Method for removing silicon tetrafluoride in boron trifluoride by chemical method

Abstract

The invention provides a method for removing silicon tetrafluoride in boron trifluoride by adopting a chemical method, and belongs to the technical field of purification and impurity removal. The preparation method comprises the following steps: introducing a boron trifluoride raw material into anisole for complex reaction to obtain complex product feed liquid; the molar ratio of the anisole to the boron trifluoride raw material is 1: (0.3-0.8); performing exhaust treatment on the complexing product feed liquid to obtain exhaust feed liquid; the temperature of the exhaust treatment is 30-40 DEG C; the exhaust feed liquid is subjected to cracking treatment, and purified boron trifluoride is obtained; the final temperature of the cracking treatment is 100-120 DEG C. The method disclosed by the invention is excellent in desilicication effect, can meet the requirement of electronic grade boron trifluoride on the content of silicon tetrafluoride, is high in product yield and low in energy consumption, and greatly reduces the cost.

Description

Technical Field

[0001] This invention relates to the field of purification and impurity removal technology, and in particular to a method for removing silicon tetrafluoride from boron trifluoride using a chemical method. Background Technology

[0002] High-purity electronic-grade gases, such as boron trifluoride (BF3), play a crucial role in the manufacturing processes of electronic industries, including semiconductors, integrated circuits, flat panel displays, and photovoltaic energy. The purity of these gases directly affects the performance of electronic components. With the continuous development of the electronics industry, the requirements for the purity, quality, and stability of electronic-grade gases are constantly increasing.

[0003] There are many methods for preparing boron trifluoride in related technologies, such as wet reaction methods and dry reaction methods. The raw materials used in the preparation of boron trifluoride contain a large amount of silicides such as silicon tetrafluoride (SiF4), while electronic-grade boron trifluoride requires a silicon tetrafluoride content ≤0.5ppm. Currently, the main industrial method for desilication of boron trifluoride is liquefaction distillation. Because boron trifluoride and silicon tetrafluoride have similar boiling points (their boiling points differ by only 11°C), repeated distillation is required to barely meet the electronic-grade silicon content requirement, resulting in high energy consumption, high costs, and a yield of only 50-65%. Some chemical methods use metal fluorides as desilication agents, but these easily introduce metal ion impurities (such as Na). + K + Furthermore, the desilication agent cannot be recycled and reused, resulting in high costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing silicon tetrafluoride from boron trifluoride using a chemical method. This method has excellent desiliconization effect, can meet the requirements of electronic-grade boron trifluoride for silicon tetrafluoride content, and has high product yield, low energy consumption, and greatly reduces costs.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for chemically removing silicon tetrafluoride from boron trifluoride, comprising the following steps: Boron trifluoride raw material is introduced into anisole to carry out a complexation reaction, and a complexation product liquid is obtained; the molar ratio of anisole to boron trifluoride raw material is 1:0.3~0.8; The complex product liquid is subjected to degassing treatment to obtain a degassed liquid; the temperature of the degassing treatment is 30~40℃. The exhaust liquid is subjected to pyrolysis treatment to obtain purified boron trifluoride; the termination temperature of the pyrolysis treatment is 100~120℃.

[0006] Preferably, the silicon tetrafluoride content in the boron trifluoride raw material is 500~1000ppm.

[0007] Preferably, the purity of the anisole is ≥99.5 wt%.

[0008] Preferably, the boron trifluoride feedstock is introduced at a rate of 50~300 g / h.

[0009] Preferably, the complexation reaction is carried out at a temperature of -10 to 30°C for 1 to 5 hours.

[0010] Preferably, the complexation reaction is carried out under stirring conditions, and the stirring rate is 150~200 rpm.

[0011] Preferably, the exhaust treatment time is 3 to 4 hours.

[0012] Preferably, the starting temperature of the pyrolysis treatment is 50~60℃.

[0013] Preferably, the pyrolysis treatment adopts a gradient heating method, with a temperature difference of 5~10℃ between adjacent gradients and a holding time of 0.5~1h for each gradient.

[0014] Preferably, the content of silicon tetrafluoride in the purified boron trifluoride is ≤0.5ppm.

