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

Abstract

The application belongs to the technical field of fluorinated material preparation, and particularly relates to a device and method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics. The device comprises a gas-liquid distributor, a spiral tube microreactor and a gas-liquid condensation separation tank connected in sequence. The gas-liquid distributor is a coaxial sleeve type gas-liquid distributor, the inner sleeve forms a central gas channel, and the annular liquid channel is formed between the outer sleeve and the inner sleeve. The preparation method is as follows: AHF gas is delivered to the central gas channel, and PCl3 liquid is delivered to the annular liquid channel at the same time. After the axial mixing of the AHF gas and the PCl3 liquid at the end of the gas-liquid distributor, the mixture enters the spiral tube microreactor to form a circular flow for reaction. The product after the reaction enters the gas-liquid condensation separation tank for cooling, separation and purification, and phosphorus trifluoride is obtained. The reaction device and method have the advantages of high efficiency, safety, environmental protection and economy.

Description

TECHNICAL FIELD

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

[0002] Phosphorus trifluoride (PF3) is an important inorganic compound, widely used in electronic industry, chemical synthesis and material science, etc. Currently, 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 them, 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. It can be carried out at a lower temperature, reducing 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 easily generates mono-substituted and di-substituted intermediates (such as PCl2F and PClF2), increasing the difficulty and cost of product purification. In addition, the reaction is highly 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 an excessive amount of HF, 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, the 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 the operating personnel and the environment, limiting its large-scale industrial application. It is usually considered to use a conventional tubular reactor / microchannel reactor to complete the fluorination reaction in a small dose, thereby reducing the safety risk of the reaction. The existing fluorination reactions using conventional tubular reactors / microchannel reactors directly mix the reactants phosphorus trichloride and anhydrous hydrogen fluoride in the reactor for reaction. Under the condition of high gas-liquid ratio, 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. SUMMARY

[0005] In view of the defects and shortcomings of the prior art, the purpose of the present application is to provide a device and method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics. The device and method of the present application realize efficient and safe preparation of phosphorus trifluoride, have the advantages of high heat and mass transfer efficiency, high safety, high reaction efficiency, high product purity, stable process flow, environmental protection and economy, and provide a new technical solution for the industrial production of phosphorus trifluoride.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A device for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, comprising a gas-liquid distributor, a spiral pipe microreactor and a gas-liquid condensation and separation tank connected in sequence; the gas-liquid distributor is a coaxial sleeve type gas-liquid distributor, the inner sleeve of the coaxial sleeve type gas-liquid distributor forms a central gas channel, the inlet of the central gas channel is connected with an AHF storage tank, the annular liquid channel is formed between the outer sleeve and the inner sleeve of the coaxial sleeve type gas-liquid distributor, the inlet of the annular liquid channel is connected with a PCl3 storage tank, and the outlet of the central gas channel is communicated with the outlet of the annular liquid channel and then connected to the spiral pipe microreactor; the material outlet of the spiral pipe microreactor is connected to the gas-liquid condensation and separation tank.

[0008] Further, the diameter of the central gas channel of the gas-liquid distributor is 0.2-0.5 mm for injecting AHF gas, and the width of the annular liquid channel is 50-100 μm for injecting PCl3 liquid.

[0009] Further, a tapered expansion is provided at the outlet of the central gas channel, and the expansion angle is 5°-10°. By providing the tapered expansion, the initial liquid movement form of PCl3 raw material entering the spiral pipe microreactor can be better formed into a circular flow on the pipe wall.

[0010] Further, the spiral pipe microreactor is a spiral groove pipe (a commonly used fluid pipe with spiral grooves on the inner and outer surfaces) arranged along the horizontal axis, the inner diameter of the spiral groove pipe is 3-6 mm, and the spiral groove pipe has a gradually increasing coil radius from front to back. By the guiding effect of the spiral grooves in the spiral groove pipe and the use of a large curvature pipe flow form with a gradually increasing coil radius, the liquid film on the pipe wall can be better maintained, the gas generated by the reaction promotes a higher gas-liquid ratio in the latter half of the reaction, and the liquid film rupture problem is overcome by reducing the centrifugal force through the expansion of the curvature, so that the liquid movement form of the PCl3 raw material can be stably formed into a circular flow on the pipe wall. The inner diameter of the spiral groove pipe of the spiral pipe microreactor of the present application can be adjusted and optimized according to the actual production scale.

