Method for catalytic depolymerization of lignin derivative and lignin depolymerization oil

Abstract

Disclosed in the present invention are a method for catalytic depolymerization of a lignin derivative, and a lignin depolymerization oil. The method relates to using a lignin derivative containing a 1,1-diphenylmethyl structure; and on the basis of the synergistic catalysis effect of a transition metal catalyst, a hydrogen supply agent and an acidic catalyst in a liquid medium, prepares the lignin depolymerization oil rich in a 1,2-diphenylethyl structured bisphenol and rich in a lignin oligomer. The present invention achieves stereospecific depolymerization of lignin by means of catalyzing an aryl migration reaction of the 1,1-diphenylmethyl structure; different from traditional reactions in which lignin monophenols are target products, the present invention can achieve the stereospecific preparation of a bisphenol product in one step, while coproducing the lignin oligomer. The method involved in the present invention develops the product types of lignin-based bisphenols, and improves the uses of catalytically depolymerizing lignin to prepare high-value chemical products, fuels and polymer materials.

Description

A method for catalytic depolymerization of lignin derivatives and lignin depolymerization oil Technical Field

[0001] The present invention relates to a method for catalytically depolymerizing lignin derivatives and lignin depolymerized oil, in particular to lignin derivatives with a 1,1-diphenylmethyl structure, and relates to a technology for catalytically depolymerizing lignin with a transition metal catalyst and high-value utilization of biomass. Background Art

[0002] Lignin is a natural aromatic polymer with enormous application potential. Due to its wide availability and low cost, it is a potential raw material for the preparation of green aromatic chemicals. Lignin is primarily composed of structural units such as p-hydroxyphenyl, guaiacyl, and syringyl. While the linkages between these units vary, C–O bonds, such as β–O–4 aryl ether bonds, are predominant. By catalytically cleaving the C–O bonds of lignin, lignin can be depolymerized into monophenolic compounds such as phenol, guaiacol, propyl guaiacol, eugenol, propyl eugenol, vanillin, and syringaldehyde. While there is currently no direct utilization pathway for these monophenols, subsequent catalytic refining can transform them into high-value-added pharmaceutical intermediates, lignin fuels, and other products.

[0003] Bisphenol A (BPA) and other bisphenol polymerization monomers are the main forms of utilization of petrochemical-based phenols, which are mainly prepared by the condensation reaction of two molecules of phenol and one molecule of acetone. At present, lignin monophenols can also be cross-linked with formaldehyde or by condensation between monophenols to prepare lignin-based bisphenols (US11414519B2; Green Chem., 2018, 20, 1050-1058; Green Chem., 2019, 21, 6622-6633). This type of lignin-based bisphenol can meet the synthesis requirements of thermoplastic polymers and thermosetting polymers, and at the same time, compared with petrochemical-based BPA, the endocrine disrupting toxicity is significantly reduced. Therefore, it can be considered that lignin-based bisphenols are expected to become an important structural monomer for the synthesis of green renewable polymer materials.

[0004] Currently, it's difficult to directly prepare lignin bisphenols through catalytic depolymerization of lignin. For example, natural lignin contains over 50% β–O–4 aryl ether bonds between its structural units, while the relative content of β–β, β–5, and β–5 C–C bonds between structural units is relatively low and exhibits poor reactivity (Nat. Chem., 2021, 13, 1118-1125). Consequently, after catalytic depolymerization of natural lignin, the yield of bisphenols is low (less than 5%), and the product structure is complex, making it difficult to generate practical value. For example, during chemical processing, random condensation and cross-linking reactions easily occur between and within lignin molecular chains, forming a large number of low-reactivity C–C bonds. Consequently, after catalytic depolymerization of industrial lignin, the C–C bonds generated by lignin self-condensation are difficult to break, resulting in oligomers as the primary product, making it difficult to generate monophenol or bisphenol products (CN202111477348.6).

[0005] Summary of the Invention

[0006] The purpose of the present invention is to overcome the limitation that the existing lignin depolymerization products are mainly monophenol compounds and to provide a technical route for preparing lignin bisphenols by catalytic depolymerization of lignin derivatives with a 1,1-diphenylmethyl structure.

[0007] The specific technical solution of the present invention is as follows: a lignin derivative having a 1,1-diphenylmethyl structure, a transition metal catalyst, a liquid solvent, an acid catalyst, and a hydrogen donor are added to a high-temperature and high-pressure reactor in a certain proportion. After the reactor is sealed, the temperature is raised to the reaction temperature while stirring at a constant speed of 600 rpm. After reaching the reaction temperature and reacting for a certain period of time, the reactor is cooled. The reaction mixture is filtered, concentrated by vacuum distillation, and extracted to obtain a lignin depolymerized oil rich in lignin bisphenols and oligomers.

[0008] In the present invention, the lignin derivative with a 1,1-diphenylmethyl structure is prepared by directing the substitution of phenol and its derivatives for the benzyl hydroxyl groups of the β-O-4 aryl ether bond structure in the lignin raw material; the aromatic ring of the arylating agent, in addition to the hydroxyl group, further contains 0, 1 or 2 substituents, and the substituents are any one of methyl, ethyl, propyl, isopropyl, methoxy, phenoxy, and phenolic hydroxyl groups, or a mixture of two or more thereof. The preferred arylating agents are phenol, p-cresol, guaiacol, and eugenol.

