Chapter 7: Mechanistic Aspects of the Reduction of the Stored NO_x by H₂ Investigated by Isotopic Labelling Experiments and FTIR Spectroscopy

The chapter is focused on the reduction process operating on a LNT model catalyst, with the aim of shedding light on fundamental aspects related to the mechanisms of stored NO_x release, of released NO_x reduction and of the formation of the various reduction products. This overview is the result of fundamental systematic studies obtained by means of catalytic tests under nearly isothermal conditions over a model Pt–Ba/Al₂O₃ catalyst where the attention is focused on the reactivity of the active sites. The gas phase analysis was combined with the surface species characterization performed by operando FT-IR spectroscopy. The results of dedicated experiments in which labeled ¹⁵NO species have been used are also reported, aiming at a better understanding of the reaction mechanisms leading to the formation of N₂.