Method for extracting lignin from lignocellulose

Abstract

The invention discloses a method for extracting lignin from lignocellulose. The method comprises the following steps: 1) cleaning and drying straws, crushing and sieving to obtain a lignocellulose raw material; 2) adding the lignocellulose raw material into a hydrogen peroxide aqueous solution, soaking for 1-2 hours, adding ethylenediamine, and reacting for 1 hour at 25 DEG C or 120 DEG C to obtain a reactant; (3) washing each gram of reactants with deionized water, and carrying out solid-liquid separation to obtain solids and washing liquid; and adding absolute ethyl alcohol into the water washing liquid, generating a precipitate, centrifuging, taking a liquid part, carrying out rotary evaporation and freeze drying to obtain lignin, and storing at-20 DEG C. Lignin obtained through the first method is low in molecular weight and more uniform in lignin chain length, more nitrogen-containing functional groups are grafted in lignin, and lignin obtained through the second method is high in fluorescence intensity and becomes an ideal raw material for manufacturing fluorescent materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of lignin extraction from biomass, and particularly relates to a method for extracting high-quality lignin from lignocellulose. Background Art

[0002] Due to the development of biorefining, lignocellulosic biomass has proven to be a game-changer for human dependence on fossil resources and is considered a good carrier for green energy and the development of clean chemicals. Lignocellulose is mainly composed of three major components: cellulose, hemicellulose, and lignin. Lignin is the second most abundant renewable aromatic polymer in nature, accounting for 15% - 30% of lignocellulosic biomass, and has great potential to replace petrochemical raw materials to prepare high-value products (such as carbon fiber, antioxidants, biofuels, etc.). However, due to the tight binding of lignin with cellulose and hemicellulose through complex chemical bonds (ester bonds, ether bonds) and physical interactions (hydrogen bonds, hydrophobic interactions), forming a dense plant cell wall structure, its efficient separation and structure retention still face major challenges. Traditional lignin extraction methods (such as the sulfate method and the sulfite method) usually use strong acids, strong bases, or high-temperature and high-pressure treatments. Although the extraction efficiency is relatively high, they often lead to irreversible condensation or degradation of lignin, resulting in a wider molecular weight distribution and a reduction in active functional groups (such as phenolic hydroxyl groups), thereby limiting its high-value utilization. In addition, these methods also have problems such as large environmental pollution, high energy consumption, and difficult solvent recovery, and it is difficult to meet the requirements of green chemistry and sustainable development.

[0003] Currently, there is no report on using alkaline hydrogen peroxide and ethylenediamine to co-treat lignocellulose to extract lignin. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for extracting lignin from lignocellulose.

[0005] The technical solution of the present invention is outlined as follows:

[0006] The first method for extracting lignin from lignocellulose includes the following steps:

[0007] 1) Wash and dry the straw, and pulverize and sieve it to obtain lignocellulose raw materials;

[0008] 2) Immerse the lignocellulose raw materials in an aqueous hydrogen peroxide solution for 1 - 2 h, add ethylenediamine, and react at 25°C for 1 h to obtain reactant 1;

[0009] 3) Wash according to the ratio of 30 - 50 mL of deionized water per gram of reactant 1, perform solid - liquid separation to obtain solid 1 and washing solution 1; add absolute ethanol according to the volume ratio of washing solution 1 to absolute ethanol of 1:2 - 4, precipitate will form, centrifuge, take the liquid part for rotary evaporation and freeze - drying to obtain lignin 1, and store it at - 20°C.

[0010] Preferably, the straw is corn straw, wheat straw, rice straw or sorghum straw.

[0011] Preferably, the particle size of the lignocellulose raw material obtained by crushing and sieving is between 20 mesh and 80 mesh.

[0012] Step 2) is preferably: Add 3 g of the lignocellulose raw material to 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 3% - 7% and soak for 1 - 2 h, add 2.1 - 3.5 mL of ethylenediamine, and react at 25°C for 1 h to obtain reactant 1.

