A process for the synthesis of trialkyl phosphates from dialkyl phosphates
The phase transfer catalysis method for converting dialkyl phosphates into trialkyl phosphates solves the problem of slow reaction rate, achieves efficient conversion and resource utilization, and provides a new route for the preparation of trialkyl phosphates.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LUOYANG JINGTIAN TECH DEV CO LTD
- Filing Date
- 2023-02-22
- Publication Date
- 2026-06-02
Smart Images
Figure BDA0004090570130000021 
Figure BDA0004090570130000022 
Figure BDA0004090570130000031
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental protection technology, specifically relating to a method for synthesizing trialkyl phosphate from dialkyl phosphate. Background Technology
[0002] Trialkyl phosphates are important phosphorus-containing organic chemical products. For example, trimethyl phosphate and triethyl phosphate are high-performance solvents, tributyl phosphate and triisobutyl phosphate are important hydrometallurgical extractants, and tri(2-ethylhexyl) phosphate can be used as a flame retardant and is also an irreplaceable solvent in the synthesis of hydrogen peroxide.
[0003] Trialkyl phosphates are usually synthesized by esterification of phosphorus oxychloride with the corresponding alcohols. For example, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and tri(2-ethylhexyl) phosphate can be obtained by reacting phosphorus oxychloride with methanol, ethanol, n-butanol and 2-ethylhexanol respectively.
[0004] In the esterification process described above, the reaction often cannot be completed, resulting in the production of dialkyl chlorophosphate intermediates. These intermediates are hydrolyzed into dialkyl phosphates during post-treatment and dissolved in alkaline wastewater, which increases the consumption of raw materials and production costs, and also puts a lot of pressure on the wastewater treatment system.
[0005] Therefore, converting dialkyl phosphates into trialkyl phosphates can realize the resource utilization of by-products, thereby reducing waste emissions and raw material consumption, and reaping environmental and economic benefits; at the same time, it can provide another way to obtain trialkyl phosphates.
[0006] Furthermore, if an alkyl group different from the original alkyl group is introduced into the dialkyl phosphate molecule, an asymmetric trialkyl phosphate ester with three alkyl groups that are not completely identical can be obtained, which is very instructive for the development of new trialkyl phosphate ester products.
[0007] The reaction of alkali metal salts of dialkyl phosphates with alkylating agents can be classified as a bimolecular nucleophilic substitution reaction. However, the solubility of alkali metal salts of dialkyl phosphates in alkylating agents is relatively low. During the reaction, a solid-liquid two-phase reaction can be observed. Therefore, under conventional reaction conditions, the reaction is very slow and it is difficult to obtain experimental results with practical value. Summary of the Invention
[0008] The purpose of this invention is to provide a method for converting dialkyl phosphates into trialkyl phosphates. This invention employs a phase transfer catalysis method, which solves the problem of slow reaction between alkali metal salts of dialkyl phosphates and alkylating agents. This method has a fast reaction rate, high yield, and broad application prospects.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] A method for synthesizing trialkyl phosphate from dialkyl phosphate includes three main steps: salt formation, alkylation, and purification.
[0011] 1) Salt formation: Dialkyl phosphate ester (R) 1 O)2POOH is converted into its alkali metal salt;
[0012]
[0013] 2) Alkylation: The alkali metal salt of the dialkyl phosphate obtained in step 1) is reacted with the alkylating agent R. 2 X reacts under the catalysis of a phase transfer catalyst to give a trialkyl phosphate-containing ester (R). 1 O)2R 2 OPO crude product;
[0014]
[0015] 3) Refining: The crude product obtained in step 2) is washed with water, acidified and distilled to obtain refined trialkyl phosphate.
[0016] In the above reaction equation, R 1 and R 2 They can be the same or different, and can be straight-chain or branched alkyl, cycloalkyl or cycloalkyl-substituted alkyl groups of C1 to C12, or substituted or unsubstituted aralkyl groups of C7 to C9;
[0017] Alkali metal M refers to sodium or potassium, and its corresponding donor is hydroxide or carbonate. That is, the alkali metal salt used to prepare dialkyl phosphate is sodium hydroxide, sodium carbonate, potassium hydroxide or potassium carbonate.
