A method of capturing hexafluoroethane

Abstract

The application discloses a method for capturing hexafluoroethane, comprising the following steps: adsorbing and capturing hexafluoroethane by using a porous material and / or a shaped porous material; the porous material is formed by carboxylate ions of an organic ligand 1,4-naphthalene dicarboxylic acid and Al 3+ forming an ionic coordination bond; and the shaped porous material is obtained by wet granulation by mixing the porous material with a binder and water. The application can realize effective greenhouse gas emission reduction and resource recycling.

Description

Technical Field

[0001] This invention relates to the field of fluorine-containing greenhouse gas capture technology, and specifically to a method for capturing hexafluoroethane. Background Technology

[0002] Perfluorocarbons (PFCs) are a class of man-made greenhouse gases with an extremely strong greenhouse effect. These compounds have an extremely long atmospheric lifetime, and their impact on the environment lasts for a longer period of time.

[0003] Perfluorinated carbons (PFCs) mainly include tetrafluorocarbons (CF4), hexafluoroethane (C2F6), and octafluoropropane (C3F8), and are classified as fluorinated greenhouse gases under global regulated control. The global warming potential of PFCs is thousands or even tens of thousands of times greater than that of carbon dioxide; for example, the warming potential of C2F6 reaches 12,400 (compared to 1 for carbon dioxide). These gases have wide industrial applications. C2F6, in particular, is widely used as a dry etching gas and cleaning agent in semiconductor plasma etching. However, the ionization rate of C2F6 is less than 50%, with the remainder being released into the atmosphere after hydrogenation and combustion. This results in the waste of C2F6, a resource with extremely high value, and also exacerbates the greenhouse effect. Effective recycling and reuse of C2F6 from exhaust gases could not only yield significant economic benefits but also mitigate the global greenhouse effect.

[0004] Currently, developing efficient fluorine-containing greenhouse gas capture technologies is of great significance.

[0005] Existing technologies for hexafluoroethane adsorption materials include:

[0006] The patent specification with publication number CN115770554A discloses a modified adsorbent and its application in removing hexafluoroethane from monofluoromethane. The modified adsorbent is prepared by: (1) dissolving cucurbit[7]urea in hydrochloric acid with a concentration of 0.5-1.5 mol / L to prepare an impregnation solution with a cucurbit[7]urea concentration of 0.1-2 g / mL; (2) adding activated carbon to the impregnation solution and impregnating for 18-24 h; (3) filtering out the impregnated activated carbon, washing it with deionized water until neutral, and then drying it overnight in a drying oven at 120-150℃ to obtain the modified adsorbent. Application method: (1) Fill the modified adsorbent into the adsorption column and activate it in situ in a nitrogen atmosphere at 250-350℃ for 2-4 hours, then cool it to room temperature; (2) Pass the crude monofluoromethane gas into the adsorption column filled with the modified adsorbent and continuously contact it with the modified adsorbent to remove hexafluoroethane impurities. The hexafluoroethane in monofluoromethane can be removed to below 20 ppb. However, its activation temperature is high and the material regeneration energy consumption is high.

[0007] Patent specification CN117244354A discloses a modified adsorbent composed of a surface-loaded hydrophobic metal-organic framework material capable of adsorbing fluorinated greenhouse gases such as hexafluoroethane in industrial exhaust gases. The hydrophobic material is a porous aromatic framework material comprising 0.1 wt.% to 30 wt.% of a material with a thickness of 200 to 1000 nm. The metal-organic framework material is constructed from aluminum ions and unsaturated dicarboxylic acid ligands selected from… At least one of the following, R is selected from at least one of H, OH, CH3, NO2, NH2, F, Cl, Br, or I. However, these materials have few interaction sites with hexafluoroethane, resulting in low separation selectivity. Summary of the Invention

[0008] This invention provides a method for capturing hexafluoroethane, which can achieve both effective greenhouse gas emission reduction and resource recycling.

[0009] The specific technical solution is as follows:

[0010] A method for capturing hexafluoroethane includes: using porous materials and / or molded porous materials to adsorb and capture hexafluoroethane;

[0011] The porous material is formed by the organic ligand 1,4-naphthalenedicarboxylic acid through the reaction of carboxylate ions with Al. 3+ Ion coordination linkages are formed;

[0012] The shaped porous material is obtained by wet granulation of the porous material with a binder and water.

