Method for producing pitch for carbon material production and naphthalene

Abstract

To provide a method for producing pitch for carbon material production from an ethylene bottom oil and co-producing high value-added naphthalene from the by-produced low-boiling point components.SOLUTION: A method for producing pitch for carbon material production and naphthalene comprises: heat-treating ethylene bottom oil; distilling the resulting heat-treated product, and recovering naphthalene as a high boiling point component from a low boiling point component that is a byproduct of producing pitch for carbon material production.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pitch for producing carbon materials and a method for producing naphthalene. [Background technology]

[0002] Heavy residual oil (ethylene bottom oil), a by-product of the production of olefins such as ethylene and propylene by steam cracking or thermal cracking of petroleum hydrocarbons such as naphtha, is mostly used as fuel, with only a portion being used as a raw material for carbon black. Therefore, converting this ethylene bottom oil into a high-value-added product is a challenge in the art. To address this challenge, attempts have been made to produce pitch for carbon material production from ethylene bottom oil by taking advantage of the characteristics of ethylene bottom oil, which contains a large amount of aromatic compounds. Various methods for producing pitch for carbon material production from ethylene bottom oil have been reported, but one of the most common is a method for producing pitch for carbon material production that includes a step of thermally treating ethylene bottom oil (thermal treatment step) and a step of distilling the heat-treated product obtained in the thermal treatment step to obtain pitch as a high-boiling point component (distillation step) (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 53-60927 [Patent Document 2] Japanese Patent Application Publication No. 49-35420 [Patent Document 3] Japanese Patent Publication No. 51-83622 Summary of the Invention [Problem to be solved by the invention]

[0004] In the methods for producing pitch for carbon material production from ethylene bottom oil, as typified by Patent Documents 1 to 3, the yield of pitch for carbon material production is about 20% by mass to 50% by mass, although it depends on the composition of the raw materials used, the conditions of each step, etc. The remaining low-boiling point components produced as by-products are still low-value-added fractions, but as far as the present inventors know, there have been almost no studies conducted on methods for effectively utilizing these low-boiling point components.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing pitch for carbon material production and naphthalene, which can produce pitch for carbon material production from ethylene bottom oil and simultaneously produce high-value-added naphthalene from the by-produced low-boiling point component. [Means for solving the problem]

[0006] As a result of intensive investigations to achieve the above-mentioned object, the present inventors have obtained the following findings. For the purpose of producing pitch for carbon material production, ethylene bottom oil is heat-treated, and the heat-treated product is distilled to produce pitch for carbon material production as a high-boiling component. The low-boiling component produced as a by-product during this process was analyzed in detail, and it was found that the low-boiling component contains a large amount of naphthalene. Based on this finding, the present inventors have further investigated the production of naphthalene as a chemical product in parallel with the production of pitch for carbon material production from ethylene bottom oil, and as a result have completed the present invention.

[0007] That is, the present invention relates to the following [1] to [5].

[0008] [1] A method for producing pitch and naphthalene for use in producing carbon materials, comprising the steps of: heat-treating petroleum-based heavy oil (step 1); distilling the heat-treated product obtained in step 1 and separating it into pitch, a high-boiling component, and low-boiling components (step 2); and recovering naphthalene from the low-boiling components obtained in step 2 (step 3). [2] The method for producing pitch for carbon material production and naphthalene according to [1], wherein the petroleum heavy oil is at least one selected from the group consisting of ethylene bottom oil and ethylene bottom oil light fraction. [3] The method for producing pitch for carbon material production and naphthalene according to [1] or [2], wherein the naphthalene concentration in the petroleum heavy oil is 5% by mass to 60% by mass. [4] The method for producing pitch for producing carbon materials and naphthalene according to any one of [1] to [3], wherein the heat treatment temperature in step 1 is 360° C. to 480° C., and the heat treatment time is 0.5 hours to 48 hours. [5] The method for producing pitch for producing a carbon material and naphthalene according to any one of [1] to [4], wherein the carbon material is a graphite electrode. [Effects of the Invention]

[0009] According to the present invention, pitch for producing carbon materials and naphthalene can be obtained from petroleum heavy oil. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram showing a petrochemical process for thermally cracking naphtha or the like and a process for producing ethylene bottom oil. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below, but it should be understood that the present invention is not limited to these embodiments and that various applications are possible within the spirit and scope of the present invention.

