Method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics

Abstract

The invention belongs to the technical field of fluorine chemical material preparation, and particularly relates to a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics. The method comprises the following steps: mixing AHF liquid with an excessive PC13 liquid material in a spherical liquid drop form, introducing the mixture into a spiral tube microreactor, controlling the pressure in the spiral tube microreactor to be 1.0-2.5 MPa and the temperature to be 60-140 DEG C, carrying out reaction, carrying out reduced pressure gas-liquid separation on the reacted material, and separating and purifying a gas-phase component to obtain phosphorus trifluoride, and the liquid-phase component enters the spiral tube microreactor as a PC13 liquid feed cycle to participate in the reaction. According to the invention, efficient, safe and continuous preparation of phosphorus trifluoride is realized through an innovative liquid-liquid microfluidic technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorine chemical material preparation, and in particular relates to a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics. Background Art

[0002] Phosphorus trifluoride (PF3) is an important inorganic compound that is widely used in the electronics industry, chemical synthesis, and materials science. Currently, its source is mainly synthesized through chemical reactions.

[0003] Existing methods for preparing phosphorus trifluoride primarily include the reaction of phosphorus trichloride with anhydrous hydrofluoric acid, the direct reaction of fluorine gas with phosphorus, the reaction of fluoride salts (such as zinc fluoride, ammonium fluoride, sodium fluoride, and potassium fluoride) with phosphorus trichloride, and the reaction of phosphoric acid with hydrofluoric acid. Each of these methods has its own unique characteristics, but the reaction of phosphorus trichloride (PCl3) with anhydrous hydrofluoric acid (AHF) to produce PF3 is a relatively viable option. This method offers advantages such as relatively mild reaction conditions, readily available raw materials, and a mature process. It can be performed at relatively low temperatures, reducing equipment requirements. Furthermore, phosphorus trichloride and anhydrous hydrofluoric acid are both common and readily available chemical raw materials.

[0004] However, existing technologies also have numerous shortcomings. For example, the reaction involves highly corrosive substances (such as HF), placing extremely high demands on equipment and the operating environment, increasing equipment costs and maintenance difficulties. Furthermore, the reaction easily generates mono- and disubstituted intermediates (such as PCl2F and PClF2), increasing the difficulty and cost of product purification. Furthermore, the reaction is highly exothermic, making it difficult to effectively control the reaction temperature within a low range, which can lead to local overheating and affect product quality and yield. Furthermore, excessive HF is often required to drive the reaction, which not only increases raw material costs but also complicates subsequent processing and poses potential environmental risks. Furthermore, the generated HCl and unreacted HF are highly corrosive and toxic, and the high pressure of the reaction products poses potential risks to operators and the environment, limiting their large-scale industrial application. Conventional tubular reactors / microchannel reactors are often considered for completing fluorination reactions with low dosages to reduce reaction safety risks. However, high gas-liquid ratios can lead to significant uneven liquid residence time and poor mass transfer efficiency. At the same time, the reaction itself produces a large amount of gas (such as PF3 and HCl), which seriously affects the flow and mass transfer effect of the liquid, resulting in gas plug flow and reducing the efficiency of the mixing reaction.

[0005] In summary, while existing technologies have made some progress in the preparation of phosphorus trifluoride, many challenges remain, particularly in precise reaction control, byproduct suppression, safety enhancement, and enhanced mass transfer in high gas-liquid ratio reactions. Therefore, developing an efficient, safe, environmentally friendly, and economical method for preparing phosphorus trifluoride is of great practical significance. Summary of the Invention

[0006] In view of the shortcomings and deficiencies of the above prior art, the object of the present invention is to provide a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics.

