A graphene preparation system and method

Abstract

The application discloses a graphene preparation system and method. The system comprises a fuel reactor, an oxygen carrier regeneration reactor and a graphene preparation reactor. The method comprises: reacting an oxygen carrier and fuel in the fuel reactor to obtain a gas product and a reduced oxygen carrier; the reduced oxygen carrier enters the oxygen carrier regeneration reactor to react with an oxidizing gas, so that the oxygen carrier is regenerated to obtain a regenerated oxygen carrier; the regenerated oxygen carrier enters the fuel reactor; and the gas product enters the graphene preparation reactor to react with a molten liquid metal catalyst medium as raw gas, so that graphene is obtained. The application can realize CO2 resource utilization, carbon chain circulation, zero emission and low-cost mass production of graphene.

Description

Technical Field

[0001] This invention relates to a graphene preparation system and method, and more particularly to a carbon chain recycling zero-emission graphene preparation system and method, relating to the fields of CO2 resource utilization and graphene preparation technology. Background Technology

[0002] Graphene is a two-dimensional material composed of a single layer of carbon atoms with a hexagonal honeycomb structure. It possesses excellent mechanical, electrical, thermal, and optical properties and is known as "black gold" and "the king of new materials." Its applications have spread to various fields around the world, such as new energy, military defense, electronic information, biomedicine, and aerospace. It is one of the important materials driving the rapid development of science and technology and is considered a super material that will dominate future high-tech competition.

[0003] Since its initial discovery in 2004, graphene research has rapidly progressed from small-scale laboratory studies to large-scale industrial production. Currently, graphene production primarily utilizes flammable and explosive gases such as methane, ethylene, and acetylene as raw materials, undergoing a series of complex chemical reactions. For example, CN111056548A discloses a method and apparatus for the co-production of few-layer graphene and hydrogen. This method includes: adding a metal-containing catalyst to a reaction vessel and heating the catalyst to a molten state; passing hydrocarbon gas into the molten metal-containing catalyst, causing the hydrocarbon gas to form micron-sized bubbles within the molten catalyst, obtaining a solid product and a gas; collecting and purifying the solid product to obtain few-layer graphene; and collecting and separating the gas to obtain hydrogen. However, using hydrocarbon gases as raw materials for processing poses potential safety risks. Furthermore, these raw materials are non-renewable fossil fuels with limited resources.

[0004] Furthermore, the environmental problems caused by the greenhouse effect are becoming increasingly prominent. While vigorously developing clean and renewable energy sources, CO2 capture and utilization technology is one of the effective methods to mitigate the greenhouse effect. It can not only reduce greenhouse gas emissions but also convert them into valuable chemical products, thereby reducing the consumption of traditional fossil fuels. Therefore, how to achieve the resource utilization of CO2 and the production of high-value products is a research hotspot in this field. CN102976320A discloses a method for preparing high-quality graphene using carbon dioxide gas as a raw material. This method involves loading metallic magnesium powder into a tubular high-temperature furnace, introducing carbon dioxide, and heating the furnace to the combustion temperature of the magnesium powder to react and obtain graphene powder. However, this method cannot achieve carbon chain recycling and zero-emission graphene preparation.

[0005] Therefore, the existing technology for preparing graphene mainly uses flammable and explosive gases such as methane, ethylene, and acetylene as raw materials, which poses safety risks; while the method of preparing graphene using CO2 as raw material cannot achieve carbon chain recycling and zero emissions. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a graphene preparation system and method. This invention enables the resource utilization of CO2 and achieves carbon chain recycling, zero emissions, and low-cost mass production of graphene.

[0007] To achieve the above objectives, a first aspect of the present invention provides a graphene preparation system, comprising: a fuel reactor, an oxygen carrier regeneration reactor, and a graphene preparation reactor; the fuel reactor is provided with at least a fuel inlet, an oxygen carrier inlet, an oxygen carrier outlet, and a gaseous product outlet; the oxygen carrier regeneration reactor is provided with at least an oxygen carrier inlet, an oxidizing gas inlet, and an oxygen carrier outlet; the oxygen carrier outlet of the fuel reactor is connected to the oxygen carrier inlet of the oxygen carrier regeneration reactor, and the oxygen carrier outlet of the oxygen carrier regeneration reactor is connected to the oxygen carrier inlet of the fuel reactor, wherein the oxygen carrier circulates between the fuel reactor and the oxygen carrier regeneration reactor; the gaseous product outlet of the fuel reactor is connected to the graphene preparation reactor, and the graphene preparation reactor is provided with a molten liquid metal catalyst medium for converting the gaseous product of the fuel reactor into graphene as a raw material gas; the oxygen carrier regeneration reactor and the graphene preparation reactor form a nested structure for supplying the energy generated by the oxygen carrier regeneration reactor to the graphene preparation reactor to achieve graphene preparation.

[0008] According to a specific embodiment of the present invention, the graphene preparation system further includes: a cyclone separator, wherein the oxygen carrier outlet of the oxygen carrier regeneration reactor is connected to the oxygen carrier inlet of the fuel reactor through the cyclone separator.

[0009] According to a specific embodiment of the present invention, the graphene preparation system further includes: a heat recovery device connected to the cyclone separator for recovering sensible heat from the gas separated by the cyclone separator.

[0010] According to a specific embodiment of the present invention, the graphene preparation system further includes: a heat exchanger for exchanging heat between the sensible heat recovered by the heat recovery device and the oxidizing gas input into the oxygen carrier regeneration reactor, and / or for exchanging heat with the raw material gas input into the graphene preparation reactor.

[0011] According to a specific embodiment of the present invention, the graphene preparation system further includes: a condenser, wherein the gas product outlet of the fuel reactor is connected to the graphene preparation reactor through the condenser.

[0012] According to a specific embodiment of the present invention, the graphene preparation reactor includes a core reaction zone and a graphene collection zone; the graphene collection zone is disposed outside the core reaction zone in an annular jacket manner for collecting graphene overflowing from the top of the core reaction zone; the molten liquid metal catalyst medium is disposed in the core reaction zone. Preferably, the core reaction zone of the graphene preparation reactor is provided with a temperature detector for detecting the temperature of the molten liquid metal catalyst medium.

