Process for the preparation of ethoxy pentafluorocyclotriphosphazene

Abstract

The application discloses a preparation method of ethoxy pentafluorocyclotriphosphazene and belongs to the technical field of electrolyte flame-retardant additives. The technical scheme comprises the following steps of S1, fluorination reaction: dissolving hexachlorocyclotriphosphazene in an organic solvent, adding ammonium hydrogen fluoride to perform fluorination reaction, and obtaining hexafluorocyclotriphosphazene; the reaction temperature of the fluorination reaction is 85-90 DEG C, the reaction time is 4-6 hours, and the reaction is performed under the state that the dimethyl carbonate is refluxed; and S2, ethoxylation reaction: reacting the hexafluorocyclotriphosphazene with an ethoxylation reagent under the catalysis of a catalyst to obtain ethoxy pentafluorocyclotriphosphazene. The application can realize efficient fluorination of hexachlorocyclotriphosphazene under mild and safe conditions, and solves the problems of difficult fluorination reaction conditions in the prior art.

Description

Technical Field

[0001] This invention belongs to the technical field of electrolyte flame retardant additives, and particularly relates to a method for preparing ethoxypentafluorocyclotriphosphazene. Background Technology

[0002] Ethoxypentafluorocyclotriphosphazene (P3N3F5OC2H5) is a colorless and transparent liquid containing phosphorus, nitrogen, and fluorine—three flame-retardant elements. Upon thermal decomposition, it releases phosphorus and fluorine-containing free radicals, which capture H· and OH· free radicals in the electrolyte combustion chain reaction, effectively interrupting the combustion process. With the continuous increase in the energy density of lithium-ion batteries, thermal runaway and combustion safety issues have become increasingly prominent, making ethoxypentafluorocyclotriphosphazene a widely recognized flame-retardant additive for electrolytes.

[0003] Currently, there are two main types of publicly disclosed methods for preparing ethoxypentafluorocyclotriphosphazene. The first type is the fluorination-then-etherification route. Using hexachlorocyclotriphosphazene (HCCP) as a raw material, a fluorination reaction is first performed to obtain a hexafluorocyclotriphosphazene (HFPN) intermediate, followed by an ethoxylation reaction to obtain the target product. For example, potassium fluoride is used as the fluorinating agent, and fluorination is carried out in a mixed solvent before reacting with an ethoxylation reagent, with yields ranging from 55.2% to 86.5%. Alternatively, pyridine hydrofluoric acid salt is used as the fluorinating agent, fluorinated at low temperatures, and then etherified with an ethoxide. The second type is the etherification-then-fluorination route. Hexachlorocyclotriphosphazene is first reacted with an ethoxylation reagent to generate a monoethoxylated pentachlorocyclotriphosphazene intermediate, followed by fluorination. For example, lithium ethoxide is used for alkylation, and the byproduct lithium chloride can be recycled.

[0004] The existing technologies mentioned above still have the following shortcomings: (i) The fluorination reaction conditions are harsh. Metal fluorinating agents have low solubility in organic solvents, poor solid-liquid multiphase mass transfer, and require high temperature and long reaction time; hydrogen fluoride is highly corrosive and toxic, requiring high-end equipment and is not suitable for industrialization; pyridine hydrofluoric acid is expensive and highly toxic. (ii) The acidic tail gas treatment method has obvious defects. Directly adding calcium carbonate into the reaction system to neutralize HF will cause the generated water to trigger HCCP hydrolysis and ring opening, and the generated calcium fluoride is a colloidal fine powder, which is difficult to filter. (iii) The ethoxylation has poor atom economy. The sodium ethoxide method produces equimolar sodium fluoride waste salt, which is a serious waste of atoms, and sodium ethoxide is hygroscopic and requires harsh anhydrous conditions. (iv) Selectivity control is difficult. All six fluorine atoms of hexafluorocyclic triphosphazene can be substituted, which easily generates disubstituted and trisubstituted byproducts with similar properties to the target product, making it difficult to separate by distillation.

[0005] Therefore, there is an urgent need for a preparation method that can achieve efficient fluorination of hexachlorocyclotriphosphazene under mild and safe conditions and properly treat acidic tail gas, and can develop a process that has high atom economy, few by-products, good selectivity for ethoxylation, and reduces waste and improves production efficiency. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is the difficulty of fluorination reaction conditions in the existing technology, and a method for preparing ethoxypentafluorocyclotriphosphazene that can achieve efficient fluorination of hexachlorocyclotriphosphazene under mild and safe conditions is proposed.

[0007] To solve the aforementioned technical problem, the technical solution adopted by the present invention includes: S1 Fluorination reaction: Hexachlorocyclotriphosphazene is dissolved in an organic solvent, and ammonium bifluoride is added to carry out a fluorination reaction to prepare hexafluorocyclotriphosphazene; the reaction temperature of the fluorination reaction is 85-90℃, the reaction time is 4-6 hours, and the reaction is carried out under the condition of reflux of the dimethyl carbonate during the reaction. S2 Ethoxylation reaction: Hexafluorocyclotriphosphazene is reacted with an ethoxylation reagent under the catalysis of a catalyst to prepare ethoxypentafluorocyclotriphosphazene.

