Preparation method of Co3O4 catalyst and application of Co3O4 catalyst in catalytic decomposition of sulfur-containing VOCs

Abstract

The invention belongs to the technical field of organic sulfur pollutant treatment, and particularly relates to a preparation method of a Co3O4 catalyst and application of the Co3O4 catalyst in catalytic decomposition of sulfur-containing VOCs. The invention provides a nano-structure Co3O4 catalyst with regular geometrical characteristics, and a preparation method comprises the following steps: mixing a cobalt source with water to obtain a mixed solution, adding an alkali liquor into the mixed solution, stirring, then carrying out a hydrothermal reaction, collecting a solid product after the reaction, washing, drying and roasting, wherein the mixed solution also comprises a surfactant and a dispersing aid. Co3O4 catalysts with different morphologies are prepared by regulating and controlling the concentration and dosage of the alkali liquor and the dosage of cobalt nitrate, the metal oxide is directly used as the catalyst, the inherent structure of a traditional supported catalyst is broken through, and the activity and stability of the catalyst are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic sulfur pollutant treatment, and more specifically relates to a preparation method of a Co3O4 catalyst and its application in catalytic decomposition of sulfur-containing VOCs. Background Art

[0002] Due to the rapid economic development and the continuous expansion of industrial production scale, the problem of atmospheric environmental pollution has become increasingly prominent, but there are relatively few measures for the problem of atmospheric malodor pollution. Atmospheric sulfur-containing malodor pollutants (such as methanethiol and ethanethiol) mainly come from industries such as petroleum, natural gas, chemical industry, sewage treatment, landfill, and food processing. Sulfur-containing malodor pollutants have characteristics such as a low olfactory threshold and a strong odor. Long-term exposure will not only cause damage to human health such as the respiratory system and nervous system, but may also lead to environmental pollution problems such as acid rain and damage to the ecological system. Therefore, the development of an efficient sulfur-containing malodor pollutant removal technology is crucial for both health and the environment.

[0003] Currently, the treatment methods for sulfur-containing malodor pollutants include adsorption method, absorption method, biodegradation method, combustion method, catalytic oxidation method, and catalytic decomposition method, etc. The adsorption method has simple equipment and convenient operation, but the adsorbent needs to be replaced regularly or regenerated, increasing the operating cost; the absorption method has high efficiency, mature technology, and wide application, but it will produce a large amount of wastewater causing secondary pollution; the biodegradation method is environmentally friendly and has low operating cost, but the reaction rate is slow and the treatment efficiency is relatively low; the combustion method has high treatment efficiency and is suitable for high-concentration sulfur-containing pollutants, but it has high energy consumption and will produce sulfur dioxide, which needs further treatment; the catalytic oxidation method has mild reaction conditions and high treatment efficiency, and is suitable for various sulfur-containing compounds, but the cost of the oxidant is high and the operating cost is relatively high.

[0004] These treatment methods focus on the removal of single components of inorganic sulfur and organic sulfur, and it is difficult to solve the problem of the simultaneous presence of multiple components of sulfur-containing pollutants in the real environment. The catalytic decomposition method has the advantages of high efficiency, energy saving, simple operation, no harmful by-products, good economy, and wide application, and is an ideal treatment technology. Currently, the catalysts for catalytic decomposition of sulfur-containing pollutants are mainly supported catalysts such as rare earth-coupled zeolite catalysts (such as CeO2 / ZSM-5, etc.) and metal oxide-supported catalysts (MoO3 / SiO2), etc. The catalytic operation cost is relatively low, but there is generally a problem of relatively low catalytic activity (generally requiring more than 400 °C to be completely converted). Therefore, it is urgent to develop a catalyst that can efficiently treat double-component sulfur-containing pollutants simultaneously. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a Co3O4 catalyst and its application in catalytic decomposition of sulfur-containing VOCs. More specifically, it provides a Co3O4 catalyst with a nanostructure having regular geometric features, its preparation method and application, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: Provide a Co3O4 catalyst with a nanostructure having regular geometric features, and the Co3O4 catalyst includes at least one of Co3O4 with hexagonal nanosheets, Co3O4 with a cubic structure, Co3O4 with a truncated octahedral structure, and Co3O4 with an octahedral structure.

