High-entropy alloy catalyst for ammonia decomposition as well as preparation method and application of high-entropy alloy catalyst

Abstract

The invention discloses a high-entropy alloy catalyst for ammonia decomposition and a preparation method thereof. The catalyst comprises at least five of Pt, Pd, Ru, Rh, Ir, Cu, Ni and Co, and the mole number of each metal element accounts for 5-35% of the total mole number of all the metal elements. The catalyst is prepared by adopting a wet chemical method and is directly synthesized by utilizing copolymer micelle self-assembly and a liquid-phase reduction method, so that the high-temperature and high-energy-consumption process of a traditional high-entropy alloy in the preparation process is avoided. The catalyst has excellent ammonia decomposition reaction activity and has application potential in the field of low-temperature ammonia decomposition hydrogen production.

Description

Technical Field

[0001] The invention relates to a high entropy alloy catalyst for ammonia decomposition and a preparation method and application thereof, belonging to the technical field of catalyst preparation. Background Art

[0002] Due to the intermittent, volatile and seasonal characteristics of renewable energy, it is difficult for the power grid to absorb it on a large scale. Therefore, it is crucial to develop new ways of safe energy storage with low cost, large capacity, long cycle, cleanness and efficiency.

[0003] Ammonia, as an efficient energy storage and hydrogen storage medium, has the following advantages: 1. High energy density: the hydrogen content in ammonia reaches 17.6%, 1L liquid ammonia = 4.5L high-pressure hydrogen (35.0MPa) = 1200L normal temperature and pressure hydrogen; 2. Easy to store and transport: the liquefaction pressure of ammonia is 0.8MPa at 20°C; 3. The terminal product has no carbon emissions; 4. High safety: ammonia itself is not flammable, and its pungent smell is a reliable alarm signal. In addition, ammonia has a mature transportation and storage system, and its transportation cost is only 1% of the storage and transportation cost. Therefore, using ammonia as an energy storage medium can solve the bottleneck problem of hydrogen storage and transportation technology. Using renewable energy to electrolyze water to produce hydrogen, and then synthesizing ammonia from hydrogen, using ammonia as an energy storage medium, the storage and transportation of hydrogen is transformed into the storage and transportation of ammonia, which is expected to realize the "long-distance" and "cross-season" storage and transportation of renewable energy, which is of great significance to the development of renewable energy.

[0004] The process of ammonia decomposition to produce hydrogen is one of the key processes for the terminal utilization of ammonia energy. The reaction of ammonia decomposition to produce hydrogen is shown in formula (1). This reaction is an endothermic reaction with an increase in volume, so increasing the temperature and reducing the pressure are conducive to the reaction. Under normal pressure and without any catalyst, the actual conversion rate of the ammonia decomposition reaction at 700°C is less than 10%. Therefore, a highly active catalyst is required to achieve efficient decomposition of ammonia.

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

[0006] At present, the main ammonia decomposition catalysts include precious metal catalysts (such as Ru, Ir, etc.), non-precious metal catalysts (such as Fe, Co, Ni, Mo, etc.), transition metal carbides and nitrides (such as WC x 、MoN x The main catalysts used in the commercial market are Ni-based catalysts, but they have the problems of high reaction temperature and high energy consumption. Therefore, the development of new high-performance low-temperature ammonia decomposition hydrogen production catalysts is of great significance for the widespread application of ammonia energy.

[0007] Multimetallic alloy (MMA) nanomaterials have been widely used in catalysis, photonics, biomedicine and other fields due to their excellent physical and chemical properties. The compositional flexibility and multi-element synergy of MMAs provide more opportunities for optimizing performance and overcoming the limitations of single-component metals. As a representative of MMA materials, high-entropy alloys (HEAs) have received widespread attention due to their multi-element composition. This type of material mainly refers to single-phase alloys or solid solution materials composed of more than five components with similar element contents (Science, 2022, 376, eabn3103; Sci. Adv., 2021, 7, eabg1600). High-entropy materials have component diversity and adjustable variability as well as unique structural and functional properties (high entropy effect in thermodynamics, lattice distortion effect in structure, hysteresis diffusion effect in kinetics, and cocktail effect in performance), and have great application potential in materials, energy, environment, catalysis and other fields. Due to the synergistic effect of multiple elements in high entropy alloys, it is expected to provide multi-site synergy for catalytic reactions and reduce the reaction energy barrier. In addition, high entropy materials have high stability and are expected to become ideal catalysts for efficient ammonia decomposition. However, there are few reports on high entropy alloys for ammonia decomposition. There are still huge challenges in developing efficient and stable low-temperature ammonia decomposition catalysts. Summary of the invention

