Method for producing nanocarbon material

Abstract

To provide a method for producing a carbon nanomaterial using waste plastic as a raw material.SOLUTION: A method for producing a nanocarbon material includes a step of adding an organotransition metal compound or a transition metal-bearing oxide and a medium to one or more kinds of polymers selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride, and reacting the resulting mixture at a temperature in the range of 350-800°C and a pressure in the range of 2-50 MPa.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a nanocarbon material. More specifically, it relates to a manufacturing method capable of mass-producing a nanocarbon material from inexpensive raw materials and a simple manufacturing apparatus.

Background Art

[0002] Plastics synthesized from petroleum resources have been used in many aspects of life due to their advantages of being inexpensive and lightweight. However, the amount discharged as industrial waste is also large, polluting the environment, reaching even the deep sea, and being taken in as microplastics inside the bodies of animals. Therefore, the recycling of plastics (waste plastics) as industrial waste has become essential and increasingly important. However, although efforts have been made to recycle waste plastics and use them partially as plastic raw materials, the recycling cost is high, and the situation is far from complete recycling. Most of the waste plastics are thermally recycled by burning them as fuel for power generation, which is not preferable in the context of global warming caused by carbon dioxide emissions. The material recycling of waste plastics requires advanced processing technologies such as the separation of mixed plastics and the separation of materials from composites, and the price of the material is not low. Further technological development for more advanced recycling is desired.

[0003] On the other hand, carbon nanotubes, a representative example of nanocarbons, are being studied for applications such as electrode materials for light-emitting devices such as FED (Field Emission Display), electrode materials for lithium secondary batteries, reinforcing materials for resins, and hydrogen storage materials for hydrogen storage systems because of their excellent field emission performance, ability to store and release lithium in electrochemical reactions, excellent ability to supplement mechanical strength, and excellent hydrogen storage capacity.

[0004] As methods for manufacturing carbon nanotubes, there are known methods such as an arc discharge method in a gas atmosphere containing a carbon raw material such as a hydrocarbon, a laser evaporation method in which graphite is irradiated with a laser and evaporated to form carbon nanotubes, and a method in which a gas serving as a carbon raw material such as acetylene is thermally decomposed on a substrate provided with a catalyst of cobalt metal or nickel metal. Patent Document 1 proposes a manufacturing method in which carbon nanotubes are vapor-phase grown by arc discharge by bringing carbon vapor into contact with nonmagnetic transition metals such as ruthenium, rhodium, palladium, and platinum. Patent Document 2 proposes a manufacturing method for carbon single-walled nanotubes with good yield by supplying a hydrogen gas or an argon gas that etches carbon independently of the supply of raw materials at the periphery of a high-frequency plasma. Patent Document 3 proposes a method for manufacturing single-walled carbon nanotubes by irradiating a carbon rod with a laser, and Patent Document 4 proposes a manufacturing method for producing a nanocarbon material by bringing a raw material containing an aromatic compound into contact with a supercritical fluid or a subcritical fluid under high temperature and high pressure in the presence of a catalyst containing a transition metal element. Non-Patent Document 1 also develops a method for manufacturing single-walled carbon nanotubes in a flowing gas phase by atomizing a hydrocarbon-based solution containing a catalyst precursor and a reaction accelerator as a raw material by spraying and introducing it into a high-temperature heating furnace.

[0005] In recent years, environmental pollution caused by plastics has become a major global issue, and there is an urgent need to reduce the use of plastics, use plastic alternative products, and recycle waste plastics. In Patent Document 5, a method for decomposing waste plastics in continuous operation is proposed, in which supercritical water or subcritical water is reacted with waste plastics to hydrolyze the waste plastics and recover high-purity monomers. In Patent Document 6, a method is proposed in which waste plastics containing halogen are contacted and reacted with high-temperature hot water containing supercritical water together with an alkali metal compound to be gasified. In Patent Document 7, a supercritical fluid excluding water is used as a heat medium to thermally decompose resin-containing waste under high-pressure heating, and then the decomposition products are cooled and depressurized to separate and reuse the volatilized chlorine, while an apparatus for recovering the extract and the desalted residue obtained in the thermal decomposition tank as fuel is proposed. In Patent Document 8, it is proposed to decompose using subcritical water at a temperature lower than the thermal decomposition temperature of unsaturated polyester resin to recover polyhydric alcohol and organic acid in high yields.

