Method for continuously preparing vinylene carbonate

Abstract

The invention discloses a method for continuously preparing vinylene carbonate. According to the preparation method, chloroethylene carbonate is taken as a raw material, p-methylacetophenone and / or halogenated methylacetophenone is taken as a solvent, a substance shown in a formula 1 is taken as an acid-binding agent # imgabs0 # (R = Me or Et), vinylene carbonate is prepared by using a continuous reactive distillation process, and a vinylene carbonate crude product with the content being greater than or equal to 98% can be directly obtained after the reaction, the crude product can directly enter a melt crystallization purification process. The method has the advantages of continuity, simple process, less equipment, high product selectivity and the like, and the production cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical synthesis and relates to a method for continuously preparing vinylene carbonate. Background Art

[0002] Vinylene carbonate (VC) is a core additive for lithium battery electrolytes and can promote the formation of a solid electrolyte interface film (SEI film) during the first charge and discharge of lithium batteries. The electrochemical performance of this film is stable, which can effectively inhibit the embedding of solvent molecules, thereby avoiding the decline of battery performance such as cycle life.

[0003] Currently, there is only one mature industrialized method for preparing VC, that is, using chloroethylene carbonate (CEC) as the raw material. A certain amount of CEC, solvent and inhibitor are added to a reaction kettle, and then triethylamine is added dropwise at a certain temperature. Triethylamine and CEC undergo an acid-binding elimination reaction to generate VC and triethylamine hydrochloride. The reaction equation is shown as follows: After the reaction, solid-liquid separation is carried out. The liquid phase containing VC is separated through processes such as desolvation, decoking, light component removal, and rectification to obtain a VC crude product with a purity of ≥97%. This VC crude product enters the melt crystallization process to obtain a qualified VC product through crystallization; triethylamine hydrochloride enters the triethylamine recovery process to recover triethylamine. The traditional production method is batch production, with a long production batch time and low production efficiency; since solid triethylamine hydrochloride is generated during the reaction, the solubility of this hydrochloride in the solvent and product is poor. If a continuous process is used, engineering problems such as pipeline blockage are inevitable; in addition, since VC is thermosensitive, during a long reaction process, the generated VC cannot leave the reaction system, so a polymerization side reaction occurs, and the reaction selectivity is <75%; the reacted VC needs to be separated through multiple processes to obtain the VC product, and during the separation process, VC further undergoes a polymerization side reaction due to heat sensitivity, resulting in a further reduction in yield. In order to reduce the residence time of VC at high temperature, the best way is to promptly remove the generated VC from the reaction system, and reactive distillation can achieve this purpose. However, for the traditional production process, since triethylamine hydrochloride will block the trays or packing, the reactive distillation process cannot be used.

[0004] One reason for the side reaction of VC is that VC itself is thermosensitive and prone to polymerization side reactions at high temperatures; another reason is that in the presence of triethylamine, the side reaction of VC will intensify. On the one hand, VC undergoes an esterification reaction with triethylamine by ring opening, and on the other hand, triethylamine promotes the polymerization reaction of VC.

[0005] In summary, the traditional process for preparing VC has high raw material energy consumption, generates a large amount of three wastes, and has high treatment costs; the process is long, the procedures are complex, and the equipment investment is high. Therefore, improving production efficiency, improving the selectivity of VC, and streamlining the VC preparation process are the main optimization directions for preparing VC.

[0006] CN115304577A uses methyl tert-butyl ether as a solvent, innovatively adds a phase transfer catalyst polyvinyl alcohol in the reaction, uses sodium bicarbonate instead of triethylamine as an acid-binding agent, reacts at 60 - 65 °C for 8 h, and the VC yield is 74.3%. CN111808064A uses CEC as a raw material, uses a mixed catalyst of iron oxide nanofibers, alumina nanofibers, and titanium oxide nanofibers, does not use an acid-binding agent, solvent, and polymerization inhibitor, bubbles nitrogen for 4 h at 40 °C, and then performs rectification and crystallization separation, and the product yield is 88%. CN111393403A uses 1,2-dibromoethylene as a raw material and basic carbonate as a catalyst, keeps the reaction at 90 °C for 10 h, and the product yield is 85%. The above patents use new catalysts or change the types of raw materials, which have improved the yield and selectivity of VC, but have not changed the problems of long batch time and low efficiency in batch kettle production, as well as the problems of many subsequent rectification separation procedures and high equipment investment.

