CN115974106B - Sodium hexafluorophosphate and recrystallization method thereof - Google Patents
Sodium hexafluorophosphate and recrystallization method thereof Download PDFInfo
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- -1 Sodium hexafluorophosphate Chemical compound 0.000 title claims abstract description 82
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000001953 recrystallisation Methods 0.000 title claims abstract description 14
- 239000002904 solvent Substances 0.000 claims abstract description 76
- 239000000843 powder Substances 0.000 claims abstract description 35
- 239000012047 saturated solution Substances 0.000 claims abstract description 30
- 239000002244 precipitate Substances 0.000 claims abstract description 16
- 239000007787 solid Substances 0.000 claims abstract description 16
- 238000001914 filtration Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 9
- 230000007935 neutral effect Effects 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims description 57
- 239000000243 solution Substances 0.000 claims description 24
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 20
- 239000012265 solid product Substances 0.000 claims description 16
- 230000032683 aging Effects 0.000 claims description 14
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 10
- WQDUMFSSJAZKTM-UHFFFAOYSA-N Sodium methoxide Chemical compound [Na+].[O-]C WQDUMFSSJAZKTM-UHFFFAOYSA-N 0.000 claims description 10
- 239000011734 sodium Substances 0.000 claims description 8
- 229910052708 sodium Inorganic materials 0.000 claims description 8
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical group COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 6
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 239000012452 mother liquor Substances 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 3
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 2
- QDRKDTQENPPHOJ-UHFFFAOYSA-N sodium ethoxide Chemical compound [Na+].CC[O-] QDRKDTQENPPHOJ-UHFFFAOYSA-N 0.000 claims 1
- 239000012670 alkaline solution Substances 0.000 abstract description 7
- 239000007864 aqueous solution Substances 0.000 abstract description 3
- 230000003287 optical effect Effects 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- YWOITFUKFOYODT-UHFFFAOYSA-N methanol;sodium Chemical compound [Na].OC YWOITFUKFOYODT-UHFFFAOYSA-N 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Classifications
-
- 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
Abstract
The invention provides sodium hexafluorophosphate and a recrystallization method thereof. The method comprises the following steps: s1, providing sodium hexafluorophosphate powder, a first solvent and a second solvent, wherein the moisture of the sodium hexafluorophosphate powder, the first solvent and the second solvent are controlled below 20ppm, the first solvent is a good solvent of the sodium hexafluorophosphate powder, the second solvent is a poor solvent of the sodium hexafluorophosphate powder, and the first solvent and the second solvent are mutually insoluble; s2, dissolving the sodium hexafluorophosphate powder in the first solvent to form a saturated solution; s3, deacidifying the saturated solution to be neutral by using an alkaline solution, wherein the alkaline solution is a non-aqueous solution; s4, adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain solid precipitate; and S5, filtering and drying the solid precipitate to obtain recrystallized sodium hexafluorophosphate.
Description
Technical Field
The invention relates to sodium hexafluorophosphate and a recrystallization method thereof.
Background
Sodium hexafluorophosphate (chemical formula: naPF) 6 ) Is an inorganic compound, colorless crystalline powder. Is sensitive to air and carbon dioxide, relative density 2.36919. The storage should be moisture-proof, and the materials are stored in a closed container, and placed in a cool, dry and well ventilated place, and far away from incompatible materials. Corrosive articles, inhalation, skin contact and ingestionHarmful, proper protective clothing, gloves and goggles or masks should be worn during the experiment. Sodium hexafluorophosphate is mainly used for preparing other hexafluorophosphates (lithium hexafluorophosphate and the like), and can also be used as sodium salt of sodium ion battery electrolyte.
At present, the existing sodium hexafluorophosphate in the market is mostly presented in a powder form (the particle size is below 0.1 mm), and has the following characteristics: 1. the pungent smell of the chemical is great; the hygroscopicity is strong, so that the fluidity is poor, and the adhesive agglomeration is easy; 3. low purity and high production cost.
Disclosure of Invention
The invention provides sodium hexafluorophosphate and a recrystallization method thereof, which can effectively solve the problems.
The invention is realized in the following way:
the invention provides a recrystallization method of sodium hexafluorophosphate, which comprises the following steps:
s1, providing sodium hexafluorophosphate powder, a first solvent and a second solvent, wherein the moisture of the sodium hexafluorophosphate powder, the first solvent and the second solvent are controlled below 20ppm, the first solvent is a good solvent of the sodium hexafluorophosphate powder, the second solvent is a poor solvent of the sodium hexafluorophosphate powder, and the first solvent and the second solvent are mutually insoluble;
s2, dissolving the sodium hexafluorophosphate powder in the first solvent to form a saturated solution;
s3, deacidifying the saturated solution to be neutral by using an alkaline solution, wherein the alkaline solution is a non-aqueous solution;
s4, adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain solid precipitate;
and S5, filtering and drying the solid precipitate to obtain recrystallized sodium hexafluorophosphate.
