Ruthenium atomic cluster composite catalyst for hydrogen production by means of ammonia decomposition, and preparation method therefor

Abstract

Provided are a ruthenium atomic cluster composite catalyst for hydrogen production by means of ammonia decomposition, and a preparation method therefor. The preparation method comprises: dispersing tripolycyanamide, cyanuric acid and an amino acid in an aqueous solution of methanol, and stirring same to form a mixed system; adding a rare earth metal precursor salt to the mixed system, continuously stirring same, heating same to evaporate the solvent, grinding a resulting white solid into powder, and transferring same to a high-temperature environment for pyrolysis, so as to obtain a nitrogen-rich carbon support that has been modified by a rare earth element; and dissolving a ruthenium precursor salt and urea in deionized water to form an impregnation solution, adding the nitrogen-rich carbon support that has been modified by a rare earth element to the impregnation solution, performing impregnation under stirring, and washing, drying and roasting a solid collected from filtration, so as to obtain a catalyst. In the present invention, on the basis of the characteristic of a high specific surface area of the nitrogen-rich carbon support and the modification of the electronic state of active sites, i.e., ruthenium atomic clusters, with rare earth elements, the amount of ruthenium is reduced, and NH3 adsorption performance and N-H bond cleavage capability are improved, thereby achieving efficient catalytic promotion of ammonia decomposition for hydrogen production under low-temperature conditions.

Description

A ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition and its preparation method

[0001] This application claims priority to Chinese Patent Application No. 202510477854.7, filed on April 16, 2025, entitled "A Ruthenium Cluster Composite Catalyst for Hydrogen Production from Ammonia Decomposition and Preparation Method thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of catalysts and their preparation technology, and in particular to a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition and its preparation method. Background Technology

[0003] Energy is a key driving force for national development and the progress of human society. Hydrogen energy, as an abundant, green, low-carbon, and widely applicable secondary energy source, not only helps in the effective absorption of renewable energy but also assists the power grid in controlled peak shaving and cross-seasonal and cross-regional energy storage. Furthermore, it accelerates the decarbonization process in industries, construction, and transportation, undoubtedly making it a crucial force in promoting the low-carbon transformation of energy. However, it must be noted that its extremely stringent storage and transportation requirements significantly restrict the wider adoption and application of hydrogen energy, preventing its full potential from being realized. Breakthroughs and innovations in storage and transportation technologies are urgently needed to bring new opportunities and vitality to the transformation of the energy sector.

[0004] Ammonia (NH3) is a common chemical hydrogen storage material with a hydrogen storage capacity as high as 17.7 wt.%, and it can be easily stored in liquid form at room temperature and low pressure. Ammonia decomposition for hydrogen production is a highly valuable, clean, and efficient in-situ green hydrogen production technology that can effectively solve the problems of traditional high-pressure hydrogen storage. However, in reality, ammonia decomposition for hydrogen production faces bottlenecks. Typically, ammonia decomposition for hydrogen production requires high temperatures of 600-800℃, which can cause catalyst deactivation through sintering and significant energy consumption.

[0005] Currently, ruthenium-based catalysts are considered to be the most active ammonia decomposition catalysts at low temperatures. However, the high ruthenium content in existing catalysts leads to high catalyst costs, making them unsuitable for commercial use. Furthermore, ruthenium-based catalysts are susceptible to hydrogen poisoning, meaning that a large amount of adsorbed hydrogen on the catalyst surface inhibits ammonia decomposition, greatly affecting the activity and stability of ruthenium-based catalysts. At the same time, the ammonia decomposition activity temperature range is still very high (>450℃), resulting in high energy consumption.

[0006] Therefore, developing novel low-ruthenium-loaded cluster composite catalysts to achieve efficient ammonia decomposition under mild conditions is of great significance. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides a ruthenium atom cluster composite catalyst for ammonia decomposition to produce hydrogen and a preparation method thereof. The catalyst modifies a nitrogen-rich carbon support with rare earth elements and supports ruthenium atom clusters. The resulting composite catalytic material has the advantage of low ruthenium loading and can achieve efficient ammonia decomposition under mild conditions.

[0008] The specific details of the invention are as follows:

[0009] In a first aspect, the present invention provides a method for preparing a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition, the method comprising:

[0010] Melamine, cyanuric acid, and amino acids were dispersed in a methanol aqueous solution and stirred to form a mixed system. Rare earth metal precursor salts were added to the mixed system and stirred continuously for 2-6 hours. The solvent was then heated to evaporate the solvent, and a white solid was obtained.

[0011] The white solid was ground into powder and then pyrolyzed at 700-850°C. The resulting black powder was a nitrogen-rich carbon support modified with rare earth elements, wherein the nitrogen content was between 10-20 wt.%.

