A monatomic ruthenium-based catalyst, its preparation method and use

Abstract

The application discloses a single-atom ruthenium-based catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: adding acetylacetone ruthenium into a nitrogen source, then adding a carbon source and a template agent in sequence, uniformly mixing, and obtaining a mixture; heating the mixture, then grinding, and obtaining black powder after calcination; etching the black powder by using an acid solution, then performing vacuum filtration to collect the solid, washing and drying the solid, and obtaining the single-atom ruthenium-based catalyst. The single-atom ruthenium-based catalyst prepared by the application embeds controllable ruthenium metal sites and weak acid sites on a high specific surface area nitrogen-doped ordered mesoporous carbon carrier, and can convert lignin into monophenolic compounds at a high yield under relatively mild conditions, so that efficient delignification of biomass can be realized, and resource utilization and high-value utilization of lignin can be realized.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a single-atom ruthenium-based catalyst, its preparation method, and its application. Background Technology

[0002] Lignocellulose is the most abundant renewable resource on Earth, comprising three major components: cellulose, hemicellulose, and lignin. Clean and efficient separation of lignin is crucial for achieving diversified and high-value biorefining. Traditional industrial production or separation processes are largely cellulose- and hemicellulose-oriented, causing irreversible damage to the lignin structure and severely limiting its subsequent utilization and application scope. Currently, the preferential depolymerization process of lignin has attracted widespread attention from researchers, and many selective catalytic degradation systems for lignin have been developed, including thermocatalytic degradation systems, as well as photocatalytic, electrocatalytic, and enzymatic degradation systems. The raw materials have also expanded from industrial lignin to organic solvent lignin and native lignin. Among these catalytic systems, the preferential catalytic degradation of native lignin has attracted more widespread attention due to its advantages such as no need for complex pretreatment processes, high product selectivity, and complete preservation of carbohydrate components.

[0003] In recent years, researchers have proposed a reduction catalytic fractionation (RCF) method based on a "lignin-first" strategy. Using lignocellulose as a raw material, this method allows lignin to immediately contact with a catalyst during separation and undergo catalytic degradation to generate monophenolic compounds, while preserving the macromolecular structure of carbohydrates to the greatest extent possible. However, due to the complex and irregular structure of lignin with multiple reaction pathways, the development of highly efficient catalysts to drive C… β Separating the -O-4 bond to produce monophenolic compounds with high yield and selectivity remains a significant challenge. Currently, noble metal catalysts (Ru, Pd, Pt, Rh) and non-noble metals (Ni, Mo, Co) are widely used in the RCF process of lignocellulose. However, compared to non-noble metal catalysts, noble metal-based catalysts exhibit superior performance in biomass depolymerization. However, noble metal catalysts prepared by impregnation methods are often limited by high preparation costs and low atom utilization, making them difficult to implement industrially. Furthermore, the optimal reaction temperature and pressure for current RCF catalytic systems are relatively high, and achieving high-yield production of phenolic monomers under mild conditions remains challenging. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-atom ruthenium-based catalyst, its preparation method, and its application. The prepared single-atom ruthenium-based catalyst, which embeds controllable ruthenium metal sites and weakly acidic sites on a nitrogen-doped ordered mesoporous carbon support with high specific surface area, can convert lignin into monophenolic compounds in high yield under relatively mild conditions. This can achieve both efficient delignination of biomass and the resource utilization and high-value utilization of lignin.

[0005] This invention provides the following technical solution:

[0006] In a first aspect, a method for preparing a single-atom ruthenium-based catalyst is provided, comprising the following steps:

[0007] Ruthenium acetylacetone was added to the nitrogen source, followed by the carbon source and template agent, and mixed thoroughly to obtain a mixture.

[0008] The mixture was heated, then ground, and calcined to obtain a black powder;

[0009] The black powder was etched with an acid solution, and the solid was collected by vacuum filtration. The solid was then washed and dried to obtain a single-atom ruthenium-based catalyst.

[0010] Furthermore, the nitrogen source is ethylenediamine or hydrazine hydrate; the carbon source is carbon tetrachloride; and the template agent is one of SBA-15, ZSM-5, and MCM-41.

