Continuous selective oxidation of methane to methanol over Cu- and Fe-modified ZSM-5 catalysts in a flow reactor

•Methane is selectively oxidised to methanol under mild, continuous flow conditions.•92% methanol selectivity observed at 0.5% conversion (0.46% yield).•Catalysts are prepared by chemical vapour impregnation.•Bimetallic FeCu/ZSM-5 catalysts undergo no on-line deactivation.•Activity is related to Brønsted acidity of the ZSM-5 support.

The selective oxidation of methane to methanol is a key challenge in catalysis. Iron and copper modified ZSM-5 catalysts are shown to be effective for this reaction using H2O2 as the oxidant under continuous flow operation. Co-impregnation of ZSM-5 with Fe and Cu by chemical vapour impregnation yielded catalysts that showed high selectivity to methanol (>92% selectivity, 0.5% conversion), as the only product in the liquid phase. The catalysts investigated did not deactivate during continuous reaction, and methanol selectivity remained high. The effect of reaction pressure, temperature, hydrogen peroxide concentration and catalyst mass were investigated. An increase in any of these led to increased methane conversion, with high methanol selectivity (≥73%) maintained throughout. Catalysts were characterised using DR-FTIR, DR-UV-Vis and 27Al MAS-NMR spectroscopy.

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