JPH08109168A - Recovery of quinolines and indoles - Google Patents

Abstract

PURPOSE: To recover quinolines and indoles from a tar oil fraction in balanced state. CONSTITUTION: A tar oil fraction containing quinolines and indoles is extracted with an aqueous solution of sulfuric acid to extract the quinolines in the water phase while leaving the indoles in the oil phase and these compounds are recovered from each phase. The process is carried out by preparatorily removing toluene-insoluble components and varying the free acid concentration in the water phase in the range of 2-12wt.%. The formation of emulsion phase can be prevented by this process to facilitate the separation of oil and water. Since the phase separation is facilitated, the restriction on the concentration and the amount of the acidic aqueous solution to be used for the extraction is lightened to enable the preferential production of either one of the quinoline compound or the indole compound taking consideration of the demands of these compounds.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering quinolines and indoles from a tar oil fraction.

[0002]

2. Description of the Related Art A tar oil fraction obtained by distilling coal tar contains tar acids and tar bases, and is therefore separated by alkali extraction and acid extraction. Of the tar bases, quinoline mainly has a boiling point range of 200-
Although it is contained in the middle oil fraction at about 260 ° C, this fraction contains a large amount of naphthalene compounds. Therefore, in addition to the purpose of recovering quinoline compounds, separation of quinoline compounds is also performed for the purpose of purifying naphthalene compounds. Is done. In addition, indoles are also included in this fraction, and indole compounds are separated for the same purpose. An example of base recovery from tar oil is shown in "Aromatic and Tar Industry Handbook" (Japan Aromatic Industry Association, December 1978), P91, and in this example, 25% sulfuric acid is used in two steps. It is extracted in. By the way, in this sulfuric acid extraction, if a high-concentration aqueous solution of sulfuric acid is used or if a large amount of sulfuric acid is used, other useful components such as indole contained in this fraction are polymerized, and the recovery rate thereof is increased. Was found to decrease. However, when an aqueous solution having a low concentration of sulfuric acid is used or the amount of sulfuric acid used is reduced, the specific gravity of the aqueous phase decreases, and there is a problem that phase separation after extraction does not work well. This problem becomes more serious as more emulsions are generated. In addition, in this sulfuric acid extraction, the indole is not extracted in the aqueous phase but remains in the oil phase, but this is recovered by using caustic alkali as indole alkali (Patent Literature 3).
No. 54,935, etc.), a method of extracting with a polar solvent (Japanese Patent Laid-Open No. 61-50966, etc.) and the like are known.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to recover quinolines and indoles from a tar oil fraction containing quinolines in good balance.

[0004]

[Means for Solving the Problems] The inventors of the present invention have made various studies in order to solve the above-mentioned problems. As a result, the occurrence of emulsion has a great relation with the difficulty of phase separation, and if the occurrence of emulsion can be suppressed, For example, it was found that the phase separation can be performed relatively easily even if the specific gravity of the aqueous phase is small. The inventors have found that the generation of emulsion is related to the toluene-insoluble content in the tar oil fraction, and the removal of this in advance can suppress the generation of emulsion. Further, they have found that there is a relation between the sulfuric acid concentration in the aqueous phase, the recovery rate of quinoline, and the recovery rate of indoles, and either of them can be preferentially recovered by changing the concentration, and the present invention was completed.

That is, according to the present invention, a tar oil fraction containing quinolines and indoles is extracted and separated using an aqueous sulfuric acid solution to extract quinolines into an aqueous phase to leave indoles in the oil phase. In recovering each of them, after removing the toluene-insoluble matter in advance, extraction and separation were performed using an aqueous solution of sulfuric acid, and the free acid concentration in the aqueous phase was varied in the range of 2 to 12% by weight to give quinolines. And a method for recovering quinolines and indoles, which is characterized by adjusting the recovery rate of indoles.

