Silica-modified metal-based catalysts and their application in the preparation of amine compounds

Abstract

This invention relates to the field of catalysts, and discloses a silica-modified metal-based catalyst and its application in the preparation of amine compounds. The silica-modified metal-based catalyst comprises active metal particles and amorphous silica partially modified on the surface of the active metal particles; the active metal particles are elemental metal particles and / or mixed-phase elemental metal particles; the metal is selected from iron, cobalt, nickel, copper, and ruthenium; the content of the amorphous silica is 0.1-20% of the total mass of the silica-modified metal-based catalyst. The catalyst of this invention is prepared by modifying metal particles with amorphous silica as the main active component; when applied to the reductive amination preparation of amine compounds, it can significantly improve the selectivity of the target product and reduce the formation of by-products; and the entire reaction process can be carried out at a relatively low temperature, avoiding the use of reaction promoters.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a silicon oxide-modified metal-based catalyst and its application in the preparation of amine compounds. Background Technology

[0002] Amines are a very important class of compounds, widely used in polymers, dyes, surfactants, agrochemicals, and pharmaceuticals. Reductive amination is one of the most common and widely used methods for industrial amine synthesis. In reductive amination, the C=O group in an aldehyde or ketone compound reacts with NH3 or an amine in the presence of a reducing agent to form a CN bond and produce various amines. NH3 and H2 are both inexpensive and widely available raw materials, and water is the main byproduct, with no toxic byproducts generated. This makes the reductive amination of carbonyl compounds a highly atom-efficient and environmentally friendly method for producing amine compounds.

[0003] However, reductive amination reactions are typically nonselective and can result in over-alkylation and reduction of carbonyl compounds to the corresponding alcohols. Furthermore, ammonia can poison many noble metals, causing them to lose their catalytic activity. Commercial Raney nickel, with its strong ability to dissociate hydrogen and resistance to poisoning, is widely used, but the reaction conditions are harsh (temperatures exceeding 120°C and hydrogen pressures greater than 3 MPa), and numerous byproducts are produced, with low selectivity for the target product, the primary amine (less than 80%).

[0004] Therefore, it is of great significance to design and synthesize inexpensive catalysts with high activity to achieve reductive amination with high selectivity under mild conditions. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a silica-modified metal-based catalyst and its application in the preparation of amine compounds. The catalyst of this invention is prepared by modifying amorphous silica with metal particles as the main active component. When applied to the reductive amination of amine compounds, it can significantly improve the selectivity of the target product and reduce the formation of byproducts. Furthermore, the entire reaction process can be carried out at a relatively low temperature, avoiding the use of reaction promoters.

[0006] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a silicon oxide-modified metal-based catalyst, comprising active metal particles and amorphous silicon oxide locally modified on the surface of the active metal particles.

[0007] The catalyst of this invention is prepared by modifying commercial metal powder particles with amorphous silica; that is, the metal powder exists in the form of elemental metal or mixed-phase elemental metal, with localized surface modification by amorphous silica. This invention discovers that after modifying the surface of active metal particles with amorphous silica, strong interactions can occur between the amorphous silica and the active metal, altering the geometric / electronic properties of the metal, thereby controlling the adsorption of intermediate substances during the reaction and changing the reaction pathway. When applied to the reductive amination to prepare amine compounds, it can significantly improve the selectivity of the target product and reduce the formation of byproducts; furthermore, the entire reaction process can be carried out at a relatively low temperature, avoiding the use of reaction promoters.

[0008] Wherein: the active metal particles in the catalyst of the present invention are elemental metal particles and / or mixed-phase elemental metal particles; the metal is selected from iron, cobalt, nickel, copper and ruthenium; the content of amorphous silica is 0.1-20% of the total mass of the silica-modified metal-based catalyst; more preferably, the metal is selected from cobalt, nickel and ruthenium; the content of amorphous silica is 1-10% of the total mass of the silica-modified metal-based catalyst.

