Aqueous Au-Pd colloids catalyze selective CH<sub>4</sub> oxidation to CH<sub>3</sub>OH with O<sub>2</sub> under mild conditions.

Agarwal, Nishtha; Freakley, Simon J; McVicker, Rebecca U; Althahban, Sultan M; Dimitratos, Nikolaos; He, Qian; Morgan, David J; Jenkins, Robert L et al. · Science · 2017

basic_science · Level V

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Abstract

The selective oxidation of methane, the primary component of natural gas, remains an important challenge in catalysis. We used colloidal gold-palladium nanoparticles, rather than the same nanoparticles supported on titanium oxide, to oxidize methane to methanol with high selectivity (92%) in aqueous solution at mild temperatures. Then, using isotopically labeled oxygen (O<sub>2</sub>) as an oxidant in the presence of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>)<sub>,</sub> we demonstrated that the resulting methanol incorporated a substantial fraction (70%) of gas-phase O<sub>2</sub> More oxygenated products were formed than the amount of H<sub>2</sub>O<sub>2</sub> consumed, suggesting that the controlled breakdown of H<sub>2</sub>O<sub>2</sub> activates methane, which subsequently incorporates molecular oxygen through a radical process. If a source of methyl radicals can be established, then the selective oxidation of methane to methanol using molecular oxygen is possible.