JPH0621018B2 - Method for producing fine graphite powder - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a carbon material, and more particularly to a method for producing fine graphite powder.

[Background of the Invention]

Generally, there are two major methods for pulverizing solid materials.
(1) pulverize mechanically, (2) dissolve in a solvent and precipitate from this solution, (3) melt and spray this solid raw material,
There is a method such as.

By the way, in the case of graphite powder, the method (1) has been mainly used conventionally. It is a substance in which graphite is chemically and thermally stable with the exception of oxidants, and is therefore usually
This is because the methods of (2) and (3) cannot be adopted.
However, as a method belonging to the method (2), there is a method for producing graphite (quiche graphite) in which carbon is dissolved in a metal such as molten iron and then cooled and precipitated. On the other hand, in the method (3), although not carbon itself, there is a method for producing carbonized carbon spheres or carbon balloons by heating and melting pitches which are the raw material thereof, and spraying them to make them spherical.

In addition, there are mesocarbon microbeads obtained by separating carbonaceous mesophases generated in pitch during carbonization of pitches as insoluble components of organic solvent at the stage of small spheres. The small spheres are about 1 μm to several tens of μm in size. Further, there is a method of producing an adsorbent having fine pores by nitrating and sulfonating such mesocarbon microbeads and then heat-treating at 400 to 600 ° C. (JP-A-60-150831). ). However, the material obtained by this method retains its original shape, and the shape of the small spheres is not destroyed and miniaturized during these processing steps.

Generally, carbonaceous or graphitic carbon materials are mechanically crushed to about 1
It is relatively easy to grind to about 0 μm, but if it is less than that, it is quite difficult and costly. In particular, in the case of graphitic carbon, since graphite crystals have developed, the crushing is not easy due to slippage between the carbon layer surfaces, and furthermore, when grinding is used as the crushing method, there is a problem that the crystal structure is destroyed. is there. The particles obtained by the methods (2) and (3) are large (in mm). Although the mesocarbon microbeads are fine, they have the drawback that they must be separated from the heat-treated pitch by a solvent fractionation method, and that the yield (about 10%) is low.

[Outline of Invention]

The present invention has been made in view of the above points, and an object thereof is to provide a method for obtaining an efficient fine graphite powder by a relatively simple means.

In order to achieve such an object, the method for producing fine graphite powder according to the present invention, a carbonaceous material is treated with nitric acid or a mixed acid of nitric acid and sulfuric acid, then treated with water, an alkali or an organic solvent, and then, It is characterized in that it is graphitized at a temperature of 2600 ° C. or higher.

[Specific Description of the Invention]

 Hereinafter, the present invention will be described in more detail including examples.

Carbonaceous Material As the carbonaceous material which is a raw material of the graphite powder according to the present invention, carbonaceous mesophase and / or raw coke produced by heat treatment of pitches which are heavy bituminous substances can be preferably used.

Pitches used as raw materials for these carbonaceous materials are coal tar pitch, coal-based pitch of coal liquefaction, petroleum distillation residue oil, naphtha tar pitch produced as a by-product during thermal decomposition of naphtha, fluid catalytic cracking method of naphtha ( It is a petroleum pitch such as FCC decant oil produced as a by-product in the FCC method) or a pitch obtained by thermal decomposition of a synthetic polymer such as PVC, and if it can give graphitizable carbon by carbonization treatment, The type does not matter. These pitches are about 35
Heat treatment is performed at 0 to 500 ° C. By this heat treatment, carbonaceous mesophase (including raw coke) is generated. The formation of carbonaceous mesophase can be easily known by observing the heat-treated product under a polarization microscope. That is, the carbonaceous mesophase is identified as an optically anisotropic phase in the pitch which is an optically isotropic phase. At this time, as a form of the carbonaceous mesophase, a stage where the heat treatment is gentle,
That is, it is not the state of the mesophase small spheres generated in the initial stage of the carbonization process, but the heat treatment needs to be performed until this large sphere grows and coalesces with each other, that is, a so-called bulk mesophase stage.

