CN114395054A - Cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification - Google Patents
Cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification Download PDFInfo
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- CN114395054A CN114395054A CN202210133590.XA CN202210133590A CN114395054A CN 114395054 A CN114395054 A CN 114395054A CN 202210133590 A CN202210133590 A CN 202210133590A CN 114395054 A CN114395054 A CN 114395054A
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- cellulose
- deacidification
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- 229920002678 cellulose Polymers 0.000 title claims abstract description 71
- 239000001913 cellulose Substances 0.000 title claims abstract description 71
- 238000000926 separation method Methods 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000000746 purification Methods 0.000 title claims abstract description 8
- 239000002159 nanocrystal Substances 0.000 claims abstract description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000012528 membrane Substances 0.000 claims abstract description 24
- 239000000413 hydrolysate Substances 0.000 claims abstract description 17
- 239000011550 stock solution Substances 0.000 claims abstract description 15
- 238000005903 acid hydrolysis reaction Methods 0.000 claims abstract description 14
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 14
- 239000002994 raw material Substances 0.000 claims abstract description 11
- 239000002253 acid Substances 0.000 claims abstract description 10
- 239000000047 product Substances 0.000 claims abstract description 10
- 239000002699 waste material Substances 0.000 claims abstract description 10
- 238000007670 refining Methods 0.000 claims abstract description 9
- 108010009736 Protein Hydrolysates Proteins 0.000 claims abstract description 6
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 26
- 238000006243 chemical reaction Methods 0.000 claims description 13
- 239000000243 solution Substances 0.000 claims description 12
- 239000006185 dispersion Substances 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 238000005119 centrifugation Methods 0.000 claims description 5
- 238000006460 hydrolysis reaction Methods 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 5
- 229920000742 Cotton Polymers 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 4
- 239000012510 hollow fiber Substances 0.000 claims description 4
- 230000007062 hydrolysis Effects 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 239000000835 fiber Substances 0.000 claims description 3
- 230000003472 neutralizing effect Effects 0.000 claims description 3
- 229920001131 Pulp (paper) Polymers 0.000 claims description 2
- 238000007865 diluting Methods 0.000 claims description 2
- 238000010298 pulverizing process Methods 0.000 claims description 2
- 125000000969 xylosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)CO1)* 0.000 claims description 2
- 230000000712 assembly Effects 0.000 claims 1
- 238000000429 assembly Methods 0.000 claims 1
- 238000001035 drying Methods 0.000 claims 1
- 239000003513 alkali Substances 0.000 abstract description 8
- 238000002360 preparation method Methods 0.000 abstract description 5
- 150000003839 salts Chemical class 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000011031 large-scale manufacturing process Methods 0.000 abstract description 2
- 238000012423 maintenance Methods 0.000 abstract 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 21
- 230000003321 amplification Effects 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 229920001046 Nanocellulose Polymers 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001502 supplementing effect Effects 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
- C08B15/08—Fractionation of cellulose, e.g. separation of cellulose crystallites
Abstract
The invention provides a cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification, which comprises the following steps: 1) pretreating raw materials to prepare cellulose nanocrystalline acid hydrolysis stock solution; 2) centrifugal separation, namely directly separating waste acid from hydrolysate; 3) after neutralization, refining and centrifuging through a butterfly centrifuge to remove salt; 4) and separating and purifying by an ultrafiltration membrane separation system, and concentrating to obtain a cellulose nanocrystalline product. The invention aims to solve the problems of high alkali consumption, high water consumption and long time consumption in the production of the cellulose nanocrystals, and the acid is separated from the hydrolysate, so that the consumption of alkali and water can be greatly reduced, and the preparation of the green and low-cost cellulose nanocrystals is realized. Through two-step centrifugal treatment, a large amount of dilute acid is separated, the water consumption can be reduced by 10-90%, the alkali consumption is reduced by 10-65%, the waste discharge is reduced by 10-65%, the cost of the cellulose nanocrystal is reduced by 10-30%, compared with the prior art, the energy consumption is low, the equipment maintenance cost is low, and a technical basis is provided for large-scale production and industrial application of the cellulose nanocrystal.
Description
Technical Field
The invention belongs to the technical field of nano material preparation, and particularly relates to a method for directly separating acid from a hydrolysate in the process of preparing cellulose nanocrystals, so that large-scale green low-cost preparation of the cellulose nanocrystals is realized.
Background
Cellulose Nanocrystals (CNCs) are rigid rod-like nanomaterials with high specific surface area, light weight, excellent mechanical properties, reproducibility, degradability, good biocompatibility and high crystallinity, and have good hydrophilicity and modifiable surface chemical modification properties. The diameter is 3-50 nm, and the length is tens to hundreds of nm.
