A continuous process and apparatus for the production of liquid lithium hexafluorophosphate

Abstract

The application discloses a continuous preparation process and device of liquid lithium hexafluorophosphate, and comprises the following operation steps: A10), continuously feeding lithium fluoride suspension to the top of a hexafluoride reaction plate tower; continuously feeding gaseous high-purity phosphorus pentafluoride to the bottom of the hexafluoride reaction plate tower; A20), carrying out reaction in the hexafluoride reaction plate tower, and feeding the reaction product from the bottom of the hexafluoride reaction tower into a bottom tank; A30), feeding the remaining reaction product output by a circulating heat exchanger into a liquid lithium hexafluorophosphate product extraction tank in one way and into a lithium fluoride suspension preparation kettle in the other way; and A40), connecting a filter to the product extraction end of the product extraction tank to remove the excessive solid-phase material after reaction, so as to obtain the liquid lithium hexafluorophosphate, the hydrogen chloride content of which is less than 25 ppm, and the hydrogen fluoride is not detected; the application has high continuous level and stability, does not need additional deacidification treatment, and has obviously higher output efficiency, and does not have the hidden troubles of shutdown maintenance due to problems such as blockage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery electrolyte solutes, and particularly relates to a continuous preparation process and device of liquid lithium hexafluorophosphate. BACKGROUND

[0002] Lithium hexafluorophosphate (LiPF6) is called the most preferred commercial electrolyte solute in current lithium ion batteries because it has good ionic conductivity and electrochemical stability, and its waste battery treatment process is simple and has little impact on the ecological environment. The current synthesis method of lithium hexafluorophosphate mainly focuses on the synthesis of solid lithium hexafluorophosphate, and the main synthesis methods include gas-solid reaction method, HF solvent method, organic solvent method and ion exchange method, etc. However, these methods generally have the disadvantages of difficult continuous process and difficult removal.

[0003] Compared with solid lithium hexafluorophosphate, liquid lithium hexafluorophosphate not only has the advantages of storage stability and convenient transportation, but also can be directly used in lithium ion battery electrolyte without dissolution. Therefore, the development of liquid lithium hexafluorophosphate has great practical significance for reducing the industrialization cost of lithium ion batteries and improving market competitiveness.

[0004] Further, the existing continuous synthesis process of liquid lithium hexafluorophosphate contains a high content of hydrogen chloride after obtaining liquid lithium hexafluorophosphate, and hydrogen fluoride can also be detected, so a special deacidification process is still needed, the treatment process is relatively complicated, and the overall continuous degree of the synthesis process is also limited. In addition, in the preparation of lithium hexafluorophosphate, lithium fluoride needs to be mixed with an organic solvent (such as a carbonate solvent). Since lithium fluoride is difficult to dissolve in the organic solvent, although real-time stirring is adopted in the mixing preparation kettle, it is difficult to ensure that lithium fluoride and the organic solvent are always fully mixed, especially when the lithium fluoride suspension in the mixing preparation kettle is transported to the top of the synthesis tower, there may be a risk of blockage of the transportation pipeline, which affects the continuous synthesis of liquid lithium hexafluorophosphate.

[0005] Therefore, the applicant hopes to conduct in-depth special research on the continuous synthesis process of liquid lithium hexafluorophosphate to further improve the industrialization batch continuous production efficiency. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a continuous preparation process and device of liquid lithium hexafluorophosphate, which has a high continuous level and is stable, and does not have the risk of shutdown maintenance due to blockage and other problems. The high-purity liquid lithium hexafluorophosphate provided by the present application can be directly applied to industrialization without additional deacidification treatment, and has obviously higher output efficiency.

[0007] The technical scheme adopted by the present application is as follows:

[0008] A continuous preparation process of liquid lithium hexafluorophosphate, comprising the following operation steps:

[0009] A10) providing a lithium fluoride suspension from a lithium fluoride suspension preparation tank, continuously feeding the lithium fluoride suspension to the top of a hexafluoride reaction plate column; providing gaseous high-purity phosphorus pentafluoride from a high-purity phosphorus pentafluoride storage tank, continuously feeding the gaseous high-purity phosphorus pentafluoride to the bottom of the hexafluoride reaction plate column, the purity of the gaseous high-purity phosphorus pentafluoride being greater than 96%;

[0010] A20) the lithium fluoride and the gaseous high-purity phosphorus pentafluoride react in the hexafluoride reaction plate column under normal temperature and pressure, and the reaction product enters a bottom storage tank from the bottom of the hexafluoride reaction column, wherein the mass ratio of the lithium fluoride to the gaseous high-purity phosphorus pentafluoride is 1:4-6;

