A method for removing r133a from hexafluoropropane

Abstract

This application belongs to the field of electronic gas purification technology, specifically relating to a method for removing R133a from hexafluoropropane. Hexafluoropropane feedstock containing R133a impurities is passed into an adsorption column packed with a modified adsorbent, and high-purity hexafluoropropane is obtained through adsorption. The modified adsorbent is any one of modified molecular sieves, modified metal-organic framework materials, or modified mesoporous silica. This application improves the specific adsorption selectivity of the adsorbent for R133a impurities by modifying adsorbents such as molecular sieves, metal-organic framework materials, and mesoporous silica. It can stably remove R133a impurities from the hexafluoropropane feedstock at a volume fraction of 0.5%~1% to an extremely low level of less than 0.5 ppm, meeting the ultra-high purity requirements of hexafluoropropane in fields such as semiconductors.

Description

Technical Field

[0001] This application belongs to the field of electronic gas purification technology, specifically relating to a method for removing R133a from hexafluoropropane. Background Technology

[0002] Hexafluoropropane, as an important fluorine-containing electronic gas, plays a crucial role in the semiconductor and integrated circuit manufacturing industry, particularly in dry etching processes for high aspect ratio contact holes, vias, and metal gates. Hexafluoropropane provides accurate etching rate and morphology control, making it a key material for advanced process node chip manufacturing. With the exponential increase in chip integration and the increasing complexity of device structures, the purity requirements for electronic gases are rising. Hexafluoropropane used in high-end manufacturing typically requires a purity of 99.999% (5N) or even higher. Under such high purity requirements, the presence of even trace impurities can severely impact the uniformity, selectivity, and repeatability of the etching process, leading to wafer defects and reduced chip yield.

[0003] In the industrial synthesis of hexafluoropropane, various impurities are inevitably introduced due to factors such as reaction route selection, starting material purity, and side reactions. Among them, R133a (chemical formula C2HClF3) is a common and extremely difficult-to-remove key impurity. Furthermore, hexafluoropropane has a boiling point of -1.4℃, while R133a has a boiling point of 6.9℃; their similar boiling points limit separation effectiveness, posing a challenge to traditional separation and purification methods.

[0004] Currently, the main industrial technique for separating near-boiling point systems is distillation. Separation is achieved by utilizing the slight differences in volatility between components. However, when this method is applied to the hexafluoropropane / R133a system, firstly, the extremely small boiling point difference increases the number of theoretical plates required for separation, leading to high costs. Secondly, an extremely high reflux ratio is needed, further increasing operating costs. Furthermore, distillation remains inefficient in handling trace impurities, failing to meet the production requirements of ultra-high purity products.

[0005] To overcome the problems of distillation, adsorption has attracted attention in the industry. The principle of adsorption is to achieve separation by utilizing the differences in adsorption affinity of porous adsorbents for different components in a gas mixture. Theoretically, adsorption has advantages such as low energy consumption, mild operating conditions, and the ability to achieve extremely high purity separation. However, when applied to the hexafluoropropane / R133a system, problems arise due to low selectivity and low adsorption capacity.

[0006] Traditional adsorbents such as activated carbon and molecular sieves fail to meet separation requirements. While activated carbon possesses a large specific surface area, its uneven pore size distribution and limited variety of surface functional groups result in weak recognition ability for structurally similar molecules like hexafluoropropane and R133a, leading to poor adsorption selectivity, competitive adsorption, and difficulty in achieving effective separation. Conventional molecular sieves, although possessing a regular pore structure, rely primarily on molecular size sieving for separation. Furthermore, these traditional adsorbents typically have low adsorption capacity for R133a, resulting in rapid bed penetration and frequent regeneration, making their processing efficiency insufficient for large-scale industrial production.