[0008] Another technical solution of the present invention: Provide a preparation method of the above Co3O4 catalyst with a nanostructure having regular geometric features, and the steps include:

[0009] Mix a cobalt source with water to obtain a mixed solution;

[0010] Add an alkali solution to the mixed solution, stir, and then carry out a hydrothermal reaction. After the reaction, collect the solid product, wash, dry and then calcine to obtain the Co3O4 catalyst.

[0011] Further, the cobalt source includes Co(NO3)2·6H2O and / or Co(CH3COO)2·4H2O.

[0012] Further, the dosage ratio of the cobalt source to water is 0.01 - 0.2 mol : 15 - 20 mL.

[0013] Further, the alkali solution is a sodium hydroxide solution with a concentration of 0.01 - 0.4 mol / L.

[0014] Further, the dosage ratio of the cobalt source to the alkali solution is 0.01 - 0.2 mol : 20 - 75 mL.

[0015] Further, the stirring time is 2 - 6 h.

[0016] Further, the temperature of the hydrothermal reaction is 80 - 240 °C, and the time is 4 - 16 h.

[0017] Further, the washing is to wash at least once with deionized water and ethanol.

[0018] Further, the drying is vacuum drying at a temperature of 60 °C.

[0019] Further, the calcination temperature is 450 - 500 °C, and the time is 2 - 3 h.

[0020] Furthermore, the mixed solution further includes a surfactant and a dispersion aid.

[0021] Optionally, the surfactant includes polyvinylpyrrolidone.

[0022] Optionally, the dispersion aid includes ethanol.

[0023] Optionally, the dosage ratio of the cobalt source, the dispersion aid and the surfactant in the mixed solution is 0.01 - 0.2 mol : 15 mL : 3 g.

[0024] By adding the dispersion aid and the surfactant, the dispersion of the raw materials is promoted, and then hexagonal nanosheet-shaped Co3O4 with regular morphology is generated.

[0025] The third technical solution of the present invention: Provide an application of the above Co3O4 catalyst with a nanostructure having regular geometric features in reducing the reaction temperature of catalytic decomposition of sulfur-containing VOCs pollutants.

[0026] Furthermore, the sulfur-containing VOCs pollutants include VOCs pollutants containing methanethiol and / or ethanethiol.

[0027] In a preferred embodiment of the present invention, nanostructured Co3O4 with different regular geometric features is prepared by regulating the concentration and dosage of the alkali solution and the dosage of cobalt nitrate. Ethanol is used as a solvent (dispersion aid), which affects the dissolution and dispersion of the reactants. The surfactant PVP is beneficial to the uniform dispersion of the material, prevents the material from agglomerating, and helps to generate a uniform and regularly shaped material. Then, the directly obtained nanostructured Co3O4 with different regular geometric features is used as a catalyst, achieving the technical effects of significantly improving the degradation rate and efficiency of sulfur-containing VOCs pollutants at a medium temperature (220 - 350 °C), reducing the temperature at which the degradation rate of methanethiol and / or ethanethiol reaches 100%, increasing the service life of Co3O4 as a catalyst, breaking the inherent structure of traditional supported catalysts, and enhancing the activity and stability of the catalyst.

[0028] The fourth technical solution of the present invention: Provide a method for medium-temperature degradation of sulfur-containing VOCs, the steps including: catalytically degrading the sulfur-containing VOCs with the above Co3O4 catalyst having a nanostructure with regular geometric features in the temperature range of 220 - 350 °C.

[0029] Furthermore, the sulfur-containing VOCs include VOCs containing methanethiol and / or ethanethiol.

[0030] Furthermore, during the catalytic degradation process, the space velocity of the sulfur-containing VOCs is 9000 - 15000 mLg -1 h -1 .

