CN116283846A - A method for high-value agricultural residues from ternary deep eutectic solvent system - Google Patents

Abstract

A method for high-value agricultural residues from a ternary deep eutectic solvent system. Two kinds of hydrogen bond donors and hydrogen bond acceptors are mixed, heated and stirred to obtain a ternary deep eutectic solvent; agricultural waste powder , ternary deep eutectic solvent, water, and organic solvent are mixed, and heated for reaction; after the reaction, the reactor is cooled to room temperature, and the reaction phase and the extraction phase are collected to prepare furfural; add acetone and water to the solid-liquid mixture for washing, and collect the filtrate ; put the filtrate into an oil bath, evaporate the acetone to dryness, add deionized water to wash, and filter and dry to obtain lignin; wash the solid obtained after suction with deionized water, and dry to obtain cellulose; Lignin and iron salt are mixed and stirred, evaporated to dryness and then calcined at high temperature to obtain a lignin-based graphitized carbon-based catalyst. This method can effectively separate the three major elements, and at the same time convert hemicellulose into high-value platform chemical furfural, which enhances the enzymatic hydrolysis efficiency of cellulose and realizes the high-value utilization of agricultural waste.

Description

A method for high-value agricultural residues from ternary deep eutectic solvent system

technical field

The invention belongs to the technical field of comprehensive utilization of biomass resources, and in particular relates to a method for using ternary deep eutectic solvent to increase the value of straw raw materials.

Background technique

With the shortage of non-renewable energy such as oil and coal and the deterioration of global environmental problems, the development and utilization of renewable energy has become a research hotspot. Compared with first-generation biofuels, second-generation biofuels are getting more and more attention. The feedstock for first-generation biofuels is edible starch, while the feedstock for second-generation biofuels is a wide range, especially pesticide residues from lignocellulosic biomass. Straw is one of the main agricultural residues with low cost and large availability. It is estimated that 6.5×10 ⁸ tons of wheat, rice and corn straw are produced as agricultural residues in China every year, but they are not effectively utilized. Wheat straw is mainly composed of cellulose (30-35%), hemicellulose (15-25%) and lignin (10-25%). Cellulose and hemicellulose fractions can be hydrolyzed and dehydrated into furanic compounds such as furfural and 5-HMF, which are then synthetically upgraded to fuels and chemicals, and lignin is used for combustion to generate electricity, converted to phenolic compounds or lignin-based materials. To resist microbial and enzymatic deconstruction, lignocellulose has a recalcitrant structure, the lignin-carbohydrate complex, which limits the separation of the three components and the subsequent production of value-added products. In order to realize the efficient utilization of agricultural waste, it is first necessary to separate these three components by green and environmentally friendly means. Biomass pretreatment is one of the most commonly used techniques for the removal and modification of lignin in biorefining, which destroys the lignin-carbohydrate structure by changing the interaction of its components cellulose, hemicellulose, and lignin. Pretreatment can not only improve the efficiency of enzymatic hydrolysis of carbohydrates, but also effectively recover cellulose, hemicellulose and lignin to realize the value addition of biomass.

A variety of pretreatment methods have been developed to overcome the recalcitrance of lignocellulose in decomposition, such as dilute acid, alkali treatment, sulfite, and organic solvent methods, but the above methods have the disadvantages of damaging the environment, being expensive, and damaging equipment. disadvantages. In 2004, Abboot et al. discovered a new solvent with similar physical and chemical properties to ionic liquids, named deep eutectic solvent (DES). Deep eutectic solvents have the advantages of low cost, nontoxicity, easy preparation, biodegradability, and easy recycling. They are composed of hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD), forming complexes through hydrogen bonds, and have been widely used in the fields of catalysis, organic synthesis, electrochemistry, and biomass processing. Deep eutectic solvents have high selectivity for dissolved lignin, which is beneficial for the high-value utilization of regenerated lignin and retained cellulose. p-Toluenesulfonic acid (p-TSA), an aromatic acid, is a hydrotrope with excellent delignification performance at low temperatures below the boiling point of water, and can be used as an acidic hydrogen bond donor for DES. Acidic hydrogen-bond donors of deep eutectic solvents can efficiently separate cellulose, hemicellulose, and lignin from lignocellulose. p-toluenesulfonic acid can depolymerize lignin by cleavage of ether bonds, and can separate carbohydrate-free lignin from lignocellulose. Ethylene glycol with poor performance is used as neutral HBD. DES containing three components of one HBA and two HBDs has been shown to be more effective in biomass deconstruction.

A Chinese invention (CN110218335A) discloses a method for extracting lignin using a ternary deep eutectic solvent. The method comprises the steps of: mixing and reacting the raw material with a ternary deep eutectic solvent, cooling to room temperature after the reaction is completed, and obtaining a reaction product, adding the reaction product to anhydrous ethanol and stirring, washing with ethanol, filtering, concentrating, adding water, and standing , to obtain a precipitate containing lignin, filter, and dry to obtain lignin. This method does not mention the subsequent utilization of the three major elements, and has not met the expectations of this field.

