CO2 Methanation Of Co/CeO2 Prepared by Wetness Impregnation of Co on Flame-Synthesized CeO2

Abstract

A set of Co/CeO₂ catalysts with varying Co loading was prepared by wet impregnation of Co onto flame-synthesized CeO₂ and tested in CO₂ methanation. At low Co loading (2.5 mol.%), Co existed as Co²⁺ ions strongly interacting with CeO₂, which remained unreduced at 300 °C. This population of highly dispersed Co²⁺ (∼2.5 mol.%) was constant across all catalysts. Higher Co loadings (5 and 10 mol.%) led to segregated Co₃O₄ nanoparticles (∼2–2.5 nm), which partially reduced to metallic Co nanoparticles (2.5 – 3 nm) at 300 °C. At low Co content, the impregnated catalysts mainly produced CO at a low CO₂ conversion, while catalysts ≥ 5 mol% Co favored CH₄ formation with minor CO and C₂H₆ by-products. Under CO hydrogenation, these samples showed high selectivity toward olefins and oxygenates (86%) and low CH₄ selectivity. All catalysts experienced deactivation during CO and CO₂ hydrogenation, attributed to carbon deposition on Co nanoparticles. The highly dispersed Co²⁺ and small Co clusters were more resistant to deactivation and selective for CO production. Oxidative regeneration effectively removed carbon deposits and restored initial activity. These results highlight the influence of Co dispersion and particle size on product selectivity and catalyst stability during CO₂ hydrogenation.