Catalyst for reductive amination of aldehyde ketone compounds, preparation method and application thereof

Abstract

The application discloses a catalyst for reductive amination of aldehyde ketone compounds and a preparation method and application thereof. The catalyst comprises a full-silica type molecular sieve and metal particles; the metal particles are distributed in the interior of the full-silica type molecular sieve; the average linear size of the crystal grains of the catalyst is 50-100 nm; the particle size of the metal particles is 0.5-4 nm; the mass percentage of the metal particles is 0.1-10 wt% based on the mass of the catalyst; and the metal elements in the metal particles are selected from at least one of Pd, Pt, Rh, Cu, Ni, Co, Zn and Ag. The catalyst can be applied to reductive amination reaction of aldehyde ketone compounds.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalyst, in particular to a catalyst for the reductive amination of aldehyde ketone compounds, a preparation method and application thereof. BACKGROUND

[0002] Primary amines are important chemicals and are widely used in the synthesis of dyes, agricultural chemicals, pharmaceuticals, detergents and polymers. There are several methods for the synthesis of primary amines, such as reductive amination of carbonyl compounds and alcohols, hydrogenation amination of olefins, amination of aryl halides, and reduction of specific nitrogen sources (amides, nitriles and nitro compounds). Among these methods, the reductive amination of carbonyl compounds (ketones or aldehydes) with ammonia (NH3) as the nitrogen source and H2 as the reducing agent is a particularly cost-effective and atom-efficient method, which can greatly reduce the generation of by-products.

[0003] Taking the process of reductive amination of furfural to tetrahydrofurfurylamine as an example, the aldehyde group first reacts with ammonia to form a primary imine, and then the primary imine reacts with hydrogen under the action of a metal catalyst to form furfurylamine and / or tetrahydrofurfurylamine. In this process, in order to improve the selectivity of tetrahydrofurfurylamine, a metal with strong hydrogenation ability is needed to hydrogenate the carbon-carbon double bond, and at the same time, the further hydrogenation of Schiff base to generate coupling products such as difurfurylamine and ditetrahydrofurfurylamine is also needed to be minimized (see document: Energy Environ. Sci., 2016, 9, 1144-1189).

[0004] US4598159 discloses that furfural is used as a raw material, dioxane and tetrahydrofurfurylamine are used as solvents, and Raney nickel is used to catalyze the hydrogenation reductive amination of furfural to tetrahydrofurfurylamine. After reacting for 6 hours under the reaction conditions of 150℃ and 3MPa H2, the conversion rate of furfural reaches 100%, and the selectivity of tetrahydrofurfurylamine is 89%. In the process, tetrahydrofurfurylamine is used as a solvent, which inevitably introduces by-products of secondary amines and tertiary amines. There is also a document (Catal. Sci. Technol., 2017, 7, 4129-4135) reporting that furfural is used as a raw material, tetrahydrofuran is used as a solvent, and Raney nickel is used to catalyze the hydrogenation reductive amination of furfural to tetrahydrofurfurylamine. After reacting for 48 hours under the reaction conditions of 180℃ and 1MPa H2, the conversion rate of furfural reaches 98.2%, and the selectivity of tetrahydrofurfurylamine is 95.7%.

[0005] CN105481701A discloses a preparation method of an itopride intermediate. In the method, p-hydroxybenzaldehyde, a base and ammonia water are used as raw materials, and Raney nickel is used to catalyze the hydrogenation reduction to obtain p-hydroxybenzylamine. However, Raney nickel catalyst is not stable and is easily oxidized and combusted in air.

[0006] Therefore, it is of great significance to develop a heterogeneous catalyst with high activity and high selectivity for the production of primary amines.

[0007] CN115487825A discloses a catalyst for the reductive amination of furfural and a preparation method thereof, which is represented as M1 / M2M3AlOx, wherein: M1 is a noble metal active component, M2M3AlOx is a carrier; the loading amount of M1 is 0.1-1wt%; the average particle size of M1 is 2.4-2.8nm, and the dispersion degree is 40-50%. The carrier M2M3AlOx is a composite metal oxide formed by topological transformation of hydrotalcite M2M3Al-LDHs, wherein the coordination structure of Al contains four-coordination and six-coordination, and the ratio of four-coordination aluminum to six-coordination aluminum is 40-60%.

[0008] While metal / molecular sieve catalysts have gradually become a research hotspot in recent years, they can combine the characteristics of metals and the shape-selective advantages of molecular sieve channels, and are widely used in biomass catalytic conversion, catalytic deoxygenation of phenols, catalytic reforming and other reactions.

