Method for preparing a hydrogen production melting catalyst from hydrocarbons and applications thereof

Abstract

The application relates to a preparation method and application of a hydrogen production molten catalyst for hydrocarbon cracking, which comprises adding bismuth in nickel-molybdenum oxide to form a modified NiMo-Bi liquid alloy so as to produce a ternary Ni 3x Mo x -Bi liquid alloy catalyst. The catalyst has low activation energy, can crack methane at 450 DEG C-1000 DEG C, and has high hydrogen production efficiency. At 800 DEG C, the Ni 12 Mo4-Bi catalyst has 100% H2 selectivity and 260 hours of stability. At 1000 DEG C, the 1cm Ni 12 Mo4-Bi catalyst can obtain 62% methane conversion. The application adopts the low-melting-point molten alloy NiMo-Bi as the catalyst, combines the high activity of a nickel-based catalyst for hydrocarbons and the low melting point of a bismuth-based alloy, has high activity and high stability, can effectively crack hydrocarbons, and can continuously and efficiently produce hydrogen through catalytic cracking. Another product of cracking can be separated through water washing to obtain elemental carbon, thereby solving the problems of poor stability, poor carbon deposition resistance and easy deactivation of existing Ni-based supported catalysts or other solid catalysts.

Description

Technical Field

[0001] This invention relates to the field of hydrocarbon cracking and hydrogen production catalysis technology, and in particular to a method for preparing nickel-based low-melting-point molten catalysts for hydrogen production from methane, ethane, and propane cracking, and their applications. Background Technology

[0002] Hydrogen is an important chemical intermediate and has attracted much attention globally as a promising clean energy solution. Currently, 90% of hydrogen production comes from water-gas shift reactions in fossil fuels. This method of hydrogen production is heavily reliant on fossil fuels such as natural gas, oil, and coal, which has led to significant carbon dioxide emissions.

[0003] Water electrolysis is a green hydrogen production technology that uses renewable energy to produce CO2-free H2. Despite its environmental advantages, the high cost (US$5-6 per kilogram of H2) and high energy consumption limit its market share, currently accounting for only 2% of hydrogen production. Besides the currently hotly researched water electrolysis for hydrogen production, direct methane cracking can also avoid CO2 emissions. Methane cracking produces hydrogen while simultaneously generating high-quality carbon byproducts such as graphene, carbon nanotubes, fullerenes, and carbon black; the system is oxygen-free, therefore emitting no CO2. Considering overall energy consumption, carbon emissions, and environmental impact, direct methane cracking for hydrogen production is a highly efficient, energy-saving, economical, and environmentally friendly technology.

[0004] Traditional methane cracking for hydrogen production primarily employs thermal cracking or catalytic cracking. However, these methods require high reaction temperatures (>1000 °C) to activate CH4, leading to high energy demands, expensive equipment, and heat losses. Thermal cracking is energy-intensive and complex, while catalytic cracking is often limited by catalyst selection and activity. Suitable reaction temperatures can reduce the formation of byproducts (ethane, ethylene, acetylene, aromatics) and minimize H2 separation and purification operations. Methane pyrolysis for hydrogen production and catalytic pyrolysis of hydrocarbons represent potential carbon dioxide-free hydrogen production technologies, generating only solid carbon byproducts. However, the development of highly efficient catalysts for the stable pyrolysis of methane at moderate temperatures remains a challenge. Furthermore, solid catalysts for the catalytic cracking of methane or other hydrocarbons are easily covered by coke deposits generated during CH4 cracking, thus losing their activity.

