Non-noble metal ammonia decomposition catalyst synthesized by spontaneous combustion method and preparation method thereof
The self-combustion synthesis of a non-precious metal ammonia decomposition catalyst on a calcium titanate support addresses dispersion and stability issues, achieving high catalytic performance and longevity.
Patent Information
- Application Number
- CN202510255602.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2025-07-15
AI Technical Summary
The existing non-precious metal-supported ammonia decomposition catalysts have problems such as large particle size, low binding strength, easy agglomeration and performance decay, resulting in low catalytic activity and poor long-term stability.
The glycine-nitrate method was used to synthesize the non-precious metal ammonia decomposition catalyst, and nanoparticles on the surface of the perovskite oxide support were obtained by in-situ dissolving, forming a unique anchoring structure, improving the uniform distribution of active components and anti-sintering ability, and preparing a catalyst with excellent catalytic activity and long-term stability.
The high-efficiency ammonia decomposition rate under medium temperature conditions was achieved, reaching 96.8%, and the ammonia decomposition rate of more than 90% was maintained during long-term use, reducing costs and improving the chemical and thermal stability of the catalyst.
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Figure CN120305975A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a non-precious metal ammonia decomposition catalyst synthesized by a self-ignition method and a preparation method thereof. Background Art
[0002] In recent years, hydrogen energy has received increasing attention, but the storage and transportation of hydrogen have high requirements. Ammonia, as a hydrogen storage medium, has many advantages. Ammonia is easy to liquefy, non-flammable, non-toxic at low concentrations, has a high hydrogen storage density, mature production, storage and transportation technologies, and has no carbon emissions during the hydrogen production process. It is an efficient, clean and safe hydrogen storage carrier. Therefore, in the future hydrogen economy, ammonia as a hydrogen carrier will have great development prospects.
[0003] Considering the limited reserves and high cost of precious metals, most industrial ammonia decomposition for hydrogen production currently uses non-precious metal supported catalysts, which mainly consist of non-precious metal active components, carrier materials, etc. Usually, the deposition-precipitation method and the impregnation method are used for preparation, so that the external active components are loaded onto the carrier materials. For example, alumina is used as the carrier material and repeatedly impregnated into a Co ion solution. After drying and calcination, the active component Co will be deposited on the carrier material. The traditional supported catalysts have the following problems: (1) The particle size of the active component metal particles is relatively large, and the reaction active area is relatively low, resulting in low catalyst activity; (2) The binding strength between the metal particles and the carrier is low, resulting in easy detachment of the metal particles under variable operating conditions; (3) During the long-term operation process, the metal particles are prone to agglomeration, resulting in performance degradation of the catalyst during the long-term operation process.
[0004] Therefore, it is necessary to provide a non-precious metal ammonia decomposition catalyst to reduce costs and improve catalytic activity and long-term stability. 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. For this purpose, the present invention provides a non-precious metal ammonia decomposition catalyst synthesized by a self-ignition method and a preparation method thereof. The non-precious metal ammonia decomposition catalyst does not contain precious metal active components, has a low cost, and at the same time has excellent catalytic activity and long-term stability.
[0006] In the first aspect of the present invention, a non-precious metal ammonia decomposition catalyst is provided, and its chemical formula is AB 1-x B’ x O 3-δ ; wherein, 0.5≤x≤0.9; δ represents oxygen vacancies; element A includes one of La, Sr, Ba, Pr, Ca; element B includes one or more of Zr, Ce, Y, Yb, Cr, Mn, Mg; element B’ includes one or two of Fe, Co, Ni.
[0007] In some embodiments of the present invention, the B' element is distributed on the surface of the support of the non-noble metal ammonia decomposition catalyst in the form of nanoparticles. The support of the non-noble metal ammonia decomposition catalyst refers to the perovskite oxide after in-situ exsolution of the B' element.
[0008] In some embodiments of the present invention, the A element is selected from Ba.
[0009] In some embodiments of the present invention, the B element includes at least 2, or at least 3, or at least 4 of Zr, Ce, Y, Yb, Cr, Mn, and Mg.
