Integrated CO₂ capture and methanation from the intermediate-temperature flue gas on dual functional hybrids of AMS/CaMgO||Ni_xCo_y

The integrated CO₂ capture and conversion (iCCC) technology has caused more and more interests for the Carbon Neutrality as it can make full use of the heat of high-temperature or intermediate-temperature flue gas to achieve efficient CO₂ chemical utilization, avoiding additional costs for CO₂ transportation and producing value-added chemicals. Herein, we developed the dual functional adsorbent||catalyst hybrids of alkali metal salts (AMS)/CaMgO||Ni_xCo_y for the integrated CO₂ capture and methanation (iCCC-methanation) at the intermediate temperature of 350 °C. By loading alkali metal salts into porous CaMgO composites, the AMS/CaMgO shows a stable CO₂ adsorption performance with an excellent saturated capacity of 12.8 mmol g⁻¹ at 350 °C. Meanwhile, CO₂ and H₂ can be simultaneously activated on the catalytic active sites of Co and Ni on the bimetal Ni_xCo_y alloy catalysts for the efficient methanation. After the temperature matching between CO₂ capture and conversion, an excellent iCCC-methanation performance with the CO₂ conversion efficiency near 93.4 % and CH₄ selectivity of 88 % are achieved in one dual-bed column at 350 °C. More importantly, the products selectivity between CH₄ and CO can be modulated by altering the packing configurations of sorbent/catalyst in the fixed-bed column, such as the dual-bed mode, multilayer mode, and physical mixing mode. Based on the elementary consecutive dynamic law, we revealed that the distance between the adsorption site and catalytic site plays a critical role for the CO₂ hydrogenation. The superior performance of this iCCC-methanation demonstrates the importance of the synergistic promotions between the CO₂ capture and in-situ conversion, as well as its promising application in CO₂ emission control.