CN112175111B - Method for efficiently separating wood fiber material to obtain high-purity components - Google Patents
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Abstract
The invention discloses a method for efficiently separating wood fiber materials to obtain high-purity components, which sequentially separates and extracts cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin from natural wood fiber materials, separates and recovers all the cellulose, hemicellulose and lignin in the natural wood fiber materials, and prepares a high-purity and high-molecular-weight product. The method of the invention is to extract, separate and purify the wood fiber material on the basis of fully knowing the characteristics of the hemicellulose components, so as to realize the separation and utilization of each component in the wood fiber material with high efficiency and low cost, and the method has high recovery rate, high purity and high utilization value of cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin.
Description
Technical Field
The invention belongs to the technical field of utilization of natural wood fiber materials, and particularly relates to a method for efficiently separating wood fiber materials to obtain high-purity components.
Background
The mass fiber material is a renewable resource abundant in nature, and the utilization of the resource as an industrial raw material is always concerned. The wood fiber material is composed of three major parts of cellulose, lignin and hemicellulose, and each component has very high industrial application value. In natural lignocellulosic materials, cellulose is tightly wrapped by hemicellulose and water-insoluble lignin, which are linked by chemical bonds, usually ester bonds, which are unstable under alkaline conditions. Thus, treatment of lignocellulosic material with a concentration of alkali liquor (usually sodium hydroxide) is considered to be an effective means of shedding components of the lignocellulosic material from fibrils.
Cellulose is the first major component of lignocellulosic material, a glycan with glucosyl groups linked by β - (1 → 4) glycosidic bonds, and accounts for approximately 50% of the dry weight of the plant cell wall. High purity cellulose has a wide range of industrial applications, for example: the high-purity cellulose can be used for papermaking, can be used for manufacturing rayon, cellophane, ester derivatives such as nitrate, acetate and the like, can also be used for manufacturing ether derivatives such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyanion cellulose and the like, and is applied to the aspects of petroleum drilling, food, ceramic glaze, daily use chemicals, synthetic washing, graphite products, pencil manufacturing, electronics, coating, building materials, decoration, mosquito-repellent incense, tobacco, papermaking, rubber, agriculture, adhesives, plastics, explosives, electricians, scientific research equipment and the like.
The water-insoluble lignin is a polymer formed by aromatic alcohol monomers (p-coumaryl alcohol, coniferyl alcohol, 5-hydroxy coniferyl alcohol, sinapyl alcohol), and mainly plays a role in hardening cell walls by forming a cross-woven net, and is a main component of secondary walls. Because a series of active groups such as aromatic group, alcoholic hydroxyl group, phenolic hydroxyl group, carbonyl group and the like exist in the molecular structure of the water-insoluble lignin, the performance of the water-insoluble lignin can be improved through chemical modification such as oxidation reaction, sulfonation reaction, graft copolymerization reaction, condensation reaction, alkylation reaction and the like, and the water-insoluble lignin is used for reinforcing rubber, preparing resin, plastics and the like. In addition, the water-insoluble lignin having high purity and good molecular weight uniformity is a superior raw material for production of high-quality graphene, capacitance carbon, and other products.
Polysaccharides other than cellulose in lignocellulosic materials are commonly referred to as hemicelluloses, the most important hemicelluloses in plants being xylans. Xylan is structurally characterized by a main chain consisting of β - (1 → 4) -linked xylose residues, and the 2, 3C of the xylosyl group of the main chain is usually linked with various substituents to form side chains. Xylan is the only five-carbon sugar polymer in nature, is the main dietary fiber of human, has irreplaceable physiological function to human body, and the effect of the physiological function is inseparable from the natural macromolecular structure. According to the difference of the structure and molecular weight of the xylan, the xylan can be subdivided into two types of water-soluble xylan and water-insoluble xylan, and the water-soluble xylan and the water-insoluble xylan respectively have the characteristics of water-soluble dietary fibers and water-insoluble dietary fibers. For example: the water-soluble xylan has the characteristics of quick fermentation and high viscosity; the water-insoluble xylan has the characteristics of slow fermentation, low viscosity and capability of reaching the tail end of an intestinal tract; two xylans with different properties have different application ranges.
