THE DEVELOPMENT OF PERVAPORATION MEMBRANES FOR ALCOHOL DEHYDRATION QIAO XIANGYI NATIONAL UNIVERSITY OF SINGAPORE 2007 THE DEVELOPMENT OF PERVAPORATION MEMBRANES FOR ALCOHOL DEHYDRATION QIAO XIANGYI (MSc. (Env. Eng.), NUS) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2007 ACKNOWLEDGEMENTS I would like to express my sincere appreciation to all who have provided me guidance and support on my path to complete the PhD study. First of all, I wish to express my deepest appreciation and thanks to my immediate PhD supervisor, Prof. Chung Tai-Shung. It was he who led me into the fascinating area of membrane research, who inspired me when I faced hard times in my research, who gave me continuous support and invaluable guidance not only limited to academic aspect but also on personal character improvement. I am also indebted to my co-supervisor, Dr. Pramoda Kumari Pallanthadka for her consistent consultation, helpful comments and the facilities provided throughout my entire PhD candidature. In addition, I would like to acknowledge here my gratitude for the unselfish guidance from Prof. Takashi Matsuura. I would like to thank my thesis committee members, Prof. Loh Kai Chee and Prof. Feng SiShen for their valuable discussion and constructive suggestions throughout my PhD candidature. Special thanks are due to all the team members in Prof. Chung’s research group for their suggestions and friendship, including Dr. Cao Chun, Dr. Li Dong Fei, Ms Guo Wei Fen, Ms Chng Mei Lin, Ms Tin Pei Shi, Ms Teoh May May, Ms Guan Huai Min, Dr. Huang Zhen, Ms Jiang Lan Ying, Ms Wang Yan, Ms Natalia Widjojo, Mr. Wang i Kai Yu, Mr. Xiao You Chang, Mr. Li Yi, Mr. Xiong Jun Ying, Mr. Zhou Chun, and Mr. Sina Bonyadi. I would also extend my thanks and appreciation to all my friends. I would also like to acknowledge the research scholarship and financial support from National University of Singapore (NUS), Merck and A*Star, with the grant numbers of R-279-000-111-112, R-279-000-165-112, R-279-000-184-112, 052-101-0014 (A*Star), N-279-000-008-001 (Merck), respectively. Last but not least, I would like to share the accomplishment with my mother Ms. Wang Chunxiang, my father Mr. Qiao Shuangding and my husband Mr. Liu Ruixue, for their unconditioned love and the moral support. ii TABLE OF CONTENTS ACKNOWLEGEMENTS i TABLE OF CONTENTS iii SUMMARY x NOMENCLATURE xiii LIST OF TABLES xvii LIST OF FIGURES xx CHAPTER INTRODUCTION OF PERVAPORATION MEMBRANES 1.1 General Introduction of Membrane Separation Processes 1.2 Overview of Pervaporation Membrane Separation Processes 1.2.1 Classifications of pervaporation membrane separation processes 1.2.2 Performance characterization of pervaporation membranes 1.3 Historical Development of Pervaporation Membrane Separation Processes 1.4 Industrial Applications of Pervaporation Processes 11 1.4.1 1.5 The importance of pervaporation as a separation process 11 1.4.2 Dehydration of alcohols or other liquid organics 13 1.4.3 Removal of volatile organics from water or solvent recovery 14 1.4.4 Organic/organic separation 16 Research Objectives and Organization of Dissertation 16 CHAPTER THEORETICAL BACKGROUND 20 2.1 20 Transport Mechanisms 2.1.1 Solution diffusion model 20 iii 2.1.2 2.2 Pore flow model 23 Pervaporation Membranes for Alcohol Dehydration 2.2.1 25 Membrane materials 25 2.2.1.1 Natural organic materials 26 2.2.1.2 Synthesized polymer materials 27 2.2.1.3 Inorganic materials 31 2.2.2 Membrane structures and configurations 32 2.2.3 Membrane preparation methods 34 2.2.4 2.2.3.1 Phase inversion 34 2.2.3.2 Other preparation methods 37 Membrane modifications 2.2.4.1 38 Heat treatment 38 2.2.4.2 Chemical modification 39 2.2.4.3 40 Mixed matrix membranes 2.3 Formation Mechanism of Phase Inversion Membranes 41 2.4 Factors Affecting Permeant Transport in Pervaporation 43 2.4.1 Interaction between permeants and membrane 43 2.4.2 Interaction between permeant and permeant 45 2.4.3 Operating conditions 45 2.4.3.1 Feed mixture composition 45 2.4.3.2 Feed temperature 46 2.4.3.3 Upstream pressure 48 2.4.3.4 Downstream pressure 49 2.4.3.5 Concentration polarization 49 2.4.3.6 Hysterisis phenomena 50 iv CHAPTER EXPERIMENTAL 51 3.1 Materials 51 3.1.1 PVA/PAN composite membranes 51 3.1.2 Polymer 52 3.1.3 Cross-linking agents 52 3.1.4 Molecular sieves 53 3.1.5 Others 3.2 54 Membrane Preparation 54 3.2.1 Fabrication of flat dense P84 membranes 54 3.2.2 Fabrication of asymmetric P84 membranes 54 3.2.3 Fabrication of P84/Zeolite mixed matrix membranes 55 3.2.4 56 Chemical and thermal modification of membranes 3.3 Sorption Experiments 56 3.4 Pervaporation Experiments 57 3.5 Gas Permeation Tests 61 3.6 Ternary Phase Diagrams 62 3.7 Membrane Characterizations 62 3.7.1 Fourier transform infrared spectrometer (FTIR) 62 3.7.2 Contact angle measurements 62 3.7.3 Wide-angle X-ray diffraction (XRD) 63 3.7.4 Differential scanning calorimeter (DSC) 63 3.7.5 63 Thermogravimetric analysis (TGA) 3.7.6 Field emission scanning electron microscope (FESEM) and SEM-EDX 64 3.7.7 Atomic Force Microscope (AFM) 64 3.7.8 Nano-indentation test 64 v 3.7.9 X-ray Photoelectron Spectroscopy (XPS) 64 3.7.10 UV-Vis measurement 65 3.7.11 Membrane density measurement 65 CHAPTER DEHYDRATION OF ISOPROPANOL AND ITS COMPARISON WITH DEHYDRATION OF BUTANOL ISOMERS FROM 66 THERMODYNAMIC AND MOLECULAR ASPECTS 4.1 Introduction 66 4.2 Results and Discussion 70 4.2.1 ATR-FTIR analysis 70 4.2.2 Influence of feed water concentration and temperature on water flux and permeance 4.2.3 71 Influence of feed water concentration and temperature on IPA flux and permeance 75 4.2.4 Separation factor and selectivity of PERVAP 2510 and PERVAP 2201 78 4.2.5 A comparison of the dehydration of aqueous homologous alcohol mixtures through PVA/PAN composite membranes 4.3 81 Conclusions 86 CHAPTER FABRICATION AND CHARACTERIZATION OF BTDATDI/MDI (P84) CO-POLYIMIDE MEMBRANES FOR THE 89 PERVAPORATION DEHYDRATION OF ISOPROPANOL 5.1 Introduction 89 5.2 93 Results and Discussions 5.2.1 The apparent intrinsic properties of P84 dense membranes 93 vi 5.2.2 P84 asymmetric membranes 96 5.2.2.1 Phase diagram of the P84/NMP/non-solvent system 96 5.2.2.2 Performance of P84 membranes prepared from different nonsolvents as additives 5.3 98 5.2.2.3 Influence of heat treatment on membrane properties and performance 100 5.2.2.4 Effects of feed temperature on separation performance and the hysteresis phenomenon 106 5.2.2.5 Effect of feed water concentration 110 Conclusions 111 CHAPTER FUNDAMENTAL CHARACTERISTICS OF SORPTION, SWELLING AND PERMEATION OF P84 CO-POLYIMIDE MEMBRANES FOR PERVAPORATION DEHYDRATION OF 113 ALCOHOLS 6.1 Introduction 113 6.2 114 Results and Discussion 6.2.1 Swelling and sorption of P84 dense membranes 114 6.2.2 Separation performances of P84 asymmetric membranes in various alcohol/water mixtures 6.3 117 Conclusions CHAPTER DIAMINE 122 MODIFICATION OF P84 CO-POLYIMIDE MEMBRANES FOR PERVAPORATION DEHYDRATION OF 124 ISOPROPANOL 7.1 Introduction 124 vii 7.2 Results and Discussion 127 7.2.1 Characterization of P84 membranes cross-linked with p-xylenediamine 7.2.2 Pervaporation performance of P84 asymmetric membranes cross-linked 