[0011] Further, the spiral tube micro-reactor is externally provided with an oil bath heating system. The spiral tube micro-reactor is immersed in the heat exchange medium by the oil bath heating system, so that the temperature in the spiral tube micro-reactor can be controlled and adjusted. The temperature in the spiral tube micro-reactor can be monitored and determined by a three-way valve and a temperature probe at the center of the three-way valve.

[0012] Further, the gas-liquid condensation separation tank is connected with a back pressure system, which is used to stabilize the pressure of the whole device.

[0013] Further, the gas-liquid condensation separation tank is an inner coil type gas-liquid condensation separation tank, and the inner coil is filled with a cooling medium. The inner coil type gas-liquid condensation separation tank can quickly cool the reaction material, so that the low-substituted material in the reaction product is condensed, and the gas phase is separated and purified in the purification unit.

[0014] A method for continuously preparing phosphorus trifluoride based on the device comprises the following preparation steps:

[0015] AHF gas is delivered to the central gas channel of the gas-liquid distributor through the AHF storage tank, and PCl3 liquid in the PCl3 storage tank is delivered to the annular liquid channel of the gas-liquid distributor. The AHF gas and the PCl3 liquid are mixed axially at the end of the gas-liquid distributor and then enter the spiral tube micro-reactor. The reaction is carried out under the condition of a pressure of 0.4 MPa to 1.2 MPa and a temperature of 90 to 160℃ to form a circular flow. The reaction product is cooled and cooled in the gas-liquid condensation separation tank, separated and purified, and phosphorus trifluoride is obtained.

[0016] In the above preparation method, the back pressure value of the whole device can be increased to 0.4 MPa to 1.2 MPa by introducing nitrogen gas through the back pressure system, so that the reaction process of the spiral tube micro-reactor can be carried out under high pressure conditions, and the reaction efficiency can be improved.

[0017] In the above preparation method, the AHF gas can be delivered by the AHF storage tank at a pressure higher than the back pressure value of the device by 0.3 to 0.5 MPa, and the AHF can be maintained in the gas phase by heating, so that the AHF can smoothly enter the central gas channel of the gas-liquid distributor.

[0018] In the preparation method, the molar ratio of the axial mixing of the AHF gas and the PCl3 liquid at the end of the gas-liquid distributor is controlled to be 3-3.2:1 by controlling the delivery flow rate of the AHF gas and the PCl3 liquid. For example, the feeding delivery volume flow rate of the AHF gas is controlled to be 20-100 L / min, and the feeding delivery volume flow rate of the PCl3 liquid is controlled to be 10-100 ml / min. The theoretical molar ratio of the reaction of the AHF and the PCl3 to generate the PF3 is 3:1, and the addition of a slight excess of the AHF is beneficial to the complete substitution of the PCl3 to generate the PF3, reduces the generation of the mono-substituted and di-substituted intermediate impurities, and improves the conversion rate and purity of the target product.

[0019] In the preparation method, the residence time of the reaction is controlled to be 1-10 min by controlling the delivery flow rate of the AHF gas and the PCl3 liquid and the length of the spiral pipe microreactor, so as to ensure the sufficient reaction and avoid the poor mixing reaction effect and the generation of by-products caused by the excessively long residence time.

[0020] In the preparation method, the temperature of the spiral pipe microreactor can be raised to 90-160℃ by the oil bath heating system, the substitution reaction of the PCl3 and the AHF can be promoted at high temperature, and the conversion rate of the target product PF3 is improved. Since the reaction of the PCl3 and the AHF is exothermic, the reaction heat can be better utilized and the reaction temperature can be better controlled at high temperature, and the reaction stability is improved. However, the PCl3 liquid film is damaged due to the high temperature, and thus the mixing reaction effect of the gas-liquid contact surface is reduced.

