A method for preparing phenolic chemicals by catalytic transfer hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material

Abstract

This invention discloses a method for preparing phenolic chemicals by hydrogenolysis of lignin catalyzed by a cobalt-based nitrogen-carbon composite material. Using organosoluble lignin as raw material, a cobalt-based nitrogen-carbon composite material as catalyst, and a mixed solvent of small organic molecule alcohol and formic acid, the reaction is carried out under an inert gas atmosphere of 0.5–3 MPa, maintaining a reaction temperature of 210–250 °C, and a reaction time of 2–6 h. This method catalyzes the depolymerization of lignin to obtain a series of p-hydroxyphenyl products, achieving high-value utilization of lignin. The lignin conversion rate of this invention is as high as 89.6%, the total yield of monophenolic products can reach 17.7%, of which the yield of p-hydroxyphenyl products reaches 9.0%, with a selectivity of 50.8%. The catalyst preparation process used in this invention is simple and can catalyze the hydrogenolysis of lignin by short-chain alcohols and carboxylic acid solvents under mild conditions to obtain high-value-added chemicals such as p-hydroxyphenyl products.

Description

Technical Field

[0001] This invention relates to the catalytic hydrogenolysis of lignin in bagasse, and in particular to a method for preparing high-value-added phenolic chemicals by catalytic hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material, which belongs to the field of high-value utilization of renewable biomass. Background Technology

[0002] Traditional fossil fuels such as oil, coal, and natural gas remain the primary energy sources for sustaining industrial operations. The large-scale development and utilization of these non-renewable resources has led to an energy crisis and exacerbated environmental problems such as global warming. Against this backdrop, China is actively advocating an energy transition strategy focused on "carbon neutrality" and "carbon peaking," and is continuously exploring and developing renewable and clean energy sources. In the exploration of new energy sources, biomass energy, with its wide distribution, abundant reserves, low pollution, and renewability, has become an ideal alternative to fossil fuels. Therefore, its efficient utilization is of great significance for promoting energy transition.

[0003] Lignin is a highly polymeric, amorphous, three-dimensional network macromolecule rich in aromatic structures, composed of different methoxylated phenylpropane structural units linked by various CO and C-C bonds. Besides structural units and CO and C-C bonds, lignin also contains various functional groups, making it an excellent raw material for producing high-value-added products such as aromatics and phenolic chemicals. However, due to its complex and disordered internal cross-linking and chemical bonds, lignin depolymerization products are complex. Therefore, the current industrial applications of lignin are very limited, with 95% of industrial lignin being directly burned as fuel.

[0004] Currently, most lignin hydrogenolysis processes rely on externally supplied hydrogen as the hydrogen source for upgrading lignin and its derivatives, increasing equipment and energy costs. Furthermore, hydrogen-involved reactions pose significant risks under high temperature and pressure conditions. Industrially available hydrogen primarily comes from fossil fuel reforming, and the depolymerization of lignin using externally supplied hydrogen is neither environmentally friendly nor costly. Therefore, catalytic transfer hydrogenolysis (CTH) is an effective alternative to avoid using high-pressure H2 to crack the aromatic ether bonds of lignin.

[0005] Catalytic transfer hydrogenolysis is a catalytic hydrogenation reaction in which an organic compound replaces hydrogen gas as the hydrogen donor in the presence of a metal catalyst. Inexpensive alcohols (methanol, ethanol, isopropanol, etc.) are commonly used as hydrogen donor solvents. On the one hand, the CH bond in alcohols is more easily broken than the HH bond in H2 molecules, and the in-situ formed H atoms are more reactive than gaseous H2 molecules; on the other hand, using a hydrogen donor organic solvent avoids the problem of poor H2 molecule solubility, thus reducing gas-liquid mass transfer resistance. Noble metals such as Re and Ru have been widely used in the catalytic hydrogenation of lignin, exhibiting excellent catalytic performance. However, their high cost limits their further application. In recent years, low-cost, high-performance non-noble metal catalysts have attracted widespread attention. For example, Ni, Cu, and Co-based catalysts have shown similar high activity to noble metal-based catalysts.

[0006] Chinese invention patent application CN202410215194.0 discloses a method for preparing C2-phenol monomers by hydrogenolysis of lignin using a nickel-based basic supported catalyst. This method uses a nickel-based basic supported catalyst, lignin as the substrate, and isopropanol as the hydrogen source. The reaction is carried out at 200–330°C for 1–6 hours to obtain C2-phenol monomer products (4-ethylphenol and 4-ethylguaiacol), with a selectivity as high as 58.2%. However, the basic supported catalyst used in this technology is prone to deactivation during the reaction, and its cycle stability needs further improvement.

[0007] Chinese invention patent application CN202311659296.3 discloses a method for preparing phenolic compounds by depolymerizing lignin using a RuNiZn / Nb2O5 catalyst. This method uses natural biomass as a substrate and reacts at 200–280°C under a hydrogen pressure of 1–3 MPa for 0.5–6 h to obtain C6–C9 aromatic hydrocarbons. The RuNiZn / Nb2O5 catalyst used in this method can improve the catalyst's reactivity and reduce the amount of precious metals used. However, the addition of exogenous hydrogen in this technology increases equipment and energy costs. Furthermore, industrial hydrogen mainly comes from the reforming of fossil resources. Therefore, this technical route does not meet the requirements of green chemistry and remains costly.

[0008] Chinese invention patent application CN202410599907.8 discloses a method for the efficient hydrogenolysis of aromatic ethers using a boron nitride-supported ruthenium catalyst. This method prepares a boron nitride-supported ruthenium catalyst by loading ruthenium metal onto commercially available boron nitride nanoparticles via ball milling and in-situ reduction. The method uses lignin-type compounds as substrates, including benzylphenyl ether, diphenyl ether, 4,4-dihydroxydiphenyl ether, phenoxyethylbenzene, and 4-benzyloxyphenol. The reaction is carried out under an inert gas atmosphere of 1–2 MPa at 150–180 °C for 6–10 h, exhibiting high product selectivity and efficient catalysis of the hydrogenolysis of aromatic ether bonds in lignin model compounds. However, this technology uses precious metal catalysts with limited reserves and high costs; moreover, compared to lignin derivatives, the structure of real lignin is more complex and stable, thus limiting the depolymerization value of this technology for real lignin. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention aims to provide a multi-level porous nitrogen-carbon composite catalyst with high stability and catalytic activity, which is used to catalyze the hydrogenolysis of lignin to prepare aromatic compounds via a hydrogen transfer pathway. Using real lignin as the reaction substrate, a highly efficient catalytic system is constructed to achieve the lignin conversion process without the addition of external hydrogen, effectively reducing hydrogen energy consumption. After the reaction, the lignin conversion rate reaches 74.4%–91.3%, the total yield of monophenolic products reaches 7.8%–17.7%, of which p-hydroxyphenyl products can reach 4.2%–9.0%, and the selectivity is 38.4%–50.8%.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A method for preparing phenolic chemicals by catalytic hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material is disclosed. The method uses organosoluble lignin as a raw material, a cobalt-based nitrogen-carbon composite material as a catalyst, and small organic molecule alcohols and formic acid as a mixed solvent and hydrogen donor. The reaction is carried out at 210–250°C for 2–6 hours under an inert gas atmosphere of 0.5–3 MPa, catalyzing the depolymerization of lignin to obtain a monophenol product mainly composed of 4-ethylphenol. The cobalt-based nitrogen-carbon composite material is obtained by heat treatment of a Co-NDC precursor at 400–700°C under a reducing atmosphere. The Co-NDC precursor is obtained by refluxing a mixed solution of cobalt nitrate hexahydrate, 2,6-naphthalenedicarboxylic acid, and 1,10-phenanthroline at 100–120°C, followed by filtration, drying, and grinding. The mixed solution consists of N,N-dimethylformamide (DMF), water, and an alkaline regulator.

[0012] To further achieve the objectives of this invention, preferably, the molar ratio of cobalt nitrate hexahydrate, 2,6-naphthalenedicarboxylic acid, and 1,10-phenanthroline is (0.5-1.5):1:1; the mass ratio of cobalt nitrate hexahydrate to the mixed solution is 1:(90-110); and the volume ratio of N,N-dimethylformamide, water, and alkalinity regulator in the mixed solution is 20:1:(1.5-2.5).

[0013] To further achieve the purpose of this invention, preferably, the reflux time at 100-120°C is 24-32 hours; the alkaline regulator is one or more of formamide, diethylamine, N,N-tetramethylhexanediamine, and isopropanolamine.

[0014] Preferably, the mass ratio of the organo-soluble lignin to the cobalt-based nitrogen-carbon composite material is 1:(0.5-1.5); the mass ratio of the organic small molecule alcohol to formic acid in the mixed solvent is 9:(0.5-1.5); and the mass ratio of the organo-soluble lignin to the mixed solvent is 1:(7-9).

[0015] Preferably, the reducing atmosphere is a carbon monoxide / nitrogen mixture; the inert gas atmosphere is any one or more of nitrogen, argon, and helium; and the catalytic depolymerization of lignin is carried out in a batch high-pressure reactor.

[0016] Preferably, the heat treatment time is 6-7 hours; the organic small molecule alcohol is any one or more of methanol, ethanol, n-propanol, isopropanol and formic acid.

[0017] Preferably, the organo-soluble lignin is obtained by extracting biomass as a substrate using an organic solvent method.

[0018] Preferably, the organic solvent extraction method involves reacting biomass with a mixed extract of 1,4-dioxane / dilute sulfuric acid at 90-150°C for 2-8 hours, filtering to obtain the filtrate, adding deionized water to the filtrate to precipitate lignin, allowing it to stand for 12-24 hours, filtering again, obtaining a filter cake, drying and grinding it to obtain organosoluble lignin.

[0019] Preferably, the biomass is any one or more of bagasse, corn stalks, corn cobs, bamboo, poplar, birch, and pine, which is obtained by mechanical crushing and sieving to 80-120 mesh; in the 1,4-dioxane / dilute sulfuric acid extract, the volume ratio of 1,4-dioxane to dilute sulfuric acid is (6-7):1; the amount of ethanol / water mixed extract used per gram of biomass raw material is 10-20 mL; the dilute sulfuric acid is prepared by adding 9-12 g of deionized water to 95-98% concentrated sulfuric acid per gram.

[0020] Preferably, the monophenols include 4-ethylphenol, 4-propylphenol, p-hydroxyphenylpropionic acid, 4-ethylguaiacol, 4-propylguaiacol, 4-propenyguaiacol, 2,6-dimethoxyphenol, 2,6-dimethoxy-4-propylphenol, and 2,6-dimethoxy-4-propenyphenol.

[0021] Compared with existing lignin catalytic transfer hydrogenolysis technology, the technical solution of this invention has the following advantages:

[0022] (1) This invention addresses the problems of low lignin depolymerization conversion rate and low product yield. On the one hand, by enhancing the electronic interaction between the metal and the support, the catalyst can significantly promote the efficient hydrogen evolution of the hydrogen-donating solvent while catalyzing the efficient depolymerization of lignin. This avoids the high temperature and high pressure reaction process of traditional hydrogenolysis under external hydrogen supply conditions, and realizes the green and safe conversion of lignin under mild conditions. On the other hand, by rationally selecting the reaction medium and catalyst, the reaction medium and catalyst can be synergistically combined. The reaction medium can not only promote the dissolution of the substrate and increase the contact area between the substrate and the catalyst, but also further promote the exposure of the active sites of the catalyst and the hydrogenolysis reaction due to its physicochemical properties (such as solubility, polarity, ionic strength, etc.). This forms a virtuous cycle of "medium promotes catalysis, and catalysis enhances the efficiency of medium", thereby promoting the hydrogenolysis of lignin and making the conversion rate of lignin reach 74.4-91.3%, the total yield of monophenol products reach 7.8-17.7%, of which the p-hydroxyphenyl products can reach 3.2-9.0%, and the selectivity is 21.3-50.8%.

