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

Abstract

This invention provides a high-entropy alloy oxide catalyst, its preparation method, and its application, belonging to the field of catalyst material technology. The catalyst is a high-entropy alloy oxide composed of any three elements selected from Fe, Mg, Ti, and Mo, along with Ru and Co. The high-entropy alloy oxide catalyst of this invention can catalyze ammonia synthesis under mild conditions; it also exhibits a high ammonia synthesis reaction rate, significantly improving the utilization rate of the high-entropy alloy oxide catalyst and demonstrating strong industrial application prospects. Furthermore, after long-term operation, the catalyst shows no significant deactivation, exhibiting extremely high stability.

Description

Technical Field

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

[0002] my country is a major agricultural country, ranking first in the world in both the production and consumption of synthetic ammonia. According to statistics from the Food and Agriculture Organization of the United Nations (FAO), fertilizers contribute over 40% to food production, and 85% of the world's ammonia is used as fertilizer to meet agricultural needs. The ammonia synthesis industry not only plays such a vital role in agriculture but is also crucial in fields such as medicine and the military. Researchers have been studying ammonia synthesis reactions for nearly a century, achieving remarkable results. This research has inspired many catalytic reactions and promoted the development of other related disciplines, playing an irreplaceable role in scientific research.

[0003] Currently, over 90% of ammonia is produced using the Haber-Bosch process, employing iron-based catalysts. Using iron-based catalysts for ammonia synthesis requires high temperature and pressure, resulting in high energy consumption. Over the past century, the energy consumption for ammonia synthesis has decreased from approximately 100 GJ / t initially to about 28 GJ / t, very close to the theoretical value of 20 GJ / t. The ammonia synthesis industry accounts for 1% of global energy consumption. Therefore, addressing the high energy consumption of the ammonia synthesis industry is imperative. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a high-entropy alloy oxide catalyst, its preparation method, and its application. The high-entropy alloy oxide catalyst of this invention can catalyze the ammonia synthesis reaction under mild conditions, while simultaneously improving the reaction performance of the ammonia synthesis catalyst and significantly reducing energy consumption during the reaction process.

[0005] One object of the present invention is to provide a high-entropy alloy oxide catalyst.

[0006] In some embodiments, the catalyst is an oxide of a high-entropy alloy composed of any three elements selected from Fe, Mg, Ti, and Mo, along with Ru and Co. For example, the high-entropy alloy oxide catalyst may contain Ru, Co, Fe, Mg, and Mo; or the high-entropy alloy oxide catalyst may contain Ru, Co, Fe, Ti, and Mo; or the high-entropy alloy oxide catalyst may contain Ru, Co, Mg, Ti, and Mo.

[0007] In some preferred embodiments, the high-entropy alloy oxide catalyst comprises Ru, Co, Fe, Ti, and Mo; in some preferred embodiments, the molar percentage of Ru, Co, Fe, Ti, and Mo is (5-35):(5-35):(5-35):(5-35):(5-35); in some more preferred embodiments, the molar percentage of Ru, Co, Fe, Ti, and Mo is (5-20):(5-20):(20-35):(5-20):(5-20); in some most preferred embodiments, the molar percentage of Ru, Co, Fe, Ti, and Mo is 5:20:35:20:20.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned high-entropy alloy oxide catalyst.

[0009] In some embodiments, the preparation method includes the following steps:

[0010] 1) Mix any three of the following elements: Fe powder, Mg powder, Ti powder and Mo powder, as well as Ru powder and Co powder, until homogeneous to obtain a mixture;

[0011] 2) The mixture is heated and cast in an inert atmosphere to obtain a high-entropy alloy block;

[0012] 3) The high-entropy alloy block is ground in an inert atmosphere to obtain high-entropy alloy powder;

[0013] 4) The high-entropy alloy powder is calcined in air to obtain a high-entropy alloy oxide catalyst.

[0014] In some implementations, in step 1), the purity of any three of the Fe element powder, the Mg element powder, the Ti element powder, and the Mo element powder, as well as the Ru element powder and the Co element powder, is higher than 99%, and the particle size is 100-500 mesh.

[0015] In some embodiments, in step 2), the inert gas is argon, and in some preferred embodiments, the purity of the argon is 99%. The heating and casting process includes: a heating temperature of 1000-3000℃ and a heating time of 10-60 min; in some preferred embodiments, a heating temperature of 1500-2500℃ and a heating time of 20-40 min; and in some more preferred embodiments, a heating temperature of 2000℃ and a heating time of 30 min.

