NiCo nanospherical alloy catalyst material, and preparation method and application thereof

Abstract

This invention belongs to the field of catalytic materials technology, and discloses a NiCo nanosphere alloy catalyst material, its preparation method, and its application. The invention involves dissolving nickel nitrate, cobalt nitrate, and anhydrous sodium acetate in ethylene glycol and stirring vigorously until homogeneous. The homogeneous solution is then transferred to a polytetrafluoroethylene (PTFE) reactor and reacted at an ambient temperature of 25–350°C for 1–120 h. The reaction product is washed, centrifuged, and the resulting pale blue precipitate is dried. The dried pale blue precipitate is then reduced in a tube furnace to obtain a NiCo alloy catalyst material with a nanosphere structure. The synthesis process of this NiCo alloy catalyst material is simple and the conditions are mild. When used for the catalytic hydrogenolysis of lignin to high-value aromatic monomers, the obtained catalyst material exhibits high selectivity for aromatic monomers, and its catalytic performance is comparable to commercially available noble metal catalysts, representing a significant breakthrough in replacing noble metals with inexpensive transition metals.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, and particularly relates to a NiCo nanosphere alloy catalyst material, its preparation method, and its application. Background Technology

[0002] With the continuous increase in global population and energy demand, the consumption of fossil fuels is escalating, undoubtedly exacerbating the already strained energy supply and causing greenhouse gas emissions to rise, drawing widespread attention and deep concern from the international community. Fully utilizing biomass resources and converting them into biofuels and high-value-added chemicals is the most promising path to solving energy and environmental problems. Lignocellulosic biomass is a renewable and abundant source of organic carbon, providing a sustainable alternative to traditional fossil fuels. The efficient conversion of lignocellulosic biomass into fuels and chemicals is crucial for alleviating energy and environmental problems and achieving carbon neutrality goals.

[0003] Lignin, as one of the three main components of lignocellulose and the only aromatic renewable raw material, shows great potential for replacing fossil fuels in the production of high-value chemicals such as phenolic monomers. However, due to the complex three-dimensional amorphous network structure of lignin, efficiently and selectively breaking the CO bonds in lignin to prepare phenolic monomers using heterogeneous catalysts remains a significant challenge. Therefore, it is necessary to develop an effective strategy to directionally break CO bonds and depolymerize lignin into smaller molecular units to generate high-value aromatic compounds. Many types of catalysts exist for lignin depolymerization. The activity of carbon-supported catalysts is mainly regulated by the active metal. A highly efficient Ni / C catalyst was prepared using Ni-containing metal-organic frameworks (Ni-MOFs) as raw materials. This catalyst exhibited high activity and selectivity in the hydrogenolysis of lignin model compounds into phenolic monomers. However, further improvements are needed to enhance its adsorption capacity for lignin and the stability of the system to avoid aggregation of active sites (Mei, Xuelei, et al. Green Chem., 2024, 26, 4544-4551.). Metal oxide catalysts, using metal oxides as supports, systematically compared the catalytic performance of different combinations of noble metals (Rh, Pt, Pd, Ru) and supports (activated carbon, Al2O3). Rh / Al2O3 showed the best performance, achieving a lignin oil yield of 36.3 wt%. Due to its higher dispersibility, mild acidic sites, and mesoporous structure, it exhibited good activity in lignin depolymerization (Hita, I., et al. Fuelprocessing technology 2018, 179.). 143-153.), but these acidic sites may also lead to over-hydrogenation, resulting in low product selectivity; bimetallic catalysts formed by combining noble metals with low-cost metals can improve the catalytic performance of lignin hydrogenolysis. A study used Co-Pd bimetal supported on porous polymer-derived nitrogen-doped carbon spheres (NDCS) to selectively hydrogenolyze organic solvent lignin, obtaining phenolic monomers with a yield of 36.38 wt% (Liang, Qiqi, et al. Energy & Fuels 2024, 38(12), 10993-11005.). However, the scarcity and high cost of noble metal resources limit their large-scale use. Summary of the Invention

[0004] To overcome the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing NiCo nanosphere alloy catalyst materials. This method involves crystallizing and precipitating a precursor for the NiCo alloy catalyst material using a solvothermal method, followed by reducing the obtained precursor in a hydrogen-argon mixed atmosphere to obtain the product. This method solves the problem of high cost of precious metals by using non-precious metals such as Fe, Co, and Ni as substitutes for precious metal catalysts. Among them, Ni-based metal catalysts exhibit significant advantages in lignin depolymerization. Although they are prone to over-hydrogenation, leading to a decrease in the selectivity of the target product, this invention effectively improves their catalytic performance by combining Ni with other transition metals.