[0031] Fifth technical solution of the present invention: Provide a method for improving the degradation rate of sulfur-containing VOCs by Co3O4 catalyst under medium temperature conditions, using Co3O4 with nanostructures having regular geometric features as the catalyst; the medium temperature conditions are 220 - 350 °C; the Co3O4 with nanostructures having regular geometric features includes at least one of Co3O4 with hexagonal nanosheets, Co3O4 with cubic structure, Co3O4 with truncated octahedron structure, and Co3O4 with octahedron structure.

[0032] The present invention discloses the following technical effects:

[0033] The Co3O4 catalyst prepared in the present invention has unique hexagonal nanosheets and octahedron structures, has a larger specific surface area and pore size compared to commercial Co3O4, and also has more acidic sites, basic sites, and active oxygen species, which is very beneficial for the degradation of sulfur-containing VOCs and has good application prospects.

[0034] The Co3O4 catalyst with hexagonal nanosheets and octahedron structures prepared in the present invention shows excellent low-temperature activity in the catalytic decomposition of sulfur-containing VOCs. Single-component methanethiol is completely degraded at 225 °C, and binary-component methanethiol is completely degraded at 250 °C; single-component ethanethiol is completely degraded at 250 °C, and binary-component ethanethiol is completely degraded at 225 °C; the activity of traditional zeolite molecular sieves (such as H-ZSM-5) and metal oxide-supported catalysts in decomposing sulfur-containing VOCs at 225 °C is only about 45%, and it usually takes 400 °C to completely degrade sulfur-containing VOCs. It can be seen that generally, the sulfur-containing VOCs mixed components are usually in a competitive relationship, while using the catalyst prepared in the present invention to catalytically degrade the sulfur-containing VOCs mixed components, the sulfur-containing VOCs mixed components are in a promoting relationship.

[0035] The different morphology Co3O4 catalysts prepared in the present invention catalytically decompose sulfur-containing VOCs at normal pressure and 350 °C. Among them, the complete conversion life of single-component methanethiol is up to 10 h, and the complete conversion life of binary-component methanethiol is 7 h; the life of single-component ethanethiol is up to 7 h, and the complete conversion life of binary-component ethanethiol is 9.5 h. This is far higher than the metal oxides reported in the existing literature, and their life is generally 1 - 3 h.

[0036] The preparation method provided by the present invention can obtain Co3O4 catalysts with different morphologies, shows excellent activity and stability in the application of sulfur-containing VOCs removal, and has practical application prospects. Description of the Drawings

[0037] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 SEM images of Co3O4-hexagonal nanosheets, Co3O4-octahedra, and Co3O4-commercial nanosheet catalysts, where a is Co3O4-hexagonal nanosheets, b is Co3O4-octahedra, and c is Co3O4-commercial nanosheet catalysts.

[0039] Figure 2 Catalytic activity diagrams for the catalytic decomposition of single-component methanethiol gas, single-component ethanethiol gas, and binary gas, where a is single-component methanethiol gas, b is single-component ethanethiol gas, and c is binary gas.

[0040] Figure 3 Stability diagrams of the catalyst during the catalytic decomposition of methanethiol gas, low-concentration methanethiol gas, single-component ethanethiol gas, and binary gas, where a is the catalytic decomposition of methanethiol gas, b is the catalytic decomposition of low-concentration methanethiol gas, c is the catalytic decomposition of single-component ethanethiol gas, and d is the catalytic decomposition of binary gas.

[0041] Figure 4 Catalytic activity diagrams of the catalysts prepared in Examples 2-4. It can be seen from the figure that the catalysts prepared in Examples 3-4 also have excellent catalytic activity. Detailed Description of the Invention

[0042] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the present invention.

[0043] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0044] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0045] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0046] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0047] It should be noted that the aspects not detailed in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0048] Unless otherwise specified, the "room temperature" and "normal temperature" involved in the specific embodiments of the present invention both refer to 20 - 30 °C.

