Preparation method of methyl chloroacetate

Abstract

The invention relates to the technical field of synthesis of methyl chloroacetate, in particular to a preparation method of methyl chloroacetate. The acidic cation exchange resin is used as a catalyst framework, and the acidic group (-SO3H) of the acidic cation exchange resin can provide acid strength equivalent to that of concentrated sulfuric acid, so that the problem of corrosivity of liquid acid is solved; carrying out acetate functionalization on the acidic cation exchange resin, capturing water molecules generated by esterification reaction, and assisting water to migrate to the hydrophilic pervaporation membrane tube; hydrophobic groups are grafted on the surface of the resin through silanization reaction, so that a catalyst skeleton is hydrophobic, water generated by reaction is effectively repelled, adsorption and retention of water at active sites are reduced, and the conversion rate of methyl chloroacetate is increased; a hydrophilic pervaporation membrane tube is combined with a vacuum pump to realize a synergistic effect with hydrophobic acetate functionalized acidic resin, so that water is removed in real time in the methyl chloroacetate synthesis process, the reaction equilibrium limitation is broken, the reaction is promoted to be carried out in a positive direction, and the conversion rate and the yield of methyl chloroacetate are improved.

Description

Technical Field

[0001] This invention relates to the field of methyl chloroacetate synthesis technology, and specifically to a method for preparing methyl chloroacetate. Background Technology

[0002] Methyl chloroacetate is an important chlorinated VOC, also known as chloroacetic acid methyl ester. It is colorless and transparent, with a boiling point of 128℃. Slightly soluble in water, it is miscible with solvents such as ethanol, ether, acetone, and benzene. It is an important organic synthesis intermediate, commonly used as an intermediate in the organic synthesis of the insecticide omethoate. It is also widely used in the production of adhesives, organic solvents, dyes, and surfactants, and has significant applications in the pesticide and medical industries. Currently, the industrial process for preparing methyl chloroacetate commonly uses the esterification reaction of chloroacetic acid and methanol. This esterification reaction is reversible and usually requires acid catalysis. In traditional processes, concentrated sulfuric acid is a commonly used catalyst. Concentrated sulfuric acid protonates chloroacetic acid molecules, lowering the activation energy and accelerating both the forward and reverse rates of the esterification reaction, allowing the reaction to reach equilibrium more quickly. However, concentrated sulfuric acid has drawbacks such as strong corrosiveness and long reaction time. Recent research has focused on novel catalysts including solid acids (such as heteropoly acids, molecular sieves, and anion exchange resins), as well as organic acids and their salts. These catalysts also promote the reaction by providing an acidic environment.

[0003] Chinese patent CN201410342356.3 discloses a method for preparing methyl chloroacetate, which involves a gas-liquid-solid three-phase reaction using an acidic resin as a catalyst and chloroacetic acid and methanol as raw materials. The process is completed in a single-stage fixed-bed membrane reactor, eliminating the need for a dehydrating agent, and utilizing a low reaction temperature, thus simplifying the process and reducing energy consumption. However, this method cannot effectively separate the water generated during the reaction from the product in a timely manner, affecting the selectivity and yield of the target product. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing methyl chloroacetate to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows: A method for preparing methyl chloroacetate, characterized by comprising the following steps: S1. Chloroacetic acid is added to methanol by stirring, and the mixture is stirred continuously at 50~60℃ until it becomes clear and transparent to obtain a liquid. Hydrophobic acetate-functionalized acidic resin is packed into the esterification reactor, and the temperature is raised to 85~95℃ under a nitrogen atmosphere to allow the liquid to flow through the esterification reactor for esterification reaction. S2. During the esterification reaction, the liquid is separated into water. After separation, the liquid flows to the outlet of the esterification reactor, and 80-90 wt% of the liquid is returned to the inlet of the esterification reactor for circulation. At the same time, 10-20 wt% of the liquid is diverted to obtain the crude product. S3. The crude product is first distilled in a first distillation column to recover excess methanol, and then distilled under reduced pressure in a second distillation column to obtain methyl chloroacetate.

