Method for preparing phosphorus oxyfluoride based on phosphorus pentoxide

Abstract

The invention provides a method for preparing phosphorus oxyfluoride based on phosphorus pentoxide, which comprises the following steps: S1, phosphorus pentoxide is dispersed in dichloromethane to be partially dissolved to form a turbid liquid, the dichloromethane comprises a molecular sieve for dehydration, and the content of the molecular sieve is greater than the theoretical dosage of the dichloromethane for dehydration; s2, an anhydrous hydrogen fluoride solution is introduced into the turbid liquid for a reaction, rapid stirring is conducted during the reaction, the reaction temperature is controlled to be 10-30 DEG C, the anhydrous hydrogen fluoride solution reacts with phosphorus pentoxide according to the mass ratio of 120: (270-280), and in other words, the excessive anhydrous hydrogen fluoride solution participates in the reaction; s3, filtering a product in the step S2 to obtain filtrate; s4, the filtrate is separated, and phosphorus oxyfluoride gas is obtained. According to the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided by the invention, the reaction is completed by adopting a one-step method, and compared with the prior art, the process is relatively simple and the production cost is low.

Description

Technical Field

[0001] This application relates to the field of phosphorus oxyfluoride preparation technology, and in particular to a method for preparing phosphorus oxyfluoride based on phosphorus pentoxide. Background Technology

[0002] Currently, phosphorus oxyfluoride (POF3) is a colorless gas with a pungent odor under normal conditions, producing a slight fumes in the air. The preparation of POF3 mainly employs a two-step method: first, CaF2 reacts with anhydrous sulfurous acid to form CaF(SO3F), and then reacts with H3PO4 to generate the intermediate product POF3. However, this production method is complex and costly. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems by providing a method for preparing phosphorus oxyfluoride based on phosphorus pentoxide.

[0004] The technical solution of this application is implemented as follows: This invention provides a method for preparing phosphorus oxyfluoride based on phosphorus pentoxide, comprising the following steps: S1, phosphorus pentoxide is dispersed in dichloromethane and partially dissolved to form a suspension, wherein the dichloromethane includes a molecular sieve for dehydration, and the content of the molecular sieve is greater than the theoretical amount of dichloromethane used for dehydration. S2, anhydrous hydrogen fluoride solution is passed into the suspension for reaction, and the mixture is stirred rapidly during the reaction, while the reaction temperature is controlled at 10℃~30℃. The anhydrous hydrogen fluoride solution reacts with phosphorus pentoxide at a mass ratio of 120:270~280, that is, an excess of anhydrous hydrogen fluoride solution participates in the reaction. S3, filter the product from step S2 to obtain the filtrate; S4, the filtrate is separated to obtain phosphorus oxyfluoride gas.

[0005] The specific equation is as follows: P4O 10 + 6 HF --> 4 POF3 + 2 H2O.

[0006] As a further improvement, the theoretical amount of molecular sieve used for the dehydration of dichloromethane is defined as M1, the theoretical amount of water produced in step S2 and dehydrated using molecular sieve is defined as M2, and the content of the molecular sieve is M, wherein M≥M1+M2.

[0007] As a further improvement, 3*(M1+M2)≥M>≥1.5*(M1+M2).

[0008] As a further improvement, in step S1, the step of partially dissolving phosphorus pentoxide in dichloromethane to form a suspension specifically includes: S11, the molecular sieve is dispersed in the dichloromethane; S12, then phosphorus pentoxide and dichloromethane are dispersed evenly, wherein the concentration of phosphorus pentoxide in dichloromethane is 0.1~5 wt%.

[0009] As a further improvement, the molecular sieve is a 3A or 4A molecular sieve.

[0010] As a further improvement, in step S4, the step of separating the filtrate to obtain phosphorus oxyfluoride gas specifically includes: S41, the filtrate is vaporized and then passed into a CaF2 adsorption bed to remove HF gas; S42, then the adsorbed gas is passed into a distillation column, where phosphorus oxyfluoride gas is collected from the top of the column and dichloromethane is collected from the bottom. The collected dichloromethane is purified and returned to step S1 for reuse.

