A method for preparing pyraclostrobin

Abstract

The application discloses a preparation method of pyraclostrobin and belongs to the technical field of pesticide synthesis. In order to solve the problems of low bromine atom utilization rate and generation of more low-concentration acid-containing wastewater in the production process of pyraclostrobin, the method is provided, which uses sodium bromide as a bromine source, controls the rate of the conversion of the sodium bromide aqueous solution into bromine and sodium chloride, and then realizes bromination in situ. After the reaction is completed, a series of post-treatments are performed to obtain o-nitrobenzyl bromide. Then, etherification and purification treatments are performed to obtain pyrazole benzyl ether (an important intermediate). Finally, reduction, acylation and methylation are performed by using mature technology, and pyraclostrobin is obtained. The sodium bromide can be directly purchased or recycled by simple recovery treatment of the waste liquid formed by the process and directly reused in the process. The method not only provides a new synthesis route for the preparation of pyraclostrobin, but also reduces the raw material cost and improves the bromine atom utilization rate under the premise of realizing the preparation of pyraclostrobin.

Description

Technical Field

[0001] This invention relates to a method for preparing pyraclostrobin, belonging to the field of pesticide synthesis technology. Background Technology

[0002] Pyraclostrobin (developed by BASF) is a methoxyacrylate fungicide that controls plant diseases caused by Ascomycetes, Basidiomycetes, Deuteromycetes, and Oomycetes, while also improving plant tolerance to environmental factors. Based on its synthetic process, it is mainly divided into pre-condensation and post-condensation routes. The pre-condensation routes (such as CN110105287, CN104211641, and CN104592117A) are as follows:

[0003] ;

[0004] Post-contraction routes (such as CN 106008347, etc.) are as follows:

[0005] ;

[0006] Whether it is the pre-condensation method or the post-condensation method, the process involves two steps: bromination and etherification. The raw materials for bromination mainly include bromine, hydrobromic acid + hydrogen peroxide, N-bromosuccinimide (NBS) and other bromine sources, while the main byproduct of etherification is sodium bromide. The byproduct sodium bromide is generally purified multiple times and used as an agricultural-grade raw material.

[0007] However, the above-mentioned bromination process also has its drawbacks: it generates a large amount of low-concentration hydrobromic acid wastewater, and the utilization rate of expensive bromine atoms in bromine and NBS is low. Summary of the Invention

[0008] This invention aims to solve the problems of low bromine atom utilization and the generation of a large amount of low-concentration acidic wastewater in the production process of pyraclostrobin. It proposes to use sodium bromide as the bromine source in the bromination process, which not only provides a new synthetic route for the preparation of pyraclostrobin, but also effectively avoids the generation of a large amount of low-concentration acidic wastewater during the bromination process. In addition, it realizes the recycling of bromine atoms in the bromination and etherification stages, which significantly reduces the cost of raw materials.

[0009] Therefore, a method for preparing pyraclostrobin is proposed.

[0010] To achieve the above technical objectives, the following technical solution is proposed:

[0011] A method for preparing pyraclostrobin includes the following steps:

[0012] X-bromination (synthesis of o-nitrobenzyl bromide)

[0013] X1: Dissolve

[0014] With a sodium bromide weight (kg, industrial grade) to deionized water volume (L) ratio of 1:1.5 to 2.5, sodium bromide is added to a bromination reactor containing deionized water and stirred at a speed of 150 to 200 r / min to dissolve it.

[0015] Then, with a sodium bromide weight (kg) to o-nitrotoluene weight (kg) ratio of 1:1.5 to 2.0, o-nitrotoluene is added to the bromination reactor while stirring.

[0016] With a sodium bromide weight (kg) to dichloroethane weight (kg, industrial grade) ratio of 1:2.5 to 3.5, dichloroethane is added to the bromination reactor while stirring to obtain a solution. The temperature inside the bromination reactor is raised to 45 to 55°C and kept at that temperature.

[0017] The above-mentioned feeding method ensures that sodium bromide dissolves completely in water and that the materials are mixed evenly, thereby guaranteeing the smooth and stable progress of subsequent reactions.

[0018] X2: Preparation of azobisisobutyronitrile-dichloroethane solution

[0019] Weigh azobisisobutyronitrile (AIBN) and dichloroethane separately to prepare an azobisisobutyronitrile-dichloroethane solution with a concentration of 8-15%. Remove suspended solids and transfer the solution to a temporary storage tank for azobisisobutyronitrile-dichloroethane for later use.

[0020] The preparation of an azobisisobutyronitrile (AIBN)-dichloroethane solution with a concentration of 8-15% is mainly based on the solubility of AIBN in dichloroethane. This aims to improve the solubility of AIBN while avoiding excessive waste of the solvent, dichloroethane.

[0021] X3: Reaction

[0022] Based on the assumption that 0.4–0.6 kg of chlorine gas corresponds to 1 kg of sodium bromide, chlorine gas is continuously added to the bromination reactor at a rate of 1.0–2.5 L / min. The temperature inside the bromination reactor is raised to 68–72 °C, and the azobisisobutyronitrile-dichloroethane solution obtained in step X2 is continuously added to the bromination reactor. When the chlorine gas flow rate reaches 2 / 3 of the total chlorine gas (the system inside the bromination reactor is red), the temperature inside the bromination reactor is then raised to 75–85 °C, the system boils, and reflux occurs. During this period, the chlorine gas flow rate is controlled at 0.5–1.0 L / min, i.e., the chlorine flow rate is controlled according to the color inside the bromination reactor to keep the reaction system between yellow and red. In this process, sodium bromide is oxidized to elemental bromine and turns red when chlorine is introduced; while bromine reacts with o-nitrotoluene in azobisisobutyronitrile and loses its color. In fact, the rate of oxidation of sodium bromide is controlled by adjusting the amount of chlorine introduced. The purpose is to keep a small amount of bromine in the system so that the free radical reaction can continue.

[0023] Continue until the remaining chlorine gas is introduced, at which point the system inside the bromination reactor will be orange-red and difficult to fade (as the reaction proceeds, the azobisisobutyronitrile in the reaction is completely consumed, free radicals decrease, and the reaction becomes more difficult, so bromine is difficult to react with the raw materials, hence the difficulty in fading). Stop stirring, and the aqueous phase will shift from the bottom to the top (the density of the reaction system changes depending on the reaction progress. When the raw materials are first added, it is a nearly saturated sodium bromide aqueous solution, which is denser than dichloroethane, so it sinks to the bottom. As the reaction proceeds, the sodium bromide aqueous solution gradually becomes a sodium chloride solution, the density decreases, and finally the density is even less than dichloroethane, so the aqueous phase floats to the top). White salt will precipitate, and oil droplets will adhere to the walls of the bromination reactor (generally, the analytical results shall prevail). Then, purge the chlorine pipeline with a small amount of nitrogen (e.g., for a 25L bromination reactor, 5L of nitrogen is sufficient to completely purge the residual chlorine gas in the chlorine pipeline).