[0009] This invention reveals that the selection of the active metal is crucial for the catalytic activity of the catalyst in the reductive amination process to prepare amine compounds. This reaction involves ammonia, which easily poisons metals; therefore, the active metal needs to possess resistance to ammonia poisoning and strong hydrogen dissociation activation capabilities.

[0010] Furthermore, this invention reveals that the content of amorphous silica is crucial to the catalytic activity of the catalyst in the reductive amination preparation of amine compounds. Silica modifies the surface of the active metal through interactions, thereby altering the catalytic performance of the catalyst. Too low a silica content results in weak interactions and minimal changes in catalyst performance, while too high a silica content leads to the covering of active sites on the active metal surface, reducing catalytic activity. Appropriate amounts of amorphous silica modification can improve the selectivity of the catalyst for primary amines without significantly reducing its activity.

[0011] Preferably, the particle size of the active metal particles is in the range of 100-1000 nm.

[0012] Secondly, the present invention provides a method for preparing a silicon oxide modified metal-based catalyst, wherein metal elemental particles are uniformly dispersed in water, a silicon source is added, the mixture is stirred and reacted, filtered and dried, and then calcined and reduced at 200-600°C.

[0013] The organic matter in the silicon source needs to be calcined at high temperatures to convert the organosilicon into silicon oxide. Simultaneously, an interaction occurs between the active metal and silicon oxide under high temperature conditions. High-temperature hydrogen reduction prevents the active metal from completely converting into oxides and losing its catalytic performance during silicon oxide loading. Too low a temperature fails to allow for a strong interaction between the active metal and silicon oxide, while too high a temperature easily causes metal agglomeration and the conversion of amorphous silicon oxide into silicon dioxide crystals, thus reducing catalyst performance.

[0014] Preferably, the silicon source is selected from one or more of methyl silicate, ethyl silicate, silica sol, dimethyldimethoxysilane, dimethyldiethoxysilane, hexadecyltrimethoxysilane, and trimethoxyphenylsilane.

[0015] Thirdly, the present invention provides the application of silicon oxide modified metal-based catalysts in the reductive amination preparation of amine compounds: hydrogen gas is pressurized and introduced into a system containing a solvent, a nitrogen source, a carbonyl compound and a silicon oxide modified metal-based catalyst. During the reaction, the catalyst catalyzes the amination and dehydration of the carbonyl compound to obtain an imine, which is then further hydrogenated to generate an amine compound.

[0016] As a preferred option, the above application specifically includes the following steps: S1: Add solvent, nitrogen source, carbonyl compound and silicon oxide modified metal-based catalyst to the reactor and mix thoroughly.

[0017] S2: Hydrogen gas is introduced into the reactor under pressure to carry out a reducing amination reaction, which produces amine compounds.

[0018] Preferably, the carbonyl compound is an aldehyde.

[0019] More preferably, the aldehyde is selected from one or more of benzaldehyde, 4-methylbenzaldehyde, 4-chlorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-bromobenzaldehyde, 4-fluorobenzaldehyde, 4-methoxybenzaldehyde, 4-trifluoromethylbenzaldehyde, n-octanal, n-heptal, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 2-naphthaldehyde.

[0020] Preferably, the carbonyl compound is a ketone.

[0021] More preferably, the ketone is selected from one or more of cyclopentanone, cyclohexanone, cycloheptanone, 5-nonanone, 2-octanone, 4-methylacetophenone, acetophenone, 1-indanone, 2-acetylthiophene, benzophenone, 4-methoxyacetophenone, and 4-hydroxyacetophenone.

[0022] Preferably, the solvent is water and / or an organic solvent; specifically, it is any one or more of the following: water, methanol, ethanol, tetrahydrofuran, toluene, tert-butanol, tert-amyl alcohol, and acetone.

[0023] Preferably, the nitrogen source is selected from one or more of methylamine, dimethylamine, ethylamine, and diethylamine; more preferably, the nitrogen source is ammonia water with a mass fraction of 25%.

