Palladium monatomic-ruthenium cluster double-active-site hydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention relates to a palladium monatomic-ruthenium cluster double-active-site hydrogenation catalyst and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing a mixed salt solution of a palladium active component precursor and a ruthenium active component precursor with a defect-rich boron nitride carrier to obtain an intermediate mixture; and (2) mixing the intermediate mixture obtained in the step (1) with a reducing agent, and carrying out low-temperature reduction treatment to obtain the palladium monatomic-ruthenium cluster double-active-site hydrogenation catalyst, wherein the defect-rich boron nitride carrier is prepared from a modifier; the modifier comprises a Zn group-containing compound. The catalyst prepared by the invention can realize efficient hydrogenation of nitro-aromatic hydrocarbon under mild conditions, shows excellent catalytic activity and stability under working conditions, and has good industrial application potential.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, its preparation method, and its applications. Background Technology

[0002] In recent years, the application of alicyclic amines in key core fields such as wind power, microelectronics industry, and rocket propellants has grown rapidly. Among them, cyclohexylamine is the most representative alicyclic amine, which can be used to prepare chemicals such as cyclohexanol, cyclohexanone, caprolactam, cellulose acetate, and nylon, as well as for the synthesis of artificial sweeteners (sodium aminosulfonate, calcium aminosulfonate), metal corrosion inhibitors, rubber vulcanization additives, dyes, plasticizers, and natural product extractants. It can also be used as a solvent in the resin, coating, fat, and paraffin oil industries. The most important characteristics of alicyclic amines are the amino and cycloalkyl groups, making their construction a key step in their synthesis. For example, the amino group can be obtained through catalytic amination or nitro hydrogenation, and the cycloalkyl group can be obtained through the hydrogenation of aromatic rings or cycloolefins.

[0003] Catalytic hydrogenation of nitroaromatics is currently the mainstream process for producing alicyclic amines. Fixed-bed gas-phase catalytic hydrogenation exhibits good maturity and stability, requiring no separation of catalyst and product, and has lower equipment costs. However, its drawbacks include the susceptibility of catalyst deactivation during the reaction, necessitating frequent catalyst replacement, and the potential for side reactions due to localized overheating. Liquid-phase hydrogenation of nitroaromatics operates at lower temperatures than gas-phase hydrogenation, resulting in higher production capacity and fewer byproducts. The hydrogenation catalyst plays a crucial role in this process. Therefore, developing efficient and selective catalysts is of great significance for the hydrogenation of nitroaromatics to produce alicyclic amines.

[0004] CN120132885A discloses a method for preparing a boron nitride-confined platinum single-atom-platinum cluster dual-site catalyst, comprising: mixing urea, boric acid, and carbon nanotubes and grinding them; placing the ground mixture in a medium ammonia-argon mixed atmosphere for a first pyrolysis to obtain powder; adding the powder to a boric acid solution and heating and stirring to obtain a defect-rich boron nitride support; washing and drying the support and immersing it in a platinum salt aqueous solution and dispersing it by ultrasonication, followed by vacuum freeze-drying; and finally, subjecting the dried sample to a second pyrolysis in a medium ammonia-argon mixed atmosphere.

[0005] CN114653371A discloses a method for preparing an atomically dispersed metal catalyst supported on high-defect boron nitride. The method involves mixing and grinding urea, boric acid, and carbon nanotubes, then reacting the mixture at 800–1100 °C under an ammonia-argon mixed atmosphere. The resulting powder is then mixed with a boric acid solution and heated, followed by washing with water to obtain a defect-rich boron nitride composite material. This composite material is then mixed with a metal salt solution, ultrasonically treated, freeze-dried, and finally heat-treated at 650–850 °C under an ammonia-argon mixed atmosphere to obtain the atomically dispersed metal catalyst supported on high-defect boron nitride.

[0006] In summary, existing catalysts still have room for improvement in terms of active component design, preparation process, and reaction conditions. Therefore, there is an urgent need to develop a novel, highly efficient catalyst that is easy to prepare, operates under mild reaction conditions, and exhibits good stability to promote the industrial application of the hydrogenation of nitroaromatics to alicyclic amines. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, its preparation method, and its applications. The preparation method of the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst of this invention is simple, exhibits high dispersion of the active components, and enhances catalytic activity, achieving highly efficient catalytic synthesis of cyclohexylamine under mild conditions and significantly improving the yield.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, the preparation method comprising:

[0010] (1) A mixed salt solution of palladium active component precursor and ruthenium active component precursor was mixed with a defect-rich boron nitride support to obtain an intermediate mixture;

[0011] (2) The intermediate mixture obtained in step (1) is mixed with a reducing agent and subjected to low-temperature reduction treatment to obtain the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst;

[0012] The defect-rich boron nitride support is prepared using a modifier; the modifier includes Zn-based compounds.

