A catalyst for the reduction of aminations, method of preparation and use

Abstract

This invention discloses a catalyst for reductive amination, its preparation method, and its application, belonging to the field of catalyst technology. The preparation method includes the following steps: S1, drying nickel, zinc, and aluminum sources separately under vacuum; S2, mixing the dried nickel, zinc, and aluminum sources with urea and ball milling to form a solid mixture; S3, calcining the solid mixture in an oxygen-free atmosphere; heating to 200-300℃ and holding at that temperature, then further heating to 400-600℃ and holding at that temperature to obtain a composite metal oxide precursor; S4, placing the composite metal oxide precursor in a mixture of hydrogen and inert gas and reducing it at 250-400℃ to obtain the catalyst; S5, stopping the hydrogen flow and continuing to flow the inert gas to cool the catalyst to room temperature. The preparation process of this invention involves no solvent addition, avoiding wastewater discharge, conforming to the principles of green chemistry and atom economy. The process is simple, with advantages of low energy consumption and high production efficiency, making it suitable for industrial-scale production.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for reductive amination, its preparation method, and its application. Background Technology

[0002] Reductive amination is a key reaction for constructing CN bonds. Carbon-based compounds (aldehydes or ketones) react with ammonia, primary amines, or secondary amines in the presence of a reducing agent to form amine compounds, playing an important role in the synthesis of fine chemical and pharmaceutical intermediates. Nickel-based catalysts are commonly used non-precious metal catalysts for reductive amination reactions due to their low cost and high hydrogenation activity. However, nickel catalysts alone are prone to over-hydrogenation (resulting in the production of alcohols or alkanes), reducing the selectivity of the target amine. Introducing zinc as a promoter can adjust the electronic state and dispersion of nickel, suppress side reactions, and improve selectivity. Traditional methods for preparing nickel-zinc based catalysts (such as impregnation and co-precipitation) are widely used, but they have inherent drawbacks: the use of solvents in the preparation process leads to long process flows, high energy consumption, and the generation of organic or saline wastewater requiring subsequent treatment; the dispersion of the active components of the catalyst is difficult to control, and they are prone to migration and aggregation during drying and calcination, forming large-sized grains and reducing the density of active sites; insufficient interaction between nickel, zinc, and the support results in limited electronic modulation effects, making it difficult to effectively suppress side reactions such as excessive hydrogenation, and the selectivity of the target amine is usually below 90%. Therefore, it is necessary to propose a new catalyst preparation method to solve the above problems. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a catalyst, preparation method, and application for reductive amination. The preparation process involves no solvent addition, avoids wastewater discharge, conforms to the principles of green chemistry and atom economy, has a simple process flow, and offers advantages such as low energy consumption and high production efficiency, making it suitable for industrial-scale production.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing a catalyst for reductive amination, comprising the following steps:

[0006] S1. Raw material pretreatment: The nickel source, zinc source and aluminum source are dried separately under vacuum to remove free moisture;

[0007] S2. Solid-phase mixing: After drying, the nickel source, zinc source and aluminum source are mixed with urea and then ball-milled to form a solid-phase mixture.

[0008] S3. Segmented roasting: The solid mixture is roasted in an oxygen-free atmosphere;

[0009] The solid mixture is heated to 200-300℃ and kept at that temperature. Then the solid mixture is heated to 400-600℃ and kept at that temperature to obtain a composite metal oxide precursor.

[0010] S4. Reduction and activation: The composite metal oxide precursor is placed in a mixture of hydrogen and inert gas and reduced at 250~400℃ to obtain the catalyst.

[0011] S5. Post-treatment: After completing step S4, stop the hydrogen supply and continue to supply inert gas to cool the catalyst to room temperature.

[0012] Preferably, in step S1, the nickel source includes nickel hydroxide and / or nickel nitrate, the zinc source includes zinc carbonate, and the aluminum source includes aluminum hydroxide.

[0013] Preferably, in step S2, the mass ratio of nickel source, zinc source, aluminum source and urea is 1:(0.1~0.5):(1~3):(0.5~2).

[0014] Preferably, in step S2, the ball milling speed is 200~400 r / min and the grinding time is 1~3 h.

