| Autor: |
Moushumy, Zannatul Mumtarin, Takeuchi, Marina, Tsushida, Masayuki, Awaya, Keisuke, Yoshida, Hiroshi, Ohyama, Junya, Machida, Masato |
| Zdroj: |
Catalysis Science & Technology; 2024, Vol. 14 Issue: 20 p5874-5884, 11p |
| Abstrakt: |
A Cu oxide catalyst supported on γ-Al2O3(Cu/A) is a promising candidate for substituting platinum group metals in automotive three-way catalysts (TWCs). Cu/A can be used by mixing with a Pd catalyst supported on γ-Al2O3(Pd/A). In this study, the effect of thermal aging on the nanostructure and TWC performance of the physically mixed powder catalyst (Pd/A + Cu/A) was investigated under different environments, that is, simulated exhaust gas mixtures dynamically fluctuating among stoichiometric, fuel-lean, and fuel-rich (SLR) compositions, compared with static fuel-lean (L) and air at 600–900 °C. The observed thermal deactivation was strongly dependent on aging atmosphere, and it increased in the sequence air < L < SLR with increasing aging temperature. Characterization studies showed Pd–Cu alloying in most deactivated SLR-aged catalysts in contrast to air-aged catalysts, which consisted of Pd oxide dispersed on the Cu2+-incorporated γ-Al2O3phase. During SLR aging, some of the incorporated Cu2+species migrated to the surface, reduced to the metallic state, and immediately reacted with Pd metal to form a Pd–Cu random alloy with face-centered cubic structure. This phenomenon severely deteriorated the NO reduction activity because the Pd surface enriched with Cu lacks NO dissociation ability. Therefore, the observed deactivation was more evident for NO reduction than C3H6oxidation but was nearly negligible for CO oxidation because Cu2+-incorporated γ-Al2O3exhibited high CO oxidation activity superior to that of Pd catalysts. Deactivation viaPd–Cu alloying was inevitable even in air- and L-aged catalysts when repeating the TWC light-off experiment under a stoichiometric gas mixture. |
| Databáze: |
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