[0013] The palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst prepared by this invention has abundant defect sites and basic sites on its support surface, resulting in highly dispersed active components and improved utilization. In the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst prepared by this invention, the Pd single-atom site has a stronger selective adsorption and activation ability for nitro (-NO2) groups, which is beneficial for achieving preferential hydrogenation of nitro groups and suppressing side reactions; the Ru cluster is more adept at H2 dissociation and aromatic ring π-bond hydrogenation, which is beneficial for achieving deep hydrogenation of benzene rings; the two work synergistically on the same support to achieve tandem hydrogenation / synergistic hydrogenation of nitro aromatics "nitro first, then aromatic ring", improving overall activity and target product selectivity.

[0014] In this invention, preferential coordination—first anchoring of Pd single atoms: by selecting a suitable Pd precursor / ligand system (organic ligands have stronger coordination ability), Pd species are more likely to form stable coordination with the anchoring sites of defective BN during the solution mixing stage, and preferentially solidify into Pd single atom sites after calcination / reduction (strong coordination, strong anchoring, and difficult migration and aggregation); subsequently, Ru is introduced—more likely to aggregate to form clusters: Ru precursors have a relatively weak tendency to anchor stable single atoms at the same support site, and are more likely to undergo metal-metal interactions and migration and aggregation during the reduction process, thus tending to form Ru clusters; by adjusting the type and amount of Ru precursor, the cluster size and distribution can be controlled.

[0015] As a preferred technical solution of the present invention, the preparation method of the defect-rich boron nitride support in step (1) includes:

[0016] The defective boron nitride support is obtained by calcining a mixture of nitrogen source, boron source and modifier.

[0017] This invention prepares defective boron nitride supports by using Zn-based compounds as modifiers. Zn-based compounds exhibit significant volatilization / migration characteristics at high temperatures (calcination temperature of 800-1000°C), while the phase-forming temperature of boron nitride is approximately 900°C. Therefore, during the calcination phase-forming process, Zn species can act as a "dynamic template / sacrificial agent," and their volatilization or migration leaves controllable pore / vacancy defects in the BN framework, thereby achieving adjustable defect size and density.

[0018] In the precursor reaction liquid stage, Zn 2+ It readily forms complexes / coordinates with N, B, and O-containing ligands, enabling it to "pre-organize" precursor structures at the molecular level. After calcination, the Zn species withdraw / rearrange, and the remaining vacancies, edge sites, and B / N unsaturated sites become stable metal anchoring points, improving subsequent metal dispersion and resistance to sintering.

[0019] Zn modification completes coordination in the solution stage and "solidifies" defects in the calcination stage, eliminating the need for additional etching or post-processing, resulting in a simpler and more repeatable process.

[0020] In this invention, the reaction mechanism for preparing defective boron nitride supports by reacting Zn-based compounds with nitrogen and boron sources is as follows: Solution stage: Zn 2+ It complexes / coordinates with the BN precursor (containing N / B / O intermediates) to form a locally enriched Zn-(N / O / B) coordination structure; during the calcination stage (~900°C): as BN forms phase and rearranges its structure, Zn species volatilize / migrate, and B / N vacancies, edge sites, or pore defects are formed at the original Zn-(N / O / B) sites; the number and size of defects can be adjusted with the amount of Zn incorporated; finally, a "defect-rich BN carrier" is obtained, providing metal anchoring points with higher density and stronger binding force.

[0021] As a preferred technical solution of the present invention, the Zn-based compound includes any one or a combination of at least two of zinc hydroxide, zinc oxide, zinc chloride, zinc sulfate, basic zinc carbonate, or zinc acetate. Typical but non-limiting examples of such combinations include: zinc hydroxide and zinc oxide, zinc oxide and zinc chloride, zinc chloride and zinc sulfate, zinc sulfate and basic zinc carbonate, basic zinc carbonate and zinc acetate, etc.

