JP2006181477A - Catalyst for manufacturing carbon fiber by vapor growth process, and method for manufacturing carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which is manufactured by a simple method and has excellent performance as a catalyst for manufacturing a carbon fiber by a vapor growth process and to provide a method for manufacturing the carbon fiber the diameter or length of which is made uniform, the impurity content of which is lowered and which does not damage the surface smoothness of a resin molding when used as a resin filler and produces the excellent resin molding. <P>SOLUTION: This catalyst for manufacturing the carbon fiber by the vapor growth process contains an oxide of a metal of group VIII obtained by firing a mixture containing a water-soluble compound of the metal of group VIII and an organic compound at the least. The amorphous oxide of the metal of group VIII accounts for ≥10 wt% of the oxide of the metal of group VIII and a crystalline metal oxide accounts for ≤85 wt% of the total metal oxide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catalyst for producing a carbon fiber having a diameter of 1 μm or less, called a carbon nanofiber (carbon nanotube), and a method for producing a carbon fiber using the same, particularly for producing a carbon fiber by a vapor growth method. The present invention relates to a catalyst and a method for producing carbon fiber using the catalyst.

Carbon fibers having a diameter of 1 μm or less, referred to as carbon nanofibers or carbon nanotubes (hereinafter simply referred to as “carbon fibers”), are used as fillers that impart properties such as conductivity and strength to resin compounds, for example. Is being studied. Such carbon fibers have heretofore been produced mainly by an arc discharge method, a laser vapor deposition method, a vapor phase growth method or the like.
Among them, the arc discharge method and the laser evaporation method have a problem in that they require an expensive device such as an exhaust device and a high-voltage high-current power source and require a high degree of attention in handling, and in addition, the amount of carbon fiber generated is small. Further, the carbon fibers obtained by these methods have a problem that they contain a large amount of impurities such as graphite and amorphous carbon, have large variations in the diameter and length of the carbon fibers, and have low production efficiency.

  In response to such problems, a carbon fiber production method using a method (vapor phase growth method) for obtaining fibrous carbon by pyrolyzing a raw material gas containing carbon such as hydrocarbon or carbon monoxide on a catalytic metal is proposed. Has been. Vapor phase epitaxy has the advantage that carbon fibers with fewer impurities can be obtained compared to arc discharge and laser deposition. In addition, by using a raw material in a gaseous state, an efficient continuous reaction (continuous production) is possible, and further, gas containing carbon such as hydrocarbon and carbon monoxide, which is a raw material gas, can be obtained at low cost. Suitable for continuous mass production of carbon fiber. Furthermore, it is possible to control the properties of the carbon fiber by adjusting the type and particle size of the catalyst metal used.

  Catalysts used in the vapor phase growth method (hereinafter sometimes referred to as “catalysts for vapor phase growth carbon fiber production”) are, for example, carriers such as silica, alumina, magnesia, zeolite, iron, cobalt, nickel, etc. A material on which a transition metal is supported has been proposed. Further, these catalysts are generally those obtained by converting a catalytic metal into an oxide, which is used after being activated in a reducing atmosphere with hydrogen or the like. As a method for producing this catalyst, for example, a method in which a metal is supported on a carrier by a so-called liquid phase method such as a coprecipitation method or a sol-gel method has been proposed (see Non-Patent Documents 1 and 2).

  A supported catalyst widely used as a catalyst for vapor phase growth carbon fiber production produces carbon fibers having a fiber diameter in the range of several nanometers to several tens of nanometers by adjusting reaction conditions for carbon fiber production. be able to. By using a porous carrier as the carrier, the diameter and distribution of the carbon fibers can be adjusted. For example, it is proposed to produce carbon fibers using a porous carrier carrying a transition metal catalyst. (For example, see Patent Documents 1 and 2).

