JPS6357420B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing C acids, particularly 2-chloro-5-aminotoluene-4-sulfonic acid (referred to as C acid) or its salts, which are useful as pigment intermediates. More specifically, 2-chloro-5-nitrotoluene-4-sulfonic acid or its structural isomers or salts thereof are mixed with a noble metal catalyst and methylene (bis) of the formula CH ₂ (SR ₁ ) ₂ in water or an aqueous medium. The present invention relates to a method for producing 2-chloro-5-aminotoluene-4-sulfonic acids or salts thereof, which is characterized by carrying out catalytic reduction in the presence of one or more thioethers. C acid has important uses as an intermediate raw material for azo dyes, organic pigment Laked C, etc., and is still produced industrially by the classical Besyan reduction method. However, in this method, the raw material is chemically reduced by boiling it with monoferric acetate or monoferrous hydrochloride, so this method requires large corrosion-resistant equipment.
There are many problems such as the large amount of iron oxide sludge being discharged, which is difficult to dispose of, and the work environment deteriorated due to the acidic gas generated.To solve these problems, special equipment is required. If equipment costs are taken into consideration, manufacturing prices will inevitably rise. Therefore, there is a strong need for the development of a non-polluting reduction technology to replace Besyan reduction. The present applicants previously filed a patent application for a method using a copper-chromium oxide catalyst as a catalytic reduction method (see Japanese Patent Publication No. 54-42968), but that method requires high temperature and high pressure, and is not fully satisfactory. It wasn't something. A method for producing a haloamino aromatic compound by a catalytic reduction method from a halonitroaromatic compound using a noble metal catalyst and a Raney-nickel catalyst is generally known, and many proposals have also been made for a method for producing C acid. The problem with the catalytic reduction method for halonitroaromatic compounds is that the dehalogenation reaction occurs simultaneously with the reduction of the nitro group to the amino group.
Taking chloro-5-nitrotoluene-4-sulfonic acid as an example, it is represented by the following formula. As a method of using an industrially inexpensive Raney nickel catalyst, Japanese Patent Application Laid-Open Nos. 49-56933 and 54-19936
There are inventions such as No. 54-84549, etc., and C
It is said that an acid can be obtained, but when using these methods, a large amount of catalyst is used, and the dehalogenation reaction occurs at the same time, so the catalyst is dissolved and poisoned by the hydrogen chloride produced, and the catalyst is damaged. Since the activity decreases significantly, it becomes difficult to regenerate and use the catalyst repeatedly, and the cost required for the catalyst is large from an industrial perspective.
This is an expensive method and cannot be superior to the old method. A method of catalytic reduction using a Raney nickel catalyst in the presence of a dehalogenation inhibitor has also been proposed.
2338), method of adding thiocyanate (Japanese Patent Publication No. 46-9689), method of adding dicyandiamide or cyanamide (Japanese Patent Publication No. 50-50327), 2-
Methods such as adding aminothiazole or benzothiazole (Japanese Patent Application Laid-Open No. 76030/1983) have been proposed, but they have poor dehalogenation prevention effects and
All of these methods are insufficient as a method for producing C acid, as they extremely reduce the activity of the catalyst and delay the reaction time, and no method superior to the conventional method has yet been developed. A method using a noble metal catalyst has also been proposed, but in this case as well, dehalogenation occurs at the same time as the reduction of the nitro group, resulting in a significant decrease in the activity of the catalyst. Therefore, the catalyst is
Palladium catalysts can only be regenerated and used repeatedly once or twice at most, and palladium catalysts have this tendency, especially in the case of halonitroaromatic compounds, making them unsuitable. In addition, noble metal catalysts are generally expensive, and the catalyst cannot be used repeatedly due to a decrease in activity due to the dehalogenation reaction, which alone is the reason why this method is not economically viable. Furthermore, Tokukai Sho
54-19935 proposes a method for producing C acid using a platinum catalyst, but when this method is used, dehalogenation also occurs at the same time, and the activity of the catalyst is also significantly reduced, so reuse is limited to at most 1. Since the process was carried out only twice, it cannot be considered as an industrial method from a very economical point of view. As described above, the development of a method for preventing dehalogenation also has the greatest problem with methods using noble metal catalysts, and the purpose of preventing dehalogenation is not only to improve the yield of the target product, but also to This is to prevent severe corrosion of the equipment caused by hydrogen and a reduction in activity due to poisoning of the catalyst, and unless dehalogenation can be effectively prevented, it cannot be an industrial method from an economical point of view. For this reason, many proposals have been made as methods for preventing the elimination of chlorine in the reduction of aromatic halonitro compounds. The methods can be roughly divided into the first method, which is a method in which the catalyst is specially modified, and the second method, which is a method in which a dehalogenation inhibitor is added to a normal catalyst. The first method is to use sulfides of precious metals (J.Am.Chem.Soc.87 (1965)).
