CN115532200A - Photocatalytic fluorination reaction process - Google Patents

Abstract

The invention discloses a photocatalytic fluorination reaction process. Under the irradiation of ultraviolet light, the unstable perfluoropolyether raw material is fluorinated with fluorinating agent gas, and the reaction temperature is controlled at 80-150°C and the pressure is 0-150°C. 0.5MPa, the reaction time is 5-40h, and after the reaction is completed, perfluoropolyether oil is obtained. The invention stabilizes the end group of the unstable perfluoropolyether raw material through the photocatalytic fluorination reaction, and can improve the defects of long reaction time and low reaction efficiency existing in the conventional fluorination by using a fluorinating agent.

Description

A photocatalytic fluorination reaction process

technical field

The invention relates to a photocatalytic fluorination reaction process, in particular to a reaction process for photocatalytic fluorination of unstable perfluoropolyether to stabilize end groups, and belongs to the technical field of fluorine chemical industry.

Background technique

Perfluoropolyether is a kind of fluorinated polymer that combines excellent high and low temperature resistance, non-combustibility, high heat resistance to oxygen, high chemical inertness, low volatility, excellent dielectric, non-toxic and excellent viscosity-temperature characteristics, etc. It is widely used as lubricating oil, grease, high vacuum pump oil, heat transfer fluid, insulating fluid, cooling fluid, etc. in aerospace, national defense equipment, electronics, nuclear energy and other fields. In the prior art, whether it is Solvay’s Fomblin Y-type, Z-type perfluoropolyether with molecular chain structure, or Chemours’ Krytox (K-type), or Japan’s Daikin’s Demnum-type (D-type) perfluoropolyether, They all come from polyether acyl fluoride or polyether carboxylic acid with highly reactive molecular chain end groups. In the production process, polyether acid fluoride or polyether carboxylic acid must be converted into a stable molecular chain end group structure through a fluorination process to meet performance requirements.

At present, there are mainly three kinds of process technologies successfully applied in fluoridation treatment. One is the Simons electrolytic fluorination technology, which uses anhydrous hydrogen fluoride as a solvent and a fluorine source, dissolves the fluoridated substance in it, and conducts electrolytic fluorination in an electrolytic cell to realize fluorination. Limited by the solubility of anhydrous hydrogen fluoride, electrolytic fluorination technology is more commonly used in the fluorination of small molecular compounds. At the same time, the use of a large amount of anhydrous hydrogen fluoride also brings great safety risks, and also requires complicated separation and purification treatment. Therefore, there are problems in the application of electrolytic fluorination technology in the stabilization treatment of unstable perfluoropolyether end groups. The second is the catalytic fluorination technology of fluorine-containing salts, using fluorine salts as fluorinating agents such as CoF ₃ , AlF ₃ , SbF ₅ , etc. This technology generally requires a high temperature of 270~400°C to have a good fluorination effect. High-temperature fluorination brings challenges and difficulties to process control and supporting equipment investment. Moreover, the prices of these fluorinating agents are relatively high, the separation is difficult, and the product quality is difficult to be guaranteed. The third is element fluorination by using fluorinating reagents, including fluorine gas, SF ₄ , SF ₆ , BF ₃ and so on. The advantage of this technology is that the post-processing of the obtained product is simple and the product quality is high. However, because fluorinating agents such as fluorine gas are in the form of gases, their solubility in unstable perfluoropolyether is low, and it is a gas-liquid heterogeneous reaction process. There are often reasons such as uneven dispersion and insufficient gas-liquid contact that cause the utilization of fluorinating agents. The efficiency is low, and the amount of fluorine gas is often required to be more than 10 times the theoretical amount. The common fluorination reaction time is too long, the reaction cost is high, the tail gas treatment volume is large, and the environmental protection pressure is high, etc. A series of problems.

In order to solve the problems existing in the above-mentioned process technology, the invention patent with the publication number CN110092901A discloses an invention patent for a fluorination process of unstable terminal groups of perfluoropolyether. , improving the contact area and mass transfer capacity of gas-liquid two-phase reaction materials, thereby increasing the rate of fluorination reaction, solving the defects of uneven material dispersion and insufficient gas-liquid contact in the existing technology, and greatly improving the Utilization efficiency of fluorine gas and conversion rate of perfluoropolyether. In addition, the invention patent with the publication number CN112876669A discloses a method for fluorinating the end groups of perfluoropolyether, which uses ultraviolet light to irradiate the mixed gas of fluorine gas and inert gas to activate it and then pass it into the The reaction is carried out in the reaction kettle of fluoropolyether acid fluoride to obtain perfluoropolyether with fluorinated terminal group, which can make the fluorination reaction proceed at room temperature, and the product obtained is easy to handle. After fluorination, the product structure, average molecular weight, viscosity, etc. No change occurs.

