Biomass component separation method based on formic acid solvent system

Abstract

The invention discloses a biomass component separation method based on a formic acid solvent system, and belongs to the technical field of biomass energy conversion and utilization. Comprising the following steps: mixing an organic solvent with water, adding formic acid, and mixing to form a ternary solvent; the method comprises the following steps: mixing a ternary solvent with a biomass raw material, heating to react, cooling to room temperature after the reaction is finished, and carrying out solid-liquid separation to obtain filter residues and filtrate; washing the filter residues with water and then drying; and concentrating the filtrate by rotary evaporation, adding excessive water, precipitating, filtering, freeze-drying to obtain lignin, and evaporating a water phase part obtained by filtering to obtain a hemicellulose degraded sugar product. By adding the organic solvent and water, dissolution of lignin and hemicellulose can be promoted respectively, the purity of cellulose in solid residues is improved, subsequent enzymolysis conversion of cellulose is facilitated, and the yield of glucose is improved.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy conversion and utilization technology, specifically relating to a biomass component separation method based on a formic acid solvent system. Background Technology

[0002] Lignocellulosic biomass is the most abundant renewable carbon source in nature. Converting it into biofuels, chemicals, and materials through efficient technologies is of great strategic significance for achieving "dual carbon" goals and sustainable development. A key prerequisite for realizing the high-value utilization of biomass is breaking down its natural resistance to degradation, effectively separating its three components—cellulose, hemicellulose, and lignin—thereby laying the foundation for the efficient conversion of each component.

[0003] Currently, lignocellulose biomass component separation technology has been widely developed and researched. Among these methods, formic acid pretreatment is a highly efficient method for biomass component separation. Formic acid can effectively break the ether and ester bonds between lignin and hemicellulose, dissolving most of the lignin and some of the hemicellulose, while retaining cellulose relatively well, creating favorable conditions for subsequent enzymatic hydrolysis and saccharification of cellulose. However, to ensure the separation effect of biomass components, the formic acid concentration used is currently quite high. Excessively high formic acid concentrations not only lead to cellulose degradation and damage to the lignin structure, but also pose significant safety hazards. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a biomass component separation method based on a formic acid solvent system, which solves the problems in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for separating biomass components based on a formic acid solvent system includes the following steps: An organic solvent and water are mixed, and then formic acid is added to form a ternary solvent. The biomass raw materials are crushed, sieved, and dried. The ternary solvent is mixed with the sieved and dried biomass raw material and heated to react. After the reaction is completed, the mixture is cooled to room temperature and the solid and liquid are separated to obtain filter residue and filtrate. The filter residue was washed with water and then dried; the filtrate was concentrated by rotary evaporation, and excess water was added. After precipitation and filtration, the filtrate was freeze-dried to obtain lignin. The aqueous phase obtained by filtration was evaporated to obtain hemicellulose degradation sugar products.

[0006] Furthermore, in the mixed solution of organic solvent and water, the concentration of the organic solvent is 0~60 vt%. Furthermore, the concentration of formic acid in the ternary solvent is 0~80wt%.

[0007] Furthermore, the organic solvent is any one of methanol, ethanol, acetone, and ethylene glycol.

[0008] Furthermore, the biomass raw material is straw, poplar or pine wood; the particle size of the biomass raw material after screening is 40-60 mesh.

[0009] Furthermore, the ratio of the biomass raw material to the ternary solvent is 1:(10~40)g / ml.

[0010] Furthermore, the heating reaction temperature is 100~140℃, and the reaction time is 1~6 h.

[0011] The above-mentioned biomass component separation method based on formic acid solvent system is applied in the enzymatic hydrolysis preparation of glucose.

[0012] Furthermore, the enzymatic hydrolysis process for preparing glucose includes: adding enzymatic hydrolysis buffer and cellulase of 20 FPU / g cellulose to the separated filter residue at a substrate concentration of 5wt%, and hydrolyzing at 50°C to obtain a glucose-rich solution.

[0013] A method for preparing glucose by enzymatic hydrolysis, comprising: The filter residue separated by the above separation method was added to an enzymatic hydrolysis buffer and cellulase with a substrate concentration of 5 wt%, and enzymatically hydrolyzed at 50 °C to obtain a glucose-rich solution.

[0014] The beneficial effects of this invention are: 1. This invention is based on formic acid solvent. By introducing organic solvents and water, the acid concentration is reduced, making the operation safer and the cost lower, which is conducive to wider industrial application.

