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

Abstract

The invention discloses a preparation method and application of a vanadium-doped titanium dioxide composite material, and relates to the technical field of titanium dioxide composites.The preparation method comprises the following steps that 1, ammonium vanadate and titanium dioxide are mixed in proportion, the doping amount of the vanadium element is controlled to range from 0.1 wt% to 12.5 wt% according to the total mass of the mixture, then high-temperature heating is conducted, and a mixture is obtained; vanadium-doped titanium dioxide powder is obtained; and (2) mixing the vanadium-doped titanium dioxide powder with a carrier in proportion, controlling the content of the vanadium-doped titanium dioxide powder to be 10-30 wt% based on the total mass of the composite material, and carrying out physical grinding to obtain the powdery vanadium-doped titanium dioxide composite material. The catalytic material disclosed by the invention is applied to degradation of sulfur hexafluoride and has excellent degradation capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium dioxide composite materials, and particularly relates to a preparation method of a vanadium-doped titanium dioxide composite material and application thereof. BACKGROUND

[0002] Sulfur hexafluoride (SF6) is a greenhouse gas that should be limited according to the Kyoto Protocol. Its global warming potential (GWP) is very high, 24300 times that of carbon dioxide (CO2). The insulating strength of SF6 gas is more than 2.5 times that of air, and its arc extinguishing capacity is more than 100 times that of air. Due to its excellent electrical properties, SF6 has been widely used in ultra-high voltage power transmission and switching devices as a protective gas. At present, the annual emission of SF6 gas into the atmosphere is equivalent to 125 million tons of CO2 gas. With the development of the power system, it is estimated that the emission of SF6 will continue to increase in the future, which will inevitably greatly increase the pressure on environmental protection. Therefore, it is urgent to control the emission of SF6 and find a method for degrading SF6.

[0003] Ammonia selective catalytic reduction (SCR) of nitrogen oxides is widely used to reduce atmospheric pollutants. For many years, the improvement of the activity of the SCR reaction has been achieved through structural effects and electronic effects, i.e. by changing the redox properties of the doped elements through induction, conjugation or electronic spin state effects. Although the TiO2 support has almost no activity for the SCR reaction under the relevant reaction conditions, it is very important for the activation of the surface doped atoms (support effect). Only in the case of deposition of vanadium atoms, the doped TiO2 catalyst material can show catalytic function for the reduction of atmospheric pollutants through the SCR reaction with ammonia.

[0004] At present, there are many methods for degrading SF6, such as adsorption, traditional industrial thermal decomposition, photodegradation, plasma method and catalytic degradation. Among them, the catalytic degradation method has attracted special attention. There are three types of catalysts for the catalytic degradation of SF6: metal oxides, metal phosphates and supported metal catalysts. These catalysts are all carried out in an argon or nitrogen atmosphere at a temperature of more than 600℃. At present, there is a lack of research on the degradation mechanism and technology under lower temperature and atmospheric environmental conditions.

[0005] CN103007736A proposed by Zhang Jia et al. discloses a relatively effective degradation of SF6 by using electroplating sludge, but the degradation process needs to be carried out in a nitrogen protective atmosphere. However, SF6 is in the atmosphere in real conditions, and the nitrogen protective atmosphere greatly hinders the practical application of SF6 degradation catalysts. Therefore, it is necessary to develop a simple and environmentally friendly catalytic material that can degrade SF6 in general air atmosphere. SUMMARY

[0006] The first aspect of the present application aims to overcome the above-mentioned defects, and provides a preparation method of a vanadium-doped titanium dioxide composite material, which can realize efficient degradation of SF6 in an air atmosphere.

[0007] The object of the present application is achieved by the following technical solutions. A preparation method of a vanadium-doped titanium dioxide composite material, characterized in that it comprises the following steps: (1) mixing ammonium vanadate and titanium dioxide in a certain proportion, controlling the doping amount of vanadium element to be 0.1wt%-12.5wt% based on the total mass of the mixture, and then heating at high temperature to obtain vanadium-doped titanium dioxide powder; (2) mixing the vanadium-doped titanium dioxide powder with a carrier in a certain proportion, controlling the content of the vanadium-doped titanium dioxide powder to be 10wt%-30wt% based on the total mass of the composite material, and physically grinding to obtain a vanadium-doped titanium dioxide composite material.