[0011] Furthermore, the method for heating the mixture includes: using an oil bath for heating, first raising the temperature to 90-100°C and heating for 16-24 hours, and then raising the temperature to 120-140°C and heating for 3-5 hours; the heating causes the carbon source and nitrogen source to completely condense.

[0012] Furthermore, the calcination method includes: calcining and reducing in a tube furnace at a temperature of 600-900℃ for 2-4 hours under an inert gas atmosphere; wherein, the preferred calcination and reduction temperature is 800℃, and the inert gas is one of nitrogen, argon, and helium.

[0013] Furthermore, the acid solution is a hydrofluoric acid solution with a concentration of 5-10 wt%.

[0014] In a second aspect, a single-atom ruthenium-based catalyst is provided, which is prepared by the method described in the first aspect. The single-atom ruthenium-based catalyst comprises a nitrogen-doped ordered mesoporous carbon support and active metal ruthenium uniformly dispersed in the nitrogen-doped ordered mesoporous carbon support in the form of single atoms.

[0015] Furthermore, the loading of the active metal ruthenium is 0.1-2.5 wt%, the average pore size of the mesopores in the nitrogen-doped ordered mesoporous carbon support is 4.0-5.0 nm, and the specific surface area of ​​the single-atom ruthenium-based catalyst is 450-800 m². 2 ·g -1 .

[0016] Thirdly, the application of the single-atom ruthenium-based catalyst described in the second aspect in depolymerization biomass is provided, comprising the following steps:

[0017] Biomass, a single-atom ruthenium-based catalyst, and a reaction solvent are added to a reaction vessel, mixed evenly, and then sealed. The air in the reaction vessel is then purged, and the vessel is pressurized with hydrogen and stirred at a specified temperature.

[0018] After the reaction is completed and cooled, the reaction product is vacuum filtered to separate the soluble liquid fraction containing lignin derivatives and the insoluble solid fraction containing carbohydrates and catalyst.

[0019] The solvent in the soluble liquid fraction containing lignin derivatives is evaporated, and then extracted to obtain lignin oil.

[0020] Used single-atom ruthenium-based catalysts were screened from the insoluble solid fraction containing carbohydrates and catalysts, and then washed and calcined to obtain regenerated single-atom ruthenium-based catalysts.

[0021] Furthermore, the mass ratio of the biomass, the single-atom ruthenium-based catalyst, and the reaction solvent is 1:(0.025-0.2):(10-50).

[0022] Furthermore, the biomass raw materials include one of the following: hardwoods (birch, poplar, eucalyptus, etc.), softwoods (pine, spruce, etc.), and herbaceous plants (corn stalks, miscanthus, etc.).

[0023] Furthermore, the reaction solvent is an alcohol or ether, preferably one of methanol, ethanol, isopropanol, and tetrahydrofuran.

[0024] Furthermore, the method for purging air from the reactor includes: first purging the reactor three times with N2, and then purging the reactor three times with H2 to completely remove the air.

[0025] Furthermore, the stirring reaction method includes: reacting at a temperature of 180-240°C for 1-9 hours under hydrogen pressure of 0.1-4 MPa.

[0026] Furthermore, after evaporating the solvent from the soluble liquid fraction containing lignin derivatives, the product was fully dissolved in dichloromethane / water and extracted three times to obtain an orange-brown lignin oil.

[0027] Furthermore, the used single-atom ruthenium-based catalyst was separated from the insoluble solid portion containing carbohydrates and catalyst using a 200-mesh sieve, and then washed three times with methanol and water respectively to complete the washing process.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The preparation method provided by this invention can produce a multifunctional single-atom ruthenium-based catalyst with controllable ruthenium metal sites and weakly acidic sites embedded in a nitrogen-doped ordered mesoporous carbon support with high specific surface area. This single-atom ruthenium-based catalyst exhibits excellent performance in the reduction catalytic fractionation process of biomass, and has the advantages of mild reaction conditions and high atom utilization, as detailed below:

[0030] (1) When the single-atom ruthenium-based catalyst provided by the present invention is applied to depolymerized biomass, the reaction conditions are mild. The milder reaction temperature is beneficial to extending the service life of the catalyst and improving the economy of the reaction process. This provides theoretical guidance for obtaining valuable aromatic products from lignin under mild conditions and promoting the industrial and economic feasibility of lignocellulose biomass. In addition, the lower reaction pressure is beneficial to reducing hydrogen consumption and improving the safety of the reaction.

