A continuous preparation method of hexafluorocyclotriphosphazene

Abstract

The present invention discloses a continuous preparation method of hexafluorocyclotriphosphazene, which is prepared from hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride. Specifically, the continuous preparation method comprises the following steps: (1) adding hexachlorocyclotriphosphazene and a catalyst into a reactor, and heating to 120-250 °C; the catalyst is selected from fluorides or chlorides of Sb, Cr, Fe, La, Mn, Ru, Rh, Sn, Ti, and Mo; (2) continuously introducing liquid hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride into the reactor, and obtaining hexafluorocyclotriphosphazene through a liquid-phase fluorine-chlorine exchange reaction; (3) continuously discharging the hexafluorocyclotriphosphazene from the reactor, and obtaining a crude product of hexafluorocyclotriphosphazene after passing through a heat exchanger. The present invention has the advantages of simple operation, high production efficiency, high product yield, high product purity, and environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the preparation of electrolyte additives, and particularly to a method for continuously preparing hexafluorocyclotriphosphazene without solvent. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, and low environmental pollution, and are considered to be one of the secondary batteries with the greatest development prospects. With the wide application of lithium batteries, the problem of thermal runaway inside the batteries has gradually emerged, which is likely to cause phenomena such as battery spontaneous combustion. In order to avoid the risks of combustion, explosion, etc. of lithium batteries in extreme environments or improper use, suitable flame retardants will be added to the lithium battery electrolyte. Cyclotriphosphazene is a flame retardant with excellent performance. It not only has good flame retardant properties of phosphorus-based flame retardants, but also has the functions of flame retardant synergism and co-flame retardancy of nitrogen compounds. It has the advantages of good thermal stability, non-toxicity, low smoke generation, and self-extinguishing properties without adding any other auxiliary flame retardants, and is recognized as one of the future development directions of flame retardants.

[0003] Hexafluorocyclotriphosphazene is a common flame retardant in lithium-ion battery electrolytes, and is mainly obtained by fluorinating hexachlorocyclotriphosphazene with different types of fluorinating reagents.

[0004] Patent CN104558045A discloses a method for preparing hexafluorocyclotriphosphazene by using tetramethylammonium chloride, tetramethylammonium bromide, 18-crown-6, phosphorus bromide, etc. as catalysts, sodium fluoride and potassium fluoride as fluorinating reagents under the condition of 40-100 °C in the presence of organic solvents. The product yield of hexafluorocyclotriphosphazene is not disclosed in this method, and a large amount of fluorine salts are required in the production process, which will generate a large amount of waste solids, with high energy consumption and high production cost.

[0005] Patent CN110066295A discloses a method for preparing hexafluorocyclotriphosphazene by using Lewis acid catalysts such as SbCl5 and TiCl4, HF as a fluorinating reagent, and reacting at a reaction temperature of 0-60 °C in a Hastelloy reaction kettle. The highest yield of hexafluorocyclotriphosphazene prepared by this method is 88%, and the highest HPLC purity of the product is 97.8%. However, this process uses a batch reaction in a kettle and uses a large amount of fluorinated solvents, with disadvantages such as multiple unit operations, high working intensity, and low efficiency. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a method for continuously preparing hexafluorocyclotriphosphazene without solvent, which has the advantages of simple operation, high production efficiency, high product yield, high product purity, and environmental friendliness.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A continuous preparation method of hexafluorocyclotriphosphazene, which is prepared from hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride, and the reaction equation is as follows:

[0009]

[0010] Specifically, the continuous preparation method includes the following steps:

[0011] (1) Add hexachlorocyclotriphosphazene and a catalyst into a reactor, and heat up to 120 - 250 °C; the catalyst is selected from fluorides or chlorides of Sb, Cr, Fe, La, Mn, Ru, Rh, Sn, Ti, Mo;

[0012] (2) Continuously introduce liquid hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride into the reactor, and obtain hexafluorocyclotriphosphazene through a liquid-phase fluorine-chlorine exchange reaction;

[0013] (3) The hexafluorocyclotriphosphazene continuously escapes from the reactor and obtains a crude product of hexafluorocyclotriphosphazene after passing through a heat exchanger.

