Method for purifying carbon byproduct and carbon material manufactured using the same

Abstract

The present invention relates to a method for purifying carbon by-products and a carbon material produced using the same. In one embodiment, the method for purifying carbon by-products comprises: a step of physically exfoliating a carbon by-product containing a metal by applying shear stress; a step of producing a functionalized carbon by-product by acid treatment of the exfoliated carbon by-product; and a step of producing an expanded product by heat treatment of the functionalized carbon by-product.

Description

Technology Field

[0001] The present invention relates to a method for purifying carbon by-products and a carbon material produced using the same. More specifically, the present invention relates to a method for purifying carbon by-products generated during the decomposition of hydrocarbon compounds and a carbon material produced using the same. Background Technology

[0003] Carbon byproducts take on a large spherical shape of 200–300 µm as a result of fluidization reactions. In addition to metal catalyst components, various types of impurities are formed, such as carbon nanotubes, graphite phases, and amorphous carbon. If metal components used as catalysts are present in the carbon byproducts, they reduce thermal stability during industrial applications and cause performance degradation issues regarding mechanical strength, thermal conductivity, and electrical conductivity. Therefore, to manufacture high-value-added carbon materials, it is necessary to purify catalyst particles, which are metal impurities, and to develop a method for producing high-purity carbon.

[0004] Among the methods for removing metal components used as catalysts and impure carbon particles, chemical synthesis is known to be the most realistic and simple method, as it allows for mass production and the use of a solution process. Chemical synthesis involves preparing hydrophilic graphite oxide using a strong oxidizing agent, followed by long-term stirring or ultrasonic grinding to produce graphene oxide (graphene oxide) in which hydroxyl groups (-OH) and epoxy groups (COC) are bonded to the surface and carboxyl groups (-COOH) are bonded to the edges, and then reducing it again to produce reduced graphene oxide from which functional groups including hydroxyl groups have been removed.

[0005] However, such conventional chemical synthesis methods have a problem in that significant defects exist because the surface graphite structure of the finally produced reduced graphene oxide is partially restored, making it difficult to expect the inherent properties of graphene. Additionally, they have the disadvantage of easily aggregating without a dispersant. Therefore, this is why a purification method is needed to produce high-purity carbon materials with stable dispersibility that minimizes defects while utilizing chemical synthesis.

[0006] The background technology related to the present invention is disclosed in Korean Registered Patent Publication No. 10-2483223 (published Jan. 02, 2023; Title of Invention: Method for Manufacturing Graphene Oxide Based on Chemical Exfoliation Method). The problem to be solved

[0008] One objective of the present invention is to provide a method for purifying carbon by-products that enables the production of high-quality carbon materials by minimizing defects in graphene and having excellent graphene exfoliation efficiency.

[0009] Another objective of the present invention is to provide a method for purifying carbon byproducts that facilitates the removal of metal catalyst components, has a low specific surface area, and excellent electrical conductivity.

[0010] Another objective of the present invention is to provide a carbon byproduct purification method that prevents environmental pollution and offers excellent eco-friendliness by recycling carbon byproducts discarded in the hydrogen production process.

[0011] Another objective of the present invention is to provide a method for purifying carbon byproducts that has excellent compatibility with organic materials such as polymers.

[0012] Another objective of the present invention is to provide a method for purifying carbon by-products that offers excellent productivity and economic efficiency.

[0013] Another objective of the present invention is to provide a carbon material produced from the carbon byproduct purification method described above. means of solving the problem

[0015] One aspect of the present invention relates to a method for purifying carbon by-products. In one embodiment, the method for purifying carbon by-products comprises the steps of: applying shear stress to a carbon by-product containing a metal to physically exfoliate it; acid-treating the exfoliated carbon by-product to produce a functionalized carbon by-product; and heat-treating the functionalized carbon by-product to produce an expanded product.

[0016] In one embodiment, the carbon byproduct may be generated in a hydrocarbon cracking process for hydrogen production.

[0017] In one embodiment, the metal may include one or more of iron (Fe), nickel (Ni) and silicon (Si).

[0018] In one embodiment, the physical peeling may utilize one or more of a ball mill and high-pressure dispersion.

[0019] In one embodiment, the physical peeling can be carried out by introducing the dispersion solution containing the carbon byproduct into the inlet of a high-pressure homogenizer while applying a pressure of 100 to 3000 bar and passing it through a flow path.

[0020] In one embodiment, the acid treatment may include the step of introducing the exfoliated carbon byproduct into an acid solution and preparing a reaction product; and the step of washing the reaction product to adjust the pH and drying it.