[0024] Preferably, in S1, the concentration of the nitrogen source in the resulting mixture is 1-20 wt%, the concentration of the carbonyl compound is 0.1-80 wt%, and the content of the catalyst is 0.1-20 wt%; more preferably, the concentration of the nitrogen source is 10-20 wt%, the concentration of the carbonyl compound is 10-50 wt%, and the content of the catalyst is 0.1-10 wt%.

[0025] Preferably, in S2, hydrogen gas is introduced until the pressure is 0.1–3.0 MPa; the reaction temperature is 30–180 °C; and the reaction time is 0.1–36 hours.

[0026] Compared with the prior art, the beneficial effects of the present invention are: (1) The catalyst of this invention is prepared by modifying the surface of the active metal particles with amorphous silica as the main active component. After the surface of the active metal particles is modified with amorphous silica, the amorphous silica can generate strong interaction with the active metal, which can change the geometric / electronic properties of the metal, thereby controlling the adsorption of intermediate substances in the reaction process and changing the reaction pathway. When it is applied to the preparation of amine compounds by reductive amination, it can significantly improve the selectivity of the target product and reduce the generation of by-products.

[0027] (2) The entire process of preparing amine compounds in this invention can be carried out at a low temperature, avoiding the use of reaction aids. The cheap and readily available ammonia and hydrogen reduce costs. No toxic or harmful byproducts are generated during the reaction, making it green, environmentally friendly and economical. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments.

[0029] General Implementation Examples In a first aspect, a silicon oxide-modified metal-based catalyst includes active metal particles and amorphous silicon oxide locally modified on the surface of the active metal particles.

[0030] Wherein: the active metal particles are elemental metal particles and / or mixed-phase elemental metal particles (particle size of 10-1000 nm); the metal is selected from iron, cobalt, nickel, copper and ruthenium (preferably cobalt, nickel and ruthenium); the content of amorphous silica is 0.1-20% (preferably 1-10%) of the total mass of silica-modified metal-based catalyst.

[0031] Secondly, a method for preparing a silicon oxide-modified metal-based catalyst involves uniformly dispersing elemental metal particles in water, adding a silicon source, stirring and reacting, filtering and drying, and then calcining and reducing at 200-600℃.

[0032] Preferably, the silicon source is selected from one or more of methyl silicate, ethyl silicate, silica sol, dimethyldimethoxysilane, dimethyldiethoxysilane, hexadecyltrimethoxysilane, and trimethoxyphenylsilane.

[0033] Thirdly, the application of silica-modified metal-based catalysts in the reductive amination preparation of amine compounds: Hydrogen gas is pressurized and introduced into a system containing a solvent, a nitrogen source, a carbonyl compound, and a silica-modified metal-based catalyst. During the reaction, the catalyst catalyzes the amination and dehydration of the carbonyl compound to obtain an imine, which is then further hydrogenated to generate an amine compound. Specifically, the steps include: S1: Add solvent, nitrogen source, carbonyl compound, and silicon oxide-modified metal-based catalyst to a reaction vessel and mix thoroughly. In the resulting mixture, the concentration of nitrogen source is 1-20 wt% (preferably 10-20 wt%), the concentration of carbonyl compound is 0.1-80 wt% (preferably 10-50 wt%), and the content of catalyst is 0.1-20 wt% (preferably 0.1-10 wt%).

[0034] S2: Pressurize the reactor with hydrogen gas until the pressure reaches 0.1–3.0 MPa to carry out the reductive amination reaction. The reaction temperature is 30–180℃ and the reaction time is 0.1–36 hours. After the reaction, amine compounds are generated.

