Method for producing catalyst carriers and fibrous carbon nanostructures

Abstract

The purpose of the present invention is to provide a catalyst support with which it is possible to produce a high-quality fibrous carbon nanostructure. The purpose of the present invention is to provide a catalyst support used when producing a fibrous carbon nanostructure, the catalyst support comprising a carrier and a catalyst layer formed on the carrier, the catalyst layer including a metal-containing compound, and the difference ΔYI in yellowness represented by the formula being 3-20, where YIA is the yellowness of the carrier, and YIB is the yellowness of the catalyst support.　ΔYI=YIB−YIA

Description

[Technical Field]

[0001] This invention relates to a method for producing catalyst supports and fibrous carbon nanostructures. [Background technology]

[0002] Fibrous carbon nanostructures, such as carbon nanotubes (hereinafter sometimes referred to as "CNTs"; see, for example, Non-Patent Document 1), are being applied to a wide range of uses because they possess excellent mechanical strength, sliding properties, flexibility, semiconducting and metallic conductivity, thermal conductivity, and high chemical stability. Therefore, in recent years, methods for efficiently and inexpensively producing fibrous carbon nanostructures with such excellent properties have been investigated.

[0003] Here, methods for manufacturing carbon nanotubes have been reported, including arc discharge, laser evaporation, and chemical vapor deposition (CVD). Among these, the CVD method is a manufacturing method that has been extensively studied as a suitable method for the mass synthesis, continuous synthesis, and high-purity synthesis of single-walled carbon nanotubes with the above-mentioned properties (see, for example, Non-Patent Document 2). In the CVD method, a catalyst support is used, in which the catalyst component is supported on the surface of a substrate or particles that serve as a support.

[0004] For example, Patent Document 1 discloses a technique for synthesizing carbon nanotubes on a support substrate by flowing a raw material gas consisting of acetylene, carbon dioxide, and an inert gas at a predetermined partial pressure over the surface of a support substrate on which a catalyst containing Fe or the like is supported.

[0005] Furthermore, Patent Document 2 discloses a fluidized bed method for synthesizing carbon nanotubes using a catalyst support in which a catalyst layer is formed on the surface of a particulate carrier. [Prior art documents] [Patent Documents]

[0006]

Patent Document 1

Patent Document 2

Non - Patent Document

[0007]

Non - Patent Document 1

Non - Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, there was room for improvement in the quality, such as the specific surface area, of the fibrous carbon nanostructure produced using the catalyst support of the above - mentioned conventional technology.

[0009] Therefore, an object of the present invention is to provide a catalyst support capable of producing a high - quality fibrous carbon nanostructure. Another object of the present invention is to provide a method for producing a fibrous carbon nanostructure capable of producing a high - quality fibrous carbon nanostructure.

Means for Solving the Problems

[0010] The inventor of the present invention conducted intensive studies to achieve the above object. As a result, the inventor found that in a catalyst support in which a catalyst layer containing a metal - containing compound is formed on a carrier, if the difference obtained by subtracting the yellowness of the carrier from the yellowness of the catalyst support is within a predetermined range, a high - quality fibrous carbon nanostructure can be produced when using the catalyst support, and thus completed the present invention.

[0011] In other words, the present invention aims to advantageously solve the above problems, and the catalyst support of the present invention is a catalyst support used in the production of fibrous carbon nanostructures, comprising a carrier and a catalyst layer formed on the carrier, wherein the catalyst layer contains a metal-containing compound and the yellowness of the carrier is YI A The yellowness of the catalyst support is set to YI B The following formula: ΔYI=YI B -YI A The difference in yellowness ΔYI, represented by , is 3 or more and 20 or less. Thus, in a catalyst support in which a catalyst layer containing a metal-containing compound is formed on a support, if the difference obtained by subtracting the yellowness of the support from the yellowness of the catalyst support is kept within a predetermined range, a high-quality fibrous carbon nanostructure can be manufactured using the catalyst support. Note that the yellowness of the carrier YI A and the yellowness of the catalyst support is YI B This can be measured by the method described in the examples of this specification. Here, in the catalyst support of the present invention, if the surface of the support is covered with a catalyst support layer described later, "support" refers to the support in the state covered with the catalyst support layer. That is, in the catalyst support of the present invention, if a support with a catalyst support layer is used in which the surface of the support is covered with a catalyst support layer, "the yellowness of the support YI A " refers to the yellowness YI obtained by measuring the catalyst support layer-equipped carrier according to the method described in the examples of this specification. Furthermore, in the present invention, for example, the BET specific surface area of ​​a fibrous carbon nanostructure containing carbon nanotubes is 600 m². 2 If the value is 1 / g or higher, the fibrous carbon nanostructure containing the carbon nanotubes can be considered high quality. Here, "BET specific surface area" refers to the nitrogen adsorption specific surface area measured using the BET method.

[0012] Here, the catalyst support of the present invention, for example, contains an iron compound such as iron oxide as the metal-containing compound.

[0013] Furthermore, the catalyst support of the present invention may have the surface of the support covered with a catalyst support layer. The catalyst support layer may include, for example, a ceramic material such as aluminum oxide.

[0014] Furthermore, this invention aims to advantageously solve the above-mentioned problems, and the method for producing fibrous carbon nanostructures of the present invention is characterized by including a step of supplying a raw material gas to any of the catalyst supporters described above and synthesizing fibrous carbon nanostructures on the catalyst layer. Since the method for producing fibrous carbon nanostructures of the present invention uses any of the catalyst supporters described above, high-quality fibrous carbon nanostructures can be produced. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a catalyst support capable of producing high-quality fibrous carbon nanostructures. Furthermore, according to the present invention, it is possible to provide a method for producing fibrous carbon nanostructures that can produce high-quality fibrous carbon nanostructures. [Brief explanation of the drawing]

[0016] [Figure 1A] This is a schematic cross-sectional view showing the schematic configuration of an example of a rotary drum type fluidizing apparatus used in an example of a method for manufacturing a catalyst support according to the present invention. [Figure 1B] Figure 1A is a cross-sectional view along the central axis showing the schematic configuration of the rotating drum in the rotary drum type fluidization apparatus. [Figure 2] This figure illustrates an example of a method for manufacturing a catalyst support using a rotary drum type fluidizing apparatus, which is used in the manufacturing method of the catalyst support of the present invention. [Modes for carrying out the invention]

[0017] (Catalyst carrier) The catalyst support of the present invention is used when manufacturing a fibrous carbon nanostructure. The catalyst support of the present invention includes a support and a catalyst layer formed on the support. Here, the catalyst layer contains a metal-containing compound. And the catalyst support of the present invention has the yellowness of the support as YI A and the yellowness of the catalyst support as YI B such that the difference in yellowness ΔYI represented by the following formula: ΔYI = YI B −YI A is within a predetermined range. When the catalyst support of the present invention is used in the production of a fibrous carbon nanostructure, a high-quality fibrous carbon nanostructure can be produced.