[0009] CN111054432A discloses a catalyst for preparing hexamethylenediamine and a preparation method and application thereof. The catalyst is a noble metal catalyst encapsulated by HZSM-5 molecular sieve, which is used as a catalyst to catalyze the reductive amination of hexamethylenedial to prepare hexamethylenediamine. SUMMARY

[0010] Therefore, one object of the present application is to provide a catalyst for the reductive amination of aldehyde ketone compounds, which contains a full-silica type molecular sieve and metal particles, and can be used for the reductive amination of aldehyde ketone compounds to generate primary amines, especially with high conversion rate and selectivity in the reductive amination of furfural and benzaldehyde. Another object of the present application is to provide a preparation method of the catalyst. Still another object of the present application is to provide the application of the catalyst. The above objects are achieved by the following technical solutions.

[0011] In one aspect, the present application provides a catalyst for the reductive amination of aldehyde ketone compounds, which comprises a full-silica type molecular sieve and metal particles; wherein,

[0012] The metal particles are distributed in the interior of the full-silica type molecular sieve;

[0013] The average linear size of the crystal grains of the catalyst is 50-100nm;

[0014] The particle size of the metal particles is 0.5-4nm; the mass percentage content of the metal particles is 0.1-10wt% based on the mass of the catalyst; and the metal element in the metal particles is selected from at least one of Pd, Pt, Rh, Cu, Ni, Co, Zn and Ag. Such a catalyst can be used as a catalyst in the reductive amination of aldehyde ketone compounds, which can improve the conversion rate of raw materials and the selectivity of target products.

[0015] In the present application, the average linear dimension refers to the mean value of the linear dimension of the crystal grains in the SEM image, i.e. the average value of the particle size of the crystal grains.

[0016] The catalyst of the present application is a full-silica type molecular sieve encapsulated metal particle catalyst, and the metal particles are distributed in the interior of the molecular sieve. The metal particles are substantially uniformly distributed in the interior of the full-silica type molecular sieve. In the present application, the alumina content of the full-silica type molecular sieve is substantially zero, and it can also be referred to as Silicalite-1 molecular sieve.

[0017] The particle size of the metal particles is 0.5-4 nm, preferably 1-3 nm. For example, it can be 2 nm, 2.5 nm, 3 nm, 3.5 nm or 4 nm.

[0018] The mass percentage content of the metal particles is 0.1-10 wt% based on the mass of the catalyst, preferably 0.2-8 wt%. For example, it can be 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 3.0 wt%, 5.0 wt% or 7.0 wt%. Such a catalyst can both improve the conversion rate of the raw material and maintain a high selectivity of the target product.

[0019] The average linear dimension of the crystal grains of the catalyst is 50-100 nm, preferably 50-90 nm. For example, it can be 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0020] The catalyst of the present application is formed by stacking crystal grains of about 80 nm in size in the shape of hexagonal prisms, and the crystal grains are uniform in size and have a relatively large specific surface area, which is beneficial to increasing the reaction sites and improving the mass transfer rate, so that when it is used in the catalytic reductive amination reaction of carbonyl compounds such as ketones or aldehydes, it has excellent catalytic activity and structural stability. In the process of catalyzing the reductive amination reaction of furfural, the conversion rate of furfural can reach 100%, and it also has high selectivity to the product tetrahydrofurfurylamine. In the process of catalyzing the reductive amination reaction of benzaldehyde, the conversion rate of benzaldehyde can reach 100%, and the selectivity to the product benzylamine is also significantly improved.

[0021] The catalyst of the present application is formed from raw materials including a metal particle precursor and a silicon-containing substance capable of forming a full-silica type molecular sieve; wherein the metal particle precursor includes a water-soluble metal salt, and preferably a complex solution of a water-soluble metal salt-ethylenediamine. The silicon-containing substance is selected from silicate or alkaline silica sol.

[0022] According to the catalyst of the present application, preferably, the morphology of the crystal grains of the catalyst is substantially hexagonal prism shape. Such morphology is beneficial to expanding the specific surface area.

[0023] According to the catalyst of the present application, preferably, the metal element in the metal particle is selected from one of Pd, Pt, Rh, Cu and Ni. More preferably, it is selected from one of Pd, Pt and Rh. This is advantageous for improving the conversion of raw materials and the selectivity of target products in the reductive amination reaction of aldehyde or ketone compounds.

[0024] In another aspect, the present application also provides a preparation method of the catalyst as described above, comprising the following steps:

[0025] 1) mixing a silicon-containing substance, alkyl ammonium hydroxide, a metal particle precursor and water and stirring at 20-45℃ to obtain a sol-gel;

[0026] 2) preliminarily crystallizing the obtained sol-gel at 70-100℃ to form nuclei, then increasing the temperature to 160-180℃ to continue the crystallization, and solid-liquid separation to obtain a solid;

[0027] 3) washing, drying and calcining the obtained solid at 500-600℃, then reducing in a hydrogen atmosphere at 350-450℃ to obtain the catalyst;

[0028] wherein,

[0029] the silicon-containing substance is selected from silicate or basic silicon sol; the alkyl ammonium hydroxide is selected from at least one of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, dimethyl diethyl ammonium hydroxide and dimethyl dipropyl ammonium hydroxide; and the metal particle precursor is a complex solution of water-soluble metal salt-ethylenediamine;

[0030] the molar ratio of silicon element in the silicon-containing substance, alkyl ammonium hydroxide and water is 1:0.1-0.4:15-25;

[0031] the molar ratio of metal element in the water-soluble metal salt and silicon element in the silicon-containing substance is 0.0004-0.055:1. This is advantageous for obtaining a full-silica type molecular sieve encapsulated metal particle catalyst with specific morphology and particle size suitable for the reductive amination reaction of aldehyde or ketone compounds.

