A method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent

Abstract

The application discloses a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent, and belongs to the technical field of biomass material extraction. The unique combination of glycerol (Gly), potassium carbonate (K2CO3) and polyethylene glycol (PEG-200) is used to optimize the reaction activity and dissolution characteristics of the system, effectively overcome the inherent stubbornness of wheat straw, promote the deconstruction and separation of lignocellulosic biomass, and the obtained cellulose-rich residue has ideal crystallinity, thermal stability and processing capacity, thereby having the potential for efficient downstream processing and application, and a more environmentally friendly and more sustainable lignocellulosic biomass treatment method is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass material extraction, and particularly relates to a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent. BACKGROUND

[0002] As the most abundant natural renewable energy on earth, lignocellulosic biomass mainly includes wood, crop waste (wheat straw, corn cob and sugarcane residue) and wood processing waste (sawdust, tree bark and pulp), and its effective development and utilization and subsequent conversion into energy fuels, chemicals and functional materials are one of the most important development directions in the future. Lignocellulosic biomass usually has a multi-scale structure and a complex component configuration, and is mainly composed of cellulose, hemicellulose and lignin, which provides a beneficial basis and guarantee for its healthy growth. However, at the same time, it also brings great challenges to subsequent processing and treatment. Therefore, in order to promote the high-value and diversified comprehensive utilization of biomass resources and realize the highly selective separation and purification of main components, it is necessary and essential to perform pretreatment, deconstruction and classification.

[0003] As a new emerging design green solvent, the eutectic solvent (DES) provides a new insight / solution / path for developing a sustainable deconstruction and classification process based on lignocellulosic biomass. Generally, DES is a liquid mixture formed by self-association of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) under the action of hydrogen bonding, and its melting point is lower than that of any one of the original components. Benefiting from the characteristics of low cost, simple preparation and biodegradability, the chemical properties and functions can be customized by modularizing and regulating different combinations of HBD and HBA, and DES has high solvent capacity and reaction activity, and is widely used in organic synthesis, catalytic reaction, separation and extraction and electrochemistry. Due to the existence of hydrogen bonding, the physicochemical properties of DES are beneficial to the deconstruction and separation of lignocellulosic biomass, and DES exhibits competitiveness in related treatment. However, related research is still in its infancy, and DES usually has high viscosity, which causes poor dissolution effect, low reaction penetration efficiency and other problems. Therefore, how to effectively reduce the viscosity and further improve the deconstruction treatment effect has become a major challenge to be solved. SUMMARY

[0004] In view of the deficiencies of the prior art, the application provides a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent, which overcomes the technical problems of high viscosity, poor solubility and low reaction penetration efficiency of the existing DES.

[0005] The technical scheme provided by the application is as follows:

[0006] The application provides a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent, which comprises the following steps:

[0007] S1, mixing and reacting the pretreated biomass raw material with the ternary eutectic solvent, magnetically stirring at a temperature of 120-160 DEG C for 12-24 h to obtain a reaction product;

[0008] S2, cooling the reaction product in S1, adding ethanol for dilution, and then performing vacuum filtration to obtain a residue rich in cellulose;

[0009] S3, washing the residue rich in cellulose by using a washing liquid until it is clear, and then performing freeze-drying to obtain the lignocellulose;

[0010] In the ternary eutectic solvent, glycerol is used as a hydrogen bond donor, potassium carbonate is used as a hydrogen bond acceptor, and polyethylene glycol 200 is added.

[0011] Further, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5, and the mass ratio of the potassium carbonate to the glycerol solvent is 0.3:1 g / g.

[0012] Further, the mass-volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL.

[0013] Further, the preparation method of the ternary eutectic solvent is as follows:

[0014] The potassium carbonate and glycerol are mixed, placed in an oil bath at 100 DEG C, and mechanically stirred for 0.5-1 h until a clear and uniform solution is formed, then polyethylene glycol 200 is added, and fully stirred for 10-30 min to prepare the ternary eutectic solvent.

[0015] Further, the pretreatment of the biomass raw material is as follows:

[0016] The biomass raw material is crushed and sieved into fine particles, then the particles are soaked in warm water and stirred, and then filtered and washed with a washing liquid, and finally dried at 60-80 DEG C to constant weight for collection.

[0017] Further, the particle size of the biomass raw material crushed and sieved into fine particles is 0.25-0.5 mm.

[0018] Further, the mass-volume ratio of the biomass raw material to the ternary eutectic solvent is 1:25-40 g / mL.

