Efficient synthesis method of vinyl magnesium chloride

Abstract

The invention relates to an efficient synthesis method of vinyl magnesium chloride, which comprises the following steps of: adding magnesium chips, tetrahydrofuran, vinyl magnesium chloride and vinyl chloride into a pressure-resistant reaction container under certain pressure; according to the method, the pressure kettle is used as a reaction container, under the condition that vinyl chloride does not need to be continuously introduced, normal operation of vinyl magnesium chloride reaction in the production process can be guaranteed, the production process can be simplified, the yield can be increased, and the reaction time can be shortened.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to an efficient method for synthesizing vinyl magnesium chloride. Background Technology

[0002] Currently, industrial-grade vinyl magnesium chloride solutions are generally synthesized using vinyl chloride and magnesium strips as raw materials, and tetrahydrofuran or diethyl ether as solvents, through the Grignard reaction. The synthesis processes typically involve continuously passing vinyl chloride gas into tetrahydrofuran or diethyl ether containing magnesium strips or powder at room temperature or around 0°C and atmospheric pressure, or dissolving vinyl chloride gas in tetrahydrofuran solution at low temperature before adding it dropwise. Because vinyl chloride has low solubility in tetrahydrofuran or diethyl ether at room temperature or 0°C and atmospheric pressure, and its absorption rate by the solvent is very slow, most of the vinyl chloride gas is released from the reaction system before it can dissolve and be absorbed. This results in a very low concentration of vinyl chloride in the solvent, a very slow reaction rate, and frequent premature termination of the reaction, posing a significant safety hazard to production.

[0003] Vinyl magnesium chloride appears as a reddish-brown transparent liquid. For example, Chinese patent CN107383073B discloses a method for preparing vinyl magnesium chloride, using vinyl chloride and magnesium as raw materials and anhydrous tetrahydrofuran as a solvent. The reaction is carried out in a pressure-resistant, thick-walled glass reactor using a Grignard reaction. This method involves dissolving vinyl chloride in a tetrahydrofuran solution at low temperature before adding it dropwise, making the operation complex and requiring harsh conditions. Chinese patent CN114478611B reports a method under nitrogen protection where magnesium shavings are added to tetrahydrofuran, stirred, heated to 65°C, and an excess of vinyl chloride gas is introduced. The reaction is maintained at 65°C with stirring until the magnesium shavings completely disappear. This method has a slow initiation rate and consumes a large amount of vinyl chloride gas.

[0004] Vinyl magnesium chloride is a typical Grignard reaction. The preparation of Grignard reagents involves reacting halogenated hydrocarbons and magnesium shavings in anhydrous THF, diethyl ether, and tertiary methyl ether. The more electron-donating groups on the substrate, the more difficult the Grignard reagent is to prepare, but the higher its stability. Conversely, the more electron-withdrawing groups on the substrate, the easier the Grignard reagent is to prepare, but the lower its stability, often resulting in self-coupling byproducts. Vinyl chloride, being a gas at atmospheric pressure and with low solubility in solvents, is difficult to initiate in the preparation of Grignard reagents, requiring large quantities of vinyl chloride gas. Traditional initiation methods are not only inefficient but also produce low concentrations of the resulting Grignard reagent. Therefore, finding an efficient method for synthesizing vinyl magnesium chloride with simple initiation conditions is particularly important. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a highly efficient method for synthesizing vinyl magnesium chloride. This method eliminates the need for continuous bubbling of vinyl chloride gas and the incorporation of vinyl chloride gas into tetrahydrofuran. This not only ensures the normal progress of the Grignard reaction during the production process but also simplifies the production process, increases the yield, and shortens the reaction time.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for efficiently synthesizing vinyl magnesium chloride, comprising the following steps: adding magnesium shavings, tetrahydrofuran, and vinyl magnesium chloride to a pressure vessel, and introducing vinyl chloride gas at a certain pressure, and reacting at 60°C to obtain vinyl magnesium chloride.

[0007] The reaction equation is:

[0008]

[0009] The further technical solution is as follows, with specific implementation steps:

[0010] (1) Add magnesium shavings, tetrahydrofuran, and initiator to a pressure-resistant reactor;

[0011] (2) Nitrogen gas is used to purge the gas in the reactor, and then vinyl chloride gas is introduced. The temperature continues to rise. After a certain amount of gas is introduced, the gas supply is stopped, and the reactor is controlled at a certain pressure and temperature to carry out the reaction.

