Phosphorus trifluoride purification method and purification system
By employing multi-stage membrane separation technology and appropriate pressure and temperature control, the problem of separating phosphorus trifluoride from hydrogen chloride was solved, achieving efficient and safe purification of phosphorus trifluoride and obtaining high-purity products.
Patent Information
- Application Number
- CN202511427213.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2025-12-23
AI Technical Summary
In existing technologies, separating phosphorus trifluoride from hydrogen chloride is difficult. Traditional distillation methods are energy-intensive and produce low purity, while solvent extraction methods pose safety risks.
Multi-stage membrane separation technology is employed, utilizing combinations of different gas pressures and membrane pore sizes to separate phosphorus trifluoride and hydrogen chloride in stages, including primary, secondary, and tertiary membrane separation. Combined with appropriate gas pressure and temperature control, the separation is carried out using materials such as polytetrafluoroethylene and ceramic membranes.
The production of high-purity phosphorus trifluoride has been achieved, reducing energy consumption and safety risks, improving separation efficiency, and enabling the production of high-purity phosphorus trifluoride products.
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Figure CN121180958A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of phosphorus trifluoride production technology, and more specifically, to a method and system for purifying phosphorus trifluoride. Background Technology
[0002] Phosphorus trifluoride (PF3) is a key material in semiconductors, new energy, and other fields, with wide applications. In semiconductor manufacturing, it serves as a high-precision dopant, enhancing chip performance and making it an essential material for advanced processes. In the field of new energy batteries, its participation in the synthesis of electrolytes can improve lithium battery performance, helping to achieve a range exceeding 1000 kilometers. In polymer modification, it can impart corrosion resistance and other properties to materials, making them suitable for extreme environments. In organic synthesis, it serves as a fluorinating agent, providing a key intermediate for the synthesis of fine chemicals.
[0003] Currently, phosphorus trifluoride is mainly produced by the reaction of phosphorus trichloride and hydrogen fluoride, as shown in the following chemical equation: PCl3(l) + 3HF(g) → PF3(g) + 3HCl(g). However, the separation of phosphorus trifluoride (PF3) and hydrogen chloride (HCl) is a key challenge in the production of high-purity chemicals. The two molecules have relatively similar properties: PF3 is a trigonal pyramidal strongly polar molecule (dipole moment 1.03 D) with a boiling point of -101.5℃; HCl is a linear polar molecule (dipole moment 1.093 D) with a boiling point of -85.05℃, a difference of only 16.45℃. Conventional distillation methods require at least 30 theoretical plates, resulting in extremely high energy consumption and low purity. Furthermore, PF3 readily hydrolyzes in water to form highly toxic hydrofluoric acid, posing a significant safety risk to traditional solvent extraction methods.
[0004] Therefore, it is necessary to provide a more efficient and safer method for purifying phosphorus trifluoride. Summary of the Invention
[0005] In view of the above-mentioned shortcomings, this application provides a method and system for purifying phosphorus trifluoride to improve the purity of phosphorus trifluoride and to improve the high energy consumption of traditional distillation purification and the safety risks of traditional solvent extraction purification.
[0006] This application is implemented as follows: In a first aspect, an example of this application provides a method for purifying phosphorus fluoride, comprising: Primary membrane separation: The feed gas containing phosphorus trifluoride and hydrogen chloride is separated by a primary membrane to form a first cut-off gas rich in phosphorus trifluoride on the first cut-off side of the primary membrane and a first permeate gas rich in hydrogen chloride on the first permeate side of the primary membrane.
[0007] Secondary membrane separation: The first cut-off gas is separated by a secondary membrane. A second cut-off gas rich in phosphorus trifluoride is formed on the second cut-off side of the secondary membrane, and a second permeate gas rich in hydrogen chloride is formed on the second permeate side of the secondary membrane; the second cut-off gas is collected.
[0008] The gas pressure on the first truncation side is higher than that on the second truncation side, and the gas pressure on the second truncation side is higher than atmospheric pressure. The pore size of the primary separation membrane is larger than that of the secondary separation membrane.
[0009] In the above process, because hydrogen chloride has a smaller diameter than phosphorus trifluoride, under the high pressure of the primary membrane separation, hydrogen chloride preferentially permeates to the first permeate side of the primary separation membrane due to its smaller molecular diameter. Meanwhile, phosphorus trifluoride, as the first cut-off gas, enters the secondary separation membrane, rapidly removing a large amount of hydrogen chloride and reducing the load on subsequent secondary membrane separation. During secondary membrane separation, appropriately reducing the gas pressure on the second cut-off side of the secondary separation membrane and the membrane pore size allows for deep removal of trace amounts of hydrogen chloride at relatively lower pressures, thereby improving the purity of the phosphorus trifluoride formed on the second cut-off side.
[0010] According to the above purification method, the feed gas containing phosphorus trifluoride and hydrogen chloride is subjected to at least two stages of membrane separation, and the gas pressure and membrane pore size on the cut-off side of the two separation membranes are controlled to decrease step by step. This method can obtain a high-purity phosphorus trifluoride product, and has higher purification efficiency and lower energy consumption compared with the distillation purification method, and lower safety risk compared with the solvent extraction purification method.
[0011] In conjunction with the first aspect, in an optional embodiment of this application, the gas pressure on the first retention side is 1.0~1.4 MPa. And / or, the pore size of the primary separation membrane is 0.2~0.3 μm.
[0012] Optionally, the gas pressure on the first permeation side is 0.7~0.8 MPa.
[0013] Optionally, the primary separation membrane includes a polytetrafluoroethylene hollow fiber membrane.
[0014] In the above process, a primary separation membrane with a pore size of 0.2~0.3μm is used to separate the feed gas, and the gas pressure on the first cut-off side of the primary separation membrane is adjusted to 1.0~1.4MPa. With a suitable separation pressure and a suitable membrane pore size, most of the hydrogen chloride in the feed gas can be separated quickly. This not only improves the separation efficiency of the entire purification process, but also reduces the processing load of the subsequent secondary membrane separation step.
[0015] By adjusting the gas pressure on the first retention side of the primary separation membrane to 1.0~1.4MPa and the gas pressure on the first permeation side to 0.7~0.8MPa, under the action of a suitable pressure difference, hydrogen chloride can be rapidly permeated to the first permeation side, reducing the content of phosphorus trifluoride in the first permeate gas, thereby improving separation efficiency while reducing phosphorus trifluoride loss.
[0016] Using polytetrafluoroethylene hollow fiber membranes for membrane separation of feed gas is effective because it is resistant to hydrogen chloride corrosion, has a suitable pore size, and exhibits higher permeation selectivity for small molecule hydrogen chloride than phosphorus trifluoride, which facilitates rapid separation of hydrogen chloride.
[0017] In conjunction with the first aspect, in an optional embodiment of this application, the gas pressure on the second retention side is 0.5~0.7 MPa. And / or, the pore size of the secondary separation membrane is 0.1~0.15 μm.
[0018] Optionally, the gas pressure on the second permeation side is 0.3~0.4 MPa.
[0019] Optionally, the secondary separation membrane includes a ceramic membrane.
[0020] In the above process, a secondary separation membrane with a pore size of 0.1~0.15μm is used to perform secondary membrane separation on the first intercepted gas, and the gas pressure on the second intercepted side of the secondary separation membrane is adjusted to 0.5~0.7MPa. By gradually reducing the gas pressure and shrinking the pore size of the separation membrane, trace amounts of hydrogen chloride can be deeply removed from the first intercepted gas after the initial separation by the primary separation membrane, thereby improving the purity of phosphorus trifluoride.