[0012] The precursor ruthenium salt and urea are dissolved in deionized water to form an impregnation solution. The rare earth element-modified nitrogen-rich carbon support is added to the impregnation solution, and the mixture is stirred and impregnated. The solid collected by filtration is washed, dried and calcined to obtain the ruthenium atom cluster composite catalyst.

[0013] Optionally, the concentration of the methanol aqueous solution is 20-50 wt.%, the molar ratio of melamine to cyanuric acid is 0.8-1.2, and the molar ratio of melamine to amino acids is 1.0-1.5.

[0014] Optionally, the amino acid is glycine, alanine, serine, or glutamic acid.

[0015] Optionally, the rare earth metal precursor salt is lanthanum nitrate, lanthanum acetate, cerium nitrate, or cerium acetate, and the amount of the rare earth metal precursor salt added accounts for 1.0-5.0 wt.% of the total mass of melamine, cyanuric acid, and amino acids.

[0016] Optionally, the pyrolysis is carried out under an argon or nitrogen atmosphere, with a heating rate of 2-5 °C / min.

[0017] Optionally, the temperature of the impregnation solution is 70-90°C;

[0018] The stirring and impregnation time is 6-12 hours.

[0019] Optionally, the precursor ruthenium salt is ruthenium trichloride or ruthenium nitrite;

[0020] The concentration of ruthenium in the impregnation solution is 0.5-5.0 mg Ru / mL, and the concentration of urea in the impregnation solution is 20-100 mg / mL;

[0021] The mass ratio of ruthenium in the impregnation solution to the mass ratio of the rare earth element-modified nitrogen-rich carbon support is 0.5-2.0 wt.%.

[0022] Optionally, the solids collected by filtration are subjected to washing, drying and calcination treatment, including: washing with ethanol and deionized water 2-3 times respectively, vacuum drying at 60-90°C for 2-12 hours, and then reducing at 200-300°C for 1-3 hours.

[0023] In a second aspect, the present invention provides a ruthenium atom cluster composite catalyst obtained by the preparation method described in the first aspect above.

[0024] Optionally, when the ruthenium cluster composite catalyst is used to catalyze the ammonia decomposition reaction to produce hydrogen, the space velocity of the ammonia gas is 5000-50000 mL·g. -1 ·h -1 The reaction temperature is 200-500℃ and the reaction pressure is 0.1-5.0MPa.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention provides a method for preparing a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition. The preparation method includes: dispersing melamine, cyanuric acid, and amino acids in a methanol aqueous solution and stirring to form a mixed system; adding a rare earth metal precursor salt to the mixed system, stirring continuously for 2-6 hours, and heating to evaporate the solvent to obtain a white solid; grinding the white solid into powder and transferring it to pyrolysis at 700-850℃ to obtain a black powder, which is a rare earth element-modified nitrogen-rich carbon support; dissolving the precursor ruthenium salt and urea in deionized water to form an impregnation solution; adding the rare earth element-modified nitrogen-rich carbon support to the impregnation solution and stirring for impregnation; filtering and collecting the solid, and then washing, drying, and calcining to obtain the ruthenium cluster composite catalyst.

[0027] The ruthenium cluster composite catalyst prepared by the method of this invention, based on the high specific surface area of ​​the nitrogen-rich carbon support and the modification of the electronic state of the ruthenium clusters at the active sites by rare earth elements, can significantly reduce the amount of precious metals used, effectively improve the NH3 adsorption performance and NH bond breaking ability, and achieve highly efficient catalytic promotion of ammonia decomposition to hydrogen production under low-temperature conditions. This catalyst exhibits high catalytic activity, achieving an ammonia decomposition conversion rate of 93.7% under reaction conditions of 375℃ and 0.1 MPa.

[0028] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 shows a flowchart of the preparation method of the ruthenium atom cluster composite catalyst provided in the embodiment of the present invention;

[0031] Figure 2 shows a transmission electron microscope image of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention;

[0032] Figure 3 shows the EDS elemental analysis diagram of the ruthenium atom cluster composite catalyst provided in the embodiment of the present invention;

[0033] Figure 4 shows the ammonia conversion rate of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention;

[0034] Figure 5 shows a comparison of the ammonia decomposition performance of the ruthenium atom cluster composite catalysts provided in the embodiments and comparative examples of the present invention;

[0035] Figure 6 illustrates the effect of reaction temperature on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention;

[0036] Figure 7 illustrates the effect of reaction pressure on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention;

[0037] Figure 8 illustrates the effect of space velocity on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention;

[0038] Figure 9 shows the long-cycle ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention. Specific Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Specific experimental steps or conditions are not specified in the examples; however, they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products.

[0041] In a first aspect, the present invention provides a method for preparing a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition. Figure 1 shows a flowchart of the preparation method of the ruthenium cluster composite catalyst provided by the present invention. As shown in Figure 1, the preparation method includes:

[0042] S1. Melamine, cyanuric acid, and amino acids are dispersed in a methanol aqueous solution and stirred to form a mixed system. Rare earth metal precursor salts are added to the mixed system and stirred continuously for 2-6 hours. The solvent is then heated to evaporate the solvent and a white solid is obtained.

