Preparation method of cyclic phosphate ester compound

Abstract

According to the method, the epoxyalkane and the phosphoric anhydride are used as reaction raw materials, and the special catalyst DMC is used for preparing the cyclic phosphate, so that the use of combustible acidic corrosion products such as phosphorus oxychloride and phosphorus trichloride is avoided, the generation of a corrosive chemical hydrogen chloride is avoided, the corrosion to equipment is reduced, and the damage to the environment is reduced; the use of precursor dangerous chemicals such as acetone, concentrated sulfuric acid and other control chemicals is avoided, the biological damage to the environment is also reduced, and the industrial mass production is facilitated.

Description

Technical Field

[0001] The invention relates to a method for preparing a cyclic phosphate compound, and belongs to the field of synthesis of flame-retardant additives for electrolytes. Background Art

[0002] Energy depletion and environmental pollution have led to the emergence of green, pollution-free, recyclable, high-energy-density lithium-ion batteries, which have been widely used in a short period of time. Lithium-ion battery products such as mobile phones, laptops, and electric vehicles are everywhere in people's daily lives and have become an indispensable part. However, lithium-ion batteries are a double-edged sword. While bringing convenience to people's lives, they also bring a series of safety issues, which has become a key factor restricting their development. Adding flame retardants has a significant effect on improving the safety of lithium-ion batteries.

[0003] As we all know, the current mainstream lithium battery uses electrolyte as a carrier to carry out chemical reaction and deintercalation between the positive and negative electrodes. Heat and gas will be generated in this process. The electrolyte is mostly a low-flash-point and flammable linear or cyclic organic carbonate mixture. It has begun to decompose at 80-100°C, and its diaphragm will react above 130°C. When the heat generation rate in the battery is greater than the heat dissipation rate, thermal runaway will occur, causing explosion or fire, and in most cases, the flammable electrolyte will be burned out before it can be extinguished.

[0004] Over the years, in order to improve the safety of lithium-ion batteries, researchers have added various additives to the electrolyte on the basis of optimizing the battery structure materials and heat dissipation methods. The results show that adding a certain amount of additives will not only not affect the chemical properties of the battery, but also effectively inhibit thermal runaway or fire. The addition of flame retardant additives can effectively inhibit the combustion of lithium-ion battery electrolytes and improve the safety of batteries, which has also made the research of flame retardant additives a hot topic in a short period of time. At present, the common flame retardants on the market are: organic phosphorus flame retardants, halogen flame retardants and composite flame retardants. Phosphorus flame retardants have become the mainstream research object due to their high flame retardant efficiency and good mutual solubility. However, there are not many studies on additives that have both electrolyte additive functions and flame retardant functions. Most of them use flammable acidic corrosives such as phosphorus oxychloride and phosphorus trichloride as raw materials, which is not conducive to industrialization. In addition, a large amount of byproduct hydrogen chloride will be produced during the reaction, which will not only corrode the equipment, but also bring a large number of waste treatment problems in the future.

[0005] For example, patent document WO2022092835A1 discloses that in a hydrophobic solvent tetrahydrofuran system, 2-chloro-2-oxo-1,3,2-dioxaphospholane reacts with a nucleating agent (such as water) to form a nucleating reaction, and under an inert gas, a nucleating agent is added dropwise to the reaction solution at a temperature of 0 to 10°C, and hydrogen chloride is removed by stirring to obtain a hydroxyl intermediate. After the nucleating agent is added, the temperature is raised to 0-40°C, and the volatile hydrogen chloride gas is removed under reduced pressure and distillation, and then recrystallized and purified to obtain a symmetrical phosphate-based compound. However, hydrogen chloride gas will be generated during the reaction, which will cause the problems mentioned above. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a cyclic phosphate compound represented by formula I, and the preparation process thereof is as follows:

[0007]

[0008] Among them, ------ indicates existence or non-existence. When it does not exist, the raw material A is When present, the raw material A is The corresponding formula I represents the products obtained by reacting the above two structures with phosphoric anhydride respectively;

