A kinetic study of oxygen adsorption/desorption and NO oxidation over Pt/Al2O3 catalysts

Laboratory tests and kinetic modeling were carried out in order to provide kinetic input data to a systematic investigation of the mechanism of nitrog en oxides (NO,) storage in catalysts used for lean-burn engines. In particu lar, we present a kinetic model of the NO oxidation to NO2 over a Pt/Al2O3 model catalyst for the temperature range 250-450 degrees C. Since the oxyge n behavior at atmospheric pressure is critical for such a model, we have al so studied the adsorption/desorption of oxygen by temperature-programmed de sorption (TPD) experiments. The experiments show that oxygen starts to deso rb at about 300 degrees C. Furthermore, the NO oxidation was studied in a t emperature ramp with NO and oxygen in the gas feed. The data from this expe riment and the above-determined values for the oxygen adsorption/desorption were used to construct a kinetic model for the NO oxidation. Finally, the model was validated with some transient experiments with either NO or NO2 a nd different oxygen concentrations in the gas feed. We found a good agreeme nt between these experiments and the model.