[0022] Preferably, the nitrogen source includes any one or a combination of at least two of urea, ethylenediamine, aniline, or naphthylamine, with typical but non-limiting examples of such combinations being urea and ethylenediamine, ethylenediamine and aniline, aniline and naphthylamine, etc.

[0023] Preferably, the boron source includes boric acid.

[0024] As a preferred technical solution of the present invention, the mass ratio of the nitrogen source, boron source and modifier is (10-50):(10-50):1, for example 10:10:1, 20:20:1, 30:30:1, 40:40:1, 50:50:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and it is further preferred to be (10-20):(10-30):1.

[0025] Preferably, the method for mixing the nitrogen source, boron source, and modifier includes heating and stirring.

[0026] Preferably, the heating and stirring temperature is 30-80℃, such as 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and 50-80℃ is more preferably preferred.

[0027] Preferably, the heating and stirring time is 2-4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0028] Preferably, the heating and stirring process further includes a drying process; the drying process is carried out at a temperature of 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0029] Preferably, the drying time is 8-12 hours, such as 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the calcination temperature is 800-1000℃, such as 800℃, 850℃, 900℃, 950℃, 1000℃, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the calcination time is 5-20 hours, such as 5 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. More preferably, it is 10-15 hours.

[0032] As a preferred technical solution of the present invention, the molar ratio of the palladium active component precursor and the ruthenium active component precursor in step (1) is (1-1.1):1, for example 1:1, 1.02:1, 1.04:1, 1.06:1, 1.08:1, 1.1:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the palladium active component precursor includes any one or a combination of at least two of [Pd(NH3)4](NO3)2, [Pd(NH3)]4SO4, (NH4)2PdCl6, K2PdCl4, Na2PdCl4, Pd(Ac)2, Pd(OAc)2, PdCl2, and Pd(NO3)2. Typical but non-limiting examples of such combinations include: [Pd(NH3)4](NO3)2 and [Pd(NH3)]4SO4, [Pd(NH3)]4SO4 and (NH4)2PdCl6, (NH4)2PdCl6 and K2PdCl4, K2PdCl4 and Na2PdCl4, Na2PdCl4 and Pd(Ac)2, Pd(Ac)2 and Pd(OAc)2, Pd(OAc)2 and PdCl2, PdCl2 and Pd(NO3)2, etc.

[0034] Preferably, the ruthenium active component precursor includes any one or a combination of at least two of RuCl3·nH2O, Ru2Cl4(CO)6, RuI3, K2RuCl, or (NH)4RuCl6. Typical but non-limiting examples of such combinations include RuCl3·nH2O and Ru2Cl4(CO)6, Ru2Cl4(CO)6 and RuI3, RuI3 and K2RuCl, K2RuCl and (NH)4RuCl6, etc.

[0035] As a preferred technical solution of the present invention, the total content of the palladium active component precursor and the ruthenium active component precursor in step (1) is in the molar ratio of the defect-rich boron nitride support to (0.01-0.05):1, for example 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, the mixing method in step (1) includes ultrasonic-assisted impregnation; the ultrasonic time for ultrasonic-assisted impregnation is 1-5h, such as 1h, 2h, 3h, 4h, 5h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] As a preferred technical solution of the present invention, the reducing agent in step (2) includes sodium borohydride;

[0038] Preferably, the molar ratio of the reducing agent to the total content of the palladium active component precursor and the ruthenium active component precursor is 20-80:1, such as 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the temperature of the low-temperature reduction treatment in step (2) is 10-30℃, such as 10℃, 12℃, 15℃, 18℃, 20℃, 22℃, 25℃, 28℃, 30℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the time for the low-temperature reduction treatment in step (2) is 30-120 min, such as 30 min, 40 min, 50 min, 60 min, 70 min, 90 min, 110 min, 120 min, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. More preferably, it is 60-80 min.

[0041] Preferably, the low-temperature reduction process in step (2) is carried out in an oxygen-free atmosphere; the gas used in the oxygen-free atmosphere includes any one or at least two combinations of nitrogen, hydrogen or argon, and typical but non-limiting examples of such combinations are: nitrogen and hydrogen, nitrogen and argon, and hydrogen and argon.

[0042] In a second aspect, the present invention provides a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, wherein the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst is prepared by the preparation method described in the first aspect.

