Synthesis gas production in the combined CO2 reforming with partial oxidation of methane over Ce-promoted Ni/SiO2 catalysts

A series of nickel-based catalyst supported on silica (Ni/SiO₂) with different loading of Ce/Ni (molar ratio ranging from 0.17 to 0.84) were prepared using conventional co-impregnation method and were applied to synthesis gas production in the combination of CO₂ reforming with partial oxidation of methane. Among the cerium-containing catalysts, the cerium-rich ones exhibited the higher activity and stability than the cerium-low ones. The temperature-programmed reduction (TPR) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) analysis revealed that the addition of CeO₂ reduced the chemical interaction between Ni and support, resulting in an increase in reducibility and dispersion of Ni. Over NiCe-x/SiO₂ (x = 0.17, 0.50, 0.67, 0.84) catalysts, the reduction peak in TPR profiles shifted to the higher temperature with increasing Ce/Ni molar ratio, which was attributed to the smaller metallic nickel size of the reduced catalysts. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) for the post-reaction catalysts confirmed that the promoter retained the metallic nickel species and prevented the metal particle growth at high reaction temperature. The NiCe-0.84/SiO₂ catalyst with small Ni particle size exhibited the stable activity with the constant H₂/CO molar ratio of 1.2 during 6-h reaction in the combination of CO₂ reforming with partial oxidation of methane at 850 °C and atmospheric pressure.