CN112079935B - Preparation method of nano-cellulose - Google Patents
Preparation method of nano-cellulose Download PDFInfo
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- CN112079935B CN112079935B CN202010871970.4A CN202010871970A CN112079935B CN 112079935 B CN112079935 B CN 112079935B CN 202010871970 A CN202010871970 A CN 202010871970A CN 112079935 B CN112079935 B CN 112079935B
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Abstract
The invention belongs to the technical field of fiber materials, and particularly relates to a preparation method of nano-cellulose. Mixing plant waste or powder with a dilute acid solution for reaction to obtain a primary fiber product; under the action of weak acid regulator, mixing the primary fiber product, sodium chlorite and water to react to obtain palm fiber product; then, mixing and reacting the palm fiber product, the alkali liquor and the oxidizing substance to obtain a bleached fiber product; then mixing the bleached fiber product with a TEMPO oxidation system for reaction to obtain oxidized fiber slurry; and finally, mechanically treating the oxidized fiber slurry to obtain the nano-cellulose. The nano-cellulose provided by the invention is processed by adopting extruder equipment, so that continuous production can be realized, the energy consumption of unit products is low, the nano-cellulose has smaller diameter and narrow diameter range distribution, the nano-cellulose has higher purity in a certain diameter range due to the narrow diameter range distribution, and various mixing and shearing equipment is provided for selection, so that the application range of the nano-cellulose is wider.
Description
Technical Field
The invention belongs to the technical field of fiber materials, and particularly relates to a preparation method of nano-cellulose.
Background
The non-sustainable consumption of non-renewable raw materials during the course of the industrialization for centuries, makes the earth experiencing serious energy and environmental crisis. Over the past 50 years, approximately 90% of the global energy demand has been met primarily by fossil fuels, with carbon dioxide being emitted to the earth's atmosphere annually at about 1.5 x 10 10 Mg, which contributes to global warming. One solution that may be helpful in achieving sustainable goals is to have lignocellulosic residues "recycled," such as crop residues (straw, corn stover, bagasse) and tree waste (wood flour, bark, leaves), among others. Lignocellulose is the most abundant and renewable but underutilized biological resource in nature, has become one of the main sources of primary renewable energy in the 21 st century, and provides nearly 14% of the energy demand worldwide. However, the lignocellulose component is complex and contains a large amount of hydrogen bonds on a cellulose chain, so that the lignocellulose component is difficult to extract and utilize. Therefore, further research on the components and structures of lignocellulose, such as hydrogen bonds of cellulose, surface modification of cellulose, rapid preparation of nanocellulose, and the like, is needed, and the application field of lignocellulose is widened.
In recent years, due to the excellent properties of nanocellulose, such as high strength, high modulus, biocompatibility, biodegradability, high specific surface area, high surface reactivity and barrier property, nanocellulose becomes a research hotspot at home and abroad. The nano-cellulose also has some special optical properties, biological properties and mechanical properties, and the properties enable the nano-cellulose to have wide application value, can be used as a reinforcing material in a nano-composite material, and has great application prospects in the fields of medicines, packaging, papermaking, food additives, paint coatings, energy storage and the like.
The main preparation method comprises the steps of obtaining the nano-cellulose by a chemical method (acidolysis, alkali treatment, TEMPO catalytic oxidation method and the like), a biological method (enzyme treatment), a mechanical method (superfine grinding, ultrasonic crushing, high-pressure homogenization and the like), an electrostatic spinning method and the like; nanocellulose is a one-dimensional nano-sized cellulose material and has the basic structure, properties of cellulose and typical characteristics of nanoparticles; depending on their size, function, preparation process and preparation conditions, nanocellulose can be roughly divided into three categories: cellulose nanocrystallites (CNC, or Cellulose nanowhisker), cellulose Nanofibers (CNF), and Bacterial Cellulose (BC).