A Chinese invention (CN113956299A) discloses a method for pretreating eucalyptus graded lignin and co-producing furfural with a DES-based two-phase system. In the method, raw materials, DES, an organic solvent and a catalyst are blended and added into a reaction kettle for reaction, and after the reaction is completed, the temperature is lowered to obtain a solvent and extract containing furfural, and the deep eutectic reaction mixture is washed and dried with acetone/water solution to obtain lignin . Although this invention realizes the co-production of furfural and lignin, it needs to add a catalyst in the reaction process, and the separation steps are cumbersome and do not conform to the principles of economy and environmental protection.

Chinese invention (CN106495132A) discloses a method for preparing graphene from lignin. First, special enzyme treatment is used to purify the lignin raw material to obtain high-purity lignin; on this basis, through oxidation, carbonization, graphitization, etc. process to obtain high-quality graphene. This method has cumbersome steps when purifying lignin, and side reactions such as decomposition, dehydration, and esterification are prone to occur during the purification process.

Contents of the invention

The technical problem to be solved: In view of the fact that the utilization of all components of agricultural residues has not been realized in the prior art, the obtained product is relatively simple, the added value is low, and the environment is not friendly, and due to the lignin-carbohydrate complex (LCC) bond The recalcitrance in the decomposition of biomass leads to the difficulty of separating the three major elements. The deep eutectic solvent has the ability to crack the ester bond between lignin and hemicellulose without affecting the CC bond in the lignin. The invention provides a method for high-value agricultural residues from the ternary deep eutectic solvent system. This method can effectively separate the three major elements, and at the same time convert hemicellulose into high-value platform chemical furfural, which enhances the enzymatic hydrolysis efficiency of cellulose. The extracted lignin and iron salt are mixed and pyrolyzed to prepare lignin Based on graphitized carbon-based catalysts, the high-value utilization of agricultural wastes has been realized.

Technical solution: a method for high-value agricultural residues from a ternary deep eutectic solvent system, comprising the following steps: (1) mixing two hydrogen bond donors and hydrogen bond acceptors, heating and stirring to prepare ternary Deep eutectic solvent; the hydrogen bond acceptor is choline chloride, and two kinds of hydrogen bond donors are p-toluenesulfonic acid and ethylene glycol respectively, the choline chloride, p-toluenesulfonic acid, ethylene glycol The molar ratio is 1:1:0.2～0.5; (2) the agricultural waste powder, ternary deep eutectic solvent, water, organic solvent are mixed, and the mass ratio of described agricultural waste powder and ternary deep eutectic solvent is 1: (10～100), 80 ℃-120 ℃, reaction 0.5h-2h; (3) After the reaction finishes, the reactor is cooled to room temperature, collects reaction phase and extraction phase, prepares furfural; (4) to step (3 ), add acetone and water to wash the solid-liquid mixture in ), the ratio of acetone to water is (1-4): 1, and collect the filtrate; (5) put the filtrate in an oil bath, evaporate the acetone to dryness, and add deionized Washing with water, suction filtration and drying to obtain lignin; (6) washing the solid obtained after suction filtration in step (4) with deionized water, drying to obtain cellulose; (7) mixing and stirring the extracted lignin and iron salt , the mass ratio of lignin to iron salt is 1:(0.2-2), evaporated to dryness and calcined at high temperature to obtain lignin-based graphitized carbon-based catalyst.

Preferably, in step (1): p-toluenesulfonic acid, choline chloride, and ethylene glycol are mixed in a molar ratio of 1:1:0.3.

Preferably, in step (2): the agricultural waste is wheat straw or corn straw, with a particle size of 40-400 mesh.

Preferably, in step (2): the organic solvent is methyl isobutyl ketone, the target reaction temperature is 100° C., and the reaction time is 1 h.

Preferably, in step (4): the ratio of the acetone to water is 1:1.

Preferably, in step (7): the iron salt is iron acetate.

Preferably, in step (7): the high-temperature calcination is performed at a temperature of 600-1000°C.

Preferably, in step (7): the mass ratio of the lignin to the iron salt is 1:0.2.

