JPH023777B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a dialkali metal salt of naphthalene-2,6-dicarboxylic acid.
Naphthalene-2,6-dicarboxylic acid dialkali metal salt can be easily converted into the corresponding carboxylic acid, that is, naphthalene-2,6-dicarboxylic acid, by acid precipitation, but this naphthalene-2,6-dicarboxylic acid is a raw material for heat-resistant polyester. It has attracted attention in recent years as an acid moiety, and is an industrially valuable compound (see Japanese Patent Publication No. 54-945). BACKGROUND ART Conventionally, the so-called Henkel method has been proposed as one of the methods for producing a dialkali metal salt of naphthalene-2,6-dicarboxylic acid. This method uses an alkali metal salt of naphthalene monocarboxylic acid (i.e. naphthoic acid) or a dialkali metal salt of naphthalene dicarboxylic acid, or a mixture thereof, with an oxide such as cadmium, zinc, or mercury, or a halide or sulfate as a catalyst. , carbonate, carboxylate, etc., under pressure of carbon dioxide gas and heated to 350°C or higher. Naphthalene-2,6-dicarboxylic acid dialkali metal salt and naphthalene are generated from naphthoic acid alkali metal salt through a disproportionation reaction, and naphthalene-2,6-dicarboxylic acid is generated from naphthalene-2,6-dicarboxylic acid dialkali metal salt through a rearrangement reaction. Dialkali metal salts are selectively produced [a) B.
Raecke, Angew. Chem., 70 , 1 (1958); b) B.
Raecke et al., Org.Syn.Coll.Vol 5, 813 (1973);
c) Yamashita et al., 20 , 501 (1962); d) E.
McNelis, J.Org.Chem., 30 , 1209 (1965); e)
See US Pat. No. 2,823,231; f) Japanese Patent Publication No. 51-10224]. The alkali metal salt of naphthoic acid or the dialkali metal salt of naphthalene dicarboxylic acid, which is the raw material of the Henkel process, and also the product, naphthalene.
Most dialkali metal salts of 2,6-dicarboxylic acids are compounds with a melting point of 400°C or higher. These alkali metal salts are soluble in protic solvents such as water and alcohol;
At temperatures above 350°C, which is the reaction temperature of the Henkel method, it reacts with the alkali metal salt and decomposes them, so it cannot be used as a reaction solvent. Due to these circumstances, naphthalene-2,6-
When producing a dialkali metal dicarboxylic acid salt using the Henkel method, a method has been proposed in which a mixed powder of a raw material and a catalyst is heated and reacted under pressure with carbon dioxide gas without a solvent to obtain a solid product. However, in this method, since the raw materials and products are solid, there is a drawback that the operations for charging them into the reactor and taking them out from the reactor are more complicated than in the case of liquids. In addition, the present inventors have clarified that due to the conventional method being a solvent-free reaction, problems arise such as poor reproducibility of the reaction and low yield and selectivity of the target product. I made it. That is, the reaction is usually carried out by heating a reactor, but since the raw materials and products are solids with high melting points and there is no solvent, heat transfer between the reaction mixtures is slow and non-uniform. For this reason, some parts of the reaction mixture are overheated and a large amount of carbide is produced, while in other parts the reaction heat is insufficient and the reaction is incomplete, resulting in the remaining raw materials and the desired naphthalene-2,
The by-product of isomers other than the dialkali metal salt of 6-dicarboxylic acid becomes noticeable. As a result, both the yield and selectivity of the desired dialkali metal salt of naphthalene-2,6-dicarboxylic acid were low, and the reproducibility of the reaction was also poor. Problems to be Solved by the Invention The present inventors have conducted intensive studies to solve the problems of the conventional method, and have improved the yield and selection of the target dialkali metal salt of naphthalene-2,6-dicarboxylic acid. The present invention was completed by discovering a method to improve the reaction rate and reproducibility of the reaction. Means for Solving the Problems The present invention provides naphthoic acid alkali metal salts and/or
Alternatively, a naphthalene dicarboxylic acid dialkali metal salt is heated together with a catalyst under carbon dioxide gas pressure using an aprotic polycyclic aromatic compound having 2 to 3 rings as a dispersion medium or solvent. This is a method for producing a dialkali metal salt of 2,6-dicarboxylic acid. The raw material for the process of the invention is an alkali metal salt of naphthoic acid or a dialkali metal salt of naphthalene dicarboxylic acid, or a mixture thereof. As the naphthoic acid alkali metal salt, 1- or 2-isomer,