[0032] In the present application, the silicon-containing substance is selected from silicate or basic silicon sol, preferably silicate. The silicate is selected from at least one of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate and butyl orthosilicate, preferably ethyl orthosilicate.

[0033] The alkyl ammonium hydroxide is preferably tetrapropyl ammonium hydroxide.

[0034] The molar ratio of silicon element in the silicon-containing material to the alkyl ammonium hydroxide can be 1:0.1-0.4, preferably 1:0.2-0.3. The molar ratio of silicon element to water can be 1:15-25, preferably 1:18-24, more preferably 1:19-21, for example 1:20. The molar ratio of metal element in the water-soluble metal salt to silicon element in the silicon-containing material can be 0.0004-0.055:1, preferably 0.0004-0.045:1, so that the mass percentage of metal particles in the catalyst can be 0.1-10wt% based on the mass of the catalyst.

[0035] In the present application, the washing is preferably water washing, and the washing is preferably to a pH value of 7 (neutral) of the washing liquid.

[0036] According to the preparation method of the present application, preferably, the silicon ester is at least one of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate and butyl orthosilicate.

[0037] According to the preparation method of the present application, preferably, the silicon ester is ethyl orthosilicate.

[0038] According to the preparation method of the present application, preferably, the alkyl ammonium hydroxide is tetrapropyl ammonium hydroxide.

[0039] According to the preparation method of the present application, preferably, the preparation method comprises the following specific steps:

[0040] 1) mixing the silicon-containing material, the alkyl ammonium hydroxide, the water-soluble metal salt-ethylenediamine complex solution and water, and stirring at 20-45℃ for 6-12h to obtain a sol-gel;

[0041] 2) preliminarily crystallizing and nucleating the obtained sol-gel at 70-100℃ for 24-48h, then increasing the temperature to 160-180℃ for further crystallization for 12-72h, and solid-liquid separation to obtain a solid;

[0042] 3) washing and drying the obtained solid, calcining at 500-600℃ for 3-12h, and then reducing in a hydrogen atmosphere at 350-450℃ for 1.5-4h to obtain the catalyst.

[0043] The present application finds that in the step of obtaining a sol-gel, the amount of water and the temperature range need to be controlled, and if the amount of water and the temperature range are not within the range of the present application, it is not conducive to the formation of a nanometer catalyst for the reductive amination of aldehyde and ketone compounds.

[0044] The present application finds that the time for preliminary crystallization and nucleation cannot be too short or too long, and it has an influence on the formation of a nanometer catalyst. The temperature for preliminary crystallization and nucleation cannot be too high or too low, and it also has an influence on the formation of a nanometer catalyst.

[0045] In step 1), the mixing temperature is 20-45°C, preferably 20-40°C, for example 30°C, 35°C. The stirring time can be 6-12h, preferably 8-10h. The feeding ratio of each substance is as described above, and is not repeated here.

[0046] In step 2), the temperature for initial crystallization nucleation can be 70-100°C, preferably 75-95°C, more preferably 80-90°C. The time for initial crystallization nucleation can be 24-48h, preferably 24-36h. The temperature for continued crystallization can be 160-180°C, preferably 170-175°C. The time for continued crystallization can be 12-72h, preferably 20-72h, for example 70-72h. The solid-liquid separation can be centrifugation.

[0047] In step 3), the temperature for drying can be 100-120°C, preferably 105-110°C. The time for drying can be 2-10h, preferably 4-8h. The temperature for calcination can be 500-600°C, preferably 520-570°C, for example 550°C. The time for calcination can be 3-12h, preferably 6-10h. After calcination, the temperature is lowered to 30-50°C. Then the temperature is raised to the temperature for reduction in the next step, with a temperature raising rate of 2-11°C / min, preferably 3-5°C / min. The temperature for reduction in a hydrogen atmosphere can be 350-450°C, preferably 380-420°C, for example 400°C. The time for reduction can be 1.5-4h, preferably 2-3h.

[0048] In another aspect, the present application further provides the use of the catalyst as described above as a catalyst for the reductive amination of aldehyde ketone compounds.

