Metal catalysts, their preparation methods and applications

Abstract

This invention discloses a metal catalyst, its preparation method, and its applications. The metal catalyst comprises a plurality of metal particles and a silicon-based support, wherein the content of the metal particles is 5 wt%-51 wt%, where the content is the percentage of the mass of the metal particles to the total mass of the metal catalyst; the metal particles are Ni particles or Cu particles; the metal particles are dispersed in the silicon-based support, and the dispersion degree of the metal particles in the metal catalyst is 50-70%; the silicon-based support comprises SiO2 and metal silicates; the metal silicates are present between the metal particles. The metal catalyst provided by this invention has high dispersion and low metal particle size, exhibiting excellent catalytic activity in catalytic processes, achieving high selectivity and high conversion rates, making it suitable for industrial production and showing good application prospects.

Description

Technical Field

[0001] This invention relates to metal catalysts, their preparation methods, and applications. Background Technology

[0002] Aromatic amines are an important class of fine chemical products with wide applications in pharmaceuticals, pesticides, dyes, and fragrances, possessing high added value. They are generally produced by the reduction of aromatic nitro compounds. Common reduction methods include iron powder reduction, electrolytic reduction, and catalytic hydrogenation. However, iron powder reduction requires multiple steps such as chlorination, nitration, and alkaline hydrolysis, resulting in low product quality and waste. Electrolytic reduction is technically challenging and consumes a large amount of electricity. In contrast, using hydrogen as a hydrogen source and employing a heterogeneous catalyst to catalytically hydrogenate readily available benzene-ring-functionalized nitrobenzene to synthesize benzene-ring-functionalized aniline compounds is an important approach that allows for product separation from the catalyst system, is environmentally friendly, and produces stable product quality.

[0003] The catalytic hydrogenation of benzene ring-functionalized nitrobenzene involves several parallel reactions and a series of consecutive reactions. The current focus and challenge lie in achieving high substrate conversion and high selectivity for the target product. However, when electron-donating groups (-OH), electron-withdrawing groups (-X), and other reducible groups (such as alkenes, alkynes, aldehydes, nitriles, ketones, etc.) are present, achieving preferential conversion of the nitro group while retaining other groups is difficult. For example, in the hydrogenation of benzene ring-functionalized nitrobenzene, the defunctionalization side reaction is a key factor affecting the reaction selectivity. The breaking of the C-functional group bond leads to the formation of aniline and some acidic substances, which not only reduces the selectivity of the target product and makes product separation difficult, but also causes a certain degree of corrosion to the equipment. Adding appropriate inhibitors such as phosphides, morpholine, polyamines, and sulfur will reduce catalyst activity and complicate product post-processing. Therefore, to simultaneously achieve high conversion and high selectivity, it is necessary to consider optimizing and modifying the metal catalyst to adjust the interaction between the active metal and the support. Studies have shown that noble metal catalysts such as Ru, Pd, Pt, and Au exhibit excellent catalytic activity under mild conditions. Patent CN113578316A describes the preparation of a supported porous nano-platinum-ruthenium alloy catalyst and its application in the hydrogenation of chloronitrobenzene to chloroaniline. The molar ratio of Pt+Ru / o-chloronitrobenzene is 1 / 1000. After reacting with 2MPa hydrogen gas at 100℃ for 3 hours, o-chloronitrobenzene is completely converted, and the selectivity of o-chloroaniline is 99.6%. Patent CN114733520A describes a method for preparing and applying a supported nano-gold catalyst. In its embodiment, anatase TiO2 is first prepared by hydrothermal method, and then a TiO2-supported Au-Pd catalyst is prepared by urea co-deposition precipitation method. When Au loading is 0.5 wt% and Pd loading is 0.01 wt%, it is used in the hydrogenation reaction of p-chloronitrobenzene. After reacting at 100°C with 1.2 MPa hydrogen gas for 2 hours, the conversion rate of p-chloronitrobenzene is 99.8%, and the selectivity for the target product, p-chloroaniline, is 98.5%. Due to the excellent hydrogenation properties of noble metals, the reaction products may contain defunctionalized groups and benzene ring hydrogenation byproducts, leading to poor reaction selectivity. Furthermore, the reaction is subject to high costs and low atom utilization, limiting its application to laboratory research.

[0004] Many non-precious metal catalysts, such as Fe, Co, and Ni, have also been developed for the catalytic hydrogenation of functionalized aromatic amines, exhibiting unique catalytic performance and price advantages. Patent CN115301275A describes a low-cost metal catalyst, its preparation method, and its application. The low-cost metal is selected from Fe, Ni, Co, Cu, or Zn, preferably Co. The resulting catalyst, Co / SiO2@CN, is applied to the hydrogenation reaction of nitrobenzene with a benzene ring functionalization, requiring a reaction time of 10 hours. The yield of the target product, functionalized aniline compounds, is between 88% and 93%. However, the harsh reaction conditions and low product yield limit its widespread industrial application.

[0005] Therefore, there is an urgent need to develop a low-cost, highly active, and highly selective hydrogenation catalyst to achieve the preparation of benzene-ring-functionalized aniline compounds from benzene-ring-functionalized nitrobenzene under mild conditions. Summary of the Invention

[0006] To overcome the shortcomings of existing metal catalysts in hydrogenation reactions, such as low catalytic activity, low substrate conversion, and poor product selectivity, this invention provides a metal catalyst, its preparation method, and its applications. The metal catalyst provided by this invention exhibits high dispersion and low metal particle size, demonstrating excellent catalytic activity in catalytic processes, achieving high selectivity and high conversion rates. It is suitable for industrial production and shows promising application prospects.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a metal catalyst comprising a plurality of metal particles and a silicon-based support, wherein the content of the metal particles is 5 wt%-51 wt%, and the content is the percentage of the mass of the metal particles to the total mass of the metal catalyst; the metal particles are Ni particles or Cu particles.

[0009] The metal particles are dispersed in the silicon-based support, and the dispersion of the metal particles in the metal catalyst is 50-70%; the silicon-based support includes SiO2 and metal silicates; the metal silicates exist between the metal particles.

[0010] This invention provides a metal catalyst comprising a plurality of metal particles and a silicon-based support, wherein the metal particles have a particle size of less than 10 nm and are Ni particles or Cu particles.

[0011] The metal particles are dispersed in the silicon-based support, and the dispersion of the metal particles in the metal catalyst is 50-70%; the silicon-based support includes SiO2 and metal silicates; the metal silicates exist between the metal particles.

[0012] In this invention, the metal silicate in the metal catalyst exists between the metal particles, which can effectively confine the metal particles and prevent them from agglomerating or growing.

