Bamboo resource fraction gradient separation and high-value conversion method

Abstract

The invention belongs to the technical field of efficient utilization of biomass resources, and particularly relates to a bamboo resource fraction gradient separation and high-value conversion method. The method comprises the following steps: firstly, selectively removing hemicellulose through a glycollic acid-assisted hydrothermal system and converting the hemicellulose into xylooligosaccharide with high additional value; a novel deep eutectic solvent (DES) system is used for conducting secondary mild reaction on the obtained acid water hot bamboo pulp, high-purity lignin is efficiently dissolved and separated out, and then bio-oil is prepared through rapid pyrolysis; and finally, carrying out enzymolysis on the residual solid residues to obtain glucose. According to the method, efficient separation and high-valued utilization of the three components of cellulose, hemicellulose and lignin are achieved, an environment-friendly solvent system is adopted in the core process (acid hydrothermal treatment and DES treatment), the process is green and environmentally friendly, and the method is particularly suitable for treatment of lignocellulose raw materials such as bamboo. The technology shows huge potential in promoting efficient utilization of biomass resources, especially in the aspect of developing sustainable new materials and chemicals.

Description

Technical Field

[0001] This invention belongs to the field of agricultural and forestry biomass processing and utilization technology, and relates to a method for graded separation and high-value conversion of bamboo resources. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Bamboo, as a representative species of natural woody biomass resources on Earth, boasts numerous advantages such as wide availability, abundant reserves, renewability, and biodegradability, making it a highly promising alternative to fossil resources. However, bamboo contains many impurities, making it more difficult to process than wood and other grasses. There is an urgent need to develop a green and efficient method for fractionating and converting bamboo into a graded product.

[0004] In recent years, deep eutectic solvent (DES) pretreatment technology has gradually become a research hotspot due to its advantages such as being environmentally friendly, having high processing efficiency, and being easy to synthesize. However, its efficiency in the fractionation and gradient separation of bamboo still needs to be improved. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a method for graded separation and high-value conversion of bamboo resources. This method requires simple reagent synthesis, involves mild reactions, and has a short reaction time. While obtaining xylooligosaccharides, it also achieves efficient separation of lignin from bamboo, resulting in high-yield bio-oil and glucose products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for graded separation and high-value conversion of bamboo resources, comprising: The plant material was subjected to a hydrothermal reaction in the presence of glycolic acid. After the reaction was completed, the solid and liquid were separated to obtain the first hydrolysate and the first residue. Extract xylooligosaccharides from the first hydrolysate; The first residue is mixed with a ternary eutectic solvent and subjected to a solvothermal reaction. After the reaction is completed, the solid and liquid are separated to obtain the second hydrolysate and the second residue. The solvent in the second hydrolysate was removed, and the solution was freeze-dried to obtain lignin. The second residue was enzymatically hydrolyzed to obtain glucose; The lignin was pyrolyzed to obtain bio-oil; The first hydrogen bond donor of the ternary eutectic solvent is a diol, and the second hydrogen bond donor is an organic acid.

[0007] This invention employs a pretreatment strategy coupled with acid hydrothermal treatment and deionization-extraction (DES). The acid hydrothermal pretreatment preferentially degrades and separates most of the hemicellulose component, creating favorable conditions for the effective penetration of DES. The specifically designed DES system can efficiently and selectively dissociate the remaining lignin, thereby retaining the highly reactive cellulose component. This technical approach successfully achieves the separation of the three major components: the cellulose component is easily enzymatically hydrolyzed into glucose; the hemicellulose component is mainly recovered in the form of xylooligosaccharides; and the lignin is separated with a high retention rate, laying a solid foundation for its subsequent high-value utilization.

[0008] In a second aspect, the present invention provides xylooligosaccharides, glucose and bio-oil prepared by the above method.

