A chemical exchange method and system for silicon isotope separation

Abstract

The application discloses a chemical exchange method and system for silicon isotope separation, and belongs to the technical field of isotope separation. The chemical exchange method comprises the following steps: S1, carrying out a complexation reaction on natural-abundance silicon tetrafluoride and a complexing agent raw material, wherein an inert component which does not participate in the complexation reaction and does not react with any component in a reaction system is premixed in the complexing agent raw material, so as to reduce the dynamic viscosity of a liquid phase of the reaction system in the complexation reaction; S2, carrying out a multistage chemical exchange on the complex generated in the step S1 and silicon tetrafluoride gas; S3, carrying out heating decomposition on the liquid-phase complex out of the exchange system; S4, purifying the complexing agent liquid obtained from a cracking tower through a decontamination tower, and returning the complexing agent liquid to the complexation tower; and S5, when the silicon isotope abundance in the complexation product reaches a target abundance, corresponding silicon isotope products are obtained. According to the scheme, the dynamic viscosity of the whole reaction system can be significantly reduced by premixing the chemically inert component in the complexing agent raw material, and the silicon isotope separation efficiency is improved.

Description

Technical Field

[0001] This application belongs to the field of isotope separation technology, and in particular relates to a chemical exchange method and system for silicon isotope separation. Background Technology

[0002] Silicon exists in nature in three stable isotopic forms: silicon-28 (Si-28) 28 Si, with an abundance of approximately 92.23%, and silicon-29 ( 29 Si, with an abundance of approximately 4.67%, and silicon-30 (Si, with an abundance of approximately 4.67%) ... 30 Si (abundance approximately 3.10%). Among them, high-abundance and even extremely high-abundance silicon-28 isotopes, due to their zero nuclear spin, can greatly eliminate nuclear spin noise and have irreplaceable strategic value in quantum computing, high-precision semiconductor devices, and cutting-edge physics research. However, the efficient and economical separation and purification of silicon-28 from naturally abundant silicon is an extremely challenging technical problem.

[0003] Currently, methods for separating silicon isotopes include gas centrifugation, laser methods, and chemical exchange methods. Among these, chemical exchange methods have attracted attention due to their potential high efficiency and relatively low energy consumption. The principle of this method is to achieve separation by utilizing the thermodynamic or kinetic differences between different isotopes in specific chemical reactions. For silicon isotopes, an effective chemical exchange pathway involves a reversible coordination reaction between silicon tetrafluoride (SiF4) and a complexing agent.

[0004] However, existing silicon isotope chemical exchange technology faces a series of bottlenecks in actual industrialization: First, separation efficiency and stability are difficult to achieve simultaneously. Single complexing agents often have performance limitations. For example, some ether complexing agents have high separation factors, but their chemical stability is insufficient during long-term operation, especially at high pyrolysis temperatures. They are prone to side reactions such as decomposition, oxidation, or polymerization, leading to complexing agent loss and impurity accumulation. This not only increases operating costs but also seriously pollutes the separation system, limiting the upper limit of the final product abundance (often below 99.9%). Second, the process has inherent defects. The large molecular complexes generated by the complexation reaction cause a sharp increase in the viscosity of the liquid phase, severely deteriorating the mass transfer and mixing effect between the gas and liquid phases in the tower. This makes it difficult to fully realize the theoretical separation efficiency in the equipment, often requiring the construction of extremely tall towers or the addition of stages to compensate for efficiency losses, thus increasing equipment costs. Third, the energy efficiency and yield of key processes are low. As a reversible reaction, the thermal decomposition of the complexes in the pyrolysis tower is limited by chemical equilibrium and cannot be completely completed, becoming a key obstacle restricting the improvement of product yield and purity.

[0005] Therefore, there is an urgent need in this field for an innovative silicon isotope separation technology to fundamentally solve the core engineering problems such as high viscosity of the inherent system, unstable complexing agent, and incomplete pyrolysis, and ultimately achieve high-efficiency, high-yield, low-energy-consumption, and long-cycle stable production of high-abundance silicon isotopes. Summary of the Invention

[0006] This application aims to at least partially address one of the technical problems in the related art. To this end, the chemical exchange method and system for silicon isotope separation provided in this application can significantly reduce the dynamic viscosity of the entire reaction system by pre-mixing chemically inert components in the complexing agent raw material, greatly improving the mass transfer efficiency of the gas-liquid two phases in the exchange tower, making the isotope exchange more complete and faster, and improving the silicon isotope separation efficiency.

[0007] To achieve the above objectives, in a first aspect, this application provides a chemical exchange method for silicon isotope separation, comprising the following steps:

[0008] S1. Naturally abundant silicon tetrafluoride and complexing agent raw materials are subjected to a complexation reaction to form a saturated complex at a corresponding temperature and pressure. The complexation reaction between the complexing agent raw material and silicon tetrafluoride gas is reversible. The complexing agent raw material is premixed with an inert component that does not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase in the reaction system during the complexation reaction.

