CN118004986A - A preparation method of battery-grade sodium metaphosphate and sodium hexafluorophosphate - Google Patents
A preparation method of battery-grade sodium metaphosphate and sodium hexafluorophosphate Download PDFInfo
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Abstract
The invention provides a preparation method of battery grade sodium metaphosphate and sodium hexafluorophosphate, which aims to solve the technical problems that the existing production process of sodium hexafluorophosphate is complex and the requirement on production equipment is high. The invention uses high-purity sodium hydroxide to remove impurities, and cooperates with the subsequent concentration crystallization and special gradient temperature drying process, so that the finally obtained sodium metaphosphate has less than 1ppm of iron, less than 5ppm of calcium and magnesium and less than 10ppm of potassium, and can meet the technical index requirements of battery-grade sodium metaphosphate. On the basis, the battery grade sodium metaphosphate is used as a raw material, and reacts with hydrofluoric acid to prepare a sodium hexafluorophosphate synthetic solution, and then the synthetic solution is filtered, centrifuged at a high speed, dried at a negative pressure and then vacuum-packed to obtain the battery grade sodium hexafluorophosphate. The invention omits the step of preparing hexafluorophosphoric acid in the traditional preparation process, so that the production process is simplified and safer; the invention has lower requirements on production equipment because of no need of configuration of hexafluorophosphoric acid.
Description
Technical Field
The invention relates to a preparation method of sodium hexafluorophosphate, in particular to a preparation method of sodium hexafluorophosphate with impurity content meeting the technical requirements of batteries and capable of mass production.
Background
Sodium hexafluorophosphate is a commonly used electrolyte, can be used as a catalyst, an acid catalyst and a dehydrating agent in chemical experiments and industrial production, and is widely applied to the fields of batteries, electrolyte, surfactants, catalysts and the like. In addition, sodium hexafluorophosphate can also be used in the fields of organic synthesis, high temperature lubricants, analytical chemistry, and the like.
The sodium hexafluorophosphate is mainly used for producing energy storage batteries to replace a part of lithium hexafluorophosphate as electrolyte, and is favored by the battery industry at a price far lower than that of lithium hexafluorophosphate and the availability of sodium ions. At present, sodium hexafluorophosphate is mainly produced by referring to the process of lithium hexafluorophosphate, and the traditional preparation method is to modify the production equipment of lithium hexafluorophosphate to produce according to the lithium hexafluorophosphate, however, the production process does have the defects of complex process and high requirement on the production equipment.
Disclosure of Invention
The invention provides a preparation method of battery grade sodium hexafluorophosphate, which aims to solve the technical problems that the existing production process of sodium hexafluorophosphate is complex and the requirement on production equipment is high.
The invention researches a preparation method of battery grade sodium hexafluorophosphate and also researches a preparation method of battery grade sodium metaphosphate.
The technical scheme of the invention is as follows:
the preparation method of the battery grade sodium metaphosphate is characterized by comprising the following steps:
Step 1.1, diluting the electronic grade phosphoric acid to a phosphoric acid solution with the mass fraction of 35-45% by using ultrapure water;
Step 1.2, adding a high-purity sodium hydroxide solution with the mass fraction of 18-22% into the phosphoric acid solution, and adjusting the pH value to be 1-2 to obtain a sodium dihydrogen phosphate synthetic solution; the content of iron in the high-purity sodium hydroxide solution is less than 1ppm, and the content of magnesium and calcium is less than 5ppm; the mass ratio of the high-purity sodium hydroxide solution to the phosphoric acid solution is 1:1.2-1.3; the pH value is adjusted to be 1-2 in the step to help the impurity metal ions to be fully dissolved so as to improve the purity of the sodium dihydrogen phosphate crystal obtained later.
