A method for synthesizing paraquat dichloride salt

Abstract

The present application relates to a kind of synthesis method of paraquat dichloride, specific steps are as follows: pyridine and first solvent are mixed, and solid catalyst is added, after being stirred sufficiently, air or oxygen is introduced into reflux coupling reaction to obtain mixture, after being filtered to remove catalyst, first solvent and water are removed by evaporation under reduced pressure, solid 4,4'-dipyridyl is obtained after cooling crystallization;4,4'-dipyridyl is redissolved with second solvent, chloromethane is introduced into reaction by increasing temperature and pressure, after the reaction product is filtered and washed with dichloromethane, filter residue is obtained, paraquat dichloride is obtained after filter residue is dried.The synthesis method provided by the present application has the advantages of simple synthesis route, safe and green reaction process, no need to use high-risk regulated materials such as liquid ammonia, sodium cyanide and chlorine, suitable for industrial green production process, cheap and easily available raw materials, low production investment cost, high yield and other advantages.

Description

TECHNICAL FIELD

[0001] The application relates to a synthesis method of paraquat dichloride, and belongs to the technical field of pesticide preparation. BACKGROUND

[0002] Paraquat dichloride is a rapid herbicide, has contact killing action and certain internal absorption, can be rapidly absorbed by plant green tissues to cause the plant to die, has no action on non-green tissues, loses the herbicidal activity relatively fast after contacting the soil, has no residue, cannot damage plant roots, and cannot pollute the environment, and at present, solid preparations of paraquat are prepared on the basis of paraquat dichloride solution, so the demand is large.

[0003] The existing synthesis route of paraquat dichloride is mainly an ammonia cyanide method production process: pyridine is chloromethylated to prepare methyl chlorinated pyridine, the methyl chlorinated pyridine is condensed to form N,N'-dimethyl dipyridyl, and then chlorine is introduced into the aqueous solution to form paraquat dichloride by chlorination. In the process, liquid ammonia, sodium cyanide, chlorine and the like are used as controlled raw materials, pollution is easily generated, and harm is caused to the human body, so high requirements are needed for the safety, environmental protection management of the production process, and the used raw materials and easily generated pollution are contrary to the development concept of green environmental protection, so it is urgent to develop a green and environmentally-friendly synthesis method of paraquat dichloride. SUMMARY

[0004] (I) Technical problem to be solved

[0005] In order to solve the above problems in the prior art, the application provides a synthesis method of paraquat dichloride.

[0006] (II) Technical scheme

[0007] In order to achieve the above purpose, the main technical scheme adopted by the application comprises:

[0008] A synthesis method of paraquat dichloride comprises the following steps:

[0009] S1, pyridine and a first solvent are mixed, and a solid catalyst is added, and the mixture is fully stirred;

[0010] S2, air or oxygen is introduced to generate a coupling reaction to obtain a mixture;

[0011] S3, after the mixture is filtered to remove the catalyst, the first solvent and water are removed by evaporation under reduced pressure, and solid 4,4'-dipyridyl is obtained after cooling and crystallization;

[0012] S4, a second solvent is added to the solid 4,4'-dipyridyl, the mixture is dissolved, chloromethane is introduced after the temperature and pressure are increased, and a solid reaction product is obtained after the reaction and cooling and filtration;

[0013] S5, the solid reaction product is washed with dichloromethane, and then filtered to obtain a filter residue;

[0014] S6, the filter residue is dried to obtain paraquat dichloride salt.

[0015] According to the synthesis method, preferably, in step S1, the first solvent is ethanol, acetonitrile, chloroform or toluene; and the pyridine is mixed with the first solvent at a molar ratio of 1:1 to 1:10.

[0016] According to the synthesis method, preferably, in step S1, the catalyst is an alkali metal halide, and the amount of the catalyst added is 0.1-1% of the mass of the pyridine.

[0017] According to the synthesis method, preferably, the alkali metal halide is CuI, KI or NaI.

[0018] According to the synthesis method, preferably, in step S2, the coupling reaction is carried out at a temperature of 80-200°C, a pressure of 0.1-0.5 MPa, and a reaction time of 12-60 h.

[0019] According to the synthesis method, preferably, in step S3, the evaporation under reduced pressure is carried out at a pressure of 0.02 MPa and a temperature of 50-85°C.

