A method for preparing a rare earth high entropy alloy catalyst and its application

Abstract

The present invention discloses a method for preparing a rare earth high-entropy alloy catalyst and its application. The method includes: (1) ball milling to obtain alloy powder; (2) pressing the alloy powder into a cylinder for sintering; (3) crushing the sintered metal cylinder into rare earth high-entropy alloy powder; (4) performing wet mechanical ball milling on the rare earth high-entropy alloy powder; (5) centrifuging the ball-milled rare earth high-entropy alloy powder and then drying it. The present invention also discloses the application of the obtained six-component rare earth high-entropy alloy catalyst, which has excellent catalytic performance and significantly improves the hydrogen absorption and desorption kinetic performance of MgH2.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to a preparation method of a hexavalent rare earth high entropy alloy catalyst and application thereof. Background Art

[0002] As a zero-carbon energy carrier, hydrogen is gaining more and more attention. In the development of the hydrogen energy industry chain, efficient and safe hydrogen storage technology is a key link in achieving the widespread application of hydrogen energy. Using transition metals and their complexes as catalysts for solid hydrogen storage materials has become a strategy to improve kinetic performance at a relatively low cost, because the electron transfer of multivalent transition metals is conducive to the dissociation and recombination of hydrogen molecules.

[0003] Contrary to traditional alloys that usually contain only one or two basic elements, high entropy alloys (HEAs) contain multiple main elements and have a wider range of compositions than traditional alloys. HEAs have four unique effects. The lattice distortion effect makes it conducive to the absorption of hydrogen in the interstitial positions of tetrahedrons and octahedrons. The cocktail effect makes it possible for different elements to have synergistic effects, making the material have rich surfaces and interfaces, thereby providing a large number of active sites and improving catalytic efficiency. Therefore, HEAs have the potential to be used as efficient catalysts for hydrogen storage materials in the future.

[0004] Rare earth elements have excellent physical and chemical properties. When mixed with transition metal elements as co-catalysts, they can increase the dispersion of active components on the surface, improve the overall activity or selectivity of the catalyst, and thus enhance the reaction kinetics.

[0005] Chinese invention patent application CN101214443A discloses a method for preparing a high entropy alloy catalyst containing rare earths, and the method for preparing a high entropy alloy catalyst containing rare earths comprises the following steps: S01: preparing an organic system solution containing palladium ions, manganese ions, iron ions or ferrous ions, cobalt ions, nickel ions, zinc ions and rare earth metal ions. S02: adding electrolyte, using titanium sheet as working electrode, and applying an electric field under the action of a magnetic field to perform electrodeposition. The preparation method of the invention belongs to a nonlinear process, and can prepare a multi-principal element high entropy alloy material with a nano-array structure without a plate.

[0006] In the field of solid-state hydrogen storage catalysis, it is important to develop an economical and efficient preparation technology to synthesize MgH 2 The reaction kinetics of high entropy alloy catalysts remains a pressing technical challenge for researchers. Summary of the invention

[0007] Based on the above reasons, the present invention proposes a preparation method and application of a hexavalent rare earth high entropy alloy catalyst. Specifically, in order to achieve the purpose of the present invention, the present invention adopts the following technical solution:

[0008] One aspect of the present invention relates to a method for preparing a rare earth high entropy alloy catalyst, which comprises the following steps:

[0009] (1) Grinding off the oxide scale of the YNi / LaNi / CeNi master alloy ingot, then crushing the alloy ingot into powder, and passing it through a 200-mesh sieve to obtain rare earth master alloy powder for standby use;

[0010] (2) Mixing vanadium powder, chromium powder, iron powder, manganese powder, nickel powder and rare earth master alloy powder with an average particle size of 85 μm, wherein the molar ratio of V, Cr, Fe, Mn, Ni, Y / La / Ce elements is 1:1:1:1:1:(0.2-1), and performing high-energy ball milling under argon atmosphere protection to obtain rare earth high entropy alloy ball milled powder;

[0011] (3) The rare earth high entropy alloy powder is ball-milled into a cylinder, and sintered in an argon atmosphere to obtain an alloy cylinder. The sintering temperature is 1000°C to 1500°C, and the sintering time is 5h to 12h;