[0008] In some embodiments, the molar ratio of hexachlorocyclotriphosphazene to ammonium bifluoride is 1:6 to 1:8.

[0009] In some embodiments, the ethoxylation agent is diethyl carbonate.

[0010] In some embodiments, the molar ratio of hexafluorocyclotriphosphazene to diethyl carbonate is 1:1 to 1:3.

[0011] In some embodiments, the catalyst is one of DBU, ethylene glycol dimethyl ether, and acetonitrile.

[0012] In some embodiments, the molar ratio of DBU to hexafluorocyclotriphosphazene is 0.05:1 to 0.2:1.

[0013] In some embodiments, the organic solvent is DMC.

[0014] In some embodiments, the S1 fluorination reaction is carried out at a temperature of 85–90°C for 4–6 hours, with the dimethyl carbonate being refluxed during the reaction.

[0015] In some embodiments, the tail gas in the S1 fluorination reaction is externally dry absorbed using a tail gas absorption device filled with calcium carbonate.

[0016] In some embodiments, the S2 ethoxylation reaction is carried out at a temperature of 30–35°C for 2–3 hours, under ultrasonic-assisted conditions, with an ultrasonic frequency of 40 kHz.

[0017] In some embodiments, a post-processing step is also included: after the ethoxylation reaction is completed, the reaction solution is filtered, washed with water, and dried. The dried organic phase is then distilled under reduced pressure, and the fraction is collected to obtain the finished product, ethoxypentafluorocyclotriphosphazene.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The use of ammonium bifluoride as a fluorinating agent in this invention results in a higher conversion rate and milder reaction conditions for the fluorination reaction; 2. The use of diethyl carbonate as the ethoxylation reagent in this invention makes the byproducts of the ethoxylation reaction easier to handle, accurately achieves monoethoxylation of hexafluorocyclotriphosphazene, and results in higher purity of the reaction product. Attached Figure Description

[0019] Figure 1 The gas chromatogram of hexafluorocyclotriphosphazene provided in Example 1 of the present invention; Figure 2 The gas chromatogram of ethoxypentafluorocyclotriphosphazene provided in Example 1 of the present invention; Detailed Implementation The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0020] This invention provides a method for preparing ethoxypentafluorocyclotriphosphazene, comprising: S1 fluorination reaction: dissolving hexachlorocyclotriphosphazene in an organic solvent, adding ammonium bifluoride to carry out a fluorination reaction, and preparing hexafluorocyclotriphosphazene; the reaction temperature of the fluorination reaction is 85-90°C, the reaction time is 4-6 hours, and the reaction is carried out under the condition of reflux of the dimethyl carbonate during the reaction; S2 Ethoxylation reaction: Hexafluorocyclotriphosphazene is reacted with an ethoxylation reagent under the catalysis of a catalyst to prepare ethoxypentafluorocyclotriphosphazene.

[0021] This invention uses ammonium bifluoride as a fluorinating agent, resulting in a higher conversion rate and milder reaction conditions for the fluorination reaction. Ammonium bifluoride (NH4HF2) is a commonly used fluorinating agent. The main reaction is: P3N3Cl6 + 6NH4HF2 → P3N3F6 + 6NH4Cl + 6HF. Under heating conditions, hydrogen fluoride (HF) is released: NH4HF2 → NH4F + HF. The released HF undergoes a fluorine-chlorine exchange reaction with the P-Cl bond of hexachlorocyclotriphosphazene, where chlorine atoms are gradually replaced by fluorine atoms, ultimately generating perfluorinated hexafluorocyclotriphosphazene. Compared to potassium fluoride (KF) used in the prior art, ammonium bifluoride has the following advantages: ammonium bifluoride has a certain solubility in organic solvents such as DMC, which is conducive to the occurrence of homogeneous or quasi-homogeneous reactions; ammonium bifluoride has a strong fluorinating ability and can achieve complete fluorination at a relatively low temperature (85-90℃); the byproduct of the reaction is ammonium chloride (NH4Cl), which is a water-soluble salt and is easily removed by washing with water.

[0022] The boiling point of DMC is 90℃, and the reaction is carried out under reflux conditions with an internal temperature stable at 85–90℃. At this temperature, ammonium bifluoride can effectively release HF, and the P-Cl bond of hexachlorocyclotriphosphazene has sufficient reactivity, allowing the fluorine-chlorine exchange reaction to complete within a reasonable time. Too low a temperature results in a slow reaction rate and incomplete fluorination; too high a temperature may lead to the decomposition of the cyclotriphosphazene skeleton or the occurrence of side reactions. A reaction time of 4–6 hours is recommended: within this time range, the fluorination reaction can proceed fully, with a conversion rate of over 95% for hexachlorocyclotriphosphazene. Too short a reaction time results in incomplete fluorination; too long a reaction time increases energy consumption and reduces economic efficiency.

