Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016     

Fabrication and structural tuning of novel composite hollow fiber membranes for pervaporation

A series of polysiloxaneimide (PSI)/polyetherimide (PEI) composite hollow fibers were fabricated by coextrusion and phase inversion. The hydrophobic PSI outer layer was set as the selective layer which was supported by the PEI inner layer. The PSI was synthesized by polycondensation of 3,3′,4,4′‐Biphenyltetracarboxylic Dianhydride (BPDA) with amino siloxane X‐22‐161A and a chain extender, 1,3‐Bis (3‐aminopropyl) ?1,1,3,3‐tertramethyldisiloxane (BATS). It was found that the macroscopic uniformity of PSI layer was dependent on the dope formulation, coagulant composition and dope flow rate: (1) the higher similarity degree of the solvent(s) for different layers in terms of solubility parameters, (2) the utilization of surfactant as a component in the water coagulant, and (3) higher flow rates of the outer layer dopes, led to the formation of more uniform and smoother PSI outer layer. The maximum outer layer thickness was around 2 μm. The bulk of the PEI layers were porous with finger like macrovoids. The outer surface of the inner PEI layer for some batches of the hollow fibers was confirmed to be porous. The original dual‐layer hollow fibers showed poor pervaporation performance. Post treatment was applied to cure the hollow fiber, delivering composite membranes with performance dominated by the coating material of PDMS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43324.     

PDMS-AMEO膜用于渗透汽化分离乙酸/水体系的性能研究

采用原位聚合法制备了氨丙基三甲氧基硅氧烷交联聚二甲基硅氧烷( PDMS- AMEO)/有机蒙脱土(OM-MT)/聚醚砜(PES)复合膜,采用SEM和TGA对PDMS-AMEO/OMMT/PES的形貌、热学性能进行了研究.考察了复合膜在乙酸-水溶液中的溶胀性,以及OMMT含量、料液温度和浓度对膜渗透汽化性能的影响.     

Silane‐modified NaA zeolite/PAAS hybrid pervaporation membranes for the dehydration of ethanol

To improve the pervaporation selectivity of poly(acrylic acid) sodium (PAAS) membranes incorporated with NaA zeolite, the interface compatibility between zeolite nanocrystals and the polymer matrix was improved by modifying NaA zeolite using 3‐aminopropyltriethoxysilane (APTES). Both X‐ray photoelectron spectra and FTIR confirmed the chemical modification, while the results of zeolite particle size analysis and scanning electron microscopy revealed the improved dispersion of the modified zeolite. Transmission electron microscopy images of these hybrid membranes indicated that the interface between the polymer and modified zeolite phases had improved. The effects of loaded NaA zeolite on the pervaporation performance of hybrid membranes were investigated. The selectivity of hybrid membranes made from APTES‐modified zeolite was higher than that using the original zeolite under the same conditions, because fewer voids resulted from the incompatibility between the zeolite and PAAS and the structure was more homogenous. Based on the Arrhenius plots, the activation energies of water and the ethanol ratio were lower for modified zeolite hybrid membranes, because water molecules experienced less restrictive passage through the membranes compared with the original zeolite‐based hybrid membrane. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

PTFE-PDMS/PET复合膜制备及其渗透汽化性能

以聚四氟乙烯(PTFE)微粉填充聚二甲基硅氧烷(PDMS)硅橡胶膜为活性皮层和PET无纺布为底膜,制备了PTFE-PDMS/PET渗透汽化复合膜并用于分离乙醇水溶液,分析了复合膜结构、疏水性、力学性能及溶胀性能.研究表明,随着PDMS复合膜中PTFE含量(质量分数,下同)增加,复合膜结晶度及水接触角增加;断裂伸长率和拉伸强度均呈现先增加后减小的趋势;膜溶胀度呈线性减少.复合膜渗透汽化选择性α和乙醇渗透系数J_E随PTFE含量的增加先增加后减少,而水渗透系数J_W呈逐渐减小的趋势,当PTFE填充量为10%时,乙醇渗透系数J_E最大.     

Pervaporative Dehydration of Binary Ethanol/Water and Ternary Ethanol/Water/Methanol Mixtures Using a Methylated Silica Membrane: A Mechanistic Approach

The pervaporation properties of a methylated-silica membrane were studied on binary ethanol/water and ternary ethanol/water/methanol mixtures. The aim was to acquire a better understanding of the pervaporation mechanisms by studying the effects of feed temperature, permeate pressure, and feed composition on molecular transport. Emphasis was placed on the role of competitive adsorption and dragging and blocking effects between the components in the context of the adsorption-diffusion model. The results show the potential of the membrane for the coupled removal of water and methanol from bioethanol. This attractive application for process intensification was suggested for the first time in this paper.     

甲基异丁基酮分离过程中精馏-渗透汽化集成工艺的研究

对丙酮一步法生产甲基异丁基酮(MIBK)部分精馏流程进行了工艺分析,MIBK脱轻塔进料液中少量水的存在使MI-BK脱轻塔运行不稳定,进而影响MIBK合成液的整个分离过程。针对这个问题,提出了精馏-渗透汽化集成的工艺方案,省去MIBK脱轻塔。建立了渗透汽化小试实验,研究了NaA分子筛膜的渗透汽化过程以及分离性能。用Aspen Plus软件对精馏-渗透汽化集成工艺进行了模拟,与精馏过程相比,在MIBK产品质量与收率相同情况下,操作成本降低了20%,总成本可降低15%。     

Separation Performance and Stability of PVDF-co-HFP/Alkylphosphonium Dicyanamide Ionic Liquid Gel-Based Membrane in Pervaporative Separation of 1-Butanol

In this study, a membrane prepared by gelling trihexyl(tetradecyl)phosphonium dicyanamide ionic liquid (IL) with poly(vinylidene fluoride-co-hexafluoropropylene) copolymer is tested for performance and stability in pervaporative separation of 1-butanol. Feed concentration and temperature affected separation performance mainly through plasticizing and swelling effects in the membrane which promoted liquid-like transport behavior. Microscale IL-in-polymer networks formed within the gel matrix where the neat IL possibly functioned as conventional liquid membrane. IL gelling has significantly improved the membrane operational lifetime to ～80 h, a significant improvement on the ～10 h shown by a simple supported IL membrane counterpart. The instability was consequent to polymer-IL incompatibility and so further investigations are underway to resolve this issue.     

有机物优先透过渗透汽化膜的改性方法研究进展

有机物优先透过渗透汽化是一种能耗低、投资少、操作简便的分离技术,综述了其发展现状,重点介绍了其渗透膜的改性方法研究进展,包括填充法、共聚/共混法和接枝法,并对其发展前景进行了展望。