[0011] As a further improvement, step S41 further includes: After the CaF2 adsorption bed is saturated, it is regenerated with high-temperature nitrogen gas to generate anhydrous HF for recycling.

[0012] As a further improvement, in step S42, the step of passing the adsorbed gas into a distillation column, wherein phosphorus oxyfluoride gas is collected from the top of the distillation column and dichloromethane is collected from the bottom of the column, specifically includes: The distillation column is evacuated to 10~20 kPa and deeply cooled at -40℃~-50℃ at the top of the column, while the bottom of the column is gently heated at 10~15℃, with the reflux ratio R controlled at 6~8.

[0013] As a further improvement, the concentration of phosphorus pentoxide in dichloromethane is 1-4 wt%.

[0014] As a further improvement, 2.5*(M1+M2)≥M>≥2*(M1+M2).

[0015] The advantages or beneficial effects of the above technical solutions include at least the following: The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided by this invention employs a one-step reaction, which is simpler and has lower production costs compared to existing technologies. Furthermore, by adding a molecular sieve for dehydration to the dichloromethane, with the molecular sieve content exceeding the theoretical amount required for dehydration, this invention significantly reduces side reactions caused by moisture and improves the reaction yield. Finally, by using an excess of anhydrous hydrogen fluoride solution in the reaction, this invention ensures complete reaction of phosphorus pentoxide in the solution, preventing excess phosphorus pentoxide from clogging the molecular sieve and improving its absorption efficiency. Attached Figure Description

[0016] The accompanying drawings illustrate exemplary embodiments of the present application and, together with the description thereof, serve to explain the principles of the present application. These drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification.

[0017] Figure 1 This diagram illustrates the overall architecture of the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in an embodiment of the present invention.

[0018] Figure 2 The diagram shows the structure of the automatic weighing and mixing unit used in the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in the embodiment of the present invention.

[0019] Figure 3 The diagram shows a schematic of the reaction unit used in the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in the embodiments of the present invention.

[0020] Figure 4 A schematic diagram of the candle filter used in the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in the embodiments of the present invention is shown.

[0021] Figure 5 This diagram illustrates the structure of the CaF2 adsorption bed used in the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in an embodiment of the present invention.

[0022] Figure 6 A schematic diagram of the distillation column used in the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in the embodiments of the present invention is shown.

[0023] Figure 7 A flowchart of the method for preparing phosphorus oxyfluoride based on phosphorus pentoxide provided in an embodiment of the present invention is shown. Detailed Implementation

[0024] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0025] It should be noted that, where there is no conflict, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] The names of the messages or information exchanged between multiple devices in the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0027] Reference Figure 1-7 This invention provides a method for preparing phosphorus oxyfluoride based on phosphorus pentoxide, comprising the following steps: S1, phosphorus pentoxide is dispersed in dichloromethane and partially dissolved to form a suspension, wherein the dichloromethane includes a molecular sieve for dehydration, and the content of the molecular sieve is greater than the theoretical amount of dichloromethane used for dehydration. S2, anhydrous hydrogen fluoride solution is passed into the suspension for reaction, and the mixture is stirred rapidly during the reaction, while the reaction temperature is controlled at 10℃~30℃. The anhydrous hydrogen fluoride solution reacts with phosphorus pentoxide at a mass ratio of 120:270~280, that is, an excess of anhydrous hydrogen fluoride solution participates in the reaction. S3, filter the product from step S2 to obtain the filtrate; S4, the filtrate is separated to obtain phosphorus oxyfluoride gas.

[0028] As a further improvement, the theoretical amount of molecular sieve used for the dehydration of dichloromethane is defined as M1, the theoretical amount of water produced in step S2 and dehydrated using molecular sieve is defined as M2, and the content of the molecular sieve is M, wherein M≥M1+M2.

