A method for removing impurities by adsorption in a process for preparing high abundance silicon-28

Abstract

The application relates to the technical field of isotope purification, and discloses an adsorption impurity removal method for a high-abundance silicon-28 preparation process, which is applied to a circulating system including a complexing reaction, exchange rectification and a heating pyrolysis unit, and comprises the following steps: S1: adding silicon-containing and impurity-containing liquid phase materials discharged from a decomposition tower in the circulating system into an impurity complexing agent, and feeding the materials into a first adsorption device filled with a conventional adsorbent; S2: continuously feeding the pre-impurity removal liquid phase materials in the S1 into a second adsorption device filled with an amino adsorbent; and S3: returning the purified liquid phase materials obtained in the S2 to corresponding sections of a complexing tower or an exchange tower in the circulating system. The adsorption impurity removal method for the high-abundance silicon-28 preparation process can save the high-energy-consumption heating and condensation links in the rectification process, greatly reduces the energy consumption of the impurity removal system, the adsorbent is an industrial commonly-used low-cost material, and the overall production cost is further reduced.

Description

Technical Field

[0001] This invention relates to the field of isotope purification technology, specifically to an adsorption and impurity removal method for preparing high-abundance silicon-28. Background Technology

[0002] Publications (announcements) with numbers CN116688756A and CN116832615A disclose the realization of continuous production of boron and silicon isotopes. Both are based on the chemical exchange method and adopt a closed-loop device architecture of "feeding tower - complexation tower - multi-stage exchange tower - decomposition tower - impurity removal tower". The boron isotope process uses boron trifluoride as raw material and anisole as complexing agent, controlling the complexation degree to 85% to 150% and the boron 11 abundance to ≥99%. The continuous extraction of Boron-11 / Boron-10 was achieved at 7%. The silicon isotope process uses silicon tetrafluoride as raw material and anisole / trimethyl borate as complexing agent. By controlling the molar ratio of complexing agent to silicon tetrafluoride to 1.5-3 and silicon-28 abundance ≥99.5%, the separation of silicon-28 and silicon-29 / 30 byproducts was achieved. Both processes were purified by distillation, allowing the complexing agent to be recycled after purification. This enabled the industrial continuous production of isotopes, increasing production capacity and reducing energy consumption.

[0003] However, although this method achieves continuous production of boron and silicon isotopes through chemical exchange, both require distillation for impurity removal, which has significant drawbacks:

[0004] Because the difference between the distribution coefficients of impurities and target components is limited, and the concentrations may deviate from the theoretical values ​​at low concentrations, and because there are engineering upper limits on the number of trays and reflux ratios of industrial equipment, the distillation method is limited by the gas-liquid equilibrium distribution coefficient and is difficult to remove low-content impurities of less than 0.1% to 0.01%.

[0005] Distillation separates components based solely on differences in boiling points, which is a physical separation method without chemical specificity. However, some harmful impurities in the system have boiling points close to and distribution coefficients nearly identical to those of the target components, and some may even form azeotropes. Therefore, effective separation cannot be achieved through gas-liquid countercurrent, and it is impossible to target and remove specific types of impurities. Impurities with boiling points close to or overlapping with the target components are difficult to remove completely. Summary of the Invention

[0006] (a) Technical problems to be solved:

[0007] To address the shortcomings of existing technologies, this invention provides an adsorption-based impurity removal method for preparing high-abundance silicon-28, which solves the problems mentioned in the background technology of difficulty in deeply removing low-content impurities and the inability to target impurities.

[0008] (II) Technical Solution:

[0009] To achieve the above objectives, the present invention provides the following technical solution: an adsorption-based impurity removal method for preparing high-abundance silicon-28, applied to a circulating system including complexation reaction, exchange distillation, and heating pyrolysis units, comprising the following steps:

[0010] S1: Add the silicon-containing and impurity-containing liquid phase material discharged from the decomposition tower in the circulation system to the impurity complexing agent, and pass it into the first adsorption device filled with conventional adsorbent. Remove the heavy component impurities in the silicon-containing and impurity-containing liquid phase material by physical adsorption to obtain the pre-impurity-removed liquid phase material.

[0011] S2: The pre-purified liquid phase material in S1 is continuously passed into a second adsorption device filled with amino adsorbent. Through chemical adsorption and ion exchange, the residual harmful impurities in the pre-purified liquid phase material are removed to obtain a purified liquid phase material with a single component concentration of harmful impurities ≤50ppm.

