Process for the preparation of lithium saccharinate

Abstract

The application discloses a preparation method of lithium saccharin, which comprises the following steps: 1, under the condition of a polar organic solvent, adding saccharin and an alkaline organic lithium reagent, controlling the temperature to form a homogeneous phase reaction system, and performing an acid-base neutralization reaction; the alkaline organic lithium reagent is selected from one of the following: methanolate, ethanolate, diisopropylaminolithium, hexamethyldisilazanide, n-butyllithium and methyllithium; 2, after the reaction is completed, cooling and crystallization or adding an inert solvent for recrystallization, and then washing and drying to obtain the lithium saccharin product. The method has the advantages of simple process route, convenient post-treatment, high yield and high product purity.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for preparing lithium saccharin. Background Technology

[0002] Lithium difluorosulfonylimide has good electrochemical stability, good hydrolysis resistance, high conductivity, and environmental friendliness, so it is widely used in electrolytes, but its production cost is relatively high.

[0003] Lithium saccharin, also known as lithium o-benzoylsulfonylimide, has the molecular formula LiC7H4O3NS. Lithium saccharin possesses a sulfonylimide structure similar to lithium difluorosulfonylimide, and its preparation cost is significantly lower. Therefore, lithium saccharin is of great significance as an additive in lithium-ion battery electrolytes.

[0004] Currently, the known methods for preparing lithium saccharin are similar to those for preparing traditional sodium saccharin, and have the following drawbacks: numerous side reactions, complex post-processing, difficulty in purification, low yield and product purity, which are not conducive to industrial production. Summary of the Invention

[0005] To address the aforementioned technical problems, the objective of this invention is to provide a method for preparing lithium saccharin, which features a simple process route, easy purification, effective avoidance of side reactions, high product purity, and good yield.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a method for preparing lithium saccharin, comprising the following steps: 1. Under polar organic solvent conditions, saccharin and a basic organic lithium reagent are added, and the temperature is controlled to form a homogeneous reaction system for acid-base neutralization reaction; the basic organic lithium reagent is selected from lithium methoxide, lithium ethanol, lithium diisopropylamino, lithium hexamethyldisilazine, lithium n-butyllithium, and lithium methyl; the reaction principle is illustrated below:

[0007] .

[0008] 2. After the reaction is complete, cool the mixture to allow it to crystallize or add an inert solvent to recrystallize it. Then wash and dry the product to obtain lithium saccharin.

[0009] Furthermore, in the aforementioned method for preparing lithium saccharin, the polar organic solvent is selected from one of acetonitrile, tetrahydrofuran, methanol, ethanol, dimethyl carbonate, and ethyl methyl carbonate; the mass ratio of the polar organic solvent to saccharin is 5-10.

[0010] Furthermore, in the aforementioned method for preparing lithium saccharin, the polar organic solvent is selected from dimethyl carbonate or methanol.

[0011] Furthermore, in the aforementioned method for preparing saccharin lithium, the alkaline organic lithium reagent is lithium methoxide.

[0012] Furthermore, in the aforementioned method for preparing lithium saccharin, the inert solvent used for recrystallization is selected from one of n-hexane, dichloromethane, dichloroethane, and toluene.

[0013] Furthermore, in the aforementioned method for preparing lithium saccharin, the inert solvent is preferably n-hexane.

[0014] Furthermore, in the aforementioned method for preparing lithium saccharin, the molar ratio of alkaline organic lithium reagent to saccharin is 1~2:1.

[0015] Furthermore, in the aforementioned method for preparing lithium saccharin, the molar ratio of alkaline organic lithium reagent to saccharin is 1.2:1.

[0016] Furthermore, in the aforementioned method for preparing lithium saccharin, the reaction temperature is -30℃ to 107℃, and the reaction time is 1h to 5h.

[0017] The advantages of this invention are: 1. The process steps are simple, and the preparation cost is greatly reduced. 2. Alkaline organolithium reagents are selected, and organic solvents are used as reaction solvents. Alkaline organolithium reagents have better solubility in organic solvents and react more efficiently and specifically with saccharin, thereby effectively improving product purity and yield. 3. Post-processing adopts cooling crystallization or recrystallization, avoiding side reactions that occur during the heating and concentration of the reaction solution. Post-processing is simple, further greatly improving product purity and yield. Attached Figure Description

[0018] Figure 1 This is the hydrogen NMR spectrum of the product in Example 1.