[0049] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0050] The Co3O4 - commercial nanosheet catalyst was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0051] Example 1

[0052] The preparation steps of the hexagonal nanosheet Co3O4 catalyst include:

[0053] S1. Weigh 3.6 g of Co(NO3)2·6H2O and completely dissolve it in 15 mL of deionized water and 15 mL of ethanol. Then add 3 g of polyvinylpyrrolidone (PVP) as a surfactant and stir at room temperature for 30 min to obtain a mixed solution;

[0054] S2. Drop 75 mL of sodium hydroxide aqueous solution (0.4 mol / L) into the mixed solution obtained in step S1, continue to stir for 3 h, then transfer it to a high - pressure reaction kettle, carry out a hydrothermal reaction at 120 °C for 10 h, cool it, and centrifuge to collect the solid product. Wash it 3 times with deionized water and 2 times with ethanol to obtain the cobalt tetroxide precursor β - Co(OH)2;

[0055] S3. Vacuum - dry the cobalt tetroxide precursor β - Co(OH)2 obtained in step S2 at 60 °C overnight, and then calcine it in a muffle furnace at 450 °C for 2 h to obtain the hexagonal nanosheet Co3O4 catalyst, denoted as Co3O4 - hexagonal nanosheet.

[0056] Example 2

[0057] The preparation steps of the octahedral - structured Co3O4 catalyst include:

[0058] Weigh 0.2 mol of Co(NO3)2·6H2O and mix it evenly with 20 mL of deionized water. Then, slowly drip 20 mL of sodium hydroxide aqueous solution (0.05 mol / L) into it, stir for 3 h, and then transfer it to a high-pressure reaction kettle. Carry out hydrothermal reaction at 180 °C for 5 h. After cooling, centrifuge to collect the solid product, wash it 3 times with deionized water and 2 times with ethanol. Then, dry it overnight in a vacuum at 60 °C, and calcine it in a muffle furnace at 500 °C for 3 h to obtain cobalt tetroxide hexagonal octahedrons, denoted as Co3O4-octahedrons.

[0059] Figure 1 Figure 4 shows the SEM images of Co3O4-hexagonal nanosheets, Co3O4-octahedrons and Co3O4-commercial nanosheet catalysts. Among them, a is Co3O4-hexagonal nanosheets, b is Co3O4-octahedrons, and c is Co3O4-commercial nanosheet catalysts.

[0060] As can be seen from Figure 1 Figure 4, the Co3O4-hexagonal nanosheet catalyst shows an obvious hexagonal nanosheet morphology with a diameter of about 250 - 300 nm, and more defects can be seen on the surface, indicating the successful preparation of the catalyst; the Co3O4-octahedron catalyst shows an obvious octahedral morphology with a diameter of about 150 nm, also indicating the successful preparation of the catalyst. While the diameter of Co3O4-commercial is about 500 nm and there are almost no defects on the surface.

[0061] Effect Example 1

[0062] Activity experiment:

[0063] Grind Co3O4-hexagonal nanosheets, Co3O4-octahedrons and Co3O4-commercial nanosheet catalysts to a particle size between 40 - 60 mesh respectively, and load them into a fixed-bed reactor. The loading mass of the catalyst is 0.2 g. Pass a single-component methanethiol gas with a concentration of 5000 ppm, a single-component ethanethiol gas with a concentration of 5000 ppm or a two-component gas (2500 ppm ethanethiol gas and 2500 ppm methanethiol gas) into the fixed-bed reactor, and control the feed mass space velocity to be 9000 mLg -1 h -1 , the reaction system pressure is atmospheric pressure, and the reaction temperature is 150 - 450 °C. Carry out a catalytic degradation catalytic activity evaluation experiment. For the single-component methanethiol gas degradation activity evaluation experiment, use CeO2-commercial as a control. The results are as Figure 2 shown.

[0064] Figure 2 Figure 5 shows the catalytic activity diagrams for the catalytic decomposition of single-component methanethiol gas, single-component ethanethiol gas and two-component gas. Among them, a is single-component methanethiol gas, b is single-component ethanethiol gas, and c is two-component gas. As can be seen from Figure 2It can be seen that:

[0065] When the catalyst is Co3O4 - hexagonal nanosheets, at a reaction temperature of 225 °C, the conversion rate of methanethiol can reach 100%; at a reaction temperature of 225 °C, the conversion rate of single - component ethanethiol is 97.98%; at a reaction temperature of 250 °C, the conversion rate of ethanethiol can reach 100%; when the treated gas is a binary gas of methanethiol and ethanethiol, the complete conversion temperature of methanethiol is 250 °C, and the complete conversion temperature of ethanethiol is 225 °C.