The tar oil fraction containing quinolines and indoles is a fraction at about 200 to 260 ° C. in the coal tar fraction, but is not limited to this in the present invention, and quinoline, methylquinoline, A tar oil fraction containing at least one quinoline such as isoquinoline and methylisoquinoline may be used, and it is preferable that the fraction distilled from coal tar is further subjected to operations such as distillation, extraction and storage. . Then, this fraction contains a toluene insoluble matter. A quinoline-soluble component (β-
Although there is a resin) and a component (α-resin) which is insoluble in quinoline, α-resin is a distillate of this fraction, so that the amount of α-resin, if included, is extremely small. Therefore, the substantial amount of toluene-insoluble matter is β-resin. According to some examples measured by the inventors, β-resin 300p
It is about 10 ppm of α-resin relative to about pm. This toluene-insoluble content is close to that of a resin, and is considered to be included in the pitch as a residue when distilled, and is not considered to be distilled as a fraction. Surprisingly, it is a trace amount or a small amount, It was found that the tar oil fraction containing this was large. The mechanism by which toluene-insoluble matter is formed is not confirmed, but even if it is not contained in the fraction immediately after distilling from coal tar, it undergoes further operations such as distillation, extraction, storage, and transportation. In the meantime, it is considered that heaviness occurs and toluene-insoluble matter is generated. To confirm this, the present inventors conducted the following experiment. That is, from the tar oil fraction containing a large amount of naphthalene, the residual methyl naphthalene obtained by distillation separation of naphthalene, a tar oil fraction of about 220 to 250 ° C. containing quinoline (toluene insoluble content 0.100%) is 200 ° C., 300 ° C, 400
When the toluene insoluble content was examined after heating for 2 hours at 0.1 ° C., 0.118%, 0.128%, and 0.1.
It was 140%, and it was recognized that one of the factors was temperature and time.

In the present invention, the toluene-insoluble matter is removed from the tar oil fraction before extracting the quinolines with the aqueous acid solution. It is desirable that the removal be performed to 0 as much as possible, but it is preferable that the removal be performed at 50 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less. An almost linear relationship was observed between the amount of toluene insolubles and the amount of emulsion generated. Even if the amount is very small, a small amount of emulsion is generated, but phase separation does not cause great difficulty. If the amount is not more than the above amount, there is no practical problem.

There is no limitation on the method of removing the toluene insoluble matter, but the method of removing by distillation is advantageous. In this case, the tar oil fraction is distilled, most of it is distilled off, and the toluene insoluble fraction is left as a distillation residue. The fraction distilled here contains substantially no toluene insoluble matter, and is used for the next extraction separation.

The sulfuric acid aqueous solution used for extraction has a concentration of 2
0 to 50% (weight%, the same applies hereinafter), preferably 25 to 3
It is desirable to set it to about 5%. If the concentration is too high, deterioration such as polymerization of indole occurs, and if it is too low, the difference in specific gravity from the oil phase is small and phase separation becomes difficult. Therefore, it is advantageous to lower the sulfuric acid concentration within a range that does not hinder phase separation.

The amount of the aqueous sulfuric acid solution used must be an amount sufficient to neutralize bases such as quinolines, but the free sulfuric acid concentration in the aqueous phase after extraction is 2 to 12%, preferably The amount is in the range of 3 to 11%. Here, when the concentration of free sulfuric acid is lowered, the recovery rate of quinolines decreases, but the recovery rate of indoles improves, and when the concentration of free sulfuric acid increases, the recovery rate of indoles decreases, but recovery of quinoline The rate will improve. Therefore, by varying the free sulfuric acid concentration within the above range, either one can be preferentially recovered. Of course, it is also possible to select conditions for recovering both with a relatively high recovery rate, and the concentration of free sulfuric acid at this time is 4 to 8%. By the way, when the concentration of free sulfuric acid is low, the difference in specific gravity between the aqueous phase and the oil phase becomes small, and phase separation becomes difficult. However, such a problem can be solved by removing the toluene insoluble component in advance.

The extraction can be carried out by bringing the tar oil fraction and the aqueous sulfuric acid solution into contact with each other with a mixer or the like, then allowing them to stand still and performing phase separation. Extraction temperature is room temperature to 100 ℃
Although the temperature is in the range of about 10 to 40 ° C., the lower the temperature is, the higher the recovery rate is. Also in this case, it is possible to lower the temperature by removing the toluene insoluble matter in advance. The extraction time depends on the degree of contact, but it is 1
About one minute is enough, and the rest time after that is about one hour. However, if a margin is taken, some improvement in the recovery rate can be recognized, so depending on the situation, it is possible to take several times this time. .

