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 degrees C in terms of reducing the CO content with maximal H-2 yield. The Cu0.15ZnFe2 spinel catalyst expressed a higher CO conversion level and H-2 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 degrees C with the Cu0.15ZnFe2 catalyst, and could be further increased to 0.86 at 350 degrees 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 O-2 when using the Cu0.30ZnFe2 catalyst at >260 degrees 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. (c) 2013 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.