Preparation method of 2-methylallyl magnesium chloride

Abstract

The invention relates to the technical field of preparation of 2-methylallyl magnesium chloride, in particular to a preparation method of 2-methylallyl magnesium chloride, which comprises the following steps: pretreatment and initial feeding, reaction initiation, continuous reaction and heat preservation, end point judgment and product transfer. Magnesium is activated through a zinc stearate ethanol solution, zinc stearate can form an ultra-thin selective adsorption layer on the surface of magnesium particles, the layer cannot completely isolate the reaction, the reaction rate can be regulated and controlled, the risks of bumping and material flushing caused by too violent local reaction are avoided, and meanwhile, the service life of magnesium particles is prolonged. Ethanol is used as a solvent to assist zinc stearate to be uniformly attached to the surface of magnesium, and the dispersity of magnesium particles can be improved when the ethanol is subsequently mixed with tetrahydrofuran; tert-butyl p-hydroxyanisole is added into 2-methylallyl chloride to serve as a stabilizer, free radicals possibly generated in a reaction system can be captured, and side reactions such as polymerization and oxidation of 2-methylallyl chloride are inhibited.

Description

Technical Field

[0001] This invention relates to the field of 2-methylallyl magnesium chloride preparation technology, specifically to a method for preparing 2-methylallyl magnesium chloride. Background Technology

[0002] 2-Methylallyl magnesium chloride is a Grignard reagent (organometallic compound) belonging to the organomagnesia compound family. It usually exists in solution form and is an important reaction reagent in organic synthesis. As a strong nucleophile, it can participate in the reactions of compounds containing carbonyl / polar functional groups such as aldehydes and ketones. It is used to prepare complex organic molecules such as allyl alcohols and can also synthesize intermediates in the fields of medicine, pesticides, and polymer materials, achieving carbon chain growth and efficient functional group transformation. It is one of the core tools for constructing complex structures in organic synthesis.

[0003] In existing technologies, magnesium metal easily forms a dense oxide film on its surface, and its surface activity is low, making it difficult to stably initiate the reaction with 2-methylallyl chloride. This often results in delayed reaction initiation or localized intense exothermic reactions after initiation, which not only reduces reaction efficiency but also easily leads to safety risks such as material overflow and overheating. The moisture, low-boiling-point impurities, and easily polymerizable components contained in crude 2-methylallyl chloride can undergo side reactions such as hydrolysis and oxidation with magnesium or the generated Grignard reagent, leading to a decrease in product purity. Furthermore, 2-methylallyl chloride that has not undergone stabilization treatment is prone to self-polymerization or decomposition during storage and reaction.

[0004] Based on this, the present invention provides a method for preparing 2-methylallyl magnesium chloride. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 2-methylallyl magnesium chloride. The 2-methylallyl magnesium chloride prepared by this invention has a high molar concentration and yield, while the content of by-products is low.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing 2-methylallyl magnesium chloride, comprising the following steps:

[0007] S1. Pretreatment and initial feeding: Replace the reactor with argon gas, and add modified magnesium, tetrahydrofuran and initiator under argon protection. Start the heating system to heat the material in the reactor to 0-50℃.

[0008] S2. Reaction initiation: Slowly add 5-8 kg of modified 2-methylallyl chloride into the reactor, observe the state inside the reactor and confirm the initiation of the reaction;

[0009] S3. Continuous reaction and heat preservation: After the reaction is initiated, the remaining modified 2-methylallyl chloride and tetrahydrofuran are added dropwise simultaneously, with the dropping rate controlled at 0.8-0.9 kg / min, and the reactor temperature is maintained at 0-50℃ during the process; after the addition is completed, the reaction is continued at this temperature for 1-2 hours.

[0010] S4. Endpoint determination and product transfer: After the heat preservation is completed, samples are taken for testing. When the molar concentration of 2-methylallyl magnesium chloride is >1.05M, it is determined to be the endpoint. Stop heating and cool down to room temperature. Press the material into the transfer tank to complete the preparation of 2-methylallyl magnesium chloride.

[0011] Preferably, the raw materials used in the 2-methylallyl magnesium chloride include 70-80 kg of modified magnesium, 240 kg of modified 2-methylallyl chloride, 1500-1600 kg of tetrahydrofuran, and 0.1-0.5% of initiator by total mass of modified magnesium.

