Method for carbon dioxide assisted organic solvent vapor-liquid phase oriented separation of wood fiber biomass

Abstract

The invention provides a method for carbon dioxide assisted organic solvent vapor-liquid phase oriented separation of wood fiber biomass, and belongs to the technical field of wood fiber biomass chemical engineering. According to the method, carbonic acid formed by CO2 and water is used as a mild and recoverable acid catalyst source, the CO2 cooperates with the extraction solvent to dissolve lignin and hemicellulose components, and vapor-liquid phase exchange of the extraction solvent is controlled by regulating and controlling the temperature change in the extraction process; the directional migration of components dissolved from lignocellulose in the vapor-phase solvent to the liquid-phase solvent is realized, the repeated recycling of the extraction solvent is realized, and the overall dosage of the extraction solvent in the treatment process is reduced. A large amount of dissolved lignin is finally enriched in a liquid phase part of the extraction solvent at the bottom of the reaction container along with phase conversion of the extraction solvent, and a cellulose component is retained in a solid phase material. The method provided by the invention not only realizes better lignin separation efficiency, but also greatly reduces the use amount of the extraction solvent.

Description

Technical Field

[0001] The invention relates to the technical field of wood fiber biomass chemical industry, and in particular to a method for carbon dioxide-assisted organic solvent vapor-liquid phase directional separation of wood fiber biomass. Background Art

[0002] Lignocellulosic biomass is mainly composed of cellulose, hemicellulose and lignin, among which lignin and hemicellulose act as binders and reinforcing agents between celluloses. Their complex structures hinder the dissociation of lignocellulosic raw materials by chemicals, enzymes and microorganisms. By pretreating lignocellulosic biomass, the anti-degradation barrier (lignin) in lignocellulosic raw materials can be effectively broken, and the carbohydrates (cellulose and hemicellulose) in lignocellulosic raw materials can be effectively utilized.

[0003] At present, different pulping processes such as kraft pulping and sulfite pulping have been well applied in industry. However, these processes use a large amount of chemicals in the treatment process, and the severe acid-base conditions are easy to corrode the reaction equipment, thereby increasing the treatment cost. The deconstruction of wood fiber raw materials by organic solvents has attracted a lot of attention due to its simple treatment process and green and pollution-free characteristics. However, the current process of pretreatment of wood fiber biomass with organic solvents is usually carried out under the condition that the ratio of wood fiber raw material to solvent is 1:10 to 1:20, and the overall solvent consumption is large. In addition, in order to achieve a better separation and deconstruction effect of wood fiber, it is usually necessary to introduce additional inorganic acid or alkali reagents as catalysts. Therefore, it is urgent to develop a more economical and low-carbon treatment process to achieve efficient separation of wood fiber biomass components. Summary of the invention

[0004] The purpose of the present invention is to provide a method for separating lignocellulosic biomass by vapor-liquid phase directional separation of lignocellulosic biomass assisted by carbon dioxide, so as to solve the problems of large amount of organic solvent, long treatment cycle and high cost in the existing lignocellulosic raw material pretreatment methods.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for separating lignocellulosic biomass by vapor-liquid phase directional separation of organic solvent assisted by carbon dioxide, comprising the following steps:

[0007] placing an extraction solvent at the bottom of the reaction vessel;

[0008] Fixing the lignocellulosic biomass raw material on the upper part of the reaction container without contacting with the extraction solvent;

[0009] After carbon dioxide is introduced into the reaction container, it is sealed and extraction is performed under carbon dioxide pressurized conditions. During the extraction process, a cooling medium is introduced to adjust the temperature. After the extraction is completed, a primary extract is obtained at the bottom of the reaction container;

[0010] Replacing the wood fiber biomass raw material at the top of the reaction container, and performing cyclic extraction at the bottom of the reaction container using the primary extraction solution as the extraction solvent to obtain a solid phase material containing crude cellulose and a liquid phase material containing lignin and hemicellulose; the number of cyclic extractions is ≥ 0 times;

[0011] The ratio of the lignocellulosic biomass raw material to the extraction solvent is 1 g: 1 to 15 mL;

[0012] The extraction temperature is 55-210°C.

[0013] Preferably, the extraction solvent is an organic solvent, water or an organic solvent-water mixture; the volume ratio of the organic solvent to water in the organic solvent-water mixture is 10:90 to 90:10; the organic solvent includes one or more of methanol, ethanol and n-propanol.

