Coal gangue-based catalyst for catalytic combustion of ultralow-concentration gas and preparation method of coal gangue-based catalyst

Abstract

The invention discloses a coal gangue-based catalyst for ultralow-concentration gas catalytic combustion and a preparation method thereof.The preparation method comprises the steps that coal gangue is smashed, washed with water and dried to remove surface impurities, and a treated carrier is obtained; immersing the coal gangue particles into a mixed solution composed of transition metal nitrate and glycine; after soaking is completed, the coal gangue carrier and the nitrate solution are separated out through filtering; putting the filtered and separated coal gangue carrier into a muffle furnace, carrying out combustion reaction, then taking out the coal gangue carrier, and cooling the coal gangue carrier to room temperature; the cooled coal gangue particles are soaked in the mixed solution again, and the soaking-filtering-combustion process is repeated for multiple times till the solution is exhausted; and calcining the coal gangue particles loaded with the active metal oxide in a muffle furnace, and cooling to obtain the coal gangue-based catalyst. The coal gangue catalyst prepared by the method has excellent low-temperature activity and thermal stability, and is suitable for catalytic combustion reaction of ultralow-concentration gas lower than 1vol%.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to a coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas and a preparation method thereof. Background Art

[0002] Coal mine gas is a greenhouse gas mainly composed of methane, and its emission will significantly exacerbate global warming. Due to ventilation in coal mines, the methane concentration of the emitted gas is usually lower than 1 vol%, making it difficult to directly burn and utilize through traditional combustion technologies. Catalytic combustion is an efficient and clean gas treatment technology, and its core lies in the catalyst. Existing catalysts mainly include noble metal catalysts and non-noble metal catalysts. Although noble metal catalysts have high activity, due to their high cost and limited resources, it is difficult to apply them on a large scale; non-noble metal catalysts are inexpensive, but have problems of insufficient low-temperature activity, and most existing catalysts are in powder form, with complex preparation processes and large pressure drops, making them unsuitable for industrial applications. Summary of the Invention

[0003] In order to overcome the defects in the prior art, the present invention provides a coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas and a preparation method thereof, and develops a catalyst with high efficiency, low cost, and strong thermal stability, which is suitable for the catalytic combustion of ultra-low concentration (<1 vol%) gas.

[0004] The technical solution adopted by the present invention is as follows: In the first aspect, the present invention provides a method for preparing a coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas, including the following steps:

[0005] Step S1, carrier pretreatment: After crushing the coal gangue, wash it with water and dry it to remove surface impurities;

[0006] Step S2, soaking: Immerse the coal gangue particles in a mixed solution composed of transition metal nitrate and glycine;

[0007] Step S3, filtration: After soaking, separate the coal gangue carrier and the nitrate solution by filtration;

[0008] Step S4, combustion: Put the coal gangue carrier separated by filtration into a muffle furnace for combustion reaction, and then take it out and cool it to room temperature;

[0009] Step S5, repeated loading: Re-immerse the cooled coal gangue particles in the mixed solution formed in Step S2, and repeatedly perform the soaking-filtration-combustion process multiple times until the solution is exhausted;

[0010] Step S6, calcination: Put the coal gangue particles loaded with active metal oxides into a muffle furnace for calcination, and obtain the coal gangue-based catalyst after cooling.

[0011] As a further improvement of the present invention, in step S1, during the carrier pretreatment process, the particle diameter of the crushed coal gangue is 1 - 8 mm.

[0012] As a further improvement of the present invention, in step S2, the transition metal nitrate used during the soaking process is one or more of Cr(NO3)3·9H2O, Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Cu(NO3)2·3H2O.

[0013] As a further improvement of the present invention, in step S2, the stoichiometric ratio of glycine to nitrate in the mixed solution is 0.1 - 0.5.

[0014] As a further improvement of the present invention, in step S2, the mass of the active metal element in the mixed solution corresponds to 20% - 40% of the mass of the coal gangue.

[0015] As a further improvement of the present invention, in step S4, during the combustion process, the temperature of the muffle furnace is 200 - 300 °C, and the combustion time is 10 - 30 minutes.

[0016] As a further improvement of the present invention, in step S5, the repeated process of soaking - filtering - burning is 8 - 10 times.

[0017] As a further improvement of the present invention, in step S6, the active metal oxide is one or more of Cr2O3, Mn2O3, Fe2O3, Co3O4, NiO, and CuO.