[0015] Preferably, in step S3, the solid mixture is heated to 200-300°C at a heating rate of 5-10°C, and the holding time is 1-2 hours.

[0016] Preferably, in step S3, the solid mixture is heated from 200-300°C to 400-600°C at a heating rate of 3-8°C, and the holding time is 2-4 hours.

[0017] Preferably, in step S4, the reduction is carried out at 250~400℃ for 2~6 h.

[0018] Preferably, in step S5, the cooling rate is 5~10℃ / min.

[0019] In a second aspect, the present invention provides a catalyst for reductive amination, which is prepared by the above method.

[0020] In a third aspect, the present invention proposes an application of a catalyst for reductive amination, wherein the catalyst prepared by the above method is used to prepare amine compounds.

[0021] Beneficial effects

[0022] The catalyst preparation process of this invention involves no solvent addition, avoids wastewater discharge, conforms to the principles of green chemistry and atom economy, has a simple process flow, and has the advantages of low energy consumption and high production efficiency, making it suitable for industrial-scale production.

[0023] The catalyst prepared by this invention has a large specific surface area. The gas generated by urea decomposition causes the material to form a porous structure, resulting in a specific surface area of ​​150-300 m². 2 / g provides sufficient active sites for the reaction.

[0024] The preparation process of this invention combines mechanochemical action with segmented calcination to ensure that the active metals (nickel and zinc) are highly dispersed on the carrier surface at the nanoscale (5~15 nm). The active metals are firmly bonded to the carrier. The introduction of zinc modulates the electron cloud density of nickel, which significantly suppresses side reactions such as CN bond hydrogenolysis or excessive carbonyl reduction. The selectivity of the target amine product is ≥95%. Detailed Implementation

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, specific implementation methods of the present invention will be described below. Obviously, the following descriptions are merely some embodiments of the present invention; those skilled in the art can obtain other implementation methods based on these embodiments without creative effort.

[0026] This invention proposes a catalyst for reductive amination, prepared using urea, a nickel source, a zinc source, and an aluminum source. The specific steps of the preparation method are as follows:

[0027] S1. Raw material pretreatment: The nickel source, zinc source and aluminum source are dried separately under vacuum to remove free moisture;

[0028] S2. Solid-phase mixing: After drying, the nickel source, zinc source and aluminum source are mixed with urea and then ball-milled to form a solid-phase mixture.

[0029] S3. Segmented roasting: The solid mixture is roasted in an oxygen-free atmosphere;

[0030] The solid mixture is heated to 200-300℃ and kept at that temperature. Then the solid mixture is heated to 400-600℃ and kept at that temperature to obtain a composite metal oxide precursor.

[0031] S4. Reduction and activation: The composite metal oxide precursor is placed in a mixture of hydrogen and inert gas and reduced at 250~400℃ to obtain the catalyst.

[0032] S5. Post-processing: After completing step S4, stop the hydrogen supply and continue to supply inert gas to cool the catalyst to room temperature to prevent oxidation caused by contact with air at high temperature. After the catalyst has cooled to room temperature, take it out and use vacuum packaging or inert gas filling packaging to ensure that the catalyst maintains its activity during storage and transportation.

[0033] In step S1, moisture in the raw materials is removed to prevent high-temperature fractionation of the raw materials and to avoid moisture affecting subsequent solid-phase mixing and reaction.

[0034] The vacuum level is preferably -0.08 to -0.1 MPa, the drying temperature is preferably 80 to 120°C, and the drying time is preferably 4 to 8 hours. More preferably, the drying temperature is 100°C and the drying time is 6 hours.

[0035] The nickel, zinc, and aluminum sources of this invention are commonly used materials in the conventional preparation of nickel-zinc based catalysts; the purity of the nickel, zinc, and support is ≥99%. The nickel source preferably includes nickel hydroxide and / or nickel nitrate, the zinc source preferably includes zinc carbonate, and the aluminum source preferably includes aluminum hydroxide.