[0019] Figure 2 This is the NMR carbon spectrum of the product in Example 2. Detailed Implementation

[0020] The preparation method of lithium saccharin according to the present invention will be described in detail below through specific embodiments.

[0021] Example 1: In a three-necked flask equipped with a thermometer, stirrer, and condenser, 183g of saccharin, 950g of acetonitrile, and 40g of lithium methoxide were added. The mixture was heated to 80°C and reacted for 3 hours before the reaction was stopped.

[0022] After cooling the reaction solution to room temperature, 1900 g of dichloromethane was added dropwise. After the addition was complete, the mixture was kept at this temperature and stirred for 2 hours, resulting in the precipitation of a large amount of white crystals. The crystals were filtered and washed with a mixture of acetonitrile and dichloromethane (mass ratio 1:2). After drying, 178 g of saccharin lithium product was obtained. Its 1H NMR spectrum is shown in [reference needed]. Figure 1 : 1 ¹H NMR (400MHz, D₂O) δ 7.86–5.84 (¹H, m), 7.77–7.76 (³H, m); its carbon NMR spectrum is shown in [reference needed]. Figure 2 : 13 C NMR (100MHz, CDCl3) δ 172.45, 141.65, 133.70, 133.19, 132.23, 123.52, 120.15. The purity was determined to be 98.92% by IC (ion chromatography), and the calculated molar yield was 94.18%.

[0023] Example 2: Add 147g of saccharin, 1200g of methyl ethyl carbonate, and 46g of lithium ethanol to a three-necked flask equipped with a thermometer, stirrer, and condenser. Heat the mixture to 107°C and react for 2 hours, then stop the reaction.

[0024] After cooling the reaction solution to -10℃, a large amount of white crystals precipitated. The crystals were filtered and washed with methyl ethyl carbonate at -10℃. After drying, 142g of lithium saccharin product was obtained. The purity was determined to be 99.23% by IC (ion chromatography), and the molar yield was calculated to be 93.54%.

[0025] Example 3: Add 220g of saccharin, 2200g of methanol, and 60g of lithium methoxide to a three-necked flask equipped with a thermometer, stirrer, and condenser. Heat the mixture to 66°C and react for 1 hour, then stop the reaction.

[0026] After cooling the reaction solution to room temperature, 2200g of n-hexane was added dropwise to the reaction solution. After the addition was completed, the mixture was kept warm and stirred for 2 hours, and a large amount of white crystals precipitated. The crystals were filtered and washed with a mixed solution of methanol and n-hexane (mass ratio 1:1). After drying, 217g of lithium saccharin product was obtained. The purity was determined to be 99.68% by IC (ion chromatography), and the molar yield was calculated to be 95.59%.

[0027] Example 4: Add 366g of saccharin, 1830g of dimethyl carbonate, and 92g of lithium methoxide to a three-necked flask equipped with a thermometer, stirrer, and condenser. Heat the mixture to 90°C and react for 5 hours, then stop the reaction.

[0028] After cooling the reaction solution to 5°C, a large amount of white crystals precipitated. The crystals were filtered, washed with cold dimethyl carbonate, and dried to obtain 365g of lithium saccharin product. The purity was determined to be 99.71% by IC (ion chromatography), and the molar yield was calculated to be 96.56%.

[0029] Example 5: Add 183g of saccharin and 1000g of tetrahydrofuran to a three-necked flask equipped with a thermometer, stirrer, nitrogen protection device, and constant pressure dropping funnel. After cooling to -30°C, add 455mL of n-butyllithium / n-hexane solution with a concentration of 2.2 mol / L. Keep the reaction at this temperature for 1 hour and then stop the reaction.

[0030] After heating the reaction solution to room temperature, 3000g of dichloromethane was added dropwise to the reaction solution. After the addition was completed, the mixture was kept warm and stirred for 2 hours, resulting in the precipitation of a large amount of white crystals. The crystals were filtered and washed with a mixed solution of tetrahydrofuran and dichloromethane (mass ratio 1:3). After drying, 173g of lithium saccharin product was obtained. The purity was determined to be 98.64% by IC (ion chromatography), and the molar yield was calculated to be 91.53%.

