JPS6056694B2 - Method for producing aromatic dicarboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing aromatic dicarboxylic acids by oxidizing xylene in the presence of bromide ions and copper ions using water as a dispersion medium.

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

However, these methods have the drawback that a considerable amount of the lower aliphatic carboxylic acid used as a solvent cannot be avoided due to combustion, etc., resulting in extra costs. Furthermore, a method of using water in place of the lower aliphatic carboxylic acid solvent has been discovered and proposed in British Patent No. 8334A and Japanese Patent Publication No. 13921/1983.

In this method, an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent is oxidized in an aqueous solvent in the presence of a bromine compound, but the oxidation reaction rate is extremely slow, such as p- When xylene is oxidized to obtain terephthalic acid, the yield of terephthalic acid after 16 hours of reaction reaches only 29%. Furthermore, British Patent No. 833438 states that vanadium, copper, and manganese are excellent catalysts for the oxidation of an aqueous dispersion medium system, and in the examples, these catalysts were used. There are examples of oxidation of paradiisopropylbenzene etc. using it, but no examples of oxidation of xylenes have been found.

Furthermore, not all of the metals mentioned herein are effective as catalysts for xylene oxidation reactions. For example, in the oxidation of xylene, it is not as effective as manganese bromide. The present inventors conducted extensive research to find a method with high reaction efficiency using an aqueous solvent, and as a result, they finally completed the present invention.

That is, in the present invention, xylene has a bromine atom of 0.3 to
0.01 to 10% by weight of bromine compound and copper atom
This is a method for producing an aromatic carboxylic acid, which is characterized by oxidizing with a molecular oxygen-containing gas in an aqueous solution containing 0.5% by weight of a copper compound. The xylenes used in this invention are ortho, meta and para xylene.

The catalyst used in the present invention is a combination of a bromine compound and a copper compound, and the bromine compound may be one that itself generates bromine ions or one that decomposes during the oxidation reaction to generate bromine ions, such as , metal bromides such as bromine, hydrogen bromide or sodium bromide, potassium bromide, manganese bromide, cobalt bromide, and organic bromides such as ethyl bromide, tetrabromoethane, etc.

The amount of bromine compound added is 0 as a bromine atom to the water solvent.
．． 3-1% heel mass, 0. Even if it is less than 1%
The yield of aromatic dicarboxylic acid obtained decreases even if the amount exceeds 0.5% to 5%. Busy %
is within the range of On the other hand, the copper compound is preferably a water-soluble salt, and specific examples include sulfate, chloride, bromide, and acetate. The amount of copper compound added is 0.01 to 0 relative to the water solvent.
．． If it is less than 0.01% by weight, the reaction will not actually proceed, and if it is more than 0.5% by weight, side reactions will increase, the product will be colored, and the yield will be reduced. It also decreases, which is not desirable. In the present invention, the reaction temperature is 160-26
Cf'C, particularly preferably 180 to 220'C.

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 70k9/CltG.

As the molecular oxygen-containing gas, any of oxygen, a mixed gas of oxygen and an inert gas such as nitrogen*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 8, Comparative Examples 1 to 4 In a titanium autoclave (inner volume: 500 m1) equipped with a reflux condenser and a stirrer, 30 y of paraxylene and 270 y of an aqueous solution containing bromide ions and copper ions in the amounts listed in Table 1 were placed. Prepare each and autoclave for 30k.
9/CFlfG Heated to 210°C under pressure, and air was heated to 12
While continuously blowing into the liquid at a rate of 0N1/Hr,
The reaction was carried out for 3 hours.

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. Example 9 An oxidation reaction was carried out in exactly the same manner as in Example 2, except that the xylene to be oxidized was replaced with meta-xylene.

After 3.0 hours of oxidation reaction, 72 mol 1 mol % of isophthalic acid was obtained based on the charged meta-xylene.

Example 10 An oxidation reaction was carried out in exactly the same manner as in Example 2, except that the xylene to be oxidized was replaced with ortho-xylene.

After 3.0 hours of oxidation reaction, orthophthalic acid was obtained in an amount of 70 mol 1 mol % based on the charged ortho-xylene.

Comparative Example 5 Cobalt atomic concentration 0.5% by weight instead of cupric sulfate
An oxidation reaction was carried out in exactly the same manner as in Example 2, except that cobalt acetate was used, but no consumption of oxygen was observed.
No terephthalic acid was obtained.

Comparative Example 6 Manganese atomic concentration 0.5% by weight instead of cupric sulfate
The oxidation reaction was carried out in exactly the same manner as in Example 2, except that manganese acetate was used, but no consumption of oxygen was observed.
No terephthalic acid was obtained.

Comparative Example 7 An oxidation reaction was carried out in the same manner as in Example 2, except that manganese bromide was used instead of hydrogen bromide and cupric sulfate, and the manganese atomic concentration was 0.5% by weight. No consumption of oxygen was observed and no terephthalic acid was obtained.

Claims (1)

[Claims] 1 xylene, 0.3 to 10% by weight of bromine compound as bromine atom and 0.01 to 0.5% by weight as copper atom
A method for producing an aromatic dicarboxylic acid, which comprises oxidizing it with a molecular oxygen-containing gas in an aqueous solution containing a copper compound.