CN113651341A - Method for synthesizing lithium hexafluorophosphate solution by using fluorine-containing waste residues - Google Patents
Method for synthesizing lithium hexafluorophosphate solution by using fluorine-containing waste residues Download PDFInfo
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- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 239000011737 fluorine Substances 0.000 title claims abstract description 47
- 229910052731 fluorine Inorganic materials 0.000 title claims abstract description 47
- 239000002699 waste material Substances 0.000 title claims abstract description 39
- -1 lithium hexafluorophosphate Chemical compound 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 27
- 230000002194 synthesizing effect Effects 0.000 title claims abstract description 8
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims abstract description 74
- 238000006243 chemical reaction Methods 0.000 claims abstract description 62
- OBCUTHMOOONNBS-UHFFFAOYSA-N phosphorus pentafluoride Chemical compound FP(F)(F)(F)F OBCUTHMOOONNBS-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000000725 suspension Substances 0.000 claims abstract description 24
- UHZYTMXLRWXGPK-UHFFFAOYSA-N phosphorus pentachloride Chemical compound ClP(Cl)(Cl)(Cl)Cl UHZYTMXLRWXGPK-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 10
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 8
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 3
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 26
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 15
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 14
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 9
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910001868 water Inorganic materials 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 4
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 claims description 4
- 239000006227 byproduct Substances 0.000 claims description 3
- 239000011521 glass Substances 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 2
- 229910001290 LiPF6 Inorganic materials 0.000 claims description 2
- 229910004014 SiF4 Inorganic materials 0.000 claims description 2
- 229910004074 SiF6 Inorganic materials 0.000 claims description 2
- 239000007864 aqueous solution Substances 0.000 claims description 2
- 239000001110 calcium chloride Substances 0.000 claims description 2
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 2
- 239000000920 calcium hydroxide Substances 0.000 claims description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- 239000006185 dispersion Substances 0.000 claims description 2
- 238000005530 etching Methods 0.000 claims description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims description 2
- 230000003472 neutralizing effect Effects 0.000 claims description 2
- 150000002825 nitriles Chemical class 0.000 claims description 2
- 238000000746 purification Methods 0.000 claims description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 2
- 239000002002 slurry Substances 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 239000011734 sodium Substances 0.000 claims description 2
- 238000002604 ultrasonography Methods 0.000 claims description 2
- 150000001733 carboxylic acid esters Chemical class 0.000 claims 1
- 239000003759 ester based solvent Substances 0.000 claims 1
- 239000004210 ether based solvent Substances 0.000 claims 1
- 239000005453 ketone based solvent Substances 0.000 claims 1
- 230000001590 oxidative effect Effects 0.000 claims 1
- 239000007789 gas Substances 0.000 abstract description 45
- 239000000463 material Substances 0.000 abstract description 5
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 2
- 229910052760 oxygen Inorganic materials 0.000 abstract description 2
- 239000001301 oxygen Substances 0.000 abstract description 2
- 238000011112 process operation Methods 0.000 abstract description 2
- 238000011084 recovery Methods 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 12
- 239000002910 solid waste Substances 0.000 description 7
- 239000003795 chemical substances by application Substances 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 239000000498 cooling water Substances 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
- 238000007789 sealing Methods 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- 229940104869 fluorosilicate Drugs 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 239000002893 slag Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 229940043430 calcium compound Drugs 0.000 description 2
- 150000001674 calcium compounds Chemical class 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000011162 core material Substances 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 238000003682 fluorination reaction Methods 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229910001610 cryolite Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000295 emission spectrum Methods 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000008093 supporting effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/005—Lithium hexafluorophosphate
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
Abstract
The invention discloses a method for synthesizing a lithium hexafluorophosphate solution by using fluorine-containing waste residues, and relates to the fields of resource recovery and comprehensive utilization and fluorine material synthesis. Drying and crushing fluorine-containing waste residues in a reaction furnace, adding oxygen for presintering, adding into a first reaction kettle, and slowly adding phosphorus pentachloride for reacting to generate gas; then the gas is led out of the first reaction kettle and purified to obtain high-purity phosphorus pentafluoride gas; adding the dried and crushed lithium fluoride into an organic solvent to form a lithium fluoride suspension; then introducing high-purity phosphorus pentafluoride gas into the lithium fluoride suspension for reaction to generate a lithium hexafluorophosphate solution; and deacidifying and filtering the solution after reaching a certain concentration to obtain the high-purity lithium hexafluorophosphate solution. The method converts the fluorine-containing waste residues with low content and low added value into the new energy material with high quality and high added value, has higher economic value and environmental protection value, is simple in process operation, low in production cost, low in equipment requirement, safe and environment-friendly, and can be quickly popularized.
