NOx Trap Catalysts and Technologies: Fundamentals and Industrial Applications
Chapter 5: Mechanism and Kinetics of NOx Storage
Published:13 Jun 2018
Special Collection: 2018 ebook collection , ECCC Environmental eBooks 1968-2022Series: Catalysis Series
J. De Abreu Goes and L. Olsson, in NOx Trap Catalysts and Technologies: Fundamentals and Industrial Applications, ed. L. Lietti and L. Castoldi, The Royal Society of Chemistry, 2018, ch. 5, pp. 127-156.
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In this chapter, experimental studies and kinetic models are presented to elucidate the fundamental mechanisms for NOx storage on the NOx storage and reduction (NSR) catalysts. A well-accepted reaction pathway for NOx storage includes, as an initial step, the oxidation of NO to NO2 under lean conditions, and subsequently storage on the NOx storage sites in the form of nitrites or nitrates. NO can also be stored directly in the presence of NO and oxygen, in the so-called nitrite route. However, the NOx storage process is largely influenced by the primary gas components in the exhaust stream, such as CO2, H2O and SO2. In particular, significant attention has been focused on sulphur poisoning and the interaction of SO2 with different NSR components due to its large potential of harming NSR catalyst activity. Finally, a kinetic model describing in detail the sulphur poisoning over a commercial LNT catalyst is discussed. The model can well describe the gradual deactivation of the catalyst during sulphur exposure.