Catalytic media, apparatus and methods for preparing graphene

Abstract

This invention provides a catalytic medium, apparatus, and method for preparing graphene. The catalytic medium comprises a first metal element (magnesium), a second metal element, and a halide salt. The apparatus includes a reaction system, a gas dispersion and treatment system, a solid carbon collection system, and a gas recovery system. The reaction system includes a first reactor and a second reactor. The gas dispersion and treatment system includes a first aeration device, a second aeration device, a first rotary stirrer, and a second rotary stirrer. The solid carbon collection system includes a first cyclone separator, a second cyclone separator, and a carbon material collection chamber. The graphene preparation method of this invention enables high-quality, low-cost mass production of graphene, extends the service life of the catalytic medium, and achieves high activity, long cycle time, and stable operation. This method utilizes CO2 resources, is environmentally friendly, low-cost, and significantly improves the feed gas conversion rate and graphene quality.

Description

Technical Field

[0001] This invention relates to the field of new chemical materials technology, and in particular to a catalytic medium, apparatus and method for preparing graphene. Background Technology

[0002] Graphene is a two-dimensional material composed of a single layer of carbon atoms arranged in a honeycomb pattern. Since its first successful isolation in the laboratory in 2004, it has attracted much attention due to its unique physical and chemical properties. It has extremely high electrical and thermal conductivity, as well as super mechanical strength. These properties make graphene a promising candidate for applications in electronic devices, energy storage, composite materials, and other fields.

[0003] Currently, the main graphene preparation technologies include mechanical exfoliation, chemical vapor deposition (CVD), and redox methods. Mechanical exfoliation, as the initial method for graphene preparation, mechanically peels single-layer or few-layer graphene from high-quality graphite. While the resulting graphene is of high quality, its efficiency is extremely low, making large-scale production difficult. Although CVD and redox methods can theoretically achieve large-scale graphene production, high cost, complex processes, and difficulty in guaranteeing product quality remain major obstacles.

[0004] On the other hand, with the continuous acceleration of industrialization, environmental pollution and other problems are becoming increasingly prominent, especially the global challenges brought about by the greenhouse effect. How to make rational use of CO2 resources and produce products with higher added value while achieving emission reduction is a hot topic of research for scientific researchers.

[0005] CN111056548A discloses a method and apparatus for the co-production of few-layer graphene and hydrogen, using molten metal as a catalyst to catalyze the cracking of hydrocarbon gases to generate graphene and hydrogen. While this patent application can produce micron-sized bubbles, the bubbles coalesce during their ascent in the molten liquid, causing them to gradually enlarge, reducing the gas-liquid contact area, and significantly degrading the conversion rate and the quality of the carbon materials. Furthermore, the catalyst composition and applicable feed gas types differ significantly from those of this invention.

[0006] CN118164478A proposes a method for preparing graphene, which uses liquid metal, carbon source gas, a first gas (composed of inert gas and hydrogen), and a second gas (the tail gas after the reaction of inert gas, hydrogen, and carbon source) to prepare graphene. This patent does not consider the uniform bubble dispersion and catalyst deactivation issues in the molten liquid system, which makes the reaction process unable to operate continuously and stably.

[0007] CN102976320A proposes a method for preparing high-quality graphene using carbon dioxide gas as a raw material. The method involves burning magnesium powder in a carbon dioxide atmosphere to prepare graphene, using elemental magnesium as the catalyst, and purifying the obtained graphene by acid washing.

[0008] CN107539976A discloses a method for preparing ultra-clean graphene using carbon dioxide. The method employs conventional CVD with a copper substrate, introducing carbon source gas and hydrogen for chemical vapor deposition to obtain graphene. After deposition, CO2 is introduced into another heating zone for further treatment, resulting in ultra-clean graphene. In this patent, the ratio of carbon source gas to hydrogen determines the domain size, growth rate, and crystallinity of the graphene; CO2 is used to selectively react with amorphous carbon contaminants on the graphene surface to obtain clean graphene with fewer contaminants.

[0009] CN104495815A proposes an apparatus and method for preparing graphene using carbon dioxide. Graphene is prepared by chemical vapor deposition in the presence of hydrogen, replacing conventional carbon source gases such as methane, ethylene, and acetylene, which are flammable and explosive gases. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a catalytic medium, apparatus, and method for preparing graphene, thereby improving the long-term stability of catalyst activity and enabling low-cost, large-scale mass production of graphene.

[0011] To achieve the above objectives, the present invention provides a catalytic medium for preparing graphene, the catalytic medium comprising a first metal element, a second metal element, and a halide salt;

[0012] Wherein, the first metallic element is magnesium, and the second metallic element is selected from one or more combinations of iron, calcium, copper, zirconium, aluminum, chromium, manganese, cobalt, zinc, bismuth, nickel, tin, and gallium.

[0013] The molar ratio of the first metal element to the second metal element is 1:9-9:1.

[0014] In the above-mentioned catalytic medium, the molar ratio (i.e. the ratio of atomic numbers) of the first metal element to the second metal element is generally controlled to be 1:9-9:1, specifically 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, etc., as well as any two of the above specific values ​​as endpoints.

[0015] In the aforementioned catalytic medium, the molar content of the halide salt is at least 5 mol% (e.g., 10 mol% or 20 mol%) of the total molar content of the first metal element, the second metal element, and the halide salt; that is, the molar content of the halide salt is greater than or equal to 5 mol% of the total molar content of the first metal element, the second metal element, and the halide salt. In some specific embodiments, the ratio of the molar content of the halide salt to the total molar content of the first metal element, the second metal element, and the halide salt can be a specific value such as 5 mol%, 10 mol%, 15 mol%, 20 mol%, or a range with any two of the above specific values ​​as endpoints.

[0016] In the aforementioned catalytic medium, the boiling points of the halide salts are respectively higher than the melting points of the first metallic element and the second metallic element. The halide salts include one or more combinations of lithium chloride, sodium chloride, potassium chloride, barium chloride, calcium chloride, magnesium chloride, copper chloride, tin chloride, chromium chloride, ferric chloride, cobalt chloride, zinc chloride, gallium chloride, vanadium chloride, titanium chloride, nickel chloride, lithium bromide, sodium bromide, potassium bromide, barium bromide, calcium bromide, magnesium bromide, copper bromide, tin bromide, chromium bromide, ferric bromide, cobalt bromide, zinc bromide, gallium bromide, vanadium bromide, titanium bromide, and nickel bromide.