Therefore, the components of cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin in the wood fiber material have very high application values, and the most economical and environment-friendly extraction and separation mode is to separate each component in the wood fiber material one by one to obtain a high-purity single product. In particular, the water-soluble part and the water-insoluble part in the xylan are separated at the same time, so that the value of the wood fiber material is utilized to the maximum extent. And because the natural characteristics of the components can be fully maintained by macromolecular state separation, the application range is wider, and the macromolecular state substances are separated and purified, the extraction energy can be saved, and the environmental management burden can be reduced. The basic route for separating the components of lignocellulosic materials is: the raw material is leached by alkali liquor, so that natural xylan is deacetylated, lignin is depolymerized and dissolved in the alkali liquor, cellulose is recovered by solid-liquid separation, and then alkali, xylan and lignin are respectively recovered from the alkali liquor. However, it is difficult to efficiently separate alkali, hemicellulose (main component: xylan), and water-insoluble lignin by the conventional separation method; moreover, it is generally not noticed that xylan in the same raw material can be actually divided into two major parts of water-soluble part and water-insoluble part due to different structures, and the water-insoluble part is mainly used, the water-insoluble xylan and the water-soluble xylan are directly separated together by an alcohol precipitation method, so that the separation effect is poor, the alcohol consumption is large, or the water-insoluble xylan is directly degraded into the water-soluble xylan under high-temperature and high-alkali conditions and then precipitated and dissolved together, and the obtained water-soluble xylan has smaller molecular weight and narrower application range compared with the water-insoluble xylan. Secondly, the recycling of alkali is not considered in many current methods, alkali liquor is directly neutralized by acid, a large amount of salt is generated and discharged, and the problem of environmental management which is difficult to solve is caused; or alkali is separated by a membrane method, the alkali is not completely recovered, the efficiency is low, and the macromolecular structure of the water-insoluble xylan can be damaged.
The applicant also searched the following documents on methods for the preparation of cellulose, hemicellulose (xylan) or lignin from lignocellulosic materials:
patent application CN110592292A discloses a pretreatment method for promoting biomass to efficiently extract xylose by a mechanical method, comprising the following steps: (1) carrying out spiral extrusion treatment on a biomass raw material to obtain a raw material; (2) further transferring the raw material obtained in the step (1) to a disc mill for further treatment; (3) transferring all the raw materials obtained in the step (2) into an autoclave, adding alkali liquor, controlling the temperature between 120 ℃ and 125 ℃, keeping for 0.5-1h, after the treatment is finished, centrifugally separating the black liquor from the solid cellulose-rich part, cleaning the solid cellulose-rich part, and drying; the black liquor comprises hemicellulose and lignin; the hemicellulose is xylose; (4) adding glacial acetic acid into the black liquor obtained in the step (3) to adjust the pH value to 5-6, adding ethanol for precipitation, filtering and separating to obtain solid precipitates, respectively washing the solid precipitates with ethanol and clear water mixed liquor, drying, and separating and washing hemicellulose precipitates in the black liquor to obtain the hemicellulose precipitate; the crude sugar precipitate comprises xylose, arabinose, galactose, glucose and lignin; (5) and (4) carrying out sulfuric acid hydrolysis on the crude sugar precipitate obtained in the step (4), weighing the ground crude sugar, hydrolyzing with concentrated sulfuric acid with the mass percentage concentration of 70-72%, controlling the temperature of a constant-temperature water bath to be 30-35 ℃, keeping for 1-1.5h, then diluting to 4-5%, transferring to an autoclave, controlling the temperature to be 120-125 ℃, treating for 45min-1h, and filtering the obtained supernatant. . According to the method, the extraction efficiency of the chemical for extracting the xylan is promoted by using a mechanical method, simultaneously, the lignin in the biomass raw material is effectively separated, the purity of the xylan is improved, and the cellulose-rich part with low lignin content and potential for producing unbleached pulp is obtained. The application has the advantages of high xylose extraction efficiency, simple process, no environmental pollution and the like. Although this patent application also describes a method for separating lignocellulosic material, this patent application is directed to extracting cellulose and xylose, and the method comprises the steps of degrading hemicellulose into monosaccharides by means of an alkaline solution at high temperature and high pressure, separating cellulose, lignin and monosaccharides in turn, and finally separating relatively pure xylose from monosaccharides.
