Metal modified Co-Bi liquid alloy catalyst and its preparation method and application

Abstract

The invention relates to the technical field of methane cracking and hydrogen production, and discloses a metal-modified Co-Bi liquid alloy catalyst, wherein the catalyst uses Co as an active component, uses Bi low melting point metal as a solvent, and uses a third metal M as an auxiliary agent; the invention also discloses a method for preparing the catalyst, comprising: calcining a cobalt salt to generate cobalt oxide, and then forming CoO-MO X The mixture powder was finally heated under N2 and H2 atmosphere to obtain CoO‑MO X The powder is mixed with elemental Bi to obtain a cobalt-bismuth ternary liquid alloy catalyst; the present invention also discloses a method for applying the catalyst to methane cracking and hydrogen production, comprising: heating the preheating furnace to a certain temperature, introducing pure methane gas, and reacting under normal pressure, at a temperature of 500 to 700°C, with a methane space velocity of 1 to 100 mL / g·min, and after the reaction is completed, the temperature drops to room temperature in an N2 atmosphere, and the carbon product is taken out of the reaction tube after cooling. The catalyst disclosed by the present invention has the advantages of high activity, good stability, strong methane cracking ability, mild reaction conditions, simple preparation process, and long life.

Description

Technical Field

[0001] The invention belongs to the technical field of methane cracking to produce hydrogen, and specifically relates to a metal-modified Co-Bi liquid alloy catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen is an important chemical intermediate and can be used as a CO2-free energy carrier in many applications that currently rely on fossil energy. However, most hydrogen is produced from fossil energy, which leads to a large amount of CO2 emissions. Water electrolysis is a green technology that uses renewable energy to produce H2. Due to its high cost and high energy consumption (286 kJ / mol H2), it currently accounts for only 2% of the total H2 production. Methane cracking is another method of hydrogen production that does not produce carbon dioxide. The hydrogen produced has a purity of 99.999% and can be directly used in downstream hydrogen fuel cells. At the same time, valuable carbon materials such as graphene, carbon nanotubes and fullerenes are produced as by-products. Traditional supported transition metal catalysts (Ni, Co, Fe, Pt or Pd) for hydrogen production by methane cracking have low apparent activation energy Ea values ​​(65-96 kJ / mol) and can catalyze methane cracking to produce hydrogen at appropriate low reaction temperatures (500 to 600 °C), but these catalysts are prone to carbon coking and aromatic contamination and rapid deactivation. Even though adding additives can improve the dispersion of metal components on the catalyst surface and slow down the rate of catalyst deactivation, it cannot achieve continuous production and the catalyst needs to be regenerated midway, which limits its large-scale application.

[0003] Liquid alloy catalysts can overcome the deactivation problem by removing low-density carbon products floating on the liquid catalyst, and provide excellent durability, which can produce hydrogen efficiently, stably and continuously. However, the strong interaction between the active metal sites and the solvent metal forms a "cage effect", which leads to a high apparent activation energy Ea value (160-310 kJ / mol) for the catalytic cracking of methane by liquid alloy catalysts, and high temperature is required to activate methane molecules; Chinese invention patent CN202410818737.8 discloses a molten metal high-temperature cracking methane hydrogen production system, which needs to react at a temperature exceeding 1100°C. Chinese invention patent CN202410526185.3 discloses a molten liquid alloy catalyst for methane cracking hydrogen production, its preparation method and use, which uses molten metal additives to adjust the properties of the catalytic active components to reduce the reaction temperature. The reaction temperature has dropped, but it is still above 800°C. The entire process has high energy consumption and poor economic efficiency, which is not conducive to further application. Breaking the "cage effect" of liquid alloy catalysts and developing high-activity, low-temperature and long-life methane cracking liquid alloy catalysts are the key to bringing the methane cracking liquid alloy catalytic hydrogen production process out of the laboratory. Summary of the invention

[0004] In view of the shortcomings of existing liquid alloy catalysts, such as low activity, high reaction temperature and short life, the present invention provides a metal-modified Co-Bi liquid alloy catalyst and a preparation method and application thereof. By adding a third metal to adjust the interaction between the active metal and the solvent metal, the special stable "cage structure" in which the positively charged Bi atoms wrap the negatively charged Co atoms is broken, thereby reducing the activation energy of the methane cracking reaction, improving the reaction activity and extending the catalyst life.

