Abstract: CO₂ methanation is one of the effective ways to alleviate the problem of large-scale CO₂ emissions, and its key is to develop stable and efficient catalysts. In this paper, the SiO₂ content in the slag-based support components was precisely regulated, and the influence of SiO₂ content was studied and analyzed. The citric acid sol-gel method was adopted to prepare four slag-like Ni catalysts (6Ni/xSiO₂- blast furnace slag (BFS)) with different proportions of SiO₂. By adjusting the proportion of SiO₂ in the slag-like material, the content of oxygen vacancy and the interaction force between the metal Ni and the support can be adjusted. Furthermore, the presence of SiO₂ in the support can effectively restrict the migration of active metals, thereby enhancing the catalyst’s performance. At 400 °C, the 6Ni/3.5SiO₂-BFS catalyst achieved the best CO₂ conversion rate (83.88 %) and CH₄ selectivity (98.46 %) in the CO₂ methanation reaction. Moreover, during the 100-hour uninterrupted test, the performance of the catalyst remained almost unchanged. There was no obvious sintering phenomenon that occurred in the active metals of the catalyst. The catalyst demonstrated quite good stability. This research provides ideas for the design of high-activity, high-stability, and low-cost catalysts in the industrial CO₂ methanation, and also offers a certain theoretical research basis for the direct utilization of industrial slag.

Key words: CO₂ methanation, Ni-slag-based catalysts, Limiting effect, Synergistic enhancement, Formate pathway