JPH07247239A - Method for producing 2,6-naphthalenedicarboxylic acid - Google Patents

Abstract

(57) [Abstract] [Purpose] 2,6-Naphthalenedicarboxylic acid can be converted from 2,6-diisopropylnaphthalene without using a large amount of metal catalyst and without depositing alkali metal salts of 2,6-naphthalenedicarboxylic acid. Efficiently produces acid. [Structure] 2,6-diisopropylnaphthalene or an oxidation intermediate thereof is used in a solvent of an aliphatic carboxylic acid and a catalyst composed of a cobalt compound and a manganese compound and a bromine compound,
It is oxidized with molecular oxygen in the presence of a pyridine compound at a temperature around 200 ° C to produce 2,6-naphthalenedicarboxylic acid. The reaction product is cooled to room temperature, and the precipitated solid is separated and washed to obtain 2,6-naphthalenedicarboxylic acid having a purity of 99% or more.
It is obtained in a yield of 80% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing 2,6-naphthalenedicarboxylic acid, and in particular 2,6-diisopropylnaphthalene or its oxidation intermediate is prepared from cobalt and manganese in a solvent containing an aliphatic carboxylic acid. The present invention relates to a method for producing 2,6-naphthalenedicarboxylic acid that is oxidized by molecular oxygen in the presence of a heavy metal and a bromine compound catalyst.

2,6-Naphthalenedicarboxylic acid is a useful compound as a raw material for highly functional resins such as polyethylene naphthalate (PEN resin).

[0003]

2. Description of the Related Art Conventionally, various methods have been known as a method for producing 2,6-naphthalenedicarboxylic acid.
Method for oxidizing 2,6-dimethylnaphthalene (JP-A-49-426)
No. 54) gives the target product in a relatively good yield, but there is a problem that it is difficult to obtain a high-purity raw material.

On the other hand, it can be relatively easily synthesized and purified.
Various proposals have been made to improve reactivity in the oxidation reaction by using 2,6-diisopropylnaphthalene as a raw material.

For example, 2,6-diisopropylnaphthalene is used as a raw material and is oxidized by molecular oxygen in the presence of a catalyst composed of a heavy metal composed of cobalt and manganese and a bromine compound in a solvent containing an aliphatic carboxylic acid. -As a method for producing naphthalenedicarboxylic acid, a method of carrying out an oxidation reaction in the presence of an alkali metal (JP-A-61-246143, etc.) and a method of adding a salt of an inorganic acid such as boric acid (JP-A-63-63)
-250344), a method of adding potassium (JP-A-1-
121240), a method of adding cesium (Japanese Patent Laid-Open No. 1-16
No. 0943), a method of adding chlorine (Japanese Patent Laid-Open No. 1-268661), and the like.

However, among the above-mentioned methods, most of the alkali metal is 2,6-
Since it is contained in the reaction product as a salt of naphthalenedicarboxylic acid, it is necessary to remove the alkali metal, and when the catalyst is repeatedly used, the alkali metal must be replenished and added each time. .

Further, the method using a salt of an inorganic acid has a problem that a large amount of trimetic acid is produced as a by-product.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrially advantageous method for producing 2,6-naphthalenedicarboxylic acid, which is free from the by-product of trimetic acid and the precipitation of alkali metal salts as described above. To do.

[0009]

Means for Solving the Problems The present invention provides a catalyst comprising 2,6-diisopropylnaphthalene or an oxidation intermediate thereof in a solvent containing an aliphatic carboxylic acid, which comprises a heavy metal consisting of cobalt and manganese and a bromine compound. A method for producing 2,6-naphthalenedicarboxylic acid in the presence of a pyridine compound in the method for producing 2,6-naphthalenedicarboxylic acid by oxidation in the presence of molecular oxygen.

[0010]

[Detailed Description of the Invention]

(Raw material) The starting material of the present invention is 2,6-diisopropylnaphthalene or an oxidized intermediate thereof.

The oxidation intermediate of 2,6-diisopropylnaphthalene is an intermediate produced by the oxidation reaction of 2,6-diisopropylnaphthalene.
It is a compound that can lead to 2,6-naphthalenedicarboxylic acid.