[0006] As a further improvement, the preparation method of the hydrophobic acetate-functionalized acidic resin is as follows: S1. Activate the strong acid cation exchange resin to obtain activated H-type resin; under a nitrogen atmosphere, mix the activated H-type resin with anhydrous toluene, slowly add trimethylchlorosilane, and reflux at 80~90℃ for 12~16h. After the reaction is completed, cool to room temperature, filter the solid, wash it with anhydrous toluene, extract it with anhydrous ethanol for 24h, and dry it under vacuum at 60℃ to obtain hydrophobic resin. S2. Immerse the hydrophobic resin in cellulose acetate solution, shake slowly at room temperature for 2-4 hours, filter, dry at 40°C under normal pressure for 1 hour, raise the temperature to 60°C, and vacuum dry at 0.05 MPa for 4 hours to obtain hydrophobic acetate-functionalized acidic resin.

[0007] As a further improvement, the preparation method of the activated H-type resin is as follows: the strong acid cation exchange resin is washed with deionized water until the effluent is colorless and clear, then immersed in 1 mol / L hydrochloric acid solution, stirred at room temperature for 4-6 hours, filtered after stirring, washed with deionized water until the washing solution is neutral, and then vacuum dried at 60°C to obtain the activated H-type resin.

[0008] As a further improvement, in step S1, the molar ratio of chloroacetic acid to methanol is 1:3.5~5.5; in step S2, the loading amount of the hydrophobic acetate-functionalized acidic resin is 5~8 wt% of the liquid.

[0009] As a further improvement, according to claim 1, the method for preparing methyl chloroacetate is characterized in that: the top of the esterification reactor is provided with a feed inlet, the lower side of the esterification reactor is provided with a discharge outlet, and multiple hydrophilic pervaporation membrane tubes are provided inside the esterification reactor; the space between the hydrophilic pervaporation membrane tubes and the inner cavity of the esterification reactor is filled with hydrophobic acetate-functionalized acidic resin; the lower end of the hydrophilic pervaporation membrane tubes is connected to a vacuum pump, the vacuum pump is connected to a condenser through a pipeline, and the discharge outlet is connected to the feed inlet and the first distillation column respectively; The water separation process is as follows: a high vacuum of 0.4~0.8 kPa is maintained inside the hydrophilic pervaporation membrane tube, so that the hydrophilic membrane selectively extracts water molecules from the feed liquid.

[0010] As a further improvement, in step S3, the first distillation column is an atmospheric distillation column with the top temperature controlled at 60~65℃; the second distillation column is a vacuum distillation column with the column system maintaining a vacuum of 0.095MPa.

[0011] As a further improvement, the mass ratio of the activated H-type resin to anhydrous toluene is 1:10; the amount of trimethylchlorosilane added is 15-20 wt% of the activated H-type resin.

[0012] As a further improvement, the method for preparing the cellulose acetate solution is as follows: dissolve cellulose acetate in acetone, stir magnetically until completely dissolved, and prepare a cellulose acetate solution with a mass concentration of 0.2~0.5%.

[0013] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1. Using an acidic cation exchange resin as the basic framework, its acidic groups (-SO3H) can provide acid strength comparable to concentrated sulfuric acid, existing in solid form to solve the corrosiveness problem of liquid acids; introducing acetate ions onto the cation exchange resin, which can capture water molecules generated in the reaction through hydrogen bonding, assisting water to migrate to the hydrophilic permeable evaporation membrane; at the same time, grafting hydrophobic groups onto the resin surface through a silanization reaction makes the catalyst framework hydrophobic, effectively repelling water generated in the reaction, reducing the adsorption and retention of water at active sites, and improving the conversion rate and yield of methyl chloroacetate.

