Solid-liquid separation process for producing carbendazim
By employing a two-stage membrane separation method, combined with the use of MCE microfiltration membrane and modified PAN membrane, the problem of low recovery rate and purity of carbendazim crystals in traditional processes has been solved, achieving efficient recovery and improved purity of carbendazim crystals.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-04-07
AI Technical Summary
Traditional solid-liquid separation processes are difficult to effectively recover submicron-sized carbendazim crystals and remove impurities, resulting in a decrease in carbendazim yield and purity.
A two-stage membrane separation method is adopted. First, an MCE microfiltration membrane is used for preliminary screening, and then a modified PAN membrane is used for deep retention and impurity adsorption. The modification treatment of the modified PAN membrane improves its adsorption capacity for impurities.
This method achieves efficient recovery and purity improvement of carbendazim crystals, thereby increasing the yield and purity of carbendazim.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of pesticide production, and in particular to a solid-liquid separation process for producing carbendazim. Background Technology
[0002] Carbendazim, also known as cotton wilt fungicide or benzimidazole 44, has the chemical name N-(2-benzimidazolyl)-methyl carbamate. It is a highly effective, low-toxicity, broad-spectrum systemic fungicide. Carbendazim inhibits cell division by interfering with microtubule formation during the mitotic process of pathogenic fungi, thereby achieving a fungicidal effect. Carbendazim can be absorbed by plant seeds, roots, and leaves, and can be transported within plant tissues. It has both protective and curative effects and is widely used to control various diseases in rice, cotton, vegetables, fruit trees, and other crops. It is particularly effective against diseases caused by ascomycetes and deuteromycetes, and can be widely used in agriculture, construction, home furnishing, and horticulture.
[0003] In the traditional post-processing stage of carbendazim production, the solid-liquid separation process is the key to determining the final yield and purity of the product. However, due to the different particle size distribution and morphology of solid particles, i.e. carbendazim crystals, in the reaction slurry, the separation efficiency is affected, resulting in direct product loss. Moreover, the mother liquor after separation still contains submicron-sized carbendazim, which is too small to be separated by centrifugation and thus remains in the mother liquor, causing a decrease in the overall yield.
[0004] Furthermore, submicron-sized microorganisms are more flexible, and their finer crystal structure helps them dissolve faster in water or on the surface of plants, allowing the active ingredients to be released and take effect more quickly. However, traditional solid-liquid separation processes cannot recover these active ingredients, resulting in a decrease in recovery rate and overall activity.
[0005] Meanwhile, during the separation process, residual byproducts, excessive o-phenylenediamine raw materials, and inorganic salts such as calcium chloride and sodium chloride may remain or be adsorbed on the surface of carbendazim solid crystals. Conventional adsorption and separation methods are difficult to completely remove these impurities, which will affect the purity of the product and even its effectiveness. Summary of the Invention
[0006] This invention provides a solid-liquid separation process for producing carbendazim, which can solve the problems of difficulty in collecting submicron-sized carbendazim crystals and the presence of impurities in the product in the post-processing solid-liquid separation steps of existing carbendazim production technologies.
[0007] A solid-liquid separation process for producing carbendazim includes the following steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original liquid material; S2. Separate the raw liquid obtained from the previous process through a primary membrane to obtain a primary permeate and a primary filtration product; S3. Mix the primary permeate with an ethanol-water solution and separate the mixture through a secondary membrane to obtain the secondary permeate and the secondary filtration product; S4. Collect the primary filtration product and the secondary filtration product, and dry them to obtain carbendazim solid; S5. The secondary permeate is mixed with the primary permeate, and the process is repeated in step S2 for secondary membrane separation.
[0008] By adopting the above technical solution, this invention uses a two-stage membrane separation method for grading and screening. The first-stage membrane separation can quickly separate most of the conventional-sized carbendazim crystals in the original feed solution. In other words, the first-stage membrane separation can almost completely retain the main crystals with a particle size larger than its pore size on one side of the membrane, achieving preliminary screening and retention. The resulting first-stage permeate contains almost all submicron-sized fine crystals, impurities, and solvents.