[0015] 2. By introducing organic solvents and water, this invention can further improve the removal efficiency of hemicellulose and lignin without reducing the cellulose retention rate. When the formic acid concentration is 60 wt% and the acetone concentration is 40 v / v, the cellulose retention rate is 98.1%, the hemicellulose retention rate is 98.1%, and the lignin removal rate is 90.3% after reacting at 120 °C for 4 h.

[0016] 3. The present invention achieves a maximum sugar yield of 98.2% by enzymatically hydrolyzing the pretreated solid residue. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a graph showing the yield of corn straw enzymatic hydrolysis and saccharification under different formic acid concentrations. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] A method for separating biomass components based on a formic acid solvent system includes the following steps: S1, mix organic solvent and water, then add formic acid to form a ternary solvent; S2, the biomass is crushed and sieved, and the portion with a particle size of 40-60 mesh is dried to absolute dryness; S3, the ternary solvent is mixed with the biomass raw material obtained by crushing and sieving, and heated to react. After the reaction is completed, the mixture is cooled to room temperature and the solid and liquid are separated to obtain a filter residue rich in cellulose and a filtrate containing hemicellulose and lignin. S4: The filter residue obtained from S3 is washed with water and dried (for enzymatic hydrolysis); the filtrate obtained from S3 is concentrated by rotary evaporation, excess water is added, precipitation and filtration are carried out, and then freeze-dried to obtain lignin; the aqueous phase obtained by filtration is evaporated to obtain hemicellulose degradation sugar products.

[0021] In S1, the concentration of the organic solvent in the mixed solution of organic solvent and water is 0~60 wt%; the concentration of formic acid in the ternary solvent is 0~80 wt%; and the organic solvent is any one of methanol, ethanol, acetone and ethylene glycol.

[0022] In S2, the biomass raw material is straw, poplar or pine wood, and the particle size of the raw material is 40-60 mesh; this avoids excessively large particle size, which would make solution penetration relatively difficult and reduce the component separation effect; it also avoids excessively small particle size, which would make subsequent filtration operations time-consuming.

[0023] In S2, the ratio of biomass feedstock to ternary solvent is 1:(10~40) (g / mL).

[0024] In S2, the heating reaction temperature is 80~140℃, and the reaction time is 1~6 h.

[0025] In S3, the amount of water added is 500 times the mass of the biomass raw material, and the sedimentation time is greater than 12 hours; 500 times the mass of water can basically completely precipitate the lignin; too little water may result in incomplete precipitation, while too much water will waste water.

[0026] In S3, the enzymatic hydrolysis conversion step includes: adding enzymatic hydrolysis buffer and cellulase with a substrate concentration of 5wt% to the cellulose-rich filter residue, and hydrolyzing at 50 °C and 150 rpm for 72 h to obtain a glucose-rich solution.

[0027] The technical solution of the present invention will be described below through the following embodiments; wherein, in the embodiments, the test methods for the recovery rate, retention rate and removal rate of each component include: determining the content of cellulose, hemicellulose and lignin in the solid residue after separation of biomass components using the National Renewable Energy Laboratory (NREL) method. Specifically: 0.3 g of biomass raw material was weighed and mixed with 3 mL of 72 wt.% sulfuric acid, and then placed on a magnetically heated stirring plate and stirred at 30 ℃ and 500 rpm for 1 h; then 84 mL of deionized water was added to dilute the sulfuric acid to 4 wt.%, and the mixture was transferred to a 100 mL reagent bottle and placed in an autoclave for hydrolysis at 121 ℃ for 1 h. After the reaction cooled to room temperature, the supernatant was taken, filtered, and the contents of glucose, xylose and arabinose were determined by high performance liquid chromatography (HPLC), and the contents of cellulose and hemicellulose could be calculated. The filtered solid residue was dried in an oven at 100℃, weighed, and then placed in a muffle furnace. It was calcined in air at 550℃ for 4 hours, and the mass of the remaining solid was recorded. The mass change during the calcination process is the lignin content.

[0028] Example 1 (1) Preparation of ternary solvent: 80 wt% formic acid and 20 wt% acetone aqueous solution (acetone / water: 40 / 60, v / v, i.e., acetone concentration of 40vt%), for later use; weigh 2 g of corn stalk raw material with a particle size of 40-60 mesh (cellulose 43 wt%, hemicellulose 25 wt%, lignin 22 wt%), add 40 ml of the prepared ternary solvent, heat and stir at 120 ℃ for 4 h, cool to room temperature, filter with a G4 sintered glass funnel, collect the filtrate, and wash the solid material with deionized water until the liquid is colorless. The filtrate is concentrated by rotary evaporation at 65 ℃ to recover formic acid and acetone at the same time. 1 L of deionized water is added to the concentrate, and after standing for 12 h, it is filtered to obtain lignin, which is then freeze-dried to obtain a lignin sample. The solid material is dried in an oven at 60 ℃ for 24 h to obtain a filter residue rich in cellulose.

