Preparation Of Co-based Catalysts For The Low Temperature CO₂ Methanation

CO₂methanation is one of the focuses in the research field of CO₂transformation.Due to the stablility of CO₂in thermodynamics,low temperature catalysis is still one of the main challenges of CO₂methanation.Although some achievements have been made in low temperature CO₂methanation,the current progress is limited to the precious metal catalysts,and the reports on cheap metal catalysts is few.After comprehensively considering the cost,operability,stability and activity,Co based CO₂methanation catalysts are worthy of further exploration.In this paper,we prepared a series of Co-based catalysts on the basis of the characteristics of amorphous materials with easy compositional adjustment,high density and uniform dispersion of the coordinatively unsaturated active sites.Then we investigated their catalytic performance for CO₂methanation reaction at low temperatures.The main research results are as follows:（1）Co based catalysts Co/MOx were prepared in different precursor states.After screening the calcination temperature,reduction temperature,metal promoters and their contents,the influence of catalyst structure on catlytic performance was studied by XRD,BET and other characterization.The results showed that the catalytic activity of Co/Zn_0.1Ox catalyst prepared by RT-5 min precursor was 14.8mmol _CO2·g^-1_cath^-1,and the selectivity of CH₄was 90.7%.It was significantly higher than that of the catalysts prepared under other conditions,and it was also better than the activities of Co based catalysts reported in the literature under similar reaction conditions.（2）A series of amorphous Co based catalysts（Co-M-B-O）were synthesized by liquid phase reduction method.By changing the metal promoters and their content,characterizing the morphology and the stucture of the catalysts systematacially,it was found that the Co-Zr_0.1-B-O catalyst demonstrated the amorphous state and better paticle dispersion.The catalyst could activate CO₂and initiate the reaction at above140℃.The most excellent activity was obtained at 180℃,which was as high as 10.7mmol _CO2g^-1_cath^-1.The yield and selectivity of CH₄were 78.1%and 97.8%,respectively.Under similar reaction conditions,the activity was significantly better than the previously reported results on the Co catalyst,and was comparable with the results of the precious metal catalyst at low temperature.In addition,the activity and selectivity of the catalyst didn’t change much after 5 cycles.