[0009] This invention establishes an integrated process for the high-value utilization of all components of bamboo biomass. The separated high-purity cellulose component is efficiently converted into glucose via enzymatic hydrolysis, which can be used as a fermentation feedstock for energy and chemical production. The hemicellulose component in the hydrothermal pretreatment solution is directionally converted into high-value-added xylooligosaccharides, serving the food and pharmaceutical industries. Crucially, the lignin obtained from DES separation can be selectively used to prepare high-quality bio-oil rich in aromatic hydrocarbons through pyrolysis, making it an ideal green chemical and fuel precursor. This integrated technology not only provides an innovative solution for the efficient utilization of bamboo resources but also significantly improves the overall economic and environmental benefits of biomass refining.

[0010] A third aspect of the present invention provides the application of an acid-hydrothermal eutectic solvent coupling system in the fractional gradient separation and high-value conversion of bamboo resources, using glycolic acid and a ternary eutectic solvent.

[0011] Beneficial effects of the present invention (1) This invention proposes a highly efficient method for the separation of all components of bamboo biomass based on an acid-hydrothermal eutectic solvent coupling system. This method can selectively separate the three major components of lignocellulose, yielding xylooligosaccharides, glucose, and bio-oil. This method is green, sustainable, and low-cost, realizing the resource conversion of all components of moso bamboo biomass.

[0012] (2) The acid hydrothermal pretreatment of the present invention is designed to address the characteristic that hemicellulose is more easily degraded than cellulose. Based on the use of a small amount of catalyst acid, it catalyzes the decomposition of long hemicellulose chains to form short-chain oligomers and sugar monomers.

[0013] (3) In the DES system of the present invention, the introduced polyol component has a significantly high boiling point (typically exceeding 200°C). Under specific pretreatment temperature conditions for bamboo raw materials, this component hardly volatilizes. This low volatility is crucial for maintaining the chemical stability of the DES system during the separation process, while significantly improving the operational safety of the process.

[0014] (4) This invention develops an environmentally friendly stepwise separation process, which successfully achieves efficient dissociation of the three major components of bamboo lignocellulose (cellulose, hemicellulose and lignin). The method is simple, practical and easy to promote. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 It is residue 2 (D) in Example 1 90-1 ) and the enzymatic saccharification rate of raw bamboo (Raw); Figure 2 It is residue 2 (D) in Example 2 100-1 ) and the enzymatic saccharification rate of raw bamboo (Raw); Figure 3 It is residue 2 ((D) in Example 4 130-1 The enzymatic hydrolysis saccharification rate of raw bamboo (Raw) is shown in the figure. Detailed Implementation

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or product instructions. Similarly, unless otherwise specified, the test methods of this invention are performed in accordance with conventional methods in the art or industry-standard methods or practices. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0019] This invention provides a method for graded separation and high-value conversion of bamboo resources, including: The plant material was subjected to a hydrothermal reaction in the presence of glycolic acid. After the reaction was completed, the solid and liquid were separated to obtain the first hydrolysate and the first residue. Extract xylooligosaccharides from the first hydrolysate; The first residue is mixed with a ternary eutectic solvent and subjected to a solvothermal reaction. After the reaction is completed, the solid and liquid are separated to obtain the second hydrolysate and the second residue. The solvent in the second hydrolysate was removed, and the solution was freeze-dried to obtain lignin. The second residue was enzymatically hydrolyzed to obtain glucose; The lignin was pyrolyzed to obtain bio-oil; The first hydrogen bond donor of the ternary eutectic solvent is a diol, and the second hydrogen bond donor is an organic acid.

[0020] The type of acid affects the effect of hydrothermal treatment. Therefore, this invention has studied the types of acids. In some embodiments, the concentration of glycolic acid is 0.1-1%. Compared with ordinary hydrothermal treatment, glycolic acid has a very strong catalytic ability and can quickly and thoroughly hydrolyze hemicellulose and cellulose into fermentable monosaccharides with a high sugar yield.