Specifically, one or both isopropyl groups of 2,6-diisopropylnaphthalene are 2-hydroperoxy-2-propyl group, 2-hydroxy-2-propyl group,
It is a compound oxidized to an acetyl group, a formyl group or a carboxyl group. When both isopropyl groups are oxidized to the above substituents, the two substituents may be different.

(Catalyst) The cobalt compound and manganese compound used as the catalyst are not particularly limited,
For example, cobalt and manganese formic acid, acetic acid, propionic acid, oxalic acid, aliphatic carboxylic acid salts such as maleic acid,
Aliphatic carboxylic acid salts such as naphthenic acid, aromatic carboxylic acid salts such as benzoic acid, terephthalic acid, naphthoic acid and naphthalene dicarboxylic acid, hydroxides, oxides and carbonates, inorganic salts such as halides You can Of these, acetate and bromide are particularly preferable.

The cobalt compound and the manganese compound are used in an atomic molar ratio of cobalt: manganese in the range of 99: 1 to 1:99, preferably 90:10 to 10:90.
0.2-10% by weight, preferably 0.4-5, as the total amount of cobalt and manganese atoms in the aliphatic carboxylate solvent.
It is in the range of% by weight.

Examples of the bromine compound contained in the catalyst component include inorganic bromine compounds such as molecular bromine, hydrogen bromide, hydrobromide, ammonium bromide and potassium bromide, and methyl bromide, ethyl bromide, Bromoform, ethylene bromide,
An organic bromine compound such as bromoacetic acid can be exemplified.

The amount of the bromine compound used is in the range of 0.1 to 10 mole times, preferably 0.2 to 5 mole times, as the total number of moles of cobalt and manganese atoms as bromine atoms in the bromine compound.

(Pyridine Compound) Examples of the pyridine compound used in the method of the present invention include monohalogenated pyridines such as pyridine, monochloropyridine and monobromopyridine, dihalogenated pyridines such as dichloropyridine and dibromopyridine, monohydroxypyridine, Alkylpyridines such as dihydroxypyridine, hydroxynitropyridine, hydroxyhalogenated pyridine, aminonitropyridine, aminohalogenated pyridine, picoline, ethylpyridine, propylpyridine, lutidine and collidine, N-oxides of these pyridine compounds, hydrogen chloride, Pyridinium salts such as hydrogen bromide, chlorochromic acid, dichromic acid, p-toluenesulfonic acid and sulfur trioxide,
Addition complexes such as pyridinium bromide perbromide, N-methyl, N-
Examples thereof include N-alkylpyridinium halides such as ethyl, N-propyl and N-butylpyridinium halides.

The pyridine compound is used in an amount of 0.1 to 50 mol, preferably 1 to 50 mol, per 1 mol of bromine atom added to the reaction system.
It is 0.5 to 20 mol.

(Aliphatic Carboxylic Acid Solvent) Examples of the aliphatic carboxylic acid solvent include formic acid, acetic acid, propionic acid, butyric acid, valeric acid and bromoacetic acid. Of these, acetic acid is most preferable, and it may be diluted with another solvent such as water or aromatic hydrocarbon.

The amount of the fatty acid carboxylic acid solvent used is not particularly limited, but is preferably 0.5 to 10 times by weight, more preferably 1 to 6 times the amount of the raw material 2,6-diisopropylnaphthalene.
It is twice the weight.

(Molecular Oxygen) As the molecular oxygen, not only pure oxygen but also pure oxygen diluted with an inert gas such as nitrogen, helium or argon to an arbitrary concentration can be used, but air is sufficient.

(Reaction conditions) The reaction can be carried out by any of a batch system, a semi-batch system and a continuous system, but a semi-batch system is usually employed.

When the reaction is carried out in a semi-batch system, a solvent and a catalyst are charged into a reaction apparatus, and 2,6-diisopropylnaphthalene is continuously melted in a molten state at a predetermined temperature and pressure while blowing a gas containing molecular oxygen. Supply a fixed amount of 2,
After the 6-diisopropylnaphthalene is supplied, the blowing of the oxygen-containing gas is continued for a certain period of time.

