Oxidation of carbon monoxide catalyzed by manganese-silver composite oxides

Abstract

The oxidation of carbon monoxide on Mn Ag composite oxides was carried out and their catalytic action was investigated. The composite oxides had much higher activities than either the Mn or the Ag single oxide catalysts. The Ag in the composite catalyst remained in the oxidized state in air even at calcination temperatures as high as 400 °C, as long as its content was less than 50 mol%, whereas it lost lattice oxygen in the absence of Mn at the same temperature. The TPD and TG analyses showed that the composite oxides had active lattice oxygen belonging to Ag which was easily liberated on heating in the absence of oxygen. It was found, however, that Ag still retained the oxidized states even after the desorption of its active lattice oxygen, but reduction of Mn occurred instead. These facts suggested that the active oxygen on Ag was mainly consumed in the oxidation of CO, and Mn served as an oxygen carrier; i.e., vapor phase oxygen was first incorporated into the composite catalyst through Mn and, then, was transferred to the reduced Ag. This concerted action of Mn and Ag in the composite catalyst provided high activity in the oxidation of CO.