Hydrogen production method

Abstract

The invention belongs to the technical field of methane resource utilization and plasma chemical hydrogen production, and relates to a hydrogen production method. High H2 selectivity and low CO content can be realized only by multi-step operation for hydrogen production by methane steam reforming. The root reason is that the overhigh operation temperature is beneficial to the reforming reaction of heat-absorbing water vapor to generate synthesis gas, and is not beneficial to the heat-releasing water vapor shift reaction. Methane, water vapor and argon are mixed and preheated and then are introduced into the dielectric barrier discharge reactor, a hydrogen production reaction with a high conversion rate at a low temperature is achieved through non-volume work provided by plasmas, and one-step hydrogen production is achieved under the action of a catalyst. The catalyst adopted by the invention has both an active center of steam reforming reaction and an active center of water vapor shift reaction, so that one-step preparation of CO-free hydrogen by catalyzing methane steam reforming under the synergistic effect of plasma and the catalyst at normal pressure is realized.

Description

Technical Field

[0001] The present invention belongs to the technical fields of methane resource utilization and plasma chemical hydrogen production, and relates to a hydrogen production method. Background Art

[0002] Methane is the main component of natural gas, shale gas, coalbed methane, biogas, and combustible ice. Its huge reserves and high hydrogen content make methane an ideal raw material for hydrogen production.

[0003] Steam methane reforming (SRM) is the main H2 production route, and currently about 70%-80% of hydrogen is produced by SMR technology. Industrially, multi-stage reaction hydrogen production is generally adopted. First, methane and steam are converted into syngas (H2 / CO) through a high-temperature steam reforming reaction at 800-1100°C, and then carbon monoxide and water are reacted to produce carbon dioxide and hydrogen through medium-temperature (400-500°C) and low-temperature (200-300°C) water-gas shift reactions. The reaction equations are as follows:

[0004] CH4 + H2O = CO + 3H2 ΔH 298 θ = 206 kJ / mol

[0005] H2O + CO = CO2 + H2 ΔH 298 θ = -41 kJ / mol

[0006] Some literature reports promoting hydrogen production from steam methane reforming by modifying catalysts.

[0007] The public literature "Petroleum Science and Technology, 2020.38(6), 618-625" prepared a bimetallic catalyst on cerium oxide nanoparticles and studied the performance of the bimetallic nanocatalyst in steam methane reforming. The results showed that the improved bimetallic catalyst had better performance than the monometallic catalyst. The best catalyst sample was Co-Ni / CeO2, with a methane conversion rate of 76.1%, a hydrogen selectivity of 58.5%, and a hydrogen yield of 44.5% at a steam ratio of 3 at 700°C.

[0008] The public literature "Catalyst, 2020, 10, 1110" tested the TOF of methane and hydrogen continuously for 9 h at a steam ratio of 3 at 600°C. On Ni-γ-Al2O3, Ni-HTASO5, and Ni-CeZrOx, the TOF (1 hour) of methane conversion on Ni / γ-Al2O3, Ni / HTASO5, and Ni / CeZrOx was 5.1×10 -2 s -1 、8.0×10-2 s -1 and 5.5×10 -2 s -1 。The TOF (1 hour) corresponding to H2 are 7.0×10 -2 s -1 、10.5×10 -2 s -1 and 6.8×10 -2 s -1 。In the activity test, the catalytic performance of Ni-HTASO5 is the best.

[0009] The open literature "International Journal of Hydrogen Energy. 2020, 45(28), 14281-14292" used Ni / zirconia catalyst to carry out steam reforming of methane at low temperature and investigated the reaction conditions. At 550 °C with H2O / CH4 of 1:2, a methane conversion rate of 46.8% and a hydrogen selectivity of 14.6% were achieved, and the selectivities of carbon monoxide and carbon dioxide were 3.2% and 18.0% respectively.

[0010] The open literature "Sustainable Energy Fuels, 2021, 5, 1845-1854" prepared Ni / La 0.7 Mg 0.3 AlO3 catalyst for methane steam reforming reaction. At a temperature of 650 °C, a methane conversion rate of 72.08% and a hydrogen selectivity of 61.18% were achieved.

[0011] The open literature "Catalysis Science & Technology, 2021, 11(5), 1965-1973" reported the enhanced activity and stability effects of a partially oxidized Ni / CeO2 catalyst on methane steam reforming. In the 1500 min performance test at 700 °C, the hydrogen production reaction on NiO / CeO2 remained stable, with a methane conversion rate of 88% and a hydrogen production rate of 5.0 mmol / min -1 , and the H2 / CO ratio was 4.3.

[0012] The open literature "ChemistrySelect, 2022, 7(45)" reported the key role of Ni valence on the performance of Ni / Al2O3 in catalytic methane steam reforming. The reaction conditions were 600 °C at atmospheric pressure and a water vapor ratio of 2. The methane conversion rate corresponding to the Ni / Al2O3 catalyst reduced at 675 °C was 62%, the carbon dioxide selectivity was 64%, and H2 / CO was 46%.

[0013] The public document "Fuel, 2022, 317, 122411" compared the catalytic performance of NiMgAl2O4 monometallic catalyst and NiCoMgAl2O4 bimetallic catalyst in the steam reforming reaction of methane. The NiCoMgAl2O4 bimetallic catalyst showed better catalytic performance. At 750 °C, the methane conversion rate was 99.7% and the hydrogen selectivity was 82.6%.

[0014] The public document "International Journal of Hydrogen Energy. 2024, 60, 729 - 739" studied the effects of freeze-drying method and magnesium oxide value on methane conversion rate, H2 yield and CO selectivity. The results showed that among the prepared catalysts, the 0.05MgO-Ni / γ-Al2O3 catalyst had the best catalytic performance. Under the conditions of S / C ratio of 2 and reforming temperature of 600 °C, after 10 h, the CH4 conversion rate, H2 yield and CO selectivity exceeded 75%, 55% and 90% respectively.

