A method for the continuous flow reaction production of boron trifluoride and complexes thereof

Abstract

The present application belongs to the field of boron trifluoride production, and relates to a method for preparing boron trifluoride and its complex by continuous flow reaction. The method comprises the following steps: uniformly mixing boric acid with concentrated sulfuric acid, then adding oleum or continuously introducing sulfur trioxide gas to obtain an oleum solution of boric acid; introducing the obtained solution and anhydrous hydrogen fluoride gas into a continuous flow reactor at a uniform speed to obtain boron trifluoride gas; purifying and removing impurities from the boron trifluoride gas generated in the reaction; continuously introducing the purified boron trifluoride gas into a complexing solvent for a complexing reaction to obtain a boron trifluoride complex. The method uses a continuous flow reactor to react anhydrous hydrogen fluoride with the oleum solution of boric acid, so that the raw materials can be continuously and uniformly mixed, the reaction is rapid and complete, the process conditions are simplified, the sulfuric acid waste liquid can be recycled after treatment, and the method has economic advantages and process innovation, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of boron trifluoride production, and in particular to a method for preparing boron trifluoride and its complexes by continuous flow reaction. Background Technology

[0002] Boron trifluoride is an inorganic compound with the chemical formula BF3, a molecular weight of 67.8, a melting point of -127 °C, and a boiling point of -100 °C. At room temperature, it is a colorless, non-flammable, and non-combustible gas with suffocating properties; at -160 °C, it is a white solid. It produces dense white smoke upon contact with moist air and is very stable to heat. It is soluble in cold water, concentrated sulfuric acid, and most organic solvents. In the molecular structure of boron trifluoride, the fluoroborate ion is a non-coordinate anion that can form complexes with various organic solvents. In chemical laboratories, boron trifluoride is often obtained from liquid boron trifluoride diethyl ether compounds, boron trifluoride tetrahydrofuran compounds, or solid acetonitrile complexes and dimethyl carbonate complexes.

[0003] Boron trifluoride is a hazardous chemical, and its industrialization is difficult. There are few domestic manufacturers, and their production capacity is small, which cannot meet the domestic market demand.

[0004] Boron trifluoride complexes were discovered in the late 19th and early 20th centuries. The preparation of boron trifluoride gas and its complexes focuses on the selection of raw materials, with the key point being the preparation of boron trifluoride gas. Because the structure of boron trifluoride is relatively simple, the main difference between various processes for synthesizing boron trifluoride gas lies in the sources of boron and fluorine.

[0005] The existing preparation of boron trifluoride complexes is mainly carried out by batch reaction, which has the following disadvantages: 1) limited reaction conversion and product yield; 2) high safety risk; 3) low utilization rate of anhydrous hydrogen fluoride; 4) risk of gas spillage, which further reduces the yield of boron trifluoride product. Summary of the Invention

[0006] The present invention aims to provide a method for preparing boron trifluoride and its complexes via a continuous flow reaction. Boric acid and anhydrous hydrogen fluoride are used as starting materials, and a tubular continuous flow reactor is used to obtain high-purity boron trifluoride gas and then a boron trifluoride complex product is obtained through solvent complexation. The raw materials can be continuously and uniformly mixed, and the reaction is rapid and complete.

[0007] The specific technical solution of this invention is as follows: A method for preparing boron trifluoride and its complexes by continuous flow reaction includes the following steps: Step (a) Mix boric acid and concentrated sulfuric acid evenly, then add fuming sulfuric acid or continuously pass sulfur trioxide gas to obtain a fuming sulfuric acid solution of boric acid; Step (b) introduces the solution obtained in step (a) and anhydrous hydrogen fluoride gas into a continuous flow reactor at a uniform rate to obtain boron trifluoride gas; The boron trifluoride gas produced in step (c) is purified and impurities are removed. In step (d), the purified boron trifluoride gas is continuously passed into the complexing solvent to carry out the complexation reaction, thereby obtaining the boron trifluoride complex.

[0008] As a preferred embodiment, step (e) further includes collecting the dilute sulfuric acid produced by the reaction, concentrating it, and using it as a raw material.

