改性复膜对微水异丙醇的渗透汽化脱水

介绍了用缩甲醛改性的PVA/PAN复合膜的制备方法,并用于质量分数低于5%的微水异丙醇体系的渗透汽化(PV)深度脱水研究,考察了操作温度、料液浓度与操作压力等因素对分离性能的影响。渗透通量J与分离系数α均随温度的升高而增大,而随料液异丙醇浓度的升高J减小而α增大,在72℃、1.6 kPa膜后压力下,该膜对含异丙醇质量分数为98%的体系,仍有α=316,J=262 g/(m.h)的分离效能,显示了较好的工业应用前景。     

PVA复合膜的渗透汽化性能研究：（Ⅰ）操作条件和长期运行的影响

本文研究了以ＰＡＮ膜为支撑层的ＰＶＡ复合膜分离醇水溶液的性能。着眼于工业应用，揭示了渗透汽化操作条件对分离性能的影响，展示了长期运行时的分离性能。结果表明，ＰＶＡ复合膜具有高渗透通量和优异分离率，长期运行性能稳定。     

优先透水渗透汽化膜的研究

本文将聚乙烯醇和壳聚糖混合物涂到聚丙烯腈中空纤维内表面制备用于渗透汽化过程的中空纤维复合膜，研究不同的聚乙烯醇和壳聚糖共混组成对膜分离性能的影响，通过适当交联，使膜性能稳定，用于渗透汽化过程分离乙醇－水混合液时，进料乙醇浓度０．９５，温度４８℃，膜分离因子１００～２００，渗透通量４０～７０ｇ／ｍ＾２．ｈ。     

NaA/PAN复合膜渗透汽化分离DMF/H_2O溶液的性能研究

采用流延法制备大面积的NaA/PAN分子筛复合膜,并用于渗透汽化分离二甲基甲酰胺/水(DMF/H2O)溶液。考察了料液组成、进料量和操作温度对膜分离性能的影响。实验结果表明:渗透通量随着温度的升高而增大,在DMF质量分数为20%,操作温度为24℃,料液量为1.5 m3/h,膜后侧压力为500 Pa的条件下,NaA/PAN膜的渗透通量达到1.84 kg/(m2·h),分离因子为11.5。     

疏水性SiO2-PDMS渗透汽化膜溶解-扩散性能

制备了疏水性纳米SiO2填充聚二甲基硅氧烷(PDMS)渗透汽化膜,研究了其溶解-扩散性能,计算了复合膜的溶解度参数(δM)及乙醇渗透系数(PE)。结果表明,填加SiO2提高了PDMS膜的乙醇溶解度(SE),SiO2填加量为10%(质量分数,下同)时,复合膜在30℃时的SE为0.0064,而未填加时仅为0.0026;PE值随SiO2含量的增加呈先增加后减小的趋势,SiO2填加量5%时,PE在60℃时为2.52×10-13 m2/s,而未填加时仅为1.42×10-13 m2/s;提高温度有利于乙醇的渗透。以乙醇/水物系为研究对象,结果表明,SiO2-PDMS复合膜渗透汽化性能与其渗透系数的变化趋势基本相同。     

渗透汽化-酯化反应耦联膜过程动力学模型

建立了渗透汽化 -酯化反应耦联复合膜反应器过程动力学模型及测量复合膜渗透率的方法 .该动力学模型较系统地考虑了复合膜反应器中可能影响酯化反应化学平衡移动的各种因素 .研究结果表明 ,模型的模拟结果能很好地与实验结果相吻合 .     

纯溶剂在线性低密度聚乙烯膜中的渗透汽化

用渗透汽化实验装置测定了5种常用化工溶剂在线性低密度聚乙烯材料中的渗透性能,考察不同温度对于5种溶剂的渗透通量的影响。通过渗透通量与温度的Arrhenius关系,回归拟合得到各种溶剂的渗透活化能;并采用吸附溶胀实验测定了5种纯溶剂在该膜材料中的平衡吸附量,以此推算出25℃条件下5种溶剂在膜材料内部的扩散系数。结果表明,5种溶剂的渗透通量的顺序为正己烷正庚烷环己烷丙酮甲基吡咯烷酮,吸附量大小顺序为甲基吡咯烷酮环己烷正己烷正庚烷丙酮。     

