CN-118105986-B - High-entropy alloy ammonia synthesis catalyst and preparation method and application thereof

Abstract

The invention discloses a high-entropy alloy ammonia synthesis catalyst which comprises a carrier and high-entropy alloy particles loaded on the surface of the carrier, wherein the average particle size of the high-entropy alloy particles is 2-20nm, the loading amount is 5-70wt%, the high-entropy alloy particles comprise active metals and auxiliary metals, the active metals comprise at least three of Fe, co, mo, ru, os, ni, rh, ir, mn, re, pt, pd, ag, and the auxiliary metals comprise at least one of Ce, ba, sr, mg, ca, li, K, la, sm, W, V, cs, tc, cu. The preparation method of the high-entropy alloy ammonia synthesis catalyst comprises the steps of uniformly mixing active metal salt, auxiliary metal salt, organic ligand and a carrier, performing ball milling in an inert atmosphere to obtain a precursor A, performing heat treatment and reduction in the inert atmosphere, and cooling to obtain the high-entropy alloy ammonia synthesis catalyst. The high-entropy alloy particles in the catalyst have small size and good dispersibility, can be applied to ammonia synthesis reaction, and show good catalytic performance.

Inventors

• LAN GUOJUN
• ZHANG LIPING
• LI YING
• Cheng Zaizhe
• SUN XIUCHENG
• QIU YIYANG

Assignees

• 浙江工业大学

Dates

Publication Date

20260508

Application Date

20240204

Claims (5)

1. 1. The application of the high-entropy alloy ammonia synthesis catalyst in the ammonia synthesis catalytic reaction is characterized in that the high-entropy alloy ammonia synthesis catalyst comprises a carrier and high-entropy alloy particles loaded on the surface of the carrier, wherein the loading amount of the high-entropy alloy particles is 5-70 wt%, the average particle size of the high-entropy alloy particles is 2-20 nm, the high-entropy alloy particles comprise active metals and auxiliary metals, the active metals comprise at least three of Fe, co, mo, ru, os, ni, rh, ir, re, pt, pd, ag, the auxiliary metals comprise at least one of Ce, ba, sr, mg, ca, li, K, la, sm, W, V, cs, and the carrier is at least one of carbon materials, alkaline earth metal oxides and rare earth metal oxides; the preparation method of the high-entropy alloy ammonia synthesis catalyst comprises the following steps: (1) Uniformly mixing active metal salt, auxiliary metal salt, organic ligand and carrier, and ball-milling in inert atmosphere to obtain precursor A, wherein the organic ligand is one or more of citric acid, malic acid, tartaric acid, acetic acid, succinic acid, oxalic acid, tannic acid and humic acid; (2) Carrying out heat treatment on the precursor A under the inert atmosphere condition, and cooling to obtain an alloy precursor B, wherein the heat treatment temperature is 200-800 ℃ and the heat treatment time is 2-6 h; (3) And (3) reducing the precursor B in a reducing atmosphere, and cooling to obtain the catalyst.
2. 2. The use of the high-entropy alloy ammonia synthesis catalyst according to claim 1, wherein the content of each active metal is independently 5-50 wt% and the content of the additive metal is 5-50 wt% based on the mass of the high-entropy alloy particles.
3. 3. The application of the high-entropy alloy ammonia synthesis catalyst according to claim 1 in ammonia synthesis catalytic reaction, wherein the mass ratio of the organic ligand to the metal precursor is 1-100:1, and the metal precursor is active metal salt and auxiliary metal salt.
4. 4. The use of the high-entropy alloy ammonia synthesis catalyst according to claim 1, wherein the ball-milling process has a ball-to-material ratio of 1-60:1, a ball-milling rotation speed of 300-800 rpm, and a ball-milling time of 3-6 h.
5. 5. The use of the high entropy alloy ammonia synthesis catalyst according to claim 1, wherein in step (3), the reduction temperature is 200-1200 ℃ and the reduction time is 1-6 h.

