Mean field modeling of NO oxidation over Pt/Al2O3 catalyst under oxygen-rich conditions

This paper deals with catalytic NO oxidation into NO2 over Pt/Al2O3 in oxygen-rich exhaust. Based upon kinetic measurements performed in a gradient free loop reactor and DRIFTS examinations, a mean field model is established to simulate catalytic data and calculate surface coverages. The kinetic model includes a network of 16 elementary reactions whereby NO oxidation is described by an Eley-Rideal-type mechanism. A comparison of measured and simulated data shows that the experimental results of the NO/O2 reaction are well described by the model. Kinetic parameters for the elementary reactions were taken from the literature or determined from a fit of the model to experimental data. To reduce the number of free parameters, we estimated the activation energy of O desorption for zero coverage and the corresponding linear constant α2 by numerically simulating the O2 TPD pattern. For the kinetic model of NO oxidation, the preexponential factors for NO2 adsorption (68 m3 s−1 m−2) and NO oxidation (104 m3 s−1 m−2); the activation energies for NO desorption (114 kJ mol−1), NO2 desorption (72 kJ mol−1), NO oxidation (35 kJ mol−1), and NO2 dissociation (51 kJ mol−1); and the linear constant α13 (14 kJ mol−1) are fitted. Furthermore, the calculated surface coverages provide evidence for the effect of CO, CO2, and H2O on the rate of NO oxidation.