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

Abstract

Catalytic activity of different complex oxides containing copper oxide for methane oxidation with O₂ has been investigated. The complex oxides of Mo and Cu oxides (Cu–MoO_x) exhibited high selectivity to formaldehyde in the oxidation compared with other oxides containing V, Cr, Mn, Fe or Ta oxides. The Cu–MoO_x catalysts showed high activity for the oxidation of methane to formaldehyde when water vapor was added to the reactants. The structure of Cu–MoO_x depended on the Cu loading in the catalysts and the most effective Cu–MoO_x catalysts were composed of Cu₃Mo₂O₉. Cu₃Mo₂O₉ was reduced with H₂ and subsequently oxidized with O₂ 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.