[0023] In some embodiments, the molar ratio of hexachlorocyclotriphosphazene to ammonium bifluoride is 1:6 to 1:8. It is understood that those skilled in the art can adjust the molar ratio of each component within the above range according to actual conditions. For example, the molar ratio of hexachlorocyclotriphosphazene to ammonium bifluoride can also be 1:6.5, 1:7, 1:7.5, or any value within the above range.

[0024] In some embodiments, the reaction system after fluorination is post-treated. After the fluorination reaction, the reaction solution contains the following components: target product: hexafluorocyclotriphosphazene (HFPN), dissolved in DMC; byproduct: ammonium chloride (NH4Cl, dissolved in DMC or suspended); solvent: DMC. The specific post-treatment steps are as follows: Filtration: The reaction solution is filtered while hot to remove some of the NH4Cl solid, resulting in a DMC filtrate containing HFPN; the filtrate is washed 1-2 times with deionized water to remove residual NH4Cl and unreacted NH4HF2; the separated organic phase is dried with anhydrous sodium sulfate or anhydrous magnesium sulfate; distillation is performed under reduced pressure to collect the hexafluorocyclotriphosphazene fraction, yielding crude hexafluorocyclotriphosphazene; the crude hexafluorocyclotriphosphazene can be further purified by reduced pressure distillation or low-temperature recrystallization to obtain a high-purity hexafluorocyclotriphosphazene intermediate.

[0025] In some embodiments, the ethoxylation reagent is diethyl carbonate. This invention uses diethyl carbonate (DEC) as the ethoxylation reagent, instead of the traditional sodium ethoxide. The DEC molecule contains two ethoxy groups (—OC₂H₅), which can serve as a source of ethoxy groups. Under the catalysis of DBU, one ethoxy group in DEC is cleaved, nucleophilically substituting the phosphorus atom of HFPN, thus achieving ethoxylation. Compared to sodium ethoxide used in the prior art, diethyl carbonate has the following advantages: DEC is a commonly used solvent component in lithium-ion battery electrolytes, with wide availability and moderate price; DEC has low toxicity, good safety, and mild operating conditions; the reaction byproducts of DEC are CO₂ and a small amount of ethanol or fluoroethyl carbonate, without producing fluorinated waste salts, resulting in higher atom economy; DEC is a liquid under reaction conditions, making it easy to meter and add.

[0026] In some embodiments, the molar ratio of hexafluorocyclotriphosphazene to diethyl carbonate is 1:1 to 1:3. It is understood that those skilled in the art can adjust the molar ratio of each component within the above range according to actual conditions. For example, the molar ratio of hexafluorocyclotriphosphazene to diethyl carbonate can also be 1:1.5, 1:2, 1:2.5 or any value within the above range.

[0027] In some embodiments, the catalyst is DBU. DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) is a strong organic base (pKa≈13.9) that plays the following roles in the ethoxylation reaction: DBU acts as a base catalyst, activating the ethoxy group of DEC, making it easier for it to launch a nucleophilic attack on the phosphorus atom of HFPN; DBU can neutralize the HF released in the reaction to form DBU·HF salt, preventing HF from corroding the equipment and inhibiting the reaction; DBU·HF salt is a solid and can be removed from the reaction system by filtration, making post-treatment simple.

[0028] Using hexafluorocyclotriphosphazene (HFPN) obtained in the first step as a raw material, diethyl carbonate (DEC) as the ethoxylation reagent, and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) as a catalyst, the reaction was carried out at 30–35 °C with ultrasonic assistance (40 kHz) for 2–3 hours, yielding the target product, ethoxypentafluorocyclotriphosphazene (EtPFPN), via ethoxylation. The actual reaction is: P3N3F6 + (C2H5O)2CO → P3N3F5OC2H5 + CO2 + C2H5OH. Under DBU catalysis, ethoxylation occurs, with one ethoxy group transferring to HFPN and the other departing as CO2 and ethanol.

[0029] In some embodiments, the molar ratio of DBU to hexafluorocyclotriphosphazene is 0.05:1 to 0.2:1.

[0030] In some embodiments, the organic solvent is one of DMC, ethylene glycol dimethyl ether, and acetonitrile.

[0031] In some preferred embodiments, dimethyl carbonate (DMC) is used as the solvent. Dimethyl carbonate (DMC) is a green and environmentally friendly polar aprotic solvent with the following characteristics: it has good solubility for both hexachlorocyclotriphosphazene and ammonium bifluoride, which is beneficial for the reaction of reactants under homogeneous conditions; DMC has a boiling point of 90°C, and the reaction is carried out under reflux (internal temperature 85–90°C), which is beneficial for stable temperature control; DMC has low toxicity and good biodegradability, making it an environmentally friendly green solvent; under the reaction conditions defined in this invention (85–90°C, anhydrous system, immediate consumption of HF and external absorption), DMC, as the main solvent, does not participate in the fluorination reaction. Small amounts of DMC that may undergo acidolysis side reactions can be removed by subsequent distillation without affecting the yield and purity of the target product, and are easy to recover and recycle.

[0032] In some embodiments, the S1 fluorination reaction is carried out at a temperature of 85–90°C for 4–6 hours, with the dimethyl carbonate being refluxed during the reaction.

