JP6673337B2 - Method for producing carbon nanostructure - Google Patents

Description

  The present invention relates to a method for producing a carbon nanostructure.

  Carbon nanostructures are attracting attention as core materials of nanotechnology. In the present invention, the “carbon nanostructure” is a nano-sized substance composed of carbon atoms, for example, a coiled carbon nanocoil, a tube-shaped carbon nanotube (hereinafter also referred to as “CNT”), There are carbon nanotwist having twisted CNT, CNT with beads formed by beading CNT, carbon nanobrush having many CNTs, spherical shell-like fullerene, graphene, diamond-like carbon thin film and the like. These carbon nanostructures are common from the viewpoint of depositing a carbon-containing nanostructure composed of sp2 hybrid orbitals on a metal (catalyst) surface using a chemical vapor deposition method. Analogy can be adapted.

  Heretofore, there has been known a method of supplying a raw material gas to a catalyst and growing a carbon nanostructure by a chemical vapor deposition method (hereinafter, also referred to as a “CVD method”). In this method, a raw material gas containing a carbon compound is supplied to metal fine particles of a catalyst under a high temperature atmosphere of about 500 ° C. to 1000 ° C. In this method, various carbon nanostructures can be manufactured by variously changing the type and arrangement of the catalyst, the type of the source gas, the reaction conditions, and the like.

For example, Patent Literature 1 describes a method for producing CNT by a CVD method using methane (CH ₄ ) or ethylene (C ₂ H ₄ ) as a raw material gas under a condition that a gas in contact with a catalyst contains alkyne. Have been. Patent Literature 2 discloses a method for producing CNT by a CVD method using a hydrocarbon gas such as methane, ethylene, or acetylene (C ₂ H ₂ ) as a raw material gas and spraying the raw material gas onto a catalyst. .

  In the technique of manufacturing CNTs by the CVD method, both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) can be manufactured. In addition, by using a substrate supporting a catalyst, the CNTs are oriented vertically to the substrate surface. It has the advantage that a large number of CNTs can be manufactured. Further, since the super growth method in which a catalyst activator such as water was brought into contact with a catalyst together with a raw material gas was developed, it has been attracting attention as being suitable for mass production of CNTs.

  By the way, the whole chemical reaction mechanism of the CNT synthesis by the CVD method has not been clarified yet, but acetylene (alkynes) is a molecule effective for CNT synthesis (that is, a molecule that actually functions as a CNT precursor). Several studies have reported that there are.

Japanese Unexamined Patent Publication No. 2012-530663 International Publication No. 05/118473

  However, in the production of CNTs by the CVD method, even if the volume concentration of acetylene supplied to the catalyst is increased, if the concentration is higher than a certain concentration (about 0.5 to 1.5%), the synthesized CNT yield is almost saturated. It was known. In addition, the yield and the quality (specific surface area or G / D described later) of the synthesized CNTs are in an inverse relationship, and even if acetylene having a saturated volume concentration or more is supplied to the catalyst to increase the yield, the yield will not increase. There is a problem that the specific surface area and the G / D are sharply reduced without increasing significantly. Therefore, there is a demand for a production technique by a CVD method that can increase the yield while maintaining the quality. In this respect, a conventional technique of supplying a gas containing only acetylene as a molecule effective for CNT synthesis to a catalyst is inadequate. Was enough.

  In view of the above problems, an object of the present invention is to provide a method for manufacturing a carbon nanostructure capable of efficiently manufacturing a high-quality carbon nanostructure.

  As a result of intensive studies, the present inventors have obtained the following knowledge in order to achieve this object. That is, the present inventor paid attention to the composition of the gas that actually comes into contact with the catalyst (hereinafter, also simply referred to as “contact gas”) instead of the raw material gas. Specifically, in the CVD method, a CNT precursor other than acetylene was newly identified from a large number of hydrocarbon gases generated by pyrolysis of ethylene, which is a kind of source gas conventionally used. . Furthermore, they have found that the efficiency of CNT synthesis can be greatly improved by contacting a catalyst with a gas obtained by mixing these CNT precursors at a predetermined volume concentration. Specifically, it has been found that a mixed gas containing a hydrocarbon A having at least one acetylene skeleton and a hydrocarbon B having at least one 1,3-butadiene skeleton at a predetermined volume concentration is effective. Was.

  In addition, the composition of the raw material gas that can make the gas components of the CNT precursor in the contact gas each have a predetermined volume concentration or more was also specified. From the above findings, a method capable of producing a high-quality carbon nanostructure with high efficiency has been established, and the present invention has been completed.

  As described above, the present invention does not merely specify the composition of the gas in contact with the catalyst in the conventional CNT production. The raw material gas used in the present invention is different from Patent Documents 1 and 2, and the contact gas is also different from Patent Document 1. Patent Document 2 does not focus on contact gas at all.

The gist configuration of the present invention completed based on the above findings is as follows.
The present invention
A method for producing a carbon nanostructure, comprising supplying a raw material gas to a catalyst and growing the carbon nanostructure by a chemical vapor deposition method,
The gas X derived from the raw material gas and contacting the catalyst includes a hydrocarbon A having at least one acetylene skeleton and a hydrocarbon B having at least one 1,3-butadiene skeleton,
The total volume concentration [A] of the hydrocarbon A is more than 0.1%, and the total volume concentration [B] of the hydrocarbon B is 0.28% or more.

  In the present invention, the gas X preferably satisfies 0.1 ≦ [A] / [B] ≦ 8.

  In the present invention, it is preferable that the gas X further contains a catalyst activator and / or a hydrogen molecule.

  In the present invention, the gas X preferably further contains a hydrocarbon C having at least one cyclopentadiene skeleton.

Also, the present invention
A method for producing a carbon nanostructure, comprising supplying a raw material gas to a catalyst and growing the carbon nanostructure by a chemical vapor deposition method,
The raw material gas includes a hydrocarbon A ′ having at least one acetylene skeleton and a hydrocarbon B ′ having at least one 1,3-butadiene skeleton.

  In the present invention, when the total volume concentration of the hydrocarbon A ′ is [A ′] and the total volume concentration of the hydrocarbon B ′ is [B ′], the raw material gas is 0.1 ≦ [A ′]. ] / [B ′] ≦ 6.

  In the present invention, it is preferable that the source gas further contains a catalyst activator and / or a hydrogen molecule.

  In the present invention, it is preferable that the source gas further contains a hydrocarbon C ′ having at least one carbon ring having 5 carbon atoms.

  In the present invention, it is preferable that the catalyst is supported on a substrate surface, and the raw material gas is supplied to the catalyst by a gas shower.

  In the present invention, it is preferable that the carbon nanostructure is a carbon nanotube.

  According to the method for producing a carbon nanostructure of the present invention, a high-quality carbon nanostructure can be produced with high efficiency.

It is a schematic diagram which shows an example of a structure of the CNT manufacturing apparatus applicable to this invention. It is a schematic diagram which shows another example of the structure of the CNT manufacturing apparatus applicable to this invention. It is a schematic diagram which shows another example of a structure of the CNT manufacturing apparatus applicable to this invention.

  Hereinafter, an embodiment of a method for manufacturing a carbon nanostructure of the present invention will be described with reference to the drawings. In the manufacturing method of the present embodiment, a raw material gas is supplied to a base material having a catalyst layer on its surface (hereinafter, referred to as “catalyst base material”), and CNT is grown on the catalyst layer by a chemical vapor deposition method. A large number of CNTs are aligned on the catalyst layer in a direction substantially perpendicular to the base material to form an aggregate. In the present invention, this is referred to as “aligned CNT aggregate”.

