JPS62230736A - Purification of methylnaphthalene - Google Patents

Abstract

PURPOSE:To improve the desulfurization ratio, by readily removing methylbenzothiophene formed as a by-product by a recrystallization method in desulfurizing and purifying the titled compound containing the methylbenzothiophene as an impurity with anhydrous aluminum chloride. CONSTITUTION:Anhydrous aluminum chloride is added to methylnaphthalene oil containing methylbenzothiophene as an impurity and the methylnaphthalene oil is heat-treated. The aluminum chloride is then extracted and removed with water or sulfuric acid solution etc. Methylnaphthalene is then purified by a recrystallization method to readily remove the methylbenzothiophene (hydrogenated substance of the above-mentioned impurity) formed as a by-produce in the above-mentioned treatment from the methylnaphthalene to afford the aimed high-purity methylnaphthalene with a low content of sulfur-containing compounds useful as a raw material for 2,6-naphthalenedicarboxylic acid (monomer for polyesters having high heat resistance and tensile strength).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a desulfurization purification method for removing sulfur compounds contained in tar-based methylnaphthalene.

Methylnaphthalene is an important substance that is used as a solvent, dyeing carrier, heating medium, etc., and as a raw material for the synthesis of taro 2,6-naphthalene dicarboxylic acid, a polyester monomer with high heat resistance and high tensile strength. It is.

In its synthesis, the raw material methylnaphthalene is
High purity, especially low in sulfur-containing compounds or nitrogen-containing compounds, is required.

On the other hand, methylnaphthalene obtained by fractional distillation of coal tar contains impurities such as sulfur-containing compounds, nitrogen-containing compounds, and oxygen-containing compounds.

Among these, nitrogen-containing compounds can be relatively easily removed by acid washing, alkali melting, etc., but oxygen-containing compounds and sulfur-containing compounds are not easily removed.

In particular, sulfur-containing compounds are large in quantity, and it is important to remove them.

The sulfur-containing compounds in methylnaphthalene are mainly methylbenzothiophenes, and since their boiling points are close to that of methylnaphthalene, they cannot be removed simply by distillation.

For this reason, various F and 9 proposals have been carried out regarding the desulfurization purification of tar-based methylnaphthalene. For example, a method of treatment with metallic sodium (February 1960, Nikkan Kogyo Shimbun Publishing, "Tar Products", p. 100, JP-A-60-18658)
No. 8), anhydrous aluminum chloride treatment method (January 15, 1980, published by Japan Aromatic Industry Association, "Aromatics", Vol. 32, No. 1.2, pages 6-9), sulfuric acid treatment method (
"Aromatic and Tar Industry Handbook" published by the Japan Aromatic Industry Association, December 1971, p. 81), melt crystallization method (JP-A-57-95923), solvent crystallization method, hydrogen desulfurization There are laws etc.

Among these, treatment with metallic sodium, sulfuric acid treatment method, melt crystallization method, and solvent crystallization method (recrystallization method) are
There are disadvantages such as low rate. On the other hand, although the hydrodesulfurization method has the advantage of obtaining a high desulfurization rate, it is only 0.5 to 0.7
In order to remove the sulfur-containing compounds contained in the sulfur-containing compounds, part of the methylnaphthalene is quenched with hydrogen to form methyltetralin, which is not a good idea.

Furthermore, removal treatment using peroxides such as hydrogen peroxide is also considered, but this has the disadvantage of a low removal rate and has not been adopted industrially.

On the other hand, a method of polymerizing methylbenzothiophene using a Lewis acid, especially the anhydrous salt 1-hyaluminum, and removing it by fractional distillation is conventionally known. However, this method has the disadvantage of a low desulfurization rate, and although research has recently been conducted on its use in combination with acetyl chloride, it has the disadvantage of high cost.

Problems to be Solved This invention provides a method for purifying methylnaphthalene that overcomes the drawback of the low desulfurization rate of the method of polymerizing and removing methylbenzothiophene using anhydrous aluminum chloride. As a result of intensive research into the reason why the desulfurization rate is not improved in the method of removing methylnaphthalene by anhydrous aluminum chloride treatment, the presenters explained in detail that the desulfurization of methylbenzthiophenes, which are the main components of sulfur-containing compounds, Although the desulfurization rate was good, we found that some methylbenzothiophene was converted to a hydrogenated product (dihydromethylbenzothiophene), reducing the desulfurization rate.

Conventionally, Lewis acid treatment of water collection aluminum chloride, etc.
Methylbenzothiophene is said to be converted into a high boiling point polymer, and it has not been found that some of it is converted into a hydrogenated product.

