JP6418690B2 - Carbon nanotube production equipment - Google Patents

Carbon nanotube production equipment Download PDF

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JP6418690B2
JP6418690B2 JP2015032114A JP2015032114A JP6418690B2 JP 6418690 B2 JP6418690 B2 JP 6418690B2 JP 2015032114 A JP2015032114 A JP 2015032114A JP 2015032114 A JP2015032114 A JP 2015032114A JP 6418690 B2 JP6418690 B2 JP 6418690B2
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gas
carbon nanotubes
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JP2016153353A (en
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野田 優
優 野田
麻衣 山口
麻衣 山口
利男 大沢
利男 大沢
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学校法人早稲田大学
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Description

  The present invention relates to a carbon nanotube production apparatus, and more particularly to a carbon nanotube production apparatus equipped with a premixed flame tube and burner.

  Single-walled carbon nanotubes have a diameter of 0.6 to several nm, a length of several μm or more, and a very high aspect ratio. Due to such an elongated shape, it is expected to be applied to a power-saving thin TV as a scanning probe needle or an electron emission source. In addition, various applications such as transistors, transparent electrodes, and electrodes for batteries and capacitors have been proposed because of their excellent electrical and electronic characteristics and stability.

  Various methods for synthesizing carbon nanotubes have been developed. However, mass synthesis of single-walled carbon nanotubes with a particularly small diameter has not been realized, and it is still very expensive at tens of thousands of yen per gram.

  On the other hand, the flame synthesis method has a track record as a method for synthesizing a large amount of carbon materials such as carbon black and fullerene by a non-catalytic reaction. An example in which this flame synthesis method is applied to the synthesis of carbon nanotubes has been reported (for example, see Non-Patent Documents 1 and 2). Non-Patent Document 1 states that single-walled carbon nanotubes could be synthesized in a narrow region where the fuel equivalence ratio of the mixed gas of acetylene and oxygen was 1.6 to 1.8. In Non-Patent Document 2, it is said that a production amount of 5 g / h was obtained by using methane as the fuel and ferrocene as the catalyst raw material and using a burner with a proven track record of fullerene synthesis.

  It has also been proposed to establish a sootless flame and provide an unsupported catalyst for synthesizing single-walled nanotubes in the post-flame region (see, for example, Patent Document 1).

  Further, a method has been proposed in which a catalytic metal is brought close to a premixed flame containing carbon in the fuel and carbon nanotubes are synthesized on the catalytic metal (see, for example, Patent Document 2).

  In addition, a method has been proposed in which a fuel, an oxidant, and metal catalyst fine particles are supplied to form a flame, and carbon nanotubes are generated and grown on the floating metal catalyst fine particles (see, for example, Patent Document 3).

  Many other carbon nanotube production methods using other combustion methods have also been reported (see, for example, Patent Documents 4 to 7).

  In addition, when carbon nanotubes are synthesized by supplying a carbon source onto a catalyst supported on a support, a proposal has been made to synthesize carbon nanotubes by heating the support in a heating furnace to increase the temperature of the catalyst. (For example, refer to Patent Document 8).

  Moreover, it is known that the yield of carbon nanotubes increases by adding sulfur (for example, refer nonpatent literature 3). Examples of the sulfur source include powdered sulfur, thiophene, and hydrogen sulfide (see, for example, Non-Patent Documents 4 to 6). Moreover, adding sulfur to the catalyst is said to have the effect of lowering the surface energy of iron and stabilizing small particles (see, for example, Non-Patent Document 7). Furthermore, it is said that the precipitation of carbon from the iron catalyst particles is promoted by forming a FeS eutectic (see, for example, Non-Patent Documents 7 and 8).

Murry J. height et al, Proceedings of the Combustion Institute 30, 2537-2543 (2005). Henning Richter et al, Nanoscience and Nanotechnology 8, 6065-6074 (2008). Hui Ming Cheng at al, Applied Physics Letters 72 (25), 3282-3284 (1998) Wencai Ren et al, Journal of Nanoscience and Nanotechnology 6, 1339-1345 (2006). Cui et al. Nanoscale Research Letters 6, 77 (2011). Gary C. Tibbetts at al, Carbon 32 (4), 569-576 (1994) Lili Zhang et al, J. Phys. Chem. Lett. 5, 1427-1432 (2014). Wencai Ren, Feng Li, Hui-Ming Cheng, J. Phys. Chem. B 110, 16941-16946 (2006).

JP-T-2006-523175 JP 2005-247644 A JP 2010-126390 A JP-A-11-116218 Special table 2009-502730 International Publication No. WO2009 / 116261 International Publication No. WO2007 / 088867 International Publication No. WO2008 / 029927

  However, in the conventional flame synthesis or combustion synthesis described in the above-mentioned prior art documents, carbon nanotubes are synthesized using unburned carbon of the flame as a raw material or a catalyst is supported, so the combustion method Losing its strength, it has not led to efficient synthesis of good quality carbon nanotubes. On the other hand, in the present invention, the flame is used for decomposition and heating of the catalyst raw material, and the carbon raw material is supplied separately, so that the carbon nanotube synthesis method according to the present invention is regarded as a kind of chemical vapor deposition (CVD) method, Aims at mass synthesis of carbon nanotubes with excellent crystallinity, especially single-walled carbon nanotubes.

