The CO2/CH4 and O2/N2 separations by commercially available PPO and Cardo-type polyimide hollow fiber membranes were investigated. Based on pure N2, O2, CH4 and CO2 permeation experiments, it was concluded that these hollow fiber membranes are good candidates for O2/N2 and CO2/CH4 separations. Gas mixture transport was determined by three different concentrations of CO2 in CO2-CH4 gas mixtures (5%, 10% and 24.6% CO2-balance CH4) at room temperature and three different stage-cuts for each feed concentration. The feed side and permeate side pressures were 100 psig and atmospheric respectively. It was concluded that at stage-cuts proportional to feed CO2 concentrations (Vol.%), the obtained separation factors were approximately equal.

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