Selective anaerobic oxidation of methane enables direct synthesis of methanol

• Published in: Science (American Association for the Advancement of Science) Vol. 356; no. 6337; pp. 523 - 527
• Main Authors: Sushkevich, Vitaly L., Palagin, Dennis, Ranocchiari, Marco, van Bokhoven, Jeroen A.
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 05.05.2017; The American Association for the Advancement of Science
• Subjects: Absorption spectroscopy; Activation; Carbon monoxide; Combustion; Copper; Copper converters; Density functional theory; Gas wells; Helium; Infrared spectroscopy; Intermediates; Isotopic labeling; Methane; Methanol; Methyl alcohol; Moles; Natural gas; Oxidation; Radioactive labeling; Reoxidation; Selectivity; Spectroscopy; Spectrum analysis; Water; X ray absorption; X-ray absorption spectroscopy; Zeolites
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.aam9035

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.