[0035] In some embodiments, the carbonyl compound is an aldehyde, and the amine compound is the corresponding primary amine; the aldehyde is selected from one or more of benzaldehyde, 4-methylbenzaldehyde, 4-chlorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-bromobenzaldehyde, 4-fluorobenzaldehyde, 4-methoxybenzaldehyde, 4-trifluoromethylbenzaldehyde, n-octanal, n-heptal, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 2-naphthaldehyde.

[0036] In some embodiments, the carbonyl compound is a ketone, and the amine compound is the corresponding primary amine; the ketone is selected from one or more of cyclopentanone, cyclohexanone, cycloheptanone, 5-nonanone, 2-octanone, 4-methylacetophenone, acetophenone, 1-indanone, 2-acetylthiophene, benzophenone, 4-methoxyacetophenone, and 4-hydroxyacetophenone.

[0037] In some embodiments, the solvent is water and / or an organic solvent; specifically, any one or more of the following: water, methanol, ethanol, tetrahydrofuran, toluene, tert-butanol, tert-amyl alcohol, acetone.

[0038] In some implementation methods, the nitrogen source is selected from one or more of methylamine, dimethylamine, ethylamine, and diethylamine; more preferably, the nitrogen source is ammonia water with a mass fraction of 25%. Specific Implementation (I) Preparation of metal catalysts modified with amorphous silica The catalyst preparation method is as follows: metal powder (particle size 100-1000nm) is uniformly dispersed in water, silicon source is added, the mixture is stirred and reacted, filtered and dried, calcined and reduced (unless otherwise specified, the calcination and reduction temperature of the catalyst is 400℃).

[0040] Examples 1-1 to 1-40 (II) Preparation of Amine Compounds by Catalytic Reductive Amination Examples 2-1 to 2-19: Add 50 mg of Metal@5SiO to 7.45 g of methanol. x (Amorphous silica loading is 5%, mass fraction in the mixture: 0.5%), 0.5g benzaldehyde (mass concentration in the mixture: 5%), add 2g ammonia water with a mass fraction of 25% (nitrogen source mass concentration in the mixture is 5%), mix well; introduce 1MPa hydrogen gas, react at 80℃ for 20 hours, and calculate the conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine. 2-1 <![CDATA[Pt@5SiO x ]]> 5 3.3 86.5 2-2 <![CDATA[Pd@5SiO x ]]> 5 5.6 76.5 2-3 <![CDATA[Au@5SiO x ]]> 5 6.8 63.7 2-4 <![CDATA[Fe@5SiO x ]]> 5 20.1 98.5 2-5 <![CDATA[Co@5SiO x ]]> 5 87.8 95.6 2-6 <![CDATA[Ni@5SiO x ]]> 5 95.9 97.5 2-7 <![CDATA[Cu@5SiO x ]]> 5 55.4 95.1 2-8 <![CDATA[Ru@5SiO x ]]> 5 97.8 96.6 2-9 <![CDATA[FeCo@5SiO x ]]> 5 95.3 95.4 2-10 <![CDATA[FeNi@5SiO x ]]> 5 97.8 95.2 2-11 <![CDATA[FeCu@5SiO x ]]> 5 73.8 94.5 2-12 <![CDATA[FeRu@5SiO x ]]> 5 96.5 96.4 2-13 <![CDATA[CoNi@5SiO x ]]> 5 93.2 98.7 2-14 <![CDATA[CoCu@5SiO x ]]> 5 98.4 93.8 2-15 <![CDATA[CoRu@5SiO x ]]> 5 96.5 96.5 2-16 <![CDATA[RuNi@5SiO x ]]> 5 98.9 98.7 2-17 <![CDATA[CoCuRu@5SiO x ]]> 5 98.5 99.3 2-18 <![CDATA[CoCuNi@5SiO x ]]> 5 99.1 98.9 2-19 <![CDATA[CoCuRuNi@5SiO x ]]> 5 93.4 95.2 The data in the table show that Fe, Pt, Pd, and Au-based catalysts exhibit low activity in the reductive amination of benzaldehyde to prepare benzylamine. This is mainly due to the weak hydrogen activation ability of Fe, while Pt, Pd, and Au are deactivated by ammonia poisoning during the reaction. Co, Cu, Ru, and Ni exhibit better catalytic performance due to their excellent resistance to ammonia poisoning.

