Low-Dimensional Indium Oxo-Species on the Surface of In2O3/Al2O3 Catalytic Material: The Sites of Dissociative Adsorption of Hydrogen

The formation and nature of surface indium species in the alumina supported indium oxide (In2O3/Al2O3) catalytic material has been investigated by means of UV-vis spectroscopy and IR spectroscopy of adsorbed probe molecules CO and H-2. It has been found for the first time that high-temperature reduction of the material in hydrogen results in substitution of protons of surface hydroxyl groups of the alumina support by indium (In+) cations that form low-dimensional surface cationic dusters/associates. Oxidation of the surface In+ cations leads to the formation of low-dimensional surface indium oxo-species. These oxo-species have been found to be active in heterolytic dissociation of hydrogen, which occurs with the formation of surface indium hydrides and hydroxyl groups. It has been suggested that the property of In2O3/Al2O3 material to catalyze oxidative dehydrogenation of hydrocarbons reported in the literature is due to the low-dimensional indium oxo-species in which indium cations are bonded to alumina surface.