A method for purifying boron-11 by rectification

Abstract

The application provides a rectification purification method of electronic special gas grade boron 11, and belongs to the technical field of electronic special gas manufacturing. The rectification purification method comprises the following steps: performing deep purification pretreatment on BF3 raw gas to obtain BF3 purified gas with a purity of not less than 99.999% and a water content of not higher than 10 ppb; delivering the BF3 purified gas to a plurality of rectification towers connected in series for multi-stage enrichment, wherein the total theoretical plate number of the plurality of rectification towers is 3000-5000, and the reflux ratio of each rectification tower is gradually increased in turn, so as to generate electronic special gas grade boron 11 with an abundance of not less than 99.999% at the top of the terminal rectification tower; and the electronic special gas grade boron 11 is extracted and subjected to packaging treatment. The rectification purification method realizes, for the first time, industrialized scale preparation of electronic special gas grade boron 11 meeting the double 99.999% standard of purity and abundance based on low-temperature rectification technology, and fills the technical gap in the field.

Description

Technical Field

[0001] This application relates to the field of manufacturing technology of electronic specialty gas-grade boron 11, and more specifically, to a distillation purification method for electronic specialty gas-grade boron 11. Background Technology

[0002] Boron has 10 B and 11 Two stable isotopes, B (natural abundances of 19.8% and 80.2%, respectively), are present, with the higher abundance... 11 Due to its extremely low neutron absorption cross section, boron (B₁₁) is often used as a p-type dopant source in semiconductor ion implantation processes, effectively suppressing single-event effects and improving the reliability of aerospace and high-performance electronic devices. Currently, the industrial production of boron isotopes mainly adopts the boron trifluoride-anisole chemical exchange distillation method. Although this method can obtain boron-11 with an abundance of not less than 99%, the process is complex, involving multiple units such as complexation, exchange, cracking, and purification. Equipment corrosion is a serious problem, and anisole is prone to decomposition, producing tar that clogs the towers, resulting in high operating costs. Furthermore, residual organic matter in the product is difficult to completely remove, causing the obtained boron-11 to fail to meet the stringent requirements of electronic specialty gas-grade boron-11 (both purity and abundance reaching 99.999%).

[0003] Based on this, cryogenic distillation has become a research hotspot for boron isotope production in recent years due to its advantages of no chemical reagent introduction, pure product, and stable continuous operation. However, existing boron isotope production processes based on cryogenic distillation all aim to produce high-purity and high-abundance boron-10, with boron-11 only as a byproduct generated simultaneously. Since the application fields of boron-10 and boron-11 differ significantly—specifically, boron-10 is mainly used in nuclear reactor control rods, nuclear protection materials, and neutron capture therapy for cancer (with an abundance requirement of not less than 96%), while boron-11 is mainly used in highly precise electronic devices (with an abundance requirement of not less than 99.999%)—the product requirements for boron-10 are significantly lower than those for boron-11. This makes it difficult for the boron-11 currently generated simultaneously with boron-10 to meet the requirements of electronic specialty gas-grade boron-11.

[0004] In addition to the significant differences in product standards between Boron-10 and Boron-11, their enrichment principles and core processes also differ considerably, making the targeted design of low-temperature distillation processes for Boron-11 extremely difficult. A detailed analysis follows: (1) Different enrichment logics: Boron 10 is generated at the bottom of the low temperature distillation column. Its enrichment logic is to take advantage of the fact that Boron 10 has a lower relative volatility and is more likely to be enriched at the bottom of the liquid phase column, so that high abundance of Boron 10 can be extracted at the bottom of the column. Boron 11 is generated at the top of the low temperature distillation column. Its enrichment logic is to take advantage of the fact that Boron 11 has a higher relative volatility and is more likely to be enriched at the top of the gas phase column, so that high abundance of Boron 11 can be extracted at the top of the column. That is, the enrichment logics of Boron 10 and Boron 11 are exactly opposite.

[0005] (2) Different core of impurity removal: Since Boron 10 is generated at the bottom of the low temperature distillation column, the core of its process control for impurity removal is to efficiently and thoroughly retain light component impurities; while Boron 11 is generated at the top of the low temperature distillation column, the core of its process control for impurity removal is to efficiently and thoroughly retain heavy component impurities. That is, the two impurity removal directions are also opposite.

[0006] (3) Electronic special gas grade boron 11 requires moisture content to be strictly below 1 ppm. In addition, BF3 itself is extremely corrosive, and even a trace amount of moisture will trigger hydrolysis side reactions, which will corrode the equipment and directly reduce the purity of the product. The moisture requirement of boron 10 (usually not exceeding 15 ppm) is much lower than that of boron 11. Therefore, moisture control is extremely important and extremely difficult in the production of boron 11.

[0007] (4) Since the abundance requirement of boron 11 is much higher than that of boron 10, the total number of theoretical plates required is much higher than that required for boron 10.

[0008] In summary, the preparation of electronic specialty gases based on BF3 cryogenic distillation technology is feasible. 11 B faces entirely different technical challenges from existing technologies in terms of enrichment logic, impurity removal direction, moisture control, and separation efficiency. Currently, there is no complete, industrially mass-producible electronic specialty gas system, either domestically or internationally. 11 A breakthrough is urgently needed in the low-temperature distillation purification process for B. Summary of the Invention

[0009] The purpose of this application is to provide a distillation purification method for electronic specialty gas-grade boron 11. This distillation purification method, through systematic process design and strict anhydrous control, has for the first time achieved the industrial-scale preparation of electronic specialty gas-grade boron 11 that simultaneously meets the standards of 99.999% purity and abundance based on low-temperature distillation technology, filling a technological gap in this field.

[0010] The embodiments of this application are implemented as follows: In a first aspect, embodiments of this application provide a method for the distillation purification of electronic specialty grade boron 11, comprising the following steps: performing deep purification pretreatment on BF3 feed gas to obtain purified BF3 gas with a purity of not less than 99.999% and a water content of not more than 10 ppb; conveying the purified BF3 gas to a multi-stage series distillation column for multi-stage enrichment, wherein the total theoretical number of the multiple distillation columns is 3000 to 5000, and the reflux ratio of each distillation column increases in a gradient, so as to generate electronic specialty grade boron 11 with an abundance of not less than 99.999% at the top of the final distillation column; and collecting and encapsulating the electronic specialty grade boron 11.

[0011] In the above technical solution, the BF3 feed gas is first subjected to deep purification pretreatment to increase its purity to electronic specialty gas grade (i.e., not less than 99.999%), while simultaneously controlling the moisture content at the source to no more than 10%. The process aims to reduce the probability of BF3 hydrolysis side reactions during subsequent distillation by lowering the ppb level at the source. Then, a specially designed cryogenic distillation process is employed, controlling the total theoretical plate number within a suitable range of 3000-5000 plates and incorporating a progressively increasing reflux ratio. This allows for the generation of electronic-grade boron 11 with an abundance and purity of no less than 99.999% at the top of the final distillation column. Finally, after collecting and encapsulating the electronic-grade boron 11, boron 11 with a purity and abundance of no less than 99.999% can be directly prepared from the BF3 feed gas (i.e., naturally abundant boron 11) through multi-stage enrichment. This distillation purification method, through systematic process design and stringent anhydrous control, is the first to achieve industrial-scale preparation of electronic-grade boron 11 that simultaneously meets the 99.999% purity and abundance standards based on cryogenic distillation technology, filling a technological gap in this field.

[0012] In some alternative implementations, the number of distillation columns in series is 2 to 6; and / or, the series connection is horizontal or vertical.

[0013] In the above technical solutions, the number of series stages and the series configuration of the distillation column can be freely combined, providing a variety of feasible solutions, thereby facilitating the promotion and application of the technical solutions provided in the embodiments of this application; at the same time, by adopting the above-mentioned range of stages, a high total theoretical plate number can be achieved using existing low-temperature distillation columns.

[0014] In some alternative implementations, the distillation column has 2 to 5 stages in series, and the series connection is horizontal.

[0015] In the above technical solutions, the appropriate number of series stages combined with the horizontal series configuration for targeted production of boron 11 has the following advantages: (1) The horizontal series configuration of 2 to 5 stages can better meet the total theoretical number of trays required for the gas phase enrichment of boron 11. Without building a 100-meter-level ultra-high single tower, the naturally abundant boron 11 can be gradually enriched to an electronic special gas level of not less than 99.999%, which helps to improve production efficiency and reduce energy consumption; (2) The short-distance series pipeline of the horizontal series configuration greatly reduces the sealing dead angle, which structurally reduces the probability of external trace moisture intrusion and can better adapt to electronic special gas grade boron 11 with a moisture content of not more than 10%. The stringent requirements of ppb effectively improve the problems of purity reduction and equipment corrosion caused by BF3 hydrolysis; (3) The horizontal series spatial layout can realize the independent and precise adjustment of core parameters such as temperature, pressure and reflux ratio of each stage of low temperature distillation column, so as to specifically enhance the gas phase mass transfer efficiency of boron 11. Compared with the vertical series multi-stage column with fixed parameters, it is easier to achieve dynamic stability of the material balance of the whole column and ensure the long-term consistency and stability of product abundance.

