Insight into the Catalytic Reduction of NO by Methane: The Reaction of Nitromethane on Oxidized Mo(110)

The reactions of nitromethane (CH 3 NO 2 ) on a thin-film oxide grown on Mo(110) are investigated to gain insight into the role of nitromethane in the catalytic reduction of NO by methane. Using a combination of temperature programmed reaction and infrared reflection-absorption spectroscopy, we find that nitromethane reacts by dissociation of the N-O bonds below 300 K, to yield methylimido (CH 3 N ads ) and terminally-bound oxygen (Mo O). Methylimido is stable on the surface up to ∼550 K. Dehydrogenation of CH 3 N to form HCN and H 2 O is the major pathway; homolytic C−N bond fission to yield gaseous methyl radicals and formaldehyde are minor pathways. Formaldehyde is proposed to form from addition of some methyl radicals to surface oxygen, forming transient methoxy (CH 3 O), which dehydrogenates to form formaldehdye. Overall, C−N bond retention is favored in the reaction of nitromethane on the thin-film oxide on Mo(110). These results are discussed in the general framework of the CH 4 -assisted reduction of NO.