  The present invention has been made in view of such circumstances, and in a manufacturing apparatus for synthesizing carbon nanotubes, established a highly productive process aimed at mass production, mainly with the temperature of the reaction region in the chamber. By controlling the mixing process of catalyst raw material gas, carrier gas, and carbon source gas, it is an object to provide an apparatus that can synthesize high-quality carbon nanotubes with excellent crystallinity at low cost and high yield and yield. To do.

  The invention according to claim 1 is an apparatus for producing carbon nanotubes, wherein a chamber in which carbon nanotubes provided therein are synthesized, a premixed flame containing a catalyst raw material, connected to the chamber, are formed, One or more first pipes for decomposing the catalyst raw material and one or more second pipes connected to the chamber, supplying a carrier gas, mixing with the decomposed catalyst raw material, and generating catalyst particles One or more third tubes connected to the chamber, supplied with a carbon source gas and mixed with the catalyst particles to grow the carbon nanotubes, and heat retaining means provided on the outer periphery of the chamber It is an apparatus characterized by comprising.

  The invention described in claim 2 is such that the gas flowing out from the first pipe joins the gas flowing out from the second pipe, and then the gas flowing out from the third pipe joins. The pipe outlet, the second pipe outlet, and the third pipe outlet are provided.

  According to a third aspect of the present invention, the third pipe is installed in the third pipe so that the carbon source gas is directly heat-exchanged with the heat retaining means or exchanged with the gas inside the chamber. After being preheated by a preheater, it is connected to the chamber so as to be supplied to the reaction region for growing the carbon nanotubes.

  The invention described in claim 4 is characterized in that a promoter is supplied from at least one of the first pipe and the second pipe.

  The invention described in claim 5 is characterized in that the heat retaining means comprises a heating furnace or a heat insulating material.

  According to the first aspect of the present invention, it is possible to synthesize a carbon nanotube having a long length, high purity and good quality in a high yield by maintaining the carbon nanotube synthesis temperature by providing a heat retaining means to maintain the growth of the carbon nanotube. A simple manufacturing apparatus can be provided.

  According to the apparatus of claim 2, the formation of catalyst particles can be optimized by flowing the carrier gas from the second pipe and joining the gas from the first pipe.

  According to the apparatus of claim 3, the carbon source gas containing the carbon raw material is preheated from the third tube and then supplied, so that the temperature suitable for the growth of the carbon nanotube is maintained, and the carbon nanotube having high crystallinity Can be synthesized.

  According to the apparatus of claim 4, the yield of carbon nanotubes can be increased by adding a cocatalyst.

  According to the apparatus of Claim 5, the range of the growth temperature of a carbon nanotube can be increased in a chamber by using a heating furnace or a heat insulating material.

It is the schematic of the manufacturing apparatus of the carbon nanotube which shows Example 1 of this invention. It is the schematic of a ferrocene supply part same as the above. It is a conceptual diagram which shows the flow of the gas which passes a premixed flame same as the above. It is a figure which shows the simulation result which shows the difference in the temperature distribution in a chamber by the presence or absence of a heating furnace same as the above. It is the schematic for demonstrating the length of a burner same as the above. It is a conceptual diagram for demonstrating the synthesis mechanism of a carbon nanotube same as the above. It is a conceptual diagram for demonstrating the synthesis mechanism of a carbon nanotube same as the above. It is a conceptual diagram for demonstrating the synthesis mechanism of a carbon nanotube same as the above. It is a conceptual diagram for demonstrating the synthesis mechanism of a carbon nanotube same as the above. It is a SEM image of the product produced | generated on each condition which changed the temperature of the heating furnace same as above, and was collected on the membrane filter. It is the schematic of the manufacturing apparatus of the carbon nanotube which shows Example 2 of this invention. It is a schematic diagram of a 1st pipe | tube, a 2nd pipe | tube, and a 3rd pipe | tube same as the above. It is the schematic of the manufacturing apparatus of the carbon nanotube which shows Example 3 of this invention. It is the photograph of the product after the synthesis | combination collected with the membrane filter same as the above. The above is a photograph of the product peeled off from the membrane filter. It is a SEM image of the product produced | generated on each condition which changed supply_amount | feed_rate of sulfur as above and collected on the membrane filter. It is a Raman spectrum of the product produced | generated on each condition which changed supply_amount | feed_rate of sulfur as above and collected on the membrane filter. It is a SEM image of the product collected on the membrane filter same as the above. It is a SEM image of the product produced | generated with the manufacturing apparatus of Example 4 of this invention, and was collected on the membrane filter. It is a Raman spectrum of the product produced | generated with the manufacturing apparatus of Example 4 of this invention, and was collected on the membrane filter. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus used for Example 1, 3 and 4 of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention. It is the schematic of the manufacturing apparatus which shows the other Example of this invention.