[0020] According to the synthesis method, preferably, in step S4, the second solvent is acetone, toluene, diethyl ether or tetrahydrofuran.

[0021] According to the synthesis method, preferably, in step S4, the second solvent is mixed with 4,4'-dipyridine at a molar ratio of 1:1 to 1:5, and the amount of the chloromethane used is 2 times the molar amount of the 4,4'-dipyridine.

[0022] According to the synthesis method, preferably, in step S4, the reaction is carried out at a temperature of 60-120°C and a pressure of 0.1-0.6 MPa after the temperature and pressure are increased, and the reaction time is 18-48 h.

[0023] According to the synthesis method, preferably, in step S5, the solid reaction product is washed with dichloromethane for 2-3 times; and in step S6, the drying is carried out at a temperature of 45-80°C for 20-60 min.

[0024] (III) Beneficial effects

[0025] The beneficial effects of the present application are:

[0026] The present application provides a synthesis method of paraquat dichloride, which uses pyridine, chloromethane, dichloromethane and the like as raw materials, has the advantages of (1) short reaction path, 2-step reaction to synthesize paraquat dichloride; (2) safe, green, environmentally friendly and economical reaction process; no need to use regulated chemicals such as liquid ammonia, sodium cyanide and chlorine, greatly reduced production management cost, and the whole production process is more green, economical and safe; (3) the raw materials are cheap and easy to obtain; (4) the catalyst can be recycled, further saving cost; (5) low investment in device equipment and production cost. DETAILED DESCRIPTION

[0027] The inventive principle of the present application is that pyridine reacts with air or oxygen under the action of a catalyst to generate 4,4'-bipyridine through dehydrogenation coupling, and then reacts with chloromethane to generate paraquat dichloride; pyridine and a solvent are mixed, and a catalyst is added, and after sufficient stirring and mixing, air or oxygen is introduced for reflux reaction; after the solid acid catalyst in the reaction product is removed by filtration, the solvent and water are removed by evaporation under reduced pressure, and 4,4'-bipyridine solid is obtained by cooling and crystallization; the 4,4'-bipyridine is mixed and dissolved in a solvent, and then chloromethane is introduced for reaction by increasing temperature and pressure; after the reaction product is cooled, dichloromethane is used for washing and filtration, and the filter residue is dried to obtain paraquat dichloride.

[0028] In order to better explain the present application and facilitate understanding, the present application is described in detail below through specific embodiments. The reagents used in the following examples can be commercially available products, wherein the single-pass conversion rate = molar amount of paraquat dichloride / molar amount of 4,4'-bipyridine x 100%, and the molar amount of 4,4'-bipyridine = mass of solid 4,4'-bipyridine / molar mass of 4,4'-bipyridine.

[0029] Example 1

[0030] A synthesis method of paraquat dichloride, comprising the following steps:

[0031] S1, 200mg of catalyst CuI is first added to 0.38mol of pyridine, 100mL of toluene is added, and after sufficient stirring and mixing;

[0032] S2, the temperature is increased to 150℃, the pressure is 0.2MPa, and oxygen is introduced for reflux reaction for 32h;

[0033] S3, after the reaction is completed, the catalyst is filtered out, and the toluene and water are evaporated at 0.02MPa and 85℃, and then the temperature is cooled to room temperature to crystallize the solid 4,4'-bipyridine;

[0034] S4, after adding the solid 4,4'-dipyridine in the ethyl ether mixed solution with the molar ratio of 1:2 with pyridine, the temperature is raised to 76℃, the pressure is raised to 0.3MPa, the molar amount of chloromethane is 2 times of pyridine, the reaction is carried out for 24h, then the temperature is lowered, the reaction product is solid, after filtration, the solid reaction product is obtained;

[0035] S5, the solid reaction product is washed with dichloromethane for 2 times, and the filter residue is obtained after filtration;

[0036] S6, the filter residue is dried at 50℃ for 30min, and the powder product is obtained.

[0037] The obtained powder product is detected by liquid chromatography-mass spectrometry in SN / T0293-2014, the peak time of the product is consistent with that of paraquat dichloride salt, the purity of paraquat dichloride salt in the reaction product is 99%, and the single-pass conversion rate is 84%.

