Method for producing high-purity fluorine-nitrogen mixed gas
By mixing high-purity nitrogen trifluoride and high-purity nitrogen, followed by cracking, condensation, compression, and deweighting distillation, a high-purity fluorine-nitrogen mixed gas can be directly prepared, solving the problems of complex processes and high energy consumption in existing technologies, and realizing low-cost and high-efficiency nitrogen recycling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI SINOPHORUS ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2025-09-25
- Publication Date
- 2026-07-28
AI Technical Summary
Existing technologies for preparing high-purity fluorine-nitrogen mixed gas suffer from problems such as complex processes, high energy consumption, high equipment requirements, and difficulties in separating nitrogen and fluorine, resulting in high production costs and hindering the comprehensive utilization of resources.
High-purity nitrogen trifluoride and high-purity nitrogen are mixed and reacted in a pyrolyzer, followed by condensation, compression, and deweighting distillation to directly produce a high-purity fluorine-nitrogen mixed gas. Nitrogen is used as a diluent and coolant, which simplifies the process and enables the recycling of nitrogen.
It reduced production costs, simplified the process, improved nitrogen utilization, reduced energy consumption, and achieved efficient preparation of high-purity fluorine-nitrogen mixed gas.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of fluorochemical technology, specifically relating to a method for producing a high-purity fluorine-nitrogen mixed gas. Background Technology
[0002] In semiconductor industry applications, nitrides such as nitrogen trifluoride are commonly used for cleaning chemical vapor deposition (CVD) reaction chambers. Fluorine gas, because it does not produce a greenhouse effect and does not generate fluorine compounds in CVD reactors, has gradually become a new generation of cleaning gas, replacing nitrogen trifluoride and making it an indispensable raw material in chip manufacturing. Due to its high reactivity and inherent danger, fluorine gas is not suitable for direct application in the fluorination reactions of organic compounds. To reduce side reactions, inert nitrogen gas is typically used to dilute the fluorine gas, creating a fluorine-nitrogen mixture. High-purity fluorine-nitrogen mixtures are prepared by electrolyzing anhydrous hydrogen fluoride. The key step is to prepare fluorine gas with a purity of over 99.9%. Because fluorine has a boiling point of -188°C, ultra-low temperature distillation purification technology is required. Distillation not only consumes a large amount of energy but also places high demands on the cryogenic distillation tower equipment. Alternatively, HF entrained during the electrolysis of fluorine can be removed through condensation, adsorption, and filtration.
[0003] CN116425118A discloses a method for producing high-purity fluorine gas by cracking nitrogen trifluoride and its cracking reactor. In this method, NF3 is fed into a drying tower, and the dried NF3 gas enters the cracking reactor for cracking. After cooling, it is compressed by a compressor. The gas after thermal cracking passes through a multi-stage distillation process. The heavy components at the bottom of the heavy component removal tower are sent to the drying tower, the N2 at the top of the light component removal tower is vented, and the fluorine gas at the bottom of the tower is compressed by a compressor and filled into steel cylinders, achieving a 100% fluorine yield. This method involves a complex production process, requiring multi-stage distillation for impurity removal, and placing high demands on the distillation tower equipment.
[0004] CN114054007A discloses a method for preparing an adsorbent for fluorine purification. Fluoride salt raw materials are mixed with a binder and solvent in a specific ratio, followed by concentration, granulation, sintering, and post-treatment. This method uses the adsorbent to adsorb and electrolyze HF impurities carried by fluorine, resulting in a fluorine product with a purity of over 99.9%. CN106698352A discloses a method and apparatus for preparing high-purity fluorine gas or a high-purity fluorine-containing mixed gas. This method pressurizes fluorine gas obtained through electrolysis or a fluorine-containing mixed gas prepared using fluorine gas obtained through electrolysis, adjusts the flow rate using a gas pressurization device, filters the gas, and then sequentially condenses it in a primary condenser at -60 to -100°C and a secondary condenser at -120 to -180°C to obtain high-purity fluorine gas or a high-purity fluorine-containing gas. The purity of the obtained fluorine product reaches over 99.9%. This method is energy-intensive and requires sophisticated condenser equipment. Summary of the Invention This invention provides a method for producing a high-purity fluorine-nitrogen mixed gas. Pure nitrogen trifluoride and high-purity nitrogen are mixed in a certain way and introduced into a pyrolyzer to realize the recycling of nitrogen. The introduction of nitrogen can ensure the safety of the reaction, and at the same time reduce the production steps of purifying fluorine gas to remove nitrogen impurities after cracking nitrogen trifluoride. This reduces the production steps, reduces the cost, and enables the production of high-purity fluorine-nitrogen mixed gas with comprehensive resource utilization. The technical solution adopted in this invention is: A method for producing a high-purity fluorine-nitrogen mixed gas, the method comprising the following steps: S1 mixes high-purity nitrogen trifluoride and high-purity nitrogen and feeds them into the pyrolyzer to react until the pressure no longer changes. The gas after the reaction is cooled by the condenser and then fed into the first buffer tank. The S2 mixture is compressed by the compressor after passing through the first buffer tank and then fed into the heavy component distillation column to remove heavy component impurities. The gas taken from the top of the distillation column is fed into the second buffer tank, compressed by the compressor, and then filled into a steel cylinder. Complete the production of high-purity fluorine-nitrogen mixed gas. Preferably, in step S1, the purity of high-purity nitrogen trifluoride is ≥99.999%, and the purity of high-purity nitrogen gas is ≥99.999%. Preferably, in step S1, the molar ratio of high-purity nitrogen trifluoride to high-purity nitrogen is 1:(5.5~10).