Due to good physicochemical property and ecological property, the nano-cellulose is widely applied to the fields of medicine, electronics, buildings, foods, coatings and the like in recent years. The nanocellulose market is expected to grow from 2.7126 billion dollars in 2017 to 10.7643 billion dollars in 2025, during which the composite annual growth rate is 18.80%. The global daily output can reach the ton grade, and mainly comprises the following components: CelluForce Inc (Canada) 1 t/d; Alberta-Pacific Forest Inc. (Canada) 500 kg/d; the company GranBio (USA) 500 kg/d.
The sulfuric acid hydrolysis method is the most important method for industrially preparing the cellulose nanocrystals at present, and has the advantages of simple and convenient operation, easy industrial amplification, good product thermal stability and good colloidal stability. The amorphous and sub-crystalline regions of the cellulosic feedstock are first hydrolyzed by high concentrations of inorganic sulfuric acid, leaving their crystalline regions. After hydrolysis reaction, adding water to quench reaction, neutralizing a large amount of generated dilute acid waste liquid by using a sodium hydroxide solution with relatively high price, standing and settling to remove partial salt, and then removing residual salt by using a continuous water adding and membrane separation method. The United states department of forestry reports data that 37200 liters of water, 300 liters of 64% sulfuric acid (296 kg sulfuric acid), 260kg sodium hydroxide are consumed to produce 530kg sodium sulfate for every 25kg of cellulose nanocrystals produced during the large-scale industrial production process. The sodium hydroxide added in the process is too large, and the energy consumption and the water consumption in the product separation and purification stage are increased due to the generation of a large amount of salt, so the production cost is higher. In addition, there are many other problems such as large water consumption, long time consumption, corrosion to equipment, large waste discharge, environmental pollution, and the like. Therefore, it is urgently needed to construct a more efficient and environment-friendly deacidification process to realize the clean and low-cost production of the cellulose nanocrystals.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a cellulose nanocrystal separation and purification method based on centrifugal separation and direct deacidification, which utilizes strong centrifugal force generated by high-speed rotation of a centrifugal machine rotor to accelerate the sedimentation speed of particles in liquid and separate substances with different sedimentation coefficients and buoyancy densities in a product, namely, a large amount of waste acid liquid is directly separated and removed from cellulose nanocrystal hydrolysate, so that the problems of high alkali consumption, high water consumption and long time consumption in the preparation process of cellulose nanocrystals are solved, the consumption of alkali and water is reduced, and the preparation of green and low-cost cellulose nanocrystals is realized.
By the scheme, the water consumption can be reduced by 10-90%, the alkali consumption can be reduced by 10-65%, the waste discharge can be reduced by 10-65%, the cost of the cellulose nanocrystal can be reduced by 10-30%, and a technical basis is provided for large-scale production and industrial application of the cellulose nanocrystal.
The technical solution of the invention is as follows:
a cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification comprises the following specific steps:
1) preparing cellulose nanocrystalline acid hydrolysis stock solution;
2) centrifuging the cellulose nanocrystal acid hydrolysis stock solution, and separating to obtain a cellulose nanocrystal hydrolysis solution;
3) neutralizing the cellulose nanocrystal hydrolysate, and controlling the pH value of the hydrolysate to be 6-7;
4) and separating by an ultrafiltration membrane separation system, and concentrating to obtain a cellulose nanocrystalline product.
Further, the step 1) of preparing the cellulose nanocrystal acid hydrolysis stock solution comprises the following specific steps:
s 1: adding sulfuric acid into the reaction kettle; the mass fraction of the sulfuric acid is 58-65%;
s 2: preheating the reaction kettle to 42-55 ℃;
s 3: putting the pretreated cellulose raw material into a reaction kettle, and stirring and reacting for 60-180min to obtain cellulose nanocrystalline acid hydrolysis stock solution.
Preferably, the pretreatment is to crush the cellulose raw material to below 7mm by a fiber cutting machine and dry the crushed cellulose raw material for standby; the cellulose raw material is one or more of paper pulp, cotton and xylose residue.
Further, the centrifugation in the step 2) is specifically to dilute the cellulose nanocrystal hydrolysis stock solution prepared in the step 1) by adding 2-8 times of water, pump the diluted solution into a deacidification centrifuge, run for 2-8min, discharge once, and separate the waste acid solution and the hydrolysate. The deacidification centrifuge is a butterfly centrifuge, and the rotating speed is 1000-2000 rpm.
Further, the pH value of the hydrolysate is controlled by a sodium hydroxide solution, and the mass fraction of the hydrolysate is 3-15%.
