JPH05163196A - Production process for 2,6-naphthalene-dicarboxylic acid - Google Patents

Abstract

PURPOSE:To produce 2,6-naphthalenedicarboxylic acid in high yield by using 2,6-diethylnaphthalene as a starting substance. CONSTITUTION:In the oxidation of 2,6-diethylnaphthalene or its oxidized derivative with molecular oxygen in a lower aliphatic acid solvent in the presence of a catalyst solution containing at least heavy metals of cobalt and manganese and bromine, the weight ratio of manganese/cobalt is set to 1.2 to 4 and the weight ratio of (cobalt+manganese)/bromine is set to 3 to 30. 2,6- Naphthalenedicarboxylic acid can be obtained in high purity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement in a method for producing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-diethylnaphthalene or an oxidized derivative thereof with molecular oxygen. The 2,6-naphthalenedicarboxylic acid obtained in the present invention is used as a synthetic raw material for polyesters such as polyethylene naphthalate and polyamides useful as films and synthetic fibers.

[0002]

2. Description of the Related Art Conventionally, as a method for producing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-dialkylnaphthalene or its oxidized derivative, 2,6-dimethylnaphthalene is used as a raw material and a heavy metal and bromine are used as catalysts. (Japanese Patent Publication Nos. 48-34, 153 and 48)
No. 43,893, Japanese Patent Publication No. 56-3,337, etc.), and a method of oxidizing 2-methyl-6-acetylnaphthalene as a raw material using heavy metals and bromine as catalysts (JP-A-62-61,946). No. 62-61,947
No. 2, JP-A-1-305,049, etc.), 2-
A method of oxidizing alkyl-6-acylnaphthalene as a raw material with heavy metals and bromine as catalysts (JP-A-1-18
No. 0,851), and 2,6-diisopropylnaphthalene as a raw material, and oxidation with heavy metals and bromine as catalysts (JP-A-60-89,445, JP-A-60-8).
No. 9,446, JP-A Nos. 61-246,144, etc.), a method of oxidizing 2,6-diethylnaphthalene as a raw material using heavy metals and bromine as catalysts (Japanese Patent Publication No. 51-
6,953, JP-A-2-188,554, JP-A-3
-227,953), and the like. However, with the method, although the liquid phase oxidation of 2,6-dimethylnaphthalene proceeds relatively easily, it is difficult to separate 2,6-dimethylnaphthalene from the methylation reaction product of naphthalene or the petroleum fraction. Also, the liquid phase oxidation of the methods such as and is relatively easy, but there is a problem that the 2-alkylnaphthalene and the 2-acylnaphthalene as the raw materials thereof are expensive. On the contrary, according to the method, although the production of 2,6-diisopropylnaphthalene is relatively easy, a large amount of a catalyst is required in the liquid phase oxidation step of 2,6-diisopropylnaphthalene, the yield is poor, and by-products are produced. There was a problem that a lot of trimellitic acid was produced.
On the other hand, the method (1) is an advantageous method because it may possibly overcome the disadvantages of the methods (1) to (3). However, in the above-mentioned methods reported so far, further improvement has been desired, such as low yield and a large amount of trimellitic acid by-product.

[0003]

In view of the above situation, the present invention provides a cheaper method for producing 2,6-naphthalenedicarboxylic acid using 2,6-diethylnaphthalene or its oxidized derivative as a raw material. With the goal.

[0004]

In order to establish the above-mentioned method, the present inventors have keenly studied a method for producing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-diethylnaphthalene or an oxidized derivative thereof. As a result of examination, by specifying the abundance ratio of cobalt and manganese used as an oxidation catalyst and the abundance ratio of (cobalt + manganese) and bromine,
It has been found that the yield is high and the by-product of trimellitic acid is extremely small as compared with the conventional method. That is, the present invention oxidizes 2,6-diethylnaphthalene or its oxidized derivative with a molecular oxygen-containing gas in the presence of a catalyst containing a heavy metal such as cobalt and manganese and bromine using a lower fatty acid as a solvent to give 2,6-dinaphthalene. In the method for producing naphthalenedicarboxylic acid, the weight ratio of manganese / cobalt used for the oxidation as an oxidation catalyst is 1.2 to 4,
The method is characterized in that the weight ratio of (cobalt + manganese) / bromine is 3 to 30.

The present invention will be described in detail below. 2,6-diethylnaphthalene used as an oxidizing raw material in the present invention is
Usually, naphthalene is ethylated or transethylated with an alkylating agent such as ethylene, ethyl chloride, polyethylbenzene using a Friedel-Crafts catalyst, and the obtained alkylated product is distilled, cooled, crystallized, pressure crystallized,
It can be obtained by isolation using a separation means such as adduct separation or adsorption. In addition to this, 2,6-diethylnaphthalene synthesized by dehydrogenation of alkylated tetralin, cyclization using a benzene ring as a starting material, or the like may be used as an oxidizing material. Further, as its oxidized derivative, there is 2-ethyl-6-carboxynaphthalene or the like in which one is oxidized.