For this reason, in conventional methylnaphthalene desulfurization treatment using a Lewis acid such as anhydrous aluminum chloride, a simple distillation operation was performed to simply remove heavy components, and then the product was produced. In this method, methylnaphthalene and dihydromethylbenzothiophene, which is a hydrogenated product, could not be separated, and it seems that a sufficient desulfurization rate could not be obtained.

The present inventors have discovered that dihydromethylbenzothiophene, a by-product, can be separated from methylnaphthalene as a result of experimental research on a method for removing it from methylnaphthalene during the desulfurization treatment of methylnaphthalene using anhydrous aluminum chloride. Subsequently, as a result of further testing and research, it was found that directly desulfurizing methylnaphthalene by the recrystallization method has a high desulfurization rate because the behavior of the sulfur-containing compound methylbenzothiophene is similar to that of methylnaphthalene, and it precipitates as a eutectic. It has been found that dihydromethylbenzothiophene, which is produced as a by-product when methylnaphthalene is treated with anhydrous aluminum chloride, can be easily removed by a recrystallization method, although it is as low as 50 to 70%.

That is, this invention involves adding anhydrous aluminum chloride to methylnaphthalene oil containing methylbenzothiophene as an impurity, heat-treating the oil, and then adding water or fi*iy
This is the M'H method for producing methylnaphthalene, which is characterized in that aluminum chloride is extracted and removed using a T solution, and then I is produced by a recrystallization method.

As the recrystallization solvent, alcohol, ether or ketone solvents can be used, and methyl alcohol is suitable.

Since it is recrystallization, the purity of methylnaphthalene (preferably high) is suitable from the viewpoint of yield etc. for α-methylnaphthalene or β-methylnaphthalene of 90% or more.

Approximately 90% of cihitromethylhensothiophene in methylnaphthane after water collection aluminum chloride treatment can be removed by recrystallization.

Moreover, since the nitrogen-containing compounds in methylnaphthalene increase the consumption of anhydrous aluminum chloride, it is desirable to remove them in advance, but this is not an essential requirement. When nitrogen-containing compounds are removed in advance, the amount of anhydrous aluminum chloride added is 0.00 molar ratio to the total sulfur content in methylnaphthalene.
0.01 to 5.0 times, preferably 0.25 to 2.0 times. The reaction is usually overheated at around 50-120'C, and if the reaction temperature is low, it will take time to dissolve the anhydrous aluminum chloride.
If the reaction temperature is high, methylnaphthalene itself undergoes isomerization (α-form and β-form), polymerization due to side reactions, and lightening. A sufficient reaction time is about 15 minutes after dissolving the anhydrous aluminum chloride. Even including the dissolution time, 60 minutes is sufficient. After completion of the reaction, it is preferable to remove anhydrous aluminum chloride and then recrystallize. This is to prevent hydrogen chloride or anhydrous aluminum chloride from being mixed into the methylnaphthalene product. Fresh water salt 1 Hyalium may be removed by a known method using water or water-soluble γα such as hydrochloric acid or chain acid.

The amount of solvent added to methylnaphthalene after anhydrous aluminum chloride treatment varies depending on the amount of solvent, or in the case of methyl alcohol, it is appropriate to add 0.5 to 3 times the weight of methylnaphthalene, preferably 1 to 2 times the weight. It is.

Example 3000 g of methylnaphthane having the properties shown in Table 1 was
Add 68.6 g of anhydrous salt f hyaluminum (1.0 times the mole of sulfur) to it in a four-bottle flask.
The reaction was carried out at 80°C for 60 minutes. Add to this 5% rare (RIte)
:(After adding 00g of water and removing aluminum chloride, wash with 300g of 5% sodium hydroxide solution α?
fought.

750 g of methanol to 500 g of methylnaphthalene after washing
350 g of methylnaphthalene was recovered by recrystallization at -10'C. The properties of the recovered methylnaphthalene are shown in Table 1. For comparison, 750 g of methanol was added to 500 g of raw material methylnaphthalene, and -
Recrystallization was performed at 10°C, and 370 g of methylnaphthane was recovered. The properties of the recovered methylnaphthalene are shown in Table 1.

Note that the total sulfur content was measured by a combustion method.

As shown in Table 1, according to the method of the present invention, which is treated with anhydrous aluminum chloride and then recrystallized by adding methanol, the removal rate is 95%, whereas in the comparative example of the conventional method, , the desulfurization rate was 51%, and about half of the methylbenzthiophene was eutectic and mixed into the methylnaphthalene.

Claims (1)

[Claims] (1) After adding anhydrous aluminum chloride to methylnaphthalene oil containing methylbenzothiophene as an impurity and heat treating it, extracting and removing the aluminum chloride with water or a sulfuric acid solution, etc., and purifying methylnaphthalene by a recrystallization method. A method for purifying methylnaphthalene, characterized by: