Method for manufacturing graphite electrodes and method for manufacturing binder pitch for graphite electrodes

Abstract

To provide a method for producing a high-density graphite electrode using a petroleum-based pitch.SOLUTION: A pitch obtained by mixing a heavy petroleum oil with a solid acid catalyst, heat-treating a mixture, and de-catalyzing to distill the mixture is used in production of graphite electrodes.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a graphite electrode and a method for manufacturing a binder pitch for manufacturing a graphite electrode.

Background Art

[0002] Carbon materials such as graphite electrodes used in electric furnaces for remelting iron are manufactured by kneading and molding an aggregate such as coke and pitch (referred to as "binder pitch") at a temperature equal to or higher than the softening point of the binder pitch, followed by firing and then graphitization. Carbon materials are preferably dense because they are required to have characteristics such as high mechanical strength, high electric conductivity, and high thermal conductivity. Usually, due to the volatilization of low molecular weight components in the binder pitch during the firing process, the fired body has a porous structure. Therefore, the porosity is reduced by impregnating the fired body with pitch (referred to as "impregnating pitch") and re-firing several times during the manufacturing process, and the resulting carbon material is made dense. [

[0003] Heavy residual oil (ethylene bottom oil) produced as a by-product when producing olefins such as ethylene and propylene by steam cracking or thermal cracking of petroleum hydrocarbons such as naphtha is only partially used as a raw material for carbon black, and most of it is used as fuel. Therefore, converting this ethylene bottom oil into a product with high added value is an issue in the technical field. To solve this issue, attempts have been made to produce a binder pitch for carbon materials from ethylene bottom oil by taking advantage of the characteristics of ethylene bottom oil rich in aromatic compounds. However, petroleum pitches produced from petroleum heavy oils such as ethylene bottom oil have a lower fixed carbon content compared to coal tar pitch having the same softening point as the petroleum pitch, and the density of the resulting carbon material tends to be low. Therefore, they are not widely used at present.

[0004] One possible method for increasing the density of carbon materials is to use a pitch with a high fixed carbon content as the binder pitch. However, since there is generally a positive correlation between the fixed carbon content of pitch and its softening point, a pitch with a high fixed carbon content also has a high softening point. Therefore, it is easy to foresee that using a pitch with a high fixed carbon content as the binder pitch will worsen the kneadability and moldability. Consequently, it is difficult to improve the density of the resulting carbon material without raising the softening point of the binder pitch.

[0005] Methods for producing pitch, which include mixing a catalyst such as a solid acid with petroleum-based heavy oil and heat-treating it, are described in Japanese Patent Publication No. 60-179493 (Patent Document 1) and Japanese Patent Publication No. 60-240790 (Patent Document 2). However, both of these relate to the production of high-softening-point pitch intended for use as a raw material for carbon fibers, and there is no knowledge of relatively low-softening-point pitch suitable for the production of carbon materials such as graphite electrodes, nor of its use in the production of carbon materials. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 179493 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 60-240790 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This invention provides a method for manufacturing high-density graphite electrodes using petroleum-based pitch. [Means for solving the problem]

[0008] The inventors diligently conducted research to improve the density of carbon material produced using petroleum-based pitch. As a result, they discovered that using pitch obtained by mixing a catalyst with petroleum-based heavy oil, followed by heat treatment, decatalysis, and distillation, in the production of graphite electrodes improves the density of the resulting graphite electrodes, leading to the present invention.

[0009] In other words, the present invention relates to the following [1] to [5].

