阅读说明：本技术 一种制备3-巯基丙酸的过程中提取双氰胺的工艺 (Process for extracting dicyandiamide in process of preparing 3-mercaptopropionic acid ) 是由 张文民 岳希贤 薄宪明 于 2020-08-05 设计创作，主要内容包括：本发明提供的一种制备3-巯基丙酸的过程中提取双氰胺的工艺,包括以下步骤：(1)制备合成液；(2)水解反应；(3)过滤：过滤得到滤液1和滤饼1；(4)提取双氰胺：向冷却罐内加入滤液1,由冷却机组将冷却罐内的温度降为0℃以下；然后将冷却罐内的物料通过压滤得到滤液2和滤饼2；纯化处理：向滤饼2中加入水,热熔；然后将温度降至20℃以下进行冷却结晶；干燥、包装即可得到双氰胺；(5)制备巯基丙酸溶液；(6)过滤；(7)萃取；(8)蒸出有机溶剂；(9)减压蒸馏；(10)冷凝、包装即可得到3-巯基丙酸；本发明具有在制备3-巯基丙酸的过程中提取出双氰胺、同时提高3-巯基丙酸收率和纯度的有益效果,适用于3-巯基丙酸的制备领域。(The invention provides a process for extracting dicyandiamide in a process of preparing 3-mercaptopropionic acid, which comprises the following steps: (1) preparing a synthetic solution; (2) carrying out hydrolysis reaction; (3) and (3) filtering: filtering to obtain filtrate 1 and filter cake 1; (4) extracting dicyandiamide: adding the filtrate 1 into a cooling tank, and reducing the temperature in the cooling tank to be below 0 ℃ by a cooling unit; then, performing filter pressing on the materials in the cooling tank to obtain filtrate 2 and a filter cake 2; and (3) purification treatment: adding water into the filter cake 2, and carrying out hot melting; then cooling the temperature to below 20 ℃ for crystallization; drying and packaging to obtain dicyandiamide; (5) preparing a mercaptopropionic acid solution; (6) filtering; (7) extracting; (8) evaporating the organic solvent; (9) carrying out reduced pressure distillation; (10) condensing and packaging to obtain 3-mercaptopropionic acid; the method has the beneficial effects of extracting dicyandiamide in the process of preparing the 3-mercaptopropionic acid and simultaneously improving the yield and purity of the 3-mercaptopropionic acid, and is suitable for the field of preparation of the 3-mercaptopropionic acid.)

1. A process for extracting dicyandiamide in a process of preparing 3-mercaptopropionic acid is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a synthetic solution: adding hydrochloric acid, thiourea and acrylic acid into a synthesis kettle in sequence, and preparing a synthetic solution under the condition that the pH value is 1-2;

(2) and (3) hydrolysis reaction: sequentially adding synthetic solution and dilute alkali into a hydrolysis kettle;

(3) and (3) filtering: filtering to obtain filtrate 1 and filter cake 1;

(4) extracting dicyandiamide:

adding the filtrate 1 into a cooling tank, and reducing the temperature in the cooling tank to be below 0 ℃ by a cooling unit;

then, performing filter pressing on the material in the cooling tank through a filter press to obtain filtrate 2 and a filter cake 2;

and (3) purification treatment: adding water into the filter cake 2, and carrying out hot melting at the temperature of 60-80 ℃; then cooling the temperature to below 20 ℃ for crystallization;

drying and packaging to obtain dicyandiamide;

(5) preparation of mercaptopropionic acid solution: dropwise adding hydrochloric acid into the filtrate 2 to obtain a solution containing 3-mercaptopropionic acid;

(6) and (3) filtering: obtaining filtrate 3 and filter cake 3;

(7) and (3) extraction: extracting the filtrate 3 by an organic solvent to obtain an organic solution containing 3-mercaptopropionic acid at the lower layer and an extracted waste liquid at the upper layer;

(8) and (3) distilling the organic solvent: evaporating the organic solvent in the organic solution containing the 3-mercaptopropionic acid;

(9) and (3) reduced pressure distillation: distilling the material from which the organic solvent is distilled out by reduced pressure distillation to distill out the 3-mercaptopropionic acid;

(10) condensation and packaging: condensing the evaporated 3-mercaptopropionic acid, collecting the condensed 3-mercaptopropionic acid in a product homogenizing kettle, and packaging.

2. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the method for preparing the synthetic liquid in the step (1) specifically comprises the following steps:

sequentially adding hydrochloric acid and thiourea into the synthesis kettle, mixing, uniformly stirring, slowly raising the temperature in the synthesis kettle to 40-90 ℃, and preserving the temperature for 0.5-2.5 hours;

and then dripping acrylic acid into the synthesis kettle, slowly raising the temperature to 70-90 ℃, and carrying out heat preservation reaction for 0.5-3 h to prepare the synthetic liquid.

3. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the hydrolysis reaction in the step (2) specifically comprises the following steps:

adding the synthetic liquid into a hydrolysis kettle, and reducing the temperature in the hydrolysis kettle to 30-40 ℃;

and adding dilute alkali into the hydrolysis kettle, slowly raising the temperature in the hydrolysis kettle to 80-110 ℃, and carrying out heat preservation reaction for 0.5-2 h.

4. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the preparation of the mercaptopropionic acid solution in the step (5) specifically comprises the following steps:

slowly reducing the temperature in the hydrolysis kettle to 20-60 ℃; then adding the filtrate 2 into a hydrolysis kettle, and then dropwise adding hydrochloric acid until the pH value is 1-2; to obtain a mixed solution containing 3-mercaptopropionic acid.

5. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the extraction in the step (7) specifically comprises the following steps:

adding the filtrate 3 into an extraction kettle, adding an organic solvent into the extraction kettle, and stirring to fully dissolve the mercaptopropionic acid in the organic solvent;

standing for 20min for layering, wherein the lower layer is an organic solution containing mercaptopropionic acid, and the organic solution containing mercaptopropionic acid is placed into a storage tank for later use; the upper layer is extracted waste liquid, and extraction is carried out for 3 times according to the method;

and (4) placing the extraction waste liquid into a recovery tank for standing, and recovering part of the organic solvent.

6. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the organic solvent is distilled out in the step (8) and the method comprises the following steps:

slowly adding the organic solution containing mercaptopropionic acid into a solvent evaporation kettle, heating to 55 ℃, and evaporating the organic solvent;

the temperature in the solvent evaporation kettle is raised to 120 ℃; until the organic solvent was completely distilled off.

7. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the reduced pressure distillation in the step (9) comprises the following steps:

adding the material after solvent evaporation into a product evaporation kettle, heating to 130 ℃, and distilling under reduced pressure under the condition of vacuum degree of 7 mmHg;

collecting the front fraction; the remaining part was continuously distilled under reduced pressure until 3-mercaptopropionic acid was completely distilled off.

8. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the dilute alkali solution is a sodium hydroxide solution with the concentration of 20-30%.

9. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: and (4) in the drying step, hot air drying is carried out by adopting hot air at the temperature of 100 ℃.

10. The process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid according to claim 1, wherein: the organic solvent is one or more of chloroform, benzene, ethyl acetate, carbon tetrachloride and dichloromethane.

Technical Field

The invention relates to a preparation process of 3-mercaptopropionic acid, in particular to a process for extracting dicyandiamide in a process of preparing the 3-mercaptopropionic acid.

Background

3-mercaptopropionic acid, an intermediate of the pharmaceutical fenamic acid, is also used as a stabilizer for polyvinyl chloride. Can be used for transparent products, and has very good thermal stability. Also useful as antioxidants, catalysts and biochemicals.

The traditional method for preparing 3-mercaptopropionic acid adopts acrylonitrile and thiourea as raw materials, but the acrylonitrile is a highly toxic product and is controlled in use; when the method is adopted for preparation, the utilization rate of the thiourea is not high, so that the waste of raw materials is caused, and the yield of the prepared 3-mercaptopropionic acid is low.

In order to solve the problems of toxic substances in the preparation raw materials, low raw material utilization rate and low yield of the prepared 3-mercaptopropionic acid, a preparation method for obtaining the 3-mercaptopropionic acid solution by reacting a 3-chloropropionic acid aqueous solution with a sodium thiosulfate aqueous solution under an acidic condition and reducing the reaction product by using zinc powder or iron powder is provided.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provides a process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid and simultaneously improving the yield and purity of the 3-mercaptopropionic acid.

