Role of Ca in Ni-Ca/Fumed-SiO₂ Catalysts for CO₂ Catalytic Conversion to Methane

This study investigates the role of calcium in facilitating the carbon dioxide methanation reaction over nickel supported on fumed-SiO₂ catalysts. The wet impregnation method was used to prepare Ni/fumed-SiO₂ catalysts with three different Ca loadings for CO₂ conversion. As part of the investigation into the effects of Ca concentration and reaction conditions on the structural and morphological properties of the catalysts, various techniques including XRD, BET, SEM, TPR and TEM were used for both fresh and used catalyst samples. The findings showed that the addition of 0.5% Ca increases the catalyst reducibility, promotes dispersion of Ni sites on the surface of fumed SiO₂ support and prevents the metal from agglomerating. Evaluation of catalytic results showed that the performance of 10%Ni-0.5Ca/fumed-SiO₂ was superior to the other tested catalysts, with CO₂ conversion and CH₄ yield of 76% and ~ 40% at 650 °C, respectively.