[0024] In this process, chlorine gas is introduced into a bromination reactor at 45–55°C, followed by the continuous addition of AIBN solution to the reactor at 68–72°C. During this process, AIBN slowly decomposes to generate free radicals. The introduced chlorine gas converts sodium bromide in the system into bromine. Once a certain amount of bromine accumulates, the bromination reaction is initiated by the free radicals generated by AIBN. As the temperature increases, the amount of bromine in the reaction system increases after the introduction of chlorine gas. Simultaneously, the reaction gradually accelerates after the free radical reaction is initiated, and more and more free radicals are generated. With stable chlorine gas introduction, the reaction stabilizes at 75–85°C under reflux. At this point, the bromine generated by the introduced chlorine gas and the bromine consumed by the free radical bromination reaction are basically in equilibrium, and the reaction proceeds stably.

[0025] As the reaction proceeds, the amount of o-nitrotoluene feedstock decreases, the amount of product increases, and the amount of sodium chloride in the reaction system also increases. The number of free radicals decreases, and the reaction gradually slows down. At this point, it is necessary to reduce the rate of chlorine gas introduction. Otherwise, the bromine produced in the system will be much higher than the bromine consumed by the bromination reaction, leading to bromine accumulation and causing side reactions such as disubstitution. Therefore, the chlorine gas rate is first controlled at 1.0–2.5 L / min, and then controlled at 0.5–1.0 L / min.

[0026] X4: Post-processing (filtration and phase separation)

[0027] The bromination reactor was kept at 75–85°C for 0.5–1 h (the reflux liquid was colorless); under stirring, it was cooled to room temperature, and a sample was taken to analyze the benzyl bromide content in the reaction system inside the bromination reactor, ensuring that the sum of the peak areas of benzyl bromide and benzyl chloride was greater than 50%; then, it was filtered, washed, and separated to obtain sodium chloride filter cake, aqueous phase I (which mainly contains hydrobromic acid, sodium bromide, hydrochloric acid, sodium chloride, etc.), and benzyl bromide organic phase, which is o-nitrobenzyl bromide, and was introduced into a benzyl bromide organic phase temporary storage tank for later use;

[0028] In this process, aqueous phase I is adjusted to neutral and then directly reused in the dissolution step of the bromination process, achieving the recovery and reuse of sodium bromide. The normal reflux temperature for the reaction is 75–85°C. After the AIBN solution is added and the reaction has progressed to a certain stage, there are no external free radicals. As the reaction continues, the number of free radicals decreases, and the reaction slows down until the deep red color does not fade even after chlorine gas is introduced. At this point, the heat preservation reaction utilizes the remaining free radicals in the reaction system to convert all unreacted bromine, avoiding the volatilization of bromine vapor during post-processing, which could cause environmental pollution or harm to operators. Because benzyl bromide is irritating, it is cooled to room temperature during post-processing to further reduce the volatilization of benzyl bromide and minimize harm to operators. Additionally, sampling and testing are required at this time to assess the progress of the bromination reaction and prepare for subsequent etherification.

[0029] Y-etherification

[0030] Y1: Feeding

[0031] The obtained o-nitrobenzyl bromide was pumped into the etherification reactor using a vacuum pump.

[0032] With a volume ratio (L) of o-nitrobenzyl bromide, a weight ratio (kg) of pyrazolol, and a weight ratio (kg) of tetrabutylammonium bromide (TBAB) of 4.0–5.0:1:2.0–2.5, pyrazolol and tetrabutylammonium bromide were added to the etherification reactor, and then the reactor wall was rinsed with dichloroethane.

[0033] Since the benzyl bromide organic phase obtained after post-processing is irritating (cause eye irritation), it is drawn into the etherification reactor under negative pressure. This liquid must be added before the reaction to avoid jamming the agitator when adding the solid. In addition, after adding the liquid, adding the solid under stirring can make the materials mix evenly and facilitate the etherification reaction. Therefore, the above-mentioned feeding method is adopted.

[0034] Y2: Heating

[0035] The temperature inside the etherification reactor should be controlled at 50–60°C. At this temperature, etherification can proceed normally. If the reaction temperature is too low, the formation of the etherification product will be slower after the subsequent addition of alkali solution; if the reaction temperature is too high, the subsequent addition of alkali solution will accelerate the hydrolysis of benzyl bromide and increase the amount of benzyl alcohol byproducts, resulting in insufficient benzyl bromide and incomplete etherification.

[0036] Y3: Add alkaline solution

[0037] With a volume ratio (L) of o-nitrobenzyl bromide to the weight (kg) of alkali solution of 3:1, a metering pump was used to add alkali solution with a concentration of 12-17% to the etherification reactor, and the addition time was controlled to be 0.8-1.2 hours. The concentration of the alkali solution was limited to ensure the yield while minimizing wastewater formation. Using a lower concentration of alkali solution for the etherification reaction would generate more wastewater, and the subsequent energy consumption for recovering sodium bromide from the distillation wastewater would be high. Conversely, an excessively high concentration of alkali solution would cause the reaction temperature to rise rapidly, and the higher concentration would also increase the hydrolysis of benzyl bromide, thus reducing the etherification yield. Therefore, the selection of this alkali solution concentration was determined by considering both the reaction yield and the wastewater.

[0038] The temperature inside the etherification reactor should be controlled at 55-65℃. During the addition of alkali solution, a large amount of heat will be released, so pay attention to temperature control and check if the mixture can be stirred. If it cannot be stirred, raise the temperature to reflux.

[0039] Y4: Detection

[0040] After adding the alkali solution, keep the temperature at 70–75℃ for 0.5–1 hour, then take a sample to test if the percentage of the pyrazol peak area is less than 0.5%.

[0041] After the alkali solution is added, some benzyl bromide and pyrazol remain unethered. However, the concentration of reactants is already low, and the activity of the materials is reduced. Therefore, the temperature needs to be increased to ensure the complete conversion of the remaining small amount of raw materials. As the reaction temperature increases, the solubility of the materials in dichloroethane increases, and the raw materials trapped in the product are released and react completely together. After holding at this temperature for 0.5–1 hour, the conversion is complete. Sampling and testing are performed to further confirm whether the reaction conversion is complete. If there are remaining raw materials, the time can be appropriately extended, or the corresponding raw materials can be added to ensure complete conversion, thereby ensuring the efficiency and quality of the etherification reaction.

[0042] Y5: Crystallization

[0043] After passing the test, the temperature inside the etherification reactor is slowly lowered to 63-67°C, and seed crystals (pyrazole benzyl ether) are added; then, the temperature is slowly lowered to 52-58°C, and then lowered to room temperature within 2-2.5 hours; finally, the cooling water in the jacket is released, and the temperature inside the etherification reactor is further lowered to 0-5°C by the refrigerant.

