JPH05339203A - Production of naphthalenedicarboxylic acid - Google Patents

Abstract

PURPOSE:To obtain a naphthalenedicarboxylic acid through suppressing the loss of a lower aliphatic carboxylic acid to be used as solvent. CONSTITUTION:The objective naphthalenedicarboxylic acid can be obtained by oxidation of a dialkylnaphthalene and/or an oxidized intermediate thereof using a molecular oxygen-contg. gas in the presence of a catalyst composed of a heavy metal and bromine at 180-230 deg.C in a solvent being a lower aliphatic monocarboxylic acid containing 5-45wt.% of water at a concentration of the heavy metal in the solvent being set at >=0.1wt.%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a naphthalenedicarboxylic acid (hereinafter sometimes abbreviated as NDCA) by oxidizing a dialkylnaphthalene and / or an oxidized derivative thereof. More specifically, it relates to an oxidation method in which the decomposition of lower aliphatic carboxylic acid used as a solvent is suppressed.

[0002]

2. Description of the Related Art NDCA and its ester (hereinafter referred to as DN
(Sometimes abbreviated as CA, etc.) is a substance useful as a polymer material, dye intermediate, and the like. Especially 2,6-NDC
Polyethylene naphthalate formed from A and the like and ethylene glycol is superior to polyethylene terephthalate in heat resistance, breaking strength and the like, and is attracting attention as a material for films, food packaging materials and the like. Further, since polybutylene naphthalate resin has a higher crystallization rate and higher wet heat resistance than polybutylene terephthalate resin, NDCA or the like is also useful as a resin raw material.

Conventionally, as a method for producing NDCA, there are many methods in which dialkylnaphthalene and / or its oxidized derivative is oxidized with molecular oxygen in a lower aliphatic carboxylic acid solvent using cobalt, manganese, bromine or the like as a catalyst. Proposed.

These methods have the advantage that the oxidation rate is fast, but on the other hand, the lower aliphatic carboxylic acid used as a solvent undergoes a large amount of oxidative decomposition, resulting in a high production cost of NDCA. ..

In a method of liquid-phase oxidizing an alkyl-substituted aromatic compound with molecular oxygen in the presence of a heavy metal compound and a bromine compound in a lower aliphatic carboxylic acid solvent,
In order to suppress the decomposition of the lower aliphatic carboxylic acid in the solvent, a method of adding a strong acid such as phosphoric acid, sulfuric acid or selenic acid has been proposed (JP-A-51-91221). But,
This method is not preferable because the strong acid to be added has strong corrosiveness and toxicity.

As another method for suppressing the decomposition of the lower aliphatic carboxylic acid in the solvent, a method of adding boron, aluminum, germanium, antimony, tellurium, vanadium, niobium, molybdenum, chromium, copper or an alkaline earth metal. (JP-A-51-127033 and JP-A-5-127033)
1-127034, JP51-127035, JP52-95626, JP52-7.
7022, JP-A-52-77023) and the like have been proposed. However, these methods are not so preferable because they are not sufficiently effective, it is difficult to recover and reuse the added metal, or there is a problem with pollution.

On the other hand, a method of using water in combination with a lower aliphatic carboxylic acid as a solvent has been proposed in JP-A-2-164845, but this method is limited to the oxidation of diisopropylnaphthalene, which is difficult to react, In addition, it focuses on the initial stage of the reaction of the batch reaction that tends to cause an abnormal reaction, and it is preferable that the water content in the solvent is low after the abnormal reaction generation period. Therefore, when a raw material other than diisopropylnaphthalene is used, or when the reaction is carried out in a semi-batch system or a continuous system, it is naturally considered not preferable to use water in combination with a lower aliphatic carboxylic acid as a solvent. It was Moreover, no mention is made of the influence of water in the solvent on the loss of lower aliphatic carboxylic acid.

[0008]

DISCLOSURE OF THE INVENTION In view of such circumstances, the present invention has an object to suppress NDCA from a dialkylnaphthalene and / or a derivative thereof by suppressing the decomposition of a lower aliphatic carboxylic acid as a solvent. To provide a manufacturing method.

[0009]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to establish the above method, and in a liquid phase oxidation reaction using a heavy metal oxidation catalyst and bromine as a catalyst, a specific reaction temperature and a specific catalyst concentration. Under this condition, by adding water in a specific concentration range to a solvent, a lower aliphatic carboxylic acid, ND
The inventors have found that the decomposition of lower aliphatic carboxylic acids can be suppressed without substantially deteriorating the yield of CA, and completed the present invention.

That is, the present invention uses a molecular oxygen-containing gas in the presence of a heavy metal oxidation catalyst and a catalyst composed of bromine in a lower aliphatic carboxylic acid solvent to produce a dialkylnaphthalene and / or an oxidation intermediate thereof. In the oxidation method, the oxidation is carried out in a lower aliphatic carboxylic acid solvent having a reaction temperature of 180 to 230 ° C., a heavy metal oxidation catalyst concentration in the solvent of 0.1% by weight or more, and containing 5 to 40% by weight of water. This is the method for producing NDCA carried out in 1.