[0014] Preferably, the lignocellulosic biomass raw material includes one or more of woody raw materials, herbaceous raw materials, rattan raw materials and gramineous raw materials.

[0015] Preferably, the pressure of carbon dioxide in the pressurized condition is 0.1-10 MPa.

[0016] Preferably, the time of each extraction is independently 10 to 300 minutes; when performing cyclic extraction, the wood fiber biomass raw material to be processed is fixed at the upper position of the reaction container, placed above the liquid phase material, and has no direct contact with the liquid phase material.

[0017] Preferably, the steps of a single cycle extraction are: using the primary extraction solution as the extraction solvent, replacing the wood fiber biomass raw material on the upper part of the reaction container, and then extracting again; the number of the cycle extraction is 1 to 3 times.

[0018] Preferably, the cooling medium includes one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen.

[0019] Preferably, the cooling medium is introduced intermittently, and the time interval for introducing the cooling medium is 1 to 30 minutes; the cooling medium is introduced until the temperature difference inside the reaction container changes by 1 to 30°C.

[0020] Preferably, the crude cellulose-containing solid phase material is washed with water and then freeze-dried in vacuum to obtain crude cellulose.

[0021] Preferably, the lignin-containing hemicellulose liquid phase material is mixed with water, allowed to stand to precipitate a precipitate, and then filtered and freeze-dried in sequence to obtain lignin.

[0022] The present invention provides a method for directional separation of lignocellulosic biomass by vapor-liquid phase with assistance of carbon dioxide and organic solvent. The present invention adopts carbonic acid formed by CO2 and water as a mild and recyclable acid catalyst source. CO2 cooperates with extraction solvent to dissolve lignin and hemicellulose components. By regulating the temperature change during the extraction process, the vapor-liquid phase exchange of the extraction solvent is controlled, and the directional migration of components dissolved from lignocellulose in the vapor phase solvent to the liquid phase solvent is achieved, and the extraction solvent is recycled multiple times, thereby reducing the overall amount of extraction solvent used in the treatment process. A large amount of dissolved lignin is finally enriched in the liquid phase part of the extraction solvent at the bottom of the reaction vessel as the extraction solvent phase transforms, while the cellulose component is retained in the solid phase material after the vapor phase solvent extraction. The method of the present invention not only achieves a good lignin separation efficiency, but also greatly reduces the amount of extraction solvent used.

[0023] The invention provides a method for directional separation of components such as lignin, hemicellulose and cellulose by non-contact pretreatment of lignocellulose by using carbon dioxide-assisted organic solvent vapor phase.

[0024] Beneficial effects of the present invention:

[0025] 1. CO2 is a mild and recyclable acid source. Its aqueous solution is acidic and the H + It can effectively promote the separation between wood fiber biomass components, and CO2 can be recovered by decompression and recycled for wood fiber raw material processing.

[0026] 2. The present invention relies on the vapor phase of the organic solvent evaporated by heat at the system temperature to pretreat the wood fiber raw material. The first pretreatment extract can be used for repeated pretreatment of wood fiber. The extraction method can be recycled and the amount of solvent used is small.

[0027] 3. The method of the present invention has mild processing conditions and is environmentally friendly; low organic solvent dosage and heating treatment can achieve directional migration of hemicellulose and lignin components in wood cellulose to liquid solvent after extraction by vapor phase solvent, while cellulose is retained in the solid phase residue after extraction by vapor phase solvent. After depressurization and discharge of CO2, a solid phase rich in cellulose and a liquid phase rich in hemicellulose and lignin can be obtained without complicated filtration and separation.

[0028] 4. The present invention provides technical support for the high-value utilization of wood fiber biomass and CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The XRD spectra of bagasse raw material and crude cellulose obtained in Example 4 are shown. DETAILED DESCRIPTION

[0030] The present invention provides a method for separating lignocellulosic biomass by vapor-liquid phase directional separation of organic solvent assisted by carbon dioxide, comprising the following steps:

[0031] placing an extraction solvent at the bottom of the reaction vessel;

[0032] Fixing the lignocellulosic biomass raw material on the upper part of the reaction container without contacting with the extraction solvent;

[0033] After carbon dioxide is introduced into the reaction container, it is sealed and extraction is performed under carbon dioxide pressurized conditions. During the extraction process, a cooling medium is introduced to adjust the temperature. After the extraction is completed, a primary extract is obtained at the bottom of the reaction container;

[0034] Replacing the wood fiber biomass raw material at the top of the reaction container, and performing cyclic extraction at the bottom of the reaction container using the primary extraction solution as the extraction solvent to obtain a solid phase material containing crude cellulose and a liquid phase material containing lignin and hemicellulose; the number of cyclic extractions is ≥ 0 times;

[0035] The ratio of the lignocellulosic biomass raw material to the extraction solvent is 1 g: 1 to 15 mL;

[0036] The extraction temperature is 55-210°C.