[0013] In this invention, the particle size of the metal particles is preferably below 10 nm, for example, 2.0-3.2 nm.

[0014] In this invention, the content of the metal particles is preferably 10wt%-33wt%, more preferably 15wt%, and the content is the percentage of the mass of the metal particles to the total mass of the metal catalyst.

[0015] In this invention, the metal particles are distributed in a watermelon seed pattern in a silicon-based carrier, and the dispersion of the metal particles is preferably 57-70%, more preferably 57.3-69.6%, for example 57.3%, 58.4%, 60.5%, 63.8% or 69.6%.

[0016] In this invention, when the metal particles are Cu, the dispersion is determined by N2O oxidation and H2 titration to measure the number of copper atoms on the surface. In the TPR experiment, the catalyst is first reduced to 300°C in a 10% H2 / Ar mixture at a flow rate of 30 mL / min. The hydrogen consumption for the first TPR is recorded as x. Then, the reactor is purged to 50°C with Ar. After oxidizing the surface copper atoms to Cu2O with N2O (30 mL / min) at 50°C, the oxidant is removed by purging with Ar. Finally, a TPR experiment is performed in a 10% H2 / Ar mixture at a flow rate of 30 mL / min. The hydrogen consumption for the second TPR is recorded as y. The dispersion D of surface Cu is calculated using the formula: D = (2 × y / x) × 100%.

[0017] In this invention, when the metal particles are Ni, the method for detecting their dispersibility is as follows: H2 chemisorption pulse chromatography is used, and the experiment is conducted on a micro-pulse reaction device with a catalyst dosage of 150 mg. The sample is reduced in H2 at 700℃ for 1 h, then purged with Ar gas for 20 min to remove the gas phase and adsorbed H2. It is then cooled to room temperature (25℃) in an Ar atmosphere. Using a TCD detector, after the baseline stabilizes, a certain amount of H2 is pulsed until no more H2 is adsorbed. The dispersibility D is determined based on the amount of H2 adsorbed: D = 2n H2 / n Ni ×100%; n H2 : Number of moles of hydrogen gas consumed; n Ni : Total number of moles of Ni in the catalyst.

[0018] In this invention, the specific surface area of ​​the metal catalyst can be 420-700 m². 2 / g, preferably 430-700m 2 / g, for example 431.7m2 / g、442.8m 2 / g、463.1m 2 / g, 475.6m 2 / g, 476.7m 2 / g, 509.8m 2 / g, 565.8m 2 / g、694.3m 2 / g or 698.5m 2 / g.

[0019] In this invention, the metal catalyst may have a sheet-like structure.

[0020] This invention also provides a method for preparing a metal catalyst, comprising the following steps:

[0021] (1) Add the silicon source to the mixture of the metal source and the complexing agent, and stir until a gel is formed; the silicon source is tetraethyl orthosilicate; the metal source is a copper source or a nickel source; the complexing agent is compound I.

[0022]

[0023] In compound I, R1 and R2 are independently selected from H or R 1-1 -COOH;R 1-1 Independently selected from C1-C4 alkylene groups or by R a Substituted C1-C4 alkylene groups; R a Independently selected from -OH, -CN, -halogen, or -C1-C6 alkyl groups;

[0024] (2) The gel obtained in step (1) is subjected to drying, calcination and reduction reaction in sequence to obtain the metal catalyst.

[0025] In this invention, the metal content in the metal source can be 5wt%-51wt%, preferably 10wt%-33wt%, and more preferably 15wt%, wherein the content is the percentage of the mass of the metal to the total mass of the metal catalyst.

[0026] In this invention, the copper source can be a conventional soluble copper salt in the art, preferably at least one of copper sulfate, copper chloride and copper nitrate, and more preferably copper nitrate trihydrate.

[0027] In this invention, the R 1-1 Preferably selected from methylene or methylene substituted with -OH.

[0028] In this invention, the complexing agent is preferably one or more of citric acid, tartaric acid, and malic acid.

[0029] In this invention, the molar ratio of the silicon source to the complexing agent can be 1:0.2-1:1; for example, 1:0.31 or 1:0.39.

[0030] In this invention, the molar ratio of the complexing agent to the solvent in the mixture can be 1:20-1:100, for example 1:35.

[0031] In step (1), the stirring time can be 30-90 minutes, for example, 60 minutes.

[0032] In step (1), the solvent of the mixture can be conventional in the art, preferably water.

[0033] In step (1), the temperature at which the gel is formed can be 5-70°C, preferably 20-65°C, for example 25°C or 65°C. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70°C, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0034] In step (2), the drying temperature can be 80-100℃, for example 100℃.

[0035] In step (2), the drying time can be 8-15 hours, for example, 12 hours.

[0036] In step (2), the calcination can be carried out in an air atmosphere.

[0037] In step (2), the calcination temperature can be 300-800℃, for example 400℃.

[0038] In step (2), the heating rate of calcination can be 1-10℃ / min, for example 2℃ / min.

[0039] In step (2), the calcination time can be 3-8 hours, for example, 5 hours.

[0040] In step (2), the reduction reaction is generally carried out by introducing a reducing gas to react with the calcined substance; the reducing gas is generally hydrogen or a hydrogen-argon mixture, preferably a hydrogen-argon mixture, and more preferably the volume fraction of hydrogen in the hydrogen-argon mixture is 5%.

[0041] In step (2), the temperature of the reduction reaction can be 100-400℃, for example 130℃, 200℃, 300℃ or 400℃.

[0042] In step (2), the heating rate of the reduction reaction can be 1-10℃ / min, for example 5℃ / min.

[0043] In step (2), the reduction reaction can take 1-6 hours, for example, 3 hours.

[0044] The present invention also provides a metal catalyst, which is prepared by the above-described preparation method.

[0045] The present invention also provides the application of the metal catalyst described in the above technical solution in hydrogenation reaction.

[0046] In this invention, the reaction substrate for the hydrogenation reaction can be compound II:

[0047]

[0048] Wherein, R can be a conventional functional group in the art, such as one or more of -Cl, -OH or -OCH3.

[0049] In some specific embodiments, the substrate for the hydrogenation reaction is one or more of compounds (1)-(9):

[0050]

[0051] In this invention, the solvent for the hydrogenation reaction can be conventional in the art, preferably one or more of methanol, ethanol, isopropanol, tetrahydrofuran, toluene and p-xylene, and more preferably ethanol or tetrahydrofuran.

[0052] In this invention, the mass ratio of the reaction substrate to the metal catalyst in the hydrogenation reaction can be 1000:1-1:1, preferably 100:1-10:1, for example 10:1.

