Device and method for producing carbon nanotubes

Abstract

A device and a method for producing carbon nanotubes are provided in which catalyst source vapor is rapidly heated and decomposed immediately downstream of an outlet of a catalyst source supply nozzle, thereby attaining both the suppression of nozzle clogging and the formation of catalyst particles at a high density.　A device 1 for producing carbon nanotubes comprises: a synthesis furnace 2 for synthesizing carbon nanotubes; a carbon source flow path 3 for supplying a carbon source as a gas to the synthesis furnace 2; a catalyst source supply nozzle 4 for supplying, as vapor, a catalyst source for synthesizing carbon nanotubes to the synthesis furnace 2; and a catalyst-source heating mechanism 5 configured so that the catalyst source vapor supplied from the catalyst source supply nozzle 4 can be rapidly heated and decomposed immediately downstream of an outlet of the catalyst source supply nozzle 4.

Description

Carbon nanotube manufacturing apparatus and manufacturing method

[0001] The present invention relates to an apparatus and method for producing carbon nanotubes.

[0002] One conventional method for synthesizing carbon nanotubes is the floating catalyst chemical vapor deposition (FCCVD) method, in which a carbon source gas containing dispersed catalyst metal particles is supplied to a synthesis furnace and carbon nanotubes are grown from the suspended catalyst metal particles. This method poses a problem in carbon nanotube productivity because the catalyst particles quickly aggregate in the gas phase, resulting in low catalyst particle density.

[0003] In response to this, a technology has been reported in which iron wire is heated by passing electricity through it to evaporate Fe, which is then cooled with a mixed gas of H2 and N2, and supplied to a reactor where it reacts with CO to continuously synthesize single-walled carbon nanotubes (e.g., Non-Patent Document 1).

[0004] Furthermore, a technique has been reported in which toluene in which ferrocene and thiophene are dissolved is sprayed into a reactor using a two-fluid nozzle with hydrogen as a carrier, thereby continuously synthesizing single-walled carbon nanotubes (for example, Non-Patent Document 2).

[0005] The present inventors have developed a method for continuously synthesizing single-walled carbon nanotubes by decomposing a catalyst raw material in a premixed flame to generate catalyst metal vapor, which is then mixed with a carrier gas and a carbon raw material gas to produce catalyst metal nanoparticles (for example, Patent Document 1).

[0006] The present inventors have also developed a method for continuously synthesizing single-walled carbon nanotubes by winding a tungsten wire around the outer periphery of an alumina catalyst raw material supply nozzle for supplying the catalyst raw material, and heating the tungsten wire by passing an electric current through it to preheat and rapidly increase the temperature of an organometallic compound as the catalyst raw material (for example, Non-Patent Document 3).

[0007] The present inventors have also developed a method for synthesizing carbon nanotubes by supplying catalyst precursor vapor through a nozzle equipped with an internal heating mechanism, decomposing the catalyst precursor vapor in the nozzle, and mixing it with CVD gas in a reactor to generate catalyst nanoparticles at a high density (for example, Patent Document 2).

[0008] Albert G. Nasibulin, et al., Chem. Phys. Lett. 402 (2005) 227-232. Takeshi Saito, et al., J. Phys. Chem. B 110 (2006) 5849-5853. Katsuya Namiki et al., 56th Fullerene, Nanotube, and Graphene General Symposium, 3-3, March 2019.

[0009] Patent No. 6455988 Patent No. 7158646

[0010] The methods disclosed in Non-Patent Documents 1 and 2 do not include the idea of ​​thermally decomposing catalyst raw material vapor at a temperature at which the catalyst metal cannot condense, or the idea of ​​rapidly mixing the catalyst metal vapor with a carbon raw material to produce catalyst metal particles.

[0011] In the method disclosed in Patent Document 1, the heating means is a flame, and there is a problem in that a large amount of water vapor and carbon dioxide are mixed into the carbon nanotube synthesis raw material.

[0012] The method disclosed in Non-Patent Document 3 does not consider the thermal decomposition of catalyst raw material vapor at a temperature at which the catalyst metal cannot be condensed.

[0013] In the method disclosed in Patent Document 2, a high-temperature field is provided within the nozzle in which the catalyst raw material is decomposed to generate catalyst vapor, which creates a medium-temperature region between the high-temperature field and the nozzle inlet, and there is a problem in that the catalyst raw material may adhere to this region and cause the nozzle to become clogged.

