Method for preparing triisopropyl phosphite
By using a low-toxicity acid-binding agent and mild reaction conditions, the environmental pollution and post-processing difficulties in the traditional pyridine process have been solved, achieving the preparation of triisopropyl phosphite with high yield and high purity, which is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-04-03
AI Technical Summary
The traditional pyridine process for preparing triisopropyl phosphite has problems such as environmental pollution, operational hazards, difficult post-processing, and low yield.
Low-toxicity acid-binding agents such as triethylamine, N,N-dimethylaniline, or potassium carbonate are used to control mild reaction conditions. Solid salts are removed by suction filtration or pressure filtration, solvents are recovered, and triisopropyl phosphite is purified by vacuum distillation.
It achieves environmentally friendly and efficient preparation with a product yield of over 89% and a purity of 98.5%. It simplifies post-processing, reduces costs and energy consumption, and is suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthetic chemistry, specifically to a green synthesis method for an organophosphorus ester compound—triisopropyl phosphite. Background Technology
[0002] Triisopropyl phosphite is an important organophosphorus chemical intermediate, widely used in pesticide synthesis, flame retardants for polymer materials, plastic stabilizers, and pharmaceutical synthesis.
[0003] Currently, the classic method for preparing triisopropyl phosphite in industry and laboratories involves esterification with phosphorus trichloride and isopropanol in the presence of an acid-binding agent. Traditional processes commonly use pyridine as the acid-binding agent to absorb the hydrogen chloride produced as a byproduct of the reaction. However, pyridine itself is highly toxic, has a foul odor, and is highly volatile, posing significant health risks to operators and causing severe environmental pollution. Furthermore, the pyridine hydrochloride formed by the reaction of pyridine and hydrogen chloride is a viscous substance, making subsequent filtration and separation extremely difficult, resulting in low solvent recovery rates. Additionally, the high price of pyridine increases production costs. Traditional pyridine processes also suffer from problems such as intense exothermic reactions, the need for deep cooling (e.g., below -10°C), and the potential for product decomposition or darkening due to improper control. Yields are typically low (generally below 85%), and product quality is unstable.
[0004] Therefore, developing a novel synthesis process that is mild, environmentally friendly, has a high yield, and is easy to industrialize is of great practical significance and application value. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a green, efficient, mild, and high-yield method for preparing triisopropyl phosphite, so as to solve the problems of environmental pollution, operational hazards and post-processing difficulties caused by traditional pyridine processes.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A green and efficient method for preparing triisopropyl phosphite includes the following steps: a) Under the protection of an inert gas (such as nitrogen) and stirring conditions, metered amounts of isopropanol, acid-binding agent and solvent are added to the reactor, mixed evenly, and then the system is cooled to 0~10℃ using an ice-water bath.
[0007] b) Slowly add a measured amount of phosphorus trichloride dropwise to the mixture from step a), ensuring that the reaction temperature does not exceed 15°C by controlling the dropping rate, preferably between 5 and 10°C.
[0008] c) After the phosphorus trichloride is added, remove the ice-water bath and allow the reaction system to naturally heat up to room temperature (20~30℃). Continue stirring the reaction at this temperature for 1~3 hours, preferably 1.5~2 hours, to ensure the reaction is complete.
[0009] d) After the reaction is complete, filter out the solid salts (such as triethylamine hydrochloride) generated in the reaction by suction filtration or pressure filtration, and collect the clear filtrate.
[0010] e) Perform atmospheric or simple vacuum distillation on the filtrate obtained in step d) to recover most of the solvent. This solvent (such as n-heptane) can be directly reused in the next batch of reaction after drying.
[0011] f) The crude product obtained after solvent removal in step e) is subjected to high-vacuum distillation, and the fraction obtained at a specific pressure (e.g., -0.095 ~ -0.098 MPa) (boiling range approximately 90~110℃) is collected to obtain a colorless, transparent, high-purity triisopropyl phosphite product. The synthetic chemical formula is as follows:
[0012] Furthermore, the acid-binding agent is one or more of triethylamine, N,N-dimethylaniline, or potassium carbonate. Compared to pyridine, these acid-binding agents have advantages such as low toxicity, low odor, low price, and the generated byproducts being easily filterable solids. Triethylamine is preferred because of its strong acid-binding ability, the salt formed with hydrogen chloride is easily filtered, and its low boiling point makes it easy to separate from high-boiling-point solvents during subsequent solvent recovery.
