具有催化与渗透汽化双功能的纳米TiO2和Al2O3填充复合膜性能

采用聚丙烯腈(PAN)中空纤维超滤膜作为支撑底膜,经戊二醛(GA)表面交联的聚乙烯醇(PVA)作为渗透汽化层,以及纳米TiO2或Al2O3填充的全氟磺酸树脂(PFSA)作为催化层,制备了催化与渗透汽化双功能复合膜,考察了其亲水性能、对乙酸乙酯塔顶粗酯的渗透汽化分离性能、催化酯化反应性能以及机械性能.实验结果表明:催化与渗透汽化双功能复合膜具有良好的亲水性和机械性能,渗透通量可达到179g/(m2.h),相对应的分离系数为95,渗透物中不含乙酸乙酯,同时可显著缩短酯化反应达到相同转化率的时间.     

高通量ZSM-5填充硅橡胶复合膜渗透汽化性能研究

以硅铝比为360的ZSM-5型沸石对聚二甲基硅氧烷(PDMS)进行填充,以聚偏氟乙烯(PVSF)为支撑层,制备了ZSM-5填充PDMS/PVDF复合膜,用于渗透汽化乙醇/水混合物的分离.研究了沸石填充量、操作温度、进料液浓度对乙醇/水的渗透汽化分离性能的影响,发现该复合膜较文献报道中的沸石填充膜,其渗透通量有了明显的提高,在50℃沸石填充量为40%时,对乙醇的分离因子为11.7,其渗透通量达到749.8 g/(m2·h).随着操作温度的升高或料液中乙醇浓度升高,渗透通量增大,分离因子下降.     

四通道中空纤维NaA分子筛内膜的制备与表征

采用错流真空抽吸涂晶与动态水热合成的方法在四通道陶瓷中空纤维载体的内表面制备出高性能的NaA分子筛膜, 并用于75℃下90wt%乙醇/水混合物渗透汽化脱水分离, 系统考察了晶种液流速、涂晶时间与合成温度对NaA分子筛膜形貌与分离性能的影响。结果表明, 当晶种液流速为100 mL/h、涂晶时间为5 s时制备的NaA分子筛膜致密均匀; 晶种液流速过慢或者涂晶时间过长会导致膜厚增加同时也会在膜表面产生缺陷。当膜在100℃下水热合成两次, 制备的NaA分子筛膜分离性能最佳, 此时膜的分离因子为1585, 通量高达8.8 kg/(m²•h)。当合成温度过低时, 膜的晶化程度较低, 膜表面出现缺陷; 当合成温度过高时, 膜晶体生长速率过快, 交互生长程度较差, 膜的断面产生缺陷, 导致膜分离性能较低。     

One-step dynamic assembly of polyelectrolyte complex membranes

During the past decades, layer-by-layer (LbL) assembly technique based on electrostatic adsorption of oppositely charged polyelectrolytes (PEs) has been one of the most frequently utilized processes for assembling ultra-thin film. However, LbL process is also recognized as a time-consuming process, especially for assembly of dense membranes. In this paper, a one-step dynamic assembly based on electrostatic adsorption was developed to prepare the PE complex membranes. The chitosan (CS), used as a model polycation, was dynamically deposited on a hydrolyzed polyacrylonitrile (PAN) support membrane with negative charges under a selected pressure to form a PE complex membrane for pervaporation separation of water–ethanol mixture. Compared with traditional dip-coating method, this new assembly process could offer some advantages such as the formation of selective layer with dilute solution, easily used for different membrane module types and suitable for large scale applications. The assembly conditions such as dynamic pressure, CS molecular weight, and CS concentration were investigated. The appropriate conditions for assembly were: dynamic pressure, 0.2 MPa; CS molecular weight, 82,000; and CS concentration, 0.5 wt.%. In the case of pervaporation of 95 wt.% ethanol/water mixtures, the separation factor and the permeate flux of the CS polyelectrolyte complex membranes were 422 and 230 g/(m² h) (60 °C), respectively. The cross-linking treatment with glutaraldehyde and sulfuric acid were subsequently performed. It was found that the separation performance was improved by the cross-linking treatment. Finally, inner skin hollow fiber PE complex membranes were also successfully explored using one-step dynamic assembly for pervaporation dehydration. The proposed process will offer a new approach to obtain a relatively integrated PE complex membrane.     

