Method for efficiently extracting lignocellulose by using novel ternary eutectic solvent

Abstract

The invention discloses a method for efficiently extracting lignocellulose by using a novel ternary eutectic solvent, belongs to the technical field of biomass material extraction, and aims to optimize the reaction activity and the dissolution characteristic of a system by using the unique combination of glycerol (Gly), potassium carbonate (KCO) and polyethylene glycol (PEG-200), effectively overcome the inherent intractability of wheat straw and improve the yield of lignocellulose. The method has the advantages that the method is simple and easy to implement, deconstruction and separation of the wood fiber biomass are promoted, and the obtained cellulose-rich residues have ideal crystallinity, thermal stability and processing capacity, so that the method has efficient downstream processing and application potential, and meanwhile, a more environment-friendly and more sustainable wood fiber biomass treatment method is provided.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass material extraction, and in particular relates to a method for efficiently extracting lignocellulose by using a novel ternary low eutectic solvent. Background Art

[0002] As the most abundant natural renewable energy on earth, lignocellulosic biomass mainly includes wood, crop waste (wheat straw, corn cobs and bagasse) and wood processing waste (sawdust, bark and pulp). The effective development and utilization of lignocellulosic biomass and its conversion into energy fuels, chemicals and functional materials is one of the most important development directions in the future. Lignocellulosic biomass usually has a multi-scale structure and complex component structure and function, mainly composed of three major components: cellulose, hemicellulose and lignin. This provides a beneficial foundation and guarantee for its healthy growth, but at the same time it also brings huge challenges to subsequent processing. Therefore, in order to promote the high-value and diversified comprehensive utilization of biomass resources and achieve highly selective separation and purification of the main components, it is necessary and primary to pre-treat, deconstruct and grade them.

[0003] As an emerging designer green solvent, deep eutectic solvent (DES) provides a new insight / solution / path for the development of sustainable deconstruction and fractionation processes based on lignocellulosic biomass. Generally speaking, DES is a liquid mixture formed by self-association of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA) under the action of hydrogen bonds, and its melting point is lower than the melting point of any of the original components. Benefiting from the characteristics of low cost, simple preparation and biodegradability, different HBD and HBA combinations can be modularly regulated to customize chemical properties and functions. It has high solvent capacity and reactivity, and is widely used in organic synthesis, catalytic reactions, separation and extraction, and electrochemistry. Due to the existence of hydrogen bonding, the physical and chemical properties presented by DES are beneficial to the deconstruction and separation of lignocellulosic biomass, and it shows competitiveness in related treatments. However, related research is still in its infancy, and DES usually has a high viscosity, which will cause problems such as poor dissolution effect and low reaction penetration efficiency. Therefore, how to effectively reduce the viscosity and further improve the deconstruction treatment effect has become a major challenge that needs to be solved urgently. Summary of the invention

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

[0005] The technical solution provided by the present invention is as follows:

[0006] The present invention provides a method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent, comprising the following steps: S1. Mixing the pretreated biomass raw material with the ternary low eutectic solvent for reaction, and reacting with magnetic stirring at a temperature of 120-160° C. for 12-24 hours to obtain a reaction product; S2, cooling the reaction product in S1, adding ethanol to dilute it, and then vacuum filtering it to obtain a cellulose-rich residue; S3, washing the cellulose-rich residue with a washing liquid until it is clear, and then freeze-drying it to obtain wood cellulose; Among them, 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 a ternary low eutectic solvent.

[0007] Furthermore, 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 solvent is 0.3:1 g / g.

[0008] Furthermore, the mass volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL.

[0009] Furthermore, the preparation method of the ternary deep eutectic solvent is: Potassium carbonate and glycerol were mixed and placed in an oil bath at 100° C. for mechanical stirring for 0.5 to 1 h until a clear and uniform solution was formed. Polyethylene glycol 200 was then added and stirred for 10 to 30 min to prepare a ternary low eutectic solvent.

[0010] Further, the biomass raw material is pretreated as follows: The biomass raw materials are crushed and sieved into fine particles, and then the particles are soaked in warm water and stirred, filtered and cleaned with washing liquid, and then dried at 60-80°C to constant weight and collected for later use.

[0011] Furthermore, the biomass raw material is crushed and sieved into fine particles with a particle size of 0.25-0.5 mm.

