Preparation, characterization and gas permeation properties of PDMS/PEI composite asymmetric membrane for effective separation of hydrogen from H2/CH4 mixed gas

In this work, PDMS/PEI membranes were synthesized and sorption and permeation of H2/CH4 mixture were studied. The influence of pressure, temperature and feed composition were investigated. It was shown that permeances increased and selectivity decreased with an increment in the feed temperature. Increasing feed pressure caused a decline in gas permeance and increased selectivity. Higher concentrations of hydrogen in the feed declined the selectivity. The effect of different non-solvents was explained by their effect on precipitation time and it was concluded that water made the membrane denser while isopropanol forms a sponge-like structure. Coagulation bath temperature made the membrane denser. Film casting and dip-coating techniques were used to prepare selective membranes. Obtained selectivity results introduced dip-coating as a better method than film casting. Sequential coating improved selectivity of the prepared membrane. Finally, sequential coating with different concentrations was applied and enhanced selectivity significantly from about 22 to more than 70.