Modeling Fundamental Characteristics and Performance of Degreened and Aged Cu-CHA NH3–SCR Catalysts

Saurabh  Joshi, Cummins Inc.

Modeling Fundamental Characteristics and Performance of Degreened and Hydrothermally Aged Cu-CHA NH3–SCR Catalysts
Saurabh Y. Joshi, Neal W. Currier, Ashok Kumar, Jinyong Luo, Krishna Kamasamudram, Aleksey Yezerets
Cummins Inc., Columbus,IN, 47201 (USA)

Selective catalytic reduction of NOx with ammonia using Cu/Fe-zeolite catalysts has emerged as the primary NOx reduction technology used to meet stringent emissions requirements for diesel engine applications. In spite of the excellent hydrothermal stability of commercial Cu-CHA catalysts, they can degrade in the field due to temperature excursions normally encountered during soot filter regenerations and uncontrolled regeneration of soot in the upstream DPF. Accurate SCR catalyst performance and degradation models are essential for optimal design of aftertreatment systems and development of control strategies.
In this work, we develop a global kinetic model considering two types of ammonia storage sites which characterize weak and strong adsorption of ammonia. The two-site global model can capture the fundamental SCR characteristics such as NH3 storage, NH3 oxidation, N2O formation, as well as standard-, fast- and slow-SCR. The intrinsic kinetic parameters are determined using the high space velocity experimental data. The model is validated under steady state and transient conditions over a wide operating window using Cummins 4-step protocol. Further, the model is extended to simulate the effect of hydrothermal aging on catalyst performance with physically significant changes in the storage sites and with minimal changes in the reaction kinetics.