UNDERSTANDING THE ACTION OF GAS HYDRATE KINETIC INHIBITORS by Nagu Daraboina Master of Engineering (Chem. Eng.), Indian Institute of Science, Bangalore, 2008 A THESIS SUBMITTED IN PARTIAL FULFILLMENT THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Chemical and Biological Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) July 2012 © Nagu Daraboina 2012 ii ABSTRACT The presence of inhibitors delayed hydrate nucleation and decreased the overall formation of methane/ethane/propane hydrate compared to pure water system. However, the two classes of inhibitors: chemical (Polyvinylpyrrolidone (PVP) and industrial inhibitor: H1W85281) and a biological (Type I and III antifreeze protein (AFP)) were distinguished by the formation of hydrates with different stabilities. A single hydrate-melting peak was seen with the AFP-III and this was consistent after re-crystallization. In contrast, multiple hydrate melting events were observed in the presence of the chemical inhibitors. In stirred reactor, onset of hydrate decomposition occurred earlier in the presence of the inhibitors compared to water controls. However, depending on the type of inhibitor present during crystallization, hydrate decomposition profiles were distinct, with a longer, two-stage decomposition profile in the presence of the chemical inhibitors. The fastest, single-stage decompositions were characteristic of hydrates in experiments with either of the AFPs. Powder X-ray diffraction and nuclear magnetic resonance spectroscopy showed that structure II hydrates dominated, as expected, but in the presence of the chemical inhibitors structure I was also present. Raman spectroscopy confirmed the complexity and the heterogeneity of the guest composition within these hydrates. However, in the presence of AFP- III, hydrates appeared to be relatively homogeneous structure II hydrates, with weaker evidence of structure I. When individual gas cage occupancies were calculated, in contrast to the near full occupancy of large cages with these inhibitors, almost 10% of the large cages were not filled when hydrates were formed in the presence of AFP-III, likely contributing to the easy decomposition of such hydrates seen in DSC and stirred reactor experiments. iii These results argue that thought must be given to inhibitor-mediated decomposition kinetics when designing and screening of new kinetic inhibitors. This is a necessary practical consideration for industry in cases when due to long shut in periods; hydrate formation may be unavoidable even when inhibitors are utilized. This heterogeneity suggests that using these chemical inhibitors (PVP and H1W85281) may present a special challenge to operators depending upon the gas mixture and environmental conditions, and that AFPs may offer a more predictable, efficacious solution in these cases. iv PREFACE The work of this thesis consists of three different manuscripts, which correspond to chapters two to four. The authors include Daraboina, N., Ripmeester, J.A., Virginia.K.Walker and Englezos P. Professor Peter Englezos is my principal research supervisor at the University of British Columbia. During the course of my research, I was fortunate enough to hold meaningful discussions with Dr. John A. Ripmeester who is a principal research officer at SIMS, National Research Council Ottawa and Professor Virginia K. Walker who is a professor at Queen’s university. The work of this thesis presented in several conferences. The literature review, experimental design, performing experiments and data analysis were done extensively by Daraboina, N under supervision of Professor P. Englezos. Finally, I did the final preparation for each manuscript after careful revision and approval of my supervisory committee. The list of published articles and conference presentations are given below: Published articles 1. Daraboina, N., Linga, P., Ripmeester, J., Walker, V. K., and Englezos, P. (2011a). "Natural Gas Hydrate Formation and Decomposition in the Presence of Kinetic Inhibitors. 2. Stirred Reactor Experiments." Energy & Fuels, 25(10), 4384-4391. 2. Daraboina, N., Ripmeester, J., Walker, V. K., and Englezos, P. (2011b). "Natural Gas Hydrate Formation and Decomposition in the Presence of Kinetic Inhibitors. 1. High Pressure Calorimetry." Energy & Fuels, 25(10), 4392-4397. 3. Daraboina, N., Ripmeester, J., Walker, V. K., and Englezos, P. (2011c). "Natural Gas Hydrate Formation and Decomposition in the Presence of Kinetic Inhibitors. 3. Structural and Compositional Changes." Energy & Fuels, 25(10), 4398-4404. v Conference presentations (with published abstracts) 1. Daraboina, N; Ripmeester, J. A.; "Englezos, P. “New insights into gas hydrate decomposition in the presence of synthetic and biological inhibitors". Presented, 61st Canadian Society Chemical Engineering conference. London, Ontario, Canada. October 23-26, 2011. 2. Walker, V.K; Daraboina, N; Gordienko, R., Ohno, H.; Ripmeester, J. A.; Englezos, P., Green gas hydrate inhibitors?” Ice -Binding Protein conference. Kingston, Ontario, Canada, August 3-6, 2011. 3. Daraboina, N; Ripmeester, J. A.; Walker, V.K.; Englezos, P., "Multi-scale assessment of the performance of kinetic hydrate inhibitors" Submitted, 7th International Conference on Gas Hydrates Edinburgh, Scotland, United Kingdom, July 17-21, 2011. 4. Daraboina, N; Ripmeester, J. A.; Linga P.; Englezos, P., "Experimental investigation of the effect of poly-N-vinyl pyrrolidone on methane/propane clathrate in the presence of silica sand" submitted, 7th International Conference on Gas Hydrates Edinburgh, Scotland, United Kingdom, July 17-21, 2011. 5. Daraboina, N; Ripmeester, J. A.; Walker, V.K.; Englezos, P., "Inhomogeneous hydrate formation induced by kinetic hydrate inhibitors". Presented American Chemical Society conference, Anaheim, USA, March 27, 2011. 6. Daraboina, N; Ripmeester, J. A.; "Englezos, P. Understanding the Action of kinetic hydrate inhibitors". Presented, 60th Canadian Society Chemical Engineering conference. Saskatoon, Saskatchewan, Canada. October 26,2010. vi TABLE OF CONTENTS ABSTRACT............................................................................................................................................................  ii   PREFACE…………………………………………………………………………………………………………………………………….……………………..  iv   TABLE  OF  CONTENTS  ……..…………………………………………………………………………………………………………………………….……vi   LIST  OF  TABLES  ……………………………………..………………………………………………………………………………………………….………  ix   LIST  OF  FIGURES  ……………………………………………………………………………………………………………………………………….……….  x   NOMENCLATURE……………………………………………………………………………………………………………………………………………..  xii   ACKNOWLEDGEMENTS……………………………………………………………………………………………………………………………………  xiv   DEDICATION…………………………………………………………………………………………………………………………………………….………  xv   1.  Introduction........................................................................................................................ 1   1.1.  Fundamentals  of  gas  hydrates................................................................................................... 1   1.2.  Kinetics  and  molecular  scale  studies  of  gas  hydrates ................................................................. 3   1.3.  Motivation ................................................................................................................................ 