The heat treatment conditions for forming the carbonaceous mesophase are determined by the elemental composition of the carbonaceous mesophase separated from the heat-treated pitch. Among the elements, it is preferable that the content of hydrogen be 2% by weight or more. This is because it is involved in the next step, that is, treatment with a mixed acid of sulfuric acid and nitric acid, that is, the introduction amount of a nitro group that is an aromatic nucleus substitution reaction.

Separation of the carbonaceous mesophase from the heat-treated pitch is performed by a precipitation method and / or a solvent fractionation method. That is, when the heat-treated pitch is allowed to stand in the molten state of the pitch, the carbonaceous mesophase precipitates downward, so only this portion is sampled. Further, the heat-treated pitch is dissolved and dispersed in an organic solvent such as quinoline or pyridine as a solvent, or an aromatic oil containing a large amount of an aromatic compound such as anthracene oil or creosote oil to obtain an insoluble component of these solvents. You can

Acid Treatment The carbonaceous material is treated in nitric acid, sulfuric acid, or a mixed acid of sulfuric acid and nitric acid.

Sulfuric acid and nitric acid are both highly concentrated, that is, sulfuric acid having a concentration of 95% or more and nitric acid having a concentration of 60% or more are preferably used. However, it need not be fuming sulfuric acid or fuming nitric acid. Only nitric acid may be used, but a mixed acid with sulfuric acid is more preferable. In the case of mixed acid, the mixing ratio of sulfuric acid and nitric acid is preferably in the range of 30:70 to 0: 100 by volume ratio, but the optimum mixing ratio is 30:70 to 70:30. Less than,
A mixed acid of sulfuric acid and nitric acid is simply called a mixed acid.

Add carbonaceous material to nitric acid or mixed acid, 0-150 ℃
Stir for 5 minutes to 5 hours in the above temperature range, or hold still. The reaction temperature and time are set according to the degree of miniaturization in the next alkali or organic solvent treatment step and the graphitization property by the graphitization treatment, but generally low temperature is a long time, high temperature is a short time. Good.

Water Treatment After the above acid treatment, the acid-treated product is treated with water. This water treatment can be carried out by dispersing the acid-treated product in water and leaving it to stand for several minutes to several hours. This water treatment promotes miniaturization.

Alkaline treatment After the above-mentioned acid treatment, alkali treatment may be performed to adjust the pH to 4 or more, whereby the miniaturization effect can be exhibited. At this time, the alkaline aqueous solution may be added directly to the acid-treated product, or the alkaline aqueous solution may be added to the product which has been filtered and washed sufficiently with water. According to the latter method, the amount of the alkaline aqueous solution used can be small. The alkaline aqueous solution used for pH adjustment is alkaline metal salt, ammonia water, etc. However, when alkaline metal salt is used, alkali metal may remain, so it is necessary to wash thoroughly with water. After adjusting the pH, water is removed by filtration, centrifugation or heating as it is.

This alkali treatment, when combined with the above-mentioned acid treatment, extremely effectively contributes to pulverization.

Organic solvent treatment The same effect can be exhibited by treating the acid-treated product with a specific organic solvent (organic compound medium) instead of the water or alkali treatment.

Examples of the organic solvent used for such a purpose include alcohols, ketones, amines, aromatic hydrocarbons and mixtures thereof. Specifically, n-butanol, isopropanol, alcohols such as ethanol, ketones such as acetone, dimethyl sulfoxide, N,
Amine such as N'-dimethylformamide and aromatic hydrocarbon such as benzene are preferably used.

Graphitization The carbonaceous material treated with water or alkali or organic solvent is graphitized at 2600 ° C or higher. If the graphitization temperature is lower than 2600 ° C., only those having a low graphitization property can be obtained. On the other hand, in consideration of economy, the graphitization temperature is preferably 3000 ° C or lower.

By each of the above treatments, the carbonaceous material is miniaturized. The degree is about 1/10 or less of the particle size of the raw material. Therefore, the particle size of the obtained product depends on that of the raw material, but since the carbonaceous mesophase is soft, it is easy to grind it to a size of about several tens of μm. The micronized particles are horny. Further, the miniaturization mainly occurs at the stage of acid treatment (nitration, sulfonation treatment) and is promoted by treatment with water, alkali or an organic solvent. The introduced nitro group and sulfone group are decomposed and eliminated at about 250 to 350 ° C. The graphitization property of the graphite powder obtained by the graphitization treatment depends on the degree of nitration and sulfonation treatment. If these reaction conditions become strict, the graphitization property will deteriorate, and in some cases, it will be completely similar to amorphous carbon. Therefore, the selection of reaction conditions is also important in order to obtain an excellent graphitizing property.