[0010] In some embodiments of the present invention, the B element is selected from the combination of Zr, Ce, and Y, and the molar ratio of Zr, Ce, and Y is 1:7:2.
[0011] In some embodiments of the present invention, the B element is selected from the combination of Zr, Ce, Y, and Yb, and the molar ratio of Zr, Ce, Y, and Yb is 1:7:1:1.
[0012] In some embodiments of the present invention, the B' element is selected from Ni, 0.5 ≤ x < 0.8, and x is preferably 0.5.
[0013] In some embodiments of the present invention, the B' element is selected from Fe and Co, and the molar ratio of Fe and Co is 1:(1 - 4), preferably 1:1, and x is preferably 0.8.
[0014] In some embodiments of the present invention, the B' element is selected from Fe and Ni, and the molar ratio of Fe and Ni is 1:(1 - 4), preferably 1:1, and x is preferably 0.8.
[0015] In the second aspect of the present invention, there is provided a method for preparing the non-noble metal ammonia decomposition catalyst described in the first aspect of the present invention, which is prepared by the glycine-nitrate method.
[0016] In some embodiments of the present invention, the glycine-nitrate method includes the following steps:
[0017] (1) Prepare a metal salt solution according to the stoichiometric ratio of the non-noble metal ammonia decomposition catalyst, and then mix it with glycine to obtain a precursor solution;
[0018] (2) Heat and stir the precursor solution to obtain a gel;
[0019] (3) Heat the gel, and the gel self-ignites when heated to obtain a powder;
[0020] (4) Calcinate the powder to obtain the perovskite oxide;
[0021] (5) The perovskite oxide is placed in a reducing atmosphere for reduction treatment to obtain a non-precious metal ammonia decomposition catalyst.
[0022] In some embodiments of the present invention, in step (1), the molar ratio of glycine to the total molar amount of metal ions in the metal salt solution is (1.5 - 3.5):1.
[0023] In some embodiments of the present invention, in step (2), the temperature of the heating and stirring is 80 - 100 °C, and the time is 2 - 5 h.
[0024] In some embodiments of the present invention, in step (3), the temperature of the heating is 150 - 300 °C.
[0025] In some embodiments of the present invention, in step (4), the temperature of the calcination is 1000 - 1400 °C, and the time is 2 - 5 h.
[0026] In some embodiments of the present invention, in step (5), the temperature of the reduction is 500 - 800 °C, and the time is 1 - 4 h.
[0027] In the third aspect of the present invention, there is provided the use of the non-precious metal ammonia decomposition catalyst described in the first aspect of the present invention in ammonia decomposition for hydrogen production.
[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0029] (1) Compared with the traditional non-precious metal supported catalyst, the non-precious metal ammonia decomposition catalyst of the present invention is obtained by in-situ exsolution of perovskite oxide, and has a higher density of active component nanoparticles on its surface, as well as a more uniform distribution and stronger anti-sintering ability, showing more excellent chemical stability and thermal stability.
[0030] (2) The active non-precious metal nanoparticles in the non-precious metal ammonia decomposition catalyst of the present invention are in-situ exsolved from the perovskite oxide and firmly embedded on the surface of the perovskite oxide. The non-precious metal active component and the perovskite oxide present a unique anchoring structure, which promotes a strong metal-support interaction and avoids problems such as agglomeration, particle coarsening, and shedding of the active component during long-term operation of the catalyst, resulting in poor durability.
[0031] (3) The perovskite oxide in the non-precious metal ammonia decomposition catalyst of the present invention is easy to regulate the components within a large range while maintaining the structure stable. The A-site element remains unchanged, and precise regulation of the catalytic performance can be achieved by changing the types, ratios, and doping ranges of the elements at the B and / or B' sites.
[0032] (4) The non-precious metal ammonia decomposition catalyst provided by the present invention has excellent catalytic activity and long-term stability. Under the conditions of 600 °C and a space velocity of 18,000 mL / (g·h), the ammonia decomposition rate can reach as high as 96.8%, which can be comparable to the performance of precious metal ruthenium-based catalysts. It is beneficial to reduce costs in the field of medium-temperature ammonia decomposition. Moreover, after the non-precious metal ammonia decomposition catalyst is placed at room temperature for 5 months and undergoes a 100-hour stability test, the ammonia decomposition rate can remain above 90%.
