Biomass pretreatment method coupled with steam explosion and twin-screw and cellulose-containing biomass and application thereof

Abstract

This invention provides a biomass pretreatment method using a steam-coupling twin-screw extruder, along with cellulose-containing biomass and its applications. The biomass pretreatment method includes the following steps: sequentially subjecting pre-softened biomass raw materials to steam treatment and twin-screw extrusion crushing to obtain biomass particles; the biomass particles are then subjected to a cooking reaction to obtain cellulose-containing biomass. This invention utilizes the synergistic effect of steaming and twin-screw extrusion crushing to overcome the mass transfer resistance of dense wood with low energy consumption, aiming to solve the problems of dense forest biomass structure, high energy consumption in traditional pretreatment methods, and difficulty in chemical penetration. This process can effectively reduce the amount of chemicals used to achieve efficient and directional separation of components, fully adapting to the needs of low-cost, continuous industrial production.

Description

Technical Field

[0001] This invention relates to the field of lignocellulose pretreatment technology, and in particular to a biomass pretreatment method using a steam-coupled twin-screw extruder, as well as cellulose-containing biomass and its applications. Background Technology

[0002] Lignocellulose, as the most abundant renewable biomass resource on Earth, is crucial for sustainable development through its efficient conversion into fermentable sugars. Compared to the relatively loose fibrous structure of grass biomass, the secondary cell walls of forest biomass such as poplar are highly developed, significantly thicker, and contain higher levels of lignin. This results in a denser three-dimensional network structure formed through the cross-linking of lignin and cellulose. This lignin-carbohydrate complex (LCC), formed by the densification of the secondary cell walls, significantly hinders the accessibility of cellulase to cellulose substrates through steric hindrance and severely limits the penetration of chemical pretreatment agents or hydrolytic enzymes. Consequently, forest resources exhibit significant degradation and penetration resistance during biorefining.

[0003] For such highly dense timber raw materials, existing pretreatment processes have revealed significant technical limitations. First, the single physical-mechanical method suffers from the dual drawbacks of low energy efficiency and insufficient structural destruction. Due to the high hardness of timber biomass, pulverization requires extremely high energy consumption, and mechanical shearing force is insufficient to effectively break down the LCC cross-linked network, leaving residual lignin in the form of micro-aggregates, resulting in limited improvement in enzymatic hydrolysis efficiency.

[0004] Secondly, traditional chemical pretreatment methods (such as high-concentration alkali methods, dilute acid methods, or organic solvent methods) are trapped in a dual dilemma of limited mass transfer and environmental burden. The extremely dense structure of forest trees severely hinders the effective penetration of chemical agents into the interior, forcing traditional processes to rely heavily on high-concentration reagents and extreme operating conditions (such as high temperature, high pressure, and long-term heat preservation) to overcome the mass transfer resistance of the reaction system. This not only increases the cost of equipment corrosion prevention but also easily leads to the excessive degradation of carbohydrates, generating a large amount of fermentation inhibitors; at the same time, the discharge of high-concentration waste liquids (such as papermaking black liquor) poses a serious environmental pollution hazard.

[0005] To overcome the mass transfer resistance of dense matrices, existing processes often incorporate steam explosion or single steam treatment. However, the instantaneous decompression process of traditional steam explosion at high temperature and pressure easily leads to severe degradation of hemicellulose and the generation of high concentrations of fermentation inhibitors.

[0006] Therefore, developing a network capable of deeply depolymerizing lignin-carbohydrate complexes (LCCs) has become a core technological bottleneck restricting the current industrialization of lignocellulose biorefining. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a biomass pretreatment method with steam coupling twin screw and cellulose-containing biomass and its application, aiming to overcome the defects of the prior art in processing dense forest biomass, such as high energy consumption of physical crushing and difficulty in chemical penetration.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a biomass pretreatment method using a steam-coupling twin-screw extruder, the biomass pretreatment method comprising the following steps:

[0010] The pre-softened biomass raw material is subjected to steam treatment and twin-screw extrusion crushing in sequence to obtain biomass pellets; the biomass pellets are then subjected to a cooking reaction to obtain cellulose-containing biomass.