[0033] In some embodiments, a tail gas absorption device filled with calcium carbonate is used in the S1 fluorination reaction to perform external dry absorption of the tail gas from the fluorination reaction. The HF and HCl gases generated during the reaction are carried out of the reaction system with nitrogen or self-generated gas, separated by a condenser reflux device, and then enter the absorption device filled with calcium carbonate packing. Calcium carbonate undergoes an acid-base neutralization reaction with HF / HCl: CaCO3 + 2HF → CaF2 + H2O + CO2; CaCO3 + 2HCl → CaCl2 + H2O + CO2. The absorbed tail gas is further treated with alkaline solution before being discharged into the atmosphere. This external absorption method avoids the potential hydrolytic effect of moisture introduced by directly adding calcium carbonate to the reaction system on hexachlorocyclotriphosphazene, and simplifies the post-reaction processing procedure.

[0034] In some embodiments, the S2 ethoxylation reaction is carried out at a temperature of 30–35°C for 2–3 hours under ultrasonic-assisted conditions at a frequency of 40 kHz. The reaction temperature of 30–35°C represents mild, low-temperature reaction conditions, which is beneficial for controlling the selectivity of the reaction and avoiding the formation of multi-substituted byproducts. At this temperature, DBU exhibits good catalytic activity, while DEC shows moderate reactivity, and the reaction can be completed within 2–3 hours. The reaction time of 2–3 hours allows for a high conversion rate to be achieved within 2–3 hours under ultrasonic-assisted conditions. Too short a reaction time results in insufficient conversion; too long a reaction time may increase the risk of over-substitution. The ultrasonic frequency of 40 kHz is a commonly used laboratory and industrial ultrasonic frequency, capable of generating effective cavitation effects in the reaction system, and the equipment is mature and easily scaled up. This invention introduces ultrasonic assistance (40 kHz) into the ethoxylation reaction. Its working principle is as follows: ultrasound generates cavitation in the liquid, creating a localized high-temperature, high-pressure microenvironment that promotes the reaction; the cavitation effect and microjets of ultrasound improve the mass and heat transfer efficiency of the reaction system, increasing the collision frequency between reactant molecules; ultrasonic assistance can effectively shorten the reaction time (from several hours in traditional methods to 2-3 hours), improving production efficiency; ultrasonic assistance may also help improve reaction selectivity and reduce the formation of over-substitution byproducts.

[0035] In some embodiments, a post-treatment process is also included: after the ethoxylation reaction is completed, the reaction solution is filtered, washed with water, and dried. The dried organic phase is then distilled under reduced pressure, and the fraction is collected to obtain the finished product, ethoxypentafluorocyclotriphosphazene. After the ethoxylation reaction is completed, the reaction solution contains the following components: target product: ethoxypentafluorocyclotriphosphazene (EtPFPN), dissolved in DEC or the reaction system; byproducts: DBU·HF salt (solid precipitate); unreacted HFPN and DEC; catalyst DBU (small amount of residue). The post-treatment steps are as follows: filtration: the reaction solution is filtered to remove the DBU·HF salt solid precipitate; washing with water: the filtrate is washed 2-3 times with deionized water to remove residual DBU and water-soluble impurities; drying: the organic phase is dried with anhydrous sodium sulfate or anhydrous magnesium sulfate; distillation under reduced pressure (about 5 mmHg), and the fraction at 70-78°C is collected to obtain the colorless and transparent liquid product—ethoxypentafluorocyclotriphosphazene. The 70–78℃ temperature range ensures purity: the true boiling point of ethoxypentafluorocyclotriphosphazene at 5 mmHg is approximately within this range. Collecting the fraction within this range ensures that the product is ethoxypentafluorocyclotriphosphazene, not impurities or other byproducts; it also avoids decomposition: ethoxypentafluorocyclotriphosphazene has a high boiling point at atmospheric pressure (above 200℃) and may decompose at high temperatures. Vacuum distillation lowers the temperature to 70–78℃, safely distilling out the product without damaging it.

[0036] In summary, this application selects ammonium bifluoride (NH4HF2) as the fluorinating agent, replacing potassium fluoride or hydrogen fluoride commonly used in the prior art, to achieve complete fluorination of hexachlorocyclotriphosphazene under moderate temperature conditions of 85–90°C. Dimethyl carbonate (DMC) is selected as the solvent for the fluorination reaction, utilizing its good solubility for both hexachlorocyclotriphosphazene and ammonium bifluoride, as well as its environmentally friendly properties. The reaction is carried out under reflux, with the internal temperature stabilized at 85–90°C. The external absorption of acidic tail gas employs a calcium carbonate-filled tail gas absorption device to dryly absorb the hydrogen fluoride gas escaping during the fluorination reaction, avoiding the potential hydrolytic effect of moisture introduced by directly adding calcium carbonate to the reaction system on hexachlorocyclotriphosphazene, while also simplifying the post-reaction processing. Diethyl carbonate (DEC) is selected as the ethoxylation reagent, replacing sodium ethoxide commonly used in the prior art, thus improving the atom economy of the reaction. DBU was selected as the catalyst for the ethoxylation reaction and also served as a HF scavenger; the byproduct DBU·HF salt could be removed by filtration. Introducing ultrasonic assistance (40 kHz) into the ethoxylation reaction significantly shortened the reaction time and improved the reaction efficiency. Simultaneously, the reaction conditions were precisely controlled: the first-step fluorination reaction was carried out at a temperature of 85–90 °C under reflux for 4–6 hours; the second-step ethoxylation reaction was carried out at a temperature of 30–35 °C for 2–3 hours with an ultrasonic frequency of 40 kHz.

