided molybdenum catalysts, Journal of Molecular Catalysis A: Chemical, 2009, 312(1-2), 7-17.  [30]  Zaman S. F, Smith K. J., A study of K promoted MoP-SiO2 catalysts for synthesis gas conversion, Applied Catalysis A: General, 2009, Submitted Manuscript.  [31]  Clark P. A., Oyama S. T., Alumina-supported molybdenum hydroprocessing catalysts, Journal of Catalysis, 2003, 218(1), 78-87.  [32]  Zuzaniuk V., Prins R., Synthesis and characterization of silica-supported transitionmetal phosphides as HDN catalysts, Journal of Catalysis, 2003, 219(1), 85-96.  [33]  Thomas R., Moulijn J. A., De Beer V. H. J., Medema J., Structure/metathesis activity relations of silica supported molybdenum and tungsten oxide, Journal of Molecular Catalysis, 1980, 8(1-3), 161-174.  [34]  Trevino, H., Lei, G.-D., Sachtler W. M. H., CO hydrogenation to higher oxygenates over promoted Rhodium: Nature of the metal-promoter interaction in RhMn/NaY, Journal of Catalysis, 1995, 154, 245-252.  [35]  Huang L., Chu W., Hong J., Luo S., Effect of carbon nanotubes on activity of Rh-CeMn/SiO2 catalyst for CO hydrogenation to oxygenates, Chinese Journal of Catalysis, 2006, 27(7), 596-600.  [36]  Stinner C., Prins R., Weber T., Formation, structure, and HDN activity of unsupported molybdenum phosphide. Journal of Catalysis 2000 4/25;191(2):438-44.  [37]  Stinner C, Prins R, Weber T., Binary and ternary transition-metal phosphides as HDN catalysts, Journal of Catalysis 2001, 202(1), 187-94.  [38]  Abu I. I., Smith K. J., The effect of cobalt addition to bulk MoP and Ni2P catalysts for the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Journal of Catalysis, 2006, 241(2), 356-366.  phosphide  205  [39]  Abu I. I., Smith K. J., HDN and HDS of model compounds and light gas oil derived from Athabasca bitumen using supported metal phosphide catalysts, Applied Catalysis A: General, 2007, 328(1), 58-67.  [40]  Phillips D. C., Sawhill S. J., Self R., Bussell M. E., Synthesis, characterization, and hydrodesulfurization properties of silica-supported molybdenum phosphide catalysts, Journal of Catalysis, 2002, 207(2), 266-273.  [41]  Ghori D.K., Sanyal R. M., Sen, B., Ghosh, S. K., Banerji K. C., Shpiro E. S., Minachev K. M., Studies on the SMSI of Rh/ZnO by XPS and XAES and its effect on CO-H2 reaction, Reaction Kinetics and Catalysis Letters, 1989, 40(2), 259-267.  [42]  Zaman S. F., Smith K. J., A study of synthesis gas conversion to methane and methanol over a Mo6P3 cluster using density functional theory. Molecular Simulation, 2008, 34(10), 1073-1084.  [43]  Zaman S. F., Smith K. J., A DFT study of the effect of K over MoP-SiO2 cluster for syngas conversion, Molecular Simulation, 2009; Accepted Manuscript doi: 10.1080/08927020903124585.  [44]  Solymosi F., Pasztor M., Infrared study of the effect of hydrogen on carbon monoxide-induced structural changes in supported rhodium, Journal of Physical Chemistry, 1986, 90(21), 5312-5317.  [45]  Solymosi F., Pasztor M., An infrared study of the influence of carbon monoxide chemisorption on the topology of supported rhodium, Journal of Physical Chemistry, 1985, 89(22), 4789-4793.  [46]  Xiang M., Li D., Li W., Zhong B., Sun Y, Synthesis of higher alcohols from syngas over K/Co/β-Mo2C catalysts, Catalysis Communications, 2007, 8(3), 503-507.  206  Chapter 7 Conclusions and recommendations  207  7.1 Conclusions  Syngas conversion to higher oxygenates (i.e. ethanol and acetaldehyde) over MoP catalysts has been studied using both experimental and molecular simulation (DFT) methods.  A Mo6P3 cluster model, representative of the (100) face of MoP, had similar adsorption energies for CO and CH3OH compared to MoP. A DFT study of CH4 and CH3OH formation over the Mo6P3 cluster showed that hydroxymethyl (CH2OH) is a common surface intermediate for both CH4 and CH3OH formation. However, the energy barrier for CH3OH formation from CH2OH was significantly higher than for the formation of methylene (CH2) and water that leads to CH4. The DFT study has shown, for the first time that the formation of methanol on MoP follows the route CO methane formation follows the route CO  CHO CHO  CH2O CH2O  CH2OH CH2OH  CH3OH and CH2  CH3  CH4. Recent DFT simulation studies have shown the similar pathway for methane formation over MoS2 catalyst [1].  The Mo6P3 cluster model was modified to investigate the effect of SiO2 and K on C-O bond breaking and methanol formation from CH2OH. The model predicted that, although adding K and SiO2 to MoP decreased the activation energy for methanol formation, it was higher than the activation energy for C-O bond scission and hence, K-MoP-SiO2 will still be expected to produce CH4 more selectively than CH3OH. Geminal carbon species was formed on the modified cluster structures upon C-O bond dissociation and this very active surface species can react with adsorbed CO and form C-C bonds. Also, higher adsorption energy of methanol  208  on MoP compared to Cu [2], Pd [3], Ni [4], Pt [5] and Mo2C [6] catalysts indicated the possibility of a homologation reaction to form higher oxygenates on the MoP catalyst.  In the experimental work, MoP was prepared with different loading of MoP (5, 10, 15 wt %) and K (0, 1, 5 wt%) on SiO2 and tested for syngas conversion at 8.27 MPa, 548 K and 3960 hr-1 GHSV. It was found that CO conversion was a function of both the Mo and K loading. CO conversion increased with an increase in surface Mo/Si ratio, but there was a maximum in CO conversion at a surface K/Mo ratio of 2. The increase in CO conversion was due to the increase in C2+ oxygenates production. The K/Mo ratio mainly affected the selectivity to CH4 and C2+ oxygenates. There was a maxima in C2+ oxygenate selectivity (72.5 C atom %) and a minimum in CH4 selectivity (9.7 C atom %) at a surface K/Mo ratio of 3. The major liquid oxygenates were acetaldehyde, ethanol and acetaldehyde. Methanol was produced in very small amounts, < 5 C atom % selectivity in all cases. MoP showed a distinct product distribution compared to other Mo based alcohol synthesis catalysts (i.e. MoS2 [7-11], Mo2C [12-14]), where liquid products were mainly linear alcohols with methanol selectivity > 10 C atom % and ethanol had the highest or second highest selectivity among the alcohols.  Addition of Rh to the K-MoP/SiO2 catalyst was shown to improve the catalyst stability compared to the K-MoP/SiO2 catalyst. However, the Rh increased the selectivity to hydrocarbon products, especially CH4, while only increasing the selectivity to ethanol marginally. The oxygenated products were mainly produced on the K-MoP surface. A power law kinetic model was developed to describe the dependence of STY on temperature and H2 and CO partial pressure for each of methane, acetaldehyde, ethanol and acetone. The kinetic  209  study suggested a common reaction intermediate for ethanol and acetaldehyde. Hydrogenation of acetaldehyde to ethanol did not occur even in the presence of Rh.  The DFT study of the present work predicted the formation of CH4 rather CH3OH over MoP. Addition of SiO2 and K promoter suppressed the formation of CH4 but CH4 remained the preferred product compared to CH3OH. Formation of geminal carbon (CH2) species on the K-MoP-SiO2 cluster suggested the formation of higher oxygenates. Experimentally, the study had also shown that over MoP, methanol was produced in very small amounts, a special characteristic of MoP catalysts for syngas conversion. MoP produced CH4 with high selectivity (35 C atom %) when it was not promoted with K. Addition of K suppressed the formation of CH4 and increased the liquid oxygenate selectivity. The DFT study is in good agreement with the experimental results, which supported the claim that DFT simulation can be used to identify new catalyst formulations for a desired reaction without experimental investigation.  MoP is a novel, promising catalyst for syngas conversion to alcohols showing low selectivity towards CH4 (9.7 C atom %) and high selectivity towards liquid oxygenates (76.5 C atom %), although MoP does not have sufficient hydrogenation capability to convert acetaldehyde to ethanol, even in the presence of Rh. More research is required to improve the performance of MoP for selective ethanol synthesis from syngas.  210  7.2 Recommendations  (1)  Investigation of MoP catalyst doped with transition metals:  In the present work, addition of Rh to MoP increased capability of the production of hydrocarbons, especially methane. Addition of other transition metals, i.e. Ni, Co, Fe, Cu, Mn, with lesser hydrogenation abilities to hydrocarbons than Rh, may enhance the production of liquid oxygenates and the hydrogenation of acetaldehyde to ethanol. (2)  Investigation of MoP catalyst doped with alkali metals:  An investigation of MoP catalyst doped with different alkali metals with higher basicity than K, such as Cs, needs to be investigated. Higher basicity of the alkali promoter may enhance the production of liquid oxygenates. (3)  Investigation of the effect of CO2 in the syngas for higher oxygenates synthesis:  On MoP the main product of syngas hydrogenation was CO2 (>40 C atom%) due to the high propensity of the WGS reaction on Mo. Addition of CO2 in the feed may suppress the WGS reaction, which could reduce the CO2 emission. It may also affect the product distribution. No detailed work has been reported for Mo catalysts on different CO2 concentrations in the feed stream. (3)  DFT study of C-C bond formation over MoP catalyst:  The mechanism of the C-C bond formation over MoP catalyst will reveal the distinct behavior of MoP catalyst for the synthesis of C2 oxygenates from syngas. In the present study  211  we have considered a small MoP cluster to simulate the formation of CH4 and CH3OH. This cluster does not have sufficient Mo sites to model C-C coupling. In the future work a large cluster system should be built to simulate the C-C coupling reaction, which will require more computational power and software licenses. (4)  Investigation of other Mo based catalysts:  A DFT study of other Mo based catalysts (MoB2 and Mo2N) for syngas hydrogenation to higher alcohols should be continued. MoB2 and Mo2N have been reported to have high hydrogenation activity for HDS and HDN and may show better CO hydrogenation properties compared to existing Mo based alcohol synthesis catalysts. These catalysts should also be evaluated for syngas conversion after promotion with suitable alkali metals.  212  7.3  References  [1]  Shi X., Jiao H., Hermann K., Wang J., CO hydrogenation reaction on sulfided molybdenum catalysts, Journal of Molecular Catalysis A: Chemical, 2009, 312 (12),7-17.  [2]  Greeley J., Mavrikakis M., Methanol Decomposition on Cu(111): A DFT Study, Journal of Catalysis, 2002, 208 (2), 291-300.  [3]  Neurock M., First-principles analysis of the hydrogenation of carbon monoxide over palladium, Topics in Catalysis, 1999, 9 (3-4), 135-52.  [4]  Remediakis I. N., Abild-Pedersen F., Norskov J.K., DFT study of formaldehyde and methanol synthesis from CO and H2 on Ni(111), Journal of Physical Chemistry, B, 2004, 108 (38), 14535-40.  [5]  Kandoi S., Greeley J., Sanchez-Castillo A.M., Evans S.T., Gokhale A.A., Dumesic J.A., Mavrikakis M., Prediction of experimental methanol decomposition rates on platinum from first principles, Topics in. Catalysis,2006, 37 (12), 17-28.  [6]  Pistonesi C., Juan A., Farkas A.P., Solymosi F., DFT study of methanol adsorption and dissociation on β-Mo2C(0 0 1), Surface Science, 2008, 602 (13), 2206-11.  [7]  Quarderer, Q. J., Cochram, G. A., PCT Publication No WO84/03696, 1984.  [8]  Li Z., Fu Y., Jiang M., Structures and performance of Rh–Mo–K/Al2O3 catalysts used for mixed alcohol synthesis from synthesis gas, Applied Catalysis A: General, 1999, 187(2), 187-198.  [9]  Iranmahboob J., Donald O. H., Hossein T., K2CO3/Co-MoS2/clay catalyst for synthesis of alcohol: influence of potassium and cobalt, Applied Catalysis A: General, 2002, 231(1-2), 99-108.  [10]  Li D., Yang C., Qi H., Zhang H., Li W., Sun Y., et al., Higher alcohol synthesis over a La promoted Ni/K2CO3/MoS2 catalyst, Catalysis Communication, 2004, 5(10), 605-609.  [11]  Li X., Feng L., Liu Z., Zhong B., Dadyburjor D. B., Kugler E. L., Higher alcohols from synthesis gas using carbon-supported doped molybdenum-based catalysts, Industrial Engineering and Chemistry Research, 1998, 37(10), 3853-3863.  [12]  Xiang M., Li D., Li W., Zhong B., Sun Y., Synthesis of Higher Alcohols from Syngas over K/Co/β-Mo2C Catalysts, Catalysis Communications, 2007, 8(3), 503-7.  213  [13]  Xiang M., Li D., Li W., Zhong B., Sun Y., Potassium and Nickel Doped β-Mo2C Catalysts for Mixed Alcohols Synthesis via Syngas, Catalysis Communications, 2007, 8(3), 513-8.  [14]  Xiang M., Li D., Xiao H., Zhang J., Qi H., Li W., et al., Synthesis of Higher Alcohols from Syngas over Fischer–Tropsch Elements Modified K/β-Mo2C Catalysts, Fuel 2008, 87(4-5), 599-603.  214  Appendix I Quantum chemistry  215  Quantum Chemistry: Derivation of the Hamiltonian operator  ∂2 y 1 ∂2 y  The wave equation  2 = 2 2  , written for a standing wave, with one end fixed as with a v ∂t   ∂x vibrating string is  d 2 f (x ) dx 2  =−  4π 2  λ2  f ( x ) ------ (1)  where, f(x) = amplitude of the wave x = distance from some chosen origin λ = wavelength =  h (using deBroglie’s equation) mv  m = mass of the particle v = velocity of particle h = Plank’s constant, 6.626x10-34 Js Equation (1) can be written as  d 2 f (x ) dx 2  =−  4π 2 m 2v 2 h2  f (x )  The total energy of the particle is the sum of the kinetic energy and potential energy.  E Kinetic = ETotal − E Potential 1 2 mv = E − V 2 The wave equation now becomes  d 2 f (x ) dx 2  =−  8π 2m h2  (E − V ) f ( x )  This is the Schrödinger equation (time independent) for one-dimensional (1D) motion along the spatial co-ordinate x. It is usually written  216  d 2ψ dx 2  +  8π 2 m h2  (E − V )ψ  =0  where ψ is the amplitude of the particle/wave at a distance x from some chosen origin. Rearranging the equation we get   h 2  d 2ψ  − + Vψ = Eψ  8π 2 m  dx 2   The one-dimensional Schrödinger equation can easily be elevated to three-dimensions by replacing the 1D operator by a 3D operator:  ∂2 ∂x  2  +  ∂2 ∂y  2  +  ∂2 ∂z  2  = ∇2  The three dimensional form of the Schrödinger equation is   h2  2 ∇ ψ + Vψ = Eψ −  8π 2 m    The Schrödinger equation relates the amplitude ψ of the particle wave to the mass of the particle, its total energy E and its potential energy V. Let us think of a system consisting of N electrons and M nuclei. The kinetic energy of electrons is expressed by the Laplacian operator term of ‫׏‬ଶ . For a single atomic system the nucleus is fixed in space and the kinetic energy is ignored. But for a large molecular system with atoms of different species, we may need to consider the kinetic energy term of the nuclei.   