[0019] Further, the washing liquid is at least one of acetone, ethanol or water.

[0020] Further, the biomass raw material is straw.

[0021] Further, the straw is selected from any one or more of rice straw, wheat straw, corncob, and sugarcane residue.

[0022] Beneficial effects

[0023] The present application solves the problems of low reaction penetration efficiency and insufficient separation in the processing of lignocellulosic biomass by using a unique combination of glycerol (Gly), potassium carbonate (K2CO3), and polyethylene glycol 200 (PEG-200), and provides a more environmentally friendly and sustainable lignocellulosic biomass processing method. The specific performance is as follows:

[0024] (1) Adding polyethylene glycol 200 (PEG-200) as the third component, as a viscosity regulator and a solubilizer, improves and optimizes the reaction activity and solubility characteristics of the system.

[0025] (2) The improvement of the performance of the ternary system is reflected in the significant removal rate of key components of biomass: the removal rate of hemicellulose is 81.93%, the removal rate of lignin is 96.37%, and the yield of cellulose is as high as 73.65%.

[0026] (3) The cellulose-rich residue obtained has ideal crystallinity, thermal stability, and processing ability, thereby having the potential for efficient downstream processing and application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Temperature-viscosity relationship curve of different DES in the examples;

[0028] Figure 2 Actual picture of different cellulose-rich residues in the examples;

[0029] Figure 3 Scanning electron microscope picture of wheat straw and different cellulose-rich residues in the examples;

[0030] Figure 4 X-ray diffraction pattern of different cellulose-rich residues in the examples;

[0031] Figure 5 Thermogravimetric curve of different cellulose-rich residues in the examples;

[0032] Figure 6 Composition ratio diagram of different cellulose-rich residues in the examples. DETAILED DESCRIPTION

[0033] The present application will be further explained and described in detail below in conjunction with the drawings and specific embodiments, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0034] The embodiment of the present application provides a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent, which comprises the following steps:

[0035] S1, mixing and reacting the pretreated biomass raw material with the ternary eutectic solvent, magnetically stirring at a temperature of 120-160 DEG C for 12-24 h to obtain a reaction product;

[0036] S2, cooling the reaction product in S1, adding ethanol for dilution, and then performing vacuum filtration to obtain a residue rich in cellulose;

[0037] S3, washing the residue rich in cellulose by using a washing liquid until it is clear, and then performing freeze-drying to obtain the lignocellulose;

[0038] In the embodiment, glycerol is used as a hydrogen bond donor, potassium carbonate is used as a hydrogen bond acceptor, and polyethylene glycol 200 is added to synthesize the ternary eutectic solvent.

[0039] In the embodiment, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5, and the mass ratio of the potassium carbonate to the glycerol solvent is 0.3:1 g / g.

[0040] In the embodiment, the mass-volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL.

[0041] In the embodiment, the preparation method of the ternary eutectic solvent is as follows:

[0042] The potassium carbonate and glycerol are mixed, placed in an oil bath at 100 DEG C, and mechanically stirred for 0.5-1 h until a clear and uniform solution is formed, then polyethylene glycol 200 is added, and fully stirred for 10-30 min to prepare the ternary eutectic solvent.

[0043] In the embodiment, the pretreatment of the biomass raw material is as follows:

[0044] The biomass raw material is crushed and sieved into fine particles, then the particles are soaked in warm water and stirred, and then filtered and washed with a washing liquid, and finally dried at 60-80 DEG C to constant weight for collection.

[0045] In the embodiment, the particle size of the biomass raw material crushed and sieved into fine particles is 0.25-0.5 mm.

[0046] In the embodiment, the mass-volume ratio of the biomass raw material to the ternary eutectic solvent is 1:25-40 g / mL.

[0047] In the embodiment, the washing liquid is at least one of acetone, ethanol or water.

[0048] In the embodiment, the biomass raw material is straw.

[0049] In this embodiment, the straw is selected from any one or more of rice straw, wheat straw, corncob, and sugarcane bagasse.

[0050] Example 1

[0051] (1) Pretreatment of wheat straw

[0052] All the biomass material, wheat straw, was ground and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water with stirring and washed thoroughly with deionized water and ethanol. Finally, the sample was dried to constant weight in an oven at 60°C and stored for use.

[0053] (2) Preparation of DES

[0054] According to a molar ratio of 1:5, 4.62 g of potassium carbonate and 15.38 g of glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear, homogeneous solution was formed. The final DES was prepared and labeled as D and stored for use.

