Catalytic methanation in a slurry-bed reactor over Ni/SiO2 catalysts: improvement by ZrO2 and β-cyclodextrin addition

Mesoporous silica (SiO2) supported highly dispersed Ni catalysts with ZrO2 and surfactant β-cyclodextrin (CD) were prepared by the impregnation method, and their catalytic performance for three-phase methanation of CO were evaluated. It is shown that ZrO2 promotes the dispersion of Ni species on mesoporous SiO2, leading to the increase in Ni dispersion and methanation activity. For the ZrO2 content, the optimum is 5 wt%. Moreover, when adding CD in the preparation of Ni5Zr/SiO2 catalyst, CD was found effectively enhanced the dispersion of Ni species and interaction between Ni species and support, leading to a smaller size of NiO particles and more exposed active surfaces, which promotes the CO adsorption capacity. As the molar ratio of CD/Ni rises, the crystallite size of metallic Ni decreased. Ni5Zr/SiO2 (1:5) catalyst prepared with 5 wt% ZrO2 and 1:5 molar ratio of CD/Ni shows the optimal catalytic activity for the three-phase CO methanation reaction. This is because of the highest dispersion of metallic Ni and smallest size of NiO particles.