Development of Polymer Ultrathin Membrane with High Green House Gas Permselectivity

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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.