Secondary fluorination system and process for synthesizing PF3

Abstract

The invention relates to a secondary fluorination system for synthesizing PF3. The secondary fluorination system comprises a main reactor, a condenser pipe, a secondary fluorination reactor and a cold trap, the invention also discloses a secondary fluorination process for synthesizing PF3, which comprises the following steps: introducing gas-phase HF into a liquid-phase PC13 raw material to generate gas-phase main products PF3 and HCl and a small amount of by-product fluorine chloride, carrying out secondary fluorination reaction on the products through a fluorinating agent ZnF2, almost completely converting the by-products into the target product PF3, and collecting the final product in a cold trap. According to the invention, the content of by-products in the cold trap is greatly reduced, the conversion rate of raw materials is improved, and the purification efficiency of the crude phosphorus trifluoride is improved.

Description

Technical Field

[0001] The invention relates to a secondary fluorination system and process for synthesizing PF3, belonging to the technical field of PF3 synthesis. Background Art

[0002] Phosphorus trifluoride is an inorganic compound that is widely used in organic synthesis, chemical analysis, and the semiconductor industry. An important application of phosphorus trifluoride is as an organic reagent for organic synthesis reactions. It can be used as a fluorinating agent to replace hydrogen atoms in organic compounds with fluorine atoms, thereby introducing fluorine functional groups. This is beneficial for the synthesis of drugs, pesticides, and other organic compounds. In addition, phosphorus trifluoride can be used for acylation reactions and can also be used as a catalyst.

[0003] Chinese patent CN117228643A discloses a method for preparing electronic grade phosphorus trifluoride. Under the protection of an inert atmosphere, phosphorus trichloride is first added to the reactor, heated, and the temperature is controlled at 40°C to 60°C for 20 to 50 minutes; then anhydrous hydrogen fluoride is slowly introduced from the bottom of the reactor to allow it to fully contact and react to generate phosphorus trifluoride, which is directly condensed and collected. The reaction of hydrogen fluoride and phosphorus trichloride to prepare phosphorus trifluoride is a common method for synthesizing phosphorus trifluoride. Since the product after passing through the main reactor contains a certain amount of by-product fluorine chloride, the raw material conversion rate is reduced, and the by-products generated will significantly reduce the distillation efficiency of crude phosphorus trifluoride.

[0004] Chinese patent CN101955173A discloses a technology for preparing phosphorus trifluoride by reacting phosphorus trichloride and zinc fluoride. However, the cost of directly using anhydrous ZnF2 to synthesize phosphorus trifluoride is relatively high. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a secondary fluorination system and process for synthesizing PF3 with high raw material conversion rate, high product purity and low cost.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A secondary fluorination system for synthesizing PF3 comprises a main reactor, a condenser, a secondary fluorination reactor and a cold trap which are connected in sequence; the main reactor is provided with a hydrogen fluoride feed bottom plug-in tube, the main reactor is equipped with a stirring device, the top of the main reactor is connected with one end of the condenser, the other end of the condenser is connected with the secondary fluorination reactor, the secondary fluorination reactor is provided with a solid fluorinating agent feed port and a solid fluorinating agent discharge port, and the bottom of the secondary fluorination reactor is connected with the cold trap.

[0008] Preferably, one end of the hydrogen fluoride feed bottom plug tube is located inside the main reactor, and the other end is located outside the main reactor.

[0009] Preferably, the main reactor, condenser and secondary fluorination reactor are all made of stainless steel lined with polytetrafluoroethylene, and the cold trap is made of stainless steel.

[0010] Preferably, the cooling medium of the condenser is dichloromethane, and the cooling temperature is -20 to -10°C;

[0011] The cooling medium of the cold trap is liquid nitrogen.

[0012] A secondary fluorination process for synthesizing PF3 comprises the following steps: passing gas phase HF to liquid phase PCl3 raw material for reaction to generate gas phase main product PF3, HCl and by-product fluorine chloride;

[0013] The gas phase main product PF3, HCl and the byproduct phosphorus fluoride undergo secondary fluorination reaction with a solid fluorinating agent, and the unreacted PCl3 and byproducts are all converted into the target product PF3, which is then condensed and collected. The condensed and collected product is a mixture of the main product PF3 and HCl.

