Preparation method and production system of phosphorus trifluoride

Abstract

The invention discloses a preparation method and a production system of phosphorus trifluoride, and belongs to the technical field of preparation of phosphorus trifluoride. Phosphorus trichloride and first mixed gas are continuously introduced into a reactor, the first mixed gas comprises anhydrous hydrogen fluoride and inert gas, phosphorus trichloride and anhydrous hydrogen fluoride in the first mixed gas are subjected to a double decomposition reaction in the reactor, and intermediate gas containing phosphorus trifluoride is generated. Collecting intermediate gas discharged from the reactor, and rectifying and purifying the intermediate gas to obtain a phosphorus trifluoride product. The inert gas carries anhydrous hydrogen fluoride and phosphorus trichloride to generate double decomposition reaction to generate phosphorus trifluoride, and the inert gas can dilute the concentration of the raw material gas anhydrous hydrogen fluoride participating in the reaction and also can take away heat generated by the reaction, so that the temperature of the reactor is more stable, and continuous production of phosphorus trifluoride is realized.

Description

Technical Field

[0001] This application relates to the technical field of the preparation of phosphorus trifluoride. Specifically, it relates to a preparation method and a production system of phosphorus trifluoride. Background Art

[0002] Phosphorus trifluoride (PF3) has a melting point of -151.3 °C, a boiling point of -101.2 °C, a critical temperature of -2 °C, and a critical pressure of 4.33 MPa. It is a colorless and odorless gas under normal temperature and pressure, and a colorless and transparent liquid when in liquid state.

[0003] Currently, phosphorus trifluoride has a wide range of applications. It can be used to improve the properties of materials. For example, in the research of lithium-ion batteries, adding phosphorus trifluoride to the electrolyte can improve the performance and lifespan of the battery. In the semiconductor industry, phosphorus trifluoride is widely used as a precursor for the preparation of nitride semiconductors and is closely related to semiconductor manufacturing. Phosphorus trifluoride can be used as a dopant, a surface treatment agent, and a key component for the preparation of specific structure materials, playing an important role in the performance optimization and manufacturing of semiconductor devices.

[0004] Currently, there are few methods for producing phosphorus trifluoride. Industrially, phosphorus trifluoride is basically produced using phosphorus trichloride and anhydrous hydrogen fluoride as raw materials. However, due to factors such as a relatively fast reaction rate, a large amount of heat released during the reaction, and the need to maintain the reaction temperature at 40 °C - 60 °C to reduce the occurrence of side reactions, only batch production can be carried out at present. Therefore, it is necessary to develop a method for continuously preparing phosphorus trifluoride with simple process, safe and controllable, low cost, and high product purity. Summary of the Invention

[0005] Based on the above deficiencies, this application provides a preparation method and a production system of phosphorus trifluoride to improve the problem of continuous production of phosphorus trifluoride in related technologies.

[0006] This application is implemented as follows:

[0007] In a first aspect, an example of this application provides a preparation method of phosphorus trifluoride, including:

[0008] Raw material preparation step: Obtain phosphorus trichloride and a first mixed gas respectively. Among them, the first mixed gas contains anhydrous hydrogen fluoride and an inert gas.

[0009] Double decomposition reaction step: Continuously introduce phosphorus trichloride and the first mixed gas into a reactor, so that phosphorus trichloride and anhydrous hydrogen fluoride undergo a double decomposition reaction in the reactor to generate an intermediate gas containing phosphorus trifluoride. Collect the intermediate gas discharged from the reactor.

[0010] Purification step: Rectify and purify the intermediate gas to obtain a phosphorus trifluoride product.

[0011] The reaction rate of phosphorus trichloride and hydrogen fluoride is fast, and a large amount of heat is released during the reaction. The reaction temperature of phosphorus trichloride and hydrogen fluoride needs to be strictly controlled at 40°C to 60°C to reduce the occurrence of side reactions. Therefore, in the traditional preparation process, it is often necessary to suspend the supply of reaction raw materials after a period of reaction, and then introduce the raw materials for reaction after the temperature in the reactor is reduced. It is intermittent production and cannot be produced continuously. In the embodiment of the present application, when preparing phosphorus trifluoride, anhydrous hydrogen fluoride is carried by the inert gas in the first mixed gas to react with phosphorus trichloride to generate phosphorus trifluoride. In the first aspect, the inert gas will dilute the concentration of anhydrous hydrogen fluoride in the raw gas gas participating in the reaction, which can reduce the reaction rate of anhydrous hydrogen fluoride and phosphorus trichloride, reduce the reaction heat in the reactor, and is conducive to the temperature stability in the reactor. In the second aspect, the inert gas will take away the heat generated by the reaction, making the reaction temperature more stable, thereby reducing the occurrence of side reactions, improving the conversion rate, and realizing continuous production of phosphorus trifluoride. In addition, the inert gas has the characteristics of high stability and low reactivity, and will not react. The intermediate gas after the reaction is distilled and purified to obtain a high-purity phosphorus trifluoride product.

[0012] In combination with the first aspect, in an optional embodiment of the present application, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to the inert gas is 1:40-120.

[0013] Optionally, the volume ratio of anhydrous hydrogen fluoride to inert gas is 1:60-80.

[0014] Optionally, the inert gas includes at least one of nitrogen or argon.

[0015] In the above implementation process, the anhydrous hydrogen fluoride and the inert gas in the first mixed gas have a suitable volume ratio, which can better take into account the continuous production requirements and the preparation efficiency requirements of phosphorus trifluoride, reduce the occurrence of side reactions, and improve the purity and yield of phosphorus trifluoride.

[0016] In combination with the first aspect, in an optional embodiment of the present application, the method of continuously introducing phosphorus trichloride and the first mixed gas into the reactor comprises:

[0017] A bubbling port is provided at the bottom of the reactor, and phosphorus trichloride with a liquid level higher than the bubbling port is introduced into the reactor in advance; according to the stoichiometric ratio, the first mixed gas is continuously introduced into the reactor through the bubbling port, and phosphorus trichloride is continuously introduced into the reactor at the same time.

[0018] In the above implementation process, phosphorus trichloride with a liquid level higher than the bubbling port is pre-introduced into the reactor, and then the first mixed gas is transported into the reactor through the bubbling port, so that the first mixed gas can make gas-liquid contact with phosphorus trichloride in the form of bubbles, making the contact between the reaction raw materials more sufficient, facilitating the occurrence of metathesis reaction to generate phosphorus trifluoride. Continuously inputting the first mixed gas and phosphorus trichloride according to the stoichiometric ratio can keep the liquid level of phosphorus trichloride in the reactor always above the bubbling port, making the content of the reaction raw materials in the reactor more stable and reducing the occurrence of side reactions.

[0019] Combined with the first aspect, in an optional implementation manner of the present application, in the reactor, the distance between the liquid level of phosphorus trichloride and the bubbling port is 40 mm to 80 mm.

[0020] Optionally, the temperature of the reactor is 40°C to 60°C.

[0021] Optionally, the pressure of the reactor is 5 kPa to 15 kPa.

[0022] In the above implementation process, the distance between the liquid level of phosphorus trichloride and the bubbling port is 40 mm to 80 mm, making the gas-liquid contact between the first mixed gas and phosphorus trichloride more sufficient, and further improving the conversion rate of raw materials. Controlling the temperature of the reactor at 40°C to 60°C can reduce the occurrence probability of side reactions and improve the conversion rate of raw materials.