[0018] <Support> The support is made of an arbitrary material and forms a matrix structure for forming and supporting a catalyst layer on the support. The shape of the support is not particularly limited. For example, it can be in the form of particles. When a particulate support is used, usually, the catalyst support produced using the particulate support is also in the form of particles. Here, "particulate" only needs to form a substantially particulate shape, and preferably has an aspect ratio of 10 or less. When the aspect ratio of the particulate support is 10 or less, the catalyst solution can be uniformly sprayed in the method for producing the catalyst support described later. In the present invention, the "aspect ratio of the particulate support" can be determined by measuring the short diameter and long diameter of 100 randomly selected particulate supports using a transmission electron microscope. <LID=

[0019] The material of the carrier is not particularly limited, but it is preferable that it contains a metal oxide, more preferably a metal oxide containing at least one element selected from the group consisting of magnesium (Mg), aluminum (Al), silicon (Si), zirconium (Zr), and molybdenum (Mo), and even more preferably composed of metal oxides such as zirconium dioxide (zirconia), aluminum oxide, and zircon. The heat resistance can be improved by making the particulate carrier out of a metal oxide. Furthermore, the heat resistance can be further improved by using zirconium dioxide (zirconia), aluminum oxide, or zircon as the metal oxide.

[0020] When the carrier is particulate, there are no particular restrictions on the particle size (diameter) of the particulate carrier, but it is preferable that it be between 50 μm and 10 mm. If the diameter of the particulate carrier is 50 μm or more, separation of the particulate carrier and CNTs after CNT synthesis can be easily performed, and if it is 10 mm or less, the total surface area of ​​particles in the same volume is increased, which can increase the production efficiency of CNTs. Note that the "particle size (diameter)" of the particulate carrier refers to the volume-average particle size D50. The volume-average particle size D50 represents the particle size at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume-based) measured by laser diffraction for the particulate carrier becomes 50%.

[0021] Furthermore, the structure of the carrier may consist only of the carrier made of the material described above, or it may be a carrier with a catalyst support layer, in which the surface of the carrier is covered with an arbitrary catalyst support layer. The catalyst support layer may be made of any material and may have a structure consisting of a single layer (single-layer structure) or a structure consisting of multiple layers (multilayer structure). However, from the viewpoint of properly supporting the catalyst on the carrier and effectively utilizing the catalyst carrier, it is preferable that the carrier is a carrier with a catalyst support layer. The composition of the catalyst support layer is not particularly limited and can be appropriately selected depending on the type of carrier and the type of catalyst described later. The catalyst support layer can be formed from, for example, ceramic materials such as alumina (aluminum oxide), titania, titanium nitride, and silicon oxide. The thickness of the catalyst support layer can also be appropriately adjusted according to the desired amount of catalyst supported. The catalyst support layer can be formed on the surface of the carrier, for example, in an example of the method for manufacturing the catalyst carrier of the present invention described later, by using a solution for forming the ceramic material instead of the catalyst solution and carrying out a spraying step, a drying step, and a firing step.

[0022] <Catalyst layer> The catalyst layer contains a metal-containing compound as a catalyst component and is formed on the carrier described above. The catalyst layer may be directly supported on the surface of the carrier to form a catalyst support, or it may be indirectly supported on the surface of the carrier via the catalyst support layer, etc., to form a catalyst support (for example, when using a particulate carrier, it may be formed in the order of particulate carrier / catalyst support layer / catalyst layer from the inside). The catalyst layer is typically located on the outermost surface of the catalyst support and promotes the synthesis of fibrous carbon nanostructures.

[0023] The metals included in the metal-containing compound are not particularly limited as long as they can function as catalysts for the synthesis of fibrous carbon nanostructures such as CNTs, and examples include iron (Fe), molybdenum (Mo), and cobalt (Co). Examples of metal-containing compounds that can be used include iron compounds such as iron oxide, iron acetate, iron nitrate, iron chloride, ferrocene, and iron acetylacetonate; and cobalt compounds such as cobalt acetate.

[0024] <Difference in yellowness ΔYI> Furthermore, in the catalyst support of the present invention, the yellowness of the support is YI A The yellowness of the catalyst support is YI B The following formula: ΔYI=YI B -YI A The difference in yellowness ΔYI, represented by , must be 3 or more, preferably 4.5 or more, more preferably 5.5 or more, even more preferably 6.5 or more, and must be 20 or less, preferably 18 or less, more preferably 15 or less, and even more preferably 12 or less. If the difference in yellowness ΔYI in the catalyst support is within the above predetermined range, high-quality fibrous carbon nanostructures can be manufactured. Note that the yellowness of the carrier YI A This can be adjusted by changing the material of the carrier, the composition and formation method of the catalyst support layer covering the surface of the carrier, and so on. Furthermore, the yellowness of the catalyst support YI B This can be adjusted by changing the catalyst components of the catalyst layer and the method of forming the catalyst layer (for example, the spraying conditions of the catalyst solution in the example of the method for producing the catalyst support of the present invention described later).

[0025] <Method for manufacturing catalyst support> The catalyst support of the present invention is not particularly limited as long as the difference in yellowness ΔYI between the carrier and the catalyst support is within a predetermined range, and can be manufactured by forming a catalyst layer on the carrier by known methods. As a method for forming a catalyst layer on a support, either a dry method, in which a catalyst raw material gas is blown onto the surface of the support, or a wet method, in which a catalyst solution is applied to the surface of the support, can be employed. Furthermore, as a wet method, a method of immersing the carrier in the catalyst solution (immersion method) may be used, or, for example, when using a particulate carrier (particulate carrier), a method of spraying the catalyst solution onto the particulate carrier while it is flowing may be used. In the case of spraying the catalyst solution onto the particulate carrier while it is flowing, the particulate carrier may be suspended. That is, the catalyst solution may be sprayed onto the particulate carrier while it is suspended and flowing.