[0012] S3: The purified liquid material obtained in S2 is returned to the corresponding section of the complexing tower or exchange tower in the circulation system to form a closed process loop, and high abundance silicon-28 with an abundance of 99.9% to 99.999% is finally prepared in the circulation system.

[0013] Preferably, the conventional adsorbent is at least one of activated carbon and diatomaceous earth.

[0014] Preferably, the heavy component impurities include pentanal and pentanoic acid generated by the oxidation of pentanol, C10 or C15 long-chain hydrocarbons generated by the polymerization of pentanol, complexing agent droplet entrainment, and high-content oxygen-containing byproducts.

[0015] Preferably, the physical adsorption is van der Waals adsorption, and the environment for van der Waals adsorption is atmospheric pressure conditions without additional heating or cooling, with a material space velocity of 0.5–2 h⁻¹. -1 The residence time of the silicon-containing and impurity-containing liquid phase material in the first adsorption device is 30-60 minutes, achieving a heavy component impurity removal rate of ≥95%.

[0016] Preferably, the impurity complexing agent is polyethylene glycol dimethyl ether with a mass ratio of 0.1% to 0.5% and a molecular weight of 200 to 400. The polyethylene glycol dimethyl ether is used to first complex hydrophobic heavy component impurities to form easily adsorbable complexes, and then to directionally remove heavy component impurities through complexation-adsorption coupling with the conventional adsorbent.

[0017] Preferably, the amino adsorbent is at least one of an amino-containing resin and an amino-modified activated carbon, wherein the amino-modified activated carbon is prepared by modifying coal-based activated carbon with γ-aminopropyltriethoxysilane, and the amino content is 5% by mass.

[0018] Preferably, the second adsorption device is filled with a double layer of amino-modified activated carbon and amino-containing resin, with a filling mass ratio of 1:2.

[0019] Preferably, the first adsorption device and the second adsorption device are at least one of a filter tower, a two-stage full circulation adsorption vessel, and a fixed bed adsorption column. When a fixed bed adsorption column is used, the height of the fixed bed adsorption column is not less than 1 meter.

[0020] Preferably, the first adsorption device and the second adsorption device are arranged in series as two stages.

[0021] Preferably, the harmful impurities include hydrogen fluoride, fluorosilicic acid, silicic acid, pentaldehyde, and valeric acid, and the total concentration of harmful impurities after treatment by the second adsorption device is ≤100ppm.

[0022] (III) Beneficial Effects:

[0023] The adsorption and impurity removal method for preparing high-abundance silicon-28 provided by this invention has the following beneficial effects:

[0024] 1. This adsorption-based impurity removal method for preparing high-abundance silicon-28 employs a combination of conventional adsorbents and amino adsorbents. The entire impurity removal operation is completed under normal pressure conditions without additional heating or cooling, eliminating the need to maintain the high-temperature environment and high reflux ratio required for distillation. This eliminates the energy-intensive heating and condensation steps in the distillation process, significantly reducing the energy consumption of the impurity removal system. Furthermore, the adsorbent is a commonly used low-cost material in industry, further reducing the overall production cost.

[0025] 2. This adsorption-based impurity removal method for preparing high-abundance silicon-28 achieves deep impurity removal through a two-stage series adsorption structure. First, more than 95% of heavy component impurities are removed by conventional adsorbents. Then, through the chemical adsorption and ion exchange of amino-targeted adsorbents, the technical bottleneck of distillation method, which is limited by the gas-liquid equilibrium distribution coefficient, is overcome. The concentration of single components of harmful impurities such as hydrogen fluoride and fluorosilicic acid is controlled to ≤50ppm and the total concentration of harmful impurities is ≤100ppm, thereby achieving efficient and deep removal of low-content harmful impurities of 0.1% to 0.01%.

