A method for producing thiodicarb using a single solvent without a catalyst

Abstract

The application discloses a method for producing thiodicarb by using a single solvent and without catalyst, which comprises the following steps: reacting SCl2 with pyridine to generate a ligand dipyrrolidone monosulfide hydrochloride in a solvent; dissolving methomyl in the solvent to obtain a methomyl solution, mixing a part of the solution with the ligand dipyrrolidone monosulfide hydrochloride to obtain a mixed solution, and continuously feeding the mixed solution and the mixed solution into two reaction kettles in sequence to synthesize thiodicarb; performing solid-liquid separation, pressure filtering the solid after washing with water, centrifuging the solid after washing with a solvent, and vacuum drying to obtain a final product. The preparation method provided by the application does not use any catalyst, avoids a subsequent catalyst removal step, uses only dichloroethane as a solvent for thiodicarb synthesis, and the feeding amount of sulfur dichloride and pyridine is close to the theoretical value, so that the reaction process is almost in a homogeneous state, the reaction speed is fast, the conversion rate of raw material methomyl is high, and the yield of finished product thiodicarb is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pesticide compound synthesis, and particularly relates to a method for producing thiodicard using a single solvent and without catalyst. BACKGROUND

[0002] Thiodicard, also known as bensultap, thiodicarb, and lavie, has a chemical name of 3,7,9,13-tetramethyl-5,11-dioxa-2,8,14-trithia-4,7,9,12-tetraazapentadec-3,12-diene-6,10-dione, N,N' [thio bis (methyleneimino) carbonyloxy] -bisiminothioacetic acid dimethyl ester. As a low-toxicity carbamoyl oxime insecticide, the mechanism of action of thiodicard is nerve blockage, that is, the reactivation of the conduction substance in the nerve fiber is hindered by inhibiting acetylcholinesterase activity, resulting in the death of pests. Thiodicard has a special effect on lepidopteran pests and has an ovicidal effect, and can also be used for controlling coleopteran, dipteran and hymenopteran pests, but is ineffective against cotton aphids, leafhoppers, thrips and mites. It is suitable for use in cotton, fruit trees, vegetables, rice and economic crops, is safe for fish and birds, has no chronic poisoning, no carcinogenic, teratogenic and mutagenic effects, is safe for crops, has a short residual period in the soil, is friendly to the environment, and has been a large insecticide in use at home and abroad in the past two decades. The existing thiodicard production method, according to the classification of raw materials, one is hydrogen fluoride-methomyl oxime method, which has a complex process flow and high cost, and also uses toxic and corrosive gas hydrogen fluoride, which has strict requirements on the material quality of equipment, large amounts of "three wastes" and great difficulty in treatment, and no industrial application value; the other is methomyl method. The synthesis process of trimethylchlorosilane-methomyl in the methomyl method has difficulties in obtaining raw material trimethylchlorosilane, complicated and dangerous production operation, low conversion rate of methomyl, and low product yield, resulting in high cost and no industrial production value; the use of sulfur dichloride and methomyl as main raw materials to synthesize thiodicard is the main method for industrial production of thiodicard at present, and according to the use of solvents and catalysts, the main research results in China are:

[0003] Henan Jinpeng Chemical in patent application CN111054296A, CN211636445U, CN211636444U proposed the production of sulfide ligand, sulfide synthesis, washing of continuous production process and device, in the saltification reactor multi-point addition of sulfur dichloride dispersion reaction heat release, realize continuous production; Chinese patent CN108047106B proposed with pyridine (toluene, xylene, etc.) as solvent, 4-dimethylamino pyridine as catalyst, respectively, drop adding sulfur dichloride containing solvent and sulfide solution containing solvent synthesis of sulfide method, the method needs to add a large amount of solvent, the mole ratio of sulfide and total solvent is 1:6-10. Chinese patent CN114031533A proposed the following synthesis process: with N-methyl formamide and sulfur dichloride as raw material to generate methyl formamide thiourea, then with sulfide under the action of catalyst to generate mixed liquid containing sulfide, add water to the mixed liquid containing sulfide to reduce temperature, filter, the filter cake is washed, centrifuged, dried to obtain sulfide, the content of sulfide obtained by the method is as high as 98%, but the synthesis process needs catalyst to improve the reaction rate, in addition, with N-methyl formamide and sulfur dichloride as raw material to generate methyl formamide thiourea, however, methyl formamide thiourea is unstable itself, and methyl formamide thiourea and catalyst will have multiple side reactions, causing multiple by-products of different structures to be left in the finished product sulfide, the finished product sulfide generated after adding catalyst has poor heat storage stability. Chinese patent CN112778179A proposed to use pyridine as solvent, 18 crown ether-6 as catalyst, under closed conditions, first add part of sulfur dichloride to the pyridine solution of 18 crown ether 6; after drop completion, add the rest of sulfur dichloride and methomyl pyridine solution to carry out reaction, while adding the rest of sulfur dichloride and methomyl pyridine solution, chlorine gas is introduced, after drop completion, stop introducing chlorine gas. After drop completion, continue to carry out heat preservation reaction to obtain sulfide, the crown ether as catalyst in the reaction is expensive, causing high production cost. Chinese patent CN112479957A proposed to use pyridine and xylene as solvent, sulfur dichloride and pyridine to react to generate complex body, then under the action of catalyst trialkyl tertiary amine, dipyridine hydrochloride sulfide and methomyl generate sulfide. Chinese patent CN114315672A uses xylene and toluene as solvent, SCl2 and pyridine to react to obtain ligand at lower than 0℃, then adds methomyl into the synthesis kettle to generate sulfide. After reaction, the reaction liquid is centrifuged, once washed with water, pressure filtered; twice washed with water, centrifuged; washed with ethanol, centrifuged; vacuum dried to obtain sulfide product; the reaction method uses toluene which has large solubility for elemental sulfur, avoiding too much solid material in the reaction system to affect the reaction process of pyridine and sulfur dichloride.

[0004] The existing sulfide synthesis process mainly has the following problems:

[0005] (1) The yield of thiamethoxam is low. Based on methomyl, the yield of thiamethoxam in industrial production is at most 90%, and many of the data are laboratory data. If applied to industrial-scale production, the conversion rate of methomyl will be even lower.

[0006] (2) In the prior art, in order to improve the reaction rate, one or more catalysts are required for the synthesis of thiodicarb. On the one hand, this increases the production cost. On the other hand, due to the process technology, some catalysts cannot be removed from the production process and remain in the finished thiodicarb, which has seriously affected the quality indicators and thermal storage stability of the finished product.

[0007] (3) Due to the large variety and high content of impurities in the thiodicarb prepared by the existing process, the product has poor thermal storage stability and fails the thermal storage stability test.

