CN110735343A - Method for preparing long rod-shaped cellulose nanofibrils through pretreatment of lignin-based solid acids - Google Patents
Method for preparing long rod-shaped cellulose nanofibrils through pretreatment of lignin-based solid acids Download PDFInfo
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- CN110735343A CN110735343A CN201910643456.2A CN201910643456A CN110735343A CN 110735343 A CN110735343 A CN 110735343A CN 201910643456 A CN201910643456 A CN 201910643456A CN 110735343 A CN110735343 A CN 110735343A
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/02—Pretreatment of the raw materials by chemical or physical means
Abstract
The invention discloses a method for preparing long rod-shaped cellulose nanofibrils by lignin-based solid acid pretreatment, which comprises the following steps of (1) putting alkali lignin in N2Partially carbonizing in the atmosphere, sulfonating with concentrated sulfuric acid, washing with distilled water, vacuum drying, grinding, and sieving to obtain lignin-based solid acid; (2) mixing the lignin-based solid acid and the dissolving pulp fiber and then carrying out pre-hydrolysis treatment; (3) centrifugally separating the hydrolysis substrate, and removing supernatant to respectively obtain fiber residue and lignin-based solid acid; mechanically dissociating the separated fiber residues by using a micro-jet homogenizer to obtain the long rod-shaped cellulose nano-fibrils; the separated lignin-based solid acids are again used for the prehydrolysis treatment of the dissolving pulp fibers. The cellulose nano-fibril obtained by the method has the characteristics of high crystallinity, high yield (more than 80 percent), low energy consumption in the production process, reusability of solid acid, no corrosion to a reactor, simple operation, high efficiency and environmental protection.
Description
Technical Field
The invention relates to a preparation method of plant cellulose nanofibrils with high yield and low energy consumption, in particular to a method for preparing long rod-shaped cellulose nanofibrils by pretreatment of lignin-based solid acids.
Background
The preparation of the cellulose nanofibrils mainly adopts high-pressure homogenization treatment as a main part, and adopts pretreatment of chemistry, biological enzyme, mechanical shearing and the like as an auxiliary part to reduce the energy consumption of high-pressure homogenization and avoid the blockage of a homogenizer, wherein the chemical reagent of the TEMPO chemical oxidation pretreatment method cannot be recycled and has high cost, the fiber yield after strong acid chemical pretreatment is obviously reduced, the acid is difficult to be recycled, and the mechanical shearing pretreatment still has the problem of high energy consumption.
Patent CN103061174B discloses methods for preparing cellulose nanofibrils with assistance of strong acid pretreatment, which first utilize 60-70 wt% concentrated sulfuric acid or hydrochloric acid to hydrolyze bleached pulp fibers for 1.0-1.5 h at 40-60 ℃, swell, dissolve and open a cellulose part amorphous region, and then utilize high-speed homogenizing mechanical shear to rapidly obtain cellulose nanofibrils, but the acidolysis solution is repeatedly washed with water to neutrality, and the unreacted acid is neutralized with quantitative alkali, which results in consumption of acid and difficult recycling, and the yield of cellulose is low.
The solid acid is a typical heterogeneous catalyst, and the solid acid catalyst not only can make up the defects of liquid acid to a certain extent at , but also has the advantages of easy separation, simple treatment and reutilization, and greatly optimizes the economical use of the solid acid.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for preparing long rod-like cellulose nanofibrils through pretreatment of lignin-based solid acids, so as to solve the above-mentioned drawbacks of the background art.
The object of the present invention is achieved by at least defined in the following claims.
method for preparing long rod-shaped cellulose nanofibrils through lignin-based solid acid pretreatment, which is different from other processes, is characterized in that recyclable lignin-based solid acid is used for pretreating dissolving pulp to destroy a part of non-crystallization area of cellulose but have limited influence on the yield of the cellulose, and then a micro-jet homogenization method is used for obtaining the long rod-shaped cellulose nanofibrils, and the method comprises the following steps:
(1) placing alkali lignin in N2Partially carbonizing in the atmosphere, sulfonating with concentrated sulfuric acid, washing with distilled water to remove free sulfate ions, vacuum drying, grinding, and sieving to obtain lignin-based solid acid;
(2) mixing the lignin-based solid acid and the dissolving pulp fiber and then carrying out pre-hydrolysis treatment;
(3) centrifugally separating the hydrolysis substrate, and removing supernatant to respectively obtain fiber residue and lignin-based solid acid; mechanically dissociating the separated fiber residues by using a micro-jet homogenizer to obtain the long rod-shaped cellulose nano-fibrils; the separated lignin-based solid acids are again used for the prehydrolysis treatment of the dissolving pulp fibers.