[0066] When the catalyst is Co3O4 - octahedron, when the treated gas is single - component methanethiol, the complete conversion temperature is 250 °C; when the treated gas is single - component ethanethiol, the complete conversion temperature is 300 °C; when the treated gas is a binary gas of methanethiol and ethanethiol, the complete conversion temperature of methanethiol is 300 °C, and the complete conversion temperature of ethanethiol is 250 °C.

[0067] When the catalyst is Co3O4 - commercial nanosheet catalyst, the complete conversion temperature of single - component ethanethiol is 450 °C; at a reaction temperature of 300 °C, the conversion rate of methanethiol can reach 100%; the complete conversion temperature of binary methanethiol is 350 °C, and the complete conversion temperature of binary ethanethiol is 300 °C. When the catalyst is CeO2 - commercial, its complete conversion temperature for single - component methanethiol gas is as high as 450 °C.

[0068] Catalyst stability (life) experiment:

[0069] The Co3O4 - hexagonal nanosheets, Co3O4 - octahedron and Co3O4 - commercial nanosheet catalysts were respectively ground to a particle size between 40 - 60 mesh, filled in a fixed - bed reactor, and the catalyst filling mass was 0.2 g. A single - component methanethiol gas with a concentration of 5000 ppm (350 °C), a single - component methanethiol gas with a concentration of 100 ppm (room temperature), a single - component ethanethiol gas with a concentration of 5000 ppm (350 °C) or a binary gas (2500 ppm ethanethiol gas and 2500 ppm methanethiol gas, 350 °C) was introduced into the fixed - bed reactor, and the feed mass space velocity was controlled at 9000 mlg -1 h -1 , and the reaction system pressure was at atmospheric pressure. The catalyst stability (life) experiment was carried out, and the results are as Figure 3 shown.

[0070] Figure 3 It is the stability diagram of the catalyst when catalyzing the decomposition of methanethiol gas, low - concentration methanethiol gas, single - component ethanethiol gas and binary gas. Among them, a is for catalyzing the decomposition of methanethiol gas, b is for catalyzing the decomposition of low - concentration methanethiol gas, c is for catalyzing the decomposition of single - component ethanethiol gas, and d is for catalyzing the decomposition of binary gas. It can be seen from Figure 3 It can be seen that:

[0071] When the catalyst is Co3O4 - hexagonal nanosheet catalyst, the Co3O4 - hexagonal nanosheet has a complete degradation stability of up to 5 h for high - concentration methanethiol (5000 ppm) at 350 °C and a complete degradation stability of up to 10 h for low - concentration methanethiol (100 ppm); the Co3O4 - hexagonal nanosheet catalyst has a complete degradation stability of up to 7 h for ethanethiol at 350 °C; the Co3O4 - hexagonal nanosheet catalyst has a complete decomposition stability of up to 7 h for binary - component methanethiol and a complete decomposition stability of up to 9.5 h for binary - component ethanethiol at 350 °C. When the catalyst is Co3O4 - octahedron catalyst, the Co3O4 - octahedron catalyst has a complete degradation stability of up to 4.5 h for methanethiol at 350 °C; the Co3O4 - octahedron catalyst has a complete degradation stability of up to 7 h for ethanethiol at 350 °C; the Co3O4 - octahedron catalyst has a complete decomposition stability of up to 4.5 h for binary - component methanethiol and a complete decomposition stability of up to 6.5 h for binary - component ethanethiol at 350 °C. When the catalyst is Co3O4 - commercial catalyst, the Co3O4 - commercial catalyst cannot completely degrade methanethiol at 350 °C; the Co3O4 - commercial catalyst cannot completely degrade ethanethiol at 350 °C; the Co3O4 - commercial catalyst cannot completely degrade binary - component methanethiol / ethanethiol at 350 °C.

[0072] The catalyst prepared in the present invention has a hexagonal nanosheet or octahedron structure. Among them, the Co3O4 hexagonal nanosheet catalyst exhibits excellent catalytic decomposition ability and stability for sulfur - containing VOCs due to its outstanding oxygen storage capacity.