As a method for producing a catalyst for vapor phase growth carbon fiber production in which a metal catalyst is supported on a porous carrier, for example, in the above liquid phase method, in addition to the metal or a compound thereof, a mixed solution further containing an organic acid such as citric acid Has been proposed (organic acid method) and the like which are calcined at a high temperature of 700 ° C. or higher to obtain a catalyst.
Specifically, for example, when a carbon fiber was produced using a vapor phase growth carbon fiber production catalyst obtained by drying a mixture containing a metal nitrate and citric acid and calcining at 700 ° C. for 5 hours, Alternatively, a method has been proposed in which carbon fibers having a diameter of about 7 to 25 nm and a tube portion having a multilayer structure are obtained (see, for example, Patent Document 3 and Non-Patent Documents 3 and 4).

The porous carrier obtained by the organic acid method has a uniform composition of the obtained carrier (and a catalyst for producing a vapor-grown carbon fiber containing the carrier) compared to the coprecipitation method and thermal decomposition method in the liquid phase method described above. In addition, the catalyst can be produced at a relatively low temperature and has a high specific surface area.
Chemical Physics Letters, 368, 299-306 (2003). React. Kinet. Catal. Lett. 64, 63-71 (1998) Carbon, 41, 2949-2959 (2002) Carbon, 40, 955-971 (2002) JP 2004-182548 A JP 2004-18309 A JP 2003-206117 A

However, even if carbon fiber is produced using a vapor phase growth carbon fiber production catalyst obtained by a liquid phase method, the catalyst still contains metal impurities derived from the catalyst in the order of several percent to several tens of percent. There was a problem of being included.
In addition, the catalyst for vapor phase growth carbon fiber production obtained by the impregnation method is difficult to carry a large amount of metal evenly when carrying a catalytic metal (catalytic metal) on the surface of a carrier such as silica. Therefore, there is a problem that the amount of metal that can be supported has to be reduced, the production efficiency of carbon fibers is lowered, and further, the amount of metal impurities in the product cannot be reduced.

The vapor growth carbon fiber production catalyst obtained by a liquid phase method such as a coprecipitation method can support a metal having a catalytic action at a higher concentration than the impregnation method described above. Since the surface area was small, there were few active points which act as a catalyst, and there existed a problem that the production | generation efficiency of carbon fiber was low.
In addition, in the preparation of a catalyst by a liquid phase method that requires high-temperature, long-time firing, if the firing is excessive, sintering occurs on the surface of the resulting catalyst, resulting in loss of pores, and the specific surface area of the catalyst. There was a problem of lowering. In addition, if a solid solution or composite oxide of the support and the catalyst metal is formed by firing at a high temperature, the strength of the catalyst particles increases due to the progress of crystallization of the support and the catalyst metal, but the crystal lattice of the support. There is a problem that the catalytic metal enters the inside, the action as a catalyst is lowered, and the production efficiency of the carbon fiber is lowered.

  The carbon fiber obtained by such a conventional organic acid method has a problem that the dispersibility of the carbon fiber in the compound is low even if it is used as a filler of a resin compound. In addition, since the strength is high because of the high-temperature firing process, the particle size of the catalyst carrier and the catalyst metal contained in the carbon fiber is not easily crushed even when the carbon fiber and the resin are kneaded, so when molding the resin compound These have the problem that the surface smoothness of the resin molding is lowered and the appearance is impaired.

  On the other hand, a large amount of metal impurities contained in a product containing carbon fiber obtained by such a vapor growth carbon fiber production catalyst is brought into contact with an acid such as hydrochloric acid or nitric acid. Although it can be removed, there is a problem that when such a treatment method is applied, the carbon fiber itself is oxidized by an acid, and the properties of its surface are impaired.

  In view of the problems as described above, the present inventors have intensively studied a catalyst for producing a vapor grown carbon fiber, particularly the catalyst obtained by the organic acid method. As a result, when a group 8 metal is used as the catalyst metal, the content of the amorphous group 8 metal oxide in the entire group 8 metal oxide in the catalyst is specified or more, specifically, 10% by weight or more. In addition, a catalyst that suppresses the content of the crystalline metal oxide in the total contained metal oxide constituting the support and the like, specifically 85% by weight or less is used as a catalyst for producing a vapor grown carbon fiber. As a result, it was found that a carbon fiber having a narrow diameter and length distribution and a reduced impurity content could be produced, and the present invention was completed.

