CO2 and CH4 gas permeation study via zeolitic imidazolate framework (ZIF)-8 membrane

In the present work, the effects of CO2 feed composition (15%-90%), pressure difference (100 kPa-700 kPa) and temperature (303 K-343 K) on the separation of CO2 from CH4 via ZIF-8 membrane were investigated. The membrane was synthesized through a simple, feasible and reproducible solvent evaporation seeding method coupled with microwave-assisted secondary solvothermal growth. Subsequently, the membrane was characterized by using scanning electron microscopy. The results showed that, for single gas permeation, CO2 permeances remained constant while CH4 permeances increased slightly with the increasing pressure differences at temperature of 303 K. Besides, CO2 permeances decreased while CH4 permeances increased slightly with the increase in temperature at pressure difference of 100 kPa. For binary gas separation, maximum CO2/CH4 separation factor of 5.07 and CO2 permeance of 6.595 × 10−8 mol m−2 s−1 Pa−1 were obtained at CO2 feed composition of 15%, pressure difference of 100 kPa and temperature of 303 K. Besides, CO2 fluxes approached constant value with the increasing CO2 partial pressure differences at CO2 feed composition of 15%, which was mainly attributed to the competitive adsorption between CO2 and CH4. On the other hand, CH4 fluxes increased with increasing CH4 partial pressure differences even at higher CO2 composition in the feed, owing to its adsorption capacity and gas transport pathway via membrane intercrystalline pores.