JP2611232B2 - Method for producing 2,6-naphthalenedicarboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to the oxidation of 2,6-dimethylnaphthalene to 2,6-dimethylnaphthalene.
The present invention relates to a method for producing naphthalenedicarboxylic acid. More specifically, the present invention relates to a method for producing 2,6-naphthalenedicarboxylic acid in high yield by oxidizing 2,6-dimethylnaphthalene in the presence of an aliphatic carboxylic acid and an aromatic compound.

(Prior Art) As a method for producing 2,6-naphthalenedicarboxylic acid, a method is known in which cadmium chloride is used as a catalyst and a potassium salt of 1,8-naphthalenedicarboxylic acid is isomerized in the presence of carbon dioxide. ing.

Also, a method for producing terephthalic acid or the like by oxidizing an alkyl-substituted aromatic hydrocarbon with molecular oxygen has been conventionally known, and 2,6-naphthalenedicarboxylic acid is converted from 2,6-dimethylnaphthalene using this method. Is also known. That is, JP-A-48-34153 and JP-A-49-42654 disclose 2,6-dimethylnaphthalene in an acetic acid solvent using molecular oxygen in the presence of an oxidation catalyst containing cobalt, manganese and bromine. A method for oxidizing to produce 2,6-naphthalenedicarboxylic acid is disclosed. However, in these methods, unless the molar ratio of 2,6-dimethylnaphthalene to acetic acid in the reaction system is kept at a low level of 1/100 or less, an oxidation intermediate such as 6-formyl-2-naphthoic acid is produced. However, there is a disadvantage that 2,6-naphthalenedicarboxylic acid cannot be obtained in high yield. That is, these methods have low productivity per unit amount of solvent and are disadvantageous as industrial production methods.

[Problems to be solved by the invention]

Accordingly, the present invention provides a method for producing 2,6-dimethylnaphthalene from the oxidation catalyst containing cobalt, manganese and bromine.
In the method for producing 2,6-naphthalenedicarboxylic acid, 2,2-dimethylnaphthalene in acetic acid at a higher concentration (molar ratio to acetic acid), even under higher conditions, with the same or higher yields of 2,2 An object is to provide a method capable of producing 6-naphthalenedicarboxylic acid. That is, an object of the present invention is to provide a method for producing 2,6-naphthalenedicarboxylic acid, in which the concentration of 2,6-dimethylnaphthalene in acetic acid is increased and the productivity per unit amount of solvent is increased.

[Means for solving the problem]

The present invention provides a method for producing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-dimethylnaphthalene with molecular oxygen in the presence of a catalyst containing cobalt, manganese and bromine, wherein the oxidation is carried out with an aliphatic carboxylic acid. The present invention relates to a method for producing 2,6-naphthalenedicarboxylic acid, which is carried out in the presence of an acid and an aromatic compound.

 Hereinafter, the present invention will be described.

In the present invention, the "catalyst containing cobalt, manganese and bromine" includes, for example, JP-A-48-34153 (JP-B-56-34153).
-3337) and JP-A-49-42654 can be used as they are, as is the conventionally known oxidation catalyst containing cobalt, manganese and bromine. That is, the catalyst used in the present invention is a catalyst containing elemental or compound cobalt, manganese, and bromine, and particularly preferably a catalyst soluble in acetic acid.

As the cobalt compound and the manganese compound contained in the catalyst, for example, formic acid, acetic acid of cobalt and manganese,
C1-C4 aliphatic carboxylic acid salts such as propionic acid, butyric acid, oxalic acid, and maleic acid: salts of alicyclic carboxylic acids such as naphthenic acid; Salts of aromatic carboxylic acids;
Inorganic compounds such as hydroxides, oxides and bromides can be mentioned. Particularly, aliphatic carboxylate is preferable, and cobalt acetate and manganese acetate are most preferable. These cobalt salts and manganese salts may be anhydrous salts or hydrated salts.

