Preparation method of carbendazim

Abstract

The invention discloses a preparation method of carbendazim, and relates to the technical field of carbendazim preparation, and the technical key points are as follows: the preparation method comprises the following steps: hydrolyzing lime nitrogen to generate a cyanamide calcium hydrogen turbid solution, and esterifying the cyanamide calcium hydrogen turbid solution with methyl chloroformate to obtain a cyanamide methyl formate turbid solution; adding carbonate and introducing carbon dioxide to 2-3 atmospheric pressures, stirring for 1-2 hours to precipitate calcium carbonate, and filtering to obtain clear liquid; and finally, condensing the clear liquid and o-phenylenediamine under an acidic condition, filtering, washing and drying to obtain a carbendazim finished product. The filtering effect of cleaning cyanamide waste residues can be improved, and the influence on the purity of a final product is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of carbendazim preparation, in particular to a method for preparing carbendazim. Background Art

[0002] Carbendazim, whose chemical name is N-(2-benzimidazolyl)-methyl carbamate, belongs to the benzimidazole family of compounds and is a systemic broad-spectrum fungicide with both high efficiency and low toxicity. The compound has stable chemical properties and exhibits excellent systemic therapeutic and protective effects. It can effectively prevent and treat a variety of diseases belonging to the Ascomycota, Basidiomycota and Deuteromycota, and therefore plays a vital role in agricultural production.

[0003] It is worth mentioning that carbendazim, also known as cotton wilt, benzimidazole 44, has a wide range of applications and can be used in various occasions such as foliar spraying, seed treatment and soil treatment. It has a significant preventive and therapeutic effect on diseases caused by fungi (such as Ascomycetes and Polyascomycetes) in various crops. In the process of preparing carbendazim, o-phenylenediamine, as an indispensable raw material, undergoes a ring-closing reaction with a cyclizing agent, which is one of the key steps. According to the different choices of cyclizing agents, the preparation process of carbendazim can be subdivided into a variety of methods such as lime nitrogen method, thiourea method, urea method and thiocyanate method. Among them, since the cyclizing agent prepared by the lime nitrogen method has the lowest cost, it has become the main method for large-scale production at present.

[0004] In China, the main preparation process of carbendazim is the lime nitrogen method. This process starts with the hydrolysis of lime nitrogen, through which calcium cyanamide is produced, and then filtered to remove the residue. Next, the pure calcium cyanamide solution is esterified with methyl chloroformate to generate a calcium salt solution of methyl cyanamide formate. This intermediate product then undergoes a key condensation reaction with o-phenylenediamine to finally obtain the target product-carbendazim. However, this traditional process is not perfect and there are some problems that need to be solved. The primary problem is that during the condensation reaction, the presence of CaCl2 not only affects the product quality of carbendazim, but also reduces its yield. Secondly, the process also produces wastewater containing a large amount of calcium chloride and ammonium chloride, which is difficult to treat and difficult to achieve resource utilization, causing considerable pressure on the environment.

[0005] In order to solve the problem of calcium ion removal, Chinese patent CN103922365A proposes a method for efficiently synthesizing cyanamide with lime nitrogen, which attempts to remove calcium ions by introducing carbon dioxide into the system after hydrolysis to generate calcium carbonate precipitation. However, this method requires a high concentration of carbon dioxide, which often cannot fully combine with calcium ions. In actual operation, the filtration of cyanamide waste residue is often not complete, which affects the purity of the final product. Summary of the invention

[0006] In view of the above technical problems, the present invention aims to develop a method for preparing carbendazim, improve the filtering effect of cleaning cyanamide waste residue, and reduce the impact on the purity of the final product.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing carbendazim comprises the following steps:

[0009] Step 1, hydrolysis of lime nitrogen: hydrolyze the lime nitrogen with water and stir for 1-2 hours to generate calcium cyanamide, calcium hydroxide and hydrolysis residue; after the hydrolysis is completed, filter and remove the hydrolysis residue to obtain a calcium cyanamide turbid solution;

