Method for preparing methyl cyanocarbamate from cyanamide
The application of amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst has solved the problems of equipment corrosion, high-salt wastewater, numerous byproducts, and high energy consumption in the traditional preparation of methyl cyanocarbamate, thus realizing the efficient and environmentally friendly synthesis of methyl cyanocarbamate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-12
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional methyl cyanurate preparation processes suffer from severe equipment corrosion, difficulty in treating high-salt wastewater, numerous byproducts, high energy consumption, and cumbersome process steps.
Using an amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst, methyl chloroformate was added dropwise to react with cyanamide by controlling the pH value and stirring rate. Combined with catalyst regeneration, impurity removal was achieved during the reaction, reducing the formation of byproducts.
It reduces equipment corrosion and high-salt wastewater problems, improves product purity and yield, simplifies the process flow, and achieves green synthesis.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of chemical synthesis, and more specifically, relates to a method for preparing methyl cyanurate from cyanamide. Background Technology
[0002] Methyl cyanurate is an important intermediate in the preparation of fungicides carbendazim and benomyl. Traditionally, the main problems in the preparation process of methyl cyanurate include: 1. Severe equipment corrosion: Traditional processes use strong alkalis such as NaOH and KOH as catalysts, which causes alkali embrittlement, or caustic embrittlement, in metal equipment. Low carbon steel and ordinary low alloy steel are extremely prone to stress corrosion in hot concentrated alkali solutions, resulting in a shortened service life of the equipment.
[0003] 2. High-salinity wastewater is difficult to treat: The COD value of wastewater generated by traditional processes is usually >10000mg / L, mainly from unreacted liquid alkali and by-product salts, such as CaCl2 and NaCl, with a salinity >10%, resulting in high treatment costs.
[0004] 3. Numerous byproducts: In traditional processes, when the reaction temperature and pH are high, byproducts such as dicyandiamide are easily generated, with a content typically >5%, affecting product quality.
[0005] 4. High energy consumption: In traditional processes, catalyst regeneration requires high-temperature treatment (>150℃), which results in high energy consumption and low regeneration efficiency.
[0006] 5. Complex process steps: Traditional processes require the addition of buffer systems such as sodium carbonate / sodium bicarbonate, which makes the process complicated and increases the difficulty of wastewater treatment. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing methyl cyanurate from cyanamide, which is environmentally friendly and efficient.
[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing methyl cyanurate from cyanamide includes the following steps: S1. Prepare a cyanamide aqueous solution; S2. Add an amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst to an aqueous cyanamide solution and adjust the pH of the system to 8.0-9.0; wherein the amount of the catalyst is 35-55% of the mass of cyanamide. S3. In a constant temperature water bath at 35-45℃, methyl chloroformate is added dropwise to an aqueous solution of cyanamide while stirring. After the addition is complete, the reaction is continued to be stirred for 1-2 hours. The molar ratio of cyanamide to methyl chloroformate is (0.98-1.02):1. S4. After the reaction is complete, the product is cooled to 20-28℃; the filter cake and filtrate are collected by pressure filtration, and the filtrate is then extracted with an organic solvent to collect the organic phase and the aqueous phase; the organic phase is dried and distilled under reduced pressure to obtain methyl cyanocarbamate.
[0009] The molar ratio of cyanamide to methyl chloroformate in this technical solution depends on the inhibitory effect of the bifunctional mesoporous SBA-15 catalyst on the hydrolysis of methyl chloroformate. Traditional liquid alkali processes cannot control the hydrolysis side reactions and must adopt a feeding strategy of 5%-15% excess methyl chloroformate.
