A method for preparing high purity, low moisture ethoxy pentafluoro-cyclotriphosphazene

Abstract

The application discloses a preparation method of high-purity and low-moisture ethoxy pentafluorocyclotriphosphazene. The crude ethoxy pentafluorocyclotriphosphazene is pretreated by a drying agent, filtered to obtain a first dried crude product, then the first dried crude product is subjected to secondary drying by removing water through reaction of a metal organic reagent, and the dried crude product is subjected to reduced-pressure rectification to obtain a target compound with a purity of 99.9% or above. The method has the advantages of simple operation, convenient post-treatment, and high-purity and low-moisture high-quality product ethoxy pentafluorocyclotriphosphazene, and is an effective method easy for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of electronic material synthesis and relates to a method for preparing high-purity, low-moisture ethoxypentafluorocyclotriphosphazene. Background Technology

[0002] Ethoxypentafluorocyclotriphosphazene (abbreviated as pentafluorocyclotriphosphazene) has the following chemical structural formula:

[0003]

[0004] Ethoxypentafluorocyclotriphosphazene, as an additive in lithium-ion battery electrolytes, is added at a proportion of 0.5% to 15.0%. It has good flame retardant effects, can effectively reduce corrosion of battery casings and current collectors, and extend battery life, showing broad market prospects. As an additive component in lithium-ion battery electrolytes, products with high purity, low moisture content, and low metal ion residue are required to meet the requirements of additive components.

[0005] Currently, there is no mature industrial synthesis route for 2-ethoxypentafluorocyclotriphosphazene, and it is mainly in the research and development stage. Patent CN117736243 A discloses a method for preparing ethoxy(pentafluoro)cyclotriphosphazene. This method uses hexachlorocyclotriphosphazene (PNC) as a raw material for synthesis. First, an ethoxylation reaction is carried out in the presence of sodium ethoxide or lithium ethoxide solution, followed by a reaction with a metal fluoride to obtain the target product, 2-ethoxypentafluorocyclotriphosphazene. The synthetic route is shown below:

[0006]

[0007] However, the phosphorus-chloride bond in hexachlorocyclotriphosphazene (PNC) is highly reactive. When reacted with alkali metal sodium alkoxides, its high reactivity makes it difficult to control the reaction at the monosubstituted stage, resulting in disubstituted, trisubstituted, and even polysubstituted impurities. Subsequent reactions produce polysubstituted impurities, and the reaction selectivity decreases, leading to poor product purity. Furthermore, residual chlorobenzene from the raw material hexachlorocyclotriphosphazene is continuously introduced into the product. Chlorobenzene's boiling point of 132℃ is close to the product's boiling point, making effective separation difficult and significantly increasing the separation challenge. Current technologies can only achieve a product purity of 99.0%–99.5% and a moisture content of 300–500 ppm, which fails to meet the quality requirements for lithium-ion battery electrolyte additives. To achieve a purity higher than 99.9% and a moisture content lower than 50 ppm or even lower, multiple distillations are required, necessitating a significant increase in distillation column height. This undoubtedly increases equipment investment costs and significantly raises production costs.

[0008] Currently, existing technologies and methods rarely mention how to improve the purity of ethoxypentafluorocyclotriphosphazene and reduce the product to trace amounts of moisture.

[0009] In order to overcome the difficulties of existing technical processes, the present invention provides a preparation method that is simple to operate, easy to control in terms of quality indicators, and easy to industrialize. Summary of the Invention

[0010] To address the aforementioned technical challenges, this invention provides a simple, convenient, and industrially applicable preparation method that yields high-purity, low-moisture products. This method employs a desiccant for pre-drying to reduce moisture content to below 200 ppm, followed by filtration, chemical dehydration, and vacuum distillation to obtain high-purity, low-moisture ethoxypentafluorocyclotriphosphazene. The preparation method of this invention is combined with... Figure 1 It was achieved.