  According to the present invention, a catalyst having excellent performance as a catalyst for producing carbon fibers by a vapor phase growth method can be provided by a simple method without using a special apparatus or the like. In addition, by using the catalyst of the present invention, carbon fibers having a uniform diameter and length and a reduced impurity content can be produced. A resin compound using this carbon fiber as a resin filler can be easily obtained by kneading with a resin because the particle size of impurities derived from the catalyst carrier and metal catalyst accompanying the carbon fiber is small and its strength is relatively low. When the resin compound is made into a resin molded body, it is possible to provide an excellent resin molded body that does not impair the surface properties.

Hereinafter, the present invention will be described in more detail.
The present invention relates to a vapor-grown carbon fiber production catalyst containing a group 8 metal oxide, which is obtained by firing a mixture containing at least a water-soluble group 8 metal compound and an organic compound. A catalyst for producing a vapor-grown carbon fiber, characterized in that the amorphous group 8 metal oxide in the product is 10 wt% or more and the crystalline metal oxide in the total metal oxide is 85 wt% or less, And a method for producing a carbon fiber using the catalyst.

Group 8 metals used in the present invention include iron, cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt ) At least one metal selected from. Among these, iron, cobalt, and nickel are preferable, and cobalt is particularly preferable.
In the present invention, this group 8 metal is used as a water-soluble metal compound. The water-soluble compound is not particularly limited as long as it is water-soluble, and examples thereof include inorganic acid salts and organic acid salts such as chloride salts, nitrate salts, sulfate salts, and acetate salts; ammonia complex salts; and metal alkoxides. Usually used. Of these, inorganic acid salts and organic acid salts are preferred for reasons such as availability and ease of handling. Among such salts, nitrates, sulfates, acetates and the like that decompose at a comparatively low temperature of about 600 ° C. are preferable because the calcining temperature can be lowered when these are used to produce the catalyst of the present invention. Acetate is preferred.

  In addition, in this invention, it is preferable that it is the catalyst obtained by baking the mixture containing water-soluble metal compounds other than a group 8 metal. As such a water-soluble metal compound other than Group 8 metal, any compound can be used as long as it can become a catalyst carrier when oxidized by firing, specifically magnesium, calcium, scandium, yttrium, And compounds containing titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, copper, silver, gold, boron, aluminum, silicon, lanthanoids, and the like.

  Among these, one or more metals selected from the group consisting of Group 2, Group 4, Group 13, and Group 14 exhibiting excellent performance as a catalyst carrier when oxidized into a metal oxide by firing In particular, a metal compound containing one metal selected from the group consisting of magnesium, titanium, zirconium, aluminum, and silicon is preferable, and magnesium, titanium, and zirconium are particularly preferable.

  In the present invention, the molar ratio between the group 8 metal compound as described above and the metal compound other than group 8 may be appropriately selected and determined. In general, the group 8 metal should be 10 mol% or more with respect to the total amount in terms of these metals, preferably 15 mol% or more, particularly preferably 20 mol% or more, and the upper limit is 50 mol%. Hereinafter, it is preferable that it is 40 mol% or less especially.

  The metal compound is not particularly limited as long as it is water-soluble, and for example, inorganic acid salts and organic acid salts such as chloride salts, nitrate salts, sulfate salts and acetate salts; ammonia complex salts; and metal alkoxides are usually used. . Of these, inorganic acid salts and organic acid salts are preferred for reasons such as availability and ease of handling. Among them, nitrates, sulfates, acetates and the like that decompose at a comparatively constant low temperature of about 600 ° C. are preferable because the firing temperature can be lowered when these are used to produce the catalyst of the present invention, and nitrates and acetates are particularly preferable. . Further, these salts are more preferably the same salts as the Group 8 metal compound, and nitrates are particularly preferable.