[0010] Furthermore, the preparation of the amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst includes the following steps: X1. Carrier pretreatment: Immerse the SBA-15 carrier in HCl solution for 20-30 hours to remove surface impurities and template agent residues; then calcine at 500-600℃ for 4-6 hours to activate the hydroxyl groups on the carrier surface; and then vacuum dry to obtain the pretreated SBA-15 carrier. X2. Grafting of amino functional groups: Pretreated SBA-15 was dispersed in anhydrous ethanol, 3-aminopropyltriethoxysilane was added, the pH was adjusted to 4-5, and the mixture was refluxed at 50-70℃ for 20-28 hours to obtain amino-modified SBA-15. X3. Grafting of quaternized functional groups: Aminated SBA-15 is dispersed in toluene, hexadecane bromo and silane coupling agents containing epoxy or amino groups are added, the pH is adjusted to 6.5-7.5, and the reaction is refluxed at 50-70℃ for 20-28 hours to obtain amino-quaternary ammonium salt bifunctionalized SBA-15 catalyst. X4. Heat treatment: The amino-quaternary ammonium salt bifunctionalized SBA-15 catalyst is dried under vacuum at 50-60℃.
[0011] Further, in step X1, the molar concentration of the HCl solution is 0.5-1.5 mol / L; the vacuum drying temperature is 50-70℃, and the time is 10-14 hours.
[0012] In step X2, the main purpose of vacuum drying at 50-60℃ is to prevent the decomposition of quaternary ammonium salt groups and the deactivation of amino groups.
[0013] Further, in step X3, the molar ratio of hexadecane bromide to amino group is (1-1.2):1; the amount of the silane coupling agent containing epoxy or amino groups is 5-15% of the mass of the aminated SBA-15, more preferably 8-12%.
[0014] Furthermore, the silane coupling agent containing epoxy or amino groups is at least one of KH550 and KH560.
[0015] SBA-15 is a highly ordered mesoporous silica material with uniform hexagonal mesoporous channels. The pore size can be precisely controlled by the synthesis conditions. It has excellent thermal and hydrothermal stability. It is rich in silanol groups (-Si-OH) and can be grafted with organic functional groups through silanization reaction.
[0016] The silane coupling agent containing epoxy or amino groups forms a rigid bridging structure on the catalyst surface, so that the distance between the retained amino and quaternary ammonium salt groups is ≥1.0 nm, thereby improving the conversion rate of quaternized functional groups and forming an ordered amino-spacer-quaternary ammonium salt structure.
[0017] Furthermore, the molar ratio of amino groups to quaternary ammonium salt groups constituting the catalyst is (2.5-3.5):1.
[0018] The catalyst has quaternary ammonium salt groups oriented on its outer surface, forming a cation adsorption layer that selectively adsorbs Cl released during the reaction. - The amino groups of the catalyst are oriented to be distributed on the inner surface and inside the pores, forming catalytic reaction active centers, promoting the reaction of cyanamide and methyl chloroformate, and forming a synergistic effect with the outer quaternary ammonium salt.
[0019] Furthermore, the SBA-15 support constituting the catalyst has a pore size of 5.8-6.8 nm.
[0020] Among them, cyanamide and methyl chloroformate have molecular dynamic diameters in the range of 5.8-6.8 nm, and can diffuse freely through the catalyst channels; while the byproduct dicyandiamide has a slightly larger molecular dynamic diameter, which theoretically would be confined outside the channels, thereby reducing the formation of byproducts.
[0021] Further, in step S1, the concentration of the cyanamide aqueous solution is 0.45-0.55 mol / L.
[0022] Further, in step S2, the quaternary ammonium salt groups constituting the catalyst adsorb Cl... - Maintain the pH of the reaction system at 8-9.
[0023] Furthermore, in step S3, the stirring speed is 200-300 rpm.
[0024] This stirring rate balances mass transfer efficiency and energy consumption while avoiding violent collisions of catalyst particles.
[0025] Further, in step S3, the methyl chloroformate is added dropwise over a period of 30-60 minutes. The dropwise addition time is directly proportional to the amount of cyanamide in the reaction system. If the dropwise addition time is too short, it may lead to excessively high local concentrations and accelerated side reactions; if the dropwise addition time is too long, it may prolong the reaction cycle and reduce efficiency. More preferably, the methyl chloroformate is added dropwise over a period of 40-50 minutes.
