A process for the preparation of a boron trifluoride diethyl ether complex

Abstract

The present application relates to the technical fields of chemical synthesis, and particularly relates to a preparation method of boron trifluoride diethyl ether complex. The method comprises the following steps: mixing diethyl ether with inert solvent toluene, pre-cooling to-10~0 DEG C, passing in BF3 gas, controlling the molar ratio of BF3:Et2O to be 1:1.05~1.10, controlling the gas passing rate to be 20~30 g / h, and obtaining complex liquid by reaction; then, the complex liquid is concentrated by reduced pressure distillation to obtain concentrated liquid; then, normal hexane is added to the concentrated liquid in two stages, and solid-liquid separation is performed by aging crystallization to obtain white crystals. The white crystals are solvent complex crystals of BF3.Et2O and normal hexane, and the colorless transparent liquid product is obtained by removing normal hexane under the condition of reduced pressure and heating at 40 DEG C. The liquid product has purity of ≥99.9% by gas chromatography, water content of ≤100ppm, and molar yield of product calculated by BF3 of ≥74%, and is suitable for electronic packaging materials and special resin synthesis.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, specifically to a method for preparing boron trifluoride diethyl ether complex. Background Technology

[0002] Boron trifluoride diethyl ether complex (BF3·Et2O) is an important Lewis acid catalyst, widely used in epoxy resin curing, phenolic resin polycondensation, unsaturated polyester resin synthesis, and pharmaceutical intermediate preparation.

[0003] Currently, the industrial production of boron trifluoride diethyl ether complexes mainly employs the method of directly absorbing boron trifluoride gas with diethyl ether. For example, the e-EROS Encyclopedia of Organic Synthesis Reagents (March 2007) describes an industrial production method for boron trifluoride diethyl ether complexes, which uses direct absorption of boron trifluoride gas with diethyl ether. This is currently the most mainstream method for the industrial production of boron trifluoride diethyl ether complexes. However, the product obtained by this method is usually pale yellow, has low purity according to gas chromatography, and often contains trace amounts of colored polymer impurities and free boron trifluoride. Although these impurities are present in extremely low amounts, they can seriously affect the dielectric properties and curing uniformity of electronic packaging materials, making it difficult to meet the stringent requirements of high-end applications for catalysts with high purity (≥99.9%) and ultra-low moisture content (≤100ppm). The paper "Synthesis and Application of Boron Trifluoride Diethyl Ether Complex" (Shanghai Journal of Chemical Industry and Engineering) also describes the preparation method of boron trifluoride diethyl ether complex. This method utilizes the generated boron fluoride gas and the diethyl ether gas evaporated from the diethyl ether vaporizer to carry out gas-phase complexation in a complexation vessel. The complexation product is a pale yellow liquid with a boron fluoride content of 45% or more. Since the complexation reaction is a strongly exothermic process, if the heat is not removed in time, it is easy to cause local overheating, which will cause the diethyl ether to decompose and generate byproducts such as acetaldehyde and ethylene, while introducing impurities such as moisture and free boron trifluoride.

[0004] To improve product purity, studies have attempted to improve the process through low-temperature reactions, molecular sieve dehydration, or recrystallization. However, low-temperature reactions still cannot completely eliminate side reactions caused by temperature gradients; while molecular sieve dehydration can reduce water content, its effectiveness in removing organic impurities is limited and yield loss is significant; traditional recrystallization is carried out directly in the diethyl ether mother liquor, which easily leads to the inclusion of solvent impurities in the product, resulting in unsatisfactory purification.

[0005] Therefore, developing a method to effectively control the exothermic reaction, specifically remove moisture and colored impurities, and obtain high-purity boron trifluoride diethyl ether complexes has significant industrial application value. Summary of the Invention

[0006] To address the problems of exothermic runaway reaction, low product purity, and high moisture content in existing technologies, this invention provides a method for preparing boron trifluoride diethyl ether complex.

