Tailoring the Structure and Surface Chemistry of High-Loading Ni-Metakaolin Catalysts Prepared by Melt Infiltration for CO2 Methanation

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 SBET 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.