The effects of minor components on the gas separation performance of membranes for carbon capture

Multi-component gas systems can have a significant influence on the separation performance of polymeric gas separation membranes for carbon capture. CO2 permeability in Matrimid 5218 membranes is reported here for a laboratory grade CO2/N2 gas mixture, as well as when H2S and CO are present at ppm concentrations. The competitive sorption effects of N2, H2S and CO reduce the permeability of CO2 in Matrimid compared to the pure gas system. Asymmetric flat sheet Matrimid 5218 membranes were also tested on industrial unshifted syngas, as part of the CO2CRC Mulgrave capture project. For this multi-gas application, minor components such as H2S, water and hydrocarbons, in addition to the significant quantities of CO, N2 and H2, all serve to reduce CO2 permeance. However, partly as a consequence of this competitive sorption, the membrane displays relatively good H2 permeance and selectivity, in the mixed gas environment. Such a membrane might be useful in reducing the gas volumes processed in a downstream solvent absorption step, or might be used in a membrane reactor as part of the water gas shift reaction.