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Process simulation and catalyst development for biodiesel production West, Alex Harris 2006

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PROCESS SIMULATION AND CATALYST DEVELOPMENT FOR BIODIESEL PRODUCTION  By  Alex Harris West B.A.Sc, University of British Columbia, 2003  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  in  The Faculty of Graduate Studies (Chemical and Biological Engineering)  UNIVERSITY O F BRITISH C O L U M B I A August 2006  © Alex Harris West, 2006  Abstract F o u r continuous biodiesel processes were designed and simulated i n H Y S Y S . T h e first t w o employed traditional homogeneous alkali and acid-catalysts.  T h e third and fourth processes  u s e d a heterogeneous a c i d catalyst a n d a s u p e r c r i t i c a l m e t h o d , r e s p e c t i v e l y , to c o n v e r t a w a s t e vegetable o i l feedstock into biodiesel. W h i l e all processes were capable of p r o d u c i n g biodiesel at h i g h p u r i t y , the h e t e r o g e n e o u s a n d s u p e r c r i t i c a l p r o c e s s e s w e r e the least c o m p l e x a n d h a d the s m a l l e s t n u m b e r o f unit o p e r a t i o n s . M a t e r i a l a n d e n e r g y f l o w s , as w e l l as s i z e d u n i t o p e r a t i o n b l o c k s , w e r e u s e d to c o n d u c t an e c o n o m i c assessment o f e a c h p r o c e s s . T o t a l c a p i t a l i n v e s t m e n t , total m a n u f a c t u r i n g c o s t a n d after tax rate-of-return ( A T R O R ) w e r e c a l c u l a t e d f o r e a c h p r o c e s s . The  heterogeneous  acid  catalyst  process  had  the  lowest  total  capital  investment  and  m a n u f a c t u r i n g c o s t s , a n d h a d the o n l y p o s i t i v e A T R O R .  F o l l o w i n g the results o f the p r o c e s s s i m u l a t i o n s , tin(II) o x i d e w a s i n v e s t i g a t e d f o r use as a heterogeneous catalyst. U n f o r t u n a t e l y , c a t a l y t i c e x p e r i m e n t s s h o w e d n o a c t i v i t y . S u b s e q u e n t l y , a c a r b o n - b a s e d a c i d catalyst w a s p r e p a r e d b y s u l f o n a t i n g p y r o l y s i s c h a r , a n d w a s s t u d i e d f o r its a b i l i t y to c a t a l y z e t r a n s e s t e r i f i c a t i o n o f v e g e t a b l e o i l . T h e catalyst s h o w e d o n l y transesterification,  but  demonstrated  good  conversion  in  free  fatty  acid  qualitative  esterification.  E x p e r i m e n t s w e r e d e s i g n e d to m e a s u r e the effect o f a l c o h o l to o i l ( A : 0 ) m o l a r ratio, r e a c t i o n t i m e a n d catalyst l o a d i n g o n the s a m p l e . It w a s o b s e r v e d that free fatty a c i d ( F F A ) c o n v e r s i o n i n c r e a s e d w i t h i n c r e a s i n g A : 0 m o l a r ratio, r e a c t i o n t i m e a n d c a t a l y s t l o a d i n g . C o n d i t i o n s that y i e l d e d the greatest c o n v e r s i o n w e r e  18:1 A : 0 m o l a r r a t i o , 3 h o u r r e a c t i o n t i m e , 5  wt.%  catalyst, 7 6 ° C u n d e r r e f l u x . T h e a b o v e c o n d i t i o n s r e d u c e d the F F A content i n a w a s t e v e g e t a b l e o i l ( W V O ) - e t h a n o l m i x t u r e f r o m 4 . 2 5 w t . % to <0.5 wt.%. U n d e r a n 78:1 A : 0 m o l a r ratio a n d i d e n t i c a l c o n d i t i o n s , the catalyst w a s able to r e d u c e the F F A content o f a W V O f e e d s t o c k f r o m 12.25 w t . % to 1 wt.%. T h e catalyst has p o t e n t i a l to b e u s e d i n a p r o c e s s c o n v e r t i n g a h i g h F F A f e e d s t o c k to b i o d i e s e l i f the l i m i t a t i o n s to t r a n s e s t e r i f i c a t i o n c a n b e o v e r c o m e . O t h e r w i s e , it w i l l serve as an e x c e l l e n t catalyst f o r r e d u c i n g the F F A content o f f e e d s t o c k s i n a t w o - s t e p a c i d a n d base c o n v e r s i o n p r o c e s s .  ii  Table of Contents Abstract  ii  Table of Contents  ;  iii  List of Tables  v  List of Figures  vi  Nomenclature  viii  Acknowledgements 1  Introduction 1.1  2  ix 1  Transesterification research  2  1.1.1  H o m o g e n e o u s alkali-catalyzed transesterification  3  1.1.2  H o m o g e n e o u s acid-catalyzed transesterification  3  1.1.3  Heterogeneously catalyzed transesterification  1.1.4  Supercritical transesterification  ;  4  ,  5  1.2  P r o c e s s m o d e l l i n g a n d e c o n o m i c assessment  6  1.3  Thesis objectives  6  1.4  Thesis format  7  1.5  References  8  Assessment of F o u r Continuous Biodiesel Production Processes using H Y S Y S . P l a n t  10  2.1  Introduction and background  10  2.2  Process simulation  13  2.3  Process design  15  2.4  Equipment sizing  16  2.4.1  Reactor vessels  17  2.4.2  Columns  17  2.4.3  G r a v i t y separators  17  2.4.4  Hydrocyclone  18  2.5  E c o n o m i c assessment  18  2.5.1  Basis of calculations  ,  18  2.5.2  Total capital investment  19  2.5.3  T o t a l m a n u f a c t u r i n g cost  19  2.6  Sensitivity analyses and optimization  21  2.7  Conclusion  22 iii  References 3  •  39  Characterization and Testing of Heterogeneous Catalysts for B i o d i e s e l Production  41  3.1  Introduction and background  41  3.2  T i n ( I I ) o x i d e s y n t h e s i s a n d testing m e t h o d s  44  3.2.1  S n O synthesis procedure  3.2.2  C a t a l y s t testing.  3.3  ••  44  T i n ( I I ) o x i d e results a n d d i s c u s s i o n  45  3.3.1  Synthesis and characterization  45  3.3.2  Catalytic activity  3.4  ;  •-  45  S u l f o n a t e d c h a r synthesis a n d testing m t h o d s  45  3.4.1  Sulfonated char synthesis procedure  45  3.4.2  S u l f o n a t e d c h a r testing p r o c e d u r e  46  S u l f o n a t e d c h a r results a n d d i s c u s s i o n  47  3.5  4  44  3.5.1  Catalyst characterization  47  3.5.2  Sulfonated char catalytic activity  51  3.6  Conclusion  54  3.7  References  66  C o n c l u s i o n , General D i s c u s s i o n and Recommendations  68  4.1  General discussion  '.  68  4.2  Conclusions  70  4.3  Recommendations  72  4.4  References  74  List of Tables Table 1.1. Selected heterogeneous acid catalysts used for transesterification of triglycerides and their results  ,  5  Table 2.1. Catalysts and reaction parameters for heterogeneously catalyzed reactions of soybean oil at 1 atm  25  Table 2.2. Summary of unit operating conditions for each process  26  Table 2.3. Feed and product stream information for the alkali-catalyzed process  27  Table 2.4. Feed and product stream information for the homogeneous acid-catalyzed process. .27 Table 2.5. Feed and product stream information for the heterogeneous acid-catalyzed process. 28 Table 2.6. Feed and product stream information for the supercritical methanol process  28  Table 2.7. Equipment sizes for various process units in all processes. (Dimensions are diameter x height, m)  29  Table 2.8. Equipment costs, fixed capital costs and total capital investments for each process. (Units: $millions) Table 2.9. Conditions for the economic assessment of each process. (Zhang et al. 2003b)  30 31  Table 2.10. Total manufacturing cost and after tax rate-of-return for each process. (Units: $millions) Table 3.1. B E T surface areas for each catalyst sample  32 47  Table 3.2. Mass per cent composition by element and molecular formula of each catalyst sample Table 3.3. Total acidity for each catalyst sample  48 49  v  List of Figures F i g u r e 2 . 1 . H o m o g e n e o u s b a s e - c a t a l y z e d p r o c e s s f l o w s h e e t ( P r o c e s s I)  33  F i g u r e 2 . 2 . H o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s f l o w s h e e t ( P r o c e s s II)  34  F i g u r e 2 . 3 . H e t e r o g e n e o u s a c i d - c a t a l y z e d p r o c e s s f l o w s h e e t ( P r o c e s s III)  ....35  F i g u r e 2.4 S u p e r c r i t i c a l a l c o h o l p r o c e s s f l o w s h e e t ( P r o c e s s I V )  36  F i g u r e 2 . 5 . A f t e r - t a x rate o f return v s . r e a c t i o n c o n v e r s i o n f o r a l l processes  37  F i g u r e 2.6. A T R O R v s . m e t h a n o l r e c o v e r y i n the m e t h a n o l r e c o v e r y c o l u m n , H A C p r o c e s s . . . 37 F i g u r e 2 . 7 . A T R O R v s . o p e r a t i n g pressure i n the m e t h a n o l r e c o v e r y c o l u m n , H A C p r o c e s s . . . . 38 F i g u r e 3 . 1 . S a m p l e o f u n k n o w n substance o b t a i n e d d u r i n g S n O p r e p a r a t i o n v i a m e t h o d o f A b r e u e t a l . (2005).....  56  F i g u r e 3.2. C o m m e r c i a l s a m p l e o f S n O  56  F i g u r e 3.3. X R D pattern o f S n O s a m p l e prepared b y m e t h o d o f F u j i t a et a l . ( 1 9 9 0 )  57  F i g u r e 3.4. X R D pattern o f c o m m e r c i a l S n O s a m p l e  57  F i g u r e 3.5. C a t a l y s t 1 X R D pattern  58  F i g u r e 3.6. X P S s u r v e y s c a n f o r C a t a l y s t 1  58  F i g u r e 3.7. N a r r o w s c a n i n S 2 p r e g i o n f o r C a t a l y s t 1  59  F i g u r e 3.8. N a r r o w s c a n i n C Is r e g i o n f o r C a t a l y s t 1  59  F i g u r e 3.9. n - P r o p y l a m i n e p u l s e a d s o r p t i o n p e a k s f o r C a t a l y s t 1  60  F i g u r e 3.10. T P D c u r v e f o r C a t a l y s t 1. R a t i o o f w e a k a c i d sites to strong a c i d sites is 0 . 8 5 : 1 . . . 6 0 F i g u r e 3 . 1 1 . T P D c u r v e f o r C a t a l y s t 2 . R a t i o o f w e a k a c i d sites to s t r o n g a c i d sites is 1.21:1... 61 F i g u r e 3.12 S E M i m a g e o f C a t a l y s t 1 i n d i c a t i n g p o r e s i z e s  61  Figure 3.13. S E M image of Catalyst 2 emphasizing fibrous channels and pore network  62  F i g u r e 3.14. S E M i m a g e o f C a t a l y s t 3, h i g h l i g h t i n g v a r i a b l e s i z e o f catalyst p a r t i c l e s  62  F i g u r e 3 . 1 5 . E f f e c t o f r e a c t i o n t i m e o n f i n a l a c i d n u m b e r . R e a c t i o n s w e r e r u n at 5 w t . % catalyst 1 w i t h e t h a n o l at A : 0 m o l a r ratios o f 6 : 1 , 9 . 5 : 1 , 1 8 : 1 , 2 8 : 1 , 3 8 : 1 , 48:1  63  F i g u r e 3.16. E f f e c t o f A : 0 m o l a r ratio at f i x e d r e a c t i o n t i m e o n final a c i d n u m b e r . 5 w t . % catalyst 1  63  F i g u r e 3.17. E f f e c t o f A : 0 m o l a r ratio o n final a c i d n u m b e r f o r the 15 h o u r set o f r e a c t i o n s . 5 wt.% Catalyst 1  64  F i g u r e 3.18. E f f e c t o f catalyst a m o u n t o n final a c i d n u m b e r . 28:1 A : 0 m o l a r r a t i o , e t h a n o l , 5 w t . % catalyst 1  64  vi  F i g u r e 3 . 1 9 . F i n a l a c i d n u m b e r o f r e a c t i o n m i x t u r e after r e a c t i o n w i t h e a c h catalyst s a m p l e . 3 h o u r r e a c t i o n , 28:1 A : 0 m o l a r ratio, 5 w t . % c a t a l y s t l o a d i n g  65  Nomenclature Definition After-tax rate of return Alcohol to oil Ammonia Auxiliary facility cost Bare module capital costs Bare module factor Bare module factor parameter Bare module factor parameter Brunauer, Emmett and Teller Capacity parameter Carbon dioxide Carboxylic acid group Contingency fee Energy dispersive X-ray Fatty acid methyl-ester Fixed capital cost Free fatty acid Gas chromatograph Green house gas Heterogeneous Acid Catalyzed Materials factor Non-random two liquid Pressure factor Purchase cost Purchase cost parameter Purchase cost parameter Scanning electron microscopy Sulfate group Temperature programmed desorption Thermal conductivity detector Tin(II) chloride Tin(U) oxide Total capital investment Total manufacturing cost Total module cost Waste vegetable oil Weight per cent Working capital cost X-ray diffraction X-ray photospectroscopy  Symbol ATROR A:0 NH  Units  CAC  -  CBM  $  FBM  B, B BET A C0 COOH7  -  CcF  $  3  2  2  EDX FAME  -  CFC  $  FFA GC GHG HAC NRTL F  -  c  $  FM  P  P  K, K SEM S0 ' TPD TCD SnCh SnO  -  CTCI CTM  $ $ $  wt.%  -  2  2  4  TMC  wvo  Cwc XRD XPS  $ -  viii  Acknowledgements I a m e x t r e m e l y g r a t e f u l to m y s u p e r v i s o r D r . N a o k o E l l i s , a n d c o m m i t t e e m e m b e r s D r . D u s k o P o s a r a c a n d D r . J o h n R . G r a c e , f o r their support, g u i d a n c e a n d p a t i e n c e t h r o u g h o u t the c o u r s e o f this d e g r e e .  T h a n k y o u to D r . K e v i n J . S m i t h f o r the use o f h i s l a b o r a t o r y f a c i l i t i e s , M r . I b r a h i m A b u f o r h i s assistance w i t h the B E T m e a s u r e m e n t s a n d D r . X u e b i n L i u f o r h i s t r e m e n d o u s assistance w i t h the n - p r o p y l a m i n e e x p e r i m e n t s a n d i n t e r p r e t i n g the r e s u l t s .  T h e f i n a n c i a l support o f the N a t u r a l S c i e n c e s a n d E n g i n e e r i n g R e s e a r c h C o u n c i l is g r a t e f u l l y acknowledged.  A s p e c i a l t h a n k - y o u to M r . J u l i a n R a d l e i n , f o r h i s ideas r e g a r d i n g the use o f s u l f o n a t e d c h a r as a p o t e n t i a l catalyst f o r b i o d i e s e l p r o d u c t i o n .  A n d last but not least, t h a n k y o u to m y f a m i l y a n d f r i e n d s f o r t h e i r e n c o u r a g e m e n t a n d support w h i l e p u r s u i n g this degree.  ix  1  Introduction  R e c e n t c o n c e r n s o v e r d i m i n i s h i n g f o s s i l f u e l s u p p l i e s a n d r i s i n g o i l p r i c e s , as w e l l as a d v e r s e environmental  a n d h u m a n health i m p a c t s f r o m the use o f p e t r o l e u m f u e l h a v e  prompted  c o n s i d e r a b l e interest i n r e s e a r c h a n d d e v e l o p m e n t o f fuels f r o m r e n e w a b l e r e s o u r c e s , s u c h as b i o d i e s e l a n d e t h a n o l . B i o d i e s e l is a v e r y attractive alternative f u e l , as it has a n u m b e r  of  advantages o v e r c o n v e n t i o n a l d i e s e l f u e l . It is d e r i v e d f r o m a r e n e w a b l e , d o m e s t i c r e s o u r c e a n d c a n therefore  reduce reliance on foreign petroleum  i m p o r t s . B i o d i e s e l reduces net  carbon  d i o x i d e e m i s s i o n s b y 7 8 % o n a l i f e - c y c l e b a s i s w h e n c o m p a r e d to c o n v e n t i o n a l d i e s e l f u e l ( T y s o n 2 0 0 1 ) . It has a l s o b e e n s h o w n to h a v e d r a m a t i c e m i s s i o n s . F o r i n s t a n c e , c o m b u s t i o n o f neat b i o d i e s e l  improvements  on engine exhaust  decreases c a r b o n m o n o x i d e  (CO)  e m i s s i o n s b y 4 6 . 7 % , p a r t i c u l a t e matter e m i s s i o n s b y 6 6 . 7 % a n d u n b u r n e d h y d r o c a r b o n s b y 4 5 . 2 % ( S c h u m a c h e r et a l . 2 0 0 1 ) . B i o d i e s e l c a n b e u s e d i n a r e g u l a r d i e s e l e n g i n e w i t h l i t t l e to n o e n g i n e m o d i f i c a t i o n s r e q u i r e d . B i o d i e s e l is safer to transport d u e to its h i g h e r f l a s h p o i n t than d i e s e l f u e l . L a s t l y , b i o d i e s e l is b i o d e g r a d a b l e a n d n o n - t o x i c , m a k i n g it u s e f u l f o r applications enclosures.  in  highly  sensitive  environments,  such  as  marine  transportation  ecosystems and  mining  H o w e v e r , b i o d i e s e l is not w i t h o u t its d i s a d v a n t a g e s . T h e s e i n c l u d e r e d u c e d e n e r g y  content o n p e r m a s s b a s i s (this is d u e to the p r e s e n c e o f o x y g e n i n the f u e l ) w h i c h leads to l o w e r p o w e r a n d t o r q u e , as w e l l as h i g h e r f u e l c o n s u m p t i o n . A d d i t i o n a l l y , c o m b u s t i o n o f b i o d i e s e l has b e e n s h o w n to c a u s e a s l i g h t i n c r e a s e i n N O  x  f o r m a t i o n ( S c h u m a c h e r et a l . 2 0 0 1 ; D o r a d o et a l .  2003).  A s s h o w n i n E q u a t i o n 1.1, b i o d i e s e l ( d e f i n e d b y the A s s o c i a t i o n f o r S t a n d a r d s a n d T e s t i n g o f Materials  as  mono-alkyl  esters  of  long  chain  fatty  acids)  is  usually  produced  by  the  t r a n s e s t e r i f i c a t i o n o f a l i p i d f e e d s t o c k . T r a n s e s t e r i f i c a t i o n is the r e v e r s i b l e r e a c t i o n o f a fat o r o i l ( b o t h o f w h i c h are c o m p o s e d o f t r i g l y c e r i d e s a n d free fatty a c i d s ) w i t h an a l c o h o l to f o r m fatty a c i d a l k y l esters a n d g l y c e r o l . S t o i c h i o m e t r i c a l l y , the r e a c t i o n requires a 3:1 a l c o h o h o i l ( A : 0 ) m o l a r r a t i o , but  b e c a u s e the r e a c t i o n is r e v e r s i b l e , e x c e s s a l c o h o l is a d d e d to d r i v e  the  e q u i l i b r i u m t o w a r d the p r o d u c t s s i d e .  1  CH -OOC-R, I CH-OOC-R2 I  Ri-COO-R'  2  + 3R'OH  Catalyst <=>  CH2-OOC-R3  Glyceride  R -COO-R' 2  CH -OH I CH-OH I 2  +  R3-COO-R'  Alcohol  (1.1)  CH2-OH  Esters  Glycerol  Transesterification can be alkali-, acid- or enzyme-catalyzed; however, enzyme catalysts are rarely used, as they are less effective (Ma and Hanna 1999). The reaction can also take place without the use of a catalyst under conditions in which the alcohol is in a supercritical state (Saka and Kusdiana 2001; Demirbas 2002). Biodiesel can also be produced by esterification of fatty acid molecules, as shown in Equation 1.2. This reaction can be catalyzed be either a base or an acid or without the use of a catalyst under supercritical conditions (Kusdiana and Saka 2004). Catalyst R,-COOH Fatty acid  + R'OH Alcohol  <=>  R^COO-R' Ester  +  H 0 2  (1.2)  Water  Currently, the high cost of biodiesel production is the major impediment to its large scale commercialization (Canakci and Van Gerpen 2001). The high cost is largely attributed to the cost of virgin vegetable oil as feedstock, which can account for up to 75% of the final product cost (Krawczyk 1996). Exploring methods to reduce the production cost of biodiesel has been the focus of much recent research. One method involves replacing a virgin oil feedstock with a waste cooking oil feedstock. The costs of waste cooking oil are estimated to be less than half of the cost of virgin vegetable oils (Canakci and Van Gerpen 2001). Furthermore, utilizing waste cooking oil has the advantage of removing a significant amount of material from the waste stream - as of 1990, it was estimated that at least 2 billion pounds of waste grease was produced annually in the United States (Canakci and Van Gerpen 2001). 1.1  Transesterification research  Biodiesel related research has progressed from initial attempts to synthesize the alkyl-ester product through a simple base catalyzed reaction of pure vegetable oil to more sophisticated attempts at bringing production costs down through less expensive feedstocks,  different 2  catalysts ( s u c h as h o m o g e n e o u s a n d h e t e r o g e n e o u s a c i d catalysts) a n d r e a c t i o n c o n d i t i o n s ( s u c h as the r e a c t i o n o f the l i p i d f e e d s t o c k w i t h a s u p e r c r i t i c a l a l c o h o l ) .  1.1.1  Homogeneous alkali-catalyzed  transesterification  T r a n s e s t e r i f i c a t i o n c a t a l y z e d b y a base s u c h as N a O H o r K O H has b e e n e x t e n s i v e l y s t u d i e d a n d r e p o r t e d ( F r e e d m a n et a l . 1 9 8 4 ; N o u r e d d i n i a n d Z h u 1 9 9 7 ; M a et a l . 1 9 9 8 ; K o m e r s et a l . 2 0 0 1 ; D o r a d o et a l . 2 0 0 2 ; D o r a d o et a l . 2 0 0 4 ) a n d o p t i m u m c o n d i t i o n s at a t m o s p h e r i c pressure ( 6 0 ° C , 1 w t . % catalyst, 6:1 A : 0 m o l a r ratio), are w e l l k n o w n ( F r e e d m a n et a l . 1 9 8 4 ) . A d d i t i o n a l l y , the k i n e t i c s o f the r e a c t i o n h a v e b e e n reported ( F r e e d m a n et a l . 1 9 8 6 ; N o u r e d d i n i a n d Z h u 1997) as f o l l o w i n g a s e c o n d o r d e r r e a c t i o n m e c h a n i s m , t h r o u g h t w o d i s t i n c t r e a c t i o n phases. T h e r e a c t i o n rate is i n i t i a l l y c o n t r o l l e d b y m a s s transfer b e t w e e n the a l c o h o l a n d o i l p h a s e s , a n d is then c o n t r o l l e d b y k i n e t i c l i m i t a t i o n s as it a p p r o a c h e s e q u i l i b r i u m .  In o r d e r to p r e v e n t s a p o n i f i c a t i o n (soap f o r m a t i o n ) d u r i n g the r e a c t i o n w h i c h l e a d s to d i f f i c u l t y d u r i n g d o w n s t r e a m p u r i f i c a t i o n , the free fatty a c i d ( F F A ) a n d w a t e r content o f the f e e d m u s t b e below  0.5  wt.%  a n d 0.05  wt.%,  r e s p e c t i v e l y ( F r e e d m a n et a l . 1984). B e c a u s e o f  these  l i m i t a t i o n s , o n l y p u r e v e g e t a b l e o i l feeds are a p p r o p r i a t e f o r a l k a l i - c a t a l y z e d t r a n s e s t e r i f i c a t i o n w i t h o u t e x t e n s i v e pretreatment.  7.7.2 A  Homogeneous acid-catalyzed  homogeneous  transesterification  acid-catalyzed process can be  employed  to  take  advantage  of  cheaper  f e e d s t o c k s , s u c h as waste c o o k i n g o i l a n d a n i m a l - b a s e d t a l l o w . T h e a c i d - c a t a l y z e d p r o c e s s c a n tolerate u p to 5 w t . %  F F A , but is s e n s i t i v e to w a t e r content greater than 0.5 wt.%.  The  d i s a d v a n t a g e o f this m e t h o d is that it is e x t r e m e l y s l o w at m i l d c o n d i t i o n s : C a n a k c i a n d V a n G e r p e n ( 1 9 9 9 ) , f o u n d that it t o o k 4 8 h o u r s to a c h i e v e a 9 8 % c o n v e r s i o n at 6 0 ° C at an A : 0 m o l a r ratio o f 30:1 w h i c h are t y p i c a l c o n d i t i o n s f o r this r e a c t i o n . A t h i g h e r temperatures a n d pressures (e.g. 1 0 0 ° C a n d 3.5 bar) r e a c t i o n t i m e s c a n b e s u b s t a n t i a l l y r e d u c e d ( d o w n to 8 h) to a c h i e v e 9 9 % c o n v e r s i o n ( G o f f et a l . 2 0 0 4 ) .  K i n e t i c studies o f the h o m o g e n e o u s a c i d - c a t a l y z e d r e a c t i o n h a v e b e e n s c a r c e c o m p a r e d to the base-catalyzed  reaction.  Freedman  et  al.  (1986)  investigated  the  acid  catalyzed  t r a n s e s t e r i f i c a t i o n o f s o y b e a n o i l w i t h b u t a n o l at 6 0 ° C . A t a 30:1 A : 0 m o l a r ratio a n d 1 w t . %  3  catalyst l o a d i n g , the f o r w a r d r e a c t i o n s w e r e o b s e r v e d to b e p s e u d o - f i r s t o r d e r w i t h the o v e r a l l r e a c t i o n o c c u r r i n g as a series o f c o n s e c u t i v e r e a c t i o n s .  1.1.3 A  Heterogeneously catalyzed  process e m p l o y i n g  transesterification  a heterogeneous  catalyst is a p p e a l i n g b e c a u s e the ease o f  s e p a r a t i o n f r o m the p r o d u c t stream p r o v i d e s an advantage o v e r the t r a d i t i o n a l processes.  