Hydrophobic cellulose aerogel as well as preparation method and application thereof
By using agricultural waste rice husks as raw material, combined with multi-stage screening and enzymatic hydrolysis, high-purity hydrophobic cellulose aerogels were prepared, solving the problems of high raw material cost and low purity in traditional methods, and realizing efficient preparation of hydrophobic aerogels and waste utilization.
Patent Information
- Application Number
- CN202511389691.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2025-12-23
AI Technical Summary
Traditional methods for preparing hydrophobic cellulose aerogels rely on high-purity raw materials, resulting in high raw material costs, low purity, and heavy enzymatic hydrolysis load.
Hydrophobic cellulose aerogels were prepared using agricultural waste rice husks as raw materials through steps such as screening, pretreatment, enzymatic hydrolysis, and 3D printing. The process included multi-stage screening to remove impurities, enzymatic hydrolysis to improve cellulose purity, and the formation of hydrophobic gels using cashew phenol epoxy resin and palm wax modifiers.
The purity of cellulose was increased to 98%, production costs were reduced, and aerogels with high porosity and good hydrophobicity were prepared, which are suitable for high-end applications such as oil-water separation.
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Figure CN121181986A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of cellulose aerogel, and particularly relates to a hydrophobic cellulose aerogel and a preparation method and application thereof. BACKGROUND
[0002] The hydrophobic cellulose aerogel has great application potential in the fields of adsorption, heat insulation and catalysis due to its light weight, high porosity and degradability, etc. However, there are certain problems in the selection and processing of raw materials in the traditional preparation method.
[0003] At present, the existing preparation methods of the hydrophobic cellulose aerogel mostly depend on high-purity raw materials such as wood pulp and microcrystalline cellulose, and the cellulose needs to be dissolved by concentrated sulfuric acid or ionic liquid. The traditional raw material source is single, resulting in high raw material cost. SUMMARY
[0004] The present application relates to the technical field of cellulose aerogel, and particularly relates to a hydrophobic cellulose aerogel and a preparation method and application thereof.
[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a preparation method of a hydrophobic cellulose aerogel, comprising: screening and pretreating agricultural waste rice husk to obtain a preparation raw material; extracting nanocellulose from the preparation raw material; preparing a cardanol epoxy resin and a palm wax microemulsion; forming a hydrogel based on the nanocellulose and the cardanol epoxy resin; vacuum freeze-drying the hydrogel to obtain a nanocellulose slurry; adopting the nanocellulose slurry for 3D printing to obtain the hydrophobic cellulose aerogel.
[0006] The specific steps of screening and pretreating the agricultural waste rice husk to obtain the preparation raw material include: screening and winnowing the agricultural waste rice husk to remove large-particle impurities and light non-cellulose components; water-washing the raw material after the winnowing, dehydrating the raw material to a water content of less than 15%, and then hot-air drying the raw material to a water content of less than 5%.
[0007] The specific steps of extracting the nanocellulose from the preparation raw material include: crushing the pretreated raw material to a particle size of less than 1 mm, adding cellulase and hemicellulase for enzymolysis in an acetic acid buffer solution at pH 4.8 for 48 hours, and then filtering and washing to obtain cellulose with a purity of greater than 95%; The enzymolyzed fiber slurry is diluted to a concentration of 2 wt%, and is treated by a high-pressure homogenizer for 5 cycles to obtain nanocellulose with a diameter of 20-50 nm.
[0008] The specific steps for preparing the cardanol epoxy resin and the palm wax microemulsion include: 30 wt% cardanol is reacted with 70 wt% epichlorohydrin under the catalysis of NaOH to generate a cardanol epoxy resin with an epoxy value of 0.45-0.55; 2 wt% palm wax is emulsified with 1 wt% Tween 80 at 70℃ to form a palm wax microemulsion with a particle size of 50-100 nm.
