A method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt

Abstract

The present invention belongs to the technical field of chemical engineering and materials, and particularly relates to a method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide. The method is a continuous reaction process with three-stage coupling. Using sulfonyl fluoride, ammonia, and triethylamine as raw materials, triethylamine bis(fluorosulfonyl)imide is synthesized in one step. The present invention adopts the method of zone temperature + zone flow rate + zone concentration to achieve the highly selective synthesis of triethylamine bis(fluorosulfonyl)imide by continuous method. The principle of its three-stage coupling action is described as follows: the first stage ensures the rapid heat removal of the reaction to avoid side reactions, the second stage ensures the conversion rate of raw materials, and the third stage completely converts by-products by changing the concentration of the acid-binding agent. This three-stage coupling continuous synthesis method can make the selectivity of triethylamine bis(fluorosulfonyl)imide exceed 98%.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical reaction processes, and particularly relates to a method for highly selectively synthesizing triethylamine salt of bis(fluorosulfonyl)imide. Background Art

[0002] Under the background of "dual carbon", increasing technical requirements are put forward for the new energy field. High-performance lithium-ion batteries have a large number of mature applications in mobile devices and power batteries. In order to further improve the performance of current commercial lithium-ion batteries, various researches are booming, including aspects such as electrode materials, electrolytes, diaphragms, and battery module development. In the research of electrolytes, lithium bis(fluorosulfonyl)imide is considered to be an excellent component of lithium-ion battery electrolytes. However, due to its complex production process, its commercial price remains high.

[0003] Bis(fluorosulfonyl)imide (FSI) is the raw material for the production of lithium bis(fluorosulfonyl)imide. The current production of FSI mainly includes a two-step method starting from sulfonyl chloride and a one-step method starting from sulfonyl fluoride. Although the two-step method has a long process, it has been industrialized; while the one-step method has the advantages of short steps and low cost, but due to the complex reaction by-product system, it has great difficulties in the actual industrialization process. In the currently reported process routes, two molecules of sulfonyl fluoride and one molecule of ammonia react under the conditions of acetonitrile and triethylamine (Et3N) as solvents and acid-binding agents (US2014142338A1) to form a sulfonamide bond, thereby obtaining the target product FSI, which exists in the form of triethylamine salt of bis(fluorosulfonyl)imide (FSI·NEt3). However, due to the overly violent reaction between sulfonyl fluoride and ammonia, ammonium fluoride is usually used as the ammonia source for the reaction. Although this can make the reaction proceed more smoothly, it will by-produce more fluorinated products, increase the circulation volume and generate more fluorine-containing waste. Another solution is to introduce ammonia under reduced pressure. Although this can also reduce the severity of the reaction, the flux of ammonia under reduced pressure is too small, which is not conducive to the formation of industrial reaction technology.

[0004] In order to solve the above problems, the present invention is proposed. Summary of the Invention

[0005] The present invention provides a method for highly selectively synthesizing bis(fluorosulfonyl)imide in the form of a triethylamine salt, which can be directly lithiated to obtain lithium bis(fluorosulfonyl)imide (LiFSI).

[0006] A method for highly selectively synthesizing triethylamine salt of bis(fluorosulfonyl)imide, the method comprising the following steps:

[0007] In a three-stage coupled continuous flow reactor, using sulfonyl fluoride, ammonia and triethylamine as raw materials, directly synthesize triethylamine salt of bis(fluorosulfonyl)imide in one step;

[0008] The three-stage coupled continuous flow reactor includes: a first reaction zone, a second reaction zone, and a third reaction zone;

[0009] The first reaction zone includes a low-temperature high-flow-rate reaction microchannel, with a residence time of the material of 5 to 60 minutes and a reaction temperature of -20 to 5 °C;

[0010] The second reaction zone includes a medium-temperature low-flow-rate reaction pipeline, with a residence time of the material of 0.5 to 5 hours and a reaction temperature of 20 to 50 °C;

[0011] The third reaction zone includes a retention kettle.

[0012] Preferably, the first reaction zone and / or the second reaction zone is at a constant temperature.

[0013] Preferably, the fluid temperature in the reaction pipeline of the first reaction zone and / or the second reaction zone shows a gradient distribution.

[0014] Preferably, the fluid temperature in the reaction pipeline of the first reaction zone and / or the second reaction zone shows a form of downstream gradient heating.