[0021] Adjusting the gas pressure on the second retentate side of the secondary separation membrane to 0.5~0.7MPa and the gas pressure on the second permeate side to 0.3~0.4MPa, under the action of a suitable pressure difference, can promote the permeation of hydrogen chloride to the second permeate side, thereby improving the separation efficiency and the purity of phosphorus trifluoride.
[0022] In conjunction with the first aspect, in an optional embodiment of this application, the purification method further includes three-stage separation: the second retentate gas is separated using a three-stage membrane, resulting in a third retentate gas rich in phosphorus trifluoride on the third retentate side of the three-stage membrane and a third permeate gas rich in hydrogen chloride on the third permeate side of the three-stage membrane. The third retentate gas is collected to obtain the phosphorus trifluoride product. The gas pressure on the third retentate side is lower than that on the second retentate side, and the pore size of the three-stage membrane is smaller than that of the two-stage membrane.
[0023] In the above process, the second intercepted gas separated by the secondary separation membrane is subjected to tertiary membrane separation, and the gas pressure on the third intercepted side and the pore size of the tertiary separation membrane are further reduced, which can further remove trace amounts of hydrogen chloride and obtain electronic-grade standard phosphorus trifluoride products.
[0024] In conjunction with the first aspect, in an optional embodiment of this application, the gas pressure on the third retention side is 0.05~0.3MPa. And / or, the pore size of the tertiary separation membrane is 0.05~0.1μm.
[0025] Optionally, the gas pressure on the third permeation side is 0.03~0.1MPa.
[0026] In the above process, the gas pressure on the third retentate side of the three-stage separation membrane is adjusted to 0.05~0.3MPa and the gas pressure on the third permeate side is adjusted to 0.05~0.1μm. A third membrane separation is performed on the second retentate gas using a three-stage separation membrane with a pore size of 0.05~0.1μm. Under the action of appropriate osmotic pressure difference and permeate pore size, the purity of phosphorus trifluoride can be improved while the separation efficiency can also be improved.
[0027] In conjunction with the first aspect, in an optional embodiment of this application, the three-stage separation membrane includes a support layer and a separation layer stacked together, with the side of the separation layer away from the support layer forming a third retention side. The material forming the separation layer contains polar groups.
[0028] In the above process, introducing polar groups into the separation layer of the three-stage separation membrane can further improve the removal efficiency of hydrogen chloride and increase the purity of phosphorus trifluoride by utilizing the polarity difference and molecular diameter difference between phosphorus trifluoride and hydrogen chloride.
[0029] In conjunction with the first aspect, in an optional embodiment of this application, the material forming the separation layer includes polysulfonamide.
[0030] Alternatively, the material forming the support layer may include polytetrafluoroethylene (PTFE).
[0031] In the above process, the separation layer of the three-stage separation membrane is prepared using polysulfonamide. Polysulfonamide has a -SO2NH- polar group with a dipole moment of approximately 3.5–4.0 D. It preferentially adsorbs and captures hydrogen chloride molecules, which then permeate to the third permeation side under the influence of pressure difference (the dipole moment of hydrogen chloride is approximately 1.093 D, and the dipole moment of phosphorus trifluoride is approximately 1.03 D, with the dipole moment of hydrogen chloride being greater than that of phosphorus trifluoride). Through the dual separation mechanism of polar sieving and membrane pore size exclusion, the purification effect of phosphorus trifluoride can be further improved.
[0032] The support layer is made of polytetrafluoroethylene, which has good support strength and good resistance to hydrogen chloride corrosion. It can stably support the polysulfonamide separation layer, enabling the three-stage separation membrane to stably separate the second intercepted gas.
[0033] In conjunction with the first aspect, in an optional embodiment of this application, the purification method further includes a reflux step: Mix 10% to 50% of the total mass of the first permeate gas with the feed gas.
[0034] Optionally, the second permeate gas can be refluxed to the first interception side.
[0035] Optionally, the third permeate gas can be refluxed to the second interception side.
[0036] In the above process, during the primary membrane separation of the feed gas, most of the hydrogen chloride permeates from the first retention side of the primary separation membrane to the first permeate side. However, a small amount of phosphorus trifluoride inevitably permeates to the first permeate side under the influence of the pressure difference. Recirculating 10% to 80% of the total mass of the first permeate gas from the first permeate side back to the feed gas for mixing and subsequent primary membrane separation can appropriately recover phosphorus trifluoride and maintain a low separation load. If the first permeate gas is completely recirculated back to the feed gas, the hydrogen chloride content in the feed gas will increase, increasing the separation load. If the first permeate gas is not recirculated, phosphorus trifluoride will be wasted.
[0037] Since the permeate gas on the second and third permeate sides has a smaller mass, it can be completely refluxed to the retrieval side of the previous stage separation membrane for further membrane separation, which can reduce the loss of phosphorus trifluoride.
[0038] In conjunction with the first aspect, in optional embodiments of this application, in the primary membrane separation step, the temperature of the feed gas is adjusted to -50 to -40°C. And / or, in the secondary membrane separation step, the temperature of the first retentate gas is adjusted to -30 to -20°C. And / or, in the tertiary membrane separation step, the temperature of the second retentate gas is adjusted to -10 to -5°C.
[0039] In the above-described process, during primary membrane separation, adjusting the temperature of the feed gas to -50 to -40°C under suitable gas pressure and membrane pore size can increase the difference between phosphorus trifluoride and hydrogen chloride, inhibit the hydrolysis of phosphorus trifluoride, and reduce phosphorus trifluoride loss. Furthermore, during secondary membrane separation, adjusting the temperature of the first intercept gas to -30 to -20°C under suitable gas pressure and membrane pore size can reduce gas viscosity, improve mass transfer efficiency, and further enhance separation efficiency. In addition, during tertiary membrane separation, adjusting the temperature of the second intercept gas to -10 to -5°C under suitable gas pressure and membrane pore size can reduce the permeation activity of phosphorus trifluoride, increase the characteristic difference between phosphorus trifluoride and hydrogen chloride, and thus improve the purity of the phosphorus trifluoride product.
[0040] In a second aspect, examples of this application provide a purification system for implementing the purification method provided in the first aspect, including a primary membrane separation assembly and a secondary membrane separation assembly. The primary membrane separation assembly includes a first housing, within which a primary separation membrane is disposed to divide the first housing into a first containment space corresponding to a first retentate side and a second containment space corresponding to a first permeate side. The first containment space is configured to be connected to a feed gas delivery component via a first conduit. The first conduit is connected to a first compressor and a first pressure regulating valve for adjusting the gas pressure in the first containment space. The secondary membrane separation assembly includes a second housing, within which a secondary separation membrane is disposed to divide the second housing into a third containment space corresponding to a second retentate side and a fourth containment space corresponding to a second permeate side. The third containment space is connected to the first containment space via a second conduit, the second conduit being provided with a second pressure regulating valve for adjusting the pressure in the third containment space. The third containment space is also connected to a third conduit to discharge a second retentate gas rich in phosphorus trifluoride.
[0041] In the above-mentioned process, when purifying the raw material gas using the purification system, the raw material gas containing phosphorus trifluoride and hydrogen chloride in the raw material gas conveying component can be transported to the first containment space in the first-stage membrane separation component through the first pipeline. The first compressor and the first pressure regulating valve at the first pipeline can adjust the gas pressure in the first containment space to the set gas pressure. Under the action of pressure difference and separation membrane pore size, most of the hydrogen chloride gas in the first containment space can first permeate through the first-stage separation membrane and flow to the second containment space, while most of the phosphorus trifluoride will be retained in the first containment space, thereby achieving rapid coarse separation of phosphorus trifluoride and hydrogen chloride.
