Method for step-by-step pretreatment of lignocellulose by dilute sulphuric acid-ethanediamine

Abstract

The invention discloses a method for step-by-step pretreatment of lignocellulose by dilute sulphuric acid-ethanediamine, which comprises the following steps: 1) uniformly mixing straws and a sulfuric acid aqueous solution, reacting, carrying out solid-liquid separation, and collecting filtrate; washing the solid with water until the pH value is 7, and drying until the water content is less than or equal to 10% to obtain a mixture of cellulose and lignin, called CL for short; 2) mechanochemical pretreatment of ethidene diamine: adding the CL obtained in the step 1) and ethidene diamine into a vertical planetary ball mill, grinding to obtain a reactant 1, washing, carrying out solid-liquid separation, and drying the solid until the water content is less than or equal to 10% to obtain a component 1 containing cellulose, namely MCC for short; (3) cellulase is added into MCC for enzymolysis, glucose is obtained, the xylan conversion rate is 97.8 + / -0.8%, and the furfural generation rate is 6.8 + / -1.6%; the removal rate of lignin is 82.4 + / -1.1% or above, and the conversion rate of glucan is 96.1 + / -1.8% or above.

Description

Technical Field

[0001] The invention belongs to the field of lignocellulose pretreatment, and in particular relates to a method for pretreating lignocellulose. Background Art

[0002] As one of Earth's most abundant renewable resources, the efficient conversion of lignocellulosic biomass is crucial for promoting energy sustainability and mitigating greenhouse gas emissions. Within the lignocellulose structure, cellulose is surrounded by a dense, complex network of hemicellulose and lignin, forming a natural barrier against degradation that severely limits cellulose accessibility and enzymatic degradation efficiency. Indeed, complete fractionation of lignocellulose requires the movement of polymer chains and the breaking of linkages, which can be achieved by accounting for the inherent structure of the cell wall. The uniformity and diversity of lignocellulose compositional characteristics reflect the differences in their conversion during pretreatment and downstream upgrading. Interestingly, hemicelluloses share several characteristics with both cellulose and lignin: similar to cellulose, they possess polarity and glucose monomers linked by glycosidic bonds; whereas, similar to lignin, they are less stable, possess branched structures, and exhibit an amorphous morphology. Consequently, hemicelluloses undergo partitioning during lignocellulose fractionation, and conventional pretreatment methods often overlook this undesirable distribution. In polysaccharide-focused pretreatments, the majority of hemicellulose remains in the solid fraction, with lignin considered a secondary component. However, hemicelluloses have also been reported to hinder enzymatic activity. Under harsh pretreatment conditions, pentose and hexose sugars dehydrate to the corresponding furfural and hydroxymethylfurfural inhibitors, accompanied by unproductive cellulase adsorption and inhibition of microbial growth during fermentation. In lignin-centric "lignin-first" pretreatment, hemicellulose partially dissolves along with the lignin, while another portion remains in the solid fraction. Therefore, simultaneous separation of lignocellulose into three distinct components requires attention to the multiphase hydrolysis of hemicellulose.

[0003] From the perspective of the structure and decomposition of the lignocellulosic matrix, starting with the extraction of hemicellulose is preferred, and dilute sulfuric acid is a well-established pretreatment solvent that effectively hydrolyzes hemicellulose. However, while dilute sulfuric acid pretreatment effectively addresses the two-phase distribution and degradation of hemicellulose, it leaves behind a complex of cellulose and lignin that requires further separation. Furthermore, the formation of highly convertible cellulose requires high holding temperatures and high acid concentrations, often at the expense of furfural formation. Harsh pretreatment conditions also result in a certain loss of carbohydrate content.

[0004] At present, there is no report on the step-by-step pretreatment of lignocellulose using dilute sulfuric acid-ethylenediamine. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for pretreating lignocellulose by using dilute sulfuric acid and ethylenediamine in steps.