[0009] R1, R2 and R3 are the same or different and are independently selected from hydrogen, C 1-6 Alkyl or halogenated C 1-6 alkyl;

[0010] When ------- indicates the presence of, R1 and R2 can be connected, together with the carbon atoms to which they are connected, to form C 4-6 Alternatively, R2 and R3 may be linked together to form a C 4-6 Alternatively, R1 and R3 may be linked together to form a C 4-6 Cycloalkyl;

[0011] When ------- indicates absence, R1 and R2 can be connected and then form C together with the carbon atoms connected to them. 4-6 Cycloalkyl;

[0012] The raw material A reacts with phosphoric anhydride in the presence of a double metal cyanide complex (DMC) catalyst to obtain a cyclic phosphate compound shown in formula I.

[0013] According to an embodiment of the present invention, the double metal cyanide complex can be purchased commercially or prepared in-house, for example, any brand of commercially available DMC double metal catalyst, such as Huaian Bader DMC (cobalt-zinc complex).

[0014] According to an embodiment of the present invention, R1, R2 and R3 are the same or different and are independently selected from hydrogen, C 1-3 Alkyl or halogenated C 1-3 alkyl.

[0015] According to an embodiment of the present invention, raw material A is Wherein R1 and R2 are the same or different, and are independently selected from hydrogen, methyl, chloromethyl, ethyl, or R1 and R2 are connected to form a ring, such as R1 and R2 together with the carbon atoms to which they are connected form 1,2-epoxycyclopentane or cyclohexene oxide.

[0016] A high-quality reactor environment can ensure better product acquisition. In order to obtain high-quality products, the reactor can be pre-treated by acidification.

[0017] According to an embodiment of the present invention, the method for preparing the cyclic phosphate ester compound includes a pre-treatment step of a reactor, such as washing the reactor with an acidic solvent to an acidic environment.

[0018] According to an embodiment of the present invention, the pretreatment step of the reactor includes: heating the washing reactor with an alcohol solvent, then heating the washing reactor with deionized water, and then heating the washing reactor with concentrated sulfuric acid or phosphoric acid until the pH inside the reactor is less than 7, then purging with an inert gas, and finally vacuum heating to remove residual water vapor in the reactor.

[0019] In some embodiments of the present invention, the pretreatment step of the reactor includes: adding 50-70% by volume of anhydrous ethanol to the reactor, stirring, heating to 80-85°C, maintaining for 0.5-12h, cooling to 30-45°C, and releasing, repeating this more than once; then adding 80-90% by volume of deionized water to the reactor, stirring, heating to 95-105°C, maintaining for 0.5-12h, cooling to 30-45°C, and releasing, repeating this more than once; then adding 80-90% by volume of deionized water to the reactor, stirring, heating to 95-105°C, maintaining for 0.5-12h, cooling to 30-45°C, and releasing, repeating this more than once; then adding 80-90% by volume of deionized water to the reactor, stirring, heating to 95-105°C, maintaining for 0.5-12h, cooling to 30-45°C, and releasing, repeating this more than once; % deionized water, and at the same time, 0.01% concentrated sulfuric acid or phosphoric acid of the total mass of deionized water is added dropwise, stirred, heated to 95-105°C, maintained for 0.5-1h, cooled to 30-45°C, and sampled to monitor the pH of the aqueous solution until the pH is <7; the deionized water in the reactor is released, and nitrogen is repeatedly purged through each pipeline for more than one time, and each valve of the reactor is closed. The temperature in the reactor is raised to 95-105°C, and finally the vacuum is opened to remove the residual water vapor in the reactor, and the temperature is maintained for 1-12h, and the heating is turned off, and the temperature is lowered to room temperature before entering the next step.

[0020] According to an embodiment of the present invention, the purity of the phosphoric anhydride is 90% or more, preferably 95% or more, further preferably 99% or more, for example 99.5% or more.

[0021] According to an embodiment of the present invention, the phosphoric anhydride is diluted with a diluent cyclohexane or methylcyclohexane, and further, the diluent is treated with 4A molecular sieve.

