A single-atom adduct cluster bimetallic active site hydrogenation catalyst, and a preparation method and application thereof

Abstract

This invention belongs to the field of catalyst preparation technology, and relates to a single-atom alloy cluster dual-active-site hydrogenation catalyst, its preparation method, and its application. The single-atom alloy cluster dual-active-site hydrogenation catalyst includes a support with anchoring sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the support, and both the palladium single-atom sites and the ruthenium-palladium alloy clusters are dispersed on the surface of the support. The single-atom alloy cluster dual-active-site hydrogenation catalyst provided by this invention can achieve site specialization for nitro hydrogenation and aromatic ring hydrogenation, reduce the activation energy of each step in the tandem reaction, improve the conversion rate of dinitroaromatic hydrocarbons and the selectivity of alicyclic diamines, and is suitable for the efficient hydrogenation conversion of dinitrobenzene, dinitrotoluene, and their derivatives.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and relates to a single-atom alloyed cluster dual-active-site hydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Alicyclic diamines are an important class of fine chemical intermediates, used in the preparation of polyamides, polyurethanes, epoxy curing agents, pharmaceutical intermediates, and other materials. The preparation of alicyclic diamines from dinitroaromatic hydrocarbons via hydrogenation is an atom-economical synthetic route. This process typically involves two consecutive steps: first, the nitro group in the dinitroaromatic hydrocarbon is hydrogenated to an amino group, generating an aromatic diamine intermediate; subsequently, the aromatic ring is further hydrogenated to generate the corresponding alicyclic diamine.

[0003] However, the tandem hydrogenation reaction of dinitroaromatics is highly complex. On the one hand, nitro hydrogenation typically requires catalysts capable of efficiently activating the nitro group and providing active hydrogen; on the other hand, aromatic ring hydrogenation usually requires strong multi-metal sites or metal cluster sites to achieve planar adsorption and multi-site activation of the aromatic ring. Traditional single-metal catalysts often struggle to simultaneously achieve selective nitro hydrogenation and deep aromatic ring hydrogenation, easily leading to problems such as the accumulation of aromatic diamine intermediates, excessive side reactions, insufficient selectivity, or low metal utilization.

[0004] CN116440898A discloses an atomically dispersed Pd-Pt catalyst for the hydrogenation reaction of dinitrotoluene, its preparation method, and its applications. This catalyst uses a co-precipitation method to support Pd and Pt in atomically dispersed clusters on a nanosupport surface, with each Pd and Pt loading at 0.1-2 wt%. This catalyst can catalyze the hydrogenation of dinitrotoluene to toluene diamine under mild conditions of 20-60 °C and hydrogen pressure of 0.2-1 MPa, exhibiting high hydrogenation activity and selectivity. However, this method primarily achieves the conversion of dinitroaromatic hydrocarbons to aromatic diamines, without further hydrogenating the aromatic ring to alicyclic diamines; therefore, it still belongs to the catalytic system of the nitro reduction step.

[0005] CN118063329A discloses a method for the catalytic hydrogenation of 2,4-dinitrotoluene to prepare 1-methyl-2,4-cyclohexanediamine. This method uses a supported ruthenium-based heterogeneous catalyst as the core, and prepares the catalyst through steps such as support pretreatment, impregnation, precipitation, drying, and reduction. This catalyst is used to simultaneously achieve the hydrogenation reduction of the nitro group and aromatic ring in 2,4-dinitrotoluene. Under conditions of 7 MPa hydrogen pressure and 180 °C for 4 h, this method can achieve a 99.9% conversion of 2,4-dinitrotoluene and a selectivity of over 95% for 1-methyl-2,4-cyclohexanediamine. However, this system still requires high hydrogen pressure and high reaction temperature, and mainly relies on a single ruthenium-based metal site. Further improvements are needed in the control of the nitro hydrogenation and aromatic ring hydrogenation processes.

[0006] Single-atom catalysts possess advantages such as high metal atom utilization, well-defined active sites, and tunable electronic structure, making them suitable for the selective adsorption and activation of nitro groups. However, isolated single-atom sites typically lack sufficient polyatomic metal clusters, hindering efficient deep hydrogenation of aromatic rings. Metal cluster catalysts, on the other hand, exhibit strong hydrogen dissociation and aromatic ring adsorption capabilities, but excessively large metal particles can lead to non-selective hydrogenation, increased side reactions, and reduced utilization of precious metals.

[0007] In summary, existing hydrogenation technologies for dinitroaromatic hydrocarbons can convert dinitrotoluene into aromatic diamines or alicyclic diamines, but they still suffer from problems such as harsh reaction conditions, insufficient utilization of precious metals, and a lack of site-specific control between nitro hydrogenation and aromatic ring hydrogenation. Therefore, developing a novel dual-active-site catalyst capable of simultaneously constructing nitro activation sites and aromatic ring hydrogenation sites is of great significance for achieving the mild, efficient, and selective tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, its preparation method, and its application. By simultaneously constructing palladium single-atom sites and ruthenium-palladium alloy cluster sites on the support surface, the palladium single-atom sites preferentially adsorb and activate nitro groups, while the ruthenium-palladium alloy cluster sites preferentially adsorb and activate aromatic rings, thereby achieving site division of labor and tandem synergy between nitro hydrogenation and aromatic ring hydrogenation.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a hydrogenation catalyst with dual active sites of single-atom alloy clusters, comprising a support having anchoring points on its surface, wherein palladium single-atom sites and ruthenium-palladium alloy clusters are loaded on the support, and both the palladium single-atom sites and the ruthenium-palladium alloy clusters are dispersed on the surface of the support.

[0010] The present invention provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. Palladium single-atom sites exist in an atomically dispersed form and interact with anchoring sites on the support surface. These sites adsorb and activate nitro groups in dinitroaromatics, promoting the hydrogenation of dinitroaromatics to aromatic diamine intermediates. The ruthenium-palladium alloy clusters, composed of ruthenium and palladium atoms, are distributed on the support surface. These clusters adsorb and activate aromatic rings, promoting further hydrogenation of the aromatic diamine intermediates to alicyclic diamines, thereby achieving a tandem hydrogenation conversion of dinitroaromatics to alicyclic diamines. This invention overcomes the problem of traditional single-metal catalysts being unable to simultaneously handle nitro hydrogenation and deep aromatic ring hydrogenation by dividing the functions of single-atom sites and alloy cluster sites, thus improving the efficiency of the tandem hydrogenation reaction.

[0011] Preferably, the palladium single-atom site forms at least one of palladium-nitrogen, palladium-oxygen, palladium-carbon, palladium-boron, or palladium-defect coordination structures with a carrier having anchoring points on its surface.

[0012] Preferably, the carrier comprises at least one of activated carbon, carbon black, graphitized carbon, nitrogen-doped carbon, carbon nanotubes, graphene, boron nitride, defective boron nitride, amino-modified boron nitride, carbon nitride, alumina, silicon dioxide, titanium dioxide, or cerium oxide.

