A method for the photocatalytic fluorination of benzene to fluorobenzene based on nitrogen trifluoride
By using nitrogen trifluoride in a photocatalytic fluorination reaction with ultraviolet light, the problems of high fluorine toxicity, harsh reaction conditions, and low product purity in existing fluorobenzene preparation methods have been solved, achieving efficient, safe, and green fluorobenzene synthesis that is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUJIAN ELEGANT CREATION ELECTRONIC CHEM CORP
- Filing Date
- 2026-03-26
- Publication Date
- 2026-05-29
AI Technical Summary
Existing methods for preparing fluorobenzene involve highly toxic fluorine sources, harsh reaction conditions, cumbersome steps, low product purity, and safety hazards, making it difficult to achieve high efficiency, green production, and industrial compatibility.
Nitrogen trifluoride (NF3) was used as the fluorine source, and fluorobenzene was prepared by one-step decarboxylation fluorination reaction combined with ultraviolet photocatalysis. The free radical reaction was initiated by ultraviolet light, and the reaction was carried out under controlled conditions of 60-150℃ and 0.1-0.4MPa. The post-treatment was carried out by alkaline washing and distillation to remove impurities.
This method enables the efficient, safe, and green synthesis of fluorobenzene, resulting in high product purity and easy removal of byproducts. It is suitable for industrial production, reduces costs and energy consumption, and aligns with the development trend of green chemistry.
Smart Images
Figure CN122102835A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of materials preparation technology, and specifically to a method for preparing fluorobenzene based on the photocatalytic fluorination of nitrogen trifluoride. Background Technology
[0002] Fluorobenzene is an important fine chemical intermediate, widely used in pharmaceuticals, pesticides, liquid crystal materials, fluoropolymers and other fields. The greening and efficiency improvement of its synthesis process is the focus of research in this field.
[0003] Existing methods for preparing fluorobenzene mainly include the electrophilic fluorination of aromatic rings, the decomposition of diazonium salts of fluoroboronic acid, and the fluorine exchange of halobenzenes. The electrophilic fluorination method often uses highly toxic and corrosive fluorine sources such as F2 and HF / SbF5, requiring harsh reaction conditions, easily generating polyfluorinated byproducts, and leaving impurities such as antimony and chlorine in the products. The diazonium salt decomposition of fluoroboronic acid requires aniline as a precursor to prepare the diazonium salt, or uses anhydrous hydrogen fluoride as a reaction solvent, with aniline and sodium nitrite reacting in a one-pot process. However, the diazonium salt has poor stability, posing an explosion risk, and the process is cumbersome with high raw material costs. The fluorine exchange of halobenzenes requires high temperature and pressure conditions and a precious metal catalyst, resulting in high energy consumption and high catalyst recovery costs, limiting its industrial application.
[0004] Nitrogen trifluoride (NF3), as a low-toxicity and chemically stable clean fluorine source, has been gradually applied in the fluorination synthesis of fluorine-containing compounds. Its reaction leaves no residual toxic impurities, and the process is highly safe. However, there are currently no patents or literature reports on the preparation of fluorobenzene by combining NF3 with benzoyl chloride via ultraviolet photocatalysis. Therefore, developing a green synthesis process for fluorobenzene using benzoyl chloride as a raw material and NF3 as a fluorine source has significant industrial application value. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing fluorobenzene preparation processes, such as high toxicity of fluorine sources, harsh reaction conditions, cumbersome steps, and low product purity. This invention provides a method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride, achieving one-step efficient synthesis of fluorobenzene while taking into account process safety, environmental friendliness, and industrial compatibility.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride, comprising the following steps: S1. Add pretreated benzoyl chloride to a closed, pressure-resistant quartz photoreactor, and then introduce high-purity argon gas to replace the air in the reactor to form an oxygen-free inert atmosphere. S2. Pretreated nitrogen trifluoride is introduced into the reactor and stirred at a temperature of 60–150°C and a pressure of 0.1–0.4 MPa, wherein the molar ratio of benzoyl chloride to nitrogen trifluoride is 1:0.5–6. S3. Start the ultraviolet light source module and use ultraviolet light with a wavelength of 200-300nm to irradiate the reaction system to carry out photocatalytic reaction. The reaction time is 2-8 hours, and finally fluorobenzene is obtained. The reaction equation is as follows: ; Its reaction mechanism is a free radical reaction initiated by ultraviolet light, as detailed below: I. Under ultraviolet light irradiation, benzoyl chloride undergoes homolytic cleavage, generating benzoyl free radicals and chlorine free radicals: ; II. Ultraviolet light simultaneously dissociates nitrogen trifluoride, generating fluorine radicals and nitrogen radicals: ; III. Benzoyl radicals undergo decarboxylation to generate phenyl radicals: ; IV. The phenyl radical combines with the fluorine radical to generate the target product, fluorobenzene: ; Side reactions: nitrogen free radicals combine to form N2, chlorine free radicals combine to form Cl2, and a small amount of CO reacts with fluorine free radicals to form COF2. All byproducts can be removed by alkaline washing and distillation.