[0016] In some implementations, the heating and casting is carried out in a Joule heater.

[0017] In some embodiments, in step 3), the inert gas is argon, and in some preferred embodiments, the purity of the argon is 99%; the grinding process is ball milling, and the grinding jar used is one or more of a vacuum stainless steel jar, a cemented carbide jar, and an agate jar; the ball is one or more of a stainless steel ball, a cemented carbide ball, and a zirconia ball; the grinding media is one or more of anhydrous ethanol, polyvinyl alcohol, stearic acid, and polymethyl methacrylate.

[0018] In some embodiments, the ball milling conditions include: a ball milling speed of 200-600 rpm, a ball-to-material ratio of 2:1-20:1, and a ball milling time of 10-100 h; in some preferred embodiments, the ball milling speed is 300-500 rpm, the ball-to-material ratio is 4:1-16:1, and the ball milling time is 20-80 h; in some more preferred embodiments, the ball milling speed is 400 rpm, the ball-to-material ratio is 10:1, and the ball milling time is 30-50 h.

[0019] In some embodiments, in step 4), the calcination is carried out in a muffle furnace; the calcination process includes: a calcination temperature of 100-800℃, a calcination time of 10-30h, and a heating rate of 5-20℃ / min; in some preferred embodiments, the calcination temperature is 200-600℃, the calcination time is 10-20h, and the heating rate is 10-15℃ / min; in some more preferred embodiments, the calcination temperature is 500℃, the calcination time is 12h, and the heating rate is 10℃ / min.

[0020] The final object of the present invention is to provide the application of the high-entropy alloy oxide catalyst described above or the high-entropy alloy oxide catalyst prepared by any of the above preparation methods in the ammonia synthesis reaction.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention proposes for the first time the application of high-entropy alloy oxide catalysts in ammonia synthesis. The catalyst uses five elements whose atoms are arranged in an orderly manner and combine with each other to form an electronic structure different from the original elements, which can break the limiting relationship, that is, it can break the bottleneck of high energy barrier required for N2 dissociation in the traditional ammonia synthesis reaction. Specifically, in the ammonia synthesis reaction, the catalyst causes N2 (N≡N bond) to no longer dissociate directly, but to be hydrogenated to generate N2H2, and then gradually hydrogenated to release NH3, thereby breaking the bottleneck of high energy barrier required for N2 dissociation in the traditional ammonia synthesis reaction. Finally, it realizes the catalytic ammonia synthesis reaction under mild conditions (<400℃ and 1MPa); and has a high ammonia synthesis reaction rate, which greatly improves the utilization rate of high-entropy alloy oxide catalysts and has strong industrial application prospects.

[0023] (2) The high-entropy alloy oxide catalyst prepared by the present invention using five metals has excellent electronic structure and synergistic catalysis of multiple elements, which makes it exhibit good catalytic activity.

[0024] (3) The high-entropy alloy oxide catalyst in this invention has higher atomic dispersion and higher utilization rate than traditional iron-based catalysts due to the mutual isolation of its multiple metals. It also has good thermal stability for ammonia synthesis under mild conditions, which is beneficial to industrial production and provides a new solution for energy saving and consumption reduction in ammonia synthesis reaction. Attached Figure Description

[0025] Figure 1 The results show the ammonia synthesis reaction rates of the high-entropy alloy oxide catalysts prepared in Examples 1-7 of this invention at a temperature of 380°C and a pressure of 1 MPa.

[0026] Figure 2 The results show the ammonia synthesis reaction rates of the high-entropy alloy oxide catalysts prepared in Comparative Examples 1-8 of this invention at a temperature of 380°C and a pressure of 1 MPa.

[0027] Figure 3 The results show the rate stability of the RuCoFeMoTi high-entropy alloy oxide catalyst prepared in Example 3 of this invention when used in the ammonia synthesis reaction. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0030] Example 1

[0031] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mg, and Ti elements.

[0032] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0033] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mg and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:20:35:20:20. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0034] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0035] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoFeMgTi high-entropy alloy powder.

[0036] 4) The fully alloyed RuCoFeMgTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMgTi high-entropy alloy oxide catalyst.

[0037] Example 2

[0038] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mg, and Mo.

[0039] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0040] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mg and Mo elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:20:35:20:20. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0041] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0042] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) to obtain fully alloyed RuCoFeMgMo high-entropy alloy powder.

[0043] 4) The fully alloyed RuCoFeMgMo high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoFeMgMo high-entropy alloy oxide catalyst.

[0044] Example 3

[0045] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mo, and Ti elements.

