JP6531560B2 - Catalyst for carbon nanotube synthesis - Google Patents

Description

  The present invention relates to a catalyst for carbon nanotube synthesis. More specifically, the present invention relates to a catalyst for carbon nanotube synthesis and a carbon nanotube produced using the same.

  For example, carbon nanotubes having a diameter of 1 μm or less are blended into a resin, and various studies have been made as a filler that imparts properties such as conductivity and strength. Such carbon nanotubes are conventionally manufactured mainly by an arc discharge method, a laser deposition method, a vapor phase growth method or the like.

  Among them, the vapor phase growth method has an advantage that carbon nanotubes with few impurities can be obtained more efficiently than the arc discharge method or the laser deposition method. In addition, continuous reaction is possible by using the raw material in the gaseous state, and furthermore, since a gas containing carbon such as hydrocarbon and carbon monoxide which is a raw material gas can be obtained at low cost, mass production of carbon nanotubes is possible. It can be said that it is a suitable technology.

  The catalyst (hereinafter referred to as a catalyst for carbon nanotube synthesis) to be used when obtaining carbon nanotubes by vapor phase growth method has an activity such as iron, cobalt, nickel, etc. for supporting components such as silica, alumina, magnesia, zeolite and the like. What supported the metal of the component etc. are proposed. (For example, refer to patent document 1)

  When carbon fibers are vapor-phase-grown using the particulate catalyst thus produced, the carbon fibers grow in a winding and entangled state. It is generally known that electrical conductivity can be imparted to an insulating resin by dispersing carbon nanotubes in a resin, but the carbon fiber entangled aggregate thus obtained has a dispersion in the resin Unfortunately, this often results in the need to incorporate large amounts of carbon fiber to achieve the desired conductivity. Moreover, when the entangled aggregate of a large amount of poorly dispersed carbon fibers is mixed into the resin, it has a problem of causing the strength deterioration of the resin.

  Moreover, in order to improve the dispersibility of the carbon fiber thus strongly coagulated, there has been proposed a method of refining by post-treatment such as pulverization (Patent Document 2). However, the grinding process may result in increased cost and cutting of carbon fibers.

  On the other hand, if the carbon fibers are independent one by one or plural fibers are gathered together in a bundle, the dispersibility in the resin is good and the conductivity is excellent with a small amount of dispersion. It is introduced that it is possible to supply the resin molded product (Patent Document 3).

  On the other hand, as a conventional method for producing bundled carbon fibers by a vapor phase growth method, a method by a base method is known. That is, a catalyst is attached to the surface of the substrate by sputtering or the like, and carbon fibers are linearly grown from the surface of the substrate. An example of producing a carbon nanotube in which a tube wall of carbon fiber having a length of 2.5 mm and 1 to 2 layers is formed by such a base method is disclosed (Non-patent Document 1). Similarly, an embodiment is also disclosed in which the catalyst component is patterned and attached to a silicon or quartz substrate (Patent Document 4). However, these methods are not suitable for industrial mass production because the area of the catalyst which is the growth point is absolutely small and the amount of carbon nanotubes grown there on is also small.

  On the other hand, a metal compound containing one or more metals selected from Co, Ni and Fe, and a metal compound containing one or more metals selected from Al and Mg, an organic compound having a decomposition temperature of 300 ° C. or less It has been proposed to obtain a powder comprising a metal-containing material having a flat surface on the surface by firing in the presence of However, in this method, since a large amount of organic compounds are used, the temperature tends to be high during catalyst calcination and sintering progresses, and as a result, the deposition efficiency of carbon nanotubes is low, and the catalyst in the generated carbon nanotubes There is a problem that a large amount of impurities derived from the catalyst remain and the productivity of carbon nanotubes is significantly reduced. Furthermore, there is a problem that the ash tends to be mixed as an impurity into the carbon nanotube because the organic compound tends to remain as ash during catalyst calcination (Patent Document 5).

Japanese Patent Publication No. 2010-540220 Unexamined-Japanese-Patent No. 2-276839 Japanese Patent Application Publication No. 2004-230690 Japanese Patent Application Publication No. 2002-530805 JP, 2009-090251, A

Science, Vol. 306, November, 19 (2004)

  The problem to be solved by the present invention is to provide a carbon nanotube synthesis catalyst for efficiently producing carbon nanotubes excellent in conductivity and a method for producing the same.

