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New insights on N2O formation pathways during lean/rich cycling of a commercial lean NOx trap catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
54717 47023 2014 10 PDF Available
Title
New insights on N2O formation pathways during lean/rich cycling of a commercial lean NOx trap catalyst
Abstract

•N2O formation investigated during regeneration of a commercial LNT catalyst.•Spatiotemporally resolved gas measurements (SpaciMS), surface analysis (DRIFTS).•Secondary N2O peak indicates incomplete reduction of the catalyst.•Adsorbed NH3, CO and/or isocyanates contribute to secondary N2O formation.•Presence of CO2 inhibits regeneration by H2, forming CO on Pt sites.

Pathways for N2O formation during lean/rich cycling of a commercial LNT catalyst (containing Pt, Pd, Rh as well as Ba, CeZr, MgAl and Al oxides) were investigated based on bench-reactor experiments with spatiotemporally resolved gas measurements (SpaciMS) and in situ surface analysis (DRIFTS). The inlet gas temperature, composition of the rich gas mixture and regeneration length were varied in order to reveal the underlying mechanisms. Particular attention was given to low temperatures where the regeneration was kinetically limited and N2O was emitted in two peaks. The primary N2O peak appeared immediately after rich-phase inception when platinum-group-metal (PGM) sites over which NOx reduction took place were only partially reduced, and tailed off with the breakthrough of the reductant front. The secondary N2O peak appeared at the rich-to-lean transition as a result of reactions between surface-deposited reductive species (NH3, CO and/or isocyanates) and residual stored NOx. Therefore, more thorough regeneration (longer rich phase, more efficient reductant, or higher temperature) led to a reduced secondary N2O peak. In contrast, CO either produced from reverse water gas shift or injected as a feed could poison PGM sites resulting in self-inhibition of the regeneration and a subsequent significant secondary N2O peak.

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Keywords
Lean NOx trap; NOx storage catalyst; NOx reduction; N2O formation; Isocyanates; Exhaust gas aftertreatment
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New insights on N2O formation pathways during lean/rich cycling of a commercial lean NOx trap catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 231, 1 August 2014, Pages 145–154
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us