[0009] In the present invention, the preparation process of the lignin derivative having a 1,1-diphenylmethyl structure is as follows:

[0010] 40 g of lignocellulose, 16 g–32 g of an arylating agent, and 400 mL of an 88 wt% aqueous solution of an organic acid were weighed and added to a reactor; the reactor was sealed, heated to 100° C. with stirring, and reacted for 120 min; the reaction mixture was cooled, filtered, the filtrate was collected, and concentrated, and the concentrate was mixed with a reverse solvent (water or an ethanol aqueous solution, with the volume fraction of ethanol in the reverse solvent being 0%–20%) to perform reverse solvent precipitation of aryl lignin; the aryl lignin was filtered and dried to obtain aryl lignin powder; the lignocellulose was any one of poplar, birch, pine, bamboo, crop straw, and reed, or a mixture of two or more thereof; the arylating agent was any one of phenol, p-cresol, guaiacol, and eugenol, or a mixture of two or more thereof; and the organic acid was any one of formic acid, acetic acid, maleic acid, oxalic acid, and p-toluenesulfonic acid, or a mixture of two or more thereof.

[0011] In the present invention, the lignin derivative catalytic depolymerization solvent system is any one of methanol, ethanol, propanol, butanol, isopropanol, dioxane, tetrahydrofuran and water, or a mixture of two or more thereof. The preferred lignin solvent is a methanol / water mixture with a volume ratio of 4:1 to 1:4, and a more preferred volume ratio of 3:1 to 1:1. The mass of the liquid medium is 5-500 times the mass of the lignin derivative, the preferred addition amount is 10-100 times the mass of the lignin derivative, and the more preferred addition amount is 20-50 times the mass of the lignin derivative.

[0012] In the present invention, the acid catalyst of the lignin derivative catalytic depolymerization solvent system is any one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, p-hydroxybenzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, phosphotungstic acid, phosphomolybdic acid, trifluoroacetic acid, zinc chloride, ferric chloride, copper chloride, aluminum chloride and lithium chloride, or a mixture of two or more thereof; the preferred acid catalyst is any one of sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid, or a mixture of two or more thereof; the concentration of the acid catalyst is 0.5-20 g / L, the preferred acid concentration is 1-10 g / L, and the more preferred acid concentration is 2-5 g / L.

[0013] In the present invention, the transition metal selected from the transition metal catalyst is any one of palladium, platinum, ruthenium, nickel, rhodium and iridium, or a mixture of two or more thereof, and the preferred transition metals are palladium and platinum; the carrier selected from the transition metal catalyst is any one of activated carbon, aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide, molybdenum oxide, molybdenum sulfide, tungsten oxide, hydrotalcite, hydroxyapatite and molecular sieve (H-ZSM-5), or a mixture of two or more thereof, and the preferred catalyst carrier is activated carbon, titanium dioxide, molybdenum oxide and molybdenum sulfide; the loading amount of the transition metal on the carrier is 0.1-15wt%, the preferred loading range is 0.5-10wt%, and the more preferred loading range is 2-5wt%; the amount of the transition metal catalyst added is 2-200wt% of the mass of the lignin derivative, the preferred amount of the transition metal catalyst added is 10-80wt%, and the more preferred amount of the transition metal catalyst added is 20-50wt%.

[0014] In the present invention, the hydrogen donor for the catalytic reduction depolymerization is any one of formic acid, methanol, ethanol, isopropanol, glucose, xylose, ethylene glycol, glycerol, and hydrogen, or a mixture of two or more thereof. The preferred hydrogen donors are formic acid, isopropanol, and hydrogen. The preferred amount of formic acid added (based on the mass of lignin) is 50–400 wt%, the preferred amount of propanol added (based on the mass of lignin) is 100–500 wt%, and the preferred hydrogen pressure is 0.2–5 MPa; the more preferred amount of formic acid added (based on the mass of lignin) is 100–300 wt%.

[0015] In the present invention, the catalytic depolymerization reaction conditions of the lignin derivative are reaction temperature of 120-300°C and reaction time of 0.2-48h; the optimal reaction temperature is 160-260°C and the optimal reaction time is 0.5-24h; the more optimal reaction temperature is 180-240°C and the more optimal reaction time is 1-12h.

[0016] The lignin depolymerization oil after catalytic depolymerization is prepared by filtering the reaction mixture after the reaction, distilling under reduced pressure and separating by liquid-liquid extraction.

[0017] In the present invention, after the catalytic depolymerization is completed and the reactor is cooled to room temperature, the reaction mixture is filtered through filter paper to remove the transition metal catalyst, the volatile solvent in the filtrate is removed by reduced pressure rotary evaporation, the concentrated filtrate is subjected to liquid-liquid extraction (dichloromethane:water, 1:1, v / v) three times, the dichloromethane phase is passed through anhydrous sodium sulfate to remove residual water, and the organic solvent is removed by reduced pressure rotary evaporation to prepare bisphenol-rich lignin depolymerized oil.

[0018] This method involves the selective preparation of lignin-based bisphenol compounds with a 1,2-diphenylethyl structure from lignin derivatives containing a 1,1-diphenylmethyl structure using the synergistic catalytic action of a transition metal catalyst and an acid catalyst in a liquid medium. This method achieves targeted depolymerization of lignin by catalyzing the aromatic migration reaction of the 1,1-diphenylmethyl structure. Unlike traditional reactions targeting lignin monophenols as the target product, this method allows for the targeted preparation of bisphenol products in a single step while simultaneously co-producing lignin oligomers, effectively promoting the high-value utilization of lignin.