  Any organic compound can be used as the organic compound used in the present invention, but generally an organic compound showing water solubility is used. Examples of such compounds include organic compounds having a carboxyl group, a hydroxyl group, an amino group, and the like in the same molecule. Specifically, carboxylic acid derivatives such as carboxylic acids, hydroxycarboxylic acids, carboxylic acid esters, Examples thereof include amino acids, amides, amines, and hydrates and anhydrides thereof.

Among these organic compounds, those having a low decomposition temperature, for example, those capable of decomposing at 300 ° C. or less are preferable. Particularly, a compound having a complex forming ability with a metal (can be a ligand) is contained in the catalyst of the present invention. This is preferable because the dispersibility of the Group 8 metal oxide is good and the particles can be made fine.
Examples of such organic compounds include citric acid, malic acid, tartaric acid, lactic acid, glycine, glutamic acid, glutamine, asparagine, arginine, phenylalanine, alanine, leucine, and isoleucine. Among them, a carboxylic acid having a low decomposition temperature and excellent complex forming ability with a metal is preferable, and citric acid is particularly preferable.

  The catalyst for producing a vapor grown carbon fiber of the present invention comprises 10% by weight or more of the amorphous group 8 metal oxide in the group 8 metal oxide and 85% by weight of the crystalline metal oxide in the total metal oxide. It is characterized by the following. As long as the content of the amorphous group 8 metal oxide in the group 8 metal oxide is 10% by weight or more, the generation efficiency of the obtained carbon fiber increases. Therefore, the content is preferably 11% by weight or more, particularly 13% by weight or more. The upper limit is not particularly limited, but is generally 50% by weight or less.

Further, the content of the crystalline metal oxide in the total metal oxide is preferably as low as 85% by weight or less, more preferably 80% by weight or less, and particularly preferably 75% by weight or less.
The content may be measured by any conventionally known method. For example, elemental analysis of a measurement target (sample) such as metal oxides is performed, and the composition is first determined. For example, in the case of metal oxides containing cobalt (Co) as a Group 8 metal, mainly containing magnesium (Mg) as another metal, and containing other carbon (C), hydrogen, etc., this is referred to as ICP emission. Analysis, measurement with a CNH meter or the like, and determination of the composition of oxygen, C, H, etc. in addition to Co and Mg. Next, X-ray analysis of a sample to which a predetermined amount of an internal standard has been added is performed, and the mass fraction of crystal components such as each metal and its oxide may be determined by the Rietveld method or the like.

  Further, the content of the amorphous group 8 metal oxide may be measured by the following method, for example. First, the X-ray diffraction intensity of the Group 8 metal oxide crystal pure product to be measured is set to 100, the X-ray diffraction intensity of the Group 8 metal oxide in the sample is measured, and the content of the crystallized Group 8 metal oxide is determined. decide. Separately, the composition of the sample was quantified by chemical analysis, and the total group 8 metal oxide content minus the crystallized group 8 metal oxide content was determined as the amorphous group 8 metal oxide content. do it.

  The particle diameters of the amorphous metal oxide and the crystalline metal oxide in the vapor-grown carbon fiber production catalyst of the present invention may be appropriately selected and determined, and are generally in the range of 5 nm or more and 50 nm or less. is there. Among these, when the particle diameter is 25 nm or less, carbon fibers having a diameter of several nm to several tens of nm can be efficiently produced, and carbon obtained using the catalyst for producing the vapor grown carbon fiber is obtained. This is preferable because the surface smoothness of a resin compound or the like obtained by mixing the fiber with the resin becomes good.