[0008] Further: In step (1): The doping amount of vanadium element is controlled to be 0.5wt% based on the total mass of the mixture.

[0009] The high-temperature heating is heating at a high temperature of 400-600℃ for 3-6h, preferably heating at a high temperature of 500℃ for 4h, to obtain the vanadium-doped titanium dioxide powder.

[0010] In step (2): The content of the vanadium-doped titanium dioxide powder is controlled to be 20wt% based on the total mass of the composite material.

[0011] The carrier is selected from any one or more of silicon carbide, silicon dioxide, cerium dioxide and the like, and is preferably silicon carbide.

[0012] The physical grinding refers to grinding with a ball mill at 200rpm for 3min to obtain a powder-like vanadium-doped titanium dioxide composite material.

[0013] The second aspect of the present application aims to provide an application of a vanadium-doped titanium dioxide composite material in catalytic degradation of sulfur hexafluoride, characterized in that: the vanadium-doped titanium dioxide composite material is used as a catalyst, ammonia gas is used as a sacrificial agent in the catalytic degradation, and the sulfur hexafluoride is catalytically degraded in an air atmosphere.

[0014] Further: An application of a vanadium-doped titanium dioxide composite material in catalytic degradation of sulfur hexafluoride, characterized in that it comprises the following steps: (1) introducing a mixed gas of sulfur hexafluoride coupled with ammonia into the vanadium-doped titanium dioxide composite material, the mixed gas comprising ammonia, sulfur hexafluoride and air, wherein the volume concentration of ammonia is not more than 5 vol.%, and the volume concentration of sulfur hexafluoride is not more than 60 vol.%; (2) high-temperature treating the vanadium-doped titanium dioxide composite material in the above-mentioned mixed gas of sulfur hexafluoride coupled with ammonia at 300-700℃; (3) treating the tail gas after step (2) with an alkaline solution.

[0015] Further, In step (1), the volume concentration of sulfur hexafluoride in the mixed gas is 2-60 vol.%, the volume concentration of ammonia is 0.1-2.0 vol.%, preferably 0.27-1.35 vol.%, and particularly preferably 1.08 vol.%.

[0016] The high-temperature treating in step (2) is preferably at 400-600℃, and particularly preferably at 500-600℃.

[0017] The alkaline solution in step (3) is a 5 mol / L sodium hydroxide solution.

[0018] Compared with the prior art, the present application has the following advantages: (1) The vanadium-doped titanium dioxide composite material prepared by the present application uses vanadium atoms doped in titanium dioxide as active site centers and uses one or more of silicon carbide, silicon dioxide and cerium dioxide as carriers, and can be prepared by simple high-temperature heating and physical grinding, thus being simple in process, low in processing cost and suitable for large-scale production.

[0019] (2) Experiments have proved that the catalytic material of the present application has superior degradation ability for sulfur hexafluoride and basically does not produce toxic gas, thus conforming to the environmental protection concept.

[0020] (3) The catalytic material of the present application can degrade sulfur hexafluoride in an air atmosphere coupled with low-concentration ammonia, which is different from the prior art which needs to be degraded in a nitrogen or argon protective atmosphere, and is very consistent with the actual situation and has great practical potential.

[0021] (4) The catalytic material of the present application has very rapid response ability for the degradation of sulfur hexafluoride and has a long service life.

[0022] The present application is further described below in combination with the accompanying drawings and specific embodiments, the following examples are implemented on the premise of the present application scheme, and detailed embodiments and specific operation procedures are given, but the protection scope of the present application is not limited to the above examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 High resolution transmission electron microscope image of the vanadium doped titanium dioxide powder prepared for Example 1.

[0024] Figure 2 Transmission electron microscope energy dispersive X-ray spectroscopy image of the vanadium doped titanium dioxide powder prepared for Example 1.

[0025] Figure 2 Middle: high angle annular dark field image, oxygen element image, titanium element image and vanadium element image of the vanadium doped titanium dioxide powder in sequence.

[0026] Figure 3 High resolution transmission electron microscope image of the vanadium doped titanium dioxide composite material (after being combined with silicon carbide carrier) prepared for Example 1.

[0027] Figure 4 Transmission electron microscope energy dispersive X-ray spectroscopy image of the vanadium doped titanium dioxide composite material (after being combined with silicon carbide carrier) prepared for Example 1.