To  this  end,  significant  effort  has  been  expended  to  identify  catalyst  homogeneous and  screen  heterogeneous catalysts that h a v e h i g h p o t e n t i a l f o r b i o d i e s e l p r o d u c t i o n .  1.1.3.1  Solid base catalysts  S e v e r a l researchers h a v e i n v e s t i g a t e d the t r a n s e s t e r i f i c a t i o n properties o f s o l i d base catalysts. K i m et a l . ( 2 0 0 4 ) f o u n d that a y i e l d o f 7 8 % c o u l d b e a c h i e v e d after 2 h o u r s u s i n g N a / N a O H / y A 1 2 0 3 as a catalyst, at 6 0 ° C , 1 a t m a n d 6:1 A : 0 m o l a r ratio. Increased y i e l d o f 9 0 % w a s a c h i e v e d b y the a d d i t i o n o f a c o s o l v e n t , n - h e x a n e , w i t h the A : 0 m o l a r ratio o f 9 : 1 . G r y g l e w i c z ( 1 9 9 9 ) reported that after 2.5 h o u r s at 6 0 ° C and 4.5:1 A : 0 m o l a r r a t i o , c a l c i u m o x i d e o r c a l c i u m m e t h o x i d e as catalyst g a v e b i o d i e s e l y i e l d s o f 9 0 % . H o w e v e r , n o reports e x i s t d e m o n s t r a t i n g the a b i l i t y o f s o l i d base catalysts to esterify F F A s present i n w a s t e v e g e t a b l e o i l a n d a n i m a l t a l l o w .  1.1.3.2 Solid acid catalysts D u e to their a b i l i t y to c a t a l y z e b o t h e s t e r i f i c a t i o n  a n d t r a n s e s t e r i f i c a t i o n r e a c t i o n s , a large  n u m b e r o f heterogeneous a c i d catalysts i n c l u d i n g s o l i d m e t a l o x i d e s a n d z e o l y t e s h a v e b e e n screened f o r a c t i v i t y as s u m m a r i z e d i n T a b l e 1 ( F u r u t a et a l . 2 0 0 4 ; L o p e z et a l . 2 0 0 5 ; J i t p u t t i et al. 2006).  E x t e n s i v e w o r k has a l s o g o n e i n t o d e v e l o p i n g a n d testing catalysts f o r e s t e r i f i c a t i o n o f free fatty acids. M b a r a k a and Shanks (2005)  d e s i g n e d a m e s o p o r o u s s i l i c a catalyst ( M C M - 4 1 ) w i t h  s p e c i a l l y t a i l o r e d h y d r o p h o b i c g r o u p s to p r e v e n t catalyst d e a c t i v a t i o n b y the w a t e r p r o d u c e d d u r i n g the e s t e r i f i c a t i o n r e a c t i o n . F u r u t a et a l . ( 2 0 0 4 ) tested their catalysts f o r  esterification  a c t i v i t y , a n d reported that c o n v e r s i o n s o f 1 0 0 % w e r e a c h i e v e d at a temperature o f 2 0 0 ° C i n the esterification of n-octanoic acid w i t h  m e t h a n o l . T o d a et a l . ( 2 0 0 5 ) r e c e n t l y d e v e l o p e d an a c i d  catalyst b y a d d i n g s u l f o n i t e g r o u p s to a c a r b o n s k e l e t o n o b t a i n e d b y p y r o l y z i n g r e f i n e d sugar. C a t a l y s t a c t i v i t y w a s m o r e than h a l f that o f the c o n v e n t i o n a l h o m o g e n e o u s a c i d r e a c t i o n , a n d  4  greater than that of other solid acid catalysts; however, the yield of the process was not mentioned. Research concerning heterogeneous catalysts is still in the catalyst screening stage. Studies regarding reaction kinetics, as well as improving reaction parameters have yet to be conducted. In addition, studies to determine the effects of free fatty acid concentration and water on the performance of the catalyst have been scarce.  Table 1.1. Selected heterogeneous acid catalysts used for transesterification of triglycerides and their results.  Reference  (Furuta et al. 2004)  (Jitputti et al. 2006)  (Lopez et al. 2005)  Catalyst Type  Feedstock  Tungstated zirconia Sulfated zirconia Sulfated tin oxide Sulfated zirconia Zinc oxide  SBO*  40  •• 300  1  90  SBO  40  300  1  80  SBO  40  300  1  68  Palm kernel oil Palm kernel oil Palm kernel oil Palm kernel oil Triacetin  6  200  40.5  90.3  6  200  40.5  86.1  6  200  40.5  90.3  6  200  40.5  71.4  6  60  1  480  79  Triacetin  6  60  1  480  33  Triacetin  6  60  1  480  57  Triacetin  6  60  1  480  10  Triacetin Triacetin  6 6  60 60  1 1  480 480  <10 <10  Sulfated tin dioxide KNO3/KL zeolyte Amberlyst15 Nafion NR50 Sulfated zirconia Tungstated zirconia Zeolyte HP ETS-10(H)  Molar ratio  Temperature  (°C)  Pressure (atm)  Time (min)  Conversion Achieved  (%)  *Soybean oil  1.1.4  Supercritical transesterification  Supercritical transesterification is also a potential alternative to the standard homogenous catalytic routes. Transesterification using supercritical methanol has been shown to give nearly complete conversion in small amount of time (15 minutes) (Warabi et al. 2004). High  temperatures, (up to 3 5 0 ° C ) a n d large A : 0 ratios ( 4 2 : 1 ) are r e q u i r e d to a c h i e v e the h i g h l e v e l s o f c o n v e r s i o n that h a v e b e e n r e p o r t e d ( K u s d i a n a a n d S a k a 2 0 0 1 ) . In a d d i t i o n to the  high  c o n v e r s i o n a n d r e a c t i o n rates, s u p e r c r i t i c a l t r a n s e s t e r i f i c a t i o n is a p p e a l i n g as it c a n tolerate f e e d s t o c k s w i t h v e r y h i g h contents o f F F A s a n d w a t e r , u p to 3 6 w t . % a n d 3 0 w t . % , r e s p e c t i v e l y ( K u s d i a n a and S a k a 2004).  1.2  Process modelling and economic assessment  A n o t h e r i m p o r t a n t t o o l f o r a d d r e s s i n g the e c o n o m i c aspects o f b i o d i e s e l is p r o c e s s m o d e l l i n g . P r o c e s s m o d e l l i n g c a n b e u s e d to i n v e s t i g a t e the effect o f p r o c e s s v a r i a b l e s , s u c h as p l a n t s c a l e , r a w m a t e r i a l costs, u t i l i t y c o s t s , p r o d u c t s e l l i n g p r i c e s etc. o n the e c o n o m i c f e a s i b i l i t y o f the process. B e n d e r (1999)  conducted a review  f e e d s t o c k s s u c h as b e e f t a l l o w  of economic feasibility  studies f r o m  different  a n d c a n o l a seed o i l . H o w e v e r , these studies are l i m i t e d  to  p r o c e s s e s e m p l o y i n g an a l k a l i - c a t a l y z e d r e a c t i o n .  M o r e r e c e n t l y , Z h a n g et a l . ( 2 0 0 3 a ) d e v e l o p e d a series o f H Y S Y S b a s e d p r o c e s s s i m u l a t i o n s to assess  the  technological  feasibility  of  four  different  biodiesel  plant  configurations  -  a  h o m o g e n e o u s a l k a l i - c a t a l y z e d p u r e v e g e t a b l e o i l p r o c e s s ; a t w o - s t e p p r o c e s s to treat w a s t e v e g e t a b l e o i l ; a s i n g l e step h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s to treat w a s t e v e g e t a b l e o i l ; a n d a h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s u s i n g h e x a n e e x t r a c t i o n to p u r i f y the b i o d i e s e l . A l l f o u r configurations  w e r e d e e m e d t e c h n o l o g i c a l l y f e a s i b l e (i.e., they w e r e c a p a b l e o f  producing  b i o d i e s e l to m e e t the A S T M s p e c i f i c a t i o n f o r p u r i t y , 9 9 . 6 5 w t . % ) , but a subsequent e c o n o m i c a n a l y s i s o f the f o u r d e s i g n s r e v e a l e d that the o n e step a c i d - c a t a l y z e d p r o c e s s w a s the m o s t e c o n o m i c a l l y attractive p r o c e s s ( Z h a n g et a l . 2 0 0 3 b ) . H a a s et a l . ( 2 0 0 6 ) d e v e l o p e d a p r o c e s s s i m u l a t i o n m o d e l to e s t i m a t e the costs o f b i o d i e s e l p r o d u c t i o n . T h e m o d e l w a s c a p a b l e o f p r e d i c t i n g the effect o n p r o d u c t i o n c o s t g i v e n f l u c t u a t i o n s i n f e e d s t o c k c o s t o r p r o d u c t s e l l i n g p r i c e . T h e m o d e l w a s a l s o d e s i g n e d to c a l c u l a t e the effects o n c a p i t a l cost a n d p r o d u c t i o n c o s t u p o n m o d i f i c a t i o n o f the p r o c e s s , s u c h as c h a n g e s i n f e e d s t o c k type a n d cost, a n d p r o c e s s c h e m i s t r y a n d t e c h n o l o g y . H o w e v e r , the m o d e l w a s l i m i t e d to the t r a d i t i o n a l a l k a l i - c a t a l y z e d production method.  1.3  Thesis objectives  In o r d e r to d e t e r m i n e w h e t h e r the s u p e r c r i t i c a l m e t h a n o l o r the heterogeneous a c i d catalyst p r o c e s s is a p r o m i s i n g alternative to the standard h o m o g e n e o u s c a t a l y t i c routes, the a i m o f P a r t I 6  of this thesis is to develop a process flowsheet and simulation, conduct an economic analysis of each process based on the material and energy balance results reported by H Y S Y S , and carry out sensitivity analyses to optimize each process. Additionally, the sizing and economic calculations are incorporated into each simulation by way of the spreadsheet tool available i n H Y S Y S . The material and energy flows, as well as some unit parameters are imported directly into the spreadsheet, thereby allowing the sizing and economic results to be  updated  automatically when any changes were made to the process flowsheet.  Based on the outcome of the process simulations, it was desired to conduct more detailed catalytic studies of the heterogeneous catalyst. Therefore Part II of this thesis has investigated the synthesis and characterization of a heterogeneous catalyst, as well as testing its activity with respect to transesterification, investigating the effects reaction time, A : 0 molar ratio and catalyst loading on the outcome of the reaction, and the effects of free fatty acid content i n the reaction mixture.  1.4  Thesis format  The remainder of this thesis continues with two manuscripts. Chapter 2 reports the results on the design and assessment of four biodiesel production processes using H Y S Y S .Plant (submitted for publication in Bioresource Technology). Chapter 3 concentrates on the synthesis and testing of a new heterogeneous catalyst (in preparation for submission). Finally, the thesis is concluded in Chapter 4 with a general discussion of the results and recommendations for further research. References are presented at the end of each chapter.  7  1.5  References  Bender, M . (1999). E c o n o m i c feasibility review for community-scale farmer cooperatives for biodiesel. Bioresource T e c h n o l o g y 70(1): 81-87. C a n a k c i , M . and V a n G e r p e n , J . (1999). B i o d i e s e l production v i a acid catalysis. Transactions o f the A S A E 4 2 ( 5 ) : 1 2 0 3 - 1 2 1 0 . C a n a k c i , M . a n d V a n G e r p e n , J . ( 2 0 0 1 ) . B i o d i e s e l p r o d u c t i o n f r o m o i l s a n d fats w i t h h i g h free fatty a c i d s . 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B i o d i e s e l fuel production w i t h solid superacid c a t a l y s i s i n f i x e d b e d reactor u n d e r a t m o s p h e r i c p r e s s u r e . C a t a l y s i s C o m m u n i c a t i o n s 5(12): 7 2 1 - 7 2 3 . G o f f , M . J . , Bauer, N . S., L o p e s , S., Sutterlin, W . R. and Suppes, G . J . (2004). A c i d - c a t a l y z e d a l c o h o l y s i s o f s o y b e a n o i l . J o u r n a l o f the A m e r i c a n O i l C h e m i s t s S o c i e t y 81(4): 4 1 5 420. G r y g l e w i c z , S . ( 1 9 9 9 ) . R a p e s e e d o i l m e t h y l esters p r e p a r a t i o n u s i n g heterogeneous catalysts. Bioresource T e c h n o l o g y 70(3): 249-253. H a a s , M . J . , M c A l o o n , A . J . , Y e e , W . C . a n d F o g l i a , T . A . ( 2 0 0 6 ) . A p r o c e s s m o d e l to e s t i m a t e b i o d i e s e l p r o d u c t i o n costs. B i o r e s o u r c e T e c h n o l o g y 9 7 ( 4 ) : 6 7 1 - 6 7 8 . Jitputti, J . , K i t i y a n a n , B . , Rangsunvigit, P., Bunyakiat, K., Attanatho, L. and Jenvanitpanjakul, P. (2006). Transesterification of crude p a l m kernel oil and crude coconut o i l by different s o l i d catalysts. C h e m i c a l E n g i n e e r i n g J o u r n a l 116(1): 6 1 - 6 6 . K i m , H . J . , K a n g , B . S., K i m , M . J . , Park, Y . M . , K i m , D . K., L e e , J . S. and L e e , K . Y . (2004). T r a n s e s t e r i f i c a t i o n o f vegetable o i l to b i o d i e s e l u s i n g h e t e r o g e n e o u s base catalyst. Catalysis Today 93-95: 315-320. K o m e r s , K . , M a c h e k , J . a n d S t l o u k a l , R . ( 2 0 0 1 ) . B i o d i e s e l f r o m rapeseed o i l , m e t h a n o l a n d K O H 2. C o m p o s i t i o n o f s o l u t i o n o f K O H i n m e t h a n o l as r e a c t i o n partner o f o i l . E u r o p e a n J o u r n a l o f L i p i d S c i e n c e a n d T e c h n o l o g y 103(6): 3 5 9 - 3 6 2 . K r a w c z y k , T . ( 1 9 9 6 ) . B i o d i e s e l . I N F O R M 7(8): 8 0 1 - 8 2 2 . K u s d i a n a , D . a n d S a k a , S . ( 2 0 0 1 ) . K i n e t i c s o f t r a n s e s t e r i f i c a t i o n i n rapeseed o i l to b i o d i e s e l f u e l as treated i n s u p e r c r i t i c a l m e t h a n o l . F u e l 8 0 ( 5 ) : 6 9 3 - 6 9 8 .  8  K u s d i a n a , D . and Saka, S. (2004). Effects o f water on biodiesel fuel production b y supercritical m e t h a n o l treatment. B i o r e s o u r c e T e c h n o l o g y 9 1 ( 3 ) : 2 8 9 - 2 9 5 . L o p e z , D . E . , G o o d w i n , J . G . , B r u c e , D . A . and Lotero, E . (2005). Transesterification of t r i a c e t i n w i t h m e t h a n o l o n s o l i d a c i d a n d b a s e catalysts. A p p l i e d C a t a l y s i s , A : G e n e r a l 295(2): 97-105. M a , F . , C l e m e n t s , L . D . a n d H a n n a , M . A . ( 1 9 9 8 ) . T h e effects o f catalyst, free fatty a c i d s , a n d water o n t r a n s e s t e r i f i c a t i o n o f b e e f t a l l o w . T r a n s a c t i o n s o f the A S A E 4 1 ( 5 ) : 1 2 6 1 - 1 2 6 4 . M a , F. R. and H a n n a , M . A . (1999). B i o d i e s e l production: A review. Bioresource T e c h n o l o g y 7 0 ( 1 ) : 1-15. M b a r a k a , I. K . a n d S h a n k s , B . H . ( 2 0 0 5 ) . D e s i g n o f m u l t i f u n c t i o n a l i z e d m e s o p o r o u s s i l i c a s f o r e s t e r i f i c a t i o n o f fatty a c i d . J o u r n a l o f C a t a l y s i s 2 2 9 ( 2 ) : 3 6 5 - 3 7 3 . N o u r e d d i n i , H . a n d Z h u , D . ( 1 9 9 7 ) . K i n e t i c s o f t r a n s e s t e r i f i c a t i o n o f s o y b e a n o i l . J o u r n a l o f the A m e r i c a n O i l Chemists Society 74(11): 1457-1463. S a k a , S . a n d K u s d i a n a , D . ( 2 0 0 1 ) . B i o d i e s e l f u e l f r o m rapeseed o i l as p r e p a r e d i n s u p e r c r i t i c a l methanol. F u e l 80(2): 2 2 5 - 2 3 1 . Schumacher, L. G . , M a r s h a l l , W . , K r a h l , J . , Wetherell, W . B . and G r a b o w s k i , M . S. (2001). B i o d i e s e l e m i s s i o n s data f r o m series 6 0 d d c e n g i n e s . T r a n s a c t i o n s o f the A S A E 4 4 ( 6 ) : 1465-1468. T o d a , M . , T a k a g a k i , A . , O k a m u r a , M . , K o n d o , J . N . , H a y a s h i , S., D o m e n , K . and H a r a , M . ( 2 0 0 5 ) . G r e e n c h e m i s t r y : B i o d i e s e l m a d e w i t h s u g a r catalyst. N a t u r e 4 3 8 ( 7 0 6 5 ) : 178. T y s o n , K . S . B i o d i e s e l : H a n d l i n g a n d use g u i d e l i n e s . http://www.eere.energy.gov/biomass/pdfs/biodiesel  handling.pdf (November 28, 2004),  W a r a b i , Y . , K u s d i a n a , D . a n d S a k a , S . ( 2 0 0 4 ) . R e a c t i v i t y o f t r i g l y c e r i d e s and fatty a c i d s o f rapeseed o i l i n s u p e r c r i t i c a l a l c o h o l s . B i o r e s o u r c e T e c h n o l o g y 9 1 ( 3 ) : 2 8 3 - 2 8 7 . Z h a n g , Y . , D u b e , M . A . , M c L e a n , D . D . and Kates, M . (2003a). B i o d i e s e l production f r o m waste c o o k i n g o i l : 1. P r o c e s s d e s i g n a n d t e c h n o l o g i c a l assessment. B i o r e s o u r c e T e c h n o l o g y 8 9 ( 1 ) : 1-16. Z h a n g , Y . , D u b e , M . A . , M c L e a n , D . D . and Kates, M . (2003b). B i o d i e s e l production f r o m waste c o o k i n g o i l : 2. E c o n o m i c assessment a n d s e n s i t i v i t y a n a l y s i s . B i o r e s o u r c e T e c h n o l o g y 90(3): 229-240.  9  2  Assessment of Four Continuous Biodiesel Production Processes using HYSYS-Plant  1  2.1  Introduction and background  R e c e n t c o n c e r n s o v e r d i m i n i s h i n g f o s s i l f u e l s u p p l i e s a n d r i s i n g o i l p r i c e s , as w e l l as a d v e r s e environmental  a n d h u m a n health  i m p a c t s f r o m the use o f p e t r o l e u m  fuel  have  prompted  c o n s i d e r a b l e interest i n r e s e a r c h a n d d e v e l o p m e n t o f f u e l s f r o m r e n e w a b l e r e s o u r c e s , s u c h as b i o d i e s e l a n d e t h a n o l . B i o d i e s e l i s a v e r y attractive alternative f u e l , as it i s d e r i v e d f r o m a r e n e w a b l e , d o m e s t i c r e s o u r c e a n d c a n therefore r e d u c e r e l i a n c e o n f o r e i g n p e t r o l e u m i m p o r t s . B i o d i e s e l r e d u c e s net c a r b o n d i o x i d e e m i s s i o n s b y 7 8 % o n a l i f e - c y c l e b a s i s w h e n c o m p a r e d to c o n v e n t i o n a l d i e s e l f u e l ( T y s o n 2 0 0 1 ) . It h a s a l s o b e e n s h o w n to h a v e d r a m a t i c o n e n g i n e e x h a u s t e m i s s i o n s . F o r i n s t a n c e , c o m b u s t i o n o f neat b i o d i e s e l  improvements  decreases c a r b o n  m o n o x i d e ( C O ) e m i s s i o n s b y 4 6 . 7 % , p a r t i c u l a t e matter e m i s s i o n s b y 6 6 . 7 % a n d u n b u r n e d h y d r o c a r b o n s b y 4 5 . 2 % ( S c h u m a c h e r et a l . 2 0 0 1 ) . A d d i t i o n a l l y , b i o d i e s e l is b i o d e g r a d a b l e a n d n o n - t o x i c , m a k i n g it u s e f u l f o r transportation  applications i n highly sensitive  environments,  s u c h as m a r i n e e c o s y s t e m s a n d m i n i n g e n c l o s u r e s .  A s s h o w n i n E q u a t i o n 2 . 1 , b i o d i e s e l ( a l k y l ester) i s u s u a l l y p r o d u c e d b y the t r a n s e s t e r i f i c a t i o n o f a l i p i d f e e d s t o c k . T r a n s e s t e r i f i c a t i o n i s the r e v e r s i b l e r e a c t i o n o f a fat o r o i l ( b o t h o f w h i c h are c o m p o s e d o f t r i g l y c e r i d e s a n d free fatty a c i d s ) w i t h a n a l c o h o l to f o r m fatty a c i d a l k y l esters a n d g l y c e r o l . S t o i c h i o m e t r i c a l l y , the r e a c t i o n r e q u i r e s a 3:1 m o l a r A : 0 r a t i o , b u t b e c a u s e the r e a c t i o n i s r e v e r s i b l e , e x c e s s a l c o h o l is a d d e d to d r i v e the e q u i l i b r i u m t o w a r d the p r o d u c t s s i d e .  CH -OOC-R,  Ri-COO-R'  2  I  CH -OH 2  Catalyst  CH-OOC-R  +  2  3R'OH  I R -COO-R' 2  I  +  CH-OH  (2.1)  I  CH -OOC-R 2  Glyceride  3  Alcohol  R3-COO-R'  CH -OH  Esters  Glycerol  2  T r a n s e s t e r i f i c a t i o n c a n b e a l k a l i - , a c i d - o r e n z y m e - c a t a l y z e d ; h o w e v e r , e n z y m e catalysts are r a r e l y u s e d , as they are less e f f e c t i v e ( M a a n d H a n n a 1 9 9 9 ) . T h e r e a c t i o n c a n also take p l a c e w i t h o u t the use o f a catalyst u n d e r c o n d i t i o n s i n w h i c h the a l c o h o l i s i n a s u p e r c r i t i c a l state (Saka and K u s d i a n a 2001; Demirbas 2002). A version of this chapter has been submitted for publication. West, A . H . , Posarac, D . and Ellis, N . (2006) Assessment of Four Continuous Biodiesel Production Processes using HYSYS.Plant. Bioresource Technology.  10  C u r r e n t l y , the h i g h cost o f b i o d i e s e l p r o d u c t i o n is the m a j o r i m p e d i m e n t  to its large s c a l e  c o m m e r c i a l i z a t i o n ( C a n a k c i a n d V a n G e r p e n 2 0 0 1 ) . T h e h i g h c o s t is l a r g e l y attributed to the c o s t o f v i r g i n v e g e t a b l e o i l as f e e d s t o c k . E x p l o r i n g m e t h o d s to r e d u c e the p r o d u c t i o n c o s t o f b i o d i e s e l has b e e n the f o c u s o f m u c h recent r e s e a r c h . O n e m e t h o d i n v o l v e s r e p l a c i n g a v i r g i n o i l f e e d s t o c k w i t h a w a s t e c o o k i n g o i l f e e d s t o c k . T h e costs o f w a s t e c o o k i n g o i l are e s t i m a t e d to b e less than h a l f o f the c o s t o f v i r g i n v e g e t a b l e o i l s ( C a n a k c i a n d V a n G e r p e n 2 0 0 1 ) . F u r t h e r m o r e , u t i l i z i n g waste c o o k i n g o i l has the advantage o f r e m o v i n g a s i g n i f i c a n t a m o u n t o f m a t e r i a l f r o m the w a s t e stream - as o f 1 9 9 0 , it w a s e s t i m a t e d that at least 2 b i l l i o n p o u n d s o f waste grease w a s p r o d u c e d a n n u a l l y i n the U n i t e d States ( C a n a k c i a n d V a n G e r p e n 2 0 0 1 ) .  In  the  last  few  years,  a  number  of  new  production  methods  have  emerged  from  l a b o r a t o r y / b e n c h - s c a l e r e s e a r c h a i m e d at r e d u c i n g the c o s t o f b i o d i e s e l ( D e m i r b a s  2002;  C a n a k c i a n d V a n G e r p e n 2 0 0 3 ; D e l f o r t et. a l . 2 0 0 3 ) . O n e s u c h m e t h o d uses a l c o h o l i n its s u p e r c r i t i c a l state, a n d e l i m i n a t e s the n e e d f o r a catalyst. A d d i t i o n a l l y , the s u p e r c r i t i c a l p r o c e s s r e q u i r e s o n l y a short r e s i d e n c e t i m e to r e a c h h i g h c o n v e r s i o n ( K u s d i a n a a n d S a k a 2 0 0 4 ) . A n o t h e r o p t i o n is to use a s o l i d catalyst to c a t a l y z e the r e a c t i o n ( F u r u t a et a l . 2 0 0 4 ; S u p p e s et a l . 2 0 0 4 ; A b r e u et a l . 2 0 0 5 ) . U s e o f a s o l i d p h a s e catalyst to p r o d u c e b i o d i e s e l w i l l  simplify  d o w n s t r e a m p u r i f i c a t i o n o f the b i o d i e s e l . T h e catalyst c a n b e separated b y p h y s i c a l m e t h o d s s u c h as a h y d r o c y c l o n e i n the case w h e r e a m u l t i p h a s e reactor is u s e d . A l t e r n a t i v e l y , a fixed b e d reactor w o u l d e l i m i n a t e the catalyst r e m o v a l step e n t i r e l y .  Z h a n g et a l . ( 2 0 0 3 a )  developed a H Y S Y S  based process simulation  m o d e l to assess  the  technological feasibility of four biodiesel plant configurations - a homogeneous alkali-catalyzed pure v e g e t a b l e o i l p r o c e s s ; a t w o - s t e p  p r o c e s s to treat w a s t e v e g e t a b l e o i l ; a s i n g l e step  h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s to treat w a s t e v e g e t a b l e o i l ; a n d a h o m o g e n e o u s a c i d c a t a l y z e d p r o c e s s u s i n g h e x a n e e x t r a c t i o n to h e l p p u r i f y the b i o d i e s e l . A l l f o u r c o n f i g u r a t i o n s w e r e d e e m e d t e c h n o l o g i c a l l y f e a s i b l e , but a subsequent e c o n o m i c a n a l y s i s o f the f o u r d e s i g n s r e v e a l e d that the one step a c i d - c a t a l y z e d p r o c e s s w a s the m o s t e c o n o m i c a l l y attractive p r o c e s s Z h a n g et a l . ( 2 0 0 3 b ) . H a a s et a l . ( 2 0 0 6 ) d e v e l o p e d a v e r s a t i l e p r o c e s s s i m u l a t i o n m o d e l to estimate b i o d i e s e l p r o d u c t i o n c o s t s ; h o w e v e r , the m o d e l w a s l i m i t e d to a t r a d i t i o n a l catalyzed production method.  