In order to solve the technical problems, the invention adopts the technical scheme that: a process for extracting dicyandiamide in the process of preparing 3-mercaptopropionic acid comprises the following steps: (1) preparing a synthetic solution: adding hydrochloric acid, thiourea and acrylic acid into a synthesis kettle in sequence, and preparing a synthetic solution under the condition that the pH value is 1-2; (2) and (3) hydrolysis reaction: sequentially adding synthetic solution and dilute alkali into a hydrolysis kettle; (3) and (3) filtering: filtering to obtain filtrate 1 and filter cake 1; (4) extracting dicyandiamide: adding the filtrate 1 into a cooling tank, and reducing the temperature in the cooling tank to be below 0 ℃ by a cooling unit; then, performing filter pressing on the material in the cooling tank through a filter press to obtain filtrate 2 and a filter cake 2; and (3) purification treatment: adding water into the filter cake 2, and carrying out hot melting at the temperature of 60-80 ℃; then cooling the temperature to below 20 ℃ for crystallization; drying and packaging to obtain dicyandiamide; (5) preparation of mercaptopropionic acid solution: dropwise adding hydrochloric acid into the filtrate 2 to obtain a solution containing 3-mercaptopropionic acid; (6) and (3) filtering: obtaining filtrate 3 and filter cake 3; (7) and (3) extraction: extracting the filtrate 3 by an organic solvent to obtain an organic solution containing 3-mercaptopropionic acid at the lower layer and an extracted waste liquid at the upper layer; (8) and (3) distilling the organic solvent: evaporating the organic solvent in the organic solution containing the 3-mercaptopropionic acid; (9) and (3) reduced pressure distillation: distilling the material from which the organic solvent is distilled out by reduced pressure distillation to distill out the 3-mercaptopropionic acid; (10) condensation and packaging: condensing the evaporated 3-mercaptopropionic acid, collecting the condensed 3-mercaptopropionic acid in a product homogenizing kettle, and packaging.

Preferably, the method for preparing the synthetic fluid in the step (1) specifically comprises the following steps: sequentially adding hydrochloric acid and thiourea into the synthesis kettle, mixing, uniformly stirring, slowly raising the temperature in the synthesis kettle to 40-90 ℃, and preserving the temperature for 0.5-2.5 hours; and then dripping acrylic acid into the synthesis kettle, slowly raising the temperature to 70-90 ℃, and carrying out heat preservation reaction for 0.5-3 h to prepare the synthetic liquid.

Preferably, the hydrolysis reaction in step (2) specifically comprises the following steps: adding the synthetic liquid into a hydrolysis kettle, reducing the temperature in the hydrolysis kettle to 30-40 ℃, adding dilute alkali into the hydrolysis kettle, slowly increasing the temperature in the hydrolysis kettle to 80-110 ℃, and carrying out heat preservation reaction for 0.5-2 hours.

Preferably, the preparation of the mercaptopropionic acid solution in step (5) specifically comprises the following steps: slowly reducing the temperature in the hydrolysis kettle to 20-60 ℃; then adding the filtrate 2 into a hydrolysis kettle, and then dropwise adding hydrochloric acid until the pH value is 1-2; to obtain a mixed solution containing 3-mercaptopropionic acid.

Preferably, the extraction in step (7) specifically comprises the following steps: adding the filtrate 3 into an extraction kettle, adding an organic solvent into the extraction kettle, and stirring to fully dissolve the mercaptopropionic acid in the organic solvent; standing for 20min for layering, wherein the lower layer is an organic solution containing mercaptopropionic acid, and the organic solution containing mercaptopropionic acid is placed into a storage tank for later use; the upper layer is extracted waste liquid, and extraction is carried out for 3 times according to the method; and (4) placing the extraction waste liquid into a recovery tank for standing, and recovering part of the organic solvent.

Preferably, the distilling off the organic solvent in the step (8) comprises the steps of: slowly adding the organic solution containing mercaptopropionic acid into a solvent evaporation kettle, heating to 55 ℃, and evaporating the organic solvent; the temperature in the solvent evaporation kettle is raised to 120 ℃; until the organic solvent was completely distilled off.

Preferably, the reduced pressure distillation in step (9) comprises the steps of: adding the material after solvent evaporation into a product evaporation kettle, heating to 130 ℃, and distilling under reduced pressure under the condition of vacuum degree of 7 mmHg; collecting the front fraction; the remaining part was continuously distilled under reduced pressure until 3-mercaptopropionic acid was completely distilled off.

Preferably, the dilute alkali solution is a sodium hydroxide solution with the concentration of 20-30%.

Preferably, in the drying step in the step (4), hot air drying is performed by using hot air at 100 ℃.

