A method for preparing vinylene carbonate

Abstract

The application provides a preparation method of vinylene carbonate. The method comprises the following steps: 1, reacting chlorovinyl carbonate with an organic base in the presence of a water azeotropic solvent and a polymerization inhibitor; 2, after the reaction is completed, adding acid and water into the reaction system in sequence until neutral, and then standing and separating to obtain a first organic layer and a first water layer; 3, heating the first organic layer to reflux to remove water, and then rectifying to obtain the water azeotropic solvent and the vinylene carbonate; 4, extracting the first water layer with an organic solvent to separate into a second water layer and a second organic layer, adding alkali into the second water layer to neutralize, and then separating to obtain the organic base. The prepared vinylene carbonate has high yield and high purity, meanwhile, the organic base and the solvent used in the reaction process can be repeatedly used, the amount of waste is less, and the method is more green and environmentally friendly.

Description

Technical Field

[0001] This invention specifically relates to a method for preparing vinylene carbonate. Background Technology

[0002] Electrolyte is one of the four main raw materials of lithium-ion batteries, serving as the medium for lithium-ion migration and charge transfer. Electrolyte consists of electrolyte, solvent, and additives. Additives, while having a small mass percentage, have high unit value and can specifically optimize various electrolyte properties. Based on their working principles, additives can be categorized into solid electrolyte interphase (SEI) film-forming additives, flame retardant additives, high and low temperature additives, and overcharge protection additives. Vinylene carbonate (VC) is a common and highly effective SEI film-forming additive. In lithium batteries, VC undergoes a polymerization reaction on the negative electrode surface, forming a dense SEI film that prevents further reduction and decomposition of the electrolyte on the negative electrode surface. With the explosive growth in sales of new energy vehicles, the demand for lithium battery electrolyte additives has grown rapidly. In 2022, global vinylene carbonate production reached approximately 30,500 tons, a year-on-year increase of 90%, maintaining high-speed growth.

[0003] Currently, the mainstream route for the synthesis of vinylene carbonate, both domestically and internationally, is as follows: using triethylamine as an acid-binding agent, adding monochloroethylene carbonate in a certain solvent or solvent-free environment to carry out a hydrogen chloride elimination reaction to obtain the product. The reaction equation is as follows.

[0004]

[0005] However, the above method generates a large amount of triethylamine hydrochloride as a byproduct. Existing companies generally do not recycle triethylamine hydrochloride because triethylamine is miscible with water and forms an azeotrope, making it difficult to reduce the moisture content below the required limit during triethylamine recovery. Therefore, when using recycled triethylamine, vinylene carbonate undergoes significant decomposition, resulting in low product purity and yield, which does not meet the requirements for electrolyte use. The ammonia-containing triethylamine hydrochloride can only be treated as hazardous waste, which is neither economical nor environmentally friendly. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing vinylene carbonate, in which the organic base and reaction solvent can be recycled and reused, resulting in less waste and making it more economical and environmentally friendly.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing vinylene carbonate includes the following steps:

[0009] Step 1: React chloroethylene carbonate with an organic base in a solvent that azeotropically reacts with water and in the presence of a polymerization inhibitor;

[0010] Step 2: After the reaction is complete, add acid and water to the reaction system and wash until neutral. Let it stand to separate the layers to obtain the first organic layer and the first aqueous layer.

[0011] Step 3: Heat the first organic layer to reflux to remove water, and then distill to obtain the solvent that azeotropically reacts with water and vinylene carbonate;

[0012] Step 4: Extract the first aqueous layer with an organic solvent to obtain a second aqueous layer and a second organic layer. Add an alkali to the second aqueous layer to neutralize it, and then perform separation to obtain the organic alkali.

[0013] The organic base is immiscible with water and the difference between its boiling point and the solvent that azeotropically reacts with water is ≥30°C; the difference between the boiling point of the vinylene carbonate and the solvent that azeotropically reacts with water is ≥30°C.

[0014] This invention avoids the problem of water-immiscible organic bases forming an azeotropic reaction with the organic base during post-processing, which would hinder the removal of impurities and achieve the recycling of organic bases. By using a solvent that forms an azeotropic reaction with water and has a low boiling point, separation from the product is facilitated, and the residual water from post-processing is reduced, thus improving product purity and yield. Using this method, the organic base and solvent used in the reaction can be reused repeatedly, resulting in less waste, making it more environmentally friendly and economically efficient.

[0015] In this invention, unless otherwise specified, the immiscibility of organic bases with water means that the organic base is insoluble in water, that is, the solubility of the organic base is <0.05g / 100g water (20℃).

