Reaction kinetics and mechanism of benzene combustion over the NiMnO₃/CeO₂/Cordierite catalyst

The kinetics of the catalytic combustion of benzene at different concentrations over the NiMnO₃/CeO₂/Cordierite catalyst were investigated to gain more insight into the catalytic reaction mechanism. A kinetic study was performed in a packed-bed tubular reactor under different conditions. The catalytic combustion kinetics were modeled using a Power-Law model and the Mars-Van Krevelen model. The results showed that the Mars-Van Krevelen kinetic model provided a significantly better fit to explain the catalytic combustion kinetics of benzene over the NiMnO₃/CeO₂/Cordierite catalyst. The results showed that the reduction reaction occurred more easily than did the oxidation reaction on the surface of the catalyst. Moreover, the values of the pre-exponential factor for the reduction steps (7.84 × 10¹¹ s^-1) is higher than those of the oxidation steps (1.04 × 10⁹ s^-1), indicating that the more is the effective collision times between the activated molecules, and the easier for chemical reaction to occur, and the degree and speed are more intense and rapid. Therefore, it can be concluded that the catalyzed surface oxidation reaction is the control step of catalytic benzene combustion. Based on this analysis of the experimental results and the assumptions of the Mars-Van Krevelen model, it was determined that the catalytic combustion of benzene over the NiMnO₃/CeO₂/Cordierite catalyst obeys the Mars-Van Krevelen mechanism. The catalytic combustion reaction occurred by the interaction between the benzene molecules and the active sites of the NiMnO₃/CeO₂/Cordierite catalyst. The catalytic oxidation of benzene involves a catalytic redox cycle of adsorption, deoxidation, desorption, oxygen supply and regeneration.