[0013] Furthermore, the molar ratio of phosphorus trichloride to isopropanol is 1:3 to 3.5 to ensure that phosphorus trichloride reacts fully.
[0014] Furthermore, the molar ratio of the acid-binding agent to phosphorus trichloride is 3~3.2:1, ensuring complete neutralization of the hydrogen chloride produced in the reaction.
[0015] Furthermore, the solvent is an inert alkane solvent such as n-heptane, cyclohexane, or petroleum ether, preferably n-heptane. The total volume of the solvent to the mass ratio of phosphorus trichloride is (8~12) mL : 1g, preferably 10 mL : 1g.
[0016] Compared with the prior art, the present invention has the following significant advantages: Environmentally friendly and safe: The use of low-toxicity, low-odor green acid binders (such as triethylamine) to completely replace toxic and malodorous pyridine greatly improves the working environment and reduces environmental pollution and harm to human health.
[0017] High yield: By optimizing the ratio of reactants and controlling the temperature gently, side reactions are effectively suppressed, and the product yield is stable at over 89%, with a maximum of 92%, which is superior to the traditional pyridine process.
[0018] Mild conditions: The reaction can proceed smoothly at 0~30℃, without the need for deep cooling, with low energy consumption, safe and simple operation, and low equipment requirements.
[0019] The post-processing is simple and low-cost: the generated ammonium salt is a solid particle that is easy to filter and separate; the solvent used can be efficiently recovered and recycled, which significantly reduces the cost of waste treatment and raw materials.
[0020] High product quality: The resulting product has a purity of over 98.5% and a light color, meeting the requirements of high-end application fields.
[0021] Easy to industrialize: The entire process is simple, and the conditions are mild and controllable, making it very suitable for industrial-scale production. Detailed Implementation
[0022] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. In the embodiments, the yield is calculated based on phosphorus trichloride. Example
[0023] In a 1000 mL four-necked flask equipped with a stirrer, thermometer, constant-pressure dropping funnel, and nitrogen delivery tube, the air was purged with nitrogen. 131.29 g (2.18 mol) of isopropanol, 221.0 g (approximately 220 mL, 2.18 mol) of triethylamine, and 680 g (approximately 980 mL) of n-heptane were added sequentially. Stirring was started, nitrogen was introduced for protection, and the mixture was cooled to 0–5 °C in a water bath. Then, 100 g (0.73 mol) of phosphorus trichloride was slowly added dropwise, controlling the dropping rate and maintaining the reaction solution temperature at 5–10 °C. The dropwise addition process took approximately 1.5 hours. After the dropwise addition was complete, the ice-water bath was removed, and the reaction solution was allowed to naturally warm to 25 °C, and the reaction was continued with stirring at 25 °C for another 1.5 hours.
[0024] After the reaction was complete, the mixture was filtered through a Buchner funnel to remove the white triethylamine hydrochloride solid. The filter cake was washed with a small amount of n-heptane (approximately 50 mL), and the filtrate and washings were combined. The filtrate was transferred to a round-bottom flask, and n-heptane was recovered by atmospheric distillation (approximately 780 mL recovered, with a recovery rate of approximately 95%). The remaining material was subjected to vacuum distillation (pressure -0.098 MPa), and the fraction collected at 98–102 °C yielded 142.5 g of colorless and transparent triisopropyl phosphite product. The yield was calculated to be 92%, and the purity was 99.2% according to gas chromatography (GC) analysis. Example
[0025] The procedure was the same as in Example 1, except that the acid-binding agent triethylamine (2.18 mol) was replaced with an equimolar amount of N,N-dimethylaniline (257.5 g). After the reaction was complete, the mixture was filtered, the solvent was recovered, and the product was obtained by vacuum distillation, yielding 138.0 g of product. The yield was 89.5%, and the GC purity was 98.7%. Example
[0026] The operating procedure was the same as in Example 1, except that the acid-binding agent triethylamine (2.18 mol) was replaced with an equimolar amount of anhydrous potassium carbonate (301.5 g). Since potassium carbonate is a solid, the stirring speed needed to be appropriately increased to ensure sufficient contact. After the reaction was complete, the mixture was filtered, the solvent was recovered, and the product was obtained by vacuum distillation, yielding 137.2 g. The yield was 89.0%, and the GC purity was 98.5%.