[0009] The specific steps for preparing the hydrogel based on the gelation of nanocellulose and cardanol epoxy resin include: 2 wt% nanocellulose is mixed with 5 wt% cardanol epoxy resin, 0.5 wt% catalyst triphenylphosphine is added, and the mixture is reacted at 60℃ for 2 hours to form a crosslinked hydrogel; The hydrogel is vacuum impregnated in the palm wax microemulsion, and the wax molecules are allowed to penetrate into the interior of the gel by vacuuming for 1 hour.
[0010] The specific steps for preparing the nanocellulose slurry by vacuum freeze-drying the hydrogel include: The modified gel is pre-frozen to -20℃, and then treated by microwave power of 100 W for 10 minutes, and then switched to vacuum freeze-drying at -60℃ for 48 hours to obtain a nanocellulose slurry.
[0011] The specific steps for preparing the hydrophobic cellulose aerogel by 3D printing using the nanocellulose slurry include: The modified nanocellulose slurry with a concentration of 1.5 wt% is loaded into a biological printing system, and a three-dimensional network is printed according to the micro-nano structure of the lotus leaf surface. After printing, the hydrophobic cellulose aerogel is prepared by heat curing at 120℃ for 2 hours and UV irradiation.
[0012] In a second aspect, the present application also provides a hydrophobic cellulose aerogel prepared by the hydrophobic cellulose aerogel preparation method.
[0013] In a third aspect, the present application also provides an application of the hydrophobic cellulose aerogel, which is applied to the heat insulation layer of a wall.
[0014] The application discloses a hydrophobic cellulose aerogel and a preparation method and application thereof, and relates to the field of cellulose aerogel preparation. BRIEF DESCRIPTION OF DRAWINGS
[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced.
[0016] Figure 1 is a flow chart of a preparation method of a hydrophobic cellulose aerogel.
[0017] Figure 2 is a flow chart of screening and pretreating agricultural waste rice husk to obtain a preparation raw material.
[0018] Figure 3 is a flow chart of extracting nanocellulose in the preparation raw material.
[0019] Figure 4 is a flow chart of preparing cashew phenol epoxy resin and palm wax microemulsion.
[0020] Figure 5 is a flow chart of forming a hydrogel by gelation based on nanocellulose and cashew phenol epoxy resin.
[0021] Figure 6 is a flow chart of preparing a hydrophobic cellulose aerogel by 3D printing using nanocellulose slurry. DETAILED DESCRIPTION
[0022] The embodiments of the present application will be described in detail below, examples of which are shown in the drawings, and the embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.
[0023] In the first aspect, referring to Figures 1-6 The application provides a preparation method of a hydrophobic cellulose aerogel, comprising: S1 screening and pretreating agricultural waste rice husk to obtain a preparation raw material; The specific steps include: S11 screening and winnowing the agricultural waste rice husk to remove large-particle impurities and light non-cellulose components; In the embodiment of the present application, the agricultural waste (the agricultural waste is one of rice husk and bagasse) is evenly spread on the vibrating screen, the vibrating motor (frequency 50 Hz) is started, and the large particle impurities (such as sand, metal fragments) are removed, so that the cellulose raw material and macroscopic impurities are preliminarily separated, and the enzyme activity is avoided from being interfered by the impurities in the subsequent enzymolysis. The raw material after coarse screening is put into the air classifier, the air speed is adjusted, the light impurities (such as dust, straw fragments) are blown away, the heavy cellulose raw material falls into the collection box, the light non-cellulose components are further removed, and the purity of the raw material is improved to more than 90%.
[0024] In S12, the raw material after air separation is washed with water, dehydrated to a water content of less than 15%, and then dried by hot air to a water content of less than 5%.
[0025] In the embodiment of the present application, the raw material after air separation is added with deionized water at a material-liquid ratio of 1:10, the stirrer (speed 200 rpm) is started for 30 minutes, and the filtration is repeated twice, so that the soluble sugars, ash and part of pectin are dissolved and removed, and the enzymolysis load is reduced. The raw material after washing is dehydrated to a water content of <15% by using a screw press, so as to avoid that the excessive water dilutes the enzymolysis liquid and improves the enzymolysis efficiency. The dehydrated raw material is dried for 4 hours to a water content of <5%, so as to provide low-moisture raw material for enzymolysis and prevent the breeding of microorganisms in the enzymolysis process.
