Kinetic modeling of ethane oxidative dehydrogenation over VO _x/Al₂O₃ catalyst in a fluidized-bed riser simulator

This study reports kinetic modeling of ethane oxidative dehydrogenation (ODH) under an oxygen-free atmosphere employing a catalyst of 10 wt % VO _x supported on c-Al₂O₃. The 10 wt % VO _x /Al₂O₃ catalyst is a stable catalyst over repeated reduction and oxidation cycles, having high dispersion of VO _x on the support surface. Kinetic experiments are carried out in the CREC Fluidized Bed Riser Simulator at 550-600 °C and atmospheric pressure. Ethane ODH experiments are developed at 550, 575, and 600 °C, with three experimental repeats per condition; this shows that the prepared catalyst displays 6.5%-27.6% ethane conversion and 57.6%-84.5% ethylene selectivity. Under oxygen-free conditions, the oxygen from the catalyst lattice is consumed by ODH. Therefore, the oxygen availability is expressed as the extent of catalyst oxidation during the experiment. Changes in the extent of oxidation are described using an exponential decay function based on ethane feed conversion. On the basis of the data obtained, a kinetic model is proposed in which each reaction rate is related to the catalyst oxidation extent. The kinetic and decay model parameters are estimated using regression analysis. Activation energies and Arrhenius pre-exponential constants are calculated with their respective confidence intervals. The proposed series-parallel kinetic model satisfactorily predicts the ODH reaction of ethane under the selected reaction conditions.