WO2018123796A1

WO2018123796A1 - Method for producing single-walled carbon nanotube-containing composition

Info

Publication number: WO2018123796A1
Application number: PCT/JP2017/045896
Authority: WO
Inventors: 宮浦健志; 西野秀和
Original assignee: 東レ株式会社
Priority date: 2016-12-26
Filing date: 2017-12-21
Publication date: 2018-07-05
Also published as: JPWO2018123796A1

Abstract

The present invention provides a method for producing a carbon nanotube-containing composition, wherein a catalyst carbon source solution containing a carbon compound, an iron compound and a sulfur compound is introduced into a reaction tube in a mixed carrier gas of hydrogen and an inert gas. According to the present invention, the molar concentration of carbon atoms in the carbon compound is from 0.16 mmol/L to 0.53 mmol/L (inclusive) based on the mixed carrier gas in a standard state; the ratio of the number of sulfur atoms in the sulfur compound to the number of iron atoms in the iron compound is 0.7-2.4; the hydrogen concentration in the mixed carrier gas is from 50% by volume to 90% by volume (inclusive) in a standard state; and the carbon compound contains an aromatic compound. According to the present invention, single-walled carbon nanotubes having high crystallinity are able to be obtained highly efficiently.

Description

Method for producing single-walled carbon nanotube-containing composition

The present invention relates to a method for producing a single-walled carbon nanotube-containing composition.

The structure of the carbon nanotube is a hollow tube (tube) in which a carbon hexagonal mesh surface called graphene is wound around a cylinder having a diameter of nanometer order. Carbon nanotubes are classified into single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes depending on the number of graphene layers constituting the cylindrical structure. Also, depending on how the graphene is wound, carbon nanotubes can have interesting electrical and mechanical properties such as being metallic and semiconducting. By controlling the diameter, the number of layers, and the length of the carbon nanotube, it is expected to improve the performance and expand the applicability.

However, since actual carbon nanotubes are obtained as a mixture having a different number of layers and structures, a technique for making carbon nanotubes is necessary to make use of the excellent characteristics. A characteristic difference is that single-walled carbon nanotubes have ballistic conduction that allows the electric charge to move without receiving any scattering, whereas multi-walled carbon nanotubes cause current to flow through multiple layers, causing diffusion of charge between the layers. It is conduction. Single-walled carbon nanotubes have properties superior to double-walled carbon nanotubes and multi-walled carbon nanotubes, such as thermal conductivity exceeding that of diamond and tough mechanical properties, while having flexibility that is extremely difficult to break. Therefore, single-walled carbon nanotubes are next-generation nanocarbon materials that are expected to be applied in the future for applications such as conductive inks, semiconductor devices, antistatic agents, and capacitor conductive members. is there.

In addition, since the semiconductor single-walled carbon nanotube has a band gap in inverse proportion to the diameter, it can be separated from the metal single-walled carbon nanotube using a chemical method. The semiconductor single-walled carbon nanotubes thus separated are expected to be applied to an excellent semiconductor device that can be bent transparently by taking advantage of its flexibility. Furthermore, since the semiconductor property becomes higher as the diameter becomes thinner, the single-walled carbon nanotube with a smaller diameter is expected to be a higher performance semiconductor material. In addition, the crystallinity of carbon nanotubes is important for application to devices and the like. The electrical conduction of carbon nanotubes is due to the movement of carriers on the surface of the carbon nanotubes, but this is scattered by structural defects and impurities, resulting in an increase in electrical resistance. Therefore, carbon nanotubes with high crystallinity are required for application to devices.

