JPH0440451B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing carbon fibers, and particularly to a method for efficiently manufacturing carbon fibers by vapor phase growth using a laser beam. [Prior Art] Conventionally, PAN-based and Pitch-based carbon fibers have been commercially produced. However, PAN-based products are expensive, and pitch-based products have fatal drawbacks such as complicated processes and difficult quality control. On the other hand, a vapor phase growth method has been proposed in recent years. Conventionally, vapor-grown carbon fibers are produced by placing a substrate made of porcelain such as alumina or graphite in an electric furnace, forming carbon growth nuclei, ultrafine particle catalysts such as iron, and nickel on this, and then forming carbonization particles such as benzene on this. Introducing a mixed gas of hydrogen gas and hydrogen carrier gas, 950 ~
A method is known in which carbon fibers are grown on a substrate by decomposing hydrocarbons at a temperature of 1300°C. However, with this method, the length tends to be non-uniform due to subtle temperature unevenness on the substrate surface and the density of surrounding fibers, and the gas that is the source of carbon is consumed by the reaction. As a result, the fiber diameter differs considerably between the inlet and the outlet of the reaction tube, and since production occurs only on the substrate surface, the central part of the reaction tube does not participate in the reaction, resulting in poor yields. However, since there are processes that must be carried out independently, such as dispersing ultrafine particles onto a substrate, reducing them, growing them, and then taking out the fibers, continuous production is impossible, and therefore, there are problems such as poor productivity. Therefore, a method for producing carbon fibers has been proposed in which a mixed gas of a carbon compound gas, an inorganic or organic transition metal compound gas, and a carrier gas is reacted at a high temperature (Japanese Patent Laid-Open Nos. 60-54998, 1983-224816, etc.). [Problems to be solved by the invention] However, the above-mentioned Japanese Patent Application Laid-Open No. 60-54998,
In methods such as 224816, the reaction vessel is also heated, which causes problems such as by-products adhering to the walls of the vessel, reducing yield and making continuous operation difficult. In addition, it is not easy to scale up, making it unsuitable for mass production, and requires an electric furnace for heating, resulting in high energy costs. [Means for Solving the Problems] The present invention solves the above problems and provides a method for producing carbon fibers at low temperatures and in high yield. The method for producing carbon fibers of the present invention is a method in which a carbon compound gas and suspended catalyst particles are brought into contact with each other under laser irradiation to precipitate carbon into fibers. This method is characterized by using at least two types of lasers, one effective for decomposition and one effective for vibrational excitation of the catalyst, each having a different wavelength. That is, as a result of intensive studies to solve the conventional problems, the present inventors discovered that under laser irradiation, carbon compound gas and
A method for producing carbon fiber, which is characterized in that carbon fibers are precipitated in the form of fibers by contacting catalyst particles in a suspended state, and a reaction vessel having a reaction zone inside thereof, and an apparatus suitable for carrying out this method. , a laser device that irradiates a laser beam toward the reaction zone, a carrier gas introduction means, a carbon compound gas introduction means, and catalyst particles or catalyst raw materials, which are connected to one side of the reaction vessel with the reaction zone in between. We have developed a carbon fiber manufacturing apparatus characterized by comprising a gas introduction means and a carbon fiber collection means connected to the other side of the reaction vessel across the reaction zone, and the present invention is directed to the present invention. The patent application was filed before the applicant (Japanese Patent Application No. 1983-234896, hereinafter referred to as the "earlier application"). As a result of further research to further improve the energy efficiency of the method of the above-mentioned prior application, the present inventors have developed a laser that is useful for photolysis of carbon compounds and a laser that is useful for vibrational excitation of catalysts. By using at least two types of lasers, each laser energy acts effectively,
The present invention was completed based on the discovery that energy efficiency can be further improved. The present invention will be explained in more detail below. The carbon compound in the present invention refers to all carbon compounds that can be gasified, including CCl ₄ ,
It covers all inorganic and organic compounds such as CHCl ₃ , CH ₂ Cl ₂ , CH ₃ Cl, CO, and CS ₂ . Particularly useful compounds are aliphatic hydrocarbons and aromatic hydrocarbons. In addition to these, nitrogen, oxygen, sulfur,