[0013] Preferably, the average particle size of the ruthenium-palladium alloy cluster is 0.3-5 nm, for example, it can be 0.3 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm or 5 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-2 nm.

[0014] Preferably, the spatial distance between the palladium single-atom site and the ruthenium-palladium alloy cluster is 0.2-20 nm, for example, it can be 0.2 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 15 nm or 20 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-10 nm.

[0015] Preferably, the ruthenium content in the single-atom alloy cluster dual-active-site hydrogenation catalyst is 0.1-10 wt%, for example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt% or 10 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-3 wt%.

[0016] Preferably, the palladium content in the single-atom alloy cluster dual-active-site hydrogenation catalyst is 0.001-5 wt%, for example, it can be 0.001 wt%, 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, or 5 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.001-1 wt%.

[0017] When the palladium loading is low, palladium species preferentially anchor to anchoring sites on the support surface, forming palladium single-atom sites; as the palladium loading increases, some palladium species interact with adjacent ruthenium species, forming ruthenium-palladium alloy cluster sites.

[0018] In a second aspect, the present invention provides a method for preparing a single-atom alloyed cluster dual-active-site hydrogenation catalyst as described in the first aspect, comprising the following steps: (1) The ruthenium precursor is loaded onto the surface of a carrier with anchoring points, and after a first reduction treatment, a ruthenium-supported catalyst is obtained; (2) The palladium precursor is loaded onto the surface of the ruthenium-supported catalyst obtained in step (1) by ultrasonic impregnation and / or atomic layer deposition, and after a second reduction treatment, the single-atom alloy cluster dual-active-site hydrogenation catalyst is obtained.

[0019] The present invention provides a method for preparing a single-atom alloy cluster dual-active-site hydrogenation catalyst. Part of the palladium species is anchored as palladium single atoms at anchoring sites on the support, forming palladium single-atom sites; another part of the palladium species interacts with ruthenium species to form ruthenium-palladium alloy cluster sites. This invention constructs palladium single-atom sites and ruthenium-palladium alloy clusters on the same support surface using atomic layer deposition or ultrasonic impregnation methods, achieving spatial coupling between nitro activation sites and aromatic ring hydrogenation sites.

[0020] It should be noted that the present invention does not specifically limit the preparation method of the carrier with anchor positioning points on the surface described in step (1). The carrier can be modified by high temperature calcination, etching, ball milling, hydrothermal and other methods, but is not limited to these. Those skilled in the art can make adaptive adjustments according to the actual application scenario.

[0021] Preferably, the molar ratio of the ruthenium precursor to the carrier with anchoring points on the surface in step (1) is 1:(400-1000), for example, it can be 1:400, 1:500, 1:600, 1:800 or 1:1000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the ruthenium precursor in step (1) includes at least one of ruthenium trichloride, ruthenium acetylacetonate, ruthenium nitrite, ruthenium chloride, or ruthenium dichlorohexacarbonyl.

[0023] Preferably, the ruthenium chloride comprises at least one of K2RuCl6, (NH4)2RuCl6, or H2RuCl6.

[0024] It should be noted that the ruthenium precursor is added in the form of a solution. The amount of solvent used is not specifically limited in this invention, but is sufficient to completely dissolve the ruthenium precursor.

[0025] Preferably, the method by which the ruthenium precursor in step (1) is loaded onto the surface of a carrier with anchoring points includes any one of equal-volume impregnation, excessive impregnation, deposition precipitation, ultrasonic impregnation, or wet chemical adsorption.

[0026] Preferably, step (1) includes a drying step before the first reduction treatment.

[0027] The present invention does not specifically limit the drying temperature and time, but aims to achieve complete drying of the load.

[0028] Preferably, the first reduction process in step (1) is carried out in any one of hydrogen, a mixture of hydrogen and nitrogen, or a mixture of hydrogen and argon.

[0029] Preferably, the temperature of the first reduction treatment in step (1) is 100-500℃, for example, it can be 100℃, 150℃, 200℃, 300℃, 350℃, 400℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 150-350℃.

[0030] Preferably, the time for the first reduction process in step (1) is 0.5-10h, for example, it can be 0.5h, 1h, 3h, 5h, 8h or 10h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1-5h.

[0031] Preferably, the molar ratio of the palladium precursor to the ruthenium-supported catalyst in step (2) is 1:(1000-2000), for example, it can be 1:1000, 1:1200, 1:1500, 1:1800 or 1:2000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the palladium precursor in step (2) includes at least one of palladium acetylacetonate, palladium chloroacetate, sodium palladium chloroacetate, potassium palladium chloroacetate, palladium nitrate, palladium acetate, ammonium hexachloropalladium, or tetraamminepalladium salt, and is preferably palladium acetylacetonate.

[0033] Preferably, the tetraamminepalladium salt comprises [Pd(NH3)4]Cl2.

[0034] Preferably, the ultrasonic impregnation time in step (2) is 5-180 min and the power is 50-1000 W.

[0035] The ultrasonic immersion time is 5-180 min, for example, it can be 5 min, 10 min, 30 min, 50 min, 100 min, 150 min or 180 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] The power of the ultrasonic impregnation is 50-1000W, for example, it can be 50W, 100W, 300W, 500W, 800W or 1000W, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the specific steps of the atomic layer deposition in step (2) include: placing the ruthenium-supported catalyst in the atomic layer deposition reactor, using the palladium precursor as the metal source, and performing palladium precursor pulse, inert protective gas purging, reaction gas pulse and inert protective gas purging in sequence for 1-100 cycles to obtain the palladium-supported intermediate.

[0038] The number of cycles is 1-100 times, for example, it can be 1 time, 5 times, 30 times, 50 times, 80 times, 90 times or 100 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 5-30 times.

[0039] Preferably, the inert protective gas includes any one of nitrogen, argon, or helium.

[0040] Preferably, the reacting gas includes ozone.

[0041] Preferably, when ultrasonic impregnation is performed in step (2), a drying step is also included before the second reduction treatment.

[0042] It should be noted that in step (2), when ultrasonic impregnation is performed, the palladium precursor is added in the form of a solution. The amount of solvent used is not specifically limited in this invention, but is determined by the requirement that it can completely dissolve the palladium precursor.

[0043] The present invention does not specifically limit the drying temperature and time, but aims to achieve complete drying of the load.

[0044] Preferably, the second reduction process in step (2) is carried out in any one of nitrogen, argon, hydrogen, a mixture of hydrogen and nitrogen, or a mixture of hydrogen and argon.

[0045] Preferably, the temperature of the second reduction treatment in step (2) is 50-400℃, for example, it can be 50℃, 100℃, 200℃, 300℃ or 400℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 100-300℃.

[0046] Preferably, the time for the second reduction process in step (2) is 0.5-8h, for example, it can be 0.5h, 1h, 2h, 4h, 6h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1-4h.

