Enhancement of catalytic activity of Ir/TiO2 by partially reduced titanium oxide in aerobic oxidation of alcohols

The catalytic activity of 2 wt% Ir/TiO2 in alcohol oxidation with molecular oxygen was enhanced by high-temperature reduction (673–873 K) of the catalyst in a hydrogen stream. Wide variety of alcohols were converted efficiently into corresponding carbonyl compounds with 2 wt% Ir/TiO2 reduced at 723 K. Kinetic analysis revealed that the alcohol adsorption was enhanced by high-temperature reduction of catalysts. Formation of partially reduced titanium oxide by high-temperature hydrogen reduction of TiO2-supported metal catalysts is a widely known phenomenon as the SMSI effect. The formed TiO(2−δ) species containing coordinatively unsaturated titanium sites might contribute to the enhancement of catalysis as a coordination site of alcohols.