[0046] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0047] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mo and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:20:35:20:20. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0048] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0049] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoFeMoTi high-entropy alloy powder.

[0050] 4) The fully alloyed RuCoFeMoTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMoTi high-entropy alloy oxide catalyst.

[0051] Example 4

[0052] The high-entropy alloy oxide catalyst contains Ru, Co, Mo, Mg, and Ti elements.

[0053] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0054] 1) Prepare alloy powder by mixing Ru, Co, Mo, Mg and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:20:35:20:20. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0055] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0056] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoMoMgTi high-entropy alloy powder.

[0057] 4) The fully alloyed RuCoMoMgTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoMoMgTi high-entropy alloy oxide catalyst.

[0058] Example 5

[0059] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mo, and Ti elements.

[0060] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0061] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mo and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 1:4:45:25:25. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0062] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0063] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoFeMoTi high-entropy alloy powder.

[0064] 4) The fully alloyed RuCoFeMoTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMoTi high-entropy alloy oxide catalyst.

[0065] Example 6

[0066] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mo, and Ti elements.

[0067] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0068] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mo and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:5:60:15:15. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0069] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0070] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 300 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoFeMoTi high-entropy alloy powder.

[0071] 4) The fully alloyed RuCoFeMoTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMoTi high-entropy alloy oxide catalyst.

[0072] Example 7

[0073] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mo, and Ti elements.

[0074] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0075] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mo and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:5:80:5:5. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0076] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0077] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 300 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoFeMoTi high-entropy alloy powder.

[0078] 4) The fully alloyed RuCoFeMoTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMoTi high-entropy alloy oxide catalyst.

[0079] Example 8

[0080] The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Mo, and Ti elements.

[0081] The preparation method of the high-entropy alloy oxide catalyst includes the following steps:

[0082] 1) Prepare alloy powder by mixing Ru, Co, Fe, Mo and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in the ratio of 5:20:35:20:20. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0083] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a muffle furnace, introduce argon gas with a purity of 99% to maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0084] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (60-80 mesh) for classification to obtain fully alloyed RuCoFeMoTi high-entropy alloy powder.

[0085] 4) The fully alloyed RuCoFeMoTi high-entropy alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeMoTi high-entropy alloy oxide catalyst.

[0086] Comparative Example 1

[0087] 1) Prepare alloy powder by mixing Ru and Co elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements of 50:50. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0088] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0089] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain a fully alloyed RuCo alloy catalyst.

[0090] Comparative Example 2

[0091] 1) Prepare alloy powder by mixing Ru, Co and Fe elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements of 5:5:90. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0092] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0093] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) to obtain fully alloyed RuCoFe alloy powder.

[0094] 4) The fully alloyed RuCoFe alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoFe alloy catalyst.

[0095] Comparative Example 3

[0096] 1) Prepare alloy powder by mixing Ru, Co and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements of 5:5:90. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0097] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0098] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoTi alloy powder.

[0099] 4) The fully alloyed RuCoTi alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoTi alloy catalyst.

[0100] Comparative Example 4

[0101] 1) Prepare alloy powder by mixing Ru, Co and Mo elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements of 5:5:90. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0102] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0103] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved (100-120 mesh) for classification to obtain fully alloyed RuCoMo alloy powder.

[0104] 4) The fully alloyed RuCoMo alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoMo alloy catalyst.

[0105] Comparative Example 5

[0106] 1) Prepare alloy powder by mixing Ru, Co, Fe and Ti elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in a ratio of 5:5:45:45. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0107] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0108] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved and classified (100-120 mesh) to obtain fully alloyed RuCoFeTi alloy powder.

[0109] 4) The fully alloyed RuCoFeTi alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500℃ at a heating rate of 10℃ / min, and calcined for 12h to obtain the RuCoFeTi alloy catalyst.

[0110] Comparative Example 6

[0111] 1) Prepare alloy powder by mixing Ru, Co, Fe and Mo elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in a ratio of 5:5:45:45. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0112] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0113] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved and classified (100-120 mesh) to obtain fully alloyed RuCoFeMo alloy powder.

[0114] 4) The fully alloyed RuCoFeMo alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoFeMo alloy catalyst.

[0115] Comparative Example 7

[0116] 1) Prepare alloy powder by mixing Ru, Co, Ti and Mo elements with a purity of higher than 99% and a particle size of 300 mesh according to the molar percentage of alloy elements in a ratio of 5:5:45:45. Mix the alloy powder evenly in a mixer to obtain unalloyed mechanically mixed powder.

