A high-entropy alloy catalyst, a preparation method and application thereof

Abstract

The application belongs to the technical field of metal catalysts, and specifically discloses a high-entropy alloy catalyst, a preparation method and application thereof; the preparation method adopts solid acid and alkaline end-capping agent and at least five kinds of metal salt to prepare a high-entropy alloy precursor, then the high-entropy alloy precursor is loaded on a carrier, and then the high-entropy alloy catalyst is obtained through calcination and reduction; the metal ion precursor, the solid acid rich in ligands, the alkaline end-capping agent and the polycondensation under hydrothermal conditions are used to generate surface functionalized carbon dots; the surface amine groups, carboxylate groups and the like are coordinated with metal ions, so that the multiple metal ions are atomically dispersed on the surface of the carbon dots, thereby promoting the formation of the high-entropy alloy; the obtained high-entropy alloy catalyst has small particles, and the high-entropy alloy can be uniformly and orderly distributed on the carrier; the high-entropy alloy catalyst has good selectivity and stability and low coke selectivity for a propane dehydrogenation reaction.

Description

Technical Field

[0001] This invention belongs to the field of metal catalyst technology, and more specifically, relates to a high-entropy alloy catalyst, its preparation method, and its application. Background Technology

[0002] In the petrochemical industry, ethylene and propylene are the most important basic organic raw materials. Propane dehydrogenation technology can convert low-value propane into high-value-added propylene. Currently, propane dehydrogenation technology has been successfully industrialized, and commercial catalysts mainly include two types: Pt-based catalysts and Cr-based catalysts. Pt-based catalysts are relatively expensive due to the use of the precious metal Pt as the active component; Cr-based catalysts, whose main active component is Cr₂O₃, have a negative impact on the environment, and the production process involves Cr… 6+ The presence of [a substance] also poses a potential carcinogenic risk to the human body. Therefore, developing inexpensive, green, and efficient new catalysts is a bottleneck problem for the propane dehydrogenation industry.

[0003] Single metals used in propane dehydrogenation tend to exhibit poor selectivity and rapid carbon deposition due to strong propylene adsorption, resulting in deep dehydrogenation. Therefore, alloy phases are widely used in propane dehydrogenation catalysts. Patents CN202111465502.8 and CN202210448891.1 disclose the application of PtSn and PtCu alloy catalysts in propane dehydrogenation to propylene, respectively. These alloy catalysts significantly improve product selectivity and catalyst stability. Additionally, the literature IsolatedFe... II The paper "On Silica Asa Selective Propane Dehydrogenation Catalyst" reports that for many transition metals such as Fe, Co, and Ni, a single metal has a stronger propylene adsorption capacity. However, propane dehydrogenation directly generates large amounts of methane, making it unsuitable as a propane dehydrogenation catalyst. Furthermore, the literature "Al2O3 Nanosheets Richin Pentacoordinate Al" states that... 3+ Ions StabilizePt~SnClusters for Propane Dehydrogenation demonstrates that the use of metal additives helps in the formation of alloy phases. However, most of these alloy phases are thermodynamically unstable and tend to form segregated phases of a single metal in high-temperature, strongly reducing environments, thus losing their propane dehydrogenation catalytic ability.

[0004] Single-phase alloys containing five or more metallic elements with similar atomic ratios are generally classified as high-entropy alloys (HEAs). Due to their high entropy and distorted lattice properties, HEAs exhibit extremely high mechanical properties, making them very useful structural materials. HEAs also have potential applications in catalysis as functional materials. Currently, methods for preparing high-entropy alloy (HEAs) catalysts mainly include carbothermal shock, fast moving bed pyrolysis, and nanodroplet dielectric deposition. However, these methods have the following problems: 1. Due to the differences in the properties of the high-entropy alloy precursor salts (such as reduction potential and thermal decomposition temperature), it is difficult to achieve simultaneous decomposition or reduction, often resulting in phase-separated products; 2. Particle size is difficult to control, making them unsuitable for preparing nanoparticles. Currently reported ball milling methods produce relatively large high-entropy alloy particles.