[0010] Step 2, esterification reaction: the cyanamide calcium hydrogen turbid solution is subjected to esterification reaction with methyl chloroformate, and after the esterification reaction is completed, an acid solution is added to adjust the pH value to 2-5 to generate a cyanamide methyl formate turbid solution; the cyanamide methyl formate turbid solution includes a calcium ion byproduct;

[0011] Step 3, precipitation: the methyl cyanamide formate turbid liquid is placed in a container, carbonate is added to the methyl cyanamide formate filtrate, the pH value is adjusted to 6-7, the container is closed and carbon dioxide is added to the methyl cyanamide formate turbid liquid until the pressure in the container reaches 2-3 standard atmospheric pressures, and the methyl cyanamide formate turbid liquid is continuously stirred for 1-2 hours, and calcium carbonate precipitation is generated by the reaction of carbonate ions and calcium ions; the container is opened and the methyl cyanamide formate turbid liquid is filtered to obtain a methyl cyanamide formate clear liquid;

[0012] Step 4, preparation of carbendazim: condensing the methyl cyanamide formate solution with o-phenylenediamine under acidic conditions to generate a crude carbendazim product; filtering, washing and drying the crude carbendazim product to obtain a finished carbendazim product.

[0013] By adopting the above scheme, in step one, calcium cyanamide, calcium hydroxide and hydrolysis residue are generated through the hydrolysis reaction of lime nitrogen and water; importantly, the residue is filtered immediately after the hydrolysis is completed, which ensures that no unnecessary impurities are mixed into the subsequent reaction, thereby improving the purity and efficiency of the overall reaction; the step of filtering and removing the hydrolysis residue is crucial to reducing the impurity content in the final product, because the residue may contain substances that affect the purity of the product; in step two, calcium cyanamide turbid solution is esterified with methyl chloroformate, and the pH value is adjusted by adding acid; this step not only promotes the esterification reaction, but also optimizes the reaction conditions by accurately controlling the pH value to reduce the generation of by-products; although this step itself does not directly involve waste residue treatment, optimizing the reaction conditions helps to reduce the need to treat in subsequent steps. impurity content; in step three, by adding carbonate and carbon dioxide, and utilizing the reaction of carbonate ions and calcium ions to produce calcium carbonate precipitation, the calcium ion byproduct in the turbid solution of methyl cyanamide formate is effectively removed; this precipitation process not only improves the quality of the clear solution of methyl cyanamide formate, but also further removes the precipitate by filtration, thereby significantly improving the filtration effect; the filtered clear solution of methyl cyanamide formate is purer, providing high-quality raw materials for the subsequent preparation of carbendazim; in step four, the clear solution of methyl cyanamide formate is condensed with o-phenylenediamine to prepare a crude carbendazim product; since impurities and by-products are effectively removed in the previous steps, the crude carbendazim product generated in this step has a higher purity; the crude product is further filtered, washed and dried, and the final carbendazim product obtained has a higher purity and a more stable quality.

[0014] Preferably, the concentration of the calcium hydrogen cyanamide turbid solution in step 1 is 5-30%, and the pH value is 7-8.

[0015] Preferably, the acid solution used in step 2 is hydrochloric acid, and the acidic condition set in step 4 is hydrochloric acid.

[0016] Preferably, the filtering method of step one is set as screen filtration, and the filtering methods of steps three and four are set as reverse osmosis membrane filtration.

[0017] Preferably, the carbonate in step three is sodium bicarbonate.

[0018] Preferably, the stirring operation in the step three uses a stirring mechanism, the container includes a container cover, a stirring motor is fixedly provided on the container cover, an extension rod is fixedly provided on the output shaft of the stirring motor, and the extension rod is fixedly provided with stirring blades, and the stirring blades are used to stir the turbid liquid of methyl para-cyanamide formate.

[0019] Preferably, the stirring blades include a plurality of stirring plates, and the plurality of stirring plates are evenly arranged in a ring shape at the bottom of the extension rod, and a plurality of stirring holes are formed on the stirring plates.