[0009] S2. The complex generated in step S1 is subjected to multi-stage chemical exchange with silicon tetrafluoride gas so that the silicon tetrafluoride-28 isotope complex is enriched in the liquid phase, and the silicon tetrafluoride-29 isotope complex and silicon tetrafluoride-30 isotope complex are enriched in the gas phase.

[0010] S3. The liquid-phase complex from the exchange system is heated and decomposed, and the resulting silicon tetrafluoride gas is fed into the bottom circulation port of the last-stage exchange tower. The inert component does not decompose during the reaction.

[0011] S4. The complexing agent liquid obtained from the pyrolysis tower is purified by the impurity removal tower and then returned to the complexing tower.

[0012] The S5 and silicon-28 enriched products are collected from the bottom of the last-stage exchange tower or the top of the cracking tower, while the silicon-29 or silicon-30 enriched products are collected from the bottom of the complexation tower or the top of the first-stage exchange tower. When the silicon isotope abundance in the complexation product reaches the target abundance, the corresponding silicon isotope product is collected.

[0013] Preferably, the inert component is a liquid hydrocarbon or carbonate, wherein the liquid hydrocarbon is selected from at least one of alkanes and aromatics.

[0014] Preferably, the aromatic hydrocarbon is at least one of benzene, toluene, and xylene, and the carbonate is at least one of dimethyl carbonate and diethyl carbonate.

[0015] Preferably, the alkane is a n-alkane or a cycloalkane with 5 to 10 carbon atoms.

[0016] Preferably, the inert component is at least one selected from n-hexane, cyclohexane, and n-heptane.

[0017] Preferably, the molar ratio between the complexing agent raw material and the inert component is 10:1 to 2:1.

[0018] Preferably, the complexing agent raw material comprises at least two different types of complexing agents selected from alcohols, ethers, esters and amines, wherein the complexing agent can undergo a reversible coordination reaction with silicon tetrafluoride to form a complex with an asymmetric octahedral structure.

[0019] Preferably, the at least two different types of complexing agents comprise a first complexing agent providing a first type of coordinating atom and a second complexing agent providing a second type of coordinating atom, wherein the isotope separation factor of the first type of coordinating atom is higher than that of the second type of coordinating atom, and the chemical bond stability of the second type of coordinating atom is higher than that of the first type of coordinating atom.

[0020] Preferably, in step S3, before heating and decomposing, a low-boiling-point component with a boiling point lower than that of the complex is added to the complex to be decomposed, in order to reduce the decomposition temperature of the complex and increase the decomposition rate of the complex.

[0021] Secondly, this application provides a chemical exchange system for silicon isotope separation, used to implement the above-mentioned chemical exchange method, comprising:

[0022] The feed tower is used to input complexing agent raw materials and naturally abundant silicon tetrafluoride gas, mix them and cause a complexation reaction. The complexing agent raw materials are premixed with inert components that do not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase of the reaction system during the complexation reaction.

[0023] A multi-stage exchange tower includes at least three exchange towers connected in sequence, wherein the exchange tower located in the middle of the multi-stage exchange tower is used to receive complexed reactants from the feed tower;

[0024] The cracking tower is used to receive the complex liquid phase output from the last-stage exchange tower and to heat and decompose it. Silicon tetrafluoride gas is obtained at the top outlet of the cracking tower and is fed to the bottom circulation port of the last-stage exchange tower. Then, it passes through multiple exchange towers from back to front and returns to the bottom circulation port of the complexing tower. There, it undergoes a complexation reaction with the purified complexing agent and lean solvent in the complexing tower to obtain the complexed product.

[0025] The impurity removal tower is used to receive the complexing agent mixture from the bottom outlet of the cracking tower. The impurity-removed complexing agent and lean solvent are collected at the upper outlet of the impurity removal tower.

[0026] The complexing tower is used to receive the complexing agent lean solvent from the impurity removal tower and the silicon tetrafluoride gas input from the first-stage exchange tower, while the inert component is input from the top of the complexing tower at a certain flow rate to carry out the complexation reaction and obtain the complexed product.

[0027] Based on the above technical solution, the chemical exchange method and system for silicon isotope separation proposed in this application have at least one of the following advantages compared to the prior art:

[0028] 1. The chemical exchange method for silicon isotope separation proposed in this application can significantly reduce the dynamic viscosity of the entire reaction system by pre-mixing chemically inert components in the complexing agent raw material, thereby greatly improving the mass transfer efficiency of the gas-liquid two phases in the exchange tower, making the isotope exchange more complete and faster, and improving the silicon isotope separation efficiency.

