SU1065401A1 - Process for purifying aromatic acids - Google Patents

Abstract

A METHOD FOR CLEANING AROMATIC ACIDS in an aqueous solution when heated, followed by crystallization and filtration, is due to the fact that, in order to simplify the process, the aqueous acid solution is treated with an ozone-containing mixture containing 0.4–16 mmol of ozone in 1 l, in the presence of an inhibitor, in which butyl alcohol or cycrhexanone is used, and the process is carried out at a molar ratio of aromatic acid and inhibitor 1:

Description

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The invention relates to organic chemistry, specifically to the method of purification of the benzoic or pyromellite or sodium salt, benzenesulfonic acid, and can be used in the chemical industry.

These acids are widely used in organic synthesis. In the preparation of dyes, fragrances, polymeric materials, they are used in the pharmaceutical and food industries, therefore, high demands are made on the degree of purification of these substances.

Methods are known for purification of aromatic acids, consisting in their distillation of fl} or in their recrystallization from aqueous solutions containing phenols 2, or, in extracting them from aqueous solutions Z.

The disadvantages of these methods are cleaning at an elevated temperature, as well as the use of complex, expensive equipment.

There is also a known method for purifying terephthalic acid, which consists in treating an aqueous or acetic acid solution of terephthalic acid with oxygen in the presence of hydrobromic acid at 30–90 atm and followed by crystallization and filtration.

The disadvantage of this method is the use of high pressures and temperatures.

The closest in technical essence and the achieved result to the invention is the method of purification of pyromellitic acid, which consists in the fact that the aqueous acid solution is treated with activated carbon at 200-317 ° C and the pressure necessary to maintain water in the liquid phase (17 atm and more) in the presence of sodium thiosulfate and sodium bisulfite, followed by crystallization and filtration of C5.

The disadvantage of this method is to carry out the process at high temperatures and pressures.

The aim of the invention is to simplify the purification process of aromatic carboxylic acids.

The goal is achieved by the fact that according to the proposed method of purification of pyromellite or benzoic or sodium salt of benzenesulfonic acid, an aqueous solution of aromatic acid is treated with an ozone-air mixture containing 0.4–16 mml of ozone in 1 liter of the mixture, in the presence of an inhibitor, which is butyl C. alcohol or cyclohexanone, with a molar ratio of aromatic carboxylic acid and inhibitor

It (0.5-1), and the process is carried out at 80-90 seconds. The desired product is isolated by crystallization and filtration. The application of the proposed method allows cleaning at atmospheric pressure and low temperature.

Aromatic acids, reacting with ozone, are destroyed. The use of inhibitors helps to prevent the process of destructive oxidation of the purified aromatic compound. During the purification of aromatic acids with ozone in the presence of inhibitors, selective oxidation of organic impurities takes place. Such impurities as beisaldehyde, p-carboxybenzaldehyde, p-toluic acid are acidified, turning into the desired product, and benzoquinone, 1,4-naphthoquinone, phenol, unsaturated aliphatic products and some other impurities that are reacted with ozone are destroyed.

When ozonizing aromatic acids, it is advisable to feed 0.51 mol of the inhibitor per 1 mol of the acid to be purified. The presence of an inhibitor in an amount of less than 0.5 mol per 1 mo of acid leads to a partial destruction of the target product, and therefore, to a decrease in yield. The use of an inhibitor in an amount of more than 1 mol per 1 mol of acid is impractical, since it does not lead to an increase in the yield. .

The cleaning process is carried out at 8090 s. Under these conditions, the solubility of aromatic acids is quite high, which contributes to an increase in the removal of the target product per unit volume.

A further increase in temperature is undesirable, since ozone decomposition is observed.

The purification of aromatic acids is carried out in an aqueous medium, followed by a stage of isolation of the target product, which consists in carrying out crystallization followed by filtration. The mother liquor obtained by filtration is reusable.

Example 1. A bubble-type glass reactor with an ozone-air spray dispenser, which serves as a Scott plate 2, is charged at 100.degree. C. with 100 ml of an aqueous solution containing 4 g (32.8 mmol) of a 99.3% technical benzoic acid. Then, 1.2 g (16.4 mmol) of normal butyl alcohol is loaded into the reactor and, over a period of 3 minutes, an oeo-air mixture with an ozone concentration of 0.8 mmol / l is passed through the solution. The crystallization is further carried out by cooling to 20-25 ° C, followed by filtration. The yield is 3/4 g or 85% per loaded product. Content of the main substance is 99.9%.

P & M 2-5. It is carried out analogously to example 1. The parameters are given in the table.

2. Benzoyl- 32.8 99.3 Cyclo- 23 0.6 per hexanone

3. 32.8 99.3 n-buty-16.4 0.4

lovogo alcohol

4. Pyrome- 26 95 26 2 lithic acid

80 3 82 99.9 (3.3) (122.4)

99.9

87.5 (122.4) (3.5)

83

99.8

10 (272.9) (5.5)

Claims (1)

METHOD FOR CLEANING AROMATIC acids in an aqueous solution by heating, followed by crystallization and filtration, which is explained by the fact that, in order to simplify the process, the aqueous acid solution is treated with an ozone-air mixture containing 0.4-16 mmol of ozone in 1 liter of mixture , in the presence of an inhibitor, which is butyl alcohol or cyclohexanone, and the process is carried out at a molar ratio of aromatic acid and inhibitor 1: (0.5-1) and • temperature 80-90 ° С.