Preparation method of high-purity phenylhydrazine

Abstract

The invention relates to a preparation method of high-purity phenylhydrazine, the method comprises the steps of diazotization, reduction, acidification, extraction and neutralization, and the extraction step comprises the following steps: extracting a phenylhydrazine hydrochloride solution prepared in the acidification step with toluene at a temperature higher than 60 DEG C, and then separating an extract liquor to obtain an extracted phenylhydrazine hydrochloride solution; and the neutralization step comprises the following steps: dropwise adding liquid caustic soda into the extracted phenylhydrazine hydrochloride solution for neutralization, and then standing for layering to obtain phenylhydrazine. In the phenylhydrazine preparation process, the phenylhydrazine hydrochloride solution is extracted by using toluene, so that the purity and yield of phenylhydrazine can be remarkably improved, the reaction steps are short, the post-treatment is simple, and the environmental pollution is small.

Description

Technical Field

[0001] The invention belongs to the field of preparation of fine chemicals, and specifically relates to a method for preparing high-purity phenylhydrazine. Background Art

[0002] The existing preparation method of phenylhydrazine is to use aniline as raw material, ammonium sulfite and ammonium bisulfite as reducing agents, and water as solvent. The specific preparation method is: hydrochloric acid and sodium nitrite solution are added to aniline in sequence, and sodium nitrite is fed at 0-5°C, the reaction time is 30-90 minutes, and then the diazo liquid is added to the reduction kettle containing ammonium sulfite solution and hydrochloric acid in a thin stream (the temperature is controlled below 20°C), the reaction time is 60-70 minutes, and the hydrolysis and acid precipitation time is 50 minutes. In this process, the decomposition of the diazonium salt in the reduction reaction will produce asphalt-like by-products. These by-products will affect the quality of the phenylhydrazine product and the yield of the phenylhydrazine product.

[0003] The invention adopts an extraction process, but the extraction process is not for the product, but for the phenylhydrazine hydrochloride solution. The extraction utilizes the characteristics that the asphalt-like byproduct and other organic impurities have high solubility in toluene and toluene is incompatible with phenylhydrazine hydrochloride, so as to remove the asphalt-like impurities and other organic impurities in the reaction solution without affecting the product yield, thereby improving the product quality.

[0004] In the prior art, extraction measures are also used in the preparation of phenylhydrazine, but the extraction is performed on the phenylhydrazine product. For example, in a synthesis method of phenylhydrazine disclosed in patent document CN104610093B, the final product is extracted and separated, and then the extract is distilled to obtain phenylhydrazine, and the purpose of extraction is to improve the purity of the product. In addition, the preparation method of phenylhydrazine disclosed in patent document JP1982004957A also extracts the product to improve the purity of the product.

[0005] The present invention extracts the phenylhydrazine hydrochloride solution generated in the acid precipitation step, thereby eliminating the solid-liquid separation step of the phenylhydrazine hydrochloride and adopts a toluene extraction step, which realizes the removal of organic impurities in the phenylhydrazine hydrochloride and improves the purity and yield of the phenylhydrazine. Summary of the invention

[0006] Specifically, in order to solve the above technical problems and achieve the above objectives, the present invention provides a method for preparing phenylhydrazine, which comprises diazotization, reduction, acid precipitation, extraction, and neutralization steps, wherein the diazotization step comprises: aniline and hydrochloric acid are salified, and then sodium nitrite is added to carry out diazotization reaction to obtain a diazo liquid; the reduction step comprises: the diazo liquid is added dropwise to a reducing agent to carry out reduction to obtain a reduction reaction product; the acid precipitation step comprises: hydrochloric acid is added to the reduction reaction product to carry out acid precipitation to obtain a solution of phenylhydrazine hydrochloride;

[0007] The extraction step comprises: extracting the phenylhydrazine hydrochloride solution with toluene at a temperature higher than 60° C., and then separating the extract to obtain the extracted phenylhydrazine hydrochloride solution;

[0008] The neutralization step is: adding liquid alkali dropwise to the extracted phenylhydrazine hydrochloride solution for neutralization, and then standing and separating the layers to obtain phenylhydrazine.