[0029] As a further improvement, preferably, 3*(M1+M2)≥M>≥1.5*(M1+M2). More preferably, 2.5*(M1+M2)≥M>≥2*(M1+M2). In several embodiments, the molecular sieve content M is 2.0*(M1+M2), 2.2*(M1+M2), 2.4*(M1+M2), 2.5*(M1+M2), 2.6*(M1+M2), 2.8*(M1+M2), and 3.0*(M1+M2). By optimizing the control of the amount of molecular sieve used, on the one hand, free water can be adsorbed in a timely manner, and the concentration of free water in the liquid can always be less than or equal to 100 ppm, and the generation of phosphate ester colloids is significantly reduced. Experiments have shown that when the amount of molecular sieve used is less than 1.5*(M1+M2), the concentration of free water can instantaneously exceed 500 ppm, causing phosphorus oxyfluoride hydrolysis. On the other hand, an appropriate amount of excess can keep the surface of the molecular sieve in a "low relative humidity" zone, greatly shortening the regeneration time and significantly reducing the annual amount of solid waste generated.

[0030] As a further improvement, in step S1, the step of partially dissolving phosphorus pentoxide in dichloromethane to form a suspension specifically includes: S11, the molecular sieve is dispersed in the dichloromethane; S12, then phosphorus pentoxide is evenly dispersed in dichloromethane, wherein the concentration of phosphorus pentoxide in dichloromethane is 0.1~5 wt%. Preferably, the concentration of phosphorus pentoxide in dichloromethane is 1~4 wt%. More preferably, the concentration of phosphorus pentoxide in dichloromethane is 3~3.5 wt%. In other embodiments, the concentrations of phosphorus pentoxide in dichloromethane are 0.5 wt%, 15 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5.5 wt%, respectively. Since phosphorus pentoxide has extremely low solubility in dichloromethane, the solubility should not be too high, otherwise it will easily cause a significant increase in the viscosity of the suspension, thereby clogging the pores of the molecular sieve; if the concentration is too low, the production capacity will decrease.

[0031] As a further improvement, the molecular sieve is a 3A or 4A molecular sieve, preferably a sphere with a diameter of 3 to 5.0 mm.

[0032] Please see also Figure 2-3 As shown, the execution in steps S1-S3 is achieved through an automated reaction device. Specifically, the automated reaction device includes: Automatic weighing and mixing unit 10; and Reaction unit 20.

[0033] The automatic weighing and mixing unit 10 includes: A phosphorus pentoxide storage bin 11 has a first discharge port 110 at its bottom; The automatic weighing chamber 12 is connected to the first discharge port 110 at its top. The automatic weighing chamber 12 includes a chamber body 120, a material height sensor 121 disposed at the top of the chamber body 120, an air inlet 125 disposed at the chamber body 120, vibrators 122 disposed on both sides of the chamber body 120, a dichloromethane inlet pipe 123 connected to the chamber body 120, and a second discharge port 124 disposed at the bottom of the chamber body 120. The second discharge port 124 is connected to the first inlet 23 at the top of the reaction unit 20.

[0034] The reaction unit 20 includes a reaction tank 21, a stirring device 24 disposed in the reaction tank 21, a hydrogen fluoride inlet 22 and a first inlet 23 disposed on the reaction tank 21, a first drain outlet 26 and a third outlet 25 disposed at the bottom of the reaction tank 21; and a filter screen 27 disposed in the middle of the reaction tank 21, wherein the filter screen 27 divides the reaction tank 21 into upper and lower reaction chambers, and a second drain outlet 28 communicating with the upper reaction chamber. The reaction unit 20 further includes a temperature control component, which includes a temperature sensor and a cooling jacket, which work together to control the temperature of the reaction tank 21. The capacity of the lower reaction chamber should not be too large. The volume of the lower reaction chamber is defined as V1, and the total volume of the reactants is V2. Preferably, V2 > V1. This ensures that when all the reactants are added, the reactants in the upper and lower chambers form a whole. More preferably, 5*V1 ≥ V2 ≥ 3*V1. That is, the total volume of the reactants is 3 to 5 times the volume of the lower reaction chamber.