[0043] In this specific implementation step, melamine, cyanuric acid, and amino acids are used as carbon and nitrogen sources. Melamine (C3H6N6) and cyanuric acid (C3H3N3O3) form a supramolecular network structure (similar to the melamine-cyanuric acid complex, MCA) in a methanol-water solution, providing a nitrogen source and carbon skeleton for the subsequent nitrogen-rich carbon support. Amino acids (such as lysine and glutamic acid) contain -NH2 and -COOH groups, which can form peptide bonds (-CO-NH-) with melamine or cyanuric acid and partially embed themselves in the MCA structure, providing additional nitrogen or carbon sources during the subsequent pyrolysis process and affecting the pore structure of the nitrogen-rich carbon support.

[0044] In practice, melamine and cyanuric acid are first dispersed in a methanol-water solution and magnetically stirred at room temperature for 2-6 hours. During this process, melamine (C3H6N6) and cyanuric acid (C3H3N3O3) form a supramolecular network structure (similar to a melamine-cyanuric acid complex, MCA) in the methanol-water solution. Then, specific types of amino acids are added to the above-mentioned suspension containing melamine and cyanuric acid and magnetically stirred at room temperature for 2-6 hours. During this process, the carboxyl groups of the amino acids combine with the amino groups of melamine, and the amino groups of the amino acids combine with the carboxyl groups of cyanuric acid, and are partially embedded in the MCA structure. This allows the exposed amino acid side chains (such as hydrophobic chains or polar groups) to play a role in regulating the pore structure and surface chemical properties of the complex.

[0045] Furthermore, after melamine, cyanuric acid, and amino acids form a complex, it is further mixed with rare earth metal precursor salt. During this process, the rare earth metal precursor salt dissolves and releases rare earth ions, which coordinate with the organic components. This coordination effect allows the rare earth ions to be uniformly dispersed in the organic framework, thereby forming a network organic supramolecular-rare earth complex. Finally, the mixed system is heated to evaporate the solvent, resulting in a white solid—the network organic supramolecular-rare earth complex. During this process, the temperature at which the solvent evaporates does not exceed 100°C. The rare earth metal and the network organic supramolecular are effectively fixed through coordination bonds, preventing aggregation during subsequent pyrolysis, thus obtaining a nitrogen-rich carbon support in which the rare earth metal is uniformly dispersed in the organic framework.

[0046] In some embodiments, the concentration of the methanol-water solution in the mixed system is 20-50 wt.%, the molar ratio of melamine to cyanuric acid is between 0.8 and 1.2, and the molar ratio of melamine to amino acids is between 1.0 and 1.5.

[0047] In some embodiments, the amino acid is selected from glycine, alanine, serine, or glutamic acid.

[0048] In some embodiments, the rare earth metal precursor salt is lanthanum nitrate, lanthanum acetate, cerium nitrate, or cerium acetate, and the amount of rare earth metal precursor salt added accounts for 1.0-5.0 wt.% of the total mass of melamine, cyanuric acid, and amino acids.

[0049] S2. Grind the white solid into powder and transfer it to pyrolysis at 700-850℃. The resulting black powder is a nitrogen-rich carbon carrier modified with rare earth elements.

[0050] In this specific step, the white solid obtained in step S1 is ground into powder and vacuum dried at 25-90℃ for 2-12 hours. The resulting solid powder is placed in a porcelain boat and transferred to a tube furnace for pyrolysis at 700-850℃ for 2-5 hours. The pyrolysis atmosphere is argon or nitrogen, and the heating rate is 2-5℃ / min. The resulting black powder is a nitrogen-rich carbon support modified with rare earth elements, and the nitrogen content in the nitrogen-rich carbon support is between 10-20 wt.%.

[0051] During pyrolysis, the melamine-cyanuric acid complex undergoes condensation polymerization to form graphite-like carbon nitride (g-C3N4), which further decomposes into nitrogen-doped graphite carbon. During pyrolysis, gases (CO2, NH3, etc.) generated by the decomposition of organic matter escape, leaving a porous structure. The decomposition behavior of amino acids further regulates the pore size distribution of the support. This results in the formation of a rare earth element-modified nitrogen-rich carbon support with high specific surface area and porosity, thereby fully exposing the rare earth single atoms coordinated and bound to the support.

[0052] S3. Dissolve the precursor ruthenium salt and urea in deionized water to form an impregnation solution. Add the nitrogen-rich carbon support modified with rare earth elements to the impregnation solution, stir and impregnate, and filter and collect the solid. Wash, dry and calcine to obtain the ruthenium atom cluster composite catalyst.

