Full-process continuous synthesis system and method of dimethoate

Abstract

The application discloses a full-process continuous synthesis system and method of dimethoate, which comprises a sulfide synthesis kettle, a first transfer kettle, a second transfer kettle, and sequentially connected sulfide transfer kettle, ammonium salt synthesis kettle, first layering device, ammonium salt transfer kettle, first-stage sulfur phosphorus ester reaction kettle, second-stage sulfur phosphorus ester reaction kettle, third-stage sulfur phosphorus ester reaction kettle, second layering device, water washing device, third layering device, rectification device, sulfur phosphorus ester transfer kettle, first-stage dimethoate reaction kettle, second-stage dimethoate reaction kettle, molten water washing kettle, crystallization kettle, filter press and drying device, and the first transfer kettle and the second transfer kettle are arranged in parallel. The full-process continuous synthesis method adopts the full-process continuous synthesis system. The system and method have the advantages that the full process can be continuously carried out and is simple and controllable, the reaction efficiency is high, the reaction time is short, the product content and yield are high, impurities are few, and the quality is stable.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical product preparation technology, specifically relating to a continuous synthesis system and method for dimethoate. Background Technology

[0002] Dimethoate, also known as O,O-dimethyl-S-(N-methylcarbamoylmethyl)dithiophosphate, has the molecular formula C5H. 12 NO3PS2, molecular weight: 229.25, molecular structure formula:

[0003] This product is a systemic contact insecticide and acaricide, widely used in agriculture. It can control a wide range of pests and mites on various crops, and is mainly used to control aphids, spider mites, scale insects, and fruit borers on crops such as cotton, fruit trees, and vegetables.

[0004] Yao Wengang (CN1702074A) synthesized high-quality dimethoate using phosphorus pentasulfide as raw material via an intermittent process. Although the yield was increased by 30% and the purity exceeded 90%, it was still insufficient compared to existing processes, with the product purity being only 90%.

[0005] Ai Qiuhong (CN104193781A) provides a method for synthesizing thiophosphates, which involves reacting an aqueous solution of thiophosphate with methyl chloroacetate and then recycling the aqueous phase. This process increases the reaction yield, reduces costs, and decreases wastewater volume. However, the method is cumbersome to operate, and the purity and yield are still relatively low.

[0006] Cheng Xiaobing (Shandong Chemical Industry, 2018, 47(5):51-52) used a one-pot sulfide method to directly synthesize thiophosphoric esters. Although the process operation is more convenient, the product yield and content are worse than the existing process.

[0007] There are two main production processes for dimethoate: a pre-amine hydrolysis method (chloroacetylmethylamine method) and a post-amine hydrolysis method (methyl chloroacetate method). The pre-amine hydrolysis method has more side reactions, higher energy consumption, and poorer product quality. Currently, domestic industrial production mainly uses the post-amine hydrolysis method; however, the purity and yield of existing processes are still relatively low, and none of them have achieved continuous synthesis throughout the entire process. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a continuous synthesis system and method for dimethoate with high purity and yield, continuous process, and effective solution to technical problems such as strong odor and environmental non-environmental impact during the production of dimethoate.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A continuous synthesis system for dimethoate includes a sulfide synthesis reactor, a first transfer reactor, a second transfer reactor, and sequentially connected sulfide transfer reactors, ammonium salt synthesis reactors, a first-stage separation device, an ammonium salt transfer reactor, a primary-stage thiophosphate reaction reactor, a secondary-stage thiophosphate reaction reactor, a tertiary-stage thiophosphate reaction reactor, a second-stage separation device, a water washing device, a third-stage separation device, a distillation device, a thiophosphate transfer reactor, a primary-stage dimethoate reaction reactor, a secondary-stage dimethoate reaction reactor, a molten water washing reactor, a crystallization reactor, a filter press, and a drying device; the first-stage... The transfer vessel and the second transfer vessel are arranged in parallel. The outlet of the sulfide synthesis vessel is connected to the inlet of the first transfer vessel and the inlet of the second transfer vessel, respectively. The outlet of the first transfer vessel and the outlet of the second transfer vessel are connected to the inlet of the sulfide transfer vessel, respectively. The primary sulfur-phosphorus ester reaction vessel, the secondary sulfur-phosphorus ester reaction vessel, and the tertiary sulfur-phosphorus ester reaction vessel are all equipped with an external circulation outlet and an external circulation inlet. Each external circulation outlet is connected to the external circulation inlet on the corresponding reaction vessel through an external circulation pump.

[0010] In the aforementioned continuous synthesis system for dimethoate, preferably, the outlet of the sulfide synthesis reactor is connected to the inlet of the first transfer pump. The first transfer pump has a first outlet and a second outlet. The first outlet is connected to the inlet of the first transfer reactor, and the second outlet is connected to the inlet of the second transfer reactor. The inlet of the sulfide transfer reactor is connected to the outlet of the second transfer pump. The second transfer pump has a first inlet and a second inlet. The outlet of the first transfer reactor is connected to the first inlet, and the outlet of the second transfer reactor is connected to the second inlet.

[0011] In the aforementioned continuous synthesis system for dimethoate, preferably, the external circulation pump corresponding to the primary sulfur phosphate reactor is equipped with a first external circulation material inlet, a first external circulation material outlet, and a first transfer material inlet. The external circulation outlet of the primary sulfur phosphate reactor is connected to the first external circulation material inlet, and the first external circulation material outlet is connected to the external circulation inlet of the primary sulfur phosphate reactor. The ammonium salt transfer reactor is connected to the first transfer material inlet through a transfer pipeline, and the transfer pipeline is equipped with a methyl chloroacetate inlet. The external circulation pump corresponding to the secondary sulfur phosphate reactor is equipped with a second external circulation material inlet, a second external circulation material outlet, and a second transfer material inlet. The external circulation outlet of the secondary sulfur phosphate reactor is connected to the second external circulation material inlet, and the second external circulation material outlet is connected to the external circulation inlet of the secondary sulfur phosphate reactor. The discharge port of the primary sulfur phosphate reactor is connected to the second transfer material inlet. The external circulation pump corresponding to the three-stage sulfur phosphate reactor is equipped with a third external circulation material inlet, a third external circulation material outlet, and a third transfer material inlet. The external circulation outlet of the three-stage sulfur phosphate reactor is connected to the third external circulation material inlet, and the third external circulation material outlet is connected to the external circulation inlet of the three-stage sulfur phosphate reactor. The discharge port of the two-stage sulfur phosphate reactor is connected to the third transfer material inlet.

[0012] Preferably, in the above-mentioned continuous synthesis system for dimethoate, the sulfide synthesis reactor is equipped with a phosphorus pentasulfide inlet, a methanol inlet, and a catalyst inlet; the ammonium salt synthesis reactor is equipped with an ammonia inlet; the water washing device is equipped with a water inlet and a wastewater outlet; the distillation device is equipped with a tail gas outlet; the primary dimethoate reaction vessel is equipped with a methylamine inlet; and the molten water washing vessel is equipped with a hot water inlet.