[0026] The following describes an example of a method for manufacturing the catalyst support of the present invention using a rotary drum fluidizer. However, the method for manufacturing the catalyst support of the present invention is not limited to this, and other devices (for example, centrifugal levitation fluidizers) may be used. Furthermore, although a particulate carrier is used in the example below, the method for manufacturing the catalyst support of the present invention is not limited to this, and carriers of shapes other than particulates may also be used.

[0027] One example of a method for producing the catalyst support of the present invention involves forming a catalyst layer on a particulate carrier using a rotary drum type fluidizing device. Figure 1A is a schematic cross-sectional view perpendicular to the central axis direction, showing the schematic configuration of an example of a rotary drum type fluidizing apparatus that can be used in the catalyst support manufacturing method of the present invention, and Figure 1B is a cross-sectional view in the direction of the central axis direction, showing the schematic configuration of the rotary drum in the rotary drum type fluidizing apparatus shown in Figure 1A. As shown in Figures 1A and 1B, the rotary drum type fluidizer 100 comprises a housing 30, a rotary drum 20 housed inside the housing 30 so as to be rotatable around a central axis X in a substantially horizontal direction, a rotary drive mechanism 23g for rotating the rotary drum 20 around the central axis X, a spray device 40 as a spraying unit for spraying a catalyst solution C onto particulate carriers A housed inside the rotary drum 20, and a drying gas supply device (not shown) for supplying drying gas G to the housing 30. Here, in this specification, "substantially horizontal direction" means that the smaller angle between the horizontal direction and the central axis X is 0° or more and 20° or less. In this embodiment, the left side of the rotary drum 20 in Figure 1B (the side with the front end opening 23d) is the front side, and the right side of the rotary drive mechanism 23g in Figure 1B is the rear side.

[0028] The housing 30 has an air inlet 30a for supplying drying gas G into the housing 30 and an exhaust port 30b for exhausting the drying gas G supplied into the housing 30 from the inside of the housing 30. Furthermore, a gap 30c is provided between the housing 30 and the rotating drum 20, and the partition plate 24, which will be described later, is configured to be movable within this gap 30c. Here, the air inlet 30a and the exhaust port 30b are located opposite each other with respect to the central axis X of the rotating drum 20.

[0029] Furthermore, as shown in Figure 1A, the drying gas G inside the rotating drum 20 is configured to flow along the inflow direction H. Here, when the spraying direction of the catalyst solution C is the arrangement direction I of the spray device 40, the arrangement direction I forms an angle θ of 0° to 45° with respect to the inflow direction H of the drying gas G inside the rotating drum 20.

[0030] The rotating drum 20 comprises a drum body 23 and a plurality of partition plates 24. As shown in Figure 1B, the drum body 23 comprises a cylindrical drum portion 23i and a tapered portion 23c provided on the rear side of the drum portion 23i and formed to decrease in diameter toward the rear. The drum portion 23i comprises a cylindrical peripheral wall portion 23a having a polygonal cross-section (in this embodiment, a dodecagonal cross-section), a ring-shaped front end ring portion 23e provided on the front side of the peripheral wall portion 23a, and a rear end ring portion 23h provided on the rear side of the peripheral wall portion 23a and having the same shape as the front end ring portion 23e.

[0031] A circular front end opening 23d is formed in the front end ring portion 23e, and through this front end opening 23d, it is possible to supply particulate carrier A into the rotating drum 20 and discharge particulate carrier A or the manufactured catalyst support from the rotating drum 20.

[0032] The tapered section 23c is formed with a hollow interior and communicates with the internal space of the drum section 23i, and is designed to accommodate the particulate carrier A introduced through the front end opening 23d. A rotary drive mechanism 23g, which rotates the rotating drum 20, is connected to the rear side of the tapered section 23c via a connecting section 23f.

[0033] The peripheral wall portion 23a has a ventilation section that connects the internal space of the rotating drum 20 with the gap portion 30c, which is the outside of the rotating drum 20. This ventilation section can be formed in the shape of a mesh, for example, with multiple holes of a size that prevents the particulate carrier from passing through but allows the drying gas to pass through.

[0034] Multiple partition plates 24 are arranged at predetermined intervals along the outer circumference of the peripheral wall portion 23a, between the front end ring portion 23e and the rear end ring portion 23h. Each partition plate 24 has approximately the same dimensions as the dimension in the direction of the central axis X of the peripheral wall portion 23a and is arranged on the outer circumference of the peripheral wall portion 23a in a direction parallel to the central axis X of the rotating drum 20. The partition plates 24 are erected radially from each vertex of the polygon (12-sided in Figure 1A) of the peripheral wall portion 23a toward the outer circumference. The partition plates 24 slide along the inner circumferential surface 30d of the housing 30 when the rotating drum 20 rotates.

[0035] Multiple communication spaces are formed on the outer circumference of the peripheral wall portion 23a, each partitioned by a front end ring portion 23e and multiple partition plates 24 provided at the vertices of the polygon. Each communication space is open on the outward side (the side facing the peripheral wall portion 23a). Therefore, multiple communication spaces are formed on the outer circumference of the peripheral wall portion 23a, corresponding to the number of sides of the polygon. In this example, since the cross-sectional shape of the peripheral wall portion 23a is dodecagonal, 12 of the aforementioned communication spaces are formed. The openings of each communication space are formed to approximately the same size as the air intake port 30a formed in the housing 30. Dry gas G supplied from the air intake port 30a is supplied to each communication space, and the partition plates 24 prevent it from flowing out into the gap portion 30c, thus ensuring that it is reliably supplied into the rotating drum 20. Furthermore, since the openings of each communication space are formed to be approximately the same size as the exhaust ports 30b formed in the housing 30, the drying gas G inside the rotating drum 20 can be reliably discharged to the outside of the housing 30 through the exhaust ports 30b via each communication space.