[0042] Then, the first intercepted gas rich in phosphorus trifluoride, which is trapped in the first containment space, is transported from the second pipeline to the third containment space in the secondary membrane separation unit after the pressure is adjusted by the second pressure regulating valve. Under the action of relatively small pressure and separation membrane pore size, hydrogen chloride gas in the third containment space can permeate through the secondary separation membrane and flow to the fourth containment space, while phosphorus trifluoride will be trapped in the third containment space, thereby achieving deep fine separation of phosphorus trifluoride and hydrogen chloride. The third intercepted gas trapped in the third containment space is discharged through the third pipeline, and phosphorus trifluoride with high purity can be obtained.
[0043] In conjunction with the second aspect, in an optional embodiment of this application, the purification system further includes a three-stage membrane separation assembly, comprising a third housing, within which a three-stage separation membrane is disposed to divide the third housing into a fifth containment space corresponding to the third retrieval side and a sixth containment space corresponding to the third permeation side. The fifth containment space is connected to the third containment space via a third conduit, the third conduit being provided with a third pressure regulating valve for adjusting the pressure of the fifth containment space; the fifth containment space is also connected to a fourth conduit to discharge the third retrieval gas rich in phosphorus trifluoride.
[0044] Optionally, the fourth pipe is connected to a phosphorus trifluoride collection bottle.
[0045] In the above process, when it is necessary to further purify the second retentate gas trapped in the third containment space, the second retentate gas can be transported to the fifth chamber of the three-stage membrane separation component through the third pipeline and the pressure is adjusted by the third pressure regulating valve. Under the action of pressure and separation membrane pore size, hydrogen chloride can be further removed to obtain a higher purity phosphorus trifluoride product.
[0046] A fourth pipe is installed in the fifth containment space to transport the third intercepted gas trapped in the fifth containment space to a phosphorus trifluoride collection bottle for collection, thereby obtaining a high-purity phosphorus trifluoride product.
[0047] In conjunction with the second aspect, in an optional embodiment of this application, the second containing space is connected to a fifth pipe, which is connected to a first back pressure valve, and the fifth pipe is used to connect to a hydrogen chloride collection bottle. The fourth containing space is connected to the first pipe via a sixth pipe, which is connected to a second back pressure valve. The sixth containing space is connected to the second pipe via a seventh pipe, which is connected to a third back pressure valve.
[0048] Optionally, a branch pipe is connected to the fifth pipeline at the position between the first back pressure valve and the hydrogen chloride collection bottle, and the branch pipe is connected to the raw material gas conveying component.
[0049] Optionally, the sixth pipe is connected to the position between the first pipe and the first compressor and the first pressure regulating valve, and the sixth pipe is connected to the position between the second back pressure valve and the first pipe, where the second compressor is located.
[0050] Optionally, the seventh pipe is connected to the position of the second pipe corresponding to the position between the second pressure regulating valve and the first receiving space, and the seventh pipe is connected to the position between the third back pressure valve and the second pipe to the third compressor.
[0051] In the above implementation process, a fifth pipe is connected to the second containment space. The first permeate gas containing hydrogen chloride, which has permeated into the second containment space, can be transported to the hydrogen chloride collection bottle through the fifth pipe. A first back pressure valve is installed at the fifth pipe to regulate the gas pressure in the second containment space and prevent backflow. A branch pipe is connected to the fifth pipe at the position corresponding to the first back pressure valve and the hydrogen chloride collection bottle. This branch pipe allows a portion of the first permeate gas to flow back to the raw material gas conveying component, recovering some phosphorus trifluoride and reducing phosphorus trifluoride loss.
[0052] Furthermore, by connecting the fourth containment space to the first pipe via the sixth pipe, the second permeate gas can be returned to the first containment space for further membrane separation, reducing phosphorus trifluoride loss. The connection point between the sixth pipe and the first pipe is located at the first compressor and the first pressure regulating valve. A second compressor is installed at the sixth pipe, which can increase the pressure of the second permeate gas and mix it with the raw material gas. After being pressurized to the set pressure by the first pressure regulating valve, the mixture is then delivered to the first containment space.
[0053] Similarly, connecting the sixth containment space to the second containment space via the seventh pipe allows the third permeate gas to be returned to the third containment space for further membrane separation, further reducing phosphorus trifluoride loss. The connection point between the seventh and second pipes is located between the second pressure regulating valve and the first containment space. A third compressor is installed at the seventh pipe, which can increase the pressure of the third permeate gas and mix it with the first intercepted gas. Then, the pressure is regulated by the second pressure regulating valve before both are delivered to the third containment space for further membrane separation, further reducing phosphorus trifluoride loss. Attached Figure Description
[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.
[0055] Figure 1 This is a schematic diagram of the connection of the purification system provided in an embodiment of this application.
[0056] Icons: 100 - Purification system; 1 - Primary membrane separation assembly; 11 - First housing; 12 - Primary separation membrane; 13 - First containment space; 14 - Second containment space; 2 - Secondary membrane separation assembly; 21 - Secondary housing; 22 - Secondary separation membrane; 23 - Third containment space; 24 - Fourth containment space; 3 - Tertiary membrane separation assembly; 31 - Third housing; 32 - Tertiary separation membrane; 33 - Fifth containment space; 34 - Sixth containment space; 41 - First conduit; 42 - Second conduit; 43 - Third conduit; 44 - Fourth conduit; 45 - Fifth conduit; 46 - Sixth conduit; 47 - 7th Pipeline; 48-Branch Pipe; 49-Backflush Main Pipe; 50-Backflush Branch Pipe; 51-First Compressor; 52-Second Compressor; 53-Third Compressor; 61-First Pressure Regulator; 62-Second Pressure Regulator; 63-Third Pressure Regulator; 71-First Back Pressure Valve; 72-Second Back Pressure Valve; 73-Third Back Pressure Valve; 81-First Temperature Regulator; 82-Second Temperature Regulator; 83-Third Temperature Regulator; 84-Fourth Temperature Regulator; 85-Fifth Temperature Regulator; 91-Raw Gas Conveying Component; 92-Phosphorus Trifluoride Collection Bottle; 93-Hydrogen Chloride Collection Bottle; 94-Backflush Medium Storage Unit. Detailed Implementation
[0057] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0058] Currently, phosphorus trifluoride is mainly prepared by reacting phosphorus trichloride and hydrogen fluoride, as shown in the following chemical reaction formula: PCl3(l) + 3HF(g) → PF3(g) + 3HCl(g).
[0059] As can be seen from the above formula, the reaction products phosphorus trifluoride and hydrogen chloride will be mixed together. In order to obtain high-purity phosphorus trifluoride products, it is usually necessary to purify the product gas.
[0060] However, due to the small difference in molecular properties between phosphorus trifluoride (PF3) and hydrogen chloride (HCl) (PF3 is a trigonal pyramidal strongly polar molecule (dipole moment 1.03 D), with a boiling point of -101.5℃; HCl is a linear polar molecule (dipole moment 1.093 D), with a boiling point of -85.05℃, and the difference in their boiling points is only 16.45℃), the separation of phosphorus trifluoride (PF3) and hydrogen chloride (HCl) is a key challenge in the production of high-purity chemicals.
