CO Oxidation Over Manganese Oxide Catalysts: Effect of Calcination Temperatures

Abstract

MnO2 catalysts were prepared by precipitation method using potassium manganate and manganese acetate. The effect of calcination temperatures of MnO2 catalysts for CO oxidation has been studied and their physicochemical properties were stu- died by X-ray diffraction (XRD), N2 sorption, temperature programmed reduction of H2 (H2-TPR), and temperature programmed desorption of CO (CO-TPD) techniques. MnO2 calcined at 300 ℃ catalyst has a large surface area 181 m 2 /g having a narrow pore size distribution at 9 nm. The results of XRD and H2-TPR showed that the catalysts calcined at different temperatures showed mixed oxidation states of Mn such as Mn 4+ and Mn 3+ . CO-TPD showed that the quantity of CO2 desorbed was decreased with increasing the calcination temperatures. The catalytic activity over the catalyst calcined at 300℃ exhibited the highest conversion reaching to 100% at 200 ℃. H2O vapor showed an inhibiting effect on the efficiency of the catalyst because of co-adsorption with CO on the active sites of manganese oxide catalysts and the initial catalytic activity of CO oxidation could be regenerated by removing H2O vapor in the reactants.