Raman Spectroscopy of Vanadium Oxide Supported on Alumina

Abstract

The molecular state of vanadium oxide supported on different alumina phases (γ, δ-θ, and α) was investigated with Raman spectroscopy. The supported vanadium oxide was found to form a molecularly dispersed overlayer on the different alumina phases. The molecular state of the surface vanadium oxide phase, however, was dependent on the nature of the alumina support. This variation was primarily due to the presence of surface impurities, in particular sodium oxide. The surface sodium oxide content was found to increase with the calcination temperature required to form the different transitional alumina phases (α, δ-θ, γ). The surface vanadium oxide phase consists of polymeric tetrahedra and distorted octahedra on γ-Al2O3, monomeric tetrahedra and distorted octahedra on δ,θ-Al2O3, and monomeric tetrahedra on α-Al2O3.