MEANS TO SOLVE THE PROBLEM The present inventors came to complete this invention, as a result of earnest examination, in order to solve the said subject. That is, the embodiment of the present invention contains Co, Mg and Mn, and the shape observed by three-dimensional analysis using a scanning electron microscope is a flat plate, and any axis on the catalyst plane is the X axis, the same. When the axis orthogonal to the X axis on the plane is Y axis and the axis orthogonal to the X axis and Y axis is Z axis, the XY plane area (the product of X axis average (μm) and Y axis average (μm) [mu] m ²⁾ is 0.2 to 10 [mu] m ^2, and relates to a catalyst for carbon nanotube synthesis, wherein the Mn content in the catalyst is 1 to 5 mol%.

In addition, an embodiment of the present invention contains Co, Mg and Mn, and the shape observed by three-dimensional analysis using a scanning electron microscope is flat, and an arbitrary axis on the catalyst plane is an X-axis, An XY plane area which is the product of the X axis average (μm) and the Y axis average (μm) in the case where an axis orthogonal to the X axis on the same plane is the Y axis and an axis orthogonal to the X axis and the Y axis is the Z axis ([mu] m ²⁾ is 0.2 to 10 [mu] m ^2, and, Mn content in the catalyst is a method of manufacturing the carbon nanotube synthesizing catalyst is 1 to 5 mol%, a catalyst precursor comprising CoHO ₂ The present invention relates to a method for producing a catalyst for carbon nanotube synthesis, which is characterized by calcining.

Further, embodiments of the present invention, a metal salt containing a metal salt and Mn containing Mg, a method of manufacturing the carbon nanotube synthesis catalyst comprising a step of mixing and CoHO _2.

In addition, an embodiment of the present invention relates to the method for producing a catalyst for carbon nanotube synthesis, which comprises calcining a catalyst precursor containing MnCO ₃ .

  Also, an embodiment of the present invention is a carbon nanotube in which a carbon source comprising a hydrocarbon and / or an alcohol is catalytically reacted in the presence of the catalyst for carbon nanotube synthesis or the catalyst for carbon nanotube synthesis produced by the method. It relates to the manufacturing method.

  By using the catalyst for carbon nanotube synthesis of the present invention, carbon nanotubes excellent in conductivity can be efficiently produced. Therefore, with a small amount of compounding, it is also excellent in conductivity development in a resin molded product, and therefore, an excellent conductive resin molded product can be realized without impairing the resin moldability and the mechanical properties of the resin molded product. it can. This conductive resin molded product can be applied to an antistatic electronic member, a resin molded product for electrostatic coating, a conductive transparent resin composition, and the like. Moreover, the carbon nanotube of this invention can be applied to resin compositions, such as a sheet | seat, a tape, a transparent film, ink, and a conductive paint, besides a molded object.

  Hereinafter, embodiments of the present invention will be described in detail.

  The catalyst for carbon nanotube synthesis of the present invention is characterized by containing Co, Mg and Mn. As a raw material of Co, Mn, and Mg, such metal simple substance and its metal salt can be used. Specifically, cobalt acetate, cobalt acetate tetrahydrate, cobalt hydroxide, cobalt citrate n hydrate, cobalt nitrate hexahydrate, cobalt sulfate, cobalt sulfate heptahydrate, magnesium chloride , Magnesium chloride hexahydrate, magnesium hydroxide, magnesium acetate tetrahydrate, magnesium citrate 9 hydrate, magnesium acetate, magnesium sulfate heptahydrate, magnesium nitrate hexahydrate, carbonate Manganese, manganese acetate tetrahydrate, manganese dioxide, manganese and the like can be mentioned.

  The catalyst for carbon nanotube synthesis of the present invention is characterized in that the Mn content in the catalyst is 1 to 5 mol%. When the Mn content is in the above range, the conductivity of the carbon nanotube produced from the catalyst becomes good, the catalyst activity is high, and the production efficiency of the carbon nanotube is high.

  The Mn content (mol%) in the catalyst is expressed by the element ratio of Mn / (Co + Mg + Mn).

  Among the above-mentioned manganese salts, manganese acetate is preferred, and manganese carbonate is more preferred. The reason is that manganese carbonate is more uniformly distributed in the catalyst because it foams during calcination.

In the catalyst for carbon nanotube synthesis of the present invention, the shape observed by three-dimensional analysis using a scanning electron microscope is a flat plate, and an arbitrary axis on the catalyst plane is an X axis, and an X axis on the same plane. When an orthogonal axis is Y axis, and an axis orthogonal to X axis and Y axis is Z axis, an XY plane area (μm ² ) which is a product of X axis average (μm) and Y axis average (μm ) is 0. It is characterized by having ² to 10 μm ² . The degree of flatness of the plane is arbitrary as long as the carbon nanotube of the present invention can be obtained. The term "plane" as used herein is not a strict plane in mathematics but refers to a plane having a flat state when viewed from a macroscopic viewpoint.

