Effect of ZrO 2 promoter on structure and catalytic activity of the Ni/SiO 2 catalyst for CO methanation in hydrogen-rich gases

Abstract

Ni-based catalysts supported on SiO 2 aerogel that is unpromoted (Ni/SiO 2) or promoted (Ni/ZrO 2–SiO 2) with ZrO 2 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/ZrO 2–SiO 2 catalyst shows higher catalytic activity, over which CO can be completely converted into CH 4 at 240 °C. However, CO cannot be completely converted until the temperature was raised to 320 °C over the Ni/SiO 2 catalyst under the same reaction conditions. Characterizations using FT-IR, XRD, TEM, NH 3-TPD, H 2-TPR and H 2-TPD suggest that the formation of Si–O–Zr bond results in stronger acid strength and larger amounts of acid of the ZrO 2–SiO 2 support. The changes of acidity lead to the increase of the interaction between NiO species and the ZrO 2–SiO 2 support and then enhance the dispersion degree and the reduction degree of NiO species. Thus, the Ni/ZrO 2–SiO 2 catalyst possesses smaller Ni crystallite size, higher Ni dispersion, more active Ni species and stronger adsorption ability for H 2, which may contribute to its higher catalytic activity for CO methanation.