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Selective anaerobic oxidation of methane enables direct synthesis of methanol

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Science  05 May 2017:
Vol. 356, Issue 6337, pp. 523-527
DOI: 10.1126/science.aam9035

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A watery route from methane to methanol

Methanol production is an expensive, energy-intensive process that initially overoxidizes methane to carbon monoxide. Sushkevich et al. used copper sites in a zeolite to oxidize methane to methoxy intermediates; they then added water to release methanol and hydrogen while reoxidizing the copper. This inexpensive process could prove useful at gas well sites for producing an easily stored and transported liquid from excess gas that at present is burned away.

Science, this issue p. 523

Abstract

Direct functionalization of methane in natural gas remains a key challenge. We present a direct stepwise method for converting methane into methanol with high selectivity (~97%) over a copper-containing zeolite, based on partial oxidation with water. The activation in helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars of methane and then water at 473 K, consistently produced 0.204 mole of CH3OH per mole of copper in zeolite. Isotopic labeling confirmed water as the source of oxygen to regenerate the zeolite active centers and renders methanol desorption energetically favorable. On the basis of in situ x-ray absorption spectroscopy, infrared spectroscopy, and density functional theory calculations, we propose a mechanism involving methane oxidation at CuII oxide active centers, followed by CuI reoxidation by water with concurrent formation of hydrogen.

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