In this case, the supply rate of the raw material 2,6-diisopropylnaphthalene cannot be unconditionally specified because the optimum value changes depending on the reaction temperature, pressure and catalyst amount.
Normally, it is sufficient to supply the whole amount in 1 to 12 hours.

When the reaction is carried out in a batch system, a reaction apparatus is charged with a solvent, a catalyst and 2,6-diisopropylnaphthalene, and an oxygen-containing gas is blown therein at a predetermined temperature for a predetermined time.

The reaction temperature is usually in the range of 100 to 300 ° C., preferably 150 to 250 ° C. If the reaction temperature is too low, the reaction rate will be remarkably slowed. The loss due to combustion increases.

The reaction pressure is not particularly limited, but considering the reaction rate, the oxygen partial pressure in the gas phase is 0.2 to 10 kg in absolute pressure.
Pressures such as / cm2 are preferred.

(Product separation) In the case of a semi-batch reaction, most of the target 2,6-naphthalenedicarboxylic acid precipitates as a solid after completion of the reaction. Therefore, the reaction mixture should be cooled and filtered. Will be collected by.

Since most of the catalyst and the pyridine compound and the reaction intermediates are dissolved in the aliphatic carboxylic acid solvent, the aliphatic carboxylic acid solution recovered by filtration may contain 2,6-naphthalenedicarboxylic acid as needed. It can be used for repeated reaction by supplementing the catalyst, the solvent and the pyridine compound which are decreased due to the adhesion to the acid and the like.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples.

The yield in the examples means that
It is a mol% based on 6-diisopropylnaphthalene.

The purity of 2,6-naphthalenedicarboxylic acid was measured by high performance liquid chromatography and was found to be UV285.
Area% in nm.

Example 1 200 g of acetic acid, 9.35 g (37.5 mmol) of cobalt acetate / tetrahydrate, acetic acid were placed in a 500 ml titanium autoclave equipped with a reflux condenser, a gas introduction pipe, a raw material feed pump, a back pressure regulator and an induction stirrer. Manganese / tetrahydrate 9.20 g (37.5 mmol), ammonium bromide 7.35 g (75.0 mmol) and pyridine 5.93
Charge g (75.0 mmol), replace the reaction system with nitrogen,
The pressure inside the system was adjusted to 30 kg / cm ² GP with a back pressure regulator. Heat the inner temperature to 200 ° C and blow air to 3-4Nl / mi.
It was supplied so that the internal pressure was maintained at 30 kg / cm ² GP at n (oxygen partial pressure 6.5 kg / cm ² ).

When the system became stable, 79.62 g (375 mmol) of 2,6-diisopropylnaphthalene was continuously fed over 4 hours. After the supply of 2,6-diisopropylnaphthalene was completed, air was continuously supplied for 1 hour while maintaining the system temperature at 200 ° C and 30 kg / cm ² GP.

After completion of the reaction, the autoclave was cooled to room temperature, and the precipitated solid matter was collected by filtration and washed with 40 g of acetic acid. The total amount of the acetic acid solution recovered from the reaction mixture and the acetic acid used for the cleaning was 254.4 g. When the solid was dried, 67.2 g of a light brown solid was obtained. This coarse 2,
The purity of 6-naphthalenedicarboxylic acid was 99.4%, and the yield was 82.4%.

Example 2 200 g of acetic acid, 6.23 g (25.0 mmol) of cobalt acetate / tetrahydrate, 6.13 g (25.0 mmol) of manganese acetate / tetrahydrate and 4.90 g (50.0 g) of ammonium bromide were placed in the same autoclave as in Example 1.
) And 7.90 g (100.0 mmol) of pyridine were charged, the inside of the reaction system was replaced with nitrogen, and the pressure inside the system was adjusted to 30 kg / cm ² GP with a back pressure regulator. The internal temperature was heated to 200 ° C, and air was supplied at 3 to 4 Nl / min so that the internal pressure was maintained at 30 kg / cm ² GP (oxygen partial pressure 6.5 kg / cm ² ).

When the system became stable, 79.62 g (375 mmol) of 2,6-diisopropylnaphthalene was continuously fed for 4 hours. After the supply of 2,6-diisopropylnaphthalene,
Air was continuously supplied for 1 hour while maintaining the system temperature at 200 ° C and 30 kg / cm ² GP.

