JPS6139302B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves neutralizing phenylhydrazine salt obtained by diazotization, reduction, and hydrolysis of aniline with an alkali, extracting with an organic solvent, and then distilling off the oil. The present invention relates to a method for obtaining almost colorless and transparent phenylhydrazine from the crude phenylhydrazine obtained in this manner.

Phenylhydrazine is used as an important key intermediate for various pharmaceuticals, agricultural chemicals, dyes, etc. Methods for producing phenylhydrazine by diazotization, reduction, and hydrolysis reactions of aniline include, for example, Organic Synthesis coll.
-vol. 1, 442, 1932, GH Coleman), aniline hydrochloride is generally diazotized with sodium nitrite to form a diazonium salt, and this is then treated with sodium sulfite. Obtain phenylhydrazine disulfonic acid sodium salt, then perform a hydrolysis reaction using hydrochloric acid,
Phenylhydrazine can be obtained by neutralizing the generated phenylhydrazine hydrochloride with alkaline water. This phenylhydrazine is converted into benzene,
After extraction with an organic solvent with high affinity for phenylhydrazine such as toluene or xylene,
The desired crude phenylhydrazine can be obtained by distilling off the oil. Usually, the crude phenylhydrazine thus obtained can be purified by distillation to obtain purified phenylhydrazine.

However, the quality of the phenylhydrazine obtained by this method is not necessarily satisfactory, and there is a particular drawback that the product is colored, and an improvement in this problem has been strongly desired.
Organic Synthesis (Organic Synthesis)
Synthesis Coll.vol.1, 443, 1932, GH
Coleman) also states that the phenylhydrazine obtained by this method is a yellow liquid, and the detailed study results by the present inventors also show that this coloring problem is solved by the crude phenylhydrazine. It turned out that the problem could not be solved by repeating the rectification of hydrazine or simply by improving the rectification conditions.

In addition, Japanese Patent Application Laid-Open No. 14932/1983 describes that it is almost colorless and transparent than crude phenylhydrazine and is JIS-
To obtain higher quality phenylhydrazine which is sufficiently transparent in the acetic acid solution test according to K8795, crude phenylhydrazine is heat treated with one or more selected hydroxides of alkali metals or alkaline earth metals, and then glycol However, this method requires the addition of glycols and is volatile due to thermal decomposition of phenylhydrazine itself during rectification or simple distillation of crude phenylhydrazine. However, it has drawbacks such as the inability to sufficiently suppress the production of coloring substances.

The present inventors have made intensive studies to improve these drawbacks, and have found that when obtaining the desired phenylhydrazine by rectification or simple distillation of the crude phenylhydrazine after distilling off the oil, alkali metal or alkali The present invention has been completed based on the discovery that an almost colorless and transparent phenylhydrazine with significantly improved color tone can be obtained by the presence of one or more selected from earth metal hydroxides. It came to this.

By the way, when crude phenylhydrazine is rectified or simple distilled in the absence of alkali metal or alkaline earth metal hydroxides, yellowish phenylhydrazine is obtained as a distillate. At 300 mmHg, the Gardner color number of the distillate (method according to JIS K5400) is approximately 4.
~5. The cause of this coloration or the substance that causes it is currently unknown, and the mechanism of action of alkali metal or alkaline earth metal hydroxides is also unknown, but as a decolorizing agent with a normal physical adsorption effect, Known activated carbon, alumina oxide, carbon dioxide, etc. do not provide any coloring prevention effect, and by using the method of the present invention, alkali metal or alkali metal hydroxide, , it is surprising that it exhibits a specific and remarkable effect.

The alkali metal or alkaline earth metal hydroxide used in the method of the present invention is preferably commercially available sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, etc. , it is also possible to use these as an aqueous solution,
Alternatively, it is also possible to use it as a solid.
When used as an aqueous solution, phenylhydrazine and water are distilled out during rectification or simple distillation of crude phenylhydrazine. If it is necessary to decompose water, it is preferable to use solid alkali metal or alkaline earth metal hydroxides that do not contain water.

