A bifunctional catalyst for hydrogen production by catalytic cracking of methane and a preparation method and application thereof

Abstract

The present application relates to hydrogen production catalyst technical field, specifically to a kind of for methane catalytic cracking hydrogen production bifunctional catalyst and its preparation method and application.For methane catalytic cracking hydrogen production bifunctional catalyst active ingredient includes:CaO, Ca 12 Al 14 O 33 And Fe.Wherein Fe has efficient catalytic methane catalytic cracking hydrogen production performance under 700~900 ℃;Water vapor gasification carbon deposition process, CaO in situ capture water vapor gasification carbon deposition generated CO2Form CaCO3, CaCO3 and water vapor gasification carbon deposition generated hydrogen gas reaction generates calcium oxide and CO, realizes carbon dioxide conversion to CO, also realizes the regeneration of catalyst;Therefore the bifunctional catalyst provided by the present application can efficiently catalyze methane cracking hydrogen production, while in the process of catalyst regeneration, CO2Conversion to CO can be catalyzed by water vapor gasification carbon deposition, furthermore Ca 12 Al 14 O 33 It has efficient anti-sintering performance, and enhances the cycle stability of bifunctional catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen production catalysts, in particular to a bifunctional catalyst for hydrogen production by catalytic cracking of methane, and a preparation method and application thereof. BACKGROUND

[0002] The equation of the reaction of hydrogen production by catalytic cracking of methane is as follows: This hydrogen production method can obtain pure hydrogen gas containing almost no carbon oxides, and does not need to consider the problem of product separation. Meanwhile, the hydrogen production process of coal, petroleum and other fossil resources needs high energy consumption, but the ΔH of hydrogen production by catalytic cracking of methane is 74.8 kJ / mol, and the energy consumption is low, so this hydrogen production method has attracted high attention at home and abroad in recent years. 298K

[0003] The commonly used catalysts at present include Ni and Co, and the Ni and Co-based catalysts have catalytic activity at 500-600 DEG C, but the toxicity and high cost of the Ni and Co-based catalysts limit their development. Meanwhile, carbon generated in the hydrogen production process by catalytic cracking of methane will be deposited on the surface and pores of the catalyst, thus causing deactivation of the catalyst. Regeneration of the deactivated catalyst by removing the accumulated carbon on the catalyst is a technical difficulty, and in the prior art, the reaction of steam with the accumulated carbon on the catalyst to realize gasification of the accumulated carbon is a promising method for realizing regeneration of the catalyst, which not only efficiently removes the accumulated carbon but also prepares hydrogen energy, but CO2 will be generated in the gasification process, and if the CO2 generated in the gasification process can be converted into CO at the lowest cost, the economic benefit of the entire process can be improved. SUMMARY

[0004] In order to overcome the above problems, the present application provides a bifunctional catalyst for hydrogen production by catalytic cracking of methane, and a preparation method and application thereof, the bifunctional catalyst provided by the present application can not only efficiently catalyze hydrogen production by cracking of methane, but also can convert CO2 generated by gasification of the accumulated carbon in the catalyst regeneration process into CO, and the bifunctional catalyst provided by the present application has good sintering resistance.

[0005] In order to achieve the above technical purposes, the present application adopts the following technical solutions:

[0006] In a first aspect of the present application, a bifunctional catalyst for hydrogen production by catalytic cracking of methane is provided, and the active components of the catalyst include CaO, Ca 12 Al 14 O 33 and Fe; and the mass ratio of the CaO, Ca 12 Al 14 O 33 and Fe is 80-85:7-8:9-9.5.​

[0007] Wherein Fe has high efficient catalytic performance of catalytic cracking of methane to produce hydrogen at 700-900 DEG C, and Fe has the advantages of low cost, non-toxicity and high temperature resistance; in the process of water vapor gasification of coke, CaO in-situ captures CO2 generated by water vapor gasification of coke to generate CaCO3, and CaCO3 reacts with hydrogen generated by water vapor gasification of coke to generate calcium oxide and CO, realizing the conversion of carbon dioxide into CO, and realizing the in-situ conversion of CaO-CaCO3-CaO (regeneration of the catalyst); therefore, the bifunctional catalyst provided by the application can not only efficiently catalyze the cracking of methane to produce hydrogen, but also catalyze the conversion of CO2 generated by water vapor gasification of coke into CO in the process of catalyst regeneration, and the Ca 12 Al 14 O 33 Has high efficient anti-sintering performance, and enhances the cycle stability of the bifunctional catalyst.