[0018] Alkylating agent R 2 X is an electrophile suitable for SN2 reactions, where X represents a leaving group. X is selected from halogens, including chlorine, bromine, and iodine, where R... 2 X is a haloalkane; X is selected from sulfonyloxy groups, including methanesulfonyloxy, trifluoromethanesulfonyloxy, p-toluenesulfonyloxy, p-nitrobenzenesulfonyloxy, and p-bromobenzenesulfonyloxy, etc., in which case R 2 X is a sulfonate ester; X is selected from alkoxythioyloxy, in which case R 2 X is a sulfate diester; X is selected from trifluoroacetoxy, where R... 2 X is trifluoroacetate;
[0019] The phase transfer catalyst is a quaternary ammonium salt or quaternary phosphonium salt, including but not limited to tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, trioctylmethylammonium chloride, triethylbenzylammonium bromide, tributylphenylammonium bromide, tetrabutylphosphonium bromide, hexadecyltributylphosphonium bromide, etc.;
[0020] The phase transfer catalyst used can be added directly in the form of a quaternary ammonium salt or a quaternary phosphorus salt, or it can be generated in situ during the reaction of a trialkylamine or a trialkylphosphine with a haloalkane. The alkyl group in the haloalkane structure is the same as the alkyl group in the alkylating agent.
[0021] The reaction equation for the in-situ formation of trialkylamines or trialkylphosphines with haloalkanes during the reaction process is as follows:
[0022]
[0023] Among them, R 2 The alkyl group, R, represents the alkylating agent. 3 R 4 R 5 The substituents represent common phase transfer catalysts, and Y represents chlorine, bromine, or iodine.
[0024] In this invention, the amount of phase transfer catalyst is 4% to 10% of the mass of dialkyl phosphate; the molar ratio of dialkyl phosphate to alkylating agent is 1:1 to 1:14; the alkylation reaction temperature is 75℃ to 145℃; and the alkylation reaction time is 5 to 19 h.
[0025] In the salt formation process of this invention, the reaction of dialkyl phosphate with alkali metal hydroxide or carbonate is carried out in an aqueous solution. After the salt formation reaction, most of the water in the reaction system is removed by distillation or azeotropic dehydration, so that the water content of the reaction system is less than 5%.
[0026] The alkylation reaction can be carried out with an excess of alkylating agent or with the addition of a third solvent, which is a non-polar organic solvent, preferably aromatic hydrocarbons such as benzene, toluene, and xylene, and alkanes such as n-hexane, cyclohexane, and n-heptane.
[0027] This invention discovers that phase transfer catalysts can assist the molecular transfer of dialkyl phosphate metal salts to alkylating agents, allowing the reaction to proceed smoothly. As shown in the following formula, the dialkyl phosphate alkali metal salt exchanges positive ions with the phase transfer catalyst. Due to the positive ion Q of the phase transfer catalyst… + It has a lipophilic group, therefore, Q + The conjugate with the dialkyl phosphate anion is lipophilic. It transfers from the solid phase to the liquid phase and dissolves in the molecular state in nucleophilic reagents or nonpolar solvents, making it easier to undergo nucleophilic substitution reactions with alkylating agents to obtain trialkyl phosphate.
[0028]
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] Phase transfer catalysts can transfer reactants between phases, thereby increasing the reaction rate. This invention applies a phase transfer catalyst to the reaction process of alkali metal salts of dialkyl phosphates with alkylating agents, achieving an increased reaction rate and realizing the conversion of dialkyl phosphates to trialkyl phosphates. Detailed Implementation
[0031] 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.
[0032] Example 1
[0033] This example illustrates a general procedure for converting dialkyl phosphates to trialkyl phosphates. 21.0 g (0.1 mol) of di-n-butyl phosphate, 13.0 g (0.1 mol) of a 32% sodium hydroxide aqueous solution, and 120.0 g (1.3 mol) of 1-chlorobutane were sequentially added to a four-necked flask equipped with a stirrer, thermometer, and water separator. The mixture was heated to an azeotropic temperature to remove water. When the water content in the flask was less than 3% (Karl Fischer process), it was transferred to a pressure vessel. Sodium di-n-butyl phosphate was visible as a suspension dispersed in 1-chlorobutane. 1.0 g of tetrabutylammonium bromide was added, the mixture was sealed, and the reaction was carried out in a bath at 135°C for 13 hours. After cooling to room temperature, the mixture was washed with water, acidified, and distilled to obtain 22.9 g of tri-n-butyl phosphate with a gas chromatographic purity of 98.9% and a yield of 86.0%.