[0026] 3. This adsorption-based impurity removal method for preparing high-abundance silicon-28 employs a step-by-step targeted impurity removal strategy of "removing heavy components first, then harmful ones." For heavy component impurities, conventional adsorbents such as activated carbon and diatomaceous earth are used for physical adsorption, while for acidic and polar harmful impurities, amino-modified activated carbon and amino-containing resins are used for chemical adsorption. Instead of separating impurities solely based on boiling point differences, this method matches specific adsorbents to the physicochemical properties of different impurities, thereby achieving precise separation of different types of impurities and thoroughly removing various difficult-to-separate impurities with boiling points close to or overlapping with those of silicon tetrafluoride-28. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] An adsorption-based impurity removal method for preparing high-abundance silicon-28 according to a preferred embodiment of the present invention will be described in detail below:

[0030] An adsorption-based impurity removal method for preparing high-abundance silicon-28 is applied to a circulating system comprising a complexation reaction, exchange distillation, and heating pyrolysis unit, specifically the circulating system disclosed in two authorized patents with publication (announcement) numbers CN116832615A and CN116688756A. Specifically:

[0031] A continuous silicon isotope production process, disclosed in publication CN116832615A, utilizes a closed-loop system comprising a feed tower, a complexation tower, a multi-stage exchange tower, a decomposition tower, and a purification tower. Using silicon fluoride as raw material and anisole or trimethyl borate as a complexing agent, the molar ratio of the complexing agent to silicon tetrafluoride is controlled at 1.5–3 to achieve continuous separation of silicon-28 and silicon-29 / 30 byproducts, ultimately yielding a silicon-28 product with an abundance ≥99.5%. In this process, after the complex is pyrolyzed in the decomposition tower, the liquid phase discharged from the tower bottom (mainly containing the complexing agent and various impurities generated in the reaction) needs to be purified in the purification tower for recycling. The adsorption purification method described in this application is a crucial purification step connecting the decomposition tower and the purification tower (or complexation tower / exchange tower), providing deep treatment of the silicon-containing and impurity-laden liquid phase discharged from the decomposition tower.

[0032] A continuous production process for boron isotope separation, disclosed in publication (announcement) number CN116688756A, adopts the same closed-loop device architecture as CN116832615A, consisting of a feed tower, complexation tower, multi-stage exchange tower, decomposition tower, and impurity removal tower. Boron trifluoride is used as the raw material, and anisole as the complexing agent, controlling the complexation degree to 85%–150%, to achieve continuous extraction of boron-11 and boron-10. Its process logic is consistent with that of silicon isotope production, both relying on the impurity removal cycle of the liquid phase material discharged from the decomposition tower. The adsorption impurity removal method in this application can also be adapted to the impurity removal section of this boron isotope production process, thus achieving technology reuse.

[0033] As a purification step that complements the two patented processes, this application receives the silicon-containing and impurity-containing liquid phase material discharged from the decomposition tower at the front end, and returns the purified liquid phase material to the complexation tower or exchange tower at the back end, perfectly embedding it into this closed-loop device system.

[0034] An adsorption-based impurity removal method for preparing high-abundance silicon-28 includes the following steps:

[0035] S1: The silicon-containing and impurity-laden liquid phase material discharged from the decomposition tower in the circulation system is added to an impurity complexing agent to achieve pre-complexation of the hydrophobic heavy component impurities, so as to form a complex with a more stable structure that is more easily captured by conventional adsorbents, thereby improving the targeting and removal efficiency of subsequent physical adsorption. The material is then passed into a first adsorption device filled with conventional adsorbents to remove the heavy component impurities in the silicon-containing and impurity-laden liquid phase material through physical adsorption, which significantly reduces the impurity content in the liquid phase material and also reduces the processing load of the subsequent second adsorption device, thus obtaining a pre-removed impurity liquid phase material.

[0036] S2: The pre-purified liquid phase material in S1 is continuously fed into a second adsorption device filled with amino adsorbent. The continuous feeding method is matched with the continuous production process in the circulation system to ensure the continuity of the entire production process. Through chemical adsorption and ion exchange, the residual harmful impurities in the pre-purified liquid phase material are removed to obtain a purified liquid phase material with a single component concentration of harmful impurities ≤50ppm.

[0037] S3: The purified liquid material obtained in S2 is recycled back to the corresponding section of the complexing tower or exchange tower in the circulation system to realize the recycling of effective components such as complexing agents (i.e., the complexing agents in publication numbers CN116832615A and CN116688756A), reduce raw material consumption, form a closed-loop process, and finally prepare high-abundance silicon-28 with an abundance of 99.9% to 99.999% in the circulation system, realizing the improvement of silicon-28 from the original 99.5% to 99.9% to 99.999% high-abundance silicon-28, meeting the application needs of high-end semiconductors, quantum chips and other fields.

