Micro-Kinetic Modeling of the CO+NO Reaction on Pd/MgO Particles
Résumé
Several experimental studies have shown the ability of Pd for the NO + CO conversion. In particular, a coherent set of results have been obtained on Pd particles supported on MgO, both concerning steady state conditions and transient regimes, temperature, and pressure dependence of the reaction rate. In this paper, we describe a microkinetic modeling of this reaction by numerical integration of the differential equations governing the different concentrations. The model is taken as simple as possible with only one type of reactive site. Parts of the parameters have been taken in order to fit specific experimental results. The simulation results agree qualitatively very well with the whole set of experiments. They clearly demonstrate that the rate-limiting step is, at low temperature, the NO decomposition and, at high temperature, the CO adsorption. The differences between experiments and simulations, beyond the intrinsic heterogeneity of the experimental set of results, reflect the approximations of the model. Nevertheless, the temperature and pressure dependence of the CO2 production rate are correctly reproduced by the simulations as well as major features of the transient signals.