JPH0321590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing pitches for carbon materials, and more particularly to a method for manufacturing pitches for carbon materials in which the resulting carbon fibers have good mechanical strength.

Traditionally, carbon fibers have been produced by firing fibers obtained from polyacrylonitrile. However, this requires expensive raw materials;
Another problem was that the carbonization yield during firing was low. Therefore, in recent years, many manufacturing methods using petroleum pitch or coal pitch as raw materials have been proposed.

However, the mechanical strength of carbon fibers obtained by conventionally proposed methods was not sufficiently high.

Therefore, the present inventors investigated the development of carbon fibers with sufficiently high mechanical strength and found that the sulfur content contained in pitch for carbon materials has a large effect on the mechanical strength of carbon fibers. , found that by reducing the amount of sulfur content, the objective was achieved. The present invention was completed based on this knowledge.

That is, in the present invention, heavy oil with a sulfur content of 0.2% by weight or less obtained by desulfurizing heavy oil with a boiling point of 250°C or higher is subjected to a first heat treatment at a temperature of 400 to 460°C and a pressure of 5 to 50 mmHg. Then the temperature is 450~500℃,
The present invention provides a method for producing a pitch for carbon material having a sulfur content of 0.2% by weight or less, which is characterized by performing a second heat treatment at a pressure of 0.1 to 5 mmHg.

Various types of heavy oil with a boiling point of 250°C or higher, preferably 400°C or higher, which is the raw material oil of the present invention, are widely used. Usually, heavy oil with a boiling point of 250°C or higher obtained from crude oil, coal, etc., tar, etc. can be used. Particularly suitable is fluid catalytic cracking residual oil of petroleum. These heavy oils usually contain about 1 to 5% sulfur.

In the present invention, first, the heavy oil as described above is subjected to a desulfurization treatment to obtain a heavy oil having a sulfur content of 0.2% by weight or less.
The desulfurization treatment may be carried out by a commonly used method and is not particularly limited. For example, cobalt-molybdenum oxide is used in the presence of hydrogen at a temperature of 300 to 400°C. After desulfurization treatment, the catalyst is removed.

Next, this heavy oil is heat treated to form mesophase pitch. Prior to heat treatment, if the heavy oil contains light oil components, particularly light oil components with a boiling point of 400° C. or lower, it is desirable to distill them off by vacuum distillation.

The heat treatment is carried out in a two-stage process. The two-stage heat treatment is performed as follows.

First, the heavy oil obtained above is subjected to a first stage heat treatment. This first stage heat treatment is performed at a temperature of 400 to 460℃ and a pressure of 5℃.
~50mmHg, preferably temperature 410~450℃, pressure 10
It is performed under conditions of ~50mmHg. Note that the heat treatment time is usually 0.1 to 20 hours, preferably 0.2 to 10 hours. If the temperature of the first stage heat treatment is less than 400℃, the reaction will be slow and the heat treatment will take a long time.
If the temperature exceeds 460°C, the amount of volatile matter removed increases, the yield decreases, and coking occurs, which is not preferable. In addition, if the pressure of the first stage heat treatment is less than 5 mmHg, the amount of volatile matter removed increases and the yield decreases, and if it exceeds 50 mmHg, the removal of light components becomes insufficient and the molecular weight distribution becomes wide, so it is preferable. do not have.

If a large amount of mesophase pits are generated in the first stage heat treatment step, it is better to remove the mesophase pits by specific gravity separation or the like. Furthermore, when mesophase pits are not generated, the next second stage heat treatment may be applied to the heavy oil as it is.

The isotropic pitch thus obtained is subjected to a second heat treatment. This second stage heat treatment is performed on isotropic pitches or isotropic pitches containing slight mesophase pitches under more severe conditions than the first stage heat treatment.
It is preferably carried out at a temperature of 460 to 500°C and a pressure of 0.5 to 3 mmHg for 0.2 to 30 minutes. If the temperature of the second stage heat treatment is less than 450°C, it will be difficult to remove light components and the heat treatment time will be longer, while if it exceeds 500°C, the yield will decrease, coking will occur, and the reaction rate will increase. This is not preferable because it becomes difficult to control. In addition, if the pressure of the second stage heat treatment is less than 0.1 mmHg, the yield will decrease and the vacuum equipment will become bulky, and if it exceeds 5 mmHg, the removal of light components will be insufficient and the molecular weight distribution will become wide, so it is preferable. do not have. Furthermore, in order to raise the softening point, the pressure may be lowered or the treatment time may be increased.

In this way, a pitch for carbon material is obtained. Carbon fibers, films, filaments, yarns, etc. produced from this pitch for carbon materials have excellent mechanical strength, particularly tensile strength and tensile modulus. Therefore, the method for producing pitches for carbon materials of the present invention is extremely useful for producing raw materials for various carbon materials, carbon fibers, films, filaments, yarns, and the like.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 80 g of fluidized catalytic cracking residual oil (sulfur content: 1.2% by weight) of heavy gas oil was placed in an autoclave with an internal volume of 300 ml.
20g of cobalt-molybdenum oxide supported alumina catalyst was added as a desulfurization catalyst, and hydrogen gas was added at 60Kg/ ^cm2.
1 at a reaction temperature of 370℃.
The reaction was carried out with stirring for hours. As a result, desulfurized heavy oil with a sulfur content of 0.1% by weight was obtained. This desulfurized heavy oil is filtered to remove the catalyst, and then the light oil is removed by vacuum distillation to achieve a softening point of 100.
A residual oil soluble in toluene at °C was obtained.

The obtained residual oil is subjected to the first heat treatment step,
Heat treatment was performed for 1 hour and 30 minutes at 420℃ and 10mmHg, followed by a second heat treatment process at 460℃ and 10mmHg.
Heat treatment was performed for 20 minutes under the condition of 1 mmHg. As a result,
A pitch for carbon material with a sulfur content of 0.1% by weight, a softening point of 30°C, and an optically anisotropic phase of 100% was obtained.

After spinning this pitch into fibers with a thread diameter of 10 μm, the fibers were made infusible by increasing the temperature from 200° C. to 400° C. over 10 minutes in air. Then 1500
Carbon fibers were obtained by firing at ℃ for 10 minutes.
The obtained carbon fiber had a tensile strength of 300 Kg/mm ² and a tensile modulus of 28 ton/mm ² and had high mechanical strength.

Comparative Example 1 A residual oil from fluid catalytic cracking of heavy gas oil (sulfur content: 1.2% by weight) was heat treated under the same conditions as in Example 1 without being desulfurized. After heat treatment, sulfur content
0.8% by weight, softening point 310℃, optically anisotropic phase 100%
A pitch for carbon material was obtained.

Carbon fibers were obtained from the resulting pitch in the same manner as in Example 1. The resulting carbon fiber has a tensile strength of 250
Kg/mm ² and tensile modulus of elasticity was 25 ton/mm ² .

Claims (1)

[Claims] 1. Heavy oil with a sulfur content of 0.2% by weight or less obtained by desulfurizing heavy oil with a boiling point of 250°C or higher at a temperature of 400°C or higher
First stage heat treatment is performed at 460℃ and pressure of 5 to 50 mmHg, followed by temperature of 450 to 500℃ and pressure of 0.1 to 5 mmHg.
1. A method for producing pitch for carbon materials with a sulfur content of 0.2% by weight or less, which comprises performing a second heat treatment at a sulfur content of 0.2% by weight or less. 2. The production method according to claim 1, wherein the heavy oil is a residual oil from fluid catalytic cracking of petroleum.