NaA分子筛膜的合成及在渗透蒸发中的应用

介绍了近几年来国内外在NaA分子筛膜的合成及应用方面的研究进展,重点介绍了NaA分子筛膜渗透蒸发的机理和在有机物脱水中的应用.提供了分子筛膜渗透蒸发与蒸馏过程在有机物脱水中的经济比较,发现渗透蒸发过程能降低一半成本.最后对NaA分子筛膜的制备和渗透蒸发进行了展望.     

聚氨酯渗透蒸发膜的研究进展

综述了聚氨酯渗透蒸发膜在渗透蒸发分离中的研究进展,分析了聚氨酯膜软硬段结构及其它因素对其分离性能的影响,并对聚氨酯膜的改性方法进行总结和评述。指出了聚氨酯膜目前研究中存在的不足及发展趋势。     

渗透蒸发膜改性技术的研究进展

物理改性和化学改性作为改变渗透蒸发膜的分离性能 (渗透通量和分离因子 )、抗污染性、物理化学稳定性的有效手段而吸引了大量的研究和开发兴趣。这些改性方法在不少场合下可以联合使用。对常用的改性方法进行了分类介绍 ,简要评述了各种方法的优缺点 ,并列举了一些实例加以具体说明     

沸石膜渗透蒸发性能研究进展

渗透蒸发由于其对近沸物和恒沸混合物高效的分离性能而成为当今一个基本的分离操作单元。本文首先对渗透蒸发装置及分离性能表征简要总结,然后重点概述了对沸石膜的渗透蒸发应用和渗透蒸发过程影响因素,最后针对当前研究现状,展望了沸石膜在渗透蒸发方面的发展前景。     

沸石分子筛膜渗透汽化分离机理及其影响因素研究进展

沸石分子筛膜在渗透汽化分离过程中的应用研究日益增多,对沸石分子筛膜渗透汽化分离机理及其影响因素作了简要综述,讨论了选择性吸附分离和分子筛分原理两种分离机理,其影响因素主要包括:分子筛膜表面特性、非沸石孔、操作温度、原料浓度、浓度极化等。     

渗透蒸发膜及其在酯化反应过程中的应用

根据３０余篇文献及有关的技术资料，从膜的结构，膜制备的材料，制备方法及表征等方面总结了近１０年来渗透蒸发膜国内外的研究情况，以及将渗透蒸发膜应用酯化反应体系的研究成果和动态。     

Silicalite-1分子筛膜渗透蒸发条件的响应面分析与优化

采用Silicalite-1分子筛膜用于低浓度乙醇/水溶液的渗透蒸发分离,运用单因素实验考察了晶种质量分数、晶化温度、晶化时间3个制备条件对Silicalite-1分子筛膜渗透蒸发分离性能的影响,借助响应面分析（RSM）研究了料液温度、乙醇质量分数、真空压力3个运行条件对分离系数和渗透通量的影响。单因素实验结果表明,在晶种质量分数为0.3%、晶化温度为175℃、晶化时间为7h条件下制备的Silicalite-1分子筛膜对乙醇/水的渗透蒸发分离效果较好。RSM结果表明,料液温度、料液配比、真空压力对分离系数和渗透通量的影响显著,根据RSM建立多项式模型并对该模型预测的最佳条件进行了实验验证,实验结果与模型预测较为吻合。在进料温度为70℃、乙醇质量分数为3.49%、真空压力为7.82kPa条件下,实际分离系数和渗透通量与预测值偏差分别小于5.46%和7.39%。     

以多次原位水热法合成Ge-ZSM-5分子筛膜及其渗透蒸发性能的研究

在α-A1_2O_3载体上,通过多次原位水热合成制备Ge-ZSM-5分子筛膜,并利用渗透蒸发膜分离技术从乙酸/水溶液中分离乙酸。考察了晶化时间和合成液中Ge含量对膜的结构和性能的影响。在溶胶物质的量组成为Ge(C_2H_5O)_4∶SiO_2∶TPAOH∶H_2O=1∶x∶5.13∶2 246(x=100,25)的合成液中,经过3次水热晶化,所得的膜均为致密膜,膜的分离因子随温度的升高而增加,渗透通量受温度影响不大。在Si/Ge=25的溶胶中,一次原位水热晶化24 h,二次原位水热晶化18 h,三次原位水热12 h合成的膜质量最优,对5%乙酸水溶液,在90℃时,分离因子可达2.0,此时渗透通量为0.8 kg/(m2·h)。     

