Preparation Of Highly Efficient Ni Catalyst And Its Catalytic In CO Methanation

Compared to the noble metal catalysts,nickel-based catalyst has advantages of the lower price and the abundant resources.Owing to the higher activity than the other transition metals,nickel-based catalyst has extensively researched in many reactions including dry reforming of methane,partial oxidation of methane and CO methanation,et al.It has been also applied in industrial production of water gas shift and steam reforming of methane.However,nickel based catalyst has poor stability for sintering at high temperature and carbon deposition in the system include CH4 and CO.How to improve the stability of nickel is one of the key and difficult points.In this paper,Ni/SiO2 catalysts are prepared by ammonia impregnation,the effect of special nickel precursor on the final structure and performance of nickel is studied.On this foundation,samples after ammonia impregnation are treated by dielectric barrier discharge plasma,the catalysts are characterized by TPR?XRD?XPS?TEM.The performance of the catalyst is evaluated in CO methanation.The effects of plasma on nickel particle size?dispersion?metal-support interaction and the crystal structure are studied,the reason that plasma can improve the performance of the catalyst is tentatively researched.We get the follow conclusions:Nickel ammonia complex and nickel-containing phyllosilicates(Ni-PS)are formed in the process of ammonia impregnation,these precursors can improve the dispersion and enhance the metal-support interaction of nickel catalyst.The catalyst prepared by ammonia impregnat-ion owns smaller particle size?higher dispersion and stronger metal-support interaction.All these factors lead to higher activity and better ability of anti-sintering and carbon resistance in methanation reaction.Catalysts prepared by plasma treatment after ammonia impregnation shows higher activity and stability in CO methanation.It can be found from XRD and TEM that plasma treatment can further decrease the particle size of nickel and improve the dispersion of nickel.And this process can also increase the percentage of Ni(111)crystal face.The metal-support interaction can be further enhanced,which can be confirmed from H2-TPR.From XPS profiles,we find that plasma increase the content of nickel in the surface of catalyst.Particles with little size and higher dispersion improve the activity in CO methanation,strong metal support interaction guarantees the ability of anti-sintering,smaller particle size and more Ni(111)face is very vital to the ability of carbon resistance.Hence,ammonia impregnation combined with DBD method is an effective approach to improve the activity and high temperature stability of Ni catalyst.