Derivatives containing elements such as fluorine, iodine, phosphorus, arsenic, etc. can also be used. Some specific examples of individual compounds include methane (natural gas may also be used), alkane compounds such as ethane, alkene compounds such as ethylene and butadiene, alkylene compounds such as acetylene, benzene, toluene, styrene, etc. aryl hydrocarbon compounds, aromatic hydrocarbons with condensed rings such as indene, naphthalene, and phenanthrene, cycloparaffin compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene and cyclohexane, and alicyclic rings having condensed rings such as steroids. Formula hydrocarbon compounds, sulfur-containing aliphatic compounds such as methylthiol, methylethylsultide, and dimethylthioketone, sulfur-containing aromatic compounds such as phenylthiol and diphenyl sulfide, and sulfur-containing complex compounds such as benzothiophene and thiophene. Cyclic compounds, as well as gasoline, class 4 hazardous materials under the Fire Service Act, class 1 petroleum, kerosene,
Secondary petroleum oils such as turpentine oil, camphor oil, and pine oil, tertiary petroleum oils such as heavy oil, and quaternary petroleum oils such as gear oil and cylinder oil can also be effectively used. It goes without saying that mixtures of these can also be used. In the present invention, the catalyst includes an inorganic transition metal compound, an inorganic Si inorganic compound, an organic transition metal compound,
Examples include organic compounds of Si. This inorganic transition metal compound is an inorganic transition metal compound that can be vaporized alone, or is soluble in water or at least one kind of water or organic solvent (a carbon raw material compound may be used as the organic solvent). Alternatively, inorganic compounds of transition metals that can be suspended as fine particles are targeted. Transition metals include iron, nickel,
Cobalt, molybdenum, vanadium, palladium, etc. are preferred, and iron is particularly preferred. The former inorganic transition metal compound that can be vaporized alone is Fe.
(NO) ₄ , FeCl ₃ , Fe(NO) ₃ Cl, Fe(NO) ₂ , Fe
Examples include (NO) ₂ I, FeF ₃ and the like. As for the latter, in addition to the compounds listed as the former, Fe
(NO ₃ ) ₂ , FeBr ₃ , Fe(HCO) ₃ , C ₂₇ H ₄₂ FeN ₉ O ₁₂ ,
Fe( _SO4 ) ₃ , Fe(SCN) ₃ , Fe(NO) _3NH3 , _Co
Representative examples include (NO) ₂ Cl, Ni(NO)Cl, Pd(NO) ₂ Cl ₂ and NiCl ₂ . The organic transition metal compounds in the present invention include alkyl metals in which an alkyl group and a metal are bonded, alkyl complexes in which an allyl group and a metal are bonded, and π-complexes in which a carbon-carbon double bond or triple bond is bonded to a metal. It is an organic transition metal compound typified by chelate type compounds. In addition, transition metals here include scandium, titanium, panadium, chromium, manganese, iron, cobalt, nickel, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, tantalum, tungsten, rhenium, iridium, and platinum. However, among these, those belonging to the periodic table group are particularly preferred, among which iron, nickel, and cobalt are particularly preferred, with iron being the most preferred. Furthermore, in the presence of a sulfur-containing carbon compound or an inorganic sulfur compound, an inorganic compound of silicon can also be used. For example, the above-mentioned inorganic metal compounds in which the metal is replaced with Si or silicon carbide can be used. Furthermore, various organosilicon compounds can be used. The organic silicon compound includes, for convenience, silane and halogen silane in addition to organic compounds having a silicon-carbon bond. Organic compounds with carbon-silicon bonds include organosilanes such as tetramethylsilane and methyltriphenylsilane; organohalogensilanes such as chlorodifluoromethylsilane and promtripropylsilane; methoxytrimethylsilane, trimethylphenoxysilane, etc. organoalkoxysilane; organoacetoxysilane such as diacetoxydimethylsilane, acetoxytripropylsilane; hexaethyldisilane,
Oneganopolysilanes such as hexaphenyldisilane and octaphenylcyclotetrasilane; organohydrogenosilanes such as dimethylsilane and triphenyltran; cyclosilanes represented by (SiH ₂ ) _o ; triphenylsilazane, hexaethyldisilazane, Organosilazane such as hexaphenylcyclotrisilazane, (SiH ₂ NH) _o Organosilanols such as diethylsilanediol and triphenylsilanol; Organosilanols such as trimethylsilylacetic acid and trimethylsilylpyropionic acid; Trimethylsilylacetic acid,
Organosilane carboxylic acids such as trimethyldilylpropionic acid; silicon isocyanates such as trimethylsilicon isocyanate and diphenylsilicon diisocyanate; organosilicon isothiocyanates such as trimethylsilicon isothiocyanate and diphenylsilicon diisothiocyanate; Organosilicon esters such as triethylsilyl cyanide; silthians such as hexamethyldisilthian and tetramethylcyclodisilthian;
(SiH ₂ S) Cyclosylthian represented by _o ; organosylmethylenes such as hexamethyldisylmethylene and octamethyltrisylmethylene; organosiloxanes such as hexamethyldisiloxane and hexapropyldisiloxane; It may also be a compound containing other carbon-silicon bonds.