[0015] Preferably, in the third reaction zone, 0.5 to 2 volume times of triethylamine is added to the incoming material (i.e., the incoming material from the second reaction zone), and the reflux reaction is carried out for 0.5 to 5 hours to completely convert the intermediate product and by-products, and after evaporating the solvent, triethylamine bis(fluorosulfonyl)imide salt is obtained.

[0016] Preferably, a first raw material mixture and a second raw material mixture are added to the first reaction zone. The first raw material mixture is a mixed solution of triethylamine, acetonitrile, and sulfonyl fluoride, and the second raw material mixture is a mixed solution of ammonia and acetonitrile;

[0017] In addition, the molar ratio of the materials continuously entering the first reaction zone of the three-stage coupled continuous flow reactor is: sulfonyl fluoride: ammonia: triethylamine = 2:1: (3 to 6), and the acetonitrile accounts for 60 to 90% of the total mass of the materials. Here, the total mass of the materials refers to the total mass of the first raw material mixture and the second raw material mixture added to the first reaction zone.

[0018] Preferably, the pipeline of the three-stage coupled continuous flow reactor is made of carbon steel or stainless steel pretreated with an ethylene glycol solution of bismuth fluoroxide.

[0019] The principle of the present invention is as follows:

[0020] From the analysis of the reaction essence, the reaction between sulfonyl fluoride and ammonia can be regarded as a multi-step process. The first step of forming fluorosulfonamide is a strongly exothermic reaction, so it is easy to have local overheating and side reactions, which will affect the product yield. Whether using ammonium fluoride as the ammonia source or introducing ammonia under reduced pressure, the reaction is controlled by reducing the effective concentration of the reactants. Moreover, according to the overall species equilibrium analysis of the reaction system, in the first step of the reaction, in addition to generating fluorosulfonamide, species such as ammonium fluoride, triethylamine hydrofluoride, and the triethylamine salt (and ammonium salt) of fluorosulfonamide will also be produced. The concentration of free ammonia will decrease significantly, but there is still a certain amount of unreacted ammonia. At this time, the temperature needs to be increased to completely react the free ammonia. In the second step of the reaction, in addition to generating the target product FSI, co-existing species will also be produced, including the ammonium salt and triethylamine salt of FSI, etc. The reaction temperature needs to be further increased to completely convert them. According to the acid dissociation constants (pKa) of FSI, fluorosulfonamide, and hydrogen fluoride, as well as the base dissociation constants (pK b ) analysis, it can be seen that to achieve an ammonia conversion rate of more than 99.9%, ammonium fluoride needs to be completely converted, which requires the ratio of triethylamine to residual ammonia to reach 100 or even higher. Therefore, a third-stage reaction needs to be set up to complete the complete conversion by adding triethylamine.

[0021] Therefore, in the present invention, a continuous flow microreaction technology is adopted. By strengthening the mass transfer and heat transfer processes and using a three-stage coupled reaction method, the problem of product selectivity is solved. The flow-type continuous reaction technology is applied to the production of FSI. Currently, there are various disclosed technologies. For example, CN201911307047.1 discloses a continuous reaction method using isocyanatochlorosulfonic acid ester as the raw material, but the raw materials in its process route are not as economical as sulfonyl fluoride and ammonia; CN202110296035.4 discloses a method for preparing FSI using a silicon carbide microchannel reactor, and the problem is that it is difficult to scale up to the production capacity required for FSI in industrialization, and the cost of scale-up is high; similarly, for some other continuous FSI synthesis technologies using microchannel reactors made of materials such as glass, since substances such as ammonium fluorosulfonamide and ammonium fluoride will be generated during the reaction, solid precipitation will occasionally occur during operation, blocking the microchannels, and it is difficult to meet the large-scale production requirements of FSI. In view of the characteristics of the stepwise reaction in FSI synthesis, the present invention proposes a three-stage coupled continuous production technology for FSI, and obtains the product in the form of triethylamine bis(fluorosulfonyl)imide.