[0005] Preferably, in step S1, the reaction temperature is 1000~1250℃ and the pressure is 0.2~0.7 MPa; more preferably, the reaction temperature is 1050~1150℃ and the pressure is 0.4~0.6 MPa.
[0006] Preferably, in step S1, the condenser is cooled to 60-65°C.
[0007] Preferably, in step S2, the condenser uses high-purity liquid nitrogen as a refrigerant, and the vaporized nitrogen is introduced into a nitrogen buffer tank to replenish the pyrolyzer.
[0008] Preferably, in step S2, the purity of the high-purity liquid nitrogen is ≥99.999%, and the temperature of the vaporized nitrogen gas is 20-25℃.
[0009] Preferably, in step S2, the top temperature of the de-heavy distillation column is 40-50℃, the bottom temperature is 60-70℃, and the pressure is 1.1-1.5 MPa. More preferably, the top temperature of the deweight removal tower is 45-48℃, the bottom temperature is 60-65℃, and the tower pressure is preferably 1.1-1.3 MPa.
[0010] Preferably, in step S3, the pyrolyzer and the deweighting tower are made of one of Monel alloy, nickel, or stainless steel.
[0011] Beneficial effects of this invention: (1) The present invention realizes the recycling of nitrogen gas. High-purity liquid nitrogen is used as a refrigerant. The nitrogen gas after vaporization is added to the cracker, reducing the consumption of nitrogen gas recompression, directly reducing the purchase cost and compression cost of high-purity nitrogen gas, and reducing the production cost.
[0012] (2) The introduction of nitrogen gas in this invention ensures the safety of the reaction while reducing the distillation process required for purifying fluorine gas after cracking nitrogen trifluoride to remove nitrogen impurities. Only one stage of distillation is needed to prepare a 20% fluorine-nitrogen mixture. In traditional processes for producing pure fluorine gas or a mixture of gases in a specific ratio, complex purification steps are required after cracking to separate unreacted NF3, byproducts, and nitrogen gas used as a diluent. This method directly produces a fluorine-nitrogen mixture and uses nitrogen gas as a component of the final product. This transforms nitrogen gas, which was originally an "impurity," into a "product," thus fundamentally eliminating the most difficult and energy-intensive fluorine / nitrogen separation step. It also enables the recycling of nitrogen gas, using high-purity liquid nitrogen as a coolant, and the vaporized nitrogen gas can be replenished in the reaction. Detailed Implementation
[0013] The technical solution of the present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. The specific embodiments described herein are only for illustration and explanation and are not intended to limit the present disclosure. Equivalent substitutions or corresponding improvements made to the content of the present invention still fall within the scope of protection of the present invention.
[0014] Detection methods: The proportions of fluorine (F2) and nitrogen (N2) content were tested according to GB / T 26251 standard, using a gas chromatograph equipped with dual thermal conductivity detectors. After the sample passes through the sampling system, HF is absorbed and enters the chromatogram via a six-way sampling valve. The sample gas passes through a conversion column, where F2 is converted to Cl2. A fluorochlorohydrin column separates oxygen, nitrogen, and Cl2. Cl2 is quantified on the fluorochlorohydrin column, and the F2 content can be calculated from the Cl2 content. The measured Cl2 content can express the F2 content. N2 is then introduced into a molecular sieve column for analysis via a switching valve.
[0015] Fluorine purity: The purity of fluorine gas was analyzed by gas chromatography with a matching PDD detector, and the purity of fluorine gas was detected by the difference method.
[0016] Example 1 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6 and introduced into the pyrolyzer. The reaction temperature was 1100℃ and the pressure was 0.3 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0017] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0018] Example 2 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6.5 and introduced into the pyrolyzer. The reaction temperature was 1100℃ and the pressure was 0.3 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0019] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0020] Example 3 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:7.5 and introduced into the pyrolyzer. The reaction temperature was 1100℃ and the pressure was 0.3 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air. The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0021] Comparative Example 1 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:5 and introduced into the pyrolyzer. The reaction temperature was 1100℃ and the pressure was 0.3 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0022] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder. Comparative Example 2 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:11 and introduced into the pyrolyzer. The reaction temperature was 1100℃ and the pressure was 0.3 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0023] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0024] Example 4 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6 and introduced into the pyrolyzer. The reaction temperature was 1000℃ and the pressure was 0.2 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0025] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0026] Example 5 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6 and introduced into the pyrolyzer. The reaction temperature was 1250℃ and the pressure was 0.7 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0027] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0028] Comparative Example 3 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6 and introduced into the pyrolyzer. The reaction temperature was 900℃ and the pressure was 0.1 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0029] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder.
