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NOx storage and reduction in model lean NOx trap catalysts studied by in situ DRIFTS

Paper ID Volume ID Publish Year Pages File Format Full-Text
47743 46481 2009 10 PDF Available
Title
NOx storage and reduction in model lean NOx trap catalysts studied by in situ DRIFTS
Abstract

NOx storage and reduction on a model Pt/BaO/Al2O3 catalyst was studied by means of in situ DRIFTS measurements. To examine the effect of ceria addition, experiments were also conducted using Pt/BaO/Al2O3 to which Pt/CeO2 was added as a physical mixture in a 74:26 weight ratio. For the former catalyst, DRIFT spectra acquired during NO/O2 and NO2/O2 storage indicated the formation of nitrite at 200 °C during the initial stages of adsorption, while increasing the adsorption temperature appeared to facilitate the oxidation of nitrite to nitrate. The ceria-containing catalyst afforded similar DRIFT spectra under these conditions, although the presence of cerium nitrates was observed at 200 and 300 °C, consistent with NOx storage on the ceria phase. DRIFT spectra acquired during NOx reduction in CO and CO/H2 showed that Ba nitrate species remained on the surface of both catalysts at 450 °C, whereas the use of H2-only resulted in complete removal of stored NOx. The observation of Ba carbonates when CO was present suggests that the inferior reduction efficiency of CO may arise from the formation of a crust of BaCO3 on the Ba phase, which inhibits further NOx reduction. DRIFT spectra acquired during lean-rich cycling (6.5 min lean, 1.0 min rich) with CO/H2 as the rich phase reductants revealed that a significant concentration of nitrates remained on the catalysts at the end of the rich phase. This implies that a large fraction of nitrate is not decomposed during cycling and thus cannot participate in NOx abatement through storage and regeneration.

Keywords
DRIFTS; IR spectroscopy; Lean NOx trap; NOx adsorber catalyst; Ceria
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NOx storage and reduction in model lean NOx trap catalysts studied by in situ DRIFTS
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 91, Issues 1–2, 7 September 2009, Pages 329–338
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