[0005] Another objective of this invention is to provide a NiCo nanosphere alloy catalyst material prepared by the above preparation method; the obtained alloy catalyst material has a spherical stacked morphology composed of nanospheres.

[0006] Another objective of the invention is to provide an application of the above-mentioned NiCo nanosphere alloy catalyst material; this alloy catalyst material can be used for the catalytic hydrogenolysis of lignin into high-value aromatic phenolic monomers, exhibiting high monomer selectivity and high lignin liquid-phase yield.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing NiCo nanosphere alloy catalyst material includes the following steps: (1) Dissolve nickel nitrate, cobalt nitrate and anhydrous sodium acetate in ethylene glycol at a molar ratio of (0.1-2):(1-5):3 and stir until completely dissolved. React the resulting solution at 25-350℃ for 1-120 h. The reaction product is washed, centrifuged and dried to obtain the NiCo alloy catalyst precursor. (2) The NiCo alloy catalyst precursor obtained in step (1) is placed in a tube furnace and heated to 100-1000℃ in a mixed atmosphere of hydrogen and argon at a rate of 1-10℃ / min and held for 1-10 h to carry out a reduction reaction. The hydrogen volume percentage in the mixed atmosphere of hydrogen and argon is 1%-20%. The reaction product is ground to obtain NiCo nanosphere alloy catalyst material.

[0008] Preferably, in step (1), the molar volume ratio of nickel nitrate to ethylene glycol is (10-100) mmol: 50 mL; and the molar volume ratio of cobalt nitrate to ethylene glycol is (10-100) mmol: 50 mL.

[0009] More preferably, the molar volume ratio of nickel nitrate to ethylene glycol is 10 mmol: 50 mL; and the molar volume ratio of cobalt nitrate to ethylene glycol is 20 mmol: 50 mL.

[0010] Preferably, the reaction temperature in step (1) is 100-200°C and the reaction time is 12-24 h; the drying is performed at 25-150°C for 0.5-120 h, more preferably at 70°C for 12 h.

[0011] Preferably, the stirring time in step (1) is 120 min; the reaction is carried out in a polytetrafluoroethylene reactor in an oven; the washing and centrifugation are performed by washing with deionized water and anhydrous ethanol in sequence and then centrifuging, and the washing and centrifugation operations are repeated 3 to 5 times.

[0012] Preferably, the reduction reaction in step (2) is carried out by heating to 300-500°C at a rate of 1-5°C / min and holding for 1-4 hours; the hydrogen volume percentage in the hydrogen and argon mixed atmosphere is 5-10%.

[0013] A NiCo nanosphere alloy catalyst material prepared by the above preparation method, wherein the NiCo nanosphere alloy catalyst material has a three-dimensional morphology of stacked nanospheres.

[0014] The application of the aforementioned NiCo nanosphere alloy catalyst in the catalytic hydrogenolysis of lignin to aromatic monomers is specifically carried out according to the following steps: Enzymatic hydrolysis of lignin and the NiCo nanosphere alloy catalyst are dispersed together in a 1:1 volume ratio mixed solution of ethanol and isopropanol to obtain a dispersion; the dispersion is transferred to a high-pressure reactor, the air inside the reactor is replaced with hydrogen 3-5 times, and then hydrogen is introduced to the initial pressure of the reactor to 0-5 MPa. The reactor is heated to a temperature of 150-320℃, and the enzymatic hydrolysis of lignin and the NiCo nanosphere alloy catalyst are allowed to react fully for 1-12 h to obtain aromatic monomers; the mass percentage concentration of the enzymatic hydrolysis of lignin in the dispersion is 0.1%-10%; the mass ratio of the enzymatic hydrolysis of lignin to the NiCo nanosphere alloy catalyst is 10:(0.1-1).

[0015] Preferably, the initial pressure of the reactor is 2 MPa; the heating temperature is 270°C; the reaction time is 6 h; and the mass ratio of the enzymatic hydrolysis lignin to the NiCo nanosphere alloy catalyst material is 10:(0.5-1).

