A process for the treatment of tertiary amine hydrogen fluoride adducts

Abstract

The application belongs to the technical field of lithium ion battery electrolyte preparation, and particularly relates to a processing method of a tertiary amine hydrogen fluoride adduct. The method realizes complete separation of triethylamine and hydrogen fluoride in the by-product tertiary amine hydrogen fluoride adduct by adding a resolving agent, successfully converts the by-product into reusable pure triethylamine and hydrogen fluoride, effectively avoids the environmental pollution and resource waste problems that may exist in the traditional processing method, and has important significance for promoting the sustainable development of the lithium ion battery industry.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolyte preparation technology, specifically relating to a method for treating a tertiary amine hydrogen fluoride adduct. Background Technology

[0002] Lithium bisfluorosulfonyl imide (LiFSI) is a novel electrolyte component for lithium-ion batteries, and its production process has attracted much attention. Among the production processes of bisfluorosulfonyl imide (FSI), the one-step method has significant advantages due to its simplicity and low cost. This method involves the reaction of sulfuryl fluoride with ammonia (NH3) to generate hydrogen fluoride (HF), followed by a strong base driving the reaction towards the formation of bisfluorosulfonyl imide. Tertiary amines, such as triethylamine, are often used as acid-binding agents to promote this reaction.

[0003] Because the bis(fluorosulfonyl)imide produced by the one-step method is highly acidic, the actual reaction system produces a tertiary amine salt of bis(fluorosulfonyl)imide (Et3N·FSI) and a triethylamine hydrogen fluoride adduct (Et3N·nHF). The triethylamine hydrogen fluoride adduct is subsequently removed by high-vacuum distillation. Since the molar ratio of the triethylamine hydrogen fluoride adduct is approximately 1:3 (Et3N:HF), the adduct is stable and cannot be directly recycled. Therefore, the triethylamine hydrogen fluoride adduct is usually cleaved with a strong base (such as NaOH) to produce triethylamine and sodium fluoride, which can then be acidified to produce hydrogen fluoride. This process consumes large amounts of acid and base, and produces aqueous triethylamine and hydrogen fluoride, requiring an additional dehydration step and consuming significant energy. Furthermore, the alkaline cleavage process generates a large amount of fluorine-containing waste, which is extremely detrimental from the perspectives of resource consumption, energy, and environmental protection. Therefore, developing a waste-free cleavage method is essential.

[0004] To address at least one of the above problems, the present invention is proposed. Summary of the Invention

[0005] The inventors discovered in their research that because hydrogen fluoride and tertiary amines can form strong hydrogen-bonded complexes, while using volatile strong acids such as hydrogen chloride can displace hydrogen fluoride, it cannot cause hydrogen fluoride to dissociate from the system; instead, hydrogen chloride will preferentially evaporate from the system. Therefore, selecting a suitable acid eluent is crucial, and it must meet the following requirements: 1. Moderate acidity to completely displace HF (pKa = 3.2). The acidity of the eluent must be at least ten times that of HF, but excessive acidity will increase the decomposition temperature of tertiary amine salts; 2. High thermal stability to adapt to the high decomposition temperature of tertiary amines; 3. Low volatility to avoid preferential escape; 4. No harmful side reactions. The eluent should not be converted into an ineffective substance during recycling. If it is converted into a substance with the same eluent function, it can still be used.

[0006] This invention relates to a one-step method for the waste-free treatment of tertiary amine hydrogen fluoride, a byproduct of lithium bis(fluorosulfonyl)imide. The method involves introducing a desorption agent and utilizing its displacement-desorption mechanism to first displace the hydrogen fluoride and then thermally dissociate the tertiary amine, thereby achieving the dissociation of the byproduct tertiary amine hydrogen fluoride adduct and obtaining pure tertiary amine and hydrogen fluoride.

[0007] This application provides a method for treating a tertiary amine hydrogen fluoride adduct, the method comprising:

[0008] Step A: The tertiary amine hydrogen fluoride adduct is mixed with the eluent and reacted at a temperature of 15-150℃ and an operating pressure of atmospheric pressure to 10kPa to obtain the hydrogen fluoride and tertiary amine eluent adduct complex.

[0009] Step B: Then, the tertiary amine eluent complex is subjected to thermal decomposition reaction to obtain a tertiary amine. The hydrogen fluoride and the tertiary amine are discharged from the reaction system. The eluent remains in the reaction system for reuse, or the secondary eluent generated by the eluent remains in the reaction system for reuse.

[0010] The eluent is one or more of polyphosphoric acid, phosphoric acid, perfluorocarboxylic acid, monofluoroacetic acid, difluoroacetic acid, monochloroacetic acid, and dichloroacetic acid;

[0011] The secondary eluent is one or more of phosphoric acid, monofluoroacetic acid, and difluoroacetic acid.

