Cobalt promotion of Au/TiO2 catalysts for the reaction of carbon monoxide with oxygen and nitrogen oxides

A range of 3d transition metal-promoted 2% Au/TiO₂ catalysts has been prepared and tested for low-temperature CO oxidation. It has been demonstrated that only cobalt acts as a promoter, with maximum effect at the same weight loading as Au, while the other additives have either no effect or severely suppress the Au/TiO₂ system. Pretreatment conditions play a critical role in establishing highest activity for the reaction. Comparative studies of the catalytic activity of Au/TiO₂ and Co-promoted Au/TiO₂ have been carried out for the reactions of CO with N₂O and NO, and cobalt acts as a promoter in these reactions also. Kinetic analysis of the reactions of CO with O₂ and N₂O indicate a slight positive order in each reactant in both cases. Measurements of CO and CO₂ adsorption under transient pulse conditions has shown that CO uptake occurs primarily on the support and is strongly dependent on the conditions of pretreatment. The uptake on samples reduced at 773 K is substantially lower than that observed after subsequent re-oxidation at the same temperature. CO₂ uptakes are substantially greater and subject to the same effect but to a lesser extent.