[0015] This invention provides a method for chemically removing silicon tetrafluoride from boron trifluoride, comprising the following steps: introducing boron trifluoride raw material into anisole to undergo a complexation reaction, obtaining a complexation product liquid; the molar ratio of anisole to boron trifluoride raw material is 1:0.3~0.8; subjecting the complexation product liquid to exhaust treatment, obtaining an exhaust liquid; the exhaust treatment temperature is 30~40℃; subjecting the exhaust liquid to pyrolysis treatment, obtaining purified boron trifluoride; the termination temperature of the pyrolysis treatment is 100~120℃. This invention utilizes the specific complexation of anisole and BF3 to achieve characteristic desilication, eliminating the need for external desilication agents, achieving excellent desilication effect, meeting the requirements of electronic-grade boron trifluoride for silicon tetrafluoride content (silicon tetrafluoride content ≤0.5ppm), and exhibiting low energy consumption. Anisole can be recycled, fundamentally solving the problems of low processing efficiency, low product purity, and high cost existing in related technologies. Furthermore, the method of this invention has a high product yield (over 95%), is simple to operate, and is easy to implement for industrial production. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the chemical method for removing silicon tetrafluoride from boron trifluoride in an embodiment of the present invention. Detailed Implementation

[0017] This invention provides a method for chemically removing silicon tetrafluoride from boron trifluoride, comprising the following steps: Boron trifluoride raw material is introduced into anisole to carry out a complexation reaction, and a complexation product liquid is obtained; the molar ratio of anisole to boron trifluoride raw material is 1:0.3~0.8; The complex product liquid is subjected to degassing treatment to obtain a degassed liquid; the temperature of the degassing treatment is 30~40℃. The exhaust liquid is subjected to pyrolysis treatment to obtain purified boron trifluoride; the termination temperature of the pyrolysis treatment is 100~120℃.

[0018] The raw materials used in the preparation of boron trifluoride contain a large amount of silicides such as silicon tetrafluoride. Both boron trifluoride and silicon tetrafluoride are strong Lewis acids, making them difficult to separate through simple complexation reactions. This invention discovers that anisole only forms a stable complex (BF3·C7H8O) with boron trifluoride, while silicon tetrafluoride does not participate in the complexation reaction. The separation of boron trifluoride and silicon tetrafluoride is achieved using the principle of "selective complexation." Compared with physical desilication methods, this invention produces a product with fewer impurities, higher purity (reaching over 99.999%), and greater stability. Furthermore, this invention eliminates the need for desilication agents, reducing the introduction of other impurities and lowering costs. Simultaneously, the anisole used in this invention can be recycled, greatly avoiding environmental pollution and effectively reducing production costs, resulting in significant economic benefits. Therefore, this invention enables the one-step production of low-silicon boron trifluoride without secondary processing, the introduction of desilication agents, and is simple to operate with a high product yield. The method of this invention will be described in detail below.

[0019] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0020] This invention involves introducing boron trifluoride as a raw material into anisole to conduct a complexation reaction, yielding a complexed product solution. In this invention, the molar ratio of anisole to boron trifluoride is 1:0.3~0.8, specifically 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, or 1:0.8. As one embodiment of this invention, the purity of the anisole can be ≥99.5wt%; the silicon tetrafluoride content in the boron trifluoride raw material can be 500~1000ppm, more specifically 700~900ppm. In one embodiment of the present invention, the feed rate of the boron trifluoride raw material can be 50~300 g / h, and more specifically 100~200 g / h. In this embodiment of the present invention, the feed rate of the boron trifluoride raw material is controlled to maintain the temperature of the liquid at the temperature required for the complexation reaction. If the feed rate of the boron trifluoride raw material is too fast, the complexation reaction will be rapidly exothermic, which will cause the material temperature to rise rapidly, which is not conducive to the stable control of the reaction temperature.