Preferably, after the neutralization in the step 3), the neutralized hydrolysate is transferred into a refining centrifuge, and 5-8 times of water is supplemented for further refining centrifugation. The refining centrifuge is a butterfly centrifuge, the rotating speed is 6000-12000rpm, and the refining centrifuge operates for 2-8min to discharge once.
Further, the hydrolysate is separated and purified by adopting an ultrafiltration membrane system in the step 4), and water is continuously supplemented in the separation process until the conductivity of the cellulose nanocrystal dispersion is less than 1000 mS/cm; and continuously concentrating the cellulose nanocrystal dispersion liquid to 200-500L to obtain the cellulose nanocrystal product.
Furthermore, the ultrafiltration membrane system is provided with a plurality of membrane modules, and the effective area of each membrane module is 8 square meters; the ultrafiltration membrane is a hollow fiber membrane, and the molecular interception amount is 6000-10000 Da. Preferably, the number of membrane modules of the ultrafiltration membrane system is 8.
The invention has the beneficial effects that:
1) the operation is simple and convenient, the safety is higher, and the industrial amplification is easy; compared with manual shaking flotation, the method is more stable and efficient;
2) the energy consumption is low, and the cost is low; short time consumption, less water consumption, large effective area of the hollow fiber membrane and high separation efficiency.
Detailed Description
A cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification comprises the following specific steps:
1) preparing cellulose nanocrystalline acid hydrolysis stock solution:
s 1: adding sulfuric acid into the reaction kettle; the mass fraction of the sulfuric acid is 58-65%;
s 2: preheating the reaction kettle to 42-55 ℃;
s 3: putting the pretreated cellulose raw material into a reaction kettle, and stirring and reacting for 60-180min to obtain cellulose nanocrystalline acid hydrolysis stock solution.
2) And (2) carrying out centrifugal separation on the cellulose nanocrystalline acid hydrolysis stock solution to obtain waste acid and hydrolysate, diluting the cellulose nanocrystalline acid hydrolysis stock solution prepared in the step 1), pumping the diluted cellulose nanocrystalline acid hydrolysis stock solution into a deacidification centrifugal machine, operating for 2-8min, discharging once, and separating the waste acid solution and the hydrolysate.
3) And controlling the pH value of the hydrolysate to be 6-7 by adopting a sodium hydroxide solution with the mass fraction of 3% -15%.
4) Refining and centrifuging, separating by an ultrafiltration membrane separation system, and concentrating to obtain a cellulose nanocrystal product.
Example 1:
(1) pretreatment of a cellulose raw material: pulverizing cotton with fiber cutter to below 7mm, and oven drying;
(2) adding 200L of 62 mass percent sulfuric acid into a 500L reaction kettle;
(3) preheating sulfuric acid to 55 ℃;
(4) putting 25kg of crushed and dried cotton into a reaction kettle, and stirring and reacting for 180 min;
(5) after the reaction is finished, transferring the raw materials into a dilution tank, and adding 500L of water to dilute the hydrolysate;
(6) pumping the diluted hydrolysate into a deacidification centrifuge, adding 1474L of water, operating the disc centrifuge at the rotating speed of 1000rpm for 10min, and discharging once;
(7) after centrifugation, transferring the residual hydrolysate in the rotary drum to a neutralization kettle, and adding 899L sodium hydroxide solution with the mass fraction of 8.28wt% for neutralization;
(8) adding 2800L of water into the neutralized hydrolysate, pumping into a butterfly centrifuge at 10000rpm, and discharging once after 8 min;
(9) pumping the discharge material of the butterfly centrifuge into an ultrafiltration membrane separation system, and continuously supplementing water in the membrane separation process until the conductivity of the cellulose nanocrystal dispersion is less than 1000mS/cm and the water consumption is 7606L;
(10) and concentrating the cellulose nanocrystal dispersion liquid to 500L by using a hollow fiber membrane to obtain the cellulose nanocrystal product.
The total water consumption of the deacidification process is 34727L, the total sodium hydroxide consumption is 154kg, the water consumption of the deacidification process is 13394L, the alkali consumption is 74kg, the water consumption is 61.43 percent, the alkali consumption is 51.95 percent, and the recovery rate of the sulfuric acid reaches 51.60 percent.
Claims (10)
1. A cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification is characterized by comprising the following specific steps:
1) preparing cellulose nanocrystalline acid hydrolysis stock solution;
2) centrifuging the cellulose nanocrystal acid hydrolysis stock solution, and separating to obtain a cellulose nanocrystal hydrolysis solution;
3) neutralizing the cellulose nanocrystal hydrolysate, and controlling the pH value of the hydrolysate to be 6-7;
4) and separating by an ultrafiltration membrane separation system, and concentrating to obtain a cellulose nanocrystalline product.
