HRP940446A2 - Process for the preparation of 4,4'-dinitrostilbene-2,2'-sulfonic acid - Google Patents

Description

The application refers to a new procedure for the preparation of 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS) and its salts are generally known and according to old methods, developed at the end of the last century, consist in the oxidation condensation of 2 moles of 4- of nitrotoluene-2-sulfonic acid (p-NTSA) under aqueous alkaline conditions. Oxygen (air) in the presence of a catalyst or sodium hypochloride have been described as oxidizing agents (compare e.g. A.G. Grenn and A.R. Wahl, Chemische Berichte 30, 3097-3101 (1897); 31, 1079 (1898); DRP 106.961; Chemische Zentralblatt 1900 I , 1085; DRP 113.514 and Chemische Zentralblatt 1900 II, 703). However, despite modern technical improvements, these processes yield 4,4'-dinitrostilbene-2,2'-disulfonic acid and its salts only in relatively low yields, which amount to between 60 and 75% (compare e.g. DE-OS-22 58 530).

Therefore, in the last 25 years, numerous efforts have been undertaken to improve the efficiency of this condensation using physical-chemical, mathematical and analytical methods, as well as computer models. however, these efforts did not lead to any decisive success (compare e.g. C:A: 83, 113.377 h (1975); C.A. 85, 192.288 z, 192.289 a, 192.290 n (1976); C. A, 86, 16029 c (1977). ); Chemie Analytique 50, 251-254 (1968) and Chemie et Industrie, Genie Chemique 101, 1439-1447 (1969).

Special mention should be made of the efforts undertaken in the last 10 years, which were practically aimed at solving major environmental problems by optimizing utilization, for example, the mother solution that cannot be biologically degraded. Thus, in accordance with GDR patent document no. 240200 carries out the aqueous oxidation of 4-nitrotoluene-2-sulfonic acid with air in two stages at two different temperatures and two different alkali concentrations, whereby 4,4'-dinitrostilbene-2,2'-disulfonic acid is partially precipitated in the first stage. It is stated that the yields of 4,4'-dinitrostilbene-2,2'-disulfonic acid are 82 to 85% of the theoretical, but without data on the quality of the obtained product.

From DE-OS-34 09 171, a procedure is known by which the aqueous oxidation of 4-nitrotoluene-2-sulfonic acid is carried out with air in the presence of lithium and hydroxyl ions, in this case with the addition of a catalyst. Yields of 4,4'-dinitrostilbene-2,2'-disulfonic acid are reported to be approximately 84 to 90% of teroic. In this procedure, the additional excretion of lithium as lithium carbonate before the isolation of 4,4'-dinitrostilbene-2,2'-disulfonic acid is unpleasant, whereby the recovery of lithium carbonate is only 75 to 83%. In addition, before it can be used again in the process, lithium carbonate must first be converted back to lithium hydroxide.

DE-OS-35 19 552 describes a procedure for preparing the salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid by aqueous oxidation of 4-dinitrotoluene-2-sulfonic acid with air, which is indicated by adding during the reaction potassium, calcium and/or magnesium ions to the same extent as when 4,4'-dinitrostilbene-2,2'-disulfonic acid is formed, whereby the amount of potassium, calcium and/or magnesium ions added at each moment of the reaction amounts to 10 to 150 mol.% with regard to the amount of 4,4'-dinitrostilbene-2,2'-disulfonic acid already present in the reaction mixture, and the secreted salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is separated. In this procedure, the processing and removal of large amounts of base and potassium, calcium and magnesium salts added in large quantities is unpleasant.

European published document 26154 describes a procedure for the preparation of 4,4'-dinitrostilbene-2,2'-disulfonic acid and its salts by oxidation of 4-nitrotoluene-2-sulfonic acid with air in an organic solvent. According to this procedure, depending on the mode of operation, utilization of up to 96% of the theoretical is achieved. With this procedure, working in aprotic dipolar solvents is unpleasant, and their recovery is required, which, as far as is known, cannot be carried out without losses.

