Impact of thermal and vehicle aging on the structure and functionalities of a lean NOx-trap

Investigations of the aging behaviour of a commercial lean NOx trap (LNT) are reported in this paper. Two aging processes were tested and compared: a hydrothermal aging at 800 °C and a vehicle aging corresponding to a 80,000 km use. Samples were characterized with Operando FTIR, XRF, XRD, SEM-EDX, TEM, and BET analyses. LNT functionalities were evaluated using a flow reactor capable of performing NOx storage and conversion measurements, and correlated with the LNT structure evolution due to aging. The results highlighted that Pt sintering had an impact on the NO oxidation functionality and also deteriorated the Pt/Ba interface. It was hence partly responsible for the NSC decrease. Both aging processes had a similar impact on the LNT NOx storage capacity (NSC) although their structural evolutions were different: BaAl2O4 formation on the hydrothermal aged catalyst versus barium poisoned by sulphur on the vehicle aged catalyst.