[0011] While single low-to-medium pressure steaming can induce the glass transition of lignin, it is difficult to achieve effective fibrillation and pore expansion, requiring subsequent deep dissociation using higher concentrations of chemicals. Therefore, this invention utilizes the synergistic effect of "steam softening" and "twin-screw hot extrusion" to construct a dense lignocellulose pretreatment system based on thermo-mechanical synergy. This technological breakthrough is reflected in:

[0012] (1) The initial dissociation of lignin-carbohydrate complex (LCC) is achieved by steam treatment. First, by utilizing the efficient heat and mass transfer characteristics of high-temperature steam, water vapor quickly penetrates into the dense interior of the forest. The hydrothermal plasticizing effect significantly reduces the glass transition temperature of lignin, driving the lignin macromolecules to cross the phase transition point and undergo a transformation from the glass state to the elastic state, thereby effectively softening the natural and extremely dense three-dimensional network of lignin cellulose at the physical level.

[0013] (2) Subsequently, a twin-screw extrusion is used to apply shear stress to the material. At this time, the wood is at the softening point of the thermophysical phase transition. The twin-screw, with its strong shearing and extrusion action, greatly reduces the yield stress of the wood fibers. This high-intensity shearing action avoids the high energy consumption barrier of traditional dry physical decomposition, while inducing efficient fibrillation of the heat-softened material, promoting the rapid decomposition of the dense wood skeleton into porous microparticles, thereby achieving a significant increase in the specific surface area and pore volume of the substrate.

[0014] This invention effectively breaks down the dense stress-resistance barrier of forest trees through the synergistic effect of hot steam and twin-screw shearing, allowing low-concentration agents to penetrate the microporous network of the substrate. While significantly reducing the energy consumption of mechanical dissociation, it completely opens the mass transfer microporous channels for the targeted dissolution of subsequent trace chemical agents, thereby achieving efficient depolymerization and separation of lignin components. It also synergistically reduces the energy consumption of mechanical dissociation and the pretreatment technology of chemical input, significantly improves the accessibility of cellulase and the enzymatic saccharification rate, and significantly reduces the overall economic cost and global warming potential, providing a practical and feasible technical path for the large-scale green refining of lignocellulose.

[0015] As a preferred embodiment of the present invention, the biomass raw material includes forest biomass.

[0016] Preferably, the forest biomass includes any one or at least two combinations of pine, poplar, willow, birch, oak or peach. Typical but non-limiting combinations include combinations of pine and poplar, pine and birch, birch and peach, poplar and peach, and pine, etc.

[0017] As a preferred embodiment of the present invention, the steam used in the steam treatment includes water steam.

[0018] Preferably, the temperature of the steam treatment is 90-110℃, such as 90℃, 92℃, 94℃, 96℃, 98℃, 100℃, 102℃, 104℃, 106℃, 108℃ or 110℃, etc., but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the steam treatment time is 2-4 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h or 4 h, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] This invention limits the steaming time to the aforementioned range. If the steaming time is too long, prolonged high temperatures may induce irreversible condensation reactions in lignin fragments, forming more stable, inert, and difficult-to-dissolve condensed lignin. Furthermore, excessively long steaming times not only increase energy consumption but also fail to simultaneously improve the softening effect on the three-dimensional network of lignocellulose. This condensed lignin strongly adsorbs cellulase, significantly reducing enzymatic hydrolysis efficiency. Conversely, if the steaming time is too short, heat and steam fail to effectively penetrate the material, resulting in insufficient destruction of the lignin macromolecular structure and reduced efficiency of subsequent enzymatic or chemical treatments.

[0021] Preferably, the pressure of the steam treatment is 95-110 kPa, for example, it can be 95 kPa, 100 kPa, 105 kPa or 110 kPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] The steam treatment described in this invention is carried out under normal pressure. Normal pressure generally refers to atmospheric pressure close to the environment, which is generally an environment without pressurization or depressurization treatment. It is related to geographical location and weather. For example, at sea level with a temperature of 0°C and a latitude of 45°, the precise value of atmospheric pressure is 101.325 kPa.

[0023] As a preferred technical solution of the present invention, the length-to-diameter ratio of the feed screw in the twin-screw extrusion crushing process is (0.7-1.3):1, for example, it can be 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1 or 1.3:1, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the rotational speed of the twin-screw extrusion crushing process is 290-350 r / min, for example, it can be 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min or 350 r / min, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0025] The present invention limits the rotation speed of the twin-screw extrusion crushing process to the above-mentioned range. If the rotation speed is too slow, the biomass particles obtained by extrusion crushing will be uneven. If the rotation speed is too fast, the applied mechanical energy will be too high, which will appear in the form of heat energy and excessive shearing. The material will be over-crushed and the particle size will be too small. It may re-agglomerate in the extruder due to high pressure and high temperature, which is not conducive to subsequent reactions.