[0055] (3) Extraction of lignocellulose

[0056] Specifically, 1 g of wheat straw was added to the prepared D and stirred magnetically at 160°C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, followed by vacuum filtration. The treated residue was washed with ethanol and deionized water until the washing liquid was clear, and freeze-dried for analysis and detection, labeled as CR.

[0057] Example 2

[0058] (1) Pretreatment of wheat straw

[0059] All the biomass material, wheat straw, was ground and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water with stirring and washed thoroughly with deionized water and ethanol. Finally, the sample was dried to constant weight in an oven at 60°C and stored for use.

[0060] (2) Preparation of DES

[0061] According to a molar ratio of 1:5, 4.62 g of potassium carbonate and 15.38 g of glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear, homogeneous solution was formed. Subsequently, 5 mL of polyethylene glycol 200 was added, stirred thoroughly for 10 min, and the final DES was prepared and labeled as D-5 and stored for use.

[0062] (3) Extraction of lignocellulose

[0063] Specifically, 1 g of wheat straw was added into the prepared D-5, and the magnetic stirring reaction was carried out at 160 °C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtration was carried out. The filter residue was treated as cellulose-rich residue, washed with ethanol and deionized water until the washing liquid was clear, and freeze-dried for analysis and detection, marked as CR5.

[0064] Example 3

[0065] (1) Pretreatment of wheat straw

[0066] All the biomass raw material wheat straw was crushed and sieved into fine particles (about 0.25 mm). Then the obtained particles were soaked in warm water with stirring, and filtered with deionized water and ethanol for thorough washing. Finally, the sample was dried in an oven at 60 °C to constant weight, and stored for use.

[0067] (2) Preparation of DES

[0068] According to a molar ratio of 1:5, 4.62 g of potassium carbonate and 15.38 g of glycerol were mixed, placed in an oil bath at 100 °C, and mechanically stirred until a clear and uniform solution was formed. Subsequently, 10 mL of polyethylene glycol 200 was added, stirred thoroughly for 10 min, and the final DES was prepared, marked as D-10, and stored for use.

[0069] (3) Extraction of lignocellulose

[0070] Specifically, 1 g of wheat straw was added into the prepared D-10, and the magnetic stirring reaction was carried out at 160 °C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtration was carried out. The filter residue was treated as cellulose-rich residue, washed with ethanol and deionized water until the washing liquid was clear, and freeze-dried for analysis and detection, marked as CR10.

[0071] Example 4

[0072] (1) Pretreatment of wheat straw

[0073] All the biomass raw material wheat straw was crushed and sieved into fine particles (about 0.25 mm). Then the obtained particles were soaked in warm water with stirring, and filtered with deionized water and ethanol for thorough washing. Finally, the sample was dried in an oven at 60 °C to constant weight, and stored for use.

[0074] (2) Preparation of DES

[0075] According to a molar ratio of 1:5, 4.62 g of potassium carbonate and 15.38 g of glycerol were mixed and placed in an oil bath at 100 °C for mechanical stirring until a clear, homogeneous solution was formed. Subsequently, 20 mL of polyethylene glycol 200 was added, stirred thoroughly for 10 min, and the final DES was prepared and labeled as D-20, ready for use.

[0076] (3) Extraction of lignocellulose

[0077] Specifically, 1 g of wheat straw was added to the prepared D-20 and stirred magnetically at 160 °C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, followed by vacuum filtration. The filter residue was treated as a cellulose-rich residue, washed with ethanol and deionized water until the rinse was clear, and freeze-dried for analysis and labeled as CR20.

[0078] (4) Related tests

[0079] The different DESs prepared in this example were subjected to rheological testing (test method according to the operating instructions of the micro-infrared rheometer), and the test results are shown in Figure 1 It can be seen that at the initial stage, i.e. at room temperature, D has a high viscosity of 76.24 Pa·s. After the addition of polyethylene glycol 200, the viscosities of D-5, D-10 and D-20 are reduced to 26.48 Pa·s, 9.90 Pa·s and 2.87 Pa·s, respectively. In addition, as the temperature gradually increases, the viscosity of all DES systems is further reduced.

[0080] The different cellulose-rich residues prepared in this example are shown in Figure 2 and subjected to scanning electron microscopy testing (test method according to the operating instructions of the scanning electron microscope). The results are shown in Figure 3 The raw material wheat straw has a clear rod-like structure, and after DES treatment, the surface of CR becomes rough and loose, with surface wrinkles and curls. The surface of CR10 presents a gully-like shape, with many cracks and fragments, and there are holes of different sizes, indicating that most of the hemicellulose and lignin components have been effectively removed.

