SU40349A1 - Method for producing benzoic aldehyde - Google Patents

Description

The present invention relates to methods for producing benzoic aldehyde by saponifying two halide compounds such as benzylidene chloride.

The trial according to the literature from various methods of obtaining benzoic aldehyde by saponification of chlorine derivatives of toluene in the technique uses two, namely, the method of saponification of technical benzylidene chloride with lime milk and the saponification of the benzylidene chloride fraction with water in the presence of iron or iron salts. These methods suffer from the following disadvantages: 1) the duration of the saponification process (5-6 hours); 2) partial oxidation of benzoic aldehyde during the saponification process, resulting in an increased yield of benzoic acid; 3) the need to use steam stripping, and 4) the need for additional purification of the benzoic aldehyde produced.

The present inventor has proposed a method for producing benzoic aldehyde, which does not have the above disadvantages.

The method consists in that benzylidene chloride is washed by heating with an aqueous solution of sodium sulphate.

Here, depending on the amount of sulfite used, the final reaction product is either benzoic aldehyde, in the form of an oil layer, easily separated from an aqueous solution of sodium benzoate, or an aqueous solution of sodium benzaldehyde sulphite. (61)

The first method of sulphite saponification makes it possible to avoid inconvenient and costly steam distillation; The second method, essentially the synthesis of a bisulphite derivative of benzoic aldehyde directly from benzylidene chloride, makes it possible to combine the saponification of benzylidene chloride and purification of the resulting benzoic aldehyde in one process. Both methods of carrying out the proposed method lead to a significant simplification of the technological process for producing benzoic aldehyde.

The advantage of the second method is time saving. Throughout the process of obtaining benzaldehyde sodium sulfite, i.e., saponification and purification takes 3 hours, whereas according to the methods used in the present technique, saponification of bapsilidene chloride lasts 5b hours, followed by a rather long purification process benzoic aldehyde. The advantage of the above method is also a relatively low saponification temperature of -80 °.

The sulfite method of benzoaldehyde production may well be applied to the un-distilled mixtures of toluene chlorination products, and saponification of benzylidene chloride containing sulfite. in the above mixture, followed by conversion of the benzoic aldehyde formed to the bisulfite derivative, is quantitative. Can be used for saponification.

sulphite, which is garbage in the production of synthetic phenol. Replacing pure sulphite with sulphite obtained from the waste of a phenol plant and containing sulphate as an impurity does not affect either the quality or the yield of benzoic aldehyde. Instead of sodium sulfite, sodium bisulfite can be used to saponify technical benzylidene chloride.

In this case, as in the case of sulfite, either benzoic aldehyde or its bisulfite derivative is obtained, depending on the amount of bisulfite used.

In the proposed method of saponification with sodium sulfite or bisulfite, the benzoic aldehyde preparation reaction takes place in a reducing medium, which excludes the possibility of benzoic aldehyde being oxidized during saponification. This is confirmed by the stability of the benzoic acid yields, which is obtained solely by the benzotrichloride mixture contained in the oily mixture.

Finally, the proposed method can be applied to quantitatively determine benzylidepe chloride and benzotrichloride in a mixture of toluene chlorination products.

Example 1. 123 g of anhydrous sodium sulfite are dissolved with stirring and with heating to 100 ° in 750 G-M water. Starting from 100 ° C, 150 g of benzylidene technical chloride (fraction from 204–207 °, specific gravity 1.27 at 15 °) are gradually added to the sulfite solution with continuous stirring. After all the benaylidene chloride has been loaded, the mixture is maintained at a temperature of up to 110 ° C and stirring for another 2 hours and 30 minutes, after which the saponification is considered complete. After saponification is complete, the reaction mixture consists of two layers: an upper oily layer of benzoic aldehyde and a lower transparent aqueous layer. The benzoic aldehyde is separated from the aqueous layer in a separating head, cleaned with ordinary sodium bisulfite or sulfuric acid and dispersed with a reflux condenser Hempel. Pure benzoic acid is recovered from the aqueous layer by adding strong hydrochloric acid to acid reaction. After cooling, the benzoic acid is filtered and dried. The yield of purified benzoic aldehyde, distilled in the range of 177.5-180 °, is 70% of the theoretical, calculated on the entire mixture (provided that the mixture used for saponification is 100% chlorobenzylidene). The yield of benzoic acid is 15% of the theoretical, calculated on the entire mixture. Synthesis Scheme:

1. SEC. CHCH + Na SOg +. CHO +

+ 2NaCl, -fH, S03 2. 2 CfiHs. CC1-f 3Na2 SOg -f 4 NgO 2CoH5. coon + 6NaCl + ZPGZOZ

Example 2. 214 g (in terms of pa 100% -fl product) anhydrous sulfite is dissolved with stirring and with heating to 75 °. Slowly over one hour, with continuous stirring, 150 g of benzylidene technical chloride (fraction from 204–207 °, specific gravity of 1.2700 at 15 °) is added to the sulfite solution. At the beginning of the loading of benzylidene chloride, the temperature is raised to 80 ° and this temperature is maintained until the end of the saponification. After all benzylidene chloride has been loaded, the mixture is kept for another 2 hours under heating and stirring to complete the bisulfite derivative. Upon completion of the reaction, the mixture is a completely homogeneous aqueous solution of benzaldehyde sulphurous sodium with no evidence of insoluble oil. When cooled, the solution almost completely encapsulates, and two layers of crystals are formed: the lower thick layer consists of pure white crystals of benzaldehyde-sulfuric acid sodium, the upper smaller one is made of white thin needles of benzoic acid. To isolate free benzoic aldehyde, the hot reaction mixture is diluted with 250 cm of water, and the bisulfite compound is destroyed by adding soda to an alkaline reaction, with continuous heating and stirring. The benzoic aldehyde which is separated out is distilled off with steam and separated from the condensate in a separatory funnel. In this case, due to the poor settling of the emulsion, part of the benzoic aldehyde remains in the water, from where it is extracted with ether. Extraction operations can be avoided if water separated from benzoic aldehyde is used at the next saponification; however, the benzoaldehyde remaining in the water is returned. The benzoaldehyde thus obtained is almost completely distilled in the range of 178-180 °. The yield is 74-75 / in theoretical, calculated on the whole mixture and about 100 / o, and the benzylidene chloride contained in the mixture is counted on. The liquor remaining after the distillation of benzoic aldehyde is filtered through suction, and pure benzoic acid is precipitated from the filtrate by adding technical hydrochloric acid until acidic. The yield of benzoic acid ISVo theoretical, counting on the entire mixture. Synthesis Scheme:

1. SEC. CHCls + NazSOa +

//about

CeH.Cf -f S02 + 2NaCl + H20

H

2. 2СвНв.СС1з + ЗМа280з + 4Н20 2 G, Ey COOH + 6NaCI + 3 ЗОг + 3 HjO 3. NaaSOa + SO, + H, 0 2 Na HSOg

/, o / OH

4.CeH5.C 4-NaHSO, CeH5 -CH

 OSOaNa.

Example 3. For saponification, an unbroken mixture of toluene chlorination products (beats weight 1.2840 at 17 °) is taken. At the end of the saponification, the reaction mixture, in addition to an aqueous solution of benzaldehyde sulphurous sodium, contains a small amount of sedimentation on the bottom of undissolved oil (the unwashed portion and side reaction products). The sodium benzaldehyde sulphite solution is separated from the undissolved oil by means of a siphon. In the future, the reaction mixture is treated in the same way as in example two. The yield of benzoic aldehyde, which is distilled almost completely in the range of 178-180, is 65-66% of the theoretical, calculated on the entire mixture, and about, calculated on the benzylidene chloride contained in the mixture. The yield of benzoic acid is 13-no / o theoretical, counting on the entire mixture.

The subject matter of the invention.

A method for producing benzoic aldehyde, characterized in that benzylidene chloride or a mixture of chlorinated toluene products containing it is heated with an aqueous solution of sodium sulphuric acid.