[0012] In this specification, when "to" is used to describe a range of values, the values ​​at both ends are the upper and lower limits, respectively, and are included in the range.

[0013] A method for producing pitch for producing a carbon material and naphthalene according to one embodiment includes at least the following steps 1 to 3 in this order, and other steps may be added. Process 1 (heat treatment process): Process of heat treating petroleum heavy oil Step 2 (distillation step): The heat-treated product obtained in step 1 is distilled and separated into pitch, which is a high-boiling component, and low-boiling components. Step 3 (naphthalene recovery step): A step of recovering naphthalene from the low boiling point components obtained in step 2

[0014] The naphthalene concentration in the petroleum heavy oil used as the feedstock is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The naphthalene concentration in the petroleum heavy oil used as the feedstock is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. These upper and lower limits can be arbitrarily combined. A preferred range is 5% by mass to 60% by mass, more preferably 10% by mass to 50% by mass, and even more preferably 15% by mass to 40% by mass. If the naphthalene concentration in the petroleum heavy oil is 5% by mass to 60% by mass, then, although this will depend on the heat treatment conditions in step 1 and the distillation conditions in step 2, a low-boiling point component containing naphthalene at a relatively high concentration can be obtained in step 2, allowing naphthalene to be efficiently recovered in step 3. The method for measuring the naphthalene concentration is not particularly limited, and examples thereof include an internal standard method using gas chromatography.

[0015] The petroleum heavy oil used as the feedstock is not particularly limited, but is preferably one that satisfies the above-mentioned naphthalene concentration. Ethylene bottom oil or an ethylene bottom light fraction obtained by separating a desired proportion (e.g., 5% to 70% by mass) of light fractions from ethylene bottom oil by distillation or the like is preferred. At least one selected from the group consisting of ethylene bottom oil and ethylene bottom light fractions may also be added with heavy oils such as fluid catalytic cracking oil (FCC decant oil), atmospheric distillation residue, vacuum distillation residue, various petroleum heavy oils hydrotreated, cracked kerosene, and coal tar. In this case, the amount of heavy oil added is preferably within a range that satisfies the above-mentioned naphthalene concentration. In one embodiment, the petroleum heavy oil is preferably at least one selected from the group consisting of ethylene bottom oil and ethylene bottom light fractions.

[0016] In the petrochemical industry, naphtha and other materials are generally thermally cracked at high temperatures, and the resulting pyrolysis product is then distilled to separate the various fractions into products such as ethylene, propylene, and other olefins, aromatic compounds such as benzene, toluene, and xylene, cracked gasoline, and cracked kerosene. Of these fractions, the heavy fraction with the highest boiling point is called ethylene bottom oil, and is used as a raw material and fuel for carbon black and other products (see Figure 1). Since naphtha and other thermal cracking plants are often called ethylene plants, the aforementioned heavy fraction is called ethylene bottom oil.

[0017] The properties of ethylene bottom oil obtained by thermal cracking of naphtha-containing feedstock vary depending on the type of naphtha-containing feedstock, the thermal cracking conditions, the operating conditions of the refinery distillation column, etc., but the general properties are: 50% distillation temperature of 200°C to 400°C, aromatic carbon content of 50% by mass or more, flash point of 70°C to 100°C, kinematic viscosity at 50°C of 40mm 2 / s or less, and the naphthalene concentration is 5% by mass to 25% by mass. However, since ethylene bottom oil is a mixture of hydrocarbon compounds, the above values ​​may vary slightly.

[0018] (Process 1: Heat treatment process) Step 1 is a step of thermally treating petroleum heavy oil. The thermal treatment is preferably carried out in a sealed container in a non-oxidizing gas atmosphere. Examples of non-oxidizing gases include nitrogen gas, argon gas, hydrogen gas, lower alkanes such as methane and ethane, and mixed gases of these non-oxidizing gases. Nitrogen gas is preferred from the viewpoints of cost and ease of handling.

