Preparation of 2,2-difluoroethanol with the participation of borane

Abstract

The present invention belongs to the technical field of fluorine chemical industry, and specifically relates to the preparation reaction of 2,2-difluoroethanol with the participation of borane. The following steps are included: (1) 1,1-difluoro-2-chloroethane is used as a raw material, and a catalytic cracking reaction occurs under the action of a catalyst, and 1,1-difluoroethylene is obtained after distillation; (2) 1,1-difluoroethylene and a borane complex are used for hydroboration reaction to obtain an alkyl boron solution; (3) an oxidant is added to the alkyl boron solution to continue the reaction, and 2,2-difluoroethanol is obtained after distillation. The present invention solves the problem of subsequent treatment of by-products by using R142b as a raw material; high-boiling-point aprotic solvents are abandoned during the reaction, the separation and purification steps are simplified, and the highly selective synthesis of the target product 2,2-difluoroethanol is achieved, which effectively avoids the generation of isomer by-products and ensures a high product yield.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and specifically relates to a preparation reaction of 2,2-difluoroethanol with the participation of borane. Background Art

[0002] As an important component of battery electrolyte, electrolyte plays a vital role in battery operating temperature, service life and safety. In recent years, with the rapid development of new energy technologies, the demand for high-performance battery electrolytes has increased. In this context, a variety of fluorinated diether compounds have attracted much attention due to their unique electrolyte properties, showing great potential as non-aqueous electrolytes in secondary batteries. In the preparation process of fluorinated diether compounds, 2,2-difluoroethanol is an indispensable raw material, and its quality and output directly affect the performance and application prospects of subsequent products.

[0003] 2,2-Difluoroethanol can not only be used to prepare fluorinated diether compounds, but also has good electrolyte additive properties, which can further improve the overall performance of batteries. Therefore, the development of 2,2-difluoroethanol preparation technology has important practical significance and market value.

[0004] However, although there are some methods for preparing 2,2-difluoroethanol, these methods often have problems such as harsh reaction conditions and environmental pollution, and it is difficult to meet the needs of industrial production. Chinese patent CN111039751A discloses a method for synthesizing 2,2-difluoroethanol using 1,1-difluoro-2-chloroethane (R142) as a raw material, wherein an intermediate product is prepared by reacting R142 with an alkali metal formate or an alkali metal acetate; under the catalysis of an oxide carrier-supported metal element catalyst, the intermediate product reacts with an alcohol to prepare 2,2-difluoroethanol, and the oxide carrier-supported metal element is used as a catalyst, which can be recycled and no alkaline waste liquid is generated. However, the high-boiling-point aprotic solvents such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) used therein have a strong solvent encapsulation effect on 1,1-difluoro-2-chloroethane and 2,2-difluoroethanol, making it difficult to separate these two substances from the solvent at boiling point temperature. Therefore, the temperature required in the product purification process will increase significantly. In addition, the reaction temperature required for this preparation method is also relatively high, which can easily cause the loss of R142 during the reflux process, thereby affecting the reaction yield. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a borane-involved 2,2-difluoroethanol preparation reaction, which solves the problem of subsequent treatment of the by-product by utilizing R142, a by-product in the production of R142b, as a raw material; during the reaction process, a high-boiling-point aprotic solvent is discarded, the separation and purification steps are simplified, and a highly selective synthesis of the target product 2,2-difluoroethanol is achieved, the generation of isomer by-products is effectively avoided, and a higher product yield is ensured.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The borane-involved 2,2-difluoroethanol preparation reaction comprises the following steps:

[0008] (1) Using 1,1-difluoro-2-chloroethane as raw material, a catalytic cracking reaction occurs under the action of a catalyst, and 1,1-difluoroethylene is obtained after distillation;

[0009] (2) introducing 1,1-difluoroethylene into the borane complex and performing a hydroboration reaction at 0-10°C to obtain an alkyl boron solution; wherein the molar ratio of 1,1-difluoroethylene to the borane complex is (2-3):1;

[0010] (3) adding an oxidant to the alkyl boron solution obtained in step (2), adjusting the system to alkaline conditions, continuing the reaction at 25-70° C., and obtaining 2,2-difluoroethanol after distillation; wherein the molar ratio of the amount of the oxidant added to the amount of 1,1-difluoroethylene added in step (2) is (1-1.5):1.

