A research on the synthesis process of Zr-MOF derived Ni-based catalysts for CO2 methanation: The role of Ce promoter, method of Ni introduction and calcination condition

CO2 methanation is a potential way for the re-utilization of CO2. MOF derivations are promising candidates for commonly used Ni-based catalysts due to their high porosity and confinement effect. Herein, we systematically investigated the synthetic pathway of Zr-MOF-derived Ni-based catalysts. It is found that Ce addition can effectively improve the thermostability, specific surface area and Ni dispersion of the derived Ni/CeO2-ZrO2 catalyst. It can also enhance the adsorption of CO2 by the generation of O-v and improve CO2 methanation activity. Calcination the MOF in inert gas leads to the formation of CNTs and amorphous carbon. Amorphous carbon results in less interaction between NiO and CeO2 as well as low amount of O-v, leading to lower catalytic activity than the catalyst calcinated in air. Compared with impregnation method, one-pot solvothermal method leads to much higher specific surface area for both MOF and derived oxides. It also benefits the uniform dispersion of NiO and higher amount of O-v. Therefore, it shows better catalytic activity and is proved to be a better method for Ni introduction. In the catalysts we discussed, St-ZrCeNi (Ce addition, one-pot solvothermal method, calcination in air) shows the highest CO2 conversion and good CH4 selectivity due to its high specific area and more O-v. It also shows good stability (>50 h) and good intrinsic activity. This research reveals the roles of several important factors in the synthesis process of Zr-MOF derived Ni-based catalysts. It also gives new insights for the design and synthesis for other MOF derived catalysts.