Description
Technical Field
The invention relates to the field of comprehensive utilization of resource recovery and the technical field of fluorine material synthesis, in particular to a method for synthesizing a lithium hexafluorophosphate solution by using fluorine-containing waste residues.
Background
With the development of science, technology and economic society in a daily and new day and night and the rapid development, the fluorine chemical industry has more and more obvious supporting effect on the traditional industries of aerospace, information communication, life science, new energy and the like, emerging industries and sustainable development. In recent years, the fluorination industry in China is greatly developed by virtue of the advantages of high-grade fluorite resources. However, in the production process of the fluorination industry, a large amount of hydrofluoric acid is adopted to generate fluorine-containing waste acid and waste residue, and the economic benefit of the waste acid and the waste residue is not obvious, so that the common treatment modes are mostly stacking or burying. The method not only causes environmental pollution, but also causes waste of fluorine resources, and restricts sustainable development of fluorine chemical industry and downstream application industry.
Lithium hexafluorophosphate is the most widely commercialized electrolyte salt in lithium battery electrolyte and is the key raw material of the core in lithium ion batteries. Due to the increase of the demand of new energy automobiles in domestic and European markets and the driving of global targets of 'carbon peak reaching' and 'carbon neutralization', the delivery volume of lithium ion batteries is rapidly increased, and a huge increment is brought to the demand of lithium hexafluorophosphate, but the demand of lithium hexafluorophosphate is short at present.
In the prior art, chinese patent application No. CN201510583160.8 discloses a safe disposal method of fluorine-containing solid waste, which comprises adding calcium compound into fluorine-containing solid waste, and using fluoride ions in the fluorine-containing solid waste and the added calcium compound to form insoluble calcium fluoride, so as to reduce free fluoride ions in the fluorine-containing solid waste; and then, the curing agent is added to play a role in bonding the fluorine-containing solid waste, and a layer of low-permeability substance is formed on the surface of the fluorine-containing solid waste to limit the transfer of harmful components in the fluorine-containing solid waste.
Chinese patent with application number CN202110444538.1 also discloses a treatment method and a treatment device for the waste residue containing fluorine and phosphorus, and the method mixes the waste residue containing fluorine and phosphorus, water quenching slag and auxiliary materials to form a mixture; smelting the mixture to obtain liquid molten slag; and carrying out water quenching treatment on the liquid molten slag to obtain the amorphous glass slag.
The literature also discloses the research on the process of regenerating cryolite from fluorine-containing waste residues, and mainly explains the research and development on the process technology of recovering and recycling fluorine products as byproducts in the electrolytic aluminum industry and the photovoltaic industry.
However, the recycling of the fluorine-containing waste residue in the prior art is still in the primary stage, and the economic value and the environmental protection value are low, so a new method for synthesizing a key core material with high added value, high quality and high performance by using the fluorine-containing waste residue is urgently needed.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method for synthesizing the lithium hexafluorophosphate solution by using the fluorine-containing waste residues is provided, and solves the problems that the fluorine-containing waste residue treatment method in the prior art is low in economic value, can cause environmental pollution, wastes fluorine resources and the like.
The technical scheme adopted by the invention is as follows:
a method for synthesizing lithium hexafluorophosphate solution by utilizing fluorine-containing waste residues comprises the steps of drying and crushing the fluorine-containing waste residues in a reaction furnace, adding oxygen for presintering, adding into a first reaction kettle, and slowly adding phosphorus pentachloride for reaction to generate gas; then the gas is led out of the first reaction kettle and is purified to obtain high-purity phosphorus pentafluoride gas; adding the dried and crushed lithium fluoride into an organic solvent to form a lithium fluoride suspension; then introducing high-purity phosphorus pentafluoride gas into a second reaction kettle to react with the lithium fluoride suspension to generate a lithium hexafluorophosphate solution; finally, after reaching a certain concentration, carrying out deacidification treatment on the solution and then filtering to obtain a high-purity lithium hexafluorophosphate solution;
the main reaction equation is:
CaF2+XSiF6+PCl5→PF5+CaCl2+XCl+SiF4；
PF5+LiF→LiPF6；
3SiF4+2Na2CO3+2H2O＝H4SiO4↓+2Na2SiF6↓+2CO2。
further, the fluorine-containing waste residue is obtained by neutralizing fluorine-containing waste acid and calcium hydroxide which are mainly derived from the fields of photovoltaic industry, glass etching and metallurgical industry; the fluorine-containing waste residue mainly contains calcium fluoride and fluosilicate, wherein the content of calcium fluoride is more than or equal to 20 percent, the content of water is less than or equal to 100ppm, and the granularity D50 after crushing is less than or equal to 10.0 mu m.
