Method for separating three major components of wood fiber biomass in one step by using carbon dioxide-assisted two-phase solvent

Abstract

The invention provides a method for separating three major components of wood fiber biomass in one step by using a carbon dioxide-assisted two-phase solvent, and belongs to the technical field of lignocellulose treatment. The method comprises the following steps: placing an extraction solvent at the bottom of a reactor, and fixing a wood fiber biomass raw material at the upper part of the reactor; introducing carbon dioxide into the reactor, extracting under a closed condition, and introducing a cooling medium to adjust the temperature in the extraction process to obtain a solid-phase material, an organic phase and a water phase; the solid-phase material contains coarse cellulose, the organic phase contains lignin, and the water phase contains hemicellulose. The CO2 adopted by the method is non-corrosive, the aqueous solution of the CO2 is acidic, the generated H < + > can effectively promote the separation of wood fiber biomass components, and the CO2 can be recycled through pressure reduction and is circularly used for wood fiber raw material treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of lignocellulose processing, in particular to a method for separating three major components of lignocellulose biomass in one step using a carbon dioxide-assisted two-phase solvent. Background Art

[0002] Lignocellulose is the most abundant renewable raw material in nature, widely derived from wood, bamboo, straw, etc., and is mainly composed of cellulose, hemicellulose and lignin (hereinafter referred to as the "three elements"). Cellulose molecules are interwoven into bundles and dispersed in the hemicellulose and lignin components, forming a structure similar to "reinforced concrete", which plays a supporting and protective role in plant growth. However, this structure also makes it difficult to separate these three components by physical means. Traditional chemical pulping methods can usually only utilize one or two of the components (mainly the cellulose component), making it difficult to achieve high-value utilization of the three components.

[0003] Organic solvent structured wood fiber raw materials have attracted a lot of attention due to their simple processing technology and green and pollution-free characteristics. Currently, the more common organic pretreatment systems mainly include single-phase solvent systems and two-phase solvent systems. The single-phase system has better heat and mass transfer effects, so it can obtain better pretreatment effects under similar pretreatment conditions. For the two-phase system, after the pretreatment components are separated, the cellulose component is mainly retained in the solid residue, the hemicellulose component is depolymerized and dissolved in the aqueous phase solvent, and the lignin component is mainly dissolved in the organic phase solvent, which well realizes the separation of the three components of wood cellulose, and thus has incomparable advantages in component separation and product recovery.

[0004] Currently, the most common organic solvent two-phase treatment systems often suffer from the use of additional acid-base catalysts, vigorous mechanical agitation, high solvent toxicity, and subsequent solid-liquid phase separation steps. Therefore, it is crucial to provide a carbon dioxide-assisted two-phase solvent method for the one-step separation of the three major components of lignocellulosic biomass. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for separating the three major components of lignocellulosic biomass in one step by using a two-phase solvent assisted by carbon dioxide, so as to solve the problems of complicated process, large amount of acid and alkali reagents and high cost in the existing lignocellulosic raw material pretreatment methods.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for separating three major components of lignocellulosic biomass in one step using a carbon dioxide-assisted two-phase solvent, comprising the following steps:

[0008] 1) placing the extraction solvent at the bottom of the reactor and fixing the lignocellulosic biomass raw material at the top of the reactor;

[0009] 2) introducing carbon dioxide into the reactor and performing extraction under closed conditions, introducing a cooling medium to adjust the temperature during the extraction process, to obtain a solid phase material, an organic phase, and an aqueous phase; the solid phase material contains crude cellulose, the organic phase contains lignin, and the aqueous phase contains hemicellulose;

[0010] The extraction solvent is a mixture of an organic solvent and water; the mass volume ratio of the lignocellulosic biomass raw material to the extraction solvent is 1g:1-20mL.

[0011] Preferably, the volume ratio of the organic solvent to water is 1-99:99-1; the organic solvent comprises one or more of n-butanol, n-pentanol, 2-methyltetrahydrofuran, methyl isobutyl ketone, dimethoxymethane and xylene.

[0012] Preferably, the lignocellulosic biomass raw material comprises one or more of woody raw materials, herbaceous raw materials, vine raw materials and gramineous raw materials.