[0013] The second method for extracting lignin from lignocellulose includes the following steps:

[0014] 1) Wash the straw, dry it, crush and sieve to obtain the lignocellulose raw material;

[0015] 2) Add the lignocellulose raw material to an aqueous hydrogen peroxide solution and soak for 1 - 2 h, add ethylenediamine, and react at 120°C for 1 h to obtain reactant 2;

[0016] 3) Wash according to the ratio of 30 - 50 mL of deionized water per gram of reactant 2, perform solid - liquid separation to obtain solid 2 and washing solution 2; add absolute ethanol according to the volume ratio of washing solution 2 to absolute ethanol of 1:2 - 4, precipitate will form, centrifuge, take the liquid part for rotary evaporation and freeze - drying to obtain lignin 2, and store it at - 20°C.

[0017] Preferably, the straw is corn straw, wheat straw, rice straw or sorghum straw.

[0018] Preferably, the particle size of the lignocellulose raw material obtained by crushing and sieving is between 20 mesh and 80 mesh.

[0019] Step 2) is preferably: Add 3 g of the lignocellulose raw material to 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 3% - 7% and soak for 1 - 2 h, add 2.1 - 3.5 mL of ethylenediamine, and react at 120°C for 1 h to obtain reactant 2.

[0020] Advantages of the present invention:

[0021] 1. The lignin 1 obtained by the first method of the present invention (the reaction temperature in step (2) is 25 °C) has a low molecular weight, with a weight-average molecular weight (Mw) and a number-average molecular weight (Mn) of 2531 and 1516 Da, respectively; the lignin 1 has a more uniform chain length, with a polydispersity index (PDI) of 1.669; more nitrogen-containing functional groups are grafted onto the lignin 1, and the nitrogen content reaches 14.18%.

[0022] 2. The lignin 2 obtained by the second method of the present invention (the reaction temperature in step (2) is 120 °C) has a high fluorescence intensity, which is 3.8 times higher than that of alkali lignin, making it an ideal raw material for manufacturing fluorescent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Two-dimensional NMR spectra of lignin extracted by different methods.

[0024] Figure 2 Fluorescence intensities of lignin extracted by different methods. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below in conjunction with specific embodiments.

[0026] The corn straw, wheat straw, rice straw or sorghum straw used in this experiment were all purchased from Tianjin, China.

[0027] Example 1

[0028] The corn straw was washed 3 times with tap water and then placed in an oven at 65 °C for three days of drying. The dried raw material was crushed and sieved, and the particle size between 20 mesh and 80 mesh was taken as the lignocellulose raw material, which was collected in a sealed plastic bag.

[0029] The cleaning, drying, crushing and sieving of wheat straw, rice straw and sorghum straw were the same as the above treatment of corn straw.

[0030] Example 2

[0031] Preparation of native enzymatically hydrolyzed lignin (abbreviated as E-L, control):

[0032] First, the lignocellulose raw material prepared in Example 1 was ground in a vertical planetary ball mill at 400 rpm for 4 h. To better dissipate heat, the instrument was turned off for 10 min every half hour during this period. The ground sample was treated with cellulase CTec3 (0.2 mL / g lignocellulose raw material) and hemicellulase HTec3 (0.1 mL / g of lignocellulosic raw material) was reacted at 50 °C for 24 h with a biomass loading of 10% g / mL. After the reaction, it was centrifuged, and the obtained solid was thoroughly washed with distilled water and freeze-dried. The freeze-dried solid was extracted with a 96% v / v dioxane aqueous solution at 250 rpm at room temperature for 48 h. After extraction, it was centrifuged, and the supernatant was concentrated using a rotary evaporator and then freeze-dried. The crude lignin obtained after freeze-drying was dissolved in an aqueous acetic acid solution with a volume concentration of 90%, and a large amount of distilled water at 4 °C was added to precipitate lignin. Finally, the precipitate was freeze-dried to obtain cellulolytic enzyme lignin (E-L), which was used as a control for native lignin and stored at -20 °C.

