NH3-SCR by monolithic Cu-ZSM-5 and Cu-AFX catalysts: Kinetic modeling and engine bench tests

A simple kinetic model for the standard NH3-SCR reaction by Cu-ZSM-5 catalysts has been developed by assuming three reaction steps: NH3 adsorption (desorption), reactions of adsorbed NH3 with O2 (NH3 oxidation) and NO (NH3-SCR). The model is based on Arrhenius parameters for NH3-SCR and NH3 oxidation by a powder catalyst, combined with models for heat and mass transport and parameters of monolithic catalysts. The model is validated with the experimental results, not included in the estimation of the model, for NH3-SCR by monolithic catalysts with different parameters (catalyst loading and cell density). NOx removal from diesel exhaust, generated by engine bench, was also carried out by using monolithic Cu-ZSM-5 and Cu-AFX catalysts. The results suggest the poisoning effect of hydrocarbons in the exhaust emissions on NOx conversion is more significant for Cu-ZSM-5 than Cu-AFX.