Iron oxide is a combustor for methanol. In this talk we will show that the reason for this is the favouring of formate production on the surface and the formate is the intermediate on the pathway to combustion. On the other hand MoO3 is very selective for formaldehyde production, due to the fact that oxygen insertion into the selective methoxy imternediate is very difficult on that surface. The non-selective route on iron oxide is rapidly suppressed by dosing low levels of Mo onto the oxide surface, however CO then becomes the major product. High selectivity is only achived at monolayer coverages of Mo. The reasons for this behaviour are that multiple Fe sites are required for combustion, while dual Mo sites are required for selective fomaldehyde synthesis. Single sites of either produce CO. We will show, by a cominbarion of single crystal and powder experiments, combined with synchrotron measurements that the selective sites are clusters of MoxO3x. Mo is used because it shows excellent selectivity and conversion when combined with Fe oxide. In light of the above it is surprising that Fe is included in the catalyst make-up, but this will be explained. Comparison will be made with the behaviour of other not so useful elements for selctive methanol oxidation such as W, V and Nb

Selectivity in methanol oxidation on Fe2O3 and the effect of Mo dosing

253rd National Meeting (2017)

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