[0009] Then, the primary permeate undergoes secondary membrane separation, using a functional membrane with even smaller pores to further retain submicron-sized fine crystals, achieving targeted deep retention of microcrystals. This two-stage membrane separation and sieving process enables precise purification based on the particle size and molecular size of carbendazim crystals, effectively recovering carbendazim products of different sizes. Simultaneously, the unique dialysis and filtration function of membrane separation achieves deep removal of impurities, thereby improving the recovery rate and purity of carbendazim solids.
[0010] Preferably, the primary membrane separation uses an MCE microfiltration membrane; the pore size of the MCE microfiltration membrane is 1–5 μm.
[0011] By adopting the above technical solution, MCE microfiltration membranes (mixed cellulose ester microfiltration membranes) are used in the primary membrane separation stage. Their physical sieving action efficiently retains the vast majority of conventional carbendazim crystals, achieving primary screening and allowing fine crystals to enter the primary permeate, preventing crystal accumulation on the membrane surface and causing fouling. Furthermore, MCE microfiltration membranes have good hydrophilicity, low resistance to the initial feed solution, and high initial flux, enabling better liquid passage through the membrane layer. Utilizing MCE microfiltration membranes allows for the efficient enrichment of the main product while simultaneously transferring the recovery of microcrystals and deep impurity removal to the secondary membrane separation stage, achieving effective functional zoning.
[0012] Preferably, the volume ratio of the primary permeate to the ethanol-water solution is 1:(1-2).
[0013] Preferably, the concentration of the ethanol aqueous solution is 20-30%.
[0014] By adopting the above technical solution, the first-stage permeate is mixed with an ethanol-water solution. The ethanol-water solution is a polar solution, which can reduce the surface tension of the first-stage permeate and increase the solubility of organic impurities in the solution. This makes it easier for organic impurities that were originally adsorbed on the crystal surface or encapsulated therein to be desorbed and dissolved in the mixed solvent. Moreover, during the second-stage membrane separation process, the addition of the ethanol-water solution can effectively remove impurities from the crystal surface during cross-flow filtration, achieving deep washing of the crystals. This allows impurities to pass through the second-stage membrane with the water flow, improving the purity of the product.
[0015] Preferably, the secondary membrane separation uses a modified PAN membrane; the surface of the modified PAN membrane is grafted with polyethyleneimine segments and compounded with hydroxyapatite.
[0016] Preferably, the pore size of the modified PAN membrane is 0.01–0.2 μm.
[0017] Preferably, the modified PAN film is prepared according to the following method: The PAN nanofiber membrane was immersed in an alkaline solution, the temperature was raised to 65-70℃, and the immersion time was 40-60 minutes. Then, it was neutralized and dried to obtain the pretreated PAN nanofiber membrane. Polyethyleneimine was dissolved in deionized water, and amino-modified hydroxyapatite was added to obtain a suspension modification solution. The pretreated PAN nanofiber membrane was added to the suspension modification solution, and the mixture was refluxed at 100-110℃ for 5-6 hours. Finally, the modified PAN membrane was obtained after washing and drying.
[0018] Preferably, the volume-to-mass ratio of the suspension modification liquid to the pretreated PAN nanofiber membrane is (3-5) mL: 1 g.
[0019] Preferably, the concentration of polyethyleneimine in the suspension modification liquid is 10-15 wt%.
[0020] Preferably, the concentration of amino-modified hydroxyapatite in the suspension modification solution is 4–8 wt%.
[0021] Preferably, the raw material for amino-modified hydroxyapatite includes hydroxyapatite and aminosilane coupling agent in a mass-to-volume ratio of 1 g:(6-8) mL.
[0022] More preferably, amino-modified hydroxyapatite is prepared by the following method: The aminosilane coupling agent was dispersed in anhydrous ethanol and stirred for 1-2 hours for hydrolysis. Then, hydroxyapatite was added, the temperature was raised to 60-70°C, and the reaction was continued for 5-6 hours. Finally, the amino-modified hydroxyapatite was obtained by filtration, washing and drying.