[0028] Figure 4 Middle: high angle annular dark field image, silicon element image, carbon element image, oxygen element image, titanium element image and vanadium element image of the vanadium doped titanium dioxide composite material (after being combined with silicon carbide carrier) in sequence.

[0029] Figure 5 Schematic diagram of the device for catalytic degradation of sulfur hexafluoride according to the present application.

[0030] Figure 5 Middle: 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 a lye recovery device; 7 is a gas chromatograph; A is an air inlet; B is a gas outlet after reaction.

[0031] Figure 6 Infrared spectrogram of the gaseous product of the catalytic degradation of sulfur hexafluoride according to the present application.

[0032] Figure 7 Comparison of degradation amounts of vanadium doping amounts in vanadium doped titanium dioxide composite materials on the degradation efficiency of sulfur hexafluoride.

[0033] Figure 8 Comparison of degradation amounts of different carriers in vanadium doped titanium dioxide composite materials on the degradation efficiency of sulfur hexafluoride.

[0034] Figure 9 Comparison of degradation amounts of proportions of catalytically active components in vanadium doped titanium dioxide composite materials on the degradation efficiency of sulfur hexafluoride.

[0035] Figure 10The degradation amount of sulfur hexafluoride under different processing temperatures is compared.

[0036] Figure 11 The degradation amount of sulfur hexafluoride under different concentrations of coupled ammonia is compared. DETAILED DESCRIPTION

[0037] The test materials and equipment used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0038] Regarding the degradation temperature and degradation rate: In the field of environmental catalysis, T 50 is an important evaluation index, which generally refers to the temperature required for a catalyst to achieve 50% conversion rate of target pollutants in a specific reaction. In the research and development process, T 50 is a fast and simple index for initially screening out materials with higher activity from a large number of candidate catalysts, thereby improving research and development efficiency. According to the embodiments of the present application, when using a vanadium-doped titanium dioxide catalyst for ammonia coupling degradation of sulfur hexafluoride, T 50 = 500℃. Therefore, each group of comparative tests is carried out at 500℃ in order to screen out the optimal parameters from a large number of experimental schemes.

[0039] Example 1

[0040] A preparation method of a vanadium-doped titanium dioxide composite material, comprising the following steps: (1) mixing ammonium vanadate and titanium dioxide in proportion, controlling the doping amount of vanadium element to be 0.5wt% based on the total mass of the mixture, and then heating at 500℃ for 4 h to obtain vanadium-doped titanium dioxide powder; (2) mixing the obtained vanadium-doped titanium dioxide powder with a carrier silicon carbide in proportion, controlling the content of vanadium-doped titanium dioxide powder in the composite material to be 20wt% based on the total mass of the composite material, using a ball mill to grind at 200 rpm for 3 min to obtain a powder-shaped vanadium-doped titanium dioxide composite material.

[0041] Product confirmation: Figures 1-2 The high-resolution transmission electron microscope image and the transmission electron microscope energy dispersive X-ray spectrum image of the vanadium-doped titanium dioxide prepared in step (1) are shown in Figure 1 , the doped nanomaterial is a 10-20 nm nanoparticle, and then the vanadium-doped titanium dioxide is characterized by transmission electron microscope energy dispersive X-ray spectrum, as shown in Figure 2High-angle annular dark field (HADDF) imaging clearly shows that the doped titanium dioxide powder consists of 10-20 nm nanoparticles with distinct boundaries and no crosslinking. Elemental images of oxygen, titanium, and vanadium show uniform distribution within the powder, indicating that vanadium is uniformly doped within the titanium dioxide powder.

[0042] Figures 3-4 The composite material of vanadium-doped titanium dioxide and silicon carbide support prepared in step (2) was characterized by high-resolution transmission electron microscopy and transmission electron microscopy energy-dispersive X-ray spectroscopy, as shown in FIG. Figures 3-4 As shown: Vanadium-doped titanium dioxide is dispersed in the silicon carbide support, and the two components are composited at the interface.