[0016] In some alternative implementations, the top pressure of the multiple distillation columns is independently selected from 80 kPa to 150 kPa, the bottom pressure is independently selected from 100 kPa to 200 kPa, the temperature at the top condenser is independently selected from -105°C to -92°C, and the temperature at the bottom reboiler is independently selected from -90°C to -80°C.

[0017] In the above technical solution, based on the horizontal series configuration of 2 to 5 levels, the pressure at the top of the distillation column, the pressure at the bottom of the column, the temperature at the top condenser, and the temperature at the bottom reboiler are all limited to the above range. Through the synergistic cooperation of multiple core parameters, it has the following advantages for the targeted production of boron 11: (1) It can reduce the pressure fluctuation in the distillation column so that boron 11 can always maintain a high separation efficiency during the enrichment process to the top of the gas phase column; at the same time, it can also improve the problem of boron 10 rising to the top of the column due to abnormal pressure fluctuations, thereby ensuring the high abundance and abundance stability of boron 11 generated at the top of the column; (2) It can allow heavy component impurities to be retained at the bottom of the column more efficiently and thoroughly during the gas-liquid exchange process so that the purity of boron 11 produced at the top of the column can always be maintained at a high level; (3) It can allow BF3 to always maintain a stable gas-liquid balance state, improve the problem of material freezing in the condenser and blocking the pipeline due to excessively low temperature, so as to meet the continuous and stable operation requirements of low temperature distillation of boron 11.

[0018] In some alternative implementations, the top pressure of the multiple distillation columns is independently selected from 80 kPa to 130 kPa, the bottom pressure is independently selected from 120 kPa to 200 kPa, the temperature at the top condenser is independently selected from -100°C to -95°C, and the temperature at the bottom reboiler is independently selected from -88°C to -82°C.

[0019] In the above technical solution, based on the horizontal series configuration of 2 to 5 levels, the pressure at the top of the distillation column, the pressure at the bottom of the column, the temperature at the top condenser, and the temperature at the bottom reboiler are all further limited within the above range. Through the synergistic cooperation of multiple core parameters, it has the following advantages for the targeted production of boron 11: (1) It can further reduce the pressure fluctuation in the distillation column, so that boron 11 can always maintain a higher separation efficiency during the enrichment process to the top of the gas phase column; at the same time, it can also better improve the problem of boron 10 rising to the top of the column due to abnormal pressure fluctuations, so as to better ensure the high abundance and abundance stability of boron 11 generated at the top of the column; (2) It can make heavy component impurities more efficient and thorough in the gas-liquid exchange process, so that the purity of boron 11 produced at the top of the column can always be maintained at a higher level; (3) It can make BF3 always maintain a more stable gas-liquid balance state, better improve the problem of material freezing and blocking pipelines in the condenser due to excessively low temperature, so as to better adapt to the continuous and stable operation requirements of low temperature distillation of boron 11.

[0020] In some alternative implementations, the reflux ratios of the multiple distillation columns are independently selected from 100 to 500, and the difference in the reflux ratio between any two adjacent distillation columns is 50 to 100; and / or, the middle feed flow rate of the first distillation column is 1 kg / h to 10 kg / h, and the top discharge flow rate of the last distillation column is 0.1 kg / h to 0.5 kg / h.

[0021] In the above technical solution, based on a horizontal series configuration of 2 to 5 stages, a reflux ratio range of 100 to 500 is set, coupled with an adjacent reflux ratio difference of 50 to 100. This allows the gas-liquid mass transfer load of each distillation column to precisely match the progressive gas-phase enrichment progress of boron-11. This effectively solves the problem of energy waste caused by excessively high reflux ratios in a single column. Simultaneously, it effectively addresses the issue of boron-10 components rising to the top of the column due to insufficient reflux ratios in a single column, thus ensuring the high abundance and stability of boron-11 generated at the top. Based on the 2 to 5 stage horizontal series configuration, a middle feed flow rate of 1 to 10 kg / h is set at the beginning to maintain stable operation within the column during feeding, allowing the material to fully complete gas-liquid mass transfer within the column. A small top discharge flow rate of 0.1 to 0.5 kg / h is set at the end to maximize the retention of heavy component impurities, ensuring that the final boron-11 abundance and purity consistently reach the electronic specialty gas standard of over 99.999%.

[0022] In some optional embodiments, the packing in multiple distillation columns is stainless steel or phosphor bronze packing that has undergone acid washing, alkali washing, water washing, drying, and boron trifluoride passivation treatment, and the specific surface area of ​​the packing is not less than 1000 m². 2 / m 3; and / or, the inner walls of multiple distillation columns are all covered with a corrosion-resistant protective layer; and / or, the inner walls of multiple distillation columns are all electropolished to ensure that the surface roughness of the inner walls is no higher than 0.2 μm.

[0023] In the above technical solution, (1) the packing is sequentially subjected to acid washing, alkali washing, water washing, drying and boron trifluoride passivation treatment. Acid washing removes the oxide layer and metal debris on the surface of the packing, alkali washing neutralizes the residual acid, ultrapure water rinsing removes the acid and alkali residue, and high-temperature drying completely removes the free water adsorbed on the surface, thus avoiding the subsequent introduction of water to cause BF3 hydrolysis from the source. BF3 passivates the surface of the packing in advance, forming a dense and stable fluoride protective film on the inner wall surface, reducing the probability of BF3 reacting with the packing during the low-temperature distillation process, so as to form electronic special gas grade boron 11. (2) Based on the horizontal cascading form of 2 to 5 stages, the specific surface area of ​​the packing in the low-temperature distillation column is limited to the above range, which can make the packing have a large gas-liquid contact area, greatly improve the gas phase mass transfer efficiency of boron 11, and generate electronic special gas grade standard boron 11 with a stable abundance and purity of over 99.999% at the top of the gas phase column based on the horizontal cascading form of 2 to 5 stages. (3) The inner wall of each low-temperature distillation column is equipped with a corrosion-resistant protective layer (e.g., pure nickel, Hastelloy C-276) and / or is pre-electrolytic polished before use (until the surface roughness is no higher than 0.2 μm). This setup, combined with high-temperature inert gas purging and vacuum treatment, can efficiently and thoroughly remove moisture and impurities from the entire low-temperature distillation system, reducing the decrease in the purity of Boron 11 products and equipment corrosion caused by BF3 hydrolysis during the low-temperature distillation process.

[0024] In some alternative implementations, any two adjacent distillation columns are connected by a first transfer tank, which is configured to: firstly condense the gaseous material output from the top of the previous distillation column into a liquid for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the middle feed inlet of the next distillation column.

[0025] In the above technical solution, any two adjacent distillation columns are connected by a first transfer tank that can both cool and liquefy the gas and heat and vaporize the liquid. This allows for the transfer of materials between the distillation columns without the use of transfer pumps or compressors. This configuration has the following advantages: (1) No transfer pumps or compressors are required to drive the seals, thus eliminating the risk of trace moisture and air intrusion at the dynamic seals. At the same time, by eliminating such power transmission equipment that drives the seals, the layout of the series pipelines is simpler, reducing dead corners in the seals and effectively reducing the probability of impurity retention. This makes it better suited for electronic special gas grade boron 11 with a moisture content not exceeding 10%. (1) The stringent control requirements of ppb effectively improve the problems of purity reduction and equipment corrosion caused by BF3 hydrolysis; (2) In view of the extremely low volatility of BF3, this transmission method can maintain the pressure stability between adjacent two-stage towers, thereby ensuring the continuous and smooth progress of the gas phase enrichment process of boron 11; (3) No transmission pump or compressor is required throughout the process, which greatly reduces the overall energy consumption of the production line. At the same time, the daily maintenance of pumps and compressors is eliminated, reducing the equipment failure points and allowing the series distillation unit to operate continuously and stably for a long time.

[0026] In some optional embodiments, the steps of deep purification and pretreatment of BF3 feed gas include: passing the BF3 feed gas sequentially through a cold trap, a chemical adsorption bed, a molecular sieve dryer, a light-light distillation column, and a heavy-light distillation column, wherein the heavy-light distillation column has a treatment temperature of -32℃ to -52℃ and a treatment pressure of 1.2 MPa to 2 MPa; the pressure of the light-light distillation column is higher than the pressure of the heavy-light distillation column.

