A method for efficiently catalyzing preparation of dihydroconiferyl alcohol from lignin by using a titanium dioxide loaded copper-nickel bimetallic catalyst

Abstract

The application belongs to the field of catalytic conversion of lignin, and discloses a method for efficiently catalyzing lignin to prepare dihydrosipartol by using a titanium dioxide supported copper-nickel bimetallic catalyst. In the method, the metal nickel with high hydrogenation activity is introduced into the copper-based catalytic system to promote the breaking of C-O bonds in lignin and the hydrogenation of cypress alcohol, while the generation of propyl by-products is inhibited, so that the highest monomer yield of 23.9wt% is obtained in the catalytic fractionation process of Yunnan pine. The key technical problem of the application is to efficiently catalyze the conversion of lignin into phenolic compounds while completely retaining cellulose and hemicellulose, thereby providing a reliable foundation for subsequent high-value utilization of lignin.

Description

Technical Field

[0001] This invention belongs to the field of lignin catalytic conversion and relates to a method for efficiently catalyzing the preparation of dihydropineol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst. Background Technology

[0002] With the continuous growth of global population and economy, and the rapid advancement of industrialization, the rapid consumption of traditional fossil energy resources not only poses a risk of resource depletion but also triggers severe greenhouse gas emissions and pollution of water, air, and land during the extraction and use of fossil fuels. Therefore, seeking an energy system dominated by renewable energy has gradually become a key research focus. Biomass, as the only renewable organic carbon resource formed through photosynthesis in nature, possesses advantages such as being carbon neutral, abundant reserves, and wide distribution. Among current biomass resources, lignocellulose biomass stands out from other biomass resources due to its unique phenylpropane structure and abundant natural reserves, showing potential to replace fossil resources in the future. Although the aromatic ring structure makes lignin irreplaceable among renewable carbon resources, its complex three-dimensional amorphous structure and difficulty in solubility are the primary challenges to its high-value conversion. Therefore, how to dissolve lignin under mild conditions while preventing structural condensation and ultimately obtaining high-quality aromatic monomers has become the key to efficient lignin depolymerization.

[0003] Among numerous depolymerization products, dihydroconiferol stands out as an indispensable molecular structure for the high-value conversion of lignin due to its unique bioactivity and application potential. As a cytokinin isolated from Acer rubrum, dihydroconiferol not only serves as a crucial component for stimulating plant callus tissue, but its phenolic hydroxyl groups are also used as important organic intermediates in small molecule synthesis. While traditional hydrogenolysis of lignin to produce dihydroconiferol has yielded some success, problems such as dependence on precious metals and low product selectivity remain to be solved. Reduction-catalyzed fractionation, as an effective strategy for selectively depolymerizing lignin macromolecules while preserving aromatic structures, holds promise as a solution to overcome current bottlenecks in biomass value-added processes. Against this backdrop, the development of a method for efficiently cleaving lignin β- O The low-cost metal catalyst that can selectively produce dihydropinene by connecting the C–O bonds in the -4 linkage system is of greater research significance and application value. Summary of the Invention

[0004] This invention relates to a method for the efficient catalytic conversion of lignin from *Pinus yunnanensis* to dihydroconiferol using a titanium dioxide-supported copper-nickel bimetallic catalyst. The method involves introducing highly active nickel into a copper-based catalytic system to promote the breaking of C–O bonds in lignin and the hydrogenation of coniferol, while simultaneously inhibiting the removal of γ-hydroxyl groups, thereby preventing the formation of propyl byproducts. This achieves a maximum monomer yield of 23.9 wt% during the catalytic fractionation of *Pinus yunnanensis*. The key technical challenge of this invention is to efficiently catalyze the conversion of lignin to phenolic compounds while fully preserving cellulose and hemicellulose, providing a reliable foundation for the subsequent high-value utilization of lignin.