[0021] In the preparation method, the material after the reaction is rapidly cooled to-20--5℃ in the gas-liquid condensation separation tank, which is beneficial to the stability of the product and the subsequent separation and purification treatment.

[0022] In the preparation method, the separation and purification step is that the gas phase component of the outlet of the gas-liquid condensation separation tank is pressurized to 4-5 MPa and cooled to-20--5℃ to liquefy and rectify the PF3, so as to obtain the phosphorus trifluoride.

[0023] The principle of the present application is that by using a coaxial sleeve type gas-liquid distributor with a specific design, the gas-liquid contact mode of the reactant mixture can be controlled to be gas passing through the central gas channel and liquid passing through the annular liquid channel to flow in a layered manner along the pipe wall. The two materials enter the spiral pipe microreactor for reaction, and the PF3 / HCl gas generated during the reaction returns to the gas phase space in the middle of the pipe, which does not affect the nearly layered flow of the liquid, avoiding the problem of gas slug flow in conventional tubular reactors after gas generation, and the problem of uneven average residence time. The spiral pipe microreactor can further use a spiral grooved pipe arranged along the horizontal axis, and the spiral grooved pipe has a gradually expanding spiral groove radius from front to back. Through the guiding effect of the spiral groove in the spiral grooved pipe and the large curvature pipe flow form with gradually expanding spiral groove radius, the liquid film formed on the pipe wall can be better maintained, the gas generated by the reaction promotes a higher gas-liquid ratio in the latter half of the reaction, and the expansion of the curvature reduces the centrifugal force to overcome the problem of liquid film rupture, thereby enabling the liquid motion form of the PCl3 raw material to form a circular flow on the pipe wall. This design not only improves the mass transfer efficiency, but also enhances the heat transfer effect, which helps to accurately control the reaction temperature, thereby significantly improving the reaction efficiency. Compared with the prior art, the present application has the following advantages:

[0024] (1) By controlling the mixing form of AHF and PCl3, the present application enables the gas and liquid to be distributed in a layered manner, so that the gas-liquid contact mode of the reactant mixture during mixing is gas passing through the central gas channel and liquid passing through the annular liquid channel to flow in a layered manner along the pipe wall into the spiral pipe microreactor. The liquid adheres to the wall of the microreactor to form a thin film, which effectively reduces the direct contact and corrosion of the strongly corrosive gas (such as AHF) to the pipe. As the reaction proceeds, the liquid gradually changes to gas phase, and the content of AHF also decreases accordingly, further reducing the corrosion. On the other hand, during the reaction, the temperature directly acts on the liquid, and the reaction occurs at the gas-liquid contact surface. By liquid heat transfer, the temperature control of the reaction interface is more accurate, the heat transfer effect of the reaction is enhanced, and the problem of poor heat transfer in conventional gas-liquid reactions is avoided. As the temperature rises, the reaction accelerates, and the final product is completely converted to gas phase, further improving the reaction efficiency.

[0025] (2) By using the specific design of the gas-liquid distributor and the microfluidic technology of the spiral pipe microreactor, the gas and liquid can be quickly contacted on the surface of the liquid, high gas-liquid ratio reaction can be achieved, the problem of gas slug flow in conventional tubular reactors or microreactors can be avoided, the gas-liquid contact area can be significantly increased, and the mass transfer efficiency and reaction rate can be improved, and the reaction safety can be improved.

[0026] (3) The reaction device of the present application has a small reactor volume and a low reactant holdup, which can effectively reduce the safety risk in the reaction process and reduce the potential danger caused by local overheating or reaction runaway. At the same time, by reacting at a high temperature (90-160℃), the conversion of the target product PF3 can be promoted, and the heat released by the reaction of PCl3 and AHF can be better utilized, the temperature control is more stable, and the reaction stability is improved. By controlling the residence time of the reaction in the spiral tube microreactor to be 1-10 min, and reducing the temperature of the reaction liquid to-20--5℃ by gas-liquid condensation separation tank after the reaction is completed, the reaction liquid is rapidly cooled to ensure that the reaction is fully carried out, and the generation of by-products caused by too long high-temperature residence time is avoided. This precise residence time control helps to improve the reaction efficiency and product purity, and is beneficial to the stability of the product and subsequent separation and purification treatment.