[0033] Example 3

[0034] Preparation of alkali lignin (abbreviated as NaOH-L, control):

[0035] Weigh 15 g of the lignocellulosic raw material prepared in Example 1 and place it in a reaction kettle;

[0036] Weigh 1.5 g of NaOH and dissolve it in 135 mL of deionized water to prepare a sodium hydroxide aqueous solution, which is then added to the reaction kettle and mixed evenly with the lignocellulosic raw material. The reaction kettle is placed in an oil bath and reacted at 130 °C for 30 min. After the reaction, the reaction kettle is taken out, cooled to room temperature with water, and the reactant is taken out. Then it is filtered with a gauze, and the liquid is collected to obtain a hydrolysis solution rich in lignin, denoted as APL. Hydrochloric acid aqueous solution is added to APL until the pH is less than 2, and precipitation occurs. After centrifugation, the precipitate is freeze-dried to obtain alkali lignin, denoted as NaOH-L, and stored at -20 °C.

[0037] Example 4

[0038] A method for extracting lignin from lignocellulose, comprising the following steps:

[0039] 1) The corn stover was operated according to Example 1 to obtain lignocellulosic raw material;

[0040] 2) 3 g of the lignocellulosic raw material was added to 7 mL of a 5% hydrogen peroxide aqueous solution and soaked for 1 h, 2.8 mL of ethylenediamine was added, and the reaction was carried out at 25 °C for 1 h to obtain Reactant 1;

[0041] 3) Wash according to the ratio of 40 mL of deionized water per gram of reactant 1, separate the solid and liquid to obtain solid 1 and washing solution 1; add absolute ethanol according to the volume ratio of washing solution 1 to absolute ethanol of 1:3, precipitate is formed, centrifuge at 12,000 rpm for 10 min, take the liquid part for rotary evaporation and freeze-drying to obtain lignin 1, denoted as 25 °C H2O2-EDA-L, and store it at -20 °C.

[0042] Determination of lignin molecular weight:

[0043] Take 1 mL of the washing solution 1 of this example, centrifuge at 12,000 rpm for 5 min, after centrifugation, absorb the liquid and filter it through a 0.22 μm aqueous filter membrane for sample preparation, use a high-performance liquid system (Waters e2695) equipped with a 2489 UV / Vis detector to determine the molecular weight of the lignin sample, and the main parameters include number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI). The detection wavelengths are 254 nm and 280 nm, the chromatographic column is a TSKgel GMPWXL gel chromatographic column with 7.8 mm × 30 cm (L.×I.D.), the temperature of the column oven is set at 30 °C, the mobile phase uses 0.1 M NaOH aqueous solution, and the flow rate is 0.5 mL / min. The third-order fitting standard curve between molecular weight and retention time is calculated through the determination of monodisperse polystyrene standard SPS (210 - 17000 Da) and guaiacylglycerol-β-guaiacyl ether, and the results are shown in Table 1.

[0044] As can be seen from Table 1, the number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI) of lignin 1 (25 °C H2O2-EDA-L) are 1516 Da, 2531 Da and 1.669 respectively.

[0045] Determination of element content in lignin:

[0046] Elemental analysis of natural enzymatic hydrolysis lignin (E-L) and the lignin extracted in this example (25 °C H2O2-EDA-L) was carried out by X-ray photoelectron spectrometer (ESCALAB 250Xi), and the results are shown in Table 2. As can be seen from Table 2, the nitrogen content of lignin 1 (25 °C H2O2-EDA-L) is 14.18%.

