JPH059152A - Method for producing 2,6-naphthalenedicarboxylic acid - Google Patents

Abstract

(57) [Abstract] [Purpose] 2,6-naphthalenedicarboxylic acid without the use of large amounts of metal catalyst, without causing the precipitation of alkali metal salts of 2,6-naphthalenedicarboxylic acid
Efficiently produce 2,6-naphthalenedicarboxylic acid by oxidation of diisopropylnaphthalene. [Structure] 2,6-diisopropylnaphthalene or its oxidized intermediate was used in an aliphatic carboxylic acid solvent with a catalyst consisting of a cobalt compound, a manganese compound and a bromine compound in the presence of amides at a temperature of around 200 ° C. Oxidized with gaseous oxygen to produce 2,6-naphthalenedicarboxylic acid. The reaction product is cooled to room temperature, and the precipitated solid is separated and washed to ensure purity.
97% or more of 2,6-naphthalenedicarboxylic acid is obtained.

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, in particular 2,6-diisopropylnaphthalene or an oxidation intermediate thereof, in a solvent containing an aliphatic carboxylic acid, a cobalt compound, The present invention relates to a method for producing 2,6-naphthalenedicarboxylic acid that is oxidized by molecular oxygen in the presence of a catalyst composed of a manganese compound and a bromine compound.

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 high 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 the 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 consisting of a cobalt compound, a manganese compound and a bromine compound in a solvent containing an aliphatic carboxylic acid. As a method for producing naphthalenedicarboxylic acid, a method of performing 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 boron (JP-A-63-250344)
JP-A No. 1-121240), a method of adding cerium (JP-A 1-160943), a method of adding chlorine (JP-A 1-268661), etc. It is disclosed.

However, when the alkali metal is used among the above methods, most of the alkali metal is 2,6-
Since the salt of naphthalenedicarboxylic acid is contained in the reaction product, it is necessary to remove the alkali metal by neutralization with an inorganic acid.

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

[0008]

The object of the present invention is to produce industrially advantageous 2,6-naphthalenedicarboxylic acid without the above-mentioned by-product of trimellitic acid and the step of neutralizing alkali metal salts. To provide a method.

[0009]

Means for Solving the Problems The present invention provides a catalyst comprising a heavy metal consisting of cobalt and manganese and a bromine compound in a solvent containing an aliphatic carboxylic acid and 2,6-diisopropylnaphthalene or an oxidation intermediate thereof. In the method for producing 2,6-naphthalenedicarboxylic acid by oxidation with molecular oxygen in the presence thereof, the method for producing 2,6-naphthalenedicarboxylic acid is characterized in that the oxidation reaction is carried out in the presence of amides.

[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, and it can be converted to 2,6-naphthalenedicarboxylic acid by further oxidation reaction. It is a general term for compounds that can be produced. Specifically, a compound in which one or both isopropyl groups of 2,6-diisopropylnaphthalene are oxidized to 2-hydroperoxy-2-propyl group, 2-hydroxy-2-propyl group, acetyl group, formyl group or carboxyl group. Is. 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, and inorganic compounds such as hydroxides, oxides, carbonates and halides Can be mentioned. Of these, acetate and bromide are preferable.

The cobalt compound and the manganese compound are used as a mixture, and the mixing ratio thereof is cobalt: manganese (atomic ratio) in the range of 99: 1 to 1:99, preferably 97: 3 to 3:97.

The amount of cobalt and manganese used is in the range of 0.2 to 10% by weight, preferably 0.4 to 5% by weight, based on the total amount of cobalt and manganese atoms in the aliphatic carboxylic acid solvent.

Examples of the bromine compound contained in the catalyst component include molecular bromine, hydrogen bromide, inorganic bromine compounds such as hydrobromide, and methyl bromide, ethyl bromide, bromoform, ethylene bromide, bromoacetic acid. Organic bromine compounds such as

The amount of the bromine compound used is such that the amount of bromine atoms is 0.1 to 10 mole times, preferably 0.2 to 5 mole times, relative to the total mole number of cobalt and manganese atoms contained in the aliphatic carboxylic acid solvent. The range is.

(Amids) Examples of amides used in the method of the present invention include formamide, N, N-dimethylformamide (DMF), N, N-diethylformamide, acetamide, N, N-dimethylacetamide (DMAc). ),
N, N-diethylacetamide, malonamide, N, N, N ', N'-
Amides of aliphatic carboxylic acids such as tetramethylmalondiamide, N, N, N ', N'-tetraethylmalondiamide, benzamide, N, N-dimethylbenzamide, N, N-diethylbenzamide, 2-naphthylamide, N , N-Dimethyl-2-naphthylamide, N, N-diethyl-2-naphthylamide, terephthaldiamide, N, N, N ', N'-tetramethylterephthaldiamide, N, N, N', N'-teto Ethyl terephthaldiamide, 2,
6-naphthalenediamide, N, N, N ', N'-tetramethyl-2,6-
Examples thereof include amides of aromatic carboxylic acids such as naphthalenediamide and N, N, N ′, N′-tetraethyl-2,6-naphthalenediamide. These may be used either individually or as a mixture of two or more kinds at an arbitrary ratio.

The amount of amides used is 1 mol of bromine atom
It is 0.01 to 50 mol, preferably 0.05 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 other 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, and more preferably 1 to 10 times the amount of the raw material 2,6-diisopropylnaphthalene.
6 times the weight.

(Molecular Oxygen) As the molecular oxygen, in addition to pure oxygen, pure oxygen diluted with an inert gas such as nitrogen, helium or argon to an arbitrary concentration can be used.
Air is enough.