alkali-  In o r d e r to d e t e r m i n e w h e t h e r the s u p e r c r i t i c a l m e t h a n o l o r the  heterogeneous a c i d catalyst p r o c e s s is a p r o m i s i n g alternative to the standard h o m o g e n e o u s  11  c a t a l y t i c routes, o u r a i m is to d e v e l o p a p r o c e s s f l o w s h e e t a n d s i m u l a t i o n , c o n d u c t an e c o n o m i c a n a l y s i s o f e a c h p r o c e s s b a s e d o n the m a t e r i a l a n d e n e r g y b a l a n c e results reported b y H Y S Y S , a n d carry out s e n s i t i v i t y analyses to o p t i m i z e e a c h p r o c e s s . A d d i t i o n a l l y , it w a s d e s i r e d to automate  the s i z i n g a n d e c o n o m i c c a l c u l a t i o n s , w h e n c e they  were incorporated  into each  s i m u l a t i o n b y w a y o f the spreadsheet t o o l a v a i l a b l e i n H Y S Y S . T h e m a t e r i a l a n d e n e r g y f l o w s , as w e l l as s o m e u n i t parameters w e r e i m p o r t e d d i r e c t l y i n t o the spreadsheet, thereby a l l o w i n g the s i z i n g a n d e c o n o m i c results to be updated a u t o m a t i c a l l y w h e n a n y c h a n g e s w e r e m a d e to the p r o c e s s f l o w s h e e t . A d d i t i o n a l c o m p a r i s o n is m a d e to the s i m u l a t i o n w o r k b y Z h a n g et a l . ( 2 0 0 3 a ) i n o r d e r to ensure that the present s i m u l a t i o n s p r o v i d e c o m p a r a b l e results.  T h e h o m o g e n e o u s a l k a l i - c a t a l y z e d s y s t e m has b e e n w e l l s t u d i e d , a n d o p t i m u m c o n d i t i o n s at 1 a t m p r e s s u r e ( 6 0 ° C , 1 w t . % catalyst, 6:1 A : 0 m o l a r ratio), are k n o w n ( F r e e d m a n et a l . 1 9 8 4 ) . In o r d e r to p r e v e n t s a p o n i f i c a t i o n d u r i n g the r e a c t i o n , the free fatty a c i d ( F F A ) a n d w a t e r content o f the f e e d m u s t b e b e l o w 0.5 w t . %  a n d 0.05 w t . % ,  r e s p e c t i v e l y ( F r e e d m a n et a l . 1 9 8 4 ) .  B e c a u s e o f these l i m i t a t i o n s , o n l y pure v e g e t a b l e o i l feeds are a p p r o p r i a t e f o r a l k a l i - c a t a l y z e d t r a n s e s t e r i f i c a t i o n w i t h o u t e x t e n s i v e pretreatment.  A  homogeneous  acid-catalyzed process can be  employed  to  take  advantage  of  cheaper  f e e d s t o c k s , s u c h as waste c o o k i n g o i l a n d a n i m a l - b a s e d t a l l o w . T h e a c i d - c a t a l y z e d p r o c e s s c a n tolerate  up to 5 wt.%  F F A , but is s e n s i t i v e to w a t e r content greater than 0.5 wt.%.  The  d i s a d v a n t a g e o f this m e t h o d is that it is e x t r e m e l y s l o w at m i l d c o n d i t i o n s : C a n a k c i a n d V a n G e r p e n ( 1 9 9 9 ) f o u n d that it t o o k 4 8 h o u r s to a c h i e v e a 9 8 % c o n v e r s i o n at 6 0 ° C at an A : 0 r a t i o o f 3 0 : 1 . A t h i g h e r temperatures a n d pressures (e.g. 1 0 0 ° C a n d 3.5 bar) r e a c t i o n t i m e s c a n b e s u b s t a n t i a l l y r e d u c e d ( d o w n to 8 h) to a c h i e v e s i m i l a r a degree o f ( 9 9 % ) c o n v e r s i o n ( G o f f et a l . 2004).  A p r o c e s s u s i n g a heterogeneous a c i d - c a t a l y s t is a p p e a l i n g b e c a u s e o f the ease o f s e p a r a t i o n o f a s o l i d catalyst. L o t e r o et a l . ( 2 0 0 5 ) reports this a d v a n t a g e , c o u p l e d w i t h the a b i l i t y o f the a c i d f u n c t i o n a l i t y to p r o c e s s l o w cost, h i g h free fatty a c i d f e e d s t o c k s , w i l l y i e l d the m o s t e c o n o m i c a l b i o d i e s e l p r o d u c t i o n m e t h o d . A s o u t l i n e d i n T a b l e 2 . 1 , a n u m b e r o f s o l i d phase catalysts h a v e b e e n i d e n t i f i e d that h o l d p o t e n t i a l f o r use. R e s e a r c h c o n c e r n i n g heterogeneous catalysts is s t i l l i n the catalyst screening.stage. S t u d i e s r e g a r d i n g r e a c t i o n k i n e t i c s , as w e l l as i m p r o v i n g r e a c t i o n  12  parameters have yet to be conducted. In addition, studies to determine the effects of free fatty acid concentration and water on the performance of the catalyst have been scarce.  Supercritical transesterification is also a potential alternative to the standard homogenous catalytic routes. Supercritical transesterification using methanol has been shown to give nearly complete conversion in a relatively short period (15 minutes) (Warabi et al. 2004). High temperatures, (up to 350°C) and large A : 0 ratios (42:1) are required to achieve the high levels of conversion (Kusdiana and Saka 2001). In addition to the high conversion and reaction rates, supercritical transesterification is appealing as it can tolerate feedstocks with very high contents of FFAs and water, up to 36 wt.% and 30 wt.%, respectively (Kusdiana and Saka 2004). 2.2  Process simulation  To assess the technological feasibility and obtain material and energy balances for a preliminary economic analysis, complete process simulations were performed. Despite some expected differences between a process simulation and real-life operation, process simulators are commonly used to provide reliable information on process operation, owing to their vast component libraries, comprehensive thermodynamic packages and advanced computational methods. H Y S Y S Plant NetVer 3.2 was used to conduct the simulation. H Y S Y S was selected as a process simulator for both its simulation capabilities and the ability to easily incorporate sizing and economic calculations within the spreadsheet tool. The first steps in developing the process simulation were selecting the chemical components for the process, as well as a thermodynamic model. Additionally, unit operations and operating conditions, plant capacity and input conditions must all be selected and specified. The unit operations, plant capacity and input conditions for the base cases, i.e., homogeneous acid and alkali-catalyzed processes, as well as distillation column operating conditions, were selected based on the research done by Zhang et al. (2003a) to ensure that each of the four processes simulated in this work could be compared in a consistent manner.  The H Y S Y S library contained information for the following components used in the simulation: methanol, glycerol, sulfuric acid, sodium hydroxide, and water. Canola oil was selected as the feedstock, and represented by triolein, as oleic acid is the major fatty acid in canola oil. Accordingly, methyl-oleate, available in the H Y S Y S component library, was taken as the product of the transesterification reaction. Where a simulation required a feedstock with some 13  a m o u n t o f free fatty a c i d s , o l e i c a c i d , a l s o a v a i l a b l e i n the H Y S Y S l i b r a r y , w a s s p e c i f i e d as the free fatty a c i d present.  C o m p o n e n t s not a v a i l a b l e i n the H Y S Y S l i b r a r y w e r e s p e c i f i e d u s i n g the " H y p o M a n a g e r " t o o l . C a l c i u m o x i d e , c a l c i u m sulfate, p h o s p h o r i c a c i d , s o d i u m p h o s p h a t e a n d t r i o l e i n  were  all  s p e c i f i e d i n this m a n n e r . S p e c i f i c a t i o n o f a c o m p o n e n t r e q u i r e s i n p u t o f a n u m b e r o f p r o p e r t i e s , s u c h as n o r m a l b o i l i n g p o i n t , d e n s i t y , m o l e c u l a r w e i g h t , as w e l l as the c r i t i c a l p r o p e r t i e s o f the substance. S i n c e t r i o l e i n is a c r u c i a l c o m p o n e n t a n d is i n v o l v e d i n o p e r a t i o n s r e q u i r i n g data f o r l i q u i d a n d v a p o u r e q u i l i b r i a , great care w a s t a k e n i n s p e c i f y i n g the v a l u e s as a c c u r a t e l y as p o s s i b l e . V a l u e s f o r d e n s i t y , b o i l i n g p o i n t a n d c r i t i c a l t e m p e r a t u r e , pressure a n d v o l u m e w e r e o b t a i n e d f r o m the A S P E N P l u s c o m p o n e n t l i b r a r y a n d w e r e i n p u t as 9 1 5 k g / m , 8 4 6 ° C , 1 3 6 6 ° C , 3  4 7 0 k P a , 3.09 m / k m o l , r e s p e c t i v e l y . A d d i t i o n a l l y , the U N D F A C 3  structure f o r t r i o l e i n  was  s p e c i f i e d i n o r d e r to p r o v i d e b i n a r y i n t e r a c t i o n p a r a m e t e r e s t i m a t e s .  O w i n g to the p r e s e n c e o f p o l a r c o m p o u n d s s u c h as m e t h a n o l a n d g l y c e r o l i n the p r o c e s s , the non-random two liquid ( N R T L ) thermodynamic/activity  m o d e l w a s s e l e c t e d f o r use as the  p r o p e r t y p a c k a g e f o r the s i m u l a t i o n . S o m e b i n a r y i n t e r a c t i o n p a r a m e t e r c o e f f i c i e n t s ( s u c h as the m e t h a n o l - m e t h y l oleate c o e f f i c i e n t ) w e r e u n a v a i l a b l e i n the s i m u l a t i o n d a t a b a n k s , a n d w e r e e s t i m a t e d u s i n g the U N E F A C v a p o u r - l i q u i d e q u i l i b r i u m a n d U N I F A C l i q u i d - l i q u i d e q u i l i b r i u m models where appropriate.  P l a n t c a p a c i t y w a s s p e c i f i e d at 8 0 0 0 m e t r i c t o n n e s / y r b i o d i e s e l ( Z h a n g et a l . 2 0 0 3 a ) . T h i s translated to v e g e t a b l e o i l feeds o f r o u g h l y 1 0 0 0 k g / h f o r e a c h p r o c e s s c o n f i g u r a t i o n .  T h e p r o c e s s units c o m m o n to a l l c o n f i g u r a t i o n s i n c l u d e r e a c t o r s , d i s t i l l a t i o n c o l u m n s , p u m p s a n d heat e x c h a n g e r s . T h e h o m o g e n e o u s a c i d - a n d a l k a l i - c a t a l y z e d p r o c e s s e s i n c l u d e d l i q u i d l i q u i d e x t r a c t i o n c o l u m n s to separate the catalyst a n d g l y c e r o l f r o m the b i o d i e s e l . In contrast to the base case s c e n a r i o s , a g r a v i t y separation unit w a s i n c l u d e d i n the s u p e r c r i t i c a l m e t h a n o l a n d heterogeneous a c i d catalyst p r o c e s s e s . In spite o f the a v a i l a b i l i t y o f k i n e t i c data f o r the a l k a l i c a t a l y z e d , h o m o g e n e o u s a c i d - c a t a l y z e d a n d , s u p e r c r i t i c a l p r o c e s s e s ( F r e e d m a n et a l . 1 9 8 6 ; K u s d i a n a a n d S a k a 2 0 0 1 ) , the reactors w e r e m o d e l e d as c o n v e r s i o n reactors s i n c e k i n e t i c i n f o r m a t i o n f o r the h e t e r o g e n e o u s a c i d - c a t a l y z e d p r o c e s s w a s u n a v a i l a b l e . T h e reactors w e r e  14  a s s u m e d to operate c o n t i n u o u s l y f o r a l l cases. L a b - s c a l e r e a c t i o n c o n d i t i o n s a n d c o n v e r s i o n d a t a w e r e a v a i l a b l e f o r a l l p r o c e s s e s , a s s u m e d to b e a p p r o p r i a t e f o r l a r g e - s c a l e p r o d u c t i o n , a n d set as the o p e r a t i n g c o n d i t i o n s f o r e a c h reactor. T h e f o l l o w i n g c o n v e r s i o n s w e r e a s s u m e d f o r e a c h p r o c e s s : 9 7 % , 9 7 % , 9 4 % a n d 9 8 % f o r the a l k a l i , a c i d , heterogeneous a n d s u p e r c r i t i c a l cases, r e s p e c t i v e l y ( Z h a n g et a l . 2 0 0 3 a ; W a r a b i et a l . 2 0 0 4 ; A b r e u et a l . 2 0 0 5 ) . T h e m o n o - a n d d i g l y c e r i d e i n t e r m e d i a t e s w e r e n e g l e c t e d d u r i n g the r e a c t i o n ( Z h a n g et a l . 2 0 0 3 a ) .  M u l t i - s t a g e d i s t i l l a t i o n w a s u s e d to r e c o v e r t h e e x c e s s m e t h a n o l , as w e l l as i n the p u r i f i c a t i o n o f b i o d i e s e l . D i s t i l l a t i o n c o l u m n s w e r e s p e c i f i e d to meet o r e x c e e d the standard f o r b i o d i e s e l p u r i t y , i.e., 9 9 . 6 5 w t . % . catalyzed and supercritical  R e f l u x ratios f o r  final  ASTM  the h e t e r o g e n e o u s  acid-  cases w e r e c a l c u l a t e d b y d e t e r m i n i n g the m i n i m u m r e f l u x  ratio  u s i n g a shortcut d i s t i l l a t i o n c o l u m n , a n d then m u l t i p l y i n g b y 1.5 to o b t a i n the o p t i m u m r e f l u x r a t i o ( M c C a b e et a l . 2 0 0 1 ) . T h e m e t h a n o l r e c o v e r y c o l u m n s w e r e able to operate at a m b i e n t pressures ( e x c e p t i n the a l k a l i - c a t a l y z e d c a s e ) , w h i l e v a c u u m o p e r a t i o n i n the  methyl-ester  p u r i f i c a t i o n c o l u m n s w a s n e c e s s a r y to k e e p the temperatures o f the d i s t i l l a t e a n d b o t t o m s streams  at  suitably  low  l e v e l s , as b i o d i e s e l a n d g l y c e r o l  are  subject  to  degradation  at  temperatures greater than 2 5 0 ° C a n d 1 5 0 ° C , r e s p e c t i v e l y ( N e w m a n 1 9 6 8 ; G o o d r u m 2 0 0 2 ) .  2.3 Four  Process design continuous  processes  were  simulated.  Two  were  based  on  an  alkali-catalyzed  t r a n s e s t e r i f i c a t i o n p r o c e s s u s i n g v i r g i n v e g e t a b l e o i l ( P r o c e s s I), a n d a h o m o g e n e o u s a c i d catalyzed process using a waste c o o k i n g o i l feedstock, containing 5 wt.% ( P r o c e s s II).  free fatty a c i d s  T h e t h i r d c o n f i g u r a t i o n e m p l o y e d a heterogeneous a c i d - c a t a l y s t ( H A C ) , t i n ( U )  o x i d e , i n a m u l t i p h a s e r e a c t o r f e d w i t h waste v e g e t a b l e o i l ( P r o c e s s III), w h i l e the final p r o c e s s u s e d a s u p e r c r i t i c a l ( S C ) m e t h a n o l treatment o f w a s t e v e g e t a b l e o i l to p r o d u c e b i o d i e s e l ( P r o c e s s T V ) . P r o c e s s f l o w s h e e t s are p r e s e n t e d i n F i g u r e s 2.1 to 2.4.  T h e p r o c e s s e s a l l f o l l o w e d the s a m e g e n e r a l s c h e m e . T h e v e g e t a b l e o i l w a s t r a n s e s t e r i f i e d i n the first  step, a n d then sent f o r d o w n s t r e a m p u r i f i c a t i o n . D o w n s t r e a m p u r i f i c a t i o n c o n s i s t e d o f the  f o l l o w i n g steps: m e t h a n o l r e c o v e r y b y d i s t i l l a t i o n ; c a t a l y s t n e u t r a l i z a t i o n ; g l y c e r o l s e p a r a t i o n a n d catalyst r e m o v a l ; a n d m e t h y l - e s t e r p u r i f i c a t i o n b y d i s t i l l a t i o n . T a b l e 2.2 g i v e s details f o r the  15  unit o p e r a t i o n s i n e a c h p r o c e s s . T a b l e s 2.3 to 2.6 present the f e e d a n d p r o d u c t m a t e r i a l f l o w details f o r e a c h p r o c e s s .  A s i l l u s t r a t e d i n T a b l e 2 . 1 , there are a n u m b e r o f k e y d i f f e r e n c e s b e t w e e n the p r o c e s s e s . T h e f i r s t d i f f e r e n c e is w i t h regards to the catalyst r e m o v a l m e t h o d . T h e s o l i d catalyst i n P r o c e s s H I is r e m o v e d b y a h y d r o c y c l o n e b e f o r e m e t h a n o l r e c o v e r y , w h e r e a s the l i q u i d p h a s e catalyst i n processes I is r e m o v e d b y w a s h i n g the p r o d u c t stream w i t h w a t e r i n a l i q u i d - l i q u i d  extraction  c o l u m n . T h e a c i d catalyst i n P r o c e s s II w a s r e m o v e d as a s o l i d p r e c i p i t a t e i n separator X - 1 0 0 after n e u t r a l i z a t i o n i n reactor C R V - 1 0 1 . A s i n the h o m o g e n e o u s a c i d - c a t a l y s t p r o c e s s , the a l k a l i - c a t a l y s t h a d to be n e u t r a l i z e d b e f o r e it c o u l d be d i s p o s e d of. T h e heterogeneous catalyst i n P r o c e s s III r e q u i r e d n o n e u t r a l i z a t i o n step; it w a s d i s c a r d e d as a w a s t e p r o d u c t . H o w e v e r , a heterogeneous catalyst has the p o t e n t i a l a d v a n t a g e o f b e i n g r e c y c l e d .  T h e s e c o n d m a j o r d i f f e r e n c e is i n the separation o f g l y c e r o l f r o m the b i o d i e s e l . In P r o c e s s e s I a n d II, g l y c e r o l i s r e m o v e d b y w a s h i n g the p r o d u c t s t r e a m w i t h water, a n d c o l l e c t e d i n the b o t t o m s p r o d u c t . In P r o c e s s e s III a n d I V , g l y c e r o l is separated f r o m the b i o d i e s e l i n a threep h a s e separator b y g r a v i t y s e t t l i n g . K r a w c z y k ( 1 9 9 6 ) i n i t i a l l y p r o p o s e d g r a v i t y s e p a r a t i o n to r e m o v e g l y c e r o l ; h o w e v e r , Z h a n g et a l . ( 2 0 0 3 a ) i n d i c a t e d f r o m their s i m u l a t i o n that s a t i s f a c t o r y s e p a r a t i o n c o u l d not b e a c h i e v e d b y g r a v i t y a l o n e . In the present w o r k , g r a v i t y s e p a r a t i o n w a s u s e d to separate the b i o d i e s e l f r o m the g l y c e r o l , a n d a satisfactory separation w a s a c h i e v e d . N o t e , h o w e v e r , that the c a l c u l a t i o n s f o r this unit o p e r a t i o n are b a s e d o n parameters that h a v e been estimated by H Y S Y S  a n d therefore m a y not t r u l y represent a r e a l s y s t e m . A d d i t i o n a l  e x p e r i m e n t a l data are n e e d e d to v e r i f y the a p p l i c a b i l i t y a n d results o f the g r a v i t y separator, i n o r d e r to use the u n i t b l o c k w i t h c o n f i d e n c e . In p r a c t i c e , a g r a v i t y s e p a r a t i o n unit has b e e n u s e d o n a p i l o t p l a n t scale to separate g l y c e r o l a n d b i o d i e s e l ( C a n a k c i a n d V a n G e r p e n 2 0 0 3 ) . A l l p r o c e s s e s p r o d u c e d b i o d i e s e l at a h i g h e r p u r i t y than r e q u i r e d b y the A S T M standard o f 9 9 . 6 5 wt.%.  2.4  Equipment sizing  P r o c e s s e q u i p m e n t w a s s i z e d a c c o r d i n g to p r i n c i p l e s o u t l i n e d i n T u r t o n et a l . ( 2 0 0 3 ) a n d S e i d e r et a l . ( 2 0 0 3 ) . T h e p r i n c i p a l d i m e n s i o n s o f e a c h u n i t are presented i n T a b l e 2.7. T h e e q u i p m e n t s i z i n g c a l c u l a t i o n s w e r e c o n d u c t e d u s i n g the S p r e a d s h e e t t o o l a v a i l a b l e w i t h i n H Y S Y S .  Key  v a r i a b l e s f o r u n i t s i z i n g w e r e i m p o r t e d f r o m the f l o w s h e e t d i r e c t l y to the spreadsheet. S i z i n g 16  e q u a t i o n s w e r e e n c o d e d w i t h i n the spreadsheet. T h e r e f o r e a n y alterations to the f l o w s h e e t , s u c h as c o m p o n e n t f r a c t i o n s , c o m p o n e n t f l o w r a t e s , c h a n g e s to the d e s i r e d r e c o v e r y i n the d i s t i l l a t i o n s columns,  etc.  are  automatically  calculated  and  implemented,  thus  eliminating  tedious  r e c a l c u l a t i o n steps.  2.4.1  Reactor vessels  R e a c t o r s w e r e s i z e d f o r c o n t i n u o u s o p e r a t i o n b y d i v i d i n g the r e s i d e n c e t i m e r e q u i r e m e n t b y the f e e d f l o w r a t e f o r e a c h p r o c e s s . R e s i d e n c e t i m e s w e r e : 4 h o u r s , 4 h o u r s , 3 h o u r s and 2 0 m i n u t e s for  the  alkali-catalyzed,  acid-catalyzed,  heterogeneous  acid-catalyzed  and  supercritical  p r o c e s s e s , r e s p e c t i v e l y . T h e vessels, w e r e s p e c i f i e d to h a v e an aspect ratio o f 3 - t o - l .  2.4.2 Columns Distillation c o l u m n diameters were sized b y two methods. A n initial diameter was estimated f r o m the F - F a c t o r M e t h o d ( L u y b e n 2 0 0 2 ) . If the c o l u m n d i a m e t e r w a s c a l c u l a t e d to be greater than 0 . 9 0 m (2.95 feet) it w a s s p e c i f i e d as a tray t o w e r , a n d thus c a l c u l a t e d f r o m the f l o o d i n g v e l o c i t y u s i n g the F a i r c o r r e l a t i o n ( S e i d e r et a l . 2 0 0 3 ) . C o l u m n s w i t h d i a m e t e r s c a l c u l a t e d at less than 0.9 m w e r e s p e c i f i e d as a p a c k e d t o w e r . T h e d i a m e t e r o f e a c h p a c k e d c o l u m n w a s calculated from  the f l o o d i n g  velocity  obtained  from  the  Leva  correlation  ( S e i d e r et a l .  2 0 0 3 ) . T r a y t o w e r h e i g h t w a s c a l c u l a t e d b y m u l t i p l y i n g the n u m b e r o f a c t u a l stages b y the tray s p a c i n g , a n d then i n c r e a s i n g the result b y 2 0 % to p r o v i d e h e i g h t f o r the c o n d e n s e r a n d r e b o i l e r . P a c k e d t o w e r h e i g h t w a s c a l c u l a t e d b y m u l t i p l y i n g the h e i g h t e q u i v a l e n t o f a t h e o r e t i c a l plate ( H E T P ) b y the n u m b e r o f stages c a l c u l a t e d f o r the t o w e r . H E T P w a s a s s u m e d to e q u a l the c o l u m n d i a m e t e r ( S e i d e r et a l . 2 0 0 3 ) . A s f o r the h e i g h t o f a tray t o w e r , the p a c k e d height w a s i n c r e a s e d b y 2 0 % . T h e l i q u i d - l i q u i d e x t r a c t i o n c o l u m n s w e r e s i z e d a c c o r d i n g to the w o r k  of  Z h a n g et a l . ( 2 0 0 3 a ) .  2.4.3  Gravity separators  T h e g r a v i t y separators i n the h e t e r o g e n e o u s a c i d - c a t a l y z e d a n d s u p e r c r i t i c a l p r o c e s s e s w e r e d e s i g n e d as v e r t i c a l p r o c e s s v e s s e l s w i t h a n aspect r a t i o o f 2 . T h e y w e r e s i z e d to a l l o w f o r continuous operation, with a residence time of 1 hour.  17  2.4.4  Hydrocyclone  T h e i n i t i a l d i m e n s i o n s o f the h y d r o c y c l o n e (used to separate the s o l i d catalyst f r o m the p r o d u c t stream i n P r o c e s s III)  w e r e c a l c u l a t e d b y the b l o c k i n H Y S Y S . T h o s e d i m e n s i o n s w e r e then  m a n i p u l a t e d s l i g h t l y to o b t a i n c o m p l e t e r e m o v a l o f the catalyst i n the h y d r o c y c l o n e u n d e r f l o w .  