DE2258530A1 - PROCESS FOR THE PREPARATION OF 4.4'DINITROSTILBEN-2.2'-DISULPHONIC ACID - Google Patents

Description

DR. BER3 DIPL.-ING. STAPF

PATEWTAK'A'XLTE β MUNICH SO. MAUCRKIRCHERSTR. 48

Lawyer File 23 137

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THE CLAYTON ANILINE COMPANY.LIMITED Clayton, Manchester, UK

Process for the preparation of 4.4'-dinitrostilbene-2.2'-disulphonic acid.

4.4 ¹ 2.2 ^{f-dinitrostilbene} -disulphonsäure is an important intermediate for the production of dyes and textile auxiliaries. The processes for their industrial production are generally known and consist in the oxidative condensation of 2 moles of 4-nitrotoluene-2-sulphonic acid

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Oxygen was used as the oxidizing agent for the condensation (Air) in the presence of a catalyst or nakriuin hypochlorite solution (see e.g. Kirk Othicer Encyl. Chemical Technology, 2nd edition, Volume 19, pp. 1 ff.).

The use of sodium hypochlorite solution as an oxidizing agent has numerous disadvantages. It must be big Quantities of liquids are transported, processed and stored, the activity of which depends on the temperature, the construction material of the reservoir and small amounts of impurities in the liquid itself, constantly changes. This instability is particularly pronounced during the warm season. In addition, the large amounts of NaCl, which is constantly present in the hypochlorite solutions, has an adverse effect, limiting the permissible concentration the intermediate products formed during the conversion and

thereby influence productivity. I.

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Oxidation with oxygen or air generally takes place think very slowly, why even in the presence of catalysts very long cycle times are required.

The invention relates to a new and simplified manufacturing process, with the help of which these disadvantages can be avoided.

According to the new process, Ij-nitrotoluene-2-sulphonic acid becomes oxidized by means of gaseous or liquid halogens, in particular by means of chlorine or bromine. These reagents are available available in good and constant quality. As a result of better stability and the required proportionate Processing and storage problems arise in internal volumes when halogens are used instead of the sodium hypochlorite solution, this is reduced. Another advantage of the invention The process lies in the use of the free acid instead of its sodium salt.

In addition, the use of halogens leads in particular of chlorine and bromine, as oxidizing agents to high reaction rates, which means increased productivity. The cost of the response is simple.

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The process is suitable for a continuous or cyclic procedure.

In the method according to the invention, an aqueous Solution of ^ -Hitrotoluene-2-sulphonic acid as a solution of the free acid gradually to an aqueous alkaline medium with simultaneous introduction of the liquid or added gaseous halogen. Appropriately, there should be a low concentration of available halogen everywhere.

The reaction is carried out at a temperature below the boiling point of the reaction mixture, preferably at 80 to 90 ⁰ C.

After the oxidative condensation has ended, the solution is neutralized, if necessary, by adding an acid and then cooled. The product is preferably isolated by filtration. By adding salt, the Yield can be increased.

According to an alternative method /, ur processing of the No neutralization takes place in the resection mixture. In diesel. Γ ;; 11 nui '< the addition of halogen continued for so long until the mixture is calibrated to a temperature of

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BATH ORIGINAL

has cooled down to about 50 C.

In the following examples, parts and percentages are by weight unless expressly stated otherwise is noted.

Example! 1

23.4 parts of a 47% caustic soda solution (specific weight: 1.5) are added to 10 8 parts of hot water. 11.07 parts of 100% 4-nitrotoluene-2-sulphonic acid (molar weight: 217) in the form of an approximately 38% weight: volume solution in water are added over the course of 20 minutes, the temperature being maintained between 80 and 90 ^° C. will. At the same time, chlorine gas is introduced below the surface with sufficient agitation, with sufficient agitation so that a constant, small excess is maintained. The addition of the chlorine (up to a total of 4.8 parts) is continued for about 40 to 60 minutes at a temperature of 80 to 90 ° C. Appropriately, a low concentration of free halogen should be detectable everywhere.

The clear solution is then neutralized by adding 3 parts of 100% H ₂ SO ^ (mol wt .: 98) in the form of an approximately 50% solution and then cooled. The yield

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the product can be increased by adding salt. The product is isolated by filtration to give 8 up to 8.5 parts 4. 4'-Dinitrostilbene-2.2'-disulphoric acid (Mol wt .: 430).

The above example can be repeated without adding sulfuric acid at the end. In this case, the supply of chlorine gas is continued during cooling until a temperature of about 50 ^° C. is reached. Salting out and isolation gives a product of similar quality and yield as above.

Example 2

385O parts of sodium hydroxide solution (specific weight: 1.50) will be added to 17,800 parts of hot water and the temperature set to 80 to 85 ° C.

The introduction of liquid chlorine under the surface is begun with thorough stirring and one after about 1 minute Solution of 1815 parts of 100% of 4-nitrotoluene-2-sulphonic acid (Mole weight: 217) in the form of a 30 to 45 weight / volume free Acid solution added over 15 to 25 minutes. The supply of liquid chlorine is continued during the entire time maintaining a slight excess.

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Preferably a low concentration of free halogen should be detectable everywhere. During about 40 to 60 A total of 770 parts of liquid chlorine are added in minutes and the product is isolated as in Example 1. A yield of 1300-1400 parts of 100 # 4.4'-dinitrostilbene-2.2'-disulphonic acid is obtained (Mol wt .: 430).

Example 3

A stream of 100 parts of 4-nitrotoluene-2-sulphonic acid in the form of a 35% solution of the free acid and a second stream per minute of 76 parts of a 47% caustic soda solution diluted with .390 parts of water are added to the first The fourth reactors have a total capacity of 40,000 parts of the reaction mixture. Sufficient amounts of chlorine are introduced into all reactors so that low concentrations of free chlorine can be detected everywhere Maintained range from 80 to QO ⁰ C, so that the total consumption of chlorine is almost 17 parts per minute.

The reaction mass overflowing from the fourth reactor is neutralized at about 15 parts per minute of TO ^ iger "ii-SOj, cooled to 40 ° C and the salt of the 4. 4 '-Dinitrostilbon ^ .2 ' -

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disulphonic acid obtained in the form of a moist pilter cake.

The yield of product, calculated as the free acid (mol by weight, is 25 to 27 parts per minute.

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(Patent claims)

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Claims (5)

Patent claims l] Process for the preparation of 4.4 ⁴ -dinitrostilbene-2.2 ^f disulphonic acid from 4-nitrotoluene-2-sulphone acid, characterized in that 4-nitrotoluene-2-sulphonic acid is treated with liquid or gaseous halogen under alkaline conditions. 2. The method according to claim 1, characterized in that that the reaction medium is an aqueous solution containing sodium hydroxide. 3. The method according to claim 1 and 2, characterized in that that gaseous or liquid chlorine is used. 4. The method according to any one of claims 1 to 3> thereby characterized in that the reaction at a Temperature is carried out below the boiling point of the reaction mixture. 5. The method according to any one of claims 1 to 4, characterized Marked that the halogen is incorporated into the reaction mixture at such a rate. - 10 309823/1040 leads to the fact that a low concentration of available halogen is always detectable. 309823/1 (HO