Effect of Film Aging on the Pervaporation Properties of Latex Membranes

Abstract

Latex membranes have recently been investigated for their application in pervaporation separation processes. Acrylonitrile-butyl acrylate copolymer latex membrane showed selective permeation to water in pervaporation with water-ethanol mixtures. Different from solvent-cast membranes, the pervaporation properties of latex membranes were found to change with the membrane aging time or under different aging conditions. It is shown that aging leads to better membrane fusion, thus decreasing the permeation rate and increasing the separation factor. Aging the membrane in a medium which keeps the latex particle from good fusion would cause a high permeation rate but a low separation factor. Based on our observations, a comprehensive transport mechanism of the permeant through latex membranes during pervaporation is proposed.     

Characterization and Pervaporation Study on Ethanol Separation Membranes

Inorganic membranes have many advantages for dehydration of azeotropic mixtures of ethanol and water for renewable fuel purposes. In this work, we developed an inorganic membrane from γ-alumina and tested it for its ability to selectively permeate water over ethanol. Ethanol adsorbed both chemically and physically on the surface of γ-alumina, blocking the 47 Å pores sufficiently to enhance water selectivity. Stable flux was observed over 6 h, but after 4–5 h of continuous testing, water selectivity rose above 200 due to this blocking phenomenon.     

EC-AHBPE渗透汽化膜的研究

为研究超支化聚合物在渗透汽化分离膜中的应用,该文以三羟甲基丙烷为核、二羟甲基丙酸为单体,用准一步法合成了端羟基超支化聚酯(HBPE),并以丙烯酸对其进行了端基改性,得到端丙烯酸酯基超支化聚酯(AHBPE)。将AHBPE作为大分子交联剂,对乙基纤维素(EC)进行紫外光引发交联改性,得到了EC-AHBPE膜。以苯/环己烷体系为考察对象,对EC-AHBPE膜的吸附溶胀行为和渗透汽化性能进行了考察,并与小分子交联剂乙二醇二丙烯酸酯交联EC膜进行了比较。结果表明:与小分子交联剂乙二醇二丙烯酸酯(EGDM)相比,AHBPE交联膜具有更高的平衡吸附量和吸附选择性。当AHBPE在膜内质量分数为40%、交联时间为30 min、二苯甲酮质量分数为10%时,对于苯质量分数为10%的混合溶液,EC-AHBPE膜的渗透通量可达42.5 kg.μm/(m2.h),分离因子为7.02。     

Effects of CNTs Content on Physicochemical and Pervaporation Separation Properties of PVA Membranes

In this study, the morphological and separation characteristics of PVA membranes incorporated with functionalized CNTs are reported. CNTs was extensively characterized using TGA, FESEM, and TEM. The physicochemical properties of PVA-CNTs membranes were characterized using FESEM, tensile test, DSC, and XRD. DSC measurements showed an increase in melting and glass transition temperature, implying enhancement of polymer chains compacting. XRD analysis confirmed the results of DSC and showed that CNTs can promote crystallinity of the PVA membranes. In addition, tensile measurements revealed that incorporating CNTs into the PVA membranes improves their mechanical properties. The synthesized nanocomposite membranes were then evaluated in pervaporation (PV) dehydration of isopropanol (IPA). The separation results showed that incorporating CNTs into the PVA membranes significantly increases water selectivity of the PVA membranes. This can be attributed to the fact that incorporating CNTs compacts and rigidifies PVA matrix and decreases its free volume. Furthermore, permeation of water molecules through the nanocomposite membranes decrease as a result of the polymer chains rigidification. Effects of feed composition and temperature on PVA-CNTs nanocomposite membranes were investigated. Besides, effects of CNTs content on permeation properties and activation energies of PVA membranes were evaluated.     

丝光沸石膜渗透汽化法脱水浓缩四氢呋喃的实验研究

采用二次生长法,在无有机模板剂的条件下于a-Al2O3载体上制备丝光沸石膜. 所制丝光沸石膜用于四氢呋喃(THF)水溶液脱水浓缩,考察了操作温度、THF浓度对其渗透汽化性能的影响. 结果表明,在操作温度为60℃、THF浓度为90%(w)时,丝光沸石膜的渗透通量和分离因数分别为0.35 kg/(m2×h)和9233,渗透液水含量达99.907%(w). THF浓度在75%~97%范围内,渗透液的水含量均在99.6%以上. 对THF浓度为97.066%(w)的模拟制药废液脱水37 h后,THF浓度达99.640%.     