[0053] In this invention, the mass ratio of the reaction substrate to the solvent in the hydrogenation reaction can be 1:1 to 1:60, preferably 1:6 to 1:10, for example 1:6.

[0054] In some specific embodiments, when the substrate of the hydrogenation reaction is compound II, the reaction temperature of the hydrogenation reaction is 80-250°C, preferably 100-180°C, for example 110°C, 130°C, 150°C or 180°C.

[0055] In this invention, the reducing agent in the hydrogenation reaction can be any conventional agent in the art, preferably hydrogen.

[0056] In some specific embodiments, the hydrogen pressure of the hydrogenation reaction is 0.5-5 MPa, preferably 1-2 MPa, for example 2 MPa.

[0057] In this invention, the reaction time of the hydrogenation reaction can be 1-8 hours, preferably 2-5 hours, such as 3 hours, 4 hours or 5 hours.

[0058] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0059] The reagents and raw materials used in this invention are all commercially available.

[0060] The positive and progressive effects of this invention are as follows:

[0061] (1) The metal catalyst of the present invention achieves high dispersion and small size with a high metal content of 5-51 wt%, with a dispersion of more than 50% and a metal particle size of less than 10 nm; and greatly reduces the cost of catalyst and effectively improves safety.

[0062] (2) Compared with other methods for preparing metal catalysts, the preparation method of the present invention is simpler and has a shorter preparation cycle. During the reaction of the metal source, complexing agent and tetraethyl orthosilicate, metal silicates are generated, which encapsulate the metal particles and prevent the metal particles from growing further, thereby reducing the particle size of the metal particles, improving the dispersion of the metal particles in the support, and the interaction between the metal particles and SiO2 also improves the catalyst performance.

[0063] (3) When the metal catalyst of the present invention is applied to the hydrogenation reaction, it can achieve a high conversion rate of the reaction substrate under relatively mild conditions and obtain a highly selective product.

[0064] In some preferred embodiments, the metal catalyst of the present invention is applied to the hydrogenation of benzene-ring-functionalized nitrobenzene to benzene-ring-functionalized aniline. Complete substrate conversion and a target product selectivity exceeding 98.5% are achieved in ethanol solvent. Side reactions caused by the removal of electron-donating groups (-OH), electron-withdrawing groups (-X), and other reducible groups (such as alkenes, alkynes, aldehydes, nitriles, ketones, etc.) are completely suppressed. The small amount of byproduct obtained is a nitrogen-alkylated product resulting from the solvation effect. By changing the solvent and removing the influence of the solvation effect on product distribution, complete substrate conversion and a target product selectivity exceeding 99.9% can be achieved by increasing the reaction temperature in tetrahydrofuran solvent. Furthermore, this high conversion rate and high selectivity can be maintained even under more demanding reaction conditions. Attached Figure Description

[0065] Figure 1 This is a transmission electron microscope (TEM) image of the Cu / SiO2 catalyst of Example 3 of the present invention.

[0066] Figure 2Energy-dispersive X-ray spectroscopy (EDX) elemental analysis of the Cu / SiO2 catalyst prepared in Example 3. In the image, a is a high-resolution scanning transmission electron microscope image of the Cu / SiO2 catalyst prepared in Example 3, b is the elemental scan of Cu, c is the elemental scan of Si, and d is the elemental scan of O.

[0067] Figure 3 The XRD patterns of the Cu / SiO2 catalysts prepared by the sol-gel method in Examples 3 and 5 of this invention are compared with those of the 15Cu / SiO2-IMP catalyst prepared by the impregnation method in Comparative Example 6.

[0068] Figure 4 The images show the H2-TPR diagrams of Cu / SiO2 catalysts with different loadings prepared in Examples 1-5 of this invention.

[0069] Figure 5 The graph shows a comparison of the catalytic performance of Cu / SiO2 catalysts with different loadings prepared in Examples 1-5 and Example 9 of this invention. Detailed Implementation

[0070] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0071] To make the technical solutions, features and advantages of the present invention more easily understood by those skilled in the art, the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0072] Example 1

[0073] (1) Dissolve 0.303 g of copper nitrate trihydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of anhydrous citric acid and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate to the solution and stir at room temperature for 60 min until a gel is formed. If the thoroughly mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0074] (2) The above gel was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours under an air atmosphere. After that, it was reduced in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours under a hydrogen-argon atmosphere containing 5% hydrogen to obtain the 5Cu / SiO2 catalyst.

[0075] Example 2

[0076] (1) Dissolve 0.640 g of copper nitrate trihydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of complexing agent anhydrous citric acid and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate (silicon source) to the solution and stir at room temperature for 60 min until a gel is formed. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0077] (2) The above gel was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours in an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours in a hydrogen-argon atmosphere containing 5% hydrogen, a 10Cu / SiO2 catalyst was obtained.

[0078] Example 3

[0079] (1) Dissolve 1.017g of copper nitrate trihydrate in 5mL of deionized water, stir for 10min, then add 1.5g of complexing agent anhydrous citric acid and stir for 30min. Once the solid is completely dissolved, add 5.255g of tetraethyl orthosilicate (a silicon source) to the solution and stir at room temperature for 60min until a gel is formed. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0080] (2) The above gel was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours under an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours under a hydrogen-argon atmosphere containing 5% hydrogen, a 15Cu / SiO2 catalyst was obtained.

[0081] Example 4

[0082] (1) Dissolve 1.439 g of copper nitrate trihydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of anhydrous citric acid as a complexing agent and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate (a silicon source) to the solution and stir at room temperature for 60 min until a gel is formed. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0083] (2) The above gel was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours under an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours under a hydrogen-argon atmosphere containing 5% hydrogen, 20Cu / SiO2 catalyst was obtained.

[0084] Example 5

[0085] (1) Dissolve 2.881 g of copper nitrate trihydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of anhydrous citric acid as a complexing agent and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate (a silicon source) to the solution and stir at room temperature for 60 min until a gel is formed. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0086] (2) The above gel was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours under an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours under a hydrogen-argon atmosphere containing 5% hydrogen, 33Cu / SiO2 catalyst was obtained.

[0087] In applications, the 33Cu / SiO2 catalyst was mainly used to explore the optimal reaction conditions for the hydrogenation of p-chloronitrobenzene to p-chloroaniline. The selection of this loading was based on the following criteria:

[0088] Examples 6-8

[0089] The preparation methods of Examples 6-8 are the same as those of Example 5, except that the reduction temperature used in step (2) is different. Specifically, the reduction temperatures of Examples 6-8 are 200℃, 400℃ and 130℃, respectively.

