Rhodium supported catalysts were prepared by impregnating γ-Al2O-Ce supports, which were prepared from boehmite and cerium nitrate with different cerium contents (1, 5, 10 and 20 Ce wt%). High specific surface areas, which diminish with the cerium content, were obtained. At high cerium contents the X-ray Diffraction (XRD) patterns showed the characteristic peaks of cerium oxide. X-ray photoelectron Spectroscopy (XPS) identified the presence of Rho and Rhδ+ on the catalysts. The analysis of the Ce 3d region showed the presence of Ce3+ and Ce4+ where their relative abundance depends on the cerium content. Small rhodium particle sizes were determined by High Angle Annular Dark Field (HAADF) Scanning Transmission Electron Microscopy (STEM). It has been found that the conversion for the wet oxidation of methyl tert-butyl ether (MTBE) depends on the cerium content; conversion ranging from 73 to 96% were reached. A correlation between the total mineralization of MTBE and the relative abundance of the Ce4+/Ce3+ ratio was observed. A total mineralization, as high as 87%, was obtained in the catalyst with the highest Ce4+/Ce3+ ratio.

Keywords: Rhodium alumina-ceria catalysts; MTBE wet oxidation; Rhodium XPS spectra; Alumina-ceria catalysts; MTBE mineralization; Rhodium HAADF-STEM.