[0013] In the above-mentioned continuous synthesis system for dimethoate, preferably, the first transfer pump and the second transfer pump are both high-speed circulating pumps, and the flow rate of the high-speed circulating pump is 15L / min to 50L / min. Material conveying pumps are provided between the sulfide transfer vessel and the ammonium salt synthesis vessel, between the tertiary sulfophosphoric acid ester reaction vessel and the second layering device, between the water washing device and the third layering device, between the distillation device and the sulfophosphoric acid ester transfer vessel, between the sulfophosphoric acid ester transfer vessel and the primary dimethoate reaction vessel, and between the molten water washing vessel and the crystallization vessel. The first transfer vessel, the second transfer vessel, and the secondary dimethoate reactor are all connected to a pressure pump.

[0014] As a general technical concept, the present invention also provides a continuous synthesis method for dimethoate, implemented using the aforementioned continuous synthesis system for dimethoate, comprising the following steps: S1. Synthesis of methyl sulfide: Phosphorus pentasulfide is added to a sulfide synthesis reactor. Methanol and catalyst are mixed and added dropwise to the sulfide synthesis reactor. The reactor temperature is controlled at 20℃~70℃, and the reaction time is 2h~4h. The resulting methyl sulfide is sent to the first transfer reactor, where negative pressure is applied, and then the methyl sulfide is sent to the sulfide transfer reactor. The same operation is repeated in the sulfide synthesis reactor. When the reactants in the first transfer reactor reach the set value, the resulting methyl sulfide is sent to the second transfer reactor, where negative pressure is applied, and then the methyl sulfide is sent to the sulfide transfer reactor. The above steps are repeated, switching between the first and second transfer reactors for material transfer, and then the methyl sulfide in the sulfide transfer reactor is sent to the next process. S2. Synthesis of methyl sulfide ammonium salt: Methyl sulfide in the sulfide transfer reactor is transferred to the ammonium salt synthesis reactor. Ammonia water is added dropwise to the ammonium salt synthesis reactor, and the reactor temperature is controlled at 10℃~50℃. The reaction yields methyl sulfide ammonium salt. The residence time in the reactor is 2h~4h. The methyl sulfide ammonium salt is continuously overflowed into the first layering device for layering. The lower layer is an oil layer, and the upper layer is methyl sulfide ammonium salt. The layered methyl sulfide ammonium salt is then transferred to the ammonium salt transfer reactor. S3. Synthesis of thiophosphoric acid esters: Methyl sulfide ammonium salt in the ammonium salt transfer vessel is sent to the primary thiophosphoric acid ester reactor, and methyl chloroacetate is sent to the primary thiophosphoric acid ester reactor for reaction. The resulting product is continuously fed into the secondary and tertiary thiophosphoric acid ester reactors for further reaction. The reactor temperatures of the primary, secondary, and tertiary thiophosphoric acid ester reactors are all controlled between 10℃ and 60℃, and the residence time of the reactants in the reactors is controlled between 1h and 2h. During the reaction, the primary, secondary, and tertiary thiophosphoric acid ester reactors are each pumped out of the reactors by an external circulation pump and then circulated back into the reactors. The reactants in the tertiary thiophosphoric acid ester reactor are continuously overflowed into the second stratification device for stratification. The crude thiophosphoric acid ester obtained from the stratification is continuously washed by a water washing device, stratified by the third stratification device, and continuously distilled by a distillation device. The refined thiophosphoric acid ester obtained is sent to the thiophosphoric acid ester transfer vessel. S4. Synthesis of Dimethoate: The refined thiophosphate in the thiophosphate transfer reactor is sent to the primary Dimethoate reactor. A methylamine aqueous solution is also sent to the primary Dimethoate reactor. The reactor temperature is controlled at 0-50℃, and the residence time of the reactants is 2-4 hours. The reactants are then sent to the secondary Dimethoate reactor, and the reactor temperature is controlled at 0-50℃. The secondary Dimethoate reactor is subjected to negative pressure, and the residence time of the reactants is 2-4 hours. The reactants obtained from the secondary Dimethoate reactor are continuously overflowed into a molten water washing reactor for washing. The resulting material is continuously overflowed into a crystallization reactor for crystallization. After filtration and drying, the Dimethoate product is obtained. The Dimethoate product is a powdered Dimethoate product.

[0015] In the above-mentioned continuous synthesis method of dimethoate, preferably, in step S1, the molar ratio of phosphorus pentasulfide, methanol, and catalyst is 1:4.01-4.1:0.01-0.03; in step S2, the molar equivalent ratio of methyl sulfide to ammonia is 1:1.05-1.30, and the mass concentration of ammonia is 5%-25%; in step S3, the molar equivalent ratio of ammonium methyl sulfide to methyl chloroacetate is 1:1.2-2.0; in step S4, the molar equivalent ratio of refined thiophosphoric acid ester to monomethylamine aqueous solution is 1:1.1-1.5, and the mass concentration of monomethylamine aqueous solution is 10%-40%.

[0016] In the above-mentioned continuous synthesis method of dimethoate, preferably, in step S1: when the reactants in the first transfer vessel reach 1 / 2 to 2 / 3 of the vessel volume, the obtained methyl sulfide is sent to the second transfer vessel; the catalyst includes one or more of diazabicyclo(DBU), pyridine, triethylamine, and tert-butylethylenediamine (TBD); when each batch of materials is added to the sulfide synthesis vessel, the liquid volume in the vessel is more than 0.5% of the total material mass, preferably 0.5% to 1.5%; the pressure of the vacuum pump is -0.09 MPa to -0.1 MPa.

[0017] In the above-mentioned continuous synthesis method of dimethoate, preferably, in step S1, a small amount of methyl sulfide obtained from the reaction in the sulfide synthesis reactor is retained in the sulfide synthesis reactor.

[0018] In the above-mentioned continuous synthesis method of dimethoate, preferably, in step S3, the temperature of the primary thiophosphate reactor is controlled at 40℃~50℃, the temperature of the secondary thiophosphate reactor is controlled at 10℃~20℃, and the temperature of the tertiary thiophosphate reactor is controlled at 10℃~20℃; the external circulation pump is a high-speed circulation pump with a flow rate of 15L / min~50L / min; in step S4, the secondary dimethoate reactor is subjected to a negative pressure of -0.03MPa~-0.05MPa.

[0019] This invention uses phosphorus pentasulfide as the initial raw material and proceeds through a continuous synthesis process of methyl sulfide, methyl sulfide ammonium salt, thiophosphoric acid ester, and dimethoate to obtain high-quality and high-yield powdered dimethoate.

[0020] The reaction formula is as follows: (1) Synthesis of methyl sulfides Equation (1) (2) Preparation of methyl sulfide ammonium salt Equation (2) (3) Synthesis of thiophospholipids Equation (3) (4) Synthesis of dimethoate Equation (4) Compared with the prior art, the advantages of the present invention are as follows: 1. This invention uses phosphorus pentasulfide as the starting material. Phosphorus pentasulfide is a flaky solid. Conventional methods cannot achieve continuous feeding and synthesis. This invention overcomes this difficulty by adopting a semi-continuous method of switching between two reactors, which makes the whole process continuous and greatly saves production costs.

