Vanadium oxide supported on mesoporous SBA-15 as highly selective catalysts in the oxidative dehydrogenation of propane

The combination of different techniques (DR UV-vis, V-51 NMR, UV-Raman, FTIR, and H-2-TPR) in the characterization of vanadia supported on mesoporous SBA-15 catalysts shows that the dispersity and the nature of the vanadium species depend strongly on the V loading. In dehydrated catalysts with V contents lower than 2.8 wt%, vanadium is mainly in a tetrahedral environment. Higher V contents in the catalyst lead to the formation of polymeric V2O5-like species. Textural, SEM/TEM, and XRD results indicate that the ordered hexagonal mesoporous structure with large pore diameters of the support is retained upon the vanadium incorporation, and therefore high surface areas were obtained on the final catalysts. Vanadium species anchored to the surface show structural properties similar to those on mesoporous V-MCM and conventional V-SiO2 catalysts, but a higher surface concentration of isolated or low polymeric VOx species could be achieved on the V-SBA samples. The number and nature of the acid sites also change with the vanadium loading. The superior performance of the present mesoporous SBA-15 catalysts in the oxidative dehydrogenation of propane has been attributed to a higher dispersion of V species achieved on the SBA-15 support with large pore diameters as well as the low surface acidity of the catalyst. (C) 2004 Elsevier Inc. All rights reserved.