Preparation And Study Of Nickel-based Catalyst For The Low Temperature Methanation In Slurry Bed

Slurry-bed reactor can shifting out of the reaction heat released because of introducing the large thermal conductivity and high heat capacity of inert media,and the slurry-bed reactor in the highly exothermic reaction,such as FT synthesis and methanol synthesis process has a wide range of applications.Therefore,according for highly exothermic methanation reaction and the disadvantage of the existing fixed-bed methanation process,the slurry-bed reactor is introduced into the methanation reaction process allows the methanation reaction is carried out under the nearly constant temperature,Slurry bed reactor with excellent heat transfer characteristics,so that the feed gas of the methanation reaction in slurry bed reactor is more adaptive,greatly reduce the amount of the circulating gas,saving heat energy.greatly reducing the investment in equipment and provide a new way for coal-to-synthetic natural gas.The advantages of the slurry bed reactor,in this paper the development efficient catalyst Ni-La₂O₃/γ-Al₂O₃ of suitable methanation in the slurry bed catalytic reaction,and the slurry bed process conditions were optimized,study the introduction of promater on the catalyst structure and catalytic properties change,to optimize the Ni loading and La loading,preferably a suitable impregnation sequence,combined with the catalyst microstructure,surface properties,This article investigated the catalytic performance of catalysts Ni-La₂O₃/γ-Al₂O₃,provided the first basic data for the scientific research of the slurry bed methanation catalyst.（1）Slurry bed methanation reaction there is an optimal reaction temperature region,The reaction temperature is 280℃ when CO conversion and methane space time yield optimal,CO and H2flow ratio in the feed gas affect the catalytic activity of methane,The CO/H2 flow in the feed gas methane synthesis optimized ratio is 1:3.5;When the WHSV of the feed gas increases,the single pass conversion of CO will decreased,while the methane space time yield will increased.（2）Rare earth metals such as of La and Ce,Zr,can effectively improve the dispersion of NiO on the surface of the γ-Al₂O₃,The reduced of Ni crystallite is finer,and has higher activity.Which the introduction of the promoter La can effectively improve the amount of NiO of easy reduced and increase the number of active centers;And beneficial to the formation of activated carbon species in the CO methanation reaction process;It can increase the number of spillover hydrogen on catalyst surface.The activation energy of H is reduced involved in the CO methanation reaction.（3）The Ni-La₂O₃/y-Al₂O₃ catalysts is prepared by impregnation and best monolayer dispersion threshold is 12%,The dispersion of NiO is a major component of the active center in the methanation reaction,and there is interaction between the monolayer dispersion of NiO and support,The close to the dispersion threshold of NiO reduction of Ni crystallite is the smallest,and the ability of adsorption CO is stronger,It has the highest methanation activity.（4）The La additives able to play a modified role of the support,and improve the stability of the support;The dispersion of NiO in the chemical environment of the surface of the support will improve with increasing La loading,It will Improve the dispersion of NiO,and the reduced Ni crystallite is smaller and has higher activity;The percentage content of the monolayer dispersion of NiO will be improved,and at the same time the formation of NiAl2O4 species will be reduced,It will Increase the amount of NiO of easy to reduced and increase the number of activity centers of the catalytic reaction;at the same time increase the amount of adsorption H2,At the same time increase the amount of H2 adsorption,and to promote the activation of the surface adsorption of hydrogen and the adsorption of CO,thereby enhancing the catalytic activity.