Method for preparing 4-propylsyringaldehyde by catalyzing hydrogenolysis of lignin with cobalt-nitrogen co-doped porous carbon

Abstract

The application discloses a method for preparing 4-propyl eugenol by catalyzing hydrogenolysis of lignin by using cobalt-nitrogen co-doped porous carbon, and belongs to the technical field of catalysis. The method comprises the following steps: taking organic-solvent lignin as raw material, taking lignin-based cobalt-nitrogen co-doped porous carbon as catalyst, taking small-molecule alcohol as reaction medium, stirring under the conditions of hydrogen pressure of 1-2 MPa and temperature of 190-260 DEG C, and selectively hydrogenolyzing the organic-solvent lignin into monophenol chemicals mainly containing 4-propyl eugenol. The catalyst does not need to experience the preparation of a carrier, impregnation and reduction, and also does not need to prepare a mofs material and then be calcined, so that obvious advantages are achieved in the catalyst preparation process. The catalyst uses a transition metal as a catalytic active metal, the metal is uniformly dispersed on the surface of the catalyst in a monatomic level, forms a complex mainly containing CoN4 with carbon and nitrogen, the catalyst has a wide source of raw materials, a very low metal content, obvious cost advantages and advantages of large-scale production.

Description

Technical Field

[0001] This invention relates to the preparation of highly dispersed metal catalysts and 4-propyl eugenol, and particularly to a method for the highly selective preparation of monophenols from lignin using a lignin-based cobalt-nitrogen co-doped porous carbon-supported highly dispersed cobalt catalyst, which belongs to the field of high-value utilization of biomass energy. Background Technology

[0002] With the development of human society, science and technology are advancing rapidly. Behind this rapid technological development lies the consumption of energy, but non-renewable fossil fuels remain the primary source of energy. As society progresses, environmental issues such as global warming and pollution are receiving increasing attention, making the search for green and renewable energy a hot topic for researchers worldwide. Currently discovered green energy sources include solar, wind, tidal, and biomass energy. Compared to other green energy sources, biomass energy is not only abundant but also rich in various functional groups, enabling a continuous and stable energy output while being convertible into various high-value-added chemicals. Therefore, biomass energy is the best alternative to fossil fuels.

[0003] Lignocellulose, the most widespread form of biomass, is mainly composed of three parts: hemicellulose (20-30%), cellulose (20-30%), and lignin (10-35%). Hemicellulose and cellulose, as polymers of pentose and hexose sugars, have been industrially utilized. Lignin, however, is difficult to directly convert into desired chemicals due to its three-dimensional amorphous structure and complex linkages. Nevertheless, as the only renewable aromatic structure in nature, lignin's high-value utilization has attracted considerable attention. Research has revealed that the lignin structure is mainly composed of three phenylpropane structural units (H unit: p-hydroxyphenyl; G unit: guaiacol; S unit: eugenol) linked by various carbon-carbon and carbon-oxygen bonds. The complex structure, large molecular volume, and high dissociation energy of the linkages are the main factors limiting the high-value utilization of lignin.

[0004] Compared to molecular sieves or metal oxide catalysts, carbon-supported catalysts are not only inexpensive and readily available, but also highly modifiable. Nitrogen-doped carbon catalysts, in particular, provide a large number of active sites, which is more conducive to metal loading, and also enrich the defects on the carbon material surface, further promoting the reaction. This makes carbon-nitrogen catalysts excellent supports for single-atom catalysts. Compared to traditional metal-supported catalysts, highly dispersed metal catalysts have a more uniform distribution on the support surface, and the high dispersion of metal particles also results in a higher specific surface energy, further promoting the catalytic activity. However, the preparation methods of single-atom highly dispersed metal catalysts are usually complex, and due to their high specific surface energy, the metal is more prone to agglomeration during the catalytic reaction, leading to deactivation.

[0005] The structural formula of 4-propylbutyrrol is: Due to its antioxidant properties and rich functional group structure, lignin is widely used in the food industry, pharmaceutical synthesis, and bio-based materials. For example, researchers have observed that smoked foods not only have a unique aroma but also have a longer shelf life at room temperature. Further investigation revealed that when using wood to smoke food, 2,6-dimethoxyphenol produced by wood pyrolysis adheres to the food surface and exhibits good antioxidant effects. Meanwhile, in the pharmaceutical field, 4-propyleugenol is also an important intermediate for the psychoactive drug cannabinoids. In terms of materials, compared to other types of lignin derivatives, 4-propyleugenol has more oxygen-containing functional groups and can serve as a precursor for biomass materials. Currently, commercially available 4-propyleugenol is mainly prepared from petroleum-based products through multi-step reactions. This preparation method faces challenges such as low selectivity and complex reactions. Therefore, the one-step hydrogenolysis preparation of 4-propyleugenol using renewable lignin resources is of great significance for the high-value utilization of lignin and is expected to replace existing organic synthesis chemical technologies.

[0006] Chinese invention patent application 202311762765.4 discloses a method for preparing a ruthenium-based catalyst Ru@RuO2 supported on zirconium phosphate and its hydrogenolysis effect on lignin and model compounds. Catalytic dealkalization of lignin under 2 MPa, 30% H2 / N2, and 250 °C for 12 h yields 23.9 wt.% of a single benzene ring product. While this technique achieves a high yield of single benzene ring products, the selectivity for individual products is low. Furthermore, the reliance on noble metals as the main active sites further increases the catalyst manufacturing cost. In particular, only a portion of the Ru in this catalyst is reduced to elemental Ru to participate in the catalytic activity, further reducing metal utilization and impacting the industrialization prospects of this technology.

[0007] Chinese invention patent 202111370517.6 discloses a method for hydrogenolysis of lignin catalyzed by nickel supported on sodium lignin sulfonate-based porous carbon. This technique uses ZnCl2 and KOH as pore-forming agents and sodium lignin sulfonate as the carbon source to prepare a carbon support with a hierarchical porous structure. Then, nickel is loaded using a wet impregnation method, and the catalyst Ni / C is obtained after reduction under a hydrogen atmosphere. LS-ZnK The reaction at 230℃ and 2MPa H2 for 4 hours yielded a total monophenol yield of 22.03 wt.%, of which 4-propyleugenol yielded 7.4 wt.%. Although this technology uses transition metals as active sites, the catalyst preparation requires multiple steps, including precursor mixing, high-temperature calcination, washing, impregnation, and reduction, making the preparation process complex and affecting its industrial application.

