Ammonia cracking hydrogen production catalyst with three-dimensional hierarchical porous structure and preparation method thereof
By using a combination of a three-dimensional layered porous structure carbon-coated metal oxide support and ruthenium nanoparticles in the ammonia cleavage hydrogen production catalyst, the existing catalysts are solved, and the efficient and low-cost hydrogen production effect of ammonia cleavage hydrogen production is achieved.
Patent Information
- Application Number
- CN202510043537.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-10
- Publication Date
- 2025-05-09
AI Technical Summary
The existing ammonia cleavage hydrogen production catalysts are costly and have insufficient activity, making it difficult to achieve a low-temperature and efficient ammonia cleavage process.
Carbon-coated metal oxides with a three-dimensional layered porous structure are used as support, and ruthenium nanoparticles are uniformly distributed on the support. This structure improves the intrinsic activity of the catalyst and the adsorption, cracking and hydrogen desorption capabilities of ammonia molecules.
It achieves efficient ammonia cleavage and rapid hydrogen desorption, reduces the cost of the catalyst, and improves the ammonia cleavage conversion efficiency, reaching a conversion efficiency of more than 98%.
Smart Images
Figure CN119951534A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalysts, and in particular relates to an ammonia cracking hydrogen production catalyst with a three-dimensional hierarchical porous structure and a preparation method thereof. Background Art
[0002] As a secondary energy source, hydrogen energy will play an important role as a bridge and link in the development of renewable energy and fossil energy, but its promotion and application are limited by factors such as high hydrogen storage cost and low transportation efficiency. Ammonia is used as a hydrogen storage carrier, which has high hydrogen storage density and mature transportation technology, and is convenient for distributed on-site hydrogen production and supply, avoiding the troubles caused by hydrogen storage and transportation. The key to the promotion and application of ammonia hydrogen technology lies in the development level of ammonia cracking catalysts. At present, the catalysts for ammonia cracking mainly include Ru-based catalysts, non-precious metal catalysts, bimetallic catalysts and nitride / carbide catalysts. Among them: Ru catalysts have high catalytic activity, but due to factors such as limited resources and high prices, their industrial applications are limited. Therefore, reducing the ruthenium content in ruthenium-based catalysts and developing efficient, low-temperature, and cheap ammonia cracking hydrogen production catalysts are the key to achieving cheap industrial ammonia cracking hydrogen production.
[0003] Based on the catalytic process of ammonia cracking catalysts, it can be seen that to achieve a low-temperature and efficient cracking process, on the one hand, a catalyst with high intrinsic active sites must be prepared, and on the other hand, there must be enough catalytic active sites and the ability to efficiently adsorb ammonia molecules, with high ammonia cracking ability and rapid hydrogen desorption.
[0004] Therefore, there is an urgent need to develop an ammonia cracking catalyst for hydrogen production that can reduce the cost of the catalyst while ensuring high catalytic activity. Summary of the invention
[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides an ammonia cracking hydrogen production catalyst having a three-dimensional hierarchical porous structure and a preparation method thereof, wherein the catalyst has not only high intrinsic active sites, but also a large number of catalytic active sites, can efficiently adsorb ammonia molecules, and has high ammonia cracking and hydrogen rapid desorption capabilities.
[0006] The inventive concept of the present invention is as follows: the active ingredient of the ammonia cracking hydrogen production catalyst of the present invention is ruthenium nanoparticles, and the carrier for loading the ruthenium nanoparticles is a carbon-coated metal oxide. The three components work together to effectively improve the intrinsic activity of the catalyst, thereby improving the adsorption, cracking, and H2 desorption capabilities of ammonia molecules; at the same time, the catalyst carrier has a three-dimensional hierarchical porous structure with high porosity and high specific surface area, which is conducive to obtaining ultrafine ruthenium nanoparticles, and the three-dimensional hierarchical porous structure can retain ammonia molecules in the catalyst for a longer time under the microstructure, thereby improving the ammonia conversion efficiency. In addition, the carbon composite is conducive to improving the thermal conductivity of the catalyst, further promoting the thermal catalytic process.
[0007] To solve the above technical problems, the first aspect of the present invention provides an ammonia cracking hydrogen production catalyst, comprising a carrier and ruthenium nanoparticles, wherein the ruthenium nanoparticles are uniformly distributed on the surface of the carrier, the carrier is a carbon-coated metal oxide, and the carrier has a three-dimensional hierarchical porous structure constructed by nanosheets.
