Method and system for producing hydrogen by cracking methane through synergy of non-thermal plasma and catalyst

Abstract

The invention discloses a method and a system for producing hydrogen by cracking methane through synergy of non-thermal plasma and a catalyst, and the method comprises the following steps: placing a nickel-based catalyst in a dielectric barrier discharge reactor, and introducing a mixed gas of methane and a carrier gas into the dielectric barrier discharge reactor; the plasma generator is started, non-thermal plasma is generated by ionization in the dielectric barrier discharge reactor, and methane is subjected to cracking reaction under the synergistic effect of the non-thermal plasma and the catalyst to obtain carbon and H2. The nickel-based catalyst with a specific structure is introduced into the DBD plasma, so that efficient methane conversion and high-selectivity hydrogen generation at low temperature and low energy consumption are realized, and the problems of high energy consumption and high carbon emission of a traditional thermal catalysis method and low conversion rate and selectivity of a pure plasma method are solved.

Description

Technical Field

[0001] This application belongs to the field of hydrogen energy production and chemical process technology, specifically relating to a method and system for non-thermal plasma synergistic catalyst cracking of methane to produce hydrogen. Background Technology

[0002] Hydrogen is a clean and efficient secondary energy source. Currently, over 95% of hydrogen is derived from fossil fuels, with steam reforming (SMR) being the dominant technology. SMR is a chemical process that reacts methane (CH4, usually from natural gas) with water vapor (H2O) under high temperature and in the presence of a catalyst to produce carbon monoxide (CO) and hydrogen (H2). It can be seen as a crucial first step in transferring the chemical energy from fossil fuels (methane) to hydrogen.

[0003] However, the SMR process not only requires high temperatures of 700℃-1000℃, resulting in huge energy consumption and the generation of large amounts of carbon dioxide (CO2), but also suffers from problems such as low methane conversion rate, relatively high energy consumption, and difficulty in controlling product selectivity. Summary of the Invention

[0004] This application aims to provide a method and system for non-thermal plasma co-catalyzed cracking of methane to produce hydrogen, which solves the problem of high energy consumption in the hydrogen production process, reduces CO2 emissions, and improves methane conversion rate and product selectivity.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application propose a method for non-thermal plasma-co-catalyst-assisted methane cracking to produce hydrogen. The method is carried out in a dielectric barrier discharge reactor equipped with a plasma generator, and includes: A nickel-based catalyst is placed in a dielectric barrier discharge reactor, and a mixture of methane and carrier gas is introduced into the dielectric barrier discharge reactor. The plasma generator is activated, causing non-thermal plasma to be generated in the dielectric barrier discharge reactor. Under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, the methane undergoes a cracking reaction to obtain carbon and H2.

[0006] Optionally, the plasma generator operates at a power of 25W-75W.

[0007] Optionally, the carrier gas is selected from one of Ar, He, and N2; Optionally, the volume percentage of methane in the gas mixture is (10-25)%.

[0008] Optionally, the feed space velocity of the mixed gas is 1800 h⁻¹. -1 -3600h-1 .

[0009] Optionally, the nickel-based catalyst comprises active metallic nickel and a support; The carrier is selected from one of ZSM-5 molecular sieve, BaTiO3, Al2O3 and Beta molecular sieve.

[0010] Optionally, the mass percentage of Ni in the nickel-based catalyst is 3wt%-8wt%.

[0011] Optionally, the nickel-based catalyst is an activated catalyst, and the activation process includes: The nickel-based catalyst was introduced into the dielectric barrier discharge reactor and activated for 2-4 hours under an inert atmosphere and at a temperature of 400-500°C. The inert atmosphere is provided by H2 and / or Ar.

