A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, a preparation method and application thereof

Abstract

The present application relates to the technical field of purification adsorption material, and particularly relates to a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent and a preparation method and application thereof, the modified molecular sieve adsorbent is composed of 85-98.5% of porous A type molecular sieve, 1-10% of cesium fluoride and 0.5-5% of lithium fluoride, and the total mass is 100%. The cesium fluoride and the lithium fluoride are loaded in the molecular sieve channel through synergistic active sites, the chemical adsorption selectivity of the adsorbent is enhanced, and the pore size is regulated; the adsorbent is applied to tungsten hexafluoride purification, can selectively adsorb WOF4, HF and low-valence tungsten fluoride impurities in crude tungsten hexafluoride under low-temperature conditions, and can greatly reduce the physical adsorption loss of the tungsten hexafluoride main body; the adsorbent has excellent regeneration stability, the active components are stably distributed in the channel, and the high removal efficiency is maintained after multiple negative pressure regeneration, and the adsorbent is suitable for industrial deep purification in the field of electronic special gas.

Description

Technical Field

[0001] This invention relates to the field of purification and adsorption material technology, specifically to a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, its preparation method, and its application. Background Technology

[0002] Tungsten hexafluoride (THF) is an important electronic specialty gas in semiconductor manufacturing, and its purity directly affects chip performance. The main impurities in crude THF include WOF4, trace amounts of HF, and low-valent tungsten fluorides. When ordinary porous molecular sieves are directly used, they exhibit poor selectivity for WOF4 adsorption and simultaneously adsorb large amounts of the main THF product, resulting in product loss. Using molecular sieves modified with a single alkali metal fluoride has limited adsorption capacity and poor regeneration stability; after multiple regenerations, active sites in the pores are lost, and the impurity removal efficiency drops significantly. Existing adsorption materials cannot simultaneously meet the industrial requirements of high selective impurity adsorption, low WF6 loss, and long-term regeneration stability.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, its preparation method and application, which aims to solve the technical problems of poor adsorption selectivity of ordinary molecular sieves for impurities such as WOF4, easy adsorption of tungsten hexafluoride main product and insufficient regeneration stability in the prior art. It achieves the technical effects of high selective adsorption of impurities under low temperature conditions, extremely low WF6 loss and excellent regeneration cycle performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, wherein, by mass percentage, it is composed of the following components: porous type A molecular sieve: 85-98.5%; cesium fluoride: 1-10%; lithium fluoride: 0.5-5%.

[0006] The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is wherein the porous type A molecular sieve is at least one of 4A molecular sieve or 5A molecular sieve.

[0007] The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is wherein the mass ratio of cesium fluoride to lithium fluoride is (1:1) to (5:1).

[0008] A method for preparing a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent as described in this invention, comprising the following steps: Porous type A molecular sieves are available; Cesium fluoride and lithium fluoride are dissolved in an oxygen-containing organic solvent to obtain an impregnation solution; The porous type A molecular sieve is impregnated with the impregnation solution; The impregnated material is then dried to remove the oxygen-containing organic solvent. The dried material is calcined to obtain the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent.

[0009] The method for preparing the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, wherein the oxygen-containing organic solvent is at least one of methanol, ethanol or isopropanol.

[0010] The method for preparing the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent includes the following steps: the impregnation treatment is carried out at room temperature for 1-6 hours; the drying treatment is performed at a temperature of 60-90℃.

[0011] The method for preparing the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent includes calcination treatment performed under an inert atmosphere or vacuum, at a temperature of 180-280℃ for 3-8 hours.

[0012] A method for purifying tungsten hexafluoride, wherein crude tungsten hexafluoride gas containing impurities is contacted with the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent described in this invention to adsorb and remove the impurities.

[0013] The purification method wherein the impurities include one or more of WOF4, HF, and low-valent tungsten fluorides.