[0016] Preferably, the difference in boiling point between the organic base and the solvent that azeotropically reacts with water is ≥40°C.

[0017] More preferably, the difference in boiling point between the organic base and the solvent that azeotropically reacts with water is ≥45°C.

[0018] In some embodiments, the organic base is N,N-dimethylcyclohexylamine or 2,4,6-trimethylpyridine.

[0019] Preferably, the molar ratio of the chloroethylene carbonate to the organic base is 1:(1-1.2), more preferably 1:(1-1.1), for example 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04 or 1:1.05.

[0020] Preferably, the solvent that azeotropically reacts with water includes one or more of toluene, cyclohexane, dimethyl carbonate, diethyl carbonate, and benzene.

[0021] In some embodiments, the solvent azeotropic with water is cyclohexane.

[0022] In other embodiments, the solvent that azeotropically reacts with water is toluene.

[0023] Preferably, the mass ratio of the organic base to the solvent that azeotropically reacts with water is 1:(1-5), more preferably 1:(1-2), for example 1:1.3, 1:1.5, 1:1.8, 1:2.

[0024] Preferably, step 1 specifically includes:

[0025] Step 1.1: Mix the solvent that azeotropically reacts with water with the organic base, and reflux the mixture to remove water until the water content in the mixture is ≤1000ppm;

[0026] Step 1.2: Add the mixture containing the polymerization inhibitor and chloroethylene carbonate dropwise to the mixture in Step 1.1 to carry out the reaction.

[0027] When the reaction system contains water, it can easily lead to product decomposition, thereby affecting product purity and yield. By azeotropically removing water from the reaction raw materials, product purity and yield can be improved.

[0028] Preferably, the pressure of the reflux dewatering in step 1.1 or step 3 is normal pressure or negative pressure.

[0029] Preferably, the temperature of the reflux dewatering in step 1.1 or step 3 is 50-80°C, more preferably 60-80°C, and even more preferably 65-75°C.

[0030] Preferably, the organic base obtained in step 4 is used in the reaction of step 1.

[0031] Preferably, the solvent obtained in step 3 that azeotropically reacts with water is used in the reaction of step 1.

[0032] Preferably, the temperature of the droplet addition in step 1.2 is controlled to be 40-45°C.

[0033] Preferably, the reaction temperature is 50–70°C, more preferably 55–65°C.

[0034] Preferably, the polymerization inhibitor is one or more of hydroquinone, p-benzoquinone, and p-tert-butylcatechol.

[0035] Preferably, the mass ratio of the polymerization inhibitor to the chloroethylene carbonate is (0.1-3):100, more preferably (0.5-2):100, for example 0.5:100, 1:100, 1.5:100, 2:100.

[0036] Preferably, in step 2, the acid includes one or more of hydrochloric acid, sulfuric acid, and phosphoric acid.

[0037] More preferably, the concentration of the acid is 2-90%, and even more preferably 2-30%.

[0038] Preferably, in step 4, the organic solvent is selected from one or more of dichloromethane, ethyl acetate, methyl tert-butyl ether, toluene, and cyclohexane.

[0039] Preferably, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate.

[0040] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0041] The method of this invention produces vinylene carbonate with high yield and high purity. At the same time, the organic base and solvent used in the reaction process can be reused repeatedly, resulting in less waste, making it more environmentally friendly and economically efficient, and suitable for large-scale production. Detailed Implementation

[0042] Existing technologies typically use triethylamine as an acid-binding agent to react with chloroethylene carbonate to produce vinylene carbonate. However, this method suffers from the problem of difficult triethylamine recovery. Other researchers have prepared vinylene carbonate by reacting high-boiling-point organic amines with chloroethylene carbonate under reduced pressure. This method, however, is inconvenient to operate, produces low-purity products, and generates organic amine hydrochloride solid waste. The method of this invention yields vinylene carbonate with high yield and high purity. Furthermore, the organic base and solvent used in the reaction process can be reused, making it more environmentally friendly. The following further discusses the scheme of this invention.

[0043] This invention provides a method for preparing vinylene carbonate, comprising the following steps:

[0044] Step 1: React chloroethylene carbonate with an organic base in a solvent that azeotropically reacts with water and in the presence of a polymerization inhibitor;

[0045] Step 2: After the reaction is complete, add acid and water to the reaction system and wash until neutral. Let it stand to separate the layers to obtain the first organic layer and the first aqueous layer.