[0012] (4) crushing the sintered alloy cylinder into powder, and passing it through a 300-mesh sieve to obtain rare earth high-entropy alloy powder;

[0013] (5) The ball milling beads, ethanol and rare earth high entropy alloy powder are filled with argon gas for protection, and wet mechanical ball milling is performed at 320 rpm to 420 rpm for 30 h to 70 h to obtain a rare earth high entropy alloy solid-liquid mixture;

[0014] (6) The rare earth high entropy alloy solid-liquid mixture is centrifuged and washed 6-8 times, and then dried under an argon atmosphere to obtain a rare earth high entropy alloy catalyst at a drying temperature of 100°C to 200°C.

[0015] In a preferred embodiment of the present invention, the molar ratio of the two elements in the YNi / LaNi / CeNi master alloy of step (1) is 1:1.

[0016] In a preferred embodiment of the present invention, the ball milling in step (2) is to weigh stainless steel ball milling beads according to a ball-to-material ratio of (10-30): 1, wherein beads with a diameter of 16 mm account for 5-15wt%, beads with a diameter of 10 mm account for 15-25wt%, and beads with a diameter of 3-7 mm account for 60-80wt%, and the ball milling beads and metal powder are poured into a ball milling jar, filled with argon for protection, and mechanically mixed at 300rpm-400rpm for 10h-30h. The present invention uses beads of different diameters for high-energy ball milling, which helps to have a larger specific surface area under appropriate weighting conditions to crush the alloy powder and reduce the size of the alloy particles.

[0017] In a preferred embodiment of the present invention, the pressing in step (3) is to weigh 3g-5g of powder and pour it into a mold, and press it into an alloy cylinder with a diameter of 10-20mm and a thickness of 2-4mm under a pressure of 30Mpa.

[0018] In a preferred embodiment of the present invention, the sintering in step (4) is followed by cooling by furnace cooling.

[0019] In a preferred embodiment of the present invention, the ball milling in step (5) is as follows: stainless steel ball milling beads are weighed according to a ball-to-material ratio of (60-120):1, wherein beads with a diameter of 10 mm account for 10-20 wt%, and beads with a diameter of 5 mm account for 80-90 wt%, ethanol and rare earth high entropy alloy powder are added in a ratio of (6-10):1, and wet mechanical ball milling is performed at 320 rpm-420 rpm for 30 h-70 h.

[0020] In a preferred embodiment of the present invention, ethanol is used as the centrifugal liquid in the centrifugation process in step (6), and a tubular furnace is used in the drying process. After four vacuum treatments, argon gas is introduced to heat and dry.

[0021] Another aspect of the present invention also relates to a hexavalent rare earth high entropy alloy catalyst prepared by the above preparation method.

[0022] Another aspect of the present invention also relates to the application of the hexavalent rare earth high entropy alloy catalyst of the present invention, wherein the application refers to the application in the absorption and release of hydrogen.

[0023] Preferably, the six-element rare earth high entropy alloy catalyst and MgH 2 After compounding, it is used to absorb and release hydrogen.

[0024] Beneficial Effects

[0025] The six-element rare earth high entropy alloy catalyst of the present invention has excellent catalytic performance and significantly improves the MgH 2 The kinetics of hydrogen absorption and desorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The sintered VCrMnFeNiY obtained by the method of Example 1 0.2 Picture of the finished product of rare earth high entropy alloy.

[0027] Figure 2 This is the EDS image of the YNi master alloy powder used in Example 1.

[0028] Figure 3 VCrMnFeNiY obtained by the method of Example 1 0.2 EDS image of rare earth high entropy alloy powder.

[0029] Figure 4 VCrMnFeNiY obtained by the method of Example 1 0.2 XRD pattern of rare earth high entropy alloy powder.

[0030] Figure 5 VCrMnFeNiY obtained by the method of Example 2 0.2 Rare earth high entropy alloy powder composite MgH 2 EDS diagram of .

