Composition/Performance Evaluation of Lean NO<sub>x</sub> Trap Catalysts for Coupling with SCR Technology
Simon Schönebaum, Jürgen Dornseiffer, Peter Mauermann, Bernd Wolkenar, Stefan Sterlepper, E. Wessel, Riza Iskandar, Joachim Mayer, Thomas E. Weirich, Stefan Pischinger, Olivier Guillon, Ulrich Simon
Abstract
Abstract The washcoat composition and the catalytic properties of two commercially available lean NO x traps (LNTs) were investigated. Both catalysts contained nominally the same NO x storage and catalytic materials but differed strongly in their amount and activity as well as in the composition of their layered washcoat architecture. In lean‐rich cycle experiments under realistic engine‐out gas compositions using a laboratory gas test bench, the LNTs showed comparable NO x storage behavior. At temperatures below 250 °C, the lean phase durations last up to 300 s until 50 % of the NO x storage capacity is reached. The simultaneously calculated NO x storage efficiencies drop rapidly below 35 %, resulting in a high NO x slip. Strong variations were observed in N 2 O and NH 3 selectivity and in CO slip during regeneration of both LNTs caused by the different oxygen storage capacity (OSC), water gas shift (WGS) activity and rhodium distribution in the catalytic layers. Based on the obtained results, proposals were made to optimize the storage and regeneration performance, leading to highly efficient LNT catalysts for coupling with a downstream SCR catalyst.