Further, the drying mode of the fluorine-containing waste residue in the reaction furnace is that vacuum and dry air replacement are alternated, the drying pre-sintering temperature is 300-500 ℃, the vacuum degree is less than or equal to-0.07 Mpa, the alternation frequency is 10-30 min/time, the drying pre-sintering time is 2-8h, and the water content of the dried waste residue is less than or equal to 100 ppm.
Further, the gas purification mode is one or combination of deep cooling, compression, rectification and washing in a washing tower, and the content of the purified phosphorus pentafluoride gas is more than or equal to 99.5%.
Further, the organic solvent is selected from any one or more of a carbonate solvent, a carboxylate solvent, a nitrile solvent, an ether solvent and a ketone solvent.
Furthermore, the particle size D50 of the lithium fluoride in the lithium fluoride suspension is less than 10.0 μm, and the mass ratio of the lithium fluoride to the organic solvent in the slurry is 1:4-1: 20.
Further, the lithium fluoride suspension is prepared by any one or more of stirring, ultrasound, high-speed dispersion and sanding.
Further, the temperature of the phosphorus pentafluoride introduced into the lithium fluoride suspension for reaction is 0-30 ℃.
Further, after the phosphorus pentafluoride is introduced into the suspension to react to generate lithium hexafluorophosphate, the solution concentration is 1.5-2.5 mol/L.
Further, a byproduct silicon tetrafluoride generated in the first reaction kettle is separated and then is introduced into a sodium carbonate aqueous solution, and the obtained sodium fluosilicate is used as a raw material.
Further, the lithium hexafluorophosphate solution is deacidified and filtered to obtain a liquid salt product, and the purity of the product is more than or equal to 99.95%.
Compared with the prior art, the invention has the following beneficial technical effects:
the method converts the fluorine-containing waste residues with low content and low added value into the new energy material with high quality and high added value, has higher economic value and environmental protection value, is simple in process operation, low in production cost, low in equipment requirement, safe and environment-friendly, and can be quickly popularized.
Detailed Description
The present invention is further illustrated by the following specific examples, but it should not be construed that the scope of the present invention is limited to the following examples, and it will be apparent to those skilled in the art that various technical features in the following examples can be appropriately combined, replaced, adjusted, modified, etc. according to the inventive concept and the entire contents of the present invention, and still fall within the scope of the protection of the present invention.
Example 1
5kg of fluorine-containing waste residue (calcium fluoride content: 30%, fluorosilicate content: 40%, D50: 3.7 μm) was charged into a reaction furnace, and the temperature was raised to 300 ℃ after sealing. Starting a vacuum pump to vacuumize the reaction furnace to-0.09 Mpa, alternately performing vacuum and dry air for 20min once, drying and presintering for 3h, then placing the reaction furnace in a first reaction kettle, slowly adding phosphorus pentachloride into the first reaction kettle, simultaneously discharging gas, introducing mixed gas into a pre-condenser, then introducing the mixed gas into a rectification system for separation to obtain 1.3kg of phosphorus pentafluoride gas, introducing the rest gas into a sodium carbonate solution for absorption, and sampling to test that the purity of the phosphorus pentafluoride gas is 99.9%. 0.3kg of lithium fluoride was added to 3kg of ethyl methyl carbonate solvent, and dispersed and suspended at high speed to obtain a lithium fluoride suspension. Introducing 1.3kg of high-purity phosphorus pentafluoride gas into the lithium fluoride suspension for reaction, wherein the reaction temperature is 5 ℃ (circulating through a circulating cooling water jacket at 5 ℃), adding 0.01kg of deacidification agent after the reaction is completed, stirring and filtering. 4.2kg of lithium hexafluorophosphate solution was obtained in a yield of 92% and a purity of lithium hexafluorophosphate of 99.99%.
The inductively coupled plasma emission spectrum analysis shows that the heavy metal content of the product is very low, such as Fe, Ni and Cr, and is respectively 0.2ppm,0.1ppm and 0.1ppm, as shown in Table 1. This indicates that the use of a non-acidic process can reduce heavy metal impurities introduced due to corrosion of equipment, thereby significantly improving product quality. Even if low-purity calcium fluoride is used, a high-purity product can be obtained by adopting the process, because the phosphorus pentafluoride generated in the first step is gas and can be introduced into the second reaction kettle in the second step, and the metal salt in the recovered low-purity calcium fluoride is nonvolatile, the metal salt cannot be brought into the second step to influence the purity of the product.
