DE3012195A1 - METHOD FOR PRODUCING A PECH FROM A TAR - Google Patents

Description

description

The invention relates to a method for producing a pitch from a tar for use in coal materials, like carbon fiber, highly activated coals, light graphitizable needle-shaped coke used in the manufacture of

used by UHP electrodes, as well as highly plasticizing ones Binders that are used to manufacture graphite electrodes.

The methods previously used to produce a pitch that is used in coal materials from one Tar can be roughly divided into the following three categories:

(I) a method in which low molecular weight fractions from a tar under reduced Pressure to be distilled off;

(II) a method in which low molecular weight fractions are carried out from a tar with a solvent extracted, and

(III) a method in which low molecular weight fractions in a tar undergo polycondensation after adding an accelerator for polycondensation.

As far as the above-mentioned methods are concerned, they are in principle very suitable and are partly used in the Industry, but are not always appropriate for the following reasons

In method (I), it is necessary to produce a pitch with a softening point of more than 100 ⁰ C to work under a high vacuum, so that the installation

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costs of the still are very high and so the process is not particularly economical. Since it is also difficult to produce a pitch having a softening point of greater than 15O ⁰ C by distillation, it is difficult to obtain a pitch having a softening point of 150 to 250 ⁰ C, which is preferably used for the production of carbon fibers.

The above-mentioned softening point of a pitch is determined by the method similar to Japanese Industrial Standard K-2425 (Standard Methods for Testing Tar as well whose products: STPTC PT 3-62).

When carrying out the method (II), the amount of the solvent must be 10 to 100 times the amount of tar, so that a - expensive device even in the case it is necessary that small amounts of the raw material be treated. Furthermore, the solvent-insoluble residue becomes rubbery after extracting the low molecular weight fraction with a solvent. This rubbery Substance can hardly be separated and removed.

The accelerator for the polycondensation to carry out the method (III), for example from dinitrobenzene or Dinitronaphthalene exists / is expensive. In addition, problems arise with regard to the graphitizability of the pitch due to certain Types of accelerators and the residue of decomposition products of a catalyst in the form of ash. The catalyst is used together with the accelerator mentioned above and consists, for example, of aluminum chloride, Molybdenum chloride or metallic potassium.

The aforementioned methods (I) and (ti) are also liable the common disadvantage is that the pitch yield is low because of the low molecular weight fractions in the tar be separated without being subjected to a polycondensation.

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Heretofore, as pitches for producing the above-mentioned carbonaceous materials, those with a high softening point, which give a high carbonization yield, are used for the following reasons.

For producing carbon fiber using a pitch as a raw material, an oxidation temperature becomes close to the softening point of the pitch when the melt-spun pitch is rendered infusible by oxidation. Since the rate of oxidation of the pitch increases as the softening point of the pitch increases, the Use of a pitch with a higher softening point is extremely advantageous for economic reasons.

Also in the production of activated carbon using the pitch as a raw material, the pitch particles become after the formation subjected to infusibilization by oxidation prior to activation by steam. Even at this stage of infusibilization, the time required for infusibilization becomes the higher the softening point of bad luck shortened.

When used as a binder for the production of graphite electrodes is a hard pitch that contains small amounts of volatile fractions and a high carbonation yield results, necessary to avoid cracks during the carbonization of the electrodes.

As mentioned above, pitch is used for production of carbonaceous materials those with a high softening point that have a high carbonization yield condition, preferable.

Any of the above-mentioned methods heretofore used is not always capable of using a pitch as a raw material for production of high quality coal materials to supply.

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To solve the disadvantages outlined above, the invention provides a method for producing a Pitch made from tar, which can be used as a raw material for the production of coal materials, which are of a higher quality than the coal materials that are manufactured using the known methods Bad luck to be obtained.

