Layered high-entropy oxide supported ruthenium catalyst, and preparation method and application thereof

Abstract

The application discloses a layered high-entropy oxide supported ruthenium catalyst and a preparation method and application thereof. The catalyst comprises a carrier and an active component, the active component is supported on the carrier; the active component is ruthenium element; the carrier is a layered high-entropy oxide, and a chemical composition formula of the layered high-entropy oxide is A(HE)TiO x wherein A is at least one of alkali metal elements Li, Na and K, HE is at least four of lanthanide metal elements La, Ce, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu and Dy, the percentage of the mole number of each HE metal element to the total mole number of all HE metal elements is 5% to 35%, and 2

Description

Technical Field

[0001] This invention relates to high-entropy oxide-supported ruthenium catalysts, their preparation methods, and applications, belonging to the field of catalyst preparation technology. Specifically, it relates to a layered high-entropy oxide-supported ruthenium catalyst, its preparation method, and its application in ammonia decomposition. Background Technology

[0002] Currently, my country is in a transitional phase from fossil fuels to renewable energy. Hydrogen, as a clean and renewable energy source, has received widespread attention, and various countries are conducting research on related technologies. The main challenge to achieving large-scale application of the hydrogen energy industry is the development of safe and efficient hydrogen storage and transportation technologies.

[0003] Ammonia, as a highly efficient hydrogen storage medium, has the following significant advantages: 1. High energy density. The volumetric energy density of ammonia is approximately 13.6 MJ / L; 1 L of liquid ammonia = 4.5 L of high-pressure hydrogen (35.0 MPa) = 1200 L of room-temperature and atmospheric-pressure hydrogen. 2. Easy to liquefy and store (liquefaction pressure is 0.8 MPa at 20℃). 3. The decomposition products of ammonia are N2 and H2, avoiding CO2 emissions. x 4. Carbon-free energy storage. Ammonia's mature technology system, standards, and low-cost synthesis, storage, and transportation enable seasonal, long-distance, and carbon-free ammonia-hydrogen energy storage. Therefore, ammonia, as a hydrogen carrier, transforms hydrogen storage and transportation into ammonia storage and transportation, and hydrogen production through ammonia decomposition has significant application prospects.

[0004] The ammonia decomposition reaction for hydrogen production is shown in equation (1). This reaction is an endothermic reaction with increasing volume, so increasing the temperature and decreasing the pressure are beneficial to the reaction. At atmospheric pressure and without any catalyst, the actual conversion rate of the ammonia decomposition reaction at 700℃ is less than 10%. Therefore, a highly active catalyst is needed to achieve efficient ammonia decomposition.

[0005] 2NH3 = N2 + 3H2, ΔH = 92.5 kJ mol -1 (1)

[0006] Currently, ammonia decomposition catalysts mainly include noble metal catalysts (such as Ru, Ir, etc.), non-noble metal catalysts (such as Fe, Co, Ni, Mo, etc.), and transition metal carbides and nitrides (such as WC). x MoN x Ru-based catalysts exhibit high activity in ammonia decomposition, but existing catalysts suffer from drawbacks such as high cost, poor stability, low activity at high reaction space velocities, and low conversion rates.

[0007] Currently, several patents have been filed for methods of preparing ammonia decomposition catalysts. The following are a few reported patents, with detailed explanations:

[0008] Chinese patent CN 202310349366.9 discloses a Ru-based catalyst for ammonia decomposition to hydrogen production and its preparation method. This patent discloses the preparation of a SiO2@C supported ruthenium catalyst for ammonia decomposition reaction using carbon-coated silica (SiO2@C) as a support and ruthenium as the active component via an impregnation method. However, the carbon-containing support involved in this patent exhibits methanation under reaction conditions, leading to structural instability and low catalyst stability in practical applications.

