Plasma catalysts suitable for degradation of sulfur hexafluoride and preparation and use thereof
By combining a γ-Al2O3-supported cerium zirconium sulfate solid solution catalyst with low-temperature plasma, the problem of efficient SF6 degradation at low temperatures was solved, achieving efficient SF6 degradation and SOx selectivity, and the catalyst exhibited good long-range stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIAXING UNIV
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-03
AI Technical Summary
Existing technologies are difficult to efficiently degrade sulfur hexafluoride (SF6) under low-temperature conditions, and traditional methods suffer from problems such as high energy consumption, low mineralization degree, and complex by-products. Research on the application of cerium-zirconium solid superacid catalysts in plasma synergistic systems is insufficient.
A cerium zirconium sulfate solid solution catalyst (CZ-S/γ-Al2O3) supported on γ-Al2O3 was used to catalytically degrade SF6 in a dielectric barrier discharge plasma reactor under low-temperature plasma discharge conditions. The high-efficiency degradation of SF6 and SOx selectivity were achieved by utilizing the strong acidic sites of CZ-S and the high-energy electron excitation of γ-Al2O3.
The catalyst achieves an SF6 degradation rate of over 95% and SOx selectivity of over 94% under low-temperature plasma discharge, and maintains a degradation rate of over 91% and selectivity of over 85% after 12 hours, demonstrating excellent long-range stability.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of fluorine-containing greenhouse gas control and catalytic materials technology, specifically to a cerium-zirconium solid superacid catalyst suitable for the degradation of sulfur hexafluoride, its preparation method, and its application. Background Technology
[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
[0003] Sulfur hexafluoride (SF6) is a typical strong greenhouse gas with a global warming potential (GWP) approximately 23,500 times that of CO2 and an atmospheric lifetime exceeding 3,200 years. Due to its excellent insulating properties and chemical stability, SF6 is widely used in power equipment, electrical switches, semiconductor manufacturing, and fluorochemical production processes.
[0004] However, leaks of SF6 are inevitable during production, use, and maintenance, which have a serious impact on global climate change.
[0005] Because of the high bond energy of the SF bond in the SF6 molecule (approximately 327 kJ / mol) and its extremely strong chemical stability, traditional techniques such as pyrolysis, photolysis, and thermocatalytic decomposition are difficult to achieve effective degradation at low temperatures.
[0006] In recent years, plasma decomposition has been considered an important potential technology for treating SF6 because it can generate high-energy electrons, active free radicals and ionic species, which can destroy stable molecular structures under mild conditions.
[0007] At present, plasma technology alone has problems such as high energy consumption, low mineralization degree and complex by-products.
[0008] Studies have shown that combining plasma technology with catalysts to form a plasma-assisted catalytic system can significantly improve reaction efficiency and reduce energy consumption. The acidic sites of the catalyst play a crucial role in the adsorption and activation of SF6 molecules.
[0009] Cerium-zirconium solid solution materials have the following advantages: excellent oxygen storage / release capacity; abundant oxygen vacancy structure; and good thermal stability. Furthermore, when sulfate ions are introduced onto their surface to form cerium-zirconium sulfate solid superacid, a large number of acidic sites can be generated, significantly enhancing the adsorption and activation capacity for fluorine-containing molecules.
[0010] Currently, there is still a lack of research on plasma-assisted solid superacid catalysts for SF6 degradation, especially on the synergistic mechanism between cerium-zirconium solid superacid systems and plasma.
[0011] Therefore, it is of great significance to develop a high-efficiency and stable cerium-zirconium solid superacid catalyst and construct a plasma synergistic system to achieve efficient degradation of SF6.
