Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst and preparation method thereof

Abstract

The invention discloses a preparation method of a Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst, production raw materials comprise composite melt metal and composite transition metal, and the mass ratio of the composite melt metal to the composite transition metal is 1: (0.3-1.2); the composite melt metal is composed of Sn and Bi according to the mass ratio of 1: (1.3-1.7); the composite transition metal is composed of Ni and Cu according to the mass ratio of 1: 0.15-1.2. The quaternary liquid alloy catalyst has the advantages that: 1) compared with the existing catalyst for hydrogen production by methane cracking, the quaternary liquid alloy catalyst provided by the invention can stably operate for more than 1000 hours in a range of normal pressure to 3MPa and air speed of 100-100mL. G <-1 >. H <-1 >, the active phase retention rate is more than 95%, and the quaternary liquid alloy catalyst is especially suitable for alkane pyrolysis hydrogen production, CO2 hydrogenation and easy carbon deposition reaction systems, and has a wide application prospect; a new material design thought and an engineering implementation scheme are provided for the field of liquid metal high-temperature catalysis; and 2) experiments show that the quaternary liquid alloy catalyst prepared by the method provided by the invention can significantly improve the carbon sequestration rate and the hydrogen yield.

Description

Technical Field

[0001] This invention relates to methane catalytic cracking for hydrogen production technology, and more particularly to a technology for preparing a methane catalytic cracking catalyst for hydrogen production. Background Technology

[0002] Methane catalytic cracking for hydrogen production is a novel method that directly decomposes methane into hydrogen and solid carbon under the action of a catalyst. Its core advantage lies in near-zero carbon emissions. Compared to traditional hydrogen production processes, it does not produce carbon dioxide, and its byproducts are high-purity solid carbon (such as carbon nanotubes) with economic value, thus turning waste into treasure.

[0003] Currently, this technology faces major challenges such as rapid catalyst deactivation due to carbon buildup and difficulty in continuous reactor operation.

[0004] Faced with the urgent need for low-cost, high-yield, and continuous hydrogen production technologies under the "dual carbon" objective, traditional Ni / Al2O3 catalytic methane cracking is difficult to scale up due to rapid carbon deposition and deactivation, as well as high regeneration energy consumption. While existing binary liquid metal (LM) systems such as Ni-Bi and Co-Sn can achieve "in-situ carbon leaching," their high activation energies (>160 kJ / mol) limit their application. -1 Due to insufficient solubility of active components (<3wt%) and high-temperature volatilization, it remains at the laboratory pilot stage, and existing catalysts generally have problems with low hydrogen yield and carbon fixation rate. Summary of the Invention

[0005] To address the problems of high activation energy, low solubility of active components, high-temperature volatilization, and low hydrogen yield and carbon fixation rate in existing methane cracking hydrogen production catalysts, this invention provides a Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst and its preparation method.

[0006] The technical solution adopted in this invention is: a method for preparing a Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst, characterized in that: the raw materials include a composite melt metal and a composite transition metal, with a mass ratio of 1:0.3 to 1.2; the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.3 to 1.7; the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.15 to 1.2.

[0007] To enable those skilled in the art to better implement the present invention, we provide a preferred embodiment, comprising the following specific steps:

[0008] S1. Take the quantities of each component according to the production raw materials described;

[0009] S2. Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under an inert atmosphere;

[0010] S3. Raise the temperature of the reaction device to 1000-1200℃ and keep it at that temperature for more than 20 hours to form a liquid metal layer;

[0011] S4. Add Cu to the liquid metal layer and keep it at a temperature for more than 10 hours to obtain a mixed melt;

[0012] S5. Lower the temperature of the reaction apparatus to 850-950℃ and keep it at that temperature for more than 0.5 hours to obtain the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst.

[0013] As will be readily understood by those skilled in the art, the aforementioned inert atmosphere can be provided by an inert gas, such as argon.

[0014] The composite melt metal and composite transition metal used in this invention need to meet certain purity standards, and it is best to use metals with a purity of ≥99.9% as raw materials.

[0015] The present invention also discloses a Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst, which is prepared by Ben Amin's method for preparing Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst.

[0016] The present invention also discloses a method for producing hydrogen by catalytic cracking of methane, characterized by including the step of using the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst of the present invention as the cracking reaction catalyst.