[0023] Combined with the first aspect, in an optional implementation manner of the present application, in the purification step, the intermediate gas is condensed to -30°C to -10°C to remove the unreacted anhydrous hydrogen fluoride in the intermediate gas, obtaining the second mixed gas. The second mixed gas is condensed to -150°C to -120°C to obtain the first mixed liquid containing phosphorus trifluoride and collect the third mixed gas containing inert gas. The first mixed liquid is subjected to rectification and purification to obtain the phosphorus trifluoride product.

[0024] Optionally, the unreacted anhydrous hydrogen fluoride is refluxed to the reactor.

[0025] Optionally, the third mixed gas is mixed with anhydrous hydrogen fluoride to form the first mixed gas.

[0026] In the above implementation process, since the gas discharged from the reactor will inevitably contain unreacted anhydrous hydrogen fluoride gas, condensing the intermediate gas discharged from the reactor to -30°C to -10°C can condense the unreacted anhydrous hydrogen fluoride in the intermediate gas into a liquid state and reflux it back into the reactor, which can improve the utilization rate of reaction raw materials and reduce production costs. Moreover, condensing the second mixed gas after removing anhydrous hydrogen fluoride by condensation to -150°C to -120°C can condense gases such as phosphorus trifluoride and hydrogen chloride in the second mixed gas into a liquid state to form a first mixed liquid, while the inert gas is in a gaseous state, and thus the inert gas can be separated, so as to remix the inert gas with anhydrous hydrogen fluoride to form a first mixed gas, realizing the reuse of the inert gas and further reducing production costs. Rectifying and purifying the first mixed liquid can obtain a high-purity phosphorus trifluoride product.

[0027] Combined with the first aspect, in an optional implementation manner of the present application, the method for rectifying and purifying includes:

[0028] Feeding the first mixed liquid into a light component removal rectification column, and obtaining a light component removal rectification product enriched with phosphorus trifluoride at the bottom of the light component removal rectification column. Feeding the light component removal rectification product into a heavy component removal rectification column, and enriching and obtaining a phosphorus trifluoride product at the top of the heavy component removal rectification column.

[0029] Optionally, collecting the bottom product of the heavy component removal rectification column, and the bottom product contains hydrogen chloride.

[0030] Combined with the first aspect, in an optional implementation manner of the present application, the top temperature of the light component removal rectification column is -30°C to -26°C, the bottom temperature of the light component removal rectification column is -11°C to -7°C, and the column pressure of the light component removal rectification column is 2.0 MPa to 2.2 MPa. And / or, the top temperature of the heavy component removal rectification column is -34°C to -31°C, the bottom temperature of the heavy component removal rectification column is -13°C to -9°C, and the column pressure of the heavy component removal rectification column is 1.8 MPa to 2.0 MPa.

[0031] In the above implementation process, feeding the first mixed liquid into the light component removal rectification column to remove components with a higher volatility than phosphorus trifluoride and feeding it into the heavy component removal rectification column to remove components with a lower volatility than phosphorus trifluoride can obtain a high-purity electronic-grade phosphorus trifluoride product. Moreover, collecting the bottom product of the heavy component removal rectification column contains relatively high-purity hydrogen chloride, and the bottom product hydrogen chloride can be further rectified and purified to obtain electronic-grade hydrogen chloride, or hydrogen chloride can be mixed with water to form hydrochloric acid as a by-product.

[0032] In combination with the first aspect, in an alternative embodiment of the present application, in the raw material preparation step, industrial-grade anhydrous hydrogen fluoride raw material is introduced into the first rectification column. The temperature at the bottom of the column is 30°C to 50°C, the temperature at the top of the column is -80°C to -75°C, and the pressure inside the column is 5 kPa to 25 kPa to obtain anhydrous hydrogen fluoride with a purity of not less than 99.99%. The anhydrous hydrogen fluoride and the inert gas are introduced into a buffer tank and mixed to form a first mixed gas. And / or, the industrial-grade phosphorus trichloride raw material is introduced into the second rectification column. The pressure inside the column is 1 kPa to 6 kPa, the temperature at the bottom of the column is 81°C to 90°C, the temperature at the top of the column is 76°C to 77°C, and the top of the column is cooled to obtain phosphorus trichloride with a purity of not less than 99.99%.

[0033] In the above implementation process, before introducing phosphorus trichloride and hydrogen fluoride into the reactor for the metathesis reaction, the phosphorus trichloride raw material and the hydrogen fluoride raw material are rectified and purified first, which can further improve the purity of phosphorus trifluoride.

[0034] In the second aspect, an example of the present application provides a production system for the preparation method provided in the first aspect, including an anhydrous hydrogen fluoride gas supply unit, an inert gas supply unit, a phosphorus trichloride liquid supply unit, a buffer tank, a reactor, and a rectification column. The buffer tank has a first air inlet, a second air inlet, and a first mixed gas exhaust port. The anhydrous hydrogen fluoride gas supply unit is connected to the first air inlet, and the inert gas supply unit is connected to the second air inlet. The reactor is provided with a liquid inlet, a bubbling port at the bottom, and a second exhaust port at the top. The first mixed gas exhaust port is connected to the bubbling port. The phosphorus trichloride liquid supply unit is connected to the liquid inlet. The feed port of the rectification column is connected to the second exhaust port.

[0035] In the above implementation process, when producing phosphorus trifluoride using the production system provided in the embodiment of the present application, one of the reaction raw materials, anhydrous hydrogen fluoride, can be transported from the first air inlet to the buffer tank, and the inert gas in the inert gas supply unit can be transported into the buffer tank through the second air inlet, so that the anhydrous hydrogen fluoride and the inert gas are mixed evenly in the buffer tank to form a first mixed gas. And the first mixed gas is transported from the bubbling port of the reactor into the reactor, and at the same time, the phosphorus trichloride in the phosphorus trichloride liquid supply unit is transported into the reactor from the liquid inlet, so that the anhydrous hydrogen fluoride and the phosphorus trichloride are in gas-liquid contact to undergo a metathesis reaction to generate an intermediate gas containing phosphorus trifluoride. Then the intermediate gas discharged from the reactor is transported to the rectification column, and the phosphorus trifluoride can be rectified and purified to obtain a high-purity phosphorus trifluoride product.

[0036] Using the production system provided in the embodiment of the present application, the inert gas in the first mixed gas carries anhydrous hydrogen fluoride and phosphorus trichloride to undergo a double decomposition reaction to generate phosphorus trifluoride. In the first aspect, the inert gas will dilute the concentration of the raw material gas anhydrous hydrogen fluoride participating in the reaction, which can reduce the reaction rate of anhydrous hydrogen fluoride and phosphorus trichloride, reduce the reaction heat in the reactor, and is conducive to the temperature stability in the reactor. In the second aspect, the inert gas will take away the heat generated by the reaction, making the reaction temperature more stable, reducing the occurrence of side reactions, and thus realizing the continuous production of phosphorus trifluoride.

[0037] In conjunction with the second aspect, in an optional embodiment of the present application, a condenser is provided at the top of the reactor for condensing unreacted anhydrous hydrogen fluoride. The third air inlet of the condenser is connected to the second exhaust port, and the third exhaust port of the condenser is connected to the feed port of the distillation tower. The distillation tower includes a light removal distillation tower and a heavy removal distillation tower, the second exhaust port is connected to the first feed port of the light removal distillation tower, the first tower reactor discharge port of the light removal distillation tower is connected to the second feed port of the heavy removal distillation tower, and the second tower top discharge port of the heavy removal distillation tower is used to discharge the phosphorus trifluoride product.

[0038] Optionally, a cold trap is provided between the second exhaust port and the light-removing distillation tower for separating the inert gas in the second mixed gas discharged from the second exhaust port and conveying the condensed first mixed liquid to the first feed port of the light-removing distillation tower.