[0013] According to a specific embodiment of the present invention, the graphene preparation reactor further includes a gas disperser, which is disposed at the bottom of the core reaction zone and is used to disperse the raw material gas entering the core reaction zone.

[0014] According to a specific embodiment of the present invention, the graphene preparation reactor is further connected to a raw material gas supply pipeline, which is connected to the core reaction zone and is used to supply the raw material gas for preparing graphene.

[0015] According to a specific embodiment of the present invention, the graphene preparation reactor is further connected to a reducing gas input pipeline, which is connected to the core reaction zone and is used to regenerate the molten liquid metal catalyst medium.

[0016] A second aspect of the present invention provides a method for preparing graphene, the method being carried out using the graphene preparation system described above, the method comprising the following steps:

[0017] The oxygen carrier and fuel are reacted in a fuel reactor to obtain gaseous products and reduced oxygen carrier; the reduced oxygen carrier enters an oxygen carrier regeneration reactor to react with oxidizing gas to regenerate the oxygen carrier, obtaining regenerated oxygen carrier; the regenerated oxygen carrier enters the fuel reactor, and the oxygen carrier circulates between the fuel reactor and the oxygen carrier regeneration reactor; the gaseous products enter a graphene preparation reactor as raw material gas to react with molten liquid metal catalyst medium to obtain graphene.

[0018] According to a specific embodiment of the present invention, the oxygen carrier includes one or more of nickel-based oxygen carriers, copper-based oxygen carriers, manganese-based oxygen carriers, iron-based oxygen carriers, and cobalt-based oxygen carriers.

[0019] According to a specific embodiment of the present invention, the fuel includes one or more of gaseous fuels, solid fuels, and liquid fuels.

[0020] According to a specific embodiment of the present invention, the regenerated oxygen carrier undergoes gas-solid separation via a cyclone separator before entering the fuel reactor.

[0021] According to a specific embodiment of the present invention, the reaction temperature of the fuel reactor is 800–1200°C; the oxygen provided by the oxygen carrier entering the fuel reactor is 1.05–1.4 times the oxygen required for the complete oxidation of the fuel input into the fuel reactor. It should be noted that the 1.05–1.4 times here is in molar terms.

[0022] According to a specific embodiment of the present invention, the graphene preparation method further includes: using a heat recovery device to recover the sensible heat of the gas separated by the cyclone separator.

[0023] According to a specific embodiment of the present invention, the graphene preparation method further includes: using a heat exchanger to exchange the sensible heat recovered by the heat recovery device with the oxidizing gas input into the oxygen carrier regeneration reactor, and / or, to exchange heat with the raw material gas input into the graphene preparation reactor.

[0024] According to a specific embodiment of the present invention, the gaseous products include carbon-containing gases and water vapor, wherein the carbon-containing gases include CO2 and / or CO, etc.

[0025] According to a specific embodiment of the present invention, the gaseous product is separated into water vapor by a condenser and then enters the graphene preparation reactor as raw material gas; the condensation temperature of the condenser is below 80°C.

[0026] According to a specific embodiment of the present invention, the oxidizing gas includes air and / or oxygen, etc.

[0027] According to a specific embodiment of the present invention, the reaction temperature of the oxygen carrier regeneration reactor is 800–1600°C. There are no special restrictions on the ratio between the reduced oxygen carrier entering the oxygen carrier regeneration reactor and the oxidizing gas input into the reactor, but an excess of oxidizing gas must be introduced to ensure complete oxidation and regeneration of the reduced oxygen carrier. Furthermore, the excess oxidizing gas can also balance the reactor temperature, maintaining it at a certain preset value.

[0028] According to a specific embodiment of the present invention, the molten liquid metal catalytic medium is molten liquid metal, or a mixture of molten liquid metal and molten liquid salt; the molten liquid metal includes one or more of magnesium, iron, copper, cobalt, nickel, gallium, tin and bismuth; the molten liquid salt does not volatilize or decompose at 800-1400°C.

[0029] According to a specific embodiment of the present invention, the graphene preparation method further includes: supplementing the graphene preparation reactor with a raw material gas, wherein the supplemented raw material gas is a carbon-containing gas, or a mixture of a carbon-containing gas and a protective gas; the carbon-containing gas includes CO2 and / or CO, etc.

[0030] According to a specific embodiment of the present invention, the reaction temperature of the core reaction zone of the graphene preparation reactor is controlled by adjusting the flow rate of the oxidizing gas input into the oxygen carrier regeneration reactor, and / or by adjusting the flow rate of the fuel input into the fuel reactor; the reaction temperature of the core reaction zone of the graphene preparation reactor is 600–1500°C, and the flow rate of the raw material gas entering the graphene preparation reactor (L·h) is... -1 The volume ratio (L) of the catalytic medium to the volume of the molten liquid metal catalyst in the graphene preparation reactor is 0.2–10 (h). -1 ).

[0031] According to a specific embodiment of the present invention, the graphene preparation method further includes: stopping the input of raw material gas into the graphene preparation reactor, and then inputting a reducing gas into the graphene preparation reactor to regenerate the molten liquid metal catalyst medium; when the volume content of water vapor in the gas discharged from the graphene preparation reactor is less than 0.1%, the regeneration of the molten liquid metal catalyst medium is considered complete, the input of reducing gas into the graphene preparation reactor is stopped, and then the input of raw material gas into the graphene preparation reactor continues.

[0032] According to a specific embodiment of the present invention, the reducing gas is hydrogen, or a mixture of hydrogen and a protective gas.