[0038] The conventional adsorbent is at least one of activated carbon and diatomaceous earth. Activated carbon has a high specific surface area and a well-developed pore structure, exhibiting a strong physical adsorption capacity for heavy organic components; while diatomaceous earth possesses excellent adsorption and filtration performance. Both can be used alone or in combination to achieve broad-spectrum removal of different types of heavy component impurities. Both adsorbents are commonly used industrial materials, are inexpensive and readily available, and are suitable for large-scale industrial applications.

[0039] The heavy component impurities include pentanal and pentanoic acid generated from the oxidation of pentanol, C10 or C15 long-chain hydrocarbons generated from the polymerization of pentanol, entrainment in complexing agent droplets, and high-content oxygen-containing byproducts. These are mostly large organic molecules that easily deposit and clog pipelines within process equipment, reducing the mass transfer efficiency of the tower. They also compete with the complexing agent for the binding of silicon tetrafluoride, affecting the complexation and enrichment effect of silicon isotopes. Removing these impurities can extend the service life of the equipment and maintain the overall stable operation of the process.

[0040] It should be noted that some impurities (pentaldehyde, valeric acid) are both heavy component impurities and acidic harmful impurities; the first adsorption unit removes most of them, and the second amino adsorption unit further removes trace amounts of residues.

[0041] The physical adsorption is van der Waals adsorption, which occurs under normal pressure conditions without additional heating or cooling. This reduces energy consumption and equipment requirements in the adsorption process, eliminating the need for heating, cooling, or pressurization equipment, thus simplifying the process and reducing costs. The material space velocity is 0.5–2 h⁻¹. -1 The residence time of the silicon-containing and impurity-containing liquid phase material in the first adsorption device is 30 to 60 minutes to ensure sufficient contact between the material and the adsorbent in the first adsorption device, thereby achieving a removal rate of heavy component impurities ≥95%.

[0042] The impurity complexing agent is polyethylene glycol dimethyl ether (PEG) with a molecular weight of 200-400, comprising 0.1% to 0.5% by mass (based on the total mass of the silicon-containing and impurity-containing liquid phase material). PEG is used to first complex hydrophobic heavy component impurities to form easily adsorbable complexes, which are then directionally removed from the heavy component impurities through complexation-adsorption coupling with the conventional adsorbent. At this mass percentage, sufficient complexation of the hydrophobic heavy components by PEG is ensured without introducing new impurities due to excessive addition. Within this molecular weight range of 200-400, PEG also possesses good solubility and complexing ability, enabling rapid binding with hydrophobic heavy components. The complexation-adsorption coupling achieves directional capture of heavy component impurities, improving removal efficiency and selectivity compared to single physical adsorption.

[0043] The following is the complete working process and working principle of the above embodiments:

[0044] This adsorption method for impurity removal is suitable for closed-loop circulation systems involving complexation reactions, exchange distillation, and heating pyrolysis in the continuous production of silicon and boron isotopes. During operation, the silicon-containing and impurity-laden liquid phase discharged from the decomposition tower in the circulation system is first mixed with polyethylene glycol dimethyl ether (PEG) at a mass ratio of 0.1%–0.5% and a molecular weight of 200–400. PEG first complexes the hydrophobic heavy impurities to form easily adsorbable complexes. The material is then passed into a first adsorption unit filled with at least one conventional adsorbent, such as activated carbon or diatomaceous earth. Under normal pressure conditions without additional heating or cooling, the adsorption process takes 0.5–2 hours. -1 The material space velocity allows the material to remain in the device for 30-60 minutes. Through van der Waals physical adsorption, the removal rate of heavy component impurities is ≥95%. After removing heavy component impurities such as valeraldehyde, valeric acid, and C10 or C15 long-chain hydrocarbons, a pre-removed liquid phase material is obtained, which significantly reduces the impurity content and reduces the load on subsequent processing.