[0021] This invention employs a pretreatment strategy that couples hydrothermal treatment with DES. Hydrothermal pretreatment preferentially degrades and separates most of the hemicellulose components, creating favorable conditions for the effective penetration of DES. Therefore, in some embodiments, the hydrothermal reaction conditions are: a solid-liquid ratio of 1:5-20, a reaction temperature of 140-170 ℃, and a reaction time of 30-90 min, to obtain a better pretreatment effect.

[0022] The present invention does not impose any special limitation on the plant raw materials to be processed. In some embodiments, the plant raw materials are bamboo raw materials; in some embodiments, the bamboo raw materials are selected from at least one of the following: moso bamboo, Ci bamboo, yellow bamboo, Xifeng bamboo, Julong bamboo, bamboo processing residues, and bamboo shoot shells.

[0023] The different hydrogen bond acceptors and hydrogen bond donors in eutectic solvents affect their physical and chemical properties. To achieve better separation results, this invention studies the composition of ternary eutectic solvents. In some embodiments, the hydrogen bond acceptor in the ternary eutectic solvent is selected from at least one of choline chloride, guanidine hydrochloride, and ethylamine chloride; in some embodiments, the diol is selected from at least one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol; in some embodiments, the organic acid is selected from at least one of lactic acid, p-toluenesulfonic acid, heteropoly acid, and Lewis acid, to efficiently and selectively dissociate the remaining lignin.

[0024] When the ratio of hydrogen bond donor to acceptor increases, the hydrogen bonding effect is enhanced, and the properties of the eutectic solvent change. Therefore, this invention studies the ratio of hydrogen bond acceptor, first hydrogen bond donor and second hydrogen bond donor. In some embodiments, the molar ratio of hydrogen bond acceptor: first hydrogen bond donor: second hydrogen bond donor is 1:1-10:0.04-2 to improve lignin separation efficiency.

[0025] Eutectic solvents can effectively remove lignin and hemicellulose at high temperatures, but excessively high temperatures may damage the cellulose structure. Therefore, this invention has investigated the conditions for solvothermal reactions. In some embodiments, the solvothermal reaction conditions are: a solid-liquid ratio of 1:10-20, a heating temperature of 90-130 °C, and a reaction time of 0.5-3 h, in order to selectively separate lignin while retaining the highly reactive cellulose components.

[0026] The conditions of enzymatic hydrolysis affect the glucose yield. Therefore, the present invention has studied the conditions of enzymatic hydrolysis. In some embodiments, the conditions of enzymatic hydrolysis are: 5-20 FPU / g of cellulase, reaction temperature of 50℃-55℃, rotation speed of 150-200 rpm, and reaction time of 12-72 h, in order to obtain a higher glucose yield.

[0027] Lignin can generate bio-oil under high-temperature pyrolysis. Therefore, this invention studies the temperature and time of pyrolysis. In some embodiments, the pyrolysis conditions are 500-800℃ under an inert atmosphere for 5-20 min to improve the yield of bio-oil.

[0028] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0029] Example 1: (1) Mix bamboo powder and 0.1% glycolic acid solution at a solid-liquid ratio of 1:10 in a high-pressure reactor and react at 170°C for 30 min. After the reaction, separate the solid and liquid to obtain reaction solution 1 and residue 1. Wash residue 1 with deionized water until neutral. Collect the washing liquid and reaction solution 1 to form hydrolysate 1. Remove excess water from hydrolysate 1 by rotary evaporation and add it to 3 times the amount of anhydrous ethanol to precipitate xylooligosaccharides. Centrifuge and freeze dry to obtain xylooligosaccharides.

[0030] (2) Preparation of DES by catalysis: Ethylamine chloride, ethylene glycol and aluminum chloride are mixed in a molar ratio of 1:2:0.04 and heated and stirred at 90 °C for 1 hour until a uniform and transparent mixture is formed for later use.