[0033] The present invention has at least the following beneficial effects:

[0034] This invention provides the energy required for CO2 conversion through coupled combustion technology. Benefiting from the inherent carbon separation characteristics of this combustion technology, zero CO2 emissions can be achieved during the energy supply process. This invention enables the rational and resource-based utilization of the greenhouse gas CO2, not only helping to reduce direct CO2 emissions into the atmosphere but also turning waste into treasure, producing economically valuable graphene products. Using carbon-containing gas generated by the fuel reactor as feedstock, this invention can further combine it with additionally supplied carbon-containing gas for graphene preparation, achieving carbon chain recycling and zero-carbon emission graphene production, and solving the greenhouse gas emissions indirectly caused by the high-temperature energy supply of the fuel reactor. Furthermore, this invention uses a molten liquid metal catalyst medium to convert the gaseous products of the fuel reactor into graphene. By utilizing the density difference between the molten liquid metal catalyst medium and graphene, the generated graphene spontaneously floats on the surface of the molten liquid metal catalyst medium. Furthermore, through the jacketed graphene preparation reactor designed in this invention, the graphene accumulates to a certain height and overflows from the core reaction zone to the graphene collection zone, achieving continuous and automatic separation of carbon materials. Furthermore, this invention can further achieve in-situ regeneration of molten liquid metal catalyst media by flexibly switching the gas supply path, changing the status of molten liquid metal catalyst media as a disposable consumable, and realizing large-scale utilization of CO2 and low-cost mass production of graphene. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the graphene preparation system in a specific embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the spatial structure of the oxygen carrier regeneration reactor embedded with graphene in a specific embodiment of the present invention.

[0037] Figure 3 The results are shown by scanning electron microscopy characterization of the graphene powder prepared in Example 1.

[0038] Figure 4 The transmission electron microscopy (TEM) characterization results are shown for the graphene powders prepared in Examples 1 and 2.

[0039] Figure 5 This is a schematic diagram of the conventional direct combustion-powered graphene preparation device in Comparative Example 1.

[0040] Explanation of icon numbers:

[0041] 1-Fuel reactor; 2-Oxygen carrier regeneration reactor; 3-Graphene preparation reactor; 4-Cyclone separator; 5-Condenser;

[0042] 301 - Core reaction zone; 302 - Graphene collection zone; 303 - Molten liquid metal catalyst medium; 304 - Product outlet; 305 - Exhaust port; 306 - Raw material gas supply line; 307 - Reducing gas input line; 308 - Temperature detector;

[0043] 6-Gas-fired pyrolysis furnace; 601-Flue gas passage; 602-Burner. Detailed Implementation

[0044] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0045] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0047] It should be understood that the terms “comprising,” “including,” and / or “containing” as used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0048] The endpoints and any values ​​of the ranges disclosed in this invention 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 in this invention.

[0049] In the description of this invention, it should be noted that the terms "upper," "lower," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0051] According to a specific embodiment of the first aspect of the present invention, the present invention provides a graphene preparation system, such as... Figure 1 As shown, it includes: a fuel reactor 1, an oxygen carrier regeneration reactor 2, and a graphene preparation reactor 3; the fuel reactor 1 is provided with at least a fuel inlet, an oxygen carrier inlet, an oxygen carrier outlet, and a gaseous product outlet; the oxygen carrier regeneration reactor 2 is provided with at least an oxygen carrier inlet, an oxidizing gas inlet, and an oxygen carrier outlet; the oxygen carrier outlet of the fuel reactor 1 is connected to the oxygen carrier inlet of the oxygen carrier regeneration reactor 2, and the oxygen carrier outlet of the oxygen carrier regeneration reactor 2 is connected to the oxygen carrier inlet of the fuel reactor 1, and the oxygen carrier circulates between the fuel reactor 1 and the oxygen carrier regeneration reactor 2; the gaseous product outlet of the fuel reactor 1 is connected to the graphene preparation reactor 3, and the graphene preparation reactor 3 is provided with a molten liquid metal catalyst medium 303, which is used to convert the gaseous product of the fuel reactor 1 into graphene as a raw material gas; the oxygen carrier regeneration reactor 2 and the graphene preparation reactor 3 form a nested structure, which is used to supply the energy generated by the oxygen carrier regeneration reactor 2 to the graphene preparation reactor 3 to achieve the preparation of graphene.

[0052] In some embodiments, fuel reactor 1 has a fuel inlet at the bottom, an oxygen carrier inlet at the top, an oxygen carrier outlet at the bottom, and a gaseous product outlet at the top; oxygen carrier regeneration reactor 2 has an oxygen carrier inlet at the bottom, an oxidizing gas inlet at the bottom, and an oxygen carrier outlet at the top. A flow meter is installed on the pipeline connected to the fuel inlet of fuel reactor 1 to regulate the flow rate of fuel input into fuel reactor 1.

[0053] In some embodiments, the graphene preparation system further includes a cyclone separator 4, wherein the oxygen carrier outlet of the oxygen carrier regeneration reactor 2 is connected to the oxygen carrier inlet of the fuel reactor 1 via the cyclone separator 4. The cyclone separator 4 is used for gas-solid separation; the separated solid is the oxygen carrier, which enters the fuel reactor 1, and the separated gas is mainly oxygen-deficient air.

[0054] In some embodiments, the graphene preparation system further includes a heat recovery device connected to the cyclone separator 4 for recovering sensible heat from the gas separated by the cyclone separator 4. The gas separated by the cyclone separator 4 can be directly discharged after sensible heat recovery.

[0055] In some embodiments, the graphene preparation system further includes: a heat exchanger for exchanging heat between the sensible heat recovered by the heat recovery device and the oxidizing gas input into the oxygen carrier regeneration reactor 2, and / or for exchanging heat with the raw material gas input into the graphene preparation reactor 3.

[0056] In some embodiments, the bottom cross-sectional diameter of the oxygen carrier regeneration reactor 2 is larger than the top cross-sectional diameter. The oxygen carrier regeneration reactor 2 of the present invention preferably adopts a structural design with a larger bottom and a smaller top, which can accelerate the airflow and carry the regenerated oxygen carrier out of the reactor.

[0057] In some embodiments, the graphene preparation system further includes a condenser 5, wherein the gaseous product outlet of the fuel reactor 1 is connected to the graphene preparation reactor 3 via the condenser 5. Preferably, a flow meter is installed on the pipeline connecting the condenser 5 and the graphene preparation reactor 3 to regulate the flow rate of the raw material gas input into the graphene preparation reactor 3.

[0058] In some embodiments, the graphene preparation reactor 3 includes a core reaction zone 301 and a graphene collection zone 302. The graphene collection zone 302 is disposed outside the core reaction zone 301 in an annular jacket manner to collect graphene overflowing from the top of the core reaction zone 301. A molten liquid metal catalyst medium 303 is disposed in the core reaction zone 301, and a temperature detector 308 is disposed thereto detect the temperature of the molten liquid metal catalyst medium. To facilitate the overflow of graphene from the top of the core reaction zone 301 to the graphene collection zone 302, there should be an appropriate spatial distance between the core reaction zone 301 and the top of the graphene preparation reactor 3.

