Process for the synthesis of monofluorophosphates

Abstract

The application discloses a synthesis method of monofluorophosphate. The method is characterized by heating reaction of phosphorus pentoxide, a siloxane compound and a fluoride in a non-aqueous solvent; the siloxane compound has a general formula, wherein R1, R2, R3, R4, R5 and R6 are independently selected from any one of methyl, ethyl, propyl, isopropyl, n-butyl, phenyl and ethynyl. The synthesis method of monofluorophosphate disclosed by the application is characterized by heating reaction of phosphorus pentoxide, a siloxane compound and a fluoride in a non-aqueous solvent. The obtained product has high purity and high yield, the process used in the reaction process is simple, and the side reaction is less. Moreover, the by-product obtained in the synthesis reaction is a gas, which is easy to handle and can be repeatedly reused after post-treatment, and the cost is lower than that of the existing equipment corrosion and other synthesis routes.

Description

Technical Field

[0001] This application relates to the technical field of lithium battery additives, and in particular to a method for synthesizing monofluorophosphate. Background Technology

[0002] With the rapid development of lithium-ion batteries, rechargeable batteries have been quickly applied in various fields. However, conventional rechargeable batteries cannot meet the increasingly stringent requirements of the market for lithium-ion batteries in terms of high and low temperature performance, battery capacity, and cycle performance. Therefore, the development of various high-performance electrolyte additives has become urgent. Monofluorophosphate, as a lithium-ion battery additive, can significantly improve the low-temperature characteristics and cycle stability of rechargeable batteries. Consequently, against the backdrop of the continued rapid expansion of the rechargeable battery market, the demand for lithium monofluorophosphate as a battery additive will also increase accordingly.

[0003] However, current methods for preparing lithium monofluorophosphate either have low yields or produce numerous byproducts during the reaction, and there is no universally applicable process. Therefore, lithium monofluorophosphate cannot be produced and applied in large quantities. For example, lithium hexafluorophosphate can be hydrolyzed to obtain lithium monofluorophosphate, but this process is difficult to control, and the final product is difficult to purify, resulting in low yields and purity. Further purification would significantly increase production costs, directly limiting its application.

[0004] Therefore, it is necessary to develop a synthetic route for sodium monofluorophosphate. Summary of the Invention

[0005] In view of this, the embodiments of this application provide a method for synthesizing monofluorophosphate, which is mild and controllable, and the reaction product is easy to purify.

[0006] This application provides a method for synthesizing monofluorophosphate, which involves heating and reacting phosphorus pentoxide, siloxane compounds, and fluorides in a non-aqueous solvent;

[0007] Among them, siloxane compounds have the following general formula,

[0008]

[0009] In this general formula, R1, R2, R3, R4, R5, and R6 are independently selected from any one of methyl, ethyl, propyl, isopropyl, n-butyl, phenyl, and ethynyl.

[0010] Preferably, the siloxane compound is hexamethyldisiloxane or hexaethyldisiloxane.

[0011] Optionally, the non-aqueous solvent is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butene carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

[0012] Optionally, the reaction temperature is 90-105℃ and the reaction time is 12-24h.

[0013] Optionally, the reaction is carried out in an inert atmosphere.

[0014] Optionally, the molar ratio of phosphorus pentoxide to fluoride is 1:4 to 8.

[0015] Optionally, the molar ratio of phosphorus pentoxide to siloxane compound is 1:1 to 2.

[0016] Optionally, after the heating reaction, the process further includes:

[0017] The gaseous components of the reaction products are passed into an alkaline solution to recover siloxane compounds and fluorides.

[0018] And / or, recrystallize the solid phase component of the reaction product to purify the crude product.

[0019] Optionally, the alkaline solution is a sodium hydroxide solution;

[0020] Preferably, the concentration of the alkaline solution is 10%-50%;

[0021] Preferably, the molar number of the alkaline solution added is 1 to 10 times that of phosphorus pentoxide;

[0022] Preferably, the recrystallization is performed using a non-aqueous solvent;

[0023] Preferably, the non-aqueous solvent for recrystallization is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butene carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

[0024] The method for synthesizing monofluorophosphate disclosed in this application involves reacting phosphorus pentoxide, siloxane compounds, and fluorides in a non-aqueous solvent under heat. The resulting product has high purity and high yield, and the reaction process is simple with few side reactions.