[0005] Given the shortcomings of current methods for preparing high-entropy alloy catalysts, it is necessary to improve them. Summary of the Invention

[0006] The present invention aims to overcome at least one defect (deficiency) of the prior art and provide a high-entropy alloy catalyst, its preparation method and application, which aims to solve the problems of large particle size and the inability of high-entropy alloy to be uniformly and orderly distributed on the support in the high-entropy alloy catalyst synthesized by the prior art, thereby affecting the catalytic performance of the high-entropy alloy.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a method for preparing a high-entropy alloy catalyst, wherein a high-entropy alloy precursor is prepared by using a solid acid, a basic end-capping agent and at least five metal salts, and then the high-entropy alloy precursor is loaded on a support, and then calcined and reduced to obtain a high-entropy alloy catalyst, wherein the solid acid is rich in ligands.

[0009] Unlike existing technologies, this invention generates surface-functionalized carbon dots by condensing a metal ion precursor with a ligand-rich solid acid and a basic end-capping agent under hydrothermal conditions. The surface amine groups and carboxylate groups coordinate with the metal ions, resulting in atomic-level dispersion of various metal ions on the carbon dot surface, thus promoting the formation of high-entropy alloys. If only a solid acid is used as a complex, its coordination effect may be too weak to form a high-entropy alloy, and the continuous condensation of the solid acid can lead to excessively large high-entropy alloy particles. By adding a basic end-capping agent, the surface amine groups and carboxylate groups of the carbon dots generated by the condensation of the basic end-capping agent coordinate with the metal ions. This not only improves the coordination ability but also acts as an end-capping agent, preventing excessive polymerization of the solid acid. Simultaneously, the carbon dot surface has abundant charges, hydrophilic and hydrophobic groups, and hydrogen bonds, which facilitates the self-assembly of the carbon dots with the support, inducing a uniform and orderly distribution of the high-entropy alloy precursor on the support.

[0010] In this invention, the solid acid and the basic capping agent work together to complex the metal. The solid acid undergoes a copolymerization reaction, and the basic capping agent acts as the capping agent in the copolymerization process. Both are indispensable.

[0011] Furthermore, the specific steps of the preparation method are as follows:

[0012] S1. Dissolve the solid acid and at least 5 metal salts in deionized water, mix them evenly, add an alkaline end-capping agent, mix them thoroughly, and then add deionized water to form a first mixed solution. Transfer the solution to a reaction vessel for static heating at a temperature of 140–200°C for 120–360 min. Then cool it to room temperature to obtain a high-entropy alloy precursor solution.

[0013] S2. Dissolve the support in the solvent and stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 4-8 hours. Then filter and wash the solid. Dry the solid after filtration and washing at 60-120°C for 6-10 hours, then calcine at 500-700°C for 2-6 hours, and finally reduce it in a reducing atmosphere at 500-700°C for 2-4 hours to obtain the high-entropy alloy catalyst.

[0014] In this invention, static heating in step S1 refers to placing the material in an oven without stirring. The preparation of high-entropy alloys requires hydrothermal conditions to undergo a condensation reaction to generate carbon dots. This process does not require stirring but requires high temperature. Therefore, this invention uses static heating to form high-entropy alloys.

[0015] In this invention, the high-entropy alloy precursor is loaded onto a carrier and then calcined in an air atmosphere. Finally, it is uniformly reduced in a hydrogen-argon mixed atmosphere, which solves the problem that multiple metals cannot be reduced simultaneously in the prior art.

[0016] Furthermore, the high-entropy alloy catalyst contains 5 to 10 metal elements selected from Fe, Co, Ni, La, Pb, In, Bi, Zn, Mn, Ce, Sn, Cu, and Zr.

[0017] Currently, when non-precious metals such as Fe, Co, and Ni are directly used for propane dehydrogenation, the product is directly converted into methane. However, in this invention, the selection of these non-precious metal elements to form a high-entropy alloy can improve the catalytic performance of non-precious metals, increase economic efficiency, and has no environmental hazards.