[0012] The following existing technologies were found through a search: The patent specification with publication number CN119588411A discloses a sulfur hexafluoride degradation catalyst, its preparation method, and its application in the catalytic degradation of SF6. The catalyst degrades sulfur hexafluoride at a temperature of 500~800℃ and does not involve the combination with plasma technology. Summary of the Invention
[0013] This invention provides a plasma catalyst suitable for the degradation of sulfur hexafluoride (SF6), its preparation method, and its application. The plasma catalyst of this invention is a cerium-zirconium solid superacid catalyst, specifically a γ-Al2O3 supported cerium-zirconium sulfate solid solution catalyst, which exhibits excellent SF6 degradation activity and sulfur oxide (SO4) degradation activity under low-temperature plasma discharge conditions. x Selectivity allows for SF6 degradation rates exceeding 95% and SO2 degradation rates exceeding 94% at an input power of 60 W. x It exhibits selectivity and excellent long-range stability, maintaining an SF6 degradation rate of over 91% and an SO2 degradation rate of over 85% even after 12 hours of continuous use. x Selectivity.
[0014] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a plasma catalyst (which may be referred to as a CZ-S / γ-Al2O3 catalyst) suitable for the degradation of sulfur hexafluoride, comprising a support and an active component; the support comprises γ-Al2O3; and the active component comprises a cerium zirconium sulfate solid solution (CZ-S). The mass ratio of cerium zirconium sulfate solid solution to γ-Al₂O₃ is (1~55):100, for example 1.5:100, 1.92:100, 1.93:100, 1.95:100, 2:100, 5:100, 10:100, 15:100, 19:100, 19.2:100, 19.3:100, 19.5:100, 20:100, 25:100, 30:100, 35:100, 38:100, 38.5:100, 38.6:100, 39:100, 40:100, 42:100, 45:100, 49:100, 50:100, etc.
[0015] In some preferred embodiments, the molar ratio of cerium to zirconium in the cerium sulfate zirconium solid solution is (0.5~2):1, for example 1:1.
[0016] In some preferred embodiments, the cerium-zirconium sulfate solid solution is obtained by sulfation of a cerium-zirconium solid solution prepared by the citric acid method through gas-phase SO2 heat treatment.
[0017] Furthermore, the citric acid method preferably includes first mixing cerium source, zirconium source and citric acid in a solvent to obtain a sol-gel mixture, then adding a carrier and mixing to obtain a mixture, and calcining the obtained mixture to obtain a cerium-zirconium solid solution.
[0018] In some preferred embodiments, the molar ratio of cerium source to support is (1~20):150, for example, 10:150.
[0019] In some preferred embodiments, the molar ratio of cerium source to zirconium source is (0.5~2):1, for example 1:1.
[0020] In some preferred embodiments, the ratio of the total moles of cerium source and zirconium source to the moles of citric acid is 1:1.
[0021] In some preferred embodiments, the cerium source includes cerium nitrate.
[0022] In some preferred embodiments, the zirconium source includes zirconium oxynitrate.
[0023] In some preferred embodiments, the solvent includes ethanol.
[0024] In some preferred embodiments, the calcination temperature is 300~400℃.
[0025] In some preferred embodiments, the calcination time is 2 to 5 hours, such as 3 hours.
[0026] Furthermore, the preferred temperature for gas-phase SO2 heat treatment sulfation is 300~400℃, and the preferred time is 2~5 h.
[0027] In some preferred embodiments, the γ-Al₂O₃ has a particle size of 10–20 μm and a specific surface area ≥200 m². 2 / g, pore volume ≥0.40 cm³ 3 / g.
[0028] In a second aspect, the present invention provides a method for preparing the plasma catalyst described in the first aspect, comprising: mixing raw materials in a solvent to obtain a mixture, wherein the raw materials include a support, citric acid, a cerium source and a zirconium source; and subjecting the obtained mixture to calcination and gas-phase SO2 sulfation treatment in sequence to obtain the plasma catalyst.
[0029] In some preferred embodiments, the molar ratio of cerium source to support is (1~20):150, for example, 10:150.
[0030] In some preferred embodiments, the molar ratio of cerium source to zirconium source is (0.5~2):1, for example 1:1.
[0031] In some preferred embodiments, the ratio of the total moles of cerium source and zirconium source to the moles of citric acid is 1:1.
[0032] In some preferred embodiments, the cerium source includes cerium nitrate.
[0033] In some preferred embodiments, the zirconium source includes zirconium oxynitrate.