[0014] It is found through research in the present invention that when cyclotriphosphazene and anhydrous HF contact at a lower temperature, there is an acid-base complexation phenomenon, resulting in poor reaction effects. The present invention not only uses a continuous process to replace the batch process, but also increases the reaction temperature, solves the complexation problem between raw materials, and improves both the production efficiency and the product yield.

[0015] In step (1), hexachlorocyclotriphosphazene and a catalyst are pre-added into the reactor, and then the reaction kettle is heated and stirring is started to make hexachlorocyclotriphosphazene in a liquid state. The molar ratio of the pre-added hexachlorocyclotriphosphazene to the catalyst is 1:(0.01 - 0.5), and the reactor temperature is 120 - 250 °C. Preferably, the molar ratio of the pre-added hexachlorocyclotriphosphazene to the catalyst is 1:(0.03 - 0.1), and the reactor temperature is 120 - 200 °C.

[0016] Furthermore, in order to improve the reaction efficiency, the catalyst is preferably selected from fluorides or chlorides of Sb, Cr, Ru, Rh, La.

[0017] In step (2), liquid hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride are continuously introduced into the reactor. The liquid hexachlorocyclotriphosphazene is pre-heated to 120 - 150 °C, and the molar ratio of the feed of liquid hexachlorocyclotriphosphazene to anhydrous hydrogen fluoride is 1:(3 - 20), and the hourly feed amount of liquid hexachlorocyclotriphosphazene is 5 - 100% of the amount of hexachlorocyclotriphosphazene added in step (1). Preferably, the molar ratio of the feed of liquid hexachlorocyclotriphosphazene to anhydrous hydrogen fluoride is 1:(6 - 10), and the hourly feed amount of liquid hexachlorocyclotriphosphazene is 10 - 50% of the amount of hexachlorocyclotriphosphazene added in step (1).

[0018] In step (3), the boiling point of hexafluorocyclotriphosphazene is lower than the reaction temperature, so it can continuously escape from the reactor; the higher-boiling raw material, hexachlorocyclotriphosphazene, carried in the escaping gas returns to the reactor for continuous reaction after heat exchange in the heat exchanger. Therefore, the temperature of the heat exchanger is set at 50 - 100°C, preferably 60 - 90°C.

[0019] The reactor and heat exchanger in the present invention are common kettle reactors and conventional heat exchangers in the chemical industry. Pressure-resistant equipment is preferred, with a pressure resistance rating of 1 - 20 MPa, and the material is selected from 316L stainless steel, Monel alloy, Inconel alloy, or Hastelloy, preferably Monel alloy or Hastelloy.

[0020] The crude hexafluorocyclotriphosphazene obtained in the present invention is purified. Therefore, the continuous preparation method further includes:

[0021] (4) The crude hexafluorocyclotriphosphazene is successively subjected to alkali washing, water washing, drying, and melt crystallization to obtain hexafluorocyclotriphosphazene product with a purity of 99.9%;

[0022] The melt crystallization includes: adding the dried crude hexafluorocyclotriphosphazene into a melt crystallizer, cooling to -50 - 20°C, and the cooling time is 1 - 24 h; discharging the crystallization residue from the bottom valve of the crystallizer, purging with nitrogen, and then heating the melt crystallizer to 25 - 50°C to collect the liquid-phase hexafluorocyclotriphosphazene product.

[0023] Specifically, the crude hexafluorocyclotriphosphazene continuously escaping from the reactor enters a collector containing liquid alkali (such as sodium hydroxide or potassium hydroxide) through a heat exchanger, and then is separated. The organic phase is washed with water, dried, and then enters the melt crystallizer for melt crystallization.