[0022] The present invention relates to a continuous reaction process with three-stage coupling, which uses sulfonyl fluoride and ammonia as raw materials and triethylamine as an acid-binding agent to synthesize triethylamine bis(fluorosulfonyl)imide by a one-step method. The present invention adopts the method of zoning temperature + zoning flow rate + zoning concentration to achieve the high-selectivity synthesis of triethylamine bis(fluorosulfonyl)imide by a continuous method. The principle of its three-stage coupling action is expressed as follows: the first stage ensures the rapid heat removal of the reaction to avoid side reactions, the second stage ensures the conversion rate of the raw materials, and the third stage completely converts the by-products by changing the concentration of the acid-binding agent. This three-stage coupling continuous synthesis method can make the selectivity of triethylamine bis(fluorosulfonyl)imide exceed 98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the reaction process route. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention will be described below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. For the experimental methods without specific conditions noted in the embodiments, they are usually carried out according to the conventional conditions and the conditions described in the manuals, or according to the conditions recommended by the manufacturers. For general equipment, materials, reagents, etc., if not otherwise specified, they can be obtained from commercial channels. The raw materials required in the following examples and comparative examples are all commercially available.

[0025] A method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide, the method comprising the following steps:

[0026] In a continuous flow reactor with three-stage coupling, using sulfonyl fluoride, ammonia and triethylamine as raw materials, triethylamine bis(fluorosulfonyl)imide is synthesized by a one-step method;

[0027] The three-stage coupling continuous flow reactor includes: a first reaction zone, a second reaction zone and a third reaction zone; the first reaction zone is a low-temperature and high-flow-rate reaction microchannel with a residence time of 5 to 60 minutes and a reaction temperature of -20 to 5 °C; the second reaction zone is a medium-temperature and low-flow-rate reaction pipeline with a residence time of 0.5 to 5 hours and a reaction temperature of 20 to 50 °C; the third reaction zone is a retention kettle.

[0028] The specific operation method is as follows:

[0029] Dissolve sulfonyl fluoride in a mixed solution of dry acetonitrile and triethylamine, and after cooling, use a constant flow pump to transport it to the microchannel tubular reactor through a static mixer as the first raw material mixture;

[0030] Dissolve ammonia in dry acetonitrile, and after cooling, also pump it into the tubular microreactor through a crystalline mixer as the second raw material mixture;

[0031] After the second raw material mixture and the second raw material mixture enter the first reaction zone, they are mixed at low temperature and then enter the first reaction channel to complete the first-step reaction;

[0032] Then it enters the second reaction zone with a relatively higher temperature to complete the synthesis of triethylamine bis(fluorosulfonyl)imide;

[0033] Finally, it enters the retention kettle in the third reaction zone. By adding additional triethylamine and heating, the residual ammonium fluoride is completely converted to obtain triethylamine bis(fluorosulfonyl)imide. The excess triethylamine enters the solvent recovery process.

[0034] Under more optimal conditions, both the first reaction zone and the second reaction zone are carried out in a heat-insulated manner. Since the reaction is an exothermic reaction, the fluid in the reaction pipeline is naturally distributed in a form of a downstream gradient temperature rise, which is beneficial to the improvement of selectivity.

[0035] The first reaction zone includes a static mixer and a low-temperature pipeline. The reaction channel of the low-temperature pipeline is a microchannel, with a residence time of 5 to 60 minutes and a reaction temperature of -20 to 5 °C. In the first reaction zone, the reaction proceeds rapidly, which is likely to cause local overheating. Therefore, under the conditions of low temperature and high flow rate in the microchannel, the reaction of free ammonia and sulfonyl fluoride is rapidly completed, and most of the ammonia is quickly converted. The generated hydrogen fluoride is captured by triethylamine. Although triethylamine and hydrogen fluoride can form polyacid salts, due to the existence of alkali balance, there will still be a small amount of ammonia or the hydrogen fluoride in triethylamine fluoride is taken away, becoming non-free state; at the same time, the product of the first step, fluorosulfonamide, will also combine with free ammonia to form a precipitable solid. Under the condition of high flow rate, this species stays in the supersaturated zone, so it will not precipitate and block the pipeline.

[0036] This mixed material liquid enters the second reaction zone to continue the reaction. The second reaction zone is a thick pipeline, with a reaction temperature of 20 to 50 °C and a residence time of 0.5 to 5 hours. In this stage, fluorosulfonamide and sulfonyl fluoride further react to form bis(fluorosulfonyl)imide (FSI). Since FSI is relatively strong in acidity, it will also bind a small amount of free ammonia, but all the fluorosulfonamide has been completely converted. This mixed material liquid enters the retention kettle for batch operation. After accumulating to a certain amount, triethylamine is added, and the reflux reaction converts all the ammonium fluoride into free ammonia, and reacts to form FSI products, and forms triethylamine bis(fluorosulfonyl)imide with the triethylamine in the system.