[0027] In the above technical solution, the deep purification and pretreatment process is carried out according to the above steps, which can purify industrial-grade BF3 feed gas from various sources to a purity of not less than 99.999% and a water content of not more than 10 ppb, and has good feed gas compatibility. More importantly, the final stage of deep purification pretreatment is completed in a low-temperature de-heavy distillation column, which means that the temperature of the obtained BF3 purified gas is also low. Therefore, the BF3 purified gas can be directly sent to the first low-temperature distillation column under low-temperature operation without additional pre-cooling process. This scientific design has many advantages: (1) The low-temperature distillation stage maintains the low temperature of BF3 throughout the process, effectively avoiding the risk of backflow of trace moisture on the inner wall of the pipeline during the normal temperature transportation of purified gas, further strengthening the deep water-free control effect of the whole process, and ensuring that the moisture index of the final boron 11 product is consistently below 10 ppb; (2) The independent refrigeration equipment at the feed end is eliminated, which greatly reduces the refrigeration energy consumption of the whole process. Compared with the traditional normal temperature feed process, the refrigeration load can be reduced by about 30%; (3) The gas-liquid state of the low-temperature BF3 purified gas is more uniform, which can effectively improve the flooding problem caused by uneven local vaporization after the purified gas enters the first column, and can greatly improve the operational stability of the horizontal series system.

[0028] In some optional implementations, before the BF3 feed gas is delivered to the cold trap, the BF3 feed gas is further subjected to a first-stage filtration process and a second-stage filtration process, wherein the filter precision of the first-stage filtration process is 5 μm to 10 μm, and the filter precision of the second-stage filtration process is 0.5 μm to 1 μm.

[0029] In the above technical solution, the BF3 feed gas is subjected to two-stage filtration before being transported to the cold trap, and the precision of the two-stage filters is limited to the aforementioned range. The first-stage filtration can intercept larger solid particles and reaction by-product debris in the BF3 feed gas, reducing the risk of large impurities directly impacting the subsequent precision filter element and causing blockage. The second-stage filtration can further remove the fine particles remaining from the first stage, while intercepting trace amounts of fluoride solid suspensions generated by BF3 hydrolysis, reducing the risk of these impurities freezing and accumulating at low temperatures after entering the cold trap and causing blockage of the cold trap flow channel.

[0030] In some optional implementations, the purified BF3 gas is further subjected to a third-stage filtration process before being delivered to the first-end distillation column, wherein the filter used in the third-stage filtration process has a filter precision of 0.003 μm to 0.01 μm.

[0031] In the above technical solution, based on the previous two-stage filtration process, the purified gas is subjected to a third-stage filtration process before it is delivered to the first distillation column of BF3, and the filter precision is limited to the above range. This can effectively intercept any submicron particles and aerosol impurities that may remain in the raw gas, thereby improving the problem of impurities depositing on the column plates and disrupting the gas-liquid mass transfer balance. At the same time, it can also ensure that the particle size of the final boron-11 obtained meets the electronic special gas grade standard.

[0032] In some alternative embodiments, the cold trap has a processing temperature of -50°C to -30°C; and / or, the adsorbent of the chemisorption bed includes alumina loaded with an alkali metal compound, the alkali metal compound including at least one of KF and NaF, and the processing temperature of the chemisorption bed is -20°C to 0°C; and / or, the molecular sieve of the molecular sieve dryer includes at least one of 3A molecular sieve and 4A molecular sieve.

[0033] In the above technical solution, limiting the temperature at the cold trap within the above range can effectively remove adsorbed high-boiling-point impurities (i.e., heavy component impurities, such as carbon dioxide, water, etc.) from the raw gas; using a chemical adsorption bed containing the above adsorbent and treating it at the above temperature can effectively remove acidic impurities such as HF from the raw gas; using a dryer containing the above-mentioned molecular sieves can further remove residual high-boiling-point impurities from the raw gas. In some optional embodiments, before the deep purification pretreatment step, the method further includes: continuously purging the light-weight removal distillation column and the heavy-weight removal distillation column with high-purity inert gas at 80°C to 120°C for 12 h to 24 h; after purging, evacuating the light-weight removal distillation column and the heavy-weight removal distillation column until the vacuum degree is not higher than 10 Pa; and / or, before the step of conveying the BF3 purified gas to a multi-stage series distillation column for multi-stage enrichment, the method further includes: continuously purging the multi-stage series distillation column with high-purity inert gas at 80°C to 120°C for 7 days to 20 days; after purging, evacuating the multi-stage series distillation column until the vacuum degree is not higher than 10 Pa.

[0034] In the above technical solution, before deep purification pretreatment, the entire light and heavy distillation columns are continuously purged with high-temperature inert gas at around 100°C for 12-24 hours, combined with vacuum treatment. This can thoroughly remove residual moisture and impurities from the entire distillation system in a comprehensive and thorough manner, thereby reducing the decrease in the purity of Boron 11 product and equipment corrosion caused by BF3 hydrolysis during low-temperature distillation. Before multi-stage enrichment, the entire distillation system is continuously purged with high-temperature inert gas at around 100°C for 7-20 days, combined with vacuum treatment. This can thoroughly remove residual moisture and impurities from the entire low-temperature distillation system in a comprehensive and thorough manner, thereby reducing the decrease in the purity of Boron 11 product and equipment corrosion caused by BF3 hydrolysis during low-temperature distillation.

[0035] In some optional embodiments, the step of collecting and encapsulating electronic specialty boron 11 includes: collecting electronic specialty boron 11 from the top of the terminal distillation column and subjecting it to a fourth-stage filtration process, wherein the filter precision of the fourth-stage filtration process is 0.003 μm to 0.01 μm; transporting the electronic specialty boron 11 after the fourth-stage filtration process to a collection bottle via a second transfer storage tank for encapsulation; wherein the second transfer storage tank is configured to: first condense the gaseous material after the fourth-stage filtration process into a liquid material for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the collection bottle.

[0036] In the above technical solution, the electronic specialty grade boron 11 undergoes a fourth-stage filtration process using a filter of the aforementioned specifications before entering the collection bottle. This effectively intercepts trace amounts of fluoride solid particles that may be generated by the hydrolysis of BF3 during the low-temperature distillation process, tiny debris detached from the inner wall of the pipeline, and residual trace amounts of moisture and light component impurities. This ensures that the particle size of the final boron 11 meets the electronic specialty grade standard. Simultaneously, the filter and the collection bottle are connected by a second transfer tank that can both cool and liquefy the gas and heat and vaporize the liquid. This allows for material transfer between the two without the use of a transfer pump or compressor. This setup eliminates the need for transfer pumps or compressors that drive the seals, thus eliminating the risk of trace moisture and air intrusion at the dynamic seals. Furthermore, by eliminating such power transmission equipment that drives the seals, the pipeline layout is simpler, reducing dead zones in the seals and effectively lowering the probability of impurity retention. Therefore, it can better meet the stringent control requirements of electronic specialty grade boron 11 with a moisture content not exceeding 10 ppb.

[0037] In some alternative implementations, prior to the encapsulation step, the collection bottle is further subjected to electrolytic polishing, vacuum drying, and passivation, and the valve of the collection bottle is a diaphragm valve and the valve seal is made of perfluoroether rubber.

[0038] In the above technical solution, by strictly following the above requirements for encapsulation, it is possible to encapsulate electronic specialty gas grade boron 11 with a purity and abundance of not less than 99.999%, and the encapsulated boron 11 product can maintain the electronic specialty gas grade standard for a long time.

[0039] In some alternative embodiments, the electropolishing step continues until the surface roughness of the inner wall of the collection bottle is no higher than 0.2 μm; and / or, the drying step includes: continuously evacuating the vacuum at 80°C to 120°C until the vacuum level inside the collection bottle is no higher than 1×10⁻⁶. -5 Pa and keep it warm and pressurized for 12 h to 24 h; and / or, the passivation treatment step includes: passivating the inner wall surface of the collection bottle with high-purity BF3.