, the alkali lignin in the step (1) is extracted from corn stalk enzymolysis residues which are byproducts of bioethanol industry by an alkali solution acidification method.
, in the carbonization process in the step (1), the carbonization temperature is 400-500 ℃, and the carbonization time is 1-3 h.
, in the sulfonation process in the step (1), the sulfonation temperature is 140-160 ℃, and the sulfonation time is 8-12 h.
, drying in vacuum in the step (1) at 40-60 ℃ for 12-24 h, and sieving with 100-200 meshes.
, the temperature of prehydrolysis in the step (2) is 120-170 ℃, the prehydrolysis time is 4-24 hours, and the stirring speed is 150-200 rpm.
, controlling the fiber solid content of the dissolving pulp in the step (2) to be 0.6-1.6 wt%.
, the mass ratio of the lignin-based solid acid to the dissolving pulp fiber in the step (2) is 0.5-2: 1.
, the rotation speed of the centrifugal separation in the step (3) is 500-1000 rpm, and the time is 2-10 min.
And , operating the pressure of the microfluidizer 25000-30000 PSI in the step (3), and repeating the treatment for 6-10 times.
When the lignin-based solid acid is used for prehydrolysis, β -1.4-glycosidic bond parts of cellulose are broken, the fiber length is reduced to be below 200um, and then the long rod-shaped cellulose nanofibrils are prepared by utilizing a micro-jet method.
Compared with the prior art, the method for preparing the long rod-shaped cellulose nanofibrils by the pretreatment of recyclable lignin-based solid acids has the following advantages:
(1) the preparation cost of the lignin-based solid acid is low, the used alkali lignin carbon source is from a byproduct of bioethanol industry, namely corn straw enzymolysis residues, and is lower in raw material cost compared with other commercial carbon sources (glucose, cellulose, starch and the like) solid acid, the method has no damage to human bodies and environment, the defects that the traditional liquid acid has high requirement on equipment, the cellulose yield is low, the preparation cost of the traditional solid acid catalyst is high, the process is complex and the like are overcome, therefore, the green, low-consumption, low-cost and recyclable lignin-based solid acid pretreatment method provides new ways for the preparation of cellulose nanofibrils, the low-added-value enzymolysis residues are converted into the high-added-value recyclable lignin-based solid acid catalyst, and the utilization efficiency and the value of the enzymolysis residues are improved.
(2) The solid acid acidic group and the carbon skeleton are combined in a covalent bond form, which is different from the physical adsorption of -type supported solid acid acidic group, so that the catalytic hydrolysis stability of the solid acid is higher.
(3) The yield of the catalytic hydrolysis cellulose of the solid acid is high, the yield of the cellulose nanofibrils is more than 80 percent and is more than that of the traditional liquid acid and the conventional solid acid (40-70 percent).
(4) The cellulose nano-fibrils prepared by the pretreatment of the solid acid are long rod-shaped and are similar to cellulose nano-crystals prepared by a sulfuric acid method.
Drawings
FIG. 1 is a scanning electron micrograph of a lignin-based solid acid in example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of long rod-shaped cellulose nanofibrils according to example 1 of the present invention;
FIG. 3 is a graph showing the number of hydrolysis repetitions of lignin-based solid acid and the yield of cellulose nanofibrils according to example 4 of the present invention.
Detailed Description
Specific implementations of the present invention are described in further with reference to the following examples and figures, but the embodiments of the present invention are not limited thereto.
The document discloses a method for obtaining alkali lignin by dissolving lignin in sodium hydroxide and separating out the alkali lignin from enzymic hydrolysis residues by using corn enzymolysis straw residues as raw materials, wherein the alkali lignin used in the examples is prepared by adopting the method.
Example 1
Step 1: placing alkali lignin in a tube furnace in N2Partially carbonizing at 400 deg.C for 3h, sulfonating lignin with concentrated sulfuric acid at 140 deg.C for 8h,washing the sulfonated lignin by distilled water for many times to remove free sulfate ions, then carrying out vacuum drying for 12h at 60 ℃, grinding and sieving by a 100-mesh sieve to obtain the lignin-based solid acid.
