Preparation method of tris (trimethylsilane) boric acid ester
When preparing tri(trimethylsilane) boric acid ester, boron oxide under specific molar ratio and temperature conditions is used to react with ammonium bicarbonate to produce ammonium dihydrogen borate, and react with hexamethyldisilazane under anhydrous and oxygen-free conditions. High-purity tri(trimethylsilane) boric acid ester is obtained by under reduced pressure distillation, which solves the problem of poor boric acid solubility and difficulty in dissociation of ammonia gas, and achieves a high yield and high purity preparation effect.
Patent Information
- Application Number
- CN202311732510.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-17
- Publication Date
- 2025-06-17
AI Technical Summary
In the prior art, when preparing tri(trimethylsilane) boric acid ester, poor solubility of boric acid leads to low reaction yield, and the difficulty of ammonia gas to detach leads to a decrease in the conversion rate of boric acid.
Boron oxide, ammonium bicarbonate, water and ethanol are reacted under specific molar ratios and temperature conditions to form an ammonium dihydrogen borate solution, and react with hexamethyldisilazane under anhydrous and oxygen-free conditions to obtain high-purity tris(trimethylsilane) borate ester by decompression distillation.
The yield and purity of trimethylsilane borate is improved, the process route is simplified, the gentleness of reaction conditions is reduced, and the reaction process is not generated by toxic products, which is safe and environmentally friendly.
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Figure CN120157699A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the preparation of an electrolyte additive for a lithium-ion battery, and particularly to a preparation method of tris(trimethylsilyl) borate. Background Art
[0002] In recent years, tris(trimethylsilyl) borate electrolyte salts have increasingly attracted the attention of researchers. It is a new material that can be used as an electrolyte additive for lithium-ion batteries. Studies have found that this kind of electrolyte salt can not only improve the high-temperature storage performance, service performance, and low-temperature capacity performance of the battery, but also inhibit the decomposition of the electrolyte on the negative electrode. This is because when a borosilicate compound with a B-O-Si structure forms a thin film on the negative electrode, the oxygen atoms generated by the cleavage of B-O-Si can fully react with the active sites on the negative electrode, reducing the reactivity of the active sites on the negative electrode, thereby inhibiting the decomposition of the electrolyte. Therefore, tris(trimethylsilyl) borate electrolyte salts have good development prospects in the market.
[0003] Chinese patent documents CN2013102683253 and CN2014100999468 both disclose a preparation method of high-purity tris(trimethylsilyl) borate. The method involves reacting silazane and boric acid under an organic ammonia or sulfonic acid-type cation dry hydrogen resin catalyst to obtain a crude product, and then filtering and rectifying the crude product to obtain high-purity tris(trimethylsilyl) borate. This type of method is the mainstream method for preparing tris(trimethylsilyl) borate at present, but there are still the following technical problems: Firstly, the solubility of boric acid in silazane is very poor. During the reaction process, boric acid will accumulate at the bottom of the reaction vessel and cannot react fully. After the reaction, a large amount of boric acid filter residue will not participate in the reaction, resulting in a low reaction yield. At the same time, high temperature will cause the decomposition of boric acid and an increase in side reactions. Secondly, the ammonia gas generated by the reaction cannot quickly escape from the system and will react with boric acid, further reducing the conversion rate of boric acid. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a preparation method of tris(trimethylsilyl) borate.
[0005] To achieve the above object, the technical solution adopted by the present invention is: A preparation method of tris(trimethylsilyl) borate, comprising the following steps: First, add boron oxide, ammonium bicarbonate, water, and the solvent ethanol to a reaction vessel, react to obtain an ammonium dihydrogen borate ethanol solution, and perform post-treatment on the ammonium dihydrogen borate ethanol solution to obtain an anhydrous ammonium dihydrogen borate solid; Second, react ammonium dihydrogen borate with hexamethyldisilazane under anhydrous and anaerobic conditions at 70-90 °C. After the reaction, a crude tris(trimethylsilyl) borate solution is obtained, and the crude tris(trimethylsilyl) borate solution is subjected to vacuum rectification to obtain high-purity tris(trimethylsilyl) borate. Tris(trimethylsilyl) borate has the following structure: ; The above reaction is shown as follows: ; .
[0006] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, the molar ratio of boron oxide, ammonium bicarbonate to water in the feed is 1:(2 - 2.2):1.
[0007] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the first step, the reaction temperature is controlled at 50 - 60 °C and the reaction time is controlled at 2 - 3 h.
[0008] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the first step, the post-treatment steps of the ammonium dihydrogen borate ethanol solution include filtration, washing, and vacuum drying, and then solid ammonium dihydrogen borate is obtained, where the temperature of the vacuum drying is 60 - 70 °C. Vacuum drying at 60 - 70 °C is beneficial to the stability of the ammonium dihydrogen borate product and it is not easily decomposed.