[0059] In some embodiments, a raw material gas inlet is provided at the bottom of the core reaction zone 301 of the graphene preparation reactor 3, the gas product outlet of the fuel reactor 1 is connected to the raw material gas inlet of the graphene preparation reactor 3, a product outlet 304 is provided at the bottom of the graphene collection zone 302 of the graphene preparation reactor 3, and an exhaust port 305 is provided at the top of the graphene preparation reactor 3 (for discharging water vapor generated during the regeneration of the molten liquid metal catalyst medium). When the graphene collected in the graphene collection zone 302 accumulates to a high amount, the graphene can be pumped out from the product outlet 304.

[0060] In some embodiments, the graphene preparation reactor further includes a gas disperser disposed at the bottom of the core reaction zone 301 for dispersing the raw material gas entering the core reaction zone 301.

[0061] In some embodiments, the graphene preparation reactor is further connected to a raw material gas supply line 306, which is connected to the core reaction zone 301 (specifically, to the bottom of the core reaction zone 301) to supply the raw material gas for graphene preparation. Preferably, a flow meter is provided on the raw material gas supply line 306 to regulate the flow rate of the supplied raw material gas.

[0062] In some embodiments, the graphene preparation reactor is further connected to a reducing gas input line 307, which is connected to the core reaction zone 301 (specifically, to the bottom of the core reaction zone 301) for regenerating the molten liquid metal catalyst medium. Preferably, a flow meter is provided on the reducing gas input line 307 for regulating the flow rate of the reducing gas.

[0063] In some embodiments, a nested structure is formed between the oxygen carrier regeneration reactor 2 and the graphene preparation reactor 3, whereby the oxygen carrier regeneration reactor 2 is embedded within the graphene preparation reactor 3, or vice versa. As described above, the nested structure is for energy supply, and the materials between the oxygen carrier regeneration reactor 2 and the graphene preparation reactor 3 do not directly contact or communicate. Figure 2 As shown, preferably, the oxygen carrier regeneration reactor 2 is embedded in the graphene preparation reactor 3. Specifically, the core reaction zone 301 of the graphene preparation reactor 3 is annularly enclosed outside the oxygen carrier regeneration reactor 2, which is more conducive to energy supply to the graphene preparation reactor 3.

[0064] According to a specific embodiment of a second aspect of the present invention, the present invention provides a method for preparing graphene, the method being carried out using the graphene preparation system described above, the method comprising the following steps:

[0065] The oxygen carrier and fuel are reacted in fuel reactor 1 to obtain gaseous products and reduced oxygen carrier; the reduced oxygen carrier enters oxygen carrier regeneration reactor 2 and reacts with oxidizing gas to regenerate the oxygen carrier, obtaining regenerated oxygen carrier; the regenerated oxygen carrier enters fuel reactor 1, and the oxygen carrier circulates between fuel reactor 1 and oxygen carrier regeneration reactor 2; the gaseous products enter graphene preparation reactor 3 as raw material gas and react with molten liquid metal catalyst medium 303 to obtain graphene.

[0066] In some embodiments, the oxygen carrier includes one or more of nickel-based oxygen carriers, copper-based oxygen carriers, manganese-based oxygen carriers, iron-based oxygen carriers, and cobalt-based oxygen carriers.

[0067] In some embodiments, the fuel includes one or more of gaseous fuels, solid fuels, and liquid fuels. Preferably, the fuel includes one or more of natural gas, alkanes, olefins, alkynes, pulverized coal, and biomass.

[0068] In some embodiments, the regenerated oxygen carrier undergoes gas-solid separation via a cyclone separator 4 before entering the fuel reactor 1.

[0069] In some embodiments, the reaction temperature of the fuel reactor 1 is 800–1200°C; the oxygen provided by the oxygen carrier entering the fuel reactor 1 is 1.05–1.4 times the oxygen required for the complete oxidation of the fuel input into the fuel reactor 1.

[0070] In some embodiments, the graphene preparation method further includes: recovering the sensible heat of the gas separated by the cyclone separator 4 using a heat recovery device. Preferably, the graphene preparation method further includes: exchanging the sensible heat recovered by the heat recovery device with the oxidizing gas input into the oxygen carrier regeneration reactor 2 using a heat exchanger, and / or exchanging the heat with the raw material gas input into the graphene preparation reactor 3.

[0071] In some embodiments, the gaseous product comprises a carbon-containing gas and water vapor, wherein the carbon-containing gas includes CO2 and / or CO, etc. Preferably, the carbon-containing gas is CO2, or a mixture of CO and CO2. The CO and CO2 in the mixture can be in any proportion.

[0072] In some embodiments, the gaseous product, after being separated into water vapor by condenser 5, enters the graphene preparation reactor as raw material gas. Preferably, the condensation temperature of condenser 5 is below 80°C, more preferably 25–40°C.

[0073] In some embodiments, the oxidizing gas includes air and / or oxygen, etc.

[0074] In some embodiments, the reaction temperature of the oxygen carrier regeneration reactor 2 is 800–1600°C. There are no special restrictions on the ratio between the reduced oxygen carrier entering the oxygen carrier regeneration reactor and the oxidizing gas input into the reactor, but an excess of oxidizing gas must be introduced to ensure complete oxidation and regeneration of the reduced oxygen carrier. Furthermore, the excess oxidizing gas can balance the reactor temperature, maintaining it at a predetermined value.

[0075] In some embodiments, the molten liquid metal catalyst medium 303 is a molten liquid metal, or a mixture of a molten liquid metal and a molten liquid salt; the molten liquid metal includes one or more of magnesium, iron, copper, cobalt, nickel, gallium, tin, and bismuth; the molten liquid salt is not easily volatilized or decomposed at 800–1400°C. When the molten liquid metal catalyst medium 303 is a mixture of a molten liquid metal and a molten liquid salt, the molar percentage of the molten liquid metal in the mixture is 10% or more. Preferably, the molten liquid metal catalyst medium 303 is a mixture of a molten liquid metal and a molten liquid salt. The addition of the molten liquid salt can significantly reduce metal impurities in graphene and reduce subsequent processing costs. There are no special limitations on the type of molten liquid salt, as long as it is not easily volatilized or decomposed at 800–1400°C, for example, it may include one or two of metal halide salts and sulfates.

