A catalytic material based on molybdenum dioxide for degrading sulfur hexafluoride in an air atmosphere

Abstract

The present invention discloses a catalytic material based on molybdenum dioxide for degrading sulfur hexafluoride in an air atmosphere, which relates to the technical field of catalytic materials. The catalytic material is characterized in that: the catalytic material uses molybdenum dioxide as the active site center and uses one or more of silicon carbide and silicon dioxide as a carrier. The molybdenum dioxide material is used for catalytic degradation of sulfur hexafluoride in an air atmosphere. The MoO 2 Based on MoO 2 As the active site center, one or more of silicon carbide and silicon dioxide materials are used as carriers and can be prepared by a simple physical grinding method. No sintering is required, the process is simple, the processing cost is low, and it is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the field of material technology, and in particular to a catalytic material based on molybdenum dioxide for degrading sulfur hexafluoride in an air atmosphere, belonging to the field of environmental protection technology for polluted gas prevention and control. Background Art

[0002] In 1997, the Kyoto Protocol included sulfur hexafluoride in the list of greenhouse gases. Sulfur hexafluoride is a strong greenhouse gas, and its global warming potential (GWP) is about 23,900 times that of the same amount of carbon dioxide (CO2) (calculated over 100 years). The emission of 1 kilogram of sulfur hexafluoride has a boost to global warming equivalent to the carbon dioxide emitted by 24 people flying back and forth between London and New York. More importantly, sulfur hexafluoride is stable and not easily decomposed, and can exist stably in the atmosphere for 3,200 years. With the large-scale use of sulfur hexafluoride, the concentration of sulfur hexafluoride accumulated in the atmosphere has become higher and higher, and its impact on the global climate has become increasingly prominent. Therefore, sulfur hexafluoride gas has also become a target for global greenhouse gas emission reduction. In addition, corrosive and highly toxic products such as S2F 10 , SF4, etc., are extremely harmful to the human body. At present, the total amount of sulfur hexafluoride gas emitted globally each year is equivalent to 125 million tons of carbon dioxide (CO2). In 2020, my country's carbon emissions caused by sulfur hexafluoride gas emissions reached 85 million tons, accounting for about 70% of the world's total. Therefore, the reduction of sulfur hexafluoride emissions is of great significance to my country.

[0003] At present, the emission reduction measures for SF6 are to recycle and compress the high-concentration sulfur hexafluoride gas used in retired equipment, and then transport it to the provincial center for unified purification treatment. The recovery rate can reach 96.5%, but the compression recovery technology is limited to the treatment of raw waste gas with a purity of more than 70% of SF6, and there is a considerable risk of leakage. In addition, scholars have widely studied a variety of methods such as adsorption, thermal decomposition, photodegradation, plasma method and catalytic degradation, among which the catalytic degradation method has received special attention. There are three main types of catalysts for sulfur hexafluoride degradation: metal oxides, metal phosphates, and supported metal catalysts. These catalysts are all carried out in an argon or nitrogen atmosphere above 600°C. At present, there is a lack of degradation mechanism and technical research under low temperature atmospheric environment conditions. For example, Zhang Jia et al. (CN103007736A) used electroplating sludge to effectively degrade sulfur hexafluoride, but the degradation process needs to be carried out under the protective atmosphere of nitrogen. Under realistic conditions, sulfur hexafluoride is in the atmosphere, and the protective atmosphere greatly hinders the practical application of SF6 degradation catalysts. Therefore, it is urgent to develop a catalytic material that can degrade SF6 at low temperature in a normal air atmosphere. Summary of the invention

[0004] The first aspect of the present invention aims to overcome the above defects and synthesize a degradation material based on molybdenum dioxide to achieve low energy consumption degradation of SF6 in an air atmosphere.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A catalytic material based on molybdenum dioxide for degrading sulfur hexafluoride in an air atmosphere, characterized in that the catalytic material uses molybdenum dioxide as the active site center and one or more of silicon carbide and silicon dioxide as a carrier, and the molybdenum dioxide material is used for catalytic degradation of sulfur hexafluoride in an air atmosphere.

[0007] The second aspect of the present invention is to provide a method for preparing the aforementioned catalytic material, comprising the following steps: physically mixing MoO2 powder with a carrier to obtain a molybdenum dioxide-based catalytic material (MoO2-based catalytic material) that efficiently degrades sulfur hexafluoride.

[0008] Further:

[0009] The carrier is selected from any one or more materials such as silicon carbide and silicon dioxide, and is preferably silicon carbide.