[0037] In the present invention, unless otherwise specified, the required materials or reagents are commercially available products well known to those skilled in the art.

[0038] The invention places the extraction solvent at the bottom of the reaction container.

[0039] In the present invention, the extraction solvent is preferably an organic solvent, water or an organic solvent-water mixture; the organic solvent preferably includes one or more of methanol, ethanol and n-propanol, more preferably ethanol; the volume ratio of the organic solvent to water in the organic solvent-water mixture is 10:90 to 90:10, more preferably 25:75 to 50:50, and further preferably 25:75. When the organic solvent is two or more of the above, the present invention has no special limitation on the ratio of different types of organic solvents, and can be adjusted according to demand.

[0040] In the present invention, the reaction container is preferably a stainless steel reactor, and the heating method of the reaction container 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 reactor well known in the art can be used.

[0041] The invention fixes the wood fiber biomass raw material on the upper part of the reaction container without contacting with the extraction solvent.

[0042] In the present invention, the lignocellulosic biomass raw material preferably includes one or more of a woody raw material, a herbaceous raw material, a rattan raw material, and a gramineous raw material; the herbaceous raw material is preferably bagasse; when the lignocellulosic biomass raw material is two or more of the above, the present invention has no special restrictions on the ratio of different types of lignocellulosic biomass raw materials, and can be adjusted according to actual needs. The present invention has no special restrictions on the specific types of the woody raw materials, herbaceous raw materials, rattan raw materials, and gramineous raw materials, and any corresponding raw materials known in the art can be used.

[0043] In the present invention, before the lignocellulosic biomass raw material is fixed on the upper part of the reaction container, the lignocellulosic biomass raw material is preferably washed, dried, crushed and sieved in sequence;

[0044] In the present invention, the drying is preferably carried out by drying the wood fiber biomass raw material at 105°C by forced air. Drying is used to avoid excessive moisture in the material during extraction, which reduces the specific gravity of the organic solvent when it enters the material, thereby affecting the dissolution of the wood fiber component.

[0045] In the present invention, the crushing and screening is preferably: the wood fiber biomass raw material is crushed by a mechanical crusher, and screened to obtain 20-100 mesh materials. The present invention controls the raw material to 20-100 mesh to prevent damage to the cellulose structure and cause its loss.

[0046] The present invention preferably places the wood fiber biomass raw material in a stainless steel mesh bag container and then places it on the top of the reaction container. The present invention has no particular limitation on the specific location of the fixation, as long as the wood fiber biomass raw material is not in contact with the extraction solvent at the bottom of the reaction container.

[0047] In the present invention, the usage ratio of the lignocellulosic biomass raw material to the extraction solvent is preferably 1 g: 1 to 15 mL, more preferably 1 g: 10 mL.

[0048] The invention introduces carbon dioxide into the reaction container, seals it, and performs extraction under carbon dioxide pressurization conditions. During the extraction process, a cooling medium is introduced to adjust the temperature. After the extraction is completed, a primary extract is obtained at the bottom of the reaction container.

[0049] The carbon dioxide described in the present invention is preferably commercially available carbon dioxide.

[0050] The present invention preferably introduces carbon dioxide into the reaction container at room temperature to evacuate the air in the cavity, fill it with CO2, avoid air interference, prevent oxygen therein from oxidizing the active groups of lignocellulose, and increase the solubility of CO2 in the extraction solvent.

[0051] In the present invention, the pressure of carbon dioxide in the pressurized condition is preferably 0.1 to 10 MPa, more preferably 2 to 6 MPa, and even more preferably 3 to 4 MPa.

