Oxidation of carbon monoxide on LaMn1 –xCuxO3 perovskite-type mixed oxides

Abstract

Catalytic oxidation of carbon monoxide has been investigated over a series of LaMn_{1 –x}Cu_xO₃(x= 0–0.5) and La₂CuO₄ catalysts having perovskite-type and perovskite-related structures. LaMn_{1 –x}Cu_xO₃ catalysts were prepared by a freeze-drying method and showed uniform compositions. The oxidation states of Cu and Mn of the perovskite catalysts as well as several other properties relating to the reactivity of oxygen, such as temperature-programmed desorption of oxygen and carbon monoxide, the reducibility of the catalysts and the adsorption of carbon monoxide and dioxide were measured. La_{1 –y}Sr_yMnO₃(y= 0.2–1.0) catalysts were also studied for comparison. A remarkable synergistic effect on the catalytic activities for the oxidation was found with Mn and Cu. The synergistic effect and the deactivation process were discussed based on the above properties. The effect was attributed to the combination of two functions, namely the activation of oxygen by Mn oxide and that of carbon monoxide by Cu ions, and the deactivation towards adsorption of carbon dioxide.