(Base material)
The base material used as the catalyst base material is, for example, a plate-shaped member, and preferably has a shape that can maintain its shape even at a high temperature of 500 ° C. or higher. Specifically, metals such as iron, nickel, chromium, molybdenum, tungsten, titanium, aluminum, manganese, cobalt, copper, silver, gold, platinum, niobium, tantalum, lead, zinc, gallium, indium, germanium, and antimony And alloys and oxides containing these metals, or nonmetals such as silicon, quartz, glass, mica, graphite, and diamond, and ceramics. Metal materials are preferable because they are low in cost and easy to process as compared with silicon and ceramics. In particular, Fe-Cr (iron-chromium) alloy, Fe-Ni (iron-nickel) alloy, and Fe-Cr-Ni ( Iron-chromium-nickel) alloys and the like are preferred.

  The form of the base material may be flat, thin film, block, wire, mesh, particles, fine particles, powder, etc., especially when a large amount of CNT is produced in a large surface area for a large volume. Is advantageous. The thickness of the flat base material is not particularly limited, and for example, a thin film having a thickness of about several μm to about several cm can be used. The thickness of the flat base material is preferably 0.05 mm or more and 3 mm or less.

(catalyst)
In the catalyst base material, a catalyst layer is formed on the base material (when the carburization prevention layer is provided on the base material, on the carburization prevention layer). The catalyst may be any catalyst capable of producing CNT, and examples thereof include iron, nickel, cobalt, molybdenum, and chlorides and alloys thereof. A plurality of these may be compounded or layered, and these may be further compounded or layered with aluminum, alumina, titania, titanium nitride, and silicon oxide. For example, an iron-molybdenum thin film, an alumina-iron thin film, an alumina-cobalt thin film, an alumina-iron-molybdenum thin film, an aluminum-iron thin film, and an aluminum-iron-molybdenum thin film can be exemplified. The amount of the catalyst may be any range as long as CNTs can be produced. For example, when iron is used, the film thickness is preferably 0.1 nm or more and 100 nm or less, and 0.5 nm or more and 5 nm or less. More preferably, it is more preferably 0.8 nm or more and 2 nm or less.

  The formation of the catalyst layer on the surface of the base material may be performed by either a wet process or a dry process (such as a sputtering deposition method). It is preferable to apply a wet process from the viewpoint of simplicity of a film forming apparatus (no vacuum process is required), high speed of throughput, low cost of raw materials, and the like.

(Catalyst formation wet process)
The wet process of forming the catalyst layer includes a step of applying a coating agent in which a metal organic compound and / or metal salt containing an element serving as a catalyst is dissolved in an organic solvent onto a substrate, and a step of subsequently heating. A stabilizer for suppressing an excessive condensation polymerization reaction of the metal organic compound and the metal salt may be added to the coating agent.

  As the application step, any method such as a method of applying by spraying or brush coating, spin coating, and dip coating may be used, but dip coating is preferred from the viewpoint of productivity and film thickness control.

  Preferably, a heating step is performed after the coating step. Heating initiates hydrolysis and polycondensation reactions of the metal organic compound and metal salt, and forms a cured film containing metal hydroxide and / or metal oxide on the surface of the substrate. The heating temperature is in the range of about 50 ° C. or more and 400 ° C. or less, and the heating time is in the range of 5 minutes or more and 3 hours or less.

  For example, when forming an alumina-iron thin film as a catalyst, an iron thin film is formed after forming an alumina film.

  Examples of the metal organic compound for forming the alumina thin film include aluminum trimethoxide, aluminum triethoxide, aluminum tri-n-propoxide, aluminum tri-i-propoxide, aluminum tri-n-butoxide, and aluminum tri-sec. Aluminum alkoxide such as -butoxide and aluminum tri-tert-butoxide. Other examples of the metal organic compound containing aluminum include a complex such as tris (acetylacetonato) aluminum (III). Examples of the metal salt for forming the alumina thin film include aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum bromide, aluminum iodide, aluminum lactate, basic aluminum chloride, and basic aluminum nitrate. Among these, it is preferable to use an aluminum alkoxide. These can be used alone or as a mixture of two or more.

  Examples of the metal organic compound for forming the iron thin film include iron pentacarbonyl, ferrocene, iron (II) acetylacetone, iron (III) acetylacetone, iron (II) trifluoroacetylacetone, and iron (III) trifluoroacetylacetone. . Examples of the metal salt for forming the iron thin film include, for example, inorganic acid irons such as iron sulfate, iron nitrate, iron phosphate, iron chloride, and iron bromide, iron acetate, iron oxalate, iron citrate, and lactic acid. Organic acid irons such as iron are exemplified. Among these, it is preferable to use organic acid iron. These can be used alone or as a mixture of two or more.

  The stabilizer is preferably at least one selected from the group consisting of β-diketones and alkanolamines. These compounds may be used alone or as a mixture of two or more. β-diketones include acetylacetone, methyl acetoacetate, ethyl acetoacetate, benzoylacetone, dibenzoylmethane, benzoyltrifluoroacetone, fluorylacetone, and trifluoroacetylacetone. preferable. Alkanolamines include monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N, N-dimethylaminoethanol, diisopropanolamine, triisopropanolamine, etc., and secondary or tertiary. It is preferably a higher alkanolamine.

  As the organic solvent, various organic solvents such as alcohols, glycols, ketones, ethers, esters, and hydrocarbons can be used, but alcohols or glycols should be used because of good solubility of the metal organic compounds and metal salts. Is preferred. These organic solvents may be used alone or as a mixture of two or more. As the alcohol, methanol, ethanol, isopropyl alcohol and the like are preferable in terms of handleability and storage stability.

  The content of the metal organic compound and / or metal salt in the coating agent is usually 0.05% by mass or more and 0.5% by mass or less, preferably 0.1% by mass or more and 0.5% by mass. It is as follows.

(Formation process)
In the manufacturing method of the present invention, it is preferable to perform a formation step before the growth step. The formation step is a step in which the environment around the catalyst is set as a reducing gas environment and at least one of the catalyst and the reducing gas is heated. By this step, at least one of the effects of reducing the catalyst, promoting the reduction of the size of the catalyst to a state suitable for the growth of CNTs, and improving the activity of the catalyst appears. For example, when the catalyst is an alumina-iron thin film, the iron catalyst is reduced into fine particles, and a large number of nanometer-sized iron fine particles are formed on the alumina layer. This brings the catalyst into a state suitable for producing an aligned CNT aggregate. Although it is possible to manufacture CNTs even if this step is omitted, the production amount and quality of the aligned CNT aggregate can be drastically improved by performing this step.

  As a reducing gas (reducing gas), a gas capable of producing CNTs may be used. For example, hydrogen gas, ammonia, water vapor, and a mixed gas thereof can be used. Alternatively, a mixed gas obtained by mixing hydrogen gas with an inert gas such as helium gas, argon gas, or nitrogen gas may be used. The reducing gas may be appropriately used in the growth step in addition to the formation step.

(Growth process)
The growth step is a step of growing an aligned CNT aggregate on the catalyst by heating at least one of the catalyst and the source gas while setting the environment around the catalyst as a source gas environment. From the viewpoint of growing high-quality CNT, it is preferable to heat at least the catalyst. The heating temperature is preferably 400 ° C. or more and 1100 ° C. or less. The growth step is performed by introducing a raw material gas containing an inert gas and optionally a reducing gas and / or a catalyst activating substance into a CNT growth furnace containing a catalyst base material.

