Kinetic Modeling of the Heterogeneously Catalyzed Oxidation of Propene to Acrolein in a Catalytic Wall Reactor

Using data from isothermal investigations in a catalytic wall reactor (Redlingshöfer, H.; Kröcher, O.; Böck, W.; Huthmacher, K.; Emig, G. Ind. Eng. Chem. Res. 2002, 41, 1445), the kinetics of the highly exothermic vapor-phase oxidation of propene was determined by statistical parameter estimation. It was shown that the oxidation of propene to acrolein follows a redox mechanism, with a change in the rate-determining step that depends on temperature. Two kinetic equations for the reduction and reoxidation regimes were necessary for a good fit to the experimental values. About a 3-fold higher activation energy for the reoxidation step and different propene and oxygen concentration dependencies of the rate equations in the two regimes were observed. An increasing water content improves catalyst reoxidation. This special catalytic effect was modeled by including an activity function. The kinetics of the byproducts acrylic acid, carbon oxides, formaldehyde, acetaldehyde, and acetic acid were considered with a reaction scheme consisting of 10 reactions. The model describes the experimental data very well. It includes 31 significant kinetic parameters.