Phase transfer catalyst of metal ion complexing crown ether for efficiently preparing aquacide dichloride

Abstract

The invention discloses a phase transfer catalyst of metal ion complexing crown ether for efficiently preparing aquacide dichloride and application of the phase transfer catalyst. The catalyst is prepared by taking crown ethers as 18-crown-6 and dicyclohexyl-18-crown-6 ether and complex ions as lewis acid active components such as potassium ions, lithium ions, cobalt ions, copper ions and the like through a direct chemical method. The catalyst synergistically catalyzes a nucleophilic substitution reaction of a pyridine derivative and alkyl halide in an aprotic polar solvent such as acetonitrile or nitrobenzene, and synthesis of diquat dichloride can be realized under the conditions of 60-140 DEG C, normal pressure and no oxygen. The mass ratio of the pyridine derivative to the catalyst to the solvent in a reaction system is 1: (0.001-0.05): (5-8), and real-time monitoring and regulation are performed through an online infrared spectrum, a liquid chromatograph and a gas chromatograph-mass spectrometer. The purity of the product is more than 99% after the product is subjected to filtration, recrystallization with an ethanol-water mixed solvent and vacuum drying. The catalyst provided by the invention has the characteristics of high activity, strong stability and recoverability, obviously improves the atom economy of the reaction, simplifies the production process, reduces the energy consumption and pollution, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention focuses on the field of organic catalytic synthesis, specifically relating to a crown ether catalyst complexing metal ions for preparing diquat dichloride, as well as its preparation method and application. This catalyst exhibits high activity, high selectivity, and excellent stability, significantly improving the synthesis yield and quality of diquat dichloride. The invention also provides a preparation method and application of this catalyst, providing new technologies for the development of related industries. Background Art

[0002] Diquat dichloride is a widely used, fast-acting contact herbicide with excellent control effectiveness against annual and perennial weeds. Current synthesis methods for diquat dichloride suffer from harsh reaction conditions, low yields, and poor selectivity, resulting in high production costs and unstable product quality.

[0003] Conventional catalysts struggle to meet the requirements for high efficiency and selectivity in the synthesis of diquat dichloride. Some catalysts are inactive, resulting in slow reaction rates and requiring long reaction times; others exhibit poor selectivity and easily produce byproducts, increasing the difficulty and cost of subsequent separation and purification. Therefore, developing a novel, highly efficient catalyst for the preparation of diquat dichloride is of great practical significance.

[0004] Against this backdrop, the use of crown ether-based phase transfer catalysts that complex metal ions to catalyze the synthesis of diquat dichloride is of great significance. Crown ether compounds possess unique ring structures and complexing properties, enabling them to form stable complexes with metal ions. Applying crown ether compounds that complex metal ions to the synthesis of diquat dichloride is expected to enhance the activity and selectivity of the catalyst through the synergistic effect of the crown ether and the metal ion, thereby improving the synthesis of diquat dichloride. Therefore, the development of crown ether catalysts that complex metal ions for the synthesis of diquat dichloride has become a key issue that needs to be addressed urgently within the industry. Summary of the Invention

[0005] The present invention provides a crown ether catalyst complexing metal ions for preparing diquat dichloride. The catalyst exhibits high activity, high selectivity, and good stability, significantly improving the synthetic yield and quality of diquat dichloride. The present invention also provides a preparation method and application of the catalyst.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] Selection of crown ether and metal ion: the selected crown ether is one or more of 18-crown-6, 15-crown-5, and dicyclohexyl-18-crown-6 ether, and the metal ion used is one or more of potassium ion, lithium ion, cobalt ion, and copper ion.

[0008] Pretreatment of crown ether: The selected crown ether was recrystallized and purified with absolute ethanol, and then dried in a vacuum drying oven at 60 - 80 °C for 6 - 12 hours to remove moisture and impurities.

[0009] Preparation of metal salt solution: Weigh an appropriate amount of metal salts (such as potassium chloride, lithium carbonate, copper sulfate, cobalt chloride, etc.), dissolve them in deionized water, and prepare a metal salt solution with a concentration of 0.01 - 1 mol / L.