<Contact gas>
The present invention has one major feature in the gas X that comes into contact with the catalyst in the growth step. The gas X is composed of various hydrocarbon gases in which the source gas has been decomposed, the source gas that has reached the catalyst without being decomposed, an inert gas, and optionally a reducing gas and / or a catalyst activator. .

In the present invention, the gas X contains a hydrocarbon A having at least one acetylene skeleton and a hydrocarbon B having at least one 1,3-butadiene skeleton, and the total volume concentration [A] of the hydrocarbon A is 0. It is important that the total volume concentration [B] of hydrocarbon B exceeds 0.28% or more. By allowing the hydrocarbon A and the hydrocarbon B to coexist in the gas X and setting the volume concentration as described above, the yield can be increased while maintaining the quality of the CNT.
In this specification, a hydrocarbon having at least one acetylene skeleton may be referred to as “acetylenes” and a hydrocarbon having at least one 1,3-butadiene skeleton may be referred to as “1,3-butadiene”. is there.

  Examples of the hydrocarbon A having at least one acetylene skeleton include acetylene, methyl acetylene (propyne), vinyl acetylene, 1-butyne (ethyl acetylene), 2-butyne, diacetylene, isopropyl acetylene, isopropenyl acetylene, 1- Examples include at least one selected from the group consisting of pentyne, 2-pentyne, isopentin, cyclopropenylacetylene, methylvinylacetylene, propenylacetylene, phenylacetylene, hexines, hexadiynes, and radicals thereof. However, from the viewpoint of structural stability at the CNT growth temperature, acetylene, methylacetylene, vinylacetylene, 2-butyne, and phenylacetylene are preferred.

  Examples of the hydrocarbon B having at least one 1,3-butadiene skeleton include at least one selected from the group consisting of 1,3-butadiene, isoprene, c-piperylene, and t-piperylene, and a radical thereof. Is mentioned. However, from the viewpoint of CNT production efficiency, 1,3-butadiene is preferred.

  According to the invention, the total volume concentration [A] of hydrocarbons A in the gas X contacting the catalyst is greater than 0.1%. [A] is more preferably at least 0.3%, further preferably at least 0.5%, as an effect of further increasing the yield while maintaining the quality of the CNT. The upper limit concentration of [A] tends to be proportional to the spatial density of the catalyst installed in the furnace, and can be increased to 88%. When a flat plate is used as the catalyst substrate, it is usually preferably at most 10%, more preferably at most 5%, further preferably at most 2%. If the concentration of hydrocarbon A is excessive with respect to the catalyst density, the amount of carbon impurities such as amorphous carbon generated increases, and depending on the application, these impurities cannot be ignored.

  The total volume concentration [B] of the hydrocarbons B in the gas X is 0.28% or more. [B] is more preferably 0.5% or more, further preferably 0.6% or more, as an effect of further increasing the yield while maintaining the quality of the CNT. The upper limit concentration of [B] tends to be proportional to the spatial density of the catalyst installed in the furnace, and can be increased to 90%. When a flat plate is used as the catalyst substrate, it is usually preferably at most 10%, more preferably at most 5%, further preferably at most 2%. If the concentration of hydrocarbon B is excessive with respect to the catalyst density, the amount of carbon impurities such as amorphous carbon generated increases, and depending on the application, these impurities cannot be ignored.

  [A] / [B] is preferably 0.1 or more and 8 or less from the viewpoint of more sufficiently obtaining the effects of the present invention. More preferably, it is 0.2 or more and 6 or less, and further preferably, 0.5 or more and 2 or less.

  The gas X preferably further contains a hydrocarbon C having at least one cyclopentadiene skeleton. As the hydrocarbon C, for example, selected from the group consisting of cyclopentadiene, indene, methylcyclopentadiene, dimethylcyclopentadiene, trimethylcyclopentadiene, tetramethylcyclopentadiene, pentamethylcyclopentadiene, and ethylcyclopentadiene, and radicals thereof At least one of them. However, from the viewpoint of structural stability at the CNT growth temperature, cyclopentadiene and methylcyclopentadiene are preferred. By including the hydrocarbon C in the gas X, it is possible to reduce the required hydrocarbon A while maintaining the yield and quality of the CNT. Since acetylenes have high chemical reactivity, there is a problem in handling and safety as compared with other gases, and the operating cost tends to increase. Therefore, it is preferable to reduce the amount of hydrocarbon A used as much as possible.

The total volume concentration [C] of the hydrocarbons C in the gas X is preferably 0.06% or more, more preferably 0.2% or more, further preferably, from the viewpoint of sufficiently obtaining the above effects. 0.3% or more. Further, the total volume concentration [C] of the hydrocarbon C in the gas X tends to be proportional to the space density of the catalyst installed in the furnace, and can be increased to 99%. From the viewpoint of suppressing the generation of carbon impurities such as amorphous carbon, when a flat plate is used as the catalyst substrate, it is usually preferably at most 10%, more preferably at most 5%, further preferably at most 2%.
In this specification, a hydrocarbon having at least one cyclopentadiene skeleton may be referred to as “cyclopentadiene”.

  In the present invention, the identification of the contact gas and the measurement of the volume concentration are performed by aspirating and sampling a predetermined amount of gas in the vicinity of the base material installation position and performing gas analysis by gas chromatography (GC). In the sampling, the gas is rapidly cooled to a temperature (about 200 ° C.) at which pyrolysis does not proceed, and then immediately introduced into the GC. This makes it possible to prevent a chemical change of the sample gas and to correctly measure the composition of the gas in contact with the catalyst.

<Raw gas>
In order for the gas X to be as described above, the raw material gas preferably contains a hydrocarbon A ′ having at least one acetylene skeleton and a hydrocarbon B ′ having at least one 1,3-butadiene skeleton. .

  The hydrocarbon A 'is preferably at least one selected from the group consisting of acetylene, methylacetylene, vinylacetylene, 1-butyne, 2-butyne, isopropylacetylene, and isopropenylacetylene. In the raw material gas, the total volume concentration [A '] of the hydrocarbons A' is preferably 0.1% or more, more preferably 0.2% or more, and further preferably 0.3% or more. [A ′] can be increased to 86%, and is usually preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. If the concentration of the hydrocarbon A 'is too low, the effect of the present invention is difficult to obtain, and if it is too high, carbon impurities such as amorphous carbon are generated, and depending on the use, these impurities tend to be not negligible.

  The hydrocarbon B 'is preferably at least one selected from the group consisting of 1,3-butadiene, isoprene, c-piperylene, and t-piperylene. In the raw material gas, the total volume concentration [B '] of the hydrocarbons B' is preferably 0.3% or more, more preferably 0.4% or more, and further preferably 0.5% or more. . [B '] can be increased to 90%, and is usually preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. If the concentration of the hydrocarbon B 'is too low, the effect of the present invention is difficult to obtain, and if it is too high, carbon impurities such as amorphous carbon are generated, and depending on the use, these impurities tend to be not negligible.

  [A '] / [B'] is preferably 0.1 or more and 6 or less. More preferably, it is 0.2 or more and 3 or less, and further preferably, it is 0.3 or more and 2 or less. By setting it within this range, the gas X can be more reliably set within the range of the present invention.

  Further, the source gas preferably contains a hydrocarbon C 'having at least one carbon ring having 5 carbon atoms.