[0081] The different cellulose-rich residues prepared in this example were subjected to X-ray diffraction testing (test method according to the operating instructions of the X-ray diffractometer), and the test results are shown in Figure 4 It can be seen that characteristic diffraction peaks appear at 2θ = 16.7 °, 22.7 ° and 34.6 °, corresponding to the (110), (200) and (004) crystal planes of cellulose I type, respectively, indicating that the original cellulose crystal structure was not damaged during the deconstruction and separation process.

[0082] The different cellulose-rich residues prepared in this example were subjected to thermogravimetric test (test method according to the operating instructions of the thermogravimetric analyzer), and the test results are shown in Figure 5 As can be seen, the initial loss temperature of the wheat straw is 220℃, and the initial decomposition temperature of CR10 is 280℃, having better thermal stability.

[0083] The different cellulose-rich residues prepared in this example were subjected to component test, and the test results are shown in Figure 6 and Table 1. The results show that in the comparative example 1, the removal rates of hemicellulose and lignin are 60.02% and 92.14% respectively, and the cellulose content is 72.38%. When different volumes of polyethylene glycol 200 are added, in examples 2-4, the removal rates of hemicellulose are increased to 76.25%, 81.93% and 81.31% respectively, the removal rates of lignin are increased to 96.19%, 96.37% and 97.29% respectively, and the cellulose contents are increased to 77.94%, 77.72% and 76.21% respectively. On the basis of ensuring the yield of cellulose, the removal rates of hemicellulose and lignin are significantly improved, highlighting the outstanding ability of the ternary DES system to decompose the complex structure of wheat straw, and providing a feasible and efficient lignocellulose extraction method.

[0084] Table 1 Detailed analysis of the effects of different treatments (test according to NREL standard)

[0085]

[0086] The above specific embodiments describe the implementation of the present application in detail, and it should be pointed out that the present application is not limited to the specific details in the above embodiments, and various simple modifications and changes can be made to the technical solutions of the present application within the scope of the claims and technical concepts of the present application. These simple modifications all belong to the protection scope of the present application.

Claims

1. A method for efficiently extracting lignocellulose using a novel ternary eutectic solvent, characterized by, The method comprises the following steps: S1, mixing and reacting the pretreated biomass raw material with a ternary eutectic solvent, magnetically stirring at a temperature of 120-160℃ for 12-24h to obtain a reaction product; S2, cooling the reaction product in S1, adding ethanol for dilution, and then performing vacuum filtration to obtain a residue rich in cellulose; S3, washing the residue rich in cellulose with a washing liquid until it is clear, and then performing freeze-drying to obtain lignocellulose; The ternary eutectic solvent is synthesized by using glycerol as a hydrogen bond donor, potassium carbonate as a hydrogen bond acceptor, and adding polyethylene glycol 200; The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5, and the mass ratio of potassium carbonate to glycerol is 0.3:1 g / g; The mass-volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL; The preparation method of the ternary eutectic solvent is as follows: Mixing potassium carbonate and glycerol, placing them in an oil bath at 100℃, and mechanically stirring for 0.5-1h until a clear and uniform solution is formed, then adding polyethylene glycol 200, and fully stirring for 10-30min to prepare the ternary eutectic solvent; The mass-volume ratio of the biomass raw material to the ternary eutectic solvent is 1:25-40 g / mL. 2.The method for efficiently extracting lignocellulose using a novel ternary eutectic solvent according to claim 1, characterized in that, The pretreatment of the biomass raw material is as follows: Grinding and sieving the biomass raw material into fine particles, then soaking the particles in warm water and stirring, and filtering and washing with a washing liquid, and then drying at 60-80℃ to a constant weight, and collecting for use. 3.The method for efficiently extracting lignocellulose using a novel ternary eutectic solvent according to claim 2, characterized in that, The particle size of the ground and sieved biomass raw material is 0.25-0.5mm. 4.The method for efficiently extracting lignocellulose using a novel ternary eutectic solvent according to claim 1 or 2, characterized in that, The washing liquid is at least one of acetone, ethanol, or water. 5.The method for efficiently extracting lignocellulose using a novel ternary eutectic solvent according to claim 1, characterized in that, The biomass raw material is straw. 6.The method for efficiently extracting lignocellulose using a novel ternary eutectic solvent according to claim 5, characterized in that, The straw is selected from any one or more of rice straw, wheat straw, corn cob, and sugarcane residue.

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