Method for realizing biomass three-element separation by utilizing organic solvent treatment

Abstract

The method comprises the following steps: uniformly mixing a plurality of proton organic solvents with an acidic additive and a magnesium-containing additive, adding a biomass raw material pretreated by using a water-phase microwave method, mixing, putting into a reaction kettle, introducing nitrogen with a certain pressure for protection, and reacting for 2-4 hours; reacting for a period of time at a certain temperature, drying filter residues obtained by filtering to obtain a cellulose-rich component, adding water into filtrate to separate out lignin, and enabling the filtrate to mainly contain hemicelluloses and decomposition products thereof. According to the pretreatment method, the lignin removal rate and the cellulose retention rate of the lignocellulose in the biomass raw material are improved, and the obtained cellulose is generally good in quality.

Description

Technical Field

[0001] This invention belongs to the field of lignocellulose three-element separation technology, and in particular, a method for separating biomass three elements based on organic extractant pretreatment. Background Technology

[0002] Biomass resources are organic matter derived from organisms such as plants, animals, and microorganisms, and are a highly sustainable green resource. However, most biomass is currently limited by technology and cannot be fully utilized, becoming difficult-to-manage waste.

[0003] To efficiently utilize biomass resources, the separation of lignin, cellulose, and hemicellulose is crucial. This separation refers to using specific methods to separate the three main components of biomass, lignin, cellulose, and hemicellulose, to facilitate subsequent comprehensive utilization. However, cellulose and lignin have almost completely opposite properties and are spatially intertwined, making effective separation of these three components very difficult.

[0004] Current biomass separation technologies mainly include organic solvent methods, acid-base methods, ionic liquid methods, and deep eutectic solvent methods. Among these, organic solvent methods and acid-base methods are simple to operate, have high throughput, and are more suitable for large-scale industrial applications. Compared to acid-base methods, organic solvent methods yield products with higher purity, less pollution, and recyclable solvents, showing great application potential. Currently, commonly used organic solvents are mainly alcohol-based solvents, with ethanol-based systems being widely studied and showing good separation effects. However, due to ethanol's low boiling point, high vapor pressure is generated at high temperatures during biomass processing, placing high demands on equipment. Ethanol's low flash point also increases operational hazards, causing difficulties in practical industrial scale-up applications. Therefore, developing green, efficient, and safe organic solvent-based biomass separation technologies is of great significance for the full utilization of biomass resources. Summary of the Invention

[0005] The goal of this invention is to break through the current technical bottleneck of lignin, cellulose and hemicellulose separation, and provide a method more suitable for large-scale industrial production to efficiently separate lignin, cellulose and hemicellulose in biomass, improve the safety of the operation process, improve the performance in subsequent conversion, and improve the utilization efficiency of biomass resources.

[0006] The specific embodiments of the present invention are described in detail below. The present invention provides a highly efficient method for separating three elements from biomass based on a combination of multi-element organic extractant separation and microwave pretreatment, comprising the following steps:

[0007] S1. Premix one or more solvents from a variety of solvents in a certain proportion to form a mixed solvent;

[0008] S2. Remove the twigs and leaves from the biomass and pulverize it thoroughly to obtain biomass raw materials;

[0009] S3. Soak the biomass raw material in water, microwave it for a period of time, and then filter it after cooling.

[0010] S4. Add the processed biomass raw materials, along with the mixed solvent and additives A and B, into the high-pressure reactor and seal the reactor.

[0011] S5. Heat the reactor to a specific temperature, stir continuously, and release the pressure after reacting for a specific time to obtain the reaction solution;

[0012] S6. Filter to obtain slurry and cellulose slurry, and dry the cellulose slurry to obtain cellulose;

[0013] S7. A certain amount of water is added to the slurry to precipitate lignin. After filtration, the filter residue is lignin, and the filtrate is a solution rich in hemicellulose components, mainly containing impurities, additives, hemicellulose and its hydrolysis products.

[0014] Furthermore, in step S1, the various solvents are methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

[0015] Furthermore, in step S3, the microwave power is 200–2000W and the microwave time is 1–10min.

