CN113651726B - Preparation method of guanidinoacetic acid - Google Patents
Preparation method of guanidinoacetic acid Download PDFInfo
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- CN113651726B CN113651726B CN202110948099.8A CN202110948099A CN113651726B CN 113651726 B CN113651726 B CN 113651726B CN 202110948099 A CN202110948099 A CN 202110948099A CN 113651726 B CN113651726 B CN 113651726B
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- cyanamide
- glycine
- guanidinoacetic acid
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C277/00—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups
- C07C277/08—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups of substituted guanidines
Abstract
The invention provides a preparation method of guanidinoacetic acid, which has the advantages of simple process, high guanidinoacetic acid yield, low dicyandiamide content and high product purity, and the method comprises the following steps: 1) After mixing alkali, glycine and water, heating to enable the PH in an initial reaction system to be 6.5-8.0; 2) Respectively and synchronously slowly adding alkali and cyanamide into a reaction system until the cyanamide is completely added, and keeping the pH value in the reaction system at 8.0-9.0; 3) Keeping the temperature for 1-3 hours, cooling to normal temperature after the reaction is completed, and adjusting the PH to 7.8 by acid; 4) And (5) centrifugally separating and drying to obtain the product. The method is beneficial to the generation of guanidinoacetic acid from the cyanamide and reduces the dicyandiamide content; after the reaction is completed and the temperature is reduced to normal temperature, the pH of the system is finally adjusted to be 7.8 of isoelectric point of guanidinoacetic acid, so that the dissolution loss of the guanidinoacetic acid can be reduced; the invention only centrifugally separates without washing, and the product can reach higher purity.
Description
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of guanidinoacetic acid.
Background
Guanidinoacetic acid is white crystal powder, and is mainly used as food or feed additive, and the preparation method commonly used at present is as follows: and (3) reacting the cyanamide and alkaline substances with glycine, cooling, washing, centrifuging and drying to obtain a finished product. The reaction equation for the synthesis of guanidinoacetic acid is as follows:
the preparation method has the advantages of simple process, few byproducts, high dicyandiamide content and even melamine content. In actual synthesis, the high dicyandiamide content in the guanyl acetic acid product leads to low product purity, and a large amount of water can be used for washing to reduce the dicyandiamide content in the product in order to improve the purity of the guanyl acetic acid product, but the water consumption is large, the loss of guanyl acetic acid is large, and finally the yield of guanyl acetic acid is reduced. In the traditional process of synthesizing guanidinoacetic acid from cyanamide and glycine under alkaline condition, alkali and glycine are added into a reaction system at one time, and Shan Qingan is added dropwise, so that the pH value of the reaction initiation 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 of the amino acid, the isoelectric point of the guanidinoacetic acid 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 guanidinoacetic acid can be reduced, and the product yield is improved. In the synthesis process, the alkali can catalyze the reaction of the cyanamide and the glycine to generate the guanyl acetic acid, and is a catalyst for polymerization of the cyanamide which is the biggest side reaction in the synthesis of the guanyl acetic acid, so that the reasonable alkalinity is maintained, and the key of not only meeting the synthesis of the guanyl acetic acid from the cyanamide and the glycine, but also reducing the polymerization of the cyanamide to the dicyandiamide as much as possible is provided.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the preparation method of the guanidinoacetic acid, which has the advantages of simple process, high yield of the guanidinoacetic acid, low dicyandiamide content and high product purity.
The technical scheme adopted for solving the technical problems is as follows: a process for the preparation of guanidinoacetic acid, comprising the steps of: 1) After mixing alkali, glycine and water, heating to enable the pH value in an initial reaction system to be 6.5-8.0; 2) Respectively and synchronously slowly adding alkali and cyanamide into a reaction system until the cyanamide is completely added, and keeping the pH value in the reaction system at 8.0-9.0; 3) Keeping the temperature for 1-3 hours, cooling to normal temperature after the reaction is completed, and adjusting the pH to 7.8 by acid; 4) And (5) centrifugally separating and drying to obtain the product.
Further, the molar ratio of glycine to cyanamide is 1:1, the weight ratio is: 100 parts of glycine; 56 parts of cyanamide. The alkali adopts 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 7.4-7.6. The temperature of the reactions described in steps 1) and 2) is 85-95 ℃, preferably 88-90 ℃. And 2) slowly increasing the pH value in the reaction system, and keeping the pH value in the reaction system at 8.4-8.7 after the addition of the cyanamide is completed. The constant temperature time in the step 3) is 2 hours. The acid in step 3) is a strong acid.
