Selective oxidation of CO over supported Au catalysts

The selective oxidation of CO on Au/Al2O3 and Au/Mo-x/Al2O3 OM = Mg, Mn) in the presence of H-2 was studied. The addition of MgO and MnOx improves the CO oxidation activity and selectivity towards CO2. The beneficial effect o f MgO can be ascribed to stabilization of small Au particles, which are int rinsically more active in CO and H-2 oxidation. MnOx is thought to be able to supply the active O needed for CO oxidation. Au catalysts containing bot h MgO and MnOx are extremely active in CO oxidation. In the presence of H-2 selectivity towards CO2 higher than 0.90 was observed for Au/MgO/Al2O3 and Au/MnOx/MgO/Al2O3 at 100 degreesC and below The H-2 oxidation at low tempe rature was affected by adsorbed CO. At temperatures above 50 degreesC the t hermal desorption rate of CO was large enough for H-2 oxidation to commence , implying a decrease in selectivity. Besides H-2, water was also found to have a pronounced effect on the CO oxidation rate even at room temperature. The effect of water is ascribed to a beneficial role of surface OH groups in CO oxidation. (C) 2001 Academic Press.