Amorphous aluminum-nickel catalyst modified by rare earth and chiral ligand and application thereof in asymmetric hydrogenation

Abstract

This invention discloses an amorphous aluminum-nickel catalyst synergistically modified with rare earth and chiral ligands and its application in asymmetric hydrogenation, belonging to the field of catalyst technology. The catalyst comprises nickel, aluminum, boron, rare earth elements, and chiral ligands, and possesses an amorphous structure. The chiral ligands coordinate with nickel atoms on the catalyst surface through their coordinating atoms, with the rare earth elements located within the coordination range of the ligands, forming a nickel-ligand-rare earth bridging structure that synergistically regulates the stereoelectronic environment of the catalytic center. The catalyst preparation method includes steps such as chemical reduction and double quenching to prepare an amorphous alloy precursor, gradient alkaline leaching activation to form a porous structure, chiral ligand modification, and passivation protection. The catalyst of this invention can be used in the asymmetric hydrogenation reaction of unsaturated compounds such as unsaturated ketones, aromatic ketones, and imines, achieving high conversion rates and high enantioselectivity, and can be recycled multiple times without significant performance degradation, showing promising industrial application prospects.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to an amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands and its application in asymmetric hydrogenation. Background Technology

[0002] Asymmetric hydrogenation is an important organic synthesis reaction in which hydrogen molecules selectively add to a specific enantiomer of a substrate molecule under the action of a chiral catalyst, preferentially generating a chiral product with a specific optical configuration. Chiral compounds have wide applications in fine chemicals such as pharmaceuticals, pesticides, and fragrances. The physiological activity of many drug molecules is closely related to their stereoconfiguration; different enantiomers often exhibit drastically different or even opposite pharmacological effects. Therefore, developing efficient asymmetric hydrogenation catalytic systems is of great significance for the synthesis of chiral compounds. Traditional asymmetric hydrogenation catalysts mainly construct catalytic active centers by forming complexes between noble metals such as rhodium, ruthenium, and iridium and chiral ligands. Although these catalysts can achieve excellent enantioselectivity, the scarcity and high cost of noble metals result in high catalyst costs, severely restricting the large-scale application of asymmetric hydrogenation technology in industrial production. Nickel, as a rich and inexpensive transition metal, possesses catalytic hydrogenation activity similar to noble metals. Developing nickel-based asymmetric hydrogenation catalysts is considered an important way to reduce production costs and achieve sustainable development of catalytic technology.

[0003] However, existing nickel-based catalysts still face numerous technical challenges in asymmetric hydrogenation applications. Traditional crystalline nickel catalysts suffer from low surface active site density due to the periodicity of their atomic arrangement, and defects such as grain boundaries and dislocations lead to uneven distribution of active sites, making it difficult to meet the requirements for highly efficient catalytic reactions. While existing amorphous catalysts such as Raney nickel exhibit high catalytic activity, they lack chiral recognition capabilities and cannot be directly applied to asymmetric catalytic reactions. When attempting to introduce chiral ligands onto the surface of nickel-based catalysts, the lattice confinement of the crystalline structure results in low coordination efficiency between the ligands and nickel active centers, and the ligands exhibit poor stability on the catalyst surface, easily detaching and being lost during the reaction. This leads to suboptimal enantioselectivity and difficulty in maintaining the catalyst. Furthermore, existing nickel-based catalysts are prone to structural transformation or deactivation during catalytic reactions, and their stability and recyclability fail to meet the requirements of practical applications.

[0004] Therefore, there is an urgent need to develop a novel nickel-based asymmetric hydrogenation catalyst that combines high catalytic activity, high enantioselectivity, and excellent stability. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides an amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands, the catalyst comprising the following components, by mass percentage:

[0006] Nickel (Ni): 40%-60%;

[0007] Aluminum (Al): 15%-30%;

[0008] Boron (B): 8%-15%;

[0009] Rare earth elements RE, selected from lanthanum (La), cerium (Ce), or mixtures thereof: 3%-8%;

[0010] Chiral ligand L, based on the total mass of the catalyst: 0.5%-3%;

[0011] The remainder is impurities;

[0012] The catalyst has an amorphous structure, and its X-ray diffraction pattern is as follows: The diffraction peaks within the range are broadened, with a full width at half maximum (FWHM) ≥ 2°.

[0013] The chiral ligand contains phosphorus (P) or nitrogen (N) coordinating atoms, which coordinate with nickel atoms on the catalyst surface, and the rare earth element is located within the coordination range of the ligand.

[0014] The molar ratio of the rare earth element to the nickel element satisfies: In the formula, This refers to the amount of rare earth elements in substance. This represents the amount of nickel.

[0015] In a preferred embodiment, the catalyst has a specific surface area of ​​80-120 m². 2 / g, with an average pore size of 8-15nm;

[0016] The catalyst comprises the following components by mass percentage: nickel 45%-55%, aluminum 18%-25%, boron 10%-13%, rare earth elements 4%-6%, and chiral ligands 1%-2%; the rare earth element is lanthanum (La). The rare earth element exists in the catalyst in the form of cerium (Ce), or the rare earth element is cerium (Ce). or It exists in the catalyst;

[0017] The chiral ligand is selected from at least one of the following: (R,R)-1,2-diphenylethylenediamine; (S,S)-1,2-diphenylethylenediamine; (R)-2,2-bis(diphenylphosphine)-1,1-naphthyl; (S)-2,2-bis(diphenylphosphine)-1,1-naphthyl; (R,R)-N,N-bis(3,5-di-tert-butylsalicylaldehyde)cyclohexanediamine.

[0018] In the preferred embodiment, the catalyst is prepared by the following method:

[0019] Preparation of S1 precursor alloy: Nickel salt, aluminum salt and rare earth salt are dissolved in water in molar ratio to prepare a mixed salt solution. Sodium borohydride reducing agent is added dropwise to the mixed salt solution under ice bath conditions. The alloy particles generated by the reaction are first quenched and placed in a cooling medium at a temperature of -30℃ to -60℃. After collection, they are quenched a second time in a cooling medium at a temperature of -150℃ to -196℃ for 10-60 minutes. They are then transferred under an inert atmosphere and vacuum dried to obtain an amorphous alloy precursor.

[0020] S2 gradient alkaline leaching activation: The amorphous alloy precursor is first added to an alkaline solution with a concentration of 0.5-1.0 mol / L and soaked at 15-30℃ for 2-4 hours for the first alkaline leaching. Then, the solid is transferred to an alkaline solution with a concentration of 2.0-3.0 mol / L and soaked at 40-60℃ for 4-6 hours for the second alkaline leaching. By adjusting the concentration, temperature and time of the two alkaline leachings, the average pore size of the catalyst is controlled within the range of 8-15 nm. The catalyst is washed with deionized water until the pH is 7-8 and then vacuum dried to obtain a porous activated catalyst.

[0021] S3 Chiral ligand modification: The porous activated catalyst is dispersed in an anhydrous organic solvent, and an organic solvent solution of chiral ligands is added. The amount of chiral ligands is 0.5%-3% of the catalyst mass. The mixture is refluxed at 80-100℃ for 6-12 hours under an inert atmosphere. During the reflux, an inert gas flow containing alkaline organic amine is introduced to promote the coordination of the ligands with the metal center. After cooling, the mixture is filtered, washed, and vacuum dried to obtain the ligand-modified catalyst.

[0022] S4 Passivation Protection: The ligand-modified catalyst is placed in an inert atmosphere and a mixture of oxygen / inert gas with an oxygen content of 0.5-2 vol% is introduced. The mixture is treated at room temperature for 2-4 hours to form a thin oxide protective layer on the catalyst surface, thus obtaining an amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands.

[0023] In the preferred embodiment, step S1 includes the following specific steps:

[0024] Preparation of S11 mixed salt solution: Weigh out nickel nitrate hexahydrate... Aluminum nitrate nonahydrate Lanthanum nitrate hexahydrate Or cerium nitrate hexahydrate Massager Dissolve in deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.3-0.5 mol / L, with a solution volume of 50-200 mL. In the formula, This represents the amount of substance (mol) of nickel. This represents the amount of aluminum in moles (mol). This represents the amount of substance (mol) of rare earth elements.

[0025] S12 reduction reaction: Preparation of sodium borohydride An aqueous solution with a concentration of 1.2-1.8 mol / L. The molar amount of the mixed salt solution should be 1.2-2.0 times the total molar amount of the mixed metal ions. Place the mixed salt solution in a three-necked flask and cool it to 0-5°C in an ice-water bath. Turn on the mechanical stirrer and set the speed to 500-800 rpm. Under stirring conditions, add the solution at a rate of 5-10 mL / min. The solution is added dropwise to the mixed salt solution. During the dropwise addition, a black precipitate is produced in the solution, accompanied by a large number of bubbles. This step achieves the reduction of metal ions into alloy particles.

[0026] S13 First Quenching: Prepare a beaker containing 100-300mL of anhydrous ethanol or isopropanol, place the beaker in a dry ice-acetone bath or a low-temperature thermostat, and lower the temperature of the alcohol solution to -30℃ to -60℃; after the reduction reaction is completed, immediately pour the reaction mixture into the cooled alcohol solution to rapidly cool the alloy particles within 2-5 seconds. This step achieves the initial amorphization of the alloy.

[0027] S14 Second Quenching: Collect alloy particles rapidly by vacuum filtration or centrifugation at 3000-5000 rpm for 5-10 minutes; wash 1-2 times with a small amount of anhydrous ethanol pre-cooled to below -30°C; under an inert atmosphere, rapidly transfer the alloy particles to liquid nitrogen at -196°C, or to other cooling media at -150°C to -196°C, and immerse for 10-60 minutes. This step inhibits the growth of alloy nuclei through two-stage quenching, further stabilizing the amorphous structure.

[0028] S15 Vacuum Drying: Under the protection of an inert atmosphere, the quenched alloy particles are taken out from the cooling medium and placed in a vacuum drying oven. They are dried for 10-14 hours at a temperature of 50-60℃ and a vacuum degree of ≤10Pa to obtain a black powdery amorphous alloy precursor. The precursor is then sealed and stored under the protection of nitrogen or argon.

[0029] In the preferred embodiment, step S2 includes the following specific steps:

[0030] S21 First alkaline leaching: Weigh 2-10g of the amorphous alloy precursor prepared in step S1 and add it to sodium hydroxide solution with a concentration of 0.5-1.0mol / L. or potassium hydroxide In an alkaline solution, the liquid-to-solid ratio is 10-20 mL / g. The mixture is magnetically stirred at 15-30℃ for 2-4 hours at a stirring speed of 200-400 rpm. This step slowly removes some aluminum, forming a preliminary porous structure, while ensuring a high retention rate of rare earth elements.

