Method and apparatus for manufacturing carbon nanotube aggregates

Abstract

The purpose of the present invention is to provide a method and a device that are for producing a carbon nanotube aggregate and that enable an improvement in efficiency of contact between a raw material gas and a catalyst and enable efficient production of a high-quality CNT aggregate. The method for producing a carbon nanotube aggregate according to the present invention comprises a growth step for growing a carbon nanotube aggregate on a base material having a catalyst on the surface. In the growth step, the base material is layered at a lower portion of a growth furnace for performing the growth step to form a base material layer. A raw material gas-feeding step for feeding a raw material gas to the base material layer from multiple gas jetting ports arrayed at a lower portion of the growth furnace, and an intra-growth furnace stirring and transporting step for mechanically stirring and / or transporting the base material layer, are carried out in an overlapping manner at least partially.

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for producing carbon nanotube aggregates. [Background technology]

[0002] In recent years, nanocarbon materials such as carbon nanotubes (hereinafter sometimes referred to as "CNTs") have attracted attention as materials with excellent conductivity, thermal conductivity, and mechanical properties. Although nanocarbon materials are recognized as being able to exhibit excellent properties, they have generally been more expensive than other materials due to their high manufacturing costs.

[0003] Therefore, various attempts have been made to efficiently produce nanocarbon materials. For example, Patent Document 1 describes a method for producing nanocarbon, which includes continuously supplying hydrocarbons and catalysts using a screw feeder so that they are in contact in a counterflow or counterflow state. Also, for example, Patent Document 2 describes a method for producing nanocarbon, which includes stirring and moving a catalyst body using a conveying means such as a belt conveyor within a reaction tube equipped with a catalyst activation zone, a nanocarbon synthesis zone, and a cooling zone.

[0004] In the production of carbon nanotubes using raw material gases such as hydrocarbons and catalysts, improving the contact efficiency between the raw material gas and catalyst improves carbon conversion efficiency and reduces the amount of raw material gas used. Furthermore, improving the contact efficiency between the raw material gas and catalyst suppresses the amount of excess raw material gas in the exhaust, reducing the adhesion of by-products such as tar derived from the excess raw material gas to the exhaust pipe, and enabling stable production over long periods during continuous production. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5285730 specification [Patent Document 2] Japanese Patent Publication No. 2011-241104 [Overview of the project] [Problems that the invention aims to solve]

[0006] Herein, the conventional method for producing nanocarbon materials described above had room for improvement in terms of improving the contact efficiency between the raw material gas and the catalyst, thereby further enhancing the quality and production efficiency of the resulting nanocarbon material.

[0007] Therefore, the present invention aims to provide a method and apparatus for producing carbon nanotube aggregates that improves the contact efficiency between the raw material gas and the catalyst, thereby enabling the efficient production of high-quality carbon nanotube aggregates. [Means for solving the problem]

[0008] The present inventors conducted diligent studies with the aim of solving the above problems. As a result, the present inventors have newly discovered that in the production of CNT assemblies, a substrate having a catalyst on its surface is stacked at the bottom of the furnace to form a substrate layer during the growth process, and raw material gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the growth furnace, and the substrate layer is mechanically stirred and / or transported, thereby improving the contact efficiency between the raw material gas and the catalyst, and thus enabling the efficient production of high-quality CNT assemblies. This discovery has led to the completion of the present invention.

[0009] In other words, the present invention aims to advantageously solve the above problems, and the CNT aggregate manufacturing method of the present invention is a method for manufacturing carbon nanotube aggregates that includes a growth step of growing carbon nanotube aggregates on a substrate having a catalyst on its surface, wherein in the growth step, the substrate is stacked at the bottom of a growth furnace for performing the growth step to form a substrate layer, and raw material gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the growth furnace, and the stirring and conveying step inside the growth furnace is carried out in at least part overlapping manner. With such a manufacturing method, the contact efficiency between the raw material gas and the catalyst is improved, thereby enabling the efficient production of high-quality CNT aggregates.

[0010] Furthermore, the present invention provides a method for producing CNT aggregates, which includes a formation step performed before the growth step in which the environment surrounding the catalyst is made into a reducing gas environment and at least one of the catalyst and the reducing gas is heated. In the formation process, The process includes a reduction gas supply step in which the aforementioned substrate is stacked at the bottom of a formation furnace for performing a formation process to form a substrate layer, and a reduction gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the formation furnace, Formation furnace stirring and conveying process, which involves mechanically stirring and / or conveying the substrate layer, These were implemented with at least some overlap, The formation furnace and the growth furnace are the same furnace. The formation process and the growth process may be carried out in the same furnace, with the atmosphere inside the furnace being switched. With such a manufacturing method, the formation process and the growth process can be carried out in a batch system, and the use of a single furnace brings the advantages of space saving and cost reduction of manufacturing equipment. In addition, the condition range of the operating factors for each process can be set to a wide range, making optimization easy.

[0011] Furthermore, the CNT assembly manufacturing method of the present invention is A formation unit that realizes a formation process that creates a reducing gas environment around the catalyst and heats at least one of the catalyst and the reducing gas, A growth unit that realizes a growth process in which the environment surrounding the catalyst is used as a raw material gas environment and at least one of the catalyst and the raw material gas is heated to grow the carbon nanotube aggregate, A connecting portion that spatially connects the furnace space of the formation unit and the furnace space of the growth unit, The first stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the formation unit, and the second stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the growth unit, wherein the first stirring and conveying unit and the second stirring and conveying unit are configured as one common unit and / or separate units, comprising first and second stirring and conveying units. A manufacturing apparatus is used that includes a gas mixing prevention device that prevents gases from mixing with each other between the furnace space of the formation unit and the furnace space of the growth unit, The process may be carried out by continuously transporting the substrate while preventing the gas environments in each process from mixing with each other, and performing the formation process and the growth process. With such a manufacturing method, the formation process and the growth process can be carried out in a continuous system, and the production rate can be dramatically improved. Furthermore, it becomes easy to individually optimize the equipment specifications for the formation process and the growth process, and continuous process control becomes possible, so the process can be stabilized more easily compared to the batch method. As a result, the quality of the obtained CNT aggregates and the production efficiency of CNT aggregates can be further improved.

[0012] Furthermore, in the CNT assembly manufacturing method of the present invention, the mechanical stirring and / or conveying in the stirring and conveying step within the growth furnace may be performed by the rotation of a screw, paddle, ribbon, or a combination thereof.

[0013] And in the method for manufacturing a CNT aggregate of the present invention, it is preferable that the raw material gas environment in the growth step is a high carbon concentration environment and contains a catalyst activating substance. By growing CNTs in a high-concentration carbon environment containing a catalyst activating substance in the growth step, CNTs can be grown while maintaining the catalyst activity for a long time, so that the quality of the obtained CNT aggregate and the production efficiency of the CNT aggregate can be further improved.

[0014] And in the method for manufacturing a CNT aggregate of the present invention, it is preferable that the raw material gas environment contains ethylene and carbon dioxide as a catalyst activating substance. By carrying out the growth step under such an environment, the quality of the obtained CNT aggregate and the production efficiency of the CNT aggregate can be further improved.

[0015] And in the method for manufacturing a CNT aggregate of the present invention, the substrate has an apparent density of 2.0 g / cm , ,

[0017] , or more preferably particles. If the substrate is particles with an apparent density of 2.0 g / cm 3 or more, the obtained CNT aggregate can be made longer. Incidentally, the "apparent density" of the support means the mass per unit volume including the voids when the support is particles having voids (closed pores) inside. The "apparent density of the support" can be measured according to the pycnometer method.

[0016] Also, in the method for manufacturing a CNT aggregate of the present invention, it is preferable that the substrate contains one or more elements among Al, Si, and Zr. By using a substrate containing one or more elements among Al, Si, and Zr, the production efficiency of the CNT aggregate can be further improved.

[0017] The present invention relates to a carbon nanotube assembly manufacturing apparatus, which involves growing carbon nanotube assemblies on a substrate having a catalyst on its surface, and is characterized by comprising a growth furnace that forms a substrate layer by stacking the substrate on the bottom, a raw material gas injection device having a plurality of gas injection ports arranged at the bottom of the growth furnace for supplying raw material gas to the substrate layer, and a stirring and conveying unit that mechanically stirs and / or conveys the substrate layer. With such a manufacturing apparatus, the contact efficiency between the raw material gas and the catalyst is improved, thereby enabling the efficient production of high-quality CNT assemblies.

[0018] Furthermore, the carbon nanotube assembly manufacturing apparatus of the present invention is A carbon nanotube assembly manufacturing apparatus that performs the formation process and the growth process in a single furnace by switching the atmosphere inside the furnace, The aforementioned growth furnace is a formation / growth furnace that can perform both the formation process and the growth process in a single furnace by switching the atmosphere inside the furnace. The aforementioned growth unit is a formation / growth unit capable of performing a formation process and a growth process. The formation / growth unit has a reduction gas injection device, which is located in the formation / growth furnace and has a gas injection port for supplying reduction gas to the substrate layer. The reduction gas injection device is the same as or different from the raw material gas injection device. The formation step is a step of supplying reducing gas from the gas injection port to the substrate layer, thereby creating a reducing gas environment around the catalyst and heating at least one of the catalyst and the reducing gas. The growth process involves supplying raw material gas to the substrate layer from multiple gas injection nozzles arranged at the bottom of the formation / growth furnace, thereby switching the furnace to a raw material gas atmosphere. It may also be a manufacturing apparatus. With such a manufacturing apparatus, the formation process and the growth process can be carried out in a batch system, and the use of a single furnace brings the advantages of space saving and cost reduction of the manufacturing equipment. In addition, the condition range of the operating factors for each process can be set to a wide range, making optimization easy.