[0005] The technical solution of the present invention: A method for efficiently catalyzing the preparation of dihydroconiferyl alcohol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst includes the following steps: 1) The lignocellulosic biomass raw material is pulverized to 40-60 mesh, extracted with ethanol, and dried to obtain biomass powder; 2) Using an organic polar solvent as the reaction solvent, the catalyst and biomass powder are placed in a high-pressure reactor at a mass ratio of 2:1; after the reaction is completed, the reactor is allowed to cool naturally to room temperature; under a hydrogen pressure of 1-3 MPa (preferably 3 MPa) and a pressure of 200... o C-260 o C (preferably 240) o C) React for 1-6 hours under temperature conditions (preferably 240°C). o C); 3) The solid-liquid mixture obtained after the reaction was filtered, extracted, and concentrated. Finally, the liquid portion of the reaction was rotary evaporated to obtain lignin oil rich in monophenol compounds. The obtained sample was then analyzed by gas chromatography and gas chromatography-mass spectrometry. The remaining sample was dried and a quantitative amount of tetrahydrofuran was added for gel permeation chromatography analysis.

[0006] The catalyst is a titanium dioxide-supported copper-nickel bimetallic catalyst, comprising a titanium dioxide support (rod-shaped titanium dioxide), metallic Cu, and metallic Ni, with a molar ratio of metallic Cu to metallic Ni of 1:1, a loading of metallic Cu of 20.9 wt%, and a loading of metallic Ni of 17.9 wt%.

[0007] In step 1), the lignocellulosic biomass is crushed into powder of 40-60 mesh (particle size range of 0.5 mm-1.0 mm). In a mixed solvent of toluene and ethanol with a volume ratio of 2:1, the mixture is refluxed in a Soxhlet extractor at a temperature of 110-130℃ until the solution is clear and transparent. The refluxed sample is then transferred to a vacuum drying oven at 50℃ and dried for 8 hours to obtain biomass powder.

[0008] In step 1), the lignocellulosic biomass raw material is Yunnan pine; In step 2), the reaction solvent includes any one of methanol, ethanol, isopropanol, or a methanol-ethanol mixture in a volume ratio of 1:1.

[0009] In step 3), the solid component obtained after rotary evaporation of the liquid portion includes carbohydrates and catalysts that do not participate in the reaction. The catalyst is separated from the carbohydrate component by a sieve, and the small-sized catalyst is screened out from the sieve pores. The recovered catalyst is then dried under vacuum and used for the next cycle test of lignin depolymerization.

[0010] The liquid products were analyzed by gas chromatography and gas chromatography-mass spectrometry; the lignin monomers in the oily products were characterized and quantified by referring to standard samples purchased from commercial sources or synthesized independently.

[0011] Formula for calculating monomer yield: Monomer yield (wt%) = [M1 (total lignin monomers) / M2 (lignin content in lignocellulosic biomass)] × 100% M1 represents the total mass of lignin depolymerized phenolic monomers, and M2 represents the mass of lignin in lignocellulosic biomass.

[0012] The beneficial effects of this invention are: 1. The raw material used in this invention is lignocellulosic biomass powder extracted with organic solvents. Its structural composition is very similar to that of natural lignin. This invention reveals the synergistic effect between two metals while highlighting the role of different components in the catalytic reaction. It precisely breaks CO bonds while significantly reducing the activation energy of the reaction. The lignocellulosic biomass is efficiently and directionally converted into dihydroconiferol while maintaining structural integrity. After gram-scaled reaction, compositional analysis of the recovered whole cellulose showed 427.10 mg of cellulose and 115.90 mg of hemicellulose, corresponding to a cellulose retention rate as high as 95.80% and a hemicellulose retention rate of 53.20%. This excellent carbohydrate retention highlights the great potential of this catalyst in the high-value-added industrial lignin production.