[0076] In some embodiments, the graphene preparation method further includes: replenishing the graphene preparation reactor 3 with a raw material gas, wherein the replenished raw material gas is a carbon-containing gas, or a mixture of a carbon-containing gas and a protective gas. The carbon-containing gas includes CO2 and / or CO, preferably CO2. The protective gas includes, but is not limited to, one or more of nitrogen, helium, argon, and neon. The carbon-containing gas and the protective gas in the mixture can be in any proportion. This invention does not impose any special restrictions on the source of the carbon-containing gas in the replenished raw material gas.

[0077] In some embodiments, the reaction temperature of the core reaction zone 301 of the graphene preparation reactor 3 is controlled by adjusting the flow rate of the oxidizing gas in the oxygen carrier regeneration reactor 2, and / or by adjusting the flow rate of the fuel in the fuel reactor 1; the reaction temperature of the core reaction zone 301 of the graphene preparation reactor 3 is 600–1500 °C, and the flow rate of the raw material gas entering the graphene preparation reactor 3 (L·h) is... -1 The volume ratio (L) of the molten liquid metal catalyst medium in the graphene preparation reactor 3 to that in the other reactor is 0.2–10 (h). -1 ).

[0078] In some embodiments, the graphene preparation method further includes: stopping the input of raw material gas into the graphene preparation reactor 3, and then inputting a reducing gas into the graphene preparation reactor 3 to regenerate the molten liquid metal catalyst medium 303; when the volume content of water vapor in the gas discharged from the graphene preparation reactor 3 (discharged through the exhaust port 305) is below 0.1%, the regeneration of the molten liquid metal catalyst medium 303 is considered complete, the input of reducing gas into the graphene preparation reactor 3 is stopped, and then the input of raw material gas into the graphene preparation reactor 3 continues. When the graphene generation rate is low or even no longer, it can be considered that the reaction between the raw material gas and the molten liquid metal catalyst medium 303 in the graphene preparation reactor 3 is complete. At this time, the input of raw material gas into the graphene preparation reactor 3 is stopped, and the injection of reducing gas is switched to achieve the regeneration of the molten liquid metal catalyst medium 303. The low graphene generation rate or even no longer graphene generation described herein can be determined by those skilled in the art based on conventional technical means, and the present invention does not impose any special limitations on it. The volume content of water vapor in the gas discharged from the graphene preparation reactor 3 can be detected by conventional techniques in the field, and the present invention does not impose any special restrictions on it.

[0079] In some embodiments, the reducing gas is hydrogen, or a mixture of hydrogen and a protective gas. The protective gas includes, but is not limited to, one or more of nitrogen, helium, argon, and neon. The hydrogen and protective gas in the mixture can be in any proportion.

[0080] In this invention, fuel reactor 1 and oxygen carrier regeneration reactor 2 are connected and form a closed loop. The oxygen carrier (MeO) circulates in both reactors to achieve lattice oxygen transfer and regeneration. This novel combustion energy supply method decomposes traditional direct combustion into two independent processes, conducted separately in fuel reactor 1 and oxygen carrier regeneration reactor 2, releasing energy equal to that released by traditional direct combustion. In fuel reactor 1, fuel enters from the bottom, and oxygen carrier enters from the top. The fuel and oxygen carrier move towards each other and are in full contact. Under the action of the oxygen carrier, the fuel is oxidized into CO2 and water vapor, while the oxygen carrier is reduced to low-valence metal oxides or elemental metals. The reduced oxygen carrier enters oxygen carrier regeneration reactor 2 from the bottom, and the oxidizing gas also enters from the bottom. The reduced oxygen carrier and oxidizing gas are in full contact, and the low-valence metal oxides or elemental metals are oxidized and regenerated by the oxidizing gas. The regenerated oxygen carrier, along with oxygen-deficient air (mainly nitrogen and a small amount of oxygen), is discharged from the top of the oxygen carrier regeneration reactor 2 and enters the cyclone separator 4 for gas-solid separation. The oxygen-deficient air is discharged from the top of the cyclone separator 4 and, after sensible heat recovery, can be directly discharged. The oxygen carrier, after passing through the cyclone separator 4, enters the fuel reactor 1, achieving oxygen carrier recycling. The CO2 and water vapor generated in the fuel reactor 1 are discharged from the top. Under the action of the condenser 5, the water vapor becomes liquid and is discharged. Since this process does not involve N2 dilution, the CO2 concentration is high. Therefore, CO2 and water vapor can be separated by simple condensation to obtain near-pure CO2. CO2 separation can be achieved with little or no additional energy, thus reducing the investment cost of CO2 separation equipment. The separated CO2, along with additional CO2, can be fed into the graphene preparation reactor 3 for graphene preparation, realizing a chain-like recycling of CO2, turning waste into treasure, and eliminating CO2 emissions.

[0081] The reactions involved in the three reactors of this invention mainly include:

[0082] Fuel reactor 1:

[0083] MeO(s) + fuel → Me(s) + CO2(g) + H2O(g)

[0084] Oxygen carrier regeneration reactor 2:

[0085] Me(s) + oxidizing gas(g) → MeO(s) + N2(g)

[0086] Graphene preparation reactor 3:

[0087] CO2 + molten liquid metal catalyst (l) → C(s) + molten liquid metal oxide (l)

[0088] Furthermore, this invention designs a nested structure between the oxygen carrier regeneration reactor 2 and the graphene preparation reactor 3. The energy released from the oxidation of the reduced oxygen carrier in the oxygen carrier regeneration reactor 2 is supplied to the graphene preparation reactor 3 via thermal radiation and heat conduction, providing the energy required for the graphene preparation reaction and maximizing resource utilization. Moreover, the temperature can be controlled by adjusting the amount of oxidizing gas input to the oxygen carrier regeneration reactor 2 and / or the amount of fuel input to the fuel reactor 1.