[0019] Furthermore, the carbon nanotube assembly manufacturing apparatus of the present invention is A formation unit that realizes a formation process that creates a reducing gas environment around the catalyst and heats at least one of the catalyst and the reducing gas, The growth unit provides a growth process in which the surrounding environment of the catalyst is used as a raw material gas environment, and at least one of the catalyst and the raw material gas is heated to grow the carbon nanotube aggregate. A connecting portion that spatially connects the furnace space of the formation unit and the furnace space of the growth unit, The first stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the formation unit, and the second stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the growth unit, wherein the first stirring and conveying unit and the second stirring and conveying unit are configured as one common unit and / or separate units, comprising first and second stirring and conveying units. A gas mixing prevention device is provided to prevent gases from mixing between the furnace space of the formation unit and the furnace space of the growth unit. The apparatus may also have the following features. With such a manufacturing apparatus, the formation process and the growth process can be carried out in a continuous system, dramatically improving the manufacturing rate. Furthermore, it becomes easier to individually optimize the equipment specifications for the formation process and the growth process, and continuous process control becomes possible, making it easier to stabilize the process compared to a batch system. As a result, the quality of the resulting CNT aggregates and the production efficiency of CNT aggregates can be further improved.

[0020] Furthermore, in the carbon nanotube assembly manufacturing apparatus of the present invention, the stirring and conveying unit may include a screw, paddle, or ribbon, or a combination thereof, that stirs and / or conveys the substrate by the rotation of its blades. [Effects of the Invention]

[0021] According to the present invention, a method and apparatus for producing carbon nanotube assemblies can be provided, which improves the contact efficiency between the raw material gas and the catalyst, thereby enabling the efficient production of high-quality CNT assemblies. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a diagram illustrating the schematic configuration of an apparatus (batch type) capable of carrying out an example of the CNT assembly manufacturing method according to the present invention. [Figure 2] Figure 2 is a diagram illustrating the schematic configuration of an apparatus (continuous type) capable of carrying out a CNT assembly manufacturing method according to another example of the present invention. [Figure 3] Figure 3 is a diagram illustrating the schematic configuration of an example of a component of a gas contamination prevention device that may be provided in the device described in Figure 2. [Modes for carrying out the invention]

[0023] Embodiments of the present invention will now be described in detail with reference to the drawings. According to the carbon nanotube aggregate manufacturing method and manufacturing apparatus of the present invention, carbon nanotube aggregates can be produced efficiently. In the following description, based on the progression of the process from the formation process to the growth process, an optional cooling process, and a separation process, operations or components of the manufacturing apparatus that perform such operations on the earlier side will be described as "preliminary side" operations or components, and operations or components on the later side will be described as "subsequent side" operations or components.

[0024] (Method for manufacturing carbon nanotube aggregates) The present invention provides a method for producing a carbon nanotube aggregate, which includes a growth step of growing a carbon nanotube aggregate on a substrate having a catalyst on its surface. The growth step includes a raw material gas supply step, in which the substrate is stacked at the bottom of a growth furnace for performing the growth step to form a substrate layer, and raw material gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the growth furnace. • A growth furnace stirring and conveying process for mechanically stirring and / or conveying the substrate layer, These steps are carried out with at least some overlap. Furthermore, the method for producing carbon nanotube assemblies of the present invention may further include a formation step (a step of creating a reducing gas environment around the catalyst and heating at least one of the catalyst and the reducing gas) as a step performed before the growth step. Furthermore, the method for producing carbon nanotube assemblies of the present invention may further include a cooling step, a separation and recovery step, and / or a reuse step as steps performed after the growth step. Details of these steps will be described later.

[0025] Examples of methods for producing the carbon nanotube aggregates of the present invention include "batch method" and "continuous method".

[0026] <Batch manufacturing method> In one embodiment, the method for producing the carbon nanotube aggregate of the present invention may be a "batch" manufacturing method. A "batch" manufacturing method is a type of manufacturing method in which the formation process and the growth process are switched within a single unit. Such a "batch" manufacturing method is, for example, The process includes performing the formation step before the growth step, In the formation process, The process includes a reduction gas supply step in which the aforementioned substrate is stacked at the bottom of a formation furnace for performing a formation process to form a substrate layer, and a reduction gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the formation furnace, Formation furnace stirring and conveying process, which involves mechanically stirring and / or conveying the substrate layer, These were implemented with at least some overlap, The formation furnace and the growth furnace are the same furnace. The formation process and the growth process are carried out in the same furnace, with the atmosphere inside the furnace being switched. This may also be a method for producing carbon nanotube aggregates. The "batch" manufacturing method may be carried out, for example, using the "batch" manufacturing apparatus (Figure 1) described later. The "batch" manufacturing method offers the advantages of space saving and cost reduction of manufacturing equipment by using a single furnace. In addition, optimization is easy because the condition range of the operating factors for each process can be set widely.

[0027] <Continuous manufacturing method> In another embodiment, the method for producing the carbon nanotube aggregate of the present invention may be a "continuous" production method. A "continuous" production method is a production method in which the formation process and the growth process are carried out in separate units. Such a "continuous" production method may be, for example, a method in which the formation process and the growth process are carried out while continuously transporting the substrate and preventing the gas environments in each of the processes below from mixing with each other, using a CNT production apparatus having the following components: A formation unit that realizes a formation process in which the environment surrounding the catalyst is a reducing gas environment, and at least one of the catalyst and the reducing gas is heated; A growth unit that enables a growth process in which carbon nanotube aggregates are grown by heating the catalyst and the catalyst, while using the catalyst's surrounding environment as a raw material gas environment; • A connection section that spatially connects the furnace space of the formation unit and the furnace space of the growth unit; - A first stirring and conveying unit for stirring and / or conveying the substrate in the furnace space of a formation unit, and a second stirring and conveying unit for stirring and / or conveying the substrate in the furnace space of a growth unit, wherein the first stirring and conveying unit and the second stirring and conveying unit can be implemented as one common unit and / or as separate units; and A gas mixing prevention device that prevents gases from mixing between the furnace space of the formation unit and the furnace space of the growth unit. The "continuous" manufacturing method may be carried out, for example, using the "continuous" manufacturing apparatus (Figure 2) described later. The "continuous" manufacturing method can dramatically improve the manufacturing rate. Furthermore, it becomes easier to individually optimize the equipment specifications for the formation process and the growth process, and continuous process control becomes possible, making it easier to stabilize the process compared to the batch method. As a result, the quality of the obtained CNT assemblies and the production efficiency of CNT assemblies can be further improved.

[0028] <Substrate having a catalyst on its surface> The substrate that constitutes the substrate having a catalyst on its surface, used in the manufacturing method of the present invention, can be formed by supporting the catalyst on the substrate.

[0029] <<Base material>> The substrate is a component capable of supporting a catalyst for synthesizing CNTs on its surface, and is not particularly limited; any material can be used. In particular, it is preferable that the substrate is made of a ceramic material containing one or more elements from Al, Si, and Zr. Furthermore, it is preferable that the substrate is made of a metal oxide containing one or more elements from Al, Si, and Zr, and more preferably zirconium dioxide (ZrO2). The substrate is preferably particulate with an aspect ratio of less than 5. The "aspect ratio" of the substrate particles can be obtained by calculating the value (major axis / width perpendicular to the major axis) for a plurality of arbitrarily selected particles on a microscope image and taking the average value. Furthermore, the substrate particles have an apparent density of 2.0 g / cm³.3 Preferably, it should be 3.8 g / cm³ or more. 3 Preferably, it is 5.8 g / cm³ or more. 3 It is more preferable that the amount be greater than or equal to 8.0 g / cm³. 3 The following are preferable. If the apparent density of the particulate substrate is above the lower limit, the resulting CNT aggregates can be made longer. If the apparent density of the particulate substrate is below the upper limit, the substrate particles are easy to handle and the production efficiency of the CNT aggregates can be further increased. Furthermore, the particle diameter of the substrate particles is preferably 0.05 mm or more, more preferably 0.3 mm or more, preferably 10 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. If the particle diameter of the substrate particles is above the lower limit, the resulting CNT aggregates can be made longer. Furthermore, if the particle diameter of the substrate particles is below the upper limit, the production efficiency of the CNT aggregates can be further increased. Note that the "particle diameter" of the substrate particles refers to the volume-average particle diameter D50. The volume-average particle diameter D50 represents the particle diameter at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction for the substrate particles becomes 50%. Note that the deposit formed by the substrate being stacked at the bottom of the furnace due to gravity, etc., is called the "substrate layer".