[0006] The second object of the present invention is to provide a second method for pretreating lignocellulose by using dilute sulfuric acid and ethylenediamine in steps.

[0007] The technical solution of the present invention is summarized as follows:

[0008] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0009] 1) Mix straw with a 3% sulfuric acid aqueous solution, react at 120°C for 1-3 hours, cool to room temperature, separate the solid and liquid, and collect the filtrate; rinse the solid with deionized water until the pH is 7, dry in a 65°C oven until the moisture content is ≤10%, and store at room temperature to obtain a mixture of cellulose and lignin, referred to as CL;

[0010] The ratio of the straw to the 3% sulfuric acid aqueous solution is 3 g: 22-27 mL;

[0011] The straw is corn straw, wheat straw, rice straw or sorghum straw;

[0012] 2) Mechanochemical pretreatment of ethylenediamine, the mechanochemical pretreatment is referred to as MC:

[0013] The CL and ethylenediamine obtained in step 1) were added to a vertical planetary ball mill and ground at 400 rpm for 1 hour to obtain a reactant 1. The reactant 1 was washed with 40 mL of deionized water per gram, and the solid and liquid were separated to obtain a solid 1 and a washing liquid 1, respectively. The solid 1 was placed in an oven at 65° C. to a moisture content of ≤10%, and then stored at room temperature to obtain a cellulose-containing component 1, referred to as MCC.

[0014] The ratio of CL to ethylenediamine is 10 g: 4-10 mL;

[0015] 3) Add cellulase to MCC for enzymatic hydrolysis to obtain glucose.

[0016] The second method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine comprises the following steps:

[0017] 1) Mix straw with a 3% sulfuric acid aqueous solution, react at 120°C for 1-3 hours, cool to room temperature, separate the solid and liquid, and collect the filtrate; rinse the solid with deionized water until the pH is 7, dry in a 65°C oven until the moisture content is ≤10%, and store at room temperature to obtain a mixture of cellulose and lignin, referred to as CL;

[0018] The ratio of the straw to the 3% sulfuric acid aqueous solution is 3 g: 22-27 mL;

[0019] The straw is corn straw, wheat straw, rice straw or sorghum straw;

[0020] 2) Thermochemical pretreatment of ethylenediamine, referred to as TC:

[0021] The CL obtained in step 1) and ethylenediamine were mixed and reacted at 130°C for 1 hour; cooled to room temperature to obtain reactant 2, washed with 40 mL of deionized water per gram of reactant 2, and separated into solid and liquid to obtain solid 2 and water washing liquid 2, respectively. Solid 2 was placed in an oven at 65°C to a moisture content of ≤10%, and stored at room temperature to obtain fraction 2 containing cellulose, referred to as TCC.

[0022] The ratio of CL to ethylenediamine is 3 g:1.2-3 mL;

[0023] 3) Add cellulase to TCC for enzymatic hydrolysis to obtain glucose.

[0024] Advantages of the present invention:

[0025] 1. Under the conditions of 3% sulfuric acid aqueous solution, 120℃ and reaction time of 2h, the xylan conversion rate and furfural production rate were 97.8±0.8% and 6.8±1.6%, respectively.

[0026] 2. Two pretreatment methods, mechanochemical and thermochemical, of ethylenediamine were designed, with the lignin removal rate (82.4±1.1% for mechanochemical pretreatment and 72.8±1.3% for thermochemical pretreatment) and the glucan conversion rate (96.1±1.8% for mechanochemical pretreatment and 92.8±1.2% for thermochemical pretreatment) significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the lignin removal rate after ethylenediamine pretreatment.

[0028] Figure 2 For enzymatic hydrolysis of raw and pretreated biomass. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Corn straw, wheat straw, rice straw, or sorghum straw used in the experiments were purchased from Tianjin, China.

[0031] For example, corn stalks were washed three times with tap water and then dried in an oven at 65°C for three days. The dried material was crushed and filtered, and the 20-80 mesh fraction was collected in a sealed plastic bag for subsequent experiments.