[0061] Current separation methods mainly include distillation and extraction. However, due to the small boiling point difference of only 16.45°C between phosphorus trifluoride and hydrogen chloride, distillation purification typically requires at least 30 theoretical plates, resulting in extremely high energy consumption and low purity. If traditional solvent extraction is used, PF3 readily hydrolyzes in water to form highly toxic hydrofluoric acid, posing a significant safety risk.
[0062] Based on this, the present application provides a method for purifying phosphorus trifluoride, which can obtain high-purity phosphorus trifluoride products without the need for high-plate-number distillation or solvent extraction. Therefore, it can improve the problems of high energy consumption, low purity and high safety risks in traditional purification methods.
[0063] The purification methods for phosphorus trifluoride include: S1. Primary membrane separation: The feed gas containing phosphorus trifluoride and hydrogen chloride is separated by a primary membrane to form a first cut-off gas rich in phosphorus trifluoride on the first cut-off side of the primary membrane and a first permeate gas rich in hydrogen chloride on the first permeate side of the primary membrane.
[0064] S2, Secondary Membrane Separation: The first cut-off gas is separated using a secondary membrane. A second cut-off gas rich in phosphorus trifluoride is formed on the second cut-off side of the secondary membrane, and a second permeate gas rich in hydrogen chloride is formed on the second permeate side of the secondary membrane. The second cut-off gas is collected.
[0065] Among them, the gas pressure on the first truncation side is higher than that on the second truncation side, and the gas pressure on the second truncation side is higher than that at atmospheric pressure; the pore size of the primary separation membrane is larger than that of the secondary separation membrane.
[0066] In primary membrane separation, high pressure combined with a high-pore membrane enables rapid and significant removal of hydrogen chloride, while also improving purification efficiency and reducing the load on subsequent separations. Secondary membrane separation, using low pressure with a small-pore membrane, allows for further, deeper removal, improving the purity of phosphorus trifluoride.
[0067] Understandably, "membrane separation" refers to the technology of selectively separating a mixture of molecules with different particle sizes (also known as diameters) at the molecular level when passing through a semipermeable membrane. The semipermeable membrane is also called a separation membrane or filter membrane, and its wall is covered with small pores.
[0068] During membrane separation, smaller molecules with smaller diameters permeate from one side of the membrane to the other, while larger molecules are retained on the original side. The side where larger molecules are retained is called the cut-off side, and the side where smaller molecules permeate is called the permeate side. The cut-off side and the permeate side are located on opposite sides of the membrane along its thickness. Phosphorus trifluoride has a diameter of approximately 3.2 Å, and hydrogen chloride has a diameter of approximately 2.8 Å. When performing membrane separation on the feed gas, the feed gas is delivered to the cut-off side of the membrane. Hydrogen chloride preferentially permeates out to the permeate side before phosphorus trifluoride, thus achieving the separation of phosphorus trifluoride and hydrogen chloride.
[0069] Because the diameters of phosphorus trifluoride and hydrogen chloride are relatively similar, direct membrane separation of the feed gas under normal pressure would result in low separation efficiency. Therefore, to improve separation efficiency, this application employs a multi-stage membrane separation technology with progressively decreasing pressure (increasing the pressure to a set level during primary membrane separation, and then reducing the pressure on the cut-off side of the primary membrane during secondary membrane separation) and progressively decreasing membrane pore size. This increases the difference between phosphorus trifluoride and hydrogen chloride, achieving a progressive effect of "rapid separation of large amounts of hydrogen chloride under high pressure → deep removal of trace amounts of hydrogen chloride under low pressure." This eliminates the need for high-plate-count distillation columns and solvent extraction, thus obtaining high-purity phosphorus trifluoride while reducing energy consumption and safety risks.
[0070] Understandably, in membrane separation, the membrane is typically fabricated into a membrane separation module. This module has a containment space corresponding to the retardation side and a containment space corresponding to the permeation side, allowing for adjustment of the gas pressure on both sides. For example, a membrane separation module usually includes a housing containing the separation membrane. The internal space of the housing is divided into a first containment space for the retardation side and a second containment space corresponding to the permeation side. Adjusting the gas pressure on the retardation side means adjusting the gas pressure in the first containment space. One method for adjusting the retardation side pressure is to pressurize the feed gas.
[0071] This application does not limit the specific gas pressure on the first retention side or the specific membrane pore size of the primary separation membrane. In some embodiments, the gas pressure on the first retention side can be adjusted to 1.0~1.4MPa, and the membrane pore size of the primary separation membrane can be set to 0.2~0.3μm.
[0072] During primary membrane separation, appropriate gas pressure combined with appropriate pore size can increase the characteristic difference between phosphorus trifluoride and hydrogen chloride, rapidly remove a large amount of hydrogen chloride, improve purification efficiency, and reduce the load on subsequent secondary membrane separation.
[0073] As an example, the gas pressure on the first interception side can be adjusted to a range of one or more of 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, or 1.4 MPa, or any two of them.
[0074] As an example, the pore size of the primary separation membrane can be one of 0.2 μm, 0.25 μm, 0.3 μm, or any range between two of them.
[0075] As an example, the gas pressure on the first retrieval side can be adjusted to 1.4 MPa, and the pore size of the primary separation membrane can be 0.2 μm.
[0076] Under normal pressure, phosphorus trifluoride has a boiling point of -101.2℃, and hydrogen chloride has a boiling point of -85.1℃. According to physicochemical principles, the boiling point of a liquid increases with increasing pressure. As pressure increases, the intermolecular forces strengthen, requiring a higher temperature to overcome these forces and achieve boiling. Therefore, under high pressure, the boiling points of phosphorus trifluoride and hydrogen chloride will increase accordingly. To ensure that phosphorus trifluoride and hydrogen chloride exist in gaseous form under high pressure and to increase the difference in their properties, the temperature of the feed gas can be appropriately increased. In some embodiments, the feed gas can be pressurized to 1.0~1.4 MPa and preheated to -50~-40℃. As an example, the feed gas can be pressurized to 1.4 MPa and preheated to -50℃.
[0077] Furthermore, in some embodiments, the pressure on the first permeation side can be adjusted to 0.7~0.8 MPa, and under the action of a suitable pressure difference, a large amount of hydrogen chloride can be rapidly removed.
[0078] As an example, the pressure on the first permeation side can be adjusted to a range of 0.7 MPa or 0.8 MPa, or between both.
[0079] As an example, when performing primary membrane separation on feed gas, the feed gas preheated to -50°C can be pressurized to 1.4 MPa and then delivered to the first retentate side of the primary separation membrane, while the gas pressure on the first permeate side of the primary separation membrane is adjusted to 0.7 MPa.
[0080] In the feed gas, the molar ratio of hydrogen chloride to phosphorus trifluoride is approximately 1 to 3:1. In some embodiments, during primary membrane separation, the feed gas can be delivered at a flow rate of 4000 to 2000 ml / min.
[0081] Furthermore, the embodiments of this application do not limit the specific type of the primary separation membrane. In some embodiments, the primary separation membrane may be selected from polytetrafluoroethylene (PTFE) hollow fiber membranes. It is understood that PTFE hollow fiber membrane modules can be used for primary membrane separation. As an example, a membrane with an inner diameter of 0.8 mm and a membrane area of 50 m² can be selected. 2 Polytetrafluoroethylene hollow fiber membrane module.
