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

Qinghe Zheng²  Robert Farrauto²  Michel Deeba¹  Ioannis Valsamakis² 

[1] BASF Corporation, Research and Development Center, 25 Middlesex Essex Tpke, Iselin, NJ 08830-0770, USA; E-Mail:;Earth and Environmental Engineering Department, Columbia University, 500 West 120th Street, New York, NY 10027, USA; E-Mails:

关键词: automotive three way catalysts (TWC);    Rh/Al₂O₃;    Rh/Ce_xO_y-ZrO₂;    fuel shutoff aging;    catalyst deactivation;    fuel rich regeneration;    metal-support interaction;   

DOI  :  10.3390/catal5041770

来源: mdpi

【 摘 要 】

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/Ce_xO_y-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.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.