Kinetic study of lean NOx storage over Pt-Ba/Al2O3 system

Transient NOx storage and TPD runs were performed for a feed of NO or NO2 in the presence or absence of O2 over Ba/Al2O3 and Pt-Ba/Al2O3. A kinetic model for NOx storage previously developed in the literature was used to simulate the majority of the results, after only the Pt and Ba dispersions had been adapted to a set of experimental data. The model describes well the NO2 storage over Ba/Al2O3 through a two-step disproportionation reaction and the oxidizing capacity of barium nitrates toward NO. However, the model cannot account at the same time for the oxidation of NO and for the storage of NOx during the adsorption of NO in the presence of oxygen over Pt-Ba/Al2O3. The lack of an appropriate balance between the NO oxidation and NOx storage routes is critical because these two characteristics are interconnected and are both involved in NOx storage. This finding ultimately motivates further modeling efforts.