Gas separation properties of commercially available polyphenylene oxide (PPO) and Cardo-type polyimide (PI) hollow fiber membranes were investigated by CO2/CH4 and O2/N2 separation experiments. The pure gas permeation and the mixed gas separation experiments indicated that the two hollow fiber membranes were suitable candidates for O2/N2 and CO2/CH4 separations. Average O2/N2 permselectivities of 3.9 and 5.7 for PPO and PI hollow fibers, respectively, average CO2/CH4 permselectivities of 16.4 and 36.0 for PPO and PI hollow fibers, respectively, CO2 permeances of 210 and 110 GPU at 100 psig for PPO and PI hollow fibers, and O2 permeances of 40 GPU and 15 GPU for PPO and PI hollow fibers were achieved. The CO2/CH4 mixture separation was carried out at three different CO2 concentrations and three stage-cuts at 100 psig pressure. Separation factors of up to 21.1 and 7.5 for PI and PPO membranes, respectively, and permeances of up to 83 GPU and 140 GPU for PI and PPO, respectively were obtained. Furthermore, it was found that CO2 permeance varied proportional to the ratio of stage-cut to feed concentration and it was observed that when the stage cuts were set equal to the concentrations of CO2 in the feed (vol.%), the obtained separation factors were approximately equal.

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