The XY plane area (also referred to as a plane direction, also referred to as “surface area”) of the catalyst is preferably 0.2 to 10 μm ² , and the Z axis (thickness direction) is preferably 100 nm or less. If it is within the above range, the catalyst becomes flat and the raw material can contact the catalyst efficiently, so that the production efficiency of carbon nanotubes is improved, which is preferable.

When an arbitrary axis on the catalyst plane is X axis, an axis orthogonal to the X axis on the same plane is Y axis, and an axis orthogonal to the X axis and Y axis is Z axis, the X axis, Y axis and Z axis are It measured and calculated | required the average value as X-axis average (micrometer), Y-axis average (micrometer), and Z-axis average (micrometer), respectively. Further, the product of the X-axis average (μm) and the Y-axis average (μm) was taken as the XY plane area (μm ² ).

  The catalyst precursor for carbon nanotube synthesis is a metal containing 30% or more of a cobalt component, a metal oxide, a metal nitride, a metal halide, a metal hydroxide, a metal hydroxide, a metal salt, and a mixture thereof There is no particular limitation as long as it functions as a catalyst for nanotube synthesis.

The catalyst for carbon nanotube production of the present invention is preferably produced by sequentially performing the following steps (1) and (2).
(1) A step of mixing a cobalt salt, a magnesium salt and a manganese salt to obtain a catalyst precursor.
(2) A step of calcining the carbon nanotube catalyst precursor to obtain a catalyst for carbon nanotube synthesis.

  The cobalt salt, magnesium salt and manganese salt are preferably hydrates, because they have a low melting point and can be easily mixed with other metal salts at the time of calcination to produce a uniform catalyst.

  When the said cobalt salt, magnesium salt and manganese salt are hydrates, it is preferable to dry at 100 degreeC or more. Moreover, when performing by pressure reduction, you may carry out at 100 degrees C or less. The reason is that dehydration is performed before firing to shorten the firing time.

When cobalt hydroxide is used as the cobalt salt, the drying is preferably performed at 150 ° C. or higher to obtain a cobalt composition containing CoHO ₂ as a catalyst precursor. The reason is that by progressing the oxidation step by step, the catalyst can be obtained without breaking the crystal structure of the cobalt salt, so it is easy to obtain a plane on the catalyst.

The cobalt composition is a cobalt metal containing CoHO ₂ as a main component, a cobalt oxide, a cobalt hydroxide, a cobalt salt, and a mixture thereof.

When cobalt hydroxide is used as a cobalt salt, the above mixing is preferably performed after obtaining a cobalt composition containing CoHO ₂ by drying. The reason is that when cobalt hydroxide is changed to CoHO ₂ , it works with other compounds to prevent the flat plate structure from being broken by changing the crystal structure.

  The “mixing” may be performed dry using a mixer or the like, or may be performed wet. In the case of wet mixing, the above precursors may be mixed and then dissolved and / or dispersed in a solvent such as water, or may be mixed after each precursor is previously dissolved in a solvent such as water Good. Moreover, when dissolving in solvents, such as water, you may heat. In the case of wet mixing, the solution and / or dispersion obtained above can be dried to obtain a catalyst precursor for carbon nanotube synthesis. The atmosphere for drying may be either air or under an inert gas such as nitrogen or argon. The drying temperature is not particularly limited, but when using water as the solvent, 150 to 200 ° C. is preferable, and 180 to 200 ° C. is more preferable.

  It is preferable that the catalyst precursor for carbon nanotube synthesis obtained by the dry process or the wet process as described above is further pulverized by using a pulverizer or the like to carry out the refining treatment. By carrying out the refining process, since appropriate voids are included, the particle diameter can be controlled to be small and uniform when the catalyst precursor is fired in the step (2) described later.

  Next, step (2) will be described. Step (2) is a step of calcining the carbon nanotube catalyst precursor to obtain a catalyst for carbon nanotube synthesis.

  When calcining the catalyst precursor, the atmosphere for calcining may be in the presence of oxygen, but is preferably air or a mixed gas of air and nitrogen. The firing temperature is preferably in the range of 450 to 550 ° C. If the firing temperature is in the range of 450 to 550 ° C., it is preferable because excessive sintering is unlikely to occur and primary particles are unlikely to be large, and carbonaceous impurities are unlikely to remain in the catalyst.