[0007] This invention is achieved through the following technical solution: A method for preparing a boron trifluoride diethyl ether complex includes the following steps: S1, Complexation reaction Diethyl ether and toluene are mixed in a mass ratio of 1:3~5 and cooled to -10~0℃. BF3 gas is then introduced at a uniform rate, controlling the BF3:Et2O molar ratio at 1:1.05~1.10 and the gas flow rate at 20~30 g / h. The reaction time is calculated based on the theoretical BF3 flow rate and gas flow rate (usually 5~7 hours). Toluene is used as an inert solvent to disperse the heat of reaction and prevent localized overheating. The reaction can be carried out in a conventional low-temperature reactor with stirring. To ensure low moisture content in the product, both diethyl ether and toluene are dried using molecular sieves or dehydrated by azeotropic distillation before use, with the water content controlled below 50 ppm. The entire reaction and subsequent crystallization process are carried out under nitrogen protection to prevent moisture intrusion from the air, ultimately yielding a complex liquid.

[0008] S2, vacuum distillation The complex solution obtained in step S1 is concentrated by vacuum distillation at an absolute pressure of 10-20 kPa and a temperature of 40-50°C to remove some of the solvent, yielding a concentrated solution. The solvent recovered by distillation is then dehydrated after adjusting the ether / toluene ratio by fractional distillation and can be recycled.

[0009] S3, Gradient crystallization and solid-liquid separation Add n-hexane as a crystallization solvent to the concentrated solution obtained in step S2 in two portions. First, add 60-80% of the total n-hexane and age at -5~5℃ for 2-3 hours to crystallize. Second, add the remaining n-hexane and age at -10~0℃ for 1-2 hours to crystallize. Then, perform solid-liquid separation at -5~0℃, which can be done by centrifugation (6000-8000 r / min) or filtration to obtain white crystals. The total mass ratio of the concentrated solution to n-hexane is 1:2-4.

[0010] The white crystals prepared by this invention are solvate crystals of BF3·Et2O and n-hexane (i.e., n-hexane molecules participate in lattice formation). This solvate precipitates stably at low temperatures, while most colored impurities, water, and unreacted diethyl ether remain in the mother liquor, thus achieving efficient purification. After removing n-hexane by heating at 40°C under reduced pressure, the white crystals revert to a colorless and transparent liquid. The water content of this colorless and transparent liquid product is ≤100ppm (Karl Fischer method), the gas chromatographic purity is ≥99.9%, and the molar yield calculated based on the total amount of BF3 introduced is ≥74%.

[0011] Compared with the prior art, the advantages of the present invention are as follows: This invention provides a method for preparing boron trifluoride diethyl ether complexes. This method has stable processes, produces high-purity products, and can be achieved using conventional commercially available equipment. Attached Figure Description

[0012] The invention will now be further described with reference to the accompanying drawings.

[0013] Figure 1 Flowchart of the preparation process of boron trifluoride diethyl ether complex; Figure 2 The molecular formula is that of a boron trifluoride diethyl ether complex. Figure 3 Infrared spectrum of boron trifluoride diethyl ether complex; Figure 4 This is the mass spectrum of the boron trifluoride diethyl ether complex. Detailed Implementation

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Example 1

[0016] The preparation process of boron trifluoride diethyl ether complex is as follows: Figure 1 As shown. 200g of diethyl ether and 800g of toluene (mass ratio 1:4) were mixed and added to a low-temperature reactor, cooled to -5℃, and then BF3 gas was introduced at a rate of 25g / h. The 200g of diethyl ether (2.70mol) required 2.50mol of BF3 (169.5g) based on a BF3:Et2O molar ratio of 1:1.08. The reaction proceeded for approximately 6.8 hours (controlled by the weight gain of the reactor, and the absence of BF3 in the tail gas after alkali absorption testing, indicating complete BF3 absorption), yielding a reaction solution. The reaction solution was transferred to a rotary evaporator and distilled under reduced pressure at 15kPa (vacuum approximately -0.086MPa) and 45℃ to obtain 480g of concentrated solution. The concentrated liquid was transferred to a crystallization vessel, and 960g of n-hexane (total 1200g) was added initially. The mixture was aged and crystallized at -5℃ for 2 hours. The remaining 240g of n-hexane was added second time, and the mixture was aged and crystallized at -10℃ for 1.5 hours to obtain a crystal slurry. The crystal slurry was then transferred to a low-temperature centrifuge and centrifuged at -5℃ and 7000 rpm for 10 minutes to obtain 317.8g of white crystals. The white crystals were then heated at 40℃ and 10 kPa absolute pressure to remove the n-hexane until constant weight was achieved, yielding 281.6g of a colorless, transparent liquid.

