Sol-gel preparation of pure and silica-dispersed vanadium and niobium catalysts active in oxidative dehydrogenation of propane

Moggi, P Predieri, G Cauzzi, D Devillers, Michel [UCL] Ruiz, Patricio [UCL] Morselli, S Ligabue, O et al.[show all]

Hydrolytic and non-hydrolytic sol-gel routes are implemented to prepare various pure and silica-dispersed vanadium- or niobium-based oxide catalysts corresponding to the compositions Nb-V, Sb-V and Nb-V-M (M = Sb, Mo, Si). Starting reagents in the hydrolytic procedure are isopropanol solutions of the metal alkoxides. The non-hydrolytic route is based on reactions between metal and Si alkoxides and hexane suspensions of niobium(V) chloride. The catalysts are tested in propane oxidative dehydrogenation. NbVO5, SbVO4 and Nb2Mo3O11 are the major crystalline phases detected in the fresh catalysts, but structural modifications are in some cases observed after the use in the catalytic tests. At 500degreesC, propane conversions of 30% and selectivities to propene between 20 and 40% are attained. When the space velocity is decreased, acrolein is in some cases found as by-product.