A method for the selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys to prepare guaiacol monomer products.

Abstract

This invention discloses a method for the selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloy catalysts to prepare guaiacol monomers. The method employs a urea precipitation method to prepare a catalyst containing both metallic nickel and a nickel-tin alloy active phase. Organosoluble lignin is used as the raw material, and a mixture of alcohols and water is added as the solvent. The alumina-supported nickel and nickel-tin alloy catalyst prepared by the urea precipitation method is then added. The air in the reactor is replaced with an inert gas, and the pressure is increased to 1.0–3.0 MPa. The reactor is then stirred at 210–270°C for 1–6 hours, resulting in the highly selective conversion of organosoluble lignin into compounds primarily composed of guaiacol monomers. This invention features a simple catalyst preparation process, low cost, and a mild and safe lignin depolymerization reaction. The obtained guaiacol products can be used to prepare food additives or pharmaceutical intermediates and other chemicals.

Description

Technical Field

[0001] This invention relates to the depolymerization of agricultural and forestry waste, and in particular to a method for selective hydrogenolysis of lignin catalyzed by alumina-supported nickel metal and nickel-tin alloy to prepare monophenolic compounds, which belongs to the field of high-value utilization of renewable biomass. Background Technology

[0002] Lignin, an important component of biomass, contains numerous aromatic ring structures and is the only naturally occurring renewable aromatic polymer containing benzene rings. Furthermore, lignin also contains various functional groups such as hydroxyl and aldehyde groups. Research indicates that lignin can be depolymerized through various chemical methods to obtain high-value-added platform chemicals, thereby facilitating the efficient utilization of all components of biomass. Pyrolysis, hydrolysis, oxidative depolymerization, and hydrodepolymerization are widely used in the catalytic conversion of lignin. Thermochemical depolymerization of lignin typically requires high reaction temperatures, resulting in high energy consumption. Hydrolysis requires acid or base catalysts, causing corrosion of reaction equipment and environmental problems. Oxidative depolymerization easily leads to deep oxidation of the lignin substrate, reducing atom economy. Selective hydrodepolymerization, however, can efficiently break specific chemical bonds in lignin without hydrogenating the benzene rings, preserving the aromaticity of the product. The selective hydrodepolymerization method for lignin has advantages such as low reaction energy consumption, environmental friendliness, and high product selectivity.

[0003] The hydrodepolymerization of lignin is typically carried out under high-pressure hydrogen conditions, but the flammable and explosive nature of hydrogen poses safety hazards during transportation and storage. Furthermore, hydrogen is currently mainly derived from the steam reforming of natural gas or methane, which inevitably releases carbon dioxide during hydrogen production, exacerbating the greenhouse effect. Catalytic reforming reactions using alcohols can provide hydrogen for lignin depolymerization in situ, avoiding the need for external hydrogen supply and offering a new method for the high-value conversion of lignin.

[0004] Guaiacin is an important fine chemical intermediate with wide applications. It can be used to produce fragrances such as vanillin, pharmaceuticals such as potassium guaiacol sulfonate, guaiacol glycerol ether, isoproterenol, and berberine, and plant growth regulators such as sodium 5-nitroguaiacol. Currently, industrially, guaiacol is mainly produced using the diazotization hydrolysis of o-methoxyaniline. However, this method inevitably uses acidic substances and diazonium salts, posing problems such as corrosion of reaction equipment and operational safety. Some existing technologies also involve the depolymerization of lignin to prepare guaiacol products, but these also suffer from the problems of high cost due to the use of precious metal catalysts, safety hazards due to the need for a high-pressure hydrogen atmosphere, and low yield of the target product. Specific details are as follows:

[0005] Chinese invention patent CN112608219B discloses a method for preparing 4-ethylphenol based on the depolymerization of lignin using a liquid-phase reforming system. This method utilizes Ru / C as a catalyst to catalyze the liquid-phase reforming reaction of methanol and water, providing hydrogen for the depolymerization of organosoluble lignin, resulting in the highly selective production of 4-ethylphenol. The entire reaction process is under mild conditions and does not require external hydrogen. However, the use of a precious metal catalyst increases the cost of this method.