[0008] (4) Two or even three organic compounds with different structures and boiling points are used as solvents in the production of thiamethoxam. After the synthesis of thiamethoxam, it is difficult to remove the multi-component solvents from the production system. They remain in the finished thiamethoxam technical material, which directly affects the purity, melting point, heat storage stability and other quality indicators of the finished product. In some cases, the test results may even be judged as "unqualified". Summary of the Invention

[0009] To address the aforementioned problems in the prior art, this invention provides a method for producing thiamethoxam using a single solvent and without a catalyst. This method avoids the need for subsequent catalyst removal processes and their impact on product quality, while simultaneously improving the conversion rate of methomyl and the yield of thiamethoxam; reducing the production cost of thiamethoxam; and reducing the variety and content of various impurities, thereby increasing the purity of thiamethoxam and improving the thermal storage stability of the product. The technical solution of this invention is as follows:

[0010] A method for producing thiodicarb using a single solvent and without a catalyst includes the following steps:

[0011] In a solvent, SCl2 reacts with pyridine to generate the ligand dipyridine monosulfide hydrochloride. Methomyl is dissolved in the solvent to prepare a methomyl solution. A portion of the solution is mixed with the ligand dipyridine monosulfide hydrochloride to prepare a mixed solution. This mixed solution is then mixed with another portion of the methomyl solution to synthesize thiodicarb. Solid-liquid separation is performed. The solid is washed with water, filtered under pressure, washed with solvent, centrifuged, and dried to obtain the final product.

[0012] The solvent is dichloroethane;

[0013] The molar ratio of methomyl to dichloroethane is 1:3.277-4.055; the molar ratio of methomyl to SCl2 is 1:0.511-0.549; and the molar ratio of methomyl to pyridine is 1:1.168-1.424. Preferably, the reaction temperature of SCl2 with pyridine to form the ligand dipyridine monosulfide hydrochloride does not exceed 10°C, preferably 0-8°C; SCl2 is added dropwise to pyridine over a time controlled at 40-60 minutes; after the addition of SCl2 is complete, stirring continues for 10-20 minutes.

[0014] Preferably, in the thiamethoxam synthesis reaction, the mixed solution obtained in step 2 and the prepared dichloroethane solution of the second part of methomyl are pre-reacted in the first thiamethoxam synthesis reactor; then transferred to the second thiamethoxam synthesis reactor for further reaction; specifically, the reaction is first carried out in the first thiamethoxam synthesis reactor, and the reaction temperature is controlled at 15-22°C by controlling the flow rate of the mixed solution and the other part of the methomyl solution; then the material in the first thiamethoxam synthesis reactor is pressurized and enters the second thiamethoxam synthesis reactor, and the material residence time is controlled at 60-110 minutes and the reaction temperature is controlled at 28-35°C.

[0015] Preferably, in the solid-liquid separation step, the material in the second synthesis reactor of thiodicarb enters a centrifugal filter press under pressure for solid-liquid separation. The liquid is reused to prepare the ligand dipyridine monosulfide hydrochloride, and the solid enters the next step for water washing.

[0016] Preferably, in the water washing process, the solid obtained from solid-liquid separation is added to the water washing tank, the temperature inside the tank is controlled at 20-30℃, and the mixture is stirred for 90-120 minutes.

[0017] Preferably, after washing, the material is pressure filtered, the filtrate is allowed to stand and separate into layers, the lower layer of dichloroethane is reused, and the upper aqueous phase is treated by a pyridine recovery device to recover pyridine from the water; the filter cake obtained from pressure filtration is washed with dichloroethane in a dichloroethane washing vessel.

[0018] Preferably, the material washed in the dichloroethane washing vessel is centrifuged, the solid is dried, and the filtrate and the dichloroethane obtained by settling and separating in the water washing process are used together for dichloroethane washing after water washing.

[0019] Furthermore, the method includes the following steps:

[0020] Step 1: Prepare materials.

[0021] After measuring dichloroethane, vacuum-suction it into the methomyl dissolving vessel, start stirring, add the weighed methomyl, and observe the dissolution of methomyl through the sight glass until all methomyl is dissolved to obtain a methomyl solution. The dichloroethane added here is used to dissolve the methomyl, and the amount used is just enough to dissolve the methomyl.

[0022] SCl2 is pressurized into the SCl2 high-level tank using nitrogen gas and then measured.

[0023] The pyridine is measured and then vacuum-sucked into the ligand dipyridyl monosulfide hydrochloride synthesis kettle;

[0024] The dichloroethane is measured and then vacuum-sucked into the ligand dipyridyl monosulfide hydrochloride synthesis kettle, to provide a reaction environment for the reaction of sulfur dichloride and pyridine.

[0025] Step 2, synthesis of a ligand,

[0026] The refrigerant is introduced into the jacket of the ligand dipyridyl monosulfide hydrochloride synthesis kettle, and the temperature in the kettle is reduced to -7-2℃. Then, SCl2 is added dropwise. SCl2 reacts with pyridine to form the ligand dipyridyl monosulfide hydrochloride. The dropping speed of SCl2 is controlled so that the reaction temperature is not higher than 10℃, preferably 0-8℃, and the dropping time is controlled to be 40-60 minutes. After the addition of SCl2 is completed, the stirring is continued for 10-20 minutes. The first part of the prepared methomyl dichloroethane solution is added into the ligand dipyridyl monosulfide hydrochloride synthesis kettle, and the stirring is continued for 10-20 minutes to obtain a mixed solution, which is ready to be injected into the first synthesis kettle of sulfotep.

[0027] Step 3, synthesis of sulfotep,

[0028] The synthesis of sulfotep is a continuous operation. The mixed solution prepared in step 2 is injected from the bottom of the ligand synthesis kettle into the first synthesis kettle of sulfotep at a set flow rate. Meanwhile, the second part of the prepared methomyl dichloroethane solution is injected from the bottom of the first synthesis kettle of sulfotep into the kettle. The residence time of the material is controlled to be 50-80 minutes, and the reaction temperature is controlled to be 15-22℃. The material in the first synthesis kettle of sulfotep is brought into the second synthesis kettle of sulfotep under pressure, and the residence time of the material is controlled to be 60-110 minutes, and the reaction temperature is controlled to be 28-35℃.

