Preparation method of methyl cyanocarbamate

Abstract

The invention relates to a preparation method of methyl cyanocarbamate, and belongs to the technical field of synthesis of pesticide intermediates. The preparation method of the methyl cyanocarbamate comprises the following steps: carrying out hydrolysis reaction on lime nitrogen and deionized water to obtain suspension reaction liquid; continuously dropwise adding methyl chloroformate into the suspension reaction liquid under the protection of nitrogen; after dropwise adding, continuously carrying out heat preservation reaction; performing filter pressing on the reaction liquid, and collecting a filter cake and filtrate; extracting the filtrate with an organic solvent, and collecting an organic phase and a water phase; and drying the organic phase, and carrying out reduced pressure distillation to obtain the methyl cyanocarbamate. By optimizing the raw material ratio, precisely controlling the reaction conditions and implementing the closed-loop resource recovery strategy, not only are many problems existing in the traditional method solved, but also the purity and production efficiency of the product are remarkably improved; waste is reduced, and the working environment is improved; the cyclic utilization of resources is realized, the production cost is reduced, and the method has important application value and wide market prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of pesticide intermediate synthesis, and more specifically, relates to a method for preparing methyl cyanocarbamate. Background Technology

[0002] Methyl cyanurate is an important intermediate in the production of various agrochemicals, particularly as a key component of fungicides such as carbendazim. Research on its preparation methods has been a hot topic in the chemical industry. Traditional synthesis methods mainly rely on the calcium cyanamide process. However, this process has significant drawbacks, including but not limited to byproduct generation, severe equipment corrosion, and the production of large amounts of difficult-to-handle waste residue. Furthermore, traditional processes typically require complex separation steps to remove byproducts, increasing energy consumption and costs, and negatively impacting the environment.

[0003] In recent years, although some studies have attempted to improve production processes, such as by optimizing raw material ratios or improving reaction conditions to improve product quality and reduce pollution, many challenges remain. For example, large amounts of pH adjusters are still needed for neutralization, leading to increased wastewater treatment costs; or the control of reaction conditions is not precise enough, affecting product yield and quality. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing methyl cyanocarbamate, which features high purity and high production efficiency.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing methyl cyanurate includes the following steps: S1. Mix calcium cyanamide and deionized water at a mass ratio of 1:1.5-2.5 and carry out hydrolysis reaction at 30-40℃. When the reaction is finished, adjust the final pH to 11.5-12.0 to obtain a suspension reaction solution containing cyanamide, calcium hydroxide particles and calcium ions. S2. Heat the above suspension reaction solution to 45-50℃, and under nitrogen protection, continuously add methyl chloroformate dropwise, controlling the molar ratio of cyanamide to methyl chloroformate to be 1:1.03-1.08; during the reaction, maintain the pH of the system at 9.0-10.5 by adding a pH adjuster; temperature fluctuation ≤±1℃; after the addition is complete, continue to keep the reaction at this temperature for 40-90 minutes until the residual amount of cyanamide is <0.5%; S3. Filter the reaction solution obtained in step S2 at 45-55℃ and collect the filter cake and filtrate. S4. Extract the filtrate with an organic solvent and collect the organic phase and the aqueous phase. S5. Dry the organic phase and distill under reduced pressure to obtain methyl cyanocarbamate.

[0006] Further, in step S1, the mass ratio of calcium cyanamide to deionized water is 1:1.6-1.8; the hydrolysis reaction time is 80-130 minutes; the hydrolysis reaction is accompanied by stirring at a speed of 100-300 rpm; the pH is monitored in real time during the hydrolysis process, and the reaction is terminated when the pH reaches 11.5-12.0, or the final pH is adjusted to 11.5-12.0 by adding pH buffer solution.

[0007] Among these measures, strictly controlling the pH at the hydrolysis endpoint is beneficial in inhibiting the formation of dicyandiamide.

[0008] Further, the pH buffer solution is selected from a sodium carbonate solution with a mass percentage of 0.5-2.0 wt%.

[0009] Furthermore, in step S2, the dropping rate of methyl chloroformate is 0.8-1.2 mL / min; the pH adjuster is a sodium hydroxide solution.