[0010] [1] A method for producing a graphite electrode, comprising kneading needle coke and binder pitch, shaping the resulting kneaded material and then firing it, and graphitizing the resulting fired body, wherein the binder pitch is produced by the following steps. Process 1 (Heat Treatment Process): A process of heat-treating raw material oil obtained by adding a solid acid catalyst to petroleum-based heavy oil. Step 2 (Catalytic De-catalysis Step): A step to separate the solid acid catalyst from the heat-treated product obtained in Step 1. Step 3 (Distillation Step): A step in which the heat-treated product decatalyzed in Step 2 is distilled to obtain binder pitch as a high-boiling point component. [2] The method for producing a graphite electrode according to [1], wherein the petroleum-based heavy oil is ethylene bottom oil. [3] A method for producing a graphite electrode according to [1] or [2], wherein the solid acid catalyst is at least one selected from activated clay, acid clay, zeolite, and silica-alumina. [4] A method for manufacturing binder pitch for graphite electrodes, comprising the following steps. Process 1 (Heat Treatment Process): A process of heat-treating raw material oil obtained by adding a solid acid catalyst to petroleum-based heavy oil. Step 2 (Catalytic De-catalysis Step): A step to separate the solid acid catalyst from the heat-treated product obtained in Step 1. Step 3 (Distillation Step): A step in which the heat-treated product decatalyzed in Step 2 is distilled to obtain binder pitch as a high-boiling point component. [5] The manufacturing method of the binder pitch for manufacturing a graphite electrode as described in [4], wherein the softening point of the binder pitch is 70°C or higher and 130°C or lower.

Effect of the Invention

[0011] According to the present invention, a high-density graphite electrode can be obtained using a petroleum-based pitch.

Brief Description of the Drawings

[0012] [Figure 1] It is a flowchart showing a petrochemical process for pyrolyzing naphtha or the like and a manufacturing process of ethylene bottom oil.

Mode for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described, but it should be understood that the present invention is not limited to only these embodiments, and various applications are possible within the spirit and scope of implementation.

[0014] <Manufacturing Process of Graphite Electrode> The carbon material refers to various shaped carbon materials such as graphite tubes, graphite crucibles, graphite boats, and graphite electrodes. The manufacturing process of a graphite electrode in one embodiment will be described below. 1. Kneading Process A process of mixing and kneading needle coke and binder pitch together 2. Forming Process A process of forming the kneaded material to obtain a formed body with a predetermined size and shape 3. Firing Process A process of firing the formed body to obtain a fired body 4. Impregnation Process A process of filling the fired body with impregnation pitch 5. Re-firing Process A process of firing the filled fired body again to obtain a re-fired body 6. Graphitization Process A process of graphitizing the re-fired body 7. Processing Process A process of forming the graphitized body into a predetermined shape by cutting or the like to obtain a graphite electrode

[0015] 1. Mixing process The needle coke, which has been crushed, classified, and mixed to a predetermined particle size ratio, is mixed and kneaded together with the binder pitch. The amount of binder pitch varies depending on the kneading and molding methods, but is generally about 20 to 30 parts by mass per 100 parts by mass of needle coke.

[0016] The kneaded mixture may contain puffing inhibitors such as iron oxide.

[0017] Commercially available mixers or kneaders can be used for mixing and kneading. Specific examples include mixers and kneaders. The kneading temperature varies depending on the binder pitch used, but is generally around 150°C. The softening point of the binder pitch is preferably 130°C or lower, and more preferably 110°C or lower. When kneading at around 150°C, if the softening point of the binder pitch is higher than 130°C, it is difficult to knead sufficiently. After kneading, the mixture is cooled to a temperature suitable for subsequent molding (100°C to 130°C).

[0018] 2. Molding process The kneaded material is molded to obtain a molded body of a predetermined size and shape. The molding method can be appropriately selected from extrusion molding, mold molding, etc., depending on the target carbon material. When the target carbon material is a graphite electrode, extrusion molding into a cylindrical shape is common.

[0019] 3. Firing process The molded body from the previous step 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 in the initial stages of heating, and at 200°C to 500°C, a large amount of decomposition gas is generated by thermal decomposition and polycondensation of the binder pitch, causing pore formation and volume shrinkage. At 500°C to 600°C, the binder pitch carbonizes. The firing process, including cooling, often takes about one month.

[0020] 4.Impregnation process During the firing process, generally 35% to 45% of the binder pitch mass is lost as volatile matter. At this time, a large number of pores are generated in the fired body. The impregnation process is to fill these pores with impregnation pitch. Impregnation is carried out, for example, by placing the fired body in an autoclave, degassing it under reduced pressure, injecting molten impregnation pitch, and injecting the impregnation pitch into the pores at a gas pressure of about 1 MPa at approximately 200°C.

[0021] 5. Re-firing process The filled fired body is fired again to obtain a refired body. The refired process can be carried out under the same conditions as the firing process described above. The impregnation process and the refired process may be repeated as needed.