[0026] Further, in step S4, the organic solvent is selected from at least one of ethyl acetate, dichloromethane, diethyl ether, and toluene; the drying refers to drying with anhydrous magnesium sulfate or anhydrous sodium sulfate. More preferably, the organic solvent is ethyl acetate, and the drying refers to drying with anhydrous sodium sulfate. The combination of ethyl acetate and anhydrous sodium sulfate is optimal in terms of yield, purity, safety, environmental friendliness, and economy.
[0027] Furthermore, in step S4, the collected filter cake mainly contains catalyst, and the catalyst is regenerated and then reused in step S2.
[0028] Furthermore, the regeneration treatment of the catalyst includes the following steps: Y1. Immerse the catalyst in NaOH solution to remove the Cl adsorbed on the outer layer. - ; Y2. Wash with water until the pH of the filtrate is 6.5-7.5; Y3. Vacuum dry at 50-70℃ for 10-14 hours to restore the catalyst's activity.
[0029] Furthermore, in step Y1, the molar concentration of the NaOH solution is 0.5-0.6 mol / L, and the soaking time is 50-70 minutes.
[0030] A methyl cyanocarbamate is prepared by the above-described preparation method.
[0031] The beneficial effects of this invention are: (1) This invention reduces COD generation in wastewater by constructing an amino-quaternary ammonium salt bifunctionalized SBA-15 catalyst, thereby achieving green synthesis of methyl cyanocarbamate. This technology reduces the use of liquid alkali, not only solving the problems of equipment corrosion and high-salt wastewater in traditional processes, but also realizing the innovative concept of simultaneous reaction and impurity removal through the spatial arrangement design of the amino-quaternary ammonium salt bifunctional groups, improving product purity and yield, and greatly simplifying the process flow.
[0032] (2) The catalyst of the present invention constructs an outer quaternary ammonium salt group to adsorb Cl -The inner amino group catalyzes a bifunctional spatial arrangement structure. The outer quaternary ammonium salt, through a specific chemical reaction, covalently bonds quaternary ammonium salt groups to the outer surface of the SBA-15 support, forming a cation adsorption layer. This layer can selectively adsorb Cl- released during the reaction. - Effectively prevents Cl - Catalyst deactivation occurs due to accumulation within the pores. The inner amino groups on the inner surface and inside the pores of the SBA-15 support are grafted with amino groups via silane coupling agents, forming catalytically active centers that catalyze the reaction of cyanamide and methyl chloroformate. Protected by the quaternary ammonium salt outer layer, the inner amino groups maintain high catalytic activity while avoiding reaction with Cl-. - Direct contact leads to active site poisoning. The synergistic effect of the bifunctional groups enables the innovative concept of simultaneous reaction and impurity removal, and effectively suppresses the formation of the byproduct dicyandiamide through pore confinement, thus improving product purity. This design, by precisely controlling the introduction sequence of functional groups and reaction conditions, achieves the directional distribution of the two functional groups, avoiding the insufficient synergistic effect caused by the random distribution of functional groups in traditional bifunctional catalysts. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to specific embodiments, but the scope of protection of this invention is not limited thereto. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or according to the manufacturer's recommendations. Unless otherwise specified, all reagents and materials used are commercially available.
[0034] Raw material description: The SBA-15 used in this example and comparative examples 1-3 has a pore size of 6.2±0.1nm.
[0035] Example 1
[0036] A method for preparing methyl cyanurate from cyanamide includes the following steps: S1. Weigh 2.1g of cyanamide (purity ≥98%), dissolve it in 80mL of deionized water, and make up to 100mL to obtain 100mL of cyanamide aqueous solution with a molar concentration of 0.5mol / L. S2. Add 1g of amino-quaternary ammonium salt bifunctional mesoporous SBA-15 catalyst to the cyanamide aqueous solution; start stirring at 50 rpm for 10 minutes to allow the catalyst pores to fully adsorb cyanamide molecules; and record the pH changes of the system in real time by online pH monitoring.