[0009] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, the molar ratio of ammonium dihydrogen borate to hexamethyldisilazane in the feed is 1:2.4 - 2.7. Hexamethyldisilazane is in excess by 60% - 80%, and its purpose is that hexamethyldisilazane also serves as a reaction solvent, effectively promoting the forward reaction.
[0010] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the second step, before adding the reaction materials, the reaction vessel is purged with nitrogen to ensure that the reaction is in an anhydrous and anaerobic environment. The purpose of controlling the moisture is to prevent the reaction of silazane with water, thereby improving the conversion efficiency.
[0011] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the second step, the moisture content of all reaction materials is ensured to be no higher than 500 ppm. Further controlling the moisture effectively prevents the reaction of silazane with water, thereby further improving the conversion efficiency.
[0012] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the second step, the reaction time is 6 - 8 h.
[0013] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the second step, the crude tris(trimethylsilyl) borate solution is subjected to vacuum distillation at 80 - 90 °C.
[0014] Furthermore, in the aforementioned method for preparing tris(trimethylsilyl) borate, in the second step, the ammonia gas generated by the reaction is absorbed by water. The formed ammonia water is a valuable by-product.
[0015] Furthermore, for the preparation method of the aforementioned tris(trimethylsilyl) borate, in the first step, the addition amount of ethanol ensures that the mass concentration of the reaction solution corresponding to the theoretical production amount of ammonium dihydrogen borate as the intermediate is 25% - 30%.
[0016] The advantages of the present invention are as follows: First, the process route is simple, the reaction conditions are mild, the operation is convenient, and it can be obtained without using complex equipment, and the synthesized product has high purity and high total yield. Second, ammonium dihydrogen borate has good solubility, and the reaction is easy to occur, thus effectively improving the product yield. Third, no harmful products are generated during the reaction process, and the basic gas generated by the reaction only needs to be absorbed with water. Description of the Drawings
[0017] Figure 1 It is the GC spectrum of the product tris(trimethylsilyl) borate prepared in Example 1.
[0018] Figure 2 For the product tris(trimethylsilyl) borate prepared in Example 1 11 B-NMR spectrum. Embodiments
[0019] The present invention will be further described in detail below in conjunction with the preferred embodiments.
[0020] Example 1: First, 1 mol of boron oxide, 2.1 mol of ammonium bicarbonate, 1 mol of water, and 10.27 mol of ethanol solvent are added to a reaction vessel, and the reaction is carried out at 50 °C for 2 h to obtain an ammonium dihydrogen borate ethanol solution. The reaction solution is filtered, washed, and vacuum dried at 60 °C for 6 h to obtain 1.6 mol of ammonium dihydrogen borate.
[0021] Second, all raw materials are pretreated before the reaction to ensure that the moisture content of all raw materials is lower than 500 ppm. After the reaction vessel is purged with high-purity nitrogen, 1 mol of ammonium dihydrogen borate and 2.5 mol of hexamethyldisilazane are added to the reaction vessel, and the reaction is carried out at 80 °C for 6 h to obtain a reaction solution of tris(trimethylsilyl) borate. The reaction solution is subjected to vacuum distillation at 90 °C to obtain 0.89 mol of pure tris(trimethylsilyl) borate, and the yield reaches 89%. The by-product ammonia gas is absorbed with water to prepare ammonia water.
[0022] The product purity is analyzed by GC spectrum and NMR spectrum to be 99.9%.
[0023] The GC spectrum is as Figure 1 shown, and the NMR B spectrum is as Figure 2 shown.
[0024] Detected by ICP: Na + : 0.08 ppm, K +: 0.15 ppm, Fe 3+ : 0.04 ppm, Ca 2+ : 0.01 ppm, Pb 2+ : 0.02 ppm.
[0025] By potentiometric titration: Cl - : 0.1 ppm.
[0026] By acid-base titration: Acid value: 1.4 ppm.
[0027] Example 2: I. Add 1 mol of boron oxide, 2.2 mol of ammonium bicarbonate, 1.1 mol of water, and 8.8 mol of ethanol solvent to a reaction vessel, react at 40 °C for 3 h to obtain an ammonium dihydrogen borate ethanol solution. The reaction solution is filtered, washed, and vacuum dried at 60 °C for 7 h to obtain 1.7 mol of ammonium dihydrogen borate.
[0028] II. Pretreat all raw materials before the reaction to ensure that the moisture content of all raw materials is less than 500 ppm. After replacing the reaction vessel with high-purity nitrogen, add 1 mol of ammonium dihydrogen borate and 2.4 mol of hexamethyldisilazane to the reaction vessel, react at 70 °C for 8 h to obtain a reaction solution of tris(trimethylsilyl) borate. The reaction solution is subjected to vacuum distillation at 80 °C to obtain 0.88 mol of pure tris(trimethylsilyl) borate, and the yield reaches 88%. The by-product ammonia gas is absorbed with water to prepare ammonia water.