[0013] Preferably, the particle size of the lignocellulosic biomass raw material is 20 to 100 meshes.

[0014] Preferably, during the extraction process, the pressure of carbon dioxide is 0.1 to 20 MPa, the extraction temperature is 80 to 230° C., and the extraction time is 10 to 300 min.

[0015] Preferably, the cooling medium comprises one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen; and the cooling medium is introduced intermittently.

[0016] Preferably, the time interval between each introduction of the cooling medium is 1 to 30 minutes; the cooling medium is introduced until the temperature difference inside the reactor changes by 1 to 30°C.

[0017] Preferably, the solid phase material is washed with water and dried in sequence to obtain crude cellulose; the organic phase is subjected to reduced pressure distillation to recover the organic solvent, water is added to the insoluble matter obtained after concentration, and the mixture is filtered and dried in sequence to obtain lignin; the aqueous phase is subjected to reduced pressure distillation to recover water, ethanol is added to the insoluble matter obtained after concentration, the mixture is allowed to stand, the precipitate is filtered after precipitation, and the precipitate is dried to obtain hemicellulose.

[0018] Preferably, the reactor is a stainless steel reactor.

[0019] Beneficial effects of the present invention:

[0020] 1) The present invention provides a method for directional separation of components such as lignin, hemicellulose and cellulose by using carbon dioxide to assist in the non-contact treatment of lignocellulosic biomass with an organic solvent vapor phase. The present invention uses CO2 and water to form carbonic acid as a mild and recyclable acid catalyst source. CO2 cooperates with the extraction solvent to dissolve the lignin and hemicellulose components. By regulating the temperature during the extraction process, the vapor-liquid phase exchange of the extraction solvent is controlled, and the directional migration of the components dissolved in the lignocellulose in the vapor phase solvent to the liquid phase solvent is achieved. The extraction solvent can be recycled multiple times, reducing the overall amount of extraction solvent used in the treatment process. The large amount of dissolved lignin is finally enriched in the liquid phase portion of the extraction solvent at the bottom of the reactor as the extraction solvent phase transforms, while the cellulose component is retained in the solid phase material in the solvent vapor phase. The method of the present invention not only achieves a better lignin separation efficiency, but also greatly reduces the amount of extraction solvent used.

[0021] 2) The CO2 used in the present invention is non-corrosive and can be used as a mild and recyclable acid source. Its aqueous solution is acidic and the H + It can effectively promote the separation of wood fiber biomass components, and CO2 can be recovered by reducing pressure and recycled for wood fiber raw material processing.

[0022] 3) The processing conditions of the present invention are mild and the method is environmentally friendly. By treating the wood fiber raw material with the vapor phase portion of the organic solvent and water that evaporates under the system temperature, a cellulose-rich solid phase material, a hemicellulose-rich aqueous phase solvent, and a lignin-rich organic phase solvent can be obtained without the need for cumbersome filtration and separation.

[0023] 4) The method of the present invention provides technical support for the high-value utilization of lignocellulosic biomass and CO2. DETAILED DESCRIPTION

[0024] The present invention provides a method for separating three major components of lignocellulosic biomass in one step using a carbon dioxide-assisted two-phase solvent, comprising the following steps:

[0025] 1) placing the extraction solvent at the bottom of the reactor and fixing the lignocellulosic biomass raw material at the top of the reactor;

[0026] 2) introducing carbon dioxide into the reactor and performing extraction under closed conditions, introducing a cooling medium to adjust the temperature during the extraction process, to obtain a solid phase material, an organic phase, and an aqueous phase; the solid phase material contains crude cellulose, the organic phase contains lignin, and the aqueous phase contains hemicellulose;

[0027] The extraction solvent is a mixture of an organic solvent and water; the mass volume ratio of the lignocellulosic biomass raw material to the extraction solvent is 1g:1-20mL.

[0028] In the present invention, the mass volume ratio of the lignocellulosic biomass raw material and the extraction solvent is preferably 1 g: 3 to 15 mL, more preferably 1 g: 5 to 12 mL, and even more preferably 1 g: 8 to 10 mL.