[0047] Determination of lignin chemical structure:

[0048] Take about 70 mg of the lignin extracted in this example, dissolve it in 0.6 mL of deuterated dimethyl sulfoxide (DMSO-d6) with tetramethylsilane (TMS) as the internal standard, then put it into an EP tube, seal it and ultrasonicate until homogeneous. Perform two-dimensional nuclear magnetic spectroscopy analysis, and the results are shown in Figure 1 . (Two-dimensional nuclear magnetic spectroscopy of the extracted lignin structure. β-O-4-alkyl aryl ether (A); γ-OH of β-O-4-aryl ether is acylated with acetate or p-coumarate (A'); resinol (β-β, B); phenylcoumarin (β-5, C); guaiacyl unit (G); p-hydroxyphenyl unit (H); syringyl unit (S); oxidized syringyl unit with a carbonyl at Cα (S'); condensed syringyl unit (S(condensed)); amine groups (AG and AG'); Schiff base (SB); p-coumaric acid (pCA); ferulic acid (FA); p-coumaramide (pCAM); ferulamide (FAM).)

[0049] It can be seen from Figure 1 that signals of p-coumaramide (pCAM), ferulamide (FAM) and Schiff base (SB) appeared in lignin 1 (25 °C H2O2-EDA-L), indicating that nitrogen-containing functional groups were successfully introduced into lignin.

[0050] Determination of lignin fluorescence intensity:

[0051] Dissolve lignin 1 extracted in this example in deionized water to prepare a 0.2 g / L solution, and use a fluorescence spectrophotometer (Hitachi F-2500) with a xenon lamp as the excitation light source to measure its two-dimensional fluorescence spectrum. The ultraviolet-visible absorption spectrum of the lignin solution was analyzed by a Hitachi ultraviolet-visible spectrophotometer (UH5300). Specifically, add 2 mL of the prepared solution into a cuvette, place it under 365 nm ultraviolet light to observe its fluorescence characteristics, and the results are shown in Figure 2 .

[0052] It can be seen from Figure 2 that lignin 1 (25 °C H2O2-EDA-L) shows weak blue-green fluorescence, and its fluorescence intensity is higher than that of alkali lignin (NaOH-L).

[0053] Example 5

[0054] A method for extracting lignin from lignocellulose, comprising the following steps:

[0055] 1) Refer to the operation of Example 1 for wheat straw to obtain lignocellulose raw materials;

[0056] 2) Add 3 g of the lignocellulosic raw material to 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 3% and soak for 2 h. Then add 3.5 mL of ethylenediamine and react at 25 °C for 1 h to obtain Reactant 1;

[0057] 3) Wash according to the ratio of 30 mL of deionized water per gram of Reactant 1, perform solid-liquid separation to obtain Solid 1 and Wash Solution 1. Add absolute ethanol according to the volume ratio of Wash Solution 1 to absolute ethanol of 1:2. Precipitation occurs. Centrifuge at 12000 rpm for 10 min. Take the liquid part for rotary evaporation and freeze-drying to obtain Lignin 1, and store it at -20 °C.

[0058] Example 6

[0059] A method for extracting lignin from lignocellulose, comprising the following steps:

[0060] 1) Refer to the operation of Example 1 for rice straw (it can also be sorghum straw) to obtain the lignocellulosic raw material;

[0061] 2) Add 3 g of the lignocellulosic raw material to 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 7% and soak for 1.5 h. Then add 2.1 mL of ethylenediamine and react at 25 °C for 1 h to obtain Reactant 1;

[0062] 3) Wash according to the ratio of 50 mL of deionized water per gram of Reactant 1, perform solid-liquid separation to obtain Solid 1 and Wash Solution 1. Add absolute ethanol according to the volume ratio of Wash Solution 1 to absolute ethanol of 1:4. Precipitation occurs. Centrifuge at 12000 rpm for 10 min. Take the liquid part for rotary evaporation and freeze-drying to obtain Lignin 1, and store it at -20 °C.

[0063] Experimental results show that for the lignin extracted by the methods of Examples 5 and 6, after measurement, the detection results of its lignin molecular weight, element content in lignin, lignin chemical structure, and lignin fluorescence intensity are similar to the above detection results of Example 4.