[0021] In one embodiment, the acid solution comprises an acid and an oxidizing agent, and the acid solution comprises one or more of sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl), and the oxidizing agent may comprise one or more of hydrogen peroxide (H2O2), permanganate (KMnO4), chromic acid (H2CrO4), lead dioxide (PbO2), manganese dioxide (MnO2), copper oxide (Cu2O), and hypochlorous acid (HClO).

[0022] In one embodiment, the step of acid-treating the exfoliated carbon byproduct can be repeated two or more times.

[0023] In one embodiment, the functionalized carbon byproduct may have oxygen-containing functional groups formed on one or more of the surface and edges of the exfoliated carbon byproduct.

[0024] In one embodiment, the heat treatment can be performed on the functionalized carbon byproduct at 800 to 5000°C in an inert gas atmosphere.

[0025] In one embodiment, the heat treatment may be performed using one or more of an electric furnace, plasma, microwave, and radio waves.

[0026] Another aspect of the present invention relates to a carbon material produced by the carbon byproduct purification method described above. In one embodiment, the carbon material comprises carbon (C) and oxygen (O) and has a specific surface area (BET) of 70 m² 2 It may be less than / g and have an electrical conductivity of 500 S / cm or more.

[0027] In one embodiment, the carbon material may contain 90 atomic percent or more and less than 100 atomic percent of carbon (C) and more than 0 atomic percent and less than 10 atomic percent of oxygen (O). Effects of the invention

[0029] The carbon byproduct purification method according to the present invention and the carbon material produced thereby have excellent graphene exfoliation efficiency, enable the production of high-quality carbon materials by minimizing defects in graphene, facilitate the removal of metal catalyst components, have a low specific surface area and excellent electrical conductivity, prevent environmental pollution by recycling carbon byproducts discarded in the hydrogen production process, and possess excellent eco-friendliness, productivity, and economic efficiency. Brief explanation of the drawing

[0031] FIG. 1 illustrates a method for purifying carbon by-products according to one embodiment of the present invention. Figure 2(a) is a carbon byproduct of the example, and Figure 2(b) is a scanning electron microscope (SEM) image of the carbon material of the example. Specific details for implementing the invention

[0032] In describing the present invention, if it is determined that a detailed description of related known technologies or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0033] Furthermore, the terms described below are defined in consideration of their functions in the present invention; since these may vary depending on the intentions or practices of the user or operator, their definitions should be based on the content throughout this specification describing the present invention.

[0035] The technical problem that the present invention aims to solve is to provide a method for purifying high-purity carbon nanomaterials with high yield by removing metal catalysts and impure carbon while using a chemical synthesis method from the composition of carbon byproducts.

[0036] The high-purity purification method of carbon byproducts according to the present invention utilizes a rapid heat treatment method, which allows for efficient exfoliation due to a higher expansion rate compared to conventional chemical exfoliation methods. Furthermore, it is possible to manufacture carbon nanomaterials with relatively fewer defects and improved conductivity, and it is evident that compatibility with organic materials such as polymers is enhanced. Additionally, since it provides a simple and economical manufacturing process, high-quality carbon nanomaterials can be mass-produced at a low cost.

[0038] Carbon byproduct purification method

[0039] One aspect of the present invention relates to a method for purifying carbon by-products. FIG. 1 illustrates a method for purifying carbon by-products according to one embodiment of the present invention. Referring to FIG. 1, the method for purifying carbon by-products comprises (S10) a physical exfoliation step; (S20) an acid treatment step; and (S30) a heat treatment step.

[0040] More specifically, the carbon byproduct purification method comprises: (S10) a step of physically exfoliating a carbon byproduct containing metal by applying shear stress; (S20) a step of producing a functionalized carbon byproduct by acid treating the exfoliated carbon byproduct; and (S30) a step of producing an expanded product by heat treating the functionalized carbon byproduct.

[0041] Below, the above-mentioned carbon byproduct purification method will be explained in detail step by step.

[0043] (S10) Physical peeling step

[0044] The above step is a step of physically peeling off carbon by-products containing metal by applying shear stress.

[0045] In one embodiment, the carbon byproduct may be generated from a hydrocarbon decomposition process for hydrogen production. For example, the carbon byproduct may be a byproduct containing various carbon compounds generated from the thermal decomposition process of methane.

[0046] The above step allows for obtaining physically exfoliated carbon by-products by performing mechanical exfoliation and crushing using a device that applies high pressure to microchannels with a micrometer-scale diameter in a state where carbon by-products are dispersed in a liquid phase (dispersion solution) and applies a strong shear force to the material passing through them.