[0013] 2. This invention proposes a method using rod-shaped titanium dioxide as a carrier, whose highly porous structure enables bimetallic nanoparticles to be uniformly distributed on the surface of the nanorods. This regularly distributed and orderly mesoporous structure and abundant stacking not only ensure the full utilization of active sites, but also emphasize the key role of the synergistic effect of bimetals in selectively guiding dihydropinene products.

[0014] 3. The two bimetallic materials used in this invention, copper and nickel, are both inexpensive metals. Under conditions without external hydrogen, methanol is used as a hydrogen donor to achieve depolymerization through a self-supplying hydrogen transfer reaction. During the catalytic process, the catalyst can dehydrogenate methanol to generate active hydrogen, which then participates in the breaking of CO bonds by combining with active sites. The synergistic effect between Cu and Ni metals effectively regulates the reaction pathway and perfectly preserves the high-value monocyclic aromatic hydrocarbon structure.

[0015] 4. This invention proposes a catalyst that is simple to prepare and can efficiently convert lignin into dihydroconiferol. The catalyst preparation process is environmentally friendly, and methanol, used as a solvent in the reaction, provides both a reaction site for lignin depolymerization and an indirect hydrogen source as a hydrogen donor. While promoting lignin dissolution under supercritical conditions, the active hydrogen in the solvent can also be captured by the catalyst and participate in the breaking of the CO bonds in lignin. This provides a framework for the rational design of bimetallic catalysts for the directional conversion of lignin into dihydroconiferol.

[0016] 5. This invention demonstrates excellent recyclability in the stability test of lignin model compounds, maintaining an 80% monomer conversion rate after five cycles. Catalyst stability was also verified in experiments with real Yunnan pine sawdust. After eight cycles, the used catalyst was calcined and regenerated in air and reused under optimal reaction conditions. The total monomer yield after regeneration recovered to 16.66 wt%, and the selectivity for dihydropinaxyl alcohol recovered to 53.84%, indicating that the regenerated catalyst still possesses high product selectivity. Attached Figure Description

[0017] Figure 1 The image shows the SEM image of the copper-nickel bimetallic catalyst NiCu / TiO2 (Cu and Ni molar ratio of 1:1) prepared in this invention. Figure 2 The XRD pattern of the copper-nickel bimetallic catalyst NiCu / TiO2 (Cu and Ni molar ratio of 1:1) prepared in this invention is shown. Figure 3 The image shows the Ni 2p XPS spectrum of the copper-nickel bimetallic catalyst NiCu / TiO2 (Cu and Ni molar ratio of 1:1) prepared in this invention. Figure 4 The Cu 2p XPS electron microscope image of the copper-nickel bimetallic catalyst NiCu / TiO2 (Cu and Ni molar ratio of 1:1) prepared in this invention; Figure 5 The BET spectrum of the copper-nickel bimetallic catalyst NiCu / TiO2 (Cu and Ni molar ratio of 1:1) prepared in this invention is shown. Figure 6 GPC spectra of Yunnan pine lignin before and after the reaction with a catalyst; Figure 7 The 2D HSQC spectrum of lignin oil after depolymerization of Yunnan pine lignin in methanol solvent is shown. Among them, (a) is the side chain region of enzymatically hydrolyzed Yunnan pine lignin, (b) is the side chain region of lignin oil, (c) is the aromatic ring region of enzymatically hydrolyzed Yunnan pine lignin, and (d) is the aromatic ring region of lignin oil. Figure 8 GC spectra of Yunnan pine lignin before and after the reaction with a catalyst. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0019] Example 1 Preparation of Titanium Dioxide-Supported Copper-Nickel Bimetallic Catalyst: A mesoporous NiCu / TiO2 catalyst was prepared using a hydrothermal method. The preparation process is as follows: 1.77 g tetrabutyl titanate, 1.74 g Ni(NO3)2·6H2O, 1.44 g Cu(NO3)2·3H2O, 1.82 g urea, 25 ml water, and 25 ml ethanol were sequentially added to a 100 ml hydrothermal reactor lined with polytetrafluoroethylene. The hydrothermal reactor was then placed in an oven and heated to 160°C. o The reaction was maintained at a constant temperature of C for 12 h. After the reaction was complete, the solid product was collected by filtration, washed with deionized water until the pH of the filtrate reached 7, and then subjected to a process at 80 °C. o The precursor was dried overnight in an oven at C to obtain the hydroxide precursor. Subsequently, the precursor was placed in a tube furnace and heated at 500°C under a nitrogen atmosphere. o The NiCu / TiO2 catalyst was finally obtained by calcination at C for 3 h. The single-metal catalyst was also prepared by the same method, with only the single-metal salt added during the preparation process. The calcination and reduction processes of the catalysts were carried out in a tube furnace at a heating rate of 5 °C / min.