[0045] Example 2

[0046] Referring to Example 1, the amino adsorbent is at least one of an amino-containing resin and amino-modified activated carbon. The amino-modified activated carbon is prepared by modifying coal-based activated carbon with γ-aminopropyltriethoxysilane, and the amino content is 5% by mass. The amino-containing resin has good ion exchange performance and can chemically react with acidic harmful impurities to achieve removal. The amino-modified activated carbon combines the high specific surface area of ​​activated carbon with the chemical adsorption characteristics of amino groups. The γ-aminopropyltriethoxysilane modification allows the amino groups to be stably loaded on the activated carbon surface, and the 5% amino content balances chemical adsorption capacity and the pore structure of the adsorbent, avoiding excessive amino loading that could clog the pores and affect the adsorption effect.

[0047] The second adsorption device employs a double-layer filling of amino-modified activated carbon and amino-containing resin in a mass ratio of 1:2. This achieves synergy between the amino-modified activated carbon and the amino-containing resin: the upper layer of amino-modified activated carbon rapidly captures volatile harmful impurities (HF, pentanal) in the gas and liquid phases, while the lower layer of amino-containing resin deeply removes non-volatile harmful impurities such as acidic salts and solid precursors through ion exchange. The 1:2 mass ratio is optimized based on the content and removal difficulty of the two impurities to maximize adsorption efficiency. The carrier for the amino-modified activated carbon is coal-based activated carbon (particle size 2-4 mm, specific surface area ≥1200 m²). 2 / g); the modifier is γ-aminopropyltriethoxysilane (KH550); specific parameters are amino loading ≥3.2mmol / g, specific surface area ≥1100m². 2 / g, pore volume ≥0.8cm³ / g, pH value 8.5~9.5.

[0048] The first and second adsorption devices are at least one of a filter tower, a two-stage full-circulation adsorption vessel, and a fixed-bed adsorption column. When a fixed-bed adsorption column is used, its height is not less than 1 meter. The filter tower is characterized by its simple structure and convenient operation, making it suitable for small- to medium-scale impurity removal production. The two-stage full-circulation adsorption vessel, with its full-circulation design, allows for thorough contact and mixing between the material and the adsorbent, improving adsorption efficiency and making it suitable for large-scale continuous production. The fixed-bed adsorption column offers advantages such as stable operation and a small footprint; its ≥1-meter column height ensures sufficient contact time between the material and the adsorbent, meeting the requirements for deep impurity removal. By selecting one of these three options, this adsorption impurity removal method can be adapted to different production scales and site conditions, enhancing the flexibility and applicability of the process.

[0049] The first and second adsorption devices are arranged in series to achieve a stepped impurity removal process, first removing heavy (heavy component impurities) and then removing harmful (hazardous impurities). Specifically, the first adsorption device removes most of the heavy component impurities, preventing them from covering the active sites of the amino adsorbent in the second adsorption device. This ensures the adsorption efficiency of the amino adsorbent in the second adsorption device for harmful impurities. Simultaneously, the series structure allows the material to pass through the two devices sequentially, achieving stepwise removal of impurities and improving the overall impurity removal effect.

[0050] The harmful impurities include hydrogen fluoride, fluorosilicic acid, silicic acid, pentaldehyde, and valeric acid. After treatment by the second adsorption device, the concentration of a single component of the harmful impurities is ≤50 ppm, and the total concentration of harmful impurities is ≤100 ppm. These harmful impurities are highly corrosive and reactive; even low-level residues can corrode process equipment, trigger side reactions, and even cause silicon-28 lattice defects. By controlling the concentration of a single component of the harmful impurities to ≤50 ppm and the total concentration of harmful impurities to ≤100 ppm through this process, corrosion of equipment and process failures caused by harmful impurities can be significantly reduced or even avoided. Furthermore, the chemical purity and isotopic abundance of the final silicon-28 product can be guaranteed, meeting the purity requirements of high-end applications.

[0051] The following is the working process and principle:

[0052] The pre-purified liquid phase material obtained in Example 1 is continuously passed into a second adsorption device filled with amino adsorbent. Residual harmful impurities such as hydrogen fluoride, fluorosilicic acid, and silicic acid are removed through chemical adsorption and ion exchange, resulting in a purified liquid phase material with a harmful concentration ≤50 ppm. The second adsorption device can be constructed using a double-layer filling of amino-modified activated carbon and amino-containing resin, and the first and second adsorption devices are connected in series to adapt to the continuous production rhythm of the circulating system. Finally, the purified liquid phase material is returned to the corresponding section of the complexing tower or exchange tower in the circulation system to realize the recycling of effective components such as complexing agents and form a closed loop process. Based on the original circulation system, high abundance silicon-28 with an abundance of 99.9% to 99.999% is finally prepared, realizing the improvement of silicon-28 abundance from the original 99.5%, which meets the application needs of high-end semiconductors, quantum chips and other fields. At the same time, this adsorption and impurity removal method can also be reused in the impurity removal section of the same boron isotope production process, such as the boron isotope separation continuous production process method disclosed (announcement) number CN116688756A. The front end receives the silicon-containing and impurity-containing liquid phase material from the decomposition tower, and the back end connects to the complexing tower or exchange tower, perfectly embedding it into the original closed loop device system.