[0011] A30) the bottom storage tank refluxes the reaction product to the hexafluoride reaction plate column through a circulating heat exchanger at a preset reflux ratio, and the remaining reaction product output from the circulating heat exchanger is divided into two parts, one part is punched into a liquid lithium hexafluorophosphate product extraction tank, and the other part is punched into the lithium fluoride suspension preparation tank; the preset reflux ratio is 4-8:1;

[0012] A40) after removing the excess solid material after the reaction through a filter connected to the product extraction end of the product extraction tank, liquid lithium hexafluorophosphate is obtained, the hydrogen chloride content of the liquid lithium hexafluorophosphate is less than 25 ppm, preferably less than 15 ppm, and no hydrogen fluoride is detected.

[0013] Preferably, the preparation step of the gaseous high-purity phosphorus pentafluoride comprises: the phosphorus pentafluoride rectification column feed is transported into a fluorosulfonate absorption tower through a phosphorus pentafluoride buffer tank to remove hydrogen fluoride and hydrogen chloride in the phosphorus pentafluoride rectification column feed under normal temperature and pressure, thereby obtaining the gaseous high-purity phosphorus pentafluoride.

[0014] Preferably, the fluorosulfonate absorption tower comprises a first fluorosulfonate absorption tower and a second fluorosulfonate absorption tower connected in series.

[0015] Preferably, in the lithium fluoride suspension preparation tank, the lithium fluoride and the organic solvent are fully combined through ultrasonic waves; wherein the solvent is any one or a mixture of any several of dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; and / or the mass ratio of the lithium fluoride to the organic solvent ranges from 1:8 to 20.

[0016] Preferably, the lithium fluoride is in the form of powder, and the maximum particle size thereof is not more than 0.2 mm, preferably not more than 0.18 mm.

[0017] Preferably, the inner wall of the conveying pipeline between the lithium fluoride suspension preparation kettle and the overhead of the hexafluoride reaction plate tower is polished to be smooth, wherein the polishing accuracy of the inner wall of the conveying pipeline is less than or equal to 0.6 microns.

[0018] Preferably, at least 40 tower plates are arranged in the hexafluoride reaction plate tower in an up-down interval, wherein the mesh size of the tower plate near the top is larger than the mesh size of the tower plate near the kettle.

[0019] Preferably, the hexafluoride reaction plate tower comprises at least a first tower plate section, a second tower plate section and a third tower plate section from bottom to top; wherein the first tower plate section is provided with at least 10 first tower plates arranged in an up-down interval, and the mesh size of the first tower plate ranges from 2 to 4 mm; the second tower plate section is provided with at least 10 second tower plates arranged in an up-down interval, and the mesh size of the second tower plate ranges from 6 to 9 mm; the third tower plate section is provided with at least 10 third tower plates arranged in an up-down interval, and the mesh size of the third tower plate ranges from 12 to 16 mm.

[0020] Preferably, a device for the continuous preparation process described above comprises a lithium fluoride suspension preparation kettle, a high-purity phosphorus pentafluoride storage tank and a hexafluoride reaction plate tower; wherein the liquid outlet of the lithium fluoride suspension preparation kettle is connected to the overhead of the hexafluoride reaction plate tower through a suspension conveying pipeline, and the outlet of the high-purity phosphorus pentafluoride storage tank is connected to the kettle of the hexafluoride reaction plate tower through a conveying pipeline.

[0021] Preferably, the high-purity phosphorus pentafluoride storage tank is connected to the gas phase output end of the fluorosulfonate absorption tower, the gas phase input end of the fluorosulfonate absorption tower is connected to the incoming material outlet of the phosphorus pentafluoride rectification tower through a phosphorus pentafluoride buffer tank; a lithium fluoride suspension feed tank is arranged on the suspension conveying pipeline, the lithium fluoride suspension preparation kettle is connected to the hexafluoride reaction plate tower through the lithium fluoride suspension feed tank; wherein the bottom of the hexafluoride reaction plate tower is connected to a bottom storage tank, the bottom storage tank is connected to the input end of a circulating heat exchanger, the output end of the circulating heat exchanger is connected to the hexafluoride reaction plate tower, the lithium fluoride suspension preparation kettle and a liquid lithium hexafluorophosphate product extraction tank.