2.5  Economic assessment  S i n c e e a c h p r o c e s s w a s c a p a b l e o f p r o d u c i n g b i o d i e s e l at the r e q u i r e d p u r i t y , it w a s o f interest to c o n d u c t a n e c o n o m i c a s s e s s m e n t to d e t e r m i n e p r o c e s s v i a b i l i t y , a n d d e t e r m i n e i f a n y one p r o c e s s w a s a d v a n t a g e o u s o v e r the others. A s w i t h the s i z i n g c a l c u l a t i o n s , a l l the e c o n o m i c c a l c u l a t i o n s w e r e p e r f o r m e d w i t h i n the H Y S Y S spreadsheet. A d d i t i o n a l l y , the v a l u e s presented f o r the e c o n o m i c a n a l y s i s are the v a l u e s o b t a i n e d after p e r f o r m i n g  s e n s i t i v i t y analyses a n d  o p t i m i z a t i o n o f e a c h p r o c e s s . T h e d e t a i l s f o r the s e n s i t i v i t y a n a l y s e s a n d o p t i m i z a t i o n studies are p r e s e n t e d i n S e c t i o n 2.6 o f this paper. A l l parameters necessary to d e t e r m i n e m a t e r i a l a n d e n e r g y costs w e r e i m p o r t e d to the spreadsheet f r o m the f l o w s h e e t . C o s t i n g e q u a t i o n s  were  i n c o r p o r a t e d d i r e c t l y i n t o the spreadsheet as w e l l . I n d i v i d u a l u n i t costs w e r e c a l c u l a t e d , as w e l l as f i g u r e s f o r e a c h p r o c e s s i n its entirety. I n c o r p o r a t i n g simulation parameters, integrating  allowed  for  automatic  s u c h as c o m p o n e n t  recalculation of flowrates  or  unit  the e c o n o m i c c a l c u l a t i o n s i n t o the  process e c o n o m i c s should any process operating  conditions  be changed.  s i z i n g a n d e c o n o m i c c a l c u l a t i o n s i n t o e a c h s i m u l a t i o n , the p o t e n t i a l to  By  perform  e c o n o m i c s e n s i t i v i t y analyses is a u t o m a t i c a l l y b u i l t - i n to e a c h s i m u l a t i o n .  2.5.7  Basis of  calculations  E a c h p r o c e s s was b a s e d o n a p l a n t c a p a c i t y o f 8 0 0 0 t o n n e s / y e a r b i o d i e s e l p r o d u c t i o n . O p e r a t i n g h o u r s w e r e set at 7 9 2 0 h o u r s / y e a r ( a s s u m i n g 3 3 0 o p e r a t i n g d a y s ) . B o t h the w a s t e a n d p u r e f e e d s t o c k s w e r e a s s u m e d free o f w a t e r a n d s o l i d i m p u r i t i e s , t o a v o i d pre-treatment o f the f e e d . Low  a n d h i g h p r e s s u r e steam w e r e u s e d as h e a t i n g m e d i a , w h i l e w a t e r w a s used f o r c o o l i n g .  E a c h p r o c e s s w a s e v a l u a t e d b a s e d o n t o t a l c a p i t a l i n v e s t m e n t ( T C I ) , total m a n u f a c t u r i n g c o s t ( T M C ) , a n d after tax rate-of-return  (ATROR).  T h e a s s e s s m e n t p e r f o r m e d i n this w o r k  is  c l a s s i f i e d as a " s t u d y e s t i m a t e , " w i t h a range o f e x p e c t e d a c c u r a c y f r o m + 3 0 % to - 2 0 % ( T u r t o n et a l . 2 0 0 3 ) . W h i l e the results o f s u c h a study w i l l l i k e l y not r e f l e c t the f i n a l c o s t o f c o n s t r u c t i n g a c h e m i c a l p l a n t , the t e c h n i q u e is u s e f u l f o r p r o v i d i n g a r e l a t i v e m e a n s to c o m p a r e c o m p e t i n g processes.  18  2.5.2  Total capital investment  T a b l e 2.8 g i v e s a b r e a k d o w n o f the total c a p i t a l i n v e s t m e n t . It a l s o presents the c o s t s f o r the i n d i v i d u a l u n i t o p e r a t i o n s i n e a c h p r o c e s s . B a r e m o d u l e c a p i t a l costs (CBM) c o n s i s t o f  the  p u r c h a s e cost o f a p i e c e o f e q u i p m e n t , m u l t i p l i e d b y the b a r e m o d u l e f a c t o r . P u r c h a s e c o s t s w e r e e s t i m a t e d f o r e a c h p i e c e o f e q u i p m e n t b a s e d o n a c a p a c i t y e q u a t i o n p r e s e n t e d b y T u r t o n et al. (2003)  io where K  t  g l 0  c;  =^,  + rr io J  2  g l 0  ( A ) + /i:3[iog, (A)]  (2.2)  2  ( )  is a constant s p e c i f i c to the u n i t type a n d A is the c a p a c i t y o f the u n i t . B a r e m o d u l e  cost was calculated f r o m CBM  ~ CF P  (2.3)  BM  w h e r e FBM is g i v e n b y F ={B,+B F F ) BM  2  M  (2.4)  P  w h e r e B] a n d B2 are c o n s t a n t s s p e c i f i c to the u n i t t y p e , a n d F  M  and F  P  are the m a t e r i a l a n d  p r e s s u r e f a c t o r s , r e s p e c t i v e l y . T h e c o n s t a n t s , Kj a n d fl„ as w e l l as the p r e s s u r e a n d m a t e r i a l f a c t o r s w e r e o b t a i n e d f r o m T u r t o n et a l . ( 2 0 0 3 ) E q u a t i o n s 2.2 - 2.4 w e r e e n c o d e d w i t h i n the c o s t i n g spreadsheet to a l l o w f o r a u t o m a t i c c o s t updates w h e n p r o c e s s p a r a m e t e r s are c h a n g e d .  2.5.3  Total manufacturing  cost  D i r e c t m a n u f a c t u r i n g e x p e n s e s w e r e c a l c u l a t e d b a s e d o n the p r i c e a n d c o n s u m p t i o n o f e a c h c h e m i c a l a n d u t i l i t y . C h e m i c a l a n d u t i l i t y p r i c e s are p r e s e n t e d i n T a b l e 2.9 a n d m a t e r i a l f l o w i n f o r m a t i o n w a s o b t a i n e d f r o m H Y S Y S . O p e r a t o r s a l a r y w a s e s t i m a t e d at $ 4 7 , 8 5 0 / y e a r , a n d it w a s a s s u m e d that a n o p e r a t o r w o r k e d 4 9 w e e k s / y e a r , a n d there w e r e three 8 - h o u r shifts p e r d a y for  the  continuous  plant  ( Z h a n g et a l . 2 0 0 3 b ) . T a b l e 2 . 1 0 presents a b r e a k d o w n o f  the  c o m p o n e n t s o f the total m a n u f a c t u r i n g c o s t as w e l l as the results f o r e a c h p r o c e s s . A f t e r tax rate-of-return i s . a g e n e r a l c r i t e r i o n f o r e c o n o m i c p e r f o r m a n c e o f a c h e m i c a l p l a n t . It is d e f i n e d as the p e r c e n t a g e o f net a n n u a l p r o f i t after t a x e s , r e l a t i v e to the total c a p i t a l i n v e s t m e n t . N e t a n n u a l p r o f i t after taxes (A ) NNP  is h a l f the net a n n u a l p r o f i t (A ) NP  a s s u m i n g a c o r p o r a t e tax rate  o f 5 0 % . T h e results f o r after tax rate o f return f o r e a c h p r o c e s s are s h o w n i n T a b l e 2 . 1 0 .  As  s h o w n i n T a b l e 2 . 8 , the t r a n s e s t e r i f i c a t i o n r e a c t o r f o r m s a l a r g e part o f the c a p i t a l c o s t ,  e s p e c i a l l y f o r P r o c e s s e s U a n d I V . T h e r e a c t o r i n P r o c e s s II w a s r e q u i r e d to c o n t a i n a l a r g e m a t e r i a l f l o w at a l o n g r e s i d e n c e t i m e . T h e p r e s e n c e o f s u l f u r i c a c i d as the catalyst r e q u i r e d a 19  stainless steel reactor, r e s u l t i n g i n a s u b s t a n t i a l l y h i g h e r r e a c t o r c o s t . C o n s e q u e n t l y the r e a c t o r i n P r o c e s s II w a s m u c h m o r e e x p e n s i v e than i n a l l other p r o c e s s e s . T h e s u p e r c r i t i c a l r e a c t o r w a s r e q u i r e d to w i t h s t a n d a h i g h p r e s s u r e , a n d w a s c o n s t r u c t e d f r o m stainless steel to  prevent  o x i d a t i o n a n d c o r r o s i o n , h e n c e its h i g h c o s t . D i s t i l l a t i o n c o l u m n s a l s o c o n t r i b u t e d a s i g n i f i c a n t part to the c a p i t a l c o s t o f e a c h p r o c e s s . T o w e r costs f o r the m e t h y l - e s t e r p u r i f i c a t i o n t o w e r w e r e r o u g h l y e q u a l b e t w e e n the p r o c e s s e s , as e a c h t o w e r w a s h a n d l i n g a p p r o x i m a t e l y the s a m e m a t e r i a l f l o w s a n d p r o d u c i n g b i o d i e s e l at e q u a l p u r i t i e s . T h e m e t h a n o l r e c o v e r y c o l u m n s i n Processes  I  and  III  were  the  least  e x p e n s i v e , as they  had  the  smallest  material  flow  r e q u i r e m e n t s . In spite o f P r o c e s s I V h a v i n g the s m a l l e s t n u m b e r o f u n i t o p e r a t i o n s , P r o c e s s  ni  h a d the s m a l l e s t total c a p i t a l i n v e s t m e n t . T h i s is d u e to the fact that P r o c e s s I V r e q u i r e d a m o r e e x p e n s i v e r e a c t o r i n o r d e r to w i t h s t a n d the h i g h pressures a n d c o r r o s i v e c o n d i t i o n s a s s o c i a t e d w i t h the s u p e r c r i t i c a l state o f the a l c o h o l , as w e l l as the l a r g e r m e t h a n o l r e c o v e r y t o w e r . T h e total c a p i t a l i n v e s t m e n t f o r P r o c e s s I i n the present w o r k w a s c a l c u l a t e d to b e $ 9 6 0 t h o u s a n d , less than the v a l u e r e p o r t e d b y Z h a n g et a l . ( 2 0 0 3 b ) o f $ 1 . 3 4 m i l l i o n . T h e d i f f e r e n c e l i e s m o s t l y i n the l o w e r c o s t s c a l c u l a t e d f o r the m e t h a n o l r e c o v e r y c o l u m n a n d m e t h y l - e s t e r p u r i f i c a t i o n c o l u m n , d u e to the d i f f e r e n c e s i n s i z i n g .  R e s u l t s f o r the total m a n u f a c t u r i n g c o s t o f e a c h p r o c e s s are s h o w n i n T a b l e 2 . 1 0 . T h e d i r e c t m a n u f a c t u r i n g c o s t represents b e t w e e n 7 1 - 7 7 % o f the total m a n u f a c t u r i n g c o s t i n e a c h p r o c e s s . T h e largest p r o p o r t i o n o f the d i r e c t m a n u f a c t u r i n g c o s t is d u e to the o i l f e e d s t o c k - u p to 5 7 % for  P r o c e s s I,  a n d a r o u n d 4 3 % f o r the other p r o c e s s e s . P r o c e s s i n  has the l o w e s t  total  m a n u f a c t u r i n g c o s t . T h i s is d u e to b o t h the a b i l i t y o f the p r o c e s s to use l o w c o s t w a s t e v e g e t a b l e o i l , as w e l l as the l o w e r u t i l i t y c o s t s o f the p r o c e s s r e s u l t i n g f r o m the s m a l l e r m a t e r i a l streams h a n d l e d i n the p r o c e s s . T h e total m a n u f a c t u r i n g c o s t o f P r o c e s s I V is s l i g h t l y m o r e than that o f P r o c e s s H I , o w i n g to the l a r g e e n e r g y r e q u i r e m e n t s n e c e s s a r y to separate the m e t h a n o l f r o m the p r o d u c t stream.  E x c e p t f o r P r o c e s s III, a l l p r o c e s s e s h a d a n e g a t i v e after tax r a t e - o f - r e t u r n . P r o c e s s I h a d the lowest A T R O R ,  at - 1 4 1 % ,  while Processes H and I V  had A T R O R s  at - 4 % a n d - 0 . 9 % ,  r e s p e c t i v e l y . T h e A T R O R f o r P r o c e s s H I w a s 5 4 % , i n d i c a t i n g that the p r o c e s s c o u l d e a r n a profit without any government subsidies.  T h e v a l u e f o r A T R O R r e p o r t e d b y Z h a n g et a l .  ( 2 0 0 3 b ) f o r P r o c e s s I w a s - 8 5 % w h i c h is q u i t e different f r o m the v a l u e reported i n this w o r k . C o m p a r i n g results, the u t i l i t i e s c o n s u m p t i o n , as w e l l as the cost o f w a s t e d i s p o s a l w e r e m u c h 20  higher in the present work, leading to a greater T M C . As well, the TCI was lower, and as its value decreases, the A T R O R becomes larger in magnitude. However, our rate of return for process II (-4%) was in close agreement with the value reported for the acid-catalyzed case by al of -15%. Although the difference in magnitude between the A T R O R calculated for Processes I and II is larger than that reported by Zhang et al. (2003b) the relative order of Processes I and II (i.e. that Process II has an A T R O R greater than that of Process I) as presented in this work is in agreement with that of Zhang et al. (2003b). As predicted by Lotero et al. (2005), the heterogeneous acid-catalyzed process was by far the most economically attractive process. 2.6  Sensitivity analyses and optimization  Sensitivity analyses were conducted to determine the effect on the process of variables that had some degree of uncertainty; and to identify any operating specifications within an individual process that could be modified to improve the process.  Since the conversion data for the heterogeneous acid-catalyzed and supercritical processes were taken from bench-scale research, the economics of scale may, not be accurately reflected. Thus the effect of reduced conversion on the overall process economics was examined for each process. As shown in Figure 5, conversion in the heterogeneous acid-catalyzed process must drop to approximately 85%, while conversion in the supercritical and homogeneous acidcatalyzed processes must increase to almost 100% before there is any overlap in the ATROR. From this, it is clear that even at reduced reactor conversion, the heterogeneous process will still be advantageous over the supercritical and homogeneous acid-catalyzed processes.  Sensitivity analyses were performed for all processes to determine the effect of changing methanol recovery in the methanol recovery distillation column on the ATROR. In all cases except the alkali-catalyzed case, increasing the methanol recovery caused an increase in the ATROR, due to decreased methanol consumption in all cases. Methanol acts as a cosolvent (Chiu et al. 2005) increasing the solubility of biodiesel in the glycerol phases. Therefore, reducing the amount of methanol entering the three phase separator (HAC and SC processes) reduced the amount of biodiesel lost in the glycerol stream, thereby boosting A T R O R for both processes. Figure 2.6 illustrates the effect of methanol recovery on A T R O R for the H A C process. Methanol recovery is limited to about 85%, as the bottoms stream temperature should not exceed 150°C. In order to increase the methanol recovery, the distillation column was 21  operated u n d e r v a c u u m c o n d i t i o n s . T h e effect o f v a c u u m p r e s s u r e ( a n d therefore c o s t o f the v a c u u m system) o n the A T R O R w a s i n v e s t i g a t e d to d e t e r m i n e i f the c o s t o f the v a c u u m s y s t e m w a s offset b y the i n c r e a s e i n r e v e n u e that results f r o m h i g h e r m e t h a n o l r e c o v e r y . A s s h o w n i n F i g u r e 2.7, the a d d i t i o n o f the v a c u u m s y s t e m r e s u l t e d i n a decrease i n A T R O R . H o w e v e r , as the m e t h a n o l r e c o v e r y w a s i n c r e a s e d u n d e r v a c u u m o p e r a t i o n , the A T R O R i n c r e a s e d , i n d i c a t i n g the p o t e n t i a l f o r o p t i m i z a t i o n o f the c o l u m n o p e r a t i n g c o n d i t i o n s to m a x i m i z e the A T R O R . Similar  analyses w e r e  conducted  for  the  homogeneous  acid  catalyzed and  supercritical  p r o c e s s e s , but it w a s f o u n d that v a c u u m o p e r a t i o n d i d not p r o v i d e a n y e c o n o m i c b e n e f i t s , as the m e t h a n o l r e c o v e r y w a s a l r e a d y greater than 9 9 % a n d the b o t t o m s temperature w a s w i t h i n the a l l o w a b l e l i m i t at a m b i e n t p r e s s u r e o p e r a t i o n . T h e H Y S Y S o p t i m i z e r t o o l w a s u s e d to v a r y the HAC  methanol  recovery  i n o r d e r to  m a x i m i z e the A T R O R ,  a c c o r d i n g to the  following  c o n s t r a i n t s : b o t t o m s temperature < 1 5 0 ° C ; 1 k P a < c o l u m n pressure < 100 k P a ; a n d 8 5 . 0 % < methanol recovery < 9 9 . 9 % .  A n optimum  w a s f o u n d at a pressure e q u a l o f 4 0 k P a a n d  methanol recovery of 99.9%. U p o n optimization 149.9°C  to  145.5°C, methanol  the b o t t o m s  temperature  decreased f r o m  r e c o v e r y i n c r e a s e d f r o m 8 5 % to 9 9 . 9 % a n d the  ATROR  i n c r e a s e d s l i g h t l y f r o m 5 3 . 7 % to 5 4 . 2 % . In a d d i t i o n to the f i n a n c i a l i n c e n t i v e , i n c l u d i n g a v a c u u m system reduces methanol consumption and eliminates 7 9 2 0 0 kg/yr of methanol f r o m the waste s t r e a m , greatly r e d u c i n g the e n v i r o n m e n t a l i m p a c t o f the p r o c e s s .  L a s t l y , the effect  o f v a c u u m o p e r a t i o n i n the fatty a c i d m e t h y l - e s t e r  (FAME)  distillation  c o l u m n s w a s i n v e s t i g a t e d f o r the heterogeneous a c i d - c a t a l y z e d a n d the s u p e r c r i t i c a l p r o c e s s e s , to d e t e r m i n e i f v a c u u m o p e r a t i o n w o u l d result i n a net s a v i n g s d u e to a decrease i n the h e a t i n g a n d c o o l i n g duties o n the c o l u m n . C o l u m n h e a t i n g a n d c o o l i n g l o a d s d i d d e c r e a s e ; h o w e v e r , the s a v i n g s i n u t i l i t i e s c o s t w a s not e n o u g h to offset the c o s t o f the v a c u u m s y s t e m , a n d i n c l u s i o n o f a v a c u u m s y s t e m therefore d e c r e a s e d the A T R O R i n b o t h cases. S i n c e the u p p e r temperature limit  of  biodiesel did  not  e x c e e d at  ambient  operation  a vacuum  system was  unnecessary for F A M E distillation i n both processes. V a c u u m operation for F A M E  deemed  distillation  w a s n e e d e d i n the h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s to k e e p the temperature o f the d i s t i l l a t e below 250°C.  2.7  Conclusion  F o u r c o n t i n u o u s p r o c e s s e s to p r o d u c e b i o d i e s e l at a rate o f 8 0 0 0 t o n n e s / y e a r w e r e d e s i g n e d a n d simulated in H Y S Y S .  T h e p r o c e s s e s w e r e as f o l l o w s :  (I)  a homogeneous alkali-catalyzed 22  p r o c e s s that u s e d p u r e v e g e t a b l e o i l as the f e e d s t o c k ; (II) a h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s that c o n v e r t e d w a s t e v e g e t a b l e o i l as the f e e d s t o c k ; (HI) a heterogeneous a c i d - c a t a l y z e d p r o c e s s that u s e d waste v e g e t a b l e o i l ; a n d ( I V ) a s u p e r c r i t i c a l n o n - c a t a l y z e d p r o c e s s , that c o n s u m e d w a s t e v e g e t a b l e o i l . F r o m a t e c h n i c a l standpoint,  a l l p r o c e s s e s are c a p a b l e o f  producing  b i o d i e s e l that meets A S T M s p e c i f i c a t i o n s f o r p u r i t y . T h e s u p e r c r i t i c a l p r o c e s s is the s i m p l e s t a n d has the f e w e s t n u m b e r o f unit o p e r a t i o n s , but r e q u i r e s severe o p e r a t i n g c o n d i t i o n s  to  a c h i e v e a h i g h c o n v e r s i o n o f the f e e d s t o c k . T h e h e t e r o g e n e o u s a c i d - c a t a l y z e d p r o c e s s has o n e m o r e unit than the s u p e r c r i t i c a l p r o c e s s (a h y d r o c y c l o n e to r e m o v e the s o l i d catalyst)  but  operates at m i l d p r o c e s s c o n d i t i o n s . T h e h o m o g e n e o u s p r o c e s s e s h a d the greatest n u m b e r o f u n i t o p e r a t i o n s , and w e r e m o r e c o m p l i c a t e d , o w i n g to the d i f f i c u l t y i n r e m o v i n g the catalyst f r o m the l i q u i d p h a s e .  A n e c o n o m i c assessment r e v e a l e d that the heterogeneous a c i d - c a t a l y z e d p r o c e s s has the l o w e s t total c a p i t a l i n v e s t m e n t , o w i n g to the r e l a t i v e l y s m a l l sizes a n d c a r b o n steel c o n s t r u c t i o n o f m o s t o f the p r o c e s s e q u i p m e n t . R a w m a t e r i a l s c o n s u m e d i n the p r o c e s s a c c o u n t f o r a m a j o r p o r t i o n o f the  total  manufacturing  cost.  Accordingly,  Processes  II,  HI  and  TV  have  much  lower  m a n u f a c t u r i n g costs than P r o c e s s I. T h e large e x c e s s e s o f m e t h a n o l i n P r o c e s s e s II a n d TV r e s u l t e d i n m u c h h i g h e r u t i l i t y costs than i n p r o c e s s H I m a k i n g p r o c e s s H I the o n l y p r o c e s s to p r o d u c e a net p r o f i t . T h e after tax rate o f return f o r P r o c e s s H I w a s 5 4 % , w h i l e P r o c e s s e s I, H a n d I V h a d rates o f return o f - 1 4 4 % , - 4 % a n d - 0 . 9 % , r e s p e c t i v e l y .  Sensitivity  analyses  were  conducted  to  identify  any  unit  operations  were  operating  s p e c i f i c a t i o n s c o u l d b e m o d i f i e d to i m p r o v e the p r o c e s s . I n c r e a s i n g m e t h a n o l r e c o v e r y l e d to a greater A T R O R . A c c o r d i n g l y , m e t h a n o l r e c o v e r y w a s set as h i g h as p o s s i b l e (>99%) b e f o r e the g l y c e r o l d e g r a d a t i o n temperature ( 1 5 0 ° C ) w a s e x c e e d e d i n the h o m o g e n e o u s a c i d - c a t a l y z e d a n d s u p e r c r i t i c a l p r o c e s s e s . U s e o f the o p t i m i z e r f u n c t i o n i n d i c a t e d a v a c u u m s y s t e m c o u l d b e i n s t a l l e d i n the h e t e r o g e n e o u s a c i d - c a t a l y z e d ( H A C ) p r o c e s s to i n c r e a s e m e t h a n o l r e c o v e r y a n d c o n s e q u e n t l y the A T R O R , w h i l e k e e p i n g the b o t t o m s s t r e a m w i t h i n the temperature l i m i t .  A n a n a l y s i s o f the effect o f r e a c t i o n c o n v e r s i o n o n A T R O R r e v e a l e d that e v e n at r e d u c e d r e a c t i o n c o n v e r s i o n (i.e., b e t w e e n 8 5 - 9 3 % ) , the A T R O R o f the H A C p r o c e s s is greater than at 1 0 0 % c o n v e r s i o n o f the h o m o g e n e o u s a c i d a n d s u p e r c r i t i c a l p r o c e s s e s .  23  T h e r e f o r e P r o c e s s in, the other  the heterogeneous a c i d - c a t a l y z e d p r o c e s s , is c l e a r l y a d v a n t a g e o u s o v e r  p r o c e s s e s , as it  h a d the h i g h e s t rate o f r e t u r n ,  lowest  capital investment,  and  t e c h n i c a l l y , w a s a r e l a t i v e l y s i m p l e p r o c e s s . F u r t h e r r e s e a r c h i n d e v e l o p i n g the h e t e r o g e n e o u s a c i d - c a t a l y z e d p r o c e s s f o r b i o d i e s e l p r o d u c t i o n is w a r r a n t e d .  Acknowledgments T h e authors  a c k n o w l e d g e the f i n a n c i a l  support  of  the N a t u r a l  Sciences and  Engineering  Research C o u n c i l of Canada.  24  Table 2.1. Catalysts and reaction parameters for heterogeneously catalyzed reactions of soybean oil at 1 atm.  Reaction Parameters ^ . i .. C a t a l y s t type W0 /Zr0 3  4  _ Temperature  . Conversion  _. Time  40:1  >250 ° C  >90%  4h  40:1  300°C  65%  4h  40:1  300°C  80%  4h  4.15:1  60°C  94.7  3h  2  ( F u r u t a et a l . 2004) S0 /Sn0  A : 0Molar ^  2  (Furuta e t a l . 2004) S0 /Zr0 4  2  (Furuta e t a l . 2004) S n O ( A b r e u et al. 2005)  25  Table 2.2. Summary of unit operating conditions for each process. AlkaliAcidCatalyzed Catalyzed (Process I) (Process II) Transesterification Catalyst NaOH H S0 Reactor Type CSTR CSTR 60 80 Temperature (°C) Pressure (kPa) 400 400 A : 0 Ratio 6:1 50:1 Residence time (hr) 4 4 Conversion (%) 95 97 Methanol Recovery Reflux Ratio 2 2 Number of stages 6 6 Condenser/Reboiler 20/30 101.3/111 Pressure (kPa) %Recovery 94 99.2 Distillate flowrate 113.14 1687 (kg/h) Distillate purity(%) 100 100 Catalyst Removal N/A N/A Glycerine Separation Water Water washing washing Water flowrate 11 kg/h 46 kg/h Catalyst Neutralization Neutralizing agent H3PO4 CaS0 Biodiesel Purification Reflux ratio 1.85 2 Number of stages 6 10 Condenser/reboiler 10/20 10/15 Pressure (kPa) %Recovery 99.9 98.65 Final purity 99.9 99.65 2  a  4  a  4  Heterogeneous Acid-Catalyzed (Process HI)  Supercritical Process (Process IV)  SnO Multiphase 60  N/A CSTR 350  101.3 4.5:1 3 94  20x10 42:1 0.333 98  3.99 14 40/50  3.42 12 101.3/105.3  99.9 66.33  99.3 1239.7  99.9  99.99  hydrocyclone  N/A  Gravity separation  Gravity separation  -  3  -  N/A  N/A  2 8 101.3/111.3  2 8 101.3/111.3  99.9 99.9  99.9 99.65  26  Table 2.3. Feed and product stream information for the alkali-catalyzed process.  