Treatment method of bis (fluorosulfonyl) imide heavy slag

Abstract

The invention provides a method for treating bis (fluorosulfonyl) imide heavy slag, which comprises the following step of: reacting a raw material system containing bis (fluorosulfonyl) imide heavy slag and a metal salt aqueous solution to obtain metal fluoride precipitate. The treatment method of the bis (fluorosulfonyl) imide heavy slag, provided by the invention, is used for realizing resource recycling of bis (fluorosulfonyl) imide, and the treatment cost can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of bisfluorosulfonyl imide purification, and particularly relates to a method for treating bisfluorosulfonyl imide heavy residue. Background Art

[0002] Bisfluorosulfonyl imide, the raw material of lithium bisfluorosulfonyl imide for lithium-ion batteries, is purified by impurity removal method. The purification process will produce bisfluorosulfonyl imide heavy residue. As the market demand for lithium bisfluorosulfonyl imide increases, the output of lithium bisfluorosulfonyl imide produced by enterprises continues to increase, which will produce more bisfluorosulfonyl imide heavy residue.

[0003] The heavy residue of bis(fluorosulfonyl)imide is a viscous solid with poor fluidity. Its main components are bis(fluorosulfonyl)imide and fluorosulfonic acid and a small amount of their salts, of which bis(fluorosulfonyl)imide and fluorosulfonic acid account for more than 95%.

[0004] Therefore, it is urgent to explore a suitable treatment method for bis(fluorosulfonyl)imide heavy slag to realize the resource recovery of the heavy slag and recycle the resources in the heavy slag. Summary of the invention

[0005] The invention provides a method for treating heavy slag of bisfluorosulfonyl imide, which is used for realizing resource recovery and utilization of bisfluorosulfonyl imide and reducing treatment cost.

[0006] The present invention provides a method for treating heavy slag of bis(fluorosulfonyl)imide, which comprises the following steps:

[0007] A raw material system including bisfluorosulfonyl imide heavy residue and an aqueous solution of a metal salt is reacted to obtain a metal fluoride precipitate.

[0008] In the treatment method as described above, the anions in the metal salt include at least one of sulfate, nitrate, hydrochloride and phosphate.

[0009] In the treatment method as described above, the cations in the metal salt include at least one of aluminum, magnesium, lithium, sodium, calcium, barium, lead and strontium.

[0010] In the above treatment method, the mass fraction of the aqueous solution of the metal salt is 10-30%.

[0011] In the treatment method as described above, the molar ratio of the bis(fluorosulfonyl)imide heavy residue to the metal salt in the aqueous solution of the metal salt is 1:(0.3-1).

[0012] The treatment method as described above, wherein the reaction temperature is 100-140° C.; and / or,

[0013] The reaction time of the reaction is 1-10h.

[0014] The processing method as described above, wherein further comprises:

[0015] The metal fluoride precipitate is subjected to elution treatment, and then the metal fluoride precipitate is purified by filtering treatment and drying treatment in sequence.

[0016] The processing method as described above, wherein further comprises:

[0017] Ammonia water is added to the reaction solution until the solution becomes neutral to obtain a crude ammonium sulfate solution.

[0018] In the treatment method as described above, the mass fraction of the ammonia water is 20-30%.

[0019] The treatment method as described above, wherein, further comprises: using the crude ammonium sulfate solution as a raw material to participate in the preparation of fertilizer.

[0020] The method for treating bisfluorosulfonyl imide heavy residue provided by the present invention comprises reacting a raw material system including the bisfluorosulfonyl imide heavy residue and an aqueous solution of a metal salt to obtain a metal fluoride precipitate, which can be used in the electrolysis field, the ceramic industry, the catalysis field and for preparing various additives, and can also effectively recover the bisfluorosulfonyl imide heavy residue, thereby realizing the resource utilization of the bisfluorosulfonyl imide heavy residue. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The present invention provides a method for treating heavy residues of bis(fluorosulfonyl)imide, comprising the following steps:

[0023] A raw material system including bisfluorosulfonyl imide heavy residue and an aqueous solution of a metal salt is reacted to obtain a metal fluoride precipitate.