The beneficial effects of the invention are as follows: the initial pH value of the reaction is set to be 6.5-8.0, the average pH value is slowly increased to 8.0-9.0 in the reaction process, so that the guanyl acetic acid generated by the cyanamide is more facilitated, and the dicyandiamide content is reduced; after the reaction is completed and the temperature is reduced to normal temperature, the pH of the system is finally adjusted to be 7.8 of isoelectric point of guanidinoacetic acid, so that the dissolution loss of the guanidinoacetic acid can be reduced; the invention only centrifugally separates without washing, and the product can reach higher purity.
Detailed Description
The preparation method of guanidinoacetic acid comprises the following steps: 1) Dividing the alkali for reaction into two parts, wherein the alkali of the first part is added before the reaction starts; after glycine and water are mixed, stirring, heating and adding alkali to enable the pH value in an initial reaction system to be 6.5-8.0, and preferably 7.4-7.6; 2) The alkali and the cyanamide in the second part are respectively and synchronously slowly added into the reaction system, so 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 at 8.0-9.0, preferably 8.4-8.7; 3) After the addition of the cyanamide and the alkali is completed, the temperature is kept for 1 to 3 hours, preferably 2 hours; cooling to normal temperature after the reaction is finished, and regulating the pH to 7.8 by using acid; 4) And (5) 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 adopts 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 second part of alkali is added in the same time as the addition time of the cyanamide; the acid described in step 3) above is a 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 condensing system and a stirrer, stirring and heating to 89+/-1 ℃, keeping the temperature constant, preparing 64kg of 30% sodium hydroxide solution, and partially adding into the kettle to adjust the pH value in the reaction system to 7.5; then 597kg of cyanamide with the content of 30% is added through a pump, the pumping speed of cyanamide is controlled to be about 200kg/h, the pumping time of cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed for 3 hours, the pH value in the reaction system is gradually increased to 8.5, the reaction temperature is controlled to be 89+/-1 ℃, the temperature is kept constant for 2 hours after the addition, cooling is started, the pH value is regulated to be 7.8 by sulfuric acid when the temperature reaches normal temperature, and the product is centrifugally separated and dried.
The wet material was dried to give guanidinoacetic acid weighing 466.8kg, purity 98.4%, dicyandiamide content 0.09%, undetected melamine, yield 92%.
In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine, cyanamide and 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 condensing system and a stirrer, stirring and heating to 89+/-1 ℃, keeping the temperature constant, preparing 64kg of 30% sodium hydroxide solution, and partially adding into the kettle to enable the pH value in the reaction system to reach 7.0; then 597kg of cyanamide with the content of 30% is added through a pump, the pumping speed of cyanamide is controlled to be about 200kg/h, the pumping time of cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed for 3 hours, the pH value in the reaction system is gradually increased to 8.5, the reaction temperature is controlled to be 89+/-1 ℃, the temperature is kept constant for 2 hours after the addition, cooling is started, the pH value is regulated to be 7.8 by sulfuric acid when the temperature reaches normal temperature, and the product is centrifugally separated and dried.
The wet material was dried to give guanidinoacetic acid weighing 462.5kg, purity 98.0%, dicyandiamide content 0.09%, undetected melamine, yield 90.8%.
In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine, cyanamide and 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 condensing system and a stirrer, stirring and heating to 89+/-1 ℃, keeping the temperature constant, preparing 69.3kg of 30% sodium hydroxide solution, and partially adding into the kettle to enable the pH value in the reaction system to reach 7.5; then 597kg of cyanamide with the content of 30% is added through a pump, the pumping speed of cyanamide is controlled to be about 200kg/h, the pumping time of cyanamide is controlled to be 3 hours, meanwhile, the rest sodium hydroxide solution is added into the system at a constant speed for 3 hours, the pH value in the reaction system is gradually increased to 8.7, the reaction temperature is controlled to be 89+/-1 ℃, the temperature is kept constant for 2 hours after the addition, cooling is started, the pH value is regulated to be 7.8 by sulfuric acid when the temperature reaches normal temperature, and the product is centrifugally separated and dried.