[0008] The specific reaction process includes:

[0009]

[0010]

[0011]

[0012] CO2+CaO→CaCO3

[0013]

[0014] The second aspect of the application provides a preparation method of the bifunctional catalyst for catalytic cracking of methane to produce hydrogen, and the preparation method comprises the following steps:

[0015] (1) calcium acetate, iron nitrate, aluminum nitrate and citric acid are respectively added to distilled water, and the mixed solution is stirred to obtain a colloidal solution;

[0016] (2) the colloidal solution is dried to obtain a solid material, and the solid material is calcined in an air atmosphere to obtain a precursor of the bifunctional catalyst;

[0017] (3) the precursor of the bifunctional catalyst is reduced to obtain the bifunctional catalyst for catalytic cracking of methane to produce hydrogen.

[0018] The third aspect of the application provides that the bifunctional catalyst for catalytic cracking of methane to produce hydrogen is used for the cracking of methane to produce hydrogen.

[0019] In a fourth aspect of the present application, a system for hydrogen production by catalytic cracking of methane is provided, which comprises a methane cracking furnace for catalytic cracking of methane, the methane cracking furnace being connected with a gasification furnace for steam gasification of carbon deposition and a hydrogen storage tank, respectively, the gasification furnace being connected with a CO2 in-situ conversion furnace for CO2 in-situ conversion and a NaOH solution tank, respectively, the CO2 in-situ conversion furnace being connected with a CO storage tank, a methane cracking furnace and a NaOH solution tank, respectively.

[0020] In a fifth aspect of the present application, a method for hydrogen production by catalytic cracking of methane is provided, which comprises:

[0021] methane is introduced into the methane cracking furnace, and the bifunctional catalyst of the first aspect is added, and methane is catalytically cracked in the methane cracking furnace, and the hydrogen produced in the reaction is stored in the hydrogen storage tank;

[0022] The bifunctional catalyst for catalytic cracking of methane in the methane cracking furnace is introduced into the gasification furnace, and the carbon deposition on the surface and in the pores of the bifunctional catalyst is gasified by steam in the gasification furnace;

[0023] The bifunctional catalyst after treatment of carbon deposition is introduced into the CO2 in-situ conversion furnace, and the gas in the gasification furnace is introduced into the CO2 in-situ conversion furnace after passing through the NaOH solution tank, and the CO2 in-situ conversion to CO is realized by regeneration of the bifunctional catalyst in the CO2 in-situ conversion furnace;

[0024] The regenerated bifunctional catalyst is introduced into the methane cracking furnace to catalytically crack methane, and the gas is stored in the CO storage tank.

[0025] The present application has the following advantages:

[0026] (1) The bifunctional catalyst provided by the present application has the following active components: CaO, Ca 12 Al 14 O 33 and Fe. Fe has high catalytic cracking performance for hydrogen production by catalytic cracking of methane at 700-900℃, and has the advantages of low cost, non-toxicity and high temperature resistance. In the process of steam gasification of carbon deposition, CaO in-situ captures CO2 generated by steam gasification of carbon deposition to form CaCO3, and CaCO3 reacts with hydrogen generated by steam gasification of carbon deposition to form calcium oxide and CO, realizing the conversion of carbon dioxide to CO and the in-situ conversion of CaO-CaCO3-CaO (catalyst regeneration). Therefore, the bifunctional catalyst provided by the present application can not only efficiently catalyze hydrogen production by catalytic cracking of methane, but also catalyze the generation of CO from CO2 generated by steam gasification of carbon deposition in the process of catalyst regeneration. Furthermore, in the present application, aluminum salt is used as an additive, and Al2O3 generated by decomposition of aluminum salt reacts with CaO to form Ca 12 Al 14O 33 , which helps to stabilize the micro-pore structure of the bifunctional catalyst material and has strong cycle stability under harsh calcination conditions (high CO2 concentration and high temperature).

