Highly selective catalytic hydrogenation conversion of CO2 to CO over lanthanum-doped supported ruthenium catalysts

Abstract

The selective catalytic hydrogenation of CO₂ to CO via the RWGS reaction is an effective avenue for resource utilization of CO₂. In this study, we prepared serial La₂O₃-doped Ru catalysts (i.e., RuLa/SBA-15) using a facile sequential impregnation method, and applied it for the selective hydrogenation conversion of CO₂ into CO. The La₂O₃ doping remarkably promotes the dispersion of Ru nanoparticles and induces the formation of electron-deficient Ru species (Ruⁿ⁺). In-situ DRIFTS study reveals that the hydrogenation of CO₂ over Ru catalysts with and without La₂O₃ doping proceeds through different pathways. Both CO and CH₄ are formed on non-doped Ru/SBA-15 with formate as the key intermediate, but only CO is generated on RuLa/SBA-15 via carbonate as the intermediate because of the weakened CO adsorption on Ruⁿ⁺. Thus, RuLa/SBA-15 exhibits outstanding CO selectivity for the hydrogenation of CO₂ without significant decline of activity. It achieves a CO₂ conversion of 51 % at 600 °C and nearly 100 % of CO selectivity across the examined reaction temperature of 300–600 °C, surpassing the performances of the non-doped counterpart (CO₂ conversion of 58 % at 600 °C and CO selectivity ranging from 2 %-63 %). This study provides a facile and cost-effective strategy to tune the structure of Ru catalysts for the hydrogenation conversion of CO₂ to obtain value-added products.