Preparation method of dipicolinic acid anhydride solution

Abstract

The invention discloses a preparation method of a dipicolinic acid anhydride solution, which comprises the following steps: 1, adding acetic anhydride into a reaction kettle, heating, adding dipicolinic acid, mixing, and further heating for reaction; 2, after the reaction is finished, acetic anhydride and acetic acid are recycled in a distillation mode; and 3, the reaction liquid without acetic anhydride and acetic acid is subjected to vacuum rectification, the obtained fraction flows into a receiving kettle in a gaseous state during rectification, the receiving kettle is filled with a solvent capable of dissolving dipicolinic acid anhydride, the mass of the distilled material is determined through a weighing method, and the mass fraction of the product in the solution is 10-15%. The method has the advantages that the process route is simple, the steps are few, the acetic anhydride is convenient and environment-friendly to reuse, the production cost is effectively reduced, and the product purity is high and can reach 99% or above. And the solution is low in water content and more convenient to use, and meets the requirements of additives of lithium ion battery electrolytes.

Description

Technical Field

[0001] The present invention relates to a preparation method of an additive for lithium battery electrolyte, and specifically to a preparation method of a pyridine dicarboxylic anhydride solution. Background Art

[0002] The electrolyte system, which is an important part of lithium-ion batteries, is constantly evolving. In order to continuously improve the performance of lithium-ion batteries, extensive research has been carried out on both electrolyte lithium salts and new organic solvents or electrolyte additives. Since electrolyte additives can have a significant impact on battery performance, they have received extensive attention.

[0003] Additives containing six-membered heterocyclic carboxylic anhydrides can form a film on the surface of the positive electrode, that is, form a positive electrode interface film with excellent lithium-ion conductivity, block the deterioration reaction of the electrolyte on the surface of the positive electrode under high voltage conditions, inhibit the continuous generation of gas during battery cycling, reduce battery swelling, and inhibit electrolyte decomposition, thereby greatly extending the service life of lithium-ion batteries.

[0004] Since six-membered heterocyclic carboxylic anhydrides are prone to hydrolysis, have a high melting point, and are prone to color change when heated, they are not easy to use. Therefore, the present invention aims to provide a preparation method of a pyridine dicarboxylic anhydride solution. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a pyridine dicarboxylic anhydride solution. The process route of this method is simple, and the prepared pyridine dicarboxylic anhydride solution is not only convenient for storage but also convenient for use.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of a pyridine dicarboxylic anhydride solution, comprising the following steps: First, acetic anhydride is put into a reaction kettle, and after heating up, pyridine dicarboxylic acid is added. After mixing, the temperature is further raised for reaction; Second, after the reaction is completed, acetic anhydride and acetic acid are recovered by distillation; Third, the reaction solution after removing acetic anhydride and acetic acid is subjected to vacuum rectification. During rectification, the obtained fraction flows into the receiving kettle in a gaseous state. The receiving kettle is filled with a solvent that can dissolve pyridine dicarboxylic anhydride. The mass of the distilled material is determined by the weighing method, and the mass fraction of the product in the solution is 10 - 15%; The structure of pyridine dicarboxylic anhydride is as follows: ; wherein R1, R2, and R3 are methyl or H.

[0007] Further, in the aforementioned preparation method of a pyridine dicarboxylic anhydride solution, in step one, the temperature is raised to 80°C ± 5°C, and then pyridine dicarboxylic acid is added. After mixing, the temperature is further raised to 130°C ± 5°C for reaction.

[0008] Further, in the aforesaid method for preparing a pyridine dicarboxylic anhydride solution, in step one, the molar ratio of acetic anhydride to pyridine dicarboxylic acid is 2.5 - 3:1.

[0009] Further, in the aforesaid method for preparing a pyridine dicarboxylic anhydride solution, in step two, when acetic anhydride and acetic acid are separated, the content of acetic anhydride in the kettle material is above 80%, and the kettle material is used for the synthesis in step one.

[0010] Further, in the aforesaid method for preparing a pyridine dicarboxylic anhydride solution, in step three, during rectification, the temperature of the fractionation head is controlled at 110 - 160°C, the temperature of the condenser is controlled at 110 - 160°C, and the temperature of the distillation tail pipe is controlled at 140 - 200°C. The rectification equipment generally includes a rectification column, a fractionation head, a condenser, and a distillation tail pipe connected in sequence. The setting of the above temperatures ensures that the gaseous fraction discharged from the distillation tail pipe enters the receiving kettle.

[0011] Further, in the aforesaid method for preparing a pyridine dicarboxylic anhydride solution, in step three, the solvent is any one of dimethyl carbonate with a certain number of carbon atoms, diethyl carbonate with a certain number of carbon atoms, and methyl ethyl carbonate with a certain number of carbon atoms, and the water content in the solvent is ≤ 10 ppm.

[0012] Further, in the aforesaid method for preparing a pyridine dicarboxylic anhydride solution, in step three, methyl ethyl carbonate is selected as the solvent.

