Synthesis method of melam

Abstract

The invention relates to the technical field of synthesis of carbon nitride flame-retardant materials, and particularly discloses a synthesis method of melam, which comprises the following steps: by taking cyanuric chloride as a raw material, carrying out ammoniation and coupling to obtain a bis-triazine intermediate, and carrying out sealed ammoniation on the bis-triazine intermediate by using ammonia water to obtain melam; the optimal potassium tert-butoxide enables the BDCAT to be obtained at the yield of more than 60% in the second-step reaction, the ammonia water ammoniation process used in the third-step reaction is relatively safe, the synthesis method is simple and efficient, and the harsh requirement of a high-temperature and high-pressure method on equipment is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of carbon nitride flame retardant materials, in particular to a synthesis method of melam. Background Art

[0002] Melam has great potential application value as a carbon nitride flame retardant due to its higher thermal stability. Most of its synthesis methods require high temperature and high pressure conditions ( Eur. J. Inorg. Chem. 2025, 28, e202500240); ; ; ; ; Patent US 2475709 describes a method for heating melamine to 205°C to produce melam, but the actual reaction does not stop at the melam stage but continues to condense into melem.

[0003] Patent CN 1067062 C discloses a method for preparing melam, which involves heating a mixture of melamine and p-toluenesulfonic acid at 290° C. to generate melam p-toluenesulfonate. This method has high energy consumption and high equipment requirements. Summary of the Invention

[0004] The object of the present invention is to provide a method for synthesizing melam by coupling cyanuric chloride as a raw material and then aminating it with ammonia water, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a method for synthesizing melam, and the process route is: ; ; The synthetic method of melam specifically comprises the following steps: (1) Add cyanuric chloride to a solvent and stir, then dropwise add ammonia water. After the amination reaction is complete, add water, filter, and dry to obtain DCAT. (2) Add DCAT to the solvent and stir, add cyanuric chloride, control the temperature at 15-20°C, add alkali, keep the temperature for 4 hours, then add water and stir for 0.5 hours, filter, and dry to obtain BDCAT; (3) Add BDCAT to the sealed tube, add the solvent and stir, add ammonia water, seal, react at room temperature for 0.5-1h, then heat to 100-110℃ and react for 8-37h, cool to room temperature, add hot water and stir, filter, and dry to obtain Melam.

[0006] Furthermore, in step (1), the molar ratio of the ammonia water to the cyanuric chloride is 2.2:1-2.5:1, and the mass ratio of the cyanuric chloride to the solvent is 1:2.3-2.4.

[0007] Furthermore, in step (1), the solvent is one or more of acetonitrile, acetone, tetrahydrofuran, methanol, ethanol, propanol, and isopropanol.

[0008] Furthermore, in step (1), the temperature of the amination reaction is 0±5° C., and the time of the amination reaction is 4 h.

[0009] Furthermore, in step (2), the molar ratio of DCAT, cyanuric chloride and alkali is 1:1:1 to 1:1:1.1, and the mass ratio of DCAT to solvent is 1:3.2 to 1:2.6.

[0010] Furthermore, in step (2), the solvent is one or more of tetrahydrofuran, dioxane, acetonitrile, and acetone; and the base is one or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, potassium carbonate, sodium carbonate, N,N-diisopropylethylamine, and triethylamine.

[0011] Preferably, in step (2), the solvent is tetrahydrofuran, and the base is potassium tert-butoxide.

[0012] Furthermore, in step (2), the temperature of the insulation reaction is 15-20° C., and the insulation reaction time is 4 hours.

[0013] Furthermore, in step (3), the molar ratio of BDCAT to aqueous ammonia is 1:41-42, and the mass ratio of BDCAT to solvent is 1:10.

[0014] Furthermore, in step (3), the solvent is any one or more of dioxane, tetrahydrofuran, acetonitrile, and acetone.

[0015] Preferably, in step (3), the solvent is dioxane.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an organic synthesis method for melam, which uses cyanuric chloride as a raw material, enhances the leaving ability of the leaving group, and obtains melam through a simple and efficient three-step conventional reaction. The preferred potassium tert-butoxide enables BDCAT to be obtained in the second step with a yield of 60%. The third step uses an ammonia aqueous ammonia process, which is relatively safe and avoids the stringent equipment requirements of traditional high-temperature and high-pressure methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the synthetic route of the present invention; Figure 2The figure is the hydrogen nuclear magnetic resonance spectrum of the product melam of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0019] Step (1), synthesis of 2-amino-4,6-dichloro-1,3,5-triazine (DCAT): Add 200 g (1.085 mol) of cyanuric chloride and 600 mL of acetonitrile to the reaction flask and stir. Add 184.7 g (2.7 mol) of 25% aqueous ammonia dropwise at 0±5°C over 3 h. Maintain the temperature and continue stirring for 1 h. After TLC, check that the reaction is complete. Add 250 mL of ice water dropwise, filter under reduced pressure, and rinse with 300 mL of water. Dry the resulting solid at 60°C for 6 h to obtain 161.83 g of DCAT as a white solid with a yield of 90.4%. LC-MS m / z : 165.1,167.0 {[M+H] +}.