[0037] The final product, after vacuum distillation, can achieve a purity of over 99.0%, which meets the purity requirements of lithium-ion battery electrolytes for flame retardant additives.

[0038] To provide a clearer and more detailed description of the preparation method of ethoxypentafluorocyclotriphosphazene provided in the embodiments of the present invention, specific examples will be described below.

[0039] Example 1 (1) Fluorination reaction Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask, and stir until the hexachlorocyclotriphosphazene is completely dissolved. Add 90.5 g (approximately 1.60 mol, molar ratio approximately 8:1) of ammonium bifluoride. Heat the reaction system to reflux (internal temperature 88 °C) and stir for 5 hours. A large amount of gas (HF, HCl, CO2) is released during the reaction. The outlet of the reflux condenser of the reaction apparatus is connected to a tail gas absorption tower filled with calcium carbonate to absorb the HF and HCl gases released during the reaction. The absorbed tail gas is further treated with alkaline solution before being discharged into the atmosphere.

[0040] After the reaction was complete, the reaction solution was filtered while hot to remove insoluble solids (CaF2, unreacted CaCO3, and some NH4Cl). The filtrate was washed twice with deionized water (200 mL each time) to separate the organic phase. The organic phase was dried overnight with anhydrous sodium sulfate. After filtering to remove the desiccant, the DMC solvent was evaporated under reduced pressure (rotary evaporator, water bath temperature 50 °C, vacuum degree 50 mmHg) to obtain crude hexafluorocyclotriphosphazene.

[0041] The crude hexafluorocyclotriphosphazene was further purified by vacuum distillation (50 mmHg, collecting the fraction at 40–50 °C) to obtain a colorless, transparent liquid, hexafluorocyclotriphosphazene. The yield was calculated by weighing, and the purity was analyzed by gas chromatography. Figure 1 As shown.

[0042] (2) Ethoxylation reaction Add the above-mentioned hexafluorocyclotriphosphazene (approximately 38.9 g, 0.16 mol) and 200 mL of diethyl carbonate to a 500 mL three-necked flask and stir to dissolve. Add 2.4 g (approximately 0.016 mol, molar ratio approximately 0.1:1) of DBU. Place the reaction flask in an ultrasonic generator (40 kHz), control the reaction temperature at 33 °C, and stir the reaction under ultrasonic assistance for 2.5 hours. During the reaction, DBU·HF salt gradually precipitates out, and a small amount of gas (CO2) is released simultaneously.

[0043] After the reaction was complete, the reaction solution was filtered to remove the DBU·HF salt solid. The filtrate was washed three times with deionized water (100 mL each time) to separate the organic phase. The organic phase was dried overnight with anhydrous sodium sulfate. After filtering to remove the desiccant, the filtrate was transferred to a vacuum distillation apparatus and distilled under a vacuum of 5 mmHg. The fraction collected at 70–78 °C yielded a colorless, transparent liquid product—ethoxypentafluorocyclotriphosphazene.

[0044] (3) Product characterization The resulting product is a colorless and transparent liquid, which was analyzed by gas chromatography (e.g.) Figure 2 As shown), the purity is 99.3%.

[0045] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.5% (based on hexachlorocyclotriphosphazene); Yield of ethoxypentafluorocyclotriphosphazene: 86.2% (based on hexafluorocyclotriphosphazene); Overall yield: 80.6% (based on hexachlorocyclotriphosphazene).

[0046] Example 2 (1) Fluorination reaction Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 90.5 g (1.60 mol) of ammonium bifluoride. Heat the reaction system to reflux (internal temperature 85 °C) and stir for 4 hours.

[0047] The post-processing steps are the same as in Example 1.

[0048] The yield of hexafluorocyclotriphosphazene was 88.7%, and the gas chromatographic purity was 97.8%.

[0049] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 36.9 g, 0.152 mol) and 200 mL of diethyl carbonate were added to a 500 mL three-necked flask, along with 1.2 g (approximately 0.008 mol, molar ratio approximately 0.05:1) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 30 °C. The mixture was stirred with ultrasonic assistance for 2 hours.

[0050] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0051] (3) Product characterization The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 98.5%.

[0052] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 88.7%; Yield of ethoxypentafluorocyclotriphosphazene: 81.5% (based on hexafluorocyclotriphosphazene); Overall yield: 72.3% (based on hexachlorocyclotriphosphazene).

[0053] Example 3 (1) Fluorination reaction Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 90.5 g (1.60 mol) of ammonium bifluoride. Heat the reaction system to reflux (internal temperature 90 °C) and stir for 6 hours.