[0009] Chinese patent CN 201611106718.4 discloses a ruthenium-based catalyst for hydrogen production from ammonia decomposition and its preparation method. This patent discloses an ammonia decomposition catalyst using carbon nanotubes as a support and loading ruthenium nanoparticles as colloids. However, the carbon nanotubes still exhibit methanation, leading to structural instability in practical applications and low catalyst efficiency.

[0010] Chinese patent CN 201611115105.7 discloses a magnesium oxide-supported ruthenium catalyst for ammonia decomposition to produce hydrogen, its preparation, and its application. The catalyst disclosed in this patent uses magnesium oxide as a support and metallic ruthenium as the active component. However, the magnesium oxide support used in this catalyst lacks the ability to modulate the electronic properties of Ru, resulting in mediocre catalyst performance.

[0011] Therefore, there is an urgent need to develop a highly efficient ammonia decomposition catalyst. High-entropy materials, as a novel type of material, have attracted widespread attention in recent years. These materials mainly refer to single-phase alloys or solid solutions containing four or more components with similar elemental content (Science, 2022, 376, eabn3103; Sci. Adv., 2021, 7, eabg1600; J. Mater. Chem. A, 2020, 8, 3814-3821). High-entropy materials possess compositional diversity and tunability, as well as unique structural and functional properties (thermodynamic high-entropy effect, structural lattice distortion effect, kinetic hysteresis diffusion effect, and performance cocktail effect), and have enormous application potential in materials, energy, environment, and catalysis. The multi-element synergy of high-entropy oxide materials can provide multifunctional active sites for catalytic reactions, thus laying the foundation for precise control of catalytic activity and selectivity; moreover, high-entropy materials exhibit high stability and are expected to become ideal supports for highly efficient ammonia decomposition catalysts. However, no catalysts using high-entropy oxides for ammonia decomposition have been reported. The development of efficient and stable low-temperature ammonia decomposition catalysts remains a significant challenge. Summary of the Invention

[0012] To address the issues of structural instability and low catalyst efficiency in the aforementioned ammonia decomposition catalysts under reaction conditions, this invention provides a layered high-entropy oxide-supported ruthenium catalyst, its preparation method, and its application. By employing a layered high-entropy oxide support and optimizing the preparation method, a highly dispersed ruthenium-based catalyst is prepared, exhibiting good high-temperature stability and excellent performance in the ammonia decomposition reaction.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows:

[0014] The present invention provides a layered high-entropy oxide-supported ruthenium catalyst, the catalyst comprising a support and an active component, wherein the active component is supported on the support; the active component is ruthenium.

[0015] The support is a layered high-entropy oxide with the chemical formula A(HE)TiO. x Where A is at least one of the alkali metal elements Li, Na, and K, and HE is at least four of the lanthanide metal elements La, Ce, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu, and Dy. The percentage of each HE metal element's molar number to the total number of HE metal elements' molar numbers is 5% to 35%. <x<5。

[0016] Preferably, the active component in the catalyst accounts for 0.1 to 10% of the catalyst's mass percentage; the support in the catalyst accounts for 90 to 99.9% of the catalyst's mass percentage.

[0017] Another aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0018] a: Lanthanide metal oxides, titanium oxides and alkali metal salts were mixed according to the chemical formula of high-entropy oxides. The resulting mixture was calcined, then washed and dried to obtain layered high-entropy oxides.

[0019] b: The layered high-entropy oxide obtained in step a is added to the ruthenium precursor salt solution and stirred evenly. A precipitant is added to the resulting suspension to carry out a precipitation reaction. The suspension is dried, heated to 200–400°C for calcination for 4–12 hours, cooled to room temperature, and then heated to 200–600°C for reduction for 1–6 hours to obtain the layered high-entropy oxide-supported ruthenium catalyst. Preferably, in step a, the lanthanide metal oxide is selected from any four or more oxides of La, Ce, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu, and Dy.

[0020] The oxide of titanium is TiO2;

[0021] The alkali metal salt is at least one of the carbonates, nitrates, and hydroxides of Li, Na, and K;

[0022] The molar ratio of metal elements in the lanthanide metal oxide and the titanium oxide is 0.8 to 1.2;

[0023] The ratio of the number of moles of the alkali metal salt to the total number of moles of the lanthanide metal oxide is greater than 1.