[0031] S22 Second Alkali Immersion: The solid after the first alkali immersion is separated by centrifugation or filtration, and quickly rinsed with deionized water 1-2 times; the rinsed solid is transferred to a sodium hydroxide or potassium hydroxide alkaline solution with a concentration of 2.0-3.0 mol / L, the liquid-to-solid ratio is 15-25 mL / g, and stirred at 40-60℃ for 4-6 hours; this step continues to remove aluminum elements, expand the pore size, and form a sponge-like porous structure;

[0032] S23 Washing and Drying: After the second alkaline leaching, the solid is repeatedly washed with deionized water, and centrifuged after each wash. The washing is repeated 5-8 times until the pH of the supernatant drops to 7-8. The washed solid is placed in a vacuum drying oven and dried for 8-12 hours at 50-60℃ and a vacuum degree ≤10Pa to obtain a gray-black porous activated catalyst.

[0033] In the preferred embodiment, step S3 includes the following specific steps:

[0034] S31 Catalyst Dispersion: Weigh 1-5g of the porous activated catalyst prepared in step S2, add it to 30-100mL of anhydrous toluene, anhydrous tetrahydrofuran or anhydrous dichloromethane, and ultrasonically disperse for 10-20 minutes to ensure that the catalyst is uniformly dispersed in the solvent.

[0035] Preparation of S32 ligand solution: Weigh the chiral ligand, and calculate the amount according to the following formula: In the formula, Ligand mass (g); The mass of the catalyst is (g). The ligand mass fraction, ranging from 0.005 to 0.03; preferably... The corresponding ligand dosage is 1%-2% of the catalyst mass; the ligand is dissolved in 10-30 mL of the same anhydrous organic solvent as in step S31 to prepare a solution with a ligand concentration of 2-10 mg / mL;

[0036] S33 Ligand Impregnation: Add the ligand solution prepared in step S32 to the catalyst suspension in step S31, and stir at room temperature for 0.5-1 hour to allow the ligand to fully wet the catalyst surface.

[0037] S34 Reflux Coordination: Transfer the mixture from step S33 to a three-necked flask equipped with a reflux condenser and a gas protection device. Introduce argon or nitrogen to establish an inert atmosphere at a flow rate of 50-100 mL / min. Heat to the solvent reflux temperature: 110°C for toluene, 66°C for tetrahydrofuran, and 40°C for dichloromethane. Maintain reflux for 6-12 hours.

[0038] S35 Gas-phase enhanced coordination: During the 2nd to 8th hour of the reflux process, an inert gas stream containing a basic organic amine is introduced into the reaction system. The basic organic amine is selected from triethylamine, pyridine, or diisopropylethylamine. The organic amine vapor is introduced into the reflux system by carrying argon or nitrogen gas. The carrier gas flow rate is controlled at 80-120 mL / min, and the organic amine vapor introduction rate is controlled at 5-15 mL / h.

[0039] S36 Post-treatment: After reflux, stop heating and cool to room temperature under argon or nitrogen protection; separate the solid by centrifugation or vacuum filtration at 3000-5000 rpm for 10 min; wash 3-5 times with anhydrous toluene or ethanol, 20-30 mL each time, to remove uncoordinated free ligands; dry the washed solid in a vacuum drying oven at 50-60℃ and a vacuum degree ≤10 Pa for 8-12 hours to obtain a dark brown ligand-modified catalyst.

[0040] In the preferred embodiment, step S4 includes the following specific steps:

[0041] S41 passivation gas preparation: Prepare an oxygen / nitrogen mixture or an oxygen / argon mixture with an oxygen volume fraction of 0.5%-2%. Precisely control the flow rate of each gas using a gas mass flow meter. The preferred oxygen volume fraction is 1%. Use a volumetric flow rate ratio... Mix, with the total flow rate set at 100-200 mL / min, preferably 150 mL / min;

[0042] S42 Passivation treatment: The ligand-modified catalyst prepared in step S3 is spread into a thin layer with a thickness of ≤5mm and placed in a passivation device. First, pure nitrogen or pure argon is introduced to purge for 10-15 minutes to remove air from the system. Then, a mixed gas is introduced and the gas is introduced at room temperature of 20-30℃ for 2-4 hours, preferably 3 hours, to form a thin layer of oxide protective layer on the catalyst surface.

[0043] S43 Packaging and Storage: After passivation, the catalyst is transferred to a sealed bottle under nitrogen or argon protection, filled with argon, and then sealed for storage.

[0044] The application of the catalyst of the present invention in the asymmetric hydrogenation reaction of unsaturated compounds, wherein the unsaturated compounds are selected from aromatic ketones or α,β-unsaturated ketones;

[0045] The reaction conditions are as follows: reaction temperature 60-80℃, hydrogen pressure 2-4 MPa, substrate to catalyst molar ratio 200:1-500:1, solvent selected from alcohols, aromatics or ethers, and reaction time 4-8 hours; the conversion rate of the asymmetric hydrogenation reaction is ≥95%, the enantiomeric excess value of the product is ≥88%, and the catalyst can be reused at least 8 times without significant decrease in activity and selectivity.

[0046] The beneficial effects achieved by this invention are as follows:

[0047] First, this invention introduces an amorphous structure into the aluminum-nickel alloy catalyst, resulting in a large number of unsaturated coordination sites and defect sites on the catalyst surface. Compared with traditional crystalline nickel-based catalysts, the active site density of this invention's catalyst is significantly increased, providing more catalytic active centers for asymmetric hydrogenation reactions. The isotropic characteristics of the amorphous structure make the distribution of chiral ligands on the catalyst surface more uniform, avoiding the problem of uneven distribution of active sites caused by grain boundaries and dislocation defects in crystalline catalysts. This facilitates full contact between substrate molecules and chiral active sites during the catalytic reaction, thereby improving the enantioselectivity of the catalytic reaction. At the same time, rare earth elements are introduced into the amorphous aluminum-nickel catalyst system, utilizing their dual role of structural stability and electronic regulation. Rare earth ions have a large ionic radius and unfilled electron orbitals. After entering the amorphous alloy structure, they can effectively increase the configuration entropy of the system, significantly suppressing the tendency of the catalyst to transform into a crystalline structure within the operating temperature range, thereby greatly improving the thermal stability and service life of the catalyst. Meanwhile, rare earth elements can effectively regulate the electron density of nickel active centers through electronic interactions with nickel, optimize the adsorption and dissociation performance of hydrogen molecules on the catalyst surface, reduce the activation energy barrier of the reaction, and enhance the intrinsic activity of catalytic hydrogenation reaction.

[0048] Second, this invention employs synergistic modification of rare earth elements and chiral ligands. The ligands are anchored by forming coordinate bonds between the coordinating atoms in the chiral ligands and nickel atoms on the catalyst surface. Simultaneously, the rare earth elements, acting as Lewis acid centers, form auxiliary coordination with another coordinating group of the ligands, thereby constructing a stable nickel-ligand-rare earth bridging coordination structure. This unique bridging structure not only enhances the anchoring stability of the chiral ligands on the catalyst surface, effectively reducing the loss and detachment of ligands during the catalytic reaction, but also makes the stereoconfiguration of the ligand molecules more rigid. This significantly improves the accuracy of the ligands' selection of the chiral facets of the substrate molecules and the chiral induction efficiency, thus achieving high enantioselectivity on nickel-based catalysts that approaches the level of noble metal catalysts.

[0049] Third, the catalyst of this invention adopts an amorphization process that combines chemical reduction and double quenching with gradient alkaline leaching activation, which effectively obtains a stable amorphous structure and ensures a high retention rate of rare earth elements. The preparation process is simple and controllable, and is suitable for industrial production.

[0050] Fourth, the catalyst of this invention achieves efficient asymmetric hydrogenation conversion of a variety of unsaturated compounds under mild conditions, exhibiting high conversion rate and high enantioselectivity. Furthermore, the catalyst can be recycled multiple times without significant decrease in activity and selectivity, demonstrating excellent catalytic stability and recyclability, and has promising prospects for industrial application. Attached Figure Description

[0051] Figure 1 This is a comparison of the XRD patterns of the catalysts in Example 1 and Comparative Example 3, where sub-figure (a) is the XRD pattern of the catalyst in Example 1 and sub-figure (b) is the XRD pattern of the catalyst in Comparative Example 3.

[0052] Figure 2 These are comparison diagrams of the pore structure characterization of the catalysts in Example 1 and Comparative Example 4. Sub-figure (a) is the N2 adsorption-desorption isotherm, and sub-figure (b) is the BJH pore size distribution curve.

[0053] Figure 3 This is a bar chart comparing the catalytic performance of the catalysts in Examples 1-5 and Comparative Examples 1-4. Sub-figure (a) is a comparison chart of conversion rates, and sub-figure (b) is a comparison chart of enantiomeric excess values ​​ee.

[0054] Figure 4 This is a comparison curve of the cycle stability of the catalysts in Example 1 and Comparative Example 1. Subplot (a) shows the conversion rate as a function of the number of cycles, and subplot (b) shows the ee value as a function of the number of cycles.

[0055] Figure 5 The bar chart shows the catalytic performance of the catalyst in Example 1 on different substrates. Subplot (a) is a comparison of the conversion rates of different substrates, and subplot (b) is a comparison of the ee values ​​of different substrates.

[0056] Figure 6 This is a flowchart of a method for preparing an amorphous aluminum-nickel catalyst with rare earth-chiral ligand synergistic modification according to the present invention.

[0057] Figure 7 This is the XRD pattern of the catalyst after 8 cycles in Experiment Example 6. Detailed Implementation

[0058] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] This invention provides an amorphous aluminum-nickel catalyst synergistically modified with rare earth and chiral ligands, comprising the following components by mass percentage: 40% to 60% nickel (Ni), 15% to 30% aluminum (Al), 8% to 15% boron (B), 3% to 8% rare earth elements (RE), 0.5% to 3% chiral ligand (L) based on the total mass of the catalyst, with the balance being unavoidable impurities.

[0060] To verify the possibility of forming a nickel-ligand-rare earth bridging structure and its impact on catalytic performance, density functional theory (DFT) was used to calculate the model system. The calculations were performed using the Gaussian 16 package, with the B3LYP functional selected. The Ni and La atoms were represented by the LANL2DZ pseudopotential basis set, and other atoms by the 6-31G(d) basis set. The structure of the complex formed by the (R,R)-1,2-diphenylethylenediamine (DPEN) ligand and the Ni-La bimetallic center was optimized.