  Hereinafter, the carbon nanotube manufacturing apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing Example 1 of a manufacturing apparatus 1 for synthesizing, for example, the carbon nanotube 2 shown in FIG.

  In this embodiment, a chamber 3 in which the carbon nanotubes 2 provided in the manufacturing apparatus 1 are synthesized, a first tube 4, a second tube 5 and a third tube 6 connected to the chamber 3, And a heat retaining means 7 provided on the outer periphery of the chamber 3.

  The chamber 3 is formed of a cylindrical container made of, for example, ceramics or stainless steel. The reaction region 8 in the chamber 3 is a region where the carbon nanotubes 2 are grown by a mechanism described later.

The first tube 4 is connected to the chamber bottom 26 of the chamber 3 and constitutes a burner for the premixed flame 12. A fuel gas 10a such as ethylene (C 2 H 4 ), for example, is supplied to the first pipe 4a from the first pipe gas supply unit 21 together with argon (Ar). On the other hand, for the purpose of supplying ferrocene (Fe (C 5 H 5 ) 2 ), which is the catalyst raw material 11, for example oxygen (O 2 ) from the first pipe gas supply unit 21 via the first pipe 4b. An oxidizing gas 10b such as argon is supplied to a catalyst raw material supply unit 35 for supplying, for example, ferrocene as the catalyst raw material 11 together with argon or the like. Then, the gas containing ferrocene sublimated in the catalyst raw material supply unit 35 is mixed with the fuel gas 10a. Thus, the premixed flame 12 containing the catalyst raw material 11 is formed at the tip of the burner which is the first pipe 4, and the catalyst raw material 11 is contained in the chamber 3 from the first pipe 4 via the first pipe outlet 50. A premixed gas 13 is supplied. When the premixed gas 13 containing the catalyst raw material 11 passes through the premixed flame 12, the catalyst raw material 11 is decomposed.

  FIG. 2 shows an example of the catalyst raw material supply unit 35 in the case of supplying ferrocene as the catalyst raw material 11. The catalyst raw material supply unit 35 charges the ferrocene powder 37 directly into the wall 36 of the catalyst raw material supply unit made of, for example, a quartz tube, and closes both sides thereof with a catalyst raw material holding material 38 made of, for example, quartz cotton. With this configuration, the supply amount of ferrocene can be made to depend only on the vapor pressure, that is, the temperature, regardless of the amount of ferrocene powder 37 charged. Temperature control is performed using a thermocouple 39.

  As the catalyst raw material 11, a catalyst component containing one or more metal elements selected from iron, cobalt, nickel, molybdenum, yttrium and copper can be used. Among these, iron is particularly preferable, and ferrocene is particularly preferable as the catalyst raw material 11.

  Since the premixed flame 12 is self-heating, it is easy to scale up. In addition, since the flame surface is automatically formed at a position where the flame propagation and the gas flow rate are balanced, it is easy to control and a stable flame surface can be formed. Therefore, as shown in FIG. It passes through the flame surface and is decomposed. Then, by forming a stable flame with a fuel equivalence ratio of about 1, preferably 0.9 to 1.1, and flowing a catalyst raw material 11 such as ferrocene sublimated with the fuel gas 10, the flame is heated to a high temperature of 2000 ° C. or higher. Ferrocene can be broken down in an instant.

  Similar to the first tube 4, the second tube 5 is connected to the chamber bottom 26 of the chamber 3. A carrier gas 14 such as argon is supplied to the second pipe 5 from the second pipe gas supply section 22, and the catalyst raw material 11 decomposed by the premixed flame 12 at the end of the first pipe 4 and Mix to generate catalyst particles 15. The carrier gas 14 is supplied from the second pipe outlet 51 into the chamber 3. In the present embodiment, the second pipe outlet 51 of the second pipe 5 is integrally formed around the first pipe 4. However, the second pipe outlet 51 may be provided separately from the first pipe 4 as long as the carrier gas 14 can be mixed with the decomposed catalyst raw material 11. In this embodiment, the decomposed catalyst raw material 11 is mixed with the carrier gas 14 to form the catalyst particles 15 and then mixed with the carbon source gas 16. As a result, direct contact between the carbon source gas 16 and the premixed flame 12 can be prevented. As a result, it is possible to prevent the deactivation of the catalyst particles 15 before sufficiently growing, and to improve the catalyst utilization rate.

The third tube 6 is provided on the outer periphery of the chamber 3 so as to cover the chamber side 27 of the chamber 3. A carbon source gas 16 such as methane (CH 4 ), for example, is supplied to the third pipe 6 from the third pipe gas supply unit 23 together with argon. The carbon source gas 16 is mixed with the catalyst particles 15 to grow the carbon nanotubes 2. The carbon source gas 16 flows from the chamber top 25 to the chamber bottom 26, that is, from the top to the bottom. Supplied.