[0023] (2) The catalyst used in this invention incorporates formamide as an alkaline regulator during the preparation process to regulate the deprotonation process of 2,6-naphthalenedicarboxylic acid, thereby controlling the growth rate of crystals and obtaining a multi-level porous material with mesoporous structure and a small amount of micropores. This pore structure is beneficial to the mass transfer of lignin macromolecules, thereby improving its reactivity.

[0024] (3) The cobalt-based nitrogen-carbon catalyst used in this invention exhibits excellent catalytic activity. Nitrogen doping enhances the electronic interaction between the active metal and the support, strengthens the stability of the active metal in the support, prevents leaching, anchors metal sites, and increases the dispersion of metal species on the support. Furthermore, it alters the electronic structure of the metal center, redistributing the charge density and thus improving the catalyst's catalytic activity. Simultaneously, it adjusts the overall acidity and basicity of the catalyst, providing suitable acid-base sites, further enhancing its catalytic activity. Compared to the nitrogen-free cobalt-based carbon catalyst, the nitrogen-doped catalyst increases the monophenol yield from 12.3% to 16.2% in the depolymerization of lignin.

[0025] (4) The catalyst preparation process used in this invention is simple and has little environmental pollution. The reaction conditions for lignin depolymerization are mild. A high monophenol yield can be obtained at a reaction pressure of 1-3 MPa and a reaction temperature of 210-250℃, which is beneficial to reduce energy consumption and achieve lignin depolymerization under mild conditions.

[0026] (5) The catalyst of the present invention has strong stability and its activity does not decrease significantly after being used 5 times, which is significantly better than existing similar catalysts.

[0027] (6) The cobalt-based nitrogen-carbon material catalyst used in this invention is mainly a mesoporous catalyst, with a small number of micropores and macropores. It exhibits a blocky support structure with sheet-like stacking, which is beneficial for the mass transfer of lignin macromolecules inside the catalyst and reduces the mass transfer resistance. It can also provide abundant active sites for chemical reactions and promote hydrogen production and hydrogenolysis reactions. Attached Figure Description

[0028] Figure 1 The XRD patterns are of different catalysts 1 to 4 in Example 1 of this invention.

[0029] Figure 2 This is the N2 physical adsorption-desorption isotherm of the Co@NC-500 catalyst in Example 1 of this invention.

[0030] Figure 3 This is a pore size distribution diagram of the Co@NC-500 catalyst in Example 1 of the present invention.

[0031] Figure 4 This is a SEM image of the Co@NC-500 catalyst in Example 1 of the present invention.

[0032] Figure 5 The image shows the Co 2p spectrum in the XPS spectrum of the Co@NC-500 catalyst in Example 1 of this invention.

[0033] Figure 6 The N1s spectrum is shown in the XPS spectrum of the Co@NC-500 catalyst in Example 1 of this invention.

[0034] Figure 7 This is a gas chromatography-flame ionization detector (GC-FID) image of the volatile products obtained by catalytic hydrogenolysis of lignin using Co@NC-500 catalyst in Example 18 of this invention.

[0035] Figure 8 This is the mass spectrum (MS) of 4-ethylphenol, the main product obtained by catalytic depolymerization of lignin from organic-soluble bagasse in Example 18 of the present invention. Detailed Implementation

[0036] To better understand the present invention, the invention will be further described below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto.

[0037] The catalytic depolymerization of lignin described in this invention is carried out in an intermittent high-pressure reactor filled with inert gas, using an organic solvent instead of hydrogen as the hydrogen donor to enhance the reducing atmosphere. Specifically, this invention provides a method for the catalytic transfer hydrogenolysis of lignin to prepare phenolic chemicals using a cobalt-based nitrogen-carbon composite material: using organic lignin as raw material, a cobalt-based nitrogen-carbon composite material as catalyst, and a mixed solvent of small organic molecule alcohol and formic acid; the mixed solvent also serves as the hydrogen donor. The reaction is carried out for 2-6 hours under an inert gas atmosphere of 0.5-3 MPa and at a temperature of 210-250°C, catalyzing the depolymerization of lignin to obtain a monophenol product mainly composed of 4-ethylphenol. The cobalt-based nitrogen-carbon composite material (Co@NC) catalyst is derived from a metal-organic framework precursor synthesized by coordination of transition metal cobalt with 2,6-naphthalenedicarboxylic acid and 1,10-phenanthroline. In the preparation of the catalyst, a Co-NDC precursor is first synthesized, and then the Co-NDC precursor is heat-treated under different reducing atmospheres (carbon monoxide / nitrogen mixture).

[0038] (1) Synthesis of Co-NDC precursor: Cobalt nitrate hexahydrate, 2,6-naphthalenedicarboxylic acid and 1,10-phenanthroline were used as raw materials, N,N-dimethylformamide (DMF) was used as solvent and formamide was used as alkaline regulator. The mixture was refluxed and stirred at 100-120℃, aged, filtered and dried to obtain Co-NDC precursor.

[0039] (2) Reduction of Co-NDC precursor: First, the Co-NDC precursor is placed in a reduction furnace and heat-treated (400-700°C) for a period of time (preferably 6-7h) in a reducing atmosphere (carbon monoxide / nitrogen mixture) to obtain a cobalt-based nitrogen-carbon composite (Co@NC) catalyst.