The invention further provides sodium hexafluorophosphate obtained by the method, wherein the sodium hexafluorophosphate is cuboid, particles with the particle size of more than 0.90 multiplied by 0.40 multiplied by 0.4mm account for more than 45% of the solid product, and the purity is more than or equal to 99.9%.
The beneficial effects of the invention are as follows: the sodium hexafluorophosphate and the recrystallization method thereof have the advantages that firstly, the solvent source is wide, the process is simple, the product is easy to separate, and the yield is higher than 90 percent. Secondly, the crystal grain of the sodium hexafluorophosphate is larger, and is not easy to absorb moisture, so that the sodium hexafluorophosphate is not easy to adhere and agglomerate, has good fluidity, is easy to store and transport, and is more beneficial to realizing subsequent mechanized production.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flow chart of a recrystallization method of sodium hexafluorophosphate provided by the embodiment of the invention.
Fig. 2 is a photomicrograph of sodium hexafluorophosphate provided by an embodiment of the present invention.
Fig. 3 is a photograph of sodium hexafluorophosphate provided in an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
In the description of the present invention, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Referring to fig. 1-3, an embodiment of the present invention provides a recrystallization method of sodium hexafluorophosphate, comprising the steps of:
s1, providing sodium hexafluorophosphate powder, a first solvent and a second solvent, wherein the moisture of the sodium hexafluorophosphate powder, the first solvent and the second solvent are controlled below 20ppm, the first solvent is a good solvent of the sodium hexafluorophosphate powder, the second solvent is a poor solvent of the sodium hexafluorophosphate powder, and the first solvent and the second solvent are mutually insoluble;
s2, dissolving the sodium hexafluorophosphate powder in the first solvent to form a saturated solution;
s3, deacidifying the saturated solution to be neutral by using an alkaline solution, wherein the alkaline solution is a non-aqueous solution;
s4, adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain solid precipitate;
and S5, filtering and drying the solid precipitate to obtain recrystallized sodium hexafluorophosphate.
In step S1, the sodium hexafluorophosphate powder may be selected from commercially available sodium hexafluorophosphate powders having a purity of 98wt% or more. The particle size of the sodium hexafluorophosphate powder is generally below 0.1mm, and the sodium hexafluorophosphate powder is small in particle size and low in purity, so that the sodium hexafluorophosphate powder is easy to absorb moisture and has great pungent smell, and finally poor in fluidity, easy to adhere and agglomerate and difficult to apply to subsequent mechanical production. Further, since moisture greatly affects the product to be recrystallized later, it is necessary to dry the sodium hexafluorophosphate powder so that the moisture is controlled to 20ppm or less. This is because after recrystallization, moisture is carried into the final product, affecting the morphology and purity of the final product.
The first solvent is preferably selected from the group consisting of dimethyl carbonate, dimethyl sulfoxide, and mixtures thereof. In one embodiment, the first solvent is selected from dimethyl carbonate.
The second solvent is preferably selected from n-pentane, cyclohexane, hexane and mixtures thereof. In one embodiment, the second solvent is selected from n-pentane.
In step S2, as a further improvement, the step of dissolving sodium hexafluorophosphate powder in the first solvent to form a saturated solution includes:
s21, adding a small amount of sodium hexafluorophosphate powder into the first solvent for multiple times, stirring and dissolving until a saturated solution is formed;
and S22, aging the saturated solution for 5-16 hours, and then filtering.
In step S21, the saturated solution is formed until the sodium hexafluorophosphate powder is no longer dissolved, which will not be described here.
In step S22, the saturated solution is preferably aged for 8-12 hours, and in one embodiment, the saturated solution is aged for about 10 hours, and insoluble fine impurities may be filtered by sedimentation and coagulation. In other embodiments, filtration is performed three times with a 0.1 μm PTFE filter membrane.
In step S3, the sodium hexafluorophosphate powder is acidic mainly due to the presence of hydrofluoric acid, which is corrosive and affects the performance and quality of the overall product, and accelerates the deterioration of the product and increases the insoluble content. Therefore, deacidification is required. As a further improvement, the step of deacidifying the saturated solution to neutrality with an alkaline solution comprises:
and S31, deacidifying the saturated solution to be neutral by using a sodium alkoxide/alcohol solution, wherein the dosage of the sodium alkoxide/alcohol solution is controlled within 5V% of the saturated solution.