[0022] The application firstly proposes that gaseous high-purity phosphorus pentafluoride and lithium fluoride are used for high-efficiency continuous reaction in a hexafluoride reaction plate tower, and the application surprisingly finds that the conversion rate of phosphorus pentafluoride reaches 99.99% or above, the hydrogen chloride content of the obtained liquid lithium hexafluorophosphate is not more than 25 ppm, and hydrogen fluoride is not detected, which can be directly applied to industrialization without additional deacidification process treatment, and has obviously higher output efficiency; meanwhile, the application proposes that a small amount of reaction product is transported to a lithium fluoride suspension preparation kettle, since the liquid lithium hexafluorophosphate can be well dissolved in an organic solvent, and the liquid lithium hexafluorophosphate and lithium fluoride have good compatibility, thereby ensuring that lithium fluoride and the organic solvent can be fully fused at all times, and the production maintenance risk caused by problems such as blockage does not occur, so that the synthesis process provided by the application has high-efficiency and stable continuous production level. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a synthesis process step block diagram of the liquid lithium hexafluorophosphate in the embodiment of the application;

[0024] Figure 2 is a cross-sectional structure schematic diagram of the hexafluoride reaction plate tower in the embodiment of the application;

[0025] Figure 3 is a partial structure schematic diagram in Figure 2 ;

[0026] Figure 4 is a liquid lithium hexafluorophosphate finished product sample photograph prepared by the embodiment 1 of the application. DETAILED DESCRIPTION

[0027] The embodiment discloses a device, including a lithium fluoride suspension preparation kettle, a high-purity phosphorus pentafluoride storage tank and a hexafluoride reaction plate tower; wherein, the liquid outlet of the lithium fluoride suspension preparation kettle is connected to the top of the hexafluoride reaction plate tower through a suspension transportation pipeline, and the outlet of the high-purity phosphorus pentafluoride storage tank is connected to the kettle of the hexafluoride reaction plate tower through a transportation pipeline; further preferably, in the embodiment, the high-purity phosphorus pentafluoride storage tank is connected to the gas phase output end of a fluorosulfonate absorption tower, and the gas phase input end of the fluorosulfonate absorption tower is connected to the incoming material outlet of a phosphorus pentafluoride rectification tower through a phosphorus pentafluoride buffer tank; a lithium fluoride suspension feed tank is arranged on the suspension transportation pipeline, and the lithium fluoride suspension preparation kettle is connected to the hexafluoride reaction plate tower through the lithium fluoride suspension feed tank; wherein, the bottom of the hexafluoride reaction plate tower is connected to a kettle bottom storage tank, the kettle bottom storage tank is connected to the input end of a circulating heat exchanger, one way of the output end of the circulating heat exchanger is connected to the hexafluoride reaction plate tower, one way is connected to a liquid lithium hexafluorophosphate product extraction tank, and the other way is connected to the lithium fluoride suspension preparation kettle.

[0028] Please refer to Figure 1The embodiment also proposes a continuous preparation process of liquid lithium hexafluorophosphate implemented by the above device, including the following operation steps:

[0029] A10)providing the lithium fluoride suspension from the lithium fluoride suspension preparation kettle, continuously feeding the lithium fluoride suspension to the top of the hexafluoride reaction plate tower; providing the gaseous high-purity phosphorus pentafluoride from the high-purity phosphorus pentafluoride storage tank, continuously feeding the gaseous high-purity phosphorus pentafluoride to the tank bottom of the hexafluoride reaction plate tower, and the purity of the gaseous high-purity phosphorus pentafluoride is greater than 96%;

[0030] Preferably, in the embodiment, the preparation step of the gaseous high-purity phosphorus pentafluoride includes: adsorbing and removing hydrogen fluoride and hydrogen chloride in the phosphorus pentafluoride rectification tower raw material under normal temperature and pressure conditions by feeding the phosphorus pentafluoride rectification tower raw material into the fluorosulfonate (1-(2-methoxyethyl)-3-ethyl imidazole trifluoromethyl sulfonate ionic liquid is used in the embodiment) absorption tower through the phosphorus pentafluoride buffer tank, to obtain the gaseous high-purity phosphorus pentafluoride; further preferably, in order to ensure the purity of the gaseous high-purity phosphorus pentafluoride, the fluorosulfonate absorption tower includes a first fluorosulfonate absorption tower and a second fluorosulfonate absorption tower connected in series.

