JPH05171156A - Purification of tar acid - Google Patents

Abstract

PURPOSE:To carry out the purification with increased tar acid concentration in an industrially advantageous way by bringing water into contact with a specific tar acid and by making an aqueous phase extraction of an alkali salt of the tar acid. CONSTITUTION:An aqueous solution of sodium carbonate produced as a by- product by decomposition reaction of an alkali salt of a tar acid with carbon dioxide is separated, and water is then brought into contact with the tar acid containing the alkali salt present in the remaining phase [e.g. in the case of treated raw material (tar acid) >=95% in decomposition rate, the weight ratio of the raw material to water is (1:1); for treated raw material >=99% in decomposition rate, the weight ratio is (0.5:1)] to carry out aqueous phase extraction, affording the tar acid ca.100% in purity, thus accomplishing the objective purification. This tar acid is used by its addition in the decomposition reaction of the alkali salt of tar acid with carbon dioxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for increasing the concentration of tar acid (decomposition rate, hereinafter expressed in mol%) in tar acid containing an alkali salt of tar acid, and more specifically, containing tar acid. Tar acid containing an alkaline salt of tar acid obtained by decomposing an aqueous solution obtained by extracting tar acid as an alkaline salt of tar acid from carbole oil, naphthalene oil, etc. with carbon dioxide gas and / or a carbon dioxide gas (hereinafter carbon dioxide gas) The present invention relates to a method for improving the concentration (decomposition rate) of tar acid.

[0002]

BACKGROUND ART As a method for recovering tar acid from coal tar, generally, among the fractionated oils obtained by distilling coal tar, carbole oil, naphthalene oil and the like containing a large amount of tar acid are used. Contact with an aqueous solution of sodium hydroxide,
The aqueous phase is extracted as an alkali salt of taric acid, which is decomposed with carbon dioxide gas and / or sulfuric acid to be recovered as crude taric acid. The crude tar acid obtained is purified tar acid containing phenol, cresol, and xylenol as main components through several times of purification distillation.

Of the above steps, the step of decomposing an alkali salt of tarrate is generally carried out by a neutralization decomposition reaction with carbon dioxide gas and / or sulfuric acid. In the decomposition reaction with carbon dioxide, it is difficult to decompose up to 100% due to the characteristics of carbon dioxide as an acid. Therefore, it is usually decomposed up to 95 to 98% with carbon dioxide and then up to 100% with sulfuric acid. To do. Furthermore, when decomposing carbonic acid gas of an alkaline salt of tar acid,
When introducing carbon dioxide into the tartaric acid alkali salt, the taric acid and the alkali carbonate salt (usually sodium carbonate) are generated.
Carbon dioxide gas is introduced to the extent that the aqueous solution causes phase separation and precipitation of crystals does not pose a problem to promote neutralization decomposition, and then they are separated to recover the primary tar acid, and then the primary tar acid.
It is carried out by a multi-stage decomposition method in which carbon dioxide gas is again introduced into the next tar acid to neutralize and decompose it to obtain a secondary tar acid having a high decomposition rate.

In particular, as a method for further improving the decomposition rate in this multistage decomposition system, Japanese Patent Publication No. 49-39660 discloses that carbon dioxide gas is introduced again into the primary tar acid of the multistage decomposition system described above. Disclosed is a method for treating taric acid, which comprises introducing 15 to 50% by volume of water relative to the primary tarric acid and introducing carbon dioxide gas again into the resulting liquid during the hydration. ing. According to this treatment method, the secondary tar acid can be decomposed up to 99% or more.

The decomposition reaction with sulfuric acid is generally carried out by the above-mentioned decomposition of carbon dioxide gas and decomposition of sulfuric acid alone, but since it has a stronger neutralizing power than carbon dioxide gas, decomposition up to 100% is possible. Become.

[0006]

However, among the above-mentioned decomposition reactions, in the neutralization decomposition reaction using normal carbon dioxide gas, it is difficult to decompose up to 100% due to the characteristics of carbon dioxide gas as an acid, so the final decomposition Is carried out with sulfuric acid having a stronger neutralizing power as an acid, but in that case the use of sulfuric acid as an auxiliary material and the need for special equipment maintenance accompanying it occur, which is uneconomical. is there.

Further, according to the method disclosed in JP-B-49-39660, tar acid having a high decomposition rate of 99% or more can be obtained only by decomposition with carbon dioxide gas. The purpose of the present invention is to propose a method for refining tar acid that is improved and can decompose up to almost 100%.