[0037] Among them, the molar ratio of the materials continuously entering the first reaction zone of the reactor is sulfonyl fluoride: ammonia: triethylamine = 2:1:(3 to 6). Acetonitrile is used as a solvent, and its proportion in the total mass of the materials continuously entering the first reaction zone of the reactor is 60 to 90%. The mass of the triethylamine added later in the retention kettle is 0.5 to 2 times the volume of the pipeline feedstock.

[0038] The reactor channel of the first reaction zone can be made of carbon steel material without obvious corrosion.

[0039] When the reactor channels in the second reaction zone are made of carbon steel or stainless steel, they can withstand the erosion of the reaction feed liquid without obvious corrosion when the pipes are pretreated with a glycol solution of bismuth oxyfluoride.

[0040] The first reaction zone includes low-temperature and high-flow-rate reaction microchannels, which are specifically a self-made microchannel reactor assembled based on 0.04 * 1 / 16-inch HPLC standard stainless steel pipelines, a constant flow pump, and supporting pipe fittings. The reactor channels in the second reaction zone selected in the following examples are assembled from 4.57 mm * 1 / 4-inch standard pipelines and supporting pipe fittings.

[0041] Example 1

[0042] Load 3.04 kg of dry triethylamine, 5 kg of dry acetonitrile, and 2.04 kg of sulfonyl fluoride into raw material tank 1. Load dry acetonitrile into raw material tank 2, introduce 0.17 kg of ammonia gas, and fill with acetonitrile to make the mass of the feed liquid in the two tanks equal. The molar ratio of the materials is: sulfonyl fluoride: ammonia: triethylamine = 20:10:30, and the acetonitrile accounts for 74% of the total mass of the materials. The tank body is kept at a low temperature not exceeding 20 °C and is in a liquid state. Use a constant flow pump to pump into a static mixer at the same mass flow rate to keep the total flow rate at 10 mL / min. The first reaction zone includes a static mixer and microchannels immersed in a freezing liquid at -20 °C, with a residence time of 60 minutes; the reaction pipelines in the second reaction zone are immersed in a water bath at 50 °C, with a residence time of 30 minutes. Use a 5 L reaction kettle (as a retention kettle) to receive for 200 minutes. During this period, add 2 L of triethylamine (equivalent to adding 1 volume multiple of triethylamine of the incoming material (i.e., the incoming material in the second reaction zone is 2 liters, calculation method: flow rate of 10 mL / min multiplied by time of 200 minutes)), heat under reflux. After all the reception is completed, heat for another 1 hour, and then distill and recover the solvent. Meanwhile, switch the tubular reactor to receive with another kettle. Sampling is carried out for HPLC internal standard-external standard method detection. The conversion of sulfonyl fluoride is complete, and the selectivity of the target product triethylamine bis(fluorosulfonyl)imide is 99.5%.

[0043] The monitoring data at each sampling point are shown in Table 1 below. Fluorosulfonamide, bis(fluorosulfonyl)amide (FSI), trifluorosulfonamide, and sulfonamide in the table are all recorded in their acid forms.

[0044] Table 1

[0045]

[0046] Example 2

[0047] The raw material tank scheme is the same as that in Example 1. Keep the total flow rate at 10 mL / min, and change the residence time of the reaction by replacing microchannels and pipelines of different lengths. The first reaction zone includes a static mixer and a microchannel immersed in a freezing liquid at 5 °C with a residence time of 5 minutes; the reaction pipeline in the second reaction zone is immersed in a water bath at 20 °C with a residence time of 5 hours. Receive for 200 minutes using a 5 L reaction kettle, during which 1 L of triethylamine is added (equivalent to adding 0.5 volume times of triethylamine of the incoming material (i.e., the incoming material in the second reaction zone)), heat under reflux. After all the reception is completed, heat for another 0.5 hour, and then distill and recover the solvent. Meanwhile, switch the tubular reactor to receive with another kettle. Sampling is carried out for HPLC internal standard-external standard method detection. The sulfonyl fluoride is completely converted, and the selectivity of the target product triethylamine bis(fluorosulfonyl)imide is 98.5%.