[0031] (3) The bamboo residue 1 obtained in step (1) and the catalytic DES obtained in step (2) are mixed in a solid-liquid ratio of 1:10 and placed in a reactor. The temperature is set at 90℃ and the reaction is carried out for 1 hour. After the reaction is completed, the solid and liquid are separated to obtain residue 2 and reaction solution 2. Residue 2 is washed with ethanol / water (volume ratio of ethanol to water is 1:1), and finally washed with water until neutral. The washing liquid and reaction solution 2 are collected and mixed to obtain hydrolysate 2. After removing the ethanol by rotary evaporation, hydrolysate 2 is centrifuged and freeze-dried to obtain lignin powder.

[0032] (4) The residue 2 obtained in step (3) above is mixed with 15 FPU / g cellulase and reacted in a shaker at 50°C and 150 rpm for 72 h to obtain glucose.

[0033] (5) The lignin obtained in step (3) above was pyrolyzed in a laboratory setting. The lignin was placed at the bottom of a quartz U-tube, and the air in the U-tube was replaced with N2. The tube was placed in a preheated furnace and pyrolyzed at 650°C for 8 minutes. The U-tube was then removed and cooled to room temperature. The pyrolysis products (bio-oil and coke) in the U-tube were washed with dichloromethane. The washing liquid was filtered to obtain filtrate and coke. The filtrate was rotary evaporated to remove dichloromethane to obtain bio-oil.

[0034] The test results showed that after treatment with an acid-hydrothermal eutectic solvent coupling system, 66.02% xylooligosaccharide was obtained from moso bamboo; 65.74% lignin was recovered with a purity of 99.32% and a pyrolysis bio-oil yield of 35.81%; 96.35% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 81.33%.

[0035] Example 2: (1) Mix bamboo powder and 1% glycolic acid solution at a solid-liquid ratio of 1:10 in a high-pressure reactor and react at 160°C for 60 min. After the reaction, separate the solid and liquid to obtain reaction solution 1 and residue 1. Wash residue 1 with deionized water until neutral. Collect the washing liquid and reaction solution 1 to form hydrolysate 1. Remove excess water from hydrolysate 1 by rotary evaporation and add it to 3 times the amount of anhydrous ethanol to precipitate xylooligosaccharides. Centrifuge and freeze dry to obtain xylooligosaccharides.

[0036] (2) Preparation of DES by catalysis: Ethylamine chloride, ethylene glycol and aluminum chloride are mixed in a molar ratio of 1:2:0.04 and heated and stirred at 90 °C for 1 hour until a uniform and transparent mixture is formed for later use.

[0037] (3) The bamboo residue 1 obtained in (1) and the catalytic DES obtained in (2) were mixed in a solid-liquid ratio of 1:10 and placed in a reactor. The temperature was set at 100℃ and the reaction was carried out for 1 hour. After the reaction was completed, the solid and liquid were separated to obtain residue 2 and reaction solution 2. Residue 2 was washed with ethanol / water (volume ratio of ethanol to water was 1:1) and finally washed with water until neutral. The washing liquid and reaction solution 2 were collected and mixed to obtain hydrolysate 2. After removing the ethanol by rotary evaporation, the hydrolysate 2 was centrifuged and freeze-dried to obtain lignin powder.

[0038] (4) The residue 2 obtained in step (3) above is mixed with 20 FPU / g cellulase and reacted in a shaker at 50°C and 150 rpm for 72 h to obtain glucose.

[0039] (5) The lignin obtained in step (3) above was pyrolyzed in a laboratory setting. The lignin was placed at the bottom of a quartz U-tube, and the air in the U-tube was replaced with N2. The tube was placed in a preheated furnace and pyrolyzed at 600°C for 5 minutes. The U-tube was then removed and cooled to room temperature. The pyrolysis products (bio-oil and coke) in the U-tube were washed with dichloromethane. The washing liquid was filtered to obtain filtrate and coke. The filtrate was rotary evaporated to remove dichloromethane to obtain bio-oil.

[0040] The test results showed that after the bamboo was treated with an acid-hydrothermal eutectic solvent coupling system, 72.72% xylooligosaccharide was obtained; 72.47% lignin was recovered with a purity of 99.81% and the pyrolysis bio-oil yield was 28.60%; 97.10% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 95.64%.