[0022] According to an embodiment of the present invention, the reaction is carried out in an inert gas environment, such as a nitrogen environment, such as a high-purity nitrogen environment.

[0023] According to an embodiment of the present invention, the reaction temperature is 50-180°C, for example 100-160°C, such as 140-150°C.

[0024] According to an embodiment of the present invention, the following steps are adopted to prepare cyclic phosphate compounds: select commercially available high-quality phosphoric anhydride and place it in a pre-treated reactor, add diluent cyclohexane or methylcyclohexane treated with 4A molecular sieve, that is, the water content of the diluent is less than 500ppm, preferably 200ppm, and at the same time add catalyst DMC, fill with high-purity nitrogen, replace 5-7 times, slowly increase the temperature to 50-180°C, preferably 140-150°C, and slowly introduce raw material A into the reactor for ring-opening addition reaction; after sufficient aging and degassing, a series of refining and post-treatment are performed to obtain a cyclic phosphate compound product.

[0025] According to an embodiment of the present invention, the cyclic phosphate compound represented by formula (I) is selected from the following:

[0026]

[0027] Wherein, R1 and R2 are consistent with the above definition.

[0028] According to an embodiment of the present invention, the raw material A is preferably ethylene oxide (EO), propylene oxide (PO), ethyl ethylene oxide, butylene oxide (BO), 1,2-cyclopentene oxide or cyclohexene oxide, and a cyclic phosphate compound having a structure shown in the following formula C1-C4 can be obtained:

[0029]

[0030] According to an embodiment of the present invention, the molar number of raw material A is 1-5 times, for example, 1-3 times, that of phosphoric anhydride.

[0031] According to an embodiment of the present invention, the amount of the catalyst used is 0.0001-0.1% of the total mass of the raw materials, for example, 0.001-0.05%, such as 0.003-0.008%.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The cyclic phosphate compound of the present invention has a relatively high HOMO orbital and can be used as an additive for high-voltage lithium-ion batteries. It also contains phosphorus and has a flame retardant effect, and can be used as a flame retardant additive;

[0034] (2) The present invention provides a new idea for preparing a cyclic lithium battery additive with flame retardant properties. Compared with conventional synthesis methods, the present invention uses alkylene oxide and phosphoric anhydride as reaction raw materials, and uses a special catalyst DMC, avoiding the use of flammable acidic corrosives such as phosphorus oxychloride and phosphorus trichloride, thereby avoiding the generation of corrosive chemicals such as hydrogen chloride, reducing corrosion to equipment and reducing damage to the environment; avoiding the use of easily made-to-drug hazardous chemicals such as acetone, concentrated sulfuric acid and other controlled chemicals, and also reducing biological damage to the environment, which is conducive to large-scale industrial production;

[0035] (3) The present invention adopts a one-step process, and compared with a multi-step reaction, the product has a light color, a high yield, and low water content;

[0036] (4) The purity of the cyclic phosphate compound product prepared by the present invention is greater than 95%, the chromaticity is less than 20 Hazen, and the yield is greater than 58%.

[0037] (5) The cyclic phosphate compound product prepared by the present invention can be widely used as an additive in the field of multifunctional materials such as polyurethane flame retardant additives, fuel additive formulation components, and lithium battery electrolyte additives. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the H NMR spectrum of the product C1 prepared in Example 2 of the present invention.

[0039] Figure 2 This is the gas chromatogram of the product C1 prepared in Example 2. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the invention more obvious and easy to understand, the specific embodiments of the invention are described in detail below.

[0041] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0042] In the following examples, the chromaticity is tested according to the national standard GB / T 9282.1-2008 (Color Assessment of Transparent Liquids by Platinum-Cobalt Grades Part 1: Visual Method), and the test instrument is: Colorimetric tube: flat bottom, capacity of 100 mL, equipped with an optically transparent, ground glass stopper. The color and thickness of the glass of each colorimetric tube should be consistent, and a scale mark should be marked between 275 mm and 295 mm above the bottom of the tube. The height difference of the scale marks of each colorimetric tube should not exceed 3 mm.