[0029] In the present invention, the extraction solvent is preferably a mixture of a water-insoluble organic solvent and water or a mixture of a slightly water-soluble organic solvent and water; the extraction solvent of the present invention can be recycled multiple times.

[0030] In the present invention, the volume ratio of the organic solvent to water is preferably 1-99:99-1, more preferably 30-70:70-30, and more preferably 50-60:40-50; the organic solvent preferably comprises one or more of n-butanol, n-pentanol, 2-methyltetrahydrofuran, methyl isobutyl ketone, dimethoxymethane and xylene.

[0031] In the present invention, when there are two or more organic solvents, there is no particular limitation on the ratio of different types of organic solvents, and the ratio can be adjusted according to needs.

[0032] In the present invention, the lignocellulosic biomass raw material preferably comprises one or more of woody raw materials, herbaceous raw materials, vine raw materials and gramineous raw materials.

[0033] When the wood fiber biomass raw materials are two or more of the above-mentioned two types, the present invention has no special restrictions on the ratio of different types of wood fiber biomass raw materials, which can be adjusted according to actual needs; there is no special restriction on the specific types of woody raw materials, herbaceous raw materials, vine raw materials and gramineous raw materials, and any raw materials well known in the art can be used.

[0034] In the present invention, the particle size of the lignocellulosic biomass raw material is preferably 20 to 100 meshes, more preferably 40 to 80 meshes.

[0035] In the present invention, before fixing the lignocellulosic biomass raw material on the upper part of the reactor, the lignocellulosic biomass is preferably washed, dried and crushed and sieved in sequence to obtain the lignocellulosic biomass raw material; the drying is preferably air-dried, and the drying temperature is preferably 100-110°C, more preferably 102-107°C, and more preferably 105°C. Drying avoids excessive moisture in the material itself during extraction, which reduces the specific gravity of the organic solvent when it enters the material, thereby affecting the dissolution of the lignocellulosic component.

[0036] The invention controls the raw material to be within the range of 20 to 100 meshes to prevent the damage to the cellulose structure and cause loss.

[0037] The present invention preferably places the lignocellulosic biomass raw material in a stainless steel mesh bag container and then fixes it to the upper part of the reactor. The present invention has no particular limitation on the specific location where the lignocellulosic biomass raw material is fixed, as long as the lignocellulosic biomass raw material is ensured not to contact the extraction solvent at the bottom of the reactor.

[0038] In the present invention, during the extraction process, the carbon dioxide pressure is preferably 0.1 to 20 MPa, more preferably 1 to 12 MPa, and more preferably 3 to 8 MPa. The extraction temperature is preferably 80 to 230° C., more preferably 120 to 220° C., and more preferably 150 to 180° C. The extraction time is preferably 10 to 300 min, more preferably 80 to 200 min, and more preferably 150 to 180 min.

[0039] In the present invention, it is preferred to introduce carbon dioxide into the reactor at room temperature to evacuate the air in the cavity and fill it with CO2, thereby avoiding air interference, preventing the oxygen therein from oxidizing the active groups of lignocellulose, and increasing the solubility of CO2 in the extraction solvent.

[0040] In the present invention, the cooling medium preferably comprises one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen; and the method of introducing the cooling medium is preferably intermittent.

[0041] In the present invention, intermittent cooling is preferably used to achieve transitions between the vapor and liquid phases of the extraction solvent and ensure sufficient processing time. This intermittent cooling is used to control the extraction temperature within the reactor, thereby enabling vapor-liquid phase exchange and recycling of the extraction solvent, thereby achieving separation of the lignocellulose components. After cooling, the extraction solvent transitions from a gaseous state to a liquid state, yielding an organic phase extract containing lignin and an aqueous phase extract containing hemicellulose at the bottom of the reactor.

[0042] In the present invention, the time interval for each introduction of the cooling medium is preferably 1 to 30 minutes, more preferably 3 to 20 minutes, and more preferably 5 to 10 minutes; the cooling medium is introduced until the temperature difference inside the reactor changes is preferably 1 to 30°C, more preferably 5 to 25°C, and more preferably 8 to 15°C.