[0026] The present invention involves steam treatment followed by direct twin-screw extrusion crushing, wherein the temperature of the twin-screw extrusion crushing is the same as the temperature of the steam treatment.

[0027] Preferably, the particle size of the biomass particles is in the range of 30-100 micrometers, for example, it can be 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers or 100 micrometers, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] As a preferred technical solution of the present invention, the pre-softening includes: alkaline leaching treatment of biomass raw materials.

[0029] Preferably, the temperature of the alkaline leaching treatment is 20-30℃, for example, it can be 20℃, 22℃, 24℃, 26℃, 28℃ or 30℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the solid-liquid mass ratio of the biomass raw material to the alkaline solution in the alkaline leaching treatment is 1:(4-6), for example, it can be 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the alkaline solution used for the alkaline leaching treatment comprises a sodium hydroxide solution.

[0032] Preferably, the concentration of the sodium hydroxide solution is 2-3 wt%, for example, it can be 2 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, or 3 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the alkaline leaching time is 10-14 h, for example, it can be 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h or 14 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] As a preferred embodiment of the present invention, the cooking reaction includes: mixing the biomass particles and an alkaline solution, and carrying out the cooking reaction.

[0035] This invention pre-softens, steams, and crushes biomass raw materials before cooking, thereby relieving the mass transfer resistance of dense wood and achieving efficient cellulose retention under low-load cooking conditions. This solves the problems of poor chemical penetration and high energy consumption caused by the need for high-concentration chemical agents in traditional technologies.

[0036] Preferably, the pH value of the alkaline solution is 7-10, for example, it can be 7, 7.5, 8, 8.5, 9 or 10, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the alkaline solution includes any one or a combination of at least two of ammonium sulfite solution, ammonium carbonate solution, ammonium sulfide solution, or ammonium bisulfite solution. Typical but non-limiting combinations include combinations of ammonium sulfite solution and ammonium carbonate solution, combinations of ammonium sulfite solution and ammonium sulfide solution, combinations of ammonium sulfide solution and ammonium carbonate solution, combinations of ammonium sulfite solution and ammonium carbonate solution, and combinations of ammonium bisulfite solution, etc.

[0038] Preferably, the solid-liquid mass ratio of the biomass pellets to the alkaline solution is 1:(6-8), for example, it can be 1:6, 1:6.5, 1:7, 1:7.5 or 1:8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the mass concentration of the alkaline solution is 1.0-3.5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3% or 3.5%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] The present invention controls the mass concentration of alkaline solution within the above range. Alkaline solutions with excessively high concentrations will promote the dehydration and condensation of carbohydrates and lignin degradation products. The resulting "pseudo-lignin" surface deposition will cause micropore blockage, leading to the secondary reconstruction of the substrate's anti-degradation barrier.

[0041] As a preferred technical solution of the present invention, the temperature of the cooking reaction is 120-175℃, for example, it can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 175℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] Preferably, the cooking reaction time is 0.5-2 hours, for example, 0.5 hours, 0.8 hours, 1.1 hours, 1.4 hours, 1.7 hours or 2 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] The present invention controls the temperature and time of the cooking reaction within the above range. If the chemical cooking temperature is too high or the time is too long, it will cause selective hydrolysis of the amorphous region of cellulose, resulting in a passive increase in the relative proportion of the tightly structured crystalline region.

[0044] Preferably, the pressure of the cooking reaction is 0.2-0.8 MPa, for example, it can be 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa or 0.8 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Secondly, the present invention provides a cellulose-containing biomass, which is obtained by the biomass pretreatment method described in the first aspect.

[0046] As a preferred embodiment of the present invention, the cellulose-containing biomass contains a type I cellulose crystal structure.

