A method for synthesizing tris(trimethylsilyl) phosphate

Abstract

This invention discloses a method for synthesizing tris(trimethylsilyl)phosphate, comprising mixing trimethylsilylacetic acid, phosphate, phase transfer catalyst, and organic solvent, and reacting them under a flowing inert gas atmosphere; after the reaction, filtering is performed, and the filtrate is distilled to obtain tris(trimethylsilyl)phosphate. This method uses phosphate and trimethylsilylacetic acid as raw materials to prepare tris(trimethylsilyl)phosphate, with low reaction temperature, high product yield and purity, and low production cost, making it suitable for industrial application.

Description

Technical Field

[0001] This invention relates to a method for synthesizing tris(trimethylsilyl)phosphate, specifically a method for synthesizing tris(trimethylsilyl)phosphate with a mild reaction temperature and low reaction cost, belonging to the field of lithium-ion battery electrolyte additive technology. Background Technology

[0002] Tris(trimethylsilyl)phosphate (TMSP) can be used as an additive in lithium-ion battery electrolytes.

[0003] It can oxidize and decompose on the surface of high-nickel ternary cathode materials to generate a cathode solid electrolyte interface (CEI) film mainly composed of silicates (rich in lithium-ion conduction properties) and inorganic lithium carbonate (electrochemically stable). Due to the low content of electrolyte decomposition products (organic lithium carbonate and lithium fluoride), the CEI film formed after the addition of TMSP is thin and uniform, which can effectively reduce the polarization voltage during charge and discharge, isolate the contact between the electrolyte and the cathode, reduce electrolyte decomposition, inhibit the dissolution of metal ions, and stabilize the cathode crystal structure. This allows the high-nickel ternary cathode material to maintain good cycle performance and rate performance even when cycling at a high voltage of 4.5V.

[0004] Numerous methods for synthesizing tris(trimethylsilyl)phosphate have been reported both domestically and internationally. Summarizing current patent literature, researchers have optimized and developed the production process of tris(trimethylsilyl)phosphate by selecting different reactants, solvents, catalysts, and reaction temperatures. Existing methods mainly include: 1. Using hexamethyldisiloxane and phosphorus pentoxide or phosphoric acid as reactants, reacting under high temperature or reflux to obtain tris(trimethylsilyl)phosphate. This reaction process requires high temperatures, is relatively dangerous, energy-intensive, time-consuming, and has a low yield. 2. Adding trimethylchlorosilane to phosphoric acid after removing free water, stirring, heating, and refluxing, followed by distillation under reduced pressure to obtain tris(trimethylsilyl)phosphate. This method significantly improves the yield (84%~85%), but the reaction temperature remains high, and the purity of the obtained tris(trimethylsilyl)phosphate is low. III. Tris(trimethylsilazane) phosphate was purified by distillation with a phase catalyst to obtain tris(trimethylsilyl) phosphate. The final product yield was over 85%, but the temperature was still relatively high.

[0005] Therefore, it is of great significance to develop a production process with low reaction temperature, high purity, and high yield to prepare tris(trimethylsilyl)phosphate. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for synthesizing tris(trimethylsilyl)phosphate. This method uses phosphate and trimethylsilylacetic acid as raw materials to prepare tris(trimethylsilyl)phosphate. The reaction temperature is low, the yield and purity of the obtained product are high, and the production cost is low, making it suitable for industrial applications.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for synthesizing tris(trimethylsilyl)phosphate, comprising mixing trimethylsilylacetic acid, phosphate, phase transfer catalyst and organic solvent, and reacting them under a flowing inert gas atmosphere; filtering after the reaction, and distilling the filtrate to obtain tris(trimethylsilyl)phosphate.

[0009] Furthermore, this invention uses trimethylsilylacetic acid and phosphate as raw materials to react and generate tris(trimethylsilyl)phosphate, as shown in the following reaction formula:

[0010]

[0011] Furthermore, there are no special requirements for the mixing order of trimethylsilylacetic acid, phosphate, phase transfer catalyst and organic solvent. The phosphate, phase transfer catalyst and organic solvent can be mixed first and then trimethylsilylacetic acid can be added; the trimethylsilylacetic acid, phosphate and organic solvent can be mixed first and then phase transfer catalyst can be added; or the trimethylsilylacetic acid, phosphate and phase transfer catalyst can be added to the organic solvent at the same time.

[0012] Furthermore, the phosphate is at least one of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate, etc., preferably ammonium dihydrogen phosphate.