[0041] Example 3: (1) Mix bamboo powder and 0.5% glycolic acid solution at a solid-liquid ratio of 1:10 in a high-pressure reactor and react at 170°C for 45 min. After the reaction, separate the solid and liquid to obtain reaction solution 1 and residue 1. Wash residue 1 with deionized water until neutral. Collect the washing liquid and reaction solution 1 to form hydrolysate 1. Remove excess water from hydrolysate 1 by rotary evaporation and add it to 3 times the amount of anhydrous ethanol to precipitate xylooligosaccharides. Centrifuge and freeze dry to obtain xylooligosaccharides.

[0042] (2) Preparation of ternary DES: Guanidine hydrochloride, ethylene glycol and lactic acid are mixed in a molar ratio of 1:1:2 and heated and stirred at 80 °C for 1 hour until a uniform and transparent mixture is formed for later use.

[0043] (3) The bamboo residue 1 obtained in (1) and the catalytic DES obtained in (2) were mixed in a solid-liquid ratio of 1:10 and placed in a reactor. The temperature was set at 130℃ and the reaction was carried out for 2 hours. After the reaction was completed, the solid and liquid were separated to obtain residue 2 and reaction solution 2. Residue 2 was washed with ethanol / water (volume ratio of ethanol to water was 1:1) and finally washed with water until neutral. The washing liquid and reaction solution 2 were collected and mixed to obtain hydrolysate 2. After removing the ethanol by rotary evaporation, the hydrolysate 2 was centrifuged and freeze-dried to obtain lignin powder.

[0044] (4) The residue 2 obtained in step (3) above is mixed with 15 FPU / g cellulase and reacted in a shaker at 50°C and 150 rpm for 72 h to obtain glucose.

[0045] (5) The lignin obtained in step (3) above was pyrolyzed in a laboratory setting. The lignin was placed at the bottom of a quartz U-tube, and the air in the U-tube was replaced with N2. The tube was placed in a preheated furnace and pyrolyzed at 650°C for 8 minutes. The U-tube was then removed and cooled to room temperature. The pyrolysis products (bio-oil and coke) in the U-tube were washed with dichloromethane. The washing liquid was filtered to obtain filtrate and coke. The filtrate was rotary evaporated to remove dichloromethane to obtain bio-oil.

[0046] The test results showed that after treatment with an acid-hydrothermal eutectic solvent coupling system, 52.91% xylooligosaccharide was obtained from moso bamboo; 88.84% lignin was recovered with a purity of 99.06% and a pyrolysis bio-oil yield of 33.96%; 97.35% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 98.75%.

[0047] Example 4: (1) Mix bamboo powder and 0.1% glycolic acid solution at a solid-liquid ratio of 1:10 in a high-pressure reactor and react at 170°C for 30 min. After the reaction, separate the solid and liquid to obtain reaction solution 1 and residue 1. Wash residue 1 with deionized water until neutral. Collect the washing liquid and reaction solution 1 to form hydrolysate 1. Remove excess water from hydrolysate 1 by rotary evaporation and add it to 3 times the amount of anhydrous ethanol to precipitate xylooligosaccharides. Centrifuge and freeze dry to obtain xylooligosaccharides.

[0048] (2) Preparation of ternary DES: Guanidine hydrochloride, ethylene glycol and lactic acid are mixed in a molar ratio of 1:5:2 and heated and stirred at 80 °C for 1 hour until a uniform and transparent mixture is formed for later use.

[0049] (3) The bamboo residue 1 obtained in (1) and the catalytic DES obtained in (2) were mixed in a solid-liquid ratio of 1:10 and placed in a reactor. The temperature was set at 130℃ and the reaction was carried out for 3 hours. After the reaction was completed, the solid and liquid were separated to obtain residue 2 and reaction solution 2. Residue 2 was washed with ethanol / water (volume ratio of ethanol to water was 1:1) and finally washed with water until neutral. The washing liquid and reaction solution 2 were collected and mixed to obtain hydrolysate 2. After removing the ethanol by rotary evaporation, the hydrolysate 2 was centrifuged and freeze-dried to obtain lignin powder.