[0034] In some preferred embodiments, the solvent includes ethanol.
[0035] This invention uses cerium nitrate, zirconium oxynitrate, citric acid, and γ-Al2O3 as raw materials to prepare a γ-Al2O3-supported cerium zirconium sulfate solid solution catalyst via citric acid method and gas-phase SO2 sulfation treatment.
[0036] In some preferred embodiments, the preparation method involves first mixing a cerium source, a zirconium source, and citric acid in a solvent to obtain a sol-gel mixture, and then adding a carrier and mixing to obtain a final mixture.
[0037] In some preferred embodiments, the calcination temperature in the preparation method is 300~400℃.
[0038] In some preferred embodiments, the preparation method involves calcination for 2 to 5 hours, such as 3 hours.
[0039] In some preferred embodiments, the preparation method involves a gas-phase SO2 sulfation treatment at a temperature of 300-400°C.
[0040] In some preferred embodiments, the preparation method involves a gas-phase SO2 sulfation treatment time of 2-5 h.
[0041] Thirdly, the present invention provides the application of the plasma catalyst described in the first aspect for the low-temperature plasma catalytic degradation of SF6.
[0042] In some preferred embodiments, the cryogenic plasma includes dielectric barrier discharge plasma. The cryogenic plasma can be generated by a dielectric barrier cryogenic plasma reactor. Further, the dielectric barrier cryogenic plasma reactor can employ a coaxial volumetric dielectric barrier cryogenic discharge, and its high-voltage electrode can include one or more combinations of metal plates, metal needles, star-shaped wires, serrated wires, and barbed wires, while the low-voltage electrode can include metal plates and / or metal mesh. Even further, the dielectric barrier cryogenic plasma reactor can use a CTP-2000K as its high-voltage power supply, and the discharge gap can be 1~20 mm.
[0043] Fourthly, the present invention provides a method for low-temperature plasma catalytic degradation of SF6, comprising: catalytically degrading SF6 using the plasma catalyst described in the first aspect under low-temperature plasma discharge conditions.
[0044] In some preferred embodiments, the cryogenic plasma includes dielectric barrier discharge plasma. The cryogenic plasma can be generated by a dielectric barrier cryogenic plasma reactor. Further, the dielectric barrier cryogenic plasma reactor can employ a coaxial volumetric dielectric barrier cryogenic discharge, and its high-voltage electrode can include one or more combinations of metal plates, metal needles, star-shaped wires, serrated wires, and barbed wires, while the low-voltage electrode can include metal plates and / or metal mesh. Even further, the dielectric barrier cryogenic plasma reactor can use a CTP-2000K as its high-voltage power supply, and the discharge gap can be 1~20 mm.
[0045] In some preferred embodiments, the input power of the cryogenic plasma discharge is 40~80 W, such as 50 W, 60 W, 70 W, etc.
[0046] In some preferred embodiments, plasma catalysts catalytically degrade SF6-containing waste gas. Further, the volume percentage of SF6 in the waste gas is preferably 1% to 10%.
[0047] In some preferred embodiments, the volume hourly space velocity (VHSV) of the plasma catalyst for catalytic degradation of SF6-containing waste gas is 1000~10000 mL / (mg·h).
[0048] This invention uses γ-Al₂O₃ as a support and loads cerium zirconium sulfate solid solution (CZ-S) onto the support as the active material. The resulting catalyst combines the advantages of both, thus exhibiting excellent low-temperature catalytic activity and SO₂. x The catalyst exhibits excellent long-range stability due to its selectivity and the fact that the strong proton donor sulfuric acid sites on CZ-S are not prone to fluoride poisoning.
