Deactivation Mechanism of Pd Only Three-way Catalysts under Aging Temperature Gradient

doi:10.15541/jim20250396

Abstract

Abstract: Pd/CZA catalyst composed of third-generation oxygen storage material CeO₂-ZrO₂-Al₂O₃ (CZA) loaded only with Pd represents a practical three-way catalyst (TWC) owing to its exceptional pollutant conversion efficiency and sintering resistance. Although the thermal degradation mechanism of Pd-based TWC has been confirmed to be closely associated with Pd sintering and the weakening of metal-support interaction (MSI), a systematic investigation into its thermal aging behavior under an extreme high temperature gradient remains necessary. A series of Pd/CZA catalysts aged at 800-1000 ℃ were prepared in this study and their thermal degradation was systematically explored, presenting a pioneering investigation into the evolution pattern of the microchemical state of Pd with aging temperature gradient. The correlation among the microchemical state of Pd, MSI and aging resistance was evaluated through different characterization techniques. The results showed that catalytic activity exhibited a nonlinear decay with increasing aging temperature. Catalytic performance declined sharply in the range of 850-900 ℃, with increases of 26-40 ℃ and 39-67 ℃ for T₅₀ and T₉₀ (the temperatures at which the pollutant conversions are 50% and 90%, respectively) of carbon monoxide (CO), nitric oxide (NO) and hydrocarbon (HCs), while showed little variation within the range of 900-1000 °C. The underlying reason for this sharp decline in activity is an abrupt transformation in the microchemical state of Pd. When the aging temperature increases to 900 °C, the Pd-O-Ce bond is weakened, which compromises the MSI. Consequently, Pd particles become unanchored, undergo rapid sintering and growth, and exhibit diminished capabilities for adsorbing and activating both reactants and oxygen.

Key words: temperature gradient, thermal aging, Pd-O-Ce bond, metal-support interaction, three-way catalyst

CLC Number:

O643

LIU Xuzi, SONG Zhaohua, ZENG Lu, QU Li, JIAO Yi, JIANG Fajun, LI Dacheng, YAN Huicheng, WANG Jianli, CHEN Yaoqiang. Deactivation Mechanism of Pd Only Three-way Catalysts under Aging Temperature Gradient[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250396.

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