A kinetic modeling study of NO oxidation over a commercial Cu-CHA SCR catalyst for diesel exhaust aftertreatment

Based on a redox kinetic mechanism, we derive a rate expression for NO oxidation over Cu-zeolite catalysts, and fit it to a set of NO oxidation experiments carried out over a commercial Cu-zeolite SCR catalyst with chabazite structure. The so developed model is able to predict the complex behavior of the NO oxidation reaction in good agreement with data covering the effects of NO, O2, NO2and H2O feed contents, GHSV and reaction temperature (150–350 °C). We show also that the dependency of the negative kinetic order of NO2on the operating temperature is consistent with the proposed mechanism. Since NO oxidation in an NH3-SCR converter may affect the overall deNOXactivity, the herein presented model is also relevant to characterize and describe the behavior of state-of-the-art SCR catalysts.