[0040] Co-NDC serves as a catalyst precursor, providing Co, O, N, C, and H elements to the catalyst. Co-NDC is called a catalyst precursor because after reduction treatment, its structure and morphology are almost completely altered, forming a cobalt-based nitrogen-carbon composite catalyst (Co@NC) with Co and Co3O4 as active centers and nitrogen-doped carbon (NC) as the support. Elemental Co in the catalyst exhibits catalytic activity for lignin hydrogenolysis and hydrogen transfer, while Co3O4 possesses hydrodeoxygenation activity, enabling one-step hydrodeoxygenation of lignin. This means that lignin depolymerization and partial hydrodeoxygenation of the depolymerization products are achieved within the same reaction process, a simple procedure suitable for both batch and continuous production. The catalyst of this invention enables the catalytic transfer hydrogenolysis of lignin to prepare monophenolic compounds under conditions without external hydrogen supply. A key advantage is the mild reaction conditions. Compared to traditional lignin hydrogenolysis, which requires high-pressure hydrogen and high reaction temperatures (250–500°C, with poor performance above 250°C), this invention uses organic solvents and endogenous hydrogen supply from lignin, achieving lignin conversion without external hydrogen supply. The catalytic hydrogen transfer and hydrodeoxygenation processes effectively reduce hydrogen consumption, improving the safety and controllability of the reaction process. In particular, the reaction temperature is further lowered; hydrogenolysis of lignin to obtain monophenolic compounds can be achieved under mild conditions of 210–250°C. Furthermore, the distribution of the target product can be controlled by adjusting the calcination temperature of the catalyst.

[0041] Preferably, the small molecule organic solvent can be any one or two of methanol, ethanol, isopropanol, n-hexanol and formic acid; lignin can be derived from any one of bagasse, corn stalks, poplar and bamboo; the mass ratio of lignin to nickel-based catalyst is 1:0.5 to 1:1.5; and the mass ratio of lignin to alcohol solvent is 1:9 to 1:10.

[0042] The monophenolic products of the present invention are one or more of 4-ethylphenol, 4-propylphenol, p-hydroxyphenylpropionic acid, 4-ethylguaiacol, 4-propylguaiacol, 4-propenyguaiacol, 2,6-dimethoxyphenol, 2,6-dimethoxy-4-propylphenol, and 2,6-dimethoxy-4-propenyphenol.

[0043] Example 1: Preparation of Co@NC-400, a cobalt-based nitrogen-carbon composite catalyst

[0044] The preparation of the cobalt-based nitrogen-carbon composite catalyst Co@NC-400 includes the following two steps:

[0045] (1) Preparation of Co-NDC precursor based on metal-organic framework: 1.545 g of cobalt nitrate hexahydrate with a purity of 99%, 1.264 g of 2,6-naphthalenedicarboxylic acid with a purity of 99%, and 0.640 g of 1,10-phenanthroline with a purity of 99% were dissolved in a mixed solvent of 20 mL of deionized water, 200 mL of DMF and 20 mL of formamide. After stirring evenly at room temperature, the mixture was placed in an oil bath and heated under reflux at 120 °C for 32 h. After filtration, washing, drying and grinding, the Co-NDC precursor was obtained.

[0046] (2) Preparation of Co@NC-400 cobalt-based nitrogen-carbon composite catalyst: The Co-NDC precursor obtained in (1) was placed in an 80 mL·min -1 Under a nitrogen atmosphere, at 2℃·min -1 Heat to 200℃ at a rate of [missing information], hold for 2 hours, then heat at 5℃·min [missing information]. -1 The temperature was heated to 400℃ at a certain rate and held for 2 hours to obtain the Co@NC-400 catalyst.

[0047] Example 2: Preparation of Co@NC-500, an oxygen-containing cobalt-based nitrogen-carbon composite catalyst

[0048] The preparation of the cobalt-based nitrogen-carbon composite catalyst Co@NC-500 also involves two steps:

[0049] (1) Preparation of Co-NDC precursor based on metal-organic framework: 1.545g of cobalt nitrate hexahydrate with a purity of 99%, 1.264g of 2,6-naphthalenedicarboxylic acid with a purity of 99%, and 0.640g of 1,10-phenanthroline with a purity of 99% were dissolved in a mixed solvent of 20mL deionized water, 200mL DMF, and 20mL formamide. After stirring evenly at room temperature, the mixture was placed in an oil bath and heated under reflux at 120℃ for 32h. After filtration, washing, drying, and grinding, the Co-NDC precursor was obtained.

[0050] (2) Preparation of Co@NC-500 cobalt-based nitrogen-carbon composite catalyst: The Co-NDC precursor obtained in (1) was placed in an 80 mL·min -1 Under a nitrogen atmosphere, at 2℃·min -1 Heat to 200℃ at a rate of [missing information], hold for 2 hours, then heat at 5℃·min [missing information]. -1 The temperature was heated to 500℃ at a certain rate and held for 2 hours to obtain the Co@NC-500 catalyst.

[0051] Example 3: Preparation of Co@NC-600, an oxygen-containing cobalt-based nitrogen-carbon composite catalyst

[0052] The preparation of the cobalt-based nitrogen-carbon composite catalyst Co@NC-600 also involves two steps:

[0053] (1) Preparation of Co-NDC precursor based on metal-organic framework: 1.545 g of cobalt nitrate hexahydrate with a purity of 99%, 1.264 g of 2,6-naphthalenedicarboxylic acid with a purity of 99%, and 0.640 g of 1,10-phenanthroline with a purity of 99% were dissolved in a mixed solvent of 20 mL of deionized water, 200 mL of DMF and 20 mL of formamide. After stirring evenly at room temperature, the mixture was placed in an oil bath and heated under reflux at 120 °C for 32 h. After filtration, washing, drying and grinding, the Co-NDC precursor was obtained.

[0054] (2) Preparation of Co@NC-600 cobalt-based nitrogen-carbon composite catalyst: The Co-NDC precursor obtained in (1) was placed in an 80 mL·min -1 Under a nitrogen atmosphere, at 2℃·min -1 Heat to 200℃ at a rate of [missing information], hold for 2 hours, then heat at 5℃·min [missing information]. -1 The temperature was heated to 600℃ at a certain rate and held for 2 hours to obtain the Co@NC-600 catalyst.

[0055] Example 4: Preparation of Co@NC-700, an oxygen-containing cobalt-based nitrogen-carbon composite catalyst

[0056] The preparation of the cobalt-based nitrogen-carbon composite catalyst Co@NC-700 also involves two steps:

[0057] (1) Preparation of Co-NDC precursor based on metal-organic framework: 1.545 g of cobalt nitrate hexahydrate with a purity of 99%, 1.264 g of 2,6-naphthalenedicarboxylic acid with a purity of 99%, and 0.640 g of 1,10-phenanthroline with a purity of 99% were dissolved in a mixed solvent of 20 mL of deionized water, 200 mL of DMF and 20 mL of formamide. After stirring evenly at room temperature, the mixture was placed in an oil bath and heated under reflux at 120 °C for 32 h. After filtration, washing, drying and grinding, the Co-NDC precursor was obtained.