[0023] More preferably, the aminosilane coupling agent includes one or more combinations of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-aminopropylmethyldiethoxysilane.
[0024] More preferably, the alkaline solution includes either a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a concentration of 3-4 mol / L.
[0025] By employing the above technical solution, the first-stage permeate obtained after primary membrane separation contains unretained carbendazim crystals, submicron-sized carbendazim microcrystals, sodium chloride, calcium chloride, excess o-phenylenediamine, carbendazim hydrochloride, and other trace impurities. Then, after mixing with an ethanol-water solution, it undergoes secondary membrane separation. The secondary membrane separation uses a modified PAN membrane (polyacrylonitrile membrane), which provides stable mechanical support and good chemical stability. Its small pore size effectively retains the unretained carbendazim crystals and submicron-sized carbendazim microcrystals from the primary membrane separation, while allowing soluble impurities to pass freely, achieving preliminary separation.
[0026] Furthermore, the modified PAN membrane is grafted with polyethyleneimine. The polyethyleneimine chain segments contain a large number of primary, secondary, and tertiary amine groups. In ethanol aqueous solution, the amino groups are easily protonated, which can capture chloride ions and hydrochloride ions in the primary permeate through electrostatic attraction, preventing them from being adsorbed or wrapped on the surface of the microcrystals, thereby affecting the purity of the carbendazim solid.
[0027] Furthermore, the modified PAN membrane is incorporating hydroxyapatite. Hydroxyapatite, with its positive charge, enhances the electrostatic adsorption of impurity ions such as chloride ions in the modified PAN membrane. Additionally, the calcium ions in its crystal structure can exchange ions with metal cations in the primary permeate, thereby reducing cation adsorption on the microcrystal surface and effectively removing organic salt ions. Hydroxyapatite also specifically adsorbs excess o-phenylenediamine, reducing its adhesion to the microcrystal surface. Moreover, the addition of hydroxyapatite significantly increases the adsorption sites of the modified PAN membrane, enhancing its adsorption capacity for impurities.
[0028] Specifically, in the preparation of the modified PAN membrane, the PAN nanofiber membrane is first pretreated by immersion in a hot alkaline solution, which hydrolyzes the cyano groups, thereby introducing a large number of carboxylate groups onto the surface of the PAN nanofiber membrane as active grafting sites. Then, a suspension modification solution is prepared. In the suspension modification solution, the carboxyl groups of the pretreated PAN nanofiber membrane can undergo a dehydration condensation reaction with the primary amino groups of polyethyleneimine, achieving polyethyleneimine grafting. Meanwhile, the aminated hydroxyapatite can interact with the polyethyleneimine segments and the pretreated PAN nanofiber membrane through the interaction of its surface amino groups, and is fixed to the surface of the pretreated PAN nanofiber membrane by the physical coating and entanglement of the polyethyleneimine segments, thus obtaining the modified PAN membrane.
[0029] The modified PAN membrane uses PAN nanofiber membrane as a framework. By grafting polyethyleneimine segments onto the surface and combining it with hydroxyapatite, it can effectively adsorb impurities in the primary permeate. After modification, the pore size is reduced, effectively retaining carbendazim microcrystals. It can also actively and selectively adsorb impurity ions adsorbed on the permeate and the microcrystal surface, effectively separating carbendazim solids and impurities, improving the yield and purity of carbendazim.
[0030] The beneficial effects of this invention are: 1. In the solid-liquid separation process for producing carbendazim of the present invention, a two-stage membrane separation method is used for classification and screening. The first-stage membrane separation can quickly separate most of the conventional-sized carbendazim crystals in the original feed solution and prevent large-diameter crystals from clogging the micropores of the second-stage membrane separation. Then, it is mixed with an ethanol-water solution to improve the solubility of organic impurities and effectively remove impurities from the crystal surface, achieving deep washing of the crystals. Finally, a second-stage membrane separation is used to retain submicron-sized fine crystals, achieving targeted deep retention of microcrystals and effectively adsorbing and removing impurities, thereby improving the yield and purity of the product.