Alternatively, mixtures of these can be used. In addition, as dialkali metal naphthalene dicarboxylic acid salts,
1,2-,1,3-,1,4-,1,5-,1,
6-, 1, 7-, 1, 8-, 2, 3-, 2, 6
-, 2,7-isomers or mixtures thereof can be used. However, among the above isomers, naphthalene-2,6-dicarboxylic acid dialkali metal salt is the target compound of the present invention, but it can be used as a raw material when it contains a small amount itself or when a crude mixture is used. As the alkali metal salt, potassium salt gives good results as in the usual Henkel method. As the catalyst, any catalyst used in the disproportionation reaction or rearrangement reaction in the general Henkel process can be used. Representative examples include cadmium, zinc, and mercury compounds. However, since cadmium and mercury compounds are toxic and expensive, it is preferable to use zinc compounds from an industrial standpoint. Zinc compounds include zinc halides such as zinc chloride, zinc bromide, zinc iodide, zinc naphthoate,
Examples include zinc carboxylates such as zinc naphthalene dicarboxylate, zinc oxide, and zinc carbonate. It is also possible to add a small amount of an alkali halide such as potassium chloride, potassium bromide, potassium iodide, sodium bromide, and sodium iodide as a cocatalyst. The amount of catalyst used is usually
It is 1 to 10 mol% based on the raw material. Further, the amount of co-catalyst used is usually 1 to 10 mol% based on the raw material. In the following text, catalysts and co-catalysts are collectively referred to as catalysts without any particular distinction. It is preferable that the raw material and the catalyst are well mixed. For this purpose, there are methods such as adding a catalyst to an aqueous solution of the raw material and mixing well, and then heating and distilling off the water to obtain a mixture of the raw material and catalyst, or thoroughly pulverizing and mixing the raw material and catalyst with a ball mill, etc. Alternatively, there is a method in which the raw material and the catalyst are thoroughly ground, and then stirred and mixed in a dispersion medium or solvent for a polycyclic aromatic compound as described below. There is no problem. In the present invention, a raw material and a catalyst are reacted by heating in a dispersion medium or solvent under pressure of carbon dioxide gas. The dispersion medium or solvent used here is a substance that has good stability under the reaction conditions and becomes liquid under the reaction conditions. Such substances may be either single compounds or mixtures. The disproportionation reaction and/or rearrangement reaction in the present invention substantially proceeds at 350 to 500°C. Therefore, the melting point is below 500℃,
Any substance with a critical temperature of 350°C or higher becomes liquid under any reaction conditions and can be used as a dispersion medium or solvent. The present inventors have searched for a substance that has such a melting point and critical temperature, is stable under reaction conditions, and improves the reaction yield, and has found that it satisfies these requirements by reducing the number of rings. We have discovered an aprotic polycyclic aromatic compound with 2 to 3 carbon atoms. Specific examples of aprotic polycyclic aromatic compounds include naphthalene, lower alkylnaphthalenes such as methylnaphthalene and dimethylnaphthalene, diphenyl, lower alkyl diphenyls such as methyldiphenyl and dimethyldiphenyl, diaryl ethers such as diphenyl ether, and terphenyl. , anthracene, phenanthrene, or a mixture thereof. The amount used is 0.5 to 10 times, usually 1 to 5 times, the amount of the raw material. The solubility of the raw material and catalyst of the present invention in the polycyclic aromatic compound is extremely low. Therefore, the raw materials and catalyst are usually subjected to the reaction in the form of a slurry dispersed in the polycyclic aromatic compound.
At this time, in order to improve the dispersion of the raw materials and the catalyst, it is desirable that the raw materials and the catalyst, or a mixture thereof, be pulverized in advance. Also, the presence of water significantly inhibits the reaction of the present invention. Therefore, in carrying out the reaction of the present invention, it is best to dehydrate and dry the raw materials, catalyst, and the polycyclic aromatic compound in advance to obtain good reaction results. As for this dehydration and drying method, any commonly used method can be used, such as heated ventilation drying or heated vacuum drying for raw materials and catalysts, and distillation purification for the polycyclic aromatic compounds. . Furthermore, the method shown below can be added as one of them. That is, it is a method in which a slurry consisting of a mixture of raw materials, a catalyst, and the polycyclic aromatic compound is heated and a portion of the slurry is