[0037] The initial pH was measured to be 6.8-7.2. The pH was adjusted to 8.5±0.2 by adding 1.2 mL of 0.1 mol / L NaOH standard solution.
[0038] S3. Measure 3.8 mL of methyl chloroformate (purity ≥98%) and place it in a constant pressure dropping funnel. Add it dropwise to the cyanamide aqueous solution at a constant temperature of 40±1℃ while stirring at 200 rpm. The dropping time is controlled at 45±5 minutes, and the pH change is monitored simultaneously. After the dropping is completed, continue the reaction at 40℃ and 200 rpm for 1.5 hours.
[0039] Among them, the pH was simultaneously detected to remain between 8.2 and 8.7 throughout the process.
[0040] S4. After the reaction is complete, the product is transferred to a 15°C cold water bath and cooled to 25±2°C within 10 minutes. Then, stirring is stopped, and the mixture is allowed to stand for 5 minutes to allow the catalyst to settle naturally. The product is then filtered using a pre-weighed glass frit funnel (G3, pore size 10–15 μm) to separate the filter cake and filtrate. The filter cake is washed twice with 10 mL of deionized water. The filtrate and washings are then combined, and 40 mL of ethyl acetate is added for extraction to separate the organic and aqueous phases. The aqueous phase is then extracted once more with 20 mL of ethyl acetate. The organic phases are then combined, and 2 g of anhydrous sodium sulfate is added for drying for 30 minutes. Finally, the mixture is filtered and distilled under reduced pressure at 40°C and -0.095 MPa using a rotary evaporator to obtain methyl cyanurate.
[0041] The preparation method of the amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst is as follows: X1. Carrier pretreatment: Take 10g of SBA-15 and disperse it in 100mL of 1mol / L HCl solution and soak for 24 hours to remove surface impurities and template agent residue; then calcine the acid-washed SBA-15 at 550℃ for 5 hours to activate the hydroxyl groups on the carrier surface; then cool the calcined SBA-15 to room temperature in a desiccator and then vacuum dry it at 60℃ for 12 hours to obtain the pretreated SBA-15 carrier; X2. Grafting of amino functional groups: 5g of pretreated SBA-15 was dispersed in 100mL of anhydrous ethanol, and 2.5g of 3-aminopropyltriethoxysilane (APTES) was added. The pH was adjusted to 4.5 with dilute hydrochloric acid, and the mixture was refluxed at 60℃ for 24 hours to allow APTES to undergo a hydrolysis-condensation reaction with the hydroxyl groups on the surface of SBA-15. After the reaction was completed, the mixture was filtered and washed with anhydrous ethanol until the filtrate was colorless. The filtrate was then dried under vacuum at 60℃ for 12 hours to obtain aminoated SBA-15. X3. Grafting of quaternized functional groups: 5g of aminated SBA-15 was dispersed in 100mL of toluene, 1.5g of hexadecane bromide was added, and 0.5g of KH550 was added as a molecular spacer. The pH was adjusted to 7.0±0.1 with dilute hydrochloric acid, and the mixture was refluxed at 60℃ for 24 hours to allow the hexadecane bromide to undergo a quaternization reaction with the amino groups on the surface of aminated SBA-15. X4. Heat treatment: After the reaction is complete, filter the solution and wash it with toluene until the filtrate is colorless. Dry the solution under vacuum at 60°C for 12 hours to obtain the bifunctionalized SBA-15 catalyst.