[0032] Compositional analysis of pulverized corn stover was performed according to National Renewable Energy Laboratory (NREL) standard analytical procedures (Sluiter A. Determination of structural carbohydrates and lignin in biomass, Technical Report NREL / TP-510-42618, National Renewable Energy Laboratory, Golden, CO[J]. 2010: 1-25). Moisture content was determined using a moisture analyzer, and carbohydrate and lignin content was determined using a two-step acid hydrolysis method.

[0033] Specifically: weigh 0.3±0.01g of raw materials (water content less than 10%), add to a 100mL stoppered bottle, first add 3.0mL of 72wt% concentrated sulfuric acid, mix well, place in a 30℃ water bath shaker at 180rpm to react for 60±1min; then quickly add 84mL of deionized water, mix well, dilute the H2SO4 concentration to 4%, the total volume of the solution is 86.73mL, tighten the stopper and place in a high-temperature steam pot to react at 121℃ for 60min. After the two-step acid hydrolysis is completed, the sample is allowed to cool to room temperature. Two 1 mL aliquots of the supernatant are then carefully aspirated and centrifuged at 12,000 rpm for 5 minutes. One aliquot is filtered through a 0.22 μm water filter and the glucose, xylose, and arabinose contents are determined using a high-performance liquid chromatography system equipped with a Waters 2414 differential detector. The glucan and xylan contents are calculated as shown in Formulas I and II. The other aliquot is diluted with deionized water and its absorbance is measured at 320 nm using a UV spectrophotometer with deionized water as a blank control to ensure a value between 0.7 and 1.0. The acid-soluble lignin (ASL) content is calculated using Formula III:

[0034] After hydrolysis, the sample was filtered through filter paper (previously oven-dried at 105°C and weighed). The precipitate was then washed, dried at 105°C, and weighed to determine the mass of acid-insoluble lignin (AIL), as shown in Equation IV. All experiments were performed in triplicate, and the average value was calculated.

[0035]

[0036] Where: c 葡萄糖 、c 木糖 、c 阿拉伯糖are the corresponding monosaccharide concentrations in the solution after acid hydrolysis (g / L); R is the correction factor for converting monosaccharides to polysaccharides, which is 0.9 for glucose and 0.88 for xylose; SRS% is the monosaccharide recovery rate before and after acid hydrolysis, which is 94.92% for glucose and 87.73% for xylose; m 原料 is the mass of raw materials weighed before acid hydrolysis (g); U is the ultraviolet absorbance measured at a wavelength of 320 nm; ε is the absorbance of biomass at the corresponding wavelength, and the absorbance of corn straw lignin at a wavelength of 320 nm is 30 L / g; D is the dilution factor.

[0037] It was determined that the main components of the collected corn straw were 35±0.5% glucan, 19.8±0.15% xylan, 3.3±0.1% arabinose, 18.2±0.3% acid-insoluble lignin and 2.5±0.2% acid-soluble lignin.

[0038] Example 1

[0039] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0040] 1) Corn straw was mixed with a 3% aqueous sulfuric acid solution, reacted at 120°C for 2 hours, cooled to room temperature, filtered through a filter cloth for solid-liquid separation, and the filtrate was collected; the solid (cellulose and lignin) was rinsed with deionized water to a pH of 7, dried in a 65°C oven to a moisture content of 5%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL;

[0041] The ratio of the corn straw to the 3% sulfuric acid aqueous solution is 3 g: 25 mL;

[0042] The concentration of xylose in the collected filtrate was determined by high performance liquid chromatography (HPLC), and the mass of xylose (g) was calculated as m 预水解木糖 ;m 木聚糖 is the mass of xylan in the untreated raw material (g); 0.88 is the correction factor for xylose.