[0082] During primary membrane separation, even when the separation gas pressure and membrane pore size are adjusted to the aforementioned range to accelerate hydrogen chloride removal, a small amount of phosphorus trifluoride will inevitably permeate to the first permeate side. Therefore, a small amount of phosphorus trifluoride will inevitably be present in the first permeate gas. To reduce phosphorus trifluoride loss, in some embodiments, 10% to 50% of the total mass of the first permeate gas can be refluxed and mixed with the feed gas before undergoing primary membrane separation again. Refluxing an appropriate proportion of the first permeate gas can simultaneously reduce the load on primary membrane separation and phosphorus trifluoride loss to a minimum. If the first permeate gas is completely refluxed, the large amount of hydrogen chloride in the first permeate gas will lead to an increasingly higher hydrogen chloride content in the feed gas, increasing the load on membrane separation. If the first permeate gas is not refluxed, phosphorus trifluoride loss will increase.
[0083] As an example, 10%, 30%, 50%, 70%, or 80% of the total mass of the first permeate gas can be refluxed and mixed with the feed gas.
[0084] Furthermore, in order to maintain the membrane flux of the primary separation membrane, in some embodiments, during the purification process, backflush medium is blown into the first permeate side every 30 to 60 minutes, and the gas pressure on the first permeate side is adjusted to 1.5 to 2.0 MPa, so that the backflush medium permeates from the first permeate side to the first interception side to remove hydrogen chloride or other impurities adsorbed on the primary separation membrane.
[0085] As an example, a pulse backflush system can be used to blow backflush medium into the first permeation side, with a pulse duration of 5~10s and a backflush pressure of 1.5~2.0MPa, which can restore the membrane flux to more than 95%.
[0086] Furthermore, in some embodiments, the backflushing medium may be ultrapure phosphorus trifluoride or an inert gas.
[0087] If an inert gas is used as the backflushing medium, under higher pressure, the inert gas can flow in the reverse direction to the retrieval side to clean the separation membrane. The inert gas flowing to the retrieval side will mix with phosphorus trifluoride. Due to the significant differences in properties between the inert gas and phosphorus trifluoride, the inert gas can be removed by simple distillation to obtain high-purity phosphorus trifluoride.
[0088] As an example, ultrapure phosphorus trifluoride can be used as the backflush medium. When using ultrapure phosphorus trifluoride, the gas pressure on the first permeate side is adjusted to 1.5~2.0 MPa. Under the action of the pressure difference, phosphorus trifluoride can permeate from the first permeate side to the first retrieval side. After entering the retrieval side, phosphorus trifluoride can mix with the first retrieval gas. Subsequently, after multi-stage membrane separation, the backflush medium can be recovered.
[0089] When performing secondary membrane separation, this application does not limit the specific gas pressure on the second permeation side or the specific pore size of the secondary separation membrane, as long as the gas pressure on the second permeation side is between the gas pressure on the first permeation side and the atmospheric pressure, and the pore size of the secondary separation membrane is smaller than that of the primary separation membrane.
[0090] In some embodiments, the gas pressure on the second retrieval side can be 0.5~0.7 MPa, and the membrane pore size of the secondary separation membrane can be 0.1~0.15 μm. Appropriate gas pressure combined with appropriate membrane pore size can effectively remove trace amounts of residual hydrogen chloride from the first retrieval gas at a low depth, thereby improving the purity of phosphorus trifluoride.
[0091] As an example, during secondary membrane separation, the pressure of the first retentate gas can be reduced to one or more of 0.5 MPa, 0.6 MPa, and 0.7 MPa, or any two of them, and then delivered to the second retentate side of a secondary separation membrane with a pore size of 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, or 0.5 μm.
[0092] Furthermore, during secondary membrane separation, the gas pressure on the second permeate side of the secondary separation membrane can be adjusted to 0.3~0.4MPa, which can achieve deep removal of trace amounts of hydrogen chloride under a suitable pressure difference.
[0093] Furthermore, the embodiments of this application do not limit the specific type of the secondary separation membrane. In some embodiments, the secondary separation membrane can be a ceramic membrane. As an example, a membrane with a pore size of 0.1 μm and a membrane area of 30 m² can be selected. 2 α-Al2O3 ceramic film.
[0094] Furthermore, during secondary membrane separation, the first intercepted gas can be heated to -30 to -20°C to reduce the gas viscosity, improve mass transfer efficiency, and enhance the efficiency of secondary membrane separation.
[0095] As an example, during secondary membrane separation, the pressure of the first retentate gas can be reduced to 0.7 MPa, the first retentate gas can be heated to -30°C and delivered to the second retentate side of the α-Al2O3 ceramic membrane, and the pressure of the second permeate side of the α-Al2O3 ceramic membrane can be reduced to 0.4 MPa.
[0096] Furthermore, in some embodiments, the second permeate gas can be refluxed, mixed with the first retentate gas, and then delivered together to the second retentate side of the secondary separation membrane.
[0097] In some embodiments, during the purification process, backflushing medium is blown into the second permeation side every 30-60 minutes, and the gas pressure on the second permeation side is adjusted to 1.5-2.0 MPa, so that the backflushing medium permeates from the second permeation side to the second retention side to remove hydrogen chloride or other impurities adsorbed on the secondary separation membrane. The backflushing method and backflushing medium can refer to the backflushing method and backflushing medium of the primary separation membrane, and will not be repeated here.
[0098] Through the above two-stage membrane separation, the purity of phosphorus trifluoride can be increased to over 99.5%.
[0099] To further improve the purity of phosphorus trifluoride, in some embodiments, the purification method further includes: S3. Three-stage separation: The second intercepted gas undergoes three-stage membrane separation. A third intercepted gas rich in phosphorus trifluoride is formed on the third intercepted side of the three-stage separation membrane, and a third permeate gas rich in hydrogen chloride is formed on the third permeate side of the three-stage separation membrane. The third intercepted gas is collected to obtain the phosphorus trifluoride product. The gas pressure on the third intercepted side is lower than that on the second intercepted side, and the pore size of the three-stage separation membrane is smaller than that of the two-stage separation membrane.
[0100] The second intercepted gas separated by the secondary separation membrane is subjected to tertiary membrane separation, and the gas pressure on the third intercept side and the pore size of the tertiary separation membrane are further reduced to further remove trace amounts of hydrogen chloride and obtain electronic-grade standard phosphorus trifluoride products.
[0101] In some embodiments, the gas pressure on the third retrieval side is 0.05~0.3MPa, and the pore size of the tertiary separation membrane is 0.05~0.1μm. After tertiary membrane separation of the feed gas, electronic-grade phosphorus trifluoride product can be obtained.
[0102] As an example, during three-stage membrane separation, the gas pressure on the third retrieval side can be adjusted to a range of 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, or 0.3 MPa, or any two of these ranges. The pore size of the three-stage separation membrane can be a range of 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, or 0.1 μm, or any two of these ranges.
[0103] Furthermore, during tertiary membrane separation, the gas pressure on the third permeate side of the tertiary separation membrane can be adjusted to 0.03~0.1MPa.
[0104] As an example, the gas pressure on the third permeation side can be adjusted to a range of one or any two of 0.03MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, or 0.1MPa.
[0105] Furthermore, in some embodiments, during tertiary membrane separation, the temperature of the second intercept gas can be adjusted to -10 to -5°C to reduce the permeation activity of phosphorus trifluoride and further reduce the loss of phosphorus trifluoride.
[0106] Furthermore, in some embodiments, the third permeate gas can be refluxed, mixed with the second retrieval gas, and then transported together to the third retrieval side for another tertiary membrane separation process, further reducing phosphorus trifluoride loss.
