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Activity and thermal stability of Rh-based catalytic system for an advanced modern TWC

Paper ID Volume ID Publish Year Pages File Format Full-Text
46178 46433 2012 13 PDF Available
Title
Activity and thermal stability of Rh-based catalytic system for an advanced modern TWC
Abstract

The catalytic activity and thermal durability of Rh supported on a variety of metal oxides for removing NOx in the three-way catalyst (TWC) converter have been investigated under realistic gasoline engine exhaust conditions. Among the Rh/metal oxide catalysts examined, the Rh/ZrO2 catalyst has the best thermal durability. The catalytic activity and thermal stability of the Rh/ZrO2 catalysts have shown strong dependence on the ZrO2 support employed, with the ZrO2 prepared by the sol–gel (SG) and precipitation (P) methods exhibiting the most favorable catalytic performance. The improved TWC performance and thermal stability of the Rh/ZrO2 (SG and P) catalysts compared to other Rh/ZrO2 catalysts are mainly due to the structural difference in the underlying ZrO2 supports. Both ZrO2 (P) and ZrO2 (SG) contain the tetragonal as well as the monoclinic phase of ZrO2, whereas the others are primarily in the monoclinic phase. Deactivation of the Rh/ZrO2 upon thermal aging is mainly caused by the loss of the active metal surface area of Rh due to sintering and/or burial of Rh into the sublattice of ZrO2. The strong interaction of Rh with the tetragonal phase of ZrO2 appears to prevent the burial of Rh into ZrO2 lattice during the thermal aging. A series of comparative kinetic experiments revealed that the Rh/ZrO2 (SG and P) catalysts among other Rh/metal oxide catalysts produce the least amount of harmful NH3, which can be subsequently oxidized to hazardous NOx over the Pd-based oxidation catalyst co-existing in the TWC converter. A dual-brick monolith system washcoated with Rh/ZrO2 (P) and Pd/Al2O3 in the front and the rear bricks, respectively, has shown superior thermal durability over monolith configurations investigated in the present study.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlight► ZrO2 is a promising support for preparing a thermally stable Rh TWC. ► The sintering and burial of Rh are primary causes for the catalyst deactivation. ► Rh-tetragonal ZrO2 interaction prevents a burial of Rh into ZrO2 support.

Keywords
TWC; Rh/ZrO2; Catalyst deactivation; NH3 formation; TWC monolith
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Activity and thermal stability of Rh-based catalytic system for an advanced modern TWC
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 121–122, 13 June 2012, Pages 75–87
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