Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry, but challenged in some cases. Compared with conventional separation technologies, pervaporation is quite promising in terms of its economical, energy-saving, and eco-friendly advantages. However, this technique has not been used in industry for separating aromatic/aliphatic mixtures yet. One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory. Membrane material is an important factor that affects the separation performance. This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade. Explored pristine polymers and their hybrid materials(as hybrid membranes) are summarized to highlight their nature and separation performance. We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.

PERVAPORATION SEPARATION OF WATER-ACETIC ACID MIXTURES THROUGH AN-co-AA MEMBRANES TREATED WITH RARE EARTH METAL IONS

Pervaporation separation of water-acetic acid mixtures through Poly(AN-co-AA) membranes and rare earth metal ions treated Poly(AN-co-AA)membranes was investigated for the first time. The results showed that the treatment with rare earth metal ions could greatly improve the characteristics of the separation of water-acetic acid mixtures.

STUDY OF COMPOSITE MEMBRANE OF CELLULOSE ACETATE OR POLYVINYL ALCOHOL BLENDED WITH METHYLMETHACRYLATE-ACRYLIC ACID COPOLYMER FOR PERVAPORATION SEPARATION

In this paper, methylmethacrylate-acrylic acid MMA-AA hydrophilic and hydrophobic copolymers were prepared by copolymerization for preparing membrane materials. The composite membrane of cellulose acetate (CA) blended with MMA-AA hydrophobic copolymer was used for the separation of methanol from pentane-methanol mixture. When the methanol concentration was only 1 wt%, the permeate flux still maintained at 350 g/m(2)h and separation factor was as big as 800. The composite membrane of PVA (polyvinyl alcohol) blended with MMA-AA hydrophilic copolymer was used for the separation of ethanol-water mixture. The permeate flux was increased to 975 g/m(2)h at 74 degrees C and the separation factor reached 3000 at 25 degrees C. The PVA/MMA-AA blended membrane surface modified by ammonia plasma was also investigated for separating ethanol-water mixture. Both permeate flux and separation factor of the membrane was improved. However, there was no obvious difference of plasma treatment time in the interval of 20 similar to 40 min.

ORGANIC PERMSELECTIVE PERVAPORATION CHARACTERISTICS OF POLY(SILYLPROPYNE) AND COPOLYMER DENSE MEMBRANES

An investigation into the organic permselective separation through poly [1-trimethylsilyl-1-propyne] (PTMSP) and (1-trimethylsily 1)-1-(1-penta-methyl-disily 1)-1-propyne copolymer (TMSP-PMDSP) dense membranes was made to gain an insight into the effect of the chemical structure of membrane materials on pervaporation (PV) characteristics. The results show that the copolymer has a higher separation factor alpha(org/water) but with a relatively lower value of flux J(t) (g/m(2).h) than pure PTMSP. This phenomenon may be attributed to the introduction of side chain with large bulk volume in copolymer, which brought about a decrease of excess free volume and the improvement of diffusion selectivity to some extent. With the same molar concentration of organic liquids in feed, THF/water solutions have the highest value of alpha(org/water) as well as J(t) in comparison with ethanol/water, iso-propanol/water and THF/water mixtures.

Mass transfer model,preparation and applications of zeolite membranes for pervaporation dehydration:A review

Pervaporation(including vapor permeation) is a kind of new membrane separation technology, possessing the advantages of high efficiency, energy saving and convenient operation. It has promising application in the separation and purification of organic solvents. Dehydration is an important step in the production and recovery of organic solvents. Zeolite membranes have attracted wide attention for pervaporation dehydration due to their high separation performance and good thermal/chemical stability. So far, zeolite membranes have been preliminarily industrialized for dehydration of organic solvents. This paper reviews the recent development of zeolite membranes for pervaporation dehydration, including mass transfer models, preparation and applications of zeolite membranes. The review also discusses the current industrial applications of zeolite membranes and their future development in pervaporation.