[0017] According to a specific embodiment of the present invention, heating the above-mentioned catalytic medium to a molten state in an inert atmosphere (helium, argon, etc.) yields a molten liquid catalytic medium capable of converting carbon source gases such as CO2 into graphene powder. Due to the density difference between the molten liquid metal and the molten liquid halide salt, the molten liquid catalytic medium undergoes stratification, with the lower liquid layer being the molten liquid metal and the upper liquid layer being the molten liquid halide salt. When the above-mentioned catalytic medium is applied to the graphene preparation process, the carbon source gas is first catalyzed by the lower molten liquid metal to generate low-density and fluffy graphene powder. Graphene powder moves upwards with the airflow to the upper layer of molten liquid halide salts. At this point, the liquid metal carried on the surface of the graphene powder is detached at the interface between the liquid metal and the liquid halide salts in the catalytic medium and enters the liquid halide salts. Then, it sinks to the liquid metal layer under gravity. The graphene powder continues to move upwards to the surface of the liquid halide salts and is collected. The collected graphene powder contains only halide salts and no metals. Compared to existing technologies that require acid washing to remove metal impurities during graphene preparation, halide salt impurities can be removed by water washing. Therefore, the catalyst of this invention simplifies the graphene purification process. Furthermore, the metal consumption in the above process is low, which can extend the service life of the catalytic medium and maintain the catalytic effect.

[0018] According to a specific embodiment of the present invention, the above-mentioned catalytic medium can be used to catalyze the reaction process of preparing graphene from at least one of CO2, CO, alcohol gases, ketone gases, aldehyde gases, and hydrocarbons. The alcohol gases include one or more combinations of methanol, ethanol, ethylene glycol, propanol, glycerol, butanol, pentanol, cyclohexanol, and benzyl alcohol; the ketone gases include one or more combinations of acetone, butanone, pentanol, phenylacetone, and cyclohexanone; the aldehyde gases include one or more combinations of formaldehyde, acetaldehyde, propionaldehyde, pentanol, aliphatic aldehydes, epoxide aldehydes, and aromatic aldehydes; and the hydrocarbon gases include one or more combinations of methane, ethane, propane, butane, pentane, ethylene, propylene, butene, acetylene, and propyne.

[0019] In this invention, in order to make rational use of CO2 resources and achieve emission reduction while obtaining high value-added products, the preferred carbon source gas is CO2.

[0020] The present invention also provides an apparatus for preparing graphene, the apparatus comprising a reaction system, a gas dispersion and processing system, a solid carbon collection system and a gas recovery system;

[0021] The reaction system includes a first reactor and a second reactor. The first reactor is used for the cracking of hydrocarbon gases to prepare graphene, and the second reactor is used for the conversion of carbon source gases to prepare graphene.

[0022] The gas dispersion treatment system includes a first aeration device, a second aeration device, a first rotary agitator, and a second rotary agitator; the solid carbon collection system includes a first cyclone separator, a second cyclone separator, and a carbon material collection chamber.

[0023] The first aeration device is located in the lower part of the first reactor, and the second aeration device is located in the lower part of the second reactor.

[0024] The blades of the first rotary agitator are located inside the first reactor and above the first aeration device; the blades of the second rotary agitator are located inside the second reactor and above the second aeration device.

[0025] The discharge port of the first reactor is connected to the inlet of the first cyclone separator, the solid phase outlet of the first cyclone separator is connected to the inlet of the carbon material collection chamber, and the gas phase outlet of the first cyclone separator is connected to the gas recovery system and the gas inlet of the second reactor, respectively.

[0026] The outlet of the second reactor is connected to the inlet of the second cyclone separator, the solid phase outlet of the second cyclone separator is connected to the inlet of the carbon material collection chamber, and the gas phase outlet of the second cyclone separator is connected to the gas recovery system.

[0027] According to a specific embodiment of the present invention, the first reactor and the second reactor are used to carry out the reaction for preparing graphene. In operation, the interior of the first reactor and the second reactor are typically filled with a metal catalytic medium, which can be heated to a molten state to catalyze the reaction and produce graphene.

[0028] According to a specific embodiment of the present invention, the device further includes a gas supply system, which is connected to the gas inlet of the first reactor and the gas inlet of the second reactor, respectively. Specifically, the gas supply system includes a gas pipeline and a gas mass flow control device. The gas pipeline is connected to the gas inlet of the first reactor and the gas inlet of the second reactor, respectively, and the gas mass flow control device is capable of controlling the amount of raw material gas supplied by the gas pipeline to the first reactor and the second reactor, respectively.

[0029] According to a specific embodiment of the present invention, the first aeration device is generally located at the lower part of the molten liquid metal catalytic medium inside the first reactor, and the second aeration device is generally located at the lower part of the molten liquid metal catalytic medium inside the second reactor. The first and second aeration devices are respectively used to cause the introduced raw material gas to form millimeter- or micrometer-sized bubbles in the molten liquid metal catalytic medium. In some specific embodiments, there may be a gap between the bottom end of the first aeration device and the air inlet of the first reactor, forming a gas chamber for containing the raw material gas; similarly, there may be a gap between the bottom end of the second aeration device and the air inlet of the second reactor, forming a gas chamber for containing the raw material gas.

[0030] According to a specific embodiment of the present invention, the first aeration device includes a microbubble generator and / or a device with a porous and breathable structure (such as a wind distribution plate).

[0031] According to a specific embodiment of the present invention, the second aeration device includes a microbubble generator and / or a device with a porous and breathable structure (such as a wind distribution plate).

[0032] According to a specific embodiment of the present invention, the bubbles formed by the raw material gas will coalesce and grow larger during the rising process. The stirring process implemented by the first and second rotary stirrers can break up and disperse the enlarged bubbles, increase the contact area between the gas and liquid (i.e., the raw material gas and the molten liquid metal catalyst medium), thereby increasing the reaction conversion efficiency and improving the quality of graphene.

[0033] According to a specific embodiment of the present invention, the first rotary stirrer may include a motor, a connecting rod, and a blade connected in sequence. The motor can control the movement of the connecting rod, and the connecting rod can drive the blade to rotate. The motor is located outside the first reactor for easy adjustment of the stirrer's rotation; the blade is located in the molten liquid metal catalytic medium of the first reactor.