[0047] Thirdly, the present invention provides an application of the single-atom alloyed cluster dual-active-site hydrogenation catalyst as described in the first aspect, wherein the single-atom alloyed cluster dual-active-site hydrogenation catalyst is used for the tandem hydrogenation of dinitroaromatics to prepare alicyclic diamines, the specific steps of which include: A dinitroaromatic hydrocarbon, a solvent, and a single-atom alloying cluster dual-active-site hydrogenation catalyst are added to a reactor, and a hydrogenation reaction is carried out under a hydrogen atmosphere to obtain an alicyclic diamine product.

[0048] This invention provides a single-atom alloy cluster dual-active-site hydrogenation catalyst for the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines. Under a hydrogen atmosphere, the dinitroaromatic hydrocarbon is contacted with a palladium single-atom-ruthenium-palladium alloy cluster dual-active-site hydrogenation catalyst. The dinitroaromatic hydrocarbon first undergoes nitro group hydrogenation at the palladium single-atom site, generating an aromatic diamine intermediate. Subsequently, the aromatic diamine intermediate undergoes aromatic ring hydrogenation at the ruthenium-palladium alloy cluster, yielding the corresponding alicyclic diamine product. In this tandem reaction, a coordination adsorption relationship forms between the palladium single-atom site and the nitro group, promoting NO bond polarization and stepwise nitro group hydrogenation. The ruthenium-palladium alloy cluster provides multi-atom metal sites, promoting parallel aromatic ring adsorption and C=C bond hydrogenation. The spatial coupling of these two types of sites facilitates active hydrogen migration and aromatic diamine intermediate transport, thereby improving the conversion rate of dinitroaromatic hydrocarbons and the selectivity of alicyclic diamines.

[0049] Preferably, the dinitroaromatic hydrocarbon includes at least one of o-dinitrobenzene, m-dinitrobenzene, p-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, dinitroxylene, dinitrochlorobenzene, dinitrobiphenyl, and their respective substituted derivatives.

[0050] The substituted derivatives include dinitroaromatic hydrocarbons whose aromatic rings are further substituted with at least one of the following: C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, amino, carboxyl, ester, cyano, acyl, amide, aryl, aryloxy, alkylthio, or sulfonic acid groups.

[0051] Preferably, the solvent includes at least one of methanol, ethanol, isopropanol, tert-butanol, tetrahydrofuran, cyclohexane, toluene, n-butanol, N-methylpyrrolidone, or water.

[0052] Preferably, the hydrogenation reaction is carried out at a temperature of 20-180°C, a hydrogen pressure of 0.1-10 MPa, and a time of 10-600 min.

[0053] The temperature of the hydrogenation reaction is 20-180℃, for example, it can be 20℃, 50℃, 80℃, 100℃, 120℃, 150℃ or 180℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 50-120℃.

[0054] The hydrogen pressure for the hydrogenation reaction is 0.1-10 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 3 MPa, 5 MPa, 8 MPa or 10 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 0.5-5 MPa being the preferred value.

[0055] The hydrogenation reaction time is 10-600 min, for example, it can be 10 min, 30 min, 100 min, 240 min, 300 min, 400 min, 500 min or 600 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30-240 min.

[0056] Preferably, the mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst is 0.1-50 wt% of the mass of the dinitroaromatic hydrocarbon, for example, it can be 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt% or 50 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1-20 wt%.

[0057] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0058] Compared with the prior art, the present invention has the following beneficial effects: (1) The single-atom alloy cluster dual-active-site hydrogenation catalyst provided by this invention has palladium single-atom sites existing in an atomically dispersed form, which interact with anchoring sites on the support surface to adsorb and activate nitro groups in dinitroaromatics, promoting the hydrogenation of dinitroaromatics to generate aromatic diamine intermediates; ruthenium-palladium alloy clusters, composed of ruthenium and palladium atoms, are distributed on the support surface to adsorb and activate aromatic rings, promoting further hydrogenation of aromatic diamine intermediates to generate alicyclic diamines, thereby realizing the tandem hydrogenation conversion of dinitroaromatics to alicyclic diamines. This invention overcomes the problem that traditional single-metal catalysts cannot simultaneously handle nitro hydrogenation and deep aromatic ring hydrogenation by functional division of labor between single-atom sites and alloy cluster sites, thus improving the efficiency of tandem hydrogenation reactions. Among them, palladium exists in the form of single atoms and small-sized alloy clusters, which significantly improves the utilization rate of noble metal atoms and reduces the amount of noble metal used.

[0059] (2) This invention constructs palladium single-atom sites and ruthenium-palladium alloy clusters on the same support surface by atomic layer deposition or ultrasonic impregnation, realizing the spatial coupling of nitro activation sites and aromatic ring hydrogenation sites. The single-atom alloy cluster dual-active-site hydrogenation catalyst can realize the one-step tandem hydrogenation of dinitroaromatic hydrocarbons to alicyclic diamines under relatively mild temperature and hydrogen pressure, with a reactant conversion rate of up to 99.8% and an alicyclic diamine selectivity of up to 99.5%, which has the advantages of mild reaction conditions, high catalytic efficiency, good selectivity and simple process flow. Attached Figure Description

[0060] Figure 1 This is a transmission electron microscope (TEM) image of the single-atom alloy cluster dual-active-site hydrogenation catalyst provided in Example 1 of this invention. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] Example 1 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, comprising an activated carbon support with defect sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the activated carbon support, both dispersed on the surface of the activated carbon support. The palladium single-atom sites and the activated carbon support form a palladium-defect coordination structure. The average particle size of the ruthenium-palladium alloy clusters is 1 nm. The spatial distance between the palladium single-atom sites and the ruthenium-palladium alloy clusters is 5 nm. The mass percentage of ruthenium in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst is 1 wt%, and the mass percentage of palladium is 0.1 wt%.

[0063] The preparation method of the single-atom alloyed cluster dual-active-site hydrogenation catalyst includes the following steps: (1) An activated carbon support with anchoring points on its surface was added to a ruthenium trichloride aqueous solution and stirred for 6 hours. The concentration of the ruthenium trichloride aqueous solution was 0.1 mol / L, and the molar ratio of ruthenium trichloride to activated carbon support was 1:800. Then, it was dried at 80°C for 12 hours. The resulting solid was subjected to a first reduction treatment in a mixture of hydrogen and nitrogen at 300°C for 2 hours to obtain a ruthenium-supported catalyst.

[0064] (2) The ruthenium-supported catalyst was placed in an atomic layer deposition reactor, and palladium acetylacetone was used as the metal source. The reactor underwent 10 cycles of pulsed palladium acetylacetone, argon purging, ozone pulse, and argon purging to obtain a palladium-supported intermediate. The molar ratio of palladium acetylacetone to the ruthenium-supported catalyst was 1:1500. A second reduction treatment was then performed in a mixture of hydrogen and nitrogen at 200°C for 2 hours to obtain the single-atom alloyed cluster dual-active-site hydrogenation catalyst. The transmission electron microscope image is shown below. Figure 1 As shown.