[0049] In this invention, γ-Al₂O₃ serves as the support, a widely used technique in plasma catalysis that effectively excites high-energy electrons and improves energy utilization efficiency. Furthermore, the surface of γ-Al₂O₃ is rich in hydroxyl groups, enabling effective adsorption of SF₆. However, γ-Al₂O₃ alone exhibits poor activity at medium and low temperatures, high byproduct levels, and poor reaction stability in plasma catalytic degradation of SF₆. Through extensive experimental research, the inventors discovered that introducing CZ-S as an active material into the γ-Al₂O₃ support enriches the catalyst surface with strong proton-donating groups, thereby enhancing the activation of SF₆ and the production of intermediate products (such as SOF₂). x The oxidation of SO₂ (etc.) can not only improve the decomposition efficiency of SF₆ at low temperatures, but also reduce the SO₂ content in the products. xThe selectivity is also improved. At the same time, CZ-S is loaded onto the surface of the γ-Al2O3 support as an active material, which can enhance the defluorination process on γ-Al2O3 by utilizing the strong proton donor sulfuric acid sites on CZ-S, thus avoiding fluoride poisoning of the catalyst during the reaction. Therefore, the catalyst of this invention also has excellent long-range stability and can maintain excellent catalytic degradation rate and target product selectivity after long-term use.
[0050] In the low-temperature plasma catalytic degradation of SF6 provided by this invention, low-temperature plasma can promote SF6 activation, further enhancing the catalytic performance of the catalyst. Specifically, the low-temperature plasma discharge process can activate SF6 on the surface of the catalyst, including the γ-Al2O3 support and CZ-S, reducing the activation energy required for SF6 degradation, while simultaneously enhancing water molecule activation to continuously supply protons, thereby promoting the low-temperature stable degradation of SF6. At the same time, the catalyst of this invention also exhibits good energy utilization capability for the low-temperature plasma discharge process, promoting the formation of surface oxygen vacancies through the plasma discharge process, thereby significantly increasing the SO2 content in the degradation products. x The selectivity is high. Therefore, there is a synergistic effect between plasma and CZ-S / γ-Al2O3 catalyst. Under low-temperature plasma discharge conditions, the catalyst used for SF6 degradation can further improve the catalytic degradation effect of SF6-containing waste gas.
[0051] Compared with the prior art, the beneficial effects of this invention are as follows: The plasma catalyst of this invention, under low-temperature plasma discharge conditions, can achieve an SF6 degradation rate of over 95% and an SO2 degradation rate of over 94% at an input power of 60 W. x It exhibits selectivity and excellent long-term stability, maintaining an SF6 degradation rate of over 91% and an SO2 degradation rate of over 85% even after 12 hours of continuous use. x Selectivity. Attached Figure Description
[0052] Figure 1 The graph shows the SF6 conversion results of the catalysts in the various embodiments and comparative examples under different input power for 5 min of low-temperature plasma catalytic degradation of SF6.
[0053] Figure 2 The specific embodiments and comparative examples use catalysts for the low-temperature plasma catalytic degradation of SF6 for 5 min under different input power conditions. x Selective results chart. Detailed Implementation
[0054] The present invention will be further illustrated below with reference to 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. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.
[0055] In the following examples, the particle size of γ-Al₂O₃ is 10–20 μm, and the specific surface area is ≥200 m². 2 / g, pore volume ≥0.40cm 3 / g.
[0056] Example 1: 1. Catalyst preparation: A plasma catalyst suitable for the degradation of sulfur hexafluoride comprises a support γ-Al2O3 and an active component CZ-S, wherein the content of CZ-S is 19.3 wt% (based on the mass of the support γ-Al2O3).
[0057] The method for preparing the plasma catalyst in this embodiment includes: 4.34 g (0.01 mol) cerium nitrate Ce(NO3)3·6H2O, 2.31 g (0.01 mol) zirconium oxynitrate ZrO(NO3)2, and 3.84 g (0.02 mol) citric acid C6H8O7 were added to 100 mL of ethanol. After stirring continuously at room temperature for 3 hours, a sol-gel mixture was obtained. Then, 15.30 g (0.15 mol) γ-Al2O3 was added and stirred continuously for 2 hours to obtain a final mixture. The resulting mixture was calcined at 400 °C for 3 h and then sulfatated with gas-phase SO2 at 400 °C for 2 h to obtain a plasma catalyst suitable for the degradation of sulfur hexafluoride.