[0043] Application Example 1 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 configured with ammonia. Air and sulfur hexafluoride gas configured with ammonia pass through the gas flow meter 2 and enter the gas mixer 3 to be mixed. The mixed gas is sent into the quartz reaction tube 4. The quartz reaction tube 4 is set in the tubular furnace 5. The quartz reaction tube 4 contains a vanadium-doped titanium dioxide composite material. The gas is heated to the processing temperature by the tubular furnace 5. The treated gas from the quartz reaction tube 4 is sent to the alkali solution recovery device 6.

[0044] A vanadium-doped titanium dioxide composite material is applied to a sulfur hexafluoride degradation process, comprising the following steps: (1) Configuration of sulfur hexafluoride waste gas: The sulfur hexafluoride waste gas used in the experiment is a simulated sulfur hexafluoride and air mixture. In this embodiment, the concentration of sulfur hexafluoride is controlled at 5 vol.% by the gas flow meter 2 and the gas mixer 3. Ammonia is added to the sulfur hexafluoride waste gas, and the ammonia concentration is 1.08 vol.%.

[0045] (2) The vanadium-doped titanium dioxide composite material prepared in Example 1 is filled into a quartz reaction tube 4, and sulfur hexafluoride, air, and ammonia are mixed in a gas mixer 3 and continuously fed into the quartz reaction tube.

[0046] (3) The quartz reaction tube 4 is heated by a tubular furnace 5, and the temperature is controlled at 500°C with a flow rate of 10 ml / min. The tail gas from the quartz reaction tube 4 is passed into the alkali solution recovery device 6. The gas after the tail gas is absorbed by a 5 mol / L sodium hydroxide solution can be directly discharged into the atmosphere.

[0047] Combine Figure 6As shown in the figure, after the ammonia-coupled degradation of sulfur hexafluoride using vanadium-doped titanium dioxide composite materials, the gaseous products obtained are mainly SO2, H2S and HF. The three types of sulfur gaseous products are due to the two reaction pathways of partial reduction and complete reduction occurring during the ammonia-coupled degradation process. The reaction equation for partial reduction is: 3NH3+SF6+2O2→NH2OH+SO2+6HF+N2O. The generated NH2OH and N2O are both shown in the infrared spectrum ( Figure 6 ) shows a clear signal. The complete reduction reaction equation is: 4NH3 + SF6 + O2 → 2N2 + 6HF + H2S + 2H2O. The completely reduced sulfur product is H2S, which shows a clear signal in the infrared spectrum. The generated N2 and H2O have no obvious signals in the spectrum due to their lack of infrared activity and background subtraction. The SO2, H2S, and HF in the products meet environmental requirements after treatment with sodium hydroxide solution.

[0048] Example 2

[0049] The preparation method is the same as that of Example 1, except that the doping ratio of vanadium element in vanadium-doped titanium dioxide in step (1) is adjusted as shown in Table 1, and the effect on the degradation efficiency of sulfur hexafluoride is tested by using Application Example 1.

[0050] Table 1 No. Vanadium doping amount Highest degradation efficiency SF6degradation quantity per unit mass of composite material Example 1 0.5 wt% 50.9% 254.3 mL g -1 ]] Example 2-1 0.1 wt% 3.5% 1.7 mL g -1 ]]> Example 2-2 2.5 wt% 41.7% 114.9 mL g -1 ]]> Example 2-3 12.5 wt% 2.3% 2.4 mL g -1 ]]>

[0051] analyze: As shown in Table 1, the vanadium doping amount has a significant impact on the SF6 degradation effect. When the vanadium doping mass ratio is 0.1wt%, the maximum degradation rate of the material is 3.5%, and the SF6 degradation amount per unit mass of the composite material is 1.7 mL g -1 When the vanadium doping ratio increases to 0.5wt%, the maximum degradation rate increases to 50.9%, and the SF6 degradation amount per unit mass of the composite material is 254.3mL g -1 However, when the vanadium doping level increases further, the SF6 degradation effect begins to show a downward trend. When the vanadium doping level reaches 2.5wt%, the SF6 degradation amount per unit mass of the composite material is reduced to 114.9 mL g -1 When the doping ratio is further increased to 12.5 wt%, the SF6 degradation per unit mass of the composite material is reduced to 2.4 mL g -1This is because the vanadium atoms in the composite material play the role of electron donor and adsorption center in the material. On the one hand, the reduction of vanadium doping ratio limits the efficiency of electron diffusion, greatly weakening the V-SF6 adsorption site; at the same time, the increase of vanadium doping amount in titanium dioxide will also cause the vanadium oxide to be resintered at high temperature to form V2O5 phase, block the gas flow, reduce the adsorption site and reduce the reaction rate. Therefore, the doping mass fraction of vanadium element in titanium dioxide is preferably 0.5 wt%.

