Process for improving the purity of acetamiprid
By using anhydrous ethanol solvent with nitric acid and controlling reaction conditions in the acetamiprid synthesis process, the problem of numerous impurities in acetamiprid synthesis was solved, and the production of high-purity acetamiprid was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 吴忠领航生物药业科技有限公司
- Filing Date
- 2023-11-02
- Publication Date
- 2026-06-02
AI Technical Summary
Existing acetamiprid synthesis processes contain many impurities, resulting in high costs and requiring multiple purification steps.
Specific solvents and controlled reaction conditions are employed, including the use of anhydrous ethanol solution of nitric acid as the condensation solvent, control of temperature and dropping rate, and integration with the crystallization process to improve purity.
It effectively inhibits the formation of impurities, promotes grain growth, reduces impurities in the finished product, and improves the purity of acetamiprid.
Abstract
Description
Technical Field
[0001] This invention relates to a chemical process, specifically to an improvement in the synthesis process of acetamiprid. Background Technology
[0002] Acetamiprid is a novel insecticide belonging to the neonicotinoid class of compounds. It has contact and stomach poison effects, providing some repellency and antifeedant activity against pests, but lacks systemic and fumigant action. Acetamiprid acts on the synaptic sites of the insect's nervous system, interfering with the transmission of stimuli and causing nerve pathway blockage. This leads to the accumulation of the neurotransmitter acetylcholine at the synaptic sites, resulting in paralysis and ultimately death of the insect.
[0003] Chinese patent document CN107353244A discloses a synthetic process for acetamiprid. This invention addresses the shortcomings of existing acetamiprid synthesis processes, such as complexity and numerous byproducts, by proposing a novel method for synthesizing acetamiprid. Specifically, N-cyano-N'-methylethyleneimine is prepared by reacting cyanoethyl ester with monomethylamine, and then N-cyano-N'-methylethyleneimine is reacted with 2-chloro-5-chloromethylpyridine to synthesize acetamiprid.
[0004] Chinese patent document CN106699646A discloses a method for synthesizing acetamiprid. The method involves the following steps: using toluene as a solvent, 2-chloro-2-chloromethyl-4-cyanobutanal as a starting material, and solid phosgene as a chlorinating agent, the intermediate 2-chloro-5-chloromethylpyridine is prepared at 45-60°C. Then, acetamiprid technical grade is synthesized via methanation and esterification.
[0005] Chinese patent document CN107353244A discloses a synthesis process for a pesticide, specifically a synthesis process for acetamiprid. This invention addresses the shortcomings of existing acetamiprid synthesis processes, such as complexity and numerous byproducts, by proposing a novel method for synthesizing acetamiprid. Specifically, it involves reacting cyanoethyl ester with monomethylamine to prepare N-cyano-N'-methylethyleneimine, which is then reacted with 2-chloro-5-chloromethylpyridine to synthesize acetamiprid.
[0006] Chinese patent document CN106187868A discloses a method for preparing acetamiprid, wherein the method involves reacting 2-chloro-5-chloromethylpyridine with an aqueous solution of methylamine to synthesize N-(6-chloro-3-pyridinemethyl)methylamine, reacting acetonitrile, ethanol, and cyanoethyl ester to synthesize cyanoethyl ester, and then further synthesizing acetamiprid from N-(6-chloro-3-pyridinemethyl)methylamine and cyanoethyl ester.
[0007] Chinese patent document CN114605319A discloses a method for preparing acetamiprid, which involves reacting 2-chloro-5-chloromethylpyridine, aqueous methylamine, acetonitrile, ethanol, and cyanamide to synthesize N-(6-chloro-3-pyridinemethyl)methylamine and cyanoethyl ester, and then further synthesizing acetamiprid from N-(6-chloro-3-pyridinemethyl)methylamine and cyanoethyl ester.