[0027] (4) The preparation device and method of the present application can realize continuous operation, realize continuous and controllable material flow, greatly improve the production capacity, and avoid the risk of batch difference and product quality fluctuation. This efficient production method not only improves the resource utilization efficiency and ensures the stability of product quality, but also meets the development trend of modern green and sustainable manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a connection structure diagram of a device for continuously preparing phosphorus trifluoride based on gas-liquid microfluidic in the embodiments of the present application.

[0029] Figure 2 is a structure diagram of a spiral tube microreactor and an oil bath heating system. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in conjunction with the embodiments and drawings, but the embodiments of the present application are not limited thereto.

[0031] Example 1

[0032] A device for continuously preparing phosphorus trifluoride based on gas-liquid microfluidic, the connection structure diagram is as follows Figure 1As shown, it comprises a gas-liquid distributor 4, a spiral tube micro-reactor 5, a gas-liquid condensation separation tank 6 and a back pressure system 7 connected in turn; the gas-liquid distributor 4 is a coaxial sleeve type gas-liquid distributor, the inner sleeve forms a central gas channel 4-1 with a diameter of 0.4 mm, the inlet of the central gas channel 4-1 is connected with anhydrous hydrogen fluoride (AHF) storage tank 1, the annular liquid channel 4-2 with a width of 80 μm is formed between the outer sleeve and the inner sleeve, the inlet of the annular liquid channel 4-2 is connected with phosphorus trichloride (PCl3) storage tank 2 through a feed pump 3, a conical expansion 4-3 with an expansion angle of 8° is arranged at the outlet of the central gas channel 4-1, and the outlet of the central gas channel 4-1 is connected to the annular liquid channel 4-2 outlet and then connected to the spiral tube micro-reactor 5; the spiral tube micro-reactor 5 is a spiral groove pipe arranged along the horizontal axis, the inner diameter of the spiral groove pipe is 5 mm, and the spiral groove pipe winding radius gradually expands from front to back (the winding radius of the material outlet end is twice the winding radius of the material inlet end), and an oil bath heating system 5-1 (the structure diagram is shown in Figure 2 As shown) is arranged outside the spiral tube micro-reactor 5, the spiral tube micro-reactor 5 is immersed in the heat exchange medium (heat conducting oil) by the oil bath heating system 5-1, so that the temperature in the spiral tube micro-reactor 5 can be controlled and adjusted. The temperature in the spiral tube micro-reactor can be monitored and determined by a three-way central point temperature probe. The material outlet of the spiral tube micro-reactor 5 is connected to the inner coil type gas-liquid condensation separation tank 6, and the inside of the coil is a cooling medium. The gas-liquid condensation separation tank 6 is connected to the back pressure system 7, and the back pressure system 7 is used to stabilize the pressure of the whole device.

[0033] Based on the above device for continuously preparing phosphorus trifluoride, the method comprises the following preparation steps:

[0034] (1) Pressure regulation: the back pressure value of the whole device is stabilized to 0.5 MPa by introducing high-pressure nitrogen through the back pressure system 7.

[0035] (2) Temperature control: the temperature of the spiral tube micro-reactor 5 is increased to 120°C by the oil bath heating system 5-1, and at the same time, the temperature of the gas-liquid condensation separation tank 6 is reduced to -15°C by the cooling medium in the coil.

[0036] (3) feeding and reaction: AHF gas outlet of AHF tank 1 is depressurized to 0.8 MPa, and AHF is delivered to the central gas channel 4-1 of the gas-liquid distributor, with a feeding volume flow rate of 2 L / min; at the same time, PCl3 in PCl3 tank 2 is delivered to the annular liquid channel 4-2 of the gas-liquid distributor by the feeding pump 3, with a feeding volume flow rate of 30 ml / min. AHF gas and PCl3 liquid are mixed axially in the gas-liquid distributor 4 at a molar ratio of AHF:PCl3 of 3.2:1, and then enter the spiral tube microreactor 5, forming a circular flow movement of gas in the center and liquid along the pipe wall, and the reaction residence time is controlled to be 3 min. The reaction product enters the gas-liquid condensation separation tank 6 for cooling to-15℃, so as to condense the low-substituted product in the reaction product, and the gas phase is sent to the purification unit from the upper part of the gas-liquid condensation separation tank 6, and then is pressurized to 4 MPa and cooled to-15℃ to liquefy and rectify the PF3, so as to obtain phosphorus trifluoride.