[0043]

[0044] The xylan conversion rate was 97.8 ± 0.8%;

[0045] The concentration of furfural in the collected filtrate was determined by high performance liquid chromatography (HPLC), and the mass (g) of furfural was calculated as m 预水解糠醛 ;

[0046]

[0047] 1.37 is the correction factor for furfural, and the furfural generation rate is 6.8 ± 1.6%;

[0048] 2) Mechanochemical pretreatment of ethylenediamine, the mechanochemical pretreatment is referred to as MC:

[0049] The CL and ethylenediamine obtained in step (1) were added to a vertical planetary ball mill and ground at 400 rpm for 1 h to obtain a reactant 1. Each gram of the reactant 1 was washed with 40 mL of deionized water, and the solid and liquid were separated to obtain a solid 1 and a water washing liquid 1, respectively. The solid 1 was placed in an oven at 65° C. and dried to a moisture content of 5%, and then stored at room temperature to obtain a cellulose-containing component 1, referred to as MCC.

[0050] The ratio of CL to ethylenediamine is 10 g:8 mL;

[0051] Determination and calculation of lignin removal rate:

[0052] MCC was subjected to two-step acid hydrolysis (see Two-step acid hydrolysis method for raw material treatment) to determine the acid-soluble lignin and acid-insoluble lignin contents. The lignin removal rate of the ethylenediamine mechanochemical pretreatment was calculated according to Formula VII:

[0053]

[0054] Where: m 预处理木质素 is the mass of lignin in MCC (g); m 原料木质素 is the mass of lignin in the raw material (g)

[0055] The lignin removal rate of mechanochemical (MC) pretreatment was 82.4±1.1%. Figure 1 .

[0056] 3) Add cellulase (Novozymes) to MCC CTec3) was enzymatically hydrolyzed to obtain glucose.

[0057] The specific steps are:

[0058] The glucan content of the solid fraction (MCC) was first determined by a two-step acid hydrolysis method (see Table 1), and then enzymatic hydrolysis was performed in duplicate (parallel experiments). Specific steps: In a 100 mL conical flask, 20 mL of sodium citrate buffer solution (50 mM) was added to maintain the pH of the system at 4.8, and 200 μL of a 2% mass concentration of sodium azide (NaN3) aqueous solution was added to inhibit microbial growth. 0.3 g of MCC was added according to a solid loading of 1.5% (w / v), and cellulase CTec3 was added at a ratio of 30 mg enzyme protein / g glucan; 1 mL of cellulase CTec3 contains 118.3892 mg enzyme protein.

[0059] The enzymatic hydrolysis process lasted for 72 hours at 50°C and 200 rpm. 500 μL of the sample was collected every 24 hours and centrifuged at 12,000 rpm for 5 minutes. The sample was diluted 5-fold with deionized water and filtered through a 0.22 μm water filter membrane. The glucose concentration was detected using a high-performance liquid chromatography (HPLC) system equipped with an HPX-87H column. The glucan conversion rate was calculated according to Formula VIII:

[0060]

[0061] Where: c g represents the concentration of glucose in the enzymatic hydrolysate (g / L); V represents the total volume of the enzymatic hydrolysis system, which is 20 mL; m 预处理葡聚糖 represents the mass of glucan in the initial MCC after enzymatic hydrolysis (g); 0.9 is the correction factor for glucose.

[0062] High lignin removal rate significantly improved the rate and extent of enzymatic hydrolysis, and the glucan conversion rate of MCC reached 96.1±1.8% at 72h. Figure 2 .

[0063] Table 1 Glucan and xylan contents in solid components after pretreatment

[0064]

[0065] Example 2

[0066] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0067] 1) Wheat straw was mixed with a 3% aqueous sulfuric acid solution, reacted at 120°C for 1 hour, cooled to room temperature, and subjected to solid-liquid separation. The filtrate was collected; the solid was rinsed with deionized water until the pH was 7, dried in a 65°C oven until the moisture content was 10%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL.

