JPH06172295A - Production of 4,4'-diaminostilbene-2,2'-disulfonic acid or its salt - Google Patents

Abstract

PURPOSE:To obtain a method for producing 4,4'-diaminostilbene-2,2'-disulfonic acid or its salt of stable quality without forming any by-products such as red colored substances even by repeatedly using a catalyst. CONSTITUTION:This method for producing 4,4'-diaminostilbene-2,2'-disulfonic acid or its salt comprises continuously charging an aqueous solution or an aqueous suspension of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its salt in the presence of a platinum-active carbon catalyst in an aqueous solution at pH5-8 and a temperature within the range of 50-150 deg.C while keeping the reactional pressure of hydrogenation under >=1kg/cm<2> (gauge pressure) and catalytically hydrogenating the 4,4'-dinitrostilbene-2,2'-disulfonic acid or its salt in the liquid phase.

Description

Detailed Description of the Invention

[0001]

The present invention relates to 4,4'-dinitrostilbene-2,2'-disulfonic acid or a salt thereof (hereinafter abbreviated as DNS) by liquid phase catalytic hydrogenation.
The present invention relates to a method for producing 4'-diaminostilbene-2,2'-disulfonic acid or a salt thereof (hereinafter abbreviated as DAS). Of the DNS and DAS, the salt is sodium salt,
It refers to potassium salt, ammonium salt, and lithium salt.

[0002]

DAS is an important compound as an intermediate for producing dyes, especially optical brightening dyes, and requires high purity quality. Conventionally, a method of reducing DNS with iron powder and an acid has been generally used for the production of DAS, but the complexity of the separation operation between the DAS after reduction and the iron powder used for reduction and the iron powder dregs are treated. There was a problem in the difficulty of things. The catalytic hydrogenation method is known as a method that does not have these drawbacks and is suitable for continuous operation mass production, but in the catalytic hydrogenation reaction of DNS, the ethylene bond is hydrogenated along with the reduction of the nitro group to the amino group. That 4,4'-diaminodibenzyl-2,2'-disulfonic acid or a salt thereof (hereinafter abbreviated as DABS) produced as a by-product is formed, and a colored product is easily formed to easily give low-purity DAS. There is. Further, the catalyst used in the catalytic hydrogenation method is more expensive than iron powder, and a catalyst that can be used repeatedly is required.

As a conventional method for producing DAS by a catalytic hydrogenation method using a platinum-based catalyst, US Pat.
The total pressure described in No. 20 is pH 5.6 under atmospheric conditions.
To 7.0, temperature 70 to 90 ° C., in the presence of platinum or palladium based catalyst, reduction by adding heated DNS aqueous solution at such a rate that unreacted substances do not exist in excess in the reaction solution No. 48-815, the pH 4 to 5.5 or 7.5 to 9.5 DNS aqueous solution, oil absorption 50 to 190.
In the presence of palladium or platinum supported on the above carbon black or a mixed catalyst thereof, at a temperature of 60 to 90.
Method of catalytic hydrogenation under a total pressure of 1 to 5 kg / cm @ 2, a solution of pH 2 or above described in JP-A No. 50-12059 or suspension under a pressure of 1 to 250 bar, 15 to 120 DEG C., elemental cycle Method for catalytic hydrogenation in the presence of Group 8 metals of the Periodic Table, British Patent 1404853
The total pressure described in No. 1kg / cm2 or more, temperature 40 ~
A method of catalytic hydrogenation in the presence of a platinum-carbon catalyst at 130 ° C., a surface area of 1000 to 1200 m in an acidic or neutral aqueous solution of DNS described in JP-B-52-29737.
There is a method in which platinum or platinum oxide supported on activated carbon having 2 / g is suspended, and excess hydrogen is introduced into the solution at a temperature of 40 to 60 ° C. to carry out catalytic hydrogenation.