[0073] Example 3

[0074] Compared with Example 2, the difference is that the amount of Co(NO3)2·6H2O is 0.04 mol, the concentration of the alkali solution is 0.01 mol / L, and the prepared product has a cubic structure, denoted as Co3O4 - cube.

[0075] Example 4

[0076] Compared with Example 2, the difference is that the amount of Co(NO3)2·6H2O is 0.08 mol, the concentration of the alkali solution is 0.01 mol / L, and the prepared product has a truncated octahedron structure, denoted as Co3O4 - truncated octahedron.

[0077] Figure 4 It is the catalytic activity diagram of the catalysts prepared in Examples 2 - 4. As can be seen from the figure, the catalysts prepared in Examples 3 - 4 also have excellent catalytic activity.

[0078] In the present specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

[0079] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Co3O4 catalyst with nanostructures having regular geometric features, characterized in that, The Co3O4 catalyst includes at least one of Co3O4 with hexagonal nanosheets, Co3O4 with cubic structure, Co3O4 with truncated octahedron structure, and Co3O4 with octahedron structure.

2. A method for preparing a Co3O4 catalyst with nanostructures having regular geometric features as described in claim 1, characterized in that the steps Comprising: Mixing a cobalt source with water to obtain a mixed solution; Adding an alkali solution to the mixed solution, stirring, then carrying out a hydrothermal reaction, collecting the solid product after the reaction, washing, drying, and then calcining to obtain the Co3O4 catalyst.

3. The preparation method according to claim 2, characterized in that, The cobalt source includes Co(NO3)2·6H2O and / or Co(CH3COO)2·4H2O; and / or, the dosage ratio of the cobalt source to water is 0.01 - 0.2 mol: 15 - 20 mL; and / or, the alkali solution is a sodium hydroxide solution with a concentration of 0.01 - 0.4 mol / L; and / or, the dosage ratio of the cobalt source to the alkali solution is 0.01 - 0.2 mol: 20 - 75 mL.

4. The preparation method according to claim 2, wherein, The stirring time is 2 - 6 h; and / or, the temperature of the hydrothermal reaction is 80 - 240 °C, and the time is 4 - 16 h; and / or, the washing is at least once with deionized water and ethanol; and / or, the drying is vacuum drying at a temperature of 60 °C; and / or, the calcination temperature is 450 - 500 °C, and the time is 2 - 3 h.

5. The preparation method according to claim 2, characterized in that, The mixed solution further includes a surfactant and a dispersion aid.

6. The preparation method according to claim 5, characterized in that, The surfactant includes polyvinylpyrrolidone; and / or, the dispersion aid includes ethanol; and / or, the dosage ratio of the cobalt source, dispersion aid, and surfactant in the mixed solution is 0.01 - 0.2 mol: 15 mL: 3 g.

7. Application of the Co3O4 catalyst with a nanostructure having regular geometric features as described in claim 1 in reducing the reaction temperature of catalytic decomposition of sulfur-containing VOCs pollutants.

8. The application according to claim 7, wherein The sulfur-containing VOCs pollutants include VOCs containing methanethiol and / or ethanethiol.

9. A method for the medium-temperature degradation of sulfur-containing VOCs, characterized in that the steps Comprising: Catalytically degrading the sulfur-containing VOCs within the temperature range of 220 - 350 °C with the Co3O4 catalyst having a nanostructure with regular geometric features as described in claim 1; The sulfur-containing VOCs include VOCs containing methanethiol and / or ethanethiol.

10. A method for improving the degradation rate of sulfur-containing VOCs by Co3O4 catalyst under medium-temperature conditions, characterized in that, Using Co3O4 with a nanostructure having regular geometric features as a catalyst; the medium temperature condition is 220 - 350 °C; the Co3O4 with a nanostructure having regular geometric features includes at least one of Co3O4 with hexagonal nanosheets, Co3O4 with cubic structure, Co3O4 with truncated octahedron structure, and Co3O4 with octahedron structure.

Images