The role of vanadium oxide species on the performance of Pd/VOx/SiO2 catalysts for HDO of phenol

Abstract

This work investigates the effect of vanadia species on the performance of Pd/VOx/SiO2 catalysts containing different vanadia loadings for HDO of phenol in the gas phase. in situ XANES experiments reveal the presence of a mixture of V2O4 and V4O7 species for all catalysts after reduction at 573 K. In situ XRD and XANES demonstrate that Pd particles and VOx species are in close contact, which is likely due to the presence of polymerized vanadate species, regardless of vanadia content, as shown by UV–Vis spectroscopy. This close contact promotes the selective hydrogenation of the C = O bond or the cleavage of the C-O bond, producing benzene. The strong interaction between the oxygen of the tautomer intermediate molecule and the oxygen vacancies associated with the presence of V3+ and V4+ cations is responsible for the deoxygenation activity of Pd/VOx/SiO2 catalysts.