6   1.4.  Research  objectives................................................................................................................. 15   1.5.  Thesis  organization ................................................................................................................. 16   2.  Natural  gas  hydrate  formation  and  decomposition   in  the  presence  of  kinetic   inhibitors.   I:   High  pressure  calorimetry..................................................................................................... 18   2.1.  Introduction............................................................................................................................ 18   2.2.  Materials................................................................................................................................. 19   2.3.  High-­‐pressure  differential  scanning  calorimetry ...................................................................... 19   2.4.  Data  analysis ........................................................................................................................... 21   2.5.  Results  and  discussion............................................................................................................. 21   2.5.1.  Isothermal  experiments .......................................................................................................... 21   2.5.2.  Ramping  experiments ............................................................................................................. 25   2.5.3.  Hydrate  heterogeneity............................................................................................................ 30   vii 3.  Natural  Gas  Hydrate  formation  and  decomposition  in  the  presence  of  kinetic  inhibitors:    II   Stirred  reactor  experiments.................................................................................................. 33   3.1.  Introduction............................................................................................................................ 33   3.2.  Materials................................................................................................................................. 33   3.3.  Experimental  setup ................................................................................................................. 34   3.4.  Experimental  procedure.......................................................................................................... 35   3.4.1.  Hydrate  formation .................................................................................................................. 35   3.4.2.  Hydrate  decomposition........................................................................................................... 37   3.5.  Results  and  discussion............................................................................................................. 38   3.5.1.  Hydrate  nucleation  and  growth  in  the  presence  of  inhibitors ................................................ 38   3.5.2.  Hydrate  decomposition  in  the  presence  of  inhibitors ............................................................ 42   4.  Natural  Gas  Hydrate  formation  and  decomposition  in  the  presence  of  kinetic  inhibitors:  III   Structural  and  compositional  changes .................................................................................. 51   4.1.  Introduction............................................................................................................................ 51   4.2.  Materials................................................................................................................................. 52   4.3.  Sample  preparation................................................................................................................. 52   4.4.  Experimental  techniques......................................................................................................... 53   4.4.1.  Gas  chromatography  (Gas  phase  analysis) ............................................................................. 53   4.4.2.  Powder  X-­‐ray  diffraction  (PXRD) ............................................................................................. 53   4.4.3.  Raman  spectroscopy ............................................................................................................... 54   4.4.4.  NMR  spectroscopy .................................................................................................................. 54   4.5.  Results  and  discussion............................................................................................................. 54   4.5.1.  Gas  phase  analysis  and  powder  XRD....................................................................................... 54   4.5.2.  Raman  spectroscopy ............................................................................................................... 59   4.5.3.  NMR  spectroscopy .................................................................................................................. 63   viii 5.  Conclusions  and  recommendations................................................................................... 69   5.1.  Summary  of  conclusions.......................................................................................................... 69   5.2.  Recommendations  for  future  work ......................................................................................... 71   References…………………………………………………………………………………………………………………..…………………………………..  73   Appendix  A  -­‐  Reactor  Design……………………………………………………………………………………………………………………….……  87   Appendix  B  -­‐  Raman  spectroscopy…………………………………………………………..……………………………………………………….  97                                       ix LIST OF TABLES Table  1.1.  Structural  properties  of  hydrates  (Sloan,  1998a). ................................................................................. 2   Table  1.2.  Kinetic  hydrate  inhibitors  (Kelland,  2006) ............................................................................................ 9   Table  2.1.  DSC  experiments  with  isothermal  formation  and  temperature  scanning  decomposition  in  the  presence   of  chemical  and  biological  inhibitors ......................................................................................................... 23   Table  2.2.  DSC   formation/decomposition  experiments  with   temperature   scanning   in   the  presence  of   chemical   and  biological  kinetic  inhibitors ................................................................................................................ 26   Table  3.1.  Experimental   conditions,   induction   times  and  mean  gas  consumption  for  methane/ethane/propane   gas  hydrate  formation  at  275.15  K  and  8.1  MPa. ....................................................................................... 40   Table  4.1.  Vapour  phase  composition  during  hydrate  formation  in  the  absence  (water)  or  the  presence  of  various   inhibitors  at  9.0MPa  and  274  K. ................................................................................................................ 