[0009] As a preferred embodiment, in step (a), the mass ratio of concentrated sulfuric acid to boric acid is 0.5:1 to 2:1, the concentration of fuming sulfuric acid is 15% to 60%, the mass ratio of fuming sulfuric acid to boric acid is 7.8:1 to 229.3:1, the material mixing temperature is 10 to 60 ℃, and the mixing time is 1 to 3 h.

[0010] As a preferred embodiment, in step (b), the rate at which the fuming sulfuric acid solution of boric acid is introduced into the continuous flow reactor is 0.5 mL / min to 5 mL / min, the rate at which anhydrous hydrogen fluoride gas is introduced into the continuous flow reactor is 0.01 mL / min to 1 mL / min, and the reaction temperature is 110 to 160 °C.

[0011] As a preferred embodiment, in step (c), the purification device for boron trifluoride gas is an adsorption purification column, and the adsorbent is one or a combination of molecular sieves, activated carbon, and chelating agents.

[0012] As a preferred embodiment, in step (d), the complexing solvent includes tetrahydrofuran, acetonitrile, diethyl ether, dimethyl carbonate, butyl acetate, acetic acid, dimethyl ether, ethylamine, ethanol, phenol, or methanol. The complexing reaction temperature is 10–60 °C, the complexing time is 3–8 h, and the residual organic solvent is recovered by vacuum distillation.

[0013] As a preferred embodiment, in step (e), the concentration temperature is 60~120 ℃ and the decompression pressure is -0.02~-0.04MPa. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of one embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0016] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0017] Unless otherwise specified, all materials, instruments, and equipment used below are conventional materials, instruments, and equipment or obtained through commercial channels; all testing methods used are existing methods unless otherwise specified.

[0018] The existing methods for preparing boron trifluoride complexes have the following main drawbacks: 1) The reaction conversion rate and product yield are limited. The yield of existing boron trifluoride batch reaction is very low, about 40% based on anhydrous hydrogen fluoride.

[0019] 2) The reaction has a high safety risk. Large reaction vessels are prone to accumulating reaction heat, which can lead to overheating and explosion risks. They also cannot disperse reaction heat, reducing the safety of production.

[0020] 3) The utilization rate of anhydrous hydrogen fluoride is low, and incomplete reaction is likely to occur, resulting in a large waste of anhydrous hydrogen fluoride.

[0021] 4) The batch process also carries the risk of gas spillage, which further reduces the yield of boron trifluoride products.

[0022] Furthermore, this invention proposes a method for preparing boron trifluoride and its complexes using a continuous flow reactor, comprising the following steps: Step (a) Mix boric acid and concentrated sulfuric acid evenly, then add fuming sulfuric acid or continuously pass sulfur trioxide gas to obtain a fuming sulfuric acid solution of boric acid.

[0023] Step (b) involves introducing the solution obtained in step (a) and anhydrous hydrogen fluoride gas into a continuous flow reactor at a uniform rate to obtain boron trifluoride gas. The reaction equation is as follows: .

[0024] The boron trifluoride gas produced in step (c) is purified and impurities are removed.

[0025] In step (d), the purified boron trifluoride gas is continuously passed into the complexing solvent to carry out a complexation reaction, yielding a boron trifluoride complex. The reaction equation is as follows (using a boron trifluoride tetrahydrofuran, boron trifluoride butyl acetate, and boron trifluoride diethyl ether complex as an example): .

[0026] This invention utilizes a continuous flow reactor to react anhydrous hydrogen fluoride with a fuming sulfuric acid solution of boric acid. This allows for continuous and uniform mixing of the raw materials, resulting in a rapid and complete reaction, simplified process steps, and improved yield. Incompletely complexed solvent can also be recycled, offering cost advantages.

[0027] The present invention uses a continuous flow reactor, which can effectively disperse the heat of reaction and greatly improve the safety of reaction production.

[0028] Through continuous optimization and screening, the continuous flow process parameters of this invention can increase the utilization rate of anhydrous hydrogen fluoride to over 90%, which is comprehensively superior to existing processes. The continuous flow process of this invention eliminates the risk of gas spillage.