[0008] In view of the problem of low reaction activity of the above-mentioned ammonia decomposition catalyst at low temperatures, the present invention provides a high entropy alloy catalyst and a preparation method and application thereof, which improves the ammonia decomposition reaction performance through the synergistic effect of multiple metal active components and has good catalyst stability.

[0009] In order to achieve the above object, the technical solution of the present invention is as follows:

[0010] In one aspect, the present invention provides a method for preparing a high entropy alloy catalyst for ammonia decomposition, wherein the high entropy alloy catalyst comprises Ru and M, wherein M is at least five of Pt, Pd, Rh, Ir, Cu, Ni, and Co, and the percentage of the molar number of each metal element to the total molar number of all metal elements is 5% to 35%;

[0011] The method comprises the following steps:

[0012] a. adding the block copolymer into an organic solvent and performing ultrasonic dissolution treatment to obtain a solution A;

[0013] b. Add hydrochloric acid and deionized water to solution A and stir evenly to obtain solution B;

[0014] c. adding an aqueous solution of a metal salt precursor required according to the chemical composition of the high entropy alloy catalyst to solution B to obtain solution C;

[0015] d. After stirring solution C, add the reducing agent solution, transfer it to a water bath, and react at 40-90°C for 2-12 hours;

[0016] e. The obtained product is centrifuged, washed, and then dried to obtain the high entropy alloy catalyst.

[0017] In the above technical solution, further, in step a, the block copolymer is a polyethylene glycol-polymethyl methacrylate block copolymer PEO 10500 -b-PMMA 18000 、PEO 10000 -b-PMMA 5500 、PEO 10500 -b-PMMA 22000 Any one of;

[0018] The organic solvent is any one of N,N-dimethylformamide and tetrahydrofuran;

[0019] In the solution A, the concentration of the block copolymer is 3-10 mg / mL.

[0020] In the above technical solution, further, in step b, the metal Ru salt is any one of RuCl3 and RuNO(NO3)3;

[0021] The metal Pt salt is any one of K2PtCl4 and Na2PtCl4;

[0022] The metal Pd salt is any one of K2PdCl4 and Na2PdCl4;

[0023] The metal Rh salt is any one of K3RhCl6 and Na3RhCl6;

[0024] The metal Ir salt is any one of K2IrCl6 and Na2IrCl6;

[0025] The metal Cu salt is any one of CuCl2 and Cu(NO3)2;

[0026] The metal Ni salt is any one of NiCl2 and Ni(NO3)2;

[0027] The metal Co salt is any one of CoCl2 and Co(NO3)2;

[0028] In the solution B, the concentration of hydrochloric acid is 3-8 mol / L.

[0029] In the above technical solution, further, in step c, the concentration of the metal salt precursor in the solution C is 20 to 80 mmol / L.

[0030] In the above technical solution, further, in step d, the reducing agent is any one of L-ascorbic acid (L-AA) and hydrazine hydrate (N2H4·H2O);

[0031] The concentration of the reducing agent is 0.05-0.2 mol / L.

[0032] In the above technical solution, further, in step e, the solvent used for washing is any one of a mixture of ethanol and water and a mixture of acetone and water.

[0033] In the above technical solution, further, in step e, the drying temperature is 60 to 120° C., and the drying time is 4 to 12 hours.

[0034] Another aspect of the present invention provides an application of the catalyst prepared by the above preparation method in ammonia decomposition, wherein the high entropy alloy catalyst is heated to the reaction temperature of ammonia decomposition and ammonia is introduced to obtain products of hydrogen and nitrogen; the reaction temperature of the ammonia decomposition is 400-800°C, preferably 400-500°C.

[0035] In the above technical solution, further, the volume space velocity of ammonia decomposition is 200 to 60000 ml / g·h.