[0041] Examples 2-20 to 2-28: Add 50 mg of Ni@nSiO to 7.45 g of methanol. x (Amorphous silica loading is n%, mass fraction in the mixture: 0.5%), 0.5g benzaldehyde (mass concentration in the mixture: 5%), add 2g ammonia water with a mass fraction of 25% (nitrogen source mass concentration in the mixture is 5%), mix well; introduce 1MPa hydrogen gas, react at 80℃ for 20 hours, and calculate the conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine. 2-20 <![CDATA[Ni@0SiO x ]]> 0 99.9 39.5 2-21 <![CDATA[Ni@0.1SiO x ]]> 0.1 99.9 40.5 2-22 <![CDATA[Ni@1SiO x ]]> 1 99.9 60.3 2-23 <![CDATA[Ni@10SiO x ]]> 10 87.3 98.3 2-24 <![CDATA[Ni@20SiO x ]]> 20 60.5 99.6 2-25 <![CDATA[Ni@30SiO x ]]> 30 40.3 96.6 2-26 <![CDATA[Ni@50SiO x ]]> 50 30.5 98.8 2-27 <![CDATA[Ni@70SiO x ]]> 70 10.6 95.8 2-28 <![CDATA[Ni@90SiO x ]]> 90 5.4 98.5 The table above shows the effect of silica content on catalyst performance. When the silica content is 0%, the catalyst exhibits high activity but low selectivity. With increasing silica content, the strong interaction between silica and the active metal regulates the adsorption state of intermediates during the reaction, improving catalyst selectivity. With further increases in silica content, the active sites on the active metal surface are covered, leading to decreased catalytic activity. The catalyst performance is optimal when the silica content is 5% (Examples 2-6).

[0042] Examples 2-29 to 2-42: 50 mg of Ni@5SiO₂ was added to 7.45 g of methanol and calcined and reduced under different conditions. x -CR (amorphous silica loading of 5%, mass fraction in the mixture: 0.5%, calcination temperature of C℃, reduction temperature of R℃), 0.5g benzaldehyde (mass concentration in the mixture: 5%), add 2g ammonia water with a mass fraction of 25% (nitrogen source mass concentration in the mixture: 5%), mix well; purge with 1MPa hydrogen gas, react at 80℃ for 20 hours, and calculate the conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine. The table above shows the effect of calcination and reduction conditions on catalyst performance. Too low a calcination temperature fails to allow strong interactions between silicon dioxide and the metal, resulting in minimal silicon dioxide modification and low catalyst selectivity. Too high a calcination temperature leads to both silicon dioxide crystallization and metal agglomeration, both of which reduce catalyst activity. Too low a reduction temperature fails to convert the metal to a metallic state, reducing catalyst activity; too high a reduction temperature also causes metal agglomeration, reducing activity. Based on the above data, the optimal calcination temperature is 300-500℃, and the optimal reduction temperature is 300-600℃. Examples 2-43 to 2-54: Add 50 mg of Ru@5SiO to methanol solvent x A catalyst (amorphous silica loading of 5%, mass fraction in the mixture: 0.1-20%), a certain mass of benzaldehyde (mass concentration in the mixture: 0.1-80%), and a certain amount of ammonia water with a mass fraction of 25% (nitrogen source mass concentration in the mixture: 1-20%) were added and mixed evenly. Hydrogen gas was introduced at 1 MPa, and the reaction was carried out at 80°C for 20 hours. The conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine were calculated.