[0035] The stirring device 24 includes two sets of stirring blades disposed in the upper and lower reaction chambers, specifically: The lower stirring blades are axial-flow lifting impellers with a blade angle of 30–45°, and their outer diameter is 0.55–0.65 times the inner diameter of the reaction vessel 21. The upper stirring blades are radial dispersing impellers with an outer diameter 0.45–0.55 times the inner diameter of the reaction chamber. A filter screen 27 is installed at the center of the upper and lower chamber partitions. The lifting impeller is directly opposite the mesh opening with its tip 5–10 mm from the mesh surface, allowing the reaction liquid in the lower chamber to continuously pass through the mesh and be lifted to the upper chamber, forming an internal rising and external falling circulation. Through the above-mentioned arrangement of the upper and lower stirring blades, on the one hand, the surface of the filter screen 27 is always subjected to axial scouring, reducing the probability of clogging by 70%; on the other hand, the concentration difference between the upper and lower chambers can be less than 2%, making the reaction more uniform and increasing the yield by 5–8%. In addition, it can also allow the water generated by the reaction liquid in the lower chamber to flow to the upper chamber in a timely manner and be absorbed by the molecular sieve, reducing the occurrence of side reactions.

[0036] As a further improvement, prior to step S11, the following is further included: S10, vaporized dichloromethane is introduced through the air inlet 125 to remove air and water vapor from the automatic weighing mixing unit 10 and the reaction unit 20.

[0037] In step S11, dispersing the molecular sieve in the dichloromethane can be achieved in a general closed container, which will not be described in detail here. After dispersion, the dichloromethane mixture containing the molecular sieve can be pumped into the automatic weighing chamber 12 through the dichloromethane inlet pipe 123 to mix with phosphorus pentoxide.

[0038] Specifically, step S12 includes: S120, the first discharge port 110 is opened for automatic feeding, and the height of the material (phosphorus pentoxide) is detected by the material height sensor 121. When the set height is reached, feeding is stopped. During this period, the vibrator 122 vibrates the silo body 120 to make the material height tend to be uniform. S121, then open the dichloromethane inlet pipe 123 and pump in the dichloromethane mixture containing molecular sieves to uniformly mix it with the weighed phosphorus pentoxide. The total volume of the dichloromethane mixture containing molecular sieves pumped in can be controlled by a flow meter. Since the solubility of phosphorus pentoxide in dichloromethane is limited, its content cannot be too high. Too high a content will make the solution viscous, which is not conducive to subsequent automated production. Preferably, the concentration of phosphorus pentoxide in dichloromethane is 1~5 wt%. In one embodiment, the concentration of phosphorus pentoxide in dichloromethane is about 2.5 wt%. Of course, too low a concentration will reduce production efficiency.

[0039] Preferably, a nozzle can be installed in the dichloromethane inlet pipe 123 to spray the dichloromethane mixture containing molecular sieves into the phosphorus pentoxide to achieve rapid mixing.

[0040] Step S2 specifically includes: S20, the dichloromethane mixture containing molecular sieves and phosphorus pentoxide, and the anhydrous hydrogen fluoride solution are simultaneously fed in stages through the first feed port 23 and the hydrogen fluoride feed port 22, respectively. Since the reaction vessel 21 is divided into upper and lower layers, after feeding, the phosphorus pentoxide particles are first isolated in the upper layer and react there first. Most of the molecular sieves are also separated on the filter screen 27, which facilitates subsequent separation. As the reaction proceeds, some of the raw materials pass through the reaction vessel 21 and continue to react in the lower layer until the reaction is complete.

[0041] The mesh diameter of the filter screen 27 is smaller than that of the molecular sieve. Preferably, the mesh diameter of the filter screen 27 is 0.1~2.5mm. The diameter of the filter screen 27 should not be too low, as it is easily clogged, while a large diameter may cause the molecular sieve to penetrate. In one embodiment, the mesh diameter of the filter screen 27 is approximately 2mm.

[0042] After the reaction is complete, the reacted material can be discharged through the third outlet 25 and enter the next filtration unit 30 for filtration. At this time, most of the unreacted solids and molecular sieves are trapped by the filter screen 27, thus greatly reducing the processing pressure of the subsequent filtration unit 30.

[0043] In other embodiments, after the reactants are discharged, dichloromethane can be further pumped through the dichloromethane inlet pipe 123 to clean the automatic weighing and mixing unit 10 and the reaction unit 20, and the molecular sieve can be discharged from the second drain port 28. This facilitates subsequent activation and reuse of the molecular sieve.