[0049] According to the use of the present application, preferably, the aldehyde ketone compound comprises furfural, benzaldehyde; the target product of reductive amination of the furfural is tetrahydrofurfurylamine; the target product of reductive amination of the benzaldehyde is benzylamine. In some preferred embodiments, the aldehyde ketone compound is selected from furfural or benzaldehyde.

[0050] The catalyst of the present application is a nano catalyst, which comprises a full-silica type molecular sieve and metal particles, and the metal particles are distributed in the interior of the full-silica type molecular sieve. The catalyst can be applied to the reductive amination reaction of aldehyde ketone compounds, so that the selectivity of the target product is higher, and the conversion rate of the raw material aldehyde ketone compound is higher. The preparation method of the present application can obtain a catalyst with specific morphology and particle size for the reductive amination of aldehyde ketone compounds. According to the preferred technical solution of the present application, the nano catalyst with specific morphology suitable for the reductive amination of aldehyde ketone compounds of the present application is obtained by using a silicon-containing substance, tetrapropylammonium hydroxide, water, and a water-soluble metal salt-ethylenediamine complex solution, controlling the amount of them within a specific range, and controlling the temperature and crystallization nucleation time. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is an X-ray diffraction pattern of the catalyst prepared in Example 1 of the present application;

[0052] Figure 2 is an SEM image of the catalyst prepared in Example 1 of the present application;

[0053] Figure 3 is a TEM image of the catalyst prepared in Example 1 of the present application;

[0054] Figure 4 is an X-ray diffraction pattern of the catalyst prepared in Example 3 of the present application;

[0055] Figure 5 is an SEM image of the catalyst prepared in Example 3 of the present application;

[0056] Figure 6 is a TEM image of the catalyst prepared in Example 3 of the present application;

[0057] Figure 7 is an X-ray diffraction pattern of the catalyst prepared in Examples 4, 5, 6, 7, 8 and 9 of the present application;

[0058] Figure 8 is an X-ray diffraction pattern of the catalyst prepared in Comparative Example 1 of the present application;

[0059] Figure 9 is an SEM image of the catalyst prepared in Comparative Example 1 of the present application;

[0060] Figure 10 is an X-ray diffraction pattern of the catalyst prepared in Comparative Example 2 of the present application;

[0061] Figure 11 is an SEM image of the catalyst prepared in Comparative Example 2 of the present application;

[0062] Figure 12 is a TEM image of the catalyst prepared in Comparative Example 2 of the present application;

[0063] Figure 13 is an X-ray diffraction pattern of the catalyst prepared in Comparative Examples 3, 4, and 5 of the present application;

[0064] Figure 14 is a SEM image of the catalyst prepared in Comparative Example 3 of the present application;

[0065] Figure 15 is a SEM image of the catalyst prepared in Comparative Example 4 of the present application;

[0066] Figure 16 is a SEM image of the catalyst prepared in Comparative Example 5 of the present application. DETAILED DESCRIPTION

[0067] <Analysis method>

[0068] The analysis method or analysis equipment used in the examples and comparative examples of the present application is described below:

[0069] X-ray diffraction pattern: Bruker D8 advance X-ray powder diffractometer was used.

[0070] SEM image: Regulus 8100 scanning electron microscope produced by Japan HITACHI Company was used; test conditions: after drying treatment of the sample, vacuum evaporation was performed to increase the conductivity and contrast effect, the accelerating voltage of the analysis electron microscope was 20.0 kV, and the magnification was 30-110K.

[0071] TEM image: JEOL-JEM-2100F field emission transmission electron microscope was used; test conditions: after drying treatment of the sample, vacuum evaporation was performed to increase the conductivity and contrast effect, the accelerating voltage of the analysis electron microscope was 20.0 kV, and the magnification was 1-20K.

[0072] Elemental analysis: the content of metal atoms in the molecular sieve was tested by using the inductively coupled plasma atomic emission spectrometer (ICP-OES) of Germany Varian Company. Before characterization, the sample was digested in an aqueous HF solution at room temperature.

[0073] Example 1

[0074] Tetraethyl orthosilicate, tetrapropylammonium hydroxide, a complex solution of palladium chloride-ethylenediamine, and deionized water were mixed, and stirring was performed at 30°C for 8h to obtain a sol-gel. The molar ratio of silicon element in tetraethyl orthosilicate, tetrapropylammonium hydroxide, and deionized water was 1:0.2:20, and the molar ratio of silicon element to palladium element was 1:0.0045.

[0075] The sol-gel obtained above was placed in a crystallization kettle, and was initially crystallized at 80℃ for 24h, then the temperature was raised to 170℃ and the crystallization was continued for 72h, and the solid was obtained by centrifugation.