The existing preparation method of the nano-cellulose generally treats cellulose raw materials through a large amount of chemical reagents or large-scale mechanical equipment, for example, a large amount of acidic waste liquid after degrading cellulose by using a large amount of concentrated acid has serious influence on the environment, or the large-scale equipment is used for producing the nano-cellulose, so that the energy consumption is high, the yield is low, the equipment is easy to lack, and the application of the nano-cellulose is greatly limited.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a method for preparing nanocellulose, wherein the process for preparing nanocellulose by the method is green and environment-friendly, and meanwhile, different pretreatment and mechanical treatment methods are adopted to obtain nanocellulose with a larger major diameter, a smaller diameter and a narrow diameter distribution range.
The purpose of the invention is realized by the following technical scheme:
a preparation method of nano-cellulose comprises the following steps:
(1) Mixing plant waste or powder thereof with a dilute acid solution for reaction, and then sequentially filtering, washing and drying to obtain a primary fiber product;
(2) Mixing the preliminary fiber product prepared in the step (1), sodium chlorite and water for reaction to obtain a reaction product, wherein in the reaction process, a weak acid regulator is used for keeping the pH value of a reaction system at 4-5; then, sequentially filtering, washing and drying the reaction product to obtain a palm fiber product;
(3) Mixing and reacting the palm fiber product prepared in the step (2), alkali liquor and an oxidizing substance, and then filtering, washing and drying to obtain a bleached fiber product;
(4) Mixing the bleached fiber product prepared in the step (3) with water to obtain slurry; then mixing the slurry with an oxidation system for reaction; then sequentially carrying out filtering and washing treatment to obtain oxidized fiber slurry;
(5) Preparing the oxidized fiber slurry prepared in the step (4) and water into slurry, mixing and shearing the slurry, and carrying out mechanical treatment to obtain nano cellulose;
preferably, the dilute acid solution in step (1) includes, but is not limited to, at least one of a dilute sulfuric acid solution, a dilute hydrochloric acid solution and a dilute nitric acid solution;
preferably, the mass fraction of the dilute acid solution is 0.8-2%;
more preferably, the dilute acid solution in the step (1) is a dilute sulfuric acid solution, and the mass fraction of the dilute sulfuric acid solution is 1.5%;
preferably, the mass ratio of the plant waste or the powder thereof to the dilute acid solution is 1 (5-50);
more preferably, the mass ratio of the plant waste or the powder thereof to the dilute acid solution is 1 (10-20);
preferably, the temperature of the mixing reaction in the step (1) is 80-150 ℃, and the stirring time of the mixing reaction is 30-120 min;
preferably, the plant waste or powder in step (1) includes but is not limited to at least one of bagasse powder, wood powder, straw powder, cornstalk powder, rice hulls, leaves, cottonseed hulls, corncob powder, paper; the mesh number of the plant waste or the powder thereof is 10-300 meshes;
preferably, the acid regulator in step (2) includes, but is not limited to, at least one of acetic acid, carbonic acid and oxalic acid;
more preferably, the acid regulator in step (2) is selected from acetic acid;
specifically, the weak acid is used because the weak acid has weak acidity, so that the influence of the pH value adjusted by the weak acid on the nano-cellulose is small, and the influence on the environment is reduced;
preferably, the mass ratio of the sodium chlorite to the primary fiber product in the step (2) is (0.1-6.0): 1;
more preferably, the mass ratio of the sodium chlorite to the primary fiber product in the step (2) is (0.1-1.5): 1.