[0022] 6. Graphitization process The re-calcined body is placed in a furnace (such as an Acheson furnace or LWG furnace) surrounded by insulating material, and heat treatment is applied to the re-calcined body by applying an electric current to the packing coke or by resistance heating of the re-calcined body. The temperature for graphitization is 2000°C to 3000°C. This temperature is necessary to convert amorphous carbon in the re-calcined body into crystalline graphite. It is preferable to heat-treat the re-calcined body for several days to convert it to graphite.

[0023] 7. Processing process The graphitized material is processed by machining, such as cutting, to produce graphite electrode products of a predetermined shape. The density (bulk density) of the graphite electrode varies depending on the electric furnace equipment and operating conditions used, but is generally around 1.5 g / cm³. 3 ~1.9g / cm 3 It is preferable that this be the case.

[0024] <Method for manufacturing binder pitch for graphite electrodes> A method for manufacturing binder pitch for graphite electrodes according to one embodiment includes at least the following steps 1 to 3 in this order, and step 4 or other steps may be added. Process 1 (Heat Treatment Process): A process of heat-treating raw material oil obtained by adding a solid acid catalyst to petroleum-based heavy oil. Step 2 (Catalytic De-catalysis Step): A step to separate the solid acid catalyst from the heat-treated product obtained in Step 1. Step 3 (Distillation Step): A step in which the heat-treated product decatalyzed in Step 2 is distilled to obtain binder pitch as a high-boiling point component. Step 4 (Catalyst Regeneration Step): A step to regenerate the used solid acid catalyst separated in Step 2.

[0025] In the petrochemical industry, naphtha and other materials are generally pyrolyzed at high temperatures, and the resulting pyrolysis products are distilled to separate them into various fractions such as ethylene, propylene, and other olefins, aromatic compounds such as benzene, toluene, and xylene, cracked gasoline, and cracked kerosene, which are then used as products. Of these fractions, the heavy fraction with the highest boiling point is called ethylene bottom oil and is used as a raw material for carbon black and as fuel (see Figure 1). Since the pyrolysis plants for naphtha and other materials are often called ethylene plants, the aforementioned heavy fraction is referred to as ethylene bottom oil.

[0026] The properties of ethylene bottom oil obtained by the thermal decomposition of naphtha-containing raw materials depend on the type of naphtha-containing raw material, thermal decomposition conditions, and operating conditions of the refining distillation column. However, typical properties include a 50% distillation temperature of 200°C to 400°C, an aromatic carbon content of 50% by mass or more, a flash point of 70°C to 100°C, and a kinematic viscosity of 40 mmHg at 50°C. 2 It is less than / s. However, since ethylene bottom oil is a mixture of hydrocarbon compounds, the above value may vary slightly.

[0027] The petroleum-based heavy oil may be ethylene bottom oil, ethylene bottom oil heavy component obtained by removing any proportion (e.g., 5% to 70% by mass) of light component from ethylene bottom oil by distillation or the like, or the removed ethylene bottom oil light component, other petroleum-based heavy oils such as heavy oil produced during catalytic cracking of petroleum products, or mixtures thereof. Heavy oils such as coal tar may be added to the petroleum-based heavy oil. Other petroleum-based heavy oils are not particularly limited, but examples include fluid catalytic cracking oil (FCC decant oil), atmospheric distillation residue, vacuum distillation residue, etc. As the petroleum-based heavy oil, ethylene bottom oil, ethylene bottom oil heavy component, ethylene bottom oil light component, and fluid catalytic cracking oil (FCC decant oil) are preferred, and ethylene bottom oil, ethylene bottom oil heavy component, and ethylene bottom oil light component are more preferred. In one embodiment, the petroleum-based heavy oil is ethylene bottom oil. The sulfur and nitrogen content in the pitch is preferable to be low because it causes buffing during firing. When graphite electrodes are manufactured using pitch containing a large amount of metal components, these metal components evaporate during graphitization, reducing the density of the graphite electrodes, which can be undesirable in terms of product quality. From these perspectives, petroleum-based heavy oils with low sulfur, nitrogen, and metal content are preferred, and fluid catalytic cracking oil (FCC decant oil) is preferred. The properties of fluid catalytic cracking oil (FCC decant oil) depend on the raw materials, operating conditions, etc., but typical properties include a 50% distillation temperature of 300°C to 450°C, a flash point of 60°C to 160°C, and a kinematic viscosity of 40 mmHg at 40°C. 2 It is less than / s. However, since fluid catalytic cracking oil (FCC decanted oil) is a complex mixture, the above value may vary slightly.