[0008]

According to the present invention, water is contacted with tar acid containing an alkali salt of tar acid, which is a residual phase obtained by separating an aqueous solution of sodium carbonate produced as a by-product during the decomposition reaction of an alkali salt of tar acid and carbon dioxide gas. A method for purifying tar acid, which comprises extracting an aqueous tar acid alkali salt with an aqueous tar phase, wherein the aqueous phase containing the extracted tar phase alkali salt is subjected to a decomposition reaction between the tar acid alkali salt and carbon dioxide gas. The method according to claim 1, wherein the tar acid is added.

[0009]

In order to achieve the present invention, the present inventors have
Attention was paid to the difference in extraction characteristics of tar acid alkali salt and tar acid into water, and the relationship between the water content and the decomposition rate in tar acid alkali salt during carbon dioxide decomposition. The present invention will be described in more detail below.

The tar acid containing an alkaline salt of tar acid according to the present invention is obtained by distilling coal tar and distilling fractions such as carbole oil and naphthalene oil with an alkaline aqueous solution. This is the tar acid phase when the tar acid alkali salt is subjected to purification and concentration treatments such as steaming, and then the tar acid alkali salt is brought into contact with carbon dioxide gas and decomposed. The rate of decomposition of the tar acid phase thus obtained usually depends on the operating conditions and process, but is usually 95%.
~ 98%, 99% by the method disclosed in Japanese Patent Publication No. 49-39660
That is all.

The application of the present invention is applicable to a tar acid containing an alkali salt of tar acid having a decomposition rate of about 70% or more, which enables separation of a tar acid phase and an aqueous phase in a carbon dioxide decomposition treatment. In a practical implementation, it is desirable to apply tar acid containing an alkaline salt of tar acid having a decomposition rate of 95% or more, and preferably 99% or more. In the present invention, the tar acid containing the tar salt alkali salt after the carbon dioxide decomposition treatment which is the oil phase is brought into contact with water, and the tar salt alkali salt is extracted to the water phase side to improve the tar acid concentration. The contact between tar acid containing an alkali salt of tar acid and water is preferably a method in which a stirring effect is sufficiently obtained, but in an industrial stirring method, stirring with a line mixer can obtain a sufficient effect. At this time, the distribution ratio of the tar acid alkali salt in the aqueous phase extraction is about 5, so that the tar acid concentration can be reduced by washing only once.
In order to improve the ratio to around 100%, the amount of water added may be increased or decreased depending on the decomposition rate of tar acid containing an alkali salt of tar acid as a raw material. However, in consideration of the process design and the amount of generated water phase, it is preferable that the total amount of water added is small, and it is desirable to perform the multi-stage treatment in which the number of washings is increased according to the decomposition rate of the treated raw material. As an example, in the case of a treated raw material with a decomposition rate of 95%, if the treated raw material decomposed rate is 99% or more by two washings with the ratio of [treated raw material: water = 1: 1] [treated raw material: water = 1: After washing with water once at a ratio of 0.5], it is almost 1
00% tar acid can be obtained.

The decomposition rate is usually measured by titration of the amount of the alkali salt of tar acid and the amount of tar acid.
If the decomposition rate becomes 99% or more, accurate measurement becomes difficult by those methods, but in that case, it is possible to estimate the amount of alkali salt of tar acid based on the sodium concentration in the oil phase. When the above-mentioned washing with water is carried out, the tar acid having a solubility of less than the extracted tar acid alkali salt is transferred to the water phase side, and the amount of the tar acids combined is such that the tar acid concentration in the water phase is 1 to 5%. It becomes a degree. Therefore, treating this aqueous phase as wastewater
It is not preferable from the standpoint of yield and the load of wastewater treatment. Therefore, in the present invention, the generated aqueous phase is added to the tartaric acid alkali salt during carbon dioxide decomposition. The method of adding tar acid to the alkaline salt of tar acid during the decomposition of carbon dioxide in the generated aqueous phase is the method described in Japanese Patent Publication No. Sho 49-39660, in which carbon dioxide is introduced again into the primary tar acid of the multi-stage decomposition method. At the time of neutralization and decomposition, the same method as that of adding carbon dioxide to the liquid obtained by adding water to the primary tar acid,
Considering the reliable decomposition of tar acid up to 99% or more, and the balance between the amount of water washed in the washing phase and the amount of added water, the addition of water to the first tar acid is 50% of the capacity of the first tar acid. % Is desirable.