[0017] The above-mentioned method for producing hydrogen from methane through catalytic cracking can be implemented according to the following steps:

[0018] A. Prepare the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst in the cracking reaction device;

[0019] B. Turn off the inert gas and introduce methane feed gas into the cracking reaction vessel to carry out the cracking reaction. The flow rate of methane feed gas is controlled at 200-500 mL / min.

[0020] C. The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected through the overflow port or drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0021] The preferred temperature for the above-mentioned cracking reaction is 870–950°C, and the preferred system pressure is 0.045–0.055 MPa. As will be readily understood by those skilled in the art, the methane feedstock gas of this invention can be methane, natural gas, or other feedstock gas whose main component is methane.

[0022] The beneficial effects of this invention are: 1) Compared with existing methane cracking catalysts for hydrogen production, the quaternary liquid alloy catalyst provided by this invention can be used at atmospheric pressure up to 3 MPa and space velocity of 100-100 mL·g. -1 ·h -1 It can operate stably for more than 1000 hours within the range, with an active phase retention rate of >95%, and is especially suitable for pyrolysis of alkanes to produce hydrogen, CO2 hydrogenation, and reaction systems that are prone to carbon deposition. It provides new material design ideas and engineering implementation schemes for the field of high-temperature catalysis of liquid metals; 2) Experiments show that the quaternary liquid alloy catalyst prepared by the method of this invention can significantly improve the carbon fixation rate and hydrogen yield. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments.

[0024] For ease of comparison, all raw materials used in the following comparative examples and embodiments were from the same batch. The purity of the metal raw materials was 99.9% in all cases.

[0025] Example 1:

[0026] The liquid alloy catalyst was prepared according to the following steps:

[0027] (1) The raw materials are measured according to the following mass ratio: composite melt metal: composite transition metal = 1:0.7; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.5; and the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.9.

[0028] (2) Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0029] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 48 hours to form a liquid metal layer;

[0030] (4) Add Cu to the liquid metal layer and keep it at the temperature for 24 hours to obtain a mixed melt;

[0031] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 1 hour to obtain a liquid alloy methane cracking catalyst.

[0032] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 300 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.050 MPa.

[0033] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0034] Example 2:

[0035] The liquid alloy catalyst was prepared according to the following steps:

[0036] (1) The raw materials are measured according to the following mass ratio: composite melt metal: composite transition metal = 1:0.35; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.3; and the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.2.

[0037] (2) Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0038] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 40 hours to form a liquid metal layer;

[0039] (4) Add Cu to the liquid metal layer and keep it at a temperature for 19 hours to obtain a mixed melt;

[0040] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 0.5h to obtain a liquid alloy methane cracking catalyst.

[0041] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 500 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.045 MPa.

[0042] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0043] Example 3:

[0044] The liquid alloy catalyst was prepared according to the following steps:

[0045] (1) The raw materials are measured according to the following mass ratio: composite melt metal: composite transition metal = 1:1; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.6; and the composite transition metal is composed of Ni and Cu in a mass ratio of 1:1.

[0046] (2) Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0047] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 37 hours to form a liquid metal layer;

[0048] (4) Add Cu to the liquid metal layer and keep it at a temperature for 22 hours to obtain a mixed melt;

[0049] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 0.6h to obtain a liquid alloy methane cracking catalyst.

[0050] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 200 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.055 MPa.

[0051] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0052] Comparative Example 1:

[0053] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, using the same batch of raw materials. The difference is that only Sn is used in the melt metal, while maintaining the total proportion of melt metal unchanged. The specific scheme is as follows:

[0054] (1) The raw materials are measured according to the following mass ratio: melt metal: composite transition metal = 1:0.7; wherein the melt metal is Sn; the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.9.

[0055] (2) Sn and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0056] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 48 hours to form a liquid metal layer;

[0057] (4) Add Cu to the liquid metal layer and keep it at the temperature for 24 hours to obtain a mixed melt;

[0058] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 1 hour to obtain a liquid alloy methane cracking catalyst.

[0059] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 300 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.050 MPa.

[0060] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0061] Comparative Example 2:

[0062] This comparative example is a control experiment of Example 1, conducted according to the same steps and conditions as Example 1, using the same batch of raw materials. The difference is that only Bi is used in the melt metal, while maintaining the total proportion of melt metal unchanged. The specific scheme is as follows:

[0063] (1) The raw materials are measured according to the following mass ratio: melt metal: composite transition metal = 1:0.35; wherein the melt metal is Bi; the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.2.

