A Comparative Study between Real-world and Accelerated Lab Aging of Cu/SSZ-13 SCR Catalysts

Feng  Gao, PNNL

Copper-exchanged chabazite catalyst Cu/SSZ-13 has been commercialized as a SCR catalyst for diesel engine exhaust deNOx for more than a decade. During this period, hydrothermal aging and sulfur poisoning have been identified as two main causes for catalyst degradation [1]. With the implementation of ever stringent emission regulations and extended warranties for medium- and heavy-duty diesel-powered automobiles in the upcoming decade, it is important to continue our efforts exploring Cu/SSZ-13 aging mechanisms. Durability of Cu/SSZ-13 catalysts is traditionally evaluated by the so-called “accelerated lab aging” protocols developed to mimic real-world aging [2]. Recent investigations at Cummins revealed, however, that real-world aging shows characteristics very different from aging based on current accelerated lab aging protocols. In order to develop accelerated aging methods that better mimic real-world aging, and to provide accurate predictive aging and performance models, PNNL and Cummins initiated a 3-year collaboration in 2020, investigating gaps between real-world and accelerated lab aging, and key causes for such gaps.

In this presentation, a wide array of catalyst characterization methods, including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), NH3 and NOx temperature-programmed desorption (TPD), and H2 temperature-programmed reduction (TPR) are used to comprehend key differences between real-world and lab aged catalysts.

[1] J.Y. Luo, D. Wang, A. Kumar, J.H. Li, K. Kamasamudram, N. Currier, A. Yezerets, Identification of two types of Cu sites in Cu/SSZ-13 and their unique responses to hydrothermal aging and sulfur poisoning, Catal Today, 267 (2016) 3-9.

[2] S.J. Schmieg, S.H. Oh, C.H. Kim, D.B. Brown, J.H. Lee, C.H.F. Peden, D.H. Kim, Thermal durability of Cu-CHA NH3-SCR catalysts for diesel NOx reduction, Catal Today, 184 (2012) 252-261.

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