[0013] The advantages of the present invention are: the process route is simple, with fewer steps; the recycling of acetic anhydride is convenient and environmentally friendly, effectively reducing the production cost; the product purity is high, reaching over 99%; the water content in the solution is low, making the solution more convenient to use, and meeting the requirements of the additive for the lithium-ion battery electrolyte. Embodiment

[0014] The following is a detailed description of the method for preparing a solution of pyridine dicarboxylic anhydride through specific examples.

[0015] Example 1: First, 255 g of acetic anhydride was put in and heated to 80°C, then 167 g of 3,4-pyridine dicarboxylic acid was put in and the mixture was heated to 130°C and reacted for 2 h. Under a vacuum of -0.08 Mpa, acetic anhydride and acetic acid were recovered until the temperature reached 90°C, and then the vacuum was switched to -0.1 Mpa to continue the recovery. A total of 260 g of the acetic anhydride and acetic acid mixture was recovered. Acetic anhydride and acetic acid were separated by atmospheric rectification. After 130 g of acetic acid was distilled out, the content of acetic anhydride in the kettle material reached 82% and could be directly used for product synthesis.

[0016] The concentrated solution from which acetic anhydride and acetic acid have been removed is rectified under -0.1 mpa. During rectification, the fractionating head is heated to 110 °C, the condenser to 110 °C, and the distillation tail pipe to 140 °C. The fractions flow into the receiving kettle in gaseous state. The receiving kettle contains 1000 g of ethyl methyl carbonate (water content ≤ 10 ppm). By the weighing method, the mass of the distilled material is determined to be 134 g, with a purity of 99.4% and a yield of 90%.

[0017] Product structure: ;

[0018] 3,4-Pyridinedicarboxylic anhydride / ethyl methyl carbonate solution, with a mass fraction of 11.82%, and the water content measured by a moisture meter is 3 ppm.

[0019] Example 2: First, 255 g of acetic anhydride is added and the temperature is raised to about 80 °C, then 209 g of 2,5,6-trimethyl-3,4-pyridinedicarboxylic acid is added. After mixing, the temperature is raised to 130 °C and the reaction proceeds for 2 h. Acetic anhydride is recovered under a vacuum of -0.08 Mpa until the temperature reaches 90 °C, and then -0.1 mpa is switched to continue recovering acetic anhydride and acetic acid. A total of 261 g of the acetic anhydride and acetic acid mixture is recovered. Acetic anhydride and acetic acid are separated by atmospheric rectification. After 135 g of acetic acid is distilled off, the acetic anhydride content in the kettle material reaches 84% and can be directly used for product synthesis.

[0020] The concentrated solution from which acetic anhydride and acetic acid have been removed is rectified under -0.1 mpa. During rectification, the fractionating head is heated to 120 °C, the condenser to 120 °C, and the distillation tail pipe to 170 °C. The fractions flow into the receiving kettle in gaseous state. The receiving kettle contains 1000 g of diethyl carbonate (water content ≤ 10 ppm). By the weighing method, the mass of the distilled material is determined to be 168 g, with a purity of 99.3% and a yield of 88%.

[0021] Product structure: ; 2,5,6-Trimethyl-3,4-pyridinedicarboxylic anhydride / diethyl carbonate solution, with a mass fraction of 14.38%, and the water content measured by a moisture meter is 8 ppm.

[0022] Example 3: First, 306 g of acetic anhydride is added and the temperature is raised to about 80 °C, then 195 g of 2,5-dimethyl-3,4-pyridinedicarboxylic acid is added. After mixing, the temperature is raised to 130 °C and the reaction proceeds for 2 h. Acetic acid and acetic anhydride are recovered under a vacuum of -0.08 Mpa until the temperature reaches 90 °C, and then -0.1 mpa is switched to continue recovering acetic anhydride. A total of 305 g of the acetic anhydride and acetic acid mixture is recovered. Acetic anhydride and acetic acid are separated by atmospheric rectification. After 150 g of acetic acid is distilled off, the acetic anhydride content in the kettle material reaches 82% and can be directly used for product synthesis.

[0023] The concentrated solution removing acetic anhydride and acetic acid is rectified under -0.1 mpa. During rectification, the fractionation head is heated to 150 °C, the condenser to 150 °C, and the distillation tail pipe to 200 °C. The fraction flows into the receiving kettle in gaseous state. The receiving kettle contains 1000 g of dimethyl carbonate (water content ≤ 10 ppm). The mass of the distilled material is determined by the weighing method to be 159 g, with a purity of 99.6% and a yield of 90%.

[0024] Product structure: ; 2,5-Dimethyl-3,4-pyridinedicarboxylic anhydride / dimethyl carbonate solution, with a mass fraction of 13.72%, and the water content is determined by a moisture meter to be 5 ppm.

[0025] Example 4: First, 306 g of acetic anhydride is added and the temperature is raised to about 80 °C, then 195 g of 2,6-dimethyl-3,4-pyridinedicarboxylic acid is added. After mixing, the temperature is raised to 130 °C and the reaction proceeds for 2 h. Acetic anhydride and acetic acid are recovered under a vacuum of -0.08 Mpa until the temperature reaches 90 °C, and then -0.1 mpa is switched to continue recovering acetic anhydride and acetic acid. A total of 304 g of the acetic anhydride and acetic acid mixture is recovered. Acetic anhydride and acetic acid are separated by atmospheric rectification. After 151 g is distilled off, the acetic anhydride content in the kettle material reaches 83% and can be directly used for product synthesis.