[0039] Optionally, the production system further comprises an alkali solution circulation spraying device. The first tower top discharge port of the light removal distillation tower is connected to the alkali solution circulation spraying device.

[0040] In the above-mentioned implementation process, the top of the reactor provided by the embodiment of the present application is provided with a condenser, and the condenser can condense the intermediate gas, so that the unreacted anhydrous hydrogen fluoride is condensed into a liquid state and refluxed into the reactor, and the double decomposition reaction is continued to improve the utilization rate of the reaction raw materials. In addition, the uncondensed second mixed gas in the condenser is transported to the cold trap for condensation, and the gases such as phosphorus trifluoride and hydrogen chloride in the second mixed gas can be condensed into a liquid state, and the inert gas is in a gaseous state, and then the inert gas can be separated, and the separated inert gas is transported to the buffer tank for recycling. The first mixed liquid formed after the cold trap condensation is transported to the light removal distillation tower, and the components with lower boiling points than phosphorus trifluoride can be removed. Then it is transported to the heavy removal distillation tower, and the components with higher boiling points than phosphorus trifluoride can be removed, so that a high-purity phosphorus trifluoride product can be obtained. In addition, the first top discharge port of the light removal distillation tower is connected to the alkali liquid circulation spraying device, and the alkali liquid can be used to absorb the fluorine-containing gas in the tail gas, and then the tail gas after the absorption treatment can be emptied. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0042] Figure 1 Process flow chart for the preparation of phosphorus trifluoride provided by the embodiment of the present application;

[0043] Figure 2 Planar schematic diagram of the production system provided by the embodiment of the present application.

[0044] Icons: 100 - production system; 1 - anhydrous hydrogen fluoride supply unit; 2 - inert gas supply unit; 3 - phosphorus trichloride liquid supply unit; 4 - buffer tank; 41 - first air inlet; 42 - second air inlet; 43 - first mixed gas exhaust port; 5 - reactor; 51 - bubbling port; 52 - liquid inlet; 53 - second exhaust port; 6 - distillation column; 61 - light component removal distillation column; 611 - first feed port; 612 - first top discharge port; 613 - first bottom discharge port; 62 - heavy component removal distillation column; 621 - second feed port; 622 - second top discharge port; 623 - second bottom discharge port; 7 - condenser; 71 - third air inlet; 72 - third exhaust port; 8 - cold trap; 81 - fourth air inlet; 82 - fourth exhaust port; 83 - first liquid discharge port; 9 - heat exchanger; 10 - alkali liquor circulating spraying device; 11 - storage tank; 12 - first distillation column; 13 - second distillation column. Specific embodiments

[0045] The following will describe the implementation schemes of the present application in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0046] Phosphorus trifluoride is widely used in industries such as lithium batteries and semiconductors. At present, there are few methods for producing phosphorus trifluoride. Industrially, phosphorus trifluoride is basically produced using phosphorus trichloride and anhydrous hydrogen fluoride as raw materials. However, due to factors such as the relatively fast reaction rate, large heat release during the reaction, and the need to maintain the reaction temperature at 40°C - 60°C to reduce side reactions, only batch production can be carried out at present.

[0047] For example, Patent CN117228643A discloses a method for preparing electronic-grade phosphorus trifluoride. After introducing a certain amount of phosphorus trichloride into the reaction flask, a quantitative amount of anhydrous hydrogen fluoride is slowly introduced into the reaction flask, and after the reaction is completed, it is condensed and collected. This production process is a batch operation, with low production efficiency and unable to achieve continuous production.

[0048] At present, in order to improve the problems of large reaction heat release and low conversion rate, the refrigeration efficiency of the reaction equipment is usually improved. For example, patent CN119098126A discloses a preparation device and preparation method of high-purity phosphorus trifluoride, which realizes the continuous and stable double decomposition reaction by designing a microchannel reactor with excellent airtightness and heat dissipation. However, since the microchannel reactor is produced by 3D printing, the industrialization cost is relatively high, and it is difficult to achieve industrial production.

[0049] Therefore, there is an urgent need to develop a method and production system for continuously preparing phosphorus trifluoride with simple process, safe and controllable, low cost and high product purity.

[0050] In a first aspect, the present application provides a method for preparing phosphorus trifluoride, comprising:

[0051] S1. Raw material preparation step: phosphorus trichloride and a first mixed gas are obtained respectively, wherein the first mixed gas contains anhydrous hydrogen fluoride and an inert gas.

[0052] S2, double decomposition reaction step: phosphorus trichloride and the first mixed gas are continuously introduced into the reactor, so that phosphorus trichloride and anhydrous hydrogen fluoride undergo double decomposition reaction in the reactor to generate an intermediate gas containing phosphorus trifluoride. The intermediate gas discharged from the reactor is collected.

[0053] S3, purification step: distill and purify the intermediate gas to obtain phosphorus trifluoride product.

[0054] According to the preparation method provided in the embodiment of the present application, anhydrous hydrogen fluoride is carried by the inert gas in the first mixed gas to undergo a double decomposition reaction with phosphorus trichloride to generate phosphorus trifluoride. In the first aspect, the inert gas will dilute the concentration of the raw gas anhydrous hydrogen fluoride participating in the reaction, which can reduce the reaction rate of anhydrous hydrogen fluoride and phosphorus trichloride, reduce the reaction heat in the reactor, and is conducive to the temperature stability in the reactor. In the second aspect, the inert gas will take away the heat generated by the reaction, making the reaction temperature more stable, and can reduce the probability of side reactions, thereby realizing continuous production of phosphorus trifluoride. The inert gas has the characteristics of high stability and low reactivity, and basically will not have side reactions with the reaction system in the reactor. The intermediate gas after the reaction is distilled and purified to obtain a high-purity phosphorus trifluoride product.

[0055] In step S1, anhydrous hydrogen fluoride does not mean that the water content is 0% in an absolute sense, and anhydrous hydrogen fluoride refers to industrial high-purity anhydrous hydrogen fluoride.

[0056] In order to reduce the impurities in the reaction raw material anhydrous hydrogen fluoride and improve the purity of the phosphorus trifluoride product obtained by the reaction, in some embodiments, the anhydrous hydrogen fluoride can be distilled and purified to remove oxygen, nitrogen or a small amount of solid impurities in the industrial grade anhydrous hydrogen fluoride.

[0057] As an example, industrial-grade anhydrous hydrogen fluoride raw material is introduced into a rectification column. The temperature of the column kettle of the rectification column is set to 30°C to 50°C, the temperature of the top of the column is set to -80°C to -75°C, and the pressure inside the column is set to 5 kPa to 25 kPa, to obtain high-purity anhydrous hydrogen fluoride with a purity of not less than 99.99%.

[0058] As an example, when rectifying and purifying industrial-grade anhydrous hydrogen fluoride raw material, the temperature of the column kettle of the rectification column can be set to one of 30°C, 35°C, 40°C, 45°C or 50°C or a range between any two of them, the temperature of the top of the column can be set to one of -80°C, -79°C, -78°C, -77°C, -76°C or -75°C or a range between any two of them, and the pressure inside the column can be set to one of 5 kPa, 10 kPa, 15 kPa, 20 kPa or 25 kPa or a range between any two of them.

[0059] As an example, anhydrous hydrogen fluoride with a purity of 98.5% to 99.9% is introduced into a rectification column. The heating temperature of the rectification column is 30°C, the condenser temperature is -78°C, the condensing medium is carbon tetrafluoride, uncondensed oxygen and nitrogen are discharged from the gas outlet at the top of the column, and the rectification column is used to remove oxygen, nitrogen and a small amount of solid impurities in the raw material, to obtain anhydrous hydrogen fluoride with a purity of 99.993%.

[0060] In step S1, the high-purity anhydrous hydrogen fluoride after the above rectification and purification can be mixed with an inert gas to form a first mixed gas.

[0061] In order to further improve the conversion rate and production rate, in some embodiments, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to the inert gas is 1:40 to 120. Mixing anhydrous hydrogen fluoride and the inert gas according to the above volume ratio to form the first mixed gas can better balance the requirements of continuous production and the preparation efficiency requirements of phosphorus trifluoride, reduce the occurrence of side reactions, and improve the purity of phosphorus trifluoride.

[0062] As an example, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to the inert gas can be one of 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110 or 1:120 or a range between any two of them.

[0063] As an example, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to inert gas can be 1:50 to 110. Or, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to inert gas can be 1:60 to 100. Or, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to inert gas can be 1:60 to 90. Or, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to inert gas can be 1:60 to 80. Or, in the first mixed gas, the volume ratio of anhydrous hydrogen fluoride to inert gas can be 1:60 to 70.

[0064] The inert gas has the characteristics of high stability and low reactivity, and basically does not react with reaction raw materials, products, by-products, etc. in the reactor, which can ensure the stability of the reaction system and improve the purity of the phosphorus trifluoride product.

[0065] This application does not limit the specific type of inert gas, and those skilled in the art can make a conventional selection from conventional inert gases. As an example, the inert gas can be at least one of nitrogen or argon.

[0066] In step S1, the industrial-grade phosphorus trichloride raw material can be rectified and purified to obtain high-purity phosphorus trichloride.

[0067] As an example, the industrial-grade phosphorus trichloride raw material is introduced into the rectification column, and the pressure inside the rectification column is controlled to be 1 kPa to 6 kPa, the temperature at the bottom of the column is 81°C to 90°C, the temperature at the top of the column is 76°C to 77°C, and phosphorus trichloride with a purity of not less than 99.99% is obtained by cooling at the top of the column.

[0068] As an example, when rectifying and purifying industrial-grade phosphorus trichloride, the temperature at the bottom of the rectification column can be set to one of 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C or the range between any two of them, the temperature at the top of the column can be set to one of 76°C or 77°C or any range between the two, and the pressure inside the column can be set to one of 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, or 6 kPa or the range between any two of them.

[0069] As an example, the phosphorus trichloride raw material with a purity of 98.5% to 99.9% is introduced into the rectification column, the pressure inside the rectification column is controlled to be 4 kPa, after the system is stable, the temperature at the bottom of the column is 84°C, the temperature at the top of the column is 76°C, impurities such as phosphoric acid and phosphorous acid in the raw material are removed at the bottom of the column, and high-purity phosphorus trichloride liquid is obtained by cooling at the top of the column. After inspection, the purity is 99.992%.

[0070] In step S2, before inputting the reaction raw materials into the reactor, the airtightness of the reactor can be detected and water can be removed first.

[0071] During airtightness detection, the entire system including the reactor can be evacuated, and then high-purity inert gas is filled into the reactor until the pressure reaches 1.0 MPa to 2.5 MPa. After the reactor is sealed and maintained for 24 to 36 hours, if the pressure change range is less than 2% to 6%, the tightness is qualified.

[0072] During water removal, the entire system including the reactor is decomposed by high-purity inert gas to remove the moisture in the reactor until the dew point temperature of the exhaust gas detected by a dew point meter is below -65°C.

[0073] The high-purity inert gas can be high-purity nitrogen or high-purity argon. As an example, in high-purity nitrogen, the content of nitrogen is greater than or equal to 99.999%, the content of water is less than or equal to 1 ppm, and the content of oxygen is less than or equal to 0.5 ppm.

[0074] In step S2, the phosphorus trichloride and the first mixed gas obtained in step S1 are continuously introduced into the reactor, and an intermediate gas containing phosphorus trifluoride can be continuously generated in the reactor. It can be understood that continuously inputting phosphorus trichloride and the first mixed gas into the reactor requires continuously discharging the intermediate gas from the reactor.

[0075] In step S2, the temperature of the reactor can be set to 40°C to 60°C to reduce the occurrence of side reactions and improve the conversion rate of raw materials. Since in this application, anhydrous hydrogen fluoride is carried by an inert gas to react with phosphorus trichloride through a metathesis reaction to generate phosphorus trifluoride, the inert gas can dilute the anhydrous hydrogen fluoride and take away the heat in the reactor, thereby maintaining the temperature in the reactor at 40°C to 60°C, and then improving the conversion rate of raw materials.

[0076] The chemical reaction formula for the metathesis reaction between hydrogen fluoride and phosphorus trichloride is as follows:

[0077] PCl3 + 3HF → 3HCl + PF3

[0078] It can be understood that the anhydrous hydrogen fluoride and phosphorus trichloride liquids transported into the reactor need to be in full contact to undergo a metathesis reaction to generate phosphorus trifluoride.

[0079] This application does not limit how to transport the first mixed gas and phosphorus trichloride liquid into the reactor to make the anhydrous hydrogen fluoride gas in the first mixed gas contact with the phosphorus trichloride liquid. In some embodiments, a bubbling port can be provided at the bottom of the reactor, and phosphorus trichloride liquid with a liquid level higher than the bubbling port is pre-introduced into the reactor. Then, according to the stoichiometric ratio, the first mixed gas is continuously input into the reactor through the bubbling port, and phosphorus trichloride is continuously input into the reactor at the same time.

[0080] Therefore, the first mixed gas will undergo gas-liquid contact with the phosphorus trichloride liquid in the reactor by bubbling. Since the first mixed gas is continuously introduced into the reactor, the first mixed gas will consume the phosphorus trichloride liquid in the reactor. If phosphorus trichloride is not continuously replenished according to the stoichiometric ratio, the reaction will be interrupted.

[0081] In some embodiments, the distance between the liquid level of the pre-introduced phosphorus trichloride in the reactor and the bubbling port is 40 mm to 80 mm.

[0082] As an example, the distance between the liquid level of the phosphorus trichloride and the bubbling port can be 40 mm, 50 mm, 60 mm, 70 mm, or 80 mm, or any range between any two of them.

[0083] As an example, the distance between the liquid level of the pre-introduced phosphorus trichloride in the reactor and the bubbling port is 40 mm to 60 mm.

[0084] The input amount of the phosphorus trichloride liquid can be adjusted according to the input amount of the first mixed gas, so that the input amount of the phosphorus trichloride and the input amount of the anhydrous hydrogen fluoride in the first mixed gas satisfy the stoichiometric ratio of 1:3.

[0085] Alternatively, due to the limited contact degree between the first mixed gas and the phosphorus trichloride, there will inevitably be some unreacted anhydrous hydrogen fluoride in the intermediate gas discharged from the reactor. Therefore, the input amount of the first mixed gas can be appropriately increased so that the input amount of the phosphorus trichloride and the input amount of the anhydrous hydrogen fluoride in the first mixed gas satisfy the stoichiometric ratio of 1:3 to 3.3 to improve the preparation efficiency of phosphorus trifluoride.

[0086] In some other embodiments, in order to enable the first mixed gas introduced into the reactor to undergo gas-liquid contact with the phosphorus trichloride, the first mixed gas can be input from the bottom of the reactor and the phosphorus trichloride liquid can be sprayed from the top of the reactor by spraying.

[0087] In step S3, the intermediate gas containing phosphorus trifluoride discharged from the reactor is collected, and the phosphorus trifluoride in the intermediate gas is rectified and purified to obtain a phosphorus trifluoride product.

