Effect of Calcination Temperature on the Properties of Mn–Zr–Ce Catalysts in the Oxidation of Carbon Monoxide

The effect of the calcination temperature of MnO х –ZrO 2 –CeO 2 catalysts on their structural properties and activity in the reaction of CO oxidation has been studied. Triple oxide systems with the cation ratio Mn : Zr : Ce = 0.3 : 0.35 : 0.35 prepared by coprecipitation have been investigated. According to the XRD, TPR-H 2 , and XPS data, an increase in the calcination temperature from 400 to 800°C caused a structural transformation of the Mn y Zr x Ce 1 – y O 2 – δ solid solution. At 400–600°C, manganese cations leaved the structure of solid solution in the form of highly dispersed MnO x particles; at 700–800°C, the initial solid solution Mn y Zr x Ce 1 – y O 2 – δ decomposed with the formation of two mixed oxides based on CeO 2 and ZrO 2 and a crystallized phase of Mn 3 O 4 . The highest catalytic activity in the CO oxidation reaction was exhibited by MnO x –ZrO 2 –CeO 2 catalysts calcined at 500–600°C; this was probably due to the presence of manganese both in the structure of the solid solution and in the form of highly dispersed MnO x particles on its surface.