A method for preparing vinylene carbonate

Abstract

The present application relates to the field of lithium ion battery electrolyte additives, and particularly relates to a preparation method of an organic film-forming additive, vinylene carbonate. The method comprises the following steps: under the atmosphere of inert gas, (Z)-1,2-dihydroxy ethylene is reacted with a urea derivative under the action of a composite catalyst in a dry organic solvent at 20-100 DEG C for 3-24 hours to generate a crude vinylene carbonate product; then the organic solvent is removed by vacuum distillation in low vacuum, and high-purity vinylene carbonate is obtained by vacuum distillation in high vacuum. The technical scheme of the present application is simple in process, strong in operability, and more safe and environmentally friendly; since the raw material does not contain chlorine, the requirement for equipment is low, no toxic and harmful waste gas and waste solid are generated, and the production cost can be greatly reduced; no water is involved in the reaction process, and the composite catalyst added can also remove the trace water in the solvent and the raw material, which can effectively avoid the hydrolysis of vinylene carbonate, so as to improve the yield, purity and quality of the product, and reduce the moisture content of the product.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrolyte additive preparation technology, specifically to a method for preparing an organic film-forming additive—ethylene carbonate. Background Technology

[0002] Vinylene carbonate (VC), also known as vinyl carbonate, is a colorless, transparent liquid with a melting point of 19-22°C and a boiling point of 162°C at normal pressure. It is an organic synthesis intermediate and, due to its low viscosity and high dielectric constant, is widely used in lithium-ion battery electrolytes as a crucial organic film-forming additive and overcharge protection additive. Its addition to electrolytes can significantly improve the cycle life of lithium-ion batteries. It can also be used as a surface coating component or as a monomer for the preparation of polyvinyl carbonate, showing promising market prospects.

[0003] Currently, the mainstream preparation methods for vinylene carbonate are largely the same. Using ethylene carbonate (EC) as a raw material, EC is first reacted with chlorine (Cl2) under light to undergo a chlorination reaction, yielding a monochloroethylene carbonate intermediate (ClEC). This monochloroethylene carbonate then reacts with an organic amine in an organic reagent, undergoing an elimination reaction to obtain crude vinylene carbonate. Further purification yields the high-purity product. However, this method not only involves the relatively hazardous gas chlorine as a raw material but also generates large amounts of hydrogen chloride waste gas and triethylamine hydrochloride waste, making safety and environmental assessments quite stringent. The reaction equation is as follows:

[0004]

[0005] For example, Chinese invention patent CN106699720A discloses a method for synthesizing vinylene carbonate: Dry chlorine gas is reacted with vinylene carbonate under ultraviolet light to undergo a chlorination reaction to obtain chloroethylene carbonate; the chloroethylene carbonate is dissolved in an organic solvent and reacted with an organic amine (such as triethylamine, ethanolamine, isopropanolamine, diethylenetriamine, formamide, or acetamide) at 0-5°C under the action of a catalyst. After approximately 1-5 hours of reaction, crude VC product is obtained, which is then filtered and freeze-dried. Although the process described in this patent uses a specific catalyst to lower the reaction temperature, prevent product self-polymerization, and improve product yield and purity, the use of chlorine gas as a raw material is still unavoidable. This results in a large solvent consumption and the generation of large amounts of hydrogen chloride waste gas and triethylamine hydrochloride waste, which can corrode equipment and require treatment of these production wastes, significantly increasing production costs.

[0006] In the industry, some methods for preparing vitamin C products have been modified to overcome the aforementioned technical shortcomings. For example, Chinese invention patent CN111393403A discloses a method involving the reaction of 1,2-dibromoethylene with basic carbonates (such as sodium carbonate and potassium carbonate) in water, and in the presence of alkali metal halide salts (such as sodium bromide and potassium bromide) and phase transfer catalysts (such as polyethylene glycol 600, tetrabutylammonium bromide TBAB, and benzyltriethylammonium chloride) to produce vinylene carbonate. However, the method described in this patent involves the introduction of water during the reaction, which causes the vinylene carbonate product to hydrolyze, resulting in low product yield and purity, making it unsuitable for industrial production. The reaction equation is as follows:

[0007]

[0008] Chinese invention patent CN200810223674.2 discloses a method for synthesizing chloroethylene carbonate from ethylene carbonate and sulfuryl chloride as raw materials, using diisopropyl peroxide as an initiator, at a relatively low reaction temperature; chloroethylene carbonate reacts with organic amines in an organic reagent in the presence of a composite antioxidant to undergo an elimination reaction to obtain vinylene carbonate. However, the scheme described in this patent uses batch operation, has a low product yield, and is relatively cumbersome, making it unsuitable for continuous production.