[0024] Preferably, in step a, the calcination temperature is 800–1300°C and the calcination time is 1–48 h.

[0025] Preferably, in step b, the ruthenium precursor salt is at least one of ruthenium chloride, ruthenium nitrate, and ruthenium acetylacetonate;

[0026] The precipitant is at least one of urea, ammonia, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate.

[0027] The molar ratio of the precipitant to the ruthenium precursor salt is 10–50:1.

[0028] Preferably, in step b, the precipitation reaction temperature is 30–90°C, and the precipitation reaction time is 1–6 hours.

[0029] The drying temperature is 60–120°C, and the drying time is 4–12 hours.

[0030] Preferably, the reducing gas is at least one of ammonia and hydrogen, and the heating rate from room temperature to the reduction temperature is 1 to 10 °C / min.

[0031] The present invention also provides an application of the above-mentioned catalyst in ammonia decomposition, wherein a layered high-entropy oxide supported ruthenium catalyst is heated to the reaction temperature of ammonia decomposition and then ammonia gas is introduced to obtain the products hydrogen and nitrogen.

[0032] Preferably, the reaction temperature for ammonia decomposition is 400–800°C, more preferably 400–500°C, and the space velocity for ammonia decomposition is 200–60000 ml / g·h.

[0033] The beneficial effects of this invention are as follows:

[0034] 1) The catalyst provided by this invention has a layered structure, which can provide more reactive sites and help reduce the diffusion resistance of reactant molecules to the catalytic sites. When applied to ammonia decomposition reaction, it can promote the catalytic conversion of ammonia molecules and has the advantages of low ammonia decomposition reaction temperature, high ammonia space velocity, and high ammonia conversion rate, thus realizing the efficient decomposition of ammonia at a lower temperature.

[0035] 2) The catalyst provided by this invention uses layered high-entropy material as a support, and the active component and the support have a unique electronic structure and interaction, which has the advantage of high stability. Attached Figure Description

[0036] Figure 1 The image shows the XRD pattern of the layered high-entropy oxide prepared in Example 1.

[0037] Figure 2 SEM image of the layered high-entropy oxide obtained in Example 1;

[0038] Figure 3 The graphs show the stability test results of the catalysts prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0039] The present invention will be described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0040] Unless otherwise specified, the raw materials used in the embodiments of this invention were all purchased through commercial channels.

[0041] Example 1

[0042] a: Preparation of layered high-entropy oxides

[0043] Add 0.6 g of anhydrous sodium carbonate, 1 mmol each of La₂O₃, Nd₂O₃, and Sm₂O₃, 2 mmol of CeO₂, and 0.33 mmol of Pr₆O₃. 11 10 mmol TiO2 was mixed evenly by ball milling at 600 r / min for 0.5 hours. The mixture was then placed in a muffle furnace and calcined at 1000 °C for 10 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 60 °C for 12 h to obtain layered high-entropy oxide Na(LaCeNdPrSm)TiO4.

[0044] b: Preparation of Ru / layered high-entropy oxide catalysts

[0045] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of Na(LaCeNdPrSm)TiO4 was added to the solution with stirring. After thorough mixing, 0.75 g of 25 wt% ammonia solution was added to the suspension. The mixture was then reacted at 60 °C for 4 h with stirring. The solution was subsequently filtered, washed, dried at 60 °C for 12 h, and calcined at 300 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the solution was reduced with hydrogen at 300 °C at a heating rate of 5 °C / min and a hydrogen volume hourly space velocity of 100 h⁻¹. -1The reduction time was 4 hours, and the catalyst was obtained, denoted as 1%Ru / Na(LaCeNdPrSm)TiO4.

