WGS reaction in a membrane reactor using a porous stainless steel supported silica membrane

Water gas shift reaction for hydrogen production was studied in a catalytic membrane reactor using a supported silica membrane at 220-290 °C temperature and 2-6 bar pressure ranges. A CO conversion higher than the thermodynamic equilibrium of a traditional reactor was obtained. The best result, 95% CO conversion, was achieved at 4 bar and 280 °C. The membrane was also characterized in terms of permeance and selectivity by means of permeation tests carried out before and after reaction. In addition, permeance and separation factor were also measured during the reaction. Permeance of all species (H2: 9.7-29; CO: 0.3-1.1; CO2: 0.4-1.5 nmol/m2 s Pa), selectivity (H2/CO, H2/CO2 and H2/N2) ranging from 15 to 40 and separation factors (H2/CO = 20-45), showed no dependence on the related permeation driving force. Differences between selectivity and separation factor were registered. Furthermore, no inhibition effects of other gases on the hydrogen flux were observed. The membrane was prepared by the soaking roller procedure depositing a silica layer on a stainless steel support with an intermediate -alumina layer. The membrane reactor allowing selective hydrogen permeation presents a good performance exceeding also the equilibrium conversion of a traditional reactor.