[0030] <<Catalyst>> The catalyst supported on the substrate is not particularly limited, but can include catalyst components such as nickel (Ni), iron (Fe), cobalt (Co), and molybdenum (Mo). In particular, from the viewpoint of further improving the production efficiency of CNT assemblies, it is preferable that the catalyst component contains at least one metal from nickel (Ni), iron (Fe), cobalt (Co), and molybdenum (Mo). Furthermore, optionally, a substrate layer formed from materials such as aluminum oxide, titanium oxide, titanium nitride, or silicon oxide can be provided as a base for supporting the catalyst on the substrate.

[0031] <<Method for preparing a substrate having a catalyst on its surface>> The method for supporting the catalyst on the substrate surface is not particularly limited, and any existing method can be used. In particular, when substrate particles are used as the substrate, a method using a rotary drum coating apparatus equipped with a substantially cylindrical rotary drum is preferred. This method includes a spraying step in which the substrate particles are agitated by placing the substrate in a substantially cylindrical rotary drum and rotating the rotary drum with an inclined axis or horizontal axis as the axis of rotation, while spraying a catalyst solution containing the above-mentioned catalyst components onto the agitated substrate particles, and a drying step in which a drying gas is introduced into the rotary drum and the drying gas is brought into contact with the substrate particles to which the catalyst solution has been sprayed, wherein at least a portion of the period of the agitation step and at least a portion of the period of the spraying step overlap. When a base layer is placed on the substrate surface before supporting the catalyst, prior to spraying and drying the catalyst solution, the same spraying step and drying step as above can be performed using a solution containing components that can constitute the base layer and the substrate particles, thereby obtaining substrate particles having a base layer on their surface. Then, by subjecting the substrate particles having a base layer on their surface to the spraying and drying processes described above, substrate particles can be obtained in which the base layer and catalyst are supported on the surface in that order.

[0032] In addition to the above, when substrate particles are used as the substrate, a method for preparing a substrate having a catalyst on its surface may include, for example, a method that involves spraying a catalyst solution while subjecting the substrate particles to centrifugal swirling flow and vertical suspending flow.

[0033] <Reducing gas> A reducing gas is a gas that has at least one effect: reduction of the catalyst, promotion of catalyst atomization, and improvement of catalyst activity. Examples of reducing gases include hydrogen gas, ammonia, water vapor, and mixtures thereof. Alternatively, a mixture of hydrogen gas with an inert gas such as helium gas, argon gas, or nitrogen gas can be used as the reducing gas. Generally, the reducing gas is used in the formation process, but it may also be used in the growth process as appropriate.

[0034] <Raw material gas> Examples of raw material gases used in the synthesis of CNT assemblies include hydrocarbons such as methane, ethane, ethylene, propane, butane, pentane, hexane, heptanepropylene, and acetylene; lower alcohols such as methanol and ethanol; and low-carbon oxygen compounds such as acetone and carbon monoxide. Multiple types of these can also be used in mixture form. Furthermore, these raw material gases may be diluted with the inert gases mentioned above.

[0035] Here, it is preferable that the raw material gas contains ethylene. By heating the ethylene within a predetermined temperature range (700°C to 900°C), the decomposition reaction of ethylene is promoted, and when the decomposition gas comes into contact with the catalyst, rapid growth of CNTs becomes possible. However, if the thermal decomposition time is too long, the decomposition reaction of ethylene proceeds too far, causing catalyst deactivation and the adhesion of carbon impurities to the CNT aggregate. In the method for producing CNT aggregates of the present invention, a thermal decomposition time of 0.5 seconds to 10 seconds is preferable for an ethylene concentration of 0.1 volume% to 40 volume%. If the time is less than 0.5 seconds, the thermal decomposition of ethylene is insufficient, making it difficult to rapidly grow CNT aggregates with a high specific surface area. If the time is longer than 10 seconds, the decomposition of ethylene proceeds too far, generating a large amount of carbon impurities, causing catalyst deactivation and a decrease in the quality of the CNT aggregate. The thermal decomposition time can be calculated from the following formula. (Thermal decomposition time) = (Volume of heated channel) / {(Flow rate of raw material gas) × (273.15 + T) / 273.15} Here, the heated channel volume is the volume of the channel heated to a predetermined temperature T°C through which the raw material gas passes before contacting the catalyst, and the raw material gas flow rate is the flow rate at 0°C and 1 atm.

[0036] <Catalyst-activating substance> A catalyst activating substance may be added during the CNT growth process. The addition of a catalyst activating substance can further improve the production efficiency and quality of the CNT assemblies. The catalyst activating substance used here is generally an oxygen-containing substance that does not cause significant damage to the CNTs at the growth temperature. Examples include water, hydrogen sulfide, low-carbon oxygen-containing compounds such as oxygen, ozone, nitrogen oxides, carbon monoxide, and carbon dioxide, alcohols such as ethanol and methanol, ethers such as tetrahydrofuran, ketones such as acetone, aldehydes, esters, nitrogen oxides, and mixtures thereof. Among these, water, oxygen, carbon dioxide, carbon monoxide, or tetrahydrofuran are preferred, with carbon dioxide being more preferred. By growing CNTs in a high-concentration carbon environment containing a catalyst activating substance during the growth process, the catalytic activity can be maintained for a long period of time, thereby further improving the quality of the resulting CNT assemblies and the production efficiency of the CNT assemblies. Furthermore, if the raw material gas contains ethylene, the presence of carbon dioxide as a catalyst activator can further improve the quality of the resulting CNT assemblies and the production efficiency of the CNT assemblies. The reason for this is presumed to be as follows: First, in the CNT synthesis reaction, ethylene has been found to be relatively low-activity as a carbon source, and carbon dioxide as a catalyst activator. Therefore, when a gas mixture containing the above-mentioned gases passes through a layer consisting of substrates having a catalyst on its surface, that is, a layer consisting of a collection of substrates continuously transported by screw rotation, the decrease in the concentration of each gas due to the CNT synthesis reaction is very gradual, and the concentration distribution of each gas within the layer can be made relatively uniform. As a result, CNT growth between substrates becomes uniform, and production efficiency can be increased.

[0037] The amount of catalyst activating substance added during the growth process is, for example, carbon dioxide, sufficient if it is 0.5 volume% or more of the atmosphere during the growth process, preferably 4 volume% or more, more preferably 5 volume% or more, and usually 40 volume% or less.

[0038] <High-carbon environment> A high-carbon concentration environment refers to an atmosphere in which 0.1 volume% or more of the atmosphere during the growth process (hereinafter sometimes referred to as the "raw material gas environment") is the raw material gas. The proportion of the raw material gas in the high-carbon concentration environment may be, for example, 40 volume% or less. Furthermore, the proportion of the raw material gas in the high-carbon concentration environment is preferably 4 volume% or more, more preferably 5 volume% or more, even more preferably 10 volume% or more, and preferably 30 volume% or less. By including a catalyst activating substance in the raw material gas environment, the catalytic activity is significantly improved. As a result, even under high-carbon concentration conditions, the catalyst does not lose its activity, allowing the CNT aggregate to grow for a long period of time, and the growth rate can also be significantly improved.

[0039] <Reaction temperature> The reaction temperature for growing the CNT aggregate is not particularly limited and may be, for example, between 400°C and 1100°C. Furthermore, if the raw material gas contains ethylene, it is preferable that the temperature be between 700°C and 900°C.

[0040] <Formation Process> The formation process is a process in which the environment surrounding the catalyst supported on the substrate is made into a reducing gas environment, and at least one of the catalyst and the reducing gas is heated. The formation process is performed before the growth process, which will be described later. - A reduction gas supply step is performed in which a substrate is stacked on the lower part of a formation furnace for performing a formation process to form a substrate layer, and a reduction gas is supplied to the substrate layer from a plurality of gas injection nozzles arranged on the lower part of the formation furnace. • A stirring and conveying step in which the substrate layer is mechanically stirred and / or conveyed, This process may be carried out by overlapping at least some of the steps. In this case, there may be a time when only the reducing gas supply step is performed, or a time when only the stirring and conveying step is performed, or the reducing gas supply step and the stirring and conveying step may be performed in their entirety. Considering the uniformity of the supplied gas, it is preferable that at least the reducing gas supply step is performed in their entirety, and it is more preferable that the reducing gas supply step and the stirring and conveying step are performed in their entirety. Mechanical stirring and / or conveying in the stirring and conveying step may be performed by the rotation of blades of a screw, paddle, ribbon, or a combination of several thereof. This step produces at least one effect: reduction of the catalyst, promotion of atomization into a state suitable for the growth of catalyst CNTs, and improvement of catalyst activity.

[0041] In the formation process, the reducing gas may be supplied in any way within the furnace space of the formation unit, but it is preferable that the reducing gas is supplied to the substrate layer from multiple gas injection ports arranged at the bottom of the formation furnace while the substrate is stacked at the bottom of the formation furnace to form a substrate layer, as this improves the contact efficiency between the reducing gas and the substrate. At this time, it is preferable that the substrate layer is mechanically stirred and / or conveyed, as this further improves the contact efficiency between the reducing gas and the substrate. This can be expected to reduce the amount of reducing gas used and shorten the formation process time, thereby further improving the quality of the CNT assemblies and the production efficiency of the CNT assemblies.

[0042] The temperature of the catalyst support or the reducing gas atmosphere during the formation process is preferably between 400°C and 1100°C. The duration of the formation process may be between 3 minutes and 120 minutes.

