Preparation method of vanadium-doped titanium dioxide composite material and application thereof

Abstract

The application discloses a preparation method of a vanadium-doped titanium dioxide composite material and application thereof, relates to the technical field of titanium dioxide composite materials, and comprises the following steps: (1) mixing ammonium vanadate and titanium dioxide according to a proportion, controlling the doping amount of vanadium elements to be 0.1 wt%-12.5 wt% according to the total mass of the mixture, and then high-temperature heating to obtain vanadium-doped titanium dioxide powder; (2) mixing the vanadium-doped titanium dioxide powder and a carrier according to a proportion, controlling the content of the vanadium-doped titanium dioxide powder to be 10 wt%-30 wt% according to the total mass of the composite material, and performing physical grinding to obtain the powder-shaped vanadium-doped titanium dioxide composite material. The catalytic material has superior degradation capacity when applied to the degradation of sulfur hexafluoride.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide composite materials technology, specifically to a method for preparing vanadium-doped titanium dioxide composite materials and their applications. Background Technology

[0002] Sulfur hexafluoride (SF6) is a greenhouse gas whose emissions are to be limited under the Kyoto Protocol. Its global warming potential (GWP) is very high, 24,300 times that of carbon dioxide (CO2). SF6 has an insulating strength more than 2.5 times that of air, and its arc-quenching ability is more than 100 times that of air. Due to its superior electrical properties, SF6 has been widely used as a protective gas in ultra-high voltage power transmission and transformation equipment and electrical switches. Currently, the annual emission of SF6 into the atmosphere is equivalent to 125 million tons of CO2. With the development of the power system, SF6 emissions are expected to continue to increase in the future, which will inevitably greatly increase environmental pressure. Therefore, controlling SF6 emissions and finding a method to degrade SF6 are urgent priorities.

[0003] Selective catalytic reduction (SCR) of nitrogen oxides with ammonia is widely used to reduce air pollutant emissions. For many years, the improvement of SCR reactivity has been achieved through structural and electronic effects, namely, altering the redox properties of dopant elements through induction, conjugation, or electronic spin states. Although TiO2 supports show almost no activity for SCR under certain reaction conditions, they are crucial for the activation of surface doped atoms (support effect). Only when vanadium atoms are deposited can doped TiO2 catalysts exhibit catalytic function in reducing air pollutants through the SCR reaction with ammonia.

[0004] Currently, there are various methods for degrading sulfur hexafluoride (SF6), including adsorption, traditional industrial thermal decomposition, photodegradation, plasma methods, and catalytic degradation. Among these, catalytic degradation has attracted particular attention. There are three main types of catalysts used in the catalytic degradation of SF6: metal oxides, metal phosphates, and supported metal catalysts. These catalysts are all used in argon or nitrogen atmospheres above 600°C. Currently, research on the degradation mechanism and technology under lower temperature atmospheric conditions is lacking.

[0005] For example, CN103007736A proposed by Zhang Jia et al. discloses a relatively effective method for degrading sulfur hexafluoride (SF6) using electroplating sludge, but the degradation process requires a nitrogen protective atmosphere. However, in reality, SF6 is present in the atmosphere, and the nitrogen protective atmosphere significantly hinders the practical application of SF6 degradation catalysts. Therefore, it is necessary to develop a simple, environmentally friendly catalytic material that can degrade SF6 in normal air. Summary of the Invention

[0006] The first objective of this invention is to overcome the above-mentioned defects and provide a method for preparing vanadium-doped titanium dioxide composite material, wherein the prepared composite material can achieve efficient degradation of SF6 in an air atmosphere.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a vanadium-doped titanium dioxide composite material, characterized by comprising the following steps:

[0009] (1) Mix ammonium vanadate and titanium dioxide in a certain proportion, and control the doping amount of vanadium element to be 0.1wt% to 12.5wt% based on the total mass of the mixture. Then heat at high temperature to obtain vanadium-doped titanium dioxide powder.

[0010] (2) Mix vanadium-doped titanium dioxide powder with the carrier in a certain proportion. Based on the total mass of the composite material, control the content of vanadium-doped titanium dioxide powder to be 10 wt% to 30 wt%. Perform physical grinding to obtain vanadium-doped titanium dioxide composite material.

[0011] Furthermore:

[0012] In step (1):

[0013] The vanadium doping amount is controlled to be 0.5 wt% based on the total mass of the mixture.

