Preparation Of Cu/Fe₃O₄ Catalyst For Water-gas Shift Reaction

Hydrogen,a highly efficient and clean energy carrier,the utilization of which is a key way to solve energy crisis and environmental problem.H₂produced by reforming or gasification of fossil fuel or biomass raw materials always contains a certain amount of CO.Water-Gas Shift（WGS）reaction,i.e.CO reacts with H₂O to form CO₂and H₂,can lower the CO concentration and transform H in H₂O into H₂,which is a key process to produce pure hydrogen.Development of a catalyst with highly catalytic performance for WGS reaction in H₂Fuel Cell that is important to utilize H₂efficiently.Cu/Fe₃O₄catalyst possesses both Cu and Fe₃O₄active species,is supposed to be have bright application prospect.In this thesis,CuFe₂O₄,prepared by sol-gel method by adjusting preparation parameters or using different surfactant,was used as precursor to synthesize Cu/Fe₃O₄.XRD,Raman,N₂physical desorption,H₂-TPR,XPS and CO₂-TPD techniques were applied for investigating the structure of CuFe₂O₄precursor and as-derived Cu/Fe₃O₄catalyst.Relationship between the structure and catalytic performance for WGS reaction was discussed.Besides,catalyst after stability evaluation was oxidized by O₂/Ar at certain temperature,and its structure and property were carefully investigated,aiming to find a feasible way to regenerate catalyst.First,CuFe₂O₄was prepared by calcined at different temperature,and the influence of calcined temperature on the activity of Cu/Fe₃O₄catalyst for WGS reaction was studied.Crystal structure of CuFe₂O₄,texture and reduction property of the as-prepared precursor are distinguished by applying different calcination temperatures.Catalytic activity of Cu/Fe₃O₄for WGS reaction is linearly correlated with the crystal size of Cu and Fe₃O₄.The catalyst with smaller crystal size of Cu and Fe₃O₄shows higher CO conversion and TOF and lower activation energy.Second,CuFe₂O₄with different crystal structures,i.e.cubic and tetragonal,were prepared by using different surfactants.Surface basicity and number of oxygen vacancy in Cu/Fe₃O₄derived from CuFe₂O₄reduction were carefully investigated.Their catalytic activity and kinetic parameters for WGS reaction were also obtained.Relationship between the crystal structure of CuFe₂O₄and catalytic property of Cu/Fe₃O₄is discussed in detail.It is found that the number and strength of basicity site are crucial to the catalytic activity of Cu/Fe₃O₄catalyst.Third,Cu/Fe₃O₄catalyst after stability evaluation was oxidized at certain temperature.The crystal structure,number of oxygen vacancy and Cu dispersion of the catalyst before and after oxidation were detailly investigated.Besides,elimination of the surface deposited bidentate carbonate was also carried out.Their effect on catalytic activity of Cu/Fe₃O₄catalyst was discussed.It is concluded that oxidation at certain temperature is an efficient way to regenerate Cu/Fe₃O₄catalyst.After regeneration,the catalyst shows comparable activity to the one freshly prepared.