Table 1 lithium hexafluorophosphate product inspection report
Example 2
5kg of fluorine-containing waste residue (calcium fluoride content 50%, fluorosilicate content 30%, D50 5.2 μm) was charged into a reaction furnace, and the temperature was raised to 350 ℃ after sealing. Starting a vacuum pump to vacuumize the reaction furnace to-0.09 Mpa, alternately performing vacuum and dry air for 30min once, drying and presintering for 2h, then placing the reaction furnace in a first reaction kettle, slowly adding phosphorus pentachloride into the first reaction kettle, simultaneously discharging gas, introducing mixed gas into a pre-condenser, then introducing the mixed gas into a rectification system for separation to obtain 1.7kg of phosphorus pentafluoride gas, introducing the rest gas into a sodium carbonate solution for absorption, and sampling to test that the purity of the phosphorus pentafluoride gas is 99.8%. 0.37kg of lithium fluoride was added to 4kg of diethyl carbonate solvent and sanded to form a lithium fluoride suspension. Introducing 1.7kg of high-purity phosphorus pentafluoride gas into the lithium fluoride suspension for reaction, wherein the reaction temperature is 5 ℃ (circulating through a circulating cooling water jacket at 5 ℃), adding 0.015kg of deacidification agent after the reaction is completed, stirring and filtering. 5.4kg of lithium hexafluorophosphate solution was obtained in a product yield of 90% and a purity of lithium hexafluorophosphate of 99.99%.
Example 3
5kg of fluorine-containing waste residue (calcium fluoride content 70%, fluorosilicate content 20%, D50 of 4.7 μm) was charged into a reaction furnace, and the temperature was raised to 330 ℃ after sealing. Starting a vacuum pump to vacuumize the reaction furnace to-0.09 Mpa, alternately performing vacuum and dry air for 10min once, drying and presintering for 4h, then placing the reaction furnace in a first reaction kettle, slowly adding phosphorus pentachloride into the first reaction kettle, simultaneously discharging gas, introducing mixed gas into a pre-condenser, then introducing the mixed gas into a rectification system for separation to obtain 2.4kg of phosphorus pentafluoride gas, introducing the rest gas into a sodium carbonate solution for absorption, and sampling to test that the purity of the phosphorus pentafluoride gas is 99.9%. 0.52kg of lithium fluoride was added to 7kg of dimethyl carbonate solvent, and suspended with stirring to form a lithium fluoride suspension. Introducing high-purity phosphorus pentafluoride gas into a lithium fluoride suspension for reaction, wherein the reaction temperature is 5 ℃ (circulating through a circulating cooling water jacket at 5 ℃), adding 0.02kg of deacidification agent after the reaction is completed, stirring and filtering. 9kg of lithium hexafluorophosphate solution was obtained in a product yield of 91% and a purity of lithium hexafluorophosphate of 99.99%.
Example 4
5kg of fluorine-containing waste residue (calcium fluoride content 25%, fluorosilicate content 50%, D50 of 7.3 μm) was charged into a reaction furnace, and the temperature was raised to 370 ℃ after sealing. Starting a vacuum pump to vacuumize the reaction furnace to-0.09 Mpa, alternately performing vacuum and dry air for 10min once, drying and presintering for 4h, then placing the reaction furnace in a first reaction kettle, slowly adding phosphorus pentachloride into the first reaction kettle, simultaneously discharging gas, introducing mixed gas into a pre-condenser, then introducing the mixed gas into a rectification system for separation to obtain 1.1kg of phosphorus pentafluoride gas, introducing the rest gas into a sodium carbonate solution for absorption, and sampling to test that the purity of the phosphorus pentafluoride gas is 99.7%. 0.25kg of lithium fluoride was added to 3kg of dimethyl carbonate solvent, and suspended with stirring to obtain a lithium fluoride suspension. Introducing high-purity phosphorus pentafluoride gas into a lithium fluoride suspension for reaction, wherein the reaction temperature is 5 ℃ (circulating through a circulating cooling water jacket at 5 ℃), adding 0.01kg of deacidification agent after the reaction is completed, stirring and filtering. 3.9kg of lithium hexafluorophosphate solution was obtained in a product yield of 90% and a purity of lithium hexafluorophosphate of 99.99%.