[0006] However, in any of the proposals in the above prior art documents, a method for producing a high-value-added nanocarbon material using waste plastics, which has become a global environmental problem, as a raw material is not disclosed, and the development of a manufacturing method for converting waste plastic materials into high-value-added materials is expected.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Document

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a method for producing a nanocarbon material that can use inexpensive waste plastics. The nanocarbon produced by the present invention can be used as a conductive aid for the electrodes of lithium-ion batteries, an additive for suppressing electrostatic generation, or a plastic additive material for enhancing strength.

Means for Solving the Problems

[0010] The present invention is a method for producing a nanocarbon material, which includes a step of adding an organic transition metal compound or a transition metal-supported oxide and a medium to one or more polymers selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride as raw materials, and reacting them under a temperature in the range of 350 to 800 °C and a pressure in the range of 2 MPa to 50 MPa. 350 °C is the lower limit temperature at which a carbon material is formed using a transition metal compound as a catalyst, and 800 °C is the upper limit temperature for using a pressure-resistant reaction apparatus that is relatively easy to manufacture. The upper limit temperature of the pressure-resistant reaction apparatus is determined by the heater performance, as well as the material of the reaction vessel and the heat-resistant temperature of the hermetic seal member.

[0011] Preferably, the medium is one or more substances selected from the group consisting of carbon dioxide, water, hydrocarbons, ethers, esters, ketones, and alcohols. Furthermore, it is preferable that the hydrocarbon is one or more hydrocarbon compounds selected from the group consisting of methane, ethane, ethylene, propane, propylene, butane, butene, pentane, pentene, pentadiene, hexane, cyclohexane, hexene, heptane, heptene, octane, octene, nonane, nonene, decane, decene, toluene, and xylene. As the alcohol, it is preferable that the alcohol is one or more alcohols selected from the group consisting of ethanol, propanol, butanol, pentanol, hexanol, and dodecanol.

[0012] In addition, one or more polycyclic aromatic hydrocarbons selected from the group consisting of naphthalene, phenanthrene, anthracene, pyrene, triphenylene, tetracene, pentacene, benzopyrene, glycerin, coronene, and ovalene may be added to the medium. The addition of polycyclic aromatic hydrocarbons promotes the growth of carbon materials with a graphene structure in a high-temperature and high-pressure reaction.

[0013] Under high temperature and high pressure within the temperature range of 350 to 800 °C and the pressure range of 2 MPa to 50 MPa, it is preferable that at least one of the media exists as a supercritical fluid or a subcritical fluid. Since the supercritical fluid or subcritical fluid has a high density while having a low viscosity and being rich in fluidity, chemical reactions are promoted. In addition, one or more inert gases selected from argon gas, helium gas, and nitrogen gas may be added to the reaction system. The pressure inside the reaction vessel can be adjusted thereby.

[0014] As the transition metal element constituting the organic transition metal compound or the transition metal-supported oxide, it is preferable that the transition metal element is one or more elements selected from the group consisting of nickel, cobalt, and iron. In addition, as the organic transition metal compound, it is preferable to use one or more selected from the group consisting of ferrocene, nickelocene, cobaltocene, nickel formate, iron acetate, nickel acetate, cobalt acetate, iron oxalate, nickel oxalate, cobalt oxalate, nickel citrate, iron citrate, nickel naphthenate, nickel phthalocyanine, cobalt phthalocyanine, nickel acetylacetonate, cobalt acetylacetonate, iron acetylacetonate, nickel carbonyl, cobalt carbonyl, iron carbonyl, bis(triphenylphosphine)dicarbonylnickel, and dibromobis(triphenylphosphine)nickel.

[0015] In addition, it is preferable to further include a step of heat-treating the reaction product obtained in the above step at a temperature in the range of 400 to 2800°C. A more preferable temperature range for the heat treatment is 600 to 2200°C. The above heat treatment is preferably performed in a gas atmosphere composed of one or more selected from argon gas, helium gas, and nitrogen gas.

