A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics

Abstract

The application belongs to the technical field of fluorinated material preparation, and particularly relates to a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidic technology. The method comprises the following steps: mixing AHF liquid in the form of spherical droplets with excessive PCl3 liquid material, and then feeding the mixture into a spiral pipe microreactor; controlling the pressure in the spiral pipe microreactor to be 1.0 MPa-2.5 MPa and the temperature to be 60-140 DEG C to perform reaction; performing gas-liquid separation on the reacted material under reduced pressure; performing separation and purification on the gas phase component to obtain phosphorus trifluoride; and feeding the liquid phase component into the spiral pipe microreactor as PCl3 liquid feed to participate in the reaction. The application realizes efficient, safe and continuous preparation of phosphorus trifluoride through innovative liquid-liquid microfluidic technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorinated chemical material preparation, and particularly relates to a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics. BACKGROUND

[0002] Phosphorus trifluoride (PF3) is an important inorganic compound, widely used in electronic industry, chemical synthesis and material science, etc. At present, its source is mainly synthesized by chemical reaction.

[0003] The existing preparation methods of phosphorus trifluoride mainly include the reaction of phosphorus trichloride and anhydrous hydrofluoric acid, the direct reaction of fluorine gas and phosphorus, the reaction of fluorinated salt (such as zinc fluoride, ammonium fluoride, sodium fluoride, potassium fluoride, etc.) and phosphorus trichloride, and the reaction of phosphoric acid and hydrofluoric acid. These methods have their own characteristics, among which the reaction of phosphorus trichloride (PCl3) and anhydrous hydrofluoric acid (AHF) to generate PF3 is a more feasible scheme. This method has the advantages of relatively mild reaction conditions, easy-to-obtain raw materials and mature process, etc., can be carried out at a lower temperature, reduces the requirements for equipment, and both phosphorus trichloride and anhydrous hydrofluoric acid are common chemical raw materials, which are easy to obtain.

[0004] However, the existing technology also has many deficiencies. For example, strong corrosive substances (such as HF) are involved in the reaction process, which has very high requirements for equipment and operating environment, increasing the cost of equipment and the difficulty of maintenance. In addition, the reaction is easy to generate mono-substituted and di-substituted intermediates (such as PCl2F, PClF2), increasing the difficulty and cost of product purification. In addition, the reaction is exothermic, and it is difficult to effectively control the reaction temperature in a lower range, which may cause local overheating, affecting the product quality and yield. Moreover, in order to promote the reaction, it is usually necessary to use HF in excess, which not only increases the cost of raw materials, but also brings complexity and potential environmental pollution risk in subsequent processing. At the same time, HCl and unreacted HF generated in the reaction have strong corrosiveness and toxicity, and the reaction product has high pressure, which poses potential risks to operators and the environment, limiting its large-scale industrial application. It is usually considered to use conventional tubular reactors / micro-channel reactors to complete the fluorination reaction in a small dose, thereby reducing the safety risk of the reaction. However, under high gas-liquid ratio conditions, there are serious problems such as uneven liquid residence time and low reaction mass transfer effect. At the same time, the reaction itself generates a large amount of gas (such as PF3 and HCl), which seriously affects the flow mass transfer effect of the liquid, leading to the formation of gas plug flow, and reducing the mixing reaction efficiency.

[0005] In summary, although the existing technology has made certain progress in the preparation of phosphorus trifluoride, there are still many problems to be solved, especially in the precise control of the reaction, the inhibition of by-products, the improvement of safety and the enhancement of mass transfer under high gas-liquid ratio. Therefore, it is of great practical significance to develop an efficient, safe, environmentally friendly and economical method for preparing phosphorus trifluoride. SUMMARY

[0006] In view of the above-mentioned defects and shortcomings of the prior art, the present application aims to provide a method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics.

[0007] The method of the present application can enhance the reaction stability and reduce the corrosion of hydrofluoric acid to the equipment by controlling the pressure of the reaction system to be 1.0-2.5 MPa and using excess PCl3 liquid material as the circulating reaction raw material and reaction heat transfer medium to make the hydrofluoric acid uniformly enter the system in the form of small droplets. Meanwhile, the generated PF3 and HCl gas products are dissolved in the excess PCl3 liquid material under high pressure, and the mixed material after reaction can maintain a liquid phase state under a smaller pressure (the vapor pressure of PCl3 at the reaction temperature is less than 0.5 MPa, and the mixed vapor pressure after dissolving HCl and PF3 under this condition is less than 1.0-2.5 MPa), thereby avoiding the damage of the gas phase products to the fluid structure and solving the problem of uneven liquid residence time, thereby effectively improving the reaction efficiency.

