Preparation method of 2-fluorobiphenyl

Abstract

The invention discloses a preparation method of 2-fluorobiphenyl, which comprises the following steps: taking 2-fluorophenylboronic acid and bromobenzene as raw materials, carrying out coupling reaction at normal temperature under the action of a mixed system of diethyl ether and water and a palladium type catalyst, controlling the reaction time to 4-8 hours, washing, drying, filtering and extracting to obtain 2-fluorobiphenyl, the product purity reaches 99.3% or more, and the yield reaches 92% or more. According to the method, diazotization is not needed, 2-fluorobiphenyl can be synthesized only through one-step coupling reaction, the synthesis process has no special requirement for temperature and can be completed at room temperature, extra energy consumption is avoided, energy consumption is reduced, and the method is more suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of battery electrolyte additives and relates to a method for preparing halogenated biphenyl, in particular to a method for preparing 2-fluorobiphenyl. Background Art

[0002] 2-Fluorobiphenyl is a common compound that can be used not only as an intermediate in the fields of medicine and pesticides, but also as an additive directly added to the electrolyte of lithium-ion batteries. 2-Fluorobiphenyl used as an electrolyte additive can effectively prevent battery overcharge and improve battery safety performance.

[0003] 2-Fluorobiphenyl belongs to the class of halogenated biphenyl compounds. Its synthesis route is generally to select suitable halogenated aniline raw materials, and then couple them with benzene after diazotization to obtain halogenated biphenyl products. For example, the Chinese invention patent "Synthesis Method of 2-Fluorobiphenyl" with document number 201710202098.2 discloses that o-fluoroaniline is first diazotized and then reacted with benzene to obtain 2-fluorobiphenyl. The disclosed preparation process requires the addition of trifluoroacetic acid, anhydrous magnesium sulfate, and a composite metal catalyst. The reaction process does not require high temperature and the reaction conditions are milder. However, the temperature needs to be constantly adjusted during the preparation process. For example, the feeding process needs to be cooled to 4°C to 15°C, the temperature needs to be controlled at 20°C to 30°C after adding isoamyl nitrite, the temperature needs to be controlled at 30°C to 45°C during the process of dropping o-fluoroaniline, and the reaction temperature is controlled at 25°C to 32°C after the feeding is completed. The entire temperature control reaction process is complicated. When this method is applied to industrial production, the temperature increase and decrease process takes time, which reduces production efficiency. In addition, the reaction yield of this method is 88%, which can be further improved.

[0004] Therefore, it is necessary to provide a method for preparing 2-fluorobiphenyl with simpler reaction operation, lower temperature requirement for the reaction process and higher yield. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing 2-fluorobiphenyl, which not only has simple reaction operation and does not require a diazotization process, but can synthesize 2-fluorobiphenyl only through a coupling reaction, and the reaction process has low temperature requirements and can be completed at room temperature.

[0006] To achieve the above object, the present invention provides the following technical scheme, a method for preparing 2-fluorobiphenyl, the key of which is to use 2-fluorophenylboric acid and bromobenzene as raw materials, to carry out a coupling reaction at room temperature under the action of a mixed system of ether and water and a palladium-type catalyst, to control the reaction time to 4h to 8h, and to obtain 2-fluorobiphenyl through washing, drying, filtering and extraction. The reaction synthesis route is:

[0007]

[0008] Furthermore, the preparation process of the above palladium-type catalyst is as follows: under nitrogen protection, ethyl diphenylphosphine acetate is first dissolved in anhydrous ethanol, and then a 30% sodium hydroxide aqueous solution is added, heated, stirred, and then ammonium tetrachloropalladate is added, and stirring is continued until a precipitate is precipitated. After standing to react, the ethanol is removed to prepare the above palladium-type catalyst.

[0009] Specifically, the above-mentioned palladium-type catalyst is an alkaline solid-liquid mixture.