[0053] In this step, the impregnation solution is formed by dissolving the precursor ruthenium salt and urea in a certain amount of deionized water. The precursor ruthenium salt is ruthenium trichloride or ruthenium nitrite. The concentration of ruthenium in the impregnation solution is 0.5-5.0 mg Ru / mL, and the concentration of urea in the impregnation solution is 20-100 mg / mL.

[0054] In practice, the temperature of the impregnation solution used is 70-90℃, and the impregnation time is 6-12 hours. The presence of urea in the impregnation solution allows for the slow decomposition of ammonium ions, making the impregnation solution weakly alkaline and promoting the absorption of Ru in the impregnation solution. 3+ Ru atoms gradually transform to form Ru clusters, which are then loaded onto a nitrogen-rich carbon support modified with rare earth elements; the mass ratio of ruthenium to the nitrogen-rich carbon support modified with rare earth elements in the impregnation solution is 0.5-2.0 wt.%.

[0055] Further, after the stirring and impregnation is completed, the resulting suspension is filtered, washed 2-3 times with ethanol and deionized water respectively, and then vacuum dried at 60-90℃ for 2-12 hours. The resulting solid powder is placed in a porcelain boat and transferred to a tube furnace, where it is reduced at 200-300℃ for 1-3 hours in an atmosphere of argon or nitrogen, with a heating rate of 2-5℃ / min.

[0056] Secondly, the present invention provides a ruthenium cluster composite catalyst obtained by the preparation method described in the first aspect above. The ruthenium cluster composite catalyst provided by the present invention is formed by supporting ruthenium clusters on a nitrogen-rich carbon support modified with rare earth elements; wherein the rare earth elements are coordinated and bonded to the nitrogen-rich carbon support, and metallic ruthenium is uniformly loaded on the rare earth element-modified nitrogen-rich carbon support in the form of clusters.

[0057] The ruthenium cluster composite catalyst provided by this invention can be represented as Ru x / [RE y -NC]; where Ru x In a ruthenium atom cluster composite catalyst, x% by mass represents ruthenium atom clusters, where x is between 0.2 and 2.5.

[0058] RE y In the ruthenium cluster composite catalyst, the rare earth element (cerium or lanthanum) with a mass percentage of y% is represented by y, where y is between 5 and 25. That is, the ruthenium cluster composite catalyst (Ru) provided in this embodiment of the invention... x / [RE yIn [NC], the mass percentage of ruthenium atom clusters is 0.2-2.5%, and the mass percentage of rare earth element cerium is 5-25%; for example, the Ru2 / [Ce] provided in the embodiments of the present invention 15 [-NC] indicates that in a ruthenium atom cluster composite catalyst, the mass percentage of ruthenium atom clusters is 2%, and the mass percentage of rare earth element cerium is 15%.

[0059] In the ruthenium atom cluster composite catalyst provided by this invention, rare earth elements are coordinated and bound to a nitrogen-rich carbon support, while metallic ruthenium is loaded atomically onto the rare earth element-modified nitrogen-rich carbon support. Based on the high specific surface area of ​​the nitrogen-rich carbon support and the modification of the electronic state of the ruthenium atom clusters at the active sites by rare earth elements, the amount of precious metals used can be greatly reduced, effectively improving the NH3 adsorption performance and NH bond breaking ability, and achieving efficient catalytic promotion of ammonia decomposition to hydrogen production under low temperature conditions.

[0060] Optionally, when the ruthenium cluster composite catalyst is used to catalyze the ammonia decomposition reaction to produce hydrogen, the space velocity of the ammonia gas is 5000-50000 mL·g. -1 ·h -1 The reaction temperature is 200-500℃ and the reaction pressure is 0.1-5.0MPa.

[0061] In practical applications, the ruthenium cluster composite catalyst provided by this invention can achieve an ammonia decomposition conversion rate of 93.7% under reaction conditions of 375°C and 0.1 MPa.

[0062] To enable those skilled in the art to more clearly understand the present invention, the following embodiments are provided to illustrate in detail a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition and its preparation method.

[0063] Example 1

[0064] Weigh 3.78 g (0.03 mol) of melamine and 3.87 g (0.03 mol) of cyanuric acid, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.67 g (0.03 mol) of alanine and add it to the mixture. Continue stirring at room temperature for 2 hours. Weigh 0.30 g of cerium nitrate and add it to the mixture. Continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0065] The resulting white solid was ground into powder and vacuum dried at 80°C for 6 hours. The resulting powder was placed in a porcelain boat and pyrolyzed at 800°C for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5°C / min. The resulting black powder was a nitrogen-rich carbon support modified with rare earth elements [Ce]. 15 -NC].

[0066] Weigh out 0.041 g of ruthenium trichloride and 1.0 g of urea, and dissolve them in 30 mL of deionized water to form an impregnation solution (the concentration of ruthenium in the impregnation solution is 0.67 mg Ru / mL, and the mass of ruthenium in the impregnation solution is 20 mg). Add 1.0 g of [Ce] to the solution. 15 -NC] was magnetically stirred and impregnated at 80℃ for 12 hours; the resulting suspension was filtered, washed three times with ethanol and deionized water respectively, and then vacuum dried at 80℃ for 6 hours. The resulting solid powder was placed in a porcelain boat and reduced in a tube furnace at 250℃ for 2 hours under an argon atmosphere at a heating rate of 5℃ / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalyst Ru2 / [Ce] 15 -NC].