[0117] 2) Place the unalloyed mechanically mixed powder obtained in step 1) into a Joule heater, introduce 99% pure argon gas, maintain an inert gas atmosphere, and melt and cast at 2000℃ for 30 minutes to obtain a high-entropy alloy block.

[0118] 3) The high-entropy alloy block obtained in step 2) is crushed and loaded into a ball mill jar at a ball-to-material ratio of 10:1 under an argon atmosphere with a purity of 99%. The ball mill jar is a vacuum stainless steel jar, the balls used are stainless steel balls, the ball milling medium is anhydrous ethanol, the ball milling process is a rotation speed of 400 rpm, and the ball milling time is 36 h. After the ball milling is completed, the prepared powder is taken out and dried in a vacuum drying oven at 80 °C for 1 h. Then it is sieved and classified (100-120 mesh) to obtain fully alloyed RuCoTiMo alloy powder.

[0119] 4) The fully alloyed RuCoTiMo alloy powder obtained in step 3) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min, and calcined for 12 h to obtain the RuCoTiMo alloy catalyst.

[0120] Catalyst performance testing

[0121] 0.15 g of each of the catalysts prepared in Examples 1-8 and Comparative Examples 1-7 were taken and the ammonia synthesis rate was determined in a continuous flow micro fixed bed reactor at a mass hourly space velocity of 60000 mL / (g·h). The change in NH3 concentration in the tail gas was determined by ion chromatography (Thermo Scientific, DIONEX, ICS 600). The composition of the reaction gas was a mixture of 75% H2 and 25% N2.

[0122] The ammonia synthesis reaction rates of the catalysts prepared in Examples 1-8 and Comparative Examples 1-7 were determined under the same test conditions (380℃ and 1 MPa). The test results are shown in the figure below. Figure 1 and Figure 2 .

[0123] from Figure 1 As can be seen, the activities of the high-entropy alloy oxide catalysts prepared in Examples 1-4 are not significantly different. Among them, the high-entropy alloy oxide catalyst prepared in Example 3 has the highest activity, reaching 31.1 mmol. NH3 / (g cat . h), the results showed that the RuCoFeMoTi high-entropy alloy oxide catalyst with a molar percentage of alloying elements of 5:20:35:20:20 exhibited the highest activity. Compared with Example 3, Examples 5, 6, and 7 showed that the proportions of some alloying elements in Ru, Co, Fe, Mo, and Ti were outside the scope of this invention. The lower content of Ru and Co elements resulted in lower activities for these catalysts compared to those in Example 3. This indicates that the alloy ratio has a certain influence on activity. Example 8 differed from Example 3 in that Joule heating was not used. The results showed that the activity of the high-entropy alloy oxide catalyst prepared in Example 3 was significantly higher than that prepared in Example 8. This is because Joule heating allows for rapid temperature rise and fall, which is beneficial for the uniformity of the metal powder alloy formation and thus improves its catalytic activity.

[0124] from Figure 2 As can be seen from Comparative Examples 1-7, the activity of the high-entropy alloy oxide catalysts increases with the increase of the number of alloy metal elements. The results show that the excellent electronic properties and synergistic effect of the prepared high-entropy alloy oxide catalysts are beneficial to the ammonia synthesis reaction; among them, the prepared pentagonal high-entropy alloy oxide catalyst has the highest catalytic activity.

[0125] The RuCoFeMoTi high-entropy alloy oxide catalyst prepared in Example 3 was used for ammonia synthesis at 380℃ and 1 MPa pressure. The effect of reaction time on catalyst activity was investigated, and the results are shown in [Figure 3]. Figure 3 .

[0126] from Figure 3 As can be seen, the RuCoFeMoTi high-entropy alloy oxide catalyst did not show a decrease in ammonia synthesis performance after running continuously for 100 hours, indicating that the RuCoFeMoTi high-entropy alloy oxide catalyst prepared in this invention has good stability.

[0127] The above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A high-entropy alloy oxide catalyst, characterized in that, The catalyst is an oxide of a high-entropy alloy composed of any three elements selected from Fe, Mg, Ti and Mo, along with Ru and Co. The preparation method of the high-entropy alloy oxide catalyst includes the following steps: 1) Mix any three of the following elements: Fe powder, Mg powder, Ti powder, and Mo powder, as well as Ru powder and Co powder, until homogeneous to obtain a mixture; 2) The mixture is heated and cast in an inert atmosphere to obtain a high-entropy alloy block; 3) The high-entropy alloy block is ground in an inert atmosphere to obtain high-entropy alloy powder; 4) The high-entropy alloy powder is calcined in air to obtain a high-entropy alloy oxide catalyst.

