A preparation method of tris(lithium methanetrisulfonate) with high purity

Abstract

The present invention discloses a preparation method of high-purity tris(lithium methanetrisulfonate), and the preparation method successively includes: A1. a step of reacting acetic anhydride and sulfur trioxide in a first solvent to obtain methanetrisulfonic acid; A2. a step of reacting the methanetrisulfonic acid and lithium hydroxide in water to obtain a crude product of tris(lithium methanetrisulfonate); A3. a step of recrystallizing the crude product of tris(lithium methanetrisulfonate) with a second solvent to obtain high-purity tris(lithium methanetrisulfonate). The present invention has the advantages of simple process, convenient operation, high product purity, etc.

Description

Technical Field

[0001] The present invention relates to the field of electrolyte additives, and specifically relates to a method for preparing high-purity tris(lithium methanesulfonate). Background Art

[0002] As a new type of electrolyte additive, tris(lithium methanesulfonate) has the effect of inhibiting gas generation, which helps to improve the performance of normal temperature cycling, high temperature storage, and high temperature cycling. However, there is no relevant report on the synthesis of tris(lithium methanesulfonate), and only the synthesis of methanesulfonic acid is known. At present, the synthesis methods of methanesulfonic acid mainly include the following several kinds:

[0003] 1) Methanesulfonic acid is synthesized using acetic anhydride and fuming sulfuric acid as raw materials, and the reaction formula is as follows:

[0004]

[0005] Patent WO2021005508A discloses a method for synthesizing methanesulfonic acid using acetic anhydride and fuming sulfuric acid (30%) as raw materials, and further synthesizing tris(halosulfonyl)methane and its salts. Patent US2012215027A discloses a method for synthesizing methanesulfonic acid using acetic anhydride and fuming sulfuric acid (30%) as raw materials, and further synthesizing trisodium methanesulfonate, with an overall yield of 44.3%.

[0006] 2) Methanesulfonic acid is synthesized using acetone and fuming sulfuric acid as raw materials, and the reaction formula is as follows:

[0007]

[0008] Patent CN102924254A discloses a method for synthesizing methanesulfonic acid using acetone and fuming sulfuric acid as raw materials, and further synthesizing an ionic liquid catalyst based on methanesulfonic acid.

[0009] 3) Methanesulfonic acid is synthesized using triethyl methanethiolate as raw material, and the reaction formula is as follows:

[0010]

[0011] Kruger, Seth et al. (Advances in Resist Materials and Processing Technology XXV, 69231O / 1-69231O / 10; 2008) disclose a method for preparing methanesulfonic acid by oxidizing triethyl methanethiolate with peracetic acid, with a yield of 100%.

[0012] In the above first and second synthesis processes, fuming sulfuric acid is used as the sulfonating reagent. However, after using fuming sulfuric acid, a large amount of sulfuric acid is entrained in the solid methanetrisulfonic acid obtained by filtration, making separation and purification difficult. If it is subsequently used to prepare trilithium methanetrisulfonate, the entrained sulfuric acid will generate by-product lithium sulfate. That is to say, the entrainment of concentrated sulfuric acid is extremely unfavorable for the separation and purification of the product, and at the same time, the recovery and reuse of by-product concentrated sulfuric acid is also a time-consuming and laborious process. As an additive for lithium-ion battery electrolytes, a relatively high purity of the additive is required. Once the purity is low, the capacity and cycle performance of the battery will be greatly reduced, which is extremely unfavorable for lithium-ion batteries.

[0013] Therefore, it is very necessary to prepare high-purity trilithium methanetrisulfonate as an electrolyte additive. Summary of the Invention

[0014] In order to solve the above technical problems, the present invention provides a method for preparing trilithium methanetrisulfonate with simple operation, high product purity, low impurity content and suitable for industrial production.

[0015] The object of the present invention is achieved by the following technical solutions:

[0016] A method for preparing high-purity trilithium methanetrisulfonate, the preparation method sequentially includes:

[0017] A1. A step of reacting acetic anhydride and sulfur trioxide in a first solvent to obtain methanetrisulfonic acid, and the reaction formula is as follows:

[0018]

[0019] A2. A step of reacting the methanetrisulfonic acid and lithium hydroxide in water to obtain a crude product of trilithium methanetrisulfonate, and the reaction formula is as follows:

[0020]

[0021] A3. A step of recrystallizing the crude product of trilithium methanetrisulfonate with a second solvent to obtain high-purity trilithium methanetrisulfonate.

[0022] Generally, salt substances have good solubility in water, and the prior art usually uses water for recrystallization of salt substances. However, the present invention uses an organic solvent to recrystallize the obtained crude product of trilithium methanetrisulfonate, which not only reduces the complexity of recrystallization (water recrystallization needs to be carried out multiple times, and high-purity products cannot be obtained by single crystallization), but also improves the purity of the product.