[0026] The concentrated solution removing acetic anhydride and acetic acid is rectified under -0.1 mpa. During rectification, the fractionation head is heated to 160 °C, the condenser to 160 °C, and the distillation tail pipe to 190 °C, so that the obtained fraction flows into the receiving kettle in gaseous state. The receiving kettle contains 1000 g of diethyl carbonate (water content ≤ 10 ppm). The mass of the distilled material is determined by the weighing method to be 161 g, with a purity of 99.4% and a yield of 91%.

[0027] Product structure: ; 2,6-Dimethyl-3,4-pyridinedicarboxylic anhydride / diethyl carbonate solution, with a mass fraction of (13.87)%, and the water content is determined by a moisture meter to be 5 ppm.

[0028] Example 5: First, 255 g of acetic anhydride is added and the temperature is raised to about 80 °C, then 181 g of 2-methyl-3,4-pyridinedicarboxylic acid is added. After mixing, the temperature is raised to 130 °C and the reaction proceeds for 2 h. Acetic anhydride and acetic acid are recovered under a vacuum of -0.08 Mpa until the temperature reaches 90 °C, and then -0.1 mpa is switched to continue recovering acetic anhydride and acetic acid. A total of 260 g of the acetic anhydride and acetic acid mixture is recovered. Acetic anhydride and acetic acid are separated by atmospheric rectification. After 125 g is distilled off, the acetic anhydride content in the kettle material reaches 82% and can be directly used for product synthesis.

[0029] The concentrated solution from which acetic anhydride and acetic acid have been removed is rectified at -0.1 mpa. During rectification, the fractionation head is heated to 160 °C, the condenser to 160 °C, and the distillation tail pipe to 200 °C, so that the obtained fraction flows into the receiving kettle in a gaseous state. The receiving kettle contains 1000 g of ethyl methyl carbonate (water content ≤ 10 ppm). The mass of the distilled material is determined by the weighing method to be 145 g, with a purity of 99.5% and a yield of 89%.

[0030] Product structure: ; 2-Methyl-3,4-pyridinedicarboxylic anhydride / diethyl carbonate solution, with a mass fraction of 12.66%, and the water content measured by a moisture meter is 8 ppm.

[0031] The advantages of the present invention obtained from the above embodiments are as follows: The process route is simple, with few steps. The recycling of acetic anhydride is convenient and environmentally friendly, effectively reducing production costs. The product has a high purity, reaching over 99%. The water content in the solution is low, making the solution more convenient to use, meeting the requirements of additives for lithium-ion battery electrolytes.

Claims

1. A method for preparing a pyridine dicarboxylic anhydride solution, comprising the following steps: I. Put acetic anhydride into a reaction kettle, heat it up, and then put pyridine dicarboxylic acid. After mixing, further heat it up for reaction; II. After the reaction is completed, recover acetic anhydride and acetic acid by distillation; III. Subject the reaction solution from which acetic anhydride and acetic acid have been removed to vacuum rectification. During rectification, the obtained fraction flows into a receiving kettle in a gaseous state. The receiving kettle is filled with a solvent capable of dissolving pyridine dicarboxylic anhydride. Determine the mass of the distilled material by the weighing method, and the mass fraction of the product in the solution is 10-15%; The structure of pyridine dianhydride is as follows: , wherein R1, R2, and R3 are methyl or H.

2. The preparation method of a pyridine dicarboxylic anhydride solution according to claim 1, characterized in that: In step I, heat it up to 80°C ± 5°C and then put pyridine dicarboxylic acid. After mixing, further heat it up to 130°C ± 5°C for reaction.

3. The preparation method of a pyridine dicarboxylic anhydride solution according to claim 1, characterized in that: In step I, the molar ratio of acetic anhydride to pyridine dicarboxylic acid is 2.5-3:

1.

4. A method for preparing a pyridine dicarboxylic anhydride solution according to claim 1, characterized in that: In step II, when acetic anhydride and acetic acid are separated, the content of acetic anhydride in the kettle material is above 80%, and the kettle material is used for the synthesis in step I.

5. A method for preparing a pyridine dicarboxylic anhydride solution according to claim 1, characterized in that: In step III, during rectification, the temperature of the fractionation head is controlled at 110-160°C, the temperature of the condenser is controlled at 110-160°C, and the temperature of the distillation tail pipe is controlled at 140-200°C.

6. The preparation method of a pyridine dicarboxylic anhydride solution according to claim 1, characterized in that: In step III, the solvent is any one of dimethyl carbonate with a certain number of carbon atoms, diethyl carbonate with a certain number of carbon atoms, and methyl ethyl carbonate with a certain number of carbon atoms, and the water content of the solvent is ≤ 10 ppm.

7. A method for preparing a pyridine dicarboxylic anhydride solution according to claim 6, characterized in that: In step III, the solvent is selected as methyl ethyl carbonate.

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