[0036] Furthermore, in the drying process described later, the ventilation section in the peripheral wall 23a located opposite the air intake port 30a functions as an inlet 23ab for introducing drying gas G into the rotating drum 20, and the ventilation section located opposite the exhaust port 30b functions as an outlet 23ac for discharging drying gas from the rotating drum 20. In other words, in one example, the mesh-like ventilation section in the peripheral wall 23a forms an inlet 23ab when it moves to a position corresponding to the air intake port 30a as the rotating drum 20 rotates during the drying process, and forms an outlet 23ac when it moves to a position corresponding to the exhaust port 30b. The inlet 23ab is located above the spray device 40 in the direction of gravity (vertical direction) relative to the surface S of the layer of particulate carrier A (particulate carrier layer) when the rotating drum 20 is rotating, and the outlet 23ac is located below the spray device 40 in the direction of gravity (vertical direction) relative to the surface S of the layer of particulate carrier A (particulate carrier layer) when the rotating drum 20 is rotating. Here, it is preferable that the length of the perpendicular from the inlet 23ab to the surface S of the layer made of particulate carrier A (particulate carrier layer) during the rotation of the rotating drum 20, La (not shown), and the length of the perpendicular from the outlet 23ac to the surface S of the layer made of particulate carrier A (particulate carrier layer) during the rotation of the rotating drum 20, Lb (not shown), satisfy the relationship La > Lb, for example, as shown in Figure 1A.

[0037] The operation of the rotary drum type fluidizer 100 will be described below. First, particulate carrier A is introduced into the rotating drum 20 through a front end opening 23d provided at the front end 23b of the rotating drum 20. Next, the rotating drum 20 into which the particulate carrier A has been introduced rotates around the central axis X by the operation of the rotation drive mechanism 23g. As the rotating drum 20 rotates, the particulate carrier A contained within the rotating drum 20 is swept upward in the direction of gravity (vertical direction), and then flows downward in the direction of gravity (vertical direction) due to the gravitational action of its own weight. Thus, the particulate carrier A can be efficiently moved up and down in the direction of gravity (vertical direction), and consequently, the particulate carrier A can be efficiently agitated.

[0038] Next, catalyst solution C is sprayed from the spray device 40 onto the particulate carrier A flowing in the rotating drum 20, and drying gas G is passed through the air inlet 30a, the inlet 23ab, the particulate carrier A housed inside the rotating drum 20, the outlet 23ac, and the exhaust port 30b in that order, thereby drying the surface of the particulate carrier A to which the catalyst solution C has adhered, and obtaining a particulate carrier A with a catalyst coating film formed thereon. Furthermore, the drying gas G supplied from the drying gas supply device to the housing 30 and reaching the air inlet 30a collides with the partition plate 24a (Figure 1A), which moves in approximately the opposite direction to the inflow direction of the drying gas G due to the rotation of the rotating drum 20. As a result, the drying gas G is prevented from passing through the gap 30c of the housing 30 without flowing into the interior of the rotating drum 20, and almost the entire amount of drying gas G supplied to the air inlet 30a can flow into the interior of the rotating drum 20. Furthermore, the opening area of ​​the exhaust port 30b is designed to be smaller than the surface area S of the layer formed by the particulate carrier A inside the rotating drum 20. This effectively prevents the dry gas G from passing through the gap 30c without coming into contact with the particulate carrier A. In this way, almost the entire amount of dry gas G supplied to the air intake port 30a can pass through the air intake port 30a, the inlet 23ab, the particulate carrier A housed inside the rotating drum 20, the outlet 23ac, and the exhaust port 30b in that order.

[0039] In the rotary drum type fluidizer 100 used in an example of the method for producing a catalyst support of the present invention, the rotational speed of the rotary drum 20 varies depending on the diameter of the apparatus, but is preferably 1 rpm or more, more preferably 3 rpm or more, particularly preferably 5 rpm or more, preferably 100 rpm or less, more preferably 50 rpm or less, and particularly preferably 30 rpm or less. If the rotation speed of the rotating drum 20 is 1 rpm or more, a sufficient stirring effect can be obtained, and if it is 100 rpm or less, the particulate carrier A can be prevented from remaining in close contact with the inner wall surface of the peripheral wall portion 23a of the rotating drum 20 due to centrifugal force.

[0040] In the rotary drum type fluidizer 100 used in an example of the method for manufacturing a catalyst support of the present invention, if the spray device 40, which serves as the spraying unit, is equipped with a constant flow rate pump, the catalyst solution C can be delivered quantitatively, and consequently, the flow rate can be easily controlled. Furthermore, if the spray device 40, which serves as the spraying unit, is equipped with an automatic spray gun, a fine and uniform mist can be sprayed, and consequently, a coating with a low aggregate formation rate, uniform particle size, and fineness can be achieved. The spray device 40, which serves as the spraying unit, is not particularly limited and may, for example, be a two-fluid nozzle or may have a mist generator such as an ultrasonic atomizer.

[0041] The following describes each step of an example of a method for producing the catalyst support of the present invention. An example of a method for manufacturing a catalyst support of the present invention includes the steps of: stirring the particulate support A by rotating a substantially cylindrical rotating drum 20 containing the particulate support A around a central axis X (stirring step); spraying a catalyst solution C onto the particulate support A inside the rotating drum (spraying step); and introducing a drying gas G into the rotating drum 20 from outside the rotating drum 20 and bringing the drying gas G into contact with the particulate support A to which the catalyst solution C was sprayed in the spraying step, thereby drying the catalyst solution C (drying step). Optionally, the method may further include a step of calcining the particulate support A at a temperature of 50°C to 900°C after the drying step (calcination step). In this example, at least a portion of the duration of the stirring step and at least a portion of the duration of the spraying step overlap.

[0042] <<Stirring process>> In the stirring process, a rotating drum 20 containing particulate carrier A is rotated around a central axis X. In this way, by rotating the rotating drum 20 around the central axis X, the particulate carrier A contained inside the rotating drum 20 is swept upward in the direction of gravity (vertical direction) as the rotating drum 20 rotates, and then flows downward in the direction of gravity (vertical direction) due to the gravitational effect of its own weight, so that the particulate carrier A can be efficiently stirred.

[0043] Furthermore, there are no particular restrictions on the temperature during stirring, and it can be appropriately selected depending on the type of particulate carrier A, the composition of the catalyst solution C described later, etc.

[0044] <<Spraying process>> In the spraying process, the catalyst solution is sprayed onto the particulate carrier inside the rotating drum. As described above, in this example, at least a portion of the duration of the stirring process and at least a portion of the duration of the spraying process overlap, so the spraying process includes a period during which the catalyst solution C is sprayed onto the stirred particulate carrier A. This allows for the uniform formation of a coating film of catalyst solution C on the surface of the particulate carrier A. There are no particular restrictions on the method of spraying the catalyst solution C onto the particulate carrier A. For example, spraying from a spray device 40 (spraying means) such as a spray gun or spray nozzle is preferred. The conditions for spraying the catalyst solution C onto the particulate support A are not particularly limited, as long as the desired effects of the present invention are obtained. The spray volume, the size of the sprayed mist particles, the spraying time, etc., can be appropriately selected. When spraying two or more catalyst solutions C, the mixture of the two or more catalyst solutions C may be sprayed from a single spray device 40 (spraying means), or it may be sprayed using separate spray devices 40 (spraying means), but it is preferable to spray using separate spray devices 40 (spraying means).