Patent application CN110241644A discloses a method for separating and comprehensively utilizing all components of crop straws, comprising the following steps: (1) the crushed crop straws are steamed and boiled for 2 to 8 hours at the temperature of between 70 and 100 ℃ by using organic acid liquid under the catalytic action of 0.05 to 0.2mol/L diluted hydrochloric acid, sulfuric acid or acetic acid; wherein the solid-liquid mass ratio is 1: 20; (2) carrying out solid-liquid separation to obtain filtrate A, washing the filter residue with water to neutrality, and drying to obtain crude cellulose; (3) adding the crude cellulose into a hydrogen peroxide solution with the mass fraction of 2-8%, adjusting the pH of the solution to 10-12, and reacting for 3-4h at 40-60 ℃; wherein the solid-liquid mass ratio is 1: 30; (4) carrying out solid-liquid separation to obtain filtrate B, washing the filter residue with water to neutrality, and drying to obtain cellulose; (5) respectively carrying out reduced pressure distillation on the solution A and the solution B, mixing, adjusting the pH of the mixed solution to 1.5-2.0, and carrying out solid-liquid separation; the filtrate is 'C liquid', and the precipitate is washed by water to be neutral and then dried to obtain lignin; (6) adjusting the pH value of the solution C to 12, and adding industrial alcohol to perform solid-liquid separation; adding the precipitate into the supernatant concentrated solution, and drying to obtain hemicellulose. The invention can successfully separate the three components of cellulose, hemicellulose and lignin in the straws, and the three components have higher recovery rate, thereby really realizing the comprehensive utilization of the straws. Although the patent application also introduces a method for separating wood fiber materials, the wood fiber materials are extracted by hydrochloric acid, sulfuric acid or acetic acid, the cellulose obtained by separation can be obtained by extracting the cellulose again by a hydrogen peroxide solution, the lignin is separated at a lower pH value and then the hemicellulose is extracted by an alcohol precipitation method, the molecular weight of the obtained hemicellulose component is small, the purity is not high, and the recovery rates of the cellulose, the hemicellulose and the lignin are not high.
Patent application CN108359026A discloses a method for preparing water-insoluble xylan, comprising the following steps: 1) taking 100 parts by weight of mildew-free and dry straw raw materials, putting into 600 parts by weight of clear water, soaking for 2 hours, removing free water by adopting a squeezer, soaking the straw raw materials again and squeezing to dry to obtain clean straw raw materials, and controlling the water content of the clean straw raw materials to be 50%; putting the cleaned straw raw material into 800-1400 parts by weight of 9% sodium hydroxide solution, mechanically grinding under alkaline conditions, carrying out centrifugal precipitation, and then carrying out solid-liquid separation to obtain centrifugal residues and extracted alkali liquor; washing the centrifugal residue twice with 6% sodium hydroxide solution for solid-liquid separation; 2) combining the extracted alkali liquor for 3 times, and performing xylan-alkali liquor separation by using an alkali-resistant ultrafiltration membrane with the molecular weight cutoff of more than 1000D, wherein the permeate is regenerated alkali liquor which can be used for extracting the next batch of raw materials; the trapped fluid is alkali solution of xylan, alkali solution of xylan is replaced and ultrafiltered for many times by dilute alkali water, after the water-insoluble xylan emulsion is separated out, the pH value of the water-insoluble xylan emulsion is adjusted to 8-13 by acid, the water-insoluble xylan emulsion is replaced and microfiltered by a microfilter device repeatedly adding diluted alkali water, and water-soluble substances in the water-insoluble xylan emulsion are fully washed to obtain xylan emulsion with water-soluble substances removed; 3) taking the xylan emulsion from which the water-soluble substances are removed, slowly adding a hydrogen peroxide solution while stirring, oxidizing and bleaching for 5-6h at 40-60 ℃, and washing the water-soluble substances through microfiltration to obtain milky xylan emulsion; and (3) carrying out spray drying on the milky xylan emulsion to obtain the grey white xylan powder. Wherein the pH value of the dilute alkaline water in the step 2) is 8-13. The microfiltration process of the step 2) can be replaced by high-speed centrifugation, and the centrifugal sediment xylan is collected. The water-insoluble xylan prepared by the method has the effects of promoting intestinal health, inhibiting starch decomposition and absorption, reducing serum cholesterol, reducing serum triglyceride, eliminating constipation, eliminating fatty liver and improving the processing performance of rice and flour foods.
Patent application CN111019015A discloses a method for preparing high purity water-insoluble xylan, comprising the following steps: (1) crushing, cleaning and dehydrating stems and leaves of gramineous plants without mildew, adding 5-15 times of sodium hydroxide or potassium hydroxide solution with the volume and the mass concentration of 3-20%, leaching for 2.5-3.5h at 60-90 ℃, carrying out solid-liquid separation, adding 5-15 times of sodium hydroxide or potassium hydroxide solution with the volume and the mass concentration of 3-20% into residues again, leaching for 2.5-3.5h at 60-90 ℃ until lignin high polymer in the raw materials is depolymerized and xylan is sufficiently deacetylated and dissolved into alkali liquor, finishing leaching, then carrying out solid-liquid separation, recovering and combining liquid phase parts obtained by two times of leaching, and clarifying to obtain xylan leaching alkali liquor; (2) carrying out dealkalization treatment on xylan extraction alkali liquor, recovering alkali in the xylan extraction alkali liquor, neutralizing residual alkali in the dealkalized extraction liquor with acid, and adjusting the pH value to 7-9 to obtain lignin-containing xylan suspension; (3) concentrating the xylan suspension, heating for dehydration and drying to obtain xylan xerogel; (4) crushing the xylan xerogel to obtain xylan gel powder, pre-swelling the xylan gel powder by using clear water, and then putting the xylan gel powder into flowing purified water for rinsing to remove lignin to obtain pure xylan gel; (5) and dehydrating and drying the pure xylan gel to obtain high-purity water-insoluble xylan, and concentrating and drying the rinsing liquid to obtain a lignin product. The dealkalization treatment in the step (2) can be electrodialysis, diffusion dialysis, ultrafiltration, nanofiltration or acid neutralization. The preparation method of the invention does not use organic solvent, effectively reduces the production cost, is easy to obtain high-purity xylan products, can recover high-purity lignin products, and has good economy, feasibility and production safety.