[0090] Examples 5-8 serve as the basis for determining the optimal reduction temperature in catalyst applications. When 33Cu / SiO2 catalysts are involved in applications, the reduction temperature of the catalyst is 300℃ unless specifically emphasized.

[0091] Example 9

[0092] (1) Dissolve 5.761g of copper nitrate trihydrate in 5mL of deionized water, stir for 10min, then add 1.5g of complexing agent anhydrous citric acid and stir for 30min. Once the solid is completely dissolved, add 5.255g of tetraethyl orthosilicate (silicon source) to the solution and stir at room temperature for 60min until a gel is formed. If the thoroughly mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0093] (2) The above gel was dried in an oven at 100°C for 12 hours, and then heated to 400°C in an air atmosphere at a heating rate of 2°C / min for 5 hours. After reduction in a reduction furnace at a hydrogen argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min for 3 hours, 51Cu / SiO2 catalyst was obtained.

[0094] In applications, the 51Cu / SiO2 catalyst was mainly used in conjunction with Examples 1-5 and Example 9 to explore the optimal copper loading for the hydrogenation catalyst of p-chloronitrobenzene. The selection of this loading was based on the following criteria:

[0095] Example 10

[0096] (1) Dissolve 3.668 g of nickel nitrate hexahydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of anhydrous citric acid and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate to the solution and stir at room temperature for 60 min until a gel is formed. If the completely mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0097] (2) The above gel was then dried in an oven at 100°C for 12 hours. Then, in a muffle furnace, under an air atmosphere, the temperature was raised to 400°C at a heating rate of 2°C / min and calcined for 5 hours. After reduction in a reduction furnace under a hydrogen-argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min, the 33Ni / SiO2 catalyst was obtained.

[0098] Comparative Example 1

[0099] (1) Dissolve 3.671 g of cobalt nitrate hexahydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of anhydrous citric acid and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate to the solution and stir at room temperature for 60 min until a gel is formed. If the thoroughly mixed solution is heat-treated and stirred in a water bath at 65-70℃, excess water can be removed more quickly, and a non-degradable gel can be formed in a short time.

[0100] (2) The above catalyst precursor was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours in an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours in a hydrogen-argon atmosphere containing 5% hydrogen, the 33Co / SiO2 catalyst was obtained.

[0101] Comparative Example 2

[0102] The silicon source was changed, but the Cu / SiO2 catalyst was still synthesized using the sol-gel method.

[0103] (1) Dissolve 1.017g of copper nitrate trihydrate in 5mL of deionized water, stir for 10min, then add 1.5g of complexing agent anhydrous citric acid and stir for 30min. Once the solid is completely dissolved, add 14.845g of silica sol to the above solution and stir at room temperature for 60min until a gel is formed.

[0104] (2) The above gel was then dried in an oven at 100°C for 12 hours. Then, in a muffle furnace, under an air atmosphere, the temperature was increased to 400°C at a heating rate of 2°C / min and calcined for 5 hours. After reduction in a reduction furnace under a hydrogen-argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min, the 15Cu / SiO2-sol catalyst was obtained.

[0105] Comparative Example 3

[0106] The silicon source was changed, but the Cu / SiO2 catalyst was still synthesized using the sol-gel method.

[0107] (1) Dissolve 1.017g of copper nitrate trihydrate in 5mL of deionized water, stir for 10min, then add 1.5g of complexing agent anhydrous citric acid and stir for 30min. Once the solid is completely dissolved, add 18.3g of sodium silicate (Na2O·3SiO2) to the above solution and stir at room temperature for 60min until a gel is formed.

[0108] (2) The above gel was then dried in an oven at 100°C for 12 hours. Then, in a muffle furnace, under an air atmosphere, the temperature was increased to 400°C at a heating rate of 2°C / min and calcined for 5 hours. After reduction in a reduction furnace under a hydrogen-argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min, the 15Cu / SiO2-sodiumsil catalyst was obtained.

[0109] Comparative Example 4

[0110] The complexing agent was changed, but the Cu / SiO2 catalyst was still synthesized using the sol-gel method.

[0111] (1) Dissolve 1.017g of copper nitrate trihydrate in 5mL of deionized water, stir for 10min, then add 1.5g of complexing agent ammonia water and stir for 30min. Once the solid is completely dissolved, add 5.255g of tetraethyl orthosilicate to the above solution and stir at room temperature for 60min until a gel is formed.

[0112] (2) The above gel was then dried in an oven at 100°C for 12 hours. Then, in a muffle furnace, under an air atmosphere, the temperature was raised to 400°C at a heating rate of 2°C / min and calcined for 5 hours. After reduction in a reduction furnace under a hydrogen-argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min, the 15Cu / SiO2(TA) catalyst was obtained.

[0113] Comparative Example 5

[0114] The complexing agent was changed, but the Cu / SiO2 catalyst was still synthesized using the sol-gel method.

[0115] (1) Dissolve 1.017 g of copper nitrate trihydrate in 5 mL of deionized water, stir for 10 min, then add 1.5 g of complexing agent oxalic acid and stir for 30 min. Once the solid is completely dissolved, add 5.255 g of tetraethyl orthosilicate to the above solution and stir at room temperature for 60 min until a gel is formed.

[0116] (2) The above gel was then dried in an oven at 100°C for 12 hours. Then, in a muffle furnace, under an air atmosphere, the temperature was increased to 400°C at a heating rate of 2°C / min and calcined for 5 hours. After reduction in a reduction furnace under a hydrogen-argon atmosphere containing 5% hydrogen at a heating rate of 5°C / min, the 15Cu / SiO2 (E296) catalyst was obtained.

[0117] Comparative Example 6

[0118] (1) Nano-silica was selected as the support. Copper nitrate trihydrate was prepared into a solution of a certain mass concentration and impregnated onto the nano-silica by an equal volume impregnation method with a loading of 15 wt%. The catalyst precursor was obtained by ultrasonic vibration.

[0119] (2) The above catalyst precursor was dried in an oven at 100°C for 12 hours, and then calcined in a muffle furnace at 400°C at a heating rate of 2°C / min for 5 hours under an air atmosphere. After reduction in a reduction furnace at 300°C at a heating rate of 5°C / min for 3 hours in a hydrogen-argon atmosphere containing 5% hydrogen, 15Cu / SiO2-IMP catalyst was obtained.

