JP2021080143A - Pitch for carbon material raw material and its manufacturing method - Google Patents

Abstract

To provide a pitch for a carbon material raw material which has a high carbonization yield and a suppressed softening point, and a method for producing the same.SOLUTION: A pitch for a carbon material raw material having a softening point of 50°C or higher and lower than 200°C, a quinoline-insoluble content of 3 mass% or less and an oxygen concentration of 0.4 mass% or more is obtained by carrying out distillation treatment in an oxidizing atmosphere using a petroleum heavy oil as a raw material.SELECTED DRAWING: None

Description

The present invention relates to a pitch for a carbon material raw material that can be a precursor of a carbon material and a method for producing the same, and more particularly to a production method using petroleum-based heavy oil as a raw material.

Pitch-like materials obtained from petroleum-based or coal-based raw materials are provided as precursors of carbon materials such as various binders and negative electrode materials for lithium-ion batteries. Specific carbon materials include, for example, a material for hard carbon of a lithium ion battery and a binder material for briquette of a coke oven.

Among the raw materials, coal-based pitch, so-called coal tar pitch, is being developed as a carbon material precursor using economically advantageous petroleum-based raw materials because of the soaring price of raw material coal. ..

However, when distilling a petroleum-based raw material (oil) to obtain a pitch, there is a problem that only a material having a low carbonization yield can be obtained by performing vacuum distillation or nitrogen distillation.

In order to solve this problem, for example, Patent Document 1 discloses a method of obtaining a heat treatment pitch having a softening point of 200 ° C. or higher by performing heat treatment while blowing a gas containing oxygen or ozone into heavy oil or pitch. ing.

Further, Patent Document 2 discloses a method of heat-treating a heavy oil or pitch in the presence of an oxidizing gas and in the presence of an additive capable of cross-linking or promoting a polymerization reaction.

Japanese Unexamined Patent Publication No. 61-28020 Japanese Unexamined Patent Publication No. 2005-281490

However, in the method disclosed in Patent Document 1 or Patent Document 2 described above, the softening point of the obtained pitch is 200 ° C. or higher, but there is a problem that the carbonization yield is still not sufficient. In particular, both documents only describe examples using coal-based raw materials (coal tar pitch), and do not show a method for solving problems with respect to the yield of precursors for carbon materials using petroleum-based raw materials.

In other words, increasing the carbonization yield and lowering the softening point are contradictory issues, and a well-balanced precursor of carbon material that has solved this problem has not been obtained.

An object of the present invention is to provide a pitch for a carbon material raw material and a method for producing the same, in which a softening point is suppressed while increasing a carbonization yield.

In order to solve the above problems, the present inventors have diligently studied a pitch for a carbon material raw material and a method for producing the same, using petroleum-based heavy oil (heavy oil) as a raw material. As a result, in order to lower the softening point while maintaining a high yield of the precursor for carbon materials, when the petroleum-based heavy oil is distilled to obtain a pitch, the polymer compound in the heavy oil is a functional group (side chain). ) Is an aliphatic or aromatic polycyclic hydrocarbon compound. That is, I came up with the idea that when oxygen is blown in, oxygen is bonded to the functional group, and the polymer compounds are further bonded to each other, that is, so-called cross-linking, so that the carbonization yield may be increased, and the oxidizing atmosphere. We have found a method for performing distillation treatment in. Based on such findings, the present inventors have completed the present invention by further studying.