2767), method using sulfite-treated platinum (JP-A-Sho
47-17689) and a method using a platinum sulfide catalyst (Japanese Patent Application Laid-open No. 47-22391).
Although reforming catalysts are commercially available industrially, there are no catalysts suitable for the production method of C acid, which is the objective of the present invention, and in order to produce a reforming catalyst suitable for the objective of the present invention, it is necessary to add Due to the toxicity of the material, special equipment is required during adjustment, and the manufacturing cost is high, making it difficult to use as an industrial method. The second method includes, for example, a method of adding morpholine or piperazine when using a noble metal catalyst (Japanese Patent Publication No. 39-30156), a method of adding a phosphorous compound such as phosphorous acid (Japanese Patent Publication No. 122029-1980), same
54-24837), the method of adding triphenyl phosphite etc. (Japanese Patent Publication No. 45-19889), the method of adding piperidine (Japanese Patent Publication No. 48-49729, 49-61126)
No.), method of adding thioether (Japanese Patent Application Laid-open No. 1983-
59121). When the addition of these dehalogenation inhibitors is applied to the method for producing C acid, which is the objective of the present invention, the effect of preventing dehalogenation is poor, and it is necessary to keep dehalogenation as low as possible to increase the activity of the catalyst. If it is not lowered, the reaction time will be longer and the yield per time and space will be lower, and neither of these methods will be an industrially satisfactory method. The present invention was developed with the aim of developing a method for producing C acid by a catalytic reduction method that is superior to the conventional Bessyan reduction method from an industrial standpoint.As a result of extensive studies, we discovered that a noble metal catalyst supported on a carbon carrier, Especially using industrial commercial catalysts, the general formula CH ₂ (SR ₁ ) (SR ₂ )
By carrying out the reduction in the presence of one or more methylene bisthioethers shown by The present invention was achieved based on the discovery that repeated use is possible and that C acid can be economically advantageously produced despite the use of expensive noble metal catalysts. Furthermore, when this additive is used, a relatively inexpensive palladium catalyst, which is considered unsuitable for the catalytic reduction of halonitroaromatics, can also be used. Another advantage of the present invention is that the method is easily reproducible, and such excellent effects of the present invention could not be inferred from conventional knowledge. Catalysts that can be used in the process of the invention include platinum, iridium, osmium, supported on carbon,
Examples include palladium, rhodium, and ruthenium, with platinum and palladium being preferred. These catalysts can be prepared by known methods, but commercially available catalysts (for example, products from Nippon Engelhard) are sufficient. The proportion of noble metal retained on the carrier is preferably 0.2 to 20% by weight, particularly 0.5 to 10% by weight. Carbon, diatomaceous earth, barium sulfate, etc. can be used as the carrier, and carbon is preferred. The amount of catalyst used is not particularly limited, but is preferably 0.01% to 10% by weight based on the halonitro compound.
It is 0.1% to 1.0%. Methylene (bisthioether) used as inhibitor of dehalogenation reaction in the method of the present invention
is represented by the general formula CH ₂ (SR ₁ ) ₂ .