[0012] Preferably, the initiator is elemental iodine or 1,2-dibromoethane.

[0013] Preferably, the modified magnesium is prepared by acid washing, water washing and drying, and activation modification with zinc stearate ethanol solution.

[0014] Preferably, the preparation steps of the modified magnesium are as follows: pulverized metallic magnesium is added to a dilute hydrochloric acid solution for acid washing, with temperature controlled and stirring continuously for 30-40 minutes to remove the surface oxide layer; the magnesium after acid washing is rinsed with deionized water 3-5 times until the pH of the rinsing solution is 6.8-7.2, and the magnesium is transferred to a vacuum drying oven for drying for 2-3 hours; after drying, the magnesium is added to a modification vessel, and a zinc stearate ethanol solution is added, and the mixture is stirred and soaked at 25-30℃ and a speed of 60-100 rpm for 1-2 hours; after soaking, the mixture is filtered to obtain modified magnesium.

[0015] Preferably, before use, the zinc stearate ethanol solution needs to be ultrasonically degassed for 15-20 minutes at an ultrasonic frequency of 40kHz and a power of 300-500W to remove dissolved oxygen in the solution; after soaking, the modified magnesium is purged with nitrogen for 15-20 minutes to remove surface ethanol.

[0016] Preferably, the concentration of the dilute hydrochloric acid used for pickling is 5-8%, and the solid-liquid ratio of magnesium to the dilute hydrochloric acid solution is 1:(5-8); the concentration of the zinc stearate ethanol solution used for activation modification is 2-3%, the ethanol is 95% industrial ethanol, and the mass ratio of magnesium to the zinc stearate ethanol solution is 1:(3-5).

[0017] Preferably, the modified 2-methylallyl chloride is obtained by crude 2-methylallyl chloride through crude pretreatment, distillation purification, and stabilization treatment.

[0018] Preferably, the preparation steps of the modified 2-methylallyl chloride are as follows: anhydrous calcium chloride is added to crude 2-methylallyl chloride, and after standing for 2-3 hours, the anhydrous calcium chloride is removed by filtration; the pretreated crude 2-methylallyl chloride is fed into a distillation column, the temperature and pressure inside the distillation column are controlled, and the top fraction is collected at a reflux ratio of 3:1 to obtain high-purity 2-methylallyl chloride; the distilled 2-methylallyl chloride is transferred to a stirred tank, tert-butyl-p-hydroxyanisole is added, the temperature is controlled and the mixture is stirred continuously for 20-30 minutes, and after stirring is completed, it is transferred to a sealed container made of polytetrafluoroethylene to obtain modified 2-methylallyl chloride.

[0019] Preferably, the anhydrous calcium chloride needs to be activated by drying at 120-130℃ for 3-4 hours before use, and the amount used accounts for 1-2% of the crude 2-methylallyl chloride; the amount of tert-butyl-p-hydroxyanisole is 0.01-0.02% of the mass of 2-methylallyl chloride; before the sealed container is filled with modified 2-methylallyl chloride, it needs to be purged with nitrogen three times, with a purging pressure of 0.05-0.06 MPa each time.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In this invention, an oxide film easily forms on the surface of metallic magnesium, which hinders the initiation and progress of the Grignard reaction. Acid washing effectively removes the oxide film on the magnesium surface, exposing a fresh magnesium metal surface with high reactivity, providing sufficient and active reaction sites for the Grignard reaction. Subsequently, activation with zinc stearate ethanol solution allows zinc stearate to form an extremely thin selective adsorption layer on the surface of magnesium particles. This layer neither completely isolates the reaction nor fails to regulate the reaction rate, avoiding the risk of excessively vigorous local reactions leading to boiling and material overflow. At the same time, ethanol, as a solvent, assists zinc stearate in uniformly adhering to the magnesium surface and can also improve the dispersibility of magnesium particles when mixed with tetrahydrofuran, allowing magnesium to come into more complete contact with 2-methylallyl chloride, further improving the efficiency and uniformity of the reaction.

