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 demo nstrated that only cobalt acts as a promoter, with maximum effect at t he same weight loading as Au, while the other additives have either no effect or severely suppress the Au/TiO2 system. Pretreatment conditio ns play a critical role in establishing highest activity for the react ion. Comparative studies of the catalytic activity of Au/TiO2 and Co-p romoted 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. Kineti c analysis of the reactions of CO with O-2 and N2O indicate a slight p ositive order in each reactant in both cases. Measurements of CO and C O2 adsorption under transient pulse conditions has shown that CO uptak e occurs primarily on the support and is strongly dependent on the con ditions of pretreatment. The uptake on samples reduced at 773 K is sub stantially lower than that observed after subsequent re-oxidation at t he same temperature. CO2 uptakes are substantially greater and subject to the same effect but to a lesser extent.