[0005] In order to achieve the above-mentioned purpose of high activity, low temperature and long life methane cracking liquid alloy catalyst, the present invention provides the following technical solutions:

[0006] A metal-modified Co-Bi liquid alloy catalyst, wherein the catalyst uses Co as an active component, uses Bi low melting point metal as a solvent, uses a third metal M as an auxiliary agent, and the mass percentage wt% of the catalyst CoM-Bi is: Co:M:Bi=1-20:1-10:70-98.

[0007] Preferably, the third metal promoter M of the catalyst is one or more of Mo, Mn, Ce, Zr, Zn, Ni, and Fe.

[0008] Preferably, the third metal modifier M of the catalyst is: Mo.

[0009] Preferably, the third metal modifier M of the catalyst is Mo, and the mass percentage wt% of the catalyst CoMo-Bi is Co:Mo:Bi=10:5:85.

[0010] A method for metal-modified Co-Bi liquid alloy catalyst comprises the following steps:

[0011] S1: Preparation of CoO-MOX precursor powder: calcining cobalt salt in a muffle furnace at 500°C to 800°C for 2 to 5 hours to generate cobalt oxide;

[0012] S2: Disperse the cobalt oxide powder in water; add the third metal M inorganic salt and then ultrasonically vibrate for 10 minutes, stir and dry in a 70-90°C water bath; then dry in a 90-120°C vacuum oven for 5-8 hours, and calcine in a 500-800°C muffle furnace for 2-5 hours to form CoO-MO X Mixture powder;

[0013] S3: CoO-MO X The powder was mixed with elemental Bi and placed in a fixed bed reactor, and N2 was injected into the reactor at room temperature for 60 min to remove air;

[0014] S4: Mix H2 and N2 and inject them into the fixed bed reactor together;

[0015] S5: The catalyst is raised from room temperature to a target temperature of 500-700°C and maintained for 90-240 minutes to be slowly reduced to a CoM-Bi liquid alloy catalyst. H2 is then turned off and N2 is continuously injected for 60 minutes to remove residual H2, thereby obtaining a cobalt-bismuth ternary liquid alloy catalyst.

[0016] Preferably, in step S2, the relationship between the mass of the cobalt salt and the mass of water is: mass of the cobalt salt: mass of water = 1:10.

[0017] Preferably, in step S3: the Bi element is a bismuth ball with a diameter of 1 to 5 mm.

[0018] Preferably, in step S4: the relationship between the nitrogen flow rate and the hydrogen flow rate is: nitrogen flow rate: hydrogen flow rate = 1:3, and the hydrogen flow rate does not exceed 150 mL / min.

[0019] Preferably, in step S5: the heating rate of the catalyst from room temperature to the target temperature is 2-5°C / min.

[0020] Preferably, S1:CoO-MO X In the preparation of the precursor powder: the inorganic cobalt salt is calcined at 600°C in a muffle furnace for 3h to generate cobalt oxide;

[0021] S2: Then disperse the cobalt oxide powder in water, the relationship between the mass of cobalt salt and the mass of water is the mass of inorganic cobalt salt: the mass of water = 1:10; add the third metal M inorganic salt and ultrasonically vibrate for 10 minutes, stir and dry in a water bath at 80°C; then dry in a vacuum drying oven at 110°C for 6 hours, and calcine in a muffle furnace at 700°C for 4 hours to form CoO-MO X Mixture powder;

[0022] S3: CoO-MO X The powder was mixed with elemental Bi, which was bismuth balls with a diameter of 2 mm, and placed in a fixed bed reactor. N2 was injected into the reactor at room temperature for 60 min to remove air.

[0023] S4: Then H2 and N2 are mixed, and the relationship between nitrogen flow rate and hydrogen flow rate is: nitrogen flow rate: hydrogen flow rate = 1:3, and the hydrogen flow rate does not exceed 150 mL / min, and they are injected into the fixed bed reactor together;

[0024] S5: The catalyst is heated from room temperature to the target temperature at a heating rate of 2.5°C / min and maintained for 180 min to slowly reduce to a CoM-Bi liquid alloy catalyst. Then, H2 is turned off and N2 is continuously injected for 60 min to remove residual H2, thereby obtaining a cobalt-bismuth ternary liquid alloy catalyst.