R ₁ shown here is an alkyl group having 12 or less carbon atoms and optionally having a substituent, and the substituent is a hydroxyl group or a hydroxyalkoxyl group. Of course, it may be a mixture containing one or more of these as active ingredients. As alkyl groups, preferably up to 6 straight-chain or branched hydrocarbons, such as methyl, ethyl,
propyl, isopropyl, butyl, isobutyl,
Groups such as pentyl, isopentyl, hexyl, and isohexyl. Further, the substituent for the alkyl group is a hydroxyl group or a hydroxyalkoxyl group. Among these additives, water-soluble ones are preferred, and methylene (bishydroxyethyl sulfide) is particularly preferred from the viewpoint of ease of synthesis and efficiency of use. The amount of methylene (bisthioether) used in the method of the invention is 1 to 200% by weight, particularly preferably 10 to 100% by weight, based on the weight of the noble metal in the catalyst. Methylene (bisthioether) is generally used in the process of the present invention only when the precious metal catalyst is used for the first time, and when the catalyst is repeatedly reused, an inhibitor is added thereafter. Without this, the activity of the catalyst can be maintained and high selectivity can be maintained, and side reactions such as dehalogenation reactions can be almost completely prevented. As the reaction medium according to the present invention, water, methanol, ethanol, isopropanol, dioxane, etc. can be used, but water is preferred from an industrial standpoint. Further, the pH value when performing the catalytic reduction in the present invention is 6.0 to 9.0, and it is particularly preferable to perform the catalytic reduction in a weakly basic medium. As the basic medium, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, etc. can be used.
Preferred is sodium hydroxide. According to the present invention, the hydrogen pressure may be normal pressure or
It can be reduced in high yield even at pressures below 10Kg/cm ² . The reaction temperature according to the present invention can be reduced in the range of room temperature to 150℃, but considering the space-time yield, it can be reduced to 60 to 100℃.
is preferred. An embodiment of the present invention is shown for C acid: 2-
Charge chloro-5-nitrotoluene-4-sulfonic acid or its salts into an autoclave with water, adjust the pH to 7.0 to 9.0 with an aqueous sodium hydroxide solution, and then add the catalyst and dehalogenation inhibitor methylene (bisthioether). and seal. After the air in the autoclave is replaced with nitrogen, it is replaced with hydrogen to adjust to a predetermined hydrogen pressure, and the temperature is raised to a predetermined temperature to perform a catalytic reduction reaction. During the reaction, hydrogen is consumed, but an equivalent amount of hydrogen is pumped in to maintain a predetermined pressure. When the absorption of hydrogen is completed, the autoclave is cooled, and after the pressure is released, the reaction liquid is separated by passing through a catalyst, and the liquid is acidified with hydrochloric acid and crystallized to obtain C acid as crystals. After drying, the obtained C acid can be compared with pure C acid to determine its purity and identification by infrared absorption spectroscopy, paper chromatography, high performance liquid chromatography, etc. In the case of quantitative determination of the dehalogenation reaction product, it can be easily determined using a separately prepared calibration curve by directly measuring the reaction solution with high performance liquid chromatography. 2-chloro-5-nitrotoluene-4-sulfonic acid or its salts used in the present invention are purified products or those obtained by sulfonating, chlorinating, and nitrating toluene in sulfuric acid, or It is possible to use a salted product or a salted product.
Furthermore, the method of the present invention can be used to produce crude 2-chloro-5-nitrotoluene-4-
As is clear from the fact that sulfonic acid can be used, 2-chloro-6-nitrotoluene-4-sulfonic acid, 2-chloro-4-nitrotoluene-6-
Sulfonic acid, 2-chloro-4-nitrotoluene-
C by catalytic reduction of structural isomers such as 5-sulfonic acid.
It is also a method of converting acids into various structural isomers. Furthermore, the method of the present invention is not only effective for chlorides, but is applicable to all halides, and is also applicable to catalytic reduction methods for halonitroaromatic compounds in general. Furthermore, the method of the present invention can be carried out either continuously or discontinuously. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 Aqueous solution containing 27.4 g (0.1 mol) of sodium 2-chloro-5-nitrotoluene-4-sulfonate
Adjust the pH of 270g to 7.5 with an aqueous sodium hydroxide solution and place in a magnetic stirring autoclave. 5% platinum-carbon catalyst (Japan Engelhard product) 200
After adding 1 mg of methylene (bishydroxyethyl sulfide) and sealing the autoclave, the air in the autoclave was replaced with nitrogen, and then with hydrogen.
