A process and system for quasi-continuous production of vinylene carbonate

Abstract

The present application aims to overcome the shortcomings of the existing intermittent production process, and provides a vinylene carbonate quasi-continuous production process and integrated system with mild reaction conditions, easy control, high production efficiency, good product purity, and efficient recycling of triethylamine. The technology is briefly described as follows: a certain amount of TEA is introduced into the reaction kettle, CEC and TEA are introduced into the reaction kettle according to a certain proportion, the reaction temperature is controlled at 20-45 degrees, the reaction time is 10-16 hours, after the reaction is completed, the mixed liquid is introduced into a three-in-one device for filtration, washing and primary drying, the obtained filtrate and washing liquid are introduced into subsequent rectification and crystallization processes for purification, the filter residue is transported into a secondary dryer through a pipe chain, and the dried triethylamine hydrochloride is introduced into a triethylamine recovery process.

Description

Technical Field

[0001] This invention belongs to the field of organic electrochemical materials and fine chemical technology, specifically relating to a method for producing vinylene carbonate (VC), an additive for lithium-ion battery electrolytes. In particular, it relates to an improved method for preparing VC using chloroethylene carbonate (CEC) and triethylamine (TEA) as raw materials through a quasi-continuous process, and for achieving efficient recovery of the byproduct triethylamine hydrochloride. Background Technology

[0002] Vinylene carbonate (VC) is an important electrolyte film-forming additive in lithium-ion batteries. It can form a stable and dense solid electrolyte interphase (SEI) film on the negative electrode surface, effectively improving the battery's cycle performance, high-temperature storage performance, and rate performance.

[0003] Currently, the mainstream industrial production method for vitamin C typically involves the dehydrochlorination reaction of ethylene chloride carbonate (CEC) with triethylamine (TEA). Traditional processes are mostly batch reactor operations, which have the following significant drawbacks: 1. Low production efficiency: The reaction, filtration, washing, and drying processes are all completed in a single reactor or batch equipment, resulting in long auxiliary times and limited capacity, making it unsuitable for large-scale continuous production needs.

[0004] 2. Inaccurate reaction control: The heat release of intermittent reactions is concentrated, and the reaction temperature (usually carried out at a high temperature, such as >50℃) and reaction time are not easy to control precisely, which may lead to an increase in side reactions (such as further reaction of TEA and VC, VC polymerization, etc.), affecting product yield and purity.

[0005] 3. Complex material separation and post-processing: The reaction product is a viscous mixture containing a large amount of tar, VC, TEA·HCl, excess TEA, etc., which is difficult to filter. The mother liquor and washing liquid contain solvent, raw materials and products, and the recovery process is lengthy and energy-intensive.

[0006] Therefore, developing a VC production process that can achieve high efficiency, stability, quasi-continuous operation, and efficient recovery of triethylamine is of great significance for reducing production costs, improving product quality, and reducing environmental pollution. Summary of the Invention

[0007] (a) Purpose of the invention The present invention aims to overcome the shortcomings of existing batch production processes and provide a quasi-continuous production process and integrated system for vinylene carbonate with mild reaction conditions, easy control, high production efficiency, good product purity, and efficient recycling of triethylamine.