[0043] The table above shows the effects of substrate concentration, catalyst content, and nitrogen source content on catalyst performance. As substrate concentration increases, the limited number of metal active sites are insufficient to adsorb and activate excess substrate, leading to a decrease in substrate conversion. Too low a substrate concentration is meaningless in actual production; therefore, the optimal concentration of the carbonyl compound is 10-50 wt%. Lower catalyst content results in poorer catalytic activity, while excessively high catalyst content increases costs; therefore, the optimal catalyst content is 0.1-10 wt%. Because the catalyst has strong resistance to ammonia poisoning, its performance does not decrease even with a large amount of ammonia. Excessive alkali in actual production can corrode equipment; therefore, the optimal nitrogen source concentration is 10-20 wt%.

[0044] Examples 2-55 to 2-66: Add 50 mg of Ru@5SiO to 7.45 g of methanol. x (Amorphous silica loading of 5%, mass fraction in the mixture: 0.5%), 0.5g benzaldehyde (mass concentration in the mixture: 5%), add 2g ammonia water with a mass fraction of 25% (nitrogen source mass concentration in the mixture: 5%), mix evenly; introduce hydrogen gas (0.1~3.0MPa), react at a certain temperature (30~180℃) for a certain time (0.1~36h), and calculate the conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine. 2-55 0.1 20 80 20.5 95.6 2-56 0.5 20 80 60.3 97.2 2-57 2 20 80 97.3 98.3 2-58 3 20 80 99.5 97.6 2-59 1 0.1 80 2.3 95.4 2-60 1 1 80 10.5 95.0 2-61 1 10 80 60.8 96.4 2-62 1 36 80 99.2 98.4 2-63 1 20 30 20.2 96.9 2-64 1 20 50 72.5 95.6 2-65 1 20 150 99.4 98.4 2-66 1 20 180 99.8 95.3

[0045] The table above shows the effects of hydrogen pressure, reaction time, and reaction temperature on catalyst performance. High temperature, high pressure, and longer reaction time are beneficial to the reaction, but they also increase reaction costs and pose greater safety risks. Based on the examples in the table, the recommended process conditions are: hydrogen (0.5–2.0 MPa), temperature (50–150 °C), and time (10–20 h).

[0046] Examples 2-67 to 2-73: Add 50 mg of Ni@5SiO to 7.45 g of solvent. x (Amorphous silica loading is 5%, mass fraction in the mixture: 0.5%), 0.5g benzaldehyde (mass concentration in the mixture: 5%), add 2g ammonia water with a mass fraction of 25% (mass concentration of nitrogen source in the mixture: 5%), mix well; introduce 1MPa hydrogen gas, react at 80℃ for 20 hours, and calculate the conversion rate of benzaldehyde and the selectivity of the corresponding benzylamine. 2-67 water 96.9 98.5 2-68 ethanol 98.2 97.6 2-69 Tetrahydrofuran 95.3 96.8 2-70 Toluene 94.2 93.4 2-71 tert-Butanol 98.1 95.5 2-72 tert-amyl alcohol 94.9 97.1 2-73 acetone 94.4 94.4

[0047] The catalyst exhibits excellent catalytic performance in different solvents, proving that the solvent has no significant effect on the catalytic performance of the catalyst in the reaction of benzaldehyde reduction amination to prepare benzylamine.

[0048] Example 2-74 Add 50 mg of Ni@5SiO to 7.45 g of methanol. x (Amorphous silica loading of 5%, mass fraction in the mixture: 0.5%), 0.5g benzaldehyde (mass concentration in the mixture: 5%), added to 2g of 25% methylamine aqueous solution (nitrogen source mass concentration in the mixture: 5%), mixed evenly; 1MPa hydrogen gas was introduced, and the reaction was carried out at 80℃ for 20 hours. The benzaldehyde conversion rate was 98.5%, and the selectivity of the corresponding N-methylaniline was 97.3%.