[0120] Effect Example

[0121] 1. In Examples 1-10 and Comparative Examples 1-3, the metal loading was calculated as follows:

[0122]

[0123] 2. In Examples 1-9 and Comparative Examples 1-4, the methods for testing the dispersion, particle size, and specific surface area of ​​the metal are as follows:

[0124] (1) Test method for metal dispersion:

[0125] Cu dispersion test: The number of surface copper atoms was determined using N2O oxidation and H2 titration. In the TPR experiment, the catalyst was first reduced to 300℃ in a 10% H2 / Ar mixture at a flow rate of 30 mL / min. The hydrogen consumption of the first TPR was recorded as x. Then, the reactor was purged to 50℃ with Ar. After oxidizing the surface copper atoms to Cu2O with N2O (30 mL / min) at 50℃, the oxidant was removed by purging with Ar. Finally, the TPR experiment was performed in 10% H2 / Ar at a flow rate of 30 mL / min. The hydrogen consumption of the second TPR was recorded as y. The surface Cu dispersion D was calculated according to the formula: D = (2 × y / x) × 100%.

[0126] Ni dispersion determination: H2 chemisorption pulse chromatography was used, conducted on a micro-pulse reaction apparatus with a catalyst dosage of 150 mg. The sample was reduced in H2 at 700℃ for 1 h, then purged with Ar gas for 20 min to remove the gas phase and adsorbed H2. The sample was then cooled to room temperature (25℃) under Ar atmosphere. Using a TCD detector, after baseline stabilization, a certain amount of H2 was pulsed until no more H2 was adsorbed. The dispersion D was determined based on the amount of H2 adsorbed: D = 2n H2 / n Ni ×100%; n H2 : Number of moles of hydrogen gas consumed; n Ni : Total number of moles of Ni in the catalyst.

[0127] (2) Test method for metal particle size: Import the TEM image into Digital Micrograph software, select more than 100 metal particles for statistical analysis, and obtain the average particle size.

[0128] (3) Test method for specific surface area of ​​metal catalyst: N2 adsorption-desorption test was performed using an adsorption analyzer. The catalyst was degassed at 200℃ for 6 hours, and then the test procedure was carried out at -196℃. The specific surface area data was calculated according to the Brunauer-Emmett-Teller (BET) equation.

[0129] The test results are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] As can be seen from the data in Table 1, under the premise of high metal content, the dispersion of the metal catalyst of the present invention can reach more than 50%, and the dispersion of the copper-based catalyst can reach as high as 69.6%, and the metal particle size is all below 10 nm. It can be seen that it is precisely because the metal silicate exists between the metal particles that it can effectively confine the metal particles. Combined with other technical features, it avoids metal agglomeration or growth, thereby achieving the effect of high dispersion and small particle size, thereby increasing the specific surface area of ​​the metal catalyst and improving the catalytic activity.

[0134] Figure 1 The transmission electron microscope image of the Cu / SiO2 catalyst in Example 3 of this invention shows that the copper particles are uniformly distributed on the support. Figure 2 Energy-dispersive X-ray spectroscopy (EDX) elemental analysis was performed on the Cu / SiO2 catalyst prepared in Example 3. Among them, Figure 2 Image a is a high-resolution scanning transmission electron microscope image of the Cu / SiO2 catalyst, image b is an elemental scan of Cu, image c is an elemental scan of Si, and image d is an elemental scan of O. It can be seen that the copper particles exist between the supports and are encapsulated by the supports, which can effectively confine the copper particles and prevent them from agglomerating or growing.

[0135] 3. Catalytic performance

[0136] Taking the hydrogenation of p-chloronitrobenzene to prepare p-chloroaniline as an example, the advantages of the examples in preparing functionalized aromatic amine compounds are described in detail. When other benzene ring-functionalized nitrobenzenes are used as reaction substrates, the application process and catalytic activity patterns of the examples are similar. The metal catalyst prepared in this invention has shown excellent catalytic performance among several non-noble metal catalysts commonly used in catalytic hydrogenation.

[0137] Test methods for substrate conversion and product selectivity:

[0138] Qualitative analysis of the reaction solution was performed using gas chromatography-mass spectrometry (7890A-5975C), and quantitative analysis was performed using gas chromatography (7890B). The substrate conversion rate was calculated using the internal standard method (with n-decane as the internal standard), and the selectivity of the target product was calculated using the area normalization method. The calculation formulas are as follows:

[0139]

[0140]

[0141] (1) Comparison of the effects of different metal catalysts on catalytic performance

[0142] When the catalysts prepared in Examples 5, 10, and Comparative Example 1 were used to catalyze the hydrogenation reaction of p-chloronitrobenzene, 1g of the reaction substrate p-chloronitrobenzene, 0.1g of catalyst, 6g of ethanol as solvent, and 2MPa of hydrogen gas as hydrogen source were added, the reaction was carried out in batch reactors at 130℃ and 150℃ for 4h, respectively. The conversion rate and product distribution of the reaction substrate in each comparative example and example were measured, and the results are as follows.

[0143] Table 2

[0144]

[0145]

[0146] In the hydrogenation process of benzene ring-functionalized nitrobenzene, the reaction includes a direct hydrogenation route and a coupled hydrogenation route. The gas chromatography-mass spectrometry (GC-MS) captures the intermediate product of the dehydration condensation reaction in the coupled hydrogenation route.

[0147] As shown in Table 2, the Ni / SiO2 catalyst in Example 10 exhibits certain catalytic activity, achieving 100% conversion of p-chloronitrobenzene at 150°C. The intermediate product generated by the coupled hydrogenation route disappears, but the dechlorination product aniline is subsequently produced, reducing the selectivity of the reaction. The Co / SiO2 catalyst in Comparative Example 1 shows the lowest reactivity and suffers from a poor carbon balance. In contrast, the Cu / SiO2 catalyst prepared in Example 5 demonstrates excellent catalytic performance, completely converting the substrate p-chloronitrobenzene at a relatively low reaction temperature. Further increases in reaction temperature do not result in dechlorination side reactions. The small amount of byproduct, nitrogen-alkylated products, is due to the substitution of hydrogen atoms on the amino group of the aromatic amine by alkyl groups in the solvent ethanol, resulting in a nitrogen-alkylation reaction. The Cu / SiO2 catalyst achieves high conversion and high selectivity in the hydrogenation of p-chloronitrobenzene to p-chloroaniline.

[0148] (2) Comparison of the effects of different preparation methods on catalytic performance

[0149] Figure 3The XRD patterns of Examples 3, 5, and Comparative Example 6 of this invention are shown. XRD diffraction was used to obtain the crystal phase information of Cu in different metal catalysts. It was found that Example 3, which exhibits the best catalytic activity, showed almost no obvious Cu diffraction peaks on XRD, indicating that the copper particles in the 15Cu / SiO2 catalyst prepared by the sol-gel method using tetraethyl orthosilicate as the silicon source are small and uniformly dispersed. In contrast, the 15Cu / SiO2-IMP catalyst prepared by the impregnation method in Comparative Example 6 showed sharp Cu diffraction peaks on XRD, indicating a larger Cu grain size. It can be observed that the catalysts prepared by the sol-gel method have a significant advantage in uniformly dispersing the supported active metal copper and maintaining a small particle size; even in Example 5 with a high loading, the copper diffraction peaks on XRD are weak.

