阅读说明：本技术 胍基乙酸的制备方法 (Preparation method of guanidinoacetic acid ) 是由 王琪 唐诗刚 王继军 邓霖 邹凯 景旭凯 许陈陈 于 2021-08-18 设计创作，主要内容包括：本发明提供一种工艺简单、胍基乙酸收率高、双氰胺含量低且产品纯度高的胍基乙酸的制备方法,该方法包括以下步骤：1)将碱与甘氨酸、水混合后,升温使初始反应体系中的PH为6.5-8.0；2)将碱与单氰胺分别同步缓慢加入反应体系中,直至单氰胺全部加入完毕,这时反应体系中PH值保持在8.0-9.0；3)恒温1-3小时反应完成后降温到常温,用酸调PH为7.8；4)离心分离、干燥即得产品。本发明方法有利于单氰胺生成胍基乙酸,降低双氰胺含量；反应完降至常温后最终将体系PH调为胍基乙酸的等电点7.8,可减少胍基乙酸的溶解损失；本发明只离心分离不用洗涤,产品也可达到较高的纯度。(The invention provides a preparation method of glycocyamine, which has the advantages of simple process, high yield of glycocyamine, low dicyandiamide content and high product purity, and comprises the following steps: 1) mixing alkali, glycine and water, and heating to make the pH value in the initial reaction system be 6.5-8.0; 2) synchronously and slowly adding alkali and cyanamide into the reaction system respectively until the cyanamide is completely added, and then keeping the pH value in the reaction system at 8.0-9.0; 3) after the reaction is finished at the constant temperature for 1-3 hours, cooling to the normal temperature, and adjusting the pH value to 7.8 by using acid; 4) centrifugally separating and drying to obtain the product. The method is beneficial to generating guanidinoacetic acid from cyanamide and reducing the content of dicyandiamide; after the reaction is finished and the temperature is reduced to normal temperature, the PH value of the system is finally adjusted to be 7.8 of the isoelectric point of the glycocyamine, so that the dissolution loss of the glycocyamine can be reduced; the invention only needs centrifugal separation without washing, and the product can also reach higher purity.)

1. a process for the preparation of guanidinoacetic acid, characterized in that it comprises the following steps: 1) mixing glycine and water, stirring, heating, adding alkali to enable the pH value in an initial reaction system to be 6.5-8.0; 2) synchronously adding alkali and cyanamide into the reaction system respectively until the cyanamide is completely added, and then keeping the pH value in the reaction system at 8.0-9.0; 3) after the reaction is finished at the constant temperature for 1-3 hours, cooling to the normal temperature, and adjusting the pH value to 7.8 by using acid; 4) centrifugally separating and drying to obtain the product.

2. The process for producing guanidinoacetic acid according to claim 1, wherein the molar ratio of glycine to cyanamide is 1: 1.

3. the process for producing guanidinoacetic acid according to claim 1, wherein the weight ratio of glycine, cyanamide and sodium hydroxide is: 100 parts of glycine; 56 parts of cyanamide; 5-7 parts of sodium hydroxide.

4. The process for producing guanidinoacetic acid according to claim 1, wherein the weight ratio of glycine, cyanamide and sodium hydroxide is: 100 parts of glycine; 56 parts of cyanamide; 6 parts of sodium hydroxide.

5. The process for producing guanidinoacetic acid according to claim 1, wherein the base is sodium hydroxide, sodium carbonate or sodium bicarbonate, and the concentration of the base is 20 to 40%.

6. The method for producing guanidinoacetic acid according to claim 1, wherein the addition of a base in the step 1) brings the pH in the initial reaction system to 7.4 to 7.6.

7. The process for producing guanidinoacetic acid according to claim 1, wherein the reaction temperature in steps 1) and 2) is 85 to 95 ℃, preferably 88 to 90 ℃.

8. The process for producing guanidinoacetic acid according to claim 1, wherein the pH in the reaction system is slowly raised in step 2) and the pH in the reaction system is maintained at 8.4 to 8.7 after the addition of all the cyanamide is completed.

9. The method for producing guanidinoacetic acid according to claim 1, wherein the holding time in step 3) is 2 hours.

10. The method for producing guanidinoacetic acid according to claim 1, wherein the acid used in step 3) is a strong acid such as sulfuric acid or hydrochloric acid.

Technical Field

The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of glycocyamine.

