Development of high-performance membranes for CO_2

以聚醚二胺和共聚二胺为原料，以酸酐为原料制备了聚醚阻段共聚物。它们具有由橡胶状聚醚段和玻璃状聚酰亚胺段组成的微相分离结构。气体通过聚醚段微畴和聚酰亚胺段微畴渗透，有助于提高材料的力学性能和成膜能力。聚氧乙烯（PEO）基共聚物具有很好的CO_2/N_2分离性能，对CO_2的渗透系数P_<CO2>=1.4 × 10^<-8> cm^3(STP)cm^2/(cm scmHg)， CO_2/N_2的渗透比P_<CO2>/P_<N2>=70。采用双层注射喷嘴制备了由peo基聚酰亚胺表层和bpda基聚酰亚胺支撑海绵层组成的复合中空纤维膜。中空纤维外径为300 μ m，表层厚度为2μ m。实验室规模的中空纤维膜模块显示出良好的CO_2/N_2分离性能，对CO2的渗透率，R_<CO2>=2.9 × 10^<-5> cm^3(STP)/(cm2 s cmHg)和渗透比，在323K下，RCO_2/RN_2=42。采用溴化法制备高透性、低过电选择性的BPDA-TrMPD聚酰亚胺，并与脂肪胺反应。所制得的化学改性聚酰亚胺在308K温度下，干燥CO_2/N_2混合物的P_<CO2>=1 × 10^<-8> cm^3 (STP) cm^2/(cm s cmHg)和分离因子α =35，湿CO_2/N_2混合物的P_<CO2>=0.7 × 10^<-8> cm^3 (STP) cm^2/(cm s cmHg)和分离因子α =50-60。化学改性聚酰亚胺的非对称中空纤维膜有望在湿CO_2/N_2混合物中表现出非常优异的性能。

Poly(ether impede)segmented copolymers were prepared from polyether diamine and comonomer diamine with acid anhydride. They have microphase-separated structure consisting of microdomaims of rubbery polyether segments and of glassy polyimide segments. The gas permeation occurs through polyether segment microdomains and polyimide segment microdomains contributes to mechanical properties and film-forming ability. The polyethlene oxide(PEO)-based copolymers displayd very high performance for CO_2/N_2 separation, permeability coefficient to CO_2, P_<CO2>=1.4x10^<-8> cm^3(STP)cm^2/(cm scmHg) and permeability ratio of CO_2 over N_2, P_<CO2>/P_<N2>=70 at 298K.Composite hollow fiber membranes, which were composed of surface layr of PEO-based polyimide and supporting sponge layr of BPDA-based polyimide, were prepared by using a double-layred injection nozzle. The outer diameter of the hollow fibers was 300 mum and the thickness of the surface layr was 2mum. Laboratory-scale modules of the hollow fiber membranes displayd high performance for CO_2/N_2 separation, permeation rate to CO2, R_<CO2>=2.9x10^<-5> cm^3(STP)/(cm2 s cmHg) and permeation ratio, RCO_2/RN_2=42 at 323K.BPDA-TrMPD polyimide with high permeability and low permselectivity was brominated and then reacted with aliphatic amine. The chemically modified polyimides thus prepared displayd, P_<CO2>=1x10^<-8> cm^3 (STP) cm^2/(cm s cmHg) and separation factor alpha=35for dry CO_2/N_2 mixtures, and P_<CO2>=0.7x10^<-8> cm^3 (STP) cm^2/(cm s cmHg) and separation factor alpha=50-60 for wet CO_2/N_2 mixtures at 308K.Assymmetric hollow fiber membranes of the chemically modified polyimide are expected to display very excellent performace for wet CO_2/N_2 mixtures.