[0065] The specific steps for using the single-atom alloyed cluster dual-active-site hydrogenation catalyst in the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines include: m-Dinitrobenzene, methanol, and a single-atom alloyed cluster dual-active-site hydrogenation catalyst were added to a high-pressure reactor. After sealing, the air inside the reactor was replaced with hydrogen, and then hydrogen was introduced to 3 MPa. The hydrogenation reaction was carried out under stirring at 100°C for 150 min. The mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst was 10 wt% of the mass of the dinitroaromatic hydrocarbon. After the hydrogenation reaction was completed, the reactor was cooled to room temperature, the pressure inside the reactor was released, and the single-atom alloyed cluster dual-active-site hydrogenation catalyst was removed by filtration. The resulting reaction solution was a hydrogenation product mainly composed of m-cyclohexanediamine.

[0066] Example 2 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, comprising an activated carbon support with defect sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the activated carbon support, both dispersed on the surface of the activated carbon support. The palladium single-atom sites and the activated carbon support form a palladium-defect coordination structure. The average particle size of the ruthenium-palladium alloy clusters is 0.5 nm. The spatial distance between the palladium single-atom sites and the ruthenium-palladium alloy clusters is 10 nm. The mass percentage of ruthenium in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst is 0.5 wt%, and the mass percentage of palladium is 0.01 wt%.

[0067] The preparation method of the single-atom alloyed cluster dual-active-site hydrogenation catalyst includes the following steps: (1) An activated carbon support with anchoring points on its surface was added to an acetone solution of ruthenium acetylacetone and stirred for 6 hours. The concentration of the acetone solution of ruthenium acetylacetone was 0.05 mol / L and the molar ratio of ruthenium acetylacetone to activated carbon support was 1:900. Then it was dried at 80°C for 12 hours. The resulting solid was subjected to a first reduction treatment in a mixture of hydrogen and nitrogen at 150°C for 5 hours to obtain a ruthenium-supported catalyst.

[0068] (2) The ruthenium-supported catalyst was placed in an atomic layer deposition reactor, and sodium chloropalladium was used as the metal source. The process was carried out in sequence with sodium chloropalladium pulse, argon purging, ozone pulse and argon purging for 5 cycles to obtain a palladium-supported intermediate. The molar ratio of sodium chloropalladium to ruthenium-supported catalyst was 1:1800. Then, a second reduction treatment was carried out in a mixture of hydrogen and nitrogen at a temperature of 100°C for 4 hours to obtain the single-atom alloy cluster dual-active-site hydrogenation catalyst.

[0069] The specific steps for using the single-atom alloyed cluster dual-active-site hydrogenation catalyst in the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines include: m-Dinitrobenzene, methanol, and a single-atom alloyed cluster dual-active-site hydrogenation catalyst were added to a high-pressure reactor. After sealing, the air inside the reactor was replaced with hydrogen, and then hydrogen was introduced to 0.5 MPa. The hydrogenation reaction was carried out under stirring at 120°C for 30 min. The mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst was 1 wt% of the mass of the dinitroaromatic hydrocarbon. After the hydrogenation reaction was completed, the reactor was cooled to room temperature, the pressure inside was released, and the single-atom alloyed cluster dual-active-site hydrogenation catalyst was removed by filtration. The resulting reaction solution was a hydrogenation product mainly composed of m-cyclohexanediamine.

[0070] Example 3 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, comprising an activated carbon support with defect sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the activated carbon support, both dispersed on the surface of the activated carbon support. The palladium single-atom sites and the activated carbon support form a palladium-defect coordination structure. The average particle size of the ruthenium-palladium alloy clusters is 2 nm. The spatial distance between the palladium single-atom sites and the ruthenium-palladium alloy clusters is 0.5 nm. The ruthenium content in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst is 3 wt% and the palladium content is 1 wt%.

[0071] The preparation method of the single-atom alloyed cluster dual-active-site hydrogenation catalyst includes the following steps: (1) An activated carbon support with anchoring points on its surface was added to an aqueous solution of ruthenium nitrite nitrate and stirred for 6 hours. The concentration of the aqueous solution of ruthenium nitrite nitrate was 0.31 mol / L and the molar ratio of ruthenium nitrite nitrate to activated carbon support was 1:600. Then it was dried at 80°C for 12 hours. The resulting solid was subjected to a first reduction treatment in a mixture of hydrogen and nitrogen at 350°C for 1 hour to obtain a ruthenium-supported catalyst.

[0072] (2) The ruthenium-supported catalyst was placed in an atomic layer deposition reactor, and palladium nitrate was used as the metal source. The process was carried out in sequence with palladium nitrate pulse, argon purging, ozone pulse and argon purging for 30 cycles to obtain a palladium-supported intermediate. The molar ratio of palladium nitrate to ruthenium-supported catalyst was 1:1200. Then, a second reduction treatment was carried out in a mixture of hydrogen and nitrogen at a temperature of 300°C for 1 hour to obtain the single-atom alloy cluster dual-active-site hydrogenation catalyst.

[0073] The specific steps for using the single-atom alloyed cluster dual-active-site hydrogenation catalyst in the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines include: m-Dinitrobenzene, methanol, and a single-atom alloyed cluster dual-active-site hydrogenation catalyst were added to a high-pressure reactor. After sealing, the air inside the reactor was replaced with hydrogen, and then hydrogen was introduced to 5 MPa. The hydrogenation reaction was carried out under stirring at 50°C for 240 min. The mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst was 20 wt% of the mass of the dinitroaromatic hydrocarbon. After the hydrogenation reaction was completed, the reactor was cooled to room temperature, the pressure inside was released, and the single-atom alloyed cluster dual-active-site hydrogenation catalyst was removed by filtration. The resulting reaction solution was a hydrogenation product mainly composed of m-cyclohexanediamine.

[0074] Example 4 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, comprising an activated carbon support with defect sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the activated carbon support, both dispersed on the surface of the activated carbon support. The palladium single-atom sites and the activated carbon support form a palladium-defect coordination structure. The average particle size of the ruthenium-palladium alloy clusters is 0.3 nm. The spatial distance between the palladium single-atom sites and the ruthenium-palladium alloy clusters is 20 nm. The mass percentage of ruthenium in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst is 0.1 wt%, and the mass percentage of palladium is 0.001 wt%.

[0075] The preparation method of the single-atom alloyed cluster dual-active-site hydrogenation catalyst includes the following steps: (1) An activated carbon support with anchoring points on its surface was added to an acetone solution of ruthenium dichlorohexacarbonyl and stirred for 6 h. The concentration of the acetone solution of ruthenium dichlorohexacarbonyl was 0.005 mol / L, and the molar ratio of ruthenium dichlorohexacarbonyl to the activated carbon support was 1:1000. Then it was dried at 80 °C for 12 h. The resulting solid was subjected to a first reduction treatment in a mixture of hydrogen and nitrogen at 100 °C for 10 h to obtain a ruthenium-supported catalyst.