Contents of the invention

The purpose of the present invention is to provide a photocatalytic fluorination reaction process, which stabilizes the terminal group of the unstable perfluoropolyether raw material through the photocatalytic fluorination reaction, and can improve the existing reaction when using a fluorinating agent for fluorination. Defects such as long time and low reaction efficiency.

The present invention is realized through the following technical scheme: a photocatalytic fluorination reaction process, under the irradiation of ultraviolet light, the unstable perfluoropolyether raw material and fluorinating agent gas are subjected to fluorination reaction, and the reaction temperature is controlled at 80-150°C , the pressure is 0-0.5MPa, and the reaction time is 5-40h. After the reaction is completed, perfluoropolyether oil is obtained.

When the ultraviolet light is irradiated, the irradiation power is controlled to be 300-800W, the irradiation time is 5-40h, and the irradiation wavelength is greater than 300nm.

The molar ratio of the unstable perfluoropolyether raw material to the fluorinating agent gas is controlled at 1: (20-1).

The fluorinating agent gas of the unstable perfluoropolyether is at least one selected from a mixed gas of F ₂ and N ₂ , SF ₄ , SF ₆ , and BF ₃ .

_The fluorinating agent gas is a mixed gas of F2 and _N2 , and the mass concentration of F2 in the mixed gas is controlled to be _20-50 %.

The fluorination reaction is carried out in a photocatalytic reaction kettle, and a gas distributor is arranged at the lower part of the photocatalytic reaction kettle, and the fluorinating agent gas is sent into the photocatalytic reaction kettle through the gas distributor.

Controlling the circulation of the materials in the photocatalytic reactor includes condensing and pressurizing the gas on the upper part of the photocatalytic reactor and then sending it into the photocatalytic reactor through a gas distributor; circulating the liquid at the bottom of the photocatalytic reactor The pump is sent in from the top of the photocatalytic reactor.

The fluorinating agent gas is sent to the gas distributor at intervals through the gas flow meter. When the pressure drops to 1/3~1/4 of the initial pressure, the vent valve is opened to discharge the inert inert gas, and then the addition of the fluorinating agent gas is controlled. .

During the fluorination reaction process, the reaction temperature is controlled to be 100-120° C., the pressure is 0.1-0.3 MPa, and the reaction time is 10-30 hours.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention treats the unstable end group of perfluoropolyether by photocatalytic fluorination, and in the process of fluorination reaction, it can not only promote the effect of fluorinating agent on the fluorination reaction of unstable perfluoropolyether, It also improves the treatment efficiency for the stabilization of unstable perfluoropolyether end groups.

(2) The present invention introduces ultraviolet light irradiation in the fluorination reaction process, which can play a photocatalytic effect on the fluorination reaction process. When the irradiation power is controlled at 300-800W, and the irradiation wavelength is greater than 300nm, the fluorination reaction can be realized Reaction at 80-150° C. and pressure of 0-0.5 MPa for 5-40 hours can obtain end group-stabilized perfluoropolyether oil, which greatly shortens the fluorination reaction time and improves the reaction efficiency.

(3) The present invention uses ultraviolet light irradiation catalysis combined with cyclic bubbling reaction to achieve efficient terminal group stabilization treatment for unstable perfluoropolyether. As a fluorinating agent, fluorine gas enters the reactor with fine bubbles from the lower part of the reactor. Combined with the double circulation of gas phase and liquid phase, it can greatly improve the uniform dispersion, contact effect and mass transfer capacity of the gas-liquid two-phase reaction materials; improve the fluorination efficiency and Improve the utilization efficiency of fluorinating agent, reduce the dosage of fluorinating agent; shorten the fluorinating reaction time and reduce the pressure of tail gas treatment.

In summary, the present invention can greatly improve the ability of unstable perfluoropolyether to achieve terminal group stabilization through the combination of ultraviolet photocatalytic fluorination and cyclic bubbling reaction, and the process control is simple, which is suitable for large-scale production .

Description of drawings

Fig. 1 is a structural schematic diagram of the photocatalytic reactor in the present invention.

Figure 2 is an infrared analysis spectrum of an unstable perfluoropolyether raw material.

Fig. 3 is the infrared analysis spectrogram of the stabilized perfluoropolyether oil.