[0007] Furthermore, the benzoyl chloride has a purity ≥99.0% and a moisture content ≤0.05%; the nitrogen trifluoride has a purity ≥99.9% and an oxygen impurity content ≤0.01%. The argon gas has a purity ≥99.99%. By controlling the moisture and oxygen impurity content in the raw materials, side reactions with NF3 are avoided, and free radicals are prevented from being oxidized.
[0008] Furthermore, the molar ratio of benzoyl chloride to nitrogen trifluoride is 1:0.5–3; the reaction temperature in the reactor is 80–120 °C, the reaction time is 3–6 h, and the stirring rate is 300–500 rpm. This optimal combination of parameters enables the high-yield and highly selective synthesis of fluorobenzene.
[0009] Furthermore, the ultraviolet light source is a 254nm low-pressure mercury lamp with a power of 200~500W, and the distance between the ultraviolet light source and the inner wall of the quartz photoreactor is 5~15cm. These parameters ensure the irradiation efficiency of the ultraviolet light and fully initiate the free radical reaction.
[0010] Furthermore, the replacement time of the air in the reactor by argon gas is ≥30 min to ensure that an oxygen-free inert atmosphere is formed in the reactor and to avoid side reactions between phenyl free radicals and oxygen.
[0011] Furthermore, it also includes post-processing purification, which includes turning off the ultraviolet light source and heating module after the reaction is completed, allowing the reactor to cool naturally to room temperature, slowly opening the pressure relief valve to release pressure; collecting the reaction mixture in the reactor, removing acidic impurities by alkaline washing, then separating the organic phase, and finally distilling the organic phase to collect the distillate and obtain the fluorobenzene product.
[0012] Furthermore, alkaline washing is performed using a 10-20% NaOH aqueous solution to remove acidic impurities such as Cl2 and COF2 generated during the reaction.
[0013] Furthermore, the distillation is atmospheric distillation at a temperature of 80–90°C. Preferably, the fraction collection temperature of the atmospheric distillation is 84–86°C, which matches the boiling point of fluorobenzene and can further improve the purity of the fluorobenzene product.
[0014] Preferably, the pressure-resistant quartz photoreactor is a dedicated reaction device, including a quartz reactor, an ultraviolet light source module, a temperature control module, a gas injection system, a tail gas absorption system, and a stirring module; the pressure resistance of the quartz reactor is ≥0.5MPa, which can meet the reaction pressure requirements; the tail gas absorption system is a two-stage absorption structure, connected in sequence to an anhydrous hydrogen fluoride absorption tank and a 10-20% NaOH aqueous solution absorption tank, which can efficiently absorb the acidic tail gas generated during the reaction and avoid environmental pollution.
