A method for synthesizing tripropargyl phosphate

Abstract

This invention relates to the field of lithium battery electrolyte technology, specifically a method for synthesizing tripropynyl phosphate, comprising the following steps: 1) In a dry reaction vessel, an organic solvent is added, and phosphorus oxychloride is dissolved in the organic solvent, and stored under an inert atmosphere at low temperature; 2) A mixture of propynyl alcohol and triethylamine is slowly added dropwise, and the reaction is continuously stirred while maintaining a low temperature; 3) The mixture is slowly added dropwise, and the reaction is stirred after the temperature is raised to room temperature; 4) The mixture is slowly added to the reaction vessel, and the reaction is stirred after the temperature is raised to room temperature; 5) The triethylamine hydrochloride is removed by filtration, and the filtrate is distilled under reduced pressure to obtain a crude product, which is then purified by reduced pressure distillation or column chromatography. This invention effectively solves the problems of violent exothermic reactions, numerous side reactions, harsh reaction conditions, and difficulties in post-processing and purification of the product in existing synthesis methods by rationally designing reaction steps and precisely controlling reaction conditions and molar ratios.

Description

Technical Field

[0001] This invention relates to the field of lithium battery electrolyte technology, and in particular to a method for synthesizing tripropyne phosphate. Background Technology

[0002] Tripropynyl phosphate is a high-performance lithium battery electrolyte additive that can form a stable protective film on the surface of the battery electrodes, effectively inhibiting electrolyte decomposition and lithium dendrite growth, thereby improving the safety and cycle life of lithium batteries.

[0003] A common synthetic method involves the esterification of propargyl alcohol (propargyl alcohol) with phosphorus oxychloride in the presence of a base (such as triethylamine). This route presents several problems: 1. A violent exothermic reaction and risk of runaway: The reaction between phosphorus oxychloride and the alcohol is inherently exothermic. Proargyl alcohol is highly reactive, and the reaction generates a large amount of HCl. Improper feeding rate or temperature control can easily lead to localized overheating, spillage, or even explosions, posing significant safety hazards in both laboratory and scale-up production. 2. Side reactions due to the high reactivity of propargyl alcohol: Under alkaline or heating conditions, propargyl alcohol readily undergoes Guerbert isomerization, producing toxic and unstable acrolein. This consumes raw materials, reduces yield, and introduces difficult-to-separate impurities. The HCl produced in the reaction may undergo electrophilic addition with the alkynyl group, generating chlorinated olefin byproducts, severely affecting product purity and yield. Proargyl alcohol is unstable in air and easily oxidized or decomposed, placing stringent requirements on raw material storage and reaction conditions. Third, the reaction conditions are harsh, typically requiring slow dropwise addition at anhydrous and low temperatures (e.g., -10℃ to 0℃), along with efficient stirring and reflux condensation. This increases equipment costs and operational difficulty, and places high demands on inert gas protection (such as nitrogen or argon) to isolate moisture and oxygen and prevent decomposition of raw materials and products. Fourth, post-processing and purification of the product are difficult. The triethylamine hydrochloride produced in the reaction is a solid with low solubility in organic solvents, making filtration cumbersome and prone to adsorption and loss. Furthermore, tripropynyl phosphate contains multiple unsaturated bonds, making it sensitive to heat, acids, and alkalis. During subsequent washing and distillation purification, excessively high temperatures or contact with trace amounts of acid / alkali can easily lead to decomposition, polymerization, or isomerization, resulting in further decreases in yield and a darkening of the product color (usually yellow or brown). In addition, tripropynyl phosphate has a high boiling point (requiring distillation under high vacuum) but is also thermally unstable. This makes vacuum distillation the most critical and difficult step in purification, requiring precise control of bath temperature and vacuum level; otherwise, decomposition can easily occur within the distillation flask.

[0004] The above problems result in a yield of tripropynyl phosphate ranging from 40% to 65%, making it increasingly difficult to meet the requirements of high-performance lithium battery electrolytes. Summary of the Invention

[0005] To address the above problems, this invention provides a method for synthesizing tripropynyl phosphate, comprising the following steps:

[0006] 1) In a dry reaction vessel, add an organic solvent to dissolve phosphorus oxychloride in the organic solvent and store it under an inert atmosphere at low temperature;

[0007] 2) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 1), and keep the reaction at a low temperature with continuous stirring;

[0008] 3) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 2), heat and stir the reaction.

[0009] 4) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 3), and stir the reaction vessel again after raising the temperature to the desired level.

