Pretreatment method and application of lignocellulose biomass

Abstract

The invention provides a pretreatment method of lignocellulose biomass, which comprises the following steps: uniformly mixing lignocellulose biomass with a solvent to obtain a first mixed solution; adding a first dielectric material as a catalyst into the first mixed solution, and uniformly mixing the first dielectric material and the first mixed solution to obtain a reactant mixed solution; adding the reactant mixed solution into a ball-milling tank, wherein the inner wall of the ball-milling tank and grinding balls are prepared from a second dielectric material; under normal temperature and normal pressure, a reactant mixed solution is subjected to ultrasonic wave and ball milling synergistic excitation by adopting an ultrasonic wave planetary ball mill. According to the invention, the electrons and free radicals generated by contact electricity are utilized to promote the depolymerization reaction of the lignocellulose, the pretreatment of the lignocellulose can be realized at normal temperature and normal pressure, the operation is simple and convenient, and the pollution to the environment can be reduced without using chemical reagents; according to the pretreatment method, the lignocellulose enzymolysis saccharification process is enhanced, the reducing sugar yield is effectively increased, and biomass high-value conversion technology development and engineering application are promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass resource conversion and utilization, and in particular to a pretreatment method for lignocellulose biomass and application thereof. Background Art

[0002] With rapid economic development, energy demand is increasing year by year. Problems such as fossil energy shortages and global warming are severely constraining human development. To reduce dependence on fossil fuels and effectively curb carbon dioxide emissions, the development and utilization of clean, sustainable, and renewable energy sources has become a top priority. Biomass energy, due to its widespread availability, abundant reserves, environmentally friendly, low-carbon nature, and low cost, has been recognized as one of the most promising clean energy sources. Globally, over 140 billion tons of biomass are produced annually, much of which is directly incinerated due to a lack of effective utilization methods, resulting in significant resource waste and environmental pollution. Therefore, the rational development and utilization of lignocellulosic biomass has become a key factor in promoting a low-carbon economy and achieving sustainable development.

[0003] Lignocellulosic biomass is primarily composed of three components: cellulose (35-50%), hemicellulose (20-35%), and lignin (15-25%). The outermost layer of lignin tightly encapsulates the cellulose and hemicellulose components, forming a natural physical barrier that hinders the penetration of enzymes into the lignocellulose to depolymerize them into reducing sugars. Lignin also nonspecifically binds to enzymes, further reducing the effectiveness of subsequent enzymatic hydrolysis. Therefore, pretreatment is a critical step in achieving value-added utilization of lignocellulose, directly impacting the conversion efficiency of subsequent enzymatic hydrolysis.

[0004] Traditional physical, chemical, thermal or biological pretreatment methods usually involve high temperature and high pressure, strong acids and bases or expensive catalysts. Although typical physical methods (such as ball milling) are simple to operate and widely used, they often consume a lot of energy and have high equipment maintenance costs. Chemical pretreatment mostly consumes materials such as strong acids and bases, ionic liquids, etc., which are not only costly, but also have drawbacks such as difficult reagent recovery and serious environmental pollution. Thermal treatment methods (such as hydrothermal pretreatment) require high temperature and high pressure, and the treatment process may produce fermentation inhibitors, reducing the subsequent biomass conversion efficiency. Biological pretreatment methods use enzymes, bacteria, etc. to achieve mild treatment of biomass. However, this method also has disadvantages such as long treatment cycle, high cost and low product yield. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention proposes a pretreatment method for lignocellulose biomass, which can achieve pretreatment of lignocellulose at normal temperature and pressure, and effectively improve the yield of reducing sugars.

[0006] The technical solution adopted in the present invention is as follows: In a first aspect, a method for pretreating lignocellulosic biomass is provided, comprising the following steps: The method comprises the following steps: uniformly mixing lignocellulosic biomass and a solvent to obtain a first mixed solution; adding a first dielectric material as a catalyst to the first mixed solution to uniformly mix the two to obtain a reactant mixed solution; adding the reactant mixed solution to a ball mill, wherein the inner wall and the grinding balls of the ball mill are both prepared from a second dielectric material; and subjecting the reactant mixed solution to ball milling excitation using an ultrasonic planetary ball mill at room temperature and pressure.