[0018] Furthermore, the molar ratio of the metal element, solid acid, and basic capping agent is 1:(2-10):(8-40).

[0019] In this invention, the preparation of metallic carbon dots mainly involves the condensation polymerization of a metal precursor with a ligand-rich solid acid and a basic capping agent under hydrothermal conditions, generating surface-functionalized carbon dots. This process includes both a complexation reaction between the metal and the solid acid, and a condensation reaction of the solid acid itself. If there is too little solid acid, the solid acid itself will undergo a condensation reaction, preventing the metal from complexing with it, and causing the metal to precipitate under the action of the basic capping agent. If there is too much solid acid, on the one hand, the loading capacity is limited when loading high-entropy alloys due to the excessive solid acid content; on the other hand, the size of the high-entropy alloy will be too small to meet the specific reaction requirements.

[0020] Furthermore, the molar ratio of the solid acid to deionized water is 1:(350-400).

[0021] In this invention, the molar ratio of solid acid to deionized water is 1:(350-400). If the molar ratio of solid acid to deionized water is too large, the resulting high-entropy alloy solution will be too concentrated, and the high-entropy alloy particles may precipitate if they are too large. If the molar ratio of solid acid to deionized water is too small, a longer or higher temperature will be required to form the high-entropy alloy, which will prolong the experimental cycle and waste energy.

[0022] Further, the solid acid is selected from at least one of citric acid, ethylenediaminetetraacetic acid, glycolic acid, and oxalic acid. In this invention, the solid acid needs to have strong polymerization and coordination capabilities during the formation of the high-entropy alloy. Citric acid possesses both of these properties, therefore, citric acid is preferred as the solid acid. The alkaline end-capping agent is selected from at least one of ethylenediamine, ammonia, pyridine, and triethylamine. In this invention, the main function of the alkaline end-capping agent is to inhibit the unlimited polymerization of the solid acid. Ethylenediamine, as a dibasic base, has a strong inhibitory ability; therefore, ethylenediamine is preferred as the alkaline end-capping agent.

[0023] Furthermore, the metal salt is at least one of hydrochloride, nitrate, and sulfate.

[0024] Further, the solvent in step S2 is at least one of water, ethanol, acetone, isopropanol, ethyl acetate, isobutanol, benzene, petroleum ether, and toluene.

[0025] A second aspect of the present invention provides a high-entropy alloy catalyst prepared by the above-described preparation method, wherein the total loading of the alloy is 0.1 to 10 wt.% based on the total mass of the high-entropy alloy catalyst.

[0026] This invention uses five or more metal elements uniformly dispersed on a support to form a high-entropy alloy catalyst. The metal elements are uniformly mixed, and the system can obtain a large mixing entropy, forming a thermodynamically stable high-entropy alloy phase. The resulting catalyst has good catalytic performance and high selectivity.

[0027] Furthermore, the molar ratio of the different metallic elements is between 0.5 and 1. High-entropy alloys are usually composed of five or more elements in equal or near-equal atomic ratios. If a certain element is too little or too much, it is not conducive to the formation of high-entropy alloys.

[0028] Furthermore, the support is one or more of the molecular sieves selected from Al2O3, SiO2, TiO2, Silicalite-1, or SBA-15. The choice of support must ensure good dispersion of the metal elements while providing a large dispersion space to prevent metal element loss, thereby ensuring the selectivity and economy of the catalyst. Simultaneously, the support should be stable at high temperatures. The selected supports meet these conditions.

[0029] A third aspect of the invention provides the application of the above-mentioned high-entropy alloy catalyst in a propane dehydrogenation reaction, wherein the propane dehydrogenation reaction temperature is 500–620°C and the propane space velocity is 0.1–10 h⁻¹. -1 .

