CN112482069A - Method for preparing high-yield dissolving pulp by using eutectic solvent - Google Patents

Method for preparing high-yield dissolving pulp by using eutectic solvent Download PDF

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CN112482069A
CN112482069A CN202011327992.0A CN202011327992A CN112482069A CN 112482069 A CN112482069 A CN 112482069A CN 202011327992 A CN202011327992 A CN 202011327992A CN 112482069 A CN112482069 A CN 112482069A
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bleaching
cooking
eutectic solvent
stage
solid
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CN112482069B (en
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沈葵忠
陈远航
房桂干
梁龙
盘爱享
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Institute of Chemical Industry of Forest Products of CAF
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/20—Pulping cellulose-containing materials with organic solvents or in solvent environment
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)

Abstract

The invention discloses a method for preparing high-yield dissolving pulp by using a eutectic solvent, which comprises the following steps: mixing a eutectic solvent and wood fiber biomass, then pretreating under a heating condition, and carrying out solid-liquid separation on a mixture obtained by pretreatment to obtain a filtrate and a solid material; removing the solute in the filtrate to obtain a eutectic solvent recovery solution, wherein the eutectic solvent recovery solution can be used for pretreating the solid material again; washing and drying the solid matter to obtain a pretreated material; performing cooking treatment on the pretreated material to obtain cooking slurry; and (4) bleaching the cooking pulp, and washing and drying the solid after bleaching to obtain the dissolving pulp. According to the method, the wood fiber biomass is pretreated by using the eutectic solvent, so that the hemicellulose content and the lignin content in the dissolving pulp can be reduced, the use amount of medicines in the processes of stewing and bleaching is reduced, the eutectic solvent can be recycled, and the production cost is reduced.

Description

Method for preparing high-yield dissolving pulp by using eutectic solvent
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to a method for preparing high-yield dissolving pulp by using a eutectic solvent.
Background
Due to the excessive exploitation and use of non-renewable energy sources, the available resources on the earth are increasingly reduced, the renewable resources such as lignocellulosic biomass are attracting great attention as biofuel and chemical production raw materials, and the efficient separation of lignocellulosic biomass will become the key. Ionic liquids (non-flammable, thermally stable, and chemically stable), known as "green solvents", are an attractive solvent for isolating lignocellulosic biomass, but have serious drawbacks: the preparation is complex, the price is high, the toxicity is high, and the application development of the compound is limited. In recent years, eutectic solvents (DESs) have similar physicochemical properties to those of ionic liquids, and have the advantages of environmental protection, simple preparation, low cost, recoverability and the like, and are widely researched as substitutes for ionic liquids.
Dissolving pulp is high-purity refined chemical pulp which removes lignin and hemicellulose in the pulp making process and only keeps cellulose, and is mainly used for producing viscose rayon, nitrocellulose, acetate fiber, cellophane, carboxymethyl cellulose (CMC) and other products. The prior methods for preparing dissolving pulp comprise a sulfite method and a prehydrolysis sulfate method, and for broad-leaved wood with high content of hemicellulose, lignin and resin, such as eucalyptus, the prehydrolysis sulfate method is generally adopted, but the method also has the inevitable defects: the hydrothermal method has limited capability of removing hemicellulose, and can only remove the content of the hemicellulose in the biomass to a certain value, and after the value is exceeded, the cellulose in the biomass is greatly degraded, so that the yield of dissolving pulp is greatly reduced, and the yield of the dissolving pulp prepared by the method is generally 30-35%. Wukejia et al, reported in the thesis "state of the art of dissolving pulp production and progress of research [ J ] paper in China, 2011,030(008): 63-67": the content of alpha-cellulose in the first-class short fiber pulp is more than 89%, the whiteness is more than 80% ISO, and the pentosan content is less than 4%; the alpha-cellulose content of the second-grade short fiber pulp is more than 88 percent, the whiteness is more than 78 percent ISO, and the pentosan content is less than 4 percent. Fock reactivity characterizes the capacity and the degree of the pulp participating in chemical reaction, the higher the Fock reactivity is, the better the dissolving pulp performance is, and the Fock reactivity is only 40% at least for general hardwood dissolving pulp.