[0031] (2) The single-atom ruthenium-based catalyst provided by the present invention has low loading and high dispersion characteristics. Reducing the loading of precious metals can greatly improve the atomic utilization efficiency. Compared with commercial Ru / C catalysts, it saves the consumption of precious metals and saves the preparation cost.

[0032] (3) When the single-atom ruthenium-based catalyst provided by this invention is applied to depolymerized biomass, it can preferentially and selectively degrade lignin in biomass components. At the same time, the remaining holocellulose structure in the biomass raw material does not change significantly, and it can be used for pulping and papermaking and the preparation of bioethanol, etc. In the monomer, in addition to 4-propylguaiacol (Pr-G) and 4-propyl eugenol (Pr-S), a portion of propenyl and propanol products (such as Pe-G, Pe-S, POH-G, POH-S) are also retained, which enriches the diversity of functional groups of the products and is more conducive to subsequent high-value utilization. The single-atom ruthenium-based catalyst and the reaction solvent used can be recycled, which improves the utilization rate of raw materials and reduces the cost of use. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of the single-atom ruthenium-based catalyst in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the biomass reduction catalytic fractionation process in an embodiment of the present invention;

[0035] Figure 3 This is a GC-MS image of Embodiment 1 of the present invention;

[0036] Figure 4 Here is a high-resolution transmission electron microscope image of the Ru-SAC catalyst prepared in Example 1 of this invention;

[0037] Figure 5 Here are the high-angle annular dark-field scanning transmission images and elemental mapping diagrams of the Ru-SAC catalyst prepared in Example 1 of this invention;

[0038] Figure 6 The N2 adsorption-desorption isotherm of the Ru-SAC catalyst prepared in Example 1 of this invention ( Figure 6 a) and pore size distribution curve ( Figure 6 b);

[0039] Figure 7 The X-ray diffraction pattern of the Ru-SAC catalyst prepared in Example 1 of this invention;

[0040] Figure 8 The X-ray electron energy spectrum of the Ru-SAC catalyst prepared in Example 1 of this invention ( Figure 8 a) and N1s high-resolution X-ray electron spectrum ( Figure 8 b);

[0041] Figure 9 The Ru K-edge X-ray absorption near-edge structure spectrum of the Ru-SAC catalyst prepared in Example 1 of this invention ( Figure 9 a) Extended X-ray absorption fine structure spectrum ( Figure 9 b) and wavelet transform spectrum ( Figure 9 c). Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0043] Example 1

[0044] S1, such as Figure 1As shown, 97.4 mg of ruthenium acetylacetonate was added to 3.75 ml of ethylenediamine, followed by the slow addition of 3 ml of carbon tetrachloride, and finally 1.2 g of the template agent SBA-15. The mixture was first heated in an oil bath at 90 °C for 24 h to condense, and then the oil bath temperature was increased to 120 °C and heated for 5 h to remove uncondensed ethylenediamine and carbon tetrachloride. The resulting brownish-yellow mixture was placed in a tube furnace and calcined at 800 °C for 2 h under an inert gas atmosphere. The black powder was then etched with a 5 wt% hydrofluoric acid solution to remove the template agent. The solid was collected by vacuum filtration and washed with deionized water until neutral. Finally, it was dried overnight in a vacuum drying oven at 60 °C to obtain a single-atom ruthenium-based catalyst. ICP testing showed an actual Ru loading of 1.4 wt%, denoted as Ru-SAC-1.4 wt%.

[0045] S2, such as Figure 2 As shown, according to the mass ratio of biomass raw material, single-atom ruthenium-based catalyst, and reaction solvent of 1:0.1:20, 0.6 g of birch biomass with a particle size of 60-80 mesh, 0.06 g of Ru-SAC-1.4wt%, and 12 ml of methanol were placed in a batch reactor and sealed. The reactor was rinsed three times with N2 and H2, and finally purged with 2 MPa of high-purity hydrogen. The reactor was then heated to 200℃, stirred, and kept at that temperature for 5 hours before heating was stopped. The reactor was cooled at room temperature and the internal pressure was released. The reaction solution was then vacuum filtered to separate the liquid fraction containing lignin derivatives and the solid fraction containing carbohydrates and catalyst. After evaporating the solvent from the liquid fraction, it was extracted three times with dichloromethane and water to obtain orange-brown lignin oil after removing organic solvents and water-soluble products. After making up to 20 ml with methanol, the monomer products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results are shown below. Figure 3 As shown.

