Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

Catalysts

Qinghe Zheng¹  Robert Farrauto¹  Michel Deeba² 

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

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

DOI  :  10.3390/catal5041797

来源: mdpi

【 摘 要 】

The Pd component in the automotive three way catalyst (TWC) experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C–1050 °C) air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al₂O₃ and 3% Pd/Ce_xO_y-ZrO₂ (CZO) as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-Ce_xO_y interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I), reduction via in situ steam reforming (SR) of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al₂O₃, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd⁺/Pd⁰ and Ce³⁺/Ce⁴⁺ couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al₂O₃. A suggestion is made for improving the catalyst performance.

【 授权许可】

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