[0008] Chinese patent document CN111808018A discloses a production process for acetamiprid, specifically revealing a preparation route in which acetamiprid is prepared by reacting monomethylamine and 2-chloro-5-chloromethylpyridine with N-cyanoethylimino ester after an amination reaction.
[0009] Chinese patent document CN107501172A discloses a production process for acetamiprid. It includes the following steps: (1) Amination: The solvent is added to the amination reaction vessel, the temperature is lowered, and a certain amount of monomethylamine gas is introduced into the solvent. Under certain temperature conditions, 2-chloro-5-chloromethylpyridine is added to the reaction vessel. After the reaction is completed, the temperature is raised to remove the amine, and then the temperature is lowered and filtered to filter out monomethylamine hydrochloride. After the filtrate is desolvated, it is transferred to the next step. (2) Condensation: Under certain temperature conditions, cyanoethyl ester is added dropwise to the material from the previous step. After the reaction is completed, the temperature is lowered and filtered to obtain acetamiprid. The filtrate is dried and the ethanol is recovered by distillation.
[0010] Chinese patent document CN104803910A discloses a production process for acetamiprid, including the following steps: a) Amination: At room temperature, chloroform is added to an amination reactor. Methylamine gas is introduced submerged into the chloroform solution. At this temperature and atmospheric pressure, 2-chloro-5-chloromethylpyridine is added dropwise to the reactor to keep the reaction temperature below 20°C. The material is cooled to room temperature, water is added, and the mixture is stirred for 1-2 hours. The mixture is allowed to stand and separate into layers. Chloroform is recovered by distillation under atmospheric pressure. After solvent removal, the material is cooled to room temperature and dissolved in ethanol before proceeding to the next reaction step. b) Condensation: At room temperature, an ethanol solution of the amination compound and cyanoethyl ester are added to a condensation reactor in a specific ratio. Stirring is started, and the mixture is cooled to 0°C by passing chilled brine to crystallize. A white solid precipitates out. The solid is then filtered, dried, and the filtrate is sent to an ethanol distillation reactor at 78-80°C under atmospheric pressure to recover ethanol.
[0011] Chinese patent document CN102174013A discloses a new technology for the synthesis of acetamiprid. Benzylmethylamine and N-cyanoethyliminocyanide methyl ester are added to a flask equipped with a stirrer, thermometer, and tail gas absorption device. The mixture is heated to 65°C and reacted for 5 hours in methanol as a solvent. The product is then washed with acetone to obtain acetamiprid. In this invention, the weight ratio of benzylmethylamine to N-cyanoethyliminocyanide methyl ester is 150:110, which ensures that the synthesis yield is increased from 90% to 95%, and the product purity is increased from 96% to 98%.
[0012] Existing technologies for the synthesis of acetamiprid are mature and stable, but they generally contain many impurities, requiring multiple purification processes, which leads to high costs. This invention addresses these problems in acetamiprid synthesis by proposing a new method. Summary of the Invention
[0013] This invention addresses the shortcomings of existing technologies by providing a process for improving the purity of acetamiprid.
[0014] To achieve the above objectives, the present invention adopts the following solution:
[0015] A process for improving the purity of acetamiprid is characterized by comprising the following steps.
[0016] Step 1: Add toluene and 40% monomethylamine aqueous solution to the benzylamine synthesis reactor. After cooling, add 2-chloro-5-chloromethylpyridine dropwise to the surface of the benzylamine synthesis reactor. After the addition is complete, transfer the benzylamine reaction solution in the benzylamine synthesis reactor to the deamination reactor.
[0017] Step 2: Add sodium hydroxide to the deamination vessel. After the reaction is complete, raise the temperature to remove monomethylamine. Transfer the oil phase in the remaining liquid after the removal of monomethylamine to the toluene desolvation vessel.
[0018] Step 3: Heat the toluene desolventizing vessel to remove toluene; transfer the remaining benzylamine in the vessel to the benzylamine intermediate tank;
[0019] Step 4: Add benzylamine from the intermediate tank to the acetamiprid synthesis reactor, add condensation solvent and stir until homogeneous. Under temperature control, slowly add cyanoethyl ester dropwise to the acetamiprid synthesis reactor until the reaction is complete.