[0088] In some embodiments, since there will inevitably be some unreacted anhydrous hydrogen fluoride in the intermediate gas, in order to improve the utilization rate of the reaction raw materials, in some embodiments, the intermediate gas can be condensed, and the condensation temperature is -30°C to -10°C, so that the unreacted anhydrous hydrogen fluoride is condensed into a liquid and refluxed to the reactor.

[0089] Then, the uncondensed second mixed gas containing phosphorus trifluoride is condensed again at a condensation temperature of -150°C to -120°C, so that phosphorus trifluoride, hydrogen chloride, etc. in the second mixed gas are condensed into a liquid state, and the inert gas in the second mixed gas remains in a gaseous state. Then, through gas-liquid separation, a first mixed liquid and a third mixed gas containing inert gas can be obtained respectively.

[0090] Separating the inert gas from phosphorus trifluoride can not only improve the purity of the phosphorus trifluoride product, but also reuse the third mixed gas containing inert gas. The third mixed gas is mixed with anhydrous hydrogen fluoride to form a first mixed gas.

[0091] The first liquid mixture usually contains phosphorus trifluoride, hydrogen chloride, hydrogen, oxygen, carbon monoxide, etc. The volatility of components such as hydrogen is higher than that of phosphorus trifluoride, and the volatility of phosphorus trifluoride is higher than that of hydrogen chloride. The difference in volatility can be utilized to obtain a high-purity phosphorus trifluoride product through rectification separation.

[0092] In some embodiments, when rectifying and purifying the first mixed liquid, the first mixed liquid can be first input into a light-component removal rectification column. In the light-component removal rectification column, components with a volatility higher than that of phosphorus trifluoride can be removed from the top of the column, and a light-component removal rectification product enriched in phosphorus trifluoride can be obtained at the bottom of the column.

[0093] As an example, when performing light-component removal rectification on the first mixed liquid, the top temperature of the light-component removal rectification column is -30°C to -26°C, the bottom temperature of the light-component removal rectification column is -11°C to -7°C, and the column pressure of the light-component removal rectification column is 2.0 MPa to 2.2 MPa.

[0094] As an example, when performing light-component removal rectification on the first mixed liquid, the bottom temperature of the light-component removal rectification column can be set to one of -11°C, -10°C, -9°C, -8°C, or -7°C or the range between any two of them, the top temperature can be set to one of -30°C, -29°C, -28°C, -27°C, or -26°C or any range between two of them, and the internal pressure of the column can be set to one of 2.0 MPa, 2.1 MPa, or 2.2 MPa or the range between any two of them.

[0095] As an example, the first mixed liquid can enter the light-component removal rectification column through a spiral centrifugal pump from the separator in the cold trap for light-component removal. During light-component removal rectification, the crude phosphorus trifluoride separated by the cold trap separator is sent into the light-component removal rectification column through a vacuum pump, heating and cooling are started, the heating method is electric heating, and the cooling method is deep cooling with a -45°C ice machine oil, so that the system is in a pressurized state, the internal pressure of the column is controlled at 2.2 MPa, the top temperature is -26°C, the bottom temperature is -9°C, the gas phase at the top is taken out for tail gas treatment, and the light-component removal rectification product enriched in phosphorus trifluoride is taken out from the bottom of the light-component removal rectification column.

[0096] In some embodiments, the gas at the top of the light component removal rectification column can be introduced into the alkali liquor circulating spray device to absorb and treat tail gases containing fluorine and the like.

[0097] Furthermore, when performing vacuum metathesis on the reactor, the tail gas extracted from the reactor can also be introduced into the alkali liquor circulating spray device for tail gas absorption.

[0098] In some embodiments, the light component removal rectification product of phosphorus trifluoride enriched at the bottom of the light component removal rectification column can be introduced into the heavy component removal rectification column, and a phosphorus trifluoride product enriched in phosphorus trifluoride can be obtained from the top of the heavy component removal rectification column.

[0099] As an example, when performing heavy component removal rectification on the light component removal rectification product of phosphorus trifluoride, the top temperature of the heavy component removal rectification column can be set to -34°C to -31°C, the bottom temperature of the heavy component removal rectification column can be set to -13°C to -9°C, and the column pressure of the heavy component removal rectification column can be set to 1.8 MPa to 2.0 MPa.

[0100] As an example, when performing heavy component removal rectification on the light component removal rectification product of phosphorus trifluoride, the top temperature of the heavy component removal rectification column can be set to one of -34°C, -33°C, -32°C, or -31°C or the range between any two of them, the bottom temperature can be set to one of -13°C, -12°C, -11°C, -10°C, or -9°C or any range between two of them, and the internal pressure of the column can be set to one of 1.8 MPa, 1.9 MPa, or 2.0 MPa or the range between any two of them.

[0101] As an example, the light component removal rectification product of phosphorus trifluoride taken out from the bottom of the light component removal rectification column is input into the heavy component removal rectification column, the heating and condensation of the heavy component removal rectification column are started, the heating method is electric heating, the cooling method is deep cooling with an ice machine at -45°C, the system is in a pressurized state, the internal pressure of the column is controlled at 2.0 MPa, the top temperature is -31°C, and the bottom temperature is -9°C. After purification, the phosphorus trifluoride enriched at the top is condensed to -35°C by a condenser, partially refluxed, and the high-purity phosphorus trifluoride product taken out from the top liquid phase is cooled by an ice machine with deep cooling oil (-45°C) and then sent to the product intermediate tank for storage. After inspection, the purity of the high-purity phosphorus trifluoride is 99.95%, meeting the use standard for electronic grade.

[0102] The bottom discharge of the heavy component removal rectification column is mainly hydrogen chloride. Furthermore, in some embodiments, the bottom product of the heavy component removal rectification column can be further purified into electronic grade hydrogen chloride or mixed with water to form hydrochloric acid as a by-product.

[0103] In some embodiments, please refer to Figure 1, when continuously preparing phosphorus trifluoride, hydrogen fluoride can be rectified to obtain high-purity anhydrous hydrogen fluoride. Then, the high-purity anhydrous hydrogen fluoride is mixed with an inert gas to form a first mixed gas. At the same time, phosphorus trichloride is rectified to obtain high-purity phosphorus trichloride. The first mixed gas and the high-purity phosphorus trichloride are simultaneously introduced into a reactor equipped with a condenser for a metathesis reaction, and then the second mixed gas after the metathesis reaction is introduced into a cold trap for condensation and gas-liquid separation. The separated third mixed gas rich in inert gas is heat-exchanged through a heat exchanger and then transported back to the mixing zone to be mixed with the high-purity anhydrous hydrogen fluoride again. At the same time, the first mixed liquid separated at the cold trap is transported to a rectification column for rectification to obtain electronic-grade phosphorus trifluoride with a purity of not less than 99.9%.

[0104] In a second aspect, an embodiment of the present application provides a production system 100, including an anhydrous hydrogen fluoride supply unit 1, an inert gas supply unit 2, a phosphorus trichloride liquid supply unit 3, a buffer tank 4, a reactor 5, and a rectification column 6.

[0105] Among them, the buffer tank 4 has a first air inlet 41, a second air inlet 42, and a first mixed gas exhaust port 43. The anhydrous hydrogen fluoride supply unit 1 is connected to the first air inlet 41, and the inert gas supply unit 2 is connected to the second air inlet 42. The reactor 5 is provided with a liquid inlet 52, a bubbling port 51 at the bottom, and a second exhaust port 53 at the top. The first mixed gas exhaust port 43 is connected to the bubbling port 51, and the phosphorus trichloride liquid supply unit 3 is connected to the liquid inlet 52. The feed port of the rectification column 6 is connected to the second exhaust port 53.

[0106] As an example, please continue to refer to Figure 2 , an inlet pipe can be extended from the top of the reactor 5 into the position near the bottom inside the reactor 5 to form the bubbling port 51.