[0017] Based on the amount of BF3 introduced (2.50 mol), the theoretical mass of BF3·Et2O was calculated to be 354.8 g, and the actual yield was 79.4% (281.6 / 354.8×100%).

[0018] The water content was determined to be 78 ppm by Karl Fischer method; the peak area percentage of the main component was determined to be 99.93% by gas chromatography; DSC analysis showed that the desolventizing endothermic peak of the solvate crystal was about 48~50℃, and under reduced pressure, complete removal of n-hexane could be achieved at 40℃.

[0019] Gas chromatography detection method: An Agilent 7890B gas chromatograph with an HP-5 capillary column (30 m × 0.32 mm × 0.25 μm) and an FID detector was used. Temperature program: 40℃ for 2 min, then increased to 200℃ at 10℃ / min and held for 5 min. Injector temperature 250℃, detector temperature 280℃, carrier gas nitrogen (1.0 mL / min), split ratio 50:1. The sample was dissolved in anhydrous diethyl ether to a concentration of 1 mg / mL, and injected in 1 μL. The retention time of BF3·Et2O was approximately 6.8 min, and purity was calculated using the area normalization method.

[0020] Example 2

[0021] 200g of diethyl ether and 1000g of toluene (mass ratio 1:5) were mixed and added to a low-temperature reactor. The mixture was cooled to -10℃, and BF3 gas was introduced at a rate of 30g / h. The 200g of diethyl ether (2.70mol) required 2.57mol of BF3 (174.3g) based on a BF3:Et2O molar ratio of 1:1.05. The reaction proceeded for approximately 5.8 hours (controlled by reactor weight gain, and the absence of BF3 in the tail gas after alkaline absorption, indicating complete BF3 absorption). Afterwards, vacuum distillation (15kPa absolute pressure, 45℃) yielded 450g of concentrated solution. 900g of n-hexane (total 1350g) was added to the concentrated solution initially, and the mixture was aged at 0℃ for 3 hours to crystallize. The remaining 450g of n-hexane was added a second time, and the mixture was aged at -5℃ for 1 hour to obtain a slurry. The crystal slurry was then centrifuged (-5℃, 8000 r / min) to obtain 306.5 g of white crystals. The white crystals were then heated at 40℃ and 10 kPa absolute pressure to remove n-hexane until constant weight was achieved, yielding 271.2 g of a colorless and transparent liquid.

[0022] The theoretical mass of BF3·Et2O was 364.8 g (2.57 mol of BF3), and the actual yield was 74.3% (271.2 / 364.8 × 100%). The purity of this liquid under gas chromatography was 99.91%, with a water content of 85 ppm.

[0023] Example 3 A method for preparing a boron trifluoride diethyl ether complex includes the following steps: S1, Complexation reaction Diethyl ether and toluene are mixed in a mass ratio of 1:3~5 and cooled to -10~0℃. BF3 gas is then introduced at a uniform rate, controlling the BF3:Et2O molar ratio at 1:1.05~1.10 and the gas flow rate at 20~30 g / h. The reaction time is calculated based on the theoretical BF3 flow rate and gas flow rate (usually 5~7 hours). Toluene is used as an inert solvent to disperse the heat of reaction and prevent localized overheating. The reaction can be carried out in a conventional low-temperature reactor with stirring. To ensure low moisture content in the product, both diethyl ether and toluene are dried using molecular sieves or dehydrated by azeotropic distillation before use, with the water content controlled below 50 ppm. The entire reaction and subsequent crystallization process are carried out under nitrogen protection to prevent moisture intrusion from the air, ultimately yielding a complex liquid.