[0029] 2. The chemical exchange method for silicon isotope separation described in this application overcomes the performance limitations of single complexing agents by combining at least two complexing agents selected from different chemical categories (alcohols, ethers, esters, amines, and chlorinated organic compounds), laying the foundation for synergistic effects. Different complexing agents differ in molecular structure, electronic effects, and steric hindrance; their combination may produce synergistic effects, resulting in a final composition that outperforms any single component or simple addition in one or more key properties such as separation factor, reaction rate, thermal stability, or chemical stability. This provides a novel material basis for achieving more efficient silicon isotope separation.

[0030] 3. The chemical exchange method for silicon isotope separation in this application adds a low-boiling-point component with a boiling point lower than that of the complex to be decomposed before thermal decomposition. This reduces the decomposition temperature of the complex, decreases side reactions, and thus improves the purity of the regenerated complexing agent. Furthermore, it can increase the decomposition rate of the complex, reduce the residual rate, and directly improve the product yield and the upper limit of system abundance. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of a chemical exchange system for silicon isotope separation provided in this application. Detailed Implementation

[0033] To facilitate understanding of this application, a more complete description will be provided below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The terms "and / or," "or / and," and "and / or" as used in this application encompass any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and "a combination of A and B."

[0036] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0037] The terms “combinations thereof,” “any combination thereof,” and “any combination thereof” as used in this application include all suitable combinations of any two or more of the listed items.

[0038] In this application, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0039] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are merely used to describe implementation methods or embodiments that achieve better results, and should be understood not to limit the scope of protection of this application.

[0040] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0041] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0042] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0043] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0044] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0045] In this application, "normal temperature" in the context generally refers to 5℃~30℃, and more preferably 25±5℃.

[0046] In this application, "atmospheric pressure" in the context generally refers to one standard atmosphere, preferably 100±10 kPa.

[0047] This application provides a chemical exchange method for silicon isotope separation, comprising the following steps:

[0048] S1. Naturally abundant silicon tetrafluoride and complexing agent raw materials are subjected to a complexation reaction to form a saturated complex at a corresponding temperature and pressure. The complexation reaction between the complexing agent raw material and silicon tetrafluoride gas is reversible. The complexing agent raw material is premixed with an inert component that does not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase in the reaction system during the complexation reaction.

[0049] S2. The complex generated in step S1 is subjected to multi-stage chemical exchange with silicon tetrafluoride gas so that the silicon tetrafluoride-28 isotope complex is enriched in the liquid phase, and the silicon tetrafluoride-29 isotope complex and silicon tetrafluoride-30 isotope complex are enriched in the gas phase.

[0050] S3. The liquid-phase complex from the exchange system is heated and decomposed, and the resulting silicon tetrafluoride gas is fed into the bottom circulation port of the last-stage exchange tower. The inert component does not decompose during the reaction.

[0051] S4. The complexing agent liquid obtained from the pyrolysis tower is purified by the impurity removal tower and then returned to the complexing tower.

[0052] The S5 and silicon-28 enriched products are collected from the bottom of the last-stage exchange tower or the top of the cracking tower, while the silicon-29 or silicon-30 enriched products are collected from the bottom of the complexation tower or the top of the first-stage exchange tower. When the silicon isotope abundance in the complexation product reaches the target abundance, the corresponding silicon isotope product is collected.

[0053] This embodiment, by pre-mixing chemically inert components into the complexing agent raw material, can significantly reduce the dynamic viscosity of the entire reaction system (especially the liquid phase) without interfering with the core complexing reaction. This improvement in physical properties brings unexpected technical benefits: 1) It greatly improves the mass transfer efficiency of the gas-liquid two-phase system in the exchange tower, making isotope exchange more complete and faster; 2) It reduces the system flow resistance, thereby reducing the energy consumption of the circulating pump; 3) It helps to form a more uniform liquid film on the packing or tray, improving the classification efficiency of the theoretical tray, enabling higher separation at the same equipment height, or reducing equipment size and cost while achieving the same separation target.

[0054] In some embodiments, the inert component is a liquid hydrocarbon or carbonate, wherein the liquid hydrocarbon is selected from at least one of alkanes and aromatics.

[0055] Liquid hydrocarbons offer advantages such as wide availability, low cost, and easily predictable physicochemical properties. They possess low viscosity and good chemical stability, making them a reliable category of substances for viscosity reduction. This example provides a clear and feasible range of material choices for industrial implementation.

[0056] In some embodiments, the aromatic hydrocarbon is at least one of benzene, toluene, and xylene, and the carbonate is at least one of dimethyl carbonate and diethyl carbonate.

[0057] In some embodiments, the alkane is a n-alkane or a cycloalkane with 5 to 10 carbon atoms.

