JPS6056695B2 - Method for producing aromatic dicarboxylic acid - Google Patents

Description

Detailed Description of the Invention The present invention produces aromatic dicarboxylic acids by oxidizing para-xylene or meta-xylene in the presence of cobalt salts and/or manganese salts and bromine salt compounds and aromatic carboxylic acids using water as a dispersion medium. Regarding how to.

Conventionally, the method of oxidizing xylene to obtain aromatic dicarboxylic acids involves oxidation using a lower aliphatic carboxylic acid such as acetic acid as a solvent in the presence of a heavy metal and bromine compound catalyst or in the presence of a promoter such as an aldehyde or ketone. Methods for conducting the reaction (see, eg, US Pat. No. 2,833,816) have been implemented.

However, these methods have the disadvantage that a considerable amount of the lower aliphatic carbonic acid used as a solvent cannot be avoided due to combustion, etc., resulting in extra costs. Furthermore, a method of using water instead of the lower aliphatic carboxylic acid solvent was discovered and proposed in Japanese Patent Publication No. 13921/1983.

This method involves oxidizing an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent in an aqueous solvent in the presence of a bromine compound. When oxidizing terephthalic acid to obtain terephthalic acid, the yield of terephthalic acid reached only 29% after 16 hours of reaction. Therefore, the present inventors conducted extensive research in order to find a method with high reaction efficiency using an aqueous solvent, and as a result, they finally completed the present invention. That is, the present invention provides a solution containing para-xylene or meta-xylene containing molecular oxygen in an aqueous solution containing a cobalt salt and/or manganese salt and an aromatic carboxylic acid in an amount equivalent to or more, preferably 2 to 1 mol, relative to the metal salt catalyst. This is a method for producing an aromatic dicarboxylic acid characterized by oxidation with a gas. Cobalt salts and manganese salts are known to be effective catalysts for the oxidation of xylene in organic solvents such as acetic acid, but their activity is extremely low in aqueous solvents. However, surprisingly, by adding aromatic carboxylic acids such as benzoic acid, toluic acid, terephthalic acid, etc. to these heavy metal salt catalysts in an equivalent mole or more, preferably 2 to 1 mole, the The present inventors have discovered that the present invention also has large catalytic activity, leading to the present invention. A method using a mixture of benzoic acid and water as an oxidation solvent is known in JP-A No. 15334, and a method using a mixture of toluic acid and water is known in JP-A No. 82744, but the former In the latter method, the amount of water is 15 to 3% by weight, and in the latter method, the molar ratio of water to balatoluic acid is 0.4 to 60 (in terms of weight %, the amount of water is 5% by weight). ~88)
These known methods mainly use organic acids and use water as a solvent to make these acids into a liquid phase or to prevent sublimation. The effects of these organic acids on the water-based solvent of the present invention cannot be inferred at all.

The xylene used in the present invention is rose or meta-xylene.

The catalyst used in the present invention is a combination of a cobalt salt and/or a manganese salt, a bromine salt compound, and an aromatic carboxylic acid. Any of the inorganic salts may be used, and the bromine salt compounds include alkali metal salts,
Any substance that generates bromine ions, such as alkaline earth metal salts and ammonium salts, may be used.

On the other hand, as the aromatic carboxylic acid, benzoic acid, bromobenzoic acid, chlorobenzoic acid, toluic acid, bromotoluic acid, chlorotoluic acid, nitrotoluic acid, terephthalic acid, isophthalic acid, etc. can be used. The amount of cobalt salt and/or manganese salt added is 0.1 to 1% by weight as total metal atoms, preferably 0.2 to 0.5% by weight based on the water solvent.
% by weight, and when using a cobalt salt, it is necessary to use 0.5% by weight or more of the manganese salt based on the cobalt atom.

The amount of bromine salt added is 0.3 to 1 bromine atom to the water solvent.
0% by weight, preferably 1 to 6% by weight. The amount of aromatic carboxylic acid added is preferably 2 to 1 molar or more relative to the metal catalyst. In the present invention, the reaction temperature is 160 to 260C, particularly preferably 180 to 230C.

When the reaction temperature is lower than 160°C, the reaction does not substantially proceed, and when it is higher than 260°C, xylene is burned violently and the yield of the product is reduced. The reaction pressure is not particularly limited as long as it can maintain the reaction liquid and the liquid phase, but it is usually 8 to 8.
It is in the range of 70 kg/CflG.

As the molecular oxygen-containing gas, any of oxygen, a mixed gas of oxygen and an inert gas such as nitrogen, and air can be used, but it is economically advantageous to use air.

The reaction method may be either a batch method or a so-called continuous method in which xylene and an aqueous solution are continuously supplied and the aromatic dicarboxylic acid is continuously extracted.

As described above, when using the method of the present invention having such a configuration, since water is used as a solvent, the cost of conventional solvents is almost eliminated, the oxidation reaction rate is fast, and the yield of aromatic dicarboxylic acids obtained is high. It is a great contribution to the invention industry.

Next, the method of the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 12, Comparative Examples 1 to 7 In a titanium autoclave (inner volume 500 m1) equipped with a reflux condenser and a stirrer, 30y of baraxylene, cobalt ions and manganese ions, and benzoic acid at the concentrations listed in Table 1 were added. and 270y of an aqueous solution containing 3% by weight of bromide ions, respectively, and the autoclave was heated for 40 hours.
k9/CltG under pressure, while continuously blowing air into the liquid at a rate of 330N1/Hr at a constant rate (5℃/M
The temperature was raised to 220°C (in) and then kept at a constant temperature of 220'C.

In this method, the temperature at which oxygen absorption starts and the time from the start of oxygen absorption until no more oxygen absorption is observed are measured as a measure of the ease with which the reaction proceeds and the reaction rate. After the reaction was completed, the autoclave was cooled, and the yield of terephthalic acid based on the charged baraxylene was determined from the amount of solid matter obtained and the amount of terephthalic acid in the solid matter. Note that cobalt acetate tetrahydrate was used as the cobalt salt compound, manganese acetate tetrahydrate was used as the manganese salt compound, and sodium bromide was used as the bromine salt compound. Table 1 shows the oxygen absorption starting temperature, the time required for the oxidation reaction, and the terephthalic acid yield.

Examples 13 to 21 An oxidation reaction was carried out in exactly the same manner as in Example 4, except that the type and amount * of the aromatic carboxylic acid added were changed as shown in Table 2.

Examples n-26. Comparative Examples 8 to 10 An oxidation reaction was carried out in exactly the same manner as in Example 7, except that the amount of sodium bromide added was changed as shown in Table 3.

Examples 27-30 An oxidation reaction was carried out in exactly the same manner as in Example 7, except that the bromine salt compound added was changed as shown in Table 4.

Example 31 An oxidation reaction was carried out in exactly the same manner as in Example 7 except that the xylene to be oxidized was replaced with meta-xylene.

Claims (1)

[Claims] 1 para-xylene or meta-xylene as all heavy metal atoms of cobalt atoms and/or manganese atoms 0.1
In an aqueous solution containing ~1% by weight of a cobalt salt compound and/or a manganese salt compound, 0.3 to 10% by weight of a bromine salt compound as a bromine atom, and an aromatic carboxylic acid in an amount of 1 to 10 times the mole based on the total heavy metal atoms. A method for producing an aromatic dicarboxylic acid, which comprises oxidizing it with a molecular oxygen-containing gas.