[0058] (2) Preparation of Co@NC-700 cobalt-based nitrogen-carbon composite catalyst: The Co-NDC precursor obtained in (1) was placed in an 80 mL·min -1 Under a nitrogen atmosphere, at 2℃·min -1 Heat to 200℃ at a rate of [missing information], hold for 2 hours, then heat at 5℃·min [missing information]. -1 The temperature was heated to 700℃ at a certain rate and held for 2 hours to obtain the Co@NC-700 catalyst.

[0059] Figure 1The XRD patterns of the catalysts prepared in Examples 1-4 at different reduction temperatures show that when the reduction temperature is above 500℃, the series of catalysts all exhibit the elemental Co (PDF#15-0806) crystal phase belonging to the face-centered cubic (FCC) structure, with the diffraction peak at 2θ = 44.2° corresponding to the (111) crystal plane of metallic Co. The intensity of the Co diffraction peak increases with increasing reduction temperature.

[0060] The prepared Co@NC-500 catalyst was characterized by N2 physical adsorption-desorption to investigate its pore structure. The results are as follows: Figure 2 and Figure 3 As shown. By Figure 2 It can be seen that the adsorption isotherm of Co@NC-500 is a typical type IV isotherm, and a distinct H4 type hysteresis loop can be observed in a moderate relative pressure range (P / P0 = 0.4–1.0), indicating the presence of a mesoporous structure in the support. Combined with… Figure 3 The pore size distribution diagram shows that the main pore structure of the carrier is mesopores of 12-50 nm, and it also contains a small number of micropores of 1-2 nm and macropores of 50-100 nm.

[0061] The prepared Co@NC-500 catalyst was characterized by SEM to investigate its surface morphology. The results are as follows: Figure 4 As shown, the morphology of the carrier can be clearly observed to be a stacked thin sheet with spherical clusters distributed on the surface.

[0062] The prepared Co@NC-500 catalyst was characterized by XPS to investigate the presence of Co and N elements on its surface. The results are as follows: Figure 5 and 6 As shown. Figure 5 The image shows the Co 2p spectrum of the Co@NC-500 catalyst, with Co in the catalyst appearing as Co. 3+ Co 2+ Co 0 The three forms exist, accounting for 43.9%, 36.6%, and 19.5% respectively. The two characteristic peaks at 778.8 eV and 794.4 eV correspond to Co, respectively. 0 2p 3 / 2 and Co 0 2p 1 / 2 The characteristic peaks at 782.3 eV and 798.0 eV of the orbital are attributed to Co. 2 + 2p 3 / 2 and Co 2+ 2p 1 / 2 The characteristic peaks at 780.5 eV and 796.2 eV of the orbital are attributed to Co. 3+ 2p 3 / 2 and Co3+ 2p 1 / 2 Compared to the standard characteristic peaks, the binding energies of the orbitals all shifted upwards, indicating electron transfer between Co and the support, further proving the interaction between the metal and the support. Most Co species on the Co@NC-500 catalyst exist in the form of metal oxides, while the unique CoO species with suitable oxygen vacancies can strongly adsorb lignin macromolecules and catalyze the homolytic / heterolytic cleavage of H2 molecules to produce highly active H+. δ- Species. Figure 6 The image shows the N 1s spectrum of the Co@NC-500 catalyst. The N element in the catalyst exists in three forms: pyridine N, Co-N, and nitrogen oxides, accounting for 72.7%, 19.6%, and 7.7%, respectively. The pyridine N and Co-N bonds can stabilize cobalt nanoparticles. The bonding between Co and N indicates that there is a significant metal-support interaction force in the catalyst, which can prevent the aggregation of cobalt nanoparticles during pyrolysis and improve the dispersion of Co.

[0063] Example 5: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0064] (1) Lignin Extraction: Bagasse was mechanically crushed and sieved, and the 80-120 mesh bagasse powder was sealed and stored for later use. The mass ratio of 1,4-dioxane / dilute sulfuric acid (1M) in the extract was 20:3. 20g of bagasse powder and 230mL of extract were placed in a hydrothermal reactor and heated at 90℃ for 2h. After the reaction, the mixture was allowed to cool naturally to room temperature. The mixture was filtered, the liquid phase was collected, 500mL of deionized water was added, and the mixture was allowed to stand to precipitate lignin. The mixture was filtered again, the solid phase was collected, vacuum dried overnight, ground, and stored in the dark. The obtained lignin was defined as organosoluble bagasse lignin.

[0065] (2) Catalytic transfer hydrogenolysis of lignin: The catalytic hydrogenolysis of lignin was carried out in a high-pressure reactor. 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid were weighed and mixed in the reactor, which was then sealed. After purging the reactor with argon gas five times, 1 MPa of argon gas was introduced. Thermocouples were connected. The reactor was rotated at 600 rpm at 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0066] The gaseous products after the reaction were collected and qualitatively and quantitatively analyzed by gas chromatography-TCD. The solid-liquid mixture in the reaction vessel was filtered, and the filter cake was washed several times with the reaction solvent. The filter cake contained the catalyst and the solid products after the reaction, while the liquid products after the reaction included the reaction solvent and the lignin hydrogenolysis products generated in the reaction. The liquid products and the washing solution were transferred together to a 25 mL volumetric flask, dimethyl phthalate (dimethyl phthalate) was added as an internal standard, and the volume was adjusted with the reaction solvent to dilute the liquid products. 1.5 mL of the test solution was pipetted into a sample vial for gas chromatography-mass spectrometry (GC-MS) detection. Temperature program: 50 °C for 1 min, then at 10 °C / min increments. -1 The temperature was increased to 250℃ and held for 31 min to quantitatively analyze the liquid products in the reaction. An appropriate amount of deionized water was added to the reaction solution, and the mixture was allowed to stand completely to precipitate regenerated lignin. The precipitated lignin was then filtered and dried to constant weight to obtain the regenerated lignin.

