Method for preparing lignin in-situ optical function material through lignocellulose pretreatment and synchronous grading

Abstract

The invention discloses a method for preparing a lignin in-situ optical functional material through pretreatment and synchronous grading of lignocellulose, which comprises the following steps of: performing high-solid pretreatment on a pretreatment organic solution consisting of an alkaline catalyst, a solvated organic solvent and water under the action of alkali to break component links so as to realize component disassembly; the method comprises the following steps of: performing in-situ solvation reaction on the disassembled lignin by using a solvation organic solvent, inhibiting condensation of the disassembled lignin, enhancing the light function effect of the disassembled lignin, remarkably inhibiting removal of cellulose and hemicelluloses, and improving the retention of carbohydrates in a raw material, and then performing 1-2wt% sodium hydroxide aqueous solution dissolution and water / organic solvent grading to obtain the high-purity lignin. The method has the advantages of simple process, mild conditions and low energy consumption, not only realizes lignocellulose pretreatment, but also can perform in-situ and controllable functional modification on lignin, and can obtain fermentable holocellulose residues, a lignin-based anti-ultraviolet material and a lignin-based photo-thermal conversion material through separation, thereby completing high-value utilization of all components of lignocellulose.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of high-value biomass, specifically to a method for the simultaneous graded preparation of lignin in situ photofunctional materials from lignocellulose pretreatment. Background Technology

[0002] Photofunctional materials play a crucial role in energy, environment, and health. For example, photothermal conversion materials can efficiently convert light energy into heat energy, and are core technologies for solar-powered seawater desalination, photothermal therapy, and de-icing. Meanwhile, UV-resistant materials are widely used in sunscreens, coatings, and polymer stabilizers to protect against damage caused by ultraviolet radiation. Currently, mainstream materials in this field mostly rely on inorganic semiconductors, precious metals, or fossil-based synthetic polymers, which generally suffer from high costs, large environmental footprints, poor biocompatibility, or unsustainable sources, necessitating the development of green alternatives derived from renewable resources.

[0003] Lignocellulose is the most abundant renewable resource on Earth, and its efficient utilization is a crucial cornerstone for building a sustainable society. Lignin, one of its three main components, possesses a unique molecular structure with aromatic rings and conjugated functional groups, providing a fundamental framework for efficient broadband light absorption and making it an ideal precursor for preparing photofunctional materials (UV protection, photothermal conversion). However, traditional biomass utilization strategies typically follow a "separation followed by modification" model. To prepare functional lignin materials, it is often necessary to first extract lignin from biomass using various methods (such as cooking, organic solvents, DES method, etc.), and then endow it with specific functions through chemical modification, high-temperature carbonization, or compounding with other materials.

[0004] This traditional approach has several drawbacks: First, the process is lengthy and complex, involving multiple independent reaction units, leading to high energy consumption and costs. Second, during lignin extraction, its natural active structure is easily damaged or undergoes uncontrollable condensation reactions, increasing the difficulty of subsequent functionalization modification. Finally, this approach typically focuses only on a single component, making it difficult to achieve high-value utilization of all components of lignocellulose, including cellulose, hemicellulose, and lignin, resulting in resource waste. Therefore, there is an urgent need to develop a novel technological approach. Summary of the Invention

[0005] The purpose of this invention is to provide a method for simultaneously preparing lignin in-situ photofunctional materials by pretreatment and grading of lignocellulose, which solves the problems of complex processes, high costs, and inability to simultaneously achieve pretreatment and functionalization in the prior art.