We have now established that 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS) and its salts can surprisingly be prepared in high yield, and while avoiding the above inconveniences, by oxidizing 4-nitrotoluene-2-sulfonic acid with oxidizing means, if the oxidation is carried out in liquid, anhydrous ammonia, its alkyl derivative, in a given case in the presence of water and/or in their mutual mixtures.

The subject of the invention is therefore a process for preparing 4,4'-dinitrostilbene-2,2'-disulfonic acid and its salts of the formula

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in which M represents hydrogen, an alkali metal cation or an ammonium cation, by oxidation of 4-nitrotoluene-2-sulfonic acid or its salts with an oxidizing agent, which is indicated by the fact that the oxidation is carried out in liquid, anhydrous ammonia, its alkyl derivative, in a given in the case in the presence of water, and/or their mutual mixtures and in the presence of strong bases and in the given case a catalyst.

4-nitrotoluene-2-sulfonic acid (p-NTSA) or its alkaline salts used as starting material in the reaction and ammonium salts in the chemical industry are known compounds, which can be prepared very easily by sulfonating 4-nitrotoluene. It can be used either as a free acid or as one of its known salts. These salts can be used either in dry form or preferably also as a wet pressed cake with a water content of 1 to 50%, preferably 1 to 25%, or as a different precursor, as a synthesis solution or suspension, a concentrated aqueous preparation, as an oil, containing water or also as a dry powder.

The term liquid, anhydrous ammonia, its alkyl derivatives, in a given case in the presence of water, and/or their mutual mixtures, which are used as reaction solvents in this process in terms of the invention, means above all the following solvents, or combinations;

a) anhydrous, liquid ammonia

b) anhydrous, liquid alkyl derivative of ammonia,

c) a mixture of a) and b),

d) ammonia and water,

e) alkyl derivative of ammonia and water,

f) ammonia and alkyl derivative of ammonia and water.

Combination d) is preferred.

4-nitrotoluene-2-sulfonic acid, which is used as a starting material, as well as 4,4'-dinitrobenzyl-2,2'-disulfonic acid, which appears as an intermediate, and the reaction product 4,4'-dinitrostilbene- 2,2'-disulfonic acid are, for example, under the reaction conditions specified in this procedure, in the above-mentioned solvents, i.e. combinations a) to f) and especially in combination d) better soluble than in water or aprotic dipolar solvents. Therefore, the reaction, which today in industry is carried out in a high dilution, can be carried out in a much higher concentration, for example with one part of one of the mentioned solvents, i.e. combinations a) to f) to a part of 4-nitrotoluene-2-sulfonic acid, primarily from the mentioned solvents, i.e. the combination of a) to f); a circumstance that is very favorable from a technical and economic point of view. In addition, ammonia is cheaper and industrially readily available. because of its low boiling point (.33, 35°C at 1013.25 mbar) and its excellent stability under the reaction conditions specified in this process, it can be recovered practically quantitatively and therefore can be reintroduced into the process.

As acrylic derivatives of ammonia, primary as well as secondary and tertiary amines of the following formulas come into consideration:

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In these formulas, n represents a number from 1 to 6, whereby these are single amines (eg dimethylamine), as well as mixed amines (eg ethyldimethylamine). Particular preference is given to dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine and especially methylamine.

Combinations d) to f), which are used as reaction solvents in the process according to the invention, preferably contain 50 to 99%, and especially 60 to 80% of ammonia and/or an alkyl derivative of ammonia with respect to the total amount of the corresponding combination. The ratio between water and ammonia can be established in different ways, for example by first adding water, an aqueous ammonia solution with, for example, an ammonia content of 1 to 30%, aqueous 4-nitrotoluene-2-sulfonic acid or its salts or liquid ammonia, and then the shortage of ammonia, water, base dissolved in water, ammonia water, or alkyl derivatives of ammonia is replenished.

Alkaline or alkaline earth metals, such as lithium, sodium, potassium, magnesium and calcium, as well as their strongly basic compounds, eg hydroxides, amides, alcoholates, as well as strongly basic ion exchangers, come into consideration as strong bases.