[0030] Comparative Example 4 The entire reaction system was evacuated and cleaned using a vacuum pump. High-purity nitrogen trifluoride and high-purity nitrogen were mixed at a molar ratio of 1:6 and introduced into the pyrolyzer. The reaction temperature was 1300℃ and the pressure was 0.8 MPa. The reaction was considered to have stopped when the pressure no longer changed. After the reaction, the pyrolyzer valve was opened, and the gas after the reaction was cooled by the condenser and introduced into buffer tank 1. The condenser used high-purity liquid nitrogen as a coolant. The high-purity nitrogen gas from the condenser outlet was introduced into the pyrolyzer in proportion, and the excess nitrogen gas was directly discharged into the air.
[0031] The gas from the buffer tank is compressed by the compressor and then fed into the deweighting distillation column to remove heavy component impurities. The top temperature of the deweighting column is 45°C, the bottom temperature is preferably 62°C, and the pressure is 1.3 MPa. The gas taken from the top of the distillation column is fed into the buffer tank 2. After the gas in the buffer tank 2 is circulated by the compressor for 2 hours, it is then compressed and filled into the steel cylinder. Table 1
[0032] As shown in Table 1, regarding the reversible reaction of nitrogen trifluoride decomposition, Examples 1-3 and Comparative Examples 1-2 indicate that excessive nitrogen trifluoride decomposition deviates from the 20% ratio. Examples 5 and Comparative Example 4 show that while increasing pressure and temperature can appropriately promote nitrogen trifluoride decomposition, it consumes a large amount of energy and requires equipment with better pressure and high temperature resistance. Excessive increases in pressure and temperature not only fail to promote nitrogen trifluoride decomposition but also consume a large amount of energy. Furthermore, excessive nitrogen trifluoride is detrimental to the reversible reaction and results in low removal efficiency in the distillation column, leading to increased impurity content. By mixing high-purity nitrogen trifluoride and high-purity nitrogen in a 1:6 molar ratio and introducing it into the cracker, at a reaction temperature of 1100℃ and a pressure of 0.3 MPa, a product with a fluoride-nitrogen mixture ratio closest to 20% can be obtained, with the lowest energy consumption, high product purity, and low cost.
[0033] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.
Claims
1. A method for producing a high-purity fluorine-nitrogen mixed gas, characterized in that, The method includes the following steps: S1 mixes high-purity nitrogen trifluoride and high-purity nitrogen and feeds them into the pyrolyzer to react until the pressure no longer changes. The gas after the reaction is cooled by the condenser and then fed into the first buffer tank. The S2 mixture is compressed by the compressor after passing through the first buffer tank and then fed into the de-heavy distillation column to remove heavy component impurities. The gas taken out from the top of the distillation column is fed into the second buffer tank, compressed by the compressor, and then filled. Complete the production of high-purity fluorine-nitrogen mixed gas.
2. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that: In step S1, the purity of high-purity nitrogen trifluoride is ≥99.999%, and the purity of high-purity nitrogen gas is ≥99.999%.
3. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that: In step S1, the molar ratio of high-purity nitrogen trifluoride to high-purity nitrogen is 1:(5.5~10).
4. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that, In step S1, the reaction temperature is 1000~1250℃ and the pressure is 0.2~0.7Mpa.
5. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 4, characterized in that, In step S1, the reaction temperature is 1050~1150℃ and the pressure is 0.4~0.6 MPa.
6. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that, In step S1, the condenser is cooled to 60-70°C.
7. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that: In step S1, the condenser uses high-purity liquid nitrogen as a refrigerant, and the vaporized nitrogen is introduced into a nitrogen buffer tank to replenish the pyrolyzer.
8. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that: In step S1, the purity of the high-purity liquid nitrogen is ≥99.999%, and the temperature of the vaporized nitrogen gas is 20-30℃.
9. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that, In step S2, the top temperature of the deweight distillation column is 40-50℃, the bottom temperature is 60-70℃, and the pressure is 1.1-1.5 MPa.
10. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 9, characterized in that, In step S2, the top temperature of the deweight distillation column is 45-48℃, the bottom temperature is 60-65℃, and the pressure is 1.1-1.3 MPa.
11. The method for producing high-purity fluorine-nitrogen mixed gas according to claim 1, characterized in that, In steps S1 and S2, the cracker and the de-heavy distillation column are made of one of Monel alloy, nickel, or stainless steel.