[0007] In summary, traditional distillation methods, due to their high energy consumption and limited separation capacity, cannot meet the requirements for impurity removal; while conventional adsorbents, due to insufficient selectivity and adsorption capacity, are insufficient to meet the requirements of industrial applications. Therefore, there is a need to develop a method that can overcome existing technologies to meet the purity requirements of electronic gases in fields such as semiconductors. Summary of the Invention

[0008] Traditional distillation methods, due to their high energy consumption and limited separation capacity, cannot meet the requirements for impurity removal; while conventional adsorbents, due to insufficient selectivity and adsorption capacity, are difficult to meet the requirements of industrial applications. This application proposes a method for removing R133a from hexafluoropropane. The technical solution of this application is as follows: A method for removing R133a from hexafluoropropane includes the following steps: Hexafluoropropane feedstock containing R133a impurity is passed into an adsorption column packed with modified adsorbent, and high-purity hexafluoropropane is obtained through adsorption. The modified adsorbent is selected from any one of the following: (a) Zeolite molecular sieve modified with metal cation exchange; (b) Metal-organic framework materials with a fluoropolymer coating on their surface; (c) Mesoporous silica loaded with active components.

[0009] Preferably, the zeolite molecular sieve modified by metal cation exchange is a modified 13X molecular sieve, and the modification method is to place the 13X molecular sieve in a solution containing metal cations Ag at a concentration of 0.05~0.5 mol / L. + Cu 2+ Zn 2+ The solution is stirred in a salt solution at 40-80°C for 12-36 hours, and then filtered, washed and dried.

[0010] Preferably, the metal-organic framework material with a fluoropolymer coating is a modified MIL-101, which is modified by in-situ polymerization of fluorinated monomer vapor on the surface of the MIL-101 material using chemical vapor deposition.

[0011] Preferably, the fluorinated monomer vapor is tetrafluoroethylene, and the chemical vapor deposition method is carried out at a temperature of 150~250℃ and a pressure of 0.05~0.2 MPa for 2~6 hours, with a fluorinated polymer coating thickness of 0.1~5μm.

[0012] Preferably, the mesoporous silica loaded with active components is modified SBA-15.

[0013] Preferably, the active component is MnO2, and the loading of the active component is 5~20%; the modification method is to impregnate SBA-15 in a 50% manganese nitrate solution, dry it at 80~120℃, and then calcine it at 400℃ to 500℃ for 2~6h.

[0014] Preferably, the volume fraction of R133a in the hexafluoropropane feedstock is 0.5%~1%, and the feedstock gas flow rate of the hexafluoropropane is 30~80L / min.

[0015] Preferably, the adsorption pressure is 0.1~0.4MPa and the temperature is 20~60℃.

[0016] Preferably, the R133a content in the high-purity hexafluoropropane is less than 0.5 ppm.

[0017] The beneficial effects of this application are: This invention specifically overcomes the shortcomings of traditional distillation methods in treating R133a impurities in hexafluoropropane, such as high energy consumption and limited separation capacity. At the same time, it makes up for the shortcomings of conventional adsorbents in industrial applications, such as poor adsorption selectivity and insufficient adsorption capacity. It provides an efficient and feasible technical path for the deep removal of impurities from hexafluoropropane, and fundamentally solves the problem that traditional technologies cannot meet the ultra-high purity requirements of high-end fields.

[0018] This application improves the specific adsorption selectivity of adsorbents for R133a impurities by modifying adsorbents such as molecular sieves, metal-organic framework materials, and mesoporous silica through ion exchange modification of molecular sieves, fluoropolymer coating modification of metal-organic framework materials, and active component loading modification of mesoporous silica. It can stably remove R133a impurities with a volume fraction of 0.5%~1% from hexafluoropropane feedstock to an extremely low level of less than 0.5ppm, which meets the ultra-high purity requirements of hexafluoropropane in fields such as semiconductors.

[0019] The adsorbent regeneration method of the present invention is simple and effective, enabling multiple cycles of adsorbent reuse. This not only reduces the frequency of adsorbent replacement and consumable consumption, thus lowering raw material costs and solid waste treatment pressure, but also, combined with mild adsorption process conditions, further reduces energy consumption and equipment maintenance costs during production, thereby enhancing the overall economic efficiency and market competitiveness of the process. Attached Figure Description

[0020] Figure 1 This is a diagram of the apparatus for removing R133a from hexafluoropropane in this application.

