Dual Role of SiC Modification in Enhancing the Stability of Ni-Based Catalysts for CO/CO2 Co-Methanation

CO/CO2 co-methanation provides an effective route for the high-value utilization of coke oven gas and carbon-rich industrial off-gases. However, the highly exothermic nature of methanation readily induces local hot spots, leading to Ni particle sintering, pore blockage, carbon deposition, and surface passivation, which severely restrict the long-term stability of catalysts. In this work, Ni-Mn/Ti-Zr-La-Ce and SiC-modified Ni-Mn/Ti-Zr-La-Ce-SiC catalysts were constructed to systematically elucidate the role of SiC in enhancing catalyst stability during CO/CO2 co-methanation. Stability tests showed that the SiC-modified catalyst maintained nearly complete CO and CO2 conversions during long-term operation at 250 °C, 1.0 MPa, and a GHSV of 5000 h−1, whereas the unmodified catalyst exhibited obvious deactivation, particularly in CO2 conversion. Spectroscopic and structural characterizations revealed a dual mechanism for the stability enhancement induced by SiC. On the one hand, SiC provides physical anchoring and thermal-management effects: it strengthens the metal–support interaction, suppresses Ni particle growth and sintering, and alleviates local hot-spot formation through its high thermal conductivity, thereby preserving the catalyst structure. On the other hand, SiC exerts electronic and surface-chemical regulation effects: it stabilizes Ni0 sites required for CO hydrogenation, moderates CO2 adsorption, promotes the hydrogenation of reaction intermediates, and inhibits carbon deposition. These two effects act synergistically to optimize both thermal management and interfacial stability. This study provides a theoretical basis and practical guidance for the design of efficient and stable CO/CO2 co-methanation catalysts for industrial applications.