[0009] In summary, existing methods for preparing vinylene carbonate either involve toxic and highly corrosive oxidant chlorine, generating large amounts of toxic and harmful waste gases and solids, resulting in high production costs and equipment wear; or introduce water into the reaction system, reducing product purity and yield. Therefore, providing a method for preparing high-purity vinylene carbonate with a simple reaction process, high operability, and suitability for industrial production is a problem that engineers in this field urgently need to solve. Summary of the Invention

[0010] In view of the problems existing in the above-mentioned synthesis process of vinylene carbonate, the purpose of this invention is to provide a safer, more environmentally friendly, more operable, higher yield, lower moisture content and more suitable for industrial production method of preparing vinylene carbonate.

[0011] The preparation method mainly includes: under an inert gas atmosphere, (Z)-1,2-dihydroxyethylene (also known as (Z)-vinyl-1,2-diol) and urea derivative react in a dried organic solvent under the catalysis of a composite catalyst to produce crude vinylene carbonate; then, the organic solvent is removed by vacuum distillation in a low vacuum (5000-50000 Pa), and high-purity vinylene carbonate product is obtained by vacuum distillation in a high vacuum (≤1000 Pa).

[0012] In the above scheme, the structure of the urea derivative is as follows:

[0013] Wherein, R1, R2, R3, and R4 are each independently a straight-chain hydrocarbon group (preferably a straight-chain alkyl group) or H. When it is a straight-chain hydrocarbon group, the number of C atoms in the straight-chain hydrocarbon group is k, 1≤k≤5, and k is an integer, preferably 1≤k≤3.

[0014] R5 and R6 are each independently a branched hydrocarbon group (preferably a branched alkyl group) or a cyclic hydrocarbon group.

[0015] When it is a branched hydrocarbon group, the number of C atoms in the branched hydrocarbon group is m, where 3≤m≤5, and m is an integer.

[0016] When the group is a cyclic hydrocarbon group (preferably cycloalkyl or aromatic (monocyclic or bicyclic)), the number of skeleton atoms of the cyclic group is n, where 5 ≤ n ≤ 10, and n is an integer, preferably 5 ≤ n ≤ 6.

[0017] In (Z)-1,2-dihydroxyethylene, the carbon atoms directly bonded to the two hydroxyl groups are unsaturated and sp2-hybridized. The OH bond energy of the hydroxyl groups attached to sp2-hybridized carbon atoms is relatively greater than that of the OH bonds of hydroxyl groups attached to sp3-hybridized carbon atoms (such as ethylene glycol), resulting in a larger energy barrier to be overcome during the reaction. Typically, (Z)-1,2-dihydroxyethylene and urea derivatives are difficult to react directly and require the addition of specific reaction accelerants.

[0018] In this preparation method, all reactions are carried out in an inert gas atmosphere, and the inert gas used is one or a mixture of two or more of nitrogen, argon and helium;

[0019] In this preparation method, the molar ratio of the raw material (Z)-1,2-dihydroxyethylene to the urea derivative is 1:(1-10), preferably 1:(1-2);

[0020] In this preparation method, the organic solvents used include one or more of the following: aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, esters, ketones, and acetonitrile. Preferred ethers: diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol ethyl ether, methyl tert-butyl ether, tetrahydrofuran, dimethyl tetrahydrofuran, 1,4-dioxane; preferred esters: ethyl acetate, methyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate; preferred aromatic hydrocarbons: benzene, toluene, xylene; preferred aliphatic hydrocarbons: n-hexane, n-heptane, isooctane, pentane; preferred alicyclic hydrocarbons: cyclohexane, cyclopentane, cycloheptane; preferred halogenated hydrocarbons: chloromethane, dichloromethane, carbon tetrachloride, chloroform, dichloroethane, trichloroethane, tetrachloroethane, trichloroethylene, trichlorotrifluoroethane, bromoethane; preferred ketones: acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone. The volume (mL) of organic solvent used is 5-20 times the mass (g) of raw material (Z)-1,2-dihydroxyethylene.