[0011] In the step (1), the catalyst is a lanthanum-based catalyst, and the catalyst composition is n% MX2 / La2O3, wherein MX2 is an active phase, La2O3 is a carrier phase, M is Mg, Ca, Sr or Ba, X is F or Cl, and n is the active phase content, and the value range of n is 20~30.

[0012] In the step (1), the amount of the catalyst used is 0.1-0.2 wt.% of the total amount of 1,1-difluoro-2-chloroethane.

[0013] In the step (1), the temperature of the catalytic cracking reaction is 340-350°C, the pressure is normal pressure, and the time is 6-10s.

[0014] In the step (1), the distillation temperature is -12 to -8°C and the pressure is 1.5 to 1.7 MPa.

[0015] In the step (2), the borane complex is one of 9-boranebicyclo[3,3,1]-nonane (9-BBN), borane dimethyl sulfide complex (BH3·S(CH3)2) or borane tetrahydrofuran complex (BH3·THF).

[0016] In the step (2), the pressure of the hydroboration reaction is normal pressure and the time is 3 to 5 hours.

[0017] In the step (3), the oxidant is one of hydrogen peroxide, sodium perborate or trimethylamine-N-oxide.

[0018] In the step (3), the reaction is continued at normal pressure for 2 to 3 hours.

[0019] In the step (3), the distillation pressure is atmospheric pressure, and the fraction at 100-105° C. is collected.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention uses R142, a by-product that is difficult to avoid in the production process of R142b, as a raw material, which not only solves the problem of subsequent treatment of R142, but also maximizes the utilization of resources and improves the economy and environmental protection of production;

[0022] (2) The present invention abandons the high-boiling-point aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide commonly used in traditional preparation methods, which not only simplifies the separation and purification steps of the product and reduces the production cost, but also significantly reduces the use and emission of harmful solvents;

[0023] (3) The present invention achieves highly selective synthesis of the target product 2,2-difluoroethanol through catalytic cracking and hydroboration reaction. Among them, the hydroboration reaction is a synergistic reaction, that is, the reaction is completed in one step, and the two molecules of reactants simultaneously achieve the breaking and regeneration of chemical bonds through a cyclic transition state, which effectively avoids the formation of isomer by-products during the reaction process, ensures a high product yield, not only improves the overall production efficiency, but also significantly optimizes the product quality;

[0024] (4) The reaction process of the present invention is carried out at a relatively low temperature, and the temperature control is simple, which not only reduces energy consumption but also reduces the potential safety hazards caused by high temperature. In addition, the reaction design under normal pressure conditions further simplifies the operating requirements and improves the safety and stability of production. DETAILED DESCRIPTION

[0025] The present invention is further described below with reference to the embodiments, but they do not limit the implementation of the present invention.

[0026] Unless otherwise specified, the raw materials used in the examples and comparative examples are conventional commercially available raw materials, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0027] Some of the raw materials used in the examples and comparative examples are described as follows:

[0028] Lanthanum-based catalyst, the catalyst composition is 30% SrCl2 / La2O3, wherein SrCl2 is the active phase and La2O3 is the carrier phase. The preparation method thereof refers to Example 2 in CN113893868A.

[0029] Example 1

[0030] The steps of the preparation reaction of 2,2-difluoroethanol with the participation of borane are as follows:

[0031] (1) 1,1-difluoro-2-chloroethane was used as a raw material, a catalyst of 30% SrCl2 / La2O3 was added, and a catalytic cracking reaction was carried out at normal pressure and 340°C for 10 seconds. After the reaction, 1,1-difluoroethylene was obtained by distillation at -8°C and 1.7MPa. The amount of the catalyst used was 0.2wt.% of the total amount of 1,1-difluoro-2-chloroethane.