[0046] The reaction conditions for the catalyst to be applied to ammonia decomposition were as follows: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, and space velocities of 200, 1000, 20000, 30000 and 60000 ml / g·h, respectively. The reaction results are shown in Table 1.

[0047] Example 2

[0048] a: Preparation of layered high-entropy oxides

[0049] 0.5 g of anhydrous lithium carbonate, 1 mmol La2O3, 1 mmol Sm2O3, 1 mmol Eu2O3, 2 mmol CeO2 and 8 mmol TiO2 were mixed evenly by ball milling at 400 r / min for 1 h. The mixture was then placed in a muffle furnace and calcined at 800 °C for 48 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 120 °C for 4 h to obtain layered high-entropy oxide Li(LaSmEuCe)TiO4.

[0050] b: Preparation of Ru / layered high-entropy oxide catalysts

[0051] 0.0627 g of ruthenium nitrate was dissolved in 50 ml of water. 2.0 g of Li(LaSmEuCe)TiO4 was added to the solution with stirring. After thorough mixing, 0.33 g of KOH was added to the suspension. The mixture was then reacted at 60 °C for 4 h with stirring. The mixture was subsequently filtered, washed, dried at 120 °C for 4 h, and calcined at 200 °C for 12 h, resulting in a Ru content of 1%. After cooling to room temperature, the mixture was reduced with hydrogen at 200 °C at a heating rate of 5 °C / min and a hydrogen volume hourly space velocity of 100 h⁻¹. -1 The reduction time was 6 hours, and the catalyst was obtained, denoted as 1%Ru / Li(LaSmEuCe)TiO4.

[0052] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0053] Example 3

[0054] a: Preparation of layered high-entropy oxides

[0055] Add 1.0 g of anhydrous potassium carbonate, 1 mmol each of La₂O₃, Yb₂O₃, and Tb₂O₃, 2 mmol of CeO₂, and 0.33 mmol of Pr₆O₃. 11 10 mmol TiO2 was mixed evenly by ball milling at 500 r / min for 1 h. The mixture was then placed in a muffle furnace and calcined at 1300 °C for 1 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 110 °C for 6 h to obtain layered high-entropy oxide K(LaCeYbTbPr)TiO4.

[0056] b: Preparation of Ru / layered high-entropy oxide catalysts

[0057] 0.0788 g of ruthenium acetylacetone was dissolved in 50 ml of 50 wt% ethanol aqueous solution. 2.0 g of K(LaCeYbTbPr)TiO4 was added to the solution under stirring. After thorough mixing, 0.1 g of NaOH was added to the suspension. The mixture was then reacted at 30 °C for 1 h under stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, yielding a Ru content of 1%. After cooling to room temperature, it was reduced with hydrogen at 300 °C at a heating rate of 5 °C / min and a hydrogen volume hourly space velocity of 100 h⁻¹. -1 The reduction time was 4 hours, and the catalyst was obtained, denoted as 1%Ru / K(LaCeYbTbPr)TiO4.

[0058] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0059] Example 4

[0060] a: Preparation of layered high-entropy oxides

[0061] Add 1.6g of anhydrous potassium nitrate, 1mmol each of La₂O₃, Yb₂O₃, and Ho₂O₃, 2mmol of CeO₂, and 0.33mmol of Pr₆O₃. 11 10 mmol TiO2 was mixed evenly by ball milling at 500 r / min for 0.5 h. The mixture was then placed in a muffle furnace and calcined at 1000 °C for 10 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 110 °C for 6 h to obtain a layered high-entropy oxide K(LaCePrYbHo)TiO4.

[0062] b: Preparation of Ru / layered high-entropy oxide catalysts

[0063] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of K(LaCePrYbHo)TiO4 was added to the solution with stirring. After thorough mixing, 0.82 g of K2CO3 was added to the suspension, and the mixture was reacted at 60 °C for 1 h with stirring. The mixture was then filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the mixture was reduced with ammonia at 600 °C. The heating rate from room temperature to the reduction temperature was 5 °C / min, and the hydrogen volume hourly space velocity was 100 h⁻¹. -1 The reduction time was 1 hour, and the catalyst was obtained, denoted as 1%Ru / K(LaCePrYbHo)TiO4.