[0021] Explanation of reference numerals in the attached diagram: 1. Raw material gas inlet; 2. Adsorption column; 3. Adsorbent bed; 4. Purified gas outlet; 5. Regeneration gas inlet; 6. Desorption gas outlet. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application is provided in conjunction with the accompanying drawings and preferred embodiments.

[0023] Device Examples This embodiment provides a device for removing R133a from hexafluoropropane. The device includes an adsorption column 2, which is provided with an adsorbent bed 3 for removing R133a from hexafluoropropane. A raw material gas inlet 1 is provided on the bottom side wall of the adsorption column 2 for introducing hexafluoropropane raw material gas containing R133a. A purified gas outlet 4 is provided on the top of the adsorption column 2 for discharging the hexafluoropropane gas after adsorption and purification. A regeneration gas inlet 5 is provided on the upper side wall of the adsorption column 2 for introducing a regeneration medium. A desorption gas outlet 6 is provided at the bottom of the adsorption column 2 for discharging the mixed gas carrying desorbed R133a.

[0024] Implementation principle of the device: Hexafluoropropane feed gas containing R133a is continuously fed into adsorption column 2 through feed gas inlet 1. The feed gas flows through the adsorption bed, and R133a is selectively retained by the adsorbent. The purified hexafluoropropane gas is continuously discharged from the purified gas outlet. When the adsorbent in the adsorption bed reaches adsorption saturation, the adsorption operation is stopped.

[0025] After the feed gas is stopped, the regeneration gas is introduced into the adsorption column 2 through the regeneration gas inlet 5. The regeneration gas flows through the saturated adsorbent, causing the adsorbed R133a to desorb. The desorbed mixed gas carrying R133a is discharged from the desorbed gas outlet 6. When the adsorbent performance is restored, the regeneration gas is stopped, and the device can re-enter the adsorption stage for cyclic operation.

[0026] Examples 1-3 provide a method for removing R133a from hexafluoropropane based on the apparatus provided in the apparatus examples.

[0027] Example 1 This embodiment provides a method for surface modification of MIL-101 using chemical vapor deposition to remove R133a adsorbent from hexafluoropropane. Adsorbent screening: Static adsorption experiments were conducted using activated carbon, 3A molecular sieve, activated alumina, and the metal-organic framework material MIL-101. 190 L of each adsorbent was placed in a sealed container, and the adsorption effect was measured. After 24 hours of adsorption at 25℃ and 1 atm, the results are shown in Table 1. MIL-101 exhibited a relatively high adsorption capacity (45 mg / g) and good adsorption selectivity (selectivity coefficient of 3) for R133a. Therefore, MIL-101 was initially selected as the adsorbent for subsequent modification. Table 1 Types of adsorbents Activated carbon 3A molecular sieve Activated alumina MIL-101 Adsorption capacity 50mg / g 30mg / g 38mg / g 45mg / g Selectivity coefficient 1.5 1.8 2 3 The content of R133a in the hexafluoropropane mixture before adsorption 0.5% 0.5% 0.5% 0.5% The content of R133a in the hexafluoropropane mixture after adsorption 1.5×10-6 5×10-6 3×10-6 0.5×10-6 Adsorbent modification: MIL-101 was surface modified using chemical vapor deposition. MIL-101 was placed in a chemical vapor deposition apparatus, and tetrafluoroethylene monomer vapor was introduced at a rate of 3.5–4 g / L·min. Deposition was carried out at 200 °C and 0.1 MPa for 4 hours, forming a uniform fluoropolymer coating on the surface of MIL-101. Adsorption separation: Modified MIL-101 adsorbent was packed into a stainless steel adsorption column with an inner diameter of 20 mm and a length of 600 mm to form an adsorption bed. Hexafluoropropane feed gas containing R133a (0.5%) was introduced from the bottom of the adsorption column at a flow rate of 50 mL / min, and adsorption separation occurred within the column at a pressure of 0.3 MPa and a temperature of 40 °C. Gas samples effluent from the top of the adsorption column were collected every hour, and the R133a content was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0028] Adsorbent regeneration: When the R133a content in the gas effluent from the top of the adsorption column reaches 0.5 ppm or higher (i.e., the adsorbent is close to adsorption saturation), the feed gas supply is stopped. The adsorbent is regenerated using thermal desorption. The adsorption column is slowly heated to 150°C and maintained for 2 hours, while nitrogen is purged to carry the desorbed R133a out of the column. Then, the heating is stopped and a vacuum is applied for 1 hour. After the regenerated adsorbent cools to room temperature, the adsorption separation experiment is repeated.