[0012] Furthermore, the mass volume ratio of the biomass raw material to the ternary low eutectic solvent is 1:25~40g / mL.

[0013] Furthermore, the washing liquid is at least one of acetone, ethanol or water.

[0014] Furthermore, the biomass raw material is straw.

[0015] Furthermore, the straw is selected from any one or more of rice straw, wheat straw, corn cob, and sugarcane bagasse.

[0016] Beneficial Effects

[0017] The present invention solves the problems of low reaction permeation efficiency and insufficient separation in the existing lignocellulosic biomass processing by utilizing 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. Specifically,

[0018] (1) Polyethylene glycol 200 (PEG-200) was added as the third component, which acts as a viscosity regulator and solubilizer to improve and optimize the reactivity and solubility characteristics of the system.

[0019] (2) The improvement in the performance of the ternary system is reflected in the significant removal rate of key biomass components: the hemicellulose removal rate is 81.93%, the lignin removal rate is 96.37%, and the cellulose yield is as high as 73.65%.

[0020] (3) The resulting cellulose-rich residue possesses desirable crystallinity, thermal stability, and processability, thus having the potential for efficient downstream processing and applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The temperature-viscosity relationship curve of different DES in the embodiment;

[0022] Figure 2 The actual pictures of different cellulose-rich residues in the examples;

[0023] Figure 3 The scanning electron microscope images of wheat straw and different cellulose-rich residues in the examples;

[0024] Figure 4 X-ray diffraction patterns of different cellulose-rich residues in the examples;

[0025] Figure 5 Thermogravimetric curves of different cellulose-rich residues in the examples;

[0026] Figure 6 Schematic diagram of the proportion of different cellulose-rich residue components in the examples. DETAILED DESCRIPTION

[0027] The present invention is further explained in detail below in conjunction with the accompanying drawings and specific embodiments, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0028] The embodiment of the present invention provides a method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent, comprising the following steps: S1. Mixing the pretreated biomass raw material with the ternary low eutectic solvent for reaction, and reacting with magnetic stirring at a temperature of 120-160° C. for 12-24 hours to obtain a reaction product; S2, cooling the reaction product in S1, adding ethanol to dilute it, and then vacuum filtering it to obtain a cellulose-rich residue; S3, washing the cellulose-rich residue with a washing liquid until it is clear, and then freeze-drying it to obtain wood cellulose; Among them, 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 a ternary low eutectic solvent.

[0029] In this embodiment, 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 solvent is 0.3:1 g / g.

[0030] In this embodiment, the mass volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL.

[0031] In this embodiment, the preparation method of the ternary deep eutectic solvent is: Potassium carbonate and glycerol were mixed and placed in an oil bath at 100° C. for mechanical stirring for 0.5 to 1 h until a clear and uniform solution was formed. Polyethylene glycol 200 was then added and stirred for 10 to 30 min to prepare a ternary low eutectic solvent.

[0032] In this embodiment, the biomass raw material is pretreated as follows: The biomass raw materials are crushed and sieved into fine particles, and then the particles are soaked in warm water and stirred, filtered and cleaned with washing liquid, and then dried at 60-80°C to constant weight and collected for later use.

[0033] In this embodiment, the biomass raw material is crushed and sieved into fine particles with a particle size of 0.25-0.5 mm.

[0034] In this embodiment, the mass volume ratio of the biomass raw material to the ternary low eutectic solvent is 1:25~40g / mL.

[0035] In this embodiment, the washing liquid is at least one of acetone, ethanol or water.

[0036] In this embodiment, the biomass raw material is straw.

[0037] In this embodiment, the straw is selected from any one or more of rice straw, wheat straw, corn cob, and sugarcane bagasse.

[0038] Example 1

[0039] (1) Pretreatment of wheat straw

[0040] All biomass raw materials, wheat straw, were crushed and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water and stirred, filtered with deionized water and ethanol, and thoroughly washed. Finally, the samples were dried in an oven at 60°C to constant weight and stored for later use.

[0041] (2) Preparation of DES

[0042] According to the molar ratio of 1:5, 4.62 g potassium carbonate and 15.38 g glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear and uniform solution was formed. The final DES was prepared and marked as D and stored for future use.