[0014] The present invention has been made in consideration of these circumstances, and its objective is to provide a carbon nanotube manufacturing apparatus and method that simultaneously prevents nozzle clogging and produces high-density catalyst particles by rapidly heating and decomposing catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

[0015] In order to solve the above problems, the present invention provides a carbon nanotube manufacturing apparatus comprising: a synthesis furnace for synthesizing carbon nanotubes; a carbon raw material flow passage for supplying a carbon raw material as vapor to the synthesis furnace; a catalyst raw material supply nozzle for supplying a catalyst raw material for synthesizing the carbon nanotubes as vapor to the synthesis furnace; and a catalyst raw material heating mechanism configured to rapidly heat and decompose the catalyst raw material vapor supplied from the catalyst raw material supply nozzle immediately downstream of the outlet of the catalyst raw material supply nozzle.

[0016] The manufacturing apparatus according to the present invention may be configured such that the catalyst raw material heating mechanism uses a high-temperature gas supply nozzle equipped with a heating device to heat a gas that does not generate solids when heated, and the heated gas supplied from the high-temperature gas supply nozzle is mixed with the catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

[0017] In the manufacturing apparatus of the present invention, the heating device may be composed of a filament that heats the gas by passing electricity through it, and the gas may be a gas containing at least one of argon gas, hydrogen gas, and nitrogen gas.

[0018] In the manufacturing apparatus according to the present invention, the catalyst raw material heating mechanism may be configured to include a filament that is provided immediately downstream of the outlet of the catalyst raw material supply nozzle and that heats the catalyst raw material vapor when energized.

[0019] In the manufacturing apparatus according to the present invention, the temperature to which the catalyst raw material vapor supplied from the catalyst raw material supply nozzle is heated by the catalyst raw material heating mechanism immediately downstream of the outlet of the catalyst raw material supply nozzle can be higher than the temperature of the reaction field in the synthesis furnace.

[0020] In the manufacturing apparatus according to the present invention, the temperature of the filament for heating the gas or the catalyst raw material vapor can be set to 1500° C. or higher.

[0021] The production apparatus according to the present invention may be configured so that the carbon raw material gas supplied from the carbon raw material flow passage is mixed with the catalyst raw material vapor that has been heated by the catalyst raw material heating mechanism.

[0022] The present invention also provides a method for producing carbon nanotubes, which comprises rapidly heating and decomposing catalyst raw material vapor supplied from a catalyst raw material supply nozzle that supplies the catalyst raw material for synthesizing the carbon nanotubes as vapor to a synthesis furnace for synthesizing the carbon nanotubes just downstream of the outlet of the catalyst raw material supply nozzle.

[0023] The manufacturing method according to the present invention can include heating a gas that does not generate solids even when heated in a high-temperature gas supply nozzle equipped with a heating device, and mixing the heated gas supplied from the high-temperature gas supply nozzle with the catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

[0024] In the manufacturing method of the present invention, the heating device may be configured to include a filament that heats the gas by passing electricity through it, and the gas may include at least one of argon gas, hydrogen gas, and nitrogen gas.

[0025] In the production method according to the present invention, a filament may be provided immediately downstream of the outlet of the catalyst raw material supply nozzle, and the catalyst raw material vapor may be heated by energizing the filament.

[0026] In the production method according to the present invention, the temperature to which the catalyst raw material vapor supplied from the catalyst raw material supply nozzle is heated immediately downstream of the outlet of the catalyst raw material supply nozzle may be higher than the temperature of the reaction field in the synthesis furnace.

[0027] In the manufacturing method according to the present invention, the temperature of the filament for heating the gas or the catalyst raw material vapor can be set to 1500° C. or higher.

[0028] In the production method according to the present invention, the carbon raw material gas supplied from the carbon raw material flow passage may be mixed with the heated catalyst raw material vapor.