[0067] The distribution and yield of volatile products in the liquid phase can be obtained by GC-MS detection, and then the conversion rate of organic lignin and the total yield of volatile products can be calculated. The calculation formulas are shown in (1) to (2):

[0068]

[0069] Where m0 is the mass of primary lignin (g), m R m represents the mass (g) of regenerated lignin after the reaction. v The mass of volatile products is expressed in grams (g).

[0070] Figure 8 This is the mass spectrum (MS) of 4-ethylphenol, the main product obtained from the catalytic depolymerization of lignin in organic-soluble bagasse in this embodiment. In mass spectrometry, the maximum mass-to-charge ratio (m / z) usually corresponds to the relative molecular mass of the molecule. As shown in the figure, the maximum mass-to-charge ratio (m / z) of this product is 122, which corresponds to the relative molecular mass (122) of 4-ethylphenol. Furthermore, by referring to the AgilentNIST MS Search 2.4 database, the product was confirmed to be 4-ethylphenol.

[0071] Comparison Figure 7 Table 1 shows the retention times and yields of different volatile products. As can be seen from the table, the yields of 4-ethylphenol, 4-propylguaiacol, 4-propyleugenol, and p-hydroxyphenylpropionic acid are relatively high, reaching 6.1%, 2.4%, 3.8%, and 2.8%, respectively, with a total yield of 17.7% for monophenolic compounds.

[0072] Table 1. Product distribution and yield of phenolic compounds prepared by catalytic transfer hydrogenolysis of lignin

[0073]

[0074]

[0075] The gas chromatography-flame ionization detector (GC-FID) chromatograms of the volatile products obtained by catalytic hydrogenolysis of lignin in the following examples, and the mass spectrometry (MS) chromatograms of the main product 4-ethylphenol obtained by catalytic depolymerization of lignin from organic-soluble bagasse, are basically similar to those in Example 5 and are not provided individually.

[0076] Example 6: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-400

[0077] The difference between this embodiment and embodiment 5 is that:

[0078] Weigh out 50 mg of Co@NC-400 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 0.5–1.5 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Stir the reaction vessel at 600 rpm at a rate of 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0079] In this example, the lignin conversion rate was 74.4%, the total yield of monophenol products was 7.8 wt.%, the yield of 4-ethylphenol was 3.2 wt.%, and the selectivity was 41.0%.

[0080] Example 7: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-600

[0081] The difference between this embodiment and embodiment 5 is that:

[0082] Weigh out 50 mg of Co@NC-600 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0083] In this example, the lignin conversion rate was 83.9%, the total yield of monophenol products was 13.8 wt.%, the yield of 4-ethylphenol was 4.2 wt.%, and the selectivity was 30.4%.

[0084] Example 8: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-700

[0085] The difference between this embodiment and embodiment 5 is that:

[0086] Weigh out 50 mg of Co@NC-700 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0087] In this example, the lignin conversion rate was 83.3%, the total yield of monophenol products was 13.6 wt.%, the yield of 4-ethylphenol was 2.9 wt.%, and the selectivity was 21.3%.

[0088] Example 9: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0089] The difference between this embodiment and embodiment 5 is that:

[0090] Weigh out 75 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0091] In this example, the lignin conversion rate was 88.6%, the total yield of monophenol products was 17.5 wt.%, the yield of 4-ethylphenol was 5.4 wt.%, and the selectivity was 30.9%.

[0092] Example 10: Preparation of monophenolic compounds by hydrogenolysis of sugarcane bagasse lignin via Co@NC-500 catalysis

[0093] The difference between this embodiment and embodiment 5 is that:

[0094] Weigh 100 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid and mix them in a reactor. Seal the reactor. After purging the reactor with argon gas five times, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reactor at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0095] In this example, the lignin conversion rate was 89.1%, the total yield of monophenol products was 15.9 wt.%, the yield of 4-ethylphenol was 5.3 wt.%, and the selectivity was 33.3%.

[0096] Example 11: Preparation of monophenolic compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0097] The difference between this embodiment and embodiment 5 is that:

[0098] Weigh out 125 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0099] In this example, the lignin conversion rate was 90.2%, the total yield of monophenol products was 15.9 wt.%, the yield of 4-ethylphenol was 5.2 wt.%, and the selectivity was 32.7%.

[0100] Example 12: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0101] The difference between this embodiment and embodiment 5 is that:

[0102] Weigh out 150 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0103] In this example, the lignin conversion rate was 90.1%, the total yield of monophenol products was 15.0 wt.%, the yield of 4-ethylphenol was 5.2 wt.%, and the selectivity was 34.7%.

[0104] Example 13: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin via Co@NC-500 catalysis

[0105] The difference between this embodiment and embodiment 5 is that:

[0106] Weigh out 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 220°C at a rate of [missing information] and maintain for 4 hours.

[0107] In this example, the lignin conversion rate was 75.8%, the total yield of monophenol products was 15.4 wt.%, the yield of 4-ethylphenol was 4.5 wt.%, and the selectivity was 29.2%.

[0108] Example 14: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0109] The difference between this embodiment and embodiment 5 is that:

[0110] Weigh out 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 240°C at a rate of [missing information] and maintain for 4 hours.

[0111] In this example, the lignin conversion rate was 89.4%, the total yield of monophenol products was 17.3 wt.%, the yield of 4-ethylphenol was 5.5 wt.%, and the selectivity was 31.8%.

[0112] Example 15: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0113] The difference between this embodiment and embodiment 5 is that:

[0114] Weigh out 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 250°C at a rate of [missing information] and maintain for 4 hours.

[0115] In this example, the lignin conversion rate was 90.1%, the total yield of monophenol products was 16.1 wt.%, the yield of 4-ethylphenol was 4.9 wt.%, and the selectivity was 30.4%.