[0076] (2) The ruthenium-supported catalyst was placed in an atomic layer deposition reactor, and ammonium hexachloropalladate was used as the metal source. The reaction was carried out in sequence with ammonium hexachloropalladate pulse, argon purging, ozone pulse and argon purging for one cycle to obtain the palladium-supported intermediate. The molar ratio of ammonium hexachloropalladate to ruthenium-supported catalyst was 1:2000. Then, a second reduction treatment was carried out in a mixture of hydrogen and nitrogen at a temperature of 50°C for 8 hours to obtain the single-atom alloy cluster dual-active-site hydrogenation catalyst.

[0077] The specific steps for using the single-atom alloyed cluster dual-active-site hydrogenation catalyst in the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines include: m-Dinitrobenzene, methanol, and a single-atom alloyed cluster dual-active-site hydrogenation catalyst were added to a high-pressure reactor. After sealing, the air inside the reactor was replaced with hydrogen, and then hydrogen was introduced to 0.1 MPa. The hydrogenation reaction was carried out under stirring at 180°C for 10 min. The mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst was 0.1 wt% of the mass of the dinitroaromatic hydrocarbon. After the hydrogenation reaction was completed, the reactor was cooled to room temperature, the pressure inside the reactor was released, and the single-atom alloyed cluster dual-active-site hydrogenation catalyst was removed by filtration. The resulting reaction solution was a hydrogenation product mainly composed of m-cyclohexanediamine.

[0078] Example 5 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst, comprising an activated carbon support with defect sites on its surface. Palladium single-atom sites and ruthenium-palladium alloy clusters are loaded onto the activated carbon support, both dispersed on the surface of the activated carbon support. The palladium single-atom sites and the activated carbon support form a palladium-defect coordination structure. The average particle size of the ruthenium-palladium alloy clusters is 5 nm. The spatial distance between the palladium single-atom sites and the ruthenium-palladium alloy clusters is 0.2 nm. The ruthenium content in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst is 10 wt% and the palladium content is 5 wt%.

[0079] The preparation method of the single-atom alloyed cluster dual-active-site hydrogenation catalyst includes the following steps: (1) An activated carbon support with anchoring points on its surface was added to a ruthenium trichloride aqueous solution and stirred for 6 hours. The concentration of the ruthenium trichloride aqueous solution was 1.16 mol / L and the molar ratio of ruthenium trichloride to activated carbon support was 1:400. Then, it was dried at 80°C for 12 hours. The resulting solid was subjected to a first reduction treatment in a mixture of hydrogen and nitrogen at 500°C for 0.5 hours to obtain a ruthenium-supported catalyst.

[0080] (2) The ruthenium-supported catalyst was placed in an atomic layer deposition reactor, and potassium chloropalladium was used as the metal source. The catalyst was subjected to potassium chloropalladium pulse, argon purging, ozone pulse and argon purging in sequence for 100 cycles to obtain a palladium-supported intermediate. The molar ratio of potassium chloropalladium to ruthenium-supported catalyst was 1:1000. Then, a second reduction treatment was carried out in a mixture of hydrogen and nitrogen at a temperature of 400°C for 0.5 h to obtain the single-atom alloy cluster dual-active-site hydrogenation catalyst.

[0081] The specific steps for using the single-atom alloyed cluster dual-active-site hydrogenation catalyst in the tandem hydrogenation of dinitroaromatic hydrocarbons to prepare alicyclic diamines include: m-Dinitrobenzene, methanol, and a single-atom alloyed cluster dual-active-site hydrogenation catalyst were added to a high-pressure reactor. After sealing, the air inside the reactor was replaced with hydrogen, and then hydrogen was introduced to 10 MPa. The hydrogenation reaction was carried out under stirring at 20°C for 600 min. The mass of the single-atom alloyed cluster dual-active-site hydrogenation catalyst was 50 wt% of the mass of the dinitroaromatic hydrocarbon. After the hydrogenation reaction was completed, the reactor was cooled to room temperature, the pressure inside the reactor was released, and the single-atom alloyed cluster dual-active-site hydrogenation catalyst was removed by filtration. The resulting reaction solution was a hydrogenation product mainly composed of m-cyclohexanediamine.

[0082] Example 6 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Example 1 is that, except for replacing the activated carbon support with a surface defect site in equal molar amounts with an activated carbon support without surface defect sites, the rest is the same as Example 1.

[0083] Ordinary activated carbon has a high specific surface area, which can disperse metal components. However, it has a limited number of surface defect sites and heteroatom coordination sites, resulting in a weak anchoring ability for palladium single atoms. Some palladium species are prone to migrate and form larger particles during reduction. This indicates that ordinary activated carbon can support metals, but its ability to stabilize palladium single-atom sites and small ruthenium-palladium clusters is limited.

[0084] Example 7 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Embodiment 1 is that, except that the activated carbon support with defect sites on the surface is replaced with an equimolar amount of carbon nanotube support without defect sites on the surface, the rest is the same as Embodiment 1.

[0085] Carbon nanotubes possess good electrical conductivity and structural stability, but their surfaces are relatively inert, with few defects and oxygen- or nitrogen-containing coordination sites. Without oxidation or nitrogen doping modification, ruthenium and palladium precursors are difficult to anchor sufficiently, easily forming aggregated metal particles on their surface. This indicates that the surface chemical environment of the support has a significant impact on the formation of palladium single-atom sites and the size control of ruthenium-palladium clusters.

[0086] Example 8 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Example 1 is that, except that the activated carbon support with defect sites on the surface is replaced with an equimolar amount of silica support without defect sites on the surface, the rest is the same as Example 1.

[0087] Silica exhibits good thermal stability, but its interaction with noble metals is typically weak. During reduction, ruthenium and palladium species migrate and aggregate more readily, making it difficult to form highly dispersed palladium single-atom sites and stable ruthenium-palladium alloy clusters. This indicates that weak metal-support interactions are detrimental to the construction of stable dual-active-site catalysts.

[0088] Example 9 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Example 1 is that, except that the activated carbon support with defect sites on the surface is replaced with an equimolar amount of alumina support without defect sites on the surface, the rest is the same as Example 1.

[0089] The alumina surface contains Lewis acid sites, which can support ruthenium and palladium components. However, its surface acidity may affect the adsorption mechanism of dinitroaromatic hydrocarbons and aromatic diamine intermediates, and may also promote side reactions or lead to strong adsorption of intermediates. Compared with defective carbon supports, palladium single-atom sites and ruthenium-palladium alloy clusters have weaker electronic structure modulation capabilities. This indicates that the acid-base properties of the support and the surface coordination environment affect the activity and selectivity of tandem hydrogenation of dinitroaromatic hydrocarbons.

