Comparative study of CuO/Ce 0.7Sn 0.3O 2, CuO/CeO 2 and CuO/SnO 2 catalysts for low-temperature CO oxidation

Abstract

CuO/Ce 0.7Sn 0.3O 2, CuO/CeO 2 and CuO/SnO 2 catalysts were prepared using impregnation methods. The catalysts were characterized by means of H 2-TPR, X-ray diffraction (XRD) and CO-TPD studies. CuO/Ce 0.7Sn 0.3O 2 catalysts have three reduction peaks, α, β, and γ. The α peak is attributed to the reduction of CuO and Sn 4+ species on the surface of Ce 0.7Sn 0.3O 2, β peak to the reduction of bulk SnO 2 and surface Ce 4+, γ peak to the reduction of bulk CeO 2. Only a small amount of CuO (6%) is needed to form the active site for CO oxidation, and the excess CuO forms bulk CuO particles which contribute little to the activity. Combining the results of CO-TPD, XRD and catalytic activity measurements, we propose that the well-dispersed CuO, which can adsorb CO, is responsible for low-temperature CO oxidation. The bulk CuO that cannot adsorb CO contributes little to the oxidation activity. Among the supported CuO catalysts, a synergistic interaction between CuO and Ce 0.7Sn 0.3O 2 makes the reduced CuO/Ce 0.7Sn 0.3O 2 catalyst easily oxidized, thus it can easily supply active species. This is responsible for the highest CO oxidation activity at low-temperature.