However, when the inventors of the present invention retested these methods, the method of Japanese Patent Publication No. 48-815 was DAB.
It was found that the suppression of S was insufficient, and when the amount of DABS produced was suppressed, other by-products were produced and the purity was significantly lowered. U.S. Pat. No. 2,784,220 and Japanese Patent Publication No. 5
In the method of No. 2-29737, since the reaction pressure is atmospheric pressure, the reaction rate of catalytic hydrogenation is very slow and the activity of the catalyst is severely deteriorated. It requires a lot of catalysts, resulting in high catalyst cost, which is not an economical method. Since the method of JP-A-50-12059 does not adjust the liquidity of the reaction solution, the pH of the reducing solution after the reaction becomes about 9 and the coloring is severe, and it cannot be used as a raw material for fluorescent brightening dyes. Further, the activity of the catalyst is severely reduced, and a large amount of additional catalyst is required for repeated use. The processes of JP-A-50-12059 and British Patent 140485 are batch processes, that is, the reaction components are initially charged together, so that the reaction temperature is extremely controlled in the hydrogenation reaction which proceeds by an exothermic reaction. However, if the cooling is insufficient, the reaction may runaway, which is not a safe process.

[0005]

SUMMARY OF THE INVENTION There is a demand for a method for obtaining DAS of stable quality and safe method even when a catalyst is repeatedly used without any by-products such as DABS and red coloring matter.

[0006]

The present inventors have used a platinum-activated carbon catalyst to maintain the reaction pressure for hydrogenation in an aqueous solution of pH 5 to 8 at 1 kg / cm 2 (gauge pressure) or higher while maintaining the pressure at 50 to 1
If liquid phase catalytic hydrogenation is carried out while continuously charging an aqueous solution or suspension of DNS in the temperature range of 50 ° C.,
By-products such as ABS and red coloring are significantly suppressed,
Moreover, even if the catalyst used is repeatedly used, a DAS of stable quality can be obtained, and an industrially very advantageous method was found.

The platinum-activated carbon catalyst used for carrying out the present invention refers to platinum supported on a porous activated carbon by a conventional method. At the time of use, 1 to 10% by weight of the weight of activated carbon of platinum is supported in powder form,
Alternatively, it can be used in the form of a wet product.

A buffer solution is preferably used to maintain the pH of the reaction solution at 5 to 8. This buffer is a salt of sodium dihydrogen phosphate (or potassium), disodium hydrogen phosphate (or potassium), sodium tetraborate, etc., an acid such as hydrochloric acid, boric acid, citric acid, etc., sodium hydroxide (or potassium). And so on using a base or the like. pH is 5
If it is below, the solubility of DAS will be lowered and DAS crystals will be deposited, making separation operation from the catalyst difficult. When the pH is 8 or more, a red colored product is produced when the catalyst is repeatedly used. Also, the activity of the catalyst is greatly reduced.