[0029] According to the present invention, it is possible to provide a carbon nanotube manufacturing apparatus and method that can simultaneously prevent nozzle clogging and generate high-density catalyst particles by rapidly heating and decomposing catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

[0030] 1 is a schematic diagram of a carbon nanotube manufacturing apparatus according to a first embodiment. FIG. 1 is a schematic diagram of a carbon nanotube manufacturing apparatus according to a first embodiment, with the vicinity of the catalyst raw material supply nozzle enlarged. FIG. 2 is a schematic diagram of another aspect of a carbon nanotube manufacturing apparatus according to a first embodiment, with the vicinity of the catalyst raw material supply nozzle enlarged. FIG. 3 is a graph showing a Raman spectrum of carbon nanotubes synthesized in Example 1-1. FIG. 4 is a graph showing the measurement results of the catalyst raw material supply nozzle and the pressure of the synthesis furnace in Example 1-1. FIG. 5 is a graph showing the yield and G / D ratio of carbon nanotubes synthesized in Example 1-2. FIG. 6 is a graph showing the yield and G / D ratio of carbon nanotubes synthesized in Example 1-3. FIG. 7 is a graph showing the yield and G / D ratio of carbon nanotubes synthesized in Example 1-5. FIG. 8 is a photographic TEM (Transmission Electron Microscopy) image of carbon nanotubes synthesized in Example 1-5 and a graph showing the diameter of the carbon nanotubes. FIG. 9 is a schematic diagram of a carbon nanotube manufacturing apparatus according to a second embodiment. 12A, 12B, and 12C are a schematic diagram of a carbon nanotube production apparatus according to a second embodiment, with an enlarged view of the vicinity of the catalyst raw material supply nozzle. 12A, 12B, and 12C are a photograph, a graph of a Raman spectrum, and a TEM image of the carbon nanotubes synthesized in Example 2-1, respectively. 12B are a graph showing the results of measuring the pressure of the catalyst raw material supply nozzle and synthesis furnace in Example 2-1. 12C are a graph showing the results of measuring the pressure of the catalyst raw material supply nozzle and synthesis furnace in Example 2-2. 12D are a graph showing the results of measuring the pressure of the catalyst raw material supply nozzle and synthesis furnace in Example 2-3. 12E are a graph showing the results of measuring the pressure of the catalyst raw material supply nozzle and synthesis furnace in Example 2-4.

[0031] Hereinafter, preferred embodiments of the carbon nanotube manufacturing apparatus and manufacturing method of the present invention will be described with reference to the drawings and examples.

[0032] 1 and 2 are schematic diagrams of a carbon nanotube production apparatus 1 according to a first embodiment. The production apparatus 1 includes a synthesis furnace 2 for synthesizing carbon nanotubes, a carbon raw material flow path 3 for supplying a carbon raw material as vapor to the synthesis furnace 2, a catalyst raw material supply nozzle 4 for supplying a catalyst raw material for synthesizing carbon nanotubes as vapor to the synthesis furnace 2, and a catalyst raw material heating mechanism 5 configured to rapidly heat and decompose the catalyst raw material vapor supplied from the catalyst raw material supply nozzle 4 immediately downstream of the outlet of the catalyst raw material supply nozzle 4.

[0033] In the present invention, the inside of the catalyst raw material supply nozzle 4 is not heated, so that adhesion of the catalyst raw material to the inside of the catalyst raw material supply nozzle 4 can be prevented.

[0034] The synthesis furnace 2 is formed of a cylindrical container made of, for example, quartz glass, ceramics, stainless steel, etc. The reaction field 6 of the synthesis furnace 2 is a region where carbon nanotubes grow.

[0035] The catalyst raw material is supplied in a vapor state from the catalyst raw material supply nozzle 4 using, for example, argon gas as a carrier gas. The catalyst raw material vapor supplied from the catalyst raw material supply nozzle 4 is heated by the catalyst raw material heating mechanism 5 immediately downstream of the outlet of the catalyst raw material supply nozzle 4 to a temperature higher than the temperature of the reaction field 6 in the synthesis furnace 2. The catalyst raw material vapor supplied from the catalyst raw material supply nozzle 4 is rapidly heated immediately downstream of the outlet of the catalyst raw material supply nozzle 4, causing the catalyst raw material to be pyrolyzed. The pyrolyzed catalyst raw material is rapidly mixed with the carbon raw material gas supplied from the carbon raw material flow channel 3 and rapidly cooled to the CVD temperature (e.g., 1200°C or less), forming catalyst metal particles. These catalyst metal particles react with the carbon raw material to produce carbon nanotubes. Because the carbon raw material reacts in contact with the catalyst raw material particles without being pyrolyzed, carbon nanotubes can be selectively synthesized without generating soot, resulting in the synthesis of higher-purity carbon nanotubes. Furthermore, by mixing a low-temperature carbon source material with a high-temperature catalyst source vapor, the catalyst source vapor is rapidly cooled to nucleate catalyst source particles at a high density, and at the same time, the carbon source is rapidly heated to initiate the growth of carbon nanotubes, thereby enabling the vapor phase growth of carbon nanotubes with small diameters at a high density.