[0064] Example 7

[0065] A method for extracting lignin from lignocellulose, comprising the following steps:

[0066] 1) Refer to the operation of Example 1 for corn straw to obtain the lignocellulosic raw material;

[0067] 2) Add 3 g of the lignocellulosic raw material to 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 5% and soak for 1 h. Then add 2.8 mL of ethylenediamine and react at 120 °C for 1 h to obtain Reactant 2;

[0068] 3) Wash according to the ratio of 40 mL of deionized water per gram of reactant 2, separate the solid and liquid to obtain solid 2 and washing liquid 2; add absolute ethanol according to the volume ratio of washing liquid 2 to absolute ethanol of 1:3, precipitate will form, centrifuge at 12000 rpm for 10 min, take the liquid part for rotary evaporation and freeze-drying to obtain lignin 2, denoted as 120 °C H2O2-EDA-L, and store it at -20 °C.

[0069] Determination of lignin molecular weight:

[0070] Refer to the determination of lignin molecular weight in Example 4, and the results are shown in Table 1. It can be seen from Table 1 that the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) of lignin 2 (120 °C H2O2-EDA-L) are 1556 Da, 2630 Da and 1.690 respectively.

[0071] Determination of lignin chemical structure:

[0072] Refer to the determination of lignin chemical structure in Example 4, and the results are shown in Figure 1 . It can be seen from Figure 1 that signals of p-coumaramide (pCAM), ferulamide (FAM) and Schiff base (SB) appear in lignin 2 (120 °C H2O2-EDA-L), indicating that nitrogen-containing functional groups have been successfully introduced into lignin.

[0073] Determination of lignin fluorescence intensity:

[0074] Refer to the determination of lignin fluorescence intensity in Example 4, and the results are shown in Figure 2 .

[0075] It can be seen from Figure 2 that lignin 2 (120 °C H2O2-EDA-L) shows strong blue fluorescence, and its fluorescence intensity is 3.8 times higher than that of alkali lignin (NaOH-L).

[0076] Example 8

[0077] A method for extracting lignin from lignocellulose, comprising the following steps:

[0078] 1) Refer to the operation in Example 1 for wheat straw to obtain lignocellulose raw materials;

[0079] 2) Immerse 3 g of the lignocellulose raw materials in 7 mL of 3% hydrogen peroxide aqueous solution for 2 h, add 3.5 mL of ethylenediamine, and react at 120 °C for 1 h to obtain reactant 2;

[0080] 3) Wash according to the ratio of 30 mL of deionized water per gram of reactant 2, separate the solid and liquid to obtain solid 2 and washing solution 2; add absolute ethanol according to the volume ratio of washing solution 2 to absolute ethanol of 1:2, precipitate will form, centrifuge at 12,000 rpm for 10 min, take the liquid part for rotary evaporation and freeze-drying to obtain lignin 2, and store it at -20 °C.

[0081] Example 9

[0082] A method for extracting lignin from lignocellulose, comprising the following steps:

[0083] 1) Refer to the operation of Example 1 for rice straw (or sorghum straw) to obtain a lignocellulose raw material;

[0084] 2) Immerse 3 g of the lignocellulose raw material in 7 mL of hydrogen peroxide aqueous solution with a mass concentration of 7% for 1.5 h, add 2.1 mL of ethylenediamine, and react at 120 °C for 1 h to obtain reactant 2;

[0085] 3) Wash according to the ratio of 50 mL of deionized water per gram of reactant 2, separate the solid and liquid to obtain solid 2 and washing solution 2; add absolute ethanol according to the volume ratio of washing solution 2 to absolute ethanol of 1:4, precipitate will form, centrifuge at 12,000 rpm for 10 min, take the liquid part for rotary evaporation and freeze-drying to obtain lignin 2, and store it at -20 °C.