distilled off. If water is contained, this is distilled as the first distillate fraction. and can be easily removed from the mixture. This method is based on the fact that all of the polycyclic aromatic compounds are high boiling point compounds with boiling points of 200°C or higher at normal pressure, and have a large boiling point difference with water. The raw material, the catalyst, and the polycyclic aromatic compound may be introduced into the reactor either singly or as a mixture. When a mixture of the three is introduced, a method of heating it above the melting point of the polycyclic aromatic compound to form a slurry and introducing this into the reactor is also a preferred embodiment that takes advantage of the features of the present invention. There is one. The raw materials, catalyst, and
And the polycyclic aromatic compound is heated under pressure of carbon dioxide gas to cause a reaction. At this time, it is preferable to stir the contents of the reactor in order to ensure uniform dispersion of the raw materials and catalyst and uniform heat transfer. There is essentially no problem whether the reactor is of a batch type or a continuous type. The pressure of carbon dioxide gas is 5 when converted to the pressure at 100℃.
~100Kg/ ^cm2・G, preferably 10-70Kg/ ^cm2・G
is within the range of The reaction temperature is basically almost the same as that of the conventionally known Henkel method. That is, the temperature is usually in the range of 350 to 500°C, although it varies depending on the type of raw material and catalyst, and is preferably in the range of 380 to 470°C from the viewpoint of causing the reaction to occur quickly and suppressing side reactions such as carbide formation. The reaction time varies depending on the reaction temperature, but is usually in the range of 5 minutes to 3 hours. After the reaction is completed, the reaction mixture is taken out from the reactor and subjected to separation and purification operations. When taking out the reaction mixture, a method of keeping the reaction mixture at a temperature higher than the melting point of the polycyclic aromatic compound and taking it out in the form of a slurry can be specially mentioned as a simple method that takes advantage of the features of the present invention. When an organic solvent such as toluene or xylene and water are added to the taken out reaction mixture, the polycyclic aromatic compound is dissolved in the organic solvent, while the product, dialkali metal salt of naphthalene-2,6-dicarboxylic acid, is dissolved in the water. dissolve in Further, the zinc compound or cadmium compound of the catalyst and the carbide produced as a by-product are insoluble in both. These are separated by filtration or liquid separation to obtain an aqueous solution of dialkali metal naphthalene-2,6-dicarboxylic acid salt. From this aqueous solution, naphthalene-2,6-dicarboxylic acid can be obtained by acid precipitation using hydrochloric acid or the like in a conventional manner. Hereinafter, the present invention will be explained in more detail with reference to Examples and comparisons. Examples 1-12 Naphthalene-1,8-dicarboxylic acid dipotassium salt, i.e. 1,8-naphthalic acid dipotassium salt 10.0
g, zinc chloride and potassium iodide are each 8 mol% or each 1 mol% relative to the dipotassium salt.
In addition, after pulverizing and mixing with a ball mill, the internal volume
A 200 ml reactor with a stirrer was charged. Add a predetermined amount of polycyclic aromatic compound to this and make 100
After heating the reactor to a temperature of 0.degree. C. and replacing the inside of the reactor with carbon dioxide gas, carbon dioxide gas was introduced to a predetermined pressure (initial pressure in Table 1). Then, while stirring the mixture in the reactor, 4
The temperature was raised to a predetermined reaction temperature at a rate of °C/min, and the reaction was completed by further stirring at the same temperature for 1 hour. After the reaction was completed, 200 ml of toluene and 200 ml of water were added to the reaction mixture and stirred well. After filtering off solids that were insoluble in both the aqueous layer and the toluene layer, the aqueous layer was separated. A portion of this aqueous layer was collected, and using high performance liquid chromatography, the naphthalene 2,6-dicarboxylic acid dipotassium salt contained therein was quantified using an internal standard method, and the yield was calculated. As the polycyclic aromatic compound, naphthalene, methylnaphthalene, diphenyl, a mixture of diphenyl ether and diphenyl (mixing ratio of about 7:3), and phenanthrene were used, respectively. The results are shown in Table 1. Comparative Example 1 The same operation as in Example 1 was performed except that naphthalene as a polycyclic aromatic compound was not added. The results are shown in Table 1.