[0024] S2, vacuum distillation The complex solution obtained in step S1 is concentrated by vacuum distillation at an absolute pressure of 10-20 kPa and a temperature of 40-50°C to remove some of the solvent, yielding a concentrated solution. The solvent recovered by distillation is then dehydrated after adjusting the ether / toluene ratio by fractional distillation and can be recycled.

[0025] S3, Gradient crystallization and solid-liquid separation Add n-hexane as a crystallization solvent to the concentrated solution obtained in step S2 in two portions. First, add 60-80% of the total n-hexane and age at -5~5℃ for 2-3 hours to crystallize. Second, add the remaining n-hexane and age at -10~0℃ for 1-2 hours to crystallize. Then, perform solid-liquid separation at -5~0℃, which can be done by centrifugation (6000-8000 r / min) or filtration to obtain white crystals. The total mass ratio of the concentrated solution to n-hexane is 1:2-4.

[0026] The white crystals prepared by this invention are solvate crystals of BF3·Et2O and n-hexane (i.e., n-hexane molecules participate in lattice formation). This solvate precipitates stably at low temperatures, while most colored impurities, water, and unreacted diethyl ether remain in the mother liquor, thus achieving efficient purification. After removing n-hexane by heating at 40°C under reduced pressure, the white crystals revert to a colorless and transparent liquid. The water content of this colorless and transparent liquid product is ≤100ppm (Karl Fischer method), the gas chromatographic purity is ≥99.9%, and the molar yield calculated based on the total amount of BF3 introduced is ≥74%.

[0027] Example 4 (Moisture Determination) The moisture content was determined using the Karl Fischer coulometric method, with the following steps: The coulometric moisture analyzer (METTLER Toledo C30) was calibrated using a 10.0 μg / μL water-methanol standard solution, repeated three times, with an error ≤ ±2%. 1.000 ± 0.001 g of the liquid product from Example 1 (after hexane removal at 40°C) was weighed into a glove box (humidity < 0.1%) and rapidly injected into a sealed titration cell containing 10 mL of anhydrous acetonitrile. The endpoint current threshold was set to ≤ 5 μA, and the titration was performed automatically to the endpoint. The moisture content was recorded. The measured moisture content was 78 ppm.

[0028] Example 5 (Structural Characterization) The prepared boron trifluoride diethyl ether complex (the liquid after removing n-hexane; the molecular formula of the boron trifluoride diethyl ether complex is shown in [reference]). Figure 2 Infrared spectroscopy, mass spectrometry, and Raman spectroscopy were performed for detection. Infrared spectroscopy detection: Approximately 5 mg of the liquid sample obtained in Example 1 was coated onto the KBr windows to form a liquid film. A Fourier transform infrared spectrometer (Nicolet iS50, 4 cm⁻¹ resolution) was used. -1 ) in 400-4000cm -1 The range was scanned 32 times. The entire test was conducted under dry nitrogen protection to avoid interference from moisture in the air. Figure 3 As shown, the infrared spectrum is in the range of 1100~1200 cm⁻¹ -1 BF stretching vibration absorption peaks appear in the range of 900–930 cm⁻¹. -1 BO coordination bond characteristic peaks were observed in the range; meanwhile, no free BF3 (~1500 cm⁻¹) was observed. -1 ) and moisture (~3400 cm -1 The obvious absorption of the broad peak proves that the coordination bond is formed and the product is pure.