[0033] (5) The non-precious metal ammonia decomposition catalyst of the present invention is prepared by synthesizing perovskite oxides through the glycine-nitrate method (GNP) and then performing a reduction treatment. It overcomes the problems of long reaction cycles and large powder particle sizes in the synthesis of perovskite oxides by the traditional solid-phase reaction method. It can prepare ultrafine perovskite oxide powders with uniform particle size distribution, large specific surface area, and easy low-temperature treatment, and also avoids the cumbersome operation of repeated impregnation required for traditional non-precious metal supported catalysts. The process is simple. Description of the Drawings
[0034] Figure 1 SEM images of the perovskite oxides prepared in Example 1 before and after reduction;
[0035] Figure 2 TEM image of the non-precious metal ammonia decomposition catalyst prepared in Example 1;
[0036] Figure 3 Results of the 100-hour stability test of the non-precious metal ammonia decomposition catalyst prepared in Example 1. Detailed Description of the Invention
[0037] The content of the present invention will be further described in detail through specific examples below. The raw materials, reagents, or devices used in the examples can be obtained from conventional commercial channels or by existing technical methods without special instructions. Unless otherwise specified, the test or measurement methods are conventional methods in the art.
[0038] Example 1
[0039] A non-precious metal ammonia decomposition catalyst with the chemical formula Ba(Zr 0.1 Ce 0.7 Y 0.1 Yb 0.1 ) 0.2 Fe 0.4 Co 0.4 O 3-δ , and is prepared by a preparation method including the following steps:
[0040] (1) According to the stoichiometric ratio, 13.067 g of barium nitrate, 0.429 g of zirconium nitrate, 3.0395 g of cerium nitrate, 0.403 g of yttrium nitrate, 0.4492 g of ytterbium nitrate, 5.8206 g of cobalt nitrate and 8.08 g of iron nitrate were added to 50 mL of deionized water, stirred and dissolved to obtain a metal salt solution, and then 17.325 g of glycine was added and the solution was stirred to obtain a precursor solution;
[0041] (2) The precursor solution was stirred at a constant temperature of 80 °C for 2 h to evaporate the excess water and obtain a gel;
[0042] (3) The gel was rapidly heated to 289 °C to cause the gel to burn spontaneously, and the ash powder after combustion was collected;
[0043] (4) The powder was placed in a muffle furnace and calcined at 1100 °C for 2 h to obtain a perovskite oxide;
[0044] (5) The perovskite oxide was placed in a tubular furnace under a hydrogen atmosphere and reduced at 600 °C for 2 h to obtain the non-noble metal ammonia decomposition catalyst of this example.
[0045] Example 2
[0046] The difference from Example 1 is only that in Example 2, the types and amounts of some metal salts in step (1) were adjusted, specifically: 13.067 g of barium nitrate, 0.429 g of zirconium nitrate, 3.0395 g of cerium nitrate, 0.403 g of yttrium nitrate, 0.4491 g of ytterbium nitrate, 5.82 g of nickel nitrate, 8.08 g of iron nitrate; the remaining preparation steps were the same as those in Example 1.
[0047] Example 3
[0048] The difference from Example 1 is only that in Example 3, the types and amounts of some metal salts in step (1) were adjusted, specifically: 13.067 g of barium nitrate, 0.2145 g of zirconium nitrate, 1.5198 g of cerium nitrate, 0.2015 g of yttrium nitrate, 0.2246 g of ytterbium nitrate, 6.548 g of cobalt nitrate, 9.09 g of iron nitrate; the remaining preparation steps were the same as those in Example 1.
[0049] Example 4
[0050] The difference from Example 1 is only that in Example 4, the types and amounts of some metal salts in step (1) were adjusted, specifically: 13.067 g of barium nitrate, 0.2145 g of zirconium nitrate, 1.5198 g of cerium nitrate, 0.2015 g of yttrium nitrate, 0.2246 g of ytterbium nitrate, 9.09 g of iron nitrate, 6.548 g of cobalt nitrate; the remaining preparation steps were the same as those in Example 1.