[0061] The model construction process is as follows: Using the surface of an amorphous Ni-Al alloy as the background, a Ni atom is selected as the active center, and a La atom is introduced near it to construct a Ni-La bimetallic site. The DPEN ligand coordinates with Ni through two N atoms, while one of the N atoms forms an auxiliary coordination with the La atom, forming a Ni-DPEN-La bridging structure.

[0062] The calculation results are as follows: The optimized structure shows that the DPEN ligand can simultaneously coordinate with Ni and La to form a stable five-membered ring structure. The Ni-N bond length is approximately 2.05 Å, the La-N bond length is approximately 2.52 Å, and the Ni-La distance is approximately 3.58 Å. The formation energy of this structure is about 15.3 kcal / mol lower than that of the structure coordinated only with Ni, indicating that the introduction of rare earth La significantly enhances the binding stability between the ligand and the metal center. Electronic structure analysis shows that the La atom, as a Lewis acid center, attracts electron density from the N atom of the ligand, thereby reducing the electron density of the Ni center, which is beneficial to the heterolytic activation of hydrogen molecules. DFT calculation results show that the formation of a Ni-ligand-rare earth bridging structure on the catalyst surface is thermodynamically feasible, and this structure can exist stably.

[0063] Nickel serves as the primary active metal component in the catalyst, providing active sites for hydrogen dissociation and transfer required for asymmetric hydrogenation reactions. Nickel's d-orbital electronic structure endows it with suitable hydrogen adsorption and activation properties. Aluminum forms an alloy with nickel during chemical reduction and is partially dissolved in the subsequent alkaline leaching activation step, resulting in a porous structure. The presence of aluminum is beneficial for increasing the specific surface area of ​​the catalyst and the accessibility of active sites. Boron is a key element in the formation of amorphous structures. Its small atomic radius disrupts long-range ordering upon entering interstitial sites, promoting the formation and stabilization of amorphous structures. Furthermore, the electron transfer effect between boron and nickel helps regulate the electron density of nickel active centers. Rare earth elements are selected from lanthanum (La), cerium (Ce), or mixtures thereof. Rare earth ions have large ionic radii and unfilled 4f electron orbitals; their addition increases the configurational entropy of the alloy system, inhibiting the transformation from amorphous to crystalline structures. Simultaneously, rare earth elements can act as Lewis acid centers to activate substrates in catalytic reactions. Chiral ligands contain coordinating atoms such as phosphorus (P) or nitrogen (N), which anchor to the catalyst surface by forming coordinate bonds with nickel atoms on the catalyst surface through their coordinating atoms. Furthermore, rare earth elements are located within the coordination range of the ligands, forming a nickel-ligand-rare earth bridging coordination structure, thereby achieving synergistic regulation of the three-dimensional electronic environment of the catalytic center.

[0064] The catalyst of this invention has an amorphous structure. When characterized by X-ray diffraction (XRD), it exhibits broadened diffraction peaks in the range of 2θ = 20° to 80°, with a full width at half maximum (FWHM) greater than or equal to 2°. XRD is an analytical method that uses X-rays to irradiate crystalline or amorphous materials and analyzes the atomic arrangement characteristics of the material by detecting the diffraction signal. Crystalline materials produce sharp diffraction peaks due to the periodic arrangement of atoms, while amorphous materials, due to their structural feature of short-range order and long-range disorder, show broadened diffuse peaks in their XRD patterns. The amorphous structure provides a large number of unsaturated coordination sites and defect sites on the catalyst surface, resulting in a higher active site density compared to crystalline catalysts. Simultaneously, the isotropic nature of the amorphous structure leads to a more uniform distribution of chiral ligands on the catalyst surface, which is beneficial for improving the enantioselectivity of the catalytic reaction.

[0065] This invention optimizes the molar ratio of rare earth elements to nickel in the catalyst, achieving a ratio of n(RE) / n(Ni) = 0.08-0.15, where n(RE) is the amount of rare earth element and n(Ni) is the amount of nickel element, expressed in mol. This molar ratio range is determined based on the dual functions of rare earth elements in the catalyst. When the molar ratio is below 0.08, the structural stabilizing and electronic regulation effects of rare earth elements are insufficient to be fully utilized; when the molar ratio is above 0.15, excessive rare earth elements may occupy too many nickel active sites, thus reducing catalytic activity and potentially causing the precipitation of rare earth oxide crystalline phases, disrupting the uniformity of the amorphous structure.

[0066] The preferred catalyst composition of this invention is as follows: nickel 45% to 55% by mass, aluminum 18% to 25% by mass, boron 10% to 13% by mass, rare earth elements 4% to 6% by mass, and chiral ligand 1% to 2% by mass. The preferred rare earth element is lanthanum (La), with La as the preferred component. 3+ It exists in the catalyst in the form of cerium (Ce), or in the form of Ce. 3+ or Ce 4+ It exists in the form of a catalyst. Preferred catalysts have a specific surface area of ​​80 to 120 m². 2 / g, a porous structure with an average pore size of 8 to 15 nm. Specific surface area refers to the total surface area per unit mass of solid material, determined by the nitrogen adsorption BET method; average pore size is a parameter characterizing the pore size of porous materials, calculated using the nitrogen adsorption-desorption isotherm BJH method.

[0067] The preferred chiral ligands of this invention are selected from at least one of the following: (R,R)-1,2-diphenylethylenediamine or (S,S)-1,2-diphenylethylenediamine, containing two primary amine groups as coordinating atoms, with phenyl groups attached to the two chiral carbon atoms providing chiral steric hindrance; (R)-2,2-bis(diphenylphosphine)-1,1-binaphthyl or (S)-2,2-bis(diphenylphosphine)-1,1-binaphthyl, containing two phosphine groups as coordinating atoms, with the axial chirality of the binaphthyl skeleton providing chiral induction; (R,R)-N,N-bis(3,5-di-tert-butylsalicylaldehyde)cyclohexanediamine, containing two imine groups and two phenolic hydroxyl groups, which can form a tetradentate coordination structure. All of the above ligands have a C2 symmetric structure, which can effectively distinguish the two enantiomers of the substrate molecule in asymmetric catalysis.

[0068] Reference Figure 6 The preparation method of the catalyst of the present invention includes the following four main steps: S1 precursor alloy preparation, S2 gradient alkaline leaching activation, S3 chiral ligand modification and S4 passivation protection.

[0069] Step S1 involves the preparation of the precursor alloy. In this step, nickel salt, aluminum salt, and rare earth salt are dissolved in water in a molar ratio to prepare a mixed salt solution. Sodium borohydride reducing agent is added dropwise to the mixed salt solution under ice bath conditions. The resulting alloy particles undergo a first quenching in a cooling medium at -30°C to -60°C. After collection, a second quenching is performed in a cooling medium at -150°C to -196°C for 10 to 60 minutes. The particles are then transferred under an inert atmosphere and vacuum dried to obtain the amorphous alloy precursor. This step utilizes a dual amorphization strategy combining chemical reduction and rapid cooling to prepare the alloy precursor. The chemical reduction method, carried out in the liquid phase, achieves uniform mixing of metal ions at the atomic scale, while the dual quenching suppresses the formation and growth of crystal nuclei in the alloy through an extremely rapid cooling rate, thereby obtaining an amorphous structure.

[0070] Step S1 can be further subdivided into the following sub-steps. Step S11 is the preparation of a mixed salt solution. Weigh out nickel nitrate hexahydrate Ni(NO3)2·6H2O, aluminum nitrate nonahydrate Al(NO3)3·9H2O, lanthanum nitrate hexahydrate La(NO3)3·6H2O, or cerium nitrate hexahydrate Ce(NO3)3·6H2O, and dissolve them in deionized water at a molar ratio n(Ni):n(Al):n(RE)=(45-55):(25-35):(1.5-3) to prepare a mixed salt solution with a total metal ion concentration of 0.3 to 0.5 mol / L and a solution volume of 50 to 200 mL. In the formula, n(Ni) is the amount of nickel (mol); n(Al) is the amount of aluminum (mol); and n(RE) is the amount of rare earth element (mol). Nitrate is used as the metal source because nitrate ions do not introduce impurity elements during the reduction reaction, and nitrate has good salt solubility, making it easy to prepare a homogeneous mixed solution. The choice of solution concentration takes into account the uniformity of the reduction reaction and the product yield. Too high a concentration will lead to excessive local concentration of metal ions, resulting in uneven reduction products, while too low a concentration will reduce production efficiency.

[0071] Step S12 is the reduction reaction. An aqueous solution of sodium borohydride (NaBH4) with a concentration of 1.2 to 1.8 mol / L is prepared. The molar amount of NaBH4 is 1.2 to 2.0 times the total molar amount of the mixed metal ions. The mixed salt solution is placed in a three-necked flask and cooled to 0 to 5°C in an ice-water bath. Mechanical stirring is started at 500 to 800 rpm. Under stirring conditions, the NaBH4 solution is added dropwise to the mixed salt solution at a rate of 5 to 10 mL / min. During the addition, a black precipitate forms accompanied by numerous bubbles. This step reduces the metal ions to alloy particles. Sodium borohydride is a strong reducing agent that can reduce nickel and aluminum ions to their metallic state in aqueous solution. Simultaneously, the boron element produced by the decomposition of sodium borohydride enters the alloy structure as an amorphous forming element. The ice-bath condition is used to control the reduction reaction rate and avoid an overly vigorous reaction that could lead to uneven product particle size or localized overheating, thus preventing the formation of a crystalline structure. The design of using an excess of reducing agent ensures complete reduction of metal ions while guaranteeing sufficient boron to enter the alloy and maintain its amorphous structure. Mechanical stirring ensures full contact between the metal ions and the reducing agent, improving reaction uniformity.

[0072] Step S13 is the first quenching. Prepare a beaker containing 100 to 300 mL of anhydrous ethanol or isopropanol. Place the beaker in a dry ice-acetone bath or a cryogenic constant temperature bath to lower the temperature of the alcohol solution to -30°C to -60°C. Immediately after the reduction reaction is complete, pour the reaction mixture into the cooled alcohol solution to rapidly cool the alloy particles within 2 to 5 seconds. This step achieves the initial amorphization of the alloy. Quenching refers to the process of rapidly immersing a high-temperature object in a low-temperature medium to achieve rapid cooling. Rapid cooling can inhibit the diffusion of atoms to their equilibrium positions, thereby maintaining the disordered arrangement structure at high temperatures. Using a low-temperature alcohol solution as the first quenching medium can achieve rapid cooling, and the alcohol is miscible with the water phase in the reaction system, facilitating the separation and collection of the products.