[0011] A method for synthesizing ethoxypentafluorocyclotriphosphazene includes the following steps: (1) adding a desiccant to crude ethoxypentafluorocyclotriphosphazene for pretreatment, reducing the moisture content to below 200 ppm, and then filtering; (2) adding an organometallic reagent to the pretreated crude ethoxypentafluorocyclotriphosphazene to react and remove water, reducing the moisture content to below 30 ppm, wherein the amount of organometallic reagent used is 0.1% to 0.5% of the crude ethoxypentafluorocyclotriphosphazene mass; (3) the low-moisture ethoxypentafluorocyclotriphosphazene is then subjected to vacuum distillation to remove impurities, thereby obtaining a high-quality product with a purity higher than 99.9% ethoxypentafluorocyclotriphosphazene.

[0012] As a preferred embodiment of the present invention, the desiccant selected in step (1) is magnesium sulfate, sodium carbonate, potassium carbonate, neutral alumina, 3A molecular sieve, 4A molecular sieve, etc., and is further preferred to be magnesium sulfate, sodium carbonate, 3A molecular sieve, 4A molecular sieve, etc.

[0013] As a preferred embodiment of the present invention, the amount of desiccant selected in step (1) is 1‰ to 5% of the crude ethoxypentafluorocyclotriphosphazene, and more preferably 3‰ to 5‰.

[0014] As a preferred embodiment of the present invention, the organometallic reagent selected in step (2) is sodium ethoxide, magnesium ethoxide, sodium tert-butoxide, aluminum isopropoxide, lithium aluminum hydride, methyl magnesium chloride, isopropyl magnesium chloride, phenyl magnesium chloride, or other Grignard reagents.

[0015] As a preferred embodiment of the present invention, the temperature of the dehydration reaction in step (2) is 30~50℃, and more preferably 35~40℃.

[0016] As a preferred embodiment of the present invention, the dehydration reaction time in step (2) is 1~24 h, and more preferably 2~4 h.

[0017] As a preferred embodiment of the present invention, step (3) employs vacuum distillation with a reflux ratio of 20:1 to 4:1.

[0018] As a preferred embodiment of the present invention, the temperature of vacuum distillation in step (3) is 30~120℃, more preferably 50~55℃, and the vacuum degree of vacuum distillation is -0.08MPa.

[0019] Beneficial effects:

[0020] (1) The present invention uses a drying reagent for pre-drying, stirs thoroughly, and dries evenly, effectively reducing the moisture content of the crude product to below 200 ppm;

[0021] (2) The present invention adds chemical reagents to remove water, effectively reducing the water content to below 30 ppm. Then, a trace amount of water and residual organic impurities are separated by two vacuum distillation processes. Finally, the target product is obtained by vacuum distillation. It has the advantages of low production cost and obvious raw material price advantage.

[0022] (3) The present invention has the advantages of simple production process and industrial production capability; Attached Figure Description

[0023] Figure 1 Process flow diagram for refining ethoxypentafluorocyclotriphosphazene.

[0024] Figure 2 Gas chromatogram of the product ethoxypentafluorocyclotriphosphazene Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1

[0027] Step 1: Pre-drying treatment

[0028] 800 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a mechanical stirrer. The purity of the crude product was determined to be 99.5%, and the water content was 450 ppm. 4.0 g of anhydrous magnesium sulfate was added at room temperature, and the mixture was stirred at room temperature to form a suspension. After stirring for 4 h, a sample was taken to determine the water content until it no longer decreased. The mixture was filtered to obtain 799 g of colorless and transparent liquid, with a water content of 258 ppm.

[0029] Step 2: Chemical dehydration and drying

[0030] Pre-dried ethoxypentafluorocyclotriphosphazene (795.0 g, 2.89 mol, 1.0 eq) was added to a 1000 mL four-necked flask equipped with a mechanical stirrer. Nitrogen protection was turned on, and 0.90 g of solid sodium ethoxide was added at room temperature. The mixture was stirred for 30 min until a small amount of solid precipitated. The temperature was raised to 35 °C and stirred for 3 h until the water content no longer decreased. The water content was measured to be 19 ppm. The mixture was then used directly for the next step of vacuum distillation without further treatment.