[0024] The bisfluorosulfonyl imide heavy residue in the present invention refers to the heavy residue produced when the bisfluorosulfonyl imide raw material is subjected to impurity removal and purification treatment when preparing the bisfluorosulfonyl imide raw material, and the main components of the heavy residue are bisfluorosulfonyl imide and its trace salts, and fluorosulfonic acid and its trace salts; in the bisfluorosulfonyl imide heavy residue, the proportion of bisfluorosulfonyl imide and fluorosulfonic acid is more than 95%; the bisfluorosulfonyl imide heavy residue is a viscous liquid with extremely poor fluidity. At present, there is no method for resource utilization of bisfluorosulfonyl imide in the prior art.

[0025] The present invention does not limit the specific type of the aqueous solution of the metal salt, and any aqueous solution of the metal salt that can form a fluoride precipitate can be used, and the fluorine in the bisfluorosulfonyl imide heavy residue can be effectively recovered, thereby realizing the resource utilization of the bisfluorosulfonyl imide heavy residue.

[0026] Specifically, taking an aqueous solution of aluminum sulfate as an example, when the bis(fluorosulfonyl)imide heavy residue reacts with an aqueous solution of aluminum sulfate, the reactions may include those shown in formula (1), formula (2) and formula (3):

[0027]

[0028] FSO3H+H2O→H2SO4+HF Formula (2)

[0029] 6HF+Al2(SO4)3→2AlF3+3H2SO4 Formula (3)

[0030] Among them, bisfluorosulfonyl imide reacts with water in an aqueous solution of aluminum sulfate to generate sulfuric acid, ammonium bisulfate and hydrogen fluoride; fluorosulfonic acid reacts with water to generate sulfuric acid and hydrogen fluoride; hydrogen fluoride reacts with aluminum sulfate to generate aluminum fluoride precipitate and sulfuric acid, and the aluminum fluoride is collected by filtration to achieve the recovery and utilization of fluorine.

[0031] The method for treating bisfluorosulfonyl imide heavy residue provided by the present invention is to react a raw material system including bisfluorosulfonyl imide heavy residue and an aqueous solution of a metal salt to obtain a metal fluoride precipitate, which can be used in the electrolysis field, the ceramic industry, the catalysis field and for preparing various additives. Taking aluminum fluoride as an example, aluminum fluoride can be used in the electrolytic aluminum industry to reduce the melting temperature of the electrolyte and improve the conductivity of the electrolyte. In the ceramic industry, aluminum fluoride can be used not only as a flux for ceramic glaze and enamel glaze, but also as a component of glaze medicine. Because aluminum fluoride has an inhibitory effect on fermentation, aluminum fluoride plays a role as an inhibitor of side fermentation in the production of essential oils and alcohols. In addition, aluminum fluoride can also be used to make optical lenses and be used for welding fluid in metal welding. It can also play a catalytic role in organic synthesis, so it is also used as a catalyst for organic synthesis. The method for treating bisfluorosulfonyl imide heavy residue provided by the present invention can also effectively recover the bisfluorosulfonyl imide heavy residue, so as to realize the resource utilization of the bisfluorosulfonyl imide heavy residue.

[0032] Furthermore, the raw material system can be tested by ion chromatography. When the content of bis(fluorosulfonyl)imide ions in the raw material system is 0, it can be judged that the reaction is complete, and at this time, the bis(fluorosulfonyl)imide has been completely converted.

[0033] Optionally, in the metal salt, the anion includes at least one of sulfate, nitrate, hydrochloride and phosphate.

[0034] When sulfate, nitrate, hydrochloride or phosphate is selected as the anion of the metal salt, it is beneficial to further collect the post-reaction solution for resource utilization.

[0035] Optionally, in the metal salt, the cation includes at least one of aluminum, magnesium, lithium, sodium, calcium, barium, lead, and strontium.