Examples of the lower fatty acid as the solvent in the present invention include formic acid, acetic acid, propionic acid, bromoacetic acid and the like, but acetic acid is preferable. The solvent used in the present invention contains at least 5 of these lower fatty acids.
0% by weight or more, preferably 70% by weight or more. Also,
The presence of a large amount of water in the solvent hinders the oxidation reaction, but a small amount may give rather good results. The water concentration in such a solvent is 0 to 20% by weight, preferably 1 to 10% by weight.

The catalyst used in the present invention is a heavy metal composed of cobalt and manganese and bromine, but other heavy metals such as nickel and cerium may be added as heavy metals. In order to allow these heavy metals to exist in the reaction system, they may be added as a compound soluble in a solvent, and examples of such compounds include heavy metal acetates, propionates, naphthenates, hydroxides and carbonates. Examples thereof include salts and bromides, with preference given to acetate, propionate and bromide. In addition, bromine may be any substance as long as it is soluble in a solvent, and examples of such a compound include molecular bromine, hydrogen bromide, metal bromide, alkyl bromide and the like, but preferably bromide They are transition metal bromides such as cobalt, manganese bromide, nickel bromide and cerium bromide, and alkali metal bromides such as potassium bromide and sodium bromide. These catalyst components are dissolved in the solvent to prepare a catalyst solution. The total concentration of heavy metals such as cobalt and manganese (calculated as metal) in this solution is 0.1% by weight or more, preferably 0.6% by weight or more. More preferably, the total concentration of cobalt and manganese is 0.5 to 3% by weight. The ratio of 2,6-diethylnaphthalene or its oxidized derivative to the catalyst solution is 1: 2-6.
(Weight ratio), the manganese / cobalt weight ratio is 1.2 to 4, preferably 2 to 4, and the (cobalt + manganese) / bromine weight ratio is 3 to 30, preferably 3
-24, more preferably 6-16.

The reaction temperature is 140 to 220 ° C, preferably 160 to 200 ° C, more preferably 170 to 190 ° C.
The range is. When the reaction temperature is lower than 140 ° C., the yield of 2,6-naphthalenedicarboxylic acid decreases with the decrease of the reaction rate, and when the reaction temperature is higher than 220 ° C., the side reaction product increases to obtain 2 The purity of 6,6-naphthalenedicarboxylic acid is reduced.

The molecular oxygen-containing gas used in the present invention is oxygen gas, molecular oxygen diluted with an inert gas, or the like. Industrially, it is advantageous to use air. The reaction pressure is set so that the solvent is kept in the liquid phase at the reaction temperature, but is usually 10 to 30 kg / cm ² · G.
The degree is appropriate. The supply amount of the oxygen-containing gas is preferably such that the oxygen concentration in the exhaust gas is 2 to 10% by volume, and is preferably continuously supplied.

The reaction type of the present invention is 2, which is an oxidizing raw material.
It is advantageous to charge 6-diethylnaphthalene or its oxidized derivative continuously into the reaction system. As such a reaction system, a catalyst solution, an oxidizing raw material and a molecular oxygen-containing gas are continuously charged into the reaction system, and the reaction mixture is continuously withdrawn, and the catalyst solution is previously fed into the reaction system before the reaction. There is a semi-continuous system in which an oxidizing raw material and a molecular oxygen-containing gas are continuously charged into the reaction system during the reaction, and after the reaction, the reaction mixture is collectively extracted.

The 2,6-naphthalenedicarboxylic acid produced by the oxidation reaction can be obtained on the solid phase side by solid-liquid separation of the reaction product. The crude 2,6-naphthalenedicarboxylic acid thus obtained can be washed with acetic acid and washed with water to remove the adhering catalyst solution, the oxidation reaction intermediate, and the trimellitic acid catalyst metal complex, thus improving the purity. is there. Further, if necessary, an ordinary highly purified 2,6-naphthalenedicarboxylic acid known as a known method can be used to obtain extremely high-purity 2,6-naphthalenedicarboxylic acid.

[0012]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. The parts and% in the examples and comparative examples are parts by weight and% by weight, respectively, unless otherwise specified.