[0010] In this process, the calcium hydroxide particles obtained in step S1 preferentially neutralize Cl in the system. - When calcium hydroxide particles are insufficient to maintain the pH of the system, a pH adjuster is added to continue maintaining the pH, which helps to save raw materials and costs.

[0011] Furthermore, the actual molar amount of sodium hydroxide accounts for 0.4-0.6% of the theoretical molar amount.

[0012] In this process, the theoretical number of moles of sodium hydroxide is equal to the number of moles of methyl chloroformate. The calcium hydroxide particles in step S1 provide the main alkali reserve, undertake the neutralization task of >99.4%, reduce the demand for exogenous sodium hydroxide from 100% in the traditional process to <1%, and provide dynamic control capability to solve the problems of calcium hydroxide dissolution kinetic lag and uneven spatial distribution, and ensure that the pH is accurately and stably maintained in the 9.0-10.5 window.

[0013] More preferably, in step S2, the pH of the system is maintained at 9.2-10.3 during the reaction process; and the reaction is continued at a constant temperature for 50-70 minutes after the addition is completed.

[0014] Further, in step S3, the components in the filter cake include CaCl2·2H2O and unreacted Ca(OH)2. After washing and drying the filter cake, calcium salt byproducts are obtained.

[0015] The calcium salt obtained after drying is mainly calcium chloride, which can be sold as a by-product, thereby increasing revenue and reducing costs.

[0016] Further, in step S4, the organic solvent is selected from toluene, dichloromethane, ethyl acetate or methyl tert-butyl ether; the volume ratio of the organic solvent to the filtrate is 1.2-1.8:1; the aqueous phase, after being decalcified by ion exchange resin, is used as deionized water and recycled for the hydrolysis process in step 1.

[0017] Furthermore, the ion exchange resin is a cation exchange resin, and after the aqueous phase is decalcified by the ion exchange resin, the calcium ion concentration is ≤20ppm and the conductivity is ≤60μS / cm.

[0018] The aqueous phase after decalcification is recycled for the hydrolysis process in step S1, which not only enables the recovery of water resources and trace amounts of cyanamide, but also further reduces costs and saves energy.

[0019] More preferably, the ion exchange resin is Dowex 50WX8 resin.

[0020] Further, in step S5, the drying refers to drying with anhydrous sodium sulfate or anhydrous magnesium sulfate, the amount of which is 3-8% of the mass of the organic phase, and the drying time is 20-40 minutes; the vacuum distillation is carried out under the conditions of heating bath temperature of 40-50℃ and system absolute pressure of 10-15 kPa.

[0021] Specifically, the vacuum distillation is carried out in a rotary evaporator, with the condenser cooling medium temperature ≤5℃. More preferably, the vacuum distillation employs a programmed temperature rise: first, the low-boiling-point solvent is removed at a heating bath temperature of 35-40℃ for 10-15 min, then the temperature is raised to a heating bath temperature of 45±3℃, and the target fraction is collected when the distillate vapor temperature stabilizes at 43-47℃.

[0022] A methyl cyanocarbamate is prepared by the above-described method for preparing methyl cyanocarbamate.

[0023] As mentioned above, methyl cyanocarbamate is used in the synthesis of carbendazim, whereby methyl cyanocarbamate is condensed with o-phenylenediamine to prepare carbendazim.

[0024] The beneficial effects of this invention are: This invention, by optimizing the raw material ratio, precisely controlling the reaction conditions, and implementing a closed-loop resource recovery strategy, not only solves many problems existing in traditional methods, but also significantly improves the purity of the product and production efficiency; reduces waste generation and improves the working environment; realizes the recycling of resources and reduces production costs, thus having significant application value and broad market prospects. Detailed Implementation

[0025] 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.

[0026] Raw material description: The industrial-grade calcium cyanamide used in this embodiment and the comparative example is the same, with a CaCN2 content of 55-60%.

[0027] Example 1

[0028] A method for preparing methyl cyanurate includes the following steps: S1. Weigh 100g of industrial-grade calcium cyanamide, add 170g of deionized water, and place in a reaction vessel; hydrolyze in a constant temperature water bath at 35±0.5℃ and 150rpm for 100 minutes, during which the pH naturally decreases; add 1mL of 1.0wt% Na2CO3 solution at the end of the hydrolysis by means of an online pH meter to control the pH at 11.8±0.1, thus obtaining a suspension reaction solution; The concentration of cyanamide was determined to be 10.2 wt% by HPLC. Therefore, the mass of cyanamide = cyanamide concentration × total mass of suspension reaction solution = 10.2 wt% × 270 g = 27.54 g. The molar mass of cyanamide is 42.041 g / mol. The molar number of cyanamide is calculated to be 27.54 g / 42.041 g / mol = 0.655 mol.

