部分水解聚醋酸乙烯酯的制备及其分离苯/环己烷混合物的渗透汽化特性

聚醋酸乙烯酯（PVAc）经醇解反应制备了不同水解度的聚醋酸乙烯酯（PHPVAc）,并探索了PHPVAc水解度、成膜技术、测试条件对膜渗透汽化性能影响的规律.实验发现,改变膜材料的水解度、铸膜溶剂组成、操作温度以及料液组成可以调节膜的分离性能,获得较佳的分离效果.     

芳烃/脂肪烃渗透汽化分离膜的研究进展

芳烃/脂肪烃分离是石油化工中重要的分离过程,渗透汽化膜分离技术是现有高能耗芳烃/脂肪烃分离过程的潜在技术。以调整石脑油的芳烃含量,生产“低苯汽油”或低芳烃含量的优质乙烯裂解原料为背景,论述了芳烃/脂肪烃混合物的渗透汽化分离膜的研究进展。     

渗透气化膜分离技术在乙醇-水体系中的应用

渗透气化是一种新型的膜分离技术,因其具有独特的优势已被广泛应用于乙醇-水的分离.从渗透气化的原理和特点出发,介绍了渗透气化膜材料以及渗透气化与精馏、化学反应耦合等技术,并概述了国内外渗透气化膜分离技术在乙醇-水分离中的应用现状.     

Pervaporation Separation of Water/Ethanol Mixtures through Polycarbonate/Cobalt(III) Acetylacetonate Membranes

ABSTRACT

In the present work, cobalt(III) acetylacetonate [Co(acac)₃] was added to polycarbonate (PC) to improve its performance on pervaporation separation of water/ethanol mixtures. By adding 3 wt% of Co(acac)₃ the resulting PC/Co(acac)₃ complex membrane possessed a permeation rate similar to a pure polycarbonate membrane, but the separation factor (water/ethanol) was about three times higher. The stability of the complex membrane was tested, and it was found that, after being immersed in an aqueous ethanol solution for 72 hours, the complex membrane was still stable. In addition, the effects of the added amount of Co(acac)₃ and the feed composition on pervaporation performance are presented in this work, and the mechanism of the improvement in pervaporation performance is briefly discussed.     

乙醇/水及乙酸/水体系的渗透汽化分离

以乙醇/水及乙酸/水体系为研究对象,研究了渗透汽化过程中料液浓度、温度因素对分离效果的影响;结合乙醇、乙酸对聚二甲基硅氧烷(PDMS)膜的溶胀特性差别,分析并讨论了两者在渗透汽化过程中可能的分离机理. 研究表明,PDMS膜能够优先透醇,但乙酸分子的缔合物以及羧基与疏水PDMS膜高分子链的强相互作用降低了其在膜中的扩散速率,使低温时乙酸/水体系优先透水,只有当温度在60℃以上时才表现出优先透酸,且分离效果较差.     

Pervaporation Separation of Benzene/Cyclohexane Mixtures by Poly(vinyl chloride) Membranes

Sorption and pervaporation of benzene/cyclohexane mixtures were studied by using poly(vinyl chloride) (PVC) polymer. The effects of composition of benzene/cyclohexane mixture and temperature on sorption and pervaporation characteristics were determined at 30, 40, and 50 °C for the membranes containing 8 wt% PVC polymer. Liquid feed composition effects on the flux and the selectivity were determined for two different membranes at 30 °C. The membranes that were prepared from the solutions containing 4 wt% and 8 wt% PVC polymer have thicknesses of 30 μm and 50 μm, respectively. Membrane thickness changes with polymer content as expected. Total sorption increased with increasing concentration of benzene. Increasing the concentration of benzene resulted in increasing flux as well as decreasing selectivity also. Fluxes were increased and selectivity decreased with increasing temperature. The selectivity was not affected significantly with varying amounts of polymer in the casting solution but the flux decreased with increasing amount of polymer in the casting solution.     

Separation of Toluene-Methanol Mixtures by Pervaporation Using Semi-IPN Polymer Membranes

Polyvinyl alcohol (PVOH) has been chemically modified by polymerizing hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH with glutaraldehyde to produce a semi-interpenetrating network (SIPN) membrane. Accordingly, three such SIPN membranes, namely SIPNI, SIPNII, and SIPNIII were synthesized with different weight ratio of PVOH: HEMA i.e., 1:0.25 (SIPNI), 1:0.50 (SIPNII), and 1:0.75 (SIPNIII). These SIPN membranes were used for pervaporative separation of methanol from its mixtures with toluene. The flux and methanol selectivity of these SIPN membranes were found to be much higher than conventional PVOH membrane crosslinked with glutaraldehyde. Among the three membranes, SIPNIII with 75 wt% HEMA incorporation shows optimum performance in terms of flux and methanol selectivity. The permeability of the membranes was also found to increase with increase in HEMA content in PVOH matrix. The novelty of the work lies in synthesis and characterization of a new kind of membrane and its potential for selective removal of methanol from its mixtures with toluene.     

金属离子固载膜及其有机物的渗透汽化分离

在简要介绍了金属离子固载促进传递膜制备方法的基础上，分析了金属离子和反离子的种类、分离体系的温度和膜厚度等对金属离子固载膜分离性能的影响；并对金属离子固载促进传递膜在烯烃／烷烃、苯／环己烷等有机物体系分离中的应用进行了综述。     

聚丙烯酸-聚乙烯醇共混膜分离甲醇-碳酸二甲酯共沸体系

采用涂敷法制备了聚丙烯酸(PAA)-聚乙烯醇(PVA)共混膜,将其用于渗透汽化法分离甲醇(MeOH)-碳酸二甲酯(DMC)共沸物,考察了共混比例、热处理条件对甲醇分离性能的影响. 渗透汽化实验结果表明,随着热处理时间延长或热处理温度提高,分离因子先升高后降低,而渗透通量则逐渐减小;随着共混膜中PAA/PVA比例增加,分离因子先升高后降低,而渗透通量先减小后增大;当PAA/PVA质量比为7/3、热处理时间为60 min、热处理温度为150℃时,选择性最佳,在料液组成为70%(w) MeOH-30%(w) DMC及70℃的操作温度下,甲醇的分离因子为9.5(透过侧MeOH浓度为95.5%, w),渗透通量为360 g/(m2×h).     