催化剂对酯化反应渗透汽化膜稳定性的影响

比较了酯化反应耦合渗透汽化膜反应器中不同的催化剂体系及其含量对ＰＰＶＡ／ＰＡＮ复合膜稳定性的影响。试验结果表明,固体超强酸催化剂体系对复合膜的稳定性没有影响。活性层酯化度为３．３％及６．２％的复合膜具有良好的稳定性。能够适合于酯化反应耦合渗透汽化过程研究及应用。     

新型渗透蒸发膜及其透醇性能研究

采用溶液聚合法合成聚丙烯酸,并利用聚丙烯酸和环氧树脂的交联作用制备出交联聚丙烯酸（ＰＡＡ）,在聚砜酰胺（ＰＳＡ）膜上涂膜形成ＰＡＡ－ＰＳＡ复合膜。发现用交联聚丙烯酸－聚砜酰胺制成的复合膜在渗透蒸发领域内具有应用价值。通过对低浓度乙醇－水的渗透蒸发的试验研究,表明该膜是一种性能较好的新型优先透醇膜。     

分子筛膜渗透蒸发技术研究进展

概述了渗透蒸发膜分离过程和分子筛膜的优点,重点综述了沸石分子筛膜在渗透蒸发中的传输机理和传质模型,以及温度、压力、组成等对渗透蒸发膜分离性能的影响因素,介绍了分子筛膜渗透蒸发技术在有机溶剂脱水、水中脱除有机物和有机混合物分离等方面的应用,展望了分子筛膜在渗透蒸发膜分离技术中的发展方向。     

渗透蒸发膜分离有机双元混合物

本文以聚酰亚胺（ＰＩ）均质膜为渗透蒸发膜来分离苯和环己烷混合液，测定其渗透通量及透过液组成，证明ＰＩ膜对苯有极强的选择性；平衡溶解度大小影响着渗透通量的大小。在一定范围内，苯在ＰＩ膜内的扩散系数与其溶解度成指数关系，并将由此得到塑化因子ｒ，与苯和ＰＩ膜的相互作用参数的计算值进行了比较。同时，发现渗透通量、溶解度和扩散系数分别与温度之间符合Ａｒｒｅｈｅｎｉｕｓ方程。     

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。     

ACHEMA 2022: Membranes and Membrane Processes

Numerous companies working in the field of membrane development, membrane production, and membrane separation engineering were present at ACHEMA 2022. Compared to the last ACHEMA in 2018, there were fewer attending companies and only few new topics since development has been blocked partially by the pandemic situation and the subsequent restrictions of this years. Nevertheless, some new developments have been identified concerning process design as well as ceramic and polymeric systems.     

Membrane Pervaporation: Separation of Organic/aqueous Mixtures

Abstract

The recovery of water-laden solvents by membrane pervaporation has become an industrially-accepted practice. A review of the technology is presented, along with discussion of the potential for removal of organics from water.     

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.     

ZrO2 和Al2O3支撑的MFI 型沸石分子筛膜:支撑体材料对膜性能的影响

采用水热合成法，以纯SiO2为源物质，在介孔Y2O3掺杂的ZrO2(YZ)及大孔α-Al2O3支撑体上制备出高质量的MFI型沸石分子筛膜，通过H2／n-C4H10气体混合物的渗透分离和p-xylene的蒸发研究了不同支撑体上MFI型沸石分子筛膜分离性能，在较低温度范围，YZ支撑的MFI型沸石分子筛膜中n-C4H10的渗透率比Al2O3支撑的膜高很多，最大n-C4H10与H2的分离率达到500，Al2O3支撑的膜中py-xylene的蒸发流量随时间下降很快，而YZ支撑的膜中的蒸发流量则变化缓慢，用XRD对膜的晶体结构进行分析，通过多种温度下热处理不同支撑体上的膜样品研究了其热稳定性与支持体材料的关系，YZ支撑的MFI型沸石分子筛膜的MFI结构在1000摄氏度后仍能保持，而Al2O3支撑的膜950摄氏度时已完全转变为石英相，研究结果表明，YZ支撑的MFI型沸石分子筛膜比Al2O3支撑的膜表现出更好的厌不性，热稳定性以及抗阻塞性。     

