DE2635852C2 - Process for the preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid or its Na or K salts - Google Patents

Description

The invention relates to a process for the preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid (the following- |

which is abbreviated as DAS) or their Na or K salts (which are abbreviated as DAS salts in the following)

by hydrogenation of 4,4'-dinitrostilbene-2 ^ '- disulfonic acid (which is abbreviated as DNS in the following) or their Na or K salts (which are abbreviated as DNS salts in the following) in the presence of Raney nickel.

In recent years, the following patent publications relating to the manufacture of DAS and DAS-SaI-I

zen, published DAS and DAS salts have been produced by catalytic hydrogenation: |

(1) in the presence of a noble metal catalyst (Japanese Patent Publication 815/1973);

(2) in the presence of Pd catalysts and iodine, bromine or their ions 0apan. Kokai 1 27 955/1974);

(3) in the presence of a Group 8 metal as a catalyst (DE-OS 23 20 416; Japan. Kolrai 12 059/1975); |

(4) in the presence of MeSx as a catalyst, where χ is an integer from 1 to 4 and Me is a metal from group B or Re (Japan. Kokai 93 927/1975);

(5) a cobalt catalyst (DE-OS 23 62 781; Japan. Kokai 93 953/1975);

(6) in alcohol as a solvent in the presence of a nickel catalyst (DE-OS 24 55 394; Japan. Kokai 84 550/1975);

(7) in the presence of a nickel catalyst and in aqueous solutions of phosphoric acid, boric acid, organijo see acids or their salts as buffer materials at pH values of 5 to 10 (Japan. Kokai

84 551/1975). |

In the processes of these patents, (1), (2), (3) and (4) noble metal catalysts for the | Hydrogenation uses the noble metal catalysts are more expensive than Raney nickel catalysts. It is very difficult to recover the noble metal catalysts in high yield in industrial hydrogenations.

However, this is important for economic reasons. «

For comparison, the Raney nickel catalyst is cheap and well suited for industrial hydrogenation. In process (3), Group 8 metals are used as catalysts for hydrogenation of DNS salt. In Example 19, a Raney nickel catalyst is used for comparison. Unsatisfactory results are obtained because a lot of 4,4'-diaminobenzyl-2,2'-disulfonic acid, which is abbreviated as DABS in the following, is formed as a by-product. 'f At (4), a high pressure for the hydrogenation is generally required. This is for industrial processes | disadvantageous. In comparison 4c, Raney nickel is used, but the result is not satisfactory. f.

In (5) a cobalt catalyst is used; this is more expensive than Raney nickel. For hydrogenation are higher temperatures and pressures required. This method is therefore not very advantageous.

According to DE-OS 24 55 394 (6) either alcohol containing less than 3% water is used as the solvent used or hydrogenated in an aqueous medium in the presence of a buffer. The use of alcohol with so low water content results in an increase in manufacturing cost compared to a process where only water is used as a solvent. In addition, water is released during the hydrogenation, which the The water content of the solvent increases. Before reusing the solvent must therefore Water content can be reduced again with considerable effort. In the case of the buffer variant, the distance is environmentally harmful phosphorus compounds from wastewater problematic.

Raney nickel is used in (7). However, higher temperatures are required. The usage inorganic or organic buffer materials often requires complicated treatments to clear up the Waste water. Such treatments add to the cost of the hydrogenation process. The known procedures for the hydrogenation of DNA or DNA salts using Raney nickel catalysts, thus give inadequate results, since DNA or DNA salts are present at the same time as the nitro group olefinic bond is reduced. This undesirable side reaction occurs very strongly with Raney nickel catalysts on.

The inventive method is characterized in that the hydrogenation in the presence of dicyandiamide in an amount of 0.5 to 50 wt .-%, based on the 4,4'-dinitrostilbene-2,2'-disulfonic acid or its Na or K salts in water at a temperature in the range of 50 to 12O ⁰ C and a hydrogen ■ pressure from atmospheric pressure to 49.1 bar (50 kg / cm ²⁾ is carried out.