Preferably, the organic solvent is one or more of chloroform, benzene, ethyl acetate, carbon tetrachloride and dichloromethane.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention provides a process for extracting dicyandiamide in a process of preparing 3-mercaptopropionic acid, which comprises the following steps: (1) preparing a synthetic solution: adding hydrochloric acid, thiourea and acrylic acid into a synthesis kettle in sequence to prepare a synthetic solution; (2) and (3) hydrolysis reaction: sequentially adding synthetic solution and dilute alkali into a hydrolysis kettle; (3) and (3) filtering: filtering to obtain filtrate 1 and filter cake 1; (4) extracting dicyandiamide: adding the filtrate 1 into a cooling tank, and reducing the temperature in the cooling tank to be below 0 ℃ by a cooling unit; then, performing filter pressing on the material in the cooling tank through a filter press to obtain filtrate 2 and a filter cake 2; and (3) purification treatment: adding water into the filter cake 2, and carrying out hot melting at the temperature of 60-80 ℃; then cooling the temperature to below 20 ℃ for crystallization; drying and packaging to obtain dicyandiamide; (5) preparation of mercaptopropionic acid solution: dropwise adding hydrochloric acid into the filtrate 2 to obtain a solution containing 3-mercaptopropionic acid; (6) and (3) filtering: obtaining filtrate 3 and filter cake 3; (7) and (3) extraction: extracting the filtrate 3 by an organic solvent to obtain an organic solution containing 3-mercaptopropionic acid at the lower layer and an extracted waste liquid at the upper layer; (8) and (3) distilling the organic solvent: evaporating the organic solvent in the organic solution containing the 3-mercaptopropionic acid; (9) and (3) reduced pressure distillation: distilling the material from which the organic solvent is distilled out by reduced pressure distillation to distill out the 3-mercaptopropionic acid; (10) condensation and packaging: condensing the evaporated 3-mercaptopropionic acid, collecting the condensed 3-mercaptopropionic acid in a product homogenizing kettle, and packaging.

The invention adopts thiourea and acrylic acid as raw materials, which are easy to obtain and do not contain highly toxic substances; dicyandiamide is extracted in the preparation process, an intermediate product is utilized, the waste of raw materials is reduced, and the yield of the 3-mercaptopropionic acid is improved after the dicyandiamide is extracted; solves the problem of low yield of the 3-mercaptopropionic acid prepared by adopting thiourea as a raw material.

The purity of dicyandiamide extracted in the process of preparing 3-mercaptopropionic acid reaches 98.0-99.3%, and the yield of dicyandiamide reaches 65-85%; meanwhile, the purity of the prepared 3-mercaptopropionic acid reaches 98.0-99.5%, and the yield of the 3-mercaptopropionic acid reaches 82-85%.

2. The dilute alkali solution is a sodium hydroxide solution with the concentration of 20-30%. The treatment effect of the sodium hydroxide solution with the concentration of 20-30% is good, and the generated waste liquid can be separated by simple separation and distillation.

3. In the drying step in the step (4), hot air drying is performed by adopting hot air at 100 ℃. The hot air drying can be performed by hot air drying the dicyandiamide crystallized by cooling, so as to completely remove the moisture in the dicyandiamide, thereby obtaining the dry dicyandiamide powder.

4. The organic solvent is one or more of chloroform, benzene, ethyl acetate, carbon tetrachloride and dichloromethane. The organic solvent is used to extract the 3-mercaptopropionic acid from the solution containing the 3-mercaptopropionic acid to separate it from the other components of the solution.

Drawings

FIG. 1 is a process flow diagram for extracting dicyandiamide in the process of producing 3-mercaptopropionic acid provided by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The preparation method provided by the invention has the following relevant reaction formulas:

step (1):

step (2):

and (4):

NH₂CN+NH₂CN→C₂H₄N₄

and (5):

65-85% of dicyandiamide generated by the reaction is extracted to prepare dicyandiamide, and the rest dicyandiamide is prepared to urea. The waste liquid after extraction comprises: the raw materials of acrylic acid and thiourea which do not participate in the reaction, the intermediate products of the reaction, namely urea, sodium chloride and water, and substances in the waste liquid can be separated and recovered through distillation and filtration steps. Wherein, the raw material acrylic acid can be continuously used as the raw material to prepare the 3-mercaptopropionic acid for use after being recovered, the thiourea and the urea can be used for synthesizing the urea-formaldehyde resin, the sodium chloride can be used as the raw material of the sodium chloride for industry, and the water can be used as the water for boilers. The waste liquid after separation and recovery is further treated to reach the discharge standard, and the pollution to the environment is less.