[0007] Therefore, developing a method for continuously preparing VC with simple process, less equipment investment, and high product selectivity is of great significance for the development of the lithium battery electrolyte industry. Summary of the Invention

[0008] The present invention discloses a method for continuously preparing vinylene carbonate, which uses a new solvent and a polymerization inhibitor and can continuously prepare vinylene carbonate in a reactive distillation process. The process of the present invention is simple and the product selectivity is high. The vinylene carbonate prepared by the present invention has a purity of ≥98% and can directly enter the melt crystallization process for separation and purification.

[0009] A method for continuously preparing vinylene carbonate (VC) comprises the following steps: using chloroethylene carbonate (CEC) as a raw material, using p-methylacetophenone and / or halomethylacetophenone as a solvent, using the substance shown in formula 1 as an acid-binding agent, and using a continuous reactive distillation process to prepare vinylene carbonate;

[0010] Formula 1 (R = Me (-CH3) or Et (-C2H5)).

[0011] The present invention can effectively solve the problems mentioned above that the reaction distillation process cannot be used for VC preparation and the selectivity of VC is low: First, the hydrochloride salt formed by the acid-binding agent and CEC has good solubility in the solvent used, and the whole reaction process is homogeneous without the generation of solids; Second, since the basicity of the acid-binding agent used is weaker than that of triethylamine and the steric hindrance is larger, it cannot undergo side reactions with the product of VC ring-opening, so it has no promoting effect on the side reactions of VC.

[0012] According to the first aspect of the present invention, the present invention provides a method for preparing an acid-binding agent, which is realized through the following steps:

[0013] (1) Acetophenone is oxidized to form p-acetylbenzoic acid;

[0014] (2) p-acetylbenzoic acid reacts with N,N-dimethylethanolamine or N,N-diethylethanolamine to form the acid-binding agent shown in Formula 1.

[0015] In step (1) of the present invention, acetophenone reacts with one selected from potassium permanganate, potassium chromate and other substances, and after the reaction, sulfuric acid or hydrochloric acid is used for neutralization to obtain p-acetylbenzoic acid; preferably, the reaction temperature is 90-200 °C, more preferably 120-170 °C.

[0016] In step (2) of the present invention, p-acetylbenzoic acid reacts with N,N-dimethylethanolamine and / or N,N-diethylethanolamine in a mixed system of xylene and sulfuric acid, and preferably the reaction temperature is 100-150 °C, more preferably 120-140 °C.

[0017] According to the preparation method of the present invention, CEC is mixed with a solvent and an inhibitor and preheated; the acid-binding agent is preheated; the two preheated materials are continuously fed into a reactive distillation device for reaction to generate VC; for the purpose of the present invention, to realize the reaction of generating VC and the separation of VC during the reactive distillation process, the requirements for the solvent are: first, the solvent should have good solubility for CEC; second, the solvent used should have good solubility for the generated hydrochloride salt to ensure that the reaction process is a homogeneous reaction without the generation of solids; third, the acid-binding agent used does not promote the polymerization side reaction of VC; fourth, the relative volatility of the solvent and VC should be large enough to ensure that the two substances can be well separated by distillation, and at the same time, the solvent should be a heavy component in the distillation column compared to VC and be discharged from the bottom of the column.