The CVD method (Chemical vapor deposition method), which is a highly efficient method for synthesizing single-walled carbon nanotubes, is roughly classified into two types from the viewpoint of the catalyst used. There are a supported catalyst method in which carbon nanotubes are grown from a substrate or carrier on which a catalyst is supported, and a gas phase flow method in which carbon nanotubes are grown from a catalyst that has been flowed into a gas phase. In particular, the gas-phase flow method is excellent as a method that can continuously supply raw materials and continuously obtain single-walled carbon nanotubes. For example, Patent Document 1 discloses a method for producing single-walled carbon nanotubes using toluene as a carbon source and supplying hydrogen gas, ferrocene and thiophene at 1 to 50 m / s. In addition, methods for producing single-walled carbon nanotubes using a plurality of carbon compounds such as aromatic compounds and aliphatic compounds as raw materials are known (Patent Documents 2 to 4). Moreover, the manufacturing method which improved the supply amount of the carbon source using the single carbon source is known (patent document 5).

International Publication No. 2006/064760 JP 2013-35750 A Japanese Patent Laying-Open No. 2015-48263 JP 2006-213590 A JP 2007-246316 A

However, the carbon nanotube synthesis methods described in Patent Documents 1 to 5 have a low yield of single-walled carbon nanotubes, and have not been put to practical use. In particular, the production methods disclosed in Patent Documents 2 to 4 have problems that the concentration of carbon source in the gas phase to be supplied is low and the yield of single-walled carbon nanotubes is low. Further, in the production method disclosed in Patent Document 5, the yield of carbon nanotubes is low, and this is also difficult to say as an efficient production method. Furthermore, in the production methods described in Patent Documents 1 to 5, only hydrogen gas is often used as the carrier gas, and there are problems in terms of safety and cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a carbon nanotube-containing composition capable of obtaining highly crystalline single-walled carbon nanotubes with high efficiency.

As a result of intensive studies to solve the above problems, the present inventors have reached the present invention described below.
A method for producing a carbon nanotube-containing composition, wherein a catalytic carbon source solution containing a carbon compound, an iron compound, and a sulfur compound is introduced into a reaction tube in a mixed carrier gas of hydrogen and an inert gas, and the mixed carrier gas in a standard state The carbon atom molar concentration in the carbon compound is 0.16 mmol / L or more and 0.53 mmol / L or less, and the ratio of the number of sulfur atoms in the sulfur compound to the number of iron atoms in the iron compound is 0.7 to 2.4. The method for producing a carbon nanotube-containing composition, wherein the hydrogen concentration in the mixed carrier gas is 50% by volume to 90% by volume in a standard state, and the carbon compound contains an aromatic compound.

According to the present invention, single-walled carbon nanotubes with high crystallinity can be obtained with high efficiency.

FIG. 1 is a schematic view of an apparatus for synthesizing a single-walled carbon nanotube-containing composition used in Examples of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not limited by the following embodiment.

The present invention is a method for producing a carbon nanotube-containing composition in which a catalytic carbon source solution containing a carbon compound, an iron compound, and a sulfur compound is introduced into a reaction tube in a mixed carrier gas of hydrogen and an inert gas, and the standard state The carbon atom molar concentration in the carbon compound is 0.16 mmol / L or more and 0.53 mmol / L or less, and the ratio of the number of sulfur atoms in the sulfur compound to the number of iron atoms in the iron compound is 0. 7 to 2.4, a method for producing a carbon nanotube-containing composition in which the hydrogen concentration in the mixed carrier gas is 50% by volume to 90% by volume in a standard state, and the carbon compound contains an aromatic compound.

In the production method of the present invention, a carbon compound containing an aromatic compound is used as a carbon source. The time when the carbon compound starts to be supplied to the reaction tube is set as the start of synthesis. The reaction tube is heated to a high temperature by a heating furnace, and the supplied carbon compound is decomposed at a high temperature to become a carbon nanotube-containing composition. Any carbon compound may be used as long as it can serve as a carbon source, but an aromatic compound that is liquid at room temperature and relatively difficult to decompose at high temperature is preferable. As the aromatic compound, for example, benzene, toluene, xylene, cumene, ethylbenzene, diethylbenzene, trimethylbenzene, naphthalene and the like can be used. Among these, benzene, toluene, ethylbenzene, and xylene are particularly preferable, and benzene is most preferable. Moreover, although an aromatic compound containing a hetero atom can be used as the raw material hydrocarbon, an aromatic hydrocarbon compound containing no hetero atom is more preferable.