[0034] According to a specific embodiment of the present invention, the second rotary stirrer may include a motor, a connecting rod, and a blade connected in sequence. The motor can control the movement of the connecting rod, and the connecting rod can drive the blade to rotate. The motor is located outside the second reactor for easy adjustment of the stirrer's rotation; the blade is located in the molten liquid metal catalytic medium of the second reactor.

[0035] According to a specific embodiment of the present invention, the number and shape of the blades of the first rotary stirrer and the second rotary stirrer can be selected according to actual needs, and the present invention does not impose any special restrictions on this.

[0036] In some specific embodiments, the length of the blades of the first rotary agitator can be 1 / 4 to 1 / 2 of the inner diameter of the first reactor. For example, the above-mentioned size ratio can be a specific value such as 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc., or a range with any two of the above-mentioned specific values ​​as endpoints.

[0037] In some specific embodiments, the length of the blades of the second rotary agitator can be 1 / 4 to 1 / 2 of the inner diameter of the second reactor. For example, the above-mentioned size ratio can be a specific value such as 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc., or a range with any two of the above-mentioned specific values ​​as endpoints.

[0038] According to a specific embodiment of the present invention, the first cyclone separator is used for gas-solid separation of the effluent from the first reactor. The first cyclone separator has an inlet, a gas phase outlet, and a solid phase outlet. The gas phase outlet is located at the top of the first cyclone separator and is connected to the gas recovery system and the air inlet of the second reactor, respectively. The solid phase outlet is located at the bottom of the first cyclone separator and is connected to the carbon material collection chamber.

[0039] According to a specific embodiment of the present invention, the device further includes a first valve and a second valve. The first valve is used to control the connection between the gas phase outlet of the first cyclone separator and the gas recovery system, and the second valve is used to control the connection between the gas phase outlet of the first cyclone separator and the gas inlet of the second reactor. By controlling the opening and closing degree of the first valve and the second valve, the gas flow rate delivered from the first cyclone separator to the second reactor can be controlled.

[0040] According to a specific embodiment of the present invention, the second cyclone separator is used for gas-solid separation of the effluent from the second reactor. The second cyclone separator has an inlet, a gas phase outlet, and a solid phase outlet. The gas phase outlet is located at the top of the second cyclone separator and is connected to a gas recovery system; the solid phase outlet is located at the bottom of the second cyclone separator and is connected to a carbon material collection chamber.

[0041] According to a specific embodiment of the present invention, the gas recovery device can collect and separate the gaseous products discharged from the first cyclone separator and the second cyclone separator.

[0042] The present invention also provides a method for preparing graphene, which is carried out in the above-mentioned apparatus for preparing graphene, and the method includes:

[0043] A first metal catalyst medium is added to a first reactor and heated to a molten state in an inert atmosphere. A first aeration device and a first rotary stirrer are then activated to introduce a first raw material gas into the molten first metal catalyst medium. The first raw material gas forms bubbles in the first metal catalyst medium and undergoes a cracking reaction, yielding solid and gaseous products, the gaseous products containing hydrogen. The solid and gaseous products are then separated in a first cyclone separator. The separated solid phase enters a carbon material collection chamber, and the separated gaseous phase enters a gas recovery system.

[0044] A second metal catalyst medium is added to the second reactor and heated to a molten state in an inert atmosphere. The second aeration device and the second rotary stirrer are started to introduce a second raw material gas into the molten second metal catalyst medium. The second raw material gas forms bubbles in the second metal catalyst medium and undergoes a cracking reaction to obtain a solid product. The solid product is carried by the airflow into the second cyclone separator for separation. The separated solid phase enters the carbon material collection chamber, and the separated gas phase enters the gas recovery system.

[0045] The first raw material gas includes hydrocarbon gases, and the second raw material gas includes carbon source gases, wherein the carbon source gases include one or more of CO2, CO, alcohol gases, ketone gases, aldehyde gases, and hydrocarbon gases.

[0046] The second metal catalytic medium includes the catalytic medium for preparing graphene provided by the present invention.

[0047] In the above preparation method, the first reactor can be used as a hydrocarbon gas cracking reactor. The first metal catalyst medium contained in the first reactor includes a copper-tin alloy and / or a nickel-tin alloy. The ratio of the metal elements in the first metal catalyst medium can be arbitrary. The heating and melting process of the first metal catalyst medium is generally carried out in an inert atmosphere (such as helium and / or argon), and the resulting molten liquid first metal catalyst medium can be used to catalyze the cracking of hydrocarbon gases to produce graphene. In some specific embodiments, an inert gas can be introduced into the first reactor before the heating and melting process begins, and this inert atmosphere is maintained during the heating and melting process.

[0048] In the above preparation method, the hydrocarbon gas can be of the general formula C x H y The gas can specifically include one or more of the following: methane, ethane, propane, butane, pentane, ethylene, propylene, butene, acetylene, and propyne.

[0049] According to a specific embodiment of the present invention, the first raw material gas can be a pure hydrocarbon gas or a combination of a hydrocarbon gas and an inert gas (helium and / or argon, etc.). When the first raw material gas contains a hydrocarbon gas and an inert gas, the molar concentration of the hydrocarbon gas in the first raw material gas is 10%-100%, for example, specific values ​​such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., and a range with any two of the above specific values ​​as endpoints. By controlling the concentration of the hydrocarbon gas in the first raw material gas, the purity of the hydrogen generated by the first reactor can be ensured, thereby ensuring the reduction capability of the hydrogen for the second catalytic medium.

[0050] In the above preparation method, the temperature of the pyrolysis reaction of the first raw material gas is 800℃-1400℃, specifically 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, etc., and a range with any two of the above specific values ​​as endpoints.

[0051] In the above preparation method, the second reactor can serve as a carbon source gas converter reactor. The second metal catalytic medium contained in the second reactor, after being heated and melted, transforms into a molten liquid second metal catalytic medium, which can be used to catalyze the cracking of carbon source gases such as CO2 to produce graphene.