[0052] Example 3

[0053] The preparation method is the same as that of 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 of the composite material on the degradation efficiency of sulfur hexafluoride is tested by using the test method of Application Example 1.

[0054] Table 2, No. Carrier selection Highest degradation efficiency SF6degradation quantity per unit mass of composite material Example 1 Silicon carbide 50.9% 254.3 mL g -1 ]] Example 3-1 Silicon dioxide 15.2% 12.0 mL g -1 ]]> Example 3-2 Cerium dioxide 10.8% 6.4 mL g -1 ]]>

[0055] Analysis: As shown in Table 2, the selection of different carriers for compounding will have a great impact on the performance of vanadium-doped titanium dioxide. When the carrier is SiO2, the degradation of SF6 at 500°C is poor. This is because the crystal size of SiO2 is large and the specific surface area is small, which is not conducive to the adsorption of SF6. When CeO2 powder is selected as the carrier, it still does not have a good degradation effect on SF6. Only when SiC is used as the carrier, the degradation of SF6 can be realized. SiC has high hardness, and after mixing with vanadium-doped titanium dioxide, the size of the material is more uniform, which is conducive to adsorption and reaction. In addition, SiC has the property of semiconductor, which can redistribute the electrons between vanadium-doped titanium dioxide and SiC, and can accelerate the activation and degradation of SF6 by using the electron effect. Therefore, the carrier of the vanadium-doped titanium dioxide composite material is most preferably silicon carbide.

[0056] Example 4

[0057] The preparation method is the same as that of Example 1, except that the mass ratio of the catalytically active component, i.e. vanadium-doped titanium dioxide powder, in step (2) is adjusted, as shown in Table 3, and the effect of the composite material on the degradation efficiency of sulfur hexafluoride is tested by using the test method of Application Example 1.

[0058] Table 3, No. Vanadium-doped titanium dioxide mass ratio Highest degradation efficiency SF6degradation quantity per unit mass of composite material Example 1 20 wt% 50.9% 254.3 mL g -1 <!-- 5 -->]]> Example 4-1 10 wt% 3.3% 6.0 mL g -1 ]] Example 4-2 30 wt% 23.7% 27.6 mL g -1 ]]>

[0059] Analysis: As shown in Table 3, the mass ratio of vanadium-doped titanium dioxide in the composite material has a greater impact on the SF6 degradation effect. The highest degradation rate of the composite material with a mass ratio of 10 wt% is 3.3%, and the SF6 degradation amount on the unit mass of the composite material reaches 6.0 mL g -1When the proportion of vanadium-doped titanium dioxide increased to 20 wt%, the highest degradation rate increased to 50.9%, and the SF6 degradation amount per unit mass of the composite material was 254.3 mL g -1 However, when the content of vanadium-doped titanium dioxide further increased, the degradation effect of SF6 began to show a downward trend. When the mass proportion of vanadium-doped titanium dioxide reached 30 wt%, the SF6 degradation amount per unit mass of the composite material decreased from 254.3 mL g -1 to 27.6 mL g -1 This is because SiC plays the role of an electron donor and a dispersant in the composite material. On the one hand, the reduction of SiC limits the efficiency of electron diffusion, greatly weakening the degradation site of vanadium atoms; on the other hand, metal oxides and metal fluorides can re-sinter at high temperatures, which may cause a decrease in contact area, block gas flow, and reduce reaction rate. Therefore, the mass proportion of vanadium-doped titanium dioxide in the composite material is preferably 20 wt%.

[0060] Example 5

[0061] The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride, and the degradation process was as in Application Example 1, except that the treatment temperature of the tube furnace in Application Example 1 was adjusted to test its effect on the degradation efficiency of sulfur hexafluoride, as shown in Table 4.