The iron compound is decomposed in a reaction tube to become iron particles, thereby acting as a catalyst for producing a carbon nanotube-containing composition. A preferable shape of the iron particles is spherical or elliptical nanoparticles. Because of the characteristics of the nanoparticles, the phase transition temperature and the like fluctuate, so that the carbon nanotube-containing composition can be synthesized at a high temperature during the growth of the carbon nanotubes while changing the shape in a specific shape or fluidly. The carbon nanotube-containing composition grows starting from iron particles derived from the iron compound. At this time, the carbon nanotube-containing composition grows by the precipitation of carbon atoms dissolved in the iron particles. Therefore, the amount of carbon atoms dissolved in the iron particles and the degree of the precipitation depend on the diameter and layer of the obtained carbon nanotubes. Affects number and length. Since the carbon nanotube-containing composition is thus grown from the iron particles, the size of the iron particles is preferably several nanometers to several tens of nanometers, and most preferably several nanometers to ten nanometers.

It is preferable to use ferrocene or a ferrocene derivative as the iron compound because the carbon nanotube-containing composition can be continuously produced with high purity. By thermally decomposing an organometallic compound such as ferrocene or a ferrocene derivative in a heating furnace, iron particles as a catalyst can be efficiently generated. Ferrocene or a ferrocene derivative is preferred because the decomposition rate of the skeleton around the iron atom of the molecule having a ferrocene skeleton and the rate of formation of iron particles accompanying the decomposition are within the carrier gas mixing ratio and the preferred temperature range set in the present invention. This is considered to be reasonably preferable. As the ferrocene derivative, ferrocene having a substituent such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an acetyl group, a carboxyl group, a hydroxyl group, an amino group, and an epoxy group can be used. Ferrocene having a phenyl group, anisyl group, phenol group, or a heterocyclic compound containing a hetero atom as a substituent can also be used. Moreover, since the side reaction at the time of manufacture of a carbon nanotube containing composition can be suppressed, the purity of an iron compound is preferable.

The sulfur compound acts as a promoter for promoting the synthesis of the carbon nanotube-containing composition. Sulfur compounds can interact with iron particles as a catalyst to promote and control the growth of the carbon nanotube-containing composition. The reason why the sulfur compound is necessary in the growth mechanism of the carbon nanotube-containing composition is not clear, but sulfur atoms are unevenly mixed in the iron particle catalyst, so that the sulfur atoms are localized in or on the iron particles, It is presumed that the diameter and directionality of the carbon nanotubes grown on the iron particle catalyst are determined. In the present invention, the ratio of the iron compound and the sulfur compound introduced into the reaction tube is such that the ratio of the number of sulfur atoms in the sulfur compound to the number of iron atoms in the iron compound is 0.7 to 2.4, more preferably 0. .7 to 1.8, most preferably 1.0 to 1.8. By adjusting the ratio of the iron compound and the sulfur compound so as to achieve this atomic ratio, the amount of carbon in which sulfur atoms can be dissolved in the iron particles can be controlled, and a carbon nanotube-containing composition having a thin average diameter can be obtained. . Usable sulfur compounds include sulfur-containing compounds such as thiophene, ethanethiol, propanethiol, butanethiol, thiophenol, and more preferably thiophene.

