Monomeric and oligomeric vanadia species supported on CeO2(111) represent very active catalysts for the selective oxidation of methanol to formaldehyde. By virtue of temperature-programmed desorption spectroscopy (TPD) as well as scanning tunneling microscopy, vanadia monomers were found to be more active than their aggregations of higher nuclearity. On the basis of a Mars-van Krevelen mechanism, different reaction pathways exploiting the cooperative effect between catalyst and support have been calculated for ceria-supported vanadium oxides. Assuming first-order kinetics with a rate-determining hydrogen transfer, desorption rates were calculated for these reaction pathways using density functional theory. The resulting desorption peaks can be compared directly with the experimental TPD spectrum. Theory and experiment are in good agreement, and it is possible to assign each desorption peak to a certain reaction pathway. This was not possible after comparing calculated intrinsic barriers with the desorption barriers obtained via Redhead analysis, since the latter assumes a constant pre-exponential factor of 10-13 s-1, which leads to deviations of up to 20% for desorption barriers.

C–H bond activation at ceria-supported vanadia clusters

256th National Meeting (2018)

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