[0036] The beneficial effects of the present invention are:

[0037] 1) The catalyst provided by the present invention has a high entropy alloy structure, which helps to exert the synergistic effect between multi-metal active sites, promotes the breaking of NH bonds in ammonia molecules and the desorption of products N2 and H2, thereby improving the activity of ammonia decomposition reaction. The catalyst provided by the present invention is applied to ammonia decomposition reaction, can promote the catalytic conversion of ammonia molecules, has the advantages of low ammonia decomposition reaction temperature, high ammonia space velocity, and high ammonia conversion rate, and realizes efficient decomposition of ammonia at a relatively low temperature.

[0038] 2) The present invention adopts a wet chemical method to prepare a high entropy alloy catalyst, avoiding the high temperature process required in traditional high entropy alloy preparation methods such as arc melting and powder metallurgy, and reducing the energy consumption of the high entropy alloy synthesis process.

[0039] 3) The catalyst provided by the present invention has a unique electronic structure and interaction between the metal components of the high entropy alloy, and has the advantage of high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The catalyst stability test charts obtained in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0042] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0043] Example 1

[0044] (1) 10 mg PEO 10500 -b-PMMA 22000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0045] (2) Add 0.5 mL of 5 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0046] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L K2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L K3RhCl6 aqueous solution, and 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution to the above solution to obtain a mixed solution C;

[0047] (4) Solution C was stirred evenly, and 3 mL of 0.1 mol / L L-AA solution was added. Then, the solution was transferred to a water bath and reacted at 90 °C for 6 h.

[0048] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 120° C. for 4 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhIr-HEA.

[0049] The catalyst prepared in Example 1 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and test space velocities of 200, 1000, 30000, and 60000 ml / g·h, respectively. The reaction results are shown in Table 1.

[0050] Example 2

[0051] (1) 3mg PEO 10500 -b-PMMA 18000 Dissolved in 1 mL THF and sonicated in a 20 mL vial to obtain block copolymer solution A;

[0052] (2) Add 1.0 mL of 3 mol / L hydrochloric acid and 0.5 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0053] (3) adding 0.8 mL of 40 mmol / L RuNO(NO3)3 aqueous solution, 0.4 mL of 40 mmol / L Na2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L Na2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L Na3RhCl6 aqueous solution, and 0.4 mL of 40 mmol / L CuCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0054] (4) Solution C was stirred evenly, and 3 mL of 0.2 mol / L hydrazine hydrate solution was added. Then, the solution was transferred to a water bath and reacted at 80° C. for 12 h.

[0055] (5) The obtained product was centrifuged and washed with a mixture of ethanol and water to remove the soft template, and finally transferred to an oven for drying at 60° C. for 12 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhCu-HEA.

[0056] The catalyst prepared in Example 2 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0057] Example 3

[0058] (1) 5mg PEO 10000 -b-PMMA 5500 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0059] (2) Add 0.5 mL of 8 mol / L hydrochloric acid and 0.8 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0060] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.5 mL of 40 mmol / L Na2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L Na2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L Na3RhCl6 aqueous solution, and 0.1 mL of 40 mmol / L NiCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0061] (4) Solution C was stirred evenly, and 3 mL of 0.05 mol / L L-AA solution was added. Then, the mixture was transferred to a water bath and reacted at 60 °C for 12 h.

[0062] (5) The obtained product was centrifuged and washed with a mixture of ethanol and water to remove the soft template, and finally transferred to an oven for drying at 80° C. for 8 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhNi-HEA.

[0063] The catalyst prepared in Example 3 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0064] Example 4

[0065] (1) 5mg PEO 10000 -b-PMMA 5500 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0066] (2) Add 0.5 mL of 6 mol / L hydrochloric acid and 0.8 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0067] (3) adding 0.2 mL of 80 mmol / L RuCl3 aqueous solution, 0.8 mL of 20 mmol / L Na2PtCl4 aqueous solution, 0.8 mL of 20 mmol / L Na2PdCl4 aqueous solution, 0.3 mL of 40 mmol / L Na3RhCl6 aqueous solution, and 0.1 mL of 40 mmol / L CoCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0068] (4) Stir solution C evenly, add 3 mL of 0.1 mol / L L-AA solution, and then transfer it to a water bath and react at 40 °C for 12 h;

[0069] (5) The obtained product was centrifuged and washed with a mixture of ethanol and water to remove the soft template, and finally transferred to an oven for drying at 120° C. for 4 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhCo-HEA.