[0026] S2, nanocellulose in the prepared raw material is extracted; The specific steps include: S21, the pretreated raw material is crushed to a particle size of less than 1 mm, cellulase and hemicellulase are added for enzymolysis in an acetic acid buffer solution at pH 4.8 for 48 hours, and then the cellulose with a purity of more than 95% is obtained after filtration and washing; S22, the fiber slurry after enzymolysis is diluted to a concentration of 2 wt%, and is treated by a high-pressure homogenizer for 5 times, so as to obtain nanocellulose with a diameter of 20-50 nm.
[0027] In the embodiment of the present application, the dried raw material is crushed to a particle size of <1 mm, so as to ensure the uniformity of enzymolysis. The crushed raw material is added into an enzymolysis tank, cellulase CTec2 and hemicellulase HTec3 are added, and then the enzymolysis is carried out at 50℃ and 150 rpm for 48 hours, so as to specifically degrade lignin and hemicellulose and retain cellulose with a purity of >95%. After enzymolysis, the liquid and solid residues are separated by filtration, the solid part is washed with deionized water to neutral (pH 6.8-7.2), so as to remove the soluble sugars and residual enzyme preparation generated in the enzymolysis. The fiber slurry after enzymolysis is diluted to a concentration of 2 wt%, and is stirred for 30 minutes (speed 300 rpm) to make the fibers uniformly dispersed. The slurry is circulated through the homogenizer for 5 times, and the treatment time is 10 minutes each time, so as to reduce the fiber diameter to 20-50 nm by mechanical shearing force, and form uniform nanocellulose (CNF).
[0028] S3 preparing cardanol epoxy resin and palm wax microemulsion; The specific steps include: S31 reacting 30 wt% cardanol with 70 wt% epichlorohydrin under the catalysis of NaOH to generate cardanol epoxy resin with an epoxy value of 0.45-0.55; In the embodiment of the present application, 30 wt% cardanol and 70 wt% epichlorohydrin are added to a reaction kettle, heated to 80℃, and NaOH is slowly added. The reaction is maintained for 4 hours to generate a bio-based epoxy resin with an epoxy value of 0.45-0.55 through epoxidation reaction. After the reaction, the NaOH residue is removed by filtration, washed with deionized water until neutral, and vacuum dried (60℃, 2 hours) to remove unreacted monomers and improve the purity of the modifier.
[0029] S32 emulsifying 2 wt% palm wax with 1 wt% Tween 80 at 70℃ to form a palm wax microemulsion with a particle size of 50-100 nm.
[0030] In the embodiment of the present application, a high-speed disperser is used to add 2 wt% palm wax and 1 wt% Tween 80 to deionized water, heated to 70℃, and high-speed dispersed for 30 minutes to form a stable microemulsion with a particle size of 50-100 nm, ensuring uniform dispersion of the wax molecules.
[0031] S4 gel forming based on nanocellulose and cardanol epoxy resin to prepare hydrogel; The specific steps include: S41 mixing 2 wt% nanocellulose with 5 wt% cardanol epoxy resin, adding 0.5 wt% catalyst triphenylphosphine, and reacting at 60℃ for 2 hours to form a cross-linked hydrogel; In the embodiment of the present application, nanocellulose (2 wt%) and cardanol epoxy resin (5 wt%) are added to a blender, and catalyst triphenylphosphine (0.5 wt%) is added. The mixture is stirred for 30 minutes at a speed of 500 rpm to uniformly coat the nanocellulose with the epoxy resin, providing conditions for cross-linking reaction. The mixed slurry is poured into a mold and reacted in a 60℃ oven for 2 hours to form a cross-linked hydrogel. A three-dimensional network structure is generated through epoxy ring-opening reaction, improving the mechanical strength of the gel.