[0024] Preferably, the melt crystallizer is cooled to -20 - 0°C, and the holding time after cooling is 3 - 12 h; the temperature of the crystallizer after heating is 25°C - 30°C.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. The present invention uses hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride as raw materials, and not only realizes the continuous preparation of hexafluorocyclotriphosphazene under solvent-free conditions, which is green, clean, has high production efficiency and low cost, but also improves the product yield and product purity through process condition design, and is very suitable for industrial application.

[0027] 2. Through the melt crystallization process, the product purity of the present invention is above 99.9%, greatly improving the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1Schematic diagram of the continuous preparation process of hexafluorocyclotriphosphazene according to the embodiment of the present invention; wherein: 1 - hexa-chlorocyclotriphosphazene storage tank; 2 - anhydrous hydrogen fluoride steel cylinder; 3 - reaction kettle; 4 - heat exchanger; 5 - lye bottle; 6 - water washing bottle.

[0029] Figure 2 GC-TCD chromatogram of the hexafluorocyclotriphosphazene product obtained in Example 1 of the present invention;

[0030] Figure 3 19F NMR spectrum of the hexafluorocyclotriphosphazene product obtained in Example 1 of the present invention;

[0031] Figure 4 31P NMR spectrum of the hexafluorocyclotriphosphazene product obtained in Example 1 of the present invention;

[0032] Figure 5 GC-MS diagram of the hexafluorocyclotriphosphazene product obtained in Example 1 of the present invention. Detailed implementation manners

[0033] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific implementation manners. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions and equivalent solutions that may be included within the scope of the claims.

[0034] Example 1

[0035] This example provides a continuous preparation method of hexafluorocyclotriphosphazene, including the following steps:

[0036] Experimental preparation: In a 500 mL Hastelloy reaction kettle equipped with a heat exchanger and magnetic stirring, add 173.8 g (0.5 mol) of hexa-chlorocyclotriphosphazene and 7.48 g (0.025 mol) of antimony pentachloride (SbCl5). Start stirring and heating the reaction kettle, and maintain the temperature in the kettle at about 140 °C. Pass 80 °C heat transfer oil through the jacket of the heat exchanger. Start heating the hexa-chlorocyclotriphosphazene storage tank and maintain the internal temperature at about 140 °C. Start heating the anhydrous hydrogen fluoride steel cylinder and maintain the internal temperature at about 40 °C.

[0037] Feeding and reaction: When the above parameters are stable, start the hexa-chlorocyclotriphosphazene feed pump and control the flow rate at 25 g / h; open the anhydrous hydrogen fluoride feed valve and control the flow rate at 10 g / h. Open the valve at the outlet of the heat exchanger, and pass the reaction product into 10% lye for collection, and maintain the temperature of the lye at 25 - 30 °C.

[0038] Work-up after reaction: After reacting for 24 h, the feeding was stopped. The lye was placed in a separatory funnel for liquid separation. The lower layer of light yellow oily liquid was separated out, washed with 500 g of warm water, and then separated by liquid separation. 20 g of anhydrous MgSO4 was added to the lower layer of oily liquid and dried overnight. After filtration, 413.6 g of light yellow liquid was obtained.

[0039] Analyzed by a GC-TCD detector, the purity of the crude product was 98.7%, the theoretical yield was 429.7 g, the yield based on 100% purity was 95.0%, and the space-time yield was: 34.5 g·L -1 ·h -1 , and the catalyst still had activity.

[0040] Melt crystallization: Weigh 400 g of the crude product, melt it and put it into a melt crystallization device. Turn on the circulating pump of the jacket of the crystallization device, control the crystallization temperature at -10 °C. After 3 h, turn the crystallization device so that the unfrozen liquid in the crystallization device flows out from the bottom valve by gravity. After purging with nitrogen, adjust the temperature of the heat transfer oil in the jacket of the crystallization device to 25 °C, and collect the product from the bottom valve. A total of 381.3 g of product was collected, and the crystallization yield was 96.6%.

