Process for the synthesis of chloroethylene carbonate based on microchannel continuous flow technology

Abstract

The application discloses a method for continuously synthesizing chloroethylene carbonate in a microchannel, a dichloroethane solution of ethylene carbonate is used as A liquid, a mixed solution of an initiator and a chlorinating agent is divided into two streams to form B liquid and C liquid; the A liquid is mixed with the B liquid after preheating and then enters a microchannel reactor, the C liquid enters the microchannel reactor at the middle section of a reaction pipeline, and chloroethylene carbonate is prepared through continuous reaction; the concentration of the dichloroethane solution of ethylene carbonate is 50wt%-65wt%; the molar ratio of a free radical initiator AIBN to the chlorinating agent sulfuryl chloride is (0.0054-0.016):1; the molar ratio of ethylene carbonate to the chlorinating agent in the A and B mixed liquid is 1:(1.0-2.0); the flow ratio of the C liquid to the B liquid is 1:(0.5-1); the application adopts the method of using sub-feed to precisely control the reaction, and the problems of excessive impurities, low conversion rate and low selectivity in the synthesis of chloroethylene carbonate are overcome, the conversion rate reaches 98.0%, and the selectivity reaches 99.9%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and particularly relates to a method for synthesizing chloroethylene carbonate. Background Art

[0002] Chloroethylene carbonate is a commonly used organic synthesis intermediate and is also used to prepare fluoroethylene carbonate and vinylene carbonate for lithium battery electrolytes. High-purity chloroethylene carbonate can also be directly used as a flame retardant additive for lithium battery electrolytes to improve the cycle performance and service life of lithium battery electrolytes. Its main synthesis methods are: 1. Using chlorine as a chlorination reagent, chloroethylene carbonate is prepared from ethylene carbonate under ultraviolet light irradiation. The advantage is low raw material cost, but the disadvantage is slow reaction rate and low product yield. 2. Using sulfuryl chloride, solid phosgene, etc. as a chlorination reagent, heating reaction in the presence of an azo initiator or peroxide initiator to prepare chloroethylene carbonate from ethylene carbonate. The advantage is that the reaction yield can reach more than 75%.

[0003] Compared with the traditional kettle process, the synthesis mass transfer efficiency using a microchannel continuous flow reactor is higher, showing good mixing performance, short residence time, small liquid holdup, good controllability and high safety.

[0004] However, the existing technology of synthesizing ethylene chlorocarbonate using microchannels still has problems such as excessive synthetic impurities, low conversion rate and low selectivity. How to use microchannel continuous flow technology to further improve the conversion rate and selectivity of ethylene chlorocarbonate has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention aims to provide a method for continuously synthesizing ethylene chlorocarbonate through a microchannel. Ethylene carbonate is used as a raw material and is dissolved in ethylene dichloride. The reaction is precisely controlled by using fractional feeding. The problems of excessive impurities, low conversion rate, and low selectivity in the synthesis of ethylene chlorocarbonate are overcome, and the conversion rate reaches 98.0% and the selectivity reaches 99.9%.

[0006] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0007] A method for continuously synthesizing ethylene chlorocarbonate in a microchannel comprises the following steps:

[0008] A dichloroethane solution of ethylene carbonate is used as liquid A, and a mixture of an initiator and a chlorination agent is divided into two streams, liquid B and liquid C. Liquid A is preheated and mixed with liquid B before entering a microchannel reactor, and liquid C enters the microchannel reactor at the middle section of the reaction pipeline, and chloroethylene carbonate is prepared by continuous reaction.

[0009] According to the above scheme, the concentration of the ethylene carbonate dichloroethane solution is 50wt%-65wt%; the molar ratio of the free radical initiator AIBN to the chlorination reagent sulfonyl chloride is (0.0054-0.016):1.

[0010] According to the above scheme, the molar ratio of ethylene carbonate and chlorination reagent in the mixed solution A and B is 1: (1.0-2.0); the flow ratio of solution C to solution B is 1: (0.5-1).

[0011] According to the above scheme, the microchannel reactor is designed as a spiral two-stage:

[0012] The first stage spiral microchannel has an inner diameter of 0.8-3.5 mm, a coil diameter of 3-10 cm, and a length of 10 m-40 m, and is located in a heating container;

[0013] The inner diameter of the spiral microchannel in the second stage is 2-4 mm, the coil diameter is 2-4 cm, and the length is 1 m-5 m, which serves as a cooling pipe.

[0014] According to the above scheme, liquid C enters the microchannel reactor at the middle section of the first-stage spiral microchannel.

[0015] According to the above scheme, the preheating temperature of the ethylene carbonate dichloroethane solution before entering the microchannel reactor is 60-97°C.

[0016] According to the above solution, the crystallization pipe of the microchannel reactor is made of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer or polytetrafluoroethylene.

[0017] According to the above scheme, the reaction temperature in the microchannel reactor is controlled to be 55-95°C, the pressure is 0-2 MPa, and the residence time is 1 s-20 min.

[0018] According to the above scheme, the inlet flow rate of liquid A, liquid B and liquid C is 5-100 ml / min.