[0045] [Catalyst solution] As the catalyst component in catalyst solution C, compounds containing the metals mentioned above in the "Catalyst Support" section (for example, nickel (Ni), iron (Fe), cobalt (Co), and molybdenum (Mo)) can be used. Specific examples of catalyst components contained in catalyst solution C include, for example, iron compounds such as iron acetate, iron nitrate, iron chloride, ferrocene, and iron acetylacetonate; cobalt compounds such as cobalt acetate; and other metal-containing compounds. Various organic solvents such as alcohols, glycols, ketones, ethers, esters, and hydrocarbons can be used as the solvent in catalyst solution C, but the use of alcohols is preferred. These organic solvents may be used individually or in mixtures of two or more. Methanol, ethanol, and isopropyl alcohol are preferred as alcohols in terms of handling and storage stability. Catalyst solution C may also contain water. Catalyst solution C may contain both the solvent and water, or only one of them. In addition, it is preferable that the catalyst components in catalyst solution C are soluble in water and / or a solvent. There are no particular restrictions on the solid content concentration of catalyst solution C, but it is preferably 20% by mass or less, and more preferably 10% by mass or less. By having a solid content concentration of 20% by mass or less of catalyst solution C, the coating film is stable, and a catalyst support is obtained in which the catalyst layer is uniformly formed on the surface of the particulate support. This allows for the highly efficient synthesis of fibrous carbon nanostructures such as carbon nanotubes, and offers excellent mass productivity.

[0046] <<Drying process>> In the drying process, a uniform catalyst coating can be formed on the surface of the particulate carrier A by drying the particulate carrier A to which the catalyst solution C has been sprayed. Specifically, as described above, drying gas G is introduced into the rotating drum 20 from outside the drum 20, and the drying gas G is brought into contact with the particulate carrier A to which the catalyst solution C has been sprayed in the spraying process, thereby drying the catalyst solution C adhering to the surface of the particulate carrier A and forming a catalyst coating. The particulate carrier A to which the catalyst coating has been formed can be used as a catalyst carrier as is, but depending on the composition of the catalyst solution C, a firing process described later may be performed on the particulate carrier A to which the catalyst coating has been formed after the drying process if necessary. Here, the catalyst coating forms a catalyst layer.

[0047] The drying gas G used in the drying process is not particularly limited and may include, for example, compressed air or nitrogen. In this specification, "drying gas" means a gas used to dry a particulate carrier on which a catalyst solution has been sprayed. Therefore, the "drying gas" itself may have any attributes. For example, the dew point of the "drying gas" is not particularly limited. There are no particular restrictions on the amount of drying gas supplied, however, if the brim volume of the rotating drum (the volume of particulate carrier that can be fed in) is less than 10L, then 0.1m 3 Preferably 0.3 m / min or more. 3 More preferably 1m / minute or more. 3 Preferably, the dry gas supply rate is 0.1 m³ / min or less. 3 If it is for more than / minutes, a sufficient drying effect can be obtained, 1m 3If the rate is less than / minute, the scattering of particulate carrier A by the drying gas G can be suppressed, and the spray droplets can be prevented from drying before they adhere to the particulate carrier A. If the brim of the rotating drum is 10L or more, 1m 3 Preferably more than / minutes, 3m 3 More preferably 50m / minute or longer. 3 Preferably, the dry gas supply rate is 1 m³ / min or less. 3 If it is for more than / minute, sufficient drying effect can be obtained, 50m 3 If the rate is less than / minute, the scattering of particulate carrier A by the drying gas G can be suppressed, and the spray droplets can be prevented from drying before they adhere to the particulate carrier A.

[0048] <<Firing Process>> In the firing process, the particulate carrier A that has undergone the drying process may be fired at a temperature of 50°C to 900°C.

[0049] Furthermore, the firing may be performed using a muffle furnace, fluidized bed, or rotary kiln after removing the particulate carrier A, on which a catalyst coating has been formed on its surface, from the rotating drum 20, or it may be performed inside the rotating drum 20 without removing it. It is preferable to perform the firing in an oxygen atmosphere. The firing temperature is preferably above approximately 200°C. The firing time is preferably 5 minutes to 60 minutes, and more preferably 5 minutes to 40 minutes. For example, a coating containing an iron compound as a catalyst component needs to be fired at 80°C or higher, preferably 130°C or higher, more preferably 180°C or higher, and usually 300°C or lower, and preferably 220°C or lower. When a catalyst support layer is formed instead of a catalyst layer, for example, a coating containing aluminum needs to be fired at 300°C or higher, preferably 340°C or higher, more preferably 390°C or higher, and usually 600°C or lower, and preferably 540°C or lower.

[0050] Furthermore, in one example of the method for producing the catalyst support of the present invention, it is preferable that at least a portion of the duration of the stirring step, at least a portion of the duration of the spraying step, and at least a portion of the duration of the drying step overlap. This improves throughput and allows for efficient production of a catalyst support in which a uniform catalyst layer is formed on the particulate support. The start timing of each step is not particularly limited; the stirring step may be started first, followed by the spraying step and the drying step, either simultaneously or sequentially. Alternatively, all three steps may be started simultaneously. Or, the spraying step may be started first, followed by the stirring and drying steps, either simultaneously or sequentially. Similarly, the end timing of each step is not particularly limited; for example, the spraying step may be finished before the other steps, followed by the stirring and drying steps, either simultaneously or sequentially. Or, all steps may be finished simultaneously.

[0051] Furthermore, in an example of the method for manufacturing a catalyst support of the present invention, droplets of catalyst solution C sprayed from the spray device 40 (spraying means) adhere to the particulate carrier A, which is the target of spraying, before drying (the solvent in the droplets evaporates). Subsequently, the adhered catalyst solution C dries (the solvent in the adhered catalyst solution C evaporates), forming a coating film, thereby enabling the uniform formation of a catalyst layer on the surface of the particulate carrier A. The drying rate of the catalyst solution C can be adjusted, for example, by adjusting (i) the volatility of the solvent in the catalyst solution C, (ii) the size of the droplets, (iii) the spraying speed of the catalyst solution C, (iv) the supply amount of drying gas G, and (v) the temperature of the drying gas G.