101 Temperature (°C) 25.0 Pressure (kPa) 101.3 Molar flow (kgmol/h) 3.61 Mass flow (kg/h) 115.71 Component mass fraction Methanol 1.000 Triolein 0.000 NaOH 0.000  Feed Streams 105-PVO  103  25.0 101.3 1.19 1050.00  25.0 101.3 0.25 10.00  0.000 1.000 0.000  0.000 0.000 1.000  Temperature (°C) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Glycerol Triolein M-oleate NaOH H3P04 Na3P04 Water  Product Streams 402  401A  401  501  502  167.8 10 0.12 4.57  167.5 10 3.38 1001.8  463.9 15 0.06 52.77  42.8 20 0.65 13.79  148.6 30 1.20 105.12  0.6114 0.0005 0.0000 0.2125 0.0000 0.0000 0.0000 0.1755  0.0001 0.0000 0.0001 0.9997 0.0000 0.0000 0.0000 0.0000  0.0000 0.0000 0.9967 0.0033 0.0000 0.0000 0.0000 0.0000  0.3432 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.6565  0.0001 0.9865 0.0014 0.0002 0.0000 0.0000 0.0000 0.0119  Table 2.4. Feed and product stream information for the homogeneous acid-catalyzed process.  101 Temperature ( ° C ) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Triolein H S0 Oleic Acid 2  t o  4  Feed Streams 103  Product Streams 105  25 101.3 3.78 121.2  25 101.3 1.53 150.06  25 101.3 1.17 1030.00  .1.000 0.000 0.000 0.000  0.000 0.000 1.000 0.000  0.000 0.950 0.000 0.050  Temperature (°C) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Glycerol Triolein H2S04 M-oleate CaO Water Oleic Acid  401A  401  402  501  502  130.7 35 0.65 20.42  234.3 45 3.42 1002.98  502.2 55 0.05 33.22  23.4 10 6.59 155.64  226.6 15 1.10 101.69  0.957 0.001 0.000 0.000 0.007 0.000 0.035 0.000  0.001 0.000 0.001 0.000 0.998 0.000 0.000 0.000  0.000 0.000 0.889 0.000 0.111 0.000 0.000 0.000  0.520 0.009 0.000 0.000 0.003 0.000 0.468 0.000  0.000 0.993 0.007 0.000 0.000 0.000 0.000 0.000  Table 2.5. Feed and product stream information for the heterogeneous acid-catalyzed process.  Feed Streams Methanol 101 Temperature (°C) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Triolein Tin(II) oxide Oleic acid  SnO 103  Product Streams  Triolein 105  25.0 101.3 3.38 108.3  25.0 101.3 0.04 10.54  25.0 101.3 1.31 1050.00  1.0000 0.0000 0.0000 0.0000  0.0000 0.0000 1.0000 0.0000  0.0000 0.9500 0.0000 0.0500  401  402  25.0 50 1.22 100.4  203.2 101.3 3.38 989.6  535.5 111.3 0.07 59.80  0.0004 0.9625 0.0064 0.0002 0.0000 0.0000 0.0304  0.0000 0.0001 0.0000 0.9995 0.0000 0.0000 0.0002  0.0000 0.0001 0.9835 0.0165 0.0000 0.0000 0.0000  302 Glycerol Out Temperature (°C) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) , Component mass fraction Methanol glycerol triolein M-oleate tin(II) oxide Oleic acid water  Table 2.6. Feed and product stream information for the supercritical methanol process.  Feed Streams 101 Methanol 103 Triolein Temperature ( ° C ) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Triolein Oleic acid  ro oo  25 100 3.67 117.8  25 100 1.31 1050.00  1.0000 0.0000 0.0000  0.0000 0.9500 0.0500  Product Streams 302 Glycerol Out Temperature (°C) Pressure (kPa) Molar flow (kgmol/h) Mass flow (kg/h) Component mass fraction Methanol Glycerol Triolein M-oleate Oleic acid water  401  402  25 105.3 1.44 110.1  134.5 101.3 3.62 1039.4  463.7 111.3 0.03 20.83  0.0501 0.9180 0.0012 0.0033 0.0000 0.0272  0.0030 0.0006 0.0000 0.9960 0.0000 0.0003  0.0000 0.0000 0.9947 0.0052 0.0000 0.0000  Table 2.7. Equipment sizes for various process units in all processes. (Dimensions are diameter x height, m).  Type  Description  Alkali-  Acid-  Heterogeneous  Supercritical  Catalyzed (Process I)  Catalyzed (Process II)  Acid-Catalyzed (Process HI)  Process (Process I V )  Reactor Transesterification  1.8x5.4  2.1x6.3  1.2x3.64  0.96x2.9  Neutralization  0.36x1.1  0.5x1.5  N/A  N/A  Methanol Recovery  0.46x3  0.9x8.6  0.31x7.4  1x8.8  Fame Purification  0.9x9.5  1x8.5  0.9x6.6  1x6.6  Water Washing  0.8x10  1x10  N/A  N/A  Purification  N/A  0.5x3.7  N/A  N/A  G r a v i t y Separators  N/A  N/A  1.2x2.4  1.1x2.4  Hydrocyclone  N/A  N/A  0.112x1.35  N/A  Columns  Glycerol Separators  29  Table 2.8. Equipment costs, fixed capital costs and total capital investments for each process. (Units: Smillions).  Type Reactor  Description  AlkaliCatalyzed  AcidCatalyzed  Solid AcidCatalyzed  Supercritical Process  Transesterification Neutralization  0.292 0.027  0.680 0.036  0.075 0  0.639 0  Methanol Recovery Fame Purification Washing Glycerol Purification  0.038 0.102 0.084 0  0.152 0.076 0.113 0.028  0.028 0.095 0 0  0.167 0.146 0 0  Gravity Separators Heat Exchangers Pumps Others (hydrocyclone etc)  0 0 0.014 0  0 0.079 0.010 0  0.057 0.079 0.014 0.015  0.058 0.109 0.141 0  0.56 0.10 0.67 0.17 0.83 0.13 0.95  1.17 0.22 1.38 0.35 1.73 0.26 1.99  0.37 0.07 0.43 0.11 0.54 0.08 0.63  1.26 0.23 1.49 0.38 1.87 0.28 2.15  Columns  Other  Total bare module cost, C B M Contingency fee, C C F = 0.1 8 C B M Total module cost, C J M = C B M + C C F Auxiliary facility cost , C A C = 0.3CBM Fixed Capital Cost, C c = C M + C C Working capital C c = 0.15C c Total capital investment C T C I = C F C + C W C F  W  T  A  F  30  Table 2.9.  Conditions for the economic assessment of each process. (Zhang et al. 2003b)  Item  Specification  Price ($/tonne)  Chemicals  Biodiesel Calcium Oxide Glycerine  92 wt.% 85 wt.% 99.85%  Methanol Phosphoric Acid Sodium Hydroxide Sulfuric Acid Tin (II) Oxide Pure canola oil Waste cooking oil  600 40 1200 750 180 340 4000 60 600 500 200  Utilities  Cooling water Electricity Low pressure steam High pressure steam  400 kPa 6 °C  a  * Value  frozen  a  601.3 kPa 160°C 4201.3 kPa 254°C  $0.007/m $0.062/kWh $7.78/GJ $19.66/GJ 3  etal. 2003)  31  Table 2.10. Total manufacturing cost and after tax rate-of-return for each process. (Units: $millions). Process I  Process II  Process III  Process rV  4.16 0.16 0.34 0.58 0.09 0.03 0.26 0.00 0.01 0.07 0.01 0.05 0.01 0.09 0.22 6.07  1.63 0.30 0.10 0.58 0.09 0.36 0.25 0.00 0.02 0.09 0.06 0.11 0.02 0.09 0.15 3.84  1.66 0.16 0.05 0.58 0.09 0.05 0.28 0.00 0.01 0.05 0.02 0.03 0.00 0.09 0.12 3.19  1.66 0.17 0.00 0.58 0.09 0.39 0.33 0.00 0.02 0.02 0.00 0.11 0.02 0.09 0.14 3.61  Overhead, packaging and storage, 60% of sum of operating labour , supervision and maintenance Local Taxes, 1.5% of C Insurance, 0.5% of C c Subtotal, A  0.43 0.01 0.00 0.43  0.46 0.03 0.01 0.47  0.42 0.01 0.00 0.42  0.47 0.03 0.01 0.47  Depreciation 10% of C  0.08  0.18  0.05  0.19  0.11 0.73 0.36 1.20  0.12 0.48 0.24 0.84  0.10 0.39 0.19 0.69  0.12 0.46 0.23 0.81  Direct manufacturing cost Oil feedstock Methanol Catalyst Operating Labour Supervisory Labour L P steam HP steam Electricity Cooling Water Liquid waste disposal Solid waste disposal Maintenance and Repairs (M&R), 6% of C Operating Supplies, 15% of M & R Lab charges, 15% of operating labour Patents and royalties, 3% T M C Subtotal A  r c  D M C  Indirect manufacturing cost  r c  F  I M C  r c  General expenses Administrative costs, 25% of overhead Distribution and selling, 10% of T M C Research &Development, 5% of T M C Subtotal Total production cost Glycerine Credit Total Manufacturing Cost, A Revenue from Biodiesel Net annual profit Income taxes, A 50% of A Net annual after tax profit, A After tax rate of return, I = [ A  T E  I T  N P  N N P  N  NP-A  B D  ]/C  T C  7.89 0.62 7.28 4.75 -2.53 -1.26 -1.26 -141.74%  5.44 0.60 4.83 4.76 -0.08 -0.04 -0.04 -10.61%  4.45 0.57 3.88 4.70 0:82 0.41 0.41 58.76%  5.19 0.60 4.59 4.92 0.33 0.17 0.17 -0.90%  32  401A  Figure 2.2. Homogeneous acid—catalyzed process flowsheet (Process II)  T-100  Figure 2.3. Heterogeneous  acid—catalyzed process flowsheet (Process III).  1D1 Methanol  103 Triolein  302 Glycerol Out  T-102 Figure 2.4. Supercritical alcohol process flowsheet (Process IV).  75 45 15 -15  cc o cc 1<  -45 -75 -105 -135 -165  80  85  90  95  100  105  Reaction Conversion (%) —•—Base Catalyzed —e—Homog. Acid Cat.  A  Heterog. Acid Cat.  X  Supercritical  Figure 2.5. After-tax rate of return vs. reaction conversion for all processes.  58  180  57  160 140  56  i-  120 3  g  55  O  54  <  53  60  52  40  CC  CO  100 a> Q .  80  20  51  m  0  50 0.75  E o> m E o o  0.8  0.85  0.9  0.95  Fractional Methanol Recovery —e— ATROR - T e m p e r a t u r e Figure 2.6. A T R O R vs. methanol recovery in the methanol recovery column, H A C process.  37  57  ,-  48 • 10  20  30  40  50  60  70  —r— —r— 80  90  i 100  100 110  Operating Pressure (kPa) —e— A T R O R  -»—Temperature  ure 2.7. 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F r e e d m a n , B . , Butterfield, R. O . and P r y d e , E . H . (1986). Transesterification kinetics o f soybean o i l . J o u r n a l o f the A m e r i c a n O i l C h e m i s t s S o c i e t y 6 3 ( 1 0 ) : 1 3 7 5 - 1 3 8 0 . F r e e d m a n , B . , P r y d e , E . H . a n d M o u n t s , T . L . ( 1 9 8 4 ) . V a r i a b l e s a f f e c t i n g the y i e l d s o f fatty esters f r o m transesterified v e g e t a b l e - o i l s . J o u r n a l o f the A m e r i c a n O i l C h e m i s t s S o c i e t y 61(10): 1638-1643. Furuta, S., M a t s u h a s h i , H . and A r a t a , K . (2004). B i o d i e s e l fuel production w i t h solid superacid c a t a l y s i s i n f i x e d b e d reactor under a t m o s p h e r i c pressure. C a t a l y s i s C o m m u n i c a t i o n s 5(12): 7 2 1 - 7 2 3 . G o f f , M . J . , Bauer, N . S., L o p e s , S., Sutterlin, W . R. and Suppes, G . J . (2004). A c i d - c a t a l y z e d a l c o h o l y s i s o f s o y b e a n o i l . 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Effects of water on biodiesel fuel production by supercritical m e t h a n o l treatment. B i o r e s o u r c e T e c h n o l o g y 9 1 ( 3 ) : 2 8 9 - 2 9 5 . Lotero, E . , L i u , Y . J . , L o p e z , D . E . , Suwannakarn, K., B r u c e , D . A . and G o o d w i n , J . G . (2005). Synthesis o f biodiesel v i a acid catalysis. Industrial & Engineering Chemistry Research 44(14): 5353-5363. L u y b e n , W . L. (2002). P l a n t w i d e dynamic simulators in c h e m i c a l processing and control. N e w York, Marcel Dekker. M a , F. R. and H a n n a , M . A . (1999). B i o d i e s e l production: A review. Bioresource T e c h n o l o g y 7 0 ( 1 ) : 1-15. M c C a b e , W . J . , S m i t h , J . C . and Harriott, P . (2001). U n i t operations o f c h e m i c a l engineering. 6th ed. 39  N e w m a n , A . A . (1968). G l y c e r o l . C l e v e l a n d , C R C Press. S a k a , S . a n d K u s d i a n a , D . ( 2 0 0 1 ) . B i o d i e s e l f u e l f r o m r a p e s e e d o i l as p r e p a r e d i n s u p e r c r i t i c a l methanol. F u e l 80(2): 2 2 5 - 2 3 1 . Schumacher, L. G . , M a r s h a l l , W . , K r a h l , J . , Wetherell, W . B . and G r a b o w s k i , M . S. (2001). B i o d i e s e l e m i s s i o n s data f r o m series 6 0 d d c e n g i n e s . T r a n s a c t i o n s o f the A S A E 4 4 ( 6 ) : 1465-1468. Seider, W . D., Seader, D . and L e w i n , D . R. (2003). Process design principles: Synthesis, analysis and evaluation. Chichester, U K , J o h n W i l e y & Sons. Suppes, G . J . , D a s a r i , M . A . , D o s k o c i l , E . J . , M a n k i d y , P. J . and G o f f , M . J . (2004). T r a n s e s t e r i f i c a t i o n o f s o y b e a n o i l w i t h z e o l i t e a n d m e t a l catalysts. A p p l i e d C a t a l y s i s a General 257(2): 213-223. Turton, R., B a i l i e , R. C , W h i t i n g , W . B . and S h a e i w i t z , J . A . (2003). A n a l y s i s , synthesis, and design o f c h e m i c a l processes. U p p e r Saddle R i v e r , N e w Jersey, Prentice H a l l . T y s o n , K . S . B i o d i e s e l : H a n d l i n g a n d use g u i d e l i n e s . http://www.eere.energy.gov/biomass/pdfs/biodiesel  handling.pdf (November 28, 2004),  W a r a b i , Y . , K u s d i a n a , D . a n d S a k a , S . ( 2 0 0 4 ) . R e a c t i v i t y o f t r i g l y c e r i d e s a n d fatty a c i d s o f rapeseed o i l i n s u p e r c r i t i c a l a l c o h o l s . B i o r e s o u r c e T e c h n o l o g y 9 1 ( 3 ) : 2 8 3 - 2 8 7 . Z h a n g , Y . , D u b e , M . A . , M c L e a n , D . D . and Kates, M . (2003a). B i o d i e s e l production f r o m waste c o o k i n g o i l : 1. P r o c e s s d e s i g n a n d t e c h n o l o g i c a l assessment. B i o r e s o u r c e T e c h n o l o g y 89(1):  1-16.  Z h a n g , Y . , D u b e , M . A . , M c L e a n , D . D . and Kates, M . (2003b). B i o d i e s e l production f r o m waste c o o k i n g o i l : 2. E c o n o m i c assessment a n d s e n s i t i v i t y a n a l y s i s . B i o r e s o u r c e T e c h n o l o g y 90(3): 229-240.  40  3 3.1  Characterization and Testing of Heterogeneous Catalysts for Biodiesel Production  2  Introduction and background  Rising  crude  o i l prices, concerns  over  diminishing  fossil  fuel  reserves a n d r e g a r d  for  e n v i r o n m e n t a l q u a l i t y , e s p e c i a l l y i n u r b a n areas, h a v e a l l c o n t r i b u t e d to the large r e s e a r c h efforts a i m e d at a c h i e v i n g e c o n o m i c a l m e a n s o f p r o d u c i n g a l t e r n a t i v e  fuels derived  from  r e n e w a b l e r e s o u r c e s , s u c h as b i o d i e s e l a n d b i o e t h a n o l .  B i o d i e s e l ( m o n o - a l k y l esters o f l o n g c h a i n fatty a c i d s ) i s a p r o m i s i n g alternative ( o r extender) to c o n v e n t i o n a l p e t r o l e u m b a s e d d i e s e l f u e l . B i o d i e s e l has a n u m b e r o f advantages w h e n c o m p a r e d w i t h r e g u l a r d i e s e l f u e l . T h e first a n d f o r e m o s t i s that it i s d e r i v e d f r o m a r e n e w a b l e d o m e s t i c r e s o u r c e (vegetable o i l ) , a n d has b e e n s h o w n to r e d u c e c a r b o n d i o x i d e e m i s s i o n s b y 7 8 % ( T y s o n 2 0 0 1 ) w h e n c o m p a r e d to d i e s e l f u e l o n a l i f e c y c l e b a s i s . C o m b u s t i o n o f b i o d i e s e l has the p o t e n t i a l to s i g n i f i c a n t l y l o w e r g r e e n h o u s e gas ( G H G ) e m i s s i o n s . F o r e x a m p l e , a 5 % b i o d i e s e l b l e n d ( B 5 ) i n s t i t u t e d n a t i o n - w i d e i n C a n a d a w o u l d r e d u c e the a m o u n t o f CO2 e n t e r i n g the a t m o s p h e r e b y 2.5 M T ( H o l b e i n et a l . 2 0 0 4 ) . B i o d i e s e l c o n t a i n s n o s u l f u r ( a n d therefore e m i t s n o S O w h i c h i s a p r e c u r s o r f o r a c i d r a i n ) , b u t p r o v i d e s greater l u b r i c i t y than c o n v e n t i o n a l x  d i e s e l f u e l , a n d c a n therefore e n h a n c e e n g i n e l o n g e v i t y . L a s t l y , b i o d i e s e l i s n o n - t o x i c a n d b i o d e g r a b l e m a k i n g it a m o r e e n v i r o n m e n t a l l y b e n i g n f u e l .  B i o d i e s e l i s p r o d u c e d f r o m the r e a c t i o n o f a v e g e t a b l e o i l o r a n i m a l fat ( w h i c h are c o m p o s e d o f c o m p l e x m i x t u r e s o f t r i g l y c e r i d e s a n d free fatty a c i d s d e p e n d i n g o n the q u a l i t y o f the o i l o r t a l l o w ) a n d a l o w m o l e c u l a r w e i g h t a l c o h o l , s u c h as m e t h a n o l , e t h a n o l o r p r o p a n o l . M e t h a n o l i s m o s t f r e q u e n t l y u s e d as it i s the least e x p e n s i v e a l c o h o l . T h e r e a c t i o n b e t w e e n the t r i g l y c e r i d e a n d the a l c o h o l i n the p r e s e n c e o f a catalyst, d e p i c t e d i n E q u a t i o n 3 . 1 , i s referred to as t r a n s e s t e r i f i c a t i o n . T h e r e a c t i o n p r o d u c e s a c o m p l e x m i x t u r e o f fatty a c i d m e t h y l esters (the b i o d i e s e l p r o d u c t , w h i c h i s d e p e n d a n t o n the v e g e t a b l e o i l type), a n d g l y c e r o l .  2  A version of this chapter is in preparation for submission for publication. West, A . H . and Ellis, N . (2006)  41  CH -OOC-R, I CH-OOC-R  Ri-COO-R'  2  2  . Catalyst + 3R'OH <=>  R -COO-R' 2  CH -OH I CH-OH 2  +  I  (3.1)  I  CH -OOC-R 2  3  Glyceride  R3-COO-R'  CH -OH  Esters  Glycerol  Alcohol  2  Biodiesel can also be produced through the reaction of free fatty acids (FFA) and alcohol in the presence of a catalyst to produce biodiesel and water (Equation 3.2). Catalyst Ri-COOH  Fatty acid  + R'OH  Alcohol  <=>  Ri-COO-R'  Ester  +  H 0 2  (3.2)  Water  This reaction becomes significant in the case where the feedstock contains high amounts of F F A which can limit the yield of the process of the Transesterification, as water can deactivate the catalyst and lead to soap formation.  The transesterification reaction can be catalyzed through a number of different methods: homoegeneous alkali (Freedman et al. 1 9 8 4 ) ; homogeneous acid (Canakci and Van Gerpen 1999);  supercritical alcohol with no catalyst (Saka and Kusdiana 2 0 0 1 ) ; and via heterogeneous  catalysts. The homogeneous alkali-catalyzed method is the most well known and common industrial method. It provides high yields in short times at mild process conditions, but is the most expensive of the processes (Zhang et al. 2 0 0 3 ) , since it requires a pure vegetable oil feed (which can account for up to 7 5 % of the cost of the process (Krawczyk 1 9 9 6 ) , as the base catalyzed process is highly intolerant of water and F F A in the feedstock (Freedman et al. 1984)). Homogeneous acid-catalyzed transesterification improves on the alkali-catalyzed method as it can accommodate lower quality (and therefore less expensive) feedstocks with F F A amounts up to 5 wt.%. However, at mild conditions, the process is extremely slow, and requires up to 4 8 hours to achieve conversions greater than 9 5 % . It also requires a large excess of methanol. Although the process is more economical than the alkali-catalyzed method (Zhang et al. 2 0 0 3 ) , it is still disadvantageous. Furthermore, both processes require water to separate the catalyst from the product stream and a catalyst neutralization step, increasing the waste output and necessitating a more complicated process. The supercritical process eliminates the need for a 42  catalyst a n d g i v e s v e r y h i g h y i e l d s i n v e r y short t i m e s ( W a r a b i et a l . 2 0 0 4 ) . H o w e v e r , these advantages are offset b y the h i g h c o s t o f the e q u i p m e n t r e q u i r e d to w i t h s t a n d s u c h h i g h pressures ( W e s t et a l . 2 0 0 6 ) . H e t e r o g e n e o u s c a t a l y s i s , i n p a r t i c u l a r a c i d c a t a l y s i s , presents a n u m b e r o f advantages s u g g e s t i n g the m o s t e c o n o m i c a l p r o c e s s f o r b i o d i e s e l p r o d u c t i o n ( L o t e r o et a l . 2 0 0 5 ) . H e t e r o g e n e o u s catalysts c a n b e e a s i l y separated f r o m the r e a c t i o n m i x t u r e w i t h o u t the use o f water, d o not r e q u i r e n e u t r a l i z a t i o n a n d c a n therefore b e p o t e n t i a l l y r e u s e d . In a d d i t i o n , a c i d catalysts s h o w the p o t e n t i a l  to c a t a l y z e b o t h e s t e r i f i c a t i o n and t r a n s e s t e r i f i c a t i o n  ( F u r u t a et a l . 2 0 0 4 ) r e a c t i o n s s i m u l t a n e o u s l y , a l l o w i n g l o w e r c o s t f e e d s t o c k s to b e p r o c e s s e d . A recent p r o c e s s s i m u l a t i o n c o n d u c t e d b y W e s t et a l . ( 2 0 0 6 ) i n d i c a t e d the heterogeneous p r o c e s s to b e the m o s t e c o n o m i c a l c o m p a r e d w i t h the s u p e r c r i t i c a l a n d t r a d i t i o n a l  homogeneous  processes.  T o this e n d , a n u m b e r o f researchers h a v e i n v e s t i g a t e d s o l i d - a c i d catalysts, s u c h as s u p e r a c i d s , ( F u r u t a et a l . 2 0 0 4 ; L o t e r o et a l . 2 0 0 5 ; J i t p u t t i et a l . 2 0 0 6 ; K i s s et a l . 2 0 0 6 ) a n d as w e l l as z e o l y t e s a n d m e t a l o x i d e s ( L o t e r o et a l . 2 0 0 5 ; K i s s et a l . 2 0 0 6 ) . A l t h o u g h the r a n g e  of  temperatures, pressures a n d f e e s t o c k s s t u d i e d v a r i e d s i g n i f i c a n t l y , o v e r a l l results w e r e p o s i t i v e , w i t h m o s t catalysts a c h i e v i n g > 9 0 % c o n v e r s i o n . R e c e n t r e s e a r c h has a l s o f o c u s e d o n d e s i g n i n g catalysts to e f f e c t i v e l y c a t a l y z e the e s t e r i f i c a t i o n o f F F A s . M b a r a k a a n d S h a n k s ( 2 0 0 5 ) d e s i g n e d a m e s o p o r o u s s i l i c a catalyst ( M C M - 4 1 ) w i t h s p e c i a l l y t a i l o r e d h y d r o p h o b i c g r o u p s to p r e v e n t catalyst d e a c t i v a t i o n b y the w a t e r p r o d u c e d d u r i n g the e s t e r i f i c a t i o n r e a c t i o n . T o d a et a l . ( 2 0 0 5 ) p r e p a r e d a h e t e r o g e n e o u s a c i d catalyst f r o m p y r o l i z e d s u g a r reacted w i t h s u l f u r i c a c i d a n d d e m o n s t r a t e d its a b i l i t y to esterify free fatty a c i d s , a l t h o u g h they d i d not report the y i e l d o f the process.  R e s e a r c h c o n c e r n i n g heterogeneous catalysts f o r  transesterification  is s t i l l  i n the  catalyst  s c r e e n i n g stage. S t u d i e s r e g a r d i n g r e a c t i o n k i n e t i c s are f e w ( L o p e z et a l . 2 0 0 5 ) , a n d studies a i m e d at i m p r o v i n g r e a c t i o n parameters h a v e yet to b e c o n d u c t e d . In a d d i t i o n , studies to d e t e r m i n e the effects o f free fatty a c i d c o n c e n t r a t i o n a n d w a t e r o n the p e r f o r m a n c e o f the catalyst h a v e b e e n scarce. B a s e d o n the p o s i t i v e i n d i c a t i o n that the heterogeneous p r o c e s s w a s e c o n o m i c a l , S n O w a s s e l e c t e d f o r c a t a l y t i c e x p e r i m e n t s to i n v e s t i g a t e the factors a f f e c t i n g S n O c a t a l y z e d t r a n s e s t e r i f i c a t i o n ( s u c h as A : 0 m o l a r ratio, F F A content, etc.). A n o t h e r g r o u p  of  e x p e r i m e n t s w a s p e r f o r m e d w i t h an a c i d catalyst d e r i v e d f r o m p y r o l y s i s c h a r ( s u l f o n a t e d c h a r ) ,  43  to test its ability to catalyze both the transesterification and esterification reactions. Fast pyrolysis processes (heating of biomass in the absence of oxygen at rapid heating rates) generally have char yields between 10-25% by weight of the feedstock (Bridgwater et al. 1999; Dynamotiv 2006). The char can either be upgraded to activated carbon or used as an energy source, as it has a heating value comparable to lignite coal. The potential for upgrading a lowvalue product presents an attractive prospect, and therefore sulfonated char was investigated as a catalyst in biodiesel production. 