[0014] The high-temperature heating is performed at 400-600°C for 3-6 hours, preferably at 500°C for 4 hours, to obtain vanadium-doped titanium dioxide powder.

[0015] In step (2):

[0016] The content of vanadium-doped titanium dioxide powder was controlled at 20 wt% based on the total mass of the composite material.

[0017] The carrier is selected from any one or more materials such as silicon carbide, silicon dioxide, and cerium dioxide, with silicon carbide being preferred.

[0018] The physical grinding refers to grinding with a ball mill at 200 rpm for 3 minutes to obtain a powdered vanadium-doped titanium dioxide composite material.

[0019] The second aspect of this invention is to provide an application of vanadium-doped titanium dioxide composite material in the catalytic degradation of sulfur hexafluoride, characterized in that: vanadium-doped titanium dioxide composite material is used as a catalyst, and ammonia is used as a sacrificial agent in the catalytic degradation, and sulfur hexafluoride is catalytically degraded in an air atmosphere.

[0020] Furthermore:

[0021] The application of a vanadium-doped titanium dioxide composite material in the catalytic degradation of sulfur hexafluoride is characterized by comprising the following steps:

[0022] (1) A mixture of sulfur hexafluoride gas coupled with ammonia gas is introduced into the vanadium-doped titanium dioxide composite material. The mixture includes ammonia gas, sulfur hexafluoride gas and air, wherein the volume concentration of ammonia gas is not greater than 5 vol.% and the volume concentration of sulfur hexafluoride gas is not greater than 60 vol.%.

[0023] (2) The vanadium-doped titanium dioxide composite material was subjected to high-temperature treatment at 300-700°C in the above-mentioned sulfur hexafluoride mixed gas atmosphere coupled with ammonia.

[0024] (3) The exhaust gas after step (2) is treated with an alkaline solution and collected.

[0025] Furthermore:

[0026] In step (1): the volume concentration of sulfur hexafluoride in the mixed gas is 2% to 60 vol.%. The volume concentration of ammonia is 0.1 vol.% to 2.0 vol.%, preferably 0.27 vol.% to 1.35 vol.%, and particularly preferably 1.08 vol.%.

[0027] The high-temperature treatment in step (2) is preferably at a temperature of 400-600℃, and more preferably at 500-600℃.

[0028] The alkaline solution in step (3) is a 5 mol / L sodium hydroxide solution.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The vanadium-doped titanium dioxide composite material prepared by the present invention uses vanadium atoms doped in titanium dioxide as active site centers and one or more of silicon carbide, silicon dioxide, and cerium dioxide as carriers. It can be prepared by simple high-temperature heating and physical grinding methods. The process is simple, the processing cost is low, and it is suitable for large-scale production.

[0031] (2) Experiments have shown that the catalytic material of the present invention has a superior ability to degrade sulfur hexafluoride and basically does not produce toxic gases, which is in line with the concept of environmental protection.

[0032] (3) The catalytic material of the present invention can degrade sulfur hexafluoride by coupling low concentration ammonia in an air atmosphere, which is different from the previous technology that requires a protective atmosphere of nitrogen or argon. It is very much in line with the actual situation and has great practical potential.

[0033] (4) The catalytic material of the present invention has a very rapid response to the degradation of sulfur hexafluoride and a long service life.

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented under the premise of the present invention and provide detailed implementation methods and specific operation procedures. However, the protection scope of the present invention is not limited to the above embodiments. Attached Figure Description

[0035] Figure 1 This is a high-resolution transmission electron microscope image of the vanadium-doped titanium dioxide powder prepared in Example 1.

[0036] Figure 2 The image shows the energy-dispersive X-ray spectroscopy (EDX) image of the vanadium-doped titanium dioxide powder prepared in Example 1.

[0037] Figure 2 In the middle: high-angle annular dark field image of vanadium-doped titanium dioxide powder, oxygen element image, titanium element image, and vanadium element image, in sequence.

[0038] Figure 3 This is a high-resolution transmission electron microscope image of the vanadium-doped titanium dioxide composite material (after composite silicon carbide carrier) prepared in Example 1.

[0039] Figure 4 The image shows the energy-dispersive X-ray spectroscopy (EDS) image of the vanadium-doped titanium dioxide composite material (after composite silicon carbide carrier) prepared in Example 1.

[0040] Figure 4 In the middle: high-angle annular dark field image, silicon element image, carbon element image, oxygen element image, titanium element image and vanadium element image of vanadium-doped titanium dioxide composite material (after composite silicon carbide carrier).

