EP-4741474-A1 - METHOD FOR PRODUCING BINDER PITCH

Abstract

A method for producing a binder pitch for a carbon material, comprising heat-treating a petroleum-based heavy oil (step 1); distilling the heat-treated product obtained in step 1 to obtain a base pitch having a softening point of 60°C or more and 110°C or less, a fixed carbon content of 50.0% by mass or more, an initial boiling point of 320°C or more and 450°C or less, and a quinoline insoluble matter (QI) of 1.0% by mass or less as a high boiling point component (step 2); adding carbon powder to the base pitch obtained in step 2 and mixing them (step 3).

Inventors

• ISHIKAWA, YUTARO
• NISHI, NOBUHIRO
• OTA, KEISUKE

Assignees

• Resonac Corporation

Dates

Publication Date

20260513

Application Date

20240419

Claims (7)

1. A method for producing a binder pitch for a carbon material, comprising heat-treating a petroleum-based heavy oil (step 1); distilling the heat-treated product obtained in step 1 to obtain a base pitch having a softening point of 60°C or more and 110°C or less, a fixed carbon content of 50.0% by mass or more, an initial boiling point of 320°C or more and 450°C or less, and a quinoline insoluble matter (QI) of 1.0% by mass or less as a high boiling point component (step 2); adding carbon powder to the base pitch obtained in step 2 and mixing them (step 3).
2. The method for producing a binder pitch for a carbon material according to claim 1, wherein a 3% distillation temperature of the base pitch is 340°C or more and 470°C or less.
3. The method for producing a binder pitch for a carbon material according to claim 1 or 2, wherein the petroleum-based heavy oil is an ethylene bottom oil light fraction.
4. The method for producing a binder pitch for a carbon material according to claim 1 or 2, wherein the carbon powder is at least one selected from the group consisting of graphite powder, coke powder, carbon black powder, and free carbon powder in coal tar.
5. The method for producing a binder pitch for a carbon material according to claim 1 or 2, wherein an amount of the carbon powder added is 1.0 parts by mass or more and 22.0 parts by mass or less with respect to 100 parts by mass of the base pitch.
6. The method for producing a binder pitch for a carbon material according to claim 1 or 2, wherein the binder pitch for a carbon material obtained in step 3 has a softening point of 80°C or more and 120°C or less, and a quinoline insoluble matter of 18.0% by mass or less.
7. The method for producing a binder pitch for a carbon material according to claim 1 or 2, wherein the carbon material is a graphite electrode.

Description

TECHNICAL FIELD The present disclosure relates to a method for producing a binder pitch for a carbon material, such as a graphite electrode. BACKGROUND Carbon materials, such as a graphite electrode used in an electric furnace for remelting iron are produced by kneading and forming aggregates, 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 baking, and then graphitizing. Since it is necessary that the carbon material have properties such as high mechanical strength, high electrical conductivity, and high thermal conductivity, the carbon material preferably has high density. However, the baked body has a structure having a large number of pores due to volatilization of low-molecular-weight components in the binder pitch during the baking step, etc. Therefore, in the production process, impregnating the baked body with pitch (referred to as "impregnation pitch") followed by re-baking several times reduces the porosity and results in the obtained carbon material having high density. Heavy residue oil (ethylene bottom oil), which is a by-product when producing olefins, such as ethylene and propylene by steam cracking or thermal cracking of petroleum hydrocarbons, such as naphtha, is used only partially as a raw material for carbon black, and mostly as a fuel. Therefore, converting this ethylene bottom oil into high value-added products is an object in the relevant technical field. In order to achieve this object, attempts have been made to produce a binder pitch for carbon materials from ethylene bottom oil, taking advantage of the characteristics of ethylene bottom oil, which contains large amounts of aromatic compounds. However, a petroleum-based pitch produced from petroleum-based heavy oil, such as ethylene bottom oil, has a lower carbon yield than a coal tar pitch having the same softening point as the petroleum-based pitch, and thus the density of the obtained carbon material tends to be lower. Therefore, petroleum-based pitches are currently not used very often. Some of the most important properties required for the binder pitch are carbon yield, softening point, and initial boiling point. The higher the carbon yield, the more the density of the obtained baked body, which is preferable, since the number of subsequent impregnations with the impregnation pitch and re-baking can be reduced. When the softening point is too high, the kneadability and the formability are lowered, and therefore the softening point is preferably about 120°C or less. When the initial boiling point is too low, the amount of light components volatilized during kneading is large, so that the viscosity increases during kneading, and the kneadability and the formability are lowered. Therefore, the initial boiling point is preferably about 320°C or more. In general, as a method of increasing the carbon yield and the initial boiling point of the binder pitch, there is a method of removing light components in the pitch by distillation, etc. However, the method has a problem in that the softening point also increases when the light components are removed. As a method of improving the carbon yield while suppressing an increase in the softening point to some extent, there is a method of adding a cutback oil pitch having a relatively high carbon yield and a high softening point (Patent Literature 1). [Citation List] [Patent Literature] [PTL 1] US 6352637 B2 SUMMARY OF INVENTION [Technical Problem] The method described in Patent Literature 1 has a problem that the initial boiling point of the obtained pitch is lowered, since it is necessary to add a cut-back oil having a relatively low boiling point. Thus, it is difficult to adjust these parameters independently using conventional methods. The present disclosure provides a method for producing pitch suitable for a binder pitch for a carbon material from petroleum-based heavy oil, wherein the pitch has a high carbon yield and excellent kneading stability. [Solution to Problem] The present inventors have conducted intensive studies to obtain an excellent binder pitch for carbon materials from petroleum-based heavy oil. As a result, the present inventors have found that pitch suitable for a binder pitch for carbon materials can be obtained by adding carbon powder to a base pitch having a high fixed carbon content, a high initial boiling point, and a low softening point, which is obtained by heat-treating petroleum-based heavy oil and then distilling it, and mixing them, thereby completing the present invention. That is, the contents of the present disclosure relate to the following methods [1] to [7]. [1] A method for producing a binder pitch for a carbon material, comprising heat-treating a petroleum-based heavy oil (step 1); distilling the heat-treated product obtained in step 1 to obtain a base pitch having a softening point of 60°C or more and 110°C or less, a fixed carbon content of 50.0% b