[0007] Furthermore, the lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; the solvent includes water or sodium citrate buffer; the first dielectric material includes SiO2 or polytetrafluoroethylene or a mixture thereof; and the second dielectric material includes polytetrafluoroethylene or polydimethylsiloxane.

[0008] Furthermore, the solid-liquid ratio of the lignocellulosic biomass to the solvent is 1~5wt%; the volume mass ratio of the first mixed solution to the first dielectric material is 1 mL:1~5 mg, and the particle size of the first dielectric material is 1-30 μm; the particle size of the grinding balls is 1-10 mm, and the mass ratio of the reactant mixture to the grinding balls is 1 mL:0.1~1 g.

[0009] In a second aspect, a method for pretreating lignocellulosic biomass is provided, comprising the following steps: uniformly mixing the lignocellulosic biomass with a solvent to obtain a first mixed solution; adding the first mixed solution to a ball mill, wherein the inner wall and grinding balls of the ball mill are made of the same dielectric material; and subjecting the first mixed solution to ball milling excitation using a ball mill at room temperature and pressure.

[0010] Furthermore, the lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; the solvent includes water or sodium citrate buffer; and the dielectric material includes polytetrafluoroethylene or polydimethylsiloxane.

[0011] Furthermore, the solid-liquid ratio of the lignocellulosic biomass to the solvent is 1-5wt%; the particle size of the grinding balls is 1-10 mm, and the mass ratio of the first mixed liquid to the grinding balls is 1 mL:0.1-1 g.

[0012] In a third aspect, a method for pretreating lignocellulosic biomass is provided, comprising the following steps: uniformly mixing the lignocellulosic biomass with a solvent to obtain a first mixed solution; adding a dielectric material to the first mixed solution, and uniformly mixing the two to obtain a reactant mixture; and ultrasonically exciting the reactant mixture under normal temperature and pressure conditions.

[0013] Furthermore, the lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; the solvent includes water or sodium citrate buffer; and the dielectric material includes SiO2 or polytetrafluoroethylene or a mixture thereof.

[0014] Furthermore, the solid-to-liquid ratio of the lignocellulosic biomass to the solvent is 1-5 wt %; and the volume-to-mass ratio of the first mixed solution to the dielectric material is 1 mL: 1-5 mg.

[0015] In a fourth aspect, the pretreatment methods described in the first, second and third aspects are used to prepare lignocellulosic biomass for use in clean energy. The lignocellulosic biomass is used to prepare biofuel ethanol, and is also used for enzymatic hydrolysis to produce sugars and provide substrates for ethanol fermentation reactions.

[0016] It can be seen from the above technical solution that the beneficial technical effects of the present invention are as follows: 1. The pretreatment method utilizes the electrons and free radicals generated by contact electricity to promote the depolymerization reaction of lignocellulose. The pretreatment of lignocellulose can be achieved at room temperature and pressure. The operation is simple and no chemical reagents are used to reduce pollution to the environment.

[0017] 2. The pretreatment method strengthens the enzymatic saccharification process of lignocellulose, effectively increases the yield of reducing sugars, and promotes the development of high-value biomass conversion technology and engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0019] Figure 1 This is a schematic flow chart of a method for pretreating lignocellulosic biomass according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope image of the original wheat straw without any pretreatment according to the embodiment of the present invention; Figure 3 This is a scanning electron microscope image of wheat straw after ultrasonic pretreatment without adding dielectric material in an embodiment of the present invention; Figure 4 This is a scanning electron microscope image of wheat straw after adding dielectric material and undergoing ultrasonic pretreatment according to an embodiment of the present invention; Figure 5 This is a comparison of Fourier transform infrared spectra of pretreated and unpretreated wheat straw in an embodiment of the present invention; Figure 6This is a comparison chart of X-ray diffraction spectra of pretreated and unpretreated wheat straw in an embodiment of the present invention; Figure 7 This is a comparison chart of glucose concentrations after enzymatic hydrolysis of pretreated and unpretreated wheat straw in an embodiment of the present invention; Figure 8 This is a comparison of xylose concentrations after enzymatic hydrolysis of pretreated and unpretreated wheat straw in an embodiment of the present invention; Figure 9 Schematic diagram of the process of the lignocellulosic biomass pretreatment system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that, unless otherwise specified, technical or scientific terms used in this application should have the same meaning as those commonly understood by those skilled in the art. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available unless otherwise specified.