[0058] This embodiment limits alkanes to C5-C10 n-alkanes or cycloalkanes, scientifically defining an effective carbon number range. If the carbon number is below C5 (such as butane), the boiling point is too low, and the vapor pressure is too high at the operating temperature, which can easily vaporize and disrupt the system. If the carbon number is above C10 (such as dodecane), the viscosity is too high, the viscosity reduction effect is weakened, and the boiling point is too high, which may make it difficult to separate from heavy component impurities.

[0059] In some embodiments, the inert component is at least one selected from n-hexane, cyclohexane, and n-heptane.

[0060] In some embodiments, the molar ratio between the complexing agent raw material and the inert component is 10:1 to 2:1. Preferably, the molar ratio between the complexing agent raw material and the inert component is 6:1 to 3:1.

[0061] The molar ratio of the complexing agent raw material to the naturally abundant silicon tetrafluoride gas is 4:1 to 2:1, preferably 3:1 to 2.5:1. The complexing agent raw material can be selected from alcohols, ethers or esters, such as trimethyl phosphate or pentanol.

[0062] In some embodiments, the complexing agent raw material comprises at least two different types of complexing agents selected from alcohols, ethers, esters and amines, wherein the complexing agent is capable of undergoing a reversible coordination reaction with silicon tetrafluoride to form a complex with an asymmetric octahedral structure.

[0063] This embodiment, by combining at least two complexing agents selected from different chemical categories (alcohols, ethers, esters, amines, and chlorinated organic compounds), breaks through the performance limitations of single complexing agents and lays the foundation for synergistic effects. Different complexing agents differ in molecular structure, electronic effects, and steric hindrance; their combination may produce synergistic effects, resulting in a final composition that outperforms any single component or simple addition in one or more key properties such as separation factor, reaction rate, thermal stability, or chemical stability. This provides a novel material basis for achieving more efficient silicon isotope separation.

[0064] In some embodiments, the at least two different types of complexing agents comprise a first complexing agent providing a first type of coordinating atom and a second complexing agent providing a second type of coordinating atom, wherein the isotope separation factor of the first type of coordinating atom is higher than that of the second type of coordinating atom, and the chemical bond stability of the second type of coordinating atom is higher than that of the first type of coordinating atom.

[0065] This embodiment explicitly requires that the complexing agent composition simultaneously contain different complexing agents with both high separation factor and high stability. This represents the ideal synergistic design, enabling the complexing agent composition to significantly improve the chemical and thermodynamic stability of the system without sacrificing separation efficiency. The resulting unexpected technical benefits include: extended complexing agent cycle life, reduced material loss and impurity accumulation due to side reactions, and increased abundance upper limit of the final product, thereby significantly reducing overall separation costs.

[0066] In some embodiments, the first complexing agent is a fatty ether or an aromatic ether, and the second complexing agent is an inorganic acid ester. The fatty ether includes diethyl ether, diisopropyl ether, and methyl tert-butyl ether, the aromatic ether includes phenethyl ether, anisole, and diphenyl ether, and the inorganic acid ester includes phosphate ester, borate ester, and carbonate ester.

[0067] This embodiment provides a highly efficient and stable preferred combination example: specifically defined as aliphatic / aromatic ethers (first complexing agent) and inorganic acid esters (second complexing agent). Ethers (especially aromatic ethers such as anisole) typically have high separation factors, while inorganic acid esters (such as trimethyl phosphate) are known for their excellent thermal stability and chemical inertness. This combination fully leverages the high separation efficiency of ethers while utilizing the "protective" effect of inorganic acid esters, greatly enhancing the overall reaction system's long-term performance, especially its tolerance at high pyrolysis temperatures, making it a reliable solution for achieving stable and efficient separation. Furthermore, the mass ratio of the first and second complexing agents is 70:30 to 40:60. By limiting the mass ratio range of ethers to inorganic acid esters (70:30 to 40:60), the specific ratio for achieving the optimal synergistic effect is clearly defined. Within this window, sufficient ether components are ensured to maintain a high separation factor, while adequate inorganic acid esters provide sufficient stability. This preferred range is an experimentally verified equilibrium point; exceeding this range may lead to a significant decrease in separation efficiency or insufficient improvement in stability.

[0068] In some embodiments, in step S3, before heating and decomposing, a low-boiling-point component with a boiling point lower than that of the complex is added to the complex to be decomposed, in order to reduce the decomposition temperature of the complex and increase the decomposition rate of the complex.

[0069] The specific low-boiling-point component can be selected from at least one of alkanes, aromatics, and carbonates.

[0070] The amount of low-boiling-point component added is 3% to 12% of the liquid phase mass of the complex to be cracked; the preferred range is 5% to 10%, and the optimal process value is 8%.

[0071] Specifically, the substances that can be used include, but are not limited to: aromatic hydrocarbons, which can be at least one of benzene, toluene, and xylene; carbonates, which can be at least one of dimethyl carbonate and diethyl carbonate; and alkanes, which can be n-alkanes or cycloalkanes, with 5 to 10 carbon atoms. Their boiling point ranges are suitable, and representative examples include pentane, hexane, cyclohexane, and heptane.