[0021] This invention connects all processes in series for a continuous reaction process. The feeding rate is simple and controllable, and there is no need to start the reactor for feeding midway. In addition, the sulfur phosphide synthesis step adopts an external circulation reaction method, which increases the material mixing effect and greatly improves the reaction efficiency. The production process is transformed from the traditional intermittent operation to a continuous operation, reducing energy consumption and ensuring stable product quality. Moreover, due to the greatly shortened reaction time, the reaction by-products are also significantly reduced, resulting in high selectivity and fewer impurities in the product. The main impurity, trimethyl ester, is less than 0.3% with a content of over 98%. The product synthesis yield is high, with an overall yield of over 90% (based on phosphorus pentasulfide).

[0022] 2. In traditional synthesis methods, the materials contain solids, which makes continuous discharge difficult. In the continuous synthesis method of dimethoate of the present invention, a slight negative pressure is applied in part of the reaction vessel, so that the materials can flow out smoothly and complete the continuous reaction.

[0023] 3. Compared with the batch process, the continuous process of the present invention has no odor leakage. The biggest drawback of the dimethoate process is that it contains elements such as sulfur and phosphorus, has a very unpleasant odor, and also contains highly toxic hydrogen sulfide gas. The continuous process can effectively avoid this drawback. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the continuous synthesis system of dimethoate in Embodiments 1-7 of the present invention.

[0025] Legend: 1. Sulfide synthesis reactor; 2. First transfer reactor; 3. Second transfer reactor; 4. Sulfide transfer reactor; 5. Ammonium salt synthesis reactor; 6. First stratification device; 7. Ammonium salt transfer reactor; 8. Primary sulfur phosphate ester reactor; 9. Secondary sulfur phosphate ester reactor; 10. Tertiary sulfur phosphate ester reactor; 11. Second stratification device; 12. Water washing device; 13. Third stratification device; 14. Distillation device; 15. Sulfur phosphate ester transfer reactor; 16. Primary dimethoate reactor; 17. Secondary dimethoate reactor; 18. Melt water washing reactor; 19. Crystallization reactor; 20. Material conveying pump; 21. External circulation pump; 22. Filter press; 23. Drying device; 24. Transfer pipeline; 25. First transfer pump; 26. Second transfer pump. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0027] Example 1 A fully continuous synthesis system for dimethoate according to the present invention, such as Figure 1As shown, the reactor includes a sulfide synthesis reactor 1, a first transfer reactor 2, a second transfer reactor 3, and sequentially connected sulfide transfer reactor 4, an ammonium salt synthesis reactor 5, a first stratification device 6, an ammonium salt transfer reactor 7, a primary sulfur-phosphorus ester reactor 8, a secondary sulfur-phosphorus ester reactor 9, a tertiary sulfur-phosphorus ester reactor 10, a second stratification device 11, a water washing device 12, a third stratification device 13, a distillation device 14, a sulfur-phosphorus ester transfer reactor 15, a primary dimethoate reactor 16, a secondary dimethoate reactor 17, a molten water washing reactor 18, a crystallization reactor 19, a filter press 22, and a dry... Drying device 23; the first transfer vessel 2 and the second transfer vessel 3 are connected in parallel. The outlet of the sulfide synthesis vessel 1 is connected to the inlet of the first transfer vessel 2 and the inlet of the second transfer vessel 3, respectively. The outlet of the first transfer vessel 2 and the outlet of the second transfer vessel 3 are connected to the inlet of the sulfide transfer vessel 4, respectively. The first-stage sulfur phosphate reactor 8, the second-stage sulfur phosphate reactor 9, and the third-stage sulfur phosphate reactor 10 are all equipped with an external circulation outlet and an external circulation inlet. Each external circulation outlet is connected to the external circulation inlet on the corresponding reactor through an external circulation pump 21.

[0028] In this embodiment, the outlet of the sulfide synthesis reactor 1 is connected to the inlet of the first transfer pump 25. The first transfer pump 25 is provided with a first outlet and a second outlet. The first outlet is connected to the inlet of the first transfer reactor 2, and the second outlet is connected to the inlet of the second transfer reactor 3. The inlet of the sulfide transfer reactor 4 is connected to the outlet of the second transfer pump 26. The second transfer pump 26 is provided with a first inlet and a second inlet. The outlet of the first transfer reactor 2 is connected to the first inlet, and the outlet of the second transfer reactor 3 is connected to the second inlet.

[0029] In this embodiment, the external circulation pump 21 corresponding to the primary sulfur phosphate reactor 8 is provided with a first external circulation material inlet, a first external circulation material outlet and a first transfer material inlet. The external circulation outlet of the primary sulfur phosphate reactor 8 is connected to the first external circulation material inlet, and the first external circulation material outlet is connected to the external circulation inlet of the primary sulfur phosphate reactor 8. The ammonium salt transfer reactor 7 is connected to the first transfer material inlet through a transfer pipe 24, and the transfer pipe 24 is provided with a methyl chloroacetate inlet. The external circulation pump 21 corresponding to the secondary sulfur phosphate reactor 9 is equipped with a second external circulation material inlet, a second external circulation material outlet, and a second transfer material inlet. The external circulation outlet of the secondary sulfur phosphate reactor 9 is connected to the second external circulation material inlet, and the second external circulation material outlet is connected to the external circulation inlet of the secondary sulfur phosphate reactor 9. The discharge port of the primary sulfur phosphate reactor 8 is connected to the second transfer material inlet. The external circulation pump 21 corresponding to the tertiary sulfur phosphate reactor 10 is equipped with a third external circulation material inlet, a third external circulation material outlet, and a third transfer material inlet. The external circulation outlet of the tertiary sulfur phosphate reactor 10 is connected to the third external circulation material inlet, and the third external circulation material outlet is connected to the external circulation inlet of the tertiary sulfur phosphate reactor 10. The discharge port of the secondary sulfur phosphate reactor 9 is connected to the third transfer material inlet.

[0030] In this embodiment, the sulfide synthesis reactor 1 is provided with a phosphorus pentasulfide inlet, a methanol inlet and a catalyst inlet, the ammonium salt synthesis reactor 5 is provided with an ammonia inlet, the water washing device 12 is provided with a water inlet and a wastewater outlet, the distillation device 14 is provided with a tail gas outlet, the primary dimethoate reactor 16 is provided with a methylamine inlet, and the molten water washing reactor 18 is provided with a hot water inlet.

[0031] In this embodiment, both the first transfer pump 25 and the second transfer pump 26 are high-speed circulation pumps, and the flow rate of the high-speed circulation pumps is 15L / min to 50L / min. Material conveying pumps 20 are provided between the sulfide transfer vessel 4 and the ammonium salt synthesis vessel 5, between the tertiary sulfophosphorus ester reaction vessel 10 and the second layering device 11, between the water washing device 12 and the third layering device 13, between the distillation device 14 and the sulfophosphorus ester transfer vessel 15, between the sulfophosphorus ester transfer vessel 15 and the primary dimethoate reaction vessel 16, and between the molten water washing vessel 18 and the crystallization vessel 19. The first transfer vessel 2, the second transfer vessel 3, and the secondary dimethoate reactor 17 are all connected to a pressure pump.