[0014] 2. A hydrophilic pervaporation membrane tube combined with a vacuum pump is set in the esterification reaction system to achieve a synergistic effect with the hydrophobic acetate-functionalized acidic resin. This can remove water in real time during the reaction of chloroacetic acid and methanol, break the reaction equilibrium limitation, promote the forward reaction, and improve the conversion rate of methyl chloroacetate. Attached Figure Description

[0015] Figure 1 The images show the infrared spectra of cation exchange resin D001 before and after modification, where a represents cation exchange resin D001 before modification and b represents cation exchange resin D001 after modification. Figure 2 A simplified flow chart of the methyl chloroacetate synthesis process provided by the present invention; The components include: 1. Feed tank; 2. Hydrophilic pervaporation membrane tube; 3. Hydrophobic acetate-functionalized acidic resin; 4. Condenser; 5. Vacuum pump; 6. First distillation column; 7. Second distillation column; 8. Esterification reactor; 9. Circulation pump. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0017] Example 1: A method for preparing methyl chloroacetate, comprising the following steps: 1. Preparation of hydrophobic acetate-functionalized acidic resin 3: S1. Wash the strong acid cation exchange resin D001 with deionized water until the effluent is colorless and clear. Immerse it in 1 mol / L hydrochloric acid solution and stir at 800 rpm for 4 h at room temperature to completely convert the resin to H form. After stirring, filter and wash with deionized water until the washing solution is neutral. Finally, vacuum dry at 60℃ and 0.08 MPa for 12 h to obtain activated H form resin. S2. Under a nitrogen atmosphere, activated H-type resin and anhydrous toluene were mixed at a mass ratio of 1:10. Trimethylchlorosilane was slowly added dropwise, and the mixture was heated to 80°C and refluxed for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with anhydrous toluene, and placed in a Soxhlet extractor. It was then continuously extracted with anhydrous ethanol for 24 hours to completely remove unreacted reagents and byproducts. Finally, the mixture was vacuum dried at 60°C and 0.05 MPa for 8 hours to obtain the hydrophobic resin. The amount of trimethylchlorosilane added was 15 wt% of the activated H-type resin. S3. Dissolve cellulose acetate powder in acetone and stir magnetically until completely dissolved to prepare a cellulose acetate solution with a mass concentration of 0.2%. Immerse the hydrophobic resin in the cellulose acetate solution and slowly shake at a rate of 30 r / min for 2 h at room temperature. Filter to remove excess surface solution, dry at 40℃ under normal pressure for 1 h, raise the temperature to 60℃, and vacuum dry at 0.05 MPa for 4 h to obtain hydrophobic acetate-functionalized acidic resin 3.

[0018] 2. Preparation of methyl chloroacetate: Methyl chloroacetate is prepared by esterification reaction using chloroacetic acid and methanol as raw materials. The specific process includes an esterification reactor 8, which is equipped with multiple hydrophilic pervaporation membrane tubes 2 inside the reactor 8. The multiple hydrophilic pervaporation membrane tubes 2 are interconnected. The space between the hydrophilic pervaporation membrane tubes 2 and the inner cavity of the esterification reactor 8 is filled with hydrophobic acetate-functionalized acidic resin 3. The lower end of the hydrophilic pervaporation membrane tubes 2 is connected to a vacuum pump 5. The vacuum pump 5 is connected to a condenser 4 through a pipeline. The top of the esterification reactor 8 is equipped with a feed inlet, which is connected to a feed tank 1. The lower side of the esterification reactor 8 is equipped with a discharge outlet, which is connected to a discharge pipe. The discharge pipe is equipped with a three-way valve. The two outlets of the three-way valve are connected to a circulating pump 9 and a first distillation column 6, respectively. The outlet of the circulating pump 9 is connected to the feed inlet. The outlet of the first distillation column 6 is connected to a second distillation column 7.