Patent applications CN108359026A and CN111019015A are both previous research results of the present inventors, but both have been mainly aimed at extracting water-insoluble xylan, and do not consider recycling cellulose, water-soluble xylan, and lignin, so that the utilization rate of lignocellulosic materials is low, and it is difficult to recycle water-soluble xylan and lignin in the preparation method, and the cost is high. In addition, the method for obtaining pure xylan by removing lignin through a membrane filtration method in patent application CN108359026A is high in cost, and large-scale industrial production of xylan is difficult to realize. Patent application CN111019015A mentions that the dealkalization method can be electrodialysis, which can better maintain the macromolecular structure of water-insoluble lignin, but the water-soluble xylan and lignin can not be recovered under this method.
In summary, due to the limitations of the level of the extraction and separation technology of the wood fiber material and the insufficient knowledge of the characteristics of the hemicellulose components, the utilization of the wood fiber material in the prior art is generally limited to the utilization of one or two components, and the utilization of the wood fiber material in the prior art is not concerned about the utilization of the characteristics of each component in the wood fiber material to achieve the separation and utilization of each component with high efficiency and low cost, so that the existing wood fiber material development and utilization industry has low comprehensive utilization rate, high cost, low added value of products and serious environmental pollution. Therefore, there is an urgent need for a method for efficiently extracting and separating and purifying components of lignocellulosic materials, particularly a method for separating water-soluble and water-insoluble components of xylan, without impairing the utility value and separation performance of the components.
Disclosure of Invention
The invention aims to provide a method for efficiently separating wood fiber materials to obtain high-purity components, which is used for extracting, separating and purifying the wood fiber materials on the basis of fully knowing the characteristics of hemicellulose components to realize the high-efficiency and low-cost separation and utilization of each component in the wood fiber materials, and has the advantages of high recovery rate, high purity and high utilization value of cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin.
A method for separating the wood fiber material to obtain each component of high purity with high efficiency, sequentially separating and extracting cellulose, water-insoluble xylan, water-soluble xylan, water-insoluble lignin from the natural wood fiber material, separating and recovering all the cellulose, hemicellulose and lignin in the natural wood fiber material, and preparing the product with high purity and high molecular weight, the steps are as follows:
(1) crushing natural wood fiber materials properly, putting the crushed materials into a sodium hydroxide solution or a potassium hydroxide solution with the mass fraction of 8-20%, and leaching for 0.5-4h, wherein the material-liquid ratio is 1: 8 to 12 ℃, and the leaching temperature is 80 to 120 ℃; after the leaching is finished, carrying out solid-liquid separation to obtain a solid phase and an extracting solution; washing the solid phase with 4-8% sodium hydroxide solution or potassium hydroxide solution for 1-3 times, and mixing the washing solution and the extracting solution to obtain a mixed solution A; and washing the solid phase with water to neutrality, and removing free liquid to obtain purified cellulose.
(2) Dealkalizing the mixed solution A by using an electrodialysis membrane, recovering alkali in the solution, adjusting the pH value of the dealkalized solution to 6-8 by using acid, performing centrifugal treatment by using a high-speed centrifuge, performing solid-liquid separation, washing the solid phase for 4-6 times by using water, and drying the solid phase to obtain water-insoluble xylan; and combining the washing liquid with the liquid phase obtained by centrifugal separation, and concentrating until the solid content is more than 15% to obtain a concentrated solution B containing lignin and water-soluble xylan.
(3) Adjusting pH of the concentrated solution B to 3-5 with acid, adding 2.5-3.5 times of 95% alcohol to precipitate water-soluble xylan, separating precipitate, washing with 50-80% alcohol repeatedly until the alcohol is colorless, removing free alcohol, and drying to obtain water-soluble xylan.