[0008] Specifically, the active component of the catalyst of the present invention is ruthenium nanoparticles, and the ruthenium nanoparticles are anchored on the surface of the carrier. Among them: the three-dimensional hierarchical porous structure of the carrier constructed by carbon-coated metal oxide is not only conducive to providing Ru in the synthesis process 3+ The three-dimensional hierarchical porous structure can also retain ammonia molecules in the catalyst for a long time, fully inducing the adsorption, dissociation and hydrogen combination of ammonia molecules, thereby greatly improving the ammonia cracking conversion efficiency.
[0009] At the same time, the carbon-coated metal oxide carrier of the present invention with a three-dimensional hierarchical porous structure can better coordinately regulate the electronic structure of the active component and promote the improvement of the catalyst activity compared with pure metal oxides; it can also improve the thermal conductivity of the catalyst and reduce the energy consumption of the catalytic process; and the porous structure carrier with a high specific surface area can adsorb a large number of ammonia molecules to the catalytic site, further improving the conversion efficiency of ammonia cracking.
[0010] In some embodiments of the present invention, the metal oxide is selected from any one of iron, cobalt and nickel oxides, and these metal oxides have good catalytic activity.
[0011] In some embodiments of the present invention, the particle size of the ruthenium nanoparticles is less than 10 nm. Ultrafine ruthenium nanoparticles are beneficial to further improve the activity of the catalyst and reduce the loading amount.
[0012] In some embodiments of the present invention, the mass ratio of the ruthenium nanoparticles to the carrier is (0.1-8):100.
[0013] In some embodiments of the present invention, the thickness of the outer carbon coating layer of the carrier is 1-50 nm.
[0014] The second aspect of the present invention provides a method for preparing the above-mentioned ammonia cracking hydrogen production catalyst, comprising the following steps:
[0015] (1) After dissolving a surfactant and a metal salt in water, an aqueous solution of an organic ligand is added to react, centrifuged, washed, dried, and sintered in an environment of nitrogen and oxygen to obtain a carbon-coated metal oxide;
[0016] (2) dispersing the carbon-coated metal oxide into an aqueous solution containing ruthenium ions, centrifuging, washing, drying, and sintering under a reducing atmosphere to obtain the ammonia cracking hydrogen production catalyst.
[0017] Specifically, in step (1), the purpose of adding a surfactant is mainly to obtain ultrafine nanoparticles. The porous material formed by self-assembly of metal salts and organic ligands is sintered in a nitrogen and oxygen environment to obtain carbon-coated metal oxides and form a hierarchical porous three-dimensional structure, thereby deeply improving the electronic structure of ruthenium nanoparticles, better retaining ammonia molecules in the catalyst for a longer time, and improving the ammonia cracking conversion rate. In step (2), the carbon-coated metal oxide is dispersed in an aqueous solution containing ruthenium ions and sintered in a reducing atmosphere, which is conducive to the uniform dispersion of ruthenium nanoparticles in the porous carrier structure and improves the catalytic activity.
[0018] In some embodiments of the present invention, in step (1), the surfactant is selected from at least one of polyvinyl alcohol, F127 surfactant, hexadecyltrimethylammonium bromide, polyacrylamide, maleic anhydride copolymer, polyacrylate, polyether, polyethylene oxide-propylene oxide, water-soluble phenolic resin, and amino resin.
[0019] In some embodiments of the present invention, in step (1), the metal salt is selected from nitrates or chlorides whose cations are any one of iron, cobalt and nickel.
[0020] In some embodiments of the present invention, in step (1), the organic ligand is selected from at least one of 2-methylimidazole and terephthalic acid.
[0021] In some embodiments of the present invention, in step (1), the volume ratio of nitrogen to oxygen is (98-99.5): 1. Sintering in an environment containing a certain amount of oxygen can obtain an ultra-thin hierarchical porous three-dimensional structure.
[0022] In some embodiments of the present invention, in step (1) and step (2), the sintering temperature is 450-600°C.
[0023] In some embodiments of the present invention, in step (2), the reducing atmosphere is a hydrogen atmosphere, or a hydrogen and argon atmosphere.
[0024] The third aspect of the present invention provides the use of the above-mentioned ammonia cracking hydrogen production catalyst in an ammonia cracking hydrogen production reaction.
[0025] Preferably, the reaction temperature is 550-650°C.