[0016] The nanocarbon material obtained by the production method of the present invention preferably has a unit shape observed under an electron microscope that is any one of spherical particles, fibrous, tubular, and flaky. In a material having such a shape, the diameter of the unit is preferably in the range of 2 nm to 400 nm. The nanocarbon material obtained by the production method of the present invention is preferably an aggregate in which carbon units having a fine structure with an average diameter of 2 nm to 400 nm are aggregated in a transmission electron microscope observation. In addition, the length of the unit of the nanocarbon material obtained by the production method of the present invention is preferably in the range of 100 nm to 10,000 nm. Furthermore, the nanocarbon material obtained in the present invention may have a transition metal element inside or at the tip. Specifically, it may have any one of a transition metal, a transition metal oxide, and a transition metal carbide. In addition, the nanocarbon, which is the reaction product obtained in the above step, may have a purification step of collecting it by the magnetic force of a permanent magnet or an electromagnet to increase the purity.

[0017] It is also preferable to have a step of recovering at least one or more substances selected from the group consisting of water, hydrogen, carbon dioxide, carbon monoxide, hydrocarbons, chlorine gas, and hydrogen chloride generated in the manufacturing process by a cooling and / or membrane separation method.

Advantages of the Invention

[0018] The present invention can provide a method for producing nanocarbon using various plastics as raw materials. Further, by the production method of the present invention, since various plastics (waste plastics) discharged as industrial waste can be converted into high-value-added nanocarbon materials, it is possible to indirectly reduce the discharge of waste plastics into the environment, suppress marine pollution, etc., and contribute to the conservation of the global environment.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described in detail. The method for producing a nanocarbon material of the present invention is characterized by including a step of adding an organic transition metal compound or a transition metal-supported oxide and a medium to various plastic materials as raw materials, and reacting them at a temperature in the range of 350 to 800 ° C and a pressure in the range of 2 MPa to 50 MPa. The plastic materials include one or more polymers selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride, but are not limited to the above polymers. In addition, in the method for producing nanocarbon of the present invention, it is preferable to bring the solubility parameter value of the medium close to the solubility parameter value of the polymer. In other words, it is preferable to select a medium so as to match the solubility parameter value of the polymer. The polymer melts at the reaction temperature of 350 ° C or higher, and by selecting a medium close to the solubility parameter value of the polymer, the medium and the polymer can be mixed uniformly, and a nanocarbon material is synthesized using an organic transition metal compound or a transition metal-supported oxide as a catalyst. The polymer already has a long carbon-carbon bond, and carbonization proceeds by high-temperature baking under an inert gas, but at the same time, hydrocarbons, carbon dioxide, and water are also generated, and it is not easy to produce a nanocarbon material having a structure such as a graphene structure. Using the production method of the present invention, the above polymer can be converted into a nanocarbon material by reacting it with a catalyst and a medium under high temperature and pressure conditions.

[0020] The shape of the raw material of the plastic is preferably in the form of a lump, flake, pellet or powder, and from the viewpoint of ease of handling, flake or pellet form is more preferable.

[0021] The medium is preferably one or more substances selected from the group consisting of carbon dioxide, water, hydrocarbons, ethers, esters, ketones, and alcohols. Carbon dioxide becomes a supercritical fluid with high fluidity at low temperatures and has a wide range of solubility parameter values by selecting the mixing ratio with polar solvents. Water is non-toxic, non-flammable, thermodynamically stable, and can decompose various polymers in the supercritical fluid state. Hydrocarbons, ethers, and ketones can be solvents that dissolve polymers. Hydrocarbons themselves can react on catalysts to form nanocarbon materials. Alcohols can be raw materials for nanocarbon materials, and having oxygen atoms in the molecule can help control the growth reaction of nanocarbon materials and form a preferred molecular structure. Ethers and ketones also have oxygen atoms in the molecule and can, like alcohols, help control the growth reaction of nanocarbon materials and form a preferred molecular structure.

[0022] The hydrocarbon is preferably one or more hydrocarbon compounds selected from the group consisting of methane, ethane, ethylene, propane, propylene, butane, butene, pentane, pentene, pentadiene, hexane, cyclohexane, hexene, heptane, heptene, octane, octene, nonane, nonene, decane, decene, toluene, and xylene.

[0023] The alcohol is preferably one or more alcohols selected from ethanol, propanol, butanol, pentanol, hexanol, and dodecanol.

[0024] In addition, it is preferable to select the type of medium or the mixing ratio with various media that has a high yield of nanocarbon materials according to the material of various plastic materials or the mixing ratio of various plastic materials. By using a medium obtained by mixing different media, the solubility parameter can be adjusted, various polymers are more likely to dissolve in the medium, and chemical reactions are more likely to occur.