[0007] The method of the present invention controls the pressure of the reaction system to be 1.0 MPa to 2.5 MPa and adopts an excess of PCl3 liquid material as a circulating reaction raw material and a reaction heat transfer medium, so that hydrofluoric acid is uniformly introduced into the system in the form of small droplets for reaction, thereby enhancing reaction stability and reducing corrosion of hydrofluoric acid on equipment. At the same time, PF3 and HCl gas products generated by the reaction are dissolved in the excess of PCl3 liquid material under high pressure, and the mixture after the reaction can maintain a liquid phase under a relatively low pressure (the vapor pressure of PCl3 at the reaction temperature is less than 0.5 MPa, and the mixed vapor pressure of HCl and PF3 under this condition after dissolution is less than 1.0 MPa to 2.5 MPa) (if there is no excess PCl3 as a dissolving medium, the vapor pressure of HCl and PF3 in the gas phase is high, and a pressure of more than 6 MPa is required to cause the mixture after the reaction to become a liquid), thereby avoiding damage to the fluid structure by the gas phase products, solving the problem of uneven liquid residence time, and effectively improving the reaction efficiency.

[0008] The purpose of the present invention is achieved through the following technical solutions: A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics comprises the following steps: Anhydrous hydrofluoric acid (AHF) liquid is mixed with excess phosphorus trichloride (PCl3) liquid material in the form of spherical droplets and then introduced into a spiral tube microreactor. The pressure in the spiral tube microreactor is controlled to be 1.0MPa~2.5MPa and the temperature is controlled to be 60~140℃ for reaction. The reacted materials are subjected to gas-liquid separation by reduced pressure, and the gas phase components are separated and purified to obtain phosphorus trifluoride; the liquid phase components enter the spiral tube microreactor as PCl3 liquid feed and circulate to participate in the reaction.

[0009] In the above-mentioned preparation method, by controlling the reaction pressure within the spiral tube microreactor to 1.0 MPa to 2.5 MPa, preferably 1.5 MPa to 2.5 MPa, and incorporating an excess of PCl3 as the liquid medium, this ensures that the reaction raw material AHF itself and the reaction products PF3 and HCl remain in a liquid state after dissolving in PCl3. This improves the mixing of the reaction raw materials while preventing the gaseous products from disrupting the fluid structure and resolving the problem of uneven liquid residence time, thereby effectively improving reaction efficiency. Furthermore, it effectively promotes the conversion of PF3 and reduces the formation of by-products, thereby improving reaction efficiency and product purity. Furthermore, it significantly reduces direct contact of highly corrosive gases (such as HF and HCl) with the equipment, thereby reducing the risk of equipment corrosion. This design ensures reaction uniformity and stability, further improving product quality, while also extending the equipment's service life and enhancing operational safety. Excessively low pressures can prevent the gaseous components from completely dissolving in the liquid phase, reducing mass transfer efficiency.

[0010] In the above preparation method, by controlling the reaction temperature of the spiral tube microreactor to 60-140°C, preferably 60-130°C, the higher temperature can promote the replacement reaction of PCl3 and AHF, increase the conversion rate of the target product PF3, and improve the reaction efficiency. At the same time, the heat released by the reaction of PCl3 and AHF can be better utilized, and the temperature can be better controlled and stabilized when an excess of PCl3 liquid material is used as a heat transfer medium. However, excessively high temperatures will cause the reaction gas phase components to not be completely dissolved in the liquid phase, reducing the mass transfer reaction efficiency.

[0011] In the above preparation method, the size of the AHF spherical droplets is controlled to 0.5±0.1μm. By uniformly dispersing the AHF liquid in liquid phosphorus trichloride (PCl3) as small spherical droplets, the specific surface area and reaction contact area are significantly increased, promoting a rapid reaction. This design not only improves mass transfer efficiency but also ensures rapid reaction progress and reduces the formation of byproducts. The AHF spherical droplets can be generated by fragmentation using a pressure oscillation nozzle or by using other discontinuous liquid feeding devices.

[0012] In the above preparation method, the molar ratio of AHF to PCl3 in the spiral tube microreactor is in the range of 1:3 to 10. The theoretical molar ratio of AHF to PCl3 is 3:1, but when the PCl3 is in a small excess, the solubility of HCl and PF3 components with higher vapor pressures in the product is reduced, resulting in the separation of some gaseous products from the liquid phase, destroying the fluid structure in the microreactor and reducing the efficiency of the mixing reaction.

