Water-gas shift reaction over Cu–Zn, Cu–Fe, and Cu–Zn–Fe composite-oxide catalysts prepared by urea-nitrate combustion

Water-gas shift reaction was investigated over Cu–Zn, Cu–Fe and Cu–Zn–Fe composite-oxide catalysts at atmospheric pressure from 200 to 375 °C in terms of reducing the CO content with maximal H2 yield. The Cu0.15ZnFe2 spinel catalyst expressed a higher CO conversion level and H2 yield at a lower temperature compared to the Cu0.15Zn and Cu0.15Fe catalysts. Adding H2O to the feed up to 30% (v/v), but not above, increased the CO reduction level, presumably by increasing the hydroxyl species to react with the adsorbed CO. Increasing the W/F ratio to 0.24 g s cm−3 increased the CO conversion level to 0.76 at 275 °C with the Cu0.15ZnFe2 catalyst, and could be further increased to 0.86 at 350 °C by increasing the Cu molar ratio to 0.30 (Cu0.30ZnFe2). Nevertheless, increasing the Cu molar content to 0.50 reduced the CO conversion level. No requirement for adding O2 when using the Cu0.30ZnFe2 catalyst at >260 °C was observed. Increasing the CO content in the reactant decreased its conversion level. The performance of the Cu0.30ZnFe2 catalyst was stable over a test period in a CO-rich condition. No undesired product was detected, suggesting a higher selectivity for hydrogen production with a low CO content.