NH3-TPD methodology for quantifying hydrothermal aging of Cu/SSZ-13 SCR catalysts

Publication date: 23 November 2018 Source:Chemical Engineering Science, Volume 190 Author(s): Jinyong Luo, Krishna Kamasamudram, Neal Currier, Aleksey Yezerets We identified a new acidic feature in Cu/SSZ-13 catalysts, related to the presence of two distinct desorption peaks in the NH3-TPD profiles, and to the changes in their relative intensity in response to mild hydrothermal aging (Luo et al., 2017). In this work, we have translated those findings into a sensitive laboratory diagnostic methodology for quantifying cumulative aging exposure, based on the ratio of the two NH3-TPD peaks. We have also addressed some practical aspects of applying this methodology to real-world aged samples, by decoupling the effects of sulfur poisoning and of the catalyst loading variability. The developed method yielded a simple kinetic model of the Cu/SSZ-13 catalysts hydrothermal aging, and some useful insights into the practically relevant aspects of the aging process. In particular, we have shown that the aging is cumulative, and that the sequence of the exposure steps does not matter. One other important consequence of the developed model is related to the steep temperature dependence of the aging process (Ea ≈ 168 kJ/mol). As a result, the majority of the on-engine operation exposure, typically below ∼400 °C, has no appreciable impact on the catalyst aging. In contrast, such aging is almost entirely induced by the periodic high-temperature events, such as those relate...
Source: Chemical Engineering Science - Category: Chemistry Source Type: research