[0043] Preferably, the total loading of the palladium active component and the ruthenium active component is 0.1-5 wt%, such as 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] Thirdly, the present invention provides the use of the hydrogenation catalyst as described in the second aspect, said hydrogenation catalyst for the hydrogenation of nitroaromatic hydrocarbons to prepare alicyclic amines.

[0045] The palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst provided by this invention can effectively suppress the formation of byproducts dicyclohexylamine and cyclohexylamine in the catalytic hydrogenation of nitroaromatic hydrocarbons to prepare alicyclic amines without the addition of auxiliary agents, reduce catalyst deactivation caused by byproducts, and achieve high conversion rate of nitroaromatic hydrocarbon hydrogenation and high selectivity for cyclohexylamine.

[0046] As a preferred embodiment of the present invention, the application includes: hydrogenating nitroaromatics using the hydrogenation catalyst under a hydrogen atmosphere.

[0047] Preferably, the mass of the hydrogenation catalyst is 1-25 wt% of the mass of the nitroaromatic hydrocarbon, such as 1 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0048] Preferably, the hydrogenation temperature of the nitroaromatic hydrocarbon is 50-100℃, such as 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0049] Preferably, the initial pressure for hydrogenating the nitroaromatic hydrocarbon is 1-3 MPa, such as 1 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa, 2 MPa, 2.3 MPa, 2.5 MPa, 3 MPa, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0050] Preferably, the reaction time for hydrogenation of the nitroaromatic hydrocarbon is 60-180 min, such as 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] Preferably, the hydrogenation of the nitroaromatic hydrocarbon is carried out in a solvent medium.

[0052] Preferably, the solvent comprises any one or a combination of at least two of tetrahydrofuran, methanol, isopropanol, ethanol, cyclohexane, cyclohexylamine, n-butanol, toluene, N-methylpyrrolidone, or tert-butanol. Typical but non-limiting examples of such combinations include: tetrahydrofuran and methanol, methanol and isopropanol, isopropanol and ethanol, ethanol and cyclohexane, cyclohexane and cyclohexylamine, cyclohexylamine and n-butanol, n-butanol and toluene, toluene and N-methylpyrrolidone, N-methylpyrrolidone and tert-butanol, etc.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] (1) The present invention prepares a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst by simple heating and mixing, low-temperature reduction treatment and ultrasonic-assisted impregnation. The hydrogenation catalyst support has a high specific surface area and contains abundant nitrogen active sites, defect sites and basic sites, which can coordinate with the active components, so that the active components are highly dispersed on the surface of the support, and the active components are utilized efficiently.

[0055] (2) The nitrogen sites and defect sites of defective boron nitride work together to regulate the valence electrons of the metal, and at the same time, they act as basic sites to enhance the basicity of the catalyst. This allows the catalyst to effectively suppress the formation of byproducts dicyclohexylamine and cyclohexylamine without the addition of auxiliary agents, reducing catalyst deactivation caused by byproducts. The reaction is carried out under relatively mild temperature and pressure, achieving high conversion rate of hydrogenation of nitro aromatics and high selectivity for alicyclic amines. The conversion rate of nitro aromatics can reach 100%, and the selectivity of alicyclic amines is stable at about 99%. Moreover, no basic auxiliary agents are introduced, and no subsequent separation operation is required, which greatly reduces the production cost and reduces the discharge of waste liquid and waste residue. Attached Figure Description

[0056] Figure 1 This is a spherical aberration electron microscopy characterization image of the catalyst obtained in Example 1 of the present invention. Detailed Implementation

[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0058] Example 1

[0059] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, the preparation method comprising:

[0060] (1) The active component precursor [Pd(NH3)4](NO3)2 and RuCl3·nH2O were mixed at a molar ratio of 1:1 and added to deionized water to prepare a homogeneous metal precursor solution; the total loading of (Pd+Ru) was controlled to be 1.0wt% based on the mass of the defect-rich boron nitride support (the molar ratio of the total content of the active component precursor to the defect-rich boron nitride support was 0.03:1), and the metal precursor solution was mixed with the defect-rich boron nitride support and ultrasonically impregnated for 3h to obtain an intermediate mixture;

