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 H-2-TPR, XRD, BET, H-2-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 H-2 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 x 10(-5) mol/g(cat)/s (CO2 conversion of 29.8%) for the Co15 catalyst to 3.91 x 10(-5) mol/g(cat)/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 degrees 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.