【table】

[Table] Examples 13 to 21 Instead of the combination of zinc chloride and potassium iodide as a catalyst in Example 3, zinc iodide,
Zinc chloride, combination of zinc chloride and potassium bromide, zinc 1,8-naphthalate, combination of zinc 1,8-naphthalate and potassium iodide, zinc oxide, combination of zinc oxide and potassium iodide, iodine A similar reaction was carried out using cadmium chloride and cadmium chloride in the presence of 30 g of naphthalene. The amount of catalyst is 8 mol% when the catalyst is a single compound based on the raw material 1,8-naphthalic acid dipotassium salt,
For each compound in the case of a combination
It is 8mol%. The results are shown in Table 2. Comparative Examples 2-10 Similar reactions were carried out in Examples 13-21 without adding naphthalene. The results are shown in Table 2.
It will be listed together with the results of 13-21.

【table】

【table】

[Table] Examples 22 to 26 Instead of the 1,8-naphthalic acid dipotassium salt as the raw material in Example 3, naphthalene-2,3-dicarboxylic acid dipotassium salt, 2-naphthoic acid potassium salt, 1,8-naphthalic acid A mixture of dipotassium salt and potassium 2-naphthoic acid salt (weight ratio 1:1),
Isomal mixture of naphthalene dicarboxylic acid dipotassium salts, i.e. 2,6-, 2,7-, 1,6-,
Using a mixture of 1,7- and 1,3-isomers as raw materials and a combination of zinc chloride and potassium iodide or cadmium iodide as a catalyst,
A similar reaction was carried out in the presence of 30 g of naphthalene.
The results are shown in Table 3. In addition, the catalyst amount is 8 mol % in the case of cadmium iodide and 8 mol % in the case of the combination of zinc chloride and potassium iodide, based on the raw material. Comparative Examples 11-15 Similar reactions were carried out in Examples 22-26 without adding naphthalene. The results are listed in Table 3 together with the results of Examples 22-26. Effects of the Invention In the present invention, by using a polycyclic aromatic compound as a reaction dispersion medium or solvent, the reproducibility of the reaction is improved, and the target naphthalene-2,6
- The yield and selectivity of dialkali metal dicarboxylic acid salts were improved. The present invention has made it possible to produce naphthalene-2,6-dicarboxylic acid cheaply and easily, paving the way for industrial production.

Claims (1)

[Scope of Claims] 1. A naphthoic acid alkali metal salt and/or a naphthalene dicarboxylic acid dialkali metal salt are prepared together with a catalyst under pressure of carbon dioxide gas, and an aprotic polycyclic aromatic compound having 2 to 3 rings is used as a dispersion medium or solvent. 1. A method for producing a dialkali metal salt of naphthalene-2,6-dicarboxylic acid, the method comprising: using a dialkali metal salt of naphthalene-2,6-dicarboxylic acid; 2. Claim 1, wherein the aprotic polycyclic aromatic compound having 2 to 3 rings is naphthalene, lower alkylnaphthalene, diphenyl, lower alkyl diphenyl, diaryl ether, terphenyl, anthracene, phenanthrene, or a mixture thereof. The method described in section.