[0006] This invention is achieved through the following technical solutions:

[0007] A method for simultaneously preparing lignin in-situ photofunctional materials by pretreatment and fractionation of lignocellulose, the method comprising the following steps:

[0008] (1) High solids pretreatment: The pretreatment organic solution composed of an alkaline catalyst, a solvating organic solvent, and water is uniformly mixed with the lignocellulose raw material. The mixture is stacked at room temperature for no less than 3 days under a high solids state with a liquid-to-solid ratio of no more than 3 mL / g, so that the chemical bonds between the lignocellulose components are broken, and the lignin fragments are disassembled and undergo in-situ solvation modification to obtain the high solids pretreated material. The concentration of the alkaline catalyst in the pretreatment organic solution is (0.005-0.05) g / mL, and the volume ratio of the solvating organic solvent to water is (0.05-0.4) mL / mL. The solvating organic solvent is an alcohol or aldehyde that can undergo a solvation reaction with lignin and graft the solvent group into the lignin molecule, including one or more of the following: triethylene glycol, phenoxyethanol, glycerol formaldehyde, dihydro-L-glucanone, tetrahydrofurfuryl alcohol, dimethyl isosorbide, phenylethanol, etc.

[0009] (2) Lignin dissolution: Add 1-2 wt% sodium hydroxide aqueous solution to the high solids pretreated material obtained in step (1), stir and extract at room temperature to fully dissolve the lignin component that has undergone in-situ solvation modification in the liquid phase. After solid-liquid separation, a lignin-rich lignin-dissolving reaction solution and a solid are obtained. The solid is washed and dried to obtain an enzymatically hydrolyzable holocellulose residue (cellulose, hemicellulose) that can be used for subsequent enzymatic hydrolysis.

[0010] (3) Lignin fractionation: Add the acid regulator dropwise to the lignin-dissolving reaction solution obtained in step (2) until the system just shows a turbid precipitate, and stop to obtain the acidified lignin-dissolving reaction solution; add the acidified lignin-dissolving reaction solution dropwise to the acidic aqueous solution, and use the rapid increase in polarity and high supersaturation generated when the droplets enter the acidic aqueous solution to promote the nucleation and precipitation of hydrophobic macromolecular lignin rich in conjugated structures. After solid-liquid separation and purification, lignin-based photothermal conversion material is obtained; then, add the supernatant obtained by separation to the reverse organic solvent, which is a low-boiling-point organic solvent that can form a homogeneous solution with a small amount of water and is sparingly soluble in lignin. Use the rapid drop in polarity generated by the instantaneous miscibility of the droplets and the reverse organic solvent to quickly peel off the hydration shell of small molecule lignin, and force the hydrophilic small molecule lignin rich in oxygen groups to precipitate out instantly. After solid-liquid separation and purification, lignin-based UV-resistant material is obtained.

[0011] Preferably, the lignocellulose raw material in step (1) is a plant, agricultural or forestry waste or processing waste containing at least cellulose and lignin with a particle size of 0.5 to 3.0 mm, including but not limited to Napier grass, Miscanthus sinensis, sawdust, straw, bagasse, poplar wood, corn cob, etc.

[0012] The high-solids state is achieved through methods such as pressure filtration and briquetting.

[0013] The alkaline catalyst is an inorganic base, organic base, or strong alkaline weak acid salt that is soluble in an organic solution, including calcium hydroxide, sodium hydroxide, potassium hydroxide, ethylenediamine, triethylamine, ammonia, sodium acetate, disodium hydrogen phosphate, etc.

[0014] Preferably, in step (2), the volume of 1-2 wt% sodium hydroxide aqueous solution added is calculated as 10 mL / g of high solids pretreatment material.

[0015] Preferably, in step (3), the acid regulator and the acidic aqueous solution are sulfuric acid, hydrochloric acid or phosphoric acid aqueous solutions with an acid content of 0.1wt%~1wt%; the volume of the acidic aqueous solution is not less than twice the volume of the acidified lignin-dissolving reaction liquid.

[0016] Preferably, the reverse organic solvent is selected from one or more of dimethyl carbonate, diethyl ether, dimethoxymethane, ethylene glycol dimethyl ether, acetone, ethanol, methyl acetate, and isopropyl ether; the volume of the reverse organic solvent is not less than twice the volume of the supernatant obtained by separation.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) This invention pre-treats the organic solution with high solids. As the stacking progresses, the alkali concentration increases continuously. Under the action of alkali, the links between components are broken to achieve component disassembly. At the same time, the solubilizing organic solvent of specific groups performs in-situ solubilization reaction on the disassembled lignin, inhibiting the condensation of disassembled lignin and enhancing the photofunctional effect of lignin. In addition, the solubilizing organic solvent can inhibit the removal of cellulose and hemicellulose and improve the retention of carbohydrates in the raw materials. Subsequently, fermentable holocellulose is obtained by dissolving lignin and fractionating lignin with water / organic solvent. It also takes into account the in-situ controllable functionalization of lignin to selectively enhance the photofunctional properties of lignin. The fractionation yields light-colored lignin-based UV-resistant materials and dark-colored lignin-based photothermal conversion materials, thereby completing the high-value utilization of all components of lignin cellulose.