[0046] Step 3: Heat the first organic layer to reflux to remove water, and then distill to obtain the solvent that azeotropically reacts with water and vinylene carbonate;

[0047] Step 4: Extract the first aqueous layer with an organic solvent to obtain a second aqueous layer and a second organic layer. Add an alkali to the second aqueous layer to neutralize it, and then perform separation to obtain the organic alkali.

[0048] The organic base is immiscible with water and the difference between its boiling point and the solvent that azeotropically reacts with water is ≥30°C; the difference between the boiling point of the vinylene carbonate and the solvent that azeotropically reacts with water is ≥30°C.

[0049] In some preferred embodiments, the method for preparing vinylene carbonate includes the following steps:

[0050] Step 1.1 Mix the solvent that azeotropically reacts with water with N,N-dimethylcyclohexylamine, and reflux the mixture to remove water until the water content in the mixture is ≤1000ppm;

[0051] Step 1.2: The mixture containing the polymerization inhibitor and ethylene chloride carbonate is added dropwise to the mixture in Step 1.1 to carry out the reaction. The reaction equation is as follows:

[0052]

[0053] Step 2: After the reaction is complete, add acid and water to the reaction system and wash until neutral. Let it stand to separate the layers to obtain the first organic layer and the first aqueous layer.

[0054] Step 3: Heat the first organic layer to reflux to remove water, and then distill to obtain a solvent that azeotropically reacts with water and vinylene carbonate. The solvent that azeotropically reacts with water can be used in step 1.1.

[0055] Step 4: Extract the first aqueous layer with an organic solvent to obtain a second aqueous layer and a second organic layer. Add alkali to the second aqueous layer to neutralize it, and then perform separation to obtain N,N-dimethylcyclohexylamine. This N,N-dimethylcyclohexylamine can be applied to step 1.1.

[0056] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0057] Unless otherwise specified, room temperature in this invention refers to "25±5℃".

[0058] Unless otherwise specified, the raw materials used in the following examples and comparative examples are commercially available products.

[0059] Example 1

[0060] Add N,N-dimethylcyclohexylamine (95.34 g, 0.75 mol, 1.02 eq) and cyclohexane (150 g) to a 500 mL three-necked flask, heat to 69 °C, and reflux to remove water. After reflux for 2 hours (when the purity of N,N-dimethylcyclohexylamine and cyclohexane is ≥99% and the water content is less than or equal to 0.1%, the reflux water removal step can be omitted; when using recycled N,N-dimethylcyclohexylamine and / or cyclohexane, or when the purity of N,N-dimethylcyclohexylamine and / or cyclohexane is <95%), the reflux water removal step can be omitted. If the moisture content is greater than 0.1%, a reflux dehydration step is required to reduce the system moisture content to less than or equal to 1000 ppm. Cool the system to 40°C and slowly add a mixture containing a polymerization inhibitor (specifically hydroquinone) and ethylene monochlorocarbonate (CAS No.: 3967-54-2, 90% purity, 100g, 0.73mol) (where the polymerization inhibitor accounts for 1% of the total mass of the mixture). After the addition is complete, raise the temperature to 60°C and keep it at that temperature for 3 hours. After the reaction is complete, cool the system to room temperature and add 50g of 2% dilute hydrochloric acid and 50g of water twice to wash until neutral. Allow the mixture to stand and separate into layers.

[0061] The organic layer was heated to reflux for 2 hours, and then distilled to obtain cyclohexane and vinylene carbonate. The cyclohexane was reused, and the vinylene carbonate had a purity of 99.99% and a yield of 85%.

[0062] The acidic aqueous layer was extracted with cyclohexane and separated into two layers. The aqueous layer was neutralized with sodium hydroxide (32g, pH=12-13). The separation yielded N,N-dimethylcyclohexylamine with a purity of 97%, which can be reused.

[0063] The following further verifies the impact of the number of times N,N-dimethylcyclohexylamine is used on product purity, yield, etc. The relevant data are shown in Table 1.

[0064] Table 1

[0065] 1-1 0 85％ 97％ 99.99％ 1-2 1 84％ 96％ 99.99％ 1-3 2 82％ 95％ 99.99％ 1-4 3 83％ 96％ 99.99％ 1-5 4 83％ 97％ 99.99％ 1-6 5 84％ 96％ 99.99％ 1-7 6 83％ 96％ 99.99％ 1-8 7 84％ 97％ 99.99％ 1-9 8 84％ 96％ 99.99％

[0066] Note: Serial number 1-1 in Table 1 is Example 1. Serial numbers 1-2 to 1-9 are roughly the same as Example 1, except that the N,N-dimethylcyclohexylamine used is recycled N,N-dimethylcyclohexylamine.