[0028] (Process 1: Heat treatment process) Step 1 is a step of heat-treating the feedstock oil obtained by adding a solid acid catalyst to petroleum-based heavy oil. Preferably, the feedstock oil is in a state where the solid acid catalyst is dispersed in the petroleum-based heavy oil at the heat treatment temperature. A solid acid catalyst suitable for one embodiment is a solid acid that does not dissolve in the reaction substrate (petroleum-based heavy oil), has Lewis acidity and / or Brønsted acidity, and does not decompose even at the heat treatment temperature. Specifically, examples of solid acids include clay minerals, metal oxides and complex oxides, and more specifically, activated clay, acid clay, silica, alumina, zeolite, silica-alumina, silica-magnesia, and silica-titania. Among these, activated clay, acid clay, zeolite and silica-alumina are preferred from the viewpoint of catalytic activity and economic efficiency, with activated clay being particularly preferred. A solid acid catalyst that does not dissolve in petroleum-based heavy oil is preferred because the catalyst can be easily separated after heat treatment. The shape of the solid acid catalyst is not particularly limited, but it is preferably in powder form from the viewpoint of the efficiency of the heat treatment reaction and the separation of the catalyst in step 2. When the solid acid catalyst is in powder form, its particle size is not particularly limited, but a solid acid catalyst having a particle size range of approximately 10 μm to 300 μm, which is generally available, is preferred.

[0029] The amount of solid acid catalyst to be added depends on the type of solid acid catalyst used, but is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 3 to 20 parts by mass per 100 parts by mass of petroleum-based heavy oil. When heat-treating petroleum-based heavy oil under relatively harsh conditions, fouling, where coke-like material produced during heat treatment adheres to the inner wall of the reactor or the stirring device, is often a problem. However, as described in Patent Documents 1 and 2, the occurrence of fouling can be suppressed by adding a solid acid catalyst. Adding 3 parts by mass or more of solid acid catalyst can effectively suppress the occurrence of fouling. While a larger amount of solid acid catalyst increases the density improvement effect of the resulting graphite electrode, it also reduces the amount of petroleum-based heavy oil that can be processed at one time, so 20 parts by mass or less is more preferable.

[0030] The heat treatment is preferably carried out in a sealed container in a non-oxidizing gas atmosphere. Examples of non-oxidizing gases include nitrogen gas, argon, hydrogen gas, lower alkanes such as methane and ethane, and mixtures of these non-oxidizing gases. Nitrogen gas is preferred from the viewpoint of cost and ease of handling.

[0031] The heat treatment temperature is preferably 360°C to 500°C, and more preferably 400°C to 450°C.

[0032] The heat treatment time is preferably 0.5 to 24 hours, and more preferably 1 to 8 hours, starting from the time the predetermined heat treatment temperature is reached.

[0033] The pressure at the start of heat treatment (initial pressure) is preferably 0 MPaG, but there are no particular restrictions. The pressure inside the sealed container will rise due to hydrogen gas and lower alkanes such as methane and ethane generated by thermal decomposition during heat treatment. There are no restrictions on the pressure inside the sealed container, but it is possible to depressurize it if necessary.

[0034] (Step 2: Decatalyst step) Step 2 is a step of separating (decatalyzing) the solid acid catalyst from the heat-treated product obtained in Step 1. If the heat-treated product is liquid at room temperature, the solid acid catalyst can be removed by centrifugation, filtration, or a combination thereof. If the viscosity of the heat-treated product is high, the solid acid catalyst can be efficiently removed by heating or adding a suitable solvent to reduce the viscosity. If the heat-treated product is solid at room temperature, the solid acid catalyst can be removed by heating or adding a suitable solvent to make it liquid, and then by centrifugation, filtration, or a combination thereof. Suitable solvents are not particularly limited, but solvents with high solubility for pitches such as benzene, toluene, pyridine, and quinoline, or mixtures thereof can be used. As solvents, cracked gasoline, cracked kerosene, ethylene bottom oil light fraction, or mixtures thereof can also be used. In particular, cracked gasoline, cracked kerosene, and ethylene bottom oil light fraction are preferred because they are fractions obtained in general petrochemical processes and are therefore very easy to procure.