[0052] In the above preparation method, the second raw material gas includes one or more of the following carbon source gases: CO2, CO, alcohol gases, ketone gases, aldehyde gases, and hydrocarbon gases. Specifically, alcohol gases include one or more of methanol, ethanol, ethylene glycol, propanol, glycerol, butanol, pentanol, cyclohexanol, and benzyl alcohol; ketone gases include one or more of acetone, butanone, pentanol, phenylacetone, and cyclohexanone; and aldehyde gases include one or more of formaldehyde, acetaldehyde, propionaldehyde, pentanol, aliphatic aldehydes, epoxide aldehydes, and aromatic aldehydes. Hydrocarbon gases include one or more of methane, ethane, propane, butane, pentane, ethylene, propylene, butene, acetylene, and propyne. When these carbon source gases are liquid at room temperature and pressure, they need to be converted into gases outside the system before being introduced into the second reactor.

[0053] In the above preparation method, the second raw material gas can be a pure carbon source gas or a combination of a carbon source gas and an inert gas (helium and / or argon, etc.). In some specific embodiments, when the second raw material gas contains a carbon source gas and an inert gas, the molar concentration of the carbon source gas in the second raw material gas is 10-100%, for example, specific values ​​such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., and a range with any two of the above specific values ​​as endpoints.

[0054] In the above preparation method, the temperature of the cracking reaction of the second raw material gas is 600℃-1200℃, specifically 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc., and a range with any two of the above specific values ​​as endpoints.

[0055] In the above preparation method, after the first aeration device is turned on, the first raw material gas can form bubbles under the action of the first aeration device and contact the molten liquid first metal catalyst medium. In a high-temperature environment, the hydrocarbon gas in the first raw material gas is decomposed to generate graphene and hydrogen. The decomposition reaction formula is as follows: Similarly, after the second aeration device is turned on, the second raw material gas forms bubbles under the action of the second aeration device and comes into contact with the molten liquid second metal catalyst medium. In a high-temperature environment, the carbon source in the second raw material gas decomposes to generate graphene. Taking the second raw material gas containing CO2 as an example, the decomposition reaction formula is: CO2(g) + 2Me(l) → C(s) + 2MeO(l), where Me is the metal from the second metal catalyst medium.

[0056] In the pyrolysis reactions occurring in the two reactors mentioned above, the generated graphene has a low density and is fluffy, floating on the surface of the liquid-phase catalytic medium and being directly carried out by the gas flow, thus achieving effective separation of solid carbon from the liquid-phase catalytic medium. Especially for the hydrocarbon gas pyrolysis reaction in the first reactor, the above process can effectively avoid the problem of carbon buildup and deactivation of the catalytic medium, maintaining the long-term stable operation of the pyrolysis reaction unit.

[0057] In both reactors mentioned above, hydrocarbon cracking and the conversion of carbon sources such as CO2 occur within a molten liquid metal system, which are gas-liquid reactions. Figure 2 As shown, there is a catalytic reaction between the carbon source on the bubble surface and the liquid metal. Figure 2 The "external cracking" in the text) and the non-catalytic reaction of the high-temperature decomposition of the carbon source inside the bubble (in the context of external cracking) Figure 2 (The process involves "internal pyrolysis"). Therefore, the types of carbon materials obtained differ. The former reaction, catalyzed by a catalyst, yields graphene powder, while the latter, without catalysis, produces carbon black powder. To reduce the amount of carbon black obtained without catalysis, bubble size should be minimized and non-catalytic decomposition of the carbon source should be avoided. However, in reality, in a molten liquid system, bubbles tend to coalesce and enlarge during their ascent. By activating the first and second rotary stirrers, the bubbles can be further broken up and dispersed to increase the gas-liquid contact area, thereby increasing the reaction conversion efficiency, improving the quality of the graphene material, and preventing the formation of carbon black byproducts.

[0058] In the above preparation method, the stirring speed of the first and second rotary stirrers should not be too fast to prevent the formation of vortices in the liquid during stirring; the stirring speed should also not be too slow to ensure that large bubbles in the reaction system can be broken up and dispersed. In some specific embodiments, the stirring speed of the first rotary stirrer can be controlled between 400-4000 rpm, for example, specific values ​​such as 400 rpm, 800 rpm, 1200 rpm, 1600 rpm, 2000 rpm, 2400 rpm, 2800 rpm, 3200 rpm, 3600 rpm, and 4000 rpm, as well as a range with any two of the above specific values ​​as endpoints. The stirring speed of the second rotary stirrer can be controlled between 400-4000 rpm, for example, specific values ​​such as 400 rpm, 800 rpm, 1200 rpm, 1600 rpm, 2000 rpm, 2400 rpm, 2800 rpm, 3200 rpm, 3600 rpm, and 4000 rpm, as well as a range with any two of the above specific values ​​as endpoints.

[0059] In the above preparation method, the particle size of the bubbles formed by the first raw material gas can be 1μm-1cm, for example, specific values ​​such as 1μm, 10μm, 100μm, 1mm, 6mm, 10mm, 100mm, 1cm, etc., and a range with any two of the above specific values ​​as endpoints; the particle size of the bubbles formed by the second raw material gas can be 1μm-1cm, for example, specific values ​​such as 1μm, 10μm, 100μm, 1mm, 6mm, 10mm, 100mm, 1cm, etc., and a range with any two of the above specific values ​​as endpoints.

[0060] In the above preparation method, the metal (Me) in the second metal catalytic medium is oxidized to metal oxide (MeO) during the reaction, resulting in decreased catalytic activity and reduced reaction efficiency and effect. Accordingly, the preparation method may further include regenerating the second metal catalytic medium. This regeneration process includes stopping the supply of the second raw material gas to the second reactor and introducing a reducing gas into the second metal catalytic medium. The reducing gas reacts with the metal oxide in the second metal catalytic medium to generate water vapor, reducing the metal oxide. When the second reactor no longer produces water vapor, it indicates that the metal oxide reduction is complete, and the supply of the reducing gas can be stopped, completing the regeneration process and achieving the cyclic regeneration of the catalytic medium. The high-temperature water vapor generated during the reaction can be discharged from the second reactor.

[0061] The reaction formula for the regeneration process is: H2(g) + MeO(l) → Me(l) + H2O(g).

[0062] In the above regeneration process, the reducing gas may include hydrogen. In some specific embodiments, the reducing gas may include the gaseous product generated by the cracking reaction of the first raw material gas (which contains hydrogen), or it may be a mixture of hydrogen and an inert gas (helium and / or argon, etc.).