[0020] Preferably, condensation waste liquid is generated during the filtration process of step 4; the condensation waste liquid is treated by evaporation and crystallization to extract ammonium chloride.

[0021] The present invention has the following beneficial effects:

[0022] 1. Efficient hydrolysis and residue removal: By hydrolyzing lime nitrogen with water and stirring for 1-2 hours, calcium cyanamide, calcium hydroxide and hydrolysis residue can be efficiently generated. After the hydrolysis is completed, the hydrolysis residue is removed by sieve filtration to ensure that the obtained calcium cyanamide turbid solution is pure, providing high-quality raw materials for subsequent steps.

[0023] 2. Precise pH value control: In the esterification step, by adding hydrochloric acid to adjust the pH value to 2-5, the reaction conditions can be precisely controlled to promote the esterification reaction of calcium hydrogen cyanamide solution and methyl chloroformate, thereby improving the reaction efficiency and product purity.

[0024] 3. Efficient precipitation and filtration: In the precipitation step, by adding carbonate and carbon dioxide, and using the reaction of carbonate ions and calcium ions to produce calcium carbonate precipitation, the calcium ion byproduct in the methyl cyanamide formate turbid solution is effectively removed. Subsequently, reverse osmosis membrane filtration can further remove the precipitate and other impurities to obtain a high-purity methyl cyanamide formate clear solution.

[0025] 4. Optimize the stirring device: The design of the stirring blade includes multiple stirring plates and stirring holes, which can stir the methyl cyanamide formate turbid solution more evenly and improve the precipitation efficiency. At the same time, the use of the stirring mechanism for stirring can ensure the stability and controllability of the stirring process.

[0026] 5. Efficient condensation under acidic conditions: In the preparation step of carbendazim, the methyl cyanamide formate clear solution is subjected to condensation reaction with o-phenylenediamine under acidic conditions to generate a crude carbendazim product. By precisely controlling the acidic conditions (using hydrochloric acid), the efficiency of the condensation reaction can be improved to obtain a crude carbendazim product of higher purity.

[0027] 6. Resource recovery and environmental protection: The condensation waste liquid generated during the filtration process can be treated by evaporation and crystallization to extract ammonium chloride, thus achieving effective resource recovery. This measure not only improves economic benefits, but also reduces environmental pollution, which is in line with the concept of green chemistry.

[0028] 7. Overall process optimization: This technical solution achieves efficient and high-purity preparation of carbendazim by optimizing the conditions and devices of each step. At the same time, through resource recovery and environmental protection measures, the production cost is reduced and the economic and environmental benefits are improved. In summary, this technical solution has multiple beneficial effects such as improving the efficiency of carbendazim preparation, improving product purity, optimizing the stirring device, achieving resource recovery and environmental protection. These effects jointly promote the development of carbendazim preparation technology and provide a more efficient and environmentally friendly production method for the pesticide industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 The figure is a flow chart of the manufacturing process of an embodiment of the present invention.

[0031] Figure 2 2 is a cross-sectional view of a stirring mechanism according to an embodiment of the present invention.

[0032] In the figure: 101, container; 102, container cover; 201, stirring motor; 202, extension rod; 203, stirring plate; 204, stirring hole. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing carbendazim, such as Figure 1As shown, it includes the following steps: Step 1, lime nitrogen hydrolysis: the lime nitrogen is hydrolyzed with water and stirred for 1 hour to generate calcium cyanamide, calcium hydroxide and hydrolysis residue; after the hydrolysis is completed, the hydrolysis residue is filtered to remove the hydrolysis residue to obtain a calcium cyanamide turbid solution; the concentration of the calcium cyanamide turbid solution in step 1 is 5%, and the pH value is 7.5. Step 2, esterification reaction: the calcium cyanamide turbid solution is esterified with methyl chloroformate, and after the esterification reaction is completed, acid solution is added to adjust the pH value to 2.5 to generate a methyl cyanamide formate turbid solution; the methyl cyanamide formate turbid solution includes calcium ion by-products; Step 3, precipitation: the methyl cyanamide formate turbid solution is placed in a container 101, carbonate is added to the methyl cyanamide formate filtrate, the pH value is adjusted to 6.5, the container 101 is closed, and carbon dioxide is added to the methyl cyanamide formate turbid solution until the container 10 1 reaches 2 standard atmospheric pressures, and continuously stirs the methyl cyanamide formate turbid liquid for 1 hour, and generates calcium carbonate precipitation by the reaction between carbonate ions and calcium ions; open the container 101 and filter the methyl cyanamide formate turbid liquid to obtain a methyl cyanamide formate clear liquid; step 4, preparation of carbendazim: condensing the methyl cyanamide formate clear liquid with o-phenylenediamine under acidic conditions to generate a crude carbendazim product; the crude carbendazim product is filtered, washed and dried to obtain a finished carbendazim product.