[0019] The specific preparation steps are as follows: S1. Add chloroacetic acid to methanol at a molar ratio of 1:3.5 while stirring at 300 rpm. Stir and mix at 50°C and 600 rpm until the solution is clear and transparent to obtain the feed solution. S2. Hydrophobic acetate-functionalized acidic resin 3 is uniformly packed into the esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 85°C, and the liquid is allowed to flow through the esterification reactor 8 filled with hydrophobic acetate-functionalized acidic resin 3, where esterification occurs at the acidic sites. The amount of hydrophobic acetate-functionalized acidic resin 3 is 5 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.4 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 80 wt% of the feed liquid to return to the inlet of the esterification reactor 8 via a circulation pump 9 for circulation. At the same time, 20 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 60°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0020] Example 2 A method for preparing methyl chloroacetate, comprising the following steps: 1. Preparation of hydrophobic acetate-functionalized acidic resin 3: S1. The strong acid cation exchange resin D001 was washed with deionized water until the effluent was colorless and clear. It was then immersed in a 1 mol / L hydrochloric acid solution and stirred at 900 rpm for 5 h at room temperature to completely convert the resin to the H form. After stirring, it was filtered and washed with deionized water until the washing solution was neutral. Finally, it was vacuum dried at 60℃ and 0.08 MPa for 12 h to obtain the activated H-form resin. S2. Under a nitrogen atmosphere, activated H-type resin and anhydrous toluene were mixed at a mass ratio of 1:10. Trimethylchlorosilane was slowly added dropwise, and the mixture was heated to 85°C and refluxed for 14 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with anhydrous toluene, and placed in a Soxhlet extractor. It was then continuously extracted with anhydrous ethanol for 24 hours to completely remove unreacted reagents and byproducts. Finally, the mixture was vacuum dried at 60°C and 0.05 MPa for 8 hours to obtain the hydrophobic resin. The amount of trimethylchlorosilane added was 17 wt% of the activated H-type resin. S3. Dissolve cellulose acetate powder in acetone and stir magnetically until completely dissolved to prepare a cellulose acetate solution with a mass concentration of 0.4%. Immerse the hydrophobic resin in the cellulose acetate solution and slowly shake at a rate of 30 r / min for 3 h at room temperature. Filter to remove excess surface solution, dry at 40℃ under normal pressure for 1 h, raise the temperature to 60℃, and vacuum dry at 0.05 MPa for 4 h to obtain hydrophobic acetate-functionalized acidic resin 3.

[0021] 2. Preparation of methyl chloroacetate: S1. Add chloroacetic acid to methanol at a molar ratio of 1:4.5 while stirring at 350 rpm. Stir and mix at 55°C and 700 rpm until the solution is clear and transparent to obtain the feed solution. S2. Hydrophobic acetate-functionalized acidic resin 3 is uniformly packed into the esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 90°C, and the liquid is allowed to flow through the esterification reactor 8 filled with hydrophobic acetate-functionalized acidic resin 3, where esterification occurs at the acidic sites. The amount of hydrophobic acetate-functionalized acidic resin 3 is 6 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.6 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 85 wt% of the feed liquid to return to the inlet of the esterification reactor 8 for circulation. At the same time, 15 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 63°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0022] Example 3 A method for preparing methyl chloroacetate, comprising the following steps: 1. Preparation of hydrophobic acetate-functionalized acidic resin 3: S1. The strong acid cation exchange resin D001 was washed with deionized water until the effluent was colorless and clear. It was then immersed in a 1 mol / L hydrochloric acid solution and stirred at 1000 rpm for 6 hours at room temperature to completely convert the resin to the H form. After stirring, it was filtered and washed with deionized water until the washing solution was neutral. Finally, it was vacuum dried at 60℃ and 0.08 MPa for 12 hours to obtain the activated H-form resin. S2. Under a nitrogen atmosphere, activated H-type resin and anhydrous toluene were mixed at a mass ratio of 1:10. Trimethylchlorosilane was slowly added dropwise, and the mixture was heated to 90°C and refluxed for 16 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with anhydrous toluene, and placed in a Soxhlet extractor. It was then continuously extracted with anhydrous ethanol for 24 hours to completely remove unreacted reagents and byproducts. Finally, it was vacuum dried at 60°C and 0.05 MPa for 8 hours to obtain the hydrophobic resin. The amount of trimethylchlorosilane added was 20 wt% of the activated H-type resin. S3. Dissolve cellulose acetate powder in acetone and stir magnetically until completely dissolved to prepare a cellulose acetate solution with a mass concentration of 0.5%. Immerse the hydrophobic resin in the cellulose acetate solution and slowly shake at a rate of 30 r / min for 4 h at room temperature. Filter to remove excess surface solution, dry at 40℃ under normal pressure for 1 h, raise the temperature to 60℃ and vacuum dry at 0.05 MPa for 4 h to obtain hydrophobic acetate-functionalized acidic resin 3.

