Characterization and gas permeation properties of polyimide/ZSM-5 zeolite composite membranes containing ionic liquid

The current study investigates the preparation, characterization, and gas permeation properties of novel composite membranes containing polyimide (PI), ionic liquid (IL), and zeolite (ZSM-5), focusing on the effect of zeolite. The free-standing composite membranes were prepared using the solvent casting method. The SEM images show that the interfacial voids between PI and ZSM-5 decreased with increasing IL content. The addition of IL and ZSM-5 into the PI membrane improved the thermal stability of the composite membranes. The gas permeability of the composite membranes was determined at 35 °C. The gas permeability of the PI+ZSM-5 membrane was higher than that of PI, but the gas selectivity was significantly reduced, suggesting that these results can be attributed to the interface defects. The CO2 selectivity of the PI+ZSM-5+IL membranes was higher than that of the PI+ZSM-5 membranes because of the suppression of the interface defects brought about by the introduction of IL. Based on the gas permeation measurement under 10 atm for the PI+ZSM-5+IL (60 wt%) membrane, the change in IL amount before and after the measurement was not observed.