[0025] A metal-modified Co-Bi liquid alloy catalyst is applied to a methane cracking hydrogen production reaction method, comprising the following steps:

[0026] S01: The reaction is carried out in a fixed bed evaluation device. The injection pressure of methane is 0.2MPa. The preheating furnace is heated to a certain temperature and then pure methane gas is introduced.

[0027] S02: Methane gas is injected through a flow valve to control the preheating furnace and then enters the reactor for reaction. The methane space velocity is 1-100 mL / g·min. The reaction is carried out under normal pressure and at a temperature of 500-700°C. The product is directly analyzed by gas chromatography online.

[0028] S03: After the reaction is completed, the temperature of the N2 atmosphere is lowered to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0029] Preferably, the preheating temperature of the preheating furnace is 30° C. lower than the reaction temperature of the reactor.

[0030] Compared with the prior art, the present invention provides a metal-modified Co-Bi liquid alloy catalyst and a preparation method and application thereof, which have the following beneficial effects:

[0031] 1. The present invention discloses a Co-based ternary liquid alloy catalyst, which greatly delays the deactivation of the catalyst and significantly improves its service life by removing the low-density carbon produced by methane cracking by floating it to the surface of the melt.

[0032] 2. The present invention breaks the "cage" effect between Co-Bi liquid alloys by introducing a third metal additive, thereby significantly enhancing the catalyst activity and exhibiting higher stability than other liquid alloy catalysts.

[0033] 3. The synthesis method of the Co-based ternary liquid alloy catalyst developed by the present invention is simple, and the catalyst preparation and cracking hydrogen production reaction can be carried out in situ in the same reactor, which simplifies the process flow and greatly saves costs.

[0034] 4. The catalyst of the present invention can be applied to methane cracking to produce hydrogen. The reaction conditions are relatively mild (<700°C, normal pressure), the process is highly safe, the methane conversion rate and hydrogen yield are high, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The preparation flow chart of CoM-Bi liquid alloy catalyst; DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0039] Example 1

[0040] 1. Preparation of Co 0.01 Mo 0.01 -Bi 0.98 Ternary liquid alloy catalyst:

[0041] S1: calcining 1.041 g of cobalt nitrate in a muffle furnace at 500° C. for 5 h to generate cobalt oxide. The cobalt nitrate in this step mainly provides a cobalt source, and the cobalt nitrate can also be replaced by other inorganic cobalt salts or organic cobalt salts;

[0042] S2: Disperse cobalt oxide powder in 10 mL of water; add 0.559 g of ammonium heptamolybdate and ultrasonically vibrate for 10 min, stir and dry in a 70°C water bath; dry in a 90°C vacuum oven for 8 h, and calcine in a 500°C muffle furnace for 5 h to form a CoO-MoO3 mixture powder;

[0043] S3: The CoO-MoO3 powder prepared in the above step was mixed with 31.36 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. N2 was injected into the reactor at room temperature at 20 mL / min for 60 min to remove air.

[0044] S4: 60 mL / min of H2 and 20 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0045] S5: The catalyst was heated from room temperature to 500°C at a rate of 2°C / min and maintained for 90 min to slowly reduce to CoMo-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected for 60 min at a flow rate of 20 mL / min to remove residual H2, thereby obtaining Co 0.01 Mo 0.01 -Bi 0.98 The ternary liquid alloy catalyst does not need to be transferred and is then evaluated for the next step of methane cracking hydrogen production reaction.

[0046] 2. The methane cracking hydrogen production reaction includes the following steps:

[0047] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 470°C and then pure methane gas was introduced.

[0048] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 1 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 500°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0049] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0050] Example 2

[0051] 1. Preparation of Co 0.2 Mo 0.1 -Bi 0.7 Ternary liquid alloy catalyst:

[0052] S1: calcining 3.015 g of cobalt nitrate in a muffle furnace at 800 °C for 2 h to generate cobalt oxide;

[0053] S2: Then disperse the cobalt oxide powder in 30 mL of water; add 0.837 g of ammonium heptamolybdate and ultrasonically oscillate for 10 min, stir and dry in a 90°C water bath; dry in a 120°C vacuum oven for 5 h, and calcine in a muffle furnace for 2 h to form a CoO-MoO3 mixture powder;

[0054] S3: The CoO-MoO3 powder prepared in the above step was mixed with 3.381 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. N2 was injected into the reactor at room temperature at 50 mL / min for 60 min to remove air.

