Structural Design And Preparation Of The Novel And Efficient Ni-based Catalysts For Carbon Dioxide Methanation

Along with the industrial development,the problem of environment pollution and energy crisis is becoming more prominent.The extensive of fossil fuels has increased carbon dioxide emissions dramatically.Conversion of carbon dioxide as carbon resource has become a hot topic.C02 methanation technology is of great significance in energy storage and transformation.This reaction can be accomplished by means of catalysts.Considering the economic cost,Ni-based catalysts are recognized the most industrial prospect catalysts.But strong exothermic characteristics in this reaction can easily produce local high temperature in catalyst bed layer,which could cause catalyst rapid deactivation due to metal sintering.Therefore,the key to this reserach is to develop a new highly efficient Ni-based catalyst with enhanced activity and improved stability.In this thesis,firstly we studied the Al2O3 nanostructure(nanosheet and nanoplate)supported Ni catalyst for CO2 methanation.Then,we investigated the Ni-Al2O3@SiC catalyst by adding different additives to modify catalytic performance.Besides,we sudied the effect of combination between NiMgAl-HTs and SiC supported Ni catalyst for catalytic performance.And we choosed superior catalysts to do a stability test.The catalysts were analyzed by N2 adsorption,XRD,TEM,H2-TPR,C02-TPD and H2-Chemisorption characterization methods.The main results are as follows:1.The Ni/Al2O3-S and Ni/Al2O3-P catalysts were prepared by hydrothermal synthesis method.The Ni/Al2O3-S catalyst possessed higher activity than the Ni/Al2O3-P catalyst obviously.Characterization results revealed that the size of Ni nanoparticles and metal dispersion have significant influence on the activity of nanostructure Ni/Al2O3 catalysts.2.The Ni-Al2O3@SiC catalysts were prepared by EISA method.After the Ce,La,and V addition,it is found that these three additives both increased the catalytic activity in C02 methanation.When compared with other additives,Ce addition increased the low temperature acitivty rapidly.Then the Ce02 additive is further studied,we found the low temperature activity of the Ni-Ce02-Al2O3@SiC catalyst outweighed the other three catalysts,such as the Ni-Al2O3@SiC,Ni-CeO2-Al2O3 and Ni/CeO2-SiC catalysts.3.When compared with the NiMgAl-HTs catalysts alone,it was found that after combining SiC and hydrotalcites structure,the low temperature activity of NiMgAl-HTs/SiC catalyst increased significantly.A series of characterization results revealed that the more Ni active sites in the NiMgAl-HTs/SiC catalyst.The incorporation of SiC can modulate metal-support interaction and enhance the reducibility of catalysts,which improved the CO2 methanation activity.