[0006] Chinese invention patent application CN115364862A discloses a method for preparing a nickel-based catalyst and its application in the lignin depolymerization process. This method utilizes a mixed alkali co-precipitation method with NaOH and Na₂CO₃ to prepare a nickel-based layered hydroxide precursor, followed by calcination and reduction to obtain the nickel-based catalyst. However, due to the problem of excessively high local alkali concentration during the mixed alkali precipitation process, and consequently uneven distribution of Ni and Sn species, the catalyst lacks a Ni-Sn alloy. (See attached technical description). Figure 1 Ni metal was found only in the sample. However, Ni metal has relatively low catalytic activity for hydrogen production from alcohols, requiring a catalyst under a 1.0 MPa H2 atmosphere to catalyze the conversion of lignin to phenolic monomers. This high hydrogen pressure also poses a safety hazard to the entire reaction. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies and prepare high-value-added guaiacol monomers, this invention aims to provide a method for the selective hydrogenolysis of lignin to prepare guaiacol monomers without using precious metals and reducing safety hazards associated with the use of added H2. This method utilizes alumina-supported nickel and nickel-tin alloys to catalyze the selective hydrogenolysis of lignin. The total yield of monophenol products from lignin depolymerization reaches 113.3–171.4 mg / g. -1 The selectivity of guaiacol monomers reached 40.2%–46.1%.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for selective hydrogenolysis of lignin to prepare guaiacol monomers using alumina-supported nickel and nickel-tin alloy catalysts is characterized by: using organosoluble lignin as a raw material, a mixture of alcohols and water as a solvent, adding an alumina-supported nickel and nickel-tin alloy catalyst prepared by urea precipitation, replacing the air in the reactor with an inert gas, pressurizing to 1.0–3.0 MPa, and stirring at 210–270°C for 1–6 h to selectively convert organosoluble lignin into compounds mainly composed of guaiacol monomers; wherein the nickel-tin alloy comprises Ni4Sn, Ni3Sn, NiSn, and Ni3Sn2; and Sn accounts for 5.9%–50.6% of the total mass of the alumina-supported nickel and nickel-tin alloy catalyst.

[0010] To further achieve the purpose of this invention, preferably, the alumina-supported nickel and nickel-tin alloy catalyst prepared by the urea precipitation method is prepared by mixing and stirring a urea solution and a mixed metal salt solution, followed by hydrothermal treatment, washing, drying, calcination, and reduction steps; the mixed metal salt solution is obtained by placing nickel salt, tin salt, and aluminum salt in deionized water.

[0011] Preferably, the ratio of nickel salt to tin salt in the mixed metal salt solution is 1:1 to 10:1, and the ratio of the sum of nickel salt and tin salt to aluminum salt is 6:1 to 3:1.

[0012] The concentration of urea in the urea solution is 0.5–2.0 mol / L. -1 ;

[0013] The hydrothermal conditions are maintained at 90℃ for 12–24 hours;

[0014] The calcination process involves heating the dried product in air at 5–10°C for 1 minute. -1 The heating rate was increased from room temperature to 450–650°C, and sintered at 450–650°C for 2–4 hours.

[0015] The reduction is achieved by passing the solid product obtained after calcination through H2 at a temperature of 5–10 °C for 1 minute. -1 The heating rate was increased from room temperature to 450–650℃, and the reduction was carried out at 450–650℃ for 2–4 hours.

[0016] Preferably, the nickel salt is nickel nitrate; the aluminum salt is aluminum nitrate; and the tin salt is tin chloride.

[0017] The concentration of the mixed metal salt solution A is 0.5–1.0 mol / L. -1 ;

[0018] The washing process involves washing the slurry with deionized water until the pH reaches 7.0.

[0019] The drying process is carried out at 100–110°C.

[0020] Preferably, the pores of the alumina-supported nickel and nickel-tin alloy catalyst are mainly mesoporous, with pore sizes concentrated in the range of 4–20 nm.

[0021] Ni accounts for 25.2% to 70.6% of the total mass of nickel and nickel-tin alloy catalysts supported on alumina, Al accounts for 7.0% to 9.6%, and the remainder is O.

[0022] Preferably, the mass ratio of the alumina-supported nickel and nickel-tin alloy catalyst to lignin is 1:1 to 1:2.

[0023] Preferably, the lignin is derived from agricultural and forestry waste, including bagasse, corn cobs, or bamboo.

[0024] Preferably, the alcohol is one or more of methanol, ethanol, and isopropanol; the volume ratio of the alcohol to water in the mixture of the alcohol and water is 1:19 to 19:1.

[0025] Preferably, the inert gas is argon or nitrogen; the reactor is a batch reactor; and the stirring speed is 600–800 rpm. -1 .

[0026] Preferably, the guaiacol monomer products are mainly 4-ethylguaiacol and 4-propylguaiacol.

[0027] The present invention has the following advantages and effects compared with the prior art:

[0028] 1) The method for selective hydrogenolysis of lignin to prepare guaiacol monomer products by alumina-supported nickel and nickel-tin alloy catalysis prepared in this invention has the advantages of inexpensive and renewable raw materials, simple reaction process and environmental friendliness compared with the existing organic synthesis preparation route.

