Detailed Kinetic Modeling of NH3 and H2O Adsorption, and NH3 Oxidation over Cu-ZSM-5

Abstract

The NH3 and H2O adsorption and desorption, and the NH3 oxidation was studied using detailed kinetic modeling and flow reactor experiments. Ammonia storage and ammonia oxidation are important for the NH3 SCR application. In this study, both ammonia storage and oxidation are investigated, with and without the presence of water. Four sites were included in the model. On each copper atom was one active site introduced, denoted S1a, where NH3, H2O, NO2 and O2 can adsorb. However, electron paramagnetic resonance studies (EPR) and also DFT calculations in the literature suggest that [Cu(NH3)4]2+complex are formed in copper zeolites. We therefore introduced three additional sites (S1b) that ammonia can adsorb on in order to add up to the four ammonia adsorbed per copper atom. It was important to separate between S1a and S1b since it is not possible for four NO2 to adsorb per copper and also in order to describe the ammonia TPD and SCR reactions simultaneously. The Cu-ZSM-5 catalyst also contains Bronsted acid sit...