[0035] (Step 3: Distillation Process) Step 3 is a step in which low-boiling-point substances are removed by distillation of the heat-treated product decatalyzed in Step 2, and binder pitch having the desired softening point and fixed carbon content as high-boiling-point components is obtained. The distillation method in Step 3 may be atmospheric pressure distillation, reduced pressure distillation (vacuum distillation), or a combination of atmospheric pressure distillation and reduced pressure distillation, and can be selected as appropriate. The internal temperature of the distillation apparatus is preferably not to exceed 360°C. If it exceeds 360°C, reactions such as polymerization will occur, and coking will occur on the inner wall of the distillation apparatus, which is undesirable. The lower limit temperature does not affect the characteristics of the pitch, but if the temperature is low, the distillation pressure must be lowered in order to remove low-boiling-point substances, so from an economic standpoint, 200°C or higher is preferable. When performing reduced pressure distillation (vacuum distillation), in order to obtain pitch with a softening point of 70°C to 130°C, the distillation pressure is preferably 100 PaA to 10000 PaA, more preferably 500 PaA to 3000 PaA, and even more preferably 800 PaA to 2000 PaA. The softening point of pitch can be controlled by the amount of low-boiling point substances removed. Generally, the more low-boiling point substances are removed, the higher the softening point. When ethylene bottom oil is used as the petroleum-based heavy oil, in order to set the pitch softening point to 70°C to 130°C, the amount of low-boiling point substances removed depends on the composition of the heat-treated material, but preferably it is 20% to 80% by mass of the heat-treated material, more preferably 25% to 70% by mass, and even more preferably 30% to 40% by mass.

[0036] (Step 4: Catalyst regeneration step) Step 4 is a process for regenerating the spent solid acid catalyst separated in Step 2. Depending on the heat treatment conditions in Step 1, the spent catalyst separated in Step 2 has carbonaceous material attached to it that burns in air at 400°C to 600°C. The amount of this carbonaceous material attached is generally several mass% to several tens of mass% of the spent catalyst. The catalyst can be regenerated by burning off these carbonaceous materials in air at around 400°C to 600°C.

[0037] As mentioned above, the softening point of the binder pitch is preferably 70°C or higher and 130°C or lower, and more preferably 110°C or lower. Generally, the higher the fixed carbon content of the binder pitch, the higher the density of the resulting graphite electrode tends to be, so it is preferably 45% by mass or higher, and more preferably 50% by mass or higher. [Examples]

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

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

[0040] <Method for measuring fixed carbon (FC) content> The measurements were taken in accordance with "11. Method for determining fixed carbon content" of JIS K 2425:2006 "Test methods for creosote oil, processed tar, and tar pitch".

[0041] <Method for measuring true pitch density> The true density of the pitch was measured using the constant volume expansion method with a Micromeritics Accupic II 1340. Helium was used as the substitution gas, and the measurement was performed at 25°C.

[0042] <Preparation of Solid Acid Catalysts> As a solid acid catalyst, activated clay (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used, which was heated and dried in an electric furnace at 350°C in air for 3 hours.

[0043] <Fouling> The presence or absence of fouling was determined after the heat treatment process was completed by opening the reaction vessel used for the heat treatment and visually and tactilely inspecting the stirring device and the inner wall of the reaction vessel.

[0044] <Molding Evaluation> Pitch and needle coke were mixed using a commercially available laboratory kneader (needle coke:pitch = 8:2, mass ratio), and molded into the shape of an electrode piece (cylindrical; 50mmΦ × 35mm) by molding to produce a molded body. The molded body was fired at approximately 1000°C under asphyxiation conditions to produce a fired body. The bulk density of the molded body and the fired body was measured in accordance with JIS R 7222:2017 "Method for measuring the physical properties of graphite materials".

