阅读说明：本技术 一种秸秆木质纤维素原料的预处理及酶解方法 (Pretreatment and enzymolysis method of straw lignocellulose raw material ) 是由 张盛明 于兴华 陈海涛 刘雨龙 金天浩 梅铁瀚 马凉非 于 2019-10-23 设计创作，主要内容包括：一种秸秆木质纤维素原料的预处理及酶解方法,它涉及木质纤维素的预处理及酶解方法。它是要解决现有的利用杂多酸降解木质素的方法的催化剂的制备成本高、所用溶剂成本高的的技术问题。预处理方法：将秸秆粉与蒸馏水混合液进行水热反应,得到一级固体残渣和一级滤液浓缩液；再将一级固体残渣与H<Sub>3</Sub>PW<Sub>12</Sub>O<Sub>40</Sub>水溶液混合液进行水热反应,完成秸秆木质纤维素预处理并得到二级滤液,再从二级滤液中回收磷钨酸。酶解方法：向一级滤液浓缩液和预处理后的秸秆木质纤维素中加入乙酸-乙酸钠缓冲溶液和纤维素酶混合,混合液酶解、分离,得到糖溶液。本发明催化剂回收率为70％～80％,总糖回收率达69％～89％。可用于生物质预处理领域。(A pretreatment and enzymolysis method of straw lignocellulose raw materials relates to pretreatment and enzymolysis methods of lignocellulose. The method aims to solve the technical problems of high preparation cost and high cost of a solvent in the existing method for degrading lignin by using heteropoly acid. The pretreatment method comprises the following steps: carrying out hydrothermal reaction on the mixed solution of the straw powder and the distilled water to obtain primary solid residue and a primary filtrate concentrated solution; then the first-stage solid residue is mixed with H 3 PW 12 O 40 Carrying out hydrothermal reaction on the aqueous solution mixed solution to finish pretreatment of straw lignocellulose and obtain secondary filtrate, and recovering phosphotungstic acid from the secondary filtrate. The enzymolysis method comprises the following steps: adding acetic acid-sodium acetate buffer solution and cellulase into the concentrated solution of the primary filtrate and the pretreated straw lignocellulose for mixing, and performing enzymolysis and separation on the mixed solutionAnd (5) separating to obtain a sugar solution. The catalyst recovery rate is 70-80%, and the total sugar recovery rate is 69-89%. Can be used in the field of biomass pretreatment.)

1. A pretreatment method of straw lignocellulose raw material is characterized by comprising the following steps:

firstly, crushing air-dried straws into 40-60 meshes of straw powder, and drying to constant weight;

adding the straw powder and distilled water into a flange magneton reaction kettle, sealing the reaction kettle, wherein the initial reaction pressure of the reaction kettle is normal pressure during sealing, and then heating to 140-200 ℃ under the condition of stirring speed of 300-400 rad/min and keeping for 15-30 min; then cooling to room temperature, taking out the materials in the reaction kettle, and carrying out reduced pressure suction filtration to obtain primary solid residues and primary filtrate; concentrating the first-stage filtrate for later use;

thirdly, mixing the solid residue obtained in the second step with H₃PW₁₂O₄₀Adding the aqueous solution into a flange magneton reaction kettle, sealing the reaction kettle, wherein the initial reaction pressure of the reaction kettle is normal pressure during sealing, then heating to 100-160 ℃ under the condition of stirring speed of 300-400 rad/min, keeping for 0.5-2 h, then cooling to room temperature, carrying out vacuum filtration on materials in the reaction kettle, and washing solid residues to be neutral by using distilled water to obtain secondary solid residues and secondary filtrate; adding ether into the secondary filtrate, oscillating to obtain a lower-layer ether-phosphotungstic acid compound, and evaporating and crystallizing the ether-phosphotungstic acid compound to obtain recovered phosphotungstic acid; the secondary solid residue is the straw lignocellulose which is pretreated.

2. The pretreatment method of straw lignocellulosic feedstock according to claim 1, wherein the temperature of drying in the first step is 60-70 ℃.

3. The pretreatment method of straw lignocellulosic feedstock according to claim 1 or 2, wherein in the second step, the ratio of the mass of straw powder to the volume of distilled water is 1 g: (10-50) mL.

4. The method for pretreating straw lignocellulosic raw material according to claim 1 or 2, wherein H is in step three₃PW₁₂O₄₀The concentration of the aqueous solution is 10 mM-50 mM.

5. The pretreatment method of straw lignocellulosic feedstock according to claim 1 or 2, characterized in that the mass of straw powder in the second step and the concentration of H in the third step are 10 mM-50 mM₃PW₁₂O₄₀The volume ratio of the aqueous solution was 1 g: (10-30) mL.