[0025] Moreover, the byproducts of this synthesis reaction are gases, which are easy to handle and can be repeatedly reused after post-processing. The cost is lower than existing synthesis routes, and the corrosion to equipment is also lower than other synthesis routes. Detailed Implementation

[0026] The embodiments of this application are disclosed in detail below. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0027] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0029] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0030] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0031] Before introducing the technical solution of this application, it is necessary to introduce the background of the creation of this invention.

[0032] In related technologies, the synthesis of lithium monofluorophosphate widely employs the hydrolysis of lithium hexafluorophosphate.

[0033] The inventors have discovered that this synthesis method involves a relatively violent and uncontrollable reaction, which makes it difficult to purify the product, thus affecting both the yield and purity.

[0034] To achieve the desired goals of controllable reaction and easy product purification, those skilled in the art typically focus on improving the reaction based on the hydrolysis of lithium hexafluorophosphate. This can be done by adding auxiliaries, such as adding aprotic solvents to the reaction system, or changing the acid-base environment of the hydrolysis reaction.

[0035] However, through experimentation with the above methods, the inventors discovered that these methods did not substantially change the principle of the hydrolysis reaction itself. This is because the process of water donating protons in the hydrolysis reaction is relatively easy, which leads to an abnormally violent reaction and thus the effect obtained is very limited.

[0036] The inventors unexpectedly discovered that the Si-O structure of siloxane compounds not only contains O, which can serve as a source of oxygen atoms for monofluorophosphate, but also that the Si-O bond breaking is more stable than that of H₂O, providing a realistic possibility for siloxane compounds. Based on this, it was further discovered that the reaction of phosphorus pentoxide, siloxane compounds, and fluorides in a non-aqueous solvent upon heating can yield monofluorophosphate, with the products consisting of a solid phase and a gaseous phase. The solid phase contains impurities other than unreacted fluorides and phosphorus pentoxide, primarily monofluorophosphate, which allows for purification of the solid phase product through recrystallization, making product purification relatively easy. Furthermore, compared to hydrolysis reactions, the reaction of siloxane compounds is more controllable, resulting in improved final yield and purity. Based on these findings, this invention was created.

[0037]

Synthesis Method

[0038] The method for synthesizing monofluorophosphate involves heating phosphorus pentoxide, siloxane compounds, and fluorides in a non-aqueous solvent.

[0039] Among them, siloxane compounds have the following general formula,

[0040]

[0041] In this general formula, R1, R2, R3, R4, R5, and R6 are independently selected from any one of methyl, ethyl, propyl, isopropyl, n-butyl, phenyl, and ethynyl.

[0042] It should be understood that the cations in fluorides correspond to the cations in the target compound monofluorophosphate, and the fluoride cations include, but are not limited to, widely used ones such as Na and Li.

[0043] Understandably, the temperature of the above heating reaction does not have a particularly significant impact on the yield, but it will directly affect the reaction time.

[0044] As a demonstration site, the reaction temperature is 90-105℃, such as 90℃, 90.5℃, 91℃, 92℃, 93℃, 95℃, 98℃, 100℃, 102℃, 103℃, 105℃, etc.; based on this reaction temperature, the reaction time is 12-24h, such as 12h, 13h, 14h, 15h, 16h, 18h, 22h, 23h, or 24h.

[0045] Siloxane compounds

[0046] As used herein, siloxane compounds refer to compounds containing a Si-O structure, encompassing both common organic compounds of small molecules and polymers. Specific examples of common organic compounds include hexamethyldisiloxane, etc. As polymeric forms, examples include dimethyl silicone oil, etc.

[0047] Taking hexamethyldisiloxane as an example of a siloxane compound and NaF as an example of a fluoride, the reaction equation is: P2O5+(CH3)6Si2O+4NaF=2Na2PO3F+2(CH3)3SiF↑.

[0048] [Non-aqueous solvent]

[0049] It should not be misunderstood that this application does not impose stringent restrictions on the water content of non-aqueous solvents. Normal levels of water content in non-aqueous solvents will not seriously impair the reaction yield or product purity. However, for the sake of more controllable reaction, the reaction in this application is carried out under anhydrous conditions.

[0050] Non-aqueous solvents are preferably polar solvents, which can dissolve the reactants well.