[0046] Quantitative analysis of the lignin oil obtained from the reaction yields the lignin removal rate and the mass yield of monophenol products. The lignin removal rate, monophenol yield, and holocellulose retention rate are calculated using the following formulas:

[0047]

[0048]

[0049]

[0050] In this embodiment, the lignin removal rate and the mass yield of monophenol products were as follows: lignin removal rate 81.5%, 4-propylguaiacol (Pr-G) 7.09%, 4-propenylguaiacol (Pe-G) 1.71%, 4-propanol-guaiacol (POH-G) 2.03%, 4-propyl eugenol (Pr-S) 20.9%, 4-propenyl eugenol (Pe-S) 5.10%, 4-propanol-eugenol (POH-S) 7.30%, other monophenols 1.81%, total monophenol yield 45.9%, and holocellulose retention rate 92.9%.

[0051] The morphology and structure of the Ru-SAC catalyst prepared in this embodiment were characterized. The prepared Ru-SAC catalyst exhibits a well-organized rod-like morphology, with C, O, N, and Ru uniformly dispersed on a nitrogen-doped carbon support (e.g., ...). Figure 4 and Figure 5 As shown in the image). The high-angle annular dark-field scanning transmission image reveals numerous tiny bright spots distributed on the support, indicating that Ru is uniformly dispersed in single-atom form on the nitrogen-doped ordered mesoporous carbon support (e.g., ...). Figure 5 (Small and medium circles). The N2 adsorption-desorption curves revealed that the Ru-SAC catalyst has a specific surface area of ​​723.7 m². 2 ·g -1 It has a mesoporous structure with an average pore size distribution of approximately 4.5 nm (e.g., Figure 6 (As shown).

[0052] The XRD pattern of the Ru-SAC catalyst prepared in this embodiment is shown below. Figure 7 As shown, a broad peak appears at 23°, which is attributed to the (002) crystal plane of graphitic carbon. At the same time, no Ru-related peaks were detected, which may be due to the low loading and high dispersion of Ru.

[0053] like Figure 8 As shown, from the X-ray electron energy full spectrum ( Figure 8 a) It can be seen that the Ru-SAC catalyst has characteristic peaks of C1s (284.8 eV), N1s (400.1 eV), and O1s (532.1 eV), but no characteristic peaks of Ru were detected, which may be due to the extremely low Ru content. The high-resolution N1s spectrum of the Ru-SAC catalyst ( Figure 8 b) From left to right, there are five peaks centered at 398.5, 399.0, 400.5, 401.4 and 403.9 eV, corresponding to pyridine N, Ru-N, pyrrole nitrogen, graphite N and nitrogen oxide. The coordination of Ru with N increases the stability of the catalyst.

[0054] To further investigate the electronic structure and coordination environment of Ru species in Ru-SAC catalysts, X-ray absorption fine structure spectroscopy analysis was performed on the K-edge of Ru species. Figure 9 (b) The energy absorption threshold of Ru-SAC falls between that of Ru foil and RuO2, indicating that the Ru species are positively charged. In the extended X-ray absorption fine structure (EXAFS) spectrum, peaks corresponding to various coordination shells around the metal center are given. Only one peak is clearly observed in the R-space plot of Ru-SAC. The main peak, which can be attributed to the Ru-N single scattering path ( Figure 9 b). However, no corresponding observation was observed. The Ru-Ru peak indicates that only light scattering exists around the Ru single-atom metal site, rather than the metal-metal scattering path in the corresponding metal foil or a higher scattering path (such as Ru-O-Ru in metal oxides). The distance and coordination number of the Ru-N / C bond are accurate to [value missing]. The values ​​of 4.1 ± 0.2 indicate that isolated Ru sites in Ru-SAC exhibit a Ru-N4 configuration. 3 The wavelet transform (WT) of the weighted EXAFS spectrum shows that there is only one intensity maximum. This is related to the Ru-N interaction pathway ( Figure 9 c). The above analytical results are consistent with high-angle annular dark-field scanning transmission and X-ray electron spectroscopy analysis, fully confirming that Ru exists in the Ru-SAC catalyst in a single-atom dispersed form.