[0008] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a process for producing vinylene carbonate, characterized by comprising the following steps: S1. Amination and dehydrogenation reaction: In the reactor, an appropriate amount of triethylamine (TEA) is added beforehand as the starting medium and acid-binding agent. Then, vinyl chloride carbonate (CEC) and triethylamine (TEA) are continuously or batch-wise introduced into the reactor at a molar ratio of (1:0.2~1:1.3). The reaction temperature is controlled at 20~45℃ and the reaction time is 10~16 hours to carry out the dehydrochlorination reaction, producing vinylene carbonate (VC) and triethylamine hydrochloride (TEA·HCl). S2. Primary Solid-Liquid Separation: After the reaction is complete, the reaction mixture containing VC, excess TEA, TEA·HCl solid, and possible impurities is transported to a three-in-one device (filtration, washing, and drying integrated machine), where the following operations are performed sequentially: a) Filtration: Separate the reaction mother liquor (mainly containing VC and TEA) from the solid TEA·HCl; b) Washing: The filter cake (TEA·HCl) is washed with an inert organic solvent (such as dimethyl carbonate, ethyl acetate, dichloromethane, MTBE, etc.) to replace and recover the VC and TEA entrained therein; c) Initial drying: The washed TEA·HCl filter cake is initially dried at a low temperature (e.g., 30-60℃) and under reduced pressure to remove most of the solvent; S3. Product purification: Combine the filtrate obtained in step S2 a) and the washing liquid obtained in step b), and send them to the subsequent purification process. They will undergo distillation and crystallization operations in sequence to obtain high-purity vinylene carbonate (VC) product. S4. Byproduct treatment and recovery: The preliminarily dried TEA·HCl filter residue obtained in step S2c) is conveyed to the secondary dryer for deep drying through a closed tubular chain conveyor. The deep-dried anhydrous TEA·HCl enters the triethylamine recovery process, where triethylamine is recovered through alkaline hydrolysis and returned to step S1 for recycling.

[0009] Preferably, in step S1, the reaction temperature is preferably 25~40℃, and the reaction time is preferably 12~15 hours. The molar ratio of CEC to TEA is preferably 1:0.5~1:1.15.

[0010] Preferably, in step S1, the reactor is equipped with a high-efficiency stirring and heat exchange system to precisely control the reaction temperature within the mild range and suppress side reactions.

[0011] Preferably, in step S2, the "three-in-one" device is a filter, wash and dry integrated machine, preferably a cylindrical or tank-type "three-in-one".

[0012] Preferably, in the washing step of step S2, the inert organic solvent is dimethyl carbonate (DMC) because it has good solubility in VC and is easy to separate in subsequent purification.

[0013] Preferably, in step S4, the secondary dryer is a double-cone rotary vacuum dryer, a rake dryer, or a ribbon dryer. The deep drying temperature is controlled at 80~120℃, and the vacuum degree is controlled at above -0.08MPa to ensure that TEA·HCl is fully dried.

[0014] Preferably, the triethylamine recovery process in step S4 includes reacting the dried TEA·HCl with a strong alkali (such as sodium hydroxide or potassium hydroxide) solution and distilling to recover TEA; or using a thermal decomposition method to heat and decompose TEA·HCl under an inert atmosphere and condense to recover TEA.

[0015] Secondly, the present invention provides a vinylene carbonate production system for implementing the above-described process, characterized in that it comprises: • Reaction unit: includes at least one reaction vessel with stirring and temperature control, and is equipped with feed lines for CEC and TEA; • Primary separation and purification unit: includes a "three-in-one" device (filtration, washing and drying integrated machine), whose inlet is connected to the outlet of the reaction vessel through a pipeline; • Product refining unit: includes a distillation column and a crystallizer connected in sequence, wherein the feed line of the distillation column is connected to the mother liquor and washing liquid outlets of the “three-in-one” equipment; • By-product processing unit: includes a tubular chain conveyor, a secondary dryer, and a triethylamine recovery device; the feed end of the tubular chain conveyor is connected to the solid discharge port of the "three-in-one" equipment, and the discharge end is connected to the feed port of the secondary dryer; the discharge port of the secondary dryer is connected to the feed port of the triethylamine recovery device; • Solvent and material recycling unit: The TEA outlet of the triethylamine recovery unit is connected to the TEA feed line of the reaction unit; the solvent separated by the distillation column and crystallizer can be returned to the washing step for recycling.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages: 1. Continuous / quasi-continuous process with high efficiency: By adopting a "three-in-one" equipment, the filtration, washing and initial drying of the mixture after reaction are integrated into a continuous operation, and the solid materials are transferred in a closed manner using a tubular chain conveyor, making the entire process more continuous and compact, significantly shortening the production cycle, and improving equipment capacity and automation level.