[0034] Comparative Example 1
[0035] This example illustrates the catalytic effect of a phase transfer catalyst. The method of Example 1 was followed, but without the addition of a phase transfer catalyst. After washing, acidification, and distillation, only a very small amount of material remained in the distillation flask, and no tributyl phosphate was obtained, indicating that the reaction was very slow without a catalyst.
[0036] Comparative Example 2
[0037] This example illustrates the effect of water in the material on the reaction. Following the method of Example 1, the salt was not dehydrated after formation, allowing the reaction to proceed in an oil-water two-phase environment. After washing, acidification, and distillation, only a very small amount of material remained in the distillation flask, and no tributyl phosphate was obtained, indicating that this reaction proceeds very slowly in an oil-water two-phase environment.
[0038] Examples 2-6
[0039] The following examples illustrate the catalytic effects of other phase transfer catalysts. The method of Example 1 was followed, with the phase transfer catalyst successively replaced by tetrabutylammonium chloride, tetrabutylphosphonium bromide, trioctylmethylammonium chloride, triethylbenzylammonium bromide, and hexadecyltributylphosphonium bromide. The results are shown in the table below.
[0040]
[0041]
[0042] Example 7
[0043] This example illustrates that phase-transfer catalysts can be generated in situ from the reaction of trialkylamines with haloalkanes, thereby playing a catalytic role. 21.0 g (0.1 mol) of di-n-butyl phosphate, 13.0 g (0.1 mol) of 32% sodium hydroxide aqueous solution, and 120.0 g (1.3 mol) of 1-chlorobutane were sequentially added to a four-necked flask equipped with a stirrer, thermometer, and water separator. The mixture was heated to an azeotropic temperature to remove water. When the water content of the material in the flask was less than 3% (Karl Fischer process), it was transferred to a pressure-resistant flask, 0.5 g of tri-n-butylamine was added, the flask was sealed, and the mixture was reacted in a bath at 135°C for 13 hours. Afterward, the mixture was cooled to room temperature, washed with water, acidified, and distilled to obtain 21.3 g of tri-n-butyl phosphate, with a yield of 79.9%.
[0044] Example 8
[0045] This example illustrates that phase transfer catalysts can be formed in situ from the reaction of trialkylphosphine with haloalkanes, thereby achieving catalytic action. Following the method of Example 7, 0.5 g of tri-n-butylamine was replaced with 0.6 g of tri-n-butylphosphine, yielding 23.4 g of tri-n-butyl phosphate, with a yield of 87.9%.
[0046] Examples 9-15
[0047] The following are variations of the alkyl group in the structure of dialkyl phosphate esters and alkylating agents. The method of Example 1 was implemented, with diethyl phosphate, di-n-butyl phosphate, and di(2-ethylhexyl) phosphate as the dialkyl esters, and 1-chlorobutane, 3-(chloromethyl)heptane, bromocyclohexane, and benzyl chloride as the alkylating agents. The results are shown in the table below.
[0048]
[0049] Examples 16-18
[0050] The following examples illustrate that, in addition to sodium hydroxide, sodium carbonate, potassium hydroxide, or potassium carbonate can also be used to prepare alkali metal salts of dialkyl phosphates. The method of Example 1 was followed, but the alkali used was replaced with an aqueous solution of sodium carbonate, potassium hydroxide, or potassium carbonate of equivalent concentration in equal amounts. The results are shown in the table below.
[0051] Example Types of alkalis purity / % Yield / % 16 Sodium carbonate 95.6 73.8 17 potassium hydroxide 99.6 89.9 18 Potassium carbonate 98.7 83.8
[0052] Examples 19-22
[0053] The following examples illustrate variations of the alkylating agent. The method of Example 1 was implemented, with the alkylating agent changed to 1-bromobutane, diethyl sulfate, n-butyl trifluoromethanesulfonate, and n-butyl p-toluenesulfonate in amounts equal to that of chlorobutane, respectively. The results are shown in the table below.