[0089] Furthermore, the graphene preparation reactor 3 of this invention has a jacketed structure, with the graphene collection zone 302 arranged in an annular jacket outside the core reaction zone 301. The core reaction zone 301 contains a molten liquid metal catalyst medium 303. Raw material gas enters from the bottom of the graphene preparation reactor and, under the action of a gas disperser, bubbles of micron or millimeter size are blown out of the molten liquid metal catalyst medium 303. During their ascent, the bubbles fully contact and react with the molten liquid metal catalyst medium 303, converting CO2 into graphene powder. The generated graphene powder, due to its much lower density than the molten liquid metal catalyst medium 303, spontaneously floats on its surface, effectively isolating the graphene from the molten liquid metal catalyst medium 303. The generated graphene overflows from the core reaction zone 301 into the graphene collection zone 302. When a high amount of graphene accumulates in the graphene collection zone 302, it can be pumped out from the product outlet 304 at the bottom of the reactor. This process enables the automatic separation of carbon products and can further improve reaction efficiency.

[0090] In addition, in the graphene preparation reactor 3, the molten liquid metal catalyst 303 reacts with CO2, transforming into molten liquid metal oxide and gradually deactivating, resulting in a gradual decrease and eventual cessation of graphene powder production. At this point, the feed gas supply must be temporarily shut off, and a reducing gas is introduced into the graphene preparation reactor 3 to achieve the cyclic regeneration of the molten liquid metal catalyst 303. The regeneration process of the molten liquid metal catalyst 303 is accompanied by the generation of water vapor, which is discharged through the exhaust port 305 at the top of the graphene preparation reactor 3. When the gas discharged from the exhaust port 305 of the graphene preparation reactor 3 contains almost no water vapor, the regeneration of the molten liquid metal catalyst 303 is complete. At this point, the reducing gas supply can be shut off, and the feed gas can be reintroduced to continue graphene preparation.

[0091] The present invention is illustrated in detail below by way of examples, but the present invention is not limited to these examples. Of course, various modifications can be made within the scope of the present invention.

[0092] Example 1

[0093] This embodiment provides a graphene preparation system, the structure of which is as follows: Figure 1 As shown above, the specific structure will not be repeated here.

[0094] In this embodiment, as Figure 2 As shown, the oxygen carrier regeneration reactor 2 is embedded in the graphene preparation reactor 3, that is, the core reaction zone 301 of the graphene preparation reactor 3 is ring-shaped and surrounded by the oxygen carrier regeneration reactor 2.

[0095] This embodiment also provides a method for preparing graphene, which includes the following steps:

[0096] Nickel-based oxygen carrier particles are loaded into fuel reactor 1, and fuel methane gas is introduced to supply appropriate initial heat, maintaining the chamber temperature of fuel reactor 1 at 1100℃. This allows the nickel-based oxygen carrier to undergo a chemical reaction with methane at high temperature, specifically CH4(g) + 4NiO(s) → 4Ni(s) + CO2(g) + 2H2O(g). The gaseous products (i.e., CO2 and water vapor) are discharged through the top of fuel reactor 1, while the solid products (i.e., Ni, also known as reduced oxygen carrier) enter oxygen carrier regeneration reactor 2. Air is also introduced into oxygen carrier regeneration reactor 2, where it reacts with the high-temperature reduced oxygen carrier (Ni), specifically Ni(s) + air(g). The reaction is NiO(s) + oxygen-deficient air(g). Driven by airflow, the product enters cyclone separator 4 for gas-solid separation. The separated gas is discharged from the top of cyclone separator 4, and a heat recovery device recovers the sensible heat of the separated gas before direct discharge. The solid separated by cyclone separator 4 (i.e., high-temperature NiO) is discharged from the bottom of cyclone separator 4 and enters oxygen carrier regeneration reactor 2, realizing the circulation of oxygen carrier between fuel reactor 1 and oxygen carrier regeneration reactor 2. The molar flow rate of oxygen carrier entering fuel reactor 1 is 4.4 times that of fuel (i.e., the oxygen provided by the oxygen carrier is 1.1 times the oxygen required for complete fuel oxidation). After the circulation begins, no additional heat is needed to fuel reactor 1; the entire process is a self-heating reaction. The temperature in oxygen carrier regeneration reactor 2 is 1300℃. This temperature is maintained by introducing excess air to ensure complete oxidation and regeneration of the reduced oxygen carrier.

[0097] A heat exchanger can be used to exchange heat between the sensible heat recovered by the heat recovery device and the air input into the oxygen carrier regeneration reactor 2, and / or, with the raw material gas input into the graphene preparation reactor 3.

[0098] The high-temperature gaseous products (i.e., CO2 and water vapor) generated in fuel reactor 1 are separated by condenser 5. The condensation temperature is below 60℃, yielding pure CO2. The separated CO2, along with additional supplementary CO2, is then fed into graphene preparation reactor 3 for graphene production.

[0099] The graphene preparation reactor 3 includes a core reaction zone 301 and a graphene collection zone 302. The core reaction zone 301 contains a copper-magnesium alloy. An oxygen carrier regeneration reactor 2 is embedded in the core reaction zone 301 of the graphene preparation reactor 3. The copper-magnesium alloy is heated into a molten liquid metal alloy through heat conduction and radiation, and the temperature is detected by a temperature detector 308. In this embodiment, the temperature of the molten liquid metal alloy is maintained at 1170°C. The flow rate of the raw material gas entering the graphene preparation reactor 3 (including the raw material gas generated by the fuel reactor 1 and the supplementary raw material gas) to the volume of the molten liquid metal alloy in the graphene preparation reactor 3 is 2.

[0100] The raw material gas CO2 enters the molten liquid metal alloy as micron-sized bubbles through the bottom of the graphene preparation reactor 3 and the gas disperser. As the bubbles rise, they react with the molten liquid metal alloy to generate graphene powder. Because the density of the generated graphene powder is much lower than that of the molten liquid metal alloy, it spontaneously floats on its surface, effectively isolating the graphene from the molten liquid metal alloy. When the generated graphene powder accumulates to a high height, it overflows from the core reaction zone 301 into the graphene collection zone 302. When a significant amount of graphene accumulates in the graphene collection zone 302, it can be pumped out from the product outlet 304 at the bottom of the reactor.