3.2 3.2.1  Tin(II) oxide synthesis and testing methods SnO synthesis  procedure  Initial attempts at synthesizing SnO followed the method of (Abreu et al. 2005). Equimolar mixtures (2 mmol) of SnCl dissolved in water (20 mL) and acetylacetone were mixed under 2  basic conditions (2 mmol NaOH in the solution) and stirred with a magnetic stirrer at 40°C for 30 minutes on a hotplate (Barnstead Thermolyne Cimarec, Fisher Scientific). The mixture was then placed in a refrigerator overnight. The precipitate was isolated via vacuum filtration (Whatman #40 filter paper), dried in a dessicator overnight and then calcined at 500°C for 24 hours in air. A second method of SnO preparation followed that of Fujita et al. (1990): an acidic solution (pH 1.1, 100 mL) of hydrocholic acid and water containing 0.02 mol/L SnCl and 0.6 2  mol/L urea was heated at 95-97°C under reflux on a hotplate under magnetic stirring for 1 hour, at which point a dark precipitate was observed to form. The precipitate was then isolated by vacuum filtration (Whatman #40) and washed with distilled water, before being dried at room temperature in a desiccator. 3.2.2  Catalyst testing  Both the prepared and commercial samples of SnO were tested as catalysts under similar conditions to the work of Abreu et al. (2005), in simple batch experiments. Reactions were carried out on a hotplate with magnetic stirring under reflux at 60°C, to determine the effect of A : 0 (methanol to canola oil respectively) molar ratio and reaction time on the conversion of the reaction. Reaction products were analyzed by GC, using a Hewlett-Packard 5890 with a flame ionization detector and a D B -5 capillary column (15 m 0.32 mm ID) (Agilent Technologies). The temperature program was as follows: Initial temperature of 45°C was held for 1 minute, and then heated at a ramp rate of 5°C/min to 300°C and held for 15 minutes. The injector and 44  detector temperatures  were 290°C  and 310°C, respectively, with no derivitization  o f the  samples.  3.3 3.3.1  Tin(II) oxide results and discussion Synthesis and  characterization  T h e first p r o c e d u r e as n o t e d i n A b r e u et a l . ( 2 0 0 5 ) to s y n t h e s i z e S n O d i d n o t result i n a n y significant yield. T h e post-calcination product w a s an u n k n o w n substance, d u l l grey-beige i n c o l o u r , i n contrast to the s h i n y b l u e - b l a c k c o l o u r o f a c o m m e r c i a l s a m p l e o f S n O as d e p i c t e d i n F i g u r e s 3.1 a n d 3 . 2 , r e s p e c t i v e l y . A subsequent r e v i e w o f the literature r e v e a l e d that S n C ^ w i l l p r e c i p i t a t e as S n O H u n d e r b a s i c c o n d i t i o n s ( F u j i t a et a l . 1 9 9 0 ) . T h u s it w a s l i k e l y that the c a l c i n e d p r o d u c t w a s s o m e f o r m o f S n O H . N e x t , the m e t h o d o f F u j i t a et a l . ( 1 9 9 0 ) w a s a d o p t e d to s u c c e s s f u l l y p r e p a r e S n O as c o n f i r m e d b y c o m p a r i s o n o f x - r a y d i f f r a c t i o n patterns o f the p r e p a r e d s a m p l e w i t h the literature ( F u j i t a et a l . 1 9 9 0 ) , a n d w i t h the pattern o f a c o m m e r c i a l s a m p l e s h o w n i n F i g u r e s 3.3 a n d 3 . 4 , r e s p e c t i v e l y .  3.3.2  Catalytic  activity  I n i t i a l attempts to p r o d u c e b i o d i e s e l b y r e a c t i n g c a n o l a o i l a n d m e t h a n o l (6:1 A : 0 m o l a r r a t i o , 6 0 ° C , 5 w t . % catalyst u n d e r m a g n e t i c s t i r r i n g a n d r e f l u x ) f o r 3 h o u r s i n the p r e s e n c e o f the s y n t h e s i z e d S n O s a m p l e p r o v e d u n s u c c e s s f u l . S u b s e q u e n t attempts h e l d the catalyst l o a d i n g constant, a n d i n c r e a s e d the A : 0 m o l a r ratio ( 9 : 1 , 15:1) a n d r e a c t i o n t i m e s ( 1 2 h o u r s , 2 4 h o u r s ) but n o c o n v e r s i o n w a s o b s e r v e d . T h e r e a c t i o n m i x t u r e w a s a n a l y z e d b y G C u p o n c o m p l e t i n g the r e a c t i o n s , a n d s h o w e d n o m e t h y l ester p e a k s w h e n c o m p a r e d to a c h r o m a t o g r a p h f r o m a p u r e b i o d i e s e l s a m p l e . F u r t h e r m o r e , n o n o t i c e a b l e r e a c t i o n h a d o c c u r r e d w h e n the c o m m e r c i a l s a m p l e o f S n O w a s u s e d u n d e r r e a c t i o n c o n d i t i o n s i d e n t i c a l to those d e s c r i b e d a b o v e . W i t h n o other m a t e r i a l i n the literature o r c o r r e s p o n d e n c e w i t h the authors A b r e u et a l . ( 2 0 0 5 ) to s u p p o r t the a c t i v i t y o f S n O i n t r a n s e s t e r i f i c a t i o n r e a c t i o n , f u r t h e r attempts to p r o d u c e b i o d i e s e l w i t h S n O as the catalyst c e a s e d .  3.4 3.4.1  Sulfonated char synthesis and testing mthods Sulfonated char synthesis procedure  P y r o l y z e d h a r d w o o d c h a r s a m p l e s w e r e o b t a i n e d f r o m R e s o u r c e T r a n s f o r m s International L t d . (Waterloo O N . ) , E n s y n Technologies Inc. (Ottawa, O N ) and D y n a m o t i v E n e r g y Systems C o r p . 45  detector temperatures  were 290°C  and 310°C, respectively, with no derivitization  of  the  samples.  3.3 3.3.1  Tin(II) oxide results and discussion Synthesis and  characterization  T h e first p r o c e d u r e as n o t e d i n A b r e u et a l . ( 2 0 0 5 ) to s y n t h e s i z e S n O d i d not result i n a n y significant y i e l d . T h e post-calcination product was an u n k n o w n substance, d u l l grey-beige i n c o l o u r , i n contrast to the s h i n y b l u e - b l a c k c o l o u r o f a c o m m e r c i a l s a m p l e o f S n O as d e p i c t e d i n F i g u r e s 3.1 a n d 3 . 2 , r e s p e c t i v e l y . A subsequent r e v i e w o f the literature r e v e a l e d that  SnCl2  will  p r e c i p i t a t e as S n O H u n d e r . b a s i c c o n d i t i o n s ( F u j i t a et a l . 1 9 9 0 ) . T h u s it w a s l i k e l y that the c a l c i n e d p r o d u c t w a s s o m e f o r m o f S n O H . N e x t , the m e t h o d o f F u j i t a et a l . (1990) w a s a d o p t e d to s u c c e s s f u l l y p r e p a r e S n O as c o n f i r m e d b y c o m p a r i s o n o f x - r a y d i f f r a c t i o n patterns o f the p r e p a r e d s a m p l e w i t h the literature ( F u j i t a et a l . 1 9 9 0 ) , a n d w i t h the pattern o f a c o m m e r c i a l s a m p l e s h o w n i n F i g u r e s 3.3 a n d 3.4, r e s p e c t i v e l y .  3.3.2  Catalytic  activity  I n i t i a l attempts to p r o d u c e b i o d i e s e l b y r e a c t i n g c a n o l a o i l a n d m e t h a n o l (6:1 A : 0 m o l a r r a t i o , 6 0 ° C , 5 w t . % catalyst u n d e r m a g n e t i c s t i r r i n g a n d r e f l u x ) f o r 3 h o u r s i n the p r e s e n c e o f the s y n t h e s i z e d S n O s a m p l e p r o v e d u n s u c c e s s f u l . S u b s e q u e n t attempts h e l d the catalyst l o a d i n g c o n s t a n t , a n d i n c r e a s e d the A : 0 m o l a r r a t i o ( 9 : 1 , 15:1) a n d r e a c t i o n t i m e s (12 h o u r s , 2 4 h o u r s ) but n o c o n v e r s i o n w a s o b s e r v e d . T h e r e a c t i o n m i x t u r e w a s a n a l y z e d b y G C u p o n c o m p l e t i n g the r e a c t i o n s , a n d s h o w e d n o m e t h y l ester p e a k s w h e n c o m p a r e d to a c h r o m a t o g r a p h f r o m a p u r e b i o d i e s e l s a m p l e . F u r t h e r m o r e , n o n o t i c e a b l e r e a c t i o n h a d o c c u r r e d w h e n the c o m m e r c i a l s a m p l e o f S n O w a s u s e d u n d e r r e a c t i o n c o n d i t i o n s i d e n t i c a l to those d e s c r i b e d a b o v e . W i t h n o other m a t e r i a l i n the literature o r c o r r e s p o n d e n c e w i t h the authors A b r e u et a l . ( 2 0 0 5 ) to support the a c t i v i t y o f S n O i n t r a n s e s t e r i f i c a t i o n r e a c t i o n , f u r t h e r attempts to p r o d u c e b i o d i e s e l w i t h S n O as the catalyst c e a s e d . .  3.4 3.4.1  Sulfonated char synthesis and testing mthods Sulfonated char synthesis procedure  P y r o l y z e d h a r d w o o d c h a r s a m p l e s w e r e o b t a i n e d f r o m R e s o u r c e T r a n s f o r m s International L t d . ( W a t e r l o o O N . ) , E n s y n T e c h n o l o g i e s Inc. ( O t t a w a , O N ) a n d D y n a m o t i v E n e r g y S y s t e m s C o r p . 45  (Vancouver BC) and sulfonated according to the method of (Toda et al. 2005). 200 mL of concentrated sulfuric acid (98%, Sigma) were added to 20 g of char in a 500 mL round bottom flask. The mixture was heated to 150°C with a heating mantle (Fisher Scientific) and monitored with a temperature controller (Omega) and corrosion-resistant Type-J thermocouple (Omega) for 24 hours. After heating, the slurry was added to cool distilled water and then vacuum filtered through #40 Whatman filter paper. The char was washed with 80°C distilled water until the wash water was neutral and free from sulfate ions. Sulfate ions were tested for by precipitation by adding several drops of a 0.66 molar barium chloride solution to the wash water. Following filtration, the char was dried in an oven at 70°C for approximately 2 hours. Samples were characterized by the following techniques: surface area was measured using nitrogen adsorption at -196°C (Micromeritics A S A P 2000) and calculated with the single-point B E T method; elemental composition was determined by elemental analysis (conducted by Canadian Microanalytical Services, Delta, British Columbia); catalyst structure was analyzed via X-ray diffraction (Rigaku Multiflex X-ray diffractometer, 2 kW); surface species bonded to the catalyst surface were determine by X-ray photon spectroscopy; the total and type of acidity of the catalyst were measured by pulse n-propylamine adsorption and temperature-programmed desorption, respectively; and scanning electron microscopy was used to assess the pore size of the catalysts. Three catalyst samples were prepared from three different char samples for catalytic testing. The char samples all originated from fast pyrolysis of the following feedstocks: Catalyst 1, hardwood (RTI); Catalyst 2, hardwoods and softwoods (Ensyn); Catalyst 3, wood waste, white wood, bark and shavings (DynaMotiv).  3.4.2  Sulfonated char testing procedure  The sulfonated char was tested for both transesterification and esterification activities in simple batch experiments. Reactions with canola oil were investigated to test Transesterification. Waste vegetable oil (from U B C Campus Food Outlets) was used to measure the esterification activity of the catalyst. Ethanol was used in order to achieve a higher reaction temperature (due to higher boiling point compared with methanol) and therefore faster reaction (Toda et al. 2005). Reactions were carried out on a hotplate with magnetic stirring under reflux at 76°C. The reaction mixture was analyzed by G C , as described in the Section 3.2.2. Esterification was quantified by measuring the acid number before and after the reaction.  Samples were 46  c e n t r i f u g e d at 5 0 0 0 r p m f o r 15 m i n u t e s to a l l o w p h a s e s e p a r a t i o n . T h e o i l p h a s e w a s t h e n r e c o v e r e d b y pipette a n d titrated f o r a c i d v a l u e u s i n g the M e t r o h m 7 9 4 B a s i c T i t r i n o a u t o m a t i c titrator. R e a c t i o n s w e r e p e r f o r m e d to d e t e r m i n e the effect o f r e a c t i o n t i m e a n d A : 0 m o l a r r a t i o (3 h o u r s , 9 h o u r s a n d 15 h o u r s ; 3 : 1 , 6:1 9 : 1 , 12:1 a n d 15:1) , c a t a l y s t l o a d i n g (1 w t . % , 2.5 w t . % a n d 5 w t . % ) , catalyst s a m p l e ( C a t a l y s t 1, 2 o r 3 ) o n the r e d u c t i o n i n a c i d n u m b e r .  3.5  Sulfonated char results and discussion  3.5.1  Catalyst  3.5.1.1  characterization  BET surface area  T h e three catalyst s a m p l e s w e r e a n a l y z e d f o r s u r f a c e area u s i n g n i t r o g e n a d s o r p t i o n at - 1 9 6 ° C t o d e t e r m i n e B E T s i n g l e p o i n t s u r f a c e area as s h o w n i n T a b l e 3 . 1 . E a c h s a m p l e w a s tested i n t r i p l i c a t e to test f o r r e p r o d u c i b i l i t y . Table 3.1. B E T surface areas for each catalyst sample.  Sample  2  Catalyst 1  A r e a ( m /g) 5.8410.33  Catalyst 2  14.38+1.55  Catalyst 3  2.74 ± 0.60  W h i l e the s u r f a c e area a m o n g s a m p l e s v a r i e s s o m e w h a t , they are a l l q u i t e l o w as is t y p i c a l f o r a b u l k p h a s e , u n s u p p o r t e d catalyst. T h e s u r f a c e area f o r C a t a l y s t 1, w h i c h w a s s y n t h e s i z e d f r o m a h a r d w o o d d e r i v e d s a m p l e o f p y r o l y s i s c h a r i s c o m p a r a b l e to other s u r f a c e area m e a s u r e m e n t s r e p o r t e d f o r h a r d w o o d d e r i v e d c h a r ( D e l i a R o c c a et a l . 1 9 9 9 ) . T h e surface areas o f the catalyst s a m p l e s w e r e a l l greater than that r e p o r t e d b y T o d a et a l . ( 2 0 0 5 ) . T h i s i s l i k e l y d u e to the nature o f the c h a r substrate, w h i c h w e r e a l l f o r m s o f w o o d b i o m a s s . T h e structure o f the c h a r h a d a h i g h l y c o m p l e x n e t w o r k o f p o r e s , c h a n n e l s a n d o t h e r w i s e f i b r o u s r i d g e d surfaces ( o b s e r v e d f r o m S E M p h o t o g r a p h s ) as o p p o s e d to the p l a n a r structure o f the s u g a r - d e r i v e d c h a r ( T o d a et al. 2005).  3.5.1.2  Elemental  Analysis  E l e m e n t a l a n a l y s i s (presented i n T a b l e 3.2) r e v e a l e d the c o m p o s i t i o n o f e a c h catalyst s a m p l e b y m a s s p e r cent, a l o n g w i t h the c o r r e s p o n d i n g m o l e c u l a r f o r m u l a .  47  Table 3.2. Mass per cent composition by element and molecular formula of each catalyst sample.  Sample  C  H  N  O  S  Molecular Formula  Catalyst 1  68.12  2.77  0.11  28.73  2.12  CH0.48Nn.001O0.32S0.011  Catalyst 2  55.17  2.72  0.23  31.62  1.71  CH0.59N0.004O0.43S0.008  Catalyst 3  70.81  2.34  0.13  20.28  1.83  CH0.39N0.001O0.22S0.009  T h e m o l e c u l a r f o r m u l a r e p o r t e d b y T o d a et a l . ( 2 0 0 5 ) f o r t h e i r c a t a l y s t w a s CH0.45S0.01O0.39, w h i c h , e x c e p t f o r the n i t r o g e n c o n t e n t i n the s a m p l e s p r e s e n t e d h e r e , is v e r y c l o s e , i n d i c a t i n g the catalysts p r e s e n t e d here h a v e s i m i l a r c o m p o s i t i o n s b y m a s s .  3.5.1.3  X-Ray Diffraction  Analysis  X R D e x p e r i m e n t s s h o w e d C a t a l y s t 1 w a s an a m o r p h o u s s o l i d , s i m i l a r to the catalyst r e p o r t e d b y T o d a et a l . ( 2 0 0 5 ) . T h e X R D s p e c t r a f o r C a t a l y s t 1 is p r e s e n t e d i n F i g u r e 3.5. X R D s p e c t r a f o r C a t a l y s t s 2 a n d 3 a l s o r e v e a l e d a m o r p h o u s structures.  3.5.1.4  XPS  Analysis  X P S e x p e r i m e n t s w e r e c o n d u c t e d to d e t e r m i n e the s u r f a c e s p e c i e s b o n d e d to the c a t a l y s t c a r b o n substrate. A b r o a d s u r v e y s c a n w a s c o n d u c t e d b e t w e e n b i n d i n g e n e r g i e s o f 0 e V a n d 1 3 5 0 e V . N a r r o w scans w e r e then c o n d u c t e d i n the S 2 p r e g i o n , C I s r e g i o n a n d the O Is r e g i o n . F i g u r e 3.6 presents the s u r v e y s c a n f o r C a t a l y s t 1, w h i l e F i g u r e s 3.7 a n d 3.8 present the n a r r o w scans f o r the S 2 p a n d C 1 s r e g i o n s , r e s p e c t i v e l y . T h e n a r r o w O l s s c a n is not s h o w n .  T h e p e a k i n F i g u r e 3.7 o c c u r s at a p p r o x i m a t e l y  169 e V , w h i c h c o r r e s p o n d s to the b o n d e d  sulfate g r o u p s ( S O 4 ) . T h i s is i n contrast to the results r e p o r t e d b y T o d a et a l . ( 2 0 0 5 ) , w h o 2  i n d i c a t e d that S O 3 H w a s the b o n d e d s u l f u r s p e c i e s .  T h e r e are t w o p e a k s i n F i g u r e 3.8. T h e first, at 2 8 5 e V , c o r r e s p o n d s to e l e m e n t a l c a r b o n , w h i c h is the substrate o f the catalyst. T h e s e c o n d , ( v e r y s m a l l p e a k ) o b s e r v e d i n F i g u r e 3.8 at 2 8 9 e V c o r r e s p o n d s to c a r b o x y l i c a c i d g r o u p s ( C O O H ) w h i c h is i n a g r e e m e n t w i t h the results o f T o d a et a l . ( 2 0 0 5 ) w h o a l s o r e p o r t e d the p r e s e n c e o f C O O H " g r o u p s .  3.5.1.5  n-Propylamine  adsorption and temperature programmed de sorption  S a m p l e s w e r e tested f o r total a c i d i t y b y p u l s e c h e m i s o r p t i o n e x p e r i m e n t s , a n d then s u b j e c t e d to a temperature p r o g r a m m e d d e s o r p t i o n ( T P D ) to d e t e r m i n e the type o f a c i d sites. S a m p l e s w e r e 48  pretreated by holding the reactor temperature at 250°C for two hours in order to remove water and any adsorbed species. The sample temperature was then decreased to 120°C. After the thermal conductivity detector (TCD) readings had stabilized, the pulse experiments were conducted. The procedure was as follows. The sample loop was opened for two minutes, which allowed 1 mL of He gas containing 17.57 pmol of n-propylamine to fill the loop. At the end of the two minute period, the sample was injected into the reactor, and the outlet flow of npropylamine measured by the TCD, logged by a multimeter (Fluke) and recorded by simple data logging software (FlukeView). After the baseline returned to an acceptable level (in all experiments the baseline was allowed to return to approximately 0.016 mV rather than 0.000 mV to reduce the length of the experiment) the sample loop was opened for two minutes and allowed to fill. The injection process was then repeated, until the peaks recorded appeared identical. In each experiment, nine pulse events were recorded. The adsorption peaks were integrated to determine the area of each one. Generally speaking, the first four of the nine peaks (Figure 3.9) of the analysis showed adsorption of the n-propylamine, while peaks 5 and beyond indicated that the catalyst sample was saturated, and therefore no n-propylamine was adsorbed.  The amount of n-propylamine adsorbed during peaks 1 -4 was determined by dividing the area of each peak (from 1-4) by the average area of the saturated peaks. The total adsorption was found by adding the per cent adsorbed for peaks 1-4 and then divided by the sample mass to give a normalized value. After the pulse experiments, samples were allowed to sit for 1 hour at 120°C to remove any physisorbed species. The reactor temperature was then increased at a rate of 5°C/min to 700°C and then held for 30 minutes. The results of the pulse experiments are shown in Table 3.3 below. Table 3.3. Total acidity for each catalyst sample.  Sample Catalyst 1 Catalyst 2 Catalyst 3  Total acidity (Limol/g) 43.3 83.4 36.3  The total acidity of the catalysts presented here is much less than that reported by Toda et al. (2005), who achieved a total acidity of 1.4 mmol/g with the catalyst prepared from sulfuric acid. It is interesting to note however, that the acidity of the prepared catalysts is similar to the acidity 49  o f the tungstated z i r c o n i a a n d s u l f a t e d z i r c o n i a (54 Limol/g a n d 9 4 | a m o l / g , r e s p e c t i v e l y ) tested b y ( L o p e z et a l . 2 0 0 5 ) .  T h e T P D c u r v e s f o r C a t a l y s t s 1 a n d 2 are p r e s e n t e d i n F i g u r e s 3.10 a n d 3 . 1 1 , r e s p e c t i v e l y . E a c h TPD  curve follows  the  s a m e pattern,  a n d e a c h p e a k o c c u r s at a p p r o x i m a t e l y  the  same  temperature, i n d i c a t i n g that the types o f a c i d sites o n e a c h catalyst are the s a m e . S i n c e the p e a k s o c c u r at temperatures greater than 3 0 0 ° C , the a c i d i t y o f the catalysts c a n b e attributed e n t i r e l y to B r 0 n s t e d a c i d sites ( M i c r o m e r i t i c s 2 0 0 3 ) . T h e T P D c u r v e s w e r e d e c o n v o l u t e d a n d f o u r s u b p e a k s c a n b e o b s e r v e d , n u m b e r e d 1 to 4 o n F i g u r e s 3.10 a n d 3 . 1 1 . T h e s o l i d l i n e s h o w s the T C D r e a d i n g as a f u n c t i o n o f t i m e ( i n d i c a t e d o n e a c h T P D c u r v e ) , w h i l e the dotted l i n e s h o w s the T C D r e a d i n g as a f u n c t i o n o f temperature. T h e t i m e - s e r i e s c u r v e has b e e n d e c o n v o l u t e d . •  A b o v e 3 0 0 ° C the n - p r o p y l a m i n e d e c o m p o s e s to p r o p y l e n e a n d a m m o n i a . In the T P D a n a l y s i s , the  NH3  peak  lags  the  peak  for  propylene.  Of  the  smaller  peaks  resulting  from  the  d e c o n v o l u t i o n , the first t w o p e a k s (1 a n d 2 , i n d i c a t e d o n F i g u r e s 3.10 a n d 3.11) c a n b e attributed to p r o p y l e n e a n d a m m o n i a d e s o r p t i o n , r e s p e c t i v e l y , f r o m a w e a k B r 0 n s t e d a c i d site, w h i c h c o r r e s p o n d s to the p r e s e n c e o f C O O H " g r o u p s as d e t e r m i n e d b y X P S . T h e t h i r d a n d f o u r t h p e a k s ( n u m b e r e d 3 a n d 4 o n F i g u r e s 3.10 a n d 3.11) represent d e s o r p t i o n o f p r o p y l e n e a n d a m m o n i a , r e s p e c t i v e l y , f r o m strong B r 0 n s t e d a c i d sites, w h i c h correlates w i t h the S 0  2 4  " groups observed i n  the X P S spectra f o r e a c h catalyst. In o r d e r to c h e c k that the d e c o n v o l u t i o n g a v e a r e a s o n a b l e result, the ratio o f the a m m o n i a p e a k area d i v i d e d b y the p r o p y l e n e p e a k area c a n b e c a l c u l a t e d . S i n c e p r o p y l e n e a n d a m m o n i a are f o r m e d i n e q u i m o l a r a m o u n t s f r o m the d e c o m p o s i t i o n o f n p r o p y l a m i n e , the p e a k areas f o r e a c h s p e c i e s s h o u l d b e e q u a l i f the d e c o n v o l u t i o n o f the T P D c u r v e w a s d o n e c o r r e c t l y . H o w e v e r , the t h e r m a l c o n d u c t i v i t y o f a m m o n i a is s l i g h t l y greater t h a n that o f p r o p y l e n e ( 0 . 0 4 0 9 a n d 0 . 0 3 2 4 W / m . K , r e s p e c t i v e l y ) ; therefore the area o f the a m m o n i a p e a k s h o u l d b e l a r g e r b y a f a c t o r o f 1.26, i.e., the r a t i o o f the t h e r m a l c o n d u c t i v i t i e s o f the t w o s p e c i e s . C h e c k i n g the area ratios f o r e a c h set o f p e a k s i n F i g u r e 3.10 g i v e s ratios o f 1.35 f o r p e a k s 1 a n d 2 , a n d 1.13 f o r p e a k s 3 a n d 4 , w h i c h are w i t h i n 7 % a n d 1 0 % error, r e s p e c t i v e l y , o f the t h e o r e t i c a l v a l u e o f 1.26. F o r catalyst 2, the area ratios w e r e . 