Structural Design And Catalytic Performance Of Ni-based Catalysts On Composite Support For Co Methanation

With the rapid development of economy and the intensity of environmental protection in our country,natural gas as a high-quality,efficient and environmentally clean energy,its demand is increasing year by year.The production of natural gas cannot meet the demand in our country and the gap is becoming bigger and bigger.Considering the current situation that is rich in coal and is short in natural gas,producing natural gas from coal has became a significant technology to make up natural gas shortage.Methanation is the key of the technology,thus the design of efficient and stable catalyst is the top priority in the methanation process.In the light of this,in the paper we successfully synthesized Al2O3-SiC,Al2O3@SiC and MgxAlyOz series of composite supports by the methods of precipitation,Evaporation-induced self-assembly(simply called EISA)and co-precipitation respectively.Subsequently we prepared the corresponding Ni-based catalysts by incipient-wetness impregnation method.Meanwhile the catalysts were systematically analyzed by using XRD,N2-sorption,SEM,TEM,H2-TPR,NH3-TPD,CO2-TPD,TG-DTG characterization techniques.The main results of this paper were as follows:1.A series of Ni/Al2O3@SiC catalysts on composite supports were prepared by EISA method.The catalyst has the best catalytic activity when Al2O3 content was 20%,the calcination and reduction temperature was 500℃and 700℃ separately.The 15Ni/20Al2O3@SiC catalyst had a better stability at high temperatures compared with 15Ni/20Al2O3-SiC catalyst during the 100 h stability reaction.2.we can clearly seen Al2O3 evenly coating on the surface of SiC among the Al2O3@SiC support from SEM pictures.XRD and TEM test results displayed Ni particles on the 15Ni/20Al2O3@SiC catalyst had a better dispersion and were smaller.TG-DTG test result showed the 15Ni/20Al2O3@SiC catalyst had less carbon deposition after the stability reaction.NH3-TPD and CO2-TPD test rusults revealed 15Ni/20Al2O3@SiC catalyst had the stronger basic site,which can effectively inhibited carbon deposition.H2-TPR test revealed that the metal-support interaction was strengthened in the 15Ni/20Al2O3@SiC catalyst,thus the catalyst had a better stability.3.We prepared Ni/MgxAlyOz catalysts by the co-precipitation method and the Mg-Al ratio were 2:1,1:1,1:2 and 1:3 separately.When the Mg-Al ratio was 2:1,the catalyst had the best catalytic activity.By adding the La2O3 promoter,15Ni-5La/MgA2 catalytic activity was significantly increased.4.XRD and TEM results displayed that Ni particles on the 15Ni-5La/MgAl2O4 catalyst had better dispersion and were smaller compared with 15Ni/MgAl2O4,which was the reason why the catalytic activity had a significanlly improving.H2-TPR test revealed that the metal-support interaction was strengthened and the degree of reduction was promoted in the 15Ni-5La/MgAl2O4 catalyst,thus the catalyst showed more excellent activity in CO methanation reaction compared with the 15Ni/MgAl2O4 catalyst.