[0022] Example 1 This embodiment provides a method for pretreating lignocellulosic biomass, such as Figure 1 The technical path 1 shown includes the following steps: S1. Evenly mixing lignocellulosic biomass and a solvent to obtain a first mixed solution; The lignocellulosic biomass and solvent are not limited. The lignocellulosic biomass can be wheat straw, wheat straw, barley straw, corn straw, or sugarcane bagasse, and the solvent can be water or sodium citrate buffer. The solid-to-liquid ratio of the lignocellulosic biomass to the solvent during mixing is 1 to 5 wt%. In a specific embodiment, wheat straw and water are used as an example: Weigh 1 g of wheat straw and place it in a beaker. Then add 30 mL of aqueous solution into the beaker and mix the two thoroughly to obtain a first mixed solution.

[0023] S2. Add dielectric material as a catalyst to the first mixed solution and mix the two evenly to obtain a reactant mixed solution. A dielectric material is added to the first mixed solution as a catalyst and the two are thoroughly mixed to obtain a reactant mixed solution. When the dielectric material is added, the volume mass ratio of the first mixed solution to the dielectric material is 1 mL: 1-5 mg. The dielectric material can be selected from SiO2, PTFE (polytetrafluoroethylene), etc. In a specific embodiment, SiO2 is used as an example: 60 mg of SiO2 microspheres were added to the obtained first mixed solution, and after the two were evenly mixed, a reactant mixed solution was obtained.

[0024] S3. Ultrasonic excitation of the reactant mixture at room temperature and pressure In this specific embodiment, the ultrasonic excitation method is not specified and can be implemented using any conventionally available method, such as an ultrasonic cleaning machine. The ultrasonic excitation parameters are set as follows: ultrasonic power 100-500 W, ultrasonic frequency 45-80 kHz, and excitation reaction time 2-8 hours. Ultrasonic waves are used as mechanical excitation to trigger repeated contact and separation between the catalyst and the liquid phase, generating a contact electrification effect, leading to electron transfer and the generation of reactive oxygen species such as free radicals, catalyzing the depolymerization of lignocellulose.

[0025] Example 2 This embodiment provides another method for pretreating lignocellulosic biomass, such as Figure 1 The technical path 2 shown includes the following steps: S1. Evenly mixing lignocellulosic biomass and a solvent to obtain a first mixed solution; The specific implementation of this step is basically the same as step S1 in Example 1.

[0026] S2. Add the first mixed solution into a ball mill, the inner wall of which and the grinding balls are made of the same dielectric material. In a specific embodiment of this step, the dielectric material used to prepare the inner wall of the ball mill and the grinding balls is polytetrafluoroethylene or polydimethylsiloxane. The particle size of the grinding balls ranges from 1 to 10 mm, and the mass ratio of the first mixed solution to the grinding balls is 1 mL: 0.1 to 1 g.

[0027] S3. At room temperature and pressure, the first mixed solution is subjected to ball milling excitation. In a specific embodiment, the parameters for ball milling in this step are set as follows: a ball milling speed of 100-400 rpm and an excitation reaction time of 2-8 hours. Ball milling serves as a mechanical stimulus, triggering repeated contact and separation between the catalyst and the liquid phase, generating a contact electrification effect, which induces electron transfer and generates reactive oxygen species such as free radicals, catalyzing the depolymerization of lignocellulose.

[0028] Example 3 This embodiment provides another method for pretreating lignocellulosic biomass, such as Figure 1 The technical path 3 shown includes the following steps: S1. Evenly mixing lignocellulosic biomass and a solvent to obtain a first mixed solution; The specific implementation of this step is basically the same as step S1 in Example 1.

[0029] S2. Add the first dielectric material as a catalyst to the first mixed solution and mix the two evenly to obtain a reactant mixed solution. When the first dielectric material is added, the volume-to-mass ratio of the first mixed solution to the first dielectric material is 1 mL: 1-5 mg. The first dielectric material can be selected from SiO2, PTFE (polytetrafluoroethylene), etc., and the particle size of the first dielectric material ranges from 1-30 μm.