Comparative example
Adding 5kg of fluorine-containing waste residues (the content of calcium fluoride is 30%, the content of fluosilicate is 40%, and the D50 is 3.7 mu m) into a reaction furnace, sealing, heating to 300 ℃ and placing in a first reaction kettle, slowly adding phosphorus pentachloride into the first reaction kettle, discharging gas while adding, introducing mixed gas into a pre-condenser and then separating in a rectification system to obtain 1.1kg of phosphorus pentafluoride gas after separation, introducing the rest gas into a sodium carbonate solution for absorption, and sampling to test that the purity of the phosphorus pentafluoride gas is 99.9%. 0.3kg of lithium fluoride was added to 3kg of ethyl methyl carbonate solvent, and dispersed and suspended at high speed to obtain a lithium fluoride suspension. Introducing 1.1kg of high-purity phosphorus pentafluoride gas into the lithium fluoride suspension for reaction, wherein the reaction temperature is 5 ℃ (circulating through a circulating cooling water jacket at 5 ℃), adding 0.01kg of deacidification agent after the reaction is completed, stirring and filtering. 3.3kg of lithium hexafluorophosphate solution was obtained in a product yield of 76.7% and a purity of lithium hexafluorophosphate of 99.99%.
The foregoing is merely a preferred embodiment of the invention, which is illustrative only and not limiting of the scope of the invention. Various modifications and improvements of the technical solution of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and the technical solution of the present invention is to be covered by the protection scope defined by the claims.
Claims (9)
1. A method for synthesizing lithium hexafluorophosphate solution by using fluorine-containing waste residues is characterized by comprising the following steps:
(1) drying and oxidizing the dried and crushed fluorine-containing waste residues in a reaction furnace for presintering, adding the dried and crushed fluorine-containing waste residues into a first reaction kettle, and slowly adding phosphorus pentachloride for reacting to generate gas;
the reaction equation is CaF2+XSiF6+PCl5→PF5+CaCl2+XCl+SiF4；
(2) The gas is led out of the first reaction kettle and purified to obtain high-purity phosphorus pentafluoride gas;
(3) adding the dried and crushed lithium fluoride into an organic solvent to form a lithium fluoride suspension;
(4) introducing high-purity phosphorus pentafluoride gas into a reaction kettle to react with the lithium fluoride suspension to generate a lithium hexafluorophosphate solution;
the reaction equation is PF5+LiF→LiPF6；
(5) And (4) after reaching a certain concentration, carrying out deacidification treatment on the lithium hexafluorophosphate solution obtained in the step (4), and filtering to obtain a high-purity lithium hexafluorophosphate solution.
2. The method of claim 1, wherein: the fluorine-containing waste residue is obtained by neutralizing fluorine-containing waste acid and calcium hydroxide mainly from the fields of photovoltaic industry, glass etching and metallurgical industry, and mainly contains calcium fluoride and fluosilicate, wherein the content of calcium fluoride is more than or equal to 20 percent, the content of water is less than or equal to 100ppm, and the granularity D50 is less than or equal to 10.0 mu m.
3. The method of claim 1, wherein: the fluorine-containing waste residue needs to be dried, oxygenated and presintered in a reaction furnace, and the presintering temperature is 300-; the reaction and synthesis temperature of the fluorine-containing waste residue and phosphorus pentachloride is 300-500 ℃, and the gas purification mode is one or combination of deep cooling, compression and rectification.
4. The method of claim 1, wherein: the organic solvent is selected from one or more of carbonate solvents, carboxylic ester solvents, nitrile solvents, ether solvents and ketone solvents.
5. The method of claim 4, wherein: the lithium fluoride suspension is prepared by any one or more of stirring, ultrasound, high-speed dispersion and sanding.
6. The method of claim 5, wherein: the granularity D50 of the lithium fluoride in the lithium fluoride suspension is less than 10.0 mu m, and the mass ratio of the lithium fluoride to the organic solvent in the slurry is 1:4-1: 20.
7. The method according to claim 4, wherein the temperature of the phosphorus pentafluoride passing through the lithium fluoride suspension for reaction is 0 ℃ to 30 ℃.
8. The method of claim 1, wherein: separating the byproduct silicon tetrafluoride in the step (1), and introducing into a sodium carbonate aqueous solution to obtain sodium fluosilicate serving as a raw material;
the reaction equation is: 3SiF4+2Na2CO3+2H2O＝H4SiO4↓+2Na2SiF6↓+2CO2。
9. The method of claim 1, wherein: phosphorus pentafluoride is introduced into the lithium fluoride suspension to react to generate lithium hexafluorophosphate, and the solution concentration is 1.5-2.5mol/L after the lithium hexafluorophosphate is dissolved in the organic solvent.
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