[0068] The ratio of the wheat straw to the 3% sulfuric acid aqueous solution is 3 g: 22 mL;

[0069] 2) Mechanochemical pretreatment of ethylenediamine, the mechanochemical pretreatment is referred to as MC:

[0070] The CL and ethylenediamine obtained in step (1) were added to a vertical planetary ball mill and ground at 400 rpm for 1 h to obtain a reactant 1. Each gram of the reactant 1 was washed with 40 mL of deionized water, and the solid and liquid were separated to obtain a solid 1 and a water washing liquid 1, respectively. The solid 1 was placed in an oven at 65° C. and dried to a moisture content of 10%, and then stored at room temperature to obtain a cellulose-containing component 1, referred to as MCC.

[0071] The ratio of CL to ethylenediamine is 10 g:4 mL;

[0072] 3) Add cellulase to MCC for enzymatic hydrolysis to obtain glucose.

[0073] Example 3

[0074] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0075] 1) Rice straw (or sorghum straw) is mixed with a 3% sulfuric acid aqueous solution, reacted at 120°C for 3 hours, cooled to room temperature, separated into a solid and a liquid, and the filtrate is collected; the solid is rinsed with deionized water to a pH of 7, dried in a 65°C oven to a moisture content of 7%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL;

[0076] The ratio of the rice straw (or sorghum straw) to the 3% sulfuric acid aqueous solution is 3 g: 27 mL;

[0077] 2) Mechanochemical pretreatment of ethylenediamine, the mechanochemical pretreatment is referred to as MC:

[0078] The CL and ethylenediamine obtained in step (1) were added to a vertical planetary ball mill and ground at 400 rpm for 1 h to obtain a reactant 1. Each gram of the reactant 1 was washed with 40 mL of deionized water, and the solid and liquid were separated to obtain a solid 1 and a water washing liquid 1, respectively. The solid 1 was placed in an oven at 65° C. and dried to a moisture content of 7%, and then stored at room temperature to obtain a cellulose-containing component 1, referred to as MCC.

[0079] The ratio of CL to ethylenediamine is 10 g:10 mL;

[0080] 3) Add cellulase to MCC for enzymatic hydrolysis to obtain glucose.

[0081] Experiments show that the xylan conversion rate, furfural production rate, lignin removal rate, and glucan conversion rate of MCC at 72 h of the methods of Examples 2 and 3 are similar to the test results of Example 1.

[0082] Example 4

[0083] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0084] 1) Corn straw was mixed with a 3% aqueous sulfuric acid solution, reacted at 120°C for 2 hours, cooled to room temperature, and subjected to solid-liquid separation. The filtrate was collected; the solid was rinsed with deionized water until the pH was 7, dried in a 65°C oven until the moisture content was 5%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL.

[0085] The ratio of the corn straw to the 3% sulfuric acid aqueous solution is 3 g: 25 mL;

[0086] The concentration of xylose in the collected filtrate was determined by high performance liquid chromatography (HPLC), and the mass of xylose (g) was calculated as m 预水解木糖 ;m 木聚糖 is the mass of xylan in the untreated raw material (g); 0.88 is the correction factor for xylose.

[0087]

[0088] The xylan conversion rate was 97.8 ± 0.8%;

[0089] The concentration of furfural in the collected filtrate was determined by high performance liquid chromatography (HPLC), and the mass (g) of furfural was calculated as m 预水解糠醛 ;

[0090]

[0091] 1.37 is the correction factor for furfural, and the furfural generation rate is 6.8 ± 1.6%;

[0092] 2) Thermochemical pretreatment of ethylenediamine, referred to as TC:

[0093] The CL obtained in step (1) and ethylenediamine were mixed and reacted at 130° C. for 1 h; cooled to room temperature to obtain reactant 2, washed with 40 mL of deionized water per gram of reactant 2, and separated into solid and liquid to obtain solid 2 and water washing liquid 2, respectively. Solid 2 was placed in an oven at 65° C. to a moisture content of 6%, and stored at room temperature to obtain component 2 containing cellulose, referred to as TCC;

[0094] The ratio of CL to ethylenediamine is 3 g:2.4 mL;

[0095] Determination and calculation of lignin removal rate:

[0096] TCC was subjected to two-step acid hydrolysis (see Two-step acid hydrolysis method for raw material treatment) to determine the acid-soluble lignin and acid-insoluble lignin contents. The lignin removal rate of the ethylenediamine thermochemical pretreatment was calculated according to Formula VII:

[0097]

[0098] Where: m 预处理木质素 is the mass of lignin in TCC (g); m 原料木质素 is the mass of lignin in the raw material (g)

[0099] The lignin removal rate of thermochemical (TC) pretreatment was 72.8±1.3%.