[0009] Preferably, in the above method for preparing phenylhydrazine, the extraction step is: heating the phenylhydrazine hydrochloride solution to 85-90°C and keeping it warm for 20-40 minutes, then adding toluene with a volume of 10-40% of the phenylhydrazine hydrochloride solution for extraction, the extraction time is 20-40 minutes, and after the extraction is completed, the toluene extract is separated to obtain the extracted phenylhydrazine hydrochloride solution, and the temperature is maintained above 60°C during the extraction process.

[0010] Preferably, in the above method for preparing phenylhydrazine, the neutralization step is: cooling the solution of phenylhydrazine hydrochloride after extraction, then adding liquid alkali to adjust the pH to 11-13, then heating to 50°C-60°C, keeping the temperature for reaction for 1 hour, standing to separate layers, separating and removing the upper aqueous solution to leave the lower phenylhydrazine layer, and preparing phenylhydrazine.

[0011] Preferably, in the above method for preparing phenylhydrazine, the diazotization step is: water and hydrochloric acid are added to the reaction flask, and then aniline is added dropwise, and the reaction temperature is maintained at 20 to 30°C during the addition of aniline. After the diazotization reaction is completed, the temperature is lowered to 0 to 5°C, and stirring is continued for 30 minutes. A sodium nitrite solution is added dropwise at 0 to 5°C to carry out a diazotization reaction to obtain a diazo liquid.

[0012] Preferably, during the process of adding sodium nitrite, Congo red test paper is continuously used to detect whether the amount of acid is sufficient, and starch potassium iodide test paper is used to detect whether the diazotization reaction is completed. When the test paper turns blue, the diazotization reaction is completed.

[0013] Preferably, in the above method for preparing phenylhydrazine, in the reduction step, the reducing agent is prepared by adding sodium bisulfite and water to a reaction bottle, and adding liquid alkali dropwise during stirring to obtain a reducing agent, wherein the temperature of the reducing agent is less than or equal to 60° C., and the pH of the reducing agent is 6.2 to 6.5.

[0014] Preferably, in the above method for preparing phenylhydrazine, the reduction step is: under stirring, adding diazo liquid to the reducing agent, controlling the speed of adding diazo liquid, and dripping all the diazo liquid within 1.5 to 2.0 hours, controlling the pH value at 6.6 to 6.9 during the process, and starting to heat to above 80°C after the dripping, and keeping warm at 80 to 85°C for 40 minutes to obtain a reduction reaction product.

[0015] Preferably, in the above method for preparing phenylhydrazine, the acid precipitation step is: lowering the temperature of the reduction reaction product to below 80° C. and starting to drop hydrochloric acid for acid precipitation, and stopping adding hydrochloric acid when the pH value of the acid precipitation reaction solution is less than or equal to 2 and does not rise again.

[0016] Beneficial effects of the present invention

[0017] In the process of preparing phenylhydrazine according to the present invention, the step of using toluene to extract the phenylhydrazine hydrochloride solution can significantly improve the purity and yield of phenylhydrazine, the reaction steps are short, the post-treatment is simple, and the environmental pollution is small.

[0018] In the method for preparing phenylhydrazine of the present invention, the extraction step realizes that the organic matter in the phenylhydrazine hydrochloride solution is dissolved in toluene, so that less phenylhydrazine produced in the subsequent neutralization step is dissolved in the aqueous solution, because the organic matter contained in the aqueous solution will increase the solubility of phenylhydrazine in the aqueous solution and reduce the yield of phenylhydrazine. Due to the removal of organic impurities, the organic impurities dissolved in phenylhydrazine will be very small, and the purity of phenylhydrazine will be improved. DETAILED DESCRIPTION

[0019] The materials used in the following examples were all purchased from the market.

[0020] Example 1

[0021] 105g water and 60g of 36% concentrated hydrochloric acid were added to the reaction flask, and then 57.2g aniline (95% mass content of aniline) was added dropwise, and the reaction temperature was maintained at 20-30°C during the addition of aniline, and after the aniline was added dropwise, it was cooled to 0-5°C, and stirring was continued for 30 minutes. At a temperature of 0-5°C, sodium nitrite solution was added dropwise to carry out diazotization to obtain diazo liquid, and whether the acid amount was sufficient was continuously detected with Congo red test paper during the addition, and the diazotization reaction was completed with starch potassium iodide test paper, and the diazotization reaction was considered to be completed when the test paper turned blue. Wherein sodium nitrite solution is a mixed solution of 36.3g sodium nitrite and 58g water.