[0043] (3) Extraction of lignocellulose

[0044] Specifically, 1 g of wheat straw was added to the prepared D and reacted with magnetic stirring at 160 ° C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtered. The treated filter residue was a cellulose-rich residue, which was washed with ethanol and deionized water until the rinse liquid was clear, and freeze-dried for analysis and detection, marked as CR.

[0045] Example 2

[0046] (1) Pretreatment of wheat straw

[0047] All biomass raw materials, wheat straw, were crushed and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water and stirred, filtered with deionized water and ethanol, and thoroughly washed. Finally, the samples were dried in an oven at 60°C to constant weight and stored for later use.

[0048] (2) Preparation of DES

[0049] According to the molar ratio of 1:5, 4.62 g potassium carbonate and 15.38 g glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear and uniform solution was formed. Subsequently, 5 mL polyethylene glycol 200 was added and stirred for 10 min to prepare the final DES, which was labeled as D-5 and stored for later use.

[0050] (3) Extraction of lignocellulose

[0051] Specifically, 1 g of wheat straw was added to the prepared D-5 and reacted with magnetic stirring at 160 °C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtered. The treated filter residue was a cellulose-rich residue, which was washed with ethanol and deionized water until the rinse liquid was clear, and freeze-dried for analysis and detection, marked as CR5.

[0052] Example 3

[0053] (1) Pretreatment of wheat straw

[0054] All biomass raw materials, wheat straw, were crushed and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water and stirred, filtered with deionized water and ethanol, and thoroughly washed. Finally, the samples were dried in an oven at 60°C to constant weight and stored for later use.

[0055] (2) Preparation of DES

[0056] According to the molar ratio of 1:5, 4.62 g potassium carbonate and 15.38 g glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear and uniform solution was formed. Subsequently, 10 mL polyethylene glycol 200 was added and stirred for 10 min to prepare the final DES, which was labeled as D-10 and stored for later use.

[0057] (3) Extraction of lignocellulose

[0058] Specifically, 1 g of wheat straw was added to the prepared D-10 and reacted with magnetic stirring at 160 °C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtered. The treated filter residue was a cellulose-rich residue, which was washed with ethanol and deionized water until the rinse liquid was clear, and freeze-dried for analysis and detection, marked as CR10.

[0059] Example 4

[0060] (1) Pretreatment of wheat straw

[0061] All biomass raw materials, wheat straw, were crushed and sieved into fine particles (about 0.25 mm). The obtained particles were then soaked in warm water and stirred, filtered with deionized water and ethanol, and thoroughly washed. Finally, the samples were dried in an oven at 60°C to constant weight and stored for later use.

[0062] (2) Preparation of DES

[0063] According to the molar ratio of 1:5, 4.62 g potassium carbonate and 15.38 g glycerol were mixed and placed in an oil bath at 100°C for mechanical stirring until a clear and uniform solution was formed. Subsequently, 20 mL polyethylene glycol 200 was added and stirred for 10 min to prepare the final DES, which was labeled as D-20 and stored for future use.

[0064] (3) Extraction of lignocellulose

[0065] Specifically, 1 g of wheat straw was added to the prepared D-20 and reacted with magnetic stirring at 160°C for 24 h. After the reaction was completed and cooled, 50 mL of ethanol was added for dilution, and then vacuum filtered. The treated filter residue was a cellulose-rich residue, which was washed with ethanol and deionized water until the rinse liquid was clear, and freeze-dried for analysis and detection, marked as CR20.

[0066] (4) Related tests

[0067] The different DES prepared in this example were subjected to rheological tests (the test method refers to the operating instructions of the micro-infrared rheometer). The test results are as follows: Figure 1 As shown. It can be seen that at the initial stage, i.e. at room temperature, D has a higher viscosity of 76.24 Pa·s. After adding polyethylene glycol 200, the viscosities of D-5, D-10 and D-20 decreased to 26.48 Pa·s, 9.90 Pa·s and 2.87 Pa·s, respectively. In addition, with the gradual increase of temperature, the viscosity of all DES systems was further reduced.