[0023] 2. Preparation of methyl chloroacetate: S1. Add chloroacetic acid to methanol at a molar ratio of 1:5.5 while stirring at 400 rpm. Stir and mix at 60°C and 800 rpm until the solution is clear and transparent to obtain the feed solution. S2. Hydrophobic acetate-functionalized acidic resin 3 is uniformly packed into the esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 95°C, and the liquid is allowed to flow through the esterification reactor 8 filled with hydrophobic acetate-functionalized acidic resin 3, where esterification occurs at the acidic sites. The amount of hydrophobic acetate-functionalized acidic resin 3 is 8 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.8 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 90 wt% of the feed liquid to return to the inlet of the esterification reactor 8 for circulation. At the same time, 10 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 65°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0024] Comparative Example 1: A method for preparing methyl chloroacetate, differing from Example 1 in that the strongly acidic cation exchange resin is not hydrophobically modified, and specifically includes the following steps: 1. Preparation of acetate-functionalized acidic resin: S1. Wash the strong acid cation exchange resin D001 with deionized water until the effluent is colorless and clear. Immerse it in 1 mol / L hydrochloric acid solution and stir at 800 rpm for 4 h at room temperature to completely convert the resin to H form. After stirring, filter and wash with deionized water until the washing solution is neutral. Finally, vacuum dry at 60℃ and 0.08 MPa for 12 h to obtain activated H form resin. S2. Dissolve cellulose acetate powder in acetone and stir magnetically until completely dissolved to prepare a cellulose acetate solution with a mass concentration of 0.2%. Immerse the activated H-type resin in the cellulose acetate solution and slowly shake at a rate of 30 r / min for 2 h at room temperature. Filter to remove excess surface solution, dry at 40℃ under normal pressure for 1 h, then heat to 60℃ and vacuum dry at 0.05 MPa for 4 h to obtain acetate-functionalized acidic resin.

[0025] 2. Preparation of methyl chloroacetate: S1. Add chloroacetic acid to methanol at a molar ratio of 1:3.5 while stirring at 300 rpm. Stir and mix at 50°C and 600 rpm until the solution is clear and transparent to obtain the feed solution. S2. Acetate-functionalized acidic resin is uniformly packed into esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 85°C, and the liquid is allowed to flow through the esterification reactor 8 filled with acetate-functionalized acidic resin, where esterification occurs at the acidic sites. The amount of acetate-functionalized acidic resin is 5 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.4 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 80 wt% of the feed liquid to return to the inlet of the esterification reactor 8 for circulation. At the same time, 20 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 60°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0026] Comparative Example 2: A method for preparing methyl chloroacetate, differing from Example 1 in that the strongly acidic cation exchange resin is not functionalized with acetate. The method specifically includes the following steps: 1. Preparation of hydrophobic acidic resins: S1. Wash the strong acid cation exchange resin D001 with deionized water until the effluent is colorless and clear. Immerse it in 1 mol / L hydrochloric acid solution and stir at 800 rpm for 4 h at room temperature to completely convert the resin to H form. After stirring, filter and wash with deionized water until the washing solution is neutral. Finally, vacuum dry at 60℃ and 0.08 MPa for 12 h to obtain activated H form resin. S2. Under a nitrogen atmosphere, the activated H-type resin was mixed with anhydrous toluene at a mass ratio of 1:10, and trimethylchlorosilane was slowly added dropwise. The mixture was heated to 80°C and refluxed for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with anhydrous toluene, placed in a Soxhlet extractor, and continuously extracted with anhydrous ethanol for 24 hours to completely remove unreacted reagents and byproducts. Finally, the mixture was vacuum dried at 60°C and 0.05 MPa for 8 hours to obtain a hydrophobic acidic resin. The amount of trimethylchlorosilane added was 15 wt% of the activated H-type resin.