Beneficial effects: (1) Compared with other traditional pretreatment methods or binary deep eutectic solvents, the present invention can improve the availability and extraction rate of the three major elements when treating straw, and can convert hemicellulose into high Value Platform Chemicals. (2) The lignin obtained by the extraction method of the present invention can be combined with iron salts to obtain a lignin-based graphitized carbon-based catalyst through processes such as carbonization and graphitization, showing an advanced oxidation technology. (3) The existing binary deep eutectic solvent processing technology has only one hydrogen bond donor, which is not enough to occupy all the sites of the hydrogen bond acceptor, resulting in weak hydrogen bond ability. When used, the solubility of lignin and hemicellulose is low. After the straw is treated with the ternary deep eutectic solvent, the invention can not only enhance the solubility and utilization rate of lignin and hemicellulose, but also retain relatively complete cellulose, thereby enhancing the enzymatic hydrolysis efficiency of cellulose. (4) Compared with traditional organic solvents and inorganic acid-base treatment methods, the extraction method used in the present invention has little damage to the environment, low cost, high economic benefit, and meets the development concept of green environmental protection.

Description of drawings

Fig. 1 is the XRD spectrum of lignin-based graphitized carbon-based catalyst prepared by the present invention;

Fig. 2 is the reaction result of tetracycline in waste water degraded by lignin-based graphitized carbon-based catalyst prepared by the present invention through Fenton reaction;

Fig. 3 is the effect of the extraction method used in the present invention on the crystallinity of cellulose.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and comprehensible, the specific implementation manners of the present invention will be described in detail below in conjunction with the embodiments of the specification.

Example 1

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.3, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment and furfural test

The straw was passed through a 40-mesh sieve, and then dried in an oven at 60°C to constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-to-liquid ratio of 1:10, and heat at 100 °C for 1 h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 69.43%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 1:1, stir well, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an 80°C oil bath, and dry in an oven. The mass ratio of ferric acetate to lignin is 1:0.2. Calcining at 2°C/min at 1000°C for 1 hour to obtain a lignin-based catalyst.

Example 2

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.6, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through an 80-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-to-liquid ratio of 1:20, and heat at 100 °C for 1 h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 57.45%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 2:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric oxalate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an oil bath at 80°C, and dry in an oven. The mass ratio of ferric oxalate to lignin is 1:0.5. Calcining at 2°C/min at 900°C for 2 hours to obtain a lignin-based catalyst.

Example 3

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:1, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through a 120-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-to-liquid ratio of 1:40, and heat at 100 °C for 1 h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 58.79%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 3:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50 mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an 80°C oil bath, and dry in an oven. The mass ratio of ferric nitrate to lignin is 1:1.5. Calcining at 2°C/min at 800°C for 2 hours to obtain a lignin-based catalyst.

Example 4

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.3, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through a 200-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-liquid ratio of 1:100, and heat at 120°C for 0.5h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 57.47%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 4:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an oil bath at 80°C, and dry in an oven. The mass ratio of ferric nitrate to lignin is 1:1. Calcining at 2°C/min at 1000°C for 2 hours to obtain a lignin-based catalyst.

Example 5

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.3, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through a 200-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-liquid ratio of 1:80, and heat at 100°C for 1.5h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 47.47%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 4:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an oil bath at 80°C, and dry in an oven. The mass ratio of ferric nitrate to lignin is 1:2. Calcining at 2°C/min at 1000°C for 3 hours to obtain a lignin-based catalyst.

Example 6

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.3, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through a 200-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-liquid ratio of 1:80, and heat at 100°C for 0.5h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 62.93%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 4:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an oil bath at 80°C, and dry in an oven. The mass ratio of ferric nitrate to lignin is 1:1. Calcining at 2°C/min at 1000°C for 1 hour to obtain a lignin-based catalyst.

Example 7

(1) Preparation of deep eutectic solvent

Mix the dried p-toluenesulfonic acid, choline chloride, and ethylene glycol at a molar ratio of 1:1:0.1, heat and stir at 80°C for 1 hour, until all solids dissolve into a clear and transparent solution.

(2) Lignocellulose pretreatment

The straw was passed through a 200-mesh sieve, and then dried in an oven at 60°C until constant weight. Add dried straw powder, methyl isobutyl ketone, water and deep eutectic solvent into the reactor, mix at a solid-liquid ratio of 1:60, and heat at 100 °C for 1 h. After the reaction, the reactant was cooled to room temperature, and deionized water was added for mixing. The reactant was suction filtered under reduced pressure to separate the solid residue and the pretreatment liquid. The furfural yield was measured to be 65.13%.

(3) Extraction and purification of lignin and cellulose

Add 80mL of acetone and water mixture to the solid residue, the volume ratio of acetone and water mixture is 4:1, stir evenly, then filter under reduced pressure, repeat 3 times. The cellulose solid after suction filtration was washed three times with deionized water, and then dried in an oven at 80°C. Combine the filtrates from three suction filtrations, put them in an oil bath at 80°C, and evaporate the acetone. Then add 200mL of deionized water to the filtrate, put it in a magnetic stirrer, stir for 2h, filter under reduced pressure, repeat 3 times until neutral. The extracted lignin was placed in an oven at 80°C until constant weight.