[0021] In one embodiment of the present invention, the temperature of the complexation reaction can be -10 to 30°C, more specifically -10 to 20°C, and even more specifically -10 to 10°C; the time of the complexation reaction can be 1 to 5 hours, more specifically 3 to 4 hours, wherein the time of the complexation reaction in the present invention begins from the completion of the introduction of boron trifluoride raw material. In this embodiment of the present invention, the complexation reaction temperature is controlled at -10 to 30°C. If the complexation reaction temperature is too low, the energy consumption will be high; if the complexation reaction temperature is too high, such as exceeding 40°C, it may cause the anisole complex to decompose, thereby resulting in a slow complexation reaction rate. In one embodiment of the present invention, the complexation reaction can be carried out under stirring conditions, and the stirring rate can be 150 to 200 rpm. In this invention, if the stirring rate is too low, it is not conducive to the smooth progress of the complexation reaction; if the stirring rate is too high, it will cause liquid splashing. In this embodiment of the invention, the complexation reaction can be carried out in a reaction vessel; before the complexation reaction, the reaction vessel is evacuated to a vacuum degree of at least -0.09 MPa, and then anisole is added to the reaction vessel and boron trifluoride raw material is introduced to carry out the complexation reaction.

[0022] After the complexation reaction, the present invention requires no post-processing; the obtained complexation product liquid is directly subjected to exhaust treatment to obtain an exhaust liquid. In the present invention, the exhaust treatment temperature is 30~40℃; the exhaust treatment time can be 3~4 hours. The present invention uses exhaust treatment to remove the regenerated gases such as nitrogen, oxygen, and argon from the complexation product; the regenerated gases mainly come from boron trifluoride raw material (industrial boron trifluoride purity is approximately 99.5%, and its impurities are mainly nitrogen, oxygen, argon, etc.) and the air remaining after vacuuming in the reaction vessel. In an embodiment of the present invention, the top of the reaction vessel is connected to a waste gas receiving tank, and the regenerated gases discharged during the exhaust treatment are collected in the waste gas receiving tank.

[0023] After the exhaust treatment, the present invention requires no post-processing and directly performs pyrolysis on the obtained exhaust liquid to obtain purified boron trifluoride. In the present invention, the termination temperature of the pyrolysis treatment is 100~120℃, specifically 100℃, 105℃, 110℃, 115℃, or 120℃. As one embodiment of the present invention, the starting temperature of the pyrolysis treatment can be 50~60℃, specifically 50℃, 52℃, 55℃, or 60℃; the pyrolysis treatment adopts a gradient heating method, the temperature difference between adjacent gradients can be 5~10℃, specifically 5℃, 8℃, or 10℃; the heating rate of adjacent gradients can be 18~22℃ / h, specifically 20℃ / h; the holding time of each gradient can be 0.5~1h. In the embodiments of the present invention, the pyrolysis treatment under the above conditions can ensure more thorough pyrolysis of boron trifluoride in the anisole complex, which is beneficial to improving the yield. The content of silicon tetrafluoride in the purified boron trifluoride of the present invention is ≤0.5ppm, specifically 0.1~0.5ppm. In this embodiment of the invention, the top of the reactor is sequentially connected to a distillation column, a condenser, and a product receiving tank. The distillation column is filled with stainless steel wire mesh packing. This invention uses the distillation column to block heavy components, preventing anisole vapor or other heavy components from entering the purified boron trifluoride product. The boron trifluoride produced by the cracking treatment is collected in the product receiving tank after passing through the distillation column and the condenser in sequence.

[0024] In one embodiment of the present invention, the anisole produced by the pyrolysis treatment is located within the reaction vessel. Preferably, the anisole in the reaction vessel after pyrolysis is recovered and reused. In this embodiment, the side wall of the reaction vessel is provided with an anisole outlet and a recovered anisole inlet. The anisole outlet is sequentially connected to an adsorption tower and an anisole receiving tank via pipelines. After pyrolysis, the anisole in the reaction vessel undergoes adsorption treatment in the adsorption tower to remove impurities, resulting in recovered anisole. The recovered anisole is collected in the anisole receiving tank, and the outlet of the anisole receiving tank is connected to the recovered anisole inlet of the reaction vessel, facilitating the recovery and reuse of the anisole. The present invention does not specifically limit the adsorption treatment method; any method well-known to those skilled in the art can be used.

