CN116640232A - Preparation method of cellulose nanocrystals - Google Patents
Preparation method of cellulose nanocrystals Download PDFInfo
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- CN116640232A CN116640232A CN202310128150.XA CN202310128150A CN116640232A CN 116640232 A CN116640232 A CN 116640232A CN 202310128150 A CN202310128150 A CN 202310128150A CN 116640232 A CN116640232 A CN 116640232A
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- 229920002678 cellulose Polymers 0.000 title claims abstract description 66
- 239000001913 cellulose Substances 0.000 title claims abstract description 66
- 239000002159 nanocrystal Substances 0.000 title claims abstract description 39
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000000843 powder Substances 0.000 claims abstract description 35
- 239000007787 solid Substances 0.000 claims abstract description 34
- 239000007864 aqueous solution Substances 0.000 claims abstract description 33
- 241000209094 Oryza Species 0.000 claims abstract description 23
- 235000007164 Oryza sativa Nutrition 0.000 claims abstract description 23
- 235000009566 rice Nutrition 0.000 claims abstract description 23
- 239000010902 straw Substances 0.000 claims abstract description 23
- 230000007062 hydrolysis Effects 0.000 claims abstract description 21
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 21
- 238000002386 leaching Methods 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 17
- 238000002791 soaking Methods 0.000 claims abstract description 16
- 239000000126 substance Substances 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 14
- 238000004140 cleaning Methods 0.000 claims abstract description 7
- 238000004108 freeze drying Methods 0.000 claims abstract description 7
- UKLNMMHNWFDKNT-UHFFFAOYSA-M sodium chlorite Chemical compound [Na+].[O-]Cl=O UKLNMMHNWFDKNT-UHFFFAOYSA-M 0.000 claims abstract description 7
- 229960002218 sodium chlorite Drugs 0.000 claims abstract description 7
- 230000003301 hydrolyzing effect Effects 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 5
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 21
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 19
- 239000000460 chlorine Substances 0.000 claims description 19
- 229910052801 chlorine Inorganic materials 0.000 claims description 19
- 150000003839 salts Chemical class 0.000 claims description 19
- 239000002253 acid Substances 0.000 claims description 18
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 12
- 150000007524 organic acids Chemical class 0.000 claims description 11
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 9
- 235000019253 formic acid Nutrition 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 6
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 claims description 3
- 239000005708 Sodium hypochlorite Substances 0.000 claims description 3
- 235000011054 acetic acid Nutrition 0.000 claims description 3
- VKJKEPKFPUWCAS-UHFFFAOYSA-M potassium chlorate Chemical compound [K+].[O-]Cl(=O)=O VKJKEPKFPUWCAS-UHFFFAOYSA-M 0.000 claims description 3
- SATVIFGJTRRDQU-UHFFFAOYSA-N potassium hypochlorite Chemical compound [K+].Cl[O-] SATVIFGJTRRDQU-UHFFFAOYSA-N 0.000 claims description 3
- VISKNDGJUCDNMS-UHFFFAOYSA-M potassium;chlorite Chemical compound [K+].[O-]Cl=O VISKNDGJUCDNMS-UHFFFAOYSA-M 0.000 claims description 3
- 235000019260 propionic acid Nutrition 0.000 claims description 3
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 3
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims description 3
- 239000002699 waste material Substances 0.000 abstract description 3
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- 239000002893 slag Substances 0.000 abstract description 2
- 239000002245 particle Substances 0.000 description 16
- 238000005406 washing Methods 0.000 description 12
- 238000000502 dialysis Methods 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229920001046 Nanocellulose Polymers 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000000921 elemental analysis Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 238000002329 infrared spectrum Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000007710 freezing Methods 0.000 description 3
- 230000008014 freezing Effects 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005903 acid hydrolysis reaction Methods 0.000 description 2
- 238000007605 air drying Methods 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- NJSUFZNXBBXAAC-UHFFFAOYSA-N ethanol;toluene Chemical compound CCO.CC1=CC=CC=C1 NJSUFZNXBBXAAC-UHFFFAOYSA-N 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 1
- 229920002488 Hemicellulose Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 150000004676 glycans Chemical class 0.000 description 1
- 238000009775 high-speed stirring Methods 0.000 description 1
- 229920005610 lignin Polymers 0.000 description 1
- 239000002029 lignocellulosic biomass Substances 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000003921 particle size analysis Methods 0.000 description 1
- 229920001282 polysaccharide Polymers 0.000 description 1
- 239000005017 polysaccharide Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000011802 pulverized particle Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000000346 sugar Nutrition 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 238000006557 surface reaction Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
- C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biochemistry (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The invention provides a preparation method of cellulose nanocrystals, and belongs to the technical field of cellulose preparation. Sequentially cleaning, drying and crushing rice straw to obtain rice straw powder; mixing the rice straw powder with leaching liquor for leaching to obtain solid powder; sequentially soaking the solid powder in a sodium chlorite aqueous solution and an inorganic alkaline substance aqueous solution, and then freeze-drying to obtain cellulose; and hydrolyzing the cellulose in a hydrolysis system to obtain the cellulose nanocrystals. Compared with the pure sulfuric acid method, the method has the advantages of less environmental pollution and small volume of waste liquid, can greatly reduce the generation rate of the slag and is safe in preparation process.