[0013] In the above preparation method, the feed flow rates of the PCl3 liquid material and the AHF spherical droplets can be adjusted according to the actual reaction scale and the circulation amount of the liquid phase component after gas-liquid separation to ensure that the molar ratio of AHF to PCl3 entering the spiral tube microreactor is in the range of 1:3~10.

[0014] In the above preparation method, the reaction residence time is controlled within 3–10 minutes by controlling the flow rates of the AHF and PCl3 liquids and the length of the helical microreactor. This ensures the reaction proceeds fully while avoiding the formation of byproducts caused by excessive residence time. For example, the flow rate of the AHF liquid can be controlled within the range of 60–100 ml / min; the flow rate of the PCl3 liquid can be controlled within the range of 130–4500 ml / min. At the same time, the channel diameter of the helical microreactor can be controlled within the range of 6–25 mm and the length within the range of 5–100 m. This stable residence time control helps improve product purity and yield.

[0015] In the above-mentioned preparation method, the decompression gas-liquid separation involves reducing the pressure to 0.5-1 MPa to rapidly separate the PF3 and HCl gases while simultaneously removing the heat generated by the reaction. This design not only stabilizes the system temperature but also reduces the need for additional cooling, thereby lowering energy consumption. The separated low-temperature liquid material (primarily excess unreacted PCl3 liquid and a small amount of low-substituted products) re-enters the spiral tube microreactor and circulates to participate in the reaction until it exits as PF3 gas. This energy recovery and recycling design further reduces system energy consumption, improves raw material utilization, minimizes waste, and lowers production costs.

[0016] In the above preparation method, the separation and purification step is: pressurizing the gas phase component to 3.5~4.2MPa and cooling it to -30~-2°C to liquefy PF3 and then separate it by distillation.

[0017] A device for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics comprises a mixer, a spiral tube microreactor and a gas-liquid separation tank which are connected in sequence; the mixer is a Y-type mixer, one feed port of the Y-type mixer is connected to a phosphorus trichloride (PCl3) storage tank via a pipeline, the other feed port is provided with a pressure oscillation nozzle and is connected to an anhydrous hydrofluoric acid (AHF) storage tank via a pipeline, and the discharge port of the Y-type mixer is connected to the spiral tube microreactor; the liquid material outlet of the gas-liquid separation tank is connected to the spiral tube microreactor via a circulation pump and a pipeline.

[0018] The present invention provides a Y-type mixer and a pressure oscillation nozzle at the feed port connected to the AHF storage tank, so that the AHF feed can be broken into spherical droplets by pressure oscillation to form a well-dispersed mixing with PCl3.

[0019] Furthermore, a metering pump is provided on the pipeline connecting the PCl3 storage tank and the Y-type mixer, and on the pipeline connecting the AHF storage tank and the Y-type mixer. By providing the metering pump, the feed ratio of AHF and PCl3 can be conveniently controlled.

[0020] Furthermore, the spiral tube microreactor has a channel diameter of 6 to 25 mm and a length of 5 to 100 m. A spiral tube microreactor is a commonly used reaction device in the art. Its structure is a spirally arranged fluid conduit. During the fluid flow process, the spiral advances, achieving plug flow and ensuring spatial reaction uniformity, while also enhancing mixing and heat exchange to a certain extent. The size of the spiral tube microreactor can be adjusted according to actual production needs.

[0021] Furthermore, the spiral tube microreactor is internally connected to a back pressure system, which can conveniently control the reaction pressure in the spiral tube microreactor.

[0022] Furthermore, a heating jacket is provided outside the spiral tube microreactor, so that the reaction temperature in the spiral tube microreactor can be conveniently controlled.

[0023] Furthermore, the gas phase material outlet of the gas-liquid separation tank is further connected to a compression cooling device and a distillation separation device.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Efficient mass transfer and reaction: The present invention conducts the reaction under high pressure (1.0 MPa~2.5 MPa), uses an excess of PCl3 liquid material as both the reaction raw material and the reaction medium, and mixes the AHF raw material in the form of spherical droplets for reaction. This can significantly improve the mixing reaction effect of the reaction raw materials, while avoiding the destruction of the fluid structure by the gas phase products, and effectively improving the mass transfer effect and reaction efficiency.