[0010] Complexation reaction: Add the pretreated crown ether to the metal salt solution, and stir at room temperature for 12 - 24 hours to fully complex the crown ether with metal ions. During the reaction, the pH value of the solution can be appropriately adjusted to 5 - 7 to promote the progress of the complexation reaction.

[0011] Product separation and drying: After the reaction, filter the reaction solution under reduced pressure to obtain a solid product. Wash the solid product with deionized water 3 - 5 times, and then dry it in a vacuum drying oven at 80 - 100 °C for 12 - 24 hours to obtain a crown ether - based catalyst complexing metal ions.

[0012] Reaction system construction: Select a pyridine derivative with a purity of over 99% as the starting material, dry it at 60 - 100 °C for 2 - 3 hours under the protection of an inert gas. Add the pretreated pyridine derivative, catalyst, and aprotic polar solvents such as acetonitrile and nitrobenzene into a special reaction kettle. The material of the reaction kettle is a high - temperature - resistant and corrosion - resistant alloy material, equipped with an accurate temperature and pressure control system; the temperature of the reaction system is controlled at 60 - 140 °C, the pressure is maintained at atmospheric pressure, and the mass ratio of pyridine derivative, catalyst, and solvent is 1:0.001 - 0.05:5 - 8.

[0013] Product separation and purification: After the reaction, cool the reaction solution to room temperature, remove the mother liquor solvent by pressure filtration, and the mother liquor solvent is recycled after rectification; the remaining solid crude product is purified by recrystallization. The recrystallization solvent is an ethanol - water mixed solvent with a volume ratio of 3:1 - 4:1. Dissolve the crude product under heating and stirring conditions, then filter to obtain the recovered activated carbon catalyst. Slowly cool the product solution to 0 - 5 °C to precipitate diquat dichloride crystals. After filtration, wash with cold recrystallization solvent 2 - 3 times, and dry in a vacuum drying oven at 5 - 80 °C for 3 - 4 hours to obtain diquat dichloride products; after the reaction, the catalyst is recovered and activated for reuse. Specific implementation mode

[0014] Example 1

[0015] Catalyst Preparation: Weigh 10 g of 18-crown-6, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 2.5 g of copper sulfate and dissolve it in 50 mL of deionized water to prepare a copper sulfate solution. Add the pretreated 18-crown-6 to the copper sulfate solution, stir at room temperature for 18 hours, and adjust the pH value of the solution to 6. After the reaction is completed, perform suction filtration, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain the 18-crown-6 catalyst complexed with copper ions.

[0016] Raw Material Preparation: Weigh 100 g of pyridine derivative with a purity of 99.5%, and dry it at 70 °C for 2.5 hours under nitrogen protection. Select a crown ether-derived phase transfer catalyst prepared using 18-crown-6 ether and CuSO4 as precursors, weigh 2 g, and prepare 500 g of acetonitrile as the solvent.

[0017] Reaction Process: Add the dried pyridine derivative, the activated and pyrolyzed catalyst, and the acetonitrile solvent to the reaction kettle. Seal the reaction kettle, turn on the stirring device, and adjust the stirring speed to 350 r / min. Raise the temperature in the reaction kettle to 120 °C through the heating device, and at the same time maintain the pressure at the natural pressure through the pressure control system. Continuously add purified chloroethane with a flow rate controlled at 6 mL / min. During the reaction process, use an on-line infrared spectrometer and a gas chromatography-mass spectrometry instrument to detect the reaction solution every 1 hour.

[0018] Product Treatment: After reacting for 6 hours, turn off the heating device and cool the reaction solution to room temperature. Recover the acetonitrile solvent by vacuum distillation, add the remaining solid crude product to 400 mL of a mixed solvent of ethanol-water (volume ratio 3.5:1), heat and stir until completely dissolved. Then slowly cool to 2 °C to precipitate diquat dichloride crystals. After filtration, wash with cold ethanol-water mixed solvent 3 times, and dry in a vacuum drying oven at 60 °C for 3.5 hours to obtain 140 g of diquat dichloride product with a purity of 99.1% and a yield of 63.7%. After the reaction is completed, recover the catalyst. After detection, the activity retention rate of the recovered catalyst is 85%, and it can be reused for subsequent reactions after being pyrolyzed and activated again.