[0027] 2. Preparation of methyl chloroacetate: S1. Add chloroacetic acid to methanol at a molar ratio of 1:3.5 while stirring at 300 rpm. Stir and mix at 50°C and 600 rpm until the solution is clear and transparent to obtain the feed solution. S2. A hydrophobic acidic resin is uniformly packed into the esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 85°C, allowing the liquid to flow through the esterification reactor 8 filled with the hydrophobic acidic resin, where esterification occurs at the acidic sites. The amount of hydrophobic acidic resin is 5 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.4 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 80 wt% of the feed liquid to return to the inlet of the esterification reactor 8 for circulation. At the same time, 20 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 60°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0028] Comparative Example 3: A method for preparing methyl chloroacetate, differing from Example 1 in that the cellulose acetate solution prepared during the acetate functionalization modification process has a mass concentration of 1.0%, specifically including the following steps: 1. Preparation of hydrophobic acetate-functionalized acidic resin 3: S1. Wash the strong acid cation exchange resin D001 with deionized water until the effluent is colorless and clear. Immerse it in 1 mol / L hydrochloric acid solution and stir at 800 rpm for 4 h at room temperature to completely convert the resin to H form. After stirring, filter and wash with deionized water until the washing solution is neutral. Finally, vacuum dry at 60℃ and 0.08 MPa for 12 h to obtain activated H form resin. S2. Under a nitrogen atmosphere, activated H-type resin and anhydrous toluene were mixed at a mass ratio of 1:10. Trimethylchlorosilane was slowly added dropwise, and the mixture was heated to 80°C and refluxed for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with anhydrous toluene, and placed in a Soxhlet extractor. It was then continuously extracted with anhydrous ethanol for 24 hours to completely remove unreacted reagents and byproducts. Finally, the mixture was vacuum dried at 60°C and 0.05 MPa for 8 hours to obtain the hydrophobic resin. The amount of trimethylchlorosilane added was 15 wt% of the activated H-type resin. S3. Dissolve cellulose acetate powder in acetone and stir magnetically until completely dissolved to prepare a cellulose acetate solution with a mass concentration of 1.0%. Immerse the hydrophobic resin in the cellulose acetate solution and slowly shake at a rate of 30 r / min at room temperature for 24 h. Filter to remove excess surface solution, dry at 40℃ under normal pressure for 1 h, raise the temperature to 60℃ and vacuum dry at 0.05 MPa for 4 h to obtain hydrophobic acetate-functionalized acidic resin 3.