[0031] Preferably, in the embodiment, in the lithium fluoride suspension preparation kettle, the lithium fluoride is fully mixed with the organic solvent by ultrasonic action; wherein the solvent is any one or a mixture of any several of dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; and / or the mass ratio of lithium fluoride to organic solvent ranges from 1:8 to 20; preferably, in order to prevent the problem of lithium fluoride deposition in the pipeline during the transportation of the lithium fluoride suspension, in the embodiment, the lithium fluoride is in powder form, and the maximum particle size thereof is not more than 0.2 millimeters, preferably not more than 0.18 millimeters; the inner wall of the conveying pipeline between the lithium fluoride suspension preparation kettle and the top of the hexafluoride reaction plate tower is polished to be smooth, wherein the polishing precision of the inner wall of the conveying pipeline is less than or equal to 0.6 microns.

[0032] A20)reacting the lithium fluoride with the gaseous high-purity phosphorus pentafluoride in the hexafluoride reaction plate tower under normal temperature and pressure conditions, and the reaction product enters the tank bottom storage tank from the bottom of the hexafluoride reaction tower, wherein the mass ratio of lithium fluoride to gaseous high-purity phosphorus pentafluoride is 1:4-6;

[0033] Preferably, please further refer to Figure 2 and Figure 3As shown, in the present embodiment, the hexafluoro reaction plate column 100 is provided with at least 40 tower plates 110 distributed in an up-down interval, wherein the tower plate screen hole aperture near the tower top a is larger than the tower plate screen hole aperture near the tower bottom b; further preferably, in the present embodiment, the hexafluoro reaction plate column 100 comprises at least a first tower plate section, a second tower plate section and a third tower plate section from bottom to top; wherein the first tower plate section is provided with at least 10 first tower plates 110a distributed in an up-down interval, the tower plate screen hole aperture of the first tower plate 110a ranges from 2-4mm; the second tower plate section is provided with at least 10 second tower plates 110b distributed in an up-down interval, the tower plate screen hole aperture of the second tower plate 110b ranges from 6-9mm; the third tower plate section is provided with at least 10 third tower plates 110c distributed in an up-down interval, the tower plate screen hole aperture of the third tower plate 110c ranges from 12-16mm;

[0034] A30), the bottom tank returns the reaction product to the hexafluoro reaction plate column through the circulating heat exchanger according to a preset reflux ratio, and the remaining reaction product output by the circulating heat exchanger is punched into a lithium hexafluorophosphate liquid product extraction tank in one way and a lithium fluoride suspension preparation kettle in another way; the preset reflux ratio is 4-8:1;

[0035] A40), a filter is connected to the product extraction end of the product extraction tank to remove the excess solid material after reaction, so as to obtain liquid lithium hexafluorophosphate, the hydrogen chloride content of the liquid lithium hexafluorophosphate is less than 25ppm, preferably less than 15ppm, and no hydrogen fluoride is detected.

[0036] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0037] On the basis of the above-described embodiments, the present application further proposes the following specific embodiments, Embodiment 1

[0038] In the present embodiment 1, the specifications of the phosphorus pentafluoride rectification tower raw material and each device are as follows:

[0039] The mass percentage of hydrogen chloride in the phosphorus pentafluoride rectification tower raw material is 52.72%, the mass percentage of phosphorus pentafluoride PF5 is 47.17%, and the content of hydrogen fluoride is 0.11%; the lithium fluoride is in powder form, and the maximum particle size is not more than 0.18mm;

[0040] The specifications of the lithium fluoride suspension preparation kettle, lithium fluoride suspension feed tank, phosphorus pentafluoride buffer tank and high-purity phosphorus pentafluoride storage tank are all DN800*1200, and the materials are all S31603;

[0041] The matching ultrasonic working frequency of the lithium fluoride suspension preparation kettle is 25KHz, and the power is 550W;

[0042] The inner walls of the conveying pipelines between the lithium fluoride suspension preparation kettle and the tower top of the hexafluoro reaction plate tower are all polished, and the polishing precision is 0.5 microns;

[0043] The specifications of the first and second fluorosulfonate absorption towers are both DN1000*1600, and the tower conditions of the first and second fluorosulfonate absorption towers are both set as normal temperature and pressure, and the liquid of each absorption tower is 1-(2-methoxyethyl)-3-ethyl imidazole trifluoromethyl sulfonate ionic liquid;