  The hydrocarbon C 'is preferably at least one selected from the group consisting of cyclopentadiene, dicyclopentadiene, cyclopentene, norbornene, norbornadiene and cyclopentane. From the viewpoint of sufficiently obtaining the above effects, the total volume concentration [C '] of the hydrocarbons C' in the raw material gas is preferably 0.1% or more, more preferably 0.2% or more, and still more preferably. 0.3% or more. If the concentration of the hydrocarbon C 'is too low, the effect of the present invention is difficult to obtain, and if it is too high, carbon impurities such as amorphous carbon are generated, and depending on the use, these impurities tend to be not negligible. In addition, the total volume concentration [C '] of hydrocarbon C' in the raw material gas tends to be proportional to the spatial density of the catalyst installed in the furnace, and can be increased to 99%. From the viewpoint of suppressing the generation of carbon impurities such as amorphous carbon, when a flat plate is used as the catalyst substrate, it is usually preferably at most 10%, more preferably at most 5%, further preferably at most 2%.

<Inert gas>
The source gas is usually diluted with an inert gas. The inert gas may be any gas that is inert at the temperature at which the CNTs grow and does not react with the growing CNTs, and is preferably a gas that does not reduce the activity of the catalyst. For example, rare gases such as helium, argon, neon, and krypton, nitrogen, hydrogen, and a mixed gas thereof can be exemplified.
In addition, by reducing the pressure inside the furnace and reducing the partial pressure of various gas concentrations without using an inert gas, it is possible to obtain the same effect as the inert gas dilution.

<Catalyst activator>
In the step of growing the CNT, a catalyst activator may be added. By adding the catalyst activator, the production efficiency and purity of CNT can be further improved. The catalyst activating substance used here is generally a substance containing oxygen, and is preferably a substance that does not cause a great deal of damage to the CNT at the growth temperature. For example, oxygen-containing compounds having a low carbon number such as water, oxygen, ozone, acid gas, nitric oxide, carbon monoxide, and carbon dioxide; alcohols such as ethanol and methanol; ethers such as tetrahydrofuran; ketones such as acetone. Aldehydes; esters; and mixtures thereof. Among them, water, oxygen, carbon monoxide, carbon dioxide, and ethers are preferable, and water, carbon monoxide, carbon dioxide, and a mixture thereof are particularly preferable.

  The volume concentration of the catalyst activating substance is not particularly limited, but may be a small amount. For example, in the case of water, the content of the raw material gas introduced into the furnace is usually 0.001% or more and 1% or less, preferably, 1% or less. 0.005% or more and 0.1% or less. In this case, in gas X, it is usually 0.001% or more and 1% or less, preferably 0.005% or more and 0.1% or less. When the catalyst activating substance is carbon dioxide, its content in the raw material gas introduced into the furnace is usually 0.5% or more and 20% or less, preferably 2% or more and 8% or less. In this case, in gas X, it is usually 0.5% or more and 20% or less, preferably 2% or more and 8% or less.

  In the present invention, the gas X preferably further contains a hydrogen gas composed of hydrogen molecules as a catalyst activator and / or a reducing gas from the viewpoint of more sufficiently obtaining the effects of the present invention.

  It is generally known that the reaction rate in the CVD method is affected by the partial pressure (volume fraction × total pressure) of the components involved in the reaction. On the other hand, the total pressure does not directly affect, and can be changed in a wide range. Therefore, it is accurate to use the partial pressure as a unit for defining the gas component concentration under the CVD conditions. However, in the present invention, the gas component concentration of the raw material gas and the contact gas is determined by using the total pressure in the growth furnace of 1 atm. It is described by the volume fraction under the premise. Therefore, when the present invention is applied when the total pressure inside the growth furnace is other than 1 atm, a partial pressure equal to the partial pressure under the above-mentioned assumption under the environment is used as the gas component concentration of the raw material gas and the contact gas. A modified volume fraction must be used as indicated. Such modifications when the total pressure inside the growth furnace is other than 1 atmosphere will be apparent to those skilled in the art, and such cases are also included in the scope of the present invention.

<Other conditions>
The pressure in the reaction furnace and the processing time in the growth step may be appropriately set in consideration of other conditions. For example, the pressure is 10 ² Pa or more and 10 ⁷ Pa or less, and the processing time is 0.1 minute or more. It can be about 120 minutes or less. The flow rate of the raw material gas introduced into the furnace can be appropriately set, for example, with reference to examples described later.

(Cooling process)
The cooling step is a step of cooling the aligned CNT aggregate, the catalyst, and the base material under a cooling gas after the growth step. Since the aligned CNT aggregate, the catalyst, and the base material after the growth process are in a high temperature state, they may be oxidized when placed in an oxygen-existing environment. In order to prevent this, the aligned CNT aggregate, the catalyst, and the substrate are cooled to, for example, 400 ° C. or lower, more preferably 200 ° C. or lower, in a cooling gas environment. As the cooling gas, an inert gas is preferable, and in particular, nitrogen is preferable in terms of safety, cost, and the like.

(Manufacturing equipment)
The manufacturing apparatus used for carrying out the present invention is not particularly limited as long as it has a growth furnace (reaction chamber) for receiving a catalyst substrate and can grow CNTs by a CVD method. An apparatus such as a reaction furnace can be used. From the viewpoint of increasing the production efficiency of the CNT, it is preferable to supply the reducing gas and the raw material gas to the catalyst on the catalyst substrate by a gas shower. Hereinafter, a gas flow can be ejected so as to be substantially orthogonal to the catalyst substrate. An example of a device having a shower head will be described.

<Example of batch type manufacturing equipment>
FIG. 1 schematically shows a CNT manufacturing apparatus 100 applied to the present invention. The apparatus 100 includes a reaction furnace 102 made of quartz, a heater 104 provided around the reaction furnace 102, for example, a resistance heating coil and the like, and a reaction furnace 102 for supplying a reducing gas and a raw material gas. It comprises a gas supply port 106 connected to one end, an exhaust port 108 connected to the other end of the reaction furnace 102, and a holder 110 made of quartz for fixing the base material. Although not shown, a control device including a flow control valve, a pressure control valve, and the like is provided at an appropriate position in order to control the flow rates of the reducing gas and the source gas.

<Other examples of batch type manufacturing equipment>
FIG. 2 schematically shows a CNT manufacturing apparatus 200 applied to the present invention. This apparatus 200 has the same configuration as the apparatus shown in FIG. 1 except that a shower head 112 for injecting a reducing gas, a raw material gas, a catalyst activator, and the like is used.

  The shower head 112 is arranged such that the ejection axis of each ejection hole is substantially orthogonal to the catalyst film forming surface of the base material. That is, the direction of the gas flow ejected from the ejection holes provided in the shower head is substantially orthogonal to the substrate.

  When the reducing gas is injected by using the shower head 112, the reducing gas can be uniformly dispersed on the base material, and the catalyst can be efficiently reduced. As a result, the uniformity of the aligned CNT aggregate grown on the base material can be improved, and the consumption of the reducing gas can be reduced. When the raw material gas is jetted using such a shower head, the raw material gas can be uniformly dispersed on the base material, and the raw material gas can be efficiently consumed. As a result, the uniformity of the aligned CNT aggregate grown on the base material can be improved, and the consumption of the raw material gas can be reduced. When the catalyst activator is sprayed using such a shower head, the catalyst activator can be evenly dispersed on the substrate, and the activity of the catalyst is increased and the life is extended, so that the growth of the oriented CNT is continued for a long time. It is possible to do.

