Manganese doping improves the sulfur resistance of nickel-based catalysts for CO₂ methanation

Coal-fired power plants, as the primary source of CO2 emissions, have garnered significant attention for carbon reduction under the “dual carbon” goals. CO2 methanation is considered to be the most practical and effective way to achieve carbon recycling, however, the most widely used nickel-based catalysts in CO2 methanation are prone to sulfur poisoning deactivation due to SO2 in the flue gas. In this paper, a series of Mn-modified Ni/γ-Al2O3 were prepared by wet impregnation method, which had anti-sulfur poisoning properties. The structure and physicochemical properties of the catalysts were investigated using various methods such as XRD, XPS, CO2-TPD, SO2-TPD and H2-TPR, and the mechanism by which the maintain high catalytic activity while possessing sulfur resistance was elucidated. The results show that 4Mn-Ni/Al2O3 exhibits the best catalytic performance and sulfur resistance, with a maximum CO2 conversion rate of 88.27%. After 3 h of SO2 exposure, the CO2 conversion rate only decreased by 11.32%. Mechanistic studies indicate that Mn can serve as a sacrificial site to protect Ni sites from sulfur poisoning, while the interaction between Ni and Mn suppresses the adsorption of SO2 on the catalyst surface, thereby enhancing sulfur resistance. This research provides a feasible solution for the direct methanation of CO2 from coal-fired SO2 flue gas.