[0116] Example 16: Preparation of monophenol compounds by Co@NC-500-catalyzed hydrogenolysis of lignin transfer from sugarcane bagasse

[0117] The difference between this embodiment and embodiment 5 is that:

[0118] Weigh out 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 2 hours.

[0119] In this example, the lignin conversion rate was 79.0%, the total yield of monophenol products was 13.6 wt.%, the yield of 4-ethylphenol was 4.6 wt.%, and the selectivity was 33.8%.

[0120] Example 17: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0121] The difference between this embodiment and embodiment 5 is that:

[0122] Weigh out 50 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid, mix them, and place them in a reaction vessel. Seal the reaction vessel. After purging the air in the reaction vessel five times with argon gas, purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reaction vessel at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 6 hours.

[0123] In this example, the lignin conversion rate was 87.4%, the total yield of monophenol products was 15.8 wt.%, the yield of 4-ethylphenol was 4.9 wt.%, and the selectivity was 31.0%.

[0124] Example 18: Preparation of monophenol compounds by hydrogenolysis of sugarcane bagasse lignin transfer catalyzed by Co@NC-500

[0125] The difference between this embodiment and embodiment 5 is that:

[0126] Weigh 75 mg of Co@NC-500 catalyst, 100 mg of bagasse lignin, 9 mL of isopropanol, and 1 mL of formic acid into a reactor and seal the reactor. Replace the air in the reactor five times with argon gas, then purge with 1 MPa of argon gas. Connect the thermocouple. Rotate the reactor at 600 rpm and increase the temperature by 5 °C / min. -1 Heat to 240°C at a rate of [missing information] and maintain for 4 hours.

[0127] In this example, the lignin conversion rate was 90.1%, the total yield of monophenol products was 17.7 wt.%, the yield of 4-ethylphenol was 6.1 wt.%, and the selectivity was 34.5%.

[0128] Example 19: Preparation of monophenol compounds by Co@NC-500-catalyzed hydrogenolysis of bamboo lignin transfer

[0129] (1) Lignin Extraction: Bamboo was mechanically crushed and sieved, and the 80-120 mesh bamboo powder was sealed and stored for later use. The ratio of ethanol to water in the extract was 4:1 (3200 mL anhydrous ethanol, 800 mL deionized water, 24 g concentrated H2SO4). 10 g of bamboo powder and 100 mL of extract were placed in a hydrothermal reactor and heated at 100 °C for 4 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The mixture was filtered, the liquid phase was collected, 500 mL of deionized water was added, and the mixture was allowed to stand to precipitate lignin. The mixture was filtered again, the solid phase was collected, vacuum dried overnight, ground, and stored in the dark. The obtained lignin is organosoluble bamboo lignin.

[0130] (2) Catalytic lignin hydrogenolysis: The catalytic lignin hydrogenolysis reaction was carried out in a high-pressure reactor. 50 mg of Co@NC-500 catalyst, 100 mg of bamboo lignin, 9 mL of isopropanol, and 1 mL of formic acid were weighed and placed in the reactor, which was then sealed. After purging the reactor with argon gas five times, 1 MPa of argon gas was introduced. Thermocouples were connected. The reactor was rotated at 600 rpm at 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0131] In this example, the lignin conversion rate was 83.7%, the total yield of monophenol products was 10.3 wt.%, the yield of 4-ethylphenol was 1.7 wt.%, and the selectivity was 16.5%.

[0132] Example 20: Preparation of monophenol compounds by Co@NC-500-catalyzed hydrogenolysis of poplar lignin transfer

[0133] (1) Extraction of lignin: Poplar wood was mechanically crushed and sieved, and the 80-120 mesh poplar powder was sealed and stored for later use. The ratio of ethanol to water in the extract was 4:1 (3200 mL anhydrous ethanol, 800 mL deionized water, 24 g concentrated H2SO4). 10 g of poplar powder and 100 mL of extract were placed in a hydrothermal reactor and heated at 100 °C for 4 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The mixture was filtered, the liquid phase was collected, 500 mL of deionized water was added, and the mixture was allowed to stand to precipitate lignin. The mixture was filtered again, the solid phase was collected, vacuum dried overnight, ground, and stored in the dark. The obtained lignin is the organosoluble poplar lignin.

[0134] (2) Catalytic lignin hydrogenolysis: The catalytic lignin hydrogenolysis reaction was carried out in a high-pressure reactor. 50 mg of Co@NC-500 catalyst, 100 mg of poplar lignin, 9 mL of isopropanol, and 1 mL of formic acid were weighed and placed in the reactor, which was then sealed. After purging the reactor with argon gas five times, 1 MPa of argon gas was introduced. Thermocouples were connected. The reactor was rotated at 600 rpm at 5 °C / min. -1 Heat to 230°C at a rate of [missing information] and maintain for 4 hours.

[0135] In this example, the lignin conversion rate was 85.2%, the total yield of monophenol products was 9.8 wt.%, the yield of 4-propylguaiacol was 2.2 wt.%, and the selectivity was 22.4%.

[0136] Example 21: Catalyst Recyclability

[0137] Catalytic cycling tests were conducted using Co@NC-500 catalyst. The reuse process was as follows: after reaction, the catalyst was filtered and dried in an oven at 100–120°C for 12–24 hours without regeneration. The resulting solid catalyst was then cycled according to the steps in Example 6. The tests showed that the catalyst activity did not significantly decrease after 5 cycles, the lignin conversion rate was 86.2%, the volatile product yield was 16.8%, and the 4-ethylphenol product yield was 5.1%.

[0138] As can be seen from the above embodiments, the cobalt-based nitrogen-carbon composite catalytic system of the present invention, combined with an organic hydrogen-donating solvent, achieves the catalytic transfer hydrogenolysis of lignin to prepare monophenolic products under conditions without external hydrogen gas. Under an inert gas atmosphere of 0.5–3 MPa, a reaction temperature of 210–250 °C, and a reaction time of 2–6 h, the conversion rate of lignin reaches 74.4–91.3%, the total yield of monophenolic products reaches 7.8–17.7%, of which p-hydroxyphenyl products can reach 4.2–9.0%, and the selectivity is 38.4–50.8%. 4-Ethylphenol has wide applications in food additives, cosmetics, and pharmaceuticals; 4-propylguaiacol is widely used in fragrance tobacco and daily chemical flavorings; p-hydroxyphenylpropionic acid and 4-propyleugenol are high-value-added chemicals widely used in the production of food additives and pharmaceutical intermediates. Therefore, high selectivity for these products can improve the economic efficiency and overall utilization value of lignin.