[0031] Step 3: Vacuum distillation of ethoxypentafluorocyclotriphosphazene

[0032] 795 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a distillation apparatus. The mixture was heated in an oil bath and distilled under reduced pressure. The oil bath temperature was increased by 50-55 °C, the vacuum degree was -0.08 MPa, and the reflux ratio was controlled at 20:1-15:1. Chlorobenzene was collected as the solvent for the initial fraction. When no chlorobenzene residue remained in the fraction, the reflux ratio was adjusted to 6:1 and the product was collected, yielding 750 g of a colorless and transparent liquid. The distillation yield was 93.8%, the product purity was determined to be 99.99% by GC, and the water content was 16 ppm.

[0033] Example 2

[0034] Step 1: Pre-drying treatment

[0035] 1000 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a mechanical stirrer. The purity of the crude product was determined to be 99.5%, and the water content was 464 ppm. 4.0 g of 3A molecular sieve was added at room temperature, and the mixture was stirred at room temperature to form a suspension. After stirring for 4 h, a sample was taken to determine the water content until it no longer decreased. The mixture was then filtered to obtain 960 g of colorless and transparent liquid, with a water content of 180 ppm.

[0036] Step 2: Chemical dehydration and drying

[0037] Pre-dried ethoxypentafluorocyclotriphosphazene (960.0 g, 3.49 mol, 1.0 eq) was added to a 1000 mL four-necked flask equipped with a mechanical stirrer. Nitrogen protection was turned on, and 1.65 g of solid magnesium isopropoxide was added at room temperature. The mixture was stirred for 30 min until a small amount of solid precipitated. The temperature was raised to 40 °C and stirred for 4 h until the moisture content no longer decreased. The moisture content was measured to be 25 ppm. The mixture was then used directly for the next step of vacuum distillation without further treatment.

[0038] Step 3: Vacuum distillation of ethoxypentafluorocyclotriphosphazene

[0039] 960 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a distillation apparatus. The mixture was heated in an oil bath and distilled under reduced pressure. The oil bath temperature was increased by 50-55 °C, the vacuum degree was -0.08 MPa, and the reflux ratio was controlled at 20:1-14:1. Chlorobenzene was collected as the solvent for the first fraction. When no chlorobenzene residue remained in the fraction, the reflux ratio was adjusted to 4:1 and the product was collected, yielding 870 g of a colorless and transparent liquid. The distillation yield was 90.6%. The purity of the product was determined by GC to be 99.95%, and the anhydrous content was 13 ppm.

[0040] Example 3

[0041] Step 1: Pre-drying treatment

[0042] 1000 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a mechanical stirrer. The purity of the crude product was determined to be 99.5%, and the water content was 400 ppm. 1.0 g of potassium carbonate was added at room temperature, and the mixture was stirred at room temperature to form a suspension. After stirring for 4 h, a sample was taken to determine the water content until it no longer decreased. The mixture was then filtered to obtain 965 g of colorless and transparent liquid, with a water content of 220 ppm.

[0043] Step 2: Chemical dehydration and drying

[0044] Pre-dried ethoxypentafluorocyclotriphosphazene (960.0 g, 3.49 mol, 1.0 eq) was added to a 1000 mL four-necked flask equipped with a mechanical stirrer. Nitrogen protection was turned on, and 2.63 g of solid lithium aluminum hydride was added at room temperature. The mixture was stirred for 30 min until a small amount of solid precipitated. The temperature was raised to 40 °C and stirred for 4 h until the moisture content no longer decreased. The moisture content was measured to be 28 ppm. The mixture was then used directly for the next step of vacuum distillation without further treatment.

[0045] Step 3: Vacuum distillation of ethoxypentafluorocyclotriphosphazene

[0046] 960 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a distillation apparatus. The mixture was heated in an oil bath and distilled under reduced pressure. The oil bath temperature was increased by 50-55 °C, the vacuum degree was -0.08 MPa, and the reflux ratio was controlled at 12:1-4:1. Chlorobenzene was collected as the solvent for the first fraction. When no chlorobenzene residue remained in the fraction, the reflux ratio was adjusted to 4:1 and the product was collected. 876 g of a colorless and transparent liquid was obtained, with a distillation yield of 91.3%. The purity of the product was determined to be 99.92% by GC, and the anhydrous content was 18 ppm.