How to separate lignin and hemicellulose from wood fiber biomass with high efficiency to prepare high-yield dissolving pulp is a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a method for preparing high-yield dissolving pulp by using a eutectic solvent, so as to solve the problems of low yield, environmental pollution and the like of the dissolving pulp prepared by the traditional method.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for preparing high-yield dissolving pulp by using a eutectic solvent comprises the following steps:
(1) pretreating eucalyptus wood by using a eutectic solvent: mixing a eutectic solvent and wood fiber biomass, then pretreating under a heating condition, and carrying out solid-liquid separation on a mixture obtained by pretreatment to obtain a filtrate and a solid material; removing the solute in the filtrate to obtain a eutectic solvent recovery solution, wherein the eutectic solvent recovery solution can be used for pretreating the solid material again; washing and drying the solid matter to obtain a pretreated material; in order to improve the pretreatment effect, the step (1) can be repeated for 1 to 3 times. Preferably, the number of pretreatments is 2.
(2) And (3) cooking: performing cooking treatment on the pretreated material to obtain cooking slurry;
(3) bleaching: and (4) bleaching the cooking pulp, and washing and drying the solid after bleaching to obtain the dissolving pulp.
As a preferable technical scheme, in the step (1), the eutectic solvent is a mixed solution of lactic acid and choline chloride; the heating temperature is 80-160 deg.C, such as 80 deg.C, 100 deg.C, 110 deg.C, 120 deg.C or 160 deg.C; the time is 1-6h, such as 1h, 3h, 5h or 6 h. Further preferably, the heating temperature is 110 ℃ and the heating time is 3 hours.
As a preferable technical scheme, in the step (1), the method for removing the solute in the filtrate to obtain the eutectic solvent recovery liquid comprises the following steps: adding water into the filtrate, refrigerating, filtering to remove precipitated solid substances, evaporating and concentrating the filtrate, filtering and separating again when solid is precipitated in the evaporation and concentration process until no solid precipitate is precipitated, and continuously evaporating to remove water to obtain the eutectic solvent recovery solution.
Aiming at different dissolving pulp requirements, different bleaching processes are adopted in different cooking methods in the cooking treatment and bleaching treatment steps in the step (3) and the step (4). The invention provides two schemes, which are respectively as follows: the bleaching process combining the sulfate cooking with the D-E-P bleaching process and the bleaching process combining the two-stage oxygen-alkali cooking with the D-Ep-D bleaching process are respectively as follows:
the higher-quality dissolving pulp can be obtained by the sulfate cooking, and the cooking reagent adopted by the sulfate cooking contains sodium hydroxide and sodium sulfide, the vulcanization degree of the sodium hydroxide and the sodium sulfide is 15-20%, and the preferred vulcanization degree is 17%; the alkali amount is 14-24%, preferably 20-22%; the D-E-P bleaching process comprises D-stage chlorine dioxide bleaching, E-stage alkali bleaching and P-stage hydrogen peroxide bleaching. Further, the concentration of chlorine dioxide in the D-stage chlorine dioxide bleaching is 0.5-1%, the bleaching time is 1-2h, and the bleaching temperature is 60-80 ℃; preferably, the concentration of the chlorine dioxide is 0.9%, the bleaching time is 2 hours, and the bleaching temperature is 70 ℃. In the E-stage alkali bleaching, the concentration of sodium hydroxide is 0.1-0.4%, the bleaching time is 0.5-1.5h, and the bleaching temperature is 60-80 ℃; preferably, the sodium hydroxide concentration is 0.3%, the bleaching time is 1.h, and the bleaching temperature is 70 ℃. The hydrogen peroxide concentration in the P-stage hydrogen peroxide bleaching is 0.1-0.3%, the bleaching time is 0.5-1.5h, and the bleaching temperature is 60-80 ℃; preferably, the hydrogen peroxide concentration is 0.3%, the bleaching time is 1h, and the bleaching temperature is 70 ℃.