[0012] Secondly, embodiments of this application also provide a system for non-thermal plasma co-catalyst cracking of methane to produce hydrogen, the system being used to operate the non-thermal plasma co-catalyst cracking of methane to produce hydrogen described in the first aspect, the system comprising: Gas source unit, dielectric barrier discharge reactor and plasma generator; The gas source unit and the plasma generator are respectively connected to the dielectric barrier discharge reactor; The gas source unit is used to supply methane and carrier gas to the dielectric barrier discharge reactor. The plasma generator is used to provide high-voltage alternating current to the dielectric barrier discharge reactor; The dielectric barrier discharge reactor is used to ionize and generate non-thermal plasma, and under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, it promotes the cracking reaction of methane to obtain carbon and H2.

[0013] Optionally, the system further includes a gas control unit; The gas control unit is connected to the gas source unit and the dielectric barrier discharge reactor, respectively. The gas control unit is used to control the intake volume of the methane and the carrier gas, respectively.

[0014] Beneficial technical effects: In this embodiment, efficient directional conversion of methane under mild conditions was successfully achieved in a dielectric barrier discharge reactor by employing non-thermal plasma in conjunction with a nickel-based catalyst. This embodiment utilizes high-energy electrons generated by non-thermal plasma to effectively dissociate stable CH bonds in methane molecules at low temperatures, activating methane molecules without external heating. This overcomes the dependence of hydrogen production processes on high-temperature external heat sources, significantly reducing reaction energy consumption.

[0015] In practice, this process achieves a green reconstruction of the reaction pathway. Methane is directly cracked into high-purity hydrogen and structurally controllable solid carbon under the synergistic effect of non-thermal plasma and catalyst, avoiding CO2 generation and achieving near-zero carbon emissions in the hydrogen production process. Moreover, the synergistic effect of non-thermal plasma and nickel-based catalyst not only improves the activation efficiency of methane but also effectively enhances the methane conversion rate and hydrogen selectivity, thereby improving reaction efficiency.

[0016] The method proposed in this application is carried out under mild conditions close to ambient temperature and pressure, has a wide operating window, low equipment requirements, and is easily coupled with renewable energy power supply systems, providing a reliable path for building flexible and efficient distributed hydrogen production systems. The entire system has a compact structure, simple process, and fast response, possessing good potential for process scale-up and prospects for continuous industrial production. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart of the non-thermal plasma synergistic catalyst cracking method for hydrogen production from methane proposed in the embodiments of this application; Figure 2 This is a flowchart illustrating the synthesis process of the nickel-based catalyst in the embodiments of this application; Figure 3 This is a schematic diagram of the system structure for non-thermal plasma synergistic catalyst cracking of methane to produce hydrogen proposed in the embodiments of this application; Figure 4 These are the Raman spectrum and transmission electron microscope image of the solid carbon product prepared in Example 1 of this application; Figure 5 This is a graph showing the methane conversion rate and hydrogen selectivity at different power levels in the embodiments of this application; Figure 6 This application describes the methane conversion rate and hydrogen selection under different reactant gas inlet rates in the embodiments of this application; Figure 7 This application illustrates the methane conversion rate and hydrogen selectivity under different methane inlet volumes in the embodiments of this application. Figure 8 This is a graph showing the performance comparison of different catalysts in the embodiments and comparative examples of this application.

[0018] Figure label: 1. Gas source unit; 2. Dielectric barrier discharge reactor; 3. Plasma generator; 4. Gas control unit; 5. Controller. Detailed Implementation

[0019] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0021] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and 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, and therefore should not be construed as a limitation of this application.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] Among related technologies, steam reforming (SMR) of methane is the dominant technology for hydrogen production. However, the SMR process requires high temperatures of 700℃-1000℃, resulting in huge energy consumption and the generation of large amounts of carbon dioxide (CO2), which does not meet the requirements of green and low-carbon development. In addition, the methane conversion rate is not high, and the product selectivity is also low.

[0024] Based on this, the embodiments of this application have found that non-thermal plasma technologies, such as dielectric barrier discharge (DBD), can provide a new pathway for activating methane molecules under low-temperature conditions. DBD can generate high-energy electrons and active species at near-ambient temperatures, initiating the methane cracking reaction (CH4→C+2H2), theoretically achieving zero carbon emissions. However, the embodiments of this application have found that the pure plasma process suffers from problems such as low methane conversion rate, relatively high energy consumption, and difficulty in controlling product selectivity.