[0048] The monitoring data at each sampling point are shown in Table 2 below. Fluorosulfonamide, bis(fluorosulfonyl)amide (FSI), trifluorosulfonamide, and sulfonamide in the table are all recorded in their acid forms.

[0049] Table 2

[0050]

[0051] Example 3:

[0052] The raw material tank scheme is the same as that in Example 1, and the heat transfer method is changed to two-stage gradient heating. The flow rate is maintained at 10 mL / min; adjust the valve to slow down the flow rate of the freezing liquid and keep the inlet temperature of the reaction zone at -20 °C and the outlet temperature at 5 °C. Slow down the flow rate of the heat transfer fluid in the second reaction zone, and the system dissipates heat naturally. The measured inlet temperature of the second reaction zone is 20 °C and the outlet temperature is 28 °C. The residence time in the first reaction zone is 30 minutes; the residence time in the second reaction zone is 3 hours. Receive for 100 minutes using a 5 L reaction kettle, during which 2 L of triethylamine is added (equivalent to adding 2 volume times of triethylamine of the incoming material (i.e., the incoming material in the second reaction zone)), heat under reflux. After all the reception is completed, heat for another 5 hours, and then distill and recover the solvent. Meanwhile, switch the tubular reactor to receive with another kettle. Sampling is carried out for HPLC internal standard-external standard method detection. The sulfonyl fluoride is completely converted, and the selectivity of the target product triethylamine bis(fluorosulfonyl)imide is 99.0%.

[0053] The monitoring data at each sampling point are shown in Table 3 below. Fluorosulfonamide, bis(fluorosulfonyl)amide (FSI), trifluorosulfonamide, and sulfonamide in the table are all recorded in their acid forms.

[0054] Table 3

[0055]

[0056] Example 4

[0057] The raw material tank solution is the same as that in Example 1. A microchannel and a reaction pipeline made of carbon steel are used. 1% bismuth oxyfluoride ethylene glycol is continuously pumped into the pipeline, soaked for 24 hours and then dried for use. The operating conditions are the same as those in Example 1. The selectivity of the target product triethylamine bis(fluorosulfonyl)imide is 99.5%. After the pipeline has been continuously operated for 24 hours, it is cleaned with acetonitrile, dried and weighed, and there is no weight loss. This indicates that the pipeline is not corroded.

Claims

1. A method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt, characterized in that, The method includes the following steps: In a three-stage coupled continuous flow reactor, using sulfuryl fluoride, ammonia, and triethylamine as raw materials, triethylamine bis(fluorosulfonyl)imide is synthesized in one step. The three-stage coupled continuous flow reactor includes: a first reaction zone, a second reaction zone, and a third reaction zone; The first reaction zone includes a low-temperature high-flow-rate reaction microchannel, with a residence time of the material of 5 to 60 minutes and a reaction temperature of -20 to 5 °C; The second reaction zone includes a medium-temperature low-flow-rate reaction pipeline, with a residence time of the material of 0.5 to 5 hours and a reaction temperature of 20 to 50 °C; The third reaction zone includes a retention kettle; The fluid temperature in the reaction pipelines of the first reaction zone and / or the second reaction zone shows a gradient distribution.

2. The method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, The fluid temperature in the reaction pipelines of the first reaction zone and / or the second reaction zone shows a form of co-current gradient heating.

3. The method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, In the third reaction zone, 0.5 to 2 volume times of triethylamine is added to the incoming material, and the reflux reaction is carried out for 0.5 to 5 hours to completely convert the intermediate product and by-products. After evaporating the solvent, triethylamine salt of bis(fluorosulfonyl)imide is obtained.

4. The method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, The first raw material mixture and the second raw material mixture are added to the first reaction zone. The first raw material mixture is a mixed solution of triethylamine, acetonitrile, and sulfuryl fluoride, and the second raw material mixture is a mixed solution of ammonia and acetonitrile; In addition, the molar ratio of the materials continuously entering the first reaction zone of the three-stage coupled continuous flow reactor is: sulfuryl fluoride: ammonia: triethylamine = 2: 1: (3 to 6), and acetonitrile accounts for 60 to 90% of the total mass of the materials.

5. The method for highly selectively synthesizing triethylamine bis(fluorosulfonyl)imide salt according to claim 1, characterized in that, The pipeline of the three-stage coupled continuous flow reactor is made of carbon steel or stainless steel pretreated with an ethylene glycol solution of bismuth oxyfluoride.

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