JPH0334979B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a reaction catalyst used in the production of a dialkali metal salt of naphthalene-2,6-dicarboxylic acid. When the dialkali metal salt of naphthalene-2,6-dicarboxylic acid is precipitated with acid, it is easily converted into the corresponding carboxylic acid, that is, naphthalene-2,6-dicarboxylic acid.
Although it can be converted to dicarboxylic acid, this naphthalene-
2,6-dicarboxylic acid has recently attracted attention as an acid moiety in heat-resistant polyester raw materials, and is an industrially valuable compound (see Japanese Patent Publication No. 54-945). BACKGROUND ART As one method for producing dialkali metal salts of naphthalene-2,6-dicarboxylic acid, application of the so-called Henkel method has been proposed. That is, an alkali metal salt of naphthalene monocarboxylic acid (namely naphthoic acid), a dialkali metal salt of naphthalene dicarboxylic acid, or a mixture thereof is heated together with a reaction catalyst under carbon dioxide gas pressure at a temperature of 350°C or higher, usually 400 to 500°C.
This is a method of heating to. Naphthalene-2,6-dicarboxylic acid dialkali metal salt and naphthalene are produced from the naphthoic acid alkali metal salt through a disproportionation reaction, and naphthalene-2,6-dicarboxylic acid dialkali metal salt is generated from the naphthalene dicarboxylic acid dialkali metal salt through a rearrangement reaction.
Dialkali metal dicarboxylic acid 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., Yuyoka, 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]. Conventionally, naphthalene-2, 6 was produced using the Henkel method.
-Cadmium or zinc compounds have been used as reaction catalysts for producing dialkali metal salts of dicarboxylic acids. Among these, cadmium compounds such as cadmium chloride are highly toxic and expensive;
Although it has the drawback of requiring a large amount of cost to recover, it has an excellent catalytic action. On the other hand, examples of the use of zinc chloride, zinc fluoride, zinc oxide, and zinc carbonate have been reported as zinc compounds.
These have low toxicity and are inexpensive, but their catalytic activity is considerably inferior to that of cadmium compounds. Therefore, in order to improve the reaction yield, it has been necessary to use highly toxic and expensive cadmium compounds. Problems to be Solved by the Invention The present inventors have conducted extensive studies to solve the problems with conventional reaction catalysts, and have developed a reaction catalyst that is low in toxicity, economical, and has excellent catalytic action. They discovered this and completed the present invention. Means for Solving the Problems The present invention provides naphthoic acid alkali metal salts and/or
Or naphthalene-2, by heating dialkali metal naphthalene dicarboxylic acid salt under carbon dioxide gas pressure.
This is a reaction catalyst consisting of a zinc compound and an alkali metal halide, which is used when producing a dialkali metal salt of 6-dicarboxylic acid. The reaction catalyst of the present invention is used when producing a dialkali metal salt of naphthalene-2,6-dicarboxylic acid using an alkali metal salt of naphthoic acid, a dialkali metal salt of naphthalene dicarboxylic acid, or a mixture thereof as a reaction raw material. It is.
As the naphthoic acid alkali metal salt, 1- or 2
- Isomers or mixtures thereof can be used. In addition, the dialkali metal naphthalene dicarboxylic acid salts include 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 when the reaction catalyst of the present invention is used, but a mixture containing a small amount of it or a crude mixture containing not high purity can be used as a reaction raw material. As the alkali metal salt, potassium salt gives good results as in the usual Henkel method. The reaction catalyst of the present invention consists of a zinc compound and an alkali metal halide. This reaction catalyst is
Compared to conventional reaction catalysts using zinc compounds alone, the catalytic activity is improved and the naphthalene-
The yield of dialkali metal 2,6-dicarboxylic acid salt is also improved. Examples of the zinc compound used as a reaction catalyst in the present invention include zinc halides such as zinc fluoride, zinc chloride, zinc bromide, and zinc iodide, zinc carboxylates such as zinc naphthoate, and zinc naphthalene dicarboxylate, zinc oxide, and zinc carbonate. Examples include zinc, various zinc compounds such as zinc sulfate, and mixtures thereof. Among these, zinc iodide itself has relatively excellent catalytic action, and when an alkali metal halide is used in combination as a reaction catalyst, the improvement in catalytic action is not so remarkable. In addition, zinc naphthoate means 1- or 2-isomer, or a mixture thereof, and zinc naphthalene dicarboxylate means:
1, 2-, 1, 3-, 1, 4-, 1, 5-, 1,
6-, 1, 7-, 1, 8-, 2, 3-, 2, 6
-, 2, 7-isomer, or a mixture thereof. The amount of these zinc compounds used is usually 0.5 to 20 mol%, preferably 1 to 20 mol%, based on the raw material.