Description
Technical Field
The invention relates to the technical field of cellulose preparation, in particular to a preparation method of cellulose nanocrystals.
Background
Cellulose is the most widely distributed and abundant polysaccharide in nature, and nanocellulose having a nano-size is receiving a great deal of attention. Nanocellulose is a cellulose material with a diameter on the nanometer scale and a length-to-length ratio. Cellulose Nanocrystals (CNCs), cellulose Nanofibrils (CNFs) and Bacterial Nanocellulose (BNCs) are largely classified into 3 types according to the size, morphology and preparation method of nanocellulose. CNCs and CNFs can be extracted from lignocellulosic biomass, and BNCs are produced by bacteria accumulating low molecular mass sugars. CNFs are mainly prepared by mechanical methods (high-pressure homogenization, micro-jet homogenization, high-speed stirring, ball milling, etc.), and have diameters of 10-100 nm and lengths of several micrometers. CNCs are needle-like or rod-like crystals with high crystallinity, and have a length of 500nm or less and a diameter of about 4 to 70nm, compared with the filament-like shape and low crystallinity of CNFs. CNCs are typically prepared by acid hydrolysis, in which non-cellulosic parts and most of the non-crystalline regions in the cellulose are removed, leaving crystalline regions of the cellulose, thereby separating highly crystalline CNCs, with sulfuric acid hydrolysis being the most common. In addition, CNCs can be prepared by oxidation, enzymolysis, and mechanical treatment. Because of their renewable, biodegradable, amphiphilic, high aspect ratio, biocompatible, and easy surface functionalization properties, CNCs are widely used in textile, chemical, pharmaceutical, environmental protection, and other fields.
In the preparation process of cellulose nanocrystals, high-concentration (mass fraction is 63-65%) sulfuric acid is generally adopted to hydrolyze the generated cellulose into nanocrystals, and a large amount of high-concentration acidic waste liquid is generated in the process, so that the environment is polluted, and hidden danger is caused to the preparation process.
Disclosure of Invention
In view of the above, the present invention is directed to a method for preparing cellulose nanocrystals. The hydrolysis system of the invention has little pollution to the environment and safe preparation process.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of cellulose nanocrystals, which comprises the following steps:
sequentially cleaning, drying and crushing rice straw to obtain rice straw powder;
mixing the rice straw powder with leaching liquor for leaching to obtain solid powder;
sequentially soaking the solid powder in an oxygen acid salt aqueous solution of chlorine and an inorganic alkaline substance aqueous solution, and then freeze-drying to obtain cellulose;
and hydrolyzing the cellulose in a hydrolysis system to obtain the cellulose nanocrystals, wherein the hydrolysis system comprises organic acid, sulfuric acid and water.
Preferably, the leaching solution comprises toluene and ethanol, wherein the volume ratio of toluene to ethanol is 2:1.
preferably, the liquid-solid ratio of the leaching is 10-30 mL:1g.