[0008] The object of the present application is achieved by the following technical solutions:

[0009] A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics, comprising the following steps:

[0010] 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, and the reaction is carried out by controlling the pressure in the spiral tube microreactor to be 1.0-2.5 MPa and the temperature to be 60-140℃. The material after reaction is subjected to pressure reduction gas-liquid separation, the gas phase components are separated and purified, and phosphorus trifluoride is obtained. The liquid phase components enter the spiral tube microreactor as PCl3 liquid feed to participate in the reaction.

[0011] In the above preparation method, by controlling the reaction pressure in the spiral tube microreactor to be 1.0 MPa to 2.5 MPa, preferably controlling the reaction pressure in the spiral tube microreactor to be 1.5 MPa to 2.5 MPa, and combining with the excess PCl3 liquid material medium, on the one hand, it can ensure that the reaction raw material AHF itself and the reaction product PF3, HCl dissolved in PCl3 all remain in a liquid state, improve the mixing effect of the reaction raw materials, avoid the damage of the gas phase product to the fluid structure, solve the problem of uneven liquid residence time, and effectively improve the reaction efficiency; on the other hand, it can effectively promote the conversion of PF3 and reduce the generation of by-products, improve the reaction efficiency and product purity; and on the other hand, it also significantly reduces the direct contact of strong corrosive gas (such as HF and HCl) with the equipment, thereby reducing the corrosion risk of the equipment. This design not only ensures the uniformity and stability of the reaction, but also further improves the quality of the product; on the other hand, it also prolongs the service life of the equipment and improves the operation safety. Too low pressure will cause the reaction gas phase components to not be completely dissolved in the liquid phase, which reduces the mass transfer reaction efficiency.

[0012] In the above preparation method, the reaction temperature of the spiral tube microreactor is controlled to be 60 to 140°C, preferably the reaction temperature of the spiral tube microreactor is controlled to be 60 to 130°C. At a higher temperature, the displacement reaction of PCl3 and AHF can be promoted, the conversion rate of the target product PF3 is improved, and the reaction efficiency is improved; 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 under the condition of excess PCl3 liquid material as heat transfer medium. But too high temperature will cause the reaction gas phase components to not be completely dissolved in the liquid phase, which reduces the mass transfer reaction efficiency.

[0013] In the above preparation method, the size of the AHF spherical droplets is controlled to be 0.5±0.1 μm. By uniformly dispersing the AHF liquid in the form of spherical small droplets in the liquid phosphorus trichloride (PCl3), the specific surface area and reaction contact area can be significantly increased, and the rapid reaction can be promoted. This design not only improves the mass transfer efficiency, but also ensures the rapid progress of the reaction and reduces the generation of by-products. The AHF spherical droplets can be generated by pressure shock nozzle breaking or other non-continuous liquid feeding devices.

[0014] In the above preparation method, the molar ratio of AHF to PCl3 in the spiral tube microreactor is 1:3 to 10. The theoretical molar ratio of AHF to PCl3 is 3:1, but under the condition of less excess PCl3, the dissolution amount of the components with high vapor pressure, such as HCl and PF3, in the product is reduced, which causes part of the gas phase product to separate from the liquid phase, damages the fluid structure in the microreactor, and thus reduces the mixing reaction efficiency.

[0015] In the preparation method, the feeding 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, so that the molar ratio of AHF to PCl3 in the spiral tube microreactor is in the range of 1:3-10.

[0016] In the preparation method, the residence time of the reaction is controlled in the range of 3-10 min by controlling the delivery flow rates of the AHF liquid and the PCl3 liquid and the length of the spiral tube microreactor, so as to ensure sufficient reaction and avoid the generation of by-products caused by too long residence time. For example, the delivery flow rate of the AHF liquid can be controlled in the range of 60-100 ml / min, the delivery flow rate of the PCl3 liquid can be controlled in the range of 130-4500 ml / min, the channel diameter of the spiral tube microreactor is controlled in the range of 6-25 mm, and the length of the spiral tube microreactor is controlled in the range of 5-100 m. The stable residence time control is helpful to improve the purity and yield of the product.