[0055] S4: 150 mL / min H2 and 50 mL / min N2 were mixed and injected into the fixed bed reactor together;

[0056] S5: The catalyst was heated from room temperature to 700°C at a rate of 5°C / min and maintained for 240 min to slowly reduce to CoMo-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 50 mL / min for 60 min to remove residual H2, thereby obtaining CoMo-Bi liquid alloy catalyst. 0.2 Mo 0.1 -Bi 0.7 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0057] 2. The methane cracking hydrogen production reaction includes the following steps:

[0058] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 670°C and then pure methane gas was introduced.

[0059] S04: Methane gas was injected through a flow valve to control the preheating furnace and then into the reactor for reaction. The methane space velocity was 100 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 700°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0060] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0061] Example 3

[0062] 1. Preparation of Co 0.1 Mo 0.05 -Bi 0.85 Ternary liquid alloy catalyst:

[0063] S1: calcining 2.501 g of cobalt nitrate in a muffle furnace at 700 °C for 4 h to generate cobalt oxide;

[0064] S2: Disperse cobalt oxide powder in 25 mL of water; add 0.698 g of ammonium heptamolybdate and ultrasonically oscillate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-MoO3 mixture powder;

[0065] S3: Mix the CoO-MoO3 powder prepared in the above step with 6.845 g of Bi metal balls with a diameter of 1 mm and place them in a reactor of a fixed bed apparatus. Inject 30 mL / min of N2 into the reactor at room temperature for 60 min to remove air;

[0066] S4: 90 mL / min of H2 and 30 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0067] S5: The catalyst was heated from room temperature to 600°C at a rate of 3°C / min and maintained for 200 min to slowly reduce to CoMo-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 30 mL / min for 60 min to remove residual H2, thereby obtaining CoMo-Bi liquid alloy catalyst. 0.1 Mo 0.05 -Bi 0.85 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0068] 2. The methane cracking hydrogen production reaction includes the following steps:

[0069] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 570°C and then pure methane gas was introduced.

[0070] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 60 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 600°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0071] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0072] Example 4

[0073] 1. Preparation of Co 0.15 Mn 0.05 -Bi 0.8 Ternary liquid alloy catalyst:

[0074] S1: calcining 3.008 g of cobalt nitrate in a muffle furnace at 600 °C for 3 h to generate cobalt oxide;

[0075] S2: Disperse cobalt oxide powder in 30 mL of water; add 1.049 g of manganese nitrate and ultrasonically vibrate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-MnO mixture powder;

[0076] S3: The CoO-MnO powder prepared in the above step was mixed with 16.228 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 40 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0077] S4: 120 mL / min of H2 and 40 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0078] S5: The catalyst was heated from room temperature to 650°C at a rate of 4°C / min and maintained for 150 min to slowly reduce to CoMn-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 40 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.15 Mn 0.05 -Bi 0.8 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0079] 2. The methane cracking hydrogen production reaction includes the following steps:

[0080] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 620°C and then pure methane gas was introduced.

[0081] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 80 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 620°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0082] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0083] Example 5

[0084] 1. Preparation of Co 0.08 Ce 0.02 -Bi 0.9 Ternary liquid alloy catalyst:

[0085] S1: calcining 3.010 g of cobalt nitrate in a muffle furnace at 600 °C for 3 h to generate cobalt oxide;

[0086] S2: Disperse cobalt oxide powder in 30 mL of water; add 0.562 g of cerium nitrate and ultrasonically vibrate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-CeO2 mixture powder;

[0087] S3: The CoO-CeO2 powder prepared in the above step was mixed with 10.872 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 30 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0088] S4: 90 mL / min of H2 and 30 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0089] S5: The catalyst was heated from room temperature to 530°C at a rate of 3°C / min and maintained for 150 min to slowly reduce to CoCe-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 30 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.08 Ce 0.02 -Bi 0.9 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0090] 2. The methane cracking hydrogen production reaction includes the following steps:

[0091] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 500°C and then pure methane gas was introduced.