[0052] The following shows a specific example of the procedure for manufacturing a catalyst support using an example of the method for manufacturing a catalyst support of the present invention. However, the method for manufacturing a catalyst support of the present invention is not limited to the following specific example, and for example, it is not necessary to form a catalyst support layer, or to perform calcination, or to form a catalyst layer other than the iron oxide layer.

[0053] Figure 2 illustrates a case in which a catalyst support having a three-layer structure consisting of particulate carrier / catalyst support layer (aluminum oxide layer) / catalyst layer (iron oxide layer) is manufactured using a rotary drum type fluidizing apparatus, which is used as an example of a method for manufacturing a catalyst support according to the present invention. First, a particulate carrier 1 is prepared (Figure 2(a)). Next, the prepared particulate carrier 1 (particulate carrier A) is introduced into the rotating drum 20 through the front opening 23d and stirred (stirring step). An aluminum-containing solution is sprayed using a spray device 40 to form a catalyst support layer (spraying step). Then, it is dried using a drying gas G that flows into the rotating drum 20 through the air inlet 30a and inlet 23ab (drying step) to form an aluminum-containing coating 2, thereby producing a coated particulate carrier 3 with a coating 2 on its surface (Figure 2(b)). Next, the coated particulate carrier 3 with a coating 2 on its surface is fired (firing step) to produce a catalyst-supported particulate carrier 5 with a catalyst support layer 4 made of an aluminum oxide layer formed on the surface of the particulate carrier 1 (Figure 2(c)). Next, the particulate carrier 5 with a catalyst support layer is introduced into the rotating drum 20 through the front opening 23d and stirred (stirring step), while an iron compound-containing solution as the catalyst solution C is sprayed using a spray device 40 (spraying step), and then dried using a drying gas G that flows into the inside of the rotating drum 20 through the air inlet 30a and inlet 23ab (drying step) to obtain a particulate carrier 7 with a catalyst coating film 6 containing an iron compound on its surface (Figure 2(d)). Finally, the particulate carrier 7 with a catalyst coating film 7 is calcined (calcination step) to obtain a catalyst carrier 11 with an iron oxide layer 10 (catalyst layer) formed on the surface of the particulate carrier 5 with a catalyst support layer (Figure 2(e)).

[0054] In this example, the central axis X is configured to be approximately horizontal, but the system is not limited to this configuration. For example, the central axis Y corresponding to the central axis X may be inclined from the horizontal direction, and the angle of inclination is not particularly limited. Furthermore, the configuration is such that the drying gas G is supplied into and discharged from the peripheral wall portion 23a corresponding to the outer circumference of the rotating drum 20, but the supply position and discharge position of the drying gas G are not particularly limited.

[0055] (Method for manufacturing fibrous carbon nanostructures) The present invention relates to a method for producing fibrous carbon nanostructures. The present invention relates to a method for producing fibrous carbon nanostructures, which includes a step (synthesis step) of supplying a raw material gas to a catalyst support obtained by the method for producing a catalyst support of the present invention to synthesize fibrous carbon nanostructures on the catalyst layer.

[0056] <Fibrous carbon nanostructures> The fibrous carbon nanostructures are not particularly limited, and examples include fibrous carbon nanostructures with an aspect ratio greater than 10. Specifically, examples of fibrous carbon nanostructures include CNTs and vapor-grown carbon fibers. In this invention, the "aspect ratio of the fibrous carbon nanostructure" can be determined by measuring the diameter (outer diameter) and length of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope. The following describes the case in which the fibrous carbon nanostructure obtained by the manufacturing method of the present invention includes CNTs, but the present invention is not limited thereto.

[0057] <<Carbon nanotubes>> CNTs are materials that have a structure in which graphene sheets are rolled into a tube and have a one-dimensional structure with a very large aspect ratio (see Non-Patent Document 1). Here, the fibrous carbon nanostructure containing CNTs may consist only of CNTs, or it may be a mixture of CNTs and fibrous carbon nanostructures other than CNTs.

[0058] Furthermore, the CNTs are not particularly limited and can be single-walled carbon nanotubes and / or multi-walled carbon nanotubes. However, from the viewpoint of improving various properties such as mechanical strength, electrical properties, and thermal conductivity, the CNTs are preferably composed of 10 layers or less, more preferably of 5 layers or less, and even more preferably single-walled carbon nanotubes. The single-walled carbon nanotubes / multi-walled carbon nanotubes can be appropriately adjusted by changing various reaction conditions, such as catalyst size, catalyst composition, reaction time, and raw material gas supply flow rate.

[0059] [Properties] Furthermore, the average diameter of the fibrous carbon nanostructures containing CNTs can be set to a desired value depending on the application. For example, if the particle size of the metal nanoparticles used as a catalyst, which are typically produced by the reduction of the catalyst layer described above, is between 1 nm and 2 nm, the average diameter of the CNTs can be adjusted to around 1 nm. If the particle size of the metal nanoparticles is around 30 nm, the average diameter of the CNTs can be adjusted to between 20 nm and 30 nm. Generally, the finer the average diameter of the CNTs, the better the various properties. The "average diameter" of fibrous carbon nanostructures, including CNTs, can be determined, for example, by measuring the diameter (outer diameter) of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope.

[0060] Furthermore, while the average length of the fibrous carbon nanostructure containing CNTs can be set to a desired value depending on the application, it is preferable that the average length during synthesis be 1 μm or more, and more preferably 50 μm or more. This is because if the average length of the fibrous carbon nanostructure containing CNTs during synthesis is 1 μm or more, the resulting fibrous carbon nanostructure can exhibit various properties such as mechanical strength, electrical properties, and thermal conductivity more effectively. Also, the longer the length of the fibrous carbon nanostructure containing CNTs during synthesis, the more susceptible it is to damage such as fracture or breakage; therefore, it is preferable that the average length of the fibrous carbon nanostructure containing CNTs during synthesis be 5000 μm or less. Furthermore, the "average length" of the fibrous carbon nanostructures containing CNTs can be adjusted as appropriate, for example, by changing the synthesis reaction time.