[0022] 2. In this invention, moisture and low / high boiling point impurities in crude 2-methylallyl chloride can interfere with the Grignard reaction and even cause the decomposition of the generated Grignard reagent. Adding anhydrous calcium chloride during pretreatment can efficiently adsorb trace amounts of moisture in the crude product, preventing hydrolysis side reactions between moisture and magnesium or the Grignard reagent, such as the generation of hydrocarbons or magnesium hydroxide impurities. The distillation process can precisely remove various impurities with different boiling points, significantly improving the purity of 2-methylallyl chloride. High-purity raw materials reduce the pathways for side reactions, ensuring the reaction mainly proceeds towards the formation of the target product and increasing product yield. Adding tert-butyl-p-hydroxyanisole as a stabilizer can capture free radicals that may be generated in the reaction system, inhibiting side reactions such as polymerization and oxidation of 2-methylallyl chloride itself, maintaining the chemical stability of the raw material during storage and reaction, thereby ensuring a smooth and controllable Grignard reaction.

[0023] 3. In this invention, the high activity and high dispersibility of modified magnesium, combined with the high purity and high stability of modified 2-methylallyl chloride, form the core raw material advantages. This, along with the efficient promotion of the reaction by an initiator, the removal of trace residual oxide films on the magnesium surface, the triggering of chain reactions, and the solubility of reactants by tetrahydrofuran and the stabilizing effect of Grignard reagents, further enhances the process. Simultaneously, argon protection prevents interference from oxygen and moisture in the air, and precise drop rate and temperature control further ensure the stability of the reaction rate. This guarantees the efficient and stable preparation of 2-methylallyl magnesium chloride, reducing byproduct formation, improving product quality, and lowering the safety risks caused by uncontrolled reaction during production. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are described clearly and completely.

[0026] Example 1: A method for preparing 2-methylallyl magnesium chloride, comprising the following steps:

[0027] S1. Pretreatment and initial feeding: The 2500L reactor was purged three times with argon gas of ≥99.99% purity. Each time, the reactor was filled with argon gas to a pressure of 0.06MPa and then vented to atmospheric pressure to remove air from the reactor. Under argon protection, the feeder cover was opened and the modified magnesium was added into the reactor. After closing the feeder cover, 100kg of tetrahydrofuran was added from the high-level tank, followed by the initiator. The heating system was then started to raise the temperature of the material in the reactor to 0℃.

[0028] S2. Slowly add 5 kg of modified 2-methylallyl chloride into the reactor and observe the state inside the reactor (such as slight reflux, turbidity of the system) to confirm the initiation of the reaction; if the reaction does not start within 30 min, add an equal amount of initiator and then add another 2 kg of modified 2-methylallyl chloride until the reaction starts.

[0029] S3. After the reaction is initiated, the remaining modified 2-methylallyl chloride and tetrahydrofuran are added dropwise simultaneously, with the dropping rate controlled at 0.8 kg / min (to be completed within 4 hours), and the reactor temperature is maintained at 0℃ during this period; after the addition is completed, the reaction is continued at this temperature for 1 hour.

[0030] S4. Endpoint determination and product transfer: After the heat preservation is completed, samples are taken for testing. When the molar concentration of 2-methylallyl magnesium chloride is >1.05M, it is determined to be the endpoint. Stop heating and cool down to room temperature. Use argon to adjust the pressure inside the reactor to 0.06MPa. Press the material into the transfer tank purged with argon to complete the preparation of 2-methylallyl magnesium chloride.

[0031] The raw materials used for 2-methylallyl magnesium chloride include 70 kg of modified magnesium, 240 kg of modified 2-methylallyl chloride, 1500 kg of tetrahydrofuran, and 0.1% of the total mass of modified magnesium as an initiator.

[0032] The initiator is elemental iodine or 1,2-dibromoethane.

[0033] Modified magnesium is prepared by acid washing, water washing and drying of metallic magnesium, and modification with zinc stearate ethanol solution.

[0034] The preparation steps for modified magnesium are as follows:

[0035] Step 1: Magnesium material pretreatment: Select metallic magnesium, crush it into particles with a particle size of 3mm, put it into an acid pickling tank, add dilute hydrochloric acid solution, and pickle at 25℃ and 80rpm for 30min to remove the oxide layer on the magnesium surface.

[0036] Step 2, Washing and Drying: The acid-washed magnesium material is rinsed three times with deionized water until the pH of the rinsing solution is 6.8. Then, the magnesium material is transferred to a vacuum drying oven and dried for 2 hours under a vacuum of -0.08 MPa and a temperature of 100℃, so that the moisture content of the magnesium material is ≤0.3%.