The gist of the present invention is as follows.
(1) A pitch for carbon material raw materials, characterized in that the softening point is 50 ° C. or higher and lower than 200 ° C., the quinoline insoluble content is 3% by mass or less, and the oxygen concentration is 0.4% by mass or more.
(2) By using petroleum-based heavy oil as a raw material and performing distillation treatment in an oxidizing atmosphere, the softening point is 50 ° C or higher and lower than 200 ° C, the quinoline insoluble content is 3% by mass or less, and the oxygen concentration is 0.4% by mass or more. A method for producing a pitch for a carbon material raw material.
(3) The method for producing a pitch for a carbon material raw material, which comprises performing the above-mentioned distillation treatment and then further performing a heat reforming treatment in (2).
(4) In (2) or (3), the petroleum-based heavy oil has a carbon to hydrogen atomic number ratio C / H of 0.6 to 1.1 and a viscosity at 50 ° C. of 30 to 1000 cP. A method for producing a pitch for a carbon material raw material, which is characterized in that.
(5) In any of (2) to (4), the oxidizing atmosphere is 300 to 350 ° C., and the amount of oxygen blown is 1300 to 2100 L / kg. Manufacturing method.

The pitch for carbon material raw materials of the present invention is a pitch suitable as a precursor of carbon materials and contains a large amount of oxygen crosslinked structures, so that not only the carbonization yield is high but also the reactivity with various chemical substances is improved. It is rich and can be expected to be used in a wide range of technical fields.

Hereinafter, the present invention will be described in more detail.
The pitch for carbon material raw materials of the present invention is characterized in that the softening point is 50 ° C. or higher and lower than 200 ° C., the quinoline insoluble content is 3% by mass or less, and the oxygen concentration is 0.4% by mass or more.

First, the softening point of the pitch for carbon material raw materials of the present invention is 50 ° C. or higher and lower than 200 ° C. If the softening point is less than 50 ° C., the carbonization yield is low, and if it is 200 ° C. or higher, the fluidity is low. More preferably, it is 80 to 180 ° C.

The softening point of the pitch is a temperature index at which the fluidity of the pitch is expressed. This index is important in the process of mixing the obtained pitch for carbon material raw materials with other raw materials. The softening point of the pitch for carbon material raw materials in the present invention can be adjusted by controlling the temperature and time during distillation and firing in the manufacturing process of the pitch for carbon material raw materials.

As a method for measuring the softening point, JIS K 2425: 2006 (creosote oil, processed tar and tar pitch test method) of 8.1 (manual measurement method) or 8.2 (automatic measurement method) is preferable, and 8. 1 (manual measurement method) is more preferable.

Further, the quinoline insoluble content (referred to as QI) of the pitch for carbon material raw materials in the present invention is 3% by mass or less. QI is a heavy component, and there is free carbon contained in the raw material oil, for example, having a particle size of about 1 μm or less. The smaller the QI, the more preferable it is from the viewpoint of the quality (uniformity, crystallinity, etc.) of the carbon material which is the final product using the pitch for the carbon material raw material, and more preferably 0.1% by mass or less. .. When the QI is within this range, the carbonization yield, which is the object of the present invention, can be increased.

The QI measurement method is preferably 15.1 (filtration method) or 15.2 (centrifugation method) of JIS K 2425: 2006 (creosote oil, processed tar and tar pitch test method), and 15.1 (filtration method). Is more preferable.

Further, the oxygen concentration of the pitch for carbon material raw material of the present invention is 0.4% by mass or more.
As will be described later, the pitch for a carbon material raw material of the present invention is obtained by using petroleum-based heavy oil as a raw material and performing distillation treatment while blowing oxygen, that is, in an oxidizing atmosphere. It is considered that the reason why the pitch obtained by this treatment improves the carbonization yield is that this pitch contains a large amount of oxygen crosslinked structures, which increases the carbonization yield. The oxygen cross-linked structure is formed by blowing oxygen into the functional groups (side chains) and oxygen of the polymer compound (aliphatic or aromatic polycyclic hydrocarbon compound) in the raw material heavy oil. It is presumed that the polymers are further bonded to each other and crosslinked with each other. The existence of this oxygen cross-linked structure is reasonably estimated from the fact that a carbon-oxygen double bond (carbonyl group) appears in the spectrum by measuring the pitch with a Fourier transform infrared spectrophotometer (FT-IR). Will be done.