[0019] Example 2

[0020] Catalyst Preparation: Weigh 10 g of 18-crown-6, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 2.5 g of potassium chloride, dissolve it in 100 mL of deionized water to prepare a potassium chloride solution. Add the pretreated 18-crown-6 to the potassium chloride solution, stir at room temperature for 14 hours, and adjust the pH value of the solution to 6. After the reaction is completed, filter under reduced pressure, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain the 18-crown-6 phase catalyst complexing copper ions.

[0021] Raw Material Preparation: Take 100 g of pyridine derivative with a purity of 99.8%, dry it at 65 °C for 2 hours under argon protection. Weigh 4 g of the crown ether-derived phase catalyst prepared with 18-crown-6 ether and KCl as the precursors. Prepare 600 g of nitrobenzene as the solvent.

[0022] Reaction Process: Add the pyridine derivative, catalyst and solvent to the reaction kettle, start stirring, and set the speed to 350 r / min. Heat up to 140 °C, control the pressure at 1.8 MPa, add chloroethane, and the flow rate is 5.5 mL / min. Use an analytical instrument to monitor the reaction process in real time.

[0023] Product Treatment: After reacting for 10 hours, cool, distill, recrystallize, wash and dry according to the method of Example 1. Obtain 146.0 g of diquat dichloride product with a purity of 99.0% and a yield of 66.4%. The activity retention rate of the recovered catalyst is 81%, and it can be reused after activation.

[0024] Example 3

[0025] Catalyst Preparation: Weigh 10 g of 18-crown-6, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 3 g of Li2CO3, dissolve it in 50 mL of deionized water to prepare a lithium carbonate solution. Add the pretreated 18-crown-6 to the lithium ion solution, stir at room temperature for 16 hours, and adjust the pH value of the solution to 6. After the reaction is completed, filter under reduced pressure, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain the 18-crown-6 catalyst complexing lithium ions.

[0026] Raw Material Preparation: Weigh 100 g of pyridine derivative with a purity of 99.6%, dry it at 75 °C for 3 hours under nitrogen protection. Select the crown ether-based phase transfer catalyst prepared with 18-crown-6 ether and Li2CO3 as the precursors, and weigh 3.5 g. Prepare 400 g of acetonitrile as the solvent.

[0027] Reaction process: Add the raw materials into the reaction kettle, adjust the stirring speed to 450 r / min, heat up to 140 °C, maintain the pressure at 2.2 MPa, introduce chlorine gas with a flow rate of 7 L / min, and monitor the reaction in real time.

[0028] Product treatment: After reacting for 3.5 hours, carry out subsequent treatment according to Example 1. Obtain 96 g of diquat dichloride product with a purity of 98.5% and a yield of 66.0%. After the catalyst is recovered and tested, the activity retention rate is 87% and it can be reused.

[0029] Example 4

[0030] Catalyst preparation: Weigh 10 g of 18-crown-6, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 2.0 g of cobalt chloride and dissolve it in 50 mL of deionized water to prepare a cobalt chloride solution. Add the pretreated 18-crown-6 to the cobalt chloride solution, stir at room temperature for 15 hours, and adjust the pH value of the solution to 6. After the reaction is completed, perform vacuum filtration, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain a phase transfer catalyst of 18-crown-6 complexed with cobalt ions.

[0031] Raw material preparation: Weigh 100 g of pyridine derivative with a purity of 99.6%, and dry it at 75 °C for 3 hours under nitrogen protection. Select a crown ether-based phase transfer catalyst prepared with 18-crown-6 ether and CoCl2 as precursors, and weigh 4.0 g. Prepare 400 g of acetonitrile as the solvent.