  With the configuration described above, the first pipe outlet 50, the second pipe outlet 51, and the third pipe outlet 52 allow the gas flowing out from the first pipe 4 to flow out from the second pipe 5. It is installed so that the gas flowing out from the third pipe 6 joins after the joining with the gas.

  In the present embodiment, each of the first tube 4, the second tube 5, and the third tube 6 is one, but a plurality of each may be provided. Examples in this case will be described later in [Other Examples].

  The heat retaining means 7 is provided on the outer periphery of the chamber 3. In this embodiment, the heat retaining means 7 is constituted by a heating furnace 33. The heating furnace 33 is provided on the outer periphery of the third tube 6 and manages the temperature by the temperature control unit 24. As the heating furnace 33, for example, an electric furnace that heats by passing a current through a nichrome wire or the like can be used. Under the manufacturing conditions of the present embodiment described later, the temperature of the heating furnace 33 is preferably maintained at 900 to 1000 ° C. This heating furnace 33 manages the temperature of the reaction region 8 in the chamber 3 to maintain the growth temperature of the carbon nanotubes 2 and increase the growth time. Further, the carbon source gas 16 flowing in the third pipe 6 is preheated by the heating furnace 33. The carbon source gas 16 is supplied into the chamber 3 after this preheating.

  FIG. 4 is a simulation result showing the temperature distribution in the chamber 3 when (A) the heating furnace 33 is provided and (B) when the heating furnace 33 is not provided. Without the heating furnace 33, the gas in the reaction region 8 is cooled quickly, and the space corresponding to the growth temperature of the carbon nanotube 2 is narrow. On the other hand, when the heating furnace 33 is provided, the range of the growth temperature can be increased by heating in the heating furnace 33.

  Further, the third pipe 6 is structured to be preheated in the process of flowing the carbon source gas 16 from the top to the bottom, so that the reaction region 8 is exchanged by heat exchange between the carbon source gas 16 and the gas in the reaction region 8. It is possible to cool the gas discharged from the gas, assist the preheating of the carbon source gas 16, and reduce the energy required for the heating furnace 33.

  The heat retaining means 7 may be provided with a heat insulating material 56 (see FIG. 5 and the like) so as to cover the outer periphery of the third pipe 6 without using the heating furnace 33. The carbon source gas 16 can be preheated by heat exchange with the gas in the reaction region 8 in the chamber 3 without using the heating furnace 33. When the heat insulating material 56 is used, the configuration of the temperature control unit 24 can be omitted.

  The flow rate of the gas flowing inside the first pipe 4, the second pipe 5 and the third pipe 6 is as follows: the first pipe gas supply part 21, the second pipe gas supply part 22 and the third pipe gas supply. The unit 23 can be controlled by a mass flow controller (not shown).

  A quartz tube having an inner diameter of 1 mm and 2 mm was used as a burner extending from the first tube 4 into the chamber 3. As shown in FIG. 5, when the length of the burner is long and the distance between the premixed flame 12 and the third pipe outlet 52 where the carbon source gas 16 blows into the chamber 3 is short, the carbon source gas 16 is burned. As a result, the amount of soot increases. Therefore, it is preferable that the length of the burner is such that the tip of the burner is positioned below the third pipe outlet 52. In this embodiment, there is one burner, but a plurality of burners may be provided.

  The premixed gas flow 17 containing the catalyst raw material flows toward the first tube outlet 50 at the tip of the first tube 4 extending into the chamber 3. The carrier gas flow 18 flows from the second pipe 5 toward the second pipe outlet 51. The carbon source gas flow 19 flows from the third pipe 6 toward the third pipe outlet 52. The carbon source gas stream 19 in the third pipe 6 is in the opposite direction to the premixed gas stream 17 containing the catalyst raw material in the burner and the carrier gas stream 18 from the second pipe outlet 51. . The carbon source gas flow 19 blown out from the third pipe outlet 52 includes the flow of the catalyst raw material 20a decomposed by the premixed flame 12 at the end of the burner and the carrier from the second pipe outlet 51. The direction is perpendicular to the gas flow 18 (horizontal direction).

  The carbon nanotubes 2 synthesized in the reaction region 8 are collected by a collecting means (not shown) provided downstream of the chamber upper portion 25. The collecting means includes, for example, a membrane filter (not shown).