[0010] Specifically, the above-mentioned method for preparing 2-fluorobiphenyl comprises the following steps:

[0011] S1. Under nitrogen protection, first dissolve ethyl diphenylphosphinate in anhydrous ethanol, then add a 30% sodium hydroxide aqueous solution, heat to 40° C. to 60° C., and stir for 30 min to 60 min to prepare an ethanol aqueous solution of ethyl diphenylphosphinate;

[0012] S2, adding ammonium tetrachloropalladate into water, stirring until dissolved, to prepare an ammonium tetrachloropalladate aqueous solution;

[0013] S3, adding the aqueous solution of ammonium tetrachloropalladate prepared in step S2 dropwise to the aqueous solution of ethyl diphenylphosphinate prepared in step S1, continuing stirring, and after precipitation, standing for 20 min to 40 min, distilling off ethanol to prepare a palladium-type catalyst;

[0014] S4. Add 2-fluorophenylboric acid to diethyl ether, add the palladium catalyst prepared in step S3, add bromobenzene, stir at room temperature and control the reaction time to 4h to 6h. After the reaction is completed, stand and separate the layers, take the upper layer of solvent, wash, dry, filter and extract to obtain 2-fluorobiphenyl.

[0015] Furthermore, the molar ratio of the above-mentioned 2-fluorophenylboric acid, bromobenzene and ammonium tetrachloropalladate is 1:1.1-1.3:0.005-0.008.

[0016] Furthermore, the molar ratio of the ammonium tetrachloropalladate to ethyl diphenylphosphinothrate is 1:2.2-3.0.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The reaction synthesis route of the present invention is simple, and diazotization is not required. 2-fluorobiphenyl can be synthesized through only one-step coupling reaction. There is no special requirement for temperature during the coupling reaction conditions, and it can be completed at room temperature, which not only has no extra energy consumption, reduces energy consumption, but also saves time for temperature control, and is more suitable for industrial production.

[0019] The palladium catalyst used in the present invention is not only highly active and has good selectivity, but also very stable and can be recovered and reused, thus greatly reducing the total production cost of the product.

[0020] The yield of the prepared 2-fluorobiphenyl product is as high as 92% or more, the purity is 99.4% or more, the maximum single impurity content is less than 0.53%, the moisture content in the product is less than 110ppm, and the impurity types in the product are few. The invention is used as an electrolyte additive to effectively enhance the battery environmental safety performance of lithium batteries, improve the thermal stability of batteries, and improve the environmental high temperature resistance performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the gas chromatogram of 2-fluorobiphenyl prepared by the present invention.

[0022] Attached Figure 1 In the figure, 1 is the standard peak, and 2 is the 2-fluorobiphenyl product peak. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative work are within the scope of protection of the present invention.

[0024] For the convenience of description, the amounts of test materials used in the embodiments and comparative examples are all pure amounts.

[0025] Embodiment 1

[0026] S1. Under nitrogen protection, first dissolve 18.3 mg (0.0643 mmol) of ethyl diphenylphosphine acetate in 5 mL of anhydrous ethanol, then add 2 mL of 30% sodium hydroxide aqueous solution, heat to 50°C, and stir for 45 min;

[0027] S2, adding 6.10 mg (0.0214 mmol) of ammonium tetrachloropalladate powder to 10 mL of water, stirring until the powder is dissolved, and the prepared palladium-type catalyst is an alkaline heterogeneous solid-liquid mixture;

[0028] S3, adding the aqueous solution of ammonium tetrachloropalladate dropwise to the aqueous solution of ethyl diphenylphosphine acetate in ethanol, continuing stirring, after precipitation, standing for 30 minutes, and distilling off ethanol to prepare a palladium-type catalyst, a palladium-type catalyst alkaline heterogeneous solid-liquid mixture;

[0029] S4, add 0.500g (3.57mmol) of 2-fluorophenylboric acid to 10mL of ether, add the palladium catalyst prepared by step S3, add 0.673g (4.29mmol) of bromobenzene, stir at room temperature and control the reaction time to 6h. After the reaction is completed, stand and separate the layers. The prepared product is in the upper layer and the palladium catalyst is in the lower layer. Take the upper layer solvent, wash, dry, filter and extract to obtain 2-fluorobiphenyl sample 1.

