Study On High Dispersive Ni Based Catalysts For Low Temperature Methanation Of CO₂

With the rapid development of modern industrialization,fossil fuels are used in large quantities.The burning of a large amount of fossil fuels results in the emission of a large amount of carbon dioxide into the atmosphere,causing a series of environmental problems such as climate warming,sea level rise,greenhouse effect,etc.,and it is urgent to reduce CO₂ in the atmosphere.However,hydrogen energy storage is still a major problem limiting its application.Methane is not only an important chemical raw material,but also a promising hydrogen storage carrier.Therefore,the study of CO₂ methanation is of great significance for the conversion and utilization of CO₂ and the storage of H2 in renewable energy.Ni-based catalysts are prone to carbon deposition,sintering and agglomeration in the course of CO₂ methanation,resulting in the decrease of their catalytic activity.In this paper,based on a detailed understanding of the mechanism of CO₂ hydrogenation methanation,the effects of different preparation methods,Ni load and mesoporous structure on the methanation performance of catalyst CO₂ were studied by controlling the mesoporous structure of catalyst,size of Ni nanoparticles and dispersion.The main contents are as follows:1.This paper uses the silicon sol auxiliary combustion of cerium oxide prepared by the solution as the carrier of different Ni load catalyst?the molar ratio of Ni/Ce?,and the catalysts used in CO₂ methanation reaction test its catalytic activity,and finally the use of XRD,BET and H₂-TPR,TEM characterization methods,such as research and analysis of the structural properties of the catalyst,determine the activity of methanation catalyst corresponding best Ni load.The experimental results showed that the methanation activity of catalyst increased linearly with the increase of Ni load,while the activity of catalyst decreased with the increase of Ni load.Finally,it was concluded that when the Ni load was 50%,the catalyst performance was the best and the stability was good.2.After determining the optimal Ni load,the effect of the preparation method on the catalyst was studied,and the efficient preparation method was studied.Firstly,three different catalysts with the same Ni load were prepared by means of solution combustion,co-precipitation and silica sol assisted solution combustion.The structural properties of the catalysts were studied and analyzed by means of XRD,BET,H₂-TPR and TEM.Characterization results show that compared with other two kinds of catalysts,silicasol auxiliary combustion of the catalyst prepared by the solution with rules of mesoporous structure,large specific surface area,metal oxide particle size small,high dispersion,etc.The other two kinds of catalysts,since mesoporous structure metal oxides have a reunion phenomenon,resulting in reduction of nickel and reaction after reunion,affect the performance of the catalyst.3.The catalytic activity?250-450??and stability?300??of catalysts prepared by different methods were tested.The experimental results show that the catalyst prepared by silica sol assisted solution combustion method has the best catalytic activity,especially at 250?,the CO₂ conversion rate is 3-4 times of the other two catalysts,indicating that it has good low temperature activity.At the same time,due to the mesoporous structure of the catalyst and the uniform distribution of metal oxides on the carrier,there will not be a large number of agglomeration,sintering and other phenomena during the reaction,so that the catalyst has maintained excellent catalytic activity and stability,CO₂ conversion and CH₄ selectivity with the reaction time almost no decline.