Preparation method of cyanamide
By controlling the response conditions of lime nitrogen and water and the speed of passing carbon dioxide, combined with the pH adjustment of inorganic acid, the problem of more impurities and products in the production of monociide production in existing technologies has achieved high purity and high revenue yields. Millarine preparation.
Patent Information
- Application Number
- CN202411261448.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2025-01-28
AI Technical Summary
In the prior art, cyanamine is produced, there are many impurities. Under long-term storage conditions, impurities react chemically with phosphoric acid, resulting in an increase in pH and precipitation, which ultimately leads to a decrease in cyanamine content and deterioration of the product.
By mixing the first reaction of lime nitrogen and water, then the carbon dioxide is passed to the first reaction product to perform a second reaction, controlling the reaction temperature and the speed of passing the carbon dioxide. Get high -purity monocidal.
Achieve small by -products, high product revenue and purity, avoid the chemical reactions of impurities and phosphate, and extend the stability and validity period of the product.
Abstract
Description
Technical Field
[0001] The present application relates to a method for preparing cyanamide. Background Art
[0002] Cyanamide is a pharmaceutical raw material and intermediate, which is mainly used to produce cytarabine hydrochloride, 3-amino-5-hydroxy 1,2,4-triazole, etc. Cyanamide is also a raw material for organic synthesis, such as the production of cyanuric acid amide, dicyandiamide, methyl carbamate, etc., and then the production of pharmaceutical barbituric acid, sulfonamide drugs, various guanidine salts, pesticides such as chlorpyrifos, carbendazim, creatine, etc. Cyanamide can be used as a plant growth regulator in agriculture, and has insecticidal and bactericidal effects. Especially in the production of cherries and grapes, it is a good dormancy terminator, which can play a role in early flowering and fruiting, increase yield, and change the quality of fruit flesh.
[0003] Crystalline cyanamide is unstable, a colorless crystalline solid, rhombus-shaped, colorless, hygroscopic, with a melting point of 42°C. It is soluble in water, ethanol, ether, and benzene, but insoluble in ethylene oxide. It can evaporate with water vapor and is toxic. Cyanamide has a large solubility in water, is weakly acidic, and is completely miscible with water at 43°C. A 50.0% aqueous solution of cyanamide is a colorless liquid with a specific gravity of 1.0724. 30.0% cyanamide is obtained by adding acid to an aqueous suspension of calcium cyanamide. It is an important organic synthesis intermediate, especially in the synthesis of medicines and pesticides, and can be used as a plant growth regulator.
[0004] At present, phosphoric acid is mostly used for acidification in the production of cyanamide, and the resulting cyanamide contains a lot of impurities. Under long-term storage conditions, the impurities react chemically with the phosphoric acid, resulting in an increase in pH and precipitation, which ultimately leads to a decrease in the cyanamide content and product deterioration. Summary of the invention
[0005] In order to solve the above technical problems existing in the prior art, the present application provides a method for preparing cyanamide. The preparation method provided by the present application has small byproducts and high product yield and purity.
[0006] The preparation method of cyanamide provided by the application comprises the following steps:
[0007] S1: mixing lime nitrogen and water to perform a first reaction to obtain a first reaction product;
[0008] S2: introducing carbon dioxide into the first reaction product to carry out a second reaction to obtain a second reaction product, wherein the second reaction temperature is greater than 8° C.;
[0009] S3: adjusting the pH of the second reaction product to 5-6.5 with an inorganic acid and filtering;
[0010] S4: Concentrate the filtrate after filtering in step S3 to obtain a material containing cyanamide.
[0011] In some embodiments, the inorganic acid is selected from one or more of formic acid, acetic acid and dilute nitric acid.
[0012] In some embodiments, in step S1, the temperature of the first reaction is 5°C-30°C, for example, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or any value therebetween. In some embodiments, the temperature of the first reaction is 10°C-20°C.
[0013] In some embodiments, in step S1, the first reaction time is 0.5 h-3 h. In some embodiments, the first reaction time is 1-2 h.
[0014] In the present application, before the carbon dioxide gas is introduced, the lime nitrogen and water are mixed to perform a first reaction, and the lime nitrogen and water are fully reacted after being evenly stirred, so as to ensure that the carbon dioxide can react quickly and improve the reaction efficiency.
[0015] In some embodiments, in step S1, the mass ratio of lime nitrogen to water is 1:2-1:10, for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or any value therebetween. In some embodiments, the mass ratio of lime nitrogen to water is 1:3-1:8, for example, 1:5.