[0150] Comparative Examples 2 and 3, and Comparative Examples 4 and 5 employed the same sol-gel method as Example 3. The differences were: in Comparative Examples 2 and 3, silica sol and sodium silicate were used as silicon sources, respectively, to prepare 15Cu / SiO2-sol and 15Cu / SiO2-sodiumsil catalysts; in Comparative Examples 4 and 5, ammonia and oxalic acid were used as complexing agents, respectively, to prepare 15Cu / SiO2(NH3·H2O) and 15Cu / SiO2(OA) catalysts; in Comparative Example 6, a copper nitrate trihydrate solution with the same loading was impregnated onto nano-silica to prepare a 15Cu / SiO2-IMP catalyst. Comparative Examples 2-6 and Example 3 were applied to the hydrogenation reaction of p-chloronitrobenzene: 1g of the substrate p-chloronitrobenzene, 0.1g of catalyst, and 6g of ethanol were added as solvent, and 2MPa hydrogen gas was introduced as the hydrogen source. The reaction was carried out in a batch reactor at 110°C for 4h. The conversion rate of the substrate and the selectivity of the product were measured, and the results are shown in Table 3.

[0151] Table 3

[0152] project catalyst p-Chloronitrobenzene conversion rate (%) Selectivity for p-chloroaniline (%) Comparative Example 2 <![CDATA[15Cu / SiO2-sol]]> 25.5 ＞99.9 Comparative Example 3 <![CDATA[15Cu / SiO2-sodiumsil]]> 29.0 ＞99.9 Comparative Example 4 <![CDATA[15Cu / SiO2(NH3·H2O)]]> 43.5 ＞99.9 Comparative Example 5 <![CDATA[15Cu / SiO2(OA)]]> 42.6 ＞99.9 Comparative Example 6 <![CDATA[15Cu / SiO2-IMP]]> 40.3 ＞99.9 Example 3 <![CDATA[15Cu / SiO2]]> 100 98.6

[0153] As can be seen from the data in Table 3, the preparation method of the metal catalyst and the selection of silicon source and complexing agent have a significant impact on its catalytic activity in the hydrogenation reaction. Comparative Examples 2 and 3 differ from Example 3 only in the use of different silicon sources. Comparative Examples 4 and 5 differ from Example 3 in the use of different complexing agents. When the copper loading is the same, although the metal catalyst prepared in Example 3 has comparable selectivity for p-chloroaniline to Comparative Examples 2-5, its p-chloronitrobenzene conversion rate is more than 60-70% higher than that of Comparative Examples 2-5, exhibiting higher catalytic activity. Comparative Example 6 uses a different preparation method than Example 3, and the p-chloronitrobenzene conversion rate of Example 3 is 59.7% higher than that of Comparative Example 6.

[0154] (3) Comparison of the effects of different copper loading on catalytic effect

[0155] Figure 4 The above are H2-TPR diagrams of Cu / SiO2 catalysts with different loadings prepared in Examples 1-5 of this invention. Figure 4 The study found that the high-temperature reduction peaks of Cu / SiO2 catalysts with different loadings appeared at 219-241℃, and the active metal components could be completely reduced before 300℃. H2-TPR plots revealed that as the copper loading of the catalyst increased, the reduction peak shifted to higher temperatures, indicating that the active metal was more difficult to reduce and that the interaction between the metal and the support was stronger.

[0156] The Cu / SiO2 catalysts with different loadings prepared in Examples 1-5 and Example 9 were used for the hydrogenation reaction of p-chloronitrobenzene: 1g of p-chloronitrobenzene substrate, 0.1g of catalyst, 6g of ethanol as solvent, and 2MPa hydrogen gas as hydrogen source were added. The reaction was carried out in a batch reactor at 110℃ for 4h. The effects of each example on the conversion rate of the reaction substrate and the product distribution were measured. The results are as follows.

[0157] Table 4

[0158] project catalyst p-Chloronitrobenzene conversion rate (%) Selectivity for p-chloroaniline (%) Example 1 <![CDATA[5Cu / SiO2]]> 61.4 ＞99.9 Example 2 <![CDATA[10Cu / SiO2]]> 83.8 ＞99.9 Example 3 <![CDATA[15Cu / SiO2]]> 100 98.6 Example 4 <![CDATA[20Cu / SiO2]]> 100 98.7 Example 5 <![CDATA[33Cu / SiO2]]> 100 98.5 Example 9 <![CDATA[51Cu / SiO2]]> 100 98.5

[0159] pass Figure 5 As shown in Table 4, increasing the copper loading within a certain range is beneficial to improving the conversion rate of the reaction substrate. At a lower loading, although the conversion rate of chloronitrobenzene is only 60%–80%, the selectivity for chloroaniline reaches over 99.9%. When the copper content is increased from 10 wt% to 15 wt%, the conversion rate of chloronitrobenzene increases by 16.2% to 100%, but the selectivity for chloroaniline decreases somewhat, though it still remains at 98.5% or higher. A small amount of byproduct is a nitrogen-alkylated product, which suppresses the dechlorination side reaction. Further increasing the copper loading maintains a substrate conversion rate and reaction selectivity at a level comparable to that at 15 wt%.

[0160] (4) Comparison of the effects of temperature on catalytic performance of different reduction reactions

[0161] The 33Cu / SiO2 catalysts prepared in Examples 5-8 were used to catalyze the hydrogenation reaction of p-chloronitrobenzene: 1g of p-chloronitrobenzene substrate, 0.1g of catalyst, 6g of ethanol as solvent, and 2MPa hydrogen gas as hydrogen source were added. The reaction was carried out in a batch reactor at 130℃ for 4h. The effects of each example on the conversion rate of the reaction substrate and the product distribution were measured. The results are shown in the table below.

[0162] Table 5

[0163] project Reduction temperature (°C) p-Chloronitrobenzene conversion rate (%) Selectivity for p-chloroaniline (%) Example 6 200 100 95.9 Example 5 300 100 96.3 Example 7 400 100 94.9 Example 8 130 100 95.1

[0164] As shown in Table 5, the reduction temperature has a certain influence on the catalytic activity of the Cu / SiO2 catalyst prepared in this invention in the hydrogenation reaction of p-chloronitrobenzene. With changes in reduction temperature, the degree of copper reduction varies within the same time frame. During the catalytic process, the dechlorination side reaction was completely suppressed without the addition of a dechlorination inhibitor. The small amount of byproducts in the product distribution are still nitrogen-alkylated products generated from the nitrogen alkylation reaction of amino groups with the solvent ethanol.