[0070] The catalyst prepared in Example 4 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0071] Example 5

[0072] (1) 5mg PEO 10500 -b-PMMA 18000Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0073] (2) Add 0.5 mL of 6 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0074] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L Na2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, and 0.4 mL of 40 mmol / L CuCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0075] (4) Stir solution C evenly, add 3 mL of 0.1 mol / L L-AA solution, and then transfer it to a water bath and react at 90 °C for 2 h;

[0076] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 60° C. for 12 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdIrCu-HEA.

[0077] The catalyst prepared in Example 5 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0078] Example 6

[0079] (1) 5mg PEO 10500 -b-PMMA 18000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0080] (2) Add 0.5 mL of 6 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0081] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L Na3RhCl6 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, 0.4 mL of 40 mmol / L CuCl2 aqueous solution, and 0.4 mL of 40 mmol / L NiCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0082] (4) Stir solution C evenly, add 3 mL of 0.1 mol / L L-AA solution, and then transfer it to a water bath and react at 90 °C for 2 h;

[0083] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 60° C. for 12 h to obtain a high entropy alloy catalyst, which was recorded as RuRhIrCuNi-HEA.

[0084] The catalyst prepared in Example 6 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0085] Example 7

[0086] (1) 5mg PEO 10500 -b-PMMA 18000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0087] (2) Add 0.5 mL of 6 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0088] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L K3RhCl6 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, and 0.4 mL of 40 mmol / L CuCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0089] (4) Stir solution C evenly, add 3 mL of 0.1 mol / L L-AA solution, and then transfer it to a water bath and react at 90 °C for 2 h;

[0090] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 60° C. for 12 h to obtain a high entropy alloy catalyst, which was recorded as RuPdRhIrCu-HEA.

[0091] The catalyst prepared in Example 7 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2

[0092] Example 8

[0093] (1) 10 mg PEO 10500 -b-PMMA 22000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0094] (2) Add 0.5 mL of 5 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0095] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L K2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L K3RhCl6 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, and 0.4 mL of 40 mmol / L CuCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0096] (4) Solution C was stirred evenly, and 3 mL of 0.1 mol / L L-AA solution was added. Then, the solution was transferred to a water bath and reacted at 90 °C for 6 h.

[0097] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 120° C. for 4 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhIrCu-HEA.

[0098] The catalyst prepared in Example 8 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0099] Example 9

[0100] (1) 10 mg PEO 10500 -b-PMMA 22000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0101] (2) Add 0.5 mL of 5 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0102] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L K2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L K3RhCl6 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, 0.4 mL of 40 mmol / L CuCl2 aqueous solution, and 0.4 mL of 40 mmol / L NiCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0103] (4) Stir solution C evenly, add 3 mL of 0.1 mol / L L-AA solution, transfer it to a water bath, and react at 90 °C for 6 h;

[0104] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 120° C. for 4 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhIrCuNi-HEA.

[0105] The catalyst prepared in Example 9 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0106] Example 10

[0107] (1) 10 mg PEO 10500 -b-PMMA 22000 Dissolved in 1 mL DMF and ultrasonicated in a 20 mL vial to obtain block copolymer solution A;

[0108] (2) Add 0.5 mL of 5 mol / L hydrochloric acid and 0.3 mL of deionized water to the above solution and stir evenly to obtain solution B;

[0109] (3) adding 0.6 mL of 40 mmol / L RuCl3 aqueous solution, 0.4 mL of 40 mmol / L K2PtCl4 aqueous solution, 0.4 mL of 40 mmol / L K2PdCl4 aqueous solution, 0.4 mL of 40 mmol / L K3RhCl6 aqueous solution, 0.4 mL of 40 mmol / L Na2IrCl6 aqueous solution, 0.4 mL of 40 mmol / L CuCl2 aqueous solution, 0.4 mL of 40 mmol / L NiCl2 aqueous solution, and 0.4 mL of 40 mmol / L CoCl2 aqueous solution to the above solution to obtain a mixed solution C;

[0110] (4) Solution C was stirred evenly, and 3 mL of 0.1 mol / L L-AA solution was added. Then, the solution was transferred to a water bath and reacted at 90 °C for 6 h.

