CN110656526A - Method for preparing nano-cellulose from fiber slurry - Google Patents
Method for preparing nano-cellulose from fiber slurry Download PDFInfo
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- CN110656526A CN110656526A CN201910949689.5A CN201910949689A CN110656526A CN 110656526 A CN110656526 A CN 110656526A CN 201910949689 A CN201910949689 A CN 201910949689A CN 110656526 A CN110656526 A CN 110656526A
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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
- 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
- D21C9/001—Modification of pulp properties
- D21C9/007—Modification of pulp properties by mechanical or physical means
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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
- 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
- D21C9/001—Modification of pulp properties
- D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
- D21C9/005—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives organic compounds
Abstract
The invention discloses a method for preparing nano-cellulose by fiber slurry, relating to the technical field of cellulose preparation; hydrolyzing the fiber slurry with acid to obtain fiber acid hydrolysate, neutralizing the fiber acid hydrolysate to neutrality to obtain total fiber suspension, adding strong electrolyte solvent which is dissolved in water and can enable the nano-cellulose to be reversibly agglomerated, dispersing uniformly, centrifuging, taking precipitate to be re-dispersed into water, repeatedly adding the strong electrolyte solvent, dispersing the precipitate into a detergent after a plurality of centrifugation steps after uniform dispersion, centrifuging, drying the precipitate to obtain fiber powder, transporting the powder to a use place, dispersing the powder into water, and preparing the nano-cellulose by mechanical treatment methods such as homogenization or ultrasonic crushing; the method greatly simplifies the preparation process, obviously shortens the preparation time, obviously improves the yield of the product nano-cellulose, and can greatly facilitate the transportation and the use of the nano-cellulose in the subsequent application.
Description
Technical Field
The invention discloses a method for preparing nano-cellulose from fiber slurry, and relates to the technical field of cellulose preparation.
Background
The nano-cellulose has the characteristics of high Young modulus, high tensile strength, high crystallinity, biodegradability, high specific surface area, high reactivity, nano-size effect, quantum tunneling effect and the like, so that the nano-cellulose has a very wide application prospect in many industries. However, the large-scale industrial preparation of the current nano-cellulose is not mature, and the nano-cellulose can be obtained only by dialysis with long time consumption and high water consumption of 2-3 weeks in the process of preparing the nano-cellulose by acid hydrolysis of fiber pulp in the existing industrial preparation, so that the price is high, and the nano-cellulose is difficult to be practically and widely applied in various industries.
On the basis of the existing method for preparing nano cellulose by acid hydrolysis of fiber pulp, a strengthening electrolyte reagent is added into the fiber pulp neutralized after acid hydrolysis to increase the content of the strong electrolyte in a fiber neutralizing solution, impurity ions in the neutralizing solution are removed by multiple times of centrifugation on the premise of retaining fiber components, the added strengthening electrolyte reagent is removed, and pure and dry fiber pulp can be prepared after drying. The method greatly simplifies the preparation process, obviously shortens the preparation time, obviously improves the yield of the product nano-cellulose, and can greatly facilitate the transportation and the use of the nano-cellulose in the subsequent application.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the method for preparing the nano-cellulose by the fiber slurry, which greatly simplifies the preparation process, obviously shortens the preparation time, obviously improves the yield of the nano-cellulose product, and can greatly facilitate the transportation and the use of the nano-cellulose in the subsequent application.
The specific scheme provided by the invention is as follows:
a method for preparing nano cellulose by fiber slurry comprises the following steps: hydrolyzing the fiber slurry with acid to obtain fiber acid hydrolysate, neutralizing the fiber acid hydrolysate to neutrality to obtain total fiber suspension, adding strong electrolyte solvent capable of dissolving in water and making the nano cellulose aggregate reversibly, dispersing homogeneously, centrifuging, re-dispersing the precipitate in water, adding the strong electrolyte solvent repeatedly, dispersing the precipitate in detergent after several times of centrifugation, centrifuging, drying the precipitate to obtain fiber powder, dispersing in water, and mechanically treating to obtain the nano cellulose.