[0107] Furthermore, in some embodiments, a condenser 7 is provided at the top of the reactor 5. The third air inlet 71 of the condenser 7 is connected to the second exhaust port 53, and the third exhaust port 72 of the condenser 7 is connected to the feed port of the rectification column 6. By providing the condenser 7 at the top of the reactor 5, the intermediate gas discharged from the reactor 5 can be condensed, and the unreacted anhydrous hydrogen fluoride can be condensed into a liquid and refluxed into the reactor 5.

[0108] Furthermore, in some embodiments, a cold trap 8 containing a separator is further provided at the rear end of the condenser 7. The fourth air inlet 81 of the cold trap 8 is connected to the third exhaust port 72 of the condenser 7, the fourth exhaust port 82 of the cold trap 8 is connected to the second air inlet 42 of the buffer tank 4 through a heat exchanger 9, and the first liquid discharge port 83 of the cold trap 8 is connected to the feed port of the rectification column 6. By providing the cold trap 8 as a separator between the condenser 7 and the rectification column 6, the inert gas can be separated, and thus partial recycling of the inert gas can be achieved, reducing the production cost.

[0109] Further, in some embodiments, the distillation tower 6 includes a light removal distillation tower 61 and a heavy removal distillation tower 62. The first feed port 611 of the light removal distillation tower 61 is connected to the first drain port 83 of the cold trap 8, the first tower top discharge port 612 of the light removal distillation tower 61 is connected to the alkali liquid circulation spray device 10, and the first tower bottom discharge port 613 of the light removal distillation tower 61 is connected to the second feed port 621 of the heavy removal distillation tower 62. The second tower top discharge port 622 of the heavy removal distillation tower 62 is used to discharge the phosphorus trifluoride product, and the second tower bottom discharge port 623 of the heavy removal distillation tower 62 is used to discharge the tower bottom material enriched with hydrogen chloride.

[0110] As an example, a storage tank 11 may be provided at the rear end of the de-heavy distillation tower 62 for storing phosphorus trifluoride products.

[0111] Furthermore, in some embodiments, a first distillation tower 12 may be provided between the anhydrous hydrogen fluoride gas supply unit 1 and the buffer tank 4 to distill and purify the anhydrous hydrogen fluoride outputted from the anhydrous hydrogen fluoride gas supply unit 1 , and then deliver the high-purity anhydrous hydrogen fluoride after distillation and purification to the buffer tank 4 .

[0112] Furthermore, in some embodiments, a second distillation tower 13 may be provided between the phosphorus trichloride liquid supply unit 3 and the reactor 5 for distilling and purifying the phosphorus trichloride output from the phosphorus trichloride liquid supply unit 3 and then delivering the purified high-purity phosphorus trichloride to the reactor 5 .

[0113] The present application does not limit the above specific connection mode. It is understandable that two adjacent interfaces can be connected through a pipeline, and a corresponding switch valve is arranged at the pipeline. In order to facilitate the transportation of materials, a delivery pump can also be arranged at the pipeline.

[0114] The present application does not limit the specific type of the alkali liquid circulation spraying device 10. As an example, the alkali liquid circulation spraying device 10 may include an absorption tower, a alkali liquid spray pipe is arranged at the top of the absorption tower, a tail gas inlet is arranged at the bottom of the absorption tower, a tail gas exhaust port is arranged at the top of the absorption tower, and a circulation pump draws the alkali liquid at the bottom of the tower to the alkali liquid spray pipe.

[0115] When the phosphorus trifluoride product is produced by using the above production system 100, the anhydrous hydrogen fluoride in the anhydrous hydrogen fluoride supply unit 1 can be transported to the first distillation tower 12 through a pipeline for distillation and purification to obtain high-purity anhydrous hydrogen fluoride with a purity of not less than 99.99%. Then, the high-purity anhydrous hydrogen fluoride is transported to the buffer tank 4, and at the same time, the inert gas in the inert gas supply unit 2 is transported to the buffer tank 4 through a pipeline, so that the anhydrous hydrogen fluoride and the inert gas are mixed according to a set volume ratio to form a first mixed gas.

[0116] Meanwhile, phosphorus trichloride in the phosphorus trichloride feeding unit 3 is transported to the second rectification column 13 through a pipeline for rectification and purification to obtain high-purity phosphorus trichloride with a purity of not less than 99.99%.

[0117] The reactor 5 is evacuated and then filled with nitrogen for gas metathesis. Then, high-purity phosphorus trichloride is pre-fed into the reactor 5 through a pipeline, so that the liquid level of phosphorus trichloride in the reactor 5 is higher than the bubbling port 51 by a certain height.

[0118] Then, the temperature of the reactor 5 is adjusted to 40-60°C. Next, the first mixed gas and phosphorus trichloride are continuously fed into the reactor 5 at the same time. The first mixed gas is in gas-liquid contact with the phosphorus trichloride liquid in a bubbling manner, and a metathesis reaction occurs.

[0119] The second exhaust port 53 of the reactor 5 continuously discharges the intermediate gas containing phosphorus trifluoride. The intermediate gas is transported to the condenser 7 through a pipeline. The condensation temperature of the condenser 7 is set to -30°C to -10°C, and the unreacted anhydrous hydrogen fluoride in the intermediate gas is condensed into a liquid and refluxed into the reactor 5. The second mixed gas containing phosphorus trifluoride that is not condensed in the condenser 7 is transported to the cold trap 8 containing a separator through a pipeline. The condensation temperature of the cold trap 8 is set to -150°C to -120°C, and the second mixed gas is condensed and separated into gas and liquid. The third mixed gas rich in inert gas is discharged from the fourth exhaust port 82 of the cold trap 8, and the first mixed liquid containing phosphorus trifluoride is discharged from the first drain port 83 of the cold trap 8.

[0120] The third mixed gas rich in inert gas is transported to the heat exchanger 9 through a pipeline for heat exchange, and then transported to the buffer tank 4 through a pipeline.

[0121] The first mixed liquid containing phosphorus trifluoride enters the light-component removal rectification column 61 through the first feed port 611. The top temperature of the light-component removal rectification column 61 is set to -30°C to -26°C, the bottom temperature is set to -11°C to -7°C, and the tower pressure is set to 2.0 MPa to 2.2 MPa. After light-component removal rectification, the components with a higher volatility than phosphorus trifluoride are discharged from the first top discharge port 612, and the light-component removal rectification product enriched in phosphorus trifluoride is discharged from the first bottom discharge port 613.

[0122] The mixed gas discharged from the first top discharge port 612 is transported to the alkali liquor circulating spray device 10 through a pipeline for absorption treatment and then discharged into the atmospheric environment.

[0123] The de-light rectification product enriched with phosphorus trifluoride discharged from the first bottom discharge port 613 enters the de-heavy rectification column 62 through a pipeline from the second feed port 621. The top temperature of the de-heavy rectification column 62 is set at -34°C to -31°C, the bottom temperature is -13°C to -9°C, and the tower pressure is 1.8 MPa to 2.0 MPa. After de-heavy rectification, high-purity phosphorus trifluoride product is discharged from the second top discharge port 622, and the bottom material enriched with hydrogen chloride is discharged from the second bottom discharge port 623.

[0124] The high-purity phosphorus trifluoride product discharged from the second top discharge port 622 can be transported through a pipeline to the storage tank 11 for storage. The bottom material enriched with hydrogen chloride discharged from the second bottom discharge port 623 can be rectified and purified into electronic-grade hydrogen chloride or mixed with water to become hydrochloric acid as a by-product.

[0125] The preparation method of phosphorus trifluoride of the present application will be further described in detail below in conjunction with embodiments.