[0111] (5) The obtained product was centrifuged and washed with a mixture of acetone and water to remove the soft template, and finally transferred to an oven for drying at 120° C. for 4 h to obtain a high entropy alloy catalyst, which was recorded as RuPtPdRhIrCuNiCo-HEA.

[0112] The catalyst prepared in Example 10 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0113] Comparative Example 1

[0114] Weigh 0.0517g RuCl3·3H2O and dissolve it in 50ml water. Add 2.0g SiO2 to the above solution under stirring. After stirring evenly, add 0.67g 25wt% ammonia water to the above suspension. Then react at 60℃ for 3h under stirring, filter, wash, dry at 80℃ for 6h, and calcine at 400℃ for 4h. The Ru mass content is 1%. After cooling to room temperature, reduce it with hydrogen at 300℃. The heating rate from room temperature to the reduction temperature is 5℃ / min. The volume space velocity of hydrogen is 1000h. -1 The reduction time is 4h, and the catalyst is obtained, recorded as 1%Ru / SiO2.

[0115] The catalyst prepared in Comparative Example 1 was applied to the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0116] Comparative Example 2

[0117] Weigh 1.0g Al2O3 carrier, weigh 0.5369g Ni(NO3)2 and dissolve it in 2g deionized water to make a mixed solution, add it to the Al2O3 carrier and mix it evenly. Soak at room temperature for 12h, dry at 80℃ for 12h, and calcine at 300℃ in air atmosphere for 4h, where the Ni mass content is 15%; then, reduce it with hydrogen at a temperature of 600℃, a heating rate of 5℃ / min from room temperature to the reduction temperature, and a hydrogen volume space velocity of 2000h -1 , the pressure was normal pressure, and the reduction time was 1 h. The catalyst was obtained and was recorded as 15% Ni / Al2O3.

[0118] The catalyst prepared in Comparative Example 2 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0119] Comparative Example 3

[0120] Weigh 5.0g Al2O3 carrier, weigh 0.1319g RuCl3·3H2O and 0.1587g Ni(NO3)2, dissolve them in 5g deionized water to make a mixed solution, add it to the Al2O3 carrier and mix it evenly. Soak at room temperature for 12h, dry at 80℃ for 12h, and calcine at 300℃ in air atmosphere for 4h, wherein the mass content of Ru is 1% and the mass content of Ni is 1%; then, reduce it with hydrogen at a temperature of 600℃, a heating rate of 5℃ / min from room temperature to the reduction temperature, and a volume space velocity of hydrogen of 2000h -1 , the pressure was normal pressure, the reduction time was 3h, and the catalyst was obtained, recorded as 1%Ru-1%Ni / Al2O3.

[0121] The catalyst prepared in Comparative Example 3 was used in the reaction conditions of ammonia decomposition: ammonia concentration of 99.9%, fixed bed reactor, reaction temperature of 400°C to 800°C, and space velocity of 30000 ml / g·h. The reaction results are shown in Table 2.

[0122] Result analysis:

[0123] From the data analysis in Table 1, it can be seen that the high entropy alloy catalyst has a higher activity in the ammonia decomposition reaction. For the RuPtPdRhIr-HEA catalyst, an ammonia conversion rate of 99% can be achieved at 500°C, and efficient decomposition of ammonia to produce hydrogen can be achieved under high space velocity and low temperature conditions. Compared with Comparative Example 3, the Ru-Ni / Al2O3 alloy catalyst prepared by the impregnation method has an ammonia conversion rate of 88.2% at 800°C. The high entropy alloy catalyst used in the present invention shows a higher ammonia decomposition reaction activity.

[0124] As shown in Table 2, the ammonia decomposition reaction activity at different space velocities in Example 1 is compared. It can be seen that at 400°C, as the space velocity gradually increases from 200ml / g·h to 60000ml / g·h, the ammonia conversion rate gradually decreases from 85.10% to 67.20%, that is, as the space velocity increases, the ammonia conversion rate gradually decreases. However, when the reaction temperature is 800°C, as the reaction space velocity increases, the ammonia conversion rate is maintained at 99.9%, indicating that the catalyst has a high activity at high temperature and can adapt to the efficient decomposition of ammonia at different space velocities. This provides a larger operating window for the catalyst in practical applications.