壳聚糖-三聚磷酸钠聚离子复合膜的研究

以红外光谱表征壳聚糖-三聚磷酸钠聚离子复合膜的结构。研究了膜组成、料液浓度、温度等对乙醇-水溶液的渗透汽化分离性能的影响。实验结果表明,该复合膜对乙醇-水溶液具有很高的渗透汽化脱水的选择分离性能和渗透通量。同时对渗透汽化机理及影响因素进行了初步探讨。     

新型聚酰亚胺渗透汽化膜

合成了三种新型聚酰亚胺,并制成渗透汽化膜用以分离乙醇-水、异丙醇-水混合物。结果表明,三种聚酰亚胺均具有较高的分离系数,在分子主链中含有—Si—(CH_3)_2—链节的聚酰亚胺膜,其透过速率高于、分离系数低于其它两种聚酰亚胺,并从聚合物分子结构的观点讨论了其原因。     

Transport Properties of Fullerene–Polyphenylene Oxide Homogeneous Membranes

Abstract

Fullerene–polyphenylene oxide (C₆₀–PPO) compositions containing up to 2 wt% C₆₀ were obtained and used for homogeneous membranes formation. Gas separation properties were estimated by measuring the permeability of individual gases H₂, O₂, N₂, CH₄, and CO₂. A correlation between gas permeability and free volume was established. The pervaporation of water/ethanol mixtures through fullerene‐containing membranes showed that C₆₀–PPO membranes exhibit dehydration properties. The degree of equilibrium sorption for PPO and C₆₀–PPO membranes in a water/ethanol system was estimated in the liquid phase. Gas separation and pervaporation properties were treated as a reflection of molecular interactions between PPO and C₆₀ molecules in compositions.     

聚乙烯醇/聚乙烯吡咯烷酮共混膜的制备和性能

制备了聚乙烯醇(PVA)、PVA/聚乙烯吡咯烷酮(PVP)与戊二醛交联的PVA/PVP膜用于渗透蒸发对乙酸乙酯/乙醇/水三元共沸体系脱水。采用傅立叶变换红外光谱(FT-IR),X射线散射(XRD)和扫描电镜(SEM)等对膜的物理化学结构及形貌进行了表征。考察了PVP含量、交联度对共混膜结构和亲水性的影响。考察了PVP含量、交联度和温度对PVA均质膜的分离性能和溶胀行为的影响。结果表明,交联的PVA/PVP共混膜对乙酸乙酯/乙醇/水有着优异的分离性能。     

Plasma-treated polyethersulfone coated with crosslinked poly(vinyl alcohol): composite membranes for pervaporation dehydration of ethanol

Composite membranes with crosslinked poly(vinyl alcohol) matrix as selective layer coated on a polyethersulfone supporting porous layer were prepared aiming at separating ethanol/water mixtures by pervaporation. A polyethersulfone asymmetric microporous membrane was synthesized by the wet phase inversion process. The support membrane was then exposed to air plasma to activate the surface. The selective dense layer was obtained by coating of PVA and a crosslinking agent over the polyethersulfone substrate, followed by thermal treatment. The morphology was examined by scanning electron microscopy (SEM) for both, support membrane and the coated polymeric layers. Surface physicochemical properties were evaluated through measuring the contact angle (θ) and the estimation of surface free energy (γ_S) and adhesion work. The surface chemical composition of support membrane and coated hydrophilic layers were characterized by infrared spectra with horizontal attenuated total reflectance (FT-IR/HATR). The swelling degree of PVA dense membranes, and the pervaporation performance of the crosslinked PVA/PES composite membranes, manufactured with several coating steps, were evaluated with water/ethanol (20/80 wt%) mixtures at temperatures in the range of 30–60 C. Results of the effective pervaporation dehydration of ethanol are discussed in terms of membrane morphology and the solution-diffusion transport mechanism.     

