基于酰氯扩散速率控制的水溶性大分子界面聚合制备超薄复合膜研究

Carbon dioxide is an impurity that must be removed from mixtures with light gases such as CH4, N2 and H2, and the scale of these separations is enormous. Among these CO2 separation methods, membrane technology is extremely attractive for its energy efficiency, and simplicity and compact modular structure. Water soluble macromolecule is a kind of promising membrane material for CO2 gas separation due to its high CO2 permeability as well as high selectivity. However, the difficulty in ultra-thin membrane preparation has limited the permeation rate of membrane. Interfacial polymerization (IP) has been proved as an effective method to prepare ultra-thin composite membrane. In our previous work, a ultra-thin composite membrane was developed by IP from organic phase to aqueous phase, with amino groups terminated polyethylene oxide as pre-polymer of aqueous phase and trimesoylchloride(TMC)as monomer of organic phase. The membrane has a very high CO2 permeation rate as well as high CO2/N2 selectivity. In the IP process, the diffusion coefficient of TMC is much higher than that of water soluble macromolecule, which will lead to the hydrolysis of TMC. The hydrolysis of TMC will induce in the formation of defects, which will decrease the membrane selectivity..In this project a novel interfacial polymerization process with restricted carboxylic acidchloride diffusion is proposed to prepare defect free ultra-thin composite membrane. The permselectivity of membrane will be improved due to the elimination of carboxylic acidchloride hydrolysis reaction. Influence of several variables on the structure and permselectivity will be investigated..The TMC hydrolysis will be eliminated by introduction of hydrophobic polymeric film (such as PDMS layer) on the support membrane before IP process. The TMC will diffuse through polymeric layer，then it can react with the amine in aqueous phase. By adapting this method,the TMC diffusion is slowed down. And, the TMC diffusion rate can be adjusted by the thickness and cross-linking degree of the polymeric film. The effects of interfacial polymerization parameters on the membrane structure and performance will also be investigated..The water-soluble macromolecule containing both amino group (primary amine or secondary amine) and other functional group (such as ether oxide, carboxyl group and tertiary amine) will be synthesized by copolymerization and hydrolysis. .The structure of water-soluble macromolecule and multi-functional acid chloride will be investigated. The structure of membrane will be determined using SEM、XRD、XPS、EA and NMR technology. .The ultra-thin membrane formation mechanism will be developed based on the research above.

水溶性大分子膜材料具有高CO2渗透选择性的优点,但其超薄膜制备困难，膜渗透速率很小。界面聚合制备超薄复合膜是提高水溶性大分子膜渗透速率的有效方法。本项目针对界面聚合过程中存在酰氯扩散速度快而水溶性大分子扩散速率慢导致酰氯发生水解副反应问题，提出酰氯扩散速率控制是界面聚合的关键。在两相界面设置疏水聚合物薄膜，酰氯扩散通过疏水聚合物膜，然后与水溶性大分子发生界面聚合反应。通过调节聚合物薄膜厚度及交联度来控制酰氯扩散速率，进而抑制酰氯水解副反应、提高膜透过分离性能。合成同时含有活泼氨基和其他功能基团的水溶性大分子。优化酰氯和水溶性大分子的分子结构；优化界面聚合过程参数制备出同时具有高渗透速率和高选择性的超薄复合膜。进一步利用SEM、NMR、EA及FTIR等对膜表面及断面结构进行分析。研究将形成水溶性大分子膜材料界面聚合制备超薄膜的理论和方法，为制备高透过选择性的CO2分离膜提供理论支持。

随着大气温室效应日益加剧，基于膜分离的CO2分离与纯化技术引起了越来越多的关注。相对于传统的精馏、吸收、吸附等分离方法，膜分离技术具有能耗低、投资小、结构紧凑、易于放大的优点。如何设计、制备高透过选择性的分离膜是制约目前CO2膜分离技术发展的关键之一。.本研究利用聚醚胺（PEA）中醚氧键与CO2具有很好亲和性以及端氨基可以与酰氯发生界面聚合反应的特点，开发了界面聚合制备聚醚胺超薄复合膜的新方法。以氨基封端聚醚（聚醚胺）水相、均苯三甲酰氯（TMC）作为油相单体，在具有硅橡胶（PDMS）预涂层的聚砜基膜表面采用界面聚合法制备了具有硅橡胶过渡层的聚醚胺复合薄膜。研究了界面聚合过程中单体扩散速率对界面聚合反应及膜性能的影响，聚醚胺结构和分子量、界面聚合参数对所制膜结构和性能的影响，并在此基础上制备了中空纤维复合膜。采用FTIR、SEM等技术手段对膜结构进行表征，研究了所制膜CO2/N2以及CO2/CH4的透过分离性能。.研究发现，TMC的水解是造成无PDMS过渡层复合膜产生缺陷的主要原因；本研究提出在基膜上涂敷PDMS过渡层，在界面聚合过程中利用硅橡胶过渡层控制TMC的扩散速率，减少酰氯的水解副反应，从而制备出无缺陷、具有高透过选择性的复合膜。通过三种不同分子量PEA所制膜的性能研究，发现分子量较低时提高PEA分子量可以提高膜内的醚氧基含量，有利于提高的膜的选择透过性；但过高的分子量会引起PEA在界面聚合过程中扩散困难，进而导致膜产生缺陷，所制膜的选择性较差；分子量为900的PEA（ED-900）所制膜具有最优的综合性能。.通过界面聚合过程参数对所制膜结构和性能的研究，发现随着单体浓度、酸吸收剂浓度、界面聚合时间以及热处理温度的增加，所制膜的CO2渗透速率减小而选择性升高；在此基础上对界面聚合参数进行了优化，得到了最佳的界面聚合参数。.考察了PEA分子结构对所制膜性能的影响。研究发现带有侧甲基的ED系列PEA所制膜具有较高的CO2渗透速率，而没有侧甲基的EDR系列PEA所制膜虽然CO2渗透速率较低，但是其选择性较好。.在上述研究的基础上，通过在中空纤维的内表面预涂PDMS，然后进行PEA（ED-900）和TMC进行界面聚合，制备具有高装填密度的中空纤维超薄复合膜。发现所制中空纤维复合膜具有很高的CO2渗透速率（964 GPU）和较高的CO2/N2选择性( 40.7)。