Composite ionic liquid–polymer–catalyst membranes for reactive separation of hydrogen from carbon monoxide

Abstract Novel composite ionic liquid and polyimide membranes with dissolved RuCl 3 catalyst for H 2 /CO reactive separation were fabricated to combine gas diffusive separation and water-gas shift reaction. The CO concentration in the membranes is reduced via its reaction with H 2 O to form CO 2 and H 2 , catalysed by the Ru carbonyl complex which forms in the reaction between dissolved RuCl 3 and CO. In order to optimize the membrane configurations and operating conditions, water-gas shift reaction turnover frequencies (TOFs) of the membranes with various concentrations of ionic liquid and RuCl 3 were determined at different pressures, temperatures and times-on-stream on a purpose-built test rig. The results show that the ionic liquid, [C 4 mim][OTf], improves TOFs by increasing the solubilities of H 2 O and the gases solubilities within the membrane. TOFs were found to increase initially, but reduce as time-on-stream increased, due to the formation and subsequent evaporation of a Ru carbonyl complex. Lower temperature and lower concentration of [C 4 mim][OTf] were found to minimize the loss of the catalyst. It is suggested that the 2 wt% RuCl 3 · x H 2 O+20 wt% [C 4 mim][OTf]+PI membrane operated at 140 °C and 2 bar has the best combination of reactivity and durability.