[0044] After the reaction is complete, the mixture is kept at 70–75°C for 0.5–1 hour, at which point the material is almost completely dissolved. As the temperature decreases, the material gradually precipitates. To ensure the precipitated product crystals are large (larger crystals are beneficial for subsequent centrifugation, allowing for drier material removal), a slow, gradient cooling process is required. Seed crystals are added during this cooling process to induce crystallization. The study found that a critical crystallization point is reached at 63–67°C, which is the optimal time to add seed crystals. Furthermore, a slow, gradient cooling process is necessary during crystallization to control the crystal form. After cooling to 52–58°C, most of the crystals have precipitated. Further cooling to 0–5°C allows as much of the product in the solvent as possible to precipitate. Additionally, the low temperature reduces solvent evaporation during subsequent centrifugation, aligning with industrial goals of resource conservation and a stable operating environment.

[0045] Y6: Centrifugation, washing

[0046] Transfer to a centrifuge and control the centrifugation speed to 1000-3000 r / min. Centrifuge to obtain the first filter cake (a large amount of benzyl ether product generated after the reaction, with few impurities and regular crystal form) and the first centrifugation mother liquor (mainly composed of dichloroethane, o-nitrotoluene, etc., among which o-nitrotoluene has poor solubility for the intermediate pyrazole benzyl ether).

[0047] For the first filter cake: wash with dichloroethane and deionized water respectively (mainly to remove a small amount of tar and salt), and dry to obtain a light yellow benzyl ether intermediate (i.e., pyrazole benzyl ether, which is an important intermediate in the synthesis process of pyrazole ether ester).

[0048] For the first centrifuged mother liquor: phase separation is performed to obtain aqueous phase II and dichloroethane organic phase. Aqueous phase II is distilled under reduced pressure and recrystallized to recover sodium bromide and water. Then, sodium bromide is directly reused in the dissolution step of the bromination process, and water is used to prepare alkaline solution, so as to realize the recovery and reuse of sodium bromide and water.

[0049] Dichloroethane organic phase is subjected to vacuum distillation to obtain dichloroethane and a concentrated solution (solid-liquid heterogeneous phase). The dichloroethane is reused in the dissolution step of the bromination process and / or in the preparation step of the azobisisobutyronitrile-dichloroethane solution, and / or in the feeding step of the etherification process. The main components of the concentrated solution are o-nitrotoluene and pyrazole benzyl ether. Since o-nitrotoluene has poor solubility in pyrazole benzyl ether, it is centrifuged twice to obtain a second filter cake (pyrazole benzyl ether with more impurities) and a second centrifugation mother liquor (mainly o-nitrotoluene). The second filter cake is reused in the heating step of the etherification process to achieve effective recovery of pyrazole benzyl ether. The second centrifugation mother liquor is subjected to vacuum distillation to obtain o-nitrotoluene. Other impurities form solid waste. Then, the o-nitrotoluene is reused in the dissolution step of the bromination process to achieve the recovery and reuse of o-nitrotoluene.

[0050] Preparation of Z. pyraclostrobin

[0051] The benzyl ether intermediate obtained in step Y6 is reduced, acylated, and methylated to obtain pyraclostrobin.

[0052] Furthermore, this technical solution provides a preparation system adapted to the preparation method, including a bromination reactor, an etherification reactor, a reduction device, an acylation device, and a methylation device, wherein:

[0053] The bromination reactor is connected to a deionized water storage tank, a sodium bromide storage tank, an o-nitrotoluene storage tank, a dichloroethane storage tank, and an azobisisobutyronitrile-dichloroethane solution storage tank via feed pipelines, with corresponding metering pumps installed on the feed pipelines. Additionally, the bromination reactor is connected to a chlorine storage tank via a chlorine gas delivery pipeline, which is equipped with a control valve and a flow meter.

[0054] A filtration device is installed at the rear of the bromination reactor. The aqueous phase outlet of the filtration device is connected to an aqueous phase collection tank, which is connected to an alkali delivery pipe. The aqueous phase collection tank is connected to the bromination reactor. The organic phase outlet of the filtration device is connected to a benzyl bromide organic phase temporary storage tank, which is connected to the etherification reactor through a delivery pipe. A vacuum pump is installed on the delivery pipe.

[0055] Etherification reactor: It is connected to pyrazol alcohol storage tank, tetrabutylammonium bromide storage tank and alkali storage tank through feed pipeline, and corresponding metering pumps are installed on the feed pipeline; and the etherification reactor is connected to dichloroethane storage tank through delivery pipe. After feeding is completed, the reactor wall is flushed with dichloroethane as required.

[0056] Centrifuge I is installed at the rear of the etherification reactor. The filter cake outlet of centrifuge I is connected to a washing tank. The washing tank is connected to a dichloroethane delivery pipe and a deionized water delivery pipe. A drying device is installed at the rear of the washing tank. A pyrazole benzyl ether temporary storage tank is installed at the rear of the drying device.

[0057] The mother liquor outlet of centrifuge I is connected to a phase separation device. The aqueous phase outlet of the phase separation device is connected to distillation vessel I. The sodium bromide outlet of distillation vessel I is connected to the bromination reactor and / or sodium bromide storage tank via a sodium bromide recycling pipe. The water outlet of distillation vessel I is connected to the alkali preparation tank (the alkali storage tank is connected to the alkali preparation tank) via a water recycling pipe. The organic phase outlet of the phase separation device is connected to distillation vessel II. The dichloroethane outlet of distillation vessel II is connected to the bromination reactor and / or dichloroethane storage tank and / or azobisisobutyronitrile-dichloroethane solution preparation tank via a dichloroethane recycling pipe. The concentrate outlet of distillation vessel II is connected to centrifuge II. The filter cake outlet of centrifuge II is connected to the etherification reactor. The mother liquor outlet of centrifuge II is connected to distillation vessel III. The o-nitrotoluene outlet of distillation vessel III is connected to the bromination reactor and / or o-nitrotoluene storage tank via an o-nitrotoluene recycling pipe.

[0058] Reduction device: Located behind the workstation of the pyrazole benzyl ether temporary storage tank, the reduction device is connected to the pyrazole benzyl ether temporary storage tank;

[0059] Acylation unit: Located behind the reduction unit, the acylation unit is connected to the reduction unit;

[0060] Methylation unit: Located behind the station of the acylation unit, the methylation unit is connected to the acylation unit;

[0061] A continuous pathway for the preparation of pyraclostrobin is formed between the bromination reactor, the filtration device, the benzyl bromide organic phase temporary storage tank, the etherification reactor, centrifuge I, the washing tank, the drying device, the reduction device, the acylation device, and the methylation device.