The temperature of the premixed flame 12 formed from ethylene and oxygen as raw materials in the first pipe 4 is supplied from the flame temperature T flame , the decomposed catalyst raw material 11 from the first pipe 4, and the second pipe 5. The temperature after mixing with argon is the catalyst formation temperature T cat , and the temperature when the carbon source gas supplied from the third tube 6 is mixed after this mixing is the mixing temperature T CVD . The flame temperature T flame and the catalyst formation temperature T cat were defined as temperatures at which all combustion heat became sensible heat, and were calculated by dividing the combustion heat by the heat capacity of the gas. However, the actual temperature is considered to be lower than the calculated temperature due to decomposition of gas molecules and heat loss. A formula for calculating the flame temperature T frame is shown in Equation 1. Here, ΔH is the heat of combustion, F is the volume flow rate, P is the pressure (= 101325 [Pa]), R is the gas constant (= 8.31 [Jmol −1 K −1 ]), T is the temperature, Cp is the constant pressure heat capacity, ρ is the density, and T 0 is the temperature of the premixed gas 13 in the first pipe 4.

  A mechanism for synthesizing the carbon nanotube 2 in this embodiment will be described. First, as shown in FIG. 6, the catalyst raw material 11 (ferrocene) is decomposed through the flame surface of the premixed flame 12. Next, as shown in FIG. 7, the decomposed catalyst raw material 11 merges with the carrier gas (argon) flow 18 supplied from the second pipe 5 and is cooled, and the catalyst particles 15 (iron particles) are nucleated. Generated. At this time, as shown in FIG. 9, carbon may be nucleated from some catalyst particles 15 to synthesize the carbon nanotubes 2. Then, as shown in FIG. 8, the carbon source gas flow 19 merges from the lateral direction, and carbon nanotubes grow from the catalyst particles 15 that are not deactivated.

The preferable temperature of each reaction field in each of the above steps is as follows. First, in the decomposition of the catalyst material 11, in the range of the actual temperature of 2,000 to 4,000 ° C., preferably in the range of 2000 to 5000 ° C. at T flame. Next, in the nucleation of catalyst particles, it is preferable that the actual temperature is in the range of 900 to 1500 ° C. and the T cat is in the range of 900 to 2000 ° C. Further, in the growth of carbon nanotubes, in the range of 800 to 1400 ° C. at the actual temperature, it is preferably in the range of 800 to 2000 ° C. at T CVD.

  Carbon nanotubes were synthesized and evaluated using the production apparatus 1 of this example. The manufacturing conditions are shown in Table 1. In order to control the catalytic reaction, the heating furnace temperature was changed within the range of 900 to 1000 ° C.

  In FIG. 10, the SEM image of the product produced | generated on each condition which changed the temperature of the heating furnace 33, and was collected on the membrane filter is shown. The temperature of the heating furnace 33 is 900 ° C. in FIG. 10 (A), 960 ° C. in (B), and 1000 ° C. in (C). FIGS. 10D to 10F are obtained by further enlarging the samples under the temperature conditions of (A) to (C), respectively.

From these SEM images, it can be seen that the carbon nanotubes 2 were well synthesized when the heating furnace temperature was 900 ° C. In this way, by adjusting the heating furnace temperature, for example, by setting the heating furnace temperature to substantially the same temperature as TCVD , the carrier gas 14 supplied from the second pipe 5 or the third pipe 6 is supplied. It is considered that a sufficient cooling rate by the carbon source gas 16 is obtained and the growth time of the carbon nanotubes 2 is prolonged.

  11 and 12 show a second embodiment of the present invention, in which the same reference numerals are given to the same portions as the above-described embodiments, and detailed description thereof is omitted. FIG. 11 is a schematic view of the manufacturing apparatus 1 of the present embodiment, and FIG. 12 is a schematic view showing the configuration of the first tube 4, the second tube 5 and the third tube 6. The basic configuration is the same as that of the first embodiment. The difference from the first embodiment is that the third tube 6 is provided not on the outer periphery of the chamber 3 but on the outer periphery of the second tube 5.

  Conventionally, the premixed gas 13 containing the catalyst raw material is supplied from the first pipe without providing the second pipe as in the present embodiment, and the carbon source gas 16 is supplied from the third pipe provided immediately outside the first pipe. Since the carbon source gas 16 and the premixed flame 12 are in contact with each other before the catalyst particles 15 are sufficiently grown, soot is generated due to carbonization deactivation of the catalyst particles 15 and thermal decomposition of the carbon source gas 16. Could have happened. Also, the carbon source gas 16 was sucked into the premixed flame 12, so that the fuel equivalence ratio changed, the flame easily disappeared, and the reproducibility of the synthesis was poor. Therefore, in this embodiment, after the decomposed catalyst raw material 11 flowing out from the premixed flame 12 is cooled by the carrier gas 14 supplied from the second pipe 5, the carbon source gas 16 supplied from the third pipe 6 is used. To separate the generation of the catalyst particles 15 and the supply of the carbon source. As a result, it is possible to prevent the deactivation of the catalyst particles 15 prior to sufficient growth. Furthermore, by preventing the carbon source gas 16 from being caught in the premixed flame 12, the premixed flame 12 can be stabilized while increasing the flow rate of the carbon source gas 16.

FIG. 11 illustrates ethylene (C 2 H 4 ) as the fuel gas 43, oxygen (O 2 ) as the oxidizing gas 44, argon (Ar) as the carrier gas 14, and acetylene (C 2 H 2 ) as the carbon source gas 16. ing.

