Preparation Of Ni/CNTs Catalysts And Their Application In Methanation

Carbon nanotubes has been widely used in various fields such as field emission and energy batteries because of their superior physical and chemical properties and it is also an excellent catalyst carrier.Methanation is a reaction of carbon oxides and hydrogen gas to produce methane.The methanation has important applications in the synthetic natural gas production and CO removal.The catalyst is the key for methanation and nickel is a catalyst for methanation reaction which has excellent catalytic activity and low costs.In this paper,nickel catalysts loaded on carbon nanotubes were prepared with different techniques,their structures and catalytic properties for methanation were also studied.(1)Nickel catalysts supported on carbon nanotubes were prepared by different techniques such as chemical plating,hydrothermal method,precipitation method and impregnation.By compraring the feasibility of mass-preparation,the dispersion and the average particle size of nickel particles on the supporter,it concludes that the carbon nanotubes supported nickel catalyst prepared by impregnation method was the most praticle one.(2)The detail processes of carbon nanotubes supported nickel catalyst prepared by impregnation were syntematically explored and the optimal conditions are as follows: carbon nanotubes were pre-treated by refluxing in 50 wt.% nitric acid;nickel acetate or nickel acetylacetonate were used as nickel precursors;dipping time is 24 to 36 h;the dehumidification of the catalyst is performed by a three-step process in 40 ?,60 ? and infrared light treatment,respectively;calcination temperature is 300 ?;reduction temperature is 500 ?.(3)The conditions of methanation catalylized by carbon nanotubes supported nickel catalyst prepared under the optimal synthetic process were also studied.The catalytic methanation has the best conversion and selectivity in conditions as follows: the loaded amount of the nickel was 14 wt.%;the ratio of the raw gas n(H2)/n(CO)= 3,reaction temperature is 550 ?;reaction pressure is 4 MPa;the reaction speed is 8000 h-1.The water gas conversion was well inhibited in the optimized conditions.