[0063] During the regeneration process described above, the first and second reactors can be connected in series by opening the second valve, and the flow rate of the gaseous product from the first reactor into the second reactor can be controlled by adjusting the first valve. After the regeneration process is completed, the second valve can be closed, connecting the first and second reactors in parallel. At this time, both the first and second reactors are supplied with raw material gas by the gas supply system and can produce graphene powder.

[0064] The beneficial effects of this invention include:

[0065] 1. The catalyst and method for preparing graphene provided by the present invention use a catalyst including halide salts and carbon source gases such as CO2 as raw materials, which can realize the low-cost mass production of high-quality graphene.

[0066] 2. This invention enables the rational utilization of waste CO2 resources, which not only helps reduce direct CO2 emissions into the atmosphere, but also produces products with certain economic value (graphene), thus turning waste into treasure.

[0067] 3. The graphene preparation method provided by this invention has no direct CO2 emissions. On the contrary, it utilizes CO2 resources, making it more green and environmentally friendly with significant environmental benefits.

[0068] 4. The graphene preparation device provided by this invention effectively solves the problem of oxidative deactivation of the catalytic medium during the preparation of graphene from carbon source gas (e.g., CO2), by coupling the carbon source gas conversion to graphene with a hydrocarbon gas cracking device. It realizes in-situ regeneration of the liquid catalytic medium, avoids the increase in energy consumption caused by frequent start-ups and shutdowns, and ensures continuous and stable operation of the device. It also changes the situation where the catalyst is a disposable consumable, and achieves high activity, long cycle, and stable operation.

[0069] 5. The component ratio of the molten liquid catalytic medium used in the graphene preparation process provided by the present invention can be flexibly adjusted, thereby flexibly changing the melting and boiling points of the catalytic medium to adapt to different reaction temperatures.

[0070] 6. The graphene preparation device provided by the present invention, by combining an aeration device with a rotary stirrer, can effectively avoid the co-aggregation of bubbles during the rising process, thereby increasing the gas-liquid contact area and improving the raw material gas conversion rate and the quality of carbon materials.

[0071] Based on the above, this invention has good application prospects and is expected to realize large-scale utilization of CO2, while paving the way for the large-scale application of graphene. Attached Figure Description

[0072] Figure 1 A schematic diagram of the apparatus for preparing graphene.

[0073] Figure 2 This is a schematic diagram of the cracking of bubbles in a molten liquid metal catalytic medium system.

[0074] Figure 3 The images shown are scanning electron microscope (SEM) images of the graphene obtained in Examples 1, 2, and 3.

[0075] Figure 4 The images show the Raman characterization diagrams of the graphene obtained in Examples 1, 2, and 3.

[0076] Figure 5 The images are scanning electron microscope (SEM) images of the graphene obtained in Examples 1 and 4.

[0077] Figure 6 The images show the Raman characterization diagrams of the graphene obtained in Example 1 and Comparative Example 1.

[0078] Symbol Explanation

[0079] 1. First raw material gas; 21. First aeration device; 22. Second aeration device; 3. Molten liquid phase catalyst medium; 4. Bubbles; 5. Graphene powder; 61. First reactor; 62. Second reactor; 71. First rotary stirrer; 72. Second rotary stirrer; 81. First cyclone separator; 82. Second cyclone separator; 91. First carbon material collection chamber; 92. Second carbon material collection chamber; 10. First valve; 11. Second raw material gas; 12. Molten liquid phase catalyst medium; 13. First filter membrane; 141. Second filter membrane; 142. Gas phase outlet; 15. Detailed Implementation

[0080] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0081] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0082] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are still within the scope of protection of the present invention.

[0083] Example 1

[0084] This embodiment provides an apparatus for preparing graphene. For example... Figure 1 As shown, the device includes a gas supply system, a reaction system, a gas dispersion and treatment system, a solid carbon collection system, and a gas recovery system.

[0085] The gas supply system includes a gas pipeline and a gas mass flow control device. The gas pipeline is used to supply raw material gas to the first reactor 61 and the second reactor 62. The gas mass flow control device controls the amount of raw material gas supplied by the gas pipeline to the first reactor and the second reactor, respectively.

[0086] The reaction system includes a first reactor 61 and a second reactor 62. The gas dispersion treatment system includes a first aeration device 21, a second aeration device 22, a first rotary agitator 71, and a second rotary agitator 72. The solid carbon collection system includes a first cyclone separator 81, a second cyclone separator 82, a first carbon material collection chamber 91, and a second carbon material collection chamber 92.

[0087] The first reactor 61 and the second reactor 62 can contain raw material gas and metal catalyst medium, and can heat the metal catalyst medium to a molten state. Both the first reactor 61 and the second reactor 62 are equipped with an inlet and an outlet. The inlet of the first reactor 61 and the inlet of the second reactor 62 are respectively connected to the gas supply system's gas pipeline.

[0088] The first aeration device 21 includes a microbubble generator and / or a device with a porous, breathable structure (such as an air distribution plate); the second aeration device 22 includes a microbubble generator and / or a device with a porous, breathable structure (such as an air distribution plate). The first aeration device 21 is located in the lower part of the interior of the first reactor 61, and the second aeration device 22 is located in the lower part of the interior of the second reactor 62. Figure 1 As shown, gaps can be left between the bottom end of the first aeration device 21 and the air inlet of the first reactor 61, and between the bottom end of the second aeration device 22 and the air inlet of the second reactor 62, respectively. These gaps form gas chambers that can be used to contain raw material gas. When the first reactor 61 and the second reactor 62 contain molten liquid metal catalyst media, the first aeration device 21 and the second aeration device 22 are respectively located below the molten liquid metal catalyst media.

[0089] The blades of the first rotary stirrer 71 are located inside the first reactor 61 and above the first aeration device 21; the blades of the second rotary stirrer 72 are located inside the second reactor 62 and above the second aeration device 22. When the first reactor 61 and the second reactor 62 contain molten liquid metal catalyst media, the blades of the first rotary stirrer 71 and the second rotary stirrer 72 are respectively located in the molten liquid metal catalyst media to break up bubbles in the metal catalyst media. In this embodiment, the blade length of the first rotary stirrer 71 is 1 / 3 of the inner diameter (i.e., the cavity diameter) of the first reactor 61, and the blade length of the second rotary stirrer 72 is 1 / 3 of the inner diameter (i.e., the cavity diameter) of the second reactor 62.