[0008] Chinese invention patent application 202311873995.8 discloses a method for preparing monophenolic chemicals by catalytic depolymerization of lignin using zeolite-like imidazole ester framework material derivatives. This technology uses ZIF-67 as a catalyst precursor, which is pyrolyzed to obtain the catalyst Co@NC. In the lignin hydrogenolysis process catalyzed by Co@NC-800, under conditions of 100 mg lignin, 125 mg catalyst, 230 °C, and 1 MPa Ar, a maximum total monophenol yield of 16.1 wt.% and 7.4 wt.% of 4-propylbutanol can be obtained. However, due to the extensive decomposition of 2-methylimidazolium ligand during pyrolysis, the metal content in the catalyst increases significantly, with the cobalt content in the Co@NC-800 catalyst reaching 29.0 wt.%. Without dispersion measures, this increased metal content leads to metal agglomeration, reduces the exposed surface area of ​​active metals, lowers metal utilization, increases the implementation cost of the technology, and hinders its industrial application. Summary of the Invention

[0009] To address the challenges encountered in the current high-value utilization of lignin, such as the large molecular size of lignin, hindered mass transfer, complex and high-energy bonds, and complex and costly catalyst preparation, which impede the industrial application of the technology, this invention provides a carbon-nitrogen catalyst with a hierarchical porous structure and highly dispersed transition metal cobalt. This catalyst offers significant advantages in catalyst preparation process and cost, facilitating large-scale production. It enables highly selective catalytic hydrogenolysis of lignin under mild conditions to produce monophenolic chemicals, primarily 4-propylbutanol. The lignin feed conversion rate reaches 75.6–94.5%, the total yield of monophenolic products reaches 14.2–28.8 wt.%, and the yield of 4-propylbutanol alone reaches 4.1–9.9 wt.%.

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

[0011] A method for preparing 4-propyl eugenol by cobalt-nitrogen co-doped porous carbon catalyzing the hydrogenolysis of lignin involves using organosoluble lignin as raw material, lignin-based cobalt-nitrogen co-doped porous carbon as catalyst, and small molecule alcohol as reaction medium. The reaction is carried out under stirring at a hydrogen pressure of 1-2 MPa and a temperature of 190-260 °C, selectively hydrogenating organosoluble lignin into monophenolic chemicals, with 4-propyl eugenol as the main component.

[0012] The lignin-based cobalt-nitrogen co-doped porous carbon is obtained by mixing a precursor with an alkaline pore-forming agent, calcining in an inert atmosphere at 800–1000°C, followed by cooling, grinding, washing, and drying. The precursor is obtained by dissolving a carbon source and a nitrogen source in deionized water at 60–80°C with stirring; adding zinc salt, potassium salt, and cobalt salt dissolved in deionized water; stirring at 60–80°C; hydrothermally reacting at 160–200°C for 8–10 hours; and then cooling and drying. The carbon source is any one of sulfate lignin, alkali lignin, or sodium lignin sulfonate. The nitrogen source is any one of dicyandiamide and melamine.

[0013] To further achieve the purpose of this invention, preferably, the zinc salt is any one of zinc acetate, zinc chloride, and zinc nitrate;

[0014] The potassium salt mentioned is any one of potassium acetate, potassium chloride, and potassium nitrate;

[0015] The cobalt salt is either cobalt acetate or cobalt chloride.

[0016] Preferably, the mass ratio of carbon source to nitrogen source is 1:3 to 1:5; the mass ratio of carbon source to cobalt salt is 1:0.13 to 1:0.62; the mass ratio of carbon source to zinc salt is 1:0.33 to 1:0.66; and the mass ratio of carbon source to potassium salt is 1:0.15 to 1:0.30. The zinc salt, potassium salt, and cobalt salt dissolved in deionized water form a metal salt aqueous solution, wherein the total metal ion concentration in the water is 50 mmol / L. -1 ~300mmol L -1 .

[0017] Preferably, the stirring reaction time at 190–260°C is 2–10 h; the alkaline pore-forming agent is any one or more of KOH and NaOH; the mass ratio of the carbon source to the alkaline pore-forming agent is 1:0.25–1:0.75; and the stirring time at 60–80°C is 8–10 h.

[0018] Preferably, the cooling, grinding, washing, and drying processes involved in calcination at 800–1000°C in an inert atmosphere refer to cooling to room temperature; the grinding refers to grinding to a uniform powder without obvious particle texture; and the washing includes water washing and acid washing. Water washing refers to dispersing the ground product in deionized water, stirring for 2–4 hours, filtering, and then rinsing the solid with a large amount of water until the filtrate is neutral. Acid washing refers to dispersing the water-washed product in an aqueous inorganic acid solution, stirring for 2–4 hours, filtering to obtain a solid, and then washing the solid with deionized water until the filtrate is neutral. The acid used for acid washing is any one of sulfuric acid, nitric acid, and hydrochloric acid, with a concentration of 1–2 mol / L. -1The drying process involves drying the washed solids in an oven at 50–80°C for 8–12 hours until constant weight.

[0019] The cooling and drying process following the hydrothermal reaction at 160–200°C for 8–10 hours involves cooling to room temperature and completely removing water in a rotary evaporator at 40–60°C. After rotary evaporation, the resulting solid is dried in an oven at 50–80°C for 8–12 hours until constant weight. The oven is a forced-air drying oven.

[0020] Preferably, the inert atmosphere is any one of nitrogen, argon, and helium.

[0021] Preferably, the roasting is carried out in a vacuum tube furnace; the hydrothermal reactor used for the hydrothermal reaction is a lined stainless steel hydrothermal reactor, which is equipped with a stir bar and is stirred and heated in an oil bath.

[0022] Preferably, the organosoluble lignin is obtained by the following extraction method: mixing biomass powder with extract, reacting at 90-110℃ for 2-4 hours, cooling to room temperature; filtering to obtain organic filtrate, adding deionized water to precipitate solid, filtering and drying to obtain organosoluble lignin.

[0023] Preferably, the biomass is derived from any one of bagasse, wheat bran, corn cob, bamboo, birch, and poplar; the extract is a mixture of acid and organic solvent; the organic solvent is any one of dioxane and ethanol; the drying after filtration is carried out in a vacuum drying oven at a temperature of 40-60°C.

[0024] Preferably, the acid is 1-2 mol / L. -1 The biomass powder is prepared in either hydrochloric acid or sulfuric acid solution; the ratio of the mass of the biomass powder to the volume of the organic solvent in the extract is 1:3 to 1:5, with mass and volume units of g and mL, respectively; the ratio of the mass of the biomass powder to the volume of the acid solution is 1:0.8 to 1:1, with mass and volume units of g and mL, respectively.

[0025] Preferably, the monophenolic chemicals include: H unit (4-ethylphenol and ethyl dihydrocoumarate), G unit (4-ethylguaiacol, 4-propylguaiacol and ethyl dihydroferulate) and S unit (4-propyleugenol).

[0026] Compared with existing technologies, the present invention has the following advantages:

[0027] 1) Compared to existing single-atom catalyst preparation methods, such as impregnation, co-precipitation, and MOF precursor methods, the catalyst of this invention is prepared using a one-pot method. This method is simple, highly reproducible, and allows for large-scale production. Furthermore, the metal loading in this invention can be as low as 0.46 wt.%, and the highly exposed active sites not only improve the conversion rate of lignin but also enhance the selectivity of the product. The highest yield of the main product, 4-propylbutanol, can reach 9.9 wt.%, with a selectivity of 28.9–39.1%. Compared to most current lignin conversion technologies, this technology offers milder conditions; the highest product yield is achieved at a reaction temperature of 230°C and a hydrogen pressure of 1 MPa. The catalyst structure is stable, and its catalytic activity can be restored through simple steam regeneration after multiple uses.