[0016] In some embodiments, in step S2, the temperature of the second reaction is 9°C-28°C, for example, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C or any value therebetween. In some embodiments, the temperature of the second reaction is 10°C-20°C. In some embodiments, the temperature of the second reaction is 10°C-15°C. When the temperature of the second reaction is too high, the reaction speed is too fast and the reaction with carbon dioxide is insufficient, and the reaction yield is low. When the temperature is too low, the reaction speed is slow, the energy consumption is high, and the production cost is high.
[0017] In some embodiments, in step S2, the second reaction time is 1 h-10 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h or 9 h. In some embodiments, the second reaction time is 3 h-8 h.
[0018] In some embodiments, in step S2, the introduction speed of carbon dioxide is 0.5L / h-15L / h, for example, 1L / h, 2L / h, 3L / h, 4L / h, 5L / h, 6L / h, 7L / h, 8L / h, 9L / h, 10L / h, 11L / h, 12L / h, 13L / h, 14L / h or any value therebetween. When the introduction speed of carbon dioxide is too high, the reaction is insufficient, resulting in a decrease in the purity of the generated cyanamide and a large loss of carbon dioxide. When the speed is too low, the reaction speed is slow, the reaction time is prolonged, and the impurity dicyandiamide increases.
[0019] In some embodiments, in step S2, the carbon dioxide is introduced within a speed of 3-8 hours, for example, within 4 hours, 5 hours, 6 hours or 7 hours, preferably within 3-5 hours.
[0020] In some embodiments, in step S2, the mass ratio of the amount of carbon dioxide fed in to the lime nitrogen is 0.5:1-1.1:1, for example, 0.51:1, 0.53:1, 0.55:1, 0.57:1, 0.59:1, 0.6:1, 0.61:1, 0.63:1, 0.65:1, 0.67:1, 0.69:1, 0.7:1, 0.71:1, 0.73:1, 0.75:1, 0.77:1, 0.79:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1.00:1, 1.05:1 or any value therebetween. In some embodiments, the mass ratio of the amount of carbon dioxide fed in to the lime nitrogen is 0.55-1.1:1. In some embodiments, the mass ratio of the amount of carbon dioxide introduced to the lime nitrogen is 0.55-0.8:1.
[0021] In some embodiments, in step S2, introducing carbon dioxide into the first reaction product comprises: introducing carbon dioxide into the first reaction product so that the pH of the reaction product is lower than 9.0, and continuing to introduce carbon dioxide for 5 min-40 min, such as 10 min, 15 min, 20 min, 25 min, 30 min or 35 min, preferably 10 min-30 min after the pH of the reaction product is lower than 9.0. Continuing to introduce carbon dioxide after the pH of the reaction product is lower than 9.0 can further improve the reaction efficiency and thus improve the reaction purity.
[0022] In some embodiments, in step S3, the pH of the second reaction product is adjusted to 5.5-6.0 with an inorganic acid and then filtered.
[0023] In some embodiments, in step S3, water is used for filtration.
[0024] In some embodiments, in step S4, the concentration is negative pressure concentration.
[0025] In some embodiments, the concentration temperature is 25°C-50°C, for example, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or any value therebetween. In some embodiments, the concentration temperature is 35°C-45°C. When the concentration temperature is too high, the impurities of the product dicyandiamide will increase. When the temperature is too low, the equipment requirements are high, the energy consumption is large, and the investment and production costs increase.
[0026] In some embodiments, the concentration is performed using a vacuum oil pump.
[0027] In some embodiments, the mass content of cyanamide in the material containing cyanamide is 30%-31%, for example, 30.1%, 30.2%, 30.3%, 30.4%, 30.5%, 30.6%, 30.7%, 30.8% or 30.9%.
[0028] In some embodiments, the mass content of dicyandiamide in the material containing cyanamide is 0.01%-2%, for example, 0.03%, 0.05%, 0.07%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.5%, 0.7%, 1% or 1.5%.
[0029] The beneficial effects of this application are:
[0030] (1) The method for preparing cyanamide provided in the present application controls the reaction rate and reaction temperature to make the reaction more complete, the by-products obtained are small, and the product yield and purity are high.
[0031] (2) The present application uses inorganic acid, especially formic acid, for acidification. Formic acid is relatively stable, has a small molecular weight, requires a small amount of addition, has little impact on purity, and has less environmental pollution than acids such as phosphoric acid. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. The specific embodiments described here are only used to explain the present application and are not intended to constitute any limitation to the present application.
[0033] Unless otherwise specified, % in the following examples and comparative examples represents mass percentage.