[0019] The heat treatment temperature is preferably 360°C or higher, more preferably 380°C or higher. The heat treatment temperature is preferably 480°C or lower, more preferably 450°C or lower. These upper and lower limit values ​​can be combined arbitrarily. A preferred range is 360°C to 480°C, more preferably 380°C to 450°C.

[0020] The heat treatment time is preferably 0.5 hours or more, and more preferably 1 hour or more, from the time when the predetermined heat treatment temperature is reached. The heat treatment time is preferably 48 hours or less, more preferably 24 hours or less, and even more preferably 12 hours or less, from the time when the predetermined heat treatment temperature is reached. These upper and lower limit values ​​can be combined arbitrarily. The preferred range is 0.5 to 48 hours, more preferably 0.5 to 24 hours, and even more preferably 1 to 12 hours.

[0021] By performing heat treatment under conditions that satisfy the above-mentioned heat treatment temperature and heat treatment time, it is possible to obtain pitch having properties particularly suitable for producing carbon materials such as graphite electrodes. This pitch can be used as binder pitch and impregnation pitch in the production of carbon materials such as graphite electrodes.

[0022] The pressure at the start of the heat treatment (initial pressure) is preferably 0 MPaG, but there are no particular limitations. The pressure inside the sealed container rises due to hydrogen gas generated by thermal decomposition during the heat treatment, and lower alkanes such as methane and ethane. There are no limitations on the pressure inside the sealed container, but it is possible to release the pressure as needed.

[0023] (Process 2: Distillation process) Step 2 is a step in which the heat-treated product obtained in Step 1 is distilled to obtain pitch, which is a high-boiling component, and low-boiling components. The distillation method in Step 2 may be atmospheric distillation, reduced-pressure distillation (vacuum distillation), or a combination of atmospheric distillation and reduced-pressure distillation, and can be selected appropriately. The internal temperature of the distillation apparatus preferably does not exceed 360°C. This is because, at temperatures above 360°C, reactions such as polymerization are likely to occur, which may cause coking on the inner walls of the distillation apparatus. The lower limit temperature does not affect the properties of the pitch, but a lower temperature requires a lower distillation pressure to distill off the low-boiling components, so from an economical standpoint, a temperature of 200°C or higher is preferable. Preferred distillation conditions vary depending on the softening point of the pitch to be produced. In general, the more the amount of low-boiling components removed, the higher the softening point of the resulting pitch.

[0024] Because the petroleum heavy oil to be distilled after heat treatment is a mixture of components with different boiling points, the distillation conditions for step 2 cannot be uniquely determined. Therefore, in step 2, 50 to 75 mass% of the petroleum heavy oil after heat treatment may be distilled off to obtain a "low-boiling component." The 5 mass% distillation temperature of the "low-boiling component" at atmospheric pressure is preferably 250°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The 90 mass% distillation temperature of the "low-boiling component" at atmospheric pressure is preferably 360°C or lower, more preferably 330°C or lower, and even more preferably 300°C or lower. The method for measuring the distillation properties of the "low-boiling component" is not particularly limited, but it is preferable to select an appropriate method from JIS K 2254:2018, ASTM D7500-15, and ASTM D7169-16 depending on the type of low-boiling component. The "high-boiling component" refers to the components remaining in the distillation apparatus after the distillation step (so-called bottoms). It is possible to introduce the distilled low-boiling point components directly into step 3, but if the intermediate-boiling point fraction with a boiling point of approximately 190°C to 230°C, which contains a high concentration of naphthalene, is introduced into step 3, naphthalene can be recovered more efficiently.

[0025] (Process 3: Naphthalene recovery process) Step 3 is a step of recovering naphthalene from the low-boiling components obtained in Step 2, preferably from the intermediate-boiling fraction of the low-boiling components. The method for recovering naphthalene is not particularly limited, and for example, a distillation method, a crystallization method, or the like, which are commonly used in the coal tar industry to recover naphthalene from naphthalene oil, can be used. In one embodiment, the method for recovering naphthalene is a crystallization method.

