Method for synthesizing chloroethylene carbonate based on microchannel continuous flow technology

Abstract

The invention discloses a method for continuously synthesizing chloroethylene carbonate through a microchannel, which comprises the following steps: taking a dichloroethane solution of ethylene carbonate as a solution A, and dividing a mixed solution of an initiator and a chlorination reagent into two parts, namely a solution B and a solution C; preheating the solution A, mixing the solution A with the solution B, feeding the mixture into a micro-channel reactor, feeding the solution C into the micro-channel reactor from the middle section of a reaction pipeline, and continuously reacting to prepare chloroethylene carbonate; the concentration of the dichloroethane solution of the 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; the molar ratio of the ethylene carbonate to the chlorination reagent in the mixed solution A and the mixed solution B is 1: (1.0-2.0); the flow ratio of the solution C to the solution B is 1: (0.5-1); according to the method, the reaction is accurately controlled by feeding in different streams, so that the problems of excessive impurities, low conversion rate and low selectivity in chloroethylene carbonate synthesis are solved, 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 in particular 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 of lithium battery electrolytes and increase service life. Its synthesis methods mainly include: 1. Using chlorine as a chlorination reagent, chloroethylene carbonate is prepared from ethylene carbonate under ultraviolet light. 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 under the action of an azo initiator or a 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 in a microchannel. Ethylene carbonate is used as a raw material and dissolved in ethylene dichloride. The reaction is precisely controlled by using split feed, thereby overcoming the problems of excessive impurities, low conversion rate and low selectivity in the synthesis of ethylene chlorocarbonate. 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: A method for continuously synthesizing ethylene chlorocarbonate in a microchannel comprises the following steps: The dichloroethane solution of ethylene carbonate is used as liquid A, and the mixed solution of the initiator and the chlorination agent is divided into two streams, namely liquid B and liquid C; liquid A is mixed with liquid B after being preheated and then enters the 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.

[0007] 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 agent sulfonyl chloride is (0.0054-0.016):1.

[0008] 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 liquid C to liquid B is 1: (0.5-1).

[0009] According to the above scheme, the microchannel reactor is designed as a spiral two-stage: The first stage spiral microchannel has an inner diameter of 0.8-3.5 mm, a coil diameter of 3-10 cm, a length of 10 m-40 m, and is located in a heating container; The inner diameter of the second-stage spiral microchannel is 2-4 mm, the coil diameter is 2-4 cm, and the length is 1 m-5 m, which serves as a cooling channel.

[0010] According to the above scheme, liquid C enters the microchannel reactor at the middle section of the spiral microchannel in the first stage.

[0011] According to the above scheme, the preheating temperature of the ethylene carbonate dichloroethane solution before entering the microchannel reactor is 60-97°C.

[0012] According to the above scheme, the crystallization pipeline material of the microchannel reactor is tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer or polytetrafluoroethylene.

[0013] According to the above scheme, the reaction temperature in the microchannel reactor is controlled to be 55-95°C, the pressure is 0-2Mpa, and the residence time is 1s-20min.

[0014] According to the above scheme, the inlet flow rate of liquid A, liquid B and liquid C is 5-100ml / min.

[0015] According to the above scheme, the inclination angle of the spiral microchannel is 1-30°.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The reaction is controlled in stages. The molar ratio 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.

[0017] (2) The prior art mostly uses continuous photochemical reactions of chlorine, but the present invention does not require photochemistry. It is difficult to scale up continuous photochemical reactions, but the present invention makes it easier to scale up.

[0018] (3) The single-pipe production capacity is high, and production can be expanded directly by simply increasing the number of pipes.

[0019] (4) High raw material conversion rate and high product selectivity.

[0020] (5) The reactor device has a simple structure and low manufacturing and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Schematic diagram of continuous synthesis of ethylene chlorocarbonate in microchannel of the present invention.

[0022] Figure 2 : Gas phase analysis spectrum of the reaction product obtained in Example 1.

[0023] Figure 3 : Gas phase analysis spectrum of the reaction product obtained in Example 2.

[0024] Figure 4 : Gas phase analysis spectrum of the reaction product obtained in Example 3.

[0025] Figure 5 : Gas phase analysis spectrum of the reaction product obtained in Example 4.

[0026] Figure 6 : Gas phase analysis spectrum of the reaction product obtained in Example 5. DETAILED DESCRIPTION

[0027] The following examples further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0028] The specific embodiment provides a method for continuously synthesizing chloroethylene carbonate through a microchannel, see the attached Figure 1 As shown: The dichloroethane solution of ethylene carbonate is used as liquid A, and the mixed solution of the initiator and the chlorination agent is divided into two streams, namely liquid B and liquid C; liquid A is mixed with liquid B after being preheated and then enters the 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.

[0029] 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 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 is used as a cooling channel.

[0030] Example 1 1) Spiral microchannel reactor: The front section uses an inner diameter of 2.5mm, a coil diameter of 8cm, and a pipeline length of 8m; the rear section connected to the second strand of material uses an inner diameter of 2.5mm, a coil diameter of 8cm, and a pipeline length of 12m; the spiral microchannel has an inclination angle of 10°. The inner diameter of the cooling pipeline is 3mm and the length is 2.5m.

[0031] 2) 100 g of ethylene carbonate was dissolved in 60 g of ethylene dichloride, kept at 65°C, and transported to the microchannel reactor as material A through a heat-insulating pump; 1 g of AIBN was dissolved in 153.3 g of sulfonyl chloride as material B and material C.

[0032] 3) The flow rate of material A is 13.5 g / min, the flow rate of material B is 8 g / min, the flow rate of material C is 8 g / min, the temperature of the spiral microchannel is 88°C, the residence time in the reaction channel is 286.2s, the cooling temperature of the cooling section channel is 13°C, and the pressure is stable at 2 bar.