[0043] The moisture content is tested according to the national standard GB / T11275-2007 (determination of moisture content of surfactants), and the testing instrument is a moisture meter (Swiss Metrohm 870).

[0044] Example 1 (reactor pretreatment)

[0045] Add 600ml of anhydrous ethanol to a 1L stainless steel pressure-resistant closed reactor, stir, heat to 85°C, keep for 1h, cool to 45°C, release, and repeat twice; then add 800ml of deionized water to the reactor, stir, heat to 95°C, keep for 0.5h, cool to 35°C, release, and repeat twice; finally, add 850ml of deionized water to the reactor, and drop 0.085g of concentrated sulfuric acid at the same time, stir, heat to 100°C, keep for 1h, cool to 45°C, sample and monitor the pH of the aqueous solution to 5, release the deionized water in the reactor, repeatedly purge each pipeline with nitrogen for 3 times, close each valve of the reactor, heat the reactor to 100°C, open the vacuum, remove the residual water vapor in the reactor, keep for 2h, turn off the heating, cool to room temperature, and standby.

[0046] Example 2 (Cyclization Synthesis)

[0047]

[0048] Preparation of compound C1: 142 g (1 mol) of high-quality phosphoric anhydride (purity 99.5%) was weighed at room temperature and added to the reactor treated in Example 1 above. 300 g of cyclohexane treated with 4A molecular sieve and 0.02 g of Huaian Bader DMC (cobalt-zinc complex) were added, and nitrogen was purged. The heating was turned on. After the temperature was raised to 150°C, 88 g (2 mol) of ethylene oxide was slowly introduced into the mixed system in the reactor. The reaction time was 2 h, and the mixture was aged for 2 h. The reaction was stopped, and the temperature was lowered to 50°C. The mixture was slowly transferred out of the reactor. After coarse filtration, the filtrate was transferred to a three-necked flask, washed with water to remove unreacted ethylene oxide, dried and separated, and cyclohexane was recovered by vacuum distillation. The white solid product was obtained by cooling, with a yield of 65%, a GC purity of 97.5%, a moisture content of 100 ppm, and a chromaticity of 15 Hazen. Its nuclear magnetic spectrum is shown as follows Figure 1 As shown in the GC spectrum Figure 2 shown.

[0049] Example 3 (Cyclization Synthesis)

[0050]

[0051] Preparation of compound C2: 213g (1.5mol) of high-quality phosphoric anhydride (purity 99.5%) was weighed at room temperature and added to the reactor treated in Example 1. 400g of methylcyclohexane treated with 4A molecular sieve and 0.025g of Huaian Bader DMC (cobalt-zinc complex) were added, and nitrogen was purged. The heating was turned on. After the temperature was raised to 145°C, 216.3g (3mol) of propylene oxide was slowly introduced into the mixed system in the kettle. The reaction time was 3h, and the mixture was aged for 2.5h. The reaction was stopped, cooled to 50°C, and slowly transferred out of the kettle. After coarse filtration, the filtrate was transferred to a three-necked flask, washed with water to remove unreacted propylene oxide, dried and separated, and methylcyclohexane was recovered by vacuum distillation. A white solid product was obtained by cooling, with a yield of 60%, a GC purity of 97%, a moisture content of 85ppm, and a chromaticity of 17Hazen.

[0052] Example 4 (Cyclization Synthesis)

[0053]

[0054] Preparation of compound C3: 142 g (1 mol) of high-quality phosphoric anhydride (purity 99.5%) was weighed at room temperature and added to the reactor treated in Example 1. 400 g of cyclohexane treated with 4A molecular sieve and 0.018 g of Huaian Bader DMC (cobalt-zinc complex) were added, and nitrogen was purged. The heating was turned on and the temperature was raised to 145°C. 180.25 g (2.5 mol) of ethyl ethylene oxide was slowly introduced into the mixed system in the reactor. The reaction time was 2.5 h, and the mixture was aged for 2 h. The reaction was stopped, cooled to 40°C, and slowly transferred out of the reactor. After coarse filtration, the filtrate was transferred to a three-necked flask, washed with water to remove unreacted ethyl ethylene oxide, dried and separated, and cyclohexane was recovered by vacuum distillation. A white solid product was obtained by cooling, with a yield of 67.1%, a GC purity of 97.2%, a moisture content of 110 ppm, and a chromaticity of 11 Hazen.

