JPH04173766A - Production of 2,6-naphthalenedicarboxylic acid - Google Patents

Abstract

PURPOSE:To inexpensively obtain the title compound in high yield by using a specific amount of a catalyst comprising Co, Mn and Br and oxidizing 2,6- diethylnaphthalene with molecular oxygen in a solvent containing acetic acid. CONSTITUTION:2,6-Diethylnaphthalene or an oxidation intermediate thereof is successively fed to a reactor and oxidized with molecular oxygen at 170-210 deg.C, preferably 180-200 deg.C in a solvent containing >=70wt.% acetic acid, preferably a mixed solvent comprising preferably acetic acid and 1-15wt.% water by using a catalyst comprising Co, Mn and Br in amounts to give 0.01-0.5mol, preferably 0.03-0.3mol Co an Mn calculated as metal based on 1l solvent, respectively and 5-200mol%, preferably 10-100mol% Br atom based on total amounts of Co metal and Mn metal.

Description

Detailed Description of the Invention The present invention is a method for producing 2,6-naphthalene dicarboxylic acid by oxidizing 2,6-diethylnaphthalene or its oxidized intermediate with molecular oxygen. Regarding.

Fibers and films obtained from conventional polyethylene naphthalate have superior strength and thermal properties compared to those obtained from polyethylene terephthalate, and are particularly useful for tire cords, magnetic tape linings, and heat-resistant (hot-fill) materials.
) Suitable for uses such as containers.

Such polyethylene naphthalate is produced using 2,6-naphthalene dicarboxylic acid derived from 2,6-dimethylnaphthalene as one of the raw materials, but since 2,6-dimethylnaphthalene is expensive, Despite its excellent performance, polyethylene naphthalate has traditionally had limited use. - By the way, 2,6-naphthalene dicarboxylic acid is oxidized under the usual conditions for oxidizing alkylated aromatic compounds, i.e. in a solvent, at elevated temperature and pressure, in the presence of a catalyst consisting of cobalt, manganese and bromine components. It can be easily obtained by oxidation with molecular oxygen.

In recent years, in such oxidation reactions, 2.
6-dimethylnafuchsin or its oxidized derivative with 2,6-
It has been proposed to replace diethylnaphthalene or its oxidized derivatives.

For example, Japanese Patent Publication No. 4B-27318 discloses that a dialkylnaphthalene having an ethyl group or an isopropyl group as at least one of the alkyl substituents is reacted at a temperature in an acetic acid solvent in the presence of a catalyst having cobalt, manganese and bromine components. A method is described for producing naphthalene dicarboxylic acid by oxidation at 90-160[deg.] C. with oxygen having an oxygen partial pressure higher than 0.5 atm absolute pressure.

In this method, at least 2.5 parts of acetic acid solvent is used per 1 part of dialkyl nuts, and cobalt, manganese, and bromine components are used as catalysts in relative amounts that satisfy the following three formulas. It is used as That is, (a) x + y > 2.0, (b) y≧0.15/x and (c) 0.2≦x/ (x+y)≦10, where x,
y and 2 mean the weight percent of cobalt, manganese and bromine, respectively, relative to the weight of dialkylnaphthalene.

On the other hand, JP-A No. 60-89445 states that when 2,6-diitupropylnaphthalene or its oxidized derivative is oxidized under the above-mentioned normal conditions, the target 2,6-naphthalene dicarboxylic acid cannot be obtained. It has been shown that the yield is extremely low and that undesirable by-products are produced in relatively large amounts, resulting in a low purity of the resulting 2,6-naphthalene dicarboxylic acid.

Furthermore, the above-mentioned publication states that even if the oxidation reaction conditions mentioned above are changed, for example, the reaction temperature is set to be relatively low in the early stage of the reaction and relatively high in the latter stage, such temperature changes can be made in stages. or continuously or by keeping the concentration of 2,6-diituprobylnaphthalene or its oxidized derivative low in the solvent.
It has been shown that naphthalene dicarboxylic acid cannot be obtained in a satisfactory yield.

Furthermore, British Patent Application Publication No. 2.187,744 discloses that a lower aliphatic monocarbon containing 2,6-diitubropylnaphthalene or its oxidized derivative as a starting material in a proportion of 30% by weight or less Carrying out an oxidation reaction in an acidic solvent at a reaction temperature of 140 to 210°C using molecular oxygen in the presence of a catalyst consisting of a brominated compound together with a water-soluble cerium salt, water-soluble cobalt salt or manganese salt. discloses a method for producing 2,6-naphthalene dicarboxylic acid.