[0019] (2) This invention utilizes the differences in solubility of lignin with different molecular weights and group contents in aqueous solutions and organic solvents to construct a water / organic solvent stepwise precipitation method. This breaks through the limitations of the single water or organic solvent precipitation method, which has limited lignin precipitation efficiency and makes it difficult to achieve functional graded lignin. It achieves effective graded lignin functionality from the dissolved lignin solution, and obtains light-colored lignin-based UV-resistant products and dark-colored lignin-based photothermal conversion products.

[0020] (3) The high solids pretreatment of organic solution in this invention is a mild pretreatment that effectively breaks down lignin components and reduces the consumption of lignin dissolution process; by adding a reverse solution to the lignin dissolution solution, the lignin nucleation rate is much greater than the crystal / particle growth rate, resulting in highly dispersed small-diameter lignin particles, which is beneficial for subsequent conversion and utilization.

[0021] (4) The reaction conditions of this invention are extremely mild and the energy consumption is extremely low, which meets the requirements of green chemical development under the dual carbon target.

[0022] In summary, this invention utilizes a high-solids pretreatment organic solution composed of an alkaline catalyst, a solvated organic solvent, and water. This pretreatment breaks down component linkages under alkaline action, achieving component disassembly. Simultaneously, the solvated organic solvent with specific groups performs in-situ solvation of the disassembled lignin, inhibiting lignin condensation and enhancing its photofunctional effect. It also significantly inhibits the removal of cellulose and hemicellulose, improving the retention of carbohydrates in the raw material. Subsequently, a method involving 1-2 wt% sodium hydroxide aqueous solution dissolution and water / organic solvent fractionation is employed. This method, with its mild conditions and low energy consumption, not only achieves lignocellulose pretreatment but also enables in-situ, controllable functional modification of lignin. Furthermore, it separates fermentable holocellulose residues (cellulose and hemicellulose), lignin-based UV-resistant materials, and lignin-based photothermal conversion materials, thus achieving high-value utilization of all components of lignocellulose. Detailed Implementation

[0023] The following is a further description of the invention, but not a limitation thereof.

[0024] Example 1:

[0025] Using sugarcane bagasse with a particle size of 3.0 mm as raw material, the pretreatment organic solution consisted of NaOH, tetrahydrofurfuryl alcohol, and water, wherein the concentration of NaOH was 0.03 g / mL, and the volume ratio of tetrahydrofurfuryl alcohol to water was 0.1. The procedure was carried out according to the following steps:

[0026] (1) High solids pretreatment: The pretreatment organic solution was mixed with the lignocellulose raw material at a liquid-to-solid ratio of 3.0 mL / g. The mixture was then piled at room temperature for 10 days in a high solids state to obtain the high solids pretreated material.

[0027] (2) Lignin dissolution: Add 1wt% NaOH aqueous solution to the high solids pretreated material, with a volume of 10mL / g of high solids pretreated material, stir at room temperature for 2h, and separate the solid and liquid. After washing and drying the solid, fermentable holocellulose residue is obtained, and the liquid is a lignin-rich lignin-dissolving reaction solution.

[0028] (3) Lignin fractionation: 0.2 wt% sulfuric acid aqueous solution was added dropwise to the lignin-dissolving reaction solution until a turbid precipitate appeared in the system, and the reaction was stopped to obtain an acidified lignin-dissolving reaction solution; the acidified lignin-dissolving reaction solution was added dropwise to 2 times the volume of 0.2 wt% sulfuric acid aqueous solution, and high molecular weight conjugated lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based photothermal conversion material was obtained; then, the supernatant obtained by separation was added dropwise to 2 times the volume of isopropyl ether, and low molecular weight oxygen-containing lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based UV-resistant material was obtained.