(4) Preparation of lignin-based graphitized carbon-based catalyst

Dissolve ferric nitrate in 50mL of water, stir until dissolved, add extracted lignin, soak for 12 hours, evaporate the water in an oil bath at 80°C, and dry in an oven. The mass ratio of ferric nitrate to lignin is 1:1. Calcining at 2°C/min at 900°C for 2 hours to obtain a lignin-based catalyst.

Performance Testing

The furfural prepared under the experimental conditions of different molar ratios of ternary deep eutectic solvents and different temperatures and times was tested by HPLC. The test results are shown in Table 1. As can be seen from Table 1, hemicellulose can be converted more efficiently It is furfural, and the highest yield of furfural can reach 69.43%.

Table 1 Yield of furfural prepared from wheat straw treated with ternary deep eutectic solvent

The prepared lignin-based graphitized carbon-based catalyst was tested by XRD. The test results are shown in Figure 1. It can be seen from Figure 1 that the diffraction peak at 43.74° belongs to Fe ₃ C (JCPDS:35–0772), and Fe ₃ The appearance of C also proved that iron salts were reduced during carbothermal reduction; the diffraction peaks at 44.64° and 65° were attributed to α-Fe (JCPDS: 06-0696).

The Fenton reaction performance test was carried out on the prepared graphitized carbon material. The test method was as follows: Weigh 6 mg of tetracycline and dissolve it in 100 mL of water, add an appropriate amount of HCl solution to adjust the pH to about 3, and take the initial sample. Add 10 mg of catalyst, stir for 1 h, and take samples every 30 min. Taking the time of adding 20 μL H ₂ O ₂ as the origin of the reaction timing, samples were taken every 5 min with a syringe. Then the absorbance of TC was measured at the maximum wavelength of 357 nm with a UV-Vis spectrophotometer. The test results are shown in Figure 2. It can be seen from Figure 2 that the degradation rate can reach 88.4% in a short period of time, which proves that the catalyst has a relatively high oxidation technology.

XRD test was carried out on the pretreated cellulose, and the test results are shown in Figure 3. It can be seen from Figure 3 that the crystallinity of the cellulose after the ternary deep eutectic solvent treatment increased significantly, which clearly proves that DES retains Ability to remove lignin while maintaining a fairly intact cellulose structure. And the crystallinity of cellulosic material is an important criterion to evaluate the applicability of cellulose to enzymatic hydrolysis, and the increase of crystallinity indicates the increase of cellulose enzymatic hydrolysis efficiency.

It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation, although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (8)

1. A method for high-valued agricultural residues by a ternary deep eutectic solvent system, which is characterized by comprising the following steps: (1) Mixing two hydrogen bond donors and hydrogen bond acceptors, heating and stirring to obtain ternary deep eutectic solvent; the hydrogen bond acceptor is choline chloride, the two hydrogen bond donors are p-toluenesulfonic acid and ethylene glycol respectively, and the molar ratio of the choline chloride to the p-toluenesulfonic acid to the ethylene glycol is 1:1:0.2-0.5; (2) Mixing agricultural waste powder, ternary deep eutectic solvent, water and organic solvent, wherein the mass ratio of the agricultural waste powder to the ternary deep eutectic solvent is 1 (10-100), and the reaction is carried out for 0.5-2 h at the temperature of 80-120 ℃; (3) After the reaction is finished, cooling the reactor to room temperature, and collecting a reaction phase and an extraction phase to prepare furfural; (4) Adding acetone and water into the solid-liquid mixture in the step (3), washing, wherein the ratio of the acetone to the water is (1-4): 1, and collecting filtrate; (5) Placing the filtrate into an oil bath pot, evaporating acetone, adding deionized water for washing, and performing suction filtration and drying to obtain lignin; (6) Washing the solid obtained after suction filtration in the step (4) with deionized water, and drying to obtain cellulose; (7) Mixing and stirring the extracted lignin and ferric salt, wherein the mass ratio of the lignin to the ferric salt is 1 (0.2-2), evaporating the water, and calcining at a high temperature to obtain the lignin-based graphitized carbon-based catalyst.

2. The method for high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (1): p-toluenesulfonic acid, choline chloride and ethylene glycol are mixed according to a molar ratio of 1:1:0.3.

3. The method for high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (2): the agricultural waste is wheat straw or corn straw, and the grain size is 40-400 meshes.

4. The method for high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (2): the organic solvent is methyl isobutyl ketone, the reaction target temperature is 100 ℃, and the reaction time is 1h.

5. The method for high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (4): the ratio of the acetone to the water is 1:1.

6. The method of high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (7): the iron salt is ferric acetate.

7. The method of high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (7): and the high-temperature calcination is carried out at the temperature of 600-1000 ℃.

8. The method of high valued agricultural residues from a ternary deep eutectic solvent system according to claim 1, wherein in step (7): the mass ratio of lignin to ferric salt is 1:0.2.

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