[0051] As a further example, the non-aqueous solvent is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

[0052] [Reaction Environment]

[0053] As a suitable but not limiting example, the reaction atmosphere of this application can be carried out in an inert atmosphere to isolate the influence of external oxygen and water vapor on the product, thereby preventing the hydrolysis reaction of the raw materials and products, and thus improving the reaction yield and product purity.

[0054] Here, the inert atmosphere can be nitrogen, an inert gas, etc.

[0055] [Ingredient Dosage]

[0056] Suitable, but not limiting, examples include a molar ratio of phosphorus pentoxide to fluoride of 1:4 to 8, such as 1:4, 1:4.2, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, etc.

[0057] In this way, a slight excess of fluoride can ensure the full formation of the gaseous components of the reaction products.

[0058] Suitable, but not limiting, examples include phosphorus pentoxide and siloxane compounds in a molar ratio of 1:1 to 2, such as 1:1, 1:1.1, 1:1.2, 1:1.5, 1:1.6, 1:1.8, 1:2, etc.

[0059] In this way, a slight excess of siloxane compounds can ensure the full generation of the gaseous components of the reaction products.

[0060] [Treatment of reaction products]

[0061] As a suitable, but not limiting, specific example, the heating reaction further includes:

[0062] The gaseous components of the reaction products are passed into an alkaline solution to recover siloxane compounds and fluorides.

[0063] As an example, the alkaline solution is sodium hydroxide solution, potassium hydroxide, sodium carbonate, etc.

[0064] Here, taking hexamethyldisiloxane as an example, the relevant reaction formula for absorbing tail gas is: 2(CH3)3SiF+2NaOH=2NaF+(CH3)6Si2O+H2O.

[0065] Preferably, the concentration of the alkaline solution is 10%-50%, for example, 10%, 10.5%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.;

[0066] Preferably, the molar amount of the alkaline solution is 1 to 10 times that of phosphorus pentoxide, for example, 1, 1.1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 8.5, 9, 9.5, or 10 times.

[0067] The solid phase component of the reaction product is recrystallized to purify the crude product.

[0068] Here, the recrystallization is performed using a non-aqueous solvent;

[0069] Here, as an exemplary example, the non-aqueous solvent for recrystallization is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butene carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

[0070] [Reaction Feeding Method]

[0071] Suitable, but not limiting, synthetic reactions that implicitly include the feeding method include:

[0072] S1. Add a non-aqueous solvent to the reaction vessel and prepare an alkaline solution separately, which is then transferred to the tail gas absorption device.

[0073] S2. Add phosphorus pentoxide and anhydrous fluoride into the reactor under an inert gas atmosphere and mix well.

[0074] S3: After heating to 90-105℃ under an inert gas atmosphere, add siloxane compound dropwise and continue the reaction for 12-24 hours;

[0075] S4: After the reaction is complete, filter the residue and recrystallize it using a non-aqueous solvent to obtain a pure white solid, which is then dried.

[0076] S5: Take the solution that has been completely absorbed in the tail gas absorption device and separate it into liquid and liquid phases. Distill the organic phase and dry the aqueous phase to obtain the raw material siloxane compound and fluoride.

[0077]

Example

[0078] Example 1

[0079] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0080] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0081] Example 2

[0082] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0083] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 20% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 113.7 g (0.7 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0084] Example 3

[0085] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0086] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 126 g (3 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 30% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 94.2 g (0.58 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0087] Example 4

[0088] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0089] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 168 g (4 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 40% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 113.7 g (0.7 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0090] Example 5

[0091] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0092] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 45% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 113.7 g (0.7 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 24 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0093] Example 6

[0094] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0095] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 50% concentration solution with 20 g of sodium hydroxide and add it to the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 113.7 g (0.7 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 18 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0096] Example 7

[0097] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0098] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 105 °C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0099] Example 8

[0100] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0101] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 100°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0102] Example 9

[0103] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0104] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 123.3 g (0.5 mol) of hexaethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0105] Example 10

[0106] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0107] Add 500 ml of acetonitrile to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0108] Comparative Example 1

[0109] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0110] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 42 g (1 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 5% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0111] Comparative Example 2

[0112] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0113] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 50% concentration solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 45°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0114] Comparative Example 3