It is also possible to use mixtures of these. Note that, in the present invention, catalyst particles (for example, dried fine powder) that have been generated in advance as fine particles may be introduced into the reaction vessel. In the present invention, when bringing the carbon compound and the catalyst particles into contact to cause a reaction, at least two types of lasers having different wavelengths are used: a laser effective for photodecomposition of the carbon compound and a laser effective for vibrational excitation of the catalyst. Uses a laser. For photodegradation of carbon compounds, excimer lasers with high quantum energy, e.g. ArF
(193nm) or KrF (249nm) laser etc. are effective. With such a high quantum energy laser, it is possible to cut the C--H bond of a carbon compound, and the production rate and production speed of carbon fibers can be improved.
For example, among the pulse excimer lasers with large peak output, the photon energy of ArF (193 nm) is
Since it is 150 Kcal/mol, the C--H bond (bond energy 98 Kcal/mol) can be easily cleaved. On the other hand, CO ₂ lasers, especially pulsed CO ₂ lasers, are effective for vibrational excitation of catalysts such as iron catalysts. Pulsed CO ₂ lasers can vibrationally excite iron catalysts with high energy efficiency and activate them at high temperatures. Therefore, in the present invention, it is preferable to use two types of lasers, a pulsed excimer laser and a pulsed CO ₂ laser, but the combination of lasers is not limited to this, and depending on the type of carbon compound and catalyst, other types of lasers may be used. Alternatively, a third and fourth laser may be used. The carrier gas in the present invention refers to all gases that are not directly involved in the reaction. Examples include H ₂ gas, N ₂ gas, NH ₃ gas, Ar gas, He
Gas, Kr gas, or a mixture of these gases. Among these, H ₂ gas is usually used. Furthermore, a component for enhancing the laser absorption effect may be added to the gas introduced into the container, such as a carrier gas. In this case, the additive component depends on the wavelength of the laser used, but for example, for a CO ₂ laser, NH ₃ or C ₂ H ₄ can be added as a laser absorption effect improver. The present invention will be described in detail below with reference to preferred embodiments shown in the drawings. FIG. 1 is a schematic cross-sectional plan view showing an example of an apparatus suitable for carrying out the present invention. Reference numeral 10 denotes a reaction vessel, which is mainly composed of three zones: a carbon compound photolysis zone 10A, a catalyst vibrational excitation zone 10B, and a carbon fiber production zone 10C. At the end of the photolysis zone 10A, a laser oscillator 12 for irradiating a laser beam effective for photolysis of carbon compounds, such as an excimer laser, is installed.
A laser absorption plate 14 is provided at the end of the carbon fiber production zone 10C facing the oscillator 12. Further, near the laser oscillator 12 installation part of the photolysis zone 10A, there is a pipe 16 for supplying carrier gas such as H ₂ or Ar gas, and near the carbon fiber production zone 10C there is a pipe 18 for supplying carbon compound gas. is connected. On the other hand, a laser oscillator 20 for irradiating a laser beam effective for vibrational excitation of the catalyst, such as a CO ₂ laser, is installed at the end of the catalyst vibration excitation zone 10B. A laser absorption plate 22 is provided at the end of the zone 10C. Further, a pipe 24 for supplying a compound containing a substance to become catalyst particles is connected to the vicinity of the laser oscillator 20 installation part in the vibrational excitation zone 10B of the catalyst, and a heater 26 for residual heat of the catalyst is connected to the connection position of this pipe 24. is set up. In addition, 16 in the figure
a, 18a, and 24a are flow rate control devices provided in each supply pipe. Further, a carbon fiber collector (not shown) is connected and provided below the carbon fiber generation zone 10C, and an exhaust gas extraction pipe is connected to this carbon fiber collector. . In the carbon fiber manufacturing apparatus configured as described above, the vibration excitation zone 10B of the catalyst is connected to the pipe 24.
