Vanadium promoted molybdenum phosphate catalysts for the vapour phase partial oxidation of methanol to formaldehyde

• (MoO2)2P2O7 is active and selective for methanol oxidation.
• Addition of vanadium to molybdenum phosphate improves catalyst performance.
• Surface vanadium phosphate phases on (MoO2)2P2O7 create enhanced performance.

The catalytic properties of (MoO2)2P2O7 promoted with vanadium have been investigated for the partial oxidation of methanol, and structure-activity relationships probed using a range of characterization techniques. All unpromoted and promoted molybdenum phosphate catalysts were active, with higher vanadium content achieving both high activity and high formaldehyde selectivity at reaction temperatures around 400 °C. The association between increasing vanadium content and the enhanced activity towards methanol oxidation was attributed to the formation of mixed phase catalysts, in particular VOHPO4·0.5H2O/VOPO4·2H2O with (MoO2)2P2O7. The dispersion of vanadium phosphate phases on the surface of (MoO2)2P2O7 was found to substantially enhance the catalytic properties of the molybdenum phosphate catalyst. The data from this study indicate that molybdenum phosphate based catalysts are promising candidates for selective oxidation, and hence worthy of further investigation.

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