[0043] In the present invention, the temperature difference inside the reactor after the cooling medium is introduced is the temperature difference inside the reactor caused by the cooling medium.

[0044] In the present invention, the solid phase material is preferably washed with water and dried in sequence to obtain crude cellulose; the organic phase is preferably subjected to reduced pressure distillation to recover the organic solvent, water is added to the insoluble matter obtained after concentration, and the mixture is filtered and dried in sequence to obtain lignin; the aqueous phase is preferably subjected to reduced pressure distillation to recover water, ethanol is added to the insoluble matter obtained after concentration, the mixture is allowed to stand, the precipitate is filtered after precipitation, and the precipitate is dried to obtain hemicellulose.

[0045] In the present invention, the reactor is preferably a stainless steel reactor.

[0046] In the present invention, the heating method of the reactor is preferably electric heating. The present invention has no special limitation on the specific specifications, models and sources of the stainless steel reactor, and any stainless steel reactor well known in the art can be used.

[0047] In the present invention, unless otherwise specified, the required materials or reagents are commercially available products well known to those skilled in the art.

[0048] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] In this example, sugarcane bagasse was used as the lignocellulosic biomass feedstock. The solid fraction of cellulose, hemicellulose, and lignin was analyzed according to standard NREL procedures. The mass percentages, calculated by weight, were: crude cellulose 48.43%, hemicellulose 23.15%, and lignin 20.36%. The crude cellulose yield was calculated based on the mass of the initial sugarcane bagasse, the hemicellulose yield was calculated based on the mass of the hemicellulose in the initial sugarcane bagasse, and the lignin yield was calculated based on the mass of the lignin in the initial sugarcane bagasse.

[0050] Example 1

[0051] The sugarcane bagasse was washed with water and dried by air blast at 105° C. After drying, it was crushed and sieved to obtain 20-60 mesh sugarcane bagasse; 10 g of the crushed sugarcane bagasse was placed in a stainless steel mesh bag container. 100 mL of extraction solvent (the volume ratio of n-butanol and water is 60:40) is placed at the bottom of the stainless steel reactor, and then the stainless steel mesh bag container is fixed at the upper position of the stainless steel reactor without contact with the extraction solvent. The reactor lid is covered and sealed, and CO2 is introduced into the reactor body to exhaust the air in the reactor cavity using CO2; CO2 is pressurized, and heating begins after the pressure reaches 4 MPa. The temperature is monitored by the sensor above the reactor lid. After the temperature rises to 180°C, it is kept warm for 180 minutes; during the insulation process, 23°C cooling water is introduced every 5 minutes for temperature control. Each time cooling water is introduced, the temperature difference inside the reactor is 5°C, so as to achieve phase transformation of the extraction solvent and separate the wood fiber components; after the insulation process is completed, the reactor is cooled to room temperature, the stainless steel mesh bag container is removed to obtain a solid residue containing crude cellulose, and the organic phase and aqueous liquid materials at the bottom of the reactor are removed.

[0052] The organic phase was distilled under reduced pressure (vacuum degree: -0.098 MPa) to recover the organic solvent. Water was added to the insoluble matter obtained after concentration, and the mixture was filtered and dried in this order to obtain lignin. The aqueous phase was distilled under reduced pressure to recover the water. To the insoluble matter obtained after concentration, 1 / 2 the volume of the aqueous phase was added with anhydrous ethanol. After standing to precipitate, the precipitate was filtered and dried to obtain hemicellulose. The solid residue was dried to obtain crude cellulose.

[0053] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 93% and 88.85%, respectively, and the cellulose retention rate was 92%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 46.5%, the lignin yield was 81.06%, and the hemicellulose yield was 59.87%.

[0054] Example 2

[0055] The n-butanol in Example 1 was replaced with n-pentanol, and the other conditions were the same as those in Example 1.

[0056] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 92.26% and 91.79%, respectively, and the cellulose retention rate was 91.08%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 49.60%, the lignin yield was 81%, and the hemicellulose yield was 62%.

[0057] Example 3

[0058] The n-butanol in Example 1 was replaced with 2-methyltetrahydrofuran, and the other conditions were the same as those in Example 1.