[0032] Reaction process: Add the dried pyridine derivative, the activated catalyst, and the acetonitrile solvent into the reaction kettle in sequence. Close the reaction kettle and ensure good sealing, turn on the stirring device, and set the stirring speed to 300 r / min. Use an electric heating mantle to heat the reaction kettle, and increase the temperature inside the reaction kettle to 150 °C at a heating rate of 2 °C / min. At the same time, with the help of a pressure pump, maintain the pressure inside the reaction kettle at atmospheric pressure. Continuously introduce chloroethane that has undergone purification processes such as dehydration and drying into the reaction kettle through a mass flow meter at a flow rate of 5 mL / min. During the reaction, every 1 hour, use an on-line infrared spectrometer and a gas chromatography-mass spectrometry instrument to analyze the composition of the reaction solution.

[0033] Product treatment: After the reaction lasted for 4 hours, the heating device was turned off, and the reaction solution was naturally cooled to room temperature in the reaction kettle. The remaining solid crude product was transferred to a three-necked flask containing 500 mL of ethanol-water (volume ratio 3:1) mixed solvent. A stirrer and a reflux condenser were installed, and the filtrate was heated and stirred at an oil bath temperature of 80 °C until the crude product was completely dissolved. Subsequently, the three-necked flask was slowly cooled in an ice bath at 0 °C to precipitate diquat dichloride crystals. After filtration with a Buchner funnel and washing the filter cake 3 times with cold ethanol-water mixed solvent, the filter cake was then dried in a vacuum drying oven at 50 °C for 4 hours, and finally 182.0 g of diquat dichloride product was obtained. By high performance liquid chromatography detection, the purity was 98.7% and the yield was 82.9%. After the reaction, the catalyst was recovered, and its activity retention rate was 84%. After being reactivated, it could be used for subsequent reactions.

[0034] Example 5

[0035] Catalyst preparation: Weigh 12 g of dicyclohexyl-18-crown-6 ether, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 2.5 g of copper sulfate and dissolve it in 50 mL of deionized water to prepare a copper sulfate solution. Add the pretreated 18-crown-6 to the copper sulfate solution, stir at room temperature for 18 hours, and adjust the pH value of the solution to 6. After the reaction, filter under reduced pressure, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain an 18-crown-6 catalyst complexed with copper ions.

[0036] Raw material preparation: Weigh 100 g of pyridine derivative with a purity of 99.5%, and dry it at 70 °C for 2.5 hours under nitrogen protection. Select a phase transfer catalyst based on crown ether derivative prepared with dicyclohexyl-18-crown-6 ether and CuSO4 as precursors, weigh 2 g, and prepare 500 g of acetonitrile as the solvent.

[0037] Reaction process: Add the pyridine derivative, catalyst and solvent into the reaction kettle together, start the stirring device, and adjust the stirring speed to 500 r / min. By means of induction heating, the temperature in the reaction kettle was raised to 140 °C at a heating rate of 3 °C / min, and the pressure was stabilized at atmospheric pressure through the pressure control system. Through a mass flow meter, purified chlorine gas was continuously introduced into the reaction kettle at a flow rate of 8 L / min. During the whole reaction process, an automated on-line analysis system was used to monitor the temperature, pressure and concentration changes of reactants and products in the reaction system in real time.

[0038] Product treatment: After the reaction lasted for 10 hours, the heating system was turned off and the reaction solution was cooled to room temperature. Using a vacuum distillation device, nitrobenzene was recovered under a vacuum of 0.09 MPa. The remaining solid crude product was transferred to a crystallizer, and 500 mL of ethanol-water (volume ratio 4:1) mixed solvent was added. Under the action of heating with a heating jacket and stirring with a stirring paddle, the crude product was completely dissolved. Subsequently, through a programmed temperature reduction system, the temperature in the crystallizer was slowly reduced to 5 °C at a temperature reduction rate of 0.5 °C / min to promote the crystallization of diquat dichloride. The crystallized product was separated from the mother liquor by centrifugation, and the product was centrifugally washed 3 times with cold ethanol-water mixed solvent. Finally, the product was placed in a vacuum drying oven at 60 °C and dried for 3 hours to obtain 143 g of diquat dichloride product. After detection, the purity was 99.3% and the yield was 65.6%. The activity retention rate of the recovered catalyst was 86%, and it could be reused after activation.