[0015] Compared with the prior art, the technical solution of this application has the following beneficial effects: 1. Innovative Fluorine Source, High Process Safety: This invention abandons the highly toxic and corrosive fluorine sources such as F2 and HF / SbF5 used in traditional methods, and adopts nitrogen trifluoride (NF3) as the fluorination reagent. NF3 has low toxicity and good chemical stability. There is no open flame or explosion risk during the reaction, and no residual antimony, residual chlorine or other impurities remain after the reaction, which significantly improves the inherent safety of the production process. 2. Raw materials are readily available and the process is simplified: This invention uses benzoyl chloride, which is industrially available and inexpensive, as a starting material to directly prepare fluorobenzene through a one-step decarboxylation fluorination reaction. Compared with the traditional diazonium salt method, which requires a special precursor, this invention effectively simplifies the process and reduces raw material costs. 3. Mild reaction conditions and low energy consumption: This invention does not require high temperature, high pressure, or precious metal catalysts. Highly efficient reactions can be achieved under mild conditions of 60-150℃ and 0.1-0.4MPa. Furthermore, the use of ultraviolet light as a clean energy source results in low energy consumption, aligning with the trend of green chemistry. 4. Excellent product quality and high selectivity: By optimizing process parameters, the reaction achieves high selectivity. Byproducts can be effectively removed through simple alkaline washing and distillation processes. The final fluorobenzene product has a gas chromatographic purity of over 99.0% and a yield of over 78%, which can meet the stringent purity requirements of raw materials in high-end applications such as pharmaceuticals and pesticides. 5. Strong industrial compatibility: The pressure-resistant quartz photoreactor used in this invention has a simple structure, making it suitable not only for small-scale laboratory research but also easy to scale up or modify into a continuous flow reactor. Furthermore, the entire reaction process generates minimal waste that is easy to treat, demonstrating excellent compatibility with industrial production. Attached Figure Description
[0016] Figure 1 This is the hydrogen spectrum of fluorobenzene in the preferred embodiment of the present invention; Figure 2 This is the fluorine spectrum of fluorobenzene in the preferred embodiment of the present invention; Figure 3 This is the carbon spectrum of fluorobenzene in the preferred embodiment of the present invention. Detailed Implementation
[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0018] Example 1 A method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride includes the following steps: Raw material pretreatment: Select anhydrous benzoyl chloride with a purity of 99.5% and a moisture content of 0.03%, nitrogen trifluoride with a purity of 99.95% and an oxygen impurity content of 0.008%, and high-purity argon gas with a purity of 99.999% for later use; Reaction system setup: Add 1 mol of the above benzoyl chloride to a 500 mL pressure-resistant quartz photoreactor, close the seal, and purge the air in the reactor with argon gas for 35 min. Ultraviolet photocatalytic reaction: The magnetic stirrer in the reactor was turned on at a stirring rate of 400 rpm. 0.8 mol of NF3 was introduced through the gas injection system. The temperature control module was adjusted to bring the temperature inside the reactor to 100℃, and the pressure control valve was adjusted to bring the pressure inside the reactor to 0.2 MPa. A 254 nm low-pressure mercury lamp with a power of 300 W was turned on, and the distance between the light source and the inner wall of the reactor was 10 cm. The reaction was continuously irradiated for 4.5 h. Post-processing and purification: After the reaction is completed, turn off the mercury lamp and heating module, allow it to cool naturally to room temperature, and slowly release the pressure; collect the reaction mixture, pass the mixture into a 15% NaOH aqueous solution for alkaline washing, separate the organic phase; send the organic phase into a distillation column, distill at atmospheric pressure, collect the fraction at 84-86℃ to obtain the fluorobenzene product; Gas chromatography (GC) analysis showed that the purity of the fluorobenzene product prepared in this example was 99.6%, and the yield was 82.5%. The obtained fluorobenzene was then subjected to proton, fluorine, and carbon spectra analysis, and the results are as follows: Figure 1-3 As shown, specifically: 1H-NMR: 7.2 (m, 2H); 6.8-7.0 (m, 4H); 19F-NMR: -116 (s, 1F); 13C-NMR: 166 (s, 1C); 130.4 (s, 2C); 124 (s, 1C); 115.5 (s, 2C).
[0019] Example 2 A method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride includes the following steps: Raw material pretreatment: Select anhydrous benzoyl chloride with a purity of 99.0% and a moisture content of 0.05%, nitrogen trifluoride with a purity of 99.9% and an oxygen impurity content of 0.01%, and high-purity argon gas with a purity of 99.99% for later use; Reaction system setup: Add 1 mol of the above benzoyl chloride to a 500 mL pressure-resistant quartz photoreactor and purge with argon gas for 30 min; Ultraviolet photocatalytic reaction: Stirring was started at 200 rpm, 0.5 mol of NF3 was introduced, and the temperature inside the reactor was adjusted to 60℃ and the pressure to 0.1 MPa; a 200 nm ultraviolet light source was turned on with a power of 200 W, and the reaction was continuously irradiated for 8 h. Post-processing purification: Same as in Example 1; GC analysis showed that the purity of the fluorobenzene product prepared in this example was 99.1%, and the yield was 78.2%.
[0020] Example 3 A method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride includes the following steps: Raw material pretreatment: Benzoyl chloride, nitrogen trifluoride and argon gas of the same specifications as in Example 1 were selected and prepared for use; Reaction system setup: Add 1 mol of benzoyl chloride to a 500 mL pressure-resistant quartz photoreactor and purge with argon gas for 35 min; Ultraviolet photocatalytic reaction: Stirring was started at 500 rpm, 6 mol of NF3 was introduced, and the temperature inside the reactor was adjusted to 150℃ and the pressure to 0.4 MPa; a 300 nm ultraviolet light source was turned on at 500 W, and the reaction was continuously irradiated for 2 h. Post-processing purification: Same as in Example 1; GC analysis showed that the purity of the fluorobenzene product prepared in this example was 99.2%, and the yield was 80.1%.