[0037] In this embodiment, the target product PF3 conversion rate reaches 99.51% (amount of substance of PF3 generated in the reaction / amount of substance of PCl3 before the reaction, which is calculated from the PCl3 / PClF2 / / PCl2F components in the sampling detection, and the PCl3 / PClF2 / / PCl2F is detected by GC-MS, and a weak polarity chromatographic column (such as DB-5MS) is used for separation), unreacted PCl3 is 0.30% (amount of substance of residual PCl3 after the reaction / amount of substance of PCl3 before the reaction), and the by-product generation rate is: PCl2F 0.10% (amount of substance of PCl2F generated in the reaction / amount of substance of PCl3 before the reaction), and PClF2 0.09% (amount of substance of PClF2 generated in the reaction / amount of substance of PCl3 before the reaction).

[0038] Examples 2-6

[0039] Examples 2-6 are compared with Example 1, and the entire device is stabilized to 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, and 1.2 MPa by the back pressure system respectively, and AHF is delivered to the central gas channel of the gas-liquid distributor at a pressure of 0.3 MPa higher than the device back pressure value, and the rest is the same as Example 1.

[0040] The target product conversion rate and by-product generation rate under different reaction pressure conditions of Examples 2-6 are shown in Table 1.

[0041] Table 1 target product conversion rate and by-product generation rate under different reaction pressure conditions

[0042] Test Example Reaction Pressure PF3 conversion unreacted PCl3 PCl2F formation rate PClF2 generation rate Example 2 0.4 MPa 99.48% 0.30% 0.20% 0.02% Example 3 0.6 MPa 99.53% 0.30% 0.10% 0.07% Example 4 0.8 MPa 99.60% 0.25% 0.15% Not detected Example 5 1.0 MPa 99.65% 0.25% 0.10% Not detected Example 6 1.2 MPa 99.62% 0.28% 0.10% Not detected

[0043] As can be seen from the results in Table 1, with the increase of the reaction pressure, the PF3 conversion rate shows a trend of first increasing and then decreasing, which indicates that appropriate pressure helps to promote the conversion of PF3, while too high pressure can cause the liquid film in the spiral tube microreactor to be destroyed, reducing the mixing reaction effect of the gas-liquid contact surface, thus resulting in the decrease of the PF3 conversion rate; in addition, too high pressure can increase the reaction energy consumption and increase the requirements on the reaction equipment.

[0044] Examples 7-11

[0045] Examples 7-11 are the same as Example 1 except that the temperature of the spiral tube microreactor is controlled at 90℃, 100℃, 130℃, 150℃ and 160℃ respectively.

[0046] The target product conversion rate and byproduct generation rate results under different reaction temperature conditions in this example are shown in Table 2.

[0047] Table 2 Target product conversion rate and byproduct generation rate results under different reaction temperature conditions

[0048] Test Example Reaction Temperature PF3 conversion unreacted PCl3 PCl2F formation rate PClF2 generation rate Example 7 90℃ 99.47% 0.40% 0.10% 0.03% Example 8 100℃ 99.48% 0.30% 0.15% 0.07% Example 9 130℃ 99.57% 0.20% 0.20% 0.03% Example 10 150℃ 99.65% 0.18% 0.15% 0.02% Example 11 160℃ 99.51% 0.36% 0.12% 0.01%

[0049] As can be seen from the results in Table 2, with the increase of the reaction temperature, the PF3 conversion rate shows a trend of first increasing and then decreasing, which indicates that appropriate high temperature helps to promote the conversion of PF3, while too high temperature can cause the PCl3 liquid film to be destroyed, thus reducing the mixing reaction effect of the gas-liquid contact surface, thus resulting in the decrease of the PF3 conversion rate; in addition, too high temperature can increase the reaction energy consumption.