[0064] The reaction conditions for applying the catalyst to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0065] Example 5

[0066] a: Preparation of layered high-entropy oxides

[0067] Add 0.6g of anhydrous sodium carbonate, 1mmol each of La₂O₃, Tm₂O₃, and Lu₂O₃, 2mmol of CeO₂, and 0.33mmol of Pr₆O₂. 11 10 mmol TiO2 was mixed evenly by ball milling at 500 r / min for 4 h. The mixture was then placed in a muffle furnace and calcined at 1200 °C for 4 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 110 °C for 6 h to obtain layered high-entropy oxide Na(LaCeTmLuPr)TiO4.

[0068] b: Preparation of Ru / layered high-entropy oxide catalysts

[0069] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of Na(LaCeTmLuPr)TiO4 was added to the solution under stirring. After thorough mixing, 0.63 g of Na2CO3 was added to the suspension. The mixture was then reacted at 60 °C for 1 h under stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the mixture was reduced using an ammonia-hydrogen mixture with a hydrogen volume concentration of 50% at 500 °C. The heating rate from room temperature to the reduction temperature was 5 °C / min, and the hydrogen volume hourly space velocity (HHSV) was 100 h⁻¹. -1The reduction time was 4 hours, and the catalyst was obtained, denoted as 1%Ru / Na(LaCeTmLuPr)TiO4.

[0070] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0071] Example 6

[0072] a: Preparation of layered high-entropy oxides

[0073] 1 mmol each of La2O3, Sm2O3, Dy2O3, and Gd2O3, 2 mmol of CeO2, and 10 mmol of TiO2 were mixed uniformly by ball milling at 500 r / min for 2 h. 15 g of potassium hydroxide was added, and the mixture was placed in a muffle furnace and calcined at 1000 °C for 8 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate. The precipitate was dried at 110 °C for 6 h to obtain the layered high-entropy oxide K(LaCeSmDyGd)TiO4.

[0074] b: Preparation of Ru / layered high-entropy oxide catalysts

[0075] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of K(LaCeSmDyGd)TiO4 was added to the solution with stirring. After thorough mixing, 0.59 g of urea was added to the suspension. The mixture was then reacted at 90 °C for 6 h with stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the mixture was reduced with hydrogen at 300 °C at a heating rate of 5 °C / min and a hydrogen volume hourly space velocity (HHSV) of 1000 h⁻¹. -1 The reduction time was 5 hours, and the catalyst was obtained, denoted as 1%Ru / K(LaCeSmDyGd)TiO4.

[0076] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0077] Example 7

[0078] a: Preparation of layered high-entropy oxides

[0079] Add 1.0 g of anhydrous sodium carbonate, 1 mmol each of La₂O₃, Nd₂O₃, and Sm₂O₃, 0.5 mmol of CeO₂, and 0.33 mmol of Pr₆O₃. 119 mmol TiO2 was mixed uniformly by ball milling at 500 r / min for 1 h. The resulting mixture was then calcined in a muffle furnace at 1000 °C for 8 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate, which was then dried at 110 °C for 6 h to obtain layered high-entropy oxide Na(LaCe). 0.25 NdPrSm)TiO4;

[0080] b: Preparation of Ru / layered high-entropy oxide catalysts

[0081] Weigh 0.0517g RuCl3·3H2O and dissolve it in 50ml of water. While stirring, add 2.0g Na(LaCe) 0.25 NdPrSm)TiO4 was added to the above solution and stirred until homogeneous. Then, 0.59 g of urea was added to the suspension, and the mixture was reacted at 90 °C for 6 h with stirring. The mixture was then filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru content of 1%. After cooling to room temperature, it was subjected to hydrogen reduction at 300 °C at a heating rate of 5 °C / min from room temperature to the reduction temperature, with a hydrogen volume hourly space velocity of 1000 h⁻¹. -1 The reduction time was 4 hours, and the catalyst was obtained, denoted as 1% Ru / Na(LaCe). 0.25 NdPrSm)TiO4.

