Effect of SiO₂ Addition to Highly Loaded Ni on CeO₂ for CO₂ Methanation

In this study, 60 wt% Ni on xSiO(2)-(1 - x)CeO2 catalysts were prepared by flame spray pyrolysis, and the effects of SiO2 fraction (x = 0-0.2) on the material properties and catalytic activity of CO2 methanation were investigated. After reducing the catalysts in 5%H-2-Ar at 500 degree celsius, the catalytic activity was evaluated; the highest catalytic activity was exhibited at x = 0.05. Furthermore, SiO2 addition was found to improve the catalytic activity after 110 hours of the reaction. Powder X-ray diffraction revealed that SiO2 addition did not alter the crystallinity of the catalysts before and after the reduction. Conversely, the appropriate amount of SiO2 doping increased the Ni surface area and pore volume of the reduced catalysts, as confirmed by H-2 chemisorption and N2 adsorption-desorption measurements. H-2-TPR measurements showed an increasing trend in the reduction temperature of particulate NiO as the SiO2 fraction increased. The shift of the reduction temperatures indicates the better contact between NiO and SiO2, which hindered the sintering of Ni particles during the reduction at 500degree celsius. Therefore, an appropriate amount of SiO2 addition prevented the growth of Ni particles, resulting in the increase of the Ni surface area. The increase of the Ni surface area contributed to the improvement of the catalytic activity.