[0012] When the exfoliating agent is phosphoric acid, polyphosphoric acid will be generated after the second reuse to play its role;

[0013] When the eluent is monochloroacetic acid, monofluoroacetic acid will be generated after the second reuse to play its role.

[0014] When the eluent is dichloroacetic acid, difluoroacetic acid will be generated after the second reuse to play its role.

[0015] Preferably, the tertiary amine is selected from one or more of the following: triethylamine, tributylamine, tripropylamine, ethyl diisopropylamine, N,N-dimethylcyclohexylamine, and pyridine.

[0016] Preferably, the molar ratio of the eluent to the tertiary amine hydrogen fluoride adduct is equal to or greater than 1.

[0017] Preferably, the molar ratio of the eluent to the tertiary amine hydrogen fluoride adduct is 1 to 10.

[0018] Preferably, when the eluent in step A is polyphosphoric acid:

[0019] In step B, when the reaction temperature is set to 150–250°C, the operating pressure is 1–2 kPa.

[0020] Alternatively, in step B, when the reaction temperature is set to 400–450°C, the operating pressure is atmospheric pressure (101.325 kPa).

[0021] When the eluent in step A is one or more of the following: phosphoric acid, perfluorocarboxylic acid, monofluoroacetic acid, difluoroacetic acid, monochloroacetic acid, and dichloroacetic acid:

[0022] In step B, the reaction temperature is set to 200–250°C, and the operating pressure is set to atmospheric pressure (101.325 kPa).

[0023] Preferably, the reaction time for step A is 1 to 3 hours, and the reaction time for step B is 1 to 3 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention proposes a waste-free treatment method for the tertiary amine hydrogen fluoride adduct, a byproduct of bis(fluorosulfonyl)imide. This method uses the addition of an acid desorption agent to achieve complete separation of the tertiary amine and hydrogen fluoride, thereby obtaining pure tertiary amine and hydrogen fluoride.

[0026] 2. The method proposed in this invention avoids the drawbacks of conventional solutions (i.e., using strong alkali to separate tertiary amine hydrogen fluoride adducts), including high resource consumption, high energy consumption, and serious environmental problems.

[0027] 3. This invention proposes selection criteria and requirements for acid desorption agents, including moderate acidity, high thermal stability, low volatility, and no harmful side reactions, providing an important theoretical basis for developing new waste-free methods. Detailed Implementation

[0028] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in the manual, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials used in the following embodiments and comparative examples are all commercially available.

[0029] The principle of this application is as follows:

[0030] This invention employs an acid-based cleavage agent to split and resolve tertiary amine hydrogen fluoride adducts (hereinafter represented by triethylamine trifluoride Et3N·3HF) to obtain pure tertiary amines and hydrogen fluoride. A suitable acid is selected as the cleavage agent (HA). First, hydrogen fluoride is obtained through an acid displacement reaction, and then the tertiary amine is obtained through thermal decomposition (with triethylamine Et3N as a typical example using a base).

[0031] Its chemical equation is as follows:

[0032] Replace HF: Et3N·3HF+HA=Et3N·HA+3HF eq.1

[0033] Deamination by heating: Et3N·HA=Et3N+HA eq.2

[0034] One specific reaction step of this application includes:

[0035] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a tertiary amine hydrogen fluoride adduct, a byproduct, is separated and introduced into a reactor. A resolving agent is then added, and the reaction is carried out at atmospheric pressure, heated from room temperature to 150°C for 1–3 hours. The pressure is then maintained, and the temperature is increased to 200–450°C, reacting for 1–2 hours. The generated gas is collected using a gas collection device. The gaseous product is separated in a distillation column to obtain hydrogen fluoride (upper part of the distillation column) and a tertiary amine (lower part of the distillation column). The resolving agent, or a secondary resolving agent generated from the resolving agent, is either directly retained in the system for reuse or returned from the distillation column for reuse. The purity of the product is determined by gas chromatography and ion chromatography.

[0036] Preferably, the eluent is one or more selected from polyphosphoric acid, phosphoric acid, perfluorocarboxylic acid, monofluoroacetic acid, difluoroacetic acid, monochloroacetic acid, and dichloroacetic acid. The secondary eluent is one or more selected from phosphoric acid, monofluoroacetic acid, and difluoroacetic acid.

[0037] Preferably, the addition ratio of polyphosphoric acid (HPi) is more than one times the molar mass of Et3N·3HF, and preferably, n(HPi):n(Et3N·3HF) = (2~6):1.