[0015] The public document "International Journal of Hydrogen Energy. 2024, 49, 937 - 948" studied the steam reforming reaction of methane on Ni-V / CeO2. The addition of V increased the catalytic performance of Ni / CeO2 to a certain extent. At 600 °C, a methane conversion rate of 62.2%, a CO2 / CO selectivity ratio of 1.76 and a H2 / CO selectivity ratio of 10.14 were achieved.

[0016] The public document "International Journal of Hydrogen Energy. 2024, 51, 1256 - 1266" reported the performance of nickel aluminate spinel (NiAl2O4) in the steam reforming reaction of methane. At a temperature of 600 °C, a pressure of 0.1 MPa and a space velocity of 12349 h -1 a methane conversion rate of 84% and a hydrogen formation rate of 0.22 mol·h -1 ·cm -3 were achieved, with a CO selectivity of 40% and a CO2 selectivity of 60%.

[0017] In addition, some patents disclosed the preparation methods and performances of catalysts for hydrogen production by steam reforming of methane.

[0018] Patent CN101224427 (application date: 2008-02-01) disclosed a nickel-based catalyst supported on nano cerium-zirconium composite oxide for hydrogen production by steam reforming of methane. At 750 °C, the methane conversion rate was 97.3%.

[0019] Patent CN101327440 (application date: December 24, 2008) invented a composite catalyst H3PMo6W6O 40 / Al2O3 / Ni-Ce-Sr. When the reaction temperature is 440 °C, the reaction pressure is 0.01 MPa, and the water vapor ratio is 1:4, the methane conversion rate reaches 100%.

[0020] Patent CN103611538A (application date: November 29, 2013) discloses a Nix / CaOy-Ca5A 16 O 14 Z multifunctional catalyst. At 650 °C, when the methane inlet flow rate is 15.6 mL / min and the water flow rate is 0.05 mL / min, a H2 tail gas content of 95% is achieved.

[0021] Patent CN105642305A (application date: December 6, 2014) discloses a catalyst composed of active components, promoters, and carriers. Through the screening of catalysts, it is found that a catalyst with Ni as the active component, Mg as the promoter, and bar-shaped Al2O3 as the carrier has the best methane conversion performance. At a reaction temperature of 750 °C and a raw material gas composition of H2O / CH4 / N2 = 6.75 / 2.25 / 1 (molar ratio), the corresponding CH4 conversion rate is 97.3% and the CO selectivity is 88.7%.

[0022] Patent CN107597171A (application date: November 9, 2014) discloses a synthesis method using nanoscale all-silicon as the carrier. And it is used for methane steam reforming. The supported metals are selected from one or two metal oxides of iron, cobalt, and nickel, and the promoters are selected from one or more metal oxides of zirconium or cerium. The results show that the methane conversion rate is the largest when the supported metal and the promoter are nickel oxide and zirconium oxide respectively. At a reaction pressure of 0.1 Mpa, a reaction temperature of 800 °C, and a water vapor ratio of 3, a CH4 conversion rate of 98.94% and a H2 tail gas content of 76.55% are achieved.

[0023] Patent CN104971727A (application date: June 19, 2015) discloses that using pyrochlore alumina composite oxide as the carrier can greatly improve the reaction activity and anti-coking performance of the catalyst, and the catalyst has excellent catalytic activity and stability for methane steam reforming in a fixed bed. By comparing the reaction performance of catalysts with three different nickel sources of nickel nitrate, nickel sulfate, and nickel oxalate, it is found that the catalyst with nickel nitrate has the best performance.

[0024] Patent CN110586111A (application date: September 7, 2019) discloses some preparation methods of bimetallic methane steam reforming catalysts. Compared with the monometallic Ni / CeO2 catalyst, the hydrogen production rate of the bimetallic catalytic reaction has been improved to a certain extent after adding Mg or Sr. At 800 °C, the CH4 conversion rate of Ni-Mg / CeO2 is 74.9%, and the CO selectivity is 23.6%. The CH4 conversion rate of Ni-Mg / CeO2 is 75.2%, and the CO selectivity is 24.4%.

[0025] Patent CN111974402B (application date: September 3, 2020) discloses a preparation method of a NiO / CeMO methane steam reforming hydrogen production catalyst. At 700 °C, the methane conversion rate is 84%, and the hydrogen selectivity is 68%.

[0026] It can be learned from the above patents and public literatures that there are still many problems in the process of methane steam reforming to produce hydrogen: Firstly, the reaction temperature of methane reforming to hydrogen is usually 800 - 1100 °C, and the high temperature will lead to high energy consumption and catalyst deactivation; Secondly, the methane steam reforming reaction is a strongly endothermic reaction that is favorable at high temperatures, while the water-gas shift reaction is a weakly exothermic reaction that is favorable at low temperatures. Therefore, it is very difficult to achieve these two reactions simultaneously in one reaction zone, but the multi-stage reaction leads to high operating costs; In addition, ammonia synthesis and proton exchange membrane fuel cells (PEMFC) are the two most important application fields of hydrogen. However, carbon monoxide will cause poisoning of the catalysts for ammonia synthesis and the platinum electrodes of PEMFC. Therefore, the industrial process of hydrogen production has strict requirements on the carbon monoxide content. To sum up, the one-step reaction of methane and water vapor to directly reform into CO2 and H2 has important scientific significance and practical value.

[0027] As the fourth state of matter, plasma can introduce non-volume work, increase the equilibrium constant of the reaction, and initiate methane steam reforming under mild conditions.

[0028] The public literature "Pure Appl.Chem,2006,78(6),1157-1172" explored the plasma-catalyzed methane steam reforming reaction. By establishing an appropriate model, it was found that the radical substances generated by high-energy electrons are the main driving force for the chemical conversion process. At the same time, it was found that plasma can not only directly excite reactant molecules, but also change the physicochemical properties of the catalyst surface.