[0073] Step S14 is the second quenching. Alloy particles are rapidly collected using vacuum filtration or centrifugation at 3000-5000 rpm for 5-10 minutes. The particles are washed 1-2 times with a small amount of anhydrous ethanol pre-cooled to below -30°C. Under an inert atmosphere, the alloy particles are rapidly transferred to liquid nitrogen at -196°C, or to other cooling media at -150°C to -196°C, and immersed for 10-60 minutes. This step, through two-stage quenching, inhibits alloy nucleus growth and further stabilizes the amorphous structure. Using liquid nitrogen for the second quenching lowers the alloy temperature to extremely low levels, completely suppressing atomic diffusion and eliminating any residual crystallization tendency. The two-stage quenching design yields a more stable amorphous structure than single-stage quenching.

[0074] Step S15 involves vacuum drying. Under an inert atmosphere, the quenched alloy particles are removed from the cooling medium and placed in a vacuum drying oven. Drying is carried out at 50-60°C and a vacuum of less than or equal to 10 Pa for 10-14 hours to obtain a black powdery amorphous alloy precursor. This precursor is then sealed and stored under nitrogen or argon protection. Vacuum drying removes adsorbed solvents and moisture from the alloy surface at a lower temperature, avoiding crystallization of the amorphous structure caused by high-temperature drying. An inert atmosphere is used because amorphous alloys have high surface activity and are prone to oxidation when exposed to air.

[0075] Step S2 is gradient alkaline leaching activation. The amorphous alloy precursor is first added to an alkaline solution with a concentration of 0.5 to 1.0 mol / L and immersed at 15 to 30°C for 2 to 4 hours for the first alkaline leaching. Then, the solid is transferred to an alkaline solution with a concentration of 2.0 to 3.0 mol / L and immersed at 40 to 60°C for 4 to 6 hours for the second alkaline leaching. By adjusting the concentration, temperature, and time of the two leachings, the average pore size of the catalyst is controlled within the range of 8 to 15 nm. The catalyst is then washed with deionized water until the pH reaches 7 to 8, and vacuum dried to obtain the porous activated catalyst. Alkaline leaching activation utilizes the reaction between the hydroxide solution and the aluminum in the alloy; after the aluminum is dissolved and removed, a porous structure remains in the catalyst. This invention employs a gradient alkaline leaching method, which involves two steps with different concentrations of alkaline leaching. The first step uses a lower concentration alkaline solution at a lower temperature to slowly dissolve some aluminum, forming a preliminary microporous structure. Simultaneously, the milder conditions effectively protect rare earth elements from excessive leaching. The second step uses a higher concentration alkaline solution at a higher temperature to continue dissolving aluminum, expanding the pore size and forming a well-developed mesoporous structure. Compared to traditional one-step high-concentration alkaline leaching, gradient alkaline leaching avoids the collapse of the alloy structure due to rapid aluminum leaching, while simultaneously achieving a higher retention rate of rare earth elements.

[0076] Step S2 can be further subdivided into the following sub-steps. Step S21 is the first alkaline leaching. Weigh 2 to 10 g of the amorphous alloy precursor prepared in step S1 and add it to a sodium hydroxide (NaOH) or potassium hydroxide (KOH) alkaline solution with a concentration of 0.5 to 1.0 mol / L. The liquid-to-solid ratio is 10 to 20 mL / g. Stir magnetically at 15 to 30 °C for 2 to 4 hours at a stirring speed of 200 to 400 rpm. This step slowly removes some aluminum elements, forming a preliminary porous structure, while ensuring a high retention rate of rare earth elements. The liquid-to-solid ratio refers to the ratio of liquid volume to solid mass. A suitable liquid-to-solid ratio ensures that the solid is fully dispersed in the liquid, allowing the reaction to proceed uniformly.

[0077] Step S22 is the second alkaline leaching. The solid from the first alkaline leaching is separated by centrifugation or filtration, and quickly rinsed 1 to 2 times with deionized water. The rinsed solid is then transferred to a sodium hydroxide or potassium hydroxide alkaline solution with a concentration of 2.0 to 3.0 mol / L, with a liquid-to-solid ratio of 15 to 25 mL / g. The solution is stirred at 40 to 60°C for 4 to 6 hours. This step continues to remove aluminum, expand the pore size, and form a sponge-like porous structure. The second alkaline leaching uses a higher alkali concentration and temperature to accelerate the aluminum dissolution rate. However, since the catalyst has already formed a preliminary pore framework after the first alkaline leaching, the structure will not collapse due to excessively vigorous reaction.

[0078] Step S23 involves washing and drying. After the second alkaline leaching, the solid is repeatedly washed with deionized water, centrifuged after each wash, and the washing is repeated 5 to 8 times until the pH of the supernatant drops to 7 to 8. The washed solid is then placed in a vacuum drying oven and dried for 8 to 12 hours at 50 to 60°C and a vacuum degree less than or equal to 10 Pa to obtain a gray-black porous activated catalyst. Thorough washing removes residual alkali and dissolved products, preventing them from interfering with the coordination of ligands and metal centers in subsequent ligand modification steps.

[0079] Step S3 involves chiral ligand modification. The porous activated catalyst is dispersed in an anhydrous organic solvent, and an organic solvent solution of chiral ligands is added. The amount of chiral ligands is 0.5% to 3% of the catalyst mass. The mixture is refluxed at 80 to 100°C for 6 to 12 hours under an inert atmosphere. During reflux, an inert gas stream containing a basic organic amine is introduced to promote coordination between the ligands and the metal center. After cooling, the mixture is filtered, washed, and vacuum dried to obtain the ligand-modified catalyst. Chiral ligand modification is a key step in achieving asymmetric catalytic function in the catalyst of this invention. The chiral ligands, through their phosphorus or nitrogen atoms, coordinate with the nickel active center on the catalyst surface. Simultaneously, rare earth elements, acting as Lewis acids, can form auxiliary coordination with another coordinating group in the ligand, forming a stable nickel-ligand-rare earth bridging structure. The introduction of a basic organic amine neutralizes any acidic sites that may exist on the catalyst surface, adjusting the alkalinity of the surface microenvironment and promoting the coordination reaction of the ligands.

[0080] Step S3 can be further subdivided into the following sub-steps. Step S31 is catalyst dispersion. Weigh 1 to 5 g of the porous activated catalyst prepared in step S2 and add it to 30 to 100 mL of anhydrous toluene, anhydrous tetrahydrofuran, or anhydrous dichloromethane. Disperse the catalyst ultrasonically for 10 to 20 min to ensure uniform dispersion in the solvent. Anhydrous solvent is used because the coordination reaction needs to be carried out under anhydrous conditions to avoid competition for coordination with water molecules. Ultrasonic dispersion can break up catalyst particle aggregates and increase the surface area accessible to ligands.

[0081] Step S32 involves preparing the ligand solution. The chiral ligand is weighed, and the amount is calculated using the following formula: In the formula, Ligand mass (g); The mass of the catalyst is (g). The ligand mass fraction, ranging from 0.005 to 0.03; preferably... The corresponding ligand dosage is 1%-2% of the catalyst mass; the ligand is dissolved in 10-30 mL of the same anhydrous organic solvent as in step S31 to prepare a solution with a ligand concentration of 2-10 mg / mL; the ligand dosage needs to be optimized. If the dosage is too small, the density of chiral active sites will be insufficient, affecting the enantiomeric excess value of the product; if the dosage is too large, the ligand will be excessively accumulated on the catalyst surface, which may cover part of the active sites and reduce the catalytic activity.

[0082] Step S33 involves ligand impregnation. The ligand solution prepared in step S32 is added to the catalyst suspension from step S31, and the mixture is stirred at room temperature for 0.5 to 1 hour to ensure the ligands fully wet the catalyst surface. Room temperature impregnation allows ligand molecules to diffuse into the pores of the catalyst and adsorb onto the surface, preparing for subsequent coordination reactions.

[0083] Step S34 is reflux coordination. The mixture from step S33 is transferred to a three-necked flask equipped with a reflux condenser and a gas protection device. Argon or nitrogen is introduced to establish an inert atmosphere at a flow rate of 50 to 100 mL / min. The mixture is heated to the solvent reflux temperature and maintained under reflux for 6 to 12 hours. The reflux temperature for toluene is 110°C, for tetrahydrofuran it is 66°C, and for dichloromethane it is 40°C. Reflux refers to the operation method where the vapor of the liquid boils and is cooled and refluxed back to the reaction vessel through a condenser. This method allows for prolonged heating at the solvent boiling point without solvent loss. Higher temperatures provide the activation energy required for the coordination reaction, accelerating the rate at which ligands form coordination bonds with the metal center.

[0084] Step S35 involves gas-phase enhanced coordination. During the reflux process, from the 2nd to the 8th hour, an inert gas stream containing a basic organic amine is introduced into the reaction system. The basic organic amine is selected from triethylamine, pyridine, or diisopropylethylamine. The organic amine vapor is introduced into the reflux system via an argon or nitrogen carrier gas, with the carrier gas flow rate controlled at 80 to 120 mL / min and the organic amine vapor introduction rate controlled at 5 to 15 mL / h. The basic organic amine neutralizes acidic sites and protons on the catalyst surface, creating a favorable alkaline microenvironment for ligand coordination. Simultaneously, the hydrogen bonding between the organic amine and the ligand helps the ligand maintain a suitable conformation for coordination. Introducing the organic amine in the gas phase ensures a continuous and stable supply, avoiding waste or product contamination caused by adding excessive amounts of organic amine at once.

[0085] Step S36 is the post-treatment. After reflux, heating is stopped, and the mixture is cooled to room temperature under argon or nitrogen protection. The solid is separated by centrifugation or vacuum filtration at 3000-5000 rpm for 10 min. The solid is washed 3-5 times with anhydrous toluene or ethanol, 20-30 mL each time, to remove uncoordinated free ligands. The washed solid is then dried in a vacuum drying oven at 50-60°C and a vacuum of less than or equal to 10 Pa for 8-12 h to obtain a dark brown ligand-modified catalyst. The purpose of the washing step is to remove free ligands that have not formed coordination bonds with the metal centers on the catalyst surface, preventing free ligands from being lost into the reaction system during the catalytic reaction and causing product contamination or interference with the reaction process.