[0029] Calculate the solid content: Take 0.85g of the hydrolyzed suspension sample, dry it at 105℃ to constant weight according to GB / T6284, and calculate the solid content as 21.8%.

[0030] S2. The above suspension reaction solution is heated to 47±0.5℃, and methyl chloroformate is added dropwise at a rate of 1.0 mL / min under nitrogen protection. The molar ratio of cyanamide to methyl chloroformate is 1:1.05. The calculated molar amount of methyl chloroformate is 0.655 mol × 1.05 = 0.688 mol, and the molar mass of methyl chloroformate is 94.494 g / mol. Therefore, the calculated mass of methyl chloroformate is 0.688 mol × 94. 494 g / mol = 65 g, corresponding to a volume of 65 g / 1.22 g / mL = 53.3 mL; therefore, the dropping time is 53 ± 1 minutes; 30 wt% NaOH is added to maintain the pH at 9.4 ± 0.2; the amount of 30 wt% NaOH added is 0.45 g, accounting for 0.49% of the theoretical amount; after the dropping is completed, the reaction is kept at the temperature for 60 minutes, and the endpoint monitoring by HPLC shows that the cyanamide residue is 0.35% and the dicyandiamide derivative is 0.26%.

[0031] S3. Heat the reaction solution obtained in step S2 to 50±0.5℃, and then filter it while hot. The filter cloth has a pore size of 30μm to obtain a wet filter cake and a filtrate. The mass of the wet filter cake is 61.2g and the volume of the filtrate is 210mL. S4. The filter cake was washed twice with deionized water and dried at 105℃ to obtain a calcium salt byproduct with a mass of 58.9g. The filtrate was extracted with 315mL of toluene (filtrate:toluene = 1:1.5, v / v), and an organic phase and an aqueous phase were obtained after extraction. S5. The organic phase was dried with anhydrous sodium sulfate for 30 min, and then distilled under reduced pressure at 45℃ and 12 kPa to obtain 61.3 g of methyl cyanurate. The aqueous phase was treated with a Dowex 50WX8 cation exchange resin for decalcification, and the Ca content of the effluent was measured. 2+ With a concentration of 9 ppm, it can be used as deionized water with a conductivity of 45 μS / cm (25℃) and can be recycled for the hydrolysis process in step 1.

[0032] Example 2

[0033] S1. Weigh 100g of industrial-grade calcium cyanamide, add 170g of deionized water, and place it in a reaction vessel; hydrolyze in a constant temperature water bath at 35±0.5℃ and 150rpm for 90 minutes, during which the pH naturally decreases; add 0.6mL of 1.0wt% sodium carbonate solution via an online pH meter to adjust the endpoint pH to 11.5±0.1, thus obtaining a suspension reaction solution; The HPLC analysis showed a cyanamide concentration of 9.8 wt%, therefore the cyanamide mass = 270 g × 9.8 wt% = 26.46 g, and the molar amount of cyanamide is calculated to be 0.629 mol. The sample solid content was 22.5%.

[0034] S2. The above suspension reaction solution was heated to 47±0.3℃ under nitrogen protection; methyl chloroformate was added dropwise at a rate of 1.0 mL / min, where the molar ratio of cyanamide to methyl chloroformate was 1:1.05. The calculated mass of methyl chloroformate was 0.629 mol × 1.05 × 94.494 g / mol = 62.4 g, corresponding to a volume of 51.1 mL. Therefore, the dropping time was 51±1 minutes. During the dropping process, 30 wt% NaOH solution was added to maintain pH = 9.3±0.2; the amount of 30 wt% NaOH added was 0.42 g, accounting for 0.48% of the theoretical amount. After the dropping was completed, the reaction was kept at this temperature for 60 minutes. HPLC monitoring showed that the cyanamide residue was 0.38% and the dicyandiamide derivative was 0.31%.

