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.