[0047] In one embodiment, the metal may include one or more of iron (Fe), nickel (Ni) and silicon (Si).

[0048] In one embodiment, the physical peeling may utilize one or more of a ball mill and high-pressure dispersion. For example, physical peeling may be performed using a homogenizer or a high-pressure homogenizer.

[0049] In one embodiment, the carbon byproduct may be applied in the form of a dispersion solution. The dispersion solution may include the carbon byproduct and a solvent.

[0050] In one embodiment, the solvent may include one or more of water and alcohol-based solvents. When the solvent is included, the miscibility and dispersibility may be excellent. For example, the alcohol-based solvent may include one or more of methanol, ethanol, isopropanol, and butanol.

[0051] For example, the dispersion solution may contain 0.1 to 20 weight% of carbon byproduct and 80 to 99.9 weight% of solvent. Under these conditions, the mixability and dispersibility are excellent, and physical peeling may be easy.

[0052] In one embodiment, the physical peeling can be carried out by introducing the dispersion solution containing the carbon byproduct into the inlet of a high-pressure homogenizer while applying a pressure of 100 to 3000 bar and passing it through a flow path.

[0053] In one embodiment, the inlet of the high-pressure homogenizer may have a flow path with a diameter of micrometers. When a dispersion solution is passed through the above diameter and high pressure is applied, a strong shear force is generated, which facilitates physical peeling and minimizes defects in the carbon material while providing excellent electrical conductivity. For example, the diameter of the above flow path may be 10 to 300 μm.

[0054] In one embodiment, the step of drying the exfoliated carbon byproduct after the physical exfoliation may be further included. The drying may be performed at 80°C or higher.

[0056] (S20) Acid treatment step

[0057] The above step is a step of producing a functionalized carbon byproduct by acid treating the exfoliated carbon byproduct.

[0058] In one embodiment, the acid treatment may include the step of introducing the exfoliated carbon byproduct into an acid solution and preparing a reaction product; and the step of washing the reaction product to adjust the pH and drying it.

[0059] In one embodiment, the acid solution comprises an acid and an oxidizing agent, and the acid solution comprises one or more of sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl), and the oxidizing agent may comprise one or more of hydrogen peroxide (H2O2), permanganate (KMnO4), chromic acid (H2CrO4), lead dioxide (PbO2), manganese dioxide (MnO2), copper oxide (Cu2O), and hypochlorous acid (HClO).

[0060] For example, the above acid solution may include sulfuric acid and hydrogen peroxide. Under the above conditions, functionalized carbon byproducts can be easily prepared, and metal components can be easily removed from the carbon byproducts during heat treatment to produce high-quality carbon materials.

[0061] For example, the acid solution may contain hydrogen peroxide and sulfuric acid in a volume ratio of 1:2 to 1:8. Under these conditions, functionalized carbon byproducts can be easily produced, and metallic components can be easily removed from the carbon byproducts during heat treatment to produce high-quality carbon materials. For example, the acid solution may contain hydrogen peroxide and sulfuric acid in a volume ratio of 1:4 to 1:6.

[0062] For example, the above-mentioned exfoliated carbon byproduct can be introduced into an acidic solution and reacted for 1 to 24 hours to produce a reaction product.

[0063] For example, the pH of the above reaction product can be adjusted to neutral when washed with water. For example, the pH of the above reaction product can be adjusted to 6.5 to 7.5 when washed with water.

[0064] For example, the washed reaction product can be dried at 60 to 120°C. Under these conditions, the occurrence of defects during heat treatment is prevented, and the expansion product can be easily manufactured. The drying can be performed at 60 to 120°C for 1 to 24 hours.

[0065] In one embodiment, the step of acid-treating the exfoliated carbon byproduct can be repeated two or more times.

[0066] In one embodiment, the functionalized carbon byproduct may have oxygen-containing functional groups formed on one or more of the surface and edges of the exfoliated carbon byproduct.

[0067] The above functionalization may mean forming functional groups containing one or more oxygen groups among hydroxyl groups (-OH) and carboxyl groups (-COOH) on one or more of the surface and edges of the exfoliated carbon byproduct.

[0068] For example, when a stripped carbon byproduct is reacted with an acidic solution, oxygen-containing functional groups (e.g., -OH and -COOH, etc.) may be formed on one or more of the surface and edges of the stripped byproduct.