[0055] Example 2

[0056] S1. Same as Example 1, except that the amount of ruthenium acetylacetone added in step S1 was replaced with 146.1 mg to prepare a single-atom ruthenium-based catalyst. The actual Ru loading was found to be 2.5 wt% by ICP test, which is denoted as Ru-SAC-2.5 wt%.

[0057] S2. Place 0.6g of birch biomass with a particle size of 60-80 mesh, 0.06g of Ru-SAC-2.5wt%, and 12ml of methanol into a batch reactor and seal it. Rinse the reactor three times with N2 and H2 successively. Finally, purge with 2MPa of high-purity hydrogen gas, then heat the reactor to 200℃, stir and maintain the temperature for 5 hours, and then stop heating. The remaining steps are consistent with those in Example 1.

[0058] Quantitative analysis of the oil obtained from the reaction revealed the following lignin removal rates and monophenol product yields: lignin removal rate 85.1%, 4-propylguaiacol (Pr-G) 8.37%, 4-propenylguaiacol (Pe-G) 2.00%, 4-propanol-guaiacol (POH-G) 1.72%, 4-propyl eugenol (Pr-S) 23.6%, 4-propenyl eugenol (Pe-S) 6.27%, 4-propanol-eugenol (POH-S) 3.77%, other monophenols 1.51%, total monophenol yield 47.2%, and holocellulose retention rate 79.8%.

[0059] Example 3

[0060] S1. Same as Example 1, except that the amount of ruthenium acetylacetone added in step S1 was replaced with 48.7 mg to prepare a single-atom ruthenium-based catalyst. The actual Ru loading was found to be 0.6 wt% by ICP test, which is recorded as Ru-SAC-0.6 wt%.

[0061] S2. Place 0.6g of birch biomass with a particle size of 60-80 mesh, 0.06Ru-SAC-0.6wt%, and 12ml of methanol into a batch reactor and seal it. Rinse the reactor three times with N2 and H2 successively. Finally, purge with 2MPa of high-purity hydrogen gas, then heat the reactor to 200℃, stir and maintain the temperature for 5 hours, and then stop heating. The remaining steps are consistent with those in Example 1.

[0062] Quantitative analysis of the oil obtained from the reaction revealed the following lignin removal rates and monophenol product yields: lignin removal rate 77.6%, 4-propylguaiacol (Pr-G) 3.47%, 4-propenylguaiacol (Pe-G) 4.52%, 4-propanol-guaiacol (POH-G) 1.89%, 4-propyl eugenol (Pr-S) 10.6%, 4-propenol-eugenol (Pe-S) 11.7%, 4-propanol-eugenol (POH-S) 5.00%, other monophenols 2.56%, total monophenol yield 39.7%, selectivity for 4-propylguaiacol (Pr-G) and 4-propyl eugenol (Pr-S) 35.4%, and holocellulose retention 94.9%.

[0063] Comparative Example 1

[0064] Same as Example 1, except that the Ru-SAC catalyst in step S2 was replaced with a commercially available Ru / C catalyst with a 5 wt% loading. 0.6 g of birch biomass with a particle size of 60-80 mesh, 0.06 g of Ru / C catalyst, and 12 ml of methanol were placed in a batch reactor and sealed. The reactor was then flushed three times with N2 and H2, and finally purged with 2 MPa of high-purity hydrogen. The reactor was then heated to 200°C and held at that temperature for 5 hours before heating was stopped. The remaining steps were the same as in Example 1.

[0065] Quantitative analysis of the oil obtained from the reaction revealed the following lignin removal rates and yields of various monophenol products: lignin removal rate 76.1%, 4-propylguaiacol (Pr-G) 9.30%, 4-propenylguaiacol (Pe-G) 0%, 4-propanol-guaiacol (POH-G) 0.57%, 4-propyl eugenol (Pr-S) 24.6%, 4-propenyl eugenol (Pe-S) 0.81%, 4-propanol-eugenol (POH-S) 1.25%, other monophenols 2.26%, total monophenol yield 38.8%, and holocellulose retention rate 91.6%.