[0031] 2. In the solid-liquid separation process for producing carbendazim in this invention, the secondary membrane separation uses a modified PAN membrane. Its small pore size can effectively retain carbendazim crystals and submicron-sized carbendazim microcrystals that were not retained in the primary membrane separation. Moreover, it is grafted with polyethyleneimine and composited with hydroxyapatite, which can adsorb chloride ions and hydrochloric acid ions, enhance the adsorption of excess o-phenylenediamine, and actively and selectively adsorb impurity ions adsorbed on the permeate and microcrystal surface. This increases the adsorption sites of the modified PAN membrane, improves the mechanical strength of the membrane, and effectively separates carbendazim crystals and impurities. Detailed Implementation
[0032] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.
[0033] Preparation Example
[0034] Preparation Example 1: A modified PAN film was prepared according to the following method: Preparation of amino-modified hydroxyapatite: 7 mL of 3-aminopropyltrimethoxysilane was dispersed in 100 mL of anhydrous ethanol and stirred for 12 h to hydrolyze. Then 100 mg of hydroxyapatite (average particle size of 20 nm) was added, the temperature was raised to 60 °C, and the reaction was stirred for another 6 h. Finally, the amino-modified hydroxyapatite was obtained by filtration, washing and drying. PAN nanofiber membranes (average pore size 0.5 μm) were immersed in a 4 mol / L sodium hydroxide solution, the temperature was raised to 65 °C, and the membranes were immersed for 50 min. Then, the membranes were neutralized and dried to obtain pretreated PAN nanofiber membranes. Polyethyleneimine (average weight-average molecular weight of 1800) was dissolved in deionized water, and the above-obtained aminated hydroxyapatite was added to obtain a suspension modification solution, wherein the concentration of polyethyleneimine in the suspension modification solution was 12 wt% and the concentration of aminated hydroxyapatite was 5 wt%. The above-obtained pretreated PAN nanofiber membrane was added to the suspension modification solution, wherein the volume-to-mass ratio of the suspension modification solution to the pretreated PAN nanofiber membrane was 4 mL: 1 g. The mixture was refluxed at 110 °C for 6 h, and finally washed and dried to obtain the modified PAN membrane.
[0035] Preparation Example 2, a modified PAN membrane, differs from Preparation Example 1 only in that the concentration of polyethyleneimine in the suspension modification liquid is 15 wt%, the concentration of amino-modified hydroxyapatite is 6 wt%, and the volume-to-mass ratio of the suspension modification liquid to the pretreated PAN nanofiber membrane is 3 mL: 1 g.
[0036] Preparation Example 3: A modified PAN membrane, which differs from Preparation Example 1 only in that the concentration of polyethyleneimine in the suspension modification liquid is 10 wt%, the concentration of amino-modified hydroxyapatite is 4 wt%, and the volume-to-mass ratio of the suspension modification liquid to the pretreated PAN nanofiber membrane is 5 mL: 1 g.
[0037] Preparation Example 4: A modified PAN film was prepared according to the following method: Preparation of amino-modified hydroxyapatite: 7 mL of 3-aminopropyltrimethoxysilane was dispersed in 100 mL of anhydrous ethanol and stirred for 12 h to hydrolyze. Then 100 mg of hydroxyapatite (average particle size of 20 nm) was added, the temperature was raised to 60 °C, and the reaction was stirred for another 6 h. Finally, the amino-modified hydroxyapatite was obtained by filtration, washing and drying. PAN nanofiber membranes (average pore size 0.5 μm) were immersed in a 4 mol / L sodium hydroxide solution, the temperature was raised to 65 °C, and the membranes were immersed for 50 min. Then, the membranes were neutralized and dried to obtain pretreated PAN nanofiber membranes. The above-obtained aminated hydroxyapatite was dispersed in deionized water to obtain a suspension modification solution, wherein the concentration of aminated hydroxyapatite in the suspension modification solution was 5 wt%. The above-obtained pretreated PAN nanofiber membrane was added to the suspension modification solution, wherein the volume-to-mass ratio of the suspension modification solution to the pretreated PAN nanofiber membrane was 4 mL: 1 g. The mixture was refluxed at 110 °C for 6 h, and finally washed and dried to obtain the modified PAN membrane.