In the method, the fiber acid hydrolysate is diluted and centrifuged for a plurality of times until the fibers can not be completely precipitated, and then neutralized to be neutral.
The rotating speed of the centrifugation in the method is 3000-9000 r/min.
In the method, the mass of the strong electrolyte solvent added is 0.2-6.0 wt% of the mass of the total fiber suspension.
The strong electrolyte solvent added in the method is any one of potassium acetate, lithium chloride and potassium propionate.
In the method, the detergent is any one of ethanol, methanol, acetone, tetrahydrofuran and glycol.
In the method, a strong electrolyte solvent is potassium acetate, and a detergent is any one of ethanol, methanol, tetrahydrofuran and glycol;
the strong electrolyte solvent is lithium chloride, and the detergent is ethanol or acetone;
the strong electrolyte solvent is potassium propionate, and the detergent is ethanol.
In the method, a strong electrolyte solvent is repeatedly added, and the centrifugation frequency after uniform dispersion is 2-4 times.
In the method, the fiber pulp is hydrolyzed by any one of concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid and mixed acid of sulfuric acid and acetic acid to obtain the fiber acid hydrolysate.
The method comprises the step of drying the precipitate in one or more combined modes of room temperature air drying, oven drying, vacuum drying or freeze drying.
In the method, after the fiber powder is dispersed in water, the nano-cellulose is obtained by homogenizing the fiber powder by using a high-pressure homogenizer with the pressure of 10000-25000psi or is obtained by dispersing the fiber powder by using a cell crusher with the power of more than 500W.
The alkali used for neutralizing the fiber acid hydrolysate can be NaOH, KOH or other alkali and the like.
The nano-cellulose prepared from the fiber slurry is obtained by the method for preparing the nano-cellulose from the fiber slurry.
The nano-cellulose prepared by the fiber slurry can be applied to medical and paper industry, composite material made of inorganic substances, food additive and the like, and the application of the nano-cellulose can be realized by the conventional method.
The invention has the advantages that:
the invention provides a method for preparing nano-cellulose by fiber pulp, which greatly shortens the preparation time of nano-cellulose, shortens the 2-3 weeks required by the existing nano-cellulose preparation to be within 12h, avoids the water change dialysis process of 2-3 times per day for 2-3 weeks, greatly reduces the consumption of high-purity water and expensive dialysis membranes, can prepare dry fiber powder by adopting the method, increases the convenience of transportation, greatly reduces the concentration cost and the transportation cost of the nano-cellulose, can add different amounts of deionized water into the fiber powder according to the requirements, directly prepares nano-cellulose suspension with required concentration, is not limited by the concentration of random nano-cellulose suspension generated under the original preparation condition, and improves the yield of the nano-cellulose compared with the existing method, the method is very suitable for industrial preparation of the nano-cellulose, and has very wide application prospect.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
Detailed Description
The invention provides a method for preparing nano-cellulose from fiber pulp, which comprises the steps of hydrolyzing fiber pulp with acid to obtain fiber acid hydrolysate, neutralizing the fiber acid hydrolysate to be neutral to obtain total fiber suspension, adding potassium acetate, dispersing uniformly, centrifuging, taking precipitate, re-dispersing the precipitate into water, repeatedly adding potassium acetate, dispersing the precipitate into ethanol after the steps of dispersing uniformly and centrifuging for multiple times, centrifuging, drying the precipitate to obtain fiber powder, dispersing the fiber powder into water, and preparing the nano-cellulose by homogenizing or ultrasonic crushing.
And simultaneously provides the nano-cellulose prepared from the fiber slurry obtained by the method for preparing the nano-cellulose from the fiber slurry.
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Example 1
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 64 percent,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 3000 rpm for 10 min, collecting precipitate, repeating the dilution and centrifugation, collecting all the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium acetate into the neutralized solution, stirring, centrifuging at 3000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 3000 rpm for 10 min with a centrifuge, drying the obtained precipitate with a vacuum drying oven at 40 deg.C to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 25000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 50.3%, the average length is 96nm, the Zeta potential is-112 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (twice centrifugation), neutralization and dialysis is 21.6 percent by using the same acid hydrolysis conditions.