[0092] S01: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 40 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 530°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0093] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0094] Example 6

[0095] 1. Preparation of Co 0.16 Zr 0.08 -Bi 0.76 Ternary liquid alloy catalyst:

[0096] S1: calcining 3.017 g of cobalt nitrate in a muffle furnace at 600 °C for 3 h to generate cobalt oxide;

[0097] S2: Disperse cobalt oxide powder in 30 mL of water; add 1.797 g of zirconium nitrate and ultrasonically oscillate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-ZrO2 mixture powder;

[0098] S3: The CoO-ZrO2 powder prepared in the above step was mixed with 4.591 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 40 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0099] S4: 120 mL / min of H2 and 40 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0100] S5: The catalyst was heated from room temperature to 700°C at a rate of 5°C / min and maintained for 210 min to slowly reduce to CoZr-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 40 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.16 Zr 0.08 -Bi 0.76 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0101] 2. The methane cracking hydrogen production reaction includes the following steps:

[0102] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 670°C and then pure methane gas was introduced.

[0103] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 20 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 700°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0104] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0105] Example 7

[0106] 1. Preparation of Co 0.12 Zn 0.02 -Bi 0.86 Ternary liquid alloy catalyst:

[0107] S1: calcining 3.009 g of cobalt nitrate in a muffle furnace at 600 °C for 3 h to generate cobalt oxide;

[0108] S2: Disperse cobalt oxide powder in 30 mL of water; add 0.466 g of zirconium nitrate and ultrasonically oscillate for 10 min, stir and dry in a water bath at 80° C.; dry in a vacuum oven at 110° C. for 6 h, and calcine in a muffle furnace at 700° C. for 4 h to form a CoO-ZnO mixture powder;

[0109] S3: The CoO-ZnO powder prepared in the above step was mixed with 6.926 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 35 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0110] S4: 105 mL / min of H2 and 35 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0111] S5: The catalyst was heated from room temperature to 680°C at a rate of 3.5°C / min and maintained for 160 min to slowly reduce to CoZn-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 35 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.12 Zn 0.02 -Bi 0.86 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0112] 2. The methane cracking hydrogen production reaction includes the following steps:

[0113] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 650°C and then pure methane gas was introduced.

[0114] S02: Methane gas was injected through a flow valve to control the preheating furnace and then into the reactor for reaction. The methane space velocity was 30 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 680°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0115] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0116] Example 8

[0117] 1. Preparation of Co 0.08 Ni 0.04 -Bi 0.88 Ternary liquid alloy catalyst:

[0118] S1: calcining 2.012 g of cobalt nitrate in a muffle furnace at 600 °C for 3 h to generate cobalt oxide;

[0119] S2: Disperse cobalt oxide powder in 20 mL of water; add 1.003 g of nickel nitrate and ultrasonically vibrate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-NiO mixture powder;

[0120] S3: The CoO-NiO powder prepared in the above step was mixed with 7.087 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 45 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0121] S4: 135 mL / min H2 and 45 mL / min N2 were mixed and injected into the fixed bed reactor together;

[0122] S5: The catalyst was heated from room temperature to 580°C at a rate of 3°C / min and maintained for 180 min to slowly reduce to CoNi-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 45 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.08 Ni 0.04 -Bi 0.88 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0123] 2. The methane cracking hydrogen production reaction includes the following steps:

[0124] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 550°C and then pure methane gas was introduced.

[0125] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 50 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 580°C. The product was directly analyzed by gas chromatography online. The results are shown in Table 1.

[0126] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0127] Example 9

[0128] 1. Preparation of Co 0.06 Fe 0.03 -Bi 0.91 Ternary liquid alloy catalyst:

[0129] S1: calcining 2.004 g of cobalt nitrate in a muffle furnace at 600° C. for 3 h to generate cobalt oxide;

[0130] S2: Disperse the cobalt oxide powder in 20 mL of water, add 1.395 g of ferric nitrate, and then ultrasonically oscillate for 10 min, stir and dry in a water bath at 80°C; dry in a vacuum oven at 110°C for 6 h, and calcine in a muffle furnace at 700°C for 4 h to form a CoO-Fe2O3 mixture powder;