[0090] The first cyclone separator 81 is used for gas-solid separation of the effluent from the first reactor 61. The first cyclone separator 81 includes an inlet, a gas phase outlet at the top, and a solid phase outlet at the bottom. The inlet of the first cyclone separator 81 is connected to the effluent outlet of the first reactor 61 via a gas pipe. The solid phase outlet of the first cyclone separator 81 is connected to the inlet of the carbon material collection chamber. The gas phase outlet of the first cyclone separator 81 is connected to both the gas recovery system and the inlet of the second reactor 62. Specifically, the gas phase outlet of the first cyclone separator 81 is connected to the second reactor 62 via a pipe, and this pipe has a branch connecting the gas phase outlet of the first cyclone separator 81 to the inlet of the gas recovery system. A first valve 10 is provided between the first cyclone separator 81 and the gas recovery system, and a second valve 11 is provided between the first cyclone separator 81 and the second reactor 62. Further, a first filter membrane 141 is provided between the gas phase outlet of the first cyclone separator 81 and the gas recovery system.

[0091] The second cyclone separator 82 is used for gas-solid separation of the effluent from the second reactor 62. The second cyclone separator 82 includes an inlet, a gas phase outlet at the top, and a solid phase outlet at the bottom. The inlet of the second cyclone separator 82 is connected to the effluent outlet of the second reactor 62 via a gas pipe; the solid phase outlet of the second cyclone separator 82 is connected to the inlet of the carbon material collection chamber; and the gas phase outlet of the second cyclone separator 82 is connected to the gas recovery system. Furthermore, a second filter membrane 142 is provided between the gas phase outlet of the second cyclone separator 82 and the gas recovery system.

[0092] This embodiment also provides a method for preparing graphene, the method comprising:

[0093] S1. Inert helium gas is introduced into the first reactor 61 and the second reactor 62 respectively, and a certain amount of Cu is weighed out. 0.7 Sn 0.3 The alloy was placed in the first reactor 61 as the first metal catalytic medium; 90 molar amounts of Mg were weighed out. 0.7 Cu 0.2 Ni 0.1 Add 10 molar amounts of potassium chloride to the second reactor 62 and mix thoroughly to serve as the second metal catalytic medium.

[0094] The metal catalyst media in the first reactor 61 and the second reactor 62 are heated to a molten liquid state in an inert helium atmosphere, forming a molten liquid phase catalyst medium 3 for the preparation of graphene from methane cracking and a molten liquid phase catalyst medium 13 for the preparation of graphene from CO2 conversion. The molten liquid phase catalyst medium 13 is layered, with a lower layer of molten liquid metal and an upper layer of molten liquid halide salt. By maintaining an inert helium atmosphere before and during the heating of the first reactor 61 and the second reactor 62, high-temperature oxidation of the metal in the catalyst media by air can be prevented. Both the first reactor 61 and the second reactor 62 are heated to 1200°C and maintained at this temperature for 30 minutes to ensure complete melting of the catalyst media. Then, the temperatures of both the first reactor 61 and the second reactor 62 are reduced to 1000°C and maintained at a constant reaction temperature.

[0095] S2. After reaching the required reaction temperature, turn on the first aeration device 21, the second aeration device 22, the first rotary stirrer 71 and the second rotary stirrer 72, and introduce a mixture of methane and inert gas into the first reactor 61 as the first raw material gas 1. The molar concentration of methane in the first raw material gas 1 is 50%, and the remaining gas component is the inert gas helium. In the second reactor 62, introduce a mixture of CO2 and inert gas as the second raw material gas 12. The molar concentration of carbon dioxide in the second raw material gas 12 is 30%, and the remaining gas component is the inert gas helium.

[0096] The first raw material gas 1 and the second raw material gas 12 are respectively transformed into micron- to millimeter-sized bubbles 4 through the first aeration device 21 and the second aeration device 22, with a particle size of 1μm-1cm. Due to the aggregation phenomenon during the rising process of the bubbles 4, small bubbles converge into large bubbles. Under the stirring action of the first rotary stirrer and the second rotary stirrer 72 (the rotation speed of the first rotary stirrer and the second rotary stirrer 72 are controlled at 1500rpm respectively, and the size of each stirrer blade is 1 / 3 of the diameter of the cavity of the reactor in which it is located), the large bubbles are broken into small bubbles. This helps to increase the gas-liquid contact area, improve the pyrolysis efficiency and graphene quality.

[0097] Due to the high temperature and catalytic properties of the molten liquid metal, the first feed gas 1 and the second feed gas 12 begin to react catalyzed. Methane is cracked into graphene powder 5 and hydrogen, and CO2 is converted into graphene powder 5. The reaction involved in the first reactor 61 is: CH4(g)→2H2(g)+C(s), and the reaction involved in the second reactor 62 is: CO2(g)+2Mg 0.7 Cu 0.2 Ni 0.1 (l)→1.4MgO(l)+0.4CuO(l)+0.2NiO(l)+C(s).

[0098] The graphene powder 5 generated in the first reactor 61 is lightweight and fluffy, floating on the surface of the molten liquid catalyst medium 3. This effectively prevents carbon buildup and deactivation of the catalyst medium. Driven by the airflow, the graphene powder 5 enters the first cyclone separator 81 through the outlet at the top of the first reactor 61. Gas-solid separation occurs under the action of the first cyclone separator 81 and the first filter membrane 141. The graphene powder 5, as a solid phase, is separated and flows into the first carbon material collection chamber 91, while the separated gas phase is discharged from the gas phase outlet at the top of the first cyclone separator 81 and enters the gas recovery and treatment system. The gas recovery and treatment system is mainly used for hydrogen purification and unreacted gas recovery.