[0029] 2) The method for selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys to prepare guaiacol monomers, as described in this invention, has relatively mild reaction conditions compared to other lignin depolymerization methods, and the total yield of monophenol products from lignin depolymerization reaches 113.3–171.4 mg / g. -1 The selectivity of guaiacol monomers reached 40.2%–46.1%.

[0030] 3) The catalyst of the present invention exhibits a mesoporous structure, which is conducive to the diffusion and adsorption of lignin macromolecules and intermediates during hydrogenolysis, and further facilitates the depolymerization of lignin.

[0031] 4) The catalyst of this invention contains two active phases: a nickel-tin alloy and nickel metal. The nickel-tin alloy accelerates the liquid-phase reforming of alcohols to produce hydrogen, while metallic nickel facilitates the breaking of CO chemical bonds in lignin. Both promote the conversion of lignin, thereby obtaining a high yield of guaiacol monomer products. Attached Figure Description

[0032] Figure 1 The image shows the XRD pattern of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0033] Figure 2 This is a TEM image of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0034] Figure 3 This is a TEM image of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0035] Figure 4 The N2 adsorption-desorption curves of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1 are shown.

[0036] Figure 5 The image shows the pore size distribution of the Ni-Sn / Al2O3-1 catalyst obtained in Example 1.

[0037] Figure 6 This is the GC-FID diagram of the volatile product obtained in Example 1.

[0038] Figure 7 The image shows the XRD pattern of the Ni / Al2O3 catalyst obtained in Comparative Example 2. Detailed Implementation

[0039] To better understand the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments. However, it should be noted that the embodiments of the present invention are not limited thereto.

[0040] To address the environmental pollution and other problems associated with existing methods for producing guaiacol products, this invention develops a method for preparing guaiacol monomers from lignin, which can significantly reduce raw material costs and dependence on petrochemical materials. Furthermore, to address the use of precious metal catalysts and high-pressure hydrogen in existing lignin hydrogenolysis technologies, this invention develops a non-precious metal Ni-based catalyst that enables lignin conversion without the addition of external H2, thus further broadening the application prospects of lignin.

[0041] Generally, Ni-based catalysts can break the CO chemical bonds in the lignin structure to obtain monophenol products, and they are widely used in the field of lignin hydrogenation and depolymerization. However, in the alcohol liquid-phase reforming hydrogen production reaction, Ni-based catalysts can break the C-OH bonds in the alcohol structure and catalyze the methanation reaction, reducing the overall H2 yield. The core feature of this invention is that the catalyst is an alumina-supported nickel and nickel-tin alloy, which simultaneously contains two active sites: nickel metal and nickel-tin alloy. These sites catalyze the hydrogen production from alcohol reforming and the breaking of CO chemical bonds in lignin, respectively, thereby achieving the goal of depolymerizing lignin to prepare guaiacol monomer products.

[0042] This invention employs a urea precipitation method to prepare a catalyst containing both Ni metal and Ni-Sn alloy. Urea is neutral at low temperatures and can form a homogeneous solution with metal particles. As the solution temperature increases, urea decomposes, gradually raising the pH value of the solution. Therefore, this method avoids the phenomenon of excessively high local alkali concentrations present in mixed alkali methods, and further allows for the synthesis of precursors with high crystallinity and uniform metal ion distribution, thereby promoting the formation of Ni-Sn alloy species. Thus, this invention uses a urea precipitation method to prepare alumina-supported nickel and nickel-tin alloy catalysts. These catalysts selectively convert organosoluble lignin into compounds primarily composed of guaiacol monomers. The nickel-tin alloy in this catalyst includes Ni4Sn, Ni3Sn, NiSn, and Ni3Sn2, with Sn accounting for 5.9%–50.6% of the total mass of the alumina-supported nickel and nickel-tin alloy catalyst. Ni accounts for 25.2% to 70.6% of the total mass of nickel and nickel-tin alloy catalysts supported on alumina, Al accounts for 7.0% to 9.6%, and the remainder is O.

[0043] The alumina-supported nickel and nickel-tin alloy catalyst prepared by the urea precipitation method of this invention is obtained by mixing and stirring a urea solution and a mixed metal salt solution, followed by hydrothermal treatment, washing, drying, calcination, and reduction steps. This urea precipitation method is somewhat similar to the mixed alkali co-precipitation method in Chinese invention patent application CN115364862A. The core feature is the use of urea solution instead of the mixed alkali solution of NaOH and Na2CO3. The key catalyst contains both nickel metal and nickel-tin alloy active sites, enabling the conversion of lignin to guaiacol monomers without added H2. The total yield of monophenol products from lignin depolymerization reaches 113.3–171.4 mg / g. -1 The selectivity of guaiacol monomers reached 40.2%–46.1%. The catalyst preparation process of this invention is simple and inexpensive. The catalyst provides mild conditions for the hydrogenation and depolymerization of lignin, exhibits high operational safety, and is suitable for industrialization. In catalyst preparation, the selection and dosage of nickel, tin, and aluminum salts in the mixed metal salt solution, the concentration of urea in the urea solution, and the specific conditions for hydrothermal treatment, washing, drying, calcination, and reduction are controlled according to the present invention and can be obtained through experiments. The alumina-supported nickel and nickel-tin alloy catalyst obtained by this invention has primarily mesoporous pores with a pore size concentrated in the range of 4–20 nm.

