CN117303389A - Method for preparing lithium tetrafluoroborate from fluosilicic acid - Google Patents
Method for preparing lithium tetrafluoroborate from fluosilicic acid Download PDFInfo
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- CN117303389A CN117303389A CN202311063499.6A CN202311063499A CN117303389A CN 117303389 A CN117303389 A CN 117303389A CN 202311063499 A CN202311063499 A CN 202311063499A CN 117303389 A CN117303389 A CN 117303389A
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- lithium tetrafluoroborate
- acid
- fluosilicic acid
- fluosilicic
- preparing lithium
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- 239000002253 acid Substances 0.000 title claims abstract description 66
- -1 lithium tetrafluoroborate Chemical compound 0.000 title claims abstract description 56
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims abstract description 25
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000013078 crystal Substances 0.000 claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims abstract description 16
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 14
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000000243 solution Substances 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 12
- 239000000706 filtrate Substances 0.000 claims abstract description 12
- 238000003756 stirring Methods 0.000 claims abstract description 12
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000004327 boric acid Substances 0.000 claims abstract description 11
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims abstract description 11
- 229910052808 lithium carbonate Inorganic materials 0.000 claims abstract description 11
- 239000012043 crude product Substances 0.000 claims abstract description 10
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 9
- 239000007864 aqueous solution Substances 0.000 claims abstract description 6
- 238000001704 evaporation Methods 0.000 claims abstract description 6
- 239000002904 solvent Substances 0.000 claims abstract description 5
- 239000007788 liquid Substances 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims abstract description 3
- 238000000926 separation method Methods 0.000 claims abstract description 3
- 230000001376 precipitating effect Effects 0.000 claims abstract 2
- 238000001914 filtration Methods 0.000 claims description 16
- 239000002808 molecular sieve Substances 0.000 claims description 14
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 9
- 239000003960 organic solvent Substances 0.000 claims description 7
- 239000000047 product Substances 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- 230000008020 evaporation Effects 0.000 claims description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 abstract description 12
- 239000011737 fluorine Substances 0.000 abstract description 12
- 229910052731 fluorine Inorganic materials 0.000 abstract description 12
- 230000007547 defect Effects 0.000 abstract description 4
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 3
- 230000006698 induction Effects 0.000 abstract 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 description 8
- 239000011734 sodium Substances 0.000 description 8
- 229910052708 sodium Inorganic materials 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 239000011591 potassium Substances 0.000 description 5
- 229910052700 potassium Inorganic materials 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 239000006229 carbon black Substances 0.000 description 4
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 4
- 239000002367 phosphate rock Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 239000006227 byproduct Substances 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 239000010436 fluorite Substances 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- WTEOIRVLGSZEPR-UHFFFAOYSA-N boron trifluoride Chemical compound FB(F)F WTEOIRVLGSZEPR-UHFFFAOYSA-N 0.000 description 2
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- RIUWBIIVUYSTCN-UHFFFAOYSA-N trilithium borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-] RIUWBIIVUYSTCN-UHFFFAOYSA-N 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- 229910015900 BF3 Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B35/00—Boron; Compounds thereof
- C01B35/06—Boron halogen compounds
- C01B35/063—Tetrafluoboric acid; Salts thereof
- C01B35/066—Alkali metal tetrafluoborates
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
Abstract
The invention relates to a method for preparing lithium tetrafluoroborate by fluosilicic acid, which comprises the following steps: 1) Reacting fluosilicic acid with ammonia water to prepare a solution containing silica sol crystal seeds; 2) Mixing fluosilicic acid and boric acid, heating to 60-90 ℃, adding the solution containing the silica sol crystal seeds, reacting for 1-2h, carrying out solid-liquid separation, and precipitating to obtain silica; 3) Adding lithium carbonate into the filtrate, stirring for reaction to obtain lithium tetrafluoroborate aqueous solution, heating for evaporating the solvent, and drying to obtain a lithium tetrafluoroborate crude product. Under the induction of the silicon dioxide seed crystal, the reaction of the fluosilicic acid and the boric acid is quicker and more sufficient, and fluorine resources are better utilized; on the basis, the fluoboric acid is converted into high-value lithium tetrafluoroborate, so that the economic benefit is good. The method overcomes the defects of insufficient fluorine resource utilization and poor economic benefit in the prior fluosilicic acid.