[0068] The different cellulose-rich residues prepared in this example are Figure 2 As shown, a scanning electron microscope test was performed (the test method refers to the operating instructions of the scanning electron microscope). Figure 3 As shown in the figure, the raw wheat straw has a distinct rod-like structure. After DES treatment, the surface of CR becomes rough and loose, with wrinkles and curls, while the surface of CR10 is grooved, with many cracks and fragments, and holes of different sizes, indicating that most of the hemicellulose and lignin components are effectively removed.

[0069] The different cellulose-rich residues prepared in this example were subjected to X-ray diffraction test (the test method refers to the operating instructions of the X-ray diffractometer). The test results are as follows: Figure 4 As shown in the figure, characteristic diffraction peaks appeared at 2θ = 16.7 °, 22.7 ° and 34.6 °, corresponding to the (110), (200) and (004) crystal planes of cellulose type I, respectively, indicating that the original cellulose crystal structure was not destroyed during the deconstruction and separation process.

[0070] The different cellulose-rich residues prepared in this example were subjected to thermogravimetric testing (the testing method refers to the operating instructions of the thermogravimetric analyzer). The test results are as follows: Figure 5 It can be seen that the initial loss temperature of wheat straw is 220℃, and the initial decomposition temperature of CR10 is 280℃, which has better thermal stability.

[0071] The different cellulose-rich residues prepared in this example were tested for composition. The test results are as follows: Figure 6As shown in Table 1. The results show that in Comparative Example 1, the removal rates of hemicellulose and lignin were 60.02% and 92.14%, respectively, and the component cellulose content was 72.38%. After adding different volumes of polyethylene glycol 200, in Examples 2-4, the hemicellulose removal rates were increased to 76.25%, 81.93% and 81.31%, respectively, the lignin removal rates were increased to 96.19%, 96.37% and 97.29%, respectively, and the component cellulose contents were increased to 77.94%, 77.72% and 76.21%, respectively. On the basis of ensuring a considerable cellulose yield, the removal rates of hemicellulose and lignin were 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 method for extracting lignocellulose.

[0072] Table 1 Detailed analysis of different treatment effects (tested according to NREL standards)

[0073]

[0074] The above specific implementation methods describe the implementation of the present invention in detail. At the same time, it should be pointed out that the present invention is not limited to the specific details in the above implementation methods. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention. These simple variations all belong to the protection scope of the present invention.

Claims

1. A method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent, characterized in that: The following steps are involved: S1. Mixing the pretreated biomass raw material with the ternary low eutectic solvent for reaction, and reacting with magnetic stirring at a temperature of 120-160° C. for 12-24 hours to obtain a reaction product; S2, cooling the reaction product in S1, adding ethanol to dilute it, and then vacuum filtering it to obtain a cellulose-rich residue; S3, washing the cellulose-rich residue with a washing liquid until it is clear, and then freeze-drying it to obtain wood cellulose; Among them, 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 a ternary low eutectic solvent.

2. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1, characterized in that: 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.

3. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 2, characterized in that: The mass volume ratio of the potassium carbonate and glycerol solvent system to polyethylene glycol 200 is 1-4:1 g / mL.

4. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1, characterized in that: The preparation method of the ternary deep eutectic solvent is: Potassium carbonate and glycerol were mixed and placed in an oil bath at 100° C. for mechanical stirring for 0.5 to 1 h until a clear and uniform solution was formed. Polyethylene glycol 200 was then added and stirred for 10 to 30 min to prepare a ternary low eutectic solvent.

5. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1, characterized in that: The pretreatment of biomass raw materials is as follows: The biomass raw materials are crushed and sieved into fine particles, and then the particles are soaked in warm water and stirred, filtered and cleaned with washing liquid, and then dried at 60-80°C to constant weight and collected for later use.

6. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 5, characterized in that: The biomass raw material is crushed and sieved into fine particles with a particle size of 0.25-0.5 mm.

7. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1, characterized in that: The mass volume ratio of the biomass raw material to the ternary low eutectic solvent is 1:25-40 g / mL.

8. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1 or 5, characterized in that: The washing liquid is at least one of acetone, ethanol or water.

9. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 1, characterized in that: The biomass raw material is straw.

10. The method for efficiently extracting lignocellulose using a novel ternary deep eutectic solvent according to claim 9, characterized in that: The straw is selected from any one or more of rice straw, wheat straw, corn cob, and sugarcane bagasse.

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