[0025] Therefore, introducing catalytic materials into the DBD plasma region to form a plasma-catalytic synergistic effect is an effective strategy to improve reaction performance. Catalysts can provide surface active sites, lower the reaction activation energy, and guide the reaction pathway, thereby improving hydrogen selectivity and yield.

[0026] This application proposes a method for producing hydrogen from methane through non-thermal plasma synergistic catalyst cracking. Figure 1 This is a flowchart of a method for non-thermal plasma-co-catalyst-based methane cracking to produce hydrogen, as proposed in this application. The method is carried out in a dielectric barrier discharge reactor equipped with a plasma generator, and specifically includes: Step S1: Place the nickel-based catalyst in a dielectric barrier discharge reactor and introduce a mixture of methane and carrier gas into the dielectric barrier discharge reactor; In some embodiments, the nickel-based catalyst comprises active metallic nickel and a support; The carrier is selected from one of ZSM-5 molecular sieve, BaTiO3, Al2O3 and Beta molecular sieve.

[0027] The nickel-based catalysts synthesized using ZSM-5 molecular sieves, BaTiO3, Al2O3, or Beta molecular sieves as supports in this application are designed to enhance the synergistic effect between the nonthermal plasma and the catalyst. This specifically structured nickel-based catalyst optimizes the electron energy distribution during the nonthermal plasma discharge process, improving the activation efficiency of methane molecules. Furthermore, the unique pore structure and surface properties of the support promote the adsorption of reactants and the desorption of hydrogen products, thereby further enhancing methane conversion and hydrogen selectivity while maintaining low temperatures and zero CO2 emissions.

[0028] In some embodiments, Figure 2This is a flowchart of the synthesis process of the nickel-based catalyst in the embodiments of this application. The nickel-based catalyst is synthesized by the equal volume impregnation method and has a suitable specific surface area and pore structure to promote mass transfer and metal dispersion.

[0029] The synthesis steps of nickel-based catalysts include: Weigh a certain amount of the carrier and prepare a certain concentration of nickel nitrate (Ni(NO3)2·6H2O) aqueous solution as a precursor; wherein the solid-liquid ratio of the carrier to the nickel nitrate aqueous solution is 1:(2-4); A nickel nitrate aqueous solution was slowly added dropwise to the support and impregnated at room temperature for 10-15 hours, followed by drying at 100-150℃ for 10-15 hours. Finally, the catalyst precursor was calcined in an air atmosphere at 400℃-600℃ for 3h-7h in a muffle furnace to obtain the catalyst precursor. After activation treatment, the nickel-based catalyst was obtained. The activation treatment was carried out in a dielectric barrier discharge reactor.

[0030] In some embodiments, the mass percentage of Ni in the nickel-based catalyst is 3wt%-8wt%.

[0031] It should be noted that, based on the mass of the nickel-based catalyst, the mass percentage of Ni is 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, and 8wt%. By controlling the mass percentage of Ni, the active component in the nickel-based catalyst, within the range of 3wt%-8wt%, the high dispersion of active sites on the support surface is ensured. Combined with the synergistic effect of non-thermal plasma, the utilization efficiency of active sites and the sustainability of the catalytic reaction are improved.

[0032] In some embodiments, the nickel-based catalyst is an activated catalyst, and the activation process includes: The nickel-based catalyst was introduced into the dielectric barrier discharge reactor and activated for 2-4 hours under an inert atmosphere and at a temperature of 400-500°C. The inert atmosphere is provided by H2 and / or Ar; preferably, the inert atmosphere is a mixture of H2 and Ar, in which calcination is carried out during activation.