Step 2: preparation of sodium dihydrogen phosphate crystals
Step 2.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic liquid, and stopping heating after concentrating to obtain crystals;
Step 2.2, cooling to 45-50 ℃ to ensure that impurity ions are fully dissolved in the solution, preserving heat for 2-3 hours to fully precipitate sodium dihydrogen phosphate, taking out the crystals after a large amount of crystallization occurs, centrifuging and moderately washing with water, wherein the iron content is less than 1ppm, the calcium and magnesium content are less than 5ppm, and the potassium content is less than 10ppm to obtain sodium dihydrogen phosphate crystals;
Step 3: preparation of Battery grade sodium metaphosphate
Step 3.1, drying the sodium dihydrogen phosphate crystal gradient:
Drying the sodium dihydrogen phosphate crystal at 200-250 ℃ for 2-3 hours, crushing, and then drying at 550-600 ℃ for 2-3 hours, wherein the water content is controlled to be less than 0.05%, thus obtaining sodium metaphosphate lump materials;
And 3.2, crushing the sodium metaphosphate lump material, and sieving the crushed sodium metaphosphate lump material by a sieve with the mesh number of at least 200 meshes to obtain the battery grade sodium metaphosphate with very fine granularity. When the battery grade sodium metaphosphate is used as a raw material for preparing the battery grade sodium hexafluorophosphate in the follow-up process, the battery grade sodium metaphosphate is convenient to dissolve and react fully due to the fine granularity, and meanwhile, the novel mechanical impurities can be prevented from being introduced due to scratch of a tetrafluoro reaction kettle caused by overlarge granularity.
Further, the high-purity sodium hydroxide in the step 1.2 is obtained according to the following method: dissolving high-purity sodium hydroxide in ultrapure water, wherein the mass ratio of the sodium hydroxide to the ultrapure water is 1:3.6-4.4, filtering mechanical impurities and precipitated impurities such as calcium hydroxide, magnesium hydroxide and the like by using a filter element filter with the precision of at least 1 micron after the dissolution is completed, wherein the iron content in the medium control solution is less than 1ppm, and the magnesium and calcium content are both less than 5ppm, so as to obtain the high-purity sodium hydroxide solution with the mass fraction of 18-22%.
Further, in the step 1.1, the electronic grade phosphoric acid is diluted into a phosphoric acid solution with the mass fraction of 40%; in the step 1.2, a high-purity sodium hydroxide solution with the mass fraction of 20% is added into the phosphoric acid solution.
Further, in the step 2.1, the sodium dihydrogen phosphate synthetic solution is heated to 110-115 ℃, stirred and concentrated until the specific gravity of the solution is 1.55-1.6.
Further, the centrifugal speed in the step 2.2 is 1000-1500 rpm, the centrifugal time is 20-30 minutes, and a proper amount of hot water with the temperature of 80 ℃ and above is added for washing. In the step, high-speed centrifugation is adopted to help the dissolved impurities to be fully removed, and hot water washing at 80 ℃ and above is adopted to remove most of free acid and partial potassium ions better.
Further, in the step 3.1, the sodium dihydrogen phosphate crystal is put in a tetrafluoro tray to be dried for 2-3 hours at 200-250 ℃, crushed and put in a quartz tray to be dried for 2-3 hours at 550-600 ℃. When the first gradient is dried, the sodium dihydrogen phosphate crystal is held by a tetrafluoro tray, so that the sodium dihydrogen phosphate crystal can be prevented from adhering to a container after dehydration, and the sodium dihydrogen phosphate crystal cannot be taken out well.
The invention also provides the battery grade sodium metaphosphate, which is characterized by being prepared by adopting the preparation method of the battery grade sodium metaphosphate.
The invention also provides a preparation method of the battery-grade sodium hexafluorophosphate, which is characterized by comprising the following steps:
step one: preparation of sodium hexafluorophosphate synthetic solution
Preparing a sodium hexafluorophosphate synthetic solution by reacting hydrofluoric acid with the mass fraction of 85-90% with the battery grade sodium metaphosphate; wherein the hydrofluoric acid is excessive by 50-100%, the reaction temperature is controlled below 10 ℃, and stirring reaction is carried out for 3-5 hours;
step two: preparation of sodium hexafluorophosphate crystals
Filtering and high-speed centrifuging the sodium hexafluorophosphate synthetic solution to obtain sodium hexafluorophosphate crystals;
Step three: preparation of Battery grade sodium hexafluorophosphate crystals
And (3) placing the sodium hexafluorophosphate crystal into a vacuum box, drying for 3-5 hours at 100-180 ℃ under 0.45-0.55 kg negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm and controlling the iron to be less than 1ppm, and carrying out vacuum packaging to obtain the battery grade sodium hexafluorophosphate.
Further, the first step is specifically: adding hydrofluoric acid with the mass fraction of 85-90% into a fully-closed PFA reaction kettle through a feed inlet, introducing brine for cooling, and controlling the temperature to be less than-5 ℃; slowly adding the battery grade sodium metaphosphate into the fully-closed PFA reaction kettle at a speed of 1-2kg/min through a charging port, controlling the temperature to be less than 0 ℃ and ensuring the hydrofluoric acid to be excessive by 50-100%; after the addition is completed, the temperature is kept below 10 ℃, and the mixture is stirred and reacts for 3 to 5 hours to obtain the sodium hexafluorophosphate synthetic solution.