[0125] like Figure 1As shown, due to the unique structure of the high entropy alloy material of the present invention, it can produce multi-element synergistic effects, the catalyst has better stability, and provides a new choice for ammonia decomposition hydrogen production catalyst.

[0126] Table 1 Reaction performance of ammonia decomposition under different space velocity conditions in Example 1

[0127] Serial number 400℃ conversion rate 450℃ conversion rate 500℃ conversion rate 800℃ conversion rate Airspeed ml / g·h 1 85.1％ 96.1％ 99.6％ 99.9％ 200 2 81.3％ 95.1％ 99.6％ 99.9％ 1000 3 72.2％ 91.1％ 99.6％ 99.9％ 30000 4 67.2％ 85.1％ 95.7％ 99.9％ 60000

[0128] Table 2 Reaction performance of ammonia decomposition of catalysts of Examples 1-10 and Comparative Examples 1-3

[0129]

[0130]

[0131] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a high entropy alloy catalyst for ammonia decomposition, characterized in that: The high entropy alloy catalyst comprises Ru and M, wherein M is at least five of Pt, Pd, Rh, Ir, Cu, Ni, and Co, and the percentage of the molar number of each metal element to the total molar number of all metal elements is 5% to 35%; The method comprises the following steps: a. adding the block copolymer into an organic solvent and performing ultrasonic dissolution treatment to obtain a solution A; b. Add hydrochloric acid and deionized water to solution A and stir evenly to obtain solution B; c. adding an aqueous solution of a metal salt precursor required according to the chemical composition of the high entropy alloy catalyst to solution B to obtain solution C; d. After stirring solution C, add the reducing agent solution, transfer it to a water bath, and react at 40-90°C for 2-12h; e. The obtained product is centrifuged, washed, and then dried to obtain the high entropy alloy catalyst.

2. The preparation method according to claim 1, characterized in that: In step a, the block copolymer is polyethylene glycol-polymethyl methacrylate block copolymer PEO 10500 -b-PMMA 18000 、PEO 10000 -b-PMMA 5500 、PEO 10500 -b-PMMA 22000 Any one of; The organic solvent is any one of N,N-dimethylformamide and tetrahydrofuran; In the solution A, the concentration of the block copolymer is 3-10 mg / mL.

3. The preparation method according to claim 1, characterized in that: In step b, the metal Ru salt is any one of RuCl3 and RuNO(NO3)3; The metal Pt salt is any one of K2PtCl4 and Na2PtCl4; The metal Pd salt is any one of K2PdCl4 and Na2PdCl4; The metal Rh salt is any one of K3RhCl6 and Na3RhCl6; The metal Ir salt is any one of K2IrCl6 and Na2IrCl6; The metal Cu salt is any one of CuCl2 and Cu(NO3)2; The metal Ni salt is any one of NiCl2 and Ni(NO3)2; The metal Co salt is any one of CoCl2 and Co(NO3)2; In the solution B, the concentration of hydrochloric acid is 3-8 mol / L.

4. The preparation method according to claim 1, characterized in that: In step c, the concentration of the metal salt precursor in the solution C is 20 to 80 mmol / L.

5. The preparation method according to claim 1, characterized in that: In step d, the reducing agent is any one of L-ascorbic acid and hydrazine hydrate; The concentration of the reducing agent solution is 0.05-0.2 mol / L.

6. The preparation method according to claim 1, characterized in that: In step e, the solvent used for washing is any one of a mixture of ethanol and water and a mixture of acetone and water.

7. The preparation method according to claim 1, characterized in that: In step e, the drying temperature is 60 to 120° C., and the drying time is 4 to 12 hours.

8. Use of a catalyst prepared by the preparation method according to any one of claims 1 to 7 in ammonia decomposition, characterized in that: After heating the high entropy alloy catalyst to the reaction temperature of ammonia decomposition, ammonia is introduced to obtain hydrogen and nitrogen products; the reaction temperature of ammonia decomposition is 400-800°C.

9. The use according to claim 8, characterized in that: The volume space velocity of the ammonia decomposition is 200 to 60000 ml / g·h.

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