以多次原位水热法合成Ge-ZSM-5分子筛膜及其渗透蒸发性能的研究

在α-A1_2O_3载体上,通过多次原位水热合成制备Ge-ZSM-5分子筛膜,并利用渗透蒸发膜分离技术从乙酸/水溶液中分离乙酸。考察了晶化时间和合成液中Ge含量对膜的结构和性能的影响。在溶胶物质的量组成为Ge(C_2H_5O)_4∶SiO_2∶TPAOH∶H_2O=1∶x∶5.13∶2 246(x=100,25)的合成液中,经过3次水热晶化,所得的膜均为致密膜,膜的分离因子随温度的升高而增加,渗透通量受温度影响不大。在Si/Ge=25的溶胶中,一次原位水热晶化24 h,二次原位水热晶化18 h,三次原位水热12 h合成的膜质量最优,对5%乙酸水溶液,在90℃时,分离因子可达2.0,此时渗透通量为0.8 kg/(m2·h)。     

NaA型分子筛膜用于医药工业异丙醇溶媒渗透汽化脱水(英文)

NaA zeolite membranes with 80 cm in length and 12.8 mm in outer diameter were prepared by our research group cooperating with Nanjing Jiusi Hi-Tech Co., China. The influence of dissolved inorganic salts and pH value in the feed of isopropanol (IPA) solution on NaA zeolite membranes was investigated. It was found that both factors exhibited strong influence on the stability of NaA zeolite membranes. A set of pretreatment steps such as pH adjustment and distillation of the IPA solution were proposed to improve stability for pervaporation dehydration. An industrial-scale pervaporation facility with 52 m2 membrane area was built to dehydrate IPA solution from industrial cephalosporin production. The facility was continuously operated at 368-378 K to dehydrate IPA solution from water mass content of 15%-20% to less than 2% with a feed flow rate of 400-500 L·h-1 and an average water flux of 1-1.5 kg·m-2·h-1. The successful application of this facility suggested a promising application of NaA zeolite mem-brane for IPA recovery from pharmaceutical production.     

Pervaporation of Acetaldehyde Aqueous Solution through Zeolite 3A-Polyurethane (PU) Composite Membrane

3A-filled hydrophilic polyurethane (PU) membranes were prepared by incorporating zeolite 3A into PU for pervaporation separation of acetaldehyde and water mixtures (acetaldehyde concentration 2 wt%–20 wt%). The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The morphology and thermal stability of these membranes were also investigated. The effects of zeolite 3A on the sorption, diffusion, and pervaporation performance were evaluated. The swelling study showed that 3A-PU membrane had higher swelling degree in acetaldehyde aqueous solution than in pure water. And the swelling degree of the composite membrane in acetaldehyde solution increased with the 3A content. The permeation flux and water/acetaldehyde separation factor first increased and then decreased with increasing 3A content. The reason may be that a proper quantity of 3A will enlarge the free volume fraction of PU while excessive 3A lead to its poor dispersion. The highest permeation flux of the composite membrane could reach 223 g · m^?2 · h^?1 and the maximum water/acetaldehyde selectivity achieved 7.5. The calculation of sorption selectivity and diffusion selectivity showed that diffusion played a more important role in this process.     

沸石膜的合成最新进展

介绍了合成沸石膜的常用方法,如：原位水热合成法、二次生长法、微波法及脉冲激光烧蚀法,并对各种方法进行了比较,指出了其优缺点。提出了沸石膜合成的目标：合成由小晶粒组成的薄而连续的定向膜。对载体的选择及处理方法进行了总绔,并对沸石膜的合成方法进行了展望。     