[0026] Preferably, the space velocity of the reaction is 50000-65000 mL / g / h.
[0027] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:
[0028] (1) The active component of the ammonia cracking hydrogen production catalyst of the present invention is ruthenium nanoparticles, which are anchored on the surface of the carrier. The carrier is a carbon-coated metal oxide and has a three-dimensional hierarchical porous structure. The carrier with a specific structure is not only conducive to providing Ru in the synthesis process, but also has a good structure. 3+ The catalyst can also increase the adsorption site to prepare ultra-small nano-ruthenium particles; it is also conducive to stabilizing the nano-particles and avoiding particle agglomeration during the catalytic reaction; it can also retain the ammonia molecules inside the catalyst for a long time, fully inducing the adsorption, dissociation and hydrogen combination of ammonia molecules, thereby greatly improving the ammonia cracking conversion efficiency. At the same time, the multi-component structure of the catalyst can optimize its electronic structure, thereby regulating the catalyst's adsorption capacity for ammonia molecules, promoting the dissociation of NH, and improving the energy conversion efficiency of ammonia decomposition.
[0029] (2) Compared with pure metal oxides, the carbon-coated metal oxide carrier of the present invention can better coordinately regulate the electronic structure of the active component and promote the improvement of catalyst activity; it can also improve the thermal conductivity of the catalyst and reduce the energy consumption of the catalytic process; and it has a porous structure carrier with a high specific surface area, which can adsorb a large number of ammonia molecules to the catalytic site, further improving the conversion efficiency of ammonia cracking.
[0030] (3) During the preparation of the ammonia cracking hydrogen production catalyst of the present invention, an organic ligand is added to form a porous material through self-assembly with a metal salt, and a surfactant is used to obtain ultrafine ruthenium nanoparticles, thereby further increasing the specific surface area of the carrier; sintering is performed in a nitrogen and oxygen environment to obtain a carbon-coated metal oxide, and an ultrathin hierarchical porous three-dimensional structure is formed, thereby deepening the electronic structure of the ruthenium nanoparticles, better retaining the ammonia molecules inside the catalyst for a longer time, and improving the ammonia cracking conversion rate.
[0031] (4) The ammonia cracking catalyst prepared by the present invention has excellent catalytic performance. At 500°C, the space velocity is 60000mL / hg -1 Under the reaction conditions, the ammonia decomposition conversion efficiency can reach more than 98%, even as high as 99.8%. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 This is a SEM image of the ammonia cracking hydrogen production catalyst prepared in Example 1;
[0033] Figure 2TEM image of the ammonia cracking hydrogen production catalyst prepared in Example 1;
[0034] Figure 3 This is the SEM image of the ammonia cracking hydrogen production catalyst prepared in Comparative Example 1. DETAILED DESCRIPTION
[0035] The present invention is described in detail below in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.
[0036] Example 1
[0037] A method for preparing a catalyst for hydrogen production by cracking ammonia comprises the following steps:
[0038] (1) Take 30 mg of hexadecyltrimethylammonium bromide and 1.5 g of Co(NO3)2·6H2O and dissolve them in 40 mL of water to obtain solution A; take 25 g of 2-methylimidazole and add it to 350 mL of water, stir evenly, and obtain solution B; pour solution A into solution B at room temperature, stir at 1000 rpm for 20 min to allow it to react fully; then centrifuge the mixed solution after the reaction at 10000 rpm for 5 min, wash it with deionized water and ethanol for 3 times respectively to remove unreacted substances; then dry the obtained powder in a vacuum oven at 60°C for 12 h; finally, sinter the dried powder at 500°C for 1.5 h in an environment of nitrogen and oxygen (volume ratio 99:1) to obtain a carbon-coated cobalt tetroxide carrier;
[0039] (2) The carrier prepared in step (1) was dispersed in a 1 wt% aqueous solution of ruthenium chloride, stirred at 1000 rpm for 3 h, centrifuged, centrifuged at 10000 rpm for 5 min, washed with deionized water 3 times, and dried at 60° C. for 12 h; finally, the dried powder was sintered at 500° C. for 2 h in an environment of hydrogen and argon (volume ratio of 3:2) to obtain the ammonia cracking hydrogen production catalyst of this embodiment.