[0035] S3. The reaction solution obtained in step S2 is filtered at 50±1℃ using a filter cloth with a pore size of 30μm to obtain a wet filter cake and filtrate. S4. The filter cake was washed twice with deionized water and dried at 105℃ to obtain a calcium salt byproduct with a mass of 58.3g. The filtrate was extracted with toluene (filtrate:toluene = 1:1.5, v / v) to obtain an organic phase and an aqueous phase. S5. The organic phase was dried with anhydrous magnesium sulfate for 30 min and then distilled under reduced pressure at 45℃ and 13 kPa to obtain 58.5 g of methyl cyanocarbamate. The aqueous phase was decalcified by a Dowex 50WX8 cation exchange resin column. The calcium ion concentration of the effluent was 10 ppm and the conductivity was 48 μS / cm (25℃). The effluent was recycled for the next batch of hydrolysis.

[0036] Example 3

[0037] S1. Weigh 100g of industrial-grade calcium cyanamide, add 170g of deionized water, and place it in a reaction vessel; hydrolyze in a constant temperature water bath at 35±0.5℃ and 150rpm for 120 minutes; the pH is measured to be 11.7 after 100 minutes of hydrolysis using an online pH meter, and 1.3mL of 1.0wt% sodium carbonate solution is added to adjust the pH to the endpoint of 12.0 to obtain a suspension reaction solution; The HPLC analysis revealed a cyanamide concentration of 10.5 wt%; therefore, the cyanamide mass = 270 g × 10.5 wt% = 28.35 g, which calculates to be 0.674 mol. The sample solid content was 20.8%.

[0038] S2. The above suspension reaction solution was heated to 47.0±0.2℃ under nitrogen protection; methyl chloroformate was added dropwise at a rate of 1.0 mL / min, where the molar ratio of cyanamide to methyl chloroformate was 1:1.05. The calculated mass of methyl chloroformate was 0.674mol×1.05×94.494g / mol=66.9g, corresponding to a volume of 54.8mL; therefore, the dropping time was 54±1 minutes; during the dropping process, 30wt% NaOH solution was added to maintain pH=9.5±0.2; the amount of 30wt% NaOH added was 0.51g, accounting for 0.54% of the theoretical amount; after the dropping was completed, the reaction was kept at this temperature for 60 minutes, and HPLC monitoring showed that the cyanamide residue was 0.41% and the dicyandiamide derivative was 0.33%.

[0039] S3. The reaction solution obtained in step S2 is filtered at 50±1℃ using a filter cloth with a pore size of 30μm to obtain a wet filter cake and filtrate. S4. The filter cake was washed twice with deionized water and dried at 105℃ to obtain a calcium salt byproduct with a mass of 59.1g. The filtrate was extracted with toluene (filtrate:toluene = 1:1.5, v / v) to obtain an organic phase and an aqueous phase. S5. The organic phase was dried with anhydrous sodium sulfate for 30 min and then distilled under reduced pressure at 45 °C and 14 kPa to obtain 62.1 g of methyl cyanocarbamate. The aqueous phase was decalcified by a Dowex 50WX8 cation exchange resin column. The calcium ion concentration in the effluent was 11 ppm and the conductivity was 50 μS / cm (25 °C). The effluent was recycled for the next batch of hydrolysis.

[0040] Comparative Example 1

[0041] Compared with Example 1, the difference of this comparative example is that step S1 of this comparative example is missing the step of adding 1 mL of 1.0 wt% Na2CO3 solution at the end of hydrolysis to control the pH at 11.8 ± 0.1, while other conditions are the same.

[0042] Comparative Example 2

[0043] Compared with Example 1, the difference of this comparative example is that in step S2 of this comparative example, nitrogen protection was not used, and methyl chloroformate was added to the suspension reaction solution at once, while other conditions were the same.

[0044] Comparative Example 3

[0045] Compared with Example 1, the difference in this comparative example is that step S2 of this comparative example lacks the step of adding NaOH to control the pH to maintain 9.4±0.2, while other conditions are the same.

[0046] Comparative Example 4

[0047] Compared with Example 1, the difference in this comparative example is that the specific operation of step S3 in this comparative example is as follows: after cooling the reaction solution obtained in step S2 to room temperature (23±2℃), it is filtered under pressure at room temperature to obtain filter cake and filtrate, with other conditions being the same.