Drying the wet material to obtain guanylacetic acid with the weight of 465.0kg, the purity of 98.2%, the dicyandiamide content of 0.08%, the melamine content being undetected and the yield of 91.5%.
In this example, the molar ratio of glycine to cyanamide is 1:1, and the weight ratio of glycine, cyanamide and sodium hydroxide is: 100:56:6.5.
comparative example:
in a 1500L reaction kettle provided with a reflux condensing system and a stirrer, 705kg of water and 320kg of glycine are added, then 64kg of 30% sodium hydroxide is added, stirring and heating are carried out until the temperature is 89+/-1 ℃, 597kg of 30% cyanamide is added through a pump, the pumping speed of cyanamide is controlled to be about 200kg/h, the temperature is continuously kept constant at 89+/-1 ℃ for 3 hours, the pumping time is kept at the constant temperature for 2 hours after the adding, cooling is started, when the temperature reaches the normal temperature, the pH value is regulated to be 7.8 by sulfuric acid, centrifugal separation is carried out, and the product is dried.
Drying the wet material to obtain 435kg of guanidinoacetic acid with a purity of 97.4%, a dicyandiamide content of 0.32%, and a melamine yield 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, cyanamide and sodium hydroxide is: 100:56:6.
Claims (8)
1. the preparation method of guanidinoacetic acid is characterized by comprising the following steps: 1) After mixing glycine and water, stirring, heating and adding alkali to enable the pH value in an initial reaction system to be 7.0-7.5; 2) Respectively and synchronously adding alkali and cyanamide into a reaction system until the cyanamide is completely added, and keeping the pH value in the reaction system at 8.0-9.0; 3) Keeping the temperature for 1-3 hours, cooling to normal temperature after the reaction is completed, and adjusting the pH to 7.8 by acid; 4) Centrifugally separating and drying to obtain a product; the alkali adopts sodium hydroxide, and the weight ratio of glycine to cyanamide to sodium hydroxide is as follows: 100 parts of glycine; 56 parts of cyanamide; 5-7 parts of sodium hydroxide; the temperature of the steps 1) and 2) is 85-95 ℃.
2. The method for preparing guanidinoacetic acid according to claim 1, wherein the alkali is sodium hydroxide, and the weight ratio of glycine to cyanamide to sodium hydroxide is: 100 parts of glycine; 56 parts of cyanamide; 6 parts of sodium hydroxide.
3. The process for preparing guanidinoacetic acid according to claim 1, wherein the addition of base in step 1) brings the pH of the initial reaction system to 7.4 to 7.5.
4. The process for preparing guanidinoacetic acid according to claim 1, wherein the reaction temperature in steps 1) and 2) is from 85 to 95 ℃.
5. The process for preparing guanidinoacetic acid according to claim 1, wherein the temperatures in steps 1) and 2) are 88 to 90 ℃.
6. The process for preparing guanidinoacetic acid according to claim 1, wherein in step 2) the pH value in the reaction system is slowly increased, and the pH value in the reaction system is kept between 8.4 and 8.7 after the addition of the cyanamide is completed.
7. The process for preparing guanidinoacetic acid according to claim 1, wherein the constant temperature time in step 3) is 2 hours.
8. The process for preparing guanidinoacetic acid according to claim 1, wherein in step 3) the acid is sulfuric acid or hydrochloric acid.
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| US2654779A (en) * | 1950-12-23 | 1953-10-06 | Int Minerals & Chem Corp | Method of preparation of guanidino fatty acids |
| DE102006016227A1 (en) * | 2006-04-06 | 2007-10-11 | Degussa Gmbh | Process for the preparation of creatine, creatine monohydrate or guanidinoacetic acid |
| CN101462983A (en) * | 2007-12-21 | 2009-06-24 | 上海浩洲化工有限公司 | Preparation of glycocyamine |
| CN102329250A (en) * | 2011-07-22 | 2012-01-25 | 周彬 | Chemical synthesis method of glycocyamine |
| CN103193681A (en) * | 2013-04-17 | 2013-07-10 | 北京君德同创农牧科技股份有限公司 | Clean preparation method of guanidinoacetic acid |
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| CN107721881A (en) * | 2016-08-11 | 2018-02-23 | 宁夏天成生化科技有限公司 | The preparation method of 2 guanidine radicals benzenpropanoic acids |
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