Examples 1 to 8 In a 300 cc titanium autoclave with electromagnetic stirring, Table 1
140 parts of the catalyst solution shown in Table 1 was charged in advance, and while maintaining the reaction temperature and reaction pressure shown in Table 2, 2,6-
Diethylnaphthalene and compressed air were continuously supplied to the reactor to carry out the oxidation reaction. 2,6-Diethylnaphthalene was fed at a rate of 14 parts per hour for 2 hours, and after the end of feeding 2,6-diethylnaphthalene, compressed air was fed for 30 minutes while maintaining the temperature and pressure of the reactor. The air was supplied so that the oxygen concentration in the exhaust gas was about 8% by volume, but 600 to 700 parts by volume per 1 part by volume of the catalyst solution.
It is the range of hr. After completion of the reaction, the reaction product in a slurry state was filtered and separated after cooling, and the obtained crystals were dried to obtain 2,6-naphthalenedicarboxylic acid. The results are shown in Table 2.

Example 9 The feed rate of 2,6-diethylnaphthalene was 23 parts / hr.
And the same as in Example 1 except that the air supply rate was 950 parts by volume per 1 part by volume of the catalyst solution / hr.
The catalyst solutions shown in Table 1 were used and reacted under the conditions shown in Table 2. The results are shown in Table 2.

Example 10 The feed rate of 2,6-diethylnaphthalene was 14 parts / hr.
And the air supply rate is 500 per volume part of the catalyst solution.
The reaction was performed under the conditions shown in Table 2 using the catalyst solutions shown in Table 1 in the same manner as in Example 1 except that the volume part / hr was used.
The results are shown in Table 2. The oxygen concentration in the exhaust gas in this case was about 5% by volume.

Comparative Examples 1 to 6 As in Example 1, the catalyst solutions shown in Table 1 were used and Table 2
The reaction was carried out under the conditions shown in. The results are shown in Table 2.

Example 11 1800 parts of the catalyst solution shown in Table 1 was charged in advance into a titanium pressure reactor with a magnetic stirring of 40 liters, and the same catalyst was used while maintaining the reaction temperature and reaction pressure shown in Table 2. The solution, 2,6-diethylnaphthalene having a purity of 99%, and compressed air were continuously supplied to the reactor to carry out an oxidation reaction. The catalyst solution was fed at a rate of 750 parts per hour, and the 2,6-diethylnaphthalene was fed at a rate of 150 parts per hour for 10 hours. Slurry
The liquid reaction product was monitored intermittently in the reactor so that the amount of liquid inside was constant. The air supply rate is in the range of 600 to 700 parts by volume / hr per 1 part by volume of the catalyst solution. The slurry-like reaction product 8 to 10 hours after the start of the reaction was filtered and separated, and the obtained crystal was dried to obtain 2,6-naphthalenedicarboxylic acid. The results are shown in Table 2.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the method of the present invention, 2,6-naphthalenedicarboxylic acid can be produced from 2,6-diethylnaphthalene with high purity and high yield, and thus inexpensive 2,6-naphthalenedicarboxylic acid can be produced. It is of extremely high industrial significance as a method.

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Claims (8)

[Claims] 1. A molecular oxygen-containing gas is used in the presence of a catalyst solution obtained by dissolving 2,6-diethylnaphthalene or an oxidized derivative thereof in a lower fatty acid solvent and a catalyst containing a heavy metal containing at least cobalt and manganese and bromine. Upon oxidation, the manganese / cobalt weight ratio of the catalyst was 1.
2 to 4, and the weight ratio of (cobalt + manganese) / bromine is 3 to 30. A method for producing 2,6-naphthalenedicarboxylic acid. 2. A catalyst having a manganese / cobalt weight ratio of 2
4 and the weight ratio of (cobalt + manganese) / bromine is 6
The method for producing 2,6-naphthalenedicarboxylic acid according to claim 1, wherein 3. The method for producing 2,6-naphthalenedicarboxylic acid according to claim 1, wherein the lower fatty acid solvent is acetic acid. 4. The method for producing 2,6-naphthalenedicarboxylic acid according to claim 1, wherein the lower fatty acid solvent contains 1 to 10% by weight of water. 5. The 2,6-naphthalene according to claim 1, wherein the molecular oxygen-containing gas is air and the oxygen concentration in the exhaust gas is 2 to 10% by volume. Method for producing dicarboxylic acid. 6. The production of 2,6-naphthalenedicarboxylic acid according to claim 1, wherein the 2,6-diethylnaphthalene or its oxidized derivative and the molecular oxygen-containing gas are continuously supplied. Method. 7. The 2,6-naphthalenedicarboxylic acid according to claim 1, wherein the total concentration of cobalt and manganese in the catalyst solution is 0.5 to 3% by weight (calculated as metal). Production method. 8. The 2,6-naphthalenedicarboxylic acid according to claim 1, wherein the ratio of 2,6-diethylnaphthalene or its oxidized derivative to the catalyst solution is 1: 2 to 6 (weight ratio). Manufacturing method.