[0082] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0083] Example 8

[0084] a: Preparation of layered high-entropy oxides

[0085] Add 1.0 g of anhydrous sodium carbonate, 1 mmol each of La₂O₃, Nd₂O₃, and Sm₂O₃, 3 mmol of CeO₂, and 0.33 mmol of Pr₆O₃. 11 12 mmol TiO2 was mixed uniformly by ball milling at 500 r / min for 1 h. The resulting mixture was then calcined in a muffle furnace at 1000 °C for 8 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate, which was then dried at 110 °C for 6 h to obtain layered high-entropy oxide Na(LaCe). 1.5 NdPrSm)TiO4;

[0086] b: Preparation of Ru / layered high-entropy oxide catalysts

[0087] Weigh 0.0517g RuCl3·3H2O and dissolve it in 50ml of water. While stirring, add 2.0g Na(LaCe) 1.5 NdPrSm)TiO4 was added to the above solution and stirred until homogeneous. Then, 0.33 g of KOH was added to the suspension, and the mixture was reacted at 60 °C for 3 h with stirring. The mixture was then filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru mass content of 1%. After cooling to room temperature, it was subjected to hydrogen reduction at 300 °C at a heating rate of 5 °C / min from room temperature to the reduction temperature, with a hydrogen volume hourly space velocity of 1000 h⁻¹. -1 The reduction time was 4 hours, and the catalyst was obtained, denoted as 1% Ru / Na(LaCe). 1.5 NdPrSm)TiO4.

[0088] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0089] Example 9

[0090] a: Preparation of layered high-entropy oxides

[0091] Add 2.0 g of anhydrous sodium carbonate, 1 mmol each of La₂O₃, Nd₂O₃, and Sm₂O₃, 5 mmol of CeO₂, and 0.33 mmol of Pr₆O₃. 11 13 mmol TiO2 was mixed uniformly by ball milling at 500 r / min for 1 h. The resulting mixture was then calcined in a muffle furnace at 1000 °C for 8 h at a heating rate of 5 °C / min. After cooling to room temperature, the mixture was washed with water and centrifuged to obtain a precipitate, which was then dried at 110 °C for 6 h to obtain layered high-entropy oxide Na(LaCe). 2.5 NdPrSm)TiO4;

[0092] b: Preparation of Ru / layered high-entropy oxide catalysts

[0093] Weigh 0.0517g RuCl3·3H2O and dissolve it in 50ml of water. While stirring, add 2.0g Na(LaCe) 2.5 NdPrSm)TiO4 was added to the above solution and stirred until homogeneous. Then, 0.33 g of KOH was added to the suspension, and the mixture was reacted at 60 °C for 3 h with stirring. The mixture was then filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru mass content of 1%. After cooling to room temperature, it was subjected to hydrogen reduction at 300 °C at a heating rate of 5 °C / min from room temperature to the reduction temperature, with a hydrogen volume hourly space velocity of 1000 h⁻¹. -1The reduction time was 4 hours, and the catalyst was obtained, denoted as 1% Ru / Na(LaCe). 2.5 NdPrSm)TiO4.

[0094] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0095] Example 10

[0096] a: Preparation of layered high-entropy oxides

[0097] The preparation method of the layered high-entropy oxide is the same as in Example 1;

[0098] b: Preparation of Ru / layered high-entropy oxide catalysts

[0099] 0.0052 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of Na(LaCeNdPrSm)TiO4 prepared in Example 1 was added to the solution under stirring. After thorough mixing, 0.067 g of 25 wt% ammonia was added to the suspension. The mixture was then reacted at 60 °C for 3 h under stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru content of 0.1%. After cooling to room temperature, it was subjected to hydrogen reduction at 300 °C. The heating rate from room temperature to the reduction temperature was 5 °C / min, and the hydrogen volume hourly space velocity was 1000 h⁻¹. -1 The reduction time was 4 hours, and the resulting catalyst was denoted as 0.1% Ru / Na(LaCeNdPrSm)TiO4.