2. The high-entropy alloy oxide catalyst according to claim 1, characterized in that, The high-entropy alloy oxide catalyst contains Ru, Co, Fe, Ti, and Mo, and the molar percentages of Ru, Co, Fe, Ti, and Mo are (5-35):(5-35):(5-35):(5-35):(5-35).

3. The high-entropy alloy oxide catalyst according to claim 2, characterized in that, The molar percentages of Ru, Co, Fe, Ti and Mo are (5-20):(5-20):(20-35):(5-20):(5-20).

4. A method for preparing a high-entropy alloy oxide catalyst, characterized in that, Includes the following steps: 1) Mix any three of the following elements: Fe powder, Mg powder, Ti powder, and Mo powder, as well as Ru powder and Co powder, until homogeneous to obtain a mixture; 2) The mixture is heated and cast in an inert atmosphere to obtain a high-entropy alloy block; 3) The high-entropy alloy block is ground in an inert atmosphere to obtain high-entropy alloy powder; 4) The high-entropy alloy powder is calcined in air to obtain a high-entropy alloy oxide catalyst.

5. The method for preparing the high-entropy alloy oxide catalyst according to claim 4, characterized in that, In step 1), the purity of any three of the Fe element powder, the Mg element powder, the Ti element powder, and the Mo element powder, as well as the Ru element powder and the Co element powder, is higher than 99%, and the particle size is 100-500 mesh.

6. The method for preparing the high-entropy alloy oxide catalyst according to claim 4, characterized in that, In step 2), the inert gas is argon; the heating and casting process includes: a heating temperature of 1000-3000℃ and a heating time of 10-60min.

7. The method for preparing the high-entropy alloy oxide catalyst according to claim 6, characterized in that, In step 2), the purity of the argon gas is 99%; the heating and casting process includes: a heating temperature of 1500-2500℃ and a heating time of 20-40 min.

8. The method for preparing the high-entropy alloy oxide catalyst according to claim 7, characterized in that, In step 2), the heating and casting process includes: a heating temperature of 2000℃ and a heating time of 30min.

9. The method for preparing the high-entropy alloy oxide catalyst according to claim 6, characterized in that, The heating and casting process is carried out in a Joule heater.

10. The method for preparing the high-entropy alloy oxide catalyst according to claim 4, characterized in that, In step 3), the inert gas is argon, and the purity of the argon is 99%; the grinding process is ball milling, and the ball milling jar is one or more of vacuum stainless steel jar, cemented carbide jar, and agate jar; the ball is one or more of stainless steel ball, cemented carbide ball, and zirconia ball; the ball milling media is one or more of anhydrous ethanol, polyvinyl alcohol, stearic acid, and polymethyl methacrylate.

11. The method for preparing the high-entropy alloy oxide catalyst according to claim 10, characterized in that, The conditions for ball milling include: a ball milling speed of 200-600 rpm, a ball-to-material ratio of 2:1-20:1, and a ball milling time of 10-100 h.

12. The method for preparing the high-entropy alloy oxide catalyst according to claim 11, characterized in that, The conditions for ball milling include: a ball milling speed of 300-500 rpm, a ball-to-material ratio of 4:1-16:1, and a ball milling time of 20-80 h.

13. The method for preparing the high-entropy alloy oxide catalyst according to claim 12, characterized in that, The conditions for ball milling include: a ball milling speed of 400 rpm, a ball-to-material ratio of 10:1, and a ball milling time of 30-50 h.

14. The method for preparing the high-entropy alloy oxide catalyst according to claim 4, characterized in that, In step 4), the calcination is carried out in a muffle furnace; the calcination treatment includes: a calcination temperature of 100-800℃, a calcination time of 10-30h, and a heating rate of 5-20℃ / min.

15. The method for preparing the high-entropy alloy oxide catalyst according to claim 14, characterized in that, In step 4), the calcination treatment includes: a calcination temperature of 200-600℃, a calcination time of 10-20h, and a heating rate of 10-15℃ / min.

16. The method for preparing the high-entropy alloy oxide catalyst according to claim 15, characterized in that, In step 4), the calcination treatment includes: a calcination temperature of 500℃, a calcination time of 12h, and a heating rate of 10℃ / min.

17. The application of the high-entropy alloy oxide catalyst prepared by the preparation method according to any one of claims 4-16 in the ammonia synthesis reaction.

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