[0047] Example 4

[0048] Step 1: Pre-drying treatment

[0049] 1000 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a mechanical stirrer. The purity of the crude product was determined to be 99.5%, and the water content was 464 ppm. 5.0 g of 4A molecular sieve was added at room temperature, and the mixture was stirred at room temperature to form a suspension. After stirring for 4 h, a sample was taken to determine the water content until it no longer decreased. The mixture was then filtered to obtain 960 g of colorless and transparent liquid, with a water content of 165 ppm.

[0050] Step 2: Chemical dehydration and drying

[0051] Pre-dried ethoxypentafluorocyclotriphosphazene (960.0 g, 3.49 mol, 1.0 eq) was added to a 1000 mL four-necked flask equipped with a mechanical stirrer. Nitrogen protection was turned on, and 4.8 g of methyl magnesium chloride solution was added at room temperature. The mixture was stirred for 30 min until a small amount of solid precipitated. The temperature was raised to 40 °C and stirred for 4 h until the water content no longer decreased. The water content was measured to be 17 ppm. The mixture was then used directly for the next step of vacuum distillation without further treatment.

[0052] Step 3: Vacuum distillation of ethoxypentafluorocyclotriphosphazene

[0053] 960 g of crude ethoxypentafluorocyclotriphosphazene was added sequentially to a 1000 mL four-necked flask equipped with a distillation apparatus. The mixture was heated in an oil bath and distilled under reduced pressure. The oil bath temperature was increased by 50-55 °C, the vacuum degree was -0.08 MPa, and the reflux ratio was controlled at 15:1-5:1. Chlorobenzene was collected as the solvent for the initial fraction. When no chlorobenzene residue remained in the fraction, the reflux ratio was adjusted to 4:1 to collect the product, yielding 872 g of a colorless and transparent liquid. The distillation yield was 90.8%, the product purity was determined to be 99.94% by GC, and the anhydrous content was 13 ppm.

Claims

1. A method for preparing low-moisture, high-purity ethoxypentafluorocyclotriphosphazene, characterized in that... The process includes the following steps: (1) adding a desiccant to the crude ethoxypentafluorocyclotriphosphazene for pretreatment until the moisture content is reduced to below 200 ppm, followed by filtration; (2) adding an organometallic reagent to the pretreated crude ethoxypentafluorocyclotriphosphazene to remove water, thereby reducing the moisture content to below 30 ppm, and obtaining low-moisture ethoxypentafluorocyclotriphosphazene; (3) removing impurities by vacuum distillation of the low-moisture ethoxypentafluorocyclotriphosphazene to obtain ethoxypentafluorocyclotriphosphazene with a purity higher than 99.9%.

2. The preparation method according to claim 1, characterized in that... The desiccant selected in step (1) is magnesium sulfate, sodium carbonate, potassium carbonate, neutral alumina, 3A molecular sieve, and 4A molecular sieve.

3. The preparation method according to claim 1, characterized in that... The amount of desiccant selected in step (1) is 1‰ to 5‰ of the crude ethoxypentafluorocyclotriphosphazene.

4. The preparation method according to claim 1, characterized in that... The organometallic reagents selected in step (2) are sodium ethoxide, magnesium ethoxide, sodium tert-butoxide, aluminum isopropoxide, lithium aluminum hydride, methyl magnesium chloride, isopropyl magnesium chloride, phenyl magnesium chloride, or magnesium isopropoxide.

5. The preparation method according to claim 1, characterized in that... In step (2), the amount of organometallic reagent used is 0.1% to 0.5% of the crude ethoxypentafluorocyclotriphosphazene.

6. The preparation method according to claim 1, characterized in that... The temperature of the dehydration reaction in step (2) is 30~50℃.

7. The preparation method according to claim 1, characterized in that... The dehydration reaction temperature in step (2) is 35~40℃.

8. The preparation method according to claim 1, characterized in that... The dehydration reaction time in step (2) is 2-4 hours.

9. The preparation method according to claim 1, characterized in that... Step (3) uses vacuum distillation to select a reflux ratio of 20:1 to 2:

1.

10. The preparation method according to claim 1, characterized in that... Step (3) uses a vacuum distillation temperature of 50~55℃ and a vacuum degree of -0.08MPa.

Images