[0029] In this embodiment, a holocellulose residue with a cellulose and hemicellulose content of 90.5 wt% was obtained. This residue was enzymatically hydrolyzed for 72 h at 50 °C using a citric acid-sodium citrate buffer solution with a substrate concentration of 5 wt% and a pH of 4.8, along with CTec3 enzyme at 10 FPU / g cellulose. The hydrolysis rate was 93.1%. The resulting lignin-based photothermal conversion material, after testing, showed a visible light absorbance of 72.1% and a surface temperature of 43.7 °C under one day of sunlight irradiation. The resulting lignin-based UV-resistant material, after testing, showed a visible light absorbance of 51.1% and a UV absorbance of 88.7%.

[0030] Comparative Example 1

[0031] Similar to Example 1, except that in step (1), the pretreated organic solution does not contain tetrahydrofurfuryl alcohol, but is composed of NaOH and water, wherein the concentration of NaOH is 0.02 g / mL.

[0032] In this comparative example, holocellulose residue with a cellulose and hemicellulose content of 70.3 wt% was obtained. Enzymatic hydrolysis was performed in a citric acid-sodium citrate buffer solution with a substrate concentration of 5 wt% and pH 4.8, using CTec3 enzyme at 10 FPU / g cellulose, on a shaker at 50°C for 72 h, with a hydrolysis rate of 75.8%. The resulting lignin-based photothermal conversion material, after testing, exhibited a visible light absorbance of 75.2% and a surface temperature of 35.1°C under one day of sunlight irradiation. This was an unobtainable lignin-based UV-resistant material.

[0033] As can be seen from the comparison between Example 1 and Comparative Example 1, under the action of solvated organic solvents containing specific groups, the carbohydrate content in the raw materials is effectively increased, and the enzymatic hydrolysis efficiency of the residue is improved; at the same time, the dissolution efficiency of lignin is increased, the efficiency of lignin fractionation is improved, and the photofunctional effect of lignin preparation is enhanced.

[0034] Comparative Example 2

[0035] Using sugarcane bagasse from Example 1 as raw material, enzymatic hydrolysate (CEL) was obtained by toluene-ethanol Soxhlet extraction, ball milling, enzymatic hydrolysis, dioxane extraction, purification, and freeze drying (reference: ACS Sustainable Chem. Eng. 2017, 5(12):11618-11627). The visible light absorbance was 50.5%, the surface temperature was 30.3℃ under one ray of sunlight, and the ultraviolet light absorbance was 84.2%.

[0036] A comparison of Example 1 and Comparative Example 2 shows that, under the action of a solvating organic solvent containing specific groups, the in-situ solvation reaction of the disassembled lignin enhances the photofunctional effect of the prepared lignin.

[0037] Comparative Example 3

[0038] Similar to Example 1, except that in step (3), the acidified lignin-dissolving reaction liquid droplets were added to 4 times the volume (excess) of 0.2wt% sulfuric acid aqueous solution to completely precipitate the lignin-based material. Subsequently, no separation was performed and the supernatant was treated with the reverse solvent isopropyl ether, that is, the lignin-based material was not graded.

[0039] In this comparative example, the lignin-based material obtained, after testing, had a visible light absorbance of 70.3%, a surface temperature of 35.8℃ under one ray of sunlight, and an ultraviolet light absorbance of 86.1%.

[0040] A comparison of Example 1 and Comparative Example 3 shows that the stepwise precipitation method using aqueous solution and the reverse organic solvent isopropyl ether effectively dissolves lignin, resulting in light-colored lignin-based UV-resistant products and dark-colored lignin-based photothermal conversion products.