[0029] The public literature "Energy & Fuels, 2006, 20, 339" reported the use of dielectric barrier discharge to enhance the steam reforming reaction of low-calorie biogas over Ni / γ-Al2O3 catalyst. The temperature of the catalyst bed was provided by the plasma. At 300 - 350 °C and a water vapor ratio of 1, the methane conversion rate was about 6%, the carbon dioxide selectivity was about 90%, and the carbon monoxide selectivity was less than 3%. Regarding the above reaction results, the public literature "Journal of the Japan Petroleum Institute, 2011, 54(3), 146 - 158" reported that the rate of the methane steam reforming reaction when Ni / γ-Al2O3 catalyst and plasma acted synergistically was expressed as r = k*[CH4] 0.54 *[H2O] 0.20 .

[0030] The public literature "Catalysis Today, 2019, 337, 69 - 75" reported the effects of specific energy input (SEI), H2O / CH4 ratio (S / C), and total inlet flow rate (Ft) on methane conversion. Under the conditions of Ni / CeO2 / Al2O3 with a specific energy input of 110 kJ / mol, a water vapor ratio of 3, and a total inlet flow rate of 3 SLM, a CH4 conversion rate of 90%, an H2 selectivity of 95%, a CO selectivity of 78%, and a CO2 selectivity of 18% were achieved.

[0031] The public literature "AIChE Journal, 2020, 66, e16880" reported a method for catalytic non-thermal plasma conversion of steam methane to hydrogen using a dielectric barrier discharge reactor. Under the conditions of pure plasma catalysis with a reaction temperature of 550 °C, a water vapor ratio of 3, and a reaction power of 500 W, the methane conversion rate of the DBD reactor was 70 - 80%. The product gas composition after continuous operation for 8 hours was 69% H2, 6% CO2, 15% CO, and 10% CH4.

[0032] The public literature "Fuel, 2021, 304, 121328" reported the integrated process and environmental impact of plasma steam methane reforming, pointing out that when the electricity cost is low, the price of H2 derived from the hybrid DBD plasma process is more competitive than that of traditional thermocatalytic methane steam reforming for hydrogen production.

[0033] The open literature "Chemical Engineering Science, 2022, 253, 117560" reported a knife-edge sliding discharge plasma reactor for steam methane reforming. And the effects of steam-to-carbon molar ratio, residence time, and input power on the methane steam reforming reaction were studied. The experimental results showed that when the steam-to-water ratio was 2.01, the residence time was 13.8 s, and the input power was 36.0 W, H2 and CO were the main gas products, and the hydrogen production reached 173.6 L / kw -1 h -1 。

[0034] The open literature "Applied Catalysis A, 2022, 647, 118903" reported that in the steam reforming reaction, in order to improve the H2 yield, it is necessary to drive the formed CO to CO2 and H2 by the water-gas shift reaction. The reaction results showed that on the Ni / CaAl4O7 and Cu / ZnO / Al2O3 / MgO tandem catalysts with a discharge power of 15 W, a reaction temperature of 300 °C, and a steam-to-water ratio of 4.5, a methane conversion rate of 60%, a hydrogen selectivity of 86%, and a CO2 / CO selectivity of more than 15 were achieved.

[0035] The open literature "International journal of hydrogen energy, 2023, 48, 24328-24341" used non-thermal plasma-assisted Cu-Mn / CeO2 to catalyze the steam methane reforming reaction to produce hydrogen. The effects of input power and flow rate on the reaction were investigated. DFT calculations showed that on the Cu-Mn / CeO2 catalyst, after adding copper oxide, the electronic structure of cerium oxide changed significantly with methane. At a specific energy input of 19.8 J / L -1 , and a methane flow rate of 50 ml / min, the methane conversion rate was 14.76%, and the selectivities of carbon monoxide and hydrogen were 5.48% and 50.6% respectively, with no carbon dioxide produced.

[0036] The open literature "Energy Conversion and Management, 2023, 286, 117082" reported the reaction of plasma combined with Pd-Ga / 13X catalyst to catalytically convert non-oxidative methane to hydrogen. The results showed that compared with the single-metal catalyst, the synergistic effect between the two metals increased the absorbed hydrogen atom and electron flux concentration, reducing coke deposition. In a DBD reactor with an input power of 10 W and a methane flow rate of 5 ml / min, a methane conversion rate of 68% and a hydrogen selectivity of 42% were achieved.

[0037] The open literature "International Journal of Hydrogen Energy, 2024, 59, 1367–1375" reported various routes for methane reforming to produce hydrogen by DBD discharge plasma catalysis. The results showed that the hydrogen production efficiency of the methane steam reforming route was the best. Under the conditions of a plasma discharge power of 40 W, a water vapor ratio of 1:1, and the action of a Ni / Al2O3 catalyst, a methane conversion rate of 24% and a hydrogen tail gas content of 74% were achieved. The open literature "ACS Sustainable Chem. Eng. 2024, 12, 18276-18286" insulated the DBD discharge device on this basis, and achieved a methane conversion rate of 17.5% and a hydrogen tail gas content of 86% on a Ni / Al2O3 catalyst at 30 W and a water vapor ratio of 1:1.

[0038] Patent CN112299373A (application date: February 2, 2021) discloses a method for reforming natural gas to produce hydrogen by magnetic rotation non-equilibrium sliding arc. Methane steam is introduced into the magnetic rotation non-equilibrium sliding arc reforming natural gas hydrogen production equipment, and hydrogen is obtained under the action of sliding arc discharge and non-thermal equilibrium plasma. The activation effect of free electrons in the plasma and highly active free radicals are used to promote the effective progress of the reaction, which can avoid the technical and cost problems of catalyst deactivation and replacement to a certain extent, and provides ideas for solving the cost and safety problems of hydrogen production.

[0039] Patent CN216377479U (application date: November 18, 2021) discloses a plasma reforming distributed natural gas hydrogen production device. The results show that the introduction of high-voltage plasma technology can significantly improve the conversion rate of methane and avoid the defect of open fire in traditional natural gas steam reforming devices.