In the production method of the present invention, a mixed carrier gas of hydrogen and inert gas is used. Nitrogen gas, helium, argon or the like is used as the inert gas. In general, hydrogen is thought to activate iron particle surfaces by reducing iron. However, since hydrogen has the property of adsorbing on the surface of iron particles, if the amount of hydrogen in the mixed carrier gas is too large, the amount of hydrogen adsorbed on the surface of the iron particles is too large and the catalytic capacity of the iron particles is reduced. There is a risk of doing. Therefore, it is preferable to dilute hydrogen with an inert gas to such an extent that the reaction is not hindered while securing the amount of hydrogen necessary for activation. By producing a carbon nanotube-containing composition in a mixed carrier gas of hydrogen and an inert gas, it is possible to continue growing single-walled carbon nanotubes while maintaining the catalytic ability of iron particles. In addition, while hydrogen promotes the thermal decomposition of the carbon compound and also serves to restore the thermal decomposition of the C—H bond, it is preferable to adjust the hydrogen concentration according to the carbon compound to be used. By setting the amount of hydrogen contained in the mixed carrier gas within an appropriate range, a single-walled carbon nanotube-containing composition having high crystallinity and high purity can be obtained with high yield.

Also, due to the difference in thermal conductivity between hydrogen and inert gas, the ratio of hydrogen and inert gas affects the activation of iron particles and the progress of decomposition of carbon compounds. Therefore, the reaction can be controlled by adjusting the hydrogen concentration in the mixed carrier gas. When nitrogen gas is used as the inert gas, it is preferable because it is inexpensive and can reduce manufacturing costs. However, since nitrogen gas, helium, argon, and the like have different thermal conductivities, it is preferable to select the type of inert gas and the hydrogen concentration according to the production conditions of the carbon nanotube-containing composition.

The hydrogen concentration in the mixed carrier gas is preferably 50% by volume or more and 90% by volume or less in the standard state. In the present invention, the standard state means 0 ° C. and 1 atm. This range is preferable particularly when nitrogen gas is used as the inert gas. More preferably, they are 60 volume% or more and 90 volume% or less, Most preferably, they are 60 volume% or more and 80 volume% or less. In addition, when argon is used as the inert gas, the thermal conductivity is lower than that of nitrogen gas. Therefore, the hydrogen concentration in the mixed carrier gas is preferably 55% by volume or more and 90% by volume or less in the standard state. When helium is used as the inert gas, since the thermal conductivity is as high as hydrogen, the hydrogen concentration in the mixed carrier gas only needs to be higher than the concentration contributing to the reaction, and is preferably 50% by volume or higher.

The carbon compound, iron compound and sulfur compound are preferably mixed and introduced into the reaction tube as a catalytic carbon source solution. As an introduction method, for example, a catalytic carbon source solution can be supplied to the reaction tube by spraying or the like. Examples of the spraying method include a method in which a catalytic carbon source solution is supplied to a two-fluid nozzle together with a carrier gas and sprayed. By introducing the mixture in advance, the carbon compound, the iron compound and the sulfur compound can be introduced into the reaction tube while maintaining a constant ratio. For that purpose, it is preferable in terms of ease of handling that the carbon compound is in a liquid state at normal temperature and normal pressure. For example, when the carbon compound is in a liquid state, a catalytic carbon source solution can be obtained by dissolving it in the carbon compound in the liquid state even if the iron compound or sulfur compound is solid. When the carbon compound is solid at normal temperature and normal pressure, the carbon compound may be heated and melted and mixed with the iron compound and sulfur compound. In addition, when there is a reason to separately introduce the carbon compound, iron compound and sulfur compound into the synthesizer, a mechanism for mixing so that the ratio of the carbon compound, iron compound and sulfur compound is kept constant in the synthesizer. It is good to synthesize after providing the inside. When the carbon compound is solid, it is preferably supplied after being melted or sublimated. Carbon compounds, iron compounds, and sulfur compounds have different decomposition temperatures and decomposition rates. Therefore, if the heating method of the reaction tube is different, the decomposition temperature and decomposition rate change, so the ratio can be finely adjusted. It may be preferable.