The present invention will be described in detail below. Examples of the dialkylnaphthalene used as an oxidizing raw material in the present invention include:
Examples thereof include dimethylnaphthalene, diethylnaphthalene, and diisopropylnaphthalene.The oxidized derivatives thereof include formylnaphthoic acid, an oxidation intermediate of the dialkylnaphthalene such as acetylnaphthoic acid, or an alkylacylnaphthalene such as methylacetylnaphthalene or methylbutyrylnaphthalene, or Examples thereof include diacylnaphthalene. Of these, the 2,6-body is industrially useful.

In the method of the present invention, an aliphatic monocarboxylic acid having 1 to 5 carbon atoms, that is, formic acid, acetic acid, propionic acid, butyric acid, etc., or a mixture thereof is used as a lower aliphatic carboxylic acid as a solvent. , Acetic acid and propionic acid are preferable, and acetic acid is particularly preferable.

The solvent used in the method of the present invention contains the aliphatic monocarboxylic acid in an amount of 5 to 45% by weight, preferably 7 to 35% by weight, more preferably 10 to 30% by weight. .. If the water content in the solvent is less than this, the combustion loss of the aliphatic monocarboxylic acid is large, and if it is more than this, the yield of NDCA and the purity are lowered, which is not preferable.

Another object of the present invention is to rationalize a solvent dehydration distillation column which requires a high equipment cost. However, in the method of the present invention, the water content in the solvent increases as described above, so that the reaction by-product water from the solvent is produced. It will be easy to remove by distillation, and it will be possible to reduce equipment costs and energy consumption.

The amount of the solvent used with respect to the dialkylnaphthalene and / or its oxidized derivative is usually 2 to 15 times by weight, preferably 3 to 10 times by weight.

The oxidation catalysts used in the method of the present invention are heavy metal compounds and bromine compounds. As the heavy metal oxidation catalyst, cobalt and / or manganese are preferable, and cerium, nickel and the like may be added if necessary. These are used in the form of organic acid salts, halides, hydroxides, oxides, carbonates and the like, and fatty acid salts, particularly acetates and bromides are preferable.

The amount of the heavy metal oxidation catalyst used in the method of the present invention varies depending on the kind of the oxidizing raw material used, but is 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight with respect to the solvent. It is more than weight%. If it is less than this, it is ND because the combustion loss of aliphatic monocarboxylic acid decreases.
The effect of lowering the CA yield is greater, which is not preferable.

On the other hand, the bromine compound may be either an organic compound or an inorganic compound as long as it dissolves in an oxidation reaction system and generates a bromine ion. Specifically, molecular bromine (Br ₂ ), Hydrogen bromide, sodium bromide, potassium bromide, inorganic bromide such as ammonium bromide,
Alternatively, organic bromides such as alkyl bromide and brominated fatty acids such as bromoacetic acid can be used. Hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, manganese bromide and the like are particularly preferable examples. Bromine is usually used in an atomic ratio of 0.01 to 2 with respect to the total weight of the heavy metal oxidation catalyst.

The oxidation reaction temperature in the method of the present invention is 18
It is in the range of 0 to 230 ° C, preferably 190 to 220 ° C. When the reaction temperature is low, the reaction rate is greatly reduced due to a synergistic effect with the influence of water in the solvent. On the contrary, when the reaction temperature is high, the side reaction products are increased and the purity of NDCA obtained is reduced. The reaction pressure may be a pressure at which the reaction system is kept in a liquid phase at the reaction temperature, but is usually 10 to 3
A range of 0 kg / cm ² G is suitable.

As the molecular oxygen-containing gas used in the method of the present invention, oxygen gas or a mixed gas obtained by diluting it with an inert gas is used. Industrially, air is the most available and preferred.

The method of the present invention can be carried out batchwise, semi-batchwise or continuously, and after completion of the reaction, so-called post-oxidation may be further carried out to complete the reaction.

The crude NDCA obtained by solid-liquid separation of the oxidation reaction product can remove the catalyst, reaction intermediates and by-products by washing with acetic acid, water and the like, and the purity can be improved. Further, if necessary, a high-purity NDCA or an ester thereof can be obtained by using a known NDCA purification method, esterification and purification.

[0023]

EFFECTS OF THE INVENTION According to the method of the present invention, the combustion loss of the aliphatic carboxylic acid as the solvent can be significantly reduced under the condition that the yield of NDCA is hardly reduced, and the solvent dehydration distillation column is also used. Since the load of is reduced, it is industrially very advantageous.

The present invention will be specifically described below based on examples. In addition, parts and% in Examples and Comparative Examples
Indicates parts by weight and% by weight, respectively. The decomposition rate of the lower aliphatic carboxylic acid was determined from the gas chromatographic analysis value of the product composition.