[0040] Patent CN 114572935 A (application date: April 13, 2022) discloses a method for producing hydrogen from biogas by dielectric barrier discharge non-thermal equilibrium plasma. Through the dielectric barrier discharge reforming hydrogen production technology of ultrasonic atomized water vapor mixed with biogas, the high-energy electrons in the non-thermal equilibrium collide with methane molecules, water molecules, and hydrogen sulfide molecules, causing the rupture of molecular bonds. The dielectric barrier discharge equipment uses nickel metal as the inner electrode material and also as a catalyst. The plasma discharge continuously activates the nickel metal on the surface of the nickel metal, reducing the energy consumption of the reforming process and increasing the reaction efficiency of hydrogen per unit time.

[0041] In summary, the existing public literature and patents related to hydrogen production by steam reforming of methane require multiple steps of operation to achieve high H2 selectivity and low CO content. The fundamental reason is that too high operating temperature is conducive to the endothermic steam reforming reaction to produce syngas (CO / H2) but not conducive to the exothermic water-gas shift reaction. Summary of the Invention

[0042] The object of the present invention is to provide a method for directly producing CO-free hydrogen by reacting methane and steam in one step. The present invention reduces the Gibbs free radical energy change of the methane steam reforming reaction through the non-volume work of plasma, so as to achieve a high-conversion steam reforming reaction and water-gas shift reaction under lower temperature conditions. At the same time, combining the catalytic characteristics of the steam reforming and water-gas shift catalysts, a bifunctional catalyst with both steam reforming active centers and water-gas shift active centers is selected. The plasma and the catalyst act synergistically to catalyze the steam reforming of methane to directly produce CO-free hydrogen.

[0043] Technical principle: Under the reaction conditions of low temperature and normal pressure, high-energy electrons (1-10 eV) generated by dielectric barrier discharge (DBD) are used to activate small molecules (CH4, H2O). Under the collision of high-energy electrons, the reactant molecules (CH4, H2O) are excited and dissociated to produce CH * , C * , OH * , H * and other active groups. By introducing the catalyst and regulating the reaction conditions, the selectivity distribution of the products is further affected.

[0044] The technical solution of the present invention:

[0045] A hydrogen production method, in which methane, steam and argon are mixed and preheated through a steam generator and then introduced into a plasma catalytic reactor (wherein, methane and steam are used as raw material gases, and the role of argon is to activate the discharge and is not used as a reaction gas). The methane and steam molecules are activated by discharging, and the activated methane steam molecules are converted into hydrogen and carbon dioxide under the action of a catalyst to achieve hydrogen production.

[0046] The molar ratio of the methane to the steam is 1:1-1:5; the space velocity of methane is 1.6-7.9 min -1 .

[0047] The reaction environment provided by the plasma catalytic reactor is normal pressure, and the reaction temperature is 250-500 °C; the dielectric barrier discharge uses a high-voltage AC power supply, and the specific energy input SEI (Specific Energy Intensity) is 4-20 J / ml.

[0048] For the described catalyst, the carrier is γ-Al2O3, and the supported metal is one or both of Ni and Cu; the mass percentage of the supported metal in the catalyst is 0-30%.

[0049] When loading one metal, it is called a single-metal catalyst. Preferably, in Ni / γ-Al2O3, the mass percentage of Ni in the catalyst is 20%.

[0050] When loading two metals, it is called a bimetallic catalyst. Preferably, in Ni-Cu / γ-Al2O3, the mass percentage of Ni in the catalyst is 20%, and the mass percentage of Cu in the catalyst is 10%.

[0051] The synthesis method of the described catalyst is equal-volume impregnation of metals and includes the following steps: First, calcine the carrier γ-Al2O3 at 540 °C to remove impurities therein, and then prepare a nitrate precursor solution with the same water absorption capacity as the carrier. The nitrate precursor solution is nickel nitrate (Ni(NO3)2·9H2O) or copper nitrate (Cu(NO3)2·3H2O) or a mixed solution of nickel nitrate and copper nitrate; add the γ-Al2O3 carrier to the prepared precursor nitrate solution and stir for 15 min. Then, put the mixture into an oven at 110 °C and dry for 12 hours to remove water to ensure that metal cations are fully loaded onto the carrier. Grind the preliminarily dehydrated catalyst and transfer it to a crucible, and calcine it in a muffle furnace at 540 °C for 5 h. Finally, crush the calcined catalyst, press it into tablets and screen it into 20-40 mesh particles, and reduce it with hydrogen at 400 °C for 1 hour to obtain the Ni / γ-Al2O3 or Ni-Cu / γ-Al2O3 catalyst.

[0052] The described plasma catalytic reactor is a dielectric barrier discharge reactor. The reactor is cylindrical, wrapped with a layer of aluminum foil on the outside, and then a metal wire is wound around the outer surface of the aluminum foil as a grounding electrode; a upper head with a central hole is provided at the upper end of the cylinder, and a metal rod is used as a high-voltage electrode and passes through the central hole along the axis of the reactor; the distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor is 5 mm; the cylindrical reactor is made of a single-layer dielectric insulating material; methane, argon, and water vapor inlets are provided at the upper end of the reactor, above the discharge area, the lower end of the reactor is connected to a collector, and the rear end of the collector is connected to a tail gas outlet; the catalyst is placed in the discharge area inside the reactor, and the catalyst bed is supported by quartz wool. Among them, the high-voltage electrode and the grounding electrode are made of copper, iron, tungsten, aluminum, or stainless steel; the barrier medium is made of quartz glass, hard glass, alumina ceramic, polytetrafluoroethylene, or non-metallic composite material.