1.24 f o r p e a k s 1 a n d 2 ( 2 % d e v i a t i o n ) a n d 1.02 f o r p e a k s 3 a n d 4 ( 1 9 % d e v i a t i o n ) . T h i s i n d i c a t e s the results o f  the  d e c o n v o l u t i o n are r e a s o n a b l e . W i t h a r e l i a b l e d e c o n v o l u t i o n , the r e l a t i v e a m o u n t s o f e a c h type o f a c i d site c a n b e d e t e r m i n e d b y c o m p a r i n g the areas o f the a m m o n i a p e a k s . In the case o f 50  C a t a l y s t 1, the p e a k area f o r the strong a c i d sites w a s greater b y a p p r o x i m a t e l y 1 7 % , i n d i c a t i n g the t o t a l a c i d i t y o f the catalyst w a s s k e w e d s l i g h t l y i n f a v o u r o f the strong SO4 " sites. T h i s is i n 2  contrast to the result r e p o r t e d b y ( T o d a et a l . 2 0 0 5 ) , i n d i c a t i n g that 0.7 m m o l / g o f the t o t a l 1.4 m m o l / g a c i d i t y c o u l d b e attributed to the S O 3 H g r o u p s i n c o r p o r a t e d i n t o the catalyst. T h e T P D c u r v e f o r C a t a l y s t 2 ( F i g u r e 3.11) s h o w s a h i g h e r p r o p o r t i o n o f w e a k a c i d sites. T h e T P D c u r v e f o r C a t a l y s t 3 (not s h o w n ) c o u l d not b e s a t i s f a c t o r i l y d e c o n v o l u t e d ; i.e.the ratio o f p e a k areas f o r e a c h p a i r o f p r o p y l e n e a n d a m m o n i a p e a k s w a s n e v e r s a t i s f a c t o r i l y c l o s e e n o u g h to the t h e o r e t i c a l ratio o f 1.26. T h i s c o u l d b e d u e to e m i s s i o n o f v o l a t i l e c o m p o n e n t s w i t h i n the c h a r that are not present w i t h i n the other t w o s a m p l e s . In any c a s e , n o i n f o r m a t i o n r e g a r d i n g the d i s t r i b u t i o n o f a c t i v e sites w a s a s c e r t a i n e d f o r C a t a l y s t 3.  3.5.1.6  SEM  Experiments  V i s u a l o b s e r v a t i o n o f the catalyst s a m p l e s v i a S E M w a s p e r f o r m e d to g a i n i n s i g h t i n t o c a t a l y s t m o r p h o l o g y a n d p o r e s i z e . A l l s a m p l e s w e r e o b s e r v e d w i t h the s a m e a c c e l e r a t i o n v o l t a g e o f 2 0 k V . A s s h o w n i n F i g u r e s 3 . 1 2 to 3 . 1 4 , the catalyst s a m p l e s h a v e a h i g h l y i r r e g u l a r , c o n v o l u t e d f i b r o u s s u r f a c e structure, w i t h l i t t l e r e g u l a r t e x t u r i n g . D i s c r e t e p o r e s w e r e v i s i b l e i n s o m e i m a g e s o f C a t a l y s t 1, (pore d i m e n s i o n s are i n d i c a t e d i n the f i g u r e ) . H o w e v e r this w a s a r a r i t y a m o n g the s a m p l e s a n a l y z e d . T h e s a m p l e s w e r e a l s o b r i e f l y i n v e s t i g a t e d v i a e n e r g y d i s p e r s i v e X - r a y a n a l y s i s ( E D X ) to attempt to l o c a t e the a c t i v e sites o f the catalyst b y a n a l y z i n g the d i s t r i b u t i o n o f x - r a y s e m i t t e d b y s u l f u r a t o m s u p o n e x c i t e m e n t b y the e l e c t r o n b e a m . H o w e v e r , the r e s o l u t i o n o f the E D X t e c h n i q u e d w a s not f i n e e n o u g h to p i n p o i n t the l o c a t i o n o f the s u l f u r e l e m e n t s . U n f o r t u n a t e l y , the S E M a n d E D X e x p e r i m e n t s y i e l d e d l i t t l e i n s i g h t i n t o n e i t h e r the nature a n d l o c a t i o n o f the catalyst a c t i v e sites, n o r the effect o f catalyst m o r p h o l o g y o n c a t a l y t i c activity.  3.5.2  Sulfonated char catalytic  activity  P r e l i m i n a r y tests w i t h the s u l f o n a t e d c h a r a n d c a n o l a o i l (6:1 A : 0 r a t i o , 3 h o u r s ) i n d i c a t e d s l i g h t transesterification  activity.  G C a n a l y s i s s h o w e d ethyl-ester p e a k s i n the r e a c t i o n  mixture;  h o w e v e r , the a m o u n t w a s t o o s m a l l to be a c c u r a t e l y q u a n t i f i e d . W h e n the r e a c t i o n w a s a l l o w e d to r u n f o r 2 4 h o u r s at a h i g h e r A : 0 ratio ( 1 5 : 1 ) , n o v i s i b l e i n c r e a s e i n the a m o u n t o f b i o d i e s e l p r o d u c e d w a s o b s e r v e d , a l t h o u g h G C a n a l y s i s s h o w e d the f o r m a t i o n o f s o m e ethyl-esters, i n d i c a t i n g there is s o m e f o r m o f r e s i s t a n c e to t r a n s e s t e r i f i c a t i o n a s s o c i a t e d w i t h the use o f the sulfonated char. 51  P r e l i m i n a r y tests w i t h w a s t e v e g e t a b l e o i l c o l l e c t e d f r o m the U B C B i o d i e s e l P i l o t P l a n t w e r e m o r e f a v o u r a b l e . T h e o i l w a s a n a l y z e d f o r a c i d n u m b e r b e f o r e a n d after the r e a c t i o n , a n d w a s f o u n d that at 12:1 A : 0 m o l a r r a t i o a n d 3 h o u r s , the a c i d n u m b e r d e c r e a s e d f r o m 8.5 m g K O H / g to 4.5 m g K O H / g .  A d d i t i o n a l l y , qualitative transesterification activity  was observed upon  a n a l y s i s o f the r e a c t i o n m i x t u r e b y G C . S i n c e the catalyst i n d i c a t e d f a v o u r a b l e e s t e r i f i c a t i o n p r o p e r t i e s , a set o f s c r e e n i n g e x p e r i m e n t s w a s c o n d u c t e d to d e t e r m i n e the effect o f A : 0 m o l a r r a t i o , t i m e a n d catalyst a m o u n t o n a b i l i t y o f the c a t a l y s t to r e d u c e the F F A present i n the o i l . M o l a r ratios i n v e s t i g a t e d w e r e 6 : 1 , 9 . 5 : 1 , 1 8 : 1 , 28:1 38:1 a n d 4 8 : 1 , a n d r e a c t i o n t i m e w a s c h a n g e d b e t w e e n 3 h, 9 h a n d 15 h at a f i x e d catalyst a m o u n t o f 5 w t . % b a s e d o n the m a s s o f w a s t e v e g e t a b l e o i l . T h e r a n g e o f m o l a r ratios w a s s e l e c t e d b a s e d o n the range o f ratios tested i n the literature ( F u r u t a et a l . 2 0 0 4 ; L o p e z et a l . 2 0 0 5 ; J i t p u t t i et a l . 2 0 0 6 ) . T o d e t e r m i n e the effect o f catalyst a m o u n t o n the r e a c t i o n , catalyst l o a d i n g w a s set at 1 w t . % , 2 . 5 % a n d 5 w t . % at a f i x e d A : 0 m o l a r r a t i o o f 28:1 a n d t i m e o f 3 h o u r s .  F i g u r e 3.15 s h o w s the effect o f r e a c t i o n t i m e at a f i x e d A : 0 m o l a r r a t i o o n the r e d u c t i o n i n F F A . E x c e p t i n the l o w m o l a r ratio cases (6:1 a n d 9.5:1 r e a c t i o n s ) , i n c r e a s i n g the r e a c t i o n t i m e a l l o w e d f o r a greater r e d u c t i o n i n F F A content. T h e f i n a l a c i d n u m b e r f o r b o t h the 6:1 a n d 9.5:1 cases stayed r e l a t i v e l y c o n s t a n t , w h i c h suggests that the r e a c t i o n reaches e q u i l i b r i u m  fairly  q u i c k l y , a n d that i n c r e a s e i n t i m e d o e s l i t t l e to f u r t h e r d r i v e the r e a c t i o n f o r w a r d . H o w e v e r , w h e n the A : 0 m o l a r ratio is i n c r e a s e d to 18:1 a n d b e y o n d , a s i g n i f i c a n t d r o p i n the f i n a l a c i d n u m b e r c a n b e o b s e r v e d , s u g g e s t i n g that the i n c r e a s e d A : 0 m o l a r ratio p l a y s an i m p o r t a n t r o l e i n d r i v i n g the e q u i l i b r i u m t o w a r d the p r o d u c t s .  A b o v e the 18:1 A : 0 m o l a r ratio, there is o n l y a s l i g h t d i f f e r e n c e b e t w e e n the f i n a l a c i d n u m b e r s that c a n b e attributed to i n c r e a s e d m o l a r ratios, i n d i c a t i n g that i n c r e a s i n g the r e a c t i o n t i m e p l a y s a greater r o l e i n the c o n v e r s i o n o f the F F A .  F i g u r e 3.16 illustrates the effect o f A : 0 m o l a r r a t i o at f i x e d r e a c t i o n t i m e o n the r e d u c t i o n i n F F A . A t l o w m o l a r ratios, c o n v e r s i o n o f F F A is r e l a t i v e l y l o w . H o w e v e r , it r a p i d l y i n c r e a s e s as the A : 0 m o l a r r a t i o i n c r e a s e s f r o m 6:1 to 1 8 : 1 , a n d b e g i n s to p l a t e a u w i t h a n y f u r t h e r i n c r e a s e s i n A : 0 m o l a r ratio. T h e e r r o r bars p r e s e n t e d o n the 15 h o u r t r i a l g i v e a sense o f the v a r i a b i l i t y  52  associated with the reaction and the quantification, and indicate that there might not be any quantifiable difference in the reduction in F F A when compared between the three reaction times, as the error bars overlap the other measurements. This has positive implications in an economic sense: since similar reaction conversion can be achieved in shorter times, this permits smaller reactor residence times, decreasing the size of the reactor; allowing for greater reactant throughput, both of which improve the economics of a production process as described by West et al. (2006).  Figure 3.17 presents the effect of A : 0 molar ratio on F F A conversion, specifically for the 15 hour reaction, to give a greater sense of the variability of the experiments. The curve clearly shows that increasing the A : 0 molar ratio to the maximum ratio investigated has an impact on the reduction in F F A . However, the variability of the 18:1, 28:1 and 38:1 measurements suggests that the improvement observed by increasing the A : 0 molar ratio beyond 18:1 may be difficult to accurately quantify.  Figure 3.18 illustrates the effect of catalyst amount on the conversion of F F A in the W V O . Increasing the catalyst amount in the reaction mixture increases the conversion of F F A . A greater amount of catalyst increases the number of active sites available for esterification which allows the reaction conversion to increase for a given amount of time. A similar effect on reaction conversion was observed by Kiss et al. (2006) for the esterification of oleic acid with sulfated zirconia.  Figure 3.19 presents the final acid number obtained at 28:1 A : 0 molar ratio, 5 wt.% catalyst after 3 hours for each catalyst sample. While Catalysts 1 and 3 performed relatively similarly under identical reaction conditions, it is curious that under the same reaction conditions Catalyst 2 could only achieve a final acid number of 1.94, i.e., double the final acid number in the Catalyst 1 and 3 reactions, especially in consideration of the higher total acidity of Catalyst 2. It is assumed that with a higher total acidity, there are a greater number of active sites available to the reactants on the catalyst, and therefore the more acidic catalyst would show greater activity. However, it may be that the type of site is an important influence on catalyst activity. Catalyst 2 indicated a higher proportion of weak acid sites (sites with the COOH" species bonded) than did Catalyst 1, and if the weak acid sites do not catalyze the reaction as quickly or effectively (i.e. 53  the p r o t o n o n the C O O H " g r o u p m a y b e v e r y s l o w to d i s s o c i a t e a n d attack the c a r b o x y l g r o u p o n the F F A ) as the s t r o n g a c i d sites (SO4 "), this m a y a c c o u n t f o r the lesser a c t i v i t y o b s e r v e d w i t h 2  C a t a l y s t 2.  It w a s also d e s i r e d to test the catalyst f o r its a b i l i t y to c a t a l y z e e s t e r i f i c a t i o n r e a c t i o n s i n a W V O w i t h a v e r y h i g h F F A content. T h e s a m p l e o f W V O u s e d i n the c a t a l y t i c trials w a s s p i k e d w i t h a s m a l l a m o u n t o f o l e i c - a c i d ( S i g m a ) i n o r d e r to i n c r e a s e the a c i d n u m b e r o f the W V O to 2 4 . 5 (approximately  12.25 w t . % F F A ) . T h e r e a c t i o n w a s r u n at a n a l c o h o l - t o - F F A m o l a r ratio o f  160:1 ( M b a r a k a a n d S h a n k s 2 0 0 5 ) , w h i c h translates to a n A : 0 m o l a r r a t i o o f 7 8 : 1 . A l t h o u g h these c o n d i t i o n s are h i g h e r than w h a t w o u l d b e u s e d i n a n i n d u s t r i a l setting, they w e r e c h o s e n to p r o v i d e a p o i n t o f c o m p a r i s o n to the h i g h l y c o m p l e x catalyst p r e p a r e d b y M b a r a k a a n d S h a n k s ( 2 0 0 5 ) . T h e catalyst l o a d i n g w a s 5 wt.%, a n d the r e a c t i o n t i m e w a s 3 h o u r s . In three separate t r i a l s , the a c i d n u m b e r w a s r e d u c e d to an average v a l u e o f 2.08 ± 0 . 1 9 m g K O H / g ( r o u g h l y 1 w t . % F F A content). In contrast, the catalyst o f M b a r a k a a n d S h a n k s (2005) w a s a b l e to r e d u c e the a m o u n t o f F F A i n a 15 w t . % p a l m i t i c a c i d / s o y b e a n o i l s a m p l e to a p p r o x i m a t e l y 2  wt.%.  W h i l e the authors d i d not i n d i c a t e the m a x i m u m a m o u n t o f F F A content the catalyst c o u l d r e m a i n a c t i v e u n d e r , it is c l e a r that the catalyst p r e p a r e d i n this study p e r f o r m s c o m p a r a b l y w e l l to the catalyst p r e p a r e d b y M b a r a k a a n d S h a n k s ( 2 0 0 5 ) , but w i t h the a d v a n t a g e o f r e q u i r i n g a considerably simpler method of preparation.  3.6  Conclusion  A study i n t o the e f f e c t i v e n e s s o f tin(II) o x i d e as a catalyst f o r the t r a n s e s t e r i f i c a t i o n o f v e g e t a b l e o i l w a s c o n d u c t e d . S n O w a s s y n t h e s i z e d v i a the m e t h o d o f F u j i t a et a l . ( 1 9 9 0 ) after attempts to s y n t h e s i z e S n O u s i n g the  procedure described by  A b r e u et  al. (2005)  failed. Both  synthesized sample and a c o m m e r c i a l sample o f S n O s h o w e d no catalytic activity  the  during  r e a c t i o n s r u n at 6 0 ° C w i t h m e t h a n o l a n d c a n o l a o i l u n d e r r e f l u x .  A s e c o n d catalyst, s u l f o n a t e d p y r o l y s i s c h a r , w a s s y n t h e s i z e d b a s e d o n the t e c h n i q u e o f T o d a et a l . ( 2 0 0 5 ) et a l . C h a r a c t e r i z a t i o n o f the catalyst r e v e a l e d a n i r r e g u l a r , p o r o u s c a r b o n f r a m e w o r k with C O O H " and S 0  2 4  " g r o u p s b o n d e d to the s u r f a c e . T h e t o t a l a c i d i t y o f the catalyst as r e v e a l e d  b y p u l s e n - p r o p y l a m i n e e x p e r i m e n t s (36 - 8 4 Limol/g) w a s s i m i l a r to that r e p o r t e d b y L o p e z et al. (2005)  for  s u l f a t e d z i r c o n i a . C a t a l y t i c tests w i t h c a n o l a o i l a n d e t h a n o l s h o w e d  only  q u a l i t a t i v e t r a n s e s t e r i f i c a t i o n . H o w e v e r , the catalyst w a s v e r y a c t i v e i n the e s t e r i f i c a t i o n  of 54  F F A s . E x p e r i m e n t s i n d i c a t e d that c o n v e r s i o n o f F F A s i n c r e a s e d w i t h i n c r e a s e d r e a c t i o n t i m e , i n c r e a s e d a l c o h o l to v e g e t a b l e o i l m o l a r r a t i o , a n d i n c r e a s e d c a t a l y s t l o a d i n g . It w a s f o u n d that at a catalyst l o a d i n g o f 5 w t . % , r e a c t i o n t i m e o f 3 h o u r s a n d A : 0 ratio o f 18:1 g a v e the best results. S l i g h t i n c r e a s e s i n F F A c o n v e r s i o n w e r e o b s e r v e d at m o l a r ratios b e y o n d 18:1 a n d r e a c t i o n t i m e s o f 9 h o u r s a n d 15 h o u r s , but the d i f f e r e n c e s w e r e not q u a n t i f i a b l e d u e to the v a r i a b i l i t y a s s o c i a t e d w i t h the m e a s u r e m e n t s . T h e c a t a l y s t w a s a l s o tested f o r feeds w i t h h i g h e r F F A c o n c e n t r a t i o n s . It w a s f o u n d that the catalyst w a s c a p a b l e o f r e d u c i n g the a m o u n t o f F F A s f r o m 12.25 w t . % to a p p r o x i m a t e l y 1.04 w t . % ( w h i c h c o r r e s p o n d s to a decrease i n a c i d n u m b e r f r o m 2 4 . 5 to 2 . 0 4 m g K O H / g ) , w h i c h w a s c o m p a r a b l e w i t h the h i g h l y c o m p l e x m e s o p o r o u s s i l i c a catalyst tested b y ( M b a r a k a a n d S h a n k s 2 0 0 5 ) .  S u l f o n a t e d c h a r s h o w s c o n s i d e r a b l e p o t e n t i a l f o r use as a catalyst i n b i o d i e s e l p r o d u c t i o n , e s p e c i a l l y i n a c o n t e x t u s e d to r e d u c e the free fatty a c i d content o f a v e g e t a b l e o i l f e e d s t o c k . H o w e v e r , f o r its true p o t e n t i a l to b e r e a l i z e d , the l i m i t a t i o n s to t r a n s e s t e r i f i c a t i o n a s s o c i a t e d w i t h this catalyst m u s t b e r e v e a l e d a n d o v e r c o m e . F u t u r e r e s e a r c h w i l l b e d i r e c t e d t o w a r d this goal.  Acknowledgements The  authors  gratefully  acknowledge  the  financial  support  of  the  Natural  Sciences  E n g i n e e r i n g R e s e a r c h C o u n c i l , the i n - k i n d support o f D r . K e v i n J. S m i t h , M r . I A b u  and for  assistance w i t h the B E T m e a s u r e m e n t s , D r . X . B . L i u f o r h i s t r e m e n d o u s h e l p w i t h the np r o p y l a m i n e e x p e r i m e n t s a n d interpretation o f the r e s u l t s , D r . A j a y K . D a l a i f o r p r o v i d i n g the E n s y n and D y n a m o t i v char samples and M r . J u l i a n R a d l e i n for his ideas, input and discussion w i t h r e g a r d to the use o f the p y r o l y s i s c h a r as a catalyst substrate.  55  Figure 3.1. Sample of unknown substance obtained during SnO preparation via method of Abreu et al. (2005).  70006000 4 5000 ^  4000  '55 B  3000 2000 1000  l— 20  40  30  50  60  2(9) (degrees)  Figure 3.3. X R D pattern of SnO sample prepared by method of Fujita et al. (1990).  12000H  10000-  8000-  <=  6000 4  4000-  2000-  I—  20  ~i  30  1  1  '  40 2(0) (degrees)  Figure 3.4. X R D pattern of commercial SnO sample.  r~  50  60  10  20  30  40  50  60  - r 80  -  I—  70  26 (degrees)  Figure 3.5. Catalyst 1 X R D pattern.  160000 -i  o  140000120000100000-  o  80000 -  o 60000 40000 20000 0-20000 1400  1200  1000  800  600  Binding energy (eV)  Figure 3.6. X P S survey scan for Catalyst 1.  400  200  90  320030002800-  jv'V  !!'  2600^  2400-  Jj  2200-  c  2000180016001400H 1200 176  174  172  170  168  166  164  162  160  282  280  Binding energy (eV)  Figure 3.7. Narrow scan in S 2p region for Catalyst 1.  c o CO  O  80000 70000 60000 >, "55  c £ _c  50000 40000  I. o o o  30000 20000 10000 0294  292  290  288  286  Binding energy (eV)  Figure 3.8. Narrow scan in C 1 s region for Catalyst 1.  284  Peaks 5-9 0.005 4  Peaks 1 -4  0.004 •  <9  0.003 •  a> w Q O  0.002 4  0.001  Li  o.ooo •  2000  4000  6000  1  8000  10000  Time (s)  Figure 3.9. n-Propylamine pulse adsorption peaks for Catalyst 1.  0.0011  n  l 100  '  1 200  '  1  300  1  1  400  '  1  500  '  1  600  '  r~ 700  Temperature (C)  Figure 3.10. T P D curve for Catalyst 1. Ratio of weak acid sites to strong acid sites is 0.85:1.  Figure 3.12 S E M image of Catalyst 1 indicating pore sizes.  —•3.5-  6:1 9.5:1  A  18:1 28:1  3.0-  38:1 4  .o> 2.5X O  48:1  E _§  1.5-  A  1.04  0.5-  0.0-  Reaction time (hours)  Figure 3.15. Effect of reaction time on final acid number. Reactions were run at 5 wt.% catalyst 1 with ethanol at ArO molar ratios of 6:1, 9.5:1, 18:1, 28:1, 38:1, 48:1.  3 hour reaction 9 hour reaction 15 hour reaction  3.0-  9  2.0-  1.5-  1.0-  O  0.5-  0.010  -r— 15  I  20  25  I 30  I 35  —i— —I— —|— 40 45 50 1  1  55  Alcohol to oil molar ratio  Figure 3.16. Effect of A : 0 molar ratio at fixed reaction time on final acid number. 5 wt.% catalyst 1.  63  3.5-  3.0-  f>  2.5  O X. °> 2.0  I i  CD  1  1-5  3  •g 'o <  1.0  I  0.5  1  1  10  20  •  1  1  30  40  50  A l c o h o l to oil molar ratio  Figure 3.17. Effect of A : Q molar ratio on final acid number for the 15 hour set of reactions. 5 wt.% Catalyst 1  3.5  _  3.0-  O *  2.5  TO I  TO  " o 2.0 n • .Q 3  H  15-  <  1.0  Catalyst amount (wt.%)  Figure 3.18. Effect of catalyst amount on final acid number. 28:1 A : 0 molar ratio, ethanol, 5 wt.% catalyst 1.  64  • Catalyst 1  2.50  • Catalyst 2 Catalyst 3  X 2.00 o O) 1.50  E  to  £ 1-00  "5 0.50 <  0.00  Catalyst s a m p l e  Figure 3.19. Final acid number of reaction mixture after reaction with each catalyst sample. 3 hour reaction, 28:1 A : 0 molar ratio, 5 wt.% catalyst loading  65  3.7  References  A b r e u , F. R., A l v e s , M . B . , M a c e d o , C . C . S . , Z a r a , L. F. and Suarez, P. A . Z . (2005). N e w m u l t i - p h a s e c a t a l y t i c systems b a s e d o n t i n c o m p o u n d s a c t i v e f o r vegetable o i l transesterification reaction. Journal of M o l e c u l a r Catalysis A : C h e m i c a l 227(1-2): 2 6 3 267. B r i d g w a t e r , A . 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G r e e n c h e m i s t r y : B i o d i e s e l m a d e w i t h sugar catalyst. N a t u r e ( L o n d o n , U n i t e d K i n g d o m ) 4 3 8 ( 7 0 6 5 ) : 178. 66  Tyson, K . S. B i o d i e s e l : H a n d l i n g and U s e Guidelines. http://www.eere.energy.gov/biomass/pdfs/biodiesel  handling.pdf (November 28, 2004).  W a r a b i , Y . , K u s d i a n a , D . a n d S a k a , S . ( 2 0 0 4 ) . R e a c t i v i t y o f t r i g l y c e r i d e s a n d fatty a c i d s o f rapeseed o i l i n supercritical alcohols. Bioresource T e c h n o l o g y 91(3): 283-287. W e s t , A . H . , Posarac, D . and E l l i s , N . (2006). Assessment o f four biodiesel production processes using hysys.Plant. Bioreseource T e c h n o l o g y (Submitted for publication February 2006). Z h a n g , Y . , D u b e , M . A . , M c L e a n , D . D . and Kates, M . (2003). B i o d i e s e l production f r o m waste c o o k i n g o i l : 2. E c o n o m i c assessment a n d s e n s i t i v i t y a n a l y s i s . B i o r e s o u r c e T e c h n o l o g y 90(3): 229-240.  67  4 4.1  Conclusion, General Discussion and Recommendations General discussion  C h a p t e r 2 f e a t u r e d f o u r c o n t i n u o u s p r o c e s s e s to p r o d u c e b i o d i e s e l at a rate o f 8 0 0 0 t o n n e s / y e a r that w e r e d e s i g n e d a n d s i m u l a t e d i n H Y S Y S . P l a n t , w i t h the a i m o f c o n d u c t i n g a n e c o n o m i c e v a l u a t i o n to d e t e r m i n e w h i c h p r o c e s s y i e l d e d the m o s t c o s t e f f e c t i v e m e a n s o f p r o d u c i n g b i o d i e s e l . A s p r e v i o u s l y m e n t i o n e d , the c o m p o n e n t t r i o l e i n w a s u n a v a i l a b l e i n the H Y S Y S d a t a b a n k s , a n d therefore h a d to b e created. C e r t a i n parameters w e r e i m p o r t e d f r o m the A S P E N Plus  databanks where  triolein  w a s a v a i l a b l e as a c o m p o n e n t .  H o w e v e r , o n e k e y set o f  p a r a m e t e r s , the A n t o i n e ' s c o e f f i c i e n t s w e r e n o t a v a i l a b l e i n A S P E N P l u s a n d therefore h a d to b e estimated i n H Y S Y S .  