One-step method for preparing diquat dichloride
The one-step method of using hydrotalcite-derived composite catalysts is used to optimize the reaction conditions to prepare dichloride dichloride salt, which solves the complex and time-consuming problems in traditional methods and achieves an efficient and low-cost preparation process.
Patent Information
- Application Number
- CN202510524981.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-08-01
AI Technical Summary
The traditional method of preparing dichlorodichloride is complex and time-consuming, resulting in long production cycles, high cost, low atomic economy, and pollution to the environment.
Using a composite catalyst based on hydrotalcite-derived, pyridine derivatives are reacted with halogenated hydrocarbons under specific conditions by a one-step method, combining precise temperature and pressure control and online monitoring to achieve efficient preparation of dichlorodichloride salt.
Significantly simplify the process flow, reduce production costs, improve atomic economy, reduce environmental pollution, and is suitable for large-scale industrial production.
Abstract
Description
Technical Field
[0001] This invention focuses on the field of organic synthesis, specifically a groundbreaking "one-step" process for preparing diquat dichloride. The core goal of this process is to significantly improve the efficiency of diquat dichloride preparation through comprehensive and systematic optimization of the reaction pathway, thereby providing important support for technological advancement in related industries. Background Art
[0002] As a key member of the pyridine herbicide family, diquat dichloride demonstrates significant application value in modern agriculture. Its rapid weed control properties allow it to effectively suppress and kill a wide range of weeds in a short period of time. Its broad spectrum of action makes it suitable for controlling a wide range of weeds. Importantly, diquat dichloride rapidly deactivates and loses its toxicity upon contact with soil. This property significantly reduces its impact on the soil ecosystem, helping to maintain soil moisture retention and fertility, thereby providing strong support for the sustainable development of agricultural ecosystems. Furthermore, this herbicide excels in accelerating crop wilting, accelerating the dehydration and drying of crop stems. This facilitates subsequent mechanized operations and significantly reduces labor and material costs, making it an ideal alternative to traditional herbicides such as paraquat and glyphosate. Globally, with growing awareness of environmental protection and the increasing demand for efficient agricultural production, market demand for highly effective and environmentally friendly herbicides is rapidly increasing. Diquat dichloride, with its unique advantages, presents a promising market prospect.
[0003] Currently, traditional methods for preparing diquat dichloride generally rely on multi-step reaction processes. This process requires multiple complex reaction steps, accompanied by product separation and purification operations at each step. This cumbersome process not only significantly prolongs the production cycle and greatly increases time costs, but also leads to a sharp increase in equipment investment costs. In addition, in multi-step reactions, raw materials inevitably suffer significant losses, atom economy is low, and a large number of by-products are produced. This not only increases the difficulty and cost of subsequent processing, but also places a serious burden on the ecological environment. Therefore, the development of an efficient, green and environmentally friendly one-step process for preparing diquat dichloride has become a key issue that needs to be urgently addressed in the industry. Summary of the Invention
[0004] The present invention aims to provide a technology for directly converting raw materials into diquat dichloride in a single step. This innovative method significantly simplifies the previously complex process flow, significantly reduces production costs, effectively improves atom economy, and greatly reduces environmental pollution, providing a new, efficient and economical technology for the large-scale industrial production of diquat dichloride.
[0005] In order to achieve the above object, the present invention adopts the following technical solutions:
[0006] Raw material selection and pretreatment: The raw materials selected are pyridine derivatives with a purity of over 99% (including 2-methylpyridine, 2,6-dimethylpyridine, 2-chloropyridine, 3-bromopyridine, 2-aminopyridine, 4-dimethylaminopyridine, 2-hydroxypyridine, etc.) and halogenated hydrocarbons (chloromethane, chloroethane, vinyl chloride, etc.) or chlorine as the starting materials. In the pretreatment stage of the raw materials, the pyridine derivatives are placed in an environment protected by inert gas and dried at a temperature range of 60 - 100°C for 5 - 10 h to thoroughly remove the possible moisture and other impurities in the raw materials.