It is in the range of 10 mol%. Use of a large amount of more than 20 mol% promotes the by-product of carbide. As the alkali metal halides used in the reaction catalyst of the present invention, alkali metal chlorides, alkali metal bromides, and alkali metal iodides are effective for improving catalytic activity, and in particular, alkali metal bromides,
Alkali metal iodides have a large effect and are particularly preferred. These alkali metal halides can be used singly or in mixtures. Furthermore, for reasons described later, when an alkali metal halide of the same element as the alkali metal salt of the reaction raw material, for example, a sodium salt or a potassium salt, is used as the reaction raw material, it is particularly desirable to use sodium halide for the former and potassium halide for the latter. From the above viewpoint, specific examples of preferable alkali metal halides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, rubidium chloride, lithium bromide, sodium bromide, potassium bromide, cesium bromide, and rubidium bromide. , lithium iodide, sodium iodide, potassium iodide, cesium iodide, rubidium iodide, and the like. The amount of alkali metal halide used is 0.1 to 10 times the molar amount of the zinc compound,
Preferably it is 0.2 to 5 times the molar amount, and a considerable effect is exhibited at 0.2 to 1 times the molar amount. It is preferable that the reaction raw materials and the zinc compound and alkali metal halide of the reaction catalyst are well mixed. For this purpose, the reaction catalyst is added to an aqueous solution of the reaction raw material and mixed well, and then the water is distilled off by heating to obtain a mixture of the raw material and the catalyst, or the reaction raw material and the reaction catalyst are thoroughly pulverized using a ball mill, etc. There are methods of mixing, but any method may be used. The reaction raw material and the reaction catalyst are heated and reacted under pressure of carbon gas, but at this time, they are in a liquid state under the reaction conditions, and it is also possible to use a substance that is stable under the same conditions as a dispersion medium or solvent. be. Examples of such substances include aprotic polycyclic aromatic compounds having 2 to 3 rings. Specific examples include naphthalene, lower alkylnaphthalenes such as methylnaphthalene and dimethylnaphthalene, diphenyl, lower alkyl diphenyls such as methyldiphenyl and dimethyldiphenyl, diaryl ethers such as diphenyl ether, terphenyl, anthracene, phenanthrene, or these. Mixtures, etc. can be mentioned. The amount used is 0.5 to 10 times the amount of the reaction raw material, usually 1 to
It is 5 times the amount. The pressure of carbon dioxide gas is 10 to 150 at the reaction temperature.
Kg/cm ² ·G, preferably in the range of 20 to 100 kg/cm ² ·G. In addition, when using the above-mentioned dispersion medium or solvent, the pressure of 5 to 100°C is calculated as follows.
It is 100Kg/cm ² ·G, preferably in the range of 10 to 70Kg/cm ² ·G. The reaction temperature varies slightly depending on the reaction raw materials and the type of zinc compound and alkali metal halide used as reaction catalysts, but is usually in the range of 350 to 500°C, allowing the reaction to occur quickly and suppressing side reactions such as carbide formation. From this point of view, the temperature range is preferably from 380 to 470°C. The reaction time varies depending on the reaction temperature, but
Usually it is in the range of 5 minutes to 3 hours. After the reaction is completed, water is added to the reaction mixture to dissolve the dialkali metal salt of naphthalene-2,6-dicarboxylic acid in the water. When a dispersion medium or solvent as described above is used in the reaction, it is dissolved by further adding an organic solvent such as toluene or xylene, and separated from the water tank containing the target product by liquid separation. The zinc compound in the reaction catalyst can be easily separated by filtration or the like as zinc oxide or zinc carbonate, which is insoluble in water and the organic solvent, together with by-product carbide which is also insoluble. It is technically easy to recover and regenerate the zinc compound from the insoluble mixture thus obtained and reuse it as one of the components of the reaction catalyst. Furthermore, since zinc compounds are inexpensive and have low toxicity, the insoluble mixture can be used for other inexpensive uses after appropriate treatment. On the other hand, the alkali metal halide used together as a reaction catalyst is dissolved in water together with the dialkali metal salt of naphthalene-2,6-dicarboxylic acid. Recovery of the alkali metal halide from this aqueous solution and reuse as one component of the reaction catalyst can be carried out very easily by the method shown below. Method (1): A strong acid such as sulfuric acid or hydrochloric acid is added to the aqueous solution to precipitate naphthalene-2,6-dicarboxylic acid, which is collected by filtration. The filtrate contains an alkali metal halide and an alkali metal salt of a strong acid, but since the latter does not inhibit the catalytic action of the reaction catalyst of the present invention, the alkali metal halide can be concentrated from the filtrate while still containing the latter. It is recovered by the following operation and reused as one component of the reaction catalyst of the present invention. Method (2): Carbon dioxide gas is passed through the aqueous solution to precipitate a monoalkali metal salt of naphthalene-2,6-dicarboxylic acid, and the precipitate is collected by filtration. The filtrate contains an alkali metal halide and an alkali metal hydrogen carbonate. Alkali metal hydrogen carbonate easily reacts with naphthoic acid and/or naphthalene dicarboxylic acid and/or an acid anhydride