[0086] Step S4 is passivation protection. The ligand-modified catalyst is placed in an inert atmosphere, and an oxygen / inert gas mixture with an oxygen content of 0.5 to 2 vol% is introduced. The mixture is treated at room temperature for 2 to 4 hours, forming a thin oxide protective layer on the catalyst surface, resulting in a rare-earth-chiral ligand synergistic modified amorphous aluminum-nickel catalyst. Due to their high surface activity and numerous unsaturated coordination sites, amorphous alloys are highly susceptible to severe oxidation and even spontaneous combustion in air. Passivation treatment involves forming an extremely thin oxide protective film on the catalyst surface through controlled micro-oxidation. This protective film prevents further contact and reaction between the catalyst and oxygen in the air, thus achieving stable storage and safe operation of the catalyst in air. Using a low concentration of oxygen allows for control of the oxidation rate, avoiding excessively exothermic oxidation that could damage the catalyst structure or cause ligand decomposition.

[0087] Step S4 can be further subdivided into the following sub-steps. Step S41 involves preparing the passivation gas by preparing an oxygen / nitrogen mixture or an oxygen / argon mixture with an oxygen volume fraction of 0.5% to 2%. The flow rate of each gas is precisely controlled using a gas mass flow meter. Preferably, the oxygen volume fraction is 1%, and the mixture is mixed using a volume flow ratio of V(O2):V(N2) = 1:99, where V(O2) is the oxygen volume flow rate and V(N2) is the nitrogen volume flow rate. The total flow rate is set to 100 to 200 mL / min, preferably 150 mL / min.

[0088] Step S42 is the passivation treatment. The ligand-modified catalyst prepared in step S3 is spread into a thin layer with a thickness of 5 mm or less and placed in a passivation device. First, pure nitrogen or pure argon gas is purged for 10 to 15 minutes to remove air from the system. Then, a mixed gas is switched, and the gas is purged at room temperature (20 to 30°C) for 2 to 4 hours, preferably 3 hours, to form a thin oxide protective layer on the catalyst surface. Spreading the catalyst into a thin layer ensures that each catalyst particle is uniformly in contact with the passivation gas, avoiding incomplete passivation of the inner catalyst layer due to excessive accumulation. Purging with an inert gas first removes air from the system, preventing the catalyst from coming into contact with the 21% oxygen concentration in the air during the initial passivation stage and causing severe oxidation.

[0089] Step S43 involves packaging and storage. After passivation, the catalyst is transferred to a sealed bottle under nitrogen or argon protection, filled with argon, and then sealed for storage. Although the passivated catalyst can be exposed to air for short periods for weighing, feeding, and other operations, long-term storage still requires an inert atmosphere to maintain the catalyst's activity.

[0090] The catalyst of this invention can be applied to the asymmetric hydrogenation reaction of unsaturated compounds. The applicable unsaturated compounds are selected from at least one of α,β-unsaturated ketones, aromatic ketones, imines, or unsaturated carboxylic acid esters. Asymmetric hydrogenation refers to a reaction in which hydrogen gas selectively attacks a specific enantiomer of the substrate molecule under the action of a chiral catalyst, thereby preferentially generating a chiral product with that configuration. This reaction is an important method for synthesizing chiral compounds and has significant application value in the fields of pharmaceuticals, pesticides, fragrances, and other fine chemicals.

[0091] The chemical structure of α,β-unsaturated ketones is R. 1 -CO-CH=CH-R 2 In the formula R 1 and R 2 Aromatic ketones are independently selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, or aryl groups having 6 to 12 carbon atoms. Alkyl groups refer to saturated hydrocarbon groups, and aryl groups refer to hydrocarbon groups containing a benzene ring structure. Specific α,β-unsaturated ketones include styrylmethyl ketones (C6H5-CH=CH-CO-CH3), styrylphenyl ketones (C6H5-CH=CH-CO-C6H5), and 4-phenyl-3-buten-2-one. The chemical structure of aromatic ketones is Ar-CO-R. 3 In the formula, Ar is aryl, and R is... 3 It is an alkyl group with 1 to 8 carbon atoms. Specific aromatic ketones include acetophenone (C6H5-CO-CH3), phenylacetone (C6H5-CO-CH2-CH3), and 1-naphthyl acetophenone (C6H5-CO-CH2-CH3). 10 H7-CO-CH3 and 4-methoxyacetophenone.

[0092] The reaction conditions are as follows: reaction temperature 60–80 °C, hydrogen pressure 2–4 MPa, substrate to catalyst molar ratio 200:1–500:1, solvent selected from alcohols, aromatics, or ethers, and reaction time 4–8 h. Alcohol solvents include methanol, ethanol, and isopropanol; aromatic solvents include toluene; and ether solvents include tetrahydrofuran. The choice of reaction temperature needs to balance catalytic activity and enantioselectivity. Too low a temperature results in a slow reaction rate and low conversion, while too high a temperature reduces the control of the chiral ligand's selectivity over the substrate surface, leading to a decrease in enantioselectivity. Hydrogen pressure affects the solubility and adsorption of hydrogen on the solvent and catalyst surfaces; appropriate pressure ensures sufficient hydrogen supply without causing side reactions due to hydrogen excess. The substrate to catalyst molar ratio, i.e., the molar excess multiple of the substrate relative to the active metal of the catalyst, affects the reaction rate and catalyst utilization efficiency.

[0093] The catalyst of this invention can achieve a conversion rate of greater than or equal to 95% for asymmetric hydrogenation under the above reaction conditions, and an enantiomeric excess value (ee) of greater than or equal to 88% for the product. Conversion rate refers to the percentage of reacted substrate relative to the total initial substrate. The enantiomeric excess value (ee) is a parameter characterizing the difference in the proportion of two enantiomers in the chiral product, defined as ee = (RS) / (R+S)×100% or ee = (SR) / (R+S)×100%, where R and S represent the mole fraction or peak area percentage of the two enantiomers, respectively. A higher ee value indicates higher enantiomeric purity of the product.

[0094] The catalyst of this invention can be reused at least 8 times without significant decrease in activity and selectivity. The method for reusing the catalyst is as follows: recover the catalyst by filtration or centrifugation at 3000 to 5000 rpm for 10 minutes; wash the catalyst 2 to 3 times with the solvent used in the reaction, 10 to 20 mL each time; dry the washed catalyst in a vacuum drying oven at 50 to 60°C for 4 to 6 hours; the dried catalyst can be directly used in the next reaction without further passivation. The reusability of the catalyst is an important indicator of its practical value. The excellent cycle stability of the catalyst of this invention is due to the stabilizing effect of rare earth elements on the amorphous structure and the stable bridging coordination structure between the chiral ligand and the bimetallic center.

[0095] The reaction is carried out in a high-pressure reactor. The specific steps include: adding 1 to 20 g of substrate, 3% to 10% of the substrate mass of catalyst, and 10 to 100 mL of solvent to a 50 to 500 mL high-pressure reactor; sealing the reactor; purging the air three times with nitrogen; then introducing hydrogen gas at a pressure of 2 to 4 MPa; heating to a set temperature of 60 to 80 °C; starting stirring at 300 to 600 rpm; reacting for 4 to 8 hours; cooling to room temperature after the reaction; slowly releasing the pressure; filtering or centrifuging to separate the catalyst; and concentrating and purifying the filtrate to obtain the chiral product. The purpose of purging the air with nitrogen before the reaction is to remove oxygen from the reactor, preventing oxygen from oxidizing the substrate or deactivating the catalyst under high temperature and pressure.

[0096] Example 1: In this example, an amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands was prepared and applied to the asymmetric hydrogenation reaction of acetophenone. The specific steps are as follows:

[0097] Step S1 is the preparation of the precursor alloy. Step S11 is the preparation of the mixed salt solution, weighing out nickel nitrate hexahydrate. 7.27g, aluminum nitrate nonahydrate 5.63g, Lanthanum nitrate hexahydrate 0.43g, molar ratio Dissolve in 100 mL of deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.4 mol / L. Step S12 is a reduction reaction, preparing a 1.5 mol / L sodium borohydride solution. 40 mL of aqueous solution The molar amount of the mixed salt solution was 1.5 times the total molar amount of the mixed metal ions. The solution was placed in a 500 mL three-necked flask and cooled to 3°C in an ice-water bath. Mechanical stirring was started at 600 rpm, and the solution was stirred at a rate of 8 mL / min. The solution was added dropwise to the mixed salt solution. Step S13 was the first quenching. A beaker containing 200 mL of anhydrous ethanol was prepared and placed in a dry ice-acetone bath to lower the temperature of the alcohol solution to -50°C. After the reduction reaction was completed, the reaction mixture was immediately poured into the cooled alcohol solution. Step S14 was the second quenching. The alloy particles were rapidly collected by centrifugation at 4000 rpm for 8 min. They were washed twice with anhydrous ethanol pre-cooled to -40°C and then transferred to liquid nitrogen for immersion for 30 min under argon protection. Step S15 was vacuum drying. The quenched alloy particles were removed under argon protection and placed in a vacuum drying oven at 55°C and a vacuum of 8 Pa for 12 h to obtain the amorphous alloy precursor.

[0098] Step S2 is gradient alkaline leaching activation. Step S21 is the first alkaline leaching, where 5g of amorphous alloy precursor is weighed and added to a solution with a concentration of 0.8mol / L. In the solution, the liquid-to-solid ratio was 15 mL / g, and the mixture was magnetically stirred at 25°C for 3 hours at a stirring speed of 300 rpm. Step S22 was the second alkaline leaching, in which the solid was separated by centrifugation, rinsed once with deionized water, and transferred to a 2.5 mol / L solution. In the solution, the liquid-to-solid ratio was 20 mL / g, and the mixture was stirred at 50 °C for 5 h. Step S23 was washing and drying. The solid was washed repeatedly with deionized water 6 times until the pH of the supernatant dropped to 7.5. The solid was then dried at 55 °C and a vacuum of 8 Pa for 10 h to obtain a porous activated catalyst.

[0099] Step S3 is chiral ligand modification. Step S31 is catalyst dispersion: 2g of porous activated catalyst is weighed and added to 50mL of anhydrous toluene, and ultrasonically dispersed for 15min. Step S32 is ligand solution preparation: 0.03g of (R,R)-1,2-diphenylethylenediamine is weighed and dissolved in 20mL of anhydrous toluene. Step S33 is ligand impregnation: the ligand solution is added to the catalyst suspension and stirred at room temperature for 0.5h. Step S34 is reflux coordination: the mixture is transferred to a three-necked flask, argon gas is introduced at a flow rate of 80mL / min, and the mixture is heated to 110℃ and refluxed for 8h. Step S35 is gas-phase enhanced coordination: triethylamine vapor is introduced from reflux 3 to 7h at a carrier gas flow rate of 100mL / min and a triethylamine introduction rate of 10mL / h. Step S36 is post-treatment: after cooling, the mixture is centrifuged, washed 4 times with anhydrous toluene, and dried under vacuum at 55℃ for 10h.