The reaction was carried out by raising the temperature to 80°C and maintaining the hydrogen pressure at 10Kg/cm ² . Hydrogen absorption was completed 30 minutes after the start of the reaction, but after maintaining this condition for an additional 30 minutes, the autoclave was cooled, the pressure was released, the reaction product was taken out, and the catalyst was separated. The reaction solution was slightly pale yellow, unchanged from before the reaction, and had a pH of 7.4. The reaction solution was measured by high performance liquid chromatography, but
No dehalogenated product could be detected. Platinum crystals were obtained by acid precipitation of the reaction solution with dilute hydrochloric acid. The weight after drying was 21.3 g, which corresponds to a yield of 96% based on the raw material. When this crystal was identified by means such as infrared absorption spectroscopy, paper chromatography, high-performance liquid chromatography, elemental analysis, and NMR spectroscopy, it was confirmed that it completely matched the standard C acid and was a pure product. Moreover, its purity was 99.8%. Furthermore, from the results of high performance liquid chromatography of the acid precipitation mother liquor, the mother liquor contains approximately 4% C acid.
As a result, it was confirmed that the reduction reaction occurred quantitatively. The catalyst recovered in this example was used 10 times under the same conditions and treatment without adding methylene (bishydroxyethyl sulfide), but the activity decreased during this period.
No phenomena such as a decrease in C acid yield or the formation of dehalogenated products were observed. Further, in this example, the same results were obtained even when a catalyst and methylene (bishydroxyethyl sulfide) were added to water. Comparative Example 1 The same reaction as in Example 1 was carried out except that methylene (bishydroxyethyl sulfide) was not used as the dehalogenation inhibitor. The time taken to complete the reaction was 30 minutes, not much different from Example 1.
Although the reaction was completed within minutes, the pH of the reaction solution had decreased to 3.6, and high-performance liquid chromatography of the reaction solution revealed that the dehalogenation product 5-aminotoluene-4
- 0.7% sodium sulfonate was produced. When the catalyst recovered in Comparative Example 1 was further subjected to the same conditions and treatments, and the catalyst was used repeatedly, it took 54 minutes for the second time, 220 minutes for the third time, and the coloring of the reaction liquid was observed in the third time. Notably, the C acid obtained was also colored. Comparative Example 2 The same conditions and treatment were carried out as in Example 1, except that 5 mg of bis(hydroxyethyl)sulfine was added instead of methylene(bishydroxyethylsulfide) as a dehalogenation inhibitor. . It took 65 minutes to complete hydrogen absorption. In addition, dehalogenation products in the reaction solution were analyzed, but no products were detected. When the recovered catalyst was used repeatedly under similar conditions and treatments, it was found that any reaction time that could be reused required 70 minutes or more, and tended to lengthen as the number of uses increased. When the amount of bis(hydroxyethyl) sulfide added was 3 mg, it took 55 minutes to complete hydrogen absorption, but 0.26% of dehalogenated products were produced in the reaction solution. That is, bis(hydroxyethyl) sulfide could not prevent the dehalogenation reaction without delaying the reaction. Example 2 5% platinum as a catalyst in the method of Example 1.
The same method and operation were carried out, except that 300 mg of 5% palladium-carbon (product of Nippon Engelhard) was used instead of carbon, and 20 mg of methylene (bishydroxyethyl sulfide) was used as a dehalogenation inhibitor. Ivy. Hydrogen absorption was completed in 120 minutes, and the pH of the reaction solution was 6.7. Analysis of the dehalogenated product in the reaction solution revealed that it was 0.23%. Comparative Example 3 The same method and operation as in Example 2 was carried out except that methylene (bishydroxyethyl sulfide) was not used. The pH of the reaction solution was 2.9, and 7.9% of dehalogenated products were produced. Methylene (bishydroxyethyl sulfide)
Bis(hydroxyethyl) sulfide 60 instead of
When using mg, it takes 190 mg before hydrogen absorption ends.