[0023] Preferably, the second solvent is selected from at least one of anhydrous methanol, anhydrous ethanol or isopropanol, and the dosage is 2 to 6 times the mass of the crude product of trilithium methanetrisulfonate. More preferably, the second solvent is anhydrous methanol, and the dosage is 3 to 4 times the mass of the crude product of trilithium methanetrisulfonate.

[0024] Specifically, the preparation process of the high-purity lithium methanetrisulfonate of the present invention is as follows:

[0025] A1. Sulfur trioxide is dissolved in a first solvent, acetic anhydride is added dropwise, and the mixture is kept at 50 - 80 °C for 4 - 12 hours for reaction. After the reaction is complete, it is cooled, and methanetrisulfonic acid precipitates. It is filtered, washed, and dried to obtain methanetrisulfonic acid.

[0026] A2. Methanetrisulfonic acid is dissolved in water, lithium hydroxide is added. When the pH of the solution reaches 8, the addition is stopped. It is distilled and concentrated, and lithium methanetrisulfonate precipitates. It is cooled, filtered, and the filter cake is washed with ice water and dried to obtain the crude product of lithium methanetrisulfonate.

[0027] A3. The crude product of lithium methanetrisulfonate is dissolved in a second solvent, kept at 5 - 35 °C for 2 - 6 hours, the insoluble substances are removed, and the filtrate is distilled, cooled, filtered, and dried to obtain high-purity lithium methanetrisulfonate.

[0028] In step A1, the first solvent is selected from at least one of dichloroethane, dichloromethane, tetrachloroethane, petroleum ether, or nitromethane, and preferably the first solvent is dichloroethane. The molar ratio of acetic anhydride to sulfur trioxide is 1:6 - 1:10, and preferably the molar ratio is 1:6 - 1:6.4; the reaction temperature is 50 - 80 °C, and the reaction time is 4 - 12 hours. Preferably, the reaction temperature is 50 - 60 °C, and the reaction time is 8 - 10 hours. After the reaction is completed, the temperature is lowered to 0 - 20 °C and kept for 1 - 2 hours, and methanetrisulfonic acid precipitates. It is filtered, and the filter cake is washed with the first solvent (such as washing three times) and dried to obtain methanetrisulfonic acid.

[0029] In step A2, deionized water is used to dissolve the methanetrisulfonic acid obtained in step A1. The amount of deionized water used is 4 - 6 times that of methanetrisulfonic acid. Solid lithium hydroxide is added in batches under stirring. The molar ratio of lithium hydroxide to methanetrisulfonic acid is 1:3 - 1:3.6. As lithium hydroxide is added, the pH of the solution changes from acidic to alkaline. When the pH is about 8, it indicates that lithium hydroxide is sufficient, and the addition is stopped. After the reaction is complete, it is distilled and concentrated, and a large amount of lithium methanetrisulfonate precipitates.

[0030] In step A3, the recrystallization temperature is 5 - 35 °C, and the recrystallization time is 2 - 6 hours. Preferably, the recrystallization temperature is 20 - 30 °C, and the recrystallization time is 2 - 4 hours. After recrystallization is completed, the insoluble substances are filtered, the filtrate is concentrated, and after filtration and drying, lithium methanetrisulfonate with a content greater than 99.5% is obtained.

[0031] Compared with the prior art, the beneficial effects of the present invention include:

[0032] 1. The present invention uses sulfur trioxide to replace fuming sulfuric acid, avoiding the entrainment problem of concentrated sulfuric acid during the separation process of intermediates. At the same time, it also avoids the processes such as the recovery and reuse of concentrated sulfuric acid brought about by using fuming sulfuric acid. The process is simple, safe, environmentally friendly, and suitable for industrial production.

[0033] 2. Through research, it is found in the present invention that trilithium methanetrisulfonate has good solubility in organic solvents, especially in alcohol organic solvents, and impurities such as lithium sulfate and lithium hydroxide generated during the synthesis process have relatively low solubility in such solvents. Therefore, the present invention uses an organic solvent to recrystallize and purify the crude trilithium methanetrisulfonate. By heating and dissolving, cooling to precipitate impurities, filtering to remove impurities, concentrating the filtrate, and drying, a trilithium methanetrisulfonate product with a purity greater than 99.5% is obtained. The operation is simple and the product purity is high. Specific Embodiments

[0034] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions, and equivalent solutions that may be included within the scope of the claims.