In the method of the present invention, the reaction pressure for catalytic hydrogenation in an aqueous solution having a pH of 5 to 8 using a platinum-activated carbon catalyst is 1 Kg / c.
The following method is used as an operation method in which a DNS aqueous solution or a water suspension is continuously charged into a reactor in a temperature range of 50 to 150 ° C. while maintaining m2 (gauge pressure) or more and the DNS is catalytically hydrogenated. However, the present invention is not limited to this operation method. A predetermined amount of platinum-activated carbon catalyst and buffer solution are put into an autoclave, and the atmosphere is replaced with nitrogen and then replaced with hydrogen, and the pressure is raised to a predetermined condition and the temperature is raised. The amount of the catalyst is not constant depending on the reaction conditions, but is 0.01 to weight (platinum metal conversion) relative to DNS
It is 1.0%, preferably 0.05 to 0.5%. The hydrogen pressure is sufficient if it is 1 kg / cm 2 (gauge pressure) or more, but it is preferably 5 kg / cm 2 (gauge pressure) or more in order to increase the reaction rate. From an economic point of view, 10 kg /
A value of not more than cm2 (gauge pressure) is suitable. The reaction temperature is not particularly limited, but is preferably selected in the range of 70 ° C to 120 ° C. What is important in the present invention is that the reaction is carried out by catalytic hydrogenation while continuously injecting an aqueous solution or suspension of DNS into the reactor with a metering pump or a metering pump for slurry. The concentration of the DNS aqueous solution is controlled by the temperature of the aqueous solution and the solubility of the DNS, but is about 5 to 20% (by weight). The concentration of the DNS aqueous suspension is about 20 to 60% (weight), preferably about 30 to 50% (weight). Further, the charging rate of DNS (sodium salt) depends on the reaction conditions, but for example, is appropriately 0.1 to 20 mol / hour, preferably 0.2 to 10 mol / hour per 1 g of platinum metal. There is no particular benefit in extending the preparation time. When the hydrogenation reaction is carried out in this way, it can be safely carried out at a relatively constant temperature. In the method of the present invention, hydrogen is constantly replenished and the pressure is kept constant. After completion of the reaction, excess hydrogen remaining is replaced with nitrogen to normal pressure, and the catalyst is recovered by sedimentation and filtration and used for the next hydrogenation. The recovered catalyst is still sufficiently active and can be used several times. Also, it can be regenerated and used by a known method. The liquid obtained by separating and recovering the catalyst can be used as it is for the production of a fluorescent whitening dye or the like using DAS as a raw material. If the reaction solution is spray-dried, it can be obtained in the form of DNS salt. If acidified to precipitate crystals of DAS and then filtered, it can be obtained as a press cake in the form of free sulfonic acid of DNS,
This can likewise be used for the production of fluorescent whitening dyes and the like. The DAS obtained as described above has a high purity of 98% or more as determined by liquid chromatography, and the DAS obtained by the method of the present invention was used to synthesize an optical brightener. D by the method (iron powder method)
The whitening property and the yield were better than those of the fluorescent whitening agent having the same structure synthesized from AS as a raw material, and the filtrate discharged during the dye synthesis was very clean.

[0010]

EXAMPLES The production method of the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the examples, "%" means "% by weight" unless otherwise specified.

Example 1 30% of 1% platinum-activated carbon, 3.1 g (water content: 55%)
The mixture was placed in a 0 ml autoclave, 100 g of distilled water, 330 mg of sodium dihydrogen phosphate and 80 mg of disodium hydrogen phosphate were added, and the atmosphere was completely replaced with hydrogen.
15% DNS aqueous solution (sodium salt) heated under conditions of 85 ° C. and total pressure of 8.5 to 9 kg / cm 2 (gauge pressure) 1
The hydrogenation reaction was carried out while press-fitting 00 g with a metering pump (heat retention). Hydrogen absorption disappeared after the injection of the DNS aqueous solution was completed, and the reaction was completed. The reaction time was 53 minutes. The reaction solution was cooled to room temperature and the catalyst was collected by filtration. An almost colorless aqueous solution was obtained, which had a pH of 6.4. The solution thus obtained was analyzed by liquid chromatography to find that DAS; 98.95%, DAB
S; 0.45%, no red coloring matter was detected.
Using this recovered catalyst, the quality was stable even if it was repeatedly used by the above method, and the reaction solution after 20 times analysis was analyzed to find that DAS: 99.48%, DABS: 0.2
2%, no red coloring was detected.

Example 2 A hydrogenation reaction was carried out in the same manner as in Example 1 except that 0.9 g of 3% platinum-activated carbon (water content: 60%) was used as the catalyst. Hydrogen absorption disappeared after completion of dropping of the aqueous DNS solution (sodium salt), and the reaction was completed. The resulting solution was almost colorless and had a pH of 6.4. As a result of analyzing this solution, DAS; 99.11%, DABS; 0.75%,
No red coloring was detected. Using this recovery catalyst,
The quality is stable even after repeated use. As a result of analyzing the reaction solution after repeating 20 times, DAS: 99.26
%, DABS; 0.18%, red coloring matter was not detected.

Example 3 A hydrogenation reaction was carried out in the same manner as in Example 1, except that 0.35 g of 5% platinum-activated carbon (dry product) was used as the catalyst. The resulting aqueous solution was almost colorless and had a pH of 6.6. The analysis result is DAS; 99.2%, DABS;
It was 0.32%. When this recovered catalyst was used repeatedly, the quality was stable as in Example 1, and 2
As a result of analyzing the reaction solution after repeating 0 times, DAS; 9
9.25%, DABS; 0.27%, no red color was detected.