Example 2
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysis liquid by 8 times, centrifuging for 12 minutes at the centrifugal speed of 5000 r/min, taking the precipitate, repeating the dilution and centrifugation processes, finding that the fiber acid hydrolysis liquid after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7.5,
adding 2.1% potassium acetate into the neutralized solution, stirring, centrifuging at 4000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting and centrifuging for 3 times,
adding the obtained precipitate into methanol, stirring to disperse uniformly, centrifuging again at 3000 rpm for 10 min, drying the precipitate at 40 deg.C in vacuum drying oven to obtain fiber powder,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 76.7%, the average length is 136nm, the Zeta potential is-97 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 45.4% by using the same acid hydrolysis conditions.
Example 3
Hydrolyzing and bleaching the dissolving pulp of the softwood by using concentrated sulfuric acid with the concentration of 56% at the temperature of 55 ℃ for 1.5h,
diluting the obtained fiber acid hydrolysate by 9 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the cellulose acid hydrolysate, neutralizing with KOH until the pH value is 7,
adding 1.1% potassium propionate into the neutralized solution, stirring, centrifuging at 7000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium propionate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, oven drying the precipitate at 60 deg.C to obtain fiber powder,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 77.3%, the average length is 163nm, the Zeta potential is-88 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 58.8 percent under the same acid hydrolysis conditions.
Example 4
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated nitric acid with the concentration of 60 percent,
diluting the obtained fiber acid hydrolysate by 10 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the cellulose acid hydrolysate, neutralizing with KOH until the pH value is 7.5,
0.5% lithium chloride was added to the neutralized solution, and after stirring well, the solution was centrifuged at 6000 rpm for 10 minutes. Taking the precipitate, repeating the steps of adding lithium chloride, diluting and centrifuging for 3 times,
adding the obtained precipitate into acetone, stirring to disperse uniformly, centrifuging again at 6000 rpm for 10 min, drying the precipitate to fiber powder at 40 deg.C in vacuum drying oven,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, the mixture was homogenized 4 times at 20000psi by a high-pressure homogenizer to disperse the dispersion into nanocellulose.
The yield of the nano-cellulose prepared by the embodiment is 78.8%, the average length is 134nm, the Zeta potential is-109 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of the nanocellulose prepared by the conventional method of centrifugation (three times of centrifugation), neutralization and dialysis to remove impurity ions was 58.7%.
Example 5
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
the obtained fiber acid hydrolysis liquid is diluted by 8 times, and then is centrifuged for 10 minutes at a centrifugal speed of 9000 r/min, and the dilution and centrifugation processes are repeated for the sediment. It is found that the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium acetate into the neutralized solution, stirring, centrifuging at 9000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into ethylene glycol, stirring thoroughly to disperse uniformly, centrifuging again with centrifuge at 9000 rpm for 10 min, drying the final precipitate with vacuum drying oven at 40 deg.C to obtain fiber powder,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, the mixture was homogenized by a high-pressure homogenizer at 11000psi for 4 times to disperse the mixture into nanocellulose.
The yield of the nano-cellulose prepared by the embodiment is 79.8%, the average length is 138nm, the Zeta potential is-95 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 54.5 percent by using the same acid hydrolysis conditions.
Example 6
The broadleaf wood dissolving pulp is hydrolyzed and bleached by concentrated sulfuric acid with the concentration of 60 percent at the temperature of 55 ℃ for 1 hour.
Diluting the obtained fiber acid hydrolysate by 10 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, and centrifuging for the third time to obtain fiber slurry with less precipitate,
taking out the cellulose acid hydrolysate, neutralizing with KOH until the pH value is 7,
adding 0.2% potassium acetate into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, drying the precipitate to fiber powder at 40 deg.C in vacuum drying oven,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 15000psi with a high pressure homogenizer to disperse into nanocellulose,
the yield of the nano-cellulose prepared by the embodiment is 77.9 percent, the average length is 135nm, the Zeta potential is-92 mV, and the concentration of the nano-cellulose suspension after dispersion is 1.0 percent. In the comparative experiment, the same acid hydrolysis conditions were used, and the yield of final nanocellulose prepared by the existing method of centrifugation (three times of centrifugation), neutralization and dialysis to remove impurity ions was 49.1%.