[0131] S3: The CoO-Fe2O3 powder prepared in the above step was mixed with 9.772 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 30 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0132] S4: 90 mL / min of H2 and 30 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0133] S5: The catalyst was heated from room temperature to 550°C at a rate of 2.5°C / min and maintained for 120 min to slowly reduce to CoFe-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 30 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.06 Fe 0.03 -Bi 0.91 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0134] 2. The methane cracking hydrogen production reaction includes the following steps:

[0135] S01: The reaction was carried out in a fixed bed evaluation device, the methane injection pressure was 0.2 MPa, the preheating furnace was heated to 520°C, and then pure methane gas was introduced;

[0136] S02: Methane gas is injected through a flow valve to control the sample, first enters the preheating furnace for preheating, and then enters the reactor for reaction. The methane space velocity is 70 mL / g·min. The reaction process is at normal pressure and the temperature is 550°C. The product is directly analyzed by gas chromatography online. The results are shown in Table 1.

[0137] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0138] Example 10 Stability Test

[0139] 1. Preparation of Co 0.1 Mo 0.05 -Bi 0.85 Ternary liquid alloy catalyst:

[0140] Steps S1 and S2 are the same as those in Example 3;

[0141] S3: The CoO-MoO3 powder prepared in the above step was mixed with 6.845 g of Bi metal balls with a diameter of 1 mm and placed in a reactor of a fixed bed apparatus. 30 mL / min of N2 was injected into the reactor at room temperature for 60 min to remove air.

[0142] S4: 90 mL / min of H2 and 30 mL / min of N2 were mixed and injected into the fixed bed reactor together;

[0143] S5: The catalyst was heated from room temperature to 700°C at a rate of 5°C / min and maintained for 200 min to slowly reduce to CoMo-Bi liquid alloy catalyst. Then H2 was turned off and N2 was injected at a flow rate of 30 mL / min for 60 min to remove residual H2, thereby obtaining Co 0.1 Mo 0.05 -Bi 0.85 The ternary liquid alloy catalyst does not need to be transferred and can be immediately used for the next step of reaction evaluation.

[0144] 2. The methane cracking hydrogen production reaction includes the following steps:

[0145] S01: The reaction was carried out in a fixed bed evaluation device. The methane injection pressure was 0.2 MPa. The preheating furnace was heated to 670°C and then pure methane gas was introduced.

[0146] S02: Methane gas was injected through a flow valve to control the preheating furnace and then entered the reactor for reaction. The methane space velocity was 50 mL / g·min. The reaction was carried out under normal pressure and at a temperature of 700°C. The product was directly analyzed by gas chromatography online. Data were collected for 10 h, 20 h, 30 h, 50 h, 100 h, 200 h, and 300 h of reaction. The results are shown in Table 2.

[0147] S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

[0148] Reaction results

[0149] Table 1 Results of methane cracking reaction over liquid alloy catalyst

[0150]

[0151] Table 2 Stability test results

[0152]

[0153]

Claims

1. A metal-modified Co-Bi liquid alloy catalyst, characterized in that: The catalyst uses Co as an active component, Bi as a low melting point metal as a solvent, and a third metal M as an auxiliary agent. The mass percentage wt% of the catalyst CoM-Bi is: Co:M:Bi=1-20:1-10:70-98.

2. The metal-modified Co-Bi liquid alloy catalyst according to claim 1, characterized in that: The third metal promoter M of the catalyst is one or more of Mo, Mn, Ce, Zr, Zn, Ni and Fe.

3. The metal-modified Co-Bi liquid alloy catalyst according to claim 1, characterized in that: The third metal promoter M of the catalyst is: Mo.

4. The metal-modified Co-Bi liquid alloy catalyst according to claim 1, characterized in that: The third metal promoter M of the catalyst is Mo, and the mass percentage wt% of the catalyst CoMo-Bi is Co:Mo:Bi=10:5:

85.