[0005] In view of the above, it is necessary to develop a stable, highly catalytically active, and highly efficient hydrocarbon cracking catalyst for hydrogen production, which has a moderate reaction temperature, excellent resistance to carbon deposition and deactivation, and facilitates the separation of carbon materials and catalysts. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for preparing and applying a NiMo-Bi molten catalyst for hydrocarbon cracking to produce hydrogen. This method involves first forming a NiO-MoO3 mixture, and then reducing it in situ with bismuth pellets in a N2 / H2 atmosphere to form a NiMo-Bi liquid alloy catalyst; Example 1 is a Ni... 7.6 Mo 2.6 -Bi, with a Bi content of 100-7.6-2.6=89.8%. This catalyst can perform hydrogen production reactions by cracking low-carbon alkanes such as methane, and features good catalytic activity, low activation energy, good stability, and easy separation of by-product carbon materials.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: A method for preparing a NiMo-Bi molten catalyst for hydrocarbon cracking to produce hydrogen includes the following steps: Step S1: Anneal 3.3 mmol of nickel nitrate hexahydrate Ni(NO3)2·6H2O in air at 500 °C for 2 hours to form NiO; Step S2: Disperse the NiO in 10 mL of water, and add 0.157 mmol of ammonium heptamolybdate ((NH4)6Mo7O). 24 The mixture was ultrasonically shaken for 10 min, stirred and dried at 90 ℃, then vacuum dried at 110 ℃ overnight, and annealed at 500 ℃ for 2 hours to form a NiO-MoO3 mixture. Step S3: Mix the NiO-MoO3 mixture with bismuth pellets and place it in a reactor. First, inject N2 at 5 mL / min at room temperature for 30 min to remove air. Step S4: Mix 15 mL / min H2 with 5 mL / min N2 and inject the mixture into the reactor. Raise the catalyst from room temperature to 700 °C at a rate of 100 °C / 30 min and maintain the temperature at 700 °C for 1 hour to allow the NiO-MoO3 mixture to be slowly reduced with bismuth pellets to form a NiMo-Bi liquid alloy catalyst. Step S5: The reactor is slowly cooled to 450 °C in a mixture of H2 and N2 flowing at 15 mL / min to keep the alloy in a liquid state. Then, H2 is turned off and N2 is injected at 5 mL / min for 60 min to remove residual H2, thus obtaining the NiMo-Bi molten catalyst.

[0008] Furthermore, the NiMo-Bi molten catalyst is Ni 7.6 Mo 2.6 -Bi, Ni9Mo3-Bi, Ni 12 Mo4-Bi, Ni 15Mo5-Bi or Ni 18 Mo6-Bi, where the Bi content is 100 minus the Ni and Mo contents.

[0009] Furthermore, the NiMo-Bi molten catalyst described in Example 1 is Ni 7.6 Mo 2.6 -Bi, of which the Bi content is 89.8%.

[0010] Furthermore, when the NiMo-Bi molten catalyst is used for methane cracking to produce hydrogen, the methane gas flow rate is 4 mL / min, the pressure is 206 kPa, and the residence time of methane in the liquid alloy catalyst is 0.13 min.

[0011] Furthermore, the methane cracking reaction for hydrogen production is conducted at temperatures ranging from 450 °C to 800 °C. No H2 is detected below 400 °C, H2 is generated at 450 °C, and the H2 generation rate increases to 6.36 mLH2gNi at 800 °C. -1 min -1 .

[0012] Furthermore, the NiMo-Bi molten catalyst is also used for the cracking of ethane and / or propane to produce hydrogen. After the reaction, the carbon material generated is located on the alloy surface and is separated and collected from the NiMo-Bi molten catalyst.

[0013] The beneficial effects of this invention are: 1. The present invention adopts a preparation route of first forming a NiO-MoO3 mixture and then reducing it in situ with bismuth pellets, which can form a stable NiMo-Bi molten catalyst.

[0014] 2. This invention sets Ni 7.6 Mo 2.6 -Bi, Ni9Mo3-Bi, Ni 12 Mo4-Bi, Ni 15 Mo5-Bi and Ni 18 Multiple NiMo-Bi compositions, including Mo6-Bi, were used to compare the effects of different Ni / Mo molar ratios on catalytic activity.

[0015] 3. The catalyst of this invention can reduce the apparent activation energy of the methane cracking reaction, which is beneficial to increasing the reaction rate.

[0016] 4. This invention can perform methane cracking to produce hydrogen within the temperature range of 450 °C to 800 °C, and the H2 generation rate reaches 6.36 mLH2gNi at 800 °C. -1 min -1 .

[0017] 5. Molten catalysts facilitate the separation and collection of carbon materials from the alloy surface, resulting in high-purity, high-value carbon materials.