[0012] (3) After the reaction is complete, cool to room temperature and take out a portion to test whether the concentration of the reagent reaches 85%-99% of the predetermined concentration.

[0013] Preferably, the initiator is vinyl magnesium chloride.

[0014] Preferably, the mass ratio of magnesium shavings, initiator, tetrahydrofuran, and vinyl chloride is 1:0.14:(9.3~18.5):(2~3).

[0015] Preferably, in step (2), the pressure in the reactor is controlled at 0.1 MPa-0.25 MPa, and the reaction is carried out at 60 °C for 3 hours.

[0016] Preferably, the amount of vinyl chloride gas introduced is equimolar based on the required Grignard reagent concentration.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. During the reaction process, the pressure inside the pressure vessel is positive pressure. Positive pressure can increase the concentration of gas molecules, increase the effective collision frequency, thereby accelerating the reaction rate, promoting the forward reaction direction, thereby increasing the yield, and increasing the solubility of gas in the liquid phase, which is beneficial to improving reaction efficiency. Under positive pressure, air (oxygen, moisture, etc.) cannot flow back into the system, which can prevent reactants from being contaminated or causing side reactions.

[0019] 2. A pressure vessel resistant to pressure was used in the reaction, which prevented vinyl chloride gas from escaping into the air due to high temperature during the process. Compared with dissolving vinyl chloride gas in tetrahydrofuran and continuously venting gas during the reaction, this greatly reduced the loss of vinyl chloride gas. Detailed Implementation

[0020] The technical solution 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0022] Example 1

[0023] Magnesium shavings (14.4 g), tetrahydrofuran (267 g), and vinyl magnesium chloride (2 mol / L in THF, 2.0 g) were weighed into a pressure vessel. A magnetic stir bar was added, and after purging with nitrogen three times, vinyl chloride gas (18.72 g) was introduced. The temperature rose significantly when vinyl chloride was introduced, reaching 60 °C. After 2 hours, the reaction was cooled to room temperature, and after purging with nitrogen three times, the pressure vessel was opened, and a sample was taken to titrate the Grignard reagent concentration.

[0024] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 0.98 mol / L in THF, with a yield of 98%.

[0025] Example 2

[0026] Magnesium shavings (14.4 g), tetrahydrofuran (267 g), and vinyl magnesium chloride (2 mol / L in THF, 2.0 g) were weighed into a pressure vessel. A magnetic stir bar was added, and after purging with nitrogen three times, vinyl chloride gas (37.44 g) was introduced. The temperature rose significantly when vinyl chloride was introduced, reaching 60 °C. After 2 hours, the reaction was cooled to room temperature, and after purging with nitrogen three times, the pressure vessel was opened, and a sample was taken to titrate the Grignard reagent concentration.

[0027] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 1.93 mol / L in THF, with a yield of 96.5%.

[0028] Example 3

[0029] Magnesium shavings (14.4 g), tetrahydrofuran (178 g), and vinyl magnesium chloride (2 mol / L in THF, 2.0 g) were weighed into a pressure vessel. A magnetic buoy was added, and after purging with nitrogen three times, vinyl chloride gas (37.44 g) was introduced. The temperature rose significantly when vinyl chloride was introduced, reaching 60 °C. After 2 hours, the reaction was cooled to room temperature, and after purging with nitrogen three times, the pressure vessel was opened, and a sample was taken to titrate the Grignard reagent concentration.

[0030] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 2.63 mol / L in THF, with a yield of 87.6%.

[0031] Example 4

[0032] Magnesium shavings (14.4 g), tetrahydrofuran (134 g), and vinyl magnesium chloride (2 mol / L in THF, 2.0 g) were weighed into a pressure vessel. A magnetic stir bar was added, and after purging with nitrogen three times, vinyl chloride gas (37.44 g) was introduced. The temperature rose significantly when vinyl chloride was introduced, reaching 60 °C. After 2 hours, the reaction was cooled to room temperature, and after purging with nitrogen three times, the pressure vessel was opened, and a sample was taken to titrate the Grignard reagent concentration.

[0033] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 3.15 mol / L in THF, with a yield of 78.8%.

[0034] Comparative Example 1

[0035] Weigh 14.4 g of magnesium shavings and 267 g of tetrahydrofuran into a glass reaction flask. Add 0.2 g of iodine as an initiator, add a magnetic initiator, and purge the mixture three times with nitrogen. Raise the reaction temperature to 60 °C and introduce excess vinyl chloride gas to form a tail gas absorption device. Continue this process until the magnesium shavings in the flask have completely reacted. Take a sample and titrate the Grignard reagent concentration. The amount of vinyl chloride used was 56.3 g.