[0007] Catalyst design and preparation: This invention innovatively selects a composite catalyst derived from hydrotalcite. This catalyst uses a specific hydrotalcite-structured material as the precursor, and with the help of advanced high-temperature pyrolysis technology and chemical reduction means, highly dispersed active metal sites are in-situ anchored on the metal oxide support derived from hydrotalcite. This unique design strategy enables the catalyst to have a strong metal-support interaction and a high active specific surface area, which can effectively promote the dispersion of the active metal, increase the contact area between the reactants and the catalyst, thereby significantly enhancing the adsorption and activation of the reactants and facilitating the efficient progress of the catalytic reaction.
[0008] Reaction system construction: The pretreated pyridine derivatives, the activated catalyst, and an appropriate amount of aprotic polar solvents such as acetonitrile, N,N-dimethylformamide, tetrahydrofuran, etc. are added together into a specially designed reaction kettle. This reaction kettle is made of high-quality alloy materials with high temperature resistance and corrosion resistance, and has excellent sealing performance as well as precise temperature and pressure control systems. During the reaction process, by precisely regulating the temperature, pressure, and material ratio of the reaction system, the most suitable conditions are created for the smooth progress of the reaction. Specifically, the reaction temperature is strictly controlled within the range of 150 - 200°C, the pressure is maintained at 1.5 - 3 MPa, and the mass ratio between the pyridine derivatives, the catalyst, and the solvent is precisely set to 1:0.03 - 0.08:5 - 8. Compared with traditional catalysts, due to its extremely high catalytic activity, the amount of the new catalyst used in this invention can be appropriately reduced during actual use. This can not only reduce production costs but also effectively reduce the potential impact of catalyst residues on the final product.
[0009] Reaction process control: Throughout the reaction process, an inert gas that has undergone strict purification treatment is introduced. Under the action of a powerful stirring device, the reaction system always maintains a uniformly mixed state, and the stirring speed is set at 300 - 500 r / min. As the reaction progresses continuously, professional analytical instruments such as advanced on-line infrared spectrometers and gas chromatography - mass spectrometers are used to comprehensively detect the reaction solution every 15 - 20 minutes. By real-time monitoring the temperature, pressure, and concentration changes of the reactants and products in the reaction system, various reaction parameters are adjusted promptly and accurately according to the detection results to ensure that the reaction always proceeds steadily in the direction of efficiently generating diquat dichloride. The composite catalyst derived from hydrotalcite plays a unique and crucial role in the reaction process. Its large specific surface area of activity can promote the adsorption and activity of reactant molecules, greatly accelerating the reaction process and significantly improving the selectivity of the reaction.
[0010] Product separation and purification: After the reaction is completed, first cool the reaction solution to room temperature, and then remove the solvent by vacuum distillation. The recovered solvent can be recycled after rectification treatment. The catalyst is recovered by filtration, effectively reducing production costs. The remaining solid crude product is further purified by recrystallization. An ethanol - water mixed solvent with a volume ratio of 3:1 - 4:1 is selected as the recrystallization solvent, and the crude product is completely dissolved under heating and stirring conditions. Then the solution is slowly cooled to 0 - 5 °C to promote the crystallization of diquat dichloride. After a series of fine operations such as filtration, washing with cold recrystallization solvent 2 - 3 times, and drying in a vacuum drying oven at 50 - 90 °C for 3 - 12 hours, a high-purity diquat dichloride product is finally obtained. Specific implementation methods
[0011] Example 1
[0012] Preparation of raw materials and catalyst: Weigh 100 g of pyridine derivative with a purity of 99.5%, and dry it at 70 °C for 2.5 h under nitrogen protection. A composite catalyst derived from hydrotalcite prepared using PdZnAl LDH as the precursor is selected. The PdZnAl LDH precursor is prepared by the co-precipitation method, and after high-temperature pyrolysis at 500 °C for 4 h and subsequent in-situ thermal reduction at 300 °C for 2 h, a monodispersed Pd nanoparticle-loaded ZnAl mixed oxide catalyst (2% Pd / ZnAl mixed metal oxide, 2% Pd / ZnAl MMO) is formed. Take 5 g of it for use. Prepare 500 g of acetonitrile as the solvent.
