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 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 degrees C. However, CO cannot be completely converted until the temperature was raised to 320 degrees 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. (C) 2010 Elsevier B.V. All rights reserved.