[0047] As a preferred technical solution of the present invention, the crystallinity index of the type I cellulose crystal structure in the cellulose-containing biomass is 45%-55%, for example, it can be 45%, 47%, 49%, 51%, 53% or 55%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the cellulose mass fraction in the cellulose-containing biomass is 48.98%-53.68%, for example, it can be 48.98%, 49%, 50%, 51%, 52% or 53.68%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the cellulose recovery rate in the cellulose-containing biomass is greater than 90%, for example, it can be 90%, 92%, 94%, 96%, 98% or 99%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the specific surface area of ​​the cellulose-containing biomass is 37.5-41.01 m². 2 / g, for example, could be 37.5m 2 / g、38 m 2 / g、39 m 2 / g、40 m 2 / g or 41.01 m 2 / g, etc., but not limited to the listed values, other unlisted values ​​within the range also apply.

[0051] Preferably, the pore volume of the cellulose-containing biomass is 0.073-0.080 cm³. 3 / g, for example, could be 0.073cm 3 / g, 0.074 cm 3 / g, 0.075 cm 3 / g, 0.076 cm 3 / g, 0.077 cm 3 / g, 0.078 cm 3 / g, 0.079 cm 3 / g or 0.08 cm 3 / g, etc., but not limited to the listed values, other unlisted values ​​within the range also apply.

[0052] The structure of the cellulose biomass in this invention facilitates the penetration of the agent into the substrate microporous network, thereby achieving efficient depolymerization and separation of lignin components and significantly improving the accessibility of cellulase and the enzymatic saccharification rate.

[0053] Thirdly, the present invention provides an application of cellulose-containing biomass as described in the second aspect, wherein the cellulose-containing biomass is used in an enzymatic hydrolysis saccharification reaction and / or the refining of lignocellulosic biomass. Preferably, the cellulose conversion rate of the enzymatic hydrolysis saccharification reaction reaches 80% or more, for example, 80%, 84%, 88%, 92%, 96%, or 99%, etc., but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0054] Preferably, the mass ratio of the substrate solids to the volume of the reaction system in the enzymatic hydrolysis saccharification reaction is 0.15-0.25, for example, it can be 0.15, 0.17, 0.19, 0.21, 0.23 or 0.25, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] The volume of the reaction system described in this invention refers to the total volume of the mixture, including all raw materials and solvents.

[0056] Preferably, the amount of vitamin B complex added for the enzymatic hydrolysis and saccharification reaction is 5-15 FPU / g DM, for example, it can be 5 FPU / g DM, 6 FPU / g DM, 7 FPU / g DM, 8 FPU / g DM, 9 FPU / g DM, 10 FPU / g DM, 11 FPU / g DM, 12 FPU / g DM, 13 FPU / g DM, 14 FPU / g DM or 15 FPU / g DM, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Preferably, the reaction medium for the enzymatic hydrolysis and saccharification reaction is an acetate-sodium acetate buffer solution.

[0058] Preferably, the pH of the reaction medium for the enzymatic hydrolysis and saccharification reaction is 4.5-5.1, for example, it can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 or 5.1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, the temperature of the enzymatic hydrolysis saccharification reaction is 40-60℃, for example, it can be 40℃, 44℃, 48℃, 52℃, 56℃ or 60℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0060] Preferably, the shaking speed of the enzymatic hydrolysis saccharification reaction is 140-160 rpm, for example, it can be 140 rpm, 44 rpm, 148 rpm, 152 rpm, 156 rpm or 160 rpm, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0061] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0062] (1) The biomass pretreatment method with steam coupling twin screw provided by the present invention significantly reduces physical decomposition energy consumption through the deep coupling of steam thermal softening and twin screw mechanical shearing. At the same time, the continuous strong shearing of the twin screw completely makes up for the shortcomings of insufficient steam decomposition force, and completes the large-scale expansion of microporous network at the physical level;

[0063] (2) The biomass pretreatment method of steam coupling twin screw provided by the present invention effectively avoids pore blockage induced by pseudolignin deposition under low load cooking conditions by relieving the mass transfer resistance of dense forest trees, and finally achieves efficient retention of carbohydrates, and the cellulose content in the obtained cellulose-containing biomass reaches more than 40%.

[0064] (3) The biomass pretreatment method with steam coupling twin-screw extruder provided by this invention not only efficiently eliminates the steric hindrance of enzymatic hydrolysis, but also exhibits high stability in large-scale operation, with a cellulose conversion rate of over 38%. Technical, economic, and environmental assessments show that this method achieves better economic feasibility and lower environmental impact. Attached Figure Description

[0065] Figure 1 These are SEM microscopic images of the biomass raw materials and cellulose-containing biomass in Examples 1, 12-14 of this invention;

[0066] Figure 2 These are SEM microscopic images of the cellulose-containing biomass in Examples 1 and 8-11 of this invention.