[0036] When the cation of the metal salt is selected from at least one of aluminum, magnesium, lithium, sodium, calcium, barium, lead and strontium, it is beneficial to generate fluoride precipitation and realize the recycling of bis(fluorosulfonyl)imide; the cation of the metal salt can be further refined into at least one of aluminum, magnesium and sodium, which is beneficial to further reduce costs.

[0037] In one specific embodiment, the mass fraction of the aqueous solution of the metal salt is 10-30%.

[0038] It can be understood that since bis(fluorosulfonyl)imide first needs to react with water in the aqueous solution, when the mass fraction of the aqueous solution of the metal salt is 10-30%, it is beneficial to the dissolution and dispersion of the bis(fluorosulfonyl)imide heavy residue, further promoting the reaction.

[0039] Furthermore, the molar ratio of the bis(fluorosulfonyl)imide heavy residue to the metal salt in the aqueous solution of the metal salt is 1:(0.3-1).

[0040] The mass ratio of the bisfluorosulfonyl imide heavy residue to the aqueous solution of the metal salt is an important influencing factor of the reaction. The inventors have found through research that when the molar ratio of the bisfluorosulfonyl imide heavy residue to the metal salt in the aqueous solution of the metal salt is 1:(0.3-1), the reaction can be further promoted to fully proceed, the bisfluorosulfonyl imide heavy residue is completely reacted, and the resource utilization of the treatment method is further improved.

[0041] In one embodiment, the reaction temperature is 100-140°C;

[0042] Further limiting the reaction temperature of the reaction in the treatment method can further control the reaction rate and promote the reaction.

[0043] In another specific embodiment, the reaction time is 1-10 hours.

[0044] The inventors found that after 1-10 hours of reaction, the heavy residue of bis(fluorosulfonyl)imide can be further reacted completely, which is more conducive to the resource utilization of bis(fluorosulfonyl)imide.

[0045] Furthermore, it also includes:

[0046] The metal fluoride precipitate is subjected to elution treatment, and then purified by filtering treatment and drying treatment in sequence.

[0047] When the reaction is completed, a metal fluoride precipitate will be obtained. In order to further separate the product and better utilize it as a resource, the metal fluoride precipitate can be rinsed with deionized water, and then separated by filtration. After further removing the residual solution on the metal fluoride by washing, it is dried to purify the metal fluoride; wherein the drying temperature is 110-120°C and the time is 3-5h.

[0048] Furthermore, the method further comprises: adding aqueous ammonia to the solution after the reaction until the solution is neutral to obtain a crude ammonium sulfate solution.

[0049] Since bis(fluorosulfonyl)imide reacts with water in an aqueous solution of a metal salt to generate sulfuric acid, ammonium bisulfate and hydrogen fluoride, the solution after the reaction includes substances such as sulfuric acid and ammonium bisulfate. Ammonia water added to the solution after the reaction reacts with sulfuric acid and ammonium bisulfate to generate ammonium sulfate. The reaction equations are shown in Formula (4) and Formula (5):

[0050] H2SO4+2NH3·H2O→(NH4)2SO4+2H2O Formula (4)

[0051] NH4HSO4+NH3·H2O→(NH4)2SO4+H2O Formula (5)

[0052] Therefore, by adding ammonia water to the post-reaction solution until the solution is neutral, the amount of ammonia water added can be further controlled, sulfuric acid and ammonium bisulfate can be completely converted into ammonium bisulfate, and the main component of the post-reaction solution becomes a crude solution of ammonium bisulfate, which is beneficial to further realize the resource utilization of the heavy residue of bis(fluorosulfonyl)imide.

[0053] Optionally, the mass fraction of the ammonia water is 20-30%.

[0054] By limiting the mass fraction of aqueous ammonia, the reaction of aqueous ammonia with sulfuric acid and ammonium bisulfate can be further promoted, and the reaction rate can be further controlled.

[0055] In one embodiment, the method further includes: using the crude ammonium sulfate solution as a raw material to participate in the preparation of fertilizer.

