Effect of CO 2 adsorbents on the Ni‐based dual‐function materials for CO 2 capturing and in situ methanation

The present work studied the effect of different carbon dioxide (CO 2 ) adsorbents on Ni‐based dual‐function materials (DFMs) for the development of carbon capture and on‐site utilization in a reactor at isothermal condition. The DFMs containing Ni functioning as a methanation catalyst with various CO 2 adsorbents (i.e., CaO, MgO, K 2 CO 3 , or Na 2 CO 3 ) were prepared on γ‐Al 2 O 3 through sequential impregnation. The result indicated that Ni‐Na 2 CO 3 /γ‐Al 2 O 3 had the highest methanation capacity (i.e., 0.1783 mmol/g) and efficiency (i.e., 71.09%) in the CO 2 adsorption–methanation test. The CO 2 uptake and the subsequent methanation capacity of the Ni‐Na 2 CO 3 /γ‐Al 2 O 3 increased to more than 24 times and more than 17 times, respectively, compared to Ni/γ‐Al 2 O 3 . The high methanation capacity was correlated to its highest amount of weak basic sites, substantial CO 2 capture capacity and capture/release efficiency, and reactivity to H 2 at a lower temperature, supported by CO 2 ‐TPD, TGA analyses for adsorption or adsorption–desorption at the isothermal condition, and H 2 ‐TPRea, respectively. A continuous cyclic CO 2 adsorption–methanation was performed by using the Ni‐Na 2 CO 3 /γ‐Al 2 O 3 and Ni‐CaO/γ‐Al 2 O 3 , showing that the CO 2 adsorption capacity was stabilized from third cycle onward, whereas the methanation capacity was stabilized at all cycles, indicating the high stability of the DFMs for both CO 2 adsorption and subsequent methanation. This work demonstrated successful synthesis of the Ni‐based, low‐cost, and stable DFMs with the ability to produce methane via the direct capture of CO 2 .