Among them, 1—photocatalytic reactor, 2—ultraviolet light generator, 3—gas distributor, 4—condenser, 5—gas booster pump, 6—spray absorption tower, 7—vent valve, 8—liquid circulation Pump, 9—gas flow meter, 10—one-way valve, 11—F ₂ /N ₂ cylinder, 12—pressure control valve.

detailed description

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1:

This embodiment is a photocatalytic fluorination reaction process.

Using the photocatalytic reactor 1 shown in Figure 1, an air inlet channel, a gas circulation channel and a liquid circulation channel are arranged on the photocatalytic reactor 1, an ultraviolet light generator 2 is arranged in the photocatalytic reactor 1, and an ultraviolet light generator 2 is installed in the photocatalytic reactor 1. 1 A gas distributor 3 is provided at the bottom.

The air inlet channel is used to send the fluorinating agent into the photocatalytic reactor 1 through the gas distributor 3 . The ultraviolet light generator 2 is arranged inside the photocatalytic reaction vessel 1. During the fluorination reaction process, the ultraviolet light has a catalytic effect on the stabilization treatment of fluorine gas, which can improve the stabilization treatment efficiency of unstable perfluoropolyether end groups. In addition, through the arrangement of the gas circulation channel and the liquid circulation channel, the gas-liquid two-phase double circulation during the fluorination reaction process can be realized, the gas-liquid contact efficiency can be improved, and the utilization rate of the fluorinating agent can be improved. Wherein, the gas circulation channel is a gas phase flow channel for controlling the circulation of the fluorinating agent gas from the top of the photocatalytic reactor 1 to the bottom of the photocatalytic reactor 1. As shown in Figure 1, a condenser 4 and a gas amplifier are arranged on the gas circulation channel. The pressure pump 5 and the fluorinating agent gas on the upper part of the photocatalytic reactor 1 are sequentially condensed and pressurized, and then sent to the gas distributor 3 and sent to the photocatalytic reactor 1 to improve the utilization efficiency of the fluorinating agent gas. The liquid circulation channel is a liquid phase flow channel for controlling the circulation of the liquid from the bottom of the photocatalytic reactor 1 to the top of the photocatalytic reactor 1, and a liquid circulation pump 8 is arranged on the liquid circulation channel. The liquid circulation pump 8 can convey the liquid material from bottom to top and return it to the photocatalytic reactor 1 by spraying from the upper part. Through the circulation, the uniform effect of the non-stirring material can be realized, and the contact effect with the fluorinating agent gas can be improved.

Photocatalytic reactor 1 shown in Fig. 1 also comprises tail gas treatment system, and this tail gas treatment system is connected on the gas circulation channel between condenser 4 and gas booster pump 5, comprises spray absorption tower 6, spray absorption tower A pressure control valve and a vent valve 7 are sequentially arranged on the pipeline between 6 and the gas circulation channel. The system pressure of the fluorination reaction can be controlled by a pressure control valve.

Using the photocatalytic reactor 1 shown in Figure 1, the photocatalytic fluorination reaction process steps are as follows:

S1. Unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene (raw material sampling for infrared testing, as shown in Figure 2, indicating that the raw materials contain unstable acyl fluoride end groups), 40°C , the viscosity is 30 sct, put into the photocatalytic reactor 1 from the feeding port, replace the vacuum with an inert gas, and then heat the photocatalytic reactor 1 to control the temperature to 100°C.

S2. adopt the mixed gas of F2 and _N2 as the fluorinating agent ₍ the mass concentration of F2 in the mixed gas is ₂₀ %), open the check valve 10, and periodically transfer the F2/N2 in the steel cylinder 11 through the gas flowmeter 9 The fluorinating agent gas is sent into the photocatalytic reactor 1 through the gas distributor 3, the pressure control valve controls the system pressure at 0.1 MPa, and the molar ratio of perfluoropolyether acyl fluoride to fluorinating agent is controlled at 1:20.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 500W, and the irradiation wavelength to 300nm, and control the reaction to continue for 25 hours before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization Stabilization treatment, as shown in Figure 3.

During the fluorination reaction, the pressure control valve can control the system pressure of the fluorination reaction. Therefore, in the above-mentioned photocatalytic fluorination reaction process, in step S2, the fluorination agent is consumed by the gas circulation pump for a period of time. When the system pressure drops to 1/3~1/4 relative to the initial pressure, the inactive gas components are discharged through the vent valve 7, and a new fluorinating agent is added again to improve the utilization efficiency of the fluorinating agent and reduce the tail gas The load pressure handled by the spray absorption tower 6 in the processing system.

Example 2:

This embodiment is a photocatalytic fluorination reaction process.

