A ruthenium atomic cluster composite catalyst for hydrogen production by ammonia decomposition and a preparation method thereof

Abstract

The application provides a ruthenium atomic cluster composite catalyst for hydrogen production by ammonia decomposition and a preparation method, comprising dispersing melamine, cyanuric acid and amino acid in a methanol aqueous solution, stirring to form a mixed system; adding a rare earth metal precursor salt into the mixed system, continuously stirring, heating to evaporate the solvent, grinding the obtained white solid into a powder, transferring to a high temperature for pyrolysis to obtain a nitrogen-rich carbon carrier modified by a rare earth element; dissolving a precursor ruthenium salt and urea in deionized water to form an impregnation solution, adding the nitrogen-rich carbon carrier modified by the rare earth element into the impregnation solution, stirring and impregnating, washing, drying and calcining the collected solid to obtain the catalyst; based on the high specific surface characteristics of the nitrogen-rich carbon carrier and the modification of the electronic state of the active site ruthenium atomic cluster by the rare earth element, the amount of ruthenium is reduced, the NH3 adsorption performance and N-H bond breaking ability are improved, and high-efficiency catalysis is realized to promote hydrogen production by ammonia decomposition under low-temperature conditions.

Description

Technical Field

[0001] 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

[0002] 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.

[0003] 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 °C, which can cause catalyst deactivation through sintering and significant energy consumption.

[0004] 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, preventing their commercial application. 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.

[0005] 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

[0006] 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.

[0007] The specific details of the invention are as follows:

[0008] 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:

[0009] 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.

[0010] The white solid was ground into powder and then pyrolyzed at 700-850 °C. The resulting black powder was a rare earth element-modified nitrogen-rich carbon support, with a nitrogen content of 10-20 wt.%.

[0011] 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.

[0012] 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.

[0013] Optionally, the amino acid is glycine, alanine, serine, or glutamic acid.

[0014] 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.

[0015] Optionally, the pyrolysis is carried out under an argon or nitrogen atmosphere, with a heating rate of 2-5 °C / min.

[0016] Optionally, the temperature of the impregnation solution is 70-90 °C;

[0017] The stirring and impregnation time is 6-12 hours.

[0018] Optionally, the precursor ruthenium salt is ruthenium trichloride or ruthenium nitrite;

[0019] 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;

[0020] 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.%.

[0021] 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.

[0022] 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.

[0023] 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 0.1-5.0 MPa.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 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 °C 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.

[0026] 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 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 °C and 0.1 MPa. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A flowchart illustrating the preparation method of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention is shown;

[0029] Figure 2 The image shown is a transmission electron microscope (TEM) image of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention.

[0030] Figure 3 The following is an EDS elemental analysis diagram of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention;

[0031] Figure 4 The ammonia conversion rate of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention is shown.

[0032] Figure 5 The ammonia decomposition performance of the ruthenium atom cluster composite catalysts provided in the embodiments and comparative examples of the present invention is shown in the figure.

[0033] Figure 6 The effect of reaction temperature on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention is shown.

[0034] Figure 7 The effect of reaction pressure on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention is shown.

[0035] Figure 8 The effect of space velocity on ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention is shown.

[0036] Figure 9 The diagram shows the long-cycle ammonia decomposition performance of the ruthenium atom cluster composite catalyst provided in the embodiments of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0038] Specific experimental steps or conditions are not specified in the embodiments; 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. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0039] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0040] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0041] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] 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 A flowchart illustrating the preparation method of the ruthenium atom cluster composite catalyst provided by the present invention is shown, as follows: Figure 1 As shown, the preparation method includes:

[0043] 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.

[0044] 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, glutamic acid, etc.) 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.

[0045] 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 in the methanol-water solution (similar to a melamine-cyanuric acid complex, MCA). Then, a specific type of amino acid is added to the above 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.

[0046] 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, avoiding aggregation during subsequent pyrolysis, thus obtaining a nitrogen-rich carbon support in which the rare earth metal is uniformly dispersed in the organic framework.

[0047] 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.

[0048] In some embodiments, the amino acid is selected from glycine, alanine, serine, or glutamic acid.

[0049] 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.

[0050] S2. Grind the white solid into powder and transfer it to 700-850 ℃ for pyrolysis. The resulting black powder is a nitrogen-rich carbon carrier modified with rare earth elements.

