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。     

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.     

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.     

新型PVA/PA复合膜的运行工艺对渗透汽化性能的影响

研究了聚乙烯醇（PVA）/聚酰胺（PA）复合膜渗透汽化（PV）分离异丙醇（IPA）/水混合物时运行工艺的影响,模拟了渗透通量（J）预测方程。结果表明,PVA/PA复合膜在料液中w（IPA）%在0～95%范围内或在25℃～100℃的操作温度范围获得的渗透液中IPA含量[w′（IPA）]都小于1%,J随料液中w（IPA）%的下降或操作温度的提高而增加。分离性能预测方程的拟合结果与试验数据有良好一致性。在室温条件下,经过90 d的间歇运行或经过120 d的长期贮存后,PVA/PA复合膜的分离性能稳定,在IPA/水混合物的共沸温度80.4℃运行时的J为73.1 g/m^2·h,渗透液中的水含量[w′（H2O）]都大于99.5%,展示了其在食品、生物、制药和化学等工业中将具有良好的应用前景。     

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.     

Synthesis and Characterization of ETS-10/Chitosan Nanocomposite Membranes for Pervaporation

Chitosan (CS) and microporous titanosilicate ETS-10/CS mixed matrix membranes (MMMs) were prepared. The pervaporation performance was tested on the water-ethanol mixtures in the range 85–96 wt.% ethanol. The permeate flux increased from 0.45 to 0.55 kg m^?2 h^?1 at 50°C for the ETS-10/CS MMM with respect to the pure CS membranes. Characterization by SEM and TEM, XRD, DSC, and TGA allowed inferring an intimate contact between the dispersed ETS-10 and the continuous chitosan phase. The 5 wt.% loading of titanosilicate scarcely decreased the hydrophilic character of the mixed matrix membrane but increased the molecular sieving effect on the transport and separation properties, thus affecting the membrane behavior on pervaporation.     

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...     

聚酰亚胺渗透汽化膜改性研究进展

详细综述了用于渗透汽化分离的聚酰亚胺膜的改性研究进展,重点评述了共聚（改变主链结构、侧基结构和引入特殊功能性单体）、填充（无机物填充和有机物填充）、交联、共混以及表面改性5种改性方法,包括其反应原理、设计思路以及对聚酰亚胺膜分子结构和分离性能的影响等。同时通过比较不同改性方法的研究结果,分析了几种改性方法在渗透汽化膜分离方面的优点和不足。在此基础上,对聚酰亚胺渗透汽化膜的改性方法发展方向和研究前景进行了总结。     

渗透汽化膜分离技术及其在化工生产上的应用

介绍了渗透汽化膜分离技术的基本原理、特点及影响分离效果的因素,并对渗透汽化膜分离技术的进展及其在化工生产上的应用进行了介绍.     

渗透汽化膜技术及其在溶剂分离领域的应用

渗透汽化膜技术是一种高效节能、绿色环保的新型膜分离技术,与传统分离技术相比优势显著,使该技术成为溶剂分离领域研究的焦点。简述了渗透汽化膜技术的基本原理和工艺流程,介绍了渗透汽化膜技术在有机溶剂/水体系、有机溶剂/有机溶剂体系分离的研究应用现状,展望了渗透汽化膜分离技术的研究应用前景。     

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。     

芳烃优先透过的渗透汽化复合膜的制备及分离性能研究

采用紫外光接枝填充聚合技术,以非对称聚丙烯腈(PAN)超滤膜为底膜,聚乙二醇甲醚甲基丙烯酸酯(MePEO300MA)为大分子单体,制备了芳烃优先透过的渗透汽化复合膜。考察了单体浓度和紫外光照射反应时间对复合膜甲苯/正庚烷渗透汽化分离性能的影响,并对复合膜降低石脑油芳烃含量,优化乙烯裂解原料进行了初步探索。研究结果表明,复合膜对甲苯质量分数为20%的甲苯/正庚烷混合物(80℃)的分离系数达到5.6,渗透通量为2.47 kg/(m2.h);当切割比为20%时,石脑油的芳烃质量分数由7.52%降至4.11%,降低了45%,初步说明渗透汽化复合膜在降低石脑油的芳烃含量,优化乙烯裂解原料方面的应用前景。     

高通量二氧化硅复合膜的制备及其渗透汽化性能研究

二氧化硅复合膜展现出的耐酸性和稳定性在渗透汽化领域有着广阔的应用前景.本文采用真空抽吸浸渍法制备二氧化硅复合膜的支撑层,得到高通量二氧化硅复合膜.本文对支撑层真空抽吸的最优条件进行探究,并采用扫描电镜对膜层的表面、截面形貌结构进行表征.结果表明,当支撑层溶胶质量浓度为2％,真空抽吸时间为10 s,真空抽吸压力为0.10...     