[0027] (2) After the precursor of the bifunctional catalyst is reduced, the oxygen vacancy concentration of the bifunctional catalyst is improved, thereby providing a reaction active site for capturing CO2. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which form a part of the present description, are included to provide a further understanding of the present application, and are incorporated herein for explanation by reference. The present application will become more fully understood from the detailed description and accompanying drawings given below.

[0029] Figure 1 A flow chart for preparing the bifunctional catalyst in Example 1 of the present application;

[0030] Figure 2 A scanning electron microscope image of the bifunctional catalyst prepared in Example 1 of the present application;

[0031] Figure 3 A methane temperature programmed desorption spectrum of the bifunctional catalyst prepared in Example 1 of the present application;

[0032] Figure 4 A structural schematic diagram of a system for hydrogen production by catalytic cracking of methane, wherein 1 is a methane storage tank, 2 is a bifunctional catalyst storage tank, 3 is a methane cracking furnace, 4 is a hydrogen storage tank, 5 is a CO storage tank, 6 is a condenser, 7 is a CO2 in-situ conversion furnace, 8 is a gasification furnace, 9 is a water vapor generator, 10 is a water tank, 11 is a deactivated bifunctional catalyst storage bin, and 12 is a NaOH solution tank;

[0033] Figure 5 A methane average conversion rate and an average hydrogen production concentration of the bifunctional catalyst prepared in Example 1 of the present application and the catalyst prepared in Comparative Example 2 in multiple cycles of catalytic cracking of methane;

[0034] Figure 6 A gas composition diagram of multiple cycle reinforced carbon deposition gasification of the bifunctional catalyst prepared in Example 1 of the present application and the catalyst prepared in Comparative Example 2 in multiple cycles of catalytic cracking of methane, wherein a is the result of the bifunctional catalyst of Example 1, and b is the result of the catalyst prepared in Comparative Example 2.

[0035] Figure 7 An X-ray diffraction spectrum of the bifunctional catalyst prepared in Example 1 of the present application before and after multiple cycles. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0037] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0038] In a first exemplary embodiment of the present application, a bifunctional catalyst for hydrogen production by catalytic cracking of methane is provided, the active components of the catalyst comprising: CaO, Ca 12 Al 14 O 33 and Fe; the mass ratio of the CaO, Ca 12 Al 14 O 33 and Fe being 80-85:7-8:9-9.5.

[0039] In one or more embodiments, the mass ratio of the CaO, Ca 12 Al 14 O 33 and Fe is 83.1:7.8:9.1.

[0040] In a second exemplary embodiment of the present application, a method for preparing the bifunctional catalyst for hydrogen production by catalytic cracking of methane described above is provided, comprising the following steps:

[0041] (1) calcium acetate, ferric nitrate, aluminum nitrate and citric acid are added to distilled water respectively, and the mixed solution is stirred to obtain a colloidal solution;

[0042] (2) the colloidal solution is dried to obtain a solid material, and the solid material is calcined in an air atmosphere to obtain a precursor of the bifunctional catalyst;

[0043] (3) the precursor of the bifunctional catalyst is reduced to obtain the bifunctional catalyst for hydrogen production by catalytic cracking of methane.

[0044] In one or more embodiments, in step (1), the molar ratio of the calcium acetate, ferric nitrate and aluminum nitrate is 95-105:8-12:4-6, preferably 100:10:5.

[0045] In one or more embodiments, in step (1), the ratio of the total moles of citric acid, calcium acetate, ferric nitrate and aluminum nitrate is 1.3-1.8:1, preferably 1.5:1.

[0046] In one or more embodiments, in step (1), the temperature of stirring is 70-90°C, preferably 80°C; the time of stirring is 2.5-4h, preferably 3h.

[0047] In one or more embodiments, in step (2), the temperature of calcination is 800-900°C, preferably 850°C; the time of calcination is 1-2h, preferably 1.5h.

[0048] In one or more embodiments, in step (3), the precursor of the bifunctional catalyst is reduced by a reducing gas, such as H2, CO or CH4, etc.; the temperature of reduction is 700-800°C, preferably 750°C; the time of reduction is 2-3h, preferably 2.5h.