[0031] Example 6: Add 238g of saccharin and 1500g of tetrahydrofuran to a three-necked flask equipped with a thermometer, stirrer, nitrogen protection device, and constant pressure dropping funnel. After cooling to -30°C, add 650mL of a 2mol / L diisopropylaminolithium / tetrahydrofuran solution. Keep the reaction at this temperature for 1 hour and then stop the reaction.

[0032] After heating the reaction solution to room temperature, 4500g of dichloroethane was added dropwise to the reaction solution. After the addition was completed, the mixture was kept at the same temperature and stirred for 2 hours, resulting in the precipitation of a large amount of white crystals. The crystals were filtered and washed with a mixed solution of tetrahydrofuran and dichloroethane (mass ratio 1:3). After drying, 227g of saccharin lithium product was obtained. The purity was determined to be 99.06% by IC (ion chromatography), and the molar yield was calculated to be 92.39%.

[0033] Example 7: Add 311g of saccharin and 1800g of tetrahydrofuran to a three-necked flask equipped with a thermometer, stirrer, nitrogen protection device, and constant pressure dropping funnel. After cooling to -20°C, add 1700mL of a 1.0 mol / L hexamethyldisilazine lithium / tetrahydrofuran solution. Keep the reaction at this temperature for 1 hour and then stop the reaction.

[0034] After heating the reaction solution to room temperature, 3600g of toluene was added dropwise to the reaction solution. After the addition was completed, the mixture was kept at the temperature and stirred for 2 hours, resulting in the precipitation of a large amount of white crystals. The crystals were filtered and washed with a mixed solution of tetrahydrofuran and toluene (mass ratio 1:2). After drying, 298g of saccharin lithium product was obtained. The purity was determined to be 99.28% by IC (ion chromatography), and the molar yield was calculated to be 92.78%.

[0035] Comparative Example 8: 183g of saccharin was added to a three-necked flask equipped with a thermometer and a stirrer and suspended in 750g of methanol. 24g of lithium hydroxide was added and the mixture was kept at 25°C for 3 hours. The reaction solution became clear and transparent, and the reaction was stopped.

[0036] The reaction solution was concentrated and methanol was removed to obtain a white powder. The powder was washed with ethyl acetate and dichloromethane and dried to obtain 102g of lithium saccharin product. The purity was determined to be 86.31% by IC (ion chromatography), and the molar yield was calculated to be 53.97%.

[0037] The experimental results of Comparative Example 8 demonstrate that the method of preparing saccharin lithium using inorganic alkaline lithium reagent has disadvantages such as low yield, many by-products, and low product purity.

[0038] As can be seen from the above embodiments, the preparation method of lithium saccharin described in this invention uses an alkaline organic lithium reagent and an organic solvent as the reaction solvent. Since the alkaline organic lithium reagent has better solubility in the organic solvent and reacts more efficiently and specifically with saccharin, the post-processing adopts cooling crystallization or recrystallization, which avoids the side reactions that occur during the heating and concentration of the reaction solution. The post-processing is simple, so the product purity and yield are very high.

Claims

1. A method for preparing lithium saccharin, characterized in that: Includes the following steps: I. Under polar organic solvent conditions, saccharin and a basic organic lithium reagent are added, and the temperature is controlled to form a homogeneous reaction system for acid-base neutralization reaction. The basic organic lithium reagent is lithium methoxide. The polar organic solvent is selected from dimethyl carbonate or methanol. The reaction temperature is 66℃~107℃. II. After the reaction is completed, the temperature is lowered to crystallize or an inert solvent is added for recrystallization. After washing and drying, the saccharin lithium product can be obtained.

2. The method for preparing lithium saccharin according to claim 1, characterized in that: The mass ratio of polar organic solvent to saccharin is 5 to 10.

3. The method for preparing lithium saccharin according to claim 1, characterized in that: The inert solvent used for recrystallization is selected from one of the following: n-hexane, dichloromethane, dichloroethane, and toluene.

4. The method for preparing lithium saccharin according to claim 3, characterized in that: The inert solvent is n-hexane.

5. A method for preparing lithium saccharin according to claim 1, characterized in that: The molar ratio of alkaline organolithium reagent to saccharin is 1 to 2:

1.

6. The method for preparing saccharin lithium according to claim 5, characterized in that: The molar ratio of alkaline organic lithium reagent to saccharin is 1.2:

1.

7. The method for preparing lithium saccharin according to claim 1, characterized in that: The reaction time is 1 hour to 5 hours.

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