55   Table  4.2.  Hydrate  phase  composition  of  the  hydrate  synthesized  in  the  presence  of  water  or  various  inhibitors. ................................................................................................................................................................. 66   Table  4.3.  Cage  occupancy  values  obtained  with  13C  MAS  NMR  spectra  in  the  presence  of  inhibitors................ 67   Table  A.1.  Dimensions  of  the  reactor  and  supply  vessel ..................................................................................... 94       x LIST OF FIGURES Figure  1.1.  Three  common  gas  hydrate  cavity  structure ....................................................................................... 2   Figure  1.2.    Molecular  structures  of  chemical  kinetic  inhibitors  (Kelland,  2006) .................................................. 10   Figure  1.3.  The  structures  of  AFP's  with  mutated  residues  Ala  (blue)  and  Thr  (yellow).. ..................................... 13   Figure  2.1.  Droplet  insert  used  for  differential  scanning  calorimeter  experiments.............................................. 20   Figure  2.2.  Isothermal  (left)  and  temperature  ramping  (right)  programs  used  in  DSC  experiments ..................... 20   Figure  2.3.  Typical  isothermal  experiments  showing  hydrate  nucleation  events  for  (a)  11  h  (b)  3  h .................... 22   Figure   2.4.   Typical   isothermal   experiments   showing   hydrate   melting   peaks   in   water   controls   or   with   kinetic   inhibitors  (a)  Heat  flow  Vs  Time  and  (b)  Heat  Flow  Vs  Temperature.......................................................... 24   Figure  2.5.  Typical  DSC  cooling  and  heating  curves  obtained  using  the  temperature  ramping  protocol   in  which   the  temperature  of  the  samples  is  dropped  from  +25  0C  to  -­‐45  0C  and  then  reheated,  all  at  9  MPa. .......... 25   Figure  2.6.  Typical  hydrate  melting  curves  in  the  presence  of  kinetic  inhibitors  at  9  MPa  using  the  temperature   ramping  protocol,  in  the  presence  or  absence  of  kinetic  inhibitors............................................................ 27   Figure  2.7.  Hydrate  melting  curves  formed  during  ramping  runs  in  (a)  pure  water  (b)  AFP  (c)  PVP  (d)  HIW8528130   Figure  3.1.  Schematic  of  the  apparatus  for  hydrate  induction  and  decomposition.............................................. 34   Figure  3.2.  Reactor  top  view  (left)  cross  sectional  view  (right)  of  the  reactor...................................................... 35   Figure   3.3.   Induction   time   for   hydrate   formation   in   the   presence   of   inhibitors   at   8.1  MPa.     The   scale   for   the   induction  time  is  logarithmic  due  to  large  differences  in  the  induction  times  between  the  inhibitors........ 39   Figure   3.4.   Effect   of   inhibitor   on   hydrate   growth   for   experiments   conducted   at   8.1   MPa   and   275.15   K   for   experiments  1,  5,  9,  13  and  17  from  Table  1.    Time  zero  in  the  graph  corresponds  to  the  nucleation  point   (induction  time  given  in  Table  1)  for  the  experiments. .............................................................................. 41   Figure  3.5.  Temperature  profiles  for  decomposition  experiments  (experiments  1,  2  and  3  from  Table  1). .......... 43   Figure  3.6.  Pressure  profiles  for  No-­‐hydrate  experiment  (NHE,  gas  expansion  due  to  temperature  increase)  and   hydrate  experiment  (HE,  gas  expansion  due  to  temperature  increase  and  gas  release  due  to  decomposition   of  hydrate)  and  difference  (HE-­‐NHE,  gas  release  due  to  hydrate  decomposition) ...................................... 44   Figure  3.7.  Typical  gas  hydrate  decomposition  along  with  heating  profile  for  experiment  1  in ........................... 45   xi Figure  3.8.  Normalized  gas  release  profiles  in  the  presence  of  inhibitors  (experiments  1,  7,  9,  13  and  17). ......... 46   Figure  3.9.  Normalized  gas  release  profiles  in  the  presence  of  (a)  Water  (b)  PVP  (c)  H1W85281  (d)  AFP-­‐I  (e)  AFP-­‐ III .............................................................................................................................................................. 49   Figure   4.1.   A   PXRD   pattern   obtained   at   125   K   for   a   hydrate   sample   synthesized   from   a   methane/ethane/   propane/water  mixture  at  9.0  MPa  and  274  K.(The  structure  I  peak  is   indicated  by  a  delta  and  ice  peaks   are  indicated  by  an  asterisk).    (a)  Control  experiments  with  no  additives  (b)  PVP  (c)  H1W85281  and  (d)  AFP-­‐ III .............................................................................................................................................................. 58   Figure  4.2.  Raman  spectra  of  methane/ethane/propane  hydrate   formed  with   (a)  Control  experiments  with  no   additives  (b)  PVP  (c)  H1W85281  and  (d)  AFP-­‐III ......................................................................................... 61   Figure   4.3.   13C   NMR   spectrum   of   methane/ethane/propane   hydrate   formed   in   the   presence   of   (a)   Control   experiments  with  no  additives  (b)  PVP  (c)  H1W85281  and  (d)  AFP-­‐III ........................................................ 65   Figure  A.1.  Front  view  of  the  reactor.................................................................................................................. 88   Figure  A.2.  Top  view  of  the  reactor .................................................................................................................... 89   Figure  A.3.  Cross  section  A  of  the  reactor ........................................................................................................... 90   Figure  A.4.  Cross  section  B  of  the  reactor. .......................................................................................................... 91   Figure  A.5.  Front  view  and  top  view  of  the  waterbath........................................................................................ 92   Figure  A.6.  Side  view  of  the  water  bath.............................................................................................................. 93   Figure  A.7.  Pressure  transmitter  setup. .............................................................................................................. 95   Figure  A.8.  Experimental  apparatus  (Back  view  showing  NI  DAQ  arrangement) ................................................. 