[0045] (Example 1) The raw material oil, obtained by adding 15 g of activated clay to 300 g of ethylene bottom oil, was introduced into a 1.0 L stainless steel autoclave. The autoclave was sealed under a nitrogen gas atmosphere, and the temperature inside the container was raised to 430°C at a rate of 4°C / min while stirring to perform heat treatment. After 1 hour from reaching 430°C, the material was allowed to cool to room temperature, and the heat-treated material was removed. The heat-treated material was separated into solid and liquid components by centrifugation, and the solid component was completely removed by filtering the liquid component through a glass filter. The solid component was washed and filtered several times with toluene, and the toluene-soluble components were mixed with the liquid component. The liquid component was subjected to vacuum distillation in a vacuum distillation apparatus so that the distillation endpoint was 360°C in terms of atmospheric pressure, thereby removing the low-boiling point components and obtaining 105 g of pitch (yield 35%) as the high-boiling point component. Molding evaluation was performed using the obtained pitch.

[0046] (Example 2) Except for changing the heat treatment and distillation conditions as shown in Table 1, pitch was obtained according to the method described in Example 1. Molding evaluation was performed using the obtained pitch.

[0047] (Comparative Example 1) Only 300 g of ethylene bottom oil was introduced into a 1.0 L stainless steel autoclave. The autoclave was sealed under a nitrogen gas atmosphere, and the temperature inside the container was raised to 430°C at a rate of 4°C / min while stirring to perform heat treatment. After 1 hour from reaching 430°C, the material was allowed to cool to room temperature, and the heat-treated material was removed. The heat-treated material was separated into solid and liquid components by centrifugation, and the solid component was completely removed by filtering the liquid component through a glass filter. The solid component was washed and filtered several times with toluene, and the toluene-soluble components were mixed with the liquid component. At this time, the mass of the obtained solid component was approximately 2 g. The liquid component was subjected to vacuum distillation in a vacuum distillation apparatus so that the distillation endpoint was 310°C in terms of atmospheric pressure, thereby removing the low-boiling point components and obtaining 111 g of pitch (yield 37%) as the high-boiling point component. Molding evaluation was performed using the obtained pitch.

[0048] [Table 1]

[0049] As shown in Table 1, when pitch produced by a manufacturing method that includes a step of adding a solid acid catalyst to the raw material ethylene bottom oil and heat-treating it is used as binder pitch for graphite electrode production, the bulk density of the resulting calcined body is higher than when no catalyst is added. Furthermore, if this calcined body is graphitized, a graphite electrode with a higher density can be obtained. As is clear from Table 1, the physical properties of the obtained pitch itself are about the same regardless of whether a catalyst is added or not, yet the improvement in the density of the graphite electrode obtained when this pitch is used in the production of graphite electrodes is a surprising result that cannot be predicted from the physical properties of the pitch itself.

Claims

1. A method for producing a graphite electrode, comprising kneading needle coke and binder pitch, shaping the resulting kneaded material and then firing it, and graphitizing the resulting fired body, wherein the binder pitch is produced by the following steps. Step 1 (Heat Treatment Step): A step in which a raw material oil is heat-treated by adding a solid acid catalyst, which is selected from activated clay, acid clay, zeolite, and silica-alumina, to petroleum-based heavy oil. Step 2 (catalysis step): A step to separate the solid acid catalyst from the heat-treated product obtained in Step 1. Step 3 (Distillation Step): A step in which the heat-treated product decatalyzed in Step 2 is distilled to obtain binder pitch as a high-boiling point component.

2. The method for producing a graphite electrode according to claim 1, wherein the petroleum-based heavy oil is ethylene bottom oil.

3. A method for manufacturing binder pitch for graphite electrodes, comprising the following steps. Step 1 (Heat Treatment Step): A step in which a raw material oil is heat-treated by adding a solid acid catalyst, which is selected from activated clay, acid clay, zeolite, and silica-alumina, to petroleum-based heavy oil. Step 2 (catalysis step): A step to separate the solid acid catalyst from the heat-treated product obtained in Step 1. Step 3 (Distillation Step): A step in which the heat-treated product decatalyzed in Step 2 is distilled to obtain binder pitch as a high-boiling point component.

4. A method for manufacturing binder pitch for graphite electrodes according to claim 3, wherein the softening point of the binder pitch is 70°C or higher and 130°C or lower.

Images