[0036] The catalyst raw material may contain one or more metal elements selected from iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), yttrium (Y), and copper (Cu) as a catalyst component. Among these, iron (Fe) is particularly preferred, and ferrocene (Fe(C5H5)2) is particularly preferred as a catalyst raw material.

[0037] A promoter may be supplied together with the catalyst raw material. The promoter is preferably sulfur (S). Examples of sulfur sources that can be used include sulfur, thiophene, and hydrogen sulfide. Sulfur is expected to stably form small catalytic metal particles and promote carbon deposition from the iron catalytic metal particles. However, the promoter is not an essential component.

[0038] The carbon raw material is supplied as a gas to the synthesis furnace 2 via the carbon raw material flow passage 3. Examples of the carbon raw material include methane (CH), acetylene (C2H2), ethylene (C2H4), toluene (C6H5CH3), and ethanol (C2H5OH), and in the present invention, methane (CH4) and ethylene (C2H4) are particularly preferred because they can suppress the generation of impurities such as tar. The carbon raw material can be supplied to the synthesis furnace 2 together with a carrier gas such as argon gas or hydrogen gas.

[0039] 1 and 2 , the carbon raw material flows from above to below through the carbon raw material flow passage 3 and is supplied horizontally into the synthesis furnace 2 from a carbon raw material outlet 7 provided on the side of the synthesis furnace 2. The method for supplying the carbon raw material is not particularly limited as long as it can be mixed with the catalyst raw material supplied from the catalyst raw material supply nozzle 4 and decomposed in the reaction field 6 of the synthesis furnace 2.

[0040] The heat retention means 8 that controls the temperature of the reaction field 6 of the synthesis furnace 2 is preferably provided, for example, on the outside of the outer periphery of the synthesis furnace 2. The heat retention means 8 can be, for example, a heating furnace such as an electric furnace that heats by passing an electric current through a nichrome wire or a ceramic heating element, or a heat insulating material that is provided to cover the outer periphery of the synthesis furnace 2. The temperature of the reaction field 6 of the synthesis furnace 2 is preferably kept within a range of 800°C to 1400°C, more preferably 1000°C to 1200°C, suitable for the growth of carbon nanotubes. The temperature of the reaction field 6 of the synthesis furnace 2 is controlled by the heat retention means 8 to maintain the growth temperature of carbon nanotubes and increase the growth time.

[0041] An inert gas such as argon gas may be supplied from above the manufacturing apparatus 1 for purging, if necessary.

[0042] Catalyst raw material heating mechanism 5 of this embodiment is configured to use high-temperature gas supply nozzle 10 equipped with heating device 9 to heat gas that does not generate solids when heated, and to mix the heated high-temperature gas supplied from high-temperature gas supply nozzle 10 with catalyst raw material vapor immediately downstream of the outlet of catalyst raw material supply nozzle 4.

[0043] The gas that does not generate a solid when heated (high-temperature gas) is a gas that contains at least one of argon gas, hydrogen gas, and nitrogen gas.

[0044] Heating device 9 may be formed, for example, by a filament 11 that heats the gas by passing electricity through it. Filament 11 may be disposed inside high-temperature gas supply nozzle 10. Filament 11 may be formed, for example, from tungsten. The temperature of filament 11 may be set to 1500°C or higher. If the temperature is set to 1500°C or higher, the temperature at which catalyst raw material vapor supplied from catalyst raw material supply nozzle 4 by catalyst raw material heating mechanism 5 immediately downstream of the outlet of catalyst raw material supply nozzle 4 can be set to a temperature higher than the temperature of reaction field 6 in synthesis furnace 2. Heating device 9 may alternatively be one that heats the gas by electrical discharge or the like.

[0045] The catalyst raw material supply nozzle 4 and the high-temperature gas supply nozzle 10 are preferably disposed obliquely so that the distance between them gradually decreases from the top to the bottom of the production apparatus 1. This allows the gas to be efficiently mixed with the catalyst raw material vapor.

[0046] Heat-resistant bricks 12 may be provided around the outer periphery of the catalyst raw material supply nozzle 4 and the high-temperature gas supply nozzle 10. Furthermore, heat-resistant bricks (not shown) may also be provided on the top of the catalyst raw material supply nozzle 4 and the high-temperature gas supply nozzle 10.