Swelling Behaviors and Pervaporation Properties of CA/PAN Composite Membranes for Separation of Caprolactam/Water Mixtures

The composite membranes with cellulose acetate（CA） as the separating layer material and polyacrylonitrile（PAN） as the supporting layer material were prepared for separating caprolactam（CPL） from CPL/water mixtures by pervaporation technique.The swelling experiments were carried out to investigate the effects of swelling time and CPL concentration on the degree of swelling.The results showed that the CA membrane reached swelling equilibrium within 24 h,and the degree of swelling first slightly decreased then increased with the increase of CPL concentration in the feed under the experimental conditions.Respectively comparing flux with permeance,and separation factor with selectivity,we found out that the separation performance of the CA/PAN composite membrane is more strongly dependent on its hydrophilic/hydrophobic nature as well as on the effects of operating parameters,such as feed composition concentration and feed temperature.

Pervaporation of organic liquid/water mixtures through a novel silicone copolymer membrane

Polydimethylsiloxane-ladder like phenylsilsesquioxane copolymer as a novel membrane material has good film-forming ability, high mechanical properties and low swelling capacity. The copolymer membrane displays the permselectivity of organic liquid for the pervaporation of organic liquid/water mixtures. The pervaporation of aqueous solution of ethanol through the membrane has been investigated. High separation factor can be obtained in the range of low ethanol concentration. The flux of ethanol increases and the flux of water keeps constant as the concentration of ethanol in feed increases. The membrane shows good stability of separation at room temperature to 70℃. The comparison of the pervaporation behavior of the aqueous solutions of methanol, ethanol, 2-propanol, acetone, THF reveals that the magnitude of the separation factors and the fluxes increases in the following order: methanol<ethanol<2-propanol<acetone<THF, in spite of the size of the permeating molecules.

SEPARATION OF DIOXANE/WATER MIXTURES BY PERVAPORATION

Pervaporation as a membrane technique of liquid mixtures separation has been rapidly developed recently. The separation process is as follows: the feed is placed in contact with upstream side of membrane, the downstream side of the membrane is kept under vacuum or under a stream of inert gas. If one of the components of the liquid mixture can

Research Progress in the Fabrication of Covalent Organic Framework Membranes for Chemical Separations

Membrane technology has become one of the most promising separation technologies for its energy saving, high separation efficiency, environmental friendliness, and economic feasibility. Covalent organic frameworks(COFs) with intrinsically high porosity, controllable pore size, uniform pore size distribution and long-range ordered channel structure, have emerged as next-generation materials to fabricate advanced separation membranes. This feature article summarizes some latest studies in the development of pure COF membranes in our lab, including their fabrication and applications in chemical separations. Finally, current challenges facing high-performance COF separation membranes are discussed.

渗透汽化高效分离有机混合体系的研究现状

主要叙述了近年来PV技术在分离有机物混和物的研究现状,详细叙述PV技术在分离极性/非极性有机混合物、芳香烃/烷烃有机混合物、同分异构体、去除汽油中硫化物这四个方面的主要研究成果,并对PV技术在分离有机混合物领域的发展方向进行展望,为后续PV技术分离有机混合物的研究提供参考。

耐有机溶剂型分离膜的制备及应用研究进展

有机溶剂的分离与纯化是近年来的研究热点,众多分离与纯化技术应运而生。耐有机溶剂膜分离技术具有高效节能、操作简便的优势,受到研究者们的普遍关注,在化工、环境、医药、纺织等领域具有广阔的应用前景。文中概括了耐有机溶剂型分离膜的分离技术与分类,阐述了耐有机溶剂型分离膜的制备方法,介绍了耐有机溶剂型分离膜的应用进展,并对耐有机溶剂型分离膜的发展趋势进行了展望。综述内容可为耐有机溶剂型分离膜的推广和应用提供策略支撑。