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention uses readily available and inexpensive nickel and cobalt transition metals as a basis to prepare nanosphere-shaped NiCo alloy catalyst materials through a controllable synthesis process. The nanosphere structure has a rich and interconnected hierarchical pore structure. This porous characteristic greatly promotes the mass transfer efficiency between reactants and products inside the catalyst, and at the same time provides a large number of accessible active sites for catalytic reactions, laying a solid structural foundation for its application in the catalytic conversion of complex macromolecules (such as industrial lignin).

[0017] (2) The synthesis process of the NiCo nanosphere alloy catalyst material of the present invention is simple and the conditions are mild. The nanostructure of the final product can be precisely controlled and mass-produced by simply adjusting the concentration, ratio and reaction parameters of the reactants. This efficient and scalable synthesis strategy avoids the use of complex templates or harsh reaction conditions, making it have great potential for industrial-scale production.

[0018] (3) The NiCo nanosphere alloy catalyst material of the present invention can catalyze the hydrogenolysis of lignin at 150-320℃, successfully break the CO bond in the lignin macromolecule, and efficiently convert it into high-value monophenolic aromatic chemicals. Its catalytic activity and product selectivity can reach the level comparable to expensive commercial precious metal Pd / C catalysts, realizing a major breakthrough in replacing precious metals with inexpensive transition metals. Attached Figure Description

[0019] Figure 1 This is the XRD pattern of the NiCo nanosphere alloy catalyst material prepared in Example 1 of this invention; Figure 2 These are SEM images of the NiCo nanosphere alloy catalyst material prepared in Example 1 of this invention; Figure 3 These are TEM images of the NiCo nanosphere alloy catalyst material prepared in Example 1 of this invention; Figure 4 The image shows a gas chromatography-mass spectrometry (GC-MS) chromatogram of the liquid products after the hydrogen hydrolysis of lignin by the NiCo nanosphere alloy catalyst material prepared in Example 1 of this invention (the horizontal axis represents time in minutes, and the vertical axis represents peak intensity). Detailed Implementation

[0020] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0021] All raw materials used in the examples are commercially available; unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0022] Example 1 (1) Weigh 2.9083 g Ni(NO3)3·6H2O, 5.8214 g Co(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace and heated to 400°C at a rate of 2°C / min in a mixed atmosphere of hydrogen and argon (where the volume percentage of hydrogen was 5%) for 2 hours to carry out the reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0023] See Figure 1 The X-ray diffraction (XRD) spectrum of the NiCo nanosphere alloy catalyst material prepared by the method described in this embodiment is shown. The diffraction peaks in the figure are all located between the diffraction planes PDF#15-0806 and PDF#01-1258, and no impure diffraction peaks were found, indicating that the prepared material is a NiCo alloy.

[0024] See Figure 2 and Figure 3 ,in, Figure 2 This is a scanning electron microscope (SEM) image of the NiCo nanosphere alloy catalyst material prepared by the method described in this embodiment. Figure 3 This is a transmission electron microscope (TEM) image of the NiCo nanosphere alloy catalyst material prepared by the method described in this embodiment. The image shows that the alloy catalyst material is a nanosphere catalyst material composed of stacked small spheres.

[0025] Example 2 (1) Weigh 5.8166 g Ni(NO3)3·6H2O, 2.9107 g Co(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace for reduction. In a mixed atmosphere of hydrogen and argon (the hydrogen volume percentage was 5%), the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours for reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0026] The NiCo nanosphere alloy catalyst material prepared according to the method described in this embodiment is observed to be a nanostructure by SEM and TEM.

[0027] Example 3 (1) Weigh 4.3625 g Ni(NO3)3·6H2O, 4.3361 g Co(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace for reduction. In a mixed atmosphere of hydrogen and argon (the hydrogen volume percentage was 5%), the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours for reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0028] The NiCo nanosphere alloy catalyst material prepared according to the method described in this embodiment is observed to be a nanostructure by SEM and TEM.

[0029] Example 4 (1) Weigh 3.4899 g Ni(NO3)3·6H2O, 5.2393 g Co(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace for reduction. In a mixed atmosphere of hydrogen and argon (the hydrogen volume percentage was 5%), the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours for reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0030] The NiCo nanosphere alloy catalyst material prepared according to the method described in this embodiment is observed to be a nanostructure by SEM and TEM.