Preferably, the mass fraction of the aqueous solution of the oxygen acid salt of chlorine is 0.5-3%, and the pH value is 3-4.
Preferably, the oxy acid salt of chlorine in the aqueous solution of oxy acid salt of chlorine comprises sodium hypochlorite, potassium hypochlorite, sodium chlorite, potassium chlorite, sodium chlorate or potassium chlorate.
Preferably, the ratio of liquid to solid soaked in the aqueous solution of the oxy acid salt of chlorine is 10-60 mL/1 g.
Preferably, the liquid-solid ratio of the inorganic alkaline substance immersed in the aqueous solution is 10-50 mL/1 g.
Preferably, the mass concentration of the organic acid in the hydrolysis system is 60-80%, and the mass concentration of the sulfuric acid is 6-15%.
Preferably, the organic acid comprises formic acid, acetic acid or propionic acid.
Preferably, the mass ratio of the cellulose to the hydrolysis system is 1.5-6:100.
The invention provides a preparation method of cellulose nanocrystals, which comprises the following steps: sequentially cleaning, drying and crushing rice straw to obtain rice straw powder; mixing the rice straw powder with leaching liquor for leaching to obtain solid powder; sequentially soaking the solid powder in an oxygen acid salt aqueous solution of chlorine and an inorganic alkaline substance aqueous solution, and then freeze-drying to obtain cellulose; and hydrolyzing the cellulose in a hydrolysis system to obtain the cellulose nanocrystals, wherein the hydrolysis system comprises organic acid, sulfuric acid and water.
Compared with the traditional method (pure sulfuric acid method), the method has the advantages of less environmental pollution and small waste liquid volume, can greatly reduce the generation rate of broken slag, is safe in preparation process, and can prepare cellulose nanocrystals with uniform size and particle size ranging from 100nm to 200nm.
Drawings
FIG. 1 is a graph showing the hydrated particle size of cellulose nanocrystals obtained in example 1;
FIG. 2 is a transmission electron microscope image of cellulose nanocrystals prepared in example 1;
FIG. 3 is an infrared spectrum of the cellulose nanocrystals prepared in example 1;
FIG. 4 is a graph showing the hydrated particle size of cellulose nanocrystals obtained in example 2;
FIG. 5 is a transmission electron microscope image of cellulose nanocrystals prepared in example 2;
FIG. 6 is a graph showing the hydrated particle size of cellulose nanocrystals produced in the comparative example;
FIG. 7 is a transmission electron microscope image of cellulose nanocrystals prepared in the comparative example.
Detailed Description
The invention provides a preparation method of cellulose nanocrystals, which comprises the following steps:
sequentially cleaning, drying and crushing rice straw to obtain rice straw powder;
mixing the rice straw powder with leaching liquor for leaching to obtain solid powder;
sequentially soaking the solid powder in an oxygen acid salt aqueous solution of chlorine and an inorganic alkaline substance aqueous solution, and then freeze-drying to obtain cellulose;
and hydrolyzing the cellulose in a hydrolysis system to obtain the cellulose nanocrystals, wherein the hydrolysis system comprises organic acid, sulfuric acid and water.
According to the invention, rice straw powder is obtained by sequentially cleaning, drying and crushing rice straw.
In the present invention, the washing is preferably a clean water washing, and the cleaning functions to wash off floating ash.
In the present invention, the drying is preferably air-dried for one week or at 35 to 60 ℃, and the drying is preferably to constant weight.
In the present invention, the pulverization is preferably grinding, and the grinding is preferably performed using a grinder, and the pulverized particle size is sieved with a 60-mesh sieve.
After rice straw powder is obtained, the rice straw powder is mixed with leaching liquor for leaching to obtain solid powder.
In the present invention, the leaching solution preferably comprises toluene and ethanol, and the volume ratio of toluene to ethanol is preferably 2:1.
in the present invention, the liquid-solid ratio of the leaching is preferably 10 to 30 mL/1 g, more preferably 15 mL/1 g.
In the present invention, the time of the leaching is preferably 12 to 36 hours, more preferably 20 hours.