[0032] In this embodiment, the ammonium salt synthesis reactor 5 is equipped with a stirrer and an upper overflow port; the primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 are all equipped with stirrers and upper overflow ports; the primary dimethoate reactor 16 and the secondary dimethoate reactor 17 are both equipped with stirrers and upper overflow ports; and the molten water washing reactor 18 is equipped with a stirrer and an upper overflow port.

[0033] The working principle of the continuous synthesis system for digo in this embodiment is as follows: Phosphorus pentasulfide is added to sulfide synthesis reactor 1. Methanol and catalyst are mixed and added dropwise to sulfide synthesis reactor 1. The resulting methyl sulfide is sent to first transfer reactor 2. A negative pressure is applied to extract low-boiling-point substances such as hydrogen sulfide and methanol from the system. Then, the methyl sulfide is sent to sulfide transfer reactor 4. The same operation is repeated in sulfide synthesis reactor 1. When the reactants in first transfer reactor 2 reach the set value, the resulting methyl sulfide is sent to second transfer reactor 3. A negative pressure is applied. Then, the methyl sulfide is sent to sulfide transfer reactor 4. The above steps are repeated, switching between first transfer reactor 2 and second transfer reactor 3 for material transfer. The methyl sulfide in sulfide transfer reactor 4 is then sent to the next process. The methyl sulfide in the sulfide transfer vessel 4 is sent to the ammonium salt synthesis vessel 5. Ammonia water is dripped into the ammonium salt synthesis vessel 5 to react and obtain methyl sulfide ammonium salt. The methyl sulfide ammonium salt is continuously overflowed into the first layering device 6 for layering. The lower layer is an oil layer (neutral oil) and the upper layer is methyl sulfide ammonium salt. The layered methyl sulfide ammonium salt is sent to the ammonium salt transfer vessel 7. The methyl sulfide ammonium salt in the ammonium salt transfer vessel 7 is sent to the primary sulfur phosphate reactor 8, and methyl chloroacetate is sent to the primary sulfur phosphate reactor 8 for reaction. The resulting product is continuously fed into the secondary sulfur phosphate reactor 9 and the tertiary sulfur phosphate reactor 10 for reaction. During the reaction, the primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 are respectively pumped out of the reactor by the external circulation pump 21 and then circulated back into the reactor to increase the mixing effect of the material and greatly improve the reaction efficiency. The reactant in the tertiary sulfur phosphate reactor 10 is continuously overflowed to the second stratification device 11 for stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, stratified by the third stratification device 13, and continuously rectified by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer vessel 15, and light components such as methyl chloroacetate are discharged. The refined thiophosphate in the thiophosphate transfer vessel 15 is sent to the primary dimethoate reactor 16. The methylamine aqueous solution is sent to the primary dimethoate reactor 16. The reactants are sent to the secondary dimethoate reactor 17. The secondary dimethoate reactor 17 is subjected to a slight negative pressure. The reactants obtained from the secondary dimethoate reactor 17 are continuously overflowed into the melting water washing vessel 18 for water washing. The obtained materials are continuously overflowed into the crystallization vessel 19 for crystallization. After filtration and drying, the dimethoate product is obtained.

[0034] A continuous synthesis method for dimethoate according to the present invention, implemented using the continuous synthesis system for dimethoate of this embodiment, includes the following steps: S1. Synthesis of methyl sulfide: Phosphorus pentasulfide is added to sulfide synthesis reactor 1. Methanol and catalyst are mixed and added dropwise to sulfide synthesis reactor 1. The reactor temperature is controlled at 20℃~70℃, and the reaction time is 2h~4h. The resulting methyl sulfide is sent to the first transfer reactor 2, and a negative pressure is drawn to -0.09MPa~-0.1MPa to remove low-boiling-point substances such as hydrogen sulfide and methanol from the system. After the negative pressure is completely drawn, the methyl sulfide is sent to sulfide transfer reactor 4. The reaction continues in the sulfide synthesis reactor 1 using the same operation described above. When the reactants in the first transfer reactor 2 reach the set value, the resulting methyl sulfide is sent to the second transfer reactor 3, and the negative pressure is drawn to -0.09MPa to -0.1MPa. After the negative pressure is drawn, the methyl sulfide is sent to the sulfide transfer reactor 4. The above steps are repeated, switching between the first transfer reactor 2 and the second transfer reactor 3 for material transport, and then the methyl sulfide in the sulfide transfer reactor 4 is sent to the next process. S2. Synthesis of methyl sulfide ammonium salt: The methyl sulfide in the sulfide transfer vessel 4 is sent to the ammonium salt synthesis vessel 5. Ammonia water is dripped into the ammonium salt synthesis vessel 5, and the vessel temperature is controlled at 10℃~50℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2h~4h. The methyl sulfide ammonium salt is continuously overflowed into the first layering device 6 for layering. The lower layer is an oil layer (neutral oil), and the upper layer is methyl sulfide ammonium salt. The layered methyl sulfide ammonium salt is sent to the ammonium salt transfer vessel 7. S3. Synthesis of thiophosphoric acid esters: Methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is sent to primary thiophosphoric acid ester reactor 8. Methyl chloroacetate is sent to primary thiophosphoric acid ester reactor 8 for reaction. The resulting products are sequentially and continuously fed into secondary thiophosphoric acid ester reactor 9 and tertiary thiophosphoric acid ester reactor 10 for reaction. The reactor temperatures of primary thiophosphoric acid ester reactor 8, secondary thiophosphoric acid ester reactor 9, and tertiary thiophosphoric acid ester reactor 10 are all controlled between 10℃ and 60℃, and the residence time of the reactants in the reactors is controlled between 1h and 2h. During the reaction, primary thiophosphoric acid ester reactor 8, secondary thiophosphoric acid ester reactor 9, and tertiary thiophosphoric acid ester reactor 10 are all controlled between 10℃ and 60℃. The sulfur phosphate ester reactor 9 and the three-stage sulfur phosphate ester reactor 10 respectively use an external circulation pump 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor to increase the mixing effect of the material and greatly improve the reaction efficiency. The reactant material in the three-stage sulfur phosphate ester reactor 10 is continuously overflowed to the second stratification device 11 for stratification. The crude sulfur phosphate ester obtained from the stratification is continuously washed by the water washing device 12, stratified by the third stratification device 13, and continuously rectified by the distillation device 14. The obtained refined sulfur phosphate ester is sent to the sulfur phosphate ester transfer reactor 15, and light components such as methyl chloroacetate are discharged. S4. Synthesis of Dimethoate: The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary Dimethoate reactor 16. Aqueous methylamine is sent to the primary Dimethoate reactor 16. The reactor temperature is controlled at 0-50℃, and the residence time of the reactants is 2-4 hours. The reactants are then sent to the secondary Dimethoate reactor 17. The reactor temperature is controlled at 0-50℃. The secondary Dimethoate reactor 17 is subjected to a slight negative pressure of -0.03MPa to -0.05MPa. The residence time of the reactants is 2-4 hours. The reactants obtained from the secondary Dimethoate reactor 17 are continuously overflowed into the molten water washing reactor 18 for washing. The resulting material is continuously overflowed into the crystallization reactor 19 for crystallization. After filtration and drying, the Dimethoate product is obtained. The Dimethoate product is a powder product.