[0054] The post-processing steps are the same as in Example 1.

[0055] The yield of hexafluorocyclotriphosphazene was 94.8%, and the gas chromatographic purity was 98.9%.

[0056] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 39.4 g, 0.162 mol) and 200 mL of diethyl carbonate were added to a 500 mL three-necked flask, along with 4.9 g (approximately 0.032 mol, molar ratio approximately 0.2:1) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 35 °C. The mixture was stirred with ultrasonic assistance for 3 hours.

[0057] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0058] (3) Product characterization The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 99.5%.

[0059] (4) Yield calculation Hexafluorocyclotriphosphazene yield: 94.8% Yield of ethoxypentafluorocyclotriphosphazene: 87.6% (based on hexafluorocyclotriphosphazene) Overall yield: 83.0% (based on hexachlorocyclotriphosphazene) Comparative Example 1 (1) Fluorination reaction (sodium fluoride method) Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 50.4 g (1.20 mol, molar ratio 6:1) of sodium fluoride (in place of ammonium bifluoride). Heat the reaction system to 88 °C and stir for 5 hours. Connect the outlet of the reflux condenser of the reaction apparatus to a tail gas absorption tower filled with calcium carbonate.

[0060] After the reaction was complete, the NaCl solid was removed by filtration. The filtrate was washed twice with deionized water, dried over anhydrous sodium sulfate, and the DMC solvent was removed by vacuum distillation to obtain crude hexafluorocyclotriphosphazene.

[0061] The yield of hexafluorocyclotriphosphazene was 51.80%, and the gas chromatographic purity was 91.20%.

[0062] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 21.50 g, 0.088 mol) and 110 mL of diethyl carbonate were added to a 250 mL three-necked flask, along with 1.30 g (0.0088 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0063] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0064] (3) Product characterization and yield The final product had a gas chromatographic purity of 94.50%.

[0065] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 51.80%; Yield of ethoxypentafluorocyclotriphosphazene: 85.6% (based on hexafluorocyclotriphosphazene); Overall yield: 44.34% (based on hexachlorocyclotriphosphazene).

[0066] Comparative Example 2 (1) Fluorination reaction (temperature 100℃) Add 69.5 g (0.20 mol) hexachlorocyclotriphosphazene and 350 mL dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 90.5 g (1.60 mol) ammonium bifluoride. Heat the reaction system to 100 °C (using a high-pressure reactor or pressurized device) and stir for 6 hours. Connect the reflux condenser outlet of the reaction apparatus to a tail gas absorption tower filled with calcium carbonate.

[0067] The post-processing steps are the same as in Example 1.

[0068] The yield of hexafluorocyclotriphosphazene was 67.30%, and the gas chromatographic purity was 92.80%.

[0069] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 28.00 g, 0.115 mol) and 145 mL of diethyl carbonate were added to a 250 mL three-necked flask, along with 1.70 g (0.0115 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0070] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0071] (3) Product characterization and yield The final product had a gas chromatographic purity of 95.6%.

[0072] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 67.30%; Yield of ethoxypentafluorocyclotriphosphazene: 85.10% (based on hexafluorocyclotriphosphazene); Overall yield: 57.27% (based on hexachlorocyclotriphosphazene).

[0073] Comparative Example 3 (1) Fluorination reaction (molar ratio 1:4) Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 45.2 g (0.80 mol) of ammonium bifluoride. Heat the reaction system to 88 °C and stir for 5 hours. Connect the outlet of the reflux condenser of the reaction apparatus to a tail gas absorption tower filled with calcium carbonate.

[0074] The post-processing steps are the same as in Example 1.

[0075] The yield of hexafluorocyclotriphosphazene was 46.30%, and the gas chromatographic purity was 89.00%.

[0076] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 19.30 g, 0.079 mol) and 100 mL of diethyl carbonate were added to a 250 mL three-necked flask, along with 1.20 g (0.0079 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0077] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0078] (3) Product characterization and yield The final product had a gas chromatographic purity of 93.2%.

[0079] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 46.30%; Yield of ethoxypentafluorocyclotriphosphazene: 86.30% (based on hexafluorocyclotriphosphazene); Overall yield: 39.03% (based on hexachlorocyclotriphosphazene).

[0080] Comparative Example 4 (1) Fluorination reaction (molar ratio 1:10) Add 69.5 g (0.20 mol) of hexachlorocyclotriphosphazene and 350 mL of dimethyl carbonate to a 1 L three-necked flask and stir to dissolve. Add 113.1 g (2.00 mol) of ammonium bifluoride. Heat the reaction system to 88 °C and stir for 5 hours. Connect the outlet of the reflux condenser of the reaction apparatus to a tail gas absorption tower filled with calcium carbonate.

[0081] The post-processing steps are the same as in Example 1.

[0082] The yield of hexafluorocyclotriphosphazene was 71.20%, and the gas chromatographic purity was 94.00%.

[0083] (2) Ethoxylation reaction The above-mentioned hexafluorocyclotriphosphazene (approximately 29.60 g, 0.122 mol) and 150 mL of diethyl carbonate were added to a 250 mL three-necked flask, along with 1.80 g (0.0122 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0084] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0085] (3) Product characterization and yield The final product had a gas chromatographic purity of 96.1%.