[0047] 3 shows another aspect of this embodiment. The high-temperature gas supply nozzle 10 extends parallel to the catalyst raw material supply nozzle 4 and bends at a right angle near the outlet of the catalyst raw material supply nozzle 4, so that the high-temperature gas is blown at an angle of 90° onto the catalyst raw material vapor supplied from the catalyst raw material supply nozzle 4.

[0048] In Example 1, evaluation was performed by laser microscopic Raman spectroscopy. The method is described below. The temperature of the filament 11 was measured using a radiation thermometer IGA8Pro / MB20 (manufactured by LumaSense Technologies).

[0049] <Laser Microscopic Raman Spectroscopic Analysis> The crystallinity of carbon nanotubes can be analyzed by, for example, laser microscopic Raman spectroscopy. -1 The peak appearing around 1350 cm is called the G-band and is derived from the in-plane stretching vibration of the carbon atoms having a six-membered ring structure. -1 The peak that appears around the D-band is called the D-band, and is likely to appear if there is a defect in the six-membered ring structure. The relative crystallinity of the carbon nanotube is expressed as the peak intensity ratio I of the G-band to the D-band. G / I D The higher the G / D ratio, the higher the crystallinity of the carbon nanotube. -1 The peak appearing near is a mode called RBM (Radial Breathing Mode), which is specific to single-walled carbon nanotubes (SWCNTs), and is a mode in which the tubes vibrate in the diameter direction. In this example, a carbon nanotube aggregate sample was placed in a laser micro-Raman spectrometer (model number: HR-800, manufactured by Horiba, Ltd.), and laser micro-Raman spectroscopy analysis was performed using a laser wavelength of 488 nm.

[0050] (First Example - 1) High-temperature gas of argon gas and hydrogen gas An apparatus having the configuration shown in Figures 1 and 2 was used. The angle between the high-temperature gas and the catalyst raw material vapor was set to 17°. Table 1 shows the gas species used in the synthesis, the flow rate conditions, the power (Input) of the filament 11, and the yield. In the table, "SLM" stands for Standard Liter / Min, and is a unit of flow rate. The relationship between power and temperature is 1738°C at 140W. The temperature of the reaction field 6 in the synthesis furnace 2 was set to 1200°C.

[0051]

[0052] The Raman spectrum of the synthesized carbon nanotubes is shown in Figure 4. The pressure in the catalyst raw material supply nozzle 4 and the pressure in the synthesis furnace 2 were measured using the first pressure gauge P1 and the second pressure gauge P2, and the pressure loss was evaluated. As shown in Figure 5, both pressures were stable at about 3 kPa, and there was no pressure loss, confirming that there was no clogging of the catalyst raw material supply nozzle 4.

[0053] (First Example - 2) High-temperature argon gas An apparatus having the configuration shown in Figures 1 and 2 was used. The angle between the high-temperature gas and the catalyst raw material vapor was set to 17°. The gas species and flow rate conditions used in the synthesis are shown in Table 2. The temperature of the reaction field 6 in the synthesis furnace 2 was set to 1150°C.

[0054]

[0055] The power and yield of the filament 11 are shown in Table 3. The relationship between power and temperature is 1738°C at 140 W, 1803°C at 160 W, 1861°C at 180 W, and 1912°C at 200 W. A graph of the yield and G / D ratio is shown in Figure 6. In all cases, it was confirmed that there was no pressure loss and no clogging of the catalyst raw material supply nozzle 4.

[0056]

[0057] (Example 1-3) High-temperature nitrogen gas An apparatus with the configuration shown in Figures 1 and 2 was used. The angle between the high-temperature gas and the catalyst raw material vapor was 17°. Table 4 shows the gas species and flow conditions used in the synthesis, the power of the filament 11, and the yield. The relationship between power and temperature was 1738°C at 140W, 1803°C at 160W, 1861°C at 180W, and 1912°C at 200W. The temperature of the reaction field 6 in the synthesis furnace 2 was 1150°C.

[0058]

[0059] A graph of the yield and G / D ratio is shown in Figure 7. In all cases, it was confirmed that there was no pressure loss and no clogging of the catalyst raw material supply nozzle 4.

[0060] (First Example - 4) High-temperature gas of argon gas and hydrogen gas The apparatus shown in Figures 1 and 2 was used. The angle between the high-temperature gas and the catalyst raw material vapor was 17°. The gas species and flow rate conditions used in the synthesis are shown in Table 5. The temperature of the reaction field 6 in the synthesis furnace 2 was 1200°C.