[0026] <Graphite electrode manufacturing process> Carbon materials refer to various molded carbon materials such as graphite pipes, graphite crucibles, graphite boats, graphite electrodes, etc. The general manufacturing process for graphite electrodes is described below. 1. Mixing process Mixing and kneading needle coke and binder pitch together 2. Molding process A process of molding the kneaded material to obtain a molded body of a predetermined size and shape. 3. Firing process A step of firing the compact to obtain a fired body. 4.Impregnation process A process of filling the fired body with impregnated pitch 5. Re-firing process A process of re-firing the fired body filled with impregnated pitch to obtain a re-fired body. 6.Graphitization process A step of graphitizing the re-fired body to obtain a graphitized body. 7. Processing process A process in which the graphitized body is formed into a predetermined shape by cutting or the like to produce a graphite electrode.

[0027] 1. Mixing process The needle coke is crushed, classified, and blended in a predetermined particle size ratio with the binder pitch, and then mixed and kneaded together. The blending amount of the binder pitch varies depending on the blending method and molding method, but is generally about 20 to 30 parts by mass per 100 parts by mass of the needle coke.

[0028] The kneaded material may contain a puffing inhibitor such as iron oxide.

[0029] A commercially available mixer or kneader can be used for mixing and kneading. Specific examples include mixers, kneaders, and other mixers and kneaders. The kneading temperature varies depending on the binder pitch used, but is generally about 140°C to 180°C. After kneading, the kneaded mixture is cooled to a temperature suitable for subsequent molding (for example, 100°C to 130°C).

[0030] Although it differs depending on the type of carbon material to be produced and the production method, the softening point of the binder pitch used is preferably 80° C. to 120° C. The fixed carbon content is preferably 45% by mass or more, more preferably 50% by mass or more.

[0031] 2. Molding process The kneaded material is molded to obtain a molded product of a predetermined size and shape. The molding method can be appropriately selected from extrusion molding, molding, etc. depending on the target carbon material. When the target carbon material is a graphite electrode, extrusion molding into a cylindrical shape is generally used.

[0032] 3. Firing process The molded body from the previous process is heated and fired at 700°C to 1000°C to obtain a fired body. The firing process is preferably carried out in a non-oxidizing atmosphere of combustion exhaust gas. The molded body softens at the beginning of the temperature rise, and at 200°C to 500°C, a large amount of decomposition gas is generated by thermal decomposition and polycondensation of the binder pitch, resulting in the formation of pores and volume shrinkage. At 500°C to 600°C, the binder pitch carbonizes. The firing process, including cooling, often takes around one month.

[0033] 4.Impregnation process In the firing process, generally, 35% to 45% of the mass of the binder pitch is lost as volatile matter. At that time, a large number of pores are generated in the fired body. The impregnation process involves filling these pores with impregnation pitch. Impregnation is carried out, for example, by placing the fired body in an autoclave, degassing it under reduced pressure, and then injecting molten impregnation pitch into the pores at approximately 200°C and a gas pressure of approximately 1 MPa.

[0034] Although it differs depending on the type of carbon material to be produced and the production method, the softening point of the impregnation pitch used is preferably 80° C. to 120° C. The fixed carbon content is preferably 45% by mass or more, more preferably 50% by mass or more.

[0035] 5. Re-firing process The fired body filled with the impregnated pitch is fired again to obtain a refired body. The refired body can be performed under the same conditions as the firing step. The impregnation step and the refired body can be repeated as necessary.

[0036] 6.Graphitization process The re-fired body is placed in a furnace (such as an Acheson furnace or an LWG furnace) surrounded by an insulating material, and is subjected to heat treatment by applying current to packing coke or by resistance heating of the re-fired body. The graphitization temperature is 2000°C to 3000°C. This temperature is necessary to convert the amorphous carbon in the re-fired body into crystalline graphite. It is preferable to heat treat the re-fired body for several days to convert it into a graphitized body.

[0037] 7. Processing process The graphitized body is machined, for example, by cutting, to form a graphite electrode product of a predetermined shape. [Example]

[0038] The present invention will be further described with reference to the following examples and comparative examples. However, these examples are merely examples of the present invention and the present invention is not limited to these examples.

[0039] <Method for measuring softening point> The softening point was measured in accordance with "8. Method for measuring the softening point of tar pitch (ring and ball method)" of JIS K 2425:2006 "Test methods for creosote oil, processed tar and tar pitch."