h2  N  h2  M EKinetic−electron = − 2 ∑∇2 and EKinetic−nucleus = − 2 ∑∇2  8π me  i=1  8π mn  i=1 The potential energy for a system composed of N electrons and M nuclei is composed of:  217  (1) Mutual potential energy of the nucleus (of charge +Ze) electron (charge -e) interaction. This will be an attractive force between two oppositely charged bodies. The potential energy between two charged bodies is given by Coulomb’s law  -e  2  U nucleus−electron = −  e N M Zα ∑ ∑ 4πεo i =1α =1 ri  εo = Permittivity of free space, 8.854x10-12 C2N-1m-2  r +Ze  ri = Distance of electron from the nucleus This equation represents the work done in bringing one of the charged particles from infinity up to a point distance r from the other. (2) Mutual potential energy of the electron-electron interaction (charge –e), a repulsive interaction:  U electron−electron =  e 2 N −1 N 1 ∑ ∑ 4πε o i =1 j =i +1 rij  (3) Mutual potential energy of the nucleus-nucleus interactions (charge +Ze), a repulsive interaction:  U nucleus− nucleus =  e 2 M −1 M ∑ ∑  Zα Z β  4πε o α =1 β =α +1 Rαβ  Quantum mechanical expression for an electronic system can be written in a simpler way using atomic units. Let’s take Plank’s constant, the electron mass, the proton charge and the permittivity of space as the building blocks of a system of units in which h/2π, m, e, 4πε0 are numerically set equal to 1. The Schrödinger equation becomes   1 N 2 1 M 2 N M Zα N −1 N 1 M −1 M Zα Z β − ∑∇ − ∑∇ − ∑ ∑ + ∑ ∑ + ∑ ∑  2 i =1 2 i =1 i =1α =1 ri i =1 j =i +1 rij α =1 β =α +1 Rαβ    ψ = Eψ    The term on the left hand side, enclosed in brackets, is known as the Hamiltonian operator, Hˆ , for the electronic system.  218  Appendix II.(a) Tabulation of experimental data set - I Evaluation of MoP catalyst activity  219  Tabulation of experimental data set - I : Activity test results Table AII(a).1.a: Hydrocarbon production with time for 0%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole Fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  2.61  5.03E-01  1.03E-03  7.95E-04  0.00E+00  0.00E+00  0.00E+00  0.00E+00  0.00E+00  0.00E+00  1.03E-03  7.43  5.14E-01  1.04E-03  7.84E-04  0.00E+00  0.00E+00  0.00E+00  0.00E+00  0.00E+00  0.00E+00  1.04E-03  10.25  5.00E-01  1.05E-03  7.87E-04  0.00E+00  0.00E+00  2.26E-04  0.00E+00  0.00E+00  0.00E+00  1.50E-03  18.67  5.00E-01  1.16E-03  9.39E-04  0.00E+00  0.00E+00  2.56E-04  0.00E+00  0.00E+00  0.00E+00  1.67E-03  22.25  4.99E-01  1.20E-03  9.82E-04  0.00E+00  0.00E+00  2.78E-04  0.00E+00  0.00E+00  0.00E+00  1.76E-03  24.25  4.97E-01  1.08E-03  9.16E-04  0.00E+00  0.00E+00  2.90E-04  0.00E+00  0.00E+00  0.00E+00  1.66E-03  27.00  4.97E-01  1.08E-03  9.16E-04  0.00E+00  0.00E+00  3.02E-04  0.00E+00  0.00E+00  0.00E+00  1.69E-03  37.20  5.04E-01  1.30E-03  1.13E-03  0.00E+00  0.00E+00  3.12E-04  0.00E+00  0.00E+00  0.00E+00  1.93E-03  46.00  5.04E-01  1.29E-03  1.14E-03  0.00E+00  0.00E+00  3.23E-04  0.00E+00  0.00E+00  0.00E+00  1.94E-03  49.00  5.02E-01  1.30E-03  1.13E-03  0.00E+00  0.00E+00  3.34E-04  0.00E+00  0.00E+00  0.00E+00  1.97E-03  52.00  5.06E-01  1.35E-03  1.18E-03  0.00E+00  0.00E+00  3.34E-04  0.00E+00  0.00E+00  0.00E+00  2.02E-03  57.90  5.06E-01  1.29E-03  1.12E-03  0.00E+00  0.00E+00  3.47E-04  0.00E+00  0.00E+00  0.00E+00  1.99E-03  68.30  5.06E-01  1.31E-03  1.12E-03  0.00E+00  0.00E+00  3.68E-04  0.00E+00  0.00E+00  0.00E+00  2.04E-03  Total HC  Total HC ( C atom %) = 1 x CH4 + 2 x C2H2+2 x C2H4+2 x C2H6+3 x C3H8+4 x isoC4H10+4 x n-C4H10  220  Table AII(a).1.b: Liquid Oxygenate production with time for 0%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole Fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  3.75  3.42E-04  1.77E-05  2.45E-05  0.00E+00  4.37E-05  1.62E-05  1.37E-06  3.78E-07  0.00E+00  9.92E-07  9.07E-04  8.47  4.32E-04  2.34E-05  7.24E-05  0.00E+00  1.09E-04  2.49E-05  2.41E-06  1.04E-06  2.33E-07  3.28E-06  1.33E-03  10.75  4.24E-04  3.30E-05  5.54E-05  0.00E+00  1.08E-04  2.75E-05  2.19E-06  9.24E-07  2.04E-07  2.72E-06  1.32E-03  19.10  4.06E-04  3.85E-05  1.12E-04  8.40E-06  1.41E-04  3.03E-05  3.60E-06  4.02E-06  1.46E-06  6.12E-06  1.49E-03  22.92  4.32E-04  3.85E-05  7.13E-05  1.83E-06  1.42E-04  3.62E-05  2.29E-06  3.51E-06  1.37E-06  1.07E-05  1.51E-03  25.10  3.84E-04  3.85E-05  2.90E-05  0.00E+00  1.40E-04  3.86E-05  7.11E-06  7.74E-06  4.35E-06  2.89E-05  1.48E-03  28.12  3.83E-04  3.64E-05  2.90E-05  0.00E+00  1.40E-04  3.86E-05  7.11E-06  7.74E-06  4.35E-06  2.89E-05  1.47E-03  38.25  3.41E-04  3.02E-05  3.93E-05  0.00E+00  1.17E-04  5.26E-05  4.78E-06  8.86E-06  7.58E-06  2.05E-05  1.35E-03  47.30  3.41E-04  2.94E-05  2.95E-05  0.00E+00  1.14E-04  3.10E-05  4.22E-06  8.46E-06  4.07E-06  2.25E-05  1.26E-03  50.57  3.32E-04  3.67E-05  3.93E-05  0.00E+00  1.11E-04  3.07E-05  5.66E-06  6.74E-06  3.93E-06  2.42E-05  1.27E-03  52.75  3.86E-04  3.90E-05  5.45E-05  0.00E+00  1.12E-04  3.33E-05  4.86E-06  8.05E-06  5.74E-06  2.81E-05  1.43E-03  58.32  3.58E-04  3.54E-05  4.87E-05  0.00E+00  1.11E-04  3.28E-05  4.81E-06  1.65E-05  6.54E-06  2.16E-05  1.35E-03  69.20  3.34E-04  2.60E-05  4.87E-05  0.00E+00  1.11E-04  3.28E-05  4.81E-06  1.65E-05  6.54E-06  2.16E-05  1.27E-03  Symbols: MeOH = Methanol; PrOH = Propanol; BuOH = Butanol; AcCOOH = Acetic Acid; PrCOOH = Propionic Acid; REST = Higher Carboxylic Acid, Higher Esters, Higher aldehydes, Higher Hydrocarbons (taking carbon number =4) Total Oxy. ( C atom %) = 2 x Acetaldehyde + 3 x Acetone+1 x MeOH+2 x Ethanol+3 x PrOH+4 x BuOH+2 x AcCOOH+3 x PrCOOH + 4 x REST  221  Table AII(a).2.a: Hydrocarbon production with time for 1%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole Fraction  Total HC  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  1.42  4.77E-01  2.78E-03  1.72E-02  0.00E+00  2.69E-04  7.49E-04  3.97E-04  3.06E-05  2.46E-05  6.22E-03  3.7  4.75E-01  2.74E-03  1.45E-02  0.00E+00  2.60E-04  7.82E-04  3.65E-04  1.89E-05  1.79E-05  6.06E-03  6.55  4.78E-01  2.65E-03  1.28E-02  0.00E+00  2.41E-04  5.57E-04  3.28E-04  1.89E-05  2.60E-05  5.41E-03  10.75  4.80E-01  2.47E-03  1.08E-02  0.00E+00  2.61E-04  6.05E-04  2.90E-04  1.89E-05  1.83E-05  5.23E-03  12.58  4.81E-01  2.48E-03  1.05E-02  0.00E+00  2.66E-04  6.03E-04  2.64E-04  5.78E-05  2.99E-05  5.36E-03  20.75  4.84E-01  2.21E-03  8.51E-03  0.00E+00  2.61E-04  5.72E-04  2.35E-04  1.89E-05  3.13E-05  4.78E-03  22.82  4.87E-01  2.12E-03  7.96E-03  0.00E+00  2.58E-04  5.07E-04  2.39E-04  1.89E-05  1.79E-05  4.51E-03  26.15  4.87E-01  1.94E-03  7.04E-03  0.00E+00  2.63E-04  4.35E-04  2.20E-04  0.00E+00  0.00E+00  3.99E-03  28.58  4.90E-01  1.90E-03  7.14E-03  0.00E+00  2.50E-04  4.18E-04  2.11E-04  0.00E+00  0.00E+00  3.87E-03  34.08  4.94E-01  1.86E-03  7.02E-03  0.00E+00  2.77E-04  4.18E-04  1.91E-04  1.89E-05  1.79E-05  3.97E-03  44.83  4.94E-01  1.74E-03  6.53E-03  0.00E+00  2.60E-04  3.53E-04  1.87E-04  1.89E-05  1.79E-05  3.67E-03  47.15  4.97E-01  1.73E-03  6.41E-03  0.00E+00  2.61E-04  3.59E-04  1.71E-04  1.89E-05  1.79E-05  3.63E-03  61.50  4.97E-01  1.73E-03  6.41E-03  0.00E+00  2.61E-04  3.59E-04  1.71E-04  1.89E-05  1.79E-05  3.63E-03  222  Table AII(a).2.b: Liquid Oxygenate production with time for 1%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  2.33  2.48E-03  1.56E-03  3.27E-04  0.00E+00  1.33E-03  3.79E-04  6.61E-05  5.42E-05  1.58E-05  3.54E-05  1.43E-02  4.70  2.22E-03  1.21E-03  2.75E-04  0.00E+00  1.04E-03  3.60E-04  7.97E-05  6.40E-05  3.27E-05  9.32E-05  1.24E-02  7.25  1.83E-03  1.10E-03  2.32E-04  0.00E+00  1.19E-03  3.11E-04  6.17E-05  6.88E-05  3.35E-05  1.30E-04  1.15E-02  11.75  1.46E-03  9.54E-04  1.63E-04  0.00E+00  6.96E-04  2.83E-04  5.44E-05  1.03E-04  3.39E-05  1.25E-04  9.21E-03  13.23  1.49E-03  1.07E-03  1.96E-04  0.00E+00  8.65E-04  2.65E-04  4.76E-05  5.72E-05  2.56E-05  1.03E-04  9.69E-03  21.70  9.81E-04  8.03E-04  1.44E-04  0.00E+00  5.28E-04  1.79E-04  5.24E-05  8.79E-05  2.71E-05  1.14E-04  7.03E-03  23.68  1.08E-03  6.66E-04  9.88E-05  0.00E+00  4.83E-04  1.90E-04  4.09E-05  5.03E-05  3.66E-05  6.88E-05  6.44E-03  27.10  8.23E-04  5.36E-04  1.33E-05  0.00E+00  3.74E-04  1.33E-04  3.65E-05  4.54E-05  2.44E-05  8.62E-05  5.07E-03  29.46  8.07E-04  5.67E-04  9.50E-05  0.00E+00  3.56E-04  1.34E-04  2.96E-05  3.86E-05  1.46E-05  1.20E-04  5.25E-03  34.83  7.81E-04  4.76E-04  9.12E-05  0.00E+00  2.75E-04  1.15E-04  3.01E-05  3.66E-05  1.76E-05  5.31E-05  4.44E-03  46.00  6.04E-04  4.68E-04  9.12E-05  0.00E+00  2.23E-04  1.07E-04  4.69E-05  5.04E-05  2.70E-05  1.14E-04  4.30E-03  47.96  6.72E-04  3.90E-04  9.12E-05  0.00E+00  2.16E-04  6.22E-05  1.93E-05  2.32E-05  1.24E-05  5.44E-05  3.60E-03  58.22  6.65E-04  3.64E-04  9.12E-05  0.00E+00  1.90E-04  6.22E-05  1.93E-05  2.32E-05  1.24E-05  5.44E-05  3.46E-03  223  Table AII(a).3.a: Hydrocarbon production with time for 5%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  1.16  4.83E-01  1.01E-03  1.25E-02  0.00E+00  5.08E-04  1.22E-04  2.73E-04  0.00E+00  0.00E+00  3.09E-03  3.33  4.82E-01  1.20E-03  1.30E-02  0.00E+00  5.72E-04  1.62E-04  2.74E-04  0.00E+00  0.00E+00  3.50E-03  8.75  4.83E-01  1.18E-03  1.13E-02  0.00E+00  4.90E-04  1.74E-04  2.77E-04  0.00E+00  1.02E-05  3.38E-03  10.71  4.85E-01  1.17E-03  1.09E-02  0.00E+00  4.94E-04  1.74E-04  2.09E-04  0.00E+00  8.29E-05  3.46E-03  21.06  4.87E-01  1.03E-03  9.25E-03  0.00E+00  4.27E-04  1.41E-04  1.72E-04  0.00E+00  1.50E-05  2.74E-03  23.21  4.89E-01  9.96E-04  8.99E-03  0.00E+00  4.33E-04  1.41E-04  1.86E-04  0.00E+00  1.17E-05  2.75E-03  25.64  4.89E-01  9.91E-04  8.80E-03  0.00E+00  3.93E-04  1.55E-04  1.81E-04  0.00E+00  1.90E-05  2.71E-03  27.40  4.88E-01  9.82E-04  8.73E-03  0.00E+00  4.06E-04  1.05E-04  1.88E-04  0.00E+00  1.79E-05  2.64E-03  32.68  4.88E-01  9.33E-04  8.26E-03  0.00E+00  4.03E-04  1.08E-04  1.72E-04  0.00E+00  4.29E-05  2.64E-03  34.49  4.88E-01  9.39E-04  8.20E-03  0.00E+00  3.68E-04  9.98E-05  1.60E-04  0.00E+00  2.10E-05  2.44E-03  44.34  4.87E-01  9.13E-04  7.87E-03  0.00E+00  3.55E-04  1.20E-04  1.62E-04  0.00E+00  2.59E-05  2.45E-03  47.53  4.85E-01  9.13E-04  7.84E-03  0.00E+00  3.84E-04  1.06E-04  1.24E-04  0.00E+00  2.51E-05  2.37E-03  49.86  4.87E-01  9.11E-04  7.77E-03  0.00E+00  3.91E-04  1.15E-04  1.10E-04  0.00E+00  1.79E-05  2.33E-03  58.66  4.85E-01  9.08E-04  7.69E-03  0.00E+00  3.71E-04  1.14E-04  1.17E-04  0.00E+00  1.79E-05  2.30E-03  68.31  4.81E-01  9.18E-04  7.59E-03  0.00E+00  3.63E-04  1.28E-04  1.82E-04  0.00E+00  1.79E-05  2.52E-03  70.91  4.81E-01  9.09E-04  7.59E-03  0.00E+00  3.61E-04  9.67E-05  1.43E-04  0.00E+00  1.79E-05  2.33E-03  72.49  4.81E-01  9.08E-04  7.54E-03  0.00E+00  3.63E-04  9.63E-05  1.41E-04  0.00E+00  1.79E-05  2.32E-03  Total HC  224  Table AII(a).3.b: Liquid Oxygenate production with time for 5%K 5% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  1.83  6.45E-04  2.60E-04  0.00E+00  0.00E+00  4.46E-04  5.22E-05  2.11E-05  2.62E-05  6.49E-06  1.88E-05  3.79E-03  3.99  5.08E-04  3.12E-05  0.00E+00  0.00E+00  5.57E-04  8.61E-06  4.58E-06  7.25E-06  4.36E-06  1.07E-05  2.89E-03  9.59  6.60E-04  3.54E-04  0.00E+00  0.00E+00  5.56E-04  5.62E-05  3.16E-05  6.18E-05  3.51E-05  9.98E-05  4.97E-03  11.33  5.74E-04  3.22E-04  0.00E+00  0.00E+00  3.79E-04  5.67E-05  2.69E-05  3.80E-05  2.95E-05  9.47E-05  4.07E-03  21.89  4.93E-04  2.60E-04  0.00E+00  0.00E+00  4.30E-04  5.14E-05  3.14E-05  6.18E-05  3.69E-05  1.16E-04  4.04E-03  24.23  3.65E-04  2.60E-04  0.00E+00  0.00E+00  3.70E-04  4.05E-05  2.58E-05  3.02E-05  2.23E-05  1.05E-04  3.39E-03  26.28  4.82E-04  2.60E-04  0.00E+00  0.00E+00  3.32E-04  4.13E-05  3.07E-05  3.24E-05  2.32E-05  1.23E-04  3.61E-03  28.13  4.08E-04  2.60E-04  0.00E+00  0.00E+00  3.40E-04  5.28E-05  3.00E-05  3.18E-05  1.17E-05  1.37E-04  3.54E-03  33.30  4.97E-04  2.60E-04  0.00E+00  0.00E+00  3.78E-04  1.01E-04  4.26E-05  4.22E-05  2.90E-05  1.55E-04  4.17E-03  35.38  4.29E-04  3.12E-04  0.00E+00  0.00E+00  4.43E-04  8.14E-05  2.58E-05  3.48E-05  2.55E-05  1.28E-04  4.13E-03  44.94  5.22E-04  3.90E-04  0.00E+00  0.00E+00  3.59E-04  7.64E-05  3.75E-05  3.71E-05  2.68E-05  1.44E-04  4.40E-03  48.08  5.40E-04  4.42E-04  0.00E+00  0.00E+00  3.78E-04  8.04E-05  2.48E-05  3.66E-05  2.87E-05  1.08E-04  4.47E-03  50.66  3.79E-04  3.67E-04  0.00E+00  0.00E+00  3.21E-04  7.43E-05  2.41E-05  3.40E-05  2.37E-05  1.27E-04  3.79E-03  58.89  3.62E-04  4.55E-04  0.00E+00  0.00E+00  3.40E-04  8.92E-05  2.45E-05  3.50E-05  2.35E-05  1.06E-04  4.04E-03  69.16  4.28E-04  4.55E-04  0.00E+00  0.00E+00  3.21E-04  7.53E-05  2.56E-05  3.54E-05  2.86E-05  1.19E-04  4.15E-03  71.06  4.72E-04  3.38E-04  0.00E+00  0.00E+00  3.17E-04  6.99E-05  3.49E-05  3.55E-05  2.49E-05  1.32E-04  3.93E-03  73.21  4.29E-04  3.09E-04  0.00E+00  0.00E+00  3.78E-04  7.04E-05  3.54E-05  3.52E-05  2.49E-05  1.41E-04  3.98E-03  225  Table AII(a).4.a: Hydrocarbon production with time for 0%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  5.75  4.93E-01  4.83E-03  7.22E-03  0.00E+00  0.00E+00  1.55E-03  1.55E-03  1.26E-04  0.00E+00  1.31E-02  17.5  4.98E-01  4.03E-03  4.95E-03  0.00E+00  0.00E+00  1.20E-03  1.63E-04  7.14E-05  0.00E+00  7.20E-03  27.5  4.93E-01  3.62E-03  4.05E-03  0.00E+00  0.00E+00  1.03E-03  1.93E-04  0.00E+00  0.00E+00  6.27E-03  30.16  4.61E-01  3.62E-03  4.05E-03  0.00E+00  0.00E+00  1.03E-03  1.93E-04  0.00E+00  0.00E+00  6.27E-03  41.75  4.97E-01  3.35E-03  3.57E-03  0.00E+00  0.00E+00  9.26E-04  1.85E-04  0.00E+00  0.00E+00  5.76E-03  45  4.98E-01  3.30E-03  3.47E-03  0.00E+00  0.00E+00  8.87E-04  1.72E-04  0.00E+00  0.00E+00  5.59E-03  51  4.97E-01  3.18E-03  3.27E-03  0.00E+00  0.00E+00  8.80E-04  1.60E-04  0.00E+00  0.00E+00  5.42E-03  64.28  4.98E-01  3.04E-03  3.03E-03  0.00E+00  0.00E+00  7.94E-04  1.58E-04  0.00E+00  0.00E+00  5.11E-03  Total HC  226  Table AII(a).4.b: Liquid Oxygenate production with time for 0%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  6.75  2.00E-03  1.47E-03  2.82E-04  1.61E-04  3.14E-04  1.77E-04  4.00E-05  2.72E-05  2.25E-05  1.58E-04  1.11E-02  18.00  1.33E-03  5.80E-04  7.22E-05  6.93E-05  1.62E-04  1.35E-04  3.06E-05  5.54E-05  2.39E-05  8.81E-05  5.99E-03  28.32  1.13E-03  6.01E-04  6.92E-05  6.18E-05  1.53E-04  7.80E-05  1.14E-05  2.65E-05  1.08E-05  3.34E-05  5.07E-03  30.83  9.14E-04  4.81E-04  5.97E-05  6.39E-05  1.33E-04  8.10E-05  1.06E-05  2.68E-05  1.29E-05  3.83E-05  4.26E-03  42.90  1.25E-03  4.91E-04  5.43E-05  6.85E-05  1.39E-04  8.55E-05  1.07E-05  3.01E-05  1.61E-05  4.05E-05  5.01E-03  46.00  1.11E-03  4.68E-04  5.70E-05  6.91E-05  1.38E-04  7.60E-05  8.21E-06  2.03E-05  7.57E-06  3.06E-05  4.54E-03  52.11  8.67E-04  5.04E-04  5.32E-05  5.95E-05  1.36E-04  6.38E-05  7.58E-06  2.11E-05  7.78E-06  3.40E-05  4.11E-03  65.23  8.47E-04  4.45E-04  4.71E-05  5.99E-05  1.40E-04  6.11E-05  6.29E-06  1.70E-05  7.03E-06  2.84E-05  3.85E-03  227  Table AII(a).5.a: Hydrocarbon production with time for 1%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  2.28  5.08E-01  7.66E-03  3.28E-02  0.00E+00  3.20E-04  2.24E-03  6.72E-04  3.47E-05  0.00E+00  1.49E-02  4.90  5.10E-01  5.73E-03  2.40E-02  0.00E+00  