[0019] According to the above scheme, the inclination angle of the spiral microchannel is 1-30°.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The reaction is controlled in sections, and the molar ratio of different stages of the reaction is precisely controlled by feeding in batches, which improves the conversion rate of the raw materials, achieves better reaction results, improves product selectivity, and reduces the content of by-products.

[0022] (2) The existing technologies mostly use continuous photochemical reactions of chlorine, but the present invention does not require photochemistry. Continuous photochemical reactions are difficult to scale up, but the present invention is easier to scale up.

[0023] (3) The single-pipe production capacity is high, and production can be expanded directly by simply increasing the number of pipes.

[0024] (4) High raw material conversion rate and high product selectivity.

[0025] (5) The reactor device has a simple structure and low manufacturing and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Schematic diagram of continuous synthesis of ethylene chlorocarbonate in microchannel of the present invention.

[0027] Figure 2 : Gas phase analysis spectrum of the reaction product obtained in Example 1.

[0028] Figure 3 : Gas phase analysis spectrum of the reaction product obtained in Example 2.

[0029] Figure 4 : Gas phase analysis spectrum of the reaction product obtained in Example 3.

[0030] Figure 5 : Gas phase analysis spectrum of the reaction product obtained in Example 4.

[0031] Figure 6 : Gas phase analysis spectrum of the reaction product obtained in Example 5. DETAILED DESCRIPTION

[0032] The following examples further illustrate the technical solutions of the present invention but are not intended to limit the scope of protection of the present invention.

[0033] The specific embodiment provides a method for continuously synthesizing chloroethylene carbonate through a microchannel. Figure 1 As shown:

[0034] A dichloroethane solution of ethylene carbonate is used as liquid A, and a mixture of an initiator and a chlorination agent is divided into two streams, liquid B and liquid C. Liquid A is preheated and mixed with liquid B before entering a microchannel reactor, and liquid C enters the microchannel reactor at the middle section of the reaction pipeline, and chloroethylene carbonate is prepared by continuous reaction.

[0035] The microchannel reactor adopts a spiral two-stage design: the inner diameter of the first-stage spiral microchannel is 0.8-3.5mm, the coil diameter is 3-10cm, and the length is 10m-40m, which is located in a heating container; the C liquid enters the microchannel reactor in the middle section of the first-stage spiral microchannel; the first-stage spiral microchannel can also be divided into two reactors, and the C liquid enters in the middle of the two reactors; the inner diameter of the second-stage spiral microchannel is 2-4mm, the coil diameter is 2-4cm, and the length is 1m-5m, which serves as a cooling channel.

[0036] Example 1

[0037] 1) Spiral Microchannel Reactor: The front section uses an inner diameter of 2.5 mm, a coil diameter of 8 cm, and a pipe length of 8 m. The rear section, which receives the second stream, uses an inner diameter of 2.5 mm, a coil diameter of 8 cm, and a pipe length of 12 m. The spiral microchannel has a 10° inclination angle. The cooling pipe has an inner diameter of 3 mm and a length of 2.5 m.

[0038] 2) 100 g of ethylene carbonate was dissolved in 60 g of ethylene dichloride, kept at 65°C, and transported to the microchannel reactor via a heat-insulating pump as material A; 1 g of AIBN was dissolved in 153.3 g of sulfonyl chloride as materials B and C.

[0039] 3) The flow rate of material A was 13.5 g / min, the flow rate of material B was 8 g / min, the flow rate of material C was 8 g / min, the temperature of the spiral microchannel was 88°C, the residence time in the reaction channel was 286.2 s, the cooling temperature of the cooling section channel was 13°C, and the pressure was stable at 2 bar.

[0040] 4) The material was collected and the pH was adjusted to 7-8. The dichloroethane layer was taken for gas phase analysis, which showed a chloroethylene carbonate content of 97.9%, an ethylene carbonate conversion of 98%, a chloroethylene carbonate selectivity of 99.9%, and no dichloroethylene carbonate was detected. The gas phase analysis spectrum is attached. Figure 2 shown.

[0041] Example 2

[0042] 1) Spiral Microchannel Reactor: The front section uses an inner diameter of 2.5 mm, a coil diameter of 8 cm, and a pipe length of 8 m. The rear section, which receives the second stream, uses an inner diameter of 2.5 mm, a coil diameter of 8 cm, and a pipe length of 12 m. The spiral microchannel has a 10° inclination angle. The cooling pipe has an inner diameter of 3 mm and a length of 2.5 m.

[0043] 2) 100 g of ethylene carbonate was dissolved in 60 g of ethylene dichloride, kept at 65°C, and transported to the microchannel reactor via a heat-insulating pump as material A; 1 g of AIBN was dissolved in 153.3 g of sulfonyl chloride as materials B and C.

[0044] 3) The flow rate of material A was 9 g / min, the flow rate of material B was 5.5 g / min, and the flow rate of material C was 5 g / min. The reaction temperature in the spiral microchannel was 90°C, the residence time was 432 s, the cooling temperature was 13°C, and the pressure was stabilized at 2 bar.