[0061]

[0062] The power and yield of the filament 11 are shown in Table 6. The relationship between power and temperature was 1803°C at 160 W, 1738°C at 140 W, and 1647°C at 120 W. In all cases, it was confirmed that there was no pressure loss and no clogging of the catalyst raw material supply nozzle 4.

[0063]

[0064] (Example 1-5) High-temperature gas of argon gas and / or hydrogen gas The apparatus shown in Figures 1 and 2 was used. The angle between the high-temperature gas and the catalyst raw material vapor was set to 17°. The gas species used in the synthesis, flow conditions, and yield are shown in Table 7. In this example, the amount of hydrogen in the side gas (CVD raw material gas) was reduced to match the amount of hydrogen in the high-temperature gas, so as to maintain a constant hydrogen concentration in the reaction field 6 of the synthesis furnace 2. The power of the filament 11 was set to 140 W (1738°C), and the temperature of the reaction field 6 of the synthesis furnace 2 was set to 1200°C.

[0065]

[0066] A graph of the yield and G / D ratio is shown in Figure 8. It was found that carbon nanotubes could be synthesized using argon gas only, hydrogen gas only, and a high-temperature gas of argon gas and hydrogen gas. In all cases, it was confirmed that there was no pressure loss and no clogging of the catalyst raw material supply nozzle 4. Figure 9 shows a TEM image of the synthesized carbon nanotubes and their diameters. It was found that carbon nanotubes with a diameter of approximately 2 nm and a ratio of single-walled carbon nanotubes to double-walled carbon nanotubes of approximately 2:1 could be synthesized regardless of the amount of hydrogen in the high-temperature gas.

[0067] (First Example - 6) High-temperature gas (90°) of argon gas and hydrogen gas The apparatus shown in Figure 3 was used. The angle between the high-temperature gas and the catalyst raw material vapor was 90°. The gas species and flow rate conditions used in the synthesis are shown in Table 8. The temperature of the reaction field 6 in the synthesis furnace 2 was set to 1200°C.

[0068]

[0069] The power and yield of the filament 11 are shown in Table 9. The relationship between power and temperature is 25°C at 0 W, 1803°C at 160 W, 1861°C at 180 W, and 1912°C at 200 W. It was found that carbon nanotubes could not be synthesized if the temperature of the filament 11 was lower than that of the reaction field 6 in the synthesis furnace 2. In all cases, it was confirmed that there was no pressure loss and that the catalyst raw material supply nozzle 4 was not clogged.

[0070]

[0071] 10 and 11 are schematic diagrams of a carbon nanotube production apparatus 21 according to a second embodiment. Similar to the first embodiment, the production apparatus 21 includes a synthesis furnace 2 for synthesizing carbon nanotubes, a carbon raw material flow path 3 for supplying a carbon raw material as vapor to the synthesis furnace 2, a catalyst raw material supply nozzle 4 for supplying a catalyst raw material for synthesizing carbon nanotubes as vapor to the synthesis furnace 2, and a catalyst raw material heating mechanism 5 configured to rapidly heat and decompose the catalyst raw material vapor supplied from the catalyst raw material supply nozzle 4 immediately downstream of the outlet of the catalyst raw material supply nozzle 4.

[0072] This embodiment is different from the first embodiment in the configuration of the catalyst raw material heating mechanism 5, but other configurations are almost the same. Components similar to those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0073] In this embodiment, catalyst raw material heating mechanism 5 can be configured with a filament 22 that is located immediately downstream of the outlet of catalyst raw material supply nozzle 4 and heats the catalyst raw material vapor by passing electricity through it. Filament 22 can be made of, for example, tungsten. The temperature of filament 22 can be set to 1500°C or higher. If the temperature is set to 1500°C or higher, the temperature at which catalyst raw material heating mechanism 5 heats the catalyst raw material vapor supplied from catalyst raw material supply nozzle 4 immediately downstream of the outlet of catalyst raw material supply nozzle 4 can be set to a temperature higher than the temperature of reaction field 6 in synthesis furnace 2. Furthermore, setting the temperature to 1500°C or higher can also prevent the catalyst raw material from adhering to filament 22. Alternatively, catalyst raw material heating mechanism 5 can be configured to heat by electrical discharge or the like instead of by filament 22.