[0017] In the preparation method, the reduced pressure gas-liquid separation refers to reducing the pressure to 0.5-1 MPa, so as to quickly separate the PF3 and HCl gas and take away the heat generated in the reaction. This design not only stabilizes the system temperature, but also reduces the additional cooling requirement and the energy consumption. The low-temperature liquid material (mainly the excess unreacted PCl3 liquid and a small amount of low-substituted product) after separation is re-entered into the spiral tube microreactor to participate in the reaction until it leaves in the form of PF3 gas. This energy recycling and utilization design further reduces the energy consumption of the system, improves the raw material utilization rate, reduces waste, and reduces the production cost.

[0018] In the preparation method, the separation and purification step is that the gas phase component is pressurized to 3.5-4.2 MPa and cooled to -30--2℃, so as to liquefy and rectify and separate the PF3.

[0019] A device for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics, comprising a mixer, a spiral tube microreactor and a gas-liquid separation tank connected in sequence; the mixer is a Y-type mixer, one feeding port of the Y-type mixer is connected with a phosphorus trichloride (PCl3) storage tank through a pipeline, the other feeding port is provided with a pressure oscillation nozzle connected with an anhydrous hydrofluoric acid (AHF) storage tank through a pipeline, and the outlet 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 through a circulating pump and a pipeline.

[0020] According to the present application, the Y-type mixer is arranged, and the pressure oscillation nozzle is arranged at the feeding port connected with the AHF storage tank, so that the AHF feeding can be broken into spherical droplets by pressure oscillation and well dispersed and mixed with PCl3.

[0021] Further, a metering pump is arranged 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. The metering pump can be used to control the feeding ratio of AHF and PCl3.

[0022] Further, the channel diameter of the spiral pipe micro-reactor is 6-25 mm, and the length is 5-100 m. The spiral pipe micro-reactor is a commonly used reaction device in the art, which has a structure of a spiral fluid pipeline. The fluid flows forward in the process, which not only realizes a plug flow and ensures the uniformity of the reaction in space, but also can strengthen the mixing and heat exchange to a certain extent. The size of the spiral pipe micro-reactor can be adjusted according to actual production requirements.

[0023] Further, the spiral pipe micro-reactor is internally connected to a back pressure system. The back pressure system can be used to conveniently control the reaction pressure in the spiral pipe micro-reactor.

[0024] Further, the spiral pipe micro-reactor is externally provided with a heating jacket. The heating jacket can be used to conveniently control the reaction temperature in the spiral pipe micro-reactor.

[0025] Further, the gas phase material outlet of the gas-liquid separation tank is further connected to a compression cooling device and a rectification separation device.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] (1) Efficient mass transfer and reaction: the present application can significantly improve the mixing reaction effect of the reaction raw materials by carrying out the reaction under high pressure (1.0-2.5 MPa), using excess PCl3 liquid material as the reaction raw material and reaction medium, and mixing the AHF raw material in the form of spherical droplets, while avoiding the damage of the gas phase product to the fluid structure, effectively improving the mass transfer effect and reaction efficiency.

[0028] (2) Improved safety: the AHF spherical small droplets are uniformly dispersed in the liquid phase PCl3 for mixing reaction by high-pressure liquefaction and pressure shock crushing, which significantly reduces the direct contact of the strong corrosive gas (such as HF and HCl) with the equipment, thereby reducing the corrosion risk of the equipment, prolonging the service life of the equipment and improving the operation safety.

[0029] (3) Energy coupling and energy saving: After the reaction, the mixture is separated by a gas-liquid separation tank to quickly separate PF3 and HCl gas, and at the same time, the heat generated in the reaction is taken away. This design not only stabilizes the system temperature, but also reduces the additional cooling requirement and reduces the energy consumption. The low-temperature liquid material after separation reenters the spiral tube microreactor to participate in the reaction, further reducing the energy consumption of the system. This energy recovery and recycling design significantly improves the energy utilization efficiency and reduces the production cost.

[0030] (4) Material circulation and resource utilization: Excess unreacted PCl3 liquid material and low-substitution material reenter the spiral tube microreactor at a lower temperature to participate in the reaction until it leaves in the form of PF3 gas. This design improves the utilization rate of raw materials, reduces waste, and reduces production costs. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Figure 1 is a schematic diagram of the connection relationship of a device for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present application are not limited thereto.