[0037] Step 3, Activation and Modification: The dried magnesium material is put into the modification kettle, zinc stearate ethanol solution is added, and the mixture is stirred and soaked at 60 rpm at 25°C for 1 hour. After soaking, it is filtered to obtain modified magnesium.

[0038] Before use, the zinc stearate ethanol solution needs to be ultrasonically degassed for 15 minutes at an ultrasonic frequency of 40kHz and a power of 300W to remove dissolved oxygen in the solution. After soaking, the modified magnesium is purged with nitrogen at a rate of 2m³ / h for 15 minutes to remove residual ethanol on the surface.

[0039] The concentration of dilute hydrochloric acid used for pickling is 5%, and the solid-liquid ratio of metallic magnesium to dilute hydrochloric acid solution is 1:5; the concentration of zinc stearate ethanol solution used for activation modification is 2%, the ethanol is 95% industrial ethanol, and the mass ratio of magnesium to zinc stearate ethanol solution is 1:3.

[0040] Modified 2-methylallyl chloride is obtained by crude 2-methylallyl chloride through crude pretreatment, distillation purification and stabilization treatment.

[0041] The preparation steps for modified 2-methylallyl chloride are as follows:

[0042] Step 1: Crude product pretreatment: Take crude 2-methylallyl chloride, add anhydrous calcium chloride, let stand at 20℃ for 2 hours to adsorb the moisture in the crude product, and then remove the anhydrous calcium chloride by filtration.

[0043] Step 2, Distillation and Purification: The pretreated crude product is fed into a distillation column. The bottom temperature of the distillation column is controlled at 70℃, the top temperature at 45℃, the operating pressure at atmospheric pressure, the reflux ratio at 3:1, and the number of distillation plates at 20. The top fraction is collected to obtain 2-methylallyl chloride with a purity ≥99.2%.

[0044] Step 3, Stabilization treatment: Transfer the distilled 2-methylallyl chloride to a stirred tank, add 0.01% of tert-butyl-p-hydroxyanisole by mass, stir at 100 rpm for 20 min at 20°C, and after stirring, transfer to a sealed container made of polytetrafluoroethylene to obtain modified 2-methylallyl chloride.

[0045] Anhydrous calcium chloride needs to be activated by drying at 120℃ for 3 hours before use, and its dosage is 1% of the crude 2-methylallyl chloride mass; the dosage of tert-butyl-p-hydroxyanisole is 0.01% of the mass of 2-methylallyl chloride; before filling the sealed container with modified 2-methylallyl chloride, it needs to be purged with nitrogen three times, with each purging pressure being 0.05 MPa.

[0046] Example 2: A method for preparing 2-methylallyl magnesium chloride, comprising the following steps:

[0047] S1. Pretreatment and initial feeding: The 2500L reactor was purged three times with argon gas of ≥99.99% purity. Each time, the reactor was filled with argon gas to a pressure of 0.065MPa and then vented to atmospheric pressure to remove air from the reactor. Under argon protection, the feeder cover was opened and the modified magnesium was added into the reactor. After closing the feeder cover, 100kg of tetrahydrofuran was added from the high-level tank, followed by the initiator. The heating system was then started to heat the material in the reactor to 25°C.

[0048] S2. Slowly add 6.5 kg of modified 2-methylallyl chloride into the reactor and observe the state inside the reactor (such as slight reflux, turbidity of the system) to confirm the initiation of the reaction; if the reaction does not start within 30 min, add an equal amount of initiator and then add another 2.5 kg of modified 2-methylallyl chloride until the reaction starts.

[0049] S3. After the reaction is initiated, the remaining modified 2-methylallyl chloride and tetrahydrofuran are added dropwise simultaneously, with the dropping rate controlled at 0.85 kg / min (to be completed within 4.5 hours), and the reactor temperature is maintained at 25°C during this period; after the addition is completed, the reaction is continued at this temperature for 1.5 h.

[0050] S4. Endpoint determination and product transfer: After the heat preservation is completed, samples are taken for testing. When the molar concentration of 2-methylallyl magnesium chloride is >1.05M, it is determined to be the endpoint. Heating is stopped and the temperature is lowered to room temperature. The pressure inside the reactor is adjusted to 0.065MPa with argon gas. The material is then pressed into the transfer tank purged with argon gas to complete the preparation of 2-methylallyl magnesium chloride.