[0067] Figure 3 These are SEM microscopic images of the cellulose-containing biomass in Examples 1 and 4-7 of this invention. Detailed Implementation

[0068] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0069] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0070] Example 1

[0071] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder, the biomass pretreatment method comprising the following steps:

[0072] 1000 g (octane dry weight) of washed and air-dried poplar wood chips were mixed with a 2.4 wt% NaOH solution at a solid-liquid ratio of 1:5 (w / w) and impregnated for 12 h under sealed conditions at a temperature of 25°C to obtain pre-softened raw material.

[0073] The pre-softened raw materials were transferred into a high-temperature steam boiler and steamed at 100 °C for 3 h at atmospheric pressure (101.1 kPa).

[0074] The steamed raw material is then fed into a twin-screw extruder. The feed screw of the twin-screw extrusion crushing process has a length-to-diameter ratio of 0.9:1 and a rotation speed of 330 r / min. It relies on high shear force to extrude and dissociate, and obtains fine wood particles with a particle size range of 30-100 micrometers.

[0075] The wood particles and a 2.5% ammonium sulfite solution were mixed, with a solid-liquid mass ratio of 1:7. The mixture was then subjected to a cooking reaction at 165°C for 1 hour at a pressure of 0.5 MPa.

[0076] Example 2

[0077] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder, the biomass pretreatment method comprising the following steps:

[0078] 1000 g (octane dry weight) of washed and air-dried poplar wood chips were mixed with a 2 wt% NaOH solution at a solid-liquid ratio of 1:6 (w / w) and impregnated under sealed conditions for 10 h at a temperature of 20°C to obtain pre-softened raw material.

[0079] The pre-softened raw materials were transferred into a high-temperature steam boiler and steamed at 90 °C for 2 h at atmospheric pressure (101.1 kPa).

[0080] The steamed raw material is then fed into a twin-screw extruder. The feed screw of the twin-screw extrusion crushing process has a length-to-diameter ratio of 0.7:1 and a rotation speed of 350 r / min. It relies on high shear force to extrude and dissociate, and obtains fine wood particles with a particle size range of 30-100 micrometers.

[0081] The wood particles and a 1.0% ammonium carbonate solution were mixed, with a solid-liquid mass ratio of 1:6. The mixture was then subjected to a cooking reaction at 175°C for 0.5 h at a pressure of 0.2 MPa.

[0082] Example 3

[0083] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder, the biomass pretreatment method comprising the following steps:

[0084] 1000 g (octane dry weight) of washed and air-dried poplar wood chips were mixed with a 3 wt% NaOH solution at a solid-liquid ratio of 1:4 (w / w) and impregnated under sealed conditions for 14 h at a temperature of 30°C to obtain pre-softened raw material.

[0085] The pre-softened raw materials were transferred into a high-temperature steam boiler and steamed at 110 °C for 4 h at atmospheric pressure (101.1 kPa).

[0086] The steamed raw material is then fed into a twin-screw extruder. The feed screw of the twin-screw extrusion crushing process has a length-to-diameter ratio of 1.3:1 and a rotation speed of 290 r / min. It relies on high shear force to extrude and dissociate, and obtains fine wood particles with a particle size range of 30-100 micrometers.

[0087] The wood particles and a 3.5% ammonium sulfide solution were mixed, with a solid-liquid mass ratio of 1:8. The mixture was then subjected to a cooking reaction at 120°C for 2 hours at a pressure of 0.8 MPa.

[0088] Example 4

[0089] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the mass concentration of the ammonium sulfite solution is changed to 1.0%, while all other aspects are the same as in Embodiment 1.

[0090] Example 5

[0091] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the mass concentration of the ammonium sulfite solution is changed to 2.0%, while all other aspects are the same as in Embodiment 1.

[0092] Example 6

[0093] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the mass concentration of the ammonium sulfite solution is changed to 3.0%, while all other aspects are the same as in Embodiment 1.

[0094] Example 7

[0095] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the mass concentration of the ammonium sulfite solution is changed to 3.5%, while all other aspects are the same as in Embodiment 1.

[0096] Example 8

[0097] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction temperature is changed to 120°C, while all other aspects are the same as in Embodiment 1.

[0098] Example 9

[0099] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction temperature is changed to 135°C, while all other aspects are the same as in Embodiment 1.

