Degradation of methyl tert-butyl ether by catalytic wet air oxidation over Rh/TiO2–CeO2 catalysts

Abstract

The catalytic wet air oxidation of methyl tert-butyl ether was carried on Rh/TiO2 and Rh/TiO2–CeO2 catalysts. The TiO2–CeO2 (1, 3, 5, 10, and 20wt% CeO2) mixed oxides were prepared by the sol–gel method. The catalysts were characterized by different techniques: surface adsorption–desorption of N2 (BET surface area), X-ray diffraction (XRD), Fourier transform infrared of CO adsorption (FTIR-CO), Fourier transformed infrared of pyridine adsorption (FTIR-pyridine), temperature programmed reduction of H2 (H2-TPR), total organic compound (TOC) and transmission electron microscopy (TEM). A higher specific surface area BET and Lewis acidity sites were obtained on catalysts containing cerium oxide. Small Rh particles <1.8nm were obtained in all catalysts. The Rh catalysts containing cerium oxide showed higher activity than the reference Rh/TiO2 and a maximum in activity at 5wt% loading of CeO2. It is assumed that the acid sites are acting as a tramp for the MTBE molecule increasing the conversion on the Rh particles joined to an additional oxygen supply by cerium oxide redox process. The presence of cerium oxide inhibits the deposit of carbon on the catalyst; the higher cerium oxide concentration, the lower carbon deposited on the Rh surface. The addition of HCl on the initial reaction solution increases the CWAO activity.