[0018] As a further improvement of the present invention, in step S6, during the calcination process, the temperature of the muffle furnace is 500 - 700 °C, and the calcination time is 2 - 4 hours.

[0019] In the second aspect, the present invention also proposes a coal gangue - based catalyst for catalytic combustion of ultra - low - concentration gas, which is prepared by the above - mentioned preparation method and is used for the catalytic combustion reaction of ultra - low - concentration gas with a methane concentration lower than 1 vol%.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The present invention uses coal gangue as the catalyst, which can reduce industrial waste emissions while significantly reducing the preparation cost of the catalyst; at the same time, coal gangue has good thermal stability and pore structure, and combines well with the active component of metal oxide, improving the overall performance of the catalyst.

[0022] (2) By designing an efficient soaking-filtration-combustion cycle process, the present invention can achieve the uniform distribution of active metal oxides on the surface of the carrier, thereby obtaining high catalytic activity; at the same time, this method is easy to operate and can be implemented in conventional laboratory and industrial production environments, with good scalability;

[0023] (3) Active metal oxides (Cr2O3, Mn2O3, Fe2O3, Co3O4, NiO, CuO) are generated by glycine-assisted solution combustion reaction to ensure the formation of a highly dispersed loading layer on the surface of the coal gangue carrier; in addition, different combinations of metal oxides can be flexibly regulated by adjusting the solution formula to further optimize the low-temperature activity and stability of the catalyst. Description of the Drawings

[0024] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0025] Figure 1 is a physical picture of coal gangue particles;

[0026] Figure 2 is a physical picture of a coal gangue-based catalyst with a NiO loading of 20% prepared by the preparation method of the present invention;

[0027] Figure 3 is an SEM-EDS diagram of the surface of a coal gangue-based NiO catalyst;

[0028] Figure 4 is a graph showing the change of methane conversion rate with temperature of a coal gangue-based NiO catalyst at different methane concentrations;

[0029] Figure 5 is a graph showing the change of methane conversion rate with time of a coal gangue-based NiO catalyst at 460°C;

[0030] Figure 6 is an SEM-EDS image of coal gangue-based Mn2O3, Fe2O3, Co3O4 and CuO catalysts;

[0031] Figure 7 is a curve showing the change of conversion rate of 1 vol% methane combustion with temperature of coal gangue-based Mn2O3, Fe2O3, Co3O4 and CuO catalysts. Detailed Embodiments

[0032] The present invention will be further described below with reference to the drawings and specific embodiments.

[0033]

Example 1

[0034] A preparation method of a coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas includes the following steps:

[0035] Step S1: After crushing the coal gangue to a particle diameter of 1 - 8 mm, rinse it with clean water until the effluent is clear to remove impurities such as sediment on the surface of the coal gangue. Then place it in a drying oven to dry and remove the residual moisture on the surface of the coal gangue, obtaining a pretreated coal gangue carrier;

[0036] Step S2: Prepare a solution using Ni(NO3)2·6H2O and glycine. Among them, Ni is the active element, and glycine serves as the fuel for the combustion reaction. The stoichiometric ratio of glycine to Ni(NO3)2·6H2O is 0.2, and the mass of Ni is 20% of the mass of the coal gangue to be loaded. Then place the coal gangue carrier in the prepared solution and stir to allow the coal gangue to be fully soaked;

[0037] Step S3: After the soaking is completed, separate the coal gangue carrier and the nickel nitrate solution by filtration, and collect the coal gangue carrier adsorbed with the nickel nitrate solution and the filtered nickel nitrate solution respectively;

[0038] Step S4: Put the coal gangue carrier separated by filtration into a muffle furnace, burn it at 250 °C for 20 minutes, and then take it out and cool it to room temperature;

[0039] Step S5: Re - soak the cooled coal gangue particles in the solution, and repeat the soaking - filtration - combustion process about 10 times until the solution is exhausted;

[0040] Step S6: Put the coal gangue particles loaded with NiO into a muffle furnace, heat it from room temperature to 500 °C at a heating rate of 5 °C / min, and calcine it at 500 °C for 4 hours. After cooling, obtain the coal gangue - based catalyst.

[0041] The coal gangue carrier used in this example is as Figure 1 shown, the prepared coal gangue - based NiO catalyst is as Figure 2 shown, and the SEM - EDS image of the catalyst surface is as Figure 3 shown. The active component Ni is evenly loaded on the surface of the coal gangue.