5. A method for preparing the metal-modified Co-Bi liquid alloy catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: calcining the cobalt salt in a muffle furnace at 500°C to 800°C for 2 to 5 hours to generate cobalt oxide; S2: Disperse the cobalt oxide powder in water; add the third metal M inorganic salt and then ultrasonically oscillate for 10 minutes, stir and dry in a 70-90°C water bath; then dry in a 90-120°C vacuum oven for 5-8 hours, and calcine in a 500-800°C muffle furnace for 2-5 hours to form CoO-MO X Mixture powder; S3: CoO-MO X The powder was mixed with elemental Bi and placed in a fixed bed reactor, and N2 was injected into the reactor at room temperature for 60 min to remove air; S4: Mix H2 and N2 and inject them into the fixed bed reactor together; S5: The catalyst is raised from room temperature to a target temperature of 500-700°C and maintained at the temperature for 90-240 minutes to be slowly reduced to a CoM-Bi liquid alloy catalyst. H2 is then turned off and N2 is continuously injected for 60 minutes to remove residual H2, thereby obtaining a cobalt-bismuth ternary liquid alloy catalyst.

6. The method for preparing a metal-modified Co-Bi liquid alloy catalyst according to claim 5, characterized in that: The relationship between the mass of the cobalt salt and the mass of water in step S2 is cobalt salt mass: water mass = 1:

10.

7. The method for preparing a metal-modified Co-Bi liquid alloy catalyst according to claim 5, characterized in that: In step S3, the simple substance Bi is a bismuth ball with a diameter of 1 to 5 mm.

8. The method for preparing a metal-modified Co-Bi liquid alloy catalyst according to claim 5, characterized in that: The relationship between the nitrogen flow rate and the hydrogen flow rate in step S4 is: nitrogen flow rate: hydrogen flow rate = 1:3, and the hydrogen flow rate does not exceed 150 mL / min.

9. The method for preparing a metal-modified Co-Bi liquid alloy catalyst according to claim 5, characterized in that: In step S5, the heating rate of the catalyst from room temperature to the target temperature is 2-5°C / min.

10. The method for preparing a metal-modified Co-Bi liquid alloy catalyst according to claim 5, characterized in that: The following steps are involved: S1: calcining the cobalt salt at 600° C. in a muffle furnace for 3 h to generate cobalt oxide; S2: Then the cobalt oxide powder is dispersed in water, and the relationship between the mass of inorganic cobalt salt and the mass of water is the mass of inorganic cobalt salt: the mass of water = 1:10; After adding the third metal M inorganic salt, ultrasonic oscillation was performed for 10 minutes, and the mixture was stirred and dried in a water bath at 80°C until there was no obvious moisture. Then, the mixture was dried in a vacuum oven at 110°C for 6 hours, and calcined in a muffle furnace at 700°C for 4 hours to form CoO-MO. X Mixture powder; S3: CoO-MO X The powder was mixed with elemental Bi, which was bismuth balls with a diameter of 2 mm, and placed in a fixed bed reactor. N2 was injected into the reactor at room temperature for 60 min to remove air. S4: Then H2 and N2 are mixed, and the relationship between nitrogen flow rate and hydrogen flow rate is nitrogen flow rate: hydrogen flow rate = 1:3, and the hydrogen flow rate does not exceed 150 mL / min, and they are injected into the fixed bed reactor together; S5: The catalyst is heated from room temperature to the target temperature at a heating rate of 2.5°C / min and maintained for 180 min to slowly reduce to a CoM-Bi liquid alloy catalyst. H2 is then turned off and N2 is continuously injected for 60 min to remove residual H2, thereby obtaining a cobalt-bismuth ternary liquid alloy catalyst.

11. A method for producing hydrogen from methane by cracking the metal-modified Co-Bi liquid alloy catalyst according to any one of claims 1 to 4, comprising the following steps: S01: The reaction is carried out in a fixed bed evaluation device. The injection pressure of methane is 0.2MPa. The preheating furnace is heated to a certain temperature and then pure methane gas is introduced. S02: Methane gas is injected through a flow valve to control the preheating furnace and then enters the reactor for reaction. The methane space velocity is 1-100 mL / g·min. The reaction is carried out under normal pressure and at a temperature of 500-700°C. The product is directly analyzed by gas chromatography online. S03: After the reaction is completed, the temperature in the N2 atmosphere drops to room temperature, and the carbon product is taken out from the reaction tube after cooling.

12. The metal-modified Co-Bi liquid alloy catalyst according to claim 11 is applied to a methane cracking hydrogen production reaction method, characterized in that: The preheating temperature of the preheating furnace is 30°C lower than the reaction temperature of the reactor.

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