According to the invention, the hydrogenation proceeds smoothly and the DABS salt is only a by-product in small amounts formed (less than 0.1% under suitable conditions). Knowing the known procedures was this surprising and was not obvious.

DMS or DNS salts and dicyandiamide are available and can be used for the hydrogenation according to the invention be wounded. The hydrogenation according to the invention proceeds so smoothly and quickly that it is used industrially

can be. Dicyandiamide will be Ln in an amount ranging from 0.5 to 50 percent based on the weight of DNA or DNA salt, used If dicyandiamide is used in an insufficient amount during hydrogenation, so simultaneously with the reduction of the nitro groups, the olefinic bonds of the DNA or of the DNA salt hydrogenated. The yield of DAS or DAS-SaIz is almost quantitative and is 97.5 to 99.0% of the theoretical yield.

The novel catalytic hydrogenation method of the present invention gives very good results when the following Conditions are met.

A certain amount of Raney nickel catalyst, suspended in water, is τ in a with a stirrer given equipped autoclave. The air in the autoclave is replaced by nitrogen and then by hydrogen replaced An increased hydrogen pressure is used

The contents are stirred and warmed to the reaction temperature. A measured amount of dicyandiamide is placed in the autoclave. (The addition of the dicyandiamide can be carried out before the introduction of nitrogen take place.)

An aqueous solution of DNA salt is introduced into the autoclave by a pump and the catalytic hydrogenation is carried out, the hydrogenation is conducted at a temperature in the range of 50 to 120 ⁰ C, preferably 55 ° to 90 ° C, the reaction was conducted at higher temperatures carried out, the product is contaminated during the hydrogenation, since DABS or DABS salt or other by-products are formed in large quantities. If the hydrogenation is carried out at a temperature below 50 ° C., the time required for the hydrogenation to be completed is too long. In the present invention, the hydrogenation is carried out at a constant water pressure of from atmospheric pressure to 49.1 bar (50 kg / cm ² ), preferably at a pressure in the range from 4.9 to 30.4 bar (5 to 31 kg / cm ² ) It is preferred to control the rate of addition of DNA or DNA salt so that substantially no DNA or DNA salt can be detected in the autoclave during the hydrogenation. If DNA or DNA salt is added faster than the rate of hydrogenation, it will remain in the autoclave and accumulate, and the hydrogenation will not go smoothly and will eventually stop. After the supply of DNA or DNA salt is stopped, the absorption of hydrogen stops in a few minutes. The reaction mixture is then cooled. The catalyst is separated off by methods known per se. The reaction product can be used as an intermediate for optical brighteners and dyes without any further post-treatment.

As explained above, the hydrogenation process according to the invention is carried out batchwise; it however, it can also be carried out continuously.

The following examples illustrate the invention. In the examples, DNA salt, DAS salt or DABS-SaIz the corresponding sodium salts.

example 1

0.6 g Raney-Nickei catalyst, slurried in water (made from 1.5 g alloy powder), 1.0 g dicyandiamide and 100 ml of water are introduced into a 500 ml autoclave equipped with a stirrer. The lid is closed, air is replaced with nitrogen, and nitrogen is then replaced with hydrogen replaced.

The hydrogen pressure is increased to 5.9 bar (6 kg / cm ² ), stirring is started and the temperature is increased to 60.degree. 140 g of a 15.0% strength aqueous solution of DNS salt are then continuously introduced into the autoclave by a pump over the course of 132 minutes. The temperature is maintained at 58 to 62 ° C. The hydrogen is passed in such that the pressure is maintained at 5.9 bar (6 kg / cm ² ) during the hydrogenation. After the supply of DNA salt is stopped, hydrogen absorption stops within a few minutes.

The reaction mixture is stirred at the same temperature for 10 minutes and then cooled. Then you hear with stirring up. The hydrogen is replaced by nitrogen. The reaction mixture is of the Separated catalyst and analyzed by liquid chromatography.

DABS salt is only found in traces, which means that it is present in an amount below 0.1%. Of the The rest consists mainly of DAS-SaIz. The yield of DAS salt is 97.8% of theory.

