Purification method of phenylhydrazine

Abstract

The phenylhydrazine crude product obtained by diazotization, reduction, hydrolysis and neutralization of aniline is used as a raw material, light components such as benzene and phenol are removed through steam distillation, then rectification is carried out in the presence of an alcohol compound to remove aniline, the high-purity phenylhydrazine product is obtained, and the quality requirement of downstream high-end medicine products is met.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology and relates to a method for purifying phenylhydrazine, specifically a method for preparing high-purity phenylhydrazine through aniline diazotization and reduction reaction processes. Background Technology

[0002] Phenylated hydrazine is mainly used as an organic intermediate in the dye, pharmaceutical, and pesticide industries. For example, it can be used to produce naphthol AS-G, the drug antipyrine, edaravone, cationic dyes, and developing agents. However, due to limitations in production processes, some small and medium-sized enterprises produce products with low purity, which means the products are primarily used in the pesticide industry. Furthermore, improper determination of certain synthetic process conditions often leads to abnormal reactions, affecting both product yield and quality.

[0003] Currently, there are many methods for synthesizing phenylhydrazine salts. Most of them use aniline as the main raw material, which reacts with sodium nitrite in an acidic medium at low temperature to produce diazonium salt diazonium chloride, and then obtains phenylhydrazine through reduction, acid precipitation, neutralization, and distillation.

[0004] The above synthetic route mainly uses a batch process to produce phenylhydrazine and substituted phenylhydrazine salts. The first step, diazotization, is completed in a reactor. During and after the diazotization reaction, a large amount of diazonium salt will remain in the reactor. Due to the poor thermal stability of diazonium salt, it is very easy to decompose and produce impurities that affect product quality.

[0005] In recent years, there have been some reports of attempts to produce phenylhydrazine and replace phenylhydrazine salts using "continuous" reactions. Through improvements to existing equipment and processes, or by adopting continuous operation in certain steps, the serious decomposition problem faced by the diazotization reaction has only been solved to a certain extent. However, since it is impossible to achieve continuity of the entire process (diazotization, reduction, and acid hydrolysis to salt), the whole process is still essentially a batch process, so the results are not ideal.

[0006] Therefore, due to the special nature of the materials, the products obtained by the above synthesis process inevitably generate highly toxic impurities such as benzene, phenol, and aniline during the production process, which cannot meet the synthesis requirements of downstream high-end pharmaceutical products.

[0007] Chinese patent CN114082209A discloses a device for purifying and refining phenylhydrazine. This device can complete the separation and purification of phenylhydrazine in one step, avoiding the instability in quality caused by purification in multiple devices. However, this patent application does not specify the final purity of phenylhydrazine or the content of impurities, meaning it is unclear whether the purification effect meets the requirements for the synthesis of high-end pharmaceutical products. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a safe, flexible, simple to operate, efficient and easy to mass-produce high-purity phenylhydrazine purification method.

[0009] The main technical solution of this invention is to use crude phenylhydrazine obtained by diazotization, reduction, hydrolysis and neutralization of aniline as raw material, remove light components such as benzene and phenol by steam distillation, and then remove aniline by distillation in the presence of alcohol compounds to obtain a high-purity phenylhydrazine product, which meets the quality requirements of downstream high-end pharmaceutical products.

[0010] Generally, according to the present invention, the temperature for steam distillation is 70-120°C, preferably 100-110°C.

[0011] According to the present invention, the amount of steam used is 0.5-2 times the mass of the crude phenylhydrazine raw material, preferably 1-1.5 times.

[0012] According to the present invention, the steam distillation time is 0.5-2 hours, preferably 1-1.5 hours.

[0013] According to the present invention, the alcohol inhibitor used in the distillation is one or a mixture of several of the following in any proportion: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, and 1,2-butanediol.

[0014] According to the present invention, the mass ratio of crude phenylhydrazine to alcohol inhibitor is 100:(0.5-5), preferably 100:(2-2.5).

[0015] According to the present invention, the distillation temperature is 160-220℃, preferably 180-200℃, and the distillation vacuum degree is 0.09-0.099 MPa.

[0016] According to the present invention, the reflux ratio during distillation is 0.2-2, preferably 0.5-1.

[0017] This invention innovatively breaks through the traditional distillation purification method, reducing the benzene content in the obtained phenylhydrazine from about 0.1% to 0.0001%, the phenol content from 0.2% to 0.0002%, and the aniline content from 0.02% to 0.0001%, which can meet the needs of high-end pharmaceutical products. Detailed Implementation

