JPH0320435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pitch, and more particularly to a method for producing high-quality pitch, which is particularly suitable as a raw material for carbon materials, at a high yield.

Several methods are known for producing raw material pitches for carbon materials such as carbon fibers. For example, there is a method of heat-treating petroleum or coal tar pitch to obtain mesophase pitch. However, this method has various problems: the raw materials are a mixture of countless chemical species with different reactivities, making reaction design difficult in terms of equipment and operating conditions; Since inferior mesophace is mixed in the reaction product, high quality mesophace pitch cannot be obtained; especially when coal tar pitch is used as a raw material, an impurity removal step is required; Pitch has poor fluidity, so it is inferior in spinnability and moldability (compressibility) when producing carbon fibers; also, when observed under a microscope during carbonization during the production of carbon materials, it is of poor quality as a carbon material. In some cases, it exhibits a fine mosaic pattern. Furthermore, the method of producing mesophase pitch by thermally decomposing and polycondensing a liquid hydrocarbon mixture has drawbacks such as low pitch yield and the quality of mesophase pitch being not necessarily satisfactory. .

The inventor of the present invention has conducted various studies while keeping in mind the problems of the conventional methods as described above. After introducing hydrogen into the aromatic rings of a 3- to 5-ring aromatic compound at a specific ratio, It has been found that by blowing, high quality pitches with excellent carbonization properties can be obtained in high yield. The present invention was completed based on this new knowledge.

It is generally known that aliphatic hydrogen introduced into pitch reduces the carbonization yield, while heating air blowing treatment of pitch improves the carbonization yield of pitch, but may also deteriorate the carbonization properties. Are known. However, according to the method of the present invention in which hydrogen is added at a specific ratio and then air blowing is performed, an unexpected effect is achieved in that the carbonization yield of the starting material can be improved and the carbonization characteristics can be improved at the same time.

The starting material of the present invention is a coal-based heavy distillate containing 80% or more of at least one type of 3- to 5-ring aromatic compound. Such aromatic compounds include anthracene derivatives such as anthracene and methylanthracene; phenanthrene derivatives such as phenanthrene and methylphenanthrene; fluoranthene derivatives such as fluoranthene and methylfluoranthene; pyrene derivatives such as pyrene and methylpyrene; Enanthrene and its methyl derivatives; oxygen-containing aromatic compounds such as dibenzofuran, diphenylene oxide, and methyldiphenylene oxide; nitrogen-containing aromatic compounds such as quinoline and carbazole; and the like.

In the present invention, the starting materials as described above are first subjected to a slight hydrogenation treatment. Although the method of hydrogenation treatment is not particularly limited, the degree of hydrogenation is important. That is, hydrogenation is carried out to such an extent that aliphatic hydrogen (Hα+Hβ+Hγ) defined as below becomes 35 to 70% in proton NMR and the raw material does not decompose.

Ha: 6~10ppm, Hα: 1.1~2ppm, Hβ: 2~
4ppm, Hγ: 0.3-1ppm As a hydrogenation method, for example, Ni-Mo-Al ₂ O ₃
To give an example of catalytic hydrogenation carried out in the presence of a catalyst such as a Co-Mo-Al ₂ O ₃ system, a hydrogen pressure of 20 to 200 Kg/cm ² , a temperature of 350 to 440°C, and a duration of about 0.3 to 2 hours. I can do it. Alternatively, Birch reduction using Li metal and ethylenediamine (normal pressure, 100-120°C, 1-
The raw material may be hydrogenated for 2 hours).

The hydrogenated starting material is then oxidized by air blowing. Oxidation is performed until the proportion of residual aliphatic hydrogen (Hα + Hβ + Hγ) in the pitch obtained after air blowing is 15 to 35%, preferably
Continue until it reaches 20-30%. The conditions during oxidation treatment are not particularly limited, but usually under normal pressure 150~
350℃, 1 to 40 hours, aeration rate 0.5 to 10 per gram of sample
Approximately ml/second. Furthermore, when the treatment temperature is higher than the boiling point of the substance to be oxidized, it is preferable to oxidize under pressure or reflux.

According to the method of the present invention, high quality mesophase pitch can be obtained in high yield without any difficulties in terms of equipment or operating conditions. The obtained mesophase pitch has excellent fluidity and, for example, when used for producing carbon fibers, has excellent spinnability and moldability. Additionally, during carbonization, there is an optical flow that is said to exhibit excellent properties as a carbon material.
flow texture).