(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 adopted.

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 melted at a predetermined temperature and pressure while blowing a gas containing molecular oxygen. Is continuously supplied, a predetermined amount of 2,6-diisopropylnaphthalene is supplied, and then the blowing of the oxygen-containing gas is continued for a certain period of time.

The feed rate of the raw material 2,6-diisopropylnaphthalene cannot be unconditionally specified because the optimum value changes depending on the reaction temperature, pressure, amount of catalyst, etc.
It is sufficient to supply the entire amount in 1 to 12 hours.

When the reaction is carried out in a batch system, a solvent, a catalyst and a raw material are charged in a reaction apparatus and an oxygen-containing gas is blown at a predetermined temperature for a predetermined time.

The reaction temperature is preferably in the range of 100 to 300 ° C., more preferably 120 to 250 ° C. When the reaction temperature is lower than this, the reaction rate becomes remarkably slow, and above this temperature, the solvent and raw materials It is not preferable because 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 / cm ² are preferred.

(Product separation) In the case of a semi-batch reaction, most of the target product, 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 reaction intermediate are dissolved in the aliphatic carboxylic acid solvent, the aliphatic carboxylic acid solution recovered by filtration is converted into 2,6-naphthalenedicarboxylic acid as necessary. It can be used for repeated reaction by supplementing the catalyst, solvent and amides reduced by adhesion 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 text is mol% based on the raw material 2,6-diisopropylnaphthalene. The purity of 2,6-naphthalenedicarboxylic acid was analyzed by high performance liquid chromatography.

Example 1 200 g of acetic acid, 9.35 g (37.5 mmol) of cobalt acetate / tetrahydrate, acetic acid were added to 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. 9.20 g (37.5 mmol) of manganese / tetrahydrate,
7.35 g (75.0 mmol) ammonium bromide and DMF
5.48 g (75.0 mmol) was charged, the inside of the reaction system was replaced with nitrogen, and the pressure inside the system was adjusted to 25 kg / cm ² GP with a back pressure regulator.

Heat the inner temperature to 200 ° C and add 5N of air.
It was supplied so that the internal pressure was kept at 25 kg / cm ² GP at l / min.
When the system is stable, 2,6-diisopropylnaphthalene
79.62 g (375 mmol) was continuously fed over 4 hours.
After the supply of 2,6-diisopropylnaphthalene was completed,
The air supply was continued for 1 hour while maintaining the temperature at 00 ° C and 25 kg / cm ² GP. The average oxygen partial pressure during the reaction was 4.5 kg / cm ² .

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 254.3 g. The solid was dried to obtain 60.1 g of a light brown solid. The purity of this crude 2,6-naphthalenedicarboxylic acid was 98.3%, and when analyzed by an infrared spectrophotometer, the salt of 2,6-naphthalenedicarboxylic acid was not contained at all, and the yield was 74.1%. there were.

Example 2 The oxidation reaction was carried out under the same conditions as in Example 1 except that 6.53 g (75 mmol) of DMAc was used instead of DMF. The average oxygen partial pressure during the reaction was 4.5 kg / cm ² .

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 207.6 g. The solid was dried to obtain 54.9 g of a light brown solid. The purity of this crude 2,6-naphthalenedicarboxylic acid was 97.7%, and when analyzed by an infrared spectrophotometer, the salt of 2,6-naphthalenedicarboxylic acid was not contained at all, and the yield was 66.0%. It was

Comparative Example 1 In the same autoclave as in Example 1, 200 g of acetic acid, 9.35 g of cobalt acetate / tetrahydrate (37.5 mmol), manganese acetate /
Tetrahydrate 9.20 g (37.5 mmol), potassium bromide 8.93 g (7
5.0 mmol) and potassium acetate 7.37 g (75.0 mmol)
Was 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. Internal temperature is 200 ° C
Until the internal pressure reaches 30 kg / c at 3-4 Nl / min.
It was supplied so that it was kept at m ² GP. 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, the air supply was continued for 1 hour while maintaining the system temperature at 210 ° C and 30 kg / cm ² GP. The average oxygen partial pressure during the reaction was 4.5 kg / cm ² .

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 148.6 g. The solid was dried to obtain 68.2 g of a light brown solid.

The 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 then dried to give a light brown solid.
62.1 g was obtained. The purity of this crude 2,6-naphthalenedicarboxylic acid was 95.6%, and the yield was 73.1%. Comparative Example 2 When the reaction and the post-treatment were carried out under the same conditions as in Example 1 except that DMF was not added, 56.1 g of a brown solid was obtained. The purity of this crude 2,6-naphthalenedicarboxylic acid is 9
It was 7.1% and the yield was 57.8%. The average oxygen partial pressure during the reaction was 4.5 kg / cm ² .

INDUSTRIAL APPLICABILITY By using the method of the present invention, a large amount of a catalyst is used, and an alkali metal salt of 2,6-naphthalenedicarboxylic acid is not precipitated in a reaction product, and 2,6-diisopropylnaphthalene can be obtained. 2,6-naphthalenedicarboxylic acid can be efficiently produced with high yield.

Claims (1)

Claim: What is claimed is: 1. 2,6-diisopropylnaphthalene or an oxidized intermediate thereof is added in a solvent containing an aliphatic carboxylic acid,
In a method for producing 2,6-naphthalenedicarboxylic acid by oxidation with molecular oxygen in the presence of a catalyst composed of a cobalt compound, a manganese compound and a bromine compound, the oxidation reaction is performed in the presence of amides. Process for producing 2,6-naphthalenedicarboxylic acid.