6. The primary filtrate concentrate and the enzymatic hydrolysis method of pretreated straw lignocellulose prepared according to claim 1, characterized in that the method is carried out according to the following steps:

mixing a primary filtrate concentrated solution obtained by pretreating a straw powder raw material and a corresponding straw lignocellulose subjected to pretreatment with an acetic acid-sodium acetate buffer solution with the concentration of 0.05-0.1M, pH being 4.5-5.0, adding cellulase after uniform mixing, placing the mixed solution in a constant-temperature oscillator, carrying out enzymolysis for 72-80 h at the temperature of 50-55 ℃ and the rotating speed of 50-60 rad/min, then carrying out centrifugal separation, collecting a supernatant, obtaining a sugar solution, and completing enzymolysis of the straw lignocellulose.

7. The primary filtrate concentrate and the enzymatic hydrolysis method of straw lignocellulose subjected to pretreatment prepared according to claim 1 as claimed in claim 6, wherein the cellulase is Cellic CTec2 cellulose complex enzyme preparation.

8. The primary filtrate concentrated solution and the pretreated straw lignocellulose enzymolysis method according to claim 1 as claimed in claim 6 or 7, wherein the cellulase is added into the mixed solution in an amount of 5-15U per gram of the straw powder raw material, calculated according to the weight of the straw powder raw material.

9. The primary filtrate concentrated solution and the pretreated straw lignocellulose enzymolysis method according to claim 6 or 7, wherein the adding amount of the acetic acid-sodium acetate buffer solution in the mixed solution is 5-20 mL per gram of the straw powder raw material according to the mass of the straw powder raw material.

10. The method for enzymolysis of the first-stage filtrate concentrated solution and the pretreated straw lignocellulose prepared according to the claim 1 of claim 6 or 7, characterized in that the rotation speed of centrifugal separation is 8000-9000 rad/min, and the centrifugal time is 10-15 min.

Technical Field

The invention relates to a pretreatment and enzymolysis method of a lignocellulose raw material.

Background

In recent years, with the large consumption of non-renewable energy, the energy problem has become a hot issue of concern for all countries in the world, and researchers are continuously reducing and replacing the use of fossil energy by developing new energy and renewable energy. China is a big agricultural country, and crop straw resources are rich. The crop straws are rich in lignocellulose, and the conversion of the straw lignocellulose into fuel ethanol is an important way for the efficient utilization of biomass resources. At present, the technical process for producing first-generation fuel ethanol by using grains as raw materials is mature and stable, and when producing second-generation cellulosic ethanol by using agricultural and forestry wastes such as straws and the like as raw materials, because the straw wood fiber has the stubborn-resistance structural characteristic, lignin and hemicellulose are tightly wrapped on the outer layer of cellulose, the problems of difficult hydrolysis and low saccharification rate caused by the contact of enzyme and substrate are hindered. Therefore, before enzymolysis and fermentation, pretreatment of the straw lignocellulose substrate is needed to improve the enzymolysis saccharification efficiency.

The traditional pretreatment methods mainly comprise a chemical method, a physical-chemical synthesis method, a biological method and the like, which have advantages but have defects, and are difficult to consider the problems of energy consumption, pretreatment efficiency, waste liquid treatment cost, environmental protection and the like, so that the industrial process of the cellulosic ethanol is greatly limited. The dilute sulfuric acid hydrolysis method is still the most main pretreatment method at present, a sulfuric acid catalyst can effectively hydrolyze and dissolve cellulose and hemicellulose, however, the sulfuric acid catalyst has poor degradation effect on lignin, needs to neutralize waste acid liquor, and has the problems of high waste liquid treatment cost and poor environmental protection property; in addition, under the action of a sulfuric acid catalyst, part of degraded lignin is mixed with degradation products of cellulose and hemicellulose, so that the lignin is difficult to separate, a substrate competition effect is generated, and the production cost of a fermentation process is increased.

The heteropoly acid belongs to the category of solid acid, has the advantages of high catalytic activity, good selectivity, good thermal stability, recyclability, low corrosivity and the like, is widely concerned in the field of catalytic chemistry, gradually shows the trend of replacing the traditional acid catalyst, particularly the heteropoly acid with a Keggin type structure has strong proton supply capability, strong acidity and strong oxidizing property, and has the behavior of storing electrons, keeping the original structure unchanged and changing a bulk phase into a pseudo liquid phase of a reaction field. Recently, domestic and foreign researchers find that some heteropoly acid catalysts can well degrade lignin, and under the action of the heteropoly acid catalysts, lignocellulose in wood can be converted into cellulose-enriched materials.