[0107] Furthermore, the embodiments of this application do not limit the specific type of the three-stage separation membrane. In some embodiments, the three-stage separation membrane includes a stacked support layer and a separation layer, with the side of the separation layer away from the support layer forming a third retention side. The material forming the separation layer contains polar groups. Through a dual separation mechanism of polar sieving and membrane pore size sieving, the purification effect of phosphorus trifluoride can be further improved.
[0108] As an example, the material that forms the separation layer includes polysulfonamide, which has a -SO2NH- polar group.
[0109] As an example, the material forming the support layer includes polytetrafluoroethylene (PTFE).
[0110] As an example, the tertiary separation membrane can be a composite nanofiltration membrane (PTFE support layer + polysulfonamide separation layer, membrane pore size 0.05μm), with a membrane area of 30m². 2 The purification temperature is -10℃, and the pressure on the third permeation side is 0.1-0.03MPa.
[0111] In some embodiments, during the purification process, backflushing medium is blown into the third permeation side every 30-60 minutes, and the gas pressure on the second permeation side is adjusted to 1.5-2.0 MPa, so that the backflushing medium permeates from the second permeation side to the second retention side to remove hydrogen chloride or other impurities adsorbed on the secondary separation membrane. The backflushing method and backflushing medium can refer to the backflushing method and backflushing medium of the primary separation membrane, and will not be repeated here.
[0112] Through the above-mentioned three-stage membrane separation with decreasing pressure and membrane pore size, a step-by-step separation target can be achieved, which can improve the purity of phosphorus trifluoride while increasing separation efficiency and reducing energy consumption and safety risks.
[0113] In a second aspect, embodiments of this application provide a purification system for implementing the above-described purification method. Please refer to [link to relevant documentation]. Figure 1 It includes a primary membrane separation unit 1 and a secondary membrane separation unit 2.
[0114] The primary membrane separation assembly 1 includes a first housing 11, within which a primary separation membrane 12 is disposed, dividing the first housing 11 into a first receiving space 13 corresponding to the first retrieval side and a second receiving space 14 corresponding to the first permeation side. The first receiving space 13 is configured to be connected to a feed gas delivery component 91 via a first conduit 41. The first conduit 41 is connected to a first compressor 51 and a first pressure regulating valve 61 for adjusting the gas pressure in the first receiving space 13.
[0115] The secondary membrane separation assembly 2 includes a second housing 21, within which a secondary separation membrane 22 is disposed, dividing the second housing 21 into a third containment space 23 corresponding to the second retention side and a fourth containment space 24 corresponding to the second permeation side. The third containment space 23 is connected to the first containment space 13 via a second conduit 42, which is equipped with a second pressure regulating valve 62 for adjusting the pressure in the third containment space 23. The third containment space 23 is also connected to a third conduit 43 to discharge the second retention gas rich in phosphorus trifluoride.
[0116] When purifying the raw material gas using the purification system 100, the raw material gas containing phosphorus trifluoride and hydrogen chloride in the raw material gas conveying component 91 can be transported to the first containment space 13 in the first-stage membrane separation component 1 via the first pipeline 41. The first compressor 51 and the first pressure regulating valve 61 can adjust the gas pressure in the first containment space 13 to the set gas pressure. Under the action of pressure difference and separation membrane pore size, most of the hydrogen chloride gas in the first containment space 13 can first permeate through the first-stage separation membrane 12 and flow to the second containment space 14, while most of the phosphorus trifluoride will be retained in the first containment space 13, thereby achieving rapid coarse separation of phosphorus trifluoride and hydrogen chloride.
[0117] Then, the first intercepted gas containing phosphorus trifluoride, which is trapped in the first containment space 13, is transported from the second pipeline 42 to the third containment space 23 in the secondary membrane separation component 2 after the pressure is adjusted by the second pressure regulating valve 62. Under the action of a smaller pressure and separation membrane pore size, the hydrogen chloride gas in the third containment space 23 can permeate through the secondary separation membrane 22 and flow to the fourth containment space 24, while the phosphorus trifluoride will be trapped in the third containment space 23, thereby achieving deep fine separation of phosphorus trifluoride and hydrogen chloride. The third intercepted gas trapped in the third containment space 23 is discharged through the third pipeline 43, and phosphorus trifluoride with high purity can be obtained.
[0118] This application does not limit how the first housing 11 and the primary separation membrane 12 form the membrane module; the structure of conventional membrane separation modules can be adjusted accordingly. The structure and type of the membrane module depend on the shape of the membrane. Industrially used membrane modules mainly include hollow fiber, tubular, spiral wound, or frame plate types, which can be selected according to needs.
[0119] As an example, the first housing 11 can be a tube, and the primary separation membrane 12 is rolled into a cylindrical shape and extends into the first housing 11, dividing the first housing 11 into two receiving spaces, inner and outer. When the inner side of the primary separation membrane 12 is the first interception side and the outer side is the first permeation side, the inner ring of the primary separation membrane 12 corresponds to the first receiving space 13, and the outer ring corresponds to the second receiving space 14. The first receiving space 13 has two ends along the length of the tube. The first pipe 41 is connected to one end of the first receiving space 13, and the second pipe 42 is connected to the other end of the first receiving space 13, so that the raw material gas can flow into the first receiving space 13 from the first pipe 41. During the flow of the raw material gas along the length of the tube, hydrogen chloride can permeate into the second receiving space 14, forming a first interception gas in the first receiving space 13, and the first interception gas can flow out from the second pipe 42.
[0120] Or, as an example, such as Figure 1As shown, a primary separation membrane 12 can be provided in the middle of the first housing 11 of the rectangular frame structure. The edge of the primary separation membrane 12 is connected to the inner wall of the first housing 11, dividing the first housing 11 into two receiving spaces, left and right.
[0121] Similarly, the specific connection method between the second housing 21 and the secondary separation membrane 22 in the secondary membrane separation assembly 2 can also be adjusted with reference to the structure of conventional membrane separation assemblies, and will not be elaborated here.
[0122] In some embodiments, the primary separation membrane 12 may be a polytetrafluoroethylene hollow fiber membrane, and the secondary separation membrane 22 may be a ceramic membrane.
[0123] Furthermore, to facilitate the discharge of the hydrogen chloride-rich first permeate gas from the second containment space 14, in some embodiments, please refer to... Figure 1 A fifth pipe 45 can be connected to the second containment space 14, and a hydrogen chloride collection bottle 93 can be connected to one end of the fifth pipe 45. In addition, in order to prevent backflow of the medium and facilitate the adjustment of the gas pressure in the second containment space 14, a first back pressure valve 71 can be installed at the fifth pipe 45.
[0124] Furthermore, to facilitate the recirculation of a portion of the first permeate gas, in some embodiments, a branch pipe 48 can be provided, with one end of the branch pipe 48 connected to the position of the fifth pipeline 45 between the first back pressure valve 71 and the hydrogen chloride collection bottle 93, and the other end of the branch pipe 48 connected to the raw material conveying component 91. Furthermore, to facilitate control of the flow rate of the first permeate gas recirculation, a corresponding flow controller can also be installed at the branch pipe 48.
[0125] Furthermore, to facilitate the recirculation of the second permeate gas in the fourth containment space 24, mixing it with the feed gas and then re-transporting it to the first containment space 13 for membrane separation, in some embodiments, please refer to... Figure 1 A sixth pipe 46 can be connected at the fourth accommodating space 24, a second back pressure valve 72 can be installed at the sixth pipe 46, and the sixth pipe 46 can be connected to the first pipe 41.
