Preparation Of Doped Nickel-based Catalysts And Their Catalytic Performance In Ethanol Water Reforming

In this paper,a series of doped mesoporous zirconia supports（doped species of lanthanum,cerium,lanthanum）were prepared by coprecipitation method using CTAB as template.The active components were loaded onto the carrier by impregnation method to obtain Ni(_xCe_0.4Zr_0.6O₂（X=0.05,0.1,0.15,0.2）,Ni_0.1Pr_0.2Zr_0.8O₂,Ni_0.1La_0.2 Zr_0.8O₂ catalyst;X-ray powder diffraction（XRD）characterization,N₂-physical adsorption（BET）measurement,temperature programmed redox（TPR/TPO）,acid-base position Test（NH3-TPD,CO2-TPD）.The effects of the type of doping metal and the amount of doping on the crystal form,specific surface area,redox,active oxygen storage,acidity and alkalinity of the support and the catalyst were investigated.The catalyst-catalyzed ethanol water gas reforming reaction activity was evaluated on a micro fixed bed evaluation apparatus.It is found that the crystal structure of the carrier prepared by doping metal is dominated by the mixed crystal form of cubic phase and tetragonal phase.The results of BET show that the carrier with yttrium is the largest than the surface,reaching 219.6m2·g-1.After the active component is loaded,the catalyst remains predominantly in the original crystalline form.But it is different from the surface.The temperature-programmed redox test of the catalyst support showed that the cerium-zirconium composite oxide had two hydrogen-reducing reduction peaks at 450℃and 650℃,corresponding to the reduction of surface and bulk phase Ce ⁴⁺respectively.The cerium-zirconium composite oxide has two hydrogen-reducing reduction peaks at 540℃and 750℃,which correspond to the reduction of fine La₂ O ₃ and the reduction of La ³⁺which are highly dispersed with weak interaction with ZrO₂.The reduction peak of the cerium-zirconium composite oxide is formed by superposing three peaks of 470℃and 600℃and 800℃.Corresponding to the reduction of Pr₆O₁₁ and the reduction of Pr⁴⁺.The temperature-programmed redox test after loading the above three kinds of carriers with nickel showed that the catalysts were all reduced by the reduction peak of the carrier and the two nickel oxides which interacted differently with the carrier.The active oxygen storage amount of each catalyst and carrier is:Ce_0.2Zr_0.8O₂ is 0.148⁰.84 molO₂/mol（Ce+Zr）;La_0.2Zr_0.8O₂ is 0.0274⁰.181molO₂/mol（La+Zr）;Pr_0.2Zr_0.8O₂ is 0.0446⁰.0616 molO₂/mol（Pr+Zr）;Ni_0.1La_0.2Zr_0.8O₂is 0.0816⁰.177molO₂/mol（La+Zr）;Ni_0.1Pr_0.2Zr_0.8O₂ is 0.0816⁰.177molO₂/mol（Pr+Zr）;Ni_xCe_0.2Zr_0.8O₂ is 0.182⁰.265 molO₂/mol（Ce+Zr）.The acid-base characterization of the cerium-zirconium composite oxide and its active component nickel showed that for the carrier,there are mainly weak bases and medium-strength bases,and weak acid sites and medium-strength acid sites are also present;As the doping amount of cerium increases,the basic position of the surface of the carrier gradually increases,and the acidity gradually decreases.The catalyst formed after loading nickel also has a weak base position,a medium strength base position,and a weak acid position and a medium strong acid position.As the amount of supported nickel increases,the medium strength alkali level of the catalyst surface gradually increases,and the weak base position gradually decreases.At the same time,the medium-strength acid level gradually increases and the weak acid level gradually decreases.After evaluating the activity of the catalyst,it was found that the difference in the amount of nickel supported affects the catalytic activity of the catalyst in the ethanol water gas reforming reaction.When the nickel loading is n_Ni:n_（Ce+Zr）,the catalytic activity is the best,and the ethanol conversion rate is 97%.When the ethanol water gas reforming reaction is completed on all the catalysts,there is no carbon dioxide in the gas phase product,which is beneficial to the catalyst having excellent oxygen storage and oxygen storage capacity.