[0014] Beneficial Effects: The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent provided by this invention utilizes a binary composite modification of porous type A molecular sieves with cesium fluoride and lithium fluoride. By leveraging the synergistic active sites formed by cesium fluoride and lithium fluoride within the molecular sieve channels, it enhances the chemical adsorption of impurity molecules such as WOF4, HF, and low-valent tungsten fluorides. Simultaneously, it reduces the physical adsorption of the main WF6 component through pore size control. This achieves high-selectivity deep impurity removal even at low temperatures (25-100℃) with extremely low WF6 loss. Furthermore, the binary composite modified structure ensures a more stable distribution of the active components within the channels, and the solidified layer formed after calcination exhibits excellent thermal shock resistance. Therefore, it can be repeatedly recycled under negative pressure regeneration conditions at 120-150℃, with adsorption performance degradation of less than 5% after more than 50 regenerations. Thus, this invention solves the problems of poor selectivity, easy adsorption of tungsten hexafluoride, and difficult regeneration of ordinary molecular sieves in the prior art, achieving low-loss, high-selectivity, and long-life tungsten hexafluoride purification. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation method of a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to the present invention. Detailed Implementation

[0016] This invention provides a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0017] Tungsten hexafluoride (THF), a key electronic specialty gas, is widely used in the tungsten metal deposition process in semiconductor manufacturing. Its purity (especially reaching 6N or even 7N levels) is crucial to chip performance. Crude THF typically contains low-valent tungsten fluoride impurities such as WOF4, trace amounts of HF, and WF5. These impurities must be removed efficiently and selectively while minimizing adsorption loss of the main product, WF6. This invention provides a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, specifically designed for in-situ or integrated purification processes of THF, aiming to solve the technical problems of poor selectivity, high product loss, and insufficient regeneration stability of traditional adsorbents.

[0018] In this application, for ease of description and understanding, some terms are first explained: Cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent: refers to a composite material obtained by loading cesium fluoride and lithium fluoride onto a porous type A molecular sieve as a matrix through impregnation and then calcining.

[0019] Porous type A molecular sieve: refers to a type of artificially synthesized zeolite crystal with a specific pore size range (such as type 4A or 5A), which has a regular structure and abundant ion exchange sites and pore system.

[0020] Oxygen-containing organic solvents: These are organic solvents whose molecules contain oxygen atoms and can form homogeneous solutions with cesium fluoride and lithium fluoride, such as methanol, ethanol, and isopropanol.

[0021] Low-temperature vacuum calcination: refers to a heating process carried out at a temperature below 280°C and in a vacuum or inert atmosphere, so that the loaded fluoride components are stably fixed inside the molecular sieve and avoid high-temperature decomposition.

[0022] Crude tungsten hexafluoride: refers to initial tungsten hexafluoride material containing impurities such as WOF4, HF and low-valent tungsten fluorides, with a purity lower than the target purity.

[0023] An embodiment of the present invention provides a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, which, based on the total mass of the modified molecular sieve adsorbent as 100%, is composed of the following components: porous type A molecular sieve: 85-98.5%; cesium fluoride: 1-10%; lithium fluoride: 0.5-5%.

[0024] This adsorbent forms synergistically activated adsorption sites by loading a binary composite of cesium fluoride and lithium fluoride onto the channels and surface of a porous type A molecular sieve. Cesium fluoride, with its large ionic radius and chemical activity, preferentially adsorbs acidic impurities such as WOF4 and HF. The introduction of lithium fluoride allows for a more stable composite structure at the lattice scale with cesium fluoride, adjusting the effective size of the molecular sieve channel inlet. This enhances the adsorption of smaller impurity molecules while creating a steric repulsion effect on the large WF6 molecule, significantly reducing its physical adsorption on the main product. Ultimately, this achieves high selectivity and high capacity adsorption of impurities at relatively low temperatures (e.g., 25-100℃) with extremely low WF6 loss. Preferably, the porous type A molecular sieve content is 92-97.5% by mass, ensuring sufficient support framework and dispersion space for the fluoride active component, while maintaining necessary physical adsorption and diffusion channels.

[0025] In some embodiments, to further improve the applicability of the adsorbent, especially to optimize pore size matching for crude tungsten hexafluoride from different sources or with different initial impurity concentrations, the porous type A molecular sieve in this adsorbent is at least one of 4A or 5A molecular sieves. The theoretical pore size of 4A molecular sieve is approximately 4 Å, while that of 5A molecular sieve is approximately 5 Å. In specific applications, for example, commercially available spherical 4A molecular sieves or strip-shaped 5A molecular sieves can be selected, or a mixture of the two can be prepared. When the main impurity molecule size is small, using 4A molecular sieves allows the effective pore size to be closer to the impurity molecule dynamic diameter, enhancing its diffusion sieving effect and further improving the steric hindrance effect on WF6; while when it is necessary to treat systems that may contain slightly larger molecular impurities, 5A molecular sieves can provide a more unobstructed mass transfer channel. In actual preparation, 90% by mass of 5A molecular sieve with concentrated pore size distribution can be used, or equal mass of 4A and 5A molecular sieves can be mixed as a matrix. After the same loading process, an adsorbent product with high selectivity for WOF4 and low loss of WF6 can be obtained.