[0076] The solid obtained above was washed with water until neutral, dried at 100℃, and the temperature was raised to 500℃ at a rate of 2℃ / min, and the calcination was carried out at this temperature for 10h, the temperature was lowered to 40℃, and the temperature was raised to 400℃ at a rate of 3℃ / min, and the reduction was carried out at this temperature under hydrogen atmosphere for 2h, and the catalyst was obtained. The X-ray diffraction pattern is shown in Figure 1 , and the SEM and TEM images are shown in Figure 2 and Figure 3 .

[0077] As can be seen from Figure 1 , the diffraction pattern shows that the catalyst is a full-silica type molecular sieve (i.e. Silicalite-1 molecular sieve), and there is no characteristic diffraction peak corresponding to the palladium element, indicating that no large Pd particles are formed in the sample after synthesis. As can be seen from Figure 2 and Figure 3 , the catalyst obtained in this example has a uniform morphology, and is basically in the form of hexagonal prism, and the average linear size of the crystal grains is 67nm. The surface of the catalyst is smooth, and there is no obvious particulate matter. The metal Pd nanoparticles are uniformly encapsulated by the full-silica type molecular sieve, and the particle size is 1.7-3.0nm. According to the elemental analysis, the content of the metal Pd element in the catalyst is 0.91wt%, which is consistent with the theoretical feeding.

[0078] Example 2

[0079] Except for the following parameters and settings, the rest is the same as in Example 1: the molar ratio of silicon element to palladium element is 1:0.0025.

[0080] The X-ray diffraction pattern of the catalyst obtained in this example shows that it is a full-silica type molecular sieve (i.e. Silicalite-1 molecular sieve), and there is no characteristic diffraction peak corresponding to the palladium element. The catalyst obtained has a uniform morphology, and is basically in the form of hexagonal prism, and the average linear size of the crystal grains is 60nm. The surface of the catalyst is smooth, and there is no obvious particulate matter. The metal Pd nanoparticles are uniformly encapsulated, and the particle size is 1.6-3.2nm. According to the elemental analysis, the content of the metal Pd element in the catalyst is 0.42wt%, which is consistent with the theoretical feeding.

[0081] Example 3

[0082] Except for the following parameters and settings, the rest is the same as in Example 1: the complex solution of palladium chloride-ethylenediamine is replaced by the complex solution of rhodium chloride trihydrate-ethylenediamine.

[0083] The X-ray diffraction pattern of the catalyst obtained in this example is shown inFigure 4 As shown in Figure 4 It can be seen that the diffraction pattern shows a full-silica type molecular sieve (i.e. Silicalite-1 molecular sieve) without any characteristic diffraction peak corresponding to rhodium element. The SEM and TEM results of the catalyst obtained in this example are shown in Figure 5 and Figure 6 As shown in Figure 5 and Figure 6 It can be seen that the catalyst obtained in this example has a uniform morphology and basically presents a hexagonal prism shape, and the average linear size of the crystal grains is 76 nm. The surface of the catalyst is smooth without obvious granular substances. The metal Rh nanoparticles are uniformly encapsulated with a particle size of 1.4-2.7 nm. According to elemental analysis, the content of the metal Rh element in the catalyst is 0.87wt%, which is consistent with the theoretical feeding.

[0084] Example 4

[0085] Except for the following parameters and settings, the rest are the same as in Example 1: the complex solution of palladium chloride-ethylenediamine is replaced by the complex solution of chloroplatinic acid-ethylenediamine, and the molar ratio of silicon element to platinum element is 1:0.005.

[0086] The X-ray diffraction pattern of the catalyst prepared in this example is shown in Figure 7 As shown in Figure 7 It can be seen that the diffraction pattern shows a full-silica type molecular sieve (i.e. Silicalite-1 molecular sieve) without any characteristic diffraction peak corresponding to platinum element. The catalyst obtained in this example has a uniform morphology and basically presents a hexagonal prism shape, and the average linear size of the crystal grains is 79 nm. The surface of the catalyst is smooth without obvious granular substances. The metal Pt nanoparticles are uniformly encapsulated with a particle size of 1.7-2.7 nm. According to elemental analysis, the content of the metal Pt element in the catalyst is 0.96wt%, which is consistent with the theoretical feeding.

[0087] Example 5

[0088] Except for the following parameters and settings, the rest are the same as in Example 1: the complex solution of palladium chloride-ethylenediamine is replaced by the complex solution of copper nitrate trihydrate-ethylenediamine.

[0089] The X-ray diffraction pattern of the catalyst prepared in this example is shown in Figure 7 As shown in Figure 7The diffraction pattern shows that it is an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to copper. The obtained catalyst has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 76 nm for its grains. The catalyst surface is smooth, without obvious particulate matter. The metallic Cu nanoparticles are uniformly encapsulated, with a particle size of 2.1–3.5 nm. Elemental analysis shows that the content of metallic Cu in the catalyst is 0.91 wt%, consistent with the theoretical feed content.