[0038] Preparation Example 5: A modified PAN film was prepared according to the following method: PAN nanofiber membranes (average pore size 0.5 μm) were immersed in a 4 mol / L sodium hydroxide solution, the temperature was raised to 65 °C, and the membranes were immersed for 50 min. Then, the membranes were neutralized and dried to obtain pretreated PAN nanofiber membranes. Polyethyleneimine (average weight-average molecular weight of 1800) was dissolved in deionized water to obtain a suspension modification solution with a polyethyleneimine concentration of 12 wt%. The pretreated PAN nanofiber membrane obtained above was added to the suspension modification solution with a volume-to-mass ratio of 4 mL:1 g. The mixture was refluxed at 110 °C for 6 h, and finally washed and dried to obtain the modified PAN membrane.
[0039] Example
[0040] Example 1: A solid-liquid separation process for producing carbendazim, comprising the following process steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original liquid solution. Specifically: The raw materials for the synthesis of methyl chloroformate include 10 parts calcium cyanamide, 10 parts carbon dioxide, 20 parts cyanamide, 15 parts methyl chloroformate, 15 parts sodium hydroxide, 20 parts sodium methyl cyanocarbamate, 10 parts o-phenylenediamine, 12 parts hydrochloric acid and 10 parts water. The steps in the synthesis of methyl chloroformate include: S1.1. Calcium cyanide reacts with water and carbon dioxide to hydrolyze and decalcify, producing an aqueous solution of cyanamide. The reaction temperature is 50℃ and the reaction time is 1 hour. S1.2. Monocyanamide reacts with methyl chloroformate and sodium hydroxide to produce sodium methyl cyanocarbamate. The reaction temperature is 70℃ and the reaction time is 0.5h. S1.3. Sodium methyl cyanurate reacts with o-phenylenediamine and hydrochloric acid to generate the initial feed solution at a reaction temperature of 50°C for 0.5 hours. S2. The raw liquid obtained from the previous process is separated by a primary membrane to obtain a primary permeate and a primary filtration product; wherein the primary membrane separation uses an MCE microfiltration membrane; the average pore size of the MCE microfiltration membrane is 4μm; S3. The primary permeate is mixed with an ethanol-water solution, wherein the volume ratio of the primary permeate to the 25% ethanol-water solution is 1:1; the mixture is then separated by a secondary membrane, wherein the secondary membrane separation is performed using the modified PAN membrane prepared in Preparation Example 1, to obtain a secondary permeate and a secondary filtration product. S4. Collect the primary filtration product and the secondary filtration product, and dry them to obtain carbendazim solid; S5. The secondary permeate is mixed with the primary permeate, and the process is repeated in step S2 for secondary membrane separation.
[0041] Example 2, a solid-liquid separation process for producing carbendazim, differs from Example 1 only in that the volume ratio of the primary permeate to the 25% ethanol aqueous solution is 1:2.
[0042] Example 3: A solid-liquid separation process for producing carbendazim, which differs from Example 1 only in that the modified PAN membrane prepared in Example 1 is replaced with an equal amount of the modified PAN membrane prepared in Example 2.
[0043] Example 4: A solid-liquid separation process for producing carbendazim, which differs from Example 1 only in that the modified PAN membrane prepared in Example 1 is replaced with an equal amount of the modified PAN membrane prepared in Example 3.
[0044] Comparative Example
[0045] Comparative Example 1 is a solid-liquid separation process for producing carbendazim, which differs from Example 1 only in that the modified PAN membrane prepared in Preparation Example 1 is replaced with an equal amount of the modified PAN membrane prepared in Preparation Example 4.