[0053] The beneficial effects of the present invention are:

[0054] The present invention regulates the distribution of reactant conversion rate and product selectivity by adjusting plasma discharge power, raw material composition, and the mass fraction of the loaded metal. On the one hand, a series of single-metal / support catalysts were prepared by the equal-volume impregnation catalyst preparation method and applied to the plasma methane steam reforming system. Under the conditions of normal pressure of 350 °C (provided by the plasma power supply, 11 J / ml), a methane-steam ratio of 1:4, and a power frequency of 13.9 kHz, 20 wt% Ni / γ-Al2O3 exhibited the best catalytic performance, achieving a CH4 conversion rate of 34% and an H2 selectivity of 98% without the generation of carbon monoxide. On the other hand, aiming at the limitations of single-metal catalysts under medium-temperature conditions, a series of bimetal / support catalysts were synthesized. Under the conditions of normal pressure of 500 °C (provided by the plasma power supply, 20 J / ml), a methane-steam ratio of 1:4, and a power frequency of 13.9 kHz, Ni-Cu / γ-Al2O3 exhibited the best catalytic performance. When the loadings of Ni and Cu were 20% and 10% respectively, a CH4 conversion rate of 90% and an H2 selectivity of 92% were achieved, with a corresponding CO selectivity of 14% and a CO2 selectivity of 83%.

[0055] The present invention uses plasma in combination with Ni / γ-Al2O3 or Ni-Cu / γ-Al2O3 catalysts, with mild conditions, simple operation, and a simple process, achieving the production of hydrogen through the methane steam reforming reaction under low temperature and normal pressure, providing a new idea for the utilization of methane and the hydrogen production reaction without carbon monoxide. Description of the Drawings

[0056] Figure 1 It is a schematic structural diagram of a cylindrical dielectric barrier discharge plasma reactor for plasma-catalytic methane steam reforming.

[0057] Figure 2 It is an experimental device diagram for plasma-catalytic methane steam reforming to produce hydrogen.

[0058] In the figure: 1 inlet; 2 tail gas outlet; 3 high-voltage electrode; 4 catalyst; 5 ground electrode; 6 aluminum foil; 7 plasma power supply; 8 mass flowmeter; 9 steam generator; 10 dielectric barrier discharge plasma reactor; 11 liquid nitrogen cold trap; 12 oscilloscope; 13 GC-7900 gas chromatograph; 14 GC-2014 gas chromatograph; 15 soap bubble flowmeter. Detailed Embodiments

[0059] The following specifically describes the embodiments of the present invention in detail in combination with the technical solutions and the drawings.

[0060] The cylindrical dielectric barrier discharge plasma reactor used in the embodiments is as Figure 1As shown, the entire experimental apparatus for plasma-catalytic steam reforming of methane to hydrogen is as Figure 2 shown.

[0061] Examples 1 - 5: Taking the Ni / γ-Al2O3 catalyst as an example, examples with different steam-to-carbon ratios are listed. The temperature in the discharge zone is maintained at 350 °C by discharging, and the discharge duration is 2 h.

[0062] Example 1

[0063] The Ni / γ-Al2O3 catalyst is loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane to steam is 1:1 (where the methane space velocity is 6.3 min -1 ) and fed into the reactor, and the preheated feed gas is at 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharging. The temperature in the discharge zone is maintained at 350 °C by discharging.

[0064] Reaction results: methane conversion rate 17.9%, hydrogen selectivity 58.1%, carbon dioxide selectivity 62.1%, carbon monoxide selectivity 0%.

[0065] Example 2

[0066] The Ni / γ-Al2O3 catalyst is loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane to steam is 1:2 (where the methane space velocity is 6.3 min -1 ) and fed into the reactor, and the preheated feed gas is at 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharging. The temperature in the discharge zone is maintained at 350 °C by discharging.

[0067] Reaction results: methane conversion rate 23.2%, hydrogen selectivity 72.6%, carbon dioxide selectivity 71.0%, carbon monoxide selectivity 0%.

[0068] Example 3

[0069] The Ni / γ-Al2O3 catalyst is loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane to steam is 1:3 (where the methane space velocity is 6.3 min -1 ) and fed into the reactor, and the preheated feed gas is at 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharging. The temperature in the discharge zone is maintained at 350 °C by discharging.

[0070] Reaction results: methane conversion rate is 30.8%, hydrogen selectivity is 77.3%, carbon dioxide selectivity is 77.0%, and carbon monoxide selectivity is 0%.

[0071] Example 4

[0072] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is irregular in shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) is 20% (by weight). The molar ratio of methane to steam is 1:4 (where the methane space velocity is 6.3 min -1 ) and introduced into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature of the discharge zone was maintained at 350°C by the discharge.

[0073] Reaction results: methane conversion rate is 35.0%, hydrogen selectivity is 98.7%, carbon dioxide selectivity is 98.9%, and carbon monoxide selectivity is 0%.

[0074] Example 5

[0075] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is irregular in shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) is 20% (by weight). The molar ratio of methane to steam is 1:5 (where the methane space velocity is 6.3 min -1 ) and introduced into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature of the discharge zone was maintained at 350°C by the discharge.

[0076] Reaction results: methane conversion rate is 36.3%, hydrogen selectivity is 96.4%, carbon dioxide selectivity is 97.0%, and carbon monoxide selectivity is 0%.

[0077] The catalyst activity and selectivity are shown in Table 1.

[0078] Table 1. Methane conversion rate and product selectivity corresponding to different water vapor ratios over the Ni / γ-Al2O3 catalyst

[0079]

[0080] Preferably, CH4:H2O is 1:4.

[0081] Examples 6 - 11, taking the Ni / γ-Al2O3 catalyst as an example, list examples with different reaction temperatures. The temperature of the discharge zone was maintained by the discharge, and the discharge duration was 2 h.

[0082] Example 6

[0083] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was switched on for discharge. The temperature of the discharge zone was maintained at 250°C through the discharge.

[0084] Reaction results: methane conversion rate 11.9%, hydrogen selectivity 63.1%, carbon dioxide selectivity 54.2%, carbon monoxide selectivity 0%.

