Preparation method of Ru-based catalyst for hydrogen production through ammonia decomposition
By combining the sol-gel method and the ball milling and kneading method, a high-dispersion Ru-based catalyst was prepared, and the ammonia decomposition performance of the catalyst was improved by using alkali metal additives, which solved the problem of low efficiency of existing Ru-based catalysts at low temperatures, and achieved efficient and low-cost hydrogen production effect of ammonia decomposition.
Patent Information
- Application Number
- CN202510234199.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-05-16
AI Technical Summary
The existing Ru-based catalysts have low efficiency in ammonia decomposition and hydrogen production under low temperature conditions, and the preparation process is complicated, making it difficult to achieve high catalytic activity.
Ru-based catalysts were prepared by combining sol-gel method and ball milling kneading method. By adding alkali metal as additives, the dispersion and ammonia decomposition properties of the catalyst were improved.
The efficiency of hydrogen production by ammonia decomposition at low temperatures is significantly improved, reaching an ammonia decomposition efficiency of 91.57%. The preparation process is simple, the cost is low, and the catalyst is stable.
Smart Images
Figure SMS_1 
Figure SMS_2 
Figure HDA0005292308010000011
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia. Background Art
[0002] As an environmentally friendly sustainable energy, hydrogen energy has the advantages of wide sources, high combustion calorific value and easy large-scale development. It is considered to be an important part of the future energy structure and has attracted widespread attention worldwide. However, there are many constraints on the development of hydrogen energy. The first is the safety of hydrogen storage and transportation. Hydrogen has low volume energy density and high danger, which has become a bottleneck for large-scale industrial application of hydrogen. Therefore, the development of efficient and convenient transportation carriers is still an urgent need for the development of hydrogen. At present, when metal materials are used to store and transport hydrogen, hydrogen molecules will enter the metal lattice to cause local dislocation of metal atoms, resulting in huge internal stress. In severe cases, cracks may occur in the metal material and hydrogen leakage may occur. When liquid hydrogen is used for transportation, the liquefaction of hydrogen is very difficult, and the liquefaction equipment has high requirements and high energy consumption. In contrast, NH3 has an extremely high hydrogen content (17.8wt%), and the infrastructure for ammonia production, storage and transportation is complete and the technology is mature. NH3 can be stored as a high-purity liquid at 20°C and 0.8MPa while decomposing without producing CO. X .
[0003] NH3 is a very promising hydrogen carrier. The development of energy storage systems with ammonia as hydrogen storage is expected to solve the problem of traditional high-pressure hydrogen storage and transportation. Hydrogen production by ammonia decomposition is increasingly attracting people's attention as a green and environmentally friendly technology. Ammonia decomposition can produce high-purity hydrogen, and at the same time can effectively solve problems such as the difficulty in hydrogen storage and transportation. According to the research of the inventors, at present, the key to the development of ammonia as a hydrogen carrier lies in low-temperature and efficient ammonia decomposition catalysts. Among the active metals that catalyze the decomposition of ammonia, Ru has the highest activity, but its scarcity leads to high prices. Therefore, it is necessary to develop low-load, highly active, highly dispersed Ru-based catalysts to further improve the efficiency of hydrogen production by ammonia decomposition and improve the atomic utilization of Ru.
[0004] Although the currently reported methods for preparing Ru-based catalysts for ammonia decomposition reactions reduce the loading amount of Ru metal, the prepared Ru-based catalysts generally have problems such as poor ammonia decomposition efficiency and a relatively complicated catalyst preparation process. Therefore, in view of the above situation, the current low-loaded Ru-based ammonia decomposition hydrogen production catalyst is difficult to achieve high catalytic activity under low temperature conditions. Research and development of efficient ammonia decomposition hydrogen production catalysts is of great significance for solving the problem of hydrogen energy storage and transportation. Summary of the invention
[0005] Based on previous research and existing problems, the present invention proposes a method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia after further research and analysis. The catalyst preparation process further improves the dispersion of Ru metal by combining the sol-gel method and the ball milling kneading method, and at the same time, adds alkali metal as an auxiliary agent, which greatly improves the ammonia decomposition performance of the catalyst. At the same time, it has the advantages of low preparation cost, simple preparation process, high activity, etc.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] A method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia comprises the following steps:
[0008] S1. Quantitatively weigh a catalyst support precursor salt and an active component metal precursor salt and simultaneously dissolve them in a solvent to obtain a mixed metal salt solution;
[0009] S2, dissolving citric acid in a solvent to prepare a metal complexing agent solution of a desired concentration;
[0010] S3, adding the solution obtained in S2 to the metal salt solution obtained in S1 respectively, and after the solution is fully mixed, stirring evenly and heating;
[0011] S4, adding ammonia water dropwise to the heated mixed solution, maintaining the pH value of the solution between 8 and 9, and continuously stirring to obtain a complex metal gel;
[0012] S5, washing and drying the gel obtained in S4 for multiple times, and then grinding it to obtain a metal complex xerogel of the active component;
[0013] S6, using the same method as S1-S5 to prepare an additive metal complex metal xerogel;
[0014] S7, mixing the complex metal dry gel of the active component obtained in S5 and the complex metal dry gel of the auxiliary metal in S6, grinding them into powder, and calcining the powder to obtain a Ru-based catalyst.