[0025] Figure 1This is a process flow diagram of the chemical method for removing silicon tetrafluoride from boron trifluoride in this invention. The apparatus used for chemical removal of silicon tetrafluoride from boron trifluoride in this invention includes a reactor for complexation reaction, exhaust gas treatment, and pyrolysis treatment. The top of the reactor is connected to a waste gas receiving tank to collect the recycled gas discharged from the exhaust gas treatment. The top of the reactor is also sequentially connected to a distillation column, a condenser, and a product receiving tank, which can condense the boron trifluoride produced by the pyrolysis treatment and collect it in the product receiving tank. The side wall of the reactor is sequentially connected to an adsorption column and an anisole receiving tank, and the outlet of the anisole is connected to the reactor, which can adsorb the anisole in the reactor after the pyrolysis treatment to remove impurities and reuse it.

[0026] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] The purity of the anisole used in the following experiments is ≥99.5wt%, and the silicon tetrafluoride content in the boron trifluoride raw material is 700ppm; the stirring rate involved in the following experiments is 200rpm.

[0028] Example 1 The reactor was evacuated to a vacuum of -0.09 MPa, and then 100 g of anisole was added. Stirring was started, and cooling water was turned on to control the temperature of the anisole in the reactor at -10~10℃. Then, 18.81 g of boron trifluoride raw material was introduced, and the gas inlet rate was controlled at 100~200 g / h. After the gas inlet was completed, the complexation reaction was carried out at -10~10℃ for 3 hours to obtain the complex product liquid. The complex product liquid is heated to 30-40°C under stirring conditions, and the mixture is stirred and vented for 3 hours to obtain vented liquid in the reactor (the regeneration gas generated during the venting process is collected in the waste gas receiving tank). The exhaust liquid was subjected to pyrolysis under stirring conditions. Specifically, the exhaust liquid was first heated to 50°C, and then gradually heated to 100°C with a temperature difference of 10°C between adjacent gradients (i.e., each temperature increase was 10°C, and the heating rate was 20°C / h). The holding time for each gradient was 0.5h. Heating was stopped after reaching 100°C. The product obtained after pyrolysis was fed into a distillation column (filled with stainless steel wire mesh packing), and then condensed in a condenser. The purified boron trifluoride obtained was collected in a product receiving tank (the anisole obtained after pyrolysis was fed into an adsorption tower for adsorption treatment, and then collected in an anisole receiving tank for reuse).

[0029] In this embodiment, the yield of purified boron trifluoride was 17.72g, with a yield of 94.20%, and the silicon tetrafluoride content was measured to be 0.17ppm.

[0030] Example 2 The reactor was evacuated to a vacuum of -0.09 MPa, and then 100 g of anisole was added. Stirring was started, and cooling water was turned on to control the temperature of the anisole in the reactor at -10~10℃. Then, 31.35 g of boron trifluoride raw material was introduced, and the gas inlet rate was controlled at 100~200 g / h. After the gas inlet was completed, the complexation reaction was carried out at -10~10℃ for 3 hours to obtain the complex product liquid. The complex product liquid is heated to 30-40°C under stirring conditions, and the mixture is stirred and vented for 3 hours to obtain vented liquid in the reactor (the regeneration gas generated during the venting process is collected in the waste gas receiving tank). The exhaust liquid was subjected to pyrolysis under stirring conditions. Specifically, the exhaust liquid was first heated to 50°C, and then gradually heated to 100°C with a temperature difference of 10°C between adjacent gradients (i.e., each temperature increase was 10°C, and the heating rate was 20°C / h). The holding time for each gradient was 0.5h. Heating was stopped after reaching 100°C. The product obtained after pyrolysis was fed into a distillation column (filled with stainless steel wire mesh packing), and then condensed in a condenser. The purified boron trifluoride obtained was collected in a product receiving tank (the anisole obtained after pyrolysis was fed into an adsorption tower for adsorption treatment, and then collected in an anisole receiving tank for reuse).

[0031] In this embodiment, the yield of purified boron trifluoride was 29.80g, with a yield of 95.04%, and the silicon tetrafluoride content was measured to be 0.28ppm.