[0052] In the present invention, the temperature of each extraction is independently preferably 55-210°C, more preferably 140-200°C, more preferably 180-190°C, and the time of each extraction is independently preferably 10-300 min, more preferably 60-300 min, further preferably 180-240 min.

[0053] In the present invention, the cooling medium is preferably one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen. In order to achieve the exchange between the vapor and liquid phases of the extraction solvent and ensure sufficient processing time, the method of introducing the cooling medium is preferably intermittent, and the time interval for introducing the cooling medium is preferably 1 to 30 minutes, more preferably 5 to 20 minutes.

[0054] The present invention controls the extraction temperature in the reaction container by intermittently introducing a cooling medium, thereby performing a solvent vapor-liquid phase exchange to achieve a cyclic renewal of the extraction solvent, thereby achieving separation of the lignocellulose components. Therefore, after the cooling, the extraction solvent is converted from a gaseous state to a liquid state, and an extraction liquid is obtained at the bottom of the reaction container.

[0055] In the present invention, the cooling medium is introduced until the temperature difference inside the reaction vessel changes by preferably 1 to 30°C, more preferably 5°C, that is, the temperature difference inside the reactor caused by the cooling medium changes by 1 to 30°C.

[0056] After obtaining the primary extract, the present invention replaces the wood fiber biomass raw material on the upper part of the reaction container, uses the primary extract as the extraction solvent at the bottom of the reaction container, performs cyclic extraction, and obtains a solid phase material containing crude cellulose and a liquid phase material containing lignin and hemicellulose.

[0057] In the present invention, the step of single cycle extraction is preferably: using the primary extraction solution as the extraction solvent, replacing the wood fiber biomass raw material on the upper part of the reaction container, and then extracting again.

[0058] The process of obtaining the primary extract is recorded as the primary extraction process. After the primary extraction process is completed, the wood fiber biomass raw material on the upper part of the reaction container is replaced, and the primary extract is used as the extraction solvent for cyclic extraction.

[0059] In the present invention, the number of cyclic extractions is ≥ 0 times, and more preferably 1 to 3 times; that is, starting from the first extraction (obtaining the initial extract is the first extraction), the total number of extraction treatments is preferably 1 to 4 times.

[0060] In the present invention, the crude cellulose-containing solid phase material is washed with water and then vacuum freeze-dried to obtain crude cellulose. In the present invention, the crude cellulose-containing solid phase material is preferably washed with water until neutral; there is no special limitation on the vacuum freeze-drying process, which can be carried out according to the process well known in the art.

[0061] In the present invention, the lignin-hemicellulose liquid phase material is mixed with water, allowed to stand to precipitate a precipitate, and then filtered and freeze-dried in sequence to obtain lignin; the volume ratio of the lignin-hemicellulose liquid phase material to water is preferably 1:2; the present invention has no special limitation on the filtration and freeze-drying, and can be carried out according to processes well known in the art.

[0062] In the present invention, when the number of cyclic extractions is ≥ 1, after all extraction reactions are completed, the solid residues and liquid materials from multiple cycles are collected and processed according to the above steps to obtain crude cellulose and lignin.

[0063] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0064] The following examples of the present invention use bagasse as the lignocellulosic biomass raw material, and the content composition of cellulose, hemicellulose and lignin in the solid part is analyzed according to the standard NREL process. The mass percentages are: cellulose 48.43%, hemicellulose 23.15%, and lignin 20.36%, respectively.

[0065] Example 1

[0066] The bagasse was washed with water, dried with forced air at 105°C, and then crushed and sieved to obtain bagasse of 20-100 meshes; 10 g of crushed bagasse was placed in a stainless steel mesh bag container, 100 mL of extraction solvent (ethanol: water = 100:0, v / v) was placed at the bottom of a stainless steel reactor, and the stainless steel mesh bag container was placed in the upper part of the stainless steel reactor body without contact with the extraction solvent, the reactor cover was closed, and after sealing, CO2 was introduced into the reactor body, and the air in the reactor cavity was exhausted by CO2, and pressurized (4MPa CO2). After the pressure reached the target value, heating was started, and the temperature was monitored by a sensor above the reactor cover. After the temperature rose to 180°C, it was kept warm for 180 minutes; during the insulation process, cooling water was introduced every 5 minutes for temperature control, and the temperature change difference inside the reactor was 5°C, so as to realize the phase transformation of the extraction solvent and deconstruction and separation of the wood fiber components; after the insulation process was completed, the reactor was cooled to room temperature, the stainless steel mesh bag container was taken out, and the solid residue containing crude cellulose was obtained, and the liquid material at the bottom of the reactor was taken out;

[0067] The liquid material is mixed with deionized water in a volume ratio of 1:2, and after standing to precipitate, the mixture is filtered and freeze-dried in sequence to obtain lignin;

[0068] The solid residue was washed with deionized water and then freeze-dried in vacuum to obtain crude cellulose.

