1D Model of a Copper Exchanged Small Pore Zeolite Catalyst Based on Transient SCR Protocol 2013-01-1578

Urea-selective catalytic reduction (SCR) catalysts are the leading aftertreatment technology for diesel engines, but there are major challenges associated with meeting future NO_x emission standards, especially under transient drive cycle conditions that include large swings in exhaust temperatures. Here we present a simplified, transient, one-dimensional integral model of NO_x reduction by NH₃ on a commercial small-pore Cu-zeolite urea-SCR catalyst for which detailed kinetic parameters have not been published. The model was developed and validated using data acquired from bench reactor experiments on a monolith core, following a transient SCR reactor protocol. The protocol incorporates NH₃ storage, NH₃ oxidation, NO oxidation and three global SCR reactions under isothermal conditions, at three space velocities and at three NH₃/NO_x ratios. NH₃ storage parameters were obtained from separate TPD experiments and were used in the individual kinetic models to identify the rate parameters of various SCR reaction pathways. With minimal parameter tuning, the model predicts the observed dynamic catalyst behavior and is proposed as a promising candidate for future studies of aging effects and model-based controls development.