Further, the second step is specifically: and (3) pumping the sodium hexafluorophosphate synthetic solution obtained in the step (A) into a PTFE filter through a pipeline for filtering, and centrifuging at a rotating speed of 2000-5000 r/min for at least 30min to obtain sodium hexafluorophosphate crystals.
The invention further provides battery-grade sodium hexafluorophosphate, which is characterized in that: the battery grade sodium hexafluorophosphate is prepared by the preparation method.
The invention also provides an energy storage battery, which is characterized in that: the battery grade sodium hexafluorophosphate is prepared by adopting the production method.
The beneficial effects of the invention are as follows:
1. The impurity content of the sodium metaphosphate prepared by the traditional method is too high to meet the mass production requirement of the battery grade sodium metaphosphate. The invention uses high-purity sodium hydroxide to remove impurities, and cooperates with the subsequent concentration crystallization and special gradient temperature drying process, so that the finally obtained sodium metaphosphate has less than 1ppm of iron, less than 5ppm of calcium and magnesium and less than 10ppm of potassium, and can meet the technical index requirements of battery grade sodium metaphosphate.
2. In the invention, when sodium metaphosphate is used, the mass fraction of the adopted phosphoric acid solution is 35-45%, enough mother liquor can be provided for the subsequent concentration crystallization step to remove potassium ions, in addition, heating is stopped after concentration crystallization, cooling is carried out to 45-50 ℃, the potassium content in sodium dihydrogen phosphate crystals in the temperature zone is lower, and the potassium ions can be removed as much as possible, thus providing support for the subsequent preparation of high-purity battery grade sodium metaphosphate.
3. Compared with the traditional sodium hexafluorophosphate preparation process, the invention omits the step of preparing hexafluorophosphate in the traditional preparation process, so that the production process is simplified and safer; the invention has lower requirements on production equipment because of no need of configuration of hexafluorophosphoric acid.
4. When the sodium hexafluorophosphate is prepared, the invention avoids the preparation of hexafluorophosphate and reduces unsafe factors in the production link.
Drawings
FIG. 1 is an XRD pattern of sodium metaphosphate prepared by the present invention.
Figure 2 is an XRD pattern of sodium hexafluorophosphate prepared in accordance with the present invention.
FIG. 3 is the data of sodium metaphosphate prepared by the present invention.
FIG. 4 is a graph showing the measurement data of sodium hexafluorophosphate prepared according to the present invention.
Detailed Description
The invention is characterized in that:
Considering that sodium hexafluorophosphate is fundamentally different from lithium hexafluorophosphate in nature, the hydrolysis resistance of the sodium hexafluorophosphate is stronger than that of lithium hexafluorophosphate under the condition of enough acid, and a small amount of water is allowed to exist in a reaction system, so that the preparation process of the sodium hexafluorophosphate can be greatly simplified, the requirement on production equipment is reduced, and the production cost of the sodium hexafluorophosphate is reduced.
The reaction equation involved in the invention is as follows:
NaOH+H3PO4＝＝＝NaH2PO4+H2O
NaH2PO4＝＝＝NaPO3+H2O
NaPO3+6HF＝＝＝NaPF6+3H2O
The invention is further illustrated by the following examples.
Example 1:
This example prepares battery grade sodium metaphosphate by the following steps and further prepares battery grade sodium hexafluorophosphate using the battery grade sodium metaphosphate:
step 1, refining sodium hydroxide
Adding 640 kg of ultra-pure water into a reaction kettle, adding 160 kg of high-purity sodium hydroxide into the reaction kettle, and passing through a filter element filter with the precision of 1 micrometer after complete dissolution, wherein the iron content is less than 1ppm, and the magnesium and calcium content is less than 5ppm, thus obtaining the high-purity sodium hydroxide solution with the mass fraction of 20%.
