Method for extracting cellulose, xylose and lignin from straw and application thereof

Abstract

The application discloses a method for extracting cellulose, xylose and lignin from straw and application thereof. The method comprises the following steps: steam explosion treatment is performed on the straw to obtain pretreated material, the pretreated material is reacted with a mixed solution, solid-liquid separation is performed, and cellulose solid and first filtrate are obtained; the mixed solution comprises an organic solvent, water and an organic acid; water is added into the first filtrate, solid-liquid separation is performed, and lignin solid and second filtrate are obtained; the organic solvent in the second filtrate is removed, and the remaining solution is xylose sugar solution; optionally, the cellulose solid and the lignin solid are washed and dried. The method adopts a neutral steam explosion coupling organic solvent dilute acid hydrolysis process, the crystalline structure of cellulose and lignin is destroyed under a milder condition, the degradation of hemicellulose is avoided, the subsequent mild dilute acid hydrolysis process increases the recovery rate and separation effect of the three elements, and the subsequent development of sugar and lignin is more favorable, so that the high-value utilization of the straw is achieved.

Description

Technical Field

[0001] This invention relates to the technical field of biomass energy chemical industry, and more specifically, to a method and application for extracting cellulose, xylose and lignin from straw. Background Technology

[0002] Straw is a biomass resource with rapid regeneration and high yield. High-value utilization of straw can not only alleviate the shortage of fossil fuels such as coal, oil, and natural gas, but also prevent environmental pollution caused by straw burning. In recent years, the industry has conducted relevant research on the utilization and composition of various crop straws. To improve straw utilization efficiency, the separation of straw components has become a key research focus for its high-value utilization. The contents of cellulose, hemicellulose, and lignin in straw are 40%–50%, 20%–30%, and 10%–15%, respectively. The key to high-value utilization of straw lies in breaking down the cross-linked structure of these three components and separating and extracting cellulose, hemicellulose, and lignin.

[0003] Cellulose is a chain-like polymer composed of D-glucose linked by β-1,4 glycosidic bonds, and is currently an important raw material for pulp and paper making, textiles, and chemical fibers. With the development of nanotechnology, cellulose is expanding into the field of nanomaterials, where it can be used to prepare high-value-added products such as nanocellulose. Furthermore, cellulose can be degraded into glucose, a key raw material in the field of bio-fermentation. Glucose can be produced through fermentation reactions by yeast and bacteria, generating various compounds such as alcohols, organic acids, and amino acids, which have applications in brewing, food, medicine, materials, and bioengineering. Hemicellulose is a heteropolymer composed of several different types of monosaccharides, and is relatively easy to hydrolyze, primarily producing xylose. Xylose is mainly used to produce xylitol, which also has wide applications in food processing and the pharmaceutical industry. Lignin can be widely used in the preparation of phenolic resins, polyurethanes, and other materials; it can be used as a filler to modify rubber; and it can also be used in carbon fiber materials, surfactants, and flocculants, demonstrating significant application value.

[0004] Based on current research, conventional strong acid and alkali treatment methods require large quantities of acids, alkalis, and water, resulting in large volumes of post-treatment wastewater containing significant amounts of solid waste and high chemical oxygen demand (COD), thus greatly increasing treatment costs. Traditional methods are not only detrimental to environmental protection but also represent a significant waste of resources and hinder the comprehensive utilization of biomass resources.

[0005] In addition, the pretreatment process of dilute acid vapor explosion can degrade hemicellulose under high temperature and high pressure by using the instantaneous depressurization process, and destroy the dense structure of cellulose and lignin. The biggest advantage of the physical method is that the cellulose after explosion is more conducive to subsequent enzymatic hydrolysis, and at the same time, complete separation of hemicellulose into xylose is achieved. However, there is also the disadvantage that xylose will continue to degrade into fermentation inhibitors such as furfural at high temperature.