[0061] Furthermore, since the method for producing fibrous carbon nanostructures of the present invention uses the catalyst support described above, the fibrous carbon nanostructures produced have a large specific surface area and are of high quality. Specifically, if the manufactured fibrous carbon nanostructure contains CNTs, the BET specific surface area of ​​the fibrous carbon nanostructure containing the CNTs is 600 m². 2 It is preferable that it be 700m or more / g. 2 It is more preferable that it be 800m or more per gram. 2 It is even more preferable that the BET specific surface area is 600 m² or more. 2 If the value is above / g, the fibrous carbon nanostructures containing CNTs are of sufficiently high quality. The BET specific surface area of ​​fibrous carbon nanostructures containing CNTs is not particularly limited, but for example, 2000 m 2 It may be less than / g, or 1800m 2 / g or less is also acceptable, or 1600m 2 It may be less than / g.

[0062] <Synthesis process> In the method for producing fibrous carbon nanostructures of the present invention, a raw material gas is supplied to a catalyst support obtained in the method for producing catalyst supporters of the present invention to synthesize fibrous carbon nanostructures on the catalyst layer. For example, by supplying a raw material gas to the outermost catalyst layer of a catalyst supporter obtained in the method for producing catalyst supporters of the present invention to generate fibrous carbon nanostructures on the catalyst layer, and growing the generated fibrous carbon nanostructures by chemical vapor deposition, fibrous carbon nanostructures such as carbon nanotubes can be synthesized and grown with high efficiency, and are excellent in terms of mass productivity. Note that the catalyst supporter is usually subjected to a reduction treatment before being used in the method for producing fibrous carbon nanostructures. In the synthesis process, at least one of the catalyst layer and the raw material gas is usually heated, but from the viewpoint of growing fibrous carbon nanostructures at a uniform density, it is preferable to heat at least the raw material gas. The heating temperature is preferably between 400°C and 1100°C. In the synthesis process, the raw material gas, and optionally an inert gas, a reducing gas, and / or a catalyst activator are introduced into a fibrous carbon nanostructure growth furnace containing the catalyst support.

[0063] Furthermore, from the viewpoint of improving the manufacturing efficiency of fibrous carbon nanostructures, it is preferable to supply the reducing gas and raw material gas to the catalyst in the catalyst layer by a gas shower.

[0064] - Raw material gas - As the raw material gas, a gaseous substance containing a carbon source at the temperature at which fibrous carbon nanostructures grow is used. Among these, hydrocarbons such as methane, ethane, ethylene, propane, butane, pentane, hexane, heptane, propylene, and acetylene are preferred. In addition, lower alcohols such as methanol and ethanol, and low-carbon oxygen compounds such as acetone and carbon monoxide may also be used. Mixtures of these can also be used.

[0065] -Inert gas- The raw material gas may be diluted with an inert gas. The inert gas should be inert at the temperature at which the fibrous carbon nanostructures grow and should not react with the growing fibrous carbon nanostructures, and preferably one that does not reduce the activity of the catalyst. Examples include noble gases such as helium, argon, neon, and krypton; nitrogen; hydrogen; and mixtures thereof.

[0066] -Reducing gas- Examples of reducing gases that can be used include hydrogen gas, ammonia, water vapor, and mixtures thereof. Alternatively, the reducing gas may be a mixture of hydrogen gas with an inert gas such as helium gas, argon gas, or nitrogen gas.

[0067] -Catalyst- Activating Substance- In the synthesis process of fibrous carbon nanostructures, catalyst activators may be added. The addition of catalyst activators can further improve the production efficiency and purity of fibrous carbon nanostructures. The catalyst activators used here are generally oxygen-containing substances and are preferably substances that do not cause significant damage to the fibrous carbon nanostructures at the temperature in which they grow. For example, water, oxygen, ozone, acidic gases, nitrogen oxides, carbon monoxide and carbon dioxide, and other low-carbon oxygen-containing compounds; alcohols such as ethanol and methanol; ethers such as tetrahydrofuran; ketones such as acetone; aldehydes; esters; and mixtures thereof are effective. Among these, water, oxygen, carbon dioxide, carbon monoxide and ethers are preferred, and water is particularly preferred.

[0068] The volume concentration of the catalyst activator is not particularly limited, but a small amount is preferred. For example, in the case of water, the concentration in the gas introduced into the furnace is usually 10 ppm to 10,000 ppm, preferably 50 ppm to 1,000 ppm.

[0069] -Other conditions- The pressure and processing time inside the reactor during the synthesis process should be set appropriately considering other conditions, but for example, the pressure should be 1 × 10⁻⁶. 2 Pa or more 1×10 7 The processing time can be set to Pa or less, and between 1 minute and 60 minutes. [Examples]

[0070] The following describes some embodiments of the present invention, but the present invention is not limited to these embodiments in any way. The yellowness and BET specific surface area were measured according to the following method.

[0071] <Yellowness> Using a small color whiteness meter Color meter NW-12 (manufactured by Nippon Denshoku Industries Co., Ltd.), the powder measurement cell was filled with 21 g or more of the beads (particulate carrier with a catalyst support layer or catalyst carrier) serving as the sample, and the yellowness YI was measured under the measurement conditions of a D65 light source and a 10° field of view. Then, the yellowness YI measured using the particulate carrier with a catalyst support layer was taken as the yellowness YI of the carrier A and the yellowness YI measured using the catalyst carrier was taken as the yellowness YI of the catalyst carrier B and the difference in yellowness ΔYI (=YI B -YI A ) was determined.

[0072] <BET specific surface area> The BET specific surface area of the carbon nanotubes was measured using a fully automatic specific surface area measuring device "Macsorb (registered trademark) HM model-1210" (manufactured by Mountech Co., Ltd.).

