Abstract
Many transition metal oxides have been evaluated as oxidative coupling catalysts for converting methane to C 2 and higher hydrocarbons. Reactions were done in a cyclic redox mode in which oxidized catalyst was reacted with methane in the absence of oxygen to form coupling products and reduced catalyst which was reoxidized with air in a separate step. Manganese, indium, germanium, antimony, tin, bismuth, and lead oxides were found to be effective coupling catalysts, giving 10 to 50% selectivity to higher hydrocarbons. Silica is a superior support compared to alumina. Mechanistic studies with manganese oxide on silica indicate that the initial coupling product is ethane which is formed via dimerization of a CH 3 radical-like species. The ethane is oxidatively dehydrogenated to ethylene which may react with CH 3 to give propylene. The major path for combustion involves sequential oxidation of products.
Published Version
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