[0100] 3) Add cellulase (Novozymes) to TCC CTec3) was enzymatically hydrolyzed to obtain glucose.

[0101] The specific steps are:

[0102] The glucan content of the solid fraction (TCC) was first determined by a two-step acid hydrolysis method (see Table 1), and then enzymatic hydrolysis was performed in duplicate (parallel experiments). Specific steps: In a 100 mL conical flask, 20 mL of sodium citrate buffer solution (50 mM) was added to maintain the pH of the system at 4.8, and 200 μL of a 2% mass concentration of sodium azide (NaN3) aqueous solution was added to inhibit microbial growth. 0.3 g of TCC was added according to a solid loading of 1.5% (w / v), and cellulase CTec3 was added at a ratio of 30 mg enzyme protein / g glucan; 1 mL of cellulase CTec3 contains 118.3892 mg enzyme protein.

[0103] The enzymatic hydrolysis process lasted for 72 hours at 50°C and 200 rpm. 500 μL of the sample was collected every 24 hours and centrifuged at 12,000 rpm for 5 minutes. The sample was diluted 5-fold with deionized water and filtered through a 0.22 μm water filter membrane. The glucose concentration was detected using a high-performance liquid chromatography (HPLC) system equipped with an HPX-87H column. The glucan conversion rate was calculated according to Formula VIII:

[0104]

[0105] Where: c g represents the concentration of glucose in the enzymatic hydrolysate (g / L); V represents the total volume of the enzymatic hydrolysis system, which is 20 mL; m 预处理葡聚糖 represents the mass of glucan in the initial TCC after enzymatic hydrolysis (g); 0.9 is the correction factor for glucose.

[0106] The high lignin removal rate significantly improved the rate and extent of enzymatic hydrolysis, and the glucan conversion rate of TCC reached 92.8±1.2% at 72 h.

[0107] Example 5

[0108] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0109] 1) Wheat straw was mixed with a 3% aqueous sulfuric acid solution, reacted at 120°C for 1 hour, cooled to room temperature, and subjected to solid-liquid separation. The filtrate was collected; the solid was rinsed with deionized water until the pH was 7, dried in a 65°C oven until the moisture content was 10%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL.

[0110] The ratio of the wheat straw to the 3% sulfuric acid aqueous solution is 3 g: 22 mL;

[0111] 2) Thermochemical pretreatment of ethylenediamine, referred to as TC:

[0112] The CL obtained in step (1) and ethylenediamine were mixed and reacted at 130° C. for 1 h; cooled to room temperature to obtain reactant 2, washed with 40 mL of deionized water per gram of reactant 2, and separated into solid and liquid to obtain solid 2 and water washing liquid 2, respectively. Solid 2 was placed in an oven at 65° C. to a moisture content of 10%, and stored at room temperature to obtain component 2 containing cellulose, referred to as TCC;

[0113] The ratio of CL to ethylenediamine is 3 g:1.2 mL;

[0114] 3) Add cellulase to TCC for enzymatic hydrolysis to obtain glucose.