[0099] In the second reactor 62, the graphene powder 5 produced by the cracking of the second raw material gas 12, along with a small amount of metal medium it carries, rises with the bubbles. When it reaches the interface between the molten liquid metal layer and the molten liquid halide salt layer, the metal medium carried by the graphene powder 5 peels off and enters the liquid halide salt layer, then settles back into the molten liquid metal layer under gravity. The graphene powder 5 continues to move upward until it floats on the surface of the molten liquid halide salt layer. Driven by the airflow, the graphene powder 5 enters the second cyclone separator 82 through the discharge port at the top of the second reactor 62 for gas-solid separation. Under the action of the second cyclone separator 82 and the second filter membrane 142, gas-solid separation occurs. The graphene powder 5, as a solid phase, is blocked and separated, flowing into the second carbon material collection chamber 92. Since the impurities carried by the graphene powder 5 are halide salts rather than metals, the graphene can be purified by washing with water. The separated gas phase is discharged from the gas phase outlet at the top of the second cyclone separator 82 and enters the gas recovery and treatment system.

[0100] During the graphene production process in the second reactor 62, the second valve 11 is closed and the first valve 10 is opened, so that the first reactor 61 and the second reactor 62 operate independently and do not interfere with each other.

[0101] S3. When the graphene yield collected in the second reactor 62 decreases significantly or even ceases to be generated, the molten liquid phase catalyst medium 13 is regenerated as follows: the first valve 10 is closed, the second valve 11 is opened, and the second raw material gas 12 is stopped from being supplied to the second reactor 62. At this time, the first reactor 61 and the second reactor 62 are connected in series. That is, the cracked hydrogen product of the first reactor 61 is introduced into the second reactor 62 after gas-solid separation by the first cyclone separator 81 to reduce the oxidized liquid metal. Specifically, the reaction involved is H2(g) + CuO(l) + MgO(l) + NiO(l) → Cu(l) + Mg(l) + Ni(l) + H2O(g). The molten liquid phase catalyst medium 13 used for CO2 to prepare graphene powder is recycled and regenerated. The generated water vapor is discharged through the gas phase outlet 15 of the second cyclone separator 82. When no water vapor is detected being discharged, it indicates that the regeneration of the molten liquid phase catalyst medium 13 is complete. During the above regeneration process, the first reactor 61 remains operational, continuously generating graphene and hydrogen.

[0102] After the regeneration process is completed, the second valve 11 is closed and the first valve 10 is opened. At the same time, the second raw material gas 12 is introduced into the second reactor 62 to continue S1 and S2, so that the first reactor 61 and the second reactor 62 produce graphene simultaneously.

[0103] Example 2

[0104] This embodiment provides a method for preparing graphene, which is similar to the preparation method in Example 1, except that:

[0105] In this embodiment, 95 moles of Mg were weighed out. 0.6 Cu 0.4 The alloy and 5 molar amounts of potassium chloride are placed in the second reactor and mixed evenly to serve as the second metal catalytic medium.

[0106] In this embodiment, the catalytic media in the two reactors are heated to a molten liquid state to form a molten liquid catalytic media for hydrocarbon gas cracking and CO2 conversion to graphene. Other conditions remain unchanged from Example 1 and will not be repeated here.

[0107] Example 3

[0108] This embodiment provides a method for preparing graphene, which is similar to the preparation method in Example 1, except that:

[0109] In this embodiment, 80 moles of Mg were weighed out. 0.4 Fe 0.6 The alloy and 20 molar parts of sodium chloride are placed in the second reactor and mixed evenly to serve as the second metal catalyst medium.

[0110] In this embodiment, the catalytic media in the two reactors are heated to a molten liquid state to form a molten liquid catalytic media for hydrocarbon gas cracking and CO2 conversion to graphene, and other conditions remain unchanged from Example 1.

[0111] Example 4

[0112] This embodiment provides a method for preparing graphene, which is similar to the preparation method in Example 1, except that:

[0113] In this embodiment, the molar concentration of CO2 in the second feed gas introduced into the second reactor is increased from 30% to 60%. Other conditions are the same as in Example 1.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing graphene, which is similar to the preparation method in Example 1, except that:

[0116] In this comparative example, the first rotary stirrer 71 and the second rotary stirrer 72 were always turned off. Other conditions were the same as in Example 1.

[0117] Experimental Results: The graphene obtained in Examples 1, 2, and 3 was characterized by scanning electron microscopy (SEM). Figure 3 , Figure 3 The scale bar of each figure is 2 μm) and Raman ( Figure 4 Analysis shows that the graphene prepared in Examples 1, 2, and 3 all exhibit a network film structure, with the G peak significantly higher than the D peak. The G peak represents the E2g mode of the C=C vibration in the graphene structure, a typical characteristic of graphene. The D peak is the Raman activity characteristic peak of the C=C bond stretching vibration in graphene caused by amorphous carbon. Characterization of the carbon material in Example 4 also shows typical graphene characteristics. In summary, this demonstrates that the second metal catalytic system provided by this invention is effective for the preparation of graphene based on CO2.

[0118] Furthermore, based on the results of Examples 1 and 4, reducing the CO2 concentration of the feed gas introduced into the second reactor 62 helps to improve its conversion rate. When the CO2 inlet concentration of the feed gas is reduced from 60% to 30%, the conversion rate increases from 50% to 72%, showing a significant improvement. Regarding the quality of graphene (e.g....), Figure 5 As shown in the figure, the graphene obtained is thinner and more transparent as the concentration of the raw material gas decreases, indicating that the quality of the obtained graphene is better.

[0119] Table 1. Comparison of conversion rates between Example 1 and Comparative Example 1

[0120]

[0121] Table 1 shows the comparison results of the catalytic performance of Example 1 and Comparative Example 1. As can be seen from Table 1, under the same reaction conditions, using a rotary stirrer is beneficial to improving the conversion rate of the feed gas (methane, CO2), thereby collecting more graphene.

[0122] Figure 6 In the figures, "without a rotary stirrer" represents the sample of Comparative Example 1, and "with a rotary stirrer" represents the sample of Example 1. Figure 6 It can be seen that the graphene prepared by starting a rotary stirrer has a higher ratio of G peak to D peak. The G / D ratio is a key indicator for evaluating the structural integrity and defects of graphene, and the higher the ratio, the better the quality of the prepared graphene. Figure 6 The results show that the graphene quality of Example 1 is higher than that of Comparative Example 1.

[0123] The above results demonstrate that the graphene preparation method provided by this invention can achieve high-quality graphene mass production at low cost, extend the service life of the catalytic medium, and achieve high activity, long cycle, and stable operation. This method can utilize CO2 resources, is environmentally friendly and low-cost, and significantly improves the feed gas conversion rate and graphene quality.