[0030] Embodiment 2

[0031] S1. Under nitrogen protection, first dissolve 11.2 mg (0.0393 mmol) of ethyl diphenylphosphine acetate in 5 mL of anhydrous ethanol, then add 2 mL of 30% sodium hydroxide aqueous solution, heat to 60°C, and stir for 30 min;

[0032] S2, adding 5.08 mg (0.0179 mmol) of ammonium tetrachloropalladate powder to 10 mL of water, stirring until the powder is dissolved, to prepare an ammonium tetrachloropalladate aqueous solution;

[0033] S3, adding the aqueous solution of ammonium tetrachloropalladate dropwise to the aqueous solution of ethyl diphenylphosphine acetate in ethanol, continuing stirring, after precipitation, standing for 40 minutes, distilling off the ethanol, and preparing a palladium-type catalyst, the prepared palladium-type catalyst is an alkaline heterogeneous solid-liquid mixture;

[0034] S4. Add 0.500 g (3.57 mmol) of 2-fluorophenylboric acid to 10 mL of ether, add the palladium catalyst prepared by step S3, add 0.617 g (3.93 mmol) of bromobenzene, stir at room temperature and control the reaction time to 4 h. After the reaction is completed, stand and separate the layers. The prepared product is on the upper layer and the palladium catalyst is on the lower layer. Take the upper layer solvent, wash, dry, filter and extract to obtain 2-fluorobiphenyl sample 2.

[0035] Embodiment 3

[0036] S1. Under nitrogen protection, first dissolve 24.4 mg (0.0858 mmol) of ethyl diphenylphosphine acetate in 8 mL of anhydrous ethanol, then add 3 mL of 30% sodium hydroxide aqueous solution, heat to 40°C, and stir for 60 min;

[0037] S2, adding 8.13 mg (0.0286 mmol) of ammonium tetrachloropalladate powder to 16 mL of water, stirring until the powder is dissolved, to prepare an ammonium tetrachloropalladate aqueous solution;

[0038] S3, adding the aqueous solution of ammonium tetrachloropalladate dropwise to the aqueous solution of ethyl diphenylphosphine acetate in ethanol, continuing to stir, after precipitation, standing for 20 minutes, distilling off the ethanol, and preparing a palladium-type catalyst, the prepared palladium-type catalyst is an alkaline heterogeneous solid-liquid mixture;

[0039] S4, add 0.500g (3.57mmol) of 2-fluorophenylboric acid to 10mL of ether, add the palladium catalyst prepared by step S3, add 0.729g (4.65mmol) of bromobenzene, stir at room temperature and control the reaction time to 8h. After the reaction is completed, stand and separate the layers. The prepared product is in the upper layer and the palladium catalyst is in the lower layer. Take the upper layer solvent, wash, dry, filter and extract to obtain 2-fluorobiphenyl sample 3.

[0040] In step S4 of Examples 1 to 3, the lower layer solvent containing the palladium-type catalyst can be recovered as a whole for recycling. Since the prepared palladium-type catalyst is very stable, it can be placed in a barrel after recovery and sealed at room temperature.

[0041] Comparative Example

[0042] Comparative Example 1

[0043] The implementation process is the same as that of Example 1, except that when performing step S1, heating is not performed, and the subsequent steps are performed after stirring for 45 minutes to prepare reference substance 1.

[0044] Comparative Example 2

[0045] The implementation process is the same as Example 1, except that steps S1, S2 and S3 are not performed. When performing step S4, 0.2 g of palladium carbon (purity 98.0%) is added, stirred and reacted for 8 hours, the reaction solution is filtered and dried to obtain reference substance 2.

