Supported catalyst for SF6 thermocatalytic conversion and preparation method thereof

Abstract

The invention relates to the technical field of sulfur hexafluoride gas thermocatalytic conversion, and discloses a supported catalyst for SF6 thermocatalytic conversion and a preparation method thereof, and the preparation method comprises the following steps: titanium dioxide is supported on the surface of SiC in a nanoscale particle form, and the mass ratio of titanium dioxide to silicon carbide is 1: 5. The catalyst and the preparation method provide possibility for harmless treatment of SF6 under milder conditions, and the provided preparation method has the advantages of high loading efficiency, simple preparation device, reduction of the preparation cost, increase of the effective reaction area of the catalyst, and good application potential and popularization prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal catalytic conversion of sulfur hexafluoride (SF6) gas, and also to the field of catalyst preparation, and in particular to a supported catalyst for thermal catalytic conversion of SF6 and a preparation method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Due to its excellent insulation performance and good chemical stability, SF6 is widely used as an insulating medium in many fields of power systems, including gas-insulated metal-enclosed switchgear (GIS) equipment, circuit breakers, transformers and other medium-voltage electrical equipment. In addition to its excellent insulation performance, SF6 is also a gas with a strong greenhouse effect. The global warming potential (GWP) of SF6 gas is as high as 23,500. Moreover, SF6 is very stable in the atmosphere, with an atmospheric life of up to 3,200 years. It has been listed as a restricted greenhouse gas in the Kyoto Protocol. With the widespread use of SF6 gas, its annual emissions have been growing rapidly since SF6 gas was applied to industrial production in 1953. By 2008, the annual emissions of SF6 gas had reached 7,420 tons. Now the annual usage of SF6 in the world has exceeded 10,000 tons. A large part of the SF6 gas emitted into the atmosphere comes from SF6 waste gas emitted in the power industry. The demand for SF6 gas will only increase in the future, so SF6 waste gas needs to be properly handled in related fields.

[0004] At present, the main treatment methods for SF6 waste gas are pyrolysis, photoconversion, thermal catalytic conversion and plasma. The traditional pyrolysis method is to react excess CaCO3 with SF6. The reaction requires a high temperature of 1100°C, which consumes a lot of energy and has a very high economic cost. In addition, toxic gases such as H2S will be generated during the conversion process. Although the photoconversion method has relatively low energy consumption, the conversion time is too long and the conversion efficiency is low. The operation process of the plasma conversion method still needs to be improved. For example, SF6 needs to be diluted first, which will cause waste of dilution gas and cannot control the conversion product. The plasma conversion method is still far from industrial application. Thermal catalytic conversion not only reduces energy consumption and has a high conversion efficiency, but also can appropriately adjust the conversion product. Therefore, the thermal catalytic conversion method has a very good prospect for industrial application.

[0005] At present, most researchers have applied metal oxides, phosphates and other catalysts to the harmless treatment of SF6. However, in this heterogeneous catalytic reaction process, the contact area between the catalyst and the experimental gas will significantly affect the catalytic efficiency of the catalyst. Therefore, we need a preparation method that can increase the effective reaction area of ​​the catalyst; preparing supported catalysts is a commonly used method to increase the effective reaction area of ​​the catalyst. Supported catalysts are catalysts in which the active components and co-catalysts are evenly dispersed and loaded on a specially selected carrier.

[0006] The existing sol-gel preparation method of supported titanium dioxide catalyst has the problems of adding a large amount of toxic organic solvents, low active ingredient loading rate, high calcination temperature, etc. Therefore, it is of great significance to reduce or even eliminate organic solvents, increase active ingredient loading rate and improve calcination process. Summary of the invention

[0007] The purpose of the present invention is to provide a supported catalyst for SF6 thermal catalytic conversion and a preparation method thereof in view of the problems of the current preparation method having the addition of toxic solvents, low active ingredient loading rate and high calcination temperature. The preparation method can not only prepare a catalyst with a larger effective contact area, but also avoid the use of a large amount of organic solvents in the preparation process, and at the same time can improve the loading rate, thereby further reducing environmental pollution while reducing costs.

[0008] The technical solution of the present invention is as follows:

[0009] On one hand, the present invention provides a method for preparing a supported catalyst for thermal catalytic conversion of SF6, comprising the following steps: supporting titanium dioxide in the form of nano-sized particles on the surface of 1000 mesh SiC, and the mass ratio of titanium dioxide to silicon carbide is 1:5.