[0050] (4) The residue 2 obtained in step (3) above is mixed with 15 FPU / g cellulase and reacted in a shaker at 50°C and 150 rpm for 72 h to obtain glucose.

[0051] (5) The lignin obtained in step (3) above was pyrolyzed in a laboratory setting. The lignin was placed at the bottom of a quartz U-tube, and the air in the U-tube was replaced with N2. The tube was placed in a preheated furnace and pyrolyzed at 600°C for 10 minutes. The U-tube was then removed and cooled to room temperature. The pyrolysis products (bio-oil and coke) in the U-tube were washed with dichloromethane. The washing liquid was filtered to obtain filtrate and coke. The filtrate was rotary evaporated to remove dichloromethane to obtain bio-oil.

[0052] The test results showed that bamboo treated with an acid-hydrothermal eutectic solvent coupling system yielded 66.02% xylooligosaccharide; 72.99% lignin was recovered with a purity of 98.86%, and the yield of pyrolysis bio-oil was 35.25%; 98.47% cellulose was retained in residue 2, and the enzymatic hydrolysis saccharification rate was 94.34%.

[0053] Comparative Example 1: Based on Example 1, ethylamine chloride was replaced with choline chloride, while all other conditions remained unchanged.

[0054] The test results showed that bamboo treated with an acid-hydrothermal eutectic solvent coupling system yielded 66.02% xylooligosaccharide; 26.53% lignin was recovered with a purity of 97.56% and a pyrolysis bio-oil yield of 10.50%; 86.53% cellulose was retained in residue 2, and the enzymatic hydrolysis saccharification rate was 61.23%.

[0055] Comparative Example 2: Based on Example 1, without adding aluminum chloride as a catalyst, the reaction temperature and time were 120 °C and 3 h, respectively, with all other conditions remaining unchanged.

[0056] The test results showed that after the bamboo was treated with an acid-hydrothermal eutectic solvent coupling system, 66.02% xylooligosaccharide was obtained; 22.57% lignin was recovered with a purity of 95.46% and the pyrolysis bio-oil yield was 13.82%; 51.30% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 7.13%.

[0057] Comparative Example 3: Based on Example 4, no lactic acid was added during the preparation of ternary DES; only guanidine hydrochloride and ethylene glycol were used, and all other conditions remained unchanged.

[0058] The test results showed that bamboo was treated with an acid-hydrothermal eutectic solvent coupling system to obtain 66.02% xylooligosaccharide; 12.65% lignin was recovered with a purity of 97.81% and a pyrolysis bio-oil yield of 10.22%; 55.12% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 13.08%.

[0059] Comparative Example 4: Based on Example 4, hydrothermal treatment was not performed, and all other conditions remained unchanged.

[0060] The test results showed that after bamboo was treated with a eutectic solvent system, 55.15% lignin was recovered, with a purity of 95.61%, and the pyrolysis bio-oil yield was 24.84%; 69.53% cellulose was retained in residue 2, and the enzymatic hydrolysis saccharification rate was 95.31%.

[0061] Comparative Example 5 Based on Example 4, in step (1), water is used instead of glycolic acid solution; The test results showed that 30.10% xylooligosaccharides were obtained; 53.81% lignin was recovered with a purity of 96.15% and the yield of pyrolysis bio-oil was 28.05%; 90.33% cellulose was retained in residue 2 and the enzymatic hydrolysis saccharification rate was 89.62%.

[0062] Comparative Example 6 Based on Example 4, in step (3), water is used to replace the catalytic DES; The test results showed that bamboo treated with an acid-hydrothermal eutectic solvent coupling system yielded 66.02% xylooligosaccharide; 1.77% lignin was recovered with a purity of 83.40% and a pyrolysis bio-oil yield of 0.55%; 49.90% cellulose was retained in residue 2, and the enzymatic hydrolysis saccharification rate was 24.88%.