[0040] <Method for measuring fixed carbon> The amount of fixed carbon was measured in accordance with "11. Fixed carbon content determination method" in JIS K 2425:2006 "Testing methods for creosote oil, processed tar and tar pitch."

[0041] <Method for measuring naphthalene concentration and purity> The concentration and purity of naphthalene were calculated using an internal standard method using a gas chromatograph mass spectrometer (GC-MS). The internal standard used was n-hexadecane (Tokyo Chemical Industry Co., Ltd., GC standard grade). The GC-MS equipment used was an Agilent Technologies 6890N Network Gas Chromatograph and an Agilent Technologies 5975C Inert XL MSD, with an Agilent Technologies HP-5MS column (0.25 mm diameter x 30 m x 0.25 μm). The analytical conditions were as follows: [GC conditions] Column: HP-5MS (0.25 mmφ×30 m×0.25 μm) Sample injection volume: 1 μL Sample vaporizer temperature: 270℃ Oven temperature: 50°C (1 min) → (3°C / min) → 200°C (1 min) → (10°C / min) → 310°C (1 min) Carrier gas: Helium [MS conditions] Measurement mode: SIM Ion source temperature: 230℃ Quadrupole temperature: 150℃

[0042] <Measurement of 5% by mass and 90% by mass distillation temperatures of the raw material (recovery process raw material) to be used in process 3> The 5% and 90% by mass distillation temperatures of the raw material used in step 3 were measured in accordance with the method described in ASTM D7500-15 "Standard Test Method for Determination of Boiling Range Distribution of Distillates and Lubricating Base Oils - in Boiling Range from 100°C to 735°C by Gas Chromatography." An AC SIMDIS Analyzer manufactured by PAC was used for the measurement.

[0043] <Method for preparing light ethylene bottom oil fraction> Using 894 kg of ethylene bottom oil (naphthalene concentration: 9.1% by mass) as a feedstock, it was purified by distillation in a distillation apparatus with 15 theoretical plates (Sulzer packing) at a vessel temperature of 101°C and an operating pressure of 533 to 1067 PaA, yielding 544 kg of a heavy ethylene bottom oil fraction as the bottom liquid. The initial boiling point of the obtained heavy ethylene bottom oil fraction was 218°C. Approximately 350 kg of components obtained as the distillate were used as a light ethylene bottom oil fraction. The naphthalene concentration in the obtained light ethylene bottom oil fraction was 23.3% by mass.

[0044] <Electrode evaluation> Binder pitch and needle coke were mixed (needle coke:binder pitch = 8:2, mass ratio) using a laboratory kneader (TDR200-3, manufactured by Toshin Corporation) and molded into the shape of an electrode piece (cylindrical; 50 mmΦ x 35 mm) to produce a green body. The green body was fired at approximately 1000 °C to produce a fired body. The bulk density of the green body and fired body was measured in accordance with JIS R 7222:2017 "Methods for measuring physical properties of graphite materials, 7. Method for measuring bulk density." The carbonization rate was calculated using equation (1).

[0045]

number

[0046] Example 1 300 g of ethylene bottom oil light fraction with a naphthalene concentration of 23.3% by mass, obtained by the above-described method for preparing ethylene bottom oil light fraction, was introduced into a 0.98 L stainless steel autoclave. The autoclave was sealed under a nitrogen gas atmosphere, and the temperature inside the vessel was raised to 430°C at a rate of 4°C / min while stirring, thereby carrying out heat treatment. Six hours after reaching 430°C, the mixture was allowed to cool to room temperature, and the heat-treated product was removed. The heat-treated product was subjected to vacuum distillation using a vacuum distillation apparatus, yielding 217 g (yield: 72% by mass) of low-boiling components and 71 g (yield: 24% by mass) of pitch as a high-boiling component. The remaining 12 g was lost during the heat-treated product recovery operation and vacuum distillation operation. The vacuum distillation was carried out by maintaining a constant pressure of 5 mmHg and gradually increasing the vessel temperature from room temperature until the vapor temperature at the top of the distillation tube reached 340°C (equivalent to atmospheric pressure). The naphthalene concentration in the obtained low-boiling point component was 44.2% by mass. 217 g of this low-boiling point component was allowed to stand at 10°C for 10 hours to crystallize naphthalene. The obtained slurry was filtered at room temperature, and the resulting residue (crystallized material) was sandwiched between two sheets of filter paper and pressed at a pressure of 5 MPa using an electric compressor (BRE-32, manufactured by Mayekawa Test Machinery Mfg. Co., Ltd.) to obtain 46 g of naphthalene (yield: 15% by mass relative to the ethylene bottom oil light fraction). The obtained naphthalene was white and had a purity of 97.9% by mass. The physical properties of the obtained pitch were as shown in Table 1.