[0029] The product purity is 99.99% by GC spectrum and NMR spectrum analysis.
[0030] By ICP detection: Na + : 0.11 ppm, K + : 0.01 ppm, Fe 3+ : 0.01 ppm, Ca 2+ : 0.02 ppm, Pb 2+ : 0.09 ppm.
[0031] By potentiometric titration: Cl - : 0.2 ppm.
[0032] By acid-base titration: Acid value: 2.5 ppm.
[0033] Example 3: I. Add 1.1 mol of boron oxide, 2.2 mol of ammonium bicarbonate, 1.0 mol of water, and 8 mol of ethanol solvent to a reaction vessel, react at 50 °C for 3 h to obtain an ammonium dihydrogen borate ethanol solution. The reaction solution is filtered, washed, and vacuum dried at 7 °C for 8 h to obtain 1.6 mol of ammonium dihydrogen borate.
[0034] II. All raw materials are pretreated before the reaction to ensure that the moisture content of all raw materials is lower than 500 ppm. After the reaction vessel is purged with high-purity nitrogen, 1 mol of ammonium dihydrogen borate and 2.7 mol of hexamethyldisilazane are added to the reaction vessel, and the reaction is carried out at 80 °C for 8 h to obtain a reaction solution of tris(trimethylsilyl) borate. The reaction solution is subjected to vacuum distillation at 80 °C to obtain 0.9 mol of pure tris(trimethylsilyl) borate, and the yield reaches 90%. The by-product ammonia gas is absorbed with water to prepare ammonia water.
[0035] The purity of the product is analyzed by GC spectrum and NMR spectrum to be 99.99%.
[0036] Detected by ICP: Na + : 0.01 ppm, K + : 0.07 ppm, Fe 3+ : 0.09 ppm, Ca 2+ : 0.22 ppm, Pb 2+ : 0.01 ppm.
[0037] Detected by potentiometric titration: Cl - : 0.17 ppm.
[0038] Detected by acid-base titration: Acid value: 2.0 ppm.
[0039] It can be obtained from the above examples that the present invention application has the following advantages: First, the process route is simple, the reaction conditions are mild, the operation is convenient, and it can be obtained without using complex equipment. Moreover, the synthesized product has high purity and high total yield, which is suitable for industrial production. Second, ammonium dihydrogen borate has good solubility and the reaction occurs easily, thus effectively improving the product yield. Third, no harmful products are generated during the reaction, and the alkaline gas generated by the reaction only needs to be absorbed with water, and the whole reaction process is safe and environmentally friendly.
Claims
1. A method for preparing tris(trimethylsilyl) borate, comprising the following steps: First, boron oxide, ammonium bicarbonate, water and the solvent ethanol are added to a reaction vessel, and a reaction is carried out to obtain an ethanol solution of ammonium dihydrogen borate. The ethanol solution of ammonium dihydrogen borate is post-treated to obtain a solid of anhydrous ammonium dihydrogen borate; Second, ammonium dihydrogen borate and hexamethyldisilazane are reacted at 70-90 °C under anhydrous and anaerobic conditions. After the reaction, a crude solution of tris(trimethylsilyl) borate is obtained, and the crude solution of tris(trimethylsilyl) borate is subjected to vacuum rectification to obtain high-purity tris(trimethylsilyl) borate.
2. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: The molar ratio of boron oxide, ammonium bicarbonate to water for feeding is 1:(2 - 2.2):
1.
3. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the first step, the reaction temperature is controlled at 50 - 60 °C and the reaction time is controlled at 2 - 3 h.
4. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the first step, the post-treatment steps of the ammonium dihydrogen borate ethanol solution include filtration, washing, vacuum drying, and then ammonium dihydrogen borate solid is obtained, where the temperature of vacuum drying is 60 - 70 °C.
5. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the second step, the molar ratio of ammonium dihydrogen borate to hexamethyldisilazane for feeding is 1:2.4 - 2.
7.
6. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the second step, before adding the reaction materials, the reaction vessel is purged with nitrogen to ensure that the reaction is in an anhydrous and oxygen-free environment.
7. The method for preparing tris(trimethylsilyl) borate according to claim 1 or 6, wherein: In the second step, the water content of all reaction materials is ensured to be no higher than 500 ppm.
8. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the second step, the reaction time is 6 - 8 h.
9. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the second step, the crude solution of tris(trimethylsilyl) borate is subjected to vacuum distillation at 80 - 90 °C.
10. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the second step, the ammonia gas generated by the reaction is absorbed by water.
11. The method for preparing tris(trimethylsilyl) borate according to claim 1, wherein: In the first step, the addition amount of ethanol is ensured so that the mass concentration of the reaction solution corresponding to the theoretical generation amount of the intermediate ammonium dihydrogen borate is 25% - 30%.