Effect of the Support Synthetic Method on the Activity of Ni/CeZrPr Mixed Oxide in the Co-Methanation of CO2/CO Mixtures for Application in Power-to-Gas with Co-Electrolysis

Synthetic natural gas (SNG) is an efficient option for transforming renewable energy into carbon-neutral fuels while using a plug-and-play infrastructure, supporting the transition to renewable energy, paving the way for a hydrogen-based economy. Captured CO2 can be processed with water through high-temperature co-electrolysis, where reduction to CO and H2 production by water splitting occurs. The outlet gas, composed of CO2, CO, H2, and small amounts of CH4, can be used to produce SNG by methanation of CO and CO2 with hydrogen. Among the parameters influencing the methanation reactions, the characteristics of the support and its interaction with the metallic active phase, usually Ni, are of crucial importance and can be tuned by the synthesis of the support. For this reason, three different synthetic methods, namely, pseudo sol–gel, coprecipitation, and colloidal combustion, were applied to the synthesis of a Ce/Zr/Pr oxide. The supports were fully characterized by nitrogen physisorption, X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), temperature-programmed reduction (TPR), and H2 temperature-programmed desorption (H2-TPD) before and after impregnation with 10 wt % Ni. The coprecipitated catalyst exhibited the best performances when subjected to CO2/CO co-methanation and typical post-co-electrolysis mixture, thanks to a combination of different characteristics such as high surface area and mesoporosity, which allowed good Ni dispersion and surface area, high support metal interaction, and reducibility. Finally, the effect of Pr seemed to be beneficial, increasing the methane yield at low temperatures.