(4) And (3) mixing the supernatant separated after alcohol precipitation in the step (3) with a precipitation washing solution, adjusting the pH value of the solution to 6-8, recovering alcohol by using a high-efficiency distillation tower, neutralizing the mother liquor at the bottom of the distillation tower by using acid until the pH value is 3-5, and drying to obtain the water-insoluble lignin.
The acid is hydrochloric acid, sulfuric acid or acetic acid.
The solid-liquid separation mode in the step (1) is centrifugal separation, and the separation and precipitation mode in the step (3) is also centrifugal separation.
The natural wood fiber material is a mildew-free and dry natural wood fiber material, and comprises straw stalks such as wood, bamboo, corn stalk, wheat straw and straw, and plant raw materials such as corn cob and bagasse.
The crushing comprises any one or more of cutting, chopping, grinding, crushing, kneading, extruding and the like.
The invention has the beneficial effects that:
the method for separating the natural wood fiber material comprises the steps of sequentially extracting, separating and purifying cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin from the natural wood fiber material on the basis of fully knowing the characteristics of the water-soluble dietary fiber and the water-insoluble dietary fiber in a hemicellulose component, so that each component in the wood fiber material can be separated and utilized at high efficiency and low cost, the obtained cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin products have the characteristics of high recovery rate, high purity and high utilization value, and the xylan part is separated respectively to obtain high-purity water-insoluble xylan and water-soluble xylan, so that the application range of the xylan can be greatly widened. The method of the invention is used for separating components of the natural wood fiber material, and has good economy, feasibility, production safety and environmental friendliness.
In the method, xylan and lignin are dissolved from the natural wood fiber material by controlling the extraction time, temperature, alkali liquor concentration and the like, the xylan and the lignin keep larger molecular structures, and then cellulose is obtained by solid-liquid separation and purification. The dissolved xylan and lignin solution after the alkali liquor is leached is used for recycling alkali by electrodialysis, so that the macromolecular structures of xylan and lignin, especially the macromolecular structures of xylan, are protected from being damaged to the maximum extent while the alkali liquor is recycled. Then, the water-insoluble part in the xylan is easily precipitated in a solution with a specific pH value, and the precipitation can be accelerated under the high-speed centrifugation condition, and the solid-liquid separation can be easily carried out to separate out the water-insoluble xylan so as to obtain the water-insoluble xylan with a macromolecular structure; the recovery of water-insoluble xylan under aqueous phase conditions can greatly save the separation cost of the main part of xylan. The solution after the water-insoluble xylan is separated is a clear true solution, the solution containing lignin and water-soluble xylan is concentrated to a small volume, and then the remaining xylan is separated by an alcohol precipitation method, so that the cost of an alcohol precipitation solvent and the solvent recovery cost can be greatly saved, and the xylan precipitated by alcohol precipitation is water-soluble xylan and has the characteristic of water-soluble dietary fiber. The method realizes the preparation of high-purity water-soluble xylan, water-insoluble xylan and water-insoluble lignin with high efficiency and low cost, and the obtained components still retain macromolecular structures thereof, so that the maximum utilization value of the components is retained to the maximum extent, and the application range of the components is expanded. The method of the invention thoroughly solves the problems of high cost, resource waste, environmental pollution and the like in the development and utilization industry of the wood fiber material, and truly realizes the clean refining of the wood fiber material.
Drawings
FIG. 1 is a process flow diagram of the present invention for the complete separation of the components of the natural lignocellulosic material;
FIG. 2 is an HPLC plot of a water-soluble xylan acid hydrolysate;
FIG. 3 is an HPLC plot of water-insoluble xylan acid hydrolysate;
FIG. 4 is a molecular weight diagram of water-insoluble xylans;
FIG. 5 is a molecular weight diagram of water-insoluble lignin.
Detailed Description
In order to describe the present invention in more detail, the present invention will be further described with reference to the following examples.
Example 1
A method for efficiently separating wood fiber materials to obtain high-purity components comprises the following steps:
(1) crushing the mildew-free and dry corncobs, and then putting the crushed corncobs into a sodium hydroxide solution with the mass fraction of 10% to leach for 3 hours, wherein the material-liquid ratio is 1: 10, the leaching temperature is 90 ℃. After the leaching is finished, centrifuging by adopting a centrifugal machine, and then carrying out solid-liquid separation to obtain a solid phase and an extracting solution; washing the solid phase with 6% sodium hydroxide solution for 2 times, and performing solid-liquid separation after each washing; mixing the washing solution and the extracting solution to obtain a mixed solution A; and washing the solid phase with water to neutrality, and removing free liquid with a centrifugal machine to obtain purified cellulose.