聚丙烯酸盐与聚乙烯醇共混膜醇水混合物分离性能研究

将自制的丙烯酸、甲基丙烯酸Ｎ,Ｎ－二甲基氨基乙酯共聚物与聚乙烯醇（ＰＶＡ）共混蛊渗透汽化膜,研究了膜对混合液的吸收溶解性能和分离性能,发现共混膜优先透水,与ＰＶＡ膜相比,选择性有所下降而透过速率得到很大提高,尤其是分离９５％的乙醇水溶液仍有较大的渗透通量。选择合适的共聚单体比例及聚盐含量能得到性能较好的共混膜。当共聚单体比例为２、聚盐含量为１６．３％时,共混分离９５％乙醇水溶液分离系数约为９００,     

陶瓷中空纤维内表面动态水热合成NaA分子筛膜及其表征

采用动态水热法在氧化铝陶瓷中空纤维内表面原位合成了NaA分子筛膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)表征了分子筛膜的物相及微观形貌,通过渗透汽化测试考察了膜的乙醇/水分离性能,研究了合成工艺参数对成膜过程及膜质量的影响。结果表明,动态下合成的分子筛膜,晶体交联紧致,膜层薄且连续性好,厚度约4μm;提高动态速度有利于降低载体内外合成液的温差和浓度差,缩短晶化时间。在温度343K下,分离质量分数90%的乙醇/水体系,膜的渗透通量和分离因子可达1.03kg/(m2·h)和3 781,对乙醇/水表现出良好的分离效果和可重复性。     

藻朊酸盐膜对水／有机物混合液的PV分离

研究了藻朊酸、藻朊酸钠及二价金属离子交联的藻朊酸钠对水／乙醇体系的渗透汽化性能，同时，还研究了藻朊酸盐膜对水／甲醇、水／异丙醇、水／丙三醇、水／丙酮体系的分离性能，表明，藻朊酸盐膜上述几种体系均具有良好的分离性能。     

微孔二氧化硅分子筛膜的制备与应用

通过溶胶-凝胶热涂法制备高通量的微孔二氧化硅分子筛膜,并将其应用于渗透蒸发乙酸脱水,评价二氧化硅分子筛膜的分离性能;利用粒度分析仪和SEM对溶胶和膜层进行表征.结果表明,溶胶中二氧化硅颗粒的直径为10～80nm,无定形微孔二氧化硅分子筛膜对该体系显示了优异的分离性能,在353K时渗透蒸发分离水质量分数为5%的乙酸水溶液时,通量为0.65kg/(m2.h),分离系数达到120,经过35h的渗透蒸发实验后分离系数增高到160左右,通量基本不变为0.60kg/(m2.h).     

Separation of IPA/water mixtures by pervaporation: sorption and pervaporation results

Homogeneous membranes were prepared by blending polyvinyl alcohol (PVA) with polyacrylic acid (PAA) and furthermore the blend membrane is cross-linked covalently through an ester linkage formation between a hydroxyl group of PVA and carboxyl group of PAA. These membranes were evaluated for separation of azeotropic isopropyl alcohol (IPA)/water mixtures by pervaporation, that is, a vacuum applying membrane process. The overall and preferential sorption of IPA/water mixtures in cross-linked membranes were determined to investigate the influence of PVA/PAA ratio and of liquid mixture composition. Pervaporation characteristics were also determined as a function of PVA/PAA ratio and of the feed mixture composition. With increasing PAA content in the membranes, solubilities and fluxes decreased and selectivities increased. Because of polarity, water permeated preferentially through the membranes. Sorption results showed the same tendency as pervaporation results.     

