Method for producing carbon nanotubes
Disclosed is a method for producing a carbon nanotube, including supplying a carbon nanotube and a catalyst to a reactor in a predetermined order or simultaneously and fluidizing them to form a fluidized bed, wherein a difference in minimum fluidization velocities (ΔV) according to Formula 1 below is 5 cm/s or less: [Formula 1] Difference in minimum fluidization velocities (ΔV, cm/s)=|V cat −V cntproduct | wherein V cat is a minimum fluidization velocity of catalyst, and V CNTproduct is a minimum fluidization velocity of carbon nanotubes supplied to a reactor in the step of forming a fluidized bed.
1. A method for producing carbon nanotubes, comprising: supplying carbon nanotubes and catalysts to a reactor in a predetermined order or simultaneously and fluidizing them to form a fluidized bed,
wherein a difference in minimum fluidization velocities (ΔV) according to the following formula 1 is not more than 5 cm/s:
Difference in minimum fluidization velocities (Δ V , cm/s)=| V cat −V CNT product | [Formula 1]
wherein V cat is a minimum fluidization velocity of catalyst, and V CNT product is a minimum fluidization velocity of carbon nanotubes supplied to a reactor in the step of forming a fluidized bed.
2. The method of claim 1 , wherein the minimum fluidization velocity of the catalyst is 0.1 cm/s to 10 cm/s.
3. The method of claim 1 , wherein the catalyst has a particle density of 1,300 kg/cm 3 to 2,200 kg/cm 3 .
4. The method of claim 1 , wherein the catalyst has a diameter of 10 μm to 300 μm.
5. The method of claim 1 , wherein, in the step of forming the fluidized bed, when the carbon nanotubes and the catalyst are filled in the reactor to form a packed bed, the packed bed is formed to have a ratio of height to diameter (L/D) of 1 or more.
6. The method of claim 1 , wherein, in the step of forming the fluidized bed, the carbon nanotubes and the catalyst are supplied to the reactor so that a weight ratio of the carbon nanotubes to the catalyst contained in the fluidized bed is 1:0.5 to 1:1.
7. The method of claim 1 , further comprising growing carbon nanotubes on the catalyst by reacting a source gas and the catalyst.
8. The method of claim 7 , wherein, in the step of growing the carbon nanotubes, the temperature difference (ΔT) according to the following formula 2 is 20° C. or less:
Temperature difference (Δ T , ° C.)= T 1 −T 2 [Formula 2]
wherein T 1 and T 2 indicate a temperature of the fluidized bed as measured at two different heights, each being selected arbitrarily from a height ranging from the bottom to the top of the fluidized bed.