2.94E-04  1.67E-03  5.05E-04  2.25E-05  0.00E+00  1.13E-02  10.67  5.13E-01  5.73E-03  1.89E-02  0.00E+00  2.94E-04  1.67E-03  5.05E-04  2.25E-05  0.00E+00  1.13E-02  21.96  4.96E-01  5.19E-03  1.49E-02  0.00E+00  2.84E-04  1.48E-03  4.04E-04  4.42E-05  4.52E-05  1.03E-02  24.70  4.94E-01  4.73E-03  1.26E-02  0.00E+00  2.41E-04  1.28E-03  3.81E-04  5.80E-05  4.69E-05  9.32E-03  28.32  4.92E-01  5.04E-03  1.39E-02  0.00E+00  3.05E-04  1.40E-03  4.01E-04  4.17E-05  2.69E-05  9.92E-03  33.46  4.97E-01  4.74E-03  1.26E-02  0.00E+00  2.80E-04  1.29E-03  3.73E-04  2.30E-05  0.00E+00  9.09E-03  35.46  4.98E-01  4.84E-03  1.22E-02  0.00E+00  3.13E-04  1.33E-03  3.60E-04  6.42E-05  4.88E-05  9.65E-03  45.53  4.99E-01  4.56E-03  1.07E-02  0.00E+00  2.95E-04  1.13E-03  3.23E-04  3.63E-05  1.92E-05  8.60E-03  49.30  4.98E-01  4.15E-03  1.01E-02  0.00E+00  2.82E-04  1.06E-03  3.25E-04  3.63E-05  1.92E-05  8.04E-03  55.60  4.98E-01  4.15E-03  1.01E-02  0.00E+00  2.82E-04  1.06E-03  3.25E-04  3.63E-05  1.92E-05  8.04E-03  Total HC  228  Table AII(a).5.b: Liquid Oxygenate production with time For 1%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  3.20  4.44E-03  2.70E-03  1.23E-03  0.00E+00  2.56E-03  4.97E-04  1.07E-04  9.09E-05  4.09E-05  8.87E-05  2.59E-02  5.83  3.78E-03  1.77E-03  1.05E-03  0.00E+00  2.08E-03  6.08E-04  1.02E-04  8.08E-05  4.21E-05  1.78E-04  2.13E-02  11.76  3.50E-03  1.42E-03  8.09E-04  0.00E+00  1.61E-03  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.72E-02  22.78  3.35E-03  1.23E-03  6.99E-04  0.00E+00  1.13E-03  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.53E-02  26.50  2.90E-03  1.00E-03  4.53E-04  0.00E+00  9.49E-04  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.31E-02  29.12  2.76E-03  1.03E-03  5.17E-04  0.00E+00  8.44E-04  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.28E-02  34.12  2.22E-03  1.12E-03  3.49E-04  0.00E+00  7.66E-04  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.16E-02  36.10  2.03E-03  9.10E-04  4.22E-04  0.00E+00  6.16E-04  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  1.04E-02  46.45  1.88E-03  6.50E-04  3.41E-04  0.00E+00  4.88E-04  2.85E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  8.99E-03  47.86  1.84E-03  7.80E-04  3.33E-04  0.00E+00  6.31E-04  2.41E-04  5.71E-05  7.14E-05  3.21E-05  1.60E-04  9.44E-03  229  Table AII(a).6.a: Hydrocarbon production with time for 5%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  2.43  4.73E-02  3.46E-03  3.42E-02  0.00E+00  1.14E-03  6.17E-04  7.43E-04  2.35E-04  0.00E+00  1.01E-02  7.52  4.89E-01  3.12E-03  2.58E-02  0.00E+00  9.84E-04  4.83E-04  5.54E-04  1.64E-04  0.00E+00  8.38E-03  12.35  4.87E-01  3.28E-03  2.61E-02  0.00E+00  9.95E-04  5.09E-04  5.57E-04  1.60E-04  0.00E+00  8.60E-03  22.46  4.88E-01  3.15E-03  2.33E-02  0.00E+00  9.40E-04  4.92E-04  5.10E-04  1.13E-04  0.00E+00  8.00E-03  26.40  4.85E-01  3.04E-03  2.24E-02  0.00E+00  9.08E-04  4.59E-04  4.51E-04  9.79E-05  0.00E+00  7.52E-03  29.76  4.86E-01  3.03E-03  2.20E-02  0.00E+00  9.09E-04  4.74E-04  4.55E-04  9.44E-05  0.00E+00  7.54E-03  35.82  4.85E-01  2.89E-03  2.11E-02  0.00E+00  8.61E-04  4.34E-04  4.43E-04  8.50E-05  0.00E+00  7.15E-03  39.10  4.86E-01  2.88E-03  2.08E-02  0.00E+00  8.67E-04  4.30E-04  4.36E-04  9.44E-05  0.00E+00  7.16E-03  41.83  4.84E-01  2.88E-03  2.05E-02  0.00E+00  8.46E-04  4.46E-04  4.32E-04  9.44E-05  0.00E+00  7.13E-03  52.30  4.80E-01  2.80E-03  1.94E-02  0.00E+00  7.91E-04  4.16E-04  3.96E-04  9.44E-05  0.00E+00  6.78E-03  61.13  4.83E-01  2.73E-03  1.87E-02  0.00E+00  7.50E-04  3.99E-04  3.96E-04  9.44E-05  0.00E+00  6.60E-03  82.73  4.84E-01  2.58E-03  1.73E-02  0.00E+00  6.69E-04  3.81E-04  3.58E-04  1.09E-04  0.00E+00  6.19E-03  94.84  4.85E-01  2.49E-03  1.66E-02  0.00E+00  6.57E-04  3.23E-04  3.50E-04  9.44E-05  0.00E+00  5.88E-03  106.25  4.81E-01  2.45E-03  1.61E-02  0.00E+00  6.11E-04  3.34E-04  3.24E-04  7.55E-05  0.00E+00  5.61E-03  118.12  4.80E-01  2.37E-03  1.56E-02  0.00E+00  6.07E-04  3.34E-04  3.10E-04  7.27E-05  0.00E+00  5.47E-03  122.72  4.81E-01  2.34E-03  1.55E-02  0.00E+00  5.95E-04  3.50E-04  3.20E-04  6.61E-05  0.00E+00  5.45E-03  125.400  4.80E-01  2.38E-03  1.55E-02  0.00E+00  5.96E-04  3.48E-04  3.22E-04  6.14E-05  0.00E+00  5.48E-03  Total HC  230  Table AII(a).6.b: Liquid Oxygenate production with time for 5%K 10% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction Total Time Oxy. Iso[hr] Acetaldehyde Acetone MeOH Ethanol PrOH BuOH AcCOOH PrCOOH REST (C atom %) propanol 3.57  1.88E-03  1.82E-03  1.42E-03  0.00E+00  2.59E-03  8.79E-04  2.52E-04  2.74E-04  1.82E-04  3.72E-04  2.21E-02  9.05  1.85E-03  1.82E-03  1.34E-03  0.00E+00  2.17E-03  6.25E-04  1.58E-04  1.77E-04  1.17E-04  3.97E-04  1.96E-02  12.28  2.27E-03  1.69E-03  1.30E-03  0.00E+00  2.19E-03  7.41E-04  2.16E-04  2.83E-04  1.55E-04  5.44E-04  2.16E-02  23.65  2.36E-03  1.56E-03  1.35E-03  0.00E+00  1.96E-03  6.04E-04  1.72E-04  1.94E-04  1.28E-04  5.73E-04  2.02E-02  27.06  2.29E-03  1.64E-03  1.19E-03  0.00E+00  2.02E-03  4.39E-04  1.30E-04  1.74E-04  9.39E-05  3.37E-04  1.86E-02  30.25  2.08E-03  1.56E-03  1.28E-03  0.00E+00  1.89E-03  5.03E-04  1.41E-04  1.79E-04  9.98E-05  3.28E-04  1.80E-02  36.70  2.27E-03  1.30E-03  1.32E-03  0.00E+00  1.90E-03  6.67E-04  1.67E-04  2.35E-04  1.07E-04  4.87E-04  1.90E-02  40.10  2.18E-03  1.09E-03  1.19E-03  0.00E+00  1.85E-03  5.09E-04  1.48E-04  1.46E-04  1.06E-04  3.65E-04  1.67E-02  42.82  2.09E-03  1.46E-03  8.90E-04  0.00E+00  1.86E-03  6.27E-04  1.58E-04  2.21E-04  1.41E-04  4.67E-04  1.84E-02  53.40  2.41E-03  1.20E-03  9.69E-04  0.00E+00  1.83E-03  5.98E-04  1.60E-04  2.12E-04  1.34E-04  3.97E-04  1.79E-02  62.49  2.55E-03  9.88E-04  7.43E-04  0.00E+00  1.67E-03  5.42E-04  1.57E-04  2.25E-04  1.10E-04  4.85E-04  1.71E-02  82.16  2.43E-03  1.04E-03  8.80E-04  0.00E+00  1.56E-03  5.59E-04  1.39E-04  1.77E-04  1.05E-04  3.32E-04  1.62E-02  95.48  2.26E-03  8.84E-04  7.84E-04  0.00E+00  1.78E-03  5.25E-04  1.53E-04  1.83E-04  1.14E-04  3.54E-04  1.58E-02  107.15  2.43E-03  8.32E-04  7.39E-04  0.00E+00  1.56E-03  5.41E-04  1.47E-04  1.91E-04  8.65E-05  3.52E-04  1.55E-02  119.40  2.22E-03  9.10E-04  7.37E-04  0.00E+00  1.60E-03  4.79E-04  1.52E-04  1.49E-04  1.44E-04  4.01E-04  1.55E-02  123.50  2.03E-03  9.10E-04  6.47E-04  0.00E+00  1.48E-03  5.82E-04  1.56E-04  2.06E-04  1.32E-04  4.22E-04  1.53E-02  126.30  1.99E-03  8.32E-04  6.78E-04  0.00E+00  1.47E-03  4.83E-04  1.38E-04  1.75E-04  1.15E-04  3.55E-04  1.42E-02  231  Table AII(a).7.a: Hydrocarbon production with time for 0%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Total HC  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  9.83  5.01E-01  5.77E-03  9.51E-03  0.00E+00  1.09E-04  1.66E-03  3.06E-04  0.00E+00  0.00E+00  1.02E-02  12.08  5.02E-01  5.73E-03  9.34E-03  0.00E+00  1.20E-04  1.65E-03  2.96E-04  0.00E+00  0.00E+00  1.02E-02  20.85  5.03E-01  5.44E-03  8.26E-03  0.00E+00  1.35E-04  1.56E-03  3.17E-04  0.00E+00  0.00E+00  9.78E-03  23.66  5.03E-01  5.34E-03  7.98E-03  0.00E+00  1.35E-04  1.49E-03  2.93E-04  0.00E+00  0.00E+00  9.48E-03  26.00  4.99E-01  5.29E-03  7.79E-03  0.00E+00  1.48E-04  1.50E-03  3.01E-04  0.00E+00  0.00E+00  9.48E-03  31.62  4.96E-01  4.97E-03  7.27E-03  0.00E+00  1.47E-04  1.42E-03  2.74E-04  6.98E-05  0.00E+00  9.20E-03  34.16  4.96E-01  5.02E-03  7.17E-03  0.00E+00  1.50E-04  1.39E-03  2.77E-04  6.98E-05  0.00E+00  9.21E-03  36.80  4.96E-01  5.04E-03  7.11E-03  0.00E+00  1.39E-04  1.39E-03  2.87E-04  5.66E-05  0.00E+00  9.18E-03  36.80  4.96E-01  5.04E-03  7.11E-03  0.00E+00  1.39E-04  1.39E-03  2.87E-04  5.82E-05  0.00E+00  9.18E-03  45.46  5.00E-01  4.88E-03  6.63E-03  0.00E+00  1.51E-04  1.36E-03  2.67E-04  6.14E-05  0.00E+00  8.94E-03  48.90  5.00E-01  4.82E-03  6.52E-03  0.00E+00  1.35E-04  1.33E-03  2.62E-04  5.97E-05  0.00E+00  8.78E-03  69.20  5.05E-01  4.59E-03  5.85E-03  0.00E+00  1.61E-04  1.26E-03  2.31E-04  6.14E-05  0.00E+00  8.37E-03  72.50  5.04E-01  4.56E-03  5.74E-03  0.00E+00  1.50E-04  1.25E-03  2.23E-04  6.14E-05  0.00E+00  8.27E-03  232  Table AII(a).7.b: Liquid Oxygenate production with time for 0%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  10.66  2.78E-03  1.26E-03  1.47E-03  0.00E+00  2.31E-04  1.03E-04  1.34E-05  4.53E-06  2.16E-06  8.54E-06  1.17E-02  13.00  1.93E-03  6.73E-04  1.18E-03  0.00E+00  4.79E-04  1.08E-04  1.58E-05  5.46E-06  4.20E-06  2.66E-05  8.54E-03  21.63  1.94E-03  5.02E-04  1.14E-03  0.00E+00  4.02E-04  1.03E-04  1.83E-05  8.43E-06  1.03E-05  3.49E-05  7.89E-03  24.50  1.51E-03  7.54E-04  9.37E-04  0.00E+00  3.08E-04  1.02E-04  1.42E-05  6.63E-06  7.95E-06  3.57E-05  7.38E-03  26.60  1.65E-03  9.65E-04  9.03E-04  0.00E+00  3.22E-04  1.03E-04  2.00E-05  9.18E-06  1.36E-05  4.46E-05  8.37E-03  32.62  1.68E-03  7.36E-04  9.37E-04  0.00E+00  3.02E-04  8.06E-05  2.05E-05  9.49E-06  1.63E-05  4.19E-05  7.66E-03  35.10  1.43E-03  5.67E-04  7.22E-04  0.00E+00  3.01E-04  7.08E-05  2.07E-05  3.19E-05  1.19E-05  7.06E-05  6.56E-03  37.63  1.19E-03  5.93E-04  7.28E-04  0.00E+00  1.89E-04  7.74E-05  1.77E-05  2.15E-05  4.99E-06  3.97E-05  5.78E-03  46.42  1.33E-03  8.81E-04  8.37E-04  0.00E+00  2.28E-04  7.74E-05  1.77E-05  2.15E-05  4.99E-06  3.97E-05  7.12E-03  49.60  1.31E-03  5.67E-04  6.97E-04  0.00E+00  2.27E-04  6.77E-05  1.96E-05  2.59E-05  6.53E-06  3.99E-05  5.98E-03  59.50  1.40E-03  5.59E-04  6.94E-04  0.00E+00  1.84E-04  6.20E-05  1.85E-05  2.60E-05  7.70E-06  3.65E-05  6.01E-03  70.00  1.11E-03  5.02E-04  5.34E-04  0.00E+00  1.89E-04  4.98E-05  1.44E-05  2.29E-05  9.78E-06  2.97E-05  5.04E-03  73.30  1.54E-03  4.52E-04  5.76E-04  0.00E+00  2.77E-04  4.58E-05  1.16E-05  2.06E-05  1.04E-05  2.58E-05  5.93E-03  233  Table AII(a).8.a: Hydrocarbon production with time for 1%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Total HC  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom %)  2.01E-02  0.00E+00  1.76E-04  2.07E-03  4.10E-04  0.00E+00  1.69E-04  1.37E-02  6.80E-03  1.69E-02  0.00E+00  1.69E-04  2.01E-03  4.08E-04  0.00E+00  9.31E-05  1.28E-02  4.84E-01  6.29E-03  1.42E-02  0.00E+00  2.01E-04  1.77E-03  3.86E-04  0.00E+00  1.02E-04  1.18E-02  10.33  4.84E-01  6.05E-03  1.33E-02  0.00E+00  2.05E-04  1.72E-03  3.82E-04  4.56E-05  1.24E-04  1.17E-02  18.33  4.84E-01  5.48E-03  1.13E-02  0.00E+00  2.15E-04  1.54E-03  3.30E-04  5.57E-05  7.19E-05  1.05E-02  21.45  4.87E-01  5.45E-03  1.08E-02  0.00E+00  2.17E-04  1.49E-03  3.14E-04  5.39E-05  7.97E-05  1.03E-02  23.5  4.86E-01  5.25E-03  1.06E-02  0.00E+00  2.19E-04  1.50E-03  3.11E-04  3.20E-05  6.99E-05  1.00E-02  25.8  4.85E-01  5.27E-03  1.02E-02  0.00E+00  2.06E-04  1.47E-03  3.20E-04  3.12E-05  4.10E-05  9.88E-03  27.47  4.86E-01  5.21E-03  1.00E-02  0.00E+00  2.08E-04  1.44E-03  3.01E-04  7.99E-05  8.58E-05  1.01E-02  33.12  4.86E-01  5.03E-03  9.47E-03  0.00E+00  2.26E-04  1.33E-03  3.09E-04  3.02E-05  5.67E-05  9.41E-03  42.43  4.88E-01  4.70E-03  8.72E-03  0.00E+00  2.25E-04  1.30E-03  3.09E-04  2.62E-05  5.74E-05  9.01E-03  44.75  4.87E-01  4.63E-03  8.58E-03  0.00E+00  2.13E-04  1.21E-03  2.91E-04  2.14E-05  4.22E-05  8.59E-03  61.5  4.87E-01  4.63E-03  8.58E-03  0.00E+00  2.13E-04  1.21E-03  2.91E-04  2.14E-05  4.22E-05  8.59E-03  Time [hr]  CO  CH4  CO2  1.5  4.77E-01  7.31E-03  3.72  4.81E-01  8.1  234  Table AII(a).8.b: Liquid Oxygenate production with time for 1%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Time [hr]  Mole fraction Acetaldehyde Acetone  MeOH  IsoEthanol propanol  PrOH  BuOH  AcCOOH PrCOOH  Total Oxy.  REST  (C atom %)  2.20  4.49E-03  1.90E-03  1.44E-03  0.00E+00  1.62E-03  5.29E-04  7.82E-05  5.41E-05  1.84E-05  6.33E-05  2.33E-02  4.45  3.95E-03  1.87E-03  1.19E-03  0.00E+00  8.16E-04  4.40E-04  5.99E-05  4.15E-05  1.57E-05  5.43E-05  1.90E-02  8.95  3.81E-03  1.43E-03  1.09E-03  0.00E+00  8.10E-04  3.41E-04  4.74E-05  6.26E-05  1.25E-05  8.98E-05  1.72E-02  11.07  2.53E-03  1.17E-03  9.05E-04  0.00E+00  9.49E-04  2.80E-04  4.59E-05  3.11E-05  1.10E-05  9.77E-05  1.38E-02  20.42  2.39E-03  1.04E-03  8.70E-04  0.00E+00  5.34E-04  2.55E-04  3.88E-05  2.95E-05  3.02E-05  8.11E-05  1.18E-02  22.12  2.13E-03  1.03E-03  7.19E-04  0.00E+00  6.09E-04  2.30E-04  3.66E-05  2.81E-05  3.32E-05  8.90E-05  1.12E-02  24.20  2.07E-03  7.80E-04  6.29E-04  0.00E+00  6.61E-04  2.48E-04  3.59E-05  3.55E-05  2.94E-05  9.33E-05  1.05E-02  26.80  2.17E-03  9.10E-04  6.63E-04  0.00E+00  6.82E-04  2.22E-04  3.18E-05  2.36E-05  2.12E-05  5.45E-05  1.09E-02  28.20  2.01E-03  7.80E-04  5.64E-04  0.00E+00  5.43E-04  2.64E-04  4.04E-05  3.27E-05  4.29E-05  1.15E-04  1.02E-02  34.00  1.92E-03  8.79E-04  5.21E-04  0.00E+00  5.24E-04  2.49E-04  4.27E-05  3.66E-05  5.14E-05  1.37E-04  1.03E-02  43.20  2.33E-03  9.70E-04  5.35E-04  0.00E+00  5.25E-04  2.31E-04  4.63E-05  3.32E-05  2.44E-05  8.62E-05  1.10E-02  44.53  2.36E-03  8.74E-04  4.93E-04  0.00E+00  4.61E-04  2.31E-04  4.63E-05  2.36E-05  2.57E-05  7.43E-05  1.05E-02  58.22  2.00E-03  8.74E-04  4.56E-04  0.00E+00  4.70E-04  2.31E-04  4.63E-05  2.36E-05  2.57E-05  7.43E-05  9.79E-03  235  Table AII(a).9.a: Hydrocarbon production with time for 5%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction C2H4 C2H6  Time [hr]  CO  CH4  CO2  C2H2  2.96  4.45E-01  6.16E-03  5.43E-02  0.00E+00  1.04E-03  7.70  4.52E-01  5.01E-03  3.87E-02  0.00E+00  10.00  4.50E-01  5.13E-03  3.83E-02  20.70  4.54E-01  5.00E-03  25.10  4.54E-01  31.05  Total HC C3H8  isoC4H10  n-C4H10  (C atom %)  1.63E-03  1.12E-03  2.00E-04  3.09E-05  1.58E-02  8.68E-04  1.23E-03  7.63E-04  2.00E-04  3.09E-05  1.24E-02  0.00E+00  8.69E-04  1.24E-03  8.21E-04  2.51E-04  3.28E-05  1.29E-02  3.48E-02  0.00E+00  8.19E-04  1.22E-03  6.86E-04  2.17E-04  2.69E-05  1.21E-02  5.01E-03  3.42E-02  0.00E+00  7.87E-04  1.26E-03  7.01E-04  2.01E-04  2.23E-05  1.21E-02  4.57E-01  4.98E-03  3.37E-02  0.00E+00  7.62E-04  1.26E-03  6.83E-04  1.90E-04  2.15E-05  1.19E-02  33.32  4.59E-01  4.89E-03  3.22E-02  0.00E+00  6.93E-04  1.18E-03  6.35E-04  2.12E-04  2.24E-05  1.15E-02  44.27  4.57E-01  4.80E-03  3.14E-02  0.00E+00  6.59E-04  1.19E-03  5.68E-04  2.01E-04  2.06E-05  1.11E-02  46.76  4.60E-01  4.59E-03  2.89E-02  0.00E+00  5.42E-04  1.17E-03  5.52E-04  1.65E-04  1.70E-05  1.04E-02  49.30  4.61E-01  4.49E-03  2.81E-02  0.00E+00  5.52E-04  1.17E-03  5.15E-04  1.60E-04  1.90E-05  1.02E-02  55.60  4.61E-01  4.30E-03  2.62E-02  0.00E+00  4.34E-04  1.22E-03  4.67E-04  1.37E-04  4.23E-05  9.71E-03  57.53  4.61E-01  4.30E-03  2.62E-02  0.00E+00  4.34E-04  1.22E-03  4.55E-04  9.68E-05  3.88E-05  9.51E-03  61.50  4.61E-01  4.23E-03  2.56E-02  0.00E+00  3.77E-04  1.20E-03  4.50E-04  1.15E-04  4.28E-05  9.36E-03  236  Table AII(a).9.b: Liquid Oxygenate production with time for 5%K 15% MoP SiO2 catalyst Reaction conditions: Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1 gm. Mole fraction  Total Oxy.  