In the production method of the present invention, in order to obtain a desired carbon nanotube, the molar concentration of carbon atoms in the carbon compound is 0.16 mmol / L or more and 0.53 mmol / L based on the mixed carrier gas in the standard state (0 ° C., 1 atm). The carbon compound concentration in the carrier gas is controlled to be L or less. When the carbon compound concentration is too high, decomposition of the carbon compound proceeds excessively, and amorphous carbon called amorphous carbon tends to be generated. Amorphous carbon adheres to the surface and inside of single-walled carbon nanotubes as impurities, which causes the purity of single-walled carbon nanotubes to decrease. Furthermore, the iron particles that serve as a catalyst are coated with amorphous carbon, which hinders the growth of single-walled carbon nanotubes, which causes a decrease in yield. If the carbon atom molar concentration based on the mixed carrier gas is larger than the predetermined concentration, double-walled carbon nanotubes grow as described in Patent Document 3, and the selectivity of single-walled carbon nanotube growth may be reduced. Are known. On the other hand, when the concentration of the carbon compound in the carrier gas is too low, the carbon atom that becomes the growth source of the carbon nanotubes becomes insufficient, resulting in a decrease in yield. In this case, even if the carbon compound density per unit time is increased by increasing the carrier gas flow rate, the time for passing through the heating furnace, that is, the reaction time is shortened, and the growth of the carbon nanotubes is decreased. As a result, the crystallinity of the carbon nanotube obtained is lowered or the length is shortened. For these reasons, in order to obtain high-purity single-walled carbon nanotubes, the carbon atom molar concentration in the carbon compound is 0.16 mmol / L or more and 0.53 mmol / L or less based on the mixed carrier gas in the standard state. More preferably, it is 0.20 mmol / L or more and 0.50 mmol / L or less, and most preferably 0.25 mmol / L or more and 0.50 mmol / L or less.

The carbon compound preferably contains an aromatic compound. The yield of the carbon nanotube-containing composition increases as the synthesis temperature increases. When chain-type saturated hydrocarbons or chain-type unsaturated hydrocarbons are used as the carbon compound, they react even at relatively low temperatures. Therefore, when the synthesis temperature is raised, excessive decomposition occurs and side reactions are likely to occur. There are drawbacks. On the other hand, when an aromatic compound is used as the carbon compound, by-products can be suppressed in the reaction at a high temperature, which is preferable in terms of improving the yield of the carbon nanotube-containing composition. Moreover, when two or more types of carbon compounds are used as the carbon source, side reactions may occur due to the complicated reaction, and the yield of the resulting carbon nanotube-containing composition may be reduced. The use of only one carbon compound as the carbon source is preferable in that the synthesis temperature can be increased while suppressing side reactions, and this is suitable for mass production.

The aromatic compound may be a compound having a substituent such as a methyl group, an ethyl group or an ethylene group. Examples of preferred aromatic compounds include benzene, toluene, ethylbenzene, xylene and the like, and more preferred is benzene.

The linear velocity of the mixed carrier gas is preferably 500 cm / min or more and 1500 cm / min or less. The linear velocity of the mixed carrier gas affects the heat conduction during the synthesis and the decomposition behavior of the carbon compound resulting therefrom. When the synthesis temperature is relatively high, the carbon compound may be excessively decomposed. Therefore, it is preferable to adjust the linear velocity of the mixed carrier gas so as to shorten the reaction time. On the other hand, when the synthesis temperature is relatively low, in order to promote the decomposition of the carbon compound, it is preferable to adjust the linear velocity of the mixed carrier gas so as to increase the reaction time to adjust the decomposition of the carbon compound. Further, it is preferable that the linear velocity is increased when the thermal conductivity of the mixed carrier gas increases due to the composition of the mixed carrier gas, and the linear velocity is decreased when the thermal conductivity decreases. When the linear velocity is too high, the reaction time is short and the yield of the carbon nanotube-containing composition is low. In addition, when the linear velocity is too low, the influence of the convection of the mixed carrier gas in the synthesis region becomes dominant. Therefore, it is preferable that the linear velocity of the mixed carrier gas is 500 cm / min or more and 1500 cm / min or less. The lower limit of the linear velocity is more preferably 600 cm / min or more, and most preferably 700 cm / min or more. The upper limit of the linear velocity is more preferably 1400 cm / min or less, and most preferably 1300 cm / min or less.

