Abstract: ESR technique has been used to study the interaction of reduced V₂O₅/SiO₂ catalyst with a variety of adsorbed molecules. It has been shown that the V⁴⁺ ions with tetrahedral coordination are active centers. Their interaction with adsorbed molecules, such as CH₃OH, HCl, and CH₃CN etc, leads to the formation of octahedrally coordinated VO²⁺ complexes on the surface of the catalyst. The calculation of bonding parameters of surface complexes formed indicates that the unpaired electron is mostly confined to the vanadium ions d-orbital. The adsorption of oxygen at 77 K leads to the formation of various oxygen radicals. But no change had been found for the coordinated state of V⁴⁺ ions after adsorption of ethylene or propylene molecules.

Key words: ESR, V₂O₅/SiO₂ catalyst, adsorption, vanadyl complexes, oxygen radical species