Example 2

0.6 g of Raney nickel catalyst, slurried in water (made from 1.5 g of alloy powder), 1.0 g of dicyandiamide and 100 ml of water are placed in a 500 ml autoclave as used in Example 1. The lid is closed and the air is replaced by hydrogen as described in Example 1. The pressure is increased to 5.9 bar (6 kg / cm ² ). Stirring is started and the temperature is increased to 78 ° C.

98 g of a 15.0% strength aqueous solution of DNS salt are continuously fed into the autoclave via a pump in the course of 87 minutes at a temperature between 78 and 82.degree. Hydrogen is passed in such that the pressure is maintained at 5.9 bar (6 kg / cm ² ).

The absorption of hydrogen ceases within a few minutes after the addition of DNA salts is complete. The reaction mixture is stirred for 5 min at the same temperature, then ^{cooled to 45 °} C., and stirring is then stopped. The hydrogen is vented to the atmosphere and then replaced with nitrogen. The reaction mixture is separated from the catalyst and analyzed by liquid chromatography. The content of DABS-SaIz is 0.4% and the rest consists mainly of DAS-SaIz.

The yield of DAS salt is 97.5% of theory.

Example 3

0.6 g Raney nickel catalyst, slurried in water (made from 1.5 g alloy powder), 2.0 g dicyandiamide and 100 ml water are placed in the autoclave used in Example 1. In the same way as described in Example 2, the hydrogen pressure is increased to 5.9 bar (6 kg / cm ² ). One begins to stir and the temperature is raised to 80 ⁰ C 100 g of a 15.0% aqueous solution of DNS salt are continuously introduced into the autoclave via a pump over 83 min at a temperature of 78-82 ° C directed

Hydrogen is introduced in such a way that a pressure of 5.9 bar (6 kg / cm ² ) is maintained during the hydrogenation ίο The reaction mixture is stirred for 5 minutes after the addition of DNS salt has ended. The autoclave is then cooled. The reaction mixture is analyzed, the content of DABS salt is 0.4%, and the remainder consists mainly of DAS salt.

The yield of DAS salt is 97.5% of theory.

Example 4

0.6 g of Raney nickel catalyst, slurried in water (made from 1.5 g of alloy powder), 1.0 g of dicyandiamide and 100 ml of water are added to the autoclave used in Example 1. In the same way as described in Example 2, the hydrogen pressure is increased to 10.8 bar (11 kg / cm ² ), stirring is started and the temperature is increased to 80.degree

100 g of a 15.0% solution of DNS salt are continuously passed into the autoclave for 74 min at a temperature between 78 and S2 ° C. Hydrogen is added to reduce the pressure during the hydrogenation to 10.8 bar (11 kg / cm ² ). The mixture is stirred for 5 minutes after the addition of DNS salt is complete. The reaction mixture is then cooled. The reaction mixture is analyzed. The content of DABS-SaIz is 0.4% and the rest consists mainly of DAS-SaIz.
The yield of DAS salt is 97.5% of theory.

Comparative experiment 1

0.6 g Raney nickel catalyst slurried in water (made from 1.5 g alloy powder) and 100 ml water are added to the 500 ml autoclave used in Example 1. In the same manner as described in Example 1, the hydrogen pressure to 10.8 bar (11 kg / cm ²⁾ increases, starting with stirring, and the temperature is raised to 80 ⁰ C.

92 g of a 15.0% strength aqueous solution of DNS salt are continuously passed into the autoclave by a pump over the course of 90 minutes. The hydrogenation takes place at a pressure of 10.8 bar (11 kg / cm ² ). After the addition of DNS salt has ended, the reaction mixture is ^{stirred for a further 5 min at 80 °} C. and then cooled. The reaction mixture is analyzed by liquid chromatography
The content of DABS-SaIz is 13.7% and the content of DAS-SaIz is 863%.