[0043] <Growth process> The growth process involves using the environment surrounding the catalyst, which has been made suitable for the production of CNT aggregates by the formation process described above, as the raw material gas environment, and growing the CNT aggregates by heating at least one of the catalyst and the raw material gas. The aforementioned growth process is, - A raw material gas supply step, in which a base material is stacked at the bottom of a growth furnace for carrying out the growth process to form a base material layer, and raw material gas is supplied to the base material layer from a plurality of gas injection nozzles arranged at the bottom of the growth furnace, • A stirring and conveying step in which the substrate layer is mechanically stirred and / or conveyed, This is carried out by performing the following steps with at least some overlap. In this case, there may be a time when only the raw material gas supply step is performed, or a time when only the stirring and conveying step is performed, or the raw material gas supply step and the stirring and conveying step may be performed in their entirety. Considering the uniformity of the supplied gas, it is preferable that at least the raw material gas supply step is performed in their entirety, and it is more preferable that the raw material gas supply step and the stirring and conveying step are performed in their entirety. Mechanical stirring and / or conveying in the stirring and conveying step may be performed by the rotation of blades of a screw, paddle, ribbon, or a combination of several thereof.

[0044] In the growth process, the substrate is stacked at the bottom of the growth furnace within the furnace space of the growth unit to form a substrate layer, while the raw material gas is supplied to the substrate layer from multiple gas injection ports arranged at the bottom of the growth furnace. This supply of raw material gas ensures that it is supplied from below the substrate layer, improving the contact efficiency between the raw material gas and the substrate. Furthermore, since the substrate layer is mechanically agitated and / or conveyed, the contact efficiency between the raw material gas and the substrate is further improved. This allows for a reduction in raw material gas usage and a shorter growth process, thereby further improving the quality and production efficiency of CNT assemblies. The total area of ​​the gas injection ports is preferably designed such that the pressure loss generated when the gas passes through the injection ports is at least 1 / 10, more preferably at least 3 / 10, and even more preferably at least 1, of the pressure loss when the gas passes through the substrate layer formed at the bottom of the growth furnace. By doing so, the gas flow rate injected from each injection port is made uniform and stable, further improving the quality of the manufactured CNT assemblies and the production efficiency of the CNT assemblies. The shape of the gas injection port can vary, including circular, oval, rectangular, and slit shapes. However, from the viewpoint of processability, a circular or slit shape is preferred, and a slit shape is preferred when base material particles are used as the base material. It is preferable to set the raw material gas supply rate such that the reciprocal of the average time the gas passes through the substrate layer formed at the bottom of the growth furnace is approximately equal to or greater than the CNT synthesis reaction rate coefficient per unit volume of the substrate layer. By doing so, the CNT synthesis process becomes the reaction-limiting step, making it possible to maintain approximately the same optimal growth time when scaling up the reactor vessel.

[0045] <Cooling process> Optionally, a cooling step can be performed after the growth step. In the cooling step, the CNT aggregates, catalyst, and substrate obtained in the growth step are cooled in an inert gas environment. Since the CNT aggregates, catalyst, and substrate are at a high temperature after the growth step, they tend to oxidize easily when placed in an oxygen-containing environment. Therefore, it is preferable to cool the CNT-oriented aggregates, catalyst, and substrate to 400°C or below, and more preferably to 200°C or below, in an inert gas environment.

[0046] <Separation and Recovery Process> In the separation and recovery process, the carbon nanotube aggregate is separated from the substrate, and the substrate and the carbon nanotube aggregate are recovered separately. The recovery method is not particularly limited, and any known method can be used. In particular, a separation and recovery method that utilizes an external force and a fluid flow as a counterforce to the external force (for example, an air vortex formed by centrifugal force and an airflow as a counterforce to the centrifugal force) is preferred (see, for example, International Publication No. 2019 / 188979).

[0047] <Reuse process> In the recycling process, the recovered substrate is made reusable by oxidizing and removing the carbon on it. The oxidation removal method is not particularly limited; for example, heating the substrate while circulating air is one such method. Implementing such a recycling process can reduce the cost associated with the substrate.

[0048] <Attributes of the CNT aggregate> The specific surface area of the CNT aggregate obtained by the production method of the present invention is the value measured by the Brunauer, Emmett, Teller method from the adsorption / desorption isotherm at 77K of liquid nitrogen for CNTs without opening treatment. For example, the specific surface area of the CNT aggregate can be measured using a BET specific surface area measuring device compliant with JIS Z8830. The specific surface area of the CNT obtained by the present invention is not particularly limited. For example, it is preferably 600 m 2 / g or more, preferably 800 m 2 / g or more, preferably 2600 m 2 / g or less, and more preferably 1400 m 2 / g or less. Further, in the case of the opened CNT aggregate, the specific surface area is preferably 1300 m 2 / g or more.

[0049] (Manufacturing apparatus for carbon nanotube aggregate) The manufacturing apparatus for the carbon nanotube aggregate of the present invention is an apparatus for manufacturing a carbon nanotube aggregate by growing a carbon nanotube aggregate on a substrate having a catalyst on its surface. And the manufacturing apparatus for the carbon nanotube aggregate of the present invention includes a growth unit. The growth unit has the following components: · A growth furnace for laminating the substrates at the bottom to form a substrate layer; · A raw material gas injection device provided with a plurality of gas injection ports arranged at the bottom of the growth furnace for supplying the raw material gas to the substrate layer; and · A stirring and conveying unit for mechanically stirring and / or conveying the substrate layer.

[0050] Examples of the form of the manufacturing apparatus for the carbon nanotube aggregate of the present invention include "batch type" and "continuous type".

[0051] <Batch type manufacturing apparatus> In one embodiment, the carbon nanotube aggregate manufacturing apparatus of the present invention may be a "batch type" manufacturing apparatus. A "batch type" manufacturing apparatus is a manufacturing apparatus used in the "batch type" manufacturing method described above, in which the formation unit and the growth unit are the same unit. An example of such a "batch type" manufacturing apparatus is shown in Figure 1. The batch type manufacturing apparatus 100 includes a formation / growth unit 100a that serves as both a formation unit and a growth unit.

[0052] <<Formation / Growth Unit>> The formation / growth unit 100a is a unit for switching between the formation process and the growth process within a single unit, and consists of a complete set of equipment for switching between the formation process and the growth process. (i) In the formation process, the surrounding environment of the catalyst formed on the surface of the substrate is made into a reducing gas environment, and the function of heating at least one of the catalyst and the reducing gas; and (ii) In the growth process, the environment surrounding the catalyst, which has been made suitable for the production of CNT aggregates by the formation process, is used as the raw material gas environment, and the function of growing the CNT aggregates by heating at least one of the catalyst and the raw material gas. It has.

[0053] The following are possible components of the formation / growth unit 100a: ·Heating device 101; Formation / Growth Reactor 102; • Gas nozzle 103; • Reducing gas / raw material gas inlet 104; • Exhaust port 105; • Stirring and conveying unit 106; and • Base material holder 108. However, typically, the formation / growth unit 100a does not have a firebox opening 109, or the firebox opening 109 is closed.

[0054] -Heating device- The heating device 101 is a device for heating at least one of the catalyst and the reducing gas in the formation process, and for heating at least one of the catalyst and the raw material gas in the growth process. The heating device 101 may be the same or separate heating device in the formation process and the growth process. The heating device 101 is not particularly limited and can be implemented by, for example, a resistance heater, an infrared heater, or an electromagnetic induction heater. The heating device 102c can also heat the system so that the temperature inside the formation / growth furnace 102 is between 400°C and 1100°C in the formation process, and between 600°C and 1000°C in the growth process.

[0055] -Formation / Growth Reactor- The formation / growth furnace 102 is a furnace that combines a furnace for retaining reducing gas in the formation process (formation furnace) and a furnace for maintaining the raw material gas environment in the growth process (growth furnace).

[0056] -Gas nozzle- The gas injection port 103 is a gas injection port for injecting gas into the formation / growth furnace 102. "Gas" refers to "reducing gas" in the formation process and "raw material gas" in the growth process. Since the raw material gas is injected from below the formation / growth furnace 102, the gas injection port 103 for the raw material gas is positioned at the bottom of the formation / growth furnace 102 so that the raw material gas can be injected from below the formation / growth furnace 102. It is preferable that the gas injection port 103 for the reducing gas is also positioned at the bottom of the formation / growth furnace 102 so that the reducing gas can be injected from below the formation / growth furnace 102. The gas injection ports 103 for the reducing gas and the raw material gas may be the same or separate gas injection ports. It is preferable that multiple gas injection ports 103 are arranged in order to improve injection efficiency. By positioning the gas injection port 103 at the bottom of the formation / growth furnace 102, the raw material gas is supplied from below the base material layer (a deposit formed by the accumulation of base material 107 at the bottom of the furnace due to gravity, etc.), improving the contact efficiency between the raw material gas and the catalyst, thereby enabling the efficient production of high-quality CNT assemblies. The total area of ​​the gas injection ports is preferably designed such that the pressure loss generated when the gas passes through the injection ports is 1 / 10 to 1 or more of the pressure loss when the gas passes through the substrate layer formed at the bottom of the formation growth furnace. By doing so, the gas flow rate injected from each injection port is made uniform and stable, further improving the quality of the manufactured CNT assemblies and the production efficiency of the CNT assemblies.