96       xii NOMENCLATURE Abbreviation Full form KHI Kinetic hydrate inhibitor Tm, hydrate Hydrate melting temperature Tm, ice Ice melting temperature Hm, ice Area of ice melting peak Hm, hydrate Area of hydrate melting peak Hm, total Total area of melting peaks CR Crystallizer R Reservoir CV Control valve DAQ Data acquisition system ER External refrigerator ¯tind Mean induction time ¯n Mean gas consumption ¯tind, Fresh Mean fresh induction time ¯tind, Memory Mean memory induction time ¯n Fresh Mean fresh experiment gas consumption ¯nMemory Mean memory experiment gas consumption θS Small cage occupancy θL Large cage occupancy ΘT Total large cage occupancy xiii N Hydration number T Temperature P Pressure IT Induction time xiv ACKNOWLEDGEMENTS It is my pleasure to thank many people and organizations who supported me throughout the duration of this thesis. I am wholeheartedly thankful to my supervisor Prof. Peter Englezos for his constant support, encouragement and guidance from initial to final level of this research project. I owe my deepest gratitude to Dr. John A. Ripmeester and Prof. Virginia K. Walker for their advice, scientific discussions and encouragement, which improved my thought process as a researcher. I would also like to show my gratitude to Four Year Fellowship (FYF), Natural Science and Engineering Research Council of Canada (NSERC) and Shell Global Solutions for providing Financial support for this project. I would also like to extend this acknowledgement to my colleagues and friends: Praveen, Nayef, Cef, Jeffry, Alireza, Iwan, Babak, Yizhou, Negar, Sima, Dongliang, Hassan, Venkat, Rakib, and Jaishankar through group meetings and personal discussions. A special thanks to Praveen and Rajneesh for all the support, discussion and fun I had with them while working together in the lab. I would also like to thank everyone at Material Structure and Function (MSF) group at NRC Ottawa: Chris, Gary, Steve, Igor, Hailong, Hiroshi, Jeff, Olga and Robin for their valuable advice. I would like to thank CHBE well wishers and friends: Helsa, Dhanesh, Dean, Amber, Ann, Lori, Richard, David, Alf, Ryan, James, Masita, Jidon, Paula, Jaime, Maziar, Monali, CHBE camping team, CHBE skiing team, CHBE drinking team, CHBE Hawks and Koerner’s pub team for their support and fun throughout my program. Finally, I wish to thank my family for their love and care. xv DEDICATED TO MY FATHER AND TO MY FAMILY 1 1. INTRODUCTION 1.1. Fundamentals  of  gas  hydrates   Natural gas hydrates are solid crystalline compounds composed of hydrocarbon guest molecules enclathrated in a hydrogen bonded water molecule framework that form under suitable temperature and pressure conditions (Davidson, 1973b; Makogon, 1981; Sloan, 1998a). Structure I (sI), Structure II (sII) and Structure H (sH) are three well known structures of gas hydrates (Davidson, 1973a; Ripmeester et al., 1987; Englezos, 1993; Ripmeester, 2000; Sloan, 2003), distinguished by the size and geometry of the water framework: structure I (sI) generally enclathrates small hydrocarbons such as methane or ethane and structure II (sII) housing larger molecules such as propane (Sloan, 2003; Uchida et al., 2007); These two structures are cubic but the third type, structure H (sH), has a hexagonal crystal structure, which can enclathrate molecules as large as methylcyclopentane or two guest molecules such as methane and dimethylbutane (Mehta and Sloan, 1993b). sH was discovered at National Research Council in Canada in 1987 by Ripmeester and co-workers (1987). Each structure is a different combination of cages formed by water molecules. sI consists of 2 small pentagonal dodecahedron cages and 6 large tetrakaidecahedron cages which are formed by 46 water molecules. sII consists of 16 small pentagonal-dodecahedron cages and 8 larger hexakaidecahedron cages formed by 136 water molecules. Like sI and sII, sH has the basic pentagonal dodecahedron (12 pentagons -512) cage and two other cavities: a medium cage consisting of three tetragonal, six pentagonal and three hexagonal faces (435663) and a large cage made up of twelve pentagonal and eight hexagonal faces (51268). Because this structure can accommodate large molecules found in crude oils it is also industrially important. A new trigonal hydrate structure with three large cavities 2 (51263, 51262 and 4151063) was also reported by Udachin et al. (2001a). The three common gas hydrate cavity structures are shown in Figure 1.1 and structural properties are given in Table 1.1. Figure 1.1. Three common gas hydrate cavity structure Reprinted from Storbel et al., 2009, with permission from Elsevier. Table 1.1. Structural properties of hydrates (Sloan, 1998a). Structure I Structure II Structure H Cavity types 512, 51262 512, 51264 512, 435663, 51268 Cages/unit cell 2, 6 16, 8 3, 2, 1 Co-ordination number 20, 24 20, 28 20, 20, 36 Crystal type Cubic Cubic Hexagonal 3   1.2. Kinetics  and  molecular  scale  studies  of  gas  hydrates   The formation of hydrate crystals is a multiphase crystallization process. The hydrate formation process is subdivided into hydrate nucleation and hydrate growth. During nucleation stable nuclei are generated which will then grow to form crystals (crystal growth period). Hydrate nucleation refers to the process where small hydrate crystals called nuclei develop until they attain a critical size, thereafter the continued growth will start. The growing of clusters of water around gas molecules is the first step of hydrate nucleation (Bishnoi and Natarajan, 1996). The time period required to reach the state where the first stable nuclei appear is called the induction time. The induction time can be obtained through a visual observation or through pressure/temperature measurements. The induction time is believed to be a stochastic phenomenon that cannot be predicted (Englezos, 1996; Klomp, 2008). Based on the result of several studies done by different research groups, it can be concluded that, the nucleation time depends on following parameters; (a) Nature and thermal history of water (Vysniauskas and Bishnoi, 1983b); (b) stirring rate (Englezos et al., 1987a); (c) temperature and pressure (Sloan, 1998a); (d) degree of super saturation (Englezos, 1987a); and (e) molecular diameter to cavity size ratio (Sloan and Fleyfel, 1991). Miller and Smythe (1970) quantified gas hydrate growth. A systematic study on the kinetics of gas hydrate formation and decomposition was started by Bishnoi in early 1980s; his group subsequently presented an empirical model that correlated the growth rate with the degree of super cooling, temperature, pressure, and interfacial area. Englezos et al. (1987a) developed a model with three steps based on theory of crystallization and mass transfer to describe the hydrate growth kinetics of methane and ethane. The model was extended to the formation of 4 hydrates from methane and ethane mixtures of various compositions (Englezos et al., 1987d). Skovborg and Rasmussen (1994) simplified the model of Englezos et al. (1987a) by assuming that mass transfer at the gas/liquid interface was the limiting step in hydrate growth. Herri et al. (1999) proposed a kinetic model including both nucleation and growth steps. Gas uptake measurement is a typical method to study the kinetics of hydrate formation (Vysniauskas and Bishnoi, 1983a; Englezos et al., 1987c; Koh et al., 2002; Sloan and Koh, 2008). Even though there is vast amounts of kinetic data available on hydrate formation and decomposition, there is still data needed to improve or control the kinetics of hydrate formation in the presence of additives. The different instrumental techniques were applied to investigate the kinetics of hydrate