[0014] Preferably, the temperature at which gaseous HF is introduced into the liquid PCl3 raw material for reaction is 20°C to 60°C, and the temperature at which the secondary fluorination reaction is carried out is 20°C to 60°C.

[0015] Preferably, the flow rate of gaseous HF to liquid PCl3 raw material is 10L / min.

[0016] Preferably, when the gas phase HF is passed to the liquid phase PCl3 raw material for reaction, the liquid phase PCl3 raw material is stirred, and the stirring speed is 90r / min.

[0017] Preferably, the solid fluorinating agent is anhydrous ZnF2.

[0018] Preferably, the condensation collection temperature is controlled at -130°C to -120°C.

[0019] The present invention has the following beneficial effects:

[0020] 1) The secondary fluorination reactor can convert the by-product fluorine chloride produced in the main reactor into the target product PF3, thereby improving the raw material conversion rate.

[0021] 2) The secondary fluorination reactor can increase the concentration of the target product PF3 in the collected cold trap, which is beneficial to improving the product distillation efficiency.

[0022] 3) Phosphorus trichloride and hydrogen chloride are extremely corrosive, and conventional stainless steel reactors are easily unable to meet the synthesis requirements for a long time. The polytetrafluoroethylene-lined stainless steel reaction device used in the present invention can extend the life of the equipment and reduce costs.

[0023] 4) The present invention first uses hydrogen fluoride to react with phosphorus trichloride, and then uses anhydrous ZnF2 to perform a secondary fluorination reaction, which greatly reduces the cost compared to directly using anhydrous ZnF2 for fluorination reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a secondary fluorination system for synthesizing PF3 in the present invention.

[0025] 1-main reactor; 2-hydrogen fluoride feed bottom tube; 3-stirring device; 4-condenser; 5-solid fluorinating agent feed port; 6-solid fluorinating agent discharge port; 7-secondary fluorination reactor; 8-cold trap. DETAILED DESCRIPTION

[0026] The following will be combined with the attached Figure 1 The present invention will be described in detail with reference to embodiments.

[0027] A secondary fluorination system for synthesizing PF3 comprises a main reactor 1, a condenser 4, a secondary fluorination reactor 7 and a cold trap 8; the main reactor 1 is equipped with a stirring device 3 for stirring raw materials; a hydrogen fluoride feed plug-in tube 2 for introducing gaseous hydrogen fluoride is provided inside, the bottom end of the hydrogen fluoride feed plug-in tube 2 is located below the liquid level of liquid PCl3, and the top end is located outside the main reactor 1 and connected to a gaseous HF pipeline or a carrier gas bottle; the condenser 4 above the main reactor 1 is used to condense and reflux phosphorus trichloride; the other end of the condenser 4 is connected to the secondary fluorination reactor 7, the secondary fluorination reactor 7 is equipped with a solid fluorinating agent feed inlet 5 and a solid fluorinating agent discharge port 6 for updating anhydrous zinc fluoride, and the bottom of the secondary fluorination reactor 7 is connected to the cold trap 8 to collect PF3.

[0028] The main reactor 1, the condenser 4 and the secondary fluorination reactor 7 are stainless steel reactors lined with polytetrafluoroethylene; the cooling medium of the condenser 4 is dichloromethane, and the cooling temperature is -20 to -10°C; the cooling medium of the cold trap 8 is liquid nitrogen, and the temperature is controlled at -130 to -120°C; the rotation speed of the stirring device 3 is 90r / min.

[0029] A secondary fluorination process for synthesizing PF3, the steps are as follows:

[0030] 1) Perform pressure-maintaining leak test on the system.

[0031] 2) Remove all air from the system and its pipes by injecting nitrogen and evacuating the air, and finally introduce nitrogen to create a nitrogen environment in the system.