[0018] According to the above requirements, the solvent can be selected from acetophenone and / or halomethylacetophenone, and among them, halomethylacetophenone is preferably 2-fluoro-5-methylacetophenone, 4-chloro-3-methylacetophenone, 3-bromo-4-methylacetophenone and other substances.

[0019] The reactive distillation apparatus used in the present invention comprises a feed preheating system, a reactive distillation column, a reboiler at the bottom of the column, a condenser at the top of the column, and a vacuum system.

[0020] As a preferred embodiment, the preparation method of the present invention comprises the following steps:

[0021] The solvent is melted at 50 - 70°C, mixed with the CEC raw material and the polymerization inhibitor, and preheated to 40 - 100°C, preferably 60 - 80°C, as one feed stream.

[0022] The acid-binding agent is preheated to 40 - 100°C, preferably 60 - 80°C, as another feed stream.

[0023] The two feed streams are respectively fed into the upper middle part of the reactive distillation column.

[0024] The CEC raw material of the present invention comprises the following components: CEC content 30 wt% - 95 wt%, ethylene carbonate (EC) content 0.2 wt% - 70 wt%, dichloroethylene carbonate (DCEC) content 0.01 wt% - 10 wt%, and other component content 0.1 wt% - 8 wt%.

[0025] In the preparation method of the present invention, the mass ratio of the CEC raw material, the solvent, and the polymerization inhibitor is 1:0.1 - 10:0.005 - 0.2.

[0026] In the preparation method of the present invention, the molar ratio of the acid-binding agent to CEC in the CEC raw material is 1 - 1.5:1.

[0027] The reactive distillation column of the present invention is a common plate column or a packed column, preferably with 5 - 25 theoretical plates, and the preferred feed position is the 1st - 10th theoretical plate; the top reflux ratio is preferably 0.5:1 - 2:1.

[0028] The pressure of the reactive distillation column of the present invention is controlled by the vacuum system, preferably the top pressure is 100 - 2000 PaA, more preferably 200 - 1000 PaA; the total column pressure drop is preferably 100 - 2000 PaA, more preferably 300 - 800 PaA.

[0029] In the preparation method of the present invention, the reaction temperature is preferably 30 - 120°C, wherein the top temperature is preferably controlled at 30 - 80°C, and the bottom temperature is preferably controlled at 60 - 120°C.

[0030] In the preparation method of the present invention, in the reactive distillation column, CEC and the acid-binding agent undergo the reaction shown in the following formula to generate VC and hydrochloride. The generated VC belongs to the light components and goes to the condenser at the top of the column in the gas phase, and is condensed into a liquid-phase VC crude product with a purity ≥ 98%, which directly enters the subsequent melt crystallization process; the condensation temperature is preferably 12 - 25°C, more preferably 16 - 22°C.

[0031]

[0032] (R = Me(-CH3) or Et(-C2H5))

[0033] In the preparation method of the present invention, the generated hydrochloride is dissolved in a solvent, and is taken out from the bottom of the tower along with the solvent and the polymerization inhibitor. The hydrochloride is precipitated from the taken-out mixture by methods such as cooling crystallization to achieve the separation of the solvent and the hydrochloride. The solvent and the polymerization inhibitor can be recycled, and the hydrochloride enters the process for recovering the acid-binding agent.

[0034] The advantages and effects of the present invention are as follows: The method prepares VC by continuous reactive distillation, and has the advantages of being continuous, having a simple process, low equipment investment, and high product selectivity. Specifically, when using this method, the equipment investment for the separation and purification process of VC can be reduced by more than 40%, and the cost of VC is reduced by more than 20% compared with the existing traditional process. Detailed implementation manners

[0035] To better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples, and should also include any other well-known changes within the scope of the claims of the present invention.

[0036] The crude VC product is diluted with acetonitrile, and the product purity is measured using gas chromatography. The gas chromatography analysis conditions are as follows: Gas chromatography column: Innowax capillary column with a size of 0.25mm×0.25mm×30m; FID detector, vaporization chamber temperature 280°C, detector temperature 280°C, nitrogen carrier gas flow rate 1ml / min, hydrogen flow rate 50ml / min, air flow rate 400ml / min, injection volume 1μL. Analysis method: Area normalization method.