[0027] Comparative example (traditional pyridine method): In a 1000 mL four-necked flask equipped with a stirrer, thermometer, constant-pressure dropping funnel, and nitrogen delivery tube, the air was purged with nitrogen. 131.29 g (2.18 mol) of isopropanol, 172.5 g (approximately 170 mL, 2.18 mol) of pyridine, and 680 g (approximately 980 mL) of n-heptane were added sequentially. Stirring was started, nitrogen was introduced for protection, and the mixture was cooled to -5 to 0°C using a saline bath. Then, 100 g (0.73 mol) of phosphorus trichloride was slowly added dropwise, controlling the dropping rate and maintaining the reaction solution temperature at 0 to 5°C. The dropwise addition process took approximately 2 hours. After the addition was complete, the reaction was stirred for another hour at 0 to 5°C.
[0028] After the reaction, the reaction solution contained a large amount of viscous pyridine hydrochloride, which could not be directly filtered. A large amount of water was added for extraction and separation, followed by back-extraction of the aqueous phase with n-heptane, a cumbersome process. The organic phases were combined, and n-heptane was recovered by atmospheric distillation (approximately 650 mL recovered, with a recovery rate of approximately 79%). The remaining material was subjected to vacuum distillation to obtain 125.8 g of a pale yellow triisopropyl phosphite product. The calculated yield was 81.5%, and the GC purity was 95.8%.
[0029] in conclusion: A comparison of Examples 1-3 with the comparative examples clearly demonstrates that the green acid-binding agent system employed in this invention not only fundamentally solves the problems of pyridine toxicity and environmental pollution, but also greatly simplifies post-processing operations (filtration vs. extraction) and significantly improves solvent recovery (95% vs. 79%) because the generated byproducts are easily filterable solids. Furthermore, at a milder reaction temperature, this invention achieves higher product yields (92% vs. 81.5%) and superior product purity (99.2% vs. 95.8%). This fully demonstrates the unexpected technical effects of this invention, showcasing its outstanding substantive features and significant advancements.
Claims
1. A method for preparing triisopropyl phosphite, characterized in that, Includes the following steps: a) Under inert gas protection and stirring conditions, add isopropanol, acid-binding agent and solvent into the reactor, mix evenly and then cool to 0~10℃; b) Slowly add phosphorus trichloride dropwise to the mixture in step a), controlling the reaction temperature during the dropwise addition process to not exceed 15°C; c) After the phosphorus trichloride is added, heat the reaction system to 20-30°C and continue to keep it at this temperature for 1-3 hours. d) After the reaction is complete, filter the reaction solution to remove the solid salts produced in the reaction and collect the filtrate; e) Distill the filtrate obtained in step d) to recover the solvent and obtain crude triisopropyl phosphite product; f) The crude product obtained in step e) is subjected to vacuum distillation to obtain high-purity triisopropyl phosphite.
2. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, The acid-binding agent is one or more of triethylamine, N,N-dimethylaniline, or potassium carbonate.
3. The method for preparing triisopropyl phosphite according to claim 2, characterized in that, The acid-binding agent is triethylamine.
4. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, The molar ratio of phosphorus trichloride to isopropanol is 1:3~3.
5.
5. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, The molar ratio of the acid-binding agent to phosphorus trichloride is 3~3.2:
1.
6. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, The solvent is one or more of n-heptane, cyclohexane, or petroleum ether.
7. The method for preparing triisopropyl phosphite according to claim 6, characterized in that, The solvent is n-heptane.
8. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, The total volume of the solvent and the mass ratio of phosphorus trichloride are (8~12) mL : 1 g.
9. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, In step b), the reaction temperature during the dropwise addition process is controlled at 5~10℃.
10. The method for preparing triisopropyl phosphite according to claim 1, characterized in that, In step f), the pressure of the vacuum distillation is -0.095 ~ -0.098 MPa, and the temperature of the collected fraction is 90 ~ 110℃.