Separation of hydrogen from methane by asymmetric PEI membranes

Hydrogen is anticipated to play an inevitable role as one of the promising sources of energy in the future. Recovery of hydrogen from flare gases is an economical and environmental policy of Marun Petrochemical Company. The asymmetric polyetherimide (PEI) membrane was synthesized and sorption and permeation of CH4 and H2 were studied. The influence of pressure and temperature as operating variables were investigated. Results showed that permeance was enhanced by temperature. The pressure increase caused a decline in H2 permeance, whereas CH4 permeance increased due to the Flory–Huggins sorption mechanism and ideal H2/CH4 selectivity reduction. The effect of different non-solvents as coagulants of the phase inversion technique in membrane morphology and behavior were explained by precipitation time. Water as a non-solvent makes membrane structures denser than others, while isopropanol leads to a porous sponge-like morphology. Lower coagulation bath temperature makes the membrane denser. Finally, a selectivity of 27.8 was achieved for the separation of H2 from CH4.