[0066] Table 1. Lignin removal rate, monophenol yield, and holocellulose retention rate in Examples 1-3 and Comparative Example 1

[0067]

[0068] As shown in Table 1, Examples 1, 2, and 3 present the reaction results of three Ru-SAC single-atom catalysts with different loadings under mild conditions. The monophenol yield increased with increasing Ru loading and was consistently higher than that of commercial catalysts, indicating that this atomically dispersed catalyst can significantly improve the atom utilization efficiency of noble metals and increase the monophenol yield. Comparative Example 1 is a control experiment comparing the performance of a commercial Ru / C catalyst with a loading of 5 wt%.

[0069] Example 4

[0070] Similar to Example 1, except that the reaction solvent in step S2 was replaced with equal volumes of ethanol, isopropanol, and tetrahydrofuran, while the remaining steps remained the same as in Example 1. The lignin removal rate and monophenol yield are shown in Table 2. Among them, ethanol had the highest lignin removal rate and monophenol yield when used as the reaction solvent, followed by isopropanol, and lastly tetrahydrofuran.

[0071] Table 2 Results of biomass depolymerization catalyzed by Ru-SAC-1.4wt% in different solvents

[0072]

[0073] Example 5

[0074] Same as Example 1, except that the reaction temperature in step S2 was replaced with 180℃ and 220℃, while the rest of the steps remained the same as in Example 1. The lignin removal rate and monophenol yield are shown in Table 3. As can be seen from Table 3, when the temperature continues to rise, it is beneficial to the removal of lignin and the formation of monophenol products.

[0075] Table 3 Results of biomass depolymerization catalyzed by Ru-SAC-1.4wt% at different reaction temperatures

[0076]

[0077] Example 6

[0078] Same as Example 1, except that the reaction time in step S2 was replaced with 3h and 7h, while the rest of the steps remained the same as in Example 1. The lignin removal rate and monophenol yield are shown in Table 4. The results show that extending the reaction time is beneficial to the removal of lignin and the depolymerization into monophenol products.

[0079] Table 4. Results of Ru-SAC-1.4wt% catalyzed biomass depolymerization at different reaction times.

[0080]

[0081] Example 7

[0082] Same as Example 1, except that the birch wood in step S2 is replaced with other biomass raw materials (such as poplar, pine, and corn stalks), while the remaining steps are consistent with Example 1. The lignin removal rate and monophenol yield are shown in Table 5.

[0083] Table 5 Results of Ru-SAC-1.4wt% catalyzing the depolymerization of different biomass feedstocks

[0084]

[0085] Example 8

[0086] Similar to Example 1, only the catalyst was recycled. The catalyst collected after the previous reaction was washed with methanol and water, then dried in a vacuum drying oven for 24 hours before use. The lignin removal rate and monophenol yield are shown in Table 6. As can be seen from Table 6, after three cycles, the yield of lignin monomers still reached 36.6 wt%, indicating that the Ru-SAC catalyst not only has high catalytic efficiency but also excellent stability and reusability.

[0087] Table 6. Results of Ru-SAC-1.4wt% catalyzed biomass depolymerization at different cycle numbers.

[0088]