[0019] The method of the present invention expands the product types of lignin-based bisphenols and promotes the application of catalytic depolymerization of lignin to prepare high-value chemicals, fuels and polymer materials.

[0020] Compared with natural lignin (lignin containing a large number of benzyl hydroxyl groups), the lignin derivatives involved in the present invention (lignin benzyl hydroxyl groups are arylated and replaced by phenol or phenol derivatives to generate 1,1-diphenylmethyl structures) have significantly reduced activity during the catalytic cleavage of β-O-4 aryl ether bonds. Therefore, lignin with a 1,1-diphenylmethyl structure (such as industrial lignin with a self-condensation structure) is generally difficult to achieve high-value catalytic conversion. The present invention utilizes the synergistic effect of acid catalysis and hydrogenation catalysts to achieve the targeted catalytic conversion of the 1,1-diphenylmethyl structure in lignin, highly selectively prepare lignin bisphenol products, and simultaneously produce lignin oligomers. In this process, the acidic additive first catalyzes the 1,2-aryl migration of the lignin aromatic group and breaks the β-O-4 aryl ether connected to the 1,1-diphenylmethyl structure to generate a stilbene-type structure intermediate. Because stilbene intermediates are unstable under high-temperature, acidic conditions and prone to double-bond coupling reactions, the present invention utilizes a hydrogenation catalyst to reduce the stilbene structure to stable 1,2-diphenylethyl bisphenol, thereby improving the selectivity and yield of the bisphenol product. The benzylic carbons in the lignin structural units of the present invention have undergone arylation, significantly reducing the benzylic hydroxyl content. Therefore, the yield of monophenols during the catalytic depolymerization process is significantly lower than that achieved during the traditional catalytic reduction depolymerization of natural lignin. The structural units of the arylated lignin of the present invention contain a small number of C–C bonds, such as β–β, β–5, and β–5. Under the catalytic depolymerization conditions of the present invention, these chemical bonds are relatively stable and do not break, thus enabling the co-production of C–C bond-rich lignin oligomers. The present invention involves the synergistic depolymerization of arylated lignin using an acidic adjuvant and a transition metal catalyst, achieving the selective production of lignin bisphenol products and the co-production of lignin oligomers.

[0021] Compared with the prior art, the present invention has the following innovations and beneficial effects:

[0022] 1. Based on the 1,1-diphenylmethyl structural characteristics of arylated lignin, the present invention designed acid-catalyzed and hydrogenation-catalyzed directional depolymerization pathways, developed a one-pot aromatic migration and stilbene reduction two-step tandem reaction, and prepared bisphenol with a 1,2-diphenylethyl structure. This catalytic conversion route and the 1,2-diphenylethyl bisphenol product are original.

[0023] 2. The present invention realizes the synergistic catalytic depolymerization of arylated lignin by an acidic adjuvant and a transition metal catalyst, and the yield of lignin-based bisphenol products is significantly higher than that reported previously. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 shows the 1H–13C HSQC NMR spectra of phenol, guaiacol, eugenol, and p-cresol arylated lignins;

[0025] FIG2 is a gas chromatogram of the catalytic depolymerization of syringol to arylate lignin to produce monophenols and bisphenols;

[0026] Figure 3 shows the 1H–13C HSQC NMR spectra of four main bisphenols produced by catalytic depolymerization of syringol to arylate lignin;

[0027] Figure 4 is the 1H–13C HSQC NMR spectrum of the oligomer components in the lignin depolymerization oil;

[0028] FIG5 is a gas chromatogram of catalytic decomposition of polyphenol arylation to generate monophenol and bisphenol;

[0029] Figure 6 shows the 1H–13C HSQC NMR spectra of two main bisphenols produced by catalytic decomposition of polyphenol arylation of lignin. DETAILED DESCRIPTION

[0030] To further elaborate and illustrate the present invention, several specific implementation cases are listed below, but the present invention is not limited to the following embodiments.

[0031] In the following examples, Pd / C (5% and 10% loading), Pt / C catalysts (5% and 10% loading), and Ru / C (5% loading) were purchased from Aladdin Biochemical Technology;

[0032] Pd / ZrO2 (1% loading), Pd / WO3 (1% loading), Pd / MoO3 (1% loading), Pd / TiO2 (2% loading), Pd / HZSM-5 (2% loading), and Pt / TiO2 (2% loading) were prepared by impregnation method.

[0033] The preparation method of the impregnation method takes Pd / TiO2 (2% loading) as an example: 1g TiO2 (P25) is dispersed in 20mL of hydrochloric acid aqueous solution dissolved with PdCl2 (palladium chloride) (pH = 1, PdCl2 concentration is 9.6mmol / L, based on 2% Pd mass loading in the catalyst). After stirring at room temperature for 12 hours, it is heated to 110°C and evaporated to dryness. The resulting solid is reduced with hydrogen at 300°C for 4 hours to obtain the catalyst Pd / TiO2 (2% loading). The preparation process of the remaining catalysts is the same as above, except that different PdCl2 concentrations (such as: 4.8mmol / L) and / or different carriers are used, or H2PtCl6 is used instead of PdCl2;

[0034] The lignin derivatives (rich in 1,1-diphenylmethyl structures) described in the following examples are prepared by directing the substitution of benzyl hydroxyl groups with phenol and its derivatives for the β–O–4 aryl ether bond structure in the lignin raw material to produce the corresponding arylated lignin. Figure 1 demonstrates that in the chemical structure of the arylated lignin prepared using the following method, the β–O–4 aryl ether bond signal containing the benzyl hydroxyl group, which is present in natural lignin, essentially disappears, replaced by the aryl ether bond signal with a 1,1-diphenylmethyl structure generated by the substitution of the benzyl hydroxyl group with the aryl group.