[0032] Example 3 The reactor was evacuated to a vacuum of -0.09 MPa, and then 100 g of anisole was added. Stirring was started, and cooling water was turned on to control the temperature of the anisole in the reactor at -10~10℃. Then, 50.166 g of boron trifluoride raw material was introduced, and the gas inlet rate was controlled at 100~200 g / h. After the gas inlet was completed, the complexation reaction was carried out at -10~10℃ for 3 hours to obtain the complex product liquid. The complex product liquid is heated to 30-40°C under stirring conditions, and the mixture is stirred and vented for 3 hours to obtain vented liquid in the reactor (the regeneration gas generated during the venting process is collected in the waste gas receiving tank). The exhaust liquid was subjected to pyrolysis under stirring conditions. Specifically, the exhaust liquid was first heated to 50°C, and then gradually heated to 100°C with a temperature difference of 10°C between adjacent gradients (i.e., each temperature increase was 10°C, and the heating rate was 20°C / h). The holding time for each gradient was 0.5h. Heating was stopped after reaching 100°C. The product obtained after pyrolysis was fed into a distillation column (filled with stainless steel wire mesh packing), and then condensed in a condenser. The purified boron trifluoride obtained was collected in a product receiving tank (the anisole obtained after pyrolysis was fed into an adsorption tower for adsorption treatment, and then collected in an anisole receiving tank for reuse).

[0033] In this embodiment, the yield of purified boron trifluoride was 47.79g, with a yield of 95.27%, and the silicon tetrafluoride content was measured to be 0.40ppm.

[0034] Example 4 The reactor was evacuated to a vacuum of -0.09 MPa, and then 100 g of anisole was added. Stirring was started, and cooling water was turned on to control the temperature of the anisole in the reactor at -10~10℃. Then, 31.35 g of boron trifluoride raw material was introduced, and the gas inlet rate was controlled at 100~200 g / h. After the gas inlet was completed, the complexation reaction was carried out at -10~10℃ for 3 hours to obtain the complex product liquid. The complex product liquid is heated to 30-40°C under stirring conditions, and the mixture is stirred and vented for 3 hours to obtain vented liquid in the reactor (the regeneration gas generated during the venting process is collected in the waste gas receiving tank). The exhaust liquid was subjected to pyrolysis under stirring conditions. Specifically, the exhaust liquid was first heated to 50°C, and then gradually heated to 120°C with a temperature difference of 10°C between adjacent gradients (i.e., each temperature increase was 10°C, and the heating rate was 20°C / h). The holding time for each gradient was 0.5h. Heating was stopped after reaching 120°C. The product obtained after pyrolysis was fed into a distillation column (filled with stainless steel wire mesh packing), and then condensed in a condenser. The purified boron trifluoride obtained was collected in a product receiving tank (the anisole obtained after pyrolysis was fed into an adsorption tower for adsorption treatment, and then collected in an anisole receiving tank for reuse).

[0035] In this embodiment, the yield of purified boron trifluoride was 30.03g, the yield rate was 30.03%, and the silicon tetrafluoride content was detected to be 0.30ppm.

[0036] Example 5 The reactor was evacuated to a vacuum of -0.09 MPa, and then 100 g of anisole was added. Stirring was started, and cooling water was turned on to control the temperature of the anisole in the reactor at -10~10℃. Then, 31.35 g of boron trifluoride raw material was introduced, and the gas inlet rate was controlled at 100~200 g / h. After the gas inlet was completed, the complexation reaction was carried out at 20~30℃ for 3 hours to obtain the complex product liquid. The complex product liquid is heated to 30-40°C under stirring conditions, and the mixture is stirred and vented for 3 hours to obtain vented liquid in the reactor (the regeneration gas generated during the venting process is collected in the waste gas receiving tank). The exhaust liquid was subjected to pyrolysis under stirring conditions. Specifically, the exhaust liquid was first heated to 50°C, and then gradually heated to 120°C with a temperature difference of 10°C between adjacent gradients (i.e., each temperature increase was 10°C, and the heating rate was 20°C / h). The holding time for each gradient was 0.5h. Heating was stopped after reaching 120°C. The product obtained after pyrolysis was fed into a distillation column (filled with stainless steel wire mesh packing), and then condensed in a condenser. The purified boron trifluoride obtained was collected in a product receiving tank (the anisole obtained after pyrolysis was fed into an adsorption tower for adsorption treatment, and then collected in an anisole receiving tank for reuse).