用于分离DMF/H2O体系的Me-silicalite-1渗透汽化分子筛膜的制备

采用二次生长法制备了用于渗透汽化分离DMF/H2O体系的杂原子取代Me-silicalite-1/α-Al2O3(Me=Co、Fe)分子筛复合膜,通过X射线衍射(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和紫外漫反射(UV-Vis)等方法对分子筛膜进行表征,结果表明金属离子进入分子筛骨架。渗透汽化实验显示,金属离子掺杂的silicalite-1/α-Al2O3分子筛复合膜,具有较好的分离性能且优先透过有机胺,有利于工业中DMF溶剂的回收和利用。随着操作温度升高,分离因子减小,渗透通量增加。40℃分离质量分数为5%的DMF/H2O混合液时,Co-silicalite-1/α-Al2O3分子筛膜和Fe-silicalite-1/α-Al2O3分子筛膜的分离因子分别为4.4和2.9,渗透通量分别为0.66和0.84 kg·m-2·h-1。     

分子筛膜的研究进展

分子筛膜是近些年发展起来的一种新型无机膜,具有很好的筛分效应、极高的耐热稳定性及良好的催化作用等优异性能。本文简单介绍了分子筛膜制备技术和分子筛膜反应器种类,分析了近年来分子筛膜在脱氢反应、酯化反应和氧化反应催化反应中的初步应用,发现其可实现催化与分离的很好结合,并对分子筛膜的应用前景进行了展望。     

地质聚合物原位合成八面沸石膜及其渗透汽化性能

以煅烧高岭土和水玻璃为原料制备地质聚合物,采用水热合成法原位合成了自支撑八面沸石(简称FAU型)膜。利用X射线衍射、扫描电子显微镜、万能压力试验机表征了沸石膜材料的抗压强度和微观结构,通过渗透汽化实验及数学模型考察了乙醇/水混合物体系进料组成和温度对沸石膜的渗透通量以及分离因数的影响。结果表明:该沸石膜表面的晶粒细小,膜覆盖完全且连续致密;提高养护时间有利于提高地质聚合物的压缩强度,提高水热时间有利于改善FAU型沸石膜表面形貌和相组成。在进料温度为50℃、原料中乙醇的含量为70%的优化条件下,FAU型沸石膜具有较高的渗透通量和分离因数,其渗透通量和分离因数分别达到1.41kg/(h m2)和16.8。     

Synthesis of NaA and NaX Zeolite Membranes by Fumed Silica Via Clear Solution Gel

NaA zeolite membranes have been used for dehydration of organic solvents in laboratory and commercial scales. There are many synthesis methods and conditions for manufacturing the membranes. The use of lactescent and clear gel solutions are two of the most important choices for high quality hydrothermal synthesis of NaA zeolite membrane in gas separation or dehydration of organic solvents. In this article, effect of hydrothermal synthesis time was investigated using the clear gel solution (Al₂O₃:5SiO₂:50Na₂O:1000H₂O). Phase transformation from NaA to NaX was recognized as the most possible event when the clear gel solution was used. XRD spectra, SEM images, and GC analyses were used for evaluation of zeolite crystal phase, the membrane layer quality, and the contents of organic substances (ethanol or 2-propanol) in feed and permeate streams in pervaporation tests, respectively. From synthesis of zeolite membrane at different times, it was revealed that for achieving the pure NaA zeolite phase the synthesis time should not exceed 3 h at 100°C.     

Mixed Matrix Silicone and Fluorosilicone/Zeolite 4A Membranes for Ethanol Dehydration by Pervaporation

The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10^?12 kmol · m/m² · s · kPa in PDMS to 5.1 × 10^?12 kmol · m/m² · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10^?12 kmol · m/m² · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane.     

Pervaporation of n‐butanol aqueous solution through ZSM‐5‐PEBA composite membranes

Composite membranes were prepared by incorporating ZSM‐5 zeolite into poly(ether‐block‐amide) (PEBA) membranes. These composite membranes were characterized by TGA, XRD, and SEM. The results showed that the zeolite could distribute well in the polymer matrix. And when the zeolite content reached 10%, the agglomeration of zeolite in the membranes was found. The composite membranes were used to the pervaporative separation of n‐butanol aqueous solution. The effect of zeolite content on pervaporation performance was investigated. With the contribution of preferential adsorption and diffusion of n‐butanol in the polymer matrix and zeolite channel, the 5% ZSM‐5‐PEBA membrane showed enhanced selectivity and flux. The effects of liquid temperature and concentration on separation performance were also investigated. All the composite membranes demonstrated increasing separation factor and permeation flux with increasing temperature and concentration. Incorporation of ZSM‐5 could decrease the activation energy of n‐butanol flux of the composite membrane. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013