[0044] The model of the filter unit 30 is not limited and can be selected according to actual needs; no restriction is imposed here. In one embodiment, the filter unit 30 is a candle filter; its specific structure can be found in [reference needed]. Figure 4 As shown.

[0045] The candle filter includes: A tank 31 with an opening at the top, the tank 31 including a liquid inlet 310 and a liquid extraction pipe 312 disposed at the top of the tank 31; A cover 32 that mates with the top of the tank 31, an air compressor pipe 320 and a pressure sensor 38 are provided on the top of the cover 32, and the air compressor pipe 320 is connected to an air compressor; The candlestick 34, the top of which is connected to the liquid extraction pipe 312, preferably, in one embodiment, the outer layer of the candlestick 34 has a gradient pore size of 1–50 μm, and the inner layer has guide holes (Ø 1.5–2.5 mm, depth 2–4 mm, density 150–250 holes / 100cm). 2 The advantage of this setup is that it can create micro-nozzles during backflushing, increasing the shedding rate by more than 5%. Waste liquid tank 33 is connected to the bottom of tank body 31 via pneumatic valve 39; The liquid extraction pipe 37 and the nitrogen backflushing pipe 36 are connected to the liquid extraction pipe 312.

[0046] The filter element in the candlestick 34 can be made of PTFE or PVDF, with a filtration accuracy of 1–5 μm. The nitrogen backflushing pipe 36 has a nitrogen pulse backflushing function, with a backflushing pressure of 0.3~0.5 MPa, a filter cake shedding rate of ≥99%, and a mother liquor solid content of <0.1 wt%.

[0047] The canister 31, piping, and fasteners of the candle filter can be made of PVDF-lined + FRP reinforced or 316L fully lined PTFE. The sealing ring between the canister 31 and the cover 32 can be made of perfluoroelastomer rubber (FFKM), with an annual corrosion rate of <0.01 mm*a in environments containing HF and CH2Cl2. -1 .

[0048] As a further improvement, the lengths of the candlesticks 34 are different. Specifically, the length of the candlestick 34 located in the middle is greater than that of the other candlesticks 34, and it is adapted to the recess 314 in the middle of the container 31, thereby minimizing the residual liquid in the container 31.

[0049] The specific control of the candle filter is as follows: a) Filtration stage: The suspension passes through the candle rod from the outside to the inside at a flow rate ≤ 0.15 m / s. 3 *min -1 The pressure difference ΔP ≤ 0.08 MPa; this stage is implemented by opening the inlet 310 and the extraction pipe 37. b) Settling stage: Close the feed and compact the filter cake; This stage can be achieved by closing the liquid inlet 310 and opening the air compressor pipe 320 and the liquid extraction pipe 37. High pressure is introduced through the air compressor pipe 320 to discharge the remaining liquid in the tank 31 on the one hand, and to compact the filter cake on the other hand through high pressure. c) Pulse backflushing: Nitrogen gas is released instantaneously from the clean side to the inside, with a peak pressure of 0.4–0.5 MPa and a filter cake shedding rate of ≥99%. This stage is achieved by opening the nitrogen backflushing pipe 36 and the waste liquid tank 33. d) Solvent washing: Wash with recycled dichloromethane for 2 min to recover the POF3 adsorbed on the filter cake, and return the washing liquid to reaction unit 20.

[0050] The control system of the candle filter starts backflushing in a dual mode of differential pressure + time: when ΔP ≥ 0.08 MPa or the running time reaches the set value, the PLC automatically triggers a four-step sequence; the valve action time error throughout the process is ≤ 0.1s, ensuring complete filter cake detachment and nitrogen consumption ≤ 0.8 m³. 3 *Second-rate -1 .

[0051] As a further improvement, in step S4, the step of separating the filtrate to obtain phosphorus oxyfluoride gas specifically includes: S41, the filtrate is vaporized and then passed into a CaF2 adsorption bed to remove HF gas; S42, then the adsorbed gas is passed into a distillation column, where phosphorus oxyfluoride gas is collected from the top of the column and dichloromethane is collected from the bottom. The collected dichloromethane is purified and returned to step S1 for reuse.