[0032] (2) Add 0.1 mol of 9-BBN to a reaction bottle containing 100 mL of tetrahydrofuran to obtain a reaction solution, place the reaction solution in a low-temperature constant temperature reaction tank at 10°C, introduce high-purity argon gas into the reaction bottle for 5 minutes, wait until the temperature of the reaction solution drops to 10°C, slowly introduce 0.2 mol of 1,1-difluoroethylene into the reaction bottle, carry out a hydroboration reaction under normal pressure, stir for 5 hours, remove the reaction bottle, and heat it to room temperature to obtain an alkyl boron solution;

[0033] (3) Add 5 mL of 2 mol / L NaOH solution to the alkyl boron solution prepared in step (2), add 0.3 mol of 30% H2O2 dropwise at room temperature through a constant pressure dropping funnel, continue the reaction at 66°C for 3 h, cool to room temperature after the reaction, perform atmospheric distillation, collect the fraction at 102.5±2.5°C, and dry it over an activated molecular sieve to obtain 2,2-difluoroethanol.

[0034] Example 2

[0035] The steps of the preparation reaction of 2,2-difluoroethanol with the participation of borane are as follows:

[0036] (1) 1,1-difluoro-2-chloroethane was used as a raw material, a catalyst of 30% SrCl2 / La2O3 was added, and a catalytic cracking reaction was carried out at normal pressure and 345°C for 8 seconds. After the reaction, distillation was carried out at -10°C and 1.6MPa to obtain 1,1-difluoroethylene; wherein the amount of the catalyst used was 0.2wt.% of the total amount of 1,1-difluoro-2-chloroethane;

[0037] (2) Take 100 mL of BH3·THF with a molar concentration of 1 mol / L in a reaction bottle, place it in a low-temperature constant temperature reaction tank at 0°C, pass high-purity argon gas into the reaction bottle for 5 minutes, wait until the temperature of the reaction liquid drops to 0°C, slowly pass 0.3 mol of 1,1-difluoroethylene into the reaction bottle, and carry out the hydroboration reaction under normal pressure. After stirring for 3 hours, remove the reaction bottle and heat it to room temperature to obtain an alkyl boron solution;

[0038] (3) Add 5 mL of 2 mol / L NaOH solution to the alkyl boron solution prepared in step (2), add 0.3 mol of 30% H2O2 dropwise at room temperature through a constant pressure dropping funnel, continue the reaction at 66°C for 2 h, cool to room temperature after the reaction, perform atmospheric distillation, collect the fraction at 102.5±2.5°C, and dry it over an activated molecular sieve to obtain 2,2-difluoroethanol.

[0039] Example 3

[0040] The steps of the preparation reaction of 2,2-difluoroethanol with the participation of borane are as follows:

[0041] (1) 1,1-difluoro-2-chloroethane was used as a raw material, a catalyst of 30% SrCl2 / La2O3 was added, and a catalytic cracking reaction was carried out at normal pressure and 350°C for 6 seconds. After the reaction, 1,1-difluoroethylene was obtained by distillation at -12°C and 1.5MPa. The amount of the catalyst used was 0.1wt.% of the total amount of 1,1-difluoro-2-chloroethane;

[0042] (2) Take 100 mL of BH3·THF with a molar concentration of 1.0 mol / L in a reaction bottle, place it in a low-temperature constant temperature reaction tank at 0°C, pass high-purity argon gas into the reaction bottle for 5 minutes, wait until the temperature of the reaction liquid drops to 0°C, slowly pass 0.3 mol of 1,1-difluoroethylene into the reaction bottle, and carry out the hydroboration reaction under normal pressure. After stirring for 3 hours, remove the reaction bottle and heat it to room temperature to obtain an alkyl boron solution;

[0043] (3) Add 4 mL of pure water to the alkyl boron solution prepared in step (2), add 0.3 mol of trimethylamine-N-oxide dropwise through a constant pressure dropping funnel at room temperature, react at 25° C. for 3 h, cool to room temperature after the reaction, perform atmospheric distillation, collect the fraction at 102.5±2.5° C., and dry it over an activated molecular sieve to obtain 2,2-difluoroethanol.

