多孔POSS/PDMS分子内杂化膜的制备及其渗透汽化优先透醇性能研究

The research background of this project is the separation and purification of ethanol with low concentration in ethanol biofuel production process. The object of the project is to investigate the design and preparation of porous Polyhedral Oligomeric Silsesquioxane/Polymdimethylsiloxane(POSS/PDMS) intermolecular hybrid membranes as well as their pervaporation performance for ethanol recovery. Based on the theoretical guidance of interfacial chemistry, materials and structural chemistry, a series of POSS/PDMS intermolecular hybrid membranes are designed and prepared via sol-gel method using alkoxylated POSS as both cross-linking agent of PDMS and precursor of porous POSS. PDMS three-dimensional network and porous POSS structure are built at the same time, while POSS and PDMS hybrid on the nanometer scale via covalent bonding, which fundamentally enhances the structure and separation performance stability of the hybrid membranes. The solution and diffusion characteristics of ethanol/water molecules in hybrid membranes, as well as macroscopic pervaporation performance are measured to explore the mass transfer disciplines of ethanol/water molecules in hybrid membranes. And finally a mass transfer mechanism model is to be established. The micro-structural properties of POSS/PDMS hybrid membranes are tuned by changing the membrane preparation conditions. The relationship between the microstructure-macroscopic separation properties of POSS/PDMS hybrid membranes is investigated quantitatively from multiple perspectives, which is used to guide the structural design of hybrid membrane materials and provide the necessary theoretical and experimental support for the industrial application of ethanol permselective membranes.

本项目以燃料乙醇生产过程中低浓度乙醇的分离提纯为研究背景，以多孔低聚倍半硅氧烷/聚二甲基硅氧烷(POSS/PDMS)分子内杂化膜的设计制备及其渗透汽化优先透醇性能为研究对象，以界面化学、材料和结构化学为理论指导，以烷氧基化POSS作为交联剂和多孔材料前体，采用溶胶-凝胶技术同时构建PDMS三维网络和POSS多孔结构，在纳米尺度上实现POSS与PDMS的分子级杂化，设计和制备一系列具有共价键合作用的POSS/PDMS分子内杂化膜，从根本上提高杂化膜结构和分离性能稳定性；通过测定乙醇/水小分子在杂化膜内的溶解、扩散特性及渗透汽化分离性能，探索小分子在杂化膜内的传质规律，建立小分子在杂化膜中的传质机理模型；通过改变膜制备条件调控杂化膜微观结构性质，从多个角度探讨杂化膜材料微观结构-宏观分离性能之间的定量关系，以指导杂化膜材料的结构设计，为渗透汽化优先透醇膜的工业应用提供必要的理论和实验支撑。

本项目以燃料乙醇生产过程中低浓度乙醇的分离提纯为研究背景，以多孔笼状低聚倍半硅氧烷/聚二甲基硅氧烷(POSS/PDMS)分子内杂化膜的设计制备及其渗透汽化优先透醇性能为研究对象，以界面化学、材料和结构化学为理论指导，借助表面修饰获得烷氧基化POSS作为交联剂和多孔材料前体，同时构建PDMS三维网络和POSS多孔结构，在纳米尺度上实现POSS与PDMS的分子级杂化，从根本上提高杂化膜结构和分离性能稳定性。以该思路为指导，设计和制备了15种具有共价键合作用的POSS/PDMS分子内杂化膜，为了做对比研究，制备了纯PDMS膜和10种POSS/PDMS物理填充膜；采用现代分析表征技术对膜材料及膜进行了微结构表征，包括化学结构确证、膜表面断面形貌、结晶结构等，测定了膜材料的热性能、拉伸性能、耐溶胀性，详细研究了各种制膜条件（包括POSS含量、PDMS粘度、膜液固含量等）和操作条件下（操作温度、料液浓度等）杂化膜和填充膜的渗透汽化分离性能，筛选具有优异分离性能的POSS/PDMS杂化膜，并探索POSS/PDMS杂化膜材料微观结构-宏观性能之间的关系；运用BET等温吸附仪测定了乙醇/水小分子在杂化膜和填充膜内的吸附溶解性，通过测定乙醇/水在膜内的溶解选择因子和扩散选择因子，研究小分子在杂化膜和填充膜内的溶解、扩散规律。项目成果可为有机/无机杂化膜的制备方法和结构改造开辟新途径，发现和制备了分离性能和结构稳定性更好的有机/无机杂化材料。通过在有机-无机相间建立强的化学键合作用，突破传统物理填充膜的缺陷，有效地发挥两者的协同效应，以PDMS和八-(三甲氧基硅基)乙基聚倍半硅氧烷(OPS)为原料，当OPS含量为7.5wt%时，OPS/PDMS杂化膜分离因子达到16.2，渗透通量为254.7g/m2h，分离因子和渗透通量较纯PDMS分别增长了107%和30%，分离性能呈现反trade-off现象；BET等温吸附实验表明OPS的加入可以显著提高PDMS对乙醇的优先吸附溶解，从而提高杂化膜的分离性能。本项目通过改变膜制备条件调控POSS/PDMS杂化膜的微观结构性质，并探索膜微观结构与宏观分离性能间的关系，以指导杂化膜材料的结构设计，为渗透汽化优先透醇膜的工业应用提供必要的理论和实验支撑。