[0020] Step 5: Pump ethanol into the acetamiprid synthesis reactor, stir, and then pump the mixture from the acetamiprid synthesis reactor into the crystallization reactor through a filter;
[0021] Step 6: Pump tap water into the crystallization vessel and add a measured amount of seed crystals; cool the crystallization vessel to crystallize acetamiprid.
[0022] Furthermore, the condensation solvent in step 4 is an anhydrous ethanol solution of nitric acid.
[0023] Furthermore, the condensation solvent in step 4 is an anhydrous ethanol solution of nitric acid, with a nitric acid content of 50-100 ppm.
[0024] Furthermore, the condensation solvent preparation process in step 4 is as follows: nitric acid is added to anhydrous ethanol under stirring to form a 1% nitric acid anhydrous ethanol solution; the 1% nitric acid anhydrous ethanol solution is added to anhydrous ethanol under stirring to form a condensation solvent with a nitric acid content of 50-100 ppm.
[0025] Furthermore, in step 1, the temperature inside the benzylamine synthesis reactor is 0-10°C when 2-chloro-5-chloromethylpyridine is added dropwise; the dropwise addition time is 0.5-3 hours.
[0026] Furthermore, the molar ratio of cyanoethyl ester added in step 4 to monomethylamine added in step 1 is 0.9 to 1.2:1.
[0027] Furthermore, in step 4, the reaction temperature for adding cyanoethyl ester is 20–60°C, and the dropping time is 2–3 hours.
[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0029] The method of this invention uses a specific solvent to suppress the generation of impurities during the condensation of benzylamine and cyanoethyl ester, which is beneficial to the subsequent grain enlargement and thus reduces the impurities in the finished product. Detailed Implementation
[0030] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.
[0031] The present invention provides a process for improving the purity of acetamiprid, comprising the following steps.
[0032] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the reactor. The temperature inside the reactor was 0-10°C during the addition of 2-chloro-5-chloromethylpyridine, and the addition time was 0.5-3 hours. After the addition was complete, the benzylamine reaction solution in the reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The remaining liquid after the removal of monomethylamine was then... The oil phase is transferred to a toluene desolventizing reactor; the toluene desolventizing reactor is heated to remove toluene; the remaining benzylamine in the reactor is transferred to a benzylamine intermediate tank; the benzylamine in the intermediate tank is added to the acetamiprid synthesis reactor, a condensation solvent is added and stirred until homogeneous, and cyanoethyl ester is slowly added dropwise to the acetamiprid synthesis reactor under controlled temperature until the reaction is complete; the condensation solvent is an anhydrous ethanol solution of nitric acid with a nitric acid content of 50-100 ppm; the molar ratio of cyanoethyl ester to monomethylamine added is 0.9-1.2:1. The reaction temperature for cyanoethyl ester is 20-60℃, and the dropping time is 2-3 hours. Ethanol is pumped into the acetamiprid synthesis reactor, stirred, and the mixture from the acetamiprid synthesis reactor is pumped into a crystallization reactor through a filter; tap water is pumped into the crystallization reactor, and a measured amount of seed crystals is added; the crystallization reactor is cooled to crystallize acetamiprid.
[0033] The condensation solvent preparation process is as follows: Nitric acid is added to anhydrous ethanol under stirring to form a 1% nitric acid anhydrous ethanol solution; the 1% nitric acid anhydrous ethanol solution is added to anhydrous ethanol under stirring to form a condensation solvent with a nitric acid content of 50-100 ppm.