[0049] Example 2-75 Add 50 mg of Ni@5SiO to 8.2 g of methanol. x (Amorphous silica loading of 5%, mass fraction in the mixture: 0.5%), 0.5 g benzaldehyde (mass concentration in the mixture: 5%), added to 1.25 g dimethylamine aqueous solution with a mass fraction of 40% (nitrogen source mass concentration in the mixture: 5%), mixed evenly; 1 MPa hydrogen gas was introduced, and the reaction was carried out at 80 °C for 20 hours. The benzaldehyde conversion rate was 95.7%, and the selectivity of N,N-dimethylaniline was 97.5%.

[0050] Example 2-76 Add 50 mg of Ni@5SiO to 8.73 g of methanol. x (Amorphous silica loading of 5%, mass fraction in the mixture: 0.5%), 0.5 g benzaldehyde (mass concentration in the mixture: 5%), added to 0.72 g ethylamine aqueous solution with a mass fraction of 70% (nitrogen source mass concentration in the mixture: 5%), mixed evenly; 1 MPa hydrogen gas was introduced, and the reaction was carried out at 80℃ for 20 hours. The benzaldehyde conversion rate was 97.8%, and the selectivity of the corresponding N-ethylaniline was 97.3%.

[0051] Example 2-77 Add 50 mg of Ni@5SiO to 8.95 g of methanol. x (Amorphous silica loading: 5%, mass fraction in the mixture: 0.5%), 0.5 g benzaldehyde (mass concentration in the mixture: 5%), 0.5 g diethylamine (nitrogen source mass concentration in the mixture: 5%), mixed thoroughly; 1 MPa hydrogen gas was introduced, and the reaction was carried out at 80 °C for 20 hours. The benzaldehyde conversion rate was 96.2%, and the selectivity of N,N-diethylaniline was 93.6%.

[0052] Examples 2-78 to 2-99 Add 50 mg of Ni@5SiO to 7.45 g of methanol. x(Amorphous silica loading of 5%, mass fraction in the mixture: 0.5%), 0.5 g of reaction substrate (mass concentration in the mixture: 5%), add 2 g of ammonia water with a mass fraction of 25% (mass concentration of nitrogen source in the mixture: 5%), mix well; purge with 1 MPa hydrogen gas, react at 80℃ for 20 hours, and calculate the conversion rate of the reaction substrate and the corresponding primary amine selectivity. 2-78 4-Methylbenzaldehyde 4-Methylanisole 97.9 98.3 2-79 4-Chlorobenzaldehyde 4-Chlorophenylamine 95.8 97.3 2-80 2-Chlorobenzaldehyde 2-Chlorophenylamine 96.4 97.2 2-81 2-Chlorophenylamine 3-Chlorophenylamine 96.8 99.2 2-82 4-Bromobenzaldehyde 4-Bromoanisole 99.1 97.8 2-83 4-Fluorobenzaldehyde 4-Fluorobenzylamine 93.2 98.2 2-84 4-Methoxybenzaldehyde 4-Methoxybenzamine 97.3 95.3 2-85 4-Trifluoromethylbenzaldehyde 4-Trifluoromethylaniline 96.4 97.4 2-86 Octal octylamine 96.8 99.3 2-87 4-Pyridinecarboxaldehyde 4-Methylaminopyridine 98.4 96.7 2-88 2-Thiophene formaldehyde 2-Thiophene Methylamine 99.3 95.7 2-89 2-Naphthaldehyde Naphthalene-2-methylamine 93.5 98.2 2-90 Cyclopentanone Cyclopentanylamine 96.2 96.1 2-91 5-Nonone 5-Aminononane 97.5 98.2 2-92 2-octyl ketone 4-Aminooctane 95.9 96.7 2-93 4-Methylacetophenone (methylphenyl)ethylamine 97.2 97.4 2-94 Acetophenone α-Phenylacetamine 93.2 92.6 2-95 1-Indanone Aminoindane 96.5 91.8 2-96 2-Acetylthiophene (2-Thiophene)ethylamine 98.5 94.7 2-97 Benzophenone diphenylmethylamine 98.4 94.3 2-98 4-Methoxyacetophenone (p-hydroxyphenyl)ethylamine 92.7 98.1 2-99 4-Hydroxyphenylacetone 4-Hydroxyamphetamine 92.6 94.2