[0036] In step S2, ball milling ensures uniform mixing of the raw materials. Preferably, the material is ground at a speed of 200-400 r / min for 1-3 hours, and more preferably at a speed of 300 r / min for 2 hours, thereby improving the uniformity of material mixing and minimizing the particle size distribution. Through mechanical grinding, the raw material particles are fully broken down and uniformly mixed to form a tightly packed solid-phase mixture.

[0037] To avoid contamination of the raw materials by external metal sources during the grinding process, an agate jar is preferably used as the container, and agate balls are used as the grinding medium. More preferably, the ratio of the mass of the agate balls to the total mass of the raw materials is (5~15):1.

[0038] In step S2, the mass ratio of nickel source, zinc source, aluminum source and urea is 1:(0.1~0.5):(1~3):(0.5~2). Preferably, the mass ratio of nickel source, zinc source, aluminum source and urea is 1:0.3:2:1.2.

[0039] In step S3, the solid mixture is placed in a muffle furnace, and a protective gas (i.e., an oxygen-free atmosphere) is introduced at a flow rate of 50-100 mL / min. A precursor is prepared using a staged roasting method. In the first stage of roasting (i.e., heating from room temperature to 200-300℃), urea gradually decomposes according to the reaction: CO(NH2)2→NH3↑+HNCO. HNCO further decomposes into NH3 and CO2. The gases produced by urea decomposition form porous channels within the material during release. Simultaneously, the urea decomposition products HNCO and their anions (cyanate, OCN) are also released. - OCN is a very strong ligand that can form stable metal-cyanate complexes with most metal cations. These complexes or adsorbed OCN form as metal ions begin to precipitate or form initial oxide nuclei. -It tightly coats the particle surface, forming a monomolecular protective layer. This protective layer physically prevents the particle cores from contacting each other through steric hindrance, inhibiting particle agglomeration. In the second stage of calcination (heating from 200~300℃ to 400~600℃), the nickel, zinc, and aluminum sources react. Taking nickel hydroxide, zinc carbonate, and aluminum hydroxide as examples, nickel hydroxide decomposes to form nickel oxide, zinc carbonate decomposes to form zinc oxide, and aluminum hydroxide decomposes to form aluminum oxide. Furthermore, nickel oxide, zinc oxide, and aluminum oxide undergo a further solid-state reaction to form Ni-Zn-Al-O composite metal oxides, ensuring a tight bond between the active components, additives, and carriers.

[0040] Preferably, in the first stage of roasting, the heating rate is 5~10℃, the temperature is raised to 200~300℃, and the holding time is 1~2 hours. For example, the temperature is raised to 250℃ and the holding time is 1.5 hours.

[0041] Preferably, in the second stage of roasting, the heating rate is 3~8℃, the temperature is raised to 400~600℃, and the holding time is 2~4h. For example, the temperature is raised to 500℃ and the holding time is 3h.

[0042] In step S3, the oxygen-free atmosphere is a nitrogen atmosphere and / or an inert gas atmosphere.

[0043] In step S4, the composite metal oxide precursor is placed in a quartz tube of a fixed-bed reactor, and a mixture of hydrogen and inert gas (preferably with a hydrogen integral of 5-20%) is introduced at a flow rate of 100-300 mL / min. Reduction is carried out at 250-400℃ for 2-6 h. In the composite metal oxide precursor, nickel oxide is reduced to catalytically active metallic nickel, while zinc oxide remains in its oxidized state and interacts electronically with metallic nickel, thus regulating the electron density of nickel.

[0044] Hydrogen gas adsorbs and dissociates into reactive hydrogen atoms on the surface of metallic nickel. These hydrogen atoms "overflow" from the nickel surface to the adjacent zinc oxide surface. The overflowing hydrogen atoms reduce zinc ions on the zinc oxide surface and its surface layer, or capture oxygen ions from the zinc oxide surface to form water. This process creates oxygen vacancies and a small amount of low-valence zinc species on the zinc oxide surface. Zinc oxide itself is an N-type semiconductor. When oxygen vacancies and low-valence zinc species are generated on the surface, these defects contribute electrons to the system. These electrons tend to flow to the lower-energy nickel particles, thereby increasing the electron density of nickel.