[0022] Add 123.8g of sodium bisulfite and 150g of water to the reaction bottle, start stirring, and drop 32% sodium hydroxide solution. When the pH value reaches 6.2, stop dropping the liquid alkali to obtain the reducing agent, and control the reducing agent temperature below 60°C.

[0023] Under stirring, add diazo liquid to part of the reducing agent, control the speed of adding diazo liquid to the reducing agent, and add all the diazo liquid within 1.5 to 2 hours. Repeat the pH detection during the process, and use the remaining diazo liquid to control the pH at 6.6 to 6.9. After the pH is normal, start to heat to above 80° C., keep warm at 80 to 85° C. for 40 minutes, and obtain a reduction reaction product.

[0024] The temperature of the reduction reaction product is lowered to below 80° C., and then 36% concentrated hydrochloric acid is added dropwise for acid precipitation. When the pH value of the solution is less than or equal to 2 and does not rise again, the addition of hydrochloric acid is stopped, and then the temperature is raised to 85° C. and kept at 85° C. to 90° C. for 20 minutes to obtain a solution of phenylhydrazine hydrochloride.

[0025] After the insulation is completed, 200 ml of toluene is directly added to the solution of phenylhydrazine hydrochloride without cooling, and the extraction is completed by stirring for 30 minutes.

[0026] During the extraction and stirring process, the mixed solution of the phenylhydrazine hydrochloride solution and toluene is heated when the temperature is lower than 60° C., and the heating is stopped after the temperature of the mixed solution is raised to above 60° C.

[0027] After the extraction is completed, the upper toluene is directly separated, and then the remaining aqueous solution is cooled to 20° C. to obtain a solution of phenylhydrazine hydrochloride after extraction.

[0028] 32% sodium hydroxide solution was added dropwise to the extracted phenylhydrazine hydrochloride solution to adjust the pH to 11, and then the temperature was raised to 50°C to 60°C, and the reaction was kept warm for 1 hour. The phenylhydrazine at the bottom was separated and the phenylhydrazine was prepared as a light yellow liquid. The weight of phenylhydrazine was 53.93g, the purity of phenylhydrazine was 99.85%, and the recovery rate based on aniline was 85.4%.

[0029] Example 2

[0030] The steps of Example 1 were followed. In the extraction step, 100 ml of toluene was used for extraction and stirring for 40 minutes. The remaining steps were the same to prepare phenylhydrazine as a light yellow liquid. The weight of phenylhydrazine was 53.65 g, the purity was 99.79%, and the yield based on aniline was 84.9%.

[0031] Example 3

[0032] The steps of Example 1 were followed. In the extraction step, 300 ml of toluene was used for extraction and stirring for 20 minutes. The remaining steps were the same to prepare phenylhydrazine as a light yellow liquid. The weight of phenylhydrazine was 54.37 g, the purity was 99.85%, and the yield based on aniline was 86.1%.

[0033] Example 4

[0034] According to the steps of Example 1, when the acid precipitation step is performed to obtain a solution of phenylhydrazine hydrochloride, continue to perform the following operations:

[0035] The temperature of the solution of phenylhydrazine hydrochloride was slowly lowered to 20°C, and then the solid was filtered out and washed to obtain phenylhydrazine hydrochloride. 32% sodium hydroxide solution was added dropwise to phenylhydrazine hydrochloride to adjust the pH to 11, and then the temperature was raised to 50°C to 60°C, and the reaction was kept for 1 hour. The phenylhydrazine at the bottom was separated to obtain phenylhydrazine as a yellow liquid. The weight of phenylhydrazine was 49.79g, the purity of phenylhydrazine was 99.21%, and the yield based on aniline was 78.2%.