[0013] The porous material described in this invention can be prepared by modifying existing technology 10.1021 / ja802589u (DOI).

[0014] A preferred method for preparing the porous material is provided herein, comprising: hydrothermally reacting 1,4-naphthalenedicarboxylic acid, trivalent aluminum salt (e.g., aluminum chloride, aluminum nitrate, etc.) and water at 115–185°C (e.g., 120°C, 180°C, etc.) for 20–28 h (e.g., 24 h); after the reaction, separating the solid and liquid, washing the solid, and removing the solvent molecules in the solid pores by displacement with anhydrous methanol to obtain the porous material.

[0015] In one embodiment, in the method for preparing the porous material, the molar ratio of 1,4-naphthalenedicarboxylic acid to the trivalent aluminum in the trivalent aluminum salt can be 1:1 to 2.

[0016] The porous material described in this invention is a metal-organic framework material synthesized from aluminum salts. It is formed by trivalent aluminum ions reacting with oxygen to form chain-like clusters or agglomerates, which are then linked by the organic ligand 1,4-naphthalenedicarboxylic acid to form a porous framework material.

[0017] In the porous material described in this invention, Al 3+ It can coordinate with the O on a carboxylic acid to form such as Figure 1 The chain-like clusters shown.

[0018] 1,4-Naphthalenedicarboxylic acid has the following chemical structure:

[0019]

[0020] The porous material described in this invention is easy to mold and has high stability. The porous material and / or molded porous material exhibit excellent selective adsorption of hexafluoroethane, and desorption and regeneration are easy and inexpensive, making it suitable for industrial applications.

[0021] The binder may be hydroxypropyl cellulose (HPC).

[0022] The amount of the adhesive used can be 1% to 5% of the sum of the mass of the adhesive and the porous material.

[0023] The particle size of the molded porous material can be 1 to 2 mm.

[0024] The porous material and / or shaped porous material may be subjected to vacuum activation treatment before being used to adsorb and capture hexafluoroethane.

[0025] Furthermore, the vacuum pressure of the vacuum activation treatment can be -0.01 to -0.1 MPa, the activation temperature can be 100 to 120°C, and the activation time can be 10 to 12 h.

[0026] The adsorption temperature can be -20 to 60°C, and the pressure can be 0.5 to 10 bar.

[0027] The method for capturing hexafluoroethane may further include: desorbing and recovering hexafluoroethane from porous materials and / or molded porous materials adsorbed with hexafluoroethane at 50–120°C and 0–1 atm, thereby regenerating the porous materials and / or molded porous materials. Vacuum desorption is preferred.

[0028] In practical operation, a gas mixture containing hexafluoroethane and / or etching tail gas can be passed into an adsorption column filled with porous material and / or shaped porous material. The hexafluoroethane in the gas mixture and / or etching tail gas is selectively adsorbed in the porous material, and the concentration of hexafluoroethane at the outlet is significantly reduced or even undetectable. Afterwards, the adsorbent can be regenerated and recycled by heating and vacuum desorption, and the recovered high-purity hexafluoroethane can be further commercialized.

[0029] The method for capturing hexafluoroethane can employ one or a combination of fixed-bed adsorption, fluidized-bed adsorption, and moving-bed adsorption.

[0030] This invention also provides the application of the aforementioned porous material or the shaped porous material in the adsorption and capture of hexafluoroethane. The definitions of the porous material and the shaped porous material are the same as above. The application can be optimized according to the specific technical solutions and parameter conditions in the above-described method for capturing hexafluoroethane.

[0031] One source of hexafluoroethane is the industrial waste gas containing hexafluoroethane discharged after the etching and cleaning stages in semiconductor manufacturing, where hexafluoroethane is used as the etching gas. This waste gas has a complex composition, also including nitrogen, oxygen, and water vapor. This necessitates that the adsorbent possesses strong selective adsorption capacity for hexafluoroethane, effectively blocking other gaseous components, especially nitrogen, which constitutes the largest proportion.

[0032] The porous material or molded porous material described in this invention can be used for the selective adsorption and desorption purification of hexafluoroethane, specifically for the adsorption and separation of hexafluoroethane from a mixed gas containing hexafluoroethane and nitrogen. Further, the volume ratio of hexafluoroethane to nitrogen in the mixed gas can be 99:1 to 1:99. Desorption of hexafluoroethane from the porous material or molded porous material yields hexafluoroethane with extremely low nitrogen content (purity >99.999%).

