Mechanistic study of water-gas shift reaction over copper/zinc-oxide/alumina catalyst in a reformed gas atmosphere: Influence of hydrogen on reaction rate

Kinetic and pulse experiments were performed to elucidate the mechanism of the water-gas shift reaction (WGSR) under practical conditions. CO conversion was found to be significantly influenced by H2. The reaction was strongly suppressed at high H2 concentrations. A simple rate equation based on a competitive redox mechanism was derived. The H2O-induced oxidation of Cu0 to Cu+ was assumed to be the rate-determining step. H2 affected the CO conversion rate because it competitively reduced Cu+ to Cu0. In the proposed rate equation, the rate constant kf determines the rate of the catalytic cycle and the selectivity factor & kappa; may control the selectivity to CO conversion. CO-pulse experiments independently yielded the selectivity factor & kappa; (1.38), which was almost identical to that obtained from the kinetic analysis (1.39). The coincidence of these values strongly corroborates the proposed competitive redox mechanism.