[0074] An inert gas supply nozzle 23 for supplying an inert gas such as argon gas may be provided around the outer periphery of the catalyst raw material supply nozzle 4. The inert gas passes around the outer periphery of the catalyst raw material supply nozzle 4 and is sprayed onto the filament 22. By passing the inert gas around the outer periphery of the catalyst raw material supply nozzle 4, it is possible to prevent the catalyst raw material and carbon from adhering to the outer tube wall of the catalyst raw material supply nozzle 4.

[0075] Heat-resistant bricks 24 may be provided on the outer periphery of the catalyst raw material supply nozzle 4 and the inert gas supply nozzle 23. The heat-resistant bricks 24 are preferably provided so as to extend to the outer periphery of the filament 22.

[0076] An inert gas such as argon gas may be supplied from above the manufacturing apparatus 21 for purging, if necessary.

[0077] In Example 2, evaluation by laser micro-Raman spectroscopy was performed in the same manner as in Example 1. The temperature of the filament 22 was measured using a radiation thermometer IGA8Pro / MB20 (manufactured by LumaSense Technologies).

[0078] (Second Example-1) The gas species and flow rate conditions used in synthesis are shown in Table 10. In the table, [at / at] is the atomic ratio. The power of the filament 22 was 200 W (1615°C), and the temperature of the reaction field 6 in the synthesis furnace 2 was 1200°C.

[0079]

[0080] The synthesis was carried out for 20 minutes, and the yield was 440 mg.

[0081] FIG. 12A shows a photograph of the synthesized carbon nanotubes, FIG. 12B shows a graph of the Raman spectrum, and FIG. 12C shows a TEM image.

[0082] The pressure in the catalyst raw material supply nozzle 4 and the pressure in the synthesis furnace 2 were measured using the first pressure gauge P1 and the second pressure gauge P2, and the pressure loss was evaluated. As shown in Fig. 13, both pressures were stable at about 3 kPa, there was no pressure loss, and it was confirmed that there was no clogging of the catalyst raw material supply nozzle 4.

[0083] (Second Example - 2) The gas species and flow rate conditions used in the synthesis are as shown in Table 10. The power of the filament 22 was 160 W (1531°C), and the temperature of the reaction field 6 in the synthesis furnace 2 was 1200°C.

[0084] The synthesis was carried out for 10 minutes, and the yield was 175 mg.

[0085] The pressure in the catalyst raw material supply nozzle 4 and the pressure in the synthesis furnace 2 were measured using the first pressure gauge P1 and the second pressure gauge P2, and the pressure loss was evaluated. As shown in Figure 14, both pressures were the same, and there was no pressure loss between the upstream (P2) and downstream (P1) of the catalyst raw material supply nozzle 4, confirming that there was no blockage of the catalyst raw material supply nozzle 4.

[0086] (Second Example - 3) The gas species and flow rate conditions used in the synthesis are as shown in Table 10. The power of the filament 22 was 220 W (1636°C), and the temperature of the reaction field 6 in the synthesis furnace 2 was 1200°C.

[0087] The synthesis was carried out for 10 minutes, and the yield was 132 mg.

[0088] The pressure in the catalyst raw material supply nozzle 4 and the pressure in the synthesis furnace 2 were measured using the first pressure gauge P1 and the second pressure gauge P2, and the pressure loss was evaluated. As shown in Figure 15, both pressures were stable at about 3 to 5 kPa, there was no pressure loss, and it was confirmed that there was no clogging of the catalyst raw material supply nozzle 4.

[0089] (Second Example-4) The gas species and flow rate conditions used in the synthesis are as shown in Table 10. The power of the filament 22 was 240 W (1645°C), and the temperature of the reaction field 6 in the synthesis furnace 2 was 1200°C.

[0090] The synthesis was carried out for 10 minutes, and the yield was 67 mg.

[0091] The pressure in the catalyst raw material supply nozzle 4 and the pressure in the synthesis furnace 2 were measured using the first pressure gauge P1 and the second pressure gauge P2, and the pressure loss was evaluated. As shown in Figure 16, both pressures were stable at about 3 to 5 kPa, there was no pressure loss, and it was confirmed that there was no clogging of the catalyst raw material supply nozzle 4.

[0092] The present invention has been described above based on embodiments and examples, but the present invention can be implemented in various modified forms. For example, although the above embodiment uses a vertical apparatus, it may also be a horizontal apparatus. The above examples are illustrative of embodiments of the present invention and should not be construed as limiting the scope of the present invention. Note that although specific gas species are shown in the figures, the gas species of the various raw materials described above can be combined as appropriate.