[0056] Since ammonium sulfate is widely used in fertilizers and is suitable for various soils and crops, the crude solution whose main component is ammonium sulfate can be used as a raw material to participate in the preparation of fertilizers, further improving the resource utilization of bis(fluorosulfonyl)imide and reducing the processing cost.

[0057] Hereinafter, a method for treating heavy bis(fluorosulfonyl)imide residue provided by the present invention is described in detail through specific examples.

[0058] Example 1

[0059] (1) Add 100 g of bis(fluorosulfonyl)imide heavy residue into a 500 ml PTFE three-necked reaction bottle, add 60 g (0.17 mol, 0.32 eq.) of aluminum sulfate to prepare an aqueous solution of aluminum sulfate with a mass fraction of 20%, place it in a 120° C. constant temperature magnetic heating stirrer, start stirring to react, and rotate at 200 rpm. When the bis(fluorosulfonyl)imide anion content in the raw material system is 0, the reaction is terminated to obtain aluminum fluoride precipitate and a post-reaction solution;

[0060] (2) The aluminum fluoride precipitate is rinsed several times with a certain amount of water and dried to obtain the aluminum fluoride product; after the reaction, 25% ammonia water is added to the solution until it becomes neutral to obtain a crude ammonium sulfate solution, which is directly used as a fertilizer raw material to supply to a fertilizer plant.

[0061] Example 2

[0062] The difference between this embodiment and embodiment 1 is that the concentration of the aqueous solution of the metal salt is 30%.

[0063] Example 3

[0064] The difference between this embodiment and embodiment 1 is that the concentration of the aqueous solution of the metal salt is 10%.

[0065] Example 4

[0066] The difference between this embodiment and embodiment 1 is that in step (1), 70 g of an aqueous solution of a metal salt is added.

[0067] Example 5

[0068] The difference between this embodiment and embodiment 1 is that in step (1), the reaction temperature is 100°C.

[0069] Example 6

[0070] The difference between this embodiment and embodiment 1 is that in step (1), the reaction temperature is 140°C.

[0071] Example 7

[0072] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of ammonia water is 15%.

[0073] Example 8

[0074] The difference between this embodiment and embodiment 1 is that in step (1), the concentration of the aqueous solution of the metal salt is 45%.

[0075] Example 9

[0076] The difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the added aqueous solution of the metal salt to the heavy residue of bis(fluorosulfonyl)imide is 0.25:1.

[0077] Example 10

[0078] The difference between this embodiment and embodiment 1 is that in step (2), the reaction temperature is 80°C.

[0079] Embodiment 11

[0080] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of ammonia water is 35%.

[0081] Example 12

[0082] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is magnesium sulfate, and the molar ratio of the added metal salt aqueous solution to the bis(fluorosulfonyl)imide heavy residue is 0.5:1.

[0083] Example 13

[0084] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is sodium sulfate, and the molar ratio of the added metal salt aqueous solution to the bis(fluorosulfonyl)imide heavy residue is 1.0:1.

[0085] Embodiment 14

[0086] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is aluminum nitrate.

[0087] Embodiment 15

[0088] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is aluminum chloride.

[0089] Example 16

[0090] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is aluminum phosphate.

[0091] Embodiment 17

[0092] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is calcium chloride, and the molar ratio of the added metal salt aqueous solution to the bis(fluorosulfonyl)imide heavy residue is 0.5:1.

[0093] Embodiment 18

[0094] The difference between this embodiment and embodiment 1 is that in step (1), the metal salt is barium chloride, and the molar ratio of the added metal salt aqueous solution to the bis(fluorosulfonyl)imide heavy residue is 0.5:1.

[0095] Embodiment 19

[0096] The difference between this embodiment and embodiment 1 is that in step (1), the concentration of the aqueous solution of the metal salt is 8%.

[0097] Embodiment 20

[0098] The difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the added aqueous solution of the metal salt to the heavy residue of bis(fluorosulfonyl)imide is 0.3:1.

[0099] Embodiment 21

[0100] The difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the added aqueous solution of the metal salt to the heavy residue of bis(fluorosulfonyl)imide is 0.5:1.