PVA复合膜的渗透汽化性能研究：（Ⅱ）贮存时间的影响与分离性能预测方程

本文研究表明，经长贮存或经反复使用，ＰＶＡ复合膜的渗透化分离性能仍然优良，其中ＰＶＡ／ＣＡ复合膜的渗透量大于９００ｇ／ｍ＾２．ｈ而渗透物中乙醇组分未检出。     

渗透汽化膜机理研究

用顺丁烯二酸酐对聚乙烯醇（ＰＶＡ）进行交联制得渗透汽化膜,并用于水－乙醇渗透汽化分离,研究了膜的溶胀平衡过程及选择溶解与渗透汽化关系,结果表明,膜对水优先溶解,其分离系数主要由溶解选择性控制,透过速率主要由溶胀度控制。     

ZSM-5/NaY型复合分子筛膜的制备及其渗透汽化性能研究

采用水热合成法在n(SiO₂)∶n(Al₂O₃)∶n(Na₂O)∶n(H₂O)为25∶1∶22∶600的合成液体系中合成高性能的ZSM-5/NaY型复合分子筛膜,考察了陈化时间、合成液中水的摩尔分数、合成时间以及合成温度对膜的渗透汽化分离性能的影响,同时,考察了ZSM-5/NaY型复合分子筛膜的稳定性。利用SEM和XRD对膜的形态结构进行表征。结果表明,在合成液陈化18 h后,在105℃下晶化6 h,可成功制备出连续致密的ZSM-5/NaY型复合分子筛膜;在75℃下分离90%的异丙醇/水体系,渗透侧水质量分数可以达到99.15%以上,渗透通量保持在2.12 kg/(m²·h)以上,并且具有良好的重复性。     

Comparative behavior of PVA/PAN and PVA/PES composite pervaporation membranes in the pervaporative dehydration of caprolactam

Flat‐sheet composite membranes were developed by the traditional phase inversion technique using poly;(vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance ε‐caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4005–4011, 2007     

Pervaporation and Vapor Permeation Tutorial: Membrane Processes for the Selective Separation of Liquid and Vapor Mixtures

Pervaporation and vapor permeation are membrane-based processes proposed as alternatives to conventional separation technologies. Applications range from organic solvent removal from water, ethanol, or butanol recovery from fermentation broths, solvent/biofuel dehydration to meet dryness specifications, and organic-organic separations such as the removal of sulfur compounds from gasoline. Unlike membrane filtration processes, which rely on an applied liquid pressure gradient and size sieving to accomplish a separation, pervaporation and vapor permeation separate compounds based on a chemical activity driving force and the sorption and diffusion of the compounds through the membrane. These properties enable the separation of even miscible liquid mixtures.     

Permeation behaviour in cellulose triacetate dense membrane during pervaporation separation of methanol/methyl tert-butyl ether mixture

The pervaporation separation of methanol/methyl tert-butyl ether through cellulose triacetate dense membranes has been carried out under different feed compositions, permeation temperatures and temperature cycles to investigate the permeation behaviour of the membrane during pervaporation process. The experimental data indicate that the plasticization effect has a decisive influence on pervaporation flux, permselectivity and permeation activation energy. The results show that the penetrants of different feeds are transported through the membrane by different pathways with the influence of plasticization effect at different temperatures. It has also been observed that plasticization had great effect on the membrane swelling and sorption selectivity. Furthermore, DSC results show that the membranes retain the influence of the plasticization effect after pervaporation separations are tested. © 2000 Society of Chemical Industry     

Influence of binding interface between active and support layers in composite PDMS membranes on permeation performance

Effect of the binding interfaces of composite polydimethylsiloxane (PDMS) membranes on their pervaporation performance was studied. The membranes were made up of PDMS as active skin layer and polysulfone (PSF) or polyamide (PA) as supporting layer. PDMS‐PSF membrane was numbered 1, and PDMS‐PA membrane numbered 2. The pervaporation experiments were carried out by using the composite membranes and dilute ethanol–water mixture. The experimental measurements for the permeation performance under various operating conditions (e.g., feed concentration and temperature) showed that the specific permeation rate of membrane 2 was over membrane 1 by seven times at least. A resistance‐in‐series model was applied to formularize the transport of the permeants. Influence of the binding interfaces between the active skin layer and support layers in these membranes on pervaporation performance was analyzed. The cross section morphology of the membranes and chemical element distribution along membrane thickness were examined by using SEM and EDS. It was found that, although the PDMS intrusion layer into PSF near the interface was only about 2 μm, it gave significant effect on the permeation performance. It implied that the resistance produced by the intrusion layer into PSF was apparently larger than that of PDMS intruding PA and over intrinsic PDMS resistance. These should be probably attributed to structures and formation of the binding interfaces. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2468–2477, 2007     