After completion of the reaction, the autoclave was cooled to room temperature, the precipitated solid matter was collected by filtration and washed with 40 g of acetic acid. The total amount of the acetic acid solution recovered from the reaction mixture and the acetic acid used for the cleaning was 236.6 g. When the solid was dried, 64,5 g of a light brown solid was obtained. This coarse 2,
The purity of 6-naphthalenedicarboxylic acid was 99.1%, and the yield was 80.3%.

Comparative Example 1 A brown solid was obtained after the reaction and post-treatment were carried out under exactly the same conditions as in Example 1 except that pyridine was not added.
6.1 g was obtained. The purity of this crude 2,6-naphthalenedicarboxylic acid was 97.1%, and the yield was 57.8%.

Comparative Example 2 200 g of acetic acid, 9.35 g of cobalt acetate.tetrahydrate (37.5 mmol), 9.20 g of manganese acetate.tetrahydrate (37.5 mmol), 8.93 g of potassium bromide (75.0 mmol) were placed in the same autoclave as in Example 1. ) And 7.37 g (75.0 mmol) of potassium acetate were charged, the inside of the reaction system was replaced with nitrogen, and the pressure inside the system was adjusted to 30 kg / cm ² GP with a back pressure regulator. The inner temperature was heated to 200 ° C, and air was supplied at 3 to 4 Nl / min so that the inner pressure was maintained at 30 kg / cm ² GP (oxygen partial pressure 6.5 kg / cm ² ).

When the system became stable, 79.62 g (375 mmol) of 2,6-diisopropylnaphthalene was continuously fed for 4 hours. After the supply of 2,6-diisopropylnaphthalene was completed, the air was continuously supplied for 1 hour while maintaining the system temperature at 210 ° C and 30 kg / cm ² GP.

After completion of the reaction, the autoclave was cooled to room temperature, and the precipitated solid matter was collected by filtration and washed with 40 g of acetic acid. The total amount of the acetic acid solution recovered from the reaction mixture and the acetic acid used for the cleaning was 148.6 g. When the solid was dried, 68.2 g of a light brown solid was obtained.

However, this crude product contained 22.0 g of potassium salt of 2,6-naphthalenedicarboxylic acid. The crude product was washed with dilute hydrochloric acid, washed with water and dried to obtain 65.1 g of a light brown solid. This coarse 2,6-
The purity of naphthalenedicarboxylic acid is 99.6% and the yield is
It was 80.0%.

[0044]

According to the method of the present invention, the yield is improved without increasing the amount of catalyst, and the alkali metal salt of 2,6-naphthalenedicarboxylic acid is not precipitated in the reaction product.
Highly pure 2,6-naphthalenedicarboxylic acid can be efficiently produced from 2,6-diisopropylnaphthalene.

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[Procedure amendment]

[Submission date] May 27, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007] In the method of using a salt of an inorganic acid, tri <br/> benefit for bets acid has a problem that a by-product in large quantities.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

The object of the present invention is to solve the above, the trimethylene Li Tsu City acids without precipitation of by-product and an alkali metal salt as described above, the production of industrially advantageous 2,6-naphthalene dicarboxylic acid To provide a method.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014] Cobalt compounds and manganese compounds, cobalt: in atomic molar ratio of manganese 99: 1 to 1: 99, preferably 97: 3 to 3: is used in the range of 97, the amount used, the aliphatic carboxylic acid 0.2 to 10 wt% as the total amount of cobalt and manganese atoms relative solvent, preferably from 0.4 to 5 wt%.

Claims (1)

[Claims] 1. 2,6-Diisopropylnaphthalene or an oxidation intermediate thereof is added in a solvent containing an aliphatic carboxylic acid,
In the method for producing 2,6-naphthalenedicarboxylic acid that is oxidized by molecular oxygen in the presence of a catalyst composed of a heavy metal composed of cobalt and manganese and a bromine compound, the oxidation reaction is carried out in the presence of a pyridine compound. Process for producing 1,6-naphthalenedicarboxylic acid.