The method of adding an alkali metal or alkaline earth metal hydroxide to crude phenylhydrazine is not particularly limited, but when the desired phenylhydrazine is purified by distillation and the product is obtained from the top of the column, distillation is recommended. It is preferable to add it to the crude phenylhydrazine feed to the column, and the effect is greater than when it is added directly to the bottom of the distillation column. In addition, when distilling the product phenylhydrazine by simple distillation, it can be added to the crude phenylhydrazine feed liquid, or an alkali metal or alkaline earth metal hydroxide can be added directly to the simple distillation vessel. However, the effect is the same. Alternatively, crude phenylhydrazine is supplied in advance to a tower filled with a solid alkali or alkaline earth metal hydroxide and brought into contact with it, and then the product phenylhydrazine is obtained as a distillate by rectification or simple distillation. However, the alkali metal or alkaline earth metal hydroxide must be present in the crude phenylhydrazine after contact with the solid at a certain concentration or higher. In the method of the present invention, one or more hydroxides selected from alkali metal or alkaline earth metal hydroxides are present when crude phenylhydrazine is rectified or simply distilled to obtain almost colorless and transparent phenylhydrazine. This significantly reduces the volatility of the volatile color-causing substances contained in the crude phenylhydrazine, and furthermore, phenylhydrazine itself during the rectification or window distillation operation. The aim is to suppress the production of volatile colored substances due to thermal decomposition.

In the method of the present invention, the amount of alkali metal or alkaline earth metal hydroxide present may generally be 0.06 to 10% by weight based on crude phenylhydrazine. When the coexisting amount is less than this lower limit, a slight coloring prevention effect is observed, but the effect is not fully satisfactory. For example, 0.05% by weight of sodium hydroxide is added to crude phenylhydrazine obtained by a general method, and the mixture is heated at 10 mmHg in a nitrogen stream.
When simple distillation was carried out under reduced pressure, phenylhydrazine having a Gardner color number of 2 to 3 was obtained. If it is added in a large amount exceeding 10% by weight, the coloring prevention effect is sufficient, but the amount of alkali metal or alkaline earth metal hydroxide used increases, which is not only not economical, but also causes problems in the rectification column. Alternatively, the viscosity of the high-boiling material extracted from the bottom of the simple distillation column becomes abnormally high, making it difficult to extract it with a normal pump or the like. For this reason, it is necessary to leave a certain amount of phenylhydrazine in the column in order to facilitate the extraction of high-boiling substances, resulting in a large loss of phenylhydrazine in the rectification column or single steamer, which is uneconomical.

By the way, when crude phenylhydrazine is treated by catalytic distillation or simple distillation in the presence of an alkali metal or alkaline earth metal hydroxide to obtain almost colorless and transparent phenylhydrazine, the operation can be continuous or batchwise. Any formula may be used, but the operation pressure must be 200 mmHg or less. Above this pressure, even in the presence of alkali metal or alkaline earth metal hydroxides, the thermal decomposition of phenylhydrazine produces volatile colored substances, which cause the phenylhydrazine in the product to It becomes yellowish and the addition of the alkali metal or alkaline earth metal hydroxide becomes meaningless. Therefore, it is necessary to lower the operating pressure as much as possible and keep the evaporation temperature of phenylhydrazine low to suppress thermal decomposition. It is also well known that care must be taken against the oxidation of phenylhydrazine by oxygen, and for this reason, rectification or simple distillation of crude phenylhydrazine is usually carried out in a nitrogen stream or under a nitrogen atmosphere. .

Crude phenylhydrazine, which is the target of the phenylhydrazine purification method according to the method of the present invention, is synthesized by diazotization, reduction, and hydrolysis reactions of aniline. It is not limited by the method of hydrolysis reaction.

The method of the present invention will be explained in more detail below with reference to Examples, but the present invention is not limited only to these Examples.

Example 1 500 parts of a 20% by weight hydrochloric acid aqueous solution and 100 parts of aniline were placed in a 1.000 cc cylindrical separable flask equipped with a stirrer, a dropping funnel, a rod thermometer, and a cooling device, and the contents were cooled to 0°C with a cryogen. While adding 36% by weight sodium nitrite aqueous solution 215 from the dropping funnel.
A diazotization reaction was carried out by pouring 815 parts of a reaction solution. Next, separately prepared sodium sulfite
The diazotization reaction solution kept at 0° C. was injected little by little into an aqueous reducing agent solution consisting of 205 parts of sodium bisulfite, 110 parts of sodium bisulfite, and 700 parts of water. Thereafter, the temperature was maintained at 45°C for 30 minutes, and then the temperature was raised to 90°C, and the reduction reaction was carried out while simply maintaining the temperature at that temperature for 60 minutes. Next, 23 parts of a 35% by weight aqueous hydrochloric acid solution was added dropwise little by little to this reduction reaction solution from the dropping funnel, and the mixture was maintained at a temperature of 90° C. for 90 minutes to carry out a hydrolysis reaction. The hydrolysis reaction solution was then cooled to 40°C, neutralized by adding 400 parts of a 49% by weight aqueous sodium hydroxide solution through the dropping funnel, and extracted three times with 300 parts of toluene. Furthermore, collect all the extracted toluene phase and
Toluene was distilled off under reduced pressure of mmHg, and 110 parts of crude phenylhydrazine was obtained from the pot.