2. The method for separating and purifying the cellulose nanocrystals based on centrifugal separation and direct deacidification as claimed in claim 1, wherein the step 1) of preparing the cellulose nanocrystal acid hydrolysis stock solution comprises the following specific steps:
s 1: adding sulfuric acid into the reaction kettle; the mass fraction of the sulfuric acid is 58-65%;
s 2: preheating a reaction kettle to 42-55 ℃;
s 3: putting the pretreated cellulose raw material into a reaction kettle, and stirring and reacting for 60-180 min.
3. The method for separating and purifying cellulose nanocrystals based on the direct centrifugal separation deacidification as claimed in claim 2, wherein the pretreatment comprises pulverizing the cellulose raw material to less than 7mm with a fiber cutter, and drying for later use; the cellulose raw material is one or more of paper pulp, cotton and xylose residue.
4. The method for separating and purifying cellulose nanocrystals based on centrifugal separation and direct deacidification as claimed in claim 1, wherein the centrifugation in step 2) is performed by diluting the prepared cellulose nanocrystal hydrolysis stock solution in step 1) with 2-8 times of water, pumping the diluted solution into a deacidification centrifuge, running for 2-8min, discharging once, and separating the waste acid solution and the hydrolysate.
5. The method as claimed in claim 4, wherein the deacidification centrifuge is a butterfly centrifuge with rotation speed of 1000-2000 rpm.
6. The method for separating and purifying cellulose nanocrystals based on centrifugal separation and direct deacidification as claimed in claim 1, wherein after the neutralization in step 3), the hydrolysate is transferred to a refining centrifuge, and 5-8 times of water is added for further refining centrifugation.
7. The method as claimed in claim 6, wherein the refining centrifuge is a butterfly centrifuge, the rotation speed is 6000-12000rpm, and the operation is performed for 2-8min for one discharge.
8. The method for separating and purifying cellulose nanocrystals based on the direct deacidification by the centrifugal separation as claimed in claim 1, wherein the step 4) is to separate and purify the hydrolysate by using an ultrafiltration membrane system, and water is continuously added during the separation process until the conductivity of the cellulose nanocrystal dispersion is less than 1000 mS/cm; and continuously concentrating the cellulose nanocrystal dispersion liquid to obtain the cellulose nanocrystal product.
9. The method for separating and purifying cellulose nanocrystals based on the direct centrifugal separation of deacidification as claimed in claim 6, wherein said ultrafiltration membrane system is provided with a plurality of ultrafiltration membrane modules, each of which has an effective area of 8 square meters; the ultrafiltration membrane is a hollow fiber membrane, and the molecular interception amount is 6000-10000 Da.
10. The method for separating and purifying cellulose nanocrystals based on centrifugal separation and direct deacidification as claimed in claim 7, wherein the number of the membrane assemblies of the ultrafiltration membrane system is 8.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210133590.XA CN114395054A (en) | 2022-02-14 | 2022-02-14 | Cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification |
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| CN202210133590.XA CN114395054A (en) | 2022-02-14 | 2022-02-14 | Cellulose nanocrystalline separation and purification method based on centrifugal separation and direct deacidification |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101942102A (en) * | 2010-09-07 | 2011-01-12 | 东南大学 | Preparation method of powder nano cellulose |
| CN103910805A (en) * | 2012-12-29 | 2014-07-09 | 青岛蔚蓝生物集团有限公司 | Method for preparing nanometer cellulose and recovering acid |
| CN108368181A (en) * | 2015-11-26 | 2018-08-03 | 有机燃料瑞典公司 | The environmental-friendly preparation method of nano-cellulose and its derivative |
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2022
- 2022-02-14 CN CN202210133590.XA patent/CN114395054A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101942102A (en) * | 2010-09-07 | 2011-01-12 | 东南大学 | Preparation method of powder nano cellulose |
| CN103910805A (en) * | 2012-12-29 | 2014-07-09 | 青岛蔚蓝生物集团有限公司 | Method for preparing nanometer cellulose and recovering acid |
| CN108368181A (en) * | 2015-11-26 | 2018-08-03 | 有机燃料瑞典公司 | The environmental-friendly preparation method of nano-cellulose and its derivative |
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Address after: 300350 12-2 Keda 1st Road, Balitai Town, Jinnan District, Tianjin Applicant after: Tianjin rumijiye New Material Co.,Ltd. Applicant after: Tianjin University Address before: 300350 12-2 Keda 1st Road, Balitai Town, Jinnan District, Tianjin Applicant before: Tianjin Rumi New Material Co.,Ltd. Applicant before: Tianjin University |
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Application publication date: 20220426 |