疏水SiO2填充PDMS膜分离水中乙酸正丁酯的性能

以聚偏氟乙烯（PVDF）为支撑层,选用疏水性纳米SiO₂粉体作为改性剂,制备出聚二甲基硅氧烷（PDMS）复合膜材料,并用于乙酸正丁酯/水溶液的渗透汽化分离。采用SEM、FTIR、XRD、拉伸实验、接触角及正电子湮没寿命谱测定等对膜材料物理化学性能进行了表征,考察了膜材料的溶胀行为及渗透汽化性能。结果表明,SiO₂在PDMS膜中分散均匀,且没有发生化学作用,并提高了膜材料的机械强度和疏水性。随着SiO₂添加量增加,膜在乙酸正丁酯溶液中的溶胀度先升后降,渗透通量呈下降趋势,而分离因子先增大后减小。当SiO₂添加量为4%（质量）时,随进料浓度的增加,渗透通量增大,分离因子先增大后减小;随着温度升高,渗透通量增大,分离因子减小;渗透通量和分离因子最大值分别为240 g·m^-2·h^-1和542。     

己二酸和甲醇酯化反应与渗透汽化脱水耦合过程的研究

以己二酸二甲酯的合成为目标反应,选用聚乙烯醇/聚丙烯腈(PVA/PAN)复合膜为渗透汽化膜,比较了蒸馏脱水与渗透汽化脱水对酯化反应转化率的影响.结果表明,在己二酸和甲醇摩尔比为1∶2时,蒸馏脱水与渗透汽化脱水都可将转化率从68%的平衡转化率提高到98%,但渗透汽化脱水方法带出来的甲醇量只有蒸馏脱水法中甲醇量的7%,因而可以大幅度降低因蒸发和提纯甲醇所需要的能耗.     

有机液优先透过渗透汽化膜的应用发展

在分析渗透汽化膜分离有机混合物体系类型的基础上,重点提出有机液优先透过渗透汽化膜,其作为渗透汽化膜的重要组成部分近年来受到高度关注.综述了各种有机物优先透过的膜材质、分离特性,以及近年来有机液优先透过膜的研究进展和应用领域.通过分析可以得出结论:有机液优先透过渗透汽化膜的研究目前尚处于基础研究阶段.提高膜的选择性和渗透通量,以及如何使两者取得适度平衡等是当前研究的重点.     

渗透蒸发过程非平衡溶解扩散模型

<正> 目前,关于渗透蒸发膜过程的机理研究已有不少成果’‘－‘’,这些工作归纳起来就是（平 衡）溶解－扩散模型．以聚乙烯醇膜分离乙醇－水体系为例,渗透蒸发过程中组分通过膜的传递 可以分为3个步骤：、（）乙醇、水溶解到膜的表面并达到溶解平衡;（2）水和乙醇依靠浓度梯 度扩散到膜的真空侧表面;（3）水和乙醇进入真空侧汽相．     

乙基叔丁基醚的催化反应与渗透蒸发膜分离耦合法的合成

以乙醇（ＥｔＯＨ）及叔丁醇（ＴＢＡ）为原料,用催化反应与渗透蒸发膜分离耦合的方法,以强酸性阳离子交换树脂Ａｍｂｅｒｌｙｓｔ１５为催化剂,合成了乙基叔丁基醚（ＥＴＢＥ）。研究考察了水－醇体系中水的渗透速率及膜的选择性,讨论了渗透蒸发膜分离耦合与否对其反应结果的影响。在考虑了试验条件下ＴＢＡ分解为水与异丁烯（ＩＢ）而引起的体积减少、水的吸附对催化剂活性的阻害效应以及水的渗透通量等因素的基础上,得出了一数学模型。试验结果与模型计算值比较一致。     

抽空涂晶法合成A型分子筛膜及渗透汽化性能研究

采用抽空涂晶二次生长法在管状α-Al2O3基膜上合成了具有高选择性、高渗透量的A型分子筛膜.XRD结果表明,分子筛膜晶相中只有A型分子筛存在;SEM表明,基膜表面覆盖了一层致密连续的分子筛膜.考察了A型分子筛膜的渗透汽化性能,结果表明,在温度为323K和343K下,当原料液中异丙醇的质量分数为95%时,其水/异丙醇分离系数都大于10000,渗透量分别为1.27kg/(m2·h)和1.74kg/(m2·h).     