[0026] In some preferred embodiments, to achieve stable impurity removal across a wide range of impurity concentrations and to balance the relationship between the loading of the active component and the stability of the support, the cesium fluoride content is preferably 2-8% by mass. Within this range, cesium fluoride provides a sufficient number of active sites for the adsorption reaction. Assuming an adsorbent preparation with a cesium fluoride content of 5% by mass, this is sufficient for a complete reaction with WOF4 molecules without clogging the molecular sieve channels due to excessive loading or causing severe aggregation of the active component during regeneration. When the cesium fluoride content is below 2% by mass, there may be insufficient active sites; when it is above 8% by mass, it may affect the pore structure. By controlling the content within the range of 2-8% by mass, the long-term stability of the adsorbent structure is ensured while maintaining high adsorption capacity.

[0027] In some preferred embodiments, to achieve a better synergistic stabilizing effect with cesium fluoride and optimize the chemical microenvironment at the pore inlet, the lithium fluoride content is preferably 1-4% by mass. As an alkali metal fluoride with a small ionic radius, lithium fluoride can intercalate into the gaps between the active sites formed by cesium fluoride, forming a more dense and stable composite fluoride solid solution. For example, in a specific adsorbent formulation, the lithium fluoride content is set at 2.2% by mass. This content can effectively regulate the local charge distribution and acid-base properties of the active sites, enhancing the chemisorption and fixation capacity for HF, while also possessing a certain adsorption capacity for WF4 and WOF4. More importantly, the presence of lithium fluoride can inhibit the migration and loss of cesium fluoride during repeated adsorption-regeneration cycles, thereby significantly improving regeneration stability. When the lithium fluoride content is below 1% by mass, its synergistic stabilizing effect is limited; exceeding 4% by mass may affect mass transfer due to excessive pore occupancy.

[0028] In some embodiments, to ensure an effective synergistic effect between the two active components, cesium fluoride and lithium fluoride, rather than a simple physical mixture, the mass ratio of cesium fluoride to lithium fluoride in the modified molecular sieve adsorbent is (1:1) to (5:1). This ratio is crucial for the formation of stable synergistic adsorption centers between the two fluorides. If the ratio is too low (e.g., excessive LiF), a LiF-dominated active phase may form, potentially resulting in insufficient adsorption capacity for WOF4. If the ratio is too high (e.g., excessive CsF), the lack of stabilizing effect from LiF may lead to easy migration and sintering of CsF during regeneration. By controlling the mass ratio within this range, it is ensured that the two components can mutually promote each other and distribute uniformly during impregnation and calcination. For example, setting cesium fluoride at 4% by mass and lithium fluoride at 3% by mass (mass ratio approximately 1.33:1), the adsorbent with this ratio exhibits particularly outstanding adsorption capacity for HF.

[0029] It should be noted that although the above preferred range provides clear guidance, within the broad range of 1-10% by mass of cesium fluoride and 0.5-5% by mass of lithium fluoride as defined in the claims, adjusting the specific ratios through conventional experiments can achieve technical effects superior to unmodified molecular sieves or single fluoride modified products. Furthermore, porous type A molecular sieves are typically pretreated under vacuum or inert atmosphere at 200-350°C before use to remove physically adsorbed water, which facilitates sufficient penetration of the subsequent impregnation solution. Cesium fluoride and lithium fluoride are preferably analytical grade or electronic grade powders, with their particle size distribution controlled by sieving to 100-200 mesh to ensure their solubility in organic solvents and uniform impregnation.

[0030] In some embodiments, a method for preparing a cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent as described in this invention is also provided. Figure 1 As shown, it includes the following steps: S10, provides porous type A molecular sieves; S20. Cesium fluoride and lithium fluoride are dissolved in an oxygen-containing organic solvent to obtain an impregnation solution; S30. The porous type A molecular sieve is impregnated with the impregnation solution. S40. The impregnated material is dried to remove the oxygen-containing organic solvent. S50. The dried material is calcined to obtain the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent.