[0013] Furthermore, the molar ratio of trimethylsilylacetic acid to ammonium dihydrogen phosphate is 3 to 4:1, for example 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, or 4:1.

[0014] Furthermore, the phase transfer catalyst is a quaternary ammonium salt catalyst. The quaternary ammonium salt catalyst can be at least one selected from benzyltributylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium acetate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, dodecylpyridine chloride, and hexadecyltrimethylammonium chloride. Preferably, the phase transfer catalyst is tetrabutylammonium chloride, dodecylpyridine chloride, or dodecyltrimethylammonium chloride, which results in better yields.

[0015] Furthermore, the mass of the phase transfer catalyst is 0.3% to 0.6% of the mass of trimethylsilylacetic acid, for example, 0.3%, 0.4%, 0.5%, or 0.6%.

[0016] Furthermore, the organic solvent is at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, methyl tert-butyl ether, tetrahydrofuran, acetonitrile, acetone, etc. Preferably, dimethyl carbonate, ethylene carbonate, or acetone is used as the organic solvent, resulting in better yields.

[0017] Furthermore, the mass-to-volume ratio of trimethylsilylacetic acid to organic solvent is 1g:1.5 to 3mL, for example, 1g:1.5ml, 1g:2.0ml, 1g:2.5ml, 1g:3.0ml.

[0018] Further, trimethylsilylacetic acid, phosphate, phase transfer catalyst, and organic solvent are mixed, an inert gas is introduced, and then the reaction is carried out at the reaction temperature. The reaction temperature is 25℃ to 60℃, for example, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃. The reaction time is generally 8 to 24 hours, for example, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, and 24 hours.

[0019] Furthermore, during the reaction, an inert gas is continuously introduced into the reaction system because the products are sensitive to moisture in the air, thus requiring the introduction of an inert gas for protection. The inert gas is nitrogen or argon, preferably nitrogen. The inert gas concentration is 0.5~2.0 m... 3 The gas is continuously introduced into the reaction system at a rate of / h, for example, 0.5m. 3 / h, 1.0m 3 / h, 1.5m 3 / h, 2.0m 3 / h.

[0020] Furthermore, after the reaction, the reaction solution is first filtered to remove the phase transfer catalyst, and the resulting filtrate is subjected to vacuum distillation under conditions of 5~10 mmHg. The fraction collected at 110~128℃ is tris(trimethylsilyl)phosphate.

[0021] This invention utilizes trimethylsilylacetic acid and phosphate via a phase transfer catalyst to catalyze the preparation of tris(trimethylsilyl)phosphate, which has the following advantages compared to existing technologies:

[0022] 1. Using trimethylsilylacetic acid results in a lower reaction temperature, lower risk, lower energy consumption, and lower cost;

[0023] 2. By utilizing quaternary ammonium salt catalysts in combination with organic solvents, and through the optimization of catalysts and organic solvents, the yield of tris(trimethylsilyl)phosphate was further improved.

[0024] 3. The product produced by this invention has high purity and a yield of over 95%. The process is simple, the reaction conditions are mild, and it is easy to carry out industrial production. Attached Figure Description

[0025] Figure 1 The image shows the gas chromatogram of the product obtained in Example 2.

[0026] Figure 2 This is the mass spectrum of the product obtained in Example 2. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments, making the advantages of the present invention more apparent. It should be understood that the content therein is for illustrative purposes only and is not intended to limit the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0028] In the following examples, product purity was determined using the area normalization method of gas chromatography.

[0029] Example 1

[0030] A method for synthesizing tris(trimethylsilyl)phosphate, comprising the following steps:

[0031] Add 223.19 g of trimethylsilylacetic acid, 57.1 g of ammonium dihydrogen phosphate, and 334.79 ml of dimethyl carbonate to a flask, then add 0.67 g of tetrabutylammonium chloride, stir, and simultaneously introduce nitrogen gas at a flow rate of 1 m³ / min. 3 A flow rate of [flow rate] / h was introduced, and the mixture was heated to 40°C and reacted for 12 hours. The tail gas generated during the reaction was treated using an aqueous solution absorption method.

[0032] After the reaction is complete, the reaction solution is filtered to obtain the filtrate, which is then distilled at 5-10 mmHg. The fraction collected at 110-128℃ is obtained to obtain the tris(trimethylsilyl)phosphate product with a purity of 99.97% and a yield of 96.1% based on ammonium dihydrogen phosphate.