Background

The glycocyamine is white crystalline powder and is mainly used as food or feed additive, and the current common preparation method is as follows: reacting cyanamide and alkaline substance with glycine, cooling, washing, centrifuging and drying to obtain the final product. The synthesis reaction equation of glycocyamine is as follows:

the preparation method has the advantages of simple process and less by-products, and has the defects of high dicyandiamide content and even melamine content. In the actual synthesis, the purity of the product is low due to the high content of dicyandiamide in the guanidinoacetic acid product, and the product purity of the guanidinoacetic acid product can be improved only by adopting a large amount of water for washing so as to reduce the content of dicyandiamide in the product, but the water consumption is large, the loss of the guanidinoacetic acid is large, and the final yield of the guanidinoacetic acid is reduced. In the traditional method for synthesizing guanidinoacetic acid from cyanamide and glycine under an alkaline condition, alkali and glycine are added into a reaction system at one time, and then cyanamide is dropwise added, so that the initial pH of the reaction is higher, and the cyanamide entering the system is easy to polymerize to generate dicyandiamide. In addition, the amino acid has the lowest solubility in water at the isoelectric point, the isoelectric point of the glycocyamine is PH7.8, and after the synthesis is finished, the PH of the system solution is adjusted to the isoelectric point, so that the dissolution loss of the glycocyamine can be reduced, and the product yield is improved. In the synthesis process, the base can catalyze the reaction of cyanamide and glycine to generate guanidinoacetic acid and is also a catalyst for synthesizing the maximum side reaction of the guanidinoacetic acid and polymerizing the cyanamide, so that the maintenance of reasonable alkalinity is the key for not only synthesizing the guanidinoacetic acid from the cyanamide and the glycine, but also reducing the polymerization of the cyanamide into dicyandiamide as far as possible.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a preparation method of glycocyamine, which has the advantages of simple process, high yield of glycocyamine, low content of dicyandiamide and high product purity.

The technical scheme adopted by the invention for solving the technical problem is as follows: a process for the preparation of guanidinoacetic acid, which process comprises the steps of: 1) mixing alkali, glycine and water, and heating to make the pH value in the initial reaction system be 6.5-8.0; 2) synchronously and slowly adding alkali and cyanamide into the reaction system respectively until the cyanamide is completely added, and then keeping the pH value in the reaction system at 8.0-9.0; 3) after the reaction is finished at the constant temperature for 1-3 hours, cooling to the normal temperature, and adjusting the pH value to 7.8 by using acid; 4) centrifugally separating and drying to obtain the product.

Further, the molar ratio of the glycine to the cyanamide is 1:1, the weight ratio is: 100 parts of glycine; 56 parts of cyanamide. The alkali is sodium hydroxide, sodium carbonate, sodium bicarbonate and the like, and the concentration of the alkali is 20-40%; the weight ratio of the sodium hydroxide to the glycine to the cyanamide is as follows: 5-7 parts of sodium hydroxide; 100 parts of glycine; 56 parts of cyanamide; preferably 6 parts of sodium hydroxide; 100 parts of glycine; 56 parts of cyanamide. .

Further, the pH in the initial reaction system in the step 1) is 7.4 to 7.6. The reaction temperature in steps 1) and 2) is 85-95 ℃, and the reaction temperature is preferably 88-90 ℃. And 2) slowly raising the pH value in the reaction system, and keeping the pH value in the reaction system at 8.4-8.7 after the cyanamide is completely added. And 3) keeping the constant temperature for 2 hours. The acid in the step 3) adopts strong acid.

The invention has the beneficial effects that: the initial pH value of the reaction is set to be 6.5-8.0, the pH value is averagely and slowly increased to 8.0-9.0 in the reaction process, the generation of guanidinoacetic acid from cyanamide is facilitated, and the content of dicyandiamide is reduced; after the reaction is finished and the temperature is reduced to normal temperature, the PH value of the system is finally adjusted to be 7.8 of the isoelectric point of the glycocyamine, so that the dissolution loss of the glycocyamine can be reduced; the invention only needs centrifugal separation without washing, and the product can also reach higher purity.

Detailed Description

The preparation method of glycocyamine comprises the following steps: 1) dividing the alkali for the reaction into two parts, wherein the alkali of the first part is added before the reaction; mixing glycine and water, stirring, heating, adding alkali to make pH of the initial reaction system be 6.5-8.0, preferably 7.4-7.6; 2) the second part of alkali and cyanamide are synchronously and slowly added into the reaction system respectively to ensure that the pH value in the reaction system is averagely and slowly increased until the cyanamide is completely added, and the pH value in the reaction system is kept between 8.0 and 9.0, preferably between 8.4 and 8.7; 3) after the addition of the cyanamide and the alkali is finished, keeping the temperature for 1-3 hours, preferably 2 hours; after the reaction is finished, cooling to normal temperature, and adjusting the pH value to 7.8 by using acid; 4) centrifugally separating and drying to obtain the product.