[0041] Comparative Example 4

[0042] Similar to Example 1, the difference is that in step (3), the lignin-dissolving reaction solution is added dropwise to two volumes of 0.2wt% sulfuric acid aqueous solution, causing high molecular weight conjugated lignin to precipitate. After centrifugation, purification, and freeze-drying, lignin-based photothermal conversion material is obtained. That is, the lignin-based photothermal conversion material is directly precipitated without first adding 0.2wt% sulfuric acid aqueous solution to the lignin-dissolving reaction solution to adjust it to the turbid point.

[0043] In this comparative example, the lignin-based photothermal conversion material obtained had a visible light absorption rate of 68.9% and a surface temperature of 38.6℃ under one ray of sunlight; the lignin-based UV-resistant material obtained had a visible light absorption rate of 63.4% and a UV light absorption rate of 85.5%.

[0044] A comparison of Example 1 and Comparative Example 4 shows that pre-treating the lignin-soluble reaction solution by adding 0.2wt% sulfuric acid aqueous solution dropwise to adjust the lignin-soluble reaction solution to the turbidity point is beneficial for the effective separation of lignin-based photothermal conversion materials and lignin-based UV-resistant materials.

[0045] Comparative Example 5

[0046] Similar to Example 1, except that in step (3), the supernatant obtained from the separation is added to twice the volume of water, causing low molecular weight oxygen-containing lignin to precipitate. After centrifugation, purification, and freeze-drying, lignin-based UV-resistant material is obtained. That is, the lignin-based UV-resistant material is precipitated by water precipitation.

[0047] In this comparative example, the lignin-based UV-resistant material obtained, after testing, had a visible light absorption rate of 54.7% and a UV light absorption rate of 80.2%.

[0048] A comparison of Example 1 and Comparative Example 5 shows that isopropyl ether is more effective than water.

[0049] Example 2

[0050] Using corn stalks with a particle size of 0.5 mm as raw material, the pretreatment organic solution consisted of NaOH, phenoxyethanol, and water, wherein the concentration of NaOH was 0.05 g / mL, and the volume ratio of phenoxyethanol to water was 0.4. The procedure was carried out according to the following steps:

[0051] (1) High solids pretreatment: The pretreatment organic solution was mixed with the lignocellulose raw material at a liquid-to-solid ratio of 0.5 mL / g. The material was piled at room temperature in a high solids state for 3 days to obtain the high solids pretreatment material.

[0052] (2) Lignin dissolution: Add 1wt% NaOH aqueous solution to the high solids pretreated material, stir at room temperature for 2h, and separate the solid and liquid. After washing and drying the solid, fermentable holocellulose residue is obtained, and the liquid is a lignin-rich lignin-dissolving reaction solution.

[0053] (3) Lignin fractionation: 0.2 wt% sulfuric acid aqueous solution was added dropwise to the lignin-dissolving reaction solution until a turbid precipitate appeared in the system, and the reaction was stopped to obtain an acidified lignin-dissolving reaction solution; the acidified lignin-dissolving reaction solution was added dropwise to 2 times the volume of 0.2 wt% sulfuric acid aqueous solution, and high molecular weight conjugated lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based photothermal conversion material was obtained; then, the supernatant obtained by separation was added dropwise to 2 times the volume of dimethyl carbonate, and low molecular weight oxygen-containing lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based UV-resistant material was obtained.

[0054] In this embodiment, a holocellulose residue with a cellulose and hemicellulose content of 83.4 wt% was obtained. This residue was enzymatically hydrolyzed for 72 h at 50 °C using a citric acid-sodium citrate buffer solution with a substrate concentration of 5 wt% and a pH of 4.8, along with CTec3 enzyme at 10 FPU / g cellulose. The hydrolysis rate was 90.2%. The resulting lignin-based photothermal conversion material, after testing, showed a visible light absorbance of 76.7% and a surface temperature of 47.8 °C under one day of sunlight irradiation. The resulting lignin-based UV-resistant material, after testing, showed a visible light absorbance of 52.3% and a UV absorbance of 90.6%.