[0053] As shown in the table above, the catalyst of this invention exhibits excellent catalytic performance in reductive amination reactions with broad applicability. It can selectively catalyze the preparation of amine compounds from aldehyde compounds containing easily reducible functional groups, with different steric hindrances, and containing heterocycles. Furthermore, the catalyst of this invention can still catalyze more stable ketones with high efficiency. This is mainly because the interaction between silicon dioxide and the active metal regulates the adsorption of substances on the surface of the active metal during the reaction, altering the reaction pathway and improving reaction selectivity.

[0054] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. Use of a silicon oxide modified metal-based catalyst for the reductive amination to prepare amine compounds, characterized in that: Hydrogen gas is introduced under pressure into a system containing a solvent, a nitrogen source, a carbonyl compound, and a silicon oxide-modified metal-based catalyst. During the reaction, the carbonyl compound is amination and dehydration catalyzed by the catalyst to obtain an imine, which is then further hydrogenated to generate an amine compound. The nitrogen source is selected from one or more of methylamine, dimethylamine, ethylamine, and diethylamine; Carbonyl compounds are aldehydes or ketones; The aldehydes are selected from one or more of benzaldehyde, 4-methylbenzaldehyde, 4-chlorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-bromobenzaldehyde, 4-fluorobenzaldehyde, 4-methoxybenzaldehyde, 4-trifluoromethylbenzaldehyde, n-octanal, n-heptal, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 2-naphthaldehyde; The ketones are selected from one or more of the following: cyclopentanone, cyclohexanone, cycloheptanone, 5-nonanone, 2-octanone, 4-methylacetophenone, acetophenone, 1-indanone, 2-acetylthiophene, benzophenone, 4-methoxyacetophenone, and 4-hydroxyacetophenone. The silica-modified metal-based catalyst includes active metal particles and amorphous silica locally modified on the surface of the active metal particles. It is obtained by uniformly dispersing metal elemental particles in water, adding a silicon source, stirring and reacting, filtering and drying, calcining at 300-500℃, and reducing at 300-600℃. The active metal particles are elemental metal particles or mixed-phase elemental metal particles. The metals are selected from cobalt, nickel, copper, and ruthenium; The content of amorphous silica is 1-10% of the total mass of the silica-modified metal-based catalyst.

2. The application according to claim 1, characterized in that: The metal is selected from cobalt, nickel, and ruthenium.

3. The application according to claim 1 or 2, characterized in that: The particle size of the active metal particles is 100-1000 nm.

4. The application according to claim 1, characterized in that: The silicon source is selected from one or more of methyl silicate, ethyl silicate, silica sol, dimethyldimethoxysilane, dimethyldiethoxysilane, hexadecyltrimethoxysilane, and trimethoxyphenylsilane.

5. The application according to claim 1, characterized in that... Specifically, the following steps are included: S1: Add solvent, nitrogen source, carbonyl compound and silicon oxide modified metal-based catalyst to the reaction vessel and mix thoroughly; S2: Hydrogen gas is introduced into the reactor under pressure to carry out a reducing amination reaction, which produces amine compounds.

6. The application according to claim 1 or 5, characterized in that: The solvent is water and / or an organic solvent.

7. The application according to claim 5, characterized in that: In S1, the concentration of the nitrogen source in the resulting mixture is 1-20 wt%, the concentration of the carbonyl compound is 0.1-80 wt%, and the content of the catalyst is 0.1-20 wt%.

8. The application according to claim 5, characterized in that: In S2, hydrogen gas is introduced until the pressure reaches 0.1–3.0 MPa.

9. The application according to claim 5, characterized in that: In S2, the reaction temperature is 30–180℃ and the reaction time is 0.1–36 hours.

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