Improving Low-Temperature CO2 Methanation by Promoting Ni-Al LDH-Derived Catalysts with Alkali Metals

Fossil fuel depletion and environmental impacts caused by greenhouse gas emissions such as CO2 are significant issues securing nature preservation within a sustainable economy. CO2 methanation is a promising process to mitigate CO2 emissions and reuse it to produce CH4, serving as fuel, chemical feedstock, and energy source. A series of LDH-derived Ni-Al catalysts promoted by Li, Mg, Ca, and La were prepared via co-precipitation. Characterization by N-2 physisorption, X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), as well as thermal techniques such as temperature programmed reduction (H-2-TPR), desorption (CO2-TPD, H-2-TPD), and oxidation (TPO) analyses were performed. Low-temperature catalytic tests (200-400 degrees C) revealed that alkali metal modification improves performance even at 200 degrees C, where the Ni55Ca11Al33 catalyst achieved 74 % CO2 conversion with 100 % CH4 selectivity by enhancing basicity and metal-support interaction, high Ni dispersion and small crystallite sizes, providing proper sites to adsorb and activate CO2. Moreover, the catalysts presented excellent resistance to deactivation, maintaining high stability during 10 h on stream. These results prove that Ni-Al mixed oxides, LDH-derived catalysts performances can be further improved by incorporating alkali metals into less energy-spending, low-temperature CO2 methanation processes.