[0028] The medium-strong acid on the catalyst surface of this invention forms a synergistic catalytic effect with the cobalt active center, promoting the cleavage of the abundant β-O-4 bonds in lignin via the carbon center free radical pathway. This synergistic effect lowers the activation energy of the reaction, improves the conversion rate of lignin and the selectivity of monophenol products. Compared with the dozens of lignin depolymerization products in the prior art, this reaction only produces six major monophenol products. Moreover, the products can be separated by simple column chromatography to obtain 8.3 wt.% 4-propylbutanol with a product purity >99%.

[0029] 2) Compared to existing molecular sieves and metal oxide catalysts, the CoNC catalyst used in this invention is inexpensive. Its carbon source is primarily derived from industrial papermaking waste, which is difficult to utilize at high value. The nitrogen source is either dicyandiamide or melamine, both widely used fertilizers and fine chemicals, produced in large quantities and with a price advantage. Cobalt, as the active site, is a transition metal element with greater abundance on Earth than precious metals, making industrialization easier, especially given its low content in the catalyst of this invention. The catalyst prepared using the precursor of this invention possesses a larger specific surface area and a hierarchical porous structure, which enhances mass transfer. Combined with uniformly dispersed active sites (single atoms and sub-nano clusters), it can maximize the effective contact between the substrate and the active sites.

[0030] 3) Compared to existing single-atom catalyst preparation methods, such as impregnation, co-precipitation, and MOF precursor methods, the catalyst of this invention is prepared using a one-pot method. This method is simple, highly reproducible, and allows for large-scale production. Furthermore, the metal loading in this invention can be as low as 0.46 wt.%, and the highly exposed active sites not only improve the conversion rate of lignin but also enhance the selectivity of the product. The highest yield of the main product, 4-propylbutanol, can reach 9.9 wt.%, with a selectivity of 28.9–39.1%. Compared to most current lignin conversion technologies, this technology offers milder conditions; the product yield reaches its maximum at a reaction temperature of 230°C and a hydrogen pressure of 1 MPa. The catalyst structure is stable, and its catalytic activity can be restored through simple steam regeneration after multiple uses.

[0031] 4) In this invention, nitrogen not only promotes the capture and fixation of metallic cobalt on the catalyst support, but also forms a CoN4 complex with cobalt. The electron transfer from nitrogen atoms to cobalt atoms can alter the electronic microenvironment on the surface of metallic cobalt, thus enhancing its catalytic effect on the hydrogenolysis of lignin. Theoretical calculations revealed that the CoN4 active sites formed by cobalt and nitrogen have the highest adsorption energy for the S units in lignin, which is one of the reasons for the high selectivity of the 4-propyleugenol product.

[0032] 5) The lignin used in this invention is derived from non-grain biomass such as agricultural waste. The monophenolic products mainly composed of 4-propylbutanol prepared by catalytic hydrogenolysis of lignin have high commercial value. At the same time, the main carbon source of the catalyst also comes from papermaking waste, so this technology follows the carbon cycle concept. Attached Figure Description

[0033] Figure 1 These are the N2 isothermal adsorption-desorption curves of the catalysts in Examples 1-4 of this invention.

[0034] Figure 2 This is a surface pore size distribution diagram of the catalyst in Examples 1-4 of the present invention.

[0035] Figure 3 This is a SEM image of the catalyst in Example 1 of the present invention.

[0036] Figure 4 This is an SEM image of the catalyst in Example 2 of the present invention.

[0037] Figure 5 This is a SEM image of the catalyst in Example 3 of the present invention.

[0038] Figure 6 This is a SEM image of the catalyst in Example 4 of the present invention.

[0039] Figure 7 These are the XRD patterns of the catalysts in Examples 1-4 of this invention.

[0040] Figure 8 The catalyst CoNC in Example 4 of this invention -M4 Aberration scanning transmission electron microscope image.

[0041] Figure 9 The catalyst CoNC in Example 4 of this invention -M4 Synchrotron radiation near-edge absorption curve.

[0042] Figure 10 The catalyst CoNC in Example 4 of this invention -M4 Synchrotron radiation Fourier transform X-ray absorption fine structure spectrum.

[0043] Figure 11 The catalyst CoNC in Example 4 of this invention -M4 Synchrotron radiation R-space fitting Fourier transform X-ray absorption fine structure spectrum.

[0044] Figure 12 The catalyst CoNC in Example 4 of this invention -M4 Adsorption energies of the surface-active site CoN4 for the basic structural units H, G, and S of lignin were calculated.

[0045] Figure 13 These are the six monophenol products produced by the catalytic hydrogenolysis of lignin in Example 5 of this invention.

[0046] Figure 14 This is the mass spectrum of 4-propylbutanol, the main product of lignin hydrogenolysis in Example 5 of the present invention. Detailed Implementation

[0047] 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.

[0048] This invention discloses a method for the hydrogenolysis of lignin to prepare 4-propyleugenol using cobalt-nitrogen co-doped porous carbon as a catalyst and small molecule alcohol as a reaction medium. The reaction is carried out under stirring at a hydrogen pressure of 1–2 MPa and a temperature of 190–260 °C, selectively hydrogenating the organic lignin to monophenolic chemicals, primarily 4-propyleugenol. The lignin-based cobalt-nitrogen co-doped porous carbon is prepared by mixing a precursor with an alkaline pore-forming agent and then reacting at 800–… The precursor is obtained by calcining in an inert atmosphere at 1000℃, followed by cooling, grinding, washing, and drying; the precursor is obtained by dissolving a carbon source and a nitrogen source in deionized water at 60-80℃ with stirring; adding zinc salt, potassium salt, and cobalt salt dissolved in deionized water, stirring at 60-80℃, hydrothermally reacting at 160-200℃ for 8-10 hours, and then cooling and drying; the carbon source is any one of sulfate lignin, alkali lignin, or sodium lignin sulfonate; the nitrogen source is any one of dicyandiamide and melamine.

[0049] The key feature of this invention is the use of sodium lignin sulfonate, sulfate lignin, or alkali lignin, waste materials from the paper industry, as a carbon source, and relatively low-cost dicyandiamide or melamine as a nitrogen source. A cobalt-nitrogen co-doped carbon-nitrogen catalyst with hierarchical pores is prepared in a one-pot process. This catalyst preparation eliminates the need for carrier preparation-impregnation-reduction and the preparation of MOFS materials followed by calcination, offering significant advantages in catalyst preparation technology. The mesoporous structure of the prepared catalyst is more conducive to the adsorption of lignin substrates, enhancing mass transfer and increasing substrate conversion. Furthermore, the highly dispersed cobalt exists in the form of single atoms and sub-nano clusters, and the uniformly dispersed active sites greatly improve product selectivity, selectively breaking ether and ester bonds in lignin and improving the selectivity of monophenolic products. The catalyst has a cobalt metal content of 0.46–10.88 wt.%, a low metal content, resulting in a significant cost advantage.

