Catalytic combustion of ethanol on pure and alumina supported K-Mn oxides: An IR and flow reactor study

Mn-based catalysts prepared by oxidation of Mn(II) by KMnO4, pure and supported on alumina, calcined at 350 and 500 °C have been characterized and tested in the total oxidation of ethanol. IR experiments allowed us to have an indication on some aspects of the reaction mechanisms. The unsupported catalysts calcined at 350 °C, mostly constituted by a cryptomelane phase were the most active, allowing the total conversion of ethanol at 180 °C, with excellent stability for at least 80 h. The reaction is initiated by the fast conversion of ethanol to acetate species via acetaldehyde. Later, the conversion of acetates to CO2 appears to be a slow step. On alumina-supported catalysts, which are (in spite of the much higher surface area) active only above 240 °C, part of acetate species are adsorbed on the support and act as inactive spectators.