Example 1 Heavy anthracene oil (distillate oil from tar distillation containing anthracene, phenanthrene, acenaphthene, pyrene, etc. as main components, and a small amount of 5-ring aromatic compounds, Hα + Hβ + Hγ = 17%) was converted into Ni-Mo-
In the presence of Al ₂ O ₃ based catalyst H ₂ initial pressure 100Kg/cm ² , temperature
Hydrogenation treatment was carried out at 380°C for 2 hours. Thus, Hα+Hβ+Hγ of heavy anthracene oil increased to 35%.

Next, the hydrogenated heavy anthracene oil was heated at 220°C for 24 hours.
Treated with air blowing for an hour. The air intake rate was 2 ml/sec per gram of hydrogenated heavy anthracene oil.

The product after air blowing is distilled under reduced pressure to remove light components with a boiling point of 350°C or less to improve yield.
57% got a pitch. The aliphatic hydrogen content of this pitch was 15%, and high molecular weight components with a molecular weight of 1000 or more were also produced.

In order to confirm the carbonization characteristics of the pitch obtained in this example, a sample was placed in a heat-resistant glass tube with a diameter of 30 mm and a length of 300 mm, and the temperature was raised to 600°C in a nitrogen gas stream for 1 hour, and then kept at the same temperature for 2 hours. It was held and carbonized. The carbonization yield, defined below, was 28%.

Carbonization yield = amount of residual carbide (g) / amount of sample prepared (g
) × 100 The obtained carbide is embedded in plastic,
A photograph (200x magnification) taken with a polarizing microscope after polishing the surface is shown as a reference drawing. The pitch carbide obtained in this example exhibits optical flow behavior.

Comparative Example 1 The same heavy anthracene oil as in Example 1 was used in Example 1.
When direct carbonization was performed in the same manner as above, the carbonization yield was only 3%.

In addition, after embedding the above carbide in plastic and polishing the surface, the results of observing it with a polarizing microscope are as follows.
It is as shown in the reference drawing, and the optical flow is also shown.

Comparative Example 2 The same heavy anthracene oil as in Example 1 was used in Example 1.
When hydrogenated in the same manner as above and immediately carbonized, the carbonization yield was almost zero.

Comparative Example 3 The same heavy anthracene oil as in Example 1 was used in Example 1.
After air blowing treatment in the same manner as above, the product was distilled under reduced pressure to remove light components with a boiling point of 350°C or lower, and pitch was obtained with a yield of 76%.

When the obtained pitch was carbonized in the same manner as in Example 1, the carbonization yield was 27%.

Further, the carbide was polished in the same manner as in Example 1 and observed under a polarizing microscope, and the results showed a fine mosaic shape as shown in the reference drawings.

Comparative Example 4 The same hydrogenated heavy anthracene oil as in Example 1 was
Air blowing was performed at ℃ for 15 hours. The air intake rate was 2 ml/sec per gram of hydrogenated heavy anthracene oil.

The product after air blowing was distilled under reduced pressure to remove light components with a boiling point of 350°C or lower, thereby obtaining pituti in a yield of 33%. The aliphatic hydrogen content of this pitch was only 2%.

When the above pitch was carbonized in the same manner as in Example 1, the carbonization yield was 56%.

Further, the carbide was polished in the same manner as in Example 1 and observed under a polarizing microscope. As shown in the reference drawing, it had a fine mosaic shape.

Example 2 420 ml of ethylenediamine was added to 50 g of the same heavy anthracene oil as in Example 1, 15 g of Li was added little by little while stirring at 90 to 95°C, and stirring was continued for an additional 20 hours. After neutralizing the reaction product with hydrochloric acid, benzene was added to recover hydrogenated heavy anthracene oil. The aliphatic hydrogen content of hydrogenated heavy anthracene oil is 60
% had been reached.

Next, the hydrogenated heavy anthracene oil was subjected to air blowing treatment in the same manner as in Example 1, and then the product was distilled under reduced pressure to remove light components with a boiling point of 350° C. or lower, thereby obtaining pituti in a yield of 68%. . The aliphatic hydrogen content of this pitch was 30%.

When the above pitch was carbonized in the same manner as in Example 1, the carbonization yield was 39%.

Moreover, the polarized light micrograph of the obtained carbide is as shown in the reference drawing, and also shows the optical flow.

Claims (1)

[Claims] 1. A method for producing pituti, which comprises hydrogenating a coal-based heavy distillate containing at least one type of 3- to 5-ring aromatic hydrocarbon and then oxidizing it.