[0034] Example 1
[0035] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the benzylamine synthesis reactor. The temperature inside the benzylamine synthesis reactor was 0°C during the addition of 2-chloro-5-chloromethylpyridine. The addition time was 3 hours. After the addition was completed, the benzylamine reaction solution in the benzylamine synthesis reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The oil phase in the remaining liquid after the removal of monomethylamine was transferred to a toluene desolventizing reactor. The toluene desolventizing reactor was heated to remove toluene. The remaining benzylamine in the reactor was transferred to a benzylamine intermediate tank. The benzylamine in the intermediate tank was added to an acetamiprid synthesis reactor. A condensation solvent was added and stirred until homogeneous. Under temperature control, cyanoethyl ester was slowly added dropwise to the acetamiprid synthesis reactor until the reaction was completed. The condensation solvent was an anhydrous ethanol solution of nitric acid with a nitric acid content of 50 ppm. The molar ratio of cyanoethyl ester to monomethylamine added was 0.9:1. The temperature for adding cyanoethyl ester was controlled at 20°C, and the dropping time was 3 hours. Ethanol was pumped into the acetamiprid synthesis reactor, and after stirring, the mixture from the acetamiprid synthesis reactor was pumped into the crystallization reactor through a filter. Tap water was pumped into the crystallization reactor to adjust the concentration to 25 g / L, at which point the temperature inside the crystallization reactor was 75°C.
[0036] The crystallization process consists of two steps: after adding a certain amount of seed crystals with a particle size of 0.016-0.032 mm, the temperature is lowered at a rate of 5 degrees Celsius / hour for 1 hour, and then cooled to 20 degrees Celsius within 1 hour.
[0037] After crystallization is complete, the wet crystals are filtered by pressure and then dried.
[0038] Example 2
[0039] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the reactor. The temperature inside the reactor was 10°C during the addition of 2-chloro-5-chloromethylpyridine. The addition time was 0.5 hours. After the addition was complete, the benzylamine reaction solution in the reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The remaining liquid after the removal of monomethylamine was then... The oil phase is transferred to a toluene desolventizing reactor; the toluene desolventizing reactor is heated to remove toluene; the remaining benzylamine in the reactor is transferred to a benzylamine intermediate tank; the benzylamine in the intermediate tank is added to the acetamiprid synthesis reactor, a condensation solvent is added and stirred until homogeneous, and cyanoethyl ester is slowly added dropwise to the acetamiprid synthesis reactor under controlled temperature until the reaction is complete; the condensation solvent is an anhydrous ethanol solution of nitric acid with a nitric acid content of 100 ppm; the molar ratio of cyanoethyl ester to monomethylamine added is 1.2:1. The temperature for adding cyanoethyl ester is controlled at 60℃, and the dropping time is 2 hours. Ethanol is pumped into the acetamiprid synthesis reactor, stirred, and the mixture from the acetamiprid synthesis reactor is pumped into the crystallization reactor through a filter; tap water is pumped into the crystallization reactor to adjust the concentration to 20 g / L, at which point the temperature inside the crystallization reactor is 60℃.
[0040] The crystallization process consists of two steps: after adding a certain amount of seed crystals with a particle size of 0.016-0.032 mm, the temperature is lowered at a rate of 5 degrees Celsius / hour for 1 hour, and then cooled to 20 degrees Celsius within 1 hour.
[0041] After crystallization is complete, the wet crystals are filtered by pressure and then dried.
[0042] Example 3
[0043] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the benzylamine synthesis reactor. The temperature inside the benzylamine synthesis reactor was 5°C during the addition of 2-chloro-5-chloromethylpyridine. The addition time was 2 hours. After the addition was completed, the benzylamine reaction solution in the benzylamine synthesis reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The oil phase in the remaining liquid after the removal of monomethylamine was transferred to a toluene desolventizing reactor. The toluene desolventizing reactor was heated to remove toluene. The remaining benzylamine in the reactor was transferred to a benzylamine intermediate tank. The benzylamine in the intermediate tank was added to an acetamiprid synthesis reactor. A condensation solvent was added and stirred until homogeneous. Under temperature control, cyanoethyl ester was slowly added dropwise to the acetamiprid synthesis reactor until the reaction was completed. The condensation solvent was an anhydrous ethanol solution of nitric acid with a nitric acid content of 80 ppm. The molar ratio of cyanoethyl ester to monomethylamine added was 1.1:1. The temperature for adding cyanoethyl ester was controlled at 40°C, and the dropping time was 2.5 hours. Ethanol was pumped into the acetamiprid synthesis reactor, and after stirring, the mixture from the acetamiprid synthesis reactor was pumped into the crystallization reactor through a filter. Tap water was pumped into the crystallization reactor to adjust the concentration to 20 g / L, at which point the temperature inside the crystallization reactor was 70°C.