[0020] Step (2), Synthesis of 4,6-dichloro-N-(4,6-dichloro-1,3,5-triazin-2-yl)-1,3,5-triazin-2-amine (BDCAT): Add 15.8 g (0.096 mol) of DCAT and 50 mL of tetrahydrofuran to a reaction flask, stir, then add 17.66 g (0.096 mol) of cyanuric chloride. Add 11.82 g (0.1 mol) of potassium tert-butoxide dissolved in 100 mL of tetrahydrofuran dropwise at 15-20°C over 50 min. Keep warm and react for 3.5 h. TLC analysis shows that the reaction is essentially complete. Add 500 mL of ice water dropwise and stir for 30 min. Filter under reduced pressure and rinse with 50 mL of water. The resulting solid is dried at 60°C for 4 h to obtain 18.37 g of BDCAT as a white solid with a yield of 61.3%. LC-MS analysis m / z : 312.0,313.9,315.9 {[M+H] +}.

[0021] Step (3), Synthesis of N2-(4,6-diamino-1,3,5-triazine-2-yl)-1,3,5-triazine-2,4,6-triamine (Melam): 4 g (12.8 mmol) of BDCAT and 40 mL of dioxane were added to a sealed tube, followed by 40 mL (0.53 mol) of 25% aqueous ammonia. The tube was sealed and stirred at room temperature for 0.5 h. The temperature was then raised to 100 °C and the reaction was continued for 37 h. The tube was cooled to room temperature, and 100 mL of hot water was added and stirred for 20 min. The tube was filtered under reduced pressure and rinsed with 50 mL of hot water (80-90 °C). The resulting solid was dried at 100 °C to obtain 2.6 g of Melam, a white solid, with a yield of 86.4%. 1 H NMR (400 MHz, DMSO- d 6) δ 9.65 (s, 1H), 6.64 (s, 8H); LC-MS m / z : 236.03 {[ M+H] +}, H NMR spectrum such as Figure 2 shown. Example 2

[0022] Step (1), synthesis of 2-amino-4,6-dichloro-1,3,5-triazine (DCAT): Add 400 g (2.17 mol) of cyanuric chloride and 1.2 L of acetonitrile to the reaction flask and stir. Add 325.2 g (4.77 mol) of 25% aqueous ammonia dropwise at 0±5°C over 3 h. Maintain the temperature and continue stirring for 1 h. After TLC, confirm the completion of the reaction. Add 600 mL of ice water dropwise, filter under reduced pressure, and rinse with 300 mL of water. Dry the resulting solid with air at 60°C for 6 h to obtain 325.28 g of DCAT as a white solid with a yield of 90.89%.

[0023] Step (2), Synthesis of 4,6-dichloro-N-(4,6-dichloro-1,3,5-triazin-2-yl)-1,3,5-triazin-2-amine (BDCAT): Add 134 g (0.8 mol) of DCAT and 350 mL of dioxane to a reaction flask, stir, then add 150 g (0.8 mol) of cyanuric chloride. Add 98.7 g (0.88 mol) of potassium tert-butoxide dissolved in 400 mL of tetrahydrofuran dropwise at 15-20°C over 1.5 h. Keep warm for 2.5 h. TLC analysis shows that the reaction is essentially complete. Add 1.5 L of ice water dropwise and stir for 0.5 h. Filter under reduced pressure and rinse with 500 mL of water. Dry the resulting solid at 60°C for 4 h to obtain 151 g of BDCAT as a white solid in a yield of 60.56%.