PVA/ P（AA-Co-AN）/ PVA渗透汽化膜的研究

制备一种PVA/P(AA-Co-AN)/PVA复合膜用于甲醇水溶液的分离,膜的主体部分P(AA-Co-AN)由添加纳米S iO2粉末的丙烯酸(AA)和丙烯腈(AN)通过溶液共聚制得,两侧为交联聚乙烯醇(PVA)。考察了复合膜在高质量分数甲醇水溶液中的溶胀性能,探讨了浸泡液温度及浸泡液质量分数对溶胀度的影响,测试了复合膜的力学性能。考察了不同单体配比〔n(AA)∶n(AN)〕所制备的复合膜在不同质量分数甲醇水溶液,不同温度下的渗透汽化性能。结果显示,复合膜在高质量分数甲醇水溶液中具有良好的溶胀性能及渗透汽化性能;在n(AA)∶n(AN)=1∶1下所制备的复合膜,对高质量分数甲醇水溶液分离效果最佳,60℃时分离w(甲醇)=98%的水溶液,分离因子可达1 534,通量为583 g/(m2.h)。     

丝光沸石/氧化铝陶瓷膜的合成及渗透分离性能的研究

以硅溶胶和铝酸钠分别为硅源和铝源,用水热合成法在多孔氧化铝陶瓷管载体上合成出丝光沸石膜.用扫描电镜、X射线衍射和核磁共振等手段对所制得的沸石膜进行了表征,证明其交联良好、覆盖完全、附着强度高.并且研究了丝光沸石膜在醇/水混合体系中的分离性能,实验结果表明,丝光沸石膜能选择性地透过水,其水/甲醇、水/乙醇、水/正丙醇和水/异丙醇的分离系数最高可分别达到2700（Xw=50%）,3900（Xw=50%）,4100（Xw=15%）和4300（Xw=50%）。     

A Review of Membrane Materials for Ethanol Recovery by Pervaporation

Due to an emerging scarcity of oil resources and an associated increase of oil prices, biofuels (e.g., ethanol) play an important role in the energy crisis. Fermentation is a common process for producing ethanol from renewable biomass. Pervaporation is an attractive technique for the recovery of ethanol from the fermentation systems. Separation membrane is the key element in the pervaporation separation equipments. In this article, the pervaporation performances of ethanol-permselective membranes presented in the recovery of ethanol from dilute ethanol aqueous solution are reviewed. An analytical overview on the challenges and opportunities, and the prospect of ethanol-permselective membranes by pervaporation is also discussed.     

Pervaporation and Dialysis of Water-Ethanol Solutions Using Silicone Rubber Membranes

Abstract

Ethanol-water solutions may be concentrated by pervaporation through silicone rubber and regenerated cellulose film. Using silicone, separation factors (SF) decrease as the ethanol concentration in the feed solution increases (SF = 6.5 using 12.9 w/w% ethanol and 1.4 using 83.2% ethanol at 30°C). The temperature effect on separation factors is negligible, but is appreciable on permeation rates.

Ethanol permeation rates in the dialysis mode are not linear with ethanol chemical potentials in solution; silicone swelling coefficients also increase noticeably with alcohol concentration in aqueous solutions, indicating that preferential ethanol sorption occurs and is responsible for the separation.     

Effect of Deacetylation Degree in Chitosan Composite Membranes on Pervaporation Performance

ABSTRACT

The effect of the degree of deacetylation in chitosan composite membranes on their pervaporation performance for ethanol dehydration was investigated. The degree of deacetylation of chitosans was measured by using an infrared spectroscopic method and elemental analysis. The chitosan composite membranes were prepared by coating a chitosan solution onto a microporous polyethersulfone membrane with 3–7 nm pore sizes. Then the surface of the top layer (chitosan) of well-dried membranes was crosslinked with sulfuric acid, and pervaporation experiments for binary mixtures (water—ethanol) were carried out at various conditions. In the case of a chitosan membrane with a high degree of deacetylation, the flux increases while the separation factor decreases compared with membranes with a low degree of deacetylation.     

PDMS/PS复合膜的渗透蒸发性能的研究

制备了高性能的PDMS/PS复合膜,可将水溶液中苯的浓度由0.2～0.8×10-3kg·kg-1浓缩至70%～96%(质量分数),膜的渗透通量为0.10～0.4 kg·m-2·h-1,分离因子可达到20 000;通过渗透蒸发实验,考察了料液浓度、料液流速、料液温度和膜下游压力等操作条件对PDMS/PS复合膜渗透蒸发性能的影响;考察了活性层厚度和基膜结构分别对活性层传质阻力、基膜传质阻力的影响.并确定总传质阻力与活性层厚度的关系式和基膜传质阻力的经验公式.在此基础上得到了渗透蒸发的传质模型,计算结果与实验结果符合良好.