It is known that the yield of the carbon nanotube-containing composition increases as the synthesis temperature increases. On the other hand, when the synthesis temperature is too high, decomposition of the carbon compound, iron compound and sulfur compound proceeds excessively. As a result, side reactions are likely to proceed, resulting in a decrease in yield and uniformity (diameter distribution, layer number ratio, crystallinity, etc.). Here, the synthesis temperature of the carbon nanotube-containing composition refers to the temperature of the heated reaction tube. For example, when heating in an electric furnace, the reaction tube temperature may be measured by inserting a thermocouple into the electric furnace and placing the tip of the thermocouple at a distance of about 1 mm from the reaction tube surface. As a synthesis temperature range of the carbon nanotube-containing composition, the temperature of the reaction tube is preferably 1100 ° C. or higher and 1500 ° C. or lower. The lower limit of the temperature of the reaction tube is more preferably 1150 ° C or higher, and most preferably 1200 ° C or higher. The upper limit of the temperature of the reaction tube is more preferably 1450 ° C. or less, and most preferably 1400 ° C. or less.

According to the production method of the present invention, a carbon nanotube-containing composition having an average diameter of 2.0 nm or less, a ratio of single-walled carbon nanotubes of 70% or more, and a G / D ratio of 50 or more can be synthesized. Here, the average diameter of the carbon nanotube-containing composition refers to an average diameter calculated by least square average of 100 carbon nanotubes observed with a transmission electron microscope. The ratio of single-walled carbon nanotubes of 70% or more means that when 100 carbon nanotubes are observed, 70 or more are single-walled carbon nanotubes. The diameter and the number of layers were observed with a transmission electron microscope at a magnification of 300,000 times or more, and the field of view in which the diameter and the number of layers of three or more carbon nanotubes in one field of view can be judged was observed over 35 fields of view. It was calculated by counting the number and diameter of carbon nanotube layers in the field of view.

Then, the G / D ratio, the ratio of the peak height of D band derived from the G band derived from graphite observed around 1590 cm ^-1 in the Raman spectrum, the defect of the amorphous carbon or graphite observed around 1350 cm ^-1 Say. A carbon nanotube with a higher G / D ratio has higher crystallinity and higher quality.

[Synthesis of carbon nanotube-containing composition]
Using the vertical carbon nanotube production apparatus shown in FIG. 1, the carbon nanotube-containing compositions shown in the following examples were produced.

1 includes an electric furnace 101, a reaction tube 102, a catalytic carbon source solution spray two-fluid nozzle 103, a microfeeder 107, a mass flow controller 105, a recovery container 104, and an exhaust gas pipe 108. The reaction tube 102 is a reaction tube for synthesizing carbon nanotubes and is a mullite vertical reaction tube having an inner diameter of 52 mm, an outer diameter of 60 mm, a length of 1500 mm, and an effective heating length of 1100 mm. The electric furnace 101 is provided on the outer periphery of the reaction tube 102, generates heat when energized, and heats the reaction tube 102 with the generated heat. The catalytic carbon source solution spray two-fluid nozzle 103 is a device that jets a catalytic carbon source solution 106 in which a carbon compound, an iron compound, and a sulfur compound are mixed into the reaction tube 102 in the form of a mist. The micro feeder 107 adjusts the supply amount of the catalytic carbon source solution 106 supplied to the catalytic carbon source solution spray two-fluid nozzle 103. The mass flow controller 105 adjusts the flow rates of the inert gas and the hydrogen gas that are carrier gases. The inert gas is supplied from an inert gas cylinder 109, and the hydrogen gas is supplied from a hydrogen gas cylinder 110, respectively. The collection container 104 is provided in the lower part of the reaction tube 102 and collects the carbon nanotube-containing composition synthesized in the reaction tube 102. The synthesized carrier gas is discharged from the exhaust pipe 108.