[0030] S3, adding the reactant mixture into a ball mill, the inner wall of the ball mill and the grinding balls are both made of the second dielectric material In a specific embodiment of this step, the second dielectric material used to prepare the inner wall of the ball mill and the grinding balls is polytetrafluoroethylene or polydimethylsiloxane. The grinding balls have a particle size range of 1-10 mm, and the mass ratio of the reactant mixture to the grinding balls is 1 mL: 0.1-1 g. The ball mill is an ultrasonic planetary ball mill.

[0031] S4. Under normal temperature and pressure, the reactant mixture is subjected to ultrasonic and ball milling synergistic excitation. In a specific embodiment, the parameters for ball milling excitation are set as follows: ball mill speed of 100-400 rpm, excitation reaction time of 2-8 hours; and ultrasonic excitation excitation parameters are set as follows: ultrasonic power of 100-500 W, ultrasonic frequency of 45-80 kHz, and excitation reaction time of 2-8 hours. The synergistic excitation of ultrasound and ball milling acts as a mechanical stimulus, triggering repeated contact and separation between the catalyst and the liquid phase, generating a contact electrification effect, leading to electron transfer and the generation of reactive oxygen species such as free radicals, catalyzing the depolymerization of lignocellulose.

[0032] In order to explore the microscopic morphology characteristics of wheat straw before and after different pretreatments, the surface morphology was first photographed using a scanning electron microscope (SEM). The experimental results are shown in Figure 2. Figures 2 to 4 shown. Figure 2 It is original wheat straw that has not undergone any pretreatment, and its surface is relatively smooth and flat with fewer cracks. Figure 3 The wheat straw is ultrasonically pretreated without adding dielectric materials; wherein, Figure 3 The above picture shows ultrasonic pretreatment in deionized water. Figure 3 The lower one is the ultrasonic pretreatment in sodium citrate buffer solution; Figure 2In comparison, the surface of wheat straw pretreated by ultrasound became rougher, and some small cracks and fragments were produced. Figure 4 It is wheat straw pretreated with ultrasonic waves with dielectric materials added; Figure 4 The upper left picture shows ultrasonic pretreatment in deionized water. Figure 4 The lower left picture shows ball milling pretreatment in sodium citrate buffer solution; Figure 4 and Figure 3 In comparison, the surface of wheat straw subjected to electrocatalytic pretreatment produced more cracks and fragments, becoming rougher and more porous ( Figure 4 2 pictures on the left). When zoomed in, some catalyst particles can be found near the micropores of the wheat straw ( Figure 4 (The two images on the right) Analyzing the mechanism, under the stimulation of ultrasound or ball milling, these catalyst particles can destroy the lignocellulose structure from within the wheat straw, increasing the porosity and specific surface area of the lignocellulose, increasing the accessibility of cellulose and hemicellulose, enhancing the pretreatment effect, and improving the sugar yield during the enzymatic hydrolysis process.

[0033] Next, the wheat straw samples before and after pretreatment were characterized by Fourier transform infrared spectroscopy (FTIR). Figure 5 The absorption spectra of wheat straw before and after pretreatment were compared. Figure 5 The picture above shows the deionized water used in the pretreatment of wheat straw samples. Figure 5 The picture below is the sodium citrate buffer solution used in the pretreatment process of wheat straw samples; Figure 5 In the middle, at 3400 cm -1 、2922 cm -1 、1640 cm -1 and 1056 cm -1 The absorption peaks at correspond to OH stretching vibration, CH stretching vibration, C=C stretching vibration and CC stretching vibration respectively; Figure 5 It can be observed that the absorbance of wheat straw pretreated with electrocatalytic catalysis is slightly higher than that of wheat straw pretreated with conventional ultrasound, indicating that more active OH, CH, C=C and CO functional groups can be released after electrocatalytic catalysis. -1 and 475 cm -1 Two new absorption peaks appeared at the -1 ) and bend (475cm -1 ) mode. This is because some SiO2 particles will remain on the wheat straw after contact electrocatalytic pretreatment (see Figure 4 (enlarged image on the right).