[0069] Example 2

[0070] The only difference from Example 1 is: extraction solvent (ethanol: water = 75:25, v / v).

[0071] Example 3

[0072] The only difference from Example 1 is: extraction solvent (ethanol: water = 50:50, v / v).

[0073] Example 4

[0074] The only difference from Example 1 is: extraction solvent (ethanol: water = 25:75, v / v).

[0075] Example 5

[0076] The only difference from Example 1 is: extraction solvent (ethanol:water=0:100, v / v).

[0077] Example 6

[0078] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 140° C., it is kept warm for 180 minutes.

[0079] Example 7

[0080] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 160° C., it is kept warm for 180 minutes.

[0081] Example 8

[0082] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 190° C., it is kept warm for 180 minutes.

[0083] Example 9

[0084] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 200° C., it is kept warm for 180 min.

[0085] Example 10

[0086] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 180° C., it is kept warm for 60 minutes.

[0087] Embodiment 11

[0088] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 180° C., it is kept warm for 120 minutes.

[0089] Example 12

[0090] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 180° C., it is kept warm for 240 minutes.

[0091] Embodiment 13

[0092] The only difference from Example 1 is that the extraction solvent (ethanol: water = 25:75, v / v) is used, the temperature is monitored by a sensor above the kettle cover, and after the temperature rises to 180° C., it is kept warm for 300 min.

[0093] Embodiment 14

[0094] The sugarcane bagasse was washed with water, dried with air at 105°C, and then crushed and sieved to obtain 20-100 mesh bagasse; 10g of the crushed bagasse was placed in a stainless steel mesh bag container, 100mL of extraction solvent (ethanol: water = 25:75, v / v) was placed at the bottom of a stainless steel reactor, and the stainless steel mesh bag container was placed in the upper part of the stainless steel reactor body without contact with the solvent, the reactor cover was covered, and after sealing, CO2 was introduced into the reactor body, and the air in the reactor cavity was exhausted by CO2, and pressurized (4MPa CO2). After the pressure reached the target value, heating was started, and the temperature was monitored by a sensor above the reactor cover. After the temperature rose to 180°C, it was kept warm for 180min; during the insulation process, cooling water was introduced every 5min to control the temperature, and the temperature change difference inside the reactor was 5°C, so as to achieve phase transformation of the extraction solvent and deconstruction and separation of the wood fiber components; after the insulation process was completed, the reactor was cooled to room temperature, and the stainless steel mesh bag container was taken out to obtain solid residue; the obtained liquid material was the primary extract. Then, a new wood fiber biomass raw material is replaced, 10 g of crushed bagasse is loaded into a stainless steel mesh bag container, and then the stainless steel mesh bag container is placed in the upper position of a stainless steel reactor body without contact with the solvent, and the initial extract is retained at the bottom of the reactor for a cycle extraction under the same conditions, and a solid residue is obtained after the insulation is completed; the liquid material obtained at the bottom of the reactor is mixed with deionized water in a volume ratio of 1:2, and after standing to precipitate, it is filtered and freeze-dried in sequence to obtain lignin; the solid residues obtained by the combined extraction are washed with deionized water, and then vacuum freeze-dried to obtain crude cellulose.