[0040] In the above technical solution, polishing according to the above standards can form a smooth surface on the inner wall of the collection bottle, greatly reducing the adsorption of moisture and impurities on the inner wall, so as to obtain electronic specialty grade boron 11 with a purity and abundance of not less than 99.999%, and also to ensure that the encapsulated boron 11 product maintains the electronic specialty grade standard for a long time; vacuum drying according to the above standards can completely remove trace amounts of moisture and impurities adhering to the inner wall of the collection bottle; passivation according to the above process can obtain electronic specialty grade boron 11 with a purity and abundance of not less than 99.999%, and also to ensure that the encapsulated boron 11 product maintains the electronic specialty grade standard for a long time. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A process flow diagram of a distillation purification method for electronic specialty gas grade boron 11 provided for embodiments of this application; Figure 2 A schematic diagram of a distillation and purification system provided in an embodiment of this application; Figure 3 A schematic diagram of a multi-level enrichment unit provided in an embodiment of this application; Figure 4 This is a schematic diagram of another distillation and purification system provided in an embodiment of this application.

[0043] Icons: Distillation and purification system-1; First-stage filter-10a; Second-stage filter-10b; Third-stage filter-10c; Fourth-stage filter-10d; Cold trap-20; Chemisorption bed-30; Molecular sieve dryer-40; Light-weight removal distillation column-50a; Heavy-weight removal distillation column-50b; Multi-stage enrichment unit-60; First-stage distillation column-60a; Second-stage distillation column-60b; Third-stage distillation column-60c; Fourth-stage distillation column-60d; Fifth-stage distillation column-60e; First transfer tank-70a; Second transfer tank-70b; Third transfer tank-70c; Collection bottle-80. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0045] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".

[0046] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0047] Although cryogenic distillation has begun to be applied to the production of boron isotopes, it currently remains in a state where boron-10 is the core product and boron-11 is a byproduct generated simultaneously. Due to numerous differences between the processes for producing boron-10 and boron-11, including but not limited to: significant differences in product specifications (the abundance requirements for boron-11 are much higher than for boron-10, especially after the abundance exceeds 96%, further enrichment is extremely difficult; the water content requirements for boron-11 are much lower than for boron-10), opposite enrichment logic (boron-10 has lower relative volatility and is enriched at the bottom of the liquid phase column, while boron-11 has higher relative volatility and is enriched at the top of the gas phase column), opposite core purification methods (the core purification method for boron-10 is to efficiently and thoroughly remove light component impurities, while the core purification method for boron-11 is to efficiently and thoroughly remove heavy component impurities), and significant differences in the number of theoretical plates (the number of theoretical plates required for boron-11 is significantly higher than that for boron-10), existing cryogenic distillation processes for boron-10 are difficult to apply to the production of boron-11. This has resulted in research on the industrial-scale production of boron-11 through cryogenic distillation remaining in its infancy. Based on this, the inventors designed a set of industrialized process routes for producing electronic specialty grade boron-11 using low-temperature distillation.

[0048] The distillation purification method of electronic special gas grade boron 11 according to the embodiments of this application will be described in detail below.

[0049] In a first aspect, embodiments of this application provide a method for the distillation purification of electronic specialty grade boron 11, comprising the following steps: performing deep purification pretreatment on BF3 feed gas to obtain purified BF3 gas with a purity of not less than 99.999% and a water content of not more than 10 ppb; conveying the purified BF3 gas to a multi-stage series distillation column for multi-stage enrichment, wherein the total theoretical number of the multiple distillation columns is 3000 to 5000 (e.g., but not limited to any one of 3000, 3500, 4000, 4500 and 5000 or any range between two), and the reflux ratio of each distillation column increases in a gradient, so as to generate electronic specialty grade boron 11 with an abundance of not less than 99.999% at the top of the final distillation column; and collecting and encapsulating the electronic specialty grade boron 11.

[0050] In this application, the BF3 feed gas is first subjected to deep purification pretreatment to increase its purity to electronic specialty gas grade (i.e., not less than 99.999%), while simultaneously controlling the moisture content at the source to no more than 10%. The process aims to reduce the probability of BF3 hydrolysis side reactions during subsequent distillation by lowering the ppb level at the source. Then, a specially designed cryogenic distillation process is employed, controlling the total theoretical plate number within a suitable range of 3000-5000 plates and incorporating a progressively increasing reflux ratio. This allows for the generation of electronic-grade boron 11 with an abundance and purity of no less than 99.999% at the top of the final distillation column. Finally, after collecting and encapsulating the electronic-grade boron 11, boron 11 with a purity and abundance of no less than 99.999% can be directly prepared from the BF3 feed gas (i.e., naturally abundant boron 11) through multi-stage enrichment. This distillation purification method, through systematic process design and stringent anhydrous control, is the first to achieve industrial-scale preparation of electronic-grade boron 11 that simultaneously meets the 99.999% purity and abundance standards based on cryogenic distillation technology, filling a technological gap in this field.

[0051] It should be noted that there is no limit to the number of stages in series in the distillation column, and adjustments can be made according to the actual situation.

[0052] As an example, the number of series stages of the distillation column is 2 to 6 (e.g., but not limited to any one of 2, 3, 4, 5, and 6 stages); and / or, the series connection is either horizontal or vertical.

[0053] In this embodiment, the number of series stages and the series configuration of the distillation column can be freely combined, providing a variety of feasible solutions, thereby facilitating the promotion and application of the technical solutions provided in this application. At the same time, by adopting the above-mentioned range of stages, a high total theoretical plate number can be achieved using existing low-temperature distillation columns.

[0054] As an example, the number of stages in a distillation column can be 2 to 5, and the series connection is horizontal.

[0055] In this embodiment, the appropriate number of series stages combined with the horizontal series configuration for targeted production of boron 11 has the following advantages: (1) The horizontal series configuration of 2 to 5 stages can better meet the total theoretical number of trays required for the gas phase enrichment of boron 11. Without building a 100-meter-level ultra-high single tower, the naturally abundant boron 11 can be gradually enriched to an electronic specialty gas level of not less than 99.999%, thereby helping to improve production efficiency and reduce energy consumption; (2) The short-range series pipeline of the horizontal series configuration greatly reduces the sealing dead angle, structurally reducing the probability of external trace moisture intrusion, and can better adapt to electronic specialty gas grade boron 11 with a moisture content not exceeding 10%. The stringent requirements of ppb effectively improve the problems of purity reduction and equipment corrosion caused by BF3 hydrolysis; (3) The horizontal series spatial layout can realize the independent and precise adjustment of core parameters such as temperature, pressure and reflux ratio of each stage of low temperature distillation column, so as to specifically enhance the gas phase mass transfer efficiency of boron 11. Compared with the vertical series multi-stage column with fixed parameters, it is easier to achieve dynamic stability of the material balance of the whole column and ensure the long-term consistency and stability of product abundance.

[0056] It should be noted that there are no restrictions on the installation method of the cryogenic distillation column. For example, it can be a cryogenic distillation column built on the ground or a cryogenic distillation column built underground using deep well technology. The specific method can be adapted to the actual site construction conditions.

[0057] As an example, in multiple distillation columns, the top pressure is independently selected from 80 kPa to 150 kPa (e.g., but not limited to any one of 80 kPa, 90 kPa, 100 kPa, 110 kPa, 120 kPa, 130 kPa, 140 kPa, and 150 kPa, or a range between any two), and the bottom pressure is independently selected from 100 kPa to 200 kPa (e.g., but not limited to 100 kPa, 120 kPa, 140 kPa, 160 kPa, 180 kPa, and 200 kPa). The temperature at the top of the column condenser is independently selected from -105℃ to -92℃ (e.g., but not limited to any one of the temperatures of -105℃, -102℃, -100℃, -98℃, -96℃, -94℃ and -92℃ or ...92℃ and -92℃ or any one of the temperatures of -92℃ and -92℃ or any one of the temperatures of -90℃ to -80℃ (e.g., but not limited to any one of the temperatures of -90℃, -89℃, -88℃, -87℃, -86℃, -85℃, -84℃, -83℃, -82℃, -81℃ and -80℃ or any one of the temperatures of -80℃ and -80℃ or any one of the temperatures of -90℃, -89℃, -88℃, -87℃, -86℃, -85℃, -84℃, -83℃, -82℃, -81℃ and -80℃ or any one of the temperatures of -80℃ and any one of the temperatures of -80℃ and -80℃ or any one of the temperatures of -80℃ and -80℃).

[0058] In this embodiment, based on a horizontal series configuration of 2 to 5 levels, the pressure at the top of the distillation column, the pressure at the bottom of the column, the temperature at the top condenser, and the temperature at the bottom reboiler are all limited to the above range. Through the synergistic cooperation of multiple core parameters, it has the following advantages for the targeted production of boron 11: (1) It can reduce pressure fluctuations in the distillation column, so that boron 11 can always maintain a high separation efficiency during the enrichment process to the top of the gas phase column; at the same time, it can also improve the problem of boron 10 rising to the top of the column due to abnormal pressure fluctuations, thereby ensuring the high abundance and abundance stability of boron 11 generated at the top of the column; (2) It can allow heavy component impurities to be retained at the bottom of the column more efficiently and thoroughly during the gas-liquid exchange process, so that the purity of boron 11 produced at the top of the column can always be maintained at a high level; (3) It can keep BF3 in a stable gas-liquid balance state, improve the problem of material freezing and blocking pipelines in the condenser due to excessively low temperature, so as to meet the continuous and stable operation requirements of low temperature distillation of boron 11.