[0033] Example 1

[0034] A device for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics, the connection relationship schematic diagram is shown in Figure 1 Figure 1. It includes a mixer 6, a spiral tube microreactor 7, a gas-liquid separation tank 8, and a back pressure system 9 connected in turn. The mixer 6 is a Y-type mixer, one of the feed ports of the Y-type mixer is connected with a phosphorus trichloride (PCl3) storage tank 1 through a pipeline, and the other feed port is provided with a pressure oscillation nozzle 5 connected with an anhydrous hydrofluoric acid (AHF) storage tank 2 through a pipeline. A metering pump 4 is arranged on the pipeline connecting the PCl3 storage tank 1 with the mixer 6, and a metering pump 3 is arranged on the pipeline connecting the AHF storage tank 2 with the mixer 6. The outlet of the Y-type mixer is connected to the spiral tube microreactor 7, the channel diameter of the spiral tube microreactor is 20 mm, the length is 25 m, and a heating jacket is arranged outside the spiral tube microreactor. The liquid material outlet of the gas-liquid separation tank 8 is connected to the spiral tube microreactor 7 through a circulating pump 10 and a pipeline; and the gas phase material outlet of the gas-liquid separation tank 8 is connected to a compressor 11, a cryogenic cooler 12, and a rectifying tower 13 in turn.

[0035] A method for continuously preparing phosphorus trifluoride based on liquid-liquid microfluidics, comprising the following preparation steps:

[0036] (1) Pressure regulation: The pressure value in the spiral tube microreactor 7 is increased to 2 MPa by introducing nitrogen through the back pressure system 9.

[0037] (2) Temperature control: The temperature in the spiral tube microreactor 7 was raised to 80°C by heating the jacket.

[0038] (3) Feeding and reaction: PCl3 liquid in the PCl3 tank 1 was fed into the mixer 6 through one feeding port of the Y-type mixer; at the same time, AHF liquid in the AHF tank 2 was fed into the pressure oscillation nozzle 5 to break to generate 0.5±0.1 μm-sized AHF spherical droplets into the mixer 6, and the PCl3 liquid and the AHF spherical droplets were axially mixed in the mixer 6, and the feeding molar ratio of AHF to PCl3 was controlled to be 1:6 by the metering pumps 3 and 4 into the spiral tube microreactor to form a circular flow for reaction, and the reaction residence time was controlled to be 3 min by the material feeding flow rate.

[0039] (4) Separation: The material at the outlet of the spiral tube microreactor 7 was depressurized to 0.5 MPa by the pressure reducing valve and entered 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) were compressed to 4.0 MPa by the compressor 11, then cooled to -15°C by the deep cooler 12 to be liquefied, and then entered the rectification column 13 for rectification separation to obtain phosphorus trifluoride. The remaining liquid material in the gas-liquid separation tank 8 was at a temperature of 50°C, and was fed into the spiral tube microreactor 7 by the circulating pump 10 as the PCl3 liquid feeding material to participate in the reaction.

[0040] In this embodiment, the outlet of the spiral tube microreactor 7 was sampled by cooling, and the conversion rate of the target product PF3 reached 99.87% (actual amount of substance of PF3 generated in the reaction / theoretical amount of substance of PF3 generated in the reaction, PF3 / PClF2 / PCl2F were detected by GC-MS, and a weak polarity chromatographic column (such as DB-5MS) was used for separation), and the by-product generation rate was: PCl2F 0.02% (actual amount of substance of PClF2 generated in the reaction / theoretical amount of substance of PF3 generated in the reaction), PClF2 0.01% (actual amount of substance of PCl2F generated in the reaction / theoretical amount of substance of PF3 generated in the reaction).

[0041] Examples 2-8

[0042] Examples 2-8 and Example 1 were compared, and the reaction pressure and reaction temperature were controlled as shown in Table 1, respectively. The target product conversion rate and by-product generation rate under different pressure and temperature conditions are shown in Table 1.