[0034] Since the crystallinity of cellulose is a key factor in determining the enzymatic hydrolysis of lignocellulosic biomass, this example also characterized the crystallinity of wheat straw by X-ray diffraction (XRD). Figure 6 As shown, Figure 6 The picture above shows the deionized water used in the pretreatment of wheat straw samples. Figure 6 The picture below is the sodium citrate buffer solution used in the pretreatment of wheat straw samples. Figure 6 It can be found that the spectral trend of wheat straw before and after pretreatment remains almost unchanged. Secondly, the crystallinity of original wheat straw is CrI=36.94, which drops to 34.62 after ultrasonic treatment in water. The crystallinity of wheat straw cellulose reaches the lowest level after contact electrocatalytic pretreatment, as low as 28.03 ( Figure 6 The same trend was observed in wheat straw samples pretreated in sodium citrate buffer ( Figure 6 The above experimental results show that contact electrocatalysis can effectively reduce the crystallinity of cellulose, converting crystalline cellulose into amorphous cellulose, thereby promoting the subsequent enzymatic hydrolysis process.

[0035] for Figure 5 、 Figure 6 In the legend, “ultrasonic pretreatment” corresponds to the case where no dielectric material is added and the material is pretreated with ultrasonic waves; “catalytic electrocatalysis” corresponds to the case where a dielectric material is added and the material is pretreated with ultrasonic waves or ball milling.

[0036] To further evaluate the pretreatment effects of different methods, wheat straw pretreated by traditional ultrasonic pretreatment (without adding dielectric materials), contact electrocatalysis with dielectric materials, ultrasonication or ball milling was subjected to enzymatic hydrolysis experiments for 72 h. The experimental method was as follows: 1 g of completely dried wheat straw was weighed and placed in a pressure tube, and then deionized water or 19 mL of 0.1 M sodium citrate buffer was added to obtain two reactant mixtures; 0.15 mL of Cellic CTEC2 enzyme with an enzyme activity of 200 FPU / mL was added to the reactant mixture, and the reactant mixture was placed in a thermostatted shaker at 50°C and 170 rpm for 72 h; 0.5 mL of the supernatant was taken at different reaction times, inactivated with boiling water, and then used to remove 0.22 m polytetrafluoroethylene filter head; the filtrate was diluted to an appropriate multiple and the monosaccharide concentration was determined by high performance liquid chromatography. Figure 7 、 Figure 8 As shown, where: Figure 7 is the glucose concentration test data, Figure 7 The upper picture uses deionized water as the liquid phase environment. Figure 7The lower one uses sodium citrate buffer solution as the liquid phase environment; Figure 8 is the experimental data of xylose concentration, Figure 8 The above picture uses deionized water as the liquid phase environment. Figure 8 The lower picture uses sodium citrate buffer solution as the liquid phase environment. Figure 7 、 Figure 8 It can be seen that the concentrations of glucose (a hydrolysis product of cellulose in wheat straw) and xylose (a hydrolysis product of hemicellulose in wheat straw) both increase rapidly over time and then gradually stabilize. This is because amorphous cellulose is first degraded during the initial hydrolysis phase, followed by crystalline cellulose. Since cellulase has difficulty entering and reacting with crystalline cellulose, the hydrolysis rate gradually slows and finally levels off. Furthermore, wheat straw pretreated with contact electrocatalysis produces more glucose and xylose during the subsequent enzymatic hydrolysis process, indicating that contact electrocatalysis pretreatment effectively disrupts the dense three-dimensional structure of lignocellulose, increases enzyme accessibility, and enables cellulase and hemicellulase to effectively act on the cellulose and hemicellulose in the wheat straw, thereby producing more monosaccharides.