The invention relates to a method for producing a pitch by mixing an extracting agent with one Tar and heating the mixture. When carrying out the process according to the invention, the pitch yield is high and is 60 to 90% by weight of the raw material, namely one Tar, whereby by changing the mixing ratio of the nitrating agent to the tar pitch with an inside softening point varying over a wide range can be obtained without reducing the yield will. In addition, the carbonization yield of the pitch obtained in this way is also high without quinoline-insoluble fractions occur and only to an extremely small extent problems due to residual ash are to be solved.

The invention is explained in more detail below:

The invention relates to a method in which one, two or more than two nitrating agents are mixed with coal tar or petroleum tar, whereupon the mixture is ^{heated to a temperature of 150 to 400 °} C. to obtain a polymer (a pitch) of the tar.

From raw material (tar) that is used to carry out the invention Process is used, a coal tar, which is a by-product in the decomposing distillation of coal accrues, a heavy fraction, which after distilling off the low-boiling fractions of coal tar accrues

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soft pitch, a purified tar, which by removing the quinoline-insoluble component is obtained from tar, tar formed in the petroleum industry, for example Ethylene floor oil, is used. Of course, tars can also be obtained by mixing two or more of the types of tar mentioned above can be used.

Dilute nitric acid and concentrated nitric acid are used as nitrating agents Nitric acid or organic nitrates, such as acetyl nitrate, in question.

The softening point of the produced pitch can be adjusted within a wide range by adjusting the mixing ratio of the nitrating agent to the tar. Usually, a pitch having a high softening point is obtained in a high yield by combining from 3 to 20% by weight of the nitrating agent with the tar. In one use of the Nitrierungsniittel in an amount of less than 3 wt .-%, the softening point of the pitch formed is below 100 ⁰ C, so that it is impossible to obtain a pitch having a high softening point. However, if the low molecular weight fraction of the pitch thus formed can be removed by distillation, then it is possible to obtain a pitch having a softening point of 150 to 250 "C, but the pitch yield is reduced to about 50%. On the other hand, it is If the nitrating agent is used in an amount of more than 20% by weight, based on the tar, then a pitch is obtained which is not particularly suitable as a raw material for the production of high-quality carbonaceous materials, since quinoline-insoluble fractions are formed must be separated.

The conditions of the above-mentioned nitration of the mixture are as follows:

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Heretofore, nitration of an aromatic hydrocarbon having a low molecular weight such as Benzene and naphthalene, using a mixture of nitric acid and sulfuric acid. Aromatic Hydrocarbon derivatives which form the tar and have more than three condensed benzene ring structures and have high reactivity to a nitrating agent when mixed with a nitrating agent spontaneous exothermic nitration with formation of nitroaromatics and nitrate esters of those mentioned above Derivatives.

The reaction of the aforementioned tar with the nitrating agent runs very easily without the reaction conditions, such as pressure, temperature, etc. need to be controlled. In order for a small amount of a nitrating agent to react effectively, the mixture can be heated.

The above-mentioned mixture is then ^{heated to a temperature between 150 and 400 °} C. in order to carry out a polymerization. The mixture in the mentioned temperature range is used in the polymerization and / or polycondensation of the above-mentioned mixture, preferably in a range of 250 to 35O ⁰ C, for a period of 1 minute to 2 hours, held to terminate the reaction. Since the unreacted low molecular weight component in the reactive tar evaporates by heating, such a low molecular weight component which evaporates can be recovered by distillation while the polymerization and / or polycondensation is carried out. In the case of using a soft pitch from which a low molecular weight component has been removed by distillation before the reaction with the nitrating agent, it is not necessary to carry out the distillation during the reaction.

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It is believed that the tar of the raw material is formed of a pitch polymerized in the following manner.

When mixing the tar with a nitrating agent (the Mixing can optionally be carried out with heating) nitro-functional groups and / or nitric acid ester-functional groups Groups formed on the organic compounds that make up the tar. These functionalities Groups are split off homolytically from the organic compound, leaving a radical behind by heating, whereupon the radicals of the organic compounds interact to form a polymeric substance together with a Polycondensation of the organic compounds react by heating. However, the invention is not limited to the above Theory limited.

