Microwave dehydrogenation catalyst and method for preparing the same

Abstract

This invention relates to the field of microwave catalysts, and discloses a microwave dehydrogenation catalyst and its preparation method. The microwave dehydrogenation catalyst comprises a metal and / or metal oxide, and silicon carbide; wherein the catalyst has a columnar structure, and along its height direction, the catalyst is divided into n layers of a honeycomb structure, where n ≥ 4, and each honeycomb structure has a pore density of 3-23 pores / cm². 2 The through-holes are staggered between any two adjacent honeycomb structures. The microwave dehydrogenation catalyst provided by this invention has high bed porosity, low bed pressure drop, and high heat transfer efficiency with inert gas. The microwave catalyst with a designable microstructure is obtained using 3D printing, and the preparation process is simple and controllable. Compared with traditional catalysts, it can significantly improve the yield of low-carbon olefins.

Description

Technical Field

[0001] This invention relates to the field of microwave catalysts, and more specifically to a microwave dehydrogenation catalyst and its preparation method. Background Technology

[0002] For a long time, my country has used naphtha to produce low-carbon olefin products. With the increasing scale of petrochemical production facilities, the processing capacity of a single oil refining unit in my country has exceeded 10 million tons per year, while the ethylene production capacity of the supporting ethylene units has reached 800,000 to 1.2 million tons per year. However, with the dwindling petrochemical resources, the production cost of the crude oil-based petrochemical industry has been increasing year by year. Against this backdrop, the development of a wider range of low-carbon olefin feedstock resources has attracted widespread attention from chemical companies worldwide. Microwaves are a highly efficient and clean heating energy source, providing a green and efficient solution to the high energy and material consumption of existing catalytic reactions. However, the catalytic effect of traditional catalysts in microwave catalysis is not ideal.

[0003] Currently, catalysts used in petrochemical industries are typically in the form of plates, rings, spheres, etc. To overcome the shortcomings of traditional catalyst beds with small porosity and large pressure drop, patent CN201871380U proposed a hollow toothed spherical support design. While this can increase the catalyst bed porosity and reduce the catalyst bed pressure drop, it also reduces the mass and heat transfer between the catalyst and reactants during the reaction process. Therefore, there is an urgent need to find a novel catalyst suitable for microwave catalysis, with high bed porosity, low pressure drop, and favorable mass and heat transfer between the catalyst and reactants. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of small porosity and large pressure drop in existing microwave catalytic dehydrogenation catalyst beds, poor mass and heat transfer between catalyst and reactants, and low yield of low-carbon olefins, and to provide a microwave dehydrogenation catalyst and its preparation method.

[0005] To achieve the above objectives, the present invention provides a microwave dehydrogenation catalyst, wherein the catalyst comprises a metal and / or a metal oxide, and silicon carbide;

[0006] The catalyst has a columnar structure and is divided into n layers of honeycomb structure along its height, where n ≥ 4, and each layer of honeycomb structure has a pore density of 3-23 pores / cm². 2 through holes;

[0007] In this structure, the through-holes of any two adjacent honeycomb layers are staggered with each other.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned microwave dehydrogenation catalyst, comprising the following steps:

[0009] (1) Impregnate silicon carbide powder with solution D containing active metal;

[0010] (2) The product obtained in step (1) is dried under an inert atmosphere to obtain supported silicon carbide powder.

[0011] (3) The supported silicon carbide powder is printed into shape using 3D printing technology;

[0012] (4) Activate the shaped catalyst obtained in step (3) under an oxidizing or reducing atmosphere.

[0013] The microwave dehydrogenation catalyst provided by this invention is divided into n-layer honeycomb structure, with high bed porosity, low bed pressure drop, and high heat transfer efficiency with inert gas.

