A comparative study on the catalytic properties of high Ni-loading Ni/SiO2 and low Ni-loading Ni-Ce/SiO2 for CO methanation

Two Ni-based catalysts of 13%Ni/SiO2 (13Ni/Si) and 7%Ni-2%Ce/SiO2 (7Ni-2Ce/Si, by weight) were prepared by the incipient-wetness impregnation method and characterized with N2-sorption, XRD, H2-TPR, FT-IR, TEM, H2-TPD and CO-TPD techniques. It was shown that addition of Ce promoter generated an interaction among NiO, CeO2 and SiO2, which changed chemical environment of Ni-O-Si bond, enhanced the dispersion and reduction of NiO, and increased the active surface area. In particular, a new type of moderately strong CO adsorption sites was formed on the surface of the 7Ni-2Ce/Si catalyst. As a result, the low Ni-loading 7Ni-2Ce/Si catalyst exhibited higher CO adsorption capacity and CO methanation catalytic activity than the high Ni-loading 13Ni/Si. Under the reaction conditions of 1% CO (volume fraction in H2 atmosphere), GHSV of 7000 h−1 and atmospheric pressure, the temperature for complete conversion of CO over the 7Ni-2Ce/Si catalyst was 230°C, being 30°C lower than that found over the high Ni loading 13Ni/Si catalyst.