Supported Au catalysts catalyze selective oxidation of propane using a mixture of H2 and O2. The primary product changed from propene over Au/TiO2 to acetone over Au/TS-1. The fact that Ti exists as isolated species in TS-1 implies that the oxo-Ti-Au interface may be active in the selective oxidation reaction. We have investigated the catalytic properties of this interface by generating it in a controlled manner. Two methods were used to form the oxo-Ti-Au interface. One method started with Au particles, formed by the reduction of tetrahydrothiophene gold chloride in the presence of polymethylhydrosilance (PMHS) containing aminopropylsiloxy and diacetylacetonate Ti ligands (Ti-PMHS). The resulting encapsulated Au particles were deposited on SiO2. The second method started with impregnating Au/TiO2 with Ti-PMHS followed by aminopropyl-modified PMHS without the Ti ligand (N-PMHS). For both methods, the samples were then subjected to oxidation to remove the hydrocarbon fragments, as confirmed by FTIR. This resulted in samples containing oxo-Ti species in close proximity of the Au particles. EXAFS and UV-vis characterization of these samples confirmed that mononuclear oxo-Ti species were present. These samples were tested for propane oxidation using a mixture containing 5% propane, 5% O2 and 5% H2 in He at 458 K. It was found that acetone was formed only on samples containing oxo-Ti species, and a roughly monolayer of silica-dispersed oxo-Ti on Au/TiO2 nearly completely suppressed the formation of propene, and acetone became the major oxidation product.  Furthermore, a sample with a layer of oxo-Ti-silica adjacent to Au was 3 times more active in the production of acetone than when this layer was one to two-atom-distance away on the average.

Selective oxidation of propane to acetone over Au-(oxoTi) catalysts

245th National Meeting (2013)

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