[0031] Figure 6 VCrMnFeNiY obtained by the method of Example 2 0.2 Rare earth high entropy alloy powder catalyzes MgH 2 Performance diagram, (a) is hydrogen absorption performance, (b) is hydrogen desorption performance. DETAILED DESCRIPTION

[0032] In order to further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels.

[0034] Embodiment 1:

[0035] First, vanadium powder, chromium powder, iron powder, manganese powder, nickel powder and YNi master alloy powder with an average particle size of 85μm are mixed and configured, wherein the molar ratio of V, Cr, Fe, Mn, Ni and Y elements is 1:1:1:1:1:0.2, and the purity of the metal powder is above 99.99%. The weighed metal powder is poured into a stainless steel ball mill, and stainless steel ball mill beads are weighed according to the ball-to-material ratio of 10:1, wherein beads with a diameter of 16mm account for 10%, beads with a diameter of 10mm account for 25%, and beads with a diameter of 5mm account for 65%. The ball mill beads and metal powder are poured into the ball mill and filled with argon for protection, and mechanical mixing is performed on a planetary ball mill at 350rpm for 20h. 4g of the mixed alloy powder is weighed and poured into a mold, and a powder tablet press is used to press it into a cylinder with a diameter of 15mm and a thickness of 3mm at a pressure of 30Mpa. The pressed metal cylindrical piece is placed in a quartz crucible and sintered in a vertical tube furnace at a sintering temperature of 1300°C and a sintering time of 10 hours. During the sintering process, argon is introduced for protection to prevent oxidation. The cooling is performed by furnace cooling. The sintered metal cylindrical piece is mechanically crushed into powder and passed through a 300-mesh sieve. The hexavalent rare earth high entropy alloy powder currently obtained has not reached the nanometer level, so high-energy ball milling is still used to reduce the particle size of the high-entropy alloy. When high-energy ball milling is performed without adding a dispersant, at a large rotation speed, a large ball-to-material ratio and a long time, the rare earth high entropy alloy powder is easily smashed on the inner wall of the ball mill, resulting in a low discharge rate and an insignificant improvement in the particle size of the rare earth high entropy alloy. The present invention adopts wet ball milling, and ethanol is selected as a dispersant. Stainless steel ball milling beads are weighed according to a ball-to-material ratio of 100:1, of which beads with a diameter of 16 mm account for 10%, beads with a diameter of 10 mm account for 25%, and beads with a diameter of 5 mm account for 65%. The dispersant and rare earth high entropy alloy powder are added in a ratio of 6:1. The ball milling beads, ethanol and rare earth high entropy alloy powder are poured into a ball milling jar and filled with argon for protection, and wet mechanical ball milling is performed at 350rpm on a planetary ball mill for 40 hours. The ball-milled rare earth high entropy alloy solid-liquid mixture is poured into a centrifuge tube and washed 6 times on the centrifuge with ethanol. The speed of the centrifuge is 10,000 rpm, and the centrifugation time is 5 minutes each time. The centrifuged rare earth high entropy alloy powder is placed in a tubular furnace and dried in an argon atmosphere for 48 hours at a drying temperature of 200°C to obtain VCrFeMnNiY 0.2 Rare earth high entropy alloy catalysts.

[0036] Embodiment 2:

[0037] The rare earth high entropy alloy catalyst prepared in Example 1 was mixed with MgH 2To compound and evaluate its hydrogen absorption and desorption, the prepared rare earth high entropy alloy powder and magnesium hydride were compounded by high-energy ball milling under argon protection at a mass ratio of 0.5:9.5. The ball milling speed was 350r, the ball milling time was 10h, and the ball-to-material ratio was 50:1. The beads with a diameter of 10mm accounted for 10% and the beads with a diameter of 5mm accounted for 90%. After compounding, the phase and surface morphology were analyzed by XRD and SEM, and then the saturated hydrogen absorption and desorption at different temperatures were tested using a PCT hydrogen storage tester. The results of the kinetic test are shown in Table 1. By comparison, it was found that the rare earth high entropy alloy had a good effect on MgH 2 The kinetic performance has excellent catalytic effect and significantly improves the MgH 2 The hydrogen absorption and desorption kinetics provide a new technical approach for the performance optimization and application development of magnesium-based hydrogen storage alloys.