[0030] The high-entropy alloy catalyst provided by this invention, used in propane dehydrogenation, contains five or more metal elements in a homogeneous mixture. This results in a large mixing entropy, forming a thermodynamically stable high-entropy alloy phase, which effectively suppresses strong propylene adsorption and improves the selectivity of propane dehydrogenation. Simultaneously, the interaction between the various metal elements inhibits the aggregation of active components, significantly reduces carbon deposition, and increases catalyst stability. This catalyst combines the two major advantages of propane dehydrogenation catalysts, exhibiting excellent selectivity and stability, and can be used in fixed-bed, fluidized-bed, and circulating fluidized-bed reactors.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) This invention generates surface-functionalized carbon dots by polycondensing a metal ion precursor, a solid acid rich in ligands, and a basic end-capping agent under static hydrothermal conditions. The surface amine groups and carboxylate groups coordinate with the metal ions, resulting in atomic-level dispersion of various metal ions on the carbon dot surface, which promotes the formation of high-entropy alloys. If only solid acid is used as a complex, on the one hand, the coordination effect of the solid acid is too weak and may not be able to form high-entropy alloys; on the other hand, the continuous polycondensation of the basic end-capping agent causes the high-entropy alloy particles to be too large. After adding the basic end-capping agent, the surface amine groups and carboxylate groups of the carbon dots generated by polycondensation coordinate with the metal ions, which not only improves the coordination ability, but the basic end-capping agent also acts as an end-capping agent, preventing the excessive polymerization of the solid acid. At the same time, the carbon dot surface has abundant charges, hydrophilic and hydrophobic groups, hydrogen bonds, etc., which are conducive to the self-assembly of carbon dots and the support, inducing the uniform and orderly distribution of high-entropy alloy precursors on the support.

[0033] (2) In this invention, the high-entropy alloy precursor is loaded onto the carrier and then calcined in an air atmosphere. Finally, it is uniformly reduced in a hydrogen-argon mixed atmosphere, which solves the problem that multiple metals cannot be reduced synchronously in solution.

[0034] (3) The high-entropy alloy catalyst provided by the present invention uses five or more non-precious metal elements uniformly dispersed on the support to form a high-entropy alloy catalyst. The metal elements are uniformly mixed, and the system can obtain a large mixing entropy, forming a thermodynamically stable high-entropy alloy phase. The resulting catalyst has good catalytic performance and high selectivity. On the other hand, the present invention uses non-precious metals and does not involve precious metals, which greatly increases the economic benefits and avoids environmental problems.

[0035] (4) The high-entropy alloy catalyst provided by this invention effectively suppresses the strong adsorption of propylene and improves the selectivity of propane dehydrogenation when used in propane dehydrogenation. At the same time, the interaction between various metal elements in this catalyst inhibits the aggregation of active components, significantly reduces carbon deposition, and increases the stability of the catalyst. This catalyst combines the two major advantages of propane dehydrogenation catalysts, exhibiting excellent selectivity and stability, and can be used in fixed-bed, fluidized-bed, and circulating fluidized-bed reactors. Attached Figure Description

[0036] Figure 1 Transmission electron microscopy image of the high-entropy alloy catalyst prepared in Example 1;

[0037] Figure 2 Transmission electron microscopy (TEM) image of the high-entropy alloy catalyst prepared in Comparative Example 1;

[0038] Figure 3 Transmission electron microscopy image of the catalyst prepared in Comparative Example 2;

[0039] Figure 4 Transmission electron microscopy (TEM) image of the catalyst prepared in Comparative Example 3. Detailed Implementation

[0040] To enable those skilled in the art to better understand this solution, the following detailed description is provided in conjunction with specific embodiments. Unless otherwise specified, the process methods used in the embodiments are conventional methods; and unless otherwise specified, the materials used are commercially available.

[0041] Example

[0042] Example 1

[0043] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0606g Bi(NO3)3·9H2O, and 0.576g citric acid respectively, and dissolve them in 5g deionized water. Then add 0.72g ethylenediamine, mix well, and then add 15g deionized water to obtain a colored and transparent first mixed solution. Then transfer it to a 100ml reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow transparent solution.