After the leaching is completed, the invention preferably further comprises solid-liquid separation and drying in sequence to obtain the solid powder.
The specific mode of the solid-liquid separation and drying is not particularly limited in the present invention, and may be any mode known to those skilled in the art.
After the solid powder is obtained, the solid powder is soaked in an oxygen acid salt aqueous solution of chlorine and an inorganic alkaline substance aqueous solution in sequence, and then the cellulose is obtained by freeze drying.
In the present invention, the aqueous solution of the oxyacid salt of chlorine preferably has a mass fraction of 0.5 to 3%, more preferably 1.4%, and a pH of 3 to 4.
In the present invention, the oxy acid salt of chlorine in the aqueous solution of oxy acid salt of chlorine preferably includes sodium hypochlorite, potassium hypochlorite, sodium chlorite, potassium chlorite, sodium chlorate or potassium chlorate.
In the present invention, the ratio of liquid to solid immersed in the aqueous solution of the oxy acid salt of chlorine is preferably 10 to 60 mL/1 g, more preferably 30 mL/1 g, and the time is preferably 5 hours, and the temperature is preferably 70 ℃.
In the present invention, the soaking in the aqueous solution of the oxy acid salt of chlorine is preferably performed under stirring, and the soaking in the aqueous solution of sodium chlorite has the effect of destroying hemicellulose in the solid powder.
After the completion of the soaking in the aqueous solution of the oxygen acid salt of chlorine, the method preferably further comprises the steps of sequentially carrying out solid-liquid separation and washing, and soaking the solid in the aqueous solution of the inorganic alkaline substance.
In the present invention, the solid-liquid separation is preferably centrifugation or filtration.
In the present invention, the washing is preferably water washing.
In the present invention, the ratio of liquid to solid immersed in the aqueous solution of the inorganic alkaline substance is preferably 10 to 50 mL/1 g, more preferably 20 mL/1 g, and the time is preferably 2 hours, and the temperature is preferably 90 ℃.
In the present invention, the mass concentration of the aqueous inorganic alkaline substance solution is preferably 5%, and the aqueous inorganic alkaline substance solution is preferably an aqueous KOH solution or an aqueous NaOH solution.
In the present invention, the soaking in the aqueous solution of the inorganic alkaline substance is preferably performed under stirring, and the soaking in the aqueous solution of the inorganic alkaline substance functions to destroy lignin and silica in the solid powder.
After the completion of the soaking in the aqueous solution of the inorganic alkaline substance, it is preferable to further include washing and filtering in order.
In the present invention, the freeze-drying is preferably liquid nitrogen freezing.
After the cellulose is obtained, the cellulose is hydrolyzed in a hydrolysis system to obtain the cellulose nanocrystals, wherein the hydrolysis system comprises organic acid, sulfuric acid and water.
In the present invention, the mass concentration of the organic acid in the hydrolysis system is preferably 60 to 80%, and the mass concentration of sulfuric acid is preferably 6 to 15%.
In the present invention, the organic acid preferably includes formic acid, acetic acid or propionic acid.
In the present invention, the mass ratio of the cellulose to the hydrolysis system is preferably 1.5 to 6:100, more preferably 3:100.
In the present invention, the temperature of the hydrolysis is preferably 80℃and the time is preferably 3 hours.
The invention preferably terminates the hydrolysis by adding water.
In the present invention, the hydrolysis is preferably further followed by centrifugation and dialysis in that order.
In the present invention, the dialysis is preferably performed using a 12-14 kd dialysis bag.
After the dialysis is completed, the present invention preferably performs drying to obtain the cellulose nanocrystals.
In order to further illustrate the present invention, the following examples are provided to illustrate the preparation of cellulose nanocrystals in detail, but they should not be construed as limiting the scope of the invention.
Example 1
Washing a plurality of rice straws with clear water to remove floating ash, air-drying for one week to constant weight, grinding by using a grinder, and sieving with a 60-mesh sieve.
30g of rice straw powder is extracted by 450mL of toluene-ethanol mixture (the volume ratio of toluene to ethanol is 2:1) for 20h, and the mixture is filtered for three times and dried to constant weight, so as to obtain solid powder.