[0067] Figure 2 shows a transmission electron microscope (TEM) image of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention. As shown in Figure 2, the catalyst exhibits a porous layered structure with a high specific surface area, and the supported ruthenium atom clusters are highly dispersed with a size between 0.5 and 1.0 nm. Figure 3 shows an EDS elemental analysis diagram of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention. As shown in Figure 3, the catalyst has a carbon content of 62.04 wt.%, a nitrogen content of 15.26 wt.%, an oxygen content of 6.19 wt.%, a ruthenium content of 1.92 wt.%, and a cerium content of 14.59 wt.%.

[0068] Example 2

[0069] Weigh 3.78 g (0.03 mol) of melamine and 3.87 g (0.03 mol) of cyanuric acid, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.25 g (0.03 mol) of glycine and add it to the mixture. Continue stirring at room temperature for 2 hours. Weigh 0.30 g of lanthanum nitrate and add it to the mixture. Continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0070] The resulting white solid was ground into powder and vacuum dried at 80°C for 6 hours. The resulting powder was placed in a porcelain boat and pyrolyzed at 800°C for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5°C / min. The resulting black powder was a nitrogen-rich carbon support modified with rare earth elements [La]. 15 -NC].

[0071] Weigh 0.041 g of ruthenium trichloride and 1.0 g of urea, respectively, and dissolve them in 30 mL of deionized water to form an impregnation solution (the concentration of ruthenium in the impregnation solution is 0.67 mg Ru / mL, and the mass of ruthenium in the impregnation solution is 20 mg). Add 1.0 g of [La] to the solution.15 -NC] was magnetically stirred and impregnated at 80℃ for 12 hours. The resulting suspension was filtered, washed three times with ethanol and deionized water respectively, and then vacuum dried at 80℃ for 6 hours. The resulting solid powder was placed in a porcelain boat and reduced in a tube furnace at 250℃ for 2 hours under an argon atmosphere at a heating rate of 5℃ / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalyst Ru2 / [La 15 -NC].

[0072] Ru2 / [La 15 The EDS elemental analysis results of [-NC] are as follows:

[0073] The catalyst has a carbon content of 61.77 wt.%, a nitrogen content of 14.65 wt.%, an oxygen content of 6.76 wt.%, a ruthenium content of 1.89 wt.%, and a lanthanum content of 14.93 wt.%.

[0074] Example 3

[0075] Weigh 3.78 g (0.03 mol) of melamine and 3.87 g (0.03 mol) of cyanuric acid, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.67 g (0.03 mol) of alanine and add it to the above mixture. Continue stirring at room temperature for 2 hours. Weigh 0.30 g of cerium nitrate and add it to the above mixture. Continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0076] The resulting white solid was ground into powder and vacuum dried at 80°C for 6 hours. The resulting powder was placed in a porcelain boat and pyrolyzed at 800°C for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5°C / min. The resulting black powder was a nitrogen-rich carbon support modified with rare earth elements [Ce]. 15 -NC].

[0077] Weigh 0.021 g of ruthenium trichloride and 1.0 g of urea, respectively, and dissolve them in 20 mL of deionized water to form an impregnation solution (the concentration of ruthenium in the impregnation solution is 0.5 mg Ru / mL, and the mass of ruthenium in the impregnation solution is 10 mg). Add 1.0 g of [Ce] to the solution. 15 -NC] was magnetically stirred and impregnated at 80℃ for 12 hours. The resulting suspension was filtered, washed three times with ethanol and deionized water respectively, and then vacuum dried at 80℃ for 6 hours. The resulting solid powder was placed in a porcelain boat and reduced in a tube furnace at 250℃ for 2 hours under an argon atmosphere at a heating rate of 5℃ / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalyst Ru1 / [Ce]15 -NC].

[0078] Ru1 / [Ce 15 The EDS elemental analysis results of [-NC] are as follows:

[0079] The catalyst has a carbon content of 62.37 wt.%, a nitrogen content of 15.56 wt.%, an oxygen content of 6.25 wt.%, a ruthenium content of 1.05 wt.%, and a cerium content of 14.77 wt.%.

[0080] Example 4

[0081] Weigh 3.78 g (0.03 mol) of melamine and 3.87 g (0.03 mol) of cyanuric acid, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.67 g (0.03 mol) of alanine and add it to the mixture. Continue stirring at room temperature for 2 hours. Weigh 0.20 g of cerium nitrate and add it to the mixture. Continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0082] The resulting white solid was ground into powder and vacuum dried at 80°C for 6 hours. The resulting powder was placed in a porcelain boat and pyrolyzed at 800°C for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5°C / min. The resulting black powder was a nitrogen-rich carbon support modified with rare earth elements [Ce]. 10 -NC].