Description
Technical Field
The invention belongs to the technical field of low-grade fluosilicic acid utilization, and particularly relates to a method for preparing lithium tetrafluoroborate serving as a lithium battery electrolyte by utilizing fluosilicic acid.
Background
Fluorine is an important strategic resource, and fluorine in nature comes from the minerals fluorite and phosphate rock. Fluorite has limited reserves despite its high fluorine content, and the fluorite resource is becoming depleted over the years of exploitation. The phosphorus ore has large accumulation and contains 3 to 4 percent of fluorine, which is an important fluorine resource. When acidolysis phosphorite is used for producing wet phosphoric acid, sulfuric acid is generally used for treating phosphate rock, and a large amount of water-based fluosilicic acid is produced as a byproduct; because the byproduct fluosilicic acid is not completely recycled, a great amount of fluorine resources are wasted in the tail gas of the phosphate fertilizer every year. The preparation of high-value fluoride by using low-grade fluosilicic acid is one of the process routes with better economic benefit in comprehensive utilization of resources. In the prior art, fluosilicic acid is further processed into inorganic fluosilicate products such as sodium fluosilicate, potassium fluosilicate and the like, however, the market demand of sodium fluosilicate and potassium fluosilicate is limited, the price is lower, and the economic benefit is poor.
Chinese patent CN101289195B discloses a method for preparing potassium fluoborate and co-producing white carbon black and sodium fluosilicate by fluosilicic acid: (1) Firstly, fluosilicic acid is added into a leaching tank, then, the leaching tank is preheated to 60-100 ℃, stirring is started, theoretical amount of boric acid is added into the fluosilicic acid, the reaction is continued for 2.0-6.0 hours in a sealing way, and leaching is carried out at the constant temperature of 60-100 ℃; (2) Filtering the qualified fluoboric acid solution, concentrating and washing the white carbon black step by using hierarchical water, and drying to obtain a white carbon black product; (3) Adding industrial salt into the filtrate and the first washing liquid to purify and desilicate, adding theoretical amount of industrial salt, and reacting for 10-30 minutes to obtain sodium fluosilicate slurry; (4) Filtering, washing and drying the prepared sodium fluosilicate slurry to obtain a sodium fluosilicate product, and using filtrate for synthesizing potassium fluoborate; (5) Adding theoretical amount of potassium chloride into the filtrate obtained in the step (4), and reacting for 10-30 minutes; (6) And (3) after the reaction in the step (5) is completed, filtering, washing the ointment with water once, and drying to obtain the potassium fluoborate. In the process, the reaction in the step (1) is incomplete, and the residual fluosilicic acid reacts with industrial salt in the step (3) to generate sodium fluosilicate, so that the sodium fluosilicate has lower value, and important fluorine resources are difficult to recycle.
Meanwhile, with the vigorous development of the lithium battery industry, lithium tetrafluoroborate is gradually becoming a shortage of lithium battery raw materials. The addition of a certain proportion of lithium tetrafluoroborate to the battery electrolyte can significantly improve the low temperature performance and the tolerance to moisture of the battery, so the market demand and price of lithium tetrafluoroborate are also increasing year by year. However, the preparation of lithium tetrafluoroborate generally requires the consumption of more hydrogen fluoride or boron trifluoride, both of which are expensive and economically disadvantageous. Based on this, the present application was developed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for preparing lithium tetrafluoroborate serving as a lithium battery electrolyte by using fluosilicic acid, which can overcome the defects of insufficient utilization of fluorine resources and poor economic benefit in the prior fluosilicic acid.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for preparing lithium tetrafluoroborate from fluosilicic acid, comprising the following steps:
1) Preparing sol by reacting fluosilicic acid with ammonia water, and preparing solution containing silica sol crystal seeds as silica crystal seeds for standby;
2) Mixing fluosilicic acid and boric acid, heating to 60-90 ℃, adding the solution containing the silica sol crystal seeds, reacting for 1-2h to generate fluoboric acid and silica precipitate, and carrying out solid-liquid separation to obtain silica;
3) Adding lithium carbonate into the filtrate, stirring and reacting to generate lithium tetrafluoroborate, obtaining lithium tetrafluoroborate aqueous solution, heating and evaporating the solvent, and drying to obtain lithium tetrafluoroborate crude product.