[0029] The solid recovery rate of the obtained filter residue was 47.5%, of which cellulose was 87.8%, hemicellulose was 2.8%, and lignin was 2.5%. The cellulose retention rate was 95.3%, the hemicellulose removal rate was 93.5%, and the lignin removal rate was 93.1%.

[0030] Examples 2 to 13 Referring to Example 1, the effects of different reaction temperatures, times, acid concentrations, and organic solvent concentrations on cellulose retention rate, hemicellulose removal rate, and lignin removal rate were investigated, and the results are shown in Table 1.

[0031] Table 1. Effects of different reaction conditions on the separation efficiency of various corn straw components. Examples 14-15 Referring to Example 1, the difference is that the biomass raw materials are poplar and pine.

[0032] Table 2. Separation effect of poplar and pine components under formic acid pretreatment system # # Reaction conditions: formic acid concentration 60 wt%, acetone concentration 40 vt%, 120 ℃, 4 h.

[0033] Example 16 In this embodiment, dried cellulose-rich filter residues obtained under different formic acid concentrations (corresponding to Examples 7, 8, 3, 8, and 10, respectively) were used as enzymatic hydrolysis substrates, and untreated straw raw materials were used as control groups. Cellulase with a mass concentration of 5% and 20 FPU / g cellulose was added, and an acetate-sodium acetate solution was used as the enzymatic hydrolysis buffer. The enzymatic hydrolysis was carried out at 50 °C and 150 rpm for 72 h to obtain a glucose-rich solution.

[0034] Specific glucose yields are as follows: Figure 1 As shown, with the formic acid concentration increasing from 0 wt% to 60 wt%, the saccharification efficiency increased from 22.9% to 98.2%, reaching a near-complete saccharification level, confirming that the removal of hemicellulose and lignin can effectively improve the accessibility of cellulase. It is noteworthy that when the formic acid concentration was further increased to 80 wt%, the saccharification efficiency slightly decreased to 95.7%. This may be because the high-concentration acidic pretreatment conditions caused a certain degree of degradation of cellulose, leading to a slight decrease in saccharification efficiency.

[0035] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for separating biomass components based on a formic acid solvent system, characterized in that, Includes the following steps: An organic solvent and water are mixed, and then formic acid is added to form a ternary solvent. The biomass raw materials are crushed, sieved, and dried. The ternary solvent is mixed with the sieved and dried biomass raw material and heated to react. After the reaction is completed, the mixture is cooled to room temperature and the solid and liquid are separated to obtain filter residue and filtrate. The filter residue was washed with water and then dried; the filtrate was concentrated by rotary evaporation, and excess water was added. After precipitation and filtration, the filtrate was freeze-dried to obtain lignin. The aqueous phase obtained by filtration was evaporated to obtain hemicellulose degradation sugar products.

2. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, In a mixed solution of organic solvent and water, the concentration of the organic solvent is 0~60vt.

3. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, In the ternary solvent, the concentration of formic acid is 0~80wt%.

4. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, The organic solvent is any one of methanol, ethanol, acetone and ethylene glycol.

5. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, The biomass raw material is straw, poplar or pine wood; the particle size of the biomass raw material after screening is 40-60 mesh.

6. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, The ratio of the biomass raw material to the ternary solvent is 1:(10~40)g / ml.

7. The method for separating biomass components based on a formic acid solvent system according to claim 1, characterized in that, The heating reaction is carried out at a temperature of 100~140℃ for a time of 1~6 h.

8. The application of the biomass component separation method based on formic acid solvent system according to any one of claims 1-7 in the enzymatic preparation of glucose.

9. The application according to claim 8, characterized in that, The process of preparing glucose by enzymatic hydrolysis includes: adding enzymatic hydrolysis buffer and cellulase with 20 FPU / g cellulose to the separated filter residue at a substrate concentration of 5wt%, and hydrolyzing at 50°C to obtain a glucose-rich solution.

10. A method for preparing glucose by enzymatic hydrolysis, characterized in that, include: The filter residue separated by the separation method according to any one of claims 1-7 is added to an enzymatic hydrolysis buffer and cellulase with a substrate concentration of 5 wt%, and enzymatically hydrolyzed at 50 °C to obtain a glucose-rich solution.

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