[0025] Under high temperature and high pressure within the range of 350 to 800 °C and pressure within the range of 2 MPa to 50 MPa, it is preferable that at least one of the media exists as a supercritical fluid or a subcritical fluid. The higher the treatment temperature, the easier it is for the crystal structure of nanocarbon to develop and the crystallinity to increase. In order to promote the growth of nanocarbon by catalytic reaction, the temperature condition is more preferably 375 °C or higher, and even more preferably 450 °C or higher. Also, in order to enhance the crystallinity of the nanocarbon material, 600 °C or higher, and further 800 °C is preferable. By increasing the temperature, the polymer melts and its fluidity increases. By increasing the pressure, it becomes easier for the medium to penetrate into the polymer and dissolution becomes easier. Furthermore, with an increase in temperature and pressure, the viscosity of the liquid decreases.

[0026] Moreover, one or more polycyclic aromatic hydrocarbons selected from the group consisting of naphthalene, phenanthrene, anthracene, pyrene, triphenylene, tetracene, pentacene, benzopyrene, glycerin, coronene, ovalene may be added to the medium. The addition of the above polycyclic aromatic hydrocarbons facilitates the formation of a graphene structure. It is also preferable to add one or more inert gases selected from argon gas, helium gas, and nitrogen gas to the reaction system.

[0027] The transition metal element constituting the organic transition metal compound or the transition metal-supported oxide is preferably one or more elements selected from the group consisting of nickel, cobalt, and iron. In addition, examples of the organotransition metal compound include ferrocene, nickelocene, cobaltocene, nickel formate, iron acetate, nickel acetate, cobalt acetate, iron oxalate, nickel oxalate, cobalt oxalate, nickel citrate, iron citrate, nickel naphthenate, nickel phthalocyanine, cobalt phthalocyanine, nickel acetylacetonate, cobalt acetylacetonate, iron acetylacetonate, nickel carbonyl, cobalt carbonyl, iron carbonyl, bis(triphenylphosphine)dicarbonylnickel, and dibromobis(triphenylphosphine)nickel. The above organotransition metal compounds may be used in combination and are selected according to the plastic material and medium of the polymer used as the raw material. Since the above organotransition metal compound contains an organic structure in its molecular structure, its compatibility with the polymer increases, and the catalytic reaction is likely to occur. Examples of the carrier of the transition metal-supported oxide include silica, alumina, zeolite, activated carbon, and titania. In the transition metal-supported oxide, transition metal elements are uniformly dispersed on the surface of the carrier with a high specific surface area, and the catalytic efficiency of the transition metal elements is increased with a small amount of transition metal.

[0028] It is preferable that the method further includes a step of heat-treating the nanocarbon material, which is the reaction product obtained in the above step, at a temperature in the range of 400 to 2,800 °C. A more preferable temperature range for the heat treatment is 600 to 2,200 °C. The above heat treatment is preferably performed in a gas atmosphere composed of one or more selected from argon gas, helium gas, and nitrogen gas. By performing the heat treatment at a high temperature, the purity of the nanocarbon material can be increased, and the crystallinity can also be increased.

[0029] The nanocarbon material obtained by the production method of the present invention preferably has a unit shape observed under an electron microscope that is any of spherical particles, fibrous, tubular, or flaky. In such a shaped material, the diameter of the unit is preferably in the range of 2 nm to 400 nm. The nanocarbon material obtained by the production method of the present invention is preferably an aggregate in which carbon units having a fine structure with an average diameter of 2 nm to 400 nm are aggregated in a transmission electron microscope observation. Also, the length of the unit of the nanocarbon material obtained by the production method of the present invention is preferably in the range of 100 nm to 10,000 nm. Furthermore, the nanocarbon material obtained in the present invention may have a transition metal element inside or at the tip. Specifically, it may have any of a transition metal, a transition metal oxide, or a transition metal carbide. Note that the nanocarbon, which is the reaction product obtained in the above step, may have a purification step of collecting it by the magnetic force of a permanent magnet or an electromagnet to increase the purity.