[0037] Example 1

[0038] This example provides a method for preparing the acid-binding agent shown in Formula 1, and the specific steps are as follows:

[0039] 1) Add 150 g of p-methylacetophenone and 50 ml of water into a 500-ml three-necked flask. Connect a condenser to the upper part of the three-necked flask and use normal-temperature circulating water for condensation. Heat the three-necked flask with an oil bath to 145 °C, and then add 135 ml of 10 mol / L potassium permanganate solution heated to 60 °C at a constant rate within 1 h. There is mechanical stirring in the flask to fully mix the solution until the solution in the flask is no longer stratified. Stop heating and stirring, filter the reaction solution under reduced pressure, put the obtained filtrate into a beaker with a jacket, and pass a 0 °C ethylene glycol aqueous solution into the jacket for cooling. After cooling to 5 °C, gradually add 201.5 g of 98% concentrated sulfuric acid, filter, wash the obtained solid with cold water, and then put it into a vacuum drying oven and perform vacuum drying at 50 °C and 10 KPaA to obtain p-acetylbenzoic acid;

[0040] 2) Add 100 g of the p-acetylbenzoic acid prepared in the first step into a 1000-ml three-necked flask, add 600 ml of p-xylene as a solvent, then add 54.7 g of N,N-dimethylethanolamine and 10 g of concentrated sulfuric acid, react at 120 °C until no p-acetylbenzoic acid is detected, cool the reaction solution to 30 °C, add 400 ml of dichloromethane, add sodium hydroxide to adjust the pH to 12, separate the phases and take the organic phase, and dry the dichloromethane to obtain the acid-binding agent shown in Formula 2.

[0041] Formula 2

[0042] Example 2

[0043] Obtain p-acetylbenzoic acid according to the first-step reaction in Example 1, and then add 100 g of p-acetylbenzoic acid into a 1000-ml three-necked flask, add 600 ml of p-xylene as a solvent, then add 72 g of N,N-diethylethanolamine and 10 g of concentrated sulfuric acid, react at 140 °C until no p-acetylbenzoic acid is detected, cool the reaction solution to 30 °C, add 400 ml of dichloromethane, add sodium hydroxide to adjust the pH to 12, separate the phases and take the organic phase, and dry the dichloromethane to obtain the acid-binding agent shown in Formula 3.

[0044] Formula 3

[0045] Application Example 1

[0046] A device for continuously preparing VC by reactive distillation: The device includes a solvation feed tank, a raw material mixer, an acid-binding agent feed tank, a reactive distillation column, a reboiler at the bottom of the column, a condenser at the top of the column, and a vacuum system.

[0047] The solvation tank is heated by hot water in the jacket. The temperature of the hot water is 65°C, and the temperature of the solvent after solvation is 60°C. The raw material mixer is heated by hot water in the jacket. The temperature of the hot water is 65°C, and the temperature of the mixed material is 60°C. The acid-binding agent feed tank is heated by hot water with a jacket. The temperature of the hot water is 65°C, and the temperature of the mixed material is 60°C.

[0048] The inner diameter of the rectification column is 2 cm, and the column height is 70 cm. It is a packed rectification column with 15 theoretical plates.

[0049] The condensation temperature of the top condenser of the column is 20°C.

[0050] A method for preparing VC using a continuous reactive distillation device includes the following steps:

[0051] (1) After dissolving p-methylacetophenone in the solvent tank, it is mixed with crude CEC and inhibitor BHT in the mixing feed tank. The CEC raw material, solvent, and BHT are fully mixed and preheated according to the mass ratio of 1:2:0.02, and then fed into the rectification column at a feeding rate of 2 g / min at the position of about the second plate.