[0041] Figure 5 This is a schematic diagram of the apparatus for the catalytic degradation of sulfur hexafluoride according to the present invention.

[0042] Figure 5 In the diagram: 1 is a mixed gas storage device; 2 is a gas flow meter; 3 is a gas mixer; 4 is a quartz reaction tube; 5 is a tube furnace; 6 is an alkali recovery device; 7 is a gas chromatograph; A is an air inlet; B is a gas outlet after the reaction.

[0043] Figure 6 The image shows the infrared spectrum of the gaseous products of the catalytic degradation of sulfur hexafluoride according to the present invention.

[0044] Figure 7 This study compares the effect of vanadium doping amount on the degradation efficiency of sulfur hexafluoride in vanadium-doped titanium dioxide composite materials.

[0045] Figure 8 This study compares the degradation efficiency of sulfur hexafluoride by different carriers in vanadium-doped titanium dioxide composite materials.

[0046] Figure 9 This study compares the degradation efficiency of sulfur hexafluoride by the proportion of catalytically active components in vanadium-doped titanium dioxide composite materials.

[0047] Figure 10 This study compares the degradation efficiency of sulfur hexafluoride at different treatment temperatures.

[0048] Figure 11 To compare the degradation efficiency of sulfur hexafluoride by different concentrations of coupled ammonia. Detailed Implementation

[0049] Unless otherwise specified, the experimental materials and equipment used in the following examples are commercially available.

[0050] Regarding degradation temperature and degradation rate:

[0051] In the field of environmental catalysis, T 50 It is an important evaluation indicator, typically referring to the temperature required for a catalyst to achieve 50% conversion of the target pollutant in a specific reaction. During the research and development process, T... 50 It is a rapid and convenient indicator used to initially screen highly active materials from a large number of candidate catalysts, thereby improving research and development efficiency. According to an embodiment of the present invention, when using a vanadium-doped titanium dioxide catalyst for the ammonia-coupled degradation of sulfur hexafluoride, T... 50 =500℃. Therefore, all comparative experiments were conducted at 500℃ in order to select the optimal parameters from a large number of experimental schemes.

[0052] Example 1

[0053] A method for preparing a vanadium-doped titanium dioxide composite material includes the following steps:

[0054] (1) Mix ammonium vanadate and titanium dioxide in a certain proportion, and control the doping amount of vanadium to be 0.5wt% based on the total mass of the mixture. Then heat at 500℃ for 4 h to obtain vanadium-doped titanium dioxide powder.

[0055] (2) The obtained vanadium-doped titanium dioxide powder was mixed with the carrier silicon carbide in proportion. The content of vanadium-doped titanium dioxide powder in the composite material was controlled to be 20 wt% based on the total mass of the composite material. The powder was ground for 3 min at 200 rpm using a ball mill to obtain powdered vanadium-doped titanium dioxide composite material.

[0056] Product confirmation:

[0057] Figures 1-2 High-resolution transmission electron microscopy (TEM) images and energy-dispersive X-ray spectroscopy (EDS) images of the vanadium-doped titanium dioxide prepared in step (1) are shown below. Figure 1 As shown, the doped nanomaterials are 10-20 nm nanoparticles. The vanadium-doped titanium dioxide was then characterized using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Figure 2 As shown: High-angle annular dark-field image (HADDF) clearly shows that the doped titanium dioxide powder consists of 10-20 nm nanoparticles with clear boundaries and no cross-linking. The elemental images of oxygen, titanium, and vanadium show that the three elements are uniformly distributed in the powder, indicating that vanadium is uniformly doped into the titanium dioxide powder.

[0058] Figures 3-4 The vanadium-doped titanium dioxide composite material prepared in step (2) and the silicon carbide support were characterized by high-resolution transmission electron microscopy and transmission electron microscopy energy-dispersive X-ray spectroscopy, as follows: Figures 3-4 As shown: Vanadium-doped titanium dioxide is dispersed in a silicon carbide support, and the two components recombine at the interface.