[0039] Example 6

[0040] Catalyst preparation: Weigh out 13 g of dicyclohexyl-18-crown-6 ether, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh out 2.5 g of potassium chloride and dissolve it in 100 mL of deionized water to prepare a potassium chloride solution. Add the pretreated 18-crown-6 to the potassium chloride solution, stir at room temperature for 14 hours, and adjust the pH value of the solution to 6. After the reaction ended, filter it under reduced pressure, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain a 18-crown-6 phase catalyst complexed with copper ions.

[0041] Raw material preparation: Take 100 g of pyridine derivative with a purity of 99.8%, and dry it at 65 °C for 2 hours under argon protection. Weigh out 4 g of a crown ether-derived phase catalyst prepared with dicyclohexyl-18-crown-6 ether and KCl as precursors. Prepare 600 g of nitrobenzene as a solvent.

[0042] Reaction process: Add the raw materials to the reaction kettle, start stirring, and set the speed to 420 r / min. Through a heat transfer oil heating system, the temperature in the reaction kettle was raised to 130 °C at a heating rate of 2.5 °C / min, and the pressure was controlled at 2 MPa. Continuously introduce purified chloroethane, with a stable flow rate of 6.5 mL / min, and at the same time use an on-line monitoring device to track the reaction process in real time.

[0043] Product treatment: After the reaction for 12 hours, cool the reaction solution to room temperature. Carry out operations such as vacuum distillation, recrystallization, washing, and drying according to the method of Example 2. Finally, 175.4 g of diquat dichloride product was obtained. After detection, the purity was 98.4% and the yield was 79.6%. After detection of the recovered catalyst, the activity retention rate was 88%, and it could be put into use again.

[0044] Example 7

[0045] Catalyst Preparation: Weigh 14 g of dicyclohexyl-18-crown-6 ether, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 3 g of Li2CO3, dissolve it in 50 mL of deionized water to prepare a lithium carbonate solution. Add the pretreated 18-crown-6 to the lithium ion solution, stir at room temperature for 16 hours, and adjust the pH value of the solution to 6. After the reaction is completed, filter under reduced pressure, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain a dicyclohexyl-18-crown-6 ether phase transfer catalyst for complexing lithium ions.

[0046] Raw Material Preparation: Weigh 100 g of pyridine derivative with a purity of 99.6%, dry it at 75 °C for 3 hours under nitrogen protection. Select a crown ether-based phase transfer catalyst prepared with dicyclohexyl-18-crown-6 ether and Li2CO3 as precursors, and weigh 3.5 g. Prepare 400 g of acetonitrile as the solvent.

[0047] Reaction Process: Add the dried pyridine derivative, the activated catalyst, and the acetonitrile solvent to the reaction kettle. Seal the reaction kettle, turn on the stirring device, and adjust the stirring speed to 400 r / min. Raise the temperature in the reaction kettle to 110 °C through the heating device, and maintain the pressure at atmospheric pressure through the pressure control system at the same time. Continuously add purified chloroethane, and control the flow rate at 6 mL / min. During the reaction process, detect the reaction solution every 2 hours using an on-line infrared spectrometer and a gas chromatography-mass spectrometry instrument.

[0048] Product Treatment: After reacting for 6 hours, turn off the heating device and cool the reaction solution to room temperature. Recover the acetonitrile solvent by vacuum distillation, add the remaining solid crude product to 400 mL of a mixed solvent of ethanol-water (volume ratio 3.5:1), heat and stir until completely dissolved. Then slowly cool to 2 °C to precipitate diquat dichloride. After filtration, wash it 3 times with a cold ethanol-water mixed solvent, and dry it in a vacuum drying oven at 55 °C for 3.5 hours to obtain 191 g of diquat dichloride product with a purity of 99.4% and a yield of 86.6%. After the reaction is completed, recover the catalyst. After detection, the activity retention rate of the recovered catalyst is 85%, and it can be reused for subsequent reactions after being pyrolyzed and activated again.