[0058] 2. Performance Testing: 2.1 Catalytic activity test: The low-temperature plasma generator was a coaxial volumetric double dielectric barrier discharge system. The plasma power supply was a CTP-2000K with an input power of 40-80 W (specifically 40 W, 50 W, 60 W, 70 W, and 80 W). 3.6 g of the plasma catalyst (40-60 mesh powder) was used to fill the discharge region. SF6-containing waste gas was introduced, with an initial composition of SF6 = 1 vol.%, O2 = 3 vol.%, H2O = 5 vol.%, and the remainder being N2. The flow rate was 300 mL / min, and the volume hourly space velocity (VHSV) of the SF6-containing waste gas was 5000 mL / (g·h). After reacting for 5 min under the specific input power conditions, the SF6 concentration in the reaction tail gas was detected using a GC9790Ⅱ gas chromatograph (Fuli) and the SF6 degradation rate was calculated. xThe content and selectivity were determined by DIONEX AQUION ion chromatography (Thermo Fisher Scientific) after absorption with NaOH.
[0059] 2.2, 12-hour long-term stability test: Except for maintaining the input power at 60W, the other experimental conditions were the same as those for the catalyst activity test described above. The reaction time was 3 hours followed by a 1-hour rest period, repeated 4 times. After the catalyst had run for 12 hours, the degradation rate of SF6 and SO2 were tested and calculated using the method described above. x The selectivity.
[0060] Example 2: The only difference from Example 1 is that the amount of cerium nitrate Ce(NO3)3·6H2O added is 0.001 mol, the amount of zirconium oxynitrate ZrO(NO3)2 added is 0.001 mol, and the amount of citric acid C6H8O7 added is 0.002 mol. All other aspects are the same. The content of CZ-S in the obtained plasma catalyst is 1.93 wt% (based on the mass of the support γ-Al2O3).
[0061] Example 3: The only difference from Example 1 is that the amount of cerium nitrate Ce(NO3)3·6H2O added is 0.02 mol, the amount of zirconium oxynitrate ZrO(NO3)2 added is 0.02 mol, and the amount of citric acid C6H8O7 added is 0.04 mol. All other aspects are the same. The content of CZ-S in the obtained plasma catalyst is 38.6 wt% (based on the mass of the support γ-Al2O3).
[0062] Comparative Example 1: Support γ-Al2O3.
[0063] Comparative Example 2: The only difference from Example 1 is that γ-Al2O3 is not added; all other aspects are the same, and the pure active component CZ-S is obtained.
[0064] Comparative Example 3: The only difference from Example 1 is the absence of gaseous SO2 sulfation treatment at 400°C; all other aspects are the same, resulting in a catalyst with no sulfation of the active component, which can be denoted as CZ.
[0065] Comparative Example 4: The only difference from Example 1 is that cerium nitrate Ce(NO3)3·6H2O is not added, and the amount of zirconium oxynitrate ZrO(NO3)2 added is 0.02 mol. All other aspects are the same, resulting in a catalyst with cerium-free active components.
[0066] Comparative Example 5: The only difference from Example 1 is that zirconium oxynitrate ZrO(NO3)2 is not added, and the amount of cerium nitrate Ce(NO3)3·6H2O added is 0.02 mol. All other aspects are the same, resulting in a catalyst with zirconium-free active components.
[0067] Comparative Example 6: Quartz sand.
[0068] The SF6 conversion rates of the catalysts in each embodiment and comparative example for 5 min of low-temperature plasma catalytic degradation of SF6 are as follows: Figure 1 Shown, SO x Selectivity such as Figure 2 As shown. Furthermore, Table 1 presents the conversion rate and SO₂ of each embodiment and comparative catalyst under low-temperature plasma catalytic degradation of SF₆ for 5 min at an input power of 60 W. x Selectivity and reaction performance after 12 hours of reaction. The performance test conditions for all examples and comparative examples are the same, and can be referred to Example 1.
[0069] Table 1 Note: In Table 1, " / " indicates that no test was performed.