[0046] Comparative Example 3

[0047] The implementation process is the same as that of Example 1, except that after completing step S1, the pH is adjusted to neutral; in step S2, ammonium tetrachloropalladate is not added, but 6.30 mg (0.0214 mmol) of sodium tetrachloropalladate is added to 10 mL of water and stirred until the powder is dissolved to prepare an aqueous sodium tetrachloropalladate solution; in step S4, the aqueous sodium tetrachloropalladate solution is added dropwise to an ethanol aqueous solution of ethyl diphenylphosphinate, and the subsequent steps are the same as in Example 1 to prepare a reference substance 3.

[0048] Comparative Example 4

[0049] The implementation process is the same as that of Example 1, except that 10 mL of tetrahydrofuran is used instead of ether in step S4. The reaction process is the same as that of Example 1, but after the reaction is completed, the prepared product is in the lower layer and the palladium-type catalyst is in the upper layer. The solvent in the lower layer is washed, dried, filtered, and extracted to obtain 2-fluorobiphenyl sample 4.

[0050] Analysis and testing

[0051] The embodiment samples 1 to 3 and the reference substances 1 to 4 were respectively tested by high-efficiency gas chromatograph (internal standard method), and the purity of the tested samples was measured. The results are shown in Tables 1 and 2; the water content in the tested samples was measured by a moisture analyzer, and the results are shown in Table 2.

[0052] The yields in the examples and control examples were calculated according to formula 1. The results are shown in Table 2.

[0053] Formula 1: Yield (%) = actual weight of the sample obtained (g) / theoretical amount calculated based on the amount of 2-fluorophenylboric acid used (g) × 100%.

[0054] Among them, the relevant test spectrum of sample 1 is shown in the attached Figure 1 .

[0055] Table 1: Gas chromatogram peak table of sample 1

[0056] Retention time Peak height Peak area Peak area% 3.040 3202 4673 0.01457 15.567 46809 58514 0.18246 15.644 133991 167793 0.52320 15.770 23883456 41758977 99.26185 15.920 63921 76272 0.23783 16.688 1545 2201 0.00686 17.215 749 1081 0.00337 total 24133673 42069511 100.0

[0057] Table 2: Summary of sample and reference yield, purity and moisture test results

[0058] sample Yield (%) purity(%) Moisture (ppm) Maximum single impurity content (%) Sample 1 92.3 99.31 95 0.53 Sample 2 93.1 99.33 98 0.50 Sample 3 92.9 99.35 102 0.49 Reference 1 36.6 75.1 120 9.65 Reference 2 —— Not detected —— —— Reference 3 55.7 86.2 110 6.12 Reference 4 85.6 80.1 105 3.25

[0059] It can be seen from the results in Tables 1 and 2 that the total yield of each embodiment of the present invention can reach 92%, the product purity can reach 99.3%, the maximum single impurity content is lower than 0.53%, the water content in the product is lower than 110ppm, and the types of impurities that can be detected by GC in this product are few.

[0060] The product 2-fluorobiphenyl was not detected in the reference sample 2, indicating that the reaction cannot proceed smoothly under the action of palladium-carbon. It can be seen that the specificity of this reaction is that it cannot be carried out at room temperature under the action of general palladium-type catalysts.

[0061] Application Testing

[0062] The test products prepared in accordance with Examples 1 to 3 and Comparative Example 3 were sequentially added as electrolyte additives to lithium battery electrolytes, with the electrolyte without 2-fluorobiphenyl added as a blank example, wherein the amount of electrolyte additive added was 2% of the total mass of the electrolyte. At the same time, these electrolytes were used to produce lithium batteries with a capacity of 1000 mAh for battery electrical safety tests and battery environmental safety tests.

[0063] Battery electrical safety test

[0064] 1. External short circuit at room temperature

[0065] After fully charging the battery, place it in an environment of 20℃±5℃. After the battery surface temperature reaches 20℃±5℃, place it for another 30 minutes. Then connect the positive and negative terminals of the battery with wires, and ensure that the total external resistance is 80mΩ±20mΩ. Monitor the battery temperature change during the test. The battery should not catch fire or explode, and the maximum temperature should not exceed 150℃.