According to the method of the present invention, fine graphite powder of high quality,
Since it can be obtained by a relatively easy method, it is industrially very useful. The graphite powder obtained by the method of the present invention can be widely applied as a finely divided carbon material such as a catalyst and an adsorbent.

Examples of the present invention will be described below, but the present invention is not limited to the description of these examples.

Example 1 (Preparation of carbonaceous mesophase) A carbonaceous mesophase prepared from coal tar pitch as a raw material was prepared as follows. Add about twice the amount of quinoline to coal tar pitch and heat to about 90 ° C to dissolve,
Dispersed. An insoluble component was settled by a centrifugal settler, and the supernatant was filtered under reduced pressure with a glass filter (No., 4). New quinoline was added to the precipitate and the same operation was performed. Quinoline was removed from the filtered supernatant by distillation under reduced pressure to obtain coal tar pitch containing no free carbon as a distillation residue. This coal tar pitch about 2
Put kg into a 3L container and stir at 3 ° C / mi
The temperature was raised to 450 ° C. at a heating rate of n and held for 2 hours.
After cooling to room temperature, cinolin was added in an amount of about 3 times and heated to about 90 ° C. to dissolve and disperse. Then, after insoluble components were settled by a centrifugal settler, the supernatant was removed, new quinoline was added to the sediment, and the same operation as above was performed until the quinoline was slightly colored. The precipitate was thoroughly washed with benzene and then with acetone to remove quinoline, and then dried to obtain a carbonaceous mesophase. The carbonaceous mesophase thus prepared has an elemental composition of carbon 9
It was 2.9%, hydrogen 4.1%, and nitrogen 0.5%. This was designated as carbonaceous mesophase A.

In addition, 2 kg of FCC decant oil from which low-melting point components having a boiling point of about 500 ° C were removed by vacuum distillation in advance was placed in a 5 L container and stirred in a nitrogen gas stream while stirring at 500
After heating to 0 ° C and holding for 2 hours, heating and stirring were stopped and the mixture was allowed to cool. When the internal temperature reached 400 ° C, while maintaining this temperature by heating, after allowing a total of 3 hours to start cooling, about 1.6 kg of pitch-like material was extracted from the extraction hole provided at the bottom of the container. I took it out. About twice the amount of quinoline was added to this pitch-like substance, and the mixture was heated to 90 ° C. to dissolve and disperse. Next, the insoluble component was separated with a centrifuge, new quinoline was added to this insoluble component, and the mixture was heated and then centrifuged. After repeating this operation 5 times, the insoluble component was thoroughly washed with benzene and acetone and dried. The amount of the insoluble component obtained was 1.2 kg, and when the structure was observed with a polarization microscope, it was an anisotropic phase having a flow structure on the entire surface. Therefore, this insoluble component was used as a carbonaceous method. The elemental composition of the carbonaceous mesophase thus prepared was as follows: carbon 93.2%, hydrogen 3.8%, and nitrogen 0.7%. This was designated as carbonaceous mesophase B.

(Nitration and sulfonation treatment) 100 ml of a mixed acid of 97% concentrated sulfuric acid and 67% concentrated nitric acid in a volume ratio of 50:50 was placed in a 300 ml triangular flask and cooled with ice water. To this, 5 g of carbonaceous mesophase having a particle size of 0.70 to 0.35 mm was added little by little. After adding the whole amount, the mixture was left at 20 or 100 ° C. for 1 hour. In this way, nitration treatment was performed. On the other hand, the sulfonation treatment was performed as follows. Add 100 ml of 97% concentrated sulfuric acid to a 300 ml triangular flask, add 5 g of carbonaceous mesophase to it, and heat to 100 or 150 ° C.
Left for hours.