[0044] The crystallization process consists of two steps: after adding a certain amount of seed crystals with a particle size of 0.016-0.032 mm, the temperature is lowered at a rate of 5 degrees Celsius / hour for 1 hour, and then cooled to 20 degrees Celsius within 1 hour.
[0045] After crystallization is complete, the wet crystals are filtered by pressure and then dried.
[0046] Comparative Example 1
[0047] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the benzylamine synthesis reactor. The temperature inside the benzylamine synthesis reactor was 10°C during the addition of 2-chloro-5-chloromethylpyridine. The addition time was 0.5 hours. After the addition was completed, the benzylamine reaction solution in the benzylamine synthesis reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The oil phase in the remaining liquid after the removal of monomethylamine was transferred to a toluene desolventizing reactor. The toluene desolventizing reactor was heated to remove toluene. The remaining benzylamine in the reactor was transferred to a benzylamine intermediate tank. The benzylamine in the intermediate tank was added to an acetamiprid synthesis reactor. A condensation solvent was added and stirred until homogeneous. Under temperature control, cyanoethyl ester was slowly added dropwise to the acetamiprid synthesis reactor until the reaction was completed. The condensation solvent was anhydrous ethanol. The molar ratio of cyanoethyl ester to monomethylamine added was 1:1. The temperature for adding cyanoethyl ester was controlled at 40°C, and the dropping time was 3 hours. Ethanol was pumped into the acetamiprid synthesis reactor, and after stirring, the mixture from the acetamiprid synthesis reactor was pumped into the crystallization reactor through a filter. Tap water was pumped into the crystallization reactor to adjust the concentration to 25 g / L, at which point the temperature inside the crystallization reactor was 75°C.
[0048] The crystallization process consists of two steps: after adding a certain amount of seed crystals with a particle size of 0.016-0.032 mm, the temperature is lowered at a rate of 5 degrees Celsius / hour for 1 hour, and then cooled to 20 degrees Celsius within 1 hour.
[0049] After crystallization is complete, the wet crystals are filtered by pressure and then dried.
[0050] Comparative Example 2
[0051] Toluene and a 40% aqueous solution of monomethylamine were added to a benzylamine synthesis reactor. After cooling, 2-chloro-5-chloromethylpyridine was added dropwise to the surface of the liquid in the benzylamine synthesis reactor. The temperature inside the benzylamine synthesis reactor was 5°C during the addition of 2-chloro-5-chloromethylpyridine. The addition time was 2 hours. After the addition was completed, the benzylamine reaction solution in the benzylamine synthesis reactor was transferred to a deamination reactor. Sodium hydroxide was added to the deamination reactor. After the reaction was completed, the temperature was raised to remove monomethylamine. The oil phase in the remaining liquid after the removal of monomethylamine was transferred to a toluene desolventizing reactor. The toluene desolventizing reactor was heated to remove toluene. The remaining benzylamine in the reactor was transferred to a benzylamine intermediate tank. The benzylamine in the intermediate tank was added to an acetamiprid synthesis reactor. A condensation solvent was added and stirred until homogeneous. Under temperature control, cyanoethyl ester was slowly added dropwise to the acetamiprid synthesis reactor until the reaction was completed. The condensation solvent was an anhydrous ethanol solution of nitric acid with a nitric acid content of 500 ppm. The molar ratio of cyanoethyl ester to monomethylamine added was 1.1:1. The temperature for adding cyanoethyl ester was controlled at 40°C, and the dropping time was 2.5 hours. Ethanol was pumped into the acetamiprid synthesis reactor, and after stirring, the mixture from the acetamiprid synthesis reactor was pumped into the crystallization reactor through a filter. Tap water was pumped into the crystallization reactor to adjust the concentration to 20 g / L, at which point the temperature inside the crystallization reactor was 70°C.
