On the reaction mechanism for methane partial oxidation over yttria/zirconia

Oxidation of methane over yttria/zirconia mixed oxide shows two parallel ox idation pathways, i.e. partial oxidation to CO+H-2+H2O and full oxidation t o CO2+2H(2)O. Both reactions proceed via a Mars van Krevelen mechanism with first order kinetics for methane and oxygen and are retarded by water. A m echanism is suggested in which methane is homolitically dissociated over O- (s)(-) sites and via the formation and decomposition of a formaldehyde prec ursor reacted to CO, H-2 and H2O. In parallel, CO2 is obtained from decompo sition of bicarbonate that is formed via further oxidation of dioxymethylen e. (C) 1998 Elsevier Science B.V. All rights reserved.