Specifically, in the step 1), fluosilicic acid and ammonia water are rapidly mixed within 15 seconds, the silica seed crystal is prepared by reaction, and the pH value of the reaction end point is controlled between 6.5 and 7.5. Further, the concentration of the ammonia water is 10-30%, and the concentration of the fluosilicic acid is 10-40%.
Specifically, in the step 2), the molar ratio of the fluosilicic acid to the boric acid is 1 (1.5-1.6).
Further, the silicon dioxide sol seed crystal is used in an amount of 0.6 to 1.4 percent by weight of the fluosilicic acid. The solution is reacted for 1 to 2 hours at the temperature of 60 to 90 ℃ and fluosilicic acid is hardly detected after the reaction is finished. The silica separated by filtration can be directly sold as white carbon black after being cleaned.
Specifically, in the step 3), the molar number of the added lithium carbonate is 0.8-0.9 times of that of the fluosilicic acid, and the lithium carbonate is slightly excessive, so that the fluoboric acid is ensured to fully react. The heating evaporation temperature is 110-120 ℃, a small amount of ammonium carbonate is decomposed and volatilized, and the obtained solid is a lithium tetrafluoroborate crude product and contains a small amount of lithium carbonate, lithium borate and lithium fluoride impurities.
Further preferably, in the step 3), the lithium tetrafluoroborate crude product is dissolved in an anhydrous organic solvent, insoluble impurities are removed by filtration, then molecular sieve is added and stirred for 30-60min to remove water, molecular sieve is filtered, and concentrated, crystallized and dried to obtain a high-purity lithium tetrafluoroborate finished product.
Furthermore, the anhydrous organic solvent can be one of dimethyl carbonate, diethyl ether and the like, the dosage of the anhydrous organic solvent is 8-12 times of the weight of the crude lithium tetrafluoroborate, and impurities such as lithium carbonate, lithium borate, lithium fluoride and the like are insoluble in the organic solvent and removed after filtration.
Further, the molecular sieve is selected from one of 3A, 4A, 5A and the like, and the dosage of the molecular sieve is 0.2-0.6 times of the weight of the lithium tetrafluoroborate crude product; filtering molecular sieve, concentrating at 60-100deg.C to 10-30% of original volume, and cooling to 5-10deg.C to precipitate lithium tetrafluoroborate crystal. The molecular sieve can be reused after regeneration, and the mother liquor can also be returned for use.
Further, specific parameters of drying are as follows: drying for 2-5 hours at the temperature of 90-120 ℃ and the vacuum degree of-60 kpa to-90 kpa to obtain a high-purity lithium tetrafluoroborate finished product.
The chemical reactions involved in the preparation process are as follows:
H 2 SiF 6 + 6NH 3 ·H 2 O → 6NH 4 F + SiO 2 ↓+ 4H 2 O
2H 2 SiF 6 + 3H 3 BO 3 → 3HBF 4 + 2SiO 2 ↓+ 5H 2 O
2HBF 4 + Li 2 CO 3 → 2LiBF 4 + CO 2 ↑ + H 2 O 。
compared with the prior art, the method has the following beneficial effects:
under the induction of the silicon dioxide seed crystal, the fluosilicic acid reacts with boric acid faster and more fully, so that fluorine resources are better utilized; on the basis, the fluoboric acid is converted into high-value lithium tetrafluoroborate, so that the economic benefit is good. The method overcomes the defects of insufficient fluorine resource utilization and poor economic benefit in the prior fluosilicic acid.