[0044] The key point of this invention is that the catalyst contains both nickel metal and nickel-tin alloy active sites; this is not a similar approach in the prior art. As for the specific preparation based on the characteristics of the catalyst and in combination with the existing technology, it is possible to achieve this, especially the ratio of raw materials and dosages as well as the process conditions, which can all be achieved based on the characteristics of the catalyst and the existing technology.

[0045] Example 1

[0046] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0047] The preparation of the catalyst includes the following steps:

[0048] (1) Weigh 19.83g Ni(NO3)2·6H2O, 1.54g SnCl2·2H2O, and 9.38g Al(NO3)3·9H2O and add them to 100mL of deionized water. Stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0g urea and dissolve it in 30mL of deionized water. Stir to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor. Then place the hydrothermal reactor in an oil bath and heat it to 90℃ for 24h while stirring vigorously. After the reaction is complete, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100℃ to obtain the catalyst precursor.

[0049] (2) After drying the catalyst precursor, place it in a muffle furnace and heat it at 5°C for 5 minutes in an air atmosphere. -1 The temperature was increased from room temperature to 550°C and calcined at this temperature for 4 hours. The resulting calcined solid was placed in a quartz tube, and H2 was introduced at a rate of 5°C / min. -1 The heating rate was increased from room temperature to 550℃, and the temperature was reduced for 4 hours to obtain an alumina-supported nickel and nickel-tin alloy catalyst, denoted as Ni-Sn / Al2O3-1.

[0050] from Figure 1 It can be seen that diffraction peaks belonging to Ni metal and Ni3Sn alloy can be clearly observed in the Ni-Sn / Al2O3-1 catalyst. For example... Figure 2 and 3 TEM analysis of the Ni-Sn / Al2O3-1 catalyst revealed two lattice stripe spacings of 0.20 nm and 0.27 nm, which are attributed to the (111) crystal plane of Ni metal (JCPDS: 04-0850) and the (110) crystal plane spacing of Ni3Sn alloy (JCPDS: 35-1362), respectively. Figure 4 As shown, the Ni-Sn / Al2O3-1 catalyst exhibits a type IV isotherm, indicating that the catalyst has a mesoporous structure, with most of the pore sizes concentrated between 4-20 nm. Figure 5 The Ni-Sn / Al2O3-1 catalyst prepared in this embodiment has a mesoporous structure, which is conducive to the diffusion of lignin macromolecules and intermediates during hydrogenolysis, thereby promoting the conversion of lignin.

[0051] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-1 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0052] The test results of this embodiment are as follows: Figure 6 As shown in Table 1, Figure 6 The GC-FID diagram of the volatile products obtained in Example 1 is shown in Table 1. The product peaks at different retention times were obtained by analysis and detection. The product distribution is shown in Table 1. The guaiacol monomer products are mainly 4-ethylguaiacol and 4-propylguaiacol.

[0053] Quantitative analysis revealed 8.27 mmol H2 after the reaction, and 171.4 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 46.1%.

[0054] Table 1. Distribution and yield of products obtained from lignin hydrogenolysis in methanol and water reforming system

[0055]

[0056]

[0057] Example 2

[0058] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0059] The preparation of the catalyst includes the following steps:

[0060] (1) Weigh 19.83g Ni(NO3)2·6H2O, 15.40g SnCl2·2H2O, and 17.05g Al(NO3)3·9H2O and add them to 360mL of deionized water. Stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0g urea and dissolve it in 120mL of deionized water. Stir to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor. Then place the hydrothermal reactor in an oil bath and heat it to 90℃ for 24h while stirring vigorously. After the reaction is complete, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100℃ to obtain the catalyst precursor.

[0061] (2) After drying the catalyst precursor, place it in a muffle furnace and heat it at 5°C for 5 minutes in an air atmosphere. -1 The temperature was increased from room temperature to 550°C and calcined at this temperature for 4 hours. The resulting calcined solid was placed in a quartz tube, and H2 was introduced at a rate of 5°C / min. -1 The heating rate was increased from room temperature to 550℃, and the temperature was reduced for 4 hours to obtain alumina-supported nickel and nickel-tin alloy catalysts, denoted as Ni-Sn / Al2O3-2.