[0061] (2) The intermediate mixture obtained in step (1) was mixed with an aqueous solution containing 3.42 mg sodium borohydride under a nitrogen atmosphere (taking 1 g of catalyst as an example, and the following calculations are based on this mass), and stirred at 10 °C for 60 min for low-temperature reduction treatment; after the reaction was completed, the mixture was centrifuged, washed with water until the washing liquid was neutral, and dried under vacuum at 60 °C to obtain the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst;

[0062] The method for preparing the defect-rich boron nitride support includes: mixing urea, boric acid and zinc acetate in a mass ratio of 20:10:1, adding 50 mL of water, heating and stirring at 50°C for 3 h; then drying the mixture at 80°C for 12 h, then transferring it to a tube furnace and calcining it at 900°C for 10 h under a nitrogen atmosphere, cooling, washing until neutral and drying to obtain the defect-rich boron nitride support.

[0063] The aberration-corrected electron microscopy characterization image of the catalyst obtained in this embodiment is as follows: Figure 1 As shown, Pd is anchored to the defect sites of the support in an atomically dispersed state, while Ru exists on the support surface in a highly dispersed cluster form, thus forming a dual-active-site synergistic structure.

[0064] Example 2

[0065] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, the preparation method comprising:

[0066] (1) The active component precursor [Pd(NH3)4](NO3)2 and RuCl3·nH2O were mixed in a molar ratio of 1:1 and added to deionized water to prepare a homogeneous metal precursor solution; based on the mass of the defect-rich boron nitride support, the total loading of (Pd+Ru) was controlled to be 0.33wt% (the molar ratio of the total content of the active component precursor to the defect-rich boron nitride support was 0.01:1), and the metal precursor solution was mixed with the defect-rich boron nitride support and ultrasonically impregnated for 1 h to obtain an intermediate mixture;

[0067] (2) The intermediate mixture obtained in step (1) was mixed with an aqueous solution containing 1.24 mg sodium borohydride under an argon atmosphere (taking 1 g of catalyst as an example, and the following calculations are based on this mass), and stirred at 25 °C for 80 min for low-temperature reduction treatment; after the reaction was completed, the mixture was centrifuged, washed with water until the washing liquid was neutral, and dried under vacuum at 60 °C to obtain the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst;

[0068] The method for preparing the defect-rich boron nitride support includes: mixing ethylenediamine, boric acid and zinc chloride in a mass ratio of 15:8:1, adding 50 mL of water, heating and stirring at 30°C for 2 h; then drying the mixture at 70°C for 10 h, then transferring it to a tube furnace and calcining it at 800°C for 15 h under a nitrogen atmosphere, cooling, washing until neutral and drying to obtain the defect-rich boron nitride support.

[0069] Example 3

[0070] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, the preparation method comprising:

[0071] (1) K2PdCl4 and (NH4)2RuCl6, the active component precursors, were mixed in a molar ratio of 1:1 and added to deionized water to prepare a homogeneous metal precursor solution. Based on the mass of the defect-rich boron nitride support, the total loading of (Pd+Ru) was controlled to be 1.67wt% (the molar ratio of the total content of the active component precursor to the defect-rich boron nitride support was 0.05:1). The metal precursor solution was mixed with the defect-rich boron nitride support and ultrasonically impregnated for 5 hours to obtain an intermediate mixture.

[0072] (2) The intermediate mixture obtained in step (1) was mixed with an aqueous solution containing 5.71 mg sodium borohydride under an argon atmosphere (taking 1 g of catalyst as an example, and the following calculations are based on this mass), and stirred at 15 °C for 120 min for low-temperature reduction treatment; after the reaction was completed, the mixture was centrifuged, washed with water until the washing liquid was neutral, and dried under vacuum at 60 °C to obtain the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst;

[0073] The method for preparing the defect-rich boron nitride support includes: mixing naphthylamine, boric acid and zinc hydroxide in a mass ratio of 18:10:1, adding 50 mL of water, heating and stirring at 60 °C for 4 h; then drying the mixture at 85 °C for 8 h, then transferring it to a tube furnace and calcining it at 1000 °C for 8 h under a nitrogen atmosphere, cooling, washing until neutral and drying to obtain the defect-rich boron nitride support.

[0074] Example 4

[0075] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that in the preparation method of the defect-rich boron nitride support, the mass ratio of urea to zinc acetate is adjusted to 50:1. All other aspects are the same as in Example 1.