双疏膜膜蒸馏处理含有机溶剂废水的研究

采用内置双疏膜的真空膜蒸馏工艺处理N-甲基吗啉-N-氧化物(NMMO)溶液、乙醇溶液、喷漆废水和气田采出水四种含有机溶剂的水溶液,考察双疏膜处理含有机溶剂废水的可行性.实验结果表明,双疏膜可用于NMMO溶液和气田采出水的浓缩.实验过程中,NMMO溶液质量分数由25.0%提高到46.0%,截留率高于99.9%;浓缩后的气田采出水COD高于15 000 mg/L,盐和有机物的截留率分别为99.8%和95%.19%乙醇溶液的产水中乙醇质量分数最高可达28.1%,始终高于浓水中的乙醇浓度,因此由于乙醇具有高挥发性,无法对其溶液进行浓缩;工业喷漆废水中有机溶剂2-丁氧基乙醇具有很强的表面活性剂功能,导致双疏膜被迅速浸润.本研究为双疏膜用于膜蒸馏技术浓缩有机溶剂废水提供了方向指导和实验支撑.

聚酰亚胺渗透汽化膜用于有机溶剂脱水的改性研究进展

聚酰亚胺有机高分子聚合物结构内含有氢键,且具有良好的耐溶剂性、易成膜性、高力学性能等优点。聚酰亚胺膜有望在渗透汽化有机溶剂脱水领域得到广泛应用。然而,聚酰亚胺膜高分子链间作用力强,链段排列紧密,往往造成溶剂分子渗透困难、渗透通量低等问题,限制其发展。对聚酰亚胺膜开展改性研究,以提高其渗透通量,同时保持高分离因子,是近年来的主要研究方向。本文对渗透汽化膜分离技术进行了概述,介绍了其工作原理及常用分离膜种类。详细综述了近年来用于渗透脱水的聚酰亚胺膜的改性研究进展,重点评述了共混、掺杂、交联和共聚改性,并分析了四种改性方法的作用原理,对分离性能的影响及其优缺点。最后,对聚酰亚胺膜在渗透汽化分离领域未来的发展方向进行展望,指出需揭示聚酰亚胺聚合物链与溶剂分子间的作用机制,解决渗透通量与选择性之间“trade-off”的制约关系。

基于沸石分子筛的无机膜渗透蒸发和气体分离技术进展

相较于传统分离技术,膜分离技术具有分离效率高、能耗低、便于与其他技术集成等优点。与有机分离膜相比,无机膜具有稳定性高、机械强度大、分离效率高、耐微生物侵蚀等优势。针对基于沸石分子筛的无机膜分离技术,介绍了当前常用分子筛膜的种类;探讨了分子筛膜的主要制备方法;详细阐述了分子筛膜在渗透蒸发以及气体分离领域中的应用进展,如氢气回收、天然气净化、二氧化碳捕集和烃混合物分离。对当前存在的问题进行了分析并对今后的发展进行了展望,强调了在降低制造成本、提升分子筛膜制备技术、应对多组分分离挑战等方面的研究重点。

工业木质素分级分离研究进展

化学制浆及生物炼制工业产生了大量工业木质素,其结构不均一,影响了进一步高值转化利用。采用分级分离的方法处理工业木质素可获得分子质量分布窄、性能良好的组分,进而实现木质素的高值化。针对工业木质素的不均一性,简要阐述了多种分级分离的方法及其研究进展。分级分离的主要方法包括有机溶剂溶解/沉淀法、低共熔溶剂分离法、改变pH的梯度沉淀法、膜分离法。有机溶剂溶解/沉淀法依据木质素在系列溶剂中溶解度的差异,采用多级溶解法或多级沉淀法得到木质素组分,该法具有操作简单,处理时间短,对设备要求低的特点。低共熔溶剂法可通过设计含不同种类和数量的氢供体和氢受体的低共熔溶剂用于分离,从而得到不同分子质量的高反应活性木质素。改变pH的梯度沉淀法添加酸溶液不断降低pH,沉淀得到不同分子质量的木质素组分。膜分离采用不同截留分子质量的分离膜将木质素溶液分离,可以去除碳水化合物、灰分,得到不同分子质量的木质素。针对上述分级分离方法的研究现状,对今后研究方向进行了展望,以期为木质素的高值化利用提供理论依据。