[0057] -Reducing gas / raw material gas inlet- The reducing gas / raw material gas inlet 104 is connected to the gas injection port 103 and is a gas inlet for supplying the reducing gas and / or raw material gas. If the gas injection port 103 for the reducing gas and the raw material gas is the same gas injection port, it is preferable that the reducing gas / raw material gas inlet 104 is a single gas inlet. If the gas injection ports 103 for the reducing gas and the raw material gas are separate gas injection ports, the reducing gas / raw material gas inlet 104 consists of a gas inlet for the reducing gas and a gas inlet for the raw material gas, which are connected to the gas injection port 103 for the reducing gas and the gas injection port 103 for the raw material gas, respectively.

[0058] - Exhaust vent - The exhaust port 105 is an exhaust port for discharging gases from inside the furnace (e.g., unreacted reducing gas, raw material gas) to the outside of the system. The formation / growth unit 100a preferably has at least one exhaust port 105, and may have multiple exhaust ports 105.

[0059] - Stirring and conveying unit - The stirring and conveying unit 106 is a unit that stirs and / or conveys the base material 107. The stirring and conveying unit 106 has at least the function of stirring the base material layer. The stirring and conveying unit 106 may also have the function of conveying the base material 107 from outside the formation / growth furnace 102 to inside the formation / growth furnace 102 and / or conveying the base material 107 from inside the formation / growth furnace 102 to outside the formation / growth furnace 102. Preferably, the stirring and conveying unit 106 is characterized by comprising a screw, paddle, or ribbon, or a combination thereof, that stirs and / or conveys the base material by the rotation of its blades. For example, as shown in Figure 1, in a "batch type" manufacturing apparatus, the stirring and conveying unit 106 can be implemented as a paddle mixer. In the formation and growth processes, it is preferable to supply gas (reducing gas, raw material gas) from the gas injection port 103 located beneath the substrate layer while stirring the substrate layer with the stirring and conveying unit 106. These operations improve the contact efficiency between the raw material gas and the catalyst, thereby enabling the efficient production of high-quality CNT assemblies.

[0060] -Substrate holder- The substrate holder 108 is a container installed inside the formation / growth furnace 102 that houses the substrate 107 in the form of a substrate layer. When the formation / growth unit 100a has a substrate holder 108, the gas injection port 103 is located at the bottom of the substrate holder 108. The substrate layer may also be stirred within the substrate holder 108 by the stirring and conveying unit 106.

[0061] <<Other Units>> The batch manufacturing apparatus 100 may further include other units. These other units include a substrate introduction unit (e.g., hopper, inlet purge device, anteroom), a cooling unit, and an outlet unit (e.g., outlet purge device).

[0062] <<Operation of batch manufacturing equipment>> In the batch-type manufacturing apparatus 100 for the production of carbon nanotube aggregates, the formation process and the growth process are carried out in a single furnace (formation / growth furnace) by switching the atmosphere inside the furnace. In the formation process, reducing gas is supplied to the substrate layer from a gas injection port, thereby creating a reducing gas environment around the catalyst and heating at least one of the catalyst and the reducing gas. In the growth process, raw material gas is supplied to the substrate layer from multiple gas injection ports arranged at the bottom of the formation / growth furnace, thereby switching the atmosphere inside the furnace to that of the raw material gas.

[0063] Referring to Figure 1, the flow of gas (reducing gas, raw material gas) in the formation / growth unit 100a will be explained. The substrate 107 is stored in a substrate holder 108 provided in the formation / growth furnace 102, forming a substrate layer. The substrate layer is stirred by the stirring and conveying unit 106. The raw material gas is injected from a gas injection port 103 located at the bottom of the substrate holder 108, via the reducing gas / raw material gas inlet 104. Since the raw material gas is supplied from the bottom of the substrate layer and stirred by the stirring and conveying unit 106 during this process, the contact efficiency between the raw material gas and the catalyst is improved, thereby enabling the efficient production of high-quality CNT assemblies.

[0064] <<Materials of equipment components exposed to reducing gas or source gas>> Equipment components exposed to reducing gas or raw material gas include parts of the formation / growth unit 100a and the stirring / conveying unit 106. The materials used for these components are those that can withstand high temperatures, such as quartz, heat-resistant ceramics, and heat-resistant alloys. Heat-resistant alloys are preferred due to their processing accuracy, flexibility, and cost-effectiveness. Examples of heat-resistant alloys include heat-resistant steel, stainless steel, and nickel-based alloys. Heat-resistant steel is generally defined as a material with Fe as the main component and other alloy concentrations of 50% or less. Similarly, stainless steel is generally defined as a material with Fe as the main component, other alloy concentrations of 50% or less, and containing approximately 12% or more Cr. Nickel-based alloys include alloys in which Mo, Cr, and Fe are added to Ni. Specifically, SUS310, Inconel 600, Inconel 601, Inconel 625, Incoloy 800, MC Alloy, and Haynes 230 Alloy are preferred due to their heat resistance, mechanical strength, chemical stability, and low cost.

[0065] Furthermore, when constructing the furnace wall and / or furnace components from metal, it is preferable to use a heat-resistant alloy as the material and to apply a hot-dip aluminum plating treatment to its surface, or to polish its surface so that its arithmetic mean roughness Ra ≤ 2 μm.

[0066] <Continuous Manufacturing Equipment> In another embodiment, the carbon nanotube aggregate manufacturing apparatus of the present invention may be a "continuous" manufacturing apparatus. A "continuous" manufacturing apparatus is a manufacturing apparatus used in the "continuous" manufacturing method described above, in which the formation unit and the units are separate units. An example of such a "continuous" manufacturing apparatus is shown in Figure 2. The "continuous" manufacturing apparatus will be described below using Figure 2 as an example.

[0067] The components that the continuous manufacturing apparatus 200 may have include, for example, the following in the order of conveying the base material 212: • Hopper 251; • Vestibule 252 (equipped with an entrance purge device 201); • First stirring and conveying unit (for formation process) 207 (equipped with first screw blade 207a and first drive unit 207b) • Connection section 253; • Formation unit 202 (equipped with a formation furnace 202a, a reducing gas injection device 202b, a heating device 202c, and an exhaust device 202d); • Gas contamination prevention device 203 (equipped with a purge gas injection device 203a and an exhaust device 203b); • Connection part 254; • Second stirring and conveying unit (for growth process) 208 (equipped with second screw blades 208a and second drive unit 208b); • Growth unit 204 (equipped with a growth furnace 204a, a raw material gas injection device 204b, a heating device 204c, and an exhaust device 204d); • Connection section 210 (equipped with outlet purge device 205); and • Cooling unit 206 (equipped with a cooling container 206a and a water cooling device 206b).

[0068] <<Entrance Purge Device>> The inlet purging device 201 consists of a set of devices for preventing external air from entering the furnace from the substrate inlet. It has the function of replacing the surrounding environment of the substrate transported into the CNT assembly manufacturing apparatus 200 with purge gas. Examples include a furnace or chamber for holding the purge gas and an injection device for injecting the purge gas. The purge gas is preferably an inert gas, and is particularly preferably nitrogen from the viewpoint of safety, cost, and purging ability. It may also contain a small amount of hydrogen for the purpose of improving catalytic activity. If the substrate inlet is always open, the purge gas injection device is preferably implemented as a gas curtain device consisting of an air supply device configured to spray the purge gas in a shower-like manner from above and below, and is configured to prevent external air from entering from the inlet of the CNT assembly manufacturing apparatus 200. In the embodiment shown in Figure 1, the inlet purging device 201 is attached to a connection part 253 that connects the pre-chamber 252, which is a component for introducing the substrate into the system via the hopper 251, and the formation furnace 202a.

[0069] <<Formation Unit>> The formation unit 202 consists of a set of devices for realizing the formation process. The formation unit 202 has the function of creating a reducing gas environment around the catalyst formed on the surface of the substrate, and heating at least one of the catalyst and the reducing gas. The formation unit 202 may consist of, for example, a formation furnace 202a for holding the reducing gas, a reducing gas injection device 202b for injecting the reducing gas, a heating device 202c for heating at least one of the catalyst and the reducing gas, and an exhaust device 202d for discharging the gas from the furnace to the outside of the system. The heating device 202c is not particularly limited and may be implemented by, for example, a resistance heater, an infrared heater, or an electromagnetic induction heater. The heating device 202c can also heat the system so that the temperature inside the formation furnace is between 400°C and 1100°C. Furthermore, the exhaust system 202d is a component for exhausting reducing gas from inside the furnace, including a reducing gas exhaust port located on the side of the furnace body of the formation furnace 202a. The formation unit 202 preferably has at least one reducing gas exhaust port, and may have more.

[0070] <<Growth Unit>> The growth unit 204 consists of a complete set of equipment for realizing the growth process. The growth unit 204 has the function of growing CNT assemblies by heating the catalyst and the catalyst, which have been brought into a state suitable for the production of CNT assemblies by the formation process, as the source gas environment. Specifically, the growth unit 204 may consist of a growth furnace 204a for maintaining the source gas environment, a source gas injection device 204b for injecting the source gas, a heating device 204c for heating the catalyst and at least one of the source gas, and an exhaust device 204d for discharging the gas from the furnace to the outside of the system. The heating device 204c is not particularly limited and can be implemented by, for example, a resistance heater, an infrared heater, or an electromagnetic induction heater. Furthermore, although not shown in the figures, it is preferable that the growth unit 204 is equipped with a catalyst activating substance addition device. The exhaust device 204d is a component for exhausting the source gas from the furnace to the outside of the system, including a source gas exhaust port located on the side of the furnace body of the growth furnace 204a. The growth unit 204 preferably has at least one raw material gas exhaust port, and may have more than one.

