Adsorptive and catalytic properties of supported metal oxides. III. Water-gas shift over supported iron and zinc oxides

Abstract

Supported iron oxide and zinc oxide samples were studied as water-gas shift catalysts at temperatures from 620 to 720 K. The supports studied were SiO2, Al2O3, TiO2, MgO, ZnO and Na-mordenite. The catalytic activity of all supported iron samples was significantly lower than that of magnetite (Fe3O4). It is suggested that whereas magnetite functions as a catalyst via an oxidation-reduction pathway, all supported iron and zinc oxide samples operate via an associative mechanism for the water-gas shift. The catalytic activities of the supported samples decreased as the acidity of the support or the electronegativity of the support cations increased. It is proposed that carbon monoxide does not readily adsorb or react with acidic catalysts, thereby leading to low water-gas shift activities. On basic oxides, the rate of water-gas shift is inhibited by the adsorption of carbon dioxide. © 1986.