The alcoholates used are mainly those derived from straight, branched or cyclic lower aliphatic alcohols with 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, such as methanol, ethanol, propanol, butanol, isopropanol and tert.butanol. These alcoholates are preferably used in the form of a suitable alcoholic solution.

Sodium or potassium compounds are primarily used, with their hydroxides and alcoholates having a special practical significance.

Depending on the type and amount of base used, it is useful to use a base dissolved in a flowable solvent. water or straight, branched or cyclic, lower aliphatic alcohols with 1 to 8 carbon atoms are used as protic solvents. The use of methanol and/or water is particularly important.

When carrying out the oxidation, the base is placed either in the reaction boiler, where p-NTSA is added, or the base is dosed simultaneously with p-NTSA via separate dosing units, or the base itself is dosed to the already added p-NTSA.

The required amount of base can vary widely. In the presence of a catalyst, catalytic amounts can be used, because the base is regenerated during the reaction. With regard to the amount of p-NTSA, amounts of bases between catalytic and equivalent, especially 0.25 to 0.5 mol, are preferably used. If the oxidation is carried out without a catalyst, at least an equivalent amount of base is used with respect to p-NTSA. The optimal amount of base to be used can be easily determined by previous experiments.

Suitable catalysts are salts, oxides or hydroxides of heavy metal compounds and/or organometallic compounds of heavy metals, such as Co, Mn, Cr, Ce, Fe, Ni, Cu, Ru, Pd, Pt or Ir (compare e.g. Homogenus Catalysis by Matal Complexes, Vol. I Chapter 2: Activation of molecular oxygen, page 79, Academic Press New York and London 1974).

However, salts, oxides and hydroxides of manganese and/or organic compounds of manganese, such as manganese sulfate and/or manganese acetate, are particularly important as catalysts.

Inorganic or organic compounds of bromine and/or iodine, such as NaJ, KJ, KBr and ammonium bromide, can also be usefully used.

Furthermore, phase transition catalysts or crown ethers can be additionally used, especially in such cases when the strong bases, which must be used, show insufficient solubility in liquid ammonia.

Examples of phase transition catalysts are ammonium chloride, ammonium bromide, methylamine hydrochloride, cyclohexylamine hydrochloride, aniline hydrochloride, dimethylamine hydrochloride, di-isobutylamine hydrochloride, triethylamine hydrochloride, triethylamine hydrochloride, tri-n-octylamine hydrochloride, benzyl-dimethylamine hydrochloride, tetramethyl-, tetraethylamine -, tetra-n-propyl-, tetra-n-butylammonium chloride, bromide and iodide, trimethyl-hexadecylammonium chloride, benzidimethyl-hexadecylammonium chloride, benzyldimethyltetradecylammonium chloride, benzyl-trimethyl-, -triethyl- and tri-n-butylammonium chloride, n -butyl-tri-n-propylammonium bromide, octadecyltrimethylammonium bromide, phenyltrimethylammonium bromide or chloride, hexadecylpyridinium bromide and chloride.

Examples of crown ethers are 15-crown-5-, 18-crown-6, di-benzo-18-crown-6, dicyclohexyl-18-crown-6,5,6,14,15-dibenzo-7,13-diaza -1,4-dioxa-cyclopentadeca-5,14-diene.

The amount of catalysts used can vary widely. In many examples, it is sufficient that catalysts are present in trace amounts. In general, however, catalysts are preferably used in an amount of approximately 0.1 to 15 wt. % with respect to 4-nitrotouene-2-sulfonic acid, i.e. its salt.

The reaction temperature is generally not critical and may be between -33°C and +50°C, preferably between -15°C and 30°C, especially between 0°C and 25°C. If the reaction is carried out at -33°C, it is carried out under atmospheric pressure. At higher temperatures, the reaction must be carried out under the vapor pressure of liquid ammonia, an alkyl derivative of ammonia, or any mixture of ammonia and/or an alkyl derivative of ammonia with water that is known from the literature ammonia with water that is known from the literature (Encyclopedia of Chemical Technology, Third Edition, Volume 2, page 474; Ullmann's Encyklopadie der technischen Chemie, 1953, Band 3, page 524).