Step2, preparing sodium dihydrogen phosphate synthetic liquid
Step 2.1, 480 kg of electronic grade phosphoric acid with mass fraction of 85% is added into an enamel reaction kettle, and 500 kg of ultrapure water is added into the enamel reaction kettle to obtain a phosphoric acid solution with mass fraction of about 40%;
step 2.2, adding the high-purity sodium hydroxide solution refined in the step 1 into the phosphoric acid solution obtained in the step 2.1, and adjusting the pH value to be 1-2 to obtain sodium dihydrogen phosphate synthetic solution;
Step 3, preparing sodium dihydrogen phosphate crystal
Step 3.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic solution obtained in the step 2.2, heating to 110 ℃, stirring at a speed of 70 r/min, concentrating to a specific gravity of 1.55-1.6, and stopping heating after a small amount of crystallization occurs;
and 3.2, cooling to 47 ℃, preserving heat for 3 hours, taking out the crystals after a large amount of crystals appear, putting the crystals into a centrifugal machine, centrifuging for 30 minutes at a rotating speed of 1500 rpm, adding a proper amount of water with the temperature of more than 80 ℃ in the process, washing with less than 1ppm of medium-control iron, less than 5ppm of calcium, less than 5ppm of magnesium and less than 10ppm of potassium, and obtaining sodium dihydrogen phosphate crystals.
Step 4, preparing battery grade sodium metaphosphate
Step 4.1, putting the sodium dihydrogen phosphate crystal obtained in the step 3.2 into a tetrafluoro plate, drying for 3 hours at 250 ℃, crushing, adding into a quartz plate, drying for 3 hours at 570 ℃, and controlling the water content to be less than 0.05% to obtain sodium metaphosphate lump materials;
and 4.2, crushing the sodium metaphosphate lump obtained in the step 4.1, and sieving the crushed sodium metaphosphate lump with a 200-mesh sieve to obtain sodium metaphosphate. The qualitative graph is shown in fig. 1, and the detection data is shown in fig. 3.
Step5, synthesizing battery grade sodium hexafluorophosphate
Step 5.1, firstly adding hydrofluoric acid with the mass fraction of 85% into a fully-closed PFA reaction kettle through a feed inlet, introducing saline water for cooling, controlling the temperature to be less than-5 ℃, then slowly adding battery-grade sodium metaphosphate obtained in the step 4.2 into the fully-closed PFA reaction kettle at the speed of 1-2kg/min through the feed inlet, controlling the temperature to be less than 0 ℃, excessively adding 100% hydrofluoric acid, preserving the temperature below 10 ℃ after the addition is finished, and stirring for reacting for 4 hours to obtain sodium hexafluorophosphate synthetic solution;
step 5.2, pumping the sodium hexafluorophosphate synthetic solution obtained in the step 5.1 into a PTFE filter through a pipeline for filtering, and centrifuging for 30 minutes by a high-speed centrifuge with the speed of 5000 revolutions per minute to obtain sodium hexafluorophosphate crystals;
And 5.3, placing the sodium hexafluorophosphate crystal obtained in the step 5.2 into a vacuum drying oven, drying for 4 hours at 180 ℃ under 0.5 kg negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm, and controlling the iron to be less than 1ppm, and vacuum packaging to obtain a target product, wherein the product is qualified into sodium hexafluorophosphate through XRD (X-ray diffraction), as shown in figure 1. The detection data of the sodium hexafluorophosphate prepared in this example are shown in fig. 4.
Example 2:
This example prepares battery grade sodium metaphosphate by the following steps and further prepares battery grade sodium hexafluorophosphate using the battery grade sodium metaphosphate:
step 1, refining sodium hydroxide
640 Kg of ultra-pure water is added into a reaction kettle, 140 kg of high-purity sodium hydroxide is added into the reaction kettle, the solution is completely dissolved and passes through a filter element filter with the precision of 1 micrometer, the iron control is less than 1ppm, and the magnesium and the calcium are less than 5ppm, so that the high-purity sodium hydroxide solution with the mass fraction of about 18% is obtained.
Step2, preparing sodium dihydrogen phosphate synthetic liquid
Step 2.1, 480 kg of electronic grade phosphoric acid with mass fraction of 85% is added into an enamel reaction kettle, 685 kg of ultrapure water is added into the enamel reaction kettle, and phosphoric acid solution with mass fraction of about 35% is obtained;
step 2.2, adding the high-purity sodium hydroxide solution refined in the step 1 into the phosphoric acid solution obtained in the step 2.1, and adjusting the pH value to be 1-2 to obtain sodium dihydrogen phosphate synthetic solution;
Step 3, preparing sodium dihydrogen phosphate crystal
Step 3.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic solution obtained in the step 2.2, heating to 115 ℃, stirring at a speed of 70 r/min, concentrating to a specific gravity of 1.58, and stopping heating after a small amount of crystallization occurs;
And 3.2, cooling to 49 ℃, preserving heat for 3 hours, taking out the crystals after a large amount of crystals appear, putting the crystals into a centrifugal machine, centrifuging for 30 minutes at a rotating speed of 1200 revolutions per minute, adding a proper amount of water with the temperature of more than 80 ℃ in the process, washing with less than 1ppm of medium-control iron, less than 5ppm of calcium, less than 5ppm of magnesium and less than 10ppm of potassium, and obtaining sodium dihydrogen phosphate crystals.