[0066] 2. High temperature external short circuit

[0067] After fully charging the battery, place it in an environment of 55℃±5℃. After the battery surface temperature reaches 55℃±5℃, place it for another 30 minutes. Then connect the positive and negative terminals of the battery with wires, and ensure that the total external resistance is 80mΩ±20mΩ. Monitor the battery temperature change during the test. The battery should not catch fire or explode, and the maximum temperature should not exceed 150℃.

[0068] 3. Overcharge

[0069] After the battery is fully discharged, first use a constant current charge of 3CA to a test voltage of 4.6V, and then use the test voltage constant voltage charge. The battery should not catch fire or explode.

[0070] After the battery is fully discharged, first use a constant current charge of 3CA to a test voltage of 4.8V, and then use the test voltage constant voltage charge. The battery should not catch fire or explode.

[0071] 4. Forced discharge

[0072] After the battery is fully discharged, reverse charge it at 1CA for 90 minutes. The battery should not catch fire or explode.

[0073] The test results of the battery electrical safety test are shown in Table 3:

[0074] Table 3: Test results of battery electrical safety test

[0075] sample External short circuit at room temperature High temperature external short circuit Overcharge (4.6V) Overcharge (4.8V) Forced discharge Sample 1 normal normal normal normal normal Sample 2 normal normal normal normal normal Sample 3 normal normal normal normal normal Reference 3 normal normal normal Fire normal Blank example Fire Temperature over 150℃ Fire Fire ——

[0076] It can be seen from the results in Table 3 that adding 2-fluorobiphenyl prepared by this product to the lithium battery electrolyte effectively enhances the electrical safety performance of the lithium battery. However, when the purity of the added 2-fluorobiphenyl is too low, it cannot well improve the overcharge safety performance of the battery under high voltage.

[0077] Battery Environmental Safety Test

[0078] 1. Low air pressure

[0079] After fully charging the battery, place it in a vacuum box at 20°C, evacuate the box to reduce the pressure to 11.6kPa, and keep it for 6 hours. The battery should not catch fire, explode or leak.

[0080] 2. Temperature Cycle

[0081] After fully charging the battery, place it in a temperature-controlled box at 20°C ± 5°C and perform the following steps:

[0082] a) Place the sample in a test chamber at 75℃±2℃ for 6 hours;

[0083] b) Then lower the temperature of the test chamber to -40℃±2℃ and maintain it for 6 hours. The temperature conversion time shall not exceed 30 minutes;

[0084] c) Raise the temperature of the test chamber to 75℃±2℃ again, and the temperature conversion time shall not exceed 30min;

[0085] d) Repeat steps a) to c) for 10 cycles in total. The battery should not catch fire, explode or leak.

[0086] 3. Acceleration shock

[0087] After the battery is fully charged, it is fixed on the impact table and subjected to a half-sine pulse impact test. Within the first 3ms, the minimum average acceleration is 75g. n , peak acceleration is 150g n ±25g n , the pulse duration is 6ms±1ms, and the battery is subjected to three acceleration shocks in each direction. The battery should not catch fire, explode or leak.

[0088] 4. Fall

[0089] After the battery is fully charged, it is dropped freely from a height of 1m onto a concrete plate for a total of four drop tests. The battery should not catch fire or explode.

[0090] 5. Extrusion

[0091] After the battery is fully charged, place the battery in two planes and squeeze it perpendicular to the direction of the plates. Apply a squeezing force of 13.0kN±0.78kN between the two plates. Once the pressure reaches the maximum value, the squeezing test can be stopped. During the test, the battery cannot have an external short circuit.

[0092] 6. Thermal abuse

[0093] After the battery is fully charged, put it in a test chamber. The temperature of the test chamber is raised at a rate of (5±2)℃ / min. When the temperature in the chamber reaches 130℃±2℃, keep the temperature constant and keep it for 30 minutes. The battery should not catch fire or explode.

[0094] 7. Combustion jet

[0095] After the battery is fully charged, it is placed on the wire mesh of the test fixture.