[0031] Example 5 (1) Weigh 6.3983 g Ni(NO3)3·6H2O, 2.3286 g Co(NO3)3·6H2O, and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace for reduction. In a mixed atmosphere of hydrogen and argon (the hydrogen volume percentage was 5%), the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours for reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0032] The NiCo nanosphere alloy catalyst material prepared according to the method described in this embodiment is observed to be a nanostructure by SEM and TEM.

[0033] Example 6 (1) Weigh 2.3266 g Ni(NO3)3·6H2O, 6.4035 g Co(NO3)3·6H2O, and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light blue product. (3) The light blue product was placed in a tube furnace for reduction. In a mixed atmosphere of hydrogen and argon (the hydrogen volume percentage was 5%), the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours for reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain the NiCo nanosphere alloy catalyst material of the present invention.

[0034] The NiCo nanosphere alloy catalyst material prepared according to the method described in this embodiment is observed to be a nanostructure by SEM and TEM.

[0035] Example 7 0.05 g of the catalyst material prepared in Example 1, 1 g of enzymatically hydrolyzed lignin, 30 mL of isopropanol, and 30 mL of ethanol were added to a high-pressure reactor. The air inside the reactor was replaced with hydrogen 3-5 times, and then hydrogen was added until the initial pressure of the reactor was 2 MPa. The temperature was raised to 270°C, and the reaction was carried out with stirring for 6 h. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The solid and liquid were separated by centrifugation, and the products were analyzed. Qualitative analysis was performed on a gas chromatograph-mass spectrometer (GC6890-MS5973, Agilent Technologies). Quantitative analysis was performed on a gas chromatograph (GC-2010, Shimadzu Corporation, Japan) after adding an internal standard. The chromatographic column used was an HP-5ms, 30 m × 0.25 mm × 0.25 μm capillary column. Liquid phase yield (%) is calculated as (mass of dissolved lignin) / (mass of lignin) × 100%; aromatic monomer yield (wt.%) is calculated as (mass of aromatic monomer) / (mass of lignin) × 100%; product selectivity (%) is calculated as (mass of individual product) / (mass of total product) × 100%.

[0036] See Figure 4 According to the method described in this embodiment, the qualitative analysis results of each product in the total ion chromatogram show that monophenols (phenol, guaiacol, 4-ethylphenol, 2,6-dimethoxyphenol, etc.) are present. This demonstrates that the liquid products obtained within the detection range are aromatic products.

[0037] Example 8 0.05 g of the catalyst material prepared in Example 1, 1 g of enzymatically hydrolyzed lignin, 30 mL of isopropanol, and 30 mL of ethanol were added to a high-pressure reactor. The air inside the reactor was replaced with hydrogen 3-5 times, and then hydrogen was added until the initial pressure of the reactor was 2 MPa. The temperature was raised to 250°C, and the reaction was carried out with stirring for 4 h. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The solid and liquid were separated by centrifugation, and the products were analyzed. Qualitative analysis was performed on a gas chromatograph-mass spectrometer (GC6890-MS5973, Agilent Technologies). Quantitative analysis was performed on a gas chromatograph (GC-2010, Shimadzu Corporation, Japan) after adding an internal standard. The chromatographic column used was an HP-5ms, 30 m × 0.25 mm × 0.25 μm capillary column. Liquid phase yield (%) is calculated as (mass of dissolved lignin) / (mass of lignin) × 100%; aromatic monomer yield (wt.%) is calculated as (mass of aromatic monomer) / (mass of lignin) × 100%; product selectivity (%) is calculated as (mass of individual product) / (mass of total product) × 100%.

[0038] See Figure 4 The qualitative analysis of the products in the total ion chromatogram, as described in Example 8, yielded monophenols (phenol, guaiacol, 4-ethylphenol, 4-ethylguaiacol, 2,6-dimethoxyphenol, etc.). This demonstrated that the liquid products obtained within the detection range were aromatic products.

[0039] Example 9 0.05 g of the catalyst material prepared in Example 1, 1 g of enzymatically hydrolyzed lignin, 30 mL of isopropanol, and 30 mL of ethanol were added to a high-pressure reactor. The air inside the reactor was replaced with hydrogen 3-5 times, and then hydrogen was added until the initial pressure of the reactor was 4 MPa. The temperature was raised to 250°C, and the reaction was carried out with stirring for 4 h. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The solid and liquid were separated by centrifugation, and the products were analyzed. Qualitative analysis was performed on a gas chromatography-mass spectrometry (GC6890-MS5973, Agilent Technologies). Quantitative analysis was performed on a gas chromatograph (GC-2010, Shimadzu Corporation, Japan) after adding an internal standard. The chromatographic column used was an HP-5ms, 30 m × 0.25 mm × 0.25 μm capillary column. Liquid phase yield (%) is calculated as (mass of dissolved lignin) / (mass of lignin) × 100%; aromatic monomer yield (wt.%) is calculated as (mass of aromatic monomer) / (mass of lignin) × 100%; product selectivity (%) is calculated as (mass of individual product) / (mass of total product) × 100%.