[0049] In a third typical embodiment of the present application, the bifunctional catalyst for the catalytic cracking of methane to produce hydrogen is provided for the catalytic cracking of methane to produce hydrogen.

[0050] In a fourth typical embodiment of the present application, a system for the catalytic cracking of methane to produce hydrogen is provided, which comprises a methane cracking furnace for the catalytic cracking of methane, which is connected to a gasification furnace for the gasification of water vapor and carbon deposition, and a hydrogen tank, which is connected to a CO2 in-situ conversion furnace for the in-situ conversion of CO2, and a NaOH solution tank, which is connected to a CO tank, a methane cracking furnace and a NaOH solution tank.

[0051] In one or more embodiments, in order to provide raw materials of methane and catalysts to the methane cracking furnace, the methane cracking furnace is connected to a methane tank and a bifunctional catalyst tank.

[0052] In one or more embodiments, in order to provide water vapor required in the gasification furnace, the gasification furnace is connected to a water vapor generator, which is connected to a water tank.

[0053] In one or more embodiments, in order to remove water vapor in CO, the CO2 in-situ conversion furnace is connected to a CO tank through a condenser;

[0054] Preferably, the condenser is connected to a water vapor generator, and the condensed water in the condenser can be reused in the water vapor generator, realizing the recycling of water.

[0055] In one or more embodiments, when the dual-function catalyst is deactivated, the CO2 in-situ conversion furnace is connected to the deactivated dual-function catalyst storage, and the deactivated dual-function catalyst can be used as raw material for the cement industry.

[0056] In a fifth exemplary embodiment of the present application, a method for hydrogen production by catalytic cracking of methane is provided, the method comprising:

[0057] Methane is introduced into the methane cracking furnace, and the dual-function catalyst of the first aspect is added, and the methane is catalytically cracked in the methane cracking furnace, and the hydrogen produced by the reaction is stored in the hydrogen storage tank;

[0058] The dual-function catalyst that has completed catalytic cracking of methane in the methane cracking furnace is introduced into the gasification furnace, and the coke on the surface and in the pores of the dual-function catalyst is gasified by steam in the gasification furnace;

[0059] The dual-function catalyst that has been treated to remove coke is introduced into the CO2 in-situ conversion furnace, and the gas in the gasification furnace is introduced into the CO2 in-situ conversion furnace after passing through the NaOH solution tank, and the CO2 is converted into CO by regeneration of the dual-function catalyst in the CO2 in-situ conversion furnace;

[0060] The regenerated dual-function catalyst is introduced into the methane cracking furnace to catalytically crack methane, and the gas is stored in the CO storage tank.

[0061] In one or more embodiments, the temperature for catalytic cracking of methane in the methane cracking furnace is 800-900°C, preferably 850°C.

[0062] In one or more embodiments, the temperature for gasification of coke by steam in the gasification furnace is 550-650°C, preferably 600°C.

[0063] In one or more embodiments, the temperature for regeneration of the dual-function catalyst in the CO2 in-situ conversion furnace is 600-700°C, preferably 650°C.

[0064] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific examples.

[0065] Example 1: Preparation of a dual-function catalyst for hydrogen production by catalytic cracking of methane

[0066] Calcium acetate (15.8 g, 0.1 mol), iron nitrate (4.04 g, 0.01 mol), aluminum nitrate (1.875 g, 0.005 mol), and citric acid (33.12 g, 0.1725 mol) were added to 50 mL of distilled water, respectively, and the mixed solution was stirred at a temperature of 80°C for 3 h to obtain a gelatinous solution.

[0067] The gel-like solution was dried in a ventilated drying oven at 140°C for 8 hours, and a solid material was obtained after complete drying. The solid material was then calcined in air at 850°C for 1.5 hours to obtain the precursor of the bifunctional catalyst.

[0068] The precursor of the bifunctional catalyst was reduced by hydrogen at a temperature of 750°C for 2.5 hours, resulting in a bifunctional catalyst for catalytic cracking of methane to produce hydrogen.

[0069] The bifunctional catalyst prepared in this embodiment was characterized. Figure 2 The image shows a scanning electron microscope (SEM) image of the bifunctional catalyst prepared in this embodiment. The bifunctional catalyst prepared in this embodiment has a well-developed porous structure.

