CO2 hydrogenation to methane over Co/KIT-6 catalysts: Effect of Co content

The ordered mesoporous Co/KIT-6 catalysts with different Co loading (15-30 wt%) were prepared by impregnation method for CO2 hydrogenation. The physicochemical properties of the catalysts were characterized by H2-TPR, XRD, BET, H2-TPD, and CO2-TPD. The results show that the crystal size of Co species increases with the increasing Co content and the dispersion of Co species reveals an opposite trend. The adsorption capacities of H2 and/or CO2 molecules achieve a maximum value at the Co loading of 25 wt%. The CO2 reaction rate and CH4 selectivity are in the following order: Co15 < Co20 < Co30 < Co25. With the increasing of Co loading, the CO2 reaction rate increases from 2.21 × 10−5 mol/gcat/s (CO2 conversion of 29.8%) for the Co15 catalyst to 3.91 × 10−5 mol/gcat/s (CO2 conversion of 52.6%) for the Co25 catalyst, and the CH4 selectivity improves from 67.0% for the Co15 catalyst to 94.5% for the Co25 catalyst at 360 °C, while the other product is CO. The catalytic performance and products distribution of the Co/KIT-6 catalysts for CO2 hydrogenation are sensitive to the crystal size of Co species which can be adjusted by changing the Co content in Co/KIT-6 catalysts.