[0100] Example 10

[0101] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction temperature is changed to 150°C, while all other aspects are the same as in Embodiment 1.

[0102] Example 11

[0103] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction temperature is changed to 175°C, while all other aspects are the same as in Embodiment 1.

[0104] Example 12

[0105] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction time is changed to 0.5 h, while all other aspects are the same as in Embodiment 1.

[0106] Example 13

[0107] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction time is changed to 1.5 h, while all other aspects are the same as in Embodiment 1.

[0108] Example 14

[0109] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and that of Embodiment 1 is that the cooking reaction time is changed to 2 hours, while all other aspects are the same as in Embodiment 1.

[0110] Example 15

[0111] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and Embodiment 1 is that the rotational speed of the twin-screw extrusion crushing process is changed to 220 r / min, while the rest is the same as Embodiment 1.

[0112] Example 16

[0113] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and Embodiment 1 is that the rotational speed of the twin-screw extrusion crushing process is changed to 400 r / min, while the rest is the same as Embodiment 1.

[0114] Example 17

[0115] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and Embodiment 1 is that the steam treatment time is changed to 1 hour, while all other aspects are the same as in Embodiment 1.

[0116] Example 18

[0117] This embodiment provides a biomass pretreatment method using a steam-coupling twin-screw extruder. The only difference between this biomass pretreatment method and Embodiment 1 is that the steam treatment time is changed to 5 hours, while all other aspects are the same as in Embodiment 1.

[0118] Comparative Example 1

[0119] This comparative example provides a biomass pretreatment method using a steam-coupled twin-screw extruder. The only difference between this biomass pretreatment method and Example 1 is that the pre-softened biomass raw material is directly subjected to twin-screw extrusion crushing without steam treatment. All other aspects are the same as in Example 1.

[0120] Comparative Example 2

[0121] This comparative example provides a biomass pretreatment method using a steam-coupled twin-screw extruder. The only difference between this biomass pretreatment method and Example 1 is that the pre-softened biomass raw material is not subjected to twin-screw extrusion and crushing after steam treatment, but instead undergoes a cooking reaction. All other aspects are the same as in Example 1.

[0122] Performance testing

[0123] The cellulose-containing biomass provided in the examples and comparative examples was subjected to crystallinity tests, specific surface area and pore volume tests, mass content tests of each substance tests, and fermentable sugar preparation performance tests. For the fermentable sugar preparation performance test, cellulose-containing biomass was used as the substrate, and a reaction system with a solid content of 20% (w / v) was prepared. Cellulase was added, with the enzyme dosage controlled at 10 FPU / g DM, and an acetate-sodium acetate buffer solution at pH = 4.8 was used as the reaction medium. The above mixture was placed in an air shaker and subjected to enzymatic hydrolysis for 96 h under constant temperature conditions of 50 °C and 150 rpm. After the reaction, the supernatant was heated at 100 °C for 10 minutes to inactivate the cellulase; insoluble matter was removed by filtration through a 0.22 μm PTFE membrane, and then the monosaccharide concentration was determined by high performance liquid chromatography (HPLC), and the cellulose conversion rate was calculated. Crystallinity was measured using X-ray diffraction (XRD, D8 Advance, Bruker, Germany) to analyze the evolution of cellulose crystallinity. The crystallinity index was calculated as Cr(%) = (I... 002 -I am The result is calculated as I / I200 × 100, where I 002 The intensity of peak (002) at a 2θ angle of approximately 22.5° is denoted as α, and Iam is the scattering intensity of the amorphous phase at a 2θ angle of approximately 18°. Surface area and pore volume were precisely measured using a fully automated specific surface area and pore volume analyzer (BET, ASAP 2420, Micromeritics, USA). The chemical content of various substances in cellulose-containing biomass was determined using high-performance liquid chromatography (HPLC) (Agilent 1200, Agilent, USA) to analyze the glucose and xylose content in the liquid. The cellulose conversion rate is calculated using the following formula:

[0124]

[0125] Where Cg is the glucose concentration of the enzymatic hydrolysate, V is the volume of the enzymatic hydrolysate, and Mg is the mass of cellulose in the substrate. The results are shown in Table 1.