[0059] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 92.1% and 90.87%, respectively, and the cellulose retention rate was 90.67%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 46.5%, the lignin yield was 84%, and the hemicellulose yield was 61.03%.

[0060] Example 4

[0061] The n-butanol in Example 1 was replaced with methyl isobutyl ketone, and the other conditions were the same as those in Example 1.

[0062] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 88.56% and 89%, respectively, and the cellulose retention rate was 90.2%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 44.05%, the lignin yield was 79.3%, and the hemicellulose yield was 60.32%.

[0063] Example 5

[0064] The sugarcane bagasse was washed with water and dried by forced air at 102° C. After drying, it was crushed and sieved to obtain 30-70 mesh sugarcane bagasse; 10 g of the crushed sugarcane bagasse was placed in a stainless steel mesh bag container. 60 mL of extraction solvent (the volume ratio of n-butanol, dimethoxymethane and water is 30:20:50) is placed at the bottom of the stainless steel reactor, and then the stainless steel mesh bag container is fixed at the upper position of the stainless steel reactor without contact with the extraction solvent. The reactor lid is covered and sealed, and CO2 is introduced into the reactor body to exhaust the air in the reactor cavity using CO2; CO2 is pressurized, and heating begins after the pressure reaches 5 MPa. The temperature is monitored by the sensor above the reactor lid. After the temperature rises to 200°C, it is kept warm for 150 minutes; during the insulation process, 23°C cooling water is introduced every 3 minutes for temperature control. Each time cooling water is introduced, the temperature difference inside the reactor is 15°C, so as to achieve phase transformation of the extraction solvent and separate the wood fiber components; after the insulation process is completed, the reactor is cooled to room temperature, the stainless steel mesh bag container is removed to obtain a solid residue containing crude cellulose, and the organic phase and aqueous liquid materials at the bottom of the reactor are removed.

[0065] The organic phase was distilled under reduced pressure (vacuum degree: -0.098 MPa) to recover the organic solvent. Water was added to the insoluble matter obtained after concentration, and the mixture was filtered and dried in this order to obtain lignin. The aqueous phase was distilled under reduced pressure to recover the water. To the insoluble matter obtained after concentration, 1 / 2 the volume of the aqueous phase was added with anhydrous ethanol. After standing to precipitate, the precipitate was filtered and dried to obtain hemicellulose. The solid residue was dried to obtain crude cellulose.

[0066] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 89.62% and 89.15%, respectively, and the cellulose retention rate was 90.33%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 44.98%, the lignin yield was 82.45%, and the hemicellulose yield was 51.63%.

[0067] Example 6

[0068] The sugarcane bagasse was washed with water and dried by air blast at 107° C. After drying, it was crushed and sieved to obtain 40-90 mesh sugarcane bagasse. 10 g of the crushed sugarcane bagasse was placed in a stainless steel mesh bag container. 150 mL of extraction solvent (the volume ratio of xylene and water is 40:60) is placed at the bottom of the stainless steel reactor, and then the stainless steel mesh bag container is fixed at the upper position of the stainless steel reactor without contact with the extraction solvent. The reactor lid is covered and sealed, and CO2 is introduced into the reactor body to exhaust the air in the reactor cavity using CO2; CO2 is pressurized, and heating begins after the pressure reaches 8 MPa. The temperature is monitored by the sensor above the reactor lid. After the temperature rises to 150°C, it is kept warm for 190 minutes; during the insulation process, 23°C cooling water is introduced every 10 minutes for temperature control. Each time cooling water is introduced, the temperature difference inside the reactor is 10°C, so as to achieve phase transformation of the extraction solvent and separate the wood fiber components; after the insulation process is completed, wait for the reactor to cool to room temperature, remove the stainless steel mesh bag container, obtain a solid residue containing crude cellulose, and remove the organic phase and aqueous liquid materials at the bottom of the reactor.