[0047] The resulting pitch was used as a binder pitch for electrode evaluation. The bulk density of the resulting compact was 1.848 g / cm. 3 The carbonization rate was 60%, and the bulk density of the fired body was 1.583 g / cm 3 It was.

[0048] Example 2 Pitch and naphthalene were obtained according to the method described in Example 1, except that the heat treatment conditions and distillation conditions were changed as shown in Table 1.

[0049] Example 3 Pitch and naphthalene were obtained in the same manner as in Example 1, except that the heat treatment raw materials, heat treatment conditions, and distillation conditions were changed as shown in Table 1.

[0050] (Comparative Example 1) 200 g of ethylene bottom oil light fraction with a naphthalene concentration of 23.3% by mass, obtained by the above-described method for preparing ethylene bottom oil light fraction, was distilled under reduced pressure to remove the fraction with a boiling point of approximately 200°C or less, thereby obtaining 122 g of ethylene bottom oil light fraction enriched in naphthalene as a high-boiling component. The vacuum distillation was carried out by maintaining a constant pressure of 65 mmHg and gradually increasing the vessel temperature from room temperature until the vapor temperature at the top of the distillation column reached 195°C (equivalent to atmospheric pressure). The naphthalene concentration in this naphthalene-enriched ethylene bottom oil light fraction was 30.7% by mass. This 122 g of ethylene bottom oil light fraction enriched in naphthalene was allowed to stand at 10°C for 10 hours to crystallize naphthalene. The resulting slurry was treated in the same manner as in Example 1 to obtain 16 g of naphthalene (yield: 8%). The resulting naphthalene was pale purple and had a purity of 96.6%.

[0051] (Comparative Example 2) 150 g of ethylene bottom oil light fraction having a naphthalene concentration of 23.3 mass%, obtained by the above-mentioned method for preparing ethylene bottom oil light fraction, was allowed to stand at 10°C for 20 hours, but naphthalene did not precipitate. This result indicated that naphthalene cannot be obtained at 10°C even if the ethylene bottom oil light fraction is crystallized directly without concentrating the naphthalene by distillation. A lower temperature is required to crystallize naphthalene from this ethylene bottom oil light fraction.

[0052] [Table 1]

[0053] It has been found that pitch, which is obtained as a high-boiling component when ethylene bottom oil or a light fraction of ethylene bottom oil is heat-treated and the heat-treated product is distilled, has properties that make it suitable for use in the production of carbon materials such as graphite electrodes. By recovering naphthalene from the low-boiling components obtained together with the pitch in the distillation process, high-purity, colorless naphthalene can be obtained.

Claims

1. A method for producing pitch and naphthalene for producing carbon materials, comprising the steps of: heat-treating petroleum heavy oil (step 1); distilling the heat-treated product obtained in step 1 and separating it into pitch, which is a high-boiling component, and a low-boiling component (step 2); and recovering naphthalene from the low-boiling component obtained in step 2 (step 3).

2. 2. The method for producing pitch for producing carbon materials and naphthalene according to claim 1, wherein the petroleum heavy oil is at least one selected from the group consisting of ethylene bottom oil and ethylene bottom oil light fraction.

3. The method for producing pitch for producing carbon materials and naphthalene according to claim 1 or 2, wherein the naphthalene concentration in the petroleum heavy oil is 5% by mass to 60% by mass.

4. 3. The method for producing pitch and naphthalene for producing carbon materials according to claim 1, wherein the heat treatment temperature in step 1 is 360° C. to 480° C., and the heat treatment time is 0.5 hours to 48 hours.

5. 3. The method for producing pitch for producing carbon materials and naphthalene according to claim 1 or 2, wherein the carbon material is a graphite electrode.

Images