[0139] Compared to the boron nitride-supported ruthenium catalyst invented in Chinese invention patent application CN202410599907.8, the transition metal-based catalyst used in this invention can effectively depolymerize actual lignin and reduce dependence on rare metal resources, thereby improving the economy and sustainability in industrial applications and giving the actual lignin depolymerization process higher practical application value and significance. Compared to the RuNiZn / Nb2O5 catalyst invented in Chinese invention patent application CN202311659296.3, the catalyst of this invention achieves efficient depolymerization of lignin without relying on external hydrogen supply, the catalytic system is greener and safer, and the requirements for reaction conditions are reduced, enabling efficient depolymerization of lignin under milder reaction conditions. Compared to the nickel-based alkaline supported catalyst invented in Chinese invention patent application CN202410215194.0, the catalyst of this invention has strong stability, and its activity does not decrease significantly after 5 cycles of use.

[0140] The implementation of the present invention is 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 of catalytic lignin transfer hydrogenolysis to produce phenolic chemicals using cobalt-based nitrogen-carbon composite, characterized in that, Using organic lignin as raw material, cobalt-based nitrogen-carbon composite material as catalyst, and organic small molecule alcohol and formic acid as mixed solvent and hydrogen donor, the reaction is carried out at 210-250℃ for 2-6 hours under an inert gas atmosphere of 0.5-3 MPa to catalyze the depolymerization of lignin to obtain a monophenol product mainly composed of 4-ethylphenol; the cobalt-based nitrogen-carbon composite material is obtained by heat treatment of Co-NDC precursor at 500-700℃ under a reducing atmosphere; the Co-NDC precursor is obtained by reflux of cobalt nitrate hexahydrate, 2,6-naphthalenedicarboxylic acid and 1,10-phenanthroline in a mixed solution at 100-120℃, followed by filtration, drying and grinding; the mixed solution is composed of N,N-dimethylformyl... The mixture comprises an amine, water, and an alkaline regulator; the alkaline regulator is one or more of formamide, diethylamine, N,N-tetramethylhexanediamine, and isopropanolamine; the volume ratio of N,N-dimethylformamide, water, and alkaline regulator in the mixed solution is 20:1:(1.5~2.5); the organic small molecule alcohol is any one or more of methanol, ethanol, n-propanol, and isopropanol; the monophenol is 4-ethylphenol, 4-propylphenol, p-hydroxyphenylpropionic acid, 4-ethylguaiacol, 4-propylguaiacol, 4-propenylguaiacol, 2,6-dimethoxyphenol, 2,6-dimethoxy-4-propylphenol, and 2,6-dimethoxy-4-propenol.

2. The process for catalytic lignin transfer hydrogenolysis to phenolic chemicals using cobalt-based nitrogen-carbon composite material according to claim 1, characterized in that, The molar ratio of cobalt nitrate hexahydrate, 2,6-naphthalenedicarboxylic acid and 1,10-phenanthroline is (0.5~1.5):1:1; the mass ratio of cobalt nitrate hexahydrate to the mixed solution is 1:(90~110).

3. The process for catalytic lignin transfer hydrogenolysis to phenolic chemicals using cobalt-based nitrogen-carbon composite material according to claim 2, characterized in that, The reflux time at 100~120℃ is 24~32h.

4. The process for catalytic lignin transfer hydrogenolysis to phenolic chemicals using cobalt-based nitrogen-carbon composite material as claimed in claim 1, wherein, The mass ratio of the organic lignin and cobalt-based nitrogen-carbon composite material is 1:(0.5~1.5); the mass ratio of the organic small molecule alcohol and formic acid in the mixed solvent is 9:(0.5~1.5); and the mass ratio of the organic lignin to the mixed solvent is 1:(7~9).

5. The process for catalytic lignin transfer hydrogenolysis to phenolic chemicals using cobalt-based nitrogen-carbon composite material as claimed in claim 1, wherein, The reducing atmosphere is a mixture of carbon monoxide and nitrogen; the inert gas atmosphere is any one or more of nitrogen, argon, and helium; the catalytic depolymerization of lignin is carried out in a batch high-pressure reactor.

6. The process for catalytic lignin transfer hydrogenolysis to phenolic chemicals using cobalt-based nitrogen-carbon composite material as claimed in claim 1, wherein, The heat treatment time is 6-7 hours.

7. The method for preparing phenolic chemicals by catalytic hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material according to claim 1, characterized in that, The organo-soluble lignin is obtained by extracting biomass as a substrate using an organic solvent method.

8. The method for preparing phenolic chemicals by catalytic hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material according to claim 7, characterized in that, The organic solvent extraction method involves reacting biomass with a mixed extract of 1,4-dioxane / dilute sulfuric acid at 90-150°C for 2-8 hours, filtering the filtrate, adding deionized water to the filtrate to precipitate lignin, allowing it to stand for 12-24 hours, filtering again, drying and grinding the filter cake to obtain organosoluble lignin.

9. The method for preparing phenolic chemicals by catalytic hydrogenolysis of lignin using a cobalt-based nitrogen-carbon composite material according to claim 8, characterized in that, The biomass is any one or more of sugarcane bagasse, corn stalks, corn cobs, bamboo, poplar, birch, and pine, which are mechanically crushed and sieved to a mesh size of 80-120. In the 1,4-dioxane / dilute sulfuric acid extract, the volume ratio of 1,4-dioxane to dilute sulfuric acid is (6-7):

1. The dilute sulfuric acid is prepared by adding 9-12g of deionized water to each gram of concentrated sulfuric acid with a mass concentration of 95-98%.

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