[0062] Among them, the aqueous phase collection tank, alkali delivery pipe, phase separation device, distillation kettle I, sodium bromide recycling pipe, water recycling pipe, distillation kettle II, centrifuge II, distillation kettle III and o-nitrotoluene recycling pipe form a continuous channel for waste liquid recycling and reuse.

[0063] Furthermore, both the bromination reactor and the etherification reactor are equipped with a stirring mechanism, and both are equipped with a temperature detector. Both the bromination reactor and the etherification reactor are fitted with a temperature control jacket.

[0064] Furthermore, the bromination reactor is equipped with a sampling port.

[0065] Furthermore, the etherification reactor is equipped with a sampling port.

[0066] Furthermore, the etherification reactor is provided with a seed inlet, which is connected to a seed feed pipe.

[0067] The equations involved in this technical solution include:

[0068] ;

[0069] ;

[0070] .

[0071] In this technical solution, the term "slow" is used in the chemical industry and the term "room temperature" is used in the chemical industry, generally referring to a temperature of 20-25℃.

[0072] The positional relationships involved in this technical solution, such as "between", "above", "front side of the workstation", and "rear side of the workstation", are defined according to the actual usage conditions and are common terms in this technical field, as well as common terms used by those skilled in the art in actual use.

[0073] The beneficial technical effects of adopting this technical solution are as follows:

[0074] I. In this invention, the solubility of sodium bromide is approximately 120 g / 100 g water (80°C), and the solubility of sodium chloride is approximately 38 g / 100 g water (80°C), with the sodium chloride solubility showing minimal change with temperature. Furthermore, by controlling the chlorine flow rate, the rate at which the sodium bromide aqueous solution transforms into bromine and sodium chloride can be effectively controlled, thereby enabling in-situ bromine production to achieve the bromination operation. After the reaction is complete, supersaturated sodium chloride solid is filtered out, and the organic phase is the bromination product. Then, etherification and purification are performed to obtain pyrazole benzyl ether. Finally, using mature technology, reduction, acylation, and methylation are carried out to obtain pyrazole ether ester. Sodium bromide can be directly purchased or the waste liquid generated by this process can be simply recycled and reused in this process. This provides a new synthetic route for the preparation of pyrazole ether ester (specifically, the preparation of the benzyl ether intermediate); on the other hand, while achieving the preparation of pyrazole ether ester, it can reduce raw material costs and improve the utilization rate of bromine atoms.

[0075] Second, this invention uses sodium bromide, a byproduct of etherification, as the raw material for the bromination process, thus avoiding the generation of a large amount of low-concentration acidic wastewater during bromination (reducing the formation of approximately 100 kg of wastewater per 100 kg of pyrazole benzyl ether produced). At the same time, it realizes the recycling of bromine atoms in the bromination and etherification stages, significantly reducing the cost of raw materials (saving 1,000 yuan per 100 kg of pyrazole benzyl ether produced). Attached Figure Description

[0076] Figure 1 This is a process flow diagram (I) of the present invention;

[0077] Figure 2 This is the process flow diagram (II) of the present invention;

[0078] Figure 3 This is a schematic diagram illustrating the working principle of the present invention;

[0079] Figure 4 This is a structural block diagram (I) of the preparation system in this invention;

[0080] Figure 5 This is a structural block diagram (II) of the preparation system in this invention;

[0081] Figure 6 This is the carbon spectrum of the pyrazole benzyl ether in this invention;

[0082] Figure 7 This is the hydrogen spectrum of pyrazole benzyl ether in this invention;

[0083] In the diagram: 1. Bromination reactor; 2. Etherification reactor; 3. Reduction unit; 4. Acylation unit; 5. Methylation unit; 6. Deionized water storage tank; 7. Sodium bromide storage tank; 8. o-nitrotoluene storage tank; 9. Dichloroethane storage tank; 10. Azobisisobutyronitrile-dichloroethane solution storage tank; 11. Metering pump; 12. Chlorine gas delivery pipeline; 13. Chlorine gas storage tank; 14. Control valve; 15. Flow meter; 16. Filtration device; 17. Aqueous phase collection tank; 18. Alkali delivery pipeline; 19. Benzyl bromide organic phase temporary storage tank; 20. Pyrazole. 21. Alcohol storage tank; 22. Tetrabutylammonium bromide storage tank; 23. Alkali storage tank; 24. Centrifuge I; 25. Washing tank; 26. Dichloroethane conveying pipe; 27. Deionized water conveying pipe; 28. Drying device; 29. ​​Pyrazole benzyl ether temporary storage tank; 30. Phase separation device; 31. Distillation kettle I; 32. Sodium bromide recycling pipe; 33. Water recycling pipe; 34. Distillation kettle II; 35. Distillation kettle III; 36. o-nitrotoluene recycling pipe; 37. Seed crystal feed pipe; 38. Centrifuge II; 39. Alkali preparation tank. Detailed Implementation

[0084] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0085] Example 1

[0086] This embodiment provides a method for preparing pyraclostrobin, such as... Figure 1 As shown, it includes the following steps:

[0087] X. Bromination

[0088] Dissolution: Based on the weight ratio of sodium bromide, volume of deionized water, weight of o-nitrotoluene, and weight of dichloroethane being 1:1.5-2.5:1.5-2.0:2.5-3.5, deionized water, sodium bromide, o-nitrotoluene, and dichloroethane are separately added to the bromination reactor for dissolution, and the temperature inside the bromination reactor is raised to 45-55°C.

[0089] Reaction: Based on 0.4–0.6 kg of chlorine per kg of sodium bromide, continuously add chlorine gas to the bromination reactor, controlling the chlorine gas rate at 1.0–2.5 L / min; raise the temperature of the bromination reactor to 68–72°C, and continuously add azobisisobutyronitrile-dichloroethane solution (the addition rate of the azobisisobutyronitrile-dichloroethane solution can be adjusted according to the reaction conditions, i.e., the amount of free radicals in the reaction system); when the amount of chlorine gas introduced accounts for 2 / 3 of the total chlorine gas, raise the temperature of the bromination reactor to 75–85°C, controlling the chlorine gas rate at 0.5–1.0 L / min, until the remaining chlorine gas is introduced;

[0090] Post-treatment: The bromination reactor is kept at 75-85℃ for 0.5-1h;

[0091] Then, the mixture was cooled to room temperature, and samples were taken to analyze the benzyl bromide content in the reaction system inside the bromination reactor, ensuring that the sum of the peak areas of benzyl bromide and benzyl chloride was greater than 50%. Subsequently, the mixture was filtered, washed, and separated to obtain sodium chloride filter cake, aqueous phase I, and benzyl bromide organic phase. The benzyl bromide organic phase is o-nitrobenzyl bromide, which was temporarily stored for later use.

