Control of product selectivity in the partial oxidation of methane

Abstract

WITH the continuing need to identify new ways of synthesizing transportation fuels and hydrocarbon-based chemicals that do not rely on petroleum products, considerable effort is being devoted to the catalytic partial oxidation of natural gas. A number of oxide and other catalysts have been identified that facilitate oxida-tive coupling of methane to give ethane and ethene as the major products¹. But although ethene is valuable as a monomer for polymerization, C₂ hydrocarbons are of only limited usefulness. C₁ oxygenates, particularly methanol and formaldehyde, are key petrochemical intermediates, but efforts to produce them catalyti-cally by direct methane oxidation have met with little success. Here we show that the selectivity of methane oxidation on magnesium oxide can be switched from C₂ hydrocarbons to high yields of formaldehyde simply by changing the reaction conditions, without modification of the catalyst. As well as providing insight into the mechanism for selectivity, which depends on the relative concentrations of methyl radicals and molecular oxygen, our results provide a new route to the catalytic formation of formaldehyde.