[0062] Table 4, No. Treatment temperature Highest degradation efficiency <![CDATA[单位质量复合材料SF6降解量]]> Example 1 500 ℃ 50.9% 254.3 mL g -1 ]] Example 5-1 300 ℃ 11.8% 8.4 mL g -1 ]]> Example 5-2 400 ℃ 15.6% 12.9 mL g -1 ]]> Example 5-3 600 ℃ 99.0% 975.2 mL g -1 ]]>

[0063] Analysis: 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 is almost unable to activate SF6. When the temperature increased to 500 ℃, the vanadium-doped titanium dioxide composite material began to react with SF6, at which time the highest degradation rate was 50.9%, and the SF6 degradation amount per unit mass of the composite material reached 254.3 mL g -1 When the temperature further increased to 600 ℃, SF6 could be degraded by 99.0%, and the unit degradation amount reached 975.2 mL g -1 Therefore, it is not difficult to see that the 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 the vanadium-doped titanium dioxide composite material.

[0064] Although the degradation rate of the catalyst for sulfur hexafluoride can reach 99% at 600°C, the energy cost behind it is huge. The energy input is not linearly increased but significantly increased when the reaction system is raised from 500°C to 600°C. This will lead to extremely high operating costs: the electricity or fuel fees will rise sharply, which is unacceptable for industrial applications that need to continuously process a large amount of gas; in addition, 600°C puts higher requirements on the reactor material, heating elements, insulation materials, and temperature control system, increasing the initial investment cost and maintenance cost; and brings safety hazards, etc. Therefore, for energy saving and economic comprehensive consideration, the degradation temperature is preferably 500°C.

[0065] Example 6

[0066] The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride, and the degradation process was as shown in Application Example 1, except that the concentration of ammonia in the mixed gas in Application Example 1 was adjusted to test its effect on the degradation efficiency of sulfur hexafluoride, as shown in Table 5.

[0067] Table 5, No. Ammonia concentration Highest degradation efficiency SF6degradation quantity per unit mass of composite material Example 1 1.08 vol.% 50.9% 254.3 mL g -1 ]] Example 6-1 0 vol.% 5.0% 3.8 mL g -1 ]]> Example 6-2 0.54 vol.% 11.5% 10.2 mL g -1 ]]> Example 6-3 0.81 vol.% 16.1% 16.5 mL g -1 ]]> Example 6-4 1.35 vol.% 26.9% 24.4 mL g -1 ]]

[0068] Analysis: As shown in Table 5, the concentration of ammonia will affect the degradation effect of the vanadium-doped titanium dioxide composite material. When the concentration of ammonia is 0 vol.%-0.81 vol.%, the degradation amount of SF6 on the unit mass of the composite material is less than 20 mL g -1 , indicating that the increase of ammonia molecules plays a promoting role in the degradation of SF6. When the concentration of ammonia reaches 1.08 vol.%, the highest degradation rate can reach 50.9%, and the degradation amount of SF6 on the unit mass of the composite material is 254.3 mL g -1 . However, when the concentration of ammonia is further increased to 1.35 vol.%, the degradation rate of the composite material for SF6 decreases to 26.9%, and the degradation amount of SF6 on the unit mass of the composite material also decreases to 24.4 mL g -1 . This shows that when the concentration of ammonia is about 1 vol.%, the coupling reaction effect of ammonia molecules and SF6 molecules is best. When the amount of ammonia molecules is continuously increased, it plays an inhibitory role in the adsorption of SF6 molecules on the reaction site, and the degradation effect becomes worse. Therefore, the optimal concentration of ammonia for the vanadium-doped titanium dioxide composite material to couple and degrade SF6 is 1.08 vol.%.

[0069] Example 7 The vanadium-doped titanium dioxide composite material prepared in Example 1 was used to degrade sulfur hexafluoride, and the degradation process was as in Application Example 1, except that multiple degradation cycles were performed to test the long cycle life of the vanadium-doped titanium dioxide composite material for degrading sulfur hexafluoride, as shown in Table 6.

[0070] Table 6, No. 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%

[0071] Analysis Summary: As shown in Table 6, the vanadium-doped titanium dioxide composite material prepared in the application has the characteristic of long cycle life. When the degradation time is continuously 1 h, the degradation efficiency can be maintained at 50.9%. When the degradation time is extended to 5 h, 10 h and 15 h, the degradation efficiency is slightly reduced, but still maintained at about 50%.

