CO₂ capture and methanation using Ru/Na₂O/Al₂O₃ dual-function materials: Effect of support synthesis method and Ru load

Ru/Na₂O/Al₂O₃ dual-function materials were prepared by varying the support synthesis method and Ru load. Different sol-gel-type and precipitation/ hydrothermal preparation methods were employed in order to synthesize materials with variable nanostructure, surface chemistry and textural properties, thereby effectively tuning the material activity for the methanation of pre-adsorbed CO₂. The materials were thoroughly characterized and evaluated during the integrated CO₂ capture and methanation process. It was found that the Pechini sol-gel synthesis method led to the structure with the highest porosity, basic site population and high dispersion of methanation and adsorption active Ru⁰ and Al-O^--Na⁺ sites. The corresponding material displayed the highest CH₄ yield (0.47 mmol/g) and fastest CH₄ production kinetics, while stable performance was achieved under successive adsorption-hydrogenation cycles and under the co-presence of O₂ and H₂O during CO₂ adsorption. Lastly, the increase in Ru load (0.25 wt% - 4 wt% range) could incrementally improve the CH₄ production kinetics during hydrogenation.