[High-resolution transmission electron microscope observation]
1 mg of the carbon nanotube-containing composition was placed in 1 mL of ethanol, and dispersion treatment was performed using an ultrasonic bath for 10 minutes. A few drops of the dispersed sample were dropped on the observation grid and dried. The grid thus coated with the sample was placed in a transmission electron microscope (JEM-2100 manufactured by JEOL Ltd.), and measurement was performed at a measurement magnification of 300,000 times and an acceleration voltage of 100 kV. The diameter and the number of layers were measured from 100 obtained carbon nanotube observation images.

[Evaluation of crystallinity by Raman spectroscopy]
A powder sample was placed in a Raman spectrometer (INF-300 manufactured by Horiba Jobin Yvon), and measurement was performed using a laser having an excitation wavelength of 532 nm. And G band derived from graphite observed around 1590 cm ^-1 in the Raman spectrum obtained, a ratio of the peak height of D band attributed to a defect of the amorphous carbon or graphite observed around 1350 cm ^-1 and G / D ratio did. A carbon nanotube-containing composition having a higher G / D ratio has higher crystallinity. Since the Raman spectroscopic analysis of powders may vary depending on sampling, at least three points were measured, and the arithmetic average was taken to calculate the G / D ratio.

[Example 1]
A carbon nanotube-containing composition was produced using the vertical carbon nanotube production apparatus shown in FIG. The electric furnace set temperature in the heating region of the reaction tube was set to 1290 ° C., and a total of 26 L / min of nitrogen gas 13 L / min and hydrogen gas 13 L / min were supplied as carrier gases to replace the inside of the reaction tube with carrier gas. A catalytic carbon source solution mixed at a ratio of benzene: ferrocene: thiophene = 75: 5: 2.5 in terms of weight was supplied at 145 mg / min to synthesize a carbon nanotube-containing composition for 30 minutes. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state (0 ° C., 1 atm) was 0.39 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 1.1. After the synthesis, the product was allowed to cool sufficiently, and the carbon nanotube-containing composition was taken out from the collection container. The obtained carbon nanotube-containing composition had an average diameter of 1.4 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 96%.

[Example 2]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 3: 1.5 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.40 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 1.1. The average diameter of the obtained carbon nanotube-containing composition was 1.3 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 74%.

[Example 3]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 8: 4 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.38 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 1.1. The average diameter of the obtained carbon nanotube-containing composition was 1.3 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 88%.

[Example 4]
A carbon nanotube-containing composition was produced in the same manner as in Example 1, except that the carrier gas was 9 L / min nitrogen gas and 9 L / min hydrogen gas, and the catalyst carbon source solution was supplied at 101 mg / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.39 mmol / L. The obtained carbon nanotube-containing composition had an average diameter of 1.4 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 90%.

[Example 5]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that toluene was used as the carbon compound. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.38 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 1.1. The obtained carbon nanotube-containing composition had an average diameter of 1.4 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 90%.

[Example 6]
A carbon nanotube-containing composition was produced in the same manner as in Example 1, except that the carrier gas was 10.4 L / min of nitrogen gas and 26 L / min in total of hydrogen gas 15.6 L / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.38 mmol / L. The average diameter of the obtained carbon nanotube-containing composition was 1.5 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 91%.

[Example 7]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that the carrier gas was changed to a total of 26 L / min of nitrogen gas 7.8 L / min and hydrogen gas 18.2 L / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.38 mmol / L. The average diameter of the obtained carbon nanotube-containing composition was 1.5 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 95%.

[Example 8]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that the carrier gas was changed to a total of 26 L / min of nitrogen gas 5.2 L / min and hydrogen gas 20.8 L / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.37 mmol / L. The average diameter of the obtained carbon nanotube-containing composition was 1.5 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 95%.

[Example 9]
A carbon nanotube-containing composition was produced in the same manner as in Example 7 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 5: 3.75 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.37 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalyst carbon source solution was 1.7. The average diameter of the obtained carbon nanotube-containing composition was 1.5 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 89%.

