Partial oxidation of methane to formaldehyde over copper-molybdenum complex oxide catalysts

Catalytic activity of different complex oxides containing copper oxide for methane oxidation with O-2 has been investigated. The complex oxides of Mo and Cu oxides (Cu-MoOx) exhibited high selectivity to formaldehyde in the oxidation compared with other oxides containing V, Cr, Mn, Fe or Ta oxides. The Cu-MoOx catalysts showed high activity for the oxidation of methane to formaldehyde when water vapor was added to the reactants. The structure of Cu-MoOx depended on the Cu loading in the catalysts and the most effective Cu-MoOx catalysts were composed of Cu3Mo2O9. Cu3Mo2O9 was reduced with H-2 and subsequently oxidized with O-2 at lower temperatures, compared with other crystallized phases containing Cu and Mo. The high redox performance of Cu3Mo2O9 contributed to the high yield of formaldehyde in the reactions.