Since the quinoline is dissolved in the aqueous phase, it is subjected to metathesis with a base such as ammonia to liberate the quinoline, which is then separated and purified by distillation or the like to obtain quinoline, quinaldine and the like. Since the oil phase contains hydrocarbons such as naphthalene and methylnaphthalene, indole and the like, indole, methylindole and the like are obtained by caustic treatment, extraction, distillation and the like.

[0013]

Most of the toluene-insoluble matter contained in the tar oil fraction is soluble in quinoline, and it is also soluble in the tar oil fraction containing quinoline. When this is extracted with an aqueous acid solution, quinoline disappears from the oil phase and free quinoline also disappears from the aqueous phase, so the toluene insoluble matter that had been dissolved up to now precipitates, and this forms an emulsion with the aqueous acid solution. It is considered that oil and water further entered the emulsion, and the emulsion phase became large, which hindered phase separation. It can be said that by removing the toluene-insoluble matter in advance, the generation of emulsion was prevented and the phase separation was successful, whereby the concentration of free sulfuric acid, temperature, etc. could be changed in a wide range.

[0014]

【Example】

Example 1 Mainly consisting of naphthalene and methylnaphthalene, indole of 4.0%, quinoline of 9.7%, and toluene insoluble content of 3%.
About 220 including 30ppm (QI content 10ppm or less)
A tar oil fraction mainly containing a fraction at 250 ° C. was sent to a distillation column, 97% was distilled out, and 3% was left as a residue. No toluene-insoluble matter was found in the distilled fraction.
25 ml of a 30% strength aqueous sulfuric acid solution was added to 100 ml of this fraction.
After adding ml and stirring to bring them into sufficient contact, put them in a graduated cylinder and let them stand, and observe the separation state of the aqueous phase and the oil phase. After standing, no emulsion phase was observed, and clear phase separation was observed. The free acid concentration in this case is 10%.

Further, the quinoline and quinaldine contained in the oil phase were measured by varying the extraction temperature, the free acid concentration of the aqueous phase, the sulfuric acid concentration, the extraction time and the standing time, and the recovery rate of each was determined. The indole contained in the aqueous phase was measured and the recovery rate was calculated. In any case, no emulsion phase was observed. The relationship between the extraction temperature and the recovery rate is shown in FIG. 1, the relationship between the free acid concentration in the aqueous phase and the recovery rate is shown in FIG. 2, and the relationship between the sulfuric acid concentration and the recovery rate is shown in FIG. In addition,
The standard conditions were an extraction temperature of 30 ° C., an aqueous phase free acid concentration of 5%, and a sulfuric acid concentration of 30%.

[0016]

According to the separation method of the present invention, the generation of an emulsion phase can be prevented, so that oil-water separation can be easily performed. Also, the emulsion phase had to be incinerated only, but not only can most of it be recovered as useful components, but the incineration cost can be greatly reduced. Furthermore, since phase separation is facilitated, restrictions on the concentration and amount of the acid aqueous solution used for extraction are relaxed, and one of them is preferentially obtained in consideration of the relationship between the demand for quinolines and indoles. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between extraction temperature and recovery rate.

FIG. 2 is a graph showing the relationship between the free acid concentration and the recovery rate.

FIG. 3 is a graph showing the relationship between sulfuric acid concentration and recovery rate.

Claims (1)

[Claims] 1. A tar oil fraction containing quinolines and indoles is extracted and separated with an aqueous sulfuric acid solution to extract quinolines into an aqueous phase, leaving indoles in the oil phase, and collecting each. In doing so, after removing the toluene insoluble matter in advance, extraction and separation using an aqueous sulfuric acid solution,
A method for recovering quinolines and indoles, which comprises adjusting the recovery rate of quinolines and indoles by varying the concentration of free acid in the aqueous phase in the range of 2 to 12% by weight.