[0035] In step S1, the molar ratio of phosphorus pentasulfide, methanol, and catalyst is 1:4.01–4.1:0.01–0.03; in step S2, the molar equivalent ratio of methyl sulfide to ammonia is 1:1.05–1.30, and the mass concentration of ammonia is 5%–25%; in step S3, the molar equivalent ratio of ammonium methyl sulfide to methyl chloroacetate is 1:1.2–2.0; in step S4, the molar equivalent ratio of refined thiophosphoric acid ester to monomethylamine solution is 1:1.1–1.5, and the mass concentration of monomethylamine aqueous solution is 10%–40%.

[0036] In step S1: when the reactants in the first transfer vessel 2 reach 1 / 2 to 2 / 3 of the vessel volume, the obtained methyl sulfide is sent to the second transfer vessel 3; the catalyst includes one or more of diazabicyclo, pyridine, triethylamine and tert-butylethylenediamine; when each batch is fed into the sulfide synthesis vessel 1, the liquid volume in the vessel is more than 0.5% of the total material mass, preferably 0.5% to 1.5%.

[0037] In step S1, a small amount of methyl sulfide obtained from the reaction in sulfide synthesis reactor 1 is retained in sulfide synthesis reactor 1.

[0038] In step S3, the external circulation pump 21 is a high-speed circulation pump with a flow rate of 15L / min to 50L / min.

[0039] Example 2 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and diazabicyclic catalyst (DBU) were mixed and added dropwise to sulfide synthesis reactor 1. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.01:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40–50°C, and the reaction time was 3 hours. After the reaction was complete, the resulting methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure at -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into sulfide transfer reactor 4. The same operation described above is continued in the synthesis reactor 1 to feed the next batch of reaction. When the reactants in the first transfer reactor 2 reach 1 / 2 to 2 / 3 of the reactor volume, the resulting methyl sulfide is pumped into the second transfer reactor 3. The reactor is then subjected to negative pressure at -0.09 to -0.1 MPa for 2 hours. After the negative pressure is removed, the methyl sulfide is sent to the sulfide transfer reactor 4. The above steps are repeated, switching between the first transfer reactor 2 and the second transfer reactor 3 for material transport and continuous feeding. The methyl sulfide in the sulfide transfer reactor 4 is then sent to the next process. The tail gas can be absorbed by passing it through a sodium hydroxide solution.

[0040] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is transferred to the ammonium salt synthesis vessel 5. At the same time, 5% ammonia water is added dropwise to the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.05. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first stratification device 6 for stratification (i.e., continuous stratification). The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The stratified methyl sulfide ammonium salt is then transferred to the ammonium salt transfer vessel 7.

[0041] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:1.2. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40-50℃, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10-20℃, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10-20℃. The residence time of the reactants in each reactor is 1 hour. During the reaction, the primary sulfur-phosphorus ester... Ester reactor 8, secondary sulfur phosphate reactor 9, and tertiary sulfur phosphate reactor 10 are respectively pumped out of the reactor by the corresponding external circulation pump 21 and then circulated back into the reactor. The external circulation pump 21 is a high-speed circulation pump with a flow rate of 20 L / min. The reactants in the tertiary sulfur phosphate reactor 10 are continuously overflowed to the second stratification device 11 for stratification (i.e., continuous stratification). The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, stratified by the third stratification device 13 (i.e., continuous stratification), and continuously distilled by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0042] S4, Synthesis of Dimethoate The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 10% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.1. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is maintained at 20-30°C and is under a slight negative pressure of -0. The pressure ranges from 0.03 to -0.05 MPa. The residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the melting and washing reactor 18 for washing. Hot water (usually at 30-40℃) is added to the melting and washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained. The content of powdered dimethoate is 98.8%, and the yield is 93% (calculated as phosphorus pentasulfide).

[0043] Example 3 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and pyridine catalyst were mixed and added dropwise to sulfide synthesis reactor 1. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.05:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40-50℃, and the reaction time was 3 hours. After the reaction was completed, methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure of -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into sulfide transfer reactor 4. The same operation was repeated in sulfide synthesis reactor 1 for the next batch of reaction. When the reactants in the first transfer reactor 2 reached 1 / 2 to 2 / 3 of the reactor volume, the resulting methyl sulfide was pumped into the second transfer reactor 3. -0.09 to -0.1 MPa is used to draw negative pressure for 2 hours. After the negative pressure is drawn, the methyl sulfide is sent to the sulfide transfer reactor 4. The above steps are repeated, and the first transfer reactor 2 and the second transfer reactor 3 are switched for material conveying and continuous feeding. The methyl sulfide in the sulfide transfer reactor 4 is then sent to the next process. The tail gas can be absorbed by passing it into a sodium hydroxide solution.

[0044] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is transferred to the ammonium salt synthesis vessel 5. At the same time, 15% ammonia water is dripped into the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.05. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first stratification device 6 for stratification (i.e., continuous stratification). The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The stratified methyl sulfide ammonium salt is then transferred to the ammonium salt transfer vessel 7.

[0045] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:1.6. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40-50℃, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10-20℃, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10-20℃. The residence time of the reactants in each reactor is 1 hour. During the reaction... The primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 each use their respective external circulation pumps 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor. The external circulation pumps 21 are high-speed circulation pumps with a flow rate of 20 L / min. The reactant material in the tertiary sulfur phosphate reactor 10 is continuously overflowed into the second stratification device 11 for continuous stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, continuously stratified by the third stratification device 13, and continuously precipitated by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0046] S4, Synthesis of Powdered Dimethoate The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 20% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.1. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is also maintained at 20-30°C. With a slight negative pressure of -0.03 to -0.05 MPa, the residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the molten water washing reactor 18 for washing. Hot water is added to the molten water washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained with a content of 99.4% and a yield of 90% (calculated as phosphorus pentasulfide).

[0047] Example 4 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and triethylamine catalyst were mixed and added dropwise to sulfide synthesis reactor 1. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.10:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40-50℃, and the reaction time was 3 hours. After the reaction was complete, methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure of -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into sulfide transfer reactor 4. In step 1, the same operation as described above is continued to feed the next batch of reaction. When the reactants in the first transfer vessel 2 reach 1 / 2 to 2 / 3 of the vessel volume, the obtained methyl sulfide is pumped into the second transfer vessel 3 and a negative pressure of -0.09 to -0.1 MPa is applied for 2 hours. After the negative pressure is applied, the methyl sulfide is sent to the sulfide transfer vessel 4. The above steps are repeated, switching between the first transfer vessel 2 and the second transfer vessel 3 for material transportation, with continuous feeding. The methyl sulfide in the sulfide transfer vessel 4 is then sent to the next process. The tail gas can be absorbed by passing it through a sodium hydroxide solution.