[0041] The collected products were subjected to chromatographic analysis, NMR analysis and mass spectrometry analysis respectively. Attached Figure 2 , 3 , 4 and 5 respectively show the gas chromatogram, 19F NMR spectrum, 31P NMR spectrum and mass spectrum of the product. From Figure 2 it can be seen that the purity of the product is 100% and it contains no other impurities; from Figures 3 - 5 it can be seen that the product is indeed hexafluorocyclotriphosphazene.

[0042] Example 2

[0043] The operation of this example is the same as that of Example 1, except that: during the experimental preparation process, the catalyst was replaced with 4.0 g (0.025 mol) of chromium(III) chloride (CrCl3), and other operations remained unchanged; the feeding reaction and work-up operations were the same, and melt crystallization was not carried out.

[0044] After work-up, 407.6 g of light yellow liquid was obtained. Analyzed by a GC-TCD detector, the purity of the crude product was 97.5%, the theoretical yield was 429.7 g, the yield based on 100% purity was 92.5%, and the space-time yield was: 34.0 g·L -1 ·h -1 , and the catalyst still had activity.

[0045] Example 3

[0046] The operation of this example is the same as that of Example 1, except that: during the experimental preparation process, the catalyst was replaced with 5.18 g (0.025 mol) of ruthenium(III) chloride, and other operations remained unchanged; the feeding reaction and work-up operations were the same, and melt crystallization was not carried out.

[0047] After post-treatment, 418.4 g of light yellow liquid was obtained. Analyzed by GC-TCD detector, the purity of the crude product was 98.8%, the theoretical yield was 429.7 g, the yield based on 100% purity was 96.2%, and the space-time yield was: 34.9 g·L -1 ·h -1 , and the catalyst still had activity.

[0048] Example 4

[0049] The operation of this example was the same as that of Example 1, except that: during the experimental preparation process, the catalyst was replaced with 5.23 g (0.025 mol) of rhodium trichloride, and other operations remained unchanged; the feeding reaction and post-treatment operations were the same, and melt crystallization was not carried out.

[0050] After post-treatment, 390.7 g of light yellow liquid was obtained. Analyzed by GC-TCD detector, the purity of the crude product was 97.1%, the theoretical yield was 429.7 g, the yield based on 100% purity was 88.3%, and the space-time yield was: 32.5 g·L -1 ·h -1 , and the catalyst still had activity.

[0051] Example 5

[0052] The operation of this example was the same as that of Example 1, except that: during the experimental preparation process, the catalyst was replaced with 6.13 g (0.025 mol) of lanthanum trichloride, and other operations remained unchanged; the feeding reaction and post-treatment operations were the same, and melt crystallization was not carried out.

[0053] After post-treatment, 329.5 g of light yellow liquid was obtained. Analyzed by GC-TCD detector, the purity of the crude product was 98.2%, the theoretical yield was 429.7 g, the yield based on 100% purity was 75.3%, and the space-time yield was: 27.5 g·L -1 ·h -1 , and the catalyst still had activity.

[0054] Example 6

[0055] The operation of this example was the same as that of Example 1, except that: in the feeding reaction step, the feeding rate of hexachlorocyclotriphosphazene was increased from the original 25 g / h to 50 g / h, and the feeding rate of anhydrous hydrogen fluoride was increased from the original 10 g / h to 20 g / h, and other operations remained unchanged; the experimental preparation process and post-treatment operations were the same, and melt crystallization was not carried out.

[0056] After post-treatment, 815.6 g of light yellow liquid was obtained. Analyzed by GC-TCD detector, the purity of the crude product was 98.3%, the theoretical yield was 859.4 g, the yield based on 100% purity was 93.3%, and the space-time yield was: 67.9 g·L -1 ·h -1 , and the catalyst still had activity.

[0057] Example 7

[0058] The operation of this example is the same as that of Example 6, except that: during the experimental preparation process, the dosage of the catalyst antimony pentachloride is increased from the original 7.48 g (0.025 mol) to 14.95 g (0.05 mol), and other operations remain unchanged; the feeding reaction and post-treatment operations are the same, and melt crystallization is not carried out.