  In FIG. 12, a first tube taper portion 28 that is tapered so that the tip of the first tube 4 is widened is provided. A similar second tube taper portion 29 is also provided at the tip of the second tube 5. By adopting the tapered shape, the cooling rate or the like of the decomposed catalyst raw material 11 can be adjusted. However, it is not always necessary to provide a tapered shape, and a straight pipe may be used. Moreover, the 1st pipe | tube 4, the 2nd pipe | tube 5, and the 3rd pipe | tube 6 may each be provided in a different body.

  In FIG. 11, reference numeral 34 denotes a heating mechanism, and for example, a ribbon heater can be used.

  FIG. 13 shows a third embodiment of the present invention, in which the same reference numerals are given to the same portions as the above-described embodiments, and detailed description thereof is omitted. FIG. 13 is a schematic view showing the manufacturing apparatus 1 of this embodiment. The basic configuration is the same as that of the first embodiment. Example 1 is different from Example 1 in that a promoter supply part 41 for supplying the promoter 9 from the second pipe 5 is provided.

  The cocatalyst 9 supplied from the cocatalyst supply unit 41 is preferably sulfur. The cocatalyst supply unit 41 has a structure in which a cocatalyst holding material 42 made of, for example, quartz cotton is disposed on both sides of the cocatalyst powder 55 in the wall 54 of the cocatalyst supply unit made of, for example, a quartz tube. As the sulfur source, powdered sulfur, thiophene, and hydrogen sulfide can be used.

  Since sulfur has the effect of lowering the surface energy of iron and stably forming small catalyst particles, the promoter 9 is preferably mixed with the decomposed catalyst raw material 11. It can also be expected to promote carbon precipitation from the iron catalyst particles 15 by forming an eutectic of iron sulfide (FeS).

  In the present embodiment, sulfur is supplied from the second pipe 5 for the purpose of separately controlling the supply amounts of ferrocene and sulfur and preventing sulfur combustion. A thermocouple (not shown) is inserted into the quartz tube 54, and the sulfur temperature is controlled by a ribbon heater (not shown). The manufacturing conditions are shown in Table 2.

  FIG. 14 is a photograph of the membrane filter in which the product synthesized in the production apparatus 1 of this example was collected. FIG. 15 is a photograph of the product (carbon nanotube free-standing film) peeled from the membrane filter.

  FIG. 16 shows an SEM image of the product generated on each membrane filter and collected on the membrane filter. The S / Fe molar ratio of sulfur and iron is 0 in FIG. 15A, 0.04 in (B), 0.13 in (C), and 0.45 in (D). Table 3 shows the C / Fe molar ratio of carbon and iron with respect to each S / Fe molar ratio. S / Fe molar ratio and C / Fe molar ratio were calculated from the back side of the synthesized product film using energy dispersive X-ray spectroscopy (EDX). FIG. 17 shows the Raman spectrum of the product synthesized under the same conditions and collected on the membrane filter.

In FIG. 17, a peak appearing in the vicinity of 1590 cm −1 is called G-band, and is derived from stretching vibration in the in-plane direction of a carbon atom having a six-membered ring structure. Moreover, the peak appearing in the vicinity of 1350 cm −1 is called D-band, and tends to appear when there is a defect in the six-membered ring structure. The relative quality of the carbon nanotube 2 can be evaluated by the ratio of G-band to D-band (G / D ratio).

In the case of a single-walled carbon nanotube, a plurality of peaks called RBM (Radial Breathing Mode) appear in the vicinity of 100 to 300 cm −1 . This is derived from vibration in the diameter direction of the tube, and it is known that the peak position is inversely proportional to the diameter of the single-walled carbon nanotube. In the case of an isolated single-walled carbon nanotube, it is assumed that there is a relationship of d = 248 / ω between the diameter d [nm] and the peak wavenumber ω [cm −1 ]. In this example, analysis was performed at an excitation wavelength of 488 nm.

  When the weight of the membrane filter was measured, it was found from the change in weight that the yield of the product was increased by adding sulfur. Moreover, it can be seen from the SEM image of FIG. 16 that the single-walled carbon nanotube 2 was most synthesized when S / Fe = 0.13 in (C). Furthermore, in the case of (C), it can be said that the amount of single-walled carbon nanotubes relative to catalytic iron is the largest, and it was confirmed that the purity was improved. (D) S / Fe = 0.45 indicates that the supply of sulfur is excessive, and (B) S / Fe = 0.04 indicates that the supply of sulfur is insufficient.

  From the Raman spectrum of FIG. 17, it was found that the synthesized carbon nanotubes were single-walled carbon nanotubes, and the diameter was 0.97 to 1.2 nm from RBM. In the case of S / Fe = 0.13 in (C), when the inside of the product film was observed by SEM, clean single-walled carbon nanotubes 2 without deposits were observed as shown in FIG. The sulfur supply temperature in (C) is 80 ° C.

