DEVELOPMENT OF NI-BASED CATALYSTS, CERIA NANO-STRUCTURES AND CATALYTIC MEMBRANE REACTOR FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION SAW ENG TOON NATIONAL UNIVERSITY OF SINGAPORE 2014 DEVELOPMENT OF NI-BASED CATALYSTS, CERIA NANO-STRUCTURES AND CATALYTIC MEMBRANE REACTOR FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION SAW ENG TOON (Master, University Science Malaysia) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2014 DECLARATION I hereby declare that the thesis is my original work and it has been written by me in its entirely I have duly acknowledged all the sources of information which have been used in the thesis This thesis has also not been submitted for any degree in any university previously _ Saw Eng Toon 30 June 2014 Acknowledgements ACKNOWLEDGEMENTS First and foremost, I would wish to convey my deepest appreciation to my supervisor, Professor Hidajat Kus and co-supervisor, Professor Kawi Sibudjing for their continual guidance, motivation, inspiration and advices which are critical in assisting me throughout my research works Under their supervisions, I am capable to produce plenty of accomplishments such as proposal writing, equipments repairing and servicing as well as the ability of in depth thinking particularly in the scientific research field I wish to utter thousands of appreciation to my lab mates, senior and friends (Dr Wu Xusheng, Dr Ni Jun, Dr Yang Nai-tao, Dr Mo Liu-ye, Dr Ashok Jangam, Dr Usman Oemar, Dr Kesada Sutthiumporn, Dr Warintorn Thitsartarn, Dr Thawatchai Maneerung, Dr Yasotha Kathiraser, Li Ziwei, Gao Xingyuan, Ang Ming Li and Wang Zhigang) for their sharing of knowledge, moral support, laughter and joy Their kindness, helpfulness, dedications and contributions really enlightened me to place my research works in a successful manner In fact, they are very keen on their research which has motivated my deep involvement in the research field particularly in catalysis and inorganic membrane Sincere thanks and appreciation go to the laboratory officers (Alyssa Tay, Ang Wee Siong, Evan Tan, Alistair Chan, Sandy Khoh, Jamie Siew, Ng Kim Poi), technical staffs (Mr Liu Zhicheng, Dr Yuan Ze Liang, Mr Chia Phai Ann, Mr Mao Ning, Mr Qin Zhen, Mr Boey, Mr Toh and Mr Rajamohan) and undergraduate students in chemical and biomolecular engineering department for their help, guide and assist in conducting the experiments and teach me plenty of technical knowledge and safety manner which are very useful for my research work Last but not least, I would like to thank my family for their full support in encouraging me to pursue my Philosophy of Doctoral Degree Thousand words of thanks, I would like to utter for their loves, care, patience, support and encouragement Although I have owed them plenty of weekend and holiday, they are still offering their vital support for me Millions of thanks, I express would only be a token of appreciation for them Thank you all i Table of Contents TABLE OF CONTENTS Acknowledgements …………………………………………………… i Table of Contents ……………………………………………………… ii Summary ………………………………………………………………… vii List of Tables …………………………………………………………… ix List of Figures …………………………………………………………… xi Nomenclature …………………………………………………………… xv Abbreviations …………………………………………………………… xvi