[0035] Example 1

[0036] This example provides a method for preparing high-purity trilithium methanetrisulfonate, which specifically includes the following steps:

[0037] S1. At room temperature, add 102.5 g (1.28 mol) of sulfur trioxide and 250 g of the solvent dichloroethane into a 500 mL reaction vessel (such as a three-necked flask). Under nitrogen protection, heat up to 50 °C, and dropwise add 20.4 g (0.2 mol) of acetic anhydride. Stir and react at 60 °C for 8 hours, then cool to 20 °C. A large amount of methanesulfonic acid precipitates. Filter, and wash three times with 90 g of dichloroethane, and dry to obtain 96.2 g of methanesulfonic acid.

[0038] S2. Dissolve the obtained 96.2 g of methanesulfonic acid in 385 g of deionized water, and add 27.5 g of solid lithium hydroxide in batches. Stop adding lithium hydroxide when the pH value reaches 8.0. Distill and concentrate the reaction solution. A large amount of solid products precipitate during the distillation process. Cool to 0 °C and keep for 2 hours, then filter. The filter cake is 90 g, and wash three times with ice water, and dry the moisture to obtain 97.1 g of crude trilithium methanetrisulfonate.

[0039] S3. Add the obtained 97.1 g of trilithium methanetrisulfonate into 291 g of anhydrous methanol, heat until completely dissolved, slowly cool to 30 °C and keep for 2 hours, filter to remove solid insoluble substances, distill and concentrate the filtrate, cool, filter, and dry to obtain 90.3 g of trilithium methanetrisulfonate.

[0040] After calculation and analysis, the yield of trisodium methanetrisulfonate product is 82.3%, and the product purity is 99.7%.

[0041] Example 2

[0042] The operation of this example is the same as that of Example 1, except that:

[0043] In step S1, the reaction solvent was changed to tetrachloroethane, and the others remained unchanged, obtaining 95.8 g of methanetrisulfonic acid.

[0044] Steps S2 and S3 are the same as those in Example 1, obtaining 88.7 g of trisodium methanetrisulfonate.

[0045] After calculation and analysis, the yield of trisodium methanetrisulfonate product is 80.8%, and the product purity is 99.7%.

[0046] Example 3

[0047] The operation of this example is the same as that of Example 1, except that:

[0048] Steps S1 and S2 are the same as those in Example 1, obtaining 98.0 g of crude trisodium methanetrisulfonate.

[0049] In step S3, 98.0 g of crude trisodium methanetrisulfonate was added to 343 g of absolute ethanol, heated until completely dissolved, slowly cooled to 20 °C and kept for 2 hours, the solid insoluble matter was filtered off, the filtrate was distilled and concentrated, cooled, filtered and dried to obtain 89.6 g of trisodium methanetrisulfonate.

[0050] After calculation and analysis, the yield of trisodium methanetrisulfonate product is 81.7%, and the product purity is 99.7%.

[0051] Example 4

[0052] The operation of this example is the same as that of Example 1, except that:

[0053] Steps S1 and S2 are the same as those in Example 1, obtaining 97.1 g of crude trisodium methanetrisulfonate.

[0054] In step S3, 97.1 g of crude trisodium methanetrisulfonate was added to 388 g of isopropanol, heated until completely dissolved, slowly cooled to 30 °C and kept for 2 hours, the solid insoluble matter was filtered off, the filtrate was distilled and concentrated, cooled, filtered and dried to obtain 89.2 g of trisodium methanetrisulfonate.

[0055] After calculation and analysis, the yield of trisodium methanetrisulfonate product is 81.4%, and the product purity is 99.7%.

[0056] Comparative Example 1

[0057] Add 273 g (1 mol) of 30% oleum into a 500 mL three-necked flask at room temperature. Under nitrogen protection, heat and raise the temperature to 50 °C, and dropwise add 20.4 g (0.2 mol) of acetic anhydride. Stir and react at 100 °C for 19 hours, then cool to 20 °C. Methanetri-sulfonic acid precipitates in large amounts. Filter to obtain methanetri-sulfonic acid (wet solid, entraining sulfuric acid).

[0058] Dissolve the obtained methanetri-sulfonic acid in 385 g of deionized water, add 42.8 g of solid lithium hydroxide in batches, adjust the pH value to 8.0, distill and concentrate the reaction solution. A large amount of solid product precipitates during the distillation process. Cool to 0 °C and maintain for 2 hours, then filter. Wash the filter cake three times with 90 g of ice water in portions, and dry to obtain 103.1 g of trilithium methanetri-sulfonate.

[0059] Add 103.1 g of the obtained trilithium methanetri-sulfonate into 310 g of anhydrous methanol, heat until completely dissolved, slowly cool to 30 °C and maintain for 2 hours, filter to remove solid insoluble substances, distill and concentrate the filtrate, cool, filter, and dry to obtain 93.4 g of trilithium methanetri-sulfonate.

[0060] Through calculation and analysis, the yield of the trilithium methanetri-sulfonate product is 85.1%, and the purity of the yield product is 91.6%.