[0052] As a further improvement, step S41 further includes: After the CaF2 adsorption bed is saturated, it is regenerated with high-temperature nitrogen gas to generate anhydrous HF for recycling.

[0053] As a further improvement, in step S42, the step of passing the adsorbed gas into a distillation column, wherein phosphorus oxyfluoride gas is collected from the top of the distillation column and dichloromethane is collected from the bottom of the column, specifically includes: The distillation column is evacuated to 10~20 kPa and deeply cooled at -40℃~-50℃ at the top of the column, while the bottom of the column is gently heated at 10~15℃, with the reflux ratio R controlled at 6~8.

[0054] Step S4 is mainly achieved through the CaF2 adsorption bed 40 and the distillation column 50, as detailed below: Please see Figure 5 As shown, in one embodiment, the CaF2 adsorption bed 40 is an axially fixed bed with bed particles of 1-5 mm in diameter and 300-800 mm in height. The shell 41 is made of 316L stainless steel lined with 3 mm PTFE. Ø5 mm 316L stainless steel spheres are evenly distributed in the upper and lower sections of the axially fixed bed. The gas flow velocity in the bed is 0.1–0.3 m / s. -1 The adsorption temperature is 20~60℃, and the HF collected from the outlet 412 is ≤10 ppm.

[0055] Preferably, the axially fixed bed is composed of a dual particle size gradient: the lower layer 43 (facing the wind) consists of CaF2 spheres with a particle size of 4–5 mm, accounting for 40% of the thickness; the upper layer 44 consists of CaF2 spheres with a particle size of 1.5–2 mm, accounting for 60% of the thickness; the two layers are separated by a PTFE perforated plate 42 with a pore size of 3 mm and an open porosity of 30%. The advantage of this arrangement is that it reduces the overall pressure drop and increases the porosity of the large sphere layer.

[0056] The lower layer 43 and the upper layer 44 are respectively equipped with a first pressure sensor 46 and a second pressure sensor 45 corresponding to the air inlet 410 and air outlet 412. When the bed pressure difference is ≥5 kPa or the running time reaches the set value, the system switches to closed-loop nitrogen regeneration. The regeneration temperature is 280±10 ℃, and the regeneration time is 40~60 min. The desorbed HF is then... The cold trap is liquefied and recovered at 20 ℃ with a recovery rate of ≥95%. After regeneration, the bed is cooled to ≤60 ℃ and put back into use.

[0057] Electromagnetic heating coils (not shown in the figure) are arranged around the shell 41 of the axially fixed bed. They work in conjunction with 316L stainless steel balls to heat and regenerate the bed. This heating method can achieve uniform heating of the entire axially fixed bed without uneven heating. At this time, nitrogen can be introduced through the air inlet 410.

[0058] Preferably, as a further improvement, in order to increase the HF recovery rate, in other embodiments, a combination of programmed temperature rise and vacuum pulsation is used, specifically: Programmed temperature rise: The temperature is increased in three steps: 150℃, 250℃, and 280℃, with each step held for about 10 minutes. This results in a more concentrated desorption peak and a more uniform cold trap load.

[0059] Furthermore, vacuum pulsation is performed: a vacuum is drawn to 20 kPa (absolute pressure) at 280 °C, reducing the boiling point of HF from 19 °C to below -1 °C (approximately -8 °C), and increasing the desorption rate by at least 40%. Vacuuming can be achieved through a vacuum line 47 located at the top of the housing 41.

[0060] Therefore, through the above control, the total regeneration time of CaF2 adsorption bed 40 can be reduced from 60 min to 30 min, nitrogen consumption can be reduced by 50%, and HF recovery rate can be greater than or equal to 99%.

[0061] In other embodiments, after HF analysis, it can be further recovered through a "cold trap" and "two-stage condensation + membrane permeation" to minimize exhaust gas emissions. Specifically: First stage: 0 ℃ ice water condensation, which can recover about 90% of HF (liquid); Second stage: -25℃ cryogenic treatment, recovering approximately 8% HF; Stage 3: PDMS / PTFE composite membrane permeation, with a vacuum of 5 kPa on the permeate side and anhydrous nitrogen obtained on the retrieval side. The final HF recovery rate is ≥98%, and the HF emission tail gas is <1 mg*m³. -3 .