[0021] Comparative Example 1 Except for turning off the ultraviolet light source and not irradiating with ultraviolet light, the other operating steps, raw material specifications and process parameters are completely consistent with those in Example 1; After the reaction was completed, GC detection showed that no fluorobenzene was generated in the reactor, and only a small amount of thermal decomposition products of benzoyl chloride were detected, proving that ultraviolet light is a necessary initiation condition for the reaction of this invention.
[0022] Comparative Example 2 The fluorine source was replaced with an equimolar amount of F2, and the remaining operating steps, raw material specifications and process parameters were completely consistent with those in Example 1. Significant corrosion was observed on the inner wall of the reactor during the reaction. After the reaction, GC analysis revealed a large number of polyfluorinated byproducts in the product. The purity of the fluorobenzene product was only 85.3%, and the yield was only 62.7%, proving that NF3 as a fluorine source has higher selectivity and process safety compared to traditional F2.
[0023] The above examples and comparative examples demonstrate that the preparation method of the present invention can efficiently prepare high-purity fluorobenzene through the free radical reaction of benzoyl chloride and NF3 catalyzed by ultraviolet light, and the process parameters are controllable. Fluorobenzene can be synthesized within the basic parameter range, and higher yield and purity can be obtained under the optimal parameters. At the same time, ultraviolet light and NF3, as the reaction initiation condition and fluorine source, respectively, are the core elements for realizing the present invention.
[0024] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.
[0025] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.
Claims
1. A method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride, characterized in that, Includes the following steps: S1. Add pretreated benzoyl chloride to a closed, pressure-resistant quartz photoreactor, and then introduce high-purity argon gas to replace the air in the reactor to form an oxygen-free inert atmosphere. S2. Pretreated nitrogen trifluoride is introduced into the reactor and stirred at a temperature of 60–150°C and a pressure of 0.1–0.4 MPa, wherein the molar ratio of benzoyl chloride to nitrogen trifluoride is 1:0.5–6. S3. Start the ultraviolet light source module and use ultraviolet light with a wavelength of 200-300nm to irradiate the reaction system to carry out photocatalytic reaction. The reaction time is 2-8 hours, and finally fluorobenzene is obtained. The reaction equation is as follows: ； Its reaction mechanism is a free radical reaction initiated by ultraviolet light, as detailed below: I. Under ultraviolet light irradiation, benzoyl chloride undergoes homolytic cleavage, generating benzoyl free radicals and chlorine free radicals: ； II. Ultraviolet light simultaneously dissociates nitrogen trifluoride, generating fluorine radicals and nitrogen radicals: ； III. Benzoyl radicals undergo decarboxylation to generate phenyl radicals: ； IV. The phenyl radical combines with the fluorine radical to generate the target product, fluorobenzene: 。 2. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: The benzoyl chloride has a purity of ≥99.0% and a moisture content of ≤0.05%; the nitrogen trifluoride has a purity of ≥99.9% and an oxygen impurity content of ≤0.01%.
3. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: The molar ratio of benzoyl chloride to nitrogen trifluoride is 1:0.5 to 3.
4. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: The reaction temperature in the reactor is 80–120°C, the reaction time is 3–6 h, and the stirring rate is 300–500 rpm.
5. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: The ultraviolet light source is a 254nm low-pressure mercury lamp with a power of 200~500W, and the distance between the ultraviolet light source and the inner wall of the quartz photoreactor is 5~15cm.
6. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: The replacement time of the air in the reactor by introducing argon gas is ≥30 min.
7. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 1, characterized in that: It also includes post-processing purification, which includes turning off the ultraviolet light source and heating module after the reaction is completed, allowing the reactor to cool naturally to room temperature, and slowly opening the pressure relief valve to release pressure. The reaction mixture in the reactor is collected, acidic impurities are removed by alkaline washing, the organic phase is separated, and finally the organic phase is distilled to collect the fraction, yielding the fluorobenzene product.
8. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 7, characterized in that: The alkaline washing is performed using a 10-20% NaOH aqueous solution to remove acidic impurities such as Cl2 and COF2 generated during the reaction.
9. The method for preparing fluorobenzene based on photocatalytic fluorination of nitrogen trifluoride according to claim 7, characterized in that: The distillation is atmospheric distillation, and the distillation temperature is 80-90℃.