[0052] The mass composition of the CEC raw material is as follows: CEC content 50%; EC content 48%; DCEC content 1%; other component content 1%.

[0053] The acid-binding agent shown in Formula 2 is fed into the rectification column at a feeding rate of 0.825 g / min at the position of about the second plate.

[0054] The pressure at the top of the rectification column is 300 PaA, the pressure drop across the whole column is 500 PaA, the temperature at the top of the rectification column is 35.5°C, and the temperature at the bottom of the rectification column is 100°C.

[0055] (2) The gaseous VC generated by the reaction enters the top condenser of the column and is condensed into a liquid. The reflux ratio at the top of the column is 1:1, and the solvent dissolved with hydrochloride at the bottom of the column enters the bottom receiving flask of the column.

[0056] Application Example 2

[0057] The difference between this application example and Application Example 1 is that in this application example, the solvent used in step (1) is changed to 2-fluoro-5-methylacetophenone. In addition, the control pressure at the top of the column is changed to 200 PaA, the temperature at the top of the column is 33°C, and the temperature at the bottom of the column is 97°C.

[0058] Application Example 3

[0059] The difference between this application example and Application Example 1 is as follows: In this application example, the solvent and acid-binding agent used in step (1) are changed. The solvent is replaced with 4-chloro-3-methylacetophenone, and the acid-binding agent is changed to the acid-binding agent shown in Formula 3; the composition of the CEC raw material is changed to 95% CEC content; 4.89% EC content; 0.01% DCEC content; 0.1% content of other components; the CEC raw material, solvent, and BHT are fed in a mass ratio of 1:10:0.2, and the feeding rate of the acid-binding agent is 0.55 g / min.

[0060] Application Example 4

[0061] The difference between this application example and Application Example 1 is as follows:

[0062] In this application example, the solvent and acid-binding agent used in step (1) are changed. The solvent is replaced with 3-bromo-4-methylacetophenone, and the acid-binding agent is changed to the acid-binding agent shown in Formula 3. The composition of the CEC raw material is changed to 28% CEC content; 70% EC content; 0.5% DCEC content; 1.5% content of other components; the CEC raw material, solvent, and BHT are fed in a mass ratio of 1:3:0.005 at a feeding rate of 4 g / min, and the feeding rate of the acid-binding agent is 0.726 g / min. The operating parameters of the distillation column are changed to: the pressure at the top of the distillation column is 1000 PaA, the pressure drop across the entire column is 500 PaA, the temperature at the top of the distillation column is [temperature value in °C], the temperature at the bottom of the distillation column is 120 °C, and the reflux ratio is adjusted to 2:1.

[0063] Application Example 5

[0064] The difference between this application example and Application Example 1 is as follows: In this application example, the acid-binding agent used in step (1) is changed. The acid-binding agent is changed to the acid-binding agent shown in Formula 3, and the feeding rate of the acid-binding agent is 0.921 g / min.

[0065] Comparative Example 1

[0066] This comparative example uses the traditional batch reactor method and device for preparing VC. The volume of the reaction kettle is 2 L. 1200 g of a mixed raw material of CEC raw material, dimethyl carbonate (solvent), and BHT is added to the reaction kettle. The composition of the CEC raw material and the ratio of the CEC raw material, solvent, and inhibitor are the same as those in Application Example 1. After preheating the reaction materials to 55 °C, 213.5 g of triethylamine is added dropwise to the reaction kettle within 2 h. After the dropping is completed, the reaction is terminated after holding at 55 °C for 3 h.

[0067] The reaction product is subjected to vacuum filtration to obtain a filtrate; the filtrate is distilled to remove the solvent at a distillation pressure of 8000 PaA and a bottom temperature of 60 °C; the material at the bottom of the distillation column is fed into the distillation column provided in Example 1 from approximately the second theoretical plate. The pressure at the top of the column is 300 PaA, the temperature at the top of the column is 36 °C, the temperature at the bottom of the column is 105 °C, the condensation temperature at the top of the column is 20 °C, and the reflux ratio is 1:1.