preferably, the temperature of the mixing reaction in the step (2) is 25-100 ℃, and the time of the mixing reaction is 30-360 min;
more preferably, the temperature of the mixing reaction in the step (2) is 60-80 ℃; the time of the mixing reaction is 120-360 min;
preferably, the alkali solution in step (3) includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide and sodium bicarbonate;
preferably, the mass fraction of the alkali liquor in the step (3) is 3-8%;
preferably, the mass ratio of the alkali liquor to the palm fiber product in the step (3) is (5-50): 1;
more preferably, the alkali liquor in the step (3) is a mixed alkali liquor of sodium hydroxide and potassium hydroxide, wherein the mass fraction of the sodium hydroxide and the potassium hydroxide in the mixed alkali liquor is 4%; the mass ratio of the alkali liquor to the palm cellulose is 20:1;
preferably, the oxidizing substance in step (3) includes, but is not limited to, a hydrogen peroxide solution or ozone, and the mass fraction of the hydrogen peroxide solution is 1% to 20%;
preferably, the mass ratio of the hydrogen peroxide to the brown fiber product is (0.05-0.2): 1;
more preferably, the oxidizing substance in the step (3) is hydrogen peroxide solution, and the mass fraction of the hydrogen peroxide solution is 9%, because the hydrogen peroxide solution has the advantages of wide sources and green and environment-friendly decomposition products; the mass ratio of the hydrogen peroxide to the brown fiber product is 0.09:1;
preferably, the temperature of the mixing reaction in the step (3) is 25-100 ℃, and the time of the mixing reaction is 30-360 min;
more preferably, the temperature of the mixing reaction in the step (3) is 60-80 ℃, and the time of the mixing reaction is 30-240 min;
preferably, the oxidation system described in step (4) includes, but is not limited to, TEMPO/NaBr/NaClO alkaline system, TEMPO/NaClO 2 Acid System, TEMPO/peroxidase/H 2 O 2 TEMPO/laccase/O 3 At least one of;
in the mixing reaction in the step (4), if the oxidation system in the mixing reaction is a TEMPO/NaBr/NaClO alkaline system, the pH value of the reaction system is maintained at 10-10.5; the sodium hydroxide solution with the mass fraction of 0.4 percent can be used for adjustment;
in the step (4), when the reaction is carried out by mixing, for example, the oxidation system during the reaction is TEMPO/NaClO 2 In an acidic system, the pH value of the reaction system is maintained at 4.8-6.8, and the pH value can be adjusted by using a hydrochloric acid solution with the mass fraction of 0.36%;
more preferably, the oxidation system described in step (4) is selected from the TEMPO/NaBr/NaClO alkaline systems;
preferably, the mass ratio of the TEMPO to the bleached fiber product is (0.01-0.5): 1;
more preferably, the mass ratio of TEMPO to bleached fiber product is (0.01-0.16): 1;
preferably, the mass ratio of NaBr to the bleached fiber product is (0.1-5): 1;
more preferably, the mass ratio of NaBr to bleached fiber product is (0.1-1.6): 1;
preferably, the mass ratio of the NaClO solution to the bleached fiber product in the oxidation system is (3.35-100.5): 1, the mass fraction of NaClO solution is 7-12%;
more preferably, the mass ratio of the NaClO solution to the bleached fiber product in the oxidation system is (3.35-33.5): 1;
preferably, the NaClO 2 The mass ratio of the bleaching fiber product to the bleaching fiber product is (0.1-100): 1;
more preferably, the NaClO 2 The mass ratio of the bleaching fiber product to the bleaching fiber product is (0.1-20): 1;
preferably, the temperature of the mixing reaction in the step (4) is 5-30 ℃, and the time of the mixing reaction is 60-720 min;
more preferably, the temperature of the mixing reaction in the step (4) is 25-30 ℃, and the time of the mixing reaction is 240-720 min;
preferably, the slurry in step (5) has a solids content of 1 to 30%;
preferably, the mechanical treatment method in step (5) includes, but is not limited to, at least one of an extruder, an internal mixer, an open mill, a juicer, and a coffee bean grinding machine;
more preferably, the mechanical treatment method in the step (5) selects an extruder, wherein the screw rotating speed of the extruder is 5-1000 r/min, the length-diameter ratio is 20-100, and the extrusion times are 1-20;
more preferably, the screw rotating speed of the extruder is 200-400 r/min, the length-diameter ratio is 45, and the extrusion times are 5-8;
in a specific embodiment, the diameter range of the nano-cellulose is 10-100 nm, the rotating speed of the extruder is 200r/min, the extrusion times are 5 times, the yield is 65%, and the solid content is 14%; the diameter range of the nano-cellulose is 5-80 nm, the rotating speed of the extruder is 400r/min, the extrusion times are 8 times, the yield is 68%, and the solid content is 15%. The application finds that different extruder rotating speeds and extrusion times have selective significance on the diameter range of the nanocellulose, and the nanocellulose in a certain nanometer range can be obtained by setting the specific extruder rotating speed and the extrusion times.