[0085] Example 7

[0086] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was switched on for discharge. The temperature of the discharge zone was maintained at 300°C through the discharge.

[0087] Reaction results: methane conversion rate 13.8%, hydrogen selectivity 68.0%, carbon dioxide selectivity 63.7%, carbon monoxide selectivity 0%.

[0088] Example 8

[0089] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was switched on for discharge. The temperature of the discharge zone was maintained at 350°C through the discharge.

[0090] Reaction results: methane conversion rate 34.7%, hydrogen selectivity 97.8%, carbon dioxide selectivity 96.0%, carbon monoxide selectivity 0%.

[0091] Example 9

[0092] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon, and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115 °C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature of the discharge zone was maintained at 400 °C through the discharge.

[0093] Reaction results: methane conversion rate 45.9%, hydrogen selectivity 97.8%, carbon dioxide selectivity 96.0%, carbon monoxide selectivity 2.9%.

[0094] Example 10

[0095] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon, and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115 °C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature of the discharge zone was maintained at 450 °C through the discharge.

[0096] Reaction results: methane conversion rate 60.6%, hydrogen selectivity 95.0%, carbon dioxide selectivity 87.7%, carbon monoxide selectivity 9.0%.

[0097] Example 11

[0098] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 15% (by weight). The molar ratio of methane, argon, and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115 °C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature of the discharge zone was maintained at 500 °C through the discharge.

[0099] Reaction results: methane conversion rate 77.1%, hydrogen selectivity 84.5%, carbon dioxide selectivity 63.7%, carbon monoxide selectivity 28.6%.

[0100] The activity and selectivity of the catalyst are shown in Table 2.

[0101] Table 2. Methane conversion rate and product selectivity corresponding to different reaction temperatures over the Ni / γ-Al2O3 catalyst

[0102]

[0103]

[0104] The preferred reaction temperature is 350 °C.

[0105] Comparative Examples 1-2, Example 4, Example 8, and Examples 12-16 list examples of Ni / γ-Al2O3 with different loadings.

[0106] Comparative Example 1

[0107] A mixture of methane, argon, and steam with a molar ratio of 1:2:4 (where the methane space velocity is 6.3 min -1 ) is fed into the reactor, and the feed gas is preheated to 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharge. The temperature in the discharge zone is maintained at 350 °C by the discharge.

[0108] Reaction results: Methane conversion rate is 13.2%, hydrogen selectivity is 52.0%, carbon dioxide selectivity is 0%, and carbon monoxide selectivity is 15.8%.

[0109] Comparative Example 2

[0110] The γ-Al2O3 catalyst is loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst is in irregular shape (20-40 mesh). A mixture of methane, argon, and steam with a molar ratio of 1:2:4 (where the methane space velocity is 6.3 min -1 ) is fed into the reactor, and the feed gas is preheated to 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharge. The temperature in the discharge zone is maintained at 350 °C by the discharge.

[0111] Reaction results: Methane conversion rate is 16.3%, hydrogen selectivity is 60.0%, carbon dioxide selectivity is 0%, and carbon monoxide selectivity is 17.5%.

[0112] Example 12

[0113] The Ni / γ-Al2O3 catalyst is loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst is in irregular shape (20-40 mesh), and the loading amount of the active component in terms of elemental nickel (Ni) is 1% (by weight). A mixture of methane, argon, and steam with a molar ratio of 1:2:4 (where the methane space velocity is 6.3 min -1 ) is fed into the reactor, and the feed gas is preheated to 115 °C. After the feed gas is mixed evenly, the plasma power supply is turned on for discharge. The temperature in the discharge zone is maintained at 350 °C by the discharge.

[0114] Reaction results: methane conversion rate 77.1%, hydrogen selectivity 84.5%, carbon dioxide selectivity 0%, carbon monoxide selectivity 17.0%.

[0115] Example 13

[0116] Load the Ni / γ-Al2O3 catalyst into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is of irregular shape (20 - 40 mesh), and the loading amount of the active ingredient calculated as elemental nickel (Ni) is 5% (by weight). The molar ratio of methane, argon, and steam is 1:2:4 (where the methane space velocity is 6.3 min -1 ) and introduce it into the reactor. The preheated raw material gas is 115°C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. Maintain the temperature of the discharge zone at 350°C through discharge.

[0117] Reaction results: methane conversion rate 20.6%, hydrogen selectivity 77.6%, carbon dioxide selectivity 68.4%, carbon monoxide selectivity 0%.

[0118] Example 14

[0119] Load the Ni / γ-Al2O3 catalyst into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is of irregular shape (20 - 40 mesh), and the loading amount of the active ingredient calculated as elemental nickel (Ni) is 10% (by weight). The molar ratio of methane, argon, and steam is 1:2:4 (where the methane space velocity is 6.3 min -1 ) and introduce it into the reactor. The preheated raw material gas is 115°C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. Maintain the temperature of the discharge zone at 350°C through discharge.

[0120] Reaction results: methane conversion rate 34.1%, hydrogen selectivity 87.2%, carbon dioxide selectivity 86.6%, carbon monoxide selectivity 0%.

[0121] Example 15

[0122] Load the Ni / γ-Al2O3 catalyst into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is of irregular shape (20 - 40 mesh), and the loading amount of the active ingredient calculated as elemental nickel (Ni) is 25% (by weight). The molar ratio of methane, argon, and steam is 1:2:4 (where the methane space velocity is 6.3 min -1 ) and introduce it into the reactor. The preheated raw material gas is 115°C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. Maintain the temperature of the discharge zone at 350°C through discharge.

[0123] Reaction results: methane conversion rate 35.7%, hydrogen selectivity 96.5%, carbon dioxide selectivity 98.0%, carbon monoxide selectivity 0%.

[0124] Example 16

[0125] The Ni / γ-Al2O3 catalyst was loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst was in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 30% (by weight). The molar ratio of methane, argon and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The temperature in the discharge zone was maintained at 350°C by the discharge.

