The Preparation And Application Of New Liquid Hydrogenation Catalysts

Carbon nanofibers(CNFs) not only had the characteristic of common carbon fibers such as low density﹑high modulus﹑strong intensity﹑good electric conductivity but also qualities of less flaws﹑big surface area﹑compact structure and so on. It can be used as catalyst carriers﹑hydrogen-storage materials﹑anodic materials of lithium ionic battery﹑ electrodes of capacitor﹑ sorbent﹑ separation reagent﹑ structure intensifier etc. More and more scholars started the research of carbon nanotubes and carbon nanofibers in many fields including their synthesis﹑property and applications after the discovery of carbon nanotubes by a Japanese electron microscope specialist Lijima in 1991.In this paper,nonuniform distribution of the activated components catalysts were researched. Factors that influenced the nonuniform distribution of the activated components were studied. The results showed that good eggshell type catalyst with more than 99wt% nickel concentratively distributed on the surface of activated alumina pellet was prepared by brushing—depositing method. CNFs were synthesized by different methods especially by catalytic decompositon of ethylene or propylene using foam nickel as catalyst. The process of CNFs synthesis was optimized. Several catalysts which were used in the hydrogenation reaction of benzene were prepared. Among of the catalysts,Ni/CNFs had good catalytic activity,the mole yield of cyclohexane was almost 100%. It had steady chemistry and long catalyst life. It was very convenient and safe to store and transport the catalyst.Brushing—depositing method was finished through the following process:the carrier was firstly dipped in solvent that could undo the pressure of capillary to activated components. Secondly,it was brushed with activated components solution containing glycerol and then was disposed with sodium hydroxide solution. So the precursor of activated components was concentratively distributed on the surface of carrier,solvable nickel nitrate was turned into unsolvable nickel hydroxide in water and glycerol,the diffusion by consistence grads was eliminated. Solvent was removed through volatilization and the precursor of activated components kept distributing on the surface of carrier after drying process. Eggshell type catalyst with more than 99wt% nickel concentratively distributed on the surface of activated alumina pellet was prepared.CNFs were synthesized by catalytic decompositon of ethylene using Ni/SiO2﹑Ni/inert-Al₂O₃ and foam nickel as catalysts. CNFs synthesized by catalytic decompositon of ethylene using Ni/SiO2﹑ Ni/inert-Al₂O₃ had small diameter,the former was 30⁴0nm,the latter was 60⁷0nm, and the products were pure but few. CNFs synthesised by catalytic decompositon of ethylene or propylene using foam nickel as catalyst had cheap cost﹑high output and simple technics. The synthesis of CNFs by foam nickel was particularly researched, Factors including different source of carbon﹑ preparation temperature﹑ preparation ambience﹑ preparation time that influenced the morphology and output of the CNFs were studied. Some conclusions were summarized. The foam nickel which was not reduced by hydrogen could prepare CNFs largely,but its output was a little fewer than the reduced foam nickel. Ethylene or propylene used as the source of carbon was almost no difference in the morphology and output of the CNFs. While ethylene was used as the source,the output and diameter of CNFs were increased with the increase of temperature,after the temperature reached 540℃,the output and diameter of CNFs increased slowly. The lowest preparation temperature was about 420℃. If the preparation temperature was under 480℃,the framework of foam nickel could not be destroyed. Using hydrogen or not in the prepatation section had almost no influence on the output and diameter of CNFs. With prolonging of preperation time,the output of CNFs firstly increased fast and then turned to be slowly.Several kinds of catalysts using in the hydrogenation of benzene were prepared in this paper. Experiment showed that Ni/inert-Al₂O₃﹑Ni/CNFs-Al₂O₃﹑Pd/CNFs-Al₂O₃﹑ foam nickel﹑ Ni/CNFs-foam nickel all can be hydrogenation catalyst to cyclohexane,but the highest yield of cyclohexane was only 53.22%. Ni/CNFs was prepared by loading activated components nickel on the pure CNFs through wet impregnation method. Ni/CNFs had good catalytic activity,the mole yield of cyclohexane was almost 100%. The catalyst was easy to separate from the product. The catalyst was steady and it was very convenient and safe to store and transport. The catalyst had long catalyst life,the deactivation was not obvious after using 5 times.