[0010] The specific steps include:

[0011] Step (1): first, weigh 5 mL of pure hydrochloric acid with a measuring cylinder, slowly add deionized water until the solution is diluted to 60 mL, thereby obtaining a 1 mol / L dilute hydrochloric acid solution, then weigh 17 mL of n-butyl titanate as a titanium source of the catalyst with a 20 mL measuring cylinder in a fume hood, add the mixture to the previously prepared 1 mol / L dilute hydrochloric acid solution, slowly add deionized water while stirring with a stirring rod until the solution is diluted to 120 mL, place the solution in a magnetic heating stirrer, and adjust the speed so that the solution is vigorously stirred in the magnetic stirrer for 1 hour;

[0012] Step (2): Take out a commercially available 1 mol / L NaOH solution, prepare a plastic dropper and a pH meter, use the plastic dropper to add the NaOH solution dropwise to the solution, and use the pH meter to measure the pH value of the supernatant of the solution. When the pH value of the supernatant is 2, stop adding the NaOH solution, use an electronic balance with an accuracy of 0.1 g to weigh 12 g of a commercially available silicon carbide carrier with a size of 1000 mesh, and then place the solution in a magnetic heating stirrer and stir vigorously for 1 hour;

[0013] Step (3): using a plastic dropper to add NaOH solution dropwise to the solution, and using a pH meter to measure the pH value of the supernatant of the solution, adding 1 mol / L NaOH solution until the pH value of the supernatant of the solution is 3, then placing the solution in a magnetic heating stirrer and vigorously stirring for 1 h to obtain a precursor solution;

[0014] Step (4): Take out the precursor solution, cover the mouth of the beaker with plastic wrap to prevent impurities from entering, let the solution stand for 12 hours, then pour the separated supernatant into a waste liquid bucket, and use a vacuum filtration device to separate the remaining viscous solution into solid and liquid to obtain a round cake-shaped solid, then rinse the solid three times with deionized water to obtain a catalyst precursor;

[0015] Step (5): Place the washed catalyst precursor in a tubular furnace, set the program to increase the temperature at 10°C / min, and calcine at a constant temperature of 400°C for 2 hours, and adopt a natural cooling method; grind the calcined TiO2 / SiC catalyst, pass it through a 90-mesh sieve, and finally obtain a TiO2 / SiC supported catalyst.

[0016] Another aspect of the present invention provides a supported catalyst for thermal catalytic conversion of SF6 prepared by the preparation method as described above.

[0017] Another aspect of the present invention provides the use of a supported catalyst for thermal catalytic conversion of SF6 prepared by the preparation method as described above in the harmless treatment of SF6 waste gas.

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

[0019] 1. A supported catalyst for SF6 thermal catalytic conversion and a preparation method thereof. The present invention improves the traditional sol-gel method. Compared with the traditional sol-gel method, the improved method has the advantages of less raw material consumption, less pollution, high titanium dioxide recovery rate, short preparation time, etc., and is more suitable for industrial production;

[0020] 2. A supported catalyst for thermal catalytic conversion of SF6, which supports the active component on SiC with a large specific surface area, increases the effective area of ​​the catalyst, and promotes the conversion of the test gas on the catalyst surface; SiC and TiO2 form a heterogeneous structure, which promotes the harmless treatment of SF6 and has a higher catalytic efficiency than only the active component TiO2;

[0021] 3. A method for preparing a supported catalyst for SF6 thermal catalytic conversion, which can increase the effective reaction area of ​​the catalyst, improve the catalytic efficiency of the heterogeneous catalytic reaction of the catalyst, and make up for the problems of small effective catalytic area and low TiO2 loading rate of the existing SF6 thermal catalytic conversion catalyst; compared with the traditional sol-gel method, this method does not need to add a large amount of toxic organic solvents, which reduces the cost and the operating risk of the preparation operator; the method has a high active ingredient loading rate, so the utilization rate of the catalyst raw material is high, which reduces the cost. In addition, the method requires simple equipment and is easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the preparation process of a supported catalyst for thermal catalytic conversion of SF6 according to Example 1 of the present application;

[0023] Figure 2 This is a scanning electron microscope image of the supported catalyst TiO2 / SiC for SF6 thermal catalytic conversion prepared in Example 1 of the present application

[0024] Figure 3 These are the catalytic efficiency data of the supported catalyst TiO2 / SiC for thermal catalytic conversion of SF6 prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0025] The specific embodiments listed in the present invention are only examples of the present invention, and the present invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of the present invention. Therefore, the equal transformations and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturers are not specified for all reagents or instruments, they are all conventional products that can be purchased commercially. In order to better illustrate the present invention, numerous specific details are given in the specific embodiments below. It should be understood by those skilled in the art that the present invention can also be implemented without certain specific details. In other embodiments, the methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the purport of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art. Unless otherwise specified, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0027] This patent adopts the sol-gel method to prepare TiO2 / SiC catalyst. The titanium source is 98% pure n-butyl titanate, which was purchased from Tianjin Xiens Technology Co., Ltd., 1000 mesh SiC was purchased from Jiangsu Top Metal Processing Plant, and 1M NaOH solution and GR purity hydrochloric acid were purchased from Wuhan Xinshenshi Chemical Co., Ltd.