In step S31, the sodium alkoxide/alcohol solution may be small molecule sodium alkoxide and its corresponding alcohol solution, for example, sodium methoxide/anhydrous methanol; sodium ethoxide/absolute ethanol, and the like. Since the sodium alkoxide/alcohol solution is not dissolved in the second solvent, the generation of subsequent impurities can be reduced.
In step S4, as a further improvement, the step of adding the second solvent to the deacidified saturated solution and recrystallizing to obtain a solid precipitate includes:
s41, slowly dropwise adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain solid precipitate, wherein the volume ratio of the second solvent to the first solvent is 1.8-2.1:1. In step S41, during the re-dripping process, stirring is not performed, so that the subsequent crystal forms are prevented from being damaged and large particles cannot be formed.
Preferably, the volume ratio of the second solvent to the first solvent is 1.9-2.05:1. In one embodiment, the volume ratio of the second solvent to the first solvent is about 2:1. Experiments prove that the volume ratio of the second solvent to the first solvent is about 2:1, so that sodium hexafluorophosphate can be basically recrystallized, and sodium hexafluorophosphate can not be recrystallized and separated out almost along with the addition of the second solvent. Further, the experiment proves that the addition of the second solvent also has an influence on the subsequent increase of the particle size of the sodium hexafluorophosphate.
In order to significantly increase the particle size of the sodium hexafluorophosphate, further, after step S41, as a further improvement, the method further comprises:
s42, aging the solid precipitate and the mother liquor for 8-15 h at normal temperature.
Preferably, in step S42, the solid precipitate and the mother liquor are aged at normal temperature for 9 to 11 hours to further increase the particle size of the sodium hexafluorophosphate. In one embodiment, the solid precipitate and the mother liquor are aged for about 10 hours at ambient temperature.
The embodiment of the invention further provides sodium hexafluorophosphate obtained by the method, wherein the sodium hexafluorophosphate is cuboid, particles with the particle size of more than 0.90mm multiplied by 0.40 multiplied by 0.4mm account for more than 45% of the solid product, and the purity is more than or equal to 99.9%.
Example 1: into a 250ml polyethylene plastic bottle, 100ml of a dimethyl carbonate solution was added, and 25.0450g of sodium hexafluorophosphate was weighed and added to dimethyl carbonate while stirring a small amount of the solution for dissolution. After complete dissolution, a saturated solution of sodium hexafluorophosphate/dimethyl carbonate was formed, which was aged for 12 hours, filtered three times with a 0.1. Mu.M PTFE filter membrane, and the filtrate was neutralized with 3mol/L sodium methoxide (0.81 g)/anhydrous methanol (5 ml) to a neutral solution. 200ml of n-pentane solution were added dropwise, with a drop rate of 1ml/10min. And (5) aging for 12 hours after the dripping is finished, and filtering and drying until the quality is constant. 23.5405g were obtained in a yield of 94.0% and a purity of 99.9%. The particle morphology is mainly cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90×0.40×0.4mm, and the particles account for about 50% of the solid product, see fig. 2.
Example 2:
substantially the same as in example 1, except that: 210ml of n-pentane solution were added dropwise, with a drop rate of 1ml/10min. 23.5417g were obtained in a yield of 94.0% and a purity of 99.9%. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 49% of the solid product.
Example 3:
substantially the same as in example 1, except that: 180ml of n-pentane solution were added dropwise, with a drop rate of 1ml/10min. 23.2668g were obtained in 92.9% yield and 99.9% purity. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 50% of the solid product.
Example 4:
substantially the same as in example 1, except that: and (5) aging for 8 hours after the dripping is finished, and filtering and drying until the quality is constant. 23.7172g were obtained in a yield of 93.9% and a purity of 99.9%. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and accounts for about 45% of the solid product. It can be seen that aging after completion of the dropwise addition determines the ratio of the subsequent large particles.
Example 5:
substantially the same as in example 1, except that: and (5) aging for 15 hours after the dripping is finished, and filtering and drying until the quality is constant. 23.5673g were obtained in a yield of 94.1% and a purity of 99.8%. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 50% of the solid product. As can be seen, the proportion of large particles is not increased substantially and the purity is reduced to a certain extent as the aging time reaches 15 hours.
Comparative example 1:
substantially the same as in example 1, except that: 250ml of n-pentane solution was added dropwise, with a drop rate of 1ml/10min. 23.4922g were obtained in a yield of 93.8% and a purity of 99.9%. The particle shape is mainly cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 41% of the solid product. It follows that as the n-pentane solution increases, its large particle solid product duty cycle decreases significantly.