[0029] In the production process, the solubility of the intermediate product needs to be considered. The precipitation of the intermediate product can also cause low yield in the synthesis process and affect the product quality. Under the technical process provided in the present application, the intermediate ligand dipyridyl monosulfide hydrochloride has a low solubility in dichloroethane and tends to settle at the bottom of the first synthesis kettle. However, in the process of condition exploration, the inventors surprisingly found that by controlling the reaction progress and reaction temperature, a part of the methomyl dichloroethane solution is mixed with the ligand dipyridyl monosulfide hydrochloride, and then the temperature is increased for reaction, a part of the ligand dipyridyl monosulfide hydrochloride is consumed, and then another part of the methomyl dichloroethane solution is added, so that the intermediate is prevented from precipitating. In the first synthesis kettle of sulfotep, the reaction of methomyl and the ligand dipyridyl monosulfide hydrochloride is completed by about 80%, and then it is transferred to the second synthesis kettle of sulfotep with a higher temperature, and the reaction is continued, so that the conversion rate of methomyl is more than 97%.

[0030] Preferably, in step 2, the first part of the prepared methomyl dichloroethane solution accounts for 40-55% of the total amount, more preferably, in step 2, the ratio of the volume of the first part of the prepared methomyl dichloroethane solution to the volume of the second part of the methomyl solution is 1:1.1-1.2.

[0031] More preferably, in step 2, the first part of the prepared methomyl dichloroethane solution accounts for 40% of the total amount, mainly by pre-mixing methomyl with the ligand dipyridyl monosulfide hydrochloride to initiate the reaction of methomyl with the ligand dipyridyl monosulfide hydrochloride in the first reaction kettle; due to the low solubility of the ligand dipyridyl monosulfide hydrochloride in dichloroethane, it has a tendency to settle at the bottom of the first synthesis kettle, therefore, in step 3, the second part of the methomyl dichloroethane solution is pumped into the kettle from the bottom of the first thiodicarb synthesis kettle, which helps to prevent the settlement of dipyridyl monosulfide hydrochloride, intensify mixing and promote the reaction.

[0032] Step 4, solid-liquid separation,

[0033] The material in the second thiodicarb synthesis kettle enters the centrifugal pressure filter for solid-liquid separation under pressure, the liquid is recycled to prepare the ligand dipyridyl monosulfide hydrochloride, and the solid enters the next step for water washing; the liquid composition contains all the reaction raw materials, generated thiodicarb, dichloroethane and a small amount of ligand dipyridyl monosulfide hydrochloride and other substances. The composition of the materials does not affect the recycling, nor does it affect the reaction of pyridine and sulfur dichloride to synthesize the ligand dipyridyl monosulfide hydrochloride under the set reaction conditions and the subsequent synthesis of thiodicarb.

[0034] Step 5, water washing,

[0035] Softened water is metered into the water washing kettle, the ratio of softened water to 100% methomyl is (1.832-2.225):1; the stirring is started, the solid obtained from the centrifugal pressure filter in step 4 is added into the water washing kettle, the temperature in the kettle is controlled at 20-30℃, and after 90-120 minutes of stirring, the pressure filtration is started;

[0036] Step 6, pressure filtration,

[0037] The material in the water washing kettle is pumped into the plate and frame filter press for pressure filtration by a mud pump, the filtrate is allowed to stand and separate into layers, the lower layer dichloroethane is continuously recycled, and the upper layer water phase is sent to the pyridine recovery device for treatment to recover pyridine in the water; the filter cake obtained by pressure filtration is sent to the dichloroethane washing kettle;

[0038] Step 7, dichloroethane washing,

[0039] Dichloroethane is metered from the dichloroethane metering tank into the dichloroethane secondary washing kettle, the stirring is started, the filter cake obtained by water washing and pressure filtration is added, the temperature in the kettle is controlled at 20-40℃, and the stirring is continued for 80-100 minutes; the centrifugation is prepared;

[0040] Step 8, centrifuge the material in the dichloroethane washing kettle prepared in step 7; the filtrate obtained by centrifugation is reused, and the dichloroethane obtained by standing and separating in the water washing process is used for dichloroethane washing after water washing; the solid is sent for drying;

[0041] Step 9, drying,

[0042] The filter cake obtained by centrifugation in step 8 is sent into a double-cone dryer, and drying is carried out while controlling the temperature to be lower than 45 DEG C and the vacuum degree to be not lower than 0.09 MPa. Since the boiling point of dichloroethane is relatively low, dichloroethane volatilizes after drying treatment, and the finished product of sulfotep is obtained.

[0043] The gas extracted from the double-cone dryer is condensed by two-stage tubular condensers (using chilled brine) in series, and the composition of the condensate includes water, dichloroethane, pyridine, etc. The condensate is reused for dichloroethane washing process, and the dichloroethane containing pyridine and a small amount of water does not affect the use.

[0044] Compared with the prior art, the beneficial effects of the present application are:

[0045] 1. The preparation method provided by the present application does not use any catalyst, avoids the subsequent step of removing the catalyst, and overcomes the problem that the catalyst cannot be completely removed and remains in the finished product of sulfotep, which seriously affects the quality index and heat storage stability of the finished product;

[0046] 2. Only one solvent, dichloroethane, is used to replace multiple solvents in the existing process, which simplifies the process and avoids the problems of removing multiple solvents and affecting product quality;

[0047] 2. The synthesis process of sulfotep adopts two-kettle continuous production under a certain pressure, and the total reaction time is shortened to only 3-4 hours;

[0048] 3. After the synthesis of sulfotep is completed, the material is directly sent to a centrifugal filter for solid-liquid separation without adding water, which reduces the process of removing the solvent; the filtrate does not need any treatment and is returned to the synthesis process for continuous use; the filter cake is washed once with water, washed once with dichloroethane, and vacuum dried to obtain the finished product, and the filter cake treatment process is simple;

[0049] 4. Only one solvent, dichloroethane, is used for the synthesis of sulfotep, and the amounts of sulfur dichloride and pyridine are close to the theoretical value. By using dichloroethane as the solvent, adding the intermediate salt of dicrotoph and the ligand dipyrone monosulfide hydrochloride in stages, and controlling the reaction temperature, the reaction process is almost in a homogeneous state, which avoids the problem of poor solubility of the intermediate in dichloroethane, and the reaction speed is fast, the conversion rate of raw material dicrotoph is high, the yield of finished product sulfotep is high, and the side reaction is reduced; the consumption of sulfur dichloride and pyridine is reduced, and the product benefit is improved;

[0050] 5. The existing production process of sulfur dioxide involves two water washings and one methanol washing. This invention uses only one water washing and one dichloroethane washing followed by drying, eliminating the need for methanol washing. During vacuum drying, the vacuum exhaust gas is condensed and reused using a two-stage refrigerated brine system. The dichloroethane-containing filtrate obtained from filtration, pressure filtration, and stratification is also reused, resulting in a reduction in dichloroethane loss overall.