Therefore, when the oxygen concentration was examined as an index containing oxygen in the pitch, it was found that the oxygen concentration should be 0.4% by mass or more. If it is less than 0.4% by mass, it is difficult to form a structure crosslinked with oxygen. Preferably, it is 0.8 to 3.6% by mass.
The oxygen concentration is measured by elemental analysis by the combustion method.

Next, a method for producing a pitch for a carbon material raw material of the present invention will be described.
The method for producing a pitch for a carbon material of the present invention uses petroleum-based heavy oil as a raw material and performs distillation treatment in an oxidizing atmosphere to have a softening point of 50 ° C. or higher and lower than 200 ° C., a quinoline insoluble content of 3% by mass or less, and This is a method for producing a pitch for a carbon material raw material having an oxygen concentration of 0.4% by mass or more. Further, the production method is characterized in that after the above-mentioned distillation treatment is performed, a heat reforming treatment is further performed. The petroleum-based heavy oil is characterized by having an atomic number ratio C / H of carbon and hydrogen of 0.6 to 1.1 and a viscosity of 30 to 1000 cP at 50 ° C. The oxidizing atmosphere is characterized in that the oxygen blowing amount is 1300 to 2100 L / kg at 300 to 350 ° C.

First, the raw material for the pitch for carbon material of the present invention is petroleum-based heavy oil. Petroleum-based heavy oil is residual oil obtained from the bottom of a tower by distilling petroleum (crude oil), or heavy petroleum products obtained by processing it. Its components are composed of aliphatic hydrocarbons and aromatic hydrocarbons, and are mainly composed of polycyclic polymer compounds, and contain some organic sulfur content and trace amounts of inorganic compounds. Specific products include residual oil (bottom oil) obtained from a fluidized catalytic decomposition (FCC) apparatus using a fluidized contact catalyst, residual oil (bottom oil) obtained from an ethylene refining apparatus, and the like.

Particularly suitable as the petroleum-based heavy oil of the present invention is a carbon to hydrogen atomic number ratio C / H of 0.6 to 1.1 and a viscosity at 50 ° C. of 30 to 1000 cP.
The atomic number ratio C / H of carbon (C) and hydrogen (H) indicates the aromaticity of the hydrocarbon compound, and the content of carbon and hydrogen is measured and expressed as a ratio of molar composition. .. The C / H of the petroleum-based heavy oil in the present invention is preferably 0.6 to 1.1. If the C / H is less than 0.6, the aromaticity is low, and if it exceeds 1.1, oxygen cross-linking becomes difficult. More preferably, it is 0.7 to 1.0.
As a method for measuring C / H, TCD (thermal conductivity method) by a combustion method is preferable.

Furthermore, since it is difficult to measure the softening point of heavy oil as an index showing the characteristics of heavy oil, viscosity was examined as an alternative index. As a result, it was found that the viscosity at 50 ° C. is preferably 30 to 1000 cP. If the viscosity at 50 ° C. is less than 30 cP, it is difficult to improve the softening point, and if it exceeds 1000 cP, handling is difficult and the softening point is likely to be too high. More preferably, it is 100 to 800 cP.
As a method for measuring the viscosity, it is preferable to use a Brookfield rotational viscometer.

Next, a method of distilling petroleum-based heavy oil in an oxidizing atmosphere will be described.
The distillation treatment performed in an oxidizing atmosphere is a distillation treatment performed while blowing oxygen or air, and the treatment temperature at that time is preferably 300 to 350 ° C. Below 300 ° C, no oxygen cross-linking occurs, and above 350 ° C, the softening point rises before oxygen cross-linking. More preferably, it is 310 to 340 ° C.

The processing time is preferably 0.5 to 10 hours. If the treatment time is too short, sufficient oxygen cross-linking cannot be obtained, and if it is too long, the fluidity of the pitch is lost. More preferably, it is 1 to 5 hours.