[0050] Example 1: Lignin-based cobalt-nitrogen co-doped porous carbon catalyst CoNC -M1 Preparation

[0051] (1) Weigh out 0.75 g of cobalt acetate (3 mmol), 0.58 g of potassium acetate (5 mmol), and 1.10 g of zinc acetate (5 mmol), and dissolve them in 20 mL of deionized water. Name the mixed solution Solution A. Separately, weigh out 2 g of sodium lignosulfonate and 8 g of dicyandiamide, and dissolve them in 30 mL of deionized water. Name this solution Solution B. After sonicating Solution A at room temperature for 40 min, slowly add it dropwise to Solution B. Stir the mixed solutions AB at 80 °C for 8 h.

[0052] (2) The solvent in the mixed solution AB was removed by rotary evaporation at 60°C to obtain a solid catalyst precursor. The solid was dried to constant weight in an 80°C forced-air drying oven. After drying, it was transferred to a 50mL quartz boat and placed in a vacuum tube furnace and heated to 900°C for 2h at a heating rate of 2°C / min.

[0053] (3) After calcination, once the tube furnace has cooled to room temperature, remove the black solid and wash it with 3 × 100 mL of deionized water. Then disperse the black solid in 30 mL of 1 mol L⁻¹ water. -1 The black solid was stirred in an aqueous sulfuric acid solution at room temperature for 2 hours. After stirring, the solution was filtered, and the filtrate was washed with deionized water until neutral. After drying at 80°C for 10 hours, the lignin-based cobalt-nitrogen co-doped porous carbon catalyst CoNC was obtained. -M1 .

[0054] The Co content in the catalyst was determined to be 1.03 wt.% by ICP-AES. The prepared catalyst, CoNC... -M1 Perform N2 physical adsorption-desorption tests, such as Figure 1 As shown, CoNC -M1 The N2 adsorption-desorption curve of the catalyst conforms to a type IV curve, indicating that CoNC -M1 Mesoporous structures exist within it, according to Figure 2 It can be seen that CoNC -M1 The pore distribution of the catalyst remains concentrated in the micropore region (<2nm). Based on the pore volume calculations, CoNC... -M1 Its mesoporous ratio is only 51.9%. From Figure 3 The same phenomenon can also be observed in CoNC. -M1 The catalyst surface is smooth with no obvious porous structure. Furthermore, there are no significant voids between the catalyst layers. This corresponds to its relatively low specific surface area and a small amount of mesoporous structure. XRD characterization of the catalyst revealed, as... Figure 7 As shown, CoNC -M1 The catalyst did not exhibit a distinct metal peak. Based on the metal content, it can be inferred that Co plays a significant role in the CoNC catalyst. -M1 The surface is evenly dispersed without agglomeration.

[0055] Example 2: Catalyst CoNC -M2 Preparation

[0056] (1) Weigh out 0.75 g of cobalt acetate (3 mmol), 0.58 g of potassium acetate (5 mmol), and 1.10 g of zinc acetate (5 mmol), and dissolve them in 20 mL of deionized water. Name the mixed solution Solution A. Separately, weigh out 2 g of sodium lignosulfonate and 8 g of dicyandiamide, and dissolve them in 30 mL of deionized water. Name this solution Solution B. After sonicating Solution A at room temperature for 40 min, slowly add it dropwise to Solution B. Stir the mixed solutions AB at 80 °C for 8 h. After stirring, transfer the mixture to a 100 mL hydrothermal reactor and hydrothermally treat it at 200 °C for 10 h.

[0057] (2) The solvent in the mixed solution AB was removed by rotary evaporation at 60°C. The catalyst precursor solid was obtained and dried to constant weight in an 80°C forced-air drying oven. After drying, it was transferred to a 50mL quartz boat and placed in a vacuum tube furnace and heated to 900°C for 2h at a heating rate of 2°C / min.

[0058] (3) After calcination, once the tube furnace has cooled to room temperature, remove the black solid and wash it with 3 × 100 mL of deionized water. Then disperse the black solid in 30 mL of 1 mol L⁻¹ water. -1 The black solid was stirred in an aqueous sulfuric acid solution at room temperature for 2 hours. After stirring, the solution was filtered, and the filtrate was washed with deionized water until neutral. The solution was then dried at 80°C for 10 hours to obtain the catalyst CoNC. -M2 .

[0059] The Co content in the catalyst was determined to be 1.80 wt.% by ICP-AES. The prepared catalyst, CoNC... -M1 Perform N2 physical adsorption-desorption tests, such as Figure 1 As shown, CoNC -M2 The N2 adsorption-desorption curve of the catalyst conforms to a type IV curve, indicating that CoNC -M1 Mesoporous structures exist within it, according to Figure 2 It can be seen that CoNC -M2 The catalyst's pore size distribution has begun to exhibit a mesoporous structure (2nm < mesopore < 50nm). Based on pore volume calculations, CoNC... -M2 The mesoporous content reached 77.5%. From Figure 4 A small number of porous structures were observed on the catalyst surface, and graphitization was observed at the catalyst edges. XRD characterization of the catalyst revealed, for example... Figure 7 As shown, CoNC -M2 The catalyst did not exhibit a distinct metal peak, suggesting that Co plays a role in the CoNC catalyst. -M2 The surface is uniformly dispersed without agglomeration. Meanwhile, CoNC... -M2 A distinct peak appeared at 26.2° in the XRD pattern, which represents the (002) surface of graphite.

[0060] Example 3: Catalyst CoNC -M3 Preparation

[0061] (1) Weigh out 0.75 g of cobalt acetate (3 mmol), 0.58 g of potassium acetate (5 mmol), and 1.10 g of zinc acetate (5 mmol) respectively, and dissolve them in 20 mL of deionized water. The mixed solution is named solution A. Separately, weigh out 2 g of sodium lignosulfonate, 8 g of dicyandiamide, and 1 g of KOH, and dissolve them together in 30 mL of deionized water. This solution is named solution B. Solution A is sonicated at room temperature for 40 min and then slowly added dropwise to solution B. The mixed solutions AB are stirred at 80 °C for 8 h. After stirring, the mixture is transferred to a 100 mL hydrothermal reactor and hydrothermally treated at 200 °C for 10 h.

[0062] (2) The solvent in the mixed solution AB was removed by rotary evaporation at 60°C. The catalyst precursor solid was obtained and dried to constant weight in an 80°C forced-air drying oven. After drying, it was transferred to a 50mL quartz boat and placed in a vacuum tube furnace and heated to 900°C for 2h at a heating rate of 2°C / min.