ASPEN  P l u s w a s u s e d to d o u b l e c h e c k the results o f the H Y S Y S  A n t o i n e ' s c o e f f i c i e n t e s t i m a t i o n , b y u s i n g A S P E N P l u s to e s t i m a t e its o w n set o f A n t o i n e ' s c o e f f i c i e n t s a n d then g r a p h i n g the v a p o u r pressure as a f u n c t i o n o f temperature. D o i n g s o r e v e a l e d s o m e t h i n g o f a n a n o m a l y . A t l o w temperatures, it w a s f o u n d that the v a p o u r pressure c u r v e f o r t r i o l e i n c r o s s e d that o f g l y c e r o l a n d m e t h y l - o l e a t e , i n d i c a t i n g it h a d a h i g h e r v a p o u r pressure, w h i c h w a s c o m p l e t e l y u n e x p e c t e d . It w a s e x p e c t e d that s u c h a l a r g e m o l e c u l e w o u l d h a v e a m u c h l o w e r v a p o u r pressure. U s i n g the H Y S Y S  A n t o i n e ' s c o e f f i c i e n t s to p r o d u c e a  v a p o u r p r e s s u r e c u r v e r e v e a l e d the s a m e p h e n o m e n a . A r e v i e w o f the literature w a s u n d e r t a k e n to o b t a i n v a p o u r p r e s s u r e d a t a f o r t r i o l e i n i n o r d e r to m o r e a c c u r a t e l y p r e d i c t the A n t o i n e ' s c o e f f i c i e n t s . U n f o r t u n a t e l y , the d a t a w e r e either t o o l i m i t e d o r w e r e u n s a t i s f a c t o r y a n d therefore u n s u i t a b l e f o r use. In l i g h t o f the s i t u a t i o n , the p a r a m e t e r s e s t i m a t e d b y H Y S Y S w e r e a s s u m e d to b e the best a v a i l a b l e a n d u s e d f o r the s i m u l a t i o n . W h i l e it i s d e s i r a b l e to use the m o s t accurate c o r r e l a t i o n p o s s i b l e s i m p l y f o r the s a k e o f c o r r e c t n e s s , c o r r e c t parameters w i l l a l s o i m p r o v e the s i m u l a t i o n r e s u l t s , b y g i v i n g a m o r e accurate s i m u l a t i o n o f the m e t h y l - o l e a t e / t r i o l e i n s e p a r a t i o n i n the s e c o n d d i s t i l l a t i o n c o l u m n . A s s u m i n g that H Y S Y S i s o v e r p r e d i c t i n g the v a p o u r p r e s s u r e f o r t r i o l e i n , this w i l l result i n h i g h temperatures r e q u i r e d to separate the t w o c o m p o n e n t s , i n c r e a s i n g the e n e r g y c o n s u m p t i o n a n d therefore the c o s t o f the p r o c e s s . O f c o u r s e , the o p p o s i t e case h o l d s true as w e l l . F o r t u n a t e l y , this p o t e n t i a l error does n o t affect the r e l a t i v e e c o n o m i c s t a n d i n g o f e a c h p r o c e s s . S i n c e the m a t e r i a l f l o w s t h r o u g h the r e l e v a n t d i s t i l l a t i o n c o l u m n are a l l a p p r o x i m a t e l y e q u a l , the error i n terms o f e n e r g y c o n s u m p t i o n ( a n d therefore cost) w i l l a l l b e s k e w e d to a p p r o x i m a t e l y the s a m e degree, l e a v i n g the standings u n a l t e r e d .  68  Another important consideration is whether the failure to reproduce the results of Abreu et al. (2005) invalidate the conclusion that the heterogeneous process would be the most economical. To that end, a second catalyst, sulfated zirconia ( S 0 7 Z r 0 ) was used in the simulation. A 2  4  number  of researchers  have  confirmed  the  ability  2  of  S0 7Zr0 2  4  2  to  catalyze  the  transesterification of vegetable oils (Furuta et al. 2004; Lopez et al. 2005; Jitputti et al. 2006). The reaction conditions investigated by Jitputti et al. (2006) were adopted for the simulation, as they were they most rigorous in terms of temperature and pressure. The result of the simulation showed that in spite of the increased cost of the unit operations necessary for handling the large material flows and withstanding the high pressure and temperature required for the reaction, the heterogeneous process was still the most economical, although the after tax rate of return was significantly reduced from 54% in the SnO catalyzed process to 24%. This part of the work is currently in preparation for presentation at the 1 International Congress on Green Process st  Engineering in Toulouse France (2007).  Based on the result from Chapter 2, Chapter 3 detailed the work that was undertaken to synthesize SnO, and then test it to assess its catalytic abilities under a variety of conditions. Unfortunately, both the commercial SnO sample obtained and the SnO sample synthesized displayed no activity during the reaction of canola oil with methanol. Discussion with Mr. J. Radlein with reference to the work of Toda et al. (2005) brought about the idea to test sulfonated pyrolysis char for transesterification acivity. Testing of the sulfonated char at an A : 0 molar ratio of 18:1 with ethanol at 76°C under reflux for 24 hours showed no visible signs of transesterification, but analysis of the reaction mixture via G C indicated the presence of some ethyl-ester. The chromatogram (not shown) also exhibited peaks associated with glycerol, diglycerides and mono-glycerides, which would not be present if the ethyl-ester was being produced exclusively through esterification of any free fatty acids present in the oil. Due to time constraints the limitations to transesterification could not be explored. There are a number of possibilities that could explain the lack of transesterification acitivity. The first is that the catalyst may not have been acidic enough. However, the total acidity measured for the sulfonated char was comparable to the acidity of sulfated zirconia reported by Lopez et al. (2005), and the activity of sulfated zirconia is well confirmed. Catalytic studies have also shown that internal resistance to mass transfer and stearic hindrance can also limit catalyst activity when microporous catalysts are used, such as Zeolite HP (pore size 5.5 A X 5.5 A ) , H-ZSM5 69  and Y ( L o p e z et a l . 2 0 0 5 ; K i s s et a l . 2 0 0 6 ) a n d that i n s u c h cases a n y a c t i v i t y w a s the result o f surface sites. S E M e x p e r i m e n t s w e r e c o n d u c t e d to assess the s u r f a c e c h a r a c t e r i s t i c s o f the catalyst, but n o r e g u l a r l y o c c u r r i n g  p o r e structures c o u l d b e o b s e r v e d . W h e r e they w e r e f o u n d  ( F i g u r e 3.12) the s u r f a c e p o r e s i z e w a s q u i t e l a r g e (>1.6 p m ) w h i c h w o u l d not present a n y r e s i s t a n c e to d i f f u s i o n . H o w e v e r , s o m e f o r m o f m a s s transfer r e s i s t a n c e m a y b e l i m i t i n g a c t i v i t y , i f p e r h a p s the a c t i v e sites w e r e a l l w i t h i n the l o n g f i b r o u s c h a n n e l s o b s e r v e d i n F i g u r e 3 . 1 3 .  To  assess w h e t h e r the a c t i v e sites w e r e l o c a t e d o n the surface o f the catalyst o r w i t h i n  the  p o r e s / c h a n n e l s , a n E D X s c a n w a s p e r f o r m e d to l o c a t e the S - c o n t a i n i n g sites. U n f o r t u n a t e l y the r e s o l u t i o n w a s not f i n e e n o u g h to p i n p o i n t the l o c a t i o n o f the s u l f u r a n d n o  information  r e g a r d i n g the l o c a t i o n o f the a c t i v e sites c o u l d b e g a i n e d .  Another  possibility  may  have  been  that  the  reaction  temperature  was  too  low  for  t r a n s e s t e r i f i c a t i o n to o c c u r . O t h e r studies ( F u r u t a et a l . 2 0 0 4 ; S u p p e s et a l . 2 0 0 4 ; J i t p u t t i et a l . ! I  2 0 0 6 ) h a v e u s e d m u c h h i g h e r temperatures ( > 1 5 0 ° C ) , than c o u l d b e a c h i e v e d w i t h the s i m p l e h o t p l a t e set-up e m p l o y e d f o r this w o r k . N o n e t h e l e s s , i f temperature is the l i m i t i n g f a c t o r , it is e x p e c t e d that s o m e t r a n s e s t e r i f i c a t i o n w o u l d b e o b s e r v e d at l o w e r temperatures ( L o p e z et a l . 2005).  4.2  Conclusions  U s i n g the H Y S Y S  simulator, process flowsheets and energy and material balances were  d e v e l o p e d to m o d e l the p r o c e s s e s . T h e integrated spreadsheet t o o l i n H Y S Y S  w a s u s e d to  c o n d u c t u n i t o p e r a t i o n s i z i n g , as w e l l as a u t o m a t e the e c o n o m i c c a l c u l a t i o n s , w h i c h i n c l u d e d a l l e q u i p m e n t c o s t i n g , t o t a l c a p i t a l i n v e s t m e n t , t o t a l m a n u f a c t u r i n g c o s t a n d after tax rate o f r e t u r n . The  p r o c e s s e s w e r e as f o l l o w s : (I) a h o m o g e n e o u s a l k a l i - c a t a l y z e d p r o c e s s that u s e d p u r e  v e g e t a b l e o i l as the f e e d s t o c k ; (II) a h o m o g e n e o u s a c i d - c a t a l y z e d p r o c e s s that c o n v e r t e d w a s t e v e g e t a b l e o i l as the f e e d s t o c k ; (III)  a h e t e r o g e n e o u s a c i d - c a t a l y z e d p r o c e s s that u s e d w a s t e  v e g e t a b l e o i l ; a n d ( I V ) a s u p e r c r i t i c a l n o n - c a t a l y z e d p r o c e s s , that c o n s u m e d waste v e g e t a b l e o i l . T h e s u p e r c r i t i c a l p r o c e s s w a s the s i m p l e s t a n d h a d the f e w e s t n u m b e r o f u n i t o p e r a t i o n s , w h i l e the h o m o g e n e o u s p r o c e s s e s h a d the greatest n u m b e r o f u n i t o p e r a t i o n s , a n d w e r e the m o s t c o m p l i c a t e d , o w i n g to the d i f f i c u l t y i n r e m o v i n g the catalyst f r o m the l i q u i d p h a s e . A n e c o n o m i c a s s e s s m e n t r e v e a l e d that the heterogeneous a c i d - c a t a l y z e d p r o c e s s h a d the l o w e s t total c a p i t a l i n v e s t m e n t a n d total m a n u f a c t u r i n g cost. It w a s f o u n d that r a w m a t e r i a l s c o n s u m e d and the s i z e o f m a t e r i a l f l o w s , s t r o n g l y a f f e c t e d p r o c e s s e c o n o m i c s . A c c o r d i n g l y , P r o c e s s e s II, 70  I l l a n d I V h a d m u c h l o w e r m a n u f a c t u r i n g costs than P r o c e s s I. T h e after tax rate o f return f o r p r o c e s s III w a s 5 4 % , w h i l e p r o c e s s e s I, II a n d I V h a d rates o f r e t u r n o f - 1 4 4 % , - 4 % a n d - 0 . 9 % , respectively.  Sensitivity  analyses  were  conducted  to  identify  any  unit  operations  where  operating  s p e c i f i c a t i o n s c o u l d b e m o d i f i e d to i m p r o v e the p r o c e s s . It w a s f o u n d that i n c r e a s i n g m e t h a n o l r e c o v e r y l e d to a greater A T R O R . A c c o r d i n g l y , m e t h a n o l r e c o v e r y w a s set as h i g h as p o s s i b l e (>99%) b e f o r e the g l y c e r o l d e g r a d a t i o n temperature ( 1 5 0 ° C ) w a s e x c e e d e d i n the h o m o g e n e o u s a c i d - c a t a l y z e d a n d s u p e r c r i t i c a l p r o c e s s e s . U s e o f the o p t i m i z e r f u n c t i o n i n d i c a t e d a v a c u u m s y s t e m c o u l d b e i n s t a l l e d i n the H A C p r o c e s s to i n c r e a s e m e t h a n o l r e c o v e r y a n d c o n s e q u e n t l y the A T R O R , w h i l e k e e p i n g the b o t t o m s stream w i t h i n the temperature l i m i t . A n a n a l y s i s o f the 1  effect o f r e a c t i o n c o n v e r s i o n o n A T R O R r e v e a l e d that e v e n at r e d u c e d r e a c t i o n c o n v e r s i o n (i.e., b e t w e e n 8 5 - 9 3 % ) , the A T R O R o f the H A C p r o c e s s is greater than at 1 0 0 % c o n v e r s i o n o f the h o m o g e n e o u s a c i d a n d s u p e r c r i t i c a l p r o c e s s e s . T h e r e f o r e P r o c e s s H I , the heterogeneous a c i d c a t a l y z e d p r o c e s s , is c l e a r l y a d v a n t a g e o u s o v e r the other p r o c e s s e s , as it h a d the h i g h e s t rate o f return, l o w e s t c a p i t a l i n v e s t m e n t ,  and technically, was a relatively simple process. Further  r e s e a r c h i n d e v e l o p i n g the heterogeneous a c i d - c a t a l y z e d p r o c e s s f o r b i o d i e s e l p r o d u c t i o n  is  warranted.  B a s e d o n the results f r o m the H Y S Y S s i m u l a t i o n , a study i n t o the e f f e c t i v e n e s s o f tin(II) o x i d e as a catalyst f o r the t r a n s e s t e r i f i c a t i o n o f v e g e t a b l e o i l w a s c o n d u c t e d . S n O w a s s y n t h e s i z e d v i a the m e t h o d o f F u j i t a et a l . ( 1 9 9 0 ) after attempts to s y n t h e s i z e S n O u s i n g the p r o c e d u r e d e s c r i b e d b y A b r e u et a l . ( 2 0 0 5 ) h a d f a i l e d . B o t h the s y n t h e s i z e d s a m p l e a n d a c o m m e r c i a l s a m p l e o f S n O s h o w e d n o c a t a l y t i c a c t i v i t y d u r i n g r e a c t i o n s r u n at 6 0 ° C w i t h m e t h a n o l a n d c a n o l a o i l u n d e r reflux.  A s e c o n d catalyst, s u l f o n a t e d p y r o l y s i s c h a r , w a s s y n t h e s i z e d b a s e d o n the t e c h n i q u e o f T o d a et a l . ( 2 0 0 5 ) et a l . C h a r a c t e r i z a t i o n o f the catalyst r e v e a l e d a n i r r e g u l a r , p o r o u s c a r b o n f r a m e w o r k w i t h C O O H " a n d SO4 " g r o u p s b o n d e d to the surface. C a t a l y t i c tests w i t h c a n o l a o i l a n d e t h a n o l 2  s h o w e d o n l y q u a l i t a t i v e (i.e., an a m o u n t t o o s m a l l to b e p h y s i c a l l y m e a s u r e d ) t r a n s e s t e r i f i c a t i o n . H o w e v e r , the c a t a l y s t w a s v e r y a c t i v e i n the e s t e r i f i c a t i o n o f F F A s . E x p e r i m e n t s s h o w e d that c o n v e r s i o n o f F F A s i n c r e a s e d w i t h i n c r e a s i n g r e a c t i o n t i m e , i n c r e a s i n g a l c o h o l to v e g e t a b l e o i l  71  m o l a r ratio, a n d i n c r e a s i n g catalyst l o a d i n g . It w a s f o u n d that at a catalyst l o a d i n g o f 5 w t . % , r e a c t i o n t i m e o f 3 h o u r s a n d A : 0 ratio o f 18:1 g a v e the best results. S l i g h t i n c r e a s e s i n F F A c o n v e r s i o n w e r e o b s e r v e d at m o l a r ratios b e y o n d 18:1 a n d r e a c t i o n t i m e s o f 9 h o u r s a n d 15 h o u r s , but the d i f f e r e n c e s w e r e not q u a n t i f i a b l e d u e to the v a r i a b i l i t y a s s o c i a t e d w i t h the m e a s u r e m e n t s . A t h i g h e r F F A c o n c e n t r a t i o n s , it w a s f o u n d that the catalyst w a s c a p a b l e o f r e d u c i n g the a m o u n t o f F F A s f r o m 12.25 w t . % to a p p r o x i m a t e l y 1.04 wt.%.  Sulfonated char  s h o w s c o n s i d e r a b l e p o t e n t i a l f o r use as a catalyst i n b i o d i e s e l p r o d u c t i o n , e s p e c i a l l y i n a c o n t e x t u s e d to r e d u c e the free fatty a c i d content o f a v e g e t a b l e o i l f e e d s t o c k . H o w e v e r , f o r its true p o t e n t i a l to b e r e a l i z e d , the l i m i t a t i o n s to t r a n s e s t e r i f i c a t i o n a s s o c i a t e d w i t h this catalyst m u s t b e r e v e a l e d a n d o v e r c o m e . F u t u r e r e s e a r c h w i l l b e d i r e c t e d t o w a r d this g o a l .  4.3  Recommendations  B a s e d o n the w o r k c o n d u c t e d f o r this t h e s i s , a n u m b e r o f r e c o m m e n d a t i o n s are p r o p o s e d to f o r future research. •  T h e e s t i m a t i o n o f the A n t o i n e ' s c o e f f i c i e n t s i n H Y S Y S  needs to be i m p r o v e d . It i s  therefore suggested that e x p e r i m e n t s d e s i g n e d to m e a s u r e the v a p o u r pressure o f t r i o l e i n (or v e g e t a b l e o i l ) b e c o n d u c t e d at the temperature r a n g e o f interest, b e t w e e n 2 5 ° C to 4 0 0 ° C . T h e A n t o i n e c o e f f i c i e n t s c a n then b e o b t a i n e d b y r e g r e s s i n g the d a t a , a n d then i n p u t i n t o the p r o c e s s s i m u l a t i o n s . •  E x p e r i m e n t s s h o u l d a l s o b e p e r f o r m e d to v e r i f y that the 3 - p h a s e separator u s e d i n P r o c e s s e s H I a n d I V t o r e m o v e g l y c e r o l c a n a c h i e v e the results o f the s i m u l a t i o n s .  •  T h e s i m u l a t e d f e e d s t o c k s c o u l d b e e x p a n d e d to i n c l u d e those w i t h F F A contents greater t h a n 5 w t . % , as i n the c a s e o f y e l l o w grease, a n d h i g h w a t e r contents. S u c h factors m a y c h a n g e the r e l a t i v e e c o n o m i c o r d e r o f the p r o c e s s e s .  •  S i n c e the h e t e r o g e n e o u s p r o c e s s i n d i c a t e d s u c h p r o m i s i n g results, it w o u l d a l s o b e o f interest to c o n d u c t a m o r e d e t a i l e d s i m u l a t i o n , w h e r e m o r e care is taken to o p t i m i z e the d i s t i l l a t i o n c o l u m n s . It w o u l d a l s o be d e s i r a b l e to i n c l u d e k i n e t i c i n f o r m a t i o n (i.e., the effects o f temperature a n d r e s i d e n c e t i m e ) i n the r e a c t o r m o d e l l i n g to g i v e a m o r e r e a l i s t i c r e p r e s e n t a t i o n o f the s y s t e m .  •  It is also r e c o m m e n d e d that the reasons f o r the f a i l u r e o f S n O to c a t a l y z e a n y r e a c t i o n s h o u l d b e i n v e s t i g a t e d , as w e l l as w h y the m e t h o d o f A b r e u et a l . ( 2 0 0 5 ) f a i l e d . S i n c e the ATROR  o f the h e t e r o g e n e o u s p r o c e s s d r o p s d r a m a t i c a l l y f r o m 5 4 % to 2 4 %  when  72  s u l f a t e d z i r c o n i a is u s e d , it b e e c o n o m i c a l l y a d v a n t a g e o u s to use the S n O c a t a l y z e d process.  W i t h respect to the s u l f o n a t e d c h a r , it is v e r y i m p o r t a n t to u n d e r s t a n d a n d o v e r c o m e the l i m i t a t i o n s to t r a n s e s t e r i f i c a t i o n a s s o c i a t e d w i t h the catalyst a n d e x p e r i m e n t s s h o u l d b e d e s i g n e d to e l u c i d a t e the p r o b l e m s . •  S y n t h e s i s o f the catalyst w i t h f u m i n g s u l f u r i c a c i d has b e e n s h o w n to i n c r e a s e the t o t a l a c i d i t y ( T o d a et a l . 2 0 0 5 ) , w h i c h m a y h a v e a n effect o n the r e a c t i o n . It is r e c o m m e n d e d that c a t a l y t i c trials b e c o n d u c t e d w i t h c h a r treated w i t h f u m i n g s u l f u r i c a c i d .  •  T h e c h a r u t i l i z e d i n this study e x h i b i t e d a h i g h l y c o m p l e x , i r r e g u l a r n e t w o r k o f p o r e s a n d f i b r o u s c h a n n e l s , w h i c h m a y p o s e m a s s i n t e r n a l m a s s transfer l i m i t a t i o n s o n the l a r g e t r i g l y c e r i d e m o l e c u l e s . C h a r o b t a i n e d f r o m the p y r o l y s i s o f c o a l has s h o w n a less c o n v o l u t e d , h i g h l y r e g u l a r p o r o u s structure ( Y u et a l . 2 0 0 4 ) w h e n c o m p a r e d to the c h a r u t i l i z e d i n this study. T e s t i n g o f a catalyst d e r i v e d f r o m c o a l c h a r c o u l d y i e l d s o m e i n s i g h t i n t o any r e s i s t a n c e that m a s s transfer m i g h t p l a y .  •  A l t e r n a t e l y , it is p o s s i b l e that the l a c k o f catalyst t r a n s e s t e r i f i c a t i o n a c t i v i t y is d u e to e x t e r n a l m a s s transfer l i m i t a t i o n s . If e t h a n o l b i n d s to the a c t i v e sites (perhaps t h r o u g h h y d r o g e n b o n d i n g ) , that c o u l d p r e v e n t the n o n - p o l a r t r i g l y c e r i d e s f r o m a c c e s s i n g the a c t i v e sites a n d b e i n g p r o t o n a t e d b y the a c i d g r o u p s . In the case o f F F A c o n v e r s i o n , the p o l a r c a r b o x y l i c a c i d g r o u p o f the F F A c o u l d s t i l l access the a c t i v e site, a l l o w i n g the r e a c t i o n to o c c u r . U s i n g a c o s o l v e n t to create o n e o i l / a l c o h o l p h a s e c o u l d o v e r c o m e a n y p o t e n t i a l e x t e r n a l m a s s transfer l i m i t a t i o n s , a n d therefore a l l o w the r e a c t i o n to o c c u r .  •  T o d e t e r m i n e i f r e a c t i o n temperature is the l i m i t a t i o n , it is r e c o m m e n d e d to test the r e a c t i o n w i t h the catalyst at e l e v a t e d temperatures.  •  A  number  of  studies to  e x a m i n e the p e r f o r m a n c e  of  the  sulfonated char in  the  e s t e r i f i c a t i o n r e a c t i o n w o u l d a l s o b e u s e f u l : i n v e s t i g a t i n g the effect o f f e e d s t o c k w a t e r content o n the r e a c t i o n ; d e t e r m i n i n g the m a x i m u m a m o u n t o f F F A s i n the f e e d s t o c k b e f o r e the r e a c t i o n is i n h i b i t e d ; a n d testing the c a t a l y s t ' s r e u s a b i l i t y . •  L a s t l y , d e t e r m i n a t i o n o f k i n e t i c parameters f o r the e s t e r i f i c a t i o n a n d t r a n s e s t e r i f i c a t i o n r e a c t i o n s w o u l d b e v e r y v a l u a b l e . S u c h data w o u l d e n h a n c e the s i m u l a t i o n f o r P r o c e s s U l , a n d b e v e r y i m p o r t a n t f o r the s c a l e - u p o f the r e a c t i o n to a n i n d u s t r i a l s c a l e .  73  4.4  References  A b r e u , F . R . , A l v e s , M . B . , M a c e d o , C . C . S . , Z a r a , L . F. a n d S u a r e z , P . A . Z . ( 2 0 0 5 ) . N e w m u l t i - p h a s e c a t a l y t i c s y s t e m s b a s e d o n tin c o m p o u n d s a c t i v e f o r vegetable o i l transesterification reaction. Journal o f M o l e c u l a r Catalysis A : C h e m i c a l 227(1-2): 2 6 3 267. F u j i t a , K . , N a k a m u r a , C , M a t s u d a , K . a n d M i t s u z a w a , S . ( 1 9 9 0 ) . P r e p a r a t i o n o f tin(JI) o x i d e b y a h o m o g e n e o u s p r e c i p i t a t i o n m e t h o d . B u l l e t i n o f the C h e m i c a l S o c i e t y o f J a p a n 6 3 ( 9 ) : 2718-2720. Furuta, S . , M a t s u h a s h i , H . and A r a t a , K . (2004). B i o d i e s e l fuel production w i t h solid superacid c a t a l y s i s i n f i x e d b e d reactor u n d e r a t m o s p h e r i c p r e s s u r e . C a t a l y s i s C o m m u n i c a t i o n s 5(12): 721-723. Jitputti, J . , K i t i y a n a n , B . , Rangsunvigit, P., Bunyakiat, K., Attanatho, L. and Jenvanitpanjakul, P. (2006). Transesterification of crude p a l m kernel oil and crude coconut o i l by different s o l i d catalysts. C h e m i c a l E n g i n e e r i n g J o u r n a l 116(1): 6 1 - 6 6 . K i s s , A . A . , D i m i a n , A . C . a n d R o t h e n b e r g , G . ( 2 0 0 6 ) . S o l i d a c i d catalysts f o r b i o d i e s e l p r o d u c t i o n - t o w a r d s s u s t a i n a b l e energy. A d v a n c e d S y n t h e s i s & C a t a l y s i s 348(1 + 2): 75-81. L o p e z , D . E . , G o o d w i n , J . G . , B r u c e , D . A . and Lotero, E . (2005). Transesterification of t r i a c e t i n w i t h m e t h a n o l o n s o l i d a c i d a n d b a s e catalysts. 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Sunnyvale 2 0
Shenzhen 1 0
Rio de Janeiro 1 0
Port Louis 1 1
Seattle 1 0
Mountain View 1 0

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