Redox properties and metal–support interaction of Pd/Ce0.67Zr0.33O2–Al2O3 catalyst for CO, HC and NOx elimination

Abstract

Abstract Ce 0.67 Zr 0.33 O 2 , Ce 0.67 Zr 0.33 O 2 –Al 2 O 3 and γ-Al 2 O 3 supported Pd catalysts (designated as Pd/CZ, Pd/CZA and Pd/Al 2 O 3 ) have been characterized by XRD, CO chemisorption, in situ DRIFTS, XPS, HRTEM, H 2 -TPR, O 2 -TPSR and catalytic performance test. The results show that the small PdO x particles dispersed in CZ would promote the conversion of HC, CO and NO 2 , while the PdO x particles dispersed in Al 2 O 3 promote the conversion of NO in the light-off process. PdO x species mainly disperse on Al 2 O 3 -rich grains surface for fresh Pd/CZA catalyst, but easily migrate onto CZ-rich grains surface due to the strong interaction between Pd and ceria-based oxide under high temperature reaction conditions. And it promotes the thermal stability of PdO species and resilience of Pd 0 to PdO, therefore enhances the catalytic performance for HC, CO and NO x elimination. Meanwhile, the interaction between CZ and Al 2 O 3 can be enhanced after aging treatment, resulting in increasing the thermal stability of Pd/CZA catalyst.