CO oxidation activity and TPR characterization of CeO2-supported manganese oxide catalysts

Cerium dioxide supported manganese oxide catalysts have been prepared and their catalytic activities for CO oxidation investigated. The catalysts have been characterized by using TPR and XRD. Only a small amount of Mn (10%) is needed to form active sites for CO oxidation, and the excess Mn oxide form bulk MnO2 particles which may cover a part of the active Mn oxide species resulting in the decrease of the catalytic activity. The catalytic activity also depends on the calcination temperature. The optimum calcination temperature is 600 degrees C. Two reduction peaks are observed in all Mn/CeO2(400 degrees C) catalyst The low-temperature peak is attributed to reduction of MnO2 or/and Mn2O3 to form Mn3O4; while the high-temperature peak is attributed to the reduction of Mn3O4 forming MnO. The MnO species on the reduced catalyst is more easily reoxidized to Mn3O4 than to MnO2. The average valence number of Mn atom in the catalyst decreases with increase in calcination temperature, and increases with Mn loading.