[0092] Y. Etherification

[0093] Feeding: Based on a volume ratio of o-nitrobenzyl bromide, pyrazolol, and tetrabutylammonium bromide of 4.0-5.0:1:2.0-2.5, o-nitrobenzyl bromide, pyrazolol, and tetrabutylammonium bromide are added to the etherification reactor, and the temperature inside the etherification reactor is raised to 50-60°C.

[0094] With a volume ratio of o-nitrobenzyl bromide to alkali solution of 3:1, alkali solution is added to the etherification reactor, and the alkali solution addition time is controlled at 0.8 to 1.2 hours, while the temperature inside the etherification reactor is controlled at 55 to 65°C.

[0095] After adding the alkali solution, keep the temperature at 70–75℃ for 0.5–1 hour, then take a sample to test if the percentage of the pyrazol peak area is less than 0.5%.

[0096] Crystallization: The temperature inside the etherification reactor is lowered to 63-67℃, and seed crystals of pyrazole benzyl ether are added; then, the temperature is lowered to 52-58℃, and then lowered to room temperature over 2-2.5 hours; finally, the temperature inside the etherification reactor is lowered to 0-5℃.

[0097] Centrifugation: Transfer to a centrifuge, centrifuge to obtain the first filter cake and the first centrifugal mother liquor;

[0098] Washing: The first filter cake was washed with dichloroethane and deionized water respectively, and then dried to obtain pyrazole benzyl ether;

[0099] Preparation of Z. pyraclostrobin

[0100] The obtained pyrazole benzyl ether was reduced, acylated, and methylated to obtain pyrazole ether ester.

[0101] Example 2

[0102] This embodiment provides a method for preparing pyraclostrobin, such as... Figure 2-3 As shown, it includes the following steps:

[0103] X-bromination (synthesis of o-nitrobenzyl bromide)

[0104] X1: Dissolve

[0105] With a sodium bromide weight (kg, industrial grade) to deionized water volume (L) ratio of 1:1.5 to 2.5, sodium bromide is added to a bromination reactor containing deionized water and stirred at a speed of 150 to 200 r / min to dissolve it.

[0106] Then, with a sodium bromide weight (kg) to o-nitrotoluene weight (kg) ratio of 1:1.5 to 2.0, o-nitrotoluene is added to the bromination reactor while stirring.

[0107] With a sodium bromide weight (kg) to dichloroethane weight (kg, industrial grade) ratio of 1:2.5 to 3.5, dichloroethane is added to the bromination reactor while stirring to obtain a solution. The temperature inside the bromination reactor is raised to 45 to 55°C and kept at that temperature.

[0108] X2: Preparation of azobisisobutyronitrile-dichloroethane solution

[0109] Weigh azobisisobutyronitrile (AIBN) and dichloroethane separately to prepare an azobisisobutyronitrile-dichloroethane solution with a concentration of 8-15%. Remove suspended solids and transfer the solution to a temporary storage tank for azobisisobutyronitrile-dichloroethane for later use.

[0110] X3: Reaction

[0111] Based on the assumption that 0.4–0.6 kg of chlorine gas corresponds to 1 kg of sodium bromide, chlorine gas is continuously added to the bromination reactor at a rate of 1.0–2.5 L / min. The temperature inside the bromination reactor is raised to 68–72 °C, and the azobisisobutyronitrile-dichloroethane solution obtained in step X2 is continuously added to the bromination reactor. When the chlorine gas flow rate reaches 2 / 3 of the total chlorine gas (the system inside the bromination reactor is red), the temperature inside the bromination reactor is then raised to 75–85 °C, the system boils, and reflux occurs. During this period, the chlorine gas flow rate is controlled at 0.5–1.0 L / min. That is, the chlorine flow rate is controlled according to the color inside the bromination reactor to keep the reaction system between yellow and red. In this process, sodium bromide is oxidized to elemental bromine and turns red when chlorine is introduced; while bromine reacts with o-nitrotoluene in azobisisobutyronitrile and loses its color. In fact, the rate of oxidation of sodium bromide is controlled by adjusting the amount of chlorine introduced. The purpose is to keep a small amount of bromine in the system so that the free radical reaction can continue.

[0112] Continue until the remaining chlorine gas is introduced, at which point the system inside the bromination reactor will be orange-red and difficult to fade (as the reaction proceeds, the azobisisobutyronitrile in the reaction is completely consumed, free radicals decrease, and the reaction becomes more difficult, so bromine is difficult to react with the raw materials, hence the difficulty in fading). Stop stirring, and the aqueous phase will shift from the bottom to the top (the density of the reaction system changes depending on the reaction progress. When the raw materials are first added, it is a nearly saturated sodium bromide aqueous solution, which is denser than dichloroethane, so it sinks to the bottom. As the reaction proceeds, the sodium bromide aqueous solution gradually becomes a sodium chloride solution, the density decreases, and finally the density is even less than dichloroethane, so the aqueous phase floats to the top). White salt will precipitate, and oil droplets will adhere to the walls of the bromination reactor (generally, the analytical results shall prevail). Then, purge the chlorine pipeline with a small amount of nitrogen (e.g., for a 25L bromination reactor, 5L of nitrogen is sufficient to completely purge the residual chlorine gas in the chlorine pipeline).

[0113] X4: Post-processing (filtration and phase separation)

[0114] The bromination reactor was kept at 75–85°C for 0.5–1 hour (the reflux liquid was colorless). Under stirring, it was cooled to room temperature, and samples were taken to analyze the benzyl bromide content in the reaction system, ensuring that the sum of the peak areas of benzyl bromide and benzyl chloride was greater than 50%. Then, the mixture was filtered, separated, and washed to obtain a sodium chloride filter cake, aqueous phase I (mainly containing hydrobromic acid, sodium bromide, hydrochloric acid, sodium chloride, etc.), and a benzyl bromide organic phase, namely o-nitrobenzyl bromide, which was introduced into a temporary storage tank for benzyl bromide organic phase for later use. Aqueous phase I was adjusted to neutral and then directly reused in the dissolution process of bromination, achieving the recovery and reuse of sodium bromide.

[0115] Y-etherification

[0116] Y1: Feeding

[0117] The obtained o-nitrobenzyl bromide was pumped into the etherification reactor using a vacuum pump.

[0118] With a volume ratio (L) of o-nitrobenzyl bromide, a weight ratio (kg) of pyrazolol, and a weight ratio (kg) of tetrabutylammonium bromide (TBAB) of 4.0–5.0:1:2.0–2.5, pyrazolol and tetrabutylammonium bromide were added to the etherification reactor, and then the reactor wall was rinsed with dichloroethane.

[0119] Y2: Heating

[0120] The temperature inside the etherification reactor should be controlled at 50–60°C.