[0126] As an example, the sixth pipe 46 is connected to the first pipe 41 at the position between the first compressor 51 and the first pressure regulating valve 61. To facilitate increasing the pressure of the returning second permeate gas, in some embodiments, a second compressor 52 can be installed at the sixth pipe 46, located at the rear end of the second back pressure valve 72. Alternatively, the sixth pipe 46 can be connected to the first pipe 41 at the front end of the first compressor 51, without a compressor installed at the sixth pipe 46.
[0127] Furthermore, in some embodiments, please refer to Figure 1The purification system 100 also includes a three-stage membrane separation assembly 3. The three-stage membrane separation assembly 3 includes a third housing 31, within which a three-stage separation membrane 32 is disposed to divide the third housing 31 into a fifth containment space 33 corresponding to the third retrieval side and a sixth containment space 34 corresponding to the third permeation side. The fifth containment space 33 is connected to the third containment space 23 via a third conduit 43, which is equipped with a third pressure regulating valve 63 for regulating the pressure in the fifth containment space 33. The fifth containment space 33 is also connected to a seventh conduit 47 to discharge the third retrieval gas rich in phosphorus trifluoride.
[0128] When further purification of the second retentate gas trapped in the third containment space 23 is required, the second retentate gas can be transported to the fifth containment space 33 of the three-stage membrane separation component 3 through the third pipeline 43 and the pressure adjusted by the third pressure regulating valve 63. Under the action of pressure and separation membrane pore size, hydrogen chloride can be further removed to obtain a higher purity phosphorus trifluoride product.
[0129] Similarly, the specific connection method between the third housing 31 and the third separation membrane 32 in the three-stage membrane separation assembly 3 can also be adjusted accordingly with reference to the structure of conventional membrane separation assemblies, and will not be elaborated here.
[0130] In some embodiments, the tertiary separation membrane 32 may be a composite nanofiltration membrane, comprising a stacked support layer and a separation layer (not shown), with the side of the separation layer away from the support layer forming a third retention side. The material forming the separation layer contains polar groups; for example, the tertiary separation membrane may comprise a polytetrafluoroethylene support layer and a polysulfonamide separation layer.
[0131] Furthermore, to facilitate the discharge of the third trapped gas at the fifth accommodating space 33, in some embodiments, please refer to [the relevant documentation / reference needed]. Figure 1 The fourth pipe 44 can be connected to the phosphorus trifluoride collection bottle 92. As an example, the phosphorus trifluoride collection bottle 92 can be a cryogenic collection bottle, capable of cooling phosphorus trifluoride to -120°C for storage.
[0132] Furthermore, to facilitate the reflux of the third permeate gas, in some embodiments, please refer to [the documentation / reference needed]. Figure 1 A seventh pipe 47 can be connected to the sixth accommodating space 34. A third back pressure valve 73 and a third compressor 53 are provided at the seventh pipe 47. The third compressor 53 is located at the rear end of the third back pressure valve 73. The seventh pipe 47 is connected between the second pressure regulating valve 62 of the second pipe 42 and the first accommodating space 13.
[0133] To facilitate the adjustment of the air pressure in the sixth containment space 34 to 0.03~0.1MPa, a vacuum pump (not shown in the figure) can be installed at the seventh pipe 47.
[0134] In some embodiments, buffer tanks can be installed at each permeate return pipe, with rupture discs on top of the buffer tanks and connected to an alkaline absorption tower to prevent hydrogen chloride leakage and contamination. As an example, a buffer tank can be installed at the location of the sixth pipe 46 between the second compressor 52 and the second back pressure valve 72.
[0135] Furthermore, in some embodiments, to facilitate adjustment of the gas temperature at each stage of the separation membrane, temperature regulators can be installed at the corresponding pipelines. For example, to facilitate adjustment of the feed gas temperature to -50 to -40°C, a first temperature regulator 81 can be installed at the first pipeline 41, located at the front end of the first compressor 51. To facilitate adjustment of the temperature of the first permeate gas delivered to the third containment space 23 to -30 to -20°C, a second temperature regulator 82 can be installed at the second pipeline 42, located at the front end of the second pressure regulating valve 62. To facilitate adjustment of the temperature of the second permeate gas delivered to the fifth containment space 33 to -10 to -5°C, a third temperature regulator 83 can be installed at the third pipeline 43, located at the front end of the third pressure regulating valve 63.
[0136] Furthermore, when recirculating the permeate gas, a temperature regulator can be installed at the corresponding pipeline to adjust the temperature of the permeate gas. For example, a fourth temperature regulator 84 can be installed at the sixth pipeline 46, located between the second compressor 52 and the second back pressure valve 72. For example, a fifth temperature regulator 85 can be installed at the seventh pipeline 47, located between the third compressor 53 and the third back pressure valve 73.
[0137] Furthermore, to facilitate backflushing and cleaning of the separation membranes at each stage, in some embodiments, please refer to [reference needed]. Figure 1 The purification system 100 also includes a backflush assembly, which includes a backflush medium storage 94. The backflush medium storage 94 is connected to a backflush main pipe 49. Three backflush branch pipes 50 are connected to the backflush main pipe 49. The three backflush branch pipes 50 are connected to the second receiving space 14, the fourth receiving space 24 and the sixth receiving space 34 respectively, and a switch valve is provided at the end of each backflush branch pipe 50 near the receiving space.
[0138] Furthermore, the phosphorus trifluoride collection bottle 92 can be connected to the backflush medium storage tank 94.
[0139] In some embodiments, the pipes in the purification system 100 can be made of polytetrafluoroethylene (PTFE) or Hastelloy tubing, which are resistant to corrosion by hydrogen chloride.
[0140] The purification method of phosphorus trifluoride is further described in detail below with reference to the embodiments.
[0141] Example 1 This embodiment provides a method for purifying phosphorus trifluoride, using... Figure 1 The purification system shown is as follows: (1) Primary membrane separation The feed gas (HCl / PF3 molar ratio approximately 3:1, flow rate 4000 ml / min) is preheated to -50°C by the first temperature regulator 81, and then pressurized to 1.4 MPa by the first compressor 51 and the first pressure regulating valve 61 before entering the first containment space 13 of the primary membrane separation assembly 1 through the first pipeline 41. The gas pressure in the second containment space 14 is adjusted to 0.8 MPa. The primary separation membrane 12 is a polytetrafluoroethylene hollow fiber membrane (inner diameter 0.8 mm, membrane area 50 m²). 2 (Membrane pore size 0.2 μm).
[0142] Hydrogen chloride preferentially permeates through the pores of the primary separation membrane 12, forming a first permeate gas, "HCl gas," on the first permeate side. The hydrogen chloride content in the first permeate gas is ≥80%. The first permeate gas is discharged from the fifth pipe 45, and 20% of the first permeate gas is returned to the feed gas conveying unit 91 via the branch pipe 48.
[0143] Phosphorus trifluoride is retained on the first retrieval side, forming a first retrieval gas rich in phosphorus trifluoride (phosphorus trifluoride purity ≥ 85%).
[0144] (2) Secondary membrane separation The first intercepted gas flows out from the first containment space 13 to the second pipe 42. After being heated to -30℃ by the second temperature regulator 82 and reduced to 0.7MPa by the second pressure regulating valve 62, it flows into the third containment space 23 of the secondary membrane separation assembly 2 from the second pipe 42. The gas pressure in the fourth containment space 24 is adjusted to 0.4MPa. The secondary separation membrane 22 is an α-Al₂O₃ ceramic membrane (pore size 0.1μm, membrane area 30m²). 2 ).
