Infrared spectroscopic evidence of adsorbed species during the oxidation of 2-propanol catalyzed by γ-Al2O3-supported gold: Role of gold as a hydrogen-subtractor

Samples of gold supported on γ-Al2O3 were prepared by deposition–precipitation and tested as catalysts for the aerobic oxidation of 2-propanol to give acetone. IR spectra recorded during catalysis show that the alcohol is first dissociatively adsorbed on the catalysts to form predominantly 2-propoxide species bonded to coordinatively unsaturated Al3+ sites. It is proposed that gold particles in the proximity of the 2-propoxide species are capable of subtracting hydrogen from the β-C–H bond to give acetone bonded to Al3+ sites, as evidenced by the appearance of a band at 1704 cm−1 at a similar temperature as that at which the onset of formation of acetone occurred. Other possible surface reaction pathways are suggested, indicating the interactions of the alcohol with support and metal sites. These results (with a model reaction) might be general and explain the activity of supported gold for the oxidation of other alcohols.

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► γ-Al2O3-supported gold is catalytically active for the oxidation of 2-propanol.
► IR spectra of functioning catalysts identified species bonded to the support.
► Results suggest that the alcohol is activated on the support.
► Role of gold consists of subtracting hydrogen from β-C–H bond of surface alkoxide.