[0089] Example 4, compared to Example 1, shows that using methanol as a solvent is more conducive to the catalytic hydrogenolysis of lignin. Example 5, compared to Example 1, shows that further increases in temperature are beneficial for lignin removal and the formation of monophenol products. Example 6, compared to Example 1, illustrates that extending the reaction time is beneficial for lignin removal and depolymerization into monophenol products. Example 7 demonstrates that this single-atom ruthenium-based catalyst has broad applicability to raw materials, efficiently depolymerizing lignin from hardwoods, softwoods, and herbs. Example 8 shows that the catalyst has high stability. In summary, by rationally controlling the reaction conditions, this system holds promise for achieving the efficient production of monophenol compounds from lignin under relatively mild conditions.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a single-atom ruthenium-based catalyst, characterized in that, Includes the following steps: Ruthenium acetylacetone was added to the nitrogen source, followed by the carbon source and template agent, and mixed thoroughly to obtain a mixture. The mixture was heated, then ground, and calcined to obtain a black powder; The black powder was etched with an acid solution, and the solid was collected by vacuum filtration. The solid was then washed and dried to obtain a single-atom ruthenium-based catalyst. The single-atom ruthenium-based catalyst comprises a nitrogen-doped ordered mesoporous carbon support and active ruthenium metal uniformly dispersed in the nitrogen-doped ordered mesoporous carbon support in the form of single atoms; the loading of the active ruthenium metal is 0.1-2.5 wt%, the average pore size of the mesopores in the nitrogen-doped ordered mesoporous carbon support is 4.0-5.0 nm, and the specific surface area of ​​the single-atom ruthenium-based catalyst is 450-800 m². 2 ·g -1 .

2. The method for preparing a single-atom ruthenium-based catalyst according to claim 1, characterized in that, The nitrogen source is ethylenediamine or hydrazine hydrate; the carbon source is carbon tetrachloride; and the template agent is one of SBA-15, ZSM-5, and MCM-41.

3. The method for preparing a single-atom ruthenium-based catalyst according to claim 1, characterized in that, The method for heating the mixture includes: using an oil bath to heat the mixture, first raising the temperature to 90-100℃ and heating for 16-24 hours, and then raising the temperature to 120-140℃ and heating for 3-5 hours.

4. The method for preparing a single-atom ruthenium-based catalyst according to claim 1, characterized in that, The calcination method includes calcining in an inert gas atmosphere using a tube furnace at a temperature of 600-900℃ for 2-4 hours.

5. The method for preparing a single-atom ruthenium-based catalyst according to claim 1, characterized in that, The acid solution is a hydrofluoric acid solution with a concentration of 5-10 wt%.

6. A single-atom ruthenium-based catalyst, characterized in that, The single-atom ruthenium-based catalyst comprises a nitrogen-doped ordered mesoporous carbon support and active ruthenium metal uniformly dispersed in the nitrogen-doped ordered mesoporous carbon support in the form of single atoms; the loading of the active ruthenium metal is 0.1-2.5 wt%, the average pore size of the mesopores in the nitrogen-doped ordered mesoporous carbon support is 4.0-5.0 nm, and the specific surface area of ​​the single-atom ruthenium-based catalyst is 450-800 m². 2 ·g -1 ; The single-atom ruthenium-based catalyst was prepared by the following method: ruthenium acetylacetone was added to a nitrogen source, followed by a carbon source and a template agent, and the mixture was stirred until homogeneous to obtain a mixture; the mixture was heated, then ground, and calcined to obtain a black powder; the black powder was etched with an acid solution, and the solid was collected by vacuum filtration, washed, and dried to obtain the single-atom ruthenium-based catalyst.

7. The application of the single-atom ruthenium-based catalyst according to claim 6 in the depolymerization of biomass, characterized in that, Includes the following steps: Biomass, a single-atom ruthenium-based catalyst, and a reaction solvent are added to a reaction vessel, mixed evenly, and then sealed. The air in the reaction vessel is then purged, and the vessel is pressurized with hydrogen and stirred at a specified temperature. After the reaction is completed and cooled, the reaction product is vacuum filtered to separate the soluble liquid fraction containing lignin derivatives and the insoluble solid fraction containing carbohydrates and catalyst. The solvent in the soluble liquid fraction containing lignin derivatives is evaporated, and then extracted to obtain lignin oil. Used single-atom ruthenium-based catalysts were screened from the insoluble solid fraction containing carbohydrates and catalysts, and then washed and calcined to obtain regenerated single-atom ruthenium-based catalysts.

8. The application of the single-atom ruthenium-based catalyst according to claim 7 in the depolymerization of biomass, characterized in that, The mass ratio of the biomass, the single-atom ruthenium-based catalyst, and the reaction solvent is 1:(0.025-0.2):(10-50).

9. The application of the single-atom ruthenium-based catalyst according to claim 7 in the depolymerization of biomass, characterized in that, The stirring reaction method includes: reacting at a temperature of 180-240°C for 1-9 hours under hydrogen pressure of 0.1-4 MPa.

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