[0006] Therefore, there is a need for a gentler and more efficient method for extracting cellulose, xylose, and lignin. Summary of the Invention

[0007] To address the problems in existing technologies, this invention proposes a method and application for extracting cellulose, xylose, and lignin from straw. Combining the advantages and disadvantages of various current processes, this invention proposes a neutral vapor explosion coupled with organic solvent dilute acid hydrolysis. This process disrupts the crystalline structure of cellulose and lignin under gentler conditions, preventing further degradation of hemicellulose. The subsequent gentle dilute acid hydrolysis process increases the recovery rate and separation effect of the three components, further facilitating the subsequent development of sugars and lignin, achieving high-value utilization of straw by fully utilizing its resources.

[0008] One objective of this invention is to provide a method for extracting cellulose, xylose, and lignin from straw, comprising the following steps:

[0009] (1) The straw is subjected to steam explosion treatment to obtain pretreated material;

[0010] (2) After reacting the pretreated material with the mixture, the solid and liquid are separated to obtain cellulose solid and first filtrate; the mixture includes organic solvent, water and organic acid;

[0011] (3) Add water to the first filtrate, and separate the solid and liquid to obtain lignin solid and a second filtrate, wherein the second filtrate contains xylose;

[0012] (4) Optionally, the organic solvent in the second filtrate is removed, and the remaining solution is xylose solution;

[0013] (5) Optionally, after washing the cellulose solids and lignin solids, dry them.

[0014] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0015] In step (1),

[0016] Saturated or supersaturated steam is used for steam explosion treatment; and / or,

[0017] The pressure for steam explosion treatment is 0.3-0.9 MPa; preferably 0.4-0.8 MPa; for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 MPa and any two of the above values; and / or,

[0018] The temperature for steam explosion treatment is 150-190℃; preferably 160-180℃; for example, 150, 160, 170, 180, 190℃, or any range of two of the above values; and / or,

[0019] The steam explosion treatment time is 20-60 min; preferably 30-40 min; for example, 20, 30, 40, 50, 60 min, or any range of two of the above values; and / or,

[0020] The straw is straw powder, preferably with a length of 1-5cm; more preferably, the straw is coarsely crushed (e.g., by a straw cutter) to a length of 2-10cm, then stone and iron are removed, and finally crushed (e.g., by a hammer mill) to a length of 1-5cm to obtain straw powder.

[0021] In the prior art, straw powder needs to have a certain moisture content when steam explosion treatment. Therefore, before steam explosion treatment, straw powder generally needs to be soaked in water and then treated by steam explosion method. The purpose is to ensure that the straw powder has a certain moisture content. The moisture content can be the same as that required for conventional steam explosion treatment. Preferably, the water soaking time is 5-30 minutes.

[0022] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0023] Step (2),

[0024] In the mixture, the organic solvent is an aprotic polar solvent, preferably selected from at least one of acetonitrile, tetrahydrofuran, acetone, nitromethane, dichloromethane, chloroform, ethyl acetate, butyl acetate, and dioxane; more preferably, the organic solvent is at least one of acetonitrile, acetone, tetrahydrofuran, and dichloromethane.

[0025] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0026] Step (2),

[0027] In the mixture, the organic acid is a polybasic organic acid; preferably, the organic acid is a C2-C10 polybasic organic acid, and more preferably, the organic acid is at least one selected from oxalic acid, malic acid, maleic acid, tartaric acid, citric acid, fumaric acid, and ethylenediaminetetraacetic acid.

[0028] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0029] Step (2),

[0030] In the mixture

[0031] The mass fraction of the organic acid is 0.1%-0.5%, preferably 0.15%-0.3%; for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and any range of two of the above values; and / or,

[0032] The volume fraction of the organic solvent is 50%-80%; preferably 60%-80%; for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and any combination of the above values.