<Example of continuous manufacturing equipment>
FIG. 3 schematically shows a CNT manufacturing apparatus 300 applied to the present invention.
As shown in FIG. 3, the manufacturing apparatus 300 includes an inlet purge unit 1, a formation unit 2, a growth unit 3, a cooling unit 4, an outlet purge unit 5, a transport unit 6, connection units 7, 8, 9, and gas mixing prevention. It has means 11, 12, and 13.

[Inlet purge section 1]
The inlet purge unit 1 is a set of devices for preventing outside air from entering the furnace from the inlet of the catalyst substrate 10. It has a function of replacing the environment around the catalyst substrate 10 transported into the manufacturing apparatus 300 with an inert purge gas such as nitrogen. Specifically, it has a chamber for holding the purge gas, an injection unit for injecting the purge gas, and the like.

[Formation Unit 2]
The formation unit 2 is a set of devices for realizing the formation process. Specifically, it includes a formation furnace 2A for holding the reducing gas, a reducing gas injection unit 2B for injecting the reducing gas, and a heater 2C for heating at least one of the catalyst and the reducing gas.

[Growth unit 3]
The growth unit 3 is a set of devices for realizing the growth process. Specifically, it includes a growth furnace 3A, a source gas injection unit 3B for injecting a source gas onto the catalyst substrate 10, and a heater 3C for heating at least one of the catalyst and the source gas. An exhaust port 3D is provided at the upper part of the growth unit 3.

[Cooling unit 4]
The cooling unit 4 is a set of devices that realizes a cooling step of cooling the catalyst substrate 10 on which the aligned CNT aggregate has grown. Specifically, a cooling furnace 4A for holding the cooling gas, a water-cooled cooling pipe 4C arranged to surround the space inside the cooling furnace in the case of a water-cooled type, and a cooling gas injected into the cooling furnace in the case of an air-cooled type It has a cooling gas injection unit 4B.

[Outlet purge section 5]
The outlet purge unit 5 is a set of devices for preventing outside air from entering the furnace from the outlet of the catalyst substrate 10. It has a function of setting the environment around the catalyst substrate 10 to an inert purge gas environment such as nitrogen. Specifically, it has a chamber for holding the purge gas, an injection unit for injecting the purge gas, and the like.

[Transport unit 6]
The transport unit 6 is a set of devices for transporting the catalyst substrate 10 into the furnace of the manufacturing apparatus. Specifically, it has a mesh belt 6A in a belt conveyor system, a belt driving unit 6B using an electric motor with a speed reducer, and the like.

[Connections 7, 8, 9]
The connection units 7, 8, and 9 are a set of devices that spatially connect the furnace space of each unit. Specifically, a furnace or a chamber that can block the surrounding environment of the catalyst base material 10 from the outside air and allow the catalyst base material 10 to pass from unit to unit can be used.

[Gas mixing prevention means 11, 12, 13]
The gas mixing preventing means 11, 12, 13 is a set of devices for preventing gas from being mixed with each other between adjacent furnaces (formation furnace 2A, growth furnace 3A, cooling furnace 4A) in the manufacturing apparatus 300. Yes, it is installed at the connection parts 7, 8, 9. The gas mixing preventing means 11, 12, and 13 mainly include seal gas injection units 11B, 12B, and 13B that jet a seal gas such as nitrogen along an opening surface of an inlet and an outlet of the catalyst base material 10 in each furnace. Exhaust units 11A, 12A, and 13A for exhausting the sealed gas to the outside.

  The catalyst base material 10 placed on the mesh belt 6A is conveyed from the apparatus inlet to the furnace of the inlet purge unit 1, and thereafter, after being treated in each furnace, from the outlet purge unit 5 via the apparatus outlet. It is transported outside the device.

(Carbon nanostructure)
According to the production method of the present invention, high-quality CNTs can be produced with high efficiency as described above. However, the production method is not limited to CNTs. Various carbon nanostructures including carbon composed of sp2 hybrid orbitals, which can be grown on a catalyst surface by a CVD method, and others, such as a coil, can be manufactured. Examples of the known documents include, for example, JP-A-2009-127059 (diamond-like carbon), JP-A-2013-86993 (graphene), JP-A-2001-192204 (coil twist), and JP-A-2003-192204. No. 277029 (fullerene) and the like.

  Hereinafter, CNTs obtained by the production method of the present invention will be described as an example of the carbon nanostructure obtained by the production method of the present invention. In addition, CNT is directly obtained as an aligned CNT aggregate by the production method of the present invention. The assembly, for example, a physical, chemical or mechanical peeling method, specifically, a method of peeling using an electric field, a magnetic field, centrifugal force or surface tension, or mechanically using tweezers or a cutter blade CNTs in a bulk state or CNTs in a powder state can be obtained by separating the CNTs from the catalyst substrate by a method of directly peeling off CNTs, a method of separating by pressure or heat such as suction by a vacuum pump, or the like.

The yield of CNTs by the production method of the present invention is preferably 2.4 mg / cm ² or more, and more preferably 2.8 mg / cm ² or more. In the present invention, the yield is calculated by the following equation.
(Yield) = (Difference in substrate weight before and after CNT production) / (Catalyst carrying area of substrate)

  In the production method of the present invention, the carbon conversion efficiency is preferably at least 1.6%, more preferably at least 2.8%. In the present invention, “carbon conversion efficiency” means (weight of manufactured CNT) / (weight of total carbon introduced into the furnace) × 100 [%], and “weight of total carbon introduced into the furnace” Can be calculated from the above three values of the gas flow rate, the carbon concentration of the source gas, and the growth time under the assumption of approximation of an ideal gas.

In the present invention, the carbon concentration indicates the concentration of carbon atoms contained in the gas, and the concentration (vol%) is D1, D2, and D3 for each hydrocarbon gas type (i = 1, 2,...) In the gas. .., And the number of carbon atoms contained in one molecule is C1, C2,.
(Carbon concentration) = ΣDiCi

  The carbon concentration in the raw material gas is preferably 1.3% or more, more preferably 2.0% or more, and still more preferably 3.0% or more, from the viewpoint of more sufficiently obtaining the effects of the present invention. The upper limit of carbon concentration tends to be proportional to the catalyst density in the furnace, and can be increased to 380%. When a flat plate is used as the catalyst substrate, the carbon concentration is usually preferably 60% or less, more preferably 30% or less, and particularly preferably 20% or less. If the carbon concentration is excessive with respect to the amount of the catalyst density, carbon impurities such as amorphous carbon are generated, and depending on the application, these impurities cannot be ignored.

  The CNT may be a single-walled carbon nanotube or a multi-walled carbon nanotube. However, according to the production method of the present invention, the single-walled carbon nanotube can be produced more suitably.

  The average diameter (Av) of the CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, more preferably 15 nm or less, and even more preferably 10 nm or less. The average diameter (Av) of carbon nanotubes is usually determined by measuring 100 carbon nanotubes using a transmission electron microscope.

CNT is obtained as an aligned CNT aggregate by the production method of the present invention, and its specific surface area is preferably at least 600 m ² / g, more preferably at least 800 m ² / g, and more preferably 2500 m ² / g. Or less, more preferably 1400 m ² / g or less. Further, when the CNT is mainly opened, the specific surface area is preferably 1300 m ² / g or more. In the present invention, the “specific surface area” refers to a BET specific surface area measured using a BET method.

