Sintering-resistant CuO/CeO2 catalysts prepared via the reversed impregnation method for ethyl acetate oxidation

Abstract

Developing a conventional preparation method for highly sintering-resistant catalysts without compromising their performance remains a significant challenge. Herein, a facile approach of reversed impregnation (RI) method was adopted to prepare CuO/CeO₂ catalysts. Among the prepared catalysts, the 5N/A-500 catalyst exhibited the best catalytic performance, achieving 100% conversion of ethyl acetate (EA) at 220 °C (T₁₀₀). Additionally, the 5N/A-500 catalyst possessed the highest content of Cu–O–Ce structures and oxygen vacancies, facilitating stronger lattice oxygen mobility and adsorption oxygen activation ability. Importantly, the 5N/A catalyst displayed superior thermal stability against high-temperature treatment. After treatment at 800 °C for 4 h, the T₁₀₀ of the 5N/A-800 catalyst only increased to 230 °C. Conversely, the T₁₀₀ of the IM-800 catalyst drastically increased from 280 to 350 °C. Interestingly, the 5N/A-500 catalyst formed a unique structure, where CuO particles were highly confined within the layered CeO₂ nanosheets, resulting in high thermal stability with spatial confinement effect. Furthermore, the immobilization of CuO particles through interactions with the CeO₂ nanosheets limited the aggregation and growth of both the CuO particles and CeO₂ nanosheets at high temperatures. Moreover, sintering resistance was further improved by restricting the migration and aggregation of Cu ions through the high content of Cu–O–Ce structures. Moreover, the 5N/A-500 catalyst exhibited excellent water resistance, with no increase in T₁₀₀ in the presence of ≤3.0% H₂O. Finally, the roles of adsorbed oxygen and lattice oxygen in the EA reaction mechanism on the 5N/A-500 catalyst were revealed, and the EA oxidation pathway was proposed.