[0083] Weigh out 0.041 g of ruthenium trichloride and 1.0 g of urea, and dissolve them in 30 mL of deionized water to form an impregnation solution (the concentration of ruthenium in the impregnation solution is 0.67 mg Ru / mL, and the mass of ruthenium in the impregnation solution is 20 mg). Add 1.0 g of [Ce] to the solution. 10 -NC] was magnetically stirred and impregnated at 80℃ for 12 hours. The resulting suspension was filtered, washed three times with ethanol and deionized water respectively, and then vacuum dried at 80℃ for 6 hours. The resulting solid powder was placed in a porcelain boat and reduced in a tube furnace at 250℃ for 2 hours under an argon atmosphere at a heating rate of 5℃ / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalyst Ru2 / [Ce] 10 -NC].

[0084] Ru2 / [Ce 10 The EDS elemental analysis results of [-NC] are as follows:

[0085] The catalyst has a carbon content of 64.21 wt.%, a nitrogen content of 16.45 wt.%, an oxygen content of 7.14 wt.%, a ruthenium content of 1.87 wt.%, and a cerium content of 10.33 wt.%.

[0086] Comparative Example 1

[0087] Weigh 3.78 g (0.03 mol) of melamine and 3.87 g (0.03 mol) of cyanuric acid, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.67 g (0.03 mol) of alanine and add it to the above mixed solution. Continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0088] The obtained white solid was ground into powder and vacuum dried at 80°C for 6 hours. The resulting solid powder was placed in a porcelain boat and pyrolyzed at 800°C for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5°C / min. The resulting black powder was a nitrogen-rich carbon support [NC].

[0089] 0.041 g of ruthenium trichloride and 1.0 g of urea were weighed and dissolved in 30 mL of deionized water to form an impregnation solution (the concentration of ruthenium in the impregnation solution was 0.67 mg Ru / mL, and the mass of ruthenium in the impregnation solution was 20 mg). 1.0 g of [NC] was added to the solution, and the mixture was magnetically stirred at 80 °C for 12 hours. The resulting suspension was filtered, washed three times with ethanol and deionized water respectively, and then vacuum dried at 80 °C for 6 hours. The resulting solid powder was placed in a porcelain boat and reduced in a tube furnace at 250 °C for 2 hours under an argon atmosphere at a heating rate of 5 °C / min. The resulting black powder was Ru2 / [NC], a nitrogen-rich carbon-supported ruthenium cluster catalyst.

[0090] Comparative Example 2

[0091] Weigh 3.78 g of melamine and 3.87 g of cyanuric acid separately, and disperse them in 100 mL of 45 wt.% methanol aqueous solution. Stir magnetically at room temperature for 2 hours. Weigh 2.67 g of alanine and add it to the above mixed solution, and continue stirring at room temperature for 2 hours. Weigh 0.30 g of cerium nitrate and add it to the above mixed solution, and continue stirring at room temperature for 2 hours. Heat to 100 °C to evaporate the solvent to dryness, obtaining a white solid.

[0092] The resulting white solid was ground into powder and vacuum dried at 80℃ for 6 hours. The resulting powder was placed in a porcelain boat and pyrolyzed at 800℃ for 3 hours in a tube furnace under an argon atmosphere at a heating rate of 5℃ / min. The resulting black powder was a rare earth element-modified nitrogen-rich carbon support [Ce]. 15 -NC].

[0093] Performance testing

[0094] Ammonia conversion rate was tested using the ruthenium cluster composite catalysts prepared in Examples 1-4 and Comparative Examples 1-2.

[0095] A ruthenium cluster composite catalyst was packed into a fixed-bed tubular reactor, and nitrogen gas was introduced at a rate of 50 mL / min at room temperature, while the temperature was increased to 500 °C at a rate of 5 °C / min. After stabilizing at 500 °C for 1 hour, a reaction gas was introduced to test the ammonia decomposition performance; the ammonia in the product gas was absorbed by dilute sulfuric acid and then detected by ion chromatography.

[0096] Figure 4 shows the ammonia conversion rate of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature 375℃, reaction pressure 0.1MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 As shown in Figure 4, the reaction was carried out at a temperature of 375℃, a reaction pressure of 0.1 MPa, an ammonia concentration of 10 vol.%, and a reaction space velocity of 30000 mL·g. -1 ·h -1 Under the given conditions, the ammonia conversion rate of the ruthenium cluster composite catalysts provided in Examples 1-4 is not less than 95%.