[0090] Example 6

[0091] Except for the following parameters and settings, the rest are the same as in Example 1: the palladium chloride-ethylenediamine complex solution is replaced with the nickel nitrate hexahydrate-ethylenediamine complex solution, and the molar ratio of silicon to Ni is 1:0.018.

[0092] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 7 As shown, by Figure 7 The diffraction pattern shows that it is an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to nickel. The obtained catalyst has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 80 nm for its grains. The catalyst surface is smooth, without obvious particulate matter. The metallic Ni nanoparticles are uniformly encapsulated, with a particle size of 2–4 nm. Elemental analysis shows that the content of metallic Ni in the catalyst is 3.74 wt%, consistent with the theoretical feed content.

[0093] Example 7

[0094] Except for the following parameters and settings, everything else is the same as in Example 1: the initial crystallization nucleation time is replaced with 48h.

[0095] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 7 As shown, by Figure 7 The diffraction pattern shows that it is an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 83 nm for its grains. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.5–2.6 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.88 wt%, consistent with the theoretical feed content.

[0096] Example 8

[0097] Except for the following parameters and settings, everything else is the same as in Example 1: the molar ratio of silicon to tetrapropylammonium hydroxide is 1:0.4.

[0098] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 7 As shown, by Figure 7 The diffraction pattern shows that it is an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 69 nm for its grains. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.2–2.5 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.90 wt%, consistent with the theoretical feed content.

[0099] Example 9

[0100] Except for the following parameters and settings, everything else is the same as in Example 1: the time for continuing crystallization is replaced with 24h.

[0101] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 7 As shown, by Figure 7 The diffraction pattern shows that it is an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 88 nm for its grains. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.4–2.5 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.90 wt%, consistent with the theoretical feed content.

[0102] Comparative Example 1

[0103] Except for the following parameters and settings, everything else is the same as in Example 1: no palladium chloride-ethylenediamine complex solution is added. This yields an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve).

[0104] The X-ray diffraction pattern of the all-silica molecular sieve prepared in this comparative example is shown below. Figure 8 As shown. By Figure 8 It can be seen that the product is an all-silica molecular sieve. The SEM analysis results are as follows: Figure 9 As shown, by Figure 9 It can be seen that the molecular sieve has a uniform morphology, basically hexagonal prism shape, and its average linear size of grains is 70 nm. Elemental analysis shows that there are no metal elements, indicating that it is an all-silica molecular sieve.

[0105] Comparative Example 2

[0106] Comparative Example 1 was added into 20 ml of aqueous solution of palladium chloride, and then stirred at room temperature for 5 h to obtain a mixture. The mixture was stirred in a water bath at 80°C for 2 h, and then placed in an oven at 105°C for drying for 20 h, cooled, ground, calcined at 500°C for 10 h, and then reduced at 400°C for 2 h in a hydrogen atmosphere to obtain a catalyst. The molar ratio of silicon in the Silicalite-1 molecular sieve to palladium in the palladium chloride solution was 1:0.0045 during the impregnation process.

[0107] The X-ray diffraction pattern of the catalyst obtained in the present comparative example is shown in Fig. 1, and it can be seen from Fig. 1 that, in addition to the diffraction peaks of the all-silica molecular sieve, there are obvious characteristic diffraction peaks of metal Pd particles. Figure 10 Figure 10 The SEM and TEM analysis results are shown in Figs. 2 and 3, respectively. Figure 11 Figure 12 It can be seen from Figs. 2 and 3 that the metal Pd particles are more distributed on the outer surface of the all-silica molecular sieve.

[0108] It can be clearly seen from Fig. 4 that the metal particles are distributed on the surface at the uppermost and rightmost edges, and the surface is not smooth, but has some metal particle protrusions. Figure 12

[0109] It can be found from Figs. 5 and 6 that the edge of the catalyst obtained in the present application is smooth, and has no protrusions, proving that the metal particles are distributed inside the molecular sieve rather than on the surface. This can also be verified by the reaction of benzaldehyde reduction amination: the metal particles of the comparative example 2 are on the outside, and a large amount of dibenzylamine is obtained in the reaction, while the metal particles of the present application are inside, and the pores limit the generation of the dibenzylamine macromolecule, and the product is mainly benzylamine. Figure 3 Figure 5

[0110] Comparative Example 3 The difference between the present example and the comparative example is only that the amount of water used in the preparation of the sol-gel is different, and the molar ratio of silicon to water is 1:50.

[0111] The X-ray diffraction pattern of the catalyst obtained in the present comparative example is shown in Fig. 9, and it can be seen from Fig. 9 that the diffraction pattern shows the all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), and has no characteristic diffraction peaks corresponding to palladium species.