Using the same photocatalytic reactor 1 as in Example 1, the specific process steps are as follows:

S1. Add the unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene, at 40°C, with a viscosity of 30sct, into the photocatalytic reactor 1 from the feeding port, replace with inert gas and vacuumize, and then put The photocatalytic reactor 1 is heated and controlled to 120°C.

S2. adopt the mixed gas of F2 and _N2 as the fluorinating agent ₍ the mass concentration of F2 in the mixed gas is ₂₀ %), open the check valve 10, and periodically transfer the F2/N2 in the steel cylinder 11 through the gas flowmeter 9 The fluorinating agent gas is sent into the photocatalytic reactor 1 through the gas distributor 3, and the pressure control valve controls the system pressure at 0.1MPa (when the system pressure drops to 1/3~1/4 of the initial pressure, it is discharged through the vent valve 7 Inactive gas components, add new fluorinating agent again), the molar ratio of perfluoropolyetheryl fluoride to fluorinating agent is controlled at 1:10.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 800W, and the irradiation wavelength to 300nm, and control the reaction to continue for 20 hours before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization stabilization treatment.

Example 3:

This embodiment is a photocatalytic fluorination reaction process.

Using the same photocatalytic reactor 1 as in Example 1, the specific process steps are as follows:

S1. Add the unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene, at 40°C, with a viscosity of 30sct, into the photocatalytic reactor 1 from the feeding port, replace with inert gas and vacuumize, and then put The photocatalytic reactor 1 is heated and controlled to 150°C.

S2. adopt the mixed gas of F2 and _N2 as the fluorinating agent ₍ the mass concentration of F2 in the mixed gas is ₂₀ %), open the check valve 10, and periodically transfer the F2/N2 in the steel cylinder 11 through the gas flowmeter 9 The fluorinating agent gas is sent into the photocatalytic reactor 1 through the gas distributor 3, and the pressure control valve controls the system pressure at 0.5MPa (when the system pressure drops to 1/3~1/4 of the initial pressure, it is discharged through the vent valve 7 Inactive gas components, add new fluorinating agent again), the molar ratio of perfluoropolyetheryl fluoride to fluorinating agent is controlled at 1:5.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 800W, and the irradiation wavelength to 300nm, and control the reaction to continue for 18 hours before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization stabilization treatment.

Example 4:

This embodiment is a photocatalytic fluorination reaction process.

Using the same photocatalytic reactor 1 as in Example 1, the specific process steps are as follows:

S1. Add the unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene, at 40°C, with a viscosity of 30sct, into the photocatalytic reactor 1 from the feeding port, replace with inert gas and vacuumize, and then put The photocatalytic reactor 1 is heated and controlled to 80°C.

S2. adopt the mixed gas of F2 and _N2 as the fluorinating agent ₍ the mass concentration of F2 in the mixed gas is 50%), open the check valve 10, and periodically and intermittently pass the F2/ _N2 in the steel cylinder 11 through the gas flowmeter 9 The fluorinating agent gas is sent into the photocatalytic reactor 1 through the gas distributor 3, and the pressure control valve controls the system pressure at 0MPa (when the system pressure drops to 1/3~1/4 of the initial pressure, the non- The active gas component is added again with a new fluorinating agent), and the molar ratio of perfluoropolyetheryl fluoride to fluorinating agent is controlled at 1:1.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 300W, and the irradiation wavelength to 320nm, and control the reaction to continue for 40h before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization stabilization treatment.

Example 5:

This embodiment is a photocatalytic fluorination reaction process.

Using the same photocatalytic reactor 1 as in Example 1, the specific process steps are as follows:

S1. Add the unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene, at 40°C, with a viscosity of 30sct, into the photocatalytic reactor 1 from the feeding port, replace with inert gas and vacuumize, and then put The photocatalytic reactor 1 is heated and controlled to 150°C.

S2. Use _SF4 as the fluorinating agent, open the one-way valve 10, periodically send the fluorinating agent gas through the gas distributor 3 into the photocatalytic reactor 1 through the gas flow meter 9, and the pressure control valve controls the system pressure at 0.4 MPa (when the system pressure drops to 1/3~1/4 relative to the initial pressure, the inactive gas components are discharged through the vent valve 7, and a new fluorinating agent is added again), perfluoropolyether fluoride and fluorinating agent The molar ratio is controlled at 1:8.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 600W, and the irradiation wavelength to 300nm, and control the reaction to continue for 5 hours before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization stabilization treatment.

Embodiment 6:

This embodiment is a photocatalytic fluorination reaction process.

