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Catalysts 2015, 5(4), 1770-1796; doi:10.3390/catal5041770

Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts

1
Earth and Environmental Engineering Department, Columbia University, 500 West 120th Street, New York, NY 10027, USA
2
BASF Corporation, Research and Development Center, 25 Middlesex Essex Tpke, Iselin, NJ 08830-0770, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Jae-Soon Choi
Received: 3 August 2015 / Revised: 30 September 2015 / Accepted: 9 October 2015 / Published: 23 October 2015
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
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Abstract

The rhodium (Rh) component in automotive three way catalysts (TWC) experiences severe thermal deactivation during fuel shutoff, an engine mode (e.g., at downhill coasting) used for enhancing fuel economy. In a subsequent switch to a slightly fuel rich condition, in situ catalyst regeneration is accomplished by reduction with H2 generated through steam reforming catalyzed by Rh0 sites. The present work reports the effects of the two processes on the activity and properties of 0.5% Rh/Al2O3 and 0.5% Rh/CexOy-ZrO2 (CZO) as model catalysts for Rh-TWC. A very brief introduction of three way catalysts and system considerations is also given. During simulated fuel shutoff, catalyst deactivation is accelerated with increasing aging temperature from 800 °C to 1050 °C. Rh on a CZO support experiences less deactivation and faster regeneration than Rh on Al2O3. Catalyst characterization techniques including BET surface area, CO chemisorption, TPR, and XPS measurements were applied to examine the roles of metal-support interactions in each catalyst system. For Rh/Al2O3, strong metal-support interactions with the formation of stable rhodium aluminate (Rh(AlO2)y) complex dominates in fuel shutoff, leading to more difficult catalyst regeneration. For Rh/CZO, Rh sites were partially oxidized to Rh2O3 and were relatively easy to be reduced to active Rh0 during regeneration. View Full-Text
Keywords: automotive three way catalysts (TWC); Rh/Al2O3; Rh/CexOy-ZrO2; fuel shutoff aging; catalyst deactivation; fuel rich regeneration; metal-support interaction automotive three way catalysts (TWC); Rh/Al2O3; Rh/CexOy-ZrO2; fuel shutoff aging; catalyst deactivation; fuel rich regeneration; metal-support interaction
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Zheng, Q.; Farrauto, R.; Deeba, M.; Valsamakis, I. Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al2O3 and Rh/CexOy-ZrO2 as Model Catalysts for Automotive Three Way Catalysts. Catalysts 2015, 5, 1770-1796.

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