[0018] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims. Example 1

[0019] 200 grams of crude phenylhydrazine (composition: 85% phenylhydrazine, 0.1% benzene, 0.2% phenol, 0.02% aniline, and the remainder water), obtained by diazotization, reduction, hydrolysis, and neutralization of aniline, was added to a four-necked flask equipped with a thermometer, stirrer, submersible vent, and condenser. Stirring was started, and the material was heated to 110°C. Steam was then introduced through the submersible vent at a flow rate of 200 g / h for 1 hour. The steam was condensed in the condenser and collected in the four-necked glass flask. After steam distillation, the sample analysis showed that the benzene content was 0.001%, the phenol content was 0.0002%, and the aniline content was 0.01%. Then, the steam distillation device was replaced with a rectification device, 4 grams of ethylene glycol were added, and the mixture was stirred for 5 minutes. The system vacuum was adjusted to 0.095 MPa, and the material was heated to 180°C to distill off phenylhydrazine. The sample analysis showed that the purity of phenylhydrazine was 99.97%, the benzene content was 0.0001%, the phenol content was 0.0002%, and the aniline content was 0.0001%. Example 2

[0020] Similar to Example 1, except that the steam distillation flow rate was 100 g / h, the purity of the obtained phenylhydrazine was 99.96%, the benzene content was 0.0003%, the phenol content was 0.0004%, and the aniline content was 0.0001%. Example 3

[0021] Similar to Example 1, except that the steam distillation flow rate is 300 g / h, the purity of the obtained phenylhydrazine is 99.97%, the benzene content is 0.0001%, the phenol content is 0.0002%, and the aniline content is 0.0001%. Example 4

[0022] Similar to Example 1, except that 1,3-propanediol was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0003%. Example 5

[0023] Similar to Example 1, except that 1,4-butanediol was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0004%. Example 6

[0024] Similar to Example 1, except that 1,4-butanediol was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0004%. Example 7

[0025] Similar to Example 1, except that 2,3-butanediol was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0006%. Example 8

[0026] Similar to Example 1, except that a 1:1 mixture of 2,3-butanediol and ethylene glycol was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0005%. Example 9

[0027] Similar to Example 1, except that a mixture of 2,3-butanediol and 1,4-butanediol in a mass ratio of 1:2 was used instead of ethylene glycol, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0005%. Example 10

[0028] Similar to Example 1, except that 5 grams of ethylene glycol were used, the resulting phenylhydrazine had a purity of 99.96%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.0001%. Example 11

[0029] Similar to Example 1, except that the distillation temperature was 200℃ and the vacuum degree was 0.09Mpa, the purity of the obtained phenylhydrazine was 99.95%, the benzene content was 0.0001%, the phenol content was 0.0002%, and the aniline content was 0.0002%. Comparative example

[0030] 200 grams of crude phenylhydrazine (composition: 85% phenylhydrazine, 0.1% benzene, 0.2% phenol, 0.02% aniline, and the remainder water), obtained by diazotization, reduction, hydrolysis, and neutralization of aniline, was added to a four-necked flask equipped with a thermometer, stirrer, submersible vent, and condenser. Stirring was started, and the material was heated to 110°C. Steam was then introduced through the submersible vent at a flow rate of 200 g / h for 1 hour. The steam was condensed in the condenser and collected in the four-necked glass flask. After steam distillation, the material was sampled and analyzed. The benzene content was 0.001%, the phenol content was 0.0003%, and the aniline content was 0.01%. Then, the steam distillation device was replaced with a rectification device, without adding ethylene glycol. The mixture was stirred for 5 minutes, and the system vacuum was adjusted to 0.095 MPa. The material was heated to 180°C and the phenylhydrazine was distilled off. The sample was analyzed and found to have a phenylhydrazine purity of 99.55%, a benzene content of 0.0001%, a phenol content of 0.0002%, and an aniline content of 0.008%.

Claims

1. A method for purifying phenylhydrazine, characterized in that... Using crude phenylhydrazine obtained by diazotization, reduction, hydrolysis and neutralization of aniline as raw material, benzene and phenol light components are removed by steam distillation, and then aniline is removed by fractional distillation in the presence of alcohol inhibitors to obtain high-purity phenylhydrazine product.

2. The purification method of phenylhydrazine according to claim 1, characterized in that... The temperature of the steam distillation is 70-120℃, preferably 100-110℃.

3. The method for purifying phenylhydrazine according to claim 1, characterized in that... The amount of steam used is 0.5-2 times that of the crude phenylhydrazine raw material, preferably 1-1.5 times.

4. The purification method of phenylhydrazine according to claim 1, characterized in that... The steam distillation time is 0.5-2 hours, preferably 1-1.5 hours.

5. The method for purifying phenylhydrazine according to claim 1, characterized in that... The alcohol inhibitors used in the distillation are one or a mixture of several of the following in any proportion: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, and 1,2-butanediol.

6. The method for purifying phenylhydrazine according to claim 1, characterized in that... The mass ratio of crude phenylhydrazine to alcohol inhibitor is 100:(0.5-5), preferably 100:(2-2.5).

7. The method for purifying phenylhydrazine according to claim 1, characterized in that... The distillation temperature is 160-220℃, preferably 180-200℃, and the distillation vacuum degree is 0.09-0.099Mpa.

8. The method for purifying phenylhydrazine according to claim 1, characterized in that... The reflux ratio during distillation is 0.2-2, preferably 0.5-1.