[0020] Figure 1 This presentation primarily showcases scanning electron microscope (SEM) images of a titanium dioxide-supported copper-nickel bimetallic catalyst, clearly revealing its distinct nanorod morphology. Furthermore, numerous nanoparticles are observed dispersed within and around the nanorods. Figure 2The characteristic peaks of the precursor, monometallic catalyst, and bimetallic catalyst in the X-ray diffraction pattern of the catalyst were analyzed. The bimetallic XRD pattern showed similarities to, yet also differences from, the monometallic catalyst. According to the Bragg equation and the results, during the preparation process, the doping of TiO2 with smaller nitrogen atoms caused a rightward shift of the diffraction peaks. The introduction of nitrogen atoms led to lattice contraction and a decrease in interplanar spacing. Furthermore, by comparing the (-111) and (111) crystal planes of CuO and the (-111) and (110) crystal planes of NiO, the bimetallic catalyst also showed (200) and (220) crystal planes. The presence of CuNiO indicates the formation of a more complex and compact mixed oxide phase between Cu and Ni metals. The broad peak of (220) indicates that the metal atoms underwent an amorphous transformation under hydrothermal high temperature.

[0021] Figure 3 This is an X-ray photoelectron spectroscopy analysis of the titanium dioxide-supported copper-nickel bimetallic catalyst prepared in this embodiment. The metal-support interaction in NiCu / TiO2 was explored by analyzing the valence states of the two metals. The Ni 2p spectrum of NiCu / TiO2 can be fitted with two distinct peaks, corresponding to two different nickel species: NiO and Ni(OH)2. The presence of hydroxide is attributed to the reaction of the surface oxides with water vapor when exposed to air. Figure 4 The mid-binding energy shift indicates that the introduction of Cu promotes oxide formation and alters the electronic states of the metal during alloying. Similarly, the Cu 2p spectrum of NiCu / TiO2 shows the presence of Cu. 2+ and Cu + / Cu 0 Simultaneously with the change in valence state, the binding energy also shifts, further confirming the electronic interaction between Ni and Cu species in the alloy structure.

[0022] Example 2 (1) Grind Yunnan pine wood into 40-mesh powder, take 50 g, and in a mixed solvent of 500 mL toluene and 250 mL ethanol, at 120 °C o Yunnan pine powder obtained after being kept under C conditions for 14 h; (2) Take 50 mg of extracted Yunnan pine powder and 25 mg of titanium dioxide supported copper-nickel bimetallic catalyst prepared in Example 1, and place them together with 10 mL of methanol in a stainless steel reactor. After purging the air, introduce 3 MPa of hydrogen gas. (3) Heat the high-pressure reactor mentioned in step (2) to 240°C. o The reaction was maintained at C for 4 h, and then cooled to room temperature. (4) The solid-liquid mixture after the reaction in step (3) was filtered through a sand core funnel. After the liquid phase was concentrated by a rotary evaporator, dichloromethane and deionized water were added in a ratio of 1:3 for extraction and separation. The separated liquid was then rotary evaporated to obtain lignin oil rich in phenolic compounds. The results are shown in Table 1.