[0014] This invention uses 3D printing to obtain microwave catalysts with designable microstructures. The preparation process is simple and controllable, and it can significantly improve the yield of low-carbon olefins compared with traditional catalysts. Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the layer-by-layer disassembly of the microstructure of the catalyst prepared by 3D printing in Example 1;

[0016] Figure 2 This is a schematic diagram of the pore offset structure of the upper and lower honeycomb structures of the catalyst prepared by 3D printing in Example 1, as observed from the top of the catalyst. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] In this invention, unless otherwise stated, the term "height direction" in the specification refers to the direction of extension of the central axis of the column of the catalyst, "top of the catalyst" refers to the two end faces of the column perpendicular to the central axis of the column, and directional terms such as "upper" and "lower" refer to the relative positions along the height direction.

[0019] The present invention provides a microwave dehydrogenation catalyst, wherein the catalyst comprises a metal and / or a metal oxide, and silicon carbide;

[0020] The catalyst has a columnar structure and is divided into n layers of honeycomb structure along its height, where n ≥ 4, and each layer of honeycomb structure has a pore density of 3-23 pores / cm². 2 through holes;

[0021] In this structure, the through-holes of any two adjacent honeycomb layers are staggered with each other.

[0022] The catalyst provided in this invention is composed of n-layer honeycomb structures. Each honeycomb structure has vertically distributed through-holes, and the through-holes of adjacent honeycomb structures are staggered to form tortuous microchannels. Along the height direction, the catalyst is composed of 6-layer honeycomb structures. A schematic diagram of layer-by-layer disassembly is shown below. Figure 1 As shown, the pore density of each layer of the honeycomb structure is 14-15 pores / cm². 2 In any two adjacent honeycomb structures, the center of the hole in the lower honeycomb structure is offset relative to the corresponding center of the hole in the upper honeycomb structure along the length of the hole's side. This offset is 0.1-0.8 times the length of the hole's side. For example, the visible offset of the holes in the upper and lower honeycomb structures when viewed from the top is as follows: Figure 2 As shown. By increasing the catalyst porosity and utilizing the staggered pore walls of each honeycomb structure to provide more active sites, segmented and regional reactions in the bed can be achieved, further improving the olefin yield of alkane dehydrogenation to produce low-carbon olefins.

[0023] According to a preferred embodiment of the present invention, the number of layers n in the honeycomb structure is 4-12, preferably 6-10. Under the above preferred conditions, it is beneficial to improve the contact efficiency between the catalyst and the material.

[0024] According to the present invention, the through-holes of the honeycomb structure can be selected as any regular opening shape. Preferably, the through-holes of the honeycomb structure are selected from one or more of the following: circular, equilateral triangular, square, and regular hexagonal cross-sections. In the above preferred cases, a larger specific surface area can be obtained, further increasing the active sites of the catalyst.

[0025] According to the present invention, in the catalyst, there is no specific limitation on the direction in which the through holes of any two adjacent honeycomb structures are staggered, as long as the above-mentioned structural requirements are met. In any two adjacent honeycomb structures, the offset direction of the hole center of the lower honeycomb structure relative to the corresponding hole center of the upper honeycomb structure can be the same or different. For example, along the height direction of the catalyst, the hole centers of each honeycomb structure layer can be successively offset in the same direction to form a stepped, partially overlapping honeycomb hole structure. Preferably, in any two adjacent honeycomb structures, the hole center of the through hole in the lower honeycomb structure is offset along the hole side length or hole diameter direction relative to the hole center of the corresponding through hole in the upper honeycomb structure.

[0026] According to a preferred embodiment of the present invention, the offset of the center of the through hole in the honeycomb structure is 0.1-0.8 times the side length or diameter of the hole, preferably 0.1-0.5 times, and more preferably 0.1, 0.125, 0.25, 0.33, or 0.5 times.

[0027] According to the present invention, the size of the catalyst can be controlled according to the specific catalytic reaction requirements, for example, it can be packed as a monolithic catalyst or packed with small-sized catalyst particles. When packed as small-sized catalyst particles, the diameter of the catalyst is preferably 5-10 mm and the height is 5-10 mm; more preferably, the diameter of the catalyst is 6-8 mm and the height is 6-8 mm. In the above preferred cases, it is beneficial to increase the porosity and specific surface area of ​​the overall catalytic system and reduce the packing density, which further helps to reduce the reactor pressure drop and increase the reaction space velocity.