[0030] Also, it is also preferable to have a step of recovering at least one or more substances selected from the group consisting of water, hydrogen, carbon dioxide, carbon monoxide, hydrocarbons, chlorine gas, and hydrogen chloride generated in the production process by a cooling and / or membrane separation method. The shape of the nanocarbon material formed by the production method of the present invention can be observed by electron microscope observation, and its crystallinity, etc. can be observed by X-ray diffraction, transmission electron microscope observation, and Raman spectroscopic analysis.

[0031] As an example of the production of nanocarbon using the production method of the present invention, it is carried out according to the following procedure. Insert the raw material plastic and a catalyst of an organic transition metal compound or a transition metal-supported oxide into a corrosion-resistant and pressure-resistant high-temperature and high-pressure reaction vessel, evacuate, and then introduce the medium. Next, raise the temperature to a predetermined reaction temperature, react for a predetermined time, cool to room temperature or lower, and then take out the reaction product. Note that when the pressure inside the reaction vessel after cooling is high, discharge the gas and then take out the reaction product. Furthermore, depending on the purity or use of the above reaction product, a washing treatment and further heat treatment are performed.

Example

[0032] Hereinafter, the present invention will be described in detail based on examples. Note that the present invention is not limited to these examples.

[0033] 〈Example 1〉 Into a pressure-resistant container made of Hastelloy (registered trademark: Ni-Mo alloy), flaky polyethylene as a raw material of the carbon source, cyclohexane as medium 1, dry ice (carbon dioxide) as medium 2, and nickel-supported silica as a catalyst are put in a mass ratio of 20:30:70:1 respectively, mixed, sealed, and reacted at a temperature of 450 °C for 6 hours to obtain a carbon material. Here, it is also possible to supply carbon dioxide from the outside into the reaction vessel by using a high-pressure cylinder of carbon dioxide instead of dry ice. The adjustment of the reaction pressure is carried out by discharging this carbon dioxide gas out of the reaction vessel by utilizing the fact that dry ice vaporizes into carbon dioxide gas. Specifically, in advance, the relationship between the pressure before heating of the reaction vessel and the pressure increase accompanying the temperature rise of the reaction vessel, that is, the temperature-pressure curve, is measured, and the carbon dioxide gas is discharged out of the reaction vessel before heating so as to obtain the desired pressure at a predetermined temperature, thereby performing the above pressure adjustment. Since this pressure adjustment is carried out at the temperature of dry ice, the vapor pressure of hydrocarbons such as cyclohexane as the raw material is extremely low, and the raw materials discharged out of the reaction vessel can be ignored.

[0034] 〈Example 2〉 Into a pressure-resistant container made of Hastelloy, flaky polypropylene as a raw material of the carbon source, 1-pentene as medium 1, dry ice as medium 2, and nickelocene as a catalyst are put in a mass ratio of 20:30:70:1 respectively, mixed, sealed, and a carbon material is produced by the same operation as in Example 1.

[0035] 〈Example 3〉 Into a pressure-resistant container made of Hastelloy, flaky polystyrene as a raw material of the carbon source, toluene as medium 1, and nickel formate as a catalyst are put in a mass ratio of 20:100:1 respectively, mixed, sealed, and a carbon material is produced by the same operation as in Example 1.

[0036] <Example 4> Into a pressure-resistant container made of Hastelloy, put flaky polyethylene terephthalate as the raw material of the carbon source, n-hexanol as Medium 1, dry ice as Medium 2, and nickel-supported silica as the catalyst at a mass ratio of 20:30:70:1 respectively, mix them, then seal, and produce a carbon material by the same operation as in Example 1.

[0037] <Example 5> Into a pressure-resistant container made of Hastelloy, put flaky polyethylene and polystyrene as the raw material of the carbon source, acetone as Medium 1, dry ice as Medium 2, and cobaltocene as the catalyst at a mass ratio of 10:10:30:70:1 respectively, mix them, then seal, and produce a carbon material by the same operation as in Example 1.

[0038] <Example 6> Into a pressure-resistant container made of Hastelloy, put flaky polyvinyl chloride as the raw material of the carbon source, ion-exchanged water as Medium 1, ethanol as Medium 2, nickel acetate as the catalyst, and dry ice as Medium 3 at a mass ratio of 20:70:20:1:10 respectively, mix them, then seal, and react at a temperature of 600 °C for 2 hours to obtain a carbon material.