The compound containing the substance introduced into the catalyst particles is excited and decomposed by the heat of the preheater 26 and the CO ₂ laser beam, and is decomposed into catalyst particles such as transition elements or SiC (the normal particle size is 0.1 to 10 μm). degree)
is generated efficiently. On the other hand, the raw material carbon compound introduced into the carbon compound photolysis zone 10A from the pipe 18 is efficiently excited and decomposed by the excimer laser beam. Thus, the excited catalyst particles and the photodecomposed carbon compound are both sent to the carbon fiber production zone 10C, where the raw material carbon compound is deposited on the catalyst particles and carbon fibers grow. In the present invention, the temperature of the vessel wall of the reaction vessel in which fine particles are generated and carbon fibers are generated using these as growth points is considerably lower than that of a reaction vessel using a conventional external heating electric furnace. No by-products will be attached to the product. Therefore, in the present invention, there is no need to limit the material of the reaction vessel to expensive materials with high corrosion resistance or high heat resistance. Additionally, since it uses a laser beam, it consumes less energy than a general external heating electric furnace, resulting in lower energy costs. However, in the present invention, if necessary, an external heating means such as an external heating type electric furnace may be provided to surround the reaction vessel to heat the vessel wall of the reaction zone (carbon fiber production zone). In this case, in order to prevent the product from adhering to the vessel wall, the vessel wall temperature should be lower than 600℃, especially 550℃.
External heating is preferably carried out so that: In the present invention, the size of the catalyst particles or the diameter and length of the carbon fibers can be adjusted by controlling the partial pressure of the raw material gas, residence time, laser intensity, etc. As mentioned above, the reaction order in the reaction vessel is to generate catalyst fine particles by vibrational excitation of the catalyst, then to generate and grow carbon fibers. No need to split. However, if necessary, a carbon fiber growth zone may be formed by additionally providing a suitable external heating means as described above. The carbon fibers produced in the reaction vessel are introduced into a lower carbon fiber collector together with a carrier gas. As this collection method, various conventionally known methods such as gravity sedimentation method and electrostatic precipitation method can be employed. Note that the carbon fiber repair device also plays the role of cooling the generated carbon fibers. According to the present invention, it is possible to easily produce carbon fibers that usually have a length of about 10 μm to 500 mm and a diameter of about 0.1 to 300 μm. The carrier gas extracted from the carbon fiber collector may be directly introduced into the exhaust treatment means and discharged, but it may also be purified and recirculated for use. In the illustrated apparatus, laser absorption plates (for example, water-cooled copper plates) 14 and 22 are installed at the end of the reaction vessel 10, but in cases where the optical path length is short, a reflecting plate is placed to lengthen the optical path length of the laser beam. It may be configured as follows. [Operation] In the present invention, at least two types of lasers having different wavelengths are used: a laser effective for photolysis of carbon compounds and a laser effective for vibrational excitation of a catalyst. Therefore, the photolysis of the carbon compound and the vibrational excitation of the catalyst can be carried out efficiently, and the reaction can be carried out at a lower temperature and with a higher yield. [Example] Hereinafter, preferred manufacturing examples will be described. Example 1 In the apparatus shown in FIG. 1, carbon fibers were manufactured under the following conditions. Catalyst side laser: CO ₂ laser (10.591μm) Raw material side laser: Excimer laser
(ArF: 193nm) Raw material: Methane Compound containing material that becomes catalyst particles:
FeCl ₃ aqueous solution Carrier gas: H ₂ pressure: Normal pressure Residence time: 1 minute Raw material concentration: 5 vol% relative to H ₂ Reactor: 20 mm ID x 450 mm L (made of quartz) The results are shown in Table 1. Comparative Example 1 Carbon fibers were produced in the same manner as in Example 1 except that a CO ₂ laser was also used as the laser on the raw material side. The results are shown in Table 1.

[Table] As is clear from Table 1, according to the method of the present invention, carbon fibers can be produced at a high yield. [Effects of the Invention] As described above, according to the present invention, carbon fibers are manufactured by a vapor phase method using a laser, which results in low energy consumption and low manufacturing costs. The inner wall surface of the reaction vessel is at a low temperature, and its material can be made of an inexpensive material. It is difficult for by-products to adhere to the inner surface of the reaction vessel, making it suitable for continuous operation and operation of large reaction vessels. The quality of the carbon fiber obtained can be easily controlled by adjusting the pressure inside the reaction vessel, the partial pressure of each gas, residence time, laser intensity, etc. Mass production and scale-up are easy. In addition to achieving these effects, by using lasers that are optimal for photolysis of raw materials and activation of catalysts, it is possible to manufacture with higher energy efficiency, high yield, and high production rate. It becomes possible. This is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a plan sectional view illustrating the configuration of a manufacturing apparatus suitable for carrying out the present invention. 10... Reaction container, 12, 20... Laser oscillator, 16... Carrier gas supply pipe, 18... Carbon compound supply pipe, 24... Catalyst supply pipe.

Claims (1)

[Claims] 1 A method of depositing carbon in the form of fibers by bringing carbon compound gas into contact with floating catalyst particles under laser irradiation. A method for manufacturing carbon fiber, comprising using at least two types of lasers having different wavelengths, including a laser effective for vibrational excitation.