CHAPTER 1.1 1.2 1.3 1.4 INTRODUCTION Research background …………………………………… Research objectives ……………………………………… Organization of thesis …………………………………… References ……………………………………………… CHAPTER LITERATURE REVIEW 2.1 Overview of catalysts in water gas shift reaction………… 2.1.1 Thermodynamic study …………………………… 2.2 Catalysts for high temperature water gas shift reaction … 2.2.1 Metal oxide catalyst …………………………… 2.2.2 Metal supported catalyst ………………………… 2.2.2.1 Copper based catalyst ………………… 2.2.2.2 Nickel based catalyst ………………… 2.3 Catalyst support ………………………………………… 10 2.3.1 Inert support ……………………………………… 10 2.3.1.1 Silica (SiO2) …………………………… 10 2.3.2 Active support …………………………………… 11 2.3.2.1 Ceria (CeO2) …………………………… 11 2.3.2.1.1 Synthesis method …………… 12 2.3.2.1.2 Intrinsic properties of CeO2 … 12 2.4 Core-shell catalyst ……………………………………… 17 2.4.1 Metal core and mixed oxide shell synthesis …… 17 2.4.2 Core-shell catalyst properties for water gas shift reaction …………………………………………… 18 2.5 Reaction mechanism study ……………………………… 19 2.5.1 Redox\Regenerative mechanism ………………… 19 2.5.2 Associative mechanism ………………………… 23 2.5.2.1 Formate mechanism …………………… 23 2.5.2.2 Carboxyl/Carboxylate mechanism … 26 2.5.2.3 Carbonate mechanism ………………… 28 2.5.2.4 Formate mechanism with redox regeneration …………………………… 29 2.5.3 Catalyst active site ………………………………… 29 2.6 Kinetic studies for water gas shift reaction ……………… 31 ii Table of Contents 2.6.1 2.7 2.8 2.9 2.10 CHAPTER 3.1 3.2 3.3 3.4 Validation of mass transfer and heat transfer limitation (Koros-Nowak) ………………………………… 32 2.6.2 Kinetic model (Power law) ……………………… 32 2.6.3 Experimental methods to identify the active/spectator intermediate species in water gas shift reaction … 33 2.6.3.1 In-situ DRIFTS study ………………… 34 2.6.3.2 Operando DRIFTS-Mass spectrometer study …………………………………… 34 2.6.3.3 Steady-state isotope transient kinetic analysisDRIFTS-MS (SSITKA-DRIFTS-MS) … 35 Limitations of current high temperature water gas shift catalysts ………………………………………………… 36 Overview of catalytic membrane reactor (CMR) for pure hydrogen production …………………………………… 37 2.8.1 Studies of dense metal membrane ……………… 38 2.8.1.1 H2 transport mechanism ……………… 38 2.8.1.2 Pd membrane fabrication ……………… 39 2.8.2 CMR for water gas shift reaction ………………… 39 2.8.2.1 Configuration of CMR for water gas shift reaction ………………………………… 40 2.8.2.2 Process variables on the operation of Pd-based CMR for WGS reaction……… 41 Limitations of CMR for water gas shift reaction ………… 42 References ……………………………………………… 43 EXPERIMENTAL AND APPARATUS Catalytic reaction system ….……………………………… 52 Catalytic activity measurement ………………………… 53 Kinetic measurement …………………………………… 54 Catalyst characterizations ……………………………… 54 3.4.1 Specific surface area and pore size measurement … 54 3.4.2 Inductive-Coupled Plasma-Mass Spectrometer (ICP-MS) measurement ……………………………………… 55 3.4.3 Pulse chemisorption for metal surface area and dispersion measurement …………………………… 55 3.4.4 X-ray diffraction measurement …………………… 56 3.4.5 EXAFS measurement (Extended X-ray Absorption Fine Structure) ………………………………………… 56 3.4.6 H2 -Temperature-programmed reduction measurement (H2-TPR) ………………………………………… 56 3.4.7 CO-Temperature-programmed reduction\desorptionMass Spectrometer measurement (CO-TPR/TPD-MS) ……………………………… 