[0064] (2) Bi and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0065] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 40 hours to form a liquid metal layer;

[0066] (4) Add Cu to the liquid metal layer and keep it at a temperature for 19 hours to obtain a mixed melt;

[0067] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 0.5h to obtain a liquid alloy methane cracking catalyst.

[0068] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 500 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.045 MPa.

[0069] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0070] Comparative Example 3:

[0071] This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions, using the same batch of raw materials. The difference lies in that only Ni is used as the transition metal, while maintaining the total proportion of transition metals unchanged. The specific scheme is as follows:

[0072] (1) The raw materials are measured according to the following mass ratio: composite melt metal: transition metal = 1:0.7; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.5; and the transition metal is Ni.

[0073] (2) Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0074] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 48 hours to form a liquid metal layer;

[0075] (4) Then continue to keep warm for another 24 hours to obtain a mixed melt;

[0076] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 1 hour to obtain a liquid alloy methane cracking catalyst.

[0077] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 300 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.050 MPa.

[0078] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0079] Comparative Example 4:

[0080] This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions, using the same batch of raw materials. The difference lies in that only Cu is used as the transition metal, while maintaining the total proportion of transition metals unchanged. The specific scheme is as follows:

[0081] (1) The raw materials are measured according to the following mass ratio: composite melt metal: transition metal = 1:0.7; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.5; and the transition metal is Cu.

[0082] (2) Sn and Bi are loaded into the catalyst bed of the cracking reactor under argon protection;

[0083] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 48 hours to form a liquid metal layer;

[0084] (4) Add Cu to the liquid metal layer and keep it at the temperature for 24 hours to obtain a mixed melt;

[0085] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 1 hour to obtain a liquid alloy methane cracking catalyst.

[0086] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 300 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.050 MPa.

[0087] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0088] Comparative Example 5:

[0089] This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions, using the same batch of raw materials. The difference lies in that the transition metal is composed of Ni, Cu, and Mo in a mass ratio of 1:0.9:0.8, while maintaining the total proportion of transition metal used. The specific scheme is as follows:

[0090] (1) The raw materials are measured according to the following mass ratio: composite melt metal: composite transition metal = 1:0.7; wherein the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.5; and the composite transition metal is composed of Ni, Cu and Mo in a mass ratio of 1:0.9:0.8.

[0091] (2) Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under argon protection;

[0092] (3) Raise the reactor temperature to 1100℃ and keep it at that temperature for 48 hours to form a liquid metal layer;

[0093] (4) Add Cu and Mo to the liquid metal layer and keep it at the temperature for 24 hours to obtain a mixed melt;

[0094] (5) Reduce the temperature of the reaction apparatus to 900℃ and keep it at that temperature for 1 hour to obtain a liquid alloy methane cracking catalyst.

[0095] (6) Turn off the argon gas and introduce methane into the cracking reactor at a flow rate of 300 mL / min to carry out the cracking reaction. The cracking reaction temperature is set to 900℃ and the system pressure is 0.050 MPa.

[0096] (7) The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected by a rotating drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

[0097] Carbon curing rate test:

[0098] The carbon curing rate of each embodiment and comparative example was tested using the following method:

[0099] (1) Inlet gas molar quantity: The inlet gas mass is obtained by measuring the mass flow meter over 30 minutes, and the inlet gas molar quantity is calculated as the ratio of gas mass to gas relative molecular mass.

[0100] (2) Molar amount of solid carbon: After passing gas for 30 min, the mixed carbon produced is separated and weighed using a 1 / 2 ppm balance. The mixed carbon contains metal and carbon. The elemental content ratio of metal and carbon is determined by inductively coupled plasma atomic emission spectrometry (ICP). The mass of pure carbon is obtained by multiplying the mass of mixed carbon by the carbon content. The molar amount of solid carbon is obtained by the ratio of the mass of pure carbon to the relative molecular mass of carbon.

[0101] (3) Carbon solidification rate: the percentage of the molar amount of solid carbon to the molar amount of gas introduced.

[0102] (4) The test results are shown in Table 1.

[0103] Table 1. Results of carbon curing rate tests for the examples and comparative examples.

[0104] Carbon curing rate % Example 1 48.5 Example 2 46.9 Example 3 47.8 Comparative Example 1 (Single Sn) 2.2 Comparative Example 2 (Single Bi) 2.1 Comparative Example 3 (Single Ni) 4.6 Comparative Example 4 (Single Cu) 2.3 Comparative Example 5 (Five Yuan) 32.3

[0105] As can be seen from Table 1, the quaternary liquid alloy catalyst prepared by the method of the present invention can increase the carbon solidification rate to more than 46%, which has significant technical effects.