  In the third embodiment, sulfur as the co-catalyst 9 is supplied from the second pipe 5, whereas in this embodiment, sulfur is supplied from the first pipe 4. Sulfur was supplied by a sublimation method in which sulfur powder as promoter powder 50 was mixed with ferrocene as catalyst raw material 11 and heated with a ribbon heater. The supply temperature was set to 60 ° C., the same as that for supplying ferrocene. The ratio of sulfur to iron was controlled by changing the weight ratio of sulfur and ferrocene to be mixed. The production conditions were the same as those in Table 2 of Example 3, and the experiment was conducted by changing the ratio of sulfur and iron, that is, the S / Fe molar ratio.

  Table 4 shows changes in the weight of the membrane filter at each S / Fe molar ratio. The S / Fe molar ratio of sulfur and iron in the raw material is 0 for (A), 0.1 for (B), 0.3 for (C), 1.0 for (D), and 3.0 for (E). FIG. 19 shows SEM images of the products generated at each S / Fe molar ratio and collected on the membrane filter. FIGS. 19F to 19J are images obtained by magnifying and observing the same samples as in FIGS. FIG. 20 shows the Raman spectrum of the product under the same conditions.

From the weight change of the membrane filter and the SEM image, it can be seen that the yield of carbon nanotubes was increased by adding sulfur. From the Raman spectrum, the synthesized carbon nanotubes were single-walled, and the RBM was found to have a diameter of 0.97 to 1.4 nm.
(Other examples)

  21 to 23 show the arrangement of the first tube 4 and the second tube 5 in the configuration in which the third tube 6 is provided so as to cover the outer periphery of the chamber 3 as in the first, third, and fourth embodiments. FIG. 6 is a schematic view of an embodiment in which the gas confluence 61 from the second pipe and the gas confluence 62 from the third pipe are changed.

  In the embodiment shown in FIG. 21, the second pipe 5 and the chamber 3 are integrally formed.

  In the embodiment shown in FIG. 22, a plurality of first tubes 4 are provided compared to the embodiment shown in FIG. 21.

  In the embodiment shown in FIG. 23, the second pipe 5 is provided outside each of the plurality of first pipes 4.

  24 to 26 are similar to the second embodiment, in the configuration in which the heat retaining means 7 is provided so as to cover the outer periphery of the chamber 3 without sandwiching the third tube 6, the first tube 4 and the second tube 5 is a schematic view of an embodiment in which the arrangement of gas No. 5 and the gas confluence 61 from the second pipe and the gas confluence 62 from the third pipe are changed.

  In the embodiment shown in FIG. 24, the third tube 6 and the chamber 3 are integrally formed.

  In the embodiment shown in FIG. 25, a plurality of third tubes 6 are provided, and in particular in this embodiment, the third tubes 6 are connected so that gas flows from the chamber side portion 27.

  In the embodiment shown in FIG. 26, the third tube 6 extends into the chamber 3 from the chamber top 25 toward the chamber bottom 26, and with respect to the gas supplied from the first tube 4 and the second tube 5. And supply gas in the opposite direction.

  27 to 29, a preheater 66 is separately installed upstream of the third pipe 6, and the preheated carbon source gas 16 is supplied to the chamber 3 through the third pipe 6. For the arrangement of the first tube 4, the second tube 5 and the third tube 6, FIG. 27 corresponds to the configuration of the second embodiment, FIG. 28 corresponds to the configuration of the embodiment of FIG. Corresponds to the configuration of the embodiment of FIG.

  FIG. 30 is a schematic view showing the arrangement of the first tube 4, the second tube 5 and the third tube 6 of the apparatus used in Examples 1, 3 and 4. In the embodiment shown in FIG. 31, the apparatus shown in FIG. 30 is turned upside down. That is, the first tube 4 and the second tube 5 are connected to the chamber upper portion 67, and the third tube 6 is connected to the chamber side portion 68. The premixed gas stream 17 containing the catalyst raw material and the carrier gas stream 18 are directed downward from the top of the chamber 3. The flow 19 of the carbon source gas flows from the bottom of the chamber 3 along the chamber side portion 68 and flows into the reaction region 8 in the horizontal direction.

  In the embodiment shown in FIG. 32, the apparatus having the structure shown in FIG. That is, the first tube 4 and the second tube 5 are connected to the chamber side portion 69, and the third tube 6 is connected to the chamber outer peripheral portion 70. The premixed gas flow 17 containing the catalyst raw material and the carrier gas flow 18 are directed from the left to the right of the chamber 3. The flow 19 of the carbon source gas flows from the right to the left of the chamber 3 along the chamber outer peripheral portion 70 and flows into the reaction region 8 in the vertical direction. Of course, a configuration opposite to that of the present embodiment may be used.

  Such an upside down and sideways configuration is applicable to all the embodiments described above.