[0029] Mass spectrometry detection: 20 mg of sample was dissolved in 1 mL of anhydrous diethyl ether, filtered through a 0.22 μm filter membrane, and injected into a gas chromatograph-mass spectrometer (Agilent 7890B / 5977B) using an electron impact ionization (EI) source. EI source parameters: electron energy 70 eV, ion source temperature 270 °C, transfer line temperature 280 °C. Full scan range m / z 50-600. Figure 4 As shown, the mass spectrum displays the molecular ion peak [M]. + The m / z value is 142 (consistent with the molecular weight of BF3·Et2O 141.93), and the major fragment ion is m / z 123 ([MF)). + ), m / z 95 ([BF2OEt] + The cleavage pattern is consistent with the literature reports.

[0030] Raman spectroscopy detection: The sample was placed on a -10℃ low-temperature sample stage (Linkam THMS600), and the signal was acquired using a confocal Raman spectrometer (Renishaw inVia, 532nm laser). Laser power was 5mW, exposure time was 30s, and three scans were performed. The spectral range was 100-1500cm⁻¹. -1 Raman spectra are in the range of 300–350 cm⁻¹. -1 The region exhibits characteristic peaks of BF bending vibration, but not at 480 cm⁻¹. -1 (BF3·H2O characteristic peak) confirms that there is no water interference during the crystallization process.

[0031] The above infrared spectrum (see) Figure 3 ), mass spectrometry (see Figure 4 Both the detection results of the PCR and Raman spectroscopy indicate that the obtained product is BF3·Et2O with the correct structure. No characteristic peaks of free BF3, water or other impurities were detected, which further confirms the high purity of the product obtained by the method of the present invention.

[0032] Equipment Selection Guide The equipment used in this invention are all conventional and general-purpose equipment in the chemical industry. For specific selection references, please refer to Table 1.

[0033] Table 1. Detailed list of equipment used in this invention .

[0034] All of the above equipment are commercially available products. Those skilled in the art can select from the above list or choose other commercially available equipment with the same or similar functions according to the production scale (laboratory level, pilot level, industrial level) and specific process requirements, and implement the technical solution of the present invention by any combination, all of which can achieve the technical effects described in the present invention.

Claims

1. A method for preparing a boron trifluoride diethyl ether complex, characterized in that, Includes the following steps: S1, Complexation reaction Diethyl ether and toluene were mixed in a mass ratio of 1:3~5, cooled, and BF3 gas was introduced at a constant rate. The entire reaction was carried out under nitrogen protection, and a complex liquid was finally obtained. S2, vacuum distillation The complex solution obtained in step S1 was concentrated by vacuum distillation at an absolute pressure of 10~20 kPa and 40~50℃ to obtain a concentrated solution. S3, Gradient crystallization and solid-liquid separation Hexane was added twice as a crystallization solvent to the concentrate obtained in step S2; then solid-liquid separation was performed to obtain white crystals. The white crystals were heated under reduced pressure to remove hexane and restored to a colorless and transparent liquid, namely boron trifluoride diethyl ether complex. The amount of hexane added for the first time was 60-80% of the total amount of hexane, and the mixture was aged and crystallized at -5 to 5°C for 2-3 hours; the remaining hexane was added for the second time, and the mixture was aged and crystallized at -10 to 0°C for 1-2 hours.

2. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S1, the temperature after mixing diethyl ether and toluene is -10℃ to 0℃.

3. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S1, the molar ratio of BF3 to diethyl ether is controlled at 1:1.05~1.10, the aeration rate is 20~30 g / h, and the reaction time is 5~7 hours.

4. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S1, the diethyl ether and toluene are dried by molecular sieve or dehydrated by azeotropic distillation before use, and the water content is controlled to be below 50 ppm.

5. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S3, the total mass ratio of the concentrate to n-hexane is 1:2~4.

6. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S3, the solid-liquid separation is carried out at a separation temperature of -5 to 0℃ and a centrifugation condition of 6000 to 8000 r / min, resulting in white crystals.

7. The method for preparing a boron trifluoride diethyl ether complex according to claim 1, characterized in that, In step S3, when the white crystals are heated under reduced pressure, the heating temperature is 40℃ and the absolute pressure is 10kPa.

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