[0115] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0116] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 50% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 65°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0117] Comparative Example 4

[0118] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0119] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Place deionized water into a tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the mixture in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0120] Comparative Example 5

[0121] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0122] Add 500 ml of diethyl carbonate to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 105 g (2.5 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 50% concentration solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 3 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0123] Comparative Example 6

[0124] A method for preparing sodium monofluorophosphate specifically includes the following steps:

[0125] Add 500 ml of n-hexane to the reactor, then add 71 g (0.5 mol) of phosphorus pentoxide and 84 g (2 mol) of anhydrous sodium fluoride under a nitrogen atmosphere in a glove box. Prepare a 10% sodium hydroxide solution with 20 g of sodium hydroxide and place it in the tail gas absorption device to absorb the reaction tail gas. Heat the reaction system to 95°C and add 81.2 g (0.5 mol) of hexamethyldisiloxane dropwise. After the addition is complete, continue heating the reaction for 16 hours. After the reaction is complete, filter the solution in a glove box and recrystallize the filter cake using 750 ml of acetonitrile. Dry the solid and weigh it. Separate the remaining solution in the tail gas absorption device, distilling to recover the organic phase and drying the aqueous phase to recover the solid.

[0126] Evaluation results

[0127] The relevant test results of the above embodiments and comparative examples are as follows:

[0128]

[0129]

[0130] Through the above comparative examples and embodiments, it can be seen that the feed ratio is the first factor controlling the completeness of the reaction. Sodium fluoride must be in sufficient or slightly excessive amounts relative to phosphorus pentoxide, which is more conducive to the formation of the target product. Excessive amounts will also lead to waste of raw materials. When the amount of sodium fluoride relative to phosphorus pentoxide is insufficient, i.e., phosphorus pentoxide is excessive, the reaction can occur, but the excess phosphorus pentoxide is difficult to separate completely, resulting in low purity of the target product. The second reaction control factor is the reaction temperature. If the reaction temperature is too low, the reaction cannot proceed completely, and uncontrollable side reactions are likely to occur, leading to a decrease in the yield and purity of the target product. The third factor is the reaction time. Insufficient reaction time cannot ensure the completeness of the reaction. For the absorption and recovery of raw materials from tail gas, the concentration of sodium hydroxide solution is critical. If the concentration of sodium hydroxide solution is too low, complete absorption of trimethylfluorosilane cannot be guaranteed, resulting in pollution and waste of raw materials that cannot be reused. The fourth factor is the choice of polar solvent. If the polarity of the solvent is too low, the reactants cannot be fully dissolved to allow the reaction to occur.

[0131] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for synthesizing monofluorophosphate, characterized in that, Phosphorus pentoxide, siloxane compounds, and fluorides are reacted by heating in a non-aqueous solvent; Among them, siloxane compounds have the following general formula, ； In this general formula, R1, R2, R3, R4, R5, and R6 are independently selected from any one of methyl, ethyl, propyl, isopropyl, n-butyl, phenyl, and ethynyl. The reaction temperature is 90-105℃, and the reaction time is 12-24h.

2. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, The siloxane compounds include hexamethyldisiloxane and hexaethyldisiloxane.

3. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, The non-aqueous solvent is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

4. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, The reaction is carried out in an inert atmosphere.

5. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, The molar ratio of phosphorus pentoxide to fluoride is 1:4~8.

6. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, The molar ratio of phosphorus pentoxide to siloxane compound is 1:1~2.

7. The method for synthesizing monofluorophosphate according to claim 1, characterized in that, Following the heating reaction, the process also includes: The gaseous components of the reaction products are passed into an alkaline solution to recover siloxane compounds and fluorides. And / or, recrystallize the solid phase component of the reaction product to purify the crude product.

8. The method for synthesizing monofluorophosphate according to claim 7, characterized in that, The alkaline solution is a sodium hydroxide solution; The concentration of the alkaline solution is 10%-50%; The molar amount of the alkaline solution added is 1 to 10 times that of phosphorus pentoxide; The recrystallization is performed using a non-aqueous solvent; The non-aqueous solvent for recrystallization is any one or a combination of at least two of the following: acetonitrile, chloroform, carbon tetrachloride, toluene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, dipropyl carbonate, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl propionate, or propyl acetate.

Images