Step 2: placing lignin-based solid acid and dissolving pulp fiber in a stainless steel high-pressure reaction kettle for pre-hydrolysis treatment. The prehydrolysis temperature and stirring in the stainless steel high-pressure reaction kettle are controlled by an external heat collection type constant-temperature heating magnetic stirrer, the stirring speed is 150rpm, the prehydrolysis temperature is set to 120 ℃, the prehydrolysis time is 4 hours, the solid content of dissolving pulp fibers is set to 0.6 wt%, and the mass ratio of lignin-based solid acid to dissolving pulp fibers is 0.5: 1.
and 3, step 3: after the pre-hydrolysis treatment, the solid acid and the partially hydrolyzed dissolving pulp fiber are centrifugally separated for 10min at the rotating speed of 500 rpm; and mechanically dissociating the separated partial hydrolyzed dissolving pulp fibers into cellulose nano-fibrils in a micro-jet homogenizer, and passing through a 75um reaction cavity for 10 times under the pressure of 25000PSI to obtain the long rod-shaped cellulose nano-fibrils with the yield of 92.8 percent.
FIG. 1 is a scanning electron microscope image of the lignin-based solid acid prepared in the present example, and it can be seen from FIG. 1 that the surface morphology of the lignin-based solid acid is relatively smooth, and the particle size distribution of the lignin-based solid acid is approximately 1 to 10 μm. Fig. 2 is a scanning electron microscope image of the cellulose nanofibril prepared in the embodiment, and it can be seen from fig. 2 that the cellulose nanofibril is in a long rod shape, and is similar to the cellulose nanocrystalline prepared by the sulfuric acid method in shape, the length distribution is about 100-400 nm, and the width distribution is about 10-20 nm.
Example 2
Step 1: placing alkali lignin in a tube furnace in N2Partially carbonizing at 450 ℃ for 2h in the atmosphere, sulfonating lignin with concentrated sulfuric acid at 150 ℃ for 10h, washing the sulfonated lignin with distilled water for multiple times to remove free sulfate ions, vacuum drying at 50 ℃ for 18h, grinding and sieving with a 150-mesh sieve to obtain the lignin-based solid acid.
Step 2: placing lignin-based solid acid and dissolving pulp fiber in a stainless steel high-pressure reaction kettle for pre-hydrolysis treatment. The prehydrolysis temperature and stirring in the stainless steel high-pressure reaction kettle are controlled by an external heat collection type constant-temperature heating magnetic stirrer, the stirring speed is 180rpm, the prehydrolysis temperature is set to be 150 ℃, the prehydrolysis time is 14 hours, the solid content of the dissolving pulp fibers is set to be 1.2 wt%, and the mass ratio of the lignin-based solid acid to the dissolving pulp fibers is 1.0: 1.
And 3, step 3: after the pre-hydrolysis treatment, the solid acid and the partially hydrolyzed dissolving pulp fiber are centrifugally separated for 5min at the rotating speed of 800 rpm; and mechanically dissociating the separated partial hydrolyzed dissolving pulp fibers into cellulose nano-fibrils in a micro-jet homogenizer, and passing through a 75um reaction cavity for 8 times under the pressure of 28000PSI to obtain the long rod-shaped cellulose nano-fibrils with the yield of 88.4 percent.
Example 3
Step 1: placing alkali lignin in a tube furnace in N2Partially carbonizing at 500 ℃ for 1h in the atmosphere, sulfonating lignin carbide with concentrated sulfuric acid at 160 ℃ for 12h, washing the sulfonated lignin with distilled water for multiple times to remove free sulfate ions, vacuum drying at 40 ℃ for 24h, grinding and sieving with a 200-mesh sieve to obtain the lignin-based solid acid.
Step 2: placing lignin-based solid acid and dissolving pulp fiber in a stainless steel high-pressure reaction kettle for pre-hydrolysis treatment. The prehydrolysis temperature and stirring in the stainless steel high-pressure reaction kettle are controlled by an external heat collection type constant-temperature heating magnetic stirrer, the stirring speed is 200rpm, the prehydrolysis temperature is set to be 170 ℃, the prehydrolysis time is 24 hours, the solid content of dissolving pulp fibers is set to be 1.6wt%, and the mass ratio of lignin-based solid acid to dissolving pulp fibers is 2.0: 1.
and 3, step 3: after the pre-hydrolysis treatment, the solid acid and the partially hydrolyzed dissolving pulp fiber are centrifugally separated for 2min at the rotating speed of 1000 rpm; and mechanically dissociating the separated partial hydrolysis dissolving pulp fibers into cellulose nano-fibrils in a micro-jet homogenizer, and passing through a 75um reaction cavity for 6 times under the pressure of 30000PSI to obtain the long rod-shaped cellulose nano-fibrils with the yield of 85.2 percent.