[0051] The raw materials used for 2-methylallyl magnesium chloride include 75 kg of modified magnesium, 240 kg of modified 2-methylallyl chloride, 1550 kg of tetrahydrofuran, and 0.3% of the total mass of modified magnesium as an initiator.

[0052] The initiator is elemental iodine or 1,2-dibromoethane.

[0053] Modified magnesium is prepared by acid washing, water washing and drying of metallic magnesium, and modification with zinc stearate ethanol solution.

[0054] The preparation steps for modified magnesium are as follows:

[0055] Step 1: Magnesium material pretreatment: Select metallic magnesium, crush it into particles with a particle size of 4.5mm, put it into an acid pickling tank, add dilute hydrochloric acid solution, and pickle at 27℃ and 100rpm for 37min to remove the oxide layer on the magnesium surface.

[0056] Step 2, Washing and Drying: The acid-washed magnesium material is rinsed 4 times with deionized water until the pH of the rinsing solution is 7.0. Then, the magnesium material is transferred to a vacuum drying oven and dried for 2.5 hours under a vacuum of -0.09 MPa and a temperature of 105℃ until the moisture content of the magnesium material is ≤0.3%.

[0057] Step 3: Activation and modification: The dried magnesium material is put into the modification kettle, zinc stearate ethanol solution is added, and the mixture is stirred and soaked at 80 rpm at 270℃ for 1.5 hours. After soaking, it is filtered to obtain modified magnesium.

[0058] Before use, the zinc stearate ethanol solution needs to be ultrasonically degassed for 17 minutes at an ultrasonic frequency of 40kHz and a power of 400W to remove dissolved oxygen in the solution. After soaking, the modified magnesium is purged with nitrogen at a rate of 2.5m³ / h for 17 minutes to remove residual ethanol on the surface.

[0059] The concentration of dilute hydrochloric acid used for pickling is 6.5%, and the solid-liquid ratio of metallic magnesium to dilute hydrochloric acid solution is 1:6.5; the concentration of zinc stearate ethanol solution used for activation modification is 2.5%, the ethanol is 95% industrial ethanol, and the mass ratio of magnesium to zinc stearate ethanol solution is 1:4.

[0060] Modified 2-methylallyl chloride is obtained by crude 2-methylallyl chloride through crude pretreatment, distillation purification and stabilization treatment.

[0061] The preparation steps for modified 2-methylallyl chloride are as follows:

[0062] Step 1: Crude product pretreatment: Take crude 2-methylallyl chloride, add anhydrous calcium chloride, let stand at 22℃ for 2.5h to adsorb the moisture in the crude product, and then remove the anhydrous calcium chloride by filtration.

[0063] Step 2, Distillation and Purification: The pretreated crude product is fed into a distillation column. The bottom temperature of the distillation column is controlled at 72℃, the top temperature at 46℃, the operating pressure at atmospheric pressure, the reflux ratio at 3:1, and the number of distillation plates at 23. The top fraction is collected to obtain 2-methylallyl chloride with a purity ≥99.2%.

[0064] Step 3, Stabilization treatment: Transfer the distilled 2-methylallyl chloride to a stirred tank, add 0.015% of tert-butyl-p-hydroxyanisole by mass, stir at 125 rpm for 25 min at 23°C, and after stirring, transfer to a sealed container made of polytetrafluoroethylene to obtain modified 2-methylallyl chloride.

[0065] Anhydrous calcium chloride needs to be activated by drying at 125℃ for 3.5h before use, and its dosage is 1.5% of the crude 2-methylallyl chloride mass; the dosage of tert-butyl-p-hydroxyanisole is 0.015% of the 2-methylallyl chloride mass; before filling the sealed container with modified 2-methylallyl chloride, it needs to be purged with nitrogen three times, with each purging pressure being 0.055MPa.

[0066] Example 3: A method for preparing 2-methylallyl magnesium chloride, comprising the following steps:

[0067] S1. Pretreatment and initial feeding: The 2500L reactor was purged three times with argon gas of ≥99.99% purity. Each time, the reactor was filled with argon gas to a pressure of 0.07MPa and then vented to atmospheric pressure to remove air from the reactor. Under argon protection, the feeder cover was opened and the modified magnesium was added into the reactor. After closing the feeder cover, 100kg of tetrahydrofuran was added from the high-level tank, followed by the initiator. The heating system was then started to heat the material in the reactor to 50℃.

