Study on the role of SBA-15 in the oxidative dehydrogenation of n-butane over vanadia catalyst using density functional theory.

The first step in the mechanism of n-butane oxidative dehydrogenation (ODH) on a V4O10 cluster and V4O10 supported SBA-15 is examined using DFT method. The activation and adsorption energies, oxidation state of V atoms are calculated. Over V4O10 the obtained results indicate that the activation of C-H bond of methylene group can occur at both the terminal and the bridging oxygen atoms with similar barrier (21.5-22.5 kcal mol(-1)). The role of SBA-15 (with and without modification by Al) in n-butane adsorption step has been studied in detail. SBA-15 itself has mild effect on the reaction process, but the substitution of silicon atoms by aluminum atoms results in an active supporter for V2O5 in ODH reaction. In that, the ratio of Si/Al will decide the direction of initial interaction steps between n-butane and catalyst surface and it will result in the selectivity of the reaction products.