[0031] Specifically, in step S10, a porous type A molecular sieve is first provided. Typically, this molecular sieve is dried at 180-220°C in a vacuum or nitrogen atmosphere for 2-6 hours to remove residual moisture from the pores, and then cooled to room temperature for later use. This step is crucial to ensure that the subsequent impregnation solution can effectively penetrate the internal pores of the molecular sieve. In step S20, calculated amounts of cesium fluoride and lithium fluoride are dissolved in an oxygen-containing organic solvent and stirred at room temperature for 10-30 minutes until completely dissolved or a homogeneous suspension is formed, thus obtaining the impregnation solution. Using an oxygen-containing organic solvent (such as methanol) can effectively dissolve cesium fluoride and lithium fluoride, and its boiling point is suitable for subsequent drying and removal. In step S30, the porous type A molecular sieve treated in step S10 is impregnated with the impregnation solution. During impregnation, an equal-volume impregnation method can be used, whereby a sufficient amount of impregnation solution is slowly added to the molecular sieve, ensuring that the liquid level just submerges all particles. The impregnation is then allowed to stand at room temperature (15-30℃) for 1-6 hours, with slight stirring during this period to ensure uniform loading. This process allows the fluoride precursor solution to fully diffuse into the pores and surface of the molecular sieve. In step S40, the impregnated material is dried to remove the oxygen-containing organic solvent. Specifically, the wet material can be transferred to an oven and dried at 60-90℃ for 2-8 hours until the solvent completely evaporates, resulting in a dried loaded precursor. Low-temperature drying helps prevent the rapid migration and aggregation of fluoride components on the molecular sieve surface, maintaining their dispersion within the pores. In step S50, the dried material is placed in a tube furnace or vacuum calcination furnace and heated to 180-280°C at a rate of 2-5°C / min under an inert atmosphere (such as nitrogen or argon) or vacuum (pressure less than 100 Pa), and maintained at this temperature for 3-8 hours, then naturally cooled to room temperature. This calcination process causes cesium fluoride and lithium fluoride to undergo a solid-phase reaction on the surface and within the pores of the molecular sieve framework, forming a stable composite fluoride active phase, which is firmly anchored on the molecular sieve, ultimately yielding a structurally stable and high-performance modified molecular sieve adsorbent. The preparation process provided by this invention is mild, avoiding the damage to the molecular sieve structure and the volatilization of active components caused by high temperatures, which is an important guarantee for achieving high performance and long lifespan of the adsorbent.

[0032] In some embodiments, for ease of operation and readily available solvents, the oxygen-containing organic solvent is at least one of methanol, ethanol, or isopropanol. Anhydrous methanol is preferred, as it has good solubility for cesium fluoride and lithium fluoride, and a low boiling point, facilitating subsequent drying removal. In this embodiment, to ensure sufficient diffusion of the fluoride precursor into the depths of the molecular sieve channels while avoiding excessively long ineffective soaking time, the impregnation process is carried out at room temperature for 1-6 hours. For example, a 3-hour impregnation time is set, which is sufficient to allow the impregnating solution to reach concentration equilibrium within the molecular sieve particles, ensuring uniform loading. In this embodiment, to safely and smoothly remove the organic solvent without causing premature migration or decomposition of the active components, the drying temperature is 60-90°C. Specifically, it can be carried out in a 70°C forced-air drying oven for approximately 4-5 hours until the material has no solvent odor and free-flowing particles are obtained.

[0033] In some embodiments, to prevent the active components from being oxidized by air or reacting with moisture during heat treatment, the calcination process is carried out under an inert atmosphere or vacuum. Dynamic nitrogen protection is preferred, with a gas flow rate of 50-100 mL / min, continuously removing potentially volatile trace components and residual solvent decomposition products to ensure the formation of a pure modified surface. In this embodiment, to ensure the loaded fluoride is fully crystallized and firmly anchored on the molecular sieve, while avoiding excessively high temperatures that could cause the molecular sieve framework to collapse or the active components to sinter, the calcination temperature is 180-280°C. For example, a calcination temperature of 240°C is set, at which temperature cesium fluoride and lithium fluoride can undergo sufficient solid-phase diffusion and reaction to form a stable composite phase, without exceeding the thermal stability limit of most type A molecular sieves. In this embodiment, to ensure sufficient treatment effect at the above calcination temperature, the calcination time is 3-8 hours. A calcination time of 4 hours is sufficient to complete the formation and stabilization process of the active phase.

