Studies on the V2O5–TiO2system. Part 2.—TiO2(anatase)–V2O5

Abstract

Mechanical mixtures of separately prepared V₂O₅, V₆O₁₃ and anatase have been used as catalysts in the dehydration of N-ethylformamide (NEF) in the presence of oxygen. Catalytic activity was measured as a function of the gas hourly space velocity (GHSV), the oxygen-to-N-ethylformamide ratio (O/N), the temperature, the V₂O₅ and V₆O₁₃ contents and the surface area of V₂O₅. The characterization was carried out using B.E.T. surface analysis, XRD and XPS techniques. It was concluded that there exists a cooperation between V₂O₅ and anatase, which brings about the stabilization of V₆O₁₃ by the anatase. V₆O₁₃ is the most selective phase in NEF dehydration. The calcination of V₂O₅–anatase mechanical mixtures results in (i) an increase of the V₂O₅ dispersion over the anatase surface, which brings about an increase of the selective product (propiononitrile), and (ii) partial anatase-into-rutile transformation, resulting in a decay of the catalytic properties. Under appropriate reaction conditions (temperature, O/N ratio) the anatase-into-rutile transformation does not take place.