[0033] The porous materials and / or molded porous materials of this invention can be used to capture the greenhouse gas hexafluoroethane from etching exhaust gases. Due to the low utilization rate of hexafluoroethane in the etching process, the etching exhaust gases still contain a large amount of hexafluoroethane. As a greenhouse gas, hexafluoroethane is directly emitted into the atmosphere, which will exacerbate the global greenhouse effect. Moreover, hexafluoroethane has many applications and industrial value. Therefore, the materials of this invention can not only capture hexafluoroethane in etching exhaust gases, but also provide a high-purity hexafluoroethane gas source.

[0034] This invention can capture hexafluoroethane from etching exhaust gas with high capacity and high selectivity, with high removal depth, easy adsorbent regeneration, and good hydrothermal stability.

[0035] Compared with the prior art, the beneficial effects of this invention are as follows:

[0036] This invention proposes a method based on metal ions Al 3+ And a method for capturing hexafluoroethane using porous materials formed by self-assembly of dicarboxylic acid ligand 1,4-naphthalenedicarboxylic acid via coordination bonds.

[0037] The porous material of the present invention is a framework material with square one-dimensional channels. The channel surface is distributed with a large number of aromatic rings, which have very high aromaticity and can provide action sites for the adsorption of hexafluoroethane, thereby achieving the capture of hexafluoroethane.

[0038] The inventors discovered that the porous material of this invention exhibits strong hydrothermal acid stability, making it particularly suitable for the adsorption and separation of hexafluoroethane in etching exhaust gases. It can efficiently exclude other gases such as nitrogen, demonstrating high selectivity. The porous material's channel surface possesses very high aromaticity, creating an electrostatic environment within the confined space of the pores. This provides sites for the adsorption of hexafluoroethane, achieving its capture.

[0039] This invention granulates porous materials to adapt them for industrial applications.

[0040] In this invention, the porous material and hexafluoroethane gas molecules have a weak physical interaction, making desorption and regeneration easy and energy consumption low.

[0041] The porous material described in this invention exhibits high separation selectivity and adsorption capacity for hexafluoroethane gas over a relatively wide temperature range. In a preferred embodiment, the specific surface area of ​​the porous material is 546 m². 2 / g, with a pore size of 0.7nm, the adsorption capacity of hexafluoroethane can reach 45cm³. 3 / g, the C2F6 selectivity in the C2F6 / N2 mixture can reach over 200 (C2F6 / N2 volume ratio = 10 / 90), and the adsorption capacity can still reach 40cm³ after granulation. 3 / g. It is evident that the porous materials and / or molded porous materials of this invention have promising applications in capturing the greenhouse gas hexafluoroethane. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the chain-like cluster structure of the porous material of the present invention.

[0043] Figure 2 This is a photograph of the adsorbent particles after they were formed in Example 2.

[0044] Figure 3 This is a single-component adsorption isotherm diagram of Al(OH)(1,4-NDC) in hexafluoroethane in Example 3.

[0045] Figure 4 The image shows the breakthrough curve of the N2 / C2F6 (v:v = 90:10) mixture in Example 4 on Al(OH)(1,4-NDC), with a gas flow rate of 5 mL / min.

[0046] Figure 5 This is the desorption curve diagram from Example 4. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0049] Example 1

[0050] 1,4-Naphthalenedicarboxylic acid (0.108 g, 0.5 mmol), AlCl3·6H2O (0.241 g, 1 mmol), and 10 mL of H2O were added to a reaction vessel and reacted at 120 °C for 24 h. After cooling to room temperature, the mixture was filtered and washed with distilled water to obtain a light yellow powder. The product was then immersed in anhydrous methanol, with the methanol being replaced every six hours for a total of more than five replacements to remove solvent molecules from the pores of the material. This yielded the inexpensive porous material Al(OH)(1,4-NDC).

[0051] Example 2

[0052] 1g of the prepared powder (undegassed) material Al(OH)(1,4-NDC) and 30.9mg of hydroxypropyl cellulose (HPC) were placed in a mortar and mixed thoroughly. During stirring, 0.25mL of deionized water was added in small amounts several times until a semi-dry solid mass was obtained. Next, spherical particles of 1-2mm were obtained using an extrusion device. After drying, shaped particles were obtained, namely Al(OH)(1,4-NDC)@3%HPC adsorbent particles with a binder mass fraction of 3%. A photograph of the shaped adsorbent (i.e., the shaped porous material) particles is shown below. Figure 2 As shown.