In this process, 2,6-diituprobylnaphthalene or its oxidized derivative is used in a molar ratio of less than 0.4 to the heavy metal as catalyst, and bromine is
The atomic ratio of the water-soluble salt of cobalt, manganese, or a mixture thereof is generally 0.03 to the water-soluble cerium salt. It is used in the range of ~30.

Similarly, U.S. Pat. No. 4,754,060 states:
In a lower aliphatic monocarboxylic acid solvent containing water in a proportion of up to 30% by weight, in the presence of a catalyst consisting of bromine together with cobalt, manganese or a mixture thereof, with molecular oxygen
A process for producing trimellitic acid together with 2,6-naphthalene dicarboxylic acid by oxidizing 2,6-diitupropylnaphthalene at temperatures between 0 and 210<0>C is disclosed.

In this method, the atomic ratio of bromine to the heavy metal component is 0.0001 to 0. Cobalt, manganese or mixtures thereof are used in the range of 100g of solvent.
It is preferably used in an amount of 0.005 to 0.2 mol.

JP-A-60-89445 also describes a method using a relatively large amount of a heavy metal catalyst selected from the group consisting of cobalt, manganese and bromine components. That is, 2,6°- A method for making naphthalene dicarboxylic acid is described. In this method, the solvent is
At least twice the total weight of 2,6-diitupropylnaphthalene is used, cobalt is used in an atomic ratio of 10:90 to 95:5 to manganese, and bromine is Atomic ratio of 0.05 to heavy metal components
:1 to 0.5:1.

Furthermore, JP-A-62-120342 discloses that in a solvent containing at least 50% by weight of propionic acid, a bromine atom is used as the first component, cobalt, manganese or a mixture thereof as the second component, and an alkyl metal as the third component. A process is described for the oxidation of 2,6-diituprobylnaphthalene to 2,6-naphthalene dicarboxylic acid using an at least ternary catalyst consisting of the elements.

A method similar to this method is described in JP-A-62-120343, in which a reaction solvent containing at least 50% by weight of at least one selected from butyric acid, valeric acid and benzoic acid is used. It will be done.

U.S. Patent No. 4.716.245 and JP-A-61
-246143, the above-mentioned Japanese Unexamined Patent Publication No. 6
The method described in Publication No. 2-120342 and 1fl
i(II), in which a reaction solvent containing at least 70 m!1% of acetic acid, propionic acid or a mixture thereof is used;
Further, as a catalyst, 1.1 to 15 g atoms of an alkali metal component are used per 1 g atom of the bromine component.

The object of the present invention is to provide a method for producing 2.6-naphthalene dicarboxylic acid in high yield using a small amount of catalyst.

! The method for producing 2,6-naphthalene dicarboxylic acid according to the present invention for producing 2,6-naphthalene dicarboxylic acid comprises oxidizing 2,6-diethylnaphthalene or its oxidized intermediate with molecular oxygen to produce 2,6-naphthalene dicarboxylic acid. In the method, a catalyst containing cobalt, manganese and bromine is added in a solvent containing 70% by weight or more of acetic acid, cobalt and manganese are cobalt metal and manganese metal, respectively, in an amount of 0.01 to 0.5 mol per solvent if, and bromine. is used in an amount satisfying 5 to 200 mol% as bromine atoms based on the total amount of cobalt metal and manganese metal, while continuously supplying 2,6-diethylnaphthalene or its oxidized intermediate to the reactor, Temperature 170-210
It is characterized by oxidation with 'C.

The starting material used in the method for producing 2,6-naphthalene dicarboxylic acid according to the present invention is 2,6-diethylnaphthalene or its oxidized intermediate, -Tsuriyo (1) (wherein II is -CHtCH3, - COCH3, -CH
(OB)CH3 and -CI(OOH)CHs, R2 is -CHtCH3, -COCH,, -
CI(OH)CH3, -CI(008)CH3, -Co
represents a group selected from ol and -CHO, where R1
and R1 may be the same or different. ). In particular, in the present invention, 2,6-diethylnaphthalene is preferably used as the starting material.