[0035] The extraction conditions for phenol aryl lignin were as follows: 40 g of birch flour (20–80 mesh), 32 g of phenol, and 400 mL of 88 wt% formic acid aqueous solution were weighed and added to a high-temperature reactor. The reactor was sealed and stirred at 500 rpm. The temperature was raised to 100°C and the reaction was continued for 120 minutes. After the reactor cooled to room temperature, the reaction mixture was filtered through filter paper. The collected filtrate was concentrated to 150 mL by rotary evaporation. The concentrated solution was then added dropwise to 1000 mL of water, causing the aryl lignin to precipitate. The aryl lignin was filtered through filter paper and oven-dried at 60°C to collect the phenol aryl lignin powder.

[0036] The extraction conditions for p-cresol arylated lignin were as follows: 40 g of bamboo powder (4–40 mesh), 32 g of p-cresol, and 400 mL of 88 wt% formic acid aqueous solution were weighed and added to a high-temperature reactor. The reactor was sealed and stirred at 500 rpm. The temperature was raised to 120°C and the reaction was allowed to proceed for 40 minutes. After the reactor cooled to room temperature, the reaction mixture was filtered through filter paper. The collected filtrate was concentrated to 150 mL by rotary evaporation. The concentrated solution was then added dropwise to 1000 mL of reverse solvent (water / ethanol, 9:1, v / v), resulting in the precipitation of the arylated lignin. The arylated lignin was filtered through filter paper and oven-dried at 60°C to collect the p-cresol arylated lignin powder.

[0037] The extraction conditions for guaiacol arylignin were as follows: 40 g of poplar wood (4–40 mesh), 32 g of guaiacol, and 400 mL of 88 wt% formic acid aqueous solution were weighed and added to a high-temperature reactor. The reactor was sealed and stirred at 500 rpm. The temperature was raised to 120°C and the reaction was continued for 40 minutes. After the reactor cooled to room temperature, the reaction mixture was filtered through filter paper. The collected filtrate was concentrated to ~150 mL by rotary evaporation. The concentrated solution was added dropwise to 1000 mL of reverse solvent (water / ethanol, 9:1, v / v), causing the arylignin to precipitate. The arylignin was filtered through filter paper and dried in an oven at 60°C to collect the guaiacol arylignin powder.

[0038] The preparation conditions for syringol aryl lignin are as follows: 40 g of poplar wood (20–80 mesh), 16 g of syringol, and 400 mL of 88 wt% formic acid aqueous solution were weighed and added to a high-temperature reactor. The reactor was sealed and stirred at 500 rpm. The temperature was raised to 120°C and the reaction was allowed to proceed for 30 minutes. After the reactor cooled to room temperature, the reaction mixture was filtered through filter paper. The collected filtrate was concentrated to ~150 mL by rotary evaporation. The concentrated solution was then added dropwise to 1000 mL of water, causing the aryl lignin to precipitate. The aryl lignin was filtered through filter paper and oven-dried at 60°C to collect the syringol aryl lignin powder.

[0039] The extraction conditions of kraft lignin are as follows: the raw material is poplar wood powder (4–40 mesh), the solution is an aqueous solution containing a final concentration of 10 wt% NaOH and 3 wt% Na2S, the material-liquid mass ratio is 4:1, the cooking temperature is 160°C, and the cooking time is 3 h.

[0040] Enzymatic lignin extraction conditions were as follows: poplar wood flour (4–40 mesh) was treated with a planetary ball mill (ball-to-material ratio of 50:1, rotation speed of 460 rpm) for 24 hours, then treated with commercial cellulase (CTec 3, 50 FPU / g wood flour) in an acetic acid / sodium acetate buffer solution (20 mL / g wood flour) at pH = 4.8 for 48 hours. The enzymatic hydrolysis temperature was 50°C and the shaking speed was 100 rpm. The undissolved residue was collected by filtration and purified with 90 wt% acetic acid solution (20 mL / g residue) at room temperature. The resulting lignin was precipitated in water (10 times the volume of the purified acetic acid solution).

[0041] Example 1

[0042] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% Pd loading on the Pd / C, the same below), 50 g of a 7:3 (v / v) methanol:water mixture (containing 1 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at a constant speed (600 rpm). The temperature was then raised to 200°C and the reaction was allowed to proceed for 24 hours. After the reactor was cooled (to room temperature, the same below), the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C), followed by extraction three times using a 250 mL separatory funnel (extraction agent, dichloromethane: water, 1:1, v / v, each time with 100 mL). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent in the dichloromethane phase was removed by rotary evaporation under reduced pressure (~40°C) to prepare bisphenol-rich lignin depolymerized oil.

