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Free keywords:
Oxidative dehydrogenation; Propane; Supported vanadia catalysts; SBA-15; Kinetics
SFB: V-oxides: clusters and catalysts; preparation & internal structure
Abstract:
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 techniques such as FTIR spectroscopy, Raman spectroscopy, DR UV-Vis spectroscopy and X-ray Phototelectron 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 formal kinetic approach. 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 the propane dehydrogenation and propene combustion indicate the participation of these species in the respective rate determining step. The zero reaction order determined for the catalyst reoxidation reveals a participation of lattice oxygen in this reaction step. Higher activation energies of propane dehydrogenation as compared to the 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 selectivites at elevated temperatures. Kinetic parameters, including apparent and real activation energies and the equilibrium constant of the propane adsorption allowed for a comparison with theoretical predictions and show a good agreement.