[0126] Example 1

[0127] Example 1 provides a continuous preparation method of phosphorus trifluoride, using the Figure 1 production system shown, and the preparation method is as follows:

[0128] (1) Pretreatment of the system

[0129] Air tightness test: After the whole system is evacuated and filled with high-purity inert gas until the pressure is 1.0 MPa to 2.5 MPa, and the system is kept airtight for 24 - 36 hours, if the pressure change range is less than 2% - 6%, the airtightness of the system is qualified.

[0130] Water removal: The whole system is subjected to metathesis through high-purity inert gas to remove the moisture in the system until the dew point temperature of the exhaust gas detected by a dew point meter is below -65°C.

[0131] (2) Purification of raw materials

[0132] Purification of phosphorus trichloride: The raw material of phosphorus trichloride with a purity of 98.5% - 99.9% is introduced into the second rectification column 13, the pressure inside the column is controlled at 4 kPa, after the system is stable, the bottom temperature is 84°C, the top temperature is 76°C, impurities such as phosphoric acid and phosphorous acid in the raw material are withdrawn from the bottom, and high-purity phosphorus trichloride liquid is obtained by cooling at the top. After inspection, the purity is 99.992%.

[0133] Purification of anhydrous hydrogen fluoride: Feed the anhydrous hydrogen fluoride raw material with a purity of 98.5% - 99.9% into the first distillation column 12. Control the pressure inside the column at 5 kPa, the heating temperature at 30 °C, the condensation temperature at -78 °C, and the condensation medium as carbon tetrafluoride. The uncondensed oxygen and nitrogen enter the alkaline solution circulating spray device 10 through the gas-phase outlet at the top of the column for tail gas treatment. Use the first distillation column 12 to remove oxygen, nitrogen, and a small amount of solid impurities from the raw material to obtain anhydrous hydrogen fluoride with a purity of 99.993%, and feed it into the buffer tank 4.

[0134] Preparation of the first mixed gas: Feed an inert gas into the buffer tank 4 to mix anhydrous hydrogen fluoride and the inert gas in a volume ratio of 1:80 to form the first mixed gas. Control the temperature of the first mixed gas at about 25 °C. The inert gas is nitrogen.

[0135] (3) Double decomposition reaction

[0136] Pre-feed high-purity phosphorus trichloride into the reactor 5 until the liquid level is higher than the bubbling port 51 inside the reactor 5. The height difference between the liquid level of phosphorus trichloride and the bubbling port 51 is 60 mm. According to the molar ratio of high-purity phosphorus trichloride to high-purity anhydrous hydrogen fluoride in the first mixed gas being 1:3, continuously feed a certain amount of high-purity phosphorus trichloride liquid and the first mixed gas into the reactor 5 to carry out the double decomposition reaction. Control the reaction temperature inside the reactor 5 at 50 °C - 60 °C. The intermediate gas mainly composed of phosphorus trifluoride, anhydrous hydrogen fluoride, hydrogen chloride, and nitrogen is obtained through the reaction.

[0137] Condense the unreacted anhydrous hydrogen fluoride in the intermediate gas through the condenser 7 above the reactor 5. The condensation temperature is -30 °C, and it flows back to the reactor 5 to further react with high-purity phosphorus trichloride to improve the raw material utilization rate and obtain the second mixed gas. The second mixed gas is then separated by a separator cooled by a low-temperature cold trap 8 to condense phosphorus trifluoride and hydrogen chloride into a first mixed liquid and separate it from the inert gas nitrogen. The condensation temperature is -150 °C. Nitrogen can be heat-exchanged through the heat exchanger 9 and mixed with anhydrous hydrogen fluoride in the buffer tank 4 in the above ratio to form the first mixed gas.

[0138] (4) Purification of the primary product

[0139] Light component removal by distillation: The first mixed liquid enters the light component removal distillation column 61 through a screw centrifugal pump from the separator at the cold trap 8 for light component removal. Turn on heating and cooling. The heating method is electric heating, and the cooling method is deep cooling with an ice machine at -45 °C to make the system in a pressurized state. Control the pressure inside the column at 2.2 MPa, the temperature at the top of the column at -26 °C, and the temperature at the bottom at -9 °C. The gas phase at the top of the condenser is taken out through the first top discharge port 612 of the column and transported to the alkaline solution circulating spray device 10 for tail gas treatment. The light component removal distillation product enriched with phosphorus trifluoride is taken out from the first bottom discharge port 613 of the light component removal distillation column 61.

[0140] Rectification for removing heavy components: The light-component-removed rectification product enriched in phosphorus trifluoride enters the heavy-component-removing rectification column 62. Heating and condensation are started. The heating method is electric heating, and the cooling method is deep cooling with an ice machine at -45°C with oil as the coolant, so that the system is in a pressurized state. The pressure inside the column is controlled at 2.0 MPa, the temperature at the top of the column is -31°C, and the temperature at the bottom of the column is -9°C. After purification, the high-purity phosphorus trifluoride product taken out from the second top discharge port 622 is cooled by deep cooling with an ice machine at -45°C with oil as the coolant and then sent to the product storage tank 11 for storage, and is transported to the off-site filling system as needed. After inspection, the purity of the high-purity phosphorus trifluoride is 99.95%. The discharge from the second bottom discharge port 623 of the heavy-component-removing rectification column is mainly hydrogen chloride, which can be further purified into electronic-grade hydrogen chloride or mixed with water to form hydrochloric acid as a by-product. The conversion rate of the raw materials is equal to the stoichiometric ratio of the obtained phosphorus trifluoride divided by the stoichiometric ratio of the phosphorus trichloride added during the reaction process, and the conversion rate of the raw materials is 85%.

[0141] (5) Tail gas treatment

[0142] The tail gas containing fluorine such as the tail gas from the first top discharge port 612 of the light-component-removing rectification column 61 and the tail gas from the vacuum-pumping metathesis is absorbed and treated by the alkali liquor circulating spray device and then sent to the high altitude for discharge by the induced draft fan.

[0143] Example 2

[0144] Example 2 provides a preparation method of phosphorus trifluoride, which is different from Example 1 in that:

[0145] (2) Purification of raw materials:

[0146] Purification of phosphorus trichloride: The phosphorus trichloride raw material with a purity of 98.5% - 99.9% is fed into the second rectification column 13. The pressure inside the column is controlled at 6 kPa. After the system is stable, the temperature at the bottom of the column is 88°C, and the temperature at the top of the column is 74.5°C. The impurities such as phosphoric acid and phosphorous acid in the raw materials are taken out from the bottom of the column, and the high-purity phosphorus trichloride liquid is obtained by cooling at the top of the column. After inspection, the purity is 99.993%.

[0147] Purification of anhydrous hydrogen fluoride: The anhydrous hydrogen fluoride raw material with a purity of 98.5% - 99.9% is fed into the first rectification column 12. The heating temperature is 40°C, and the condensation temperature is -78°C. The condensation medium is liquid nitrogen. The uncondensed oxygen and nitrogen enter the alkali liquor circulating spray device 10 from the top gas outlet of the column for tail gas treatment. The first rectification column 12 is used to remove oxygen, nitrogen and a small amount of solid impurities in the raw materials, and anhydrous hydrogen fluoride with a purity of 99.994% is obtained and fed into the buffer tank 4.

[0148] Preparation of the first mixed gas: An inert gas is fed into the buffer tank 4 to mix anhydrous hydrogen fluoride and the inert gas in a volume ratio of 1:60 to form the first mixed gas. The temperature of the first mixed gas is controlled at about 30°C. The inert gas is nitrogen.