[0086] Experiments have proved that the lignin extracted by the methods of Examples 8 and 9, after measurement, its lignin molecular weight, lignin chemical structure and lignin fluorescence intensity are similar to the above detection results of Example 7.

[0087] Comparative Example 1

[0088] 1) Refer to the operation of Example 1 for corn straw to obtain a lignocellulose raw material;

[0089] 2) For 3 g of the lignocellulose raw material, absorb 7 mL of hydrogen peroxide aqueous solution with a mass concentration of 5%, adjust the pH to 11.5 with 6 M NaOH aqueous solution, then mix it evenly with 3 g of lignocellulose raw material, and react at 25 °C for 1 h to obtain reactant 3;

[0090] 3) Wash according to the ratio of 40 mL of deionized water per gram of reactant 3, separate the solid and liquid to obtain solid 3 and washing solution 3 respectively. Add hydrochloric acid aqueous solution to washing solution 3 to adjust the pH to less than 2, precipitate will form, and after centrifugation, freeze-dry the precipitate to obtain lignin, denoted as 25 °C H2O2-L, and store it at -20 °C.

[0091] The detection methods for the molecular weight of lignin, the elemental content in lignin, the chemical structure of lignin, and the fluorescence intensity of lignin are shown in Example 4.

[0092] Comparative Example 2

[0093] 1) Referring to the operation of Example 1, corn straw was used to obtain lignocellulose raw materials;

[0094] 2) For 3 g of the lignocellulose raw materials, 7 mL of a 5% hydrogen peroxide aqueous solution was taken, and the pH was adjusted to 11.5 with 6 M NaOH aqueous solution, then it was mixed evenly with 3 g of lignocellulose raw materials and reacted at 120 °C for 1 h to obtain Reactant 4;

[0095] 3) Wash according to the ratio of 40 mL of deionized water per gram of Reactant 4, perform solid-liquid separation to obtain solid 4 and washing liquid 4 respectively. Add hydrochloric acid aqueous solution to the washing liquid 4 to adjust the pH to less than 2, precipitate is formed, and after centrifugation, the precipitate is freeze-dried to obtain lignin, denoted as 120 °C H2O2-L, and stored at -20 °C.

[0096] The detection methods for the molecular weight of lignin, the chemical structure of lignin, and the fluorescence intensity of lignin are shown in Example 4.

[0097] Comparative Example 3

[0098] 1) Referring to the operation of Example 1, corn straw was used to obtain lignocellulose raw materials;

[0099] 2) For 3 g of the lignocellulose raw materials, 7 mL of deionized water was taken, 2.8 mL of ethylenediamine was added, mixed evenly, and then added to 3 g of lignocellulose raw materials and reacted at 25 °C for 1 h to obtain Reactant 5;

[0100] 2) Wash according to the ratio of 40 mL of deionized water per gram of Reactant 5, perform solid-liquid separation to obtain solid 5 and washing liquid 5 respectively. Add absolute ethanol according to the volume ratio of washing liquid 5 to absolute ethanol of 1:3, precipitate is formed, centrifuge at 12000 rpm for 10 min, take the liquid part for rotary evaporation and freeze-dry to obtain lignin, denoted as 25 °C EDA-L, and stored at -20 °C.

[0101] The detection methods for the molecular weight of lignin, the elemental content in lignin, the chemical structure of lignin, and the fluorescence intensity of lignin are shown in Example 4.

[0102] Comparative Example 4

[0103] 1) Referring to the operation of Example 1, corn straw was used to obtain lignocellulose raw materials;

[0104] 2) Take 3 g of the lignocellulosic raw material, absorb 7 mL of deionized water, add 2.8 mL of ethylenediamine, mix well, and then add it to 3 g of the lignocellulosic raw material. React at 120 °C for 1 h to obtain Reactant 6;

[0105] 2) Wash according to the ratio of 40 mL of deionized water per gram of Reactant 6, perform solid-liquid separation to obtain Solid 6 and Wash Liquid 6 respectively. Add absolute ethanol according to the volume ratio of Wash Liquid 6 to absolute ethanol of 1:3. Precipitation occurs. Centrifuge at 12000 rpm for 10 min. Take the liquid part for rotary evaporation and freeze-drying to obtain lignin, denoted as 120 °C EDA-L, and store it at -20 °C.