[0044] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as A1.

[0045] Example 2

[0046] S1. Weigh out 0.202g Fe(NO3)3·9H2O, 0.146g Ni(NO3)2·6H2O, 0.146g Co(NO3)2·6H2O, 0.148g Zn(NO3)2·9H2O, 0.216g La(NO3)3·6H2O, 0.242g Bi(NO3)3·9H2O, and 2.304g citric acid, and dissolve them in 10g deionized water. Then add 2.88g ethylenediamine, mix well, and then add 70g deionized water to obtain a first mixed solution of color and transparency. Then transfer it to a 100ml reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow transparent solution.

[0047] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as A2.

[0048] Example 3

[0049] S1. Weigh out 0.101g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0728g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.108g La(NO3)3·6H2O, 0.0606g Bi(NO3)3·9H2O, and 0.576g citric acid, and dissolve them in 5g deionized water. Then add 0.72g ethylenediamine, mix well, and then add 15g deionized water to obtain a colored and transparent first mixed solution. Then transfer it to a 100ml reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow and transparent solution.

[0050] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst A3.

[0051] Example 4

[0052] S1. Weigh out 0.037g Zn(NO3)2·9H2O, 0.0364g Co(NO3)2·6H2O, 0.0414g Pb(NO3)2·9H2O, 0.0447g Mn(NO3)3 (aq(50%)), 0.054g Ce(NO3)3·6H2O, 0.0477g In(NO3)3·9H2O, and 0.576g citric acid, and dissolve them in 5g deionized water. Then add 0.72g ethylenediamine, mix well, and then add 15g deionized water to obtain a colored and transparent first mixed solution. Then transfer it to a 100ml reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow and transparent solution.

[0053] S2. Weigh 6.8g of Al2O3 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then, add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. After that, filter and wash the solid. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine it at 550°C for 4 hours. Finally, reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as A4.

[0054] Example 5

[0055] S1. Weigh out 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.0537g Zr(NO3)4·5H2O, 0.0477g In(NO3)3·9H2O, 0.0303g Cu(NO3)2·9H2O, 0.0606g Bi(NO3)3·9H2O, and 0.48g citric acid, and dissolve them in 5g deionized water. Then add 0.6g ethylenediamine, mix thoroughly, and then add 11.7g deionized water to obtain a colored and transparent first mixed solution. Transfer this solution to a 100ml reactor and statically heat it at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution, a pale yellow and transparent solution, is obtained.

[0056] S2. Weigh 5.7g of Silicalite-1 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as A5.

[0057] Example 6

[0058] S1. Weigh out 0.0297g NiCl2·6H2O, 0.0213g CuCl2·2H2O, 0.0438g SnCl4·5H2O, 0.0203g FeCl3, 0.0162g CoCl2, and 0.96g citric acid, respectively, and dissolve them in 5g deionized water. Then add 1.2g ethylenediamine, mix well, and then add 28.4g deionized water to obtain a colored and transparent first mixed solution. Then transfer it to a 100ml reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow and transparent solution.

[0059] S2. Weigh 5.7g of Silicalite-1 and dissolve it in 35g of deionized water. Stir until homogeneous to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C, then calcine at 550°C for 4 hours. Finally, reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst A6.

[0060] Example 7

[0061] S1. Weigh 0.0505g Fe(NO3)3·9H2O, 0.0364g Co(NO3)2·6H2O, 0.0364gNi(NO3)2·6H2O, 0.054g La(NO3)3·6H2O, 0.0414g Pb(NO3)2·9H2O, 0.0303g respectively. Bi(NO3)3·9H2O, 0.0371gZn(NO3)2·9H2O, 0.0537g Zr(NO3)4·5H2O, 0.0303g Cu(NO3)2·9H2O, 0.0477g In(NO3)3·9H2O and 1.152g of citric acid were dissolved in 5g of deionized water, followed by the addition of 1.44g of ethylenediamine. After mixing thoroughly, 35g of deionized water was added to obtain a colored and transparent first mixed solution. This solution was then transferred to a 100ml reactor for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution was obtained, which was a pale yellow and transparent solution.