[0072] Summary: 1. The vanadium-doped titanium dioxide composite material prepared in the application uses vanadium-doped titanium dioxide as the active site center and one or more of silicon carbide and silicon dioxide material as the carrier, which can be prepared by 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 proved that the catalytic material of the application can couple low-concentration ammonia to degrade sulfur hexafluoride in air atmosphere, which is different from the technology that needs to be degraded in nitrogen or argon protective atmosphere in the past, and is very consistent with the actual situation, and has great practical potential.

[0073] 2. By optimizing the vanadium doping amount of the vanadium-doped titanium dioxide composite material, the selection of the carrier, the mass ratio of the vanadium-doped titanium dioxide in the composite material, and the degradation temperature and ammonia concentration in the degradation process, the degradation efficiency of sulfur hexafluoride waste gas can be effectively improved. The best implementation scheme is: the vanadium doping amount is 0.5 wt%, the carrier is silicon carbide, the mass ratio of vanadium-doped titanium dioxide in the composite material is 20 wt%, the degradation temperature is 500 degrees, and the coupling ammonia concentration is 1.08 vol.%.

Claims

1. A method for preparing a vanadium-doped titanium dioxide composite material, characterized in that: The following steps are involved: (1) ammonium vanadate and titanium dioxide are mixed in proportion, and the doping amount of vanadium element is controlled to be 0.1 wt% to 12.5 wt% based on the total mass of the mixture, and then heated at high temperature to obtain vanadium-doped titanium dioxide powder; (2) The vanadium-doped titanium dioxide powder and the carrier are mixed in proportion, and the content of the vanadium-doped titanium dioxide powder is controlled to be 10 wt% to 30 wt% based on the total mass of the composite material. Physical grinding is performed to obtain a vanadium-doped titanium dioxide composite material.

2. The method for preparing a vanadium-doped titanium dioxide composite material according to claim 1, characterized in that: In step (1): based on the total mass of the mixture, the doping amount of vanadium element is controlled to be 0.5 wt%.

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 heating at a high temperature of 400 to 600°C for 3 to 6 hours.

4. 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°C for 4 h.

5. The method for preparing a vanadium-doped titanium dioxide composite material according to claim 1, characterized in that: In step (2): based on the total mass of the composite material, the content of vanadium-doped titanium dioxide powder is controlled to be 20 wt%.

6. The method for preparing a vanadium-doped titanium dioxide composite material according to claim 1, characterized in that: In step (2): the carrier is selected from any one or more of silicon carbide, silicon dioxide, and ceria.

7. Use of the vanadium-doped titanium dioxide composite material prepared by the preparation method of claim 1 in catalytic degradation of sulfur hexafluoride, characterized in that: The vanadium-doped titanium dioxide composite material was used as a catalyst and ammonia was used as a sacrificial agent in the catalytic degradation to catalyze the degradation of sulfur hexafluoride in an air atmosphere.

8. Use of a vanadium-doped titanium dioxide composite material in catalytic degradation of sulfur hexafluoride according to claim 7, characterized in that: The following steps are involved: (1) introducing a mixed gas of sulfur hexafluoride coupled with ammonia into the vanadium-doped titanium dioxide composite material, wherein the mixed gas comprises ammonia, sulfur hexafluoride and air, wherein the volume concentration of ammonia is not greater than 5 vol.%, and the volume concentration of sulfur hexafluoride is not greater than 60 vol.%; (2) subjecting the vanadium-doped titanium dioxide composite material to a high-temperature treatment at 300-700° C. in the above-mentioned sulfur hexafluoride mixed gas atmosphere coupled with ammonia; (3) The tail gas after treatment in step (2) is treated with an alkaline solution and collected.

9. Use of a vanadium-doped titanium dioxide composite material in catalytic degradation of sulfur hexafluoride according to claim 8, characterized in that: In step (1), the volume concentration of sulfur hexafluoride in the mixed gas is 2% to 60 vol.%, and the volume concentration of ammonia is 0.1 vol.% to 2.0 vol.%. The high-temperature treatment in step (2) is performed at a temperature of 400 to 600°C. The alkaline solution in step (3) is a 5 mol / L sodium hydroxide solution.

10. Use of a vanadium-doped titanium dioxide composite material in catalytic degradation of sulfur hexafluoride according to claim 8, characterized in that: In step (1), the volume concentration of ammonia is 1.08 vol.%; in step (2), the high temperature treatment temperature is 500-600°C.

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