[0070] Comparative Example 1

[0071] Compared with the preparation method in Example 1, only ferric nitrate was added, while calcium acetate and aluminum nitrate were not added; the other preparation methods were the same.

[0072] Compared to Example 1, Comparative Example 1 only produced catalyst iron, from Figure 3 As can be seen from the accompanying diagram of the methane temperature-programmed desorption process, the bifunctional catalyst prepared in Example 1 has a better adsorption effect on methane due to its well-developed pore structure.

[0073] Comparative Example 2

[0074] Compared with the preparation method in Example 1, aluminum nitrate was not added, but the other preparation methods were the same.

[0075] Example 2: A system for catalytic cracking of methane to produce hydrogen

[0076] like Figure 4 As shown, the system for producing hydrogen from methane through catalytic cracking includes a methane cracking furnace for catalytic cracking of methane. The methane cracking furnace is connected to a gasification furnace for steam vaporization of carbon deposits and a hydrogen storage tank. The gasification furnace is connected to a CO2 in-situ conversion furnace for in-situ CO2 conversion and a NaOH solution tank. The CO2 in-situ conversion furnace is connected to a CO storage tank, the methane cracking furnace, and the NaOH solution tank.

[0077] In order to supply the methane and catalyst to the methane cracking furnace, the methane cracking furnace is connected to a methane storage tank and a dual-function catalyst storage tank.

[0078] To provide the steam required in the gasifier, the gasifier is connected to a steam generator, which in turn is connected to a water tank.

[0079] In order to remove water vapor in CO, the CO2 in-situ conversion furnace is connected with the CO storage tank through a condenser; the condenser is connected with a water vapor generator, and the condensed water in the condenser enters the water vapor generator for reuse, thereby realizing water recycling.

[0080] When the dual-functional catalyst is deactivated, the CO2 in-situ conversion furnace is connected with the deactivated dual-functional catalyst storage bin, and the deactivated dual-functional catalyst can be used as raw material for the cement industry.

[0081] Example 3: Method for preparing hydrogen by catalytic cracking of methane

[0082] Methane in the methane storage tank and the dual-functional catalyst in the dual-functional catalyst storage tank enter the methane cracking furnace, and the methane is catalytically cracked in the methane cracking furnace; the hydrogen generated by the reaction enters the hydrogen storage tank for storage.

[0083] The dual-functional catalyst that has completed catalytic cracking of methane in the methane cracking furnace enters the gasification furnace, and the water in the water tank enters the water vapor generator to generate water vapor, which enters the gasification furnace to gasify the carbon deposition on the surface and in the pores of the dual-functional catalyst in the gasification furnace; the product of the gasification of the carbon deposition by the water vapor includes CO2, CO and hydrogen; the CaO in the dual-functional catalyst will adsorb CO2 to react to generate CaCO3.

[0084] The dual-functional catalyst after the post-treatment of the carbon deposition (at this time, the CaO has reacted with CO2 to generate CaCO3) enters the CO2 in-situ conversion furnace, and the gas in the gasification furnace enters the NaOH solution tank; the CO2 that is not adsorbed reacts with the NaOH, while the CO and hydrogen enter the CO2 in-situ conversion furnace. In the dual-functional catalyst, the CaCO3 generated by the reaction of the CaO with CO2 will react with the hydrogen from the NaOH solution tank that enters the CO2 in-situ conversion furnace to generate CaO, thereby realizing regeneration of the dual-functional catalyst, and at the same time, CO is generated, thereby realizing in-situ conversion of CO2.

[0085] The regenerated dual-functional catalyst enters the methane cracking furnace to catalytically crack methane, and the CO generated in the CO2 in-situ conversion furnace and the CO from the NaOH solution tank that enters the CO2 in-situ conversion furnace enter the CO storage tank for storage after being cooled by the condenser to remove water vapor; the condensed water enters the water vapor generator for reuse, thereby realizing water recycling.

[0086] When the dual-functional catalyst is deactivated, the deactivated dual-functional catalyst enters the deactivated dual-functional catalyst storage bin, and the deactivated dual-functional catalyst can be used as raw material for the cement industry.