[0032] 3) Liquid phosphorus trichloride is added into the main reactor 1, a certain amount of anhydrous zinc fluoride is loaded into the secondary fluorination reactor 7, the main reactor 1 (20°C to 60°C), the condenser 4 (-20 to -10°C) and the cold trap 8 are turned on to control the temperature (-130 to -120°C), then the stirring device 3 is turned on at a speed of 90r / min, and finally gaseous hydrogen fluoride is slowly introduced into the main reactor 1 through the hydrogen fluoride feed bottom tube 2 at a speed of 10L / min, and PF3 is collected in the cold trap 8.

[0033] Comparative Example 1

[0034] In this embodiment, the temperature of the main reactor and the secondary fluorination reactor are both 35° C., and the reaction pressure is both normal pressure reaction.

[0035] 1) Connect all the devices in the system and inject 0.1MPa nitrogen, then evacuate to -0.1MPa. Repeat 30 times until the pressure of the entire system is evacuated to -0.1MPa. Use dichloromethane as a refrigerant to control the temperature of the condenser 4 at -10°C, and use liquid nitrogen as a refrigerant to control the temperature of the cold trap 8 at -120°C. Then disconnect all the devices through valves for standby use.

[0036] 2) Add 7.5L of liquid phosphorus trichloride into the main reactor 1 by pressure, turn on the temperature control equipment, heat the main reactor 1 to 35°C, and set the speed of the stirring device 3 of the main reactor 1 to 90r / min. Then open the hydrogen fluoride feed bottom pipe 2, HF feed, and the flow rate of gaseous HF to the main reactor 1 is 10L / min. At this time, the pressure of the main reactor 1 gradually increases. When the pressure rises to normal pressure (0MPa), connect to the secondary fluorination reactor 7.

[0037] 3) Add 0kg of solid anhydrous zinc fluoride into the secondary fluorination reactor 7, then control the temperature of the secondary fluorination reactor 7 at 35°C, and pump it to -0.1MPa. After completing the above actions, it is ready for use. When the main reaction is connected to the secondary fluorination reactor 7, its pressure gradually rises. When the pressure of the secondary fluorination reactor 7 rises to normal pressure (0MPa), adjust the cold trap inlet so that the rate at which the cold trap 8 collects the product is balanced with the gas production rate of the secondary fluorination reactor 7. At this time, the pressure of the entire system is in a steady state, and phosphorus trifluoride products can be continuously synthesized.

[0038] 4) The cold trap 7 collects the main product PF3 and HCl mixture and then samples it for analysis. The component contents in the product are analyzed using a gas chromatograph equipped with a DB-1 chromatographic column and a TCD detector, and the raw material conversion rate is calculated, as shown in Table 1.

[0039] Example 1

[0040] In this embodiment, the temperature of the main reactor 1 and the secondary fluorination reactor 7 are both 35° C., and the reaction pressure is both normal pressure reaction.

[0041] 1) Connect all the devices in the system and inject 0.1MPa nitrogen, then evacuate to -0.1MPa. Repeat 30 times until the pressure of the entire system is evacuated to -0.1MPa. Use dichloromethane as a refrigerant to control the temperature of the condenser 4 at -10°C, and use liquid nitrogen as a refrigerant to control the temperature of the cold trap 8 at -120°C. Then disconnect all the devices through valves for standby use.

[0042] 2) Add 7.5L of liquid phosphorus trichloride into the main reactor 1 by pressure, turn on the temperature control equipment, heat the main reactor 1 to 35°C, and set the speed of the stirring device 3 of the main reactor 1 to 90r / min. Then open the hydrogen fluoride feed bottom pipe 2, HF feed, and the flow rate of gaseous HF to the main reactor 1 is 10L / min. At this time, the pressure of the main reactor 1 gradually increases. When the pressure rises to normal pressure (0MPa), connect to the secondary fluorination reactor 7.

[0043] 3) Add 10 kg of solid anhydrous zinc fluoride into the secondary fluorination reactor 7 through the solid fluorinating agent feed port 5, then control the temperature of the secondary fluorination reactor 7 at 35°C, and pump it to -0.1 MPa. After completing the above actions, it is ready for use. When the main reaction is connected to the secondary fluorination reactor 7, its pressure gradually rises. When the pressure of the secondary fluorination reactor 7 rises to normal pressure (0 MPa), adjust the inlet of the cold trap 8 so that the rate at which the cold trap 8 collects the product is balanced with the gas production rate of the secondary fluorination reactor 7. At this time, the pressure of the entire system is in a steady state, and phosphorus trifluoride products can be continuously synthesized.