[0126]

[0127] Depend on Figure 1-3 It can be seen that, compared with the untreated dense logs, the solid phase of the logs after the "steam-twin screw" coupled pretreatment exhibits a significantly rough and loose surface morphology. Poplar fibers gradually dissociate into tiny fragments and separated fiber bundles, and the micro-mesoporous network inside the substrate is significantly amplified, effectively removing the steric hindrance that restricts enzymatic hydrolysis and greatly improving the accessibility of cellulase.

[0128] As shown in Table 1, this invention achieves efficient deconstruction of the dense structure of lignocellulose by relying on the synergistic effect of "steam softening" and "twin-screw shearing." This process achieves efficient selective separation of biomass components under low chemical reagent load during the cooking reaction. The final 96-hour cellulose enzymatic saccharification conversion rate of the substrate reached 85%, effectively meeting the green biorefining criteria of low energy consumption and low environmental impact, and possessing broad prospects for industrial transformation. During the cooking process, as the mass concentration of ammonium sulfite solution increased, the cellulose crystallinity index (CrI) of the products in each example showed an evolutionary pattern of first decreasing and then increasing. Under the conditions of 165 ℃, 2.5 wt.%, and 1 h, the crystallinity significantly decreased to the lowest level; while excessive treatment would induce selective hydrolysis of cellulose and hemicellulose, leading to an increase in the proportion of crystalline regions of cellulose. Under optimal cooking conditions (165 °C, 2.5 wt.%, 1 h), a large amount of lignin is released through bond breakage, resulting in a significant increase in the relative cellulose content. However, further increases in ammonium sulfite concentration, cooking temperature, or cooking time lead to excessive degradation and hydrolysis of thermodynamically unstable hemicellulose and some cellulose, resulting in a decrease in the relative proportion of cellulose. Changes in substrate structure directly affect enzymatic accessibility. A 96-h enzymatic hydrolysis experiment confirmed that when the cooking temperature increased from 120 °C to 165 °C, the enzymatic conversion rate of the originally extremely difficult-to-degrade poplar substrate increased significantly. However, when the temperature increased to 175 °C, the saccharification rate did not show a significant increase, limited by pore collapse and pseudolignin encapsulation. Considering the degree of dissociation of the substrate microporous network structure, the conversion limit of the final fermentable sugars, and the macro-industrial requirement for continuous energy saving, this invention identifies "ammonium sulfite concentration 2.5 wt.%, 165 °C, 1 h" as the optimal combination of cooking reaction parameters.

[0129] A comprehensive comparison of Examples 1 and 15-18 shows that if the rotation speed is too slow, the biomass particles obtained from the extrusion crushing will be uneven. If the rotation speed is too fast, the applied specific mechanical energy will be too high, manifesting as heat and excessive shearing. The material will be over-crushed, resulting in excessively small particle sizes, which may lead to re-agglomeration within the extruder due to high pressure and temperature, thus hindering subsequent reactions. If the steaming time is too long, prolonged high temperatures will cause irreversible condensation reactions in lignin fragments, forming more stable, inert, and difficult-to-dissolve condensed lignin. Furthermore, excessively long steaming times not only increase energy consumption but also fail to simultaneously improve the softening effect on the three-dimensional network of lignocellulose, resulting in no increase in the relative cellulose content and cellulose conversion rate in the solid phase. This condensed lignin strongly adsorbs cellulase, significantly reducing enzymatic hydrolysis efficiency. If the steaming time is too short, heat and steam cannot effectively penetrate into the material, resulting in insufficient destruction of the lignin macromolecular structure and reducing the efficiency of subsequent enzymatic hydrolysis or chemical treatment.

[0130] A comprehensive comparison of Example 1 and Comparative Examples 1-2 shows that the present invention effectively breaks down the dense stress resistance barrier of forest trees through the synergistic effect of hot steam-twin-screw shearing, allowing low-concentration agents to penetrate into the microporous network of the substrate. While significantly reducing the energy consumption of mechanical dissociation, it completely opens the mass transfer microporous channels for the targeted dissolution of subsequent trace chemical agents, thereby achieving efficient depolymerization and separation of lignin components. The pretreatment technology, which synergistically reduces the energy consumption of mechanical dissociation and the input of chemicals, significantly improves the accessibility of cellulase and the enzymatic saccharification rate. Without steam treatment or twin-screw extrusion crushing, the synergistic effect cannot be achieved.