[0032] S42 vacuum impregnating the hydrogel in the palm wax microemulsion and vacuuming for 1 hour to allow the wax molecules to penetrate into the interior of the gel.
[0033] In the embodiment of the present application, the hydrogel is immersed in a palm wax microemulsion in a vacuum drying box, vacuumized for 1 hour, so that the wax molecules penetrate into the gel interior, and the microemulsion is driven into the gel pores by negative pressure to realize internal hydrophobic modification. After modification, the gel surface is washed with deionized water to remove the residual microemulsion, and then placed at room temperature for natural drying for 2 hours to remove the excess wax molecules on the surface and avoid blocking the pores.
[0034] S5 vacuum freeze-drying the hydrogel to obtain nanocellulose slurry; The specific steps include: The modified gel is pre-frozen to-20℃, first treated by microwave power of 100 W for 10 minutes, and then switched to-60℃ vacuum freeze-drying for 48 hours to obtain nanocellulose slurry.
[0035] In the embodiment of the present application, the modified gel is frozen in a refrigerator for 12 hours to form a uniform ice crystal structure. The pre-frozen gel is placed in the drying chamber of a microwave vacuum drying machine, vacuumized to a pressure of <50 Pa, and microwave heating is started for 10 minutes. After microwave treatment, the vacuum state is maintained and the temperature is lowered to-60℃, and the drying is continued for 48 hours to completely remove the residual water, while avoiding the structure collapse caused by excessive microwave heating.
[0036] S6 3D printing is performed using the nanocellulose slurry to obtain a hydrophobic cellulose aerogel; The specific steps include: S61 The modified nanocellulose slurry with a concentration of 1.5 wt% is loaded into a biological printing system, and a three-dimensional network is printed according to the micro-nano structure on the surface of a lotus leaf. S62 After printing, heat curing at 120℃ for 2 hours and UV irradiation are performed to obtain a hydrophobic cellulose aerogel.
[0037] In the embodiment of the present application, the modified nanocellulose slurry with a concentration of 1.5 wt% is loaded into a biological printing system, and a three-dimensional network is printed according to the micro-nano structure on the surface of a lotus leaf. The protrusions of the micro-nano structure on the surface of the lotus leaf have a diameter of 5-10 μm and a spacing of 20-30 μm. By copying the surface structure of the lotus leaf, a hierarchical pore structure with a macroscopic pore size of 100-300 μm and a microscopic pore size of 20-50 nm is formed. The printed aerogel is placed in a 120℃ oven for heat treatment for 2 hours to increase the crosslinking density of the cardanol epoxy resin, and then irradiated by a UV lamp (wavelength 365 nm) for 5 minutes to cure the palm wax coating and improve the hydrophobicity (water contact angle >150°) to obtain a hydrophobic cellulose aerogel.
[0038] The hydrophobic cellulose aerogel preparation method of the application uses agricultural waste (rice husk, bagasse) as raw material, through multi-stage screening (coarse screening, air separation) and enzyme pretreatment, the purity of cellulose is improved to more than 98%, and impurities (such as sand, metal) are removed, improving the quality of the final product. Through water washing, dewatering and hot air drying process, the water content of the raw material is reduced to <5%, the enzyme hydrolysis efficiency (yield >85%) is improved, and the problems of low purity of raw material and high enzyme hydrolysis load in traditional methods are solved. Combined with bio-based modifier (cashew phenol epoxy resin + palm wax) and 3D printing biomimetic structure, the aerogel with porosity >92%, water contact angle >150° and oil absorption rate 65-70 g / g is prepared, which meets the high-end application requirements such as oil-water separation. The hydrophobic cellulose aerogel prepared by the application uses agricultural waste rice husk as raw material, which can realize waste utilization and reduce production cost.
[0039] In a second aspect, the application further provides a hydrophobic cellulose aerogel prepared by the hydrophobic cellulose aerogel preparation method.
[0040] The hydrophobic cellulose aerogel of the application is prepared by using agricultural waste rice husk as raw material, which can realize waste utilization and reduce production cost.