[0050] Examples 12-17

[0051] Examples 12-17 are the same as Example 1 except that the reaction residence time of the spiral tube microreactor is controlled at 0.5min, 1min, 5min, 8min, 10min and 12min respectively.

[0052] The target product conversion rate and byproduct generation rate results under different reaction time conditions in this example are shown in Table 3.

[0053] Table 3 Target product conversion rate and byproduct generation rate results under different reaction time conditions

[0054] Test Example Reaction Time PF3 conversion unreacted PCl3 PCl2F formation rate PClF2 generation rate Example 12 0.5 min 99.10% 0.50% 0.20% 0.20% Example 13 1 min 99.30% 0.45% 0.20% 0.05% Example 14 5 min 99.54% 0.30% 0.10% 0.06% Example 15 8 min 99.61% 0.30% 0.09% Not detected Example 16 10 min 99.67% 0.20% 0.13% Not detected Example 17 12 min 99.64% 0.30% 0.06% Not detected

[0055] As can be seen from the results in Table 3, with the increase of the reaction time, the conversion rate of PF3 presents a trend of first increasing and then decreasing. If the reaction time is too short, the reaction is insufficient, and if the reaction time is too long, the liquid flowability and mixing effect are poor, resulting in the decrease of the conversion rate of PF3. Under the condition that the reaction time is 1-10 min, the comprehensive reaction efficiency is good.

[0056] Example 18

[0057] A method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, compared with Example 1, the molar ratio of AHF:PCl3 is adjusted to 3.1:1, and the rest is the same.

[0058] After testing, the conversion rate of the target product PF3 in the product at the outlet of the spiral tube microreactor of this example was 99.50%, unreacted PCl3 was 0.30%, and the byproduct generation rate was: PCl2F 0.11%, PClF2 0.09%.

[0059] Example 19

[0060] A method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, compared with Example 1, the molar ratio of AHF:PCl3 is adjusted to 3.0:1, and the rest is the same.

[0061] After testing, the conversion rate of the target product PF3 in the product at the outlet of the spiral tube microreactor of this example was 99.45%, unreacted PCl3 was 0.32%, and the byproduct generation rate was: PCl2F 0.18%, PClF2 0.05%.

[0062] Example 20

[0063] A method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, compared with Example 1, the spiral groove pipe of the spiral tube microreactor is not wound in a step-by-step expanding manner from front to back (the winding radius from the material inlet end to the material outlet end is fixed and unchanged), and the rest is the same.

[0064] After testing, the conversion rate of the target product PF3 in the product at the outlet of the spiral tube microreactor of this example was 99.21%, unreacted PCl3 was 0.43%, and the byproduct generation rate was: PCl2F 0.28%, PClF2 0.08%.

[0065] From the comparison results of Example 1, it can be seen that the spiral tube microreactor of the application adopts the setting mode of gradually expanding the coiled radius, which can further improve the conversion rate of PF3. The reason is that the flow form of large curvature pipeline with gradually expanding coiled radius can better maintain the liquid film on the pipeline wall, the gas produced by the reaction promotes the higher gas-liquid ratio in the latter half of the reaction, and the centrifugal force is reduced by expanding the curvature to overcome the problem of liquid film rupture, so that the liquid movement form of annular flow of PCl3 raw material on the pipeline wall can be stabilized, and the mixing reaction effect of the gas-liquid contact surface in the reactor can be significantly improved.

[0066] Comparative Example 1

[0067] A method for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, compared with Example 1, cancels the coaxial sleeve type gas-liquid distributor, and directly introduces AHF gas and PCl3 liquid into the spiral tube microreactor for mixing, and carries out the reaction under the same material ratio and pressure, temperature, and time process conditions.

[0068] It is tested that the conversion rate of target product PF3 in the product at the outlet of the microchannel reactor of the present comparative example is 98.50%, the unreacted PCl3 is 1.00%, and the byproduct generation rate is: PCl2F 0.43%, PClF2 0.07%.