Step 4, preparing battery grade sodium metaphosphate
Step 4.1, putting the sodium dihydrogen phosphate crystal obtained in the step 3.2 into a tetrafluoro plate, drying for 3 hours at 250 ℃, crushing, adding into a quartz plate, drying for 3 hours at 600 ℃, and controlling the water content to be less than 0.05% to obtain sodium metaphosphate lump materials;
And 4.2, crushing the sodium metaphosphate lump obtained in the step 4.1, and sieving the crushed sodium metaphosphate lump with a 200-mesh sieve to obtain sodium metaphosphate. The qualitative graph is shown in fig. 2, and the detection data is shown in fig. 3.
Step5, synthesizing battery grade sodium hexafluorophosphate
Step 5.1, firstly adding hydrofluoric acid with the mass fraction of 90% into a fully-closed PFA reaction kettle through a feed inlet, introducing saline water for cooling, controlling the temperature to be less than-7 ℃, then slowly adding battery-grade sodium metaphosphate obtained in the step 4.2 into the fully-closed PFA reaction kettle at the speed of 1-2kg/min through the feed inlet, controlling the temperature to be less than 0 ℃, and keeping the temperature below 10 ℃ after the addition is finished, and stirring for reacting for 4 hours to obtain sodium hexafluorophosphate synthetic solution;
step 5.2, pumping the sodium hexafluorophosphate synthetic solution obtained in the step 5.1 into a PTFE filter through a pipeline for filtering, and centrifuging for 30 minutes by a high-speed centrifuge at 3500 rpm to obtain sodium hexafluorophosphate crystals;
And 5.3, placing the sodium hexafluorophosphate crystal obtained in the step 5.2 into a vacuum drying oven, drying for 5 hours at 150 ℃ under 0.45 kg of negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm, and controlling the iron to be less than 1ppm, and vacuum packaging to obtain a target product, wherein the product is qualified into sodium hexafluorophosphate through XRD (X-ray diffraction), as shown in figure 1. The detection data of the sodium hexafluorophosphate prepared in this example are shown in fig. 4.
Example 3:
This example prepares battery grade sodium metaphosphate by the following steps and further prepares battery grade sodium hexafluorophosphate using the battery grade sodium metaphosphate:
step 1, refining sodium hydroxide
640 Kg of ultra-pure water is added into a reaction kettle, 180 kg of high-purity sodium hydroxide is added into the reaction kettle, the solution is completely dissolved and passes through a filter element filter with the precision of 1 micrometer, the iron control is less than 1ppm, and the magnesium and the calcium are less than 5ppm, so that the high-purity sodium hydroxide solution with the mass fraction of about 22% is obtained.
Step2, preparing sodium dihydrogen phosphate synthetic liquid
Step 2.1, 480 kg of electronic grade phosphoric acid with mass fraction of 85% is added into an enamel reaction kettle, 426 kg of ultrapure water is added into the enamel reaction kettle, and a phosphoric acid solution with mass fraction of about 45% is obtained;
step 2.2, adding the high-purity sodium hydroxide solution refined in the step 1 into the phosphoric acid solution obtained in the step 2.1, and adjusting the pH value to be 1-2 to obtain sodium dihydrogen phosphate synthetic solution;
Step 3, preparing sodium dihydrogen phosphate crystal
Step 3.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic solution obtained in the step 2.2, heating to 112 ℃, stirring at a speed of 65 revolutions per minute, concentrating to a specific gravity of 1.6, and stopping heating after a small amount of crystallization occurs;
And 3.2, cooling to 45 ℃, preserving heat for 2 hours, taking out the crystals after a large amount of crystals appear, putting the crystals into a centrifugal machine, centrifuging for 30 minutes at a rotating speed of 1000 revolutions per minute, adding a proper amount of water with the temperature of more than 80 ℃ in the process, washing with less than 1ppm of medium-control iron, less than 5ppm of calcium, less than 5ppm of magnesium and less than 10ppm of potassium, and obtaining sodium dihydrogen phosphate crystals.