[0072] To verify the effectiveness of the technical solution in this application, a series of comparative experiments were conducted.

[0073] The basic experimental conditions were uniformly set, including the following basic parameters for the raw materials:

[0074] 1) Gas source: Naturally abundant silicon tetrafluoride, 28 Si=92.23%, 29 Si=4.67%, 30 Si=3.10%;

[0075] 2) Composite complexing agent system: First complexing agent (anisole, high separation factor) + Second complexing agent (trimethyl phosphate, high thermal stability), mass ratio 55:45;

[0076] 3) Inert viscosity-reducing component: cyclohexane;

[0077] 4) Cracking-assisted low-boiling-point component: n-hexane;

[0078] 5) Standard operating conditions: atmospheric pressure, constant system temperature of 45℃, four-stage multi-stage exchange towers connected in series, and pyrolysis operation reference temperature of 145℃;

[0079] 6) Comparison with the baseline group: a pure composite complexing agent system without the addition of inert components, with all other process parameters being completely identical.

[0080] The detection indicators are defined as follows:

[0081] 1) Liquid phase dynamic viscosity: measured by rotational viscometer at 45℃, unit mPa·s;

[0082] 2) Complexation degree: The molar percentage of SiF4 in the system that is coordinated and bound to the complexing agent out of the total feed SiF4;

[0083] 3) Degree of pyrolysis: The percentage of free SiF4 released after pyrolysis relative to the molar percentage of bound SiF4 in the feed complex;

[0084] 4) Single-level separation factor The determination is made after the gas and liquid phases reach reversible chemical exchange equilibrium, and is defined as the liquid complex phase. 28 Si and 29 Si The molar abundance ratio, divided by the molar abundance ratio of gaseous free SiF4 28 Si and 29 Si The molar abundance ratio, calculated using the formula ;

[0085] The larger the value, the stronger the isotope enrichment and differentiation ability in a single-stage column, and the higher purity silicon isotope products can be obtained under the same number of columns.

[0086] All single-stage separation factor data in this application are the average values ​​of three parallel measurements obtained by online mass spectrometry after gas-liquid contact for 30 minutes at 45℃ and normal pressure to reach exchange equilibrium.

[0087] 5) Overall separation efficiency: After 4 stages in series 28 Si Enrichment limit abundance;

[0088] 6) Cycle loss rate: The proportion of total loss of complexing agent after 72 hours of continuous operation to the initial feed.

[0089] I. First group of comparative experiments - different proportions of inert components added

[0090] The molar ratio gradient of complexing agent: cyclohexane (inert component) was set as follows: 10:1, 6:1, 3:1, 2:1, 1:1 (overprotection ratio control group). The experimental results of the inert component addition ratio gradient are shown in Table 1.

[0091] Table 1. Experimental results of inert component addition ratio gradient

[0092] Five complexing systems with different cyclohexane addition ratios were prepared, with anisole-trimethyl phosphate composite system as the complexing agent. The system was subjected to countercurrent complexation reaction with naturally abundant SiF4 at 45℃ and normal pressure. The dynamic viscosity of the liquid phase was measured by rotational viscometer, and the degree of complexation and isotope separation factor were detected by online gas chromatography-mass spectrometry. The loss of complexing agent was statistically analyzed after 72 hours of continuous operation. The experimental results are shown in Table 1. The results indicate that the viscosity of the system drops sharply after the addition of inert cyclohexane. The viscosity in the range of 10:1 to 2:1 molar ratio of complexing agent to cyclohexane decreases from 128.6 to 18.3 mPa·s, with a maximum reduction of 85.7%, significantly improving gas-liquid mass transfer. The degree of complexation remains at 87% to 89.7% within the range of 10:1 to 2:1, which is close to the baseline group, and the inert component does not disrupt the reversible complexation reaction. When the molar ratio of complexing agent to cyclohexane is lower than 2:1 (e.g., 1:1), the complexing agent is over-diluted, the degree of complexation drops to 82.4%, and the reaction efficiency decreases significantly, verifying the rationality of limiting the molar ratio between the complexing agent raw material and the inert component to 10:1 to 2:1. The inert component does not change the isotope separation factor α, and the separation performance does not decline. At the same time, it reduces the loss of complexing agent in the high-temperature cracking stage and improves the stability of long-term operation.

[0093] Preferably, the molar ratio between the complexing agent raw material and the inert component is 6:1 to 3:1.

[0094] Second set of comparative experiments - different types of inert components

[0095] The molar ratio of the immobilizing complexing agent to the inert component was 3:1. Experimental results were tested for three types of inert media: alkanes, aromatics, and carbonates.

[0096] Table 2. Experimental results for different types of inert components.