Therefore, the particle diameter is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 15 nm or more, and is preferably 25 nm or less, and particularly preferably 20 nm or less. The crystallite size of amorphous and crystalline metal oxides is the crystallite size calculated from the half width of the intrinsic diffraction peak of each component by X-ray diffraction.
The catalyst for producing a vapor grown carbon fiber of the present invention is a vapor grown carbon fiber containing a group 8 metal oxide, which is obtained by firing a mixture containing at least a water-soluble group 8 metal compound and an organic compound. Catalyst. The firing temperature at this time is preferably a relatively low temperature of less than 700 ° C., specifically 650 ° C. or less, particularly 600 ° C. or less, more preferably 450 ° C. or less, particularly 400 ° C. or less. Preferably there is.

  The catalyst for producing a vapor-grown carbon fiber of the present invention is a so-called vapor-grown carbon fiber that deposits fibrous carbon by pyrolyzing a gas containing carbon such as hydrocarbon or carbon monoxide on a catalyst metal. It is a catalyst for production. The carbon fiber production method by this method is generally a method in which a raw material gas of carbon fiber is brought into contact with a powdered catalyst, a method in which the gas and an organometallic compound as a catalyst are simultaneously introduced into a reactor, etc. There is.

The catalyst for producing a vapor grown carbon fiber of the present invention is used after being activated in a reducing atmosphere or in contact with a carbon fiber raw material gas together with a reducing gas.
As the raw material gas for carbon fiber, any conventionally known gas can be used. Specifically, for example, hydrocarbons such as methane, ethylene, and acetylene, carbon monoxide, alcohol, and the like are used as the gas containing carbon. it can. Further, the temperature at the time of production, the supply amount of the raw material gas, and the like may be appropriately selected and determined from conventionally known arbitrary values.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the analysis methods of the catalyst etc. in the following examples and comparative examples are as follows.
X-ray diffraction measurement was performed using a sample prepared by adding an internal standard Al ₂ O ₃ powder so as to have a concentration of 10 wt% to a gas phase growth method carbon fiber production catalyst to be analyzed. The measurement was performed using a CuKα X-ray source and using a variable slit mode so that the irradiation width did not exceed the width of the sample. The details of the measurement conditions were as follows, and quantitative analysis was performed by the Rietveld method. In the Rietveld method, simultaneous analysis of three components (Al ₂ O ₃ , Co ₃ O ₄ , and MgO) was performed, and from the mass fraction calculated from the scale factor of each obtained phase and the amount of internal standard added The crystal components of Co ₃ O ₄ and MgO in the sample were quantified.
Start angle 15 °, end angle 155 °, step width 0.02 °, scanning speed 0.3 ° / min, divergence / scattering slit: variable (irradiation width: 10.00 mm), light receiving slit 0.2 mm,

Example 1
An aqueous solution obtained by dissolving 60 mmol (mmol) of cobalt nitrate hexahydrate, 140 mmol of magnesium nitrate hexahydrate, and 60 mmol of citric acid monohydrate (decomposition temperature is 195 ° C.) in 200 g of water is heated to yellow. It was evaporated to dryness until gas evolution ceased. The solid was sufficiently dried at 105 ° C., heated to 450 ° C. in an air atmosphere using an electric furnace, and then fired at 450 ° C. for 30 minutes. After calcination, the solid was pulverized after cooling to room temperature to obtain a catalyst for producing a vapor grown carbon fiber.

As a result of X-ray analysis of the obtained catalyst, the content of the crystalline metal oxide in the total metal oxide in the catalyst precursor was 74.53% by weight, and the content of the amorphous group 8 metal oxide was 13.19% by weight. The particle size of the crystalline group 8 metal oxide (Co ₃ O ₄ ) particles was 14.6 nm, and the particle size of the MgO particles was 16.7 nm.
After this catalyst was subjected to hydrogen reduction treatment, carbon fiber was produced by contacting with a mixed gas of carbon monoxide and hydrogen at a reaction temperature of 600 ° C. for 3 hours.
When the obtained product containing carbon fiber was observed with a transmission electron microscope, its diameter was 15 to 25 nm, and it was a multilayered tubular carbon fiber. The carbon fiber deposition amount (C / Cat) per gram of catalyst was 6.8 [g carbon / g catalyst], and the carbon content in the product was 87% by weight.