[0063] As can be seen from the comparison of Example 1 and Comparative Examples 1-2, the composition of DES significantly affects the separation effect of lignin and cellulose in bamboo. The DES of the present invention can significantly improve the lignin yield, pyrolysis bio-oil yield, cellulose yield and saccharification rate.

[0064] As can be seen from the comparison between Example 4 and Comparative Example 3, compared with binary DES, ternary DES can significantly improve the separation effect of various components of bamboo, and the yield of lignin, pyrolysis bio-oil, cellulose and saccharification rate are significantly improved.

[0065] As can be seen from the comparison between Example 4 and Comparative Example 5, compared with ordinary hydrothermal treatment, the glycolic acid-catalyzed hydrothermal treatment can significantly increase the content of xylooligosaccharides, and also improve the yield of lignin, pyrolysis bio-oil, cellulose and saccharification rate.

[0066] As can be seen from the comparison between Example 4 and Comparative Example 6, DES treatment can significantly improve the yield of lignin and pyrolysis bio-oil, and also significantly improve the cellulose and saccharification rates.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for graded separation and high-value conversion of bamboo resources, characterized in that, include: The plant material was subjected to a hydrothermal reaction in the presence of glycolic acid. After the reaction was completed, the solid and liquid were separated to obtain the first hydrolysate and the first residue. Extract xylooligosaccharides from the first hydrolysate; The first residue was mixed with a ternary eutectic solvent and subjected to a solvothermal reaction. After the reaction was completed, the solid and liquid were separated to obtain the second hydrolysate and the second residue. The solvent in the second hydrolysate was removed, and the solution was freeze-dried to obtain lignin. The second residue was enzymatically hydrolyzed to obtain glucose; The lignin was pyrolyzed to obtain bio-oil; The first hydrogen bond donor of the ternary eutectic solvent is a diol, and the second hydrogen bond donor is an organic acid.

2. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The concentration of glycolic acid is 0.1-1%.

3. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The conditions for the hydrothermal reaction are: a solid-liquid ratio of 1:5-20, a reaction temperature of 140-170 ℃, and a reaction time of 30-90 min.

4. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The plant material is bamboo. Alternatively, the bamboo raw material may be selected from at least one of the following: moso bamboo, Ci bamboo, yellow bamboo, Xifeng bamboo, Julong bamboo, bamboo processing residues, and bamboo shoot shells.

5. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, In the ternary eutectic solvent, the hydrogen bond acceptor is selected from at least one of choline chloride, guanidine hydrochloride, and ethylamine chloride; Alternatively, the diol is selected from at least one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol; Alternatively, the organic acid is selected from at least one of lactic acid, p-toluenesulfonic acid, heteropoly acid, and Lewis acid; The molar ratio of the hydrogen bond acceptor: the first hydrogen bond donor: the second hydrogen bond donor is 1:1-10:0.04-2.

6. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The conditions for the solvothermal reaction are: a solid-liquid ratio of 1:10-20, a heating temperature of 90-130 ℃, and a reaction time of 0.5-3 h.

7. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The enzymatic hydrolysis conditions are as follows: cellulase 5-20 FPU / g, reaction temperature 50℃-55℃, rotation speed 150-200 rpm, and reaction time 12-72 h.

8. The method for graded separation and high-value conversion of bamboo resources as described in claim 1, characterized in that, The pyrolysis conditions are: under an inert atmosphere, at 500-800℃, for 5-20 minutes.

9. The xylooligosaccharides, glucose and bio-oil prepared by the method according to any one of claims 1-8.

10. The application of an acid-hydrothermal eutectic solvent coupling system in the fractional gradient separation and high-value conversion of bamboo resources, characterized in that, Glycolic acid and a ternary eutectic solvent are used.

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