[0061] Comparative Example 2

[0062] The operation of this comparative example is the same as that of Example 1, with the only difference being that:

[0063] In steps S1 and S2, the same as in Example 1, 98.8 g of crude trilithium methanetri-sulfonate is prepared;

[0064] In step S3, dissolve 98.8 g of the crude trilithium methanetri-sulfonate in 180 g of deionized water, filter to remove insoluble substances, distill and concentrate the filtrate by evaporating 80 g of water, cool to 0 °C and maintain for 2 hours, filter. The filter cake is 60 g, which is washed three times with ice water in portions, and dried to obtain 87.3 g of the product with a purity of 97.4%.

[0065] Crystallize 87.3 g (97.4%) of trilithium methanetri-sulfonate for the second time by the above method, and dry to obtain 78.5 g of the product with a purity of 98.9%.

[0066] Crystallize 78.5 g (98.9%) of trilithium methanetri-sulfonate for the third time by the above method, and dry to obtain 69.7 g of the product with a purity of 99.7%.

[0067] Through calculation, the yield of the trilithium methanetri-sulfonate product is 63.5%, and the product purity is 99.7%.

[0068] Comparative Example 3

[0069] The operation of this comparative example is the same as that of Example 1, with the only difference being that:

[0070] In step S1 and step S2, the same as in Example 1, 97.7 g of crude lithium tris(methanesulfonate) is obtained through preparation;

[0071] In step S3, 97.7 g of crude lithium tris(methanesulfonate) is added to 450 g of acetonitrile, heated until completely dissolved, slowly cooled to 30 °C and maintained for 2 hours, the solid insoluble matter is filtered off, the filtrate is concentrated by distillation, cooled, filtered and dried to obtain 87.4 g of lithium tris(methanesulfonate).

[0072] Through calculation and analysis, the yield of the lithium tris(methanesulfonate) product is 79.6%, and the product purity is 99.1%.

Claims

1. A preparation method of trilithium methanetrisulfonate, characterized in that: the preparation method successively includes: A1. A step of reacting acetic anhydride and sulfur trioxide in a first solvent to obtain methanetrisulfonic acid; A2. A step of reacting the methanetrisulfonic acid and lithium hydroxide in water to obtain a crude product of trilithium methanetrisulfonate; A3. A step of recrystallizing the crude product of trilithium methanetrisulfonate with a second solvent to obtain trilithium methanetrisulfonate, where the second solvent is selected from at least one of anhydrous methanol, anhydrous ethanol or isopropanol, the recrystallization temperature is 5 - 35°C, and the recrystallization time is 2 - 6 hours.

2. The preparation method of trilithium methanetrisulfonate according to claim 1, characterized in that: the amount of the second solvent used is 2 - 6 times the mass of the crude product of trilithium methanetrisulfonate.

3. The preparation method of trilithium methanetrisulfonate according to claim 1, characterized in that: the first solvent is selected from at least one of dichloroethane, dichloromethane, tetrachloroethane, petroleum ether or nitromethane.

4. The preparation method of trilithium methanetrisulfonate according to claim 1, characterized in that: the molar ratio of acetic anhydride to sulfur trioxide is 1:6 - 1:

10.

5. The preparation method of trilithium methanetrisulfonate according to claim 1, characterized in that: in step A1, the reaction temperature is 50 - 80°C and the reaction time is 4 - 12 hours.

6. The preparation method of trilithium methanetrisulfonate according to claim 1, characterized in that: step A2 is carried out in deionized water.

7. The preparation method of trilithium methanetrisulfonate according to claim 6, characterized in that: the molar ratio of lithium hydroxide to methanetrisulfonic acid is 1:3 - 1:3.

6.

8. The preparation method of trilithium methanetrisulfonate according to any one of claims 1 - 7, characterized in that: the preparation method specifically includes: A1. Sulfur trioxide is dissolved in the first solvent, acetic anhydride is added dropwise, and the reaction is carried out at 50 - 80°C for 4 - 12 hours, then cooled, and methanetrisulfonic acid precipitates out. After filtration, washing and drying, methanetrisulfonic acid is obtained; A2. Methanetrisulfonic acid is dissolved in water, lithium hydroxide is added, and the addition is stopped when the pH of the solution is 8. Then it is distilled and concentrated, and trilithium methanetrisulfonate precipitates out. After cooling and filtration, the filter cake is washed with ice water and dried to obtain the crude product of trilithium methanetrisulfonate; A3. The crude product of trilithium methanetrisulfonate is dissolved in the second solvent, kept at 5 - 35°C for 2 - 6 hours, the insoluble substances are removed, and the filtrate is distilled, cooled, filtered and dried to obtain trilithium methanetrisulfonate.

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