[0062] S2. Weigh 13.6g of SBA-15 and dissolve it in 70g of deionized water. Stir until a mixed solution is formed. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solid. Dry the filtered and washed solid at 80°C for 8 hours, then calcine at 550°C for 4 hours. Finally, reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as A7.

[0063] Comparative Example

[0064] Comparative Example 1

[0065] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0303g Bi(NO3)3·9H2O and 0.576g citric acid respectively and dissolve them in 20g deionized water. Then add 0.72g ethylenediamine and mix thoroughly to obtain a high-entropy alloy precursor solution.

[0066] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir thoroughly to form a mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the mixed solution. Stir for 6 hours and then filter and wash. Dry the filtered and washed solid at 80℃ for 8 hours, then calcine at 550℃ for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600℃ for 2 hours to obtain the alloy catalyst, denoted as B1.

[0067] Comparative Example 2

[0068] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0606g Bi(NO3)3·9H2O, and 0.576g citric acid respectively, dissolve them in 20g deionized water, mix thoroughly, and transfer to a 100mL reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, the high-entropy alloy precursor is obtained as a pale yellow transparent solution.

[0069] S1. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir thoroughly to form a mixed solution. Then add the high-entropy alloy precursor obtained in step S1 to the mixed solution and stir for 6 hours. Then filter and wash, dry at 80℃ for 8 hours, calcine at 550℃ for 4 hours, and finally reduce in a hydrogen-argon mixed atmosphere at 600℃ for 2 hours to obtain the alloy catalyst, denoted as B2.

[0070] Comparative Example 3

[0071] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0303g Bi(NO3)3·9H2O, and 0.72g ethylenediamine, dissolve them in 20g deionized water, mix thoroughly, and then transfer to a 100mL reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, the high-entropy alloy precursor is obtained as a pale yellow transparent solution.

[0072] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir thoroughly to form a mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the mixed solution. Stir for 6 hours, filter and wash, dry at 80℃ for 8 hours, then calcine at 550℃ for 4 hours, and finally reduce in a hydrogen-argon mixed atmosphere at 600℃ for 2 hours to obtain alloy catalyst B1.

[0073] Comparative Example 4

[0074] S1. Weigh out 0.152g Fe(NO3)3·9H2O, 0.11g Ni(NO3)2·6H2O, 0.11g Co(NO3)2·6H2O, 0.11g Zn(NO3)2·9H2O, 0.162g La(NO3)3·6H2O, and 0.09g Bi(NO3)3·9H2O respectively, dissolve them in 20g ethylene glycol, add surfactant CTAB, and stir thoroughly to obtain a high-entropy alloy precursor solution; then, in a cell disruptor, sonicate the above solution for 30min at 750W power and room temperature, wash and dry to obtain FeCoNiZnLaBi high-entropy alloy powder;

[0075] S4. Subsequently, 20.4g of SiO2 and high-entropy alloy powder were weighed and thoroughly mixed in a mortar and ground for 2 hours. The mixture was then transferred to a porcelain boat and evenly dispersed. The mixture was placed in a tube furnace and sintered at a low temperature of 200℃ for 2 hours to obtain the FeCoNiZnLaBi / SiO2 composite catalyst, denoted as B4.

[0076] Comparative Example 5

[0077] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0606g Bi(NO3)3·9H2O, and 0.045g citric acid respectively, and dissolve them in 5g deionized water. Then add 0.225g ethylenediamine, mix thoroughly, and then add 15g deionized water to obtain a colored and transparent first mixed solution. Then transfer the first mixed solution to a 100mL reaction vessel for static heating at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow transparent solution.

[0078] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir thoroughly to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as B5.