Time [hr]  AcCHO  Acetone MeOH  IsoEthanol PrOH propanol  BuOH  AcCOOH PrCOOH REST  (C atom %)  3.66  3.83E-03  2.34E-03  4.84E-04  0.00E+00  3.78E-03  1.01E-03  2.09E-04  2.34E-04  6.26E-05  9.60E-05  2.76E-02  8.56  3.33E-03  2.26E-03  4.12E-04  0.00E+00  3.15E-03  8.79E-04  2.68E-04  3.45E-04  1.72E-04  7.17E-04  2.79E-02  10.66  3.42E-03  2.22E-03  4.29E-04  0.00E+00  3.33E-03  9.07E-04  3.58E-04  4.47E-04  1.94E-04  1.89E-03  3.38E-02  21.33  3.56E-03  2.16E-03  4.09E-04  0.00E+00  3.67E-03  6.91E-04  2.09E-04  3.21E-04  2.20E-04  7.05E-04  2.84E-02  22.67  3.36E-03  1.95E-03  3.41E-04  0.00E+00  3.32E-03  5.83E-04  1.67E-04  2.75E-04  1.49E-04  6.60E-04  2.56E-02  25.96  4.14E-03  1.92E-03  4.08E-04  0.00E+00  3.22E-03  6.11E-04  1.75E-04  2.69E-04  1.81E-04  5.87E-04  2.68E-02  31.85  3.47E-03  2.00E-03  3.91E-04  0.00E+00  3.01E-03  6.22E-04  1.56E-04  2.50E-04  1.33E-04  5.87E-04  2.51E-02  34.15  3.27E-03  1.92E-03  3.41E-04  0.00E+00  3.10E-03  6.73E-04  1.93E-04  2.79E-04  1.44E-04  6.71E-04  2.53E-02  45.15  3.65E-03  1.82E-03  4.55E-04  0.00E+00  2.64E-03  5.88E-04  1.85E-04  2.79E-04  2.03E-04  7.02E-04  2.50E-02  47.86  3.84E-03  1.85E-03  3.66E-04  0.00E+00  2.31E-03  5.88E-04  1.68E-04  2.59E-04  1.63E-04  7.18E-04  2.45E-02  51.40  4.14E-03  1.82E-03  4.21E-04  0.00E+00  2.44E-03  5.76E-04  2.37E-04  4.23E-04  2.94E-04  1.33E-03  2.88E-02  56.33  2.99E-03  1.82E-03  3.41E-04  0.00E+00  2.13E-03  4.37E-04  1.31E-04  1.93E-04  1.36E-04  5.11E-04  2.07E-02  58.22  2.85E-03  1.70E-03  4.29E-04  0.00E+00  2.27E-03  4.37E-04  1.31E-04  1.93E-04  1.36E-04  5.11E-04  2.04E-02  237  Appendix II.(b) Tabulation of experimental data set - II : Kinetic rate law experiment results Catalyst : 1 wt% Rh 5 wt% K 10 wt% MoP/SiO2  238  Table AII(b).1.a : Hydrocarbon production with time at  Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1.0 gm Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  1.58  4.76E-01  2.08E-03  2.57E-02  0.00E+00  7.95E-04  3.99E-04  5.88E-04  1.79E-04  0.00E+00  6.94E-03  5.13  4.73E-01  2.67E-03  2.83E-02  0.00E+00  9.34E-04  4.63E-04  5.93E-04  1.89E-04  3.91E-05  8.15E-03  7.45  4.72E-01  2.38E-03  2.51E-02  0.00E+00  8.68E-04  5.12E-04  5.62E-04  2.21E-04  2.29E-05  7.80E-03  11.53  4.39E-01  2.86E-03  2.81E-02  0.00E+00  9.65E-04  5.10E-04  5.71E-04  2.08E-04  3.26E-05  8.48E-03  21.83  4.43E-01  2.55E-03  2.33E-02  0.00E+00  8.58E-04  4.04E-04  4.99E-04  1.65E-04  1.79E-05  7.31E-03  24.9  4.44E-01  2.61E-03  2.38E-02  0.00E+00  8.61E-04  4.09E-04  4.80E-04  1.76E-04  1.79E-05  7.37E-03  27.56  4.46E-01  2.71E-03  2.45E-02  0.00E+00  8.83E-04  4.44E-04  4.82E-04  1.69E-04  3.74E-05  7.64E-03  29.78  4.46E-01  2.82E-03  2.54E-02  0.00E+00  9.06E-04  4.63E-04  5.46E-04  2.08E-04  2.19E-05  8.12E-03  Total HC  Total HC ( C atom %) = 1 x CH4 + 2 x C2H2+2 x C2H4+2 x C2H6+3 x C3H8+4 x isoC4H10+4 x n-C4H10  239  Table AII(b).1.b : Experiment 1: Liquid Oxygenate production with time at Temperature - 548 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 3960 h-1, Catalyst wt. - 1.0 gm Mole fraction-  Time [hr]  AcCHO  Acetone  MeOH  Iso Ethanol propanol  3.25  1.33E-03  3.17E-04  2.46E-04  0.00E+00  6.11  1.59E-03  5.12E-04  2.06E-04  8.28  1.63E-03  5.13E-04  12.35  2.34E-03  22.83  PrOH  BuOH  AcCOOH PrCOOH  8.93E-04  5.95E-04  1.84E-04  2.14E-04  0.00E+00  1.96E-03  5.16E-04  1.93E-04  2.39E-04  0.00E+00  2.21E-03  5.20E-04  4.98E-04  1.78E-04  0.00E+00  2.00E-03  1.79E-03  3.81E-04  1.71E-04  0.00E+00  25.68  2.17E-03  4.16E-04  1.66E-04  28.45  2.39E-03  3.98E-04  30.00  2.25E-03  3.74E-04  Total Oxy.  REST  (C atom %)  9.47E-05  1.29E-04  9.40E-03  2.17E-04  1.42E-04  1.78E-04  1.27E-02  1.72E-04  3.27E-04  2.56E-04  6.26E-04  1.56E-02  5.18E-04  1.70E-04  2.82E-04  1.91E-04  6.04E-04  1.62E-02  1.73E-03  4.37E-04  1.82E-04  3.43E-04  2.18E-04  6.86E-04  1.45E-02  0.00E+00  1.72E-03  5.67E-04  2.60E-04  4.14E-04  2.41E-04  8.07E-04  1.67E-02  1.43E-04  0.00E+00  1.96E-03  4.58E-04  1.52E-04  2.13E-04  1.57E-04  5.90E-04  1.53E-02  1.96E-04  0.00E+00  1.96E-03  4.58E-04  1.52E-04  2.13E-04  1.57E-04  5.90E-04  1.50E-02  Symbols: AcCHO = Acetaldehyde; MeOH = Methanol; PrOH = Propanol; BuOH = Butanol; AcCOOH = Acetic Acid; PrCOOH = Propionic Acid; REST = Higher Carboxylic Acid, Higher Esters, Higher aldehydes, Higher Hydrocarbons (taking carbon number =4) Total Oxy. ( C atom %) = 2 x Acetaldehyde + 3 x Acetone+1 x MeOH+2 x Ethanol+3 x PrOH+4 x BuOH+2 x AcCOOH +3 x PrCOOH + 4 x REST  240  Table AII(b).2.a : Hydrocarbon production with time at Temperature - 573 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 7920 h-1, Catalyst wt. - 0.5 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  3.25  4.84E-01  4.94E-03  3.75E-02  0.00E+00  1.35E-03  9.46E-04  8.66E-04  2.82E-04  5.49E-05  1.35E-02  10.5  4.78E-01  4.60E-03  3.37E-02  0.00E+00  1.21E-03  8.60E-04  7.53E-04  2.81E-04  5.37E-05  1.23E-02  22.62  4.76E-01  5.41E-03  3.76E-02  0.00E+00  1.37E-03  9.81E-04  8.37E-04  3.10E-04  7.16E-05  1.41E-02  31.3  4.78E-01  5.60E-03  3.79E-02  0.00E+00  1.40E-03  9.93E-04  8.70E-04  3.33E-04  7.35E-05  1.46E-02  34.67  4.79E-01  5.68E-03  3.80E-02  0.00E+00  1.40E-03  1.02E-03  8.39E-04  3.35E-04  5.71E-05  1.46E-02  47.21  4.75E-01  5.91E-03  3.71E-02  0.00E+00  1.35E-03  1.03E-03  7.98E-04  2.69E-04  5.88E-05  1.44E-02  50.27  4.80E-01  5.81E-03  3.71E-02  0.00E+00  1.32E-03  1.05E-03  8.17E-04  2.79E-04  6.27E-05  1.44E-02  53.58  4.81E-01  5.81E-03  3.68E-02  0.00E+00  1.32E-03  1.05E-03  7.95E-04  2.90E-04  6.75E-05  1.44E-02  56.7  4.81E-01  5.91E-03  3.63E-02  0.00E+00  1.28E-03  1.08E-03  7.95E-04  2.92E-04  5.76E-05  1.44E-02  59.83  4.84E-01  5.91E-03  3.63E-02  0.00E+00  1.28E-03  1.08E-03  7.95E-04  2.92E-04  5.76E-05  1.44E-02  Total HC  241  Table AII(b).2.b : Liquid Oxygenate production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 7920 h-1, Catalyst wt. - 0.5 gm.  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  3.93  3.52E-03  9.44E-04  4.58E-04  0.00E+00  11.38  3.42E-03  1.08E-03  4.13E-04  23.65  4.11E-03  1.07E-03  32.06  4.32E-03  35.58  PrOH  BuOH  AcCOOH PrCOOH  3.81E-03  4.98E-04  1.57E-04  2.17E-04  0.00E+00  3.14E-03  5.85E-04  1.77E-04  4.72E-04  0.00E+00  4.12E-03  6.20E-04  1.38E-03  5.05E-04  0.00E+00  4.21E-03  4.43E-03  1.40E-03  5.91E-04  0.00E+00  47.98  4.46E-03  1.54E-03  4.71E-04  51.08  4.25E-03  1.16E-03  54.35  4.49E-03  57.58 59.83  Total Oxy.  REST  (C atom %)  1.63E-04  3.62E-04  2.24E-02  2.55E-04  1.89E-04  5.24E-04  2.24E-02  2.63E-04  3.15E-04  2.47E-04  6.15E-04  2.69E-02  7.74E-04  3.03E-04  4.21E-04  2.91E-04  8.36E-04  3.03E-02  4.40E-03  7.13E-04  2.80E-04  3.34E-04  2.38E-04  6.87E-04  2.99E-02  0.00E+00  4.20E-03  8.10E-04  3.05E-04  4.25E-04  2.86E-04  8.49E-04  3.11E-02  5.54E-04  0.00E+00  4.11E-03  7.00E-04  2.78E-04  3.37E-04  3.16E-04  6.49E-04  2.82E-02  1.24E-03  5.32E-04  0.00E+00  4.25E-03  7.00E-04  2.78E-04  3.37E-04  3.16E-04  6.49E-04  2.92E-02  4.35E-03  1.49E-03  5.19E-04  0.00E+00  4.15E-03  8.84E-04  3.57E-04  4.00E-04  2.95E-04  1.11E-03  3.22E-02  3.93E-03  1.49E-03  5.05E-04  0.00E+00  3.43E-03  8.84E-04  3.57E-04  4.00E-04  2.95E-04  1.11E-03  2.99E-02  242  Table AII(b).3.a : Hydrocarbon production with time at Temperature - 598 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  4.2  4.82E-01  5.27E-03  3.01E-02  0.00E+00  1.14E-03  1.13E-03  7.22E-04  2.20E-04  4.48E-05  1.30E-02  12.35  4.73E-01  6.43E-03  3.49E-02  0.00E+00  1.11E-03  1.43E-03  8.42E-04  2.65E-04  7.57E-05  1.54E-02  24.05  4.68E-01  7.58E-03  3.77E-02  0.00E+00  1.25E-03  1.52E-03  9.32E-04  3.06E-04  5.14E-05  1.73E-02  31  4.67E-01  7.93E-03  4.03E-02  0.00E+00  1.41E-03  1.57E-03  9.78E-04  3.41E-04  7.20E-05  1.85E-02  33.77  4.73E-01  7.35E-03  3.53E-02  0.00E+00  1.27E-03  1.46E-03  8.68E-04  3.17E-04  8.00E-05  1.70E-02  35.2  4.70E-01  7.54E-03  3.65E-02  0.00E+00  1.32E-03  1.46E-03  9.06E-04  3.06E-04  5.88E-05  1.73E-02  37.85  4.76E-01  7.50E-03  3.64E-02  0.00E+00  1.21E-03  1.55E-03  8.88E-04  3.05E-04  7.11E-05  1.72E-02  40.13  4.77E-01  7.41E-03  3.57E-02  0.00E+00  1.24E-03  1.47E-03  8.56E-04  3.02E-04  6.75E-05  1.69E-02  44.05  4.73E-01  7.40E-03  3.54E-02  0.00E+00  1.18E-03  1.51E-03  8.44E-04  3.01E-04  7.38E-05  1.68E-02  46.03  4.73E-01  7.44E-03  3.54E-02  0.00E+00  1.22E-03  1.50E-03  8.52E-04  2.87E-04  5.13E-05  1.68E-02  Total HC  243  Table AII(b).3.b : Liquid Oxygenate production with time at  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  5.08  2.67E-03  1.90E-04  5.02E-04  0.00E+00  13.13  3.72E-03  7.18E-04  6.27E-04  24.93  4.59E-03  3.06E-04  31.87  5.45E-03  33.55  PrOH  BuOH  AcCOOH PrCOOH  2.65E-03  3.92E-04  1.24E-04  1.20E-04  0.00E+00  3.72E-03  6.33E-04  2.05E-04  6.71E-04  0.00E+00  4.34E-03  6.12E-04  9.40E-04  7.05E-04  0.00E+00  4.98E-03  5.14E-03  6.48E-04  6.42E-04  0.00E+00  36.03  5.33E-03  7.24E-04  6.23E-04  38.7  5.38E-03  6.50E-04  40.97  5.28E-03  44.97 46.83  Total Oxy.  REST  (C atom %)  7.58E-05  2.29E-04  1.48E-02  2.32E-04  1.41E-04  4.51E-04  2.31E-02  1.82E-04  2.60E-04  1.52E-04  4.43E-04  2.48E-02  7.13E-04  2.23E-04  2.54E-04  1.77E-04  5.04E-04  3.05E-02  4.46E-03  5.58E-04  1.75E-04  2.36E-04  1.58E-04  4.21E-04  2.68E-02  0.00E+00  4.36E-03  6.35E-04  1.50E-04  1.91E-04  1.35E-04  6.10E-04  2.79E-02  6.67E-04  0.00E+00  4.44E-03  5.74E-04  1.46E-04  1.82E-04  1.22E-04  5.41E-04  2.75E-02  6.50E-04  6.19E-04  0.00E+00  4.46E-03  5.96E-04  1.45E-04  1.80E-04  1.15E-04  5.36E-04  2.73E-02  4.83E-03  8.04E-04  6.99E-04  0.00E+00  4.31E-03  6.59E-04  1.52E-04  1.90E-04  1.33E-04  6.25E-04  2.73E-02  5.37E-03  7.23E-04  6.49E-04  0.00E+00  4.42E-03  5.58E-04  1.86E-04  1.83E-04  1.24E-04  6.63E-04  2.82E-02  244  Table AII(b).4.a : Hydrocarbon production with time at Temperature - 615 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  2.03  4.51E-01  1.00E-02  5.26E-02  0.00E+00  1.68E-03  2.61E-03  1.42E-03  3.96E-04  1.37E-04  2.50E-02  5.03  4.49E-01  1.08E-02  5.30E-02  0.00E+00  1.65E-03  2.68E-03  1.38E-03  3.79E-04  9.92E-05  2.56E-02  9.5  4.48E-01  1.09E-02  5.12E-02  0.00E+00  1.58E-03  2.59E-03  1.29E-03  3.74E-04  1.37E-04  2.51E-02  20.1  4.54E-01  1.12E-02  5.03E-02  0.00E+00  1.44E-03  2.70E-03  1.28E-03  3.72E-04  1.33E-04  2.53E-02  22.8  4.57E-01  1.15E-02  5.18E-02  0.00E+00  1.46E-03  2.78E-03  1.30E-03  4.03E-04  1.33E-04  2.60E-02  25.3  4.55E-01  1.23E-02  5.45E-02  0.00E+00  1.68E-03  2.84E-03  1.40E-03  4.38E-04  1.35E-04  2.79E-02  27.8  4.55E-01  1.15E-02  5.48E-02  0.00E+00  1.61E-03  2.93E-03  1.40E-03  4.37E-04  1.32E-04  2.70E-02  33.5  4.47E-01  1.25E-02  5.39E-02  0.00E+00  1.51E-03  2.95E-03  1.35E-03  4.19E-04  1.26E-04  2.77E-02  45.13  4.52E-01  1.23E-02  5.16E-02  0.00E+00  1.43E-03  2.89E-03  1.27E-03  4.03E-04  1.13E-04  2.68E-02  47.5  4.54E-01  1.23E-02  5.10E-02  0.00E+00  1.41E-03  2.99E-03  1.27E-03  3.97E-04  1.23E-04  2.70E-02  50  4.60E-01  1.24E-02  5.12E-02  0.00E+00  1.40E-03  2.90E-03  1.27E-03  3.95E-04  1.17E-04  2.68E-02  52.5  4.61E-01  1.24E-02  5.09E-02  0.00E+00  1.39E-03  2.93E-03  1.27E-03  3.78E-04  1.17E-04  2.68E-02  Total HC  245  Table AII(b).4.b : Liquid Oxygenate production with time at Temperature - 615 K, Pressure - 8.27 MPa, H2:CO - 1:1 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  2.30  4.13E-03  5.04E-04  1.13E-03  0.00E+00  6.02  4.70E-03  1.11E-03  1.19E-03  10.40  5.06E-03  7.00E-04  20.98  5.80E-03  23.63  PrOH  BuOH  AcCOOH PrCOOH  4.58E-03  9.52E-04  2.06E-04  1.88E-04  0.00E+00  4.85E-03  9.92E-04  2.59E-04  1.11E-03  0.00E+00  5.16E-03  1.09E-03  1.11E-03  1.17E-03  0.00E+00  5.37E-03  6.10E-03  1.09E-03  1.19E-03  0.00E+00  26.15  7.30E-03  1.14E-03  1.21E-03  28.62  7.54E-03  1.14E-03  34.23  7.59E-03  46.05  Total Oxy.  REST  (C atom %)  1.16E-04  4.55E-04  2.63E-02  2.27E-04  1.17E-04  6.26E-04  3.09E-02  2.99E-04  3.07E-04  2.20E-04  8.07E-04  3.26E-02  9.25E-04  2.24E-04  2.49E-04  1.39E-04  6.82E-04  3.41E-02  6.05E-03  9.56E-04  2.30E-04  2.53E-04  1.41E-04  5.91E-04  3.58E-02  0.00E+00  6.72E-03  9.56E-04  2.47E-04  2.68E-04  1.56E-04  7.43E-04  4.05E-02  1.24E-03  0.00E+00  6.88E-03  1.02E-03  3.06E-04  2.62E-04  1.50E-04  6.86E-04  4.15E-02  1.32E-03  1.19E-03  0.00E+00  6.77E-03  1.18E-03  3.26E-04  2.83E-04  1.64E-04  7.25E-04  4.27E-02  7.58E-03  1.16E-03  1.18E-03  0.00E+00  6.63E-03  9.67E-04  2.79E-04  2.59E-04  1.60E-04  7.10E-04  4.09E-02  48.37  7.44E-03  9.38E-04  1.17E-03  0.00E+00  6.52E-03  8.31E-04  2.62E-04  2.57E-04  1.65E-04  7.57E-04  3.95E-02  50.8  7.72E-03  9.91E-04  1.18E-03  0.00E+00  6.64E-03  8.86E-04  2.29E-04  2.41E-04  1.42E-04  6.91E-04  4.01E-02  53.38  7.66E-03  1.09E-03  1.16E-03  0.00E+00  6.92E-03  1.04E-03  2.67E-04  2.82E-04  1.60E-04  8.35E-04  4.22E-02  246  Table AII(b).5.a : Hydrocarbon production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 7920 h-1, Catalyst wt. - 0.50 gm.  Mole fraction C2H4 C2H6  Time [hr]  CO  CH4  CO2  C2H2  4.23  4.10E-01  5.56E-03  3.37E-02  0.00E+00  1.37E-03  6.33  4.08E-01  5.61E-03  3.33E-02  0.00E+00  19.33  4.08E-01  6.06E-03  3.50E-02  22.5  4.06E-01  6.03E-03  27.38  4.03E-01  29.36  Total HC C3H8  isoC4H10  n-C4H10  (C atom%)  9.60E-04  8.11E-04  2.69E-04  3.42E-05  1.39E-02  1.35E-03  9.99E-04  8.07E-04  2.57E-04  6.33E-05  1.40E-02  0.00E+00  1.41E-03  1.01E-03  7.92E-04  2.50E-04  4.30E-05  1.45E-02  3.44E-02  0.00E+00  1.35E-03  1.02E-03  8.00E-04  2.66E-04  4.33E-05  1.44E-02  6.18E-03  3.48E-02  0.00E+00  1.38E-03  1.05E-03  7.65E-04  2.79E-04  5.27E-05  1.47E-02  4.07E-01  6.25E-03  3.50E-02  0.00E+00  1.37E-03  1.06E-03  7.93E-04  2.68E-04  3.76E-05  1.47E-02  42.75  4.04E-01  6.27E-03  3.41E-02  0.00E+00  1.34E-03  1.07E-03  7.76E-04  2.65E-04  4.17E-05  1.47E-02  45.5  4.07E-01  6.35E-03  3.42E-02  0.00E+00  1.31E-03  1.08E-03  7.83E-04  2.75E-04  5.60E-05  1.48E-02  49.9  4.11E-01  6.34E-03  3.38E-02  0.00E+00  1.28E-03  1.08E-03  7.71E-04  2.58E-04  5.45E-05  1.46E-02  55.35  4.11E-01  6.33E-03  3.29E-02  0.00E+00  1.24E-03  1.11E-03  7.71E-04  2.71E-04  5.45E-05  1.46E-02  67.95  4.10E-01  6.06E-03  3.00E-02  0.00E+00  9.84E-04  1.12E-03  6.40E-04  2.19E-04  5.22E-05  1.33E-02  93.38333  4.10E-01  6.06E-03  3.00E-02  0.00E+00  9.84E-04  1.12E-03  6.40E-04  2.19E-04  5.22E-05  1.33E-02  247  Table AII(b).5.b : Liquid Oxygenate production with time Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 7920 h-1, Catalyst wt. - 0.50 gm. Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  5.20  3.16E-03  1.49E-03  5.28E-04  0.00E+00  7.10  3.86E-03  1.42E-03  4.61E-04  20.50  4.19E-03  1.42E-03  23.42  4.37E-03  28.20  PrOH  BuOH  AcCOOH PrCOOH  3.10E-03  7.73E-04  2.44E-04  3.23E-04  0.00E+00  3.51E-03  6.05E-04  1.61E-04  4.84E-04  0.00E+00  3.84E-03  6.78E-04  1.46E-03  4.95E-04  0.00E+00  3.83E-03  4.37E-03  1.46E-03  4.65E-04  0.00E+00  30.23  4.40E-03  1.55E-03  4.99E-04  43.53  4.51E-03  1.50E-03  46.35  4.49E-03  50.73  Total Oxy.  