[0033] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0034] Step (2),

[0035] The solid-liquid mass ratio of the pretreated material to the mixture is 1 / 5 to 1 / 50, preferably 1 / 10 to 1 / 15; for example, it is 1 / 5, 1 / 10, 1 / 15, 1 / 25, 1 / 35, 1 / 45, 1 / 50, or any range of two of the above values; and / or,

[0036] The reaction temperature is 50-160℃, preferably 80-100℃; for example, 50, 60, 80, 100, 120, 120, 140, 160℃, or any range of two of the above values; and / or,

[0037] The reaction time is 30-60 min, preferably 45-60 min; for example, 30, 40, 50, 60 min, or any two of the above values.

[0038] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0039] Step (3),

[0040] The amount of water added is 3-4 times the volume of the first filtrate; and / or,

[0041] The solid-liquid separation method is filtration.

[0042] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0043] Step (4),

[0044] The organic solvent in the second filtrate is removed by evaporation; preferably, the evaporated organic solvent is recovered.

[0045] In the method for extracting cellulose, xylose, and lignin from straw according to the present invention, preferably,

[0046] Step (5),

[0047] The drying temperature is 60-80℃, and the drying time is 6-12 hours.

[0048] In this invention, neutral steam explosion treatment can maximize the structural destruction of cellulose and lignin without excessive degradation of hemicellulose, followed by separation of the three components under mild conditions. Furthermore, this invention employs an organic solvent dilute acid hydrolysis process, which disrupts the crystalline structure of cellulose and lignin under even milder conditions, preventing further degradation of hemicellulose. Compared to traditional dilute acid hydrolysis processes, this process uses lower temperatures and acid concentrations, and the aprotic polar solvent makes the reaction process easier to control, resulting in fewer byproducts. In terms of the choice of common organic acids, polybasic acids such as oxalic acid and malic acid exhibit better catalytic separation effects than monobasic acids such as formic acid and acetic acid. This is because polybasic acids possess the proton ionization ability of strong inorganic acids, and the conjugate acid pairs formed after primary ionization can buffer the pH of the solution. The unionized carboxylate group can form hydrogen bonds with the hydroxyl groups on the sugar chain, stabilizing the glycosidic bonds and inhibiting the hydrolysis and degradation of cellulose and hemicellulose, thus improving the separation efficiency of the three components.

[0049] A second objective of this invention is to provide the application of the method described in one objective of this invention in the extraction of cellulose, xylose, and lignin from straw or straw-containing biomass materials.

[0050] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0051] Compared with the prior art, the present invention has at least the following advantages:

[0052] This invention utilizes lignocellulose raw materials to co-produce cellulose, xylose, and lignin, achieving the separation of each component in lignocellulose. This creates conditions for the high-value-added utilization of each component, resulting in a high separation rate of the three elements. Furthermore, the processing temperature is low, acid usage is low, and the solvent is easily recoverable, making it suitable for the biomass industrial application of straw. It contributes to ensuring food security and achieving green and low-carbon development, demonstrating significant social and environmental benefits. Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0054] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0055] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0056] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials and reagents used can be purchased from domestic chemical companies. The straw is not limited to common wheat, corn, and sugarcane straw, but can be straw from various crops.

[0057] In the following embodiments of the present invention, the method for crushing and removing impurities from straw is as follows: after the straw is manually unpacked, it is coarsely crushed to a length of 2-10cm by a straw cutter, then conveyed by a belt to a straw impurity remover and an iron remover for stone and iron removal, and finally conveyed to a hammer crusher to be crushed to a length of 1-5cm to obtain straw powder.

[0058] The following are various embodiments of the method of the present invention:

[0059] Example 1

[0060] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with a mixture of acetone / water / oxalic acid. The mixture contained 0.1% acid by mass, 80% organic solvent by volume, and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0061] Example 2

[0062] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.4 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / oxalic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0063] Example 3

[0064] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 180℃ and 0.8 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / oxalic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0065] Example 4

[0066] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / oxalic acid. The mixture contained 0.3% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0067] Example 5

[0068] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / maleic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0069] Example 6

[0070] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetonitrile / water / maleic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0071] Example 7

[0072] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with tetrahydrofuran / water / citric acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0073] Example 8

[0074] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with dioxane / water / tartaric acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0075] Example 9