[0051] Example 5
[0052] The difference from Example 1 is only that in Example 5, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 0.2145 g of zirconium nitrate, 1.5198 g of cerium nitrate, 0.2015 g of yttrium nitrate, 0.2246 g of ytterbium nitrate, 9.09 g of iron nitrate, and 6.5475 g of nickel nitrate; the remaining preparation steps are the same as those in Example 1.
[0053] Example 6
[0054] The difference from Example 1 is only that in Example 6, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 1.0725 g of zirconium nitrate, 7.5989 g of cerium nitrate, 2.015 g of yttrium nitrate, 4.365 g of nickel nitrate, and 4.04 g of iron nitrate; the remaining preparation steps are the same as those in Example 1.
[0055] Example 7
[0056] The difference from Example 1 is only that in Example 7, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 1.075 g of zirconium nitrate, 7.5988 g of cerium nitrate, 2.015 g of yttrium nitrate, and 7.275 g of nickel nitrate; the remaining preparation steps are the same as those in Example 1.
[0057] Example 8
[0058] The difference from Example 1 is only that in Example 8, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 0.429 g of zirconium nitrate, 3.0395 g of cerium nitrate, 0.403 g of yttrium nitrate, 0.4491 g of ytterbium nitrate, and 11.64 g of nickel nitrate; the remaining preparation steps are the same as those in Example 1.
[0059] Comparative Example 1
[0060] The difference from Example 1 is only that in Comparative Example 1, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 18.34 g of zirconium nitrate, 1.9143 g of yttrium nitrate, and 0.7275 g of nickel nitrate; the remaining preparation steps are the same as those in Example 1.
[0061] Comparative Example 2
[0062] The difference from Example 1 is only that in Comparative Example 2, the types and dosages of some metal salts in step (1) are adjusted, specifically using: 13.067 g of barium nitrate, 17.3745 g of zirconium nitrate, 1.8135 g of yttrium nitrate, and 1.455 g of nickel nitrate; the remaining preparation steps are the same as those in Example 1.
[0063] Comparative Example 3
[0064] The difference from Example 1 is only that in Comparative Example 3, the types and dosages of some metal salts in step (1) were adjusted, specifically using: 13.067 g of barium nitrate, 0.1073 g of zirconium nitrate, 0.76 g of cerium nitrate, 0.1008 g of yttrium nitrate, 0.1123 g of ytterbium nitrate, and 13.8225 g of nickel nitrate; the remaining preparation steps were the same as those in Example 1.
[0065] Material Characterization and Ammonia Decomposition Performance Test
[0066] 1. Material Characterization
[0067] Figure 1 SEM images of the perovskite oxide prepared in Example 1 before (a) and after (b) reduction. From Figure 1 it can be seen that after hydrogen reduction, dense nanoparticles were precipitated on the surface of the perovskite oxide. After XRD and EDX tests, they were determined to be active metals α-Fe and Co-Fe alloy.
[0068] Figure 2 TEM image of the non-noble metal ammonia decomposition catalyst prepared in Example 1. From Figure 2 it can be seen that the precipitated nanoparticles only contain Co and Fe metal elements.
[0069] 2. Ammonia Decomposition Performance Test
[0070] 0.1 g of the non-noble metal ammonia decomposition catalyst was mixed evenly with 2 mL of gaseous SiO2 and then fixed in a quartz tube. The quartz tube was fixed in a fixed-bed reactor, and ammonia was introduced for ammonia decomposition performance test. The decomposition efficiencies of the catalysts prepared in Examples 1-6 and Comparative Examples 1-6 were measured respectively under the conditions of a temperature of 600 °C and a space velocity of 18,000 mL / (g·h). The results are shown in Table 1.
[0071] Table 1
[0072]
[0073]
[0074] As can be seen from Table 1, the ammonia decomposition rates of the non-noble metal ammonia decomposition catalysts prepared in Examples 1-8 of the present invention are significantly better than those of the ammonia decomposition catalysts prepared in Comparative Examples 1-3; under the conditions of 600 °C and 18,000 mL / (g·h), the ammonia decomposition rate of Example 1 is the best, reaching 96.8%.