[0045] Preferably, the hydrogen component in the mixed gas is 10%, and the gas flow rate is 200 mL / min. Preferably, the reduction temperature is 300℃, and the reduction time is 4 h.

[0046] In step S5, the cooling rate is 5~10℃ / min.

[0047] The technical solution of the present invention will be described in detail below with specific embodiments.

[0048] Example 1

[0049] S1. Raw material pretreatment: Nickel hydroxide, zinc carbonate and aluminum hydroxide are dried separately under vacuum to remove free moisture. The vacuum degree is -0.09 MPa, the drying temperature is 100℃ and the drying time is 6 h.

[0050] S2. Solid-phase mixing: Add 10 g of dried nickel hydroxide, 3 g of zinc carbonate, 20 g of aluminum hydroxide and 12 g of urea to the agate jar of a planetary ball mill at a mass ratio of 1:0.3:2:1.2, add 450 g of agate balls (ball-to-material ratio of 10:1), and grind at 300 r / min for 2 h to form a solid-phase mixture.

[0051] S3. Segmented calcination: The solid mixture is placed in a muffle furnace, nitrogen is introduced at a flow rate of 80 mL / min, the temperature is increased to 250℃ at 8℃ / min, and held for 1.5 h. Then the temperature is increased to 500℃ at 5℃ / min and held for 3 h to obtain the composite metal oxide precursor.

[0052] S4. Reduction and Activation: The composite metal oxide precursor was placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction 10%) was introduced at a flow rate of 200 mL / min. Reduction was carried out at 300℃ for 4 h to obtain the catalyst.

[0053] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the catalyst to room temperature at 8℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst A1.

[0054] Example 2

[0055] S1. Raw material pretreatment: Nickel hydroxide, zinc carbonate and aluminum hydroxide are dried separately under vacuum to remove free moisture. The vacuum degree is -0.08 MPa, the drying temperature is 80℃ and the drying time is 8 h.

[0056] S2. Solid-phase mixing: Add 10 g of dried nickel hydroxide, 1 g of zinc carbonate, 10 g of aluminum hydroxide and 5 g of urea to the agate jar of a planetary ball mill at a mass ratio of 1:0.1:1:0.5, add 130 g of agate balls (ball-to-material ratio of 5:1), and grind at 200 r / min for 3 h to form a solid-phase mixture.

[0057] S3. Segmented calcination: The solid mixture is placed in a muffle furnace and argon gas is introduced at a flow rate of 50 mL / min. The temperature is increased to 200℃ at a rate of 5℃ / min and held for 2 h. Then, the temperature is increased to 400℃ at a rate of 3℃ / min and held for 4 h to obtain the composite metal oxide precursor.

[0058] S4. Reduction and Activation: The composite metal oxide precursor was placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction of 5%) was introduced at a flow rate of 100 mL / min. Reduction was carried out at 250℃ for 6 h to obtain the catalyst.

[0059] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the catalyst to room temperature at 5℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst A2.

[0060] Example 3

[0061] S1. Raw material pretreatment: Nickel hydroxide, zinc carbonate and aluminum hydroxide are dried separately under vacuum to remove free moisture. The vacuum degree is -0.1 MPa, the drying temperature is 120℃ and the drying time is 4 h.

[0062] S2. Solid-phase mixing: Add 10 g of dried nickel hydroxide, 5 g of zinc carbonate, 30 g of aluminum hydroxide and 20 g of urea to the agate jar of a planetary ball mill at a mass ratio of 1:0.5:3:2, add 975 g of agate balls (ball-to-material ratio of 15:1), and grind at 400 r / min for 1 h to form a solid-phase mixture.

[0063] S3. Segmented calcination: The solid mixture is placed in a muffle furnace, nitrogen is introduced at a flow rate of 100 mL / min, the temperature is increased to 300℃ at 10℃ / min, and held for 1 h. Then the temperature is increased to 600℃ at 8℃ / min and held for 2 h to obtain the composite metal oxide precursor.

[0064] S4. Reduction and Activation: The composite metal oxide precursor was placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction of 20%) was introduced at a flow rate of 300 mL / min. Reduction was carried out at 400℃ for 2 h to obtain the catalyst.