有机溶剂纳滤在精细化工领域中的应用

精细化工生产中存在产品浓缩纯化、溶剂回收和催化剂回收等分离工序,其操作费用占生产成本比重较高.有机溶剂纳滤(OSN)可替代或耦合精馏等传统工艺以节约大量生产成本,符合“双碳”战略,对精细化工的绿色发展具有重要意义.本文综述了近年来OSN在制药工程、食品加工、均相催化等精细化工领域的应用案例,针对不同分离任务讨论了传统分离工艺的不足和OSN的优势,介绍了各领域的典型OSN工艺流程,商业及高性能实验室自制膜的研发进展,分析了当前OSN应用研究所面临的难题及未来的发展方向.

有机聚合物渗透汽化膜研究进展

渗透汽化作为一种高效、低能耗、环境友好的膜技术,广泛应用于能源、环境、食品、化工与制药等领域.有机聚合物是一种重要的渗透汽化膜材料,具有成本低、易于制备和放大等优点.本文综述了聚乙烯醇、聚酰胺、聚酰亚胺等主要有机聚合物渗透汽化膜材料近期的研究进展,阐述了材料的性质特点、制备改性方法和在渗透汽化领域的应用,并对有机聚合物渗透汽化材料未来的发展进行了展望.

三嗪框架聚合物膜用于有机纳滤甲醇/正己烷分离

具备耐各种有机溶剂的微孔聚合物膜在有机纳滤领域逐渐受到重视。采用双氰基单体的超酸催化成环聚合反应,制备微孔框架聚合物薄膜(CTF-BP),该膜具备良好的力学性能,可耐受甲醇和正己烷等常见有机溶剂。CTFBP膜内大量<1.0 nm的微孔通道使膜具备良好的筛分性能,其截留分子量为550。膜内含有的三嗪结构与羟基具有较强的亲和性,使甲醇的跨膜通量[1.10 L/(m^(2)·h·bar)]显著高于黏度更低的正己烷通量[0.23 L/(m^(2)·h·bar)]。采用纳滤操作将膜用于分离含低浓度甲醇的正己烷溶液[含5%(质量)甲醇的正己烷溶液],结果显示甲醇/正己烷分离因子最高可达到1485,渗透液的总流量超过3.21 kg/(m^(2)·h)。证实CTF-BP膜有望实现高效甲醇/正己烷分离。

碳点在膜技术中的应用进展

碳点(CDs)是一种新型的零维碳基材料,其具有超小尺寸、亲水性强、丰富的表面官能团、易于合成和良好的水溶性等优异特性.通过调控CDs的性质可以提高复合膜的水通量和分离性能,将其引入膜材料中对开发高渗透性和高选择性复合膜具有重要意义.因此,CDs在膜分离领域展现了巨大的应用前景.本文介绍了CDs或改性CDs的合成方法,总结了CDs复合膜的制备及其在气体分离、水净化、有机溶剂分离等领域的应用,并对CDs在膜技术领域的应用中所面临的机遇与挑战进行了展望.

膜法碳八芳烃异构体分离技术研究进展

碳八芳烃是工业生产中的重要原料,其中对二甲苯(PX)的市场需求量最高,被广泛用于生产聚对苯二甲酸乙二醇酯(PET)等材料。目前PX的工业分离技术主要为高能耗的结晶法和吸附法,与之相比,新兴的膜分离技术具有能耗低、效率高等潜在特点,有望推动碳八芳烃异构体分离的工艺变革。文章主要介绍了近些年来国内外聚合物膜、MFI(Mobil-type five)型沸石分子筛膜、金属有机框架膜以及碳分子筛膜在碳八芳烃异构体分离中的研究进展,评述了膜材料的优势与不足之处,并展望了膜法碳八芳烃异构体分离的发展方向与应用前景。