[0013] Reaction process: The dried pyridine derivative, 2% Pd / ZnAl MMO catalyst, and acetonitrile solvent were successively added to the reaction kettle. Subsequently, the reaction kettle was sealed, the stirring device was started, and the stirring rate was set at 400 r / min. The temperature inside the reaction kettle was raised to 160 °C through the heating system, and the internal pressure was stabilized at 2 MPa through the pressure control system. Meanwhile, purified chloroethane was continuously introduced into the reaction system at a flow rate of 6 mL / min. During the reaction process, the reaction solution was analyzed and detected in real time every 2 hours using an on-line infrared spectrometer and a gas chromatography-mass spectrometry instrument.
[0014] Product treatment: After the reaction continued for 6 h, the heating device was turned off, and the reaction solution was naturally cooled to room temperature. Subsequently, the acetonitrile solvent was recovered by vacuum distillation. The obtained solid crude product was transferred to 300 mL of ethanol-water (volume ratio 3.5:1) mixed solvent, and stirred until completely dissolved under heating conditions. Then the solution was slowly cooled to 2 °C to precipitate diquat dichloride crystals. The crystals were collected by suction filtration, washed three times with cold ethanol-water mixed solvent, and finally dried in a vacuum drying oven at 55 °C for 3.5 h. Finally, 96 g of diquat dichloride product was obtained, with a purity of 98.8% and a yield of 58.7%. After the reaction was completed, the catalyst was recovered. The test results showed that the activity retention rate of the recovered catalyst was 85%. After being pyrolyzed and activated again, the catalyst could be used for subsequent reactions.
[0015] Example 2
[0016] Raw material preparation: 120 g of pyridine derivative with a purity of 99.8% was taken and dried at a constant temperature of 65 °C for 2 h under an argon protection atmosphere. A composite catalyst based on hydrotalcite-derived prepared using NiZnAl LDH as the precursor was selected. The NiZnAl LDH precursor was prepared by the co-precipitation method, and was pyrolyzed at 500 °C for 4 h and then in-situ thermally reduced at 500 °C for 2 h to form a monodispersed Ni nanoparticle-loaded ZnAl mixed oxide catalyst (10% Ni / ZnAl mixed metal oxide, 10% Ni / ZnAlMMO). 6 g of it was taken for standby. Meanwhile, 600 g of N,N-dimethylformamide was prepared as the reaction solvent.
[0017] Reaction process: The pyridine derivative, 10% Ni / ZnAl MMO catalyst, and N,N-dimethylformamide solvent were successively added to the reaction kettle. Subsequently, the reaction kettle was sealed, the stirring device was started, and the stirring rate was set at 350 r / min. The temperature inside the reaction kettle was raised to 175 °C through the heating system, and the internal pressure was stabilized at 1.8 MPa through the pressure control system. Meanwhile, purified chloroethane was continuously introduced into the reaction system at a flow rate of 5.5 mL / min. The reaction process was monitored in real time every 2 h by an analytical instrument to ensure that the reaction conditions were stable and controllable.
[0018] Product treatment: After the reaction continued for 10 hours, the reaction mixture was cooled, distilled, recrystallized, washed, and dried according to the method described in Example 1. Finally, 110 g of the diquat dichloride product was obtained, with a purity of 99.0% and a yield of 67.0%. In addition, the recovered catalyst had an activity retention rate of 81% and could be reused after activation treatment.