[0023] Preparation of Yunnan pine lignin by enzymatic hydrolysis: The wood powder (5 g) obtained from ball milling in step (1) was placed in 100 mL of acetate buffer for digestion, with 2.5 mL of cellulase and 0.5 mL of hemicellulase added. The mixture was shaken at 150 rpm at 50°C. o The reaction was carried out at C for 48 h. Afterwards, the insoluble matter after enzymatic hydrolysis was collected by centrifugation, washed with deionized water, and freeze-dried.

[0024] The insoluble matter (crude lignin) was further processed using a dioxane / water solution (containing 0.01 mol / L). -1 The product was subjected to mild acid hydrolysis with HCl. After centrifugation, the product was neutralized with sodium bicarbonate, and finally precipitated by acidification (pH = 2). The lignin was then obtained by centrifugation, washing, and freeze-drying. GPC and two-dimensional NMR spectroscopy were used to compare the enzymatically hydrolyzed Yunnan pine lignin with the depolymerized Yunnan pine lignin oil.

[0025] GPC analysis of the enzymatically hydrolyzed Yunnan pine lignin and the depolymerized Yunnan pine lignin oil prepared in this embodiment is as follows: Figure 7 As shown: the molecular weight decreased significantly after depolymerization, proving the successful depolymerization of lignin from Yunnan pine. To further reveal the structural changes of lignin during hydrogenolysis, such as... Figure 7 The two-dimensional NMR analysis of enzymatically hydrolyzed and depolymerized Yunnan pine lignin is shown below. Figure 7 The aromatic ring region at (d) corresponds to β- O The signals from the -4′, β-β′, and β-5′ structures almost completely disappeared, indicating that the structure of natural lignin had been successfully disrupted. Meanwhile, the signals located at... Figure 7 The (b) side chain region shows a C-H correlation signal of lignin phenol monomers. The cross peaks (marked in blue) at δC / δH 31.3 / 2.48, 34.4 / 1.67, and 57.4 / 3.19 ppm are attributed to the C-H groups of the propanol group in dihydroconiferyl alcohol. α C β and C γ Location. These 2D HSQCNMR results are consistent with... Figure 8 The observations from the GC-MS analysis were highly consistent.

[0026] Table 1. Depolymerization of Yunnan pine powder using titanium dioxide-supported copper-nickel bimetallic catalyst in methanol solvent.

[0027] Example 3 Same as Example 2. The depolymerization results of the titanium dioxide-supported copper-nickel bimetallic catalyst in step (2) were compared with those of two bimetallic catalysts with different metal molar ratios, while other reaction conditions remained unchanged. By comparing the monomer yield and product selectivity under different conditions, it was finally determined that the optimal reaction conditions were 3 MPa hydrogen pressure and 240 °C. o The highest yield of dihydropine resin was obtained under the condition of reaction C for 4 h, and the results are shown in Table 2.

[0028] Table 2. Depolymerization of Yunnan pine powder by titanium dioxide-supported copper-nickel bimetallic catalysts with different metal ratios.

[0029] Example 4 Same as Example 2. The amount of catalyst in step (2) was replaced with 10 mg, 20 mg, 40 mg, and 50 mg, respectively, while the other reaction conditions remained unchanged. The results are shown in Table 3.

[0030] Table 3. Depolymerization of Yunnan pine powder using titanium dioxide-supported copper-nickel bimetallic catalyst at different dosages.

[0031] Example 5 Same as Example 2. The reaction solvent in step (2) was replaced with ethanol, methanol / ethanol (1:1, v:v), and isopropanol, respectively, while the other reaction conditions remained unchanged. The results are shown in Table 4.

[0032] Table 4. Depolymerization of Yunnan pine powder using titanium dioxide-supported copper-nickel bimetallic catalysts in different reaction solvents.