[0100] Step S4 is passivation protection. Step S41 is passivation gas preparation, with a volumetric flow rate ratio of... The mixed gas was used at a total flow rate of 150 mL / min. Step S42 was passivation treatment, in which the catalyst was spread into a thin layer with a thickness of 3 mm, first purged with pure nitrogen for 12 min, and then the mixed gas was used to purge at 25 °C for 3 h. Step S43 was packaging and storage, in which the catalyst was transferred to a sealed bottle for storage under argon protection.

[0101] ICP-OES elemental analysis revealed the following catalyst composition: 50.2%, 19.8%, 11.5% 5.1% and 1.5% ligands. XRD characterization showed that the catalyst... The surface exhibits broadened diffraction peaks within the range, with a full width at half maximum (FWHM) of 4.2°. BET analysis indicates a specific surface area of ​​98 m². 2 / g, with an average pore size of 11nm.

[0102] The above catalyst was applied to the asymmetric hydrogenation reaction of acetophenone. 5 g of acetophenone, 0.3 g of catalyst, and 30 mL of isopropanol were added to a 100 mL high-pressure reactor. After sealing, the reactor was purged with nitrogen three times, and hydrogen was introduced to a pressure of 3 MPa. The reactor was heated to 70 °C, stirred at 500 rpm, and reacted for 6 h. After the reaction was completed, the reactor was cooled, depressurized, and filtered to separate the catalyst. Gas chromatography analysis of the filtrate showed a conversion rate of 96.5%. Chiral gas chromatography analysis showed that the ee value of the product (R)-1-phenylethanol was 90.2%.

[0103] Example 2, the difference between this example and Example 1 is that the rare earth element used is cerium ( ) replace lanthanum ( Weigh out 7.27 g of nickel nitrate hexahydrate, 5.63 g of aluminum nitrate nonahydrate, and cerium nitrate hexahydrate. 0.43 g of a mixed salt solution was prepared at the same molar ratio, and other preparation steps and parameters were the same as in Example 1. The resulting catalyst composition was as follows: 49.8%, 20.1% 11.3%, 5.3% for the component and 1.5% for the ligand. Applied to the hydrogenation reaction of acetophenone, the conversion rate was 95.8%, and the ee value was 88.5%.

[0104] Example 3 differs from Example 1 in that the chiral ligand used is (R)-2,2-bis(diphenylphosphine)-1,1-binaphthylene instead of (R,R)-DPEN. In step S32, 0.03 g of (R)-BINAP was weighed and dissolved in anhydrous toluene. Other preparation steps and parameters were the same as in Example 1. The ligand content in the obtained catalyst was 1.5%. When applied to the hydrogenation reaction of acetophenone, the conversion rate was 95.2%, and the ee value was 86.8%.

[0105] Example 4, in step S11 of this example, the molar ratio Prepare a mixed salt solution, with the ligand amount in step S32 being 0.5% of the catalyst mass. Other preparation steps are the same as in Example 1. The resulting catalyst composition is as follows: 40.5% 15.2% 8.3%, 3.2% amine and 0.5% ligand. Applied to the hydrogenation reaction of acetophenone, with a conversion rate of 91.2% and an ee value of 82.5%.

[0106] Example 5, in step S11 of this example, the molar ratio Prepare a mixed salt solution, with the ligand amount in step S32 being 3% of the catalyst mass. Other preparation steps are the same as in Example 1. The resulting catalyst composition is as follows: 59.2%, 29.5% 14.8%, 7.8% and 3% ligand. Applied to the hydrogenation reaction of acetophenone, with a conversion rate of 93.5% and an ee value of 84.2%.

[0107] Comparative Example 1: This comparative example prepared a catalyst without rare earth elements. In step S11, only nickel nitrate hexahydrate and aluminum nitrate nonahydrate were weighed out in molar ratio. A mixed salt solution was prepared without adding rare earth salts. Other preparation steps and parameters were the same as in Example 1. The resulting catalyst composition was as follows: 55.3%, 22.1%, 12.8% catalyst and 1.5% ligand. Applied to the hydrogenation reaction of acetophenone, the conversion rate was 92.1% and the ee value was 72.5%. After the catalyst was recycled 5 times, the conversion rate dropped to 68.3% and the ee value dropped to 58.2%.

[0108] Comparative Example 2: This comparative example prepared a catalyst without chiral ligands. Chiral ligand modification in step S3 was omitted during the preparation process; after step S2, passivation protection in step S4 was performed directly. Other preparation steps and parameters were the same as in Example 1. The resulting catalyst composition was as follows: 51.0%, 20.2% 11.8%, 5.2%. Applied to the hydrogenation reaction of acetophenone, the conversion rate was 94.5%, and the ee value was 3.2%.

[0109] Comparative Example 3: This comparative example prepared a catalyst that underwent only a single quenching. In step S1, after the first quenching in step S13, the second liquid nitrogen quenching in step S14 was skipped, and the process proceeded directly to step S15, vacuum drying. Other preparation steps and parameters were the same as in Example 1. The obtained catalyst was characterized by XRD. Appear at place The crystal phase diffraction peak has a full width at half maximum (FWHM) of 1.5°. Applied to the hydrogenation reaction of acetophenone, it achieved a conversion rate of 88.2% and an ee value of 78.5%.

[0110] Comparative Example 4: This comparative example prepared a catalyst through a one-step alkaline leaching process. In step S2, instead of gradient alkaline leaching, the amorphous alloy precursor was directly added to a solution with a concentration of 4.0 mol / L. The catalyst was further leached with alkali in the solution at 60°C for 6 hours. Other preparation steps and parameters were the same as in Example 1. The resulting catalyst had a specific surface area of ​​125 m². 2 / g, with an average pore size of 28nm. ICP analysis showed that the rare earth element retention rate was only 52% in the catalyst. The content is 2.7%. It is used in the hydrogenation reaction of acetophenone, with a conversion rate of 90.5% and an ee value of 75.8%.

[0111] Comparative Experiment 1: XRD Structure Characterization of Catalysts; Phase analysis of the catalysts prepared in Example 1 and Comparative Example 3 was performed using X-ray diffraction. The test conditions were CuKα rays, and the scanning range was [missing information]. The scanning speed was 5° / min. Tests were performed according to the general rules of X-ray diffraction phase analysis for polycrystalline materials (GB / T30904-2014). The diffraction peak positions and full width at half maximum (FWHM) data were read from the XRD patterns, and the results are shown in Table 1.

[0112] Table 1: Comparison of X-ray diffraction (XRD) structural characterization data of different catalysts

[0113]

[0114] Comparative Experiment 2: Characterization of Catalyst Pore Structure; The specific surface area and pore size of the catalysts prepared in Examples 1, 4, 5, and Comparative Example 4 were analyzed using nitrogen adsorption-desorption. Before testing, the samples were degassed under vacuum at 150℃ for 6 h. The specific surface area of ​​the solid material was determined according to the BET method for gas adsorption (GB / T19587-2017). The specific surface area was calculated using the BET multi-point method, and the pore size distribution was calculated using the BJH method. The results are shown in Table 2.

[0115] Table 2: Comparison of pore structure parameters (specific surface area, average pore diameter, pore volume) of different catalysts

[0116]

[0117] Comparative Experiment 3: Analysis of Catalyst Elemental Composition and Rare Earth Retention Rate; Elemental content analysis of each catalyst was performed using inductively coupled plasma atomic emission spectrometry (ICP-OES) according to the general rules of GB / T15337-2008 Atomic Absorption Spectrometry. Rare earth retention rate was determined theoretically based on the formula. Calculation, actual measurement in the formula The mass of rare earth elements in the catalyst after alkaline leaching activation is theoretically... The value represents the mass of rare earth elements at the time of feeding. The results are shown in Table 3.

[0118] Table 3: Elemental composition and rare earth retention rate analysis results of different catalysts

[0119]

[0120] Comparative Experiment 4: Catalytic Performance Evaluation; The performance of each catalyst in the asymmetric hydrogenation reaction of acetophenone was evaluated using a high-pressure reactor. Substrate conversion was determined by gas chromatography with internal standard method, according to GB / T9722-2006 General Rules for Gas Chromatography of Chemical Reagents. The enantiomeric excess value (ee) of the product was determined by gas chromatography equipped with a chiral column (Chirasil-DEXCB), column temperature 100℃, carrier gas flow rate 1.0 mL / min. The results are shown in Table 4.

[0121] Table 4: Comparison of catalytic performance of different catalysts in the asymmetric hydrogenation reaction of acetophenone

[0122] sample Conversion rate (%) ee value (%) <![CDATA[TOF(h -1 )]]> Example 1 96.5 90.2 215 Example 2 95.8 88.5 205 Example 3 95.2 86.8 198 Example 4 91.2 82.5 168 Example 5 93.5 84.2 182 Comparative Example 1 92.1 72.5 185 Comparative Example 2 94.5 3.2 195 Comparative Example 3 88.2 78.5 155 Comparative Example 4 90.5 75.8 172

[0123] Comparative Experiment 5: Catalyst Cyclic Stability Test; The catalysts prepared in Example 1 and Comparative Example 1 were subjected to 8 cycles of use. After each reaction, the catalyst was recovered by centrifugation, washed twice with isopropanol, and dried under vacuum at 55°C for 4 hours before being used in the next reaction. The conversion rate and ee value after each cycle were measured, and the results are shown in Table 5.

[0124] Table 5: Stability test results of catalyst recycling in Example 1 and Comparative Example 1

[0125]

[0126] Experimental Example 1: XRD Structure Characterization Experiment; This experimental example uses the methods of Example 1 and Comparative Example 3 to prepare the catalyst and performs X-ray diffraction characterization. The experimental method involves uniformly spreading the catalyst powder on the XRD sample stage and using a Rigaku SmartLab X-ray diffractometer (Japan). The CuKα ray wavelength is 0.15418 nm, the tube voltage is 40 kV, the tube current is 40 mA, and the scanning range is [not specified in the original text]. The step size is 0.02°, and the scanning speed is 5° / min.