[0065] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the catalyst to room temperature at 10℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst A3.

[0066] Comparative Example 1

[0067] Urea was not used in this comparative example.

[0068] S1. Raw material pretreatment: Nickel hydroxide, zinc carbonate and aluminum hydroxide are dried separately under vacuum to remove free moisture. The vacuum degree is -0.09 MPa, the drying temperature is 100℃ and the drying time is 6 h.

[0069] S2. Solid-phase mixing: Add 10 g of dried nickel hydroxide, 3 g of zinc carbonate, and 20 g of aluminum hydroxide to the agate jar of a planetary ball mill at a mass ratio of 1:0.3:2, add 330 g of agate balls (ball-to-material ratio of 10:1), and grind at 300 r / min for 2 hours to form a solid-phase mixture.

[0070] S3. Segmented calcination: The solid mixture is placed in a muffle furnace, nitrogen is introduced at a flow rate of 80 mL / min, the temperature is increased to 250℃ at 8℃ / min, and held for 1.5 h. Then the temperature is increased to 500℃ at 5℃ / min and held for 3 h to obtain the composite metal oxide precursor.

[0071] S4. Reduction and Activation: The composite metal oxide precursor was placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction 10%) was introduced at a flow rate of 200 mL / min. Reduction was carried out at 300℃ for 4 h to obtain the catalyst.

[0072] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the catalyst to room temperature at 8℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst B1.

[0073] Comparative Example 2

[0074] This comparative example uses the traditional impregnation method.

[0075] S1. Carrier pretreatment: Carriers with a specific surface area of ​​200 m² 2 / g of alumina was dried at 110℃ for 12 h;

[0076] S2. Preparation of impregnation solution: Dissolve 10 g of Ni(NO3)2・6H2O and 3 g of Zn(NO3)2・6H2O in 50 mL of deionized water, add 10 g of Al2O3 support, and stir to impregnate for 12 h.

[0077] S3. Drying and calcining: Evaporate the moisture at 80℃, then dry at 110℃ for 12 h, and then calcin at 500℃ for 3 h.

[0078] S4. Reduction and activation: The calcined product is placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction of 10%) is introduced at a flow rate of 200 mL / min. The product is reduced at 300℃ for 4 h to obtain the reduced product.

[0079] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the reduction product to room temperature at 8℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst B2.

[0080] Comparative Example 3

[0081] Zinc was not introduced in this comparative example.

[0082] S1. Raw material pretreatment: Nickel hydroxide, zinc carbonate and aluminum hydroxide are dried separately under vacuum to remove free moisture. The vacuum degree is -0.09 MPa, the drying temperature is 100℃ and the drying time is 6 h.

[0083] S2. Solid-phase mixing: Add 10 g of dried nickel hydroxide, 20 g of aluminum hydroxide and 12 g of urea to the agate jar of a planetary ball mill at a mass ratio of 1:2:1.2, add 420 g of agate balls (ball-to-material ratio of 10:1), and grind at 300 r / min for 2 hours to form a solid-phase mixture.

[0084] S3. Segmented calcination: The solid mixture is placed in a muffle furnace, nitrogen is introduced at a flow rate of 80 mL / min, the temperature is increased to 250℃ at 8℃ / min, and held for 1.5 h. Then the temperature is increased to 500℃ at 5℃ / min and held for 3 h to obtain the composite metal oxide precursor.

[0085] S4. Reduction and Activation: The composite metal oxide precursor was placed in a fixed-bed reactor, and a mixture of hydrogen and inert gas (hydrogen volume fraction 10%) was introduced at a flow rate of 200 mL / min. Reduction was carried out at 300℃ for 4 h to obtain the catalyst.

[0086] S5. Post-treatment: Stop the hydrogen flow and continue to flow inert gas to cool the catalyst to room temperature at 8℃ / min. After the catalyst is cooled to room temperature, take it out and vacuum package it as catalyst B3.