[0037] In this embodiment, the yield of purified boron trifluoride was 29.98g, the yield was 95.63%, and the silicon tetrafluoride content was 0.44ppm.

[0038] Comparative Example 1 The procedure was followed as in Example 1, except that the amount of boron trifluoride raw material used in this comparative example was 62.71 g, and the final yield of purified boron trifluoride was 59.78 g, with a yield of 95.32%. The silicon tetrafluoride content was measured to be 0.62 ppm.

[0039] Comparative Example 2 The method of Example 1 was followed, except that the exhaust temperature in this comparative example was 10~20°C. The final yield of purified boron trifluoride was 17.78g, with a yield of 94.52%, and the silicon tetrafluoride content was tested to be 0.65ppm.

[0040] Comparative Example 3 The procedure was followed as in Example 1, except that the amount of boron trifluoride raw material used in this comparative example was 31.35 g, and the termination temperature of the pyrolysis treatment was 150°C. The final yield of purified boron trifluoride was 30.06 g, with a yield of 95.88%. The silicon tetrafluoride content was measured to be 0.68 ppm.

[0041] Table 1 shows the conditions and results for removing silicon tetrafluoride from boron trifluoride in each example and comparative example. As can be seen from Table 1, excessively high total boron trifluoride levels, exhaust gas treatment temperatures below 30°C, and excessively high pyrolysis temperatures can all lead to unqualified silicon tetrafluoride impurity content. Conversely, excessively low total boron trifluoride levels and excessively low pyrolysis termination temperatures can both result in low product yields.

[0042] Table 1. Conditions and results for removing silicon tetrafluoride from boron trifluoride in each example and comparative example.

[0043] The results above show that the present invention achieves desilication based on the selective complexation of boron trifluoride with anisole, including a continuous process of complexation reaction, exhaust treatment, and pyrolysis treatment. The molar ratio of anisole to BF3 is 1:0.3~0.8, and the complexation reaction temperature is controlled at -10~10℃, enabling efficient complexation and impurity retention. Furthermore, the anisole can be recycled, reducing reagent consumption and avoiding environmental pollution. Simultaneously, no desilication agent needs to be added, preventing the introduction of new impurities from the source, simplifying the process steps, and demonstrating broad market prospects and high comprehensive social benefits.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for chemically removing silicon tetrafluoride from boron trifluoride, comprising the following steps: Boron trifluoride raw material is introduced into anisole to carry out a complexation reaction, and a complexation product liquid is obtained; the molar ratio of anisole to boron trifluoride raw material is 1:0.3~0.8; The complex product liquid is subjected to degassing treatment to obtain a degassed liquid; the temperature of the degassing treatment is 30~40℃. The exhaust liquid is subjected to pyrolysis treatment to obtain purified boron trifluoride; the termination temperature of the pyrolysis treatment is 100~120℃.

2. The method according to claim 1, characterized in that, The silicon tetrafluoride content in the boron trifluoride raw material is 500~1000ppm.

3. The method according to claim 1, characterized in that, The purity of the anisole is ≥99.5wt%.

4. The method according to claim 1, characterized in that, The feed rate of the boron trifluoride raw material is 50~300 g / h.

5. The method according to claim 1, characterized in that, The complexation reaction is carried out at a temperature of -10 to 30°C for 1 to 5 hours.

6. The method according to claim 1 or 5, characterized in that, The complexation reaction is carried out under stirring conditions, and the stirring rate is 150~200 rpm.

7. The method according to claim 1, characterized in that, The exhaust treatment time is 3-4 hours.

8. The method according to claim 1, characterized in that, The initial temperature of the pyrolysis treatment is 50~60℃.

9. The method according to claim 1 or 8, characterized in that, The pyrolysis process employs a gradient heating method, with a temperature difference of 5~10℃ between adjacent gradients and a holding time of 0.5~1h for each gradient.

10. The method according to claim 1, characterized in that, The content of silicon tetrafluoride in the purified boron trifluoride is ≤0.5ppm.

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