Example 4 300 g of 0.9% of 5% platinum-activated carbon (water content: 62%)
Charged into a ml autoclave, distilled water 80 ml, sodium dihydrogen phosphate 0.4 g, sodium tetraborate 0.8 g
Is added, the temperature is 80 to 90 ° C, hydrogen pressure (total pressure) is 8 to 9 kg
17% DNS heated under the condition of / cm2 (gauge pressure)
100 g of aqueous solution (sodium salt) metering pump (heat retention)
Then, the mixture was pressed in to carry out the hydrogenation reaction. The hydrogen absorption disappeared after the dropwise addition of the DNS aqueous solution, and the reaction was completed. Reaction time is 1
It was 5 minutes. The reaction solution was cooled to room temperature and the catalyst was collected by filtration. An almost colorless solution is obtained with a pH of 6.
It was 5. As a result of analyzing this solution, DAS; 99.
19%, DABS; 0.35%, red coloring matter was not detected. The quality of the recovered catalyst is stable even if it is repeatedly used by the above method, and the reaction solution after 20 times of analysis shows that DAS: 99.42%, DAB
S; 0.14%, no red color was detected.

Example 5 1.2 g of 5% platinum-activated carbon in a 300 ml autoclave
(Water content: 59%), distilled water 100 g, potassium dihydrogen phosphate 1 g, and sodium hydroxide 0.14 g were added, and the mixture was heated under conditions of a temperature of 115 to 120 ° C. and a hydrogen pressure of 9.5 kg / cm 2 (gauge pressure). The hydrogenation reaction was carried out while 100 g of a 20% DNS aqueous solution (sodium salt) was being introduced under pressure with a metering pump (heat retention). Hydrogen absorption disappeared after the completion of charging the aqueous DNS solution, and the reaction was completed. The reaction time was 1 hour and 15 minutes. The reaction solution was cooled to room temperature and the catalyst was collected by filtration. An almost colorless solution was obtained, the pH of which was 6.5. As a result of analyzing the solution, DAS; 99.15%, D
ABS; 0.26%, no red color was detected. Using this recovered catalyst, the quality is stable even if it is repeatedly used by the above-mentioned method, and as a result of analyzing the reaction solution after repeating 20 times, DAS; 99.18% DAS;
21%, no red product was detected.

Example 6 A hydrogenation reaction was carried out in the same manner as in Example 1. However D
Lithium salt was used for NS. After the catalyst was collected by filtration, an almost colorless solution was obtained and the pH was 6.5. As a result of analyzing this solution, DAS; 99.27%, DADS;
0.22%, no red product detected.

Example 7 57 g of distilled water, 46 mg of sodium dihydrogen phosphate in advance,
A slurry is prepared by thoroughly stirring 11.4 mg of disodium hydrogen phosphate and 41 g of DNS (sodium salt). 60g distilled water, 48mg sodium dihydrogen phosphate,
Disodium hydrogen phosphate 12 mg, 5% platinum-activated carbon 2.
58 g (water content; 53.4%) are added to a 300 ml autoclave. Complete hydrogen substitution, temperature 85-90
The hydrogenation reaction was carried out while press-fitting a DNS slurry prepared in advance under the conditions of ℃ and total pressure of 9.0 to 9.5 Kg / cm 2 (gauge pressure) with a metering pump for slurry. The hydrogen absorption disappeared immediately after the injection of the DNS slurry was completed, and the reaction was completed. The reaction time was 1 hour and 20 minutes. The reaction solution was cooled to 40 ° C. and the catalyst was collected by filtration. An almost colorless aqueous solution was obtained, which had a pH of 6.8. The aqueous solution thus obtained was analyzed by liquid chromatography to find that DAS; 98.95%, DABS;
It was 0.82%, and no red coloring matter was detected. The quality of the recovered catalyst was stable even after repeated use under the above reaction conditions, and the reaction solution after 10 times was analyzed to find that DAS: 99.37%, DA
BS; 0.26%, and no red coloring matter was detected.