REST  (C atom %)  1.54E-04  3.30E-04  2.32E-02  2.43E-04  1.59E-04  3.31E-04  2.42E-02  1.99E-04  3.35E-04  1.51E-04  6.72E-04  2.74E-02  6.38E-04  2.34E-04  3.72E-04  2.17E-04  5.56E-04  2.77E-02  3.89E-03  6.51E-04  2.27E-04  3.38E-04  1.89E-04  4.31E-04  2.72E-02  0.00E+00  3.95E-03  6.87E-04  2.35E-04  3.79E-04  2.12E-04  4.73E-04  2.81E-02  5.43E-04  0.00E+00  3.98E-03  7.31E-04  2.33E-04  3.64E-04  2.07E-04  4.08E-04  2.81E-02  1.48E-03  5.16E-04  0.00E+00  3.86E-03  6.74E-04  2.35E-04  3.75E-04  2.22E-04  5.25E-04  2.81E-02  4.41E-03  1.16E-03  5.08E-04  0.00E+00  3.80E-03  5.93E-04  2.01E-04  3.03E-04  1.60E-04  4.08E-04  2.57E-02  56.13  4.35E-03  1.22E-03  5.70E-04  0.00E+00  3.69E-03  6.35E-04  1.88E-04  2.76E-04  1.47E-04  3.66E-04  2.54E-02  68.76  3.89E-03  1.22E-03  5.16E-04  0.00E+00  3.15E-03  6.35E-04  1.88E-04  2.76E-04  1.47E-04  3.66E-04  2.34E-02  248  Table AII(b).6.a : Hydrocarbon production with time at  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  2.6  4.03E-01  9.27E-03  4.57E-02  0.00E+00  1.69E-03  1.76E-03  1.05E-03  3.10E-04  8.19E-05  2.09E-02  8  4.04E-01  8.90E-03  4.26E-02  0.00E+00  1.47E-03  1.74E-03  9.87E-04  3.10E-04  8.04E-05  1.98E-02  20.8  3.96E-01  8.70E-03  4.03E-02  0.00E+00  1.30E-03  1.72E-03  8.94E-04  2.62E-04  8.95E-05  1.88E-02  25.5  4.11E-01  8.85E-03  4.05E-02  0.00E+00  1.28E-03  1.75E-03  9.43E-04  3.37E-04  7.36E-05  1.94E-02  32.08333  4.06E-01  8.75E-03  3.96E-02  0.00E+00  1.29E-03  1.76E-03  9.11E-04  3.00E-04  1.07E-04  1.92E-02  45.15  4.07E-01  8.57E-03  3.79E-02  0.00E+00  1.19E-03  1.74E-03  8.50E-04  2.42E-04  7.34E-05  1.82E-02  47.5  4.05E-01  8.35E-03  3.59E-02  0.00E+00  1.19E-03  1.63E-03  8.00E-04  2.35E-04  7.04E-05  1.76E-02  49.61667  4.04E-01  8.30E-03  3.54E-02  0.00E+00  1.16E-03  1.64E-03  7.80E-04  2.48E-04  8.96E-05  1.76E-02  52.16667  4.06E-01  8.57E-03  3.63E-02  0.00E+00  1.36E-03  1.55E-03  8.23E-04  2.76E-04  7.75E-05  1.83E-02  54.5  4.05E-01  8.47E-03  3.57E-02  0.00E+00  1.35E-03  1.60E-03  8.19E-04  2.96E-04  7.90E-05  1.83E-02  57.5  4.05E-01  8.47E-03  3.57E-02  0.00E+00  1.35E-03  1.60E-03  8.19E-04  2.96E-04  7.90E-05  1.83E-02  59  4.05E-01  8.47E-03  3.57E-02  0.00E+00  1.35E-03  1.60E-03  8.19E-04  2.96E-04  7.90E-05  1.83E-02  Total HC  249  Table AII(b).6.b : Liquid Oxygenate production with time  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm.  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  3.32  4.62E-03  1.46E-03  8.33E-04  0.00E+00  8.97  3.86E-03  1.58E-03  8.61E-04  21.58  4.25E-03  1.15E-03  26.25  4.61E-03  33.00  PrOH  BuOH  AcCOOH PrCOOH  4.56E-03  4.51E-04  1.54E-04  2.74E-04  0.00E+00  4.39E-03  4.85E-04  1.85E-04  8.32E-04  0.00E+00  4.08E-03  3.72E-04  1.19E-03  8.68E-04  0.00E+00  4.31E-03  4.59E-03  1.09E-03  7.99E-04  0.00E+00  46.00  4.52E-03  1.21E-03  8.48E-04  48.35  4.60E-03  1.64E-03  50.62  4.30E-03  53.17  Total Oxy.  REST  (C atom %)  1.89E-04  4.38E-04  2.84E-02  3.02E-04  1.97E-04  3.96E-04  2.71E-02  1.78E-04  2.97E-04  1.66E-04  3.86E-04  2.54E-02  4.01E-04  1.49E-04  1.90E-04  9.13E-05  2.56E-04  2.57E-02  4.61E-03  5.73E-04  2.31E-04  2.70E-04  1.66E-04  3.78E-04  2.77E-02  0.00E+00  4.05E-03  6.10E-04  2.55E-04  3.12E-04  1.65E-04  5.09E-04  2.76E-02  7.33E-04  0.00E+00  3.97E-03  7.62E-04  2.89E-04  3.28E-04  1.63E-04  6.32E-04  2.99E-02  9.48E-04  7.03E-04  0.00E+00  3.88E-03  7.62E-04  2.89E-04  3.28E-04  1.63E-04  6.32E-04  2.70E-02  4.99E-03  1.02E-03  7.67E-04  0.00E+00  4.20E-03  6.01E-04  2.08E-04  2.15E-04  1.04E-04  4.94E-04  2.76E-02  55.00  4.83E-03  9.42E-04  7.37E-04  0.00E+00  4.13E-03  5.16E-04  2.08E-04  2.22E-04  1.57E-04  5.73E-04  2.71E-02  58.00  4.83E-03  9.42E-04  7.37E-04  0.00E+00  4.13E-03  5.16E-04  2.08E-04  2.22E-04  1.57E-04  5.73E-04  2.71E-02  60.00  4.83E-03  9.42E-04  7.37E-04  0.00E+00  4.13E-03  5.16E-04  2.08E-04  2.22E-04  1.57E-04  5.73E-04  2.71E-02  250  Table AII(b).7.a : Hydrocarbon production with time at  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm.  [Repeat experiment] Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  5.62  3.72E-01  8.70E-03  4.25E-02  0.00E+00  1.64E-03  1.64E-03  1.02E-03  3.25E-04  7.69E-05  1.99E-02  9.00  3.78E-01  9.00E-03  4.21E-02  0.00E+00  1.45E-03  1.68E-03  9.83E-04  3.28E-04  9.09E-05  1.99E-02  21.00  3.80E-01  8.87E-03  4.14E-02  0.00E+00  1.42E-03  1.65E-03  9.55E-04  3.00E-04  8.06E-05  1.94E-02  24.00  3.79E-01  8.77E-03  4.07E-02  0.00E+00  1.41E-03  1.64E-03  9.37E-04  3.43E-04  8.75E-05  1.94E-02  26.50  3.76E-01  8.60E-03  3.92E-02  0.00E+00  1.33E-03  1.56E-03  8.94E-04  2.96E-04  8.35E-05  1.86E-02  32.47  3.81E-01  8.20E-03  3.60E-02  0.00E+00  1.27E-03  1.49E-03  8.26E-04  2.62E-04  8.06E-05  1.76E-02  36.40  3.83E-01  8.08E-03  3.50E-02  0.00E+00  1.24E-03  1.47E-03  7.87E-04  2.91E-04  8.23E-05  1.73E-02  Total HC  251  Table AII(b).7.b : Liquid Oxygenate production with time Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. [Repeat experiment] Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  6.83  4.22E-03  7.61E-04  5.47E-04  0.00E+00  9.67  4.96E-03  1.19E-03  5.57E-04  21.67  4.96E-03  1.04E-03  24.58  4.86E-03  27.33  PrOH  BuOH  AcCOOH PrCOOH  4.67E-03  4.91E-04  1.01E-04  1.22E-04  0.00E+00  4.64E-03  6.73E-04  1.99E-04  5.34E-04  0.00E+00  4.47E-03  6.07E-04  9.40E-04  5.41E-04  0.00E+00  4.51E-03  4.95E-03  1.15E-03  5.02E-04  0.00E+00  33.3  4.42E-03  9.22E-04  5.12E-04  37.08333  4.03E-03  8.46E-04  4.81E-04  Total Oxy.  REST  (C atom %)  5.95E-05  1.88E-04  2.37E-02  1.83E-04  8.40E-05  4.92E-04  2.87E-02  1.67E-04  2.32E-04  1.22E-04  5.61E-04  2.81E-02  7.88E-04  3.02E-04  3.54E-04  2.10E-04  7.84E-04  3.02E-02  4.34E-03  6.03E-04  1.87E-04  2.59E-04  9.56E-05  6.21E-04  2.84E-02  0.00E+00  4.04E-03  5.57E-04  2.36E-04  2.47E-04  1.12E-04  7.33E-04  2.66E-02  0.00E+00  3.78E-03  5.51E-04  2.02E-04  2.16E-04  8.89E-05  4.42E-04  2.36E-02  252  Table AII(b).8.a : Hydrocarbon production with time at  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm.  [Repeat experiment] Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  10.55  3.63E-01  1.02E-02  5.16E-02  0.00E+00  2.01E-03  1.83E-03  1.19E-03  4.19E-04  1.09E-04  2.36E-02  23.18  3.66E-01  9.62E-03  4.56E-02  0.00E+00  1.74E-03  1.70E-03  1.03E-03  3.65E-04  8.05E-05  2.14E-02  25.40  3.70E-01  9.74E-03  4.59E-02  0.00E+00  1.76E-03  1.68E-03  1.04E-03  3.84E-04  9.01E-05  2.17E-02  27.52  3.71E-01  9.79E-03  4.45E-02  0.00E+00  1.76E-03  1.72E-03  1.05E-03  3.80E-04  8.76E-05  2.18E-02  32.55  3.70E-01  9.75E-03  4.50E-02  0.00E+00  1.69E-03  1.71E-03  1.02E-03  3.64E-04  8.92E-05  2.14E-02  34.33  3.69E-01  9.65E-03  4.43E-02  0.00E+00  1.70E-03  1.89E-03  1.01E-03  3.43E-04  8.81E-05  2.16E-02  36.00  3.69E-01  9.65E-03  4.43E-02  0.00E+00  1.70E-03  1.89E-03  1.01E-03  3.43E-04  8.81E-05  2.16E-02  Total HC  253  Table AII(b).8.b : Liquid Oxygenate production with time Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 1.5 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. [Repeat experiment]  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  11.33  5.44E-03  2.65E-03  6.32E-04  0.00E+00  24.00  5.38E-03  2.50E-03  5.88E-04  26.13  5.68E-03  2.32E-03  28.50  5.65E-03  33.33  PrOH  BuOH  AcCOOH PrCOOH  5.69E-03  1.41E-03  5.24E-04  3.65E-04  0.00E+00  5.25E-03  1.14E-03  3.85E-04  5.73E-04  0.00E+00  5.47E-03  9.63E-04  1.96E-03  5.85E-04  0.00E+00  5.39E-03  5.57E-03  2.85E-03  5.58E-04  0.00E+00  35.17  5.71E-03  2.37E-03  5.50E-04  37.00  5.71E-03  2.37E-03  5.50E-04  Total Oxy.  REST  (C atom %)  1.78E-04  7.50E-04  4.14E-02  3.74E-04  2.15E-04  7.99E-04  3.89E-02  3.71E-04  3.46E-04  1.62E-04  7.37E-04  3.83E-02  1.01E-03  3.87E-04  3.47E-04  1.79E-04  7.12E-04  3.72E-02  5.35E-03  1.00E-03  4.13E-04  4.09E-04  1.96E-04  8.05E-04  4.02E-02  0.00E+00  5.25E-03  1.12E-03  4.61E-04  3.49E-04  1.64E-04  5.50E-04  3.82E-02  0.00E+00  5.25E-03  1.12E-03  4.61E-04  3.49E-04  1.64E-04  5.50E-04  3.82E-02  254  Table AII(b).9.a : Hydrocarbon production with time at Temperature - 548 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 3960 h-1, Catalyst wt. - 1.0 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  27.72  3.36E-01  5.60E-03  3.29E-02  0.00E+00  1.31E-03  8.38E-04  7.07E-04  2.58E-04  0.00E+00  1.31E-02  31.75  3.27E-01  5.61E-03  3.25E-02  0.00E+00  1.29E-03  8.46E-04  7.06E-04  2.49E-04  0.00E+00  1.30E-02  45.33  4.07E-01  7.40E-03  4.27E-02  0.00E+00  1.67E-03  1.08E-03  9.06E-04  3.40E-04  8.48E-05  1.73E-02  48.15  4.48E-01  8.20E-03  4.71E-02  0.00E+00  1.84E-03  1.26E-03  1.03E-03  3.64E-04  7.65E-05  1.93E-02  51.15  4.28E-01  7.94E-03  4.54E-02  0.00E+00  1.79E-03  1.19E-03  9.61E-04  3.54E-04  7.76E-05  1.85E-02  54.17  4.53E-01  8.06E-03  4.60E-02  0.00E+00  1.82E-03  1.17E-03  1.00E-03  3.41E-04  7.58E-05  1.87E-02  69.03  5.82E-01  1.07E-02  6.01E-02  0.00E+00  2.36E-03  1.56E-03  1.29E-03  4.40E-04  8.59E-05  2.46E-02  71.48  5.56E-01  1.03E-02  5.74E-02  0.00E+00  2.26E-03  1.50E-03  1.21E-03  4.41E-04  8.91E-05  2.35E-02  74.00  5.62E-01  1.05E-02  5.86E-02  0.00E+00  2.31E-03  1.53E-03  1.17E-03  4.46E-04  1.01E-04  2.39E-02  76.32  5.81E-01  1.08E-02  5.98E-02  0.00E+00  2.35E-03  1.58E-03  1.26E-03  4.46E-04  9.31E-05  2.46E-02  78.32  5.48E-01  1.03E-02  5.72E-02  0.00E+00  2.23E-03  1.60E-03  1.21E-03  4.49E-04  1.00E-04  2.38E-02  93.38  5.48E-01  1.03E-02  5.72E-02  0.00E+00  2.23E-03  1.60E-03  1.21E-03  4.49E-04  1.00E-04  2.38E-02  Total HC  255  Table AII(b).9.b : Liquid Oxygenate production with time  Temperature - 548 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 3960 h-1, Catalyst wt. - 1.0 gm.  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  28.72  4.04E-03  1.25E-03  3.04E-04  0.00E+00  32.63  5.31E-03  9.37E-04  3.25E-04  46.05  5.30E-03  1.56E-03  49.08  6.06E-03  52.08  PrOH  BuOH  AcCOOH PrCOOH  3.54E-03  6.40E-04  2.97E-04  3.78E-04  0.00E+00  3.35E-03  6.45E-04  2.47E-04  4.24E-04  0.00E+00  4.95E-03  7.47E-04  1.42E-03  5.01E-04  0.00E+00  5.52E-03  5.79E-03  1.34E-03  4.61E-04  0.00E+00  55.33  5.69E-03  1.29E-03  4.81E-04  69.77  7.97E-03  2.63E-03  72.03  7.65E-03  74.90  Total Oxy.  REST  (C atom %)  3.12E-04  7.84E-04  2.72E-02  3.81E-04  3.82E-04  5.77E-04  2.76E-02  3.05E-04  3.96E-04  3.38E-04  7.44E-04  3.39E-02  8.54E-04  4.39E-04  5.77E-04  5.32E-04  1.48E-03  4.09E-02  5.18E-03  8.48E-04  3.23E-04  5.00E-04  3.13E-04  9.14E-04  3.58E-02  0.00E+00  5.43E-03  6.26E-04  2.21E-04  3.65E-04  2.96E-04  9.04E-04  3.46E-02  6.47E-04  0.00E+00  7.23E-03  1.31E-03  5.03E-04  5.32E-04  4.73E-04  9.47E-04  5.12E-02  2.33E-03  6.47E-04  0.00E+00  7.23E-03  1.26E-03  4.92E-04  5.71E-04  4.81E-04  1.34E-03  5.11E-02  7.65E-03  2.19E-03  6.12E-04  0.00E+00  6.94E-03  1.27E-03  5.07E-04  5.79E-04  4.87E-04  1.46E-03  5.07E-02  77.13  7.86E-03  2.45E-03  6.05E-04  0.00E+00  7.07E-03  1.19E-03  4.79E-04  5.18E-04  4.68E-04  1.30E-03  5.09E-02  79.58  7.43E-03  2.33E-03  6.13E-04  0.00E+00  7.22E-03  1.31E-03  4.94E-04  5.64E-04  4.62E-04  1.48E-03  5.13E-02  94.28  7.43E-03  2.33E-03  6.05E-04  0.00E+00  6.75E-03  1.31E-03  4.94E-04  5.64E-04  4.62E-04  1.48E-03  5.03E-02  256  Table AII(b).10.a : Hydrocarbon production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 7960 h-1, Catalyst wt. - 0.5 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  3.53  3.28E-01  8.03E-03  4.22E-02  0.00E+00  1.58E-03  2.60E-03  1.04E-03  3.19E-04  9.71E-05  2.12E-02  7.4  3.10E-01  7.53E-03  3.81E-02  0.00E+00  1.48E-03  1.38E-03  9.29E-04  2.94E-04  8.68E-05  1.75E-02  19.53  2.91E-01  6.83E-03  3.33E-02  0.00E+00  1.36E-03  1.19E-03  7.81E-04  2.69E-04  5.26E-05  1.56E-02  22.45  2.94E-01  6.94E-03  3.38E-02  0.00E+00  1.36E-03  1.18E-03  7.85E-04  2.50E-04  5.17E-05  1.56E-02  25.2  2.97E-01  6.97E-03  3.39E-02  0.00E+00  1.35E-03  1.18E-03  7.95E-04  2.51E-04  4.90E-05  1.56E-02  27.63  2.97E-01  7.01E-03  3.41E-02  0.00E+00  1.36E-03  1.18E-03  8.08E-04  2.54E-04  4.81E-05  1.57E-02  30.95  2.99E-01  7.09E-03  3.43E-02  0.00E+00  1.37E-03  1.18E-03  8.01E-04  2.77E-04  7.89E-05  1.60E-02  44.35  2.97E-01  7.13E-03  3.45E-02  0.00E+00  1.29E-03  1.24E-03  7.73E-04  2.63E-04  5.95E-05  1.58E-02  47.03  2.95E-01  7.09E-03  3.42E-02  0.00E+00  1.27E-03  1.32E-03  7.79E-04  2.63E-04  6.15E-05  1.59E-02  50.367  3.05E-01  7.50E-03  3.61E-02  0.00E+00  1.33E-03  1.32E-03  8.09E-04  2.82E-04  6.30E-05  1.66E-02  52.9  2.97E-01  7.32E-03  3.52E-02  0.00E+00  1.27E-03  1.32E-03  8.10E-04  2.87E-04  8.32E-05  1.64E-02  54.85  2.99E-01  7.60E-03  3.64E-02  0.00E+00  1.30E-03  1.31E-03  8.47E-04  2.68E-04  5.51E-05  1.67E-02  Total HC  257  Table AII(b).10.b : Liquid Oxygenate production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 7960 h-1, Catalyst wt. - 0.5 gm.  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  4.37  5.64E-03  1.81E-03  7.46E-04  0.00E+00  8.20  5.21E-03  1.86E-03  6.91E-04  20.32  4.57E-03  1.96E-03  23.45  4.61E-03  26.01  PrOH  BuOH  AcCOOH PrCOOH  5.34E-03  9.54E-04  3.73E-04  5.49E-04  0.00E+00  4.78E-03  1.30E-03  4.30E-04  6.03E-04  0.00E+00  3.78E-03  1.12E-03  1.98E-03  5.96E-04  0.00E+00  3.91E-03  4.69E-03  1.91E-03  6.22E-04  0.00E+00  28.58  4.69E-03  1.75E-03  6.97E-04  31.85  4.78E-03  2.04E-03  45.18  4.92E-03  47.9  Total Oxy.  REST  (C atom %)  2.51E-04  5.03E-04  3.63E-02  5.17E-04  2.31E-04  5.05E-04  3.56E-02  5.47E-04  6.55E-04  3.03E-04  7.32E-04  3.39E-02  1.11E-03  4.74E-04  4.78E-04  2.27E-04  6.19E-04  3.29E-02  4.00E-03  9.05E-04  3.75E-04  5.11E-04  2.65E-04  7.01E-04  3.26E-02  0.00E+00  3.79E-03  8.23E-04  3.41E-04  4.81E-04  2.93E-04  8.08E-04  3.18E-02  6.76E-04  0.00E+00  4.29E-03  8.07E-04  3.35E-04  4.67E-04  2.75E-04  7.43E-04  3.34E-02  1.68E-03  6.59E-04  0.00E+00  4.06E-03  6.77E-04  3.09E-04  4.70E-04  3.11E-04  6.66E-04  3.15E-02  4.76E-03  1.93E-03  6.91E-04  0.00E+00  5.39E-03  7.86E-04  3.22E-04  4.47E-04  2.77E-04  6.95E-04  3.49E-02  51.33  5.11E-03  1.88E-03  6.87E-04  0.00E+00  4.29E-03  8.66E-04  3.46E-04  4.79E-04  3.29E-04  8.31E-04  3.44E-02  53.62  5.06E-03  1.73E-03  6.90E-04  0.00E+00  4.08E-03  8.11E-04  2.24E-04  3.53E-04  2.47E-04  6.70E-04  3.16E-02  55.65  4.80E-03  1.88E-03  7.32E-04  0.00E+00  4.03E-03  8.73E-04  3.40E-04  4.30E-04  3.19E-04  8.13E-04  3.31E-02  258  Table AII(b).11.a : Hydrocarbon production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 7960 h-1, Catalyst wt. - 0.5 gm.  [Repeat experiment] Mole fraction C2H4 C2H6  Time [hr]  CO  CH4  CO2  C2H2  8.5  2.65E-01  8.63E-03  4.57E-02  0.00E+00  1.65E-03  20  2.66E-01  8.69E-03  4.51E-02  0.00E+00  22.25  2.59E-01  8.12E-03  4.19E-02  24.16667  2.71E-01  8.03E-03  29.5  2.72E-01  42.75  Total HC C3H8  isoC4H10  n-C4H10  (C atom%)  1.62E-03  1.04E-03  3.50E-04  8.35E-05  2.00E-02  1.68E-03  1.41E-03  9.81E-04  3.33E-04  8.48E-05  1.95E-02  0.00E+00  1.61E-03  1.27E-03  9.26E-04  3.28E-04  6.51E-05  1.82E-02  4.12E-02  0.00E+00  1.57E-03  1.27E-03  9.04E-04  3.26E-04  8.43E-05  1.81E-02  8.06E-03  4.07E-02  0.00E+00  1.54E-03  1.28E-03  8.83E-04  3.15E-04  7.76E-05  1.79E-02  2.72E-01  8.15E-03  4.01E-02  0.00E+00  1.47E-03  1.31E-03  8.50E-04  3.16E-04  8.87E-05  1.79E-02  57.66667  2.72E-01  8.15E-03  4.01E-02  0.00E+00  1.47E-03  1.31E-03  8.50E-04  3.16E-04  8.87E-05  1.79E-02  60.5  2.72E-01  8.15E-03  4.01E-02  0.00E+00  1.47E-03  1.31E-03  8.50E-04  3.16E-04  8.87E-05  1.79E-02  259  Table AII(b).11.b : Liquid Oxygenate production with time at  Temperature - 573 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 7960 h-1, Catalyst wt. - 0.5 gm.  [Repeat experiment]  Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  9.2500  5.28E-03  2.07E-03  5.68E-04  0.00E+00  20.7833  5.22E-03  1.43E-03  5.61E-04  23.0333  4.83E-03  1.15E-03  25.0333  4.82E-03  30.3333  PrOH  BuOH  AcCOOH PrCOOH  5.15E-03  1.25E-03  6.60E-04  6.67E-04  0.00E+00  5.13E-03  6.91E-04  3.70E-04  5.22E-04  0.00E+00  4.78E-03  6.25E-04  1.36E-03  4.68E-04  0.00E+00  4.68E-03  4.78E-03  1.48E-03  5.06E-04  0.00E+00  43.6667  4.66E-03  1.36E-03  5.04E-04  59.0000  4.66E-03  1.36E-03  61.3333  4.66E-03  1.36E-03  Total Oxy.  REST  (C atom %)  3.40E-04  1.33E-03  4.17E-02  3.90E-04  1.77E-04  7.04E-04  3.32E-02  2.83E-04  3.17E-04  1.56E-04  5.55E-04  2.95E-02  5.34E-04  2.78E-04  4.37E-04  2.37E-04  6.09E-04  3.03E-02  4.64E-03  8.39E-04  2.91E-04  4.40E-04  1.98E-04  6.88E-04  3.17E-02  0.00E+00  4.39E-03  6.60E-04  2.57E-04  3.03E-04  1.59E-04  6.83E-04  2.95E-02  5.04E-04  0.00E+00  4.39E-03  6.60E-04  2.57E-04  3.03E-04  1.59E-04  6.83E-04  2.95E-02  5.04E-04  0.00E+00  4.39E-03  6.60E-04  2.57E-04  3.03E-04  1.59E-04  6.83E-04  2.95E-02  260  Table AII(b).12.a : Hydrocarbon production with time Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  2.60  3.52E-01  9.96E-03  4.06E-02  0.00E+00  1.61E-03  1.44E-03  9.36E-04  3.00E-04  1.04E-04  2.05E-02  8.00  3.53E-01  9.96E-03  4.06E-02  0.00E+00  1.61E-03  1.44E-03  9.36E-04  3.00E-04  1.04E-04  2.05E-02  20.80  3.53E-01  9.96E-03  4.06E-02  0.00E+00  1.36E-03  1.44E-03  9.36E-04  3.00E-04  1.04E-04  2.00E-02  25.50  3.06E-01  8.58E-03  3.48E-02  0.00E+00  1.32E-03  1.44E-03  8.02E-04  2.62E-04  6.49E-05  1.78E-02  32.08  3.02E-01  8.49E-03  3.43E-02  0.00E+00  1.21E-03  1.52E-03  7.81E-04  2.46E-04  9.38E-05  1.77E-02  45.15  2.95E-01  8.29E-03  3.29E-02  0.00E+00  1.01E-03  1.59E-03  7.30E-04  2.42E-04  7.34E-05  1.69E-02  47.50  2.93E-01  8.25E-03  3.27E-02  0.00E+00  9.88E-04  1.59E-03  7.30E-04  2.42E-04  7.34E-05  1.69E-02  49.62  2.94E-01  8.23E-03  3.25E-02  0.00E+00  9.88E-04  1.61E-03  7.31E-04  2.40E-04  8.25E-05  1.69E-02  52.17  2.94E-02  8.23E-03  3.24E-02  0.00E+00  9.71E-04  1.60E-03  7.16E-04  2.28E-04  6.44E-05  1.67E-02  54.50  2.94E-02  8.23E-03  3.24E-02  0.00E+00  9.71E-04  1.60E-03  7.16E-04  2.28E-04  6.44E-05  1.67E-02  57.50  2.94E-02  8.23E-03  3.24E-02  0.00E+00  9.71E-04  1.60E-03  7.16E-04  2.28E-04  6.44E-05  1.67E-02  59.00  2.94E-02  8.23E-03  3.24E-02  0.00E+00  9.71E-04  1.60E-03  7.16E-04  2.28E-04  6.44E-05  1.67E-02  Total HC  261  Table AII(b).12.b : Liquid Oxygenate production with time  Temperature - 598 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  3.32  5.63E-03  1.50E-03  6.19E-04  0.00E+00  8.97  5.63E-03  1.50E-03  6.19E-04  21.58  5.63E-03  1.50E-03  26.25  5.04E-03  33.00  PrOH  BuOH  AcCOOH PrCOOH  5.13E-03  7.90E-04  2.73E-04  3.86E-04  0.00E+00  5.13E-03  7.90E-04  2.73E-04  6.19E-04  0.00E+00  5.13E-03  7.90E-04  1.05E-03  5.61E-04  0.00E+00  5.37E-03  4.96E-03  9.90E-04  5.07E-04  0.00E+00  46.00  4.96E-03  1.15E-03  5.47E-04  48.35  4.30E-03  1.63E-03  50.62  4.79E-03  53.17  Total Oxy.  REST  (C atom %)  1.98E-04  5.26E-04  3.36E-02  3.86E-04  1.98E-04  5.26E-04  3.36E-02  2.73E-04  3.86E-04  1.98E-04  5.26E-04  3.36E-02  6.04E-04  1.91E-04  3.08E-04  1.52E-04  3.70E-04  2.97E-02  5.61E-03  6.60E-04  2.54E-04  3.22E-04  1.79E-04  4.45E-04  3.06E-02  0.00E+00  3.87E-03  6.35E-04  2.13E-04  3.35E-04  1.76E-04  5.37E-04  2.78E-02  5.47E-04  0.00E+00  3.81E-03  7.02E-04  2.92E-04  3.88E-04  2.08E-04  5.74E-04  2.86E-02  1.62E-03  5.24E-04  0.00E+00  3.69E-03  7.64E-04  3.16E-04  4.19E-04  2.44E-04  5.86E-04  2.98E-02  4.50E-03  1.28E-03  4.96E-04  0.00E+00  3.77E-03  7.98E-04  3.49E-04  4.57E-04  2.48E-04  6.99E-04  2.91E-02  55.00  4.50E-03  1.28E-03  4.96E-04  0.00E+00  3.77E-03  7.98E-04  3.49E-04  4.57E-04  2.48E-04  6.99E-04  2.91E-02  58.00  4.50E-03  1.28E-03  4.96E-04  0.00E+00  3.77E-03  7.98E-04  3.49E-04  4.57E-04  2.48E-04  6.99E-04  2.91E-02  60.00  4.50E-03  1.28E-03  4.96E-04  0.00E+00  3.77E-03  7.98E-04  3.49E-04  4.57E-04  2.48E-04  6.99E-04  2.91E-02  262  Table AII(b).13.a : Hydrocarbon production with time  Temperature - 615 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  CO  CH4  CO2  C2H2  C2H4  C2H6  C3H8  isoC4H10  n-C4H10  (C atom%)  4.00  2.81E-01  1.62E-02  5.63E-02  0.00E+00  2.12E-03  2.93E-03  1.31E-03  4.13E-04  1.76E-04  3.26E-02  9.90  2.73E-01  1.30E-02  4.57E-02  0.00E+00  1.88E-03  2.21E-03  1.07E-03  3.44E-04  1.37E-04  2.63E-02  21.10  2.77E-01  1.23E-02  4.29E-02  0.00E+00  1.71E-03  2.13E-03  1.02E-03  3.41E-04  1.29E-04  2.49E-02  24.75  2.75E-01  1.22E-02  4.22E-02  0.00E+00  1.64E-03  2.14E-03  1.01E-03  3.24E-04  1.15E-04  2.46E-02  27.00  2.74E-01  1.21E-02  4.21E-02  0.00E+00  1.63E-03  2.10E-03  1.02E-03  3.07E-04  1.05E-04  2.43E-02  32.75  2.72E-01  1.21E-02  4.19E-02  0.00E+00  1.62E-03  2.08E-03  9.97E-04  3.29E-04  1.18E-04  2.43E-02  35  2.74E-01  1.22E-02  4.21E-02  0.00E+00  1.59E-03  2.12E-03  1.01E-03  3.32E-04  1.16E-04  2.44E-02  45.2  2.70E-01  1.22E-02  4.19E-02  0.00E+00  1.48E-03  2.19E-03  1.00E-03  3.30E-04  1.15E-04  2.43E-02  47.41  2.71E-01  1.22E-02  4.19E-02  0.00E+00  1.46E-03  2.20E-03  1.01E-03  3.08E-04  1.13E-04  2.43E-02  50.75  2.70E-01  1.23E-02  4.20E-02  0.00E+00  1.42E-03  2.27E-03  1.00E-03  3.11E-04  1.21E-04  2.44E-02  56  2.69E-01  1.23E-02  4.18E-02  0.00E+00  1.30E-03  2.32E-03  9.84E-04  3.37E-04  1.25E-04  2.44E-02  57.5  2.70E-01  1.23E-02  4.19E-02  0.00E+00  1.29E-03  2.35E-03  1.01E-03  3.12E-04  1.19E-04  2.43E-02  Total HC  263  Table AII(b).13.b : Liquid Oxygenate production with time  Temperature - 615 K, Pressure - 8.27 MPa, H2:CO – 2.0 and GHSV - 15840 h-1, Catalyst wt. - 0.25 gm. Mole fraction  Time [hr]  AcCHO  Acetone  MeOH  IsoEthanol propanol  5.33  6.30E-03  7.37E-04  1.57E-03  0.00E+00  10.70  5.94E-03  6.07E-04  1.12E-03  21.75  6.55E-03  4.49E-04  25.60  6.51E-03  27.83  PrOH  BuOH  AcCOOH PrCOOH  6.30E-03  7.38E-04  2.29E-04  2.05E-04  0.00E+00  5.39E-03  6.03E-04  1.85E-04  1.11E-03  0.00E+00  5.36E-03  5.71E-04  6.50E-04  1.11E-03  0.00E+00  5.34E-03  6.75E-03  6.65E-04  1.06E-03  0.00E+00  33.53  6.61E-03  6.48E-04  1.10E-03  35.83  6.49E-03  4.80E-04  46.03  6.61E-03  48.33  Total Oxy.  REST  (C atom %)  5.47E-05  4.33E-04  3.44E-02  1.66E-04  8.45E-05  4.07E-04  3.04E-02  1.40E-04  1.44E-04  7.58E-05  4.07E-04  3.07E-02  6.78E-04  1.81E-04  1.97E-04  6.59E-05  6.82E-04  3.28E-02  5.39E-03  7.48E-04  1.65E-04  2.02E-04  4.52E-05  3.67E-04  3.22E-02  0.00E+00  5.33E-03  8.28E-04  2.60E-04  2.99E-04  4.28E-05  4.98E-04  3.32E-02  1.09E-03  0.00E+00  5.43E-03  6.48E-04  2.17E-04  1.79E-04  4.67E-05  4.62E-04  3.15E-02  5.86E-04  1.05E-03  0.00E+00  5.35E-03  7.88E-04  2.57E-04  2.17E-04  6.13E-05  5.69E-04  3.30E-02  6.78E-03  5.54E-04  1.10E-03  0.00E+00  5.28E-03  6.68E-04  2.37E-04  2.09E-04  5.17E-05  5.10E-04  3.25E-02  51.45  6.93E-03  6.76E-04  1.08E-03  0.00E+00  5.49E-03  8.19E-04  2.90E-04  2.39E-04  6.56E-05  6.25E-04  3.48E-02  56.76  6.97E-03  7.41E-04  1.10E-03  0.00E+00  5.61E-03  9.60E-04  2.24E-04  2.26E-04  5.07E-05  6.48E-04  3.55E-02  58.33  6.88E-03  6.68E-04  1.13E-03  0.00E+00  5.50E-03  9.27E-04  2.00E-04  2.27E-04  8.18E-05  6.08E-04  3.46E-02  264  Appendix II.(c) XPS data fitting fresh and spent catalyst  265  18000  29000  (a)  28000  (b)  17500  27000 17000  Intensity,au  Intensity,au  26000 25000 24000 23000  16500 16000  22000  15500  21000  15000  20000 242  240  238  236  234  232  230  228  226  224  138  222  136  134  132  130  128  126  124  B.E.(eV)  B.E.(eV)  21000  (c)  13500  (d) Intensity,au  Intensity,au  20000  19000  18000  17000  13000 12500 12000  16000 242  240  238  236  234  232  B.E.(eV)  230  228  226  224  222  138  136  134  132  130  128  126  124  B.E.(eV)  Figure AII(c).1: XPS analysis of Fresh MoP catalyst (a) Mo 3d of 15%MoP5%K (b) P2p2 of 15%MoP5%K (c) Mo 3d of 15%MoP (d) P2p2 of 15%MoP.  266  21500  16500  21000  16000  20000  Intensity  Intensity,au  20500  19500  15500  15000  19000  14500  18500 18000 242  240  238  236  234  232  230  228  226  14000 138  224  137  136  B.E.(eV)  135  134  133  132  131  B.E.(eV)  30000 16500  28000  16000  Intensity  Intensity, au  26000 24000  15000 14500  22000  14000  20000 18000 242  15500  13500 138  240  238  236  234  232  230  228  226  224  136  134  132  130  128  126  B.E.(eV)  B.E.(eV)  Figure AII(c).2: XPS analysis of Spent MoP catalyst (a) Mo 3d of 15%MoP5%K (b) P2p2 of 15%MoP5%K (c) Mo 3d of 15%MoP (d) P2p2 of 15%MoP. 267  27000  18000  26000  17500  25000  Intensity  Intensity, au  28000  24000  17000 16500  23000 16000  22000 21000  15500  240 238 236 234 232 230 228 226 224 136  B.E. (eV)  134  132  130  128  126  124  B.E.(eV)  13500  21000 20000  13000  Intensity, au  Intensity, au  19000 18000 17000  12500  12000  16000 11500  15000 242 240 238 236 234 232 230 228 226 224 222  B.E.(eV)  140  138  136  134  132  130  128  126  124  B.E.(eV)  Figure AII(c).3: XPS analysis of fresh MoP catalyst (a) Mo 3d of 10%MoP5%K (b) P2p2 of 10%MoP5%K (c) Mo 3d of 10%MoP (d) P2p2 of 10%MoP. 268  7600  4800  7400  4600  7000  Intensity, au  Intensity, au  7200 6800 6600 6400 6200  4400 4200 4000  6000 5800  3800 138  240 238 236 234 232 230 228 226 224  136  134  132  130  128  126  B.E. (eV)  B.E.(eV)  14000  18500 18000  Intensity  Intensity  17500 17000 16500 16000  13000  12000  15500 242  240  238  236  234  232  B.E.(eV)  230  228  226  224  138  136  134  132  B.E.(eV)  Figure AII(c).4: XPS analysis of spent MoP catalyst (a) Mo 3d of 10%MoP5%K (b) P2p2 of 10%MoP5%K (c) Mo 3d of 10%MoP (d) P2p2 of 10%MoP. 269  22000  15500  21500  15000  20500  Intensity, au  Intensity, au  21000  20000 19500 19000  14500  14000  13500  18500 18000 242  240  238  236  234  232  230  228  226  224  13000  222  138  136  134  B.E.(eV)  132  130  128  126  124  B.E.(eV)  22000 21500  15000  20500  Intensity  Intensity, au  21000  20000 19500  14000  19000 18500 18000 17500 242  240  238  236  234  232  B.E.(eV)  230  228  226  224  13000 138  137  136  135  134  133  132  131  130  B.E.(eV)  Figure AII(c).5: XPS analysis of Fresh MoP catalyst (a) Mo 3d of 5%MoP5%K (b) P2p2 of 5%MoP5%K (c) Mo 3d of 5%MoP (d) P2p2 of 5%MoP. 270  19000 15000  18000  Intensity, au  Intensity, au  14500 14000 13500 13000  17000  12500  242 240 238 236 234 232 230 228 226 224 222  B.E.(eV)  138  136  134  132  130  128  B.E.(eV)  Figure AII(c).6: XPS analysis of Spent MoP catalyst (a) Mo 3d of 5%MoP5%K (b) P2p2 of 5%MoP5%K .  126  124  271  Appendix III  Miscellaneous  272  Appendix III.1  :  Catalyst activity evaluation procedure  Reactor preparation: Glass beads are put into the reactor up to a certain level. The glass beads are rested on a wire mesh fixed at the bottom of the reactor. On the top of the glass beads tightly packed quartz wool is placed. Catalyst particles are placed on the quartz wool bed. On the top of the catalyst bed another layer of quartz wool is placed. High temperature thermocouple is placed at the middle of the catalyst bed. The outlet of the thermocouple is attached to the temperature controller. Thus the temperature controller will try to maintain the reactor bed temperature to the desired value (< ± 1 oC). These steps are shown in the figure below. At the reactor outlet, a high pressure filter (0.5 micron) is placed to retain any catalyst particle blocking the outlet tubing.  Three way union  Copper lined SS tube Thermocouple  Quartz wool  Catalyst  Glass beads  Wire mesh  Figure AIII.1 : Catalyst pouring into the tubular reactor. 273  TI  Thermocouple  Sampling valves  PI  Catalyst Bed GAS CHROMATOGRAPH  TCD  FID  Integrator PR  PR  PR  Mass flow Controller  Reactor  To Vent  BPR  Liquid sample collection Heating box CO+H2  H2  He  Figure AIII.2: Experimental setup to evaluate catalyst activity. In situ reduction of catalyst: The furnace temperature is increased from room temperature to 650 oC at an increment of 1 oC and kept at 650 oC for 2 hrs in the flow of hydrogen at 120 cc/gm catalyst. The temperature is then reduced to the desired reaction temperature i.e. 275 o  C, 300 oC, 325oC and 340 oC.  Increasing the reactor pressure: A back pressure regulator is placed after the filter, kept in a heated box (195 oC). Reactant (CO+H2) flows downward through the catalyst bed. The back pressure regulator is slowly tightened to increase the reactor pressure taking precaution that there is always exit flow. The reactor pressure is steadily increased to the target value, i.e. 1200 psi. 274  Reactor outlet: The outlet of the BPR (back pressure regulator) is divided into two streams using a three way valve. One goes to vent, and the other goes to the TCD-FID GC analyzer. The lines to vent and to the GC are heated to 200 oC to prevent any condensation in the 1/8 inch SS tube line. End of reaction: Heater is switched off. Exit flow direction is to the vent. Reactor pressure is slowly decreased to the atmospheric pressure. Stopping the syngas flow when the reactor pressure is below 1000 psi and starting the flow of helium instead.  Reactor design: The reactor is a combination of two tubes as shown in the figure. One is 3/8 inch OD SS tube and the other is ¼ inch OD copper tube. The copper tube is slide inside the 3/8 inch OD SS tube. The copper tube was then pressurized to fit tightly with SS tube. The end of the tube is properly welded to seal any gap between SS and copper tube.  49 cm  Properly weld/ fitted/ tightened Should withstand 2000psi  3/8 inch OD ss tube  ¼ inch OD copper tube  Properly weld/ fitted/ tightened Should withstand 2000 psi  Figure AIII.3: Design of the copper lined reactor for alcohol synthesis.  275  Selection of reactor material:  The reactor was built with a SS tube of grade 316/316L and of thickness 0.12 cm to withstand the reactor pressure of 1200 psi. A copper tube (0.635 cm OD) was inserted inside of the SS tube and pressed to adhere with the inner wall of SS tube. The copper lining was used to suppress the formation of hydrocarbons from syngas reacting with the SS tube wall.  276  Appendix III.2  :  Column initial temperature  TCD temperature programming  =  35 oC  Initial temperature hold time =  10 min  Temperature program rate  =  6 oC/min  Column final temperature  =  135 oC  Final temperature hold time =  10 min  Appendix III.3  :  FID temperature programming  =  35 oC  Initial temperature hold time =  6 min  Temperature program rate  =  25 oC/min  Column final temperature  =  210 oC  Final temperature hold time =  40 min  Column initial temperature  277  Appendix III.4:  GC switch design Inlet 1  10  Outlet 2  9  3  8 Sample loop  Capillary tube  To FID  7 6  4  5  Purge(He)  Inlet 1  Outlet  2 3  6 To TCD  4 5  Purge(He)  Sample loop  Figure AIII.4.a.: GC switch in close position (reactant effluent purging).  