Catalytic Combustion of Methyl Tert-Butyl Ether on Rh/γ-Al₂O₃ and Rh/γ-Al₂O₃–CeO₂ Catalysts: Effects of Thermal Treatments, Cerium Oxide and Particle Size

The effects of activation pretreatments, Rh particle size and content of cerium oxide on Rh/γ-Al₂O₃ catalysts for the oxidation of methyl tert-butyl ether (MTBE) were investigated. Three different conditions were used for the activation of the catalysts: (1) with air flow, (2) using a mixture of air and MTBE, and (3) by hydrogen reduction followed by oxidation with air. On Rh/γ-Al₂O₃ catalyst the thermal pretreatments are of great importance for the MTBE oxidation. However, on Rh/γ-Al₂O₃–Ce1 catalyst, the total combustion of MTBE was reached at a temperature of 200 °C lower than that obtained with the Rh/γ-Al₂O₃ catalyst at whatever thermal treatment applied. A Rhº/Rh^δ+ and Ce³⁺/Ce⁴⁺ species were identified by XPS suggesting that they are the responsible of the high activity showed by the Rh/γ-Al₂O₃–Ce1 catalyst. A particle size effect for MTBE oxidation was observed on Rh/γ-Al₂O₃ catalysts, large Rh particles are more active than the small ones.