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/gamma-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.