[0073] (Example 1) <Manufacture of catalyst carrier> In the same manner as the embodiment shown in FIG. 2, a catalyst carrier was manufactured. 3000 g of zirconia (zirconium dioxide) beads (volume average particle diameter D50: 650 μm) as a metal oxide were put into the rotary drum 20 of the rotary drum type fluidizing device 100 shown in FIGS. 1A and 1B, and while stirring the zirconia beads (particulate carrier A) (rotation speed of the rotary drum 20: 30 rpm, rotating around the central axis X with the horizontal direction as the central axis X), in order to form a catalyst support layer, an aluminum-containing solution was spray-sprayed by a spray gun (spray device 40) (spray amount 3 g / minute, spray time 2840 seconds), and while spray-spraying, compressed air as a drying gas G was supplied into the rotary drum 20 at 0.7 m 2、 / minute and discharged from the rotary drum 20 to be dried, and a coating film by the aluminum-containing solution was formed on the zirconia beads. Next, a calcination treatment was performed at 540 °C for 45 minutes to obtain a particulate carrier with a catalyst support layer in which an aluminum oxide layer as a catalyst support layer was formed. Using the obtained particulate carrier with a catalyst support layer, the yellowness YI of the carrier 3 was measured. A Furthermore, the obtained particulate carrier with catalyst support layer is introduced into the rotating drum 20 of another rotating drum type fluidizer 100, and while stirring (rotation speed of the rotating drum 20: 20 rpm, rotating around the central axis X with the horizontal line as the central axis X), an iron catalyst solution (catalyst solution C) prepared by dissolving iron(II) acetate in isopropyl alcohol (IPA) is sprayed using a spray gun (spray device 40) (spray volume 5 g / min, spraying time 170 seconds), and while spraying, compressed air as dry gas G is introduced at a rate of 0.3 m³. 3 The material was supplied into the rotating drum 20 at a rate of / min and dried by discharge from the rotating drum 20, forming a coating film of iron catalyst solution (catalyst solution C) on a particulate support with a catalyst support layer. Next, a firing treatment was performed at 220°C for 10 minutes to obtain a catalyst support in which an iron oxide layer as a catalyst layer was further formed. Using the obtained catalyst support, the yellowness YI of the catalyst support was determined. B Measure the difference in yellowness ΔYI(=YI B -YI A We calculated the value of ). The results are shown in Table 1.

[0074] <Synthesis of carbon nanotubes> To the catalyst support obtained as described above, a raw material gas containing ethylene gas (C2H4) was supplied into the reaction tube at atmospheric pressure, a temperature of 850°C, and a total flow rate of 1500 sccm for 10 minutes. By supplying the raw material gas in this manner, carbon nanotubes were synthesized on the catalyst support using a fluidized bed method. The BET specific surface area of ​​the obtained carbon nanotubes was then measured. The results are shown in Table 1.

[0075] (Examples 2-5, Comparative Examples 2-3) In the production of the catalyst support, the catalyst support and CNT synthesis were carried out in the same manner as in Example 1, except that the spraying time when spraying the iron catalyst solution was changed as shown in Table 1, and various measurements were performed. The results are shown in Table 1.

[0076] (Examples 6-7) In the production of the catalyst support, the catalyst support and CNT synthesis were carried out in the same manner as in Example 1, except that the components of the iron catalyst solution were changed as shown in Table 1, and the spraying time when spraying the iron catalyst solution was also changed as shown in Table 1. Various measurements were then performed. The results are shown in Table 1.

[0077] (Comparative Example 1) In the production of the catalyst support, a particulate support with a catalyst support layer was obtained in the same manner as in Example 1, except that the operations after spraying the iron catalyst solution were omitted. In the synthesis of CNTs, the same procedure as in Example 1 was followed, except that the particulate support with a catalyst support layer obtained above was used instead of the catalyst support, but carbon nanotubes could not be synthesized.

[0078] [Table 1]

[0079] Table 1 shows that if catalyst support structures comprising a catalyst layer containing a metal-containing compound formed on a support, and the difference between the yellowness of the catalyst support and the yellowness of the support, as in Examples 1 to 7, are used, it is possible to produce carbon nanotubes with a large BET specific surface area and high quality. On the other hand, in Comparative Example 1, where no catalyst layer containing a metal-containing compound was formed on the support, it was found that carbon nanotubes could not be produced. Furthermore, when using the catalyst supporters of Comparative Examples 2 and 3, where the difference between the yellowness of the catalyst support and the yellowness of the support falls outside the predetermined range, it can be seen that the carbon nanotubes produced have a small BET specific surface area and are of inferior quality. [Industrial applicability]

[0080] According to the present invention, it is possible to provide a catalyst support capable of producing high-quality fibrous carbon nanostructures. Furthermore, according to the present invention, it is possible to provide a method for producing fibrous carbon nanostructures that can produce high-quality fibrous carbon nanostructures. [Explanation of Symbols]

[0081] 1. Particulate carrier 2. Coating film 3. Particulate carrier with coating 4 Catalyst support layer 5. Particulate carrier with catalyst support layer 6. Coating 7. Particulate carrier with catalyst coating 10 Iron oxide layer 11 Catalyst support 20 RPM drum 23 Drum body 23a Peripheral wall part 23ab inlet 23ac outlet 23b Front end 23c tapered section 23d Front end opening 23e Front end ring section 23f Connecting part 23g Rotary drive mechanism 23h Rear end ring section 23i Drum Section 24 partition plates 30 cabinets 30a Air supply port 30b Exhaust port 30cm gap 30d inner surface 40 Spray device 100 Rotating Drum Type Fluidized System A particulate carrier C catalyst solution G Dry gas H Inflow direction I. Arrangement direction S surface X center axis θ angle

Claims

1. A method for producing a catalyst support used in the production of fibrous carbon nanostructures, The catalyst support comprises a carrier made of a metal oxide containing at least one element selected from the group consisting of magnesium, aluminum, silicon, zirconium, and molybdenum, and a catalyst layer formed on the carrier. The catalyst layer contains one or more metal-containing compounds selected from the group consisting of iron oxide, iron acetate, iron nitrate, iron chloride, ferrocene, iron acetylacetonate, and cobalt acetate. The yellowness of the aforementioned carrier is YI Ａ The yellowness of the catalyst support is set to YI Ｂ The following formula: ΔYI=YI Ｂ -YI Ａ A method for producing a catalyst support, comprising the step of adjusting the yellowness of the catalyst support such that the difference in yellowness ΔYI, represented by , is 3 or more and 20 or less.

2. The method for producing a catalyst support according to claim 1, wherein the surface of the support is covered with a catalyst support layer.

3. The method for producing a catalyst support according to claim 2, wherein the catalyst support layer includes a ceramic material.

4. The method for producing a catalyst support according to claim 3, wherein the ceramic material contains aluminum oxide.

5. The method for producing a catalyst support according to Claim 1, wherein the yellowness YI B of the catalyst support is a measured value obtained when the catalyst support is subjected to a calcination treatment at 220°C for 10 minutes.

6. A method for producing a fibrous carbon nanostructure, comprising the step of supplying a raw material gas to a catalyst support produced by a method for producing a catalyst support according to any one of claims 1 to 5, to synthesize a fibrous carbon nanostructure on the catalyst layer.

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