[0096] If the battery slips during the test, a single metal wire can be used to fix the battery sample on the wire mesh; if no such situation occurs, the battery shall not be bundled.

[0097] Heat the battery with flame and stop heating when any of the following three situations occur: a) the battery explodes; b) the battery burns completely; c) heating continues for 30 minutes but the battery does not catch fire or explode.

[0098] After the test, the components of the battery (except for dust-like products) or the battery as a whole shall not penetrate the aluminum mesh.

[0099] The test results of the battery environmental safety test are shown in Table 4:

[0100] Table 4: Test results of battery environmental safety test

[0101] sample Low pressure Temperature Cycle Acceleration shock fall extrusion Thermal Abuse Combustion Injection Sample 1 normal normal normal normal normal No change Fire Sample 2 normal normal normal normal normal No change Fire Sample 3 normal normal normal normal normal No change Fire Reference 3 normal normal normal normal normal Fire Fire Blank example normal Leakage Leakage normal Short Circuit explode explode

[0102] It can be seen from the results in Table 4 that the 2-fluorobiphenyl prepared by the present invention can effectively enhance the environmental safety performance of the lithium battery, improve the thermal stability of the battery, and enhance the environmental high temperature resistance performance in the lithium battery electrolyte.

Claims

1. A method for preparing 2-fluorobiphenyl, characterized in that: With 2-fluorophenylboric acid and bromobenzene as raw materials, a coupling reaction occurs at room temperature under the action of a mixed system of ether and water and a palladium-type catalyst, and the reaction time is controlled to be 4h to 8h. After washing, drying, filtering and extraction, 2-fluorobiphenyl is obtained. The reaction synthesis route is:

2. The method for preparing 2-fluorobiphenyl according to claim 1, characterized in that: The preparation process of the palladium-type catalyst is as follows: under nitrogen protection, ethyl diphenylphosphine acetate is first dissolved in anhydrous ethanol, then a sodium hydroxide aqueous solution with a mass concentration of 30% is added, heated, stirred, and then ammonium tetrachloropalladate is added, and stirring is continued until a precipitate is precipitated. After standing to react, the ethanol is removed by distillation to prepare the palladium-type catalyst.

3. The method for preparing 2-fluorobiphenyl according to claim 1, characterized in that: The palladium-type catalyst is an alkaline solid-liquid mixture.

4. A method for preparing 2-fluorobiphenyl according to any one of claims 1 to 3, characterized in that: The specific preparation steps are: S1. Under nitrogen protection, first dissolve ethyl diphenylphosphinate in anhydrous ethanol, then add a 30% sodium hydroxide aqueous solution, heat to 40° C. to 60° C., and stir for 30 min to 60 min to prepare an ethanol aqueous solution of ethyl diphenylphosphinate; S2, adding ammonium tetrachloropalladate into water, stirring until dissolved, to prepare an ammonium tetrachloropalladate aqueous solution; S3, adding the aqueous solution of ammonium tetrachloropalladate prepared in step S2 dropwise to the aqueous solution of ethyl diphenylphosphinate prepared in step S1, continuing stirring, and after precipitation, standing for 20 min to 40 min, distilling off ethanol to prepare a palladium-type catalyst; S4. Add 2-fluorophenylboric acid to diethyl ether, add the palladium catalyst prepared in step S3, add bromobenzene, stir at room temperature and control the reaction time to 4h to 6h. After the reaction is completed, stand and separate the layers, take the upper layer of solvent, wash, dry, filter and extract to obtain 2-fluorobiphenyl.

5. The method for preparing 2-fluorobiphenyl according to claim 2, characterized in that: The molar ratio of the 2-fluorophenylboric acid, bromobenzene and ammonium tetrachloropalladate is 1:1.1-1.3:0.005-0.

008.

6. The method for preparing 2-fluorobiphenyl according to claim 2, characterized in that: The molar ratio of ammonium tetrachloropalladate to ethyl diphenylphosphinothrate is 1:2.2-3.0.

Images