Nitro-functional groups can only be found to a small extent in the pitch obtained by the process according to the invention and / or determine nitric acid ester functional groups or not at all. Hence the elemental analysis values the pitch obtained by the process according to the invention is the same as that of the pitch, which has been obtained according to the previously used method (I).

When a nitrating agent is added in an amount falling within the above-mentioned range, nothing becomes disadvantageous Influence of the nitrating agent on the quality of the pitch obtained was found.

If the heating temperature during the pitch formation lower than 150 ⁰ C, then the elimination of the nitro groups and the Salpetersäureestergruppen of the organic compounds that form the tar is not sufficient to accelerate the polymerization and / or polycondensation, so that it is impossible to obtain a pitch with a high softening point.

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The pitch yield is even in the case that the low molecular weight components are removed by distillation recovered at the same time as the polymerization and / or polycondensation, 60 to 90% and in the case that no recovery is carried out, more than 90%, while the carbonization yield (amount of fixed Carbon) is higher than the carbonization yield in the case of the conventional methods.

Therefore, the method of the invention is for production a pitch extremely advantageous on an industrial scale.

The invention is explained in more detail below with reference to the examples. The softening point, the methods to determine the fixed carbon and the solvent-insoluble components are carried out in accordance with the Japanese Industrial Standards (JIS) -K 2425.

example 1

Concentrated nitric acid (specific gravity: 1.42, concentration: 70%) is added to a heavy fraction of coal tar obtained by recovering the fraction obtained at a temperature of less than 230 ^° C. The addition takes place in a weight ratio of 8:92. The mixture is heated at 25 to 250 ⁰ C at a rate of 5 ° C / min with continuous stirring. After the mixture has been kept at 250 ^° C. for 2 hours, it is allowed to cool to room temperature, yielding a pitch of 93%. The softening point of the pitch is 12O ⁰ C. The content of the pitch to solvent-insoluble fractions is apparent from the Table I.

The pitch is then placed in an autoclave from Zimmer-

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temperature to 500 ⁰ C at a rate of 3 ° C / min under a pressure of 5 kg / cm ² and heated for 20 hours at a temperature of 500 ⁰ C to obtain a raw coke with a yield of 83%, based on the pitch, obtain. In the thus obtained raw coke, a developed flowing texture expected from raw materials for coal materials can be observed with the naked eye. The graphitized product obtained by graphitization of the raw coke in an electric furnace at a temperature of 2,000 ⁰ C in an inert gas atmosphere shows the results summarized in Table II properties.

Comparative example 1

The same heavy fraction of coal tar as was used to carry out Example 1 is distilled under reduced pressure to obtain fractions with a low molecular weight which ^{boil at a temperature of less than 350 °} C. to give a pitch with the in the properties summarized in Table I with a yield of 52%. The pitch has a softening point of 72 ⁰ C.

Raw coke is by coking the pitch in an autoclave under the conditions described in Example 1 in a 56% yield obtained. The flowing texture mentioned in Example 1 is not clear in the case of the one obtained Detect coke. The properties of the graphitized coke are shown in Table II.

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- 12 Table I.

Properties of the raw material and the products

^ "~~" - ~ -> ^^^ sample example 1 bad luck Comparative example 1 Associations "- *** - ^^^ Heavy fraction 93 bad luck Pitch yield,% - 120 52 Softening point, ⁰ C - 38.9 72 fixed carbon -
material, % 12.7 72 *. 3 21.6 heptane insolubles
Components,% «.. 27.6 *" 24.5 67.2 non-solvent
Pocj-l-anrJ-f-iai 1 <3. % 4.5 1.0 '18.3 quinoline-insoluble
Components,% 0.9 1.7

gene

Table II

shafts of raw coke materials

—- ~ —____ ^^ sample
Features ~ -_ ^ ___ example 1 Comparison
example 1 specific weight 2.13 2.09 Thermal expansion coefficient
(x 10 ~ ⁶ / ^o C) 0.47 1.05 X-ray diffraction,
Co (002) A 6,721 6,833 X-ray diffraction /
Lc (002) A. 370 280

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As can be clearly seen from Tables I and II, the process according to the invention provides a better one Coke with a needle-like appearance and with a larger specific gravity and a smaller coefficient of thermal expansion which shows excellent crystal development as compared with that Coke produced by the method of Comparative Example 1.

