Physicochemical properties of the non-stoichiometric rutile-type VSbO4 phase

HERNAN SEITZ; SUSANA GESARI; ALFREDO JUAN; BEATRIZ IRIGOYEN

Saint Louis

Congreso; 7th World Congress on Oxidation Catalysis; 2013

AICHE

V-Sb-O mixed oxides form a cation-deficient VSbO4 phase. This rutile-type phase exhibits good catalytic performance in oxidation reactions, particularly during selective ammoxidation of C3 hydrocarbons to acrylonitrile. In this work we performed DFT+U calculations, implemented with the VASP code, to study the V0.92Sb0.92O4(110) surface´s physicochemical properties. We used a superstructure of 12 rutile VSbO4 unit cells, with 16.67% vacancies (*) of V and Sb. The spin-polarized Bader charge analysis indicates that our model is well represented by the formula V0.644+V0.283+Sb0.925+*0.16O4. The obtained (110) surface exhibits oxidized V4+ cations separated by Sb, in agreement with the site isolation concept. The cation deficiency enhances the formation of V4+/V3+ redox couples and also originates electron vacancies in the O(2p) valence band. Our results indicate that Sb and V deficiency promotes the formation of surface V-O moieties, with significant redox character, and strongly oxidizing O- species; improving the activity of the VSbO4 catalysts.