[0069] The organic phase was distilled under reduced pressure (vacuum degree: -0.098 MPa) to recover the organic solvent. Water was added to the insoluble matter obtained after concentration, and the mixture was filtered and dried in this order to obtain lignin. The aqueous phase was distilled under reduced pressure to recover the water. To the insoluble matter obtained after concentration, 1 / 2 the volume of the aqueous phase was added with anhydrous ethanol. After standing to precipitate, the precipitate was filtered and dried to obtain hemicellulose. The solid residue was dried to obtain crude cellulose.

[0070] The solid residue of this example was subjected to component analysis, and the hemicellulose and lignin removal rates were 90.21% and 79.65%, respectively, and the cellulose retention rate was 90.38%. The recovered crude cellulose, lignin, and hemicellulose were weighed, and the crude cellulose yield was 44.08%, the lignin yield was 72.06%, and the hemicellulose yield was 55.31%.

[0071] The present invention uses carbonic acid formed in situ by CO2 as a source of pretreatment acid catalyst, and as a solvent penetration enhancer to cooperate with an extraction solvent containing an organic phase and an aqueous phase to dissolve lignin and hemicellulose components. By regulating the extraction temperature, the vapor-liquid phase conversion of the organic phase and the aqueous phase extraction solvent is controlled, and the components dissolved by the vapor phase solvent are directional migrated to the organic phase and the aqueous phase in the liquid phase below. A large amount of dissolved lignin and hemicellulose are enriched in the organic phase and the aqueous phase of the extraction solvent at the bottom of the reactor as the extraction solvent phase is converted, while the cellulose component is retained in the initial solid phase material, so that lignin, hemicellulose and cellulose are independently separated after one-step treatment. The present invention uses a two-phase solvent to completely separate lignocellulose in a one-step process under mild carbon dioxide conditions to obtain cellulose, lignin and hemicellulose, thereby achieving green and efficient biomass pretreatment.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for separating the three major components of lignocellulosic biomass in one step using a carbon dioxide-assisted two-phase solvent, characterized in that: The following steps are included: 1) placing the extraction solvent at the bottom of the reactor and fixing the lignocellulosic biomass raw material at the top of the reactor; 2) introducing carbon dioxide into the reactor and performing extraction under closed conditions, introducing a cooling medium to adjust the temperature during the extraction process, to obtain a solid phase material, an organic phase, and an aqueous phase; the solid phase material contains crude cellulose, the organic phase contains lignin, and the aqueous phase contains hemicellulose; The extraction solvent is a mixture of an organic solvent and water; the mass volume ratio of the lignocellulosic biomass raw material to the extraction solvent is 1g:1-20mL.

2. The method according to claim 1, characterized in that The volume ratio of the organic solvent to water is 1-99:99-1; the organic solvent comprises one or more of n-butanol, n-pentanol, 2-methyltetrahydrofuran, methyl isobutyl ketone, dimethoxymethane and xylene.

3. The method according to claim 1 or 2, characterized in that The wood fiber biomass raw material comprises one or more of woody raw materials, herbaceous raw materials, vine raw materials and gramineous raw materials.

4. The method according to claim 3, characterized in that The particle size of the wood fiber biomass raw material is 20 to 100 meshes.

5. The method according to claim 4, characterized in that During the extraction process, the pressure of carbon dioxide is 0.1-20 MPa, the extraction temperature is 80-230° C., and the extraction time is 10-300 min.

6. The method according to claim 4 or 5, characterized in that The cooling medium comprises one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen; and the cooling medium is introduced intermittently.

7. The method according to claim 6, characterized in that The time interval for each introduction of the cooling medium is 1 to 30 minutes; the cooling medium is introduced until the temperature difference inside the reactor changes by 1 to 30°C.

8. The method according to claim 7, characterized in that The solid phase material is washed with water and dried in sequence to obtain crude cellulose; the organic phase is subjected to reduced pressure distillation to recover the organic solvent, and water is added to the insoluble matter obtained after concentration, and the mixture is filtered and dried in sequence to obtain lignin; the aqueous phase is subjected to reduced pressure distillation to recover water, and ethanol is added to the insoluble matter obtained after concentration, and the mixture is allowed to stand, and the precipitate is filtered after precipitation, and the precipitate is dried to obtain hemicellulose.

9. The method according to claim 7 or 8, characterized in that The reactor is a stainless steel reactor.