[0015] Preferably, in S1, the active component is Ru, the catalyst carrier is a sheet-structured CeO2, and the Ru component accounts for 0.5-5wt% of the catalyst mass according to the element content.
[0016] Preferably, in S6, the promoter metal is one or a combination of sodium, potassium, and cesium, and the promoter metal component accounts for 1 to 20 wt% of the catalyst mass in terms of metal element content;
[0017] Preferably, in S1, the metal precursor salt of the catalyst carrier in the metal salt solution is one or a combination of cerium nitrate, cerium oxalate and cerium sulfate.
[0018] Preferably, in S6, the additive metal salt precursor salt used to prepare the additive metal complex metal xerogel is one or more of sodium nitrate, potassium nitrate, cesium acetate, and barium nitrate.
[0019] Preferably, in S1, S2 and S6, the solvent used to prepare the metal complex gel is one of deionized water, ethanol, ethylene glycol and propylene glycol.
[0020] Preferably, the ratio of the molecular weight of citric acid as a complexing agent to the metal ion in the mixed solution of S3 and S6 is 0.5:1 to 3:1, and the mixed solution is heated to 80-120° C. to prepare the gel.
[0021] Preferably, in S7, the calcination temperature is 450-650° C.; the calcination heating rate is 1-5° C. / min; and the calcination time is 3-6 h.
[0022] In addition, the present invention also proposes a Ru-based catalyst for ammonia decomposition to produce hydrogen, which is prepared by the above method. The catalyst is loaded into a reaction device and is reduced in an H2 or NH3 atmosphere to carry out ammonia decomposition to produce hydrogen reaction.
[0023] Preferably, the catalyst is used in the process of hydrogen production by decomposition of ammonia, and the hydrogen production by decomposition of ammonia is carried out in an NH3 atmosphere at normal pressure, the reaction temperature is within 350-650°C, and the NH3 gas flow rate ranges from 2000mL to 30000mL / (g cat h).
[0024] Compared with the existing technology, the present invention provides a method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia, which has the following beneficial effects:
[0025] (1) The present invention proposes a method for preparing a catalyst with Ru as an active component, a lamellar CeO2 carrier, and an alkali metal as an auxiliary agent, which improves the overall alkalinity of the catalyst carrier, enhances the overall electronegativity of the catalyst during the reaction, promotes the electron shift to the Ru metal, and modifies the electronic structure of the Ru metal. It can reduce the strength of the Ru-N bond, promote the desorption of N2 on the catalyst surface at low temperatures, and is beneficial to the further decomposition of the intermediates in the ammonia decomposition reaction, greatly improving the activity of the catalyst in the ammonia decomposition reaction. In addition, the use of a low load of precious metal ruthenium reduces the preparation cost of the catalyst.
[0026] (2) Compared with traditional catalysts, the catalyst prepared in the present invention has improved low-temperature ammonolysis efficiency. The ammonia decomposition efficiency of the catalyst prepared in the present invention for hydrogen production by ammonia decomposition reaches a maximum of 91.57% at 400°C and 97.31% at 450°C, which is much higher than the ammonia decomposition activity of catalysts prepared by other methods at the same loading amount.
[0027] (3) The preparation method proposed in the present invention combines the sol-gel method with the ball milling method to avoid the agglomeration of Ru due to the addition of additives during the gel preparation process, thereby improving the dispersion of Ru metal.