[0019] Example 3
[0020] Raw material preparation: 80 g of pyridine derivative with a purity of 99.6% was weighed and dried at 75 °C for 3 hours under nitrogen protection. A composite catalyst based on hydrotalcite-derived prepared from CuZnAl LDH as the precursor was used. The CuZnAl LDH precursor was prepared by the co-precipitation method, and a monodispersed Cu nanoparticle-loaded ZnAl mixed oxide catalyst (10% Cu / ZnAl mixed metal oxide, 10% Cu / ZnAl MMO) was formed by high-temperature pyrolysis at 500 °C for 4 h and subsequent in-situ thermal reduction at 450 °C for 2 h. 5 g of it was taken for standby. Meanwhile, 600 g of acetonitrile was prepared as the reaction solvent.
[0021] Reaction process: The dried pyridine derivative, 10% Cu / ZnAl MMO catalyst, and acetonitrile solvent were successively added to the reaction kettle. After confirming that the sealing performance of the reaction kettle was good, the stirring device was started and the rotation speed was set at 450 r / min. The temperature inside the reaction kettle was raised to 170 °C through the heating system, and the internal pressure was stabilized at 2.2 MPa through the pressure control system. Chlorine gas that had been purified was continuously introduced into the reaction system at a flow rate of 7 L / min. The reaction process was monitored in real time every 1 h by an analytical instrument to ensure that the reaction conditions were stable and controllable.
[0022] Product treatment: After the reaction continued for 3.5 hours, the reaction mixture was subjected to subsequent separation and purification according to the method described in Example 1. Finally, 72 g of the diquat dichloride product was obtained, with a purity of 98.5% and a yield of 55%. In addition, the recovered catalyst was detected to have an activity retention rate of 87%, indicating that it could be used for catalytic reactions again.
[0023] Example 4
[0024] Raw material preparation: Weigh 150 g of pyridine derivative with a purity of 99.7%, and place it in an oven at 60 °C for 3 h of drying under a nitrogen protection environment. Select a hydrotalcite-derived composite catalyst prepared using CoZnAl LDH as the precursor. Prepare the CoZnAl LDH precursor by the co-precipitation method, and form a monodispersed Ni nanoparticle-loaded ZnAl mixed oxide catalyst (10% Co / ZnAl mixed metal oxide, 10% Co / ZnAl MMO) through high-temperature pyrolysis at 500 °C for 4 h and subsequent in-situ thermal reduction at 500 °C for 2 h. Take 9 g of it for standby. In addition, prepare 800 g of acetonitrile as the reaction solvent.
[0025] Reaction process: Add the dried pyridine derivative, 10% Co / ZnAl MMO catalyst, and acetonitrile solvent into the reaction kettle in sequence. After confirming that the sealing performance of the reaction kettle is good, close it, start the stirring device and set the rotation speed to 300 r / min. Increase the temperature to 170 °C at a rate of 2 °C / min through the heating system, and at the same time use a pressure pump to stabilize the pressure in the reaction kettle at 1.5 MPa. Continuously introduce chloroethane gas that has been purified through dehydration and drying at a flow rate of 5 mL / min. During the reaction process, the composition of the reaction solution is monitored and analyzed in real time every 1 h using an in-situ infrared spectrometer and a gas chromatography-mass spectrometry combined instrument.
[0026] Product treatment: After the reaction lasts for 4 h, turn off the heating device and let the reaction solution cool naturally to room temperature in the reaction kettle. Subsequently, recover the acetonitrile solvent under a vacuum of 0.08 MPa through a vacuum distillation device. Transfer the obtained solid crude product to a three-necked flask containing 500 mL of ethanol-water (volume ratio 3:1) mixed solvent, install a stirrer and a reflux condenser, and heat and stir in an 80 °C oil bath until the crude product is completely dissolved. Then, move the three-necked flask to a 0 °C ice bath and slowly cool it to promote the crystallization and precipitation of diquat dichloride. Filter the crystals using a Buchner funnel and wash the filter cake 3 times with cold ethanol-water mixed solvent. Subsequently, place the filter cake in a vacuum drying oven at 50 °C for 4 h to finally obtain 132 g of diquat dichloride product with a purity of 98.7% and a yield of 53.9%. After the reaction is completed, the catalyst is recovered, and its activity retention rate is 84%. It can be reused for subsequent reactions after being reactivated.