[0069] Since the above functional groups are formed from the edges of the exfoliated carbon byproduct where there are relatively many defects, the degree of functionalization of the expanded graphite can be controlled according to the concentration of the acid solution, reaction temperature, and reaction time, and in particular, it is possible to functionalize only the edges of the carbon.

[0071] (S30) Heat treatment step

[0072] The above step is a step of manufacturing an expansion product by heat-treating the functionalized carbon byproduct.

[0073] The above functionalized carbon byproduct is in a state where sulfur or nitrogen compounds are injected between the carbon layers, and when the above functionalized carbon byproduct is subjected to high-temperature heat treatment, the layers can separate and expand like an accordion.

[0074] In one embodiment, the heat treatment can be performed on the functionalized carbon byproduct in an inert gas atmosphere at 800 to 5000°C. Under these conditions, an expansion product is easily formed, defects in the carbon material are minimized, and electrical conductivity can be excellent. For example, the heat treatment can be performed at 4000 to 5000°C.

[0075] In one embodiment, the inert gas may include one or more of nitrogen, argon, and helium. Under these conditions, an expansion material can be easily formed.

[0076] In one embodiment, the heat treatment may be performed using one or more of an electric furnace, plasma, microwave, and radio waves.

[0077] The expansion material produced by the above manufacturing method can have improved exfoliation levels and conductivity characteristics compared to conventional carbon by-products. The expansion material (carbon material) has improved compatibility with organic materials such as polymers, allowing it to be applied in various applications.

[0079] Carbon material produced by a carbon byproduct purification method

[0080] Another aspect of the present invention relates to a carbon material produced by the carbon byproduct purification method described above. In one embodiment, the carbon material comprises carbon (C) and oxygen (O) and has a specific surface area (BET) of 70 m² 2 It may be less than / g and have an electrical conductivity of 500 S / cm or more. Under the above specific surface area and electrical conductivity conditions, the mechanical strength and electrical conductivity of the carbon material may be excellent. For example, the carbon material has a specific surface area (BET) of 10 to 70 m² 2 / g and electrical conductivity can be 500~800 S / cm.

[0081] In one embodiment, the carbon material may contain 90 atomic percent or more and less than 100 atomic percent of carbon (C) and more than 0 atomic percent and less than 10 atomic percent of oxygen (O). For example, the carbon material may contain 99 atomic percent or more and less than 100 atomic percent of carbon (C) and more than 0 atomic percent and less than 1 atomic percent of oxygen (O).

[0082] The above carbon material may not contain metal. For example, the metal may include one or more of iron (Fe), nickel (Ne), and silicon (Si). Under the above conditions, the added value of the carbon material may be excellent.

[0084] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments. However, these are presented as preferred examples of the present invention and should not be interpreted in any way as limiting the present invention. Details not described herein can be sufficiently technically inferred by those skilled in the art, so such descriptions will be omitted.

[0086] Examples and Comparative Examples

[0087] Examples

[0088] (1) A dispersion solution containing a metal-containing carbon byproduct (2% (w / v)) and ethanol was prepared during the thermal decomposition of a hydrocarbon (methane) for hydrogen production, and the solution was dispersed using a homogenizer for at least 1 hour. Then, the dispersion solution was introduced into the inlet of a high-pressure homogenizer while applying a pressure of 1000 bar or more, and physically separated carbon byproducts were obtained by passing through the flow path. The carbon byproducts were dried at 80°C or higher to completely remove the ethanol.

[0089] (2) The exfoliated carbon byproduct was added to an acid solution containing sulfuric acid and hydrogen peroxide in a 5:1 volume ratio and stirred at room temperature for more than 3 hours to produce a functionalized carbon byproduct. Then, the functionalized carbon byproduct was washed and filtered repeatedly until the pH became neutral, and dried in an oven at 100°C for 12 hours to obtain a functionalized carbon byproduct in powder form.

[0090] (3) Next, the above functionalized carbon byproduct was heat-treated at 4000°C using a plasma device to produce a carbon material (expanded material).

[0092] Comparative Example 1

[0093] A carbon material (functionalized carbon byproduct powder) was prepared using the same method as in the above example, except that the above functionalized carbon byproduct was not heat-treated with a plasma device.

[0095] Comparative Example 2

[0096] A carbon byproduct was added to an acid solution containing sulfuric acid and hydrogen peroxide in a 5:1 volume ratio and acid-treated by stirring at room temperature for more than 3 hours to produce a functionalized carbon byproduct. Then, the functionalized carbon byproduct was washed and filtered repeatedly until the pH became neutral, and dried in an oven at 100°C for 12 hours to obtain a functionalized carbon byproduct in powder form.