[0043] The yields of monophenols (primarily phenol, guaiacol, 4-alkylguaiacol, eugenol, 4-alkyleugenol, etc., where the alkyl carbon number is not more than 3) and bisphenols (primarily 3-(4-hydroxy-3-methoxyphenethyl)-2,6-dimethoxyphenol, 4-(4-hydroxy-3-methoxyphenethyl)-2,6-dimethoxyphenol, 3-(4-hydroxy-3,5-dimethoxyphenethyl)-2,6-dimethoxyphenol, 3-(4-hydroxy-3,5-dimethoxyphenethyl)-2,6-dimethoxyphenol, and 4-(4-hydroxy-3,5-dimethoxyphenethyl)-2,6-dimethoxyphenol) in the lignin depolymerization oil were quantitatively analyzed by an Agilent 7890A gas chromatograph. The gas chromatogram is shown in Figure 2. The yield of lignin depolymerization oil is the percentage of the mass of lignin depolymerization oil to the mass of aromatized lignin (raw material). The yield of lignin oligomers (mainly oligomeric lignin products with a molecular weight of ∼400–900 g / mol, in which the aromatic units of lignin oligomers are mainly connected by C–C bonds) was calculated by the difference method, which was equal to the yield of lignin depolymerization oil minus the total yield of monophenols and bisphenols.

[0044] Example 2

[0045] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was then raised to 180°C and the reaction was continued for 12 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0046] The lignin depolymerized oil sample was separated by preparative chromatography (the stationary phase was 200–300 mesh silica gel, and the eluent was a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:4). The 2D NMR spectra of the four main bisphenols are shown in Figure 3. The results show that the lignin bisphenol has a 1,2-diphenylethyl bridge structure. BP2 bisphenol crystals and terephthaloyl chloride can be used to synthesize polyarylate plastics according to the method described in the literature (Green Chem., 2018, 20, 1050-1058). The weight-average molecular weight of the polymer is about 30 kg / mol and has good thermal stability (T d5％ 390℃, T dmax is 425℃).

[0047] The lignin depolymerized oil sample was subjected to solvent reflux extraction to separate the monophenol and bisphenol components from the lignin oligomer component. This extraction was performed using a Soxhlet apparatus with n-hexane as the solvent at a reflux temperature of 100°C. The 2D NMR spectrum of the lignin oligomer component is shown in Figure 4. The results indicate that the aromatic structural units within the lignin oligomer component are primarily linked by C–C bonds, resulting in a relatively rigid chemical structure. This allows for the preparation of epoxy resins with a rigid backbone structure via epoxidation.

[0048] Example 3

[0049] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0050] Example 4

[0051] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 8 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0052] Example 5

[0053] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 10 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was then raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0054] Example 6

[0055] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 10 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was then raised to 160°C and the reaction was continued for 24 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0056] Example 7

[0057] 2 g of p-cresol-arylated lignin, 1 g of Pd / ZrO2 (1 wt% Pd loading in the Pd / ZrO2), 50 g of a methanol:water (2:1, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was then raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0058] Example 8

[0059] 2 g of p-cresol-arylated lignin, 1 g of Pd / WO3 (1 wt% loading), 50 g of a methanol:water (2:1, v / v) mixture (containing 10 g / L hydrochloric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 220°C and the reaction was continued for 8 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0060] Example 9

[0061] 1 g of phenol-arylated lignin, 0.5 g of Pd / MoO3 (1 wt% Pd loading in the Pd / MoO3), 50 g of a methanol:water (2:1, v / v) mixture (containing 10 g / L phosphoric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was then raised to 240°C and the reaction was continued for 2 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times with a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0062] Example 10

[0063] 1 g of phenol-arylated lignin, 0.5 g of Pd / TiO2 (2 wt% loading), 50 g of a methanol:water (2:1, v / v) mixture (containing 5 g / L sulfuric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0064] Example 11

[0065] 1 g of phenol-arylated lignin, 0.5 g of Pd / H-ZSM-5 (2 wt% Pd loading in Pd / H-ZSM-5), 50 g of a methanol:water (2:1, v / v) mixture (containing 1 g / L hydrochloric acid), and 200 wt% (based on lignin weight) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was then raised to 240°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0066] Example 12

[0067] 1 g of phenol-arylated lignin, 0.5 g of Ru / C (5 wt% loading), 50 g of a methanol:water (2:1, v / v) mixture (containing 10 g / L hydrochloric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 220°C and the reaction was continued for 8 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0068] Example 13

[0069] 2 g of phenol-arylated lignin, 1 g of Pt / C (5 wt% loading), 50 g of a methanol:water (4:1, v / v) mixture (containing 5 g / L sulfuric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was then raised to 180°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0070] Example 14

[0071] 1 g of phenol-arylated lignin, 0.5 g of Pt / C (5 wt% loading), 50 g of a methanol:water (3:1, v / v) mixture (containing 5 g / L sulfuric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 8 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0072] Example 15

[0073] 1 g of phenol-arylated lignin, 0.5 g of Pt / TiO2 (2 wt% Pd loading in the Pd / TiO2), 50 g of a methanol:water (1:1, v / v) mixture (containing 5 g / L sulfuric acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 220°C and the reaction was continued for 1 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times with a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. The quantitative analysis of the lignin depolymerized oil is the same as in Example 1.