[0095] Embodiment 15

[0096] The sugarcane bagasse was washed with water, dried with air at 105°C, and then crushed and sieved to obtain 20-100 mesh bagasse; 10g of the crushed bagasse was placed in a stainless steel mesh bag container, 100mL of extraction solvent (ethanol: water = 25:75, v / v) was placed at the bottom of a stainless steel reactor, and the stainless steel mesh bag container was placed in the upper part of the stainless steel reactor body without contact with the solvent, the reactor cover was covered, and after sealing, CO2 was introduced into the reactor body, and the air in the reactor cavity was exhausted by CO2, and pressurized (4MPa CO2). After the pressure reached the target value, heating was started, and the temperature was monitored by a sensor above the reactor cover. After the temperature rose to 180°C, it was kept warm for 180min; during the insulation process, cooling water was introduced every 5min to control the temperature, and the temperature change difference inside the reactor was 5°C, so as to achieve phase transformation of the extraction solvent and deconstruction and separation of the wood fiber components; after the insulation process was completed, the reactor was cooled to room temperature, and the stainless steel mesh bag container was taken out to obtain solid residue; the obtained liquid material was the primary extract. Then, a new wood fiber biomass raw material is replaced, 10 g of crushed bagasse is loaded into a stainless steel mesh bag container, and the stainless steel mesh bag container is placed in the upper position of a stainless steel reactor body without contact with the solvent, the primary extract is retained at the bottom of the reactor for a circulation extraction under the same conditions, and a solid residue and a circulating extract are obtained after the insulation process is completed; a new wood fiber biomass raw material is replaced, 10 g of crushed bagasse is loaded into a stainless steel mesh bag container, and the stainless steel mesh bag container is placed in the upper position of a stainless steel reactor body without contact with the solvent, the circulating extract is retained at the bottom of the reactor for a secondary circulation extraction under the same conditions, and a solid residue is obtained after the insulation process is completed; the liquid material obtained at the bottom of the reactor is mixed with deionized water in a volume ratio of 1:2, and after standing to precipitate, it is filtered and freeze-dried in sequence to obtain lignin; the solid residue obtained by the combined extraction is washed with deionized water, and then vacuum freeze-dried to obtain crude cellulose.

[0097] Example 16

[0098] The sugarcane bagasse was washed with water, dried with air at 105°C, and then crushed and sieved to obtain 20-100 mesh bagasse; 10g of the crushed bagasse was placed in a stainless steel mesh bag container, 100mL of extraction solvent (ethanol: water = 25:75, v / v) was placed at the bottom of a stainless steel reactor, and the stainless steel mesh bag container was placed in the upper part of the stainless steel reactor body without contact with the solvent, the reactor cover was covered, and after sealing, CO2 was introduced into the reactor body, and the air in the reactor cavity was exhausted by CO2, and pressurized (4MPa CO2). After the pressure reached the target value, heating was started, and the temperature was monitored by a sensor above the reactor cover. After the temperature rose to 180°C, it was kept warm for 180min; during the insulation process, cooling water was introduced every 5min to control the temperature, and the temperature change difference inside the reactor was 5°C, so as to achieve phase transformation of the extraction solvent and deconstruction and separation of the wood fiber components; after the insulation process was completed, the reactor was cooled to room temperature, and the stainless steel mesh bag container was taken out to obtain solid residue; the obtained liquid material was the primary extract. Then, a new wood fiber biomass raw material is replaced, 10 g of crushed bagasse is loaded into a stainless steel mesh bag container, and the stainless steel mesh bag container is placed in an upper position inside a stainless steel reactor body without contacting with the solvent, and the primary extract is retained at the bottom of the reactor for a circulation extraction under the same conditions, and a solid residue and a circulation extract are obtained after the insulation process is completed; a new wood fiber biomass raw material is replaced, 10 g of crushed bagasse is loaded into a stainless steel mesh bag container, and the stainless steel mesh bag container is placed in an upper position inside a stainless steel reactor body without contacting with the solvent, and the circulation extract is retained at the bottom of the reactor for a secondary circulation extraction under the same conditions. , after the insulation process is over, the treated solid residue is taken out; then a new wood fiber biomass raw material is replaced, 10g of crushed bagasse is loaded into a stainless steel mesh bag container, and then the stainless steel mesh bag container is placed in the upper position of the stainless steel reactor body without contact with the solvent, and the circulating extract is retained at the bottom of the reactor for three cycles of extraction under the same conditions, and the final solid residue is obtained after the insulation is completed; the liquid material obtained at the bottom of the reactor is mixed with deionized water, precipitated, filtered and freeze-dried in sequence to obtain lignin; the solid residue obtained by the combined extraction is washed with deionized water, and then vacuum freeze-dried to obtain crude cellulose.