[0097] As shown in Table 2, the experimental results of the different types of inert components show that C5~C10 alkanes (cyclohexane, n-hexane, n-heptane) have the best viscosity reduction effect and the lowest liquid phase viscosity; aromatics and carbonates have the second best viscosity reduction effect, but both can meet the process requirements; all inert components do not decompose under the pyrolysis temperature of 145℃ and no by-products are introduced, thus meeting the limiting conditions of "not participating in the reaction and not decomposing".

[0098] Third group of comparative experiments - Gradient control experiment on the addition ratio of low-boiling-point components

[0099] The basic system consists of a complexing agent (anisole:trimethyl phosphate mass ratio of 55:45) + cyclohexane inert component (complexing agent:cyclohexane molar ratio of 3:1); the liquid phase to be pyrolyzed is enriched at the bottom of a four-stage exchange tower. 28 Si complex solution; reference pyrolysis temperature 145℃; low boiling point component selected: n-hexane; test indicators: pyrolysis temperature, degree of pyrolysis, impurity content of regenerated complexing agent, and condensation recovery loss rate.

[0100] Addition ratio definition: The percentage of the mass of the low-boiling-point component to the total mass of the liquid phase of the complex to be cracked.

[0101] Table 3 Results of the Gradient Comparison Experiment for the Addition Proportions of Low-Boiling-Point Components

[0102] Using n-hexane as a low-boiling-point pyrolysis aid, six addition ratio gradients (0%, 3%, 5%, 8%, 12%, and 18%) were established, while other process conditions remained consistent. The effects of the addition ratio on pyrolysis temperature, degree of pyrolysis, complexing agent impurities, and solvent loss were investigated. Table 3 shows that when the addition amount of the low-boiling-point component is controlled within the range of 3%–12% of the liquid phase mass of the complex, it can significantly reduce the pyrolysis operating temperature, increase the complex decomposition rate, and reduce thermal degradation impurities of the complexing agent. When the addition amount is below 3%, the synergistic effect is weak; when the addition amount is above 12%, it leads to increased gas phase load and significantly increased light component circulation loss. Considering pyrolysis efficiency, energy consumption, and material loss, the optimal addition mass fraction of the low-boiling-point component is 5%–10%, with the optimal addition ratio being 8%.

[0103] This application limits the addition of low-boiling-point components before pyrolysis to 3%~12% of the liquid phase mass of the complex to be pyrolyzed. Gradient experiments have confirmed that this range can achieve a pyrolysis temperature reduction of more than 30°C and a pyrolysis degree increase of more than 18 percentage points with low material loss. When 7%~9% of C5-C6 alkanes are used, the overall performance is optimal, taking into account low-temperature pyrolysis, high decomposition rate and low solvent circulation loss, and solving the engineering shortcomings of traditional processes such as high-temperature pyrolysis, incomplete decomposition and large loss of complexing agent.

[0104] This embodiment integrates a key optimization technique for the pyrolysis process: the addition of a low-boiling-point component. This component, by forming an azeotrope or lowering the system's bubble point, enables the complex to enter a boiling state at a lower overall temperature, thereby significantly reducing the operating temperature for thermal decomposition. This not only directly reduces energy consumption, but more importantly, low-temperature pyrolysis greatly suppresses side reactions such as thermal decomposition and polymerization of the complexing agent, reducing impurity formation and improving the purity of the regenerated complexing agent. Simultaneously, more thorough low-temperature boiling decomposition helps increase the decomposition rate of the complex, reduce residue, and directly improve product yield and the upper limit of system abundance.

[0105] Regarding the subsequent processing of the low-boiling-point component, this embodiment designs a simple and efficient separation and recovery process. Because the selected low-boiling-point component differs significantly in boiling point from the target product silicon tetrafluoride (SiF4) gas (e.g., typical low-boiling-point components have boiling points in the range of approximately 80°C to 180°C, while SiF4 has a boiling point of approximately -86°C), they are easily separated. Specifically, the mixed vapor discharged from the top of the cracking tower mainly consists of the product SiF4 gas and the volatilized low-boiling-point component vapor. This mixed gas undergoes simple cooling via a condenser. At a set condensation temperature (e.g., between 0°C and -20°C, appropriately selected based on the freezing point of the selected low-boiling-point component), the low-boiling-point component vapor is condensed into a liquid, while the SiF4 gas remains gaseous. The condensed low-boiling-point component liquid can be collected and returned (refluxed) to the cracking tower for recycling, achieving closed-loop operation of this auxiliary solvent with minimal material loss. The separated pure SiF4 gas is then transported back to the exchange system (input to the bottom circulation port of the last-stage exchange tower) for the next round of separation and enrichment or extracted as a product.

[0106] The addition of low-boiling-point components not only effectively reduces the operating temperature of core technologies through physicochemical methods, bringing comprehensive benefits of energy saving, stability, and high efficiency, but also achieves efficient separation and recycling of auxiliary components and main products through a simple condensation separation process based on a large boiling point difference. The entire technical solution is highly operable and easy to implement industrially.

