Effect of ZrO2 promoter on structure and catalytic activity of the Ni/SiO2 catalyst for CO methanation in hydrogen-rich gases

Ni-based catalysts supported on SiO2 aerogel that is unpromoted (Ni/SiO2) or promoted (Ni/ZrO2–SiO2) with ZrO2 are prepared by the incipient-wetness impregnation method. Their catalytic activities for CO methanation in hydrogen-rich gases with 1 vol.% CO are studied with a continuous flowing microreactor. It is found that the Ni/ZrO2–SiO2 catalyst shows higher catalytic activity, over which CO can be completely converted into CH4 at 240 °C. However, CO cannot be completely converted until the temperature was raised to 320 °C over the Ni/SiO2 catalyst under the same reaction conditions. Characterizations using FT-IR, XRD, TEM, NH3-TPD, H2-TPR and H2-TPD suggest that the formation of Si–O–Zr bond results in stronger acid strength and larger amounts of acid of the ZrO2–SiO2 support. The changes of acidity lead to the increase of the interaction between NiO species and the ZrO2–SiO2 support and then enhance the dispersion degree and the reduction degree of NiO species. Thus, the Ni/ZrO2–SiO2 catalyst possesses smaller Ni crystallite size, higher Ni dispersion, more active Ni species and stronger adsorption ability for H2, which may contribute to its higher catalytic activity for CO methanation.