[0099] Embodiment 17

[0100] The sugarcane bagasse was washed with water, dried under blast air at 105°C, and then crushed and sieved to obtain 20-100 mesh bagasse; 10 g of the crushed bagasse was placed in a stainless steel mesh bag container, 33 mL of extraction solvent (ethanol: water = 25:75, v / v) was placed at the bottom of a stainless steel reactor, and the stainless steel mesh bag container was placed in the upper part of the stainless steel reactor body without contact with the solvent, the reactor cover was closed, and after sealing, CO2 was introduced into the reactor body to exhaust the air in the reactor cavity using CO2, and pressurized (4 MPa) CO2), and heating begins after the pressure reaches the target value. The temperature is monitored by a sensor on the kettle cover. After the temperature rises to 180°C, it is kept warm for 180 minutes. During the insulation process, cooling water is introduced every 5 minutes to control the temperature. The temperature change difference inside the reactor is 5°C, so as to achieve the phase transformation of the extraction solvent and deconstruct 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 taken out to obtain the solid residue, and the liquid material at the bottom of the reactor is taken out; the liquid material is mixed with deionized water, precipitated, filtered and freeze-dried in sequence to obtain lignin; the solid residue is washed with deionized water, and then vacuum freeze-dried to obtain crude cellulose.

[0101] Table 1 Treatment conditions of Examples 1 to 17

[0102]

[0103]

[0104] Characterization and testing

[0105] 1) Figure 1 is the XRD spectrum of the bagasse raw material and the crude cellulose obtained in Example 4; Figure 1 It can be seen that after bagasse is treated by the method of the present invention, the cellulose crystal structure in the crude cellulose does not change, indicating that the cellulose crystal structure is not destroyed. In addition, since components such as lignin and hemicellulose are largely removed in Example 4, the crystallinity of the obtained crude cellulose increases from 46.84% to 61.80%.

[0106] 2) According to the NREL standard method, the cellulose content and the residual hemicellulose and lignin component contents in the crude cellulose recovered in Examples 1 to 17 were determined. The results are shown in Tables 2 to 5.

[0107] Table 2 Effect of ethanol dosage in extraction solvent on separation of lignocellulosic biomass components

[0108]

[0109] Table 2 shows that the lignocellulosic biomass raw material was processed under the conditions of a raw material to extraction solvent ratio (m / v) of 1:10, a temperature of 180°C, a time of 3 h, and different ethanol dosage ratios.

[0110] It can be seen from Table 2 that by adjusting the composition ratio of the extraction solvent and reducing the amount of ethanol in the extraction solvent, a better separation effect of wood fiber biomass components can be achieved. When the proportion of ethanol in the extraction solvent is 25%, the cellulose content in the crude cellulose obtained in Example 4 reaches a maximum of 80.45%, and the hemicellulose and lignin contents are 6.55% and 5.01%, respectively. While retaining cellulose, a large amount of lignin and hemicellulose are selectively removed.

[0111] Table 3 Effect of treatment temperature on the separation of lignocellulosic biomass components

[0112]

[0113]

[0114] Table 3 shows that the lignocellulosic biomass raw material was processed under the conditions of a raw material to extraction solvent ratio (m / v) of 1:10, ethanol usage of 25%, a time of 3 h and different temperatures.

[0115] As shown in Table 3, as the treatment temperature gradually increases, it is beneficial to remove hemicellulose and lignin from lignocellulosic biomass. However, too high a temperature will lead to partial degradation of the cellulose component and significantly reduce the crude cellulose yield. The cellulose content in the crude cellulose obtained in Example 8 is as high as 83.72%, and the hemicellulose and lignin contents are 6.28% and 3.03%, respectively.

[0116] Table 4 Effect of treatment time on the separation of lignocellulosic biomass components

[0117]

[0118] Table 4 shows that the lignocellulosic biomass raw material was processed under the conditions of a raw material to extraction solvent ratio (m / v) of 1:10, ethanol usage of 25%, a temperature of 180°C and different time conditions.

[0119] As shown in Table 4, gradually extending the treatment time is beneficial to the removal of hemicellulose and lignin from the lignocellulosic biomass, but too long a treatment time will lead to partial degradation of the cellulose component and reduce the crude cellulose recovery rate. The crude cellulose yield obtained in Example 13 was 40.9%, of which the cellulose content was 83.71%, and the hemicellulose and lignin contents were 6.02% and 3.1%, respectively.