[0042] Using the coal gangue - based NiO catalyst prepared in this example for catalytic combustion experiments of methane with different concentrations (0.1, 0.3, 0.5, 0.7, 1.0 vol%), the experimental results are as Figure 4 shown. For concentrations below 1 vol%, complete conversion can occur at about 470 °C, demonstrating excellent catalytic activity.

[0043] Using the coal gangue - based NiO catalyst prepared in this example in an environment of 460 °C and a methane concentration of 1 vol% for a long - cycle catalytic combustion experiment of 60 hours, the experimental results are as Figure 5 shown. After 60 hours, the methane conversion rate has no obvious decrease, demonstrating excellent thermal stability.

[0044]

Example 2

[0045] In this example, the nitrate used is Fe(NO3)3·9H2O. The SEM-EDS images of the surface of the coal gangue-based Fe2O3 catalyst are as Figure 6 shown, and the active components are evenly distributed. The activity of the catalyst is as Figure 7 shown, demonstrating excellent activity.

[0046]

Example 3

[0047] In this example, the nitrate used is Co(NO3)2·6H2O, and the Co element loading is 30%. The SEM-EDS images of the surface of the coal gangue-based Co3O4 catalyst are as Figure 6 shown, and the active components are evenly distributed. The activity of the catalyst is as Figure 7 shown, demonstrating excellent activity.

[0048]

Example 4

[0049] In this example, the nitrate used is Mn(NO3)2·4H2O, and the combustion temperature is 300°C. The SEM-EDS images of the surface of the coal gangue-based Mn2O3 catalyst are as Figure 6 shown, and the active components are evenly distributed. The activity of the catalyst is as Figure 7 shown, demonstrating excellent activity.

[0050]

Example 5

[0051] In this example, the nitrate used is Cu(NO3)2·3H2O, and the calcination temperature is 600°C. The SEM-EDS images of the surface of the coal gangue-based CuO catalyst are as Figure 6 shown, and the active components are evenly distributed. The activity of the catalyst is as Figure 7 shown, demonstrating excellent activity.

[0052] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. All changes that can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas, characterized in that, It includes the following steps: Step S1, carrier pretreatment: After crushing the coal gangue, wash it with water and dry it to remove surface impurities; Step S2, soaking: Immerse the coal gangue particles in a mixed solution composed of transition metal nitrate and glycine; Step S3, filtration: After soaking, separate the coal gangue carrier and the nitrate solution by filtration; Step S4, combustion: Put the coal gangue carrier separated by filtration into a muffle furnace for combustion reaction, and then take it out and cool it to room temperature; Step S5, repeated loading: Re-immerse the cooled coal gangue particles in the mixed solution formed in Step S2, and repeatedly perform the soaking-filtration-combustion process multiple times until the solution is exhausted; Step S6, calcination: Put the coal gangue particles loaded with active metal oxide into a muffle furnace for calcination, and obtain the coal gangue-based catalyst after cooling.

2. The preparation method according to claim 1, characterized in that In Step S1, during the carrier pretreatment process, the particle diameter of the crushed coal gangue is 1-8 mm.

3. The preparation method according to claim 1, characterized in that, In Step S2, the transition metal nitrate used during the soaking process is one or more of Cr(NO3)3·9H2O, Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Cu(NO3)2·3H2O.

4. The preparation method according to claim 1, characterized in that, In Step S2, the stoichiometric ratio of glycine to nitrate in the mixed solution is 0.1-0.

5.

5. The preparation method according to claim 1, characterized in that, In Step S2, the mass of the active metal element in the mixed solution corresponds to 20%-40% of the mass of the coal gangue.

6. The preparation method according to claim 1, characterized in that, In Step S4, during the combustion process, the temperature of the muffle furnace is 200-300 °C, and the combustion time is 10-30 minutes.

7. The preparation method according to claim 1, characterized in that, In Step S5, the repeated process of soaking-filtration-combustion is 8-10 times.

8. The preparation method according to claim 1, wherein, In Step S6, the active metal oxide is one or more of Cr2O3, Mn2O3, Fe2O3, Co3O4, NiO, and CuO.

9. The preparation method according to claim 1, wherein, In Step S6, during the calcination process, the temperature of the muffle furnace is 500-700 °C, and the calcination time is 2-4 hours.

10. A coal gangue-based catalyst for catalytic combustion of ultra-low concentration gas, prepared by using the preparation method described in any one of Claims 1-8, and used for the catalytic combustion reaction of ultra-low concentration gas with a methane concentration lower than 1 vol%.

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