Example 7
Hydrolyzing and bleaching broadleaf wood dissolving pulp by using concentrated nitric acid with the concentration of 60 percent at the temperature of 55 ℃ for 1.5h,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
after all the slurry was taken out, the slurry was neutralized with NaOH to pH 7,
6.0% potassium acetate was added to the neutralized solution, and after stirring well, the mixture was centrifuged at 6000 rpm for 10 minutes. The precipitation was taken and the steps of adding potassium acetate, diluting and centrifuging were repeated 3 times.
Adding the obtained precipitate into tetrahydrofuran, stirring thoroughly to disperse uniformly, centrifuging again with a centrifuge at 6000 rpm for 10 min, drying the precipitate at 40 deg.C with a vacuum drying oven to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 25000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 67.2%, the average length is 132nm, the Zeta potential is-96 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 45.6 percent by using the same acid hydrolysis conditions.
Example 8
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1.5h at 95 ℃ by using mixed acid of sulfuric acid with the concentration of 30% and acetic acid with the concentration of 50%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 8000 rpm for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, collecting the precipitate, centrifuging for the fourth time to obtain fiber slurry with incomplete precipitation,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 4% potassium acetate into the neutralized solution, stirring, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, oven drying the precipitate at 60 deg.C to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 25000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 79.4%, the average length is 134nm, the Zeta potential is-94 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (four times of centrifugation), neutralization and dialysis is 54.3 percent by using the same acid hydrolysis conditions.
Example 9
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the diluting and centrifuging processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
5.1% potassium acetate was added to the neutralized solution, and after stirring well, the mixture was centrifuged at 6000 rpm for 10 minutes. The precipitation was taken and the steps of adding potassium acetate, diluting and centrifuging were repeated 3 times.
Adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min with centrifuge, air drying the precipitate to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 20000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 79.2%, the average length is 139nm, the Zeta potential is-98 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 54.0 percent by using the same acid hydrolysis conditions.
Example 10
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 90 ℃ by using hydrochloric acid with the concentration of 8mol/L,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, taking precipitate, repeating the dilution and centrifugation processes, finding that the fiber pulp after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium acetate into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous methanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min with a centrifuge, freeze drying to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 25000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 79.7%, the average length is 135nm, the Zeta potential is-92 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 55.0 percent by using the same acid hydrolysis conditions.
Example 11
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium propionate into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium propionate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, drying the precipitate to fiber powder at 40 deg.C in vacuum drying oven,
adding 5g of dried fiber powder into 495g of water, stirring and dispersing, performing ultrasonic treatment for 20 minutes by using a cell ultrasonic crusher under the power of 1000w to disperse the fiber powder into nano cellulose,
the yield of the nano-cellulose prepared by the embodiment is 78.8%, the average length is 130nm, the Zeta potential is-95 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of nanocellulose prepared by the existing method of centrifugation (three times of centrifugation), neutralization and dialysis to remove impurity ions was 46.7%.
Example 12
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 7000 rpm for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% lithium chloride into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding lithium chloride, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, and drying the precipitate to fiber powder at 40 deg.C with vacuum drying oven.
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 78.5%, the average length is 133nm, the Zeta potential is-98 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the yield of the final nano-cellulose prepared by the existing method of removing impurity ions by centrifugal separation (three times of centrifugation), neutralization and dialysis is 55.0 percent by using the same acid hydrolysis conditions.
Example 13
The broadleaf wood dissolving pulp is hydrolyzed and bleached by concentrated sulfuric acid with the concentration of 60 percent at the temperature of 55 ℃ for 1 hour.
Diluting the obtained fiber acid hydrolysis liquid by 8 times, centrifuging for 10 minutes at a centrifugal speed of 9000 r/min, taking the precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysis liquid after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium propionate into the neutralized solution, stirring, centrifuging at 7000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium propionate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous ethanol, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, drying the precipitate to fiber powder at 40 deg.C in vacuum drying oven,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 78.0%, the average length is 134nm, the Zeta potential is-92 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of nanocellulose prepared by the conventional method of centrifugation (three times of centrifugation), neutralization and dialysis to remove impurity ions was 63.9%.