[0087] Experimental Example 1

[0088] To detect the performance of the bifunctional catalyst prepared in the present application, the performance of the catalyst prepared in Example 1 and Comparative Example 2 in catalytic cracking of methane to produce hydrogen and in gasification of coke to produce hydrogen was detected and compared in a vertical fixed bed reactor.

[0089] The detection method was as follows: the bifunctional catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 2 were respectively put into a vertical fixed bed reactor to perform methane catalytic cracking reaction, the methane catalytic cracking reaction temperature was 850℃, the methane catalytic cracking time was 3h, and the weight space velocity was 2L / (g·h). Then the reactor temperature was reduced to 600℃, the atmosphere was switched to 30%H2O / 70%N2 to start the coke gasification reaction, and the reaction time was 20min. After the gasification reaction, the reactor was heated to 800℃, calcined in 100%N2 for 30min to convert CaCO3 into CaO, and after the calcination, the reactor was heated to 850℃ to start the methane catalytic cracking reaction in the next cycle. The gas obtained in the methane catalytic cracking and coke gasification process was condensed, dedusted and dried, and then entered a coal gas analyzer, and the volume fraction of H2, CO, CH4 and CO2 in the product gas was measured in real time.

[0090] The calculation formula of the methane conversion rate in the methane catalytic cracking process was as follows:

[0091]

[0092] In the formula, X CH4 was the methane conversion rate, %; was the volume fraction of H2 in the product gas, %; was the volume fraction of CH4 in the product gas, %.

[0093] The calculation formula of the average methane conversion rate in each methane catalytic cracking cycle was as follows:

[0094]

[0095] In the formula, X Ave CH4 represented the average methane conversion rate in the methane catalytic cracking process, %; and t was the methane catalytic cracking reaction time, 3h.

[0096] The calculation formula of the average hydrogen production concentration in the methane catalytic cracking process was as follows:

[0097]

[0098] In the formula, C Ave,H2 was the average hydrogen production concentration in the methane catalytic cracking process.

[0099] In the coke gasification process, the calculation formula of the flow rate of various gases such as H2, CO, CH4 or CO2 was as follows:

[0100]

[0101] In the formula, i represents the components of the gas produced by the gasification of carbon deposits, such as H2, CO, CH4, or CO2. Fi is the flow rate of H2, CO, CH4, or CO2 in the syngas, in mL / min. This represents the volume fraction (%) of H2, CO, CH4, or CO2 in the produced gas.

[0102] The formula for calculating the yield of various gases from carbon deposit gasification within a certain time is as follows:

[0103]

[0104] In the formula Y i t1 represents the volume fraction of H2, CO, CH4, or CO2 in the produced gas over a certain period of time, expressed as %. t1 represents the carbon deposition gasification time, expressed as min.

[0105] The average methane conversion and average hydrogen production concentration of the bifunctional catalyst in Example 1 and the catalyst prepared in Comparative Example 2 after multiple cycles of catalytic methane cracking are as follows: Figure 5 As shown. From Figure 5 As can be seen, the bifunctional catalyst of Example 1 exhibits good catalytic performance in methane cracking. After 8 cycles, the average methane conversion rate of the bifunctional catalyst prepared in Example 1 was 71%, and the average hydrogen concentration was 83%, representing increases of 18% and 14% respectively compared to Comparative Example 2. Furthermore, the hydrogen production performance remained stable compared to the first cycle. However, the material prepared in Comparative Example 2 showed a significant decrease in its methane cracking performance. This is because, during multiple cycles, the catalyst in Example 2 underwent sintering and agglomeration, leading to a rapid decline in catalytic performance.

[0106] The gas yields of the bifunctional catalyst in Example 1 and the catalyst prepared in Comparative Example 2 during the carbon deposition gasification hydrogen production process are as follows: Figure 6 As shown. From Figure 6 As can be seen, after 8 cycles, the bifunctional catalyst still showed good performance in enhancing the hydrogen production from carbon deposit gasification, with a hydrogen yield of 78.08%, which is 7.76% higher than the hydrogen yield of the material prepared in Comparative Example 2, while the CO2 yield decreased by 4.04%. This is because the CO2 capture performance of CaO in Example 2 decreases due to sintering, thus reducing the effectiveness of enhancing the hydrogen production from carbon deposit gasification.