[0039] <Example 7> Into a pressure-resistant container made of Hastelloy, put flaky polyethylene as the raw material of the carbon source, n-hexane as Medium 1, and ferrocene as the catalyst at a mass ratio of 20:100:1 respectively, mix them, then seal, and react at a temperature of 800 °C for 1 hour to obtain a carbon material.

[0040] <Example 8> Into a pressure-resistant container made of Hastelloy, put flaky polyethylene terephthalate as the raw material of the carbon source, 1-butanol as Medium 1, and nickel-supported silica as the catalyst at a mass ratio of 20:100:1 respectively, mix them, then seal, and react at a temperature of 800 °C for 1 hour to obtain a carbon material.

[0041] <Example 9> Into a Hastelloy pressure vessel, add flaky polystyrene as the raw material of the carbon source, ethanol as medium 1, dry ice as medium 2, and iron-cobalt supported zeolite as the catalyst, each in a mass ratio of 20 to 30 to 70 to 1, and mix them. Then, seal the vessel and react at a temperature of 800 °C for 1 hour to obtain a carbon material.

[0042] <Example 10> A carbon material is obtained by performing the same operations as in Example 1, except that the reaction temperature is set to 350 °C.

[0043] <Example 11> A carbon material is obtained by performing the same operations as in Example 1, except that the reaction temperature is set to 375 °C.

[0044] <Example 12> A part of the carbon material obtained in Example 1 is heat-treated at 1500 °C for 2 hours in an argon gas stream to prepare a carbon material.

[0045] <Comparative Example 1> In Example 1, perform the same operations as in Example 1 without adding the polymer material to obtain a carbon material.

[0046] <Comparative Example 2> In Example 2, perform the same operations as in Example 2 without adding the polymer material to obtain a carbon material.

[0047] <Comparative Example 3> In Example 3, perform the same operations as in Example 3 without adding the polymer material to obtain a carbon material.

[0048] <Comparative Example 4> In Example 4, perform the same operations as in Example 4 without adding the polymer material to obtain a carbon material.

[0049] <Comparative Example 5> In Example 5, perform the same operations as in Example 5 without adding the polymer material to obtain a carbon material.

[0050] <Comparative Example 6> In Example 6, the same operations as in Example 6 are performed without adding a polymer material to obtain a carbon material.

[0051] <Comparative Example 7> In Example 7, the same operations as in Example 7 are performed without adding a polymer material to obtain a carbon material.

[0052] <Comparative Example 8> In Example 8, the same operations as in Example 8 are performed without adding a polymer material to obtain a carbon material.

[0053] <Comparative Example 9> In Example 9, the same operations as in Example 9 are performed without adding a polymer material to obtain a carbon material.

[0054] <Comparative Example 10> A carbon material is obtained by the same operations as in Example 1, except that the reaction temperature is 300 °C in Example 1.

[0055] <Comparative Example 11> In Example 9, without adding a polymer material, ethanol is used as Medium 1, dry ice is used as Medium 2, and iron-cobalt supported zeolite is used as a catalyst. After mixing them in a mass ratio of 50:70:1 respectively, it is sealed and reacted at a temperature of 800 °C for 1 hour to obtain a carbon material.

[0056] Note that the pressure under the temperature conditions of the above Examples 1 to 11 and Comparative Examples 1 to 10 is within the range of 2 to 50 MPa.

[0057] [Evaluation of Products] The carbon materials obtained in the above Examples and Comparative Examples are evaluated in terms of yield, shape by electron microscope observation, peak position and half-width of the X-ray diffraction chart, and peak position and intensity of the Raman spectrum.

[0058] When comparing the yields of the obtained carbon materials between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, Example 5 and Comparative Example 5, Example 6 and Comparative Example 6, Example 7 and Comparative Example 7, Example 8 and Comparative Example 8, Example 9 and Comparative Example 9, Example 9 and Comparative Example 11, the yields of the carbon materials obtained in the examples using the polymer material as the carbon raw material are all larger than those in the comparative examples. Also, as in Example 5, it is possible to produce carbon materials even when different types of polymers are mixed.

[0059] In the scanning electron microscope observation of the carbon materials obtained in each example, innumerable substantially uniform fibrous nanocarbons with a diameter of about 10 to 100 nm and a length of about 200 to 1000 nm are observed. Also, in the transmission electron microscope observation of the carbon materials obtained in Examples 7, 8, and 9 obtained by treatment at 800 °C, multi-walled carbon nanotubes are observed.