[0090] Example 10 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Example 1 is that, except for replacing the activated carbon support with defective sites on the surface with an equal molar amount of low-defect carbon support, everything else is the same as in Example 1.

[0091] Low-defect carbon surfaces have regular structures and low defect density, limiting the number of metal anchoring sites they can provide. Palladium precursors are difficult to stabilize and tend to migrate and form palladium particles during reduction; ruthenium-palladium alloy clusters also grow more readily. This indicates that carrier defect sites are key factors in stabilizing palladium single atoms and limiting the growth of ruthenium-palladium clusters.

[0092] Example 11 This embodiment provides a single-atom alloyed cluster dual-active-site hydrogenation catalyst. The difference from Embodiment 1 is that, except that the activated carbon support with defect sites on the surface is replaced with an equal molar amount of nitrogen-doped carbon support, everything else is the same as in Embodiment 1.

[0093] Nitrogen-doped carbon supports can anchor palladium species through pyridine N, pyrrole N, or graphite N sites, which is beneficial for improving the dispersion of palladium single atoms. Compared with ordinary activated carbon, this catalyst exhibits higher metal dispersion and stronger metal-support interactions. This demonstrates that introducing nitrogen-containing coordination sites is beneficial for improving the stability and catalytic activity of palladium single atoms.

[0094] Example 12 This embodiment provides a single-atom alloy cluster dual-active-site hydrogenation catalyst. The difference from Example 1 is that, except that the activated carbon support with defective sites on the surface is replaced with an equimolar amount of a defective boron nitride support, everything else is the same as in Example 1.

[0095] The surface of defective boron nitride contains B / N vacancies, edge sites, and polar BN bonds, which can interact strongly with palladium or ruthenium precursors, thus stabilizing single metal atoms and small-sized clusters. Simultaneously, the basic sites on the boron nitride surface are beneficial for regulating the adsorption of dinitroaromatics and amine intermediates, reducing side reactions caused by strong adsorption.

[0096] Example 13 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the preparation method of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the preparation of the palladium-supported intermediate in step (2) is adjusted as follows: the ruthenium-supported catalyst is added to an aqueous palladium nitrate solution for ultrasonic impregnation for 5-180 min at a power of 50-1000 W, the concentration of the aqueous palladium nitrate solution is 0.01 mol / L, and then dried at 80 °C for 12 h. The rest is the same as in Example 1.

[0097] During ultrasonic impregnation, cavitation and micromixing promote the uniform dispersion of palladium and ruthenium precursors on the support surface, inhibit local enrichment of metal salts, and facilitate the formation of small-sized ruthenium-palladium clusters and some palladium single-atom sites. When used for the hydrogenation of dinitroaromatics, this catalyst exhibits higher conversion rates and selectivity for the target alicyclic diamines than conventional co-impregnated catalysts.

[0098] Example 14 This embodiment provides a single-atom alloyed cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom alloyed cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of p-dinitrobenzene, and the resulting reaction solution is a hydrogenation product mainly composed of p-cyclohexanediamine. All other aspects are the same as in Example 1.

[0099] Compared to m-dinitrobenzene, p-dinitrobenzene has less steric hindrance at its two nitro sites, which is more conducive to the adsorption of the substrate on the catalyst surface and the stepwise hydrogenation, thus exhibiting higher conversion and target product selectivity.

[0100] Example 15 This embodiment provides a single-atom alloyed cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom alloyed cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of o-dinitrobenzene, and the resulting reaction solution is a hydrogenation product mainly composed of o-cyclohexanediamine. All other aspects are the same as in Example 1.

[0101] Because the ortho-dinitro structure has strong steric hindrance and easily forms various configurational isomers during hydrogenation, its target product selectivity is slightly lower than that of meta and para substrates, but it still maintains a high conversion rate and good hydrogenation effect, indicating that the catalyst provided in this embodiment is also well applicable to dinitro aromatics with strong steric hindrance.

[0102] Example 16 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 2,4-dinitrotoluene, and the resulting reaction solution is a methyl-substituted cyclohexanediamine product. All other aspects are the same as in Example 1.

[0103] The presence of methyl substituents did not significantly inhibit the hydrogenation conversion of dinitro groups, indicating that the catalyst provided in this embodiment has good catalytic activity for dinitro aromatics containing electron-donating alkyl substituents.

[0104] Example 17 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 2,6-dinitrotoluene, and the resulting reaction solution is a methyl-substituted alicyclic diamine product. All other aspects are the same as in Example 1.

[0105] Due to the strong steric hindrance between the 2,6-dinitro group and the methyl group, the adsorption of the substrate on the catalyst surface and the deep hydrogenation of the aromatic ring are somewhat affected. However, the substrate can still achieve a high degree of conversion, further demonstrating that the catalyst provided in this embodiment has a certain adaptability to sterically hindered dinitro aromatics.

[0106] Example 18 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 1,5-dinitronaphthalene, and the resulting reaction solution is a hydrogenated naphthalene diamine product. All other aspects are the same as in Example 1.

[0107] The catalyst provided in this embodiment is applicable not only to monocyclic dinitroaromatics but also to polycyclic dinitroaromatics substrates, and has a wide range of substrate applicability.

[0108] Example 19 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 4-chloro-1,3-dinitrobenzene, and the resulting reaction solution is a chlorocyclohexanediamine product. All other aspects are the same as in Example 1.

[0109] During the reaction, only a small amount of dechlorination byproducts were detected, indicating that the catalyst provided in this embodiment can promote the hydrogenation of nitro and aromatic rings while suppressing the hydrogenolysis side reaction of halogen substituents to a certain extent, and is suitable for the conversion of dinitro aromatics containing halogen substituents.

[0110] Example 20 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 4-methoxy-1,3-dinitrobenzene, and the resulting reaction solution is a methoxy-substituted alicyclic diamine product. All other aspects are the same as in Example 1.

[0111] The methoxy group, as an electron-donating substituent, can affect the electron cloud density of the aromatic ring and the substrate adsorption mode, but it does not significantly reduce the catalytic hydrogenation efficiency, indicating that the catalyst provided in this embodiment has good applicability to dinitroaromatics containing electron-donating substituents.

[0112] Example 21 This embodiment provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the application of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and that of Example 1 is that the m-dinitrobenzene is replaced by an equal mass of 4-trifluoromethyl-1,3-dinitrobenzene, and the resulting reaction solution is a trifluoromethyl-substituted alicyclic diamine product. All other aspects are the same as in Example 1.

[0113] Trifluoromethyl has a strong electron-withdrawing effect, which may weaken the activity of further hydrogenation of the aromatic ring. Therefore, its target product selectivity is slightly lower than that of alkyl or methoxy substituted substrates, but the overall conversion effect is still good. This shows that the catalyst provided in this example is also applicable to dinitroaromatics containing strong electron-withdrawing substituents.

