Vanadium species supported on inorganic oxides as catalysts for propene epoxidation in the presence of N2O as an oxidant

The surface structure of vanadium species supported on SiO2, Al2O3, TiO2, and MgO and the effect of these supports on the activity of vanadium catalysts for propylene to propylene oxide oxidation with N2O as an oxidant were studied using ultraviolet visible diffuse reflectance spectroscopy and Raman spectroscopy, infrared spectra (IR) of adsorbed reagents, and the measurements of catalytic activity. The acidity of the samples was estimated from temperature-programmed desorption of ammonia and from IR spectra of adsorbed pyridine. On the basis of spectroscopic measurements, it was concluded that positively charged V5+ ions formed on silica support are responsible for N2O adsorption through nitrogen with the formation of weakly electronegative oxygen capable of interacting with a double Cdouble bond; length as m-dashC bond with the formation of epoxide. Analysis of different vanadium bonds present on the V/(oxide support) system indicates that mainly Vsingle bondOsingle bondSi groups are responsible for activity in propylene epoxidation.