[0106] For the detection methods of the molecular weight of lignin, the chemical structure of lignin, and the fluorescence intensity of lignin, refer to Example 4.

[0107] Table 1 Molecular weight distribution of different lignin samples

[0108]

[0109] The molecular weight and fluorescence intensity of the extracted lignin are affected by the treatment temperature: The molecular weight of the lignin extracted by the synergistic treatment of alkaline hydrogen peroxide and ethylenediamine at 25 °C is the lowest, which is an ideal raw material for manufacturing adhesives; The fluorescence intensity of the lignin extracted by the synergistic treatment of alkaline hydrogen peroxide and ethylenediamine at 120 °C is the highest, which is an ideal raw material for manufacturing fluorescent materials.

[0110] According to different performance requirements, lignin with different properties can be extracted by this method at different temperatures.

[0111] Table 2 Element content analysis of different lignin samples

[0112]

Claims

1. A method for extracting lignin from lignocellulose, characterized in that It includes the following steps: 1) Wash and dry the straw, crush and sieve it to obtain the lignocellulose raw material; 2) Immerse the lignocellulose raw material in an aqueous hydrogen peroxide solution for 1 - 2 h, add ethylenediamine, and react at 25 °C for 1 h to obtain Reactant 1; 3) Wash according to the ratio of 30 - 50 mL of deionized water per gram of Reactant 1, perform solid-liquid separation to obtain Solid 1 and Wash Solution 1; add absolute ethanol according to the volume ratio of Wash Solution 1 to absolute ethanol of 1:2 - 4, precipitate will form, centrifuge, take the liquid part for rotary evaporation and freeze-drying to obtain Lignin 1, and store it at -20 °C.

2. The method according to claim 1, wherein The straw is corn straw, wheat straw, rice straw or sorghum straw.

3. The method according to claim 1, wherein The particle size of the lignocellulose raw material obtained by crushing and sieving is between 20 mesh and 80 mesh.

4. The method according to claim 1 or 3, characterized in that Step 2) is: Immerse 3 g of the lignocellulose raw material in 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 3% - 7% for 1 - 2 h, add 2.1 - 3.5 mL of ethylenediamine, and react at 25 °C for 1 h to obtain Reactant 1.

5. A method for extracting lignin from lignocellulose, characterized in that It includes the following steps: 1) Wash and dry the straw, crush and sieve it to obtain the lignocellulose raw material; 2) Immerse the lignocellulose raw material in an aqueous hydrogen peroxide solution for 1 - 2 h, add ethylenediamine, and react at 120 °C for 1 h to obtain Reactant 2; 3) Wash according to the ratio of 30 - 50 mL of deionized water per gram of Reactant 2, perform solid-liquid separation to obtain Solid 2 and Wash Solution 2; add absolute ethanol according to the volume ratio of Wash Solution 2 to absolute ethanol of 1:2 - 4, precipitate will form, centrifuge, take the liquid part for rotary evaporation and freeze-drying to obtain Lignin 2, and store it at -20 °C.

6. The method according to claim 1, characterized in that The straw is corn straw, wheat straw, rice straw or sorghum straw.

7. The method according to claim 1, characterized in that The particle size of the lignocellulose raw material obtained by crushing and sieving is between 20 mesh and 80 mesh.

8. The method according to claim 5 or 7, characterized in that Step 2) is: Immerse 3 g of the lignocellulose raw material in 7 mL of an aqueous hydrogen peroxide solution with a mass concentration of 3% - 7% for 1 - 2 h, add 2.1 - 3.5 mL of ethylenediamine, and react at 120 °C for 1 h to obtain Reactant 2.

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