【作者】 郭瑞丽；

【导师】 姜忠义；

【作者基本信息】 天津大学 ， 制药工程， 2007， 博士

【摘要】 渗透蒸发以其绿色、高效、节能的突出特点在乙二醇脱水中具有良好的应用前景,渗透蒸发技术的核心是高性能渗透蒸发膜的研制。本论文以聚乙烯醇(PVA)为主体膜材料,制备了PVA-氧化硅(SiO2)高分子-无机杂化膜、表面交联改性PVA膜和以聚砜或聚醚砜为基膜,交联PVA为活性层的复合膜。针对乙二醇-水-膜之间的氢键作用,考察了乙二醇和水之间的耦合效应对PVA膜溶胀吸附性能和渗透蒸发性能的影响。针对乙二醇物性,系统考察了进料温度、进料流速等工艺条件的改变对渗透蒸发分离性能的影响。以PVA高分子为主体材料,基于硅烷结构不同导致水解-缩聚速率差异的特性,以有机取代基具有网络形成作用的GPTMS原位生成改性TEOS水解缩聚产物,制备PVA-SiO2杂化膜。基于酸碱催化硅烷水解-缩聚产物结构的差异,以有机取代基具有网络修饰作用的MPTMS原位生成带有巯基的PVA-SiO2杂化膜。系统研究了有机硅氧烷含量和催化剂的改变,对杂化膜结构形态及物理化学性质的影响,以及对渗透蒸发分离性能的影响。考虑到乙二醇和水对PVA膜均有较强的塑化作用,首次采用表面交联法改性PVA膜分离乙二醇/水体系。该改性法将反应限制在膜表面,在膜表面形成均匀的交联层,有效地抑制了膜的溶胀,提高了膜的稳定性。所制备的表面交联改性PVA膜对乙二醇/水(80wt% EG)混合物的渗透通量和分离因子分别为211 gm -2h-1和934。通过溶胀平衡实验及渗透传质结果分析,乙二醇和水之间的耦合效应阻止了乙二醇在膜内的吸附和扩散,且这种影响随着原料液中水含量的增加而增加。乙二醇具有极低的饱和蒸汽压,因此进料温度对乙二醇的渗透影响较大。采用界面反应吸附的方法制备了表面交联PVA/PES(PS)复合膜。结果表明,支撑层经界面反应交联剂硼砂处理后,与PVA界面作用力明显增强,从而快速形成超薄、均质的活性分离层。当硼砂浓度为0.1wt%,铸膜液中PVA含量为2wt%,浸涂两次可制得活性分离层厚度为1-1.5μm的表面交联PVA/PES复合膜,其对乙二醇/水(80wt% EG)混合物的渗透通量和分离因子分别为427gm -2h-1和438。通过60h工艺条件的考察,PVA/PES(PS)复合膜的渗透蒸发分离性能没有改变,显示出较好的稳定性。更多还原

【Abstract】 Pervaporation process will find promising applications in dehydration of ethylene glycol (EG), due to its inherent green, efficient and energy-saving characteristics. The core of pervaporation process is the development of appropriate membrane material. In this dissertation, Poly(vinyl alcohol) (PVA) was selected as main membrane material. PVA-SiO2 hybrid membranes, surface crosslinked PVA membranes and surface crosslinked PVA/PES (or PS) composite membranes were prepared. The coupling effect was investigated in consideration of the hydrogen-bonding interaction among ethylene glycol, water and PVA membrane. In addition, the optimization of process conditions was carried out systematically.PVA-SiO2 hybrid membranes were prepared by sol-gel process using PVA as the host material, tetraethoxysilane (TEOS) andγ-glycidyloxypropyltrimethoxysilane (GPTMS) as mixed silica precursors based on the different hydrolysis-condensation rate of siloxane with different structures. The organic functional group of GPTMS has the function of network former, which can in situ modify the product of TEOS. Mercapto PVA-SiO2 hybrid membranes were prepared by in situ sol-gel reaction ofγ-mercaptopropyltrimethoxysilane (MPTMS) with organic functional group as network modifier and PVA based on the different hydrolysis-condensation structure of alkoxyorganosilane under acidic or basic conditions. The effects of alkoxyorganosilane content and preparation conditions on the structure, physical and chemical properties of hybrid membranes, as well as pervaporation performance were systemically investigated.Considering the strong plasticizing effect of water and EG on PVA membrane, dehydration of EG aqueous solution by pervaporation was studied by surface crosslinked PVA membrane for the first time, the homogeneous and stable crosslinking structure surpressed the swelling of PVA membrane and showed desirable stability. The surface crosslinked PVA membrane exhibited good separation performance with a separation factor of 934 and a permeation flux of 211 gm-2h-1 for 80wt% EG in feed at 70℃. The results of swelling, sorption measurments and the permeation and diffusion data indicated that there exists strong coupling effect between water and EG, which inhibited the sorption and diffusion of EG within membrane. The feed temperature is dominant factor of EG permeation because of the low saturated vapor pressure of EG.Interfacial reaction technique has been employed to fabricate PVA/PES (or PS) thin film composite membrane. The results indicated that dispersion of the interfacial crosslinking agent borax in the support layer intensified the interface interaction between the PVA layer and PES (PS) support layer. A homogeneous, defect-free thin film of PVA on the support layer produced due to a strong interaction between the thin PVA layer and the support layer. The PES support layer was treated with 0.1wt% borax aqueous solution, and then the dried support layer was immersed into 2wt% PVA aqueous solution. The PVA separating layer with an approximate thinkness of 1-1.5μm was formed through two time’s dip-coating process. The permeation flux and separation factor is 427 gm-2h-1 and 438 for 80wt% EG in feed at 70℃, respectively. The surface crosslinked PVA/PES (or PS) composite membrane showed desirable stablily and separation performance for EG/water mixture during the investigation of process conditions for 60h. The structural stability of the composite membrane is satisfactory.更多还原