A method for isolating holocellulose and active lignin from lignocellulosic biomass

Abstract

The application relates to a method for separating holocellulose and active lignin from lignocellulose biomass, which comprises the following steps: mixing lignocellulose biomass with an alkaline composite solvent system for pretreatment, and then carrying out solid-liquid separation after the reaction; washing and drying the obtained solid residue to obtain a holocellulose solid matrix; precipitating the pretreatment-dissolved hemicellulose from the filtrate, carrying out solid-liquid separation, and recovering lignin; and the alkaline composite solvent system comprises a combination of ethanolamine and ethylene glycol. The application can realize efficient separation of lignocellulose biomass components, obtain high cellulose and hemicellulose retention rates, improve the lignin removal rate, effectively inhibit the condensation of lignin, and be helpful to subsequent lignin conversion and utilization; the overall process of the application has mild reaction conditions, high separation efficiency, strong controllability and operability.

Description

Technical Field

[0001] This application relates to the field of biomass resource utilization technology, and in particular to a method for separating holocellulose and active lignin from lignocellulose biomass. Background Technology

[0002] With the large-scale consumption of traditional fossil resources such as coal and natural gas, energy and environmental problems are becoming increasingly severe, making the development of clean and renewable alternative energy sources an inevitable trend. Biomass, as an abundant, green, and low-carbon renewable resource, can be efficiently converted into energy, materials, and chemicals through chemical conversion technology, effectively alleviating the shortage of fossil resources. Therefore, achieving the green and efficient conversion and utilization of biomass resources has significant practical importance and application value for ecological environmental protection and sustainable energy development.

[0003] In the process of biomass resource utilization, the pretreatment of lignocellulose biomass is a key step in improving conversion efficiency. Currently, pretreatment methods mainly include four categories: physical methods, chemical methods, biological methods, and physical-chemical methods. Among them, physical methods such as mechanical crushing can effectively reduce the particle size of biomass, but they suffer from high energy consumption and low raw material utilization. Therefore, physical methods are often used in combination with chemical methods. The representative technology, steam explosion, has excellent processing efficiency, but it has stringent requirements for the performance of production equipment and high investment costs. Biological methods have the advantages of being green and environmentally friendly and having low energy consumption, but they suffer from long processing cycles and low conversion efficiency, making them difficult to adapt to large-scale industrial production.

[0004] Chemical methods mainly include alkali treatment, acid treatment, ionic liquid treatment, and organic solvent pretreatment. Alkali treatment is time-consuming and easily produces large amounts of black liquor; acid treatment is highly corrosive to equipment and consumes a large amount of water; ionic liquids, as high-performance novel green solvents, have been widely used in biomass pretreatment research (CN106282265A, CN119371560A), but some ionic liquids have limited mass transfer during the pretreatment process due to their high viscosity; organic solvent pretreatment can effectively break the bonds between hemicellulose and lignin, improving biomass porosity and cellulase accessibility; however, commonly used solvents generally have drawbacks such as flammability, volatility, and high cost. Therefore, developing low-cost, high-performance novel green solvents has become an important research direction in the field of organic solvent pretreatment.

[0005] Compared to traditional organic solvents, eutectic solvents (DES) possess physicochemical properties similar to ionic liquids, are simple to synthesize, and have low toxicity, showing promising application prospects in the field of biomass pretreatment (CN121991378A). However, some DES have high viscosity, which can easily restrict mass transfer in the reaction and reduce pretreatment efficiency. Compared to acidic DES, alkaline DES has a superior effect on lignin removal, maximizing the retention of cellulose and protecting the polysaccharide structure; while acidic DES easily degrades polysaccharides, reducing the yield of fermentable sugars, and can also cause lignin condensation, which is detrimental to subsequent conversion and utilization.

[0006] Therefore, how to better separate holocellulose and active lignin from lignocellulose biomass, and retain the active functional groups of lignin while improving the cellulose retention rate, has become an urgent problem to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a method for separating holocellulose and active lignin from lignocellulose biomass. This method enables efficient separation of lignocellulose biomass components, achieving high retention rates of cellulose and hemicellulose, improving lignin removal rates, effectively inhibiting lignin condensation, increasing lignin recovery rates, and facilitating subsequent lignin conversion and utilization. Furthermore, the overall process of this application features mild reaction conditions, high separation efficiency, and strong controllability and operability.

[0008] To achieve this objective, the following technical solution is adopted in this application: This application provides a method for separating holocellulose and active lignin from lignocellulose biomass, the method comprising the following steps: (1) The lignocellulose biomass was mixed with an alkaline composite solvent system for pretreatment, and the solid and liquid were separated after the reaction was completed; (2) Wash and dry the solid residue obtained in step (1) to obtain holocellulose solid matrix; precipitate the pretreated dissolved hemicellulose from the filtrate, separate the solid and liquid, and recover the lignin; The alkaline composite solvent system includes a combination of ethanolamine and ethylene glycol.

