Kinetic modeling of steady-state NH₃-SCR over a monolithic Cu-CHA catalyst

A steady-state kinetic model for the NH₃-SCR and NH₃ oxidation by a monolithic Cu-exchanged chabazite (Cu-CHA) catalyst has been developed by a combination of flow reactor experiments and kinetic modeling with an in-house computational code. Arrhenius parameters for NH₃-SCR and NH₃ oxidation and reaction orders with respect to H₂O and O₂ are collected using a Cu-CHA catalyst coated onto a honeycomb cordierite substrate. While H₂O is shown to affect NH₃-SCR and low temperature NH₃ oxidation to N₂ negatively, it promotes high temperature NH₃ oxidation to NO. By a combination of calculations for heat and mass transfer and the parameters of the monolithic catalyst, a kinetic model is proposed. The model is validated with eight new experiments for NH₃-SCR and NH₃ oxidation. The calculated conversions of NO and NH₃ are in good agreement with the experimental values over a wide range of temperatures (150 °C–600 °C), indicating that the model can be used for predicting the catalyst performance of the monolithic Cu-CHA for NH₃-SCR.