[0097] Next, the above functionalized carbon byproduct was heat-treated at 4000℃ using plasma equipment to produce an expanded product.

[0098] Next, a dispersion solution containing the above-mentioned expansion agent and ethanol was prepared and dispersed using a homogenizer for at least one hour. Then, the dispersion solution was introduced into the inlet of a high-pressure homogenizer while applying a pressure of 1000 bar or more, passed through a flow path to be physically separated, and then dried at 80°C or higher to completely remove the ethanol to produce a carbon material.

[0099] Figure 2(a) shows the carbon byproduct of the example, and Figure 2(b) shows a scanning electron microscope (SEM) image of the carbon material (expanded material) of the example.

[0101] Experimental Example

[0102] The components of the carbon materials of the above examples and comparative examples 1 and 2, and carbon materials produced by a conventional chemical synthesis method (preparation of carbon materials such as graphene oxide using a strong oxidizing agent from carbon byproducts) were analyzed using energy dispersive X-ray spectroscopy (EDS), and the specific surface area (BET) and powder conductivity were measured, and the results are shown in Table 1 below.

[0103]

[0104] Referring to Table 1 above, it was confirmed that the metal component was removed from the carbon material in the example, and that the specific surface area value and powder conductivity were improved. On the other hand, in the case of the carbon material manufactured through a comparative example deviating from the conditions of the present invention, residual metal component was confirmed, and lower specific surface area and powder conductivity values ​​were confirmed compared to the example.

[0105] As such, the method for purifying carbon byproducts according to the present invention not only effectively removes metal catalysts contained in byproduct carbon generated during the hydrogen production process, but also enables the production of high-quality carbon nanomaterials capable of high value-added production.

[0107] The present invention has been described above with reference to embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the invention.

Claims

Claim 1 A method for purifying carbon by-products, comprising: a step of physically exfoliating a carbon by-product containing metal by applying shear stress; a step of producing a functionalized carbon by-product by acid treating the exfoliated carbon by-product; and a step of producing an expanded product by heat treating the functionalized carbon by-product; wherein the physical exfoliation is performed by introducing a dispersion solution containing the carbon by-product into the inlet of a high-pressure homogenizer while applying a pressure of 100 to 3000 bar and passing it through a flow path. Claim 2 A method for purifying carbon by-products according to claim 1, wherein the carbon by-product is generated in a hydrocarbon cracking process for hydrogen production. Claim 3 A method for purifying carbon byproducts according to claim 1, wherein the metal comprises one or more of iron (Fe), nickel (Ni), and silicon (Si). Claim 4 delete Claim 5 delete Claim 6 A method for purifying carbon by-products according to claim 1, wherein the acid treatment comprises the steps of: introducing the exfoliated carbon by-product into an acid solution and preparing a reaction product; and washing the reaction product with water to adjust the pH and drying it. Claim 7 A method for purifying carbon byproducts according to claim 6, wherein the acid solution comprises an acid and an oxidizing agent, the acid solution comprises one or more of sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl), and the oxidizing agent comprises one or more of hydrogen peroxide (H2O2), permanganate (KMnO4), chromic acid (H2CrO4), lead dioxide (PbO2), manganese dioxide (MnO2), copper oxide (Cu2O), and hypochlorous acid (HClO). Claim 8 A carbon byproduct purification method according to claim 1, wherein the step of acid-treating the exfoliated carbon byproduct is performed two or more times. Claim 9 A carbon byproduct purification method according to claim 1, wherein the functionalized carbon byproduct is formed with an oxygen-containing functional group on one or more of the surface and edges of the exfoliated carbon byproduct. Claim 10 A method for purifying carbon by-products according to claim 1, wherein the heat treatment is performed on the functionalized carbon by-product at 800 to 5000°C in an inert gas atmosphere. Claim 11 A method for purifying carbon by-products according to claim 1, wherein the heat treatment is carried out using one or more of an electric furnace, plasma, microwave, and radio waves. Claim 12 A carbon material produced by the carbon byproduct purification method of any one of paragraphs 1 to 3 and 6 to 11. Claim 13 Contains carbon (C) and oxygen (O), with a specific surface area (BET) of 70 m² 2 Carbon material with a g or less and an electrical conductivity of 500 to 800 S / cm. Claim 14 In paragraph 13, the carbon material comprises 90 atomic% or more and less than 100 atomic% of carbon (C) and more than 0 atomic% and less than 10 atomic% of oxygen (O).

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