[0067] As can be seen from Table 1, when using cyclohexane as a solvent, the yield and purity of vinylene carbonate and the purity of N,N-dimethylcyclohexylamine remain basically unchanged during the reuse of N,N-dimethylcyclohexylamine. This indicates that the product prepared by the method of the present invention has both high yield and high purity, and N,N-dimethylcyclohexylamine can be reused repeatedly, resulting in better economic benefits and a more environmentally friendly approach.

[0068] Example 2

[0069] Add N,N-dimethylcyclohexylamine (95.34 g, 0.75 mol, 1.02 eq) and toluene (150 g) to a 500 mL three-necked flask. Heat to 75 °C under negative pressure and reflux to remove water. After reflux for 2 hours (when the purity of N,N-dimethylcyclohexylamine and toluene is ≥99% and the water content is less than or equal to 0.1%, the reflux step can be omitted; when using recycled N,N-dimethylcyclohexylamine and / or toluene, or N,N-dimethylcyclohexylamine and / or toluene...), When the purity is low (<95%) or the moisture content is greater than 0.1%, a reflux dehydration step is required to reduce the moisture content of the system to less than or equal to 1000 ppm. Cool the system to 40°C and slowly add a mixture containing a polymerization inhibitor (specifically p-tert-butylcatechol) and ethylene monochlorocarbonate (90% purity, 100g, 0.73mol) (where the polymerization inhibitor accounts for 1% of the total mass of the mixture). After the addition is complete, raise the temperature to 60°C and keep it at that temperature for 3 hours. After the reaction is complete, cool the system to room temperature and add 50g of 2% dilute hydrochloric acid and 50g of water twice to wash until neutral. Allow the mixture to stand and separate into layers.

[0070] The organic layer was heated under reflux for 2 hours to remove water, and then distilled to obtain toluene and vinylene carbonate. The toluene was reused, and the purity of the vinylene carbonate was 99.99%, with a yield of 83%.

[0071] The acidic aqueous layer was extracted twice with dichloromethane. Sodium hydroxide (32g, pH=12-13) was added to the aqueous layer to neutralize it. The resulting N,N-dimethylcyclohexylamine was obtained with a purity of 97%, which can be reused.

[0072] The following further verified the effect of N,N-dimethylcyclohexylamine, and the relevant data are shown in Table 2.

[0073] Table 2

[0074] 2-1 0 83％ 97％ 99.99％ 2-2 1 84％ 97％ 99.99％ 2-3 2 85％ 96％ 99.99％ 2-4 3 84％ 96％ 99.99％ 2-5 4 83％ 97％ 99.99％ 2-6 5 83％ 96％ 99.99％ 2-7 6 84％ 96％ 99.99％ 2-8 7 84％ 97％ 99.99％ 2-9 8 83％ 96％ 99.99％

[0075] Note: Serial number 2-1 in Table 2 is Example 2. Serial numbers 2-2 to 2-9 are roughly the same as Example 2, except that the N,N-dimethylcyclohexylamine used is recycled N,N-dimethylcyclohexylamine.

[0076] As can be seen from Table 2, when using toluene as a solvent, the yield and purity of vinylene carbonate and the purity of N,N-dimethylcyclohexylamine remain basically unchanged during the reuse of N,N-dimethylcyclohexylamine. This indicates that the product prepared by the method of the present invention has both high yield and high purity, and N,N-dimethylcyclohexylamine can be reused repeatedly, resulting in better economic benefits and a more environmentally friendly approach.

[0077] Comparative Example 1

[0078] Add N,N-dimethylaniline (90.89 g, 0.75 mol, 1.02 eq) and toluene (150 g) to a 500 mL three-necked flask. Heat to 75 °C under negative pressure and reflux to remove water. After reflux for 2 hours (the water content of the system is less than 1000 ppm), cool to 40 °C and slowly add a mixture containing a polymerization inhibitor (specifically hydroquinone) and ethylene monochlorocarbonate (90% purity, 100 g, 0.73 mol) (where the polymerization inhibitor accounts for 1% of the total mass of the mixture). After the addition is complete, raise the temperature to 60 °C and keep it at that temperature for 3 hours. After the reaction is complete, cool to room temperature and add 50 g of 2% dilute hydrochloric acid and 50 g × 2 g of water to wash until neutral. Let stand to separate the layers.

[0079] The organic layer was heated under reflux for 2 hours to remove water, and then distilled to obtain toluene and vinylene carbonate. The toluene was reused, and the purity of the vinylene carbonate was 99.99%, with a yield of 42%.