2018 Master thesis of northeast forestry university heteropolyacid H₃PW₁₂O₄₀And H₅PV₂Mo₁₀O₄₀The research on catalytic degradation of lignin discloses a method for utilizing H₃PW₁₂O₄₀A method for the catalytic degradation of wheat straw alkali lignin and enzymatic lignin as a catalyst, but in the method, H₃PW₁₂O₄₀To be loaded on ZrO₂In the framework, the composite material is used for catalyzing and degrading wheat straw alkali lignin and enzymatic hydrolysis lignin in an ethanol-water solvent. The preparation cost of the catalyst is high.

The resource chemical research laboratory of Xinjiang physical and chemical technology institute of Chinese academy of sciences adopts typical solid heteropolyacids (silicotungstic acid, phosphotungstic acid and phosphomolybdic acid) as catalysts to effectively remove lignin in raw wood powder in a gamma-valerolactone/water solvent system, so that a material rich in cellulose is obtained. The solvent used in the method has high cost.

Disclosure of Invention

The invention provides a pretreatment and enzymolysis method for straw lignocellulose raw materials, aiming at solving the technical problems of high preparation cost of a catalyst and high cost of a used solvent in the existing method for degrading lignocellulose by using heteropoly acid.

The invention relates to a pretreatment method of straw lignocellulose raw material, which comprises the following steps:

firstly, crushing air-dried straws into 40-60 meshes of straw powder, and drying to constant weight;

adding the straw powder and distilled water into a flange magneton reaction kettle, sealing the reaction kettle, wherein the initial reaction pressure of the reaction kettle is normal pressure during sealing, and then heating to 140-200 ℃ under the condition of stirring speed of 300-400 rad/min and keeping for 15-30 min; then cooling to room temperature, taking out the materials in the reaction kettle, and carrying out reduced pressure suction filtration to obtain primary solid residues and primary filtrate; concentrating the first-stage filtrate for later use;

thirdly, mixing the solid residue obtained in the second step with H₃PW₁₂O₄₀Adding the aqueous solution into a flange magneton reaction kettle, sealing the reaction kettle, wherein the initial reaction pressure of the reaction kettle is normal pressure during sealing, then heating to 100-160 ℃ under the condition of stirring speed of 300-400 rad/min, keeping for 0.5-2 h, then cooling to room temperature, carrying out vacuum filtration on materials in the reaction kettle, and washing solid residues to be neutral by using distilled water to obtain secondary solid residues and secondary filtrate; adding ether into the secondary filtrate, oscillating to obtain a lower-layer ether-phosphotungstic acid compound, and evaporating and crystallizing the ether-phosphotungstic acid compound to obtain recovered phosphotungstic acid; the secondary solid residue is the straw lignocellulose which is pretreated.

The first-stage filtrate concentrated solution prepared by the method and the enzymolysis method of the straw lignocellulose subjected to pretreatment are carried out according to the following steps:

mixing a primary filtrate concentrated solution generated by pretreating a straw powder raw material and a corresponding straw lignocellulose subjected to pretreatment with an acetic acid-sodium acetate buffer solution with the concentration of 0.05-0.1M, pH ═ 4.5-5.0, adding cellulase after uniform mixing, placing the mixed solution in a constant temperature oscillator, carrying out enzymolysis for 72-80 h at the temperature of 50-55 ℃ and the rotating speed of 50-60 rad/min, then carrying out centrifugal separation, and collecting a supernatant to obtain a sugar solution.

The invention adopts heteropolyacid H with a Keggin type structure₃PW₁₂O₄₀The aqueous solution is used as a catalyst, straw lignocellulose is pretreated by a two-step method of hot water pre-extraction and heteropoly acid pretreatment, then the collected hemicellulose and cellulose residues are mixed, and enzymolysis saccharification is carried outObtaining C₆Sugar, C₅A sugar solution. The sugar solution may be further converted to fuel ethanol by a fermentation process.

The invention has the following advantages: the pretreatment method adopted by the invention takes water as a solvent, so that the cost is reduced, meanwhile, the reaction time is short, the total heating time is not more than 2.5h, and the energy consumption is relatively low; the amount of the waste liquid generated is small, the main components of the waste liquid are water and lignin, no waste acid liquid is contained, the environment is friendly, and the lignin in the waste liquid can be further separated and utilized, so that the full-component utilization of straw resources is realized; III, H₃PW₁₂O₄₀The catalyst has less dosage and can be recycled, and the recovery rate is 70-80% of the additive amount; fourthly, the total sugar recovery rate is high and can reach 69 to 89 percent.

The method is a novel method with low energy consumption, environmental friendliness, recyclable catalyst and high total sugar recovery rate, provides a novel idea and a novel method for establishing green and efficient straw biomass pretreatment, and is beneficial to accelerating the industrialization process of the cellulose-based ethanol fuel.

Detailed Description