Soaking the solid powder with sodium chlorite with the mass fraction of 1.4 percent (the pH value is adjusted to 3-4 by using formic acid), and the liquid-solid ratio is 30mL:1g, stirring for 5 hours at 70 ℃ by using a magnetic stirrer, centrifuging and washing to obtain a thick material, soaking the material by using a KOH aqueous solution with the mass concentration of 5%, wherein the liquid-solid ratio is 20mL:1g, 2 at 90℃followed by washing, filtration and liquid nitrogen freezing.
30g of cellulose and 1000g of formic acid/sulfuric acid/water mixed system (the mass concentration of formic acid is 65 percent and the mass concentration of sulfuric acid is 12 percent) are taken to hydrolyze for 3 hours at 80 ℃, 2000mL of water is added to stop the reaction, then the reaction is centrifuged, the dialysis is carried out by using a dialysis bag for 12-14 kd, the conductivity or pH of liquid outside the dialysis bag is detected by using a conductivity meter until no numerical value change is generated before and after 3 hours, thus obtaining cellulose nanocrystal suspension, and cellulose nanocrystal is obtained after drying.
Elemental analysis was performed on the cellulose nanocrystals obtained in example 1, and the results are shown in table 1.
TABLE 1 elemental analysis results (example 1)
The hydrated particle size of the cellulose nanocrystals was shown in FIG. 1, and the average particle size was 160nm.
The morphology of the cellulose nanocrystalline is characterized by a transmission electron microscope, as shown in fig. 2, the morphology of the particles is rod-shaped, the aspect ratio is large, the diameter of the cross section is about a few nanometers, and the length is about 100-200 nm.
As shown in fig. 3, the fourier infrared spectrum shows that the cellulose nanocrystals have functional groups that the cellulose nanocrystals should possess. The infrared spectrum is shown in Table 2.
TABLE 2 Infrared Spectrum data for cellulose nanocrystals prepared in example 1
Example 2
Washing a plurality of rice straws with clear water to remove floating ash, air-drying for one week to constant weight, grinding by using a grinder, and sieving with a 60-mesh sieve.
30g of rice straw powder is taken, 300mL of toluene-ethanol mixture is taken for leaching (the volume ratio of toluene to ethanol is 2:1) for 20h, the filtration is carried out for three times, and the solid powder is obtained after drying to constant weight.
Soaking the solid powder with sodium chlorite with the mass fraction of 2 percent (the pH value is adjusted to 3-4 by using formic acid), and the liquid-solid ratio is 20mL:1g, stirring for 5 hours at 70 ℃ by using a magnetic stirrer, centrifuging and washing to obtain a thick material, soaking the material by using a KOH aqueous solution with the mass concentration of 5%, wherein the liquid-solid ratio is 30mL:1g, 2 at 90℃followed by washing, filtration and liquid nitrogen freezing.
30g of cellulose and 1500g of acetic acid/sulfuric acid/water mixed system (wherein the mass concentration of formic acid is 80 percent and the mass concentration of sulfuric acid is 8 percent) are taken to hydrolyze for 3 hours at 80 ℃, 2000mL of water is added to stop the reaction, then the reaction is centrifuged, the dialysis is carried out by using a dialysis bag for 12-14 kd, the conductivity or pH of liquid outside the dialysis bag is detected by using a conductivity meter until no numerical value change is generated before and after 3 hours, thus obtaining cellulose nanocrystal suspension, and cellulose nanocrystal is obtained after drying.
The cellulose nanocrystals obtained in example 2 were subjected to elemental analysis, and the results obtained are shown in table 3.
TABLE 3 elemental analysis results (example 2)
The hydrated particle size of the cellulose nanocrystals was shown in FIG. 4, and the average particle size was found to be 141nm.
The morphology of the cellulose nanocrystalline is characterized by a transmission electron microscope, as shown in fig. 5, the morphology of the particles is rod-shaped, the aspect ratio is large, the diameter of the cross section is about a few nanometers, and the length is about 100-200 nm.
Comparative example
The same as in example 1, except that 1000g of formic acid/sulfuric acid/water mixed system was replaced with 570mL and 64wt% sulfuric acid was hydrolyzed at 45℃for 30min.