[0028] According to a preferred embodiment of the present invention, the metal element in the metal and metal oxide is selected from at least one element of Group VB, Group VIII, and Group IB, preferably at least one of vanadium, niobium, tantalum, iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, silver, and gold, and more preferably at least one of platinum, gold, palladium, silver, copper, nickel, and vanadium. By employing the above preferred embodiment, the reactivity can be further improved.

[0029] According to a preferred embodiment of the present invention, the content of the metal and / or metal oxide, based on the total amount of catalyst and in terms of elements, is 0.1-10% by mass; preferably 0.1-5% by mass.

[0030] According to a preferred embodiment of the present invention, the silicon carbide content is 90-99.9% by mass, based on the total amount of catalyst; preferably 95-99.9% by mass. In the above preferred embodiment, it is beneficial to improve the reactivity.

[0031] Another aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0032] (1) Impregnate silicon carbide powder with solution D containing active metal;

[0033] (2) The product obtained in step (1) is dried under an inert atmosphere to obtain supported silicon carbide powder;

[0034] (3) The supported silicon carbide powder is printed into shape using 3D printing technology;

[0035] (4) Activate the shaped catalyst obtained in step (3) under an oxidizing or reducing atmosphere.

[0036] In this invention, silicon carbide powder is first impregnated with a solution D containing active metal, which helps to improve the dispersion of active metal. Then, it is 3D printed to form a low-pressure-drop porous catalyst quickly.

[0037] According to a preferred embodiment of the present invention, the active metal is selected from at least one element of Group VB, Group VIII, and Group IB, preferably at least one of vanadium, niobium, tantalum, iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, silver, and gold, and more preferably at least one of platinum, gold, palladium, silver, copper, nickel, and vanadium.

[0038] According to a preferred embodiment of the present invention, the molar concentration of the active metal in solution D is 0.1-10%, preferably 0.1-5%, with the remainder being solvent. In this invention, there are no specific requirements regarding the type of solvent, as long as it can sufficiently disperse the active metal and does not participate in the reaction. Preferably, the solvent is water and / or oxalic acid.

[0039] According to a preferred embodiment of the present invention, the immersion conditions include an immersion time of 30-180 min.

[0040] According to a preferred embodiment of the present invention, the drying conditions include a drying temperature of 150-300°C, preferably 150-200°C.

[0041] According to a preferred embodiment of the present invention, the inert atmosphere is selected from one of vacuum, nitrogen or argon atmosphere; wherein the vacuum degree under the vacuum atmosphere is less than 150 Pa.

[0042] According to a preferred embodiment of the present invention, a three-dimensional object can be modeled using computer-aided design and modeling software, and the model can be decomposed into an STL format document that can be built layer by layer. This document is then provided to a 3D printer, which uses liquid or powdered building materials to form the desired three-dimensional object layer by layer. More preferably, the 3D printing technology is selective laser sintering (SLS).

[0043] This invention does not impose any particular limitations on the parameters and conditions for 3D printing, as long as the above-mentioned catalyst can be formed, any conditions known in the art can be used. According to a preferred embodiment of the present invention, the 3D printing conditions include: a printing temperature of 150-1600℃ and a printing speed of 10-200mm / s.

[0044] According to a preferred embodiment of the present invention, the oxidizing atmosphere includes at least one of air, oxygen, and water vapor.

[0045] According to a preferred embodiment of the present invention, the reducing atmosphere is hydrogen and / or organic hydrocarbons; wherein the organic hydrocarbons are selected from at least one of methane, ethane, propane, butane, ethylene, propylene and butene.

[0046] According to a preferred embodiment of the present invention, the activation conditions are: an activation temperature of 250-800℃, preferably 400-600℃.

[0047] The present invention will be described in detail below through embodiments.

[0048] Example 1

[0049] Silicon carbide powder was placed in a 0.2% platinum chloride solution, stirred for 30 min, filtered, and dried at 200 °C under a nitrogen atmosphere to obtain metal-loaded silicon carbide powder, wherein the platinum content was 0.3% by mass and the silicon carbide content was 99.7% by mass.

