Tailoring the Structure and Surface Chemistry of High-Loading Ni-Metakaolin Catalysts Prepared by Melt Infiltration...

CO₂ methanation is a promising power-to-gas technology that enables the conversion of carbon dioxide into methane. However, the development of efficient catalysts based on naturally abundant and inexpensive support remains an important challenge. In this work, metakaolin from natural kaolin was investigated as a novel support for high-loading (30 wt.%) Ni catalysts prepared using a melt infiltration method. The influence of CeO₂ and alkaline earth metal oxides (MgO, CaO) on the physicochemical properties and catalytic performance was systematically evaluated. It was evidenced that CeO₂ improved NiO reducibility, whereas MgO and CaO promoted Ni⁰ dispersion and modified textural and surface properties. In particular, Mg addition increased the S_BET from 23 to 39 m²/g and the total pore volume from 0.06 to 0.17 cm³/g compared with the Ni-MK sample. The promoted catalysts exhibited enhanced low-temperature activity and reached approximately 80% CO₂ conversion at 400 °C, close to thermodynamic equilibrium, maintaining CH₄ selectivity above 97%. Stable catalytic performance was preserved during 24 h time-on-stream tests. The results demonstrate that metakaolin is a promising sustainable support for Ni CO₂ methanation catalysts and that melt infiltration provides a simple and effective preparation route for obtaining high nickel loading.