[0086] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 71.2%; Yield of ethoxypentafluorocyclotriphosphazene: 84.8% (based on hexafluorocyclotriphosphazene); Overall yield: 60.38% (based on hexachlorocyclotriphosphazene).

[0087] Comparative Example 5 The diethyl carbonate / DBU system was replaced with sodium ethoxide, and the other conditions were the same as in Example 1.

[0088] (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0089] The yield of hexafluorocyclotriphosphazene was 93.2%, and the gas chromatographic purity was 98.6%.

[0090] (2) Ethoxylation reaction (sodium ethoxide method) Hexafluorocyclotriphosphazene (approximately 38.80 g, 0.160 mol) was dissolved in 200 mL of anhydrous tetrahydrofuran (THF). An ethanol solution containing 10.90 g (0.160 mol) of sodium ethoxide was slowly added dropwise at 0 °C. After the addition was complete, the mixture was brought to room temperature and stirred for 4 hours.

[0091] After the reaction was complete, the generated NaF precipitate was removed by filtration. The solvent in the filtrate was evaporated under reduced pressure, and the residue was purified by reduced pressure distillation.

[0092] (3) Product characterization The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 97.8%.

[0093] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.20%; Yield of ethoxypentafluorocyclotriphosphazene: 70.5% (based on hexafluorocyclotriphosphazene); Overall yield: 65.71% (based on hexachlorocyclotriphosphazene).

[0094] Comparative Example 6 (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0095] The yield of hexafluorocyclotriphosphazene was 93.40%, and the gas chromatographic purity was 98.70%.

[0096] (2) Ethoxylation reaction Approximately 38.90 g (0.160 mol) of hexafluorocyclotriphosphazene and 23.60 g (0.080 mol) of diethyl carbonate were added to a 500 mL three-necked flask, along with 2.40 g (0.016 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0097] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0098] (3) Product characterization and yield The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 96.5%.

[0099] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.4%; Yield of ethoxypentafluorocyclotriphosphazene: 56.8% (based on hexafluorocyclotriphosphazene); Overall yield: 53.05% (based on hexachlorocyclotriphosphazene).

[0100] Comparative Example 7 (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0101] The yield of hexafluorocyclotriphosphazene was 93.10%, and the gas chromatographic purity was 98.50%.

[0102] (2) Ethoxylation reaction Approximately 38.80 g (0.160 mol) of hexafluorocyclotriphosphazene and 75.60 g (0.640 mol) of diethyl carbonate were added to a 500 mL three-necked flask, along with 2.40 g (0.016 mol) of DBU. The flask was placed in an ultrasonic generator (40 kHz), and the reaction temperature was controlled at 33 °C. The mixture was stirred with ultrasonic assistance for 2.5 hours.

[0103] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0104] (3) Product characterization and yield The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 97.7%.

[0105] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.10%; Yield of ethoxypentafluorocyclotriphosphazene: 70.50% (based on hexafluorocyclotriphosphazene); Overall yield: 65.26% (based on hexachlorocyclotriphosphazene).

[0106] Comparative Example 8 (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0107] The yield of hexafluorocyclotriphosphazene was 93.30%, and the gas chromatographic purity was 98.50%.

[0108] (2) Ethoxylation reaction (low temperature, short time) Add approximately 38.80 g (0.160 mol) of hexafluorocyclotriphosphazene and 200 mL of diethyl carbonate to a 500 mL three-necked flask, then add 2.40 g (0.016 mol) of DBU. Place the flask in an ultrasonic generator (40 kHz), control the reaction temperature at 25 °C, and stir with ultrasonic assistance for 1.5 hours.

[0109] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0110] (3) Product characterization and yield The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 95.2%.

[0111] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.3%; Yield of ethoxypentafluorocyclotriphosphazene: 51.3% (based on hexafluorocyclotriphosphazene); Overall yield: 47.86% (based on hexachlorocyclotriphosphazene).

[0112] Comparative Example 9 (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0113] The yield of hexafluorocyclotriphosphazene was 93.10%, and the gas chromatographic purity was 98.40%.

[0114] (2) Ethoxylation reaction (high temperature and long time) Add approximately 38.80 g (0.160 mol) of hexafluorocyclotriphosphazene and 200 mL of diethyl carbonate to a 500 mL three-necked flask, then add 2.40 g (0.016 mol) of DBU. Place the flask in an ultrasonic generator (40 kHz), control the reaction temperature at 45 °C, and stir with ultrasonic assistance for 4 hours.

[0115] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0116] (3) Product characterization and yield The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 97.1%.

[0117] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.1%; Yield of ethoxypentafluorocyclotriphosphazene: 68.2% (based on hexafluorocyclotriphosphazene); Overall yield: 63.49% (based on hexachlorocyclotriphosphazene).

[0118] Comparative Example 10 Without ultrasound assistance, all other conditions are the same as in Example 1. (1) Fluorination reaction The fluorination reaction conditions were exactly the same as in Example 1 (88°C, 5 hours, DMC solvent, NH4HF2 fluorinating agent, and external tail gas absorption of calcium carbonate).