[0038] The reaction temperature for HF displacement is from room temperature to 150°C, and the pressure is atmospheric pressure (101.325 kPa) to 10 kPa. The reaction process involves gradually desorbing HF by heating from room temperature to 150°C.

[0039] When the HF displacement agent is polyphosphoric acid: when the reaction temperature in the thermal decomposition of tertiary amine is set to 150-250℃, the operating pressure is 1-2 kPa; when the reaction temperature is set to 400-450℃, the operating pressure is atmospheric pressure (101.325 kPa).

[0040] When the eluent for replacing HF is any of the other eluents listed above, the reaction temperature in the thermal decomposition of the tertiary amine is set to 200–250 °C, and the operating pressure is set to atmospheric pressure (101.325 kPa).

[0041] Example 1

[0042] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a byproduct, triethylamine hydrogen fluoride adduct (concentration 0.005 mol / L), was separated and added to a reactor (1 L). Then, 0.015 mol of polyphosphoric acid was added, and the reaction was carried out at atmospheric pressure (101.325 kPa) while the temperature was increased from room temperature to 150°C for 3 hours. The temperature was then maintained at 2 kPa, and the reaction was continued for 1 hour. The product was separated by a distillation column to obtain hydrogen fluoride (upper part of the distillation column) and triethylamine (lower part of the distillation column). The polyphosphoric acid was either retained in the system for reuse or returned to the system from the distillation column for reuse. The purity of the triethylamine and hydrogen fluoride products was 99.8%.

[0043] Example 2

[0044] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a byproduct, triethylamine hydrogen fluoride adduct (concentration 0.005 mol / L), was separated and added to a reactor (1 L). Then, 0.05 mol of polyphosphoric acid was added, and the reaction was carried out at 10 kPa and 15 °C for 3 hours. The pressure was then maintained at atmospheric pressure (101.325 kPa), and the temperature was raised to 450 °C, followed by a 1-hour reaction. The product was separated by a distillation column to obtain hydrogen fluoride (upper part of the distillation column) and triethylamine (lower part of the distillation column). The polyphosphoric acid was either retained directly in the system for reuse or returned from the distillation column for reuse. The purity of the triethylamine and hydrogen fluoride products was 99.8%.

[0045] Example 3

[0046] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a triethylamine hydrogen fluoride adduct (concentration 0.005 mol / L) was separated and added to a reactor. Then, 0.005 mol of polyphosphoric acid was added, and the reaction was carried out at atmospheric pressure (101.325 kPa) while the temperature was increased from room temperature to 150°C for 3 hours. Then, while maintaining constant pressure, the temperature was increased to 400°C and the reaction was carried out for 1 hour. The product was separated by a distillation column to obtain hydrogen fluoride (upper part of the distillation column) and triethylamine (lower part of the distillation column). The polyphosphoric acid was either retained directly in the system for reuse or returned from the distillation column for reuse. The purity of the triethylamine and hydrogen fluoride products was 99.8%.

[0047] Example 4

[0048] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a triethylamine hydrogen fluoride adduct (concentration 0.005 mol / L) was separated and added to a reactor. Then, 0.015 mol of polyphosphoric acid was added, and the reaction was carried out at 10 kPa and 15 °C for 1 hour. The reaction pressure was then maintained at 1 kPa, and the temperature was raised to 250 °C, with a reaction time of 1 hour. The product was separated by a distillation column to obtain triethylamine and hydrogen fluoride, respectively. The eluent was either retained in the system for reuse or returned from the distillation column for reuse. The purity of the triethylamine and hydrogen fluoride products was 99.8%.

[0049] Example 5

[0050] Following the one-step preparation of lithium bis(fluorosulfonyl)imide, a byproduct triethylamine hydrogen fluoride adduct (concentration 0.005 mol / L) was separated and added to a reactor. Then, 0.015 mol of the eluent listed in Table 1 was added. The reaction was carried out at atmospheric pressure (101.325 kPa) and the temperature was increased from room temperature to 150°C for 3 hours. Then, while maintaining constant pressure, the temperature was increased to 200°C and the reaction was carried out for 1 hour. The product was separated by a distillation column to obtain triethylamine and hydrogen fluoride. The eluent was either retained in the system for reuse or returned to the system from the distillation column for reuse. The purity of the triethylamine and hydrogen fluoride products is listed in Table 1.

[0051] Table 1

[0052]

[0053]

[0054] For reaction group 1, the phosphoric acid used is commercial phosphoric acid (85wt%) with phosphorus pentoxide. After one implementation, it is recycled and becomes polyphosphoric acid to play the role of the desorbent.