[0033] It should be noted that when the nickel-based catalyst is activated in the dielectric barrier discharge reactor, the temperatures are 400℃, 420℃, 450℃, 470℃, and 500℃, and the activation times are 2h, 2.5h, 3h, 3.5h, and 4h, respectively. In this embodiment, the catalyst undergoes activation pretreatment by placing it in the dielectric barrier discharge reactor and treating it for 2h-4h at 400℃–500℃ under an inert atmosphere composed of H2 and / or Ar, thereby optimizing the physical state of the catalyst before it enters the formal reaction. This activation process causes the catalyst's pore structure to pre-adsorb a certain amount of reactant gas (e.g., Ar), improving its interfacial compatibility and mass transfer efficiency with the non-thermal plasma catalytic synergistic reaction, and reducing the energy barrier in the reaction initiation stage.

[0034] In some embodiments, when the inert atmosphere consists of H2 and Ar, the volume ratio of H2 to Ar is 1:(7-9); preferably, the volume ratio of H2 to Ar is 1:9.

[0035] In some embodiments, the carrier gas is selected from Ar, He, and N2; preferably, the carrier gas is Ar; Ar is used to mix with methane as the reactant gas in this application embodiment because the metastable argon ions generated by Ar when excited by an electric field have a high lifetime and can effectively transfer energy to methane molecules; secondly, its metastable energy is higher than the energy required to dissociate CH bonds, which can efficiently promote the methane cracking reaction; finally, Ar, as a chemically inert gas, will not participate in the actual chemical reaction and will not produce side reactions or generate excess gaseous products; In some embodiments, the volume percentage of methane in the gas mixture is (10-25)%. It should be noted that the volume percentage of methane in the gas mixture is 10%, 12%, 15%, 17%, 20%, 22%, and 25%. A suitable methane concentration range helps to ensure sufficient contact between reactant molecules and plasma and catalyst active sites.

[0036] In some embodiments, the feed space velocity of the mixed gas is 1800 h⁻¹. -1 -3600h -1 .

[0037] It should be noted that the feed space velocity of the mixed gas is 1800 h⁻¹. -1 -3600h -1 This indicates that the intake flow rate of the mixed gas is 60 mL / min - 120 mL / min; The feed space velocity of the mixed gas is 1800 h⁻¹. -1 2400h -1 3000h -1 3600h -1The feed space velocity setting allows methane molecules sufficient contact and reaction time with the active sites of the nickel-based catalyst and non-thermal plasma active species, avoiding excessive deposition and clogging of the reactor due to excessively low space velocity, or insufficient conversion of reactants due to excessively high space velocity.

[0038] Step S2: Start the plasma generator to ionize and generate non-thermal plasma in the dielectric barrier discharge reactor. Under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, the methane undergoes a cracking reaction to obtain carbon and H2. It should be noted that non-thermal plasma has a higher energy utilization rate than thermal plasma, as its energy is used to generate more high-energy electrons rather than heating the gas. In terms of discharge mode, the dielectric barrier reactor generates many micro-discharges, and the pyrolysis reaction is carried out at atmospheric pressure; while thermal plasma is usually a concentrated and continuous electric arc, and the pressure in the reactor is higher. During the pyrolysis reaction, the dielectric barrier discharge reactor does not require an additional heating device and can be carried out at a temperature of room temperature to 200°C. During the generation of non-thermal plasma, the transfer of electron energy to gas molecules, the heat of chemical reaction, and dielectric loss will cause the internal temperature of the reactor to rise to no more than 200°C. In some embodiments, the plasma generator operates at a power of 25W-75W.

[0039] It should be noted that the working power of the plasma generator is 25W, 30W, 35W, 40W, 45W, 50W, 55W, 60W, 65W, 70W, and 75W. The working power of the plasma generator is controlled within the range of 25W-75W to enable the dielectric barrier discharge to generate sufficiently high-energy non-thermal plasma, effectively activating methane molecules and exciting the active sites of the catalyst.