[0018] 6. The catalyst prepared by the method of the present invention can be applied to the catalytic cracking of low-carbon alkanes such as methane, ethane, and propane to produce hydrogen, which solves the problems of poor stability and easy carbon deposition and deactivation of existing Ni-based supported catalysts or other solid catalysts. Attached Figure Description

[0019] Figure 1 The apparent activation energy of the catalysts obtained in Examples 1-5 of this invention and Ni 3x Mo x Plot of methane conversion, selectivity and hydrogen production of -Bi; Figure 2 Ni obtained in different embodiments of the present invention 7.6 Mo 2.6 -Bi and Ni 12 XRD patterns of Mo4-Bi catalysts, with each curve corresponding to the catalyst obtained in the respective example; Figure 3 The Ni catalyst obtained in Examples 1-5 of this invention 3x Mo x -Bi hydrogen production rate at different temperatures, where the x-axis represents the reaction temperature and the y-axis represents the hydrogen production rate. Figure 4 The Ni obtained in Example 3 of this invention 12 The hydrogen production rates and apparent activation energies of Mo4-Bi catalysts for methane, ethane, and propane. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] The NiMo-Bi catalysts for catalytic cracking of methane to produce hydrogen prepared in Examples 1-5 below are all in a molten state. The Ni, Mo and Bi in each example are molar compositions, and the Bi content is 100 minus the Ni and Mo content. Example 1

[0022] 7.6 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was annealed in air at 500 °C for 2 hours to form NiO; Then, nickel oxide powder was dispersed in 10 mL of water, and 0.371 mmol of ammonium heptamolybdate ((NH4)6Mo7O) was added. 24), corresponding to 2.6 mmol Mo, ultrasonically shaken the solution for 10 min, then dried under stirring at 90 °C, vacuum dried at 110 °C overnight, and annealed at 500 °C for 2 hours to form a NiO-MoO3 mixture; NiO-MoO3 powder was mixed with 89.8 mmol of bismuth pellets to obtain the target molar composition of Ni. 7.6 Mo 2.6 The raw material system of -Bi, wherein the Bi content = 100 - 7.6 - 2.6 = 89.8; is placed in a thicker tube at the top of the molten block, and N2 gas at a flow rate of 5 mL / min, regulated by a mass flow controller, is injected into the reactor at room temperature for 30 min to remove air. Then, H2 gas at a flow rate of 15 mL / min, regulated by another mass flow controller, is mixed with 5 mL / min N2 and injected into the reactor together. The catalyst was heated from room temperature to 700 °C at a heating rate of 100 °C / 30 min and then stored at 700 °C for 1 hour, slowly reducing it to Ni. 7.6 Mo 2.6 -Bi liquid alloy catalyst; then the reactor was slowly cooled to 450 °C in a flowing gas mixture of 15 mL / min H2 and 5 mL / min N2. At this temperature, the alloy remained liquid. Then H2 was turned off and N2 was injected at a flow rate of 5 mL / min for 60 min to remove H2. After confirmation by gas chromatography, the liquid alloy catalyst was prepared for further catalytic determination. In the catalytic assay, 4 mL / min of pure methane (CH4) gas was passed through a straight tube at a pressure of 206 kPa (30 psi), with a residence time of approximately 0.13 min. The product was analyzed online using an HP-5890 GC (Hayesep D column and Hayesep Q column) equipped with TCD and FID detectors. Gas chromatographic analysis of the reaction gaseous products was used to evaluate Ni. 7.6 Mo 2.6 Performance of Bi liquid alloy catalysts for methane cracking and hydrogen production; After the experiment, the reaction apparatus was cooled to obtain a mixture of carbon materials on the surface of the alloy, and the reaction carbon material products were extracted and collected. Example 2