[0075] Generally, when the same active metal loading is dissolved in-situ, the alloying effect of the bimetallic components results in a better ammonia decomposition conversion rate than that of the monometallic components; for example, the catalytic performances of Example 1 and Example 2 are better than those of Example 8, and the catalytic performances of Example 5 and Example 6 are better than those of Example 7.
[0076] Compared with Example 2, the catalytic performance of Example 1 is better; compared with Example 4, the catalytic performance of Example 3 is better; thus, it can be seen that the catalytic performance of the iron-cobalt bimetal is better than that of the iron-nickel bimetal, and optimizing the combination type of the bimetals can further improve the catalytic performance.
[0077] Comparing the ammonia decomposition rates of Examples 1-6, it can be seen that the catalytic performance is the best when the content x of the B'bimetal is 0.8, which is better than the catalytic performances when the content x is 0.9 and 0.5. Thus, it can be seen that optimizing the content of the bimetals can further improve the catalytic performance.
[0078] Comparing the ammonia decomposition rates of Example 7, Example 8, and Comparative Examples 1-3, it can be seen that the catalytic performance is the best when the content x of the monometallic nickel is 0.5, which is better than the catalytic performance when the content x is 0.8, and significantly better than the catalytic performances when the content x is 0.05, 0.1, and 0.95. Thus, it can be seen that optimizing the content of the monometallic nickel can further improve the catalytic performance.
[0079] Figure 3 The results of the 100h stability test after the non-noble metal ammonia decomposition catalyst prepared for Example 1 was placed at room temperature for 5 months. From Figure 3 It can be seen that under the conditions of 600°C and 18000 mL / (g·h), after 100h of stability test, the ammonia decomposition rate still remained above 90%.
[0080] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.
Claims
1. A non-noble metal ammonia decomposition catalyst, characterized in that, Its chemical formula is AB 1-x B’ x O 3-δ ; where 0.5 ≤ x ≤ 0.9; δ represents oxygen vacancies; element A includes one of La, Sr, Ba, Pr, and Ca; element B includes one or several of Zr, Ce, Y, Yb, Cr, Mn, and Mg; element B’ includes one or two of Fe, Co, and Ni.
2. The non-noble metal ammonia decomposition catalyst according to claim 1, characterized in that, The B' element is distributed on the surface of the carrier of the non-noble metal ammonia decomposition catalyst in the form of nanoparticles.
3. The non-noble metal ammonia decomposition catalyst according to claim 1, characterized in that, The B' element is selected from Fe and Co, or the B' element is selected from Fe and Ni.
4. The preparation method of the non-noble metal ammonia decomposition catalyst according to any one of claims 1-3, characterized in that, It is prepared by the glycine-nitrate method.
5. The preparation method according to claim 4, wherein The glycine-nitrate method includes the following steps: (1) Prepare a metal salt solution according to the stoichiometric ratio of the non-noble metal ammonia decomposition catalyst, and then mix it with glycine to obtain a precursor solution; (2) Heat and stir the precursor solution to obtain a gel; (3) Heat the gel, and the gel undergoes spontaneous combustion upon heating to obtain a powder; (4) Calcinate the powder to obtain a perovskite oxide; (5) Place the perovskite oxide in a reducing atmosphere for reduction treatment to obtain a non-noble metal ammonia decomposition catalyst.
6. The preparation method according to claim 5, wherein In step (1), the molar ratio of glycine to the total molar amount of metal ions in the metal salt solution is (1.5-3.5):
1.
7. The preparation method according to claim 5, characterized in that, In step (3), the heating temperature is 150-300°C.
8. The preparation method according to claim 5, characterized in that In step (4), the calcination temperature is 1000-1400°C, and the time is 2-5 h.
9. The preparation method according to claim 5, characterized in that, In step (5), the reduction temperature is 500-800°C, and the time is 1-4 h.
10. Application of the non-noble metal ammonia decomposition catalyst according to any one of claims 1-3 in ammonia decomposition for hydrogen production.