Microcalorimetry, adsorption, and reaction studies of CO, O-2, and CO+O-2 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 fun ction 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/Fe2 O3 to CO + O-2 resulted in an O-2(ad)/CO(ad) ratio >1 as well as the reoxid ation of the support and the progressive restoration of its catalytic activ ity, The reaction routes involved in the oxidation of CO over polycrystalli ne gold were different from those over the Au/Fe2O3 catalyst, Thus, while t he simultaneous adsorption of the reactant molecules was responsible for th is reaction on Au metal, the redox mechanism involving the removal and subs equent replenishment of lattice oxygen played a role in both the Au/Fe2O3 a nd Fe2O3 catalysts, where the presence of gold promoted these steps. (C) 19 99 Academic Press.