[0033] Example 6 Same as Example 2. The reaction temperature in step (2) was changed to 200℃, 220℃, and 260℃ respectively, while the other reaction conditions remained unchanged. The results are shown in Table 5.

[0034] Table 5. Depolymerization of Yunnan pine powder using titanium dioxide-supported copper-nickel bimetallic catalysts at different reaction temperatures.

[0035] Example 7 Same as Example 2. The reaction time in step (2) was changed, while the other reaction conditions remained the same. The results are shown in Table 6.

[0036] Table 6. Depolymerization of Yunnan pine powder using titanium dioxide-supported copper-nickel bimetallic catalyst at different reaction times.

[0037] Example 8 Same as Example 2. The catalyst after the reaction in step (2) was separated from the insoluble slag through a sieve and cyclically tested under the same conditions as in Example 2. The results are shown in Table 7.

[0038] Table 7. Depolymerization of Yunnan pine powder by titanium dioxide-supported copper-nickel bimetallic catalyst under different cycling conditions.

[0039] Comparative Example 1 Same as Example 2. Only the copper-nickel bimetallic supported silicon-based material in step (2) was replaced with monometallic supported Cu / TiO2 and Ni / TiO2, respectively. To clarify the reaction pathway for the selective hydrogenolysis of lignin to prepare dihydropinene catalyzed by NiCu / TiO2, under optimized conditions, β- O Hydrogenolysis experiments were conducted on the -4' type lignin model compound and its monophenol intermediate. When D1 was used as the substrate, the reaction behavior was similar to that of real wood flour. Significant differences in product distribution were observed under different catalysts. The reaction using the Ni / TiO2 catalyst mainly produced guaiacol and 4-propylguaiacol. In contrast, the catalytic hydrogenation reaction using the Cu / TiO2 catalyst mainly produced guaiacol and 4-propylguaiacol, and a small amount of 4-propenylguaiacol with unsaturated side chains was also detected. The application of the NiCu / TiO2 catalyst significantly altered the product distribution: the yield of dihydropinene increased dramatically to 27.24%. The fact that dihydropinene remained unchanged in the NiCu / TiO2 catalyst reaction indicates that the substrate is relatively stable under hydrogenolysis conditions. When D3 was used as the substrate, dihydropinene was the main product formed in NiCu / TiO2, indicating that NiCu / TiO2 promotes C=C hydrogenation while retaining the γ-hydroxyl (γ-OH) group. In contrast, the hydrogenolysis results of Ni / TiO2 show that Ni / TiO2 more readily promotes the removal of Cγ–OH and subsequent hydrogenation. Cu / TiO2 also shows the ability to convert D3, but to a limited extent. Ni alone tends to push the reaction further towards Pr-G. In contrast, NiCu / TiO2 provides a more suitable balance between hydrogenation activity and γ-OH retention, thus favoring the formation of Pol-G. Cu / TiO2 can participate in the reaction, but its activity is insufficient for the formation of dihydroconiferol. Compared to single-metal catalysts, NiCu / TiO2 significantly increases the formation of propanol-type products and inhibits excessive propyl product formation.

[0040] Table 8 Depolymerization of Yunnan pine powder using different catalysts

[0041] Comparative Example 2 Same as Example 2. Only the Yunnan pine powder in step (2) is replaced with β-O -4' model compounds. By associating real lignin with the depolymerization products of the model compounds, the practical application of this catalyst in complex real biomass systems was further promoted. The NiCu / TiO2 catalyst still maintained the precise ability to break the β-O-4' bond. The results are shown in Table 9.