[0034] Example 1
[0035] Add 400g of water to a four-necked bottle, cool it to 10℃-15℃, add 80g of lime nitrogen at one time, keep warm for 1h after adding, and introduce carbon dioxide at a rate of 5.6L / h to ensure that the temperature is 10℃-15℃ when the carbon dioxide gas is introduced. After the pH of the material is below 9 (about 4h), continue to introduce carbon dioxide for 20min. Then add formic acid to the material, adjust the pH to 5.8 and filter the material. The mass ratio of the amount of carbon dioxide introduced to the lime nitrogen is 0.58:1.
[0036] The filter cake was filtered and rinsed with 40 g of water to obtain 413 g of filtrate, which had a small amount of white turbidity and no other color.
[0037] The filtrate was tested, and the cyanamide content in the filtrate was 6.62%, and the dicyandiamide content was 0.01%. The filtrate was concentrated by vacuum using an oil pump, and the temperature was controlled at 35°C-45°C, and concentrated to a cyanamide content of 30.5%, to obtain 88.9g of material. The dicyandiamide content in the material was 0.06%, and the molar yield of cyanamide was 98.3%.
[0038] Example 2
[0039] The only difference from Example 1 is that the temperature when the carbon dioxide gas is introduced is 18°C-20°C.
[0040] The filtrate finally obtained has a cyanamide content of 5.3% and a dicyandiamide content of 0.5%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-45°C, and the cyanamide content is concentrated to 30.3%, thereby obtaining 70.6 g of material. The dicyandiamide content in the material is 3.2%, and the molar yield of cyanamide is 76.3%.
[0041] Example 3
[0042] The only difference from Example 1 is that the temperature when the carbon dioxide gas is introduced is 23°C-25°C.
[0043] The filtrate finally obtained has a cyanamide content of 4.2% and a dicyandiamide content of 1.1%. The filtrate is concentrated by an oil pump under vacuum, and the temperature is controlled at 35°C-45°C, and concentrated to a cyanamide content of 30.1%, to obtain 51.3 g of material. The dicyandiamide content in the material is 6.8%, and the molar yield of cyanamide is 58.1%.
[0044] Example 4
[0045] The only difference from Example 1 is that the rate of introducing carbon dioxide gas is 10 L / h.
[0046] The filtrate finally obtained has a cyanamide content of 4.2% and a dicyandiamide content of 0.02%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-45°C, and the cyanamide content is concentrated to 30.3%, thereby obtaining 55.3 g of material. The dicyandiamide content in the material is 0.13%, and the molar yield of cyanamide is 63.2%.
[0047] Example 5
[0048] The only difference from Example 1 is that the rate of introducing carbon dioxide gas is 3.5 L / h.
[0049] The final filtrate has a cyanamide content of 4.5% and a dicyandiamide content of 0.01%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-45°C, and the cyanamide content is 30.2%, to obtain 60.5 g of material. The dicyandiamide content in the material is 0.08%, and the molar yield of cyanamide is 76.3%.
[0050] Example 6
[0051] The only difference from Example 1 is that acetic acid is added to the material to adjust the pH of the material to 5.8.
[0052] The filtrate finally obtained has a cyanamide content of 6.61% and a dicyandiamide content of 0.01%. The filtrate is concentrated by an oil pump under vacuum, and the temperature is controlled at 35°C-45°C, and concentrated to a cyanamide content of 30.1%, to obtain 87.6g of material. The dicyandiamide content in the material is 0.09%, and the molar yield of cyanamide is 97.8%.
[0053] Example 7
[0054] The only difference from Example 1 is that dilute nitric acid is added to the material to adjust the pH of the material to 5.8.
[0055] The final filtrate has a cyanamide content of 6.63% and a dicyandiamide content of 0.01%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-40°C, and the cyanamide content is concentrated to 30.3%, thereby obtaining 89.5 g of material. The dicyandiamide content in the material is 0.15%, and the molar yield of cyanamide is 98.1%.
[0056] Example 8
[0057] The only difference from Example 1 is that the filtrate is concentrated by vacuum using an oil pump, the temperature is controlled at 25°C-30°C, and the filtrate is concentrated to a cyanamide content of 30.5%, to obtain 85.6 g of material. The dicyandiamide content in the material is 0.56%, and the molar yield of cyanamide is 96.2%.
[0058] Example 9
[0059] The only difference from Example 1 is that the filtrate is concentrated by vacuum using an oil pump, the temperature is controlled at 50°C-55°C, and the filtrate is concentrated to a cyanamide content of 30.2%, to obtain 81.2 g of material. The dicyandiamide content in the material is 1.32%, and the molar yield of cyanamide is 86.5%.