[0071] <<Catalyst Activating Substance Addition Device>> A catalyst activator addition device consists of a set of equipment for adding catalyst activators to the raw material gas or for directly adding catalyst activators to the environment surrounding the catalyst in the growth furnace space. The catalyst activator addition device is not particularly limited in terms of supplying catalyst activators, but may include a supply system that can, for example, supply by bubbler, supply by vaporizing a solution containing catalyst activators, supply as a gas, and supply by liquefying and vaporizing solid catalyst activators. Such a supply system may include, for example, a vaporizer, mixer, stirrer, diluent, sprayer, pump, and compressor. Furthermore, a device for measuring the concentration of catalyst activators may be provided in the supply pipe of the catalyst activator. By using this output value for feedback control, a stable supply of catalyst activators with little change over time can be achieved.

[0072] <<Agitation and Conveying Unit>> The stirring and conveying units (first and second) 207 and 208 are units for stirring and / or conveying the substrate 212. The stirring and conveying units may be equipped with a screw, paddle, or ribbon, or a combination thereof, or a combination thereof, for stirring and / or conveying the substrate by the rotation of the blades. For example, as shown in Figure 2, in a "continuous" manufacturing apparatus, the stirring and conveying units 207 and 208 may be implemented by a screw conveyor. The screw conveyor may be implemented by screw blades (first and second) 207a and 208a and drive devices (first and second) 207b and 208b, such as motors, which can rotate the screw blades 207a and 208a to exert the ability to stir and / or convey the substrate. As shown in Figure 2, the substrate 212 may be introduced into the apparatus from outside the system via, for example, a hopper 251. Furthermore, the area around the drive units 207b and 208b can be heated by heating devices 202c and 204c, which are configured to heat the system at a lower temperature than the heating temperature in the formation unit. The diameter and winding pitch of the screw blades 207a and 208a that make up the screw conveyor can be arbitrarily adjusted according to the size of the base material 212 used.

[0073] Furthermore, the first stirring and conveying unit 207 and the second stirring and conveying unit 208 may be arranged at an angle to each other, rather than parallel to each other. Such an angle may be, for example, 10° or less.

[0074] In the configuration shown in Figure 2, the first drive unit 207b is positioned on the downstream side of the formation unit 202, and the second drive unit 208b is positioned on the upstream side of the growth unit 204. This configuration allows for a design in which the connection between the formation unit 202 and the growth unit 204 is fixed, while the ends on the sides where the drive units 207b and 208b are not installed are movably held. As a result, even if the heated components such as the formation furnace 202a and the growth furnace 204a undergo thermal expansion and size changes, the ends of these components are movably held, thereby suppressing the equipment load caused by heat.

[0075] Furthermore, by arranging the formation unit 202 and the growth unit 204 as separate components spaced apart vertically, as shown in the embodiment of Figure 2, and connecting them in series via the connecting part 254, the conditions for each of the formation unit 202 and the growth unit 204 can be easily optimized. This further improves the quality of the resulting CNT aggregates and the manufacturing efficiency of the CNT aggregates.

[0076] <<Gas contamination prevention device>> The gas contamination prevention device 203 is installed in the connection section 254 that spatially connects the formation unit 202 and the growth unit 204, and consists of a set of devices that prevents gases from mixing with each other in the furnace space between the formation unit 202 and the growth unit 204. The gas contamination prevention device 203 is not particularly limited and can be implemented by a gate valve device or rotary valve device that can mechanically shut off the spatial connection between each unit when the substrate is not moving from unit to unit, a gas curtain device consisting of a supply device configured to inject purge gas, and an exhaust device that discharges gas present in the connection section 254, inside the formation unit 202 near the connection section 254, and inside the growth unit 204 near the connection section 254 to the outside of the system. In particular, it is preferable that the gas contamination prevention device 203 has an exhaust device 203b that sucks in at least one of the reducing gas flowing in from the formation unit 202 side and the raw material gas flowing in from the growth unit 204 side and exhausts it to the outside of the CNT assembly manufacturing apparatus 200. Furthermore, it is preferable that the gas contamination prevention device 203 also has a purge gas injection device 203a that injects purge gas (seal gas) along the opening surface of the connection part 254 in addition to the exhaust device 203b, and that the exhaust device 203b sucks in the purge gas and exhausts it to the outside of the manufacturing apparatus. With a CNT assembly manufacturing apparatus 200 having such a configuration, the reduction of the catalyst in the formation process is less likely to be inhibited, and the quality of the obtained CNT assemblies and the production efficiency of CNT assemblies can be further improved. Furthermore, the screw conveyors, which are stirring and conveying units 207 and 208, straighten the gas flow within the furnace space to flow along the screw blades 207a and 208a, thereby suppressing the diffusion of gas due to suction and / or injection by the gas contamination prevention device 203, and further improving the gas contamination prevention effect. These can also be used in combination with a gate valve device and / or a rotary valve device.

[0077] <<Cooling Unit>> The cooling unit 206 consists of a complete set of equipment necessary for cooling the substrate on which the CNT aggregates have grown. The cooling unit 206 has the function of preventing oxidation and cooling the CNT aggregates, catalyst, and substrate after the growth process in the growth unit 204. The cooling unit 206 shown in Figure 2 includes a cooling container 206a for holding inert gas, and a water cooling device 206b arranged to surround the space inside the cooling container 206a. Notwithstanding the illustrated embodiment, if the cooling unit is air-cooled, the cooling unit may include an injection unit for injecting inert gas into the space inside the cooling container. In the illustrated embodiment, the cooling container 206a is connected to the growth furnace 204a via a connection part 210.

[0078] <<Connection> As described above, the pre-chamber 252, formation furnace 202a, growth furnace 204a, and cooling vessel 206a are spatially connected to each other by connecting parts 253, 254, and 210, respectively. In other words, the connecting parts 253, 254, and 210 are a set of devices that spatially connect the furnace spaces of each unit and prevent the substrate 212 from being exposed to the outside air when the substrate 212 is transported from unit to unit. Examples of connecting parts 253, 254, and 210 include furnaces or chambers that isolate the substrate environment from the outside air and allow the substrate 212 to pass from unit to unit. For example, the material of connecting parts 253, 254, and 210 may be Inconel 601.

[0079] In the embodiment shown in Figure 2, the connection section 254 connects the formation unit 202 and the growth unit 204, which are arranged as separate components spaced apart vertically, in series. The connection section 254 comprises a first connecting pipe 254a connected to the downstream side of the formation furnace 202a, a second connecting pipe 254b connected to the upstream side of the growth furnace 204a, and a connecting pipe 254c that connects these vertically. Preferably, these pipes are equipped with heating devices for maintaining the temperature of the internal substrate 212. As shown in Figure 2, the first connecting pipe 254a is equipped with a purge gas injection device 203a, and the connecting pipe 254c is equipped with an exhaust device 203b. Furthermore, a purge gas injection device 203a is provided near the inlet of the growth furnace 204a. These work together to constitute the gas contamination prevention device 203.

[0080] Here, as shown in Figure 3, the connecting pipe 254c may be equipped with a rotary valve device 203c. The rotary valve device 203c comprises a rotary valve case 203c-1, a rotary valve 203c-2, and a rotary valve driver 203c-3 that drives it. The rotation of the rotary valve 203c-2 controls the movement of the substrate 212, and by combining this control with the control of the airflow by the exhaust device 203a and the purge gas injection device 203b, the atmosphere between the formation process and the growth process can be separated more effectively. As a result, the quality of the resulting CNT assemblies and the manufacturing efficiency of the CNT assemblies can be improved.

[0081] <<Outlet purge device>> The outlet purge device 205 consists of a set of devices for preventing external air from entering the device furnace from the substrate outlet. The outlet purge device 205 has the function of creating a purge gas environment around the substrate 212. Specifically, the outlet purge device 205 can be implemented by a furnace or chamber for maintaining the purge gas environment, an injection unit for injecting the purge gas, etc. An inert gas is preferred as the purge gas, and nitrogen is particularly preferred from the viewpoint of safety, cost, and purging performance. If the substrate outlet is always open, it is preferable to provide a gas curtain device as a purge gas injection unit that sprays the purge gas from above and below in a shower-like manner to prevent external air from entering from the device outlet.

