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CN-122011425-A - Extraction and purification method and application of high-purity high-activity lignin

CN122011425ACN 122011425 ACN122011425 ACN 122011425ACN-122011425-A

Abstract

The invention provides a method for extracting and purifying high-purity high-activity lignin and application thereof, belonging to the technical field of lignin extraction. The method provided by the invention can efficiently and mildly separate high-purity lignin from the wood fiber raw material, the lignin product has low impurity content, the active group remains intact, and excellent dispersibility and reactivity are shown. The obtained lignin can be directly used as a high-performance additive or a reaction monomer, is used for preparing composite materials such as epoxy resin, phenolic resin and the like, can obviously improve the thermo-mechanical property, mechanical strength and thermal stability of the materials, expands the application prospect of the lignin in the field of high-added-value materials, has mild whole process conditions, and has good environmental benefit and industrialization potential due to green and recyclable solvent.

Inventors

  • SHEN YUHONG
  • SHEN SHENG

Assignees

  • 廊坊天辰化工有限公司

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. The preparation method of the high-purity lignin is characterized by comprising the following steps of: S1, preprocessing a wood fiber raw material by adopting an ethanol water solution; S2, performing enzymolysis treatment on the pretreated solid by using a complex enzyme system containing feruloyl esterase, xylanase, cellulase and glucose oxidase; s3, performing solid-liquid separation on the pulp after enzymolysis to obtain supernatant containing lignin; S4, adding polyethylene glycol and sodium citrate into the supernatant to form a mixed system, phase-separating the mixed system by adjusting the pH value of the mixed system, collecting an upper phase rich in lignin, mixing the upper phase with a blank lower phase solution, adjusting the pH value for back extraction, and finally separating to obtain a purified lignin upper phase; s5, carrying out acid precipitation treatment on the upper phase of the purified lignin, collecting precipitates and drying to obtain the high-purity lignin.
  2. 2. The method according to claim 1, wherein in step S1, the volume concentration of the aqueous ethanol solution is 30% to 50%, the pretreatment temperature is 85 ℃ to 100 ℃, the pretreatment time is 45 minutes to 90 minutes, and the liquid-solid ratio of the aqueous ethanol solution to the lignocellulosic feedstock is 10:1 to 20:1 mL/g.
  3. 3. The preparation method according to claim 1, wherein in the step S2, the complex enzyme system is added in an amount of 5 to 15U, 300 to 800U, 3 to 8 FPU and 30 to 80U of feruloyl esterase, xylanase and glucose oxidase per gram of pretreated solid; the pH value of the enzymolysis treatment is 4.8-5.2, the temperature is 48-55 ℃, and the reaction time is 12-24 hours.
  4. 4. The method according to claim 3, wherein in step S2, the concentration of hydrogen peroxide in the reaction system is monitored and maintained at 0.1 to 1.0 mM during the enzymolysis treatment; in step S2, after the enzymolysis treatment is completed, the method further comprises a step of heating the slurry to 75 ℃ to 85 ℃ and maintaining the slurry for 5 to 15 minutes to inactivate the enzyme.
  5. 5. The method according to claim 1, wherein in the step S4, the polyethylene glycol is PEG4000 added in an amount of 0.3 to 0.5 times the volume of the supernatant, and the sodium citrate is added in an amount of 0.2 to 0.4 times the volume of the supernatant; in the step S4, the mixed system is subjected to first phase separation by adjusting the pH value to 4.4 to 4.6, a first upper phase is obtained through separation, the first upper phase and the blank lower phase solution are mixed in the back extraction step, the pH value is adjusted to 4.2 to 4.4, the second phase separation is carried out, and the volume of the blank lower phase solution is 40 to 60 percent of the volume of the first upper phase.
  6. 6. The preparation method according to claim 1, wherein in step S5, 1 to 5 volumes of water are added to the purified lignin upper phase for dilution, followed by adjusting pH to 2.0 to 3.0, and standing for 1 to 4 hours for lignin precipitation.
  7. 7. A high purity lignin, characterized in that it is prepared by the preparation method according to any one of claims 1 to 6.
  8. 8. Use of the high purity lignin according to claim 7 for the preparation of polymeric material modifiers, surfactants, dispersants or carbon material precursors.
  9. 9. An epoxy resin composite comprising the high purity lignin of claim 7 and an epoxy resin.
  10. 10. The epoxy resin composite of claim 9, wherein the high purity lignin is present in the composite in an amount of 1% to 10% by mass of the epoxy resin prepolymer; The preparation method of the epoxy resin composite material comprises the steps of dispersing the high-purity lignin in a solvent, mixing the lignin with an epoxy resin prepolymer, removing the solvent, and then adding a curing agent for curing.