Example 14
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, and centrifuging for the third time to obtain fiber slurry with less precipitate,
taking out the cellulose acid hydrolysate, neutralizing with KOH until the pH value is 7,
adding 3.1% lithium chloride into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding lithium chloride, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous acetone, stirring thoroughly to disperse uniformly, centrifuging again at 6000 rpm for 10 min, drying the precipitate at 50 deg.C with vacuum drying oven to obtain fiber powder,
adding 5g of dried fiber powder into 495g of water, stirring for dispersion, homogenizing for 4 times under 25000psi with a high pressure homogenizer to disperse into nanometer cellulose,
the yield of the nano-cellulose prepared by the embodiment is 79.2%, the average length is 138nm, the Zeta potential is-91 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of the nanocellulose prepared by the existing method of removing impurity ions by centrifugation (three times of centrifugation), neutralization and dialysis was 44.8%.
Example 15
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, finding that the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 5.1% potassium acetate into the neutralized solution, stirring, centrifuging at 5000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
the obtained precipitate was added to anhydrous methanol, sufficiently stirred to be uniformly dispersed, and centrifuged again at a centrifugation speed of 6000 rpm for 10 minutes by a centrifuge. The resulting precipitate was dried to a fiber powder at 40 c using a vacuum drying oven,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 79.5%, the average length is 134nm, the Zeta potential is-97 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of the nanocellulose prepared by the conventional method of removing impurity ions by centrifugation (three times of centrifugation), neutralization and dialysis was 53.4%.
Example 16
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysis liquid by 8 times, centrifuging for 10 minutes at the centrifugal speed of 4000 rpm, taking the precipitate, repeating the dilution and centrifugation processes, wherein the fiber pulp after the third centrifugation cannot be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 2.1% potassium acetate into the neutralized solution, stirring, centrifuging at 6000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous tetrahydrofuran, stirring thoroughly to disperse uniformly, centrifuging again with a centrifuge at 6000 rpm for 10 min, drying the obtained precipitate with a vacuum drying oven at 50 deg.C to obtain fiber powder,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 78.6%, the average length is 131nm, the Zeta potential is-92 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of the nanocellulose prepared by the existing method of removing impurity ions by centrifugation (three times of centrifugation), neutralization and dialysis was 44.3%.
Example 17
Hydrolyzing and bleaching broadleaf wood dissolving pulp for 1h at 55 ℃ by using concentrated sulfuric acid with the concentration of 60%,
diluting the obtained fiber acid hydrolysate by 8 times, centrifuging at 6000 r/min for 10 min, collecting precipitate, repeating the dilution and centrifugation processes, wherein the fiber acid hydrolysate after the third centrifugation can not be completely precipitated,
taking out the fiber acid hydrolysate, neutralizing with NaOH until pH is 7,
adding 3.1% potassium acetate into the neutralized solution, stirring, centrifuging at 4000 rpm for 10 min, collecting precipitate, repeating the steps of adding potassium acetate, diluting, and centrifuging for 3 times,
adding the obtained precipitate into anhydrous glycol, stirring thoroughly to disperse uniformly, centrifuging again with a centrifuge at 6000 rpm for 10 min, drying the precipitate at 40 deg.C with a vacuum drying oven to obtain fiber powder,
5g of the dried fiber powder was added to 495g of water, and after dispersion by stirring, it was dispersed into nanocellulose by homogenizing 4 times with a high-pressure homogenizer at 25000 psi.
The yield of the nano-cellulose prepared by the embodiment is 79.0%, the average length is 133nm, the Zeta potential is-95 mV, and the concentration of the dispersed nano-cellulose suspension is 1.0%. In the comparative experiment, the same acid hydrolysis conditions were used, and the final yield of the nanocellulose prepared by the existing method of removing impurity ions by centrifugation (three times of centrifugation), neutralization and dialysis was 54.7%.
