Studies on catalytically active surface compounds. III. ESR Studies on the formation of oxygen radicals adsorbed on silica supported V₂O₅P₂O₅ catalysts

Abstract

Abstract Using the ESR method the formation of O − and O 2 − on silica supported vanadiumphosphorus catalysts has been investigated. Studying catalysts with varying phosphorus contents it was found that the concentration of O − and O 2 − can be related to the contents of phosphate ions. The admixture of increasing amounts of phosphorus obviously increases the reducibility of the catalysts and stabilizes the square‐pyramidical coordination of V 4+ ions. Comparing these results with activity and selectivity of the catalytic butene oxidation to maleic anhydride we point out that both the changed catalytic properties and the formation of oxygen radicals may be influenced by the same structural effects.