The amount of oxygen or air blown is preferably 1300 to 2100 L / kg in terms of the amount of oxygen blown. If it is less than 1300 L / kg, oxygen cross-linking cannot be sufficiently obtained, and if it exceeds 2100 L / kg, the fluidity of the pitch is lost. More preferably, it is 1500 to 2000 L / kg.
The method for determining the amount of oxygen blown is preferably measured using a gas flow meter.
After performing the above distillation treatment, a heat reforming treatment may be performed.
Since the pitch obtained by the distillation treatment may lack the β component, which is a quinoline-soluble and toluene-insoluble heavy component, the pitch is made heavy by the heat modification treatment and then carbonized. It is possible to suppress a decrease in carbonization yield.

As the treatment conditions for thermal reforming, it is preferable that the treatment temperature is 350 to 450 ° C. and the treatment time is 0.5 to 6 hours. If the treatment temperature is less than 350 ° C, heaviness is unlikely to occur, and if it exceeds 450 ° C, the pitch is carbonized and fluidity is lost. More preferably, it is 360 to 410 ° C. for 1 to 5 hours.

Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

First, a test method for each characteristic of coal tar pitch will be described.
[Softening point]
It was measured by the METTLER method according to ASTM D3104. First, a sample crushed to 1.6 mm or less is heated and melted at a temperature not exceeding 50 ° C. from the estimated softening point, and poured into an aluminum cup having a diameter of 2.8 mm and a height of 6.35 mm to be fixed. Next, this aluminum cup was installed in a softening point measuring device manufactured by METTLER TOLEDO, and the temperature was raised at 2 ° C./min, and the temperature at which the sample softened to block the light source was set as the softening point.
[Quinoline insoluble]
Measured according to JIS K2425. First, 1 g of a sample under a 250 μm (60 mesh) sieve was dissolved in 20 mL of quinoline at 75 ° C. for 30 minutes. Next, the soluble component was removed by suction filtration, and the residue was washed with quinoline and acetone, dried, and weighed to calculate the quinoline insoluble component.
[Toluene insoluble]
Measured according to JIS K2425. First, 2 g of a sample under a 250 μm (60 mesh) sieve was mixed with 100 mL of warm toluene and dissolved by heating for 30 minutes by a reflux operation. Next, the soluble component was removed by suction filtration while it was hot, and the residue was washed with toluene and acetone, dried, and weighed to calculate the toluene insoluble component.
[Fixed carbon]
Measured according to JIS K2425. First, 1 g of a sample under a 250 μm (60 mesh) sieve was placed in a crucible with a porcelain drop lid and heated in an electric furnace kept at 430 ° C. without a lid for 30 minutes to remove volatile components. Next, cover it and place it in a porcelain B-shaped crucible, cover it with coke grains, heat it in an electric furnace kept at 800 ° C for 30 minutes, cool it, weigh it, and fix carbon. Was calculated.

(Example 1)
Using bottom oil (C / H = 0.9, viscosity at 50 ° C. is 500 cP) obtained by a fluidized contact catalyst of petroleum as a raw material, 1800 L / kg of air was blown in, and distillation was performed at 320 ° C. for 5 hours to soften point 85. A pitch of 0.4 ° C., 0% by mass of quinoline insoluble matter, 7.8% by mass of toluene insoluble matter, 48.0% by mass of fixed carbon, and 1.72% by mass of oxygen concentration was obtained. The product yield with respect to the raw material at this time was 54.8% by mass.
(Example 2)
Using bottom oil (C / H = 0.9, viscosity at 50 ° C. is 500 cP) obtained by a fluidized contact catalyst of petroleum as a raw material, 2023 L / kg of air was blown in, distilled at 330 ° C. for 4 hours, and softened point 109. A pitch of 0.4 ° C., 0% by mass of quinoline insoluble matter, 13.4% by mass of toluene insoluble matter, 49.6% by mass of fixed carbon, and 2.71% by mass of oxygen concentration was obtained. The product yield with respect to the raw material at this time was 45.7% by mass.
(Example 3)
Using bottom oil (C / H = 0.9, viscosity at 50 ° C. is 500 cP) obtained by a fluidized contact catalyst of petroleum as a raw material, 2098 L / kg of air was blown in, distilled at 330 ° C. for 5 hours, and softened point 132. A pitch of 0.2 ° C., 0% by mass of quinoline insoluble matter, 18.1% by mass of toluene insoluble matter, 53.3% by mass of fixed carbon, and 3.66% by mass of oxygen concentration was obtained. The product yield with respect to the raw material at this time was 41.9% by mass.
(Example 4)
The pitch obtained in (Example 1) was thermally reformed at 410 ° C. for 3 hours to soften at 101.4 ° C., quinoline insoluble content 1.7% by mass, toluene insoluble content 16.4% by mass, and fixed carbon 56. A pitch of 0.3% by mass and an oxygen concentration of 1.73% by mass was obtained. The product yield with respect to the pitch of (Example 1) at this time was 94.5% by mass.