[0120] Table 5 Effect of the number of extraction cycles on the separation of lignocellulosic biomass components

[0121]

[0122]

[0123] Table 5 shows that when the ratio of the total amount of raw materials to the amount of extraction solvent (m / v) is 1:10, the ethanol usage accounts for 25%, the temperature is 180°C and the single treatment time is 3h, the extraction liquid is used as the extraction solvent to continue the recycling treatment of fresh bagasse.

[0124] As shown in Table 5, a good separation effect of lignocellulosic biomass is still maintained within a certain number of cyclic extractions, but the lignin recovery rate decreases significantly when the number of cycles is large. After 2 cycles, the cellulose content in the crude cellulose obtained in Example 15 reaches 78.45%, and the hemicellulose and lignin contents are 6.95% and 6.11% respectively. While retaining cellulose, a large amount of lignin and hemicellulose are selectively removed; after 3 cycles, the cellulose content in the crude cellulose obtained in Example 16 reaches 78.64%, and the hemicellulose and lignin contents are 7.98% and 6.65% respectively, which still has a good separation effect, but more lignin exceeds the solubility of the extraction solvent and is deposited at the bottom of the reactor to form a carbon layer, which will reduce the final lignin recovery rate. In Example 15, the ratio of the total amount of raw materials to the extraction solvent can reach 1:3.3. When the ratio of the amount of lignocellulosic raw materials to the amount of extraction solvent is 1:3.3 (the ratio of the amount of lignocellulosic raw materials to the amount of organic solvent is 1:0.83) and is not circulated, the separation effect of the crude cellulose components obtained in Example 17 is poor. According to the technical solution of the present invention, the separation of wood fiber biomass components with low solvent dosage can be achieved while maintaining excellent separation effect.

[0125] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for directional separation of lignocellulosic biomass by vapor-liquid phase of organic solvent assisted by carbon dioxide, comprising the following steps: placing an extraction solvent at the bottom of the reaction vessel; Fixing the lignocellulosic biomass raw material on the upper part of the reaction container without contacting with the extraction solvent; After carbon dioxide is introduced into the reaction container, it is sealed and extraction is performed under carbon dioxide pressurized conditions. During the extraction process, a cooling medium is introduced to adjust the temperature. After the extraction is completed, a primary extract is obtained at the bottom of the reaction container; Replacing the wood fiber biomass raw material at the top of the reaction container, and performing cyclic extraction at the bottom of the reaction container using the primary extraction solution as the extraction solvent to obtain a solid phase material containing crude cellulose and a liquid phase material containing lignin and hemicellulose; the number of cyclic extractions is ≥ 0 times; The ratio of the lignocellulosic biomass raw material to the extraction solvent is 1 g: 1 to 15 mL; The extraction temperature is 55-210°C.

2. The method according to claim 1, characterized in that The extraction solvent is an organic solvent, water or an organic solvent-water mixture; the volume ratio of the organic solvent to water in the organic solvent-water mixture is 10:90 to 90:10; the organic solvent includes one or more of methanol, ethanol and n-propanol.

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

4. The method according to any one of claims 1 to 3, characterized in that: The pressure of carbon dioxide in the pressurized condition is 0.1 to 10 MPa.

5. The method according to claim 1, characterized in that The time of each extraction is independent and is 10 to 300 minutes. When performing cyclic extraction, the wood fiber biomass raw material to be processed is fixed at the upper position of the reaction container, placed above the liquid phase material, and has no direct contact with the liquid phase material.

6. The method according to claim 1 or 5, characterized in that: The steps of single cycle extraction are: using the primary extraction solution as the extraction solvent, replacing the wood fiber biomass raw material on the upper part of the reaction container, and then extracting again; the number of cycle extractions is 1 to 3 times.

7. The method according to claim 1, characterized in that The cooling medium includes one or more of water, ice, ethanol, acetone, dry ice and liquid nitrogen.

8. The method according to claim 1 or 7, characterized in that: The cooling medium is introduced intermittently, and the time interval for introducing the cooling medium is 1 to 30 minutes; the cooling medium is introduced until the temperature difference inside the reaction container changes by 1 to 30°C.

9. The method according to claim 1, characterized in that: The crude cellulose-containing solid phase material is washed with water and then freeze-dried in vacuum to obtain crude cellulose.

10. The method according to claim 1, characterized in that The lignin-containing hemicellulose liquid phase material is mixed with water, allowed to stand to precipitate a precipitate, and then filtered and freeze-dried in sequence to obtain lignin.

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