JPH0597721A - Production of methylnaphthalene - Google Patents

Abstract

PURPOSE:To separate purified methylnaphthalene from a methylnaphthalene- containing oil with simple procedure in high yield and purity. CONSTITUTION:A methylnaphthalene-containing oil obtained by the fractional distillation of coal tar is distilled to collect a fraction having a boiling point of 220-250 deg.C. The fraction is extracted with an inorganic acid such as sulfuric acid and hydrochloric acid to remove the basic nitrogen-containing compound such as quinoline and isoquinoline and to obtain purified methylnaphthalene. The preparatory distillation process enables the fractional removal of the light component such as naphthalene and the heavy component such as indole, biphenyl, dimethylnaphthalenes, acenaphthene and dibenzofuran and prevents the generation of sludge in the subsequent acid extraction process.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for separating and purifying methylnaphthalene from a methylnaphthalene-containing oil obtained by fractional distillation of coal tar.

[0002]

BACKGROUND OF THE INVENTION Methylnaphthalene is useful in various industries as a raw material for solvents, dye carriers, vitamins, high-performance resins, etc. The method is known. However, methylnaphthalene-containing oil obtained by fractional distillation of coal tar contains basic nitrogen-containing compounds such as quinoline and isoquinoline which have a boiling point close to that of methylnaphthalene. High-purity methylnaphthalene cannot be obtained without removing biphenyl, dimethylnaphthalene, acenaphthene, dibenzofuran, and the like.

As means for removing the basic nitrogen-containing compound, conventionally, a coal tar fractionated distillate is reacted with an acid to remove the basic nitrogen-containing compound as a water-soluble salt, and then fractionated. A method for obtaining separated and purified methylnaphthalene is known. However, with this method,
When the acid is reacted, a large amount of tar-like sludge is generated, which lowers the operability, lowers the recovery rate of the target methylnaphthalene, and has a problem of waste disposal. Further, as a method of separating and refining methylnaphthalene, a method of mixing methylnaphthalene-containing oil with polyalkylene glycol as an azeotropic agent and performing azeotropic distillation is also known (Japanese Patent Publication No. 63-6531).
However, this method has the disadvantage that a large amount of azeotropic agent must be used, and since the azeotropic agent is mixed in the separated and purified methylnaphthalene, the azeotropic agent must be separated from the methylnaphthalene. There is a drawback that a recovery process is required.

The inventors of the present invention have conducted extensive studies for the purpose of developing a means for efficiently separating and purifying high-purity methylnaphthalene by solving the above-mentioned drawbacks of the prior art. After the distillation, when performing acid extraction, we discovered the fact that basic nitrogen-containing compounds can be removed satisfactorily without generating sludge during the acid extraction, and we completed the invention based on this finding earlier. Filed a patent application [Japanese Patent Application No. 3-248900].

According to the invention, a methylnaphthalene-containing oil obtained by fractional distillation of coal tar is distilled to obtain a boiling point of 200-2.
A 90 ° C. fraction was obtained, which was then acid extracted to give quinoline,
It was a method of removing isoquinoline and the like to obtain semi-purified methylnaphthalene, and then fractionally distilling and removing naphthalene and the like from this semi-purified methylnaphthalene. Since three steps are required, the manufacturing process is complicated, the costs such as equipment cost and manufacturing cost are high, and the thermal efficiency is slightly poor.

As a result of subsequent research, the present inventors have found a new method capable of eliminating the above-mentioned drawbacks of the invention, and have completed the present invention.

[0007]

That is, according to the present invention,
The methylnaphthalene-containing oil obtained by fractional distillation of coal tar is distilled to obtain a fraction having a boiling point of 220 to 250 ° C., which is then acid-extracted to separate and purify methylnaphthalene from the methylnaphthalene-containing oil. It relates to a method for producing naphthalene.

According to the method of the present invention, methylnaphthalene-containing oil is previously distilled at 220 to 250 ° C. to obtain naphthalene and the like (light weight components such as naphthalene and the weight of indole, biphenyl, dimethylnaphthalene, acenaphthene, dibenzofuran and the like). Of the basic nitrogen-containing compounds such as quinoline and isoquinoline without the generation of sludge, which is found in the conventional method of directly acid-extracting oil containing methylnaphthalene, based on the acid extraction after fractional removal of Therefore, there is no need for sludge treatment, and there is no reduction in the recovery rate of the target substance due to sludge.
The desired methylnaphthalene can be separated with high purity and high thermal efficiency with a simple operation. Although the reason why such an excellent effect can be achieved by the method of the present invention is not yet clear, the generation of sludge during acid extraction is caused by the polymerization of olefins such as indole present in the methylnaphthalene-containing oil using the acid as a catalyst. It is considered that this is because, according to the present invention, the olefins and the like that cause the sludge can be removed by distillation. In any case, according to the method of the present invention, methylnaphthalene can be separated from a fractionated oil of coal tar with high yield and high purity, and this method does not require the use of an expensive azeotropic agent. Therefore, the method of the present invention is suitable for industrial practice.