[0079] Comparative Example 6

[0080] S1. Weigh out 0.0505g Fe(NO3)3·9H2O, 0.0364g Ni(NO3)2·6H2O, 0.0364g Co(NO3)2·6H2O, 0.037g Zn(NO3)2·9H2O, 0.054g La(NO3)3·6H2O, 0.0606g Bi(NO3)3·9H2O, and 2.16g citric acid, and dissolve them in 5g deionized water. Then add 2.025g ethylenediamine and mix thoroughly. Add 15g deionized water to obtain a colored and transparent first mixed solution. Transfer the first mixed solution to a 100mL reaction vessel and statically heat it at 170℃ for 180min. After cooling to room temperature, a high-entropy alloy precursor solution is obtained, which is a pale yellow transparent solution.

[0081] S2. Weigh 6.8g of SiO2 and dissolve it in 35g of deionized water. Stir thoroughly to form a second mixed solution. Then add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 6 hours. Then filter and wash the solution. Dry the solid after filtration and washing at 80°C for 8 hours, then calcine at 550°C for 4 hours, and finally reduce it in a hydrogen-argon mixed atmosphere at 600°C for 2 hours to obtain the high-entropy alloy catalyst, denoted as B6.

[0082] Performance testing

[0083] The TEM spectra of the alloy catalysts prepared in Example 1 and Comparative Examples 1-3 were tested, and the results are as follows: Figures 1-4 As shown.

[0084] The particle sizes of the high-entropy alloy catalysts A1-A7 prepared in Examples 1-7 and the alloy catalysts B1-B6 prepared in Comparative Examples 1-6 were tested and the results are recorded in Table 1.

[0085] Table 1. Particle sizes of catalysts A1-A7 and B1-B6

[0086]

[0087]

[0088] from Figure 1-4 It can be seen that the high-entropy alloy catalyst prepared by the present invention has a small particle size and the high-entropy alloy precursor is uniformly and orderly distributed on the carrier. The alloy catalysts prepared by comparative examples 1-3 have a large particle size and exhibit agglomeration.

[0089] As can be seen from the data in Table 1, the high-entropy alloy catalysts prepared in Examples 1-7 all have relatively small particle sizes, while the alloy catalysts prepared in Comparative Examples 1-5 have much larger particle sizes than the high-entropy alloy catalysts prepared in Examples 1-7.

[0090] application

[0091] The high-entropy alloy catalysts A1-A7 prepared in Examples 1-7 and the metal catalysts B1-B4 prepared in Comparative Examples 1-6 were used in the propane dehydrogenation reaction. The high-entropy alloy catalysts obtained in Examples 1-3 and 6-7 were used in the reaction at a temperature of 600°C and a propane space velocity of 1 h⁻¹. -1 The reaction was carried out under the following conditions: the high-entropy alloy catalysts obtained in Examples 4-5 were reacted at a temperature of 550°C and a propane space velocity of 3.3 h⁻¹. -1 The reaction was carried out under the following conditions: the alloy catalysts obtained in Comparative Examples 1-6 were reacted at a temperature of 600 °C and a propane space velocity of 1 h⁻¹. -1 The reaction was carried out under the specified conditions. The evaluation results of the propane dehydrogenation reaction in the examples and comparative examples, using pure propane as the raw material and nitrogen as the carrier gas, are recorded in Table 2.

[0092] Table 2 Results of propane dehydrogenation reaction

[0093]

[0094]

[0095] As shown in Table 2, the high-entropy alloy catalyst prepared in this invention has the advantages of high initial propane conversion, high initial propylene selectivity, and low carbon deposition selectivity when applied to propane dehydrogenation reaction.

[0096] Compared with Example 1, Comparative Example 1 did not use static heating during preparation. As a result, the alloy catalyst obtained was used for propane dehydrogenation reaction, and the initial propane conversion and initial propylene selectivity were much lower, while the coking selectivity was much higher. This indicates that static heating is a necessary condition for the formation of high-entropy alloys.