[0037] In order to compare the physical and chemical properties of pretreated and unpretreated wheat straw samples, the contents of the three components of wheat straw before and after pretreatment were tested according to the standard method of the National Renewable Energy Laboratory (NREL). The test method is as follows: 0.15 g of completely dried wheat straw was weighed and placed in a pressure tube, and then 1.5 mL of 72% sulfuric acid was added to obtain a reactant mixture; the pressure tube containing the reactant mixture was placed in a 30°C water bath for 1 hour, and stirred with a glass rod every 5-10 minutes to ensure that the acid and particles reacted completely; after the reaction was completed, 42 mL of deionized water or sodium citrate buffer solution was added to the pressure tube to dilute the reaction mixture to a sulfuric acid concentration of 4%, tighten the pressure tube cap, and repeatedly invert it several times to mix evenly to eliminate the phase separation between the high-concentration and low-concentration acid layers; the pressure tube was placed in a high-pressure sterilizer at 121°C for 1 hour, taken out and shaken evenly, and allowed to cool to room temperature, 8 mL of the supernatant was taken out, and then 0.22 The filtrate was filtered through a polytetrafluoroethylene filter; monosaccharide concentrations were analyzed using a high-performance liquid chromatograph equipped with a Bio-rad 87H column and a differential refractive index detector; the mass of cellulose, hemicellulose, and lignin in the lignocellulose was then calculated. The pore structure parameters of wheat straw before and after different pretreatments were measured using mercury porosimetry. The experimental data are shown in Table 1: Table 1 compares the porosity and component content changes of wheat straw before and after pretreatment. As shown in Table 1, the porosity of the original wheat straw was 84.5%, and the average pore diameter was 4176.70 nm. The porosity of the wheat straw after ultrasonic pretreatment increased slightly, and the average pore diameter doubled. The wheat straw treated with both electrocatalysis and ultrasonic pretreatment exhibited the highest porosity and average pore diameter, with a maximum porosity of 87.65% and a maximum average pore diameter of 9270.20 nm. This is due to the intense mechanical action during pretreatment, which disrupted the structure of the wheat straw and resulted in increased porosity. Electrocatalysis pretreatment of wheat straw facilitated the subsequent entry of cellulase into the wheat straw particles and their reaction with cellulose and hemicellulose, resulting in a higher monosaccharide yield. Finally, a comparison of the chemical composition changes of the wheat straw before and after pretreatment revealed a slight decrease in the hemicellulose and lignin contents of the ultrasonically pretreated sample compared to the original sample, while the lignin content of the electrocatalytically pretreated wheat straw sample increased slightly. This may be because the catalyst introduced by the electrocatalytic process, due to its small particle size, penetrates into the wheat straw, making it difficult to filter and separate. This results in an increase in the mass of acid-insoluble lignin, which in turn slightly increases the total weight of the lignin. The reduction in hemicellulose content indicates that electrocatalytic degradation can partially degrade hemicellulose. Therefore, electrocatalytic degradation can be used as a highly efficient pretreatment method for lignocellulose, achieving value-added utilization of lignocellulose and enhancing the subsequent enzymatic saccharification process.

[0038] The above experimental data indicate that, compared with ultrasonic pretreatment alone, contact electrocatalytic pretreatment with ultrasound or ball milling excitation produces more cracks and fragments on the lignocellulose surface, making the surface structure rougher and looser, accompanied by the appearance of pores. This significantly disrupts the dense three-dimensional structure of the lignocellulose, increases the porosity and specific surface area of the lignocellulose, reduces the degree of polymerization and crystallinity of the cellulose, and enhances the enzymatic saccharification process of the lignocellulose. When the Cellic CTEC2 complex enzyme was used to hydrolyze pretreated wheat straw (50°C, 170 rpm, 72 h), the conversion rates of hemicellulose and cellulose increased by 35.8% and 78.1%, respectively, compared with traditional ultrasonic pretreatment. This suggests that the proposed pretreatment method for lignocellulosic biomass effectively improves the conversion rate of cellulose and hemicellulose during enzymatic hydrolysis and the yield of soluble monosaccharides.

[0039] The pretreatment method for lignocellulosic biomass provided in this example utilizes electrons and free radicals generated by contact electricity to promote the depolymerization of lignocellulose. This method can be performed at room temperature and pressure, is simple to operate, and eliminates the use of chemical reagents, reducing environmental pollution. The pretreatment method enhances the enzymatic saccharification of lignocellulose, effectively increasing the yield of reducing sugars and promoting the development of high-value biomass conversion technologies and their engineering applications. Experimental data demonstrate that the pretreatment method of Example 3 is the most effective.