[0048] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is transferred to the ammonium salt synthesis vessel 5. At the same time, 25% ammonia water is dripped into the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.05. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first stratification device 6 for stratification (i.e., continuous stratification). The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The stratified methyl sulfide ammonium salt is then transferred to the ammonium salt transfer vessel 7.

[0049] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:2.0. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40–50°C, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10–20°C, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10–20°C. The residence time of the reactants in each reactor is 1 hour. During the reaction... The primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 each use their respective external circulation pumps 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor. The external circulation pumps 21 are high-speed circulation pumps with a flow rate of 20 L / min. The reactant material in the tertiary sulfur phosphate reactor 10 is continuously overflowed into the second stratification device 11 for continuous stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, continuously stratified by the third stratification device 13, and continuously precipitated by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0050] S4, Powder Synthesis The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 30% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.1. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is also maintained at 20-30°C. With a slight negative pressure of -0.03 to -0.05 MPa, the residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the melting and washing reactor 18 for washing. Hot water is added to the melting and washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained with a content of 99.2% and a yield of 92% (calculated as phosphorus pentasulfide).

[0051] Example 5 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and the catalyst tert-butylethylenediamine (TBD) were mixed and added dropwise. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.05:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40–50°C, and the reaction time was 3 hours. After the reaction was complete, methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure of -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into the sulfide transfer reactor 4. The same operation as described above continues to feed the next batch of reaction. When the reactants in the first transfer vessel 2 reach 1 / 2 to 2 / 3 of the vessel volume, the resulting methyl sulfide is pumped into the second transfer vessel 3 and a negative pressure of -0.09 to -0.1 MPa is applied for 2 hours. After the negative pressure is applied, the methyl sulfide is sent to the sulfide transfer vessel 4. The above steps are repeated, switching between the first transfer vessel 2 and the second transfer vessel 3 for material transportation, with continuous feeding. The methyl sulfide in the sulfide transfer vessel 4 is then sent to the next process. The tail gas can be absorbed by passing it through a sodium hydroxide solution.

[0052] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is transferred to the ammonium salt synthesis vessel 5. At the same time, 15% ammonia water is dripped into the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.15. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first stratification device 6 for stratification (i.e., continuous stratification). The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The stratified methyl sulfide ammonium salt is then transferred to the ammonium salt transfer vessel 7.

[0053] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:1.6. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40-50℃, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10-20℃, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10-20℃. The residence time of the reactants in each reactor is 1 hour. During the reaction... The primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 each use their respective external circulation pumps 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor. The external circulation pumps 21 are high-speed circulation pumps with a flow rate of 20 L / min. The reactant material in the tertiary sulfur phosphate reactor 10 is continuously overflowed into the second stratification device 11 for continuous stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, continuously stratified by the third stratification device 13, and continuously precipitated by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0054] S4, Powder Synthesis The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 40% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.1. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is also maintained at 20-30°C. With a slight negative pressure of -0.03 to -0.05 MPa, the residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the molten water washing reactor 18 for washing. Hot water is added to the molten water washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained with a content of 99.0% and a yield of 91% (calculated as phosphorus pentasulfide).

[0055] Example 6 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and triethylamine catalyst were mixed and added dropwise to sulfide synthesis reactor 1. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.05:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40-50℃, and the reaction time was 3 hours. After the reaction was complete, methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure of -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into sulfide transfer reactor 4. In step 1, the same operation as described above is continued to feed the next batch of reaction. When the reactants in the first transfer vessel 2 reach 1 / 2 to 2 / 3 of the vessel volume, the obtained methyl sulfide is pumped into the second transfer vessel 3 and a negative pressure of -0.09 to -0.1 MPa is applied for 2 hours. After the negative pressure is applied, the methyl sulfide is sent to the sulfide transfer vessel 4. The above steps are repeated, switching between the first transfer vessel 2 and the second transfer vessel 3 for material transportation, with continuous feeding. The methyl sulfide in the sulfide transfer vessel 4 is then sent to the next process. The tail gas can be absorbed by passing it through a sodium hydroxide solution.

[0056] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is sent to the ammonium salt synthesis vessel 5. At the same time, 15% ammonia water is dripped into the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.3. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first layering device 6 for continuous layering. The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The layered methyl sulfide ammonium salt is sent to the ammonium salt transfer vessel 7.

[0057] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:1.6. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40-50℃, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10-20℃, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10-20℃. The residence time of the reactants in each reactor is 1 hour. During the reaction... The primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 each use their respective external circulation pumps 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor. The external circulation pumps 21 are high-speed circulation pumps with a flow rate of 20 L / min. The reactant material in the tertiary sulfur phosphate reactor 10 is continuously overflowed into the second stratification device 11 for continuous stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, continuously stratified by the third stratification device 13, and continuously precipitated by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0058] S4, Powder Synthesis The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 20% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.3. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is also maintained at 20-30°C. With a slight negative pressure of -0.03 to -0.05 MPa, the residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the molten water washing reactor 18 for washing. Hot water is added to the molten water washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained with a content of 99.2% and a yield of 90% (calculated as phosphorus pentasulfide).

[0059] Example 7 A continuous synthesis method for dimethoate according to the present invention is implemented using the continuous synthesis system for dimethoate of Example 1, and includes the following steps: S1, Synthesis of Methyl Sulfides Phosphorus pentasulfide and a small amount of methyl sulfide were added to sulfide synthesis reactor 1. Methanol and triethylamine catalyst were mixed and added dropwise to sulfide synthesis reactor 1. The molar ratio of phosphorus pentasulfide, methanol, and catalyst was 1:4.05:0.02. The liquid volume in the reactor was 0.5% of the total material mass. The reactor temperature was controlled at 40-50℃, and the reaction time was 3 hours. After the reaction was complete, methyl sulfide was pumped into the first transfer reactor 2 and subjected to negative pressure of -0.09 to -0.1 MPa for 2 hours. After the negative pressure was removed, it was pumped into sulfide transfer reactor 4. In step 1, the same operation as described above is continued to feed the next batch of reaction. When the reactants in the first transfer vessel 2 reach 1 / 2 to 2 / 3 of the vessel volume, the obtained methyl sulfide is pumped into the second transfer vessel 3 and a negative pressure of -0.09 to -0.1 MPa is applied for 2 hours. After the negative pressure is applied, the methyl sulfide is sent to the sulfide transfer vessel 4. The above steps are repeated, switching between the first transfer vessel 2 and the second transfer vessel 3 for material transportation, with continuous feeding. The methyl sulfide in the sulfide transfer vessel 4 is then sent to the next process. The tail gas can be absorbed by passing it through a sodium hydroxide solution.