[0062] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-2 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-2, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity nitrogen, and then nitrogen gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0063] Quantitative analysis revealed 7.07 mmol H2 after the reaction, and 160.2 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 40.3%.

[0064] Example 3

[0065] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0066] The preparation of the catalyst includes the following steps:

[0067] (1) Weigh 19.83g Ni(NO3)2·6H2O, 1.54g SnCl2·2H2O, and 4.69g Al(NO3)3·9H2O and add them to 100mL of deionized water. Stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0g urea and dissolve it in 30mL of deionized water. Stir to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor. Then place the hydrothermal reactor in an oil bath and heat it to 90℃ for 24h while stirring vigorously. After the reaction is complete, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100℃ to obtain the catalyst precursor.

[0068] (2) After drying the catalyst precursor, place it in a muffle furnace and heat it at 5°C for 5 minutes in an air atmosphere. -1 The temperature was increased from room temperature to 550°C and calcined at this temperature for 4 hours. The resulting calcined solid was placed in a quartz tube, and H2 was introduced at a rate of 5°C / min. -1 The heating rate was increased from room temperature to 550℃, and the temperature was reduced for 4 hours to obtain alumina-supported nickel and nickel-tin alloy catalysts, denoted as Ni-Sn / Al2O3-3.

[0069] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-3 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-3, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity nitrogen, and then nitrogen gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0070] Quantitative analysis revealed 6.68 mmol H2 after the reaction, and 158.2 mg g of lignin was converted. -1The monophenol products, of which the selectivity of guaiacol monomer products was 41.6%.

[0071] Example 4

[0072] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0073] The catalyst preparation process was the same as in Example 1, except that the oil bath time was adjusted to 12 h to prepare the Ni-Sn / Al2O3-4 catalyst.

[0074] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-4 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-4, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0075] Quantitative analysis revealed 8.01 mmol H2 after the reaction, and 168.5 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 43.2%.

[0076] Example 5

[0077] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0078] The catalyst preparation process was the same as in Example 1, except that the calcination temperature of the catalyst was adjusted to 650℃ to prepare the Ni-Sn / Al2O3-5 catalyst.

[0079] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-5 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-5, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity nitrogen, and then nitrogen gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0080] Quantitative analysis revealed 7.12 mmol H2 after the reaction, and 140.3 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 41.7%.

[0081] Example 6

[0082] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0083] The catalyst preparation process was the same as in Example 1, except that the calcination temperature of the catalyst was adjusted to 450℃ to prepare the Ni-Sn / Al2O3-7 catalyst.

[0084] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-7 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-7, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0085] Quantitative analysis revealed 7.01 mmol H2 after the reaction, and 144.5 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 43.2%.

[0086] Example 7

[0087] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys.

[0088] The catalyst preparation process was the same as in Example 1, except that the reduction temperature of the catalyst was adjusted to 650℃ to prepare the Ni-Sn / Al2O3-6 catalyst.

[0089] The specific operation of the selective hydrogenolysis of lignin catalyzed by Ni-Sn / Al2O3-6 is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-6, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0090] Quantitative analysis revealed 7.39 mmol H2 after the reaction, and 156.9 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products was 41.8%.

[0091] Example 8

[0092] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0093] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was performed as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.2 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0094] Quantitative analysis revealed 5.29 mmol H2 after the reaction, and 141.8 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 42.4%.

[0095] Example 9

[0096] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0097] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was carried out as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity nitrogen, and then 1.0 MPa of nitrogen was introduced. The reactor was heated to 210 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the resulting liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0098] Quantitative analysis revealed 3.34 mmol H2 after the reaction, and 118.6 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 43.6%.

[0099] Example 10

[0100] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0101] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was performed as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 270 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0102] Quantitative analysis revealed 8.96 mmol H2 after the reaction, and 165.3 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 40.9%.

[0103] Example 11

[0104] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0105] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C with mechanical stirring and maintained for 1 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0106] Quantitative analysis revealed 2.09 mmol H2 after the reaction, and lignin was converted to 88.4 mg g. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 43.1%.

[0107] Example 12

[0108] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0109] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 6 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0110] Quantitative analysis revealed 8.46 mmol H2 after the reaction, and 167.9 mg g of lignin was converted. -1 The monophenol products, of which the selectivity of guaiacol monomer products is 45.0%.

[0111] Example 13

[0112] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0113] The specific steps for the Ni-Sn / Al2O3-1 catalytic conversion of lignin are as follows: First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 18 mL of methanol, and 2 mL of water were added to the above-mentioned reaction vessel. The air inside the vessel was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reaction vessel was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0114] Quantitative analysis revealed 7.52 mmol H2 after the reaction, and 156.6 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 42.0%.