Examples of the bromine compound contained in the catalyst include hydrogen bromide, hydrobromic acid, metal salts of hydrobromic acid, ammonium bromide, and organic bromine compounds. Preferred bromine compounds include hydrobromic acid, ammonium bromide, sodium bromide, potassium bromide, cobalt bromide, manganese bromide, and bromoacetic acid.

As the molecular oxygen used in the present invention, for example, a mixed gas of pure oxygen and an inert gas (eg, a gas such as nitrogen, helium, or argon) and oxygen is used. Air can also be used as it is as a molecular oxygen source.

As the "aliphatic carboxylic acid" used in the present invention, for example, acetic acid, propionic acid, butyric acid and the like can be mentioned. Acetic acid is particularly preferred.

As the "aromatic compound", a compound represented by the formula (Wherein, X is a halogen and n is an integer of 0 to 2). In the formula, X is preferably chlorine or bromine. Specific examples of the compound represented by the formula (I) include, for example, benzene, chlorobenzene, dichlorobenzene, bromobenzene, dibromobenzene and the like.

In the present invention, the amount of the aliphatic carboxylic acid and the aromatic compound used and the ratio of both are not particularly limited.
The aliphatic carboxylic acid may be present in an amount necessary to dissolve the cobalt compound, manganese compound, bromine compound and the like used as a catalyst. It is appropriate that the mixing ratio of the aromatic compound to the aliphatic carboxylic acid is 0.5 to 10, preferably 1 to 5, relative to 1 aliphatic carboxylic acid by volume.

The addition amount of the cobalt compound as a catalyst and the manganese compound to the reaction system is such that cobalt and manganese are each 0.001 to 1.0 gram atom with respect to the mixture 1 of the aliphatic carboxylic acid and the aromatic compound. It is particularly preferable that the content be in the range of 0.002 to 0.5 gram atom. The amount of bromine or bromine compound to be added to the reaction system is preferably such that the amount of bromine atoms is at least 0.001 to 3.0 g atoms per mixture 1 of the aliphatic carboxylic acid and the aromatic compound.

In the method of the present invention, the starting material 2,6-dimethylnaphthalene is used in an amount of 0.05 to 2.0 mol, preferably 0.1 to 1.0 mol, based on the mixture 1 of the aliphatic carboxylic acid and the aromatic compound.
It can be added to the reaction system in a molar amount. However, the amount of 2,6-dimethylnaphthalene added varies depending on the mixing ratio of the aliphatic carboxylic acid and the aromatic compound.

In the process according to the invention, the reaction temperature is between 120 and 260 ° C, preferably between 140 and 240 ° C. 2,6 if the reaction temperature is lower than 120 ° C
-The yield of naphthalenedicarboxylic acid tends to decrease. When the reaction temperature is higher than 260 ° C., trimellitic acid and the like are easily generated by oxidative cleavage of the naphthalene nucleus, and an aliphatic carboxylic acid such as acetic acid used as a solvent is easily burned.

The pressure in the reaction system is not particularly limited as long as it is equal to or higher than the vapor pressure of the reaction mixture. However, the oxygen partial pressure is usually 0.5kg / cm
It is preferably at least ² and at least 1.0 kg / cm ² . The reaction is carried out by blowing an oxygen-containing gas (for example, air) into the reaction mixture so as to maintain a predetermined pressure, and can be carried out batchwise or continuously.

The reaction time is suitably from 0.15 to 5 hours, preferably from 0.25 to 2 hours.

(Examples) Hereinafter, the present invention will be further described with reference to examples.