Preferably, in the preparation method, the step 5 further comprises sequentially performing ultrasonic dispersion and centrifugal washing treatment on the nanocellulose obtained by the mechanical treatment;
preferably, the power of the ultrasonic dispersion is 100-1000W; the centrifugal rotating speed is 3000-10000 r/min;
compared with the prior art, the invention has the following advantages and effects:
(1) The invention provides a preparation method of nano-cellulose, wherein plant residue powder (bagasse powder, wood powder and crop residue powder) is used as a raw material, and the purposes of waste utilization and environmental protection can be achieved.
(2) The specific mechanism of the preparation method of the nano-cellulose provided by the invention is as follows: (1) mixing plant waste or powder thereof with dilute acid for reaction, swelling the whole plant residue powder, so that lignin and hemicellulose can be removed more easily, subsequent impurity removal is facilitated, and the purpose of primary purification is achieved; the method adopts dilute acid solution as reaction solution, is green and environment-friendly, and reduces environmental pollution. (2) And (3) carrying out bleaching treatment by using sodium chlorite in a weak acid environment to remove lignin and partial pigments in the fiber plant powder. (3) The semi-lignin and pigment of the fiber plant powder are removed by mixing and reacting the alkali liquor and the oxidizing substance. (4) And (3) TEMPO catalytic oxidation is used to convert hydroxyl on the cellulose into carboxyl groups with negative electricity, so that subsequent dispersion is facilitated. (5) Through extrusion processing mechanical disintegration processing, obtain the diameter less, diameter range distributes the narrow nano cellulose, and diameter range distributes narrowly and makes the nano cellulose of this application purity higher in certain diameter range to have multiple mixed shearing equipment to supply in the selection, make its range of application wider.
(2) The nano-cellulose provided by the invention is processed by adopting an extruder device, so that continuous production can be realized, the energy consumption of unit products is low, the solid content of the obtained nano-cellulose is high, and the production cost of the nano-cellulose is greatly reduced.
Drawings
FIG. 1 is a scanning electron micrograph of nanocellulose prepared in example 1 of the present invention.
FIG. 2 is a particle size distribution diagram of the nanocellulose prepared in example 1 of the present invention.
FIG. 3 is a scanning electron micrograph of the nanocellulose prepared in example 2 of the present invention.
FIG. 4 is a scanning electron micrograph of the nanocellulose prepared in example 3 of the present invention.
FIG. 5 is a particle size distribution diagram of nanocellulose prepared in example 3 of the present invention.
FIG. 6 is a scanning electron micrograph of nanocellulose prepared in comparative example 1 of the present invention.
FIG. 7 is a scanning electron micrograph of nanocellulose prepared in comparative example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
The invention provides a preparation method of nano-cellulose, aiming at solving the technical defect that the nano-cellulose with smaller diameter and narrow diameter range is difficult to prepare due to the lack of large mechanical equipment (such as a high-pressure homogenizer and a large grinding machine) for mechanical disintegration in the prior art.
Wherein, the raw materials used in the following examples are all commercially available or self-made, and the particle size in the figure is the diameter of the nanometer microfiber filament.
Example 1
The embodiment of the invention provides a first nano-cellulose, which comprises the following specific preparation steps:
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite to react every 30min, reacting for 120min (namely adding 4 sodium chlorite totally), and dripping a proper amount of acetic acid in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Preparing the oxidized fiber slurry prepared in the step (4) and deionized water into slurry with the mass fraction of 20%, and placing the slurry into an extruder, wherein the rotating speed is 200r/min, the length-diameter ratio is 45, and the extrusion times are 5 times; diluting the extruded slurry by 10 times, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, centrifuging at 8000r/min for layering, repeating the centrifugation until the supernatant reaches colorless clear liquid from bluish clear liquid, and centrifuging each time to obtain supernatant, i.e. nanocellulose, wherein the yield is 65% and the solid content is 14%. The scanning electron microscope image of the prepared nanocellulose is shown in fig. 1, the diameter distribution diagram of the nanocellulose is shown in fig. 2, and fig. 1 and 2 show that the nanocellulose is successfully prepared in the embodiment, the diameter of the nanocellulose is 10-100 nm, and the nanocellulose is mainly concentrated in the range of 50-80 nm.