[0060] Synthesis of S2 and methyl sulfide ammonium salts The methyl sulfide in the sulfide transfer vessel 4 is transferred to the ammonium salt synthesis vessel 5. At the same time, 15% ammonia water is dripped into the ammonium salt synthesis vessel 5. The molar equivalent ratio of methyl sulfide to ammonia water is 1:1.3. The vessel temperature is controlled at 30-35℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2 hours. The methyl sulfide ammonium salt is continuously overflowed into the first stratification device 6 for stratification (i.e., continuous stratification). The lower layer of this device is an oil layer, and the upper layer is methyl sulfide ammonium salt. The stratified methyl sulfide ammonium salt is then transferred to the ammonium salt transfer vessel 7.

[0061] Synthesis of S3 and Thiophosyl Phosphate The methyl sulfide ammonium salt in ammonium salt transfer vessel 7 is transferred to the primary sulfur-phosphorus ester reactor 8, and methyl chloroacetate is also transferred to the primary sulfur-phosphorus ester reactor 8. The molar equivalent ratio of methyl sulfide ammonium salt to methyl chloroacetate is 1:1.6. The resulting product is sequentially and continuously fed into the secondary sulfur-phosphorus ester reactor 9 and the tertiary sulfur-phosphorus ester reactor 10. The temperature of the primary sulfur-phosphorus ester reactor 8 is maintained at 40-50℃, the temperature of the secondary sulfur-phosphorus ester reactor 9 is maintained at 10-20℃, and the temperature of the tertiary sulfur-phosphorus ester reactor 10 is maintained at 10-20℃. The residence time of the reactants in each reactor is 1 hour. During the reaction... The primary sulfur phosphate reactor 8, the secondary sulfur phosphate reactor 9, and the tertiary sulfur phosphate reactor 10 each use their respective external circulation pumps 21 to extract a set amount of reactant material from the reactor and then circulate it back into the reactor. The external circulation pumps 21 are high-speed circulation pumps with a flow rate of 20 L / min. The reactant material in the tertiary sulfur phosphate reactor 10 is continuously overflowed into the second stratification device 11 for continuous stratification. The crude sulfur phosphate obtained from the stratification is continuously washed by the water washing device 12, continuously stratified by the third stratification device 13, and continuously precipitated by the distillation device 14. The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor 15.

[0062] S4, Powder Synthesis The refined thiophosphate in the thiophosphate transfer reactor 15 is sent to the primary dimethoate reactor 16, and simultaneously, a 20% (w / w) aqueous solution of monomethylamine is sent to the primary dimethoate reactor 16. The molar equivalent ratio of the refined thiophosphate to the monomethylamine aqueous solution is 1:1.5. The temperature of the primary dimethoate reactor 16 is maintained at 20-30°C. The material obtained from the reaction is sent to the secondary dimethoate reactor 17, which is also maintained at 20-30°C. With a slight negative pressure of -0.03 to -0.05 MPa, the residence time of the material in each stage of the reactor is 2 hours. The material in the secondary dimethoate reactor 17 overflows into the molten water washing reactor 18 for washing. Hot water is added to the molten water washing reactor 18 to wash the dimethoate in a liquid state. The resulting material continuously overflows into the crystallization reactor 19 for crystallization. After filtration and drying, powdered dimethoate product is obtained with a content of 99.1% and a yield of 91% (calculated as phosphorus pentasulfide).

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A fully continuous synthesis system for dimethoate, characterized in that, Includes a sulfide synthesis reactor (1), a first transfer reactor (2), a second transfer reactor (3), and sequentially connected sulfide transfer reactor (4), an ammonium salt synthesis reactor (5), a first stratification device (6), an ammonium salt transfer reactor (7), a primary sulfur-phosphorus ester reactor (8), a secondary sulfur-phosphorus ester reactor (9), a tertiary sulfur-phosphorus ester reactor (10), a second stratification device (11), a water washing device (12), a third stratification device (13), a distillation device (14), and a sulfur-phosphorus ester transfer reactor (15). 5) Primary dimethoate reactor (16), secondary dimethoate reactor (17), molten water washing reactor (18), crystallization reactor (19), filter press (22), and drying device (23); the first transfer reactor (2) and the second transfer reactor (3) are connected in parallel. The outlet of the sulfide synthesis reactor (1) is connected to the inlet of the first transfer reactor (2) and the inlet of the second transfer reactor (3), respectively. The outlet of the first transfer reactor (2) and the second transfer reactor (3) are connected in parallel. The discharge port of (3) is connected to the feed port of the sulfide transfer vessel (4); the first-stage sulfophosphorus ester reactor (8), the second-stage sulfophosphorus ester reactor (9), and the third-stage sulfophosphorus ester reactor (10) are all provided with an external circulation outlet and an external circulation inlet. Each external circulation outlet is connected to the external circulation inlet on the corresponding reactor through an external circulation pump (21); the discharge port of the sulfide synthesis vessel (1) is connected to the inlet of the first transfer pump (25). The first transfer pump (25) is provided with a first outlet and a second outlet. The first outlet is connected to the feed port of the first transfer vessel (2), and the second outlet is connected to the feed port of the second transfer vessel (3). The feed port of the sulfide transfer vessel (4) is connected to the outlet of the second transfer pump (26). The second transfer pump (26) is provided with a first inlet and a second inlet. The discharge port of the first transfer vessel (2) is connected to the first inlet, and the discharge port of the second transfer vessel (3) is connected to the second inlet.

2. The continuous synthesis system for dimethoate according to claim 1, characterized in that, The external circulation pump (21) corresponding to the primary sulfur phosphate reactor (8) is provided with a first external circulation material inlet, a first external circulation material outlet and a first transfer material inlet. The external circulation outlet of the primary sulfur phosphate reactor (8) is connected to the first external circulation material inlet, and the first external circulation material outlet is connected to the external circulation inlet of the primary sulfur phosphate reactor (8). The ammonium salt transfer reactor (7) is connected to the first transfer material inlet through a transfer pipe (24). The transfer pipe (24) is provided with a methyl chloroacetate inlet. The external circulation pump (21) corresponding to the secondary sulfur phosphate reactor (9) is provided with a second external circulation material inlet, a second external circulation material outlet and a second transfer material inlet. The external circulation outlet of the secondary sulfur phosphate reactor (9) is connected to the second external circulation material inlet, the second external circulation material outlet is connected to the external circulation inlet of the secondary sulfur phosphate reactor (9), and the discharge port of the primary sulfur phosphate reactor (8) is connected to the second transfer material inlet. The external circulation pump (21) corresponding to the three-stage sulfur phosphate reactor (10) is provided with a third external circulation material inlet, a third external circulation material outlet and a third transfer material inlet. The external circulation outlet of the three-stage sulfur phosphate reactor (10) is connected to the third external circulation material inlet, the third external circulation material outlet is connected to the external circulation inlet of the three-stage sulfur phosphate reactor (10), and the discharge port of the two-stage sulfur phosphate reactor (9) is connected to the third transfer material inlet.

3. The fully continuous synthesis system for dimethoate according to claim 1 or 2, characterized in that, The sulfide synthesis reactor (1) is provided with a phosphorus pentasulfide inlet, a methanol inlet and a catalyst inlet, the ammonium salt synthesis reactor (5) is provided with an ammonia inlet, the water washing device (12) is provided with a water inlet and a wastewater outlet, the distillation device (14) is provided with a tail gas outlet, the first-stage dimethoate reactor (16) is provided with a methylamine inlet, and the molten water washing reactor (18) is provided with a hot water inlet.