[0010] 5) After the reaction is complete, filter to remove triethylamine hydrochloride, distill the filtrate under reduced pressure to obtain crude product, and continue to distill under reduced pressure or column chromatography to obtain tripropynyl phosphate.

[0011] In the method of this invention, the molar ratio of phosphorus oxychloride to propargyl alcohol is 1:(1~1.1). This specific molar ratio ensures the reaction proceeds fully while avoiding resource waste caused by excess propargyl alcohol and potential side reactions. Anhydrous dichloromethane or tetrahydrofuran is chosen as the organic solvent in step 1 because they have good solubility and low boiling points, facilitating subsequent separation operations. Nitrogen or argon protection effectively isolates the air from moisture and oxygen, preventing the reaction of phosphorus oxychloride with water and the oxidation of propargyl alcohol.

[0012] In step 1), the organic solvent is anhydrous dichloromethane or tetrahydrofuran; the inert atmosphere is nitrogen or argon. Using anhydrous dichloromethane or tetrahydrofuran as the solvent ensures complete dissolution of phosphorus oxychloride and provides a stable reaction environment for the subsequent dropwise addition of the mixture. The low temperature (0~5℃) and inert atmosphere storage conditions further reduce the possibility of unnecessary reactions between phosphorus oxychloride and the solvent or components in the air.

[0013] In steps 2) through 4), the mixture of propargyl alcohol and triethylamine is added slowly dropwise each time, with the molar ratio of propargyl alcohol to triethylamine controlled at 1:1. This design allows the reaction to proceed relatively smoothly. Because triethylamine acts as a base, it can neutralize the HCl produced in the reaction, reducing the probability of electrophilic addition of HCl to the alkynyl group to form chlorinated olefin byproducts. Simultaneously, adding the mixture dropwise in three stages while gradually increasing the temperature and stirring the reaction allows for more precise control of the reaction process, avoiding excessively vigorous reactions due to adding too much propargyl alcohol at once, and reducing safety hazards such as localized overheating and material spillage.

[0014] Steps 1) and 4, through temperature control, can significantly improve the safety of the reaction and the quality and yield of the product. In step 1), controlling the temperature at 0-5°C effectively reduces the reactivity of phosphorus oxychloride, minimizing the possibility of unnecessary reactions with the solvent and air components, providing a stable reaction environment for the subsequent addition of the mixture, and avoiding violent reactions and safety risks caused by excessively high temperatures. In step 4), raising the temperature to 35-45°C and stirring for 5-7 hours helps the reaction proceed more fully. This temperature range ensures sufficient energy to advance the reaction without being too high, which could lead to the Guerbert isomerization of propargyl alcohol to form toxic and unstable acrolein. It also reduces the possibility of propargyl alcohol being oxidized or decomposed, thereby reducing side reactions and improving the utilization rate of raw materials and the purity of the product. Such precise temperature control also optimizes the kinetics and thermodynamic conditions of the reaction process. In step 1, the low-temperature environment results in a relatively slow reaction rate, but it ensures a stable initial reaction. The heating process in step 4 provides sufficient energy at the appropriate time, propelling the reaction towards the formation of tripropynyl phosphate, thus improving selectivity and yield. Simultaneously, this temperature control method reduces equipment requirements and operational complexity, making the entire synthesis process more stable, efficient, and safe. Specifically, in step 1), the low temperature is 0–5°C, and in step 4), the temperature is raised to 35–45°C.

[0015] Steps 2) through 4) can further optimize the reaction effect and improve the yield and purity of the product by controlling the stirring time. In step 2), controlling the stirring time to 1-3 hours ensures that the mixture of propargyl alcohol and triethylamine fully contacts and reacts with the substances in the reactor. Under low temperature conditions, slow and continuous stirring allows the reaction to start smoothly and avoids local overheating. At the same time, sufficient stirring time ensures that triethylamine fully neutralizes the HCl produced in the reaction, reducing the probability of electrophilic addition reaction between HCl and alkynyl groups, thereby reducing the formation of chlorinated olefin byproducts. In step 3), the temperature of the reaction system increases, and the reaction rate accelerates. Extending the stirring time allows the reaction to proceed more fully, enabling the reaction intermediate of propargyl alcohol and phosphorus oxychloride to further react with propargyl alcohol, promoting the formation of tripropargyl phosphate. Moreover, thorough stirring at this stage helps to evenly disperse the heat of reaction and prevents side reactions caused by excessively high local temperatures, such as the Guerbert isomerization reaction of propargyl alcohol. In step 4), at a temperature of 35-45°C, longer stirring time can achieve a higher conversion rate. During this process, the reaction system gradually approaches equilibrium. Continuous stirring can break the local concentration equilibrium, allowing unreacted raw materials to continue participating in the reaction and improving the utilization rate of raw materials. Simultaneously, prolonged stirring also facilitates the uniform dispersion of triethylamine hydrochloride, making it easier to remove via subsequent filtration, reducing product loss during filtration, and thus improving product yield and purity. Precise control of the stirring time in steps 2) to 4) allows the entire synthesis reaction to proceed more stably and efficiently, overcoming problems inherent in traditional synthesis methods and meeting the requirements of high-performance lithium battery electrolytes for tripropynyl phosphate. Specifically, in step 2), the stirring time is 1–3 hours; in step 3), the stirring time is 3–5 hours; and in step 4), the stirring time is 5–7 hours.