[0029] 2. Preparation of methyl chloroacetate: S1. Add chloroacetic acid to methanol at a molar ratio of 1:3.5 while stirring at 300 rpm. Stir and mix at 50°C and 600 rpm until the solution is clear and transparent to obtain the feed solution. S2. Hydrophobic acetate-functionalized acidic resin 3 is uniformly packed into the esterification reactor 8. Under a nitrogen atmosphere, the temperature is raised to 85°C, and the liquid is allowed to flow through the esterification reactor 8 filled with hydrophobic acetate-functionalized acidic resin 3, where esterification occurs at the acidic sites. The amount of hydrophobic acetate-functionalized acidic resin 3 is 5 wt% of the liquid. S3. During the reaction, the feed liquid undergoes water separation via a hydrophilic pervaporation membrane tube 2 and a vacuum pump 5: A high vacuum of 0.4 kPa is maintained inside the hydrophilic pervaporation membrane tube 2. Water molecules generated during the reaction enter the hydrophilic pervaporation membrane tube 2 due to the hydrophilic selectivity of the membrane, and then enter the condenser 4 via the vacuum pump 5, where they are condensed into pure water. The water molecules generated during the esterification reaction are separated during the reaction, allowing the esterification reaction to proceed in the forward direction. After water separation, the feed liquid flows to the outlet of the esterification reactor 8. A three-way valve is installed at the outlet to control 80 wt% of the feed liquid to return to the inlet of the esterification reactor 8 for circulation. At the same time, 20 wt% of the material is diverted to obtain the crude product. S4. The crude product is passed through the first distillation column 6 to recover excess methanol. The top temperature of the column is controlled at 60°C, and the distillate is anhydrous methanol. Finally, it is passed through the second distillation column 7, and the column system is maintained at a vacuum of 0.095 MPa to obtain methyl chloroacetate.

[0030] Comparative Example 4: A method for preparing methyl chloroacetate, differing from Example 1 in that concentrated sulfuric acid is used as a catalyst, specifically including the following steps: S1. Chloroacetic acid and methanol are mixed in a molar ratio of 1:3.5 to form a mixture. The mixture is pumped into a mixing metering tank at 55°C and then dripped into a reaction vessel. Esterification reaction is carried out at 110°C using concentrated sulfuric acid as a catalyst to obtain crude methyl chloroacetate. S2. Crude methyl chloroacetate is washed with soda ash solution in a neutralization vessel. After washing, it is placed in an ester-water separator to separate the lower ester and the upper water. The lower ester is then subjected to a high-pressure distillation column to recover excess methanol. The top temperature of the column is controlled at 65°C, and the distillate is anhydrous methanol. Then, it is passed through a vacuum distillation column, with the column system maintained at a vacuum of 0.095 MPa, to obtain methyl chloroacetate.

[0031] The conversion rate and purity of methyl chloroacetate obtained in each example were calculated, and the results are shown in Table 1.

[0032] Table 1. Conversion rate and purity of methyl chloroacetate

[0033] As shown in Table 1, the methyl chloroacetate obtained in the examples had higher conversion rates, purity, and yields than the comparative examples. The examples utilized an acidic cation exchange resin, acetate ions, and silanized hydrophobic groups to form a synergistic dehydration mechanism. The silanized hydrophobic groups strongly repel water molecules generated in the reaction, forcing them to leave the active sites on the surface of the acidic cation exchange resin. Acetate ions capture water molecules through hydrogen bonding, guiding them to migrate towards the hydrophilic membrane interface, allowing water molecules to be selectively and continuously extracted from the feed solution, thus improving the conversion rate and yield of methyl chloroacetate. The resin catalysts prepared in Comparative Examples 1 and 2 lacked hydrophobic modification or acetate functionalization, failing to form a hydrophobic-water molecule capture synergistic mechanism. Water molecules could not be discharged from the reaction system in a timely manner, leading to a decrease in the conversion rate and yield of methyl chloroacetate. The cellulose acetate solution used in Comparative Example 3 had a higher mass concentration than the examples, resulting in an excessively thick coating layer formed by cellulose acetate on the resin surface, leading to a decrease in the catalytic efficiency of the resin and reducing the conversion rate and yield of methyl chloroacetate.