57 3.4.8 Field-Emission Scanning Electron Microscope (FESEM) ………………………………………… 57 3.4.9 Field Emission Transmission Electron Microscopy Energy Dispersive X-ray (FETEM-EDX) ………… 58 3.4.10 X-ray Photoelectron Spectroscopy measurement (XPS) ……………………………………………… 58 iii Table of Contents 3.4.11 Diffuse Reflectance Infrared Fourier Transform Spectroscopy measurement (DRIFTS) …………… 58 3.5 Catalytic membrane reactor system ……………………… 59 3.6 Hydrogen permeance and selectivity measurement ……… 60 3.7 Pd-membrane characterizations ………………………… 60 3.7.1 Scanning Electron Microscope (SEM) …………… 60 CHAPTER BIMETALLIC Ni-Cu CATALYST SUPPORTED ON CeO2 FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION: SELECTIVE AND ACTIVE CATALYST 4.1 Introduction ……………………………………………… 61 4.2 Experimental ……………………………………………… 64 4.2.1 Catalysts preparation ……………………………… 64 4.2.2 Catalysts characterizations ………………………… 64 4.2.3 Catalysts activity ………………………………… 67 4.2.4 Kinetic measurement ……………………………… 69 4.3 Results and discussions …………………………………… 69 4.3.1 Catalysts characterizations ……………………… 69 4.3.1.1 Surface area and chemical compositions of xNiyCu/CeO2 catalysts ………………… 69 4.3.1.2 X-ray diffraction measurement ………… 71 4.3.1.3 EXAFS measurement ………………… 73 4.3.1.4 H2-TPR measurement ………………… 74 4.3.1.5 XPS measurement ……………………… 76 4.3.1.6 DRIFTS study of CO adsorption on Ni/Cu Ration for bimetallic catalyst………… 79 4.3.1.7 CO-TPR-MS analysis ………………… 87 4.3.1.8 CO-TPD-MS analysis ………………… 89 4.3.2 Catalytic activity and selectivity ………………… 92 4.3.3 The role of Ni-Cu alloy supported on CeO2 in methane suppression ……………………………………… 95 4.3.4 Kinetic study of the 5Ni5Cu/CeO2 catalyst ……… 96 4.4 Conclusions ……………………………………………… 105 4.5 References ………………………………………………… 106 CHAPTER THE EFFECT OF CERIA CRYSTAL SIZES AS CATALYST SUPPORT FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION: THE ROLE OF CeO2 CRYSTAL SIZE 5.1 Introduction ……………………………………………… 112 5.2 Experimental ……………………………………………… 114 5.2.1 Catalysts preparation ….………………………… 114 5.2.2 Catalysts characterizations ……………………… 115 5.2.3 Catalysts activity ……………………………… 115 5.3 Results and discussions ………………………………… 116 5.3.1 X-ray Diffraction measurement ………………… 116 5.3.2 Catalyst morphology (FESEM) ………………… 120 5.3.3 Textural properties of catalyst supports (ceria) and catalysts ………………………………………… 120 5.3.4 H2-TPR measurement …………………………… 121 5.3.5 X-ray Photoelectron Spectroscopy (XPS) measurement ……………………………………… 123 iv Table of Contents Catalytic activity ………………………………… 128 TPR-CO-MS measurement ……………………… 131 In-Situ DRIFTS for CO adsorption ……………… 135 5.3.8.1 Support ………………………………… 135 5.3.8.2 Reduced catalyst ……………………… 139 Discussions ……………………………………………… 141 5.4.1 The role of CeO2 catalyst support size …………… 141 5.4.2 Plausible reaction mechanism …………………… 141 Conclusions ……………………………………………… 143 References ………………………………………………… 144 5.3.6 5.3.7 5.3.8 5.4 5.5 5.6 CHAPTER THERMALLY-STABLE CEO2 NANO-SHAPES AS CATALYST SUPPORTS FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION: EFFECT OF MORPHOLOGY ON SURFACE AND CATALYTIC PROPERTIES 6.1 Introduction ……………………………………………… 149 6.2 Experimental ……………………………………………… 151 6.2.1 Catalysts preparation ……………………………… 151 6.2.2 Catalysts characterizations …………………………152 6.2.3 