The particle size distribution of the nitrated and sulfonated product thus obtained was measured in the range of 188 to 1.9 μm by a particle size distribution measuring device by a laser diffraction method manufactured by Malvern UK. As the measuring method, water was put in the cell and gently stirred, and 2-3 drops of a sample taken with a pipette was added thereto. Immediately after the addition, the particle size distribution was measured. With this as the measurement time of 0 minutes, the particle size distribution after the elapse of time was sequentially measured, and the change in the particle size distribution due to the elapsed time was examined. The pH at this time was 1 or less.

(Graphitization) On the other hand, after adding the nitration and sulfonation products to about 500 ml of water, a membrane filter (opening 0.1 μm)
After filtration under reduced pressure with, washed with water, and dried. Then, it was heated to 800 ° C. in a nitrogen gas in a tubular furnace, further heated to 2800 ° C. in a stream of argon at a temperature rising rate of 400 ° C./min in a Tammann furnace, and held for 30 minutes for graphitization. Then, the graphitization property was examined by the X-ray diffraction method.

The obtained results are summarized in Tables 1 and 2.

Example 2 Nitration was adjusted as described in Example 1.
Collect 1 part of this in a beaker containing 50 ml of water and
-Adjusted to pH 4.6 with NaOH solution.
Then, the particle size distribution was measured using an aqueous solution of the same pH as a medium. The results are shown in Table 3.

When comparing the results in this table with those in Table 1, the pH was 4
By adjusting as described above, it can be seen that the entire particle is miniaturized. At the same time, in the case of Table 1, particles with a size of 10 μm or less are aggregated and become apparently large particles with the passage of time in an aqueous medium. It can be seen that, despite the passage of time, the particles become finer without aggregation of particles.

Example 3 A carbonaceous mesophase similar to that in Example 1 was used. This 2
g was added to 50 ml of a mixed acid of 97% concentrated sulfuric acid and 67% concentrated nitric acid in a volume ratio of 50:50, and the mixture was left at 20 and 100 ° C. for 1 hour. Further, 2 g of the same carbonaceous mesophase was added to 50 ml of 97% concentrated sulfuric acid, left at 100 ° C. for 1 hour, and then allowed to cool to room temperature. The particles thus treated were directly measured for particle size distribution as follows.

About 20 ml of the medium was placed in the cell for measuring the particle size distribution, and 1 to 2 drops of the treated material (mixture of carbonaceous mesophase and acid) collected in a glass tube having an inner diameter of 1 mm was added thereto while stirring. Immediately after the addition, the particle size distribution was measured. Then, the measurement was repeated with the lapse of time as it was, and the change of the particle size distribution was examined according to the elapsed time. In addition, as a medium, ethanol, n-butanol, isopropanol as an alcohol, acetone as a ketone, dimethyl sulfoxide as an amine, N, N'-dimethylformamide, benzene containing a small amount of ethanol as an aromatic hydrocarbon (ethanol Is a dispersion medium). The results obtained are shown in Table 4.

From these results, in the case of n-butanol or isopropanol, almost no change with time of the particles was observed, but with ethanol, benzene, acetone, which is a ketone, or dimethyl sulfoxide, which is an amine, the particles became finer over time. Oxidation occurs remarkably and equilibrium is reached in about 30 minutes. This means that treatment with an acid causes miniaturization, but this miniaturization is promoted in ethanol, aromatic hydrocarbons, ketones and amines.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidemasa Honda 3-29-23 Wada, Suginami-ku, Tokyo (72) Inventor Masayoshi Fujii 290-13 Kamikoga, Chikushino-shi, Fukuoka (72) Inventor Masanori Minohata Noriko Kuriyama, Examiner, 4-21 Daisen Nakamachi, Sakai City, Osaka Prefecture

Claims (1)

[Claims] 1. A carbonaceous mesophase containing 2% by weight or more of hydrogen and / or a carbonaceous material consisting of raw coke is treated with nitric acid, sulfuric acid or a mixed acid of nitric acid and sulfuric acid, and then water, alkali or organic. Treated with solvent, then 2
A method for producing fine graphite powder, which comprises performing graphitization at a temperature of 600 ° C. or higher.