[0070] Comparing the data from Example 1 with Comparative Examples 1 and 2, it is evident that γ-Al₂O₃ alone does not exhibit good low-temperature SF₆ degradation performance. This is mainly due to its poor hydroxyl activity, which fails to effectively activate SF₆. While CZ-S alone shows acceptable activity, it does not demonstrate good reaction stability. This is primarily due to its relatively low specific surface area, leading to catalyst blockage and deactivation caused by the deposition of byproducts generated during the reaction. However, the CZ-S / γ-Al₂O₃ catalyst provided by this invention can enhance the SF₆ activation ability of the catalyst through the strong synergistic effect between the two, while simultaneously inhibiting the poisoning effect of degradation byproducts on active sites, ultimately exhibiting excellent low-temperature SF₆ degradation performance and long-term reaction stability.
[0071] According to Comparative Examples 3-5, replacing CZ-S with CZ (Comparative Example 3) leads to poor long-term reaction stability of the catalyst, while replacing CZ-S with a single metal active component without zirconium or cerium (Comparative Examples 4-5) both result in the inability to achieve the excellent SF6 degradation performance of this invention.
[0072] Comparing the data of Example 1 and Comparative Example 6, it can be seen that the SF6 degradation performance of the reaction system is poor when no catalyst is added to the reactor, which confirms that there is a synergistic effect between the catalyst and plasma. The high efficiency of SF6 degradation can be achieved by combining the initial activation of plasma with the deep degradation of the catalyst.
[0073] 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. A plasma catalyst suitable for the degradation of sulfur hexafluoride, characterized in that, It includes a support and an active component; the support includes γ-Al2O3; the active component includes a cerium zirconium sulfate solid solution; The mass ratio of cerium zirconium sulfate solid solution to γ-Al2O3 is (1~55):
100.
2. The plasma catalyst according to claim 1, characterized in that, The molar ratio of cerium to zirconium in the cerium sulfate zirconium solid solution is (0.5~2):
1.
3. The plasma catalyst according to claim 1, characterized in that, The cerium-zirconium sulfate solid solution is obtained by sulfation of cerium-zirconium solid solution prepared by citric acid method through gas phase SO2 heat treatment.
4. The method for preparing the plasma catalyst according to any one of claims 1 to 3, characterized in that, include: The raw materials are mixed in a solvent to obtain a mixture, which includes a support, citric acid, cerium source and zirconium source; the resulting mixture is then subjected to calcination and gas-phase SO2 sulfation treatment to obtain the plasma catalyst.
5. The preparation method according to claim 4, characterized in that, The molar ratio of cerium source to support is (1~20):150; The molar ratio of cerium source to zirconium source is (0.5~2):1; The ratio of the total molar number of cerium source and zirconium source to the molar number of citric acid is 1:1; The cerium source includes cerium nitrate; The zirconium source includes zirconium oxynitrate; The solvent includes ethanol.
6. The preparation method according to claim 4 or 5, characterized in that, First, cerium source, zirconium source and citric acid are mixed in a solvent to obtain a sol-gel mixture, and then a carrier is added and mixed to obtain a final mixture. The calcination temperature is 300~400℃, and the time is 2~5 h; The temperature for gas-phase SO2 sulfation treatment is 300~400℃, and the time is 2~5 h.
7. The application of the plasma catalyst according to any one of claims 1 to 3 for the low-temperature plasma catalytic degradation of SF6.
8. A method for low-temperature plasma catalytic degradation of SF6, characterized in that, include: Under low-temperature plasma discharge conditions, the plasma catalyst according to any one of claims 1 to 3 is used to catalytically degrade SF6.
9. The method for low-temperature plasma catalytic degradation of SF6 according to claim 8, characterized in that, Low-temperature plasmas include dielectric barrier discharge plasmas; The input power of the low-temperature plasma discharge is 40~80 W; Plasma catalyst is used to catalytically degrade SF6-containing waste gas; the volume percentage of SF6 in the waste gas is 1% to 10%. The volume hourly space velocity (VHSV) of plasma catalyst for catalytic degradation of SF6-containing waste gas is 1000~10000 mL / (mg·h).