[0055] Example 3

[0056] Using poplar wood with a particle size of 0.5 mm as raw material, the pretreatment organic solution consisted of ethylenediamine, phenoxyethanol, and water, wherein the concentration of ethylenediamine was 0.05 g / mL, and the volume ratio of phenoxyethanol to water was 0.2. The procedure was carried out according to the following steps:

[0057] (1) High solids pretreatment: The pretreatment organic solution and lignocellulose raw material were mixed evenly at a liquid-to-solid ratio of 5.0 mL / g. After briquetting, the liquid-to-solid ratio was not more than 3.0 mL / g. The high solids material was then stacked at room temperature for 15 days to obtain the high solids pretreatment material.

[0058] (2) Lignin dissolution: Add 1wt% NaOH aqueous solution to the high solids pretreated material, stir at room temperature for 2h, and separate the solid and liquid. After washing and drying the solid, fermentable holocellulose residue is obtained, and the liquid is a lignin-rich lignin-dissolving reaction solution.

[0059] (3) Lignin fractionation: 0.2 wt% sulfuric acid aqueous solution was added dropwise to the lignin-dissolving reaction solution until a turbid precipitate appeared in the system, and the reaction was stopped to obtain an acidified lignin-dissolving reaction solution; the acidified lignin-dissolving reaction solution was added dropwise to 2 times the volume of 0.2 wt% sulfuric acid aqueous solution, and high molecular weight conjugated lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based photothermal conversion material was obtained; then, the supernatant obtained by separation was added dropwise to 3 times the volume of isopropyl ether, and low molecular weight oxygen-containing lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based UV-resistant material was obtained.

[0060] In this embodiment, a holocellulose residue with a cellulose and hemicellulose content of 80.3 wt% was obtained. This residue was enzymatically hydrolyzed for 72 h at 50 °C using a citric acid-sodium citrate buffer solution with a substrate concentration of 5 wt% and a pH of 4.8, along with CTec3 enzyme at 10 FPU / g cellulose. The hydrolysis rate was 86.1%. The resulting lignin-based photothermal conversion material, after testing, showed a visible light absorbance of 80.3% and a surface temperature of 50.1 °C under one day of sunlight irradiation. The resulting lignin-based UV-resistant material, after testing, showed a visible light absorbance of 54.4% and a UV absorbance of 92.2%.

[0061] Example 4

[0062] Using corn cobs with a particle size of 0.5 mm as raw material, the pretreatment organic solution consisted of NaOH, tetrahydrofurfuryl alcohol, and water, wherein the concentration of NaOH was 0.005 g / mL, and the volume ratio of tetrahydrofurfuryl alcohol to water was 0.2. The procedure was carried out according to the following steps:

[0063] (1) High solids pretreatment: The pretreatment organic solution was mixed evenly with the lignocellulose raw material at a liquid-solid ratio of 5.0 mL / g. After briquetting, the liquid-solid ratio was not more than 3.0 mL / g. The material was then piled at room temperature in a high solids state for 30 days to obtain the high solids pretreated material.

[0064] (2) Lignin dissolution: Add 1wt% NaOH aqueous solution to the high solids pretreated material, stir at room temperature for 2h, and separate the solid and liquid. After washing and drying the solid, fermentable holocellulose residue is obtained, and the liquid is a lignin-rich lignin-dissolving reaction solution.

[0065] (3) Lignin fractionation: 0.1 wt% sulfuric acid aqueous solution was added dropwise to the lignin-dissolving reaction solution until a turbid precipitate appeared in the system, and the reaction was stopped to obtain an acidified lignin-dissolving reaction solution; the acidified lignin-dissolving reaction solution was added dropwise to 2 times the volume of 0.1 wt% sulfuric acid aqueous solution, and high molecular weight conjugated lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based photothermal conversion material was obtained; then, the supernatant obtained by separation was added dropwise to 3 times the volume of isopropyl ether, and low molecular weight oxygen-containing lignin was precipitated. After centrifugation, purification and freeze-drying, lignin-based UV-resistant material was obtained.