Example 2

Concentrated nitric acid is added to a purified tar listed in Table III. This tar has been obtained by removing the quinoline-insoluble fraction from a coal tar, the quinoline-insoluble fraction being carried out according to the determination method for determining quinoline-insoluble materials according to Japanese Industrial Standards K 2425. The addition takes place in a weight ratio of 12:88. The mixture is heated to a temperature of 60 ⁰ C in 30 minutes under stirring, and then at 300 ⁰ C at a rate of 5 ° C / min. After the heated mixture has been ^{kept at 300 °} C. for 30 minutes and the tar oil, which has distilled off from the mixture during this period, has been recovered, the mixture is allowed to cool to room temperature, a pitch of 72% being obtained. The softening point of the pitch obtained in this way is 203 ⁰ C. The properties of the pitch are shown in the Table III.

As can be seen from Table III, no quinoline becomes insoluble Fraction formed during the process according to the invention, rather a purified state is maintained.

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The pitch obtained in this way is then ^{spun at a temperature of 220 °} C. into a filament-like shape. The filaments or fibers are then rendered infusible by heating of 150 to 240 ⁰ C at a rate of 15 ⁰ CZmIn, wherein the temperature is maintained for 6 hours in an oxidizing atmosphere at 240 ⁰ C. During melt spinning, the spinning properties of the pitch are excellent, with no breakage of the filaments into pieces. The filaments infusibilized in this manner are at a temperature of 1100 ⁰ C in an inert atmosphere to carbon ilamenten in a yield of 85%, based on the pitch filaments, carbonized. The properties of the carbon filaments obtained in this way are shown in Table IV. Table IV also lists the properties of carbon filaments obtained from a lignin derivative raw material for comparison.

Example 3

The coal tar purified and used according to Example 2, a dilute nitric acid with a concentration of 25% and acetyl nitrate are mixed in a weight ratio of 82: 12: 6. After stirring for 1 hour at 20 ⁰ C the mixture to 350 ⁰ C is heated at a rate of 3 ° C / min and kept at 350 ⁰ C for 1 hour. During this time, tar oil distilling off is recovered under reduced pressure. When the heated mixture is allowed to cool to room temperature, a pitch with a softening point of 225 ° C. is obtained in a yield of 63%. The insoluble fractions of the pitch in solvents are shown in Table III. No formation of quinoline-insoluble fractions is observed during the above-mentioned method, which documents the favorable purification of the tar.

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Then, the pitch thus obtained is melt-spun at a temperature of 240 ⁰ C for the preparation of filaments or fibers. The filaments are treated as in Example 2 to obtain carbon filaments. The properties of the carbon filaments obtained in this way are shown in Table IV.

Comparative example 2

Example 2 The purified according coal tar is heated to a temperature of 330 ⁰ C under a reduced pressure of 1 mmHg until no distillate escapes more, wherein a pitch is obtained with a softening point of 145 ° C with a yield of 36%.

Since the softening point of the pitch obtained in this way is too low to be used as a raw material for the production of To be able to use carbon filaments is the pitch of a heat treatment to improve the softening point subjected.

The heat treatment is carried out at a temperature of 400 ^° C. for 6 hours in a nitrogen atmosphere under normal pressure. A pitch is obtained in a yield of 24% based on the purified tar as the raw material. The softening point of the pitch obtained in this way is 182 ⁰ C. The other characteristics of the pitch are shown in the Table III. Quinoline-insoluble fractions are formed in an amount of 9.3%. The development of spherulites is observed microscopically in the pitch. In melt spinning of the pitch at a temperature of 200 ⁰ C, a significant number of the nozzles is clogged by the spherulites, further, the filaments obtained in this manner are prone to breaking into chips, reflecting the unfavorable spin properties, which makes the production of carbon filaments difficult.