The weight density of the aligned CNT aggregate is preferably 0.002 g / cm ³ or more and 0.2 g / cm ³ or less. When the weight density is 0.2 g / cm ³ or less, the binding between the CNTs constituting the aligned CNT aggregate becomes weak, so that when the aligned CNT aggregate is stirred in a solvent or the like, it can be easily dispersed uniformly. become. Further, when the weight density is 0.002 g / cm ³ or more, the alignment of the aligned CNT aggregate can be improved and the CNTs can be prevented from being loosened, so that the handling becomes easy.

  The aligned CNT aggregate preferably has a high degree of orientation. Whether or not it has a high degree of orientation is determined by the following 1. From 3. Can be evaluated by at least one of the methods.

  1. When X-rays are incident from a first direction parallel to the longitudinal direction of the CNT and a second direction perpendicular to the first direction and the X-ray diffraction intensity is measured (θ-2θ method), There is a θ angle and a reflection azimuth at which the reflection intensity is greater than the reflection intensity from the first direction, and a θ angle and a reflection azimuth at which the reflection intensity from the first direction is greater than the reflection intensity from the second direction. That there is.

  2. When X-ray diffraction intensity is measured (Laue method) with a two-dimensional diffraction pattern image obtained by entering X-rays from a direction perpendicular to the longitudinal direction of the CNT, a diffraction peak pattern showing the presence of anisotropy appears. To do.

  3. When the X-ray diffraction intensity obtained by the θ-2θ method or the Laue method is used, the orientation coefficient of Hermann should be larger than 0 and smaller than 1, more preferably 0.25 or more and 1 or less.

  The height (length) of the aligned CNT aggregate is preferably in the range of 10 μm or more and 10 cm or less. When the height is 10 μm or more, the degree of orientation is improved. When the height is 10 cm or less, the generation can be performed in a short time, so that the attachment of carbon-based impurities can be suppressed, and the specific surface area can be improved.

The G / D ratio of the aligned CNT aggregate is preferably 2 or more, and more preferably 4 or more. The G / D ratio is an index generally used to evaluate CNT quality. The Raman spectra of CNT measured by Raman spectroscopy system, the vibration mode is observed, called G band (1600 cm ^-1 vicinity) and D-band (1350 cm around ^-1). The G band is a vibration mode derived from a hexagonal lattice structure of graphite which is a cylindrical surface of CNT, and the D band is a vibration mode derived from an amorphous portion. Therefore, a higher peak intensity ratio (G / D ratio) between the G band and the D band can be evaluated as a CNT having higher crystallinity.

  Further, the purity of the aligned CNT aggregate is usually 98% by mass or more, and preferably 99.9% by mass or more, without performing the purification treatment. The aligned CNT aggregate obtained by the production method of the present invention hardly contains impurities, and can sufficiently exhibit the original characteristics of CNT. The purity can be determined by elemental analysis using fluorescent X-rays.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Base material)
A flat plate of Fe-Cr alloy SUS430 (manufactured by JFE Steel Corporation, Cr: 18% by mass) having a length of 500 mm x a width of 500 mm and a thickness of 0.6 mm was prepared. When the surface roughness was measured at a plurality of positions using a laser microscope, the arithmetic average roughness Ra was about 0.063 μm.

(Catalyst formation)
A catalyst was formed on the above substrate by the following method. First, 1.9 g of aluminum tri-sec-butoxide was dissolved in 100 mL (78 g) of 2-propanol, and 0.9 g of triisopropanolamine was added and dissolved as a stabilizer to prepare a coating agent for forming an alumina film. The above-described coating agent for forming an alumina film was applied onto the substrate by dip coating in an environment at room temperature of 25 ° C. and a relative humidity of 50%. As the application conditions, the substrate was immersed, held for 20 seconds, pulled up at a pulling speed of 10 mm / sec, and air-dried for 5 minutes. Next, after heating in an air environment of 300 ° C. for 30 minutes, the resultant was cooled to room temperature. Thus, an alumina film having a thickness of 40 nm was formed on the substrate.

  Subsequently, 174 mg of iron acetate was dissolved in 100 mL of 2-propanol, and 190 mg of triisopropanolamine was added and dissolved as a stabilizer to prepare an iron film coating agent. An iron film coating agent was applied on the substrate on which the alumina film was formed by dip coating in an environment at room temperature of 25 ° C. and a relative humidity of 50%. As the application conditions, the substrate was immersed, held for 20 seconds, pulled up at a lifting speed of 3 mm / sec, and air-dried for 5 minutes. Next, after heating in an air environment of 100 ° C. for 30 minutes, the resultant was cooled to room temperature. Thus, a catalyst generation film having a thickness of 3 nm was formed.

  Hereinafter, in all the experimental examples, the substrate on which the catalyst was formed in this manner was used.

(Experimental example 1)
The CNT was manufactured by sequentially performing the formation step and the growth step in a batch type growth furnace as shown in FIG. Using the above-mentioned catalyst base material cut out to a size of 40 mm long × 40 mm wide as a catalyst base material, a formation step and a growth step were sequentially performed to produce CNTs on the surface of the base material. Table 1 shows the gas flow rate, gas composition, heater set temperature, and processing time in each step.

  The heating time of the raw material gas was adjusted by changing the position where the catalyst base material was installed, and the base material position having the best balance between the yield of CNT to be produced and the specific surface area was determined. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 2 shows the analysis results.

The “raw material gas heating time” is an approximate average time from when the raw material gas enters the in-furnace heating region to when the raw material gas reaches the catalyst base material, and is calculated by the following equation.
Raw material gas heating time [min] = (volume of heating region upstream of substrate [mL]) / {(gas flow rate [sccm]) × (furnace temperature [K]) × 1 / (273 [K])}

In Table 2, CPD is cyclopentadiene, _pC 3 _{H 4} are methyl acetylene (propyne), VA is vinyl acetylene, 2B 2-butyne, _aC 3 _{H 4} is propadiene (allene), 13BD 1,3-butadiene, t -PPL is t- _{piperylene, C} 10 _{H 8} means naphthalene. The same applies to the following tables. As components other than Table 2, 1-butyne, diacetylene, and phenylacetylene are used as acetylenes, isoprene and c-piperylene are used as 1,3-butadienes, and methylcyclopentadiene is used as a cyclopentadiene, and as allenes. 1,2-butadiene and trace amounts (10 ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene, and anthracene were detected as PAHs, which are the main components of exhaust tar. In addition, hydrogen, methane, ethylene, ethane, propylene, benzene, toluene, styrene and the like were detected as other components. In this experimental example, since the total volume concentration [B] of the hydrocarbon B is less than 0.28%, it is referred to as “Comparative Example 1”.
The properties of the CNTs obtained under the above conditions were evaluated. Table 3 shows the results.

  Hereinafter, the yield and carbon conversion efficiency of each experimental example were evaluated based on the yield and carbon conversion efficiency of Comparative Example 1.

(Experimental example 2)
Using the same manufacturing apparatus as in Experimental Example 1, CNTs were manufactured by changing the composition of the source gas in the growth step as shown in Table 4. Conditions not described in Table 4 were the same as in Experimental Example 1.

Under each condition, the concentration ratio ([A ′] / [B ′]) of C ₂ H ₂ and 13BD of the raw material gas is fixed (0.4) and the concentration of carbon atoms contained in the raw material gas (hereinafter referred to as “carbon concentration”) "). Further, under each condition, the concentrations of hydrogen H ₂ and the catalyst activator H ₂ O added to the raw material gas were changed so as to be proportional to the carbon concentration.

  The heating time of the raw material gas was adjusted by changing the position where the catalyst base material was installed. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 5 shows the analysis results.