[0034] In some preferred embodiments, to optimize production efficiency while ensuring performance, the calcination temperature is 220-250°C and the calcination time is 4-6 hours. For example, calcination at 240°C for 4 hours under nitrogen protection has been shown to enable the active component to achieve ideal crystallinity and dispersion, resulting in an adsorbent with both high adsorption capacity and excellent regeneration stability.

[0035] In some embodiments, a method for purifying tungsten hexafluoride is also provided. This method includes contacting crude tungsten hexafluoride gas containing impurities with the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent described in any one of the preceding embodiments to adsorb and remove the impurities. The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent of the present invention is packed into a fixed-bed adsorption tower, and the crude tungsten hexafluoride gas is passed through the adsorption bed at a certain space velocity under temperature conditions of 25-100°C. During the contact process, the adsorbent selectively adsorbs impurities such as WOF4, HF, and WF5, while WF6 molecules pass through in high yield due to steric hindrance and weak interactions. After adsorption saturation, regeneration can be performed by purging with negative pressure or inert gas at 120-150°C, and the desorbed impurities can be recovered.

[0036] In this embodiment, the impurities include one or more of WOF4, HF, and low-valent tungsten fluorides. This adsorbent exhibits extremely high chemical affinity and selectivity for these impurities. In this embodiment, the contact is carried out at a temperature of 25-100°C. This low-temperature operating condition matches the synthesis or storage temperature of WF6 and can be directly integrated into existing process pipelines to achieve in-situ impurity removal without additional heating or cooling energy consumption, making it particularly suitable for continuous industrial production.

[0037] The present invention will be further explained and illustrated below through specific embodiments and test data:

[0038] Example 1 A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is provided, with the following raw material ratio: 5.0 wt% cesium fluoride, 2.2 wt% lithium fluoride, and 92.8 wt% 5A molecular sieve; the preparation steps include: S1 and 5A molecular sieves were vacuum dried at 200℃ for 5 hours and then cooled to room temperature. S2. Dissolve CsF and LiF in anhydrous methanol to prepare a mixed impregnation solution; S3, immerse in equal volume at room temperature for 3 hours; dry at 70℃ to remove methanol; The finished adsorbent was obtained by vacuum calcining at 240℃ for 4 hours under S4 and N2 protection.

[0039] Application test: At an adsorption temperature of 30℃ and an initial WOF4 concentration of 120ppm in crude WF6, the WOF4 concentration at the outlet after treatment was <8ppb, and the WF6 adsorption loss was <0.8‰; after 50 consecutive regenerations, the impurity removal efficiency decreased by 3.2%.

[0040] Example 2 A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is provided, with the following raw material ratio: 7.5 wt% cesium fluoride, 3.5 wt% lithium fluoride, and 89.0 wt% 5A molecular sieve; the preparation process is the same as in Example 1.

[0041] Application test: adsorption temperature 30℃, initial WOF4 concentration in crude WF6 120ppm, WOF4 at the outlet after treatment <9.2ppb, WF6 adsorption loss <1.1‰; after 50 consecutive regenerations, the impurity removal efficiency decreased by 4.1%.

[0042] Example 3 A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is provided, with the following raw material ratio: 2.5wt% cesium fluoride, 1.2wt% lithium fluoride, and 96.3wt% 4A molecular sieve; the preparation process is the same as in Example 1.

[0043] Application test: At an adsorption temperature of 30℃, the initial concentration of WOF4 in crude WF6 was 120ppm. After treatment, the WOF4 concentration at the outlet was <12ppb, and the WF6 adsorption loss was <0.9‰. After 50 consecutive regenerations, the impurity removal efficiency decreased by 4.8%.

[0044] Example 4 A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is provided, with the following raw material ratio: 4.8 wt% cesium fluoride, 2.3 wt% lithium fluoride, and 92.9 wt% 4A molecular sieve; the preparation process is the same as in Example 1.

