Effect of the loading content of CuO on the activity and structure of CuO/Ce-Mn-O catalysts for CO oxidation

A urea-nitrate combustion method was used to prepare Ce-Mn-O material, which was applied as the support for a series of CuO/Ce-Mn-O catalysts. The structure of the catalysts was characterized with N-2 adsorption/desorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the catalysts for the oxidation of CO was evaluated on a conventional fixed-bed quartz reactor. XRD results showed that the synergetic effect between manganese and cerium led to a little higher electron density of Ce3+ in the mixed oxides. When the CuO content was lower than 5 wt.%, Cu species were well dispersed onto the Ce-Mn-O support or/and they formed a solid solution with CeO2 (inside the fluorite lattice). At higher CuO content (CuO>5 wt.%), large CuO particles were observed. There was strong interaction among ceria, manganese and copper oxide because of the doping of Mn. This interplay changed the reducibility and the valence states of the components, leading to the improved activity of the CuO/Ce-Mn-O catalysts.