[0010] The physical mixing method comprises: mixing the carrier and MoO2 powder, and then physically grinding them to obtain a powdered MoO2-based catalytic material.

[0011] The mass ratio of MoO2 in the catalytic material is 5wt% to 50wt%, and is particularly preferably 10wt%.

[0012] The third aspect of the present invention aims to provide an application of the MoO2-based catalytic material in catalytic degradation of sulfur hexafluoride, characterized in that it comprises the following steps:

[0013] (1) introducing a sulfur hexafluoride mixed gas into the MoO2-based catalytic material, wherein the sulfur hexafluoride mixed gas is prepared by mixing sulfur hexafluoride and air, and the volume concentration of sulfur hexafluoride is controlled to be no more than 60 vol.%

[0014] (2) subjecting the MoO2-based catalytic material to a high temperature treatment at 300-700° C. in the above-mentioned sulfur hexafluoride mixed gas atmosphere;

[0015] (3) The tail gas is treated with sodium hydroxide solution and collected.

[0016] Further:

[0017] The high temperature treatment in step (2) is carried out at a temperature of 300 to 700°C, preferably 450 to 600°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The MoO2-based catalytic material of the present invention uses MoO2 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 method without sintering, has a simple process, low processing cost, and is suitable for large-scale production.

[0020] (2) Experiments have confirmed that the catalytic material of the present invention has excellent degradation ability for sulfur hexafluoride, further reduces the temperature compared with the previous one, has low energy consumption and basically does not produce toxic gases, which is in line with the concept of environmental protection.

[0021] (3) The catalytic material of the present invention can degrade sulfur hexafluoride in an air atmosphere, which is different from the previous technology that requires degradation in a protective atmosphere of nitrogen or argon. It is very consistent with the actual situation and has great practical potential.

[0022] (4) The catalytic material of the present invention has a very rapid response to the degradation of sulfur hexafluoride and a long service life.

[0023] The following is a further description of the implementation scheme of the present invention in conjunction with the accompanying drawings. The following examples are implemented on the premise of the scheme of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above-mentioned examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the MoO2-based catalytic material prepared in Example 1.

[0025] Figure 2 This is a high-resolution transmission electron microscope image of the MoO2-based catalytic material prepared in Example 1.

[0026] Figure 3 This is a schematic diagram of the device for catalytic degradation of sulfur hexafluoride according to the present invention.

[0027] Figure 4 This is the curve showing the change of sulfur hexafluoride degradation efficiency with increasing duration.

[0028] Figure 5 The figure shows the influence curve of different compositions of MoO2-based catalytic materials on the degradation efficiency of sulfur hexafluoride and the comparison of degradation amounts.

[0029] Figure 6 This is the influence curve of different carrier selections of MoO2-based catalytic materials on the degradation efficiency of sulfur hexafluoride.

[0030] Figure 7 This is the effect curve of different treatment temperatures on the degradation efficiency of sulfur hexafluoride. DETAILED DESCRIPTION

[0031] Embodiment 1:

[0032] 1. Preparation of MoO2-based catalytic materials

[0033] MoO2 is used as the active center and silicon carbide is used as the carrier. The mass ratio of MoO2 in the material is controlled to be 10wt%. After the two are mixed, they are ground to obtain a powdered MoO2-based catalytic material.

[0034] Backscattered electron images of the prepared MoO2-based catalytic materials, such as Figure 1 As shown in the figure, the bright part is MoO2 and the dark part is silicon carbide. Then, high-resolution transmission electron microscopy was used to characterize the MoO2-based catalytic material, as shown in the figure. Figure 2 As shown in Figure 2, MoO2 is dispersed in the silicon carbide carrier, and the two components fuse at the interface to form a MoO2 / SiC heterojunction.

[0035] 2. Device for treating sulfur hexafluoride using MoO2-based catalytic materials

[0036] like Figure 3 The figure shows a schematic diagram of the structure of a device for treating sulfur hexafluoride with MoO2-based catalytic materials, which includes the following components: 1 pure sulfur hexafluoride gas cylinder; 2 gas flow meter; 3 gas mixer; 4 quartz reaction tube; 5 tubular furnace; 6 alkali solution recovery device; 7 gas chromatograph; A air inlet; B reacted gas outlet. Among them: air and sulfur hexafluoride gas pass through the gas flow meter 2, enter the gas mixer 3 to be mixed, and then are sent to the quartz reaction tube 4, which has MoO2-based catalytic materials built in it. The quartz reaction tube 4 is set in the tubular furnace 5, and is heated to the treatment temperature by the tubular furnace 5. The gas treated from the quartz reaction tube 4 is sent to the alkali solution recovery device 6, and the alkali solution recovery device 6 uses 5 mol / L sodium hydroxide solution to treat and collect the tail gas.