[0059] Application Example 1

[0060] The vanadium-doped titanium dioxide composite material prepared in Example 1 was applied to the degradation process of sulfur hexafluoride. The equipment used in the degradation process was as follows: Figure 5 As shown: The mixed gas storage device 1 is used to store sulfur hexafluoride gas containing ammonia. Air and sulfur hexafluoride gas containing ammonia enter the gas mixer 3 through the gas flow meter 2 and are mixed. The mixed gas is sent into the quartz reaction tube 4, which is set in the tube furnace 5. Vanadium-doped titanium dioxide composite material is placed inside the quartz reaction tube 4. The gas is heated to the processing temperature by the tube furnace 5. The gas processed from the quartz reaction tube 4 is sent into the alkali recovery device 6.

[0061] A vanadium-doped titanium dioxide composite material is applied to the degradation process of sulfur hexafluoride, comprising the following steps:

[0062] (1) Prepare sulfur hexafluoride waste gas:

[0063] The sulfur hexafluoride waste gas used in the experiment was a simulated mixture of sulfur hexafluoride and air. In this embodiment, the concentration of sulfur hexafluoride was controlled at 5 vol.% by gas flow meter 2 and gas mixer 3. Ammonia was added to the sulfur hexafluoride waste gas at a concentration of 1.08 vol.%.

[0064] (2) The vanadium-doped titanium dioxide composite material prepared in Example 1 was filled into the quartz reaction tube 4. Sulfur hexafluoride, air and ammonia were mixed by the gas mixer 3 and then continuously fed into the quartz reaction tube.

[0065] (3) The quartz reaction tube 4 is heated by the tube furnace 5, the temperature is controlled at 500℃ and the flow rate is 10ml / min. The tail gas coming out of the quartz reaction tube 4 is passed into the alkali recovery device 6. After the tail gas is absorbed by the 5 mol / L sodium hydroxide solution, the gas can be directly discharged into the atmosphere.

[0066] Combination Figure 6 As shown, after using vanadium-doped titanium dioxide composite material to couple the degradation of sulfur hexafluoride with ammonia, the main gaseous products obtained are SO2, H2S, and HF. The presence of three gaseous products of sulfur is due to two reaction pathways during the ammonia-coupled degradation process: partial reduction and complete reduction. The reaction equation for partial reduction is: 3NH3 + SF6 + 2O2 → NH2OH + SO2 + 6HF + N2O. Both NH2OH and N2O produced are shown in the infrared spectrum (…). Figure 6 The complete reduction reaction equation is: 4NH3 + SF6 + O2 → 2N2 + 6HF + H2S + 2H2O. The sulfur product after complete reduction is H2S, which shows a clear signal in the infrared spectrum. The generated N2 and H2O, due to their lack of infrared activity and background subtraction, show no obvious signals in the spectrum. The SO2, H2S, and HF in the products, after treatment with sodium hydroxide solution, meet environmental protection requirements.

[0067] Example 2

[0068] The preparation method is the same as in Example 1, except that the doping ratio of vanadium in the vanadium-doped titanium dioxide in step (1) is adjusted as shown in Table 1, and the effect of application Example 1 on the degradation efficiency of sulfur hexafluoride is tested.

[0069] Table 1

[0070] Serial Number Vanadium doping Maximum degradation efficiency <![CDATA[SF6 degradation amount per unit mass of composite material]]> Example 1 0.5wt% 50.9% <![CDATA[254.3 mL g -1 ]]> Example 2-1 0.1wt% 3.5% <![CDATA[1.7 mL g -1 ]]> Example 2-2 2.5wt% 41.7% <![CDATA[114.9 mL g -1 ]]> Example 2-3 12.5wt% 2.3% <![CDATA[2.4 mL g -1 ]]>

[0071] analyze:

[0072] As shown in Table 1, the vanadium doping concentration has a significant impact on the SF6 degradation effect. When the vanadium doping concentration is 0.1 wt%, the highest degradation rate of the material is 3.5%, and the SF6 degradation amount per unit mass of composite material reaches 1.7 mL g. -1 When the vanadium doping ratio increased to 0.5 wt%, the highest degradation rate increased to 50.9%, and the SF6 degradation amount per unit mass of composite material was 254.3 mL g. -1 However, as the vanadium doping concentration increased further, the degradation effect of SF6 began to decline. When the vanadium doping concentration reached 2.5 wt%, the SF6 degradation amount per unit mass of composite material decreased to 114.9 mL g. -1When the doping ratio was further increased to 12.5 wt%, the SF6 degradation amount per unit mass of composite material decreased to 2.4 mL g. -1 This is because vanadium atoms in the composite material act as electron donors and adsorption centers. On the one hand, reducing the vanadium doping ratio limits electron diffusion efficiency, significantly weakening the V-SF6 adsorption site; on the other hand, increasing the vanadium doping content in titanium dioxide also leads to the re-sintering of vanadium oxide at high temperatures, generating the V2O5 phase, which blocks gas flow, reduces adsorption sites, and lowers the reaction rate. Therefore, the preferred vanadium doping mass ratio in titanium dioxide is 0.5 wt%.