[0121] Y3: Add alkaline solution

[0122] With a volume ratio (L) of o-nitrobenzyl bromide to the weight (kg) of alkali solution of 3:1, a metering pump is used to add alkali solution of 12-17% to the etherification reactor, and the time for adding alkali solution is controlled to be 0.8-1.2h.

[0123] The temperature inside the etherification reactor should be controlled at 55-65℃. During the addition of alkali solution, a large amount of heat will be released, so pay attention to temperature control and check if the mixture can be stirred. If it cannot be stirred, raise the temperature to reflux.

[0124] Y4: Detection

[0125] After adding the alkali solution, keep the temperature at 70–75℃ for 0.5–1 hour, then take a sample to test if the percentage of the pyrazol peak area is less than 0.5%.

[0126] Y5: Crystallization

[0127] After passing the test, the temperature inside the etherification reactor is slowly lowered to 63-67°C, and seed crystals (pyrazole benzyl ether) are added; then, the temperature is slowly lowered to 52-58°C, and then lowered to room temperature within 2-2.5 hours; finally, the cooling water in the jacket is released, and the temperature inside the etherification reactor is further lowered to 0-5°C by the refrigerant.

[0128] Y6: Centrifugation, washing

[0129] Transfer to a centrifuge and control the centrifugation speed to 1000-3000 r / min. Centrifuge to obtain the first filter cake (a large amount of benzyl ether product generated after the reaction, with few impurities and regular crystal form) and the first centrifugation mother liquor (mainly composed of dichloroethane, o-nitrotoluene, etc., among which o-nitrotoluene has poor solubility for the intermediate pyrazole benzyl ether).

[0130] For the first filter cake: wash with dichloroethane and deionized water respectively (mainly to remove a small amount of tar and salt), and dry to obtain a light yellow benzyl ether intermediate (i.e., pyrazole benzyl ether, which is an important intermediate in the synthesis process of pyrazole ether ester).

[0131] For the first centrifuged mother liquor: phase separation is performed to obtain aqueous phase II and dichloroethane organic phase. Aqueous phase II is distilled under reduced pressure and recrystallized to recover sodium bromide and water. Then, sodium bromide is directly reused in the dissolution step of the bromination process, and water is used to prepare alkaline solution, so as to realize the recovery and reuse of sodium bromide and water.

[0132] Dichloroethane organic phase is subjected to vacuum distillation to obtain dichloroethane and a concentrated solution (solid-liquid heterogeneous phase). The dichloroethane is reused in the dissolution step of the bromination process and / or the preparation step of the azobisisobutyronitrile-dichloroethane solution, and / or the feeding step of the etherification process. The main components of the concentrated solution are o-nitrotoluene and pyrazole benzyl ether. Since o-nitrotoluene has poor solubility in pyrazole benzyl ether, it is centrifuged twice to obtain a second filter cake (pyrazole benzyl ether with more impurities) and a second centrifugation mother liquor (mainly o-nitrotoluene). The second filter cake is reused in the heating step of the etherification process to achieve effective recovery of pyrazole benzyl ether. The second centrifugation mother liquor is subjected to vacuum distillation to obtain o-nitrotoluene. Other impurities form solid waste. Then, the o-nitrotoluene is reused in the dissolution step of the bromination process to achieve the recovery and reuse of o-nitrotoluene.

[0133] Preparation of Z. pyraclostrobin

[0134] The benzyl ether intermediate obtained in step Y6 is reduced, acylated, and methylated to obtain pyraclostrobin.

[0135] Example 3

[0136] Based on Examples 1-2, this example provides a preparation system adapted to the preparation method, such as... Figure 4 As shown, it includes a bromination reactor 1, an etherification reactor 2, a reduction device 3, an acylation device 4, and a methylation device 5, wherein:

[0137] Bromination reactor 1: It is connected to a deionized water storage tank 6, a sodium bromide storage tank 7, an o-nitrotoluene storage tank 8, a dichloroethane storage tank 9, and an azobisisobutyronitrile-dichloroethane solution storage tank 10 via feed pipelines. A corresponding metering pump 11 is installed on the feed pipeline. Furthermore, bromination reactor 1 is connected to a chlorine storage tank 13 via a chlorine gas delivery pipeline 12. A control valve 14 and a flow meter 15 are installed on the chlorine gas delivery pipeline 12.

[0138] A filtration device 16 is installed at the rear of the work station of the bromination reactor 1. The organic phase outlet of the filtration device 16 is connected to a benzyl bromide organic phase temporary storage tank 19. The benzyl bromide organic phase temporary storage tank 19 is connected to the etherification reactor 2 through a conveying pipe. A vacuum pump is installed on the conveying pipe.

[0139] Etherification reactor 2: It is connected to pyrazol storage tank 20, tetrabutylammonium bromide storage tank 21 and alkali storage tank 22 through feed pipelines, and corresponding metering pumps 11 are installed on the feed pipelines; and the etherification reactor 2 is connected to dichloroethane storage tank 9 through a conveying pipe. After the feeding is completed, the reactor wall of the etherification reactor 2 is flushed with dichloroethane as required.

[0140] Centrifuge I 23 is installed at the rear of the station of etherification reactor 2. The filter cake outlet of centrifuge I 23 is connected to washing tank 24. Washing tank 24 is connected to dichloroethane delivery pipe 25 and deionized water delivery pipe 26. Drying device 27 is installed at the rear of the station of washing tank 24. Pyrazole benzyl ether temporary storage tank 28 is installed at the rear of the station of drying device 27.

[0141] Reduction device 3: Located at the rear of the workstation of pyrazole benzyl ether temporary storage tank 28, and connected to pyrazole benzyl ether temporary storage tank 28;

[0142] Acylation device 4: Located behind the station of reduction device 3, acylation device 4 is connected to reduction device 3;

[0143] Methylation device 5: Located behind the station of acylation device 4, methylation device 5 is connected to acylation device 4;

[0144] A continuous pathway for the preparation of pyraclostrobin is formed between bromination reactor 1, filtration device 16, benzyl bromide organic phase temporary storage tank 19, etherification reactor 2, centrifuge I 23, washing tank 24, phase separation device 29, drying device 27, reduction device 3, acylation device 4 and methylation device 5.

[0145] Both the bromination reactor 1 and the etherification reactor 2 are equipped with stirring mechanisms, and both are equipped with temperature detectors. Both the bromination reactor 1 and the etherification reactor 2 are fitted with temperature control jackets.

[0146] A sampling port is provided on both the bromination reactor 1 and the etherification reactor 2. This facilitates the sampling of substances inside the corresponding reactors to understand the extent of the reaction.

[0147] The etherification reactor 2 is equipped with a seed inlet, which is connected to a seed inlet pipe 37.