[0029] One implementation method further includes: step (e) collecting the dilute sulfuric acid produced in the reaction, concentrating it, and using it as a raw material. The sulfuric acid waste liquid at the outlet of the tubular continuous flow reactor can be recycled after treatment, offering economic advantages and technological innovation, making it suitable for large-scale industrial production.

[0030] In one embodiment, in step (a), the mass ratio of concentrated sulfuric acid to boric acid is 0.5:1 to 2:1, preferably 1:1 to 1.5:1; the concentration of fuming sulfuric acid is 15% to 60%, for example, 20% to 40%; the equivalent ratio of fuming sulfuric acid to boric acid is 7.8:1 to 229.3:1, for example, 8:1 to 20:1; the material mixing temperature is 10 to 60°C, for example, 20 to 45°C; and the mixing time is 1 to 3 h, for example, 1.5 to 2.5 h.

[0031] The above parameters are set to ensure the optimal yield of boron trifluoride. Exceeding these parameters will result in incomplete boric acid reaction or waste of raw materials, reducing the economic efficiency of the product.

[0032] In one embodiment, in step (b), the rate at which the fuming sulfuric acid solution of boric acid is introduced into the continuous flow reactor is 0.5 mL / min to 5 mL / min, for example, 1.5 mL / min to 3 mL / min; the rate at which anhydrous hydrogen fluoride gas is introduced into the continuous flow reactor is 0.01 mL / min to 1 mL / min, for example, 0.05 mL / min to 0.8 mL / min; and the reaction temperature is 110 to 160 °C, for example, 120 to 140 °C. These parameters optimize the yield and reaction efficiency of boron trifluoride. Exceeding these parameters will result in waste of anhydrous hydrogen fluoride or incomplete conversion of boric acid, reducing the economic viability of the product.

[0033] In one implementation, in step (c), the boron trifluoride gas purification device is an adsorption purification column, and the adsorbent used is one or a combination of molecular sieves, activated carbon, and chelating agents. For example, it can be one or a combination of two of molecular sieves and activated carbon. The adsorbent can be a commercially available product, such as commercially available ordinary 4A molecular sieves, conventional activated carbon, conventional EDTA chelating agents, etc.

[0034] The choice of adsorbent is crucial to ensure the optimal purity of boron trifluoride; otherwise, other impurity gases may be mixed into the boron trifluoride gas.

[0035] In one embodiment, in step (d), the complexing solvent includes tetrahydrofuran, acetonitrile, diethyl ether, dimethyl carbonate, butyl acetate, acetic acid, dimethyl ether, ethylamine, ethanol, phenol, or methanol. For example, it can be tetrahydrofuran, acetonitrile, diethyl ether, dimethyl carbonate, butyl acetate, phenol, or methanol. The complexing reaction temperature is 10–60 °C, for example, 20–45 °C. The complexing time is 3–8 h, for example, 4–6 h. The residual organic solvent can be recovered by vacuum distillation. These parameters optimize the yield of the boron trifluoride complex. Too low a complexing reaction temperature will reduce the complexing efficiency, while too high a temperature will lead to other side reactions, affecting product quality. Too long a complexing time will also cause side reactions, while too short a time will affect product production efficiency.

[0036] In one implementation, in step (e), the concentration temperature is 60~120 ℃, preferably 80~105 ℃; the depressurization pressure is -0.02~-0.04 MPa, preferably -0.01~-0.03 MPa. These parameters ensure that the recovered sulfuric acid meets commercial or usage standards. Excessively high concentration temperatures can lead to impurities being distilled off, affecting the purity of the recovered sulfuric acid product; excessively low concentration temperatures result in low distillation efficiency and low production efficiency of the recovered sulfuric acid product. The effect of pressure is similar.

[0037] This invention utilizes a tubular continuous flow reactor to prepare boron trifluoride. The main technical challenges lie in controlling the reaction process, including the flow rate of the liquid component, the introduction rate of the gas component, and the residence time in the reactor. Through multiple experiments and optimization of process parameters, optimal reaction parameters were obtained, enabling the continuous preparation of boron trifluoride gaseous products using a tubular reactor. Unexpectedly, the reaction efficiency was significantly improved; on the same scale, the reaction time for preparing boron trifluoride using continuous flow equipment was reduced by more than 50%.