[0052] The crystallization process consists of two steps: after adding a certain amount of seed crystals with a particle size of 0.016-0.032 mm, the temperature is lowered at a rate of 5 degrees Celsius / hour for 1 hour, and then cooled to 20 degrees Celsius within 1 hour.
[0053] After crystallization is complete, the wet crystals are filtered by pressure and then dried.
[0054] The finished acetamiprid from the above examples was obtained and analyzed.
[0055] Acetamiprid crystal particles (mesh size) Acetamiprid content (wt%) Example 1 7 99.94 Example 2 7 99.92 Example 3 7 99.95 Comparative Example 1 24 97.76 Comparative Example 2 18 97.50
[0056] In this invention, an anhydrous ethanol solution of nitric acid is used in the condensation process. The small amount of nitric acid inhibits the formation of some products that affect crystallization and also suppresses side reactions. The crystals have larger particles and higher purity.
[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A process for improving the purity of acetamiprid, characterized in that... Includes the following steps: Step 1: Add toluene and 40% monomethylamine aqueous solution to the benzylamine synthesis reactor. After cooling, add 2-chloro-5-chloromethylpyridine dropwise to the surface of the benzylamine synthesis reactor. After the addition is complete, transfer the benzylamine reaction solution in the benzylamine synthesis reactor to the deamination reactor. Step 2: Add sodium hydroxide to the deamination vessel. After the reaction is complete, raise the temperature to remove monomethylamine. Transfer the oil phase in the remaining liquid after the removal of monomethylamine to the toluene desolvation vessel. Step 3: Heat the toluene desolventizing vessel to remove toluene; transfer the remaining benzylamine in the vessel to the benzylamine intermediate tank; Step 4: Add benzylamine from the intermediate tank to the acetamiprid synthesis reactor, add condensation solvent and stir evenly. Under temperature control, slowly add cyanoethyl ester dropwise to the acetamiprid synthesis reactor until the reaction is complete. The condensation solvent in Step 4 is an anhydrous ethanol solution of nitric acid with a nitric acid content of 50-100 ppm. Step 5: Pump ethanol into the acetamiprid synthesis reactor, stir, and then pump the mixture from the acetamiprid synthesis reactor into the crystallization reactor through a filter; Step 6: Pump tap water into the crystallization vessel and add a measured amount of seed crystals; cool the crystallization vessel to crystallize acetamiprid.
2. The process for improving the purity of acetamiprid according to claim 1, characterized in that: The condensation solvent preparation process in step 4 is as follows: nitric acid is added to anhydrous ethanol under stirring to form a 1% nitric acid anhydrous ethanol solution; the 1% nitric acid anhydrous ethanol solution is added to anhydrous ethanol under stirring to form a condensation solvent with a nitric acid content of 50-100 ppm.
3. The process for improving the purity of acetamiprid according to claim 1, characterized in that: In step 1, the temperature inside the benzylamine synthesis reactor is 0-10℃ when 2-chloro-5-chloromethylpyridine is added dropwise; the dropwise addition time is 0.5-3 hours.
4. The process for improving the purity of acetamiprid according to claim 1, characterized in that: The molar ratio of cyanoethyl ester added in step 4 to monomethylamine added in step 1 is 0.9 to 1.2:
1.
5. The process for improving the purity of acetamiprid according to claim 1, characterized in that: In step 4, the reaction temperature for adding cyanoethyl ester is 20–60°C, and the dropping time is 2–3 hours.