[0040] In some embodiments, a lignocellulosic biomass is also provided, which is prepared using the lignocellulosic biomass pretreatment method described above.

[0041] In some embodiments, the application of lignocellulosic biomass prepared by the lignocellulosic biomass pretreatment method described above in clean energy is also provided for the preparation of biofuel ethanol. The lignocellulose prepared by the pretreatment method of this embodiment reacts with cellulase extracted from microorganisms to produce sugar through enzymatic hydrolysis, providing a substrate for the ethanol fermentation reaction.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for pretreating lignocellulosic biomass, characterized in that: The following steps are involved: uniformly mixing the lignocellulosic biomass and the solvent to obtain a first mixed solution; Adding a first dielectric material as a catalyst to the first mixed solution and mixing the two uniformly to obtain a reactant mixed solution; The reactant mixture is added into a ball mill, wherein the inner wall and the grinding balls of the ball mill are both made of the second dielectric material; At room temperature and pressure, an ultrasonic planetary ball mill is used to perform synergistic excitation of ultrasonic wave and ball milling on the reactant mixture.

2. The method for pretreating lignocellulosic biomass according to claim 1, characterized in that: The lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; The solvent includes water or sodium citrate buffer; The first dielectric material comprises SiO2 or polytetrafluoroethylene or a mixture thereof; The second dielectric material includes polytetrafluoroethylene or polydimethylsiloxane.

3. The method for pretreating lignocellulosic biomass according to claim 2, characterized in that: The solid-to-liquid ratio of the lignocellulosic biomass to the solvent is 1 to 5 wt %; The volume mass ratio of the first mixed solution to the first dielectric material is 1 mL: 1-5 mg, and the particle size of the first dielectric material is 1-30 μm; The particle size of the grinding balls is 1-10 mm, and the mass ratio of the reactant mixture to the grinding balls is 1 mL: 0.1-1 g.

4. A method for pretreating lignocellulosic biomass, characterized in that: The following steps are involved: uniformly mixing the lignocellulosic biomass and the solvent to obtain a first mixed solution; The first mixed solution is added into a ball mill, wherein the inner wall and the grinding balls of the ball mill are made of the same dielectric material; At room temperature and pressure, the first mixed liquid is subjected to ball milling excitation using a ball mill.

5. The method for pretreating lignocellulosic biomass according to claim 4, characterized in that: The lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; The solvent includes water or sodium citrate buffer; The dielectric material includes polytetrafluoroethylene or polydimethylsiloxane.

6. The method for pretreating lignocellulosic biomass according to claim 5, characterized in that: The solid-to-liquid ratio of the lignocellulosic biomass to the solvent is 1 to 5 wt %; The particle size of the grinding balls is 1-10 mm, and the mass ratio of the first mixed liquid to the grinding balls is 1 mL: 0.1-1 g.

7. A method for pretreating lignocellulosic biomass, characterized in that: The following steps are involved: uniformly mixing the lignocellulosic biomass and the solvent to obtain a first mixed solution; Adding a dielectric material to the first mixed solution and mixing the two uniformly to obtain a reactant mixed solution; Under normal temperature and pressure conditions, the reactant mixture is subjected to ultrasonic excitation.

8. The method for pretreating lignocellulosic biomass according to claim 7, characterized in that: The lignocellulosic biomass includes wheat straw, barley straw, corn straw or sugarcane bagasse; The solvent includes water or sodium citrate buffer; The dielectric material includes SiO2 or polytetrafluoroethylene or a mixture thereof.

9. The method for pretreating lignocellulosic biomass according to claim 8, characterized in that: The solid-to-liquid ratio of the lignocellulosic biomass to the solvent is 1 to 5 wt %; The volume mass ratio of the first mixed solution to the dielectric material is 1 mL: 1-5 mg.

10. Application of lignocellulosic biomass prepared by the pretreatment method according to any one of claims 1 to 9 in clean energy, wherein the lignocellulosic biomass is used to prepare biofuel ethanol, and is also used for enzymatic hydrolysis to produce sugars and provide substrates for ethanol fermentation reactions.

Images