(Example 2)
A product containing carbon fiber was obtained and evaluated in the same manner as in Example 1 except that the reaction temperature in the production of carbon fiber was 512 ° C. The carbon fiber had a diameter of 10 to 20 nm and was a multilayered tubular carbon fiber. C / Cat was 10.8 [g carbon / g catalyst], and the carbon content in the product was 91% by weight.

(Example 3)
A catalyst for vapor phase growth carbon fiber production was obtained in the same manner as in Example 1 except that 80 mmol of cobalt nitrate hexahydrate, 120 mmol of magnesium nitrate hexahydrate, and 120 mmol of citric acid monohydrate were used. And using this, the product containing carbon fiber was obtained similarly to Example 2, and was evaluated.
As a result of X-ray analysis of the obtained catalyst, the particle diameter of MgO particles in the catalyst was 15.7 nm. And the diameter of carbon fiber was 10-15 nm, and it was a multilayer tubular carbon fiber. C / Cat was 12.6 [g carbon / g catalyst], and the carbon content in the product was 93% by weight.

Example 4
In the production of the catalyst, a vapor growth carbon fiber production catalyst was obtained in the same manner as in Example 1 except that the calcination temperature was 400 ° C., and a product containing carbon fiber was obtained and evaluated using this catalyst. . As a result of X-ray analysis of the obtained catalyst, the content of the crystalline metal oxide in the total metal oxide in the catalyst was 40.59% by weight, and the content of the amorphous group 8 metal oxide was 10. It was 87% by weight. The particle size of the crystalline group 8 metal oxide particles was 18.5 nm, and the particle size of the MgO particles was 25.8 nm.
And the diameter of carbon fiber was 10-15 nm, and it was a multilayer tubular carbon fiber. C / Cat was 4.3 [g carbon / g catalyst], and the carbon content in the product was 81% by weight.

(Example 5)
In the production of the catalyst, a vapor growth carbon fiber production catalyst was obtained in the same manner as in Example 1 except that the calcination temperature was 600 ° C., and a product containing carbon fiber was obtained and evaluated using this catalyst. .
As a result of X-ray analysis of the obtained catalyst, the content of the crystalline metal oxide in the total metal oxide in the catalyst was 73.64% by weight, and the content of the amorphous group 8 metal oxide was 11. It was 07% by weight. The particle size of the crystalline group 8 metal oxide particles was 22.3 nm, and the particle size of the MgO particles was 16.4 nm.
And the diameter of carbon fiber was 10-30 nm, and it was a multilayer tubular carbon fiber. C / Cat was 9.9 [g carbon / g catalyst], and the carbon content in the product was 91% by weight.

(Example 6)
Vapor grown carbon fiber in the same manner as in Example 1 except that cobalt acetate tetrahydrate and magnesium acetate tetrahydrate were used instead of cobalt nitrate hexahydrate and magnesium nitrate hexahydrate. A production catalyst was obtained and used to obtain and evaluate a product containing carbon fiber.
As a result of X-ray analysis of the obtained catalyst, a peak of crystalline group 8 metal oxide in all metal oxides in the catalyst could not be confirmed. The particle diameter of the MgO particles was 21.1 nm. Met. And the diameter of carbon fiber was 15-25 nm, and it was a multilayer tubular carbon fiber. C / Cat was 10.1 [g carbon / g catalyst], and the carbon content in the product was 91% by weight.

(Comparative Example 1)
Except for the firing temperature of 700 ° C. and the firing time of 5 hours, a catalyst for producing a vapor-grown carbon fiber was obtained in the same manner as in Example 3, and a product containing carbon fiber was obtained using this catalyst. evaluated.
As a result of X-ray analysis of the obtained catalyst, the particle size of the crystalline group 8 metal oxide particles in the total metal oxide in the catalyst was 26.8 nm, and the particle size of the MgO particles was 25.8 nm. And the diameter of carbon fiber was 5-15 nm, and it was a multilayer tubular carbon fiber. However, C / Cat was as extremely low as 0.53 [g carbon / g catalyst], and the carbon content in the product was 35% by weight.