Step 4, preparing battery grade sodium metaphosphate
Step 4.1, putting the sodium dihydrogen phosphate crystal obtained in the step 3.2 into a tetrafluoro plate, drying for 3 hours at 200 ℃, crushing, adding into a quartz plate, drying for 3 hours at 600 ℃, and controlling the water content to be less than 0.05% to obtain sodium metaphosphate lump materials;
And 4.2, crushing the sodium metaphosphate lump obtained in the step 4.1, and sieving the crushed sodium metaphosphate lump with a 200-mesh sieve to obtain sodium metaphosphate. Qualitative graph as in fig. 2, and detection data as in fig. 3.
Step5, synthesizing battery grade sodium hexafluorophosphate
Step 5.1, firstly adding 87% of hydrofluoric acid in mass percent into a fully-closed PFA reaction kettle through a feed inlet, introducing saline water for cooling, controlling the temperature to be less than-7 ℃, then slowly adding the battery grade sodium metaphosphate obtained in step 4.2 into the fully-closed PFA reaction kettle at the speed of 1-2kg/min through the feed inlet, controlling the temperature to be less than 0 ℃, and keeping the temperature below 10 ℃ after the addition is completed, and stirring for reacting for 4 hours to obtain sodium hexafluorophosphate synthetic solution;
Step 5.2, pumping the sodium hexafluorophosphate synthetic solution obtained in the step 5.1 into a PTFE filter through a pipeline for filtering, and centrifuging for 40 minutes by a high-speed centrifuge at 2000 rpm to obtain sodium hexafluorophosphate crystals;
And 5.3, placing the sodium hexafluorophosphate crystal obtained in the step 5.2 into a vacuum drying oven, drying for 5 hours at 100 ℃ under 0.55 kg of negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm, and controlling the iron to be less than 1ppm, and vacuum packaging to obtain a target product, wherein the product is qualified into sodium hexafluorophosphate through XRD (X-ray diffraction), as shown in figure 1. The detection data is shown in fig. 4.
Example 4:
This example prepares battery grade sodium metaphosphate by the following steps and further prepares battery grade sodium hexafluorophosphate using the battery grade sodium metaphosphate:
step 1, refining sodium hydroxide
640 Kg of ultra-pure water is added into a reaction kettle, 150 kg of high-purity sodium hydroxide is added into the reaction kettle, the solution is completely dissolved and passes through a filter element filter with the precision of 1 micrometer, the iron control is less than 1ppm, and the magnesium and the calcium are less than 5ppm, so that the high-purity sodium hydroxide solution with the mass fraction of about 19% is obtained.
Step2, preparing sodium dihydrogen phosphate synthetic liquid
Step 2.1, 480 kg of electronic grade phosphoric acid with mass fraction of 85% is added into an enamel reaction kettle, 593 kg of ultrapure water is added into the enamel reaction kettle, and a phosphoric acid solution with mass fraction of about 38% is obtained;
step 2.2, adding the high-purity sodium hydroxide solution refined in the step 1 into the phosphoric acid solution obtained in the step 2.1, and adjusting the pH value to be 1-2 to obtain sodium dihydrogen phosphate synthetic solution;
Step 3, preparing sodium dihydrogen phosphate crystal
Step 3.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic solution obtained in the step 2.2, heating to 112 ℃, stirring at a speed of 65 r/min, concentrating to a specific gravity of 1.55, and stopping heating after a small amount of crystallization occurs;
And 3.2, cooling to 50 ℃, preserving heat for 3 hours, taking out the crystals after a large amount of crystals appear, putting the crystals into a centrifugal machine, centrifuging for 20 minutes at the rotating speed of 1400 r/min, adding a proper amount of water with the temperature of more than 80 ℃ in the process, washing with less than 1ppm of medium-control iron, less than 5ppm of calcium, less than 5ppm of magnesium and less than 10ppm of potassium, and obtaining sodium dihydrogen phosphate crystals.
Step 4, preparing battery grade sodium metaphosphate
Step 4.1, putting the sodium dihydrogen phosphate crystal obtained in the step 3.2 into a tetrafluoro plate, drying for 2 hours at 230 ℃, crushing, adding into a quartz plate, drying for 3 hours at 550 ℃, and controlling the water content to be less than 0.05% to obtain sodium metaphosphate lump materials;
And 4.2, crushing the sodium metaphosphate lump obtained in the step 4.1, and sieving the crushed sodium metaphosphate lump with a 200-mesh sieve to obtain sodium metaphosphate. Qualitative graph as in fig. 2, and detection data as in fig. 3.