[0126] Reaction results: methane conversion rate 32.9%, hydrogen selectivity 88.2%, carbon dioxide selectivity 96.5%, carbon monoxide selectivity 0%.

[0127] The catalyst activity and selectivity are shown in Table 3.

[0128] Table 3. Methane conversion rate and product selectivity corresponding to different Ni loadings on the Ni / γ-Al2O3 catalyst

[0129]

[0130] The preferred Ni loading is 20%.

[0131] Comparative Example 3, Examples 17 - 23 investigated the catalytic activities of Ni-Cu / γ-Al2O3 catalysts with different mass fractions (denoted as xNiyCu, where x and y are the loading mass fractions of Ni and Cu respectively).

[0132] Comparative Example 3

[0133] The γ-Al2O3 catalyst was loaded into the discharge zone of the wire-cylinder type discharge reactor. The catalyst was in irregular shape (20 - 40 mesh). The molar ratio of methane, argon and steam was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and fed into the reactor, and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500°C by the discharge, and the discharge duration was 2 h.

[0134] Reaction results: methane conversion rate 42.3%, hydrogen selectivity 67.3%, carbon dioxide selectivity 0%, carbon monoxide selectivity 13.8%.

[0135] Example 17

[0136] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 30% (by weight), and the loading amount of the active component calculated as elemental copper (Cu) was 0% (by weight). Methane, argon, and steam were fed into the reactor at a molar ratio of 1:2:4 (with a methane space velocity of 6.3 min -1 ), and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500°C through discharge.

[0137] Reaction results: methane conversion rate 75.1%, hydrogen selectivity 84.5%, carbon dioxide selectivity 63.7%, carbon monoxide selectivity 28.6%.

[0138] Example 18

[0139] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 25% (by weight), and the loading amount of the active component calculated as elemental copper (Cu) was 5% (by weight). Methane, argon, and steam were fed into the reactor at a molar ratio of 1:2:4 (with a methane space velocity of 6.3 min -1 ), and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500°C through discharge.

[0140] Reaction results: methane conversion rate 85.2%, hydrogen selectivity 89.6%, carbon dioxide selectivity 82.4%, carbon monoxide selectivity 15.0%.

[0141] Example 19

[0142] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was of irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) was 20% (by weight), and the loading amount of the active component calculated as elemental copper (Cu) was 10% (by weight). Methane, argon, and steam were fed into the reactor at a molar ratio of 1:2:4 (with a methane space velocity of 6.3 min -1 ), and the raw material gas was preheated to 115°C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500°C through discharge.

[0143] Reaction results: methane conversion rate is 90.6%, hydrogen selectivity is 92.6%, carbon dioxide selectivity is 88.6%, and carbon monoxide selectivity is 11.3%.

[0144] Example 20

[0145] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in an irregular shape (20-40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 15% (by weight), and the loading amount of the active ingredient in terms of elemental copper (Cu) was 15% (by weight). The molar ratio of methane, argon, and water vapor was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and introduced into the reactor, and the raw material gas was preheated to 115 °C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500 °C through discharge.

[0146] Reaction results: methane conversion rate is 88.4%, hydrogen selectivity is 91.1%, carbon dioxide selectivity is 84.8%, and carbon monoxide selectivity is 12.6%.

[0147] Example 21

[0148] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in an irregular shape (20-40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 10% (by weight), and the loading amount of the active ingredient in terms of elemental copper (Cu) was 20% (by weight). The molar ratio of methane, argon, and water vapor was 1:2:4 (where the methane space velocity was 6.3 min -1 ) and introduced into the reactor, and the raw material gas was preheated to 115 °C. After the raw material gas was mixed evenly, the plasma power supply was turned on for discharge. The discharge power was 40 W, and the temperature in the discharge zone was maintained at 500 °C through discharge.

[0149] Reaction results: methane conversion rate is 82.2%, hydrogen selectivity is 88.7%, carbon dioxide selectivity is 83.1%, and carbon monoxide selectivity is 13.8%.

[0150] Example 22

[0151] The Ni-Cu / γ-Al2O3 catalyst was loaded into the discharge zone of a wire-cylinder type discharge reactor. The catalyst was in an irregular shape (20-40 mesh), and the loading amount of the active ingredient in terms of elemental nickel (Ni) was 5% (by weight), and the loading amount of the active ingredient in terms of elemental copper (Cu) was 25% (by weight). The molar ratio of methane, argon, and water vapor was 1:2:4 (where the methane space velocity was 6.3 min -1) Feed into the reactor and preheat the raw material gas to 115 °C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. The discharge power is 40 W, and the temperature in the discharge zone is maintained at 500 °C through discharge.

[0152] Reaction results: Methane conversion rate is 38.6%, hydrogen selectivity is 99.0%, carbon dioxide selectivity is 97.2%, and carbon monoxide selectivity is 0%.

[0153] Example 23

[0154] Load the Ni-Cu / γ-Al2O3 catalyst into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient calculated as elemental nickel (Ni) is 0% (by weight), and the loading amount of the active ingredient calculated as elemental copper (Cu) is 30% (by weight). The molar ratio of methane, argon and water vapor is 1:2:4 (where the methane space velocity is 6.3 min -1 ) Feed into the reactor and preheat the raw material gas to 115 °C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. The discharge power is 40 W, and the temperature in the discharge zone is maintained at 500 °C through discharge.

[0155] Reaction results: Methane conversion rate is 10.9%, hydrogen selectivity is 24.6%, carbon dioxide selectivity is 0%, and carbon monoxide selectivity is 0%.

[0156] The catalyst activity and selectivity are shown in Table 4.

[0157] Table 4. Methane conversion rate and product selectivity corresponding to different Ni-Cu loadings on the Ni-Cu / γ-Al2O3 catalyst

[0158]

[0159] The preferred Ni loading amount is 20% and the Cu loading amount is 10%.

