Mechanism-based kinetic modeling of N2O formation on SCR activity over Cu-SSZ-13 catalysts for diesel vehicle

Abstract

A three-site SCR model including Z2Cu, ZCuOH and Brönsted acid sites has been developed for accurately describing SCR reactions and N2O formation over Cu-SSZ-13. The N2O formation mechanism proposed by recent works was adopted. Low-temperature N2O formation is attributed to NH4NO3 decomposition on ZCuOH and Brönsted acid sites with different NH4NO3 formation routes. High-temperature N2O formation is derived from NOx-assisted NH3 oxidation on different sites with different routes. NH3 storage, NH3 oxidation, NO oxidation, Standard SCR, Fast SCR, NO2 SCR, NH4NO3 formation and decomposition were included. The NH4NO3 inhibition on low-temperature NH3-SCR reactions and N2O formation due to its deposition on catalyst surface were considered. The model has been validated by different steady-state and transient experiments. The results indicate the model can accurately predict SCR reactions, as well as N2O formation under different conditions. The model can improve NOx and N2O cooperative emission control performance in diesel engine after-treatment system.