The two-stage oxygen-alkali cooking can obtain dissolving pulp with higher yield, and comprises two identical oxygen-alkali cooking steps, namely, oxygen is introduced into sodium hydroxide alkali liquor, the temperature in the oxygen-alkali cooking is 70-100 ℃, the time is 0.5-1h, the preferred temperature is 100 ℃, and the time is 1 h. The D-Ep-D bleaching process comprises D stage primary chlorine dioxide bleaching, Ep stage alkaline hydrogen peroxide bleaching and D stage secondary chlorine dioxide bleaching. Furthermore, the method of the D-stage primary chlorine dioxide bleaching and the D-stage secondary chlorine dioxide bleaching is the same, the concentration of the chlorine dioxide in the used bleaching reagent is 0.5-1%, the bleaching time is 1-2h, and the bleaching temperature is 60-80 ℃; preferably, the concentration of chlorine dioxide is 0.5%, the bleaching time is 1h, and the bleaching temperature is 70 ℃. In the Ep-section alkaline hydrogen peroxide bleaching, the concentration of hydrogen peroxide is 5-10%, the concentration of sodium hydroxide is 2-6%, the bleaching temperature is 70-100 ℃, and the bleaching time is 0.5-1.5 h; preferably, the hydrogen peroxide concentration is 8%, the sodium hydroxide concentration is 4%, the bleaching temperature is 95 ℃, and the bleaching time is 1 h.
The invention has the following beneficial effects:
according to the invention, the wood fiber biomass is pretreated by using the eutectic solvent composed of lactic acid and choline chloride, on one hand, the eutectic solvent has good solubility on lignin, can not dissolve cellulose, has good selectivity, and can reduce the content of lignin in dissolving pulp; in addition, the lactic acid/choline chloride has acidity, and can remove part of hemicellulose, reduce the using amount of medicines in the cooking and bleaching processes, and save the production cost; on the other hand, the eutectic solvent can be recycled, the waste of chemical reagents in the preparation process of dissolving pulp is reduced, and the utilization rate of medicines in the pulping process is increased.
The invention combines the eutectic solvent pretreatment with different cooking and bleaching processes to obtain dissolving pulp with different requirements. When the method is combined with the sulfate cooking and the D-E-P bleaching process, high-quality dissolving pulp with excellent Fock reactivity and higher yield can be prepared; when the method is matched with a two-stage oxygen-alkali cooking and D-Ep-D bleaching process, the high-yield dissolving pulp with the yield of more than 44 percent can be obtained.
Drawings
FIG. 1 is a flow chart of a process for preparing a dissolving slurry from a low eutectic solvent in example 1;
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the eucalyptus wood selected in the following examples is available from agricultural paper limited, Yu province in Hunan province.
The preparation method of the eutectic solvent used in the following examples was: 259.7g of lactic acid and 40.3g of choline chloride were weighed out in a molar ratio of 10: 1, and reacting at 60 ℃ and 200rpm for 2 hours to form a uniform transparent liquid, which is reserved as a eutectic solvent.
Example 1
(1) Pretreatment: adding 300.0G eutectic solvent into 30.0G oven dried eucalyptus wood, placing in 500mL high pressure reaction kettle, heating to 110 deg.C, reacting for 3h, centrifuging the mixture at 10000rpm for 10min, and adding G2Filtering with a filter element of a marmite, alternately washing the filtered solid with ethanol and water until the liquid is colorless, and placing the solid in an oven at 40 ℃ for air drying to obtain a solid material. Adding 3.0kg deionized water into the filtrate, refrigerating in 0-4 deg.C refrigerator overnight, and collecting the solid3The filter is vacuumized and filtered. Heating the filtrate at 60 deg.C under 0.6MPa, evaporating until solid is separated out, and adding G3Filtering by a filter, repeating the operation until no solid is precipitated, and continuously heating until no water exists to obtain a eutectic solvent recovery liquid which can be recycled.
Carrying out primary pretreatment on the solid material obtained by the pretreatment by using the eutectic solvent recovery liquid, wherein the steps are the same as the steps of the method, so as to obtain a pretreated material;
(2) and (3) cooking: and (3) carrying out sulfate cooking treatment on the pretreated material, wherein the adopted cooking reagent contains sodium hydroxide and sodium sulfide, the concentration of the slurry is 20%, the temperature is kept at 130 ℃ for 0.5h, and then the pretreated material is heated to 160 ℃ to react for 2h for cooking. And (3) filtering the cooked material in a Buchner funnel to obtain solid residues, washing the object residues to be neutral by using deionized water, and placing the object residues in an oven at 40 ℃ for air drying to obtain the cooked slurry.