As an oxidizing agent, pure oxygen or its mixtures with inert gases, such as nitrogen, and air come into consideration. Oxidizing agents are used in excess of p-NTSA. Generally an excess of about 300%, preferably 50% to 100%, is used with respect to p-NTSA. Of particular practical importance is the use of pure oxygen in a closed circular flow, whereby the spent oxygen is constantly replaced.

In a preferred embodiment, 1 part of 4-nitrotoluene-2-sulfonic acid, or its salts in the form of a wet pressed cake, is suspended with a catalytic amount of manganese (II) salt, as manganese sulfate and/or manganese acetate, in 0.5 to 3 part of an aqueous solution of ammonia or water, 1 to 5 parts of liquid ammonia is added, so that the ammonia content in the entire reaction mixture is 60% to 80%, and in the presence of oxygen as an oxidizing agent and sodium hydroxide as a base, it is chemically converted at temperatures of 0 up to 25°C and under pressure.

The processing is done in a known way.

The process according to the invention yields 4,4'-dinitrotoluene-2,2'-disulfonic acid, i.e. its salts in almost quantitative yield and with high purity, whereby no colored extraneous products are formed.

A further advantage of the process is that DNS, prepared according to the invention, can be further reduced to (4-amino-4''-nitro)-stilbene-2,2' directly without additional cleaning and using liquid ammonia, also without processing. -disulfonic acid and °C, which is an important intermediate for the preparation of dyes and optical brighteners. This reduction is carried out in a manner known per se with hydrogen in the presence of a catalyst.

The following examples illustrate the invention and do not limit it. Proportions and percentages mean mass fractions and mass percentages, respectively.

Example 1

Into a 1 L BEUCHI glass autoclave, equipped with a cooling/heating jacket, a manometer, a gas distribution mixer, a thermometer, a dropping funnel, a submerged gas distribution pipe, two one-way valves, and two rotometers for the introduction and removal of oxygen and a splash glass ( 10 bar), under atmospheric pressure and at -40°C, put with 97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 4.5 g of manganese (II) acetate tetrahydrate and 360 g of liquid ammonia, which corresponds to a ratio of 1 part p-NTSA salt to 3.8 parts ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +5°C, whereby the internal pressure rises to 4 bar.

At a mixer speed of 600 to 700 rpm, an oxygen flow of 10 1/h is introduced into the resulting clear solution. Additionally, 21.6 g of a 30% methanol solution of sodium methylate is added during 20 minutes at an internal temperature of 5 to 7°C. The resulting reaction mixture is now stirred with the introduction of oxygen (10 1h) for another 1 hour and 40 minutes at 5°C.

For processing, the internal pressure in the autoclave is reduced by partial evaporation of ammonia from 4 bar to atmospheric pressure, whereby the internal temperature drops from +5°C to -27°C. Then, 6.5 g of ammonium chloride is added to the reaction mixture under atmospheric pressure and it is slowly diluted with 400 ml of methanol, whereby the reaction product is precipitated in crystalline form. The flow of oxygen is stopped and ammonia is removed from the resulting suspension by slowly heating it to +30°C. The mixer is turned off and the autoclave is emptied.

Now the reaction mixture is evaporated to dryness in a vacuum, taken up in 2 l of water, made alkaline with 200 ml of 2 N sodium hydroxide and neutralized with 200 ml of 2 N hydrochloric acid, the catalyst is removed by filtration and the obtained light yellow solution is evaporated to dryness in a vacuum. the residue is taken up in 300 ml of water and, with the addition of 34 g of sodium chloride, the reaction product is precipitated, filtered with suction, washed with 100 ml of a 7.5% sodium chloride solution and dried to a constant mass in a vacuum at 110°C. 95.0 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active substance content (determined by UV-spectral photometry) of 94, 0%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 94.1% of the theoretical. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 93.6% of the theoretical.