Comparative experiment 2

0.6 g Raney nickel catalyst, slurried in water (made from 1.5 g alloy powder), and 100 ml water are placed in the 500 ml autoclave used in Example 1. In the same way as described in Example 1, the hydrogen pressure is increased to 5.9 bar (6 kg / cm ² ), stirring is started and the temperature is increased to 80.degree.

113 g of a 15.0% strength aqueous solution of DNS salt are continuously pumped for 90

min in the autoclave. The hydrogenation is carried out at a temperature between 78 and 82 ° C The absorption of the hydrogen stops a few minutes after the addition of the DNA salt is complete.

The reaction mixture is stirred for a further 5 min at the reaction temperature and cooled. The reaction mixture will be analysed.

The content of DABS-SaIz is 6.7% and the content of DAS-SaIz is 93.3%.

Example 5

1.0 g Raney nickel catalyst, slurried in water (made from 2.5 g alloy powder), and 100 ml water are added to the autoclave used in Example 1. The lid is closed, the air is replaced with nitrogen and then with hydrogen. The hydrogen pressure is increased to 6 kg / cm ² (absolute). One begins to stir. The temperature is raised to 60 ⁰ C. 0.16 g of dicyanamide, dissolved in 133 ml of 15.0% strength aqueous solution of DNS salt (containing 20.0 g of DNS salt), are continuously introduced into the autoclave for 146 minutes with a pump. The temperature is at Maintained 58 to 62 ° C. Hydrogen is passed in such that the pressure is maintained at 5.9 bar (6 kg / cm ² ) during the hydrogenation.

After the supply of the DNA salt has ended, the absorption of the hydrogen stops within a few minutes. The reaction mixture is stirred for 10 min. At the same temperature and then cooled to 40 ⁰ C. You stop stirring. The hydrogen is released into the atmosphere and replaced by nitrogen. The reaction mixture is separated from the catalyst and analyzed by liquid chromatography. The DABS-SaIz content is 0.3%. The rest is DAS-SaIz.

Examples 6 to 9

The amounts of Raney nickel catalyst listed in Table 1, 100 ml of water and the amounts of dicyandiamide given in Table 1 are added to the autoclave used in Example 1. The lid is closed and the air is replaced with hydrogen as described in Example 1. The pressure s is increased to 5.9 bar (6 kg / cm ² ). You start stirring. The temperature is raised to the reaction temperature given in Table 1

133 ml of a 15.0% strength aqueous solution of DNS salt are continuously fed into the autoclave via a pump, and then hydrogenation is carried out. The temperature is maintained at the temperatures shown in Table 1. Hydrogen is passed in during the hydrogenation in such a way that a pressure of 5.9 bar (6 kg / cm ² ) (absolute) is maintained.

After the supply of the DNA salt has ended, the absorption of hydrogen ceases within a few minutes. The reaction mixture is stirred for a few minutes at the same temperature and then ^{cooled to 40 °} C. The stirring is stopped.

The hydrogen is released into the atmosphere and replaced with nitrogen. The reaction mixture is 15 separated from the catalyst and analyzed by liquid chromatography. The content of DABS salt is listed in the following table The yields of DAS-SaIz are almost quantitative.

example catalyst Dicyandiamide DNA salt Reaction DNA salt DNS SaIz Content of (G) (G) (G) temperature Feed time yield DABS SaIz ("C) (min) (%) 6th 15.0 4.0 20.0 59-61 29 98.7 03 7th 10.0 10.0 20.0 69-71 91 98.5 0.6 8th 3.0 1.0 203 59-61 90 98.8 0.4 9 6.0 2.0 20.2 59-61 41 98.8 0.4

Claims (1)

Claim: Process for the preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid or its Na or K salts, by hydrogenation of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its Na or K salts in the presence of Raney nickel, characterized in that the hydrogenation is carried out in the presence of dicyandiamide in an amount of 0.5 to 50% by weight, based on the 4,4'-dinitrostilbene-2,2'-disulfonic acid or its Na or K salts in water at a temperature in the range from 50 to 120 ° C and a hydrogen pressure of | Atmospheric pressure up to 49.1 bar (50 kg / cm ² ) carries out