Claims

1. A catalytic medium for preparing graphene, characterized in that, The catalytic medium comprises a first metal element, a second metal element, and a halide salt; Wherein, the first metallic element is magnesium, and the second metallic element is selected from one or more combinations of iron, calcium, copper, zirconium, aluminum, chromium, manganese, cobalt, zinc, bismuth, nickel, tin, and gallium. The molar ratio of the first metal element to the second metal element is 1:9-9:

1.

2. The catalytic medium for preparing graphene according to claim 1, characterized in that, In the catalytic medium, the molar content of the halide salt is at least 5 mol% of the total molar content of the first metal element, the second metal element, and the halide salt.

3. The catalytic medium for preparing graphene according to claim 1, characterized in that, The halogen salts include one or more of the following: lithium chloride, sodium chloride, potassium chloride, barium chloride, calcium chloride, magnesium chloride, copper chloride, tin chloride, chromium chloride, ferric chloride, cobalt chloride, zinc chloride, gallium chloride, vanadium chloride, titanium chloride, nickel chloride, lithium bromide, sodium bromide, potassium bromide, barium bromide, calcium bromide, magnesium bromide, copper bromide, tin bromide, chromium bromide, ferric bromide, cobalt bromide, zinc bromide, gallium bromide, vanadium bromide, titanium bromide, and nickel bromide.

4. An apparatus for preparing graphene, characterized in that, The apparatus for preparing graphene includes a reaction system, a gas dispersion and processing system, a solid carbon collection system, and a gas recovery system. The reaction system includes a first reactor and a second reactor; the gas dispersion treatment system includes a first aeration device, a second aeration device, a first rotary stirrer and a second rotary stirrer; the solid carbon collection system includes a first cyclone separator, a second cyclone separator and a carbon material collection chamber. The first aeration device is located in the lower part of the first reactor, and the second aeration device is located in the lower part of the second reactor. The blades of the first rotary agitator are located inside the first reactor and above the first aeration device; the blades of the second rotary agitator are located inside the second reactor and above the second aeration device. The discharge port of the first reactor is connected to the inlet of the first cyclone separator, the solid phase outlet of the first cyclone separator is connected to the inlet of the carbon material collection chamber, and the gas phase outlet of the first cyclone separator is connected to the gas recovery system and the gas inlet of the second reactor, respectively. The outlet of the second reactor is connected to the inlet of the second cyclone separator, the solid phase outlet of the second cyclone separator is connected to the inlet of the carbon material collection chamber, and the gas phase outlet of the second cyclone separator is connected to the gas recovery system.

5. The apparatus for preparing graphene according to claim 4, characterized in that, The device also includes a gas supply system, which is connected to the gas inlet of the first reactor and the gas inlet of the second reactor, respectively.

6. The apparatus for preparing graphene according to claim 4 or 5, characterized in that, The first aeration device and the second aeration device each independently include a microbubble generator and / or a device with a porous and breathable structure.

7. The apparatus for preparing graphene according to claim 4, characterized in that, The length of the blades of the first rotary agitator is 1 / 4 to 1 / 2 of the inner diameter of the first reactor; And / or, the length of the blades of the second rotary agitator is 1 / 4 to 1 / 2 of the inner diameter of the second reactor.

8. A method for preparing graphene, characterized in that, The preparation method is carried out using the apparatus for preparing graphene as described in any one of claims 4-7, and the preparation method includes the following steps: A first metal catalyst medium is added to a first reactor and heated to a molten state under an inert atmosphere. A first aeration device and a first rotary stirrer are then activated to introduce a first raw material gas into the molten first metal catalyst medium. The first raw material gas forms bubbles in the first metal catalyst medium and undergoes a cracking reaction, yielding solid and gaseous products, the gaseous products containing hydrogen. The solid and gaseous products are then separated in a first cyclone separator. The separated solid phase enters a carbon material collection chamber, and the separated gaseous phase enters a gas recovery system. A second metal catalyst medium is added to the second reactor and heated to a molten state under an inert atmosphere. The second aeration device and the second rotary stirrer are started, and a second raw material gas is introduced into the molten second metal catalyst medium. The second raw material gas forms bubbles in the second metal catalyst medium and undergoes a cracking reaction to obtain a solid product. The solid product is carried by the airflow into the second cyclone separator for separation. The separated solid phase enters the carbon material collection chamber, and the separated gas enters the gas phase recovery system. The first raw material gas includes hydrocarbon gases, and the second raw material gas includes carbon source gases, wherein the carbon source gases include one or more of CO2, CO, alcohol gases, ketone gases, aldehyde gases, and hydrocarbon gases. The second metal catalytic medium includes the catalytic medium for preparing graphene as described in any one of claims 1-3.

9. The preparation method according to claim 8, characterized in that, The first metal catalytic medium includes a copper-tin alloy and / or a nickel-tin alloy.

10. The preparation method according to claim 8, characterized in that, When the first raw material gas contains hydrocarbon gas and inert gas, the molar concentration of the hydrocarbon gas in the first raw material gas is 10%-100%.

11. The preparation method according to claim 8, characterized in that, The temperature of the first raw material gas cracking reaction is 800℃-1400℃.

12. The preparation method according to claim 8, characterized in that, When the second raw material gas contains a carbon source gas and an inert gas, the molar concentration of the carbon source gas in the second raw material gas is 10%-100%.

13. The preparation method according to claim 8, characterized in that, The temperature of the second raw material gas pyrolysis reaction is 600℃-1200℃.

14. The preparation method according to claim 8, characterized in that, The stirring speeds of the first and second rotary stirrers are 400 rpm and 4000 rpm, respectively.

15. The preparation method according to claim 8, characterized in that, The particle size of the bubbles formed by the first raw material gas is 1μm-1cm; the particle size of the bubbles formed by the second raw material gas is 1μm-1cm.

16. The preparation method according to claim 8, characterized in that, The preparation method further includes regenerating the second metal catalyst medium. The regeneration process includes stopping the supply of the second raw material gas to the second reactor, and supplying a reducing gas to the second metal catalyst medium until the second reactor no longer produces water vapor. The supply of the reducing gas is then stopped to complete the regeneration process. The reducing gas includes gaseous products generated from the first raw material gas through a cracking reaction.

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