Description

High-entropy alloy ammonia synthesis catalyst and preparation method and application thereof Technical Field The invention belongs to the field of catalyst preparation technology and application, and particularly relates to a high-entropy alloy ammonia synthesis catalyst and a preparation method and application thereof. Background Ammonia is of interest as a hydrogen storage and transport medium because it can be stored in the liquid phase at a higher volumetric hydrogen density than liquid H 2 under mild conditions. Because NH 3 is liquid at lower pressures and higher temperatures than H 2, the energy consumption for liquefaction is lower and the containers for storage and transport are smaller and lighter. And the development of modern industrial and agricultural economy is inseparable from the use of ammonia. Ammonia is a focus of attention as an important chemical raw material and energy carrier. Currently, ammonia is synthesized industrially by hydrogenating nitrogen gas at high temperature and high pressure (400-600 ℃ C., 20-40 MPa) by the Haber-Bosch process to produce ammonia, but the synthesis conditions of high temperature and high pressure require high energy consumption and are liable to sinter and deactivate the ammonia synthesis catalyst. Therefore, development of an ammonia synthesis catalyst having high activity under mild conditions has been a goal pursued by researchers. The stronger the adsorption energy of the transition metal surface to nitrogen is, the stronger the dissociation capability to N (identical to that of N) is, the better the catalytic activity is, and meanwhile, the stronger the adsorption energy of the transition metal surface to NH x is, the more difficult NH x is to dissociate. Therefore, the relationship between the ammonia synthesis rate of the metal and the adsorption energy of nitrogen on the metal is in a volcanic type trend. Since high entropy alloys mix multiple metals, the surface is highly heterogeneous, there is a large number of possible atomic arrangements. Compared with a single metal catalyst and a non-high entropy catalyst, the high entropy alloy nanoparticle catalyst breaks through an immiscible gap between metals, and can effectively adjust metal types and proportions, so that the electronic structure and d-band center of the metal are adjusted, and the continuous adjustment of the adsorption energy of nitrogen and NH x on the alloy surface can be realized in an ammonia synthesis reaction, so that the effective regulation and control of the catalytic performance of ammonia synthesis are realized. In the electro-catalytic nitrogen reduction synthesis of ammonia, VS 2@Bi2O3/CC prepared by Chinese patent CN113862717B has ammonia yield of 24.3X10- -10mol s-1cm-2 and Faraday efficiency of 11.5% at-0.10V (relative to standard hydrogen electrode). Chinese patent CN111686758B prepared RuFeCoNiCu high entropy alloy nanoparticles by solvothermal method, the activity of 0.1M KOH electrolyte is optimal, NH 3 yield is 58.57 μg -1mg-1cat, area yield is 29.28 μ g h -1cm-2, faradaic efficiency is 26.4%. However, the current electrocatalytic ammonia synthesis efficiency is too low and has no industrial application prospect. There is no example report of a high entropy alloy catalyst for synthesizing ammonia by thermocatalysis. Although the high-entropy alloy nanoparticle catalyst shows good application prospects in the field of catalysis, the controllable synthesis of the high-entropy alloy catalyst still has a plurality of problems. At present, the high-entropy alloy nanoparticle catalyst is mainly obtained by methods such as transient heating, mechanical alloying, wet chemical method, sputtering deposition and the like, and is applied to the fields of ammonia decomposition, CO oxidation, CO 2 reduction and the like. Literature (Nature communications,2019,10 (1): 4011) reports that the preparation of HEA CoMoFeNiCu nano particles with the particle size of 22nm by a carbon thermal shock method can realize the stable adjustment of Co/Mo ratio, breaks the miscible phase limit of the traditional bimetallic Co-Mo catalyst, shows good catalytic activity and stability in an ammonolysis reaction, but the method has higher requirements on equipment. In the preparation process of the platinum-series high-entropy alloy nanoparticle catalyst reported in China patent CN111111693A, organic solvents such as THF, CHCl 3 and the like are used for dissolving metal precursors, and then the block high-entropy material prepared by a template method is subjected to strong acid and strong alkali etching to obtain the monodisperse platinum-series high-entropy alloy nanoparticle catalyst with controllable particle size and good dispersibility, but a large amount of waste liquid is generated in the process, so that serious environmental pollution is caused. The high-entropy alloy nano particles prepared by adopting a spray drying and calcining method in China patent CN111545767A have uniform dis