[0042] Example 2
[0043] Compared with Example 1, the difference in this example is that step S3 in this example is as follows: S3. Measure 3.72 mL of methyl chloroformate and place it in a constant pressure dropping funnel. While stirring at 250 rpm, add it dropwise to the cyanamide aqueous solution at a constant temperature of 40±1℃. The addition time is controlled at 45±5 minutes, and the pH change is monitored simultaneously. The pH was found to be maintained at 8.0-9.0. After the addition is completed, continue the reaction at 40℃ and 250 rpm for 2 hours. Steps X2 and X3 in this embodiment are as follows: X2. Grafting of amino functional groups: 5g of pretreated SBA-15 was dispersed in 100mL of anhydrous ethanol, 2g of APTES was added, the pH was adjusted to 4.5, and the reaction was refluxed at 60℃ for 24 hours. After the reaction was completed, the mixture was filtered, washed with anhydrous ethanol until the filtrate was colorless, and dried under vacuum at 60℃ for 12 hours to obtain aminoated SBA-15. X3. Grafting of quaternized functional groups: 5g of aminated SBA-15 was dispersed in 100mL of toluene, 1.25g of hexadecane bromide was added, and 0.5g of KH550 was added as a molecular spacer. The pH was adjusted to 7.0±0.1, and the mixture was refluxed at 60℃ for 24 hours to allow the hexadecane bromide to undergo a quaternization reaction with the amino groups on the surface of the aminated SBA-15.
[0044] The remaining components, preparation steps, and parameters are all the same.
[0045] Example 3
[0046] Compared with Example 1, the difference in this example is that step S3 in this example is as follows: S3. Measure 3.72 mL of methyl chloroformate and place it in a constant pressure dropping funnel. While stirring at 300 rpm, add it dropwise to the cyanamide aqueous solution at a constant temperature of 40±1℃. The addition time is controlled at 45±5 minutes, and the pH change is monitored simultaneously. The pH was found to be maintained at 8.0-9.0. After the addition is completed, continue the reaction at 40℃ and 300 rpm for 2 hours. The catalyst in this embodiment is the catalyst used in Example 1, which is reused after regeneration. The regeneration process is as follows: Y1. Soak the catalyst used in Example 1 in 0.6 mol / L NaOH solution for 1 hour; Y2. Wash with water until the pH of the filtrate is close to neutral; Y3. Vacuum dry at 60℃ for 12 hours.
[0047] The catalyst recovery rate was measured to be 98.7%, and the activity retention rate was 99.2%. The remaining components, preparation steps, and parameters were all consistent.
[0048] Comparative Example 1
[0049] Compared to Example 1, this comparative example differs in that the catalyst used in this comparative example only undergoes amination treatment and not quaternization treatment; the remaining components, preparation steps, and parameters are the same. Specifically, in step S3, because Cl... - Accumulation caused the pH to plummet from 8.5 to 6.8.
[0050] Comparative Example 2
[0051] Compared to Example 1, this comparative example differs in that the catalyst used in this comparative example only underwent quaternization treatment and did not undergo amination treatment. All other components, preparation steps, and parameters remained the same.
[0052] Comparative Example 3
[0053] Compared with Example 1, the difference in this comparative example is that in step S3 of this comparative example, the amount of methyl chloroformate added is 4.18 mL, while the other components, preparation steps and parameters are the same.
[0054] Comparative Example 4
[0055] Compared with Example 1, the difference in this comparative example is that the SBA-15 used in step X1 of the catalyst preparation in this comparative example has a pore size of 5±0.2nm, while the other components, preparation steps and parameters are the same.