The pH of the reaction solution was 4.5, and the dehalogenated product was present at 1.1%. The reaction solution was colored reddish brown, and the obtained C acid was also colored light brown. Examples 3 to 5 The same method and operation as in Example 1 was carried out by changing the amount of the dehalogenation inhibitor methylene (bishydroxyethyl sulfide), and the following results were obtained.

[Table] Examples 6 to 8 In the method of Example 1, the pH of the reducing raw material aqueous solution was adjusted to the specified pH with hydrochloric acid if it was acidic, or with a sodium hydroxide aqueous solution if it was alkaline, and then the same reactions and operations were carried out. I got the result.

[Table] Examples 9 to 15 In the method of Example 1, various methylenes (bisthioethers) were added instead of methylene (bishydroxyethyl sulfide) as a dehalogenation inhibitor, and the same reactions and operations were carried out. When I went there, I got the following results.

[Table] Example 16 The method of Example 1 except that 2-chloro-6-nitrotoluene-4-sulfonic acid was used.
When exactly the same conditions and operations were performed, 21.0 g of white crystals were obtained. When this substance was identified by means such as infrared absorption spectrum, high performance liquid chromatography, and NMR spectrum, it was found to be completely identical to standard 2-chloro-6-aminotoluene-4-sulfonic acid (also called L acid). It was confirmed that the product was genuine. In addition, high performance liquid chromatography of the reaction solution revealed that the dehalogenated product 6-
Aminotoluene-4-sulfonic acid could not be detected. Example 17 In the method of Example 1, sodium 2-chloro-4-nitrotoluene-6-sulfonate (0.1 mol) was used instead of sodium 2-chloro-5-nitrotoluene-4-sulfonate, and methylene (bishydroxyethyl 1.5 mg of methylene (bishydroxybutyl sulfide) instead of sulfide
2 was carried out in the same manner as in Example 1 except that
20.8 g of white crystals of -chloro-4-aminotoluene-6-sulfonic acid were obtained. 0.03% of the dehalogenated product 4-aminotoluene-6-sulfonic acid was detected in the reaction solution. Example 18 In the method of Example 1, sodium 2-chloro-4-nitrotoluene-5-sulfonate (0.1 mol) was used as the raw material, and 1.0 mg of methylene (bisisopropylsulfide) was used as the methylene (bisthioether). Except for this, 2-chloro-4-aminotoluene-5- was prepared in the same manner as in Example 1.
21.1 g of white crystals of sulfonic acid were obtained. No dehalogenation products were detected.

Claims (1)

[Claims] 1 2-chloro-5-nitrotoluene-4-sulfonic acid, 2-chloro-6-nitrotoluene-4-
Sulfonic acid, 2-chloro-4-nitrotoluene-
An acid selected from the group consisting of 6-sulfonic acid and 2-chloro-4-nitrotoluene-5-sulfonic acid or a salt thereof, with a noble metal catalyst, and the general formula: CH ₂ (SR ₁ ) ₂ (wherein R ₁ is an alkyl group having 12 or fewer carbon atoms and optionally having a substituent, and the substituent represents a hydroxyl group or a hydroxyalkoxyl group)
The nitro group of the acid is converted into an amino group by catalytic reduction in a weakly basic medium, if necessary, in the coexistence of one or more methylenes (bisthioethers) represented by A method for producing the respective reduced 2-chloro-5-aminotoluene-4-sulfonic acids or salts thereof. 2. The method for producing 2-chloro-5-aminotoluene-4-sulfonic acid according to claim 1, using 2-chloro-5-nitrotoluene-4-sulfonic acid as a raw material. 3. The method according to claim 1 or 2, wherein the catalytic reduction reaction is carried out in a pH range of 6.0 to 9.0, particularly under weak basic conditions. 4. The method according to claim 1, 2 or 3, wherein methylene (bisthioether) is adsorbed on a noble metal catalyst in advance of the catalytic reduction reaction.