[0068] S2. Slowly add 8 kg of modified 2-methylallyl chloride into the reactor and observe the state inside the reactor (such as slight reflux, turbidity of the system) to confirm the initiation of the reaction; if the reaction does not start within 30 min, add an equal amount of initiator and then add another 3 kg of modified 2-methylallyl chloride until the reaction starts.

[0069] S3. After the reaction is initiated, the remaining modified 2-methylallyl chloride and tetrahydrofuran are added dropwise simultaneously, with the dropping rate controlled at 0.9 kg / min (to be completed within 5 hours), and the reactor temperature is maintained at 50°C during this period; after the addition is completed, the reaction is continued at this temperature for 2 hours.

[0070] S4. Endpoint determination and product transfer: After the heat preservation is completed, samples are taken for testing. When the molar concentration of 2-methylallyl magnesium chloride is >1.05M, it is determined to be the endpoint. Stop heating and cool down to room temperature. Use argon to adjust the pressure inside the reactor to 0.07MPa. Press the material into the transfer tank purged with argon to complete the preparation of 2-methylallyl magnesium chloride.

[0071] The raw materials used for 2-methylallyl magnesium chloride include 80 kg of modified magnesium, 240 kg of modified 2-methylallyl chloride, 1600 kg of tetrahydrofuran, and 0.5% of the total mass of modified magnesium as an initiator.

[0072] The initiator is elemental iodine or 1,2-dibromoethane.

[0073] Modified magnesium is prepared by acid washing, water washing and drying of metallic magnesium, and modification with zinc stearate ethanol solution.

[0074] The preparation steps for modified magnesium are as follows:

[0075] Step 1: Magnesium material pretreatment: Select metallic magnesium, crush it into particles with a particle size of 6mm, put it into an acid pickling tank, add dilute hydrochloric acid solution, and pickle at 30℃ and 120rpm for 45min to remove the oxide layer on the magnesium surface.

[0076] Step 2, Washing and Drying: The acid-washed magnesium material is rinsed 5 times with deionized water until the pH of the rinsing solution is 7.2. Then, the magnesium material is transferred to a vacuum drying oven and dried for 3 hours under a vacuum of -0.1 MPa and a temperature of 110℃ until the moisture content of the magnesium material is ≤0.3%.

[0077] Step 3: Activation and modification: The dried magnesium material is put into the modification kettle, zinc stearate ethanol solution is added, and the mixture is stirred and soaked at 100 rpm at 30°C for 2 hours. After soaking, it is filtered to obtain modified magnesium.

[0078] Before use, the zinc stearate ethanol solution needs to be ultrasonically degassed for 20 minutes at an ultrasonic frequency of 40kHz and a power of 500W to remove dissolved oxygen in the solution. After soaking, the modified magnesium is purged with nitrogen at a rate of 3m³ / h for 20 minutes to remove residual ethanol on the surface.

[0079] The concentration of dilute hydrochloric acid used for pickling is 8%, and the solid-liquid ratio of metallic magnesium to dilute hydrochloric acid solution is 1:8; the concentration of zinc stearate ethanol solution used for activation modification is 3%, the ethanol is 95% industrial ethanol, and the mass ratio of magnesium to zinc stearate ethanol solution is 1:5.

[0080] Modified 2-methylallyl chloride is obtained by crude 2-methylallyl chloride through crude pretreatment, distillation purification and stabilization treatment.

[0081] The preparation steps for modified 2-methylallyl chloride are as follows:

[0082] Step 1: Crude product pretreatment: Take crude 2-methylallyl chloride, add anhydrous calcium chloride, let stand at 25℃ for 3 hours to adsorb the moisture in the crude product, and then remove the anhydrous calcium chloride by filtration.

[0083] Step 2, Distillation and Purification: The pretreated crude product is fed into a distillation column. The bottom temperature of the distillation column is controlled at 75℃, the top temperature at 48℃, the operating pressure at atmospheric pressure, the reflux ratio at 3:1, and the number of distillation plates at 25. The top fraction is collected to obtain 2-methylallyl chloride with a purity ≥99.2%.

[0084] Step 3, Stabilization treatment: Transfer the distilled 2-methylallyl chloride to a stirred tank, add 0.02% of its mass of tert-butyl-p-hydroxyanisole, stir at 150 rpm for 30 min at 25°C, and after stirring, transfer to a sealed container made of polytetrafluoroethylene to obtain modified 2-methylallyl chloride.