Example 2

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 3.1 g of manganese (II ) sulfate monohydrate and 360 g of liquid ammonia - this corresponds to a ratio of 1 part Na salt p-NTSA to 3.8 parts ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +15°C, whereby the internal pressure rises to 6 bar.

An oxygen flow of 10 1/h is introduced into the resulting clear solution at a mixer speed of 600 to 700 rpm. Additionally, 11 g of a 30% methanol solution of sodium methylate are added during 25 minutes at an internal temperature of 15°C. The resulting reaction mixture is now stirred with the introduction of oxygen (10 1/h) for another 1 hour and 35 minutes at 15°C.

The processing is carried out as described in example 1, with the exception that 4.5 g of ammonium chloride is added to the reaction mixture. 96.2 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 91.7 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 93.0% of the theoretical.

Similar results are obtained if the reaction is carried out in a ratio of 1 part Na salt p-NTSA to 2.5 parts ammonia.

Example 3

Into a 1 1 BUECHI glass autoclave, equipped with a cooling/heating jacket, manometer, gas distribution mixer, thermometer, dropping funnel, submerged gas distribution tube, two one-way valves and two rotometers for introducing and removing oxygen and a splash glass ( 10 bar), at -40°C, add 97.0 g of sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 4.6 g of manganese (II) nitrate tetrahydrate and 375 g of liquid ammonia - this corresponds to a ratio of 1 part Na salt p-NTSA to 3.9 parts ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +15°C, whereby the internal pressure rises to 6 bar. At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 13 1/h. Additionally, 4.8 g of sodium hydroxide in 24 g of ethanol are added during 30 minutes at an internal temperature of 15°C. The resulting reaction mixture is now stirred with the introduction of oxygen (13 1/h) for another 1 hour at 15°C.

Processing is carried out as described in example 1. 95.2 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 93.5%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 93.8% of the theoretical.

Example 4

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98%), 4.5 g of manganese (II)-acetate tetrahydrate are placed in the glass autoclave according to example 3 under atmospheric pressure and at -40°C and 360 g of liquid ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +15°C, whereby the internal pressure rises to 6 bar.

At a mixer speed of 600 to 700 rpm, an oxygen flow of 13 1/h is introduced above the surface of the resulting clear solution. Additionally, 19.2 g of a 505% aqueous solution of sodium hydroxide is added during 15 minutes at an internal temperature of 15°C. The resulting reaction mixture, which contains an ammonia/water mixture with 97.5% ammonia and 2.5% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 3.9 parts solvent mixture), is now mixed with the introduction of oxygen ( 13 1/h) for another 1 hour at 15°C.

The processing is carried out as described in example 1. 97.2 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 89.1%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 91.3% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 92.8% of the theoretical.

Example 5

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 4.5 g of manganese (II) acetate are placed in the glass autoclave according to example 1 under atmospheric pressure and at -40°C tetrahydrate and 360 g of liquid ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to + 15°C, whereby the internal pressure rises to 6 bar. At a mixer speed of 600 to 700 rpm, oxygen is introduced into the resulting clear solution with a flow rate of 13 1/h. Additionally, 16.0 g of a 30% aqueous solution of sodium hydroxide is added during 30 minutes at an internal temperature of 15°C.

The resulting reaction mixture, which contains an ammonia/water mixture with 97% ammonia and 3% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 3.9 parts solvent mixture), is now mixed with the introduction of oxygen (13 1/h ) for another 45 minutes at 15°C.

The processing is carried out as described in example 1. 97.0 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 92.2%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 94.3% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 95.0% of the theoretical.

Example 6

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 3.1 g of manganese (II) sulfate are placed in the glass autoclave according to example 3 under atmospheric pressure and at -40°C monohydrate and 360 g of liquid ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C, whereby the internal pressure rises to 6 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 13 1/h. Additionally, during 30 minutes at an internal temperature of 15°C to 17°C, 32 g of an aqueous solution of sodium hydroxide is added.

The resulting reaction mixture, which contains an ammonia/water mixture with 93% ammonia and 7% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.1 parts solvent mixture) is now mixed with the introduction of oxygen (13 1/h) another 45 minutes at 15°C.

