Kinetic Modeling of Propane Oxidative Dehydrogenation over VO_<i>x</i>/γ-Al₂O₃Catalysts in the Chemical Reactor Engineering Center Riser Reactor Simulator

Abstract

This study reports kinetic modeling of propane oxidative dehydrogenation (ODH) employing a new VOx/γ-Al2O3 catalyst especially designed for propane ODH with a controlled acidity. This catalyst is prepared with different vanadium loadings (5–10 wt %). Kinetic experiments are carried out under an oxygen-free atmosphere in the Chemical Reactor Engineering Center fluidized bed riser simulator at 475–550 °C and atmospheric pressure. Successive-injection propane ODH experiments (without catalyst regeneration) over partially reduced catalysts show good propane conversions (11.73%-15.11%) and promising propylene selectivity (67.65–85.89%). Regarding propylene selectivity, it increases while that for COx decreases as the catalyst degree of reduction augments with the consecutive propane injections. This suggests that a controlled degree of catalyst reduction is needed for high propylene selectivity. Under such oxygen-free conditions, the lattice oxygen of the catalyst is consumed via the ODH reaction. On the basis of the data obtained, a kinetic model is proposed. In this model, reaction rates are related to the degree of catalyst reduction using an exponential decay function. The kinetic and decay model parameters are estimated using nonlinear regression analysis. Activation energies and Arrhenius pre-exponential constants are calculated with their respective confidence intervals. The proposed parallel-series kinetic model satisfactorily predicts the ODH reaction of propane under the selected reaction conditions.