[0038] Example 2

[0039] A synthesis method of paraquat dichloride salt, comprising the following steps:

[0040] S1, first, 50mg of catalyst KI is put into 0.38mol of pyridine, 70mL of acetonitrile is added, and after the mixture is stirred sufficiently;

[0041] S2, the temperature is raised to 180℃, the pressure is 0.5MPa, and oxygen is refluxed for 48h;

[0042] S3, after the reaction is completed, the catalyst is filtered out, the acetonitrile and water are distilled out at 0.02MPa and 76℃, and the temperature is lowered to obtain crystals, i.e. solid 4,4'-dipyridine;

[0043] S4, in the solid 4,4'-dipyridine, tetrahydrofuran is added with the molar ratio of 1:3 with pyridine, mixed and dissolved, the temperature is raised to 90℃, the pressure is raised to 0.2MPa, chloromethane is introduced with the molar amount of 2 times of pyridine, the reaction is carried out for 36h, then the temperature is lowered, and the solid reaction product is obtained after filtration;

[0044] S5, the solid reaction product is washed with dichloromethane for 3 times, and the filter residue is obtained after filtration;

[0045] S6, the filter residue is dried at 60℃ for 20min, and the powder product is obtained.

[0046] The obtained powder product is detected by liquid chromatography-mass spectrometry in SN / T0293-2014, the peak time of the product is consistent with that of paraquat dichloride salt, the purity of paraquat dichloride salt in the reaction product is 98%, and the single-pass conversion rate is 91%.

[0047] Example 3

[0048] A synthesis method of paraquat dichloride salt, comprising the following steps:

[0049] S1, 30mg of catalyst KI was put into 0.38mol of pyridine, 120mL of ethanol was added, and after the mixture was fully stirred and mixed;

[0050] S2, the temperature was raised to 80°C, the pressure was 0.1MPa, and air was introduced to reflux for 60h;

[0051] S3, after the reaction was completed, the catalyst was filtered out, and the ethanol and water were distilled out at 0.02MPa and 50°C under reduced pressure, and the obtained solid 4,4'-dipyridyl was crystallized by cooling;

[0052] S4, toluene was added to the solid 4,4'-dipyridyl at a molar ratio of 1:3 with respect to pyridine, the temperature was raised to 120°C, 0.3MPa, and 2 times the molar amount of chloromethane was introduced to react for 48h, and then the temperature was lowered, and the solid reaction product was obtained after filtration;

[0053] S5, the solid reaction product was washed with dichloromethane for 3 times, and the filter residue was obtained after filtration;

[0054] S6, the filter residue was dried at 50°C for 30min to obtain a powder product.

[0055] The reaction product was detected by liquid chromatography-mass spectrometry according to SN / T0293-2014, and the peak time of the product was consistent with that of paraquat dichloride salt, the purity of paraquat dichloride salt in the reaction product was 98%, and the single-pass conversion rate was 82%.

[0056] Example 4

[0057] A synthesis method of paraquat dichloride salt, comprising the following steps:

[0058] S1, 70mg of catalyst NaI was put into 0.38mol of pyridine, 90mL of toluene was added, and after the mixture was fully stirred and mixed;

[0059] S2, the temperature was raised to 135°C, the pressure was 0.3MPa, and air was introduced to reflux for 48h;

[0060] S3, after the reaction was completed, the catalyst was filtered out, and the toluene and water were distilled out at 0.02MPa and 85°C under reduced pressure, and the obtained solid 4,4'-dipyridyl was crystallized by cooling;

[0061] S4, toluene was added to the solid 4,4'-dipyridyl at a molar ratio of 1:5 with respect to pyridine, the temperature was raised to 60°C, 0.2MPa, and 2 times the molar amount of chloromethane was introduced to react for 18h, and then the temperature was lowered, and the solid reaction product was obtained after filtration;

[0062] S5, after washing the solid reaction product with dichloromethane for 2 times, filtering to obtain a filter residue;

[0063] S6, drying the filter residue at 50°C for 30 min to obtain a powder product.

[0064] The powder product is detected by liquid chromatography-mass spectrometry in SN / T0293-2014, and the peak time of the product is consistent with that of paraquat dichloride salt. The purity of paraquat dichloride salt in the reaction product is 99%, and the single-pass conversion rate is 86%.