[0148] Example 4

[0149] Based on Example 3, this example recycles and reuses the waste liquid generated in the pyraclostrobin production process, thereby improving the utilization rate of raw materials and reducing emissions, which is environmentally friendly. Therefore, the following limitations are imposed:

[0150] like Figure 5 As shown, the aqueous phase outlet of the filtration device 16 is connected to an aqueous phase collection tank 17, which is connected to an alkali delivery pipe 18. The aqueous phase collection tank 17 is connected to the bromination reactor 1 to neutralize the aqueous phase I, and then the recovered sodium bromide is reused in the bromination process, thereby improving the utilization rate of the bromine source.

[0151] In addition, the mother liquor outlet of centrifuge I23 is connected to a phase separation device 29, the aqueous phase outlet of phase separation device 29 is connected to a distillation vessel I30, the sodium bromide outlet of distillation vessel I30 is connected to the bromination reaction vessel 1 and / or the sodium bromide storage tank 7 via a sodium bromide recycling pipe 31, and the water outlet of distillation vessel I30 is connected to the alkali preparation tank 39 via a water recycling pipe 32; the organic phase outlet of phase separation device 29 is connected to a distillation vessel II33, and the dichloroethane outlet of distillation vessel II33 is connected to the dichloroethane... Alkane recycling pipe 34 is connected to bromination reactor 1 and / or dichloroethane storage tank 9 and / or azobisisobutyronitrile-dichloroethane solution preparation tank. The concentrate outlet of distillation vessel II 33 is connected to centrifuge II 38. The filter cake outlet of centrifuge II 38 is connected to etherification reactor 2. The mother liquor outlet of centrifuge II 38 is connected to distillation vessel III 35. The o-nitrotoluene outlet of distillation vessel III 35 is connected to bromination reactor 1 and / or o-nitrotoluene storage tank 8 via o-nitrotoluene recycling pipe 36. This achieves the recovery and utilization of sodium bromide, water, dichloroethane, and o-nitrotoluene, as well as the effective collection of solid waste for subsequent centralized treatment.

[0152] Example 5

[0153] This embodiment provides a preparation process for pyrazole benzyl ether, specifically including:

[0154] 1.1 Weigh 5.68 kg of deionized water and pump it into a 25 L glass reactor using a centrifugal pump. Then turn on the stirrer at 150-200 r / min.

[0155] 1.2 Weigh 2.94 kg of industrial-grade sodium bromide and add it into a 25 L glass reactor through the solid feed port;

[0156] 1.3 Weigh 4.85 kg of o-nitrotoluene and add it to the glass reactor while stirring;

[0157] 1.4 Weigh 8 kg of industrial-grade dichloroethane and add it to the reactor;

[0158] 1.5 Turn on the power to the circulating water bath and start heating;

[0159] 1.6 When the temperature inside the reactor reaches 50℃, weigh 0.25 kg of azobisisobutyronitrile (AIBN), dissolve it in 1.78 kg of dichloroethane, remove the suspended solids, and transfer it to a constant pressure dropping funnel for later use.

[0160] 1.7 Open the chlorine valve and slowly pass chlorine through until the system turns red. At around 70°C, start adding azobisisobutyronitrile solution dropwise into the reactor. When the temperature rises to around 80°C, the system boils and reflux occurs. Control the chlorine flow rate between yellow and red based on the color inside the reactor.

[0161] 1.8 When 1.5 kg of chlorine gas is introduced, the system turns orange-red and is difficult to fade. Stop stirring. The aqueous phase changes from the bottom layer to the top layer, and white salt precipitates out. Oil droplets and other phenomena are observed on the vessel wall (generally based on the analysis results). Stop chlorination and purge the chlorination pipeline with a small amount of nitrogen gas.

[0162] 1.9 Keep warm until the reflux liquid is colorless, generally 0.5 to 1 hour;

[0163] 1.10 Cool to room temperature with stirring. Take samples to analyze the benzyl bromide content, ensuring that the sum of the peak areas of benzyl bromide and benzyl chloride is greater than 50%;

[0164] 1.11 Filtration and phase separation: The material is discharged from the bottom of the glass reactor into the funnel for filtration. After the filtrate is separated into phases in batches, the organic phase is temporarily stored in a 25L storage tank, and the aqueous phase is stored in another storage tank for later use. After the material in the glass reactor is discharged, the organic phase in the storage tank is transferred back into the glass reactor.

[0165] 1.12 The organic phase in a 25L glass reactor was washed with 1.0 kg of dichloroethane and then washed again with deionized water to obtain o-nitrobenzyl bromide organic phase. The resulting filter cake was sodium chloride, which was treated as solid waste. The resulting aqueous phase contained a large amount of hydrobromic acid and sodium bromide.

[0166] The total weight of the aqueous phase was 17.72 kg, the total weight of the combined organic phase was 17.1 kg, the wet weight of the filter cake was 0.91 kg, and the weight of the dried filter cake was 0.76 kg.

[0167] 2.1 Etherification feeding: Use a vacuum pump to transfer the o-nitrobenzyl bromide organic phase to another 25L glass reactor, then add 3.75kg of pyrazolol and 0.08kg of tetrabutylammonium bromide through the solid feed port, and rinse the reactor wall with 0.25kg of dichloroethane;

[0168] 2.2 Turn on the power to the water bath, control the temperature inside the glass reactor to 55℃, and begin the next step;

[0169] 2.3 Adding alkali: Add 5.8 kg of 15% liquid alkali and control the adding time to 1 hour; maintain the temperature at 55-65℃ during this process (the alkali addition process will release a lot of heat, so pay attention to temperature control and see if it can be stirred. If it cannot be stirred, raise the temperature to reflux).

[0170] 2.4 After the alkali addition is complete, maintain the temperature at 70–75℃ for 0.5–1 hour. Take samples for analysis; the percentage of the pyrazol peak area should be less than 0.5%.

[0171] 2.5 Crystallization: Slowly lower the temperature to 65°C, add seed crystals, and then slowly lower the temperature to 55°C. Allow 2–2.5 hours for the temperature to drop to room temperature. Drain the cooling water from the jacket and further cool the temperature to 0–5°C using a refrigerant.

[0172] 2.6 Centrifugation: Wash the centrifuged filter cake with 2.44 kg of dichloroethane and 1.3 kg of deionized water respectively, dry it, and measure the moisture content to obtain pyrazole benzyl ether (e.g. Figure 6-7 (as shown)

[0173] The centrifuged mother liquor was transferred to a 25L glass reactor using a vacuum pump. Then, the phases were separated to obtain an aqueous phase and an organic phase. The aqueous phase was used for recrystallization to recover sodium bromide. Specifically, about 3kg of aqueous phase was first distilled under reduced pressure, and then the pH was adjusted to below 3 using the brominated aqueous phase. The insoluble matter was filtered out, and the aqueous phase was directly returned to the bromide for reuse.