[0050] The 3D structure of the catalyst was modeled using SolidWorks software. The catalyst has a diameter of 6 mm and a length of 6 mm, and is cut into 6 layers along the height direction, with a layer height of 1 mm. Four circular holes with a diameter of 2 mm are made in each layer. Starting from the bottom, the center of the holes in the upper layer is offset by 1.66 mm relative to the center of the holes in the lower layer along the side length. The resulting structure is shown below. Figure 2 As shown. The 3D model is converted into an STL format file of layer stacking using the export module in the software. The obtained STL model file is then provided to the EOSINT P760 selective laser sintering 3D printer. Silicon carbide ceramic powder loaded with metal active components is added to the material cylinder of the 3D printer. The printing temperature is set to 1450℃ and the printing speed is 20mm / s to print catalyst particles.

[0051] The catalyst particles were placed in a quartz boat and then placed in a quartz tube sealed at both ends. Dry nitrogen gas was introduced into the quartz tube to replace the air in the tube. The quartz tube was heated to 450°C. After the temperature stabilized, high-purity hydrogen gas was introduced for 15 minutes, followed by the introduction of dry nitrogen gas to replace the air, and then cooled to room temperature to obtain the activated Pt-SiC catalyst S1.

[0052] Measure 10 mL of catalyst S1 using a graduated cylinder and fill it into a quartz tube with an inner diameter of 20 mm, a wall thickness of 6 mm, and a length of 500 mm. Fill the middle section of the quartz tube with catalyst particles, and insert 5 mm diameter Al2O3 ceramic rings into both ends of the catalyst. Fix the filled quartz tube in the microwave radiation cavity of a microwave reactor, and control the flow rate of high-purity nitrogen gas to 15000 h⁻¹. -1The microwave radiation source was turned on and the power was adjusted to bring the catalyst temperature to 500℃. After the system stabilized for 30 minutes, ethane gas was introduced. After 20 minutes, the tail gas was introduced into an Agilent 7890 gas chromatograph to analyze the composition of the gas after the reaction. The conversion rate of low-carbon alkanes, the selectivity of low-carbon olefins and the yield were calculated. The results are shown in Table 1.

[0053] Example 2

[0054] Silicon carbide powder was placed in a 0.5% palladium chloride solution, stirred for 30 min, filtered, and dried at 200 °C under a nitrogen atmosphere to obtain metal-loaded silicon carbide powder, wherein the palladium content was 0.5% by mass and the silicon carbide content was 99.5% by mass.

[0055] The 3D structure of the catalyst was modeled using SolidWorks software. The catalyst was 8mm in diameter and 8mm in length, and cut into 8 layers along the height direction, with a layer height of 1mm. Each layer had four square holes with a side length of 2mm. Starting from the bottom, the center of the hole in the upper layer was offset by 0.50mm relative to the center of the hole in the lower layer along the side length. The constructed 3D model was converted into an STL format file of layer stacking using the software's export module. The obtained STL model file was provided to an EOSINT P760 selective laser sintering 3D printer. Silicon carbide ceramic powder loaded with metal active components was added to the material cylinder of the 3D printer. The printing temperature was set to 1500℃ and the printing speed to 15mm / s to print catalyst particles.

[0056] The catalyst particles were placed in a quartz boat and then placed in a quartz tube sealed at both ends. Dry nitrogen gas was introduced into the quartz tube to replace the air in the tube. The quartz tube was heated to 420°C. After the temperature stabilized, high-purity hydrogen gas was introduced for 15 minutes, followed by the introduction of dry nitrogen gas to replace the air, and then cooled to room temperature to obtain the activated Pt-SiC catalyst S2.

[0057] Measure 10 mL of catalyst S2 using a graduated cylinder and fill it into a quartz tube with an inner diameter of 20 mm, a wall thickness of 6 mm, and a length of 500 mm. Fill the middle section of the quartz tube with catalyst particles, and insert 5 mm diameter Al2O3 ceramic rings into both ends of the catalyst. Fix the filled quartz tube in the microwave radiation cavity of a microwave reactor, and control the flow rate of high-purity nitrogen gas to 17500 h⁻¹. -1 Turn on the microwave radiation source and adjust the power to make the catalyst temperature reach 450℃. After the system stabilizes for 30 minutes, propane gas is introduced. After 20 minutes, the tail gas is introduced into an Agilent 7890 gas chromatograph to analyze the composition of the gas after the reaction, and calculate the conversion rate of low-carbon alkanes, the selectivity of low-carbon olefins and the yield. The results are shown in Table 1.