4. The fully continuous synthesis system for dimethoate according to claim 1 or 2, characterized in that, The first transfer pump (25) and the second transfer pump (26) are both high-speed circulating pumps, and the flow rate of the high-speed circulating pump is 15L / min to 50L / min; Material conveying pumps (20) are provided between the sulfide transfer vessel (4) and the ammonium salt synthesis vessel (5), between the tertiary sulfophosphorus ester reaction vessel (10) and the second layering device (11), between the water washing device (12) and the third layering device (13), between the distillation device (14) and the sulfophosphorus ester transfer vessel (15), between the sulfophosphorus ester transfer vessel (15) and the primary dimethoate reaction vessel (16), and between the molten water washing vessel (18) and the crystallization vessel (19). The first transfer vessel (2), the second transfer vessel (3), and the secondary dimethoate reactor (17) are all connected to a pressure pump.

5. A continuous synthesis method for dimethoate, characterized in that, The process is implemented using the continuous synthesis system of dimethoate as described in any one of claims 1 to 4, and includes the following steps: S1. Synthesis of methyl sulfide: Phosphorus pentasulfide is added to the sulfide synthesis reactor (1). Methanol and catalyst are mixed and added dropwise to the sulfide synthesis reactor (1). The reactor temperature is controlled at 20℃~70℃ and the reaction time is 2h~4h. The obtained methyl sulfide is sent to the first transfer reactor (2), and negative pressure is drawn. Then the methyl sulfide is sent to the sulfide transfer reactor (4). The reaction continues to be fed into the sulfide synthesis reactor (1). When the reactant in the first transfer reactor (2) reaches the set value, the obtained methyl sulfide is sent to the second transfer reactor (3), and negative pressure is drawn. Then the methyl sulfide is sent to the sulfide transfer reactor (4). Repeat the above steps, switch the first transfer reactor (2) and the second transfer reactor (3) for material transportation, and then send the methyl sulfide in the sulfide transfer reactor (4) to the next process. S2. Synthesis of methyl sulfide ammonium salt: The methyl sulfide in the sulfide transfer vessel (4) is sent to the ammonium salt synthesis vessel (5). Ammonia water is dripped into the ammonium salt synthesis vessel (5). The temperature of the vessel is controlled at 10℃~50℃. The reaction yields methyl sulfide ammonium salt. The residence time in the vessel is 2h~4h. The methyl sulfide ammonium salt is continuously overflowed into the first layering device (6) for layering. The lower layer is the oil layer and the upper layer is the methyl sulfide ammonium salt. The layered methyl sulfide ammonium salt is sent to the ammonium salt transfer vessel (7). S3. Synthesis of thiophosphoric acid esters: Methyl sulfide ammonium salt in ammonium salt transfer vessel (7) is sent to primary thiophosphoric acid ester reactor (8), and methyl chloroacetate is sent to primary thiophosphoric acid ester reactor (8) for reaction. The resulting products are sequentially and continuously fed into secondary thiophosphoric acid ester reactor (9) and tertiary thiophosphoric acid ester reactor (10) for reaction. The reactor temperatures of primary thiophosphoric acid ester reactor (8), secondary thiophosphoric acid ester reactor (9), and tertiary thiophosphoric acid ester reactor (10) are all controlled at 10℃~60℃, and the residence time of the reactants in the reactors is controlled at 1h~2h. The reaction process... In the process, the first-stage sulfur phosphate reactor (8), the second-stage sulfur phosphate reactor (9), and the third-stage sulfur phosphate reactor (10) respectively extract the set amount of reactant material from the reactor through the external circulation pump (21) and then circulate it back into the reactor; the reactant material in the third-stage sulfur phosphate reactor (10) is continuously overflowed to the second stratification device (11) for stratification, and the crude sulfur phosphate product obtained from the stratification is continuously washed by the water washing device (12), stratified by the third stratification device (13), and continuously rectified by the distillation device (14). The obtained refined sulfur phosphate is sent to the sulfur phosphate transfer reactor (15); S4. Synthesis of dimethoate: The refined thiophosphate in the thiophosphate transfer vessel (15) is sent to the first-stage dimethoate reactor (16). The aqueous solution of monomethylamine is sent to the first-stage dimethoate reactor (16). The reactor temperature is controlled at 0-50℃, and the reaction material residence time is 2h-4h. The reaction material is sent to the second-stage dimethoate reactor (17). The reactor temperature is controlled at 0-50℃. The second-stage dimethoate reactor (17) is evacuated to negative pressure, and the reaction material residence time is 2h-4h. The reaction material obtained from the second-stage dimethoate reactor (17) is continuously overflowed into the melting water washing vessel (18) for water washing. The obtained material is continuously overflowed into the crystallization vessel (19) for crystallization. After filtration and drying, dimethoate product is obtained. The dimethoate product is a powder dimethoate product.

6. The continuous synthesis method for dimethoate according to claim 5, characterized in that, In step S1, the molar ratio of phosphorus pentasulfide, methanol, and catalyst is 1:4.01-4.1:0.01-0.03; in step S2, the molar equivalent ratio of methyl sulfide to ammonia is 1:1.05-1.30, and the mass concentration of ammonia is 5%-25%; in step S3, the molar equivalent ratio of ammonium methyl sulfide to methyl chloroacetate is 1:1.2-2.0; in step S4, the molar equivalent ratio of refined thiophosphoric acid ester to monomethylamine aqueous solution is 1:1.1-1.5, and the mass concentration of monomethylamine aqueous solution is 10%-40%.

7. The continuous synthesis method for dimethoate according to claim 5, characterized in that, In step S1: when the reactants in the first transfer vessel (2) reach 1 / 2 to 2 / 3 of the vessel volume, the resulting methyl sulfide is sent to the second transfer vessel (3); the catalyst includes one or more of diazabicyclo, pyridine, triethylamine and tert-butylethylenediamine; when each batch of materials is fed into the sulfide synthesis vessel (1), the liquid volume in the vessel is more than 0.5% of the total material mass; the pressure of the negative pressure is -0.09MPa to -0.1MPa.

8. The continuous synthesis method for dimethoate according to claim 7, characterized in that, In step S1, a small amount of methyl sulfide obtained from the reaction in the sulfide synthesis reactor (1) is retained in the sulfide synthesis reactor (1).

9. The continuous synthesis method of dimethoate according to any one of claims 5 to 8, characterized in that, In step S3, the temperature of the primary sulfur phosphate reactor (8) is controlled at 40℃~50℃, the temperature of the secondary sulfur phosphate reactor (9) is controlled at 10℃~20℃, and the temperature of the tertiary sulfur phosphate reactor (10) is controlled at 10℃~20℃; the external circulation pump (21) is a high-speed circulation pump with a flow rate of 15L / min~50L / min; in step S4, the secondary dimethoate reactor (17) is subjected to a negative pressure of -0.03MPa~-0.05MPa.

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