[0021] In this preparation method, the catalyst used is a composite catalyst of sodium alkoxide (R-ONa) and anhydrous basic carbonate (M2CO3). The sodium alkoxide is one of sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, and sodium tert-butoxide, preferably sodium methoxide or sodium ethoxide. These sodium alkoxides are sensitive to moisture and can remove trace amounts of moisture in the raw materials and solvents by reacting with water, effectively preventing the hydrolysis of vinylene carbonate products, reducing the moisture content in the product, and improving the yield and quality. The anhydrous basic carbonate (M2CO3) is one of anhydrous lithium carbonate, anhydrous sodium carbonate, and anhydrous potassium carbonate, preferably anhydrous potassium carbonate.

[0022] In the composite catalyst used in this preparation method, the mass ratio of sodium alkoxide (R-ONa) to anhydrous basic carbonate (M2CO3) is 1:1-10, preferably 1:4-8.

[0023] In this preparation method, the mass ratio of the composite catalyst to the raw material (Z)-1,2-dihydroxyethylene is 1:(10-500).

[0024] In this preparation method, the reaction temperature is 20℃-100℃, preferably 40℃-60℃. The reaction time is 3-24h, preferably 4-8h.

[0025] Compared with the prior art, the technical solution of this application has the following advantages and beneficial effects:

[0026] 1. This preparation method is simple, highly operable, and safer and more environmentally friendly. Since the raw materials do not contain toxic or highly corrosive gases such as chlorine, the equipment requirements are lower, which can significantly reduce production costs.

[0027] 2. This preparation method produces no toxic or harmful waste gases or solid waste, which can greatly reduce production costs. Its byproducts are very mature chemical products that, after purification, can be sold as high-value-added chemicals.

[0028] 3. This preparation method involves no water throughout the entire process, and the added composite catalyst can also remove trace amounts of water from the solvent / raw materials, effectively preventing the hydrolysis of vinylene carbonate, reducing the moisture content of the product, and improving the product yield, purity, and quality. In this preparation method, the product purity can reach 99.5% or higher after high-vacuum distillation. For products requiring higher purity, further operations such as freeze crystallization can be performed after vacuum distillation. The product yield after high-vacuum distillation is ≥80%. Attached Figure Description

[0029] Figure 1 This is a gas chromatogram of the high-purity vinylene carbonate obtained in Example 1. Detailed Implementation

[0030] To make the purpose and content of this invention clearer, the applicant will now describe the invention in further detail with reference to the embodiments and accompanying drawings. However, the scope of protection of this invention is not limited to these embodiments.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0032] The organic solvents used in the following examples were dried before use as follows: 4A molecular sieves were dried at a high temperature of 400-450°C, then added to the organic solvent to be dried, stored for more than 24 hours to remove water, and then filtered to obtain the dried solvent.

[0033] Example 1: Under an argon atmosphere and at 50°C in an oil bath, a 300ml solution of ethyl acetate containing 50g of (Z)-1,2-dihydroxyethylene was slowly added dropwise to a container containing 213.6g of tetraethylurea (Ethylene(Z)-1,2-dihydroxyethylene) over a period of 50 minutes. Bailingwei Technology, product number: 493291, purity: 99% (GC), composite catalyst (1.5g anhydrous potassium carbonate + 0.5g sodium methoxide), and 500ml ethyl acetate (the ethyl acetate in this example was dried using 4A molecular sieves) were added dropwise to a 2L four-necked round-bottom flask with magnetic stirring and condensation. After the addition was complete, the mixture was heated and stirred at 45°C for 1 hour, then heated to 55°C and stirred for another 4 hours to obtain a reaction solution containing crude vinylene carbonate. Under a low vacuum of 11000-12000Pa, the solvent ethyl acetate was removed by vacuum distillation at 40°C. Then, the temperature was increased to 60-65°C, and vacuum distillation was performed under a high vacuum of 200-400Pa. The distillate was collected to obtain high-purity vinylene carbonate. Gas chromatography (GC) analysis showed a product purity of 99.95%, a yield of 82.6%, and a water content of 12ppm. The GC chromatogram is shown below. Figure 1 The peak at 6.5 min in the figure is the peak of high-purity vinylene carbonate product.

[0034] In this GC spectrum, the peak at 6.5 min represents the high-purity vinylene carbonate product. The smaller peaks at 3.4 min, 13.4 min, and 13.8 min are impurity peaks in the high-purity vitamin C product. The impurity content is extremely low, but the vitamin C content in the product is relatively high. To more intuitively display the peak times and peak areas of all components in the sample, the complete peaks of the vitamin C product are difficult to observe.

[0035] It should also be noted that the black vertical line at 13.8min is the mouse cursor in the GC system, not an impurity peak.