[0038] Meanwhile, the purity of the product is improved compared to traditional batch reactors. The continuous flow equipment is more conducive to the full mixing of reactants, allowing hydrogen fluoride gas and other substances to fully participate in the reaction, resulting in lower residues and higher purity of the product boron trifluoride.

[0039] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for preparing boron trifluoride and its complexes by continuous flow reaction provided by the present invention.

[0040] like Figure 1 As shown, in one embodiment, the apparatus for preparing boron trifluoride and its complexes includes a tubular continuous flow reactor. The inlet of the tubular continuous flow reactor is connected to a mixer. A dispensing tank and a hydrogen fluoride cylinder are respectively connected to the mixer via metering pumps. The outlet of the tubular continuous flow reactor is connected to a purification device, and the dilute sulfuric acid produced at the outlet is recovered and reused. There are two purification devices connected in series. The last purification device is connected to a buffer tank, and the buffer tank is connected to a complexing vessel.

[0041] It should be noted that the continuous flow reactors used in this invention are all continuous flow pipeline reactors with stirring, and each reactor is equipped with a heat exchange component. The effective volume of the reactor is 1000 mL. The metering pump, purifier, etc. are all existing products, and their specific structures will not be described in detail.

[0042] The process involves the continuous production of boron trifluoride and its various complexes using parallel liquid preparation tanks, hydrogen fluoride gas cylinders, and complexing reactors, making the operation simple.

[0043] Device model used in the embodiments: Liquid preparation tank: EX-QYSS316-100B (316L explosion-proof stainless steel reactor) Tubular continuous flow reactor: JTGR1L0.6 (jacketed tubular reactor, 1L, 0.6MPa atmospheric / micro pressure) Mixer: SK25 / 50 (National Standard SK Type Spiral Static Mixer, DN50, Most Common for Continuous Flow) The purification device is a stainless steel tube filled with the corresponding adsorbent. The tube is about 1 meter long and about 10 centimeters in diameter.

[0044] Buffer tank: Pressure vessel (with pressure vessel certificate, 0.6MPa), BFG-50-0.6 Complexation vessel: S212-100L (National standard general-purpose double-layer glass reactor model, GG-17 high borosilicate glass) Example 1

[0045] The method for preparing boron trifluoride and its complexes by continuous flow reaction in this embodiment includes the following steps: In step (a), at 30 °C, 20% fuming sulfuric acid (55.3 kg, 485.2 mol), boric acid (10.0 kg, 161.7 mol), and concentrated sulfuric acid (10.0 kg, 102.1 mol) were added to a mixing tank to dissolve and mix evenly, and stirred continuously for 2.5 h until the mixture was a homogeneous milky white liquid solution.

[0046] Step (b) Preheat the tubular continuous flow reactor to 110 °C, and simultaneously start the metering pump of the dispensing tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the mixer at a flow rate of 1.5 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.6 mL / min, and then into the tubular continuous flow reactor. Control the temperature of the continuous flow reactor to stabilize at 120~130 °C.

[0047] Step (c) introduces the boron trifluoride gas generated in the continuous flow reactor into the purification device, and uses molecular sieves as adsorbents to perform deep purification of the boron trifluoride gas.

[0048] Sampling and testing analysis showed that boron trifluoride has a purity of 99.8%.

[0049] In step (d), purified boron trifluoride gas, after purification and deimpurification, is introduced from the bottom of 3-4 complexing reactors connected in series into a tetrahydrofuran (50 L, 617.1 mol) solvent. The mixture is stirred while being aerated at 35 °C for 4.5 h until complete complexation. After removing excess solvent by vacuum distillation, a boron trifluoride tetrahydrofuran complex (22.8 kg, yield 97.8%) is obtained. Excess tetrahydrofuran can be further used to complex boron trifluoride.

[0050] In step (e), the dilute sulfuric acid solution that flows out synchronously from the tubular continuous flow reactor enters the vacuum concentration process to remove water, and obtains concentrated sulfuric acid that can be recycled. The concentration temperature is 95 °C and the vacuum pressure is 0.01 MPa.