Detailed Description
The following describes the technical scheme of the present invention in further detail with reference to examples, but the scope of the present invention is not limited thereto.
In the examples below, the starting materials used were all commercially available products which were commercially available as they are. Percentages refer to mass percentages unless otherwise indicated. The fluosilicic acid is derived from byproducts generated in the process of producing phosphoric acid by acidolysis of phosphorite in a certain chemical plant.
Example 1
The method for preparing lithium tetrafluoroborate by fluosilicic acid specifically comprises the following steps:
1) 100g of 20% fluosilicic acid and 150g of 20% ammonia water are used for quick reaction to prepare a solution containing silica sol crystal seeds, and the pH=7.2;
2) Adding 65g boric acid into 500g fluosilicic acid with concentration of 20%, stirring and heating to 60 ℃ to dissolve completely, adding 20g of silica sol seed crystal solution, reacting for 2h to generate fluoboric acid and silica precipitate, and filtering to remove silica; at this time, the fluosilicic acid content in the filtrate is detected to be 0.02%;
3) Adding 42g of lithium carbonate into the filtrate, stirring and reacting for 20min to obtain lithium tetrafluoroborate aqueous solution, heating to 110 ℃ to completely evaporate water, and continuing heating for 3h to obtain 99.5g of dried lithium tetrafluoroborate crude product;
4) Dissolving the lithium tetrafluoroborate crude product in 800g of dimethyl carbonate, filtering to remove insoluble impurities, adding 20g of 3A molecular sieve, stirring for 40min, filtering out the molecular sieve, evaporating the solvent at 100 ℃ to concentrate to 30% of the original volume, and cooling to 5 ℃ to crystallize and precipitate the lithium tetrafluoroborate. Drying for 2 hours at the temperature of 120 ℃ and the vacuum degree of-90 kpa to obtain 84g of high-purity lithium tetrafluoroborate, wherein the purity is 99.96%, the water content is 12ppm, and the requirements of lithium battery electrolyte are met.
Example 2
The method for preparing lithium tetrafluoroborate by fluosilicic acid specifically comprises the following steps:
1) 100g of 20% fluosilicic acid and 146g of 20% ammonia water are used for quick reaction to prepare a solution containing silica sol crystal seeds, and the pH=6.5;
2) Adding 68g boric acid into 500g fluosilicic acid with concentration of 20%, stirring and heating to 90 ℃ to dissolve completely, adding 40g of silica sol seed solution, reacting for 1h to generate fluoboric acid and silica precipitate, and filtering to remove silica; at this time, the fluosilicic acid content in the filtrate is detected to be 0.01%;
3) Adding 46g of lithium carbonate into the filtrate, stirring and reacting for 20min to obtain a lithium tetrafluoroborate aqueous solution, heating to 120 ℃ to completely evaporate water, and continuing heating for 3h to obtain 105.9g of dried lithium tetrafluoroborate crude product;
4) Dissolving the lithium tetrafluoroborate crude product in 1270g diethyl ether, filtering to remove insoluble impurities, adding 63g of 4A molecular sieve, stirring for 40min, filtering out the molecular sieve, concentrating the evaporated solvent at 60 ℃ to 10% of the original volume, and cooling to 10 ℃ to crystallize and precipitate lithium tetrafluoroborate. Drying for 5 hours at the temperature of 90 ℃ and the vacuum degree of-60 kpa to obtain 89g of high-purity lithium tetrafluoroborate, wherein the purity is 99.94%, the water content is 14ppm, and the requirements of lithium battery electrolyte are met.