The processing is carried out as described in example 1. 94.4 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 96.1%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 95.6% of the theoretical. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 96.4% of the theoretical.

Example 7

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 4.6 g of manganese (II) nitrate are placed in the glass autoclave according to example 3 under atmospheric pressure and at -40°C tetrahydrate and 360 g of liquid ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +15°C, whereby the internal pressure rises to 6 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 13 1/h. Additionally, during 30 minutes at an internal temperature of 15°C to 20°C, 64 g of a 7.5% aqueous solution of sodium hydroxide is added. The resulting reaction mixture, which contains an ammonia/water mixture with 86% ammonia and 14% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.4 parts solvent mixture) is now mixed with the introduction of oxygen (13 1/h) another 45 minutes at 15°C.

The processing is carried out as described in example 1. 93.4 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 96.9%. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 95.4% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 94.7% of the theoretical.

Example 8

77.6 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient; 98.6%), 1.6 g of manganese (II) acetate tetrahydrate and 66 g of 25% -tne aqueous solution of ammonia. The autoclave is closed and at an internal temperature of 15°C, 242 g of liquid ammonia is now added, whereby the internal pressure rises to 4.4 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 10 1/h. Additionally, 42.7 g of aqueous sodium hydroxide solution are added during 20 minutes at an internal temperature of 15°C to 17°C. The resulting reaction mixture, which contains an ammonia/water mixture with 76.5% ammonia and 23% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.4 parts of the solvent mixture), is now mixed with the introduction of oxygen (10 1/h ) for another 2 hours at 15°C.

The processing is carried out as described in example 1, with the exception that 17 g of ammonium chloride is added to the reaction mixture and that it is diluted with 100 ml of water instead of methanol. 75.4 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid are obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 96.7 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 96.0% of the theoretical. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid from the reaction mixture before processing, determined by LC analysis, is 96.5% of the theoretical.

Example 9

97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98%), 94.4 g of water, 4.5 g of manganese (II) acetate tetrahydrate and 266 g of liquid ammonia. The autoclave is closed and the internal temperature is raised from -33.3°C to +13°C, whereby the internal pressure rises to 3.3 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced into the resulting clear solution at a flow rate of 10 1/h. Additionally, 16.0 g of an aqueous solution of sodium hydroxide is added during 15 minutes at an internal temperature of 13 to 15°C. The resulting reaction mixture, which contains an ammonia/water mixture with 71.5% ammonia and 28.5% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 3.9 parts solvent mixture) is now mixed with the introduction of oxygen (10 1/h for another 1 hour at 15°C.

Processing is carried out as described in example 1, whereby 300 ml of water is used instead of 400 ml of methanol. 96.3 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 91.6 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 93.0% of the theoretical. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid, determined by LC analysis, is 92.8% of the theoretical.

If instead of 97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid, 115.1 g of the compound is used as a wet pressed cake (active ingredient 83.1%, water content 15.7%) and accordingly 76.3 g water, the same results are obtained.

Example 10

97.0 g of sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 2 g of manganese (II) acetate tetrahydrate and 195 g of aqueous ammonia solution are placed in the glass autoclave according to example 3 under atmospheric pressure. The autoclave is closed and at an internal temperature of 15°C, 210 g of liquid ammonia is now added, whereby the internal pressure rises to 2.6 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 10 1/h. Additionally, 26.7 g of a 30% aqueous solution of sodium hydroxide is added during 20 minutes at an internal temperature of 10°C to 15°C. The resulting reaction mixture, which contains an ammonia/water mixture with 61% ammonia and 39% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.4 parts solvent mixture) is now mixed with the introduction of oxygen (10 1/h) another 2 hours at 15°C.

The processing is carried out as described in example 1 with the exception that 11 g of ammonium chloride is added to the reaction mixture and diluted with 100 ml of water instead of methanol. 95.4 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid are obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 92.4 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 92.9% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid from the reaction mixture before processing, determined by LC analysis, is 95.7% of the theoretical.