[0063] (3) After calcination, once the tube furnace has cooled to room temperature, remove the black solid and wash it with 3 × 100 mL of deionized water. Then disperse the black solid in 30 mL of 1 mol L⁻¹ water. -1 The black solid was stirred in an aqueous sulfuric acid solution at room temperature for 2 hours. After stirring, the solution was filtered, and the filtrate was washed with deionized water until neutral. The solution was then dried at 80°C for 10 hours to obtain the catalyst CoNC. -M3 .

[0064] The Co content in the catalyst was determined to be 10.88 wt.% by ICP-AES. The prepared catalyst, CoNC... -M1 Perform N2 physical adsorption-desorption tests, such as Figure 1 As shown, CoNC -M3 The N2 adsorption-desorption curve of the catalyst conforms to a type IV curve, indicating that CoNC -M3 Mesoporous structures exist within it, according to Figure 2 It can be seen that CoNC -M3 The catalyst exhibits a distinct mesoporous structure (2nm < mesopore < 50nm). Based on pore volume calculations, CoNC... -M3 The mesoporous content reached 78.8%. From Figure 5 Numerous irregular pore structures were observed on the catalyst surface, along with a distinct layered structure, indicating graphitization. SEM also revealed CoNC... -M3 The surface was covered with a large number of regular cubic shapes. XRD characterization of the catalyst revealed, for example... Figure 7As shown, CoNC -M3 The catalyst exhibits distinct peaks, corresponding to the (002) facet of graphite and the (200), (220), and (400) faces of Co3[Co(CN)6]2, respectively. Co3[Co(CN)6]2 is commonly used as a dye and adsorbent, but it does not catalyze hydrogenolysis reactions, therefore it is presumed to be a non-active site.

[0065] Example 4: Catalyst CoNC -M4 Preparation

[0066] (1) Weigh out 0.75 g of cobalt acetate (3 mmol), 0.58 g of potassium acetate (5 mmol), and 1.10 g of zinc acetate (5 mmol), and dissolve them in 20 mL of deionized water. Name the mixed solution Solution A. Separately, weigh out 2 g of sodium lignosulfonate and 8 g of dicyandiamide, and dissolve them in 30 mL of deionized water. Name this solution Solution B. After sonicating Solution A at room temperature for 40 min, slowly add it dropwise to Solution B. Stir the mixed solutions AB at 80 °C for 8 h. After stirring, transfer the mixture to a 100 mL hydrothermal reactor and hydrothermally treat it at 200 °C for 10 h.

[0067] (2) The solvent in the mixed solution AB was removed by rotary evaporation at 60°C. The catalyst precursor solid was obtained and dried to constant weight in an 80°C forced-air drying oven. After drying, it was ground together with 1g KOH until homogeneous. The solid mixture was transferred to a 50mL quartz boat and placed in a vacuum tube furnace and heated to 900°C for 2h at a heating rate of 2°C / min.

[0068] (3) After calcination, once the tube furnace has cooled to room temperature, remove the black solid and wash it with 3 × 100 mL of deionized water. Then disperse the black solid in 30 mL of 1 mol L⁻¹ water. -1 The black solid was stirred in an aqueous sulfuric acid solution at room temperature for 2 hours. After stirring, the solution was filtered, and the filtrate was washed with deionized water until neutral. The solution was then dried at 80°C for 10 hours to obtain the catalyst CoNC. -M4 .

[0069] The Co content in the catalyst was determined to be 0.46 wt.% by ICP-AES. The prepared catalyst, CoNC... -M4 Perform N2 physical adsorption-desorption tests, such as Figure 1 As shown, CoNC -M4 The N2 adsorption-desorption curve of the catalyst conforms to a type IV curve, indicating that CoNC -M4 Mesoporous structures exist within it. According to... Figure 2 It can be seen that CoNC -M4 The catalyst exhibits a distinct mesoporous structure (2nm < mesopore < 50nm). Based on pore volume calculations, CoNC... -M4Its mesopority is as high as 92.9%. From Figure 6 Numerous irregular pore structures were observed on the catalyst surface, along with a distinct layered structure, indicating significant graphitization. XRD characterization of the catalyst revealed, for example... Figure 7 As shown, CoNC -M4 The catalyst exhibits a relatively distinct graphite peak, corresponding to the (002) plane of graphite. From... Figure 8 Aberration-corrected scanning transmission electron microscopy revealed that most cobalt metal existed as single atoms (atomic diameter < 0.1 nm) on the catalyst surface, while a small portion existed as sub-nano clusters (cluster diameter < 1 nm). This demonstrates that the cobalt metal is highly dispersed on the catalyst surface, hence CoNC is not visible in XRD. -M4 The metallic peak crystalline phase, along with the highly dispersed cobalt at the active center, promotes the catalyst's high selectivity for catalytic ether bond cleavage. Through... Figure 9 It can be seen that CoNC -M4 The valence state of Co is close to +2, and there is a significant peak at 7714 eV, which represents the 1s→4p electronic transition. This phenomenon indicates that a CoN4 planar structure has appeared in the catalyst. Figure 10 It is possible to observe more intuitively the catalyst CoNC -M4 The R space mainly appeared (Co-N) and a small amount The (Co-Co) peak indicates that the main coordinating element of Co in this catalyst is N. For example... Figure 11 As shown, further fitting of the R space revealed that Co and N exist in the form of CoN4, which is consistent with... Figure 9 The conclusions are consistent, and this also verifies that... Figure 8 Aberration-corrected electron microscopy revealed that Co in the catalyst primarily exists in monatomic form. Further, using CoN4 as the catalytic active center, theoretical calculations of the chemisorption energies were performed based on H, G, and S-type model compounds. Figure 12 As shown, the S-type model compound exhibits the strongest adsorption energy at the CoN4 site, which is one of the main reasons for the highest selectivity of S-unit products among lignin-derived monophenol products.

[0070] Example 5: CoNC -M4 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

[0071] (1) Extraction of lignin: Sugarcane bagasse was dried in a 60℃ forced-air drying oven for 12 hours. The dried sugarcane bagasse was then pulverized and passed through a 60-mesh sieve. 10g of the sieved sugarcane bagasse powder, 10mL of concentrated hydrochloric acid, and 120mL of 1,4-dioxane were weighed and added sequentially to a pressure-resistant bottle. The mixture was stirred and reacted at 100℃ for 4 hours. After the reaction was completed, the mixture was immediately cooled to room temperature. The residue was removed by filtration, and the filter cake was washed with dioxane. The filtrates were combined, and deionized water was added to precipitate the solid. After filtration and drying, organic-soluble sugarcane bagasse lignin was obtained.

[0072] (2) Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved sugarcane bagasse lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was added with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0073] GCMS was performed using an FBX-5MS column (30m × 0.25μm × 0.25mm). The instrument was run at 50℃ for 1 min, then increased to 250℃ at a rate of 10℃ / min and held for another 10 min. Figure 13 As shown, GCMS analysis revealed only six major products: 4-ethylphenol, ethyl dihydro-p-coumarate, 4-ethylguaiacol, 4-propylguaiacol, ethyl dihydroferulate, and 4-propyleugenol. The mass spectrum of the major product, 4-propyleugenol, is shown below. Figure 14 As shown, this indicates that the main product is indeed 4-propylbutyrrol. An NMR spectrum can also be added to further confirm the structure of this substance.