Comparative example 2:
substantially the same as in example 1, except that: 150ml of n-pentane solution were added dropwise, with a drop rate of 1ml/10min. 21.4635g were obtained in a yield of 85.7% and a purity of 99.9%. The particle shape is mainly cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 47% of the solid product. It follows that as the n-pentane solution decreases, its yield decreases significantly.
Comparative example 3:
substantially the same as in example 1, except that: neutralization to a neutral solution was carried out without sodium methoxide (0.81 g)/absolute methanol (5 ml). 25.5923g were obtained in a yield of 94.2% and a purity of 99.1%. The particle shape is mainly cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particles account for about 42% of the solid product. It can be seen that the impurities of the final product increased significantly since neutralization was not performed using sodium methoxide (0.81 g)/absolute methanol (5 ml).
Comparative example 4:
substantially the same as in example 1, except that: and (5) aging for 5 hours after the dripping is finished, and filtering and drying until the quality is constant. 23.4421g were obtained in a yield of 93.6% and a purity of 99.9%. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particles account for about 42% of the solid product. It follows that the ratio of large-particle solid products decreases significantly with decreasing aging time.
Comparative example 5:
substantially the same as in example 1, except that: and (5) aging for 20 hours after the dripping is finished, and filtering and drying until the quality is constant. 23.3669g were obtained in a yield of 93.3% and a purity of 99.7%. The particle shape is a cuboid when observed by an optical microscope, and the particle diameter measured by a particle size analyzer is more than 0.90 multiplied by 0.40 multiplied by 0.4mm, and the particle accounts for about 46% of the solid product. It can be seen that the ratio of the large-particle solid product is also reduced to some extent with the increase of the aging time, and impurities are reattached to the large particles with the increase of the aging time, so that the purity is reduced to some extent.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, and various modifications and variations may be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A method for recrystallizing sodium hexafluorophosphate, comprising the steps of:
s1, providing sodium hexafluorophosphate powder, a first solvent and a second solvent, wherein the moisture of the sodium hexafluorophosphate powder, the first solvent and the second solvent are controlled below 20ppm, the first solvent is a good solvent of the sodium hexafluorophosphate powder, the second solvent is a poor solvent of the sodium hexafluorophosphate powder, and the first solvent and the second solvent are mutually insoluble;
s2, dissolving the sodium hexafluorophosphate powder in the first solvent to form a saturated solution;
s3, deacidifying and adjusting the saturated solution to be neutral by using a sodium alkoxide/alcohol solution, wherein the dosage of the sodium alkoxide/alcohol solution is controlled within 5V percent of the saturated solution, and the sodium alkoxide/alcohol solution is sodium methoxide/anhydrous methanol solution or sodium ethoxide/anhydrous ethanol solution;
s4, adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain solid precipitate;
s5, filtering and drying the solid precipitate to obtain recrystallized sodium hexafluorophosphate;
the first solvent is selected from dimethyl carbonate, dimethyl sulfoxide and mixtures thereof; the second solvent is selected from the group consisting of n-pentane, cyclohexane, hexane, and mixtures thereof.
2. The recrystallization method of sodium hexafluorophosphate as claimed in claim 1, wherein in step S2, the step of dissolving sodium hexafluorophosphate powder in the first solvent to form a saturated solution comprises:
s21, adding a small amount of sodium hexafluorophosphate powder into the first solvent for multiple times, stirring and dissolving until a saturated solution is formed;
and S22, aging the saturated solution for 5-16 hours, and then filtering.
3. The recrystallization method of sodium hexafluorophosphate as claimed in claim 1, wherein in the step S4, the step of adding the second solvent to the deacidified saturated solution for recrystallization to obtain solid precipitate comprises:
s41, slowly dropwise adding the second solvent into the deacidified saturated solution, and recrystallizing to obtain a solid precipitate, wherein the volume ratio of the second solvent to the first solvent is 1.8-2.1:1.
4. The method for recrystallizing sodium hexafluorophosphate as defined in claim 3, further comprising, after step S41:
and S42, aging the solid precipitate and the mother liquor for 8-15 hours at normal temperature.
5. The recrystallization method of sodium hexafluorophosphate according to claim 1, wherein the purity of the sodium hexafluorophosphate powder is 98.0% by weight or more.
6. Sodium hexafluorophosphate obtained by the process according to any one of claims 1 to 5, which is rectangular parallelepiped, and has a particle size of 0.90×0.40×0.4mm or more, 45% or more of the solid product, and a purity of 99.9% or more.
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