[0097] Comparing the data from Example 1 and Comparative Examples 2-3, it can be seen that when either the solid acid or the basic end-capping agent is missing, the catalyst prepared for propane dehydrogenation has a much lower initial propane conversion and a much higher initial propylene selectivity than the entropy alloy catalyst of Example 1 for propane dehydrogenation. This indicates that when preparing high-entropy alloy catalysts, the solid acid and the basic end-capping agent need to work together and neither can be omitted.

[0098] Comparing the data from Examples 1-7 and Comparative Example 4, it can be seen that the catalyst prepared by the conventional method has poor catalytic performance when used in the propane dehydrogenation reaction.

[0099] Comparing the data from Example 1, Comparative Examples 5 and 6, it can be seen that in preparing high-entropy alloys, a suitable ratio of metal elements to solid acid and basic end-capping agents is required. Too much or too little solid acid and basic end-capping agent will affect the catalytic performance of the catalyst. When the content of solid acid and basic end-capping agent is too low, the prepared catalyst, when used for propane dehydrogenation, exhibits low initial propane conversion, low initial propylene selectivity, and high coking selectivity. When the content of solid acid and basic end-capping agent is too low, although the initial propylene selectivity and coking selectivity are not significantly different from those of the catalysts prepared in the examples, the initial propane conversion is lower.

[0100] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-entropy alloy catalyst, characterized in that, A high-entropy alloy precursor was prepared using a solid acid, a basic end-capping agent, and at least five metal salts. The high-entropy alloy precursor was then loaded onto a support, followed by calcination and reduction to obtain a high-entropy alloy catalyst. The specific steps of the preparation method are as follows: S1. Dissolve a solid acid and at least five metal salts in deionized water, mix thoroughly, add an alkaline end-capping agent, mix thoroughly again, and then add more deionized water to form a first mixed solution. Transfer this solution to a reaction vessel for static heating at 140-200°C for 120-360 minutes. After cooling to room temperature, the high-entropy alloy precursor solution is obtained. S2. Dissolve the support in the solvent and stir until homogeneous to form a second mixed solution. Then, add the high-entropy alloy precursor solution obtained in step S1 to the second mixed solution and stir for 4-8 hours. Filter and wash the solution. Dry the filtered and washed solid at 60-120°C for 6-10 hours, then calcine at 500-700°C for 2-6 hours. Finally, reduce the solid in a reducing atmosphere at 500-700°C for 2-4 hours to obtain the high-entropy alloy catalyst. The solid acid is selected from at least one of citric acid, ethylenediaminetetraacetic acid, glycolic acid and oxalic acid, and the alkaline capping agent is selected from at least one of ethylenediamine, ammonia, pyridine and triethylamine.

2. The method for preparing the high-entropy alloy catalyst according to claim 1, characterized in that, The high-entropy alloy catalyst contains 5 to 10 metal elements selected from Fe, Co, Ni, La, Pb, In, Bi, Zn, Mn, Ce, Sn, Cu, and Zr.

3. The method for preparing the high-entropy alloy catalyst according to claim 2, characterized in that, The molar ratio of the metal element, solid acid, and basic capping agent is 1:(2~10):(8~40).

4. The method for preparing the high-entropy alloy catalyst according to claim 1, characterized in that, The metal salt is at least one of hydrochloride, nitrate, and sulfate.

5. The method for preparing the high-entropy alloy catalyst according to claim 1, characterized in that, The solvent in step S2 is at least one of water, ethanol, acetone, isopropanol, ethyl acetate, isobutanol, benzene, petroleum ether, and toluene.

6. The high-entropy alloy catalyst prepared by the preparation method according to any one of claims 1 to 5 is characterized in that, The total loading of the alloy is 0.1 to 10 wt., based on the mass of the high-entropy alloy catalyst.

7. The application of the high-entropy alloy catalyst as described in claim 6, characterized in that, The high-entropy alloy catalyst is used for the propane dehydrogenation reaction.

8. The application of the high-entropy alloy catalyst according to claim 7, characterized in that, The propane dehydrogenation reaction temperature is 500~620℃, and the propane space velocity is 0.1~10h. -1 .

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