Particle size analysis of the hydrated particle size zetasier is shown in fig. 6, and it is found that the hydrated particle size is not uniform enough and has two significant values that differ greatly.
As shown in figure 7, the morphology of the particles is rod-shaped, the particles have small aspect ratio and cross section diameter of about several nanometers and are 70-120 nm long due to the fact that the particles have small particles.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A method for preparing cellulose nanocrystals, comprising the steps of:
sequentially cleaning, drying and crushing rice straw to obtain rice straw powder;
mixing the rice straw powder with leaching liquor for leaching to obtain solid powder;
sequentially soaking the solid powder in an oxygen acid salt aqueous solution of chlorine and an inorganic alkaline substance aqueous solution, and then freeze-drying to obtain cellulose;
and hydrolyzing the cellulose in a hydrolysis system to obtain the cellulose nanocrystals, wherein the hydrolysis system comprises organic acid, sulfuric acid and water.
2. The method of claim 1, wherein the leaching solution comprises toluene and ethanol in a volume ratio of 2:1.
3. the method according to claim 1 or 2, wherein the leaching has a liquid-to-solid ratio of 10-30 ml:1g.
4. The preparation method according to claim 1, wherein the mass fraction of the aqueous solution of the oxy-acid salt of chlorine is 0.5-3% and the pH value is 3-4.
5. The method according to claim 1 or 4, wherein the oxy acid salt of chlorine in the aqueous solution of oxy acid salt of chlorine comprises sodium hypochlorite, potassium hypochlorite, sodium chlorite, potassium chlorite, sodium chlorate or potassium chlorate.
6. The method according to claim 1 or 4, wherein the ratio of liquid to solid immersed in the aqueous solution of the oxy acid salt of chlorine is 10 to 60 mL/1 g.
7. The method according to claim 1, wherein the ratio of liquid to solid immersed in the aqueous solution of the inorganic alkaline substance is 10 to 50 mL/1 g.
8. The preparation method according to claim 1, wherein the mass concentration of the organic acid in the hydrolysis system is 60-80% and the mass concentration of the sulfuric acid is 6-15%.
9. The method of claim 1 or 8, wherein the organic acid comprises formic acid, acetic acid, or propionic acid.
10. The preparation method according to claim 1 or 8, wherein the mass ratio of the cellulose to the hydrolysis system is 1.5-6:100.
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Citations (8)
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|---|---|---|---|---|
| CN101235604A (en) * | 2007-01-31 | 2008-08-06 | 中国科学院化学研究所 | Method for extracting cellulose from straw |
| CN109336986A (en) * | 2018-10-31 | 2019-02-15 | 梧州学院 | Utilize the method for manioc waste preparation nano-crystal cellulose |
| CN109879973A (en) * | 2019-04-25 | 2019-06-14 | 天津科技大学 | A method of Cellulose nanocrystal body is prepared with mixed-acid hydrolysis |
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| CN113321523A (en) * | 2021-06-22 | 2021-08-31 | 武汉纺织大学 | Cellulose/graphene composite high-strength carbon fiber aerogel plate and preparation method thereof |
| CN114874343A (en) * | 2022-05-30 | 2022-08-09 | 河南工业大学 | Spherical nanocrystalline cellulose based on furfural residues and preparation method thereof |
| CN114989498A (en) * | 2022-06-23 | 2022-09-02 | 福州大学 | Method for preparing nano-cellulose crystal iridescent film by hydrolyzing solid organic acid |
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| CN113321523A (en) * | 2021-06-22 | 2021-08-31 | 武汉纺织大学 | Cellulose/graphene composite high-strength carbon fiber aerogel plate and preparation method thereof |
| CN114874343A (en) * | 2022-05-30 | 2022-08-09 | 河南工业大学 | Spherical nanocrystalline cellulose based on furfural residues and preparation method thereof |
| CN114989498A (en) * | 2022-06-23 | 2022-09-02 | 福州大学 | Method for preparing nano-cellulose crystal iridescent film by hydrolyzing solid organic acid |
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