[0053] Example 3

[0054] The molded adsorbent particles were activated under vacuum at 100°C for 10 hours to obtain activated molded porous material for gas separation. The activated particles were then tested for hexafluoroethane (H2F) at 278K, 298K, and 308K. Figure 3 The single-component adsorption isotherms of nitrogen and, based on the Ideal Adsorption Solution Theory (IAST) and adsorption data fitting calculations, show that the separation selectivity for a C2F6 / N2 mixture (volume ratio 10 / 90) is as high as 200 or more, indicating that the molded particles can efficiently capture hexafluoroethane from the etching exhaust gas. It should be noted that the single-component adsorption isotherms of nitrogen at 278K, 298K, and 308K for the activated particles show that the material of this invention has a very low nitrogen adsorption capacity, exhibiting exclusion characteristics.

[0055] Example 4

[0056] The granulated product from Example 2 was loaded into an adsorption column and activated under vacuum at 100°C for 10 hours. At room temperature (25°C), a C2F6 / N2 (volume ratio 10 / 90) mixture was introduced into the adsorption column at a rate of 5 mL / min. For the first 16 minutes, N2 with extremely low C2F6 content was obtained; adsorption was stopped after 16 minutes. The adsorption results are shown in [reference needed]. Figure 4 At 50°C, hexafluoroethane gas was desorbed under vacuum; the results are shown below. Figure 5 .

[0057] In summary, the present invention has the following characteristics:

[0058] 1) The porous material channel surface has very high aromaticity, forming an electrostatic environment in the confined space of the pores, providing sites for the adsorption of hexafluoroethane, achieving high capacity of hexafluoroethane while exhibiting good selectivity and deep removal.

[0059] 2) Porous materials are easy to desorb and regenerate, which can reduce energy consumption. At the same time, the material can be recycled and reused.

[0060] 3) Porous materials have extremely strong hydrothermal stability, as well as stability against acid vapors and cycle stability. The excellent stability also shows the potential of this porous material in industrial applications.

[0061] 4) By using granulation molding technology, the separation effect is not changed, but the problem of pipeline blockage caused by powder is alleviated, making filling convenient and thus adapting to industrial applications.

[0062] 5) Porous materials are relatively inexpensive.

[0063] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. The application of a porous material or shaped porous material in the adsorption and capture of hexafluoroethane, characterized in that, The porous material is formed by the organic ligand 1,4-naphthalenedicarboxylic acid through the reaction of carboxylate ions with Al. 3+ Ion coordination linkages are formed; The shaped porous material is obtained by wet granulation of the porous material with a binder and water; the binder is hydroxypropyl cellulose. The porous material or shaped porous material is used to adsorb and separate hexafluoroethane from a mixed gas containing hexafluoroethane and nitrogen; the porous material or shaped porous material is first subjected to vacuum activation treatment before being used to adsorb and capture hexafluoroethane.

2. The application according to claim 1, characterized in that, The amount of the adhesive used is 1% to 5% of the sum of the mass of the adhesive and the porous material.

3. The application according to claim 1, characterized in that, The particle size of the molded porous material is 1~2 mm.

4. The application according to claim 1, characterized in that, The vacuum activation treatment has a vacuum pressure of -0.01 to -0.1 MPa, an activation temperature of 100 to 120°C, and an activation time of 10 to 12 h.

5. The application according to claim 1, characterized in that, The adsorption temperature is -20~60℃ and the pressure is 0.5~10 bar.

6. The application according to claim 1, characterized in that, Porous materials or molded porous materials adsorbed with hexafluoroethane are desorbed and recovered from hexafluoroethane under conditions of 50~120℃ and 0~1 atm, thereby achieving the regeneration of the porous materials or molded porous materials.

7. The application according to claim 1, characterized in that, One or a combination of fixed-bed adsorption, fluidized-bed adsorption, and moving-bed adsorption are employed.

8. The application according to claim 1, characterized in that, The volume ratio of hexafluoroethane to nitrogen in the mixed gas is 99:1 to 1:99.

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