| Since carbon nanotubes (CNTs) have been discovered in 1991, they are mainly produced by arc-discharge evaporation and Chemical Vapor Deposition (CVD) method. Because its yield is high, equipment is simple, technology parameter is easy to control, and has good repeatability, the CVD method is one of the most usual preparation methods of carbon nanotubes. This paper studied the influence of the preparation method and kind of catalyst, synthesis temperature, and carrier gas flowrate on the diameter, diameter distribution, graphitized extent, and the composition of carbon nanotubes through XRD, TG-DTA, TEM and SEM technique. We also analyzed the oxidization reaction kinetic mechanism and the oxidization reaction stability of carbon nanotubes. To study the catalytic ability of Ni/CNTs, the heterogeneous hydrogenation of o-nitrotoluene was used as the probe reaction.The catalyst prepared by complex impregnation supporting method has smaller cobalt grain size and better dispersion than its reference catalyst prepared by traditional method. The volatilization of the complex builder (NH3) could result in some small hollow structures that may induce a higher local partial pressure. Hence the growth of carbon nanotubes is promoted.During the synthesis of carbon nanotubes, the interaction between Ni and y- Al2O3 is stronger than that between Co and y- Al2O3. More new phase materials were generated. At the optimum reaction temperature(650C), the yield of carbon nanotubes produced on Co/Al2O3 is 457g/100g-cat, which is higher than those produced onNi/Al2O3, 342g / 100g- cat . However the graphitized extent is reversed.Compared with the yield of carbon nanotubes produced on Co/Al2Oa, the yield of carbon nanotubes with the outer diameter of 25nm~40nm produced on Co/SiO2 is only131g/100g-cat . at the optimum reaction temperature 650 ℃. However, the DTAexperiments under air atmosphere show that the oxidation resistance of carbon nanotubes produced on Co/SiO2 is stronger than that produced onThe TG-DTA data at a heating rate of 10℃ showed that the exothermic peak temperture of amorphous carbon was lower than 380℃ and its content was lowing as the reaction temperature rising. The exothermic peak temperature of carbon nanotubes was raised up when the diameter and graphitized extent increased.On Co/Al2O3 and Ni/Al2O3, the crystal plane distance of layer d(002) of carbon nanotubes decreased with the synthesis temperature raised, meanwhile the graphitized extent enhenced, the diameter increased, and the diameter distribution broadened. Low temperature(650℃) is favorable to the production of thinner carbon nanotubes with the diameter from 10 to 30nm, while higher tempereture(750℃) is favorable to the production of thicker carbon nanotubes with the diameter from 30 to 50nm.The diameter and the graphitized extent of carbon nanotubes decreased with increase of the carrier gas flowrate. High flowrate is favorable to produce thinner carbon nanotubes, while lower flowrate is favorable to produce thicker carbon nanotubes.Because of their different intrinsic structure, there are difference in the resistant to oxidation, thermal stability, and apparent activation energy among carbon nanotubes, Ceo and graphite. DTA analysis indicates that carbon nanotubes is more resistant to oxidation than C60, but carbon nanotubes is less resistant to oxidation than graphite. The oxidation behavior of carbon nanotubes follows R3 mechanism with the apparent activation energy of 145 kJ/mol, but for graphite it obeys R2 mechanism with the apparent activation energy of 193 kJ/mol. However, the kinetic model of oxidation reaction in air atmosphere for Ceo does not a single kinetic model.The heterogeneous hydrogenation of o-nitrotoluene was used as the probe reaction. Ni-catalysts supported on carbon nanotubes, active carbon, Y-A12O3 and SiO2 were evaluated respectively. The results show that the conversion of o-nitrotoluene and the selectivity of o-Toluidine were 80% and 100% on the carbon nanotubes supported Ni-catalyst at 493...
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