[0051] 6. The filtrate containing dichloroethane obtained from the first washing is used in the thiamethoxam synthesis process. All mother liquor obtained from washing with dichloroethane is reused or recycled. The dichloroethane extracted under vacuum during the drying process is also recovered. Although thiamethoxam has a high solubility in dichloroethane, the actual loss of thiamethoxam is minimal because the dichloroethane is recycled, ensuring a high yield of thiamethoxam. After the mother liquor is reused 10 times, the content of the thiamethoxam product obtained is still over 96%, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiamethoxam Technical". After the mother liquor is reused 10 times, it is centrifuged and scraped under vacuum conditions. The condensate containing dichloroethane and pyridine under the specified process conditions can be directly used in the thiamethoxam synthesis process. Due to separation under low temperature and high vacuum conditions, the content of the thiamethoxam product obtained is still over 95%, which is qualified. The solvent can be recycled multiple times, reducing washing steps and lowering production costs. Detailed Implementation

[0052] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0053] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0054] Unless otherwise specified, the main technical requirements for the raw materials used are as follows:

[0055] Dichloroethane, with a mass content of not less than 98.0%;

[0056] Methoxyfen, with a mass content of 97.0%;

[0057] Sulfur dichloride, mass content 97.0%;

[0058] Pyridine, with a mass content of 99.5%;

[0059] The above material ratios are calculated based on 100% purity of the raw materials, unless otherwise specified.

[0060] Example 1

[0061] 1. Preparation of materials

[0062] 780 Kg of dichloroethane was vacuum-sucked into the methomyl dissolving kettle, stirring was started, 500 Kg of methomyl was added, and the dissolving of methomyl was observed through the sight glass until all the methomyl was dissolved.

[0063] 160 Kg of SCl2 was pressurized into the SCl2 high tank by nitrogen.

[0064] 280 Kg of neopyridine was vacuum-sucked into the ligand dipyridyl monosulfide hydrochloride synthesis kettle.

[0065] 630 Kg of dichloroethane was measured and vacuum-sucked into the ligand dipyridyl monosulfide hydrochloride synthesis kettle.

[0066] 2. Synthesis of ligand

[0067] The ligand synthesis kettle jacket was connected to a refrigerant, and the temperature inside the kettle was lowered to -6°C. Then SCl2 was added dropwise, the dropwise speed was controlled, and the reaction temperature was controlled at 2°C. The dropwise time was controlled at 40 minutes. After the dropwise addition of SCl2 was completed, stirring was continued for 10 minutes, and the ligand dipyridyl monosulfide hydrochloride was generated. The prepared methomyl pyridine solution 320 Kg was measured and added to the ligand synthesis kettle, and the temperature inside the kettle was controlled to be no more than 2°C. After stirring for 10 minutes, the first sulprofos synthesis kettle was prepared.

[0068] 3. Synthesis of sulprofos

[0069] The synthesis of sulprofos was operated continuously. The prepared ligand and the dichloroethane solution of the part of methomyl added were pumped from the ligand synthesis kettle to the first sulprofos synthesis kettle at a set flow rate from the bottom of the kettle. At the same time, the prepared dichloroethane solution of methomyl was pumped from the methomyl dissolving kettle to the first sulprofos synthesis kettle at a set flow rate from the bottom of the kettle. The flow rates of the two feeds were adjusted to control the residence time of the material to be 50 minutes and the reaction temperature to be 15°C. The material in the first sulprofos synthesis kettle was pressurized to enter the second sulprofos synthesis kettle, the residence time of the material was controlled to be 70 minutes, and the reaction temperature was controlled to be 30°C.

[0070] 4. Liquid separation

[0071] The material in the second sulprofos synthesis kettle was pressurized to enter the centrifugal pressure filter for solid-liquid separation, the liquid was recycled to prepare the ligand, and the solid was washed with water.

[0072] 5. Water washing

[0073] To the water washing kettle metering softening water 930Kg, open the stirring, the solid obtained from centrifugal filter is added into the water washing kettle, control the kettle temperature 20℃, after stirring for 90 minutes, start filter pressing;

[0074] 6, filter pressing

[0075] The material in the water washing kettle is pumped into the plate and frame filter press by mud pump, the filtrate is layered, the lower layer dichloroethane is reused, and the upper layer water phase is removed to the pyridine recovery device to recover pyridine in water; the filter cake obtained by filter pressing is washed in the dichloroethane washing kettle.

[0076] 7, dichloroethane washing

[0077] From the dichloroethane metering tank to the dichloroethane secondary washing kettle, add dichloroethane 1275Kg, open the stirring, add the filter cake obtained by primary washing, control the kettle temperature 20℃, stirring for 80 minutes. Prepare centrifugation;

[0078] 8, put the material in the dichloroethane washing kettle into the centrifuge for centrifugation. The filtrate obtained by centrifugation is reused; the solid is sent to drying.

[0079] 9, drying

[0080] The filter cake obtained by centrifugation is sent into the double-cone dryer, and the temperature is controlled below 45℃, and the vacuum degree is not less than 0.09MPa for drying, and 519.99Kg of thiodicarb finished product is obtained. The analysis of thiodicarb content is 98.15%, and other indicators are qualified, meeting the quality requirements of industry standard “NY / T 3776-2020 Thiodicarb Technical Material”. The thiodicarb yield is 96.31%. According to the standard “GB / T19136-2003 Pesticide Thermal Storage Stability Test Method”, the thermal storage stability test of thiodicarb is carried out, and the decomposition rate of thiodicarb is 3.2%, which is lower than 5%, and at the same time, other indicators are qualified, meeting the quality requirements of industry standard “NY / T 3776-2020 Thiodicarb Technical Material”. The gas extracted from the double-cone dryer is condensed by two-stage tube condensers in series (using chilled brine) and then reused.

[0081] Example 2

[0082] 1, preparation of materials

[0083] The filtrate obtained from the centrifugal filter separation in example 1 is measured 790Kg and dissolved in the vacuum suction methomyl dissolving kettle, the stirring is opened, 500Kg of methomyl is added, and the methomyl dissolving condition is observed until the methomyl is completely dissolved;

[0084] 172Kg of SCl2 is pressurized into the SCl2 high tank by nitrogen;

[0085] The filtrate from the centrifugal pressure filtration separation obtained in Example 1 is metered, and 630 Kg of fresh pyridine is added to the ligand synthesis kettle for the synthesis of the ligand dithiopyridine hydrochloride salt;

[0086] 2. Synthesis of ligand

[0087] The ligand synthesis kettle jacket is supplied with refrigerant, and the temperature in the kettle is lowered to -6°C. SCl2is then added dropwise, with the dropwise addition rate and the reaction temperature being controlled at 6°C, and the dropwise addition time being controlled at 45 minutes. After the addition of SCl2is completed, stirring is continued for 15 minutes. The prepared 330 Kg of methomyl in pyridine is added to the ligand synthesis kettle, with the temperature in the kettle being controlled at no more than 6°C. After stirring for 10 minutes, the first sulprofos synthesis kettle is prepared.