(2) And (3) dealkalizing the mixed solution A by using an alkali-resistant electrodialysis membrane, recovering alkali in the solution, and realizing the regeneration and cyclic utilization of alkali liquor. And regulating the pH value of the mixed solution after dealkalization to 6 by using hydrochloric acid, performing centrifugal treatment by using a high-speed centrifuge, performing solid-liquid separation, washing the solid phase for 6 times by using water to remove water-soluble components, and drying the solid phase by adopting a spray drying mode to obtain water-insoluble xylan powder. And combining the washing liquid with the liquid phase obtained by centrifugal separation, and concentrating until the solid content is more than 15% to obtain a concentrated solution B containing lignin and water-soluble xylan.
(3) And (3) regulating the pH value of the concentrated solution B to 4 by using hydrochloric acid, adding 95% alcohol in an amount which is 3 times the volume of the concentrated solution B to carry out alcohol precipitation on the water-soluble xylan, separating out precipitates, repeatedly washing the precipitates by using 65% alcohol in volume concentration until the alcohol is colorless, finally removing free alcohol by using a centrifugal machine, and drying by using a spray drying mode to obtain water-soluble xylan powder.
(4) And (3) mixing the supernatant separated after alcohol precipitation in the step (3) with a precipitation washing solution, adjusting the pH value of the solution to 8, recovering alcohol by using a high-efficiency distillation tower, neutralizing the mother liquor at the bottom of the distillation tower by using hydrochloric acid until the pH value is 4, and concentrating and drying by adopting a centrifugal drying mode to obtain the water-insoluble lignin.
The enzymolysis rate of the cellulose prepared by the method is 95 percent, and the recovery rate is 98 percent; the purity of the water-insoluble xylan was 90%, and the recovery rate was 98%; the purity of the water-soluble xylan is 85 percent, and the recovery rate is 98 percent; the purity of the water-insoluble lignin was 99% and the recovery rate was 98%.
Example 2
A method for efficiently separating wood fiber materials to obtain high-purity components comprises the following steps:
(1) cutting, finely cutting and kneading mildew-free and dry bamboos, and then putting the bamboos into a sodium hydroxide solution with the mass fraction of 12% for leaching for 2 hours, wherein the material-liquid ratio is 1: 12, when the leaching temperature is 120 ℃, after the leaching is finished, centrifuging by adopting a centrifugal machine, and then carrying out solid-liquid separation to obtain a solid phase and an extracting solution; washing the solid phase with 6% sodium hydroxide solution for 2 times, and performing solid-liquid separation after each washing; mixing the washing solution and the extracting solution to obtain a mixed solution A; and washing the solid phase with water to neutrality, and removing free liquid with a centrifugal machine to obtain purified cellulose.
(2) And (3) dealkalizing the mixed solution A by using an alkali-resistant electrodialysis membrane, recovering alkali in the solution, and realizing the regeneration and cyclic utilization of alkali liquor. Adjusting pH of the dealkalized mixed solution to 6 with sulfuric acid, centrifuging with a high-speed centrifuge, performing solid-liquid separation, washing the solid phase with water for 6 times, and drying the solid phase by spray drying to obtain water-insoluble xylan powder. And combining the washing liquid with the liquid phase obtained by centrifugal separation, and concentrating until the solid content is more than 15% to obtain a concentrated solution B containing lignin and water-soluble xylan.
(3) Adjusting the pH value of the concentrated solution B to 5 by using sulfuric acid, adding 3 times of 95% alcohol by volume to carry out alcohol precipitation on the water-soluble xylan, separating out precipitates, repeatedly washing the precipitates by using 50% alcohol by volume until the alcohol is colorless, finally removing free alcohol by using a centrifugal machine, and drying by using a spray drying mode to obtain water-soluble xylan powder.
(4) And (3) mixing the supernatant separated after alcohol precipitation in the step (3) with a precipitation washing solution, adjusting the pH value of the solution to 8, recovering alcohol by using a high-efficiency distillation tower, neutralizing the mother liquor at the bottom of the distillation tower by using sulfuric acid until the pH value is 4, and concentrating and drying by adopting a centrifugal drying mode to obtain the water-insoluble lignin.
The enzymolysis rate of the cellulose prepared by the method is 97 percent, and the recovery rate is 98 percent; the purity of the water-insoluble xylan was 92% and the recovery rate was 96%; the purity of the water-soluble xylan is 89.2 percent, and the recovery rate is 97 percent; the purity of the water-insoluble lignin was 99.5%, and the recovery rate was 98%.