[0101] Embodiment 22

[0102] The difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the added aqueous solution of the metal salt to the heavy residue of bis(fluorosulfonyl)imide is 1:1.

[0103] Embodiment 23

[0104] The difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the added aqueous solution of the metal salt to the heavy residue of bis(fluorosulfonyl)imide is 1.2:1.

[0105] Embodiment 24

[0106] The difference between this embodiment and embodiment 1 is that in step (2), the reaction temperature is 150°C.

[0107] Embodiment 25

[0108] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of ammonia water is 20%.

[0109] Embodiment 26

[0110] The difference between this embodiment and embodiment 1 is that in step (2), the mass fraction of ammonia water is 30%.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that in step (1), the metal salt is potassium sulfate.

[0113] Test Example 1

[0114] The bisfluorosulfonyl imide anion content in the bisfluorosulfonyl imide heavy slag is detected by an ion chromatograph to obtain the bisfluorosulfonyl imide content, and the fluorine content in the metal fluorides obtained in the above embodiments and comparative examples is detected by an ion chromatograph, and the fluorine content is converted into the bisfluorosulfonyl imide content and compared with the bisfluorosulfonyl imide content in the heavy slag to calculate the recovery rate of the bisfluorosulfonyl imide heavy slag;

[0115] The experimental parameters and results in the above examples are shown in Table 1;

[0116] Table 1

[0117]

[0118]

[0119] As can be seen from the table, the method for treating the heavy residue of bisfluorosulfonyl imide provided by the present invention can obtain a metal fluoride precipitate by reacting a raw material system including the heavy residue of bisfluorosulfonyl imide and an aqueous solution of a metal salt, while in the comparative example, an aqueous solution of potassium sulfate is used for the reaction, and no metal fluoride precipitate can be obtained, and fluorine cannot be recovered; further, an aqueous solution containing ammonium sulfate can be obtained to participate in the production of fertilizers, thereby reducing the processing cost and realizing the resource recovery and utilization of the heavy residue of bisfluorosulfonyl imide; specifically, the reaction time can be controlled and the processing effect can be improved by adjusting factors such as the concentration, dosage, and reaction time of the aqueous solution of the metal salt, or the requirements for the reaction time, product purity, and recovery rate can be reduced to reduce the amount of raw materials and reaction energy consumption.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating heavy residues of bis(fluorosulfonyl)imide, characterized in that: The following steps are involved: A raw material system including bisfluorosulfonyl imide heavy residue and an aqueous solution of a metal salt is reacted to obtain a metal fluoride precipitate.

2. The processing method according to claim 1, characterized in that: In the metal salt, the anion includes at least one of sulfate, nitrate, hydrochloride and phosphate.

3. The processing method according to claim 1 or 2, characterized in that: In the metal salt, the cation includes at least one of aluminum, magnesium, lithium, sodium, calcium, barium, lead and strontium.

4. The processing method according to any one of claims 1 to 3, characterized in that: The mass fraction of the aqueous solution of the metal salt is 10-30%.

5. The processing method according to claim 4, characterized in that: The molar ratio of the bis(fluorosulfonyl)imide heavy residue to the metal salt in the aqueous solution of the metal salt is 1:(0.3-1).

6. The processing method according to any one of claims 1 to 5, characterized in that: The reaction temperature is 100-140°C; and / or, The reaction time of the reaction is 1-10h.

7. The processing method according to any one of claims 1 to 6, characterized in that: Also includes: The metal fluoride precipitate is subjected to elution treatment, and then the metal fluoride precipitate is purified by filtering treatment and drying treatment in sequence.

8. The processing method according to any one of claims 1 to 7, characterized in that: Also includes: Ammonia water is added to the reaction solution until the solution becomes neutral to obtain a crude ammonium sulfate solution.

9. The processing method according to claim 8, characterized in that: The mass fraction of the ammonia water is 20-30%.

10. The processing method according to claim 8 or 9, characterized in that: Also includes: The crude ammonium sulfate solution is used as a raw material to participate in the preparation of fertilizer.

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