[0054] Example Alkylating agents product purity / % Yield / % 19 1-Bromobutane Tributyl phosphate 99.5 90.7 20 diethyl sulfate Monoethyl di-n-butyl phosphate 99.8 93.2 21 n-Butyl trifluoromethanesulfonate Tributyl phosphate 97.3 98.0 22 p-Butyl p-toluenesulfonate Tributyl phosphate 97.5 91.0
[0055] Examples 23-25
[0056] The following examples illustrate the range of phase transfer catalyst dosages. The method of Example 1 was followed, with variations in the dosage of the phase transfer catalyst tetrabutylammonium bromide. The results are shown in the table below.
[0057] Example Catalyst dosage / g purity / % Yield / % 23 0.8 98.5 84.0 24 1.3 99.2 88.5 25 2.0 99.7 95.3
[0058] Examples 26-28
[0059] The following examples illustrate the range of molar ratios of dialkyl phosphate to alkylating agent. The method of Example 1 was implemented, but the alkylating agent was changed to 1-bromobutane, and its dosage was varied. The results are shown in the table below.
[0060]
[0061] Examples 29-31
[0062] The following examples illustrate the range of alkylation reaction temperatures. The method of Example 1 was followed, with variations in the alkylation reaction temperature; the results are shown in the table below.
[0063] Example Alkylation reaction temperature / °C purity / % Yield / % 29 75 88.9 49.3 30 120 98.7 80.1 31 145 99.3 87.9
[0064] Examples 32-34
[0065] The following examples illustrate the range of alkylation reaction times. The method of Example 1 was followed, with variations in the alkylation reaction time; the results are shown in the table below.
[0066] Example Alkylation reaction time / h purity / % Yield / % 32 5 89.6 52.1 33 10 97.8 85.0 34 19 99.5 88.9
[0067] Examples 35-36
[0068] The following examples illustrate that the reaction can be carried out in a third solvent. The method of Example 1 was followed, but the amount of chlorobutane was reduced to 50 g (0.54 mol), and 50 g of toluene or cyclohexane was added to carry out the reaction. The results are shown in the table below.
[0069] Example solvent purity / % Yield / % 35 Toluene 96.1 79.9 36 Cyclohexane 99.5 73.0
[0070] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values of the present invention can all achieve the method, and examples are not listed here.
[0071] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.
[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for synthesizing trialkyl phosphate from dialkyl phosphate, the method mainly comprising the following steps: 1) Salt formation: Dialkyl phosphate (R...) 1 O)2POOH reacts with MOH or M2CO3 to form an alkali metal salt of dialkyl phosphate, where M is an alkali metal; 2) Alkylation: The alkali metal salt of the dialkyl phosphate obtained in step 1) is reacted with the alkylating agent R. 2 X reacts under the catalysis of a phase transfer catalyst to give a trialkyl phosphate-containing ester (R). 1 O)2R 2 OPO crude product; R 1 and R 2 It is n-butyl, alkylating agent R 2 X is 1-chlorobutane; The phase transfer catalyst is tetrabutylammonium bromide; During the salt formation process, the reaction of dialkyl phosphate with alkali metal hydroxides or carbonates takes place in an aqueous solution. After the salt formation reaction, the water content of the reaction system is reduced to less than 5% by distillation or azeotropic dehydration.
2. The method for synthesizing trialkyl phosphate from dialkyl phosphate according to claim 1, characterized in that, The amount of phase transfer catalyst used is 4% to 10% of the mass of dialkyl phosphate.
3. The method for synthesizing trialkyl phosphate from dialkyl phosphate according to claim 1, characterized in that, The molar ratio of dialkyl phosphate to alkylating agent is 1:1 to 1:14; the alkylation reaction temperature is 75℃ to 145℃, and the alkylation reaction time is 5 to 19 h.
4. The method for synthesizing trialkyl phosphate from dialkyl phosphate according to claim 1, characterized in that, The alkylation reaction is carried out in excess alkylating agent or in an alkylating agent with a third solvent added; the third solvent is a nonpolar organic solvent.
5. The method for synthesizing trialkyl phosphate from dialkyl phosphate according to any one of claims 1-4, characterized in that, The method also includes a refining step: the crude product obtained in step 2) is washed with water, acidified and distilled to obtain a refined trialkyl phosphate.