[0042] Table 9 Depolymerization of Yunnan pine powder using different catalysts

[0043] To achieve the maximum yield of dihydropinene from lignin, this patent systematically analyzes the effects of different experimental parameters on the total yield of phenolic monomers and the selectivity of the target product in the above embodiments. First, screening the metal ratio reveals the significant advantages of bimetallic compounds. The catalytic performance of NiCu / TiO2 reaches its maximum when the bimetallic molar ratio is 1:1, with a monomer yield of 22.01%. This excellent catalytic effect can be attributed to the close synergistic effect of the Ni-Cu bimetal at the nanoscale, which can regulate the acid site distribution to a more balanced state. In the catalyst, the Ni-Cu electronic balance induced by hydroxide is disrupted. By guiding electron flow to the copper and TiO2 supports, the hydrogenation capacity of the metal is weakened, and the reaction activity is greatly reduced, ultimately leading to the formation of dihydropinene. Furthermore, increasing the catalyst dosage can improve the monomer yield to some extent by increasing the number of active sites, but the improvement is actually quite limited. Solvent screening results show that methanol plays a certain promoting role in lignin dissolution, hydrogen supply to the reaction system, and stabilization of lignin phenolic intermediates.

[0044] Time and temperature demonstrate the thermodynamic dependence of the reaction on kinetics. At 240... o At temperature C, the total yield of depolymerized monomers reaches its peak, but further increases in temperature lead to condensation side reactions of the lignin hydrogenolysis fragments, resulting in a decrease in the yield of dihydropinyl alcohol. While lower temperatures yield higher product selectivity, the actual monomer yield of lignin oil is lower; therefore, these conditions were not selected as the overall optimal conditions for monomer production. The inherent structural complexity and resilient nature of coniferous lignin make these highly competitive performance indicators strong evidence of the effectiveness of the developed catalytic system.

Claims

1. A method for the efficient catalytic preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst, characterized in that, Includes the following steps: 1) The lignocellulosic biomass raw material is pulverized to 40-60 mesh, extracted with ethanol, and dried to obtain biomass powder; 2) Using an organic polar solvent as the reaction solvent, the catalyst and biomass powder were placed in a high-pressure reactor at a mass ratio of 2:1; after the reaction was completed, the reactor was allowed to cool naturally to room temperature; under a hydrogen pressure of 1-3 MPa and a temperature of 200... o C-260 o The reaction is carried out at temperature C for 1-6 hours. 3) The solid-liquid mixture obtained after the reaction is filtered, extracted, and concentrated. Finally, the liquid part of the reaction is rotary evaporated to obtain lignin oil rich in monophenol compounds.

2. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 1, characterized in that, The catalyst is a titanium dioxide supported copper-nickel bimetallic catalyst, comprising a titanium dioxide support, metal Cu and metal Ni, with a molar ratio of metal Cu to metal Ni of 1:1, a loading of metal Cu of 20.9 wt%, and a loading of metal Ni of 17.9 wt%.

3. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 1, characterized in that, In step 1), the lignocellulosic biomass is crushed into 40-60 mesh powder. In a mixed solvent of toluene and ethanol with a volume ratio of 2:1, the mixture is refluxed in a Soxhlet extractor at a temperature of 110-130℃ until the solution is clear and transparent. The refluxed sample is then transferred to a vacuum drying oven at 50℃ and dried for 8 hours to obtain biomass powder.

4. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 1, characterized in that, In step 1), the lignocellulosic biomass raw material is Yunnan pine.

5. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 1, characterized in that, In step 2), the reaction solvent includes any one of methanol, ethanol, isopropanol, or a methanol-ethanol mixture in a volume ratio of 1:

1.

6. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 1, characterized in that, In step 3), the solid component obtained after rotary evaporation of the liquid portion includes carbohydrates and catalysts that do not participate in the reaction. The catalyst is separated from the carbohydrate component by a sieve, and the small-sized catalyst is screened out from the sieve pores. The recovered catalyst is then dried under vacuum and used for the next cycle test of lignin depolymerization.

7. The method for efficiently catalyzing the preparation of dihydroconiferol from lignin using a titanium dioxide-supported copper-nickel bimetallic catalyst according to claim 2, characterized in that, The titanium dioxide carrier is rod-shaped titanium dioxide.

Images