[0073] Example 3

[0074] The preparation method is the same as in Example 1, except that the carrier selection in the vanadium-doped titanium dioxide composite material in step (2) is adjusted as shown in Table 2, and the effect on the degradation efficiency of sulfur hexafluoride is tested using Application Example 1.

[0075] Table 2

[0076] Serial Number Carrier selection Maximum degradation efficiency <![CDATA[SF6 degradation amount of composite material per unit mass]]> Example 1 silicon carbide 50.9% <![CDATA[254.3 mL g -1 ]]> Example 3-1 silicon dioxide 15.2% <![CDATA[12.0 mL g -1 ]]> Example 3-2 Cerium dioxide 10.8% <![CDATA[6.4 mL g -1 ]]>

[0077] analyze:

[0078] As shown in Table 2, the choice of different supports significantly impacts the performance of vanadium-doped titanium dioxide. When SiO2 is used as the support, the degradation of SF6 at 500℃ is poor. This is because SiO2 has a large crystal size and a small specific surface area, which is unfavorable for SF6 adsorption. Even when CeO2 powder is used as the support, the degradation effect on SF6 remains poor. Only when SiC is used as the support can the degradation of SF6 be achieved. SiC has high hardness, and when mixed with vanadium-doped titanium dioxide, the material becomes more uniform in size, which is beneficial for adsorption and reaction. Furthermore, SiC possesses semiconductor properties, enabling the redistribution of electrons between vanadium-doped titanium dioxide and SiC, which can accelerate the activation and degradation of SF6 through electronic effects. Therefore, silicon carbide is the optimal support for vanadium-doped titanium dioxide composite materials.

[0079] Example 4

[0080] The preparation method is the same as in Example 1, except that the mass ratio of the catalytic active component, i.e., vanadium-doped titanium dioxide powder, in step (2) is adjusted as shown in Table 3, and its effect on the degradation efficiency of sulfur hexafluoride is tested using Application Example 1.

[0081] Table 3

[0082] Serial Number Vanadium-doped titanium dioxide mass percentage Maximum degradation efficiency <![CDATA[SF6 degradation amount of composite material per unit mass <!-- 5 -->]]> Example 1 20 wt% 50.9% <![CDATA[254.3 mL g -1 ]]> Example 4-1 10 wt% 3.3% <![CDATA[6.0 mL g -1 ]]> Example 4-2 30 wt% 23.7% <![CDATA[27.6 mL g -1 ]]>

[0083] analyze:

[0084] As shown in Table 3, the mass ratio of vanadium-doped titanium dioxide in the composite material has a significant impact on the SF6 degradation effect. The highest degradation rate of the composite material with a 10 wt% mass ratio is 3.3%, and the amount of SF6 degraded per unit mass of composite material reaches 6.0 mL g. -1 When the proportion of vanadium-doped titanium dioxide increased to 20 wt%, the highest degradation rate increased to 50.9%, and the amount of SF6 degraded per unit mass of composite material was 254.3 mL g. -1 However, as the content of vanadium-doped titanium dioxide increased further, the degradation effect of SF6 began to decline. When the mass percentage of vanadium-doped titanium dioxide reached 30 wt%, the SF6 degradation amount per unit mass of composite material decreased from 254.3 mL g. -1 Decreased to 27.6 mL g -1 This is because SiC acts as both an electron donor and a dispersant in the composite material. On the one hand, the reduction of SiC limits the electron diffusion efficiency, significantly weakening the vanadium atom as a degradation site; on the other hand, metal oxides and metal fluorides will re-sinter at high temperatures, potentially reducing the contact area, blocking gas flow, and lowering the reaction rate. Therefore, the preferred mass percentage of vanadium-doped titanium dioxide in the composite material is 20 wt%.

[0085] Example 5

[0086] The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride. The degradation process was the same as in Example 1, except that the processing temperature of the tubular furnace in Example 1 was adjusted and its effect on the degradation efficiency of sulfur hexafluoride was tested, as shown in Table 4.