[0051] Example 2

[0052] The method for preparing boron trifluoride and its complexes by continuous flow reaction in this embodiment includes the following steps: In step (a), at 40 °C, 20% fuming sulfuric acid (55.3 kg, 485.2 mol), boric acid (10.0 kg, 161.7 mol), and concentrated sulfuric acid (10.0 kg, 102.1 mol) were added to a mixing tank to dissolve and mix evenly, and stirred continuously for 2.5 h until the mixture was a homogeneous milky white liquid solution.

[0053] Step (b) Preheat the tubular continuous flow reactor to 105 °C, and simultaneously start the metering pump of the dispensing tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the mixer at a flow rate of 1.8 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.8 mL / min, and then into the tubular continuous flow reactor. Control the temperature of the continuous flow reactor to stabilize at 125~135 °C.

[0054] Step (c) introduces the boron trifluoride gas generated in the continuous flow reactor into the purification device, and uses molecular sieves as adsorbents to perform deep purification of the boron trifluoride gas.

[0055] Sampling and testing analysis showed that boron trifluoride has a purity of 99.9%.

[0056] In step (d), purified boron trifluoride gas, after purification and deimpurification, was introduced into anhydrous diethyl ether (50 L, 481.7 mol) solvent through the bottom of three complexation reactors connected in series. The mixture was stirred while being aerated at 20 °C for 3.5 h until complete complexation. After removing excess solvent by vacuum distillation, boron trifluoride diethyl ether complex (21.7 kg, yield 93.1%) was obtained. Excess diethyl ether could be further recovered for further complexation of boron trifluoride.

[0057] In step (e), the dilute sulfuric acid solution that flows out synchronously from the tubular continuous flow reactor enters the vacuum concentration process to remove water, and obtains concentrated sulfuric acid that can be recycled. The concentration temperature is 95 °C and the vacuum pressure is 0.01 MPa.

[0058] Example 3

[0059] The method for preparing boron trifluoride and its complexes by continuous flow reaction in this embodiment includes the following steps: In step (a), at 30 °C, 40% fuming sulfuric acid (73.6 kg, 566.1 mol), boric acid (10.0 kg, 161.7 mol), and concentrated sulfuric acid (15.0 kg, 153.1 mol) were added to a mixing tank to dissolve and mix evenly, and stirred continuously for 2.5 h until the mixture was a homogeneous milky white liquid solution.

[0060] Step (b) Preheat the tubular continuous flow reactor to 110 °C, and simultaneously start the metering pump of the liquid preparation tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the mixer at a flow rate of 2.5 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.8 mL / min, and then into the tubular continuous flow reactor. Control the temperature of the continuous flow reactor to stabilize at 125~135 °C.

[0061] Step (c) introduces the boron trifluoride gas generated in the continuous flow reactor into a purification device, using activated carbon as an adsorbent to perform deep purification of the boron trifluoride gas.

[0062] Sampling and testing analysis showed that boron trifluoride has a purity of 99.9%.

[0063] In step (d), purified boron trifluoride gas, after purification and deimpurification, was introduced from the bottom of three series-connected complexing reactors into a butyl acetate (50 L, 379.9 mol) solvent. The mixture was stirred while being aerated at 45 °C for 3.5 h until complete complexation. After removing excess solvent by vacuum distillation, a boron trifluoride butyl acetate complex (34.8 kg, yield 95.3%) was obtained. Excess butyl acetate could be further used to complex boron trifluoride.

[0064] In step (e), the dilute sulfuric acid solution that flows out synchronously from the tubular continuous flow reactor enters the vacuum concentration process to remove water, and obtains concentrated sulfuric acid that can be recycled. The concentration temperature is 95 °C and the vacuum pressure is 0.01 MPa.

[0065] Example 4

[0066] The method for preparing boron trifluoride and its complexes by continuous flow reaction in this embodiment includes the following steps: In step (a), sulfur trioxide (45.3 kg, 566.1 mol) was continuously introduced into a mixing tank containing boric acid (10.0 kg, 161.7 mol) and concentrated sulfuric acid (15.0 kg, 102.1 mol) at 30 °C, and the mixture was dissolved and mixed evenly. The mixture was stirred continuously for 2.5 hours until it became a homogeneous milky white liquid solution.