[Example 10]
A carbon nanotube-containing composition was produced in the same manner as in Example 7 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 5: 5 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.37 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalyst carbon source solution was 2.2. The average diameter of the obtained carbon nanotube-containing composition was 1.4 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 82%.

[Comparative Example 1]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 5: 1.5 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.4 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 0.66. The average diameter of the obtained carbon nanotube-containing composition was 2.1 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 93%.

[Comparative Example 2]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed in a ratio of benzene: ferrocene: thiophene = 75: 5: 0.5 was used. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.40 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 0.22. The average diameter of the obtained carbon nanotube-containing composition was 2.1 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 92%.

[Comparative Example 3]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed at a ratio of benzene: ferrocene: thiophene = 75: 5: 0.5 was supplied at 73 mg / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.20 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 0.22. The obtained carbon nanotube-containing composition had an average diameter of 2.2 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 90%.

[Comparative Example 4]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that a catalytic carbon source solution mixed at a ratio of benzene: ferrocene: thiophene = 75: 5: 0.5 was supplied at 381 mg / min. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 1.05 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 0.22. The obtained carbon nanotube-containing composition had an average diameter of 2.2 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 22%.

[Comparative Example 5]
A carbon nanotube-containing composition was produced in the same manner as in Example 1 except that decalin was used as the carbon compound. The carbon atom molar concentration in the carbon compound based on the mixed carrier gas in the standard state at this time was 0.35 mmol / L. The ratio of the number of sulfur atoms to the number of iron atoms contained in the catalytic carbon source solution was 1.1. The average diameter of the obtained carbon nanotube-containing composition was 1.4 nm, and the single-walled carbon nanotube ratio in the carbon nanotube-containing composition was 82%. However, since the G / D ratio indicating the crystallinity of the carbon nanotube-containing composition was 9, it is considered that a carbon nanotube-containing composition with many defects or carbon by-products was obtained.

In the production method of the present invention, highly crystalline single-walled carbon nanotubes can be produced with high efficiency and high yield. The single-walled carbon nanotubes obtained by the present invention are expected to be widely applied in various technical fields such as conductive inks, semiconductor devices, antistatic agents, capacitor conductive members, etc. by utilizing the characteristics.

101 Electric furnace 102 Reaction tube 103 Catalytic carbon source solution spray two-fluid nozzle 104 Recovery vessel 105 Mass flow controller 106 Catalytic carbon source solution 107 Microfeeder 108 Exhaust gas tube 109 Inert gas cylinder 110 Hydrogen gas cylinder

Claims

A method for producing a carbon nanotube-containing composition, wherein a catalytic carbon source solution containing a carbon compound, an iron compound, and a sulfur compound is introduced into a reaction tube in a mixed carrier gas of hydrogen and an inert gas, and the mixed carrier gas in a standard state The carbon atom molar concentration in the carbon compound is 0.16 mmol / L or more and 0.53 mmol / L or less, and the ratio of the number of sulfur atoms in the sulfur compound to the number of iron atoms in the iron compound is 0.7 to 2.4. The method for producing a carbon nanotube-containing composition, wherein the hydrogen concentration in the mixed carrier gas is 50% by volume to 90% by volume in a standard state, and the carbon compound contains an aromatic compound.
The method for producing a carbon nanotube-containing composition according to claim 1, wherein the linear velocity of the mixed carrier gas is 500 cm / min or more and 1500 cm / min or less.
The method for producing a carbon nanotube-containing composition according to claim 1 or 2, wherein the temperature of the reaction tube is 1100 ° C or higher and 1500 ° C or lower.
The method for producing a carbon nanotube-containing composition according to any one of claims 1 to 3, wherein the inert gas contains at least one selected from nitrogen, helium, and argon.
The method for producing a carbon nanotube-containing composition according to any one of claims 1 to 4, wherein the iron compound is ferrocene or a ferrocene derivative.
6. The method for producing a carbon nanotube-containing composition according to claim 1, wherein the sulfur compound contains at least one selected from thiophene, ethanethiol, propanethiol, butanethiol, and thiophenol.