[0009] This application employs an alkaline composite solvent system comprising ethanolamine and ethylene glycol to dissolve and separate lignocellulose biomass. This effectively breaks the bonds between lignin and carbohydrates in the lignocellulose biomass, thereby achieving lignin dissolution. Ethylene glycol interacts with the active intermediates generated during lignin depolymerization, inhibiting condensation between lignin molecules. Therefore, the combined action of ethanolamine and ethylene glycol effectively protects the β-O-4 bonds in lignin, significantly reducing their breakage and resulting in a substantial increase in the β-O-4 bond content of the extracted lignin. This enhances the lignin removal rate and yields active lignin.

[0010] In some embodiments, the lignocellulosic biomass includes any one or a combination of at least two of corn stalks, reeds, or bamboo.

[0011] The overall process of this application features mild reaction conditions, high separation efficiency, strong controllability and operability, and a wide range of applicable raw materials, including agricultural and forestry waste lignocellulosic biomass from different sources.

[0012] In some embodiments, the alkaline composite solvent system is a combination of ethanolamine and ethylene glycol.

[0013] The alkaline composite solvent system in this application is a combination of ethanolamine and ethylene glycol, which can achieve a higher retention rate of cellulose and hemicellulose while efficiently removing lignin.

[0014] In some embodiments, the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 10:1 to 1:10, for example, it can be 10:1, 8:1, 7:1, 5:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:5, 1:8, or 1:10, etc.

[0015] In some embodiments, the temperature of the pretreatment in step (1) is 50-130°C, for example, it can be 50°C, 65°C, 80°C, 90°C, 100°C, 110°C, 120°C or 130°C.

[0016] In some implementations, the pretreatment time in step (1) is 0.5-5 hours, for example, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0017] In some embodiments, the mass ratio of the lignocellulose biomass to the alkaline composite solvent system is 1:(10-30), for example, it can be 1:10, 1:12, 1:15, 1:20, 1:22, 1:25 or 1:30, etc.

[0018] In some embodiments, the method for separating holocellulose and active lignin from lignocellulose biomass includes the following steps: (1) Mix lignocellulose biomass with an alkaline composite solvent system at a mass ratio of 1:(10-30), heat to 50-130℃ and heat for 0.5-5h; after the reaction is completed, separate the solid and liquid; the alkaline composite solvent system is composed of ethanolamine and ethylene glycol at a molar ratio of 10:1-1:10; (2) The solid residue obtained in step (1) is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix; the pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose, the solid and liquid are separated, the anhydrous ethanol is removed by rotary evaporation of the filtrate, and water is added to precipitate and recover lignin.

[0019] Compared with the prior art, this application has at least the following beneficial effects: (1) This application uses an ethanolamine-ethylene glycol alkaline composite solvent system to dissolve and separate lignocellulose biomass, thereby achieving efficient separation of lignocellulose biomass components under mild conditions and obtaining cellulose and hemicellulose products with high retention rates.

[0020] (2) Synergistic improvement of lignin activity and yield: In the alkaline composite solvent pretreatment process, not only can the solubility of lignin be improved, but ethylene glycol can also protect the β-O-4 bond of lignin, effectively reduce the breakage of β-O-4 bond, effectively inhibit the condensation of lignin, and significantly increase the content of β-O-4 bond of extracted lignin, which is beneficial to the subsequent conversion and utilization of lignin.

[0021] (3) The alkaline composite solvent used in this application has low cost and low viscosity, excellent system miscibility and material mixing, and simple subsequent solid-liquid separation operation, which can effectively promote the industrialization of biomass pretreatment process. Detailed Implementation

[0022] The technical solution of this application will be further described below through specific embodiments. However, the examples below are merely simplified examples of this application and do not represent or limit the scope of protection of this application. The scope of protection of this application shall be determined by the claims.

[0023] Treatment of lignocellulose biomass with neutral detergent: Add 1g of lignocellulose biomass to 50mL of neutral detergent, heat to boiling for 1 hour with magnetic stirring, cool to room temperature, filter, wash with water, filter and dry for later use. Preparation steps for neutral detergent: Add 18.6g of disodium ethylenediaminetetraacetate and 6.8g of Na₂B₄O₇•10H₂O to a 1000mL beaker, add an appropriate amount of deionized water; after complete dissolution, add 30g of sodium dodecyl sulfate and 10mL of ethylene glycol monoethyl ether; after complete dissolution again, weigh 4.56g of Na₂HPO₄ and dissolve it in 50mL of aqueous solution, add this aqueous solution to the above solution and mix thoroughly, finally dilute to 1000mL for later use.