[0087] Table 4

[0088] Serial Number Processing temperature Maximum degradation efficiency <![CDATA[SF6 degradation amount per unit mass of composite material]]> Example 1 500 ℃ 50.9% <![CDATA[254.3 mL g -1 ]]> Example 5-1 300 ℃ 11.8% <![CDATA[8.4 mL g -1 ]]> Example 5-2 400 ℃ 15.6% <![CDATA[12.9 mL g -1 ]]> Example 5-3 600 ℃ 99.0% <![CDATA[975.2 mL g -1 ]]>

[0089] analyze:

[0090] As shown in Table 4, the degradation temperature affects the degradation effect of the vanadium-doped titanium dioxide composite material. At 300 ℃ and 400 ℃, the vanadium-doped titanium dioxide composite material can hardly activate SF6. When the temperature is increased to 500 ℃, the vanadium-doped titanium dioxide composite material begins to react with SF6, at which point the highest degradation rate is 50.9%, and the SF6 degradation amount per unit mass of composite material reaches 254.3 mL g. -1 When the temperature is further increased to 600℃, SF6 can achieve 99.0% degradation, with a unit degradation amount of 975.2 mL g. -1 Therefore, it is easy to see that temperature has a great influence on the degradation effect of SF6, and high temperature is beneficial to the activation and degradation of SF6 molecules by vanadium-doped titanium dioxide composite materials.

[0091] Although the catalyst can achieve a 99% degradation rate of sulfur hexafluoride at 600℃, the energy cost behind this is enormous. Increasing the reaction temperature from 500℃ to 600℃ does not result in a linear increase in energy input, but rather a significant increase. This leads to extremely high operating costs: electricity or fuel costs rise sharply, which is unacceptable for industrial applications requiring continuous processing of large volumes of gas; furthermore, 600℃ places higher demands on reactor materials, heating elements, insulation materials, and temperature control systems, increasing initial investment and maintenance costs; and introducing safety hazards. Therefore, considering both energy conservation and overall economic factors, the preferred degradation temperature is 500℃.

[0092] Example 6

[0093] The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride. The degradation process was the same as in Example 1, except that the concentration of ammonia in the mixed gas in Example 1 was adjusted and its effect on the degradation efficiency of sulfur hexafluoride was tested, as shown in Table 5.

[0094] Table 5

[0095] Serial Number ammonia concentration Maximum degradation efficiency <![CDATA[SF6 degradation amount of composite material per unit mass]]> Example 1 1.08 vol.% 50.9% <![CDATA[254.3mL g -1 ]]> Example 6-1 0 vol.% 5.0% <![CDATA[3.8 mL g -1 ]]> Example 6-2 0.54 vol.% 11.5% <![CDATA[10.2 mL g -1 ]]> Example 6-3 0.81 vol.% 16.1% <![CDATA[16.5 mL g -1 ]]> Example 6-4 1.35 vol.% 26.9% <![CDATA[24.4 mL g -1 ]]>

[0096] analyze:

[0097] As shown in Table 5, ammonia concentration affects the degradation effect of vanadium-doped titanium dioxide composite materials. When the ammonia concentration is 0 vol.% to 0.81 vol.%, the SF6 degradation amount per unit mass of composite material is less than 20 mL g. -1 This indicates that the increase in ammonia molecules promotes the degradation of SF6. When the ammonia concentration reaches 1.08 vol.%, the highest degradation rate reaches 50.9%, and the amount of SF6 degraded per unit mass of composite material is 254.3 mL g. -1 However, when the ammonia concentration was further increased to 1.35 vol.%, the degradation rate of SF6 by the composite material decreased to 26.9%, and the degradation amount of SF6 per unit mass of the composite material also decreased to 24.4 mL g. -1 This indicates that the coupling reaction between ammonia molecules and SF6 molecules is most effective when the ammonia concentration is around 1 vol.%. As the amount of ammonia molecules continues to increase, it inhibits the adsorption of SF6 molecules at the reaction sites, resulting in a worse degradation effect. Therefore, the optimal ammonia concentration for the coupling degradation of SF6 by vanadium-doped titanium dioxide composite materials is 1.08 vol.%.

[0098] Example 7

[0099] The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride. The degradation process was the same as in Example 1, except that multiple degradation cycles were performed. The long cycle life of the vanadium-doped titanium dioxide composite material for sulfur hexafluoride degradation was tested, as shown in Table 6.