formation and decomposition in addition to the conventional gas uptake experiments. Thermal analysis instruments like high pressure-micro differential scanning calorimetry (HP-µDSC) have been widely used as for the study of hydrate formation (Dalmazzone et al., 2002a; Koh, 2002; Dalmazzone et al., 2004; Le Parlouer et al., 2004; Ripmeester et al., 2007; Lachance et al., 2009), decomposition (Rueff et al., 1988; Dalmazzone et al., 2002b; Kawamura et al., 2006; Hughes, 2008; Koh et al., 2008a; Koh et al., 2008b; Nakagawa et al., 2008) and inhibition (Koh et al., 2002; Koh et al., 2009; Lachance et al., 2009; Nihous et al., 2010). Using molecular level techniques like diffraction, Raman spectroscopy, optical microscopy and NMR spectroscopy etc., information about hydration number, structural identification, cage occupancy and meta- stable phase identification is obtained. Such information is not accessible with macroscopic measurement techniques such as gas uptake measurements. Powder x-ray diffraction (PXRD) is a technique widely used to identify the crystalline structures of compounds by using a beam of X-rays. The details of the working principle of XRD were given elsewhere (Grieken and 5 Markowicz, 2002; Hughes, 2008). PXRD is a powerful and robust technique to determine the structure of gas hydrate (sI, sII and sH) formation (Davidson, 1986; Koh et al., 1996; Udachin et al., 2001b; Takeya et al., 2002; Uchida et al., 2002; Uchida et al., 2004; Susilo et al., 2005; Kumar et al., 2008b). Raman spectroscopy has also been identified as a powerful technique to characterize gas hydrates and has been used to detect the structure of the hydrate (Morita et al., 2000; Schicks et al., 2005; Ripmeester et al., 2007; Kumar et al., 2008b), transition of hydrate structures (Subramanian, 2000; Subramanian et al., 2000a; Subramanian et al., 2000b; Schicks et al., 2006) mixed gas hydrate formation kinetics (Uchida et al., 2002; Uchida et al., 2007), meta- stability of hydrates (Ohno et al., 2009) and effect of inhibitors on the kinetics and structure of hydrates (Sloan et al., 1998; Carstensen et al., 2002; Koh, 2002; Sloan and Koh, 2008). The details of the working principle of Raman spectroscopy has been given in literature (Skoog, 1982; Hughes, 2008). 13C Nuclear magnetic resonance (NMR) spectroscopy has also proved useful for obtaining quantifiable hydrate compositions and cage occupancies of mixed gas hydrate (Ripmeester and Ratcliffe, 1988; Ripmeester and Ratcliffe, 1999; Kida et al., 2007; Kumar et al., 2008b; Kida et al., 2009). Ripmeester (2000) reviewed the early correlations, instrumental methods and computational modeling used for the calculation of hydration numbers, and the characterization of hydrate structures. Moudrakovski et al., (2001) studied the nucleation and growth of xenon hydrates on the surface of frozen heavy water by NMR spectroscopy using xenon. The results suggested that the average hydrate composition varies during the nucleation step, but remains constant during the growth step. Koh (2002) discussed the industrial significance and technological importance of gas hydrates. She suggested that the fundamental understanding on gas hydrate formation and decomposition using macro and microscopic tools is necessary and 6 have wide implications on the exploitation of sediments and managing flow assurance in oil and gas pipelines. Moudrakovski et al (2004) showed through micro imaging that hydrate shells around the water droplets could be detected. Susilo et al. (2007) demonstrated the use of PXRD, DSC, NMR and Raman spectroscopy to characterize sI and sH hydrates and obtain consistent results for hydrate structure, degree of conversion and gas content in the hydrate phase with the different techniques. Susilo et al. (2006) also monitored the kinetics of structure I and H methane hydrate growth by employing NMR spectroscopy and imaging (MRI) and found out that the rates of hydrate formation agree with the results from gas uptake measurements obtained by Lee et al. (2005). Kumar et al. (2008) reported the kinetics and structure of gas hydrates from methane/ethane/propane mixtures relevant to the design of operations involving natural gas hydrate storage and transport. The results (gas phase composition and fractionation effect) obtained from kinetics at macroscopic level (gas uptake) were found agreed with the results (hydrate phase composition and cage occupancies of individual gases) obtained at molecular level (powder x-ray diffraction, NMR, and Raman spectroscopy). The composition of the gas phase and the hydrate phase were found to evolve over time, suggesting that kinetic and transport factors contribute in addition to thermodynamics. The information obtained with these molecular techniques combined with traditional gas uptake measurements can provide useful insights to understanding the mechanism of hydrate formation and decomposition. 1.3. Motivation   Humphrey Davy, who observed that a solution of chlorine gas in water freezes faster than pure water, first found the existence of gas hydrates in 1811 (Davy, 1811). From 1811 until the 1930s gas hydrates were a scientific curiosity. Gas hydrates gained industrial interest when Hammerschmidt reported the formation of gas hydrates in oil and gas production and 7 transportation pipelines (Hammerschmidt, 1934). Currently, gas hydrates are important to study for variety of applications: a potential energy source, natural gas hydrate transportation, carbon dioxide capture and sequestration and separation of gases. Hydrates are also a serious safety concern in offshore hydrocarbon drilling (Hammerschmidt, 1934; van der Waals and Platteeuw, 1959a; Davidson, 1973a; Makogon, 1981; Ripmeester et al., 1987; Englezos, 1993; Englezos, 1996; Herri et al., 1999; Koh, 2002; Koh et al., 2002; Kvamme et al., 2005; Kelland, 2006; Hughes, 2008; Ribeiro and Lage, 2008; Sloan and Koh, 2008; Walker et al., 2008). This thesis focuses on kinetic inhibition of gas hydrate formation in pipelines of the oil and gas industry. The unexpected formation of gas hydrates in hydrocarbon production facilities and transportation pipelines can lead to blockages and shutdowns therefore is a serious economic and safety issue (Sloan, 1998a; Sloan and Koh, 2008). Significant research has been carried out in order to manage the risk arising from the formation of solid gas hydrate crystals in the oil and gas industry. There are four methods based on thermodynamic considerations to prevent the hydrate formation in pipelines, a) removing water (dehydration); b) increasing the temperature of the system beyond the hydrate formation temperature at a constant pressure; c) decreasing the pressure of the system below hydrate stability at a constant temperature, and d) injecting a thermodynamic inhibitor (methanol) to change the hydrate forming conditions. This allows the pipeline to operate outside the thermodynamic stability conditions to prevent hydrate formation (Long et al., 1994). However, the use of thermodynamic inhibitors is both uneconomical (high concentrations are needed >40 vol %) and not environmentally friendly because methanol is flammable, corrosive and has a negative effect on processing catalysts in downstream operations (refiners). Currently the oil