[0028] (4) The catalyst of the present invention is easy to prepare, and the prepared catalyst has a short start-up time for reaction and can operate stably for a long period of time. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 This is a TEM image of the catalyst proposed in Example 5 of the present invention.
[0030] Figure 2 This is the X-ray photoelectron spectrum of the catalyst proposed in Example 5 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION
[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.
[0032] Example 1
[0033] Take 10g of Ru(acac)3 and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120°C, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100°C to obtain the catalyst Ru-Ce complex metal dry gel. Take 9g of NaNO3·6H2O and 313.5g of Ce(NO3)3·6H2O and prepare Na-Ce complex metal dry gel using the same method as above. The two obtained dry gel precursors were mixed and placed in a ball mill for grinding. The ground mixed powder was calcined at 550°C in an air atmosphere for 4 hours to obtain a 1wtNa-1wt%Ru / CeO2 catalyst. After the calcination, the catalyst was pressed into tablets and then crushed into 20-40 mesh particles for hydrogen production by ammonolysis.
[0034] Example 2
[0035] Take 10g of Ru(acac)3 and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120℃, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100℃ to obtain the catalyst Ru-Ce complex metal dry gel. Take 6.6g of KNO3·6H2O and 313.5g of Ce(NO3)3·6H2O and use the same method as above to prepare K-Ce complex metal dry gel. The two obtained dry gel precursors were mixed and placed in a ball mill for grinding. The ground mixed powder was calcined at 550°C in air for 4 hours to obtain a 1wtK-1wt% Ru / CeO2 catalyst. After calcination, the catalyst was pressed into tablets and then crushed into 20-40 mesh particles for hydrogen production by ammonolysis.
[0036] Example 3
[0037] Take 10g of Ru(acac)3 and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120℃, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100℃ to obtain the catalyst Ru-Ce complex metal dry gel. Take 4.8g of Ba(NO3)2·6H2O and 313.5g of Ce(NO3)3·6H2O and prepare Ba-Ce complex metal dry gel using the same method as above. The two obtained dry gel precursors were mixed and placed in a ball mill for grinding. The ground mixed powder was calcined at 550°C in air for 4 hours to obtain a 1wtBa-1wt%Ru / CeO2 catalyst. After calcination, the catalyst was pressed into tablets and then crushed into 20-40 mesh particles for hydrogen production by ammonolysis.
[0038] Example 4
[0039] Take 10g of Ru(acac)3 and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120℃, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100℃ to obtain the catalyst Ru-Ce complex metal dry gel. Take 3.7g of CH3COOCs and 313.5g of Ce(NO3)3·6H2O and prepare Cs-Ce complex metal dry gel using the same method as above. The two obtained dry gel precursors were mixed and placed in a ball mill for grinding. The ground mixed powder was calcined at 550°C in air for 4 hours to obtain a 1wtCs-1wt%Ru / CeO2 catalyst. After calcination, the catalyst was pressed into tablets and then crushed into 20-40 mesh particles for hydrogen production by ammonolysis.
[0040] Example 5
[0041] Take 10g of Ru(acac)3 and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120℃, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100℃ to obtain the catalyst Ru-Ce complex metal dry gel. Take 18.5g of CH3COOCs and 313.5g of Ce(NO3)3·6H2O and prepare Cs-Ce complex metal dry gel using the same method as above. The two obtained dry gel precursors were mixed and placed in a ball mill for grinding. The ground mixed powder was calcined at 550°C in air for 4 hours to obtain a 5wtCs-1wt%Ru / CeO2 catalyst. After calcination, the catalyst was pressed into tablets and then crushed into 20-40 mesh particles for hydrogen production by ammonolysis.
[0042] Comparative Example 1
[0043] Take 313.5g of Co(NO3)2·6H2O and dissolve it in 500mL of ethylene glycol, and stir until it is completely dissolved to obtain a solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, and stir until it is completely dissolved. After the two solutions are fully mixed, stir and heat to 120℃, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, and stir for 4h to promote the continuous production of colloid. After the reaction is complete, continue to heat and evaporate the solvent to obtain a complex metal gel. After washing the obtained gel several times and drying it at 100℃, grind it to obtain a catalyst precursor dry gel, and calcine it at 550℃ in an air atmosphere for 4h to obtain a CeO2 carrier. Dissolve 5g of Ru(acac)3 and 4.5g of NaNO3 in methanol solution to prepare an equal volume of impregnation solution, and impregnate the impregnation solution on 126.4g of CeO2 powder. The catalyst precursor was obtained by impregnation for 24 hours, and then placed in an oven at 80°C for drying for 12 hours to obtain the desired catalyst precursor. The precursor was calcined at 550°C in air atmosphere for 4 hours to obtain a 1wtNa-1wt%Ru / CeO2-1 catalyst.
