(591a) Direct Conversion of Methane on Metal-Oxide and Oxide-Oxide Interfaces: Fundamental Studies on the Production of Hydrogen and Methanol

The transformation of methane into H₂ or methanol at moderate temperature and pressure conditions is of great environmental interest and remains a challenge despite many efforts. We have found that on Ni/CeO₂ and Pt/CeO₂ systems strong metal-support interactions modify the chemical activity of the admetals and help to dissociate methane at room temperature. These systems are very efficient for the production of H₂ through the dry reforming of CH₄ with CO₂. Recent studies have shown that several oxide-oxide interfaces (X-CuO; X= ZnO, CeO₂, or SnO) are active for a direct CH₄ to CH₃OH conversion. The selectivity towards methanol production is usually enhanced when water is added to mixtures of methane and O₂. The results of ambient pressure X-ray photoemission spectroscopy and density functional theory calculations have shown that water preferentially dissociates on active sites of the metal-oxide and oxide-oxide interfaces. The adsorbed OH blocks O-O bond cleavage that would dehydrogenate CH₃O to CO and CO₂, and it directly converts the CH₃ species to methanol. Water adsorption also helps to displace the produced methanol into the gas phase. The combination of these three phenomena helps to improve the selectivity for a direct CH₄ to CH₃OH conversion.