[0056] Comparative Example 5
[0057] A method for preparing methyl cyanurate from cyanamide includes the following steps: S1. Weigh 2.1g of cyanamide (purity ≥98%), dissolve it in 80mL of deionized water, and make up to 100mL to obtain 100mL of cyanamide aqueous solution with a molar concentration of 0.5mol / L. S2. Measure 3.8 mL of methyl chloroformate (purity ≥98%) and place it in a constant pressure dropping funnel. Add it dropwise to the cyanamide aqueous solution at a constant temperature of 40±1℃ while stirring at 200 rpm. The addition time is controlled at 45±5 minutes, and the pH change is monitored simultaneously. Since no alkali is added and HCl is generated, the pH is detected to drop to 5.0±0.5. S3. After the addition is complete, add 8.7 mL of 30% sodium hydroxide solution at a temperature below 45℃ to adjust the pH to 8.5±0.3; then keep warm at 45±2℃ for 1 hour to obtain an aqueous solution of methyl cyanurate. During this period, due to large pH fluctuations, it is necessary to continuously add 30% sodium hydroxide solution to adjust the pH, as it has no self-stabilizing ability. S4. After the reaction was completed, the mixture was cooled to 25°C, filtered to remove residue, and the filtrate was transferred to a separatory funnel. It was extracted twice with 40 mL of ethyl acetate to separate the organic and aqueous phases. The organic phases were then combined, dried for 30 minutes with 2 g of anhydrous sodium sulfate, filtered, and finally distilled under reduced pressure at 40°C and -0.095 MPa using a rotary evaporator to obtain methyl cyanurate. HPLC analysis showed a yield of 65.7% and a purity of 95.2%. The residue mainly consisted of CaCO3, which was found to be 1.8 g after drying.
[0058] The test results of the samples prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1 below.
[0059] The yield and purity of the reaction products were determined in accordance with GB / T601 standard and HPLC quantitative specifications. The mobile phase was acetonitrile:0.1% phosphoric acid aqueous solution = 80:20 (v / v), pH 3.0, flow rate 1.0 mL / min, column temperature 30℃, detection wavelength 254 nm, and injection volume 20 μL.
[0060] The COD determination of wastewater was performed according to GB / T11914-89 standard. The specific procedure was as follows: Take 20 mL of the aqueous phase obtained after filtration following the reaction, add 10 mL of 0.25 mol / L potassium dichromate standard solution, slowly add 30 mL of silver sulfate-sulfuric acid catalyst (containing 10 g Ag₂SO₄ per liter of concentrated sulfuric acid), add anti-bumping glass beads, reflux at 150℃ for 2 hours, cool, and titrate with 0.1 mol / L ferrous ammonium sulfate standard solution. The COD (mg / L) was calculated using the formula: COD = [(V₀-V₁)×C×8×1000] / Vs, where V₀ = blank consumption volume, V₁ = water sample consumption volume, C = ferrous ammonium sulfate concentration, and Vs = water sample volume.
[0061] Table 1
[0062] As shown in Table 1, compared with Comparative Examples 1-4, the methyl cyanurate obtained in Examples 1-3 maintains high yield and high purity while being more environmentally friendly. In Comparative Example 1, the lack of quaternary ammonium salt leads to... - Accumulation leads to an increase in dicyandiamide content; in Comparative Example 2, the lack of amino groups results in the absence of basic catalytic sites, ultimately leading to incomplete reaction; in Comparative Example 3, the excess of methyl chloroformate leads to Cl... -Accumulation requires additional alkali neutralization, ultimately producing more salt byproducts; in Comparative Example 4, the small pore size of the SBA-15 catalyst increases the diffusion resistance of the air islands, ultimately affecting the yield; in Comparative Example 5, the use of traditional soda ash to replace the catalyst results in a high-salt environment, which ultimately promotes the formation of dicyandiamide and produces solid residue CaCO3.
[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing methyl cyanurate from cyanamide, characterized in that, Includes the following steps: S1. Prepare a cyanamide aqueous solution; S2. Add an amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst to an aqueous cyanamide solution and adjust the pH of the system to 8.0-9.0; wherein the amount of the catalyst is 35-55% of the mass of cyanamide. S3. In a constant temperature water bath at 35-45℃, methyl chloroformate is added dropwise to an aqueous solution of cyanamide while stirring. After the addition is complete, the reaction is continued to be stirred for 1-2 hours. The molar ratio of cyanamide to methyl chloroformate is (0.98-1.02):
1. S4. After the reaction is complete, the product is cooled to 20-28℃; the filter cake and filtrate are collected by pressure filtration, and the filtrate is then extracted with an organic solvent to collect the organic phase and the aqueous phase; the organic phase is dried and distilled under reduced pressure to obtain methyl cyanocarbamate.