[0058] Example 3

[0059] Ammonium metavanadate with a molar concentration of 3% was dissolved in oxalic acid, silicon carbide powder was placed in it, stirred for 30 min, filtered, and dried at 200 °C under a nitrogen atmosphere to obtain metal-loaded silicon carbide powder, wherein the vanadium content was 0.6% by mass and the silicon carbide content was 99.4% by mass.

[0060] The 3D structure of the catalyst was modeled using SolidWorks software. The catalyst was 6mm in diameter and 6mm in length, and cut into 6 layers along the height direction, with a layer height of 1mm. Each layer had four regular hexagonal holes with a side length of 2mm. Starting from the bottom, the center of the hole in the upper layer was offset by 0.33mm relative to the center of the hole in the lower layer along the side length. The constructed 3D model was converted into an STL format file of layer stacking using the software's export module. The obtained STL model file was provided to an EOSINT P760 selective laser sintering 3D printer. Silicon carbide ceramic powder loaded with metal active components was added to the material cylinder of the 3D printer. The printing temperature was set to 1480℃ and the printing speed to 15mm / s to print catalyst particles.

[0061] The catalyst particles were placed in a quartz boat and then placed in a quartz tube sealed at both ends. Dry air was passed through the quartz tube, and the quartz tube was heated to 560°C to activate the catalyst for 60 minutes. After cooling to room temperature, the activated vanadium oxide-SiC catalyst S3 was obtained.

[0062] Measure 10 mL of catalyst S3 using a graduated cylinder and pack it into a quartz tube with an inner diameter of 20 mm, a wall thickness of 6 mm, and a length of 500 mm. Fill the middle section of the quartz tube with catalyst particles, and insert 5 mm diameter Al2O3 ceramic rings into both ends of the catalyst. Fix the packed quartz tube in the microwave radiation cavity of a microwave reactor, and control the flow rate of high-purity nitrogen gas to 10000 h⁻¹. -1 The microwave radiation source was turned on and the power was adjusted to bring the catalyst temperature to 630°C. After the system stabilized for 30 minutes, n-butane gas was introduced. After 20 minutes, the tail gas was introduced into an Agilent 7890 gas chromatograph to analyze the composition of the gas after the reaction. The conversion rate of low-carbon alkanes, the selectivity of low-carbon olefins and the yield were calculated. The results are shown in Table 1.

[0063] Comparative Example 1

[0064] Silicon carbide powder was placed in a 0.5% palladium chloride solution and stirred for 30 min. After filtration, metal-loaded silicon carbide powder was obtained, with a palladium content of 0.5% by mass and a silicon carbide content of 99.5% by mass. After extrusion, shearing, and drying, catalyst particles with a particle size of 5 mm were obtained. The catalyst particles were placed in a quartz boat and then placed in a quartz tube sealed at both ends. Dry nitrogen gas was introduced into the quartz tube to replace the air in the tube. The quartz tube was heated to 450℃. After the temperature stabilized, high-purity hydrogen gas was introduced for 15 min, followed by replacement with dry nitrogen gas. The mixture was then cooled to room temperature to obtain the activated Pd-SiC catalyst DS1.

[0065] Measure 10 mL of catalyst using a graduated cylinder and pack it into a quartz tube with an inner diameter of 20 mm, a wall thickness of 6 mm, and a length of 500 mm. Fill the middle section of the quartz tube with the catalyst, and insert 5 mm Al₂O₃ ceramic rings at both ends of the catalyst. Fix the packed quartz tube in the microwave radiation cavity of a microwave reactor, and control the flow rate of high-purity nitrogen gas to 10,000 h⁻¹. -1 Turn on the microwave radiation source and adjust the power to make the catalyst temperature reach 400℃. After the system stabilizes for 30 minutes, ethane gas is introduced. After 20 minutes, the tail gas is introduced into an Agilent 7890 gas chromatograph to analyze the composition of the gas after the reaction, and calculate the conversion rate of low-carbon alkanes, the selectivity of low-carbon olefins and the yield. The results are shown in Table 1.