[0127] Experimental results are as follows Figure 1 As shown. Figure 1 This is a comparison of the XRD patterns of the catalysts in Example 1 and Comparative Example 3. Figure 1 (a) is the XRD pattern of the catalyst in Example 1. Figure 1 (b) shows the XRD pattern of the catalyst in Comparative Example 3. Figure 1 It can be seen that the catalyst in Example 1... A broadened diffuse peak with a full width at half maximum (FWHM) of 4.2° is observed nearby, without any sharp crystalline diffraction peaks, indicating that the catalyst has a typical amorphous structure. Comparative Example 3 catalyst exhibits a sharper diffraction peak at the same position, with a FWHM of only 1.5°, and... Metal appears at 51.8°. The characteristic diffraction peaks indicate that the catalyst has undergone partial crystallization. These results demonstrate that the dual quenching process employed in this invention can effectively suppress the formation and growth of alloy crystal nuclei. The first quenching achieves preliminary amorphization, while the second liquid nitrogen quenching further eliminates any residual crystallization tendency. The amorphous structure endows the catalyst with numerous unsaturated coordination sites and a uniform surface structure, which is beneficial for the uniform distribution of chiral ligands and the selective adsorption of substrates.

[0128] Experimental Example 2: Characterization of Pore Structure and Rare Earth Retention Rate; In this experimental example, the catalyst was prepared using the methods of Examples 1, 4, 5, and Comparative Example 4, and characterized by nitrogen adsorption-desorption and elemental analysis. Nitrogen adsorption-desorption testing was performed using a Micron ASAP2460 surface area and pore size analyzer (USA), with samples tested after vacuum degassing at 150℃ for 6 hours. Elemental analysis was performed using an Agilent 5110 ICP-OES (USA), with samples dissolved in aqua regia and diluted before determination.

[0129] Experimental results are as follows Figure 2 As shown. Figure 2 The figures show the N2 adsorption-desorption isotherms and pore size distribution of the catalysts in Example 1 and Comparative Example 4. Figure 2 (a) is the N2 adsorption-desorption isotherm. Figure 2 (b) shows the BJH aperture distribution curve. Figure 2 (a) It can be seen that the adsorption-desorption isotherm of the catalyst in Example 1 is type IV, with a significant H3-type hysteresis loop, indicating that the catalyst has a mesoporous structure. From Figure 2 (b) It can be seen that the pore size distribution of the catalyst in Example 1 is concentrated in the range of 8-15 nm, with an average pore size of 11 nm; the pore size distribution of the catalyst in Comparative Example 4 is wider, with an average pore size of 28 nm.

[0130] Table 3 shows that Example 1, using gradient alkaline leaching, achieved a rare earth element retention rate of 92%, while Comparative Example 4, using a one-step high-concentration alkaline leaching, only achieved a retention rate of 52%. The gradient alkaline leaching process of this invention, through the first step of low-concentration alkaline leaching under relatively mild conditions, slowly removes aluminum and establishes a preliminary pore framework, effectively protecting rare earth elements from excessive dissolution; the second step of high-concentration alkaline leaching further expands the pores based on the preliminary framework, preventing structural collapse. The suitable pore size distribution facilitates substrate molecules entering the pores and contacting active sites, while the high rare earth element retention rate ensures the synergistic regulation of the electronic structure of the catalytic center by rare earth elements and chiral ligands.

[0131] Experiment Example 3: Catalytic Performance Evaluation Experiment; This experiment uses the methods of Examples 1-5 and Comparative Examples 1-4 to prepare the catalyst and evaluate its performance in the asymmetric hydrogenation reaction of acetophenone. The reaction was carried out in a 100mL stainless steel high-pressure reactor. 5g of acetophenone, 0.3g of catalyst, and 30mL of isopropanol were added. After sealing, the reactor was purged with nitrogen three times, and hydrogen gas was introduced to 3MPa. The reaction was carried out at 70℃ for 6 hours. The conversion rate was determined using an Agilent 7890B gas chromatograph equipped with an FID detector and an HP-5 capillary column. The ee value was determined using a similar gas chromatograph equipped with a Chirasil-DEXCB chiral column.

[0132] Experimental results are as follows Figure 3 As shown. Figure 3 This is a bar chart comparing the catalytic performance of the examples and comparative examples. Figure 3 (a) shows the conversion rate comparison. Figure 3 (b) Comparison of ee values. Figure 3 It can be seen that the conversion rates of Examples 1-5 are all greater than 91%, and the ee values ​​are all greater than 82%. Among them, Example 1 has the best performance, with a conversion rate of 96.5% and an ee value of 90.2%. The ee value of Comparative Example 1 without rare earth catalyst is only 72.5%, the ee value of Comparative Example 2 without ligand catalyst is only 3.2%, the ee value of Comparative Example 3 with single-quenching catalyst is 78.5%, and the ee value of Comparative Example 4 with one-step alkaline leaching catalyst is 75.8%. It can be seen that rare earth elements and chiral ligands are two key factors for achieving high enantioselectivity. The results of Comparative Example 2 prove that chiral ligands are the direct cause of enantioselectivity. The chiral structure in the ligand molecule determines which side the substrate molecule approaches the catalytic active center from. The results of Comparative Example 1 prove that rare earth elements can increase the ee value by about 18 percentage points. Rare earth elements, as Lewis acid centers, form a bridging coordination structure with chiral ligands, enhancing the rigidity and orientation ability of the ligands, making their selection of the chiral facet of the substrate molecule more precise.

[0133] Experiment Example 4: Cyclic Stability Test; In this experiment, the catalyst was prepared using the methods of Example 1 and Comparative Example 1, and was subjected to 8 cycles of use. The reaction conditions were the same as in Experiment Example 3 each time. After the reaction was completed, the catalyst was recovered by centrifugation, washed twice with isopropanol, and dried under vacuum at 55°C for 4 hours before being used in the next reaction.

[0134] Experimental results are as follows Figure 4 As shown. Figure 4 The graphs show the cyclic stability of the catalysts in Example 1 and Comparative Example 1. Figure 4 (a) is the curve of conversion rate as a function of the number of cycles. Figure 4 (b) shows the curve of ee value changing with the number of iterations. From Figure 4It can be seen that after 8 cycles, the conversion rate of the catalyst in Example 1 decreased from 96.5% to 94.2%, a decrease of only 2.3 percentage points, and the ee value decreased from 90.2% to 87.8%, a decrease of only 2.4 percentage points, demonstrating excellent cycle stability. The conversion rate of the catalyst in Comparative Example 1 decreased to 68.3% after 5 cycles and to 55.0% after 8 cycles, with the ee value decreasing to 48.5%. Both activity and selectivity decreased significantly, indicating that rare earth elements play an important role in the cycle stability of the catalyst. The catalyst in Comparative Example 1, which does not contain rare earth elements, showed a rapid decrease in activity after multiple cycles. This is because the amorphous structure gradually transforms into a crystalline state during the reaction, leading to a reduction in active sites and the shedding of chiral ligands. In this invention, rare earth elements have a large atomic radius. After entering the amorphous alloy, they increase the configurational entropy of the system, improve the thermodynamic stability of the amorphous structure, and inhibit the crystallization process. Simultaneously, the bridging coordination structure formed by rare earth elements and chiral ligands enhances the anchoring stability of the ligands on the catalyst surface and reduces the loss of ligands during the reaction.

[0135] Example 5: Substrate Applicability Experiment; In this example, the catalyst was prepared using the method of Example 1 and applied to asymmetric hydrogenation reactions of different types of substrates to verify the substrate applicability of the catalyst. The reaction conditions were the same as in Example 3. Specific data are shown in Table 6.

[0136] Table 6: Data on asymmetric hydrogenation reactions of different substrates using the catalyst from Example 1

[0137]

[0138] Experimental results are as follows Figure 5 As shown. Figure 5 The bar chart shows the catalytic performance of the catalyst in Example 1 for different substrates. Figure 5 (a) represents the conversion rate. Figure 5 (b) represents the ee value. From Figure 5 It can be seen that the catalyst in Example 1 exhibits good catalytic activity and enantioselectivity for both aromatic ketones and α,β-unsaturated ketones, with conversion rates greater than 93% and ee values ​​greater than 85%, indicating that the catalyst of the present invention has a wide range of applicable substrates.

[0139] Example 6: Characterization of the structural stability of the catalyst after recycling; In this example, the catalyst was prepared using the method of Example 1 and used in the asymmetric hydrogenation reaction of acetophenone. After recycling 8 times, the catalyst was recovered and characterized by XRD and BET to evaluate the effect of recycling on the catalyst structure.

[0140] Following the asymmetric hydrogenation reaction conditions of acetophenone in Example 1, the catalyst was recovered by centrifugation at 4000 rpm for 10 min after each reaction. It was washed twice with 15 mL of isopropanol each time, dried at 55°C and a vacuum of ≤10 Pa for 4 h, and then directly used for the next reaction. A total of 8 cycles were performed. The catalyst sample after the 8th cycle was subjected to X-ray diffraction (XRD) and nitrogen adsorption-desorption tests under the same conditions as in Examples 1 and 2.

[0141] The XRD pattern of the catalyst after 8 cycles is as follows: Figure 7 As shown. Compared with the fresh catalyst in Example 1, the recycled catalyst still exhibits a broadened diffraction peak near 2θ = 44°, with a full width at half maximum (FWHM) of 4.0°, and no obvious crystalline diffraction peaks are observed, indicating that the catalyst retains its amorphous structure after recycling. The specific surface area of ​​the recycled catalyst is 95 m². 2 / g, with an average pore size of 11.5nm and a pore volume of 0.26 cm³. 3 / g. Specific surface area compared to fresh catalyst: 98 m² 2 / g, average pore size 11 nm, pore volume 0.27 cm³ 3 Compared to / g, the specific surface area and pore structure parameters changed very little, with a change rate of <5%, indicating that the porous structure of the catalyst remained basically stable during the cycle.

[0142] After being cycled 8 times, the catalyst in Example 1 did not show any significant changes in its amorphous or porous structure, which is consistent with its excellent cycle stability, indicating the stabilizing effect of rare earth elements on the amorphous structure.