[0048] Comparative Example 5

[0049] This comparative example uses the traditional calcium cyanamide method to prepare methyl cyanurate. The specific steps are as follows: A1. Weigh 100g of industrial calcium cyanamide, add 170g of deionized water, and stir and hydrolyze in a water bath at 45±2℃ for 120min to obtain a grayish-white turbid reaction solution. A2. The reaction solution was filtered under normal pressure using a filter cloth with a pore size of 50 μm to obtain a filter cake and a filtrate. The filter cake was washed twice with 100 mL of deionized water, and the filtrates were combined to obtain a monocyanamide aqueous solution. HPLC analysis showed that the monocyanamide concentration was 9.5 wt% and the dicyandiamide concentration was 2.1 wt%. The filter cake was dried at 105 °C to constant weight to obtain 63.4 g of dry waste residue, accounting for 63.4% of the calcium cyanamide feed. Based on the product yield, the waste residue generated per ton of product was 1642 kg. XRD analysis of the dry waste residue showed that the Ca(OH)₂ content was 68.3%, the unreacted calcium cyanamide content was 12.1%, and the silicon and aluminum impurities content was 19.6%, classifying it as hazardous waste (HW45).

[0050] A3. Cool the cyanamide aqueous solution to 5±1℃ in an ice-water bath, then slowly add 85g of 30wt% NaOH solution, where the molar ratio of NaOH to cyanamide is 1.35:1. When the pH of the system rises to 11.5, add 68g of methyl chloroformate dropwise at 8℃, where the molar ratio of cyanamide to methyl chloroformate is 1:1.1, over a period of 60±5min. After the addition is complete, maintain the reaction at 10±2℃ for 60min. During this period, if the pH drops to 8.7, add NaOH solution to maintain the pH > 10.0. After the reaction is complete, HPLC analysis shows that the cyanamide residue is 1.8% and the dicyandiamide derivative content is 3.5%. A4. The reaction solution was extracted twice with 200 mL of toluene (reaction solution:toluene = 1:1, v / v). The organic phases were combined and washed with 5% NaHCO3 solution and deionized water. After drying, the mixture was distilled under reduced pressure at 45℃ and 12 kPa. Finally, it was purified by silica gel column chromatography (petroleum ether:ethyl acetate = 5:1) to obtain 38.6 g of methyl cyanurate. All aqueous phases were combined to obtain 620 mL of high-salt wastewater, equivalent to 16.1 m³ of wastewater per ton of product. 3 The high-salt wastewater contained 8.3 wt% NaCl, 1.2 wt% phosphate, and 12,500 mg / L COD.

[0051] The test results of the samples prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1. The yield is calculated as (actual yield / theoretical yield) × 100%, and the theoretical yield (g) is calculated as the measured molar number of cyanamides × the molar mass of methyl cyanurate (100.08 g / mol). Solid content, cyanamide concentration, and other physical properties were obtained by sampling (≤1.0 g). The mass loss of the main reaction solution was <0.5%, having no substantial impact on the process. Equipment corrosion weight loss was calculated using 304 stainless steel hangers, referring to GB / T18590.

[0052] Table 1

[0053] As shown in Table 1, the comprehensive test results of Examples 1-3 are superior to those of Comparative Examples 1-5: the product purity of Examples 1-3 is consistently ≥98.8%, the yield is ≥92.0%, and the dicyandiamide derivative is ≤0.33%, significantly better than all comparative examples. Specifically, this application converts the "hazardous waste filter cake" of traditional processes into high-value calcium salt byproducts. After five cycles of aqueous phase decalcification, the product purity remains ≥98.6%, achieving "zero high-salt wastewater," demonstrating a clear advantage over Comparative Example 5. Comparative Example 1 lacks pH control at the hydrolysis endpoint, leading to increased dicyandiamide content, decreased yield, and decreased purity after only three aqueous phase cycles. Comparative Example 2 lacks nitrogen protection and the one-time addition of methyl chloroformate, resulting in oxidation and localized overheating, high dicyandiamide derivative levels, and reduced yield. Comparative Example 3 lacks pH alkali replenishment control, leading to pH loss in the reaction system, high dicyandiamide derivative levels, and significantly increased equipment corrosion. Comparative Example 4 uses ambient temperature pressure filtration, resulting in prolonged filtration time and reduced product yield.