  According to the apparatus of Example 1 as described above, a chamber 3 in which carbon nanotubes 2 provided therein are synthesized, and a premixed flame 12 including a catalyst raw material 11 connected to the chamber 3 are formed. One or more first tubes 4 for decomposing the catalyst raw material 11 and one or more connected to the chamber 3, supplying a carrier gas 14 and mixing with the decomposed catalyst raw material 11 to generate catalyst particles 15. The second tube 5, one or more third tubes 6 that are connected to the chamber 3, are supplied with the carbon source gas 16 and mixed with the catalyst particles 15 to grow the carbon nanotubes 2, and the outer periphery of the chamber 3. Is provided with the heat retaining means 7 provided in the manufacturing apparatus, so that the synthesis temperature of the carbon nanotubes can be maintained and the growth of the carbon nanotubes can be maintained, and the high-purity and high-quality carbon nanotubes 2 can be synthesized in a high yield. 1 can be provided. The third tube 6 is preheated by the carbon source gas 16 directly by the heat retaining means 7, by heat exchange with the gas in the chamber 3, or by the preheater 66 installed in the third tube 6. Then, the carbon nanotubes 2 having high crystallinity can be synthesized because they are connected to the chamber 3 so as to be supplied to the reaction region 8 where the carbon nanotubes 2 are grown. Further, the formation of the catalyst particles 15 can be optimized by flowing the carrier gas 14 from the second pipe 5 and joining the gas from the first pipe 4.

  Further, according to the production apparatus 1 of the second embodiment, after the decomposed catalyst raw material 11 is cooled by the carrier gas 14 supplied from the second pipe 5, the carbon source gas 16 supplied from the third pipe 6 is used. As a result of separating the production of the catalyst particles 15 and the supply of the carbon source by mixing with the carbonization, it is possible to prevent deactivation of the carbon before formation of the catalyst particles 15. Furthermore, by preventing the carbon source gas 16 from being caught in the premixed flame 12, the premixed flame 12 can be stabilized while increasing the flow rate of the carbon source gas 16.

  Moreover, according to the manufacturing apparatus 1 of Example 3, by supplying sulfur from the second pipe 5 as the co-catalyst 9, it is possible to synthesize the carbon nanotubes 2 having high purity and high quality with a high yield.

  Moreover, according to the manufacturing apparatus 1 of Example 4, the yield of carbon nanotubes can be increased by supplying sulfur from the first pipe 4 as the promoter 9.

  Furthermore, as shown in the other embodiments, the arrangement of the first tube 4, the second tube 5 and the third tube 6 can be variously changed.

  As mentioned above, although this invention was demonstrated based on the Example, this invention can carry out various deformation | transformation implementation. For example, in Examples 3 and 4 above, the promoter 9 is supplied from one of the first tube 4 or the second tube 5, but the promoter is supplied from both the first tube 4 and the second tube 5. 9 may be supplied. Moreover, in the said Example, although the small experiment apparatus was used, it is also possible to scale up to large apparatuses, such as a plant.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Carbon nanotube 3 Chamber 4 1st pipe | tube 5 2nd pipe | tube 6 3rd pipe | tube 7 Thermal insulation means 8 Reaction area 9 Promoter
11 Catalyst raw material
12 Premixed flame
14 Carrier gas
15 Catalyst particles
16 Carbon source gas
33 Heating furnace
50 First pipe outlet
51 Second pipe outlet
52 Third pipe outlet
56 Thermal insulation
66 Preheater

Claims (5)

  1. An apparatus for producing carbon nanotubes,
    A chamber for synthesizing the carbon nanotubes provided in the interior;
    One or more first tubes connected to the chamber, forming a premixed flame containing the catalyst feedstock, and decomposing the catalyst feedstock;
    One or more second tubes connected to the chamber for supplying a carrier gas and mixing with the decomposed catalyst raw material to generate catalyst particles;
    One or more third tubes connected to the chamber, fed with a carbon source gas and mixed with the catalyst particles to grow the carbon nanotubes;
    An apparatus for producing carbon nanotubes, comprising a heat retaining means provided on an outer periphery of the chamber.
  2.   After the gas flowing out from the first pipe merges with the gas flowing out from the second pipe, the gas flowing out from the third pipe merges, the first pipe outlet, the second pipe The apparatus for producing carbon nanotubes according to claim 1, wherein a tube outlet and a third tube outlet are installed.
  3.   The third pipe is configured such that after the carbon source gas is preheated directly by the heat retaining means, by heat exchange with the gas inside the chamber, or by a preheater installed in the third pipe. The carbon nanotube production apparatus according to claim 1, wherein the carbon nanotube production apparatus is connected to the chamber so as to be supplied to a reaction region for growing the carbon nanotube.
  4.   The carbon nanotube production apparatus according to any one of claims 1 to 3, wherein a promoter is supplied from at least one of the first tube and the second tube.
  5.   The carbon nanotube manufacturing apparatus according to any one of claims 1 to 4, wherein the heat retaining means comprises a heating furnace or a heat insulating material.
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