and gas industry is searching for hydrocarbons in deeper waters, which have 8 more favorable conditions for hydrate formation. High concentrations (>60 vol %) of methanol would be required to prevent the hydrate formation under these conditions. It is estimated that the operating costs also can be greater than $500,000,000 per year (Koh, 2002). In the last two decades economic and environmental factors have motivated research and development to identify alternative low dosage (less than 1 wt %) hydrate inhibitors (LDHIs). The main idea behind these LDHIs is to prolong induction time for hydrate nucleation, reduce growth and agglomeration instead of shifting the thermodynamic equilibrium conditions. Thus, LDHIs are divided into two basic categories: kinetic inhibitors (KIs) which prolong induction time for hydrate formation and affect growth of hydrate crystals, and anti agglomerates (AAs) which permit hydrates to form but prevent their agglomeration and accumulation in the pipelines. Commercially, kinetic inhibitors are synthetic polymers like polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap) etc, and anti agglomerates are usually quaternary ammonium salts (QAS). The search for KI is ongoing in order to improve their performance and reduce cost. Newly discovered KIs are first used in the laboratory and if successful they are then tested with field fluids and finally under field conditions (Mehta and Sloan, 1993a). A large number of synthetic chemicals, mostly polymers, have been explored as potential KHIs (Freer and Sloan, 2000; Kelland, 2006). These inhibitors are water-soluble polymers and are known as low dosage hydrate inhibitors (LDHIs) because they are used at low concentrations to control hydrate formation, as opposed to the high concentrations required of thermodynamic hydrate inhibitors. Table 1.2 shows some of the known KI’s from Kelland’s review(2006). Several molecular dynamic simulation studies attempted to show how the kinetic inhibitors effect hydrate formation (Kvamme et al., 1997; Freer and Sloan, 2000; Storr and Rodger, 2000; Moon et al., 2002; Anderson et al., 2005; Kvamme et al., 2005; Kelland, 2006; Klomp, 2008; 9 Ribeiro and Lage, 2008). Kvamme et al., (1997) suggested that inhibitor structure and free energy of active groups in the inhibitor as well as diffusivity of these groups towards hydrate crystals are important characteristics of kinetic inhibitor. Table 1.2. Kinetic hydrate inhibitors (Kelland, 2006) The molecular structures of these compounds are given below: Polyvinylpyrrolidone polyvinylcaprolactam polyethylacrylamide polyvinyl-N-methylacetamide Kinetic Hydrate Inhibitor (KHI) Polyvinylpyrrolidone (PVP) Polyvinylcaprolactam (PVCap) Polyethylacrylamide Polyvinyl-N-methyl acetamide Polyethyloxazoline Polyisobutylacrylamide Polyacryloylpyrrolidine polydiethylacrylamide polyisopropylacrylamide polyethylmaleimide polyethyloxazoline polyisobutylacrylamide 10 polyethyloxazoline N-methyl-N-vinylacetamide: vinylcaprolactam copolymer polyacryloylpyrrolidine polydiethylacrylamide polyisopropylacrylamide polyethylmaleimide polyethyloxazoline polyisobutylacrylamide polyisopropylmethacrylamide Figure 1.2. Molecular structures of chemical kinetic inhibitors (Kelland, 2006). 11 Anderson et al., (2005) proposed a two-step mechanism for gas hydrate inhibition by kinetic inhibitors. The hypothesis is that the inhibitor molecules first disrupt the local organization of water and guest molecules, increasing the barrier to nucleation and nucleation propagation. In the second step the degree of inhibition is related to the strength of the binding of the inhibitor molecule to the surface of the hydrate crystal. Kvamme et al., (2005) reported that the presence of inhibitor molecules decreases the hydrate-water interactions by increasing the hydrate-inhibitor interactions. Moon et al., (2007) also reported that inhibitor molecules (PVP) are effective in destabilizing hydrate crystals prior to nucleation and delay the nucleation. However, the mechanism of inhibition was not clear. Kumar et al.,(2008b) studied the effect of PVP on the morphology of methane/propane hydrate formation and found that induction time increases with the decrease in under cooling and increase in PVP concentration. The growth after nucleation was catastrophic at higher concentrations of PVP. Makogon and Holditch (1981) reported that the presence of kinetic inhibitors increased the temperature at which hydrate decomposed completely. As well, Bruusgaard et al., (2009) visually noted that methane hydrate formed in the presence of the copolymer poly(VP/VC) took longer to decompose completely as compared to the hydrate formed in the absence of inhibitor. Of course, visual observations do not reveal the actual complexities of melting behavior, and this remains unknown in these cases. Although the hydrate inhibition mechanism is unknown, from these results it is evident that PVP and PVCap are effective nucleation and growth inhibitors. It is interesting to note that polymers exist that even though they are unable to exhibit kinetic inhibition by themselves but improve the performance of inhibitors (King et al., 2000). Cohen et al. (1998) investigated that the addition of butoxyethanol to a kinetic inhibitor delayed the induction time by thirty fold. Lee and Englezos (2005) found that addition of poly ethylene oxide 12 (PEO) to starches enhances the performance of the inhibitor by an order of magnitude. The presence of small amount of PEO in the kinetic inhibitor (GHI 101 from ISP technologies and Luvicap EG from BASF Corporation) solutions reduced the memory effect on induction time of hydrate crystals. Lee et al. (2007) observed that a starch solution showed weak inhibition effect, but the addition of PEO to this starch solution enhanced the performance of the inhibitor. Unfortunately, since some of the synthetic polymeric inhibitors are non biodegradable, there has been some interest in assessing the utility of biological inhibitors (Zeng et al., 2003; Kelland, 2006; Zeng et al., 2006a; Zeng et al., 2006b; Al-Adel et al., 2008; Walker et al., 2008; Ohno et al., 2010). These biological inhibitors are labeled green inhibitors. They are natural inhibitors that have been engineered by evolutionary processes in organisms over a very long period of time. An example of a green inhibitor is antifreeze protein (AFP), which enable certain organisms to survive freezing winters by lowering freezing point (Raymond, 1977). Antifreeze proteins (AFPs) are best known from ocean fish that have evolved at high latitudes where these proteins adsorb to embryonic ice crystals and prevent serum freezing in the equilibrium crystallization gap (Yeh and Feeney, 1996; Davies et al., 2002). AFPs lower the freezing point relative to the melting point by adsorbing to the ice surface (Davies et al., 2002). AFPs can inhibit tetrahydrofuran (THF), propane, methane and CO2 hydrates (Zeng et al., 2003; Zeng et al., 2006a; Zeng et al., 2006b; Uchida et al., 2007; Al-Adel et al., 2008). Gordienko et al.