Example 1 In a 100 ml titanium reactor, glacial acetic acid was added as a solvent.
0 ml and 30 ml of orthodichlorobenzene, and
-4.68 g of dimethylnaphthalene and cobalt acetate tetrahydrate
0.300 g, 0.293 g of manganese acetate tetrahydrate, 0.493 of sodium bromide, and react at 40 ° C for 40 minutes at a temperature of 160 ° C and a pressure of 3.5 kg / cm ² G while blowing oxygen into the liquid phase at 0.5 L / min. Was done. The reaction mixture was evaporated and the residue was washed with hot acetic acid.
I passed. As a result of analyzing the obtained solid and the product in the filtrate, the yield of 2,6-naphthalenedicarboxylic acid was 86.4 mol% as shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was performed except that glacial acetic acid was used as a solvent and the reaction time was 90 minutes. The yield of 2,6-naphthalenedicarboxylic acid was as low as 77.6 mol%,
Acetoxymethyl-2-naphthoic acid was produced at 9.6 mol%.

Examples 2-4 Instead of orthodichlorobenzene as solvent, Example 2
Bromobenzene, chlorobenzene in Example 3, and benzene in Example 4, respectively. Example 4 was the same as Example 1 except that the pressure was 7.5 kg / cm ² G and the reaction time was 30 minutes. I went.

Example 5 The reaction temperature was 180 ° C., the pressure was 5.4 kg / cm ² G, and the reaction time was 3
The procedure was performed in the same manner as in Example 1 except that the time was 0 minutes.
As a result, the yield of 2,6-naphthalenedicarboxylic acid was 93.5 mol.
%Met.

Comparative example 2 It carried out like Example 5 except having used glacial acetic acid as a solvent 60 ml. The yield of the produced 2,6-naphthalenedicarboxylic acid was 77.7 mol%, and 6-formyl-2-naphthoic acid was 17.5 mol%.

Comparative Example 3 The operation was performed in the same manner as in Comparative Example 2 except that the reaction time was 90 minutes. The yield of 2,6-naphthalenedicarboxylic acid is 80.
9 mol%, but 12.5 mol% of 6-acetoxymethyl-2-naphthaldehyde was produced.

Example 6 As a solvent, 12 ml of glacial acetic acid and ortho-dichlorobenzene were used.
The procedure was performed in the same manner as in Example 5 except that the amount was 48 ml.

Example 7 It carried out like Example 5 except having used 0.199 g of cobalt acetate tetrahydrate, 0.049 g of manganese acetate tetrahydrate, and 0.103 g of sodium bromide as a catalyst.

Example 8 The same operation as in Example 5 was performed except that 0.051 g of cobalt acetate tetrahydrate, 0.196 g of manganese acetate tetrahydrate and 0.103 g of sodium bromide were used as the catalyst.

Example 9 It carried out like Example 5 except having used 0.149 g of cobalt acetate tetrahydrate, 0.147 g of manganese acetate tetrahydrate, and 0.246 g of sodium bromide as a catalyst.

Example 10 1.25 g of 2,6-dimethylnaphthalene acid, cobalt acetate 4
The procedure was performed in the same manner as in Example 5 except that the amount of the water salt was 0.195 g, the amount of manganese acetate tetrahydrate was 0.192 g, and the amount of ammonium bromide was 0.100 g.

The yield of 2,6-naphthalenedicarboxylic acid was 96.9 mol%.

(Effect of the Invention) According to the method of the present invention, 2,6 in a reaction system (mainly a solvent)
2,6-naphthalenedicarboxylic acid can be produced in high yield while maintaining the concentration of dimethylnaphthalene higher than before, and the productivity per unit amount of solvent can be increased.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-75563 (JP, A) JP-A-61-286342 (JP, A) JP-A-52-17453 (JP, A) 2666 (JP, B1)

Claims (1)

(57) [Claims] 1. A method for producing 2,6-naphthalenedicarboxylic acid by oxidizing 2,6-dimethylnaphthalene with molecular oxygen in the presence of a catalyst containing cobalt, manganese and bromine, wherein the oxidation is carried out with an aliphatic compound. Carboxylic acid and formula (Wherein, X is a halogen and n is an integer of 0 to 2), and the method is carried out in the presence of an aromatic compound represented by the formula: 2,6-Naphthalenedicarboxylic acid.