Ceria-silica mesoporous catalysts for CO preferential oxidation in H2-rich stream: The effect of Ce:Si ratio and copper modification

In this work mesoporous CeO2-SiO2 catalysts with the Ce:Si molar ratios of 1:1 and 4:1 were synthesized by template method and modified with copper to elucidate the role of copper-ceria and ceria-silica interactions in the catalyst efficiency in CO-PROX. The catalysts were characterized by SEM-EDS, AAS, XRD, TPR-H2, TEM, and spectroscopic methods (Raman, EPR and in situ DRIFT of adsorbed CO). The binary catalyst with the equimolar Ce:Si ratio demonstrated better catalytic performance in CO-PROX due to its favorable textural properties and strong ability to anion vacancy formation as confirmed by N2 physisorption and Raman spectroscopy. CuOx/ CeSiOy (Ce:Si = 4:1) demonstrated better low-temperature activity, CO2 selectivity and stability than CuOx/ CeSiOy (Ce:Si = 1:1) and both binary systems because of its unique structure, comprising fine CeO2 particles with a narrow size distribution of 2-3 nm well dispersed on a large surface area, high concentration of the most active in CO oxidation Cu+ sites, formed on CuOx-CeO2 interfaces, and improved ability to surface reoxidation after reduction with the reagents resulted in the decreased Ce3+ concentration. It was also stable in the presence of CO2 and H2O in the reaction mixture. These properties would be difficult to achieve via template preparation methods without SiO2 addition.

Automated summary

This study focused on the synthesis and characterization of mesoporous CeO2-SiO2 catalysts with different Ce:Si ratios, as well as the addition of copper for modification, to understand their effects on CO-PROX reactions. The catalyst with an equimolar Ce:Si ratio showed better catalytic performance, while CuOx/CeSiO (Ce:Si=4:1) exhibited superior low-temperature activity, CO2 selectivity, and stability due to its unique structure and properties.