[0088] 3. Synthesis of sulprofos

[0089] The synthesis of sulprofos is performed continuously. The prepared ligand and the pyridine solution with part of the methomyl added are pumped from the ligand synthesis kettle into the first sulprofos synthesis kettle at a set flow rate. Meanwhile, the prepared methomyl in pyridine is pumped from the methomyl dissolving kettle into the first sulprofos synthesis kettle at a set flow rate. The flow rates of the two streams are adjusted to control the residence time of the material in the first sulprofos synthesis kettle at 70 minutes and the reaction temperature at 17°C. The material in the first sulprofos synthesis kettle is pumped into the second sulprofos synthesis kettle under pressure, and the residence time of the material in the second sulprofos synthesis kettle is controlled at 100 minutes and the reaction temperature is controlled at 29°C.

[0090] 4. Solid-liquid separation

[0091] The material in the second sulprofos synthesis kettle is pumped into the centrifugal pressure filter under pressure for solid-liquid separation. The liquid is recycled to prepare the ligand, and the solid is added to the water washing kettle for water washing.

[0092] 5. Water washing

[0093] The water washing kettle is supplied with 1000 Kg of softened water, and stirring is started. The solid obtained from the centrifugal pressure filter is added to the water washing kettle. The temperature in the water washing kettle is adjusted to 30°C, and stirring is continued for 100 minutes. Filtration is then started.

[0094] 6. Filtration

[0095] The material in the water washing kettle is pumped into the plate-and-frame filter for filtration. The filtrate is allowed to stand and separate into layers. The lower layer of dichloroethane is recycled, and the upper layer of water phase is sent to the pyridine recovery device for the recovery of pyridine from the water. The filter cake obtained from the filtration is sent to the dichloroethane washing kettle.

[0096] 7. Dichloroethane washing

[0097] Dichloroethane is added to the dichloroethane secondary washing kettle from the dichloroethane metering tank, and stirring is started. The filter cake obtained from the primary washing is added. The temperature in the kettle is adjusted to 25°C, and stirring is continued for 80 minutes. Centrifugation is then prepared.

[0098] 8, The material in the dichloroethane washing kettle is put into a centrifuge for centrifugation. The filtrate obtained by centrifugation is reused; the solid is sent for drying.

[0099] 9, The filter cake obtained by centrifugation is sent into a double-cone dryer for drying while controlling the temperature to be lower than 45℃ and the vacuum degree to be not lower than 0.08MPa, and sulfur bifen product 519.4Kg is obtained. The analysis of sulfur bifen content is 98.19%, other indicators are qualified, which meet the quality requirements of industry standard "NY / T 3776-2020 Sulfur Bifen Technical Material". The calculation of sulfur bifen yield is 96.11%. The thermal storage stability test of sulfur bifen is carried out according to the standard "GB / T19136-2003 Pesticide Thermal Storage Stability Test Method", the decomposition rate of sulfur bifen is 3.2% which is lower than 5%, and other indicators are qualified which meet the quality requirements of industry standard "NY / T 3776-2020 Sulfur Bifen Technical Material". The gas extracted from the double-cone dryer is condensed by two-stage tube condensers in series (using chilled brine) and then reused.

[0100] Example 3

[0101] 1, Preparation of materials

[0102] The filtrate from the centrifugal pressure filtration separation obtained in Example 2 is measured at 780Kg pyridine, which is used to dissolve the methomyl dissolving kettle by vacuum suction. Start stirring, add 500Kg methomyl, and observe the methomyl dissolution from the sight glass until all the methomyl is dissolved.

[0103] Use nitrogen to press 171Kg SCl2 into the SCl2 high tank;

[0104] The filtrate from the centrifugal pressure filtration separation obtained in Example 2 is measured, and the pyridine obtained from the pyridine recovery post is supplemented with new pyridine, a total of 650Kg, which is used to synthesize ligand dipyridyl monosulfide hydrochloride in a ligand synthesis kettle.

[0105] 2, Synthesis of ligand

[0106] Pass cold liquid into the jacket of the ligand synthesis kettle, and when the temperature in the kettle is reduced to-4℃, start dropping SCl2, control the dropping speed and the reaction temperature to be 4℃, and the dropping time is controlled to be 50 minutes. After the dropping of SCl2 is completed, continue stirring for 10 minutes; measure 340Kg of prepared methomyl pyridine solution and add it to the ligand synthesis kettle, control the temperature in the kettle to be not more than 4℃, and after stirring for 15 minutes, prepare to inject the first sulfur bifen synthesis kettle.

[0107] 3, Synthesis of sulfur bifen

[0108] The synthesis of thiodicofen is operated continuously. The prepared ligand and pyridine solution of part of methomyl added in the pyridine solution are pumped into the first synthesis reactor of thiodicofen from the bottom of the reactor at a set flow rate by a mud pump, and the prepared pyridine solution of methomyl is pumped into the first synthesis reactor of thiodicofen from the bottom of the reactor by a metering pump, the residence time of the material is controlled to be 65 minutes and the reaction temperature is controlled to be 21℃ by adjusting the flow rates of the two feeds; the material in the first synthesis reactor of thiodicofen is brought into the second synthesis reactor of thiodicofen under pressure, the residence time of the material is controlled to be 90 minutes and the reaction temperature is controlled to be 30℃;

[0109] 4. Solid-liquid separation

[0110] The material in the second synthesis reactor of thiodicofen is brought into a centrifugal pressure filter for solid-liquid separation, the liquid is recycled to prepare the ligand, and the solid is added into a water washing reactor for water washing.

[0111] 5. Water washing

[0112] Softened water 950Kg is added into the water washing reactor, stirring is started, the solid obtained by the solid-liquid separation of the centrifugal pressure filter is added into the water washing reactor, the temperature in the water washing reactor is adjusted to be 28℃, and after 100 minutes of stirring, pressure filtration is started.

[0113] 6. Pressure filtration

[0114] The material in the water washing reactor is pumped into a plate-and-frame pressure filter for pressure filtration by a mud pump, the filtrate is allowed to stand and separate into layers, the lower layer of dichloroethane is recycled, and the upper layer of water phase is sent to a pyridine recovery device for recovering pyridine in the water; the filter cake obtained by pressure filtration is sent to a dichloroethane washing reactor.