Example 8 A slurry concentration of DNS (sodium salt) was adjusted to 60% (DN
The hydrogenation reaction was carried out in the same manner as in Example 7 except that S: 60 g / distilled water: 40 g) was used. The resulting aqueous solution was almost colorless and had a pH of 6.8. The analysis result is DAS; 9
It was 8.69%, DABS; 0.31%, and when this recovered catalyst was repeatedly used, the quality was stable as in Example 7, and the reaction solution after repeated 10 times was analyzed. When I did, DAS; 99.51%, DA
BS; 0.19%, and no red coloring matter was detected.

Comparative Example 1 The hydrogenation reaction was carried out in the same manner as in Example 1 except that the liquid properties of the reaction solution were not adjusted. After filtering off the catalyst, a reddish solution was obtained, and the pH of the reaction solution at this time was 10.1. As a result of analyzing this solution, DAS; 99.25%,
DABS: 0.36%, no red coloring was detected. When this recovered catalyst was used repeatedly by the above-mentioned method, the solution became reddish brown from the third time, and the DN was used at the sixth time.
During the dropping of the S aqueous solution, the hydrogen absorption disappeared and the reaction was interrupted. As a result of analyzing this anti-solution, DNS was 1
0.53% remained.

Comparative Example 2 The hydrogenation reaction was carried out in the same manner as in Example 7 except that the liquid properties of the reaction solution were not adjusted. A reddish solution was obtained after the catalyst was filtered off, and the pH of the reaction solution at this time was 10.4. As a result of analyzing this solution, DAS; 98.22%,
DABS; 0.59%, no red coloring was detected. When this recovered catalyst was used repeatedly by the above-mentioned method, the solution became reddish brown from the second time and the DN was used at the fifth time.
During the dropping of the S aqueous solution, the hydrogen absorption disappeared and the reaction was interrupted. Analysis of this anti-solution revealed that the DNS was 2
There was 3.12% left.

Comparative Example 3 41 g of DNS (sodium salt), 153.5 g of distilled water,
Sodium dihydrogen phosphate 122.8 mg, disodium hydrogen phosphate 30.7 mg and 5% platinum-activated carbon 2.6 g
(Water content; 53.4%) was added to a 300 ml autoclave and replaced with hydrogen, and the temperature was 85 to 95 ° C and the hydrogen pressure was 9 to 9.5.
I tried to carry out catalytic hydrogenation under the reaction conditions of kg / cm2 (gauge pressure), but the reaction heat was so large that it was difficult to control the reaction temperature, and the temperature was 130 ° C due to insufficient cooling and 65 ° C due to overcooling. It has changed greatly. Hydrogen absorption disappeared in about 15 minutes and the reaction was completed. When the catalyst was filtered off, a yellow solution was obtained, at which time the pH was 6.7. As a result of analyzing this solution, DAS; 96.96
%, DABS; 4.24%, no red coloring matter was detected, but 1.75% other by-products.

[0022]

EFFECT OF THE INVENTION Using a platinum-activated carbon catalyst, p in an aqueous solution
Adjusting H to 5-8, hydrogen pressure of hydrogenation reaction is 1 Kg / c
When a liquid phase catalytic hydrogenation reaction is carried out while continuously charging an aqueous solution or suspension of DNS in a temperature range of 50 to 150 ° C. while maintaining m2 (gauge pressure) or more, a red colored product is obtained. By-production of by-products such as DABS and DABS was suppressed, high-purity DAS was obtained, and even if the recovered catalyst was repeatedly used, a high-quality and stable DAS production method was established.

Claims (1)

[Claims] 1. In the presence of a platinum-activated carbon catalyst, while maintaining the reaction pressure for hydrogenation in an aqueous solution of pH 5 to 8 at 1 kg / cm 2 (gauge pressure) or higher, 4, 4 ′ in a temperature range of 50 to 150 ° C.
An aqueous solution or suspension of dinitrostilbene-2,2'-disulfonic acid or a salt thereof is continuously charged into the reactor,
A method for producing 4,4'-diaminostilbene-2,2'-disulfonic acid or a salt thereof, which comprises liquid phase catalytic hydrogenation.