Preparation and characterization of CMCS/PVA blend membranes and its sorption and pervaporation performance (I)

Novel pervaporation (PV) membranes for ethanol dehydration were prepared by blend poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCS), followed by the crosslinking reaction with glutaraldehyde; the structure and miscibility of the blend membranes were characterized by Fourier transform infrared, X‐ray diffraction, and differential scanning calorimetry; the results indicated that the blends were miscible. The effect of feed concentration, operation temperature, crosslinking agent content, etc. on sorption performance and PV performance of the blend membrane is investigated. The membrane of CMCS/PVA blend ratio of 8 : 2 exhibited a high separation factor of 2959 with a reasonably high water flux value of 0.14 kg m^?2h^?1 at the azeotropic feed composition (95 wt % of ethanol) at a temperature of 45°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

溶胶修饰陶瓷膜的气体渗透

本文用纯氮气、氢气及氮氢混合气以静态法和流动法分别研究了自研制的复合不对称陶瓷膜的气体渗透性能，并获得了较适宜的涂膜次数及尖透工条件（温度、压差）对膜渗透性能的变化规律。作者对氮氢混俣气流动体系中混合气流速、组成及吹扫气量对渗透性能的影响也进行了详细研究。     

Separation Characteristics of Dimethylformamide/Water Mixtures through Alginate Membranes by Pervaporation,Vapor Permeation and Vapor Permeation with Temperature Difference Methods

Abstract

In this study permeation and separation characteristics of dimethylformamide (DMF)/water mixtures were investigated by pervaporation (PV), vapor permeation (VP), and vapor permeation with temperature difference (TDVP) methods using alginate membranes crosslinked with calcium chloride. The effects of membrane thickness (30–90 µm), feed composition (0–100 wt%), operating temperature (30–50°C) on the permeation rates and separation factors were investigated. The permeation rate was found to be inversely proportional to the membrane thickness whereas separation factor increased as the membrane thickness was increased. It was observed that the permeation rates in VP and TDVP were lower than in PV however the highest separation factors were obtained with TDVP method. Alginate membranes gave permeation rates of 0.97–1.2 kg/m² h and separation factors of 17–63 depending on the operation conditions and the method. In addition, sorption‐diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was dominant factor for the separating of DMF/water mixtures.     

中空纤维PVA/PAN复合膜填料的乙醇水溶液精馏性能

以乙醇/水溶液为分离对象,中空纤维PVA/PAN复合膜作为精馏填料,考察了不同膜组件的传质分离效率。实验结果表明:各种组件的分离效率均随塔釜加热功率的增加而减小;和大多数中空纤维膜接触器一样,其总传质系数Ky随中空纤维膜组件填充密度φ的增加而减少;相比于传统精馏填料而言,用中空纤维膜做精馏填料分离乙醇水溶液的分离效果更好,可以在常规填料不能操作的液泛线以上进行操作。当塔釜加热功率为120 W,45根中空纤维膜封装在内径为1.6 cm玻璃管中的传质单元高度(HTU)为5.64 cm。     

Polysiloxaneimide membranes for removal of VOCs from water by pervaporation

For the separation of volatile organic compounds (VOCs) from water by pervaporation, three polysiloxaneimide (PSI) membranes were prepared by polycondensation of three aromatic dianhydrides of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) with a siloxane‐containing diamine. The PSI membranes were characterized using ¹H‐NMR, ATR/IR, DSC, XRD, and a Rame‐Hart goniometer for contact angles. The degrees of sorption and sorption selectivity of the PSI membranes for pure organic compounds and organic aqueous solutions were investigated. The pervaporation properties of the PSI membrane were investigated in connection with the nature of organic aqueous solutions. The effects of feed concentration, feed temperature, permeate pressure, and membrane thickness on pervaporation performance were also investigated. The PSI membranes prepared have high pervaporation selectivity and permeation flux towards hydrophobic organic compounds. The PSI membranes with 150‐μm thickness exhibit a high pervaporation selectivity of 6000–9000 and a high permeation flux of 0.031–0.047 kg/m² h for 0.05 wt % of the toluene/water mixture. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2691–2702, 2000