Example 3
A method for efficiently separating wood fiber materials to obtain high-purity components comprises the following steps:
(1) grinding the mildew-free and dry bagasse, and then putting the ground bagasse into a potassium hydroxide solution with the mass fraction of 8% to leach for 2 hours, wherein the material-liquid ratio is 1: 10, the leaching temperature is 100 ℃. After the leaching is finished, centrifuging by adopting a centrifugal machine, and then carrying out solid-liquid separation to obtain a solid phase and an extracting solution; washing the solid phase with 6% potassium hydroxide solution for 2 times, and performing solid-liquid separation after each washing; mixing the washing solution and the extracting solution to obtain a mixed solution A; and washing the solid phase with water to neutrality, and removing free liquid with a centrifugal machine to obtain purified cellulose.
(2) And (3) dealkalizing the mixed solution A by using an alkali-resistant electrodialysis membrane, recovering alkali in the solution, and realizing the regeneration and cyclic utilization of alkali liquor. Adjusting pH of the mixed solution to 6 with acetic acid, centrifuging with high speed centrifuge, separating solid and liquid, washing solid phase with water for 4 times, and spray drying to obtain water insoluble xylan powder. And combining the washing liquid with the liquid phase obtained by centrifugal separation, and concentrating until the solid content is more than 15% to obtain a concentrated solution B containing lignin and water-soluble xylan.
(3) Adjusting the pH value of the concentrated solution B to 4 with acetic acid, adding 3 times of 95% alcohol, precipitating with ethanol, separating out precipitate, repeatedly washing with 70% alcohol until the alcohol is colorless, removing free alcohol with centrifuge, and spray drying to obtain water soluble xylan powder.
(4) And (3) mixing the supernatant separated after alcohol precipitation in the step (3) with a precipitation washing solution, adjusting the pH value of the solution to 8, recovering alcohol by using a high-efficiency distillation tower, neutralizing the mother liquor at the bottom of the distillation tower by using acetic acid until the pH value is 3, and concentrating and drying by adopting a centrifugal drying mode to obtain the water-insoluble lignin.
The enzymolysis rate of the cellulose prepared by the method is 96 percent, and the recovery rate is 97 percent; the purity of the water-insoluble xylan was 87% and the recovery rate was 95%; the purity of the water-soluble xylan is 89%, and the recovery rate is 98%; the purity of the water-insoluble lignin was 98%, and the recovery rate was 98%.
The method for measuring the enzymolysis rate of the cellulose, the purity of the water-insoluble lignin, the purity of the water-soluble xylan and the purity of the water-insoluble xylan comprises the following steps:
1. the method for determining the enzymolysis rate of the cellulose comprises the following steps:
accurately weighing 2g of cellulose sample, adding 100mL of 0.1mol/L citric acid-trisodium citrate buffer solution (pH 4.8-5.0), adding 1mL of cellulase, shaking uniformly, placing in a 50 ℃ water bath for enzymolysis for 24h, taking out, centrifuging, placing the supernatant in a triangular flask for preservation, adding 50mL of 0.1mol/L citric acid-trisodium citrate buffer solution and 1mL of cellulase to the lower-layer precipitate, performing enzymolysis for 24h in the 50 ℃ water bath, finishing the enzymolysis, performing centrifugal separation again, washing the centrifuged precipitate for 5 times by using pure water, transferring into a weighed glass surface dish with the mass of M1, drying in an oven at 85 ℃ to constant weight, and taking out and weighing the weight of the centrifuged precipitate to be M2. The weight of the enzymolysis residue W = M2-M1.
The enzymolysis rate calculation formula is as follows: a =1-W/2
In the formula: a-the enzymolysis rate of the sample, the unit is gram per hundred grams (g/100 g); w represents the weight of the enzymolysis residue in grams.
2. The purity detection method of the water-insoluble lignin comprises the following steps:
accurately weighing 10g of water-insoluble lignin sample, placing the sample into a conical flask with a plug, adding 30mL of sulfuric acid with the volume concentration of 75%, reacting for 2h at 25 ℃, hydrolyzing the water-insoluble lignin into polysaccharide or monosaccharide, adding water to dilute until the concentration of the sulfuric acid is 3%, boiling and refluxing for 4h, further hydrolyzing the polysaccharide into the monosaccharide, standing, performing suction filtration, washing to neutrality, then moving the filter paper together with the residue into a drying oven, drying at 105 ℃ to constant weight, and weighing the water-insoluble lignin separately to obtain the weight of the water-insoluble lignin as w. The content of water-insoluble lignin = w/10.
3. The method for determining the purity of the water-insoluble xylan or the water-insoluble xylan comprises the following steps:
accurately weighing 1g of sample in a volume of 100mLIn a bottle, 0.6% H by volume concentration is added2SO4About 90mL of solution was sonicated to disperse the sample evenly in the solution. Placing the test tube into a sterilizing pot after plugging, hydrolyzing at 121 ℃ for 1H, taking out, cooling, and adding H with the volume concentration of 0.6%2SO4The solution was brought to 100 mL. Centrifuging the hydrolysate, diluting appropriate amount of supernatant by 5 times, taking 10mL, adding 0.8g of strong basic anion exchange resin, 0.4g of strong acidic cation exchange resin, and 0.02g of active carbon, shaking for 5min, and allowing the conductivity of the sample solution to decrease to 5 μ s/cm3Next, the solution was passed through a 0.22 μm aqueous microfiltration membrane to be measured.