[0165] The metal catalyst of this invention exhibits excellent catalytic performance at different reduction temperatures, with a substrate conversion rate of up to 100% and a target product selectivity of 94.9% or higher. When preparing the Cu / SiO2 catalyst, a reduction temperature of 300°C is used, and the target product selectivity can reach 96.3%, ensuring good application in scale-up experiments or industrial applications.

[0166] (5) Effects of different catalytic reaction conditions on catalytic performance

[0167] The catalytic activity of the catalyst prepared in Example 5 under different reaction conditions (including reaction temperature, hydrogen pressure, and reaction time) was tested, and the test results are shown in Table 6.

[0168] Table 6

[0169]

[0170]

[0171] As shown in Table 6, under different reaction conditions, the Cu / SiO2 catalyst prepared in Example 5 completely suppressed the dechlorination side reaction in the hydrogenation of p-chloronitrobenzene. The small amount of byproducts in the product distribution were nitrogen-alkylated products generated by the nitrogen-alkylation reaction of amino groups with solvent ethanol, and the product selectivity reached over 92.5%. At a hydrogen pressure of 2 MPa, higher reaction temperature led to more nitrogen-alkylated byproducts, but even under harsh reaction conditions, no dechlorination side reaction occurred. At a hydrogen pressure of 1 MPa, higher reaction temperature resulted in a worse carbon balance, and the conversion rate at low pressure was significantly lower than that at the same reaction temperature and time. Therefore, the optimal catalytic reaction conditions for Example 5 in a batch reactor were 110°C with 2 MPa hydrogen for 4 hours, achieving complete conversion of p-chloronitrobenzene and a 98.5% selectivity for p-chloroaniline.

[0172] After verification, this principle also applies to the application of the Cu / SiO2 catalyst described in other embodiments in the hydrogenation reaction of benzene ring-functionalized nitrobenzene.

[0173] (6) The effect of other reaction media on catalytic activity

[0174] As can be seen from the applications of the above embodiments, the metal catalyst prepared by the present invention can suppress the occurrence of functional group removal side reactions under various reaction conditions. Based on the complete conversion of the benzene ring-functionalized nitrobenzene substrate, the target product can be obtained with high selectivity. A small amount of byproduct is the nitrogen-alkylated byproduct generated when the hydrogen atom on the amino group of the aromatic amine is replaced by the alkyl group in the solvent ethanol. The present invention also investigated the hydrogenation effect of p-chloronitrobenzene in other media, finding that the metal catalyst of the present invention can be applied to various reaction media, thereby eliminating byproducts generated due to solvation effects and further improving the selectivity of p-chloroaniline. The conditions for the hydrogenation reaction of p-chloronitrobenzene in a batch reactor were: 1g of the reactant p-chloronitrobenzene, 0.1g of catalyst, 6g of solvent, and 2MPa hydrogen gas as the hydrogen source, reacting at different reaction temperatures for 4 hours in a batch reactor. Table 7 mainly lists the effects of the catalyst of Example 4 on the conversion rate of the reactant substrate and the selectivity of the product in ethanol and tetrahydrofuran solvent.

[0175] Table 7

[0176] solvent Reaction temperature (°C) p-Chloronitrobenzene conversion rate (%) Selectivity for p-chloroaniline (%) ethanol 110 100 98.7 ethanol 130 100 97.5 ethanol 150 100 94.5 Tetrahydrofuran 150 100 ＞99.9 Tetrahydrofuran 180 100 ＞99.9 Toluene 180 100 ＞99.9

[0177] Table 7 shows that the statistical catalyst of this invention can be applied to a variety of reaction media. In ethanol solvent: although increasing the reaction temperature does not produce dechlorination side reactions, the nitrogen alkylation reaction caused by the reaction of amino groups with ethanol may reduce the selectivity of the target product. Although the catalytic activity in tetrahydrofuran in Example 4 decreased, increasing the temperature can completely convert the substrate and eliminate the effect of the solvent on the product distribution. The selectivity for p-chloroaniline is higher than 99.9%, based on the fact that no other products besides the target product p-chloroaniline are observed on gas chromatography-mass spectrometry. Furthermore, in tetrahydrofuran solvent, p-chloronitrobenzene can still be completely converted under more stringent reaction conditions, maintaining a p-chloroaniline selectivity of higher than 99.9%.

[0178] (7) Effects of metal catalysts on hydrogenation reactions of different substrates

[0179] Taking o-chloronitrobenzene, m-chloronitrobenzene, p-hydroxynitrobenzene and o-nitrobenzene as examples, when Example 3 was used for the selective hydrogenation of their benzene ring functionalization: 1g of reaction substrate, 0.1g of catalyst, 6g of ethanol / tetrahydrofuran solvent were added, and 2MPa of hydrogen gas was introduced as the hydrogen source. The reaction was carried out in a batch reactor for 4h. The conversion rate and product distribution of the example in different reaction substrates were measured. The results are shown in Table 8.

[0180] Table 8

[0181]

[0182]

[0183] As shown in Table 8, the metal catalyst in this invention can catalyze the selective hydrogenation of various benzene-ring-functionalized nitrobenzenes, exhibiting good substrate versatility. Even when easily reducible groups are present in the reactant molecule, it can still selectively reduce the nitro group while preserving other groups, completely suppressing side reactions involving the removal of functional groups. However, in ethanol solvent, at high temperatures, the hydrogen atom in the amino group of the aromatic amine is easily replaced by the alkyl group in the solvent ethanol, resulting in a nitrogen alkylation reaction, and the small amount of nitrogen alkylation products produced is unavoidable. The catalytic hydrogenation reaction in tetrahydrofuran solvent eliminates the aforementioned solvation effect. By increasing the temperature, benzene-ring-functionalized nitrobenzenes can achieve a selectivity of over 99.9% while maintaining 100% conversion. The target products obtained by hydrogenation, benzene-ring-functionalized aromatic amine compounds and intermediates, have significant application value and are widely used in pharmaceuticals, pesticides, dyes, fragrances, and the synthesis of functional polymers.