[0016] Furthermore, in step S4, additive A is one or more combinations of formic acid, acetic acid, propionic acid, sulfuric acid, hydrochloric acid, phosphoric acid, and acetone, and additive B is one or more combinations of magnesium sulfate, magnesium chloride, and magnesium hydroxide colloid.

[0017] Moreover, in step S4, the ratio of the raw material to the solvent is 1:50 to 1:2.

[0018] Furthermore, in step S5, the reaction time is 1-12 hours.

[0019] Furthermore, in step S5, the reaction temperature is 80-240℃ and the nitrogen pressure is 0.5-4MPa.

[0020] Furthermore, in step S7, the volume of water added is 0.5 to 3 times the total volume of the reaction solution.

[0021] This invention utilizes a multi-element organic extractant to pretreat and separate biomass, obtaining cellulose-rich components, lignin-rich components, and hemicellulose-rich components. The biomass is agricultural and forestry waste rich in lignocellulose, such as straw, reeds, and sawdust.

[0022] The multi-component organic extractant is prepared by mixing various monohydric alcohols, dihydric alcohols, and additives A and B. This invention utilizes the excellent solubility of alcohols in lignin, while adding dihydric alcohols to increase the overall boiling point of the solvent and reduce the pressure during the reaction. Simultaneously, acidic additive A protects the lignin structure and disrupts hemicellulose, while magnesium-containing additive B protects the cellulose structure.

[0023] The microwave pretreatment process should have sufficient microwave power and time, and the biomass raw material should be softened at the end. Sufficient softening can improve the efficiency of subsequent processing, but excessive softening will waste energy. For a total volume of 1L, it is preferred to process with 500W power for 5 minutes.

[0024] The molar ratio of monohydric alcohol to dihydric alcohol in the multi-component organic extractant is 2:1 to 3:2. The optimal amount of additives depends on the type of biomass. For herbaceous plants, additive A is taken as 0.1 to 0.3% of the total molar amount of solvent, and additive B is taken as 0.3 to 1% of the total molar amount of solvent. The mass ratio of biomass to multi-component organic solvent extractant is 1:10.

[0025] During the mixing of the multi-element organic extractant and biomass raw materials, it is important to avoid situations such as biomass raw materials adhering to the wall, clumping, or incomplete degassing, which could lead to insufficient reaction. After the reaction is completed, allow the reactor to cool naturally to room temperature, depressurize, remove the reaction liquid, filter, and dry the filter residue to obtain a cellulose-rich component. Add a certain amount of water to the filtrate to precipitate lignin, filter, and dry the filter residue to obtain a lignin component. The filtrate is a hemicellulose-rich component.

[0026] The nitrogen pressure in the reactor is preferably 0.5–1 MPa, the reaction time is preferably 4–6 h, and the reaction temperature is preferably 120–220 °C. When water is added to precipitate, it is preferably added to about twice the original volume.

[0027] The equipment used in the reaction needs to withstand a pressure of about 3 MPa, and stainless steel is preferred. Although the reaction solution is relatively weak and no corrosion was observed after multiple tests, the equipment still needs to have a certain acid resistance for long-term use.

[0028] The preferred temperature for drying the cellulose-rich component is 55°C, and the preferred drying time is 12 hours. During drying, care should be taken to disperse the solids as much as possible, and the temperature and time should preferably be controlled near the above-mentioned preferred values.

[0029] The preferred drying temperature for lignin is 80°C, and the preferred drying time is 48 hours. It is preferable to control the temperature and time near the above-mentioned preferred values ​​to fully dry the lignin.

[0030] The advantages and effective gains of this invention are:

[0031] 1. This invention uses biomass from various sources as raw materials to achieve efficient and comprehensive utilization of biomass resources. This invention can be applied to highly lignified raw materials such as poplar wood, as well as raw materials with a low degree of lignification such as straw. The processing range covers almost all lignin-containing biomass that are difficult to process. It can efficiently and selectively break the connection between sugars and lignin structures, dissolve and separate a large amount of lignin, and then obtain lignin components by adding water.