[0037] 3. The process of treating sulfur hexafluoride with MoO2-based catalytic materials comprises the following steps:

[0038] (1) Configuration of sulfur hexafluoride waste gas:

[0039] The sulfur hexafluoride waste gas used in the experiment is a mixture of sulfur hexafluoride and air in a simulated configuration. In this embodiment, the concentration of sulfur hexafluoride is controlled at 2 vol.% by a gas flow meter and a gas mixing device.

[0040] (2) The mixed and ground MoO2-based catalytic material is filled into a quartz reaction tube, and the sulfur hexafluoride mixed gas is continuously fed into the quartz reaction tube to wait for treatment.

[0041] (3) Place the quartz reaction tube in a tube furnace, control the temperature at 500°C, and record the degradation efficiency every 10 minutes until the degradation efficiency is poor or 0. The results are as follows: Figure 4 shown.

[0042] from Figure 4 It can be seen that when the temperature is 500 °C, sulfur hexafluoride has a good degradation efficiency, the degradation duration is greater than 120 minutes, and the maximum degradation rate reaches 73.33% at 40 minutes. The SF6 degradation amount per unit mass of MoS2 is 123.49 mL g -1 The tail gas coming out of the reaction tube is passed into the alkali solution recovery device, and the gas after tail gas absorption by 5 mol / L sodium hydroxide solution can be directly discharged into the atmosphere.

[0043] Embodiment 2:

[0044] The MoO2-based catalytic material preparation method, treatment device and treatment process of Example 1 are used, except that the ratio of silicon carbide and MoO2 in the MoO2 catalytic material is adjusted as shown in Table 1, and its effect on the degradation efficiency is tested. The results are as follows: Figure 5 shown.

[0045] Table 1. Composition and ratio of different MoO2-based catalytic materials

[0046]

[0047] analyze:

[0048] The mass ratio of MoO2 in the degradation material has a great influence on the SF6 degradation effect. The highest degradation rate of 5wt% MoO2-based catalytic material is 50.09%, and the SF6 degradation amount per unit mass of MoO2 is 122.49mL g -1 , the degradation life is 110 minutes. When the specific gravity of MoO2 increases to 10wt%, the maximum degradation rate increases to 73.33%, and the SF6 degradation amount per unit mass of MoO2 is 123.42mL g -1 , which is almost the same as the degradation per unit mass of 5wt% MoO2-based catalytic material. However, when the MoO2 content increases further, the degradation effect of SF6 begins to show a downward trend. When the MoO2 content reaches 20wt%, although the total amount of SF6 degraded during the entire degradation process remains almost unchanged (12.34mL at 10wt% and 12.93mL at 20wt%), the SF6 degradation per unit mass of MoO2 is almost halved, from 123.42mL g -1 Down to 64.65 mL g -1. When the content of MoO2 further increases to 50wt%, the degradation amount of SF6 per unit MoO2 and the total degradation amount of SF6 both decrease significantly. This is because SiC plays the role of electron donor and dispersant in the composite material. On the one hand, the reduction of SiC limits the electron diffusion efficiency and greatly weakens the Mo degradation site; at the same time, the metal oxide fluoride will re-sinter at high temperature, which may cause a reduction in contact area, block gas flow, and reduce the reaction rate. Therefore, the content of MoO2 in the MoO2-based catalytic material is preferably 10wt%.

[0049] Embodiment 3:

[0050] The MoO2-based catalytic material preparation method, treatment device and treatment process of Example 1 are used, except that the choice of carrier is adjusted as shown in Table 2, and its effect on the degradation efficiency is tested. The results are as follows: Figure 6 shown.

[0051] Table 2. Different carrier selection

[0052]

[0053] analyze:

[0054] Choosing different carriers will have a huge impact on the performance of MoO2-based catalytic materials. Pure MoO2 cannot degrade SF6 at 500°C. This is because the crystal size of MoO2 is large and the specific surface area is small, which is not conducive to the adsorption of SF6. At the same time, the charge distribution inside the pure MoO2 material is very uniform, which is not conducive to the transfer of electrons to SF6 molecules, and thus the degradation effect cannot be achieved. When SiO2 powder is selected as a carrier, the degradation effect on SF6 is poor. Only when SiC is used as a carrier can the degradation of SF6 be achieved. SiC has high hardness and is a commonly used abrasive. After mixing with MoO2, the size of the material is more uniform, which is conducive to adsorption and reaction. In addition, SiC has the properties of a semiconductor, which can redistribute electrons between MoO2 and SiC, and the electronic effect can be used to accelerate the activation and degradation of SF6. Therefore, the most preferred carrier for MoO2-based catalytic materials is silicon carbide.