Separation of Azeotropic Dimethylcarbonate/Methanol Mixtures by Pervaporation: Sorption and Diffusion Behaviors in the Pure and Nano Silica Filled PDMS Membranes

In this article, polydimethylsiloxane and hydrophobic nano-silica filled polydimethylsiloxane membranes were prepared and employed in dimethylcarbonate (DMC) removal from the DMC/methanol mixture via pervaporation. The sorption and diffusion behavior of the binary molecule were discussed separately to provide qualitative estimation of the PV performance in both membranes. Compared with the polydimethylsiloxane membrane, hydrophobic nano-silica filled polydimethylsiloxane membranes had a little lower sorption selectivity but higher diffusion selectivity. In both membranes, the sorption value was obtained by both experimentation and model prediction. The Flory-Huggins model was performed to predict the solvent uptakes and the sorption concentrations based on the experimental results. The sorption behavior of DMC was predictable, while the methanol solubility was a little higher than the experimental results. Moreover, the diffusion behavior was studied by Fick's law, the calculated diffusion coefficients of the permeates demonstrated a diffusion-coupling phenomenon, especially in hydrophobic nano-silica filled polydimethylsiloxane membranes. Methanol molecules diffused faster than DMC, suggesting the low diffusion selectivity. The PV performance was affected by both sorption and diffusion. Sorption was demonstrated to be a decisive factor in this pervaporation process.     

自具微孔聚合物在渗透汽化膜分离中的应用进展

介绍了自具微孔聚合物(PIMs)及其改性膜材料在渗透汽化膜分离领域中的应用研究进展,评述了在优先脱有机物、优先脱水以及有机混合物分离3个领域中所应用的PIMs膜的分子结构设计、改性方法以及分离效果.PIMs是一种依靠自身分子扭曲而具有大量微孔的新型聚合物,具有憎水性以及均一的孔结构,对于不同体系中的目标分离物均有较好的...     

丙炔醇-丁炔二醇-水溶液的渗透汽化分离研究

用PDMS复合膜从实际的丙炔醇-丁炔二醇-水溶液中渗透汽化分离丙炔醇。实验证明,膜渗透汽化可以实现丙炔醇的选择性分离,对水的分离因子可达3.78;丁炔二醇被膜完全截留;丙炔醇通量对温度具有敏感性,通量随着温度的增加上升得很快,丙炔醇通量在25℃时为45.28g/(m2.h),在60℃时为243.24g/(m2.h),显示了PDMS膜从这个体系中分离丙炔醇具有某种优势;对实验数据进行线性回归,证明丙炔醇通量和温度的关系可以用Arrhenius公式表征。为工业上用PDMS膜渗透汽化分离提纯丙炔醇提供参考。     

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.     

Effect of Operating Conditions on PV Performance of PVA Membranes: Experimental and Neural Network Modeling

Poly (vinyl alcohol) membranes were prepared by in-situ crosslinking of poly(vinyl alcohol) with glutaraldehyde as crosslinking agent and hydrochloric acid as catalyst and used for dehydration of IPA mixtures. Effects of feed composition, operating temperature, vacuum pressure, and Reynolds number on the permeation performance of the membranes were evaluated. Eighty-nine experimental data was applied to investigate ANN modeling. A multi layered feedforward neural network was applied to model the PV membranes. Two major training algorithms and optimum number of neurons and layers were investigated. As a result, Bayesian regularization successfully predicted experimental data. Different network structures were optimized, using multi object genetic optimization algorithm. The results concluded that the network with structure composing two hidden layers performs better than the other with one hidden layer, and also there is an excellent compatibility between the experimental data and the predicted values of optimum network structure (4:3:2:2). Furthermore, the optimum network was applied to predict extrapolation data and the results showed that this network can extrapolate data as well as interpolating.     

Comparative Study of Separation of Acetonitrile from Aqueous Solutions by Pervaporation using Different Membranes

Pervaporation of acetonitrile-water mixtures was carried out using three commercial membranes, viz: polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). The effects of feed concentration and feed temperature on the pervaporation performance, total and partial permeate fluxes, as well as acetonitrile selectivity, were investigated. It was found that increase in temperature yields higher total fluxes and lower selectivity for acetonitrile-water system. Changing concentration of acetonitrile in the range concerned leads to significant effect on total flux and selectivity. PDMS membrane was found to be most selective for acetonitrile separation. The total flux through the membranes was found to be in the order of PTFE > PVDF > PDMS, and the acetonitrile selectivity was found to be in the order of PDMS > PVDF > PTFE. The activation energies of water and acetonitrile associated with the permeation process for the PDMS, PTFE, and PVDF membranes were calculated to be in the ranges of 0.29–0.99, 0.6–0.87, 0.45–2.73 kJ/mol for acetonitrile and 1.23–1.95, 1.37–1.71, 1.16–3.37 kJ/mol for water at different concentrations, respectively.