[0027] Example 5
[0028] Raw material preparation: Weigh 200 g of pyridine derivative with a purity of 99.9%. Place it in a 65°C constant-temperature drying oven and dry it for 2 hours in a dry environment under argon protection. Select a hydrotalcite-derived composite catalyst prepared using NiZnAl LDH as the precursor. Prepare the NiZnAl LDH precursor by the co-precipitation method. After pyrolysis at 500°C for 4 hours and subsequent in-situ thermal reduction at 500°C for 2 hours, a monodisperse Ni nanoparticle-loaded ZnAl mixed oxide catalyst (10% Ni / ZnAl mixed metal oxide, 10% Ni / ZnAl MMO) is formed. Take 12 g of it for standby. Finally, prepare 1200 g of tetrahydrofuran as the reaction solvent.
[0029] Reaction process: Add the pyridine derivative, 10% Ni / ZnAl MMO catalyst, and tetrahydrofuran solvent into the reaction kettle in sequence. Then seal the reaction kettle, start the stirring device, and set the stirring rate to 500 r / min. Raise the temperature in the reaction kettle to 200°C at a heating rate of 3°C / min through the heating system, and at the same time, maintain the pressure at 2.5 MPa stably with the help of the pressure control system. Chlorine gas after purification is continuously introduced into the reaction kettle at a flow rate of 8 L / min through a mass flow meter. During the whole reaction process, use an automated on-line analysis system to monitor the temperature, pressure, and concentration changes of reactants and products in the reaction system in real time.
[0030] Product treatment: After the reaction lasts for 12 hours, turn off the heating system and let the reaction solution cool to room temperature. Use a vacuum distillation device to recover tetrahydrofuran 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. Then, through a programmed cooling system, slowly lower the temperature in the crystallizer to 5°C at a cooling 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 wash the product 3 times with cold ethanol-water mixed solvent by centrifugation. Finally, place the product in a 60°C vacuum drying oven and dry it for 3 hours to obtain 178 g of diquat dichloride product. After testing, the purity is 99.1% and the yield is 54.5%. The activity retention rate of the recovered catalyst is 86%, and it can be reused after activation.
[0031] Example 6
[0032] Raw material preparation: Weigh 150 g of pyridine derivative with a purity of 99.4%, and dry it at 72 °C for 3 hours under nitrogen protection. Select a hydrotalcite-derived composite catalyst prepared using NiZnAl LDH as the precursor. The NiZnAl LDH precursor is prepared by the co-precipitation method, and is pyrolyzed at 500 °C for 4 h and then in-situ thermally reduced at 500 °C for 2 h to form a ZnAl mixed oxide catalyst loaded with monodispersed Ni nanoparticles (10% Ni / ZnAl mixed metal oxide, 10% Ni / ZnAl MMO). Take 7 g of it for standby. At the same time, prepare 1000 g of N,N-dimethylformamide as the reaction solvent.
[0033] Reaction process: Add the pyridine derivative, 10% Ni / ZnAl MMO catalyst, and N,N-dimethylformamide solvent into the reaction kettle in sequence. Then seal the reaction kettle, start the stirring device and set the stirring rate to 420 r / min. Through the heat transfer oil heating system, raise the temperature in the reaction kettle to 190 °C at a heating rate of 2.5 °C / min, and control the pressure at 2 MPa. Continuously introduce purified chloroethane with a stable flow rate of 6.5 mL / min, and at the same time use on-line monitoring equipment to track the reaction process in real time.