[0044] 4) After collecting a certain amount of the main product PF3 and HCl mixture in the cold trap 8, sampling and analysis were performed. The component contents in the product were analyzed using a gas chromatograph equipped with a DB-1 chromatographic column and a TCD detector, and the raw material conversion rate was calculated, as shown in Table 1.

[0045] Example 2

[0046] In this embodiment, the temperature of the main reactor 1 and the secondary fluorination reactor 7 are both 35° C., and the reaction pressure is both normal pressure reaction.

[0047] 1) Connect all the devices in the system and inject 0.1MPa nitrogen, then evacuate to -0.1MPa. Repeat 30 times until the pressure of the entire system is evacuated to -0.1MPa. Use dichloromethane as a refrigerant to control the temperature of the condenser 4 at -20°C, and use liquid nitrogen as a refrigerant to control the temperature of the cold trap 8 at -130°C. Then disconnect all the devices through valves for standby use.

[0048] 2) Add 7.5L of liquid phosphorus trichloride into the main reactor 1 by pressure, turn on the temperature control equipment, heat the main reactor 1 to 60°C, and set the speed of the stirring device 3 of the main reactor 1 to 90r / min. Then open the hydrogen fluoride feed bottom pipe 2, HF feed, and the flow rate of gaseous HF to the main reactor 1 is 10L / min. At this time, the pressure of the main reactor 1 gradually increases. When the pressure rises to normal pressure (0MPa), connect to the secondary fluorination reactor 7.

[0049] 3) Add 20g of solid anhydrous zinc fluoride into the secondary fluorination reactor 7 through the solid fluorinating agent feed port 5, then control the temperature of the secondary fluorination reactor 7 at 60°C, and pump it to -0.1MPa. After completing the above actions, it is ready for use. When the main reaction is connected to the secondary fluorination reactor 7, its pressure gradually rises. When the pressure of the secondary fluorination reactor 7 rises to normal pressure (0MPa), adjust the inlet of the cold trap 8 so that the rate at which the cold trap 8 collects the product is balanced with the gas production rate of the secondary fluorination reactor 7. At this time, the pressure of the entire system is in a steady state, and phosphorus trifluoride products can be continuously synthesized.

[0050] 4) After collecting a certain amount of the main product PF3 and HCl mixture in the cold trap 8, sampling and analysis were performed. The component contents in the product were analyzed using a gas chromatographic analysis with a DB-1 chromatographic column and a TCD detector, and the raw material conversion rate was calculated as shown in Table 1.

[0051] Example 3

[0052] In this embodiment, the temperature of the main reactor 1 and the secondary fluorination reactor 7 are both 35° C., and the reaction pressure is both normal pressure reaction.

[0053] 1) Connect all the devices in the system and inject 0.1MPa nitrogen, then evacuate to -0.1MPa. Repeat 30 times until the pressure of the entire system is evacuated to -0.1MPa. Use dichloromethane as the refrigerant to control the temperature of condenser 4 at -15°C, and use liquid nitrogen as the refrigerant to control the temperature of cold trap 8 at -125°C. Then disconnect all the devices through valves for standby use.

[0054] 2) Add 7.5L of liquid phosphorus trichloride into the main reactor 1 by pressure, turn on the temperature control equipment, heat the main reactor 1 to 20°C, and set the speed of the stirring device 3 of the main reactor 1 to 90r / min. Then open the hydrogen fluoride feed bottom pipe 2, feed HF, and the flow rate of gaseous HF to the main reactor is 10L / min. At this time, the pressure of the main reactor 1 gradually increases. When the pressure rises to normal pressure (0MPa), connect to the secondary fluorination reactor 7.