FIG. 1 shows an example of an operation flow chart and material balance when the present invention is carried out in a continuous manner.

[0014]

[Examples] In Examples 1 to 3, a tar acid containing a tar acid alkali salt after carbon dioxide decomposition treatment, which is an oil phase, was brought into contact with water, and the tar acid alkali salt was extracted to the water phase side to obtain a tar acid concentration. The experimental example in which the
An operation example in which an aqueous phase generated by the same treatment as in (1) above was added to a tarric acid alkali salt at the time of carbon dioxide decomposition to improve the decomposition rate, Example 5 includes Examples 1 to 3 and Example 4. The flow chart and material balance for continuous operation are shown below.

Example 1 As a processing raw material, the decomposition rate was 95.6% (sodium concentration 8430 pp
m) Add 100 ml of water to 100 ml of taric acid containing alkaline salt of tarrate after carbon dioxide decomposition, stir for 5 minutes at room temperature in batch method and let stand for 30 minutes to separate oil phase and water phase When the decomposition rate of the phase was calculated, the decomposition rate was 99.3% (sodium concentration 1320 ppm). In addition, 4.5 wt% of taric acid was detected in the aqueous phase after separation.

Example 2 As a processing raw material, the decomposition rate was 95.6% (sodium concentration 8430 pp
100 ml of water was added to 100 ml of taric acid containing tar acid alkali salt after carbon dioxide decomposition treatment of m), and the mixture was stirred at room temperature for 5 minutes and left standing for 30 minutes to separate an oil phase and an aqueous phase,
Further, the obtained oil phase (approximately 100 ml) was washed with water and separated again under the same conditions, and the decomposition rate of the oil phase was calculated. The decomposition rate was 99.9% (sodium concentration 230 ppm). Again 1
Tar acid was detected in an amount of 4.9 wt% in the aqueous phase after the second separation, and 4.1 wt% was detected in the aqueous phase after the second separation.

Example 3 As a processing raw material, the decomposition rate was 99.2% (sodium concentration 1520 pp
50 ml of water is added to 100 ml of taric acid containing alkaline salt of tar acid after carbon dioxide decomposition treatment of m), stirred for 5 minutes at room temperature in a batch system, and allowed to stand for 30 minutes to separate an oil phase and an aqueous phase. When the decomposition rate of the phase was determined, the decomposition rate was 99.8% (sodium concentration 560 ppm). In addition, 5.0 wt% of taric acid was detected in the separated aqueous phase.

Example 4 About tar acid generated by the same treatment as in Examples 1 to 3
When neutralizing and decomposing the aqueous phase containing 4.8 wt% into the primary tar acid (decomposition rate 80%) when decomposing carbon dioxide of the tartaric acid alkali salt, it is converted into the primary tar acid. On the other hand, 10
%, 30% and 50% by volume were added. As a result, the decomposition rate was 95.0% with no addition, whereas the decomposition rate was 97.0% at 10% addition, the decomposition rate was 98.0% at 30% addition, and the decomposition rate was 99.0% or more at 50% and the addition rate of the aqueous phase. The decomposition rate also improved with the increase of.

Example 5 FIG. 1 shows an execution flow chart and material balance when Examples 1 to 3 and Example 4 are continuously carried out.

[0020]

EFFECTS OF THE INVENTION According to the present invention, the tar acid concentration (decomposition rate) of tar acid containing an alkali salt of tar acid after carbon dioxide decomposition can be improved by a simple operation with less facility corrosion. Therefore, it can be effectively used in industry.

[Brief description of drawings]

FIG. 1 is a flow chart when the present invention is carried out in a continuous manner.

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Claims (2)

[Claims] 1. An aqueous tartaric acid salt is obtained by contacting taric acid containing taric acid-containing alkali salt, which is a residual phase obtained by separating an aqueous solution of sodium carbonate produced as a by-product during the decomposition reaction of tarric acid alkali salt and carbon dioxide gas, with water. A method for purifying tarric acid, which comprises extracting. 2. The method for purifying tar acid according to claim 1, wherein the aqueous phase containing the extracted tar acid alkali salt is added during the decomposition reaction of the tar acid alkali salt and carbon dioxide gas.