consisting of these, and reacts with naphthoic acid alkali metal salt and/or naphthalene dicarboxylic acid dialkali metal salt as reaction raw materials. The filtrate is used for this purpose. The resulting reaction raw material is mixed with an alkali metal halide, which is one component of the reaction catalyst of the present invention, and is one of the very preferred recovery and reuse methods. Method (3): When the aqueous solution is concentrated, a dialkali metal salt of naphthalene-2,6-dicarboxylic acid is preferentially deposited as a precipitate, which is collected by filtration. Since the alkali metal halide is dissolved in the filtrate, the alkali metal halide is recovered by a method such as distilling off water and reused as one of the components of the reaction catalyst of the present invention. By the above method or a modification thereof, the alkali metal halide can be easily and economically reused as one component of the reaction catalyst of the present invention. In addition, alkali metal halides and naphthalene
Since a metal exchange reaction can occur with the dialkali metal salt of 2,6-dicarboxylic acid, in the case of methods (2) and (3), it is important for the reproducibility of the recovery operation that the alkali metals in both are the same. This is preferable in this respect. As described above, the dialkali metal salt of naphthalene-2,6-dicarboxylic acid is separated from the reaction mixture as an aqueous solution and converted to naphthalene-2,6-dicarboxylic acid by acid precipitation or the like. Effect When using the reaction catalyst consisting of the zinc compound and alkali metal halide of the present invention, the catalytic action is improved compared to the case where the zinc compound is used alone,
Some cases were found to exhibit catalytic activity equivalent to or higher than that of cadmium compounds (see Examples and Reference Examples below). Zinc compounds have low toxicity and are inexpensive, and alkali metal halides have low toxicity and can be recovered and reused at low cost. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, Comparative Examples, and Reference Examples. Examples 1 to 17 To 10.0 g of naphthalene-1,8-dicarboxylic acid dipotassium salt, that is, 1,8-naphthalic acid dipotassium salt, as a reaction raw material, a zinc compound and an alkali metal halide were added as reaction catalysts in respective predetermined amounts relative to the dipotassium salt. After adding mol% and pulverizing and mixing with a ball mill, the mixture was charged into an autoclave with an internal volume of 200 ml and equipped with a stirrer. The autoclave was heated to 100° C. with or without the addition of 30 g of naphthalene as a dispersion medium or solvent, and after replacing the inside of the autoclave with carbon dioxide gas, carbon dioxide gas was introduced to a predetermined pressure (initial pressure in Table 1). Next, the mixture in the autoclave was heated to a predetermined reaction temperature at a rate of 4°C/min while stirring,
The mixture was further stirred at the same temperature for 1 hour to complete the reaction. 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 the naphthalene 2,6-dicarboxylic acid dipotassium salt contained therein was quantified by an internal standard method using high performance liquid chromatography, and the yield was calculated. The results are shown in Table 1. Comparative Examples 1-8 Examples 1-3, 9, 10, 11, 12 and 14, 15, 16,
In No. 17, the reaction was carried out in the same manner as in Example 1, except that no alkali metal halide was added. The results are shown in Table 1. Reference Example 1 The reaction was carried out in the same manner as in Example 1 except that cadmium iodide was used in an amount of 8 mol % based on the reaction raw materials instead of zinc chloride and potassium iodide. The results are shown in Table 1.

[Table] Examples 18-22 Naphthalene-2,3-dicarboxylic acid dipotassium salt, isomer mixture of naphthalene dicarboxylic acid dipotassium salt, i.e. 2,6-, 2,7-, 1,6
-, 1,7-, 1,3-isomer mixture, 2-naphthoic acid potassium salt, 1,8-naphthalic acid dipotassium salt and 2-naphthoic acid potassium salt mixture (weight ratio 1:1). or 10g each as the reaction raw material, and a zinc compound and an alkali metal halide as reaction catalysts for each raw material.
8 mol% and in the presence or absence of 30 g of naphthalene, 450
The reaction was allowed to proceed for 1 hour at <RTIgt;C,</RTI> and the product was separated and quantified. The carbon dioxide pressure is 40Kg/at 100℃.
cm ²・G. The results are shown in Table 2. Comparative Examples 9-13 In Examples 18-22, the same reactions were carried out without adding the alkali metal halide. The results are shown in Table 2.

[Table] Effects of the Invention In the present invention, by using both an inexpensive and low-toxicity zinc compound and an alkali metal halide as a reaction catalyst, the catalytic action is improved, and the dialkali metal salt of naphthalene-2,6-dicarboxylic acid is produced in a high yield. I started getting better results. As a result, naphthalene-2,6-dicarboxylic acid can be produced safely and inexpensively, paving the way for industrial production.

Claims (1)

[Claims] 1 Used in producing a dialkali metal salt of naphthalene-2,6-dicarboxylic acid by heating an alkali metal salt of naphthoic acid and/or a dialkali metal salt of naphthalene dicarboxylic acid under pressure of carbon dioxide gas, A reaction catalyst consisting of a zinc compound and an alkali metal halide. 2. The reaction catalyst according to claim 1, wherein the alkali metal halide is an alkali metal chloride, an alkali metal bromide, or an alkali metal iodide. 3. The reaction catalyst according to claim 1, wherein the alkali metal halide is used in an amount of 0.1 to 10 times the molar amount of the zinc compound.