[0115] Example 14

[0116] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0117] The specific steps for the Ni-Sn / Al2O3-1 catalytic conversion of lignin are as follows: First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 2 mL of methanol, and 18 mL of water were added to the above-mentioned reaction vessel. The air inside the vessel was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reaction vessel was heated to 250℃ and maintained for 4 h. After the reaction was completed, the gaseous products obtained were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0118] Quantitative analysis revealed 3.65 mmol H2 after the reaction, and 113.3 mg g of lignin was converted. -1The selectivity of monophenol products, specifically guaiacol monomer products, was 41.6%.

[0119] Example 15

[0120] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0121] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was performed as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of ethanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0122] Quantitative analysis revealed 7.69 mmol H2 after the reaction, and 155.1 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 40.4%.

[0123] Example 16

[0124] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0125] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was carried out as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of isopropanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0126] Quantitative analysis revealed 7.16 mmol H2 after the reaction, and 138.4 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 40.2%.

[0127] Example 17

[0128] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0129] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was carried out in a 50 mL stainless steel reactor. First, 0.1 g of corn cob lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0130] Quantitative analysis revealed 8.04 mmol H2 after the reaction, and 158.7 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 41.3%.

[0131] Example 18

[0132] The specific steps of the method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel and nickel-tin alloys are as follows:

[0133] The conversion of lignin using Ni-Sn / Al2O3-1 catalysis was performed as follows: The conversion experiment was conducted in a 50 mL stainless steel reactor. First, 0.1 g of bamboo lignin, 0.1 g of Ni-Sn / Al2O3-1, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0134] Quantitative analysis revealed 7.85 mmol H2 after the reaction, and 155.2 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, is 40.5%.

[0135] Comparative Example 1

[0136] The depolymerization of lignin without a catalyst is carried out as follows:

[0137] The conversion of lignin was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the resulting liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. 1.0 mL of the mixture was added to a sample vial, and the volatile products obtained from the hydrogenolysis of lignin were analyzed using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0138] Quantitative analysis showed that no H2 was detected after the reaction, and lignin was converted to 20.8 mg g. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 30.2%.

[0139] Comparative Example 2

[0140] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin using alumina-supported nickel catalyst.

[0141] The preparation of the catalyst includes the following steps:

[0142] (1) Weigh 21.81 g Ni(NO3)2·6H2O and 9.38 g Al(NO3)3·9H2O and add them to 100 mL of deionized water. Stir vigorously to obtain a mixed metal salt solution A. Weigh 60.0 g urea and dissolve it in 30 mL of deionized water. Stir for 12 h to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor and heat it in an oil bath at 90 °C for 24 h with vigorous stirring. After the reaction is complete, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100 °C to obtain the catalyst precursor.

[0143] (2) Place the dried catalyst precursor mentioned above in a muffle furnace and heat it at 5°C for 5 minutes in an air atmosphere. -1 The temperature was increased from room temperature to 550°C and calcined at this temperature for 4 hours. The calcined solid was then placed in a quartz tube, and H2 was introduced at a rate of 5°C / min. -1 The heating rate was increased from room temperature to 550℃, and the catalyst was reduced at this temperature for 4 hours to obtain an alumina-supported nickel catalyst, denoted as Ni / Al2O3.

[0144] from Figure 7It can be seen that only diffraction peaks attributable to metallic Ni were observed in the Ni / Al2O3 catalyst.

[0145] The specific operation of Ni / Al2O3-catalyzed selective hydrogenolysis of lignin is as follows: The lignin conversion experiment was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni / Al2O3, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0 MPa was introduced. Under mechanical stirring, the reactor was heated to 250 °C and maintained for 4 h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0146] Quantitative analysis after the reaction showed that 96.9 mg g of lignin was converted in the Ni / Al2O3 catalytic system. -1 The monophenol products showed a selectivity of 34.3% for guaiacol monomers and 5.57 mmol H2 was detected.

[0147] Comparative Example 3

[0148] A method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported tin metal.

[0149] The preparation of the catalyst includes the following steps:

[0150] (1) Weigh 1.54 g of SnCl2·2H2O and 9.38 g of Al(NO3)3·9H2O and add them to deionized water to obtain solution A. Weigh 60.0 g of urea and dissolve it in deionized water to obtain a urea solution. Add the mixed metal salt solution A and the urea solution to a hydrothermal reactor and heat it in an oil bath at 90°C for 24 h with vigorous stirring. After the reaction is complete, wash the slurry with deionized water until the pH is 7. Dry the above solid at 100°C to obtain the catalyst precursor.