[0049] Example 8

[0050] Catalyst Preparation: Weigh 12 g of dicyclohexyl-18-crown-6 ether, recrystallize and purify it with absolute ethanol, and then dry it in a vacuum drying oven at 70 °C for 8 hours. Weigh 2.0 g of cobalt chloride, dissolve it in 50 mL of deionized water to prepare a cobalt chloride solution. Add the pretreated dicyclohexyl-18-crown-6 ether to the cobalt chloride solution, stir at room temperature for 15 hours, and adjust the pH value of the solution to 6. After the reaction is completed, perform vacuum filtration, wash the solid product 4 times with deionized water, and then dry it in a vacuum drying oven at 90 °C for 16 hours to obtain a dicyclohexyl-18-crown-6 ether phase transfer catalyst complexed with cobalt ions.

[0051] Raw Material Preparation: Weigh 100 g of pyridine derivative with a purity of 99.6%, and dry it at 75 °C for 3 hours under nitrogen protection. Select a crown ether-based phase transfer catalyst prepared using dicyclohexyl-18-crown-6 ether and CoCl2 as precursors, and weigh 4.0 g. Prepare 500 g of acetonitrile as the solvent.

[0052] Reaction Process: Add the pyridine derivative, catalyst, and solvent into the reaction kettle together, start the stirring device, and adjust the stirring speed to 500 r / min. Using the method of induction heating, raise the temperature in the reaction kettle to 140 °C at a heating rate of 3 °C / min, and stabilize the pressure at atmospheric pressure through the pressure control system. Continuously introduce purified chlorine gas into the reaction kettle at a flow rate of 8 L / min through a mass flowmeter. During the entire reaction process, use an automated on-line analysis system to monitor the temperature, pressure, and concentration changes of the reactants and products in the reaction system in real time.

[0053] Product Treatment: After the reaction has lasted for 12 hours, turn off the heating system and let the reaction solution cool to room temperature. Use a vacuum distillation device to recover nitrobenzene under a vacuum degree of 0.09 MPa. Transfer the remaining solid crude product to a crystallizer, add 800 mL of ethanol-water (volume ratio 4:1) mixed solvent, and under the action of heating with a heating jacket and stirring with a stirring paddle, completely dissolve the crude product. Subsequently, through a programmed temperature reduction system, slowly reduce the temperature in the crystallizer to 5 °C at a temperature reduction rate of 0.5 °C / min to promote the crystallization of diquat dichloride. Use centrifugal separation to separate the crystallized product from the mother liquor, and perform 3 times of centrifugal washing of the product with cold ethanol-water mixed solvent. Finally, place the product in a vacuum drying oven at 60 °C and dry it for 3 hours to obtain 161 g of diquat dichloride product. After testing, the purity is 99.3% and the yield is 74.3%. The activity retention rate of the recovered catalyst is 86%, and it can be reused after activation.

[0054] As can be seen from different embodiments, the present invention uses a phase transfer catalyst derived from crown ether to prepare qualified products under various parameter conditions, with strong stability and operability. In actual production, the raw material selection and process parameters for catalyst preparation can be flexibly adjusted according to the characteristics of raw materials and product requirements to obtain the best catalytic performance and economic benefits.