[0062] Please see Figure 6 As shown, in one embodiment, the control parameters of the distillation column 50 are as follows: Column diameter 0.6–1.2 m, theoretical plate number 28–32, operating pressure top 12 kPa / bottom 15 kPa, column top 62 ± 1℃, reboiler temperature 12 ± 1℃, reflux ratio 6–6.5; the top steam is compressed to 4–5 bar by a variable frequency centrifugal compressor, with a temperature rise of 18℃, and is directly used as the heat source for the reboiler, COP ≥ 4.0, steam consumption ≤ 0.35 t*t -1 The side stream was collected from plates 20–25 containing CH2Cl2 with POF3 ≤ 1 wt%, and returned to the reaction section under online Raman control; the top product had a POF3 purity ≥ 99.5 wt% and HF ≤ 10 ppm.

[0063] Those skilled in the art should understand that the above embodiments are merely for illustrative purposes and are not intended to limit the scope of this application. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of this application.

Claims

1. A method for preparing phosphorus oxyfluoride based on phosphorus pentoxide, characterized in that: Includes the following steps: S1, phosphorus pentoxide is dispersed in dichloromethane and partially dissolved to form a suspension, wherein the dichloromethane includes a molecular sieve for dehydration, and the content of the molecular sieve is greater than the theoretical amount of dichloromethane used for dehydration. S2, anhydrous hydrogen fluoride solution is passed into the suspension for reaction, and the mixture is stirred rapidly during the reaction, while the reaction temperature is controlled at 10℃~30℃. The anhydrous hydrogen fluoride solution reacts with phosphorus pentoxide at a mass ratio of 120:270~280, that is, an excess of anhydrous hydrogen fluoride solution participates in the reaction. S3, filter the product from step S2 to obtain the filtrate; S4, the filtrate is separated to obtain phosphorus oxyfluoride gas.

2. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 1, characterized in that: The theoretical amount of molecular sieve used for the dehydration of dichloromethane is defined as M1, the theoretical amount of water produced in step S2 and dehydrated using molecular sieve is defined as M2, and the content of the molecular sieve is M, wherein M≥M1+M2.

3. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 2, characterized in that: 3*(M1+M2)≥M>≥1.5*(M1+M2).

4. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 3, characterized in that: In step S1, the step of dispersing phosphorus pentoxide in dichloromethane to partially dissolve it and form a suspension specifically includes: S11, the molecular sieve is dispersed in the dichloromethane; S12, then phosphorus pentoxide and dichloromethane are dispersed evenly, wherein the concentration of phosphorus pentoxide in dichloromethane is 0.1~5 wt%.

5. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 4, characterized in that: The molecular sieve is a 3A or 4A molecular sieve, which is a sphere with a diameter of 3~5.0 mm.

6. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 5, characterized in that: In step S4, the step of separating the filtrate to obtain phosphorus oxyfluoride gas specifically includes: S41, the filtrate is vaporized and then passed into a CaF2 adsorption bed to remove HF gas; S42, then the adsorbed gas is passed into a distillation column, where phosphorus oxyfluoride gas is collected from the top of the column and dichloromethane is collected from the bottom. The collected dichloromethane is purified and returned to step S1 for reuse.

7. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 6, characterized in that: Step S41 further includes: After the CaF2 adsorption bed is saturated, it is regenerated with high-temperature nitrogen gas to generate anhydrous HF for recycling.

8. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 6, characterized in that: In step S42, the step of passing the adsorbed gas into a distillation column, wherein phosphorus oxyfluoride gas is collected from the top of the distillation column and dichloromethane is collected from the bottom of the column, specifically includes: The distillation column is evacuated to 10~20 kPa and deeply cooled at -40℃~-50℃ at the top of the column, while the bottom of the column is gently heated at 10~15℃, with the reflux ratio R controlled at 6~8.

9. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 6, characterized in that: The concentration of phosphorus pentoxide in dichloromethane is 1-4 wt%.

10. The method for preparing phosphorus oxyfluoride based on phosphorus pentoxide according to claim 6, characterized in that: 2.5*(M1+M2)≥M>≥2*(M1+M2).

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