[0036] Example 2: Under an argon atmosphere, 50 g of (Z)-1,2-dihydroxyethylene and 300.1 g of 1-(naphthyl-2-yl)-3-phenylurea were added to a 2 L four-necked flask. CAS: 6299-42-9, Leyan Reagent - Shanghai Haohong Biomedical Technology Co., Ltd., Product No.: 1312607, Purity: 97%), composite catalyst (1.25g anhydrous sodium carbonate + 0.96g sodium tert-butoxide), and 800ml of dimethyl carbonate dried using 4A molecular sieves. The reaction system was heated and stirred at 55℃ and kept under reflux for approximately 6 hours to obtain a reaction solution containing crude vinylene carbonate. Under a low vacuum of 7000-8000Pa, the solvent dimethyl carbonate was removed by vacuum distillation at 40℃. Then, the temperature was increased to 60℃, and vacuum distillation was performed under a high vacuum of 100-350Pa. The distillate was collected to obtain a high-purity vinylene carbonate product. GC analysis showed a product purity of 99.86%, a yield of 84.5%, and a water content of 8ppm.

[0037] Example 3: Under a nitrogen atmosphere, 50 g of (Z)-1,2-dihydroxyethylene and 271.3 g of 1,3-dibutylurea were added to a 2 L four-necked flask. Aladdin (product number: D113393, purity: 98%), a composite catalyst (3.1g anhydrous lithium carbonate + 1.5g sodium propoxide), and 1000ml of diethyl carbonate dried using 4A molecular sieves were reacted. The reaction system was heated and stirred at 60°C and kept under reflux for approximately 6 hours to obtain a reaction solution containing crude vinylene carbonate. Under a low vacuum of 7000-9000 Pa, the solvent diethyl carbonate was removed by vacuum distillation at 40°C. The temperature was then increased to 60°C, and vacuum distillation was performed under a high vacuum of 100-400 Pa. The distillate was collected to obtain a high-purity vinylene carbonate product. GC analysis showed a product purity of 99.81%, a yield of 82.5%, and a water content of 21 ppm.

[0038] Example 4: Under an argon atmosphere, 50 g of (Z)-1,2-dihydroxyethylene and 361.2 g of 1,3-diisopropylurea were added to a 2 L four-necked flask. Leyan Reagent - Shanghai Haohong Biomedical Technology Co., Ltd., Product No.: 1299540, Purity: 97%), composite catalyst (2.7g anhydrous potassium carbonate + 1.2g sodium ethoxide), and 900ml of tetrahydrofuran dried with 4A molecular sieve. The reaction system was heated and stirred at 50℃ and kept under reflux for 4 hours to obtain a reaction solution containing crude vinylene carbonate. Under a low vacuum of 5000-6000Pa, the solvent tetrahydrofuran was removed by vacuum distillation at 35-40℃. Then, the temperature was increased to 60℃, and vacuum distillation was performed under a high vacuum of 150-400Pa. The distillate was collected to obtain high-purity vinylene carbonate. GC analysis showed a product purity of 99.75%, a yield of 82.1%, and a water content of 18ppm.

[0039] Example 5: Under a nitrogen atmosphere, 50 g of (Z)-1,2-dihydroxyethylene and 294.6 g of 1,3-diphenylurea were added to a 2 L four-necked flask. The reaction mixture consisted of Maclean (product number: N806997, purity: 98%), a composite catalyst (2.7g anhydrous potassium carbonate + 2.0g sodium methoxide), and 1000ml of methyl tert-butyl ether dried using 4A molecular sieves. The reaction system was heated and stirred at 50°C and refluxed for 8 hours to obtain a reaction solution containing crude vinylene carbonate. The solvent methyl tert-butyl ether was removed by vacuum distillation at 35-38°C under a low vacuum of 5000-6000Pa. The temperature was then increased to 60°C, and vacuum distillation was performed under a high vacuum of 100-500Pa. The distillate was collected to obtain high-purity vinylene carbonate. GC analysis showed a purity of 99.69%, a yield of 83.2%, and a water content of 9ppm.

[0040] Example 6: Under a nitrogen atmosphere, 50 g of (Z)-1,2-dihydroxyethylene and 304.7 g of 1,3-dicyclopentylurea were added to a 2 L four-necked flask. Jiangsu Aikon Biopharmaceutical R&D Co., Ltd., product number: 679661, purity: 95%), composite catalyst (2.1g anhydrous potassium carbonate + 1.6g sodium methoxide), and 950ml of acetonitrile dried using 4A molecular sieves. The reaction system was heated and stirred at 55℃ and kept under reflux for 8 hours to obtain a reaction solution containing crude vinylene carbonate. The solvent acetonitrile was removed by vacuum distillation at 40-45℃ under a low vacuum of 5500-7000Pa. Then, the temperature was increased to 60℃, and vacuum distillation was performed under a high vacuum of 100-500Pa. The distillate was collected to obtain high-purity vinylene carbonate product. GC analysis showed a product purity of 99.87%, a yield of 84.7%, and a water content of 8ppm.