[0112] The SEM result is shown in Fig. 10. Figure 13 Figure 13 It can be seen from Fig. 10 that the edge of the catalyst obtained in the present comparative example is not smooth, and has some protrusions. Figure 14 Figure 14 ​​​​​​As can be seen, the catalyst obtained in this comparative example has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 152 nm. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.5–3.5 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.85 wt%, consistent with the theoretical feed content. In Comparative Example 3, the catalyst obtained has larger crystallites.

[0113] Comparative Example 4

[0114] The only difference from the example is that the initial crystallization nucleation temperature is 110°C.

[0115] The X-ray diffraction pattern of the catalyst obtained in this comparative example is as follows: Figure 13 As shown, by Figure 13 As can be seen, the diffraction pattern indicates an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to palladium species. Its SEM results are shown below. Figure 15 .Depend on Figure 15 As can be seen, the catalyst obtained in this comparative example has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 110 nm. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.6–3.2 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.89 wt%, consistent with the theoretical feed content. The catalyst obtained in Comparative Example 4 has a larger grain size.

[0116] Comparative Example 5

[0117] The only difference from the example is that the preliminary crystallization nucleation step is not performed.

[0118] The X-ray diffraction pattern of the catalyst obtained in this comparative example is as follows: Figure 13 As shown, by Figure 13 As can be seen, the diffraction pattern indicates an all-silica molecular sieve (i.e., Silicalite-1 molecular sieve), with no characteristic diffraction peaks corresponding to palladium species. Its SEM results are shown below. Figure 16 .Depend on Figure 16 As can be seen, the catalyst obtained in this comparative example has a uniform morphology, basically exhibiting a hexagonal prism shape, with an average linear size of 330 nm. The catalyst surface is smooth, without obvious particulate matter. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 1.5–3.2 nm. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.9 wt%, consistent with the theoretical feed content.

[0119] Experimental Example 1 - Reductive amination for furfural

[0120] The catalysts of Examples 1, 3 and Comparative Example 2, and the product of Comparative Example 1 were used to test the catalytic reduction amination reaction of furfural.

[0121] The specific test conditions were as follows: the test was conducted in a batch reactor, the catalyst mass was 30 mg, and the catalytic process conditions were as follows: the reaction pressure was 1.0 MPa, the molar ratio of hydrogen to furfural was 12.5:1, the molar ratio of ammonia to furfural was 400:1, the reaction temperature was 100℃, and the reaction time was 12 h.

[0122] Detection method: Samples were taken after the reaction was completed, and the composition of the products was analyzed by gas chromatography. Then, the furfural conversion rate and the selectivity of tetrahydrofurfural were calculated. The results are shown in Table 1.

[0123] The formula for calculating furfural conversion rate is: Furfural conversion rate = [(number of carbon moles in furfural in feed) - (number of carbon moles in furfural in discharge)] ÷ (number of carbon moles in furfural in feed) × 100%.

[0124] The formula for calculating the selectivity of tetrahydrofurfuryl is: Tetrahydrofurfuryl selectivity = (number of carbon moles in tetrahydrofurfuryl in the discharge) ÷ (total number of carbon moles in all carbon-containing products in the discharge) × 100%.

[0125] Table 1

[0126]

[0127] As shown in Table 1, the all-silica molecular sieve (i.e., Silicalite-1 molecular sieve) obtained in Comparative Example 1 has no catalytic activity for the reductive amination of furfural. The catalytic activity of the catalyst obtained in the examples of the present invention is significantly higher than that of the catalyst obtained by the impregnation method in Comparative Example 2. The catalyst obtained in the examples of the present invention has high selectivity for tetrahydrofurfurylamine, which can reduce the cost of product separation and has significant economic benefits.

[0128] Experimental Example 2 - Reductive amination for benzaldehyde

[0129] The catalysts used in Examples 1 and 2 and Comparative Examples 2, 3, 4, and 5 were tested for their application in the reductive amination reaction of benzaldehyde.

[0130] The testing method is as follows:

[0131] The test was conducted in a batch reactor with a catalyst mass of 20 mg. The catalytic process conditions were as follows: reaction pressure of 1.0 MPa, molar ratio of hydrogen to benzaldehyde of 12.5:1, molar ratio of ammonia to benzaldehyde of 500:1, reaction temperature of 50℃, and reaction time of 3 h.

[0132] The detection method is as follows: sampling after reaction, analyzing the product composition by gas chromatography, and then calculating the conversion rate of benzaldehyde and the selectivity of benzylamine. The test results are shown in Table 2.

[0133] The calculation formula of the conversion rate of benzaldehyde is as follows: benzaldehyde conversion rate = [(carbon molar number of benzaldehyde in the feed) - (carbon molar number of benzaldehyde in the discharge)] ÷ (carbon molar number of benzaldehyde in the feed) × 100%.

[0134] The calculation formula of the selectivity of benzylamine is as follows: benzylamine selectivity = (carbon molar number of benzylamine in the discharge) ÷ (total sum of carbon molar numbers of all carbon-containing products in the discharge) × 100%.

