期刊
APPLIED CATALYSIS B-ENVIRONMENTAL
卷 258, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.apcatb.2019.118032
关键词
Cold start; Engine emissions; Passive NOx adsorber; NOx storage; Catalyst deactivation; Palladium zeolite catalyst
资金
- Department of Energy, Vehicle Technologies Office [DE- EE0008233]
Passive NOx adsorbers (PNAs) are a proposed solution for cold start NOx emissions, via low temperature NOx trapping and subsequent release at a temperature where downstream NOx reduction catalysts are active. Pd/zeolites have been reported to have significant NOx storage capacities. However, their real exhaust compatibility has not been completely evaluated. In this work, Pd/BEA was used to study the mechanism of an observed PNA degradation. NO adsorption, NO and CO co-adsorption and temperature programmed desorption/oxidation were performed on a series of differently aged Pd/BEA catalysts to evaluate the NOx storage capacity and desorption temperature. An irreversible NOx storage degradation mode caused by low temperature CO exposure was observed. H-2 temperature programmed reduction results indicate this irreversible degradation can be attributed to the loss of Pd2+. Additionally, STEM images revealed Pd particle migration/agglomeration after hydrothermal aging and CO/H-2 exposure. Larger particles, formed during CO exposure, lead to the irreversible degradation.
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