Promoting Effects of Zr on CO₂ Hydrogenation over Porous Co/Ce_xZr_1-xO_2-δ Catalyst

The porous Co/Ce_xZr_1-xO_2-δ catalysts were prepared by using a template agent-impregnation method. The physicochemical properties of the prepared catalysts were studied by using the XRD, BET, H₂-TPR, and H₂-TPD. The effects of the catalyst structure and Zr dosage on CO₂ hydrogenation performances were also investigated. The porous Ce_xZr_1-xO₂ support prepared by the hard-template method has a large specific surface area and developed pore structure. With the increment of Zr dosage, the crystal phase structure of the prepared porous Ce_xZr_1-xO₂ support transforms from cubic phase to tetragonal phase. The Co-Ce-O-Zr solid solution was formed in the corresponding catalyst by introducing an appropriate amount of Zr and significantly improved the reducibility of the Co₃O₄/Ce_xZr_1-xO₂ precursors, by which the interaction between the active Co⁰ and support was enhanced. At the same time, it is conducive to the formation of oxygen vacancies and highly dispersed Co⁰ to promote the hydrogenation active sites to be formed in the corresponding catalyst, and thus promoting the CO₂ hydrogenation. The porous CoCe_0.99Zr_0.01 catalyst with the Zr content of 1.0 mol% has the best catalytic performances. At 400 °C and atmospheric pressure, the CO₂ hydrogenation conversion and CH₄ selectivity on the CoCe_0.99Zr_0.01 catalyst reached 59.8% and 94.7%, respectively.