On the Behavior of O2− and O− Radicals over V2O5–SiO2 Catalyst

The behavior of oxygen, O2− and O− radicals adsorbed on the partially reduced V2O5–SiO2 catalysts has been investigated. Oxygen is adsorbed mainly in a molecular state at room temperature, the sum of amounts of paramagnetic adsorbed species O2− and O− being less than 10% of total amount of adsorbed oxygen. High degree of reduction, high content of V2O5 and low pressure of oxygen at adsorption equilibrium are favorable for the formation of O− radical. It was confirmed by the quantitative analysis of reaction products and the adsorbed species that O2−, not O−, is the active species in the oxidation of propylene at room temperature. A mechanism involving an intermediate of an epoxide structure was proposed.