The molar ratio of glycine to cyanamide in the invention is 1:1, the weight ratio is: 100 parts of glycine; 56 parts of cyanamide. The alkali is sodium hydroxide, sodium carbonate, sodium bicarbonate and the like, and the concentration of the alkali is 20-40%; the weight ratio of the sodium hydroxide to the glycine to the cyanamide is as follows: 5-7 parts of sodium hydroxide; 100 parts of glycine; 56 parts of cyanamide. Preferably 6 parts of sodium hydroxide; 100 parts of glycine; 56 parts of cyanamide. The reaction temperature of the steps 1) and 2) is 85-95 ℃, and the preferable reaction temperature is 88-90 ℃; the reaction time of the step 2) is the time required by adding the cyanamide; the time for adding the second part of the alkali is the same as the time for adding the cyanamide; the acid in the step 3) is strong acid, such as sulfuric acid, hydrochloric acid, etc.

Example 1:

adding 705kg of water and 320kg of glycine into a 1500L reaction kettle provided with a reflux condensation system and a stirrer, stirring and heating until the temperature reaches 89 +/-1 ℃, keeping the temperature constant, preparing 64kg of 30% sodium hydroxide solution, and partially adding the sodium hydroxide solution into the kettle to adjust the pH value in the reaction system to 7.5; then 597kg of cyanamide with the content of 30 percent is added through a pump, the pumping speed of the cyanamide is controlled to be about 200kg/h, the pumping time of the cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed within 3 hours, the pH value in the reaction system is slowly increased to 8.5, the reaction temperature is controlled to be 89 +/-1 ℃, the temperature is kept for 2 hours after the addition, the cooling is started, when the temperature reaches the normal temperature, the pH value is adjusted to be 7.8 by sulfuric acid, the centrifugal separation is carried out, and the product is dried.

The wet material was dried to obtain 466.8kg of guanidinoacetic acid with a purity of 98.4%, a dicyandiamide content of 0.09%, no melamine detected, and a yield of 92%.

In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine to cyanamide to sodium hydroxide is: 100: 56: 6.

example 2:

adding 705kg of water and 320kg of glycine into a 1500L reaction kettle provided with a reflux condensation system and a stirrer, stirring and heating until the temperature reaches 89 +/-1 ℃, keeping the temperature constant, preparing 64kg of 30% sodium hydroxide solution, and partially adding the sodium hydroxide solution into the kettle to ensure that the pH value in the reaction system reaches 7.0; then 597kg of cyanamide with the content of 30 percent is added through a pump, the pumping speed of the cyanamide is controlled to be about 200kg/h, the pumping time of the cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed within 3 hours, the pH value in the reaction system is slowly increased to 8.5, the reaction temperature is controlled to be 89 +/-1 ℃, the temperature is kept for 2 hours after the addition, the cooling is started, when the temperature reaches the normal temperature, the pH value is adjusted to be 7.8 by sulfuric acid, the centrifugal separation is carried out, and the product is dried.

The wet material was dried to give 462.5kg weight of guanidinoacetic acid with a purity of 98.0%, dicyandiamide content of 0.09%, no melamine detected, and a yield of 90.8%.

In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine to cyanamide to sodium hydroxide is: 100: 56: 6.

example 3:

adding 705kg of water and 320kg of glycine into a 1500L reaction kettle provided with a reflux condensation system and a stirrer, stirring and heating until the temperature reaches 89 +/-1 ℃, keeping the temperature constant, preparing 69.3kg of 30% sodium hydroxide solution, and partially adding the sodium hydroxide solution into the kettle to ensure that the pH value in the reaction system reaches 7.5; then 597kg of cyanamide with the content of 30 percent is added through a pump, the pumping speed of the cyanamide is controlled to be about 200kg/h, the pumping time of the cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed within 3 hours, the pH value in the reaction system is slowly increased to 8.7, the reaction temperature is controlled to be 89 +/-1 ℃, the temperature is kept for 2 hours after the addition, the cooling is started, when the temperature reaches the normal temperature, the pH value is adjusted to be 7.8 by sulfuric acid, the centrifugal separation is carried out, and the product is dried.

The wet material was dried to obtain 465.0kg of guanidinoacetic acid with a purity of 98.2%, a dicyandiamide content of 0.08%, no melamine detected, and a yield of 91.5%.

In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine to cyanamide to sodium hydroxide is: 100: 56: 6.5.

comparative example:

adding 705kg of water and 320kg of glycine into a 1500L reaction kettle provided with a reflux condensation system and a stirrer, adding 64kg of 30% sodium hydroxide, stirring and heating to 89 +/-1 ℃, adding 597kg of 30% cyanamide through a pump, controlling the pumping speed of the cyanamide to be about 200kg/h, continuously keeping the temperature at 89 +/-1 ℃, pumping for 3 hours, keeping the temperature for 2 hours after the addition is finished, starting cooling, adjusting the pH value to 7.8 by using sulfuric acid when the temperature reaches the normal temperature, carrying out centrifugal separation, and drying the product.

The wet material was dried to give 435kg of guanidinoacetic acid with a purity of 97.4%, a dicyandiamide content of 0.32%, melamine content of 8mg/kg and a yield of 84.9%.

In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine to cyanamide to sodium hydroxide is: 100: 56: 6.