[0101] In the graphene preparation reactor 3, the molten liquid metal alloy reacts with CO2, transforming into an oxidized catalytic medium and gradually deactivating. The generated graphene powder also gradually decreases and eventually ceases to be produced. Specifically, the reactions are 2Cu(l) + CO2(g) → C(s) + 2CuO(l) and 2Mg(l) + CO2(g) → C(s) + 2MgO(l). At this point, the feed gas CO2 needs to be temporarily shut off, and the reducing gas hydrogen is switched to be introduced into the graphene preparation reactor 3 to achieve the recycling and regeneration of the molten liquid metal alloy. The reactions involved are MgO(l) + H2(g) → H2O(g) + Mg(l) and CuO(l) + H2(g) → H2O(g) + Cu(l). The regeneration process of the molten liquid metal alloy is accompanied by the generation of water vapor, which is discharged through the exhaust port 305 at the top of the graphene preparation reactor 3. When the volume content of water vapor in the gas discharged from the exhaust port 305 of the graphene preparation reactor 3 is less than 0.1%, it can be considered that the regeneration of the molten liquid metal alloy is complete. At this time, the hydrogen reducing gas can be shut off and the CO2 raw material gas valve can be opened to continue the graphene preparation.

[0102] The CO2 conversion rate in this embodiment reaches 71%. The formula for calculating the CO2 conversion rate is as follows: The microscopic characterization results of the prepared graphene powder are as follows: Figure 3 and Figure 4 As shown, the graphene powder has approximately 8 layers. It can be seen that this embodiment exhibits a high conversion rate and produces high-quality graphene powder. Furthermore, this embodiment achieves CO2 resource utilization and realizes carbon chain recycling, zero emissions, and low-cost mass production of graphene.

[0103] Example 2

[0104] This embodiment is basically the same as Embodiment 1, except that the oxygen carrier is selected as an iron-based oxygen carrier, specifically Fe2O3 / FeO. This is because iron-based oxygen carriers have a relatively low melting point. In this embodiment, the temperature in the oxygen carrier regeneration reactor 2 is controlled at 1100℃, and the temperature of the molten liquid metal alloy is maintained at 960℃. The microscopic characterization results of the obtained graphene powder are as follows: Figure 4 As shown in Table 1, the CO2 conversion rate and the number of layers of the obtained graphene powder in this embodiment are as follows.

[0105] Example 3

[0106] This embodiment is basically the same as Embodiment 1, except that the temperature in the oxygen carrier regeneration reactor 2 is controlled at 1100℃, the oxygen carrier is the same as in Embodiment 1, and the temperature of the molten liquid metal alloy is maintained at 960℃. The CO2 conversion rate and the number of layers of the obtained graphene powder in this embodiment are shown in Table 1 below.

[0107] Comparative Example 1

[0108] Comparative Example 1 is basically the same as Example 1, except that it uses a conventional direct combustion method for heating. The structure of the specific device used in this comparative example is as follows: Figure 5 As shown, it employs a jacketed heating system. Gas is injected into the gas-heated pyrolysis furnace 6 via burner 602 for combustion. High-temperature flue gas provides heat to the gas-heated pyrolysis furnace 6 through flue gas channel 601 to achieve the pyrolysis reaction and obtain graphene. The gas-heated pyrolysis furnace 6 contains the same molten liquid metal alloy as in Example 1, and the injected gas is also the same as in Example 1. The temperature of the molten liquid metal alloy is maintained at 1170°C.

[0109] The results of the above embodiments and comparative examples are shown in Table 1 below.

[0110] From the perspective of methane cracking performance, methane cracking is an endothermic reaction, and the higher the reaction temperature, the more favorable it is for its complete conversion. The comparison results between Example 1 and Example 3 in Table 1 also confirm the above conclusion. This is because the ordered assembly between carbon atoms is an endothermic and energy-consuming process, and the higher cracking reaction temperature can provide this energy, allowing carbon materials to be better ordered and assembled, transforming into high-quality graphene, and reducing the number of graphene layers from 21 layers to about 8 layers.

[0111] As can be seen from the comparison results of Examples 1 and 2 in Table 1, the main function of the oxygen carrier is to provide oxygen atoms to enable the fuel to fully oxidize. Because the physicochemical properties of the oxygen carriers differ, their maximum carrying capacity varies, thus requiring control of their regeneration temperature. Comparatively, nickel-based oxygen carriers have stronger high-temperature resistance than iron-based oxygen carriers, therefore, they can supply a higher temperature for methane cracking, exhibit better catalytic cracking performance, and produce a relatively lower number of graphene layers.

[0112] The comparison results between Example 2 and Example 3, and between Example 1 and Comparative Example 1, show that when the temperature of the pyrolysis reactor is kept constant, the use of different or oxygen-free carriers has almost no effect on the CO2 conversion rate and graphene quality.

[0113] Comparing Example 1 and Comparative Example 1, the process technology route of the present invention achieves zero CO2 emissions and carbon chain recycling compared with the conventional direct combustion method. It can also make additional use of some external CO2 gas sources, reduce the impact of greenhouse gases on the environment, and realize the high-value transformation of waste gas resources.

[0114] Table 1 Comparison results between the examples and the comparative examples

[0115]

[0116]

[0117] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A graphene preparation system, comprising: The reactor comprises a fuel reactor, an oxygen carrier regeneration reactor, and a graphene preparation reactor; the fuel reactor is provided with at least a fuel inlet, an oxygen carrier inlet, an oxygen carrier outlet, and a gaseous product outlet; the oxygen carrier regeneration reactor is provided with at least an oxygen carrier inlet, an oxidizing gas inlet, and an oxygen carrier outlet. The oxygen carrier outlet of the fuel reactor is connected to the oxygen carrier inlet of the oxygen carrier regeneration reactor, and the oxygen carrier outlet of the oxygen carrier regeneration reactor is connected to the oxygen carrier inlet of the fuel reactor. The oxygen carrier circulates between the fuel reactor and the oxygen carrier regeneration reactor. The gaseous product outlet of the fuel reactor is connected to the graphene preparation reactor, which is equipped with a molten liquid metal catalyst medium to convert the gaseous product of the fuel reactor into graphene as a raw material. The oxygen carrier regeneration reactor and the graphene preparation reactor form a nested structure, which allows the energy generated by the oxygen carrier regeneration reactor to supply the graphene preparation reactor to achieve the preparation of graphene.