Catalysts activity ………………………………… 152 6.3 Results …………………………………………………… 153 6.3.1 X-ray Diffraction analysis ………………………… 153 6.3.2 Catalyst morphology (FESEM) …………………… 156 6.3.3 Textural properties of ceria nano-shapes supports and catalysts …………………………………………… 157 6.3.4 H2-TPR and N2O pulse titration analyses ………… 158 6.3.5 X-ray Photoelectron Spectroscopy (XPS) analysis 160 6.3.6 Catalytic activity ………………………………… 165 6.3.7 TPR-CO-MS analysis …………………………… 170 6.3.8 In-situ DRIFTS for CO adsorption on ceria nanoshapes ……………………………………… 174 6.3.9 The intrinsic properties for ceria nano-shape …… 178 6.3.10 The role of CeO2 nano-shapes in water gas shift reaction …………………………………………… 179 6.4 Conclusions ……………………………………………… 180 6.5 References ………………………………………………… 181 CHAPTER BIMETALLIC Ni-Cu CORE CERIA SHELL FOR HIGH TEMPERATURE WATER GAS SHIFT: THE UNIQUE PROPERTIES OF CORE-SHELL STRUCTURE 7.1 Introduction ……………………………………………… 185 7.2 Experimental ……………………………………………… 187 7.2.1 Catalysts preparation …………………………… 187 7.2.2 Catalysts characterizations ……………………… 189 7.2.3 Catalytic activity ………………………………… 190 7.3 Results and discussions ………………………………… 190 7.3.1 Surface area and chemical compositions of core shell catalysts …………………………………………… 190 7.3.2 XRD analysis ……………………………………… 192 7.3.3 Catalyst morphology (FETEM) ………………… 195 v Table of Contents 7.3.4 H2-TPR measurement …………………………… 196 7.3.5 X-ray Photoelectron Spectroscopy (XPS) analysis 200 7.3.6 Catalytic activity ………………………………… 204 7.3.7 CO-TPR-MS ……………………………………… 207 7.3.8 In-situ DRIFTS for CO adsorption ……………… 209 7.4 Discussions ……………………………………………… 215 7.5 Conclusions ……………………………………………… 216 7.6 References ………………………………………………… 217 CHAPTER CATALYTIC HOLLOW FIBER MEMBRANE REATOR FOR HIGH TEMPERATURE WATER GAS SHIFT REACTION 8.1 Introduction ……………………………………………… 220 8.2 Experimental ……………………………………………… 223 8.2.1 Pd/Al2O3-YSZ hollow fiber composite membrane preparation ……………………………………… 223 8.2.2 Synthesis of NiCu/CeO2 catalyst ……………… 226 8.2.3 Water gas shift (WGS) catalytic membrane reaction studies …………………………………………… 227 8.2.4 Characterization of the Pd membrane/ membrane support - Scanning Electron Microscope (SEM) … 227 8.3 Results and discussions ………………………………… 228 8.3.1 Fabrication of membrane support (Al2O3-YSZ) … 228 8.3.1.1 The effect of sintering temperature …… 229 8.3.1.2 The effect of internal coagulant (bore fluid) composition …………………………… 230 8.3.2 Fabrication of Pd membrane - parameter optimization ……………………………………… 231 8.3.2.1 The effect of coating solution flow rates 232 8.3.2.2 The effect of coating time …………… 234 8.3.3 Hydrogen permeation test ………………………… 236 8.3.4 Catalytic activity test ……………………………… 237 8.4 Conclusions ……………………………………………… 239 8.5 References ………………………………………………… 240 CHAPTER CONCLUSIONS AND RECOMMENDATIONS 9.1 Conclusions ……………………………………………… 242 9.2 Future works ……………………………………………… 244 APPENDICES Appendix A Appendix B Appendix C Appendix D Appendix E vi Summary SUMMARY Hydrogen is envisioned as a renewable and clean energy in near future The water gas shift (WGS) reaction is one of the important downstream processes to remove carbon monoxide and upgrade hydrogen production The thermodynamic favorable and kinetically limited of WGS reaction at low reaction temperature (