[0023] 9 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was annealed in air at 500 °C for 2 hours to form NiO; Then, nickel oxide powder was dispersed in 10 mL of water, and 0.429 mmol of ammonium heptamolybdate ((NH4)6Mo7O) was added. 24), corresponding to 3 mmol Mo, ultrasonically shake the solution for 10 min, then dry it under stirring at 90 °C, vacuum dry it overnight at 110 °C, and then anneal it at 500 °C for 2 hours to form a NiO-MoO3 mixture; NiO-MoO3 powder was mixed with 88 mmol of bismuth pellets to obtain a raw material system with a target molar composition of Ni9Mo3-Bi, where the Bi content = 100-9-3 = 88. The mixture was placed in a thicker tube at the top of the molten metal and injected into the reactor at a flow rate of 5 mL / min N2, regulated by a mass flow controller, for 30 min at room temperature to remove air. Then, 15 mL / min H2 gas, regulated by another mass flow controller, was mixed with 5 mL / min N2 and injected into the reactor together. The catalyst was heated from room temperature to 700 °C at a heating rate of 100 °C / 30 min and stored at 700 °C for 1 hour to slowly reduce it to a Ni9Mo3-Bi liquid alloy catalyst. The reactor was then slowly cooled to 450 °C in a flowing gas mixture of 15 mL / min H2 and 5 mL / min N2. At this temperature, the alloy remained liquid. H2 was then turned off, and N2 was injected at a flow rate of 5 mL / min for 60 min to remove H2. After confirmation by gas chromatography, the prepared liquid alloy catalyst was subjected to further catalytic analysis. In the catalytic measurement, 4 mL / min of pure methane (CH4) gas was passed through a straight tube at a pressure of 206 kPa (30 psi), with a residence time of approximately 0.13 min. The product was analyzed online using an HP-5890 GC (Hayesep D column and Hayesep Q column) equipped with TCD and FID detectors. The gaseous products of the reaction were analyzed by gas chromatography to evaluate the methane cracking hydrogen production performance of the Ni9Mo3-Bi liquid alloy catalyst. After the experiment, the reaction apparatus was cooled to obtain a mixture of carbon materials on the surface of the alloy, and the reaction carbon material products were extracted and collected. Example 3

[0024] 12 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was annealed in air at 500 °C for 2 hours to form NiO; Then, nickel oxide powder was dispersed in 10 mL of water, and 0.571 mmol of ammonium heptamolybdate ((NH4)6Mo7O) was added. 24 ), corresponding to 4 mmol Mo, ultrasonically shake the solution for 10 min, then dry it under stirring at 90 °C, vacuum dry it overnight at 110 °C, and then anneal it at 500 °C for 2 hours to form a NiO-MoO3 mixture; NiO-MoO3 powder was mixed with 84 mmol of bismuth pellets to obtain the target molar composition of Ni. 12 The raw material system of Mo4-Bi, wherein the Bi content = 100-12-4 = 84, is placed in a thicker tube at the top of the molten metal. A flow rate of 5 mL / min N2 gas, regulated by a mass flow controller, is injected into the reactor at room temperature for 30 min to remove air. Then, a flow rate of 15 mL / min H2 gas, regulated by another mass flow controller, is mixed with 5 mL / min N2 and injected into the reactor together. The catalyst was heated from room temperature to 700 °C at a heating rate of 100 °C / 30 min and then stored at 700 °C for 1 hour, slowly reducing it to Ni. 12 Mo4-Bi liquid alloy catalyst; then the reactor was slowly cooled to 450 °C in a flowing gas mixture of 15 mL / min H2 and 5 mL / min N2. At this temperature, the alloy remained liquid. Then H2 was turned off, and N2 was injected at a flow rate of 5 mL / min for 60 min to remove H2. After confirmation by gas chromatography, the liquid alloy catalyst was prepared for further catalytic determination. In the catalytic assay, 4 mL / min of pure methane (CH4) gas was passed through a straight tube at a pressure of 206 kPa (30 psi), with a residence time of approximately 0.13 min. The product was analyzed online using an HP-5890 GC (Hayesep D column and Hayesep Q column) equipped with TCD and FID detectors. Gas chromatographic analysis of the reaction gaseous products was used to evaluate Ni. 12 Performance of Mo4-Bi liquid alloy catalyst for methane cracking and hydrogen production; After the experiment, the reaction apparatus was cooled to obtain a mixture of carbon materials on the surface of the alloy, and the reaction carbon material products were extracted and collected. Example 4

