SU40343A1 - Purification of methadinitrobenzene - Google Patents

Description

The production of high-purity technical dinitrobenol free of ortho and para isomers is of great importance in the aniline-Erachnoi industry for the production of meta-phenylenediamine, since it is known that the use of meta-diamine containing small admixtures of ortho and parasimeters, causes a sharp drop in the outputs of azo dyes. For example, the drop in the yield of the dye Anil-brown DZG will reach 30%, Anil-black.

The use of crude meta-dinitrobenzene containing ortho and para isomers is also extremely unfavorable in other industries; for example, the fall in the yield of meta-nitro-aniline in this case reaches 30-35%.

As a result of this influence of ortho and paraisomers, the use of crude meta-dinitrobenzene (usually containing isomers of about 14-15%) leads to significant material losses in a number of productions of the aniline-dye industry.

Two technical methods for the purification of crude dinitrobenzene are currently known. Method Bettenhauser recommended germs. pat No. 72253 of 1893, based on the observations of Laubenheimer (Veg. 9,771,1876) on the conversion of chlorine derivatives of orthodinitrobenzene into aryl chloronitroanilines when heated in an autoclave with primary and secondary amines; this method has never been used in either foreign or allied avidivo-beauty industry

(N)

because of the obvious irrationality. The second way is Eve. Gubelmana and Weylanda recommended Amer. pat No. 1665005 of 1928, also based on Laubenheimer's observations (Veg. 9, 1828, 1876) on the transformation of the ortho and para isomers of dinitrobenzene during their boiling with aqueous solutions of caustic and carbonate alkalis.

The temperature of the 11.11 prescription of meta-dinitrobenzene, purified by this method, rises only from 80 to 84-85 °, while the content of ortho and paraisomers decreases from 14 to 7%.

This method eliminates to a small extent the above-noted drop in outputs. The quality of the technical meta-dinitrobenzene obtained in this way remains well below the requirements of the ani-paint industry. Experience has shown that the implementation of this method in production causes mass poisoning of dinitrobenzene vapors working.

Thus, both of these methods do not provide a satisfactory solution to the problem.

From the observations of Netsky (Veg. 29, p. 2448, 1896) and Weil and Wasserman (Veg. 55, p. 2537, 1922) over the conditions for the formation of sulfamic acids under the action of salts of sulfurous acid on methadinitrobenzene and from the observations of Laubenheimer (Veg. 15, 597, 1882) over the conditions for the formation of chloro-vitrosulfo-acids of benzene under the action of the same salts of the sulfuric acid on chlorine-producing opxQ (c) dgitrobevzola,

that all three isomerically dinitrobenzenes react with sulfuric acid salts. with the formation of the above water-soluble compounds under almost identical conditions, namely, the meta-isomer reacts with salts of sulfurous acid at 80 ° and above, the ortho and para isomers react with boiling.

This coincidence of reaction conditions for all three isomers has hitherto prevented the use of Laubenheimer's extremely important observations to develop a technical method for purifying crude methynitrobenzene from accompanying isomers (cf. 23, 1932).

Studies of the author of the present invention by the reaction conditions have shown that both the meta, and ortho and para isomers of dinitrobenzene react easily and almost quantitatively with salts of sulfurous acid already at 70 °, however, if the process is conducted at a temperature of 65 70 °, and taking sulfite in an amount corresponding to the content of ortho and paraisomers in the mixture, with continuous vigorous stirring the reaction of formation of water-soluble nitrosulfonic acids and ortho and para-isomers is quantitative and ends in 2-3 hours, the meta-isomer is the same. under these conditions it is not involved in the reaction.

After 3-4 times washing the reaction mass with water, technical methadinitrobenzene is obtained with a quantitative yield of the meta-isomer, having a melting point of 89.5-90 ° and almost free from ortho para-isomers.

Example. 1 mol. technical meta-dipitrobenzene, as it is obtained directly after the nitric oxide, is granulated in wood

to 200 d of water, the temperature is brought to 65-70 ° with vigorous stirring, then 0.15 mol. The sodium sulfite prepared in advance is aged at this temperature until the sample, taken from the tank, is well washed and dried in the laboratory, does not give a solidification temperature of 89-90 °. for this, a sufficient exposure time of 2–3 hours (if in the initial product the amount of ortho and para isomers is greater than 14–15%, then the amount of sulfite must be increased accordingly).

Upon reaching the desired point of solidification, the mass is cooled by the addition of water and thoroughly washed first by decanting, and the iodine ends on the suction to a colorless filtrate.

It is clear that, instead of sodium sulfite, other salts of sulfuric acid can be used, and the purification process can be carried out either by adding sulfite to the heated mass of dinitrobenzene, or in the reverse way, adding dinitrobenzene to the sulfite solution heated to 65-70 °.

The subject of the invention.

The method of purification of meta-dinitrobenzene with sulfur-acid salts, characterized in that technical meta-dinitrobenzene, containing ortho and para-isomers, is treated at temperatures of 70 or below with an aqueous solution of either sulfite or in the nitrosulfonic acid of benzene, the technical product contains ortho and para-dinitrobenzenes, after which, separating unchanged metinitrobeneol from the aqueous solution, it is washed with water.