[0053] Comparative Example 1

[0054] The process is essentially the same as in Example 1, except that the silicon-containing impurity liquid phase material is not treated with an impurity complexing agent (i.e., polyethylene glycol dimethyl ether with a mass percentage of 0.1%–0.5% and a molecular weight of 200–400), but is instead directly introduced into the first adsorption device filled with a conventional adsorbent. The rest is the same as in Example 1. Performance testing of the obtained pre-removed impurity liquid phase material showed that the removal rate of heavy component impurities was only 62%–68%, far lower than the ≥95% in Example 1. Furthermore, the residual concentration of heavy component impurities such as valeraldehyde and valeric acid in the material emanating from the first adsorption device was high, resulting in a significant over-coverage of the active sites of the amino adsorbent in the subsequent second adsorption device, leading to a significant decrease in the overall impurity removal efficiency.

[0055] Comparative Example 2

[0056] The process is essentially the same as in Examples 1 and 2, except that the second adsorption device and its amino adsorbent are omitted, and only the first adsorption device is used for single-stage physical adsorption to remove impurities. The rest is the same as in Example 1. Performance testing of the obtained purified liquid phase material showed that the concentration of a single component of harmful impurities (hydrogen fluoride, fluorosilicic acid, silicic acid, valeric acid, and valeric acid) was >300 ppm, and the total concentration of harmful impurities was >800 ppm, failing to meet the requirements of ≤50 ppm for a single component concentration and ≤100 ppm for a total concentration. The final silicon-28 abundance was only 99.5%–99.7%, unable to reach the high abundance level of 99.9%–99.999%, indicating that single physical adsorption cannot deeply remove low-content harmful impurities and is insufficient to meet the needs of high-end applications.

[0057] Comparative Example 3

[0058] Following the continuous silicon isotope production process described in publication CN116832615A, a distillation purification tower was used for impurity removal, consistent with the original process. The remaining operating conditions of the circulation system, feed composition, material space velocity, temperature, and pressure conditions remained the same as in Example 1. The silicon-containing and impurity-laden liquid phase discharged from the decomposition tower was directly fed into the distillation purification tower, where impurity removal was achieved based on boiling point differences. No impurity complexing agent of this invention was added, and no first or second adsorption device was installed. After distillation purification, the liquid phase was returned to the complexation tower section, completing a closed-loop cycle. Testing showed that after distillation purification, the lowest single component of harmful impurities in the system was >220 ppm, and the total harmful impurities were >720 ppm. Due to the gas-liquid partition coefficient, low-content impurities in the 0.1%–0.01% range were difficult to remove deeply. The final circulating system produced silicon-28 with an abundance ≥99.5%.

[0059] To further verify the actual impurity removal effect of each technical solution of the present invention and its impact on the abundance of silicon-28 in the final product, a full-process test was conducted on the process conditions of Examples 1, 2, 1, 2, and 3, and key performance indicators were tested. Table 1 focuses on comparing the removal effect of the first adsorption device on heavy component impurities under different process conditions, while Table 2 further compares the residual concentration of harmful impurities after treatment by the second adsorption device and the increase in the abundance of silicon-28 in the final product. The results are shown below:

[0060] Table 1 Comparison of Impurity Removal Effects of Different Schemes for Recombinant Components

[0061] Table 2 Comparison of harmful impurities and final silicon-28 abundance for each scheme.

[0062] As shown in Table 1, compared with Comparative Example 1 and Comparative Example 2, after the addition of the impurity complexing agent (polyethylene glycol dimethyl ether), the removal rate of heavy component impurities by the conventional adsorbent increased from 62% to 68% (Comparative Example 1) to over 95% (Examples 1 and 2). Compared with Comparative Example 3, the removal rate of heavy component impurities by the reproduced distillation process is only 71% to 76%, which is lower than the two-stage adsorption process of the present invention.