Pervaporation behavior of asymmetric sulfonated polysulfones and sulfonated poly(ether sulfone) membranes

The sulfonation of polymers and the pervaporation behavior of asymmetric polymeric membranes are described in this study. We confirmed that the sulfonic acid group was successively introduced into the polymer chain by FTIR and ¹H‐NMR characterization. The phase diagram indicated that the modified polymer could have water tolerance, implying that the polymer–solvent miscibility was lower. The hyperthin skin layer, suitable for pervaporation, depended on the NMP–DGDE composition, which was important for the fabrication of an asymmetric membrane with high water permeance. The asymmetric membrane exhibited water selectivities equal to or slightly lower than those determined for the dense film. The hyperthin skin layer, which had hardly any defects, was possibly formed by the phase‐inversion method. It is obvious that these membranes can be used for the industrial pervaporation process. The permeability and the selectivity of the water–butanol mixture for the asymmetric membranes at 50°C were measured. The permeation rates for water–butanol in the asymmetric membrane were about 80 times greater than those of film, and the separation factor was slightly lower. The NMP–DGDE solvent system might be suitable for a high permeation rate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 787–798, 2000     

Modification of poly(vinyl alcohol) membranes using sulfur-succinic acid and its application to pervaporation separation of water–alcohol mixtures

For the purposes of the water-selective membrane material development for pervaporation separation, we crosslinked poly(vinyl alcohol) (PVA) with sulfur-succinic acid (SSA), which contains —SO₃OH, by heat treatment and investigated the effect of the crosslinking density on the separation of water–alcohol mixtures by pervaporation technique. The crosslinking reaction between PVA and SSA was characterized through Fourier transform infrared spectroscopy and differential scanning calorimetry tests by varying the amount of the crosslinking agent, the reaction temperature, and the swelling measurements of each pure component. The separation performance of the water–methanol mixture is not good due to the existence of sulfonic acid, hydrophilic group, in the crosslinking agent. However, for the water–ethanol mixture, the flux of 0.291 kg/m²h and the separation factor of 171 were obtained at 70°C when PVA-crosslinked membrane containing 7 wt % SSA was used. The same membrane also showed flux of 0.206 kg/m²h and a separation factor of 1969 at the same operating temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1717–1723, 1998     

A qualitative investigation on the importance of boundary layer in pervaporation separation of an aqueous organic reaction

The importance of boundary layer was investigated for the hydrolysis of ethyl acetate using a dense standard poly(vinyl alcohol) (PVA) membrane. A resistance in a series model approach was used to study the effect of a boundary layer for the permeation of aqueous organic mixtures involved in the study. The initial feed mixture consisted of 10% water (H₂O), 40% ethyl acetate (EA), 50% acetic acid (AA), and 0% ethanol (E) (all weight percentage basis). The experiments were conducted at 65°C. The amount of all species in the feed reservoir was found to decrease with time. Selectivity calculations based on a resistance in the series model approach indicates that the boundary layer contributes to selective permeation of aqueous organic compounds. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2361–2369, 1998     

Preparation of N-methylol nylon-6 membranes for pervaporation of ethanol-water mixtures

N-methylol nylon 6 membranes were prepared by reacting nylon-6 with formaldehyde. Elemental analysis, used to analyze the composition of modified membranes, showed that the degree of substitution increased with formaldehyde content in the reaction solution. The modified nylon-6 membranes exhibited a high affinity to ethanol. Pervaporation results for the separation of ethanol-water mixtures showed that these membranes were water-selective, indicating that the diffusion property is the dominant factor. An N-methylol nylon-6 membrane with 33% degree of substitution showed the best membrane performance. In order to control the swelling of N-methylol nylon-6 membranes in the feed solutions of high ethanol content, thermal crosslinking was applied at 180°C for different times. It was found that heat treatment of 10 minutes gave the optimal permselectivity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 855–863, 1997