[0025] 15 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was annealed in air at 500 °C for 2 hours to form NiO; Then, nickel oxide powder was dispersed in 10 mL of water, and 0.714 mmol of ammonium heptamolybdate ((NH4)6Mo7O) was added. 24 ), corresponding to 5 mmol Mo, ultrasonically shake the solution for 10 min, then dry it under stirring at 90 °C, vacuum dry it overnight at 110 °C, and then anneal it at 500 °C for 2 hours to form a NiO-MoO3 mixture; NiO-MoO3 powder was mixed with 80 mmol of bismuth pellets to obtain the target molar composition of Ni. 15The raw material system of Mo5-Bi, wherein the Bi content = 100-15-5 = 80, is placed in a thicker tube at the top of the molten metal. A flow rate of 5 mL / min N2 gas, regulated by a mass flow controller, is injected into the reactor at room temperature for 30 min to remove air. Then, a flow rate of 15 mL / min H2 gas, regulated by another mass flow controller, is mixed with 5 mL / min N2 and injected into the reactor together. The catalyst was heated from room temperature to 700 °C at a heating rate of 100 °C / 30 min and then stored at 700 °C for 1 hour, slowly reducing it to Ni. 15 Mo5-Bi liquid alloy catalyst; then the reactor was slowly cooled to 450 °C in a flowing gas mixture of 15 mL / min H2 and 5 mL / min N2. At this temperature, the alloy remained liquid. Then H2 was turned off, and N2 was injected at a flow rate of 5 mL / min for 60 min to remove H2. After confirmation by gas chromatography, the liquid alloy catalyst was prepared for further catalytic determination. In the catalytic assay, 4 mL / min of pure methane (CH4) gas was passed through a straight tube at a pressure of 206 kPa (30 psi), with a residence time of approximately 0.13 min. The product was analyzed online using an HP-5890 GC (Hayesep D column and Hayesep Q column) equipped with TCD and FID detectors. Gas chromatographic analysis of the reaction gaseous products was used to evaluate Ni. 15 Performance of Mo5-Bi liquid alloy catalyst for methane cracking and hydrogen production; After the experiment, the reaction apparatus was cooled to obtain a mixture of carbon materials on the surface of the alloy, and the reaction carbon material products were extracted and collected. Example 5

[0026] 18 mmol of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was annealed in air at 500 °C for 2 hours to form NiO; Then, nickel oxide powder was dispersed in 10 mL of water, and 0.857 mmol of ammonium heptamolybdate ((NH4)6Mo7O) was added. 24 ), corresponding to 6 mmol Mo, ultrasonically shake the solution for 10 min, then dry it under stirring at 90 °C, vacuum dry it overnight at 110 °C, and then anneal it at 500 °C for 2 hours to form a NiO-MoO3 mixture; NiO-MoO3 powder was mixed with 76 mmol of bismuth pellets to obtain the target molar composition of Ni. 18The raw material system of Mo6-Bi, wherein the Bi content = 100-18-6 = 76, is placed in a thicker tube at the top of the molten metal. A flow rate of 5 mL / min N2 gas, regulated by a mass flow controller, is injected into the reactor at room temperature for 30 min to remove air. Then, a flow rate of 15 mL / min H2 gas, regulated by another mass flow controller, is mixed with 5 mL / min N2 and injected into the reactor together. The catalyst was heated from room temperature to 700 °C at a heating rate of 100 °C / 30 min and then stored at 700 °C for 1 hour, slowly reducing it to Ni. 18 Mo6-Bi liquid alloy catalyst; then the reactor was slowly cooled to 450 °C in a flowing gas mixture of 15 mL / min H2 and 5 mL / min N2. At this temperature, the alloy remained liquid. Then H2 was turned off, and N2 was injected at a flow rate of 5 mL / min for 60 min to remove H2. After confirmation by gas chromatography, the liquid alloy catalyst was prepared for further catalytic determination. In the catalytic measurement, pure methane (CH4), pure ethane (C2H6), and pure propane (C3H8) gases were passed through a straight tube at a pressure of 206 kPa (30 psi) with a residence time of approximately 0.13 min. The products were analyzed online using an HP-5890 GC (Hayesep D column and Hayesep Q column) equipped with TCD and FID detectors. The gaseous products of the reaction were analyzed by gas chromatography, the H2 generation rate was calculated, and the apparent activation energies of different hydrocarbons on the NiMo-Bi alloy were obtained according to the Arrhenius equation. After the experiment, the reaction apparatus was cooled to obtain a mixture of carbon materials on the surface of the alloy, and the reaction carbon material products were extracted and collected.

[0027] When using the liquid alloy catalyst prepared by the method of this invention: For example, after the NiMo-Bi catalyst was prepared, methane was introduced into the reactor, and the MP performance was studied under different temperatures, flow rates of 4 mL / min for methane, and pressures of 206 kPa (30 psi) using a liquid catalyst. The residence time of methane through a 1 cm liquid alloy catalyst was approximately 0.13 min. No H2 was detected below 400 °C, but H2 formation began to be detected at 450 °C. Higher temperatures favored H2 production and methane conversion; increasing the temperature to 800 °C increased the H2 formation rate to 6.36 mLH2gNi. -1 min -1 The methane conversion rate reached 9.87%, which is higher than that of the Ni-Bi catalyst (0.11 mL H2g Ni). -1 min -1The methane content was 37 times higher than that of ethylene. No other byproducts (e.g., ethane, ethylene, acetylene, aromatics) were detected at the operating temperature, indicating complete methane decomposition. Furthermore, this reaction system avoided the formation of aromatics, which could lead to acetylene byproduct contamination, catalyst deactivation, and reaction blockage.