[0051] In this specific step, the white solid obtained in step S1 is ground into powder and vacuum dried at 25-90 °C 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 °C for 2-5 hours. The atmosphere used for pyrolysis is argon or nitrogen, and the heating rate is 2-5 °C / 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.%.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] In practice, the temperature of the impregnation solution used for impregnation is 70-90 ℃, and the impregnation time is 6-12 hours. The presence of urea in the impregnation solution can slowly decompose to release ammonium ions, thereby making the impregnation solution weakly alkaline, which promotes the gradual transformation of Ru³⁺ in the impregnation solution into Ru atom clusters, which are then loaded onto the nitrogen-rich carbon support modified with rare earth elements. The mass ratio of ruthenium in the impregnation solution to the mass ratio of the nitrogen-rich carbon support modified with rare earth elements is 0.5-2.0 wt.%.

[0056] 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 °C 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 °C for 1-3 hours in an atmosphere of argon or nitrogen, with a heating rate of 2-5 °C / min.

[0057] 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.

[0058] 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% of the ruthenium atom clusters by mass are represented, where x is between 0.2 and 2.5.

[0059] RE y In the ruthenium cluster composite catalyst, the rare earth element (cerium or lanthanum) has a mass percentage of 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 y In the [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%.

[0060] 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.

[0061] 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 0.1-5.0 MPa.

[0062] In practice, 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.

[0063] 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.

[0064] Example 1

[0065] 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.

[0066] 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 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].

[0067] 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 [Ce] to the solution. 15 The ruthenium ion cluster composite catalytic material Ru2 / [Ce] was magnetically stirred and impregnated 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 at 250 °C for 2 hours in a tube furnace under an argon atmosphere at a heating rate of 5 °C / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalytic material Ru2 / [Ce]. 15 -NC].

[0068] Figure 2 Transmission electron microscopy (TEM) images of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention are shown, as follows: Figure 2 As shown, the catalyst exhibits a porous sheet 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 The following is an EDS elemental analysis diagram of the ruthenium atom cluster composite catalyst provided in an embodiment of the present invention, as shown. Figure 3As shown, 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.%.

[0069] Example 2

[0070] 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.

[0071] 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 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].

[0072] 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 [La] to the solution. 15 The ruthenium ion cluster composite catalytic material Ru2 / [La] was magnetically stirred and impregnated 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 at 250 °C for 2 hours in a tube furnace under an argon atmosphere at a heating rate of 5 °C / min. The resulting black powder was a rare-earth element-modified nitrogen-rich carbon support ruthenium atom cluster composite catalytic material. 15 -NC].

[0073] Ru2 / [La 15 The EDS elemental analysis results of [-NC] are as follows:

[0074] 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.%.

[0075] Example 3

[0076] 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.

[0077] 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 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].

[0078] 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 °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 a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalyst Ru1 / [Ce] 15 -NC].

[0079] Ru1 / [Ce 15 The EDS elemental analysis results of [-NC] are as follows:

[0080] 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.%.

[0081] Example 4

[0082] 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.

[0083] 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 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].

[0084] 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 [Ce] to the solution. 10 The ruthenium ion cluster composite catalytic material Ru2 / [Ce] was magnetically stirred and impregnated 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 at 250 °C for 2 hours in a tube furnace under an argon atmosphere at a heating rate of 5 °C / min. The resulting black powder was a rare earth element modified nitrogen-rich carbon support ruthenium atom cluster composite catalytic material Ru2 / [Ce]. 10 -NC].

[0085] Ru2 / [Ce 10 The EDS elemental analysis results of [-NC] are as follows:

[0086] 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.%.

[0087] Comparative Example 1

[0088] 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.

[0089] 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].

[0090] 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.

[0091] Comparative Example 2

[0092] Weigh 3.78 g of melamine and 3.87 g 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 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.

[0093] 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 argon atmosphere at a heating rate of 5 °C / min. The resulting black powder was a rare earth element-modified nitrogen-rich carbon support [Ce]. 15 -NC].

[0094] Performance testing

[0095] Ammonia conversion rate was tested using the ruthenium cluster composite catalysts prepared in Examples 1-4 and Comparative Examples 1-2.

[0096] 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.