[0131] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A biomass pretreatment method using a steam-coupling twin-screw extruder, characterized in that, The biomass pretreatment method includes the following steps: The pre-softened biomass raw material is subjected to steam treatment and twin-screw extrusion crushing in sequence to obtain biomass pellets; the biomass pellets are then subjected to a cooking reaction to obtain cellulose-containing biomass.

2. The biomass pretreatment method according to claim 1, characterized in that, The biomass raw materials include forest biomass; Preferably, the forest biomass includes any one or a combination of at least two of pine, poplar, willow, birch, oak, or peach.

3. The biomass pretreatment method according to claim 1 or 2, characterized in that, The steam used in the steam treatment includes water steam; Preferably, the temperature of the steam treatment is 90-110℃; Preferably, the steam treatment time is 2-4 hours; Preferably, the pressure of the steam treatment is 95-110 kPa.

4. The biomass pretreatment method according to any one of claims 1 to 3, characterized in that, The length-to-diameter ratio of the feed screw in the twin-screw extrusion crushing process is (0.7-1.3):1; Preferably, the rotational speed of the twin-screw extrusion crushing process is 290-350 r / min; Preferably, the particle size of the biomass particles ranges from 30 to 100 micrometers.

5. The biomass pretreatment method according to any one of claims 1 to 4, characterized in that, The pre-softening includes: alkaline leaching treatment of biomass raw materials; Preferably, the temperature of the alkaline leaching treatment is 20-30°C; Preferably, the solid-liquid mass ratio of the biomass raw material to the alkaline solution in the alkaline leaching treatment is 1:(4-6). Preferably, the alkaline solution for the alkaline leaching treatment includes a sodium hydroxide solution; Preferably, the concentration of the sodium hydroxide solution is 2-3 wt%; Preferably, the alkaline immersion treatment time is 10-14 h.

6. The biomass pretreatment method according to any one of claims 1 to 5, characterized in that, The cooking reaction includes: mixing the biomass particles and an alkaline solution, and then carrying out the cooking reaction; Preferably, the pH value of the alkaline solution is 7-10; Preferably, the alkaline solution includes any one or a combination of at least two of the following: ammonium sulfite solution, ammonium carbonate solution, ammonium sulfide solution, or ammonium bisulfite solution; Preferably, the solid-liquid mass ratio of the biomass pellets to the alkaline solution is 1:(6-8). Preferably, the mass concentration of the alkaline solution is 1.0-3.5%.

7. The biomass pretreatment method according to any one of claims 1 to 6, characterized in that, The temperature of the cooking reaction is 120-175℃; Preferably, the cooking reaction time is 0.5-2 hours; Preferably, the pressure of the cooking reaction is 0.2-0.8 MPa.

8. A cellulose-containing biomass, characterized in that, The cellulose-containing biomass is obtained by the biomass pretreatment method according to any one of claims 1 to 7.

9. The cellulose-containing biomass according to claim 8, characterized in that, The cellulose-containing biomass contains a type I cellulose crystal structure; Preferably, the crystallinity index of the type I cellulose crystal structure in the cellulose-containing biomass is 45%-55%; Preferably, the cellulose content in the cellulose-containing biomass is 48.98%-53.68% by mass; Preferably, the cellulose recovery rate in the cellulose-containing biomass is greater than 90%; Preferably, the specific surface area of ​​the cellulose-containing biomass is 37.5-41.01 m². 2 / g; Preferably, the pore volume of the cellulose-containing biomass is 0.073-0.080 cm³. 3 / g.

10. An application of cellulose-containing biomass according to claim 8 or 9, characterized in that, The cellulose-containing biomass is used in enzymatic hydrolysis and / or refining of lignocellulose biomass; Preferably, the cellulose conversion rate of the enzymatic hydrolysis and saccharification reaction reaches 80% or more; Preferably, the mass ratio of the substrate solids to the volume ratio of the reaction system in the enzymatic hydrolysis saccharification reaction is 0.15-0.25; Preferably, the amount of vitamin B complex added in the enzymatic hydrolysis and saccharification reaction is 5-15 FPU / g DM; Preferably, the reaction medium for the enzymatic hydrolysis and saccharification reaction includes an acetate-sodium acetate buffer solution; Preferably, the pH range of the reaction medium for the enzymatic hydrolysis and saccharification reaction is 4.5-5.1; Preferably, the temperature of the enzymatic hydrolysis and saccharification reaction is 40-60℃; Preferably, the shaking speed of the enzymatic hydrolysis saccharification reaction is 140-160 rpm.

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