[0074] Table 1 Summary of Monophenol Products from Lignin Hydrogenation

[0075]

[0076]

[0077] The formulas for calculating lignin conversion rate and monophenol product yield are shown below, where the lignin conversion rate is calculated based on the mass comparison of regenerated lignin and initial lignin (Equation 1). The monophenol yield is determined based on the mass of the monophenol product and the initial lignin mass (Equation 2). The selectivity of the monophenol product is determined by the weight percentage of the mass of a single product in the total monophenols (Equation 3).

[0078]

[0079] Where m o m Re m p Yield p and Yield Total These represent the initial lignin mass, the regenerated lignin mass, the yield of a single product, and the total product yield, respectively. The total yield of the monophenol products was calculated to be 28.8 wt.%, with the highest yield of 4-propylbutanol from the S unit (9.9 wt.) and a selectivity of 34.4%. Simple column chromatography separation yielded 8.3 wt% 4-propylbutanol with a purity exceeding 99%. (CoNC) -M4 Under catalysis, the lignin conversion rate can reach 94.5%.

[0080] Example 6: CoNC -M1 Catalytic hydrogenolysis of bagasse lignin

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

[0082] Weigh out 0.1g of organically soluble sugarcane bagasse lignin and 0.1g of CoNC, respectively. -M1 The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0083] Calculations showed that the lignin conversion rate was 75.6%, and the monophenol product yield was 14.2 wt.%. The yield of 4-propyleugenol was 4.1 wt.%, with a selectivity of 28.9%.

[0084] Example 7: CoNC -M2 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

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

[0086] Weigh out 0.1g of organically soluble sugarcane bagasse lignin and 0.1g of CoNC, respectively. -M2 The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0087] Calculations showed that the lignin conversion rate was 82.4%, and the monophenol product yield was 19.2 wt.%. The yield of 4-propyleugenol was 7.5 wt.%, with a selectivity of 39.1%.

[0088] Example 8: CoNC -M3 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

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

[0090] Weigh out 0.1g of organically soluble sugarcane bagasse lignin and 0.1g of CoNC, respectively. -M3The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0091] Calculations showed that the lignin conversion rate was 94.4%, and the monophenol product yield was 21.2 wt.%. The yield of 4-propyleugenol was 7.9 wt.%, with a selectivity of 37.3%.

[0092] Example 9: CoNC -M4 Catalytic hydrogenolysis of organosoluble birch lignin

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

[0094] (1) Extraction of lignin: Weigh 10g of birch powder, 10mL of concentrated hydrochloric acid and 120mL of 1,4-dioxane and add them sequentially to a pressure-resistant bottle. Stir the mixture at 100℃ for 4h. After the reaction is complete, immediately cool to room temperature. Filter to remove residue, and wash the filter cake with dioxane. Combine the filtrates, add deionized water to precipitate the solid, filter and dry to obtain organosoluble birch lignin.

[0095] (2) Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organosoluble birch lignin and 0.1g of CoNC, respectively. -M4The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0096] The yield of the monophenol product was calculated to be 19.6 wt.%, of which 4-propyleugenol yielded 8.0 wt., with a selectivity of 40.8%.

[0097] Example 10: CoNC -M4 Catalytic hydrogenolysis of organic-soluble poplar lignin

[0098] The difference between this implementation case and implementation case 5 is that:

[0099] (1) Extraction of lignin: Weigh 10g of poplar powder, 10mL of concentrated hydrochloric acid and 120mL of 1,4-dioxane and add them sequentially to a pressure-resistant bottle. Stir the mixture at 100℃ for 4h. After the reaction is complete, immediately cool to room temperature. Filter to remove residue, and wash the filter cake with dioxane. Combine the filtrates, add deionized water to precipitate the solid, filter and dry to obtain organosoluble poplar lignin.

[0100] (2) Catalytic hydrogenolysis of lignin: Weigh out 0.1 g of organically dissolved poplar lignin and 0.1 g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0101] The yield of the monophenol product was calculated to be 17.3 wt.%, of which 4-propyleugenol yielded 7.4 wt.%, with a selectivity of 42.8%.

[0102] Example 11: CoNC -M4 Catalytic hydrogenolysis of organosoluble wheat bran lignin

[0103] The difference between this implementation case and implementation case 5 is that:

[0104] (1) Extraction of lignin: Weigh 10g of wheat bran powder, 10mL of concentrated hydrochloric acid and 120mL of 1,4-dioxane and add them to a pressure-resistant bottle in sequence. Stir the mixture at 100℃ for 4h. After the reaction is complete, immediately cool to room temperature. Filter to remove the residue and wash the filter cake with dioxane. Combine the filtrates, add deionized water to precipitate the solid, filter and dry to obtain organosoluble wheat bran lignin.

[0105] (2) Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organosoluble wheat bran lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, and 10 mL of EtOH was added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction was completed, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0106] The yield of the monophenol product was calculated to be 11.6 wt.%, of which 4-propyleugenol yielded 3.4 wt.%, with a selectivity of 29.3%.

[0107] Example 12: CoNC -M4 Catalytic hydrogenolysis of organosoluble bamboo lignin

[0108] The difference between this implementation case and implementation case 5 is that:

[0109] (1) Extraction of lignin: Weigh 10g of bamboo powder, 10mL of concentrated hydrochloric acid and 120mL of 1,4-dioxane and add them to a pressure-resistant bottle in sequence. Stir the mixture at 100℃ for 4h. After the reaction is complete, immediately cool to room temperature. Filter to remove residue, and wash the filter cake with dioxane. Combine the filtrates, add deionized water to precipitate the solid, filter and dry to obtain organosoluble bamboo lignin.

[0110] (2) Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organosoluble bamboo lignin and 0.1g of CoNC respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was added with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0111] The yield of the monophenol product was calculated to be 19.0 wt.%, of which 4-propyleugenol yielded 7.2 wt.%, with a selectivity of 37.9%.

[0112] Example 13: CoNC -M4 Catalytic hydrogenolysis of organic-soluble corn cob lignin

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

[0114] (1) Extraction of lignin: Weigh 10g of corn cob powder, 10mL of concentrated hydrochloric acid and 120mL of 1,4-dioxane and add them sequentially to a pressure-resistant bottle. Stir the mixture at 100℃ for 4h. After the reaction is complete, immediately cool to room temperature. Filter to remove residue, and wash the filter cake with dioxane. Combine the filtrates, add deionized water to precipitate the solid, filter and dry to obtain organosoluble corn cob lignin.

[0115] (2) Catalyst-catalyzed hydrogenolysis of lignin: Weigh out 0.1 g of organically dissolved corn cob lignin and 0.1 g of CoNC, respectively. -M4The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was added with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0116] The yield of the monophenol product was calculated to be 21.7 wt.%, of which 4-propyleugenol yielded 4.8 wt.%, with a selectivity of 22.1%.