Step5, synthesizing battery grade sodium hexafluorophosphate
Step 5.1, firstly adding 88 mass percent of hydrofluoric acid into a fully-closed PFA reaction kettle through a feed inlet, introducing brine for cooling, controlling the temperature to be less than-5 ℃, then slowly adding the battery grade sodium metaphosphate obtained in the step 4.2 into the fully-closed PFA reaction kettle at the speed of 1-2kg/min through the feed inlet, controlling the temperature to be less than 0 ℃, controlling the excessive amount of hydrofluoric acid to be 75%, preserving the temperature below 10 ℃ after the addition is completed, and stirring for reacting for 4 hours to obtain sodium hexafluorophosphate synthetic solution;
Step 5.2, pumping the sodium hexafluorophosphate synthetic solution obtained in the step 5.1 into a PTFE filter through a pipeline for filtering, and centrifuging for 30 minutes by a high-speed centrifuge of 4500 rpm to obtain sodium hexafluorophosphate crystals;
And 5.3, placing the sodium hexafluorophosphate crystal obtained in the step 5.2 into a vacuum drying oven, drying for 5 hours at 160 ℃ under 0.52 kg of negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm, and controlling the iron to be less than 1ppm, and vacuum packaging to obtain a target product, wherein the product is qualified into sodium hexafluorophosphate through XRD (X-ray diffraction), as shown in figure 1. The detection data is shown in fig. 4.
From the above examples and the detection data thereof, the preparation methods of the battery grade sodium metaphosphate and the sodium hexafluorophosphate provided by the invention are very stable, and the obtained product has higher repeatability and meets the requirements of indexes.
Claims (11)
1. The preparation method of the battery grade sodium metaphosphate is characterized by comprising the following steps:
step 1: preparation of sodium dihydrogen phosphate synthetic liquid
Step 1.1, diluting the electronic grade phosphoric acid to a phosphoric acid solution with the mass fraction of 35-45% by using ultrapure water;
Step 1.2, adding a high-purity sodium hydroxide solution with the mass fraction of 18-22% into the phosphoric acid solution, and adjusting the pH value to be 1-2 to obtain a sodium dihydrogen phosphate synthetic solution; the content of iron in the high-purity sodium hydroxide solution is less than 1ppm, and the content of magnesium and calcium is less than 5ppm; the mass ratio of the high-purity sodium hydroxide solution to the phosphoric acid solution is 1:1.2-1.3;
step 2: preparation of sodium dihydrogen phosphate crystals
Step 2.1, heating, stirring and concentrating the sodium dihydrogen phosphate synthetic liquid, and stopping heating after concentrating to obtain crystals;
Step 2.2, cooling to 45-50 ℃, preserving heat for 2-3 hours, taking out the crystals after a large amount of crystals appear, centrifuging and moderately washing with water, wherein the iron content is less than 1ppm, the calcium and magnesium content are less than 5ppm, and the potassium content is less than 10ppm to obtain sodium dihydrogen phosphate crystals;
Step 3: preparation of Battery grade sodium metaphosphate
Step 3.1, drying the sodium dihydrogen phosphate crystal gradient:
Drying the sodium dihydrogen phosphate crystal at 200-250 ℃ for 2-3 hours, crushing, and then drying at 550-600 ℃ for 2-3 hours, wherein the water content is controlled to be less than 0.05%, thus obtaining sodium metaphosphate lump materials;
And 3.2, crushing the sodium metaphosphate lump material, and sieving the crushed sodium metaphosphate lump material by a sieve with the mesh number of at least 200 meshes to obtain the battery grade sodium metaphosphate.
2. The method for preparing battery grade sodium metaphosphate according to claim 1, characterized in that: the high-purity sodium hydroxide in the step 1.2 is obtained according to the following method: dissolving high-purity sodium hydroxide in ultrapure water, wherein the mass ratio of the sodium hydroxide to the ultrapure water is 1:3.6-4.4, filtering by a filter element filter with the precision of at least 1 micron after the dissolution is completed, wherein the iron content in the medium control solution is less than 1ppm, and the magnesium and calcium content are both less than 5ppm, thus obtaining the high-purity sodium hydroxide solution with the mass fraction of 18-22%.
3. The method for preparing battery grade sodium metaphosphate according to claim 2, characterized in that: in the step 1.1, diluting the electronic grade phosphoric acid into a phosphoric acid solution with the mass fraction of 40%; and (2) adding a high-purity sodium hydroxide solution with the mass fraction of 20% into the phosphoric acid solution in the step (1.2).