[0082] <<Injection device for reducing gas, raw material gas, and catalyst activator>> The reducing gas injection device 202b, the raw material gas injection device 204b, and the catalyst activator injection device are equipped with multiple nozzles. For example, multiple nozzles are provided from the wall surface of the formation furnace and / or growth furnace toward the center of the screw. One or more injection ports may be provided at the tip of each nozzle. Alternatively, the tip of the nozzle may be pinned, and multiple injection ports may be provided on the side and / or tip of each pin. In that case, notches must be provided on the screw blades to avoid interference with each pin. By providing multiple nozzles in the reducing gas injection device 202b in this manner, the reducing gas can be uniformly dispersed onto the substrate, enabling efficient reduction of the catalyst. As a result, the uniformity of the CNT aggregates growing on the substrate can be improved, and the consumption of reducing gas can also be reduced. By providing multiple nozzles in the raw material gas injection device 204b in this manner, the raw material gas can be uniformly dispersed onto the substrate, and the raw material gas can be consumed efficiently. As a result, the uniformity of the CNT orientation aggregates growing on the substrate can be improved, and the amount of raw material gas consumed can also be reduced. By providing multiple nozzles in the catalyst activator injection device, the catalyst activator can be uniformly dispersed onto the substrate, increasing catalyst activity and extending its lifespan, thus enabling the continuous growth of oriented carbon nanotubes (CNTs) for extended periods. This is also true when the catalyst activator is added to the raw material gas and a showerhead is used as the injection device.

[0083] <<Materials of equipment components exposed to reducing gas or source gas>> The equipment components exposed to reducing gas or raw material gas include the formation unit 202, the growth unit 204, the stirring and conveying units 207 and 208, the gas contamination prevention device 203, and some parts of the connection parts 253, 254, and 210. The materials used to make up these components are materials that can withstand high temperatures, such as quartz, heat-resistant ceramics, and heat-resistant alloys, but heat-resistant alloys are preferred in terms of processing precision, flexibility, and cost. Examples of heat-resistant alloys include heat-resistant steel, stainless steel, and nickel-based alloys. Materials with Fe as the main component and other alloy concentrations of 50% or less are generally called heat-resistant steel. Also, steel with Fe as the main component and other alloy concentrations of 50% or less, and containing approximately 12% or more Cr, is generally called stainless steel. Nickel-based alloys include alloys in which Mo, Cr, and Fe are added to Ni. Specifically, SUS310, Inconel 600, Inconel 601, Inconel 625, Incoloy 800, MC alloy, and Haynes 230 alloy are preferred in terms of heat resistance, mechanical strength, chemical stability, and low cost.

[0084] Furthermore, when constructing the furnace wall and / or furnace components from metal, it is preferable to use a heat-resistant alloy as the material and to apply a hot-dip aluminum plating treatment to its surface, or to polish its surface so that its arithmetic mean roughness Ra ≤ 2 μm. [Examples]

[0085] The method and apparatus for producing carbon nanotube (CNT) aggregates according to the present invention will be described in detail below with reference to specific examples, but the present invention is not limited to these examples.

[0086] [Example 1: Batch-type CNT manufacturing] Figure 1 shows a diagram of the manufacturing apparatus (batch type) of this embodiment. The CNT aggregate manufacturing apparatus 100 consists of a formation / growth unit 100a equipped with a heating device 101, a formation / growth furnace 102, a gas injection port 103, a reduction / growth gas inlet 104, an exhaust port 105, a paddle mixer 106, a substrate 107, and a substrate holder 108, but with the furnace end port 109 closed. The formation / growth furnace is made of quartz, and the paddle mixer and substrate holder are made of Inconel 601.

[0087] Zirconia (zirconium dioxide) beads (ZrO2, volume average particle size D50: 650 μm) were placed in a rotary drum coating apparatus and, while stirring the zirconia beads (20 rpm), an aluminum-containing solution was sprayed using a spray gun (spray volume 3 g / min, spray time 940 seconds, spray air pressure 10 MPa) while compressed air (300 L / min) was supplied into the rotary drum to dry the beads, forming an aluminum-containing coating film on the zirconia beads. Next, a firing treatment was performed at 480°C for 45 minutes to produce primary catalyst particles with an aluminum oxide layer formed on them. Furthermore, these primary catalyst particles were placed in another rotary drum coating apparatus and, while stirring (20 rpm), an iron catalyst solution was sprayed using a spray gun (spray volume 2 g / min, spray time 480 seconds, spray air pressure 5 MPa) while compressed air (300 L / min) was supplied into the rotary drum to dry the particles, forming an iron-containing coating film on the primary catalyst particles. Next, a substrate was prepared by firing it at 220°C for 20 minutes to further form an iron oxide layer.

[0088] The substrates with catalysts on their surfaces, prepared in this manner, were stacked in a substrate holder of a manufacturing apparatus. While injecting process gases from multiple gas nozzles arranged on the bottom surface of the substrate holder, the process was carried out in the order of formation, growth, and cooling to produce CNT aggregates.

[0089] The conditions for each process were set as follows:

[0090] Base material amount: 100g Formation process ·Set temperature: 800℃ • Reducing gases: Nitrogen 0.05 sLm, Hydrogen 0.45 sLm • Paddle mixer: 3 rpm Processing time: 30 minutes Growth process ·Set temperature: 800℃ • Raw material gases: Nitrogen 0.325 sLm, Ethylene 0.1 sLm, Carbon dioxide 0.025 sLm, Hydrogen 0.05 sLm • Paddle mixer: 3 rpm Processing time: 10 minutes cooling process ·Cooling temperature: room temperature • Purge gas: Nitrogen 2 sLm

[0091] The CNTs synthesized on the substrate were subjected to forced vortex classification (rotation speed 1600 rpm, airflow 2.5 Nm³). 3 Separation and recovery were performed using ( / min). The average recovery rate of CNT aggregates was approximately 98%.

[0092] The properties of the CNT aggregates produced by this embodiment are, as a typical value, a tap bulk density of 0.006 g / cm³. 3 CNT average length: 200 μm, BET specific surface area: 900 m 2 The results were as follows: / g, average outer diameter: 4.0 nm, carbon purity: 99%, CNT yield: 6 mg / g-beads, carbon conversion efficiency: 56%.

[0093] The present invention demonstrates that the apparatus can produce long, high-surface-area CNT aggregates with high carbon conversion efficiency.

[0094] [Example 2: Continuous CNT manufacturing] Figure 2 shows a diagram of the manufacturing apparatus (continuous type) of this embodiment. The CNT assembly manufacturing apparatus 200 consists of an inlet purge device 201, a formation unit 202, a gas contamination prevention device 203, a growth unit 204, an outlet purge device 205, a cooling unit 206, a first stirring and conveying unit (for formation) 207, a second stirring and conveying unit (for growth) 208, and connection parts 210, 253, and 254. Inconel 601 was used for the furnace and gas injection section of the formation / growth unit, the exhaust section of the gas contamination prevention means, the screw conveyor, each purge section, and each connection part.

[0095] The catalyst support prepared in the same manner as in Example 1 was placed into the feeder hopper of the manufacturing apparatus, and while being stirred and conveyed by a screw conveyor, the crystal nanotube aggregate was produced by processing in the order of formation, growth, and cooling steps.

[0096] The conditions for the manufacturing equipment's inlet purge section, formation unit, gas contamination prevention means, growth unit, outlet purge section, and cooling unit were set as follows.

[0097] Feed rate: 7.5 kg / h Entrance purge section 201 • Purge gas: Nitrogen 40 sLm Formation Unit 202 ·Furnace temperature: 800℃ • Reducing gases: Nitrogen 3 sLm, Hydrogen 27 sLm Processing time: 30 minutes Gas contamination prevention means 203 • Seal gas injection unit 203a: 40 sLm • Exhaust section displacement: 203b: 40sLm Growth Unit 204 ·Furnace temperature: 830℃ • Raw material gases: Nitrogen 15.4 sLm, Ethylene 4.8 sLm, Carbon dioxide 1.4 sLm, Hydrogen 2.4 sLm Processing time: 15 minutes Outlet purge section 205 • Purge gas: Nitrogen 45 sLm Cooling unit 206 ·Cooling temperature: room temperature Continuous manufacturing was carried out under the above conditions.

[0098] The CNTs synthesized on the substrate were subjected to forced vortex classification (rotation speed 1600 rpm, airflow 2.5 Nm³). 3 Separation and recovery were performed using ( / min). The average recovery rate of CNT aggregates was approximately 98%.

[0099] The properties of the CNT aggregates produced by this embodiment are, as a typical value, a tap bulk density of 0.006 g / cm³. 3 CNT average length: 200 μm, BET specific surface area: 800 m 2 The results were as follows: / g, average outer diameter: 4.0 nm, carbon purity: 99%, CNT yield: 6 mg / g-beads, carbon conversion efficiency: 15%. The results of continuous production are shown in Table 1.

[0100] [Table 1]

[0101] Sampling was performed every hour. Comparing the first sample with the 300th sample, no decrease in the amount of CNT aggregate produced or deterioration in quality was observed.

[0102] The present invention demonstrates that the apparatus can continuously manufacture long, high-surface-area carbon nanotube (CNT) aggregates with high efficiency without causing a decrease in production volume or deterioration in quality during continuous manufacturing.

[0103] [Example 3: Catalyst Reuse]

[0104] Three kilograms of the catalyst support used to produce the CNT aggregate in Example 2 were recovered and subjected to an oxidation treatment in a rotary kiln (atmosphere: air, temperature: 800°C, treatment time: 30 minutes) to remove carbon adhering to the surface of the catalyst support in a reuse process. Using the catalyst support after the reuse process, CNT aggregates were manufactured by performing each step treatment in the same manner as in Example 2.

[0105] The properties of the CNT aggregates produced by this example were almost the same as those of Example 2, except that the yield was reduced to 4.7 mg / g-beads, which was about 80% of the results.