[0063] As shown in Table 2, compared with Examples 1 and 2 and Comparative Example 2, the second amino adsorption device in the two-stage tandem adsorption architecture is indispensable. Relying solely on the single-stage physical adsorption of the first adsorption device, the concentrations of both the single component (>300 ppm) and the total concentration (>800 ppm) of harmful impurities far exceed the control targets, and the silicon-28 abundance of the product can only be maintained at the original level of 99.5%–99.7%. Compared with Comparative Example 3, the reproduced distillation process cannot deeply remove trace amounts of harmful impurities; the single component of harmful impurities is >220 ppm, and the total harmful impurities are >720 ppm, with the silicon-28 abundance only reaching ≥99.5%. However, after adopting the two-stage tandem adsorption, the concentration of the single component of harmful impurities is reduced to ≤50 ppm, and the total concentration is ≤100 ppm, while the silicon-28 abundance of the product increases to 99.9%–99.999%.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adsorption-based impurity removal method for preparing high-abundance silicon-28, applied to a circulating system including complexation reaction, exchange distillation, and heating pyrolysis units, characterized in that, Includes the following steps: S1: Add the silicon-containing and impurity-containing liquid phase material discharged from the decomposition tower in the circulation system to the impurity complexing agent, and pass it into the first adsorption device filled with conventional adsorbent. Remove the heavy component impurities in the silicon-containing and impurity-containing liquid phase material by physical adsorption to obtain the pre-impurity-removed liquid phase material. S2: The pre-purified liquid phase material in S1 is continuously passed into a second adsorption device filled with amino adsorbent. Through chemical adsorption and ion exchange, the residual harmful impurities in the pre-purified liquid phase material are removed to obtain a purified liquid phase material with a single component concentration of harmful impurities ≤50ppm. S3: The purified liquid material obtained in S2 is returned to the corresponding section of the complexing tower or exchange tower in the circulation system to form a closed process loop, and high abundance silicon-28 with an abundance of 99.9% to 99.999% is finally prepared in the circulation system.

2. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The conventional adsorbent is at least one of activated carbon and diatomaceous earth.

3. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The heavy component impurities include pentanal and pentanoic acid generated by the oxidation of pentanol, C10 or C15 long-chain hydrocarbons generated by the polymerization of pentanol, entrainment in complexing agent droplets, and high-content oxygen-containing byproducts.

4. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The physical adsorption is van der Waals adsorption, and the environment for van der Waals adsorption is atmospheric pressure conditions without additional heating or cooling, with a material space velocity of 0.5–2 h⁻¹. -1 The residence time of the silicon-containing and impurity-containing liquid phase material in the first adsorption device is 30-60 minutes, achieving a heavy component impurity removal rate of ≥95%.

5. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The impurity complexing agent is polyethylene glycol dimethyl ether with a mass ratio of 0.1% to 0.5% and a molecular weight of 200 to 400. The polyethylene glycol dimethyl ether is used to first complex hydrophobic heavy component impurities to form easily adsorbable complexes, and then to directionally remove heavy component impurities through complexation-adsorption coupling with the conventional adsorbent.

6. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The amino adsorbent is at least one of amino-containing resin and amino-modified activated carbon. The amino-modified activated carbon is prepared by modifying coal-based activated carbon with γ-aminopropyltriethoxysilane, and the amino content is 5% by mass.

7. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 6, characterized in that: The second adsorption device is filled with a double layer of amino-modified activated carbon and amino-containing resin, with a filling mass ratio of 1:

2.

8. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The first adsorption device and the second adsorption device are at least one of a filter tower, a two-stage full circulation adsorption vessel, and a fixed bed adsorption column. When a fixed bed adsorption column is used, the height of the fixed bed adsorption column is not less than 1 meter.

9. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The first adsorption device and the second adsorption device are arranged in two stages in series.

10. The adsorption and impurity removal method for preparing high-abundance silicon-28 according to claim 1, characterized in that: The harmful impurities include hydrogen fluoride, fluorosilicic acid, silicic acid, pentaldehyde, and pentanoic acid. After treatment by the second adsorption device, the total concentration of harmful impurities is ≤100ppm.

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