To this crude phenylhydrazine was added 2 parts of sodium hydroxide in the form of pellets with a diameter of about 5 mm, and 300 c.c.
Using a round bottom flask, simple distillation was carried out under a reduced pressure of 10 mmHg while introducing nitrogen gas from the capillary to obtain 100 parts of phenylhydrazine as a distillate. This phenylhydrazine was almost colorless and transparent, and its Gardner color number was 1 or less.

Example 2 The same procedure as in Example 1 was carried out except that 2 parts of calcium hydroxide was used instead of 2 parts of sodium hydroxide used in Example 1 to obtain 100 parts of phenylhydrazine, which was almost colorless and transparent. , its Gardner color number was 1 or less.

Example 3 4 parts, 6 parts, 8 parts instead of 2 parts of sodium hydroxide
Simple distillation was carried out in the same manner as in Example 1, except that the phenylhydrazine was used separately, and the distilled phenylhydrazine was almost colorless and transparent in all cases, and the Gardner color number was 1 or less in all cases.

Example 4 Phenylhydrazine was added in the same manner as in Example 1 except that 2 parts of potassium hydroxide, magnesium hydroxide, and lithium hydroxide were used separately in place of 2 parts of sodium hydroxide. The samples were also almost colorless and transparent, and the Gardner color numbers were all 1 or less.

Example 5 Sodium hydroxide in pellet form with a diameter of approximately 5 mm
110 parts of crude phenylhydrazine obtained in exactly the same manner as in Example 1 was passed through a column packed with 100 parts of phenylhydrazine, and then charged into a distillation flask equipped with a packed column with 5 theoretical plates, and nitrogen gas was introduced into the capillary. Rectification was carried out under a reduced pressure of 5 mmHg and a reflux ratio of 2 while introducing the phenylhydrazine as a fraction.
95 parts were obtained, and this phenylhydrazine was almost colorless and transparent and had a Gardner color number of 1 or less. In addition, the sodium hydroxide concentration in the crude phenylhydrazine after passing through the sodium hydroxide packed tower is 0.15% by weight.
It was hot.

Comparative Example 1 110 parts of crude phenylhydrazine obtained in exactly the same manner as in Example 1 was subjected to simple distillation under a reduced pressure of 10 mmHg while introducing nitrogen gas without adding sodium hydroxide. enylhydrazine
100 copies were obtained, which had a yellowish brown color and a Gardner color number of about 5.

Comparative Example 2 The same procedure as in Example 1 was carried out except that crude phenylhydrazine was simply distilled under a reduced pressure of 300 mmHg, and 100 parts of phenylhydrazine was obtained, but it was colored yellowish brown and its Gardner color number was 4. Ta.

Comparative Example 3 The same procedure as Example 1 was carried out except that 0.05 part of sodium hydroxide was used instead of 2 parts of sodium hydroxide used in Example 1, and 100 parts of phenylhydrazine was used.
However, it was slightly yellow in color and had a Gardner color number of approximately 2.5.

Claims (1)

[Claims] 1. A salt of phenylhydrazine obtained by diazotization, reduction, and hydrolysis of aniline is neutralized with an alkali, extracted with an organic solvent, and the oily agent is distilled off. The crude phenylhydrazine obtained is rectified or simply distilled in the presence of one or more selected from alkali metal or alkaline earth metal hydroxides to obtain almost colorless and transparent phenylhydrazine. A method for purifying crude phenylhydrazine. 2. The method according to claim 1, wherein the amount of one or more selected from alkali metal or alkaline earth metal hydroxides is 0.06 to 10% by weight based on the crude phenylhydrazine. 3. The method according to claim 1, wherein the operating pressure of rectification or simple distillation is 200 mmHg or less.