[0041] The sample addition method in Example 1 differs from that in Examples 2, 3, 4, 5, and 6 because: in organic chemical reactions, if one reactant is in excess, adding the reactant in smaller quantities to the reactant in larger quantities will make the reaction more stable and increase the yield.

Claims

1. A method for preparing vinylene carbonate, characterized in that, Includes the following steps: In an inert gas atmosphere, (Z)-1,2-dihydroxyethylene is reacted with... At 40–60°C, in a dry organic solvent and under the action of a composite catalyst, the reaction proceeds for 4–8 hours to produce crude vinylene carbonate. Then, the organic solvent is removed by vacuum distillation under a low vacuum of 5000–50000 Pa, and high-purity vinylene carbonate is obtained by vacuum distillation under a high vacuum of ≤1000 Pa. In this configuration, R1, R2, R3, and R4 are each independently a straight-chain alkyl group or H, and R1, R2, R3, and R4 are not simultaneously H. When it is a straight-chain alkyl group, the number of C atoms in the straight-chain alkyl group is k, where 1≤k≤5, and k is an integer. R5 and R6 are each independently a branched alkyl or cyclic hydrocarbon group, wherein the cyclic hydrocarbon group is a cycloalkyl or aromatic group, and the aromatic group is monocyclic or bicyclic. When it is a branched alkyl group, the number of C atoms of the branched alkyl group is m, where 3≤m≤5, and m is an integer. When it is a cyclic hydrocarbon group, the number of skeleton atoms of the cyclic group is n, where 5≤n≤10, and n is an integer; The composite catalyst is a mixture of sodium alkoxide and anhydrous carbonate; wherein the sodium alkoxide is one of sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, and sodium tert-butoxide, and the anhydrous carbonate is one of anhydrous lithium carbonate, anhydrous sodium carbonate, and anhydrous potassium carbonate.

2. The preparation method according to claim 1, characterized in that, 1≤k≤3。 3. The preparation method according to claim 1, characterized in that, 5≤n≤6。 4. The preparation method according to claim 1, characterized in that, The sodium alkoxide is sodium methoxide or sodium ethoxide.

5. The preparation method according to claim 1, characterized in that, The anhydrous carbonate is anhydrous potassium carbonate.

6. The preparation method according to claim 1, characterized in that, The organic solvent is one or more of the following: aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, esters, ketones, and acetonitrile.

7. The preparation method according to claim 6, characterized in that, The aromatic hydrocarbon is one of benzene, toluene, and xylene; The aliphatic hydrocarbon is one of n-hexane, n-heptane, isooctane, and pentane; The alicyclic hydrocarbon is one of cyclohexane, cyclopentane, and cycloheptane; The halogenated hydrocarbons are one of the following: chloromethane, dichloromethane, carbon tetrachloride, chloroform, dichloroethane, trichloroethane, tetrachloroethane, trichloroethylene, trichlorotrifluoroethane, and bromoethane; The ether is one of the following: diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol ethyl ether, methyl tert-butyl ether, tetrahydrofuran, dimethyl tetrahydrofuran, and 1,4-dioxane; The ester is one of ethyl acetate, methyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. The ketone is one of acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone.

8. The preparation method according to claim 1, characterized in that, The inert gas is one or more of nitrogen, argon, and helium.

9. The preparation method according to claim 1, characterized in that, The (Z)-1,2-dihydroxyethylene and The molar ratio is 1:1-10.

10. The preparation method according to claim 9, characterized in that, The (Z)-1,2-dihydroxyethylene and The molar ratio is 1:1-2.

11. The preparation method according to claim 1, characterized in that, The mass ratio of the composite catalyst to (Z)-1,2-dihydroxyethylene is 1:10-500.

12. The preparation method according to claim 1, characterized in that, The mass ratio of sodium alkoxide to anhydrous carbonate in the composite catalyst is 1:1-10.

13. The preparation method according to claim 1, characterized in that, The ratio of the organic solvent to (Z)-1,2-dihydroxyethylene is (5-20) mL:1 g.

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