[0097] Figure 5 shows a comparison of the ammonia decomposition performance of the ruthenium cluster composite catalysts provided in the embodiments and comparative examples of the present invention (reaction conditions: reaction temperature 250-500℃, reaction pressure 0.1MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 As shown in Figure 5, comparing Example 1 and Comparative Example 1, it can be seen that the modification of the ruthenium atom cluster composite catalyst by rare earth metals can effectively improve the ammonia decomposition activity. This is mainly due to the high specific surface area of ​​the nitrogen-rich carbon support and the electronic additives of rare earth elements, which enable the catalyst to have higher NH3 adsorption performance and NH bond breaking ability. As shown in Comparative Example 1 and Comparative Example 2, the ruthenium atom cluster in the catalyst is also essential in the ammonia decomposition reaction. The combination of rare earth element modification of the high specific surface area nitrogen-rich carbon support and the ruthenium atom cluster can achieve efficient catalytic promotion of ammonia decomposition to hydrogen production under low temperature conditions.

[0098] The performance of the ruthenium cluster composite catalyst provided in Example 1 was tested below.

[0099] (1) Effect of reaction temperature on ammonia decomposition performance

[0100] Ru2 / [Ce] was loaded into a fixed-bed tubular reactor. 15The ammonia decomposition to hydrogen reaction was carried out using a catalyst with nitrogen gas flowing at a rate of 50 mL / min at room temperature, and the temperature was increased to 500 °C at a rate of 5 °C / min. After stabilizing at 500 °C for 1 hour, the ammonia decomposition performance was tested by introducing a reaction gas. The ammonia in the product gas was absorbed by dilute sulfuric acid and then detected by ion chromatography. Reaction conditions: reaction space velocity was 30000 mL·g⁻¹. -1 ·h -1 The reaction temperature range is 375-500℃, the reaction pressure is 0.1MPa, and the ammonia concentration is 10 vol.%.

[0101] Figure 6 shows the effect of reaction temperature on the ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature of 375, 400, 425, 450, 475, 500 °C, reaction pressure of 0.1 MPa, ammonia concentration of 10 vol.%, and reaction space velocity of 30000 mL·g). -1 ·h -1 As shown in Figure 6, the ammonia conversion rates at ammonia decomposition reaction temperatures of 375, 400, 425, 450, 475, and 500℃ are 93.7%, 99.7%, 99.8%, 99.9%, 99.9%, and 99.8%, respectively; the corresponding hydrogen production rates are 284.6, 302.9, 303.4, 303.5, 303.6, and 303.4 mmol g, respectively. -1 ·h -1 .

[0102] (2) Effect of reaction pressure on ammonia decomposition performance

[0103] Ru2 / [Ce] was loaded into a fixed-bed tubular reactor. 15 The ammonia decomposition to hydrogen reaction was carried out using a catalyst with nitrogen gas flowing at a rate of 50 mL / min at room temperature, and the temperature was increased to 500 °C at a rate of 5 °C / min. After stabilizing at 500 °C for 1 hour, the ammonia decomposition performance was tested by introducing a reaction gas. The ammonia in the product gas was absorbed by dilute sulfuric acid and then detected by ion chromatography. Reaction conditions: reaction space velocity was 30000 mL·g⁻¹. -1 ·h -1 The reaction temperature was 400℃, the reaction pressure range was 0.1-1 MPa, and the ammonia concentration was 10 vol.%.

[0104] Figure 7 shows the effect of reaction pressure on the ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature 400℃, reaction pressure 0.1, 0.3, 0.6, 1.0 MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1As shown in Figure 7, the ammonia conversion rates at ammonia decomposition reaction pressures of 0.1, 0.3, 0.6, and 1.0 MPa were 99.7%, 95.9%, 91.8%, and 90.1%, respectively; the corresponding hydrogen production rates were 302.9, 291.5, 278.9, and 273.7 mmol g, respectively. -1 ·h -1 .

[0105] (3) Effect of space velocity on ammonia decomposition performance

[0106] Ru2 / [Ce] was loaded into a fixed-bed tubular reactor. 15 The ammonia decomposition to hydrogen reaction was carried out using a catalyst with nitrogen gas flowing at a rate of 50 mL / min at room temperature, and the temperature was increased to 500 °C at a rate of 5 °C / min. After stabilizing at 500 °C for 1 hour, the ammonia decomposition performance was tested by introducing a reaction gas. The ammonia in the product gas was absorbed by dilute sulfuric acid and then detected by ion chromatography. Reaction conditions: reaction space velocity was 30000 mL·g⁻¹. -1 ·h -1 The reaction temperature was 400℃, the reaction pressure was 0.1-1 MPa, and the ammonia concentration was 10 vol.%.

[0107] Figure 8 shows the effect of space velocity on ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature 400℃, reaction pressure 0.1MPa, ammonia concentration 10 vol.%, reaction space velocity 12000, 18000, 30000, 48000 mL·mL·g). -1 ·h -1 As shown in Figure 8, the space velocities for ammonia decomposition were 12000, 18000, 30000, and 48000 mL·g. -1 ·h -1 At these times, the corresponding ammonia conversion rates were 99.9%, 99.8%, 99.7%, and 96.8%, respectively; the corresponding hydrogen production rates were 303.6, 303.4, 302.9, and 294.3 mmol g, respectively. -1 ·h -1 .