[0024] Step (3), Synthesis of N2-(4,6-diamino-1,3,5-triazine-2-yl)-1,3,5-triazine-2,4,6-triamine (Melam) 20 g (64 mmol) of BDCAT and 200 mL of dioxane were added to a sealed tube, followed by 200 mL (2.67 mol) of 25% aqueous ammonia. The tube was sealed and stirred at room temperature for 1 h. The temperature was then raised to 110 °C and the reaction was continued for 8 h. The tube was then cooled to room temperature, 500 mL of hot water was added and stirred for 30 min, and the mixture was filtered under reduced pressure and rinsed with 200 mL of hot water. The resulting solid was dried at 100 °C to obtain 14 g of white solid Melam with a yield of 93%. Comparative Example

[0025] Step (1), synthesis of 2-amino-4,6-dichloro-1,3,5-triazine (DCAT): Add 60 g (0.3 mol) of cyanuric chloride and 0.2 L of acetonitrile to the reaction flask and stir. Add 110.4 g (1.6 mol) of 25% aqueous ammonia dropwise at 0±5°C over 3 h. Maintain the temperature and continue stirring for 1 h. After TLC detection, the reaction is complete. Add 600 mL of ice water dropwise, filter under reduced pressure, and rinse with 100 mL of water. The resulting solid is dried under forced air at 60°C for 6 h to obtain 20.2 g of DCAT as a white solid with a yield of 93.5% (including disubstituted by-products).

[0026] Step (2), Synthesis of 4,6-dichloro-N-(4,6-dichloro-1,3,5-triazin-2-yl)-1,3,5-triazin-2-amine (BDCAT): To a reaction flask, add 5.16 g (0.0313 mol) of DCAT and 75 mL of acetone, stir, then add 6.34 g (0.0344 mol) of cyanuric chloride. Add 1.25 g (0.0313 mol) of sodium hydroxide dissolved in 10 mL of water dropwise at 8-15°C over 10 minutes. Incubate for 2.5 hours. TLC analysis indicates that the reaction is stable in the middle. Add water, extract with methyl tert-ether, dry over sodium sulfate, concentrate, and filter by column chromatography to obtain 1 g of BDCAT as a white solid (10.2% yield).

[0027] Step (3), Synthesis of N2-(4,6-diamino-1,3,5-triazine-2-yl)-1,3,5-triazine-2,4,6-triamine (Melam): 20 g (64 mmol) of BDCAT and 40 mL (0.535 mol) of 25% aqueous ammonia were added to the sealed tube. The tube was sealed and heated to 100 °C for 9 h. The reaction was detected to be incomplete.

[0028] It is to be noted that the terms such as first and second, etc. are used herein merely to differentiate one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Also, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0029] It is to be noted that the above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. For those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements all fall within the protection scope of the claims of the present application.

Claims

1. A method for synthesizing melam, characterized in that: The following steps are involved: (1) Add cyanuric chloride to a solvent and stir, add aqueous ammonia dropwise, add water after the amination reaction is complete, filter, and dry to obtain DCAT; ； (2) DCAT was added to the solvent and stirred, cyanuric chloride was added, the temperature was controlled at 15-20°C, alkali was added, the reaction was kept warm, and then water was added and stirred for 0.5 h, filtered, and dried to obtain BDCAT; ； (3) Add BDCAT to a sealed tube, add a solvent and stir, add ammonia water, seal, and react at room temperature for 0.5-1 hour, then heat to 100-110°C and react for 8-37 hours, cool to room temperature, add hot water and stir, filter, and dry to obtain Melam; 。 2. The method for synthesizing melam according to claim 1, wherein: In step (1), the molar ratio of the ammonia water to the cyanuric chloride is 2.2:1-2.5:1, and the mass ratio of the cyanuric chloride to the solvent is 1:2.3-2.

4.

3. The method for synthesizing melam according to claim 2, wherein: The solvent is one or more of acetonitrile, acetone, tetrahydrofuran, methanol, ethanol, propanol, and isopropanol.

4. The method for synthesizing melam according to claim 1, wherein: In step (1), the temperature of the amination reaction is 0±5° C., and the time of the amination reaction is 4 h.

5. The method for synthesizing melam according to claim 1, wherein: In step (2), the molar ratio of DCAT, cyanuric chloride and alkali is 1:1:1 to 1:1:1.1, and the mass ratio of DCAT to solvent is 1:3.2 to 1:2.

6.

6. The method for synthesizing melam according to claim 5, wherein: The solvent is one or more of tetrahydrofuran, dioxane, acetonitrile, and acetone; the base is one or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, potassium carbonate, sodium carbonate, N,N-diisopropylethylamine, and triethylamine.

7. The method for synthesizing melam according to claim 6, wherein: The solvent is tetrahydrofuran, and the base is potassium tert-butoxide.

8. The method for synthesizing melam according to claim 1, wherein: In step (2), the temperature of the insulation reaction is 15-20° C., and the insulation reaction time is 4 hours.

9. The method for synthesizing melam according to claim 1, wherein: In step (3), the molar ratio of BDCAT to aqueous ammonia is 1:41-42, and the mass ratio of BDCAT to solvent is 1:

10.

10. The method for synthesizing melam according to claim 8, characterized in that: In step (3), the solvent is any one or more of dioxane, tetrahydrofuran, acetonitrile, and acetone.

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