[0024] Example 1 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat to 110℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0025] Example 2 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 1:4. After mixing evenly, heat to 100℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0026] Example 3 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat to 130℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0027] Example 4 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat to 90℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0028] Example 5 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat the mixture to 80°C and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0029] Example 6 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 1:1. After mixing evenly, heat to 100℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0030] Example 7 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 3:1. After mixing evenly, heat to 100℃ and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0031] Example 8 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat to 90℃ and continue heating for 5 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0032] Example 9 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take the bamboo treated with neutral detergent and mix it with an alkaline composite solvent system. The mass ratio of solid to liquid in the pretreatment is 1:20. The molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 1:10. After mixing evenly, heat the mixture to 130℃ and continue heating for 0.5h. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0033] Example 10 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take the reeds treated with neutral detergent and mix them with the alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20. The molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 10:1. After mixing evenly, heat the mixture to 90°C and continue heating for 2 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0034] Example 11 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat the mixture to 50°C and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0035] Example 12 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:20, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat the mixture to 90°C and continue heating for 1 hour. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0036] Example 13 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The mass ratio of solid to liquid in the pretreatment is 1:10. The molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat the mixture to 90°C and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0037] Example 14 This embodiment provides a method for separating holocellulose and active lignin from lignocellulose biomass, including the following steps: (1) Take corn stalks treated with neutral detergent and mix them with an alkaline composite solvent system. The pretreatment solid-liquid mass ratio is 1:30, and the molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 2:1. After mixing evenly, heat the mixture to 90°C and continue heating for 3 hours. (2) After the reaction is completed, solid and liquid are separated. The solid residue is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix. The pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose. Ethanol is removed by rotary evaporation and lignin is recovered by adding water to precipitate.

[0038] Calculation method Table 1 summarizes the cellulose retention rate, hemicellulose retention rate, lignin removal rate, and lignin recovery rate in each example and comparative example.

[0039] Table 1 As can be seen from Examples 1 to 14, this application can achieve high cellulose retention rate, hemicellulose retention rate and lignin removal rate by adjusting the molar ratio of the solvent in the alkaline composite solvent system and the temperature and time of pretreatment.

[0040] In summary, this application pretreats lignocellulose biomass using an alkaline composite solvent system of ethanolamine and ethylene glycol, achieving high cellulose and hemicellulose retention rates while improving lignin removal rates and obtaining active lignin, thus realizing efficient separation of lignocellulose biomass components.

[0041] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for separating holocellulose and active lignin from lignocellulose biomass, characterized in that, The method includes the following steps: (1) The lignocellulose biomass was mixed with an alkaline composite solvent system for pretreatment, and the solid and liquid were separated after the reaction was completed; (2) Wash and dry the solid residue obtained in step (1) to obtain holocellulose solid matrix; precipitate the pretreated dissolved hemicellulose from the filtrate, separate the solid and liquid, and recover the lignin; The alkaline composite solvent system includes a combination of ethanolamine and ethylene glycol.

2. The method for separating holocellulose and active lignin from lignocellulose biomass as described in claim 1, characterized in that, The lignocellulose biomass includes any one or a combination of at least two of corn stalks, reeds, or bamboo.

3. The method for separating holocellulose and active lignin from lignocellulose biomass as described in claim 1 or 2, characterized in that, The alkaline composite solvent system is a combination of ethanolamine and ethylene glycol.

4. The method for separating holocellulose and active lignin from lignocellulose biomass according to any one of claims 1-3, characterized in that, The molar ratio of ethanolamine to ethylene glycol in the alkaline composite solvent system is 10:1 to 1:

10.

5. The method for separating holocellulose and active lignin from lignocellulose biomass according to any one of claims 1-4, characterized in that, The temperature for the pretreatment in step (1) is 50-130℃.

6. The method for separating holocellulose and active lignin from lignocellulose biomass according to any one of claims 1-5, characterized in that, The pretreatment time in step (1) is 0.5-5 hours.

7. The method for separating holocellulose and active lignin from lignocellulose biomass according to any one of claims 1-6, characterized in that, The mass ratio of the lignocellulose biomass to the alkaline composite solvent system is 1:(10-30).

8. The method for separating holocellulose and active lignin from lignocellulose biomass according to any one of claims 1-7, characterized in that, The method includes: (1) Mix lignocellulose biomass with an alkaline composite solvent system at a mass ratio of 1:(10-30), heat to 50-130℃ and heat for 0.5-5h; after the reaction is completed, separate the solid and liquid; the alkaline composite solvent system is composed of ethanolamine and ethylene glycol at a molar ratio of 10:1-1:10; (2) The solid residue obtained in step (1) is washed and dried with anhydrous ethanol to obtain holocellulose solid matrix; the pH of the filtrate is adjusted and anhydrous ethanol is added to precipitate the pretreated and dissolved hemicellulose, the solid and liquid are separated, the anhydrous ethanol is removed by rotary evaporation of the filtrate, and water is added to precipitate and recover lignin.

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