Example 2
The embodiment of the invention provides a second nano-cellulose, which comprises the following specific preparation steps:
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite every 30min for reaction, reacting for 120min (namely adding 4 times of sodium chlorite totally), and dripping a proper amount of acetic acid simultaneously in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to be stirred and react for 120 minutes, and slowly dripping 35ml of H2O2 with the mass fraction of 9% in the reaction process; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction process to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Preparing the oxidized fiber slurry prepared in the step (4) and deionized water into slurry with the mass fraction of 20%, and placing the slurry into an extruder, wherein the rotating speed is 200r/min, the length-diameter ratio is 45, and the extrusion times are 8 times; diluting the extruded slurry by 10 times, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, centrifuging at 8000r/min for layering, repeating the centrifugation until the supernatant reaches colorless clear liquid from bluish clear liquid, and centrifuging each time to obtain supernatant, i.e. nanocellulose, wherein the yield is 67% and the solid content is 15%. The scanning electron micrograph of the prepared nanocellulose is shown in fig. 3, and fig. 3 shows that the nanocellulose is successfully prepared in the embodiment, the diameter of the nanocellulose is 5-150 nm, and the nanocellulose is mainly concentrated in the range of 5-50 nm.
Example 3
The embodiment of the invention provides a third nano-cellulose, which comprises the following specific preparation steps:
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite to react every 30min, reacting for 120min (namely adding 4 sodium chlorite totally), and dripping a proper amount of acetic acid in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the brown fiber product prepared in the step (2), and adding the brown fiber product into 700ml of sodium hydroxide (the mass fraction is 4%) and potassium hydroxide (the mass fraction is 4%) Preparing slurry in the mixed alkali liquor; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction process to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Preparing the oxidized fiber slurry prepared in the step (4) and deionized water into slurry with the mass fraction of 20%, and placing the slurry into an extruder, wherein the rotating speed is 400r/min, the length-diameter ratio is 45, and the extrusion times are 8 times; diluting the extruded slurry by 10 times, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, centrifuging at 8000r/min for layering, repeating the centrifugation until the supernatant reaches colorless clear liquid from bluish clear liquid, and centrifuging each time to obtain supernatant, i.e. nanocellulose, wherein the yield is 68% and the solid content is 15%. The scanning electron microscope image of the prepared nanocellulose is shown in fig. 4, the diameter distribution diagram of the nanocellulose is shown in fig. 5, and fig. 4 and 5 show that the nanocellulose is successfully prepared in the embodiment, and the diameter of the nanocellulose is 5-80 nm and mainly concentrated in the range of 5-30 nm.
Example 4
The embodiment of the invention provides a fourth nano-cellulose, which comprises the following specific preparation steps:
(1) Weighing 50g of bagasse powder sieved by a 80-mesh sieve, adding the bagasse powder into 1000ml of dilute sulfuric acid solution (the mass percent of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to neutrality and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite every 30min for reaction, reacting for 120min (namely adding 4 times of sodium chlorite totally), and dripping a proper amount of acetic acid simultaneously in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction process to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Preparing the oxidized fiber slurry prepared in the step (4) and deionized water into slurry with the mass fraction of 20%, and placing the slurry into an extruder, wherein the rotating speed is 400r/min, the length-diameter ratio is 45, and the extrusion times are 8 times; diluting the extruded slurry by 10 times, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, centrifuging at 8000r/min for layering, repeating the centrifugation until the supernatant reaches colorless clear liquid from bluish clear liquid, and centrifuging each time to obtain supernatant, i.e. nanocellulose, wherein the yield is 60% and the solid content is 14%.