(3) Bleaching: and bleaching the cooked pulp by adopting a DEP bleaching process. The D-E-P bleaching process comprises D-stage chlorine dioxide bleaching, E-stage alkali bleaching and P-stage hydrogen peroxide bleaching. Wherein: the concentration of the pulp in the D-stage chlorine dioxide bleaching is 10 percent; ClO in bleaching agents2The concentration is 0.9 percent, the bleaching temperature is 70 ℃, and the bleaching time is 2 hours; in the E-stage alkali bleaching, the concentration of the pulp is 10 percent, the concentration of NaOH in a bleaching reagent is 0.3 percent, the bleaching temperature is 70 ℃, and the bleaching time is 1 h; the concentration of the pulp in the P-stage hydrogen peroxide bleaching is 10 percent; h in bleaching agents2O2Concentration 0.3%, MgSO4The concentration is 0.05%, Na2SiO4The concentration is 3%; the bleaching temperature is 70 ℃, and the bleaching time is 1 h. And (3) washing the bleached eucalyptus pulp to be neutral, and placing the eucalyptus pulp in a drying oven with the temperature of 40 ℃ for air drying to prepare dissolving pulp.
The performance indexes of the prepared dissolving pulp are as follows: the total yield is 37.0 percent, the xylan content is 1.7 percent, the glucan content is 88.0 percent, the lignin content is 0.6 percent, the alpha-cellulose content is 94.0 percent, the whiteness is 89.0 percent ISO, the copper ethylene diamine intrinsic viscosity is 396.3mL/g, the polymerization degree is 540, and the Fock reactivity is 98.9 percent. Can meet the requirements of first-class short fiber pulp, and Fock reactivity reaches up to 98.9 percent.
Example 2
(1) Pretreatment: the same procedure as in example 1.
(2) And (3) cooking: the pre-treated material is steamed and boiled by two-stage oxygen-alkali method, the method is: mixing the pretreated material and sodium hydroxide liquid in a 500mL high-pressure reaction kettle, adding 0.05% MgSO 2, wherein the slurry concentration is 12% and the sodium hydroxide liquid concentration is 3%4Introducing 0.5MPa oxygen into the high-pressure reaction kettle (by taking the concentration of sodium hydroxide liquid as a reference), preserving the temperature at 100 ℃ for 1h, and performing primary oxygen-alkali cooking; washing the solid after first-stage oxygen-alkali cooking to be neutral by using deionized water, and placing the solid in an oven at 40 ℃ for air drying to obtain an air-dried solid; performing two-stage oxygen-alkali cooking on the air-dried solid by adopting the same process as the one-stage oxygen-alkali cooking; two-stage oxygen alkaliAnd (3) filtering the material subjected to the cooking in the method in a Buchner funnel to obtain solid residues, washing the solid residues with deionized water to be neutral, and placing the solid residues in an oven at 40 ℃ for air drying to obtain the cooking slurry.
(3) Bleaching:
and bleaching the cooking pulp by adopting a D-Ep-D bleaching process. The D-Ep-D bleaching process comprises D stage primary chlorine dioxide bleaching, Ep stage alkaline hydrogen peroxide bleaching and D stage secondary chlorine dioxide bleaching. The concentration of the pulp in the D-stage primary chlorine dioxide bleaching is 10 percent, and the pulp is ClO2The concentration is 0.9 percent, the bleaching temperature is 70 ℃, and the bleaching time is 2 hours; h in bleaching agent for Ep-stage alkaline hydrogen peroxide bleaching2O2The concentration is 8%, the NaOH concentration is 4%, and Na2SiO4The concentration is 2 percent, and the concentration of DTPA is 0.5 percent; the concentration of the pulp is 10 percent, the bleaching temperature is 95 ℃, and the bleaching time is 1 h; finally, D-stage secondary chlorine dioxide bleaching is carried out, wherein the concentration of chlorine dioxide in the used bleaching reagent is 0.5%; the concentration of the pulp is 10 percent, the bleaching temperature is 70 ℃, and the bleaching time is 1 h. And (3) washing the bleached eucalyptus pulp to be neutral, and placing the eucalyptus pulp in a drying oven with the temperature of 40 ℃ for air drying to prepare dissolving pulp.
