Effect of the support on the catalytic properties of vanadyl phosphate in the oxidative dehydrogenation of propane

Propane oxidative dehydrogenation has been investigated on vanadyl orthophosphate dispersed on different supports (Al2O3, TiO2, SiO2, ZrO2, MgO and SnO) in a fixed bed reactor in the temperature range 300-550 degrees C. Catalysts have been characterized by bulk and surface sensitive techniques, such as X-ray diffraction (XRD), BET analysis, temperature programmed reduction with H-2 (H-2-TPR) and X-ray photoelectron spectroscopy (XPS). A different dispersion of vanadium species has been found depending on the different nature of the supports. Al2O3, ZrO2 and TiO2 promote the best dispersion of vanadium and provide the highest catalytic performances, due to the strong interaction of the support with the phosphate phase and the enhanced vanadium reducibility. A different reaction path is activated by catalysts supported on SiO2, MgO and SnO due to the formation of vanadyl phosphate aggregates and in some cases also to the reducibility of the support which favour propane overoxidation leading to a larger CO2 production. (C) 2010 Elsevier B.V. All rights reserved.