128 with p-xylenediamine 7.2.3 7.3 136 Characterization and pervaporation performance of P84 membranes crosslinked with ethylenediamine (EDA) 137 7.2.4 Effect of heat treatment on p-xylenediamine cross-linked membranes 140 7.2.5 Effects of operating temperature on cross-linked membranes 145 Conclusions 146 CHAPTER ZEOLITE FILLED P84 CO-POLYIMIDE MEMBRANES FOR DEHYDRATION OF ISOPROPANOL THROUGH 148 PERVAPORATION PROCESS 8.1 Introduction 148 8.2 Results and Discussions 151 8.3 8.2.1 Effects of annealing temperature 151 8.2.2 Effects of different types of zeolite: 13X vs. 5A 154 8.2.3 Gas separation performance of zeolite 5A and 13X filled P84 membranes 161 8.2.4 Effects of zeolite 13X content 162 Conclusions 166 CHAPTER CONCLUSIONS AND RECOMMENDATIONS 167 9.1 167 Conclusions 9.1.1 The dehydration of IPA and a comparison of coupled transport in aqueous IPA and butanol 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Pramoda, Fabrication and characterization of BTDA-TDI/MDI (P84) co-polyimide membranes for the pervaporation dehydration of isopropanol, Journal of Membrane Science 264 (2005) 176. 5. X.Y. Qiao, T.S. Chung, W.F. Guo, T. Matsuura, M.M. Teoh, Dehydration of isopropanol and its comparison with dehydration of butanol isomers from thermodynamic and molecular aspects, Journal of Membrane Science 252 (2005) 37. 6. R.X. Liu, X.Y. Qiao, T.S. Chung, The development of high performance P84 copolyimide hollow fibers for pervaporation dehydration of isopropanol, Chemical Engineering Science 60 (2005) 6674. 7. Z. Huang, H.M.Guan, W.L. Tan, X.Y. Qiao, S. Kulprothipanja, Pervaporation study of aqueous ethanol solution through zeolite-incorporated multilayer poly(vinyl alcohol) membranes: Effect of zeolites, Journal of Membrane Science 276 (2006) 260. 209 Conference papers: 1. X.Y. Qiao, T.S. Chung, Dense and asymmetric BTDA-TDI/MDI (P84) copolyimide membranes for pervaporation dehydration of different alcohol systems, NAMS 2005, Providence, Rhode Island, U.S.A. 2. R.X. Liu, X.Y. Qiao, T.S. Chung, The pervaporation dehydration of isopropanol by BTDA-TDI/MDI (P84) co-polyimide membranes, AIChE 2005 annual meeting, Cincinnati, U.S.A. 3. X.Y. Qiao, R.X. Liu, T.S. Chung, The sorption characteristic and pervaporation performance of BTDA-TDI/MDI (P84) co-polyimide membranes for alcohol dehydration, NAMS 2006, Chicago, U.S.A. Patent: 1. T.S. Chung, X.Y. Qiao, R.X. Liu, A method of treating a permeable membrane, U.S. Patent PCT/SG2005/00430. 210 [...]... characterization of BTDA-TDI/MDI (P84) co-polyimide membranes for the pervaporation dehydration of IPA 9.1.3 169 The sorption, swelling and permeation characteristics of P84 co-polyimide membranes for pervaporation dehydration of alcohols 9.1.4 169 Diamine modifications of P84 co-polyimide membranes for pervaporation dehydration of IPA 9.1.5 170 P84-based zeolite mixed matrix membranes for pervaporation dehydration. .. asymmetric membranes Table 7.4 Nano-indentation results of the original and modified P84 asymmetric membranes Table 7.5 Pervaporation performance of the original and p-xylenediamine crosslinked P84 asymmetric membranes Table 7.6 Pervaporation performance of the original and EDA cross-linked P84 asymmetric membranes Table 7.7 UV wavelength and color changes of modified P84 membranes Table 7.8 Pervaporation. .. that by EDA For pervaporation dehydration of IPA, an increase in the degree of cross-linking initially resulted in an increase in selectivity with the compensation of lower permeance However, further increase in the degree of cross-linking might swell up the polymeric chains because of the hydrophilic nature of diamine compounds; this resulted in decreased separation performance Cross-linked membranes. .. 