  The fired product obtained above is preferably further subjected to a refinement treatment. When the calcined product is crushed, the carbon nanotube synthesis catalyst is brought into contact with a carbon source comprising a hydrocarbon and / or an alcohol to synthesize carbon nanotubes, and the carbon source is sufficient as a carbon nanotube production catalyst. It is preferable because it can be in contact with

  The means for pulverizing treatment is not particularly limited, but in the case of a small amount, a mortar may be used, and in the case of treating a large amount at one time, a pin mill, hammer mill, palperizer, jet mill or the like may be used.

(Carbon nanotube and its manufacturing method)
Next, a method for producing carbon nanotubes using the catalyst for carbon nanotube synthesis of the present invention will be described.

  In order to produce carbon nanotubes, the catalyst for carbon nanotube synthesis is used as a catalyst, and a raw material gas as a carbon source is brought into contact with the catalyst under heating to produce carbon nanotubes.

  As a source gas as a carbon source, any conventionally known one can be used, and for example, as a gas containing carbon, hydrocarbons such as methane, ethylene, propane, butane and acetylene, carbon monoxide, alcohol and the like can be used However, hydrocarbons and / or alcohols are preferred, in particular for reasons of ease of use.

  In addition, it is preferable that the catalyst be activated in a reducing atmosphere, or be brought into contact with a carbon nanotube source gas together with a reducing gas, if necessary. Hydrogen, ammonia, etc. can be used as the reducing gas at the time of activation, but hydrogen is preferred, and its concentration is preferably 0.1 to 100% by volume with respect to 100% by volume of the source gas concentration, 1 to 100 More preferably, it is volume%. If it is in the range of 1 to 100% by volume, the effect as a reducing gas can be expected, and the concentration of the source gas will be appropriate, and carbon nanotubes can be efficiently recovered, which is preferable.

  The temperature at the time of production and the supply amount of the raw material gas may be appropriately selected and determined from conventionally known arbitrary values, but in the catalyst of the present invention, 600 to 850 ° C., particularly 650 to 750 ° C. are preferable, and the reaction The pressure is preferably atmospheric pressure or more and 40 kPa or less, and particularly preferably atmospheric pressure or more and 30 kPa or less. The reaction time is arbitrarily set according to the reaction temperature and the catalyst ratio between the catalyst and the raw material gas, but is usually about 0.5 to 6 hours. The reaction rate in the present invention reaches its maximum in about 20 minutes from the start of the reaction, and then gradually slows down and stops in 5 to 5.5 hours from the start of the reaction. Therefore, it is preferable to manage reaction time in 0.5 to 6 hours.

  It is preferable to use inert gas, such as argon gas and nitrogen, for source gas substitution after completion | finish of reaction.

  According to the method of producing a carbon nanotube using the catalyst for producing a carbon nanotube of the present invention, the carbon nanotube is precipitated and grown from the plane portion of the catalyst, with the cobalt oxide portion of the fine particles uniformly supported on the support portion as a core. Carbon nanotubes are obtained.

  EXAMPLES The present invention will be more specifically described below by way of Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. Also, "carbon nanotube" may be abbreviated as "CNT".

[Production of catalyst for carbon nanotube synthesis (catalyst)]
Example 1 Production of Catalyst (a)
It was weighed in a 37 g heat resistant container of cobalt (II) hydroxide and dried at a temperature of 170 ± 5 ° C. for 1 hour using an electric oven to obtain a cobalt composition (A) containing CoHO ₂ . 86 g of magnesium acetate tetrahydrate and 5 g of manganese acetate tetrahydrate are weighed in a heat resistant container and dried at a temperature of 170 ± 5 ° C. for 1 hour using an electric oven, and then CoHO ₂ is dissolved. The cobalt composition (A) contained was mixed with 36 g to obtain a precursor of catalyst (a). After 50 g of the obtained catalyst (a) precursor was weighed in a heat resistant container and calcined in an atmosphere of 500 ° C. ± 5 ° C. in air for 30 minutes in a muffle furnace, it was pulverized in a mortar to obtain a catalyst (a) .

(Examples 2 to 6) [Production of Catalysts (b) to (f)]
Catalysts (b) to (f) were produced in the same manner as in Example 1 except that the raw materials and charge amounts listed in Table 1 were changed.