[0032] 2. The microwave heating method in this invention can rapidly and uniformly heat biomass. The protons generated by local water dissociation cause the cellulose and hemicellulose macromolecules in the raw material to break down initially, and gaps begin to form between the fibers. A large amount of water penetrates into the biomass, which not only makes it difficult for aprotic solvents to destroy carbohydrate macromolecules, but also makes it easier for subsequent water-miscible organic solvents to enter the interior of lignocellulose, shortening the time required for subsequent processing and improving the lignin removal rate.

[0033] 3. The nitrogen atmosphere used in this invention can prevent lignin from being oxidized at high temperatures, thus protecting the natural structure of lignin to the maximum extent. At the same time, it reduces the coking phenomenon of the separated lignin, preserves the structural differences of lignin from different biomass sources, and improves the quality of the produced product, making its chemical properties stable and controllable.

[0034] 4. The mixed alcohol solvent used in this invention has a strong affinity for lignin and is a highly efficient extraction medium. The boiling point increases significantly after the solvents are mixed, thereby avoiding high pressure in the reactor during the high-temperature reaction process. At 200°C, the pressure increase is less than 1 MPa compared to when the temperature is not increased. Compared to using ethanol alone, the pressure can be reduced by up to 90%, which greatly reduces the cost and loss of the reactor and improves the safety of the experimental operation.

[0035] 5. Additive A used in this invention protects the lignin structure and decomposes macromolecular sugars through appropriate acidity. The former can improve the quality of the separated lignin and maintain the original state of lignin; the latter helps to deeply change the microstructure of lignocellulose, degrade and break the intertwined sugar chains, greatly increase the accessibility of organic solvents to lignin, and improve the processing speed and separation effect.

[0036] 6. The magnesium ions in additive B used in this invention can competitively bind with metal ions in the system, adsorb onto the cellulose surface to reduce the attack of other ions on the cellulose glycosidic bonds, avoid excessive breakage of cellulose chains during the processing, and improve the fiber quality of the obtained cellulose components. At the same time, magnesium ions can stabilize free radical intermediates through coordination, reducing the impact of reactive oxygen free radicals on the final properties of various products.

[0037] 7. In the two-stage extraction process of this invention, lignin is gradually purified. The content of common ions such as potassium ions and chloride ions in the final product is significantly reduced compared with the biomass raw material. Therefore, the corrosion of metal equipment by the lignin obtained in the subsequent reaction and conversion is also greatly reduced. The impurity deposition and equipment wear generated when the product is used for long-term circulation are reduced. Detailed Implementation

[0038] The specific embodiments of the present invention will be described in further detail below with reference to the examples. The following examples are only descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0039] Example 1

[0040] S1, ethanol, ethylene glycol and water are mixed in a ratio of 6:3:1 to make 1L of mixed solvent;

[0041] S2. Remove the fine branches and leaves of Spartina alterniflora, and then pulverize it thoroughly to obtain biomass raw materials;

[0042] S3. Soak 50g of biomass raw material in 1L of water, microwave at 500W for 5 minutes, cool and filter.

[0043] S4. Add 1.5 mL of formic acid and 9 g of anhydrous magnesium chloride to the mixed solvent to prepare a multi-element organic extractant. Add the extractant to the high-pressure reactor along with the treated biomass raw material and seal the reactor.

[0044] S5. Heat the reactor to 190°C and stir continuously. After reacting for 6 hours, release the pressure to obtain the reaction solution.

[0045] S6. Filter the slurry and cellulose slurry, and dry the cellulose slurry at 55°C for 12 hours to obtain the cellulose-rich component.

[0046] S7. Add a certain amount of water to the slurry to precipitate lignin. After filtration and drying, the filter residue is lignin and the filtrate is rich in hemicellulose components.