[0076] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method. The water soaking time was 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. Then, it was steam-exploded at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with dichloromethane / water / ethylenediaminetetraacetic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0077] Comparative Example 1

[0078] 1 kg of straw was crushed and impurities removed to obtain straw powder. The material was added to a reaction vessel with acetone / water / oxalic acid. The acid fraction of the mixture was 0.1%, the volume fraction of the organic solvent was 80%, and the solid-liquid mass ratio was 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, and then filtered to obtain lignin solid and a second filtrate. The organic solvent was recovered by concentrating the second filtrate, and the remaining solution was xylose syrup. After washing the cellulose solid and lignin solid separately with water, they were dried at 60℃ for 12 hours.

[0079] Comparative Example 2

[0080] 1 kg of corn straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method, with soaking time of 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. The mixture was then treated at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / acetic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0081] Comparative Example 3

[0082] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method, with soaking time of 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. The mixture was then treated at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with acetone / water / sulfuric acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed separately with water and then dried at 60℃ for 12 hours.

[0083] Comparative Example 4

[0084] 1 kg of straw was crushed and impurities removed to obtain straw powder. The powder was then soaked in water, followed by squeezing to remove the soaking liquid. The corn straw raw material was then pretreated using a steam explosion method, with soaking time of 10 minutes at room temperature. After soaking, some water was removed by squeezing, keeping the straw moist. The mixture was then treated at 160℃ and 0.6 MPaG for 30 minutes to obtain pretreated material. The pretreated material was added to a reaction vessel with ethanol / water / oxalic acid. The mixture contained 0.1% acid, 80% organic solvent (volume fraction), and a solid-liquid mass ratio of 1 / 10. The mixture was reacted at 100℃ for 1 hour, then cooled to room temperature, allowed to stand, and filtered to obtain cellulose solid and filtrate. Three times the volume of water was added to the filtrate, followed by filtration to obtain lignin solid and a second filtrate. The second filtrate was concentrated to recover the organic solvent, leaving a xylose solution. The cellulose solid and lignin solid were washed with water and then dried at 60℃ for 12 hours.

[0085] The mass of cellulose, hemicellulose, and lignin was estimated by determining the mass of their hydrolyzed monomer products. The method followed the standard analytical procedures of the National Renewable Energy Laboratory (NREL, USA) and was performed using a high-performance liquid chromatograph (HPLC, Waters 1515, USA) equipped with an Aminex HPX-87H column (Bio-Rad, USA) and a refractive index detector (Waters 2414). The operating conditions were: sample treatment with 5 mM H₂SO₄ at a flow rate of 0.6 mL / min and a temperature of 338 K.

[0086] in,

[0087]

[0088]

[0089]

[0090] The separation results of cellulose, lignin and xylose by the methods of the above embodiments and comparative examples of the present invention are shown in Table 1 below.

[0091] Table 1

[0092]

[0093] As shown in Table 1, compared with the comparative examples, the separation efficiency of the three elements in Examples 1 to 9 is higher, indicating that steam explosion, aprotic solvents, and organic polybasic acids are crucial for the separation effect. Organic polybasic acids have higher separation efficiency than inorganic acids and organic monobasic acids, and aprotic solvents have higher separation efficiency than protic solvents. Among them, under certain process parameters, the combination of acetone and oxalic acid has the highest overall separation efficiency of the three elements, and the yield and purity of cellulose can reach over 90% and 85%, respectively. The comparative examples show that the steam explosion method can obtain a cellulose yield of about 80%, but if appropriate subsequent processes are not adopted, it will promote product degradation, resulting in a lower total yield of xylose and lignin.

[0094] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0095] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0096] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0097] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A method for extracting cellulose, xylose, and lignin from straw, characterized in that, Includes the following steps: (1) The straw is subjected to steam explosion treatment to obtain pretreated material; (2) After reacting the pretreated material with the mixture, solid-liquid separation is performed to obtain cellulose solid and first filtrate; the mixture includes an organic solvent, water and organic acid; the organic solvent is an aprotic polar solvent; the organic acid is a polybasic organic acid; (3) Add water to the first filtrate, and separate the solid and liquid to obtain lignin solid and second filtrate, the second filtrate containing xylose.

2. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that, It also includes the following steps: (4) Remove the organic solvent from the second filtrate, and the remaining solution is xylose solution.

3. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that, It also includes the following steps: (4) Remove the organic solvent from the second filtrate, and the remaining solution is xylose solution; (5) After cleaning the cellulose solids and lignin solids, dry them.

4. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: In step (1), Saturated or supersaturated steam is used for steam explosion treatment; and / or, The pressure for steam explosion treatment is 0.3-0.9 MPa; and / or, The temperature for steam explosion treatment is 150-190℃; and / or, The steam explosion treatment time is 20-60 min; and / or, Straw is straw powder.

5. The method for extracting cellulose, xylose, and lignin from straw according to claim 4, characterized in that: In step (1), The pressure for steam explosion treatment is 0.4-0.8 MPa; and / or, The temperature for steam explosion treatment is 160-180℃; and / or, The steam explosion treatment time is 30-40 min; and / or, The length of the straw powder is 1-5 cm.

6. The method for extracting cellulose, xylose, and lignin from straw according to claim 5, characterized in that: Straw is coarsely crushed to a length of 2-10 cm, then stones and iron are removed, and finally crushed to a length of 1-5 cm to obtain straw powder.

7. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: Step (2), The organic solvent is selected from at least one of acetonitrile, tetrahydrofuran, acetone, nitromethane, dichloromethane, chloroform, ethyl acetate, butyl acetate, and dioxane.

8. The method for extracting cellulose, xylose, and lignin from straw according to claim 7, characterized in that: The organic solvent is at least one of acetonitrile, acetone, tetrahydrofuran, and dichloromethane.

9. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: Step (2), The organic acid is a C2-C10 polybasic organic acid.

10. The method for extracting cellulose, xylose, and lignin from straw according to claim 9, characterized in that: The organic acid is at least one of oxalic acid, malic acid, maleic acid, tartaric acid, citric acid, fumaric acid, and ethylenediaminetetraacetic acid.

11. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: Step (2), In the mixture The organic acid content is 0.1%-0.5% by mass; and / or, The volume fraction of the organic solvent is 50%-80%.

12. The method for extracting cellulose, xylose, and lignin from straw according to claim 11, characterized in that: Step (2), In the mixture The organic acid content is 0.15%-0.3% by mass; and / or, The volume fraction of the organic solvent is 60%-80%.

13. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: Step (2), The solid-liquid mass ratio of the pretreated material to the mixture is 1 / 5 to 1 / 50; and / or, The reaction temperature is 50-160℃; and / or, The reaction time is 30-60 min.

14. The method for extracting cellulose, xylose, and lignin from straw according to claim 13, characterized in that: Step (2), The solid-liquid mass ratio of the pretreated material to the mixture is 1 / 10 to 1 / 15; and / or, The reaction temperature is 80-100℃; and / or, The reaction time is 45-60 minutes.

15. The method for extracting cellulose, xylose, and lignin from straw according to claim 1, characterized in that: Step (3), The amount of water added is 3-4 times the volume of the first filtrate; and / or, The solid-liquid separation method is filtration.

16. The method for extracting cellulose, xylose, and lignin from straw according to claim 2, characterized in that: Step (4), The organic solvent in the second filtrate is removed by evaporation.

17. The method for extracting cellulose, xylose, and lignin from straw according to claim 16, characterized in that: The evaporated organic solvents are recovered.

18. The method for extracting cellulose, xylose, and lignin from straw according to claim 3, characterized in that: Step (5), The drying temperature is 60-80℃, and the drying time is 6-12 hours.

19. The application of the method according to any one of claims 1-18 in the extraction of cellulose, xylose and lignin from straw or straw-containing biomass materials.

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