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The impact of aging environment on the evolution of Al2O3 supported Pt nanoparticles and their NO oxidation activity

Paper ID Volume ID Publish Year Pages File Format Full-Text
46001 46428 2013 11 PDF Available
Title
The impact of aging environment on the evolution of Al2O3 supported Pt nanoparticles and their NO oxidation activity
Abstract

The impact of the aging environment on the size, morphology and distribution of Pt nanoparticles supported on Al2O3 and on their NO oxidation activity is studied. To this end, the fresh catalyst Pt/Al2O3 (Pt/Al/F) is aged under different aging environments mimicking the aging process of a real diesel oxidation catalyst (DOC) including phosphorus (P) poison as a chemical contaminant. These catalysts are characterized by N2-physisorption, CO chemisorption, XRD, solid state 27Al MAS NMR, HAADF-STEM, HR-TEM, EDX analyses and CO-DRIFTS. The characterization results reveal that the thermal aging in air at 800 °C leads to a heterogeneous size and spatial distribution of Pt nanoparticles in the catalyst (Pt/Al/O). The morphology is mainly limited to truncated cubic structures that are dominated with (1 0 0) crystal facets. Differently, aging in a lean diesel exhaust environment (Pt/Al/R) restricts the extensive Pt particle growth, size distribution to narrow and morphology predominantly to cuboctahedral that contains both (1 1 1) and (1 0 0) planes, though the former tends to dominate the surface. P seems to control both the growth of Pt particles and the morphology that is mainly limited to spherical irrespective of the aging environment (P/Pt/Al/O or P/Pt/Al/R). The normalized (per surface Pt atoms) forward rate constant of NO oxidation and the corresponding activation energy are determined for the differently treated catalysts and compared them with those reported in previous relevant studies. From these results it is evident that the reaction is indeed structure sensitive. The catalyst treated in lean diesel exhaust environment (Pt/Al/R) presents the best activity followed by the fresh Pt/Al/F and thermally Pt/Al/O aged catalysts. The difference in the NO oxidation activity of the catalysts is attributed to the morphology of Pt nanoparticles. These results correlate very well with the real DOC monolith that was aged on a heavy duty small truck for 250 h under different driving profiles.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The evolution of Pt nanoparticles supported on alumina is sensitive to the aging environment. ► NO oxidation is structure sensitive. ► Cuboctahedral Pt nanoparticles show better activity than spherical and truncated cubic structures.

Keywords
Diesel oxidation catalyst; Aging environment; Thermal aging; Chemical aging; Phosphorus poison; Pt nanoparticles; Particle size; Particle morphology; NO oxidation; Structure sensitivity
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The impact of aging environment on the evolution of Al2O3 supported Pt nanoparticles and their NO oxidation activity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 129, 17 January 2013, Pages 214–224
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