[0174] The organic phase is used to recover dichloroethane and o-nitrotoluene, specifically including: vacuum distillation, the distillate being dichloroethane, the bottom liquid after dichloroethane recovery being centrifuged, the filter cake being recovered, the concentrate being washed with a small amount of dichloroethane and then returned to the heating step in the etherification process to achieve the recovery of a small amount of pyrazole benzyl ether; the resulting filtrate is used to recover o-nitrotoluene under high vacuum, the temperature inside the reactor not exceeding 125℃, and the reactor residue is cooled and treated as solid waste.

Claims

1. A method for preparing pyraclostrobin, characterized in that, Includes the following steps: X. Bromination Dissolution: Based on the weight ratio of sodium bromide, volume of deionized water, weight of o-nitrotoluene, and weight of dichloroethane being 1:1.5-2.5:1.5-2.0:2.5-3.5, deionized water, sodium bromide, o-nitrotoluene, and dichloroethane are separately added to the bromination reactor for dissolution, and the temperature inside the bromination reactor is raised to 45-55°C. Reaction: Based on the principle that 0.4-0.6 kg of chlorine gas corresponds to 1 kg of sodium bromide, chlorine gas is continuously added to the bromination reactor at a rate of 1.0-2.5 L / min. The temperature inside the bromination reactor is raised to 68-72°C, and an azobisisobutyronitrile-dichloroethane solution is continuously added. When the amount of chlorine gas introduced accounts for 2 / 3 of the total amount of chlorine gas, the temperature inside the bromination reactor is raised to 75-85°C, and the chlorine gas rate is controlled at 0.5-1.0 L / min, until the remaining chlorine gas is introduced. Post-treatment: The bromination reactor is kept at 75-85℃ for 0.5-1h; Then, after cooling to room temperature, samples were taken and the benzyl bromide content in the reaction system inside the bromination reactor was analyzed to ensure that the sum of the peak areas of benzyl bromide and benzyl chloride was greater than 50%. Subsequently, the mixture was filtered, washed, and separated to obtain sodium chloride filter cake, aqueous phase I, and benzyl bromide organic phase. The benzyl bromide organic phase is o-nitrobenzyl bromide, which was temporarily stored for later use. Y. Etherification Feeding: Based on a volume ratio of o-nitrobenzyl bromide, pyrazolol, and tetrabutylammonium bromide of 4.0-5.0:1:2.0-2.5, o-nitrobenzyl bromide, pyrazolol, and tetrabutylammonium bromide are added to the etherification reactor, and the temperature inside the etherification reactor is raised to 50-60°C. With a volume ratio of o-nitrobenzyl bromide to alkali solution of 3:1, alkali solution is added to the etherification reactor, and the alkali solution addition time is controlled at 0.8 to 1.2 hours, while the temperature inside the etherification reactor is controlled at 55 to 65°C. After adding the alkali solution, keep the temperature at 70–75℃ for 0.5–1 hour, then take a sample to test if the percentage of the pyrazol peak area is less than 0.5%. Crystallization: The temperature inside the etherification reactor is lowered to 63-67℃, and seed crystals of pyrazole benzyl ether are added; then, the temperature is lowered to 52-58℃, and then lowered to room temperature over 2-2.5 hours; finally, the temperature inside the etherification reactor is lowered to 0-5℃. Centrifugation: Transfer to a centrifuge, centrifuge to obtain the first filter cake and the first centrifugal mother liquor; Washing: The first filter cake was washed with dichloroethane and deionized water respectively, and then dried to obtain pyrazole benzyl ether; Preparation of Z. pyraclostrobin The obtained pyrazole benzyl ether was reduced, acylated, and methylated to obtain pyrazole ether ester.

2. The method for preparing pyraclostrobin according to claim 1, characterized in that, In step X, the dissolution process involves adding materials while stirring at a speed of 150–200 r / min.

3. The method for preparing pyraclostrobin according to claim 1, characterized in that, The aqueous phase I in step X is neutralized and then directly reused in the dissolution step of the bromination process.

4. The method for preparing pyraclostrobin according to claim 1, characterized in that, In step Y, the concentration of the alkali solution is 12-17%.

5. The method for preparing pyraclostrobin according to claim 1, characterized in that, In step Y, the centrifugation speed is 1000-3000 r / min.

6. The method for preparing pyraclostrobin according to claim 1, characterized in that, The first centrifuged mother liquor in step Y is separated into aqueous phase II and dichloroethane organic phase. Aqueous phase II is distilled under reduced pressure and recrystallized to recover sodium bromide and water. Then, sodium bromide is directly reused in the dissolution step of the bromination process, and water is used to prepare alkali solution.

7. The method for preparing pyraclostrobin according to claim 6, characterized in that, The organic phase of dichloroethane is subjected to vacuum distillation to obtain dichloroethane and a concentrated solution. Then, the dichloroethane is reused in the dissolution step of the bromination process and / or the preparation step of the azobisisobutyronitrile-dichloroethane solution, and / or the feeding step of the etherification process.

8. The method for preparing pyraclostrobin according to claim 7, characterized in that, The concentrate is centrifuged to obtain a second filter cake and a second centrifuged mother liquor. The second filter cake is reused in the heating step of the etherification process. The second centrifuged mother liquor is distilled under reduced pressure to obtain o-nitrotoluene. The o-nitrotoluene is reused in the dissolution step of the bromination process.

9. The method for preparing pyraclostrobin according to claim 7, characterized in that, The pyraclostrobin preparation system includes: a bromination reactor (1), an etherification reactor (2), a reduction device (3), an acylation device (4), and a methylation device (5). The bromination reactor (1) is connected to a deionized water storage tank (6), a sodium bromide storage tank (7), an o-nitrotoluene storage tank (8), a dichloroethane storage tank (9), and an azobisisobutyronitrile-dichloroethane solution storage tank (10). The bromination reactor (1) is connected to a chlorine storage tank (13) via a chlorine gas pipeline (12). A control valve (14) and a flow meter (15) are installed on the chlorine gas pipeline (12). The etherification reactor (2) is located behind the bromination reactor (1). The etherification reactor (2) is connected to the pyrazol storage tank (20), the tetrabutylammonium bromide storage tank (21), and the alkali storage tank (22). The reduction device (3) is located behind the etherification reactor (2). The reduction device (3) is connected to the etherification reactor (2). The acylation device (4) is located behind the reduction device (3). The acylation device (4) is connected to the reduction device (3). The methylation device (5) is located behind the acylation device (4). The methylation device (5) is connected to the acylation device (4). A continuous pathway for the preparation of pyraclostrobin is formed between the bromination reactor (1), the etherification reactor (2), the reduction device (3), the acylation device (4), and the methylation device (5).

10. The method for preparing pyraclostrobin according to claim 9, characterized in that, The preparation system also includes a waste liquid recycling system.

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