[0076] Example 5

[0077] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that in the preparation method of the defect-rich boron nitride support, the calcination temperature is adjusted to 700℃ and the calcination time is adjusted to 20h. All other aspects are the same as in Example 1.

[0078] Example 6

[0079] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that the ultrasonic-assisted impregnation time in step (1) is adjusted to 0.5 h, while the rest is the same as in Example 1.

[0080] Example 7

[0081] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that the temperature of the low-temperature reduction treatment in step (2) is adjusted to 35°C. All other aspects are the same as in Example 1.

[0082] Example 8

[0083] This embodiment provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that, in the preparation method of the defect-rich boron nitride support, urea is replaced by ammonia gas by mass, and the catalyst is mixed with boric acid and zinc acetate in a gas-passing manner. All other aspects are the same as in Example 1.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that in the preparation method of the defect-rich boron nitride support, only urea and boric acid are mixed, and zinc acetate is not added. All other aspects are the same as in Example 1.

[0086] Comparative Example 2

[0087] This comparative example provides a method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The only difference from Example 1 is that in the preparation method of the defect-rich boron nitride support, zinc acetate is replaced by cyanamide by mass. All other aspects are the same as in Example 1.

[0088] Application Example 1

[0089] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 1 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine. The application includes:

[0090] 0.123 g of nitrobenzene, 0.01 g of the hydrogenation catalyst prepared in Example 1, and 10 mL of tetrahydrofuran were added to a stainless steel autoclave. The autoclave was purged with nitrogen and hydrogen three times, and finally purged with 3 MPa of H2. After confirming that the autoclave was well sealed, the autoclave was heated to 80 °C and held for 120 min. After the reaction was completed, the autoclave was cooled to room temperature with cold water to release the gas inside. The autoclave was then opened, the catalyst was separated by centrifugation, and the supernatant was analyzed by gas chromatography. The results are listed in Table 1.

[0091] Application Example 2

[0092] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 1 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine. The application includes:

[0093] 0.123 g of nitrobenzene, 0.03 g of the hydrogenation catalyst prepared in Example 1, and 10 mL of tetrahydrofuran were added to a stainless steel autoclave. The autoclave was purged with nitrogen and hydrogen three times, and finally purged with 3 MPa of H2. After confirming that the autoclave was well sealed, the autoclave was heated to 80 °C and held for 120 min. After the reaction was completed, the autoclave was cooled to room temperature with cold water to release the gas inside. The autoclave was then opened, the catalyst was separated by centrifugation, and the supernatant was analyzed by gas chromatography. The results are listed in Table 1.

[0094] Application Example 3

[0095] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 1 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine. The application includes:

[0096] 0.123 g of nitrobenzene, 0.0012 g of the hydrogenation catalyst prepared in Example 1, and 10 mL of tetrahydrofuran were added to a stainless steel autoclave. The autoclave was purged with nitrogen and hydrogen three times, and finally purged with 1 MPa of H2. After confirming that the autoclave was well sealed, the autoclave was heated to 50 °C and held for 180 min. After the reaction was completed, the autoclave was cooled to room temperature with cold water, the gas inside the autoclave was released, the autoclave was opened, the catalyst was separated by centrifugation, and the composition of the supernatant was analyzed by gas chromatography. The results are listed in Table 1.

[0097] Application Example 4

[0098] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 2 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0099] Application Example 5

[0100] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 3 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0101] Application Example 6

[0102] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 4 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0103] Application Example 7

[0104] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 5 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0105] Application Example 8

[0106] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 6 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0107] Application Example 9

[0108] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 7 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0109] Application Example 10

[0110] This application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Example 8 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and the rest is the same as in Application Example 1.

[0111] Comparative Application Example 1

[0112] This comparative application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Comparative Example 1 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and all other aspects are the same as in Application Example 1.

[0113] Comparative Application Example 2

[0114] This comparative application example provides the use of a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst. The hydrogenation catalyst prepared in Comparative Example 2 is used for the hydrogenation of nitroaromatics to prepare cyclohexylamine, and all other aspects are the same as in Application Example 1.