The performance indexes of the prepared dissolving pulp are as follows: the total yield is 44.4 percent, the xylan content is 2.1 percent, the glucan content is 84.6 percent, the lignin content is 3.4 percent, the alpha-cellulose content is 88.0 percent, the whiteness is 88.5 percent ISO, the copper ethylene diamine intrinsic viscosity is 461.0mL/g, the polymerization degree is 639, and the Fock reactivity is 96.8 percent; the requirements of second-grade short fiber pulp are met.
Comparative example 1
The method comprises the following steps of pretreating eucalyptus wood by a conventional hydrothermal method, and then cooking and bleaching the eucalyptus wood, wherein the conventional hydrothermal method comprises the following steps:
(1) pretreatment: adding 210.0g of water into 30.0g of oven-dried eucalyptus, placing in a 500mL high-pressure reaction kettle, heating to 160 ℃, reacting for 2h, filtering the mixture by using a Buchner funnel after the reaction is finished, alternately washing the filtered solid with water until the liquid is colorless, and placing in a 40 ℃ oven for air drying to obtain a solid material.
(2) And (3) cooking: the same procedure as in example 1.
(3) Bleaching: the same procedure as in example 1.
The performance indexes of the prepared dissolving pulp are as follows: the total yield is 38.6 percent, the xylan content is 3.3 percent, the glucan content is 83.7 percent, the lignin content is 0.6 percent, the alpha-cellulose content is 89.8 percent, the whiteness is 88.0 percent ISO, the copper ethylene diamine intrinsic viscosity is 436.2mL/g, the polymerization degree is 601, and the Fock reactivity is 61.0 percent. The requirements of first-class short fiber dissolving pulp are met, but the Fock reactivity is only 61.0 percent.
Comparative example 2
(1) Without pretreatment
(2) And (3) cooking: the same procedure as in example 1.
(3) Bleaching: the same procedure as in example 1.
The performance indexes of the prepared dissolving pulp are as follows: the total yield is 41.0 percent, the xylan content is 17.8 percent, the glucan content is 78.0 percent, the lignin content is 0.5 percent, the alpha-cellulose content is 86.3 percent, the whiteness is 85.7 percent ISO, the copper ethylene diamine intrinsic viscosity is 702.0mL/g, the polymerization degree is 1016, and the Fock reactivity is 34.7 percent. The requirements of short fiber dissolving pulp grade are not met.
Comparative example 3
The method comprises the following steps of pretreating eucalyptus by adopting a conventional dilute acid hydrolysis method, and then cooking and bleaching the eucalyptus, wherein the steps are as follows:
(1) pretreatment: adding 210.0g of dilute sulfuric acid solution with the pH value of 2 into 30.0g of oven-dried eucalyptus, placing the mixture into a 500mL high-pressure reaction kettle, heating to 160 ℃, reacting for 2 hours, filtering the mixture by using a Buchner funnel after the reaction is finished, alternately washing the filtered solid by using water until the liquid is colorless, and placing the mixture into an oven at 40 ℃ for air drying to obtain a solid material.
(2) And (3) cooking: the same procedure as in example 1.
(3) Bleaching: the same procedure as in example 1.
The performance indexes of the prepared dissolving pulp are as follows: the total yield is 29.8 percent, the xylan content is 2.62 percent, the glucan content is 88.7 percent, the lignin content is 0.5 percent, the alpha-cellulose content is 92.2 percent, the whiteness is 88.3 percent ISO, the copper ethylene diamine intrinsic viscosity is 382.2mL/g, the polymerization degree is 519, and the Fock reactivity is 90.0 percent. The requirements of first-class short fiber pulp are met, but the yield is low.

Claims (9)

1. A method for preparing high-yield dissolving pulp by using a eutectic solvent is characterized by comprising the following steps: the method comprises the following steps:
(1) pretreatment: mixing a eutectic solvent and wood fiber biomass, then pretreating under a heating condition, and carrying out solid-liquid separation on a mixture obtained by pretreatment to obtain a filtrate and a solid material; removing the solute in the filtrate to obtain a eutectic solvent recovery solution, wherein the eutectic solvent recovery solution can be used for pretreating the solid material again; washing and drying the solid matter to obtain a pretreated material;
(2) and (3) cooking: performing cooking treatment on the pretreated material to obtain cooking slurry;
(3) bleaching: and (4) bleaching the cooking pulp, and washing and drying the solid after bleaching to obtain the dissolving pulp.