[0080] Comparative Example 2

[0081] N,N-dimethylaniline (90.89 g, 0.75 mol, 1.02 eq) and toluene (150 g) were added to a 500 mL three-necked flask. The mixture was heated to 75 °C under negative pressure and refluxed to remove water. After refluxing for 2 hours (the water content of the system was less than 1000 ppm), the temperature was lowered to 40 °C, and a mixture containing a polymerization inhibitor (specifically hydroquinone) and ethylene monochlorocarbonate (90% purity, 100 g, 0.73 mol) was slowly added dropwise (the polymerization inhibitor accounted for 1% of the total mass of the mixture). After the addition was completed, the temperature was raised to 60 °C and maintained for 3 hours. After the reaction was completed, toluene and vinylene carbonate were obtained by distillation. The toluene was reused, and the purity of the vinylene carbonate was 96.5%, with a yield of 46%.

[0082] Comparative Example 3

[0083] N,N-dimethylcyclohexylamine (95.34 g, 0.75 mol, 1.02 eq) and toluene (150 g) were added to a 500 mL three-necked flask. The mixture was heated to 75 °C under negative pressure and refluxed to remove water. After refluxing for 2 hours (the water content of the system was less than 1000 ppm), the temperature was lowered to 40 °C, and ethylene carbonate monochlorocarbonate (90% purity, 100 g, 0.73 mol) containing 1% polymerization inhibitor was slowly added dropwise. After the addition was completed, the temperature was raised to 60 °C and maintained for 3 hours. After the reaction was completed, toluene and vinylene carbonate were obtained by distillation. The toluene was reused, and the purity of vinylene carbonate was 95.7%, with a yield of 79%.

[0084] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be covered within the scope of protection of the invention.

Claims

1. A method for producing vinylene carbonate, characterized by, The preparation method includes the following steps: Step 1: React chloroethylene carbonate with an organic base in a solvent that azeotropically reacts with water and in the presence of a polymerization inhibitor; Step 2: After the reaction is complete, add acid and water to the reaction system and wash until neutral. Let it stand to separate the layers to obtain the first organic layer and the first aqueous layer. Step 3: Heat the first organic layer to reflux to remove water, and then distill to obtain the solvent that azeotropically reacts with water and vinylene carbonate. Use the obtained solvent that azeotropically reacts with water in the reaction of step 1. Step 4: Extract the first aqueous layer with an organic solvent to obtain a second aqueous layer and a second organic layer. Add an alkali to the second aqueous layer to neutralize it, and then separate the layers to obtain the organic base. Use the obtained organic base in the reaction of step 1. The organic base is immiscible with water and the difference between its boiling point and the solvent that azeotropically interacts with water is ≥30°C; the difference between the boiling point of the vinylene carbonate and the solvent that azeotropically interacts with water is ≥30°C.

2. The preparation method according to claim 1, characterized in that, The organic base is N,N-dimethylcyclohexylamine or 2,4,6-trimethylpyridine.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of the chloroethylene carbonate to the organic base is 1:(1~1.2).

4. The preparation method according to claim 1, characterized in that, The solvent that azeotropically reacts with water includes one or more of toluene, cyclohexane, dimethyl carbonate, diethyl carbonate, and benzene.

5. The preparation method according to claim 1 or 4, characterized in that, The mass ratio of the organic base to the solvent that azeotropically reacts with water is 1:(1~5).

6. The preparation method according to claim 1, characterized in that, Step 1 specifically includes: Step 1.1: Mix the solvent that azeotropically reacts with water with the organic base, and reflux the mixture to remove water until the water content in the mixture is ≤1000ppm; Step 1.2: Add the mixture containing the polymerization inhibitor and chloroethylene carbonate dropwise to the mixture in Step 1.1 to carry out the reaction.

7. The preparation method according to claim 6, characterized in that, The temperature of the dripping is controlled to be 40~45℃.

8. The preparation method according to claim 1, characterized in that, The reaction temperature is 50~70℃.

9. The preparation method according to claim 1, characterized in that, The polymerization inhibitor is one or more of hydroquinone, p-benzoquinone, and p-tert-butylcatechol; and / or The mass ratio of the polymerization inhibitor to the chloroethylene carbonate is (0.1~3):

100.

10. The preparation method according to claim 1, characterized in that, In step 2, the acid includes one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; and / or, In step 4, the organic solvent is selected from one or more of dichloromethane, ethyl acetate, methyl tert-butyl ether, toluene, and cyclohexane; and / or, In step 4, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate.

Images