[0117] Example 14: CoNC at 190℃ -M4 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

[0118] The difference between this implementation case and implementation case 5 is that:

[0119] Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved corn cob lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 190 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0120] The yield of the monophenol product was calculated to be 12.7 wt.%, of which 4-propyleugenol yielded 4.2 wt.%, with a selectivity of 33.3%.

[0121] Example 15: CoNC at 260℃ -M4 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

[0122] The difference between this implementation case and implementation case 5 is that:

[0123] Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved corn cob lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 260 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0124] The yield of the monophenol product was calculated to be 23.8 wt.%, of which 4-propyleugenol yielded 5.9 wt.%, with a selectivity of 24.7%.

[0125] Example 16: CoNC -M4 Catalytic reaction of organic-soluble sugarcane bagasse lignin for 2 hours

[0126] The difference between this implementation case and implementation case 5 is that:

[0127] Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved corn cob lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 2 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0128] The yield of the monophenol product was calculated to be 17.5 wt.%, of which 4-propyleugenol yielded 7.0 wt., with a selectivity of 40.2%.

[0129] Example 17: CoNC -M4 Catalytic organic soluble sugarcane bagasse lignin reaction for 10 hours

[0130] The difference between this implementation case and implementation case 5 is that:

[0131] Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved corn cob lignin and 0.1g of CoNC, respectively. -M4 The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 1 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 10 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0132] The yield of the monophenol product was calculated to be 26.1 wt.%, of which 4-propyleugenol yielded 7.2 wt.%, with a selectivity of 27.8%.

[0133] Example 18: CoNC under 2MPa hydrogen pressure -M4 Catalytic hydrogenolysis of organic soluble sugarcane bagasse lignin

[0134] The difference between this implementation case and implementation case 5 is that:

[0135] Catalytic hydrogenolysis of lignin: Weigh out 0.1g of organically dissolved corn cob lignin and 0.1g of CoNC, respectively. -M4The catalyst was placed in a 50 mL batch reactor, with 10 mL of EtOH added as the reaction solvent. The atmosphere inside the reactor was replaced with H2 (4 times), and the final H2 pressure was maintained at 2 MPa as before the reaction. After the reactor was closed, the temperature was increased to 230 °C at a rate of 10 °C / min and maintained for 4 h. After the reaction, the reactor was immediately cooled to room temperature, and the catalyst and reaction solution were separated by filtration. The catalyst was washed with EtOH (3 mL × 3), and the organic phases were combined. A quantitative amount of internal standard solution (dimethyl phthalate) was added to the organic phase, and after thorough mixing, 1 mL of the organic phase solution was taken for further purification. The product was then qualitatively and quantitatively analyzed by GC-MS. The remaining organic phase was mixed with 5 times its volume of deionized water to precipitate a solid. After filtration and drying, regenerated lignin was obtained. The lignin conversion rate could be calculated by comparing the mass of the reactant lignin with the mass of the regenerated lignin.

[0136] The yield of the monophenol product was calculated to be 22.2 wt.%, of which 4-propyleugenol yielded 8.0 wt.%, with a selectivity of 36.0%.

[0137] Example 19: Catalyst Stability

[0138] The catalyst used in Example 5 was collected and washed with THF (30 mL × 3). After washing, it was dried to constant weight in a 60°C forced-air drying oven, and repeated tests were performed as in Example 5. After four reuses, the catalyst still maintained high activity, with a total monophenol yield of 15.7 wt.% and a yield of 4.3 wt.% for the main product 4-propylbutanol, with a selectivity of 27.4%. After washing the catalyst with only organic solvents, the catalyst activity decreased slightly during reuse. ICP-AES analysis showed that the cobalt metal content decreased from 0.46 wt.% in the fresh catalyst to 0.35 wt.%, while the carbon content increased slightly from 70.76 wt.% to 73.30 wt.%. After simple steam regeneration, the catalyst activity was basically restored, with a total monophenol yield of 24.3 wt.% and a 4-propylbutanol yield of 9.9 wt.%. X-ray photoelectron spectroscopy, N2 physical adsorption-desorption, and scanning electron microscopy revealed that lignin residues and oligomers adsorbed on the surface of the reused catalyst covered the active Co sites, making it difficult for them to contact the reaction substrate. The regenerated catalyst, with its fully exposed active sites, facilitated a near-complete recovery of its activity.

[0139] As can be seen from the above embodiments, the present invention provides a lignin-based cobalt-nitrogen co-doped porous carbon catalyst for the hydrogenolysis of lignin, selectively preparing monophenolic chemicals, primarily 4-propyleugenol. The lignin conversion rate is 75.6%–94.5%, the total monophenol yield is 14.2–28.8 wt.%, the yield of the main product 4-propyleugenol is 4.1–9.9 wt.%, and its selectivity is 28.9–39.1%. In particular, the catalyst prepared by the present invention does not require the precious metal Ru, uses lower raw material costs, can be prepared by a one-pot method, has a simple preparation process, stable catalyst structure, high reproducibility, significantly improved metal utilization, and does not require the use of high-pressure hydrogen. The catalyst has a hierarchical porous structure, with a mesoporous ratio of 51.9–92.9%, which is more conducive to the adsorption of the substrate by the catalyst and enhances the mass transfer effect. The catalytic active center Co mainly exists in single-atom form on the catalyst surface; the highly dispersed active centers further increase the probability of catalyst contact with the substrate, promote the catalytic effect, and improve the product selectivity.

[0140] Compared to Chinese invention patent 202311762765.4, which uses the noble metal Ru as the active center and requires 12 hours of catalytic conversion at 250°C under a 2MPa atmosphere to obtain 23.9 wt.% of the monobenzene ring product, this invention uses the transition metal cobalt as the active center. Cobalt is more abundant than Ru, and the main carbon and nitrogen sources for the catalyst are inexpensive and widely available, resulting in a lower overall catalyst cost and facilitating industrialization. Although cobalt constitutes only a minimum of 0.46 wt.% of the catalyst, it catalyzes the depolymerization of lignin to achieve a total monophenol yield of 28.8 wt.%, with the main product, 4-propylbutanol, yielding as high as 9.9 wt.%. Furthermore, the reaction conditions are milder, solving the problems of high catalyst cost and harsh reaction conditions in existing technologies.