  In Table 5, IP means isoprene, c-PPL means c-piperylene, and 12BD means 1,2-butadiene. The same applies to the following tables. As components other than those in Table 5, diacetylene, methylvinylacetylene, and phenylacetylene were detected as acetylenes, and methylcyclopentadiene was detected as trace amounts (several ppm or less) as cyclopentadienes. As the PAHs as the main component of the exhaust tar, naphthalene was detected most frequently and several tens ppm or less, and as the other components, trace amounts (10 ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene, and anthracene were detected. In addition, hydrogen, methane, ethylene, propylene, acetone, benzene, toluene, styrene and the like were detected as other components.

  The properties of the CNT obtained under each condition were evaluated. Table 6 shows the results.

Example 2-1 where the C ₂ H ₂ concentration (concentration [A] of hydrocarbon A) in the contact gas exceeded 0.1% and the 13BD concentration (concentration [B] of hydrocarbon B) was 0.28% or more. In Examples 2 to 4, it was shown that the yield increased about 1.4 to 2.5 times as compared with Comparative Example 1 while maintaining the specific surface area at 1000 m ² / g or more. It was also shown that the carbon conversion efficiency was improved about 1.7 to 2.8 times.

(Experimental example 3)
Using the same manufacturing apparatus as in Experimental Example 1, CNTs were manufactured by changing the composition of the source gas in the growth step as shown in Table 7. Conditions not described in Table 7 were the same as in Experimental Example 2.

Under each condition, the production was carried out while keeping the carbon concentration constant (6.0%) and changing the C ₂ H ₂ and 13BD concentration ratio ([A ′] / [B ′]) of the raw material gas as shown in Table 7. Was. In each condition, the concentration of hydrogen H ₂ added to the raw material gas was fixed at 2.00%, and the concentration of the catalyst activator H ₂ O was fixed at 0.02%.

  The position where the catalyst base material was placed was the same as in Experimental Example 2. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 8 shows the analysis results.

  As components other than those in Table 8, diacetylene, phenylacetylene, and methylvinylacetylene were detected as acetylenes, and methylcyclopentadiene was detected as trace amounts (several ppm or less) as cyclopentadienes. As the main component of exhaust tar, PAHs contained naphthalene most frequently and several tens of ppm or less, and other components contained trace amounts (several ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene and anthracene. In addition, hydrogen, methane, ethylene, acetone, benzene and the like were detected as other components.

  The properties of the CNT obtained under each condition were evaluated. Table 9 shows the results.

In Example 3-1 to Example 3-6 in which [A] is more than 0.1% and [B] is 0.28% or more, the yield is about 1.2 to 2.0 times that of Comparative Example 1. It has been shown that the specific surface area can be increased and the specific surface area can be maintained at 900 m ² / g or more. It was also shown that the carbon conversion efficiency was improved by about 1.6 to 2.7 times. This tendency was particularly remarkable when [A] / [B] was in the range of 0.1 to 8.

(Experimental example 4)
Using the same manufacturing apparatus as in Experimental Example 1, CNTs were manufactured using IP as the 1,3-butadiene (hydrocarbon B ′) as the raw material gas in the growth step as shown in Table 10. Conditions not described in Table 10 were the same as in Experimental Example 1.

The production was performed with a carbon concentration of 6.0% and a concentration ratio of C ₂ H ₂ and IP of the source gas ([A ′] / [B ′]) of 0.4.

  The position where the catalyst base material was placed was the same as in Experimental Example 2. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 11 shows the analysis results.

  As components other than those in Table 11, 1-butyne, methylvinylacetylene, and phenylacetylene were detected as acetylenes, and trace amounts (10 ppm or less) of methylcyclopentadiene were detected as cyclopentadienes. As the main component of the exhaust tar PAH, naphthalene was detected most frequently and several tens ppm or less, and as for other components, trace amounts (several ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene and anthracene were detected. In addition, hydrogen, methane, ethylene, propylene, benzene, toluene and the like were detected as other components.

  The properties of the obtained CNT were evaluated. Table 12 shows the results.

It was shown that, even when the hydrocarbon B ′ of the raw material gas was changed to IP, the yield was increased 1.7 times as compared with Comparative Example 1, and the specific surface area could be maintained at 1000 m ² / g or more. It was also shown that the carbon conversion efficiency was improved 2.3 times.

(Experimental example 5)
Using the same manufacturing apparatus as in Experimental Example 1, the composition of the source gas in the growth step was changed to pC ₃ H ₄ , 1,3-butadiene (hydrocarbon B ′) as acetylenes (hydrocarbon A ′) as shown in Table 13. ) Was manufactured using IP as IP. Conditions not described in Table 13 were the same as in Experimental Example 1.

The production was performed with the carbon concentration in the source gas set to 6.0% and the concentration ratio of pC ₃ H ₄ and IP ([A ′] / [B ′]) of the source gas set to 0.4.

  The position where the catalyst base material was placed was the same as in Experimental Example 2. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 14 shows the analysis results.

  As components other than those in Table 14, 1-butyne, methylvinylacetylene, and phenylacetylene were detected as acetylenes, and a small amount (10 ppm or less) of methylcyclopentadiene was detected as cyclopentadienes. As the main component of the exhaust tar PAH, naphthalene was detected most frequently and several tens ppm or less, and as for other components, trace amounts (several ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene and anthracene were detected. In addition, hydrogen, methane, ethylene, propylene, benzene, toluene and the like were detected as other components.

  The properties of the obtained CNT were evaluated. Table 15 shows the results.

Even if the hydrocarbon A ′ of the raw material gas is changed to pC ₃ H ₄ and the hydrocarbon B ′ is changed to IP, the yield is increased by a factor of 1.4 compared to Comparative Example 1, and the specific surface area is at least 1000 m ² / g. It was shown that it could be maintained. It was also shown that the carbon conversion efficiency was improved 1.8 times.

(Experimental example 6)
Using the same production apparatus as in Experimental Example 1, CNTs were produced by changing the composition of the source gas in the growth step as shown in Table 16. Conditions not described in Table 16 were the same as in Experimental Example 1.

Under each condition, the carbon concentration is kept constant (4.0%), and the ratio [A '] / [B'] of the volume concentration [A '] of C ₂ H ₂ and the volume concentration [B'] of 13BD of the raw material gas. Was changed as shown in Table 16. In each condition, the concentration of hydrogen H ₂ added to the raw material gas was fixed at 1.33%, and the concentration of the catalyst activator H ₂ O was fixed at 0.01%.

  The position where the catalyst base material was placed was the same as in Experimental Example 2. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 17 shows the analysis results.

  As components other than those in Table 17, diacetylene and phenylacetylene were detected as acetylenes, and methylcyclopentadiene was detected as trace amounts (several ppm or less) as cyclopentadienes. Trace amounts (several ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene and anthracene were detected as other components of the exhaust tar main component PAHs. In addition, hydrogen, methane, ethylene, benzene, and the like were detected as other components.

  The properties of the CNT obtained under each condition were evaluated. The results are shown in Table 18.

  Compared with the case where the raw material gas is ethylene (Comparative Example 1), in Examples 6-1 to 6-4 in which [A ′] / [B ′] is in the range of 0.1 to 6, the ratio is The carbon conversion efficiency was improved to 1.8 to 2.8 times while maintaining the surface area, the G / D, and the yield substantially the same or higher, and the concentration of naphthalene, which is the main component of exhaust tar, was about the same as Comparative Example 1. It was shown to be reduced to 1/20 or less.