[0151] (2) Place the dried catalyst precursor mentioned above in a muffle furnace and heat it at 5°C for 5 minutes in an air atmosphere. -1 The temperature was increased from room temperature to 550°C and calcined at this temperature for 4 hours. The calcined solid was then placed in a quartz tube, and H2 was introduced at a rate of 5°C / min. -1The heating rate was increased from room temperature to 550℃, and the catalyst was reduced at this temperature for 4 hours to obtain an alumina-supported tin catalyst, denoted as Sn / Al2O3.

[0152] The specific operation of the selective hydrogenolysis of lignin catalyzed by Sn / Al2O3 is as follows: The lignin conversion experiment was carried out in a 50mL stainless steel reactor. First, 0.1g of bagasse lignin, 0.1g of Sn / Al2O3, 10mL of methanol, and 10mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then argon gas at 1.0MPa was introduced. Under mechanical stirring, the reactor was heated to 250℃ and maintained for 4h. After the reaction was completed, the gaseous products obtained after the reaction were collected and analyzed by gas chromatography. The liquid product was filtered, the obtained solid components were washed with methanol, and 0.08g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0g of dimethyl phthalate was added to 19.0g of n-propanol to obtain a 5wt.% internal standard solution) was added to the liquid. The volume was adjusted to 25mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0153] Quantitative analysis after the reaction showed that 31.3 mg g of lignin was converted in the Sn / Al2O3 catalytic system. -1 The selectivity for monophenol products, specifically guaiacol monomer products, was 29.6%, and no H2 generation was detected.

[0154] Comparative Example 4

[0155] The method for selective hydrogenolysis of lignin to prepare guaiacol monomers using a Ni / Al2O3 and Sn / Al2O3 mixed catalyst is as follows:

[0156] The conversion of lignin was carried out in a 50 mL stainless steel reactor. First, 0.1 g of bagasse lignin, 0.1 g of Ni / Al₂O₃, 0.1 g of Sn / Al₂O₃, 10 mL of methanol, and 10 mL of water were added to the reactor. The air inside the reactor was replaced with high-purity argon, and then 1.0 MPa of H₂ was introduced. The reactor was heated to 250 °C under mechanical stirring and maintained for 4 h. After the reaction, the gaseous products were collected and analyzed by gas chromatography. The liquid product was filtered, the solid components were washed with methanol, and 0.08 g of internal standard solution (dimethyl phthalate was used as the internal standard; 1.0 g of dimethyl phthalate was added to 19.0 g of n-propanol to obtain a 5 wt.% internal standard solution) was added to the resulting liquid. The volume was adjusted to 25 mL with methanol to obtain the liquid product. Take 1.0 mL of the above mixture with a syringe and add it to a sample vial. Analyze the volatile products obtained from the hydrogenolysis of lignin using an Agilent 5977A gas chromatography-mass spectrometry (GC-MS) system.

[0157] Quantitative analysis revealed 5.48 mmol H2 after the reaction, and 96.0 mg g of lignin was converted. -1 The selectivity of monophenol products, specifically guaiacol monomer products, was 36.8%.

[0158] As can be seen from Examples 1, 2, and 3, the monophenol yield and selectivity of guaiacol monomer products in the Ni / Al2O3 and Sn / Al2O3 catalytic systems are lower than those in the Ni-Sn / Al2O3-1 catalytic system. Furthermore, Comparative Example 4 shows that even with a simple physical mixture of Ni / Al2O3 and Sn / Al2O3 catalysts, the monophenol yield and selectivity of guaiacol monomer products from lignin depolymerization in this mixed system are also lower than those in the Ni-Sn / Al2O3-1 catalytic system. Moreover, the selectivity of guaiacol monomer products in all embodiments of this invention exceeds 40%, which is difficult to achieve with existing technologies.

[0159] Further comparison of Example 1 and Comparative Example 2 revealed that introducing Sn species into the Ni / Al2O3 catalyst enhances the activity of hydrogen production from alcohol liquid-phase reforming, increasing hydrogen yield from 5.57 mmol to 8.27 mmol. Higher hydrogen yield promotes the hydrogenolysis of lignin, leading to a higher yield of monophenol products (96.9 mg g). -1 vs 171.4mg g -1 It also showed higher selectivity for guaiacol monomer products (46.1% vs 34.3%).

[0160] As can be seen from Examples 17 and 18, the Ni-Sn / Al2O3-1 catalyst of the present invention can also efficiently convert corn cob and bamboo lignin, demonstrating good substrate applicability.