2001) New developments in membrane science and technology have significant impact in industries technically and commercially, and therefore remain in the frontier of researches The selective transport of certain species across the membrane is determined by the driving force difference across the membrane, the mobility and concentration of each species in the membrane The driving force across the membrane... evidently reflected the intrinsic properties of pervaporation membranes such as degree of crosslinking and hydrophilicity, and revealed the coupled transport between IPA and water The comparison of separation performance of IPA and butanol isomers showed that the magnitude of coupled transport mainly depended on the molecular linearity (or the aspect ratio) of penetrant molecules and their affinity with... compensation of lower permeance However, further increase in the degree of cross-linking might swell up the polymeric chains because of the hydrophilic nature of diamine compounds; this resulted in decreased separation performance Cross-linked membranes had significantly enhanced formation of CTCs after heat treatment compared to membranes without cross-linking, while the selectivity of cross-linked membranes. .. (CTCs) formation of the cross-linked membranes after post heat treatment The cross-linking reaction induced by EDA was much faster than that by p-xylenediamine On the other xi hand, membranes cross-linked by p-xylenediamine were thermally more stable than that by EDA For pervaporation dehydration of IPA, an increase in the degree of cross-linking initially resulted in an increase in selectivity with the. .. extended to the development of asymmetric membranes with superior selectivity and relatively high flux for pervaporation dehydration of IPA with BTDATDI/MDI (P84) co-polyimide by a dry-wet phase inversion method The best separation performance had a flux of 432g/m2hr and a separation factor of 3508 at 60°C for a feed stream containing 85wt% IPA The membrane showed imperceptible degree of swelling even... boiling point mixtures The purpose of this work is to identify important factors in pervaporation transport process, to fabricate high-performance pervaporation dehydration membranes through phase inversion method, and to investigate the effects of modifications on membrane performance Emphases were put on the separation of isopropanol (IPA)/water mixture because of the high market value of IPA This study... TGA Thermogravimetric Analysis XRD Wide-angle X-ray Diffraction XPS X-ray Photoelectron Spectroscopy xvi LIST OF TABLES Table 1.1 Industrial membrane separation processes Table 1.2 Scientific milestones in the development of pervaporation processes Table 2.1 Collection of pervaporation performance of different polyimide membranes in aqueous alcohol systems Table 2.2 Collection of pervaporation performance . THE DEVELOPMENT OF PERVAPORATION MEMBRANES FOR ALCOHOL DEHYDRATION QIAO XIANGYI NATIONAL UNIVERSITY OF SINGAPORE 2007 THE DEVELOPMENT OF PERVAPORATION MEMBRANES. co-polyimide membranes for the pervaporation dehydration of IPA 169 9.1.3 The sorption, swelling and permeation characteristics of P84 co-polyimide membranes for pervaporation dehydration of alcohols. milestones in the development of pervaporation processes Table 2.1 Collection of pervaporation performance of different polyimide membranes in aqueous alcohol systems Table 2.2 Collection of pervaporation