Asymmetric polybenzimidazole membranes with thin selective skin layer containing ZIF-8 for H2/CO2 separation at pre-combustion capture conditions

Abstract This work addresses an optimization in the fabrication of flat PBI membranes containing ZIF-8 nanoparticles for gas separation purposes. The PBI membranes were prepared in an asymmetric configuration on P84 ® supports, representing a new way of preparing flat PBI membranes. An optimization of the conditions for the PBI phase inversion preparation method, including the dope composition (in the 15–26 wt% range), has been carried out to obtain PBI membranes with a 1 µm selective skin layer. The asymmetric membranes showed an unprecedented gas separation capacity in pre-combustion CO 2 capture, much superior to that of dense membranes, under harsh operating conditions (250 °C and 6 bar feed), performing up to 20.3 GPU of H 2 and a H 2 /CO 2 selectivity of 35.6. Their much thinner selective layer made possible the increase in selectivity because of the saturation of the CO 2 flow at high pressures. The reduction in the amount of ZIF-8 for obtaining a membrane with the same filler loading (3.7 vs. 9.3 g/m 2 ) was also possible; the performance of this ZIF-8 containig membrane was 22.4 GPU of H 2 and a H 2 /CO 2 selectivity of 22.3. The activation energy of the membranes, as well as the flow resistances, were calculated, providing a resistance in series model to understand the flow inside the membrane.