[0044] Comparative Example 2
[0045] Take 5g of Ru(acac)3, 4.5g of NaNO3·6H2O and 313.5g of Ce(NO3)3·6H2O and dissolve them in 500mL of ethylene glycol, stir until completely dissolved to obtain a mixed metal salt solution. Then take 306.1g of citric acid and dissolve it in 500mL of ethylene glycol, stir until completely dissolved. After the two solutions are fully mixed, stir and heat to 120°C, add ammonia water drop by drop to the heated mixed solution, maintain the pH of the solution between 8-9, stir for 4h to promote the continuous production of colloid, and continue to heat and evaporate the solvent after the reaction is complete to obtain Ru-Ce complex metal gel. The obtained gel is washed several times and dried at 100°C to obtain the catalyst Ru-Na-Ce complex metal dry gel. The obtained dry gel is roasted at 550°C in air atmosphere for 4h to obtain 1wtNa-1wt%Ru / CeO2-2 catalyst. After calcination, the catalyst is pressed into tablets and then crushed into 20-40 mesh particles for use in the hydrogen production reaction by ammonolysis.
[0046] Figure 1The structural morphology of the 5wtCs-1wt%Ru / CeO2 catalyst in Example 5 was characterized. The TEM image of the catalyst showed a lamellar CeO2 structure, and no clusters and diffraction peaks of Ru and Cs elements were found on the catalyst surface. The Ru and Cs atoms on the surface were highly dispersed in the carrier. The distribution of various elements was observed by high-angle annular dark field scanning transmission electron microscopy-energy spectrum scanning (HAADF-STEM-mapping) technology. The Ru, Ce, and Cs elements were evenly dispersed on the catalyst, further confirming the high dispersion characteristics of Ru and Cs.
[0047] like Figure 2 As shown, the composition and chemical state of the surface elements of the catalysts of Example 5 and Comparative Example 1 were analyzed by X-ray photoelectron spectroscopy, wherein the 3p3 / 2 orbital located near 463.1eV was deconvoluted into two peaks at 462.6eV and 465.9eV, and the 3p1 / 2 orbital located near 486eV was deconvoluted into two peaks at 485.1eV and 487.2eV. The peaks at 462.6eV and 485.1eV correspond to Ru 4+ , 465.9 eV and 487.2 eV correspond to Ru 6+ In Example 1, the interaction between Ru and the carrier is enhanced, the electron density on the Ru surface increases, and the Ru binding energy moves toward the low binding energy direction. 4+ Species can promote the transfer of electrons to the active center Ru during the reaction, accelerate the recombination and desorption of N2, and thus effectively improve the hydrogen production performance of Ru / CeO2 catalyst.
[0048] The catalysts of the above five embodiments and two comparative examples were tested under the same conditions, wherein the feed gas was 99.999% high purity ammonia and the air velocity was 6000 ml / (g cat h), the test results are shown in Table 1 below:
[0049]
[0050]
[0051] As shown in Table 1, the ammonia decomposition performance of the modified 1wtNa-1wt%Ru / CeO2 catalyst prepared by the method is significantly higher than that of the comparative example 1 prepared by the co-impregnation method and the comparative example 2 prepared by the sol-gel method in one step, and its ammonia decomposition efficiency reaches 89.07% at 450°C and 95.82% at 500°C. This is because the Ru dispersion in the Ru / CeO2 catalyst prepared by the method is higher, and the Ru-Ce bimetallic synergistic effect effectively promotes the formation of a high content of electron-rich Ru atomic active sites, which can weaken the hydrogen inhibition effect on the catalyst surface, and is conducive to the activation of NH3 and the recombination and desorption of N. The type and loading of the auxiliary metal are selected to further optimize the surface alkalinity and pore structure of the catalyst, improve the electron transfer ability between the reduced catalyst CeO2 carrier and the Ru metal surface, and further contribute to the breaking of the Ru-N bond during the reaction, thereby improving the reaction activity. Therefore, CeO2 has a higher ammonia decomposition performance than other metal oxide carriers. In Example 5, which uses 5 wt % Cs metal as an auxiliary agent, the catalyst has more strong alkaline sites and further strengthens the synergistic effect between the active metal and the carrier metal, thereby maximally improving the ammonia decomposition performance of the catalyst.