[0040] Example 2
[0041] A method for preparing a catalyst for hydrogen production by cracking ammonia comprises the following steps:
[0042] (1) 30 mg of polyvinyl alcohol and 1.5 g of Ni(NO3)2·6H2O were dissolved in 40 mL of water to obtain solution A; 25 g of terephthalic acid was added to 350 mL of water and stirred to obtain solution B; solution A was poured into solution B at room temperature and stirred at 1000 rpm for 20 min to allow sufficient reaction; the mixed solution after the reaction was centrifuged at 10000 rpm for 5 min, and washed with deionized water and ethanol for 3 times respectively to remove unreacted substances; the obtained powder was dried in a vacuum oven at 60°C for 12 h; finally, the dried powder was sintered at 550°C for 1.5 h in an environment of nitrogen and oxygen (volume ratio 99:1) to obtain a carbon-coated cobalt tetroxide carrier;
[0043] (2) The carrier prepared in step (1) was dispersed in a 1 wt% aqueous solution of ruthenium chloride, stirred at 1000 rpm for 3 h, centrifuged, centrifuged at 10000 rpm for 5 min, washed with deionized water 3 times, and dried at 60° C. for 12 h; finally, the dried powder was sintered at 550° C. for 1.5 h in an environment of hydrogen and argon (volume ratio of 3:2) to obtain the ammonia cracking hydrogen production catalyst of this embodiment.
[0044] Example 3
[0045] A method for preparing a catalyst for hydrogen production by cracking ammonia comprises the following steps:
[0046] (1) 30 mg of F127 surfactant and 1.5 g of Fe(NO3)3·9H2O were dissolved in 40 mL of water to obtain solution A; 25 g of 2-methylimidazole was added to 350 mL of water and stirred to obtain solution B; solution A was poured into solution B at room temperature and stirred at 1000 rpm for 20 min to allow sufficient reaction; the mixed solution after the reaction was centrifuged at 10000 rpm for 5 min, and washed with deionized water and ethanol for 3 times respectively to remove unreacted substances; the obtained powder was dried in a vacuum oven at 60°C for 12 h; finally, the dried powder was sintered at 580°C for 1 h in an environment of nitrogen and oxygen (volume ratio 99:1) to obtain a carbon-coated cobalt tetroxide carrier;
[0047] (2) The carrier prepared in step (1) was dispersed in a 1 wt% aqueous solution of ruthenium chloride, stirred at 1000 rpm for 3 h, centrifuged, centrifuged at 10000 rpm for 5 min, washed with deionized water 3 times, and dried at 60° C. for 12 h; finally, the dried powder was sintered at 580° C. for 2 h in an environment of hydrogen and argon (volume ratio of 3:2) to obtain the ammonia cracking hydrogen production catalyst of this embodiment.
[0048] Comparative Example 1
[0049] The only difference between Comparative Example 1 and Example 1 is that hexadecyltrimethylammonium bromide is not added in step (1).
[0050] Comparative Example 2
[0051] The only difference between Comparative Example 2 and Example 1 is that 2-methylimidazole is not added in step (1).
[0052] Comparative Example 2
[0053] The only difference between Comparative Example 3 and Example 1 is that the sintering atmosphere in step (1) is a pure nitrogen environment.
[0054] Characterization and performance testing
[0055] 1. Microstructure
[0056] Figure 1 This is a SEM image of the ammonia cracking hydrogen production catalyst prepared in Example 1. Figure 1 It can be seen that the catalyst carrier has a three-dimensional pore structure constructed by nanosheets, and the nanosheet layer has a porous structure, that is, a three-dimensional hierarchical porous structure.
[0057] Figure 2 TEM image of the ammonia cracking hydrogen production catalyst prepared in Example 1. Figure 2 It can be seen that the ruthenium nanoparticles are uniformly dispersed on the surface of the carbon-coated cobalt tetroxide carrier, and the particle size of the ruthenium nanoparticles is less than 10 nm.
[0058] Figure 3 This is a SEM image of the ammonia cracking hydrogen production catalyst prepared in Comparative Example 1. Figure 3 It can be seen that although the catalyst carrier also has a three-dimensional pore structure constructed by nanosheets, the thickness of the nanosheets is relatively thick and the nanosheets do not have a porous structure.
[0059] 2. Ammonia cracking performance test
[0060] Activity test conditions: the raw gas is pure ammonia, the test space velocity is 60000 mL / g / h, the test temperature is 500°C, and the ammonia decomposition conversion efficiency is shown in Table 1.