[0060] In the X-ray diffraction analysis using the characteristic X-ray of CuKα for diffraction, an observation peak derived from carbon at 2θ = 25.5 to 26.5° is observed in the carbon materials obtained in the examples and comparative examples. For the carbon materials of Example 1 and Example 12, in the X-ray diffraction analysis, the half-value width of the observation peak derived from carbon is slightly narrower for Example 12. For the carbon materials of each example obtained by heat treatment at 450 °C and 800 °C, the heat treatment at 800 °C results in a sharper peak with a narrower half-value width of the observation peak derived from carbon in the X-ray diffraction chart, indicating higher crystallinity.

[0061] In the Raman spectrum obtained by Raman spectroscopic measurement of the carbon material, the peak around 1580 cm 2 (derived from the graphene structure (sp -1 bond)) (hereinafter abbreviated as the G band) and the peak at 1360 cm -1 known as a band caused by structural disorder and defects (hereinafter abbreviated as the D band), the R value of the peak intensity of the D band with respect to the G band (I 1360 / I 1580) is known to increase the structural disorder as it becomes larger. The R value of the carbon material prepared at 800 °C in the above Examples and Comparative Examples is smaller than that of the carbon material prepared at 450 °C and has a structure with a developed graphene structure.

[0062] As described above, in the manufacturing method of the present invention, it can be seen that polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride, which are discarded as industrial waste, can also be used as raw materials to produce nanocarbon materials. Further, unlike the case of plastic recycling, in the manufacturing method of the present invention, even plastics with mixed polymer species can be used as raw materials for manufacturing carbon materials without separating the polymer species of the plastics.

Industrial Applicability

[0063] As described above, according to the present invention, it is possible to provide a method for manufacturing a carbon nanomaterial using inexpensive waste plastic as a raw material.

Claims

1. A method for producing a nanocarbon material, comprising a step of adding an organotransition metal compound or a transition metal-supported oxide and a medium having a solubility parameter value in the vicinity of the solubility parameter value of the polymer to one or more polymers selected from the group consisting of polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and polyvinyl chloride as raw materials, and reacting them at a temperature in the range of 350 to 800 ° C and a pressure in the range of 2 MPa to 50 MPa.

2. The method for producing a nanocarbon material according to claim 1, wherein one or more substances are selected from the group consisting of carbon dioxide, water, hydrocarbons, ethers, esters, ketones, and alcohols as the medium, and the solubility parameter value of the medium is brought close to the solubility parameter value of the polymer.

3. The method for producing a nanocarbon material according to claim 2, wherein the hydrocarbon is one or more compounds selected from the group consisting of methane, ethane, ethylene, propane, propylene, butane, butene, pentane, pentene, pentadiene, hexane, cyclohexane, hexene, heptane, heptene, octane, octene, nonane, nonene, decane, decene, toluene, and xylene.

4. The method for producing a nanocarbon material according to claim 2, wherein the alcohol is one or more alcohols selected from ethanol, propanol, butanol, pentanol, hexanol, and dodecanol.

5. The method for producing a nanocarbon material according to claim 1, wherein the transition metal element constituting the organotransition metal compound or the transition metal-supported oxide is one or more elements selected from the group consisting of nickel, cobalt, and iron.

6. The method for producing a nanocarbon material according to claim 1, characterized in that one or more selected from the group consisting of ferrocene, nickelocene, cobaltocene, nickel formate, iron acetate, nickel acetate, cobalt acetate, iron oxalate, nickel oxalate, cobalt oxalate, nickel citrate, iron citrate, nickel naphthenate, nickel phthalocyanine, cobalt phthalocyanine, nickel acetylacetonate, cobalt acetylacetonate, iron acetylacetonate, nickel carbonyl, cobalt carbonyl, iron carbonyl, bis(triphenylphosphine)dicarbonylnickel, and dibromobis(triphenylphosphine)nickel are used as the organic transition metal compound.

7. The method for producing a nanocarbon material according to claim 1, characterized in that the diameter of the unit constituting the obtained nanocarbon material is in the range of 2 nm to 400 nm.

8. The method for producing a nanocarbon material according to claim 1, characterized in that the length of the unit of the obtained nanocarbon material is in the range of 100 nm to 10,000 nm.