(2010) observed that AFP adsorption could modify THF hydrate morphology, therefore indicating that AFPs could inhibit hydrate growth likely by an adsorption-inhibition mechanism. The structures of AFP’s were shown in Figure 1.3. To our knowledge, only two reports have documented the utility of AFPs to inhibit hydrates formed from a natural gas mixture. Recently, Ohno et al., (2010) used HP-µDSC with a silica gel medium and reported biological 13 inhibitors can inhibit the natural gas hydrate formation. In addition, Jensen et al.,(2011) reported that an ice structuring protein was found to outperform PVCap for both structure I and structure II hydrate inhibition. Figure 1.3. The structures of AFP's with mutated residues Ala (blue) and Thr (yellow). Reprinted from ( Steffen et al., 2001), with permission from Elsevier. Thus, it is evident that these biological inhibitors can inhibit natural gas hydrate formation but how well they perform compared to commercial KHIs in an environment that approximates field conditions remains unknown. Despite this progress, however, the reasons behind the activities of either chemical or biological inhibitors towards hydrate crystal nucleation and growth are not well understood. The knowledge of kinetics and molecular level information of hydrate formation in the presence of kinetic inhibitors is important to ensure that these hydrates will not have enough time to form and block flow in pipelines at hydrate formation conditions. In addition to these restrictions, when a gas mixture is present, the formed hydrates are more complex than with a single component. For example, a mixture of methane and ethane can form sI if the methane concentration is below 75% or above 99%, but sII at intermediate 14 compositions (Ballard and Sloan, 2000; Subramanian et al., 2000a). Uchida et al.,(2004) reported that mixed methane and propane gases form sI and sII in two steps, with propane favored for enclathration, resulting in the an enriched methane gas phase, or a fractionation effect. In natural gas mixtures with three components, methane, ethane and propane, both sI and sII hydrates can form simultaneously depending on the gas composition (Uchida et al., 2006). Although the structures, cage occupancies and compositions of mixed gas hydrates have been reported (Subramanian, 2000; Uchida et al., 2004; Kida et al., 2007; Kumar et al., 2008b; Kida et al., 2009), the hydrate preparation protocol may impact these (Susilo et al., 2005; Seo et al., 2009), strongly suggesting that kinetics can play a significant role. Although the complexity associated with natural gas hydrates is daunting, it is nevertheless crucial information for industry in their efforts to manage hydrate formation. The majority of inhibition studies use single hydrate formers rather than gas mixtures, because of the inherit complexity of natural gas blends with regards to the different hydrate equilibria, structural characteristics, and diffusion constants of each of the components (Uchida et al., 2007; Kumar et al., 2008b; Seo et al., 2009). Makogon et al. (1997) studied tetrahydrofuran (THF) hydrate analogue of sII natural gas hydrate and their kinetic inhibition. Larsen et al. (1999) reported results for ethylene oxide (EO) hydrate as an analogue of methane hydrate (sI). Since both THF and EO are liquids, and are miscible in water, thereby eliminating mass transfer limitations. However, these liquid hydrates may not be suitable analogs to the kinetic studies of the inhibition process of gas hydrates. There is evidence that hydrates crystallized in the presence of gas mixtures do not behave like those formed from single gases (Rydzy et al., 2007; Nakagawa et al., 2008; Bruusgaard et al., 2009; Nihous et al., 2010). Even less understood is the decomposition kinetics of mixed gas hydrates in the presence of KHIs. 15 Nevertheless, understanding hydrate decomposition kinetics and predicting hydrate decomposition rates in presence of KHIs is important for efficient hydrate plug removal in pipelines. 1.4. Research  objectives   In spite of the fact that KHIs are deployed in the field we still do not completely understand how these molecules work at the molecular level. This lack of knowledge does not allow us to assess how a kinetic hydrate inhibitor would perform in the field (Klomp et al., 2008). In view of the fact that new synthetic and green inhibitors are being developed this thesis aims to employ several macroscopic and molecular-level methods to assess the performance of (a) synthetic inhibitors provided by industry and (b) newly discovered green inhibitors by Professor Virginia K. Walker at Queens University (Biology). The idea is to subject the inhibitors to a variety of testing conditions and thus understand their performance and the mechanism by which nucleation and crystal growth is affected. The assessment will be conducted with the use of a model methane/ethane/propane gas mixture as the hydrate forming substance. The specific objectives of this thesis and the anticipated outcomes are as follows; (a) To determine the performance of chemical and biological kinetic inhibitors on multi component hydrate formation and decomposition by isothermal and temperature ramping using high-pressure differential scanning calorimetry. This will reveal the extent of hydrate formation, hydrate nucleation temperature, hydrate nucleation time and hydrate stability in presence of inhibitors. (b) To fabricate a small-scale apparatus (crystallizer volume of 58 cm3), which is suitable to test inhibitors (many biological inhibitors are available in limited quantities). The possible 16 outcome is direct comparison of the formation and dissociation kinetics of mixed gas hydrates in the presence of chemical and biological kinetic hydrate inhibitors (KHIs). (c) To determine the effect of chemical and biological kinetic hydrate inhibitors on the structure (powder x-ray diffraction) and composition of hydrate (Raman and NMR spectroscopy). This will provide information about the hydrate structure and degree of filling of the hydrate small and large cavities in the presence of inhibitors. 1.5. Thesis  organization   The fundamental information and importance of gas hydrates is described in Chapter 1. This chapter also discusses the safety and flow assurance challenges of oil and gas industry due to gas hydrate formation in pipelines. The state of the art on hydrate research relevant to hydrate inhibition is also discussed. Chapter 2 discusses the effect of chemical and biological inhibitors on methane/ ethane/propane gas hydrate formation and decomposition in a custom small reactor using HP-DSC. Two types of temperature programming were used to investigate the performance of these inhibitors on hydrate nucleation, growth, and decomposition. Measurements of nucleation time of hydrate formation, amount of hydrate formed and hydrate decomposition temperature in the presence of inhibitors are presented and compared with pure water (control). In addition this chapter illustrates the differences in complex melting behavior of hydrate formed in two classes of inhibitors. Chapter 3 provides the details of the procedure developed to observe the decomposition kinetics in the presence of kinetic inhibitors using a newly fabricated stirred reactor (crystallizer volume of 58 cm3). The hydrate nucleation times, growth and decomposition kinetics in the presence of chemical and biological inhibitors reported and compared with a 17 control system. The inhibition strength