[0028] Principle of this invention All catalysts in this invention are in a molten state during the reaction process, which is beneficial for the separation and collection of carbon materials, and no byproducts other than H2 and CH4 are generated throughout the process. The aim is to provide a highly active, stable, and selective hydrocarbon cracking hydrogen production catalyst to meet the needs of industrial-scale production and realize zero-carbon emission hydrogen production and hydrogen production technology from high-value carbon materials.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a molten catalyst for hydrogen production from hydrocarbon cracking, characterized in that, This method uses bismuth added to nickel-molybdenum oxide to form a modified NiMo-Bi liquid alloy, thereby producing a ternary NiMo-Bi liquid alloy catalyst. Ni is the active component, Mo is the modifier, and Bi is the solvent. The molar percentage of the NiMo-Bi catalyst is: Ni:Mo:Bi = 7.6~24:2.6~8:68~89.8, which is used for hydrocarbon cracking to produce hydrogen within a certain temperature range.

2. A method for preparing a NiMo-Bi molten catalyst for hydrocarbon cracking to produce hydrogen, characterized in that, This method uses nickel salts and molybdenum salts as raw materials for catalyst preparation, first forming the corresponding oxides, and then mixing them with bismuth powder to form an alloy, including the following steps: Step S1: Anneal 3.3 mmol of nickel nitrate hexahydrate Ni(NO3)2·6H2O in air at 500 °C for 2 hours to form NiO; Step S2: Disperse the NiO in 10 mL of water, and add 0.157 mmol of ammonium heptamolybdate ((NH4)6Mo7O). 24 The mixture was ultrasonically shaken for 10 min, stirred and dried at 90 ℃, then vacuum dried at 110 ℃ overnight, and annealed at 500 ℃ for 2 hours to form a NiO-MoO3 mixture. Step S3: Mix the NiO-MoO3 mixture with bismuth pellets and place it in a reactor. First, inject N2 at 5 mL / min at room temperature for 30 min to remove air. Step S4: Mix 15 mL / min H2 with 5 mL / min N2 and inject the mixture into the reactor. Raise the catalyst from room temperature to 700°C at a rate of 100°C / 30 min and maintain the temperature at 700°C for 1 hour to allow the NiO-MoO3 mixture to be slowly reduced with bismuth pellets to form a NiMo-Bi liquid alloy catalyst. Step S5: The reactor is slowly cooled to 450°C in a mixture of H2 and N2 flowing at 15 mL / min to keep the alloy in a liquid state. Then, H2 is turned off and N2 is injected at 5 mL / min for 60 min to remove residual H2, thus obtaining the NiMo-Bi molten catalyst.

3. The preparation method according to claim 2, characterized in that, The NiMo-Bi melt catalyst is Ni 7.6 Mo 2.6 -Bi, Ni9Mo3-Bi, Ni 12 Mo4-Bi, Ni 15 Mo5-Bi or Ni 18 Mo6-Bi, where the Bi content is 100 minus the Ni and Mo contents.

4. The preparation method according to claim 2, characterized in that, The NiMo-Bi melt catalyst is Ni 7.6 Mo 2.6 -Bi, of which the Bi content is 89.8%.

5. The preparation method according to claim 2, characterized in that, When the NiMo-Bi molten catalyst is used for methane cracking to produce hydrogen, the methane gas flow rate is 4 mL / min, the pressure is 206 kPa, and the residence time of methane in the liquid alloy catalyst is 0.13 min.

6. The preparation method according to claim 5, characterized in that, The methane cracking reaction for hydrogen production is conducted at temperatures ranging from 450 °C to 800 °C. No H2 is detected below 400 °C, H2 is produced at 450 °C, and the H2 production rate increases to 6.36 mLH2gNi at 800 °C. -1 min -1 .

7. The preparation method according to claim 2, characterized in that, The NiMo-Bi molten catalyst is also used for the cracking of ethane and / or propane to produce hydrogen. After the reaction, the carbon material generated is located on the alloy surface and is separated and collected from the NiMo-Bi molten catalyst.

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