[0028] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0029] Example 1

[0030] See also Figure 1 In this example, in order to detect the decomposition products of the SF6 gas medium, the present invention proposes a method for preparing a supported TiO2 / SiC catalyst and its application in the harmless treatment of SF6 waste gas. The intrinsic TiO2 / SiC material prepared by this method has been verified to have a high efficiency in harmless treatment of SF6 waste gas. 1.5g of the catalyst can harmlessly treat more than 250mL of SF6 waste gas at 700°C, and has good application value. Specifically, the material preparation method and effect verification in this example are as follows:

[0031] A method for preparing a supported titanium dioxide supported catalyst comprises the following steps:

[0032] Step (1): first, weigh 5 mL of pure hydrochloric acid with a measuring cylinder, and slowly add deionized water until the solution is diluted to 60 mL, thereby obtaining a 1 mol / L dilute hydrochloric acid solution; then, in a fume hood, weigh 17 mL of n-butyl titanate as a titanium source of the catalyst with a 20 mL measuring cylinder, add the mixture to the previously prepared 1 mol / L dilute hydrochloric acid solution, slowly add deionized water while stirring with a stirring rod, until the solution is diluted to 120 mL, and place the solution in a magnetic heating stirrer, and adjust the speed so that the solution is vigorously stirred in the magnetic stirrer for 1 hour;

[0033] Step (2): Take out a commercially available 1 mol / L NaOH solution, prepare a plastic dropper and a pH meter, use the plastic dropper to add the NaOH solution dropwise to the solution, and use the pH meter to measure the pH value of the supernatant of the solution. When the pH value of the supernatant is 2, stop adding the NaOH solution, use an electronic balance with an accuracy of 0.1 g to weigh 12 g of a commercially available silicon carbide carrier with a size of 1000 mesh, and then place the solution in a magnetic heating stirrer and stir vigorously for 1 hour;

[0034] Step (3): using a plastic dropper to add NaOH solution dropwise to the solution, and using a pH meter to measure the pH value of the supernatant of the solution, adding 1 mol / L NaOH solution until the pH value of the supernatant of the solution is 3, and then placing the solution under magnetic heating and stirring, and vigorously stirring for 1 hour to obtain a precursor solution;

[0035] Step (4): Take out the precursor solution, cover the mouth of the beaker with plastic wrap to prevent impurities from entering, let the solution stand for 12 hours, then pour the separated supernatant into a waste liquid bucket, and use a vacuum filtration device to separate the remaining viscous solution into solid and liquid to obtain a round cake-shaped solid, then rinse the solid three times with deionized water to obtain a catalyst precursor;

[0036] Step (5): Place the washed catalyst precursor in a tubular furnace, set the program to increase the temperature at 10°C / min, and calcine at a constant temperature of 400°C for 2 hours, and adopt a natural cooling method; grind the calcined TiO2 / SiC catalyst, pass it through a 90-mesh sieve, and finally obtain a TiO2 / SiC supported catalyst.

[0037] After preparation, the product was characterized. Figure 2 This is the material scanning electron microscope image of TiO2 / SiC.

[0038] The prepared TiO2 / SiC new catalyst was placed in the harmless treatment platform of SF6 waste gas. Under the conditions of 700℃ and 0.16MPa, 4% SF6 in the mixed gas could be harmlessly treated within 10 hours. Figure 3 As shown, combined with the ideal gas state equation, converted to standard atmospheric pressure is equivalent to 288mL of SF6 waste gas. Therefore, this new type of supported catalyst has great application potential in the future. This preparation method further brings out the excellent catalytic performance of the active ingredient TiO2.

[0039] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for preparing a supported catalyst for thermal catalytic conversion of SF6, characterized in that: The steps include: Titanium dioxide is loaded on the surface of SiC in the form of nano-sized particles, and the mass ratio of titanium dioxide to silicon carbide is 1:

5.

2. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 1, characterized in that: The specific steps include: Step (1): adding a titanium source into a dilute hydrochloric acid solution and stirring; Step (2): adding SiC carrier and stirring; Step (3): adjusting the pH of the solution again and stirring again; Step (4): solid-liquid separation to obtain a catalyst precursor; Step (5): calcine the catalyst precursor obtained in step (4) at 400°C for 2h; and grind it after natural cooling to obtain a TiO2 / SiC supported catalyst.

3. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 2, characterized in that: The titanium source is n-butyl titanate.

4. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 2, characterized in that: The size of the SiC is 1000 mesh.

5. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 2, characterized in that: Step (2) is carried out when the pH of the solution is 2.

6. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 2, characterized in that: In step (3), the pH of the solution is adjusted to 3.

7. The method for preparing a supported catalyst for thermal catalytic conversion of SF6 according to claim 2, characterized in that: In step (5), the temperature is increased to 400°C at a heating rate of 10°C / min.

8. A supported catalyst for thermal catalytic conversion of SF6 prepared by the method for preparing a supported catalyst for thermal catalytic conversion of SF6 as described in any one of claims 1 to 7.

9. Use of a supported catalyst for thermal catalytic conversion of SF6 prepared by the method for preparing a supported catalyst for thermal catalytic conversion of SF6 as described in any one of claims 1 to 7 in harmless treatment of SF6 waste gas.

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