Chromatographic conditions are as follows: a chromatographic column: transgenomic Ca2+Column (column length 250mm, inner diameter 4.6mm, particle size 5 μm), or equivalent chromatography column. Column temperature: 85 ℃. Mobile phase: ultrapure water. Flow rate: 0.5 mL/min. The amount of the sample was 20. mu.L.
The total glycan content in the sample was calculated according to the following formula:
in the formula: x-total glycan content in grams per hundred grams (g/100g) in the sample; m-xylose and arabinose content in mg per mL (mg/mL) in sample volume; 5-dilution factor; v-sample volumetric volume in milliliters (mL); m-sample mass in grams (g).
The water-soluble xylan and the water-insoluble xylan prepared in example 1 were subjected to acid hydrolysis and then detected by high performance liquid chromatography, and the HPLC profile of the obtained water-soluble xylan acid hydrolysate and the HPLC profile of the obtained water-insoluble xylan acid hydrolysate were shown in fig. 2 and 3, respectively.
The molecular weights of the water-insoluble xylan and the water-insoluble lignin prepared in example 1 were analyzed, and the molecular weight spectra of the water-insoluble xylan and the water-insoluble lignin are shown in fig. 4 and 5, respectively, from which it can be seen that the water-insoluble xylan and the water-insoluble lignin both maintain a relatively large molecular weight.
Claims (4)
1. A method for efficiently separating wood fiber materials to obtain high-purity components is characterized in that cellulose, water-insoluble xylan, water-soluble xylan and water-insoluble lignin are sequentially separated and extracted from natural wood fiber materials, all the cellulose, hemicellulose and lignin in the natural wood fiber materials are separated and recovered, and a high-purity high-molecular-weight product is prepared by the following steps:
(1) crushing natural wood fiber materials properly, putting the crushed materials into a sodium hydroxide solution or a potassium hydroxide solution with the mass fraction of 8-20%, and leaching for 0.5-4h, wherein the material-liquid ratio is 1: 8 to 12 ℃, and the leaching temperature is 80 to 120 ℃; after the leaching is finished, carrying out solid-liquid separation to obtain a solid phase and an extracting solution; washing the solid phase with 4-8% sodium hydroxide solution or potassium hydroxide solution for 1-3 times, and mixing the washing solution and the extracting solution to obtain a mixed solution A; then washing the solid phase with water to neutrality, and removing free liquid to obtain purified cellulose;
(2) dealkalizing the mixed solution A by using an electrodialysis membrane, recovering alkali in the solution, adjusting the pH value of the dealkalized solution to 6-8 by using acid, performing centrifugal treatment by using a high-speed centrifuge, performing solid-liquid separation, washing the solid phase for 4-6 times by using water, and drying the solid phase to obtain water-insoluble xylan; combining the washing liquid with the liquid phase obtained by centrifugal separation, and concentrating until the solid content is more than 15% to obtain a concentrated solution B containing lignin and water-soluble xylan;
(3) adjusting the pH value of the concentrated solution B to 3-5 with acid, adding 2.5-3.5 times of 95% alcohol to precipitate water-soluble xylan, separating the precipitate, washing with 50-80% alcohol repeatedly until the alcohol is colorless, removing free alcohol, and drying to obtain water-soluble xylan;
(4) and (3) mixing the supernatant separated after alcohol precipitation in the step (3) with a precipitation washing solution, adjusting the pH value of the solution to 6-8, recovering alcohol by using a high-efficiency distillation tower, neutralizing the mother liquor at the bottom of the distillation tower by using acid until the pH value is 3-5, and drying to obtain the water-insoluble lignin.
2. The method for separating lignocellulosic materials with high efficiency to obtain high purity of each component as claimed in claim 1, wherein the acid used is hydrochloric acid, sulfuric acid or acetic acid.
3. The method for separating the lignocellulosic materials with high purity according to claim 1, wherein the solid-liquid separation in step (1) is centrifugal separation, and the separation and precipitation in step (3) is centrifugal separation.
4. The method for efficiently separating lignocellulosic materials to obtain high purity fractions according to claim 1, wherein the natural lignocellulosic materials are non-mold, dried natural lignocellulosic materials including wood, bamboo, corn stover, wheat straw, rice straw, corn cobs, sugar cane bagasse.
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