[0107] In some embodiments, such as Figure 1 As shown, this application provides a chemical exchange system for silicon isotope separation, used to implement the above-mentioned chemical exchange method, comprising:

[0108] The feed tower is used to input complexing agent raw materials and naturally abundant silicon tetrafluoride gas, mix them and cause a complexation reaction. The complexing agent raw materials are premixed with inert components that do not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase of the reaction system during the complexation reaction.

[0109] A multi-stage exchange tower includes at least three exchange towers connected in sequence. The exchange tower located in the middle position of the multi-stage exchange tower is used to receive complexed reactants from the feed tower. If the number of exchange towers is even, either of the two exchange towers in the middle position can be selected to receive complexed reactants from the feed tower.

[0110] Through multi-stage countercurrent operation, a continuous and stable concentration gradient field is formed in a system consisting of at least three exchange towers connected in series, in which the abundance of silicon-28 decreases stepwise from right to left (or from the product end to the raw material depletion end) and the abundance of silicon-29 / 30 increases stepwise.

[0111] The rightmost exchange column bottom (near the reflux port of the cracking column) is the region with the highest silicon-28 abundance in the system. The silicon tetrafluoride gas (rich in silicon-28), which has already undergone one round of enrichment and is returning from the cracking column, enters here. As this silicon-28-enriched gas phase flows to the left (i.e., towards the feed inlet), it comes into contact with a complex from the liquid phase on the left, which has a relatively lower silicon-28 abundance, in each exchange column. According to chemical equilibrium, the heavier isotopes (silicon-29 / 30) in the gas phase tend to enter the liquid phase, while the lighter silicon-28 in the liquid phase tends to enter the gas phase. Therefore, as the silicon-28-enriched gas phase flows to the left, silicon-28 is continuously "displaced" and re-enters the liquid phase, while silicon-29 / 30 is continuously concentrated in the gas phase. By the time it reaches the leftmost exchange column (or the depleted end), the silicon-28 abundance in the gas phase has decreased to its lowest point, while the silicon-29 / 30 abundance reaches its highest point.

[0112] This structural design in this embodiment improves cascade efficiency, enabling the simultaneous production of high-abundance products and deeply depleted tailings with minimal energy consumption and reflux ratio.

[0113] The cracking tower receives the complex liquid phase output from the last-stage exchange tower (i.e., the exchange tower directly connected to the cracking tower) and heats and decomposes it. Silicon tetrafluoride gas is obtained at the top outlet of the cracking tower and is fed to the bottom circulation port of the last-stage exchange tower. Then, it passes through multiple exchange towers sequentially from back to front and returns to the bottom circulation port of the complexing tower. There, it undergoes a complexation reaction with the purified complexing agent in the complexing tower to obtain the complexed product. The purified complexing agent in the complexing tower is a regenerated complexing agent liquid phase that contains almost no coordinated silicon tetrafluoride after cracking and decomposition of silicon tetrafluoride and purification by the impurity removal tower. It contains inert components retained in the cycle and can be returned to the complexing tower to participate in the complexation reaction again.

[0114] The impurity removal tower is used to receive the complexing agent mixture from the bottom outlet of the cracking tower. The impurity-removed complexing agent and lean solvent are collected at the upper outlet of the impurity removal tower.

[0115] The complexing tower is used to receive the complexing agent lean solvent from the impurity removal tower and the silicon tetrafluoride gas input from the first-stage exchange tower (i.e., the exchange tower directly connected to the complexing tower), while the inert component is input from the top of the complexing tower at a certain flow rate to carry out the complexing reaction and obtain the complexed product.

[0116] This embodiment describes a dedicated system for achieving the aforementioned chemical exchange method for silicon isotope separation. Through specific connection methods and material flow design of the "feeding tower," "multi-stage exchange tower," "pyrolysis tower," "impurity removal tower," and "complexing tower," this system organically integrates inert component viscosity reduction technology with the chemical exchange separation process. The system design ensures that: 1) the inert component can effectively participate in the circulation and exert a continuous viscosity reduction effect; 2) the enriched silicon isotope products and depleted materials are efficiently separated in multi-stage countercurrent exchange; and 3) the complexing agent can be regenerated and purified online, ensuring long-term operation. This dedicated system is the equipment guarantee for achieving high-efficiency, low-energy-consumption, and stable production of high-abundance silicon isotopes. The silicon-28 isotopes produced by this system can reach an abundance of over 99.999%.

[0117] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0118] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0119] The foregoing has described specific embodiments of the present application. In some cases, the described actions or steps may be performed in a different order than those shown in the embodiments and the desired results may still be achieved. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are also possible or may be advantageous.

[0120] In the description of the embodiments of this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In the embodiments of this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in the embodiments of this application, as well as the features of different embodiments or examples.