[0055] 3) Add 25 kg of solid anhydrous zinc fluoride into the secondary fluorination reactor 7 through the solid fluorinating agent feed port 5, then control the temperature of the secondary fluorination reactor 7 at 20°C, and pump it to -0.1 MPa. After completing the above actions, it is ready for use. When the main reaction is connected to the secondary fluorination reactor 7, its pressure gradually rises. When the pressure of the secondary fluorination reactor 7 rises to normal pressure (0 MPa), adjust the cold trap inlet so that the rate at which the cold trap 8 collects the product is balanced with the gas production rate of the secondary fluorination reactor. At this time, the pressure of the entire system is in a steady state, and phosphorus trifluoride products can be continuously synthesized.

[0056] 4) After collecting a certain amount of the main product PF3 and HCl mixture in the cold trap 8, sampling and analysis were performed. The component contents in the product were analyzed using a gas chromatographic analysis with a DB-1 chromatographic column and a TCD detector, and the raw material conversion rate was calculated as shown in Table 1.

[0057] Table 1

[0058] project Comparative Example 1 Example 1 Example 2 Example 3 Hydrogen fluoride conversion rate 83.4％ 91.3％ 92.6％ 93.4％ Impurity content 19.3％ 2.1％ 1.9％ 1.9％

[0059] As can be seen from Table 1, the present invention provides a secondary fluorination system and process for synthesizing PF3, with a hydrogen fluoride conversion rate higher than 91.3% and an impurity content lower than 2.1%. Impurities refer to components other than the main products PF3 and HCl.

[0060] It should be pointed out that the above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A secondary fluorination system for synthesizing PF3, characterized in that: The invention comprises a main reactor, a condenser, a secondary fluorination reactor and a cold trap which are connected in sequence; the main reactor is provided with a hydrogen fluoride feed bottom plug-in tube, the main reactor is equipped with a stirring device, one end of the condenser is connected to the top of the main reactor, the other end of the condenser is connected to the secondary fluorination reactor, the secondary fluorination reactor is provided with a solid fluorination agent feed port and a solid fluorination agent discharge port, and the bottom of the secondary fluorination reactor is connected to the cold trap.

2. A secondary fluorination system for synthesizing PF3 according to claim 1, characterized in that: One end of the hydrogen fluoride feed bottom plug pipe is located in the main reactor, and the other end is located outside the main reactor.

3. A secondary fluorination system for synthesizing PF3 according to claim 1, characterized in that: The main reactor, condenser and secondary fluorination reactor are all made of stainless steel lined with polytetrafluoroethylene, and the cold trap is made of stainless steel.

4. A secondary fluorination system for synthesizing PF3 according to claim 1, characterized in that: The cooling medium of the condenser is dichloromethane, and the cooling temperature is -20~-10℃; The cooling medium of the cold trap is liquid nitrogen.

5. A secondary fluorination process for synthesizing PF3, using a secondary fluorination system for synthesizing PF3 according to any one of claims 1 to 4, characterized in that: The following steps are involved: The gas phase HF is passed into the liquid phase PCl3 raw material to react, generating the gas phase main product PF3, HCl and the by-product fluorine chloride; The gas phase main product PF3, HCl and by-product phosphorus fluoride are subjected to secondary fluorination reaction by solid fluorinating agent, and the unreacted PCl3 and by-product phosphorus fluoride are completely converted into the target product PF3, and then the main product PF3 and HCl mixture are condensed and collected.

6. A secondary fluorination process for synthesizing PF3 according to claim 5, characterized in that: The temperature at which gaseous HF is introduced into the liquid PCl3 raw material for reaction is 20°C to 60°C, and the temperature at which the secondary fluorination reaction is carried out is 20°C to 60°C.

7. A secondary fluorination process for synthesizing PF3 according to claim 5, characterized in that: The flow rate of gaseous HF to liquid PCl3 raw material is 10L / min.

8. A secondary fluorination process for synthesizing PF3 according to claim 5, characterized in that: When the gas phase HF is passed to the liquid phase PCl3 raw material for reaction, the liquid phase PCl3 raw material is stirred at a stirring speed of 90r / min.

9. A secondary fluorination process for synthesizing PF3 according to claim 5, characterized in that: The solid fluorinating agent is anhydrous ZnF2.

10. A secondary fluorination process for synthesizing PF3 according to claim 5, characterized in that: The condensation collection temperature is controlled at -130℃~-120℃.

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