[0135] Table 2

[0136]

[0137] As shown in Table 2, the catalyst obtained by the embodiment of the present application has a high conversion rate of benzaldehyde and a high selectivity of benzylamine.

[0138] In addition, the catalyst obtained by the embodiment 1 of the present application has high stability, and no obvious activity decrease is observed even after three repeated uses in the process of catalyzing the reductive amination of furfural or the reductive amination of benzaldehyde, while the catalyst described in the comparative example 2 has poor stability and gradually deactivates with the progress of the catalytic reaction.

[0139] The present application is not limited to the above-described embodiments, and any modification, improvement or replacement conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.

Claims

1. A catalyst for the reductive amination of aldehydes and ketones, characterized in that, It includes all-silica molecular sieves and metal particles; among which, The metal particles are distributed inside the all-silica molecular sieve; The average linear size of the catalyst crystals is 60–90 nm; the morphology of the catalyst crystals is basically hexagonal prism; the average linear size refers to the average value of the crystal size. The metal particles have a particle size of 0.5–4 nm; based on the mass of the catalyst, the mass percentage of the metal particles is 0.2–1.0 wt%; the metal element in the metal particles is selected from at least one of Pd, Pt, and Rh. The catalyst is prepared by the following steps: 1) Mix silicon-containing material, alkyl ammonium hydroxide, metal particle precursor and water and stir at 20-45°C to obtain sol-gel; 2) The obtained sol-gel was initially crystallized into nuclei at 70-100℃, and then the temperature was raised to 160-180℃ for further crystallization. Solid-liquid separation was performed to obtain a solid. 3) The obtained solid was washed, dried, calcined at 500-600°C, and then reduced in a hydrogen atmosphere at 350-450°C to obtain the catalyst; in, The silicon-containing material is selected from silicate esters or alkaline silica sols; the alkyl ammonium hydroxide is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, dimethyldiethylammonium hydroxide, and dimethyldipropylammonium hydroxide; the metal particle precursor is a water-soluble metal salt-ethylenediamine complex solution; The molar ratio of silicon, alkyl ammonium hydroxide, and water in the silicon-containing material is 1:0.1-0.4:15-25; The molar ratio of the metal element in the water-soluble metal salt to the silicon element in the silicon-containing material is 0.0004 to 0.055:

1.

2. The method for preparing the catalyst according to claim 1, characterized in that, Includes the following steps: 1) Mix silicon-containing material, alkyl ammonium hydroxide, metal particle precursor and water and stir at 20-45°C to obtain sol-gel; 2) The obtained sol-gel was initially crystallized into nuclei at 70-100℃, and then the temperature was raised to 160-180℃ for further crystallization. Solid-liquid separation was performed to obtain a solid. 3) The obtained solid was washed, dried, calcined at 500-600°C, and then reduced in a hydrogen atmosphere at 350-450°C to obtain the catalyst; in, The silicon-containing material is selected from silicate esters or alkaline silica sols; the alkyl ammonium hydroxide is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, dimethyldiethylammonium hydroxide, and dimethyldipropylammonium hydroxide; the metal particle precursor is a water-soluble metal salt-ethylenediamine complex solution; The molar ratio of silicon, alkyl ammonium hydroxide, and water in the silicon-containing material is 1:0.1-0.4:15-25; The molar ratio of the metal element in the water-soluble metal salt to the silicon element in the silicon-containing material is 0.0004 to 0.055:

1.

3. The preparation method according to claim 2, characterized in that, The silicate ester is selected from at least one of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate, and butyl orthosilicate.

4. The preparation method according to claim 3, characterized in that, The silicate ester is tetraethyl orthosilicate.

5. The preparation method according to claim 2, characterized in that, The alkyl ammonium hydroxide is tetrapropylammonium hydroxide.

6. The preparation method according to claim 2, characterized in that, The specific steps include the following: 1) Mix a solution of silicon-containing material, alkyl ammonium hydroxide, water-soluble metal salt-ethylenediamine complex and water, and stir at 20-45°C for 6-12 hours to obtain a sol-gel. 2) The obtained sol-gel was initially crystallized at 70-100℃ for 24-48 hours, and then the temperature was raised to 160-180℃ for 12-72 hours for further crystallization. The solid was then separated from the liquid to obtain the solid. 3) The obtained solid is washed, dried, calcined at 500-600℃ for 3-12 hours, and then reduced at 350-450℃ in a hydrogen atmosphere for 1.5-4 hours to obtain the catalyst.

7. The application of the catalyst according to claim 1 or the catalyst prepared by the method according to claim 2 in the reductive amination of aldehydes and ketones.

8. The application according to claim 7, characterized in that, The aldehydes and ketones include furfural and benzaldehyde; the target product of furfural reduction amination is tetrahydrofurfuralamine; and the target product of benzaldehyde reduction amination is benzylamine.

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