[0040] Secondly, embodiments of this application also provide a system for non-thermal plasma-assisted catalyst cracking of methane to produce hydrogen. Figure 3 This is a schematic diagram of a system structure for non-thermal plasma co-catalyst cracking of methane to produce hydrogen, as proposed in an embodiment of this application. The system is used to operate the method for non-thermal plasma co-catalyst cracking of methane to produce hydrogen, specifically including: Gas source unit 1, dielectric barrier discharge reactor 2, and plasma generator 3; The gas source unit 1 and the plasma generator 3 are respectively connected to the dielectric barrier discharge reactor 2; The gas source unit 1 is used to supply methane and carrier gas to the dielectric barrier discharge reactor 2. The plasma generator 3 is used to provide high-voltage AC power to the dielectric barrier discharge reactor 2; The dielectric barrier discharge reactor 2 is used to ionize and generate non-thermal plasma, and under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, the methane undergoes a cracking reaction to obtain carbon and H2.

[0041] It should be noted that, as Figure 3 As shown, the gas source unit 1 includes a methane cylinder and a carrier gas cylinder (when the carrier gas is Ar, the carrier gas cylinder is an Ar cylinder); the methane cylinder and the carrier gas cylinder are respectively connected to the gas inlet of the dielectric barrier discharge reactor 2; In some embodiments, such as Figure 3 As shown, the system also includes a gas control unit 4; The gas control unit 4 is connected to the gas source unit 1 and the dielectric barrier discharge reactor 2 respectively; The gas control unit 4 is used to control the intake volume of the methane and the carrier gas, respectively. It should be noted that, as Figure 3 As shown, the gas control unit 4 is the gas flow controller 5; The methane cylinder and the carrier gas cylinder are respectively connected to the inlet of the gas control unit 4, and the outlet of the gas control unit 4 is connected to the inlet of the dielectric barrier discharge reactor 2. In this embodiment, by setting up a gas source unit 1 containing both a methane cylinder and a carrier gas cylinder, and equipping it with a gas control unit 4 capable of independently controlling the flow rate of each gas, the mixing ratio of methane and carrier gas (10%-25% methane) and the feed space velocity (1800 h⁻¹) can be more accurately controlled. -1 -3600h -1 This provides a stable reaction atmosphere with controllable flow rate for the dielectric barrier discharge reactor 2.

[0042] In some embodiments, such as Figure 3 As shown, the dielectric barrier discharge reactor 2 consists of two parallel electrodes (inner electrode and outer electrode) with a dielectric material between them; in this embodiment, the dielectric material is a quartz tube; the outer electrode (stainless steel mesh) is wound around the surface of the quartz tube and directly connected to the plasma generator 3, and the inner electrode (stainless steel rod) is placed inside the quartz tube and grounded to the outside. When high-voltage alternating current is applied, the gas between the electrodes is ionized to form non-thermal plasma. Many micro-discharges are generated in the gap between the two electrodes, producing many high-energy electrons. The energy of these high-energy electrons is transferred to other gas molecules through collisions, thereby triggering chemical reactions. The plasma generator 3 is a power supply unit that can provide high-voltage AC power to the dielectric barrier discharge reactor 2; In some embodiments, such as Figure 3As shown, a controller 5 is installed at the front end of the dielectric barrier discharge reactor 2 to determine the power of the plasma generator 3. The greater the power, the more non-thermal plasma micro-discharges (high-energy electrons) are generated in the quartz tube, and the greater the role of the non-thermal plasma in the catalytic reaction process, and the more violent the reaction.

[0043] The non-thermal plasma synergistic catalyst cracking system for methane to produce hydrogen provided in this application embodiment constructs a highly efficient, stable, and continuously operating hydrogen production platform through the integrated configuration of a gas source unit 1, a dielectric barrier discharge reactor 2, and a plasma generator 3. This system can control the flow rate of the reactant gas and optimize plasma power parameters, providing a stable and efficient synergistic reaction environment for the nickel-based catalyst. In implementation, this system not only achieves efficient methane cracking under low-temperature conditions, eliminating dependence on high-temperature reactions and reducing energy consumption, but also produces no CO2 emissions during the reaction process, with the products being only high-purity hydrogen and recoverable solid carbon. The entire system has a reasonable structure, clear synergistic effects among units, a wide operating window, and good process stability and scalability, providing a reliable equipment foundation for the industrial-scale continuous production of green hydrogen technology.