[0045] Application test: adsorption temperature 30℃, initial WOF4 concentration in crude WF6 120ppm, WOF4 at the outlet after treatment < 7.5ppb, WF6 adsorption loss < 0.7‰; after 50 consecutive regenerations, the impurity removal efficiency decreased by 2.5%.

[0046] Example 5 A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent is provided. The raw material ratio is the same as in Example 1. The difference between the preparation process and Example 1 is that the calcination temperature is changed to 225℃ and the calcination time is changed to 5h, while the other steps remain the same.

[0047] Application test: adsorption temperature 30℃, initial WOF4 concentration in crude WF6 120ppm, WOF4 at the outlet after treatment < 8.3ppb, WF6 adsorption loss < 0.85‰; after 50 consecutive regenerations, the impurity removal efficiency decreased by 2.9%.

[0048] Comparative Example 1 When blank 5A molecular sieves are directly filled with coarse WF6, under the same operating conditions, the WOF4 at the outlet after treatment is found to be >45ppm, and the WF6 adsorption loss is >3.5%, which cannot meet the requirements for high-purity production.

[0049] Comparative Example 2 A cesium fluoride modified molecular sieve adsorbent is provided, wherein the raw material ratio by mass percentage is: 5 wt% cesium fluoride and 95 wt% 5A molecular sieve.

[0050] Application test: Adsorption temperature 30℃, initial WOF4 concentration in crude WF6 120ppm, WOF4 at the outlet after treatment > 22ppm, WF6 adsorption loss < 1.5‰, after 20 consecutive regenerations, the impurity removal efficiency decreased by 20%.

[0051] As can be seen from the application test data of Examples 1-5 and Comparative Examples 1-2 above, compared with the unmodified Comparative Example 1, all examples showed excellent removal ability of WOF4 (the outlet concentration decreased from >45,000 ppb to the single digit ppb level) and extremely low WF6 loss (from >35‰ to <1‰), which verifies the fundamental advantages of the composite modification of cesium fluoride and lithium fluoride.

[0052] Compared to Comparative Example 2, which only supported cesium fluoride, Example 1 (with added LiF) not only had a higher initial impurity removal efficiency (<8 ppb vs>22,000 ppb), but also significantly improved regeneration stability (3.2% attenuation after 50 cycles vs>20% attenuation after 20 cycles). This strongly demonstrates the crucial role of lithium fluoride in forming a stable and synergistic active phase and preventing the loss of active components; that is, the synergistic effect of binary composite modification is the core mechanism for its long lifetime.

[0053] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent, characterized in that, It consists of the following components by mass percentage: porous type A molecular sieve: 85-98.5%; cesium fluoride: 1-10%; lithium fluoride: 0.5-5%.

2. The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to claim 1, characterized in that, The porous type A molecular sieve is at least one of 4A molecular sieve or 5A molecular sieve.

3. The cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to claim 1, characterized in that, The mass ratio of cesium fluoride to lithium fluoride is (1:1) to (5:1).

4. A method for preparing the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent as described in any one of claims 1-3, characterized in that, Including the following steps: Porous type A molecular sieves are available; Cesium fluoride and lithium fluoride are dissolved in an oxygen-containing organic solvent to obtain an impregnation solution; The porous type A molecular sieve is impregnated with the impregnation solution; The impregnated material is then dried to remove the oxygen-containing organic solvent. The dried material is calcined to obtain the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent.

5. The preparation method of the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to claim 4, characterized in that, The oxygen-containing organic solvent is at least one of methanol, ethanol, or isopropanol.

6. The preparation method of the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to claim 4, characterized in that, The impregnation treatment is carried out at room temperature for 1-6 hours; the drying treatment is carried out at a temperature of 60-90°C.

7. The preparation method of the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to claim 4, characterized in that, The calcination process is carried out under an inert atmosphere or vacuum, at a temperature of 180-280°C, for 3-8 hours.

8. A method for purifying tungsten hexafluoride, characterized in that, The crude tungsten hexafluoride gas containing impurities is contacted with the cesium fluoride-lithium fluoride composite modified molecular sieve adsorbent according to any one of claims 1-3 to adsorb and remove the impurities.

9. The purification method according to claim 8, characterized in that, The impurities include one or more of WOF4, HF, and low-valent tungsten fluorides.

Images