[0016] In step 5), the boiling point range of vacuum distillation is 120~130℃ / mmHg. Controlling the boiling point range of vacuum distillation ensures effective separation and purification of the product. Performing vacuum distillation within this specific boiling point range avoids side reactions such as decomposition, polymerization, or isomerization of tripropyne phosphate due to excessively high temperatures. Because tripropyne phosphate contains multiple unsaturated bonds and is relatively sensitive to heat, excessively high temperatures can damage its structure, thereby reducing the quality and yield of the product. Further vacuum distillation or column chromatography of the crude product can further remove these residual impurities. Column chromatography can utilize the difference in partition coefficients between different substances in the stationary and mobile phases to achieve fine separation of impurities and products. Further vacuum distillation can further refine the product, ensuring that the final tripropyne phosphate meets the stringent requirements of high-performance lithium battery electrolytes, improving product stability and purity, and meeting the performance improvement needs of lithium batteries in terms of safety and cycle life.

[0017] The synthesis method of this invention effectively solves the problems of violent exothermic reactions, numerous side reactions, harsh reaction conditions, and difficulties in post-processing and purification of products in existing synthesis methods by rationally designing reaction steps and precisely controlling reaction conditions and molar ratios. It can improve the yield and purity of tripropyne phosphate and better meet the needs of high-performance lithium battery electrolytes. Detailed Implementation

[0018] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0019] A method for synthesizing tripropynyl phosphate, the core of which lies in the stepwise and slow dropwise addition of equimolar amounts of propynyl alcohol and triethylamine to an organic solution of phosphorus oxychloride, coupled with a precise gradient temperature control strategy, to achieve fine regulation of the reaction thermodynamics and kinetics.

[0020] Example 1: Preparation of tripropynyl phosphate by batch feeding using dichloromethane solvent.

[0021] 1. Establishment of the reaction system

[0022] In a 5L reactor that has undergone rigorous drying and is equipped with a mechanical stirrer, a constant pressure dropping funnel, a low-temperature thermostat and a nitrogen protection device, 2.5L of anhydrous dichloromethane (moisture content <50ppm) is added. Then, 153.3g (1.0mol) of phosphorus oxychloride is added while stirring. The low-temperature thermostat is turned on to lower the temperature inside the reactor to 0~5℃ and maintain it. High-purity nitrogen is continuously introduced to replace the air inside the reactor and maintain an inert atmosphere.

[0023] 2. Stepwise esterification reaction

[0024] 21. Substitution (Low Temperature): Preparation of the first mixture: 61.7 g (1.1 mol) propargyl alcohol and 111.3 g (1.1 mol) triethylamine are mixed evenly. This mixture is slowly added dropwise to the reaction vessel over 1.5 hours using a constant pressure dropping funnel under vigorous stirring. After the addition is complete, the temperature is maintained at 0-5°C, and the reaction is continued with stirring for 2.0 hours. The reaction is significantly exothermic during this stage, and stability is maintained through cooling and cycling.

[0025] 22. Substitution (room temperature): Prepare a second mixture (with the same composition as the first mixture), and continue to slowly add it dropwise over 1.5 hours. After the addition is complete, remove the ice bath and allow the reaction system to naturally heat up to room temperature (25°C). Turn on the heating / cooling system to maintain 25±2°C and stir the reaction for 4.0 hours. The reaction solution gradually thickens and a large amount of white solid (triethylamine hydrochloride) precipitates out.

