Insights into the cyclic CO2 capture and catalytic methanation over highly performing Li-Ru/Al2O3 dual function materials

The combined CO2 capture and in-situ methanation using renewable hydrogen over dual function sorbent-catalyst materials is a chemical looping process with strong potential to increase the efficiency and reduce the cost of current CCU technologies. In this work, we set out to develop highly performing Lithium-Ruthenium/Al2O3 investigating synergic and mechanistic aspects involved in the alternate CO2 adsorption and hydrogenation phases. Catalysts with low Ru loading (max 1% wt.) and fixed dispersion on Al2O3 spheres were promoted with variable amounts of Li (1-5% wt.) and characterized by BET, PSD, XRD, H2 chemisorption, CO2-TPD, TG-MS, H2-TPSRx and CO2 catalytic methanation under continuous flow conditions. Transient CO2 storage/methanation cycles were studied in a fixed bed reactor that was operated at several temperature levels (250-350 °C) with alternate feed conditions of variable duration. The cycled CO2 adsorption and methanation were also investigated by in-situ DRIFT comparing results for xLi-Ru/Al2O3 materials against the reference Ru/Al2O3 catalyst. The favourable synergism existing at the nanoscale between the Li-aluminate sorbent phase and the catalytic Ru sites enhances the intrinsic activity of the DFMs that can guarantee high methane productivity and selectivity with low noble metal loadings.