[0100] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0101] Example 11

[0102] a: Preparation of layered high-entropy oxides

[0103] The preparation method of the layered high-entropy oxide is the same as in Example 1;

[0104] b: Preparation of Ru / layered high-entropy oxide catalysts

[0105] 0.2586 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of Na(LaCeNdPrSm)TiO4 prepared in Example 1 was added to the solution under stirring. After thorough mixing, 3.4 g of 25 wt% ammonia was added to the suspension. The mixture was then reacted at 60 °C for 3 h under stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru content of 5%. After cooling to room temperature, it was subjected to hydrogen reduction at 300 °C. The heating rate from room temperature to the reduction temperature was 5 °C / min, and the hydrogen volume hourly space velocity was 1000 h⁻¹. -1 The reduction time was 4 hours, and the catalyst was obtained, denoted as 5%Ru / Na(LaCeNdPrSm)TiO4.

[0106] The reaction conditions for applying the catalyst to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0107] Example 12

[0108] a: Preparation of layered high-entropy oxides

[0109] The preparation method of the layered high-entropy oxide is the same as in Example 1;

[0110] b: Preparation of Ru / layered high-entropy oxide catalysts

[0111] 0.5173 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of Na(LaCeNdPrSm)TiO4 prepared in Example 1 was added to the solution under stirring. After stirring until homogeneous, 6.7 g of 25 wt% ammonia was added to the suspension. The mixture was then reacted at 60 °C for 3 h under stirring. The mixture was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, with a Ru content of 10%. The mixture was then subjected to hydrogen reduction at 300 °C, with a heating rate of 5 °C / min from room temperature to the reduction temperature and a hydrogen volume hourly space velocity of 1000 h⁻¹. -1 The reduction time was 4 hours, and the catalyst was obtained, denoted as 10%Ru / Na(LaCeNdPrSm)TiO4.

[0112] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0113] Comparative Example 1

[0114] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of SiO2 was added to the solution with stirring. After thorough mixing, 0.67 g of 25 wt% ammonia was added to the suspension. The mixture was then reacted at 60 °C for 3 h with stirring. The solution was then filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the solution was reduced with hydrogen at 300 °C at a heating rate of 5 °C / min, with a hydrogen volume hourly space velocity (HHSV) of 1000 h⁻¹. -1 The reduction time was 4 hours, and the resulting catalyst was denoted as 1% Ru / SiO2.

[0115] The reaction conditions for the catalyst to be applied to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, space velocity of 30000ml / g·h, and the reaction results are shown in Table 1.

[0116] Comparative Example 2

[0117] 0.0517 g of RuCl3·3H2O was dissolved in 50 ml of water. 2.0 g of CeO2 was added to the solution with stirring. After thorough mixing, 0.67 g of 25 wt% ammonia solution was added to the suspension. The mixture was then reacted at 60 °C for 3 h with stirring. The solution was subsequently filtered, washed, dried at 80 °C for 6 h, and calcined at 400 °C for 4 h, resulting in a Ru content of 1%. After cooling to room temperature, the solution was subjected to hydrogen reduction at 300 °C. The heating rate from room temperature to the reduction temperature was 5 °C / min, and the hydrogen volume hourly space velocity (HHSV) was 1000 h⁻¹. -1 The reduction time was 4 hours, and the resulting catalyst was denoted as 1% Ru / CeO2.

[0118] The reaction conditions for applying the catalyst to ammonia decomposition were: ammonia concentration of 99.9%, fixed-bed reactor, reaction temperature of 400℃~800℃, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 1.