[0074] Example 16

[0075] 1 g of phenol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (1:3, v / v) mixture (containing 5 g / L sulfuric acid), and 50 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0076] Example 17

[0077] 1 g of phenol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (1:4, v / v) mixture (containing 5 g / L sulfuric acid), and 100 wt% (based on lignin mass) formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 160°C and the reaction was continued for 12 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0078] Example 18

[0079] 1 g of phenol-arylated lignin, 0.5 g of Pd / C (10 wt% Pd loading on the Pd / C), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L methanesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was then raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0080] Example 19

[0081] 5 g of phenol-arylated lignin, 2.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 400 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0082] Example 20

[0083] 2 g of phenol-arylated lignin, 1 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 300 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0084] Example 21

[0085] 1.5 g of phenol-arylated lignin, 0.75 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0086] Example 22

[0087] 1 g of phenol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1. The quantitative analysis of the lignin depolymerized oil was the same as in Example 1. The gas chromatograms of the monophenols and bisphenols in the lignin depolymerized oil are shown in Figure 5. The 2D NMR spectra of the two main bisphenols (4-(4-hydroxyphenethyl)-2-methoxyphenol and 4-(4-hydroxyphenethyl)-2,6-dimethoxyphenol) are shown in Figure 6. The results show that the lignin bisphenols have a 1,2-diphenylethyl bridged structure.

[0088] Example 23

[0089] 0.5 g of phenol-arylated lignin, 0.25 g of Pd / C (5 wt% loading), 50 g of a methanol:water (3:1, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. The quantitative analysis of lignin depolymerized oil was the same as in Example 1.

[0090] Example 24

[0091] 1 g of phenol-arylated lignin, 0.1 g of Pd / C (10 wt% Pd loading on the Pd / C), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and stirred at 600 rpm. The temperature was then raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil.

[0092] Example 25

[0093] 1 g of phenol-arylated lignin, 0.25 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0094] Example 26

[0095] 1 g of phenol-arylated lignin, 0.8 g of Pd / C (10 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0096] Example 27

[0097] 2 g of guaiacol-arylated lignin, 1 g of Pt / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0098] Example 28

[0099] 2 g of guaiacol-arylated lignin, 1 g of Pt / C (10 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of isopropanol were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0100] Example 29

[0101] 2 g of guaiacol-arylated lignin, 1 g of Pt / C (10 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid), and 400 wt% (based on lignin mass) of isopropanol were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0102] Example 30

[0103] 1 g of guaiacol-arylated lignin, 0.5 g of Pt / C (5 wt% loading), and 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid) were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and filled with 0.5 MPa of hydrogen at room temperature. After constant stirring (600 rpm), the temperature was raised to 220°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0104] Example 31

[0105] 1 g of guaiacol-arylated lignin, 0.5 g of Pt / C (5 wt% loading), and 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L p-toluenesulfonic acid) were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon, and filled with 2 MPa of hydrogen at room temperature. After constant stirring (600 rpm), the temperature was raised to 220°C and the reaction was allowed to proceed for 4 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil rich in bisphenols. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0106] Example 32

[0107] 1 g of syringol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L tungstic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 6 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0108] Example 33

[0109] 1 g of syringol-arylated lignin, 0.5 g of Pt / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 5 g / L tungstic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0110] Example 34

[0111] 1 g of phenol-arylated lignin, 0.5 g of Pt / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixed solvent, 0.3 g of tungsten trioxide solid acid catalyst, and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was continued for 6 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent removed by rotary evaporation under reduced pressure (~40°C) to produce a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0112] Example 35

[0113] 1 g of phenol-arylated lignin, 0.5 g of Pt / WO3 (1 wt% loading), 50 g of a methanol:water (7:3, v / v) mixed solvent, and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper. The filtrate was concentrated by rotary evaporation under reduced pressure (~40°C) and then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate and the organic solvent removed by rotary evaporation under reduced pressure (~40°C) to prepare a bisphenol-rich lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0114] Comparative Example 1

[0115] 1 g of kraft lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0116] Comparative Example 2

[0117] 1 g of enzymatically hydrolyzed lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0118] Comparative Example 3

[0119] 1 g of phenol-arylated lignin, 50 g of a methanol:water (7:3, v / v) mixture (containing 2 g / L p-toluenesulfonic acid), and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin-rich depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0120] Comparative Example 4

[0121] 1 g of phenol-arylated lignin, 0.5 g of Pd / C (5 wt% loading), 50 g of a methanol:water (7:3, v / v) mixture, and 200 wt% (based on lignin mass) of formic acid were weighed and added to a high-temperature, high-pressure reactor. The reactor was sealed, purged with argon gas, and stirred at 600 rpm. The temperature was raised to 200°C and the reaction was allowed to proceed for 6 h. After cooling, the reaction mixture was filtered through filter paper, and the filtrate was concentrated by rotary evaporation under reduced pressure (~40°C). The mixture was then extracted three times using a 250 mL separatory funnel (extractant: dichloromethane:water, 1:1, v / v, 100 mL each time). The dichloromethane phase was dried over anhydrous sodium sulfate, and the organic solvent was removed by rotary evaporation under reduced pressure (~40°C) to prepare a lignin depolymerized oil. Quantitative analysis of the lignin depolymerized oil was performed as in Example 1.

[0122] Table 1. Preparation of monophenols, bisphenols, and lignin oligomers by catalytic depolymerization of lignin samples

[0123] Note: The yield calculations are based on the mass of the aromatized lignin sample or the extracted lignin sample.