[0038] Table 1. MgH 2 Load VCrMnFeNiY 0.2 Comparison of hydrogen absorption and desorption of the catalyst at different temperatures before and after 2 hours

[0039]

[0040] The above describes the preferred embodiments of the present invention, which are however not intended to limit the present invention. A person skilled in the art may make improvements and changes to the embodiments disclosed herein without departing from the scope and spirit of the present invention.

Claims

1. A method for preparing a rare earth high entropy alloy catalyst, characterized in that: The steps include: (1) Grinding off the oxide scale of the YNi / LaNi / CeNi master alloy ingot, then crushing it into powder, and passing it through a 200-mesh sieve to obtain rare earth master alloy powder; (2) mixing vanadium powder, chromium powder, iron powder, manganese powder, nickel powder and rare earth master alloy powder with an average particle size of 85 μm, wherein the molar ratio of V, Cr, Fe, Mn, Ni, Y / La / Ce elements is 1:1:1:1:1:0.2, and performing high-energy ball milling under argon atmosphere protection to obtain rare earth high entropy alloy ball milled powder; (3) Pressing the rare earth high entropy alloy ball-milled powder into a cylinder, sintering it in an argon atmosphere to obtain an alloy cylinder, the sintering temperature is 1000°C~1500°C, and the sintering time is 5h~12h; (4) The sintered alloy cylinder is crushed into powder by mechanical means, and passed through a 300-mesh sieve to obtain rare earth high entropy alloy powder; (5) The ball milling beads, ethanol and rare earth high entropy alloy powder are filled with argon gas for protection, and wet mechanical ball milling is performed at 320 rpm to 420 rpm for 30 h to 70 h to obtain a rare earth high entropy alloy solid-liquid mixture; (6) The rare earth high entropy alloy solid-liquid mixture is centrifuged and washed 6-8 times, and then dried under an argon atmosphere to obtain a rare earth high entropy alloy catalyst at a drying temperature of 100°C to 200°C.

2. The method according to claim 1, characterized in that The molar ratio of the two elements in the YNi / LaNi / CeNi master alloy of step (1) is 1:

1.

3. The method according to claim 1, characterized in that The high-energy ball milling in step (2) is performed by weighing stainless steel ball milling beads according to a ball-to-material ratio of (10-30):1, wherein beads with a diameter of 16 mm account for 5-15 wt%, beads with a diameter of 10 mm account for 15-25 wt%, and beads with a diameter of 3-7 mm account for 60-80 wt%. The ball milling beads and metal powder are filled with argon gas for protection, and mechanical mixing is performed at 300 rpm-400 rpm for 10 h-30 h.

4. The method according to claim 1, characterized in that: The pressing in step (3) is to weigh 3g-5g of powder and pour it into a mold, and press it into a cylinder with a diameter of 10-20mm and a thickness of 2-4mm under a pressure of 30Mpa.

5. The method according to claim 1, characterized in that After the sintering in step (4), the sintering is cooled by furnace cooling.

6. The method according to claim 1, characterized in that The ball milling in step (5) is as follows: stainless steel ball milling beads are weighed according to a ball-to-material ratio of (60-120):1, wherein beads with a diameter of 10 mm account for 10-20 wt%, and beads with a diameter of 5 mm account for 80-90 wt%, ethanol and rare earth high entropy alloy powder are added in a ratio of (6-10):1, and wet mechanical ball milling is performed at 320 rpm-420 rpm for 30 h-70 h.

7. The method according to claim 1, characterized in that In the centrifugation process in step (6), ethanol is used as the centrifugal liquid, and a tubular furnace is used in the drying process. After four vacuum treatments, argon gas is introduced to heat and dry.

8. A rare earth high entropy alloy catalyst prepared by the method described in any one of claims 1 to 7.

9. Use of the rare earth high entropy alloy catalyst according to claim 8 in magnesium-based hydrogen storage materials.

10. The use according to claim 9, characterized in that: The rare earth high entropy alloy catalyst is used to absorb and release hydrogen after being compounded with MgH2.

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