(Example 7) [Manufacture of catalyst (g)]
After weighing and mixing 37 g of cobalt (II) hydroxide, 86 g of magnesium acetate tetrahydrate and 5 g of manganese acetate tetrahydrate in a heat resistant container, in a muffle furnace, an atmosphere of 500 ° C. ± 5 ° C. in air. After firing for 30 minutes under, the mixture was ground in a mortar to obtain a catalyst (g).

Example 8 Production of Catalyst (h)
After mixing 37 g of cobalt (II) hydroxide, 86 g of magnesium acetate tetrahydrate, and 5 g of manganese acetate tetrahydrate, the mixture is transferred to the same heat-resistant container, and an electric oven is used at a temperature of 170 ± 5 ° C. The resultant was dried for 1 hour to obtain a precursor of catalyst (h). After 50 g of the obtained catalyst (h) precursor was weighed in a heat resistant container and calcined in an atmosphere of 500 ° C. ± 5 ° C. in air for 30 minutes in a muffle furnace, it was pulverized in a mortar to obtain a catalyst (h) .

(Comparative Example 1) [Production of Catalyst (i)]
A catalyst (i) was produced in the same manner as in Example 1 except that the preparation amounts listed in Table 1 were changed.

<XRD measurement>
An XRD measurement (Ultima 2100, manufactured by Rigaku Denki Co., Ltd.) was performed on a substance obtained by drying cobalt (II) hydroxide at 170 ° C. for 1 hour. Peaks were observed at 19.8 °, 36.8 °, and 50.3 °, and it was confirmed that CoHO ₂ was contained.

<Shape observation by scanning electron microscope and measurement of XY plane area>
The morphology of the catalyst for carbon nanotube synthesis was observed by a scanning electron microscope (JSM-6700M, manufactured by JEOL Ltd.). The observation was carried out by spraying a catalyst for carbon nanotube synthesis as it is on carbon paper.

Furthermore, the carbon nanotube synthesis catalyst was subjected to three-dimensional analysis with a scanning electron microscope (ERA-9000 manufactured by Elionix Co., Ltd.), and for nine carbon nanotube synthesis catalysts, an arbitrary axis on the catalyst plane was taken along the X axis. When an axis orthogonal to the X axis on the same plane is the Y axis and an axis orthogonal to the X axis and the Y axis is the Z axis, the X axis, the Y axis and the Z axis are measured, and the average value is the X axis The average (μm), the Y-axis average (μm), and the Z-axis average (μm) were determined. The product of the X-axis average (μm) and the Y-axis average (μm) was determined as the XY plane area (μm ² ).

Table 2 shows the shape of the catalyst, X-axis average (μm), Y-axis average (μm), Z-axis average (μm), and XY plane area (μm ² ).

  From Table 2, it became clear that catalysts (a)-(i) have a plane on the surface.

(Example 9) [Production of carbon nanotube]
In a central portion of a horizontal reaction tube capable of being pressurized and heated by an external heater and having an inner volume of 10 liters, a quartz glass heat-resistant dish in which 1 g of a catalyst (a) for carbon nanotube synthesis was dispersed was installed. The exhaust was performed while injecting argon gas, the air in the reaction tube was replaced with argon gas, and the atmosphere in the horizontal reaction tube was adjusted to an oxygen concentration of 1% by volume or less. Subsequently, it heated with an external heater and heated until the center temperature in a horizontal reaction tube became 700 degreeC. After reaching 700 ° C., hydrogen gas was introduced into the reaction tube for 1 minute at a flow rate of 0.1 liter per minute to activate the catalyst. Thereafter, ethanol as a carbon source was introduced into the reaction tube at a flow rate of 1 liter per minute, and contact reaction was carried out for 4 hours. After completion of the reaction, the gas in the reaction tube was replaced with argon gas, the temperature in the reaction tube was cooled to 100 ° C. or less, and the obtained carbon nanotubes were collected. The obtained carbon nanotubes were ground and filtered with an 80 mesh wire mesh in order to compare conductivity and dispersibility.

(Examples 10 to 16, Comparative Example 2)
Carbon nanotubes were obtained in the same manner as in Example 9, except that the catalyst for carbon nanotube synthesis listed in Table 3 was changed to the catalyst for carbon nanotube synthesis (a) used in Example 9.

<Method of measuring physical properties>
The physical properties of the catalyst for carbon nanotube synthesis and the carbon nanotube were measured by the following method.