4. The method for preparing battery grade sodium metaphosphate according to claim 3, characterized in that: and in the step 2.1, heating the sodium dihydrogen phosphate synthetic solution to 110-115 ℃, stirring and concentrating until the specific gravity of the solution is 1.55-1.6.
5. The method for preparing battery grade sodium metaphosphate according to claim 4, characterized in that: the centrifugal speed in the step 2.2 is 1000-1500 rpm, the centrifugal time is 20-30 minutes, and a proper amount of hot water with the temperature of 80 ℃ and above is added for washing.
6. A battery grade sodium metaphosphate, which is characterized in that: prepared by the method of any one of claims 1-5.
7. The preparation method of the battery grade sodium hexafluorophosphate is characterized by comprising the following steps of:
step one: preparation of sodium hexafluorophosphate synthetic solution
Preparing a sodium hexafluorophosphate synthetic solution by reacting hydrofluoric acid with the mass fraction of 85-90% with the battery grade sodium metaphosphate of claim 6; wherein the hydrofluoric acid is excessive by 50-100%, the reaction temperature is controlled below 10 ℃, and stirring reaction is carried out for 3-5 hours;
step two: preparation of sodium hexafluorophosphate crystals
Filtering and high-speed centrifuging the sodium hexafluorophosphate synthetic solution to obtain sodium hexafluorophosphate crystals;
Step three: preparation of Battery grade sodium hexafluorophosphate crystals
And (3) placing the sodium hexafluorophosphate crystal into a vacuum box, drying for 3-5 hours at 100-180 ℃ under 0.45-0.55 kg negative pressure, controlling the water content to be less than 50ppm, controlling the calcium, magnesium and potassium to be less than 10ppm and controlling the iron to be less than 1ppm, and carrying out vacuum packaging to obtain the battery grade sodium hexafluorophosphate.
8. The method for preparing battery grade sodium hexafluorophosphate according to claim 7, wherein: the first step is as follows: adding hydrofluoric acid with the mass fraction of 85-90% into a fully-closed PFA reaction kettle through a feed inlet, introducing brine for cooling, and controlling the temperature to be less than-5 ℃; slowly adding the battery grade sodium metaphosphate into the fully-closed PFA reaction kettle at a speed of 1-2kg/min through a charging port, controlling the temperature to be less than 0 ℃ and ensuring the hydrofluoric acid to be excessive by 50-100%; after the addition is completed, the temperature is kept below 10 ℃, and the mixture is stirred and reacts for 3 to 5 hours to obtain the sodium hexafluorophosphate synthetic solution.
9. The method for preparing battery grade sodium hexafluorophosphate according to claim 8, wherein: the second step is specifically as follows: and (3) pumping the sodium hexafluorophosphate synthetic solution obtained in the step (A) into a PTFE filter through a pipeline for filtering, and centrifuging at a rotating speed of 2000-5000 r/min for at least 30 min to obtain sodium hexafluorophosphate crystals.
10. A battery grade sodium hexafluorophosphate, characterized by: prepared by the method of any one of claims 7-9.
11. An energy storage battery, characterized in that: is prepared by adopting the battery grade sodium hexafluorophosphate of claim 10.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102134065A (en) * | 2006-08-22 | 2011-07-27 | 三菱化学株式会社 | Preparation method of lithium difluorophosphate, nonaqueous electrolytic solution, and nonaqueous electrolyte secondary battery using the nonaqueous electrolytic solution |
| CN106927440A (en) * | 2017-04-24 | 2017-07-07 | 东北大学 | A kind of preparation method of LITHIUM BATTERY sodium dihydrogen phosphate |
| CN115159488A (en) * | 2022-07-22 | 2022-10-11 | 承德莹科精细化工股份有限公司 | Preparation method of high-water-solubility glass-state sodium metaphosphate |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102134065A (en) * | 2006-08-22 | 2011-07-27 | 三菱化学株式会社 | Preparation method of lithium difluorophosphate, nonaqueous electrolytic solution, and nonaqueous electrolyte secondary battery using the nonaqueous electrolytic solution |
| CN106927440A (en) * | 2017-04-24 | 2017-07-07 | 东北大学 | A kind of preparation method of LITHIUM BATTERY sodium dihydrogen phosphate |
| CN115159488A (en) * | 2022-07-22 | 2022-10-11 | 承德莹科精细化工股份有限公司 | Preparation method of high-water-solubility glass-state sodium metaphosphate |
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