[0161] Compared to Chinese invention patent CN112608219B, this invention uses a non-precious metal Ni-based catalyst to achieve efficient depolymerization of lignin to prepare guaiacol monomer products, avoiding the use of precious metals and reducing catalyst preparation costs. This invention utilizes the catalyst to catalyze alcohol reforming for hydrogen production, providing H2 in situ for lignin depolymerization. Compared to Chinese invention patent application CN115364862A, this invention uses a urea precipitant method to avoid the phenomenon of excessively high local alkali concentrations present in mixed alkali methods, further enabling the synthesis of precursors with high crystallinity and uniform metal ion distribution, thereby promoting the formation of Ni-Sn alloy species.

[0162] Characterization of the catalyst by XRD and TEM revealed that the Ni-Sn / Al2O3-1 catalyst of this invention simultaneously contains Ni metal and Ni-Sn alloy species. The Ni-Sn alloy promotes the hydrogen production reaction of alcohol liquid-phase reforming, while the Ni metal enhances the breaking of CO chemical bonds in lignin, thereby improving the depolymerization efficiency of lignin and the yield of guaiacol products. Therefore, the mesoporous structure and the simultaneous presence of Ni-Sn alloy and Ni metal on the surface of the Ni-Sn / Al2O3-1 catalyst of this invention enhance the depolymerization efficiency of lignin, thereby promoting the formation of guaiacol monomer products.

[0163] The embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for the selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys to prepare guaiacol monomer products, characterized in that: Using organosoluble lignin as a raw material and a mixture of alcohols and water as a solvent, an alumina-supported nickel and nickel-tin alloy catalyst prepared by urea precipitation method is added. The air inside the reactor is replaced with an inert gas and pressurized to 1.0–3.0 MPa. The reactor is then stirred at 210–270 °C for 1–6 h to selectively convert organosoluble lignin into compounds primarily composed of guaiacol monomers. The nickel-tin alloy comprises Ni4Sn, Ni3Sn, NiSn, and Ni3Sn2; Sn accounts for 5.9%–50.6% of the total mass of the alumina-supported nickel and nickel-tin alloy catalyst. The alumina-supported nickel and nickel-tin alloy catalysts prepared by the urea precipitation method are obtained by mixing and stirring urea solution and mixed metal salt solution, followed by hydrothermal treatment, washing, drying, calcination, and reduction steps. The mixed metal salt solution is obtained by placing nickel salt, tin salt and aluminum salt in deionized water; The ratio of nickel salt to tin salt in the mixed metal salt solution is 1:1 to 10:1, and the ratio of the sum of nickel salt and tin salt to aluminum salt is 6:1 to 3:

1.

2. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The concentration of urea in the urea solution is 0.5 ~ 2.0 mol L. -1 ; The hydrothermal conditions are maintained at 90 ℃ for 12 to 24 hours; The calcination process involves calcining the dried product in air at 5-10 °C for 1 minute. -1 The heating rate was increased from room temperature to 450 ~ 650 ℃, and sintered at 450 ~ 650 ℃ for 2 ~ 4 h; The reduction is achieved by passing the solid product obtained after calcination through H2 at 5-10 °C for 1 minute. -1 The heating rate was increased from room temperature to 450 ~ 650 ℃, and the reduction was carried out at 450 ~ 650 ℃ for 2 ~ 4 h.

3. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The nickel salt is nickel nitrate; the aluminum salt is aluminum nitrate; the tin salt is tin chloride; The concentration of the mixed metal salt solution is 0.5 ~ 1.0 mol L. -1 ; The washing process involves washing the slurry with deionized water until the pH reaches 7.

0. The drying process is carried out at 100-110°C.

4. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The channels of the alumina-supported nickel and nickel-tin alloy catalysts are mainly mesoporous, with pore sizes concentrated in the range of 4 to 20 nm. Ni accounts for 25.2% to 70.6% of the total mass of nickel and nickel-tin alloy catalysts supported on alumina, Al accounts for 7.0% to 9.6%, and the remainder is O.

5. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The mass ratio of the alumina-supported nickel and nickel-tin alloy catalysts to lignin is 1:1 to 1:

2.

6. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The lignin is derived from agricultural and forestry waste, including bagasse, corn cobs, or bamboo.

7. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The alcohol is one or more of methanol, ethanol, and isopropanol; the volume ratio of the alcohol to water in the mixture of the alcohol and water is 1:19 to 19:

1.

8. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The inert gas is argon or nitrogen; the reactor is a batch reactor; the stirring speed is 600-800 r / min. -1 .

9. The method for preparing guaiacol monomer products by selective hydrogenolysis of lignin catalyzed by alumina-supported nickel and nickel-tin alloys according to claim 1, characterized in that: The guaiacol monomer products are mainly 4-ethylguaiacol and 4-propylguaiacol.

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