[0115] 7. Dichloroethane washing

[0116] Dichloroethane 1280Kg is added into the dichloroethane secondary washing reactor from a dichloroethane metering tank, stirring is started, the filter cake obtained by the first washing is added, the temperature in the reactor is adjusted to be 30℃, and stirring is continued for 95 minutes, and then centrifugation is prepared.

[0117] The material in the dichloroethane washing reactor is put into a centrifuge for centrifugation, and the filtrate obtained by centrifugation is recycled; and the solid is sent to drying.

[0118] 9. The dried filter cake obtained by centrifugation is fed into a double-cone dryer, and drying is carried out while controlling the temperature to be lower than 45°C and the vacuum degree to be not lower than 0.08 MPa, to obtain thiodicarb product 517.7 kg. Analysis of thiodicarb content is 98.29%, and other indicators are qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The thiodicarb yield is calculated to be 96.11%. The thiodicarb is subjected to heat storage stability test according to the standard "GB / T 19136-2003 Pesticide Heat Storage Stability Test Method", and the thiodicarb decomposition rate is 3.2%, which is lower than 5%, and at the same time, other indicators are qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The gas extracted from the double-cone dryer is condensed by two-stage tube condensers (using chilled brine) in series and then reused.

[0119] Example 4

[0120] 1. Preparation of materials

[0121] The 770 kg of filtrate from the centrifugal pressure filtration separation obtained in Example 3 is measured and vacuum-sucked into a methomyl dissolving kettle, and stirring is started. 500 kg of methomyl is added, and the dissolution of methomyl is observed through a sight glass until all the methomyl is dissolved.

[0122] Nitrogen is used to press 173 kg of SCl2 into an SCl2 high tank;

[0123] The 640 kg of filtrate from the centrifugal pressure filtration separation obtained in Example 3 and new pyridine are measured and vacuum-sucked into a ligand dipyridyl monosulfide hydrochloride synthesis kettle;

[0124] 2. Synthesis of ligand

[0125] The ligand synthesis kettle jacket is connected to a refrigerant, and when the temperature in the kettle is lowered to -2°C, the SCl2 is started to be added dropwise, the dropwise addition speed is controlled, and the reaction temperature is controlled at 8°C. The dropwise addition time is controlled to be 55 minutes. After the dropwise addition of SCl2 is completed, stirring is continued for 20 minutes. 340 kg of prepared methomyl pyridine solution is measured and added to the ligand synthesis kettle, and the temperature in the kettle is controlled to be not higher than 8°C. After stirring for 15 minutes, the first thiodicarb synthesis kettle is prepared.

[0126] 3. Synthesis of thiodicarb

[0127] The synthesis of thiodicofen is operated continuously. The prepared ligand and pyridine solution of part of methomyl added in the pyridine solution are pumped into the first synthesis reactor of thiodicofen from the bottom of the reactor at a set flow rate by a mud pump, and the prepared pyridine solution of methomyl is pumped into the first synthesis reactor of thiodicofen from the bottom of the reactor by a metering pump, the residence time of the material is controlled to be 65 minutes and the reaction temperature is controlled to be 22℃ by adjusting the flow rates of the two feeds; the material in the first synthesis reactor of thiodicofen is brought into the second synthesis reactor of thiodicofen under pressure, the residence time of the material is controlled to be 90 minutes and the reaction temperature is controlled to be 30℃;

[0128] 4. Solid-liquid separation

[0129] The material in the second synthesis reactor of thiodicofen is brought into a centrifugal pressure filter for solid-liquid separation, the liquid is recycled to prepare the ligand, and the solid is added into a water washing reactor for water washing.

[0130] 5. Water washing

[0131] Softened water 900Kg is added into the water washing reactor, stirring is started, the solid obtained by the solid-liquid separation of the centrifugal pressure filter is added into the water washing reactor, the temperature in the water washing reactor is adjusted to be 32℃, and after 110 minutes of stirring, pressure filtration is started.

[0132] 6. Pressure filtration

[0133] The material in the water washing reactor is pumped into a plate-and-frame pressure filter for pressure filtration by a mud pump, the filtrate is allowed to stand and separate into layers, the lower layer of dichloroethane is recycled, and the upper layer of water phase is sent to a pyridine recovery device for recovering pyridine in the water; the filter cake obtained by pressure filtration is sent to a dichloroethane washing reactor.

[0134] 7. Dichloroethane washing

[0135] Dichloroethane 1275Kg is added into the dichloroethane secondary washing reactor from a dichloroethane metering tank, stirring is started, the filter cake obtained by the first washing is added, the temperature in the reactor is adjusted to be 30℃, and stirring is performed for 90 minutes to prepare for centrifugation.

[0136] The material in the dichloroethane washing reactor is put into a centrifuge for centrifugation, and the filtrate obtained by centrifugation is recycled; the solid is sent to drying.

[0137] 9. The dried filter cake obtained by centrifugation is fed into a double-cone dryer, and drying is carried out while controlling the temperature to be lower than 45°C and the vacuum degree to be not lower than 0.08 MPa, to obtain thiodicarb product 517.8 kg. Analysis of thiodicarb content is 98.12%, and other indicators are qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The thiodicarb yield is calculated to be 96.11%. The thiodicarb is subjected to heat storage stability test according to the standard "GB / T 19136-2003 Pesticide Heat Storage Stability Test Method", and the thiodicarb decomposition rate is 3.2%, which is lower than 5%, and at the same time, other indicators are qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The gas extracted from the double-cone dryer is condensed by two-stage tube condensers in series (using chilled brine) and then reused.

[0138] Example 5

[0139] 1. Preparation of materials

[0140] The filtrate from the centrifugal pressure filtration separation obtained in Example 4 is measured at 775 kg and is vacuum-sucked into a methomyl dissolving kettle, and stirring is started. 500 kg of methomyl is added, and the dissolution of methomyl is observed through a sight glass until all the methomyl is dissolved.

[0141] 170 kg of SCl2 is pressurized into an SCl2 high tank by nitrogen;

[0142] The filtrate from the centrifugal pressure filtration separation obtained in Example 4 is measured, and 635 kg of pyridine recovered from the pyridine recovery post and new pyridine is added to a ligand dipyridyl monosulfide hydrochloride synthesis kettle.

[0143] 2. Synthesis of ligand

[0144] The ligand synthesis kettle jacket is passed through a refrigerant, and when the temperature in the kettle is lowered to 1°C, SCl2 is started to be added dropwise, the dropwise addition speed is controlled, and the reaction temperature is controlled at 9°C, and the dropwise addition time is controlled at 50 minutes. After the dropwise addition of SCl2 is completed, stirring is continued for 10 minutes; 340 kg of prepared methomyl pyridine solution is measured and added to the ligand synthesis kettle, and the temperature in the kettle is controlled to be not more than 9°C, and after stirring for 15 minutes, the first thiodicarb synthesis kettle is prepared.