[0143] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands, characterized in that, The catalyst comprises the following components, by mass percentage: Nickel (Ni): 40%-60%; Aluminum (Al): 15%-30%; Boron (B): 8%-15%; Rare earth elements RE, selected from lanthanum (La), cerium (Ce), or mixtures thereof: 3%-8%; Chiral ligand L, based on the total mass of the catalyst: 0.5%-3%; The chiral ligand is selected from at least one of the following: (R,R)-1,2-diphenylethylenediamine; (S,S)-1,2-diphenylethylenediamine; (R)-2,2-bis(diphenylphosphine)-1,1-naphthyl; (S)-2,2-bis(diphenylphosphine)-1,1-naphthyl; (R,R)-N,N-bis(3,5-di-tert-butylsalicylaldehyde)cyclohexanediamine; The remainder is impurities; The catalyst has an amorphous structure, and its X-ray diffraction pattern is as follows: The diffraction peaks within the range are broadened, with a full width at half maximum (FWHM) ≥ 2°. The chiral ligand contains phosphorus (P) or nitrogen (N) coordinating atoms, which coordinate with nickel atoms on the catalyst surface, and the rare earth element is located within the coordination range of the ligand. The molar ratio of the rare earth element to the nickel element satisfies: In the formula, This refers to the amount of rare earth elements in substance. This represents the amount of substance of nickel. The catalyst is prepared by the following method: Preparation of S1 precursor alloy: Nickel salt, aluminum salt and rare earth salt are dissolved in water in molar ratio to prepare a mixed salt solution. Sodium borohydride reducing agent is added dropwise to the mixed salt solution under ice bath conditions. The alloy particles generated by the reaction are first quenched and placed in a cooling medium at a temperature of -30℃ to -60℃. After collection, they are quenched a second time in a cooling medium at a temperature of -150℃ to -196℃ for 10-60 minutes. They are then transferred under an inert atmosphere and vacuum dried to obtain an amorphous alloy precursor. S2 gradient alkaline leaching activation: The amorphous alloy precursor is first added to an alkaline solution with a concentration of 0.5-1.0 mol / L and soaked at 15-30℃ for 2-4 hours for the first alkaline leaching. Then, the solid is transferred to an alkaline solution with a concentration of 2.0-3.0 mol / L and soaked at 40-60℃ for 4-6 hours for the second alkaline leaching. By adjusting the concentration, temperature and time of the two alkaline leachings, the average pore size of the catalyst is controlled within the range of 8-15 nm. The catalyst is washed with deionized water until the pH is 7-8 and then vacuum dried to obtain a porous activated catalyst. S3 Chiral Ligand Modification: The porous activated catalyst is dispersed in an anhydrous organic solvent, and an organic solvent solution of chiral ligands is added. The amount of chiral ligands is 0.5%-3% of the catalyst mass. The mixture is heated to the solvent reflux temperature under an inert atmosphere and refluxed for 6-12 hours. The solvent is toluene, tetrahydrofuran, or dichloromethane, wherein the reflux temperature of toluene is 110°C, the reflux temperature of tetrahydrofuran is 66°C, and the reflux temperature of dichloromethane is 40°C. The mixture is kept under reflux for 6-12 hours. During the reflux process, an inert gas stream containing alkaline organic amines is introduced to promote coordination between the ligands and the metal center. After cooling, the catalyst is filtered, washed, and vacuum dried to obtain the ligand-modified catalyst. S4 Passivation Protection: The ligand-modified catalyst is placed in an inert atmosphere and a mixture of oxygen / inert gas with an oxygen content of 0.5-2 vol% is introduced. The mixture is treated at room temperature for 2-4 hours to form a thin oxide protective layer on the catalyst surface, thus obtaining an amorphous aluminum-nickel catalyst synergistically modified with rare earth-chiral ligands.

2. The catalyst according to claim 1, characterized in that: The catalyst has a specific surface area of ​​80-120 m². 2 / g, with an average pore size of 8-15nm; The catalyst comprises the following components by mass percentage: nickel 45%-55%, aluminum 18%-25%, boron 10%-13%, rare earth elements 4%-6%, and chiral ligands 1%-2%; the rare earth element is lanthanum (La). The rare earth element exists in the catalyst in the form of cerium (Ce), or the rare earth element is cerium (Ce). or It exists in the catalyst.

3. The catalyst according to claim 1, characterized in that, Step S1 includes the following specific steps: Preparation of S11 mixed salt solution: Weigh out nickel nitrate hexahydrate... Aluminum nitrate nonahydrate Lanthanum nitrate hexahydrate Or cerium nitrate hexahydrate Massager Dissolve in deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.3-0.5 mol / L, with a solution volume of 50-200 mL. In the formula, This represents the amount of substance of nickel. This represents the amount of substance of aluminum. This refers to the amount of rare earth elements in substance. S12 reduction reaction: Preparation of sodium borohydride An aqueous solution with a concentration of 1.2-1.8 mol / L. The molar amount of the mixed salt solution should be 1.2-2.0 times the total molar amount of the mixed metal ions. Place the mixed salt solution in a three-necked flask and cool it to 0-5°C in an ice-water bath. Turn on the mechanical stirrer and set the speed to 500-800 rpm. Under stirring conditions, add the solution at a rate of 5-10 mL / min. The solution is added dropwise to the mixed salt solution. During the dropwise addition, a black precipitate is produced in the solution, accompanied by a large number of bubbles. This step achieves the reduction of metal ions into alloy particles. S13 First Quenching: Prepare a beaker containing 100-300mL of anhydrous ethanol or isopropanol, place the beaker in a dry ice-acetone bath or a low-temperature thermostat, and lower the temperature of the alcohol solution to -30℃ to -60℃; after the reduction reaction is completed, immediately pour the reaction mixture into the cooled alcohol solution to rapidly cool the alloy particles within 2-5 seconds. This step achieves the initial amorphization of the alloy. S14 Second Quenching: Collect alloy particles rapidly by vacuum filtration or centrifugation at 3000-5000 rpm for 5-10 minutes; wash 1-2 times with a small amount of anhydrous ethanol pre-cooled to below -30°C; under an inert atmosphere, rapidly transfer the alloy particles to liquid nitrogen at -196°C, or to other cooling media at -150°C to -196°C, and immerse for 10-60 minutes. This step inhibits the growth of alloy nuclei through two-stage quenching, further stabilizing the amorphous structure. S15 Vacuum Drying: Under the protection of an inert atmosphere, the quenched alloy particles are taken out from the cooling medium and placed in a vacuum drying oven. They are dried for 10-14 hours at a temperature of 50-60℃ and a vacuum degree of ≤10Pa to obtain a black powdery amorphous alloy precursor. The precursor is then sealed and stored under the protection of nitrogen or argon.

4. The catalyst according to claim 1, characterized in that, Step S2 includes the following specific steps: S21 First alkaline leaching: Weigh 2-10g of the amorphous alloy precursor prepared in step S1 and add it to sodium hydroxide solution with a concentration of 0.5-1.0mol / L. or potassium hydroxide In an alkaline solution, the liquid-to-solid ratio is 10-20 mL / g. The mixture is magnetically stirred at 15-30℃ for 2-4 hours at a stirring speed of 200-400 rpm. This step slowly removes some aluminum, forming a preliminary porous structure, while ensuring a high retention rate of rare earth elements. S22 Second Alkali Immersion: The solid after the first alkali immersion is separated by centrifugation or filtration, and quickly rinsed with deionized water 1-2 times; the rinsed solid is transferred to a sodium hydroxide or potassium hydroxide alkaline solution with a concentration of 2.0-3.0 mol / L, the liquid-to-solid ratio is 15-25 mL / g, and stirred at 40-60℃ for 4-6 hours; this step continues to remove aluminum elements, expand the pore size, and form a sponge-like porous structure; S23 Washing and Drying: After the second alkaline leaching, the solid is repeatedly washed with deionized water, and centrifuged after each wash. The washing is repeated 5-8 times until the pH of the supernatant drops to 7-8. The washed solid is placed in a vacuum drying oven and dried for 8-12 hours at 50-60℃ and a vacuum degree ≤10Pa to obtain a gray-black porous activated catalyst.

5. The catalyst according to claim 1, characterized in that, Step S3 includes the following specific steps: S31 Catalyst Dispersion: Weigh 1-5g of the porous activated catalyst prepared in step S2, add it to 30-100mL of anhydrous toluene, anhydrous tetrahydrofuran or anhydrous dichloromethane, and ultrasonically disperse for 10-20 minutes to ensure that the catalyst is uniformly dispersed in the solvent. Preparation of S32 ligand solution: Weigh the chiral ligand, and calculate the amount according to the following formula: In the formula, For ligand mass; For catalyst mass; The mass fraction of the ligand is 0.005-0.03; the ligand is dissolved in 10-30 mL of the same anhydrous organic solvent as in step S31 to prepare a solution with a ligand concentration of 2-10 mg / mL. S33 Ligand Impregnation: Add the ligand solution prepared in step S32 to the catalyst suspension in step S31, and stir at room temperature for 0.5-1 hour to allow the ligand to fully wet the catalyst surface. S34 Reflux Coordination: Transfer the mixture from step S33 to a three-necked flask equipped with a reflux condenser and a gas protection device. Introduce argon or nitrogen to establish an inert atmosphere at a flow rate of 50-100 mL / min. Heat to the solvent reflux temperature: 110°C for toluene, 66°C for tetrahydrofuran, and 40°C for dichloromethane. Maintain reflux for 6-12 hours. S35 Gas-phase enhanced coordination: During the 2nd to 8th hour of the reflux process, an inert gas stream containing a basic organic amine is introduced into the reaction system. The basic organic amine is selected from triethylamine, pyridine, or diisopropylethylamine. The organic amine vapor is introduced into the reflux system by carrying argon or nitrogen gas. The carrier gas flow rate is controlled at 80-120 mL / min, and the organic amine vapor introduction rate is controlled at 5-15 mL / h. S36 Post-treatment: After reflux, stop heating and cool to room temperature under argon or nitrogen protection; separate the solid by centrifugation or vacuum filtration at 3000-5000 rpm for 10 min; wash 3-5 times with anhydrous toluene or ethanol, 20-30 mL each time, to remove uncoordinated free ligands; dry the washed solid in a vacuum drying oven at 50-60℃ and a vacuum degree ≤10 Pa for 8-12 hours to obtain a dark brown ligand-modified catalyst.

6. The catalyst according to claim 1, characterized in that, Step S4 includes the following specific steps: S41 passivation gas preparation: Prepare an oxygen / nitrogen mixture or an oxygen / argon mixture with an oxygen volume fraction of 0.5%-2%. Use a gas mass flow meter to precisely control the flow rate of each gas. The oxygen volume fraction is 1%, and the volumetric flow rate ratio is used. Mix, with the total flow rate set to 100-200 mL / min; S42 Passivation treatment: The ligand-modified catalyst prepared in step S3 is spread into a thin layer with a thickness of ≤5mm and placed in a passivation device. First, pure nitrogen or pure argon is introduced to purge for 10-15 minutes to remove air from the system. Then, the mixed gas is switched and the gas is introduced at room temperature of 20-30℃ for 2-4 hours to form a thin layer of oxide protective layer on the catalyst surface. S43 Packaging and Storage: After passivation, the catalyst is transferred to a sealed bottle under nitrogen or argon protection, filled with argon, and then sealed for storage.

7. The use of a catalyst as described in any one of claims 1-6 in the asymmetric hydrogenation reaction of unsaturated compounds.

Images