[0068] The VC content, VC selectivity and VC yield in the crude VC products prepared by the methods described in Application Examples 1-5 and Comparative Example 1 are shown in Table 1.

[0069] Table 1

[0070] VC content / % VC selectivity / % VC yield / % Tar selectivity / % Application Example 1 99 99 96.5 1 Application Example 2 98.5 98.9 96.4 1.1 Application Example 3 98.1 98.3 95.1 1.7 Application Example 4 98.0 98.0 94.3 2 Application Example 5 98.7 98.8 96.2 1.2 Comparative Example 1 7.2 73 55.3 27

[0071] In summary, the crude VC product with a purity of ≥98% can be directly obtained by the one-step reactive distillation process of the present invention, which has the advantages of continuous operation, simple process flow, low equipment investment, high product selectivity, etc., and greatly reduces the production cost.

[0072] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived within the technical scope disclosed by the present invention by those skilled in the art all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for continuously preparing vinylene carbonate, comprising the following steps: Using vinyl chloroformate as a raw material, using p-methylacetophenone and / or halomethylacetophenone as solvents, using the substance shown in Formula 1 as an acid-binding agent, and preparing vinylene carbonate by a continuous reactive distillation process; Formula 1 wherein R = Me or Et.

2. The method according to claim 1, wherein The preparation method of the acid-binding agent includes the following steps: (1) p-Methylacetophenone undergoes an oxidation reaction to form p-acetylbenzoic acid; (2) p-Acetylbenzoic acid and N,N-dimethylethanolamine or N,N-diethylethanolamine undergo esterification.

3. The method according to claim 2, wherein In the step (1), p-methylacetophenone reacts with one selected from potassium permanganate and potassium chromate, and after the reaction, it is neutralized with sulfuric acid or hydrochloric acid to obtain p-acetylbenzoic acid; preferably, the reaction temperature is 90-200 °C, more preferably 120-170 °C.

4. The method according to any one of claims 1-3, characterized in that In the step (2), p-acetylbenzoic acid and N,N-dimethylethanolamine and / or N,N-diethylethanolamine react in a mixed system of xylene and sulfuric acid, preferably at a reaction temperature of 100-150 °C, more preferably 120-140 °C.

5. The method according to any one of claims 1 to 4, characterized in that The solvent is selected from p-methylacetophenone and / or halomethylacetophenone, and among them, halomethylacetophenone is preferably 2-fluoro-5-methylacetophenone, 4-chloro-3-methylacetophenone, 3-bromo-4-methylacetophenone.

6. The method according to any one of claims 1-5, characterized in that, It includes the following steps: melting the solvent at 50-70 °C, mixing it with the CEC raw material and the inhibitor and preheating it to 40-100 °C, preferably 60-80 °C, as one feed; preheating the acid-binding agent to 40-100 °C, preferably 60-80 °C, as another feed; feeding the two feeds separately from the middle-upper part of the reactive distillation column.

7. The method according to any one of claims 1-6, characterized in that The CEC raw material contains the following components: CEC content is 30 wt% - 95 wt%, ethylene carbonate content is 0.2 wt% - 70 wt%, dichloro vinyl carbonate content is 0.01 wt% - 10 wt%, and the content of other components is 0.1 wt% - 8 wt%.

8. The method according to any one of claims 1 to 7, characterized in that The mass ratio of the CEC raw material, the solvent, and the inhibitor is 1:0.1 - 10:0.005 - 0.

2.

9. The method according to any one of claims 1-8, characterized in that The molar ratio of the acid-binding agent to CEC in the CEC raw material is 1 - 1.5:

1.

10. The method according to any one of claims 1-9, characterized in that, The reaction temperature is preferably 30-120 °C, wherein the top temperature of the column is 30-80 °C, and the bottom temperature of the column is 60-120 °C.

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