[0044] In some embodiments, the gaseous products after the reaction flow through the stainless steel tube at the end of the dielectric barrier discharge reactor 2 and enter the gas chromatograph for online analysis of their composition; while the solid carbon products are deposited in large quantities on the internal electrode inside the dielectric barrier discharge reactor 2 and need to be collected periodically.

[0045] To enable those skilled in the art to better understand this application, the following embodiments are provided to illustrate in detail a method and system for non-thermal plasma synergistic catalyst cracking of methane to produce hydrogen.

[0046] Example 1 use Figure 3 The system for nonthermal plasma co-catalyst cracking of methane to produce hydrogen, as shown, includes the following steps: (1) The nickel-based catalyst (supported by ZSM-5, with a mass percentage of 5wt% Ni) was placed in a dielectric barrier discharge reactor and activated under an inert atmosphere provided by H2 and Ar. The activation temperature was set to 470℃ and the reduction was carried out for 3h to obtain the active catalyst Ni / ZSM-5. (2) Mix methane and inert carrier gas Ar at a volume ratio of 20%:80% to form a mixed gas (or reaction gas). (3) The mixed gas prepared in step (2) is fed at a feed space velocity of 720 h⁻¹. -1The plasma is introduced into a dielectric barrier discharge plasma reactor filled with active catalyst Ni / ZSM-5. The plasma power supply is started and the working power is set to 50W to ionize the dielectric barrier discharge reactor and generate non-thermal plasma. Under the synergistic effect of non-thermal plasma and active catalyst Ni / ZSM-5, a cracking reaction is initiated at a temperature of room temperature to 200℃ to obtain H2 and carbon. (4) The gaseous product H2 after the reaction flows through the stainless steel tube at the end of the dielectric barrier discharge reactor and enters the gas chromatograph for online analysis of its composition; a large amount of solid carbon products are deposited on the inner electrode inside the dielectric barrier discharge reactor and are collected periodically.

[0047] Based on Example 1, the carbon products collected on the electrodes inside the dielectric barrier discharge reactor were characterized. Figure 4 These are the Raman spectra and transmission electron microscope images of the solid carbon product prepared in Example 1 of this application, as shown below. Figure 4 As shown, the carbon products under these reaction conditions contain a certain graphitized phase.

[0048] To verify the reaction conditions in Example 1, the following independent experiments were conducted in this application: Experiment 1: Without adding any catalyst and keeping the total flow rate of the reaction gas (methane + Ar) at 60 mL / min and the volume ratio of methane in the reaction gas constant at 15%, the effect of the plasma generator's operating power on the methane cracking reaction was investigated by adjusting the working power of the plasma generator. Figure 5 This is a graph showing the methane conversion rate and hydrogen selectivity at different power levels in the embodiments of this application, such as... Figure 5 As shown, the results indicate that the higher the power provided by the plasma generator, the higher the methane conversion rate and the higher the hydrogen selectivity. However, from an economic perspective, higher energy consumption means higher costs; therefore, a power of 50W was used in Example 1.

[0049] Experiment 2: Without adding any catalyst and controlling the plasma generator power to 50W, the methane cracking reaction was evaluated by adjusting the total flow rate of the reactant gas and keeping the volume ratio of methane in the reactant gas constant at 15%.

[0050] Figure 6 This application describes the methane conversion rate and hydrogen selection under different reactant gas inlet rates in the embodiments of this application, such as... Figure 6 As shown, the highest methane conversion rate and the highest hydrogen selectivity were achieved at a total gas flow rate of 60 mL / min. Therefore, in Example 1, the preferred total gas flow rate is 60 mL / min (i.e., the feed space velocity of the mixed gas is 1800 h⁻¹). -1 ).