[0046] Comparative Example 2, a solid-liquid separation process for producing carbendazim, differs from Example 1 only in that the modified PAN membrane prepared in Example 1 is replaced with an equal amount of the modified PAN membrane prepared in Example 5.
[0047] Comparative Example 3 is a solid-liquid separation process for producing carbendazim, which differs from Example 1 only in that an equal amount of PAN nanofiber membrane is used to replace the modified PAN membrane prepared in Example 1.
[0048] Comparative Example 4, a solid-liquid separation process for producing carbendazim, includes the following process steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original solution, specifically by following the steps in Example 1; S2. The raw liquid obtained from the previous process is separated by a primary membrane to obtain a primary permeate and a primary filtration product; wherein the primary membrane separation uses an MCE microfiltration membrane; the average pore size of the MCE microfiltration membrane is 4μm; S3. Mix the primary permeate with an ethanol-water solution, wherein the volume ratio of the primary permeate to the 25% ethanol-water solution is 1:1; then separate the mixture through a secondary membrane, wherein the secondary membrane separation still uses an MCE microfiltration membrane; the average pore size of the MCE microfiltration membrane is 4μm; to obtain the secondary permeate and the secondary filtration product; S4. Collect the primary filtration product and the secondary filtration product, and dry them to obtain carbendazim solid; S5. The secondary permeate is mixed with the primary permeate, and the process is repeated in step S2 for secondary membrane separation.
[0049] Comparative Example 5, a solid-liquid separation process for producing carbendazim, includes the following process steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original solution, specifically by following the steps in Example 1; S2. The raw liquid obtained from the previous process is separated by a primary membrane to obtain a primary permeate and a primary filtration product; wherein the primary membrane separation uses an MCE microfiltration membrane; the average pore size of the MCE microfiltration membrane is 4μm; S3. The primary permeate is separated by a secondary membrane, wherein the secondary membrane separation uses the modified PAN membrane prepared in Preparation Example 1, to obtain the secondary permeate and the secondary filtration product; S4. Collect the primary filtration product and the secondary filtration product, and dry them to obtain carbendazim solid; S5. The secondary permeate is mixed with the primary permeate, and the process is repeated in step S2 for secondary membrane separation.
[0050] Comparative Example 6, a solid-liquid separation process for producing carbendazim, comprising the following process steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original solution, specifically by following the steps in Example 1; S2. The raw feed solution obtained in the previous step is mixed with an ethanol-water solution, wherein the volume ratio of the raw feed solution and the 25% ethanol-water solution is 1:1; and the mixture is separated by a primary membrane, wherein the primary membrane separation is performed using the modified PAN membrane prepared in Preparation Example 1, to obtain a primary permeate and a primary filtration product. S3. Collect the primary filtration product and dry it to obtain carbendazim solid; S4. The primary permeate is mixed with the original feed solution and returned to step S2 for primary membrane separation.
[0051] Performance testing
[0052] The yield and purity of the carbendazim solids obtained in the examples and comparative examples were calculated and measured respectively, and the results are shown in Table 1: Table 1 Performance test results
[0053] According to Table 1, and in conjunction with Example 1 and Comparative Examples 1 to 3, it can be seen that the yield and purity of Comparative Examples 1 to 3 are lower than those of Example 1. This is because the modified PAN membrane in Comparative Example 1 did not have polyethyleneimine grafted onto it. This affects the interfacial forces of aminated hydroxyapatite on the surface of the pretreated PAN nanofiber membrane, leading to hydroxyapatite shedding during the solid-liquid separation process. This not only significantly reduces the adsorption of impurities but also contaminates the carbendazim solid product, resulting in a decrease in purity. The modified PAN membrane in Comparative Example 2 lacked composite hydroxyapatite, greatly reducing the adsorption sites on the modified PAN membrane surface. During solid-liquid separation, impurities could not be effectively and completely adsorbed and removed, thus affecting the yield and purity. In Comparative Example 3, no modification treatment was applied to the PAN membrane, making it difficult for impurities on the crystal surface to undergo competitive desorption, resulting in a decrease in product purity.