[0115] Example 6

[0116] A method for pretreating lignocellulose in steps using dilute sulfuric acid and ethylenediamine, comprising the following steps:

[0117] 1) Rice straw (or sorghum straw) is mixed with a 3% sulfuric acid aqueous solution, reacted at 120°C for 3 hours, cooled to room temperature, separated into a solid and a liquid, and the filtrate is collected; the solid is rinsed with deionized water to a pH of 7, dried in a 65°C oven to a moisture content of 5%, and stored at room temperature to obtain a mixture of cellulose and lignin, referred to as CL;

[0118] The ratio of the rice straw to the 3% sulfuric acid aqueous solution is 3 g: 27 mL;

[0119] 2) Thermochemical pretreatment of ethylenediamine, referred to as TC:

[0120] The CL obtained in step (1) and ethylenediamine were mixed and reacted at 130° C. for 1 h; cooled to room temperature to obtain reactant 2, washed with 40 mL of deionized water per gram of reactant 2, and separated into solid and liquid to obtain solid 2 and water washing liquid 2, respectively. Solid 2 was placed in an oven at 65° C. to a moisture content of 5%, and stored at room temperature to obtain component 2 containing cellulose, referred to as TCC;

[0121] The ratio of CL to ethylenediamine is 3 g:3 mL;

[0122] 3) Add cellulase to TCC for enzymatic hydrolysis to obtain glucose.

[0123] Experiments show that the xylan conversion rate, furfural production rate, lignin removal rate, and glucan conversion rate of TCC at 72 h of the methods of Examples 5 and 6 are similar to the test results of Example 4.

Claims

1. A method for pretreating lignocellulose by dilute sulfuric acid and ethylenediamine, characterized in that The steps include: 1) Mix straw with a 3% sulfuric acid aqueous solution, react at 120°C for 1-3 hours, cool to room temperature, separate the solid and liquid, and collect the filtrate; rinse the solid with deionized water until the pH is 7, dry in a 65°C oven until the moisture content is ≤10%, and store at room temperature to obtain a mixture of cellulose and lignin, referred to as CL; The ratio of the straw to the 3% sulfuric acid aqueous solution is 3 g: 22-27 mL; The straw is corn straw, wheat straw, rice straw or sorghum straw; 2) Mechanochemical pretreatment of ethylenediamine, the mechanochemical pretreatment is referred to as MC: The CL and ethylenediamine obtained in step 1) were added to a vertical planetary ball mill and ground at 400 rpm for 1 hour to obtain a reactant 1. The reactant 1 was washed with 40 mL of deionized water per gram, and the solid and liquid were separated to obtain a solid 1 and a washing liquid 1, respectively. The solid 1 was placed in an oven at 65° C. to a moisture content of ≤10%, and then stored at room temperature to obtain a cellulose-containing component 1, referred to as MCC. The ratio of CL to ethylenediamine is 10 g: 4-10 mL; 3) Add cellulase to MCC for enzymatic hydrolysis to obtain glucose.

2. A method for pretreating lignocellulose by dilute sulfuric acid and ethylenediamine, characterized in that The steps include: 1) Mix straw with a 3% sulfuric acid aqueous solution, react at 120°C for 1-3 hours, cool to room temperature, separate the solid and liquid, and collect the filtrate; rinse the solid with deionized water until the pH is 7, dry in a 65°C oven until the moisture content is ≤10%, and store at room temperature to obtain a mixture of cellulose and lignin, referred to as CL; The ratio of the straw to the 3% sulfuric acid aqueous solution is 3 g: 22-27 mL; The straw is corn straw, wheat straw, rice straw or sorghum straw; 2) Thermochemical pretreatment of ethylenediamine, referred to as TC: The CL obtained in step 1) and ethylenediamine were mixed and reacted at 130°C for 1 hour; cooled to room temperature to obtain reactant 2, washed with 40 mL of deionized water per gram of reactant 2, and separated into solid and liquid to obtain solid 2 and water washing liquid 2, respectively. Solid 2 was placed in an oven at 65°C to a moisture content of ≤10%, and stored at room temperature to obtain fraction 2 containing cellulose, referred to as TCC. The ratio of CL to ethylenediamine is 3 g:1.2-3 mL; 3) Add cellulase to TCC for enzymatic hydrolysis to obtain glucose.

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