[0044] The hexafluoro reaction plate tower is provided with a total of 65 tower plates which are distributed in an up-down interval, and the spacing between each adjacent tower plate is 380mm; the hexafluoro reaction plate tower comprises a first tower plate section, a fourth tower plate section, a second tower plate section, a fifth tower plate section and a third tower plate section from bottom to top; wherein the first tower plate section is provided with 15 first tower plates which are distributed in an up-down interval, and the tower plate screen hole diameter of the first tower plate is 3mm; the fourth tower plate section is provided with 10 fourth tower plates which are distributed in an up-down interval, and the tower plate screen hole diameter range of the fourth tower plate is 4.5mm; the second tower plate section is provided with 15 second tower plates which are distributed in an up-down interval, and the tower plate screen hole diameter of the second tower plate is 7mm; the fifth tower plate section is provided with 10 fifth tower plates which are distributed in an up-down interval, and the tower plate screen hole diameter of the fifth tower plate is 10mm; the third tower plate section is provided with 15 third tower plates which are distributed in an up-down interval, and the tower plate screen hole diameter range of the third tower plate is 14mm; the tower condition of the hexafluoro reaction plate tower is set as normal temperature and pressure;

[0045] The specification of the bottom storage tank is DN1100*1600, the refrigerant of the circulating heat exchanger is selected as -15℃ cold water, and the specification of the product production tank is DN800*1200;

[0046] The purity detection is performed by a chromatography-mass spectrometry instrument.

[0047] The high-purity phosphorus pentafluoride feed: the phosphorus pentafluoride rectification tower is fed into the first fluorosulfonate absorption tower and the second fluorosulfonate absorption tower through the phosphorus pentafluoride buffer tank at a speed of 5.4kg / h, the gas phase output end of the second fluorosulfonate absorption tower is connected to the high-purity phosphorus pentafluoride storage tank (the purity of the high-purity phosphorus pentafluoride reaches 99.4% after purity detection), and the high-purity phosphorus pentafluoride storage tank is connected to the tower kettle of the hexafluoro reaction plate tower for continuous feeding;

[0048] Lithium fluoride suspension feed: raw lithium fluoride is fed into a lithium fluoride suspension preparation kettle at a flow rate of 0.52 kg / h, and methyl ethyl carbonate (EMC) is fed at a flow rate of 8.2 kg / h, under the action of ultrasonic waves, lithium fluoride and methyl ethyl carbonate are fully mixed to obtain lithium fluoride suspension, which is transferred to a lithium fluoride suspension feed tank, and the lithium fluoride suspension feed tank is connected to the top of the hexafluoride reaction plate tower for continuous feeding;

[0049] Reaction and reflux: lithium fluoride reacts with gaseous high-purity phosphorus pentafluoride in the hexafluoride reaction plate tower in the presence of methyl ethyl carbonate; liquid reaction products are collected from the bottom of the hexafluoride reaction plate tower, and after passing through the bottom tank, they are cooled by a circulating heat exchanger, then they are fed into the hexafluoride reaction tower 400 at a pre-set reflux ratio of 6:1, while the remaining reaction products from the circulating heat exchanger are fed into the product collection tank at a speed of 10.04 kg / h, and finally, after passing through a filter to remove excess solid materials (usually lithium fluoride) after the reaction, liquid lithium hexafluorophosphate product is obtained, and the other part is fed into the lithium fluoride suspension preparation kettle at a speed of 0.78 kg / h, forming another loop; the gaseous methyl ethyl carbonate with a flow rate of 1.29 kg / h is collected from the top of the hexafluoride reaction plate tower and is sent to the subsequent section for compression and condensation recovery.

[0050] After purity detection, the liquid lithium hexafluorophosphate product obtained in Example 1 (see Figure 4 ) contains 10 ppm of hydrogen chloride and no hydrogen fluoride, and does not need to be treated by deacidification, and the production efficiency of liquid lithium hexafluorophosphate is significantly higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0051] Example 2: The remaining technical solutions of Example 2 are the same as those of Example 1, except that in Example 2, the second fluorosulfonate absorption tower is not used, and only the first fluorosulfonate absorption tower is used, and the gaseous output end of the first fluorosulfonate absorption tower is directly connected to the high-purity phosphorus pentafluoride storage tank.

[0052] After detection, the purity of the high-purity phosphorus pentafluoride obtained in Example 2 is 96.5%, the liquid lithium hexafluorophosphate product contains 24 ppm of hydrogen chloride and no hydrogen fluoride, and the production efficiency of liquid lithium hexafluorophosphate is significantly higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0053] Example 3: The remaining technical solutions of Example 3 are the same as those of Example 1, except that in Example 3, dimethyl carbonate is used instead of methyl ethyl carbonate in Example 1.