[0025] (2) Improved safety: Through high-pressure liquefaction and pressure shock crushing, AHF spherical droplets are evenly dispersed in liquid PCl3 for mixing reaction, which significantly reduces the direct contact of highly corrosive gases (such as HF and HCl) with the equipment, thereby reducing the risk of equipment corrosion, extending the service life of the equipment and improving operational safety.

[0026] (3) Energy coupling and energy saving: The mixed material after the reaction passes through the gas-liquid separation tank to quickly separate the PF3 and HCl gases, while taking away the heat generated by the reaction. This design not only stabilizes the system temperature, but also reduces the need for additional cooling and reduces energy consumption. The separated low-temperature liquid material re-enters the spiral tube microreactor to participate in the reaction cycle, further reducing the energy consumption of the system. This energy recovery and recycling design significantly improves energy utilization efficiency and reduces production costs.

[0027] (4) Material circulation and resource utilization: Excess unreacted PCl3 liquid material and low-substituted materials re-enter the spiral tube microreactor at a lower temperature and participate in the reaction cycle until they leave in the form of PF3 gas. This design improves raw material utilization, reduces waste, and lowers production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the connection relationship of a device for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0030] Example 1 A device for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics, the connection relationship diagram of which is shown as follows Figure 1 As shown. It includes a mixer 6, a spiral tube microreactor 7, a gas-liquid separator 8, and a back pressure system 9, which are connected in sequence. The mixer 6 is a Y-type mixer. One feed port of the Y-type mixer is connected to the phosphorus trichloride (PCl3) storage tank 1 via a pipeline, and the other feed port is provided with a pressure oscillation nozzle 5 and is connected to the anhydrous hydrofluoric acid (AHF) storage tank 2 via a pipeline. A metering pump 4 is provided on the pipeline connecting the PCl3 storage tank 1 and the mixer 6, and a metering pump 3 is provided on the pipeline connecting the AHF storage tank 2 and the mixer 6. The discharge port of the Y-type mixer is connected to the spiral tube microreactor 7. The channel diameter of the spiral tube microreactor is 20 mm and the length is 25 m. A heating jacket is provided on the outside of the spiral tube microreactor. The liquid material outlet of the gas-liquid separator 8 is connected to the spiral tube microreactor 7 via a circulation pump 10 and a pipeline. The gas phase material outlet of the gas-liquid separator 8 is connected to the compressor 11, the cryogenic cooler 12, and the distillation tower 13 in sequence.

[0031] A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics comprises the following preparation steps: (1) Pressure regulation: nitrogen is introduced through the back pressure system 9 to increase the pressure in the spiral tube microreactor 7 to 2 MPa.

[0032] (2) Temperature control: The temperature inside the spiral tube microreactor 7 was raised to 80°C by heating the jacket.

[0033] (3) Feeding and reaction: The PCl3 liquid in the PCl3 storage tank 1 is transported to the mixer 6 through a feed port of the Y-type mixer; at the same time, the AHF liquid in the AHF storage tank 2 is transported to the pressure oscillation nozzle 5 to break up into AHF spherical droplets of 0.5±0.1μm in size and enter the mixer 6. The PCl3 liquid and the AHF spherical droplets are axially mixed in the mixer 6. The feed molar ratio of AHF to PCl3 is controlled to be 1:6 by metering pumps 3 and 4, and enters the spiral tube microreactor to form an annular flow for reaction. The reaction residence time is controlled to be 3 min by the material delivery flow rate.

[0034] (4) Separation: The outlet material of the spiral tube microreactor 7 is depressurized to 0.5 MPa by a pressure reducing valve and enters the gas-liquid separation tank 8 for gas-liquid separation. The obtained gas phase components (mainly including PF3, HCl and a small amount of PCl2F and PClF2 by-products) are compressed to 4.0 MPa by a compressor 11, then cooled to -15°C by a cryogenic refrigerator 12 for liquefaction, and then enter the distillation tower 13 for distillation separation to obtain phosphorus trifluoride. The temperature of the remaining liquid material in the gas-liquid separation tank 8 is 50°C. It enters the spiral tube microreactor 7 through a circulation pump 10 as PCl3 liquid feed and circulates to participate in the reaction.