[0059] After post-treatment, 836.6 g of a light yellow liquid is obtained. Analyzed by a GC-TCD detector, the crude product purity is 97.8%, the theoretical yield is 859.4 g, the yield based on 100% purity is 95.2%, and the space-time yield is: 69.7 g·L -1 ·h -1 , and the catalyst still has activity.

[0060] Example 8

[0061] The operation of this example is the same as that of Example 1, except that: in the feeding reaction step, the feeding rate of hexachlorocyclotriphosphazene is increased from the original 25 g / h to 50 g / h, and the feeding rate of anhydrous hydrogen fluoride is increased from the original 10 g / h to 30 g / h, and other operations remain unchanged; the experimental preparation process and post-treatment operations are the same, and melt crystallization is not carried out.

[0062] After post-treatment, 863.8 g of a light yellow liquid is obtained. Analyzed by a GC-TCD detector, the crude product purity is 98.0%, the theoretical yield is 859.4 g, the yield based on 100% purity is 98.5%, and the space-time yield is: 71.9 g·L -1 ·h -1 , and the catalyst still has activity.

[0063] Example 9

[0064] The operation of this example is the same as that of Example 6, except that: during the experimental preparation process, the temperature of the reaction kettle is raised to about 170 °C, and other operations remain unchanged; the feeding reaction and post-treatment operations are the same, and melt crystallization is not carried out.

[0065] After post-treatment, 810.3 g of a light yellow liquid is obtained. Analyzed by a GC-TCD detector, the crude product purity is 96.3%, the theoretical yield is 859.4 g, the yield based on 100% purity is 90.8%, and the space-time yield is: 67.5 g·L -1 ·h -1 , and the catalyst still has activity.

[0066] Example 10

[0067] The operation of this example is the same as that of Example 1, with the only difference being that in the post-treatment step, the reaction time is extended to 48 h, the feeding is stopped after 48 h, and other operations remain unchanged; the experimental preparation process and the feeding reaction process remain unchanged, and melt crystallization is not carried out.

[0068] After post-treatment, 827.1 g of light yellow liquid is obtained. Analyzed by a GC-TCD detector, the purity of the crude product is 98.5%, the theoretical yield is 859.4 g, the yield based on 100% is 94.8%, and the space-time yield is: 34.4 g·L -1 ·h -1 , and the catalyst still has activity.

[0069] Example 11

[0070] The operation of this example is the same as that of Example 1, with the only difference being that in the melt crystallization process, the crystallization temperature is controlled at -20 °C and the crystallization time is 6 h, and other operations remain unchanged. A total of 384.4 g of product is collected, and the crystallization yield is 97.3%.

[0071] Chromatographic analysis of the collected product shows that the product purity is 99.95%.

[0072] Comparative Example 1

[0073] The operation of this example is the same as that of Example 1, with the only difference being that in the experimental preparation process, the catalyst antimony pentachloride is not added, and other operations remain unchanged; the feeding reaction and post-treatment operations are the same, and melt crystallization is not carried out.

[0074] After post-treatment, 68.1 g of light yellow liquid is obtained. Analyzed by a GC-TCD detector, the purity of the crude product is 98.5%, the theoretical yield is 429.7 g, the yield based on 100% is 15.6%, and the space-time yield is: 5.7 g·L -1 ·h -1 .

[0075] Comparative Example 2

[0076] The operation of this example is the same as that of Example 1, with the only difference being that in the experimental preparation process, 200 g of trifluorotoluene is added as a solvent, and the temperature of the reaction kettle is reduced to 60 °C, and other operations remain unchanged; the feeding reaction and post-treatment operations are the same, and melt crystallization is not carried out.

[0077] After post-treatment, 189.5 g of light yellow liquid is obtained. Analyzed by a GC-TCD detector, the purity of the crude product is 98.5%, the theoretical yield is 429.7 g, the yield based on 100% is 43.4%, and the space-time yield is: 15.8 g·L -1 ·h -1 , and the catalyst still has activity.