[0040] See Figure 4The qualitative analysis of the products in the total ion chromatogram, as described in Example 9, yielded monophenols (phenol, guaiacol, 4-ethylphenol, 4-ethylguaiacol, 2,6-dimethoxyphenol, etc.). This demonstrated that the liquid products obtained within the detection range were aromatic products.

[0041] Example 10 0.05 g of the catalyst material prepared in Example 1, 1 g of enzymatically hydrolyzed lignin, 30 mL of isopropanol, and 30 mL of ethanol were added to a high-pressure reactor. The air inside the reactor was replaced with hydrogen 3-5 times, and then hydrogen was added until the initial pressure of the reactor was 4 MPa. The temperature was raised to 270°C, and the reaction was carried out with stirring for 6 h. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The solid and liquid were separated by centrifugation, and the products were analyzed. Qualitative analysis was performed on a gas chromatograph-mass spectrometer (GC6890-MS5973, Agilent Technologies). Quantitative analysis was performed on a gas chromatograph (GC-2010, Shimadzu Corporation, Japan) after adding an internal standard. The chromatographic column used was an HP-5ms, 30 m × 0.25 mm × 0.25 μm capillary column. Liquid phase yield (%) is calculated as (mass of dissolved lignin) / (mass of lignin) × 100%; aromatic monomer yield (wt.%) is calculated as (mass of aromatic monomer) / (mass of lignin) × 100%; product selectivity (%) is calculated as (mass of individual product) / (mass of total product) × 100%.

[0042] See Figure 4 The qualitative analysis of the products in the total ion chromatogram, as described in Example 10, yielded monophenols (phenol, guaiacol, 4-ethylphenol, 4-ethylguaiacol, 2,6-dimethoxyphenol, etc.). This demonstrated that the liquid products obtained within the detection range were aromatic products.

[0043] As can be seen from Examples 7-10, by changing the reaction pressure, reaction time, and reaction temperature, and by adjusting the ratio of raw materials and catalysts, the catalytic hydrogenolysis of lignin can be achieved to obtain small molecule monophenol products, according to the technical solution of the invention.

[0044] Comparative Example 1: Preparation of a single-metal Ni catalyst (1) Weigh 8.7249 g Ni(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light green product. (3) The light green product was placed in a tube furnace and heated to 400°C at a rate of 2°C / min in a mixed atmosphere of hydrogen and argon (where the volume percentage of hydrogen was 5%) and held for 2 hours to carry out the reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain a single metal Ni catalyst.

[0045] Comparative Example 2: Preparation of a single-metal Co catalyst (1) Weigh 8.7321 g Co(NO3)3·6H2O and 4.9218 g anhydrous CH3COONa respectively and dissolve them in 50 mL ethylene glycol. Stir vigorously for 120 min until completely dissolved. Transfer the resulting solution to a 100 mL polytetrafluoroethylene reactor and place it in an oven to heat and react for 16 h at a temperature of 200℃. (2) Take out the product after the reaction, separate the precipitate, wash it with deionized water and anhydrous ethanol respectively and centrifuge it 3 times to obtain the precipitate; place the precipitate in an oven and heat it at 70°C for 12 h to collect the light purple product. (3) The light purple product was placed in a tube furnace and heated to 400°C at a rate of 2°C / min in a mixed atmosphere of hydrogen and argon (where the volume percentage of hydrogen was 5%) and held for 2 hours to carry out the reduction reaction. After the temperature was cooled to room temperature, the reaction product was collected and ground to obtain a single metal Co catalyst.