[0066] In this embodiment, a holocellulose residue with a cellulose and hemicellulose content of 86.2 wt% was obtained. This residue was enzymatically hydrolyzed for 72 h at 50 °C using a citric acid-sodium citrate buffer solution with a substrate concentration of 5 wt% and a pH of 4.8, along with CTec3 enzyme at 10 FPU / g cellulose. The hydrolysis rate was 94.1%. The resulting lignin-based photothermal conversion material, after testing, showed a visible light absorbance of 75.6% and a surface temperature of 40.4 °C under one day of sunlight irradiation. The resulting lignin-based UV-resistant material, after testing, showed a visible light absorbance of 51.1% and a UV absorbance of 86.8%.

[0067] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for simultaneously preparing lignin in-situ photofunctional materials by pretreatment and fractionation of lignocellulose, characterized in that, The method includes the following steps: (1) High solids pretreatment: The pretreatment organic solution composed of an alkaline catalyst, a solvating organic solvent, and water is uniformly mixed with the lignocellulose raw material and stacked at room temperature for no less than 3 days under a high solids state with a liquid-to-solid ratio of no more than 3 mL / g to obtain the high solids pretreated material; the concentration of the alkaline catalyst in the pretreatment organic solution is (0.005-0.05) g / mL, the volume ratio of the solvating organic solvent to water is (0.05-0.4) mL / mL, and the solvating organic solvent is one or more of triethylene glycol, phenoxyethanol, glycerol formaldehyde, dihydro-L-glucanone, tetrahydrofurfuryl alcohol, dimethyl isosorbide, and phenylethanol; (2) Lignin dissolution: Add 1-2wt% sodium hydroxide aqueous solution to the high solids pretreated material obtained in step (1), stir and extract at room temperature, and separate the solid and liquid to obtain lignin-rich lignin-dissolving reaction solution and solid. The solid is washed and dried to obtain enzymatically hydrolyzable holocellulose residue that can be used for subsequent enzymatic hydrolysis. (3) Lignin classification: Add the acidic regulator dropwise to the lignin-dissolving reaction solution obtained in step (2) until the system just shows a turbid precipitate, and stop to obtain the acidified lignin-dissolving reaction solution; add the acidified lignin-dissolving reaction solution dropwise to the acidic aqueous solution, and after solid-liquid separation and purification, obtain the lignin-based photothermal conversion material; then, add the supernatant obtained from solid-liquid separation dropwise to the reverse organic solvent, and after solid-liquid separation and purification, obtain the lignin-based UV-resistant material.

2. The method according to claim 1, characterized in that, The lignocellulose raw material mentioned in step (1) is a plant, agricultural and forestry waste or processing waste containing at least cellulose and lignin with a particle size of 0.5~3.0 mm.

3. The method according to claim 2, characterized in that, The lignocellulose raw material is selected from one or more of the following: Napier grass, Miscanthus sinensis, sawdust, straw, sugarcane bagasse, poplar wood, and corn cob.

4. The method according to claim 1, characterized in that, The high-solids state is achieved through pressure filtration and briquetting.

5. The method according to claim 1, characterized in that, The alkaline catalyst is an inorganic base, an organic base, or a strong alkaline weak acid salt that is soluble in an organic solution.

6. The method according to claim 5, characterized in that, The alkaline catalyst is selected from one or more of calcium hydroxide, sodium hydroxide, potassium hydroxide, ethylenediamine, triethylamine, ammonia, sodium acetate, and disodium hydrogen phosphate.

7. The method according to claim 1, characterized in that, In step (2), the volume of 1-2 wt% sodium hydroxide aqueous solution added is calculated as 10 mL / g of high solids pretreatment material.

8. The method according to claim 1, characterized in that, In step (3), the acid regulator and the acidic aqueous solution are sulfuric acid, hydrochloric acid or phosphoric acid aqueous solutions with an acid content of 0.1wt%~1wt%; the volume of the acidic aqueous solution is not less than twice the volume of the acidified lignin-dissolving reaction liquid.

9. The method according to claim 1, characterized in that, The reverse organic solvent is selected from one or more of dimethyl carbonate, diethyl ether, dimethoxymethane, ethylene glycol dimethyl ether, acetone, ethanol, methyl acetate, and isopropyl ether; the volume of the reverse organic solvent is not less than twice the volume of the supernatant obtained by separation.