[0059] As an example, in multiple distillation columns, the top pressure is independently selected from 80 kPa to 130 kPa (e.g., but not limited to any one of 80 kPa, 90 kPa, 100 kPa, 110 kPa, 120 kPa, and 130 kPa, or a range between any two), and the bottom pressure is independently selected from 120 kPa to 200 kPa (e.g., but not limited to 120 kPa, 130 kPa, 140 kPa, 150 kPa, 160 kPa, 170 kPa, 180 kPa, 190 kPa, and 200 kPa). The temperature at the top of the column condenser is independently selected from -100℃ to -95℃ (e.g., but not limited to any one of -100℃, -99℃, -98℃, -97℃, -96℃ and -95℃ or any range between two), and the temperature at the bottom of the column reboiler is independently selected from -88℃ to -82℃ (e.g., but not limited to any one of -88℃, -87℃, -86℃, -85℃, -84℃, -83℃ and -82℃ or any range between two).

[0060] In this embodiment, based on the horizontal series configuration of 2 to 5 levels, the pressure at the top of the distillation column, the pressure at the bottom of the column, the temperature at the top condenser, and the temperature at the bottom reboiler are all further limited within the above range. Through the synergistic cooperation of multiple core parameters, it has the following advantages for the targeted production of boron 11: (1) It can further reduce the pressure fluctuation in the distillation column, so that boron 11 can always maintain a higher separation efficiency during the enrichment process to the top of the gas phase column; at the same time, it can also better improve the problem of boron 10 rising to the top of the column due to abnormal pressure fluctuations, so as to better ensure the high abundance and abundance stability of boron 11 generated at the top of the column; (2) It can make heavy component impurities more efficient and thorough in the gas-liquid exchange process and retain them at the bottom of the column, so that the purity of boron 11 produced at the top of the column can always be maintained at a higher level; (3) It can make BF3 always maintain a more stable gas-liquid balance state, better improve the problem of material freezing and blocking pipelines in the condenser due to excessively low temperature, so as to better adapt to the continuous and stable operation requirements of low temperature distillation of boron 11.

[0061] As an example, the reflux ratios of multiple distillation columns are independently selected from 100 to 500 (e.g., but not limited to any one of 100, 200, 300, 400, and 500, or any range between any two), and the difference in reflux ratios between any two adjacent distillation columns is 50 to 100 (e.g., but not limited to any one of 50, 60, 70, 80, 90, and 100, or any range between any two); and / or, the middle feed flow rate of the first distillation column is 1 kg / h to 10 kg / h (e.g., but not limited to any one of 1 kg / h, 2 kg / h, 4 kg / h, 6 kg / h, 8 kg / h, and 10 kg / h, or any range between any two), and the top discharge flow rate of the last distillation column is 0.1 kg / h to 0.5 kg / h (e.g., but not limited to 0.1 kg / h, 0.2 kg / h, 0.3 kg / h, 0.4 kg / h, etc.). (A point value of either kg / h or 0.5 kg / h, or a range value between the two).

[0062] In this embodiment, based on a horizontal series configuration of 2 to 5 stages, a reflux ratio range of 100 to 500 is set, coupled with an adjacent reflux ratio difference of 50 to 100. This allows the gas-liquid mass transfer load of each distillation column to precisely match the progressive gas-phase enrichment progress of boron-11. This effectively solves the problem of energy waste caused by excessively high reflux ratios in a single column. Simultaneously, it effectively addresses the issue of boron-10 components rising to the top of the column due to insufficient reflux ratios in a single column, thus ensuring high abundance and stability of boron-11 generated at the top. Based on the 2 to 5 stage horizontal series configuration, a middle feed flow rate of 1 kg / h to 10 kg / h is set at the beginning of the distillation column to maintain stable operation within the column during feeding, allowing the material to fully complete gas-liquid mass transfer within the column. A small top discharge flow rate of 0.1 kg / h to 0.5 kg / h is set at the end to maximize the retention of heavy component impurities, ensuring that the final boron-11 abundance and purity consistently reach the electronic specialty gas standard of over 99.999%.

[0063] As an example, in a cryogenic distillation column, the specific surface area of ​​the packing is not less than 1000 m². 2 / m 3 For example, but not limited to, 1000 m 2 / m 3 1200 m 2 / m 3 1400 m 2 / m 3 1600 m 2 / m 3 1800 m 2 / m 3 and 2000 m 2 / m 3 The value of any one of the points or the range between any two.

[0064] In this embodiment, based on a horizontal series configuration of 2 to 5 stages, the specific surface area of ​​the packing in the cryogenic distillation column is limited to the above range, which allows the packing to have a large gas-liquid contact area, significantly improving the gas-phase mass transfer efficiency of boron 11. Based on a horizontal series configuration of 2 to 5 stages, electronic special gas grade standard boron 11 with an abundance and purity of 99.999% or higher is generated at the top of the gas column.

[0065] As an example, the packing in several distillation columns is stainless steel or phosphor bronze packing that has undergone acid washing, alkali washing, water washing, drying and boron trifluoride passivation treatment.

[0066] In this embodiment, the packing material undergoes acid washing, alkali washing, water washing, drying, and boron trifluoride passivation treatment in sequence. Acid washing removes the oxide layer and metal debris from the surface of the packing material, alkali washing neutralizes residual acid, ultrapure water rinsing removes acid and alkali residues, and high-temperature drying thoroughly removes the free water adsorbed on the surface, preventing the subsequent introduction of moisture that could trigger BF3 hydrolysis. BF3 passivates the surface of the packing material in advance, forming a dense and stable fluoride protective film on the inner wall surface, reducing the probability of BF3 reacting with the packing material during low-temperature distillation, so as to form electronic special gas grade boron 11.

[0067] As an example, the inner walls of multiple distillation columns are all covered with a corrosion-resistant protective layer; and / or, the inner walls of multiple distillation columns are electropolished to achieve a surface roughness of no more than 0.2 μm.

[0068] In this embodiment, the inner wall of each cryogenic distillation column is equipped with a corrosion-resistant protective layer (e.g., pure nickel, Hastelloy C-276) and / or is pre-treated with electrolytic polishing (until the surface roughness is no higher than 0.2 μm) before use. This setup, combined with high-temperature inert gas purging and vacuum treatment, can efficiently and thoroughly remove moisture and impurities from the entire cryogenic distillation system, reducing the decrease in the purity of Boron 11 products and equipment corrosion caused by BF3 hydrolysis during cryogenic distillation.

[0069] As an example, any two adjacent distillation columns are connected by a first transfer tank, which is configured to: firstly condense the gaseous material output from the top of the previous distillation column into a liquid for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the middle feed port of the next distillation column.

[0070] In this embodiment, any two adjacent distillation columns are connected by a first transfer tank that can both cool and liquefy the gas and heat and vaporize the liquid. This allows for the transfer of materials between the distillation columns without the use of transfer pumps or compressors. This configuration has the following advantages: (1) No transfer pumps or compressors are required to drive the seals, thus eliminating the risk of trace moisture and air intrusion at the dynamic seals. At the same time, by eliminating such power transmission equipment that drives the seals, the layout of the series pipelines is simpler, reducing dead zones in the seals and effectively reducing the probability of impurity retention. This makes it better suited for electronic special gas grade boron 11 with a moisture content not exceeding 10%. (1) The stringent control requirements of ppb effectively improve the problems of purity reduction and equipment corrosion caused by BF3 hydrolysis; (2) In view of the extremely low volatility of BF3, this transmission method can maintain the pressure stability between adjacent two-stage towers, thereby ensuring the continuous and smooth progress of the gas phase enrichment process of boron 11; (3) No transmission pump or compressor is required throughout the process, which greatly reduces the overall energy consumption of the production line. At the same time, the daily maintenance of pumps and compressors is eliminated, reducing the equipment failure points and allowing the series distillation unit to operate continuously and stably for a long time.