[0052] The present invention uses Ru metal as an active component, CeO2 as a carrier, and alkali metal as an auxiliary agent to prepare a series of high-performance low-load Ru ammonia decomposition hydrogen production catalysts. The synergistic effect of the CeO2 carrier, the Ru metal active component, and the alkali metal auxiliary agent optimizes the surface properties of the catalyst, promotes Ru dispersion, and optimizes the reduction performance of surface Ru through electron transfer, which helps to break the Ru-N bond during the reaction, and achieves nearly complete ammonia decomposition conversion (97.31%) at low loading and low temperature (450°C). The catalyst prepared by this method has the advantages of relatively low price, high activity, good stability, etc.
[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.
Claims
1. A method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia, characterized in that: The steps include: S1. Quantitatively weigh a catalyst support precursor salt and an active component metal precursor salt and simultaneously dissolve them in a solvent to obtain a mixed metal salt solution; S2, dissolving citric acid in a solvent to prepare a metal complexing agent solution of a desired concentration; S3, adding the solution obtained in S2 to the metal salt solution obtained in S1 respectively, and after the solution is fully mixed, stirring evenly and heating; S4, adding ammonia water dropwise to the heated mixed solution, maintaining the pH value of the solution between 8 and 9, and continuously stirring to obtain a complex metal gel; S5, washing and drying the gel obtained in S4 for multiple times, and then grinding it to obtain a metal complex xerogel of the active component; S6, using the same method as S1-S5 to prepare an additive metal complex metal xerogel; S7, mixing the complex metal dry gel of the active component obtained in S5 and the complex metal dry gel of the auxiliary metal in S6, grinding them into powder, and calcining the powder to obtain a Ru-based catalyst.
2. A method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 1, characterized in that: In S1, the active component is Ru, the catalyst carrier is CeO2 with a lamellar structure, and the Ru component accounts for 0.5 to 5 wt% of the catalyst mass in terms of element content.
3. The method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 1, characterized in that: In S6, the promoter metal is one or a combination of sodium, potassium and cesium, and the promoter metal component accounts for 1 to 20 wt% of the catalyst mass in terms of metal element content.
4. The method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 2, characterized in that: In S1, the metal precursor salt of the catalyst carrier in the metal salt solution is configured to be one or a combination of cerium nitrate, cerium oxalate, and cerium sulfate.
5. The method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 3, characterized in that: In S6, the additive metal salt precursor salt used to prepare the additive metal complex metal xerogel is one or more of sodium nitrate, potassium nitrate, cesium acetate, and barium nitrate.
6. The method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 1, characterized in that: In S1, S2 and S6, the solvent used to prepare the metal complex gel is one of deionized water, ethanol, ethylene glycol and propylene glycol.
7. The method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 1, characterized in that: The ratio of the molecular weight of citric acid as a complexing agent to the metal ion in the mixed solution of S3 and S6 is 0.5:1 to 3:1, and the mixed solution is heated to 80-120° C. to prepare a gel.
8. A method for preparing a Ru-based catalyst for hydrogen production by decomposing ammonia according to claim 7, characterized in that: In S7, the calcination temperature is 450-650°C; the calcination heating rate is 1-5°C / min; and the calcination time is 3-6h.
9. A Ru-based catalyst for hydrogen production by decomposing ammonia, prepared according to the method according to any one of claims 1 to 8, characterized in that: The catalyst is loaded in a reaction device and reduced in an atmosphere of H2 or NH3 to carry out ammonia decomposition and hydrogen production reaction.
10. The use of the Ru-based catalyst in hydrogen production by decomposing ammonia according to claim 9, characterized in that: The catalyst is used in the process of hydrogen production by decomposition of ammonia. The reaction of hydrogen production by decomposition of ammonia is carried out in an NH3 atmosphere at normal pressure. The reaction temperature is within 350-650℃ and the flow rate of NH3 gas is in the range of 2000mL~30000mL / (g cat h).