[0055] For reaction group number 6, the monochloroacetic acid used, after one implementation, is recycled and becomes monofluoroacetic acid;

[0056] For reaction group number 7, the dichloroacetic acid used, after one implementation, is recycled and becomes difluoroacetic acid.

[0057] This indicates that the above-mentioned reagents have good cycle stability and long service life.

[0058] Example 6

[0059] Except for replacing the byproducts with substances listed in Table 2 below, all of which have a concentration of 0.005 mol / L, the synthesis was carried out in the same manner as in Example 1. The purity of the tertiary amine and the purity of the hydrogen fluoride are listed in Table 2 below.

[0060] Table 2

[0061]

[0062] Comparative Example 1

[0063] Except for replacing the added eluent with butyric acid and controlling the amount added to 0.015 mol, the synthesis was carried out in the same manner as in Example 1. Subsequent analysis of the product revealed that almost no pure triethylamine and hydrogen fluoride were produced. The reason was found to be that butyric acid has a low boiling point and high volatility, which prevents it from effectively separating the tertiary amine hydrogen fluoride adduct.

[0064] Comparative Example 2

[0065] Except that the added eluent was replaced with hydrogen chloride and the amount added was controlled to be 0.015 mol, the synthesis was carried out in the same way as in Example 1. Hydrogen chloride is a volatile strong acid that is easy to volatilize and cannot be dissociated from the system. Therefore, no pure triethylamine and hydrogen fluoride were produced, which proves that hydrogen chloride has almost no effect on separating the tertiary amine hydrogen fluoride adduct.

[0066] Comparative Example 3

[0067] Except for replacing the added eluent with sulfuric acid and controlling the amount added to 0.015 mol, the synthesis was carried out in the same manner as in Example 1. Subsequent analysis of the products revealed that almost no pure triethylamine and hydrogen fluoride were produced. The reason was found to be that the acidity of sulfuric acid was too strong to elute triethylamine. This proves that sulfuric acid has almost no effect on separating the tertiary amine hydrogen fluoride adduct.

[0068] Comparative Example 4

[0069] Except that the added eluent was changed to a sulfonic acid-type ion exchange resin, and the amount added was controlled at 0.015 mol, the synthesis was carried out in the same manner as in Example 1. Subsequent analysis of the products revealed that the sulfonic acid-type ion exchange resin decomposed, with almost no pure triethylamine and hydrogen fluoride produced. This proves that the sulfonic acid-type ion exchange resin cannot separate the tertiary amine hydrogen fluoride adduct.

Claims

1. A method for treating tertiary amine hydrogen fluoride adducts, characterized in that, The processing method includes: Step A: The tertiary amine hydrogen fluoride adduct is mixed with the eluent and reacted at a temperature of 15-150℃ and an operating pressure of atmospheric pressure to 10kPa to obtain the hydrogen fluoride and tertiary amine eluent adduct complex. Step B: Then, the tertiary amine eluent complex is subjected to thermal decomposition reaction to obtain a tertiary amine. The hydrogen fluoride and the tertiary amine are discharged from the reaction system. The eluent remains in the reaction system for reuse, or the secondary eluent generated by the eluent remains in the reaction system for reuse. The eluent is one or more of polyphosphoric acid, phosphoric acid, perfluorocarboxylic acid, monofluoroacetic acid, difluoroacetic acid, monochloroacetic acid, and dichloroacetic acid; The secondary eluent is one or more of phosphoric acid, monofluoroacetic acid, and difluoroacetic acid.

2. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 1, characterized in that, The tertiary amine is selected from one or more of the following: triethylamine, tributylamine, tripropylamine, ethyl diisopropylamine, N,N-dimethylcyclohexylamine, and pyridine.

3. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 1, characterized in that, The molar ratio of the excipient to the tertiary amine hydrogen fluoride adduct is equal to or greater than 1.

4. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 3, characterized in that, The molar ratio of the eluent to the tertiary amine hydrogen fluoride adduct is 1 to 10.

5. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 1, characterized in that, When the eluent in step A is polyphosphoric acid: In step B, the reaction temperature is set to 150–250°C, and the operating pressure is 1–2 kPa. Alternatively, in step B, the reaction temperature can be set to 400–450°C, and the operating pressure to be atmospheric pressure.

6. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 1, characterized in that, When the eluent in step A is one or more of the following: phosphoric acid, perfluorocarboxylic acid, monofluoroacetic acid, difluoroacetic acid, monochloroacetic acid, and dichloroacetic acid: In step B, the reaction temperature is set to 200–250°C, and the operating pressure is atmospheric pressure.

7. The method for treating the tertiary amine hydrogen fluoride adduct according to claim 1, characterized in that, The reaction time for step A above is 1 to 3 hours, and the reaction time for step B above is 1 to 3 hours.

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