Example 5
The embodiment of the invention provides a fifth nano-cellulose, which comprises the following specific preparation steps:
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite to react every 30min, reacting for 120min (namely adding 4 sodium chlorite totally), and dripping a proper amount of acetic acid in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Placing the oxidized fiber slurry prepared in the step (4) into an internal mixer, wherein the rotating speed is 200r/min, the internal mixing time is 5min, and the internal mixing frequency is 10 times; diluting the obtained internally mixed slurry by 10 times, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, then performing centrifugal layering, wherein the centrifugal rotation speed is 8000r/min, repeating the centrifugation until the supernatant reaches the colorless clear liquid from bluish clear liquid, and taking the supernatant after each centrifugation to obtain the nano-cellulose, wherein the yield is 38% and the solid content is 5%.
Comparative example 1
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite to react every 30min, reacting for 120min (namely adding 4 sodium chlorite totally), and dripping a proper amount of acetic acid in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration and washing to be neutral to obtain a bleached fiber product;
(4) Diluting the bleached fiber product prepared in the step (3) by 10 times with deionized water, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, then performing centrifugal layering at a centrifugal rotation speed of 8000r/min, repeating the centrifugation until the supernatant reaches a clear solution with colorless light from bluish clear solution, and taking the supernatant after each centrifugation to obtain the product of the comparative example 1, wherein the yield of the product is lower than 1%, a scanning electron microscope image of the nano product prepared in the comparative example 1 is shown in fig. 6, and the product of the comparative example 1 is filamentous in appearance and has a diameter of 0.1-3 μm.
Comparative example 2
(1) Weighing 50g of wood powder passing through an 80-mesh sieve, adding the wood powder into 1000ml of dilute sulfuric acid solution (the mass percentage of the dilute sulfuric acid solution is 1.5%), then placing the mixture into a 130 ℃ water bath, stirring for 120min, and after the reaction is finished, sequentially performing suction filtration, washing to be neutral and drying treatment to obtain a primary fiber product;
(2) Weighing 40g of the primary fiber product prepared in the step (1), adding the primary fiber product into 800ml of deionized water, dispersing by magnetic stirring, adding 6g of sodium chlorite to form a reaction solution, setting the temperature of a water bath to be 80 ℃, adding 6g of sodium chlorite to react every 30min, reacting for 120min (namely adding 4 sodium chlorite totally), and dripping a proper amount of acetic acid in the whole reaction process to keep the pH value of the reaction system between 4 and 5; after the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a palm fiber product;
(3) Weighing 35g of the palm fiber product prepared in the step (2), and adding the palm fiber product into 700ml of mixed alkali liquor of sodium hydroxide (with the mass fraction of 4%) and potassium hydroxide (with the mass fraction of 4%) to prepare slurry; then placing the mixture into a water bath kettle at the temperature of 80 ℃ to stir and react for 120 minutes, and slowly dripping 35ml of H with the mass fraction of 9 percent in the reaction process 2 O 2 (ii) a After the reaction is finished, carrying out suction filtration, washing to neutrality and drying treatment to obtain a bleached fiber product;
(4) Preparing slurry with the mass fraction of 1% by using 30g of the bleached fiber product prepared in the step (3) and deionized water; mixing 1000ml of the slurry with 0.16g of TEMPO and 1.6g of sodium bromide under stirring, adding 75ml of sodium hypochlorite solution (the content of available chlorine is more than or equal to 7.5%), stirring for 360min at room temperature, and dropwise adding sodium hydroxide solution during the reaction to maintain the pH of the reaction system at 10; after the reaction is finished, carrying out suction filtration, and washing to be neutral to obtain oxidized fiber slurry;
(5) Diluting the oxidized fiber slurry prepared in the step (4) by 10 times by using deionized water, performing ultrasonic dispersion, performing ultrasonic treatment at 1000w for 5min, then performing centrifugal delamination, wherein the centrifugal rotation speed is 8000r/min, repeating centrifugation until the supernatant reaches the clear solution with bluish light to colorless light, and taking the supernatant after each centrifugation, namely the product of the comparative example 2, wherein the yield is 45%, the scanning electron microscope image of the nano product prepared in the comparative example 2 is shown in figure 7, and the product of the comparative example 2 is fibrous in appearance and 20-500 nm in diameter.
Effects of the embodiment
This example is conducted to examine the morphology, crystallinity, maximum decomposition temperature and yield of the above examples and comparative examples, and the results are shown in Table 1.