[0069] From the results of the present comparative example, it can be seen that the spiral tube microreactor of the application with the specifically designed gas-liquid distributor can significantly improve the efficiency of the reaction of AHF and PCl3 to synthesize PF3.

[0070] The above examples are the preferred embodiments of the application, but the embodiments of the application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application should be equivalent replacement methods, and are all included in the protection scope of the application.

Claims

1. A device for continuously preparing phosphorus trifluoride based on gas-liquid microfluidics, characterized in that: It comprises a gas-liquid distributor, a spiral tube microreactor and a gas-liquid condensation separation tank which are connected in sequence; the gas-liquid distributor is a coaxial sleeve gas-liquid distributor, the inner sleeve of the coaxial sleeve gas-liquid distributor forms a central gas channel, the inlet of the central gas channel is connected to the AHF storage tank, an annular gap liquid channel is formed between the outer sleeve and the inner sleeve of the coaxial sleeve gas-liquid distributor, the inlet of the annular gap liquid channel is connected to the PCl3 storage tank, the outlet of the central gas channel is connected to the outlet of the annular gap liquid channel and then connected to the spiral tube microreactor; the material outlet of the spiral tube microreactor is connected to the gas-liquid condensation separation tank; The diameter of the central gas channel of the gas-liquid distributor is 0.2-0.5 mm, which is used to inject AHF gas, and the width of the annular liquid channel is 50-100 μm, which is used to inject PCl3 liquid; The spiral tube microreactor is a spiral corrugated tube coiled along a horizontal axis. The inner diameter of the spiral corrugated tube is 3-6 mm, and the coiling radius of the spiral corrugated tube gradually increases from front to back.

2. The device for continuous preparation of phosphorus trifluoride based on gas-liquid microfluidics according to claim 1, characterized in that: A conical expansion is provided at the outlet of the central gas channel, and the expansion angle is 5° to 10°.

3. The device for continuous preparation of phosphorus trifluoride based on gas-liquid microfluidics according to claim 1, characterized in that: An oil bath heating system is arranged outside the spiral tube microreactor; the gas-liquid condensation separation tank is an inner coil type gas-liquid condensation separation tank, and the inside of the coil is a cooling medium; the gas-liquid condensation separation tank is connected to a back pressure system, and the back pressure system is used to stabilize the pressure of the entire device.

4. A method for continuously preparing phosphorus trifluoride using the apparatus according to any one of claims 1 to 3, characterized in that: The method comprises the following preparation steps: The AHF gas is transported to the central gas channel of the gas-liquid distributor through the AHF storage tank, and the PCl3 liquid in the PCl3 storage tank is transported to the annular liquid channel of the gas-liquid distributor. The AHF gas and PCl3 liquid are axially mixed at the end of the gas-liquid distributor and then enter the spiral tube microreactor. The pressure is controlled to be 0.4MPa~1.2MPa and the temperature is 90~160℃ to form an annular flow for reaction. The reaction product enters the gas-liquid condensation separation tank for cooling, separation and purification to obtain phosphorus trifluoride.

5. The method for continuously preparing phosphorus trifluoride according to claim 4, characterized in that: By controlling the delivery flow rates of AHF gas and PCl3 liquid, the molar ratio of the AHF gas and PCl3 liquid axially mixed at the end of the gas-liquid distributor is 3-3.2:

1.

6. The method for continuously preparing phosphorus trifluoride according to claim 5, characterized in that: The feed delivery volume flow rate of the AHF gas is 20-100 L / min, and the feed delivery volume flow rate of the PCl3 liquid is 10-100 ml / min.

7. The method for continuously preparing phosphorus trifluoride according to claim 5, characterized in that: By controlling the flow rates of AHF gas and PCl3 liquid and the length of the spiral tube microreactor, the residence time of the reaction was controlled between 1 and 10 min.

8. The method for continuously preparing phosphorus trifluoride according to claim 4, characterized in that: The separation and purification steps are as follows: pressurizing the outlet gas phase component of the gas-liquid condensation separation tank to 4-5 MPa and cooling it to -20--5°C to liquefy and separate the PF3 to obtain phosphorus trifluoride.

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