[0108] (4) Long-cycle ammonia decomposition performance

[0109] Ru2 / [Ce] was loaded into a fixed-bed tubular reactor. 15 The ammonia decomposition to hydrogen reaction was carried out using a catalyst with nitrogen gas flowing at a rate of 50 mL / min at room temperature, and the temperature was increased to 500 °C at a rate of 5 °C / min. After stabilizing at 500 °C for 1 hour, the ammonia decomposition performance was tested by introducing a reaction gas. The ammonia in the product gas was absorbed by dilute sulfuric acid and then detected by ion chromatography. Reaction conditions: reaction space velocity was 30000 mL·g⁻¹. -1 ·h-1 The reaction temperature was 400℃, the reaction pressure was 0.1MPa, and the ammonia concentration was 10 vol.%.

[0110] Figure 9 shows the long-cycle ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature 400℃, reaction pressure 0.1MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 As shown in Figure 9, in the 100-hour long-cycle ammonia decomposition performance test, Ru2 / [Ce] 15 The ammonia conversion rate of [-NC] was 99.4%; the corresponding hydrogen production rate was 302.1 mmol g. -1 ·h -1 .

[0111] In summary, the ruthenium cluster composite catalyst provided by this invention uses rare earth elements to modify a carbon support to support a low-content ruthenium cluster composite catalytic material Ru. x / [RE y [-NC] exhibits excellent ammonia decomposition activity, achieving an ammonia decomposition conversion rate of no less than 92% at temperatures of 375-500℃ and pressures of 0.1-1MPa, demonstrating broad prospects for practical applications.

[0112] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this application. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0113] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0114] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a ruthenium atomic cluster composite catalyst for hydrogen production by ammonia decomposition, characterized by, The preparation method includes: Melamine, cyanuric acid, and amino acids were dispersed in a methanol aqueous solution and stirred to form a mixed system. Rare earth metal precursor salts were added to the mixed system and stirred continuously for 2-6 hours. The solvent was then heated to evaporate the solvent, and a white solid was obtained. The white solid was ground into powder and then pyrolyzed at 700-850°C. The resulting black powder was a nitrogen-rich carbon carrier modified with rare earth elements. The precursor ruthenium salt and urea are dissolved in deionized water to form an impregnation solution. The nitrogen-rich carbon support modified with rare earth elements is added to the impregnation solution and stirred for impregnation. The solid collected by filtration is washed, dried and calcined to obtain the ruthenium atom cluster composite catalyst.

2. The production method according to claim 1, characterized by, In the mixed system, the concentration of the methanol aqueous solution is 20-50 wt.%, the molar ratio of melamine to cyanuric acid is 0.8-1.2, and the molar ratio of melamine to amino acids is 1.0-1.

5.

3. The preparation method according to claim 1, characterized in that, The amino acid is glycine, alanine, serine, or glutamic acid.

4. The method of claim 1, wherein, The rare earth metal precursor salt is lanthanum nitrate, lanthanum acetate, cerium nitrate, or cerium acetate, and the amount of the rare earth metal precursor salt added accounts for 1.0-5.0 wt.% of the total mass of melamine, cyanuric acid, and amino acids.

5. The preparation method according to claim 1, characterized in that, The pyrolysis is carried out under an argon or nitrogen atmosphere, with a heating rate of 2-5℃ / min.

6. The method of claim 1, wherein, The temperature of the impregnation solution is 70-90℃; The stirring and impregnation time is 6-12 hours.

7. The preparation method according to claim 1, characterized in that, The precursor ruthenium salt is ruthenium trichloride or ruthenium nitrite; The concentration of ruthenium in the impregnation solution is 0.5-5.0 mg Ru / mL, and the concentration of urea in the impregnation solution is 20-100 mg / mL; The mass ratio of ruthenium in the impregnation solution to the mass ratio of the rare earth element-modified nitrogen-rich carbon support is 0.5-2.0 wt.%.

8. The method of claim 1, wherein, The solids collected by filtration are subjected to washing, drying and calcination treatment, including: washing with ethanol and deionized water 2-3 times respectively, vacuum drying at 60-90℃ for 2-12 hours, and then reduction at 200-300℃ for 1-3 hours.

9. A ruthenium cluster composite catalyst obtained by any of the preparation methods described in claims 1-8.

10. The ruthenium atomic cluster complex catalyst of claim 9, wherein, The ruthenium atomic cluster complex catalyst is used for catalyzing ammonia to carry out ammonia decomposition hydrogen production reaction, the reaction space velocity of the ammonia is 5000-50000 mL·g -1 ·h -1 , the reaction temperature is 200-500 DEG C, and the reaction pressure is 0.1-5.0 MPa.

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