[0061] Table 1: Comparison of ammonia cracking conversion efficiency prepared in Examples 1-3 and Comparative Examples 1-3
[0062] sample Ammonia cracking conversion efficiency % Example 1 99.8 Example 2 98.7 Example 3 98.1 Comparative Example 1 90.4 Comparative Example 2 92.5 Comparative Example 3 85.4
[0063] As shown in Table 1, the ammonia cracking hydrogen production catalyst prepared in Example 1 exhibits excellent ammonia decomposition performance at a test space velocity of 60000 mL / g / h and a test temperature of 500° C., and its conversion efficiency can reach up to 99.8%.
[0064] Compared with Example 1, since the surface active hexadecyltrimethylammonium bromide is not added during the preparation process, the carbon-coated cobalt tetroxide carrier cannot form an ultra-thin hierarchical porous three-dimensional structure, the specific surface area of the catalyst is reduced, and the electronic structure of the ruthenium nanoparticles cannot be further optimized, and the ammonia molecules cannot be better retained in the catalyst. Therefore, the ammonia cracking conversion efficiency is significantly reduced compared with Example 1.
[0065] In Comparative Example 2 relative to Example 1, since the organic ligand 2-methylimidazole is not added during the preparation process, the metal salt forms a porous material, which leads to a decrease in the specific surface area of the catalyst. Therefore, the ammonia cracking conversion efficiency is lower than that of Example 1.
[0066] In Comparative Example 3 relative to Example 1, since an inert atmosphere sintering is adopted in the preparation process of the carrier, a carbon outer coating layer cannot be formed, resulting in the inability to form a multi-component synergistically optimized ruthenium electronic structure, the electronic synergistic effect is lost, and the catalyst activity decreases. Therefore, the ammonia cracking conversion efficiency is significantly lower than that of Example 1.
[0067] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, without having to go through creative labor. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the protection scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should belong to the protection scope of the present invention.
Claims
1. A catalyst for hydrogen production by cracking ammonia, characterized in that: The invention comprises a carrier and ruthenium nanoparticles, wherein the ruthenium nanoparticles are uniformly distributed on the surface of the carrier, the carrier is a carbon-coated metal oxide, and the carrier has a three-dimensional hierarchical porous structure constructed by nanosheets.
2. The ammonia cracking hydrogen production catalyst according to claim 1, characterized in that: The metal oxide is selected from any one of iron, cobalt and nickel oxides.
3. The ammonia cracking hydrogen production catalyst according to claim 1, characterized in that: The particle size of the ruthenium nanoparticles is less than 10 nm.
4. The ammonia cracking hydrogen production catalyst according to claim 1, characterized in that: The mass ratio of the ruthenium nanoparticles to the carrier is (0.1-8):
100.
5. The ammonia cracking hydrogen production catalyst according to claim 1, characterized in that: The thickness of the outer carbon coating layer of the carrier is 1-50 nm.
6. A method for preparing the catalyst for hydrogen production by cracking ammonia according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) After dissolving a surfactant and a metal salt in water, an aqueous solution of an organic ligand is added to react, centrifuged, washed, dried, and sintered in an environment of nitrogen and oxygen to obtain a carbon-coated metal oxide; (2) dispersing the carbon-coated metal oxide into an aqueous solution containing ruthenium ions, centrifuging, washing, drying, and sintering under a reducing atmosphere to obtain the ammonia cracking hydrogen production catalyst.
7. The method for preparing ammonia cracking hydrogen production catalyst according to claim 6, characterized in that: In step (1), the surfactant is selected from at least one of polyvinyl alcohol, F127 surfactant, hexadecyltrimethylammonium bromide, polyacrylamide, maleic anhydride copolymer, polyacrylate, polyether, polyethylene oxide-propylene oxide, water-soluble phenolic resin, and amino resin; And / or, the metal salt is selected from nitrates or chlorides whose cation is any one of iron, cobalt and nickel; And / or, the organic ligand is selected from at least one of 2-methylimidazole and terephthalic acid.
8. The method for preparing ammonia cracking hydrogen production catalyst according to claim 6, characterized in that: In step (1), the volume ratio of nitrogen to oxygen is (98-99.5):
1.
9. The method for preparing ammonia cracking hydrogen production catalyst according to claim 6, characterized in that: In step (1) and step (2), the sintering temperature is 450-600°C.
10. Use of the ammonia cracking hydrogen production catalyst according to any one of claims 1 to 5 in an ammonia cracking hydrogen production reaction.