[0114] Comparative Example 1 This comparative example provides a single-atom active site hydrogenation catalyst. The preparation method of the single-atom active site hydrogenation catalyst differs from that of Example 1 in that step (2) is omitted, while the rest is the same as that of Example 1.

[0115] Ruthenium / activated carbon catalysts possess certain hydrogen activation and aromatic ring hydrogenation capabilities, but lack efficient palladium nitro adsorption and activation sites. Therefore, the initial hydrogenation rate of dinitroaromatics is low, the formation efficiency of aromatic diamine intermediates is insufficient, and the overall DNT conversion and alicyclic diamine yield are lower than those of the catalyst in Example 1. This demonstrates that a single ruthenium site is insufficient to simultaneously and efficiently complete both nitro hydrogenation and deep aromatic ring hydrogenation.

[0116] Comparative Example 2 This comparative example provides a hydrogenation catalyst. The preparation method of the hydrogenation catalyst differs from that of Example 1 in that the ruthenium trichloride aqueous solution in step (1) is replaced with an aqueous palladium nitrate solution, while the rest is the same as in Example 1.

[0117] Introducing highly dispersed palladium species via the ALD method can also effectively enhance the hydrogenation activity of dinitroaromatics. However, this comparative catalyst lacks ruthenium, making it impossible to construct the ruthenium-palladium alloy clusters and palladium single-atom synergistic active sites found in the catalyst of this application. Consequently, it is difficult to simultaneously achieve nitro hydrogenation, aromatic ring hydrogenation, and rapid intermediate conversion. In contrast, in the single-atom alloy cluster dual-active-site hydrogenation catalyst of this application, the ruthenium-palladium alloy clusters are beneficial for improving hydrogen activation and aromatic ring hydrogenation capabilities, while the palladium single-atom sites are beneficial for regulating the adsorption and conversion of nitroaromatics and intermediates. The synergistic effect of these two types of active sites enhances the selectivity and stability of the conversion of dinitroaromatics to the target alicyclic diamine. Therefore, although this comparative catalyst exhibits certain hydrogenation activity, its selectivity for the target alicyclic diamine, deep hydrogenation efficiency, and resistance to deactivation are all lower than those of the catalyst of this application.

[0118] Comparative Example 3 This comparative example provides a hydrogenation catalyst. The preparation method of the hydrogenation catalyst differs from that of Example 1 in that the ruthenium trichloride aqueous solution in step (1) is replaced with an aqueous palladium nitrate solution, and step (2) is omitted. All other steps are the same as in Example 1.

[0119] Palladium / activated carbon catalysts can promote the reduction of nitro groups, but due to the lack of polyatomic aromatic ring adsorption and hydrogenation sites provided by ruthenium-palladium alloy clusters, the ability of aromatic diamine intermediates to further hydrogenate to form alicyclic diamines is insufficient. This indicates that palladium sites alone are more favorable for nitro hydrogenation, but have limited ability to deeply hydrogenate aromatic rings.

[0120] Comparative Example 4 This comparative example provides a single-atom active site hydrogenation catalyst. The preparation method of the single-atom active site hydrogenation catalyst differs from that of Example 1 in that step (2) is omitted, and a ruthenium-supported catalyst is obtained; then, the ruthenium trichloride aqueous solution in step (1) is replaced with an equimolar amount of palladium nitrate aqueous solution, and step (2) is omitted, and a palladium-supported catalyst is obtained; the ruthenium-supported catalyst and the palladium-supported catalyst are mixed to obtain a single-atom active site hydrogenation catalyst, and the rest is the same as in Example 1.

[0121] Although both ruthenium and palladium sites coexist in the physically mixed catalyst, these two types of sites are located on different catalyst particles and are spatially far apart, making it difficult to form an effective interfacial synergistic effect. The migration efficiency of the aromatic diamine intermediate and active hydrogen between the ruthenium and palladium sites is low, resulting in a lower tandem hydrogenation efficiency than the catalyst in Example 1. This demonstrates that the simple physical coexistence of ruthenium and palladium sites cannot replace a spatially coupled dual-active-site structure.

[0122] Comparative Example 5 This comparative example provides a single-atom plus alloy cluster dual-active-site hydrogenation catalyst. The difference between the preparation method of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst and Example 1 is that the preparation of the palladium-supported intermediate in step (2) is adjusted as follows: the ruthenium-supported catalyst is added to an aqueous palladium nitrate solution for ordinary impregnation for 5-180 min, the concentration of the aqueous palladium nitrate solution is 0.01 mol / L, and then dried at 80 °C for 12 h. The rest is the same as in Example 1.

[0123] Conventional co-impregnation methods tend to cause localized enrichment of ruthenium and palladium precursors during drying and reduction, forming larger metal particles. This leads to a reduction in the number of palladium single-atom sites, a wider size distribution of ruthenium-palladium clusters, and a decrease in metal utilization. Therefore, atomic layer deposition (ALD) or ultrasonic impregnation methods are more effective in controlling the formation of palladium single atoms and ruthenium-palladium alloy clusters.

[0124] The reaction solutions prepared in Examples 1-21 and Comparative Examples 1-5 were analyzed by liquid chromatography to calculate the reactant conversion rate and alicyclic diamine selectivity. The results are shown in Tables 1 and 2.

[0125] Table 1 Table 2 As can be seen from the above embodiments and comparative examples, the advantage of the single-atom plus alloy cluster dual-active-site hydrogenation catalyst provided by the present invention does not stem from the simple superposition of ruthenium and palladium sites, but rather from the spatial coupling of palladium single-atom sites and ruthenium-palladium alloy cluster sites on the same support surface. Compared with monometallic catalysts, the single-atom plus alloy cluster dual-active-site hydrogenation catalyst provided by the present invention can simultaneously promote the hydrogenation of nitro groups and the deep hydrogenation of aromatic rings; compared with physically mixed catalysts, the two types of active sites in the single-atom plus alloy cluster dual-active-site hydrogenation catalyst provided by the present invention are closer together, which is beneficial to the migration of active hydrogen and the transfer of aromatic diamine intermediates; compared with ordinary co-impregnation catalysts, atomic layer deposition or ultrasonic impregnation methods can more effectively suppress metal agglomeration and increase the ratio of palladium single atoms and small-sized ruthenium-palladium clusters. In addition, different supports have a significant impact on catalyst performance. Supports rich in defects or containing heteroatom coordination sites are more conducive to stabilizing palladium single-atom sites and controlling the size of ruthenium-palladium clusters, thereby improving the activity and selectivity of tandem hydrogenation of dinitroaromatics to prepare alicyclic diamines.

