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/O-2 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 cc by numerically simulating the O-2 TPD pattern. For the kinetic model of NO oxidation, the preexponential factors for NO2 adsorption (68 m(3) s(-1) m(-2)) and NO oxidation (104 m(3) 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 alpha(13) (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. (C) 2004 Elsevier Inc. All rights reserved.