[0035] In this embodiment, the outlet of the spiral tube microreactor 7 was cooled and sampled, and the conversion rate of the target product PF3 was tested to be 99.87% (the amount of substance generated by the actual reaction to generate PF3 / the amount of substance generated by the theoretical reaction, PF3 / PClF2 / / PCl2F was detected by GC-MS and separated by a weak polarity chromatographic column (such as DB-5MS)), and the by-product generation rate was: PCl2F 0.02% (the amount of substance generated by the actual reaction to generate PClF2 / the amount of substance generated by the theoretical reaction to generate PF3), PClF2 0.01% (the amount of substance generated by the actual reaction to generate PCl2F / the amount of substance generated by the theoretical reaction to generate PF3).

[0036] Examples 2 to 8 Compared with Example 1, Examples 2 to 8 respectively controlled the reaction pressure and reaction temperature as described in Table 1. The target product conversion rate and by-product generation rate under different pressure and temperature conditions are shown in Table 1.

[0037] Table 1 Results of target product conversion and by-product generation rates under different pressure and temperature conditions Test Case Reaction pressure Reaction temperature <![CDATA[PF3 conversion rate]]> <![CDATA[PCl2F production rate]]> <![CDATA[PClF2 generation rate]]> Example 2 1.0MPa 80℃ 99.70% 0.07% 0.03% Example 3 1.5MPa 60℃ 99.84% 0.05% 0.01% Example 4 1.8MPa 70℃ 99.85% 0.04% 0.01% Example 5 2.2MPa 100℃ 99.86% 0.02% 0.02% Example 6 2.4MPa 120℃ 99.85% 0.02% 0.03% Example 7 2.5MPa 130℃ 99.84% 0.02% 0.04% Example 8 2.0MPa 140℃ 99.71% 0.02% 0.06%

[0038] From the results of Table 1 and Example 1, it can be concluded that appropriately increasing the reaction temperature and pressure is beneficial to improving the PF3 conversion rate. However, too low a reaction pressure and too high a reaction temperature will lead to a decrease in the PF3 conversion rate. This is because too low a pressure or too high a temperature prevents the reaction gas phase components from completely dissolving in the liquid phase, reducing the mass transfer reaction efficiency. The PF3 conversion rate can be further improved when the reaction pressure is between 1.5 MPa and 2.5 MPa and the reaction temperature is between 60°C and 130°C.

[0039] Examples 9-14 Compared with Example 1, Examples 9 to 14 respectively control the material delivery flow rate to make the reaction residence time of the spiral tube microreactor 0.5 min, 1 min, 5 min, 8 min, 10 min, and 12 min, and the rest are the same as Example 1.

[0040] The target product conversion rate and by-product generation rate results of Examples 9 to 14 under different reaction time conditions are shown in Table 2 below.

[0041] Table 2 Results of target product conversion and by-product generation rate under different reaction time conditions Test Case Reaction time <![CDATA[PF3 conversion rate]]> <![CDATA[PCl2F production rate]]> <![CDATA[PClF2 generation rate]]> Example 9 0.5min 99.51% 0.15% 0.04% Example 10 1min 99.57% 0.10% 0.01% Example 11 5min 99.88% 0.02% Not detected Example 12 8min 99.89% 0.01% Not detected Example 13 10min 99.89% 0.01% Not detected Example 14 12min 99.81% 0.09% Not detected

[0042] From the results of Table 2 and Example 1, it can be concluded that the PF3 conversion rate can be further improved by controlling the reaction residence time of the spiral tube microreactor to be in the range of 3 to 10 min.

[0043] Examples 15-20 Compared with Example 1, Examples 15 to 20 are the same as Example 1, except that the feed molar ratio of AHF to PCl3 is adjusted to 1:1, 1:3, 1:5, 1:7, 1:10, and 1:12, respectively.

[0044] The target product conversion rate and by-product generation rate results of Examples 15 to 20 under different feed molar ratios of AHF to PCl3 are shown in Table 3 below.