(Experimental example 7)
As shown in Table 19, CNT was produced by adding cyclopentene (CPE) as a hydrocarbon C ′ in addition to C ₂ H ₂ and 13BD in the growth process using the same production apparatus as in Experimental Example 1. did. Conditions not described in Table 19 were the same as in Experimental Example 1.

Under each condition, the carbon concentration in the source gas was kept constant (6.0%), and the concentration ratio of C ₂ H ₂ to 13BD ([A ′] / [B ′]) and the concentration of CPE in the source gas were as shown in Table 19 The production was carried out with the changes as shown in Table 1.

  The position where the catalyst base material was placed was the same as in Experimental Example 2. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. The results of the analysis are shown in Table 20.

  As components other than those in Table 20, diacetylene and phenylacetylene were detected as acetylenes, and methylcyclopentadiene was detected in trace amounts (10 ppm or less) as cyclopentadienes. Trace amounts (several ppm or less) of acenaphthylene, biphenyl, fluorene, phenanthrene and anthracene were detected as other components of the exhaust tar main component PAHs. In addition, hydrogen, methane, ethylene, cyclopentene, benzene and the like were detected as other components.

  The properties of the obtained CNT were evaluated. The results are shown in Table 21.

It was shown that by adding the hydrocarbon C ′ to the raw material gas, the yield was increased 2.1 times or more and the specific surface area could be maintained at 800 m ² / g or more as compared with Comparative Example 1. Further, it was shown that the carbon conversion efficiency was improved to 2.7 times or more as compared with Comparative Example 1. Further, it was shown that the concentration of naphthalene, which is the main component of the exhaust tar, was reduced to about 1/16 or less of Comparative Example 1.

(Experimental example 8)
The CNT was manufactured by sequentially performing the formation step and the growth step in a batch type growth furnace as shown in FIG. Using the above-mentioned catalyst base material cut out to a size of 40 mm in length × 120 mm in width, the formation step and the growth step were sequentially performed to produce CNT on the surface of the base material. Table 22 shows the gas flow rate, gas composition, heater set temperature, and processing time in each step.

The production was performed with a carbon concentration of 6.0% and a concentration ratio ([A '] / [B']) of C ₂ H ₂ and 13BD of the raw material gas of 0.4.

  The heating time of the raw material gas was adjusted by changing the position where the catalyst base material was installed. First, a growth process was performed without installing a catalyst substrate, and a gas near the substrate installation position was suction-sampled at about 200 sccm to perform gas analysis. Table 23 shows the analysis results.

  As components other than those in Table 23, diacetylene, methylvinylacetylene and phenylacetylene were detected as acetylenes, and methylcyclopentadiene was detected as trace amounts (several ppm or less) as cyclopentadienes. In naphthalene, naphthalene was the most numerous and several tens ppm or less, and as for other components, trace amounts (several ppm or less) of asenaphthylene, biphenyl, fluorene, phenanthrene and anthracene were detected. In addition, hydrogen, methane, ethylene, propylene, benzene, toluene and the like were detected as other components.

  The properties of the CNTs obtained under the above conditions were evaluated. The results are shown in Table 24.

Compared with Comparative Example 1, the yield increased about 1.8 times, the specific surface area was maintained at 1000 m ² / g or more, and the carbon conversion efficiency was improved about 17 times.

(Experimental example 9)
In a continuous growth furnace as shown in FIG. 3, a process including a formation process and a growth process was continuously performed to produce an aligned CNT aggregate. The above-mentioned catalyst base material was placed on a mesh belt of a manufacturing apparatus as it was (length 500 mm × width 500 mm), and an aligned CNT aggregate was manufactured on the base material while changing the conveyance speed of the mesh belt. Table 25 shows the conditions of each part of the manufacturing apparatus.

  The apparatus is operated under the same conditions as in the production of the aligned CNT aggregate, except that a probe for gas sampling is installed in the growth unit 3 in the vicinity of the position where the catalyst substrate passes, and the probe is not passed through the catalyst substrate. The inside of the furnace was heated while the furnace was kept empty, the gas was sampled with the probe, and the obtained gas was subjected to gas analysis. As a result, the composition of the contact gas was almost the same as that of Example 8, and the result was 500 mm × It was confirmed that CNTs substantially equivalent to those in Experimental Example 8 could be uniformly produced on a large-sized base material of 500 mm.

  According to the method for producing a carbon nanostructure of the present invention, a high-quality carbon nanostructure can be produced with high efficiency.

100, 200, 300 CNT manufacturing apparatus 102 Reactor 104 Heater 106 Gas supply port 108 Exhaust port 110 Holder 112 Shower head 1 Inlet purge section 2 Formation unit 2A Formation furnace 2B Reduction gas injection section 2C Heater 3 Growth unit 3A Growth furnace 3B Source gas injection unit 3C Heater 3D exhaust port 4 Cooling unit 4A Cooling furnace 4B Cooling gas injection unit 4C Water-cooled cooling pipe 5 Outlet purge unit 6 Transport unit 6A Mesh belt 6B Belt drive unit 7, 8, 9 Connection unit 10 Catalyst base 11 , 12, 13 Gas mixing prevention means 11A, 12A, 13A Exhaust unit 11B, 12B, 13B Seal gas injection unit

Claims (10)

A method for producing a carbon nanostructure, comprising supplying a raw material gas to a catalyst and growing the carbon nanostructure by a chemical vapor deposition method,
The gas X derived from the raw material gas and contacting the catalyst includes a hydrocarbon A having at least one acetylene skeleton and a hydrocarbon B having at least one 1,3-butadiene skeleton,
A method for producing a carbon nanostructure, wherein the total volume concentration [A] of the hydrocarbon A is more than 0.1% and the total volume concentration [B] of the hydrocarbon B is 0.28% or more. The gas X is
0.1 ≦ [A] / [B] ≦ 8
The method for producing a carbon nanostructure according to claim 1, which satisfies the following.   The method for producing a carbon nanostructure according to claim 1, wherein the gas X further includes a catalyst activator and / or a hydrogen molecule.   The method for producing a carbon nanostructure according to any one of claims 1 to 3, wherein the gas X further includes a hydrocarbon C having at least one cyclopentadiene skeleton. A method for producing a carbon nanostructure, comprising supplying a raw material gas to a catalyst and growing the carbon nanostructure by a chemical vapor deposition method,
The method for producing a carbon nanostructure, wherein the source gas includes a hydrocarbon A 'having at least one acetylene skeleton and a hydrocarbon B' having at least one 1,3-butadiene skeleton. When the total volume concentration of the hydrocarbon A 'is [A'] and the total volume concentration of the hydrocarbon B 'is [B'], the raw material gas is:
0.1 ≦ [A ′] / [B ′] ≦ 6
The method for producing a carbon nanostructure according to claim 5, which satisfies the following.   The method for producing a carbon nanostructure according to claim 5, wherein the source gas further includes a catalyst activator and / or a hydrogen molecule.   The method for producing a carbon nanostructure according to any one of claims 5 to 7, wherein the source gas further includes a hydrocarbon C 'having at least one carbon ring having 5 carbon atoms.   The method for producing a carbon nanostructure according to any one of claims 1 to 8, wherein the catalyst is supported on a substrate surface, and the raw material gas is supplied to the catalyst by a gas shower.   The method for producing a carbon nanostructure according to any one of claims 1 to 9, wherein the carbon nanostructure is a carbon nanotube.

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