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Table III

Properties of purified tar and pitch according to Examples 2 and 3 and Comparative Example 2

* ~ ^^ sample Example 2 bad luck Example 3 Comparison
example 2 Features ^^ - >> ^^ cleaned
tar 72 bad luck Bad luck' Pitch yield,% - 203 63 24 Softening point, ⁰ C - 60.1 225 182 Fixed carbon,% 11.2 89.4
53.1
0 63.3 52.8 insoluble in heptane
Components,%
insoluble in benzene
Components,%
insoluble in quinoline
■ components, Λ 24.3
3.2
0 92.3
55.5
0 80.8
42.1
9.3

Table IV Properties of the carbon filaments

■ ~~ - ~ - ^^ _ ^^ sample
Features -—-_ ^ _ ^ Example 2 Example 3 the end Lignin derivative Diameter (micrometers) 8 to 10 8 to 10 10 to 15 Tensile strength, kg / mm ² 90 85 50 to 60 Young's modulus, kg / mm ²
! 5,300 5,000 3 , 300 to 4,000 Elongation at break,% 1.7 1.7 1.5

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The pitch produced according to the invention for the extraction of Carbon fiber is obtained in a higher yield than that obtained by the conventional method of the comparative example 2 obtained pitch and has more favorable spinning properties, while the carbon fibers in a high carbonization yield of 85%. The carbon fibers made from a pitch made according to the invention have been, carbon fibers obtained from a lignin derivative are superior in terms of tensile strength and the modulus of elasticity as shown in Table III.

According to the invention, pitches for coal materials with a high quality can accordingly be produced in an economical manner.

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Claims (6)

MÜLLER-BOItK · I) KUFEL · SCEON PATENTANWÄLTE DR. WOLFGANG MÜLLER-BORE (PATENT ADVERTISER FROM 1927-1S75) DR. PAUL DEUFEL. DIPL.-CHEM. DR. ALFRED SCHÖN. DIPL.-CHEM. WERNER HERTEL. DIPL.-PHYS. APPROVED REPRESENTATIVES TO THE EUROPEAN PATENT OFFICE REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE MANDATA1RES AGREES PRES L1OFFICE EUROPEEN DES BREVETS 21, March 1980 K 1468 Kureha Kagaku Kogyo Kabushiki Kaisha 9-11 Horidome-cho-cho-choome, Japan, Japan Metal Industries, Ltd. 15 Kitahama 5-chome, Higashi-ku, Osaka, Japan Method for producing a pitch from a tar Claims 1. A method for producing a pitch from a tar, characterized in that the tar with a nitrating agent, selected from the group consisting of nitric acid, an organic nitrate, nitrogen pentoxide or a mixture thereof, is mixed. 2. The method according to claim 1, characterized in that the nitrating agent used is mixed with the -Teer and then the mixed tar is heated to a temperature of 150 to 400 ⁰ C. 0300A0 / 08Ö7 • MUNICH K. SIEBERTSTR. 4 ■ POB 860720 · CABLE: MUEBOPAT ■ TEL. (OM) 474OW ■ TELECOPIER XEROX 400- TELEX S-24 W 3. The method according to claim 1, characterized in that the mixed tar is heated to a temperature of up to 35O ⁰ C. 4. The method according to claim 1, characterized in that the tar used is a coal tar and / or a Petroleum tar is. 5. The method according to claim 1, characterized in that the nitrating agent used with the tar is mixed in an amount of 3 to 20 wt .-%, based on the tar. 6. The method according to claim 1, characterized in that that the organic nitrate used consists of acetyl nitrate. 030040/089?