[0043] Table 1: Target product conversion rate and by-product generation rate under different pressure and temperature conditions

[0044] Test Example Reaction pressure Reaction temperature PF3 conversion PCl2F formation rate PClF2 generation rate Example 2 1.0 MPa 80℃ 99.70% 0.07% 0.03% Example 3 1.5 MPa 60℃ 99.84% 0.05% 0.01% Example 4 1.8 MPa 70℃ 99.85% 0.04% 0.01% Example 5 2.2 MPa 100℃ 99.86% 0.02% 0.02% Example 6 2.4 MPa 120℃ 99.85% 0.02% 0.03% Example 7 2.5 MPa 130℃ 99.84% 0.02% 0.04% Example 8 2.0 MPa 140℃ 99.71% 0.02% 0.06%

[0045] From the results of Table 1 and Example 1, it can be concluded that appropriate increase of the reaction temperature and the reaction pressure is beneficial to the increase of the conversion rate of PF3, but too low reaction pressure and too high reaction temperature will result in the decrease of the conversion rate of PF3, because too low pressure or too high temperature will result in the incomplete dissolution of the reaction gas phase components in the liquid phase, thus reducing the mass transfer reaction efficiency. The conversion rate of PF3 can be further increased under the conditions of the reaction pressure of 1.5 MPa to 2.5 MPa and the reaction temperature of 60 to 130℃.

[0046] Examples 9-14

[0047] Examples 9-14 are the same as Example 1, except that the residence time of the spiral tube microreactor is controlled to be 0.5 min, 1 min, 5 min, 8 min, 10 min and 12 min, respectively, by controlling the material delivery flow rate.

[0048] The results of the conversion rate of the target product and the generation rate of the byproduct under the conditions of different reaction times in Examples 9-14 are shown in Table 2.

[0049] Table 2 Results of the conversion rate of the target product and the generation rate of the byproduct under the conditions of different reaction times

[0050] Test Example Reaction time PF3 conversion PCl2F formation rate PClF2 generation rate Example 9 0.5 min 99.51% 0.15% 0.04% Example 10 1 min 99.57% 0.10% 0.01% Example 11 5 min 99.88% 0.02% Not detected Example 12 8 min 99.89% 0.01% Not detected Example 13 10 min 99.89% 0.01% Not detected Example 14 12 min 99.81% 0.09% Not detected

[0051] From the results of Table 2 and Example 1, it can be concluded that the conversion rate of PF3 can be further increased by controlling the residence time of the spiral tube microreactor to be in the range of 3 to 10 min.

[0052] Examples 15-20

[0053] Examples 15-20 are the same as Example 1, except that the molar ratio of AHF to PCl3 is adjusted to be 1:1, 1:3, 1:5, 1:7, 1:10 and 1:12, respectively.

[0054] The results of the conversion rate of the target product and the generation rate of the byproduct under the conditions of different molar ratios of AHF to PCl3 in Examples 15-20 are shown in Table 3.

[0055] Table 3 Results of the conversion rate of the target product and the generation rate of the byproduct under the conditions of different molar ratios of AHF to PCl3

[0056] Test Example [HF:PC13] PF3 conversion PCl2F formation rate PClF2 generation 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%

[0057] From the results of Table 3, it can be concluded that when the amount of PCl3 feed is less excessive, the conversion rate of PF3 is significantly reduced. The reason is that there is a lack of a large amount of excess PCl3 as a dissolving medium, and the amount of dissolved components with high vapor pressure, such as HCl and PF3, in the product is reduced. Some HCl and PF3 in the product are separated from the liquid phase, which destroys the fluid structure in the microreactor, thereby reducing the mixing reaction efficiency. When the amount of PCl3 feed is too high, the generation rate of by-products increases, and the conversion rate of PF3 decreases. The present application can further improve the conversion rate of PF3 when the molar ratio of AHF to PCl3 feed is controlled to be 1:3-10.

[0058] Comparative Example 1

[0059] 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 pressure shock nozzle, and continuous liquid feed is directly used for axial mixing with PCl3 liquid in a mixer. The rest is the same.

[0060] It is tested that the conversion rate of the target product PF3 in the product at the outlet of the spiral tube microreactor of this comparative example is 97.60%, and the generation rates of by-products are PCl2F 0.34% and PClF2 0.15%.

[0061] From the results of this comparative example and Example 1, it can be concluded that the present application uses AHF in the form of spherical droplets for reaction, which can significantly improve the reaction efficiency and reduce the generation of by-products.

[0062] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples. Any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

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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