2. The method of claim 1, wherein: in the step (1), the pretreatment of the wood fiber biomass by the eutectic solvent is repeated for 1 to 3 times.
3. The method of claim 1, wherein: in the step (1), the eutectic solvent is a mixed solution of lactic acid and choline chloride; the heating temperature is 110 ℃ and the heating time is 3 h.
4. The method of claim 1, wherein: in the step (1), the method for removing the solute in the filtrate to obtain the eutectic solvent recovery liquid comprises the following steps: adding water into the filtrate, refrigerating, filtering to remove precipitated solid substances, evaporating and concentrating the filtrate, filtering and separating again when solid is precipitated in the evaporation and concentration process until no solid precipitate is precipitated, and continuously evaporating to remove water to obtain the eutectic solvent recovery solution.
5. The method of claim 1, wherein: the cooking treatment is sulfate cooking, and the adopted cooking reagent contains sodium hydroxide and sodium sulfide, the degree of vulcanization is 15-20%, and the alkali content is 14-24%; the bleaching treatment is a D-E-P bleaching process, which comprises D-stage chlorine dioxide bleaching, E-stage alkali bleaching and P-stage hydrogen peroxide bleaching.
6. The method of claim 5, wherein: the concentration of the chlorine dioxide in the D-stage chlorine dioxide bleaching is 0.5-1%, the bleaching time is 1-2h, and the bleaching temperature is 60-80 ℃; in the E-stage alkali bleaching, the concentration of sodium hydroxide is 0.1-0.4%, the bleaching time is 0.5-1.5h, and the bleaching temperature is 60-80 ℃; the hydrogen peroxide concentration in the P-stage hydrogen peroxide bleaching is 0.1-0.3%, the bleaching time is 0.5-1.5h, and the bleaching temperature is 60-80 ℃.
7. The method of claim 1, wherein: the cooking treatment is two-stage oxygen-alkali cooking, and comprises two identical oxygen-alkali cooking steps, namely introducing oxygen into sodium hydroxide alkali liquor, wherein the temperature in the oxygen-alkali cooking is 70-100 ℃, and the time is 0.5-1 h; the bleaching treatment is a D-Ep-D bleaching process, which comprises D-stage primary chlorine dioxide bleaching, Ep-stage alkaline hydrogen peroxide bleaching and D-stage secondary chlorine dioxide bleaching.
8. The method of claim 7, wherein: the method of the D-stage primary chlorine dioxide bleaching and the D-stage secondary chlorine dioxide bleaching is the same, the concentration of the chlorine dioxide in the used bleaching agent is 0.5-1%, the bleaching time is 1-2h, and the bleaching temperature is 60-80 ℃; the bleaching reagent used in the Ep-section alkaline hydrogen peroxide bleaching has the hydrogen peroxide concentration of 5-10%, the sodium hydroxide concentration of 2-6%, the bleaching temperature of 70-100 ℃ and the bleaching time of 0.5-1.5 h.
9. The method of any one of claims 1-8, wherein: the lignocellulosic biomass is eucalyptus.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102587179A (en) * 2012-03-08 2012-07-18 山东太阳纸业股份有限公司 Preparation process for eucalyptus dissolving pulp
CN104153229A (en) * 2014-07-16 2014-11-19 华南理工大学 Preparation method of bamboo dissolving pulp
CN108660837A (en) * 2018-05-29 2018-10-16 南京林业大学 The separation method of three component of cellulose, hemicellulose and lignin in one plant fiber raw material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102587179A (en) * 2012-03-08 2012-07-18 山东太阳纸业股份有限公司 Preparation process for eucalyptus dissolving pulp
CN104153229A (en) * 2014-07-16 2014-11-19 华南理工大学 Preparation method of bamboo dissolving pulp
CN108660837A (en) * 2018-05-29 2018-10-16 南京林业大学 The separation method of three component of cellulose, hemicellulose and lignin in one plant fiber raw material

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