[0160] Examples 4 and Examples 24 - 27 list examples with different methane space velocities.

[0161] Example 24

[0162] Load the Ni / γ-Al2O3 catalyst into the discharge zone of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active ingredient calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane, argon and water vapor is 1:2:4 (where the methane space velocity is 1.6 min -1 ) Feed into the reactor and preheat the raw material gas to 115 °C. After the raw material gas is mixed evenly, turn on the plasma power supply for discharge. The temperature in the discharge zone is maintained at 350 °C through discharge.

[0163] Reaction results: methane conversion rate 30.6%, hydrogen selectivity 99.8%, carbon dioxide selectivity 99.9%, carbon monoxide selectivity 0%.

[0164] Example 25

[0165] Load the Ni / γ-Al2O3 catalyst into the discharge area of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane, argon and steam is 1:2:4 (where the methane space velocity is 3.2 min -1 ) and introduce it into the reactor, and the preheated feed gas is 115°C. After the feed gas is mixed evenly, turn on the plasma power supply for discharge. Maintain the temperature of the discharge area at 350°C through discharge.

[0166] Reaction results: methane conversion rate 33.4%, hydrogen selectivity 97.6%, carbon dioxide selectivity 99.9%, carbon monoxide selectivity 0%.

[0167] Example 26

[0168] Load the Ni / γ-Al2O3 catalyst into the discharge area of the wire-cylinder type discharge reactor. The catalyst is in irregular shape (20 - 40 mesh), and the loading amount of the active component calculated as elemental nickel (Ni) is 20% (by weight). The molar ratio of methane, argon and steam is 1:2:4 (where the methane space velocity is 7.9 min -1 ) and introduce it into the reactor, and the preheated feed gas is 115°C. After the feed gas is mixed evenly, turn on the plasma power supply for discharge. Maintain the temperature of the discharge area at 350°C through discharge.

[0169] Reaction results: methane conversion rate 36.9%, hydrogen selectivity 99.0%, carbon dioxide selectivity 96.4%, carbon monoxide selectivity 0%.

[0170] The activity and selectivity of the catalyst are shown in Table 5.

[0171] Table 5. Methane conversion rate and product selectivity corresponding to different space velocities over the Ni / γ-Al2O3 catalyst

[0172]

[0173] There is no obvious difference in the reaction results at different methane space velocities.

Claims

1. A method for producing hydrogen, characterized in that: Methane, water vapor and argon are mixed and preheated in a water vapor generator and then introduced into a plasma catalytic reactor. The methane and water vapor molecules are activated by discharge, and the activated methane and water vapor molecules are converted into hydrogen and carbon dioxide under the action of the catalyst to achieve hydrogen production.

2. A method for producing hydrogen according to claim 1, characterized in that: The molar ratio of methane to water vapor is 1:1-1:5; the space velocity of methane is 1.6-7.9min -1 .

3. A method for producing hydrogen according to claim 1, characterized in that: The plasma catalytic reactor provides a reaction environment of normal pressure and a reaction temperature of 250-500° C. The dielectric barrier discharge uses a high-voltage AC power supply, and the specific energy input SEI is 4-20 J / ml.

4. A method for producing hydrogen according to claim 1, characterized in that: The catalyst has a carrier of γ-Al2O3 and a loaded metal of one or two of Ni and Cu; the mass percentage of the loaded metal in the catalyst is 0-30%.

5. A method for producing hydrogen according to claim 4, characterized in that: When a metal Ni is loaded, it is Ni / γ-Al2O3, and the mass percentage of Ni in the catalyst is 20%.

6. A method for producing hydrogen according to claim 4, characterized in that: When two metals are loaded, it is Ni-Cu / γ-Al2O3, the mass percentage of Ni in the catalyst is 20%, and the mass percentage of Cu in the catalyst is 10%.

7. A method for producing hydrogen according to claim 4, characterized in that: The catalyst is prepared by metal equal volume impregnation, comprising the following steps: firstly, calcining a carrier γ-Al2O3 at 540°C to remove impurities therein, and then preparing a nitrate precursor solution with the same water absorption as the carrier, wherein the nitrate precursor solution is nickel nitrate or copper nitrate or a mixed solution of nickel nitrate and copper nitrate; adding the γ-Al2O3 carrier to the prepared precursor nitrate solution and stirring for 15 minutes; then putting the mixture into an oven at 110°C and drying it for 12 hours to remove moisture and ensure that the metal cations are fully loaded on the carrier; grinding the catalyst after preliminary dehydration and transferring it to a crucible, and roasting it in a muffle furnace at 540°C for 5 hours; finally, crushing the roasted catalyst, pressing it into tablets and sieving it into particles of 20-40 mesh, and reducing it with hydrogen at 400°C for 1 hour to obtain a Ni / γ-Al2O3 or Ni-Cu / γ-Al2O3 catalyst.

8. A method for producing hydrogen according to claim 1, characterized in that: The plasma catalytic reactor is a dielectric barrier discharge reactor, which is cylindrical and wrapped with a layer of aluminum foil. A metal wire is then wound around the surface of the aluminum foil as a grounding electrode. An upper end cap with a center hole is arranged at the upper end of the cylinder, and a metal rod is passed into the center hole along the axis of the reactor as a high-voltage electrode. The distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor is 5 mm. The cylindrical reactor is made of a single-layer dielectric insulating material. The upper end of the reactor is provided with inlets for methane, argon and water vapor, which are located above the discharge zone. The lower end of the reactor is connected to a collector, and the rear end of the collector is connected to an exhaust gas outlet. The catalyst is placed in the discharge zone in the reactor, and the catalyst bed is supported by quartz wool.

9. A method for producing hydrogen according to claim 8, characterized in that: in, The high voltage electrode and the grounding electrode are made of copper, iron, tungsten, aluminum or stainless steel; the blocking medium is made of quartz glass, hard glass, alumina ceramics, polytetrafluoroethylene or non-metallic composite materials.

Images