<Volume Resistivity of Coating Film Containing Carbon Nanotube and Conductivity Evaluation of Carbon Nanotube>
In order to evaluate the conductivity of the carbon nanotube, a coating film in which the carbon nanotube is dispersed is prepared, and the conductivity is evaluated by measuring its volume resistivity.
An epoxy resin grade 1256 manufactured by Mitsubishi Chemical Corp. is dissolved in butyl carbitol acetate to prepare an epoxy resin solution having a solid content of 40%, and 0.789 g of carbon nanotubes for evaluation with respect to 15 g of solid content of the epoxy resin solution. The resulting mixture was mixed with a Hoover-Maller at 150 lb and 100 revolutions three times respectively to obtain a carbon nanotube dispersion for evaluation. After that, using a applicator, apply polyethylene terephthalate (PET) film manufactured by Toyobo Co., Ltd. so that the thickness of the coated film after drying becomes 10 ± 1 μm, then, in an electric oven, at 150 ± 5 ° C. for 60 minutes After drying, a coating film containing carbon nanotubes was obtained. It was set as the volume resistivity (ohm * cm) of the said coating film using Mitsubishi Chemical Analytech Co., Ltd. make: Loresta GP powder resistivity measuring system MCP-PD-51.

The evaluation criteria for the conductivity of the carbon nanotube are: ◎ (excellent), 3 × 10 ⁰ (Ω · cm) when the surface resistance of the coating film of the above three times is 3 × 10 ⁰ (Ω · cm) or less In the case of exceeding 6 × 10 ⁰ (Ω · cm) or less, the case of) (good) and the case of exceeding 6 × 10 ⁰ (Ω · cm) are shown as x (defect).

  From Table 3, Examples 9, 11, 13, 15 and 16 have superior conductivity as compared to the carbon nanotubes produced from the catalyst having a high Mn content of Comparative Example 2.

From Table 3, a catalyst prepared by calcining a precursor containing CoHO ₂ of Example 9 in comparison with a carbon nanotube produced from a catalyst prepared by calcining a precursor containing cobalt hydroxide of Example 15 It became clear that the carbon nanotube manufactured from has excellent conductivity.

From Table 3, compared with Example 16, the carbon nanotube manufactured from the catalyst manufactured by the manufacturing method including the process of mixing the metal salt containing magnesium and manganese of Example 9 with CoHO ₂ has excellent conductivity. Have sex.

  From Table 3, it is compared with the carbon nanotube produced from the catalyst produced using manganese acetate tetrahydrate as a raw material of the manganese component of Example 9, 11 and 13 compared with the carbon nanotube of Example 10, 12 and 14 Carbon nanotubes produced from catalysts made using manganese carbonate have excellent conductivity.

  While the present invention has been described in terms of specific embodiments, variations and modifications obvious to one skilled in the art are included within the scope of the present invention.

Claims (5)

Containing Co, Mg and Mn, the shape observed by three-dimensional analysis using a scanning electron microscope is flat, and any axis on the catalyst plane is orthogonal to the X axis and the X axis on the same plane The XY plane area (μm ² ) which is the product of the X axis average (μm) and the Y axis average (μm) when the axis is Y axis and the axis orthogonal to the X axis and Y axis is Z axis is 0.2 to 0.2 A catalyst for carbon nanotube synthesis, characterized in that it is 10 μm ² and the Mn content in the catalyst is 1 to 5 mol%. Containing Co, Mg and Mn, the shape observed by three-dimensional analysis using a scanning electron microscope is flat, and any axis on the catalyst plane is orthogonal to the X axis and the X axis on the same plane The XY plane area (μm ² ) which is the product of the X axis average (μm) and the Y axis average (μm) when the axis is Y axis and the axis orthogonal to the X axis and Y axis is Z axis is 0.2 to 0.2 A method for producing a catalyst for carbon nanotube synthesis, having a particle size of 10 μm ² and an Mn content in the catalyst of 1 to 5 mol%, comprising calcining a catalyst precursor containing CoHO _2. Method for producing a catalyst for synthesis. The method for producing a catalyst for carbon nanotube synthesis according to claim 2, comprising the step of mixing CoHO ₂ with a metal salt containing Mg and a metal salt containing Mn. The method for producing a catalyst for carbon nanotube synthesis according to claim 2 or 3, wherein the catalyst precursor containing MnCO ₃ is calcined. A catalyst for carbon nanotube synthesis comprising a hydrocarbon and / or an alcohol in the presence of the catalyst for carbon nanotube synthesis according to claim 1 or the catalyst for carbon nanotube synthesis produced by the method according to any one of claims 2 to 4 Method of producing carbon nanotubes.