[0051] Experiment 3: With the total gas flow rate kept constant at 60 mL / min and the plasma generator power at 50 W, the methane cracking reaction was investigated by changing the volume ratio of methane in the reaction gas.

[0052] Figure 7 This application describes the methane conversion rate and hydrogen selectivity under different methane inlet rates in the embodiments of this application, such as... Figure 7 As shown, the lower the methane gas volume percentage, the higher the methane conversion rate and the higher the hydrogen selectivity in the reaction. Conversion rates and hydrogen selectivity are similar for methane volume percentages of 15% and 20%. Considering the efficiency of the methane cracking reaction, a higher methane inlet volume ratio can process more reactant gas in the same reaction time. Therefore, a methane inlet volume ratio of 20% was used in Example 1.

[0053] Example 2 The only difference between Example 2 and Example 1 is that the nickel-based catalyst used in Example 2 is Ni / Al2O3.

[0054] Example 3 The only difference between Example 3 and Example 1 is that the nickel-based catalyst used in Example 3 is Ni / Beta.

[0055] Example 4 The only difference between Example 4 and Example 1 is that the nickel-based catalyst used in Example 4 is Ni / BaTiO3.

[0056] Comparative Examples 1-5 are set up based on Examples 1-4, including: Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not add a nickel-based catalyst.

[0057] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 adds ZSM-5 as a catalyst.

[0058] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 adds commercial Al2O3 as a catalyst.

[0059] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that Beta was added as a catalyst in Comparative Example 4.

[0060] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that BaTiO3 was added as a catalyst in Comparative Example 5.

[0061] Under optimal reaction conditions (power 50 W, total reactant flow rate 60 mL / min, methane volume percentage 20%), the catalytic performance of the blank reaction (without catalyst), ZSM-5, commercial Al2O3, Beta, BaTiO3, Ni / ZSM-5, Ni / Al2O3, Ni / Beta, and Ni / BaTiO3 was evaluated. The results are shown in Table 1 below. Figure 8 As shown, where, Figure 8 This is a graph showing the performance comparison of different catalysts in the embodiments and comparative examples of this application.

[0062] According to Table 1 and Figure 8 It was found that, compared to the case without any catalyst (methane conversion rate of 41.5%, hydrogen selectivity of 44.2%), all four catalyst supports (Comparative Examples 2-5) showed a certain improvement in catalytic performance. Among them, Beta molecular sieve (Comparative Example 4) and BaTiO3 (Comparative Example 5) showed the most significant improvement in hydrogen selectivity, at 54.5% and 52.4%, respectively. After loading the active metal Ni onto the four catalysts, their performance differed: the conventional catalyst ZSM-5 (Example 1), commercial Al2O3 (Example 2), and Beta molecular sieve (Example 3) showed higher hydrogen selectivity, with Ni / Beta exhibiting the highest hydrogen selectivity at 56.7%, while the hydrogen selectivity of Ni / BaTiO3 (Example 4) actually decreased.

[0063] Table 1. Catalytic performance of catalysts under optimal reaction conditions

[0064] In summary, Ni / ZSM-5, Ni / Beta, and Ni / Al2O3 significantly outperformed Ni / BaTiO3, demonstrating that the support properties greatly influence overall performance in non-thermal plasma catalysis processes. For molecular sieve supports (ZSM-5 and Beta), their high specific surface area, well-defined micropores, and tunable surface acidic sites make them excellent catalyst supports in plasma-catalyzed methane cracking reactions. They provide highly dispersed Ni and acidic sites for efficient catalysis of surface chemical reactions. They also act as effective plasma enhancers: their moderate dielectric constant alters the electric field distribution within the reactor, promoting more and more uniform micro-discharges. More importantly, the confined space effect within their pores confines plasma-generated active species (such as free radicals and excited-state molecules) within the nanopores, significantly increasing the probability and residence time of contact between active species and the catalyst surface, thereby significantly improving reaction efficiency.