Claims

1. A complex metal ion crown ether type phase transfer catalyst for preparing diquat dichloride, characterized in that, It includes the following steps: Selection of crown ether and metal ions: The selected crown ether is one or more of 18-crown-6 and dicyclohexyl-18-crown-6 ether, and the metal ions used are one or more of potassium ions, lithium ions, cobalt ions, and copper ions. Pretreatment of crown ether: The selected crown ether is recrystallized and purified with absolute ethanol, and then dried in a vacuum drying oven at 60-80 °C for 6-12 hours to remove moisture and impurities. Preparation of metal salt solution: Weigh an appropriate amount of metal salt (such as potassium chloride, lithium carbonate, copper sulfate, cobalt chloride, etc.), dissolve it in deionized water, and prepare a metal salt solution with a concentration of 0.01-1 mol / L. Complexation reaction: Add the pretreated crown ether to the metal salt solution, stir at room temperature for 12-24 hours to allow the crown ether to fully complex with the metal ions. During the reaction process, the pH value of the solution can be appropriately adjusted to 5-7 to promote the progress of the complexation reaction. Catalyst separation and drying: After the reaction is completed, filter the reaction solution under reduced pressure to obtain a solid product. Wash the solid product 3-5 times with deionized water, and then dry it in a vacuum drying oven at 80-100 °C for 12-24 hours to obtain a crown ether-based catalyst complexed with metal ions. Reaction system construction: Select a pyridine derivative with a purity of over 99% as the starting material, dry it at 60-100 °C for 2-3 hours under the protection of an inert gas. Add the pretreated pyridine derivative, catalyst, and aprotic polar solvents such as acetonitrile and nitrobenzene into a special reaction kettle. The material of the reaction kettle is a high-temperature and corrosion-resistant alloy material, equipped with an accurate temperature and pressure control system; the temperature of the reaction system is controlled at 60-140 °C, and the pressure is maintained at atmospheric pressure. The mass ratio of pyridine derivative, catalyst, and solvent is 1:0.001-0.05:5-8. Product separation and purification: After the reaction is completed, cool the reaction solution to room temperature, remove the mother liquor solvent by pressure filtration, and the mother liquor solvent is recycled after rectification treatment; the remaining solid crude product is purified by recrystallization. The recrystallization solvent is an ethanol-water mixed solvent with a volume ratio of 3:1-4:

1. Dissolve the crude product under heating and stirring conditions, and then filter to obtain the recovered activated carbon catalyst. Slowly cool the product solution to 0-5 °C to precipitate diquat dichloride crystals. After filtration, wash with cold recrystallization solvent 2-3 times, and dry in a vacuum drying oven at 50-80 °C for 3-4 hours to obtain diquat dichloride product; after the reaction is completed, the catalyst is recovered, cleaned, dried, and activated to make it reusable.

2. The preparation method according to claim 1, characterized in that, The concentration of the metal salt solution is adjusted according to the type of crown ether, the type of metal ion, and the target complexation effect to ensure the full complexation of the crown ether and the metal ion.

3. A metal ion complex crown ether catalyst prepared by the method according to claim 1, characterized in that: The catalyst contains metal ions with a mass fraction of 0.1 to 5%, and the metal is K + , Li + , Co 2+ , Cu 2+ or a combination of one or more of them.

4. The catalyst according to claims 1 to 3, characterized in that, In the reaction of preparing diquat dichloride, the catalyst can reduce the activation energy of the reaction by 20-50 kJ / mol, significantly accelerating the reaction rate; compared with the reaction system without using this catalyst, the reaction time is shortened by 30-70%.

5. The catalyst according to claim 4, wherein After being reused 5 to 10 times, the catalytic activity loss of the crown ether phase transfer catalyst does not exceed 20%; after each use, it can be continued to be used in the preparation reaction of diquat dichloride through simple washing and drying treatment.

6. The catalyst according to claims 3 to 5, characterized in that, In the reaction system for preparing diquat dichloride, this catalyst can improve the selectivity of the product, making the selectivity of diquat dichloride reach 90 - 98%, effectively reducing the generation of by-products. In a closed stirred reactor, at a temperature of 60 - 140 °C, a stirring speed of 300 - 500 rpm, and reacting for 6 - 12 hours under an oxygen-free environment after nitrogen replacement, in the preparation experiments of diquat dichloride on different scales, this catalyst can maintain stable catalytic performance, with the product purity ≥ 95%, the conversion rate 50 - 90%, and the yield 50 - 95%.