(Comparative Example 2)
Except for setting the firing temperature to 900 ° C., a catalyst for producing a vapor-grown carbon fiber was obtained and evaluated in the same manner as in Example 1.
As a result of X-ray analysis of the obtained catalyst, other amorphous metal oxides including a group 8 metal oxide were not found in all metal oxides in the catalyst. The crystalline metal oxide particles were a solid solution of CoO and MgO, and the particle size was 37.6 nm.
And although it was going to manufacture carbon fiber like Example 1 using this catalyst, the production | generation of carbon was not able to be confirmed even if reaction time passed, and carbon fiber was not able to be manufactured.

(Comparative Example 3)
100 g of an aqueous solution containing 240 mmol of oxalic acid was added dropwise to 100 g of an aqueous solution containing 80 mmol of cobalt nitrate hexahydrate and 120 mmol of magnesium nitrate hexahydrate to obtain a precipitated product. This precipitate was filtered by suction filtration, and the precipitate was washed with distilled water, and then sufficiently dried in the same manner as in Example 1, and then calcined in an electric furnace to obtain a catalyst for producing a vapor-grown carbon fiber, This was used to obtain and evaluate products containing carbon fibers.

As a result of X-ray analysis of the obtained catalyst, the content of the crystalline metal oxide in the total metal oxide in the catalyst was 90.79% by weight, and the content of the amorphous group 8 metal oxide was 6. It was 92% by weight. The crystalline group 8 metal oxide particles had a particle size of 19.8 nm, and the MgO particles had a particle size of 22.9 nm.
And the diameter of the carbon fiber had a wide distribution of 10 to 50 nm. The carbon fiber was a multi-layered tubular carbon fiber, but C / Cat was 6.2 [g carbon / g catalyst], and the carbon content in the product was 86% by weight.

  The above results are summarized in Table 1. As can be seen from Table 1, by using the vapor-grown carbon fiber production catalyst obtained by the present invention, the content of carbon fiber in the product is high, the production efficiency is improved, and the diameter of the carbon fiber and its A good carbon fiber having a relatively small distribution width can be provided. Further, since the particle size of the metal oxide, which is a catalyst residue contained in the obtained carbon fiber, is smaller than that of the conventional one, it can be expected that the effect on the surface characteristics is small when a resin compound is used. .

Claims (7)

A catalyst for producing a vapor grown carbon fiber containing a Group 8 metal oxide, which is obtained by calcining a mixture containing at least a water-soluble Group 8 metal compound and an organic compound, the amorphous material in the Group 8 metal oxide A catalyst for producing vapor-grown carbon fibers, characterized in that the content of the group 8 metal oxide is 10% by weight or more and the crystalline metal oxide in the total metal oxide is 85% by weight or less. The catalyst for producing vapor-grown carbon fiber according to claim 1, further comprising calcining a mixture containing a water-soluble metal compound other than Group 8 metal. The catalyst for producing a vapor-grown carbon fiber according to claim 1 or 2, wherein the organic compound contains an organic compound having a decomposition temperature of 300 ° C or lower. The catalyst for producing vapor grown carbon fiber according to any one of claims 1 to 3, wherein the organic compound has a complex forming ability with a metal. The catalyst for producing vapor grown carbon fiber according to any one of claims 1 to 4, wherein the particle diameter of the amorphous metal oxide and the crystalline metal oxide is 25 nm or less. The catalyst for producing vapor grown carbon fiber according to any one of claims 1 to 5, wherein a calcination temperature is 650 ° C or lower. A method for producing carbon fiber, comprising using the vapor growth carbon fiber production catalyst according to any one of claims 1 to 6.