Molecular oxygen for oxidizing such a starting material may be oxygen gas or air, but air is usually preferably used.

In the method of the present invention, the reaction solvent is preferably a mixture of 70% by weight or more of acetic acid and water, particularly 0.1 to 30% by weight of acetic acid and water, most preferably 1 to 1% by weight of acetic acid and water.
-15% by weight is used.

In the process of the invention, the oxidation of the starting materials with molecular oxygen is carried out in the presence of a catalyst consisting of cobalt, manganese and bromine. Cobalt and manganese are
As long as it is a cobalt compound and a manganese compound that are soluble in the above-mentioned solvent, it is not particularly limited, but usually, acetate, carbonate, bromide, etc. are each 0.01 to 0.5 mol per solvent 11, Preferably 0.03 to 0.3
Used in the molar range.

Bromine, on the other hand, may be an ionic bromine compound or an organic bromine compound, thus, for example, hydrobromic acid, sodium bromide, potassium bromide, lithium bromide, cobalt bromide, manganese bromide, tetrabromoethane, etc. is preferably used. These bromine compounds are usually used in an amount of 5 to 200 mol %, preferably 10 to 100 mol % as bromine atoms, based on the total amount of cobalt and manganese metals.

The reaction method may be either a semi-continuous method or a continuous method. The reaction temperature is usually 170 to 210°C, preferably 1
It is in the range of 80 to 200°C.

1) The method of the present invention is industrially advantageous because 2,6-naphthalene dicarboxylic acid can be obtained at low cost and in high yield.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 140 ml of acetic acid, cobalt acetate tetrahydrate 4.
7 g (0,019 mol), manganese acetate tetrahydrate 9.
2 g (0,038 mol) and 0.98 47% hydrobromic acid
g (0,0057 mol) and was vigorously stirred while maintaining a temperature of 200'C and a pressure of 30 kg/c.

Next, 2,6-diethylnaphthalene was supplied into the autoclave at a rate of 20 g/hour, and at the same time air was supplied at 13 g/hour.
It was supplied at a rate of 3 Nf/hour. The supply of 2,6-diethylnaphthalene was stopped after 1 hour, and then air was supplied for 2 hours, after which the reactor was cooled to room temperature and the reaction mixture was taken out.

Analysis of the resulting reaction mixture by high performance liquid chromatography and gas chromatography revealed that the conversion rate of 2.6-diethylnaphthalene was 93.2% and the yield of 2°6-naphthalene dicarboxylic acid was 83.9 mol%. . Further, the production rate of trimellitic acid was 7.7 mol%.

Example 2 In the same manner as in Example 1, 140 m of acetic acid was placed in an autoclave.
1. 2.3 g (0,0094 mol) of cobalt acetate tetrahydrate
, manganese acetate tetrahydrate 4.6 g (0,019 mol)
and 0.98 g (0,0057 mol) of 47% hydrobromic acid were charged, and the mixture was vigorously stirred while maintaining a temperature of 200° C. and a pressure of 30 kg/cdG.

Next, in the same manner as in Example 1, 2.6
- Diethylnaphthalene was fed at a rate of 20 g/h, and at the same time air was fed at a rate of 133 Nf/h. 2.
The supply of 6-diethylnaphthalene was stopped after 1 hour, and then air was supplied for 2 hours, after which the reactor was cooled to room temperature and the reaction mixture was taken out.

As a result of analyzing the obtained reaction mixture by high performance liquid chromatography and gas chromatography, the conversion rate of 2,6-diethylnaphthalene was 92.2%, and the yield of 2°6-naphthalene dicarboxylic acid was 89.3 mol%. Ta. Also,
The production rate of trimellitic acid was 2.4 mol%.

Claims (1)

[Claims] (1) In a method for producing 2,6-naphthalene dicarboxylic acid by oxidizing 2,6-diethylnaphthalene or its oxidized intermediate with molecular oxygen, cobalt, manganese, and bromine-containing catalyst, cobalt and manganese are respectively 0.01 to 0.5 mol per liter of solvent as cobalt metal and manganese metal, and bromine is 5 mol as bromine atom relative to the total amount of cobalt metal and manganese metal. 2,6-diethylnaphthalene or its oxidized intermediate is continuously supplied to the reactor at a temperature of 170 to 210 mol %.
A method for producing 2,6-naphthalene dicarboxylic acid, which comprises oxidizing at ℃.