Structure and acidity of vanadium oxide layered on titania (anatase and rutile)

Abstract

The adsorption of pyridine on, and the structure of, two series of V₂O₅/TiO₂(anatase and rutile) samples, prepared by the gas-phase method (1.2–3.4 wt.%), have been studied. V–Ti oxides show both Brønsted- and Lewis-acidic sites. The Brønsted sites increases with increasing vanadium loadings. The number of Lewis sites on the anatase samples is greater than on the rutile form. From Raman and in situ FTIR studies the vanadium oxides on both series are composed mainly of surface vanadia species. These are stable during heat treatment at 673 K. The VO character of a monolayer rutile sample is different from that of a monolayer anatase sample, and resembles that of multilayer samples.