ZEOLITIC IMIDAZOLATE FRAMEWORKS/ POLYBENZIMIDAZOLE NANOCOMPOSITE MEMBRANES FOR HYDROGEN PURIFICATION YANG TINGXU NATIONAL UNIVERSITY OF SINGAPORE 2012 ZEOLITIC IMIDAZOLATE FRAMEWORKS/ POLYBENZIMIDAZOLE NANOCOMPOSITE MEMBRANES FOR HYDROGEN PURIFICATION YANG TINGXU (B. Eng., Shanghai Jiao Tong University, P. R. China) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY NUS GRADUATE SCHOOL FOR INTEGRATIVE SCIENCES AND ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2012 ACKNOWLEDGEMENTS I wish to take this opportunity to express my sincere appreciation to all the contributors during my years in the National University of Singapore. First of all, I am especially grateful to my supervisor, Professor Chung Tai-Shung, Neal, for his generously guidance and support without hesitation. Over the past three years, he has added value to me with numerous opportunities and well-equipped research facilities. He has trained me as an independent researcher and enlighten me to achieve more than what I ever expect. I wish to express my gratefully thanks to my mentor, Dr. Xiao Youchang, who has provided invaluable advice, inspiration and encouragement to me during my starting period of PhD candidate. Without him, I may undergo a harder time for the first year, and a significant portion of the work included herein may not have been achieved. I also appreciate the assistance from my TAC members, Professor Zeng Hua Chun and Dr. Pramoda Kumari Pallathadka, for their valuable comments and discussions. I would like to acknowledge the research scholarship by the NUS Graduate School of Integrative Sciences and Engineering (NGS) and thank the Singapore National Research Foundation (NRF) for the financial support that enables this work to be successfully completed. I am also thankful to Ms. Tricia Chong and Ms. Yong Yoke Ping for their kindest advice and help during the patent documentation. I would like to convey my appreciation to all members of Prof. Chung‘s group, especially Ms. Wang Huan, Mr. Chen Hangzheng, Mr. Li Fuyun, Miss Chua Mei Ling, Dr. Low Bee Ting, Mr. Ong Yee Kang, Dr. Dave William Mangindaan, Dr. Su i Jincai, Mr. Wang Peng, Miss Xing Dingyu, Dr. Wang Rongyao, and many others for plenty of good times, discussion and sharing of knowledge. Special thanks are due to Mr. Shi Gui Min for all his kind cooperation and help in the laboratory. Finally, I must express my deepest gratefulness to my family for their endless support, especially to my dearest husband Jiye for his unfailing love, patience, and understanding during the three and a half years period of 5450 km long-distance relationship. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................ i TABLE OF CONTENTS ............................................................................................. iii SUMMARY ................................................................................................................ ix NOMENCLATURE ..................................................................................................... xi LIST OF TABLES ...................................................................................................... xiv LIST OF FIGURES .................................................................................................... xvi CHAPTER 1 INTRODUCTION ................................................................................... 1 1.1 Hydrogen for industrial feed and sustainable development ................................. 2 1.2 Membrane technology for gas separation ............................................................ 5 1.3 Diversity of membrane materials ......................................................................... 9 1.3.1 Polymers ....................................................................................................... 9 1.3.2 Inorganics .................................................................................................... 10 1.3.3 Organic-inorganic hybrids .......................................................................... 12 1.4 Gas transport mechanism ................................................................................... 14 1.5 Membrane fabrication and structures ................................................................. 18 1.6 Types of membrane module configurations ...................................................... 19 1.7 Process and cost optimization ............................................................................ 21 1.8 Research objectives and organization of dissertation ........................................ 23 1.9 References .......................................................................................................... 27 CHAPTER 2 LITERATURE REVIEW ...................................................................... 34 iii 2.1 Membrane material design principles for hydrogen purification ...................... 35 2.2 H2-selective polymeric membranes for hydrogen purification .......................... 36 2.3 CO2-selective polymeric membranes for hydrogen purification ....................... 40 2.4 Polybenzimidazole based membranes for gas separation .................................. 41 2.5 ZIFs based crystalline membranes and mixed matrix membranes .................... 44 2.6 Particle synthesis and dispersion methods for mixed matrix membranes ......... 46 2.7 Challenges and future prospects ........................................................................ 48 2.8 References .......................................................................................................... 50 CHAPTER 3 METHODOLOGY ................................................................................ 58 3.1 Materials ............................................................................................................ 59 3.1.1 Polymers and solvents................................................................................. 59 3.1.2 ZIFs synthesis agents .................................................................................. 60 3.2 ZIFs nanoparticle synthesis................................................................................ 60 3.2.1 ZIF-7 nanoparticle synthesis ....................................................................... 60 3.2.2 ZIF-8 nanoparticle synthesis ....................................................................... 61 3.2.3 ZIF-90 nanoparticle synthesis ..................................................................... 62 3.3 Membrane fabrication and post treatment protocols ......................................... 63 3.3.1 ZIFs/PBI dense films .................................................................................. 64 3.3.2 Co-extrusion of ZIF-8-PBI/Matrimid dual-layer hollow fibers .................. 64 3.4 ZIFs nanoparticles and membranes characterization ......................................... 65 3.4.1 Dynamic light scattering (DLS) .................................................................. 65 3.4.2 Transmission electron microscope (TEM).................................................. 66 3.4.3 Field emission scanning electron microscopy (FESEM) ............................ 66 3.4.4 Wide-angle X-ray diffraction (XRD).......................................................... 67 iv 3.4.5 Nuclear magnetic resonance spectroscopy (NMR) ..................................... 67 3.4.6 Fourier transform infrared spectroscopy (FTIR) ........................................ 68 3.4.7 Thermo gravimetric analysis (TGA) ........................................................... 68 3.4.8 Positron annihilation lifetime spectroscopy (PALS) .................................. 68 3.4.9 Positron annihilation spectroscopy (PAS) .................................................. 69 3.4.10 Differential scanning calorimetry (DSC) .................................................. 70 3.4.11 Density measurement ................................................................................ 70 3.5 Determination of gas transport properties .......................................................... 71 3.5.1 Pure gas permeation .................................................................................... 71 3.5.2 Mixed gas permeation ................................................................................. 73 3.5.3 Measurements of gas sorption .................................................................... 76 3.6 References .......................................................................................................... 78 CHAPTER 4 ZIF-7/PBI NANO-COMPOSITE MEMBRANES FOR HYDROGEN PURIFICATION ................................................................................... 81 4.1 Introduction ........................................................................................................ 82 4.2 Results and discussion ....................................................................................... 86 4.2.1 ZIF-7 particle dispersion in the PBI matrix ................................................ 86 4.2.2 Characterizations......................................................................................... 91 4.2.3 Gas transport properties .............................................................................. 96 4.3 Conclusions ...................................................................................................... 101 4.4 References .......................................................................................................