支撑层对PDMS复合膜渗透汽化性能的影响

以相转化法制备的聚偏氟乙烯(PVDF)、聚丙烯腈(PAN)、聚砜(PSF)三种多孔膜作为支撑层,制备聚二甲基硅氧烷(PDMS)复合膜用于渗透汽化乙醇/水混合物的分离。采用能量色散X射线光谱仪(EDX)定量表征了PDMS在支撑层表面的厚度(L0)和支撑层内的渗入深度(Li),研究发现,PDMS在各支撑层表面的厚度、支撑层内渗入的厚度有显著差异,PDMS复合膜的渗透通量与(L0+Li)间存在近似的线性关系,表明PDMS在支撑层中渗入深度不同是造成不同底膜支撑的PDMS复合膜渗透汽化性能差异的根本原因。文中提出选择层总厚度(Lt=L0+Li)概念,通过线性拟合得到PDMS复合膜渗透通量与Lt之间的定量关系,可以用来估算PDMS复合膜的渗透通量,并预测复合膜渗透通量极大值。     

Preparation of zeolite T membranes by microwave-assisted in situ nucleation and secondary growth

Zeolite T membranes were firstly prepared on the α-Al₂O₃ tubes by microwave-assisted in situ nucleation and secondary growth. The obtained membranes were characterized by XRD, SEM, single gas permeation, and pervaporation (PV). In the PV dehydration of ethanol and 2-propanol, the as-synthesized membranes displayed high separation performance. For the 90 wt.% alcohol/water mixtures at 338 K, the water flux reached 1.23 kg m^− 2 h^− 1 for the dehydration of ethanol and 1.52 kg m^− 2 h^− 1 for the dehydration of 2-propanol; both separation factors were higher than 10, 000.     

多元酸交联聚乙烯醇渗透汽化膜

研究了交联聚乙烯醇(PVA)渗透汽化膜。所用交联剂包括:马来酸酐、草酸、柠檬酸、偏苯三酸酐、邻苯二甲酸酐及1.6己二酸。渗透汽化的结果表明,交联剂的结构对渗透汽化膜的性能有很大的影响。当使用同样当量交联剂时,交联剂的官能度越大,当量越小,膜的分离系数越大而流量越小。交联剂分子中芳香基的存在导致流量增大,分离系数下降。交联膜的热分析结果进一步证实了交联剂结构对选择分离性能的影响。     

Synthesis and characterization of porous polyurethaneurea membranes for pervaporative separation of 4-nitrophenol from aqueous solution

Hydroxyterminated polybutadiene (HTPB) based porous polyurethaneurea (PUU) membranes were prepared. The porosity was developed by incorporation of lithium chloride into polymer matrix with subsequent leaching of the same in hot water. Scanning electron microscopic analysis of the prepared membrane surfaces was performed. The pervaporation performance of the synthesized membrane was studied with aqueous 4-nitrophenol solution as feed. The effects of various parameters on 4-nitrophenol separation factor and total as well as 4-nitrophenol flux were studied. Polyurethaneurea membrane was found to permeate 4-nitrophenol selectively with high separation factors for the organic component. Pore size and number of pores on the surface of the membrane were calculated from SEM image of the membranes. Effects of pore size and porosity on pervaporation flux were also investigated.     

Removal of water from aroma aqueous mixtures using pervaporation processes

In the field of food technology the main applications of pervaporation through hydrophilic membranes are the removal or extraction of water from aroma azeotropic aqueous mixtures. In this study, experiments for removal of water containing aroma compounds of ethanol, propanol, butanol, hexanol, ethyl acetate and acetic acid were performed through a composite, plate and frame type hydrophilic PVA (poly vinyl alcohol) membrane in a 0.5 m² plane module at constant feed temperature and permeate Vacuum pressure. The analysis is presented in terms of variations in permeation flux and separation factor. The results show the decrease in separation factor as well as permeation flux with the increase of alcohol in feed. Hexanol does not permeate through PVA membrane. Activity coefficient of water is higher than that of organic. Pervaporation selectivity differ from Liquid-vapor thermodynamic equilibrium.     

多元酸交联聚乙烯醇渗透汽化膜

研究了交联聚乙烯醇(PVA)渗透汽化膜。所用交联剂包括:马来酸酐、草酸、柠檬酸、偏苯三酸酐、邻苯二甲酸酐及1.6己二酸。渗透汽化的结果表明,交联剂的结构对渗透汽化膜的性能有很大的影响。当使用同样当量交联剂时,交联荆的官能度越大,当量越小,膜的分离系数越大而流量越小。交联剂分子中芳香基的存在导致流量增大,分离系数下降。交联膜的热分析结果进一步证实了交联荆结构对选择分离性能的影响。