Development of Polymer Ultrathin Membrane with High Green House Gas Permselectivity

由于化石燃料的大量消耗，二氧化碳排放到大气中已成为一个重大的全球环境问题。该项目旨在开发一种技术，通过聚合物膜过程从固定来源(如燃煤和发电厂)中连续回收高浓度二氧化碳。本研究的目的是制备一种具有超薄和无缺陷表层的不对称聚酰亚胺薄膜。通过控制蒸发时间，可以控制非对称膜的皮层厚度。在CO_2浓度为1.5×10~(-3)[cm~3(STP)/(cm~2秒厘米汞)]的条件下，表面层厚度为10 nm的膜对(CO_2/N_2)的选择性为23，不需要额外的镀膜过程。结果表明，超分子筛的气体选择性大于稠油分子筛。不对称膜具有较高的选择性，这是由于其表层结构较紧密所致。还制备了一种新型的不对称氟化聚酰亚胺中空纤维。将干/湿相反相法应用于纺丝工艺，制备了不对称聚酰亚胺中空纤维。中空纤维的外表面由一层超薄的皮肤组成。这意味着不对称聚酰亚胺中空纤维是一种很有前途的气体分离材料。

The discharge of CO2 into the atmosphere due to the consumption of fossil fuels in large amounts has become a major global environment problem. This project aims at developing a technology to continuously recover high-concentrations of CO2 from stationary sources, such as coal combustion and power plants by the polymer membrane process. The aim of this study is to prepare an asymmetric polyimide membrane with an ultrathin and defect-free skin layr.Asymmetric polyimide membranes have been made by a dry/wet phase inversion technique. By controlling the evaporation time it was possible to control the thickness of the skin layr of the asymmetric membrane. The selectivity for (CO2/N2) of the membrane with a skin layr of 10 nm was 23 for a CO2 of 1.5 x 10-3 [cm3(STP)/(cm2 sec cmHg)] without the necessity of an additional coating process. The gas selectivity of the mebmrane was larger than that of the dense one. The higher selectivity of the asymmetric membrane appears to be due to the more packed structure of the skin layr.A novel asymmetric hollow fiber of fluorinated polyimide has also been fabricated. A dry/wet phase in-version process has been applied to a spinning process to prepare an asymmetric polyimide hollow fiber. The outer surface of the hollow fiber consisted of an ultrathin skin layr. This means that the asymmetric polyimide hollow fiber is a promising gas separation material.