[0071] It should be noted that the specific form of the transfer storage tank is not described in this application embodiment, as long as it has both cooling and liquefaction functions as well as heating and vaporization functions. For specific structural design and functional description, please refer to the collection unit in patent CN121927399A. The specific way to achieve the function is as follows: when it is necessary to collect and temporarily store gaseous boron trifluoride from the previous stage distillation column, the gaseous boron trifluoride is cooled and liquefied by using a low-temperature heat exchange medium (such as liquid nitrogen), so that liquid boron trifluoride can be collected and temporarily stored in liquid form; when it is necessary to transport materials to the next stage distillation column, the liquid boron trifluoride can be vaporized and transported to the next stage low-temperature distillation column by heating and pressurizing the heating element built into the collection chamber.

[0072] As an example, the steps for deep purification and pretreatment of BF3 feed gas include: passing the BF3 feed gas sequentially through a cold trap, a chemical adsorption bed, a molecular sieve dryer, a light-weight distillation column, and a heavy-weight distillation column. In the heavy-weight distillation column, the processing temperature is -32℃ to -52℃ (e.g., but not limited to any one of -32℃, -40℃, -50℃, and -52℃, or a range between any two), and the processing pressure is 1.2 MPa to 2 MPa (e.g., but not limited to any one of 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, and 2 MPa, or a range between any two). The pressure in the light-weight distillation column is higher than the pressure in the heavy-weight distillation column.

[0073] In this embodiment, the deep purification pretreatment process is carried out according to the above steps, which can purify industrial-grade BF3 feed gas from various sources to a purity of not less than 99.999% and a water content of not more than 10 ppb, thus having good feed gas compatibility.

[0074] More importantly, the final stage of deep purification pretreatment is completed in a low-temperature de-heavy distillation column, which means that the temperature of the obtained BF3 purified gas is also low. Therefore, the BF3 purified gas can be directly sent to the first low-temperature distillation column under low-temperature operation without additional pre-cooling process. This scientific design has many advantages: (1) The low-temperature distillation stage maintains the low temperature of BF3 throughout the process, effectively avoiding the risk of backflow of trace moisture on the inner wall of the pipeline during the normal temperature transportation of purified gas, further strengthening the deep water-free control effect of the whole process, and ensuring that the moisture index of the final boron 11 product is consistently below 10 ppb; (2) The independent refrigeration equipment at the feed end is eliminated, which greatly reduces the refrigeration energy consumption of the whole process. Compared with the traditional normal temperature feed process, the refrigeration load can be reduced by about 30%; (3) The gas-liquid state of the low-temperature BF3 purified gas is more uniform, which can effectively improve the flooding problem caused by uneven local vaporization after the purified gas enters the first column, and can greatly improve the operational stability of the horizontal series system.

[0075] As an example, in a light distillation column, the processing temperature is -50°C to -30°C (e.g., but not limited to any one of -50°C, -45°C, -40°C, -35°C, and -30°C, or any range between any two), and the processing pressure is 1.4 MPa to 2.2 MPa (e.g., but not limited to any one of 1.4 MPa, 1.6 MPa, 1.8 MPa, 2.0 MPa, and 2.2 MPa, or any range between any two).

[0076] In this embodiment, controlling the process parameters of the light component removal distillation column within the above-mentioned range can effectively remove light component impurities (such as nitrogen, oxygen, and argon) from the feed gas.

[0077] As an example, the temperature at the cold trap is -50°C to -30°C, for example, but not limited to any one of -50°C, -45°C, -40°C, -35°C and -30°C, or any range between two of them.

[0078] In this embodiment, limiting the temperature at the cold trap to the above-mentioned range can effectively remove high-boiling-point impurities (such as carbon dioxide, water, etc.) adsorbed in the raw material gas.

[0079] As an example, the adsorbent in the chemical adsorption bed is selected from alumina loaded with an alkali metal compound, wherein the alkali metal compound includes at least one from KF and NaF, and the processing temperature is -20°C to 0°C (e.g., but not limited to any one of -20°C, -15°C, -10°C, -5°C and 0°C or any range between two of them).

[0080] In this embodiment, a chemical adsorption bed containing the above-mentioned adsorbent is used and the process is carried out at the above-mentioned temperature, which can effectively remove acidic impurities such as HF from the raw gas.

[0081] As an example, the molecular sieve in the molecular sieve dryer is selected from at least one of 3A molecular sieve and 4A molecular sieve.

[0082] In this embodiment, a dryer containing the aforementioned molecular sieves can further remove residual high-boiling-point impurities from the raw material gas.

[0083] As an example, before the BF3 feed gas is delivered to the cold trap, it also includes a first-stage filtration process and a second-stage filtration process. The filter precision of the first-stage filtration process is 5 μm to 10 μm (e.g., but not limited to any one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm and 10 μm or any range between two), and the filter precision of the second-stage filtration process is 0.5 μm to 1 μm (e.g., but not limited to any one of 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm and 1 μm or any range between two).

[0084] In this embodiment, the BF3 feed gas is subjected to two-stage filtration before being delivered to the cold trap, and the precision of the two-stage filters is limited to the aforementioned range. The first-stage filtration can intercept larger solid particles and reaction by-product debris in the BF3 feed gas, reducing the risk of large impurities directly impacting the subsequent precision filter element and causing blockage. The second-stage filtration can further remove the fine particles remaining from the first stage, while intercepting trace amounts of fluoride solid suspensions generated by BF3 hydrolysis, reducing the risk of these impurities freezing and accumulating at low temperatures after entering the cold trap and causing blockage of the cold trap flow channel.

[0085] As an example, before the BF3 purified gas is delivered to the first-end distillation column, a third-stage filtration process is also included, wherein the filter precision of the third-stage filtration process is 0.003 μm to 0.01 μm (e.g., but not limited to any one of precisions of 0.003 μm, 0.005 μm, 0.006 μm, 0.008 μm, 0.009 μm and 0.01 μm or any range between two).

[0086] In this embodiment, based on the previous two-stage filtration process, a third-stage filtration process is performed on the purified gas before it is delivered to the first distillation column of BF3, and the filter precision is limited to the above-mentioned range. This can more thoroughly intercept any submicron-sized particles and aerosol impurities that may remain in the raw gas, thereby improving the problem of impurities depositing on the trays and disrupting the gas-liquid mass transfer balance. At the same time, it can also ensure that the particle size of the final boron 11 obtained meets the electronic special gas grade standard.

[0087] As an example, before the deep purification pretreatment step, the process includes: continuously purging the light-to-heavy distillation column and the heavy-to-light distillation column with high-purity inert gas at 80°C to 120°C (e.g., but not limited to any one of 80°C, 90°C, 100°C, 110°C, and 120°C or any range between two) for 12 h to 24 h (e.g., but not limited to any one of 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, and 24 h or any range between two). After purging, the light-to-heavy distillation column and the heavy-to-light distillation column are evacuated until the vacuum level is no higher than 10 Pa.

[0088] In this embodiment, before deep purification pretreatment, the entire light and heavy distillation columns are continuously purged with high-temperature inert gas at around 100°C for 12-24 hours, and vacuum treatment is also performed. This can thoroughly remove residual moisture and impurities from the entire distillation system in a comprehensive and thorough manner, thereby reducing the decrease in the purity of Boron 11 products and equipment corrosion caused by BF3 hydrolysis during low-temperature distillation.

[0089] It should be noted that the high-temperature inert gas purging and subsequent vacuuming are part of a whole process, and this process can be repeated as many times as desired.

[0090] It should be noted that the type of high-purity inert gas is not limited; for example, it can be at least one of nitrogen and argon.

[0091] As an example, before the step of feeding the purified BF3 gas into a multi-stage series distillation column for multi-stage enrichment, the process includes: continuously purging the multi-stage series distillation column with high-purity inert gas at 80°C to 120°C (e.g., but not limited to any one of 80°C, 90°C, 100°C, 110°C, and 120°C, or any range between two) for 7 to 20 days (e.g., but not limited to any one of 7 days, 10 days, 12 days, 14 days, 16 days, 18 days, and 20 days, or any range between two). After purging, the multi-stage series distillation column is evacuated until the vacuum level does not exceed 10 Pa.

[0092] In this embodiment, before multi-stage enrichment, the entire distillation system is continuously purged with high-temperature inert gas at around 100°C for 7 to 20 days, and vacuum treatment is also performed. This can thoroughly remove residual moisture and impurities from the entire low-temperature distillation system in a comprehensive and thorough manner, thereby reducing the decrease in the purity of Boron 11 products and equipment corrosion caused by BF3 hydrolysis during the low-temperature distillation process.

[0093] It should be noted that the high-temperature inert gas purging and subsequent vacuuming are part of a whole process, and the number of times this process can be repeated is unlimited, for example, 2 to 8 times.

[0094] It should be noted that the type of high-purity inert gas is not limited; for example, it can be at least one of nitrogen and argon.