Claims

1. A chemical exchange method for the separation of silicon isotopes, characterized in that, Includes the following steps: S1. Naturally abundant silicon tetrafluoride and complexing agent raw materials are subjected to a complexation reaction to form a saturated complex at a corresponding temperature and pressure. The complexation reaction between the complexing agent raw material and silicon tetrafluoride gas is reversible. The complexing agent raw material is premixed with an inert component that does not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase in the reaction system during the complexation reaction. S2. The complex generated in step S1 is subjected to multi-stage chemical exchange with silicon tetrafluoride gas so that the silicon tetrafluoride-28 isotope complex is enriched in the liquid phase, and the silicon tetrafluoride-29 isotope complex and silicon tetrafluoride-30 isotope complex are enriched in the gas phase. S3. The liquid-phase complex from the exchange system is heated and decomposed, and the resulting silicon tetrafluoride gas is fed into the bottom circulation port of the last-stage exchange tower. The inert component does not decompose during the reaction. S4. The complexing agent liquid obtained from the pyrolysis tower is purified by the impurity removal tower and then returned to the complexing tower. The S5 and silicon-28 enriched products are collected from the bottom of the last-stage exchange tower or the top of the cracking tower, while the silicon-29 or silicon-30 enriched products are collected from the bottom of the complexation tower or the top of the first-stage exchange tower. When the silicon isotope abundance in the complexation product reaches the target abundance, the corresponding silicon isotope product is collected.

2. The chemical exchange method according to claim 1, characterized in that, The inert component is a liquid hydrocarbon or carbonate, wherein the liquid hydrocarbon is selected from at least one of alkanes and aromatics.

3. The chemical exchange method according to claim 2, characterized in that, The aromatic hydrocarbon is at least one of benzene, toluene, and xylene, and the carbonate is at least one of dimethyl carbonate and diethyl carbonate.

4. The chemical exchange method according to claim 2, characterized in that, The alkane is a n-alkanes or cycloalkanes with 5 to 10 carbon atoms.

5. The chemical exchange method according to claim 2, characterized in that, The inert component is at least one of n-hexane, cyclohexane, and n-heptane.

6. The chemical exchange method according to claim 1, characterized in that, The molar ratio between the complexing agent raw material and the inert component is 10:1 to 2:

1.

7. The chemical exchange method according to claim 1, characterized in that, The complexing agent raw material comprises at least two different types of complexing agents selected from alcohols, ethers, esters and amines. The complexing agent can undergo a reversible coordination reaction with silicon tetrafluoride to form a complex with an asymmetric octahedral structure.

8. The chemical exchange method according to claim 7, characterized in that, The at least two different types of complexing agents comprise a first complexing agent providing a first type of coordinating atom and a second complexing agent providing a second type of coordinating atom, wherein the isotope separation factor of the first type of coordinating atom is higher than that of the second type of coordinating atom, and the chemical bond stability of the second type of coordinating atom is higher than that of the first type of coordinating atom.

9. The chemical exchange method according to claim 1, characterized in that, In step S3, before heating and decomposing, a low-boiling-point component with a boiling point lower than that of the complex is added to the complex to be decomposed, in order to lower the decomposition temperature of the complex and increase the decomposition rate of the complex.

10. A chemical exchange system for silicon isotope separation, used to implement the chemical exchange method according to any one of claims 1-9, characterized in that, include: The feed tower is used to input complexing agent raw materials and naturally abundant silicon tetrafluoride gas, mix them and cause a complexation reaction. The complexing agent raw materials are premixed with inert components that do not participate in the complexation reaction or react with any component in the reaction system, in order to reduce the dynamic viscosity of the liquid phase of the reaction system during the complexation reaction. A multi-stage exchange tower includes at least three exchange towers connected in sequence, wherein the exchange tower located in the middle of the multi-stage exchange tower is used to receive complexed reactants from the feed tower; The cracking tower is used to receive the complex liquid phase output from the last-stage exchange tower and to heat and decompose it. Silicon tetrafluoride gas is obtained at the top outlet of the cracking tower and is fed to the bottom circulation port of the last-stage exchange tower. Then, it passes through multiple exchange towers from back to front and returns to the bottom circulation port of the complexing tower. There, it undergoes a complexation reaction with the purified complexing agent and lean solvent in the complexing tower to obtain the complexed product. The impurity removal tower is used to receive the complexing agent mixture from the bottom outlet of the cracking tower. The impurity-removed complexing agent and lean solvent are collected at the upper outlet of the impurity removal tower. The complexing tower is used to receive the complexing agent lean solvent from the impurity removal tower and the silicon tetrafluoride gas input from the first-stage exchange tower, while the inert component is input from the top of the complexing tower at a certain flow rate to carry out the complexation reaction and obtain the complexed product.

Images