[0055] Embodiment 4:

[0056] The MoO2-based catalytic material preparation method, treatment device and treatment process of Example 1 are used, except that the treatment temperature of the tube furnace is adjusted as shown in Table 3, and the effect of the treatment temperature on the degradation efficiency is tested. The results are as follows: Figure 7 shown.

[0057] Table 3. Different degradation temperatures

[0058]

[0059]

[0060] analyze:

[0061] The degradation temperature affects the degradation effect of MoO2-based catalytic materials. At 450°C, MoO2-based catalytic materials can hardly activate SF6. When the temperature rises to 500°C, MoO2-based catalytic materials begin to react with SF6, with the highest degradation rate of 73.33% at this time, and the SF6 degradation amount per unit MoO2 reaches 123.42 mL g -1 As the temperature increases, the maximum degradation rate and degradation amount of SF6 by MoO2-based catalytic materials also increase. At 550°C, the maximum degradation rate reaches 94.89%, and the SF6 degradation amount reaches 391.13 mL g -1 , the degradation life is extended to 260 minutes. When the temperature is further increased to 600 °C, SF6 can achieve 100% degradation, and the unit degradation amount reaches 664.79 mL g -1 , the degradation life is as long as 400 minutes. Therefore, it is not difficult to see that temperature has a great influence on the degradation effect of SF6, and high temperature is conducive to the activation and degradation of SF6 molecules by MoO2-based catalytic materials. For energy saving and economic considerations, the degradation temperature is preferably 500℃.

[0062] Summarize:

[0063] 1. The MoO2-based catalytic material of the present invention uses MoO2 as the active site center and silicon carbide material as the carrier. It can be prepared by a simple physical grinding method without sintering, simple process, low processing cost, and is suitable for large-scale production. Experiments have confirmed that the catalytic material of the present invention can degrade sulfur hexafluoride in an air atmosphere, which is different from the previous technology that requires degradation in a protective atmosphere of nitrogen or argon. It is very consistent with the actual situation and has huge practical potential.

[0064] 2. By optimizing the iron doping ratio, carrier selection, MoO2 to carrier ratio, treatment temperature, etc., excellent degradation efficiency can be effectively obtained at a lower temperature. The best implementation scheme is: the carrier is selected as silicon carbide, the mass ratio of MoO2 in the catalytic material is 10wt%, and the treatment temperature is 500 degrees.

Claims

1. An application of a catalytic material based on molybdenum dioxide in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: The following steps are involved: (1) introducing a sulfur hexafluoride mixed gas into the MoO2-based catalytic material, wherein the sulfur hexafluoride mixed gas is prepared by mixing sulfur hexafluoride and air, and the volume concentration of sulfur hexafluoride is controlled to be no more than 60 vol.%; The catalytic material uses molybdenum dioxide as the active site center and one or more of silicon carbide and silicon dioxide as a carrier, and the catalytic material is used to catalyze the degradation of sulfur hexafluoride in an air atmosphere; (2) subjecting the MoO2-based catalytic material to a high temperature treatment at 300 to 700° C. in the above-mentioned sulfur hexafluoride mixed gas atmosphere; (3) The tail gas is treated with sodium hydroxide solution and collected.

2. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: In step (1): MoO2 powder is physically mixed with a carrier to obtain a molybdenum dioxide-based catalytic material for degrading sulfur hexafluoride in an air atmosphere.

3. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: In step (1): the carrier is silicon carbide.

4. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: In step (1): the carrier and MoO2 powder are mixed and then physically ground to obtain a powdered MoO2-based catalytic material.

5. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: In step (1): the mass ratio of MoO2 in the catalytic material is 5 wt% to 50 wt%.

6. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: In step (1): the mass ratio of MoO2 in the catalytic material is 10 wt%.

7. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: The high temperature treatment in step (2) is performed at a temperature of 450 to 600°C.

8. Use of a catalytic material according to claim 1 in the degradation of sulfur hexafluoride in an air atmosphere, characterized in that: The high temperature treatment in step (2) is at a temperature of 500°C.

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