[0095] As an example, the steps of collecting and encapsulating electronic specialty grade boron 11 include: collecting electronic specialty grade boron 11 from the top of the terminal distillation column and subjecting it to a fourth-stage filtration process, wherein the filter precision of the fourth-stage filtration process is 0.003 μm to 0.01 μm (e.g., but not limited to any one of precisions of 0.003 μm, 0.005 μm, 0.006 μm, 0.008 μm, 0.009 μm, and 0.01 μm, or a range between any two); transporting the electronic specialty grade boron 11 after the fourth-stage filtration process to a collection bottle via a second transfer tank for encapsulation; wherein the second transfer tank is configured to: first condense the gaseous material after the fourth-stage filtration process into a liquid material for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the collection bottle.

[0096] In this embodiment, the electronic specialty grade boron 11 undergoes a fourth-stage filtration process using a filter of the aforementioned specifications before entering the collection bottle. This effectively intercepts trace amounts of fluoride solid particles that may be generated from the hydrolysis of BF3 during the low-temperature distillation process, tiny debris detached from the inner wall of the pipeline, and residual trace amounts of moisture and light component impurities. This ensures that the particle size of the final boron 11 meets the electronic specialty grade standard. Simultaneously, the filter and the collection bottle are connected by a second transfer tank that can both cool and liquefy the gas and heat and vaporize the liquid. This allows for material transfer between the two without the use of a transfer pump or compressor. This configuration eliminates the need for transfer pumps or compressors that drive the seals, thus eliminating the risk of trace amounts of moisture and air intrusion at the dynamic seals. Furthermore, by eliminating such power transmission equipment that drives the seals, the pipeline layout is simpler, sealing dead zones are reduced, and the probability of impurity retention is effectively lowered. This allows it to better meet the stringent control requirement that the moisture content of the electronic specialty grade boron 11 not exceed 10 ppb.

[0097] It should be noted that the specific form of the second transfer tank can be set up according to that of the first transfer tank.

[0098] As an example, prior to the encapsulation process, the collection bottle undergoes electrolytic polishing, vacuum drying, and passivation. The valve of the collection bottle is a diaphragm valve, and the valve seal is made of perfluoroether rubber.

[0099] In this embodiment, by strictly following the above requirements for encapsulation, it is possible to encapsulate electronic specialty gas grade boron 11 with a purity and abundance of not less than 99.999%, and the encapsulated boron 11 product can maintain the electronic specialty gas grade standard for a long time.

[0100] As an example, in the polishing process, electropolishing is used until the roughness of the inner wall of the collection bottle is no higher than 0.2 μm.

[0101] In this embodiment, polishing according to the above standards can make the inner wall of the collection bottle form a smooth surface, which greatly reduces the adsorption of moisture and impurities on the inner wall, so that the packaged product can obtain electronic special gas grade boron 11 with a purity and abundance of not less than 99.999%, and can also maintain the electronic special gas grade standard for a long time after packaging.

[0102] As an example, in the vacuum drying process, under heating conditions of 80℃~120℃, the vacuum level inside the collection bottle is continuously evacuated until it does not exceed 1×10⁻⁶. -5 Pa and keep it warm and pressurized for 12 h to 24 h.

[0103] In this embodiment, vacuum drying according to the above standards can completely remove trace amounts of moisture and impurities adhering to the inner wall of the collection bottle.

[0104] As an example, in the passivation process: the inner wall surface of the collection bottle is passivated in advance with high-purity BF3, forming a dense and stable fluoride protective film on the inner wall surface.

[0105] In this embodiment, passivation treatment according to the above process can result in electronic specialty gas grade boron 11 with a purity and abundance of not less than 99.999%, and can also ensure that the encapsulated boron 11 product maintains the electronic specialty gas grade standard for a long time.

[0106] It should be noted that, for the distillation purification method of electronic special gas grade boron 11, the process steps that are not specifically described or limited can be set according to the conventional process in this field.

[0107] As an example, a process flow diagram of the distillation purification method for electronic specialty grade boron 11 is exemplarily provided. Figure 1 .

[0108] To better understand the technical solution, a structural diagram of a distillation and purification preparation system is provided here for illustration. (See attached diagram for details.) Figure 2 and Figure 3 Along the material conveying direction, the distillation and purification preparation system 1 includes, in sequence, a first-stage filter 10a, a second-stage filter 10b, a cold trap 20, a chemical adsorption bed 30, a molecular sieve dryer 40, a light-weight removal distillation column 50a, a heavy-weight removal distillation column 50b, a third-stage filter 10c, a five-stage multi-stage enrichment unit 60 connected in series (specifically including, in sequence, a first-stage distillation column 60a, a second-stage distillation column 60b, a third-stage distillation column 60c, a fourth-stage distillation column 60d, and a fifth-stage distillation column 60e, with any two adjacent distillation columns connected via a first transfer tank 70a), a fourth-stage filter 10d, a second transfer tank 70b, and a collection bottle 80.

[0109] Continue reading Figure 4 A third transfer tank 70c is also provided between the third filter 10c and the multi-stage enrichment unit 60.

[0110] In this embodiment, a third transfer tank 70c is added between the third-stage filter 10c and the multi-stage enrichment unit 60. The liquefaction buffering effect of the third transfer tank 70c helps to connect and coordinate the pretreatment stage and the multi-stage enrichment treatment stage.

[0111] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0112] Example 1 This application provides a method for the distillation purification of electronic special gas grade boron 11, including the following steps: (1) Purification of raw gas The light and heavy phase removal distillation columns were continuously purged with high-purity nitrogen at 100℃ for 20 h. After purging, the light and heavy phase removal distillation columns were evacuated until the vacuum level did not exceed 10 Pa. This process was repeated three times until the moisture content did not exceed 10 ppb. The industrial-grade BF3 feed gas (boron 11 abundance of 80.2%) underwent first-stage and second-stage filtration treatments. The first-stage filter had a filter precision of 6 μm, and the second-stage filter had a filter precision of 0.5 μm.

[0113] The filtered feed gas is sequentially passed through a cold trap, a chemical adsorption bed, a molecular sieve dryer, a light component removal distillation column, and a heavy component removal distillation column. The temperature in the cold trap is -40°C to remove heavy component impurities (e.g., carbon dioxide and water). The adsorbent in the chemical adsorption bed is selected from alumina loaded with NaF, and the processing temperature is -10°C to remove acidic impurities such as HF. The molecular sieve in the molecular sieve dryer is 3A molecular sieve to further remove residual heavy component impurities in the feed gas. In the light component removal distillation column, the processing temperature is -40°C and the processing pressure is 2.2 MPa to remove light component impurities (e.g., nitrogen, oxygen, and argon). In the heavy component removal distillation column, the processing temperature is -50°C and the processing pressure is 2 MPa to completely remove residual heavy component impurities in the feed gas. The feed gas after passing through the heavy component removal distillation column is then passed through a filter with a filter precision of 0.003 μm (third-stage filtration) to obtain purified BF3 gas with a purity of not less than 99.999% and a water content of not more than 10 ppb.

[0114] (2) Multi-stage low-temperature distillation enrichment The multi-stage series distillation columns consist of five horizontally connected stages. All cryogenic distillation columns are installed above ground and are of identical specifications. Specifically, the inner walls of each column have a corrosion-resistant protective layer (pure nickel) and are pre-treated with electrolytic polishing (until the surface roughness is no higher than 0.2 μm). The packing material in the cryogenic distillation columns is 316L stainless steel that has undergone sequential acid washing, alkali washing, water washing, drying, and boron trifluoride passivation treatment. The specific surface area of ​​the packing material is 1400 m². 2 / m 3 The multi-stage distillation column was continuously purged with high-purity nitrogen at 100℃ for 10 days. After purging, the multi-stage distillation column was evacuated until the vacuum level was no higher than 10 Pa. The entire process was repeated 3 times until the moisture content was no higher than 10 ppb.

[0115] Then, the low-temperature purified gas in (1) is introduced into the first-stage low-temperature distillation column after impurity removal and enriched in multiple stages in sequence. The total theoretical number of plates is 4000, the feed flow rate is 4 kg / h, the reflux ratios in the five-stage low-temperature distillation columns are 150, 200, 250, 300 and 400 respectively, the top pressure of the five-stage low-temperature distillation columns is 100 kPa, the bottom pressure is 160 kPa, the temperature at the top condenser is -98℃, and the temperature at the bottom reboiler is -86℃. The two adjacent low-temperature distillation columns are connected by the first transfer storage tank (to cool down and liquefy the gaseous boron trifluoride in the previous stage distillation column, and then heat up and pressurize it through the heating element in the collection chamber to vaporize the liquid boron trifluoride and transport it to the next stage low-temperature distillation column) so as to generate electronic special gas grade boron 11 with an abundance of not less than 99.999% at the top of the terminal distillation column.