交联壳聚糖渗透蒸发膜的制备及其在偏二甲肼/水体系分离中的应用

采用壳聚糖为原料,聚酯无纺布为支撑层,用戊二醛交联制备了高选择性、高通量的交联壳聚糖渗透蒸发复合膜.考察了料液浓度、料液温度、膜厚等对偏二甲肼/水体系分离性能的影响.结果表明:在料液温度为10℃,膜厚度为25 μm,进料液中偏二甲肼的质量分数为50％时,改性复合膜的分离因子最高达到5.25,渗透通量可达167 g/(m...     

Ultrasound Assisted Pervaporation Separation of Pyridine/Water Mixtures Using Poly(vinyl alcohol)/Polyacrylonitrile Blend Membranes

Poly(vinyl alcohol)/polyacrylonitrile blend membranes were prepared to separate pyridine/water mixtures by pervaporation. The membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The effects of membrane composition, feed pyridine concentration, operating temperature, downstream pressure and ultrasound irradiation on the separation process were evaluated. The experimental results indicated that with increasing PVA mass ratio and operating temperature the permeate flux increased but the separation factor decreased, while with increasing feed concentration and downstream pressure the separation factor increased and the permeate flux decreased. It was observed that Ultrasound irradiation enhanced the permeate flux.     

聚氨酯膜的制备及渗透汽化分离水中苯酚性能研究

研究通过两步反应法制备端羟基聚丁二烯基聚氨酯（HTPB-PU）渗透汽化膜,采用红外、热分析、扫描电镜等手段对其结构与性能进行了表征,研究了该膜从水中分离苯酚的渗透汽化性能。结果发现,该膜表现出良好的优先透过苯酚的分离性能。以0.5%苯酚水溶液作为料液,随着操作温度从60℃增加到80℃,渗透通量增加而分离因子下降,在60℃时,分离因子与渗透通量可分别达到23.80与2.85 kg.μm.m-2.h-1。     

Pervaporation Separation of p-/o-Xylene Mixtures Using HTPB-Based Polyurethaneurea Membranes

Hydroxy terminated polybutadiene (HTPB)-based polyurethaneurea membranes with and without cross-linkage were synthesized and first used as membrane material to separate p-/o-xylene mixtures by pervaporation. Compared with HTPB-PU (without cross-linkage) membranes, HTPB-DVB-PU (cross-linked HTPB-PU with divinyl benzene) membranes demonstrated a lower degree of swelling in xylene isomer solutions and noticeable improved separation factor of p-/o-xylene. On the other hand, the amount of p-xylene adsorbed in HTPB-DVB-PU membranes increased significantly rather than that of o-xylene. While the separation factor of p-/o-xylene increased but the total flux decreased with increasing DVB content, which can be ascribed to the improved chemical structure and more homogeneous chain structures of the HTPB-DVB-PU membranes. The p-xylene normalized permeation rate and separation factor of p-/o-xylene of HTPB-DVB-PU membrane reached 2.70 kgµm/m²h and 2.23, respectively, at a feed concentration of 10 wt% p-xylene at 30°C.     

Pervaporation separation of isopropanol–water mixtures using mixed matrix blend membranes of poly(vinyl alcohol)/poly(vinyl pyrrolidone) loaded with phosphomolybdic acid

Mixed matrix membranes of poly(vinyl alcohol) and poly(vinyl pyrrilidone) blends were prepared by loading with phosphomolybdic acid (PMA) and their pervaporation (PV) properties were investigated for the PV separation of isopropanol. Membrane performance shown a dependence on the extent of PMA loading. The 4 wt % PMA‐loaded blend membrane had the highest separation factor of 29991, which declined considerably at higher loading. The flux of 4 wt % PMA‐loaded membrane was lower than that of nascent blend membrane. Feed water composition and temperature influenced the PV performance. Solubility selectivity was higher than diffusion selectivity. Degree of swelling was smaller after PMA loading exhibiting better separation ability. The PV results were analyzed using the Flory‐Huggins theory and sorption was dominated by Langmuir's mode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Silicon Microseparator based Pervaporation Process for Separation of Ethanol/Water Mixtures using a Polymer Membrane

Abstract

The selective removal of water from ethanol through pervaporation was demonstrated in a microchannel device using a commercial membrane. Photolithography and dry etching techniques were employed for fabrication of the microseparator with hydraulic diameters of 30 µm to 80 µm. Experiments conducted at 90°C and 2–3 Torr, with Reynolds Numbers ranging from 8 to 91, resulted in an average water and ethanol permeance of 1.2×10^?3 and 8×10^?5 cm³/cm² · s · cmHg respectively. A mass transfer analysis involving Sherwood correlations was used to calculate the theoretical boundary layer resistance. The comparison of overall mass transfer coefficient with the boundary layer coefficients suggests that the membrane was the dominant resistance for this system.     

用于脱除C5及MTBE中甲醇的渗透汽化膜研究

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA), MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmenthanol =350g.m-2.h-1 and separation factor a > 400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.     

用于脱除C5及MTBE中甲醇的渗透汽化膜研究

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA),MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmethanol = 350 g.m-2.h-1 and separation factor α＞400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.     

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.     

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.