[0184] The above description is merely a preferred embodiment of the present invention, and the embodiments of the present invention are not limited to the described embodiments. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a metal catalyst in a hydrogenation reaction, characterized in that, The preparation method of the metal catalyst includes the following steps: (1) Add the silicon source to the mixture of the metal source and the complexing agent, and stir until a gel is formed; the silicon source is tetraethyl orthosilicate; the metal source is copper source; the complexing agent is one or more of citric acid, tartaric acid and malic acid; (2) The gel obtained in step (1) is subjected to drying, calcination and reduction reaction in sequence to obtain the metal catalyst; the heating rate of the calcination is 1-10℃ / min; the temperature of the reduction reaction is 200-300℃; The content of the metal is 15wt%-51wt%, where the content is the percentage of the mass of the metal to the total mass of the metal catalyst; The reaction substrate for the hydrogenation reaction is compound II: Ⅱ， In compound II, R is one or more of -Cl, -OH, or -OCH3.

2. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The solvent for the hydrogenation reaction is one or more of methanol, ethanol, isopropanol, tetrahydrofuran, toluene, and p-xylene. And / or, the mass ratio of the reaction substrate to the metal catalyst in the hydrogenation reaction is 1000:1 to 1:1; And / or, the mass ratio of the reaction substrate to the solvent in the hydrogenation reaction is 1:1 to 1:60; And / or, the hydrogen pressure in the hydrogenation reaction is 0.5-5 MPa; And / or, the reaction time of the hydrogenation reaction is 1-8 h.

3. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The solvent for the hydrogenation reaction is ethanol or tetrahydrofuran; And / or, the mass ratio of the reaction substrate to the metal catalyst in the hydrogenation reaction is 100:1 to 10:1; And / or, the mass ratio of the reaction substrate to the solvent in the hydrogenation reaction is 1:6 to 1:10; And / or, the hydrogen pressure of the hydrogenation reaction is 1-2 MPa; And / or, the reaction time of the hydrogenation reaction is 2-5 hours.

4. The application of the metal catalyst as described in claim 3 in hydrogenation reactions, characterized in that, The mass ratio of the reaction substrate to the metal catalyst in the hydrogenation reaction is 10:1; And / or, the mass ratio of the reaction substrate to the solvent in the hydrogenation reaction is 1:6; And / or, the hydrogen pressure of the hydrogenation reaction is 2 MPa; And / or, the reaction time of the hydrogenation reaction is 3h, 4h or 5h.

5. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The metal content is 15wt%-33wt%, where the content is the percentage of the metal's mass to the total mass of the metal catalyst; And / or, the molar ratio of the silicon source to the complexing agent is 1:0.2-1:1; And / or, the molar ratio of the complexing agent to the solvent in the mixture is 1:20 to 1:100; And / or, the copper source is at least one of copper sulfate, copper chloride, and copper nitrate.

6. The application of the metal catalyst as described in claim 5 in hydrogenation reactions, characterized in that, The metal content is 15 wt%; And / or, the molar ratio of the silicon source to the complexing agent is 1:0.31 or 1:0.39; And / or, the molar ratio of the complexing agent to the solvent in the mixture is 1:35; And / or, the copper source is copper nitrate trihydrate.

7. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The temperature at which the gel is formed is 5-70℃; And / or, the stirring time is 30-90 min; And / or, the drying temperature is 80-100°C; And / or, the drying time is 8-15 hours; And / or, the calcination is carried out in an air atmosphere; And / or, the calcination temperature is 300-800℃; And / or, the heating rate of the calcination is 2°C / min; And / or, the calcination time is 3-8 h.

8. The application of the metal catalyst as described in claim 7 in hydrogenation reactions, characterized in that, The temperature at which the gel is formed is 20-65℃; And / or, the stirring time is 60 min; And / or, the drying temperature is 100°C; And / or, the drying time is 12 hours; And / or, the calcination temperature is 400°C; And / or, the calcination time is 5 hours.

9. The application of the metal catalyst as described in claim 8 in hydrogenation reactions, characterized in that, The temperature at which the gel is formed is 25°C or 65°C.

10. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The reducing gas in the reduction reaction is hydrogen or a hydrogen-argon mixture. And / or, the temperature of the reduction reaction is 200°C or 300°C; And / or, the heating rate of the reduction reaction is 1-10 °C / min; And / or, the reduction reaction takes 1-6 hours.

11. The application of the metal catalyst as described in claim 10 in a hydrogenation reaction, characterized in that, The reducing gas in the reduction reaction is a mixture of hydrogen and argon; And / or, the heating rate of the reduction reaction is 5 °C / min; And / or, the reduction reaction takes 3 hours.

12. The application of the metal catalyst as described in claim 11 in hydrogenation reactions, characterized in that, The hydrogen volume fraction in the hydrogen-argon mixture is 5%.

13. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The metal catalyst comprises several metal particles and a silicon-based support, wherein: The content of the metal particles is 15wt%-51wt%, where the content is the percentage of the mass of the metal particles to the total mass of the metal catalyst; the metal particles are Cu particles. The metal particles are dispersed in the silicon-based support, and the dispersion of the metal particles in the metal catalyst is 50-70%. The silicon-based support comprises SiO2 and metal silicates; the metal silicates are present between the metal particles; The specific surface area of ​​the metal catalyst is 430-700 m². 2 / g.

14. The application of the metal catalyst as described in claim 1 in hydrogenation reactions, characterized in that, The metal catalyst comprises several metal particles and a silicon-based support, wherein: The metal particles have a particle size of less than 10 nm, and the metal particles are Cu particles; The metal particles are dispersed in the silicon-based support, and the dispersion of the metal particles in the metal catalyst is 50-70%. The silicon-based support comprises SiO2 and metal silicates; the metal silicates are present between the metal particles; The specific surface area of ​​the metal catalyst is 430-700 m². 2 / g.

15. The application of the metal catalyst as described in claim 13 or 14 in hydrogenation reactions, characterized in that, The particle size of the metal particles is 2.0-3.2 nm; And / or, the dispersion of the metal particles is 57-70%; And / or, the content of the metal particles is 15wt%-33wt%, where the content is the percentage of the mass of the metal particles to the total mass of the metal catalyst; And / or, the specific surface area of ​​the metal catalyst is 431.7 m². 2 / g、442.8 m 2 / g、463.1 m 2 / g, 475.6 m 2 / g、476.7 m 2 / g, 509.8 m 2 / g、565.8 m 2 / g、694.3 m 2 / g or 698.5 m 2 / g.

16. The application of the metal catalyst as described in claim 15 in hydrogenation reactions, characterized in that, The dispersion of the metal particles is 57.3-69.6%; And / or, the content of the metal particles is 15 wt%.

17. The application of the metal catalyst as described in claim 16 in hydrogenation reactions, characterized in that, The dispersion of the metal particles is 57.3%, 58.4%, 60.5%, 63.8%, or 69.6%.

Images