[0097] Figure 4 The ammonia conversion of the ruthenium cluster composite catalyst provided in the embodiments of the present invention is shown (reaction conditions: reaction temperature 375 °C, reaction pressure 0.1 MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 ),like Figure 4 As shown, the reaction was carried out at a temperature of 375 °C, a pressure of 0.1 MPa, an ammonia concentration of 10 vol.%, and a space velocity of 30,000 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%.

[0098] Figure 5 The comparison of ammonia decomposition performance of the ruthenium cluster composite catalysts provided in the embodiments and comparative examples of the present invention is shown (reaction conditions: reaction temperature 250-500 °C, reaction pressure 0.1 MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 ),like Figure 5 As shown in Comparative Example 1 and Comparative Example 2, the modification of the ruthenium atom cluster composite catalyst with 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 aids 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.

[0099] The performance of the ruthenium cluster composite catalyst provided in Example 1 was tested below.

[0100] (1) Effect of reaction temperature on ammonia decomposition performance

[0101] 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, followed by a temperature increase to 500 °C at a rate of 5 °C / min. After stabilization 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 0.1 MPa, and the ammonia concentration is 10 vol.%.

[0102] Figure 6 The effect of reaction temperature on the ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention is shown (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 ),like Figure 6 As shown, the ammonia conversion rates at ammonia decomposition reaction temperatures of 375, 400, 425, 450, 475, and 500 °C 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 .

[0103] (2) Effect of reaction pressure on ammonia decomposition performance

[0104] 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, followed by a temperature increase to 500 °C at a rate of 5 °C / min. After stabilization 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.%.

[0105] Figure 7 The effect of reaction pressure on the ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention is shown (reaction conditions: reaction temperature 400 °C, reaction pressure 0.1, 0.3, 0.6, 1.0 MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g).-1 ·h -1 ),like Figure 7 As shown, the ammonia conversion rates at ammonia decomposition reaction pressures of 0.1, 0.3, 0.6, and 1.0 MPa are 99.7%, 95.9%, 91.8%, and 90.1%, respectively; the corresponding hydrogen production rates are 302.9, 291.5, 278.9, and 273.7 mmol g, respectively. -1 ·h -1 .

[0106] (3) Effect of space velocity on ammonia decomposition performance

[0107] 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, followed by a temperature increase to 500 °C at a rate of 5 °C / min. After stabilization 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.%.

[0108] Figure 8 The effect of space velocity (SHV) on ammonia decomposition performance of the ruthenium cluster composite catalyst provided in this embodiment of the invention is shown (reaction conditions: reaction temperature 400℃, reaction pressure 0.1 MPa, ammonia concentration 10 vol.%, reaction space velocities 12000, 18000, 30000, and 48000 mL·mL·g). -1 ·h -1 ),like Figure 8 As shown, 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 .

[0109] (4) Long-cycle ammonia decomposition performance

[0110] 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, followed by a temperature increase to 500 °C at a rate of 5 °C / min. After stabilization 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 MPa, and the ammonia concentration was 10 vol.%.

[0111] Figure 9 The diagram shows the long-term ammonia decomposition performance of the ruthenium cluster composite catalyst provided in the embodiments of the present invention (reaction conditions: reaction temperature 400 °C, reaction pressure 0.1 MPa, ammonia concentration 10 vol.%, reaction space velocity 30000 mL·g). -1 ·h -1 ).like Figure 9 As shown, in a 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 .

[0112] 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 0.1-1 MPa, demonstrating broad prospects for practical applications.

[0113] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0114] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0115] The foregoing has provided a detailed description of a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a ruthenium cluster composite catalyst for hydrogen production from ammonia decomposition, characterized in that, 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 preparation method according to claim 1, characterized in that, 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 preparation method according to claim 1, characterized in that, 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 °C / min.

6. The preparation method according to claim 1, characterized in that, 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 nitrogen-rich carbon support modified with rare earth elements is 0.5-2.0 wt.%.

8. The preparation method according to claim 1, characterized in that, 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 reduction at 200-300 °C 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 cluster composite catalyst according to claim 9, characterized in that, When the ruthenium cluster composite catalyst is used to catalyze the ammonia decomposition reaction to produce hydrogen, the reaction 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 0.1-5.0 MPa.

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