(Comparative Example 1)
Quinoline insoluble content was removed from 3.2% by mass of coal tar generated from the coke oven for blast furnace, and distilled at 320 ° C. for 7 hours in a nitrogen atmosphere, softening point 221.0 ° C., quinoline insoluble content 13.7. A pitch of mass%, toluene insoluble content 58.3 mass%, fixed carbon 72.3 mass%, and oxygen concentration 1.20% was obtained. The product yield with respect to coal tar as a raw material at this time was 46.2% by mass.
(Comparative Example 2)
Using bottom oil (C / H = 0.9, viscosity at 50 ° C. is 500 cP) obtained by a fluid contact catalyst of petroleum as a raw material, 1800 L / kg of toluene was blown in, and distillation was performed at 330 ° C. for 5 hours to soften point 71. At 1 ° C., a pitch of 0% by mass of quinoline insoluble matter, 4.5% by mass of toluene insoluble matter, 34.6% by mass of fixed carbon, and 0.35% by mass of oxygen concentration was obtained. The product yield with respect to the raw material at this time was as low as 25.4% by mass.
Table 1 shows the raw materials in the above Examples and Comparative Examples, the distillation treatment conditions, the characteristics of the obtained pitch, and the results of the carbonization yield of the product.

From the above results, the carbon material products obtained by the pitches produced in Examples 1 to 4 exhibited excellent properties. On the other hand, Comparative Example 1 using coal tar as a raw material was not satisfactory because it had a high softening point and a high quinoline insoluble content. Further, in Comparative Example 2 distilled under nitrogen, the softening point was low and the carbonization yield was low. Therefore, the pitch for a carbon material raw material of the present invention can obtain a carbon material having an excellent carbonization yield.

Claims (5)

A pitch for a carbon material raw material, characterized in that the softening point is 50 ° C. or higher and lower than 200 ° C., the quinoline insoluble content is 3% by mass or less, and the oxygen concentration is 0.4% by mass or more. A carbon material that uses petroleum-based heavy oil as a raw material and is distilled in an oxidizing atmosphere to have a softening point of 50 ° C or higher and lower than 200 ° C, a quinoline insoluble content of 3% by mass or less, and an oxygen concentration of 0.4% by mass or more. Method of manufacturing pitch for raw materials. The method for producing a pitch for a carbon material raw material according to claim 2, wherein after performing the distillation treatment, a heat reforming treatment is further performed. The petroleum-based heavy oil has a carbon to hydrogen atomic number ratio C / H of 0.6 to 1.1 and a viscosity at 50 ° C. of 30 to 1000 cP. The method for producing a pitch for a carbon material raw material according to. The production of a pitch for a carbon material raw material according to any one of claims 2 to 4, wherein the oxidizing atmosphere is 300 to 350 ° C. and the amount of oxygen blown is 1300 to 2100 L / kg. Method.