Mean Field Modelling of NOx Storage on Pt/BaO/Al2O3
Journal article, 2002
A mean field model, for storage and desorption of NOx in a Pt/BaO/Al2O3 catalyst is developed using data from flow reactor experiments. This relatively complex system is divided into five smaller sub-systems and the model is divided into the following steps: (i) NO oxidation on Pt/Al2O3; (ii) NO oxidation on Pt/BaO/Al2O3; (iii) NOx storage on BaO/Al2O3; (iv) NOx storage on Pt/BaO/Al2O3 with thermal regeneration and (v) NOx storage on Pt/BaO/Al2O3 with regeneration using C3H6. In this paper, we focus on the last sub-system. The kinetic model for NO, storage on Pt/BaO/Al2O3 was constructed with kinetic parameters obtained from the NO oxidation model together with a NO, storage model on BaO/Al2O3. This model was not sufficient to describe the NO, storage experiments for the Pt/BaO/Al2O3, because the NO, desorption in TPD experiments was larger for Pt/BaO/Al2O3, compared to BaO/Al2O3. The model was therefore modified by adding a reversible spill-over step. Further, the model was validated with additional experiments, which showed that NO significantly promoted desorption of NOx from Pt/BaO/Al2O3. To this NOx storage model, additional steps were added to describe the reduction by hydrocarbon in experiments with NO2 and C3H6. The main reactions for continuous reduction of NOx occurs on Pt by reactions between hydrocarbon species and NO in the model. The model is also able to describe the reduction phase, the storage and NO breakthrough peaks, observed in experiments.