Influence of the co-precipitation pH on the physico-chemical and catalytic properties of vanadium aluminum oxide catalyst Original Research Article

Vanadium-aluminum oxide catalysts for propane oxidative dehydrogenation (ODH) are investigated with respect to their physico-chemical properties and catalytic activity as a function of the co-precipitation pH. Modifications of the specific surface area, the particle size distribution, and the chemical nature of the active phase are found. At co-precipitation pH 5.5, an amorphous V-Al-Ox mixed phase was formed by condensation of tetrahedral polymeric [VOx]nn− and amorphous aluminum hydroxide species. At pH between 7.5 and 8.5, the catalyst consists of [VOx]nn− species supported on amorphous aluminum hydroxide. At pH = 10, V2O74− ions are presumably adsorbed on boehmite surface. The propane conversion and the rate of propylene formation per gram-atom of vanadium are higher for the samples prepared at pH ≥8.5. A correlation exists between the reduction temperature of the vanadium species and the catalytic activity for the propane oxidative dehydrogenation reaction.