Cobalt–Nickel Catalysts Supported on Opoka and Diatomite for CO2 Hydrogenation

5 wt % Co–5 wt % Ni catalysts supported on natural opoka and diatomite silica minerals from the Republic of Kazakhstan were prepared via low-temperature combustion and characterized using XRD, SEM/EDS, and BET analyses. The supports primarily comprised various SiO2 modifications, with opoka also containing sodium, magnesium, and iron silicate and aluminosilicate impurities. Diatomite-supported catalysts exhibited specific surface areas ranging from 60.0 to 71.5 m2/g, while for opoka-supported catalysts, it ranged from 28.6 to 62.8 m2/g. During CO2 hydrogenation to methane, the highest conversion (50.9% at 450°C) was achieved with a catalyst supported on untreated diatomite. However, the highest methane selectivity (90.1% at 450°C) was observed for a catalyst supported on opoka calcined at 500°C.