[0046] The single-metal Ni catalyst obtained in Comparative Example 1 and the single-metal Co catalyst obtained in Comparative Example 2 were used to replace the catalyst materials prepared in Example 1, respectively. Lignin catalytic hydrogenolysis was performed using the same methods and procedures as in Example 7. Quantitative and qualitative analyses of the resulting products were conducted. A hydrogenolysis experiment without any catalyst was also performed for comparison. The results are shown in Table 1 below: Table 1 Comparison of the effects of catalytic hydrogenolysis and enzymatic hydrolysis of lignin

[0047] This invention presents a NiCo nanosphere alloy catalyst, constructed by combining metallic Ni and metallic Co, which exhibits excellent catalytic performance in the catalytic hydrogenolysis of lignin. Compared with single-metallic Ni catalysts, single-metallic Co catalysts, and catalyst-free systems, the yield of aromatic monomers is significantly improved (e.g., from 10% without catalyst to over 20%) using this NiCo alloy catalyst, indicating that the alloy structure formed between Ni and Co has a significant synergistic enhancing effect on the efficient conversion of lignin into aromatic monomers.

[0048] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing NiCo nanosphere alloy catalyst material, characterized in that... The following steps are included: (1) Dissolve nickel nitrate, cobalt nitrate and anhydrous sodium acetate in ethylene glycol at a molar ratio of (0.1-2):(1-5):3 and stir until completely dissolved. React the resulting solution at 25-350℃ for 1-120 h. The reaction product is washed, centrifuged and dried to obtain the NiCo alloy catalyst precursor. (2) The NiCo alloy catalyst precursor obtained in step (1) is placed in a tube furnace and heated to 100-1000℃ in a mixed atmosphere of hydrogen and argon at a rate of 1-10℃ / min and held for 1-10 h to carry out a reduction reaction. The hydrogen volume percentage in the mixed atmosphere of hydrogen and argon is 1%-20%. The reaction product is ground to obtain NiCo nanosphere alloy catalyst material.

2. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 1, characterized in that: The molar volume ratio of nickel nitrate to ethylene glycol in step (1) is (10-100) mmol: 50 mL; the molar volume ratio of cobalt nitrate to ethylene glycol is (10-100) mmol: 50 mL.

3. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 2, characterized in that: The molar volume ratio of nickel nitrate to ethylene glycol is 10 mmol: 50 mL; the molar volume ratio of cobalt nitrate to ethylene glycol is 20 mmol: 50 mL.

4. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 1, characterized in that: The reaction temperature in step (1) is 100-200℃ and the reaction time is 12-24 h; the drying is carried out at 25-150℃ for 0.5-120 h.

5. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 4, characterized in that: The drying process involved drying at 70°C for 12 hours.

6. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 1, characterized in that: The stirring time in step (1) is 120 min; the reaction is carried out in a polytetrafluoroethylene reactor in an oven; the washing and centrifugation are performed by washing with deionized water and anhydrous ethanol in sequence and then centrifuging, and the washing and centrifugation operations are repeated 3 to 5 times.

7. The method for preparing a NiCo nanosphere alloy catalyst material according to claim 1, characterized in that: The reduction reaction in step (2) involves heating to 300-500°C at a rate of 1-5°C / min and holding for 1-4 hours; the hydrogen volume percentage in the hydrogen and argon mixed atmosphere is 5-10%.

8. A NiCo nanosphere alloy catalyst material prepared by the preparation method according to any one of claims 1-7, characterized in that: The NiCo nanosphere alloy catalyst material has a three-dimensional morphology of stacked nanospheres.

9. The application of the NiCo nanosphere alloy catalyst material according to claim 8 in the catalytic hydrogenolysis of lignin to aromatic monomers, characterized in that: Enzymatically hydrolyzed lignin and NiCo nanosphere alloy catalyst were dispersed together in a 1:1 volume ratio of ethanol and isopropanol to obtain a dispersion. The dispersion was transferred to a high-pressure reactor, and the air inside the reactor was replaced with hydrogen 3-5 times. Then, hydrogen was introduced into the reactor until the initial pressure was 0-5 MPa. The reactor was heated to 150-320℃, and the enzymatically hydrolyzed lignin and NiCo nanosphere alloy catalyst were allowed to react in full contact for 1-12 h to obtain aromatic monomers. The mass percentage concentration of the enzymatically hydrolyzed lignin in the dispersion was 0.1%-10%, and the mass ratio of the enzymatically hydrolyzed lignin to the NiCo nanosphere alloy catalyst was 10:(0.1-1).

10. The application according to claim 9, characterized in that: The initial pressure of the reactor is 2 MPa; the heating temperature is 270°C; the reaction time is 6 h; and the mass ratio of the enzymatic hydrolysis lignin to the NiCo nanosphere alloy catalyst material is 10:(0.5-1).

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