2. The graphene preparation system according to claim 1, wherein, The graphene preparation system further includes a cyclone separator, wherein the oxygen carrier outlet of the oxygen carrier regeneration reactor is connected to the oxygen carrier inlet of the fuel reactor via the cyclone separator.

3. The graphene preparation system according to claim 2, wherein, The graphene preparation system further includes a heat recovery device connected to the cyclone separator for recovering sensible heat from the gas separated by the cyclone separator.

4. The graphene preparation system according to claim 3, wherein, The graphene preparation system further includes: a heat exchanger for exchanging heat between the sensible heat recovered by the heat recovery device and the oxidizing gas input into the oxygen carrier regeneration reactor, and / or for exchanging heat with the raw material gas input into the graphene preparation reactor.

5. The graphene preparation system according to claim 1, wherein, The graphene preparation system further includes a condenser, through which the gas product outlet of the fuel reactor is connected to the graphene preparation reactor.

6. The graphene preparation system according to claim 1, wherein, The graphene preparation reactor includes a core reaction zone and a graphene collection zone; the graphene collection zone is arranged in an annular jacket outside the core reaction zone to collect graphene overflowing from the top of the core reaction zone; the core reaction zone contains the molten liquid metal catalyst medium.

7. The graphene preparation system according to claim 6, wherein, The graphene preparation reactor further includes a gas disperser, which is disposed at the bottom of the core reaction zone and is used to disperse the raw material gas entering the core reaction zone.

8. The graphene preparation system according to claim 6, wherein, The graphene preparation reactor is further connected to a raw material gas supply pipeline, which is connected to the core reaction zone and is used to supply the raw material gas for graphene preparation.

9. The graphene preparation system according to claim 6, wherein, The graphene preparation reactor is further connected to a reducing gas input pipeline, which is connected to the core reaction zone and is used to regenerate the molten liquid metal catalyst medium.

10. A method for preparing graphene, wherein the method is performed using the graphene preparation system according to any one of claims 1-9, the method comprising the following steps: The oxygen carrier and fuel are reacted in a fuel reactor to obtain gaseous products and reduced oxygen carrier; the reduced oxygen carrier enters an oxygen carrier regeneration reactor to react with oxidizing gas to regenerate the oxygen carrier, obtaining regenerated oxygen carrier; the regenerated oxygen carrier enters the fuel reactor, and the oxygen carrier circulates between the fuel reactor and the oxygen carrier regeneration reactor; the gaseous products enter a graphene preparation reactor as raw material gas to react with molten liquid metal catalyst medium to obtain graphene.

11. The method for preparing graphene according to claim 10, wherein, The oxygen carrier includes one or more of nickel-based oxygen carriers, copper-based oxygen carriers, manganese-based oxygen carriers, iron-based oxygen carriers, and cobalt-based oxygen carriers.

12. The method for preparing graphene according to claim 10, wherein, The fuel includes one or more of gaseous fuels, solid fuels, and liquid fuels.

13. The method for preparing graphene according to claim 10, wherein, The regenerated oxygen carrier undergoes gas-solid separation via a cyclone separator before entering the fuel reactor.

14. The method for preparing graphene according to claim 10, wherein, The reaction temperature of the fuel reactor is 800–1200°C; the oxygen provided by the oxygen carrier entering the fuel reactor is 1.05–1.4 times the oxygen required for the complete oxidation of the fuel input into the fuel reactor.

15. The method for preparing graphene according to claim 13, wherein, The graphene preparation method further includes: using a heat recovery device to recover the sensible heat of the gas separated by the cyclone separator.

16. The method for preparing graphene according to claim 15, wherein, The graphene preparation method further includes: using a heat exchanger to exchange the sensible heat recovered by the heat recovery device with the oxidizing gas input into the oxygen carrier regeneration reactor, and / or, with the raw material gas input into the graphene preparation reactor.

17. The method for preparing graphene according to claim 10, wherein, The gaseous products include carbon-containing gases and water vapor, wherein the carbon-containing gases include CO2 and / or CO.

18. The method for preparing graphene according to claim 10, wherein, The gaseous product, after being separated into water vapor by a condenser, enters the graphene preparation reactor as raw material gas; the condensation temperature of the condenser is below 80°C.

19. The method for preparing graphene according to claim 10, wherein, The reaction temperature of the oxygen carrier regeneration reactor is 800–1600 °C.

20. The method for preparing graphene according to claim 10, wherein, The molten liquid metal catalyst medium is molten liquid metal, or a mixture of molten liquid metal and molten liquid salt; the molten liquid metal includes one or more of magnesium, iron, copper, cobalt, nickel, gallium, tin and bismuth; the molten liquid salt does not volatilize or decompose at 800–1400°C.

21. The method for preparing graphene according to claim 10, wherein, The graphene preparation method further includes: supplementing the graphene preparation reactor with a raw material gas, wherein the supplemented raw material gas is a carbon-containing gas, or a mixture of a carbon-containing gas and a protective gas; the carbon-containing gas includes CO2 and / or CO.

22. The method for preparing graphene according to claim 10, wherein, The reaction temperature in the core reaction zone of the graphene preparation reactor is controlled by adjusting the flow rate of the oxidizing gas input into the oxygen carrier regeneration reactor, and / or by adjusting the flow rate of the fuel input into the fuel reactor; the reaction temperature in the core reaction zone of the graphene preparation reactor is 600–1500°C; the ratio of the flow rate of the raw material gas entering the graphene preparation reactor to the volume of the molten liquid metal catalyst medium in the graphene preparation reactor is 0.2–10.

23. The method for preparing graphene according to claim 10, wherein, The graphene preparation method further includes: stopping the input of raw material gas into the graphene preparation reactor, and then inputting a reducing gas into the graphene preparation reactor to regenerate the molten liquid metal catalyst medium; when the volume content of water vapor in the gas discharged from the graphene preparation reactor is less than 0.1%, the regeneration of the molten liquid metal catalyst medium is considered complete, the input of reducing gas into the graphene preparation reactor is stopped, and then the input of raw material gas into the graphene preparation reactor continues.

24. The method for preparing graphene according to claim 23, wherein, The reducing gas is hydrogen, or a mixture of hydrogen and a protective gas.

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