[0066] Table 1

[0067] Loaded metal Alkane conversion rate, % Olefin selectivity, % Olefin yield, % S1 platinum 72.93 85.33 62.23 S2 palladium 70.56 81.68 57.63 S3 Vanadium oxide 87.64 61.93 54.28 DS1 palladium 34.32 61.74 21.19

[0068] As can be seen from the results in Table 1, the catalysts prepared by the 3D printing method in Examples 1-3 showed a significant improvement in the yield of low-carbon olefins prepared by the dehydrogenation reaction of alkanes compared with the comparative examples.

[0069] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A microwave dehydrogenation catalyst for improving the yield of low-carbon olefins, characterized in that, The catalyst comprises a metal and / or a metal oxide, and silicon carbide; the metal element in the metal and metal oxide is selected from platinum and / or palladium; the content of the metal and / or metal oxide, based on the total amount of catalyst and by element, is 0.1-0.5% by mass; the content of silicon carbide, based on the total amount of catalyst, is 99.5-99.9% by mass. The catalyst has a columnar structure and is divided into n layers of honeycomb structure along its height, where n ≥ 4, and each layer of honeycomb structure has a pore density of 3-23 pores / cm². 2 through holes; In any two adjacent honeycomb structures, the center of the through hole in the lower honeycomb structure is offset relative to the center of the corresponding through hole in the upper honeycomb structure along the side length or diameter of the through hole; the offset is 0.1-0.9 times the side length or diameter of the through hole. The catalyst has a diameter of 5-10 mm and a height of 5-10 mm.

2. The catalyst according to claim 1, wherein, The number of layers n in the honeycomb structure is 4-12.

3. The catalyst according to claim 2, wherein, The number of layers n in the honeycomb structure is 6-10.

4. The catalyst according to claim 1, wherein, The through holes in the honeycomb structure are selected from one or more of the following: circular, equilateral triangular, square, and regular hexagonal cross-sections.

5. The catalyst according to claim 1 or 2, wherein, The offset is 0.1-0.5 times the hole side length or hole diameter.

6. The catalyst according to any one of claims 1-3, wherein, The catalyst has a diameter of 6-8 mm and a height of 6-8 mm.

7. A method for preparing the microwave dehydrogenation catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Impregnate silicon carbide powder with solution D containing active metal; (2) The product obtained in step (1) is dried under an inert atmosphere to obtain supported silicon carbide powder; (3) The supported silicon carbide powder is printed into shape using 3D printing technology; (4) Activate the shaped catalyst obtained in step (3) under an oxidizing or reducing atmosphere.

8. The method according to claim 7, wherein, The active metal is selected from platinum and / or palladium.

9. The method according to claim 7, wherein, The conditions for immersion include an immersion time of 30-180 min.

10. The method according to claim 7, wherein, The drying conditions include: a drying temperature of 150-300℃; And / or, the inert atmosphere is selected from one of vacuum, nitrogen or argon atmosphere; wherein the vacuum degree under the vacuum atmosphere is less than 150 Pa.

11. The method according to claim 10, wherein, The drying conditions include a drying temperature of 150-200℃.

12. The method according to claim 7, wherein, The 3D printing technology mentioned is selective laser sintering.

13. The method according to claim 7, wherein, The oxidizing atmosphere includes at least one of air, oxygen, and water vapor.

14. The method according to claim 7, wherein, The reducing atmosphere is hydrogen and / or organic hydrocarbons; wherein the organic hydrocarbons are selected from at least one of methane, ethane, propane, butane, ethylene, propylene, and butene.

15. The method according to claim 7, wherein, The activation conditions are: activation temperature of 250-800℃.

16. The method according to claim 15, wherein, The activation conditions are: activation temperature of 400-600℃.

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