[0054] The purity detection shows that the hydrogen chloride content in the liquid lithium hexafluorophosphate product obtained in this embodiment 1 is 12 ppm, no hydrogen fluoride is detected, no subsequent deacidification treatment is needed, the output efficiency of the liquid lithium hexafluorophosphate is obviously higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0055] Embodiment 4: The remaining technical solutions of this embodiment 4 are the same as those of embodiment 1, except that in this embodiment 4, 1:1 dimethyl carbonate and methyl ethyl carbonate are used to replace the methyl ethyl carbonate in embodiment 1.

[0056] The purity detection shows that the hydrogen chloride content in the liquid lithium hexafluorophosphate product obtained in this embodiment 4 is 11 ppm, no hydrogen fluoride is detected, no subsequent deacidification treatment is needed, the output efficiency of the liquid lithium hexafluorophosphate is obviously higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0057] Embodiment 5: The remaining technical solutions of this embodiment 5 are the same as those of embodiment 1, except that in this embodiment 5, 1:1 dimethyl carbonate and diethyl carbonate are used to replace the methyl ethyl carbonate in embodiment 1.

[0058] The purity detection shows that the hydrogen chloride content in the liquid lithium hexafluorophosphate product obtained in this embodiment 5 is 13 ppm, no hydrogen fluoride is detected, no subsequent deacidification treatment is needed, the output efficiency of the liquid lithium hexafluorophosphate is obviously higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0059] Embodiment 6: The remaining technical solutions of this embodiment 6 are the same as those of embodiment 1, except that this embodiment 6 includes the following operation steps:

[0060] High-purity phosphorus pentafluoride feed: The phosphorus pentafluoride rectification column feed is sequentially introduced into the first fluorosulfonate absorption tower and the second fluorosulfonate absorption tower through the phosphorus pentafluoride buffer tank at a speed of 6.5 kg / h, the gas phase output end of the second fluorosulfonate absorption tower is connected to the high-purity phosphorus pentafluoride storage tank (the purity of the high-purity phosphorus pentafluoride reaches 98.1% after purity detection), and the high-purity phosphorus pentafluoride storage tank is connected to the tower bottom of the hexafluoride reaction plate tower for continuous feeding;

[0061] Lithium fluoride suspension feed: the raw material lithium fluoride is introduced into the lithium fluoride suspension preparation kettle at a flow rate of 0.64 kg / h, and the methyl ethyl carbonate is introduced at a flow rate of 8.2 kg / h, under the action of ultrasonic waves, the lithium fluoride and the methyl ethyl carbonate are fully combined to obtain the lithium fluoride suspension, which is transferred to the lithium fluoride suspension feed tank, and the lithium fluoride suspension feed tank is connected to the top of the hexafluoride reaction plate tower for continuous feeding;

[0062] Reaction and reflux: the lithium fluoride reacts with the gaseous high-purity phosphorus pentafluoride in the atmosphere of methyl ethyl carbonate in the hexafluoro reaction plate column; the liquid reaction product is taken out from the bottom of the hexafluoro reaction plate column, and after the heat exchange and cooling by the circulating heat exchanger, it is punched into the hexafluoro reaction column 400 at a preset reflux ratio of 8:1, while the remaining reaction product output by the circulating heat exchanger is punched into the product taking tank at a speed of 11.75 kg / h, and finally, after the filter removes the excess solid material after the reaction, the liquid lithium hexafluorophosphate product is obtained, and the other way is punched into the lithium fluoride suspension preparation kettle at a speed of 0.82 kg / h, forming another loop; the gaseous methyl ethyl carbonate with a flow rate of 0.16 kg / h is taken out from the top of the hexafluoro reaction plate column and enters the subsequent section for compression and condensation recovery.

[0063] After purity detection, the hydrogen chloride content in the liquid lithium hexafluorophosphate product obtained in Example 6 is 15 ppm, and no hydrogen fluoride is detected, so no subsequent deacidification treatment is needed, and the output efficiency of the liquid lithium hexafluorophosphate is significantly higher, and the conversion rate of phosphorus pentafluoride reaches more than 99.99%.

[0064] Example 7: The remaining technical solutions of Example 7 are the same as those of Example 1, except that in Example 7, each tray is set to a uniform size specification, which is the same as the first tray in Example 1; after actual application, the mass transfer efficiency of lithium fluoride is significantly slower, the output efficiency of liquid lithium hexafluorophosphate is significantly lower, and the conversion rate of phosphorus pentafluoride is less than 98%.

