Oxidative dehydrogenation of propane on silica (SBA-15) supported vanadia catalysts: A kinetic investigation

Silica (SBA-15) supported vanadium oxide was used for a kinetic study of the oxidative dehydrogenation of propane in a fixed bed reactor. Prior to this study, spectroscopic characterization using a variety of analytic techniques such as FTIR-, Raman-, DR UV-vis- and X-ray photoelectron spectroscopy revealed the absence of bulk vanadia and a high dispersion of active surface sites for the investigated catalyst. The kinetic data evaluation was based on a first order rate law. Calorimetric measurements were used to determine the heat of adsorption of propane on the catalyst. The data indicate that the primary combustion of propane is negligible. Reaction orders of one for propane dehydrogenation and propene combustion indicate their participation in the respective rate-determining step. The zero reaction order determined for the catalyst reoxidation reveals participation of lattice oxygen in this reaction step. Higher activation energies of propane dehydrogenation as compared to propene combustion indicate the participation of the weaker allylic C-H bond of propene in the rate-determining step of the propene combustion. This results in higher propene selectivities at elevated temperatures. Kinetic parameters, including apparent and intrinsic activation energies and the equilibrium constant of propane adsorption allowed a comparison with theoretical predictions and show good agreement. (C) 2009 Elsevier B.V. All rights reserved.