Description

Extraction and purification method and application of high-purity high-activity lignin Technical Field The invention relates to the technical field of lignin extraction, in particular to a method for extracting and purifying high-purity high-activity lignin and application thereof. Background Lignin is the second largest natural high molecular polymer with reserves next to cellulose in nature, widely existing in the cell walls of plants, and forms the basic skeleton of lignocellulosic raw materials together with cellulose and hemicellulose. The compound three-dimensional network polymer is formed by connecting a phenylpropane unit through an ether bond and a carbon-carbon bond, and contains rich active functional groups such as phenolic hydroxyl, alcoholic hydroxyl, methoxy and the like. However, lignin is tightly crosslinked with carbohydrates in its natural state and is difficult to separate. The main lignin sources in the industry today are byproducts of the pulping and papermaking industry, such as kraft lignin and sulfonated lignin. These conventional methods generally employ severe conditions of strong alkali, strong acid or high temperature and high pressure, which cause serious condensation, degradation and chemical structure change of lignin during separation, and have wide molecular weight distribution, high impurity (such as sugar and ash) content and large loss of active groups. The obtained lignin product has low chemical reaction activity, poor uniformity and deep color, can be used as cheap fuel, and is difficult to meet the strict requirements of high-performance material synthesis on raw material purity, structural integrity and reaction activity. Although some research has been devoted to developing milder separation techniques, such as organic solvent processes, ionic liquid processes, enzymatic processes, etc., it is often difficult to achieve a good balance between separation efficiency, product purity, structural protection, and process costs and complexity, limiting its practical application. Therefore, development of a separation and purification technology capable of efficiently, cleanly and inexpensively obtaining lignin with high purity and high reactivity is a key to realizing high-value utilization of lignin resources. Disclosure of Invention The invention aims to provide a method for extracting and purifying high-purity high-activity lignin and application thereof, and solves the problems of low product purity, serious structural damage, complex process, unfriendly environment and difficulty in being used in the field of high-performance materials in the existing lignin extraction method. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of high-purity lignin, which comprises the following steps: S1, preprocessing a wood fiber raw material by adopting an ethanol water solution; S2, performing enzymolysis treatment on the pretreated solid by using a complex enzyme system containing feruloyl esterase, xylanase, cellulase and glucose oxidase; s3, performing solid-liquid separation on the pulp after enzymolysis to obtain supernatant containing lignin; S4, adding polyethylene glycol and sodium citrate into the supernatant to form a mixed system, phase-separating the mixed system by adjusting the pH value of the mixed system, collecting an upper phase rich in lignin, mixing the upper phase with a blank lower phase solution, adjusting the pH value for back extraction, and finally separating to obtain a purified lignin upper phase; s5, carrying out acid precipitation treatment on the upper phase of the purified lignin, collecting precipitates and drying to obtain the high-purity lignin. Preferably, in step S1, the volume concentration of the aqueous ethanol solution is 30% to 50%, the pretreatment temperature is 85 ℃ to 100 ℃, the pretreatment time is 45 minutes to 90 minutes, and the liquid-solid ratio of the aqueous ethanol solution to the lignocellulosic feedstock is 10:1 to 20:1 mL/g. Preferably, in the step S2, the addition amount of the complex enzyme system is 5 to 15U, 300 to 800U, 3 to 8 FPU and 30 to 80U of feruloyl esterase and xylanase per gram of pretreated solid; the pH value of the enzymolysis treatment is 4.8-5.2, the temperature is 48-55 ℃, and the reaction time is 12-24 hours. Preferably, in step S2, the concentration of hydrogen peroxide in the reaction system is monitored and maintained at 0.1 to 1.0 mM during the enzymolysis treatment; in step S2, after the enzymolysis treatment is completed, the method further comprises a step of heating the slurry to 75 ℃ to 85 ℃ and maintaining the slurry for 5 to 15 minutes to inactivate the enzyme. Preferably, in the step S4, the polyethylene glycol is PEG4000, and the addition amount of the polyethylene glycol is 0.3 to 0.5 times of the volume of the supernatant, and the addition amount of the sodium citrate is 0.2 to 0.4 times o