[0106] As can be seen from the test results of Examples 1, 1, 2, 3 and 4 in Table 1, under the premise that the total proportion of melt metal used is exactly the same, the carbon solidification rate of the ternary liquid alloy catalyst composed of Sn or Bi alone and composite transition metal is only 2.2% and 2.1%, respectively; while under the premise that the total proportion of transition metal used is exactly the same, the carbon solidification rate of the ternary liquid alloy catalyst composed of Ni or Cu alone and composite melt metal is only 4.6% and 2.3%, respectively, both of which are far lower than the carbon solidification rate (48.5%) obtained by the quaternary liquid alloy catalyst of Example 1. This indicates that Sn, Bi, Ni and Cu in the quaternary liquid alloy catalyst of the present invention have a significant synergistic effect in improving the carbon solidification rate of methane catalytic cracking reaction. The inventors believe that the reason is related to the fact that the quaternary catalytic system can utilize the excellent dissolution-precipitation reversibility of the Sn-Bi composite melt to the composite transition metal Ni-Cu system and the short-range order formed by the Sn-Bi composite melt and the Cu-Ni composite system to form Ni-Cu atomic clusters in the Sn-Bi solvent system, realize the dynamic regeneration of active centers within the operating window of 800-1000 °C, and synergistically suppress the volatilization of liquid melt metal to maintain stability.

[0107] As can be seen from the comparison between Example 1 and Comparative Example 5 in Table 1, when Mo was added to the quaternary catalytic system to form a quinary catalytic system, the carbon solidification rate was significantly reduced. The inventors believe that one reason may be that after Mo enters the catalytic system, it forms a certain Ni-Mo or Mo-Sn intermetallic compound. Although these phases catalytically decompose rapidly, the carbon dissolution barrier on their surface is too high, or their geometry is not conducive to the nucleation and growth of carbon nanotubes.

Claims

1. A method for preparing a Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst, characterized in that: The raw materials for production include composite melt metal and composite transition metal, with a mass ratio of 1:0.3 to 1.2; the composite melt metal is composed of Sn and Bi in a mass ratio of 1:1.3 to 1.7; the composite transition metal is composed of Ni and Cu in a mass ratio of 1:0.15 to 1.

2.

2. The preparation method of the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst according to claim 1, characterized in that, Includes the following steps: S1. Take the quantities of each component according to the production raw materials described; S2. Sn, Bi, and Ni are loaded into the catalyst bed of the cracking reactor under an inert atmosphere; S3. Raise the temperature of the reaction device to 1000-1200℃ and keep it at that temperature for more than 20 hours to form a liquid metal layer; S4. Add Cu to the liquid metal layer and keep it at a temperature for more than 10 hours to obtain a mixed melt; S5. Lower the temperature of the reaction apparatus to 850-950℃ and keep it at that temperature for more than 0.5 hours to obtain the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst.

3. The preparation method of the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst according to claim 2, characterized in that: The inert atmosphere is an argon protective atmosphere.

4. The preparation method of the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst according to claim 2, characterized in that: The purity of the composite melt metal and the composite transition metal is ≥99.9%.

5. The Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst prepared by the preparation method of any one of claims 1 to 4.

6. A method for producing hydrogen from methane by catalytic cracking, characterized in that: The step includes using the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst as described in claim 5 as a cracking reaction catalyst.

7. The method for producing hydrogen from methane by catalytic cracking according to claim 6, characterized in that, Includes the following steps: A. Prepare the Sn-Bi-Ni-Cu quaternary liquid alloy methane cracking catalyst in the cracking reaction device; B. Turn off the inert gas and introduce methane feed gas into the cracking reaction vessel to carry out the cracking reaction. The flow rate of methane feed gas is controlled at 200-500 mL / min. C. The carbon products generated by pyrolysis continuously float on the surface of the melt in the form of solid graphite and are collected through the overflow port or drum; the hydrogen generated by pyrolysis is collected after being cooled, dusted, and pressure swing adsorption in sequence.

8. The method for producing hydrogen from methane by catalytic cracking according to claim 7, characterized in that: The pyrolysis reaction was carried out at a temperature of 870–950 °C and a system pressure of 0.045–0.055 MPa.

9. The method for producing hydrogen from methane by catalytic cracking according to claim 7, characterized in that: The methane feedstock gas is methane or natural gas.