Example 4
Step 1: placing alkali lignin in a tube furnace in N2Partially carbonizing at 400 deg.C for 1 hr, sulfonating lignin with concentrated sulfuric acid at 150 deg.C for 12 hr, washing sulfonated lignin with distilled water for several times to remove free sulfate ions, vacuum drying at 60 deg.C for 12 hr, and grindingGrinding and sieving with 100 mesh sieve to obtain lignin-based solid acid.
Step 2: placing lignin-based solid acid and dissolving pulp fiber in a stainless steel high-pressure reaction kettle for pre-hydrolysis treatment. The prehydrolysis temperature and stirring in the stainless steel high-pressure reaction kettle are controlled by an external heat collection type constant-temperature heating magnetic stirrer, the stirring speed is 150rpm, the prehydrolysis temperature is set to be 160 ℃, the prehydrolysis time is 12 hours, the solid content of the dissolving pulp fibers is set to be 1.2 wt%, and the mass ratio of the lignin-based solid acid to the dissolving pulp fibers is 1.5.
And 3, step 3: after the prehydrolysis treatment, centrifugally separating the solid acid and the partially hydrolyzed dissolving pulp fibers at the rotating speed of 5000rpm for 5 min; the separated solid acid is used again for the hydrolysis of step 2. And mechanically dissociating the dissolved pulp fiber after each centrifugal separation into cellulose nanofibrils in a micro-jet homogenizer, and passing through a 75um reaction cavity for 6 times under the pressure of 30000PSI to obtain the long rod-shaped cellulose nanofibrils.
Fig. 3 is a graph showing the number of repeated hydrolysis of the lignin-based solid acid and the yield of the cellulose nanofibrils in this example, and it can be seen from fig. 3 that the catalytic hydrolysis stability of the solid acid is high. The used lignin-based solid acid is separated and recovered, and directly put into repeated hydrolysis pretreatment, the repeated utilization times can reach 6 times, and the yield of the cellulose nano-fibrils is over 80 percent.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any equivalent alterations, modifications or improvements made by those skilled in the art to the above-described embodiments using the technical solutions of the present invention are still within the scope of the technical solutions of the present invention.
Claims (10)
- A method for preparing long rod-like cellulose nanofibrils by pretreatment of lignin-based solid acids, characterized in that it comprises the following steps:(1) placing alkali lignin in N2Partially carbonizing in the atmosphere, sulfonating with concentrated sulfuric acid, washing with distilled water to remove free sulfate ions, vacuum drying, grinding, and sieving to obtain lignin-based solid acid;(2) mixing the lignin-based solid acid and the dissolving pulp fiber and then carrying out pre-hydrolysis treatment;(3) centrifugally separating the hydrolysis substrate, and removing supernatant to respectively obtain fiber residue and lignin-based solid acid; mechanically dissociating the separated fiber residues by using a micro-jet homogenizer to obtain the long rod-shaped cellulose nano-fibrils; the separated lignin-based solid acids are again used for the prehydrolysis treatment of the dissolving pulp fibers.
- 2. The method as claimed in claim 1, wherein in the step (1), the alkali lignin is extracted from the enzymolysis residue of the corn stalks by an alkali solution acidification method.
- 3. The method according to claim 1, wherein in the step (1), the carbonization temperature is 400-500 ℃ and the carbonization time is 1-3 h during carbonization.
- 4. The method according to claim 1, wherein in the step (1), the sulfonation temperature is 140-160 ℃ and the sulfonation time is 8-12 h in the sulfonation process.
- 5. The method according to claim 1, wherein in the step (1), the temperature of vacuum drying is 40-60 ℃ and the time is 12-24 h; the number of the screening meshes is 100-200 meshes.
- 6. The method according to claim 1, wherein in the step (2), the temperature of the prehydrolysis is 120-170 ℃, the prehydrolysis time is 4-24 h, and the stirring speed is 150-200 rpm.
- 7. The method of claim 1, wherein the dissolved pulp fiber solid content in step (2) is controlled to be 0.6-1.6 wt%.
- 8. The method according to claim 1, wherein the mass ratio of the lignin-based solid acid to the dissolving pulp fiber in the step (2) is 0.5-2: 1.
- 9. the method according to claim 1, wherein the centrifugation in the step (3) is performed at a rotation speed of 500-1000 rpm for 2-10 min.
- 10. The method according to claim 1, wherein the operating pressure of the microfluidizer in the step (3) is 25000 to 30000PSI, and the treatment is repeated 6 to 10 times.
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| CN117461830A (en) * | 2023-11-14 | 2024-01-30 | 北京工商大学 | Cellulose nanofiber and sodium alginate composite microgel with lubricating effect and preparation method thereof |
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