[0036] The acid solution used in step 2 is set to hydrochloric acid. In the esterification step, the pH value is adjusted using hydrochloric acid to provide a suitable acidic environment to promote the esterification reaction between calcium hydrogen cyanamide and methyl chloroformate. Hydrochloric acid, as a strong acid, can quickly and effectively reduce the pH value of the solution, which is conducive to the esterification reaction. The acidic conditions used in step 4 are set to hydrochloric acid; in the preparation step of carbendazim, hydrochloric acid is also used to set the acidic conditions. This is because the condensation reaction is usually carried out more smoothly under acidic conditions, and the addition of hydrochloric acid can ensure the acidic environment of the reaction system, which is conducive to the generation of carbendazim crude product.

[0037] The filtering method of step one is set to screen filtration, which is mainly used to remove larger solid particles and impurities, such as hydrolysis residues. This filtering method is simple and easy, and can quickly separate solids from liquids, providing a relatively pure cyanamide calcium hydrogen turbid solution for subsequent steps. The filtering method of steps three and four is set to reverse osmosis membrane filtration; reverse osmosis membrane filtration is a more sophisticated filtering method that can remove tiny particles, soluble solids, and bacteria in the solution. In step three, it is used to remove suspended matter and tiny impurities after calcium carbonate precipitation; in step four, it is used to further purify the crude carbendazim product to ensure the purity of the final product.

[0038] In step 3, the carbonate is sodium bicarbonate; in step 3, sodium bicarbonate is used as the carbonate in order to react with calcium ions to generate calcium carbonate precipitation. When sodium bicarbonate reacts with calcium ions, water-insoluble calcium carbonate and water-soluble sodium chloride are generated, thereby effectively removing the calcium ion byproduct in the solution.

[0039] During the filtration process of step 4, condensation waste liquid is generated; the condensation waste liquid is treated by evaporation and crystallization to extract ammonium chloride; during the filtration process of step 4, condensation waste liquid is generated. This waste liquid contains valuable compounds such as ammonium chloride. By treating the condensation waste liquid by evaporation and crystallization, the ammonium chloride therein can be extracted. The principle of evaporation and crystallization is to use the evaporation of water in the solution during the heating process, and the solute concentration gradually increases. When the saturation concentration is reached, the solute will precipitate in the form of crystals. This can not only achieve the recycling of resources, but also reduce environmental pollution.

[0040] like Figure 2 As shown, the stirring operation in step three uses a stirring mechanism, and the container 101 includes a container 101 cover, and a stirring motor 201 is fixedly arranged on the container 101 cover. The container 101 serves as a carrier of the stirring process, and its shape, size and material selection all have an impact on the stirring effect. Usually, the container 101 is designed to be cylindrical or conical to facilitate the flow and mixing of the liquid. The design of the container 101 cover not only ensures the airtightness of the stirring process and prevents the volatilization and leakage of harmful substances, but also provides an installation position for the stirring motor 201. By fixing the stirring motor 201 on the container 101 cover, it can be ensured that the stirring blades are always located at the center of the container 101 to achieve the best stirring effect.