[0116] (3) Packaging process Before encapsulation, the collection bottle undergoes electrolytic polishing, vacuum drying, and passivation. The valves on the collection bottle are diaphragm valves, and the valve seals are made of perfluoroether rubber. In the polishing step, electrolytic polishing is used until the inner wall roughness of the collection bottle is no higher than 0.2 μm. In the vacuum drying step, under heating at 100℃, a vacuum is continuously evacuated until the vacuum level inside the collection bottle does not exceed 1×10⁻⁶. -5 Pa and keep it warm and pressure for 20 h; in the passivation process: high-purity BF3 is used to passivate the inner wall surface of the collection bottle in advance, forming a dense and stable fluoride protective film on the inner wall surface.

[0117] Then, the electronic special gas-grade boron 11 is collected from the top of the terminal distillation column and subjected to a fourth-stage filtration process. The top discharge flow rate of the terminal distillation column is 0.3 kg / h, and the filter precision of the fourth-stage filtration process is 0.003 μm. The electronic special gas-grade boron 11 after the fourth-stage filtration process is transported to the collection bottle via the second transfer storage tank for sealing (the gaseous boron trifluoride from the distillation column is cooled and liquefied for temporary storage, and then heated and pressurized by the heating element in the collection chamber to vaporize the liquid boron trifluoride and pressurize it for delivery to the collection bottle; the entire sealing process is completed in a Class 1000 cleanroom, and a traceability label can be affixed to the outside of the collection bottle after sealing).

[0118] Test case The electronic special gas grade boron 11 prepared in Example 1 of this application was used as a sample, and its composition was tested. The test results were then compared with those required by existing manufacturers. 11 A comparative analysis of the indicators of BF3 was conducted, and the specific results can be found in Table 1.

[0119] Table 1

[0120] As shown in Table 1, the samples prepared in the embodiments of this application are as follows: 11 The purity and abundance of BF3 both reach 99.999%, the HF content is less than 1 ppmv, and all other components meet the gas usage standards of existing manufacturers.

[0121] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for the distillation purification of electronic special gas grade boron 11, characterized in that, Includes the following steps: The BF3 feed gas is subjected to deep purification pretreatment to obtain purified BF3 gas with a purity of not less than 99.999% and a water content of not more than 10 ppb. The purified BF3 gas is fed into a multi-stage series of distillation columns for multi-stage enrichment. The total theoretical number of the multiple distillation columns is 3,000 to 5,000, and the reflux ratio of each distillation column increases in a gradient, so as to generate electronic special gas grade boron 11 with an abundance of not less than 99.999% at the top of the final distillation column. The electronic special gas grade boron 11 is extracted and packaged.

2. The distillation purification method according to claim 1, characterized in that, The number of stages in the distillation column is 2 to 6; and / or, the series connection is horizontal or vertical.

3. The distillation purification method according to claim 2, characterized in that, The distillation column has 2 to 5 stages in series, and the series connection is horizontal.

4. The distillation purification method according to claim 3, characterized in that, In multiple distillation columns, the top pressure is independently selected from 80 kPa to 150 kPa, the bottom pressure is independently selected from 100 kPa to 200 kPa, the temperature at the top condenser is independently selected from -105℃ to -92℃, and the temperature at the bottom reboiler is independently selected from -90℃ to -80℃. Optionally, in multiple distillation columns, the top pressure is independently selected from 80 kPa to 130 kPa, the bottom pressure is independently selected from 120 kPa to 200 kPa, the temperature at the top condenser is independently selected from -100℃ to -95℃, and the temperature at the bottom reboiler is independently selected from -88℃ to -82℃.

5. The distillation purification method according to claim 3, characterized in that, The reflux ratios of multiple distillation columns are independently selected from 100 to 500, and the difference between the reflux ratios of any two adjacent distillation columns is 50 to 100. And / or, the feed flow rate in the middle of the first distillation column is 1 kg / h to 10 kg / h, and the top discharge flow rate in the last distillation column is 0.1 kg / h to 0.5 kg / h.

6. The distillation purification method according to claim 3, characterized in that, The packing materials in multiple distillation columns are all stainless steel or phosphor bronze packing materials that have undergone acid washing, alkali washing, water washing, drying, and boron trifluoride passivation treatment, and the specific surface area of ​​the packing materials is not less than 1000 m². 2 / m 3 ; And / or, the inner walls of multiple distillation columns are equipped with a corrosion-resistant protective layer; And / or, the inner walls of multiple distillation columns are electropolished to ensure that the surface roughness of the inner walls is no higher than 0.2 μm.

7. The distillation purification method according to any one of claims 1 to 6, characterized in that, Any two adjacent distillation columns are connected by a first transfer storage tank, which is configured to: firstly condense the gaseous material output from the top of the previous distillation column into a liquid material for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the middle feed port of the next distillation column.

8. The distillation purification method according to any one of claims 1 to 6, characterized in that, The steps for deep purification and pretreatment of BF3 feed gas include: passing the BF3 feed gas sequentially through a cold trap, a chemical adsorption bed, a molecular sieve dryer, a light-weight distillation column, and a heavy-weight distillation column, wherein the heavy-weight distillation column has a processing temperature of -32℃ to -52℃ and a processing pressure of 1.2 MPa to 2 MPa; the pressure of the light-weight distillation column is higher than the pressure of the heavy-weight distillation column. Optionally, before the BF3 feed gas is delivered to the cold trap, the BF3 feed gas is further subjected to a first-stage filtration process and a second-stage filtration process, wherein the filter precision of the first-stage filtration process is 5 μm to 10 μm, and the filter precision of the second-stage filtration process is 0.5 μm to 1 μm. Optionally, before the BF3 purified gas is delivered to the first distillation column, a third-stage filtration process is performed on the BF3 purified gas, wherein the filter precision of the third-stage filtration process is 0.003 μm to 0.01 μm.

9. The distillation purification method according to claim 8, characterized in that, The processing temperature of the cold trap is -50℃ to -30℃; And / or, the adsorbent of the chemical adsorption bed includes alumina loaded with an alkali metal compound, the alkali metal compound including at least one of KF and NaF, and the processing temperature of the chemical adsorption bed is -20℃ to 0℃; And / or, the molecular sieve of the molecular sieve dryer includes at least one of 3A molecular sieve and 4A molecular sieve.

10. The distillation purification method according to claim 8, characterized in that, Before performing the deep purification pretreatment step, the process further includes: continuously purging the light distillation column and the heavy distillation column with high-purity inert gas at 80℃~120℃ for 12 h~24 h. After the purging is completed, the light distillation column and the heavy distillation column are evacuated until the vacuum degree is not higher than 10 Pa. And / or, before the step of conveying the BF3 purified gas to a multi-stage series distillation column for multi-stage enrichment, the method further includes: continuously purging the multi-stage series distillation column with high-purity inert gas at 80℃~120℃ for 7 to 20 days; after the purging is completed, vacuuming the multi-stage series distillation column until the vacuum degree is not higher than 10 Pa.

11. The distillation purification method according to any one of claims 1 to 6, characterized in that, The step of extracting and encapsulating the electronic special gas-grade boron 11 includes: The electronic special gas grade boron 11 is collected from the top of the terminal distillation column and subjected to a fourth-stage filtration process, wherein the filter precision of the fourth-stage filtration process is 0.003 μm to 0.01 μm; The electronic special gas-grade boron 11, after undergoing the fourth stage filtration, is transported to a collection bottle via a second transfer storage tank for sealing. The second transfer storage tank is configured to: first condense the gaseous material after the fourth stage filtration into a liquid for temporary storage, and then vaporize the liquid material into a gaseous state by heating and transport it to the collection bottle. Optionally, before performing the encapsulation process, the collection bottle may be subjected to electrolytic polishing, vacuum drying, and passivation treatment, and the valve of the collection bottle is a diaphragm valve and the valve seal is made of perfluoroether rubber.

12. The distillation purification method according to claim 11, characterized in that, In the electropolishing process, the surface roughness of the inner wall of the collection bottle is not higher than 0.2 μm. And / or, the drying process includes: continuously evacuating the vacuum at 80°C to 120°C until the vacuum level inside the collection bottle does not exceed 1×10⁻⁶. -5 Pa and keep it under heat and pressure for 12 h~24 h; And / or, the passivation process includes: passivating the inner wall surface of the collection bottle with high-purity BF3.

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