A non-NH 3 pathway for NO x conversion in coupled LNT-SCR systems

Jin Wang, Yaying Ji, Zhengwang He, Mark Crocker, Mark Dearth, Robert W. McCabe

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


NO x storage-reduction experiments were performed using a coupled LNT-SCR system consisting of a low-precious metal loaded Pt/Rh LNT catalyst and a commercial Cu-zeolite SCR catalyst. Cycling experiments revealed that when a CO+H 2+C 3H 6 mixture or C 3H 6 by itself was used as the reductant, the NO x conversion over the SCR catalyst exceeded the conversion of NH 3 over the same catalyst. This is explained by the presence of propene, which slipped through the LNT catalyst and reacted with the LNT NO x slip. Separate experiments, conducted under continuous flow and lean-rich cycling conditions, confirmed the ability of propene, as well as ethene, to function as a NO x reductant over the SCR catalyst. Cycling experiments also revealed that the SCR catalyst was able to store propene, such that NO x reduction by stored propene continued into the lean phase (after the switch from rich conditions). According to adsorption experiments, significant co-adsorption of NH 3 and propene occured in the SCR catalyst, while under lean-rich cycling conditions the contributions of NH 3 and C 3H 6 to NO x conversion were found to be essentially additive. These findings suggest that under actual driving conditions, NO x reduction by non-NH 3 reductants (olefins and possibly other hydrocarbons) in the SCR catalyst can contribute to the mitigation of lean and rich phase NO x.

Original languageEnglish
Pages (from-to)562-570
Number of pages9
JournalApplied Catalysis B: Environmental
StatePublished - Jan 12 2012


  • Hydrocarbon
  • Lean NO trap
  • NO storage/reduction catalyst
  • SCR

ASJC Scopus subject areas

  • Catalysis
  • Environmental Science (all)
  • Process Chemistry and Technology


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