[0067] Step (b) Preheat the tubular continuous flow reactor to 120 °C, and simultaneously start the metering pump of the liquid preparation tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the mixer at a flow rate of 1.5 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.8 mL / min, and then into the tubular continuous flow reactor. Control the temperature of the continuous flow reactor to stabilize at 130~135 °C.

[0068] Step (c) introduces the boron trifluoride gas generated in the continuous flow reactor into the purification device, and uses molecular sieves as adsorbents to perform deep purification of the boron trifluoride gas.

[0069] Sampling and testing analysis showed that boron trifluoride has a purity of 99.7%.

[0070] In step (d), purified boron trifluoride gas, after purification and deimpurification, was introduced into a methanol (50 L, 1234.3 mol) solvent through the bottom of three complexation reactors connected in series. The mixture was stirred while being aerated at 25 °C for 5 h until complete complexation. After removing excess solvent by vacuum distillation, a boron trifluoride methanol complex (20.3 kg, yield 92.6%) was obtained. Excess methanol could be further used to complex boron trifluoride.

[0071] In step (e), the dilute sulfuric acid solution that flows out synchronously from the tubular continuous flow reactor enters the vacuum concentration process to remove water, and obtains concentrated sulfuric acid that can be recycled. The concentration temperature is 100 °C and the vacuum pressure is 0.02 MPa.

[0072] Example 5

[0073] like Figure 1 As shown, the method for preparing boron trifluoride and its complexes by continuous flow reaction in this embodiment includes the following steps: Step (a) At 30 °C, 30% fuming sulfuric acid (59.2 kg, 485.2 mol), boric acid (10.0 kg, 161.7 mol), and concentrated sulfuric acid (10.0 kg, 102.1 mol) were added to a mixing tank to dissolve and mix evenly, and stirred continuously for 2.5 hours until the mixture was a homogeneous milky white liquid solution.

[0074] Step (b) Preheat the tubular continuous flow reactor to 110 °C, and simultaneously start the metering pump of the liquid preparation tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the mixer at a flow rate of 1.8 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.5 mL / min, and then into the tubular continuous flow reactor. Control the temperature of the continuous flow reactor to stabilize at 125~135 °C.

[0075] Step (c) introduces the boron trifluoride gas generated in the continuous flow reactor into the combined purification device, which is connected in series. Molecular sieves and activated carbon are used as adsorbents to deeply purify the boron trifluoride gas.

[0076] Sampling and testing analysis showed that boron trifluoride has a purity of 99.8%.

[0077] In step (d), purified boron trifluoride gas, after purification and deimpurification, is introduced from the bottom of three series-connected complexing reactors into acetonitrile (50 L, 957.3 mol) solvent. The mixture is stirred while being aerated at 25 °C for 4.5 h until complete complexation. The incompletely complexed acetonitrile boron trifluoride mother liquor is filtered and recovered. The white crystalline filter cake collected is the boron trifluoride acetonitrile complex (17.6 kg, yield 96.4%). The incompletely complexed acetonitrile boron trifluoride mother liquor can be further used for complexing boron trifluoride.

[0078] In step (e), the dilute sulfuric acid solution that flows out synchronously from the tubular continuous flow reactor enters the vacuum concentration process to remove water, and obtains concentrated sulfuric acid that can be recycled. The concentration temperature is 95 °C and the vacuum pressure is 0.01 MPa.

[0079] Comparative Example 1 Unlike Example 5, step (b): Preheat the tubular continuous flow reactor to 60 °C. Simultaneously start the metering pump of the liquid preparation tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the tubular continuous flow reactor at a flow rate of 1.8 mL / min and the anhydrous hydrogen fluoride at a flow rate of 0.5 mL / min. Control the temperature of the continuous flow reactor to stabilize at 80~90 °C.

[0080] After purification, sampling and analysis showed that the boron trifluoride purity was 99.6%.