[0017] 2. Mild and controllable reaction conditions, resulting in high product quality: By strictly controlling the reaction temperature within a low range of 20~45℃, side reactions caused by local overheating (such as the addition of TEA to VC, VC polymerization, etc.) are effectively suppressed, thereby improving reaction selectivity and the purity and yield of the VC product.

[0018] 3. High separation efficiency and full material recovery: The "three-in-one" equipment completes multiple operations within the same unit, reducing material transfer losses and exposure risks. Solvent washing of the filter cake fully recovers the high-value vitamin C and TEA entrained within, improving raw material utilization.

[0019] 4. High efficiency and good recycling of triethylamine: The innovative "preliminary drying (three-in-one internal) + deep drying (secondary dryer) + tubular chain conveyor" path ensures that TEA·HCl is thoroughly dried, creating conditions for subsequent efficient TEA recovery (alkali hydrolysis or thermal decomposition). The recovered TEA has high purity and can be stably recycled, significantly reducing production costs and waste salt emissions.

[0020] 5. Significant safety and environmental advantages: Material transfer throughout the entire process is mainly accomplished through pumps and closed tubular chain conveyors, reducing manual operation and material exposure, and lowering safety risks. The closed-loop recovery of triethylamine reduces the generation of "three wastes" (waste gas, wastewater, and solid waste), which is more in line with green chemical engineering requirements. Attached Figure Description

[0021] Fig. 1 This is a process flow diagram of the vinylene carbonate production process described in this invention.

[0022] Appendix Fig. 2 Schematic diagram of core equipment structure of VC production system Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto. Example

[0024] Reference Figs. 1-2 The system and method of this invention are used to produce VC: 1. Reaction: 500 kg of triethylamine was pre-added to a 5000 L jacketed reactor with an anchor stirrer. The stirring and cooling system was started, and the reactor temperature was controlled at 25 ± 2 °C. CEC and supplementary TEA were continuously and stably pumped into the reactor via a metering pump at a CEC: TEA ratio of 1:0.8 (molar ratio), with the total feeding time controlled at 8 hours. After feeding was completed, the reaction was continued at this temperature for 6 hours, for a total reaction time of 14 hours.

[0025] 2. Primary Separation: The reaction solution was transferred entirely to an 8000L cylindrical "three-in-one" equipment via a diaphragm pump. First, pressure filtration was performed to separate the mother liquor (mainly containing vitamin C, excess TEA, and solvent). Then, the filter cake (TEA·HCl) was washed three times with 1000 kg of dimethyl carbonate (DMC). After washing, the filter cake was initially dried for 2 hours at -0.095 MPa and 50℃.

[0026] 3. Product Purification: The mother liquor and washing liquid from step 2 are combined and first passed through a distillation column to recover excess TEA and DMC (which are then returned to the system for reuse). Crude VC is obtained from the bottom of the column. The crude VC is then fed into a crystallizer and cooled for crystallization to obtain high-purity VC crystals. HPLC analysis shows a purity ≥99.995% and a yield (based on CEC) of 75.5%.

[0027] 4. Byproduct Recovery: The TEA·HCl filter cake, after preliminary drying of the "three-in-one" process, is fed into a double-cone rotary vacuum dryer via a closed tubular chain conveyor and deeply dried at 100℃ and -0.098 MPa for 4 hours. The dried anhydrous TEA·HCl is then reacted with 30% NaOH solution, and distilled to recover triethylamine with a purity ≥99.0%, with a recovery rate ≥90%, which is then returned to the reaction step for reuse.