[0036] Experimental analysis

[0037] It can be seen from Examples 1 to 3 that the purity of phenylhydrazine after using the extraction process is above 99.7%, which is 0.5% higher than the original process quality. Compared with Example 4, the yield of phenylhydrazine is also increased by more than 8%. This is mainly because phenylhydrazine hydrochloride has a large solubility in water but is insoluble in toluene. The generated impurities are dissolved in toluene during extraction, so that the solution of phenylhydrazine hydrochloride can improve the neutralization effect during neutralization. Since no impurities are dissolved in water in the neutralized solution, phenylhydrazine will not be dissolved in water. Otherwise, because some organic impurities dissolved in water will increase the solubility of phenylhydrazine in water, the yield of phenylhydrazine will be reduced. Also, due to the removal of organic impurities, the impurities in the phenylhydrazine product will be reduced accordingly, so the purity of phenylhydrazine will increase. It can be seen from Example 4 that impurities exist in the solution of phenylhydrazine hydrochloride produced by the original process. In the process of filtering phenylhydrazine hydrochloride, the impurities will enter the phenylhydrazine hydrochloride solid, and the impurities will also partially enter the alkali solution in the neutralization stage. When there are organic impurities in the alkali solution, the amount of phenylhydrazine dissolved in the alkali solution will increase, which will affect the purity of phenylhydrazine and the yield of phenylhydrazine. Therefore, the color of the product phenylhydrazine is yellow, which is darker than the color of phenylhydrazine in Examples 1 to 3, which also illustrates from the side that extraction has an effect on reducing impurities in phenylhydrazine.

[0038] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing phenylhydrazine, the method comprising diazotization, reduction, acid precipitation, extraction, and neutralization steps, wherein the diazotization step comprises: aniline and hydrochloric acid are salified, and then sodium nitrite is added to carry out diazotization reaction to obtain diazo liquid; the reduction step comprises: the diazo liquid is added dropwise to a reducing agent to carry out reduction to obtain a reduction reaction product; The acid precipitation step comprises: adding hydrochloric acid to the reduction reaction product for acid precipitation to obtain a solution of phenylhydrazine hydrochloride; The extraction step comprises: extracting the phenylhydrazine hydrochloride solution with toluene at a temperature higher than 60° C., and then separating the extract to obtain the extracted phenylhydrazine hydrochloride solution; The neutralization step is: adding liquid alkali dropwise to the extracted phenylhydrazine hydrochloride solution for neutralization, and then standing and separating the layers to obtain phenylhydrazine.

2. The method according to claim 1, characterized in that The extraction step comprises: heating the phenylhydrazine hydrochloride solution to 85-90° C. and keeping the temperature for 20-40 minutes, then adding toluene which accounts for 10-40% of the volume of the phenylhydrazine hydrochloride solution for extraction, and the extraction time is 20-40 minutes. After the extraction is completed, the toluene extract is separated to obtain the extracted phenylhydrazine hydrochloride solution, and the temperature is maintained above 60° C. during the extraction process.

3. The method according to claim 1, characterized in that The neutralization step is as follows: cooling the extracted phenylhydrazine hydrochloride solution, then dropping a liquid alkali to adjust the pH to 11-13, then heating to 50-60°C, keeping the temperature for reaction for 1 hour, standing to separate the layers, separating and removing the upper aqueous solution to leave the lower phenylhydrazine layer, and preparing phenylhydrazine.

4. The method according to claim 1, characterized in that The diazotization step is as follows: water and hydrochloric acid are added to the reaction flask, and then aniline is added dropwise. During the addition of aniline, the reaction temperature is maintained at 20-30°C. After the diazotization reaction is completed, the temperature is lowered to 0-5°C, and stirring is continued for 30 minutes. A sodium nitrite solution is added dropwise at 0-5°C to carry out a diazotization reaction to obtain a diazo liquid.

5. The method according to claim 1, characterized in that In the reduction step, the reducing agent is prepared by adding sodium bisulfite and water into a reaction bottle, and adding liquid alkali dropwise during stirring to obtain the reducing agent. The temperature of the reducing agent is less than or equal to 60° C., and the pH of the reducing agent is 6.2 to 6.

5.

6. The method according to claim 5, characterized in that The reduction step comprises: adding diazo liquid to the reducing agent under stirring, controlling the adding speed of the diazo liquid, and dropping all the diazo liquid within 1.5 to 2.0 hours, controlling the pH value at 6.6 to 6.9 during the process, and starting to heat to above 80° C. after the dropping is completed, and keeping the temperature at 80 to 85° C. for 40 minutes to obtain a reduction reaction product.

7. The method according to claim 1, characterized in that The acid precipitation step is: lowering the temperature of the reduction reaction product to below 80° C. and starting to drop hydrochloric acid for acid precipitation, and stopping adding hydrochloric acid when the pH value of the acid precipitation reaction solution is less than or equal to 2 and does not rise again.