of biological inhibitors was validated and compared with chemical inhibitors. The differences in onset and complete decomposition in the presence of inhibitors compared to control were presented. The importance, possible reasons and differences in decomposition behavior in the presence of inhibitors were discussed. Chapter 4 describes the observed differences in structure and composition of mixed hydrates formed in the presence of chemical and biological inhibitors using gas chromatography, powder x-ray diffraction, Raman and NMR spectroscopy. Powder X-ray diffraction and NMR spectroscopy showed that structure II hydrates dominated, as expected, but in the presence of the chemical inhibitors structure I was also present. The localized compositional complexity and heterogeneity were also observed in hydrate samples prepared in the presence of chemical inhibitor using Raman spectroscopy. The detailed procedure to calculate individual gas cage occupancy and calculated values were given in this chapter. The differences in cage occupancies and possible reasons were explained and correlated with complex melting and decomposition behavior observed in chapter 3 and 4. The conclusions of this work and recommendations for potential future work are given in chapter 5. 18 2. NATURAL GAS HYDRATE FORMATION AND DECOMPOSITION IN THE PRESENCE OF KINETIC INHIBITORS. I: HIGH PRESSURE CALORIMETRY 2.1. Introduction   Differential scanning calorimetry (DSC) is a thermo analytical technique that is used to measure the differential heat flow between the sample and a reference. The sample and the reference are cooled or heated at an identical rate. Gas hydrate formation and decomposition are phase transition processes. Hence, heat is released or absorbed in the sample cell compared to the reference under similar temperature environment. This differential heat flow signal is recorded and plotted versus temperature to identify the phase changes. High pressure-micro differential scanning calorimetry (HP-µDSC) has proved useful for the study of hydrate formation (Dalmazzone et al., 2002a; Koh, 2002; Dalmazzone et al., 2004; Le Parlouer et al., 2004; Ripmeester et al., 2007; Lachance et al., 2009), decomposition (Rueff et al., 1988; Dalmazzone et al., 2002b; Kawamura et al., 2006; Hughes, 2008; Koh et al., 2008a; Koh et al., 2008b; Nakagawa et al., 2008) and inhibition (Koh et al., 2002; Koh et al., 2009; Lachance et al., 2009; Nihous et al., 2010). Recently, Ohno et al., (2010) used HP-µDSC with a silica gel medium to examine the effect of chemical and biological kinetic inhibitors on natural gas hydrates formation. The strength of this work was that it allowed the collection of sufficient data for statistical analysis without any serious effects of pore size on the thermodynamics of hydrate formation (pore size > 1 micron). The formation equilibrium of mixed hydrates is complex and has been observed to shift (Uchida et al., 2007; Kumar et al., 2008b). Indeed, in the presence of small (< 1 micron) silica 19 pores the shift is to higher pressure and lower temperatures (Seo et al., 2009). Here we have used HP-µDSC to analyze the effect of chemical and biological kinetic hydrate inhibitors on a methane/ethane/propane hydrate formation, but without the use of silica. Therefore, the matrix does not influence the hydrate compositional changes, and we believe that this will provide insight into the mechanism of inhibition for the two types of inhibitors. 2.2. Materials   Two commercial hydrate kinetic inhibitors polyvinylpyrrolidone (average molecular weight ~10 kDa, from Sigma Aldrich), H1W85281 (average molecular weight ~3 kDa, a proprietary commercial product of unknown composition) and Type-III AFP (Swiss Prot Database accession number P19414; average molecular weight: 7 kDa) purchased from A/F Protein Canada Inc. This AFP was obtained by fermentation and secretion from recombinant Saccharomyces cerevisiae yeast cells, purified by differential diafiltration and kept at -20 ºC until used. Deionised water was used for the water controls and to dilute each of the inhibitors to 0.1 mM. The methane (93%)/ethane (5%)/propane (2%) gas mixture (UHP grade) was supplied by Praxair Technology Inc. 2.3. High-­pressure  differential  scanning  calorimetry   The HP–µ-DSC (DSC) used in this work was model VIIa; Setaram Inc., located at the National Research council, Ottawa, Canada and can be operated between 0.1 and 40 MPa and - 45 and +1000C. A ‘droplet insert’ (Figure 2.1) was fabricated using Torlon ® (polyamide-imide; Boedeker Plastics, Texas). Briefly, a base (dia-5.4 mm) with four depressions (dia-1.4 mm, depth-1.3 mm) was supported by rod (dia-1.68 mm, length-9 mm). 20 Figure 2.1. Droplet insert used for differential scanning calorimeter experiments Samples of water or inhibitor soutions (1 µL) were placed into the depressions using a micro-syringe and then transferred to a high-pressure cell, and then pressurized (9 MPa) with the methane/ethane/propane gas mixture. When the pressure in the sample cells reached the desired value, one of two types of temperature programs were used (Figure 2.2). For isothermal experiments, the temperature remained constant at -8 °C for 10 h and the pressure was kept at 9.0 MPa. For temperature ramping experiments, the temperature was decreased from +25 to -45 0C at a rate of 0.25°C per min and then increased to 25 0C at the same rate. Figure 2.2. Isothermal (left) and temperature ramping (right) programs used in DSC experiments. 21 In some experiments several temperature ramping protocols were followed sequentially so that the samples were effectively cycled through several freeze-thaw events with 5 min at 25 0C between cycles. The first re-crystallization was designated as cycle two, the subsequent re- crystallization designated as cycle three, and so on. Temperature ramping and isothermal experiments were repeated with each sample analyzed in quadruplicate a total of four times (n=16). 2.4. Data  analysis   The amount of hydrate formed depends on the rate of the hydrate growth and the duration of the run, thus it was important that these parameters be well controlled in all experiments. The amount of hydrate formed was estimated by subtracting the ice to hydrate transformation (calculated from the observed exothermic peak areas) from the amount of total hydrate formed (calculated from the hydrate melting peak areas). The mean hydrate was then expressed as a percent relative to the hydrate formed from the water samples. The average nucleation time is defined as the average of all the nucleation times associated with the observed nucleation events in a particular isothermal experiment. 2.5. Results  and  discussion   2.5.1. Isothermal experiments Isothermal experiments provided information on the induction time for hydrate nucleation, determined by the appearance of exothermic peaks (Figure 2.3). 22 Figure 2.3. Typical isothermal experiments showing hydrate nucleation events for (a) 11 h (b) 3 h The first nucleation event observed in three experiments without hydrate inhibitors was at ~ 48 min with the first nucleation event delayed almost 10-20 min in the presence of PVP and AFP, and more than 1.5 h with H1W85281 (Table 1). Overall, average hydrate nucleation times were: water (114 min)