[0065] Example 8: The remaining technical solutions of Example 8 are the same as those of Example 1, except that in Example 8, each tray is set to a uniform size specification, which is the same as the third tray in Example 1; after actual application, the mass transfer efficiency of gaseous phosphorus pentafluoride is significantly slower, the output efficiency of liquid lithium hexafluorophosphate is significantly lower, and the conversion rate of phosphorus pentafluoride is less than 96%.

[0066] Comparative Example 1: The remaining technical solutions of Comparative Example 1 are the same as those of Example 1, except that in Comparative Example 1, the first and second fluorosulfonate absorption towers are not set, and the phosphorus pentafluoride rectification tower feed is directly connected to the phosphorus pentafluoride storage tank, that is, the phosphorus pentafluoride rectification tower feed is directly used as the hexafluoro reaction plate column feed;

[0067] After detection, the hydrogen chloride content in the liquid lithium hexafluorophosphate product obtained in Comparative Example 1 is greater than 600 ppm, and the hydrogen fluoride content is greater than 50 ppm, so additional deacidification treatment is needed, and because the phosphorus pentafluoride rectification tower feed contains a large amount of hydrogen chloride gas, the conversion rate of phosphorus pentafluoride is relatively low, and the hexafluoro reaction plate column is in a strong acidic environment for a long time, so the plate column needs to be frequently stopped for maintenance, affecting the continuity of production.

[0068] Comparative Example 2: The remaining technical solutions of Comparative Example 2 are the same as those of Example 1, except that in Comparative Example 2, the first sodium fluoride adsorber and the second sodium fluoride adsorber are used instead of the first fluorosulfonate absorber and the second fluorosulfonate absorber in Example 1;

[0069] It is detected that the phosphorus pentafluoride obtained after adsorption treatment still has a high content of hydrogen chloride, which further causes the content of hydrogen chloride in the obtained liquid lithium hexafluorophosphate product to be greater than 600 ppm, hydrogen fluoride is not detected, and additional deacidification treatment is still required subsequently. Moreover, the use of a sodium fluoride adsorber requires relatively harsh process conditions, and the adsorption effect is unstable. In addition, as in Comparative Example 1, due to the presence of a large amount of hydrogen chloride gas in the feed of the phosphorus pentafluoride rectification tower, the conversion rate of phosphorus pentafluoride is relatively low, and the six-fluorine reaction plate tower is in a strong acidic environment for a long time, so the plate tower needs to be frequently stopped for maintenance, which affects the continuity of production.

[0070] Comparative Example 3: The remaining technical solutions of Comparative Example 3 are the same as those of Example 1, except that in Comparative Example 3, the connecting path between the output end of the circulating heat exchanger and the lithium fluoride suspension preparation kettle is cancelled, that is, the reaction product is no longer transported to the lithium fluoride suspension preparation kettle.

[0071] After actual circulation test, since the lithium fluoride particle size is small, and the inner wall of the lithium fluoride suspension conveying pipeline is polished, no blockage problem is found in the pipeline part. However, the gas phase supplied in the six-fluorine reaction plate tower is the reaction raw material gas phase high-purity phosphorus pentafluoride, which no longer has a high content of hydrogen chloride gas, and the mass transfer speed is slow, which can cause the screen holes of each tower plate to be blocked, and the output efficiency is significantly reduced, so it is not suitable for continuous production process application.

[0072] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the elements of the claims. Any reference signs in the claims should not be considered as limiting the claims involved.

[0073] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A continuous preparation process for liquid lithium hexafluorophosphate, characterized in that, The following steps are included: (A10) A lithium fluoride suspension is provided through a lithium fluoride suspension preparation vessel and continuously fed to the top of a hexafluoro reaction plate column; a high-purity phosphorus pentafluoride gaseous phase is provided through a high-purity phosphorus pentafluoride storage tank and continuously fed to the bottom of the hexafluoro reaction plate column, wherein the purity of the high-purity phosphorus pentafluoride gaseous phase is greater than 96%; (A20) The lithium fluoride and the gaseous high-purity phosphorus pentafluoride react in the hexafluoro reaction plate tower under normal temperature and pressure conditions. The reaction products enter the bottom storage tank from the bottom of the hexafluoro reaction tower. The mass ratio of the lithium fluoride to the gaseous high-purity phosphorus pentafluoride is 1:4-6. (A30) The bottom storage tank of the tower refluxes the reaction products back to the hexafluoro reaction plate tower through a circulating heat exchanger at a preset reflux ratio. The remaining reaction products output from the circulating heat exchanger are pumped into the liquid lithium hexafluorophosphate product collection tank and into the lithium fluoride suspension preparation kettle. The preset reflux ratio is 4-8:

1. A40) After connecting a filter to the product collection end of the product collection tank to remove excess solid material after the reaction, liquid lithium hexafluorophosphate is obtained. The hydrogen chloride content of the liquid lithium hexafluorophosphate is less than 25 ppm, and no hydrogen fluoride is detected.

2. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 1, characterized in that, The preparation steps of the gaseous high-purity phosphorus pentafluoride include: conveying the feed from the phosphorus pentafluoride distillation column through the phosphorus pentafluoride buffer tank into the fluorosulfonate absorption column, and adsorbing and removing hydrogen fluoride and hydrogen chloride from the feed from the phosphorus pentafluoride distillation column under normal temperature and pressure conditions to obtain the gaseous high-purity phosphorus pentafluoride.

3. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 2, characterized in that, The fluorosulfonate absorption tower includes a first fluorosulfonate absorption tower and a second fluorosulfonate absorption tower connected together.

4. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 1, characterized in that, In the lithium fluoride suspension preparation vessel, the lithium fluoride and the organic solvent are fully mixed by ultrasonic action; wherein the solvent is any one or a mixture of any of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; and / or the mass ratio of lithium fluoride to organic solvent is in the range of 1:8-20.

5. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 1 or 4, characterized in that, Lithium fluoride is produced in powder form, with a maximum particle size not exceeding 0.2 mm.

6. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 5, characterized in that, The maximum particle size of lithium fluoride is no more than 0.18 mm.

7. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 5, characterized in that, The inner wall of the conveying pipe between the lithium fluoride suspension preparation vessel and the top of the hexafluoro reaction plate tower is polished to a smooth finish, wherein the polishing precision of the inner wall of the conveying pipe is less than or equal to 0.6 micrometers.

8. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 1, characterized in that, The hexafluoro reaction plate tower is equipped with at least 40 plates arranged at intervals, wherein the sieve aperture of the plate near the top of the tower is larger than that of the plate near the bottom of the tower.

9. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 8, characterized in that, The hexafluoro reaction plate column comprises at least a first plate section, a second plate section, and a third plate section from bottom to top; wherein, the first plate section has at least 10 first plates arranged vertically at intervals, and the sieve aperture of the first plates ranges from 2 to 4 mm; the second plate section has at least 10 second plates arranged vertically at intervals, and the sieve aperture of the second plates ranges from 6 to 9 mm; the third plate section has at least 10 third plates arranged vertically at intervals, and the sieve aperture of the third plates ranges from 12 to 16 mm.

10. The continuous preparation process of liquid lithium hexafluorophosphate according to claim 1, characterized in that, The hydrogen chloride content of the liquid lithium hexafluorophosphate is less than 15 ppm.

11. An apparatus for a continuous preparation process according to any one of claims 1-10, characterized in that, The system includes a lithium fluoride suspension preparation vessel, a high-purity phosphorus pentafluoride storage tank, and a hexafluoride reaction plate tower; wherein, the outlet of the lithium fluoride suspension preparation vessel is connected to the top of the hexafluoride reaction plate tower through a suspension delivery pipeline, and the outlet of the high-purity phosphorus pentafluoride storage tank is connected to the bottom of the hexafluoride reaction plate tower through a delivery pipeline.

12. The apparatus used in the continuous preparation process according to claim 11, characterized in that, The high-purity phosphorus pentafluoride storage tank is connected to the gas phase output end of the fluorosulfonate absorption tower, and the gas phase input end of the fluorosulfonate absorption tower is connected to the feed outlet of the phosphorus pentafluoride distillation tower through the phosphorus pentafluoride buffer tank; a lithium fluoride suspension feed tank is provided on the suspension conveying pipeline, and the lithium fluoride suspension preparation kettle is connected to the hexafluorophosphate reaction plate tower through the lithium fluoride suspension feed tank; wherein, the bottom of the hexafluorophosphate reaction plate tower is connected to the bottom storage tank, the bottom storage tank is connected to the input end of the circulating heat exchanger, and the output end of the circulating heat exchanger is connected to the hexafluorophosphate reaction plate tower, the liquid lithium hexafluorophosphate product collection tank, and the lithium fluoride suspension preparation kettle.

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