[0028] Comparative example (traditional batch process) The reaction was carried out in a batch reactor of the same size at a temperature of 55-65℃ for 8 hours. After the reaction, the material was transferred to a centrifuge for filtration, and the filter cake was manually discharged to a drying tray, then transferred to a dryer for further drying. Subsequent purification steps were similar. The final product had a VC purity of approximately 99.99%, a yield of approximately 60%, and a TEA recovery rate of approximately 85%. However, the production cycle was long, the operation was complex, and solvent consumption was high.

[0029] The above embodiments demonstrate that the present invention, through mild reaction conditions, integrated separation equipment, and continuous material handling, significantly improves production efficiency and triethylamine recovery efficiency while ensuring high product purity and yield, thus exhibiting significant industrial advantages.

Claims

1. A process for preparing vinylene carbonate, characterized in that, Includes the following steps: S1. Amination and dehydrogenation reaction: Vinyl chlorocarbonate and triethylamine are introduced into a reactor pre-added with TEA at a molar ratio of 1:0 to 1:1.

3. The amount of TEA pre-added is 20% to 100% of the total TEA feed. The reaction is carried out at 20 to 45°C for 8 to 16 hours to produce a reaction mixture containing vinylene carbonate and triethylamine hydrochloride. S2. Primary solid-liquid separation: The reaction mixture obtained in S1 is filtered, washed and preliminarily dried in a "three-in-one" device to obtain filtrate, washing liquid and preliminarily dried triethylamine hydrochloride filter residue; S3. Product purification: The filtrate and washing liquid obtained in S2 are subjected to distillation and crystallization to obtain vinylene carbonate product; S4. Byproduct Treatment and Recovery: The preliminarily dried triethylamine hydrochloride filter residue obtained in S2 is conveyed to a secondary dryer via a tubular chain conveyor for further drying. The further dried triethylamine hydrochloride is then recovered to obtain triethylamine.

2. The process according to claim 1, characterized in that, In step S1, the reaction temperature is 25~35℃ and the reaction time is 8~12 hours; the molar ratio of chloroethylene carbonate to triethylamine is 1:0.5~1:1.15, and the amount of triethylamine added first is 30%~50% of the total amount of triethylamine added.

3. The process according to claim 1, characterized in that, In step S2, the solvent used for washing is one of dimethyl carbonate, ethyl acetate, methyl tert-butyl ether, or dichloromethane.

4. The process according to claim 1, characterized in that, In step S2, the "three-in-one" equipment is a filter, wash and dry integrated machine; the preliminary drying is carried out at 30-60℃ and under reduced pressure.

5. The process according to claim 1, characterized in that, In step S4, the operating conditions of the secondary dryer are: temperature 80~120℃, vacuum degree not lower than -0.08 MPa.

6. The process according to claim 1, characterized in that, In step S4, the recovery treatment of the triethylamine hydrochloride is carried out by alkaline hydrolysis or thermal decomposition.

7. A production system for implementing the process according to any one of claims 1-6, characterized in that, include: The reaction unit includes at least one reaction vessel; The primary separation and purification unit is a "three-in-one" device, with its inlet connected to the outlet of the reaction vessel; The product refining unit includes a distillation column and a crystallizer connected in sequence, with its inlet connected to the liquid outlet of the "three-in-one" equipment; the by-product processing unit includes a tubular chain conveyor, a secondary dryer, and a triethylamine recovery device connected in sequence via pipelines; the inlet of the tubular chain conveyor is connected to the solid outlet of the "three-in-one" equipment.

8. The system according to claim 7, characterized in that, It also includes a material circulation pipeline, wherein the triethylamine outlet of the triethylamine recovery device is connected to the triethylamine feed pipeline of the reaction unit.

9. The system according to claim 7 or 8, characterized in that, The "three-in-one" equipment is a drum or tank-type filtration, washing, and drying integrated machine.

10. A vinylene carbonate prepared by the process described in any one of claims 1-6, characterized in that, The purity of the vinylene carbonate is not less than 99.995%.

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