[0041] In a third aspect, the application further provides a hydrophobic cellulose aerogel, which is applied to the heat insulation layer of a wall. After the hydrophobic cellulose aerogel of the application is applied to the heat insulation layer of a wall, the heat preservation and insulation effect of the wall can be improved.
[0042] The above only discloses one or more preferred embodiments of the application, and cannot limit the scope of the application. Those skilled in the art can understand that all or part of the above-mentioned embodiments can be implemented, and equivalent changes made according to the claims of the application still fall within the scope of the application.
Claims
1. A method for preparing hydrophobic cellulose aerogel, characterized in that, include: Agricultural waste rice husks are screened and pretreated to obtain the raw materials for preparation; Extracting nanocellulose from the raw materials for preparation; Preparation of cashew phenol epoxy resin and palm wax microemulsion; Hydrogels were prepared by gel molding based on nanocellulose and cashew phenol epoxy resin. The hydrogel was freeze-dried under vacuum to obtain a nanocellulose slurry; Hydrophobic cellulose aerogels were prepared by 3D printing using nanocellulose slurry.
2. The method for preparing hydrophobic cellulose aerogel as described in claim 1, characterized in that, The specific steps for screening and pretreating agricultural waste rice husks to obtain the raw materials include: Agricultural waste rice husks are screened and air-separated to remove large particles and light non-cellulose components; After air separation, the raw materials are washed and dehydrated to a moisture content of less than 15%, and then dried with hot air to a moisture content of less than 5%.
3. The method for preparing hydrophobic cellulose aerogel as described in claim 2, characterized in that, The specific steps for extracting and preparing nanocellulose from the raw materials include: The pretreated raw material was crushed to a particle size of less than 1 mm, and cellulase and hemicellulase were added and enzymatically hydrolyzed in an acetate buffer solution at pH 4.8 for 48 hours. After filtration and washing, cellulose with a purity of more than 95% was obtained. The enzymatically hydrolyzed fiber slurry was diluted to a concentration of 2 wt% and then circulated five times using a high-pressure homogenizer to obtain nanocellulose with a diameter of 20-50 nm.
4. The method for preparing hydrophobic cellulose aerogel as described in claim 3, characterized in that, The specific steps for preparing the cashew phenol epoxy resin and palm wax microemulsion include: 30 wt% cashew nut phenol and 70 wt% epichlorohydrin were reacted under NaOH catalysis to produce cashew nut phenol epoxy resin with an epoxy value of 0.45-0.
55. 2 wt% palm wax and 1 wt% Tween 80 were emulsified at 70°C to form a palm wax microemulsion with a particle size of 50-100 nm.
5. The method for preparing hydrophobic cellulose aerogel as described in claim 4, characterized in that, The specific steps for preparing a hydrogel based on nanocellulose and cashew phenol epoxy resin include: 2 wt% nanocellulose and 5 wt% cashew phenol epoxy resin were mixed, and 0.5 wt% triphenylphosphine catalyst was added. The mixture was reacted at 60°C for 2 hours to form a cross-linked hydrogel. The hydrogel was vacuum impregnated in palm wax microemulsion, and vacuum was applied for 1 hour to allow the wax molecules to penetrate into the gel.
6. The method for preparing hydrophobic cellulose aerogel as described in claim 5, characterized in that, The specific steps for preparing nanocellulose slurry by vacuum freeze-drying of hydrogel include: The modified gel was pre-frozen to -20°C, then microwaved at 100 W for 10 minutes, and then freeze-dried at -60°C under vacuum for 48 hours to obtain nanocellulose slurry.
7. The method for preparing hydrophobic cellulose aerogel as described in claim 6, characterized in that, The specific steps for 3D printing hydrophobic cellulose aerogels using nanocellulose slurry include: The modified 1.5 wt% nanocellulose slurry was loaded into the bioprinting system and a three-dimensional network was printed according to the micro-nano structure of the lotus leaf surface. After printing, hydrophobic cellulose aerogels