If instead of 97.0 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid, 115.1 g of the compound is used as a wet pressed cake (active ingredient 83.1%, water content 15.7%) and accordingly 171 g 25% of aqueous ammonia solution and 216 g of liquid ammonia, the same results are obtained.

Example 11

77.6 g of sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 1.6 g of manganese (II) acetate tetrahydrate and 202 g of 25% -tne aqueous solution of ammonia. The autoclave is closed and at an internal temperature of 20°C, 210 g of liquid ammonia is added, whereby the internal pressure rises to 4 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 10 1/h. Additionally, 21.3 g of a 30% aqueous solution of sodium hydroxide is added during 20 minutes at an internal temperature of 18°C to 20°C. The resulting reaction mixture, which contains an ammonia/water mixture with 61% ammonia and 39% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 5.6 parts solvent mixture) is now mixed with the introduction of oxygen (10 1/h) another 2 hours at 20°C.

The processing is carried out as described in example 1 with the exception that 9 g of ammonium chloride is added to the reaction mixture and diluted with 100 ml of water instead of methanol. 76.8 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid are obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV spectral photometry) of 89.1% . The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 95.9% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid from the reaction mixture before processing, determined by LC analysis, is 96.5% of the theoretical.

Similar results are obtained if the reaction is carried out with a ratio of 1 part Na salt p-NTSA to 8 parts solvent mixture.

Example 12

In the glass autoclave according to example 3, put under atmospheric pressure 77.6 g of the sodium salt of 4-trotoluene-2-sulfonic acid (active ingredient: 98.6%), 1.6 g of manganese (II) acetate tetrahydrate and 148 g of 25%- tne aqueous solution of ammonia. The autoclave is closed and at an internal temperature of 15°C, 172 g of liquid ammonia is now added, whereby the internal pressure rises to 3.5 bar.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 10 1/h. Additionally, 32 g of a 30% aqueous solution of sodium hydroxide is added during 20 minutes at an internal temperature of 10°C to 15°C. The resulting reaction mixture, which contains an ammonia/water mixture with 61% ammonia and 39% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.5 parts solvent mixture) is now mixed with the introduction of oxygen (10 1/h) another 2 hours at 15°C.

The processing is carried out as described in example 1 with the exception that 12.8 g of ammonium chloride is added to the reaction mixture and that it is diluted with 100 ml of water instead of methanol. 78.2 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid are obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 93.4 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 96.2% of the theoretical one. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid from the reaction mixture before processing, determined by LC analysis, is 97.3% of the theoretical.

Example 13

97.7 g of 4-nitrotoluene-2-sulfonic acid (active ingredient: 73.4%, water content 18.2%, sulfuric acid content 8.4%) is placed in the glass autoclave according to example 3 under atmospheric pressure, and 1 .6 g of manganese (II) acetate tetrahydrate. The autoclave is closed and at an internal temperature of 20°C to 24°C for 35 minutes, 257 g of liquid ammonia is added, whereby the internal pressure rises to 5.6 bar. Now 64.8 g of 30% aqueous sodium hydroxide solution are added to the reaction mixture at an internal temperature of 10°C to 15°C over 15 minutes.

At a mixer speed of 600 to 700 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 10 1/h. Additionally, 21.3 g of a 30% aqueous solution of sodium hydroxide is added during 290 minutes at an internal temperature of 15°C to 20°C. The resulting reaction mixture, which contains an ammonia/water mixture with 77% ammonia and 23% water (this corresponds to a ratio of 1 part Na salt p-NTSA to 4.7 parts solvent mixture) is now mixed with the introduction of oxygen (10 1/h) another 2 hours at 15°C.

The processing is carried out as described in example 1 with the exception that 8.6 g of ammonium chloride is added to the reaction mixture and diluted with 100 ml of water instead of methanol. 76.1 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 93.8 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 94.0% of the theoretical. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid from the reaction mixture before processing, determined by LC analysis, is 94.5% of the theoretical.

