SU48294A1 - Method for producing benzoic acid - Google Patents

Description

In order to process the waste produced in the production of benzylcellulose into useful industrial products, it is most expedient to subject the oxidation process to a ifa process. Already from preliminary experiments, it was found that nitric acid is the most beneficial oxidant. The original. The experiments were carried out with dibenzyl ether distilled from waste; later it turned out that oxidation of raw waste directly without prior distillation to individual products is more convenient and cost-effective.

As a result of the experiments, it was found that the optimum reaction conditions are a temperature of 90-95 ° C and that iron salts act catalytically, significantly accelerating the oxidation process. In the latter case, reactors: and oxidation by mixing components began on its own, accompanied by a strong release of brown vapors of nitrogen oxides and an increase in temperature.

Separation of the mixture of oxidized products did not present much difficulty. Benzaldehyde was isolated as a bisulfite compound; benzoic acid is released from the oily residue of its extraction with hot water

and crystallization from the same water upon cooling. Fatty acids resulting from hydrolysis of soap with nitric acid were obtained in the residue. In further experiments, the process was directed so that the oxidation products were mainly benzaldehyde or benzoic acid.

For the oxidation of waste, mainly benzaldehyde was applied following its change of process. With the gradual oxidation of waste, the resulting benzaldehyde was removed from the oxidizing environment with water vapor, thereby eliminating the possibility of its further oxidation to benzoic acid. Keeping the liquid level constant in the reaction vessel and not diluting the oxidizing environment in this way, we managed to achieve optimal conditions for benzaldehyde to reach 85-90% (based on the organic part of the waste, not counting soap) at a concentration of 87-93% bizaldehyde.

This simultaneous combination of the process of oxidation and steam stripping made it possible, without resorting to the isolation of benzaldehyde through the bisulfite compound, to obtain it from distillation by simple fractionation after drying with calcium chloride.

Approximate composition of waste in the bottoms (in percent):

dibenzyl ester45-51

benzyl alcohol7-8

be1 zaldagida2-3

toluene0,6

fatty acids6-8

benzylcellulose2-5

water 8-10

the rest is salt and alkali.

The oxidation process is carried out as follows. The obtained bottoms are loaded into the reaction vessel, where they are also given an equal amount of water by weight.

The process begins with the start-up of water vapor from the bubbler, with a simultaneous gradual addition of nitric acid from the measuring device until a strong foaming and rapid release of nitrogen oxides occur. The resulting benzaldehyde is removed from the reaction sphere with water vapor and, after passing through the refrigerator, is condensed together with the steam, entering the receiver. Fresh portions of oxidant are added each time the benzaldehyde drops no longer appear in the distillate. The total amount of nitric acid used (concentrated technical, beats in. 1.4) is about 0.65 kg per 1 kg of raw waste.

 The resulting benzaldehyde, after its separation from water, requires purification, as the tick contains nitrogen oxides. The latter are neutralized with an aqueous solution of soda ash until a moderate reaction appears, then the benzaldehyde is separated from the soda solution, washed with water and calcium chloride. The dried product is dispersed into fractions in a distillation column, and the fraction boiling at 178-182 ° is used as benzaldehyde.

Obtained after oxidation of waste

and distilling off benzaldehyde, a hardened oil containing fatty acids, is purified in several steps with hot water from benzoic acid, which when cooled, water falls out in the form of scaly crystals. The fatty acids washed with HKM can be directly used to emulsify the benzyl cellulose dough.

To obtain benzoic acid, the process is started by heating the mixture of waste and water with open water vapor, up to about 90-95. Then stop the start of steam and begin the gradual leap of nitric acid. Oxidation is refluxed for 2-25 hours. The reaction is considered complete when, after a flurry of acid, the vigorous evolution of nitrogen oxides ceases. The amount of acid used is 0.7 kg per 1 kg of waste.

The mass obtained after oxidation is cooled, separated from water and repeatedly leached from it with hot water benzoic acid. The latter is isolated, as indicated above, when the water is cooled.

After leaching the benzoic acid in the residue, fatty acids are obtained, which, as indicated, can be used to emulsify the benzyl cellulose dough after etherization.

The subject matter of the invention.

A method for producing benzoic acid by oxidizing dibenzyl ether or waste containing it from the production of benzyl cellulose, characterized in that nitric acid is used as an oxidizing agent.