Surface Oxide—Support Interactions in the Molecular Design of Supported Metal Oxide Selective Oxidation Catalysts

A series of metal oxides were deposited on the surface of different oxide supports to study the surface oxide support interactions. The dehydrated Raman spectra of the supported metal oxide catalysts reveal the presence and structure of the supported metal oxide phases. The same surface metal oxide species were found on the different oxide supports for each of the supported metal oxide systems. The reactivity of the surface metal oxide species, however, depends on the specific oxide support (TiO 2~ZrO 2>Nb 2O 5>Al 2O 3~SiO 2). For a given oxide support, the reactivity depends on the specific surface metal oxide species (e.g. VOx > MoOy). The redox activation energy for a l l the surface metal oxide phases l ie in the range of 18-22 kcal/mole. The similar activation energies suggests that the number of active sites and/or the activity per site is responsible for the difference in reactivity. The redox TON for the methanol oxidation reaction correlates with the reduction temperature during TPR experiments, which suggests that the bridging M-O-Support bond controls the activity during redox reactions.