Using the same photocatalytic reactor 1 as in Example 1, the specific process steps are as follows:

S1. Add the unstable perfluoropolyether containing acyl fluoride end groups obtained by photooxidative polymerization of 30L hexafluoropropylene, at 40°C, with a viscosity of 30sct, into the photocatalytic reactor 1 from the feeding port, replace with inert gas and vacuumize, and then put The photocatalytic reactor 1 is heated and controlled to 140°C.

S2. Use the mixed gas of SF ₆ and BF ₃ as the fluorinating agent (the mass concentration of BF ₃ in the mixed gas is 40%), open the check valve 10, and pass the fluorinating agent gas through the gas flow meter 9 intermittently and regularly The sparger 3 is sent into the photocatalytic reactor 1, and the pressure control valve controls the system pressure at 0.3MPa (when the system pressure drops to 1/3~1/4 of the initial pressure, the inactive gas components are discharged through the vent valve 7, and the Adding a new fluorinating agent), the molar ratio of perfluoropolyetheryl fluoride to fluorinating agent is controlled at 1:3.

S3. Turn on the ultraviolet light generator 2, the gas circulation pump and the liquid circulation pump 8 to carry out the photocatalytic fluorination reaction, adjust the irradiation power of the ultraviolet light generator 2 to 600W, and the irradiation wavelength to 350nm, and control the reaction to continue for 15 hours before stopping the reaction .

S4. Perform cooling and nitrogen purging, and discharge the end group stabilization treatment product perfluoropolyether oil. Sampling and infrared testing show that the product does not contain acyl fluoride or carboxylic acid groups (1766cm ^-1 ), and 100% end group realization stabilization treatment.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications and equivalent changes made to the above embodiments according to the technical essence of the present invention all fall within the scope of the present invention. within the scope of protection.

Claims (10)

1. A photocatalytic fluorination reaction process is characterized in that: under the irradiation of ultraviolet light, the unstable perfluoropolyether raw material and fluorinating agent gas are subjected to fluorination reaction, the reaction temperature is controlled to be 80-150 ℃, the pressure is 0-0.5 MPa, the reaction time is 5-40 h, and the perfluoropolyether oil is obtained after the reaction is finished.

2. The photocatalytic fluorination process of claim 1, wherein: when the ultraviolet light is irradiated, the irradiation power is controlled to be 300-800W, the irradiation time is 5-40 h, and the irradiation wavelength is more than 300nm.

3. The photocatalytic fluorination process of claim 1, wherein: the molar ratio of the unstable perfluoropolyether raw material to the fluorinating agent gas is controlled to be 1: (20-1).

4. The photocatalytic fluorination process of claim 1, wherein: the unstable perfluoropolyether raw material is perfluoropolyether acyl fluoride and/or perfluoropolyether carboxylic acid.

5. The photocatalytic fluorination process of claim 1, wherein: said fluorinating agent gas is selected from F ₂ And N ₂ Mixed gas of (1), SF ₄ 、SF ₆ 、BF ₃ At least one of (1).

6. A photocatalytic fluorination process according to claim 5, wherein: the fluorinating agent gas is F ₂ And N ₂ Controlling F in the mixed gas ₂ The mass concentration of (2) is 20-50%.

7. The photocatalytic fluorination process of claim 1, wherein: the fluorination reaction is carried out in a photocatalytic reaction kettle (1), a gas distributor (3) is arranged at the lower part of the photocatalytic reaction kettle (1), and the fluorinating agent gas is sent into the photocatalytic reaction kettle (1) through the gas distributor (3).

8. The photocatalytic fluorination process of claim 7, wherein: controlling the circulation of the materials in the photocatalytic reaction kettle (1), wherein the method comprises the steps of condensing and pressurizing the gas at the upper part of the photocatalytic reaction kettle (1) and then feeding the gas into the photocatalytic reaction kettle (1) through a gas distributor (3); liquid at the bottom of the photocatalytic reaction kettle (1) is fed in from the top of the photocatalytic reaction kettle (1) through a circulating pump.

9. The photocatalytic fluorination process of claim 7, wherein: the fluorinating agent gas is sent to a gas distributor (3) at intervals through a gas flowmeter (9), when the pressure is reduced to 1/3-1/4 of the initial pressure, an emptying valve (7) is opened to discharge inactive inert gas, and then the addition of the fluorinating agent gas is controlled.

10. The photocatalytic fluorination process of claim 1, wherein: in the fluorination reaction process, the reaction temperature is controlled to be 100-120 ℃, the pressure is 0.1-0.3 MPa, and the reaction time is 10-30 h.

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