2. The method for preparing methyl cyanurate from cyanamide according to claim 1, characterized in that, The preparation of the amino-quaternary ammonium salt bifunctionalized mesoporous SBA-15 catalyst includes the following steps: X1. Carrier pretreatment: Immerse the SBA-15 carrier in HCl solution for 20-30 hours to remove surface impurities and template agent residues; then calcine at 500-600℃ for 4-6 hours to activate the hydroxyl groups on the carrier surface; and then vacuum dry to obtain the pretreated SBA-15 carrier. X2. Grafting of amino functional groups: Pretreated SBA-15 was dispersed in anhydrous ethanol, 3-aminopropyltriethoxysilane was added, the pH was adjusted to 4-5, and the mixture was refluxed at 50-70℃ for 20-28 hours to obtain amino-modified SBA-15. X3. Grafting of quaternized functional groups: Aminated SBA-15 is dispersed in toluene, hexadecane bromo and silane coupling agents containing epoxy or amino groups are added, the pH is adjusted to 6.5-7.5, and the reaction is refluxed at 50-70℃ for 20-28 hours to obtain amino-quaternary ammonium salt bifunctionalized SBA-15 catalyst. X4. Heat treatment: The amino-quaternary ammonium salt bifunctionalized SBA-15 catalyst is dried under vacuum at 50-60℃.
3. The method for preparing methyl cyanurate from cyanamide according to claim 2, characterized in that, In step X1, the molar concentration of the HCl solution is 0.5-1.5 mol / L; the vacuum drying temperature is 50-70℃ and the time is 10-14 hours; in step X3, the molar ratio of hexadecane bromo to amino group is (1-1.2):1; the amount of silane coupling agent containing epoxy or amino groups is 5-15% of the mass of aminated SBA-15.
4. The method for preparing methyl cyanurate from cyanamide according to claim 3, characterized in that, The silane coupling agent containing epoxy or amino groups is at least one of KH550 and KH560.
5. A method for preparing methyl cyanurate from cyanamide according to claim 1 or 2, characterized in that, The molar ratio of amino groups to quaternary ammonium salt groups constituting the catalyst is (2.5-3.5):1; the pore size of the SBA-15 support constituting the catalyst is 5.8-6.8 nm.
6. The method for preparing methyl cyanurate from cyanamide according to claim 1, characterized in that, In step S1, the concentration of the cyanamide aqueous solution is 0.45-0.55 mol / L; in step S2, the quaternary ammonium salt groups constituting the catalyst adsorb Cl... - The pH of the reaction system is maintained at 8-9; in step S3, the stirring speed is 200-300 rpm; the methyl chloroformate drop rate is 30-60 minutes.
7. The method for preparing methyl cyanurate from cyanamide according to claim 1, characterized in that, In step S4, the organic solvent is selected from at least one of ethyl acetate, dichloromethane, diethyl ether, and toluene; the drying refers to drying with anhydrous magnesium sulfate or anhydrous sodium sulfate; the collected filter cake mainly contains the catalyst, and the catalyst is regenerated and reused in step S2.
8. The method for preparing methyl cyanurate from cyanamide according to claim 7, characterized in that, The catalyst regeneration process includes the following steps: Y1. Immerse the catalyst in NaOH solution to remove the Cl adsorbed on the outer layer. - ; Y2. Wash with water until the pH of the filtrate is 6.5-7.5; Y3. Vacuum dry at 50-70℃ for 10-14 hours to restore the catalyst's activity.
9. The method for preparing methyl cyanurate from cyanamide according to claim 8, characterized in that, In step Y1, the molar concentration of the NaOH solution is 0.5-0.6 mol / L, and the soaking time is 50-70 minutes.
10. A methyl cyanocarbamate, prepared by the method described in any one of claims 1-9.