The fiber pulp is not limited to hardwood dissolving pulp and softwood dissolving pulp, but can also be fiber pulp mixed by a plurality of dissolving pulps, and the examples are only used for illustrating the specific implementation process and do not limit the fiber pulp.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. A method for preparing nano cellulose from fiber pulp is characterized in that the fiber pulp is hydrolyzed by acid to obtain fiber acid hydrolysate, the fiber acid hydrolysate is neutralized to be neutral to obtain total fiber suspension, a strong electrolyte solvent which is dissolved in water and enables the nano cellulose to be reversibly agglomerated is added, the mixture is dispersed uniformly and then centrifuged, sediment is taken to be re-dispersed into the water, the strong electrolyte solvent is repeatedly added, the sediment is dispersed into a detergent after the centrifugation step is carried out for multiple times after the uniform dispersion, the sediment is centrifuged, dried and precipitated to obtain fiber powder, and the fiber powder is dispersed into the water and then mechanically treated to obtain the nano cellulose.
2. The method as set forth in claim 1, wherein the acidic hydrolysate of the fiber is subjected to dilution centrifugation for a plurality of times until the fiber is not completely precipitated, and then neutralized to neutrality.
3. The method according to claim 1 or 2, characterized in that the rotational speed of the centrifugation is 3000-9000 rpm.
4. A method according to any one of claims 1 to 3, characterized in that the mass of strong electrolyte solvent added is between 0.2% and 6.0% by weight of the mass of the total fibre suspension.
5. The method as set forth in claim 4, wherein the strong electrolyte solvent is any one of potassium acetate, lithium chloride and potassium propionate.
6. The method as set forth in claim 1 or 5, wherein the detergent is any one of ethanol, methanol, acetone, tetrahydrofuran and ethylene glycol.
7. The method as claimed in claim 6, wherein the strong electrolyte solvent is potassium acetate, and the detergent is any one of ethanol, methanol, tetrahydrofuran, and ethylene glycol;
the strong electrolyte solvent is lithium chloride, and the detergent is ethanol or acetone;
the strong electrolyte solvent is potassium propionate, and the detergent is ethanol.
8. The method as claimed in claim 1 or 7, wherein the nano-cellulose is obtained by homogenizing the fiber powder in a high pressure homogenizer with pressure ranging from 10000 to 25000psi or by a cell crusher with power higher than 500W after dispersing the fiber powder in water.
9. A nanocellulose prepared from a fibre slurry, characterized by being obtainable by the process of any one of claims 1 to 8.
10. Use of nanocellulose prepared using a fibre slurry according to claim 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104448007A (en) * | 2014-11-14 | 2015-03-25 | 中国科学院青岛生物能源与过程研究所 | Method for preparing nano-cellulose |
| CN107201678A (en) * | 2017-06-15 | 2017-09-26 | 华南理工大学 | A kind of highly concentrated Inner dyeing method of nano-cellulose |
| CN107460759A (en) * | 2017-08-18 | 2017-12-12 | 华南理工大学 | A kind of method for quickly purifying of nano-cellulose suspension |
| CN108457112A (en) * | 2018-01-31 | 2018-08-28 | 华南理工大学 | A method of preparing nano-cellulose whisker and fibril using oxalic acid acidolysis |
| CN110129909A (en) * | 2019-06-06 | 2019-08-16 | 江苏赛清科技有限公司 | Nano-cellulose fibril and its preparation method and application |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104448007A (en) * | 2014-11-14 | 2015-03-25 | 中国科学院青岛生物能源与过程研究所 | Method for preparing nano-cellulose |
| CN107201678A (en) * | 2017-06-15 | 2017-09-26 | 华南理工大学 | A kind of highly concentrated Inner dyeing method of nano-cellulose |
| CN107460759A (en) * | 2017-08-18 | 2017-12-12 | 华南理工大学 | A kind of method for quickly purifying of nano-cellulose suspension |
| CN108457112A (en) * | 2018-01-31 | 2018-08-28 | 华南理工大学 | A method of preparing nano-cellulose whisker and fibril using oxalic acid acidolysis |
| CN110129909A (en) * | 2019-06-06 | 2019-08-16 | 江苏赛清科技有限公司 | Nano-cellulose fibril and its preparation method and application |
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