[0044] Comparative Example 1

[0045] The difference from Example 2 is that in step (2), the molar ratio of 1,1-difluoroethylene to the borane complex is 4:1, and the rest is the same as Example 2.

[0046] Comparative Example 2

[0047] The difference from Example 2 is that in step (2), the temperature of the hydroboration reaction is 25° C., and the rest is the same as Example 2.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that in step (3), the molar ratio of the amount of the oxidant added to the amount of 1,1-difluoroethylene added in step (2) is 2:1, and the rest is the same as Example 1.

[0050] Comparative Example 4

[0051] The difference from Example 1 is that in step (3), the temperature for continuing the reaction is 80° C., and the rest is the same as Example 1.

[0052] The 2,2-difluoroethanol products obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were analyzed by gas chromatography, and their yields (%) and selectivities (%) were calculated respectively.

[0053] The test results are shown in Table 1.

[0054] Table 1 Performance test results

[0055]

[0056] It can be seen from Table 1 that the 2,2-difluoroethanol prepared in Examples 1 to 3 has a high yield and good selectivity.

[0057] In Comparative Example 1, due to the reduced amount of borane complex input, part of 1,1-difluoroethylene cannot be converted into alkyl boron to participate in the subsequent reaction.

[0058] In Comparative Example 2, due to the excessively high reaction temperature, the hydroboration reaction rate was too fast, the reaction process was difficult to control, and the reaction yield and selectivity were reduced to varying degrees.

[0059] In Comparative Example 3, due to excessive input of oxidant, part of the raw materials or products will undergo oxidative decomposition reaction, thereby affecting the yield and selectivity.

[0060] In Comparative Example 4, since the reaction temperature of step (3) is too high, part of the oxidant and the product itself will be decomposed and consumed, thereby affecting the yield and selectivity.

Claims

1. A borane-involved 2,2-difluoroethanol preparation reaction, characterized in that: The following steps are involved: (1) Using 1,1-difluoro-2-chloroethane as raw material, a catalytic cracking reaction occurs under the action of a catalyst, and 1,1-difluoroethylene is obtained after distillation; The catalyst is a lanthanum-based catalyst, and the catalyst composition is 30% SrCl2 / La2O3, wherein SrCl2 is the active phase and La2O3 is the carrier phase; (2) introducing 1,1-difluoroethylene into the borane complex and performing a hydroboration reaction at 0-10°C to obtain an alkyl boron solution; wherein the molar ratio of 1,1-difluoroethylene to the borane complex is (2-3):1; (3) adding an oxidant to the alkyl boron solution obtained in step (2), continuing the reaction at 25-70° C., and obtaining 2,2-difluoroethanol after distillation; wherein the molar ratio of the amount of the oxidant added to the amount of 1,1-difluoroethylene added in step (2) is (1-1.5):

1.

2. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (1), the amount of the catalyst used is 0.1-0.2 wt.% of the total amount of 1,1-difluoro-2-chloroethane.

3. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (1), the temperature of the catalytic cracking reaction is 340-350°C, the pressure is normal pressure, and the time is 6-10s.

4. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (1), the distillation temperature is -12 to -8°C and the pressure is 1.5 to 1.7 MPa.

5. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (2), the borane complex is one of 9-boranebicyclo[3,3,1]-nonane, borane dimethyl sulfide complex or borane tetrahydrofuran complex.

6. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (2), the pressure of the hydroboration reaction is normal pressure and the time is 3 to 5 hours.

7. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (3), the oxidant is one of hydrogen peroxide, sodium perborate or trimethylamine-N-oxide.

8. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (3), the reaction is continued at normal pressure for 2 to 3 hours.

9. The borane-assisted 2,2-difluoroethanol preparation reaction according to claim 1, characterized in that: In the step (3), the distillation pressure is atmospheric pressure, and the fraction at 100-105° C. is collected.

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