[0065] For commercial Al2O3, it also possesses advantages similar to molecular sieves: high specific surface area, making it a commonly used high specific surface area support, which is beneficial for Ni dispersion; good thermal stability and mechanical strength, making it very suitable for long-term use in reaction environments; and the presence of both acidic and basic sites on its surface, allowing for effective adsorption and polarization of CH4 molecules. Its basic sites may also be effective against H+. + It has a certain affinity, which may help with the generation and desorption of H2.

[0066] For BaTiO3, its core function is as a dielectric material rather than a traditional catalyst support. Its dielectric constant is extremely high (reaching several thousand), so it can indeed indirectly improve catalytic performance to some extent by altering plasma discharge behavior. However, its low specific surface area and lack of catalytically active sites make it far inferior to porous materials in promoting surface chemical reactions. Therefore, its catalytic performance decreases after loading with metallic Ni (Ni loading may block the only available pores). The experimental results of the above embodiments and comparative examples fully demonstrate the excellent performance of the non-thermal plasma-nickel-based catalyst synergistic method and system provided in this application for hydrogen production from low-temperature methane cracking. This application not only provides a highly efficient hydrogen production method but also offers new ideas for catalyst design in the field of plasma catalysis.

[0067] Other configurations of the embodiments of this application, such as ... and ..., and operations, are known to those skilled in the art and will not be described in detail here.

[0068] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for producing hydrogen from methane by cracking with a non-thermal plasma-co-catalyst, characterized in that, The method is carried out in a dielectric barrier discharge reactor equipped with a plasma generator, and the method includes: A nickel-based catalyst is placed in a dielectric barrier discharge reactor, and a mixture of methane and carrier gas is introduced into the dielectric barrier discharge reactor. The plasma generator is activated, causing non-thermal plasma to be generated in the dielectric barrier discharge reactor. Under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, the methane undergoes a cracking reaction to obtain carbon and H2.

2. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The plasma generator operates at a power of 25W-75W.

3. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The carrier gas is selected from one of Ar, He and N2.

4. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The volume percentage of methane in the mixture is (10-25)%.

5. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The feed space velocity of the mixed gas is 1800 h⁻¹. -1 -3600h -1 .

6. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The nickel-based catalyst comprises: active metallic nickel and a support; The carrier is selected from one of ZSM-5 molecular sieve, BaTiO3, Al2O3 and Beta molecular sieve.

7. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The mass percentage of Ni in the nickel-based catalyst is 3wt%-8wt%.

8. The method for producing hydrogen from methane by non-thermal plasma synergistic catalyst cracking according to claim 1, characterized in that, The nickel-based catalyst is an activated catalyst, and the activation process includes: The nickel-based catalyst was introduced into the dielectric barrier discharge reactor and activated for 2-4 hours under an inert atmosphere and at a temperature of 400-500°C. The inert atmosphere is provided by H2 and / or Ar.

9. A system for non-thermal plasma-co-catalyst-assisted methane cracking to produce hydrogen, characterized in that, The system is used to operate the nonthermal plasma co-catalyst cracking method for hydrogen production from methane according to any one of claims 1-8, the system comprising: Gas source unit, dielectric barrier discharge reactor and plasma generator; The gas source unit and the plasma generator are respectively connected to the dielectric barrier discharge reactor; The gas source unit is used to supply methane and carrier gas to the dielectric barrier discharge reactor. The plasma generator is used to provide high-voltage alternating current to the dielectric barrier discharge reactor; The dielectric barrier discharge reactor is used to ionize and generate non-thermal plasma, and under the synergistic effect of the non-thermal plasma and the nickel-based catalyst, it promotes the cracking reaction of methane to obtain carbon and H2.

10. The system for non-thermal plasma-co-catalyst cracking of methane to produce hydrogen according to claim 9, characterized in that, The system also includes a gas control unit; The gas control unit is connected to the gas source unit and the dielectric barrier discharge reactor, respectively. The gas control unit is used to control the intake volume of the methane and the carrier gas, respectively.

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