[0026] 23. Substitution (Medium Temperature): Prepare the third mixture (with the same composition), add it dropwise over 1.5 hours, then heat the reaction system to 40°C, precisely controlling the temperature between 38 and 42°C, and continue stirring for 6.0 hours. During this time, monitor the reaction progress by thin-layer chromatography (TLC, developing solvent: petroleum ether / ethyl acetate = 4:1) or ¹¹P NMR until the phosphorus oxychloride starting material spot disappears and the phosphorus peak of the target product no longer increases, indicating that the reaction is complete.

[0027] 3. Post-processing and purification

[0028] After the reaction solution was cooled to room temperature, it was filtered using a Buchner funnel (or filter press) to remove the triethylamine hydrochloride generated in the reaction (theoretical amount approximately 151.5 g, actual recovery approximately 145 g). The filter cake was washed with a small amount of anhydrous dichloromethane (2 × 100 mL), and the washing liquid and filtrate were combined. The combined liquid was transferred to a rotary evaporator, and the dichloromethane solvent was distilled off under reduced pressure at a water bath temperature of 35 °C (recovery rate >90%), yielding approximately 210 g of a yellowish-brown viscous crude product. The crude product was transferred to a vacuum distillation apparatus, and the vacuum was evacuated to 1 mmHg using an oil pump. The fraction collected at 120–130 °C was finally obtained as a colorless to pale yellow transparent liquid tripropynyl phosphate, weighing 196.8 g. The purity was determined to be 95.2% by gas chromatography (GC) or high performance liquid chromatography (HPLC) normalization method. Based on phosphorus oxychloride, the reaction yield was 92.0%, yielding tripropynyl phosphate with a purity of 95% and a yield of 92%.

[0029] Example 2: Preparation of tripropynyl phosphate using tetrahydrofuran solvent with fine-tuned parameters

[0030] 1. Establishment of the reaction system

[0031] In a dry reaction vessel, add 2.5 L of anhydrous tetrahydrofuran (THF, moisture <50 ppm) to dissolve 153.3 g (1.0 mol) of phosphorus oxychloride. Cool the mixture to 0~5°C using an ice-salt bath and purge it with argon gas. THF has higher solubility than dichloromethane, which is beneficial for high-concentration reaction systems.

[0032] 2. Stepwise esterification reaction (the molar amount of the three batches of raw materials was adjusted to 1.0 equivalent).

[0033] The difference between this example and step 2 of Example 1:

[0034] Prepare three batches of the mixture, each batch consisting of 56.0 g (1.0 mol) propargyl alcohol and 101.2 g (1.0 mol) triethylamine mixed evenly (phosphorus oxychloride: total propargyl alcohol = 1:3, strictly control the ratio).

[0035] 21. Add the first batch dropwise and react at 0~5°C for 1.5 hours.

[0036] 22. Add the second batch dropwise, and heat to 25°C to react for 3.5 hours.

[0037] 23. Add the third batch dropwise, heat to 42°C and react for 6.5 hours. Monitor the reaction using HPLC (C18 column, acetonitrile / water as mobile phase). Stop the reaction when the peak area of ​​the phosphorus oxychloride derivative is <0.5%.

[0038] 3. Post-processing and purification

[0039] The difference between this and step 3 of Example 1:

[0040] The triethylamine hydrochloride was removed by filtration, and the filter cake was washed with a small amount of THF.

[0041] Double purification: First, most of the THF is recovered by atmospheric distillation, and then the remaining solvent is recovered by vacuum distillation. The crude product is then purified by column chromatography (5 cm inner diameter column, 200-300 mesh silica gel, dichloromethane / methanol gradient elution: 100:0-95:5). After collecting the target eluent, the eluents are combined, concentrated, and then subjected to high-vacuum vacuum distillation (122-128°C / mmHg).

[0042] Finally, 198.5 g of tripropynyl phosphate was obtained, with an HPLC purity of 96.3% and a yield of 93.0%.

[0043] As can be seen from Examples 1 and 2, the synthesis method of the present invention can effectively improve the yield and purity of tripropynyl phosphate under different solvent selections and fine-tuning of specific reaction conditions, providing a reliable raw material source for the preparation of high-performance lithium battery electrolytes. In actual production, appropriate reaction parameters and purification methods can be flexibly selected according to specific equipment conditions, raw material costs, and product requirements to achieve optimal production results. At the same time, the method of the present invention reduces the safety risks and operational difficulties of the reaction to a certain extent, which is beneficial for large-scale industrial production.