Comparative example
In order to highlight the effect of adding silica sol seed crystal in the invention, experiments without adding silica sol seed crystal are specially designed, and the silica sol seed crystal is eliminated on the basis of the embodiment 1, and the specific steps are as follows:
1) Adding 65g of boric acid into 500g of 20% fluosilicic acid, stirring and heating to 60 ℃ to dissolve completely, reacting for 2h to generate fluoboric acid and silica precipitate, and filtering to remove silica; at this time, the fluosilicic acid content in the filtrate is detected to be 3.7%;
2) 42g of lithium carbonate is added into the filtrate, and stirring reaction is carried out for 20min to obtain a lithium tetrafluoroborate aqueous solution, the solution is heated to 110 ℃ to fully evaporate water, and heating is continued for 3h to obtain 110g of a mixture mainly comprising lithium fluoroborate and lithium hexafluorosilicate.
Claims (10)
1. A method for preparing lithium tetrafluoroborate by fluosilicic acid, which is characterized by comprising the following steps:
1) Reacting fluosilicic acid with ammonia water to prepare a solution containing silica sol crystal seeds;
2) Mixing fluosilicic acid and boric acid, heating to 60-90 ℃, adding the solution containing the silica sol crystal seeds, reacting for 1-2h, carrying out solid-liquid separation, and precipitating to obtain silica;
3) Adding lithium carbonate into the filtrate, stirring for reaction to obtain lithium tetrafluoroborate aqueous solution, heating for evaporating the solvent, and drying to obtain a lithium tetrafluoroborate crude product.
2. The method for preparing lithium tetrafluoroborate from fluosilicic acid according to claim 1, wherein in step 1), fluosilicic acid and ammonia water are rapidly mixed within 15 seconds, and the pH value of the reaction end point is controlled between 6.5 and 7.5.
3. The method for preparing lithium tetrafluoroborate from fluorosilicic acid according to claim 2, wherein the concentration of ammonia water is 10-30% and the concentration of fluorosilicic acid is 10-40%.
4. The method for preparing lithium tetrafluoroborate from fluorosilicic acid according to claim 1, wherein in step 2), the molar ratio of fluorosilicic acid to boric acid is 1 (1.5-1.6).
5. The method of preparing lithium tetrafluoroborate from fluorosilicic acid according to claim 4, wherein the silica sol seed is used in an amount of 0.6 to 1.4% by weight of the fluorosilicic acid.
6. The method for preparing lithium tetrafluoroborate from fluorosilicic acid according to claim 1, wherein in step 3), the molar amount of lithium carbonate added is 0.8 to 0.9 times the molar amount of fluorosilicic acid, and the heating evaporation temperature is 110 to 120 ℃.
7. The method for preparing lithium tetrafluoroborate by fluosilicic acid according to claim 1, wherein in step 3), the crude lithium tetrafluoroborate is dissolved in anhydrous organic solvent, insoluble impurities are removed by filtration, molecular sieve is added and stirred for 30-60min to remove water, molecular sieve is filtered, and concentrated, crystallized and dried to obtain the finished lithium tetrafluoroborate product.
8. The method for preparing lithium tetrafluoroborate by fluosilicic acid as claimed in claim 7, wherein the anhydrous organic solvent is one of dimethyl carbonate and diethyl ether, and the amount of the anhydrous organic solvent is 8-12 times of the weight of the crude lithium tetrafluoroborate.
9. The method for preparing lithium tetrafluoroborate from fluosilicic acid according to claim 7, wherein the molecular sieve is one of 3A, 4A and 5A types, and the amount of the molecular sieve is 0.2-0.6 times of the weight of the crude lithium tetrafluoroborate; filtering molecular sieve, concentrating at 60-100deg.C to 10-30% of original volume, and cooling to 5-10deg.C to precipitate lithium tetrafluoroborate crystal.
10. The method for preparing lithium tetrafluoroborate from fluorosilicic acid according to claim 7, wherein the specific parameters of drying are: drying at 90-120 deg.c and vacuum degree of-60 kpa to-90 kpa for 2-5 hr.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311063499.6A CN117303389A (en) | 2023-08-23 | 2023-08-23 | Method for preparing lithium tetrafluoroborate from fluosilicic acid |
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| CN202311063499.6A CN117303389A (en) | 2023-08-23 | 2023-08-23 | Method for preparing lithium tetrafluoroborate from fluosilicic acid |
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