[0033] 4) Collect the material and adjust the pH to 7-8. Take the dichloroethylene layer for gas phase analysis, and the content of chloroethylene carbonate is 97.9%, the conversion rate of ethylene carbonate is 98%, the selectivity of chloroethylene carbonate is 99.9%, and dichloroethylene carbonate is not detected. The gas phase analysis spectrum is attached. Figure 2 shown.

[0034] Example 2 1) Spiral microchannel reactor: The front section uses an inner diameter of 2.5mm, a coil diameter of 8cm, and a pipeline length of 8m; the rear section connected to the second strand uses an inner diameter of 2.5mm, a coil diameter of 8cm, and a pipeline length of 12m; the spiral microchannel has an inclination angle of 10°. The inner diameter of the cooling pipeline is 3mm and the length is 2.5m.

[0035] 2) 100 g of ethylene carbonate was dissolved in 60 g of ethylene dichloride, kept at 65°C, and transported to the microchannel reactor as material A through a heat-insulating pump; 1 g of AIBN was dissolved in 153.3 g of sulfonyl chloride as material B and material C.

[0036] 3) The flow rate of material A is 9 g / min, the flow rate of material B is 5.5 g / min, the flow rate of material C is 5 g / min, the reaction temperature of the spiral microchannel is 90°C, the residence time is 432s, the cooling temperature is 13°C, and the pressure is stable at 2 bar.

[0037] 4) Collect the material and adjust the pH to 7-8. Take the dichloroethane layer for gas phase analysis, and the content of chloroethylene carbonate is 85.1%, the conversion rate of ethylene carbonate is 97.8%, the selectivity of chloroethylene carbonate is 87.0%, and the dichloroethylene carbonate is 0.2%. The gas phase analysis spectrum is attached. Figure 3 shown.

[0038] Example 3 Example 1 was repeated, but the feed was not divided into shares, and the other 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 ethylene dichlorocarbonate was 1.2%. The gas phase analysis spectrum is attached. Figure 4 shown.

[0039] Example 4 Example 1 was repeated, but without the cooling pipe, and the other processes and parameters remained unchanged. The obtained ethylene chlorocarbonate content was 84.1%, the ethylene carbonate conversion rate was 89.7%, the ethylene chlorocarbonate selectivity was 93.8%, and dichloroethylene carbonate was not detected. The gas phase analysis spectrum is attached Figure 5 shown.

[0040] Example 5 10g of ethylene carbonate was dissolved in 6g of ethylene dichloride in a three-necked glass reaction bottle, and the reaction bottle was preheated at 65°C. 0.1g of AIBN was dissolved in 15.33g of sulfonyl chloride and dripped into the reaction bottle at a rate of 8ml / h using a syringe pump. After the addition was completed, the temperature was raised to 80°C and reacted 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.

[0041] Example 3 highlights the necessity of split feed in the process. Without split feed, the conversion rate and selectivity are lower than those with split feed.

[0042] Example 4 highlights the necessity of cooling pipes, which cool the end of the reaction system and maintain a certain pressure in the reaction system, providing a certain pressure for the entire ethylene dichloride and sulfonyl chloride to maintain them in a liquid state to complete the liquid phase reaction. From the results, it can be seen that the reaction conversion rate is reduced without cooling pipes, and cooling pipes are necessary.

[0043] Embodiment 1 and embodiment 2 are methods for synthesizing ethylene dichloride carbonate by a split-feed process at different temperatures and flow rates. Embodiment 5 Compared with embodiment 1 and embodiment 2, the residence time is reduced from 3 h in the bottle reaction to 9 min in the microchannel reaction, and the conversion rate of ethylene dichloride carbonate is increased from 95.5% to 100%.

[0044] The above embodiments describe the technical solutions of the present invention in detail. Obviously, the present invention is not limited to the described embodiments. Based on the embodiments of the present invention, people familiar with the technical field can also make various changes accordingly, but any changes that are equivalent or similar to the present invention belong to the scope of protection of the present invention.

Claims

1. A method for continuously synthesizing ethylene chlorocarbonate in a microchannel, characterized in that The following steps are involved: The dichloroethane solution of ethylene carbonate is used as liquid A, and the mixed solution of the initiator and the chlorination agent is divided into two streams, namely liquid B and liquid C; liquid A is mixed with liquid B after being preheated and then enters the 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.

2. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The concentration of the ethylene carbonate dichloroethane solution is 50wt%-65wt%; the molar ratio of the free radical initiator AIBN to the chlorination agent sulfonyl chloride is (0.0054-0.016):

1.

3. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The molar ratio of ethylene carbonate to 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 in a microchannel as claimed in claim 1, characterized in that The microchannel reactor adopts 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, a length of 10 m-40 m, and is located in a heating container; The inner diameter of the second-stage spiral microchannel is 2-4 mm, the coil diameter is 2-4 cm, and the length is 1 m-5 m, which serves as a cooling channel.

5. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 4, characterized in that Liquid C enters the microchannel reactor at the middle section of the first-stage spiral microchannel.

6. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The preheating temperature of the ethylene carbonate dichloroethane solution before entering the microchannel reactor is 60-97°C.

7. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The crystallization pipeline of the microchannel reactor is made of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer or polytetrafluoroethylene.

8. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The reaction temperature in the microchannel reactor is controlled to be 55-95°C, the pressure to be 0-2Mpa, and the residence time to be 1s-20min.

9. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The inlet flow rate of liquid A, liquid B and liquid C is 5-100ml / min.

10. The method for continuously synthesizing ethylene chlorocarbonate in a microchannel as claimed in claim 1, characterized in that The inclination angle of the spiral microchannel is 1-30°.

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