[0054] The above comparative examples illustrate that this application achieves a synergistic breakthrough in product quality, equipment safety, and green manufacturing through precise pH control at the hydrolysis endpoint in step S1 and the addition of trace amounts of Na2CO3 to inhibit dicyandiamide formation; in step S2, Ca(OH)2 in the suspension is used as the main alkali source, with the amount of alkali added being ≤0.6% of the theoretical amount; and in step S3, processes such as hot-press filtration are employed. These processes eliminate the risks of high-salt wastewater and strong corrosion from the source, demonstrating significant economic and industrial value.

[0055] 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, characterized in that, Includes the following steps: S1. Mix calcium cyanamide and deionized water at a mass ratio of 1:1.5-2.5 and carry out hydrolysis reaction at 30-40℃. When the reaction is finished, adjust the final pH to 11.5-12.0 to obtain a suspension reaction solution containing cyanamide, calcium hydroxide particles and calcium ions. S2. Heat the above suspension reaction solution to 45-50℃, and under nitrogen protection, continuously add methyl chloroformate dropwise, controlling the molar ratio of cyanamide to methyl chloroformate to be 1:1.03-1.08; during the reaction, maintain the pH of the system at 9.0-10.5 by adding a pH adjuster; temperature fluctuation ≤±1℃; after the addition is complete, continue to keep the reaction at this temperature for 40-90 minutes until the residual amount of cyanamide is <0.5%; S3. Filter the reaction solution obtained in step S2 at 45-55℃ and collect the filter cake and filtrate. S4. Extract the filtrate with an organic solvent and collect the organic phase and the aqueous phase; S5. Dry the organic phase and distill under reduced pressure to obtain methyl cyanocarbamate.

2. The method for preparing methyl cyanurate according to claim 1, characterized in that, In step S1, the mass ratio of calcium cyanamide to deionized water is 1:1.6-1.8; the hydrolysis reaction time is 80-130 minutes; the hydrolysis reaction is accompanied by stirring at a speed of 100-300 rpm; the pH is monitored in real time during the hydrolysis process, and the reaction is terminated when the pH reaches 11.5-12.0, or the final pH is adjusted to 11.5-12.0 by adding pH buffer solution.

3. The method for preparing methyl cyanurate according to claim 2, characterized in that, The pH buffer solution is selected from a sodium carbonate solution with a mass percentage of 0.5-2.0 wt%.

4. The method for preparing methyl cyanurate according to claim 1, characterized in that, In step S2, the dropping rate of methyl chloroformate is 0.8-1.2 mL / min; the pH adjuster is sodium hydroxide solution.

5. The method for preparing methyl cyanurate according to claim 4, characterized in that, The actual molar amount of sodium hydroxide accounts for 0.4-0.6% of the theoretical molar amount; the pH of the system is maintained at 9.2-10.3 during the reaction; and the reaction is kept at a constant temperature for 50-70 minutes after the addition is complete.

6. The method for preparing methyl cyanurate according to claim 1, characterized in that, In step S3, the components in the filter cake include CaCl2·2H2O and unreacted Ca(OH)2. After washing and drying the filter cake, calcium salt byproducts are obtained.

7. The method for preparing methyl cyanurate according to claim 1, characterized in that, In step S4, the organic solvent is selected from toluene, dichloromethane, ethyl acetate or methyl tert-butyl ether; the volume ratio of the organic solvent to the filtrate is 1.2-1.8:1; the aqueous phase, after being decalcified by ion exchange resin, is used as deionized water and recycled for the hydrolysis process in step 1.

8. The method for preparing methyl cyanurate according to claim 7, characterized in that, The ion exchange resin is a cation exchange resin. After the aqueous phase is decalcified by the ion exchange resin, the calcium ion concentration is ≤20ppm and the conductivity is ≤60μS / cm.

9. The method for preparing methyl cyanurate according to claim 1, characterized in that, In step S5, the drying refers to drying with anhydrous sodium sulfate or anhydrous magnesium sulfate, the amount of which is 3-8% of the mass of the organic phase, and the drying time is 20-40 minutes; the vacuum distillation is carried out under the conditions of heating bath temperature of 40-50℃ and system absolute pressure of 10-15 kPa.

10. A methyl cyanocarbamate, prepared by the method for preparing methyl cyanocarbamate according to claims 1-9.

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