[0115] Performance testing

[0116] After the reaction was completed, the autoclave was cooled to room temperature and the pressure was slowly released. The autoclave was then opened and the reaction mixture was removed. The solid catalyst was separated by centrifugation or filtration, and the supernatant was collected as the analyte. If necessary, the volume was adjusted with tetrahydrofuran (THF), and the mixture was filtered through a 0.22 μm organic filter membrane before gas chromatography analysis. The composition of the supernatant obtained from Application Examples 1-10 and Comparative Application Examples 1-2 was analyzed by gas chromatography, and the results are shown in Table 1.

[0117] Nitroaromatic hydrocarbons (e.g., nitrobenzene) are used as reactants, and alicyclic amines (e.g., cyclohexylamine) are used as target products. Conversion and selectivity are calculated in moles (mol).

[0118] Nitroaromatic conversion rate: ;

[0119] in, : The initial amount of nitroaromatic hydrocarbons before the reaction;

[0120] The amount of nitroaromatic hydrocarbon remaining after the reaction;

[0121] The amount of the target alicyclic amine after the reaction;

[0122] : after the reaction The amount of substance of a product (including intermediates / byproducts).

[0123] Considering that one nitroaromatic molecule corresponds to one alicyclic amine molecule after complete hydrogenation (taking nitrobenzene → cyclohexylamine as an example with a 1:1 stoichiometry), the selectivity of alicyclic amines is defined as "the proportion of alicyclic amines formed in the converted nitroaromatic hydrocarbons";

[0124] Alicyclic amine selectivity: ;

[0125] in, : The initial amount of nitroaromatic hydrocarbons before the reaction;

[0126] The amount of nitroaromatic hydrocarbon remaining after the reaction;

[0127] : The amount of the target alicyclic amine after the reaction.

[0128] Table 1

[0129]

[0130] The test results show that:

[0131] (1) As can be seen from Application Examples 1 to 5, the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst obtained by the preparation method described in this invention has excellent catalytic performance, with a nitroaromatic hydrocarbon conversion rate of 100% and a cycloaliphatic amine selectivity of over 99%, thus achieving highly efficient catalysis for the hydrogenation of nitroaromatic hydrocarbons to prepare cyclohexylamine.

[0132] (2) As can be seen from Application Example 1 and Application Examples 6-10, when the parameters deviate from the preferred range during the preparation process, such as excessive modifier ratio, abnormal calcination temperature / ultrasound time, or excessive reduction temperature, the catalyst activity will decrease significantly and the conversion rate of nitroaromatic hydrocarbons will decrease significantly. However, the selectivity of alicyclic amines will be less affected, indicating the rationality and controllability of the catalyst preparation process parameters.

[0133] (3) By comparing Application Example 1 with Comparative Application Example 1-2, it can be seen that in Comparative Application Example 1, without the use of Zn-based compounds for modification, the use of defect-free boron nitride as a support significantly reduces the activity of the catalyst, with the conversion rate of nitroaromatic hydrocarbons decreasing to 10.5%, further confirming the key role of defect-rich boron nitride support in the dispersion of active components and catalytic activity; in Comparative Application Example 2, cyanamide containing nitrogen is used as a modifier. Nitrogen-based modifiers mainly introduce defects by changing the condensation and phase formation pathways of precursors, which is mainly chemically regulated; while Zn-based modifiers have the dual function of "solution coordination pre-organization + high-temperature volatilization sacrificial template", which is chemically regulated + physical / structural template coupling, and has more advantages in terms of the adjustability, repeatability and anchoring point strength of the support defects; therefore, the defect-rich boron nitride support prepared by using Zn-based compound modifiers can improve the conversion rate of nitroaromatic hydrocarbons.

[0134] In summary, this invention provides a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, its preparation method, and its applications. A palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst is prepared through a simple heating-mixing, low-temperature reduction treatment, and ultrasonic-assisted impregnation method. The resulting hydrogenation catalyst support has a high specific surface area and contains abundant nitrogen active sites, defect sites, and basic sites, which can coordinate with the active components, resulting in high dispersion of the active components on the support surface and achieving efficient utilization of the active components. The nitrogen sites and defect sites of defective boron nitride synergistically regulate the metal valence electrons and simultaneously enhance its basicity as basic sites. This allows the catalyst to effectively suppress the formation of byproducts dicyclohexylamine and cyclohexylamine without the addition of auxiliary agents, reducing catalyst deactivation caused by byproducts. The reaction is carried out under relatively mild temperature and pressure conditions, achieving high conversion rates for nitroaromatic hydrogenation and high selectivity for alicyclic amines. The conversion rate of nitroaromatics can reach 100%, and the selectivity for alicyclic amines is stable at around 99%. Moreover, no basic auxiliary agents are introduced, and no subsequent separation operations are required, significantly reducing production costs and the discharge of waste liquid and residue.

