Rare earth oxide promoted Ru/Al2O3 dual function materials for CO2 capture and methanation: An operando DRIFTS and TGA study

Abstract

Dual-function materials (DFMs) combine sorbent and catalytic components to perform selective CO capture and subsequent hydrogenation. This study explores the performance of rare-earth oxides (REOs) as CO adsorption sites on Ru/AlO. REOs increase CO uptake by upwards of +60 % by enhancing the overall catalyst surface basicity and favoring metal–support interactions. Thermogravimetric analysis during CO adsorption-hydrogenation cycles exhibited significant catalytic activity and enhanced stability of Ru-REO/AlO at temperatures as low as 200 °C. This leads to methane production of 50–85 µmol g, surpassing recently reported values obtained for alkali and alkali-earth promoted Ru-based materials operated at 250 °C. The highest performing studied DFM, RuNdO/AlO, achieved 85 % CO capture efficiency and steadily produced methane in cyclic operation (+120 % CO uptake relative to Ru/AlO). DRIFTS revealed that the dominant mechanism for methane formation is the hydrogenation of ruthenium carbonyls, which are stabilized by REOs. Upon CO exposure, surface carbonates and bicarbonate species form more abundantly on DFMs than on Ru/AlO. This confirms that REOs enhance the adsorption and retention of carbonates, which generate additional promoter-related reaction pathways during low-temperature hydrogenation. These findings are crucial in the advancement of sustainable, wider operation range carbon capture and utilization technologies.