[0093] REFERENCE SIGNS LIST 1 Carbon nanotube manufacturing apparatus 2 Synthesis furnace 3 Carbon raw material flow passage 4 Catalyst raw material supply nozzle 5 Catalyst raw material heating mechanism 6 Reaction field 7 Carbon raw material outlet 8 Heat insulation means 9 Heating device 10 High-temperature gas supply nozzle 11 Filament 12 Heat-resistant brick 21 Carbon nanotube manufacturing apparatus 22 Filament 23 Inert gas supply nozzle 24 Heat-resistant brick

Claims

1. An apparatus for producing carbon nanotubes, comprising: a synthesis furnace for synthesizing carbon nanotubes; a carbon raw material flow path for supplying a carbon raw material as a gas to the synthesis furnace; a catalyst raw material supply nozzle for supplying a catalyst raw material for synthesizing the carbon nanotubes as a vapor to the synthesis furnace; and a catalyst raw material heating mechanism configured to rapidly heat and decompose the catalyst raw material vapor supplied from the catalyst raw material supply nozzle immediately downstream of the outlet of the catalyst raw material supply nozzle.

2. The carbon nanotube manufacturing apparatus of claim 1, wherein the catalyst raw material heating mechanism is configured to heat a gas that does not generate solids when heated using a high-temperature gas supply nozzle equipped with a heating device, and to mix the heated gas supplied from the high-temperature gas supply nozzle with the catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

3. The carbon nanotube manufacturing apparatus according to claim 2, wherein the heating device is composed of a filament that heats the gas by passing electricity through it, and the gas is a gas containing at least one of argon gas, hydrogen gas, and nitrogen gas.

4. The carbon nanotube manufacturing apparatus according to claim 1, wherein the catalyst raw material heating mechanism is composed of a filament that is provided immediately downstream of the outlet of the catalyst raw material supply nozzle and heats the catalyst raw material vapor when energized.

5. A carbon nanotube manufacturing apparatus according to any one of claims 1 to 4, wherein the temperature at which the catalyst raw material vapor supplied from the catalyst raw material supply nozzle is heated by the catalyst raw material heating mechanism immediately downstream of the outlet of the catalyst raw material supply nozzle is higher than the temperature of the reaction site in the synthesis furnace.

6. The carbon nanotube manufacturing apparatus according to claim 3 or 4, wherein the temperature of the filament for heating the gas or the catalyst raw material vapor is set to 1500° C. or higher.

7. The carbon nanotube manufacturing apparatus according to claim 1, wherein the carbon raw material gas supplied from the carbon raw material flow passage is mixed with the catalyst raw material vapor after being heated by the catalyst raw material heating mechanism.

8. A method for producing carbon nanotubes, comprising: rapidly heating and decomposing a catalyst raw material vapor supplied from a catalyst raw material supply nozzle, which supplies the catalyst raw material for synthesizing the carbon nanotubes as vapor to a synthesis furnace for synthesizing the carbon nanotubes, immediately downstream of the outlet of the catalyst raw material supply nozzle.

9. A method for producing carbon nanotubes as described in claim 8, wherein a gas that does not produce solids when heated is heated in a high-temperature gas supply nozzle equipped with a heating device, and the heated gas supplied from the high-temperature gas supply nozzle is mixed with the catalyst raw material vapor immediately downstream of the outlet of the catalyst raw material supply nozzle.

10. The method for producing carbon nanotubes according to claim 9, wherein the heating device is composed of a filament that heats the gas by passing electricity through it, and the gas is a gas containing at least one of argon gas, hydrogen gas, and nitrogen gas.

11. The method for producing carbon nanotubes according to claim 8, wherein a filament is provided immediately downstream of the outlet of the catalyst raw material supply nozzle, and the catalyst raw material vapor is heated by energizing the filament.

12. A method for producing carbon nanotubes according to any one of claims 8 to 11, wherein the temperature at which the catalyst raw material vapor supplied from the catalyst raw material supply nozzle is heated immediately downstream of the outlet of the catalyst raw material supply nozzle is higher than the temperature of the reaction site in the synthesis furnace.

13. The method for producing carbon nanotubes according to claim 10 or 11, wherein the temperature of the filament for heating the gas or the catalyst raw material vapor is set to 1500° C. or higher.

14. The method for producing carbon nanotubes according to claim 8, wherein the carbon raw material gas supplied from the carbon raw material flow passage is mixed with the heated catalyst raw material vapor.

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