[0041] The stirring motor 201 is used as the power source of the entire stirring system, and the stirring motor 201 provides the necessary energy for the stirring process through its rotational motion. The selection of the motor is usually based on factors such as the required stirring power, rotation speed, and operational stability. The output shaft of the stirring motor 201 is directly connected to the extension rod 202, and the rotational motion of the motor is transmitted to the stirring blade. The design of the extension rod 202 ensures that the stirring blade can penetrate into every corner inside the container 101 to achieve all-round stirring. The stirring blade is used to stir the methyl cyanamide formate turbid liquid; when the stirring motor 201 is started, the output shaft drives the extension rod 202 and the stirring blade to rotate. The rotation of the blade will generate tangential force and radial force, which act on the methyl cyanamide formate turbid liquid to produce flow and shear effect. The rotation of the blade promotes the liquid to form a circulation flow in the container 101, which helps to lift the liquid at the bottom of the container 101 to the top, and push the liquid at the top to the wall of the container 101, thereby achieving comprehensive mixing of the liquid. The rotation of the fan blades also generates shear force in the liquid, which can destroy aggregates and bubbles in the liquid, making the liquid more uniform and delicate.

[0042] like Figure 2 As shown, the stirring blade includes a plurality of stirring plates 203, and the stirring blade is composed of a plurality of stirring plates 203, and these stirring plates 203 are evenly arranged in a ring at the bottom of the extension rod 202. This design ensures that the stirring blade can generate uniform fluid power when rotating, and promotes the cyanamide methyl formate turbid liquid to form a comprehensive circulation flow in the container 101. The uniform arrangement of the stirring plates 203 in a ring at the bottom of the extension rod 202 helps to achieve the uniformity and consistency of stirring. Each stirring plate 203 can produce a driving effect on the surrounding liquid, and the annular arrangement ensures that this driving effect is evenly distributed throughout the container 101. A plurality of stirring holes 204 are provided on the stirring plate 203; a plurality of stirring holes 204 are provided on the stirring plate 203, and the presence of these stirring holes 204 further enhances the stirring effect. The stirring holes 204 can be regarded as small fluid channels. When the stirring blade rotates, the liquid produces a jet and reflux effect through these stirring holes 204. The design of the stirring hole 204 causes the liquid to be ejected and refluxed during the stirring process. When the stirring blade rotates to the stirring hole 204, the liquid is ejected to form a stream of small fluid jets. These jets collide and mix with the surrounding liquid in the container 101, thereby achieving more efficient stirring. At the same time, the presence of the stirring hole 204 also promotes the reflux phenomenon of the liquid, that is, the ejected liquid will flow back after the collision, forming a more complex fluid dynamic effect.

[0043] In step 2, a methyl cyanamide formate turbid solution is generated, in which the concentration of methyl cyanamide formate calcium salt in the turbid solution is 7.0%, wherein the calcium ion content is 2.8%; in step 4, o-phenylenediamine is added at a molar ratio of 0.95 according to the amount of methyl cyanamide formate.

[0044] During the reaction, hydrochloric acid was added dropwise to adjust the pH value to 4.5; based on o-phenylenediamine, the yield was 92.5% and the product purity was 99.26%.

[0045] Example 2

[0046] The difference from Example 1 is that in step 1, lime nitrogen and water are hydrolyzed and stirred for 2 hours, and the concentration of the cyanamide calcium hydrogen turbid solution in step 1 is 30%, and the pH value is 7.5; in step 2, acid solution is added during the esterification reaction to adjust the pH value to 4.5 to generate a cyanamide methyl formate turbid solution; at this time, the concentration of cyanamide methyl formate calcium salt in the turbid solution is 10.0%, wherein the calcium ion content is 4.0%; in step 3, the container is closed and carbon dioxide is added to the cyanamide methyl formate turbid solution until 3 standard atmospheres are reached in the container; based on o-phenylenediamine, the yield is 94.5%, and the product purity is 99.54%.