[0107] The above results demonstrate that the bifunctional catalyst prepared in this invention exhibits excellent performance in catalyzing methane cracking for hydrogen production, enhancing carbon deposit gasification for hydrogen production, and capturing CO2, while also demonstrating superior cycle stability. This phenomenon is attributed to the reaction of Al2O3, generated from the decomposition of aluminum salts added during the preparation process, with CaO to form Ca2+. 12 Al14 O 33 , which has strong anti-sintering performance and can keep the microstructure of the bifunctional catalyst stable in multiple cycles of catalyzing methane cracking and gasifying carbon deposition. Figure 7 The X-ray diffraction patterns of the bifunctional catalyst prepared in Example 1 of the present application before and after multiple cycles are shown in the following table. Figure 7 As can be seen from the table, the catalyst prepared in the present application still keeps the microstructure stable after multiple cycles.

[0108] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for hydrogen production by catalytic decomposition of methane, characterized in that, The method comprises: The method comprises: The active ingredients of the bifunctional catalyst include: CaO, Ca 12 Al 14 O 33 and Fe; the mass ratio of the CaO, Ca 12 Al 14 O 33 and Fe is 80-85:7-8:9-9.5; The preparation method of the bifunctional catalyst comprises the following steps: (1) calcium acetate, ferric nitrate, aluminum nitrate and citric acid are added into distilled water respectively, and the mixed solution is stirred to obtain a colloidal solution; (2) the colloidal solution is dried to obtain a solid material, and the solid material is calcined under an air atmosphere to obtain a precursor of the bifunctional catalyst; (3) the precursor of the bifunctional catalyst is reduced to obtain the bifunctional catalyst for catalytic cracking of methane to produce hydrogen.

2. The method of claim 1, wherein, In step (1), the molar ratio of the calcium acetate, the ferric nitrate and the aluminum nitrate is 95-105:8-12:4-6. Alternatively, in step (1), the ratio of the total molar amount of the citric acid to the calcium acetate, the ferric nitrate and the aluminum nitrate is 1.3-1.8:

1.

3. The method of claim 2, wherein, In step (1), the molar ratio of the calcium acetate, the ferric nitrate and the aluminum nitrate is 100:10:

5.

4. The method of claim 2, wherein, In step (1), the ratio of the total molar amount of the citric acid to the calcium acetate, the ferric nitrate and the aluminum nitrate is 1.5:

1.

5. The method of claim 1, wherein, In step (1), the stirring temperature is 70-90°C; and the stirring time is 2.5-4 h.

6. The method of claim 5, wherein, In step (1), the stirring temperature is 80°C.

7. The method of claim 5, wherein, In step (1), the stirring time is 3 h.

8. The method of claim 1, wherein, In step (2), the calcination temperature is 800-900°C; and the calcination time is 1-2 h. Alternatively, in step (3), the precursor of the bifunctional catalyst is reduced by using a reducing gas, the reducing gas comprises H2, CO or CH4, the reduction temperature is 700-800°C, and the reduction time is 2-3 h.

9. The method of claim 8, wherein, In step (2), the calcination temperature is 850°C.

10. The method of claim 8, wherein, In step (2), the calcination time is 1.5 h.

11. The method of claim 8, wherein, In step (3), the precursor of the bifunctional catalyst is reduced by using a reducing gas, and the reduction temperature is 750°C.

12. The method of claim 8, wherein, In step (3), the precursor of the bifunctional catalyst is reduced by using a reducing gas, and the reduction time is 2.5 h.

13. The method of claim 1, wherein, The temperature for catalytic cracking of methane in the methane cracking furnace is 800-900°C; Alternatively, the temperature for gasification of the accumulated carbon by water vapor in the gasification furnace is 550-650°C; Alternatively, the temperature for regeneration of the bifunctional catalyst in the CO2 in-situ conversion furnace is 600-700°C.

14. The method of claim 13, wherein, The temperature for catalytic cracking of methane in the methane cracking furnace is 850°C.

15. The method of claim 13, wherein, The temperature for gasification of the accumulated carbon by water vapor in the gasification furnace is 600°C.

16. The method of claim 13, wherein, The temperature for regeneration of the bifunctional catalyst in the CO2 in situ reformer is 650 °C.

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