[0124] As can be seen from Table 1, the method of catalytic depolymerization of 1,1-diphenylmethyl lignin derivatives disclosed herein effectively reduces monophenol yields, selectively produces lignin bisphenols, and simultaneously co-produces lignin oligomers. Aromatized lignin prepared from eugenol, p-cresol, phenol, and guaiacol undergoes depolymerization under the catalytic depolymerization conditions described herein, efficiently producing bisphenols containing a 1,2-diphenylethyl structure. Compared to Comparative Example 1 (kraft lignin) and Comparative Example 2 (enzymatically hydrolyzed lignin), Example 2 (eugenol arylated lignin) achieves a 910%–6400% increase in lignin bisphenol yield under the same catalytic depolymerization conditions; Example 22 (phenol arylated lignin) achieves a 1100%–8000% increase in lignin bisphenol yield under the same catalytic depolymerization conditions.

[0125] In the catalytic depolymerization process of the present invention, acid catalysts and transition metal catalysts are key factors affecting the catalytic depolymerization of 1,1-diphenylmethyl lignin derivatives to produce lignin bisphenols. Comparative Example 3 shows that when the transition metal catalyst is not used during the catalytic depolymerization process, the yield of lignin monophenols does not change significantly, but the yield of lignin bisphenols drops to 1.5%. This is mainly due to the instability of the bisphenol products (containing double bonds) produced by depolymerization under acidic conditions, resulting in a significant decrease in the bisphenol yield due to condensation reactions. Comparative Example 4 shows that when the acid catalyst is not used during the catalytic depolymerization process, the yields of lignin monophenols, lignin bisphenols, and lignin oligomers all decrease significantly. This is mainly due to the inability of transition metal catalysts to depolymerize lignin derivatives with 1,1-diphenylmethyl structures under neutral conditions. These results demonstrate that this method for catalytic depolymerization of lignin derivatives can achieve a one-step, targeted production of bisphenol compounds while simultaneously co-producing lignin oligomers, promoting the industrial application of catalytic depolymerization of lignin to produce high-value chemicals, fuels, and polymer materials.

[0126] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the basic principles of the chemical reactions involved in the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for catalytic depolymerization of lignin derivatives, characterized in that: The lignin derivative with a 1,1-diphenylmethyl structure is used in a liquid medium to prepare lignin depolymerized oil rich in 1,2-diphenylethyl structure bisphenol and lignin oligomers through the synergistic catalytic action of a transition metal catalyst, a hydrogen donor and an acid catalyst.

2. The method according to claim 1, characterized in that: The lignin derivative with a 1,1-diphenylmethyl structure is a selectively α-arylated modified lignin (as shown in the raw material structural formula on the left side of Formula 1); in the structure of the lignin derivative (as shown in the raw material structural formula on the left side of Formula 1), Ar1 is an aromatic ring originally present in the lignin, and contains 0, 1 or 2 methoxy groups at the ortho position of the aromatic ring hydroxyl group on the aromatic ring; Ar2 is an aromatic ring of an arylating agent, and in addition to a hydroxyl group, the aromatic ring also contains 0, 1 or 2 substituents, and the substituents are any one or a mixture of two or more of methyl, ethyl, propyl, isopropyl, methoxy, phenoxy, and phenolic hydroxyl groups, and the preferred arylating agent is any one or more of phenol, p-methylphenol, guaiacol, and syringol; R1 is a hydroxyl group or an acyl group; Formula 1. Schematic diagram of the reaction of catalytic depolymerization of lignin derivatives with 1,1-diphenylmethyl structure to produce 1,2-diphenylethyl structure bisphenol products 1,2-diphenylethyl structure bisphenol product (as shown in the product structure on the right side of Formula 1), wherein there is an ethyl bridge structure between the aromatic ring Ar1 and the aromatic ring Ar2, and the substituents R2 and R3 of the ethyl are independently hydrogen, methyl and hydroxymethyl respectively; Ar1 ​​is an aromatic ring originally present in lignin, and the ortho position of the aromatic ring hydroxyl contains 0 or 1 or 2 methoxy groups; Ar2 is an aromatic ring of an arylating agent, which contains 0 or 1 or 2 substituents in addition to a hydroxyl group, and the substituents are any one or a mixture of two or more of methyl, ethyl, propyl, isopropyl, methoxy, phenoxy, and phenolic hydroxyl groups, and the preferred arylating agent is any one or more of phenol, p-methylphenol, guaiacol, and eugenol; R1 is a hydroxyl group or an acyl group.