[0029] After 15 adsorption-regeneration cycle experiments, the results showed that the modified MIL-101 adsorbent could reduce the R133a content in hexafluoropropane to below 0.5 ppm in each adsorption process. The adsorbent had good regeneration performance, and after 10 cycles, the adsorption performance could still be maintained at more than 90% of the initial performance. Example 2 This embodiment provides a method for removing R133a adsorbent from hexafluoropropane by ion exchange modification of 13X molecular sieve. Adsorbent screening: Static adsorption experiments were conducted on 4A molecular sieve, 5A molecular sieve, 13X molecular sieve, and the metal-organic framework material ZIF-8. The experimental conditions were the same as in Example 1, and the results are shown in Table 2. 13X molecular sieve showed a high adsorption capacity (40 mg / g) and good adsorption selectivity (selectivity coefficient of 2.5) for R133a, and was selected for subsequent modification.

[0030] Table 2 Types of adsorbents 4A molecular sieve 5A molecular sieve 13X molecular sieve ZIF-8 Adsorption capacity 30mg / g 35mg / g 40mg / g 30mg / g Selectivity coefficient 2 2.1 2.5 1.5 The content of R133a in the hexafluoropropane mixture before adsorption 1% 1% 1% 1% The content of R133a in the hexafluoropropane mixture after adsorption 10×10-6 8×10-6 0.5×10-6 5×10-6 Adsorbent modification: 13X molecular sieve was modified by ion exchange. The 13X molecular sieve was immersed in a 0.1 mol / L silver nitrate solution and stirred at 60℃ for 24 hours to carry out the ion exchange reaction. After the reaction, the sieve was filtered, washed, and dried to obtain Ag. + The 13X molecular sieve after exchange. Adsorption separation: Modified 13X molecular sieve adsorbent was packed into a glass adsorption column with an inner diameter of 25 mm and a length of 600 mm. Hexafluoropropane feed gas containing 1% R133a was introduced from the bottom of the adsorption column at a flow rate of 80 mL / min for adsorption separation experiments. The adsorption pressure was 0.1 MPa, and the adsorption temperature was 60 °C. The R133a content in the gas effluent from the top of the adsorption column was monitored in real time using an online infrared spectrometer. Adsorbent regeneration: When the R133a content in the gas effluent from the top of the adsorption column reaches 0.5 ppm or higher, the feed gas supply is stopped. The adsorbent is regenerated using a pressure-reducing desorption method, where the pressure inside the adsorption column is slowly reduced to 0.01 MPa and maintained for 1 hour to desorb the R133a adsorbed on the 13X molecular sieve. The regenerated adsorbent is then used again for adsorption separation experiments. Experimental results show that Ag + The exchange-modified 13X molecular sieve adsorbent can effectively reduce the R133a content in hexafluoropropane to below 0.5 ppm. After 8 adsorption-regeneration cycles, the adsorbent's adsorption capacity for R133a can still be maintained at about 85% of the initial adsorption capacity. Example 3 This embodiment provides a method for removing R133a adsorbent from hexafluoropropane by loading MnO2 onto the surface of SBA-15 using an impregnation method. Adsorbent screening: Activated carbon, activated alumina, and a novel mesoporous silica material, SBA-15, were selected for static adsorption experiments. The experimental conditions were the same as in Example 1, and the results are shown in Table 3. SBA-15 showed a certain adsorption capacity (35 mg / g) and adsorption selectivity (selectivity coefficient of 2.5) for R133a, and was therefore selected for modification.