[0135] The applicant declares that 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 method for preparing a palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, characterized in that, The preparation method includes: (1) A mixed salt solution of palladium active component precursor and ruthenium active component precursor was mixed with a defect-rich boron nitride support to obtain an intermediate mixture; (2) The intermediate mixture obtained in step (1) is mixed with a reducing agent and subjected to low-temperature reduction treatment to obtain the palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst; The defect-rich boron nitride support is prepared using a modifier; the modifier includes Zn-based compounds.

2. The preparation method according to claim 1, characterized in that, The preparation method of the defect-rich boron nitride support in step (1) includes: The defective boron nitride support is obtained by calcining a mixture of nitrogen source, boron source and modifier.

3. The preparation method according to claim 2, characterized in that, The Zn-based compound includes any one or a combination of at least two of zinc hydroxide, zinc oxide, zinc chloride, zinc sulfate, basic zinc carbonate, or zinc acetate; The nitrogen source includes any one or a combination of at least two of ammonia, urea, ethylenediamine, aniline, or naphthylamine; the boron source includes boric acid.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the nitrogen source, boron source and modifier is (10-50):10-50):1; The method for mixing the nitrogen source, boron source, and modifier includes heating and stirring; The heating and stirring temperature is 30-80℃; the heating and stirring time is 2-4 hours. The roasting process is carried out at a temperature of 800-1000℃ for 5-20 hours.

5. The preparation method according to claim 1, characterized in that, The palladium active component precursor in step (1) includes any one or a combination of at least two of the following: [Pd(NH3)4](NO3)2, [Pd(NH3)]4SO4, (NH4)2PdCl6, K2PdCl4, Na2PdCl4, Pd(Ac)2, Pd(OAc)2, PdCl2, and Pd(NO3)2. The ruthenium active component precursor includes any one or a combination of at least two of RuCl3·nH2O, Ru2Cl4(CO)6, RuI3, K2RuCl, or (NH)4RuCl6.

6. The preparation method according to claim 1, characterized in that, The total content of the palladium active component precursor and the ruthenium active component precursor in step (1) is in a molar ratio of (0.01-0.05):1 with respect to the defect-rich boron nitride support. The mixing method in step (1) includes ultrasonic-assisted impregnation; the ultrasonic time for ultrasonic-assisted impregnation is 1-5 hours.

7. The preparation method according to claim 1, characterized in that, The reducing agent in step (2) includes sodium borohydride; The molar ratio of the reducing agent to the total content of the palladium active component precursor and the ruthenium active component precursor is 20-80:1; The temperature for the low-temperature reduction treatment in step (2) is 10-30℃; The low-temperature reduction treatment in step (2) takes 30-120 minutes; The low-temperature reduction process in step (2) is carried out in an oxygen-free atmosphere; the gas used in the oxygen-free atmosphere includes any one or a combination of at least two of nitrogen, hydrogen or argon.

8. A palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst, characterized in that, The palladium single-atom-ruthenium cluster dual-active-site hydrogenation catalyst is prepared by the preparation method described in any one of claims 1-7.

9. Use of the hydrogenation catalyst as described in claim 8, characterized in that, The hydrogenation catalyst is used for the hydrogenation of nitroaromatics to prepare alicyclic amines.

10. The use according to claim 9, characterized in that, The applications include: hydrogenating nitroaromatics using the hydrogenation catalyst under a hydrogen atmosphere; The hydrogenation catalyst has a mass of 1-25 wt% of the nitroaromatic hydrocarbon. The hydrogenation temperature of the nitroaromatic hydrocarbon is 50-100℃; The initial pressure for hydrogenating the nitroaromatic hydrocarbon is 1-3 MPa; The reaction time for hydrogenating the nitroaromatic hydrocarbon is 60-180 min; The hydrogenation of the nitroaromatic hydrocarbon is carried out in a solvent medium; The solvent includes any one or a combination of at least two of tetrahydrofuran, methanol, isopropanol, ethanol, cyclohexane, cyclohexylamine, n-butanol, toluene, N-methylpyrrolidone, or tert-butanol.

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