Example 14

77.6 g of the sodium salt of 4-nitrotoluene-2-sulfonic acid (active ingredient: 98.6%), 3.2 g of manganese (II) acetate tetrahydrate and 415 g of liquid methylamine - this corresponds to a ratio of 1 part Na salt p-NTSA to 5.5 parts solvent.

At a mixer speed of 1800 rpm, oxygen is introduced above the surface of the resulting clear solution with a flow rate of 8 1/h. Additionally, 28.8 g of a 30% methanol solution of sodium methylate are added during 20 minutes at an internal temperature of -10°C to -5°C. The resulting reaction mixture is now stirred with the introduction of oxygen (8 1/h) for another 40 minutes at -10°C. The processing is carried out as described in example 1 with the exception that 8.6 g of ammonium chloride is added to the reaction mixture and diluted with 200 ml of methanol.

61.5 g of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid are obtained in the form of a light yellow crystalline powder with a melting point above 300°C, which shows an active content (determined by UV-spectral photometry) of 92.3 %. The yield of the disodium salt of 4,4'-dinitrostilbene-2,2'-disulfonic acid is 74.8% of the theoretical one.

Claims (17)

1. Process for preparing 4,4'-dinitrostilbene-2,2'-disulfonic acid or its salts of the formula [image] in which M represents hydrogen, an alkali metal cation or an ammonium cation, by oxidation of 4-nitrotoluene-2sulfonic acid or its salts with an oxidizing agent, indicated by the fact that the oxidation is carried out in liquid, anhydrous ammonia, its alkyl derivative, in the given case in the presence of water , and/or their mutual mixtures and in the presence of strong bases. 2. The method according to claim 1, characterized in that the oxidation is carried out in a mixture of ammonia and water. 3. The method according to claim 1, characterized in that a base dissolved in a flowable solvent is used. 4. The method according to claim 3, characterized in that a lower alcohol and/or water is used as a protic solvent. 5. The method according to claim 1, characterized in that an alkaline or alkaline earth compound is used as a strong base. 6. The method according to claim 5, characterized in that hydroxides and alcoholates of alkali or alkaline earth metals or mixtures of such compounds are used as strong bases, as well as strong base ion exchangers. 7. Process according to claim 1, characterized in that catalysts are additionally used. 8. The method according to claim 7, characterized in that salts, oxides or hydroxides of heavy metal compounds and/or organometallic compounds of heavy metals are used as catalysts. 9. Process according to claim 7, characterized in that phase transition catalysts or crown ethers are used as catalysts. 10. The method according to claim 1, characterized in that the oxidation is carried out at temperatures between -33°C and +50°C. 11. The method according to claim 10, characterized in that the oxidation is carried out at temperatures between -15°C and 30°C. 12. The method according to claim 1, indicated by the fact that 1 to 10 parts of ammonia, its alkyl derivative, in the absence or presence of water, or their mixture is taken per one part of 4-nitrotoluene-2-sulfonic acid. 13. The method according to claim 12, indicated by the fact that 3 to 6 parts of ammonia, its alkyl derivative, in the absence or presence of water, or their mixture are taken for one part of 4-nitrotoluene-2-sulfonic acid. 14. The method according to claim 10, characterized in that pure oxygen and its mixtures with inert gases or air are used as the oxidizing agent. 15. The method according to claim 1, characterized in that 1 part of 4-nitrotoluene-2-sulfonic acid, or its salts in the form of a wet filter cake, is suspended with a catalytic amount of manganese II salt in 0.5 to 3 parts of an aqueous ammonia solution or water and 1 to 5 parts of liquid ammonia are added, so that the ammonia content in the entire reaction mixture is 60 to 80%, and this mixture is chemically converted in the presence of oxygen as an oxidizing agent and sodium hydroxide as a base at temperatures from 0 to 25° C and under pressure. 16. The method according to claim 1, characterized in that the proportion of ammonia or alkyl derivatives of ammonia in the mixture with water is 50% to 99%. 17. The method according to claim 16, characterized in that the proportion of ammonia or alkyl derivatives of ammonia in the mixture with water is 60% to 80%.