[0065] Example 5

[0066] A synthesis method of paraquat dichloride salt, comprising the following steps:

[0067] S1, adding 270 mg of catalyst CuI to 0.38 mol of pyridine, adding 100 mL of ethanol, and stirring the mixture thoroughly;

[0068] S2, heating to 90°C, pressure 0.4 MPa, and refluxing with oxygen for 32 h,

[0069] S3, after the reaction is completed, filtering out the catalyst, and evaporating ethanol and water at 0.02 MPa and 50°C, cooling and crystallizing to obtain solid 4,4'-bipyridine;

[0070] S4, adding toluene to the solid 4,4'-bipyridine at a molar ratio of 1:1 with pyridine, heating to 120°C, 0.5 MPa, and reacting with chloromethane which is 2 times the molar amount of pyridine for 18 h, and then cooling and filtering to obtain a solid reaction product;

[0071] S5, washing the solid reaction product with dichloromethane for 3 times, and filtering to obtain a filter residue;

[0072] S6, drying the filter residue at 50°C for 30 min to obtain a powder product.

[0073] The powder product is detected by liquid chromatography-mass spectrometry in SN / T0293-2014, and the peak time of the product is consistent with that of paraquat dichloride salt. The purity of paraquat dichloride salt in the reaction product is 99%, and the single-pass conversion rate is 93%.

[0074] Comparative Example 1

[0075] This comparative example is based on Example 1, except that water is used as the solvent in S4, but the single-pass conversion rate of the obtained product is 24%.

[0076] Comparative Example 2

[0077] The comparative example was carried out on the basis of Example 5, except that the amount of chloromethane used was equivalent to the molar amount of pyridine, and a single-pass conversion of 45% was obtained.

[0078] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can modify or change the above disclosed technical content into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application without departing from the technical solution of the present application still falls within the protection scope of the present application.

Claims

1. A method for synthesizing paraquat dichloride, characterized in that, It includes the following steps: S1, pyridine, and the first solvent are mixed, and a solid catalyst is added and stirred thoroughly; wherein the catalyst is CuI, KI, or NaI; S2. A coupling reaction occurs when air or oxygen is introduced and the mixture is obtained by reflux. S3. After filtering the mixture to remove the catalyst, the first solvent and water are removed by vacuum evaporation, and solid 4,4'-bipyridine is obtained after cooling and crystallization. S4. Add a second solvent to solid 4,4'-bipyridine, mix and dissolve, then heat and pressurize and pass chloromethane through to carry out the reaction. After the reaction, cool and filter to obtain solid reactants. S5. After washing the solid reaction product with dichloromethane, filter to obtain filter residue; S6. After drying the filter residue, paraquat dichloride is obtained.

2. The synthesis method according to claim 1, characterized in that, In step S1, the first solvent is ethanol, acetonitrile, chloroform or toluene; pyridine is mixed with the first solvent in a molar ratio of 1:1 to 1:

10.

3. The synthesis method as described in claim 1, characterized in that, In step S1, the amount of catalyst added is 0.1 to 1% of the mass of pyridine.

4. The synthesis method according to claim 1, characterized in that, In step S2, the coupling reaction is carried out at a temperature of 80~200℃, a pressure of 0.1~0.5MPa, and a reaction time of 12~60h.

5. The synthesis method according to claim 1, characterized in that, In step S3, the conditions for vacuum evaporation are 0.02 MPa and 50~85℃.

6. The synthesis method according to claim 1, characterized in that, In step S4, the second solvent is acetone, toluene, diethyl ether, or tetrahydrofuran.

7. The synthesis method according to claim 1, characterized in that, In step S4, the molar ratio of the second solvent to 4,4'-bipyridine is 1:1 to 1:5, and the amount of chloromethane used is twice the molar amount of 4,4'-bipyridine.

8. The synthesis method according to claim 1, characterized in that, In step S4, the reaction temperature after heating and pressurization is 60~120℃, the reaction pressure is 0.1~0.6MPa, and the reaction time is 18~48h.

9. The synthesis method according to claim 1, characterized in that, In step S5, the product is washed 2-3 times with dichloromethane; in step S6, the drying temperature is 45-80℃ and the drying time is 20-60 min.