[0085] Anhydrous calcium chloride needs to be activated by drying at 130℃ for 4 hours before use, and its dosage accounts for 2% of the crude 2-methylallyl chloride mass; the dosage of tert-butyl-p-hydroxyanisole is 0.02% of the mass of 2-methylallyl chloride; before filling the sealed container with modified 2-methylallyl chloride, it needs to be purged with nitrogen three times, with a purging pressure of 0.06 MPa each time.

[0086] Comparative Example 1: The difference between this comparative example and Example 1 is that commercially available metallic magnesium is used in this comparative example.

[0087] Comparative Example 2 differs from Example 1 in that crude 2-methylallyl chloride is used in this comparative example.

[0088] Performance testing: Performance tests were conducted on the products prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2.

[0089] Product molar concentration test: First, dry the experimental apparatus and then purge it with argon to ensure an oxygen-free and anhydrous environment. Simultaneously, prepare and standardize iodine standard solution, sodium thiosulfate standard solution, and starch indicator. Under argon protection, accurately transfer a certain volume of sample into an iodine flask containing anhydrous tetrahydrofuran using a dry pipette. Add excess iodine standard solution and react in an ice-water bath at 0-5℃ for 10 min. Then add starch indicator and titrate with sodium thiosulfate standard solution until the blue color fades and does not recover within 30 seconds. Record the volume consumed. Finally, obtain the product molar concentration based on the stoichiometric relationship. Test standard: "Quantitative Determination of Grignard Reagents".

[0090] Byproduct content test: First, the sample was treated under argon protection. 10 mL of the sample was taken, anhydrous ethanol was added to terminate the reaction, and the solution was diluted and filtered to obtain the organic byproduct test solution. Another 50 mL of the sample was taken, centrifuged, the precipitate was washed, dried, and weighed to obtain the mass of the inorganic byproduct. Then, GC conditions were set, and the types of organic byproducts were determined by preparing standards. Then, a standard curve was plotted using the external standard method, and the total concentration of organic byproducts was calculated. Finally, the contents of organic and inorganic byproducts were calculated separately, and the two were added together to obtain the total byproduct content. The test was conducted according to the "General Rules for the Determination of Organic Compound Content by Gas Chromatography".

[0091] Product yield test: First, record the mass of modified magnesium, the volume and density of modified 2-methylallyl chloride, and the purity of both. Calculate the amount of magnesium and 2-methylallyl chloride respectively, and determine the reactant with the smaller value as the limiting reactant to calculate the theoretical yield. Then, measure the actual yield using two methods: one is to determine the molar concentration of the product in the reaction solution using iodometric titration, combined with the total volume of the reaction solution; the other is to collect the fraction by vacuum distillation of the reaction solution under argon protection, and simultaneously measure the product concentration in the residual liquid to correct for the residual amount, finally obtaining the actual yield. Finally, calculate the yield (%) as (actual yield / theoretical yield) × 100%, with the result of the first actual yield determination method as the main basis and the second method used for verification. The test is based on: "General Rules for the Determination of Yield of Organic Synthesis Reactions".

[0092] The obtained test data are recorded in Table 1 below:

[0093]

[0094] By comparing and analyzing the relevant data in Table 1, it can be seen that the 2-methylallyl magnesium chloride prepared by the method of the present invention has a high molar concentration and yield, while the content of by-products is low. This indicates that the 2-methylallyl magnesium chloride preparation method provided by the present invention has a broader market prospect and is more suitable for promotion.

[0095] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0096] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

A method for preparing 1,2-methylallyl magnesium chloride, characterized in that, Includes the following steps: S1. Pretreatment and initial feeding: Replace the reactor with argon gas, and add modified magnesium, tetrahydrofuran and initiator under argon protection. Start the heating system to heat the material in the reactor to 0-50℃. S2. Reaction initiation: Slowly add 5-8 kg of modified 2-methylallyl chloride into the reactor, observe the state inside the reactor and confirm the initiation of the reaction; S3. Continuous reaction and heat preservation: After the reaction is initiated, the remaining modified 2-methylallyl chloride and tetrahydrofuran are added dropwise simultaneously, with the dropping rate controlled at 0.8-0.9 kg / min, and the reactor temperature is maintained at 0-50℃ during the process; after the addition is completed, the reaction is continued at this temperature for 1-2 hours. S4. Endpoint determination and product transfer: After the heat preservation is completed, samples are taken for testing. When the molar concentration of 2-methylallyl magnesium chloride is >1.05M, it is determined to be the endpoint. Stop heating and cool down to room temperature. Press the material into the transfer tank to complete the preparation of 2-methylallyl magnesium chloride.