3. The method according to claim 1, characterized in that: The lignin derivative with a 1,1-diphenylmethyl structure is a selectively α-arylated modified lignin (as shown in the raw material structure on the left side of Formula 1), which is prepared by directing the substitution of the benzyl hydroxyl group in the β-O-4 aryl ether bond structure in the lignin raw material by an arylation agent, and retains the β-O-4 aryl ether bond structure of the natural lignin (as shown in Formula 2); In the structure of the lignin derivative (the raw material structure on the left side as shown in Formula 1), Ar1 is an aromatic ring originally present in lignin, and contains 0, 1 or 2 methoxy groups at the ortho position of the aromatic ring hydroxyl group on the aromatic ring; Ar2 is an aromatic ring of an arylating agent, and contains 0, 1 or 2 substituents on the aromatic ring in addition to the hydroxyl group, and the substituents are any one or a mixture of two or more of methyl, ethyl, propyl, isopropyl, methoxy, phenoxy, and phenolic hydroxyl groups, and the preferred arylating agent is any one or more of phenol, p-methylphenol, guaiacol, and eugenol; R1 is a hydroxyl group or an acyl group (the acyl group is derived from an organic acid solvent such as formic acid, acetic acid, etc., in the preparation process of the lignin derivative); Formula 2. Schematic diagram of the reaction for preparing lignin derivatives with 1,1-diphenylmethyl structure by selective α-arylation 4. The method according to claim 1, 2 or 3, characterized in that: The preparation process of the lignin derivative having a 1,1-diphenylmethyl structure is as follows: Weigh 40-80g of lignocellulose, 16-40g of arylation reagent, and 400mL of 60-95wt% organic acid aqueous solution, and add them into a reactor; after the reactor is sealed, heat it to 80-140°C while stirring, and react for 30-180min; after cooling, the reaction mixture is filtered, the filtrate is collected and concentrated, and the concentrate is mixed with a reverse solvent (water or ethanol aqueous solution, the volume fraction of ethanol in the reverse solvent is 0%-20%) to perform reverse solvent precipitation of arylated lignin, and the arylated lignin is filtered and dried to obtain arylated lignin powder; The wood cellulose is any one of poplar, birch, pine, bamboo, crop straw, and reed, or a mixture of two or more thereof; The arylating agent is any one of phenol, cresol, guaiacol, eugenol and catechol or a mixture of two or more thereof; the organic acid is any one of formic acid, acetic acid, maleic acid, oxalic acid and p-toluenesulfonic acid or a mixture of two or more thereof.

5. The method according to claim 1, characterized in that: The liquid medium for the catalytic depolymerization reaction is any one of dioxane, tetrahydrofuran, methanol, ethanol, propanol, butanol, isopropanol, glycerol, toluene and water, or a mixture of two or more thereof; the preferred solvent for the catalytic depolymerization reaction of lignin is a methanol / water mixture with a volume ratio of 4:1 to 1:4, and a more preferred volume ratio of 3:1 to 1:1; The mass of the liquid medium is 5-500 times the mass of the lignin derivative, the optimal amount is 10-100 times the mass of the lignin derivative, and the more optimal amount is 20-50 times the mass of the lignin derivative.

6. The method according to claim 1, characterized in that: The acid catalyst is any one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, p-hydroxybenzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, phosphotungstic acid, phosphomolybdic acid, tungstic acid, tungstic acid, tungsten trioxide, trifluoroacetic acid, zinc chloride, ferric chloride, cupric chloride, aluminum chloride and lithium chloride, or a mixture of two or more thereof; the preferred acid catalyst is any one of sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid, or a mixture of two or more thereof; the concentration of the acid catalyst in the liquid medium is 0.5-20 g / L, the preferred acid catalyst concentration is 1-10 g / L, and the more preferred acid concentration is 2-5 g / L.

7. The method according to claim 1, characterized in that: The transition metal selected as the transition metal catalyst in the catalytic depolymerization reaction is any one of palladium, platinum, ruthenium, nickel, rhodium and iridium, or a mixture of two or more thereof; the transition metal catalyst is a supported catalyst, and the carrier selected as the transition metal catalyst is any one of activated carbon, aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide, molybdenum oxide, molybdenum sulfide, tungsten oxide, hydrotalcite, hydroxyapatite and molecular sieve (H-ZSM-5) or a mixture of two or more thereof; the loading amount of the active component transition metal on the carrier is 0.1-15wt%, the preferred loading range is 0.5-10wt%, and the more preferred loading range is 2-5wt%; The amount of the transition metal catalyst used is 2-100wt% of the mass of the lignin derivative, the preferred amount of the transition metal catalyst used is 10-80wt%, and the more preferred amount of the transition metal catalyst used is 20-50wt% of the mass of the lignin derivative.

8. The method according to claim 1, characterized in that: The hydrogen donor for the catalytic depolymerization reaction is any one of formic acid, methanol, ethanol, isopropanol, glucose, xylose, ethylene glycol, glycerol, and hydrogen, or a mixture of two or more thereof; when the hydrogen donor is not hydrogen, the amount of the hydrogen donor (based on the mass of the lignin derivative) is 50-400wt%; when the hydrogen donor is hydrogen, the hydrogen pressure during the reaction is 0.1-8MPa; The preferred hydrogen donor is any one or more of formic acid, isopropanol and hydrogen, the preferred formic acid dosage (based on the mass of lignin) is 50-400wt%, the preferred propanol dosage (based on the mass of lignin) is 100-500wt%, the preferred hydrogen pressure during the reaction process is 0.2-5MPa; the more preferred formic acid addition amount (based on the mass of lignin derivative) is 100-300wt%.

9. The method according to any one of claims 1 to 8, characterized in that: The reaction conditions for the catalytic depolymerization of the lignin derivative are as follows: a reaction temperature of 120-300°C and a reaction time of 0.1-48h; a preferred reaction temperature of 160-260°C and a preferred reaction time of 0.5-24h; and a more preferred reaction temperature of 180-240°C and a more preferred reaction time of 1-12h.

10. The lignin depolymerized oil rich in 1,2-diphenylethyl structure bisphenol and lignin oligomers obtained by the method according to any one of claims 1 to 9.

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