[0081] The final white crystalline filter cake collected was the boron trifluoride acetonitrile complex (8.2 kg, yield 44.9%). In step (b), the reaction temperature was 80–90 °C, which significantly reduced the yield of the boron trifluoride acetonitrile complex. This demonstrates that the reaction temperature in a tubular reactor has a substantial impact on the yield.

[0082] Comparative Example 2 Unlike Example 5, step (b): Preheat the tubular continuous flow reactor to 110 °C. Simultaneously start the metering pump of the liquid preparation tank and the metering pump of the anhydrous hydrogen fluoride cylinder to introduce the fuming sulfuric acid solution of boric acid into the tubular continuous flow reactor at a flow rate of 5.0 mL / min and the anhydrous hydrogen fluoride at a flow rate of 2.0 mL / min. Control the temperature of the continuous flow reactor to stabilize at 125~135 °C.

[0083] After purification, sampling and analysis showed that the boron trifluoride purity was 92.7%.

[0084] The final white crystalline filter cake collected was the boron trifluoride acetonitrile complex (7.9 kg, yield 43.2%). The purity of boron trifluoride was significantly reduced, and the yield of the boron trifluoride acetonitrile complex was also significantly reduced. This demonstrates that the flow rate of the fuming sulfuric acid solution containing boric acid and the flow rate of anhydrous hydrogen fluoride have a significant impact on both purity and yield.

[0085] It should be noted that the continuous flow reactors used in this invention are all continuous flow pipeline reactors with stirring, and each reactor is equipped with a heat exchange component. The effective volume of the reactor is 1000 mL. The metering pump, purifier, etc. are all existing products, and their specific structures will not be described in detail.

[0086] The process involves the continuous production of boron trifluoride and its various complexes using parallel liquid preparation tanks, hydrogen fluoride gas cylinders, and complexing reactors, making the operation simple.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing boron trifluoride and its complexes via a continuous flow reaction, characterized in that: Includes the following steps: Step (a) Mix boric acid and concentrated sulfuric acid evenly, then add fuming sulfuric acid or continuously pass sulfur trioxide gas to obtain a fuming sulfuric acid solution of boric acid; Step (b) introduces the solution obtained in step (a) and anhydrous hydrogen fluoride gas into a continuous flow reactor at a uniform rate to obtain boron trifluoride gas; The boron trifluoride gas produced in step (c) is purified and impurities are removed. In step (d), the purified boron trifluoride gas is continuously passed into the complexing solvent to carry out the complexation reaction, thereby obtaining the boron trifluoride complex.

2. The method according to claim 1, characterized in that: Also includes: Step (e) collects the dilute sulfuric acid produced in the reaction, concentrates it, and uses it as a raw material.

3. The method according to claim 1, characterized in that: In step (a), the mass ratio of concentrated sulfuric acid to boric acid is 0.5:1 to 2:1, the concentration of fuming sulfuric acid is 15% to 60%, the mass ratio of fuming sulfuric acid to boric acid is 7.8:1 to 229.3:1, the material mixing temperature is 10 to 60 ℃, and the mixing time is 1 to 3 h.

4. The method according to claim 1, characterized in that: In step (b), the rate at which the fuming sulfuric acid solution of boric acid is introduced into the continuous flow reactor is 0.5 mL / min to 5 mL / min, the rate at which anhydrous hydrogen fluoride gas is introduced into the continuous flow reactor is 0.01 mL / min to 1 mL / min, and the reaction temperature is 110 to 160 °C.

5. The method according to claim 1, characterized in that: In step (c), the purification device for boron trifluoride gas is an adsorption purification column, and the adsorbent is one or a combination of molecular sieves, activated carbon, and chelating agents.

6. The method according to claim 1, characterized in that: In step (d), the complexing solvent includes tetrahydrofuran, acetonitrile, diethyl ether, dimethyl carbonate, butyl acetate, acetic acid, dimethyl ether, ethylamine, ethanol, phenol, or methanol. The complexing reaction temperature is 10~60℃, the complexing time is 3~8 h, and the residual organic solvent is recovered by vacuum distillation.

7. The method according to claim 2: In step (e), the concentration temperature is 60~120 ℃ and the decompression pressure is -0.02~-0.04 MPa.

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