Microcalorimetry, adsorption, and reaction studies of CO, O2, and CO+O2 over Fe2O3, Au/Fe2O3, and polycrystalline gold catalysts as a function of reduction treatment

Thermochemical and volumetric measurements were made for the adsorption and reaction of CO, O-2, and CO + O-2 on catalysts from 300 to 470 K, as a function of Hz pretreatment. The transformation of Au/Fe2O3 to Au/Fe3O4 led to inhibited adsorption and oxidation of CO. The exposure of a reduced Au/Fe2O3 to CO + O-2 resulted in an O-2(ad)/CO(ad) ratio >1 as well as the reoxidation of the support and the progressive restoration of its catalytic activity, The reaction routes involved in the oxidation of CO over polycrystalline gold were different from those over the Au/Fe2O3 catalyst, Thus, while the simultaneous adsorption of the reactant molecules was responsible for this reaction on Au metal, the redox mechanism involving the removal and subsequent replenishment of lattice oxygen played a role in both the Au/Fe2O3 and Fe2O3 catalysts, where the presence of gold promoted these steps. (C) 1999 Academic Press.