TABLE 1 Performance test
Experimental data show that the diameter and span range of the obtained nanocellulose is large and the nanocellulose in a certain nanometer range cannot be intensively obtained if the fiber is not subjected to TEMPO catalytic oxidation and extrusion treatment. If the relevant parameters of TEMPO catalytic oxidation and extrusion treatment are optimized, the nano-cellulose with small diameter distribution can be obtained.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.
Claims (8)
1. A preparation method of nano-cellulose is characterized by comprising the following steps:
(1) Mixing plant waste or powder thereof with a dilute acid solution for reaction, and then sequentially filtering, washing and drying to obtain a primary fiber product; the plant waste or the powder thereof is bagasse powder or wood powder;
(2) Mixing the preliminary fiber product prepared in the step (1), sodium chlorite and water for reaction to obtain a reaction product, wherein in the reaction process, a weak acid regulator is used for keeping the pH value of a reaction system to be 4-5; then filtering, washing and drying the reaction product in sequence to obtain a palm fiber product;
(3) Mixing and reacting the palm fiber product prepared in the step (2), alkali liquor and an oxidizing substance, and then filtering, washing and drying to obtain a bleached fiber product;
(4) Mixing the bleached fiber product prepared in the step (3) with water to obtain slurry; then mixing the slurry with an oxidation system for reaction; then sequentially filtering and washing to obtain oxidized fiber slurry; the oxidation system comprises a TEMPO/NaBr/NaClO alkaline system, TEMPO/NaClO 2 Acid System, TEMPO/peroxidase/H 2 O 2 TEMPO/laccase/O 3 At least one of (a);
(5) Preparing the oxidized fiber slurry prepared in the step (4) and water into slurry, mixing and shearing the slurry, and performing mechanical treatment, ultrasonic dispersion and centrifugal washing treatment to obtain nano cellulose;
the temperature of the mixing reaction in the step (1) is 80-150 ℃, and the stirring time of the mixing reaction is 30-120 min;
the temperature of the mixing reaction in the step (2) is 25-100 ℃, and the time of the mixing reaction is 30-120 min;
the oxidizing substance in the step (3) is hydrogen peroxide solution or ozone, and the mass fraction of the hydrogen peroxide solution is 1-20%;
selecting an extruder by the mechanical treatment method in the step (5), wherein the screw rotation speed of the extruder is 200-400 r/min, the length-diameter ratio is 45, and the extrusion times are 5~8.
2. The method for producing nanocellulose according to claim 1, characterized by: the mesh number of the plant waste or the powder thereof in the step (1) is 10-300 meshes.
3. The method for producing nanocellulose according to claim 1, characterized in that: the dilute acid solution in the step (1) is at least one of dilute sulfuric acid solution, dilute hydrochloric acid solution and dilute nitric acid solution.
4. The method for producing nanocellulose according to claim 1, characterized in that: the mass ratio of the plant waste or the powder thereof to the dilute acid solution is 1 (5 to 50).
5. The method for producing nanocellulose according to claim 1, characterized in that: the mass ratio of the sodium chlorite to the primary fiber product in the step (2) is (0.1-6.0): 1.
6. the method for producing nanocellulose according to claim 1, characterized in that: the mass fraction of the alkali liquor in the step (3) is 3~8%;
the mass ratio of the alkali liquor to the palm fiber product in the step (3) is (5 to 50): 1;
the mass ratio of the hydrogen peroxide to the brown fiber product is (0.05 to 0.2): 1.
7. the method for producing nanocellulose according to claim 1, characterized by: the temperature of the mixing reaction in the step (3) is 25-100 ℃, and the time of the mixing reaction is 30-360 min.
8. The method for producing nanocellulose according to claim 1, characterized in that: the power of the ultrasonic dispersion is 100-1000W; the rotating speed of the centrifugation is 3000-10000 r/min.
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| CN116623458A (en) * | 2023-07-11 | 2023-08-22 | 浙江科技学院 | Preparation method of lignocellulose |
| CN117069870B (en) * | 2023-08-17 | 2024-03-12 | 广东省农业科学院蔬菜研究所 | Preparation methods of micro-nano cellulose, hydrogel material and barrier coating |
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