[0047] Example 3

[0048] The difference from Example 1 is that in step 1, lime nitrogen and water are hydrolyzed and stirred for 1.4 hours, the concentration of the cyanamide calcium hydrogen turbid solution in step 1 is 15%, and the pH value is 7.5; in step 2, acid solution is added during the esterification reaction to adjust the pH value to 3.5 to generate a cyanamide methyl formate turbid solution, at which the concentration of cyanamide methyl formate calcium salt in the turbid solution is 9.0%, wherein the calcium ion content is 3.65%; in step 3, the container is closed and carbon dioxide is added to the cyanamide methyl formate turbid solution until the pressure in the container reaches 2.5 standard atmospheres; based on o-phenylenediamine, the yield is 93.6% and the product purity is 99.48%.

[0049] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all within the scope of protection of the present invention.

Claims

1. A method for preparing carbendazim, characterized in that: The following steps are involved: Step 1, hydrolysis of lime nitrogen: hydrolyze the lime nitrogen with water and stir for 1-2 hours to generate calcium cyanamide, calcium hydroxide and hydrolysis residue; after the hydrolysis is completed, filter and remove the hydrolysis residue to obtain a calcium cyanamide turbid solution; Step 2, esterification reaction: the cyanamide calcium hydrogen turbid solution is subjected to esterification reaction with methyl chloroformate, and after the esterification reaction is completed, an acid solution is added to adjust the pH value to 2-5 to generate a cyanamide methyl formate turbid solution; the cyanamide methyl formate turbid solution includes a calcium ion byproduct; Step 3, precipitation: placing the methyl cyanamide formate turbid liquid into a container (101), adding carbonate to the methyl cyanamide formate filtrate, adjusting the pH value to 6-7, closing the container (101) and adding carbon dioxide to the methyl cyanamide formate turbid liquid until the pressure in the container (101) reaches 2-3 standard atmospheric pressures, and continuously stirring the methyl cyanamide formate turbid liquid for 1-2 hours, and utilizing the reaction between carbonate ions and calcium ions to generate calcium carbonate precipitation; opening the container (101) and filtering the methyl cyanamide formate turbid liquid to obtain a methyl cyanamide formate clear liquid; Step 4, preparation of carbendazim: condensing the methyl cyanamide formate solution with o-phenylenediamine under acidic conditions to generate a crude carbendazim product; filtering, washing and drying the crude carbendazim product to obtain a finished carbendazim product.

2. A method for preparing carbendazim according to claim 1, characterized in that: The concentration of the calcium hydrogen cyanamide turbid solution in the step 1 is 5-30%, and the pH value is 7-8.

3. A method for preparing carbendazim according to claim 1, characterized in that: The acid solution used in step 2 is set to hydrochloric acid, and the acidic condition used in step 4 is set to hydrochloric acid.

4. The method for preparing carbendazim according to claim 1, characterized in that: The filtering method of step one is set as screen filtration, and the filtering methods of steps three and four are set as reverse osmosis membrane filtration.

5. The method for preparing carbendazim according to claim 1, characterized in that: In the step 3, the carbonate is set to sodium bicarbonate.

6. The method for preparing carbendazim according to claim 1, characterized in that: The stirring operation in step 3 uses a stirring mechanism, the container (101) comprises a container (101) cover, a stirring motor (201) is fixedly arranged on the container (101) cover, an extension rod (202) is fixedly arranged on the output shaft of the stirring motor (201), and the extension rod (202) is fixedly arranged with a stirring blade, and the stirring blade is used to stir the methyl para-cyanamide formate turbid liquid.

7. The method for preparing carbendazim according to claim 6, characterized in that: The stirring blades include a plurality of stirring plates (203), and the plurality of stirring plates (203) are evenly arranged in a ring shape at the bottom of the extension rod (202), and a plurality of stirring holes (204) are provided on the stirring plates (203).

8. The method for preparing carbendazim according to claim 1, characterized in that: The filtration process in step 4 generates condensation waste liquid; the condensation waste liquid is treated by evaporation and crystallization to extract ammonium chloride.

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