[0141] Compared to Chinese Invention Patent 202111370517.6, although both are lignin-based porous carbon catalysts, the catalyst preparation process is much simpler. Specifically, Chinese Invention Patent 202111370517.6 requires a process of calcining the support, impregnation, and then reduction, making it difficult to precisely control the metal dispersion and catalyst morphology. In contrast, this invention uses a one-pot method to prepare the catalyst, resulting in a stable catalyst structure, high reproducibility, and greater suitability for industrial production. Furthermore, this technology results in lower metal content, significantly improved metal utilization, and a significantly reduced catalyst preparation cost. In Chinese Invention Patent 202111370517.6, catalytic conditions require 230℃ and 2MPa H2 for 4 hours to achieve a total monophenol yield of only 22.03 wt.%, with 4-propylbutanol yielding only 7.4 wt.%. In contrast, the present invention can obtain a total monophenol yield of 28.8 wt.% under only 1 MPa H2 conditions, of which the yield of 4-propyleugenol reaches 9.9 wt.%, while the product selectivity is high, and 8.3 wt.% of pure 4-propyleugenol can be obtained by simple column chromatography separation.

[0142] Compared to Chinese Invention Patent 202311873995.8, the metal in the catalyst of this invention is uniformly dispersed on the catalyst surface at the single-atom level, resulting in a larger exposed metal surface and a richer pore structure. This effectively improves the contact between the catalytic active center and the substrate lignin, thereby enhancing its hydrogenolysis efficiency of lignin and its selectivity for 4-propylbutanol monomer. The metal content of the catalyst in this invention is 0.46–10.88 wt.%, which is significantly lower than the 29.0 wt.% of Chinese Invention Patent 202311873995.8.

[0143] In summary, as can be seen from the above embodiments, the present invention employs a one-pot method, eliminating the need for carrier preparation, impregnation, and reduction processes, as well as the preparation of MOFS materials followed by calcination, thus offering significant advantages in catalyst preparation technology. Furthermore, the catalyst of the present invention uses transition metals as catalytic sites, with the metals uniformly dispersed on the catalyst surface at a single-atom level. This results in a rich pore structure, numerous exposed metal surfaces on the gold catalyst surface, high metal catalytic efficiency, and a very low metal content—as low as 0.46 wt.% and at most 10.88 wt.%—leading to a significant cost advantage. These two advantages make the present invention highly industrializable while ensuring good conversion efficiency in the preparation of 4-propylbutanol from lignin.

[0144] 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 for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon-catalyzed hydrogenolysis of lignin, characterized in that, Using organosoluble lignin as raw material, lignin-based cobalt-nitrogen co-doped porous carbon as catalyst, and small molecule alcohol as reaction medium, the organosoluble lignin is selectively hydrogenated to monophenolic chemicals, mainly 4-propyleugenol, under stirring at a hydrogen pressure of 1-2 MPa and a temperature of 190-260°C. The small molecule alcohol medium is any one of ethanol, methanol, and isopropanol; the monophenolic chemicals are 4-ethylphenol, ethyl dihydro-p-coumarate, 4-ethylguaiacol, 4-propylguaiacol, ethyl dihydroferulate, and 4-propyleugenol. The lignin-based cobalt-nitrogen co-doped porous carbon is obtained by mixing a precursor with an alkaline pore-forming agent, calcining in an inert atmosphere at 800-1000℃, followed by cooling, grinding, washing, and drying. The precursor is obtained by dissolving a carbon source and a nitrogen source in deionized water at 60-80℃ with stirring; adding zinc salt, potassium salt, and cobalt salt dissolved in deionized water, stirring at 60-80℃, and then hydrothermally reacting at 160-200℃ for 8-10 hours, followed by cooling and drying. The carbon source is sodium lignin sulfonate; the nitrogen source is dicyandiamide; the mass ratio of carbon source to cobalt salt is 1:0.13-1:0.62; the mass ratio of carbon source to zinc salt is 1:0.33-1:0.66; and the alkaline pore-forming agent is any one or more of KOH and NaOH.

2. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The zinc salt mentioned is any one of zinc acetate, zinc chloride, and zinc nitrate; The potassium salt mentioned is any one of potassium acetate, potassium chloride, and potassium nitrate; The cobalt salt is either cobalt acetate or cobalt chloride.

3. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The mass ratio of carbon source to nitrogen source is 1:3 to 1:5; the mass ratio of carbon source to potassium salt is 1:0.15 to 1:0.30; the zinc salt, potassium salt, and cobalt salt dissolved in deionized water form a metal salt aqueous solution, wherein the total metal ion concentration in the water is 50 mmol / L. -1 ~300 mmol L -1 .

4. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The stirring reaction time at 190~260℃ is 2~10h; the mass ratio of carbon source to alkaline pore-forming agent is 1:0.25~1:0.75; and the stirring time at 60~80℃ is 8~10h.

5. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The cooling, grinding, washing, and drying processes described in the calcination at 800-1000℃ in an inert atmosphere refer to cooling to room temperature; the grinding refers to grinding to a uniform powder with no obvious particle texture; and the washing includes water washing and acid washing. Water washing involves dispersing the ground product in deionized water, stirring for 2-4 hours, filtering, and then rinsing the solid with plenty of water until the filtrate is neutral. Acid washing involves dispersing the water-washed product in an aqueous inorganic acid solution, stirring for 2-4 hours, filtering to obtain a solid, and then washing the solid with deionized water until the filtrate is neutral. The acid used for acid washing is any one of sulfuric acid, nitric acid, and hydrochloric acid, with a concentration of 1-2 mol / L. -1 The drying involved is drying the washed solids in an oven at 50-80℃ for 8-12 hours until the sample reaches constant weight; The cooling and drying process following the hydrothermal reaction at 160-200℃ for 8-10 hours involves cooling to room temperature and completely removing water in a rotary evaporator at 40-60℃. After rotary evaporation, the resulting solid is dried in an oven at 50-80℃ for 8-12 hours until constant weight. The oven is a forced-air drying oven.

6. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The inert atmosphere is any one of nitrogen, argon, and helium.

7. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The roasting is carried out in a vacuum tube furnace; the hydrothermal reactor used for the hydrothermal reaction is a lined stainless steel hydrothermal reactor with a stir bar inside, which is stirred and heated in an oil bath.

8. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 1, characterized in that, The organosoluble lignin is obtained by the following extraction method: biomass powder is mixed with the extract and reacted at 90-110℃ for 2-4 hours, then cooled to room temperature; the organic filtrate is obtained by filtration, deionized water is added to precipitate the solid, and the solid is dried after filtration to obtain organosoluble lignin.

9. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 8, characterized in that, The biomass is derived from any one of bagasse, bamboo, birch, and poplar; the extract is a mixture of acid and organic solvent; the organic solvent is any one of dioxane and ethanol; the drying after filtration is carried out in a vacuum drying oven at a temperature of 40-60℃.

10. The method for preparing 4-propylbutanol by cobalt-nitrogen co-doped porous carbon catalytic hydrogenolysis of lignin according to claim 9, characterized in that, The acid is 1~2 mol L. -1 The biomass powder is prepared in either hydrochloric acid or sulfuric acid solution; the ratio of the mass of the biomass powder to the volume of the organic solvent in the extract is 1:3 to 1:5, with mass and volume units of g and mL, respectively; the ratio of the mass of the biomass powder to the volume of the acid solution is 1:0.8 to 1:1, with mass and volume units of g and mL, respectively.

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