[0036] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 0.92 mol / L in THF, with a yield of 92%.

[0037] Comparative Example 2

[0038] Anhydrous ethanol was first cooled to -20°C using a low-temperature circulating bath (ethylene glycol was used as the refrigerant). Then, 135 g of anhydrous tetrahydrofuran was placed in the low-temperature circulating bath and cooled to -15°C. The total mass was then quickly weighed. Separately, vinyl chloride from a steel cylinder was piped into the flask containing the pre-cooled -15°C anhydrous tetrahydrofuran (the pipe opening was below the surface of the tetrahydrofuran). The pressure reducing valve on the steel cylinder was adjusted to a suitable degree so that the vinyl chloride was absorbed in the -15°C anhydrous tetrahydrofuran. The mass of absorbed vinyl chloride was obtained from the mass difference before and after absorption. The required absorption amount was: 135 g of tetrahydrofuran absorbed 18.72 g of vinyl chloride.

[0039] Weigh out 14.4 g of magnesium shavings and 132 g of tetrahydrofuran, add 0.2 g of iodine, and circulate 40°C warm water into the jacket of the reactor. Open the constant pressure dropping funnel and first add about 10 g of tetrahydrofuran solution that has absorbed vinyl chloride to the reactor. Then add 2 ml of 1,2-dibromoethane as an initiator. After a few minutes, bubbles will be seen on the surface of the magnesium shavings, the solution will become slightly turbid, and the color of the iodine will begin to disappear slowly. After the reaction slows down, add the remaining tetrahydrofuran to the reactor in several portions, adding it at a rate that keeps the reaction solution at a gentle boil. Take a sample to titrate the Grignard reagent concentration.

[0040] Titration analysis showed that the concentration of vinyl magnesium chloride in this example was 0.68 mol / L in THF, with a yield of 68%.

[0041] Comparing Comparative Example 1 and Example 1, it was found that the two examples differed in that Comparative Example 1 used continuous aeration, while Example 1 used a pressurized reaction in a pressure vessel. Although the Grignard reagent concentration and yield of Comparative Example 1 were not much different from those of Example 1, Comparative Example 1 adopted a continuous aeration method, and the amount of vinyl chloride consumed was three times that of Example 1. The raw material loss caused by Comparative Example 1 was much higher than that of Example 1.

[0042] Compared with Example 1, Comparative Example 2 involved dissolving vinyl chloride gas in a tetrahydrofuran solution at a low temperature beforehand, and then adding the tetrahydrofuran solution of vinyl chloride dropwise while raising the temperature inside the reactor. Since the boiling point of vinyl chloride gas is -13.8 ℃, a small amount of vinyl chloride gas would escape if added at 40 ℃, resulting in a lower concentration and yield of the Grignard reagent. In Example 1, the gas did not escape from the reactor under closed conditions and was consumed during the reaction, greatly reducing the loss of vinyl chloride gas.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A highly efficient method for synthesizing vinyl magnesium chloride, characterized in that, Includes the following steps: (1) Add magnesium shavings, tetrahydrofuran, and initiator to a pressure-resistant reactor; (2) Nitrogen gas is used to purge the gas in the reactor, and then vinyl chloride gas is introduced. The temperature continues to rise. After a certain amount of gas is introduced, the gas supply is stopped, and the reactor is controlled at a certain pressure and temperature to carry out the reaction. (3) After the reaction is complete, cool to room temperature and take out a portion to test whether the concentration of the reagent reaches 85%-99% of the predetermined concentration.

2. The efficient synthesis method of vinyl magnesium chloride according to claim 1, characterized in that: The initiator is vinyl magnesium chloride.

3. The efficient synthesis method of vinyl magnesium chloride according to claim 1, characterized in that: The mass ratio of magnesium shavings, initiator, tetrahydrofuran, and vinyl chloride is 1:0.14:(9.3~18.5):(2~3).

4. The efficient synthesis method of vinyl magnesium chloride according to claim 1, characterized in that: In step (2), the pressure in the reactor is controlled at 0.1 MPa-0.25 MPa, and the reaction is carried out at 60 °C for 3 h.

5. The efficient synthesis method of vinyl magnesium chloride according to claim 1, characterized in that: The amount of vinyl chloride gas introduced is based on the required Grignard reagent concentration in equimolar amounts.

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