[0100] Table 6

[0101] Serial Number Degradation time Degradation efficiency Example 1 1 h 50.9% Example 7-1 5 h 50.5% Example 7-2 10 h 49.8% Example 7-3 15 h 49.0%

[0102] analyze

[0103] In summary, as shown in Table 6, the vanadium-doped titanium dioxide composite material prepared in this invention exhibits a long cycle life. During continuous degradation for 1 hour, the degradation efficiency remained at 50.9%. Although the degradation efficiency decreased slightly when the degradation time was extended to 5 hours, 10 hours, and 15 hours, it still remained around 50%.

[0104] Summarize:

[0105] 1. The vanadium-doped titanium dioxide composite material prepared by this invention uses vanadium-doped titanium dioxide as the active site center and one or more of silicon carbide and silicon dioxide materials as the carrier. It can be prepared by a simple physical grinding and high-temperature calcination method. The process is simple, the processing cost is low, and it is suitable for large-scale production. Experiments have confirmed that the catalytic material of this invention can degrade sulfur hexafluoride in an air atmosphere coupled with low-concentration ammonia gas. This is different from the previous technology that required degradation in a nitrogen or argon protective atmosphere, which is very practical and has great practical potential.

[0106] 2. By optimizing the vanadium doping amount, carrier selection, mass ratio of vanadium-doped titanium dioxide in the vanadium-doped titanium dioxide composite material, as well as the degradation temperature and ammonia concentration in the degradation process, the degradation efficiency of sulfur hexafluoride waste gas can be effectively improved. The optimal implementation scheme is as follows: vanadium doping amount is 0.5 wt%, silicon carbide is selected as the carrier, the mass ratio of vanadium-doped titanium dioxide in the composite material is 20 wt%, the degradation temperature is 500 degrees, and the coupled ammonia concentration is 1.08 vol.

Claims

1. A method for preparing a vanadium-doped titanium dioxide composite material, characterized in that, Includes the following steps: (1) Mix ammonium vanadate and titanium dioxide in a certain proportion, and control the doping amount of vanadium to be 0.5wt% based on the total mass of the mixture. Then heat at high temperature to obtain vanadium-doped titanium dioxide powder. (2) Mix vanadium-doped titanium dioxide powder with the carrier in a certain proportion. Based on the total mass of the composite material, control the content of vanadium-doped titanium dioxide powder to be 20 wt%, and perform physical grinding to obtain vanadium-doped titanium dioxide composite material. In step (2): the carrier is silicon carbide.

2. The method for preparing a vanadium-doped titanium dioxide composite material according to claim 1, characterized in that: In step (1): the high-temperature heating is heating at a high temperature of 400-600℃ for 3-6 hours.

3. The method for preparing a vanadium-doped titanium dioxide composite material according to claim 1, characterized in that: In step (1): the high-temperature heating is carried out at 500℃ for 4 hours.

4. The application of a vanadium-doped titanium dioxide composite material prepared by the method described in claim 1 in the catalytic degradation of sulfur hexafluoride, characterized in that: Using vanadium-doped titanium dioxide composite material as a catalyst and ammonia as a sacrificial agent in the catalytic degradation, sulfur hexafluoride was catalytically degraded in an air atmosphere.

5. The application according to claim 4, characterized in that, Includes the following steps: (1) A mixture of sulfur hexafluoride gas coupled with ammonia gas is introduced into the vanadium-doped titanium dioxide composite material. The mixture includes ammonia gas, sulfur hexafluoride gas and air, wherein the volume concentration of ammonia gas is not greater than 5 vol.% and the volume concentration of sulfur hexafluoride gas is not greater than 60 vol.%. (2) The vanadium-doped titanium dioxide composite material was subjected to high-temperature treatment at 300-700°C in the above-mentioned sulfur hexafluoride mixed gas atmosphere coupled with ammonia. (3) The exhaust gas after step (2) is treated with an alkaline solution and collected.

6. The application according to claim 5, characterized in that: In step (1): the volume concentration of sulfur hexafluoride in the mixed gas is 2% to 60 vol.%; the volume concentration of ammonia is 0.1 vol.% to 2.0 vol.%; the high temperature treatment in step (2) is 400 to 600 °C; and the alkaline solution in step (3) is a 5 mol / L sodium hydroxide solution.

7. The application according to claim 5, characterized in that: In step (1): the volume concentration of ammonia is 1.08 vol.%; in step (2), the high temperature treatment is 500-600℃.

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