[0045] Table 3 Results of target product conversion and by-product generation rate under different feed molar ratios of AHF to PCl3 Test Case <![CDATA[AHF:PCl3]]> <![CDATA[PF3 conversion rate]]> <![CDATA[PCl2F production rate]]> <![CDATA[PClF2 production rate]]> Example 15 1:1 80.71% 0.10% 0.05% Example 16 1:3 99.83% 0.07% Not detected Example 17 1:5 99.86% 0.03% 0.01% Example 18 1:7 99.85% 0.03% 0.02% Example 19 1:10 99.82% 0.05% 0.03% Example 20 1:12 99.10% 0.50% 0.10%

[0046] The results in Table 3 indicate that the PF3 conversion rate significantly decreases when the PCl3 feed amount is too low. This is because the lack of a large excess of PCl3 as a dissolving medium reduces the solubility of the HCl and PF3 components with higher vapor pressures in the product. This causes some HCl and PF3 in the product to separate from the liquid phase, disrupting the fluid structure in the microreactor and thus reducing the efficiency of the mixed reaction. Excessive PCl3 feed leads to increased byproduct formation and reduced PF3 conversion. The present invention further improves PF3 conversion by controlling the feed molar ratio of AHF to PCl3 to 1:3 to 10.

[0047] Comparative Example 1 A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics. Compared with Example 1, the AHF liquid feed is not broken into spherical droplets by a pressure oscillation nozzle, and is directly axially mixed with the PCl3 liquid in a mixer using continuous liquid feeding. The rest of the process is the same.

[0048] The test showed that the conversion rate of the target product PF3 in the outlet product of the spiral tube microreactor of this comparative example was 97.60%, and the by-product generation rates were: PCl2F 0.34%, PClF2 0.15%.

[0049] It can be concluded from the results of this comparative example and Example 1 that the present invention reacts AHF in the form of spherical droplets, which can significantly improve the reaction efficiency and reduce the generation of by-products.

[0050] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics, characterized in that: The steps include: AHF liquid is mixed with excess PCl3 liquid material in the form of spherical droplets and then introduced into a spiral tube microreactor. The pressure in the spiral tube microreactor is controlled to be 1.0MPa~2.5MPa and the temperature is controlled to be 60~140℃ for reaction. The reacted materials are subjected to gas-liquid separation by reduced pressure, and the gas phase components are separated and purified to obtain phosphorus trifluoride; the liquid phase components enter the spiral tube microreactor as PCl3 liquid feed and circulate to participate in the reaction.

2. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 1, characterized in that: The reaction pressure in the spiral tube microreactor is 1.5MPa~2.5MPa, and the reaction temperature is 60~130℃.

3. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 1, characterized in that: The size of the AHF spherical droplets is controlled to be 0.5±0.1 μm.

4. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 3, characterized in that: The size of the AHF spherical droplets was controlled to be 0.5±0.1 μm by using a pressure oscillation nozzle to break them up.

5. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 1, characterized in that: The molar ratio of AHF to PCl3 in the spiral tube microreactor is in the range of 1:3 to 10.

6. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 5, characterized in that: By controlling the flow rates of AHF liquid and PCl3 liquid and the length of the spiral tube microreactor, the residence time of the reaction was controlled between 3 and 10 min.

7. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 6, characterized in that: The delivery flow rate of the AHF liquid is 60~100ml / min; the delivery flow rate of the PCl3 liquid is 130~4500ml / min.

8. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 6, characterized in that: The channel diameter of the spiral tube microreactor is 6-25 mm, and the length is 5-100 m.

9. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 1, characterized in that: The decompression gas-liquid separation refers to reducing the pressure to 0.5~1MPa to quickly separate PF3 and HCl gases and take away the heat generated by the reaction.

10. The method for continuous preparation of phosphorus trifluoride based on liquid-liquid microfluidics according to claim 1, characterized in that: The separation and purification steps are as follows: pressurizing the gaseous components to 3.5-4.2 MPa and cooling to -30--2°C to liquefy PF3 and then separating by rectification.

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