[0054] Combining Example 1 and Comparative Example 4, it can be seen that the yield and purity of Comparative Example 4 are lower than those of Example 1. The reason is that Comparative Example 4 did not perform secondary membrane separation, which greatly reduced the yield of carbendazim microcrystals, resulting in a decrease in the overall yield. In addition, the lack of the functional role of the modified PAN membrane reduced the removal effect of impurities, leading to a decrease in purity.
[0055] Combining Example 1 and Comparative Example 5, it can be seen that the yield and purity of Comparative Example 5 are lower than those of Example 1. The reason is that the primary permeate in Comparative Example 5 was not mixed with an aqueous ethanol solution, which would affect the effective removal of impurities in the secondary membrane separation, thus leading to a decrease in purity.
[0056] Combining Example 1 and Comparative Example 6, it can be seen that the yield and purity of Comparative Example 6 are lower than those of Example 1. The reason is that Comparative Example 6 did not undergo primary membrane separation. A large number of solid crystals were trapped on the surface of the modified PAN membrane. The modified PAN membrane has a small pore size and is very easy to become clogged, which will directly cause the loss of carbendazim solids.
[0057] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.
Claims
1. A solid-liquid separation process for producing carbendazim, characterized in that, The process includes the following steps: S1. Carbendazim was prepared using the methyl chloroformate synthesis method to obtain the original liquid material; S2. Separate the raw liquid obtained from the previous process through a primary membrane to obtain a primary permeate and a primary filtration product; S3. Mix the primary permeate with an ethanol-water solution and separate the mixture through a secondary membrane to obtain the secondary permeate and the secondary filtration product; S4. Collect the primary filtration product and the secondary filtration product, and dry them to obtain carbendazim solid; S5. The secondary permeate is mixed with the primary permeate, and the process is repeated in step S2 for secondary membrane separation.
2. The solid-liquid separation process for producing carbendazim according to claim 1, characterized in that, The primary membrane separation uses an MCE microfiltration membrane; the pore size of the MCE microfiltration membrane is 1–5 μm.
3. The solid-liquid separation process for producing carbendazim according to claim 1, characterized in that, The volume ratio of the primary permeate to the ethanol-water solution is 1:(1-2).
4. The solid-liquid separation process for producing carbendazim according to claim 1, characterized in that, The secondary membrane separation uses a modified PAN membrane; the surface of the modified PAN membrane is grafted with polyethyleneimine segments and compounded with hydroxyapatite.
5. The solid-liquid separation process for producing carbendazim according to claim 4, characterized in that, The modified PAN film has a pore size of 0.01–0.2 μm.
6. The solid-liquid separation process for producing carbendazim according to claim 4, characterized in that, The modified PAN film was prepared according to the following method: The PAN nanofiber membrane was immersed in an alkaline solution, the temperature was raised to 65-70℃, and the immersion time was 40-60 minutes. Then, it was neutralized and dried to obtain the pretreated PAN nanofiber membrane. Polyethyleneimine was dissolved in deionized water, and amino-modified hydroxyapatite was added to obtain a suspension modification solution. The pretreated PAN nanofiber membrane was added to the suspension modification solution, and the mixture was refluxed at 100-110℃ for 5-6 hours. Finally, the modified PAN membrane was obtained after washing and drying.
7. The solid-liquid separation process for producing carbendazim according to claim 6, characterized in that, The volume-to-mass ratio of the suspension modification liquid to the pretreated PAN nanofiber membrane is (3-5) mL: 1 g.
8. The solid-liquid separation process for producing carbendazim according to claim 6, characterized in that, The concentration of polyethyleneimine in the suspension modified liquid is 10-15 wt%.
9. The solid-liquid separation process for producing carbendazim according to claim 6, characterized in that, The concentration of aminated hydroxyapatite in the suspension modification solution is 4–8 wt%.
10. The solid-liquid separation process for producing carbendazim according to claim 6, characterized in that, The raw materials for the amino-modified hydroxyapatite include hydroxyapatite and aminosilane coupling agent in a mass-to-volume ratio of 1g:(6-8)mL.