[0087] The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were evaluated for reductive amination reactions as follows:

[0088] The reaction was carried out using a fully automated hydrogenation apparatus in a continuous flow manner. The reaction conditions were: reaction temperature 100℃, pressure 3.0 MPa, injection rate 0.3 mL / min, hydrogen flow rate 35 mL / min, and aldehyde to amine molar ratio of 1:3. The results are shown in Tables 1-4. Based on the test results, it can be seen that the catalyst prepared in this invention has high selectivity for reductive amination reactions, and the yields of the target products in Examples 1-3 are significantly higher than those in the comparative examples.

[0089] Table 1. Catalyst evaluation results (synthesis of dibenzylamine using benzaldehyde and benzylamine as raw materials)

[0090] catalyst Yield % Selectivity% Example 1 A1 96 97 Example 2 A2 91 95 Example 3 A3 93 96 Comparative Example 1 B1 53 70 Comparative Example 2 B2 74 82 Comparative Example 3 B3 83 85

[0091] Table 2 Catalyst evaluation results (synthesis of benzyl-(3-bromobenzyl)amine from m-bromobenzaldehyde and benzylamine)

[0092] catalyst Yield % Selectivity% Example 1 A1 95 97 Example 2 A2 90 95 Example 3 A3 94 96 Comparative Example 1 B1 50 71 Comparative Example 2 B2 70 80 Comparative Example 3 B3 80 88

[0093] Table 3 Catalyst evaluation results (Synthesis of N-(3,5-dichlorobenzaldehyde)-1-phenylethylamine using 3,5-dichlorobenzaldehyde and alpha-methylbenzylamine as raw materials)

[0094] catalyst Yield % Selectivity% Example 1 A1 95 98 Example 2 A2 94 96 Example 3 A3 92 95 Comparative Example 1 B1 47 68 Comparative Example 2 B2 71 79 Comparative Example 3 B3 84 89

[0095] Table 4 Catalyst evaluation results (Synthesis of N-(4-chlorobenzyl)aniline using p-chlorobenzaldehyde and aniline as raw materials)

[0096] catalyst Yield % Selectivity% Example 1 A1 92 96 Example 2 A2 91 94 Example 3 A3 93 96 Comparative Example 1 B1 45 69 Comparative Example 2 B2 65 80 Comparative Example 3 B3 79 87

[0097] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a catalyst for reductive amination, characterized in that, The steps are as follows: S1. Raw material pretreatment: The nickel source, zinc source and aluminum source are dried separately under vacuum to remove free moisture; S2. Solid-phase mixing: After drying, the nickel source, zinc source and aluminum source are mixed with urea and then ball-milled to form a solid-phase mixture. The mass ratio of the nickel source, zinc source, aluminum source and urea is 1:(0.1~0.5):(1~3):(0.5~2). S3. Segmented roasting: The solid mixture is roasted in an oxygen-free atmosphere; The solid mixture is heated to 200-300℃ at a heating rate of 5-10℃ / min and held for 1-2 hours. Then, the solid mixture is heated to 400-600℃ at a heating rate of 3-8℃ / min and held for 2-4 hours to obtain a composite metal oxide precursor. S4. Reduction and activation: The composite metal oxide precursor is placed in a mixture of hydrogen and inert gas and reduced at 250~400℃ to obtain the catalyst. S5. Post-treatment: After completing step S4, stop the hydrogen supply and continue to supply inert gas to cool the catalyst to room temperature.

2. The method for preparing the catalyst for reductive amination according to claim 1, characterized in that, In step S1, the nickel source includes nickel hydroxide and / or nickel nitrate, the zinc source includes zinc carbonate, and the aluminum source includes aluminum hydroxide.

3. The method for preparing the catalyst for reductive amination according to claim 1, characterized in that, In step S2, the ball milling speed is 200~400 r / min, and the grinding time is 1~3 h.

4. The method for preparing the catalyst for reductive amination according to claim 1, characterized in that, In step S4, the reduction is carried out at 250~400℃ for 2~6 h.

5. The method for preparing the catalyst for reductive amination according to claim 1, characterized in that, In step S5, the cooling rate is 5~10℃ / min.

6. The application of a catalyst for reductive amination, characterized in that, The catalyst prepared by the method according to any one of claims 1-5 is used to prepare amine compounds.