[0060] Example 10
[0061] The only difference from Example 1 is that after the pH of the material reaches below 9 (about 4 hours), carbon dioxide is not introduced further, and formic acid is directly added to the material to adjust the pH to 5.8.
[0062] The final filtrate has a cyanamide content of 6.36% and a dicyandiamide content of 0.01%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-45°C, and the cyanamide content is 30.2%, thereby obtaining 85.3 g of material. The dicyandiamide content in the material is 0.07%, and the molar yield of cyanamide is 93.6%.
[0063] Comparative Example 1
[0064] The only difference from Example 1 is that 400 g of water is added into a four-necked bottle, the temperature is lowered to 10° C.-15° C., the same amount of lime nitrogen is added thereto at one time, and then carbon dioxide is immediately introduced.
[0065] The filtrate finally obtained has a cyanamide content of 3.36% and a dicyandiamide content of 0.15%. The filtrate is concentrated by an oil pump under vacuum, the temperature is controlled at 35°C-45°C, and the cyanamide content is concentrated to 30.3%, thereby obtaining 49.6 g of material. The dicyandiamide content in the material is 1.86%, and the molar yield of cyanamide is 53.6%.
[0066] Comparative Example 2
[0067] The only difference from Example 1 is that the temperature when the carbon dioxide gas is introduced is 5°C-8°C.
[0068] The filtrate finally obtained has a cyanamide content of 2.6% and a dicyandiamide content of 0.01%. The filtrate is concentrated by vacuum using an oil pump, and the temperature is controlled at 35°C-45°C, and concentrated to a cyanamide content of 30.6%, to obtain 35.5 g of material. The dicyandiamide content in the material is 0.08%, and the molar yield of cyanamide is 39.2%.
[0069] The technical solution of the present application is not limited to the above-mentioned specific embodiments, and all technical variations made according to the technical solution of the present application fall within the protection scope of the present application.
Claims
1. A method for preparing cyanamide, comprising the following steps: S1: mixing lime nitrogen and water to perform a first reaction to obtain a first reaction product; S2: introducing carbon dioxide into the first reaction product to carry out a second reaction to obtain a second reaction product, wherein the second reaction temperature is greater than 8° C.; S3: adjusting the pH of the second reaction product to 5-6.5 with an inorganic acid and filtering; S4: Concentrating the filtrate after filtering in step S3 to obtain a material containing cyanamide, Preferably, the inorganic acid is selected from one or more of formic acid, acetic acid and dilute nitric acid.
2. The preparation method according to claim 1, characterized in that: In step S1, the temperature of the first reaction is 5°C-30°C, preferably 10°C-20°C; and / or The time of the first reaction is 0.5h-3h, preferably 1-2h.
3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the mass ratio of lime nitrogen to water is 1:2-1:10, preferably 1:3-1:
8.
4. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the temperature of the second reaction is 9°C-28°C, preferably 10°C-20°C; and / or In step S2, the second reaction time is 1 h-10 h, preferably 3 h-8 h.
5. The preparation method according to any one of claims 1 to 4, characterized in that: In step S2, the rate of introduction of carbon dioxide is 0.5 L / h-15 L / h, preferably 1 L / h-10 L / h, more preferably 5 L / h-7 L / h; and / or The mass ratio of the amount of carbon dioxide introduced to the lime nitrogen is 0.5:1-1.1:1, preferably 0.55:1-0.8:
1.
6. The preparation method according to any one of claims 1 to 5, characterized in that: In step S2, introducing carbon dioxide into the first reaction product comprises: introducing carbon dioxide into the first reaction product to make the pH of the reaction product lower than 9.0, and after the pH of the reaction product is lower than 9.0, continuing to introduce carbon dioxide for 5 min-40 min, preferably 10 min-30 min.
7. The preparation method according to any one of claims 1 to 6, characterized in that: In step S3, the pH of the second reaction product is adjusted to 5.5-6.0 with an inorganic acid and then filtered; and / or Filtration was performed using water.
8. The preparation method according to any one of claims 1 to 7, characterized in that: In step S4, the concentration is negative pressure concentration.
9. The preparation method according to claim 8, characterized in that: The concentration temperature is 25°C-50°C, preferably 35°C-45°C.
10. The preparation method according to any one of claims 1 to 9, characterized in that: In the material containing cyanamide, the mass content of cyanamide is 30%-31%, and the mass content of dicyandiamide is 0.01%-2%.