[0145] 3. Synthesis of thiodicarb

[0146] The synthesis of thiodicofen is operated continuously. The prepared ligand and pyridine solution of part of methomyl added in the first synthesis kettle of thiodicofen are pumped into the first synthesis kettle of thiodicofen from the bottom of the first synthesis kettle of thiodicofen at a set flow rate, and the prepared pyridine solution of methomyl is pumped into the first synthesis kettle of thiodicofen from the bottom of the first synthesis kettle of thiodicofen by a metering pump, the residence time of the material is controlled to be 55 minutes and the reaction temperature is controlled to be 19℃ by adjusting the flow rates of the two feeds;

[0147] 4. Solid-liquid separation

[0148] The material in the second synthesis kettle of thiodicofen is brought into a centrifugal pressure filter for solid-liquid separation, the liquid is recycled to prepare the ligand, and the solid is added into a water washing kettle for water washing.

[0149] 5. Water washing

[0150] Softened water 1050 Kg is added into the water washing kettle, stirring is started, the solid obtained by the solid-liquid separation of the centrifugal pressure filter is added into the water washing kettle, the temperature in the water washing kettle is adjusted to be 28℃, and after 110 minutes of stirring, pressure filtration is started.

[0151] 6. Pressure filtration

[0152] The material in the water washing kettle is pumped into a plate-and-frame pressure filter for pressure filtration by a mud pump, the filtrate is allowed to stand and separate into layers, the lower layer of dichloroethane is recycled, and the upper layer of water phase is sent to a pyridine recovery device for recovering pyridine in the water; the filter cake obtained by pressure filtration is sent to a dichloroethane washing kettle.

[0153] 7. Dichloroethane washing

[0154] Dichloroethane 1280 Kg is added into the dichloroethane secondary washing kettle from a dichloroethane metering tank, stirring is started, the filter cake obtained by the first washing is added, the temperature in the kettle is adjusted to be 30℃, and stirring is performed for 90 minutes. Centrifugation is prepared.

[0155] The material in the dichloroethane washing kettle is put into a centrifuge for centrifugation. The filtrate obtained by centrifugation is recycled, and the solid is sent to drying.

[0156] 9. The filter cake obtained by centrifugation was sent to a double-cone dryer for drying while controlling the temperature to be lower than 45°C and the vacuum degree to be not lower than 0.08 MPa, to obtain 519.8 kg of thiodicarb product. Analysis showed that the thiodicarb content was 98.31%, and other indicators were qualified, meeting the quality requirements of the industry standard “NY / T 3776-2020 Thiodicarb Technical Material”. The thiodicarb yield was calculated to be 96.11%. The thiodicarb was subjected to a heat storage stability test according to the standard “GB / T19136-2003 Pesticide Heat Storage Stability Test Method”, and the thiodicarb decomposition rate was 3.2%, which was lower than 5%. At the same time, other indicators were qualified, meeting the quality requirements of the industry standard “NY / T 3776-2020 Thiodicarb Technical Material”. The gas extracted from the double-cone dryer was condensed by two-stage tube condensers (using chilled brine) in series and then reused.

[0157] Comparative Example 1

[0158] The production operation was the same as in Example 1. The difference was that the amount of SCl2 fed was 165 kg.

[0159] The filter cake obtained by centrifugation was dried to obtain 511.7 kg of thiodicarb product. Analysis showed that the thiodicarb content was 96.47%, and other indicators were qualified, meeting the quality requirements of the industry standard “NY / T 3776-2020 Thiodicarb Technical Material”. The thiodicarb yield was calculated to be 93.15%. The thiodicarb was subjected to a heat storage stability test according to the standard “GB / T19136-2003 Pesticide Heat Storage Stability Test Method”, and the thiodicarb decomposition rate was 4.1%, which was lower than 5%. At the same time, other indicators were qualified, meeting the quality requirements of the industry standard “NY / T 3776-2020 Thiodicarb Technical Material”.

[0160] The reasons for the low thiodicarb content and yield in this batch of operation were as follows: when the molar ratio of methomyl to SCl2 was lower than 1:0.527, the reaction of pyridine with SCl2 was not good, the amount of SCl2 was insufficient, the total amount of ligand generated was small, and the reaction of ligand with methomyl was not sufficient during the synthesis of thiodicarb, the conversion rate of methomyl was low, and the purity and yield of thiodicarb were both low.

[0161] Comparative Example 2

[0162] The production operation was the same as in Example 1. The difference was that the amount of SCl2 fed was 195 kg.

[0163] The filter cake obtained by centrifugation was dried to obtain 521.4 kg of thiodicarb product. The thiodicarb content was 95.77%, and other indicators were qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The thiodicarb yield was calculated to be 94.23%. The thiodicarb was tested for thermal storage stability according to the standard "GB / T19136-2003 Pesticide Thermal Storage Stability Test Method", and the thiodicarb decomposition rate was 5.2%, which was higher than 5%. Although the analysis of other indicators met the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material", the product was still determined to be unqualified.

[0164] The reasons for the low thiodicarb content and yield in this batch were as follows: when the molar ratio of methomyl to SCl2 was higher than 0.605, SCl2 was excessive, and when the ligand was synthesized by reacting with pyridine, the ratio of pyridine as a solvent and raw material in the reaction system was definitely excessive, which generated excessive ligand; although the conversion rate of methomyl was improved when the ligand reacted with methomyl, the excessive ligand remained in the final thiodicarb product, affecting the purity of thiodicarb and the appearance and thermal storage stability of thiodicarb product. The product prepared in this batch was light yellow, while the products of other batches were white.

[0165] Comparative Example 3

[0166] The production operation was the same as in Example 1. The difference was that toluene and xylene were used as solvents, 1122 kg of xylene and 50 kg of toluene were used, and the xylene and toluene were fully mixed before use. The mixed solution was used later, which was the same as the use of dichloromethane.

[0167] The filter cake obtained by centrifugation was dried to obtain 485.71 kg of thiodicarb product. The thiodicarb content was 96.12%, and other indicators were qualified, meeting the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material". The thiodicarb yield was calculated to be 88.1%. The thiodicarb was tested for thermal storage stability according to the standard "GB / T19136-2003 Pesticide Thermal Storage Stability Test Method", and the thiodicarb decomposition rate was 0.82%, which was lower than 5% and qualified. Although several of the other indicators met the quality requirements of the industry standard "NY / T 3776-2020 Thiodicarb Technical Material", the melting point and pH value were unqualified, and the product was still determined to be unqualified.

[0168] The thiodicarb products prepared in Comparative Example 3 and Example 1 were analyzed for purity, melting point, and thermal storage stability, and the results are shown in Table 1.