[0033] Example 2

[0034] A method for preparing a tris(trimethylsilyl)phosphate ester includes the following steps:

[0035] Add 230.52 g of trimethylsilylacetic acid, 55.7 g of ammonium dihydrogen phosphate, and 461.04 ml of dimethyl carbonate to a flask, then add 0.92 g of tetrabutylammonium chloride, stir, and simultaneously introduce nitrogen gas at a flow rate of 1.5 m³ / min. 3 A flow rate of [flow rate] / h was introduced, and the mixture was heated to 40°C and reacted for 16 hours. The tail gas generated during the reaction was treated using an aqueous solution absorption method.

[0036] After the reaction was complete, the reaction solution was filtered to obtain the filtrate, which was then distilled at 5–10 mmHg. The fraction collected at 110–128 °C yielded the tris(trimethylsilyl)phosphate product with a purity of 99.98% and a yield of 98.6% based on ammonium dihydrogen phosphate. The gas chromatogram and mass spectrum of the obtained product are shown below. Figure 1 and 2 As shown in the figure, tris(trimethylsilyl)phosphate was successfully synthesized.

[0037] Example 3

[0038] A method for preparing a tris(trimethylsilyl)phosphate ester includes the following steps:

[0039] Add 232.28 g of trimethylsilylacetic acid, 53.17 g of ammonium dihydrogen phosphate, and 348.42 ml of dimethyl carbonate to a flask, then add 1.39 g of tetrabutylammonium chloride, stir, and simultaneously introduce nitrogen gas at a flow rate of 2 m³ / min. 3 A flow rate of [flow rate] / h was introduced, and the mixture was heated to 40°C and reacted for 12 hours. The tail gas generated during the reaction was treated using an aqueous solution absorption method.

[0040] After the reaction is complete, the reaction solution is filtered to obtain the filtrate, which is then distilled at 5-10 mmHg. The fraction collected at 110-128℃ is obtained to obtain the tris(trimethylsilyl)phosphate product with a purity of 99.95% and a yield of 96.7% based on ammonium dihydrogen phosphate.

[0041] Examples 4-8

[0042] The preparation method for synthesizing tris(trimethylsilyl)phosphate according to Example 2 differs in that the compositions of the organic solvent and phase transfer catalyst are shown in Table 1 below:

[0043]

[0044] Examples 9-10

[0045] The preparation method of tris(trimethylsilyl)phosphate according to Example 2 differs in that the reaction temperature and reaction time are shown in Table 2 below:

[0046]

[0047] Examples 11-12

[0048] The preparation method of tris(trimethylsilyl)phosphate is the same as that in Example 2, except that the phosphates are shown in Table 3 below:

[0049]

[0050] Comparative Example 1

[0051] The preparation method for synthesizing tris(trimethylsilyl) phosphate was the same as in Example 2, except that ethyl acetate was used as the organic solvent. The yield of the obtained product, based on ammonium dihydrogen phosphate, was 80.4%, and the purity was 96.95%.

[0052] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing tris(trimethylsilyl) phosphate, characterized by: Trimethylsilylacetic acid, phosphate, phase transfer catalyst and organic solvent are mixed and reacted under a flowing inert gas atmosphere; after reaction, the mixture is filtered and the filtrate is distilled to obtain tri(trimethylsilyl)phosphate; the phosphate is ammonium dihydrogen phosphate, the phase transfer catalyst is tetrabutylammonium chloride, and the organic solvent is dimethyl carbonate; the reaction temperature is 40℃~60℃.

2. The method of synthesis of claim 1, wherein: The molar ratio of trimethylsilylacetic acid to ammonium dihydrogen phosphate is 3–4:

1.

3. The method of synthesis of claim 1, wherein: The mass of the phase transfer catalyst is 0.3% to 0.6% of the mass of trimethylsilylacetic acid.

4. The method of synthesis of claim 1, wherein: The mass-to-volume ratio of trimethylsilylacetic acid to organic solvent is 1 g: 1.5–3 mL.

5. The method of synthesis of claim 1, 2, 3, or 4, wherein: The reaction time is 8–24 hours.

6. The method of synthesis of claim 1, 2, 3, or 4, wherein: Inert gas is used at a concentration of 0.5~2.0 m. 3 It is introduced into the reaction system at a rate of / h.

7. The method of synthesis of claim 6, wherein: The inert gas is nitrogen or argon.

8. The synthesis method according to claim 1, 2, 3 or 4, characterized in that: The filtrate was subjected to vacuum distillation at 5-10 mmHg, and the fraction collected at 110-128℃ was tris(trimethylsilyl)phosphate.

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