Measures to reduce the N2O formation at perovskite-based lean NOx trap catalysts under lean conditions

Sabrina I. Ecker*, Jürgen Dornseiffer, Stefan Baumann, Olivier Guillon, Henny J.M. Bouwmeester, Wilhelm A. Meulenberg

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)
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Abstract

The net oxidising atmosphere of lean burn engines requires a special after-treatment catalyst for NOx removal from the exhaust gas. Lean NOx traps (LNT) are such kind of catalysts. To increase the efficiency of LNTs at low temperatures platinised perovskite-based infiltration composites La0.5Sr0.5Fe1-xMxO3-δ/Al2O3 with M = Nb, Ti, Zr have been developed. In general, platinum based LNT catalysts show an undesired, hazardous formation of N2O in the lean operation mode due to a competing C3H6-selective catalytic reduction (SCR) at the platinum sites. To reduce N2O emissions an additional Rh-coating, obtained by incipient wetness impregnation, besides the Pt coating and a two-layered oxidation catalyst (2 wt.% Pd/20 wt.% CeO2/alumina)-LNT constitution, has been investigated. Though the combined Rh-Pt coating shows a slightly increased NOx storage capacity (NSC) at temperatures above 300C, it does not decrease N2O formation. The layered oxidation catalyst-LNT system shows a decrease in N2O formation of up to 60% at 200C, increasing the maximum NSC up to 176 µmol/g. Furthermore, the NSC temperature range is broadened compared to that of the pure LNT catalyst, now covering a range of 250–300C.

Original languageEnglish
Article number917
JournalCatalysts
Volume11
Issue number8
DOIs
Publication statusPublished - Aug 2021

Keywords

  • CH-SCR (selective catalytic reduction)
  • Layered catalyst constitution
  • Lean NO trap (LNT)
  • NO formation
  • Precious metal (Pt, Rh, Pd)
  • UT-Gold-D

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