[0047] The composition of each product was tested and calculated using the NREL / TP-510-42618 method. In this example, the cellulose-rich fraction contained 91.75% cellulose, 3.92% lignin, and 2.14% hemicellulose; the lignin fraction contained 98.42% lignin; and the hemicellulose-rich fraction contained 20.57% lignin, 60.89% hemicellulose, and 16.05% cellulose by dry weight. The final delignification rate was 79.57%, and the cellulose retention rate was 80.63%.

[0048] Example 2

[0049] S1, methanol, ethylene glycol and water are mixed in a ratio of 5:3:2 to make 1L of mixed solvent;

[0050] S2. Remove the fine branches and leaves from the corn stalks and crush them thoroughly to obtain biomass raw materials;

[0051] S3. Soak 50g of biomass raw material in 1L of water, microwave at 500W for 5 minutes, cool and filter.

[0052] S4. Add 2 mL of formic acid and 18 g of magnesium sulfate to the mixed solvent to prepare a multi-element organic extractant, and add it together with the treated biomass raw material into a high-pressure reactor, and seal the reactor.

[0053] S5. Heat the reactor to 200°C, stir continuously, and release the pressure after 5 hours to obtain the reaction solution.

[0054] S6. Filter the slurry and cellulose slurry, and dry the cellulose slurry at 55°C for 12 hours to obtain the cellulose-rich component.

[0055] S7. Add a certain amount of water to the slurry to precipitate lignin. After filtration and drying, the filter residue is lignin and the filtrate is rich in hemicellulose components.

[0056] The composition of each product was tested and calculated using the NREL / TP-510-42618 method. In this example, the cellulose-rich fraction contained 94.55% cellulose, 2.10% lignin, and 1.95% hemicellulose; the lignin fraction contained 97.9% lignin; and the hemicellulose-rich fraction contained 19.65% lignin, 52.84% hemicellulose, and 20.21% cellulose by dry weight. The final delignification rate was 91.40%, and the cellulose retention rate was 65.09%.

[0057] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A highly efficient method for separating three biomass elements based on pretreatment with a multi-element organic extractant, characterized in that: Includes the following steps: S1. Premix one or more solvents from a variety of solvents in a certain proportion to form a mixed solvent; S2. Remove the twigs and leaves from the biomass and pulverize it thoroughly to obtain biomass raw materials; S3. Soak the biomass raw material in water, microwave it for a period of time, and then filter it after cooling. S4. Add the processed biomass raw materials, along with the mixed solvent and additives A and B, into the high-pressure reactor and seal the reactor. S5. Heat the reactor to a specific temperature, stir continuously, and release the pressure after reacting for a specific time to obtain the reaction solution; S6. Filter to obtain slurry and cellulose slurry, and dry the cellulose slurry to obtain cellulose; S7. A certain amount of water is added to the slurry to precipitate lignin. After filtration, the filter residue is lignin, and the filtrate is a solution rich in hemicellulose components, mainly containing impurities, additives, hemicellulose and its hydrolysis products.

2. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 1, characterized in that: The molar ratio of monohydric alcohol to dihydric alcohol in the multi-component organic extractant described in step S1 is 2:1 to 3:

2.

3. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 2, characterized in that: The monohydric alcohol and dihydric alcohol are methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

4. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 1, characterized in that: In step S3, the biomass is soaked in 5-10 times its weight of water and then microwaved.

5. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 4, characterized in that: The microwave power is 200-2000W, the microwave time is 1-10min, and the biomass includes various types of biomass such as straw, reeds, bamboo reeds, Spartina alterniflora, and poplar.

6. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 1, characterized in that: In step S4, additive A is taken as 0.1 to 0.3% of the total molar amount of the solvent, and additive B is taken as 0.3 to 1% of the total molar amount of the solvent.

7. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 6, characterized in that: Additive A is one or more organic acids, and additive B is one or more magnesium salts.

8. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 1, characterized in that: In step S5, the reaction temperature is 80-240℃ and the nitrogen pressure is 0.5-4.0MPa.

9. The efficient separation method for three biomass elements based on pretreatment with a multi-element organic extractant according to claim 1, characterized in that: In step S7, the amount of water added is approximately equal to the volume of the filtrate.