[0169] Table 1 Analysis results of products prepared in Example 1 and Comparative Example 3

[0170]

[0171]

[0172] Compared with Example 1, the methomyl content, melting point and pH value of the product of Comparative Example 3 are all unqualified, which is determined as unqualified product. The main reason is that the solubility of methomyl, thiodicarb and the ligand dipyridyl monosulfide hydrochloride in toluene and xylene is relatively low, and if the reaction process is not strictly monitored, the material is prone to incomplete reaction.

[0173] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing thiodicarb using a single solvent without a catalyst, characterized by, Includes the following steps: In a solvent, SCl2 reacts with pyridine to generate the ligand dipyridine monosulfide hydrochloride. Methomyl is dissolved in the solvent to prepare a methomyl solution. A first portion of the methomyl solution, comprising 40-55% of the total volume of the methomyl solution, is mixed with the ligand dipyridine monosulfide hydrochloride to prepare a mixed solution. Another portion of the methomyl solution is then added from the bottom to mix and react, with the reaction temperature controlled at 15-22℃. Subsequently, the material from the first methomyl synthesis reactor is pressurized and transferred to the second methomyl synthesis reactor, with the material residence time controlled at 60-110 minutes and the reaction temperature controlled at 28-35℃ to synthesize methomyl. Solid-liquid separation is performed, and the solid is washed with water, filtered under pressure, washed with solvent, centrifuged, and dried to obtain the final product. The solvent is dichloroethane; The molar ratio of methomyl to dichloroethane is 1:3.277-4.055; the molar ratio of methomyl to SCl2 is 1:0.511-0.549; and the molar ratio of methomyl to pyridine is 1:1.168-1.

424.

2. The method for producing thiodicarb using a single solvent without a catalyst according to claim 1, wherein, The reaction of SCl2 with pyridine to form the ligand dipyridine monothioether hydrochloride should not exceed 10℃. SCl2 is added dropwise to pyridine over a period of 40-60 minutes. After the addition of SCl2 is complete, stirring is continued for 10-20 minutes.

3. The method for producing thiodicarb using a single solvent without a catalyst according to claim 1, wherein, The method includes the following steps: Step 1: Prepare materials. Dissolve all of the methomyl in dichloroethane to obtain a methomyl solution; SCl2 is pressurized into the SCl2 high-level tank using nitrogen gas and then measured. After metering, pyridine was drawn into the synthesis reactor of dipyridine monosulfide hydrochloride ligand under vacuum. Dichloroethane was vacuum-absorbed into the synthesis vessel for dipyridine monosulfide hydrochloride ligand, serving as a reaction solvent to provide the reaction environment for sulfur dichloride and pyridine. Step 2, Ligand synthesis, A cooling liquid was introduced into the jacket of the synthesis reactor for ligand dipyridine monosulfide hydrochloride. Once the temperature inside the reactor dropped to -7 to -2°C, SCl2 was started to be added dropwise. SCl2 reacted with pyridine to generate ligand dipyridine monosulfide hydrochloride. The dropping rate of SCl2 was controlled to maintain the reaction temperature range of 0 to 8°C, with a dropping time of 40 to 60 minutes. After the SCl2 addition was complete, stirring was continued for 10 to 20 minutes. The first portion of the prepared methomyl dichloroethane solution was added to the synthesis reactor for ligand dipyridine monosulfide hydrochloride and stirred for 10 to 20 minutes to obtain a mixed solution, ready to be pumped into the first synthesis reactor for thiodicarb. Step 3: Synthesis of thiamethoxam. The mixed solution obtained in step 2 and the prepared dichloroethane solution of methomyl in the second part were pre-reacted in the first thiamethoxam synthesis reactor; then transferred to the second thiamethoxam synthesis reactor to continue the reaction. Step 4: Solid-liquid separation. The material in the second synthesis reactor of thiodicarb enters a centrifugal filter press under pressure for solid-liquid separation. The liquid is reused to prepare the ligand dipyridine monosulfide hydrochloride, and the solid enters the next step for water washing. Step 5, wash with water. The solid obtained from solid-liquid separation is added to a water washing vessel, and the temperature inside the vessel is controlled at 20-30℃. The mixture is stirred for 90-120 minutes. Step 6, pressure filtration; Step 7: Wash with dichloroethane; Step 8: Centrifuge; Step 9: Drying.

4. The method for producing thiodicarb using a single solvent without a catalyst according to claim 3, characterized by, In step 2, the ratio of the volume of the first part of the prepared methomyl dichloroethane solution to the volume of the second part of the methomyl solution is in the range of 1:1.1-1.

2.

5. The method for producing thiodicarb using a single solvent without a catalyst according to claim 3, wherein, In step 3, the thiodicarb synthesis reaction is carried out in the thiodicarb first synthesis kettle, and the reaction temperature is controlled in the range of 15-22℃ by controlling the flow rate of the mixed solution and the other part of the methomyl solution; then the material in the thiodicarb first synthesis kettle is brought into the thiodicarb second synthesis kettle under pressure, and the residence time of the material is controlled in the range of 60-110 minutes, and the reaction temperature is controlled in the range of 28-35℃.

6. The method for producing thiodicarb using a single solvent without a catalyst according to claim 5, wherein, In step 3, the prepared mixed solution of step 2 is punched into the thiodicarb first synthesis kettle from the bottom of the kettle according to the set flow rate, and the prepared second part of the methomyl dichloroethane solution is punched into the kettle from the bottom of the thiodicarb first synthesis kettle.

7. The method for producing thiodicarb using a single solvent without a catalyst according to claim 3, wherein, In the solid-liquid separation step, the material in the thiodicarb second synthesis kettle is brought into the centrifugal pressure filter under pressure for solid-liquid separation, the liquid is reused to prepare the ligand dipyridyl monosulfide hydrochloride, and the solid is subjected to water washing in the next step.

8. A method for producing thiodicarb using a single solvent and without a catalyst according to claim 3, characterized in that, After water washing, the material is subjected to pressure filtration, the filtrate is allowed to stand and separate into layers, the lower dichloroethane continues to be reused, the upper aqueous phase is subjected to pyridine recovery treatment to recover pyridine in the water, and the filter cake obtained by pressure filtration is added into a dichloroethane washing kettle for dichloroethane washing.

9. A method for producing thiodicarb using a single solvent and without a catalyst according to claim 3, characterized in that, The material in the dichloroethane washing kettle after washing is centrifuged, the solid is dried, and the dichloroethane obtained by allowing the filtrate and the dichloroethane obtained by allowing the upper layer obtained in the water washing process to stand and separate to stand and separate is used for dichloroethane washing after water washing.

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