2. The method for preparing 2-methylallyl magnesium chloride according to claim 1, characterized in that: The raw materials used in the 2-methylallyl magnesium chloride include 70-80 kg of modified magnesium, 240 kg of modified 2-methylallyl chloride, 1500-1600 kg of tetrahydrofuran, and 0.1-0.5% of initiator by total mass of modified magnesium.

3. The method for preparing 2-methylallyl magnesium chloride according to claim 1, characterized in that: The initiator is elemental iodine or 1,2-dibromoethane.

4. The method for preparing 2-methylallyl magnesium chloride according to claim 1, characterized in that: The modified magnesium is prepared by acid washing, water washing and drying of metallic magnesium, and activation modification by zinc stearate ethanol solution.

5. The method for preparing 2-methylallyl magnesium chloride according to claim 4, characterized in that, The preparation steps of the modified magnesium are as follows: pulverize metallic magnesium and put it into a dilute hydrochloric acid solution for acid washing, controlling the temperature and continuously stirring for 30-40 minutes to remove the surface oxide layer; rinse the magnesium after acid washing with deionized water 3-5 times until the pH of the rinsing solution is 6.8-7.2, and transfer the magnesium to a vacuum drying oven to dry for 2-3 hours; after drying, put the magnesium into a modification vessel, add zinc stearate ethanol solution, and stir and soak at 25-30℃ and a speed of 60-100 rpm for 1-2 hours; after soaking, filter to obtain modified magnesium.

6. The method for preparing 2-methylallyl magnesium chloride according to claim 5, characterized in that: Before use, the zinc stearate ethanol solution needs to be ultrasonically degassed for 15-20 minutes at an ultrasonic frequency of 40kHz and a power of 300-500W to remove dissolved oxygen from the solution; after soaking, the modified magnesium is purged with nitrogen for 15-20 minutes to remove surface ethanol.

7. The method for preparing 2-methylallyl magnesium chloride according to claim 5, characterized in that: The concentration of the dilute hydrochloric acid used for pickling is 5-8%, and the solid-liquid ratio of magnesium to the dilute hydrochloric acid solution is 1:(5-8); the concentration of the zinc stearate ethanol solution used for activation modification is 2-3%, the ethanol is 95% industrial ethanol, and the mass ratio of magnesium to zinc stearate ethanol solution is 1:(3-5).

8. The method for preparing 2-methylallyl magnesium chloride according to claim 1, characterized in that: The modified 2-methylallyl chloride is obtained by crude 2-methylallyl chloride through crude pretreatment, distillation purification, and stabilization treatment.

9. The method for preparing 2-methylallyl magnesium chloride according to claim 8, characterized in that, The preparation steps of the modified 2-methylallyl chloride are as follows: add anhydrous calcium chloride to the crude 2-methylallyl chloride, let it stand for 2-3 hours, and then filter to remove the anhydrous calcium chloride. The pretreated crude 2-methylallyl chloride was fed into a distillation column. The temperature and pressure inside the distillation column were controlled, and the top fraction was collected at a reflux ratio of 3:1 to obtain high-purity 2-methylallyl chloride. The distilled 2-methylallyl chloride was transferred to a stirred tank, tert-butyl-p-hydroxyanisole was added, the temperature was controlled, and the mixture was stirred continuously for 20-30 minutes. After stirring, the mixture was transferred to a sealed container made of polytetrafluoroethylene to obtain modified 2-methylallyl chloride.

10. The method for preparing 2-methylallyl magnesium chloride according to claim 9, characterized in that: The anhydrous calcium chloride needs to be activated by drying at 120-130℃ for 3-4 hours before use, and the amount used accounts for 1-2% of the crude 2-methylallyl chloride mass; the amount of tert-butyl-p-hydroxyanisole is 0.01-0.02% of the mass of 2-methylallyl chloride; before the sealed container is filled with modified 2-methylallyl chloride, it needs to be purged with nitrogen three times, with a purging pressure of 0.05-0.06 MPa each time.

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