[0025]

Example 1 A titanium autoclave having a gas discharge pipe with a reflux condenser, a gas blowing pipe, a continuous feed pump for raw materials, and a stirrer was placed in 174 parts of acetic acid, 6.74 parts of cobalt acetate (tetrahydrate), and manganese acetate. (Tetrahydrate) 13.26
Parts, 47% hydrogen bromide water 1.40 parts, and water 12 parts. The water concentration in this catalyst liquid was 9%. This catalyst liquid was vigorously stirred at a temperature of 200 ° C. and a pressure of 30 kg / cm ² G, 55 parts of 2,6-diethylnaphthalene and compressed air were continuously fed into the catalyst liquid over 1.3 hours to oxidize it. The reaction was carried out. After the feeding of the raw material 2,6-diethylnaphthalene was completed, compressed air was supplied for another 14 minutes while maintaining the temperature at 200 ° C. and 30 kg / cm ² G. After completion of the reaction, the reaction product was taken out to separate a solid precipitate mainly composed of 2,6-NDCA, washed with acetic acid and dried to obtain a product. The yield of 2,6-NDCA was 93.2 mol% and the acetic acid decomposition loss was 14.7 parts.

[0026]

Examples 2 to 4 and Comparative Examples 1 and 2 A reaction similar to that of Example 1 was carried out except that the feed rates of acetic acid and water were changed so that the water concentration in the catalyst solution became the concentration shown in Table 1. went. The results are shown in Table 1.

[0027]

[Table 1]

[0028]

Example 5 Acetic acid 161 was added to a reactor similar to that of Example 1.
Parts, cobalt acetate (tetrahydrate) 1.68 parts, manganese acetate (tetrahydrate) 3.29 parts, 47% hydrogen bromide water 3.47 parts,
28 parts of water was introduced. Moisture concentration in this catalyst liquid is 16%
Met. This catalyst liquid is used at a temperature of 200 ° C. and a pressure of 30 kg /
While stirring vigorously under the condition of cm ² G, add 2,6-
48 parts of dimethylnaphthalene and compressed air were continuously added to 1.
After being fed for 3 hours, the oxidation reaction was performed under the same reaction conditions and operation as in Example 1 except for the above. At this time, 2, 6
-NDCA yield 92.0 mol%, acetic acid decomposition loss was 8.
It was 6 parts.

[0029]

Comparative Example 3 The same reaction as in Example 5 was performed except that the water concentration in the catalyst solution was adjusted to 2%. in this case,
The yield of 2,6-NDCA was 94.0 mol% and the acetic acid decomposition loss was 17.6 parts.

[0030]

Example 6 Acetic acid 177 was added to a reactor similar to that in Example 1.
Parts, cobalt acetate (tetrahydrate) 7.63 parts, manganese acetate (tetrahydrate) 7.51 parts, potassium bromide 14.58 parts, potassium acetate 12.02 parts, and water 33.34 parts. ..
The water concentration in this catalyst liquid was 15%. This catalyst solution was vigorously stirred under the conditions of a temperature of 200 ° C. and a pressure of 30 kg / cm ² G, and 65 parts of 2,6-diisopropylnaphthalene and compressed air were continuously fed thereto over 1.3 hours. Then, the oxidation reaction was performed under the same reaction conditions and operation as in Example 1 except for the above. At this time, the yield of 2,6-NDCA was 87.0 mol%, and the acetic acid decomposition loss was 12.4 parts.

[0031]

Comparative Example 4 The same reaction as in Example 6 was carried out except that the water concentration in the catalyst solution was adjusted to 2%. in this case,
The yield of 2,6-NDCA was 88.2 mol% and the loss of acetic acid decomposition was 27.6 parts.

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Claims (4)

[Claims] 1. A method of oxidizing a dialkylnaphthalene and / or an oxidized derivative thereof with a molecular oxygen-containing gas in the presence of a heavy metal oxidation catalyst and a catalyst composed of bromine, wherein the reaction temperature is 180 to 230. ℃, the concentration of heavy metal oxidation catalyst in the solvent is 0.1 weight percent or more,
And a method for producing naphthalenedicarboxylic acid in a lower aliphatic carboxylic acid solvent containing 5 to 45% by weight of water. 2. The heavy metal oxidation catalyst is cobalt, manganese,
The method for producing naphthalenedicarboxylic acid according to claim 1, which is at least one component selected from the group consisting of cerium and nickel. 3. The method for producing naphthalenedicarboxylic acid according to claim 1, wherein the concentration of the heavy metal oxidation catalyst in the solvent is 0.5% by weight or more. 4. The method for producing naphthalenedicarboxylic acid according to claim 1, wherein the lower aliphatic carboxylic acid is at least one component selected from the group consisting of acetic acid and propionic acid.