Particularly, the distillation step in the method of the present invention is different from the distillation step of the invention according to the earlier application of the present inventors, in addition to preventing sludge generation during the subsequent acid extraction, removal of naphthalene and the like. According to this, there is an advantage that the facility cost and the manufacturing cost of the method of the present invention can be reduced and the thermal efficiency in the method can be improved.

In the conventional acid extraction technique, that is, the technique of distilling methylnaphthalene-containing oil after acid treatment, quinoline, isoquinoline and the like which can be removed by acid extraction can be neutralized and recovered as a by-product. It is common knowledge that the distillation step is carried out after acid extraction, and sludge generation was inevitable by this method. On the other hand, the method of the present invention was made by paying attention to the purification of methylnaphthalene, and especially when considering the equipment cost, the manufacturing cost, the thermal efficiency, etc., when the recovery of quinoline or the like is a secondary purpose, This is an effective method.

In the method of the present invention, as the methylnaphthalene-containing oil obtained by fractional distillation of coal tar as a raw material to be treated, any of various oils obtained by ordinary fractional distillation operation can be used. A typical example is about 200
An example is a fraction of 300 ° C. The composition of the representative methylnaphthalene-containing oil [by gas chromatography] is
It is as shown in Table 1 below.

[0012]

[Table 1]

In the method of the present invention, the methylnaphthalene-containing oil is first distilled to obtain a fraction having a boiling point of 220 to 250 ° C. This distillation operation can be carried out according to a well-known general method using an ordinary distillation apparatus such as a multistage distillation column under atmospheric pressure or reduced pressure, and it is not necessary to carry out rectification. The representative composition of the thus obtained fraction is as shown in Table 2 below as a result of measurement by the same measurement method as above.

[0014]

[Table 2]

Next, in the method of the present invention, the fraction obtained above is acid-extracted. This acid extraction operation is not substantially different from the operation conventionally performed, and can generally be performed using inorganic acids such as sulfuric acid and hydrochloric acid. The acid may be a concentrated acid or a dilute acid, and there is no particular limitation on the ratio of the acid to the fraction to be treated.

A desired purified methylnaphthalene can be obtained by the above-mentioned acid extraction.

[0017]

EXAMPLES Examples will be given below to explain the present invention in more detail.

[0018]

Example 1 Methylnaphthalene-containing fraction (hereinafter “%”) obtained by fractional distillation of coal tar having the composition shown in Table 1 above.
There is 1 part of the methylnaphthalene-containing fraction that is the raw material.
00%, which means the weight% relative to this), using a distillation column with 50 theoretical plates and a reflux ratio of 5 (5
Distillation at 0 mmHg), and the outflow temperature from 128 ℃ 1
45 ° C (converted to atmospheric pressure, 220 ° C to outflow temperature 25
A fraction up to 0 ° C.) was obtained. Its composition is as shown in Table 2 above.

The distillation fraction (53%) obtained above was mixed with 3
The mixture was mixed with 0% sulfuric acid at a volume ratio of 3: 2, stirred at 40 ° C. for 2 hours, and then allowed to stand and separate. At this time, the separated state of the interface was good, and the generation of sludge was not substantially observed.

The desired purified methylnaphthalene (45%) was obtained as described above.

The recovery of the purified methylnaphthalene thus obtained was 84%. The composition of this product according to the above-mentioned measurement method is as shown in Table 3, the basic nitrogen-containing compound was completely removed, and the loss of methylnaphthalene due to the acid extraction was not substantially observed.

[0022]

Example 2 Distillation obtained in the same manner as in Example 1 was mixed with 60% sulfuric acid at a volume ratio of 2: 1 to obtain 10
After stirring for a minute, stationary separation was performed. At this time, the separated state of the interface was good, and the generation of sludge was not substantially observed. That is, it is generally confirmed that sludge is not likely to be generated even with a high concentration of acid in the method of the present invention, although the possibility of generation of sludge is generally high when the concentration of sulfuric acid is high.

Thus, the desired purified methylnaphthalene was obtained. In this product, the basic nitrogen-containing compound was completely removed, and the loss of methylnaphthalene due to acid extraction was not substantially observed.

[0024]

Comparative Example 1 The methylnaphthalene-containing fraction shown in Table 1 above was mixed with 40% sulfuric acid at a volume ratio of 100: 45 to obtain 40
After stirring at 0 ° C. for 2 hours, stationary separation was performed. At this time, generation of a large amount of sludge (10%) was recognized near the interface. Next, the oil layer (85%) was distilled at a reflux ratio of 5: 1 (50 mmHg) using a distillation column having 50 theoretical plates.
Naphthalene etc. (7%) at 125 ° C to 140 ° C outflow temperature
Biphenyl, dimethylnaphthalene, acenaphthene, dibenzofuran, etc. are further removed at 140 ° C. to an outflow temperature of 145 ° C. to obtain purified methylnaphthalene (42%).
Got The composition of this product was measured in the same manner and the results are shown in Table 3. The recovery of methylnaphthalene was 76.
Stopped at%.

[0025]

[Table 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Futoku Sato, 1-2-2 Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd.

Claims (1)

[Claims] 1. A methylnaphthalene-containing oil obtained by distilling coal tar to obtain a distillate having a boiling point of 220 to 250 ° C., followed by acid extraction. A method for producing methylnaphthalene, which comprises isolating and purifying