[0119] Results analysis:

[0120] Analysis of the data in Table 1 shows that the ruthenium-based catalyst supported by layered high-entropy oxides exhibits good activity in the ammonia decomposition reaction. The 1% Ru / Na(LaCeNdPrSm)TiO4 catalyst can achieve an ammonia conversion rate >99% at 500℃, demonstrating efficient ammonia decomposition under high space velocity and low temperature conditions.

[0121] like Figure 3 As shown, due to the unique stability of the high-entropy support material of this invention, the active component and the support have a unique electronic structure and interaction, resulting in better catalyst stability and potential for industrial application.

[0122] Table 1 Reaction performance of ammonia decomposition on different catalysts

[0123]

[0124] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A layered high-entropy oxide-supported ruthenium catalyst, characterized in that, The catalyst includes a support and an active component, wherein the active component is supported on the support; The active component is ruthenium. The support is a layered high-entropy oxide with the chemical formula A(HE)TiO. x Where A is at least one of the alkali metal elements Li, Na, and K, and HE is at least four of the lanthanide metal elements La, Ce, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu, and Dy. The percentage of each HE metal element's molar number to the total number of HE metal elements' molar numbers is 5% to 35%. <x<5。 2. The catalyst according to claim 1, characterized in that, The active component in the catalyst accounts for 0.1% to 10% of the catalyst's mass percentage; The support in the catalyst accounts for 90% to 99.9% of the catalyst's mass percentage.

3. A method for preparing the catalyst according to any one of claims 1-2, characterized in that, Includes the following steps: a: Lanthanide metal oxides, titanium oxides and alkali metal salts were mixed according to the chemical formula of high-entropy oxides. The resulting mixture was calcined, then washed and dried to obtain layered high-entropy oxides. b: Add the layered high-entropy oxide obtained in step a to the ruthenium precursor salt solution, stir evenly, add a precipitant to the resulting suspension to carry out the precipitation reaction, dry, heat to 200~400 ℃ for calcination for 4~12 h, cool to room temperature, heat to 200~600 ℃ for reduction for 1~6 h, and obtain the layered high-entropy oxide supported ruthenium catalyst.

4. The preparation method according to claim 3, characterized in that: In step a, the lanthanide metal oxide is selected from any four of the oxides of La, Ce, Sm, Pr, Nd, Gd, Yb, Tb, Eu, Ho, Er, Tm, Lu, and Dy; The oxide of titanium is TiO2; The alkali metal salt is at least one of the carbonates and nitrates of Li, Na, and K; The molar ratio of metal elements in the lanthanide metal oxide and the titanium oxide is 0.8~1.2; The ratio of the number of moles of the alkali metal salt to the total number of moles of the lanthanide metal oxide is greater than 1.

5. The preparation method according to claim 3, characterized in that: In step a, the calcination temperature is 800~1300℃ and the calcination time is 1~48 h.

6. The preparation method according to claim 3, characterized in that: In step b, the ruthenium precursor salt is at least one of ruthenium chloride, ruthenium nitrate, and ruthenium acetylacetonate; The precipitant is at least one of urea, ammonia, potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate. The molar ratio of the precipitant to the ruthenium precursor salt is 10~50:

1.

7. The preparation method according to claim 3, characterized in that, In step b, the precipitation reaction is carried out at a temperature of 30-90 °C for 1-6 h. The drying temperature is 60~120 ℃, and the drying time is 4~12 h.

8. The preparation method according to claim 3, characterized in that, In step b, the reducing gas is at least one of ammonia and hydrogen; The heating rate from room temperature to reduction temperature is 1~10 °C / min.

9. The application of the catalyst according to any one of claims 1-2 in ammonia decomposition, characterized in that, After heating the layered high-entropy oxide-supported ruthenium catalyst to the reaction temperature of ammonia decomposition, ammonia gas is introduced to obtain the products hydrogen and nitrogen.

10. The application according to claim 9, characterized in that, The reaction temperature for ammonia decomposition is 400~800 ℃, and the space velocity for ammonia decomposition is 200~60000 ml / g·h.

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