[0149] Step (3) Double decomposition reaction

[0150] Previously, introduce high-purity phosphorus trichloride into the reactor 5 until the liquid level is higher than the bubbling port 51 in the reactor 5. The height difference between the liquid level of phosphorus trichloride and the bubbling port 51 is 50 mm. According to the molar ratio of high-purity phosphorus trichloride to high-purity anhydrous hydrogen fluoride in the first mixed gas being 1:3.2, continuously introduce a certain amount of high-purity phosphorus trichloride liquid and the first mixed gas into the reactor 5 to carry out a double decomposition reaction. The reaction temperature in the reactor 5 is controlled at 40°C to 50°C. Through the reaction, an intermediate gas mainly composed of phosphorus trifluoride, anhydrous hydrogen fluoride, hydrogen chloride, and nitrogen is obtained. Condense the unreacted anhydrous hydrogen fluoride in the intermediate gas through the condenser 7 above the reactor 5 and reflux it to the reactor 5 to further react with high-purity phosphorus trichloride, improving the raw material utilization rate to obtain a second mixed gas. The second mixed gas is then separated by a separator cooled by a low-temperature cold trap 8 to condense phosphorus trifluoride and hydrogen chloride into a first mixed liquid and separate it from the inert gas nitrogen. Nitrogen can be mixed with anhydrous hydrogen fluoride in the buffer tank 4 in the above ratio after heat exchange through the heat exchanger 9 to form the first mixed gas.

[0151] Upon inspection, the purity of high-purity phosphorus trifluoride is 99.95%. The conversion rate of the raw materials is 87%.

[0152] It can be seen from the above Examples 1 and 2 that the conversion rate of the raw materials is above 85%, indicating that according to the preparation method provided in the embodiments of the present application, the occurrence of side reactions can be reduced, the temperature in the reactor can be made more stable, and the continuous production of phosphorus trifluoride can be achieved.

[0153] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing phosphorus trifluoride, characterized in that, Including: Raw material preparation step: obtaining phosphorus trichloride and a first mixed gas respectively, wherein the first mixed gas contains anhydrous hydrogen fluoride and an inert gas; Double decomposition reaction step: continuously introducing the phosphorus trichloride and the first mixed gas into a reactor, causing the phosphorus trichloride and the anhydrous hydrogen fluoride to undergo a double decomposition reaction in the reactor to generate an intermediate gas containing phosphorus trifluoride; collecting the intermediate gas discharged from the reactor; Purification step: subjecting the intermediate gas to rectification and purification to obtain a phosphorus trifluoride product.

2. The preparation method according to claim 1, characterized in that, In the first mixed gas, the volume ratio of the anhydrous hydrogen fluoride to the inert gas is 1:40 - 120; Optionally, the volume ratio of the anhydrous hydrogen fluoride to the inert gas is 1:60 - 80; Optionally, the inert gas includes at least one of nitrogen or argon.

3. The preparation method according to claim 1, characterized in that, The method for continuously introducing the phosphorus trichloride and the first mixed gas into the reactor includes: A bubbling port is provided at the bottom of the reactor, and the phosphorus trichloride with a liquid level higher than the bubbling port is pre-introduced into the reactor; according to the stoichiometric ratio, the first mixed gas is continuously input into the reactor through the bubbling port, and at the same time, the phosphorus trichloride is continuously input into the reactor.

4. The preparation method according to claim 3, characterized in that, In the reactor, the distance between the liquid level of the phosphorus trichloride and the bubbling port is 40 mm - 80 mm; Optionally, the temperature of the reactor is 40°C - 60°C; Optionally, the pressure of the reactor is 5 kPa - 15 kPa.

5. The preparation method according to claim 1, characterized in that, In the purification step, the intermediate gas is condensed to -30°C - -10°C to remove the unreacted anhydrous hydrogen fluoride in the intermediate gas to obtain a second mixed gas; the second mixed gas is condensed to -150°C - -120°C to obtain a first mixed liquid containing the phosphorus trifluoride and collect a third mixed gas containing the inert gas; the first mixed liquid is subjected to rectification and purification to obtain the phosphorus trifluoride product; Optionally, the unreacted anhydrous hydrogen fluoride is refluxed to the reactor; Optionally, the third mixed gas is mixed with the anhydrous hydrogen fluoride to form the first mixed gas.

6. The preparation method according to claim 5, characterized in that The method for rectification and purification includes: Introducing the first mixed liquid into a light component removal rectification column to obtain a light component removal rectification product enriched with phosphorus trifluoride at the bottom of the light component removal rectification column; Introducing the light component removal rectification product into a heavy component removal rectification column to obtain the phosphorus trifluoride product enriched at the top of the heavy component removal rectification column; Optionally, collecting the bottom product of the heavy component removal rectification column, and the bottom product contains hydrogen chloride.

7. The preparation method according to claim 6, characterized in that, The top temperature of the light component removal rectification column is -30°C - -26°C, the bottom temperature of the light component removal rectification column is -11°C - -7°C, and the column pressure of the light component removal rectification column is 2.0 MPa - 2.2 MPa; And / or, the top temperature of the heavy component removal rectification column is -34°C - -31°C, the bottom temperature of the heavy component removal rectification column is -13°C - -9°C, and the column pressure of the heavy component removal rectification column is 1.8 MPa - 2.0 MPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that, Feed the industrial anhydrous hydrogen fluoride raw material into the first rectification column. The temperature at the bottom of the column is 30°C to 50°C, the temperature at the top of the column is -80°C to -75°C, and the pressure inside the column is 5 kPa to 25 kPa to obtain the anhydrous hydrogen fluoride with a purity of not less than 99.99%. Feed the anhydrous hydrogen fluoride and the inert gas into a buffer tank and mix them to form the first mixed gas; And / or, in the raw material preparation step, feed the industrial phosphorus trichloride raw material into the second rectification column. The pressure inside the column is 1 kPa to 6 kPa, the temperature at the bottom of the column is 81°C to 90°C, the temperature at the top of the column is 76°C to 77°C, and the phosphorus trichloride with a purity of not less than 99.99% is obtained by cooling at the top of the column.

9. A production system for implementing the preparation method according to any one of claims 1 to 8, characterized in that, Comprising: An anhydrous hydrogen fluoride gas supply unit, an inert gas supply unit, and a phosphorus trichloride liquid supply unit; A buffer tank having a first air inlet, a second air inlet, and a first mixed gas exhaust port. The anhydrous hydrogen fluoride gas supply unit is connected to the first air inlet, and the inert gas supply unit is connected to the second air inlet; A reactor provided with a liquid inlet, a bubbling port at the bottom, and a second exhaust port at the top. The first mixed gas exhaust port is connected to the bubbling port; the phosphorus trichloride liquid supply unit is connected to the liquid inlet; A rectification column, the feed port of which is connected to the second exhaust port.

10. The production system according to claim 9, characterized in that, A condenser is provided at the top of the reactor. The third air inlet of the condenser is connected to the second exhaust port, and the third exhaust port of the condenser is connected to the feed port of the rectification column; The rectification column includes a light component removal rectification column and a heavy component removal rectification column. The second exhaust port is connected to the first feed port of the light component removal rectification column. The first bottom discharge port of the light component removal rectification column is connected to the second feed port of the heavy component removal rectification column. The second top discharge port of the heavy component removal rectification column is used to discharge the phosphorus trifluoride product; Optionally, a cold trap is provided between the second exhaust port and the light component removal rectification column to separate the inert gas in the second mixed gas discharged from the second exhaust port and convey the condensed first mixed liquid to the first feed port of the light component removal rectification column; Optionally, the production system further includes an alkali liquor circulating spraying device. The first top discharge port of the light component removal rectification column is connected to the alkali liquor circulating spraying device.

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