[0044] Example 3

[0045] A method for synthesizing tripropynyl phosphate includes the following steps:

[0046] 1. Raw material preparation and reaction system setup

[0047] In a dry reactor, anhydrous dichloromethane is added as a solvent; phosphorus oxychloride (1 mol) is dissolved in the solvent, and the temperature inside the reactor is lowered to 2-3°C using a cryogenic cooling liquid circulation pump, maintaining an inert atmosphere (Ar). This precise temperature control further reduces the reactivity of phosphorus oxychloride and minimizes unnecessary side reactions. Moreover, the use of argon provides a more stable inert environment compared to nitrogen, preventing the raw materials from being oxidized.

[0048] 2. Stepwise esterification reaction

[0049] The first step involves slowly adding a mixture of propargyl alcohol (1.05 mol) and triethylamine (1.05 mol) dropwise, using a peristaltic pump to precisely control the dropping rate and ensure a stable reaction. After the addition is complete, the mixture is stirred at 2–3 °C for 2.5 hours. This low-temperature and precise stirring process allows the reaction to start more fully, reducing local overheating and side reactions.

[0050] The second step, substitution, involves adding a mixture of propargyl alcohol (1.05 mol) and triethylamine (1.05 mol) dropwise again. The reaction system is then slowly heated to 28°C and stirred for 3.8 hours. Appropriately increasing the temperature and extending the stirring time allows the reaction intermediates to react more fully, promoting the formation of tripropynyl phosphate.

[0051] The third step, substitution, involves adding the remaining propargyl alcohol (1.05 mol) and triethylamine (1.05 mol) dropwise, heating to 43°C, and stirring for 6.2 hours. The reaction progress is monitored using GC-MS until completion. At this temperature and stirring time, a high conversion rate is achieved, and GC-MS monitoring allows for more accurate determination of the reaction endpoint.

[0052] 3. Post-processing and purification

[0053] After the reaction, the generated triethylamine hydrochloride was rapidly removed by pressure filtration to reduce adsorption loss of the product during filtration. Part of the solvent was first recovered at a low temperature using a rotary evaporator, followed by vacuum distillation to recover the remaining solvent, yielding the crude product. The crude product was then subjected to column chromatography (silica gel, hexane / ethyl acetate gradient elution), a system that effectively separates impurities and product. Further purification was then performed by vacuum distillation (boiling range: 121–129 °C / mmHg), ultimately yielding tripropynyl phosphate with a purity of 97% and a yield of 94%.

[0054] Example 3 further demonstrates that the synthesis method of the present invention, under more precise control of reaction conditions, can significantly improve the yield and purity of tripropyne phosphate, providing a higher-quality raw material for the production of high-performance lithium battery electrolytes. In practical applications, the reaction parameters can be further optimized and adjusted according to different production needs and conditions to achieve more efficient and stable industrial production.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synthesizing tripropynyl phosphate, characterized in that, Includes the following steps: 1) In a dry reaction vessel, add an organic solvent to dissolve phosphorus oxychloride in the organic solvent and store it under an inert atmosphere at low temperature; 2) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 1), and keep the reaction at a low temperature with continuous stirring; 3) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 2), heat and stir the reaction. 4) Slowly add the mixture of propargyl alcohol and triethylamine dropwise to the reaction vessel in step 3), and stir the reaction vessel again after raising the temperature to the desired level. 5) After the reaction is complete, filter to remove triethylamine hydrochloride, distill the filtrate under reduced pressure to obtain crude product, and continue to distill under reduced pressure or column chromatography to obtain tripropynyl phosphate.

2. The method according to claim 1, characterized in that, The molar ratio of phosphorus oxychloride and propargyl alcohol is 1:(1~1.1).

3. The method according to claim 2, characterized in that, In step 1), the organic solvent is anhydrous dichloromethane or tetrahydrofuran; the inert atmosphere is nitrogen or argon protection.

4. The method according to claim 2, characterized in that, In steps 2) to 4), the molar ratio of propargyl alcohol to triethylamine is 1:1; the amount of the mixture used in steps 2) to 4) is the same.

5. The method according to claim 2, characterized in that, In step 1), the low temperature is 0~5℃; in step 4), the temperature is raised to 35~45℃.

6. The method according to claim 2, characterized in that, In step 2), the stirring time is 1-3 hours; in step 3), the stirring time is 3-5 hours; in step 4), the stirring time is 5-7 hours.

7. The method according to claim 2, characterized in that, In step 5), the boiling point range of vacuum distillation is 120~130℃ / mmHg.