Achieving Sulfur Tolerance in CO2 Methanation over Ni-Based Catalysts: Protective Effects of Fe

Direct methanation of carbon dioxide (CO2) in coal-fired flue gas presents a promising approach for achieving carbon neutrality without the energy-intensive CO2 capture process. However, traditional Ni-based catalysts are easily deactivated by sulfur poisoning. In this study, a sulfur-tolerant Ni/γ-Al2O3 catalyst with Fe modification (xFe–Ni/A) was developed, and the promoting mechanisms were elucidated. Experimental results showed that the 1Fe–Ni/A catalyst exhibited optimal Fe loading and maintained good activity in the presence of SO2. It was revealed that Fe addition facilitated the formation of the Ni–Fe alloy and modulated the catalyst’s surface chemistry, thereby promoting the reaction activity. Furthermore, the physicochemical and SO2 adsorption properties of the catalyst suggested that Fe not only functioned as a protective agent for Ni sites against SO2 but also inhibited overall SO2 adsorption, resulting in enhanced sulfur resistance. This study provides valuable guidance for the design of sulfur-tolerant catalysts by doping sacrificial sites and modulating SO2 adsorption using non-noble metals, laying the foundation for the scale-up industrial applications of CO2 utilization in the SO2-containing environment.