[0126] In summary, the single-atom alloy cluster dual-active-site hydrogenation catalyst provided by this invention features palladium single-atom sites that exist in an atomically dispersed form and interact with anchoring sites on the support surface. These sites adsorb and activate nitro groups in dinitroaromatic hydrocarbons, promoting the hydrogenation of dinitroaromatic hydrocarbons to aromatic diamine intermediates. The ruthenium-palladium alloy clusters, composed of ruthenium and palladium atoms, are distributed on the support surface and adsorb and activate aromatic rings, further promoting the hydrogenation of aromatic diamine intermediates to alicyclic diamines. This achieves a tandem hydrogenation conversion of dinitroaromatic hydrocarbons to alicyclic diamines. This invention overcomes the problem of traditional single-metal catalysts being unable to simultaneously handle nitro hydrogenation and deep aromatic ring hydrogenation by dividing the functions of single-atom sites and alloy cluster sites, thus improving the efficiency of the tandem hydrogenation reaction. Furthermore, the presence of palladium as single-atom and small-sized alloy clusters significantly improves the utilization rate of precious metal atoms and reduces the amount of precious metal required.

[0127] This invention constructs palladium single-atom sites and ruthenium-palladium alloy clusters on the same support surface using atomic layer deposition or ultrasonic impregnation, achieving spatial coupling between nitro activation sites and aromatic ring hydrogenation sites. The single-atom alloy cluster dual-active-site hydrogenation catalyst can achieve one-step tandem hydrogenation of dinitroaromatics to alicyclic diamines under relatively mild temperature and hydrogen pressure, with a reactant conversion rate of up to 99.8% and an alicyclic diamine selectivity of up to 99.5%. It has the advantages of mild reaction conditions, high catalytic efficiency, good selectivity, and a simple process flow.

[0128] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A single-atom alloyed cluster dual-active-site hydrogenation catalyst, characterized in that, The carrier includes a carrier with anchoring points on its surface, and the carrier is loaded with palladium single-atom sites and ruthenium-palladium alloy clusters, both of which are dispersed on the surface of the carrier.

2. The single-atom alloy cluster dual-active-site hydrogenation catalyst according to claim 1, characterized in that, The palladium single-atom site forms at least one of the following structures with a carrier having anchoring points on its surface: palladium-nitrogen, palladium-oxygen, palladium-carbon, palladium-boron, or palladium-defect coordination structure; Preferably, the carrier comprises at least one of activated carbon, carbon black, graphitized carbon, nitrogen-doped carbon, carbon nanotubes, graphene, boron nitride, defective boron nitride, amino-modified boron nitride, carbon nitride, alumina, silicon dioxide, titanium dioxide, or cerium oxide. Preferably, the average particle size of the ruthenium-palladium alloy clusters is 0.3-5 nm, more preferably 0.5-2 nm; Preferably, the spatial distance between the palladium single-atom site and the ruthenium-palladium alloy cluster is 0.2-20 nm, and more preferably 0.5-10 nm.

3. The single-atom alloy cluster dual-active-site hydrogenation catalyst according to claim 1 or 2, characterized in that, The ruthenium content in the single-atom alloyed cluster dual-active-site hydrogenation catalyst is 0.1-10 wt%, preferably 0.5-3 wt%. Preferably, the palladium content in the single-atom alloy cluster dual-active-site hydrogenation catalyst is 0.001-5 wt%, more preferably 0.001-1 wt%.

4. A method for preparing a single-atom alloyed cluster dual-active-site hydrogenation catalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) The ruthenium precursor is loaded onto the surface of a support with anchoring points, and after a first reduction treatment, a ruthenium-supported catalyst is obtained; (2) The palladium precursor is loaded onto the surface of the ruthenium-supported catalyst obtained in step (1) by ultrasonic impregnation and / or atomic layer deposition, and after a second reduction treatment, the single-atom alloy cluster dual-active-site hydrogenation catalyst is obtained.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the ruthenium precursor to the carrier with anchoring points on its surface in step (1) is 1:(400-1000); Preferably, the ruthenium precursor in step (1) includes at least one of ruthenium trichloride, ruthenium acetylacetonate, ruthenium nitrite, ruthenium chloride, or ruthenium dichlorohexacarbonyl.

6. The preparation method according to claim 4 or 5, characterized in that, Step (1) The first reduction process is carried out in any one of hydrogen, a mixture of hydrogen and nitrogen, or a mixture of hydrogen and argon; Preferably, the temperature of the first reduction treatment in step (1) is 100-500℃, more preferably 150-350℃; Preferably, the time for the first reduction process in step (1) is 0.5-10h, and more preferably 1-5h.

7. The preparation method according to any one of claims 4-6, characterized in that, The molar ratio of the palladium precursor to the ruthenium-supported catalyst in step (2) is 1:(1000-2000); Preferably, the palladium precursor in step (2) includes at least one of palladium acetylacetonate, palladium chloroacetate, sodium palladium chloroacetate, potassium palladium chloroacetate, palladium nitrate, palladium acetate, ammonium hexachloropalladium, or tetraamminepalladium salt, and is preferably palladium acetylacetonate.

8. The preparation method according to any one of claims 4-7, characterized in that, The ultrasonic impregnation time in step (2) is 5-180 min, and the power is 50-1000 W; Preferably, the specific steps of the atomic layer deposition in step (2) include: placing the ruthenium-supported catalyst in the atomic layer deposition reactor, using the palladium precursor as the metal source, and sequentially performing palladium precursor pulse, inert protective gas purging, reaction gas pulse and inert protective gas purging for 1-100 cycles to obtain the palladium-supported intermediate; Preferably, the second reduction treatment in step (2) is carried out in any one of nitrogen, argon, hydrogen, a mixture of hydrogen and nitrogen, or a mixture of hydrogen and argon; Preferably, the temperature of the second reduction treatment in step (2) is 50-400℃, and more preferably 100-300℃; Preferably, the time for the second reduction treatment in step (2) is 0.5-8h, and more preferably 1-4h.

9. The application of a single-atom alloyed cluster dual-active-site hydrogenation catalyst as described in any one of claims 1-3, characterized in that, The single-atom alloy cluster dual-active-site hydrogenation catalyst is used for the tandem hydrogenation of dinitroaromatics to prepare alicyclic diamines. The specific steps include: A dinitroaromatic hydrocarbon, a solvent, and a single-atom alloying cluster dual-active-site hydrogenation catalyst are added to a reactor, and a hydrogenation reaction is carried out under a hydrogen atmosphere to obtain an alicyclic diamine product.

10. The application according to claim 9, characterized in that, The dinitroaromatic hydrocarbons include at least one of o-dinitrobenzene, m-dinitrobenzene, p-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, dinitroxylene, dinitrochlorobenzene, dinitrobiphenyl, and their respective substituted derivatives; Preferably, the hydrogenation reaction is carried out at a temperature of 20-180°C, a hydrogen pressure of 0.1-10 MPa, and a time of 10-600 min. Preferably, the mass of the single-atom alloy cluster dual-active-site hydrogenation catalyst is 0.1-50 wt% of the mass of the dinitroaromatic hydrocarbon, and more preferably 1-20 wt%.

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