[0055] Example 5 (Cyclization Synthesis)

[0056]

[0057] Preparation of compound C4: 142 g (1 mol) of high-quality phosphoric anhydride (purity 99.5%) was weighed at room temperature and added to the reactor treated in Example 1. At the same time, 400 g of cyclohexane treated with 4A molecular sieve and 0.018 g of Huaian Bader DMC (cobalt-zinc complex) were added, and nitrogen was purged. The heating was turned on and the temperature was raised to 145°C. 245 g (2.5 mol) of cyclohexene oxide was slowly introduced into the mixed system in the reactor. The reaction time was 4 h, and the temperature was ripened for 3 h. The reaction was stopped, and the temperature was lowered to 40°C. The mixture was slowly transferred out of the reactor. After coarse filtration, the filtrate was transferred to a three-necked flask, washed with water to remove unreacted cyclohexene oxide, dried and separated, and cyclohexane was recovered by vacuum distillation. The white solid product was obtained by cooling, with a yield of 65.1%, a GC purity of 97.4%, a moisture content of 70 ppm, and a chromaticity of 11 Hazen.

[0058] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a cyclic phosphate compound represented by formula I, characterized in that: include: in, Indicates presence or absence. When absent, raw material A is When present, the raw material A is The corresponding formula I represents the products obtained by reacting the above two structures with phosphoric anhydride respectively; R1, R2 and R3 are the same or different and are independently selected from hydrogen, C 1-6 Alkyl or halogenated C 1-6 alkyl; when When present, R1 and R2 can be linked together to form a C 4-6 Alternatively, R2 and R3 may be linked together to form a C 4-6 Alternatively, R1 and R3 may be linked together to form a C 4-6 Cycloalkyl; when When it does not exist, R1 and R2 can be connected and then form C 4-6 Cycloalkyl; The raw material A reacts with phosphoric anhydride to obtain a cyclic phosphate compound shown in formula I.

2. The method according to claim 1, characterized in that The reaction is carried out in the presence of a double metal cyanide complex (DMC) catalyst; Preferably, R1, R2 and R3 are the same or different and are independently selected from hydrogen, C 1-3 Alkyl or halogenated C 1-3 alkyl.

3. The method according to claim 1 or 2, characterized in that: Raw material A is Wherein R1 and R2 are the same or different and are independently selected from hydrogen, methyl, chloromethyl, ethyl, or R1 and R2 are connected to form a ring, such as R1 and R2 together with the carbon atoms to which they are connected form 1,2-epoxycyclopentane or cyclohexene oxide.

4. The method according to any one of claims 1 to 3, characterized in that: The method for preparing the cyclic phosphate compound comprises the step of washing the reactor with an acidic solvent to an acidic environment.

5. The method according to any one of claims 1 to 4, characterized in that: The purity of the phosphoric anhydride is above 90%.

6. The method according to any one of claims 1 to 5, characterized in that: The reaction is carried out under an inert gas environment.

7. The method according to any one of claims 1 to 6, characterized in that: The reaction temperature is 50-180°C.

8. The method according to any one of claims 1 to 7, characterized in that: Raw material A is ethylene oxide (EO), propylene oxide (PO), ethyl ethylene oxide, butylene oxide (BO), 1,2-cyclopentene oxide or cyclohexene oxide, and a cyclic phosphate compound having a structure shown in the following formula C1-C4 can be obtained:

9. The method according to any one of claims 1 to 8, characterized in that: The molar number of raw material A is 1-5 times that of phosphoric anhydride.

10. The method according to any one of claims 1 to 9, characterized in that: The amount of the catalyst used is 0.0001-0.1% of the total mass of the raw materials.

Images