[0031] Table 3 Types of adsorbents Activated carbon Activated alumina SBA-15 Adsorption capacity 50mg / g 38mg / g 35mg / g Selectivity coefficient 1.5 2 2.5 The content of R133a in the hexafluoropropane mixture before adsorption 0.8% 0.8% 0.8% The content of R133a in the hexafluoropropane mixture after adsorption 5×10-6 3×10-6 0.5×10-6 Adsorbent modification: MnO2 was loaded onto the surface of SBA-15 using an impregnation method. SBA-15 was impregnated in a 50% manganese nitrate solution, ultrasonically dispersed for 30 minutes, dried at 90°C, and then calcined in a muffle furnace at 450°C for 4 hours to obtain the MnO2-loaded SBA-15 adsorbent with a MnO2 loading of 8% (mass fraction).

[0032] Adsorption separation: SBA-15 adsorbent loaded with MnO2 was packed into a quartz adsorption column with an inner diameter of 15 mm and a length of 600 mm. Hexafluoropropane feed gas containing R133a impurity (content 0.8%) was introduced from the bottom of the adsorption column at a flow rate of 30 mL / min for adsorption separation. The adsorption pressure was 0.4 MPa, and the adsorption temperature was 20 °C. The R133a content was analyzed by gas chromatography using periodic samples of the gas effluent from the top of the adsorption column. Adsorbent regeneration: When the R133a content in the gas effluent from the top of the adsorption column reaches 1 ppm or higher, the feed gas supply is stopped. The adsorbent is regenerated by inert gas purging and desorption, using high-purity nitrogen gas and purging at 150°C for 5 hours. After cooling, the regenerated adsorbent is used for the next round of adsorption experiments. Experimental results show that the SBA-15 adsorbent loaded with MnO2 can reduce the R133a content in hexafluoropropane to below 0.5 ppm. After 10 adsorption-regeneration cycles, the adsorbent performance remains stable, and the adsorption selectivity and adsorption capacity for R133a do not decrease significantly. The above description is merely a preferred embodiment of this application and is not intended to limit the application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit the application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for removing R133a from hexafluoropropane, characterized in that, Includes the following steps: Hexafluoropropane feedstock containing R133a impurity is passed into an adsorption column packed with modified adsorbent, and high-purity hexafluoropropane is obtained through adsorption. The modified adsorbent is selected from any one of the following: (a) Zeolite molecular sieve modified with metal cation exchange; (b) Metal-organic framework materials with a fluoropolymer coating on their surface; (c) Mesoporous silica loaded with active components.

2. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The zeolite molecular sieve modified by metal cation exchange is a modified 13X molecular sieve. The modification method involves placing the 13X molecular sieve in a solution containing metal cations Ag at a concentration of 0.05~0.5 mol / L. + Cu 2+ Zn 2+ The solution is stirred in a salt solution at 40-80°C for 12-36 hours, and then filtered, washed and dried.

3. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The metal-organic framework material with a fluoropolymer coating on its surface is a modified MIL-101, which is modified by in-situ polymerization of fluorinated monomer vapor on the surface of the MIL-101 material using chemical vapor deposition.

4. The method for removing R133a from hexafluoropropane according to claim 3, characterized in that, The fluorinated monomer vapor is tetrafluoroethylene, and the chemical vapor deposition method is carried out at a temperature of 150~250℃ and a pressure of 0.05~0.2 MPa for 2~6 hours, with a fluorinated polymer coating thickness of 0.1~5μm.

5. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The mesoporous silica loaded with active components is modified SBA-15.

6. The method for removing R133a from hexafluoropropane according to claim 5, characterized in that, The active component is MnO2, and the loading of the active component is 5~20%; the modification method is to impregnate SBA-15 in a 50% manganese nitrate solution, dry it at 80~120℃, and then calcine it at 400℃ to 500℃ for 2~6h.

7. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The volume fraction of R133a in the hexafluoropropane feedstock is 0.5%~1%, and the feed rate of the hexafluoropropane feedstock gas is 30~80L / min.

8. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The adsorption pressure is 0.1~0.4MPa and the temperature is 20~60℃.

9. The method for removing R133a from hexafluoropropane according to claim 1, characterized in that, The R133a content in the high-purity hexafluoropropane is less than 0.5 ppm.

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