[0145] The residual HCl (approximately 10%-15%) in the first permeate gas passes through the membrane pores of the secondary separation membrane 22, while phosphorus trifluoride is retained on the second retentate side, forming a second retentate gas with a purity ≥99.5%.
[0146] (III) Three-stage membrane separation The second intercepted gas flows out from the third containment space 23 to the third pipe 43. After being heated to -10℃ by the third temperature regulator 83 and reduced to 0.3MPa by the third pressure regulating valve 63, it flows into the fifth containment space 33 of the three-stage membrane separation assembly 3 from the third pipe 43. The gas pressure in the sixth containment space 34 is adjusted to 0.1MPa. The three-stage separation membrane 32 is a composite nanofiltration membrane (PTFE support layer + polysulfonamide separation layer, membrane pore size 0.05μm, membrane area 25m²). 2 ).
[0147] The residual HCl (≤0.05%) in the second permeate gas passes through the membrane pores of the tertiary separation membrane 32, and phosphorus trifluoride is retained on the third retentate side to form the third retentate gas. The third retentate gas flows into the phosphorus trifluoride collection bottle 92 through the fourth pipe 44 for low-temperature storage (-120℃) to obtain an electronic-grade standard phosphorus trifluoride product with a purity ≥99.999%.
[0148] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for purifying phosphorus trifluoride, characterized in that, include: Primary membrane separation: The feed gas containing phosphorus trifluoride and hydrogen chloride is separated by a primary membrane to form a first cut-off gas rich in phosphorus trifluoride on the first cut-off side of the primary membrane and a first permeate gas rich in hydrogen chloride on the first permeate side of the primary membrane. Secondary membrane separation: The first retentate gas is separated by a secondary membrane to form a second retentate gas rich in phosphorus trifluoride on the second retentate side of the secondary membrane and a second permeate gas rich in hydrogen chloride on the second permeate side of the secondary membrane; Collect the second trapped gas; Wherein, the gas pressure on the first truncation side is higher than the gas pressure on the second truncation side, and the gas pressure on the second truncation side is higher than atmospheric pressure; the pore size of the primary separation membrane is larger than the pore size of the secondary separation membrane.
2. The purification method according to claim 1, characterized in that, The gas pressure on the first interception side is 1.0~1.4MPa; and / or, the pore size of the primary separation membrane is 0.2~0.3μm; Optionally, the gas pressure on the first permeation side is 0.7~0.8 MPa; Optionally, the primary separation membrane comprises a polytetrafluoroethylene hollow fiber membrane.
3. The purification method according to claim 1, characterized in that, The gas pressure on the second interception side is 0.5~0.7MPa; and / or, the pore size of the secondary separation membrane is 0.1~0.15μm; Optionally, the gas pressure on the second permeation side is 0.3~0.4 MPa; Optionally, the secondary separation membrane comprises a ceramic membrane.
4. The purification method according to any one of claims 1 to 3, characterized in that, The purification method further includes three-stage membrane separation: the second retentate gas is subjected to three-stage membrane separation using a three-stage separation membrane to form a third retentate gas rich in phosphorus trifluoride on the third retentate side of the three-stage separation membrane, and a third permeate gas rich in hydrogen chloride on the third permeate side of the three-stage separation membrane. The third retentate gas is collected to obtain phosphorus trifluoride product. The gas pressure on the third truncation side is lower than that on the second truncation side, and the pore size of the tertiary separation membrane is smaller than that of the secondary separation membrane.
5. The purification method according to claim 4, characterized in that, The gas pressure on the third interception side is 0.05~0.3MPa; and / or the pore size of the three-stage separation membrane is 0.05~0.1μm; Optionally, the gas pressure on the third permeation side is 0.03~0.1MPa.
6. The purification method according to claim 4, characterized in that, The three-stage separation membrane includes a support layer and a separation layer stacked together, with the third retention side formed on the side of the separation layer away from the support layer; the material forming the separation layer contains polar groups.
7. The purification method according to claim 6, characterized in that, The material forming the separation layer includes polysulfonamide; Optionally, the material forming the support layer includes polytetrafluoroethylene.
8. The purification method according to claim 4, characterized in that, The purification method further includes a reflux step: Mix 10% to 50% of the total mass of the first permeate gas with the raw material gas; Optionally, the second permeate gas is refluxed to the first interception side; Optionally, the third permeate gas is refluxed to the second interception side.
9. The purification method according to claim 4, characterized in that, In the first-stage membrane separation step, the temperature of the feed gas is adjusted to -50 to -40°C; and / or, in the second-stage membrane separation step, the temperature of the first retentate gas is adjusted to -30 to -20°C; and / or, in the third-stage membrane separation step, the temperature of the second retentate gas is adjusted to -10 to -5°C.
10. A purification system for implementing the purification method according to any one of claims 1 to 9, characterized in that, include: A primary membrane separation assembly includes a first housing, within which the primary separation membrane is disposed to divide the first housing into a first containment space corresponding to the first retrieval side and a second containment space corresponding to the first permeation side; the first containment space is configured to be connected to a feed gas conveying component via a first pipe; the first pipe is connected to a first compressor and a first pressure regulating valve for adjusting the gas pressure in the first containment space; A secondary membrane separation assembly includes a second housing, within which the secondary separation membrane is disposed to divide the second housing into a third containment space corresponding to the second retrieval side and a fourth containment space corresponding to the second permeation side; the third containment space is connected to the first containment space via a second conduit, the second conduit being provided with a second pressure regulating valve for adjusting the pressure of the third containment space; the third containment space is also connected to a third conduit to discharge the second retrieval gas rich in phosphorus trifluoride.
11. The purification system according to claim 10, characterized in that, The purification system further includes a three-stage membrane separation assembly, comprising a third housing, within which a three-stage separation membrane is disposed to divide the third housing into a fifth containment space corresponding to the third retrieval side and a sixth containment space corresponding to the third permeation side; the fifth containment space is connected to the third containment space via a third conduit, the third conduit being provided with a third pressure regulating valve for adjusting the gas pressure in the fifth containment space; the fifth containment space is also connected to a fourth conduit to discharge the third retrieval gas rich in the phosphorus trifluoride; Optionally, the fourth pipe is connected to a phosphorus trifluoride collection bottle.
12. The purification system according to claim 11, characterized in that, The second containment space is connected to a fifth pipe, the fifth pipe is connected to a first back pressure valve, and the fifth pipe is used to connect to a hydrogen chloride collection bottle; and / or, the fourth containment space is connected to the first pipe through a sixth pipe, the sixth pipe is connected to a second back pressure valve; and / or, the sixth containment space is connected to the second pipe through a seventh pipe, the seventh pipe is connected to a third back pressure valve; Optionally, the fifth pipeline is connected to a branch pipe at the position between the first back pressure valve and the hydrogen chloride collection bottle, and the branch pipe is connected to the raw material gas conveying component. Optionally, the sixth pipe is connected to the position of the first pipe corresponding to the position between the first compressor and the first pressure regulating valve, and the sixth pipe is connected to the position of the second compressor corresponding to the position between the second back pressure valve and the first pipe; Optionally, the seventh pipe is connected to the second pipe at the position corresponding to the second pressure regulating valve and the first accommodating space, and the seventh pipe is connected to the third compressor at the position corresponding to the third back pressure valve and the second pipe.