Experimental, detailed, and global kinetic reaction model for NO oxidation over platinum/alumina catalysts

Abstract

The oxidation of nitric oxide (NO) is a critical step when promoting lean NOx trap and selective catalytic reduction conversion effectiveness; hence, it is important to understand the fundamental reaction mechanism. This awareness of the detailed reaction mechanism allows for the determination of an appropriate global reaction rate expression for numerical simulation efforts in the automotive field. This work succinctly reviews the literature in this area and derives a global expression for NO oxidation from stoichiometry using the detailed reactions steps. In this version, the parameters used to simulate the global expression are derived from the kinetic theory of gases and the detailed study of each NO reaction step; ensuring the correct functional dependency of each reaction parameter. Moreover, the global model is adapted to simulate different surface morphologies. The effect of temperature and surface changes (dispersion, particle size) are included while determining the parameters, so that the same variables can be used over wide range of catalysts effectively. This work summarizes the literature of experimentally observed NO oxidation in terms of surface coverage, species concentration dependency, and temperature variation. Finally, the authors verify the global model by simulating experimental data obtained for catalysts with varying noble metal particle size. As a result, the adaptive global model predicts NO oxidation conversion with changes in surface morphologies at greater than 93 % accuracy for the experimental data taken.