[0034] Product treatment: After reacting for 20 hours, cool the reaction solution to room temperature. Perform operations such as vacuum distillation, recrystallization, washing, and drying according to the method of Example 1. Finally, 112 g of diquat dichloride product is obtained. After testing, the purity is 98.4% and the yield is 52.8%. After the catalyst is recovered and tested, the activity retention rate is 88% and it can be reused.
[0035] Through different examples, it can be seen that the one-step process for preparing diquat dichloride using a hydrotalcite-derived composite catalyst according to the present invention can prepare products with qualified performance under various parameter conditions, and has strong stability and operability. In actual production, the process parameters can be flexibly adjusted according to the characteristics of raw materials and product requirements to obtain the best product performance and economic benefits.
Claims
1. A method for preparing diquat dichloride by a "one-step method", characterized in that, It includes the following steps: (1) Selection and pretreatment of raw materials and catalyst: Select pyridine derivatives with a purity of over 99% as the starting materials, and dry them at 60 - 100 °C for 2 - 3 h under the protection of inert gas. Select an active metal in-situ supported composite catalyst derived from hydrotalcite. This catalyst uses a specific hydrotalcite material as the precursor, and through high-temperature pyrolysis at 400 - 600 °C and subsequent chemical reduction, highly dispersed active metal sites and strong metal-support interactions are introduced. The loading amount of the active metal is 1 - 20 wt%. (2) Construction of reaction system: Add the pretreated pyridine derivatives, catalyst, and aprotic polar solvent into a special reaction kettle. The material of the reaction kettle is a high-temperature resistant and corrosion-resistant alloy material, equipped with precise temperature and pressure control systems. The temperature of the reaction system is controlled at 150 - 190 °C, the pressure is maintained at 1.5 - 3 MPa, and the mass ratio of pyridine derivatives, catalyst, and solvent is 1:0.03 - 0.08:5 - 8. (3) Control of reaction process: During the reaction process, continuously add purified halogenated hydrocarbons or chlorine gas. Under the action of the stirring device, the stirring speed of the reaction system is maintained at 300 - 500 r / min. Use analytical instruments such as on-line infrared spectrometer and gas chromatography-mass spectrometry to detect the reaction solution every 1 - 2 h, and adjust the reaction parameters in a timely manner according to the detection results. (4) Separation and purification of products: After the reaction is completed, cool the reaction solution to room temperature, remove the solvent by vacuum distillation, and the recovered solvent is recycled after rectification. The remaining solid crude product is purified by recrystallization. Dissolve the crude product under heating and stirring conditions, and slowly cool it 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 - 60 °C for 3 - 4 h to obtain diquat dichloride products. After the reaction is completed, recycle and activate the catalyst to make it reusable.
2. The method for preparing diquat dichloride by a one-step process according to claim 1, characterized in that, In the steps of catalyst design and preparation, the carrier precursors in the composite catalyst derived from hydrotalcite include but are not limited to at least one of zinc hydroxide aluminum hydroxide, magnesium hydroxide, zinc aluminum hydroxide, etc.; the introduced active metal nanoparticles include but are not limited to at least one of palladium, platinum, iron, nickel, copper, cobalt, etc.
3. The method for preparing diquat dichloride by a one-step method according to claim 1, characterized in that, In the step of constructing the reaction system, the aprotic polar solvent includes but is not limited to at least one of acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, etc., and the heating rate of the temperature in the reaction kettle is 2 - 3 °C / min.
4. The method for preparing diquat dichloride by a one-step method according to claim 1, characterized in that, In the control of the reaction process, the monitoring of the temperature, pressure, and changes in the concentrations of reactants and products in the reaction system is carried out using an automated on-line analysis system.
5. The method for preparing diquat dichloride by a one-step method according to claim 1, characterized in that, In the step of product separation and purification, the solvent used for recrystallization is an ethanol-water mixed solvent with a volume ratio of 3:1 - 4:1, and the vacuum degree during vacuum distillation for recovering the solvent is 0.08 - 0.09 MPa.