[0119] The yield of hexafluorocyclotriphosphazene was 93.40%, and the gas chromatographic purity was 98.60%.

[0120] (2) Ethoxylation reaction (without ultrasound assistance) Add approximately 38.90 g (0.160 mol) of hexafluorocyclotriphosphazene and 200 mL of diethyl carbonate to a 500 mL three-necked flask, then add 2.40 g (0.016 mol) of DBU. Maintain the reaction temperature at 33 °C and react for 5 hours under standard stirring conditions (without sonication).

[0121] The post-processing steps are the same as in Example 1. The fraction at 70–78 °C / 5 mmHg is collected by vacuum distillation.

[0122] (3) Product characterization The resulting product is a colorless and transparent liquid with a gas chromatographic purity of 97.2%.

[0123] (4) Yield calculation Yield of hexafluorocyclotriphosphazene: 93.4%; Yield of ethoxypentafluorocyclotriphosphazene: 78.2% (based on hexafluorocyclotriphosphazene); Overall yield: 73.04% (based on hexachlorocyclotriphosphazene).

[0124] The specific yields and purities of each embodiment and comparative example are shown in Table 1.

[0125] Table 1. Experimental Results of Examples and Comparative Examples

[0126] A comparison of Examples 1 to 3 shows that the process parameters of the present invention exist within an optimal range. The parameter combination of Example 1 (fluorination temperature reflux internal temperature 88°C, time 5 hours; ethoxylation temperature 33°C, time 2.5 hours, DBU molar ratio 0.1:1) achieved the best balance between yield, purity, and economy. The reaction temperature (reflux internal temperature 85°C) and time (4 hours) of Example 2 were slightly lower, resulting in insufficient fluorination and a decrease in both HFPN yield and overall yield. The reaction temperature (reflux internal temperature 90°C) and time (6 hours) of Example 3 were higher, leading to a slight increase in yield. However, as the comparative examples show, if the fluorination reaction temperature is further increased to 100℃ (Comparative Example 2), the ammonium bifluoride decomposes too quickly, resulting in a large amount of HF escaping and not being able to participate in the reaction. The HFPN yield decreases from 93.5% to 67.3%, and the overall yield decreases to 57.27%. If the ethoxylation reaction time is further extended to 4 hours or the temperature is increased to 45℃ (Comparative Example 8), the polysubstituted side reactions increase significantly, and the yield decreases from 51.3% to 68.9%, with the product purity decreasing to 95.2%. If ultrasonic assistance is omitted (Comparative Example 10), the reaction time needs to be doubled (from 2.5 hours to 5 hours), the yield decreases to 78.2%, and the product purity decreases to 97.2%. If the traditional sodium ethoxide method is used (Comparative Example 5), the atom economy is poor, and the yield is only 70.5%.

Claims

1. A method for preparing ethoxypentafluorocyclotriphosphazene, characterized in that, include: Fluorination reaction: Hexachlorocyclotriphosphazene is dissolved in an organic solvent, and ammonium bifluoride is added to carry out a fluorination reaction to prepare hexafluorocyclotriphosphazene; the reaction temperature of the fluorination reaction is 85-90℃, the reaction time is 4-6 hours, and the reaction is carried out under the condition of reflux of the dimethyl carbonate during the reaction; the molar ratio of hexachlorocyclotriphosphazene to ammonium bifluoride is 1:6-1:8; Ethoxylation reaction: Hexafluorocyclotriphosphazene is reacted with an ethoxylation reagent under the catalysis of a catalyst to prepare ethoxypentafluorocyclotriphosphazene; the ethoxylation reagent is diethyl carbonate; the molar ratio of hexafluorocyclotriphosphazene to diethyl carbonate is 1:1 to 1:3; the reaction temperature of the ethoxylation reaction is 30 to 35°C, the reaction time is 2 to 3 hours, and the reaction is carried out under ultrasonic-assisted conditions.

2. The method for preparing ethoxypentafluorocyclotriphosphazene according to claim 1, characterized in that, The catalyst is DBU.

3. The method for preparing ethoxypentafluorocyclotriphosphazene according to claim 2, characterized in that, The molar ratio of DBU to hexafluorocyclotriphosphazene is 0.05:1 to 0.2:

1.

4. The method for preparing ethoxypentafluorocyclotriphosphazene according to claim 1, characterized in that, The organic solvent is one of DMC, ethylene glycol dimethyl ether, and acetonitrile.

5. The method for preparing ethoxypentafluorocyclotriphosphazene according to claim 1, characterized in that, Calcium carbonate is used in the fluorination reaction for external dry absorption of the tail gas.

6. The method for preparing ethoxypentafluorocyclotriphosphazene according to claim 1, characterized in that, It also includes post-processing: after the ethoxylation reaction is completed, the reaction solution is filtered, washed with water, and dried. The dried organic phase is then distilled under reduced pressure, and the fraction is collected to obtain the finished product, ethoxypentafluorocyclotriphosphazene.

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