[0045] 4) Collect the material and adjust the pH to 7-8. Take the dichloroethane layer for gas phase analysis, and the result is 85.1% ethylene chlorocarbonate content, 97.8% ethylene carbonate conversion, 87.0% ethylene chlorocarbonate selectivity, and 0.2% ethylene dichlorocarbonate. See the attached gas phase analysis chart. Figure 3 shown.

[0046] Example 3

[0047] Example 1 was repeated, but without the split feed. The remaining processes and parameters remained unchanged. The obtained ethylene chlorocarbonate content was 63.6%, the ethylene carbonate conversion was 78.1%, the ethylene chlorocarbonate selectivity was 81.4%, and the dichloroethylene carbonate selectivity was 1.2%. The gas phase analysis spectrum is attached. Figure 4 shown.

[0048] Example 4

[0049] Example 1 was repeated, but without the cooling pipe. The other processes and parameters remained unchanged. The obtained ethylene chlorocarbonate content was 84.1%, the ethylene carbonate conversion was 89.7%, the ethylene chlorocarbonate selectivity was 93.8%, and no dichloroethylene carbonate was detected. The gas phase analysis spectrum is attached. Figure 5 shown.

[0050] Example 5

[0051] 10g of ethylene carbonate was dissolved in 6g of ethylene dichloride in a three-necked glass reaction flask, which was preheated at 65°C. 0.1g of AIBN was dissolved in 15.33g of sulfonyl chloride and added dropwise to the reaction flask at a rate of 8ml / h using a syringe pump. After the addition was complete, the temperature was raised to 80°C and the reaction was continued for 3h. The obtained ethylene chlorocarbonate content was 71%, the ethylene carbonate conversion rate was 86.6%, the ethylene chlorocarbonate selectivity was 82%, and the dichloroethylene carbonate content was 4.5%. The gas phase analysis spectrum is attached. Figure 6 shown.

[0052] Example 3 highlights the necessity of split feeding in the process. Without split feeding, the conversion rate and selectivity are lower than those in the split feeding case.

[0053] Example 4 highlights the necessity of a cooling pipe. This pipe cools the reaction system's internal temperature and maintains a constant pressure, providing a constant pressure for the dichloroethane and sulfonyl chloride, keeping them in a liquid state and completing the liquid-phase reaction. The results indicate that the conversion rate decreases without the cooling pipe, demonstrating its necessity.

[0054] Examples 1 and 2 illustrate methods for synthesizing ethylene dichloride carbonate using a split-feed process at different temperatures and flow rates. Compared to Examples 1 and 2, Example 5 reduces the residence time from 3 hours in a flask to 9 minutes in a microchannel, and increases the conversion of ethylene dichloride carbonate from 95.5% to 100%.

[0055] The above embodiments provide a detailed description of the technical solutions of the present invention. Obviously, the present invention is not limited to the described embodiments. Based on the embodiments of the present invention, those skilled in the art may make various modifications. However, any modifications that are equivalent to or similar to the present invention fall within the scope of protection of the present invention.

Claims

1. A method for continuously synthesizing ethylene chlorocarbonate through a microchannel, characterized in that The following steps are involved: A dichloroethane solution of ethylene carbonate is used as liquid A, and a mixture of an initiator and a chlorination agent is divided into two streams, liquid B and liquid C. Liquid A is preheated and mixed with liquid B before entering a microchannel reactor. Liquid C enters the microchannel reactor at the middle section of the reaction pipe, and the reaction is continued to prepare chloroethylene carbonate. The microchannel reactor is a spiral two-stage design: The first-stage spiral microchannel has an inner diameter of 0.8-3.5 mm, a coil diameter of 3-10 cm, and a length of 10 m-40 m, and is located in a heating container; liquid C enters the microchannel reactor at the middle section of the first-stage spiral microchannel; The inner diameter of the spiral microchannel in the second stage is 2-4 mm, the coil diameter is 2-4 cm, and the length is 1 m-5 m, which serves as a cooling pipe.

2. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The concentration of the dichloroethane solution of ethylene carbonate is 50wt%-65wt%; the molar ratio of the free radical initiator AIBN to the chlorination reagent sulfonyl chloride is (0.0054-0.016):

1.

3. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The molar ratio of ethylene carbonate and chlorination reagent in the mixed solution A and B is 1: (1.0-2.0); the flow ratio of solution C to solution B is 1: (0.5-1).

4. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The preheating temperature of the ethylene carbonate dichloroethane solution before entering the microchannel reactor is 60-97°C.

5. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The crystallization pipe of the microchannel reactor is made of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer or polytetrafluoroethylene.

6. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The reaction temperature in the microchannel reactor is controlled to be 55-95°C, the pressure to be 0-2 MPa, and the residence time to be 1s-20min.

7. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The inlet flow rate of liquid A, liquid B and liquid C is 5-100ml / min.

8. The method for continuously synthesizing ethylene chlorocarbonate through microchannel according to claim 1, wherein The inclination angle of the spiral microchannel is 1-30°.

Images