Effect of Ageing Atmosphere on Three-way Catalytic Performance of Supported Rh Catalysts

Abstract

Deactivation of a mixture of Rh/Al 2 O 3 and CeO 2 _ ZrO 2 (CZ) by high-temperature ageing was clearly observed in three-way catalytic reactions under lean/rich perturbation conditions. The light-off temperature at which 50 % conversion was achieved was increased in the order of fresh ＜ stoichi. ≈ rich ＜ rich/lean ＜ lean ageing conditions. Rh dispersion and presence of isolated Rh sites, revealed from in-situ FT-IR spectroscopy following CO adsorption, were responsible for the high light-off activity. NO conversion in higher temperature regions under lean/rich perturbation conditions was influenced by the ageing atmosphere. H 2 -TPR measurements suggested the formation of Rh _ CZ interactions with different strengths depending on the atmosphere during high-tempera-ture ageing. The strength of the Rh _ CZ interaction was suspected to be important to achieve high NO conversion in higher temperature regions.