[0078] Comparative Example 3

[0079] Experimental preparation: In a 500 mL Hastelloy reactor equipped with a heat exchanger and magnetic stirring, add 173.8 g (0.5 mol) of hexachlorocyclotriphosphazene, 200 g (1.37 mol) of benzotrifluoride, and 7.48 g (0.025 mol) of antimony pentachloride (SbCl5). Start stirring and cool the reactor to 0 °C.

[0080] Feeding and reaction: When the above parameters are stable, open the anhydrous hydrogen fluoride feed valve, introduce 80 g of anhydrous hydrogen fluoride, and then close the valve. Heat the reactor to 60 °C and react for 6 h to end the reaction.

[0081] Post-treatment of the reaction: After the reaction is completed, purge with high-purity nitrogen to discharge the excessive hydrogen fluoride and by-product hydrogen chloride to the water and alkali washing systems. Perform atmospheric distillation and collect the fraction at 49 °C - 52 °C to obtain 101.8 g of a light yellow liquid. Analyzed with a GC-TCD detector, the purity of the crude product is 96.3%, the theoretical yield is 124.4 g, and the yield based on 100% product is 78.8%.

Claims

1. A continuous preparation method of hexafluorocyclotriphosphazene, which is prepared from hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride, and is characterized in that: The continuous preparation method comprises the following steps: (1) Hexachlorocyclotriphosphazene and a catalyst are pre-added into a reactor, and then the reaction kettle is heated and stirring is started to make hexachlorocyclotriphosphazene in a liquid state, and the temperature of the reactor is 120-200 °C; the catalyst is selected from fluorides or chlorides of Sb, Cr, Fe, Ru, Sn, Ti, and Mo; (2) Liquid hexachlorocyclotriphosphazene and anhydrous hydrogen fluoride are continuously introduced into the reactor, and hexafluorocyclotriphosphazene is obtained through a liquid-phase fluorine-chlorine exchange reaction; the liquid hexachlorocyclotriphosphazene is pre-heated to 120-150 °C and then enters the reactor; (3) The hexafluorocyclotriphosphazene continuously escapes from the reactor and obtains a crude hexafluorocyclotriphosphazene product after passing through a heat exchanger, and the temperature of the heat exchanger is 50-100 °C.

2. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 1, characterized in that: In step (1), the molar ratio of hexachlorocyclotriphosphazene to the catalyst is 1:(0.01-0.5).

3. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 2, wherein: In step (2), the molar ratio of the liquid hexachlorocyclotriphosphazene to the anhydrous hydrogen fluoride fed is 1:(3-20), and the hourly feed amount of the liquid hexachlorocyclotriphosphazene is 5-100% of the addition amount of hexachlorocyclotriphosphazene in step (1).

4. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 1, characterized in that: In step (3), the temperature of the heat exchanger is 60-90 °C.

5. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 1, characterized in that: The catalyst is selected from fluorides or chlorides of Sb, Cr, and Ru.

6. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 1, characterized in that: The reactor and the heat exchanger are pressure-resistant equipment, and the material is selected from 316L stainless steel, Monel alloy, Inconel alloy, or Hastelloy alloy.

7. The continuous preparation method of hexafluorocyclotriphosphazene according to any one of claims 1-6, characterized in that: The continuous preparation method further comprises: (4) The crude hexafluorocyclotriphosphazene product is successively subjected to alkali washing, water washing, drying, and melt crystallization to obtain a hexafluorocyclotriphosphazene product with a purity of over 99.9%; The melt crystallization includes: adding the dried crude hexafluorocyclotriphosphazene product into a melt crystallizer, cooling to -50-20 °C, discharging the crystallization residue liquid from the bottom valve of the crystallizer, purging with nitrogen, and then heating the melt crystallizer to 25-50 °C to collect the liquid-phase hexafluorocyclotriphosphazene product.

8. The continuous preparation method of hexafluorocyclotriphosphazene according to claim 7, characterized in that: The cooling time is 1-24 h.

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