[0034] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A process for the preparation of methyl chloroacetate, characterized in that, The method comprises the following steps: S1, stirring chloroacetic acid into methanol, continuously stirring at 50-60℃ until clear and transparent, obtaining a feed liquid; filling the hydrophobic acetate functionalized acid resin in an esterification reactor, under nitrogen atmosphere, heating to 85-95℃, and making the feed liquid flow through the esterification reactor for esterification reaction; S2, during the esterification reaction, water separation is performed on the feed liquid; after the separation, the feed liquid flows to the discharge port of the esterification reactor, and 80-90wt% of the feed liquid is controlled to return to the feed inlet of the esterification reactor for circulation; meanwhile, 10-20wt% of the feed liquid is branched out to obtain a crude product; S3, the crude product is first recovered with excess methanol through the first rectifying column, and then subjected to reduced pressure distillation through the second rectifying column to obtain methyl chloroacetate.

2. The process for the preparation of methyl chloroacetate as claimed in claim 1, wherein, The preparation method of the hydrophobic acetate functionalized acid resin is as follows: S1, activating the strong acid cation exchange resin to obtain activated H-type resin; under nitrogen atmosphere, mixing the activated H-type resin with anhydrous toluene, slowly adding trimethylchlorosilane, refluxing at 80-90℃ for 12-16h, after the reaction, cooling to room temperature, washing the filtered solid with anhydrous toluene, then continuously extracting with anhydrous ethanol for 24h, vacuum drying at 60℃ to obtain the hydrophobic resin; S2, immersing the hydrophobic resin in a cellulose acetate solution, slowly oscillating at room temperature for 2-4h, filtering, drying at 40℃ under normal pressure for 1h, heating to 60℃, vacuum drying at 0.05MPa for 4h to obtain the hydrophobic acetate functionalized acid resin.

3. The process for the preparation of methyl chloroacetate as claimed in claim 2, wherein, The preparation method of the activated H-type resin is as follows: washing the strong acid cation exchange resin with deionized water until the effluent is colorless and clear, then immersing in a 1mol / L hydrochloric acid solution, stirring at room temperature for 4-6h, after the stirring, filtering, washing with deionized water until the washing liquid is neutral, vacuum drying at 60℃ to obtain the activated H-type resin.

4. The process for the preparation of methyl chloroacetate as claimed in claim 1, wherein, In step S1, the molar ratio of chloroacetic acid to methanol is 1:3.5-5.5; in step S2, the loading amount of the hydrophobic acetate functionalized acid resin is 5-8wt% of the feed liquid.

5. The process for the preparation of methyl chloroacetate as claimed in claim 1, wherein, The top end of the esterification reactor is provided with a feed inlet, the lower part of one side of the esterification reactor is provided with a discharge port, and a plurality of hydrophilic pervaporation membrane tubes are arranged in the esterification reactor; the hydrophilic pervaporation membrane tubes and the inner cavity of the esterification reactor are filled with hydrophobic acetate functionalized acid resin; the lower end of the hydrophilic pervaporation membrane tube is connected with a vacuum pump, the vacuum pump is connected with a condenser in communication through a pipeline, and the discharge port is in communication with the feed inlet and the first rectifying column; The water separation process is as follows: maintaining a high vacuum of 0.4-0.8kPa in the hydrophilic pervaporation membrane tube, so that the hydrophilic membrane selectively extracts water molecules from the feed liquid.

6. The method according to claim 1, wherein In step S3, the first rectifying column is a normal pressure rectifying column, and the top temperature is controlled to be 60-65℃; the second rectifying column is a reduced pressure rectifying column, and the tower system maintains a vacuum degree of 0.095MPa.

7. The process for the preparation of methyl chloroacetate as claimed in claim 2, wherein, The mass ratio of the activated H-type resin to anhydrous toluene is 1:10; the addition amount of the trimethylchlorosilane is 15-20 wt% of the activated H-type resin.

8. The process for the preparation of methyl chloroacetate as claimed in claim 2, wherein, The preparation method of the cellulose acetate solution is: dissolving cellulose acetate in acetone, magnetically stirring until completely dissolved, and preparing a cellulose acetate solution with a mass concentration of 0.2-0.5%.

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