Low-temperature oxidation of ethanol over a Mn_(0.6)Ce_(0.4)O2 mixed oxide

摘要

A Mn_(0.6)Ce_(0.4)O2 mixed oxide exhibited rather high activity and stability for ethanol oxidation. Complete conversion of ethanol to CO2 was obtained at a temperature as low as 463 K and the activity maintained for 120h on-stream without obvious deactivation. The Mn_(0.6)Ce_(0.4)O2 catalyst showed higher ethanol oxidation rate and better selectivity to CO2 which was even superior to a Pt/Al2O3 catalyst. Temperature-programmed surface reaction and spectroscopic studies have revealed that ethoxy species were formed immediately upon ethanol adsorption on the catalyst at room temperature. These intermediates were further oxidized to acetate and carbonate species, and finally converted to CO2 at elevated temperatures. The effective activation of molecule oxygen over the Mn_(0.6)Ce_(0.4)O2 solid solution plays an essential role in determining the catalytic performance. Oxygen transfer from molecular oxygen to MnO2 active sites through CeO2 in the solid solution realized the effective activation of molecular oxygen. At lower temperatures, the oxidation of ethanol mainly produced acetaldehyde, and the direct oxidation of ethanol to CO2 became the major route at higher temperatures, depending on the activation of molecular oxygen.