[0106] The present invention demonstrates that the manufacturing method allows for the production of long, high-surface-area carbon nanotube (CNT) aggregates by reusing catalyst supports.

[0107] (Verification example) Using the same catalyst substrate particles and manufacturing apparatus as in Example 1, we attempted to manufacture CNT aggregates under the same conditions as in Example 1, but with the reduction / raw material gases introduced from the furnace port 109 instead of being injected from multiple gas injection ports arranged on the bottom surface of the substrate holder during each formation / growth process, and without rotating the paddle mixer.

[0108] As a result, CNT aggregates grew only near the outermost surface of the substrate layer, and no growth of CNT aggregates was observed inside the substrate layer. The average CNT yield across the entire substrate layer decreased to approximately 1 mg / g-beads, and the carbon conversion efficiency decreased to approximately 2.5%.

[0109] This demonstrated that, in the production of CNT aggregates, it is necessary to perform at least overlapping raw material gas injection from the bottom of the substrate layer and mechanical stirring of the substrate layer to improve production efficiency and carbon conversion efficiency. [Industrial applicability]

[0110] According to the present invention, the contact efficiency between the raw material gas and the catalyst is improved, thereby enabling the efficient production of high-quality CNT assemblies. [Explanation of Symbols]

[0111] 100: CNT assembly manufacturing equipment (batch type manufacturing equipment) 100a: Formation / Growth Unit 101: Heating device 102: Formation / Growth Reactor 103: Gas nozzle 104: Reducing gas / raw material gas inlet 105: Exhaust vent 106: Agitation and conveying unit (paddle mixer) 107: Base material 108: Base material holder 109:Robataguchi 200: CNT aggregate manufacturing apparatus (continuous manufacturing apparatus) 201: Inlet purge device 202: Formation Unit 202a: Formation Furnace 202b: Reducing gas injection device 202c: Heating device 202d: Exhaust system 203: Gas contamination prevention device 203a: Purge gas injection device 203b: Exhaust system 204: Growth Unit 204a: Growth furnace 204b: Raw material gas injection device 204c: Heating device 204d: Exhaust system 205: Outlet purge device 206: Cooling Unit 206a: Cooling container 206b:Water-cooled chiller 207: First stirring and conveying unit (for formation process) 207a: First screw blade 207b: First drive unit 208: Second stirring and conveying unit (for growth process) 208a: First screw blade 208b: First drive unit 210, 253, 254: Connection part 212: Base material 251: Hopper 252: Vestibule 254a: First connecting pipe 254b: Second connecting pipe 254c: Connecting pipe 203c: Rotary valve device 203c-1: Rotary valve case 203c-2: Rotary valve 203c-3: Rotary Valve Driver

Claims

1. A method for producing a carbon nanotube aggregate, comprising a growth step of growing a carbon nanotube aggregate on a substrate having a catalyst on its surface, In the aforementioned growth process, The process involves stacking the aforementioned substrates at the bottom of a growth furnace for performing the growth process to form a substrate layer, and supplying raw material gas to the substrate layer from a plurality of gas injection ports arranged at the bottom of the growth furnace, A growth furnace stirring and conveying step, in which the substrate layer is mechanically stirred and / or conveyed, These were implemented with at least some overlap, The total area of ​​the gas injection ports is designed such that the pressure loss generated when the gas passes through the injection ports is at least 1 / 10th of the pressure loss when the gas passes through the substrate layer formed at the bottom of the growth furnace. The aforementioned substrate is particles, The aforementioned substrate contains Zr, The atmosphere in the aforementioned growth process contains 5% to 40% by volume of carbon dioxide. A method for producing carbon nanotube aggregates.

2. Prior to the growth step, a formation step is performed in which the surrounding environment of the catalyst is made into a reducing gas environment and at least one of the catalyst and the reducing gas is heated. In the formation process, The process includes a reduction gas supply step in which the aforementioned substrate is stacked at the bottom of a formation furnace for performing a formation process to form a substrate layer, and a reduction gas is supplied to the substrate layer from a plurality of gas injection ports arranged at the bottom of the formation furnace, A formation furnace stirring and conveying process for mechanically stirring and / or conveying the substrate layer, These were implemented with at least some overlap, The formation furnace and the growth furnace are the same furnace. The formation process and the growth process are carried out in the same furnace, with the atmosphere inside the furnace being switched. A method for producing a carbon nanotube aggregate according to claim 1.

3. A formation unit that realizes a formation process that creates a reducing gas environment around the catalyst and heats at least one of the catalyst and the reducing gas, A growth unit that realizes a growth process in which the environment surrounding the catalyst is used as a raw material gas environment and at least one of the catalyst and the raw material gas is heated to grow the carbon nanotube aggregate, A connecting portion that spatially connects the furnace space of the formation unit and the furnace space of the growth unit, The first stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the formation unit, and the second stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the growth unit, wherein the first stirring and conveying unit and the second stirring and conveying unit are configured as one common unit and / or separate units, comprising first and second stirring and conveying units. A manufacturing apparatus is used that includes a gas mixing prevention device that prevents gases from mixing with each other between the furnace space of the formation unit and the furnace space of the growth unit, The formation process and the growth process are carried out while continuously transporting the substrate and preventing the gas environments in each process from mixing with each other. A method for producing a carbon nanotube aggregate according to claim 1.

4. A method for producing a carbon nanotube aggregate according to any one of claims 1 to 3, characterized in that the mechanical stirring and / or conveying in the growth furnace stirring and conveying step is performed by the rotation of blades of a screw, paddle, ribbon, or a combination thereof.

5. A method for producing a carbon nanotube aggregate according to any one of claims 1 to 4, wherein the raw material gas environment in the growth process is a high carbon concentration environment and contains a catalyst activating substance.

6. The method for producing a carbon nanotube aggregate according to claim 5, wherein the raw material gas environment includes ethylene and carbon dioxide as the catalyst activator.

7. The aforementioned substrate has an apparent density of 2.0 g / cm³. ３ A method for producing a carbon nanotube aggregate according to any one of claims 1 to 6, wherein the particles are as described above.

8. A method for producing a carbon nanotube aggregate according to any one of claims 1 to 7, comprising: a catalyst layer formation step of forming a catalyst layer on the substrate; a separation and recovery step of separating the carbon nanotube aggregate from the substrate and recovering the substrate and the carbon nanotube aggregate separately; and a reuse step of making the substrate reusable by oxidizing and removing the carbon on the recovered substrate.

9. A apparatus for producing carbon nanotube aggregates by growing carbon nanotube aggregates on a substrate having a catalyst on its surface, A growth furnace in which the aforementioned substrate is stacked on the lower part to form a substrate layer, A raw material gas injection device, which has multiple gas injection ports for supplying raw material gas to the substrate layer, is arranged in a plurality at the lower part of the growth furnace. A stirring and conveying unit for mechanically stirring and / or conveying the substrate layer, Equipped with a growth unit having, The total area of ​​the gas injection ports is designed such that the pressure loss generated when the gas passes through the injection ports is at least 1 / 10th of the pressure loss when the gas passes through the substrate layer formed at the bottom of the growth furnace. The aforementioned substrate is particles, An apparatus for producing carbon nanotube aggregates, characterized in that the substrate contains Zr.

10. A carbon nanotube assembly manufacturing apparatus that performs the formation process and the growth process in a single furnace by switching the atmosphere inside the furnace, The aforementioned growth furnace is a formation / growth furnace that can perform both the formation process and the growth process in a single furnace by switching the atmosphere inside the furnace. The aforementioned growth unit is a formation / growth unit capable of performing a formation process and a growth process. The formation / growth unit has a reduction gas injection device, which is located in the formation / growth furnace and has a gas injection port for supplying reduction gas to the substrate layer. The reduction gas injection device is the same as or different from the raw material gas injection device. The formation step is a step of supplying reducing gas from the gas injection port to the substrate layer, thereby creating a reducing gas environment around the catalyst and heating at least one of the catalyst and the reducing gas. The growth process involves supplying raw material gas to the substrate layer from multiple gas injection ports arranged at the bottom of the formation / growth furnace, thereby switching the furnace to a raw material gas atmosphere. The apparatus for producing carbon nanotube aggregates according to claim 9.

11. A formation unit that realizes a formation process that creates a reducing gas environment around the catalyst and heats at least one of the catalyst and the reducing gas, The growth unit provides a growth process in which the surrounding environment of the catalyst is used as a raw material gas environment, and at least one of the catalyst and the raw material gas is heated to grow the carbon nanotube aggregate. A connecting portion that spatially connects the furnace space of the formation unit and the furnace space of the growth unit, The first stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the formation unit, and the second stirring and conveying unit stirs and / or conveys the substrate in the furnace space of the growth unit, wherein the first stirring and conveying unit and the second stirring and conveying unit are configured as one common unit and / or separate units, comprising first and second stirring and conveying units. A gas mixing prevention device is provided to prevent gases from mixing between the furnace space of the formation unit and the furnace space of the growth unit. An apparatus for producing a carbon nanotube aggregate according to claim 9, comprising the features described in claim 9.

12. The apparatus for producing a carbon nanotube aggregate according to any one of claims 9 to 11, characterized in that the stirring and conveying unit comprises a screw, paddle, or ribbon, or a combination thereof, which stirs and / or conveys the substrate by the rotation of a blade.

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