278  Inlet 1  10  Outlet  2  9  3  8 4 Capillary tube  Sample loop  Purge(He)  7  5 6  To FID  Inlet 1  Outlet  2  6  3  To TCD 5  4  Purge(He)  Sample loop  Figure AIII.4.b.: GC switch in open position (sample collection).  279  Appendix III.5:  Retention function of measured components by TCD and FID  Mole fraction = Area under the curve (TCD/FID response peak area) x Retention function Table AIII.1 : Retention function of measured components by TCD and FID Hydrocarbons/ gaseous component  Liquid Oxygenate  Component  Retention function  Component  Retention function  CO  2.72 e-7  CH3CHO  1.67 e-7  CH4  3.51 e-7  CH3COCH3  2.60 e-8  CO2  2.56 e-7  CH3OH  2.32 e-7  C 2 H4  2.50 e-7  C2H5OH  1.89 e-7  C 2 H6  2.32 e-7  C3H7OH  9.38 e-10  C 3 H8  1.32 e-7  C4H9OH  4.91 e-10  iso C4H10  9.44 e-8  CH3COOH  6.20 e-10  n C4H10  8.95 e-8  C2H5COOH  4.16 e-10  280  Appendix III.6 :  Antoine equation for chemicals  Table AIII.2 : Antoine equation for chemicals Chemical name  Formula  A  B  C  Methanol  CH3OH  8.08097  1582.27  239.7  Ethanol  C2H5OH  8.20417  1642.89  230.3  n-Propanol  C3H7OH  7.7291  1428.977  197.585  n-Butanol  C4H9OH  7.92484  1617.52  203.296  Acetone  CH3COCH3  7.1327  1219.97  230.65  CH3CHO  5.18830  1637.083  22.317  CH3COOH  7.5596  1644.05  233.524  C2H5COOH  18.1057  5640.34  277.46  [1]  [2]  Acetaldehyde  Acetic Acid [3]  Propionic acid  Antoine Equation for Chemicals:  Temperature range  Unit P=mmHg T= oC P=mmHg T= oC P=mmHg T= oC P=mmHg T= oC P=mmHg T= oC P=Bar T= K P=mmHg T= oC P=kPa T= oC  logଵ଴ ሺܲ, ݉݉‫݃ܪ‬ሻ ൌ ‫ ܣ‬൅  15 to100 oC -57 to80oC 65-108 oC 0 to 118 oC -64 to 70oC 272.9 307.5K 17-118 oC N/A ஻  ஼ ା ௧ሺԨሻ  Reference [1] Adolph J. Kubicek, Philip T. Eubank , Thermodynamic properties of propyl alcohol, J. Chem. Eng. Data, 1972, 17 (2), pp 232–235 [2] logଵ଴ ሺܲ, ܾܽ‫ݎ‬ሻ ൌ ‫ ܣ‬൅  ஻  ஼ ା ௧ሺ௄ሻ  L. D. Christensen, J. M. Smith, Pressure-Enthalpy Diagram for Acetaldehyde, Ind. Eng. Chem., 1950, 42 (10), pp 2128–2130 [3] lnሺܲ, ݇ܲܽሻ ൌ ‫ ܣ‬൅  ஻  ஼ ା ௧ሺԨሻ  S.L. Clifford, D. Ramjugernath and J.D. Raal, J. Chem. Eng. Data 49 (2004), pp. 1189–1192. Other references http://ddbonline.ddbst.de/AntoineCalculation/AntoineCalculationCGI.exe http://s-ohe.com/index.html  281  Appendix III.7:  Numerical calculation of heat and mass transfer limitation  The following calculations provide the evidence to obey the mass and heat transfer limitation criteria in the micro-reactor and heterogeneous catalyst pellets.  Appendix III.7.(a) :  Calculation of parameters  Diffusion of CO-H2 Dଵଶ  ሾMଵ ൅ Mଶ ሿ 0.001858 T ଷ/ଶ ට M ଵ Mଶ ൌ ଶ Pσଵଶ Ωୈ  Molecular weight M1 = Molecular wt. of CO = 28 M2 = Molecular weight of H2 = 2 Total pressure, P = 81.63 atm Temperature, T = 548 K Force constant of Lennard Jones potential function, σ12 = 3.2585 Collision integral, ΩD = 0.78213  ‫ܦ‬஼ைିுమ  ܿ݉ଶ ൌ 0.025735 ‫ܿ݁ݏ‬  Calculation of effective diffusivity Void fraction, θ = 0.73 Tortuosity, τ =2  Dଵଶିୣ୤୤ ൌ  Dେ୓ିୌଶ ൈ θ 0.025735 ൈ 0.73 cmଶ cmଶ ൌ ൌ 0.009393 τ 2.0 sec sec  282  Calculation of knudsen diffusion, Dk Surface area, Sg = 60 x 104 cm2/gm Pellet density, ρp =2.2 gm/cc Tortuosity, τ =2 Void fraction, θ = 0.73 Molecular weight of CO, M = 28 gm / mol Temperature, T = 548 K  ‫ܦ‬௞ ௘௙௙ ൌ 19400  ఏమ  ఛ ௌ೒ ఘ೛  ට ൌ 0.0173 ܿ݉ଶ /‫ܿ݁ݏ‬ ெ ்  Total effective diffusivity  1 1 1 1 1 ൌ ൅ ൌ ൅ ‫ܦ‬௘௙௙ ‫ܦ‬ଵଶି௘௙௙ ‫ܦ‬௞ି௘௙௙ 0.009393 0.0173 ‫ܦ‬௘௙௙ ൌ 0.006091 ܿ݉ଶ /‫ܿ݁ݏ‬  Physical properties at 548 K and 1200psi Mixture CO:H2 =1 Density, gm/m3  27.26  Viscosity, kg/m-s  2.219 x10 -5  Particle diameter, dp = 150 x 10-6 m [75-250 µm particle size distribution] Cross sectional area of the reactor tube = π r2 = 3.14 x (0.003175)2 =3.165 x 10-5 m2 Volumetric flow rate, V = 56 cc/min = 0.933 x 10-6 m3/sec Velocity, U = 2.95 x 10-2 m/sec Mass velocity G = ρ x U = 0.0273 x 106 x 2.95 x10-2 = 8.04 x 102 gm /sec. m2 Reynolds number, ܴ݁ ൌ  ௗ೛ ீ ఓ  ൌ  ଵହ଴ൈଵ଴షల ൈ଼.଴ସൈଵ଴మ ଶ.ଶଶൈଵ଴షఱ ൈଵ଴଴଴  = 4.56 283  Molar mass of syngas = [0.5 x 28 + 0.5 x 2] = 15 g/mol Molar velocity =  ଺.଻ହହൈଵ଴మ ௚௠ ௠మ ௦௘௖  Schmidt number = ܰௌ௖ ൌ  ఓ  ൈ  ఘ஽భ೘  ௠௢௟ ௦௬௡௚௔௦  ൌ  ଵହ ௚௠  ൌ 45.03  ௠௢௟ ௦௬௡௚௔௦  ଶ.ଶଶൈଵ଴షఱ ൈଵ଴଴଴  ௠మ ௦௘௖  ଴.଴ଶ଻ଷൈଵ଴ల ൈ଴.଴଴଺଴ଽଵ ൈଵ଴షర  = 1.34  Pressure, PAS = 40.82 atm Gas constant, R = 8.205746 x 10-5  ௠య ௔௧௠ ௄ ௠௢௟  Temperature, T =548 K Concentration of CO, C୅ୗ ൌ  ୔ఽ౏ ୖ୘  , C୅ୗ ൌ 908  ୫୭୪ େ୓ ୫య  [CAS = surface concentration of CO]  284  Appendix III.7.(b) :  Mass transfer controlling reaction criteria  Lack of significant intraphase diffusion effect ሺ௥೚್ೞ ሻ൫ோ೛ ൯ ஽೅ಲ ஼ಲೄ  మ  ଵ  ൏ ,  [taking n=1, 1st order reaction]  ௡  Observed reaction rate, r୭ୠୱ ൌ 2.74  ୫୭୪ େ୓  ୫య ୡୟ୲ୟ୪୷ୱ୲ିୱୣୡ  Particle radius, Rp = 75 x 10-6 m Diffusivity, DTA = 6.091 x 10-7 m2/s  ሺ2.74ሻሺ75 ൈ 10ି଺ ሻଶ ൌ 2.79 ൈ 10ିହ ൏ 1 6.091 ൈ 10ି଻ ൈ 908  Calculation of mass transfer coefficient [Thodos and co-workers] based on the Chilton and Colburn co-relation  ߳‫ܬ‬஽ ൌ  0.357 ଴.ଷହ଻ ܰோ௘  ε = 0.73 JD = 0.266  ‫ܬ‬஽ ൌ  ݇௖ ߩ ଶ/ଷ ܰ ‫ ܩ‬ௌ௖  Mass transfer coefficient, kc = 0.0063 m/s  Interphase mass transfer ሺ௥೚್ೞ ሻ൫ோ೛ ൯ ௞೎ ஼ಲೄ  ൏  ଴.ଵହ ௡  [Taking n=1, 1st order reaction]  ሺ‫ݎ‬௢௕௦ ሻ൫ܴ௣ ൯ 2.74 ൈ ሺ75 ൈ 10ି଺ ሻ ൌ ൌ 3.5 ൈ 10ିହ ൏ .15 ݇௖ ‫ܥ‬஺ௌ 0.0063 ൈ 908  285  Appendix III.7.(c) :  Criteria for isothermal operation  Methane is taken as the only product from syngas as that reaction. − ∆H RX (− rA ) ρ b RE < 0.15 hT 2 R g  ∆HRX = Heat of reaction of methane = 216.73 kJ/mol -rA = Reaction rate of methane = 2.503 x 10-7 kmol/Kg catalyst/sec E = Activation energy methane = 1.06 x 105 kJ/kmol h = Heat transfer coefficient of syngas = 0.001 kJ/m2/sec/K Rg = Gas constant = 8.314 kJ/mol/K T = Temperature = 548K R = Radius of the catalyst particle = 75 x10-6 m  ρb = bulk density of the catalyst = 700 kg catalyst / m3. − ∆H RX ( − rA ) ρ b R E = 1.2 × 10 − 4 < 0.15 h T 2 Rg  286  Table AIII.3: Thermochemical data of liquid oxygenates and hydrocarbons produced in the reaction:  Methanol  ∆H o f (kJ/mol) -201.13  ∆G o f (kJ/mol) -162.45  Methane  ∆H o f (kJ/mol) -74.8798  ∆G o f (kJ/mol) -50.8156  Ethanol  -234.53  -167.98  Ethane  -84.7038  -32.9004  n-Propanol  -256.72  -162.20  Propane  -103.892  -23.4991  n-Butanol  -274.80  -151.15  n-Butane  -126.202  -17.1618  Acetaldehyde  -166.26  -128.96  Iso-Butane  -134.573  -20.929  Acetone  -216.78  -152.78  Ethene  52.28064  68.1532  Liquid Oxygenates  Hydrocarbons  Reference: Hill C. G., “Introduction to Chemical Engineering Kinetics & Reactor Design”, John Wiley & Sons, New Work, 1977. [Appendix A: Thermochemical Data] Table AIII.4: Heats of reaction and Gibbs’ free energy of reaction for the reaction products Liquid Oxygenates Methanol Ethanol n-Propanol n-Butanol Acetaldehyde Acetone  ∆H Ro (kJ/mol) -90.56 -255.32 -408.86 -558.31 -187.05 -368.93  ∆GRo (kJ/mol) -25.15 -122.07 -207.69 -288.04 -83.06 -208.27  ∆H Ro  ∆GRo  (kJ/mol)  (kJ/mol)  Methane  -206.24  -142.21  Ethane  -347.42  -215.69  Propane  -497.97  -297.68  n-Butane  -651.64  -382.74  Iso-Butane  -660.01  -386.51  Ethene  -210.44  -114.64  Hydrocarbons  Calculation is done based on the following reactions Formation of higher alcohols from syngas  nCO + 2nH 2` ⇔ Cn H 2n +1OH + (n − 1) H 2O ; (n = 1,2,3..) Formation of hydrocarbons from syngas.  nCO + (2n + 1)H 2 ⇔ C n H 2n + 2 + nH 2O ; (n = 1,2,3..)  287  Appendix III.7.(d) :  Criteria for plug flow reactor  Calculation of heat transfer coefficient Syngas property [H2 : CO =1] at 548 K Prandtl number , Pr = 0.69 Reynolds number, Re = 4.56 Thermal conductivity, k = 1.16x10-3 W/m/K Nussetl number, Nu = (0.43 + 0.5 Re0.5) Pr0.38 = h dp/k   0.23  l Calculation of Peclet number, N Pe = 0.087 N Re d  p    = 82.2    1  Minimum Peclet number, N Pe min = 8 n ln   1− x   n = Reaction order = 1 x = conversion of reactants = 0.12 N Pe min = 1.022 N Pe 〉 N Pe min  So, acceptable deviation from plug flow can be assumed. Minimum L/dp ratio,  L  1  −0.23 〉 92.0 N Re n ln  = 8.29 dp 1− x   Minimum effect of reactor wall on flow pattern, d tube  Minimizing axial gradients due to conversion, L  dp  dp  =  =  6.3 × 10 −3 = 15 .74 〉 10 1.5 × 10 − 4  1×10−2 = 667 〉 50 − 4 1.5 ×10  288  Appendix III.8.(a) :  Deactivation treatment of data  Catalyst deactivation for coke deposition can be modeled as  ‫ ܣ‬ൌ ‫ܣ‬଴ exp ሺെ݇ௗ ‫ݐ‬ሻ  (AIII-8-1)  A = Current activity of the catalyst A0 = Initial activity of the catalyst kd = Deactivation rate constant t = Time  Taking log of the equation  log ‫ ܣ‬ൌ log ‫ܣ‬௢ െ ݇ௗ ‫ݐ‬  (AIII-8-2)  In our case we had sharp deactivation at the beginning and then the deactivation slowed down after 20 hrs of operation. We took the averaged data from 20 – 60 hrs to calculate the activity and selectivity of the reaction.  Plotting the activity data with time in a semi-log plot we can see two distinct region of deactivation. Both regimes fitted a straight line with negative slope according to the equation AIII-8-2. The breakthrough occurred between 20 – 30 hrs of operation in all cases. The deactivation process for this period (20hrs and beyond) was minimal as indicated by the low value of the slope. Figures for the deactivation curves and breakthrough points are shown in the next page, for 5 wt% K with 5, 10 and 15 wt% MoP/SiO2 catalysts.  289  0.1  1  Slope = -3.76 x 10 -4  % CO Conversion  5 wt % K - 10 wt % MoP  % CO Conversion  5 wt% K - 5 wt% MoP  Slope = -5.17 x 10 -5  0.01 0  10  20  30  40  50  60  Slope = -1.08x10-3 0.1  Slope = -2.10x10-4  0.01  70  0  Time (hr)  20  40  60  80  % CO Conversion  Time (hr)  5 wt % K - 15 wt % MoP  Slope = -1.91x10-3  Slope = -7.28 x 10-4  0.1 0  10  20  30  40  50  60  Time (hr)  Figure AIII.5 : Deactivation breakthrough curve for MoP catalyst for syngas conversion.  70  100  120  140  290  Appendix III.8.(b) :  Standard deviation calculation for fraction CO conversion  Over the MoP catalysts, CO fractional conversion data was averaged over data points generated after 20 hrs of operation to avoid the sharp deactivation effect. The deactivation didn’t die out after 20 hrs but it slowed down considerably. Calculation of standard deviation was performed to check the spread of data points from the average value.  ܵ‫ ܦ‬ൌ ඨ  ଶ ∑ே ௜ୀଵሺܺ௜ െ ܺ௔௩௚ ሻ ܰെ1  Where, SD = Standard deviation; Xi = Sample variable; Xavg = Average value of sample; N= Number of samples.  Standard deviation  % SD/Average  9 7 13  Average fractional CO conversion 8.55 x 10-3 3.11 x 10-2 2.84 x 10-2  3.46 x 10-4 3.13 x 10-3 1.16 x 10-3  4.05 10.06 4.08  10 wt% MoP-SiO2 1 wt% K-10 wt% MoP-SiO2 5 wt% K-10 wt% MoP-SiO2  7 8 14  2.91 x 10-2 6.33 x 10-2 8.14 x 10-2  3.39 x 10-3 9.04 x 10-3 8.30 x 10-3  11.65 14.28 10.20  15 wt% MoP-SiO2 1 wt% K-15 wt% MoP-SiO2 5 wt% K-15 wt% MoP-SiO2  9 9 9  4.26 x 10-2 5.70 x 10-2 1.23 x 10-1  3.98 x 10-3 3.69 x 10-3 1.03 x 10-2  9.34 6.47 0.84  Catalyst  Sample number, N  5 wt% MoP-SiO2 1 wt% K-5 wt% MoP-SiO2 5 wt% K-5 wt% MoP-SiO2  Small standard deviation allows us to take the average CO conversion value to calculate the activity and selectivity of the catalyst for the syngas reaction. 291  Appendix III.9:  Repeatability analysis of the experimental data  The analysis was done for the catalyst 1 wt% Rh-5 wt% K-10 wt% MoP/SiO2 at 325 oC, H2:CO =1.5 and at 8.27 psi. The experiment was repeated for three times. Repeatability analysis is reported in the table AIII-5. Standard deviation was analyzed for rate, % CO conversion, HC selectivity, methane, acetaldehyde, ethanol, C2 oxygenates, C3+ oxygenates selectivity and space time yield of liquid oxygenates. Standard deviation of the mean was calculated using the following formula  SDOM ൌ ඨ y୧ ൌ Response value  ∑ሺy୧ െ yതୟ୴ ሻଶ ሺn െ 1ሻn  yതୟ୴ ൌ Mean value of response  n ൌ Number of repeat experiments The values can be reported as Rate (µmole.g cat-1.h-1) = 4.76 x 10-2 ± 6.89 x 10-4 % CO conversion = 16.97 ± 0.24 HC selectivity (C atom %) = 38.5 ± 1.36 Methane selectivity (C atom %) = 17.7 ± 0.74 Ethanol selectivity (C atom %) = 18.3 ± 0.46 Acetaldehyde selectivity (C atom %) = 20.0 ± 0.67 C2 oxygenate selectivity (C atom %) = 39.41 ± 0.92 C3+ oxygenate selectivity (C atom %) = 20.80 ± 2.39  292  Table AIII.5 : Repeatability analysis of experimental data [Temperature = 325 oC, Pressure = 8.27 MPa, H2:CO = 1.5, GHSV = 15840 h-1]  Temp (oC)  Total HC  Rate of CO conversion  Error  % CO conversion  Error  selectivity (C atom  325 325 325 Mean =  4.63E-02 4.80E-02 4.86E-02 4.76E-02  -1.33E-03 3.67E-04 9.67E-04 Sum of Error2=  2.85E-06  SDOM =  6.89E-04  Methane Selectivity (C atom %)  Error  325 325 325  18.3 16.2 18.5  6.33E-01 -1.47E+00 8.33E-01  1.77E+01  16.5 17.1 17.3 Mean =  -4.67E-01 1.33E-01 3.33E-01 16.97  Sum of Error2=  3.47E-01  SDOM =  2.40E-01  Ethanol  Temp (oC)  Mean =  Error  %)  [µmole.g cat-1.h-1]  3.25E+00  Error  SDOM =  7.36E-01  SDOM = Standard deviation of the mean  Sum of Error2=  1.11E+01  SDOM =  1.36E+00  selectivity  -3.00E-01 -6.00E-01 9.00E-01  18.3  3.85E+01  Error  (C atom %)  18.0 17.7 19.2 Mean =  Mean =  6.00E-01 -2.60E+00 2.00E+00  Acetaldehyde  selectivity (C atom %)  Sum of Error2=  39.1 35.9 40.5  Sum of Error2=  1.26E+00  SDOM =  4.58E-01  9.00E-01 -1.30E+00 4.00E-01  20.9 18.7 20.4 Mean =  2.00E+01  Sum of Error2=  2.66E+00  SDOM =  6.66E-01  293  Table AIII.5 : Repeatability analysis of experimental data (continued) Temp (oC)  STY Liquid Oxygenates  Error  325 325 325  634.07 677.89 647.62  -1.91E+01 2.47E+01 -5.57E+00  Mean =  6.53E+02  Sum of Error2=  SDOM =  1.01E+03 1.30E+01  SDOM = Standard deviation of the mean  C2 oxygenate Selectivity (C atom %)  Error  40.03 37.61 40.60  0.62 -1.80 1.19  Mean =  39.41  C3+ Oxygenate  selectivity  Error  (C atom %)  Sum of Error2=  SDOM =  5.04 9.17E-01  19.27 25.51 17.70 Mean =  20.80  -1.53E+00 4.71E+00 -3.10E+00 Sum of Error2=  3.41E+01  SDOM =  2.39E+00  294  Appendix III.10 : Statistical analysis and error calculation Calculation of lack of fit or adequacy of the chosen model [Model calculation shown for methane only] Calculate the total sum of squares N  SS E = ∑ ( y i − y pred ,i ) = 2.12 × 10 − 6 2  i =1  yi  =  Experimental response  y pred,i  =  Response obtained from using the proposed model.  Calculate the pure error sum of squares N Runs N Re ps ,i  ∑ ∑ (y  SS PE =  i =1  − yav,i ) = 1.83 × 10−6 2  ij  j =1  This requires repeat experiments The summation goes over all the runs for which replicates exist. yij  =  The experimental response of run i, replicate j.  yav,i  =  The average of all the replicates of run i.  Calculate the lack of fit sum of squares  SS LOF = SS E − SS PE = 2.91 × 10 −7 Degrees of freedom associated with each sum of squares Total degrees of freedom is the total number of runs minus the number of parameters in the fitted equation.  DOFE = N − p = 7 − 1 = 6 The pure error degrees of freedom is the sum overall runs of the member of replicates of each run 295  N Runs  DOFPE =  ∑ (N  reps,i  − 1) = 2 + 1 + 1 = 4  i =1  The lack of fit degrees of freedom  DOFLOF = DOFE − DOFPE = 6 − 4 = 2 The mean square value is then obtained  MSLOF =  MSPE =  SS LOF = 1.46 × 10−7 DOFLOF  SS PE = 4.56 × 10−7 DOFPE  Calculate the value of Fo  Fo =  MS LOF = 0.319 MS PE  Read the upper limit of F from the F table F (DOF LOF , DOF PE ; 5% ) = 6.94  Thus  F0 〈 F We can accept our model a better fit to our experimental data points.  296  Table AIII.6.a:  Mean  Mean  Mean  F- test and error calculation table for methane  Experimental Y 8.48E-03 7.78E-03 8.98E-03 8.41E-03 7.73E-03 9.21E-03 8.47E-03 3.41E-03 3.51E-03 3.46E-03  (Y-Ym) 6.67E-05 -0.00063 0.000567  (Y-Ym)2 4.444E-09 4.011E-07 3.211E-07  Model Abs(Ypred-Yi) 1.53E-04 5.47E-04 6.53E-04  (Ypred-Yi)2 2.34E-08 2.99E-07 4.26E-07  -0.00074 0.00074  5.476E-07 5.476E-07  1.11E-03 3.72E-04  1.23E-06 1.38E-07  -5E-05 5E-05  2.5E-09 2.5E-09  5.00E-05 5.00E-05  2.50E-09 2.50E-09  Pure error  SSPE = DoF = Variance =  1.83E-06 4 4.57E-07  Experimental error  SSE= Variance= SSLOF= Fo =  2.12E-06 3.53E-07 2.91E-07 0.319  DOFE= DOFLOF= VarianceLOF =  6 2 1.46E-07  LOF = Lack of fit DOF = Degrees of freedom E = Experimental error PE= Pure error  297  Table AIII.6.b:  Mean  Mean  Mean  F- test and error calculation table for acetaldehyde  Experimental Y 4.84E-03 4.49E-03 4.95E-03 4.76E-03 4.25E-03 5.16E-03 4.71E-03 2.28E-03 2.40E-03 2.34E-03  (Y-Ym) -3.57E-03 -3.92E-03 -3.46E-03  (Y-Ym) 1.277E-05 1.539E-05 1.199E-05  Model Abs(Ypred-Yi) 7.92E-05 4.29E-05 3.07E-05  -4.22E-03 -3.31E-03  1.781E-05 1.096E-05  3.49E-04 5.61E-04  1.22E-07 3.15E-07  -6.00E-05 6.00E-05  3.6E-09 3.6E-09  1.36E-04 2.06E-04  1.85E-08 4.24E-08  2  (Ypred-Yi)2 6.27E-09 1.84E-09 9.42E-10  Pure error  SSPE = DoF = Variance =  6.893E-05 4 1.723E-05 Experimental error  SSE= Variance= SSLOF= Fo =  5.07E-07 8.44E-08 6.84E-05 1.99E+00  DOFE= DOFLOF= VarianceLOF =  6 2 3.42E-05  LOF = Lack of fit DOF = Degrees of freedom E = Experimental error PE= Pure error  298  Table AIII.6.c:  Mean  Mean  Mean  F- test and error calculation table for ethanol  Experimental Y 4.17E-03 4.25E-03 4.66E-03 4.36E-03 3.54E-03 4.40E-03 3.97E-03 1.99E-03 1.96E-03 1.98E-03  (Y-Ym) -4.24E-03 -4.16E-03 -3.75E-03  (Y-Ym) 1.801E-05 1.733E-05 1.409E-05  Model Abs(Ypred-Yi) 1.59E-04 7.88E-05 3.31E-04  -4.93E-03 -4.07E-03  2.43E-05 1.656E-05  4.62E-04 3.98E-04  2.13E-07 1.58E-07  1.50E-05 -1.50E-05  2.25E-10 2.25E-10  9.58E-05 6.58E-05  9.18E-09 4.33E-09  2  (Ypred-Yi)2 2.52E-08 6.20E-09 1.10E-07  Pure error  SSPE = DoF = Variance =  9.03E-05 4 2.257E-05 Experimental error  SSE= Variance= SSLOF= Fo =  5.26E-07 8.77E-08 8.98E-05 1.99E+00  DOFE= DOFLOF= VarianceLOF =  6 2 4.49E-05  LOF = Lack of fit DOF = Degrees of freedom E = Experimental error PE= Pure error  299  Table AIII.6.d:  Mean  Mean  Mean  F- test and error calculation table for acetone  Experimental Y 1.09E-03 1.10E-03 1.04E-03 1.08E-03 1.30E-03 9.86E-04 1.14E-03 8.72E-04 8.75E-04 8.74E-04  (Y-Ym) -7.32E-03 -7.31E-03 -7.37E-03  (Y-Ym) 5.363E-05 5.348E-05 5.437E-05  Model Abs(Ypred-Yi) 8.50E-05 6.08E-05 9.08E-05  -7.17E-03 -7.48E-03  5.141E-05 5.601E-05  1.22E-04 2.02E-04  1.48E-08 4.09E-08  -1.50E-06 1.50E-06  2.25E-12 2.25E-12  2.24E-05 3.70E-06  5.02E-10 1.37E-11  2  (Ypred-Yi)2 7.23E-09 3.70E-09 8.24E-09  Pure error  SSPE = DoF = Variance =  2.69E-04 4.00E+00 6.72E-05 Experimental error  SSE= Variance= SSLOF= Fo =  7.54E-08 1.26E-08 2.69E-04 2.00E+00  DOFE= DOFLOF= VarianceLOF =  6 2 1.34E-04 6  LOF = Lack of fit DOF = Degrees of freedom E = Experimental error PE= Pure error  300  Appendix III.11 : Statistical analysis : Confidence interval calculation Mathematical equation for power law rate equation k2 k3 r = k1 PCO PH 2  The sensitivity matrix ∂f k2 G1,1 = = PCO PHk 32 ∂k 1 ∂f k2 G1, 2 = = k 1 PCO × log (PCO ) × PHk 32 ∂k 2 ∂f k2 G1, 3 = = k1 PCO PHk 32 × log (PH 2 ) ∂k 3  A = ∑ G T QG Q = Weighting matrix, here we have used unit matrix. N  Objective function, S (k ) = ∑ [ri − rcalc ]2 i =1  Scaling of matrix A When the parameters differ by more than one order of magnitude, matix ‘A’ may appear to be ill conditioned even if the estimation problem is well posed. The reduced sensitivity coefficients are defined as   ∂f GRij =   ∂k  j   k j    The reduced A matrix is then defined as  AR = GRT QGR −1 = ARii  Aii−1 ki  =  βi 100  301  Parameters can be reported as k i = k i* ± β i  More conventional way: Standard error of the estimated parameters are  σˆ ki = σˆ ε Aii = σˆ ε k i ARii = σˆ ε k i 2 Variance , σˆ ε =  S(k*) N m p  = = = =  Nm-p =  βi 100  S (k * ) Nm − p  Objective function evaluated at optimized K values. Number of experiments Number of measurements Number of estimated parameters Degrees of freedom  The (1-α)100% marginal confidence interval for each parameter, ki is given by, k i* − t αv / 2σˆ ki ≤ k i ≤ k i* + tαv / 2σˆ ki  [Reference : Englezos, P., Kalogerakis, N., “Applied parameter estimation for chemical engineers”, Marcel-Dekker, New York, 2001 ( Chapter 8)]  302  Table AIII.7 : Parameter estimation and confidence interval for four major products  Methanol Parameter k n m  Lower limit 3.19 x 10-7 0.537 0.974  Estimated value 3.19 x 10-7 0.559 1.1025  Upper limit 3.19 x 10-7 0.575 1.0769  Lower limit 4.54 x 10-6 0.44 0.61  Estimated value 4.54 x 10-6 0.46 0.64  Upper limit 4.54 x 10-6 0.49 0.66  Lower limit 3.94 x 10-6 0.41 0.65  Estimated value 3.94 x 10-6 0.43 0.68  Upper limit 3.94 x 10-5 0.45 0.710  Lower limit 8.24 x 10-6 -0.250 0.873  Estimated value 8.24 x 10-6 -0.237 0.956  Upper limit 8.24 x 10-6 -0.223 1.04  Acetaldehyde Parameter k n m Ethanol Parameter k n m Acetone Parameter k n m  303  Appendix III.12: Kinetic modeling of major components of syngas conversion over Rh-K-MoP/SiO2 catalyst  0.012  Rate, R CH4 [mol CH 4 /gm catal./hr]  0.01  0.008  0.006  0.004  0.002  0 0  100  200  300  400 500 PH2 [Psi]  600  700  800  900  Figure AIII.6.a. : Kinetic data fitting of methane -3  Rate, R CH3COCH3 [mol CH 3 COCH 3 /gm catal./hr]  1.4  x 10  1.2  1  0.8  0.6  0.4  0.2  0 0  100  200  300  400 500 PH2 [Psi]  600  700  800  900  Figure AIII.6.b. : Kinetic data fitting of acetone  304  -3  Rate, RCH3CHO [mol CH3CHO/gm catal./hr]  8  x 10  7 6 5 4 3 2 1 0 0  100  200  300  400 500 PH2 [Psi]  600  700  800  900  Figure AIII.6.c.: Kinetic data fitting of acetaldehyde -3  7  x 10  Rate, RC2H5OH [mol EtOH/gm catal./hr]  6  5  4  3  2  1  0 0  100  200  300  400 500 PH2 [Psi]  600  700  800  900  Figure AIII.6.d. : Kinetic data fitting of ethanol  305  Appendix III.13 : Matlab program for kinetic analysis of syngas gas conversion over MoP catalyst % Sharif Fakhruz Zaman % Chemical Kinetics of K-Rh-MoP-SiO2 Catalyst % Acetaldehyde rate model % Department of Chemical & Biological Engineering % University of British Columbia, Vancouver, BC, Canada % MAIN PROGRAM FILE% close all clear all clc global Pco PH2 R X2 X3 %%--======================================--%% %% 325 oC %%--======================================--%% disp('Values at 325 oC') % Initial value for iteration x0=[1e-8;.1;.1]; % Set options to LSQNONLIN. [x,Resnorm]=lsqnonlin('OF325CH3CHO',x0,... [1e-10;-3;-3],[1e-2;1;2],... optimset('Disp','iter','TolFun',1e-10,'MaxFunEvals',1e5,'MaxIter',1e5,... 'TolX',1e-20)); disp(x) RR=x(1).*Pco.^x(2).*PH2.^x(3); X2=x(2); X3=x(3); %% Storing fitted power value, i.e. m,n Rc325=RR; Rm325=R; % Storing measured and simulated data compare=[R,RR, abs(R-RR)*1e3]; disp( 'Experimental Simulated Diffx10^3') disp('--------------------------------') format short E disp(compare) disp('Resnorm'); disp(Resnorm); disp('Values of the fitted parameter') disp('Rate constant, k ='); disp(x(1)); disp('n Power of Y_CO='); disp(x(2)); 306  disp('m Power of P_H2='); disp(x(3)); Pco1=0:1:1200; PH21=1200-Pco1; %% Statistical analysis : Calling the statistical subroutine [k,n,m]= Stat_func(x,R,Pco,PH2,Resnorm); %% RR=x(1).*(Pco1.^x(2).*PH21.^x(3)); plot(PH2,R,'d',PH21,RR,'linewidth',2) xlabel('P_H_2 [Psi]') ylabel('Rate, R_C_H_3_C_H_O [mol CH_3CHO/gm catal./hr]') hold on %%--======================================--%% %% 275 oC %%--======================================--%% disp('Values at 275 ^oC') % Initial value for iteration x0=[1e-2]; % Set options to LSQNONLIN. [x,Resnorm]=lsqnonlin('OF275CH3CHO',x0,... [1e-10],[1e-2],... optimset('TolFun',1e-30,'MaxFunEvals',1e7,'MaxIter',100000,... 'TolX',1e-30)); x(2)=X2;x(3)=X3; disp(x) RR=x(1).*Pco.^x(2).*PH2.^x(3); Rc275=RR; Rm275=R; compare=[R,RR, abs(R-RR)*1e3]; disp( 'Experimental Simulated Diffx10^3') disp('--------------------------------') disp(compare) disp('Resnorm'); disp(Resnorm); disp('Values of the fitted parameter') disp('Rate constant, k ='); disp(x(1)); disp('n Power of Y_CO='); disp(x(2)); disp('m Power of P_H2='); disp(x(3)); 307  %disp('z Power of Total P ='); disp(x(4)); RR=x(1).*(Pco1.^x(2).*PH21.^x(3)); plot(PH2,R,'>',PH21,RR,'linewidth',2) %%--======================================--%% %% 300 oC %%--======================================--%% disp('Values at 300 oC') % Initial value for iteration x0=[1e-2]; % Set options to LSQNONLIN. [x,Resnorm]=lsqnonlin('OF300CH3CHO',x0,... [1e-10],[1e-2],... optimset('TolFun',1e-30,'MaxFunEvals',1e7,'MaxIter',100000,... 'TolX',1e-20)); x(2)=X2;x(3)=X3;  RR=x(1).*Pco.^x(2).*PH2.^x(3); disp('300 ^oC') %% Input X must be in column format %[k,n,m]= Stat_func(x,R,Pco,PH2,Resnorm) Rc300=RR; Rm300=R; compare=[R,RR, abs(R-RR)*1e3]; disp( 'Experimental Simulated Diffx10^3') disp('--------------------------------') disp(compare) disp('Resnorm'); disp(Resnorm); disp('Values of the fitted parameter') disp('Rate constant, k ='); disp(x(1)); disp('n Power of Y_CO='); disp(x(2)); disp('m Power of P_H2='); disp(x(3)); RR=x(1).*(Pco1.^x(2).*PH21.^x(3)); plot(PH2,R,'o',PH21,RR,'linewidth',2) %%--======================================--%% %% 340 oC 308  %%--======================================--%% disp('Values at 340 oC') % Initial value for iteration x0=[1e-2]; % Set options to LSQNONLIN. [x,Resnorm]=lsqnonlin('OF340CH3CHO',x0,... [1e-10],[1e-2],... optimset('TolFun',1e-30,'MaxFunEvals',1e7,'MaxIter',100000,... 'TolX',1e-30)); x(2)=X2;x(3)=X3; disp(x) RR=x(1).*Pco.^x(2).*PH2.^x(3); Rc340=RR; Rm340=R; compare=[R,RR, abs(R-RR)*1e3]; disp( 'Experimental Simulated Diffx10^3') disp('--------------------------------') disp(compare) disp('Resnorm'); disp(Resnorm); disp('Values of the fitted parameter') disp('Rate constant, k ='); disp(x(1)); disp('n Power of Y_CO='); disp(x(2)); disp('m Power of P_H2='); disp(x(3)); RR=x(1).*(Pco1.^x(2).*PH21.^x(3)); plot(PH2,R,'h',PH21,RR,'linewidth',2) hold off %%--======================================================--%% %% Peity plot %%--======================================================--%% Rc=[Rc275; Rc300; Rc325; Rc340]; Rm=[Rm275; Rm300; Rm325; Rm340]; x=0:.0001:1; y=x; figure set(gcf,'defaultaxesfontname','Times New Roman') set(gcf,'defaultaxesfontsize',12) set(gcf,'defaulttextcolor','black') 309  plot(Rm,Rc,'*',x,y,'k','linewidth',2,'MarkerEdgeColor','k',... 'MarkerFaceColor','k','MarkerSize',10) axis([0 .8e-2 0 .8e-2]) xlabel('Experimental Rate[mol CH_3CHO/g cat./h]') ylabel('Calculated Rate[mol CH_3CHO/g cat./h]')  310  Statistical analysis subroutine %% Function file for Statistical Analysis function [ka,n,m]=Stat_func(x,R,Pco,PH2,Resnorm) %% Statistical analysis %% Reduced matrix procedure %% Scaling of sensitivity matrix syms x1 x2 k1 k2 k3 Rr % Rr = Reaction rate % x1 = partial pressure of CO % x2 = Partial pressure of H2 % k = Estimated parameters %----------------------------------------------------------------------%Function k=[k1 k2 k3]; Fnc=k(1).*x1.^k(2).*x2.^k(3); %----------------------------------------------------------------------if R(1)==0 R=R(2:end); Pco=Pco(2:end); PH2=PH2(2:end); end %----------------------------------------------------------------------LSOF=Resnorm; %% Function value at optimized condition %----------------------------------------------------------------------% Differentiating the rate equation d1=subs(diff(Fnc,k(1)),{x1,x2},{Pco,PH2}); d2=subs(diff(Fnc,k(2)),{x1,x2},{Pco,PH2}); d3=subs(diff(Fnc,k(3)),{x1,x2},{Pco,PH2}); %------------------------------------------------------------------format long e % Optimized estimated parameter k_opt1=[x(1) x(2) x(3)]; k_opt=double(k_opt1); %------------------------------------------------------------------% sensitivity matrix element is multiplied with optimized parameter x(1), % x(2) and x(3)to form The Reduced Sensitivity Matrix D1=double(subs(d1,{k(1),k(2),k(3)},{k_opt(1),k_opt(2),k_opt(3)})*x(1)); D2=double(subs(d2,{k(1),k(2),k(3)},{k_opt(1),k_opt(2),k_opt(3)})*x(2)); D3=double(subs(d3,{k(1),k(2),k(3)},{k_opt(1),k_opt(2),k_opt(3)})*x(3)); %--------------------------------------------------------------------311  g=[D1 D2 D3]; %--------------------------------------------------------------------Q=eye(6,6); % weighting factor A=g'*Q*g; %--------------------------------------------------------------------%Statistical Analysis of 95% confidence interval m=size(R); % Number of measured variable N=1;DOF=N*m-size(k); % Degrees of Freedom varience=LSOF/DOF(1); %sigma^2 IAM=inv(A); % Inverse of A Matrix RAM=sqrt(diag(IAM)); beta=k_opt.*RAM; Sigma_e = sqrt(varience); delK=beta.*k_opt*Sigma_e/100; % Standerd error of estimated parameters %% Confidence Interval Calculation upper_limit=k_opt+delK*1.98; lower_limit=k_opt-delK*1.98; format short e disp('Sensitivity Analysis 95% Confidence interval') disp(' LL Actual K UL') ka=[lower_limit(1) k_opt(1) upper_limit(1)] n=[lower_limit(2) k_opt(2) upper_limit(2)] m=[lower_limit(3) k_opt(3) upper_limit(3)]  312  Function files % Function file for Acetaldehyde at 275 C function fit_OF275=OF275CH3CHO(x) global Pco PH2 R X2 X3 R = [0; 7.22; 9.71]*1e-4; %% Mole CO/gm Catal/hr Pco = [1200; 600; 400]; %% psi PH2 = [0; 600; 800]; %% psi x(2)=X2; x(3)=X3; fit_OF275=R-x(1).*Pco.^x(2).*PH2.^x(3); %function file % Function file for Acetaldehyde at 300 C function fit_OF300=OF300CH3CHO(x) global Pco PH2 R X2 X3 R = [2.15; 2.27; 2.28; 2.35]*1e-3; %% Mole CO/gm Catal/hr Pco = [600; 480; 400; 400]; %% psi PH2 = [600; 720; 800; 800]; %% psi x(2)=X2; x(3)=X3; fit_OF300=R-x(1).*Pco.^x(2).*PH2.^x(3); % Function file of acetaldehyde at 325C function fit_OF325=OF325CH3CHO(x) global Pco PH2 R X2 X3 R = [5.48; 4.84; 4.49; 4.95; 4.25; 5.16]*1e-3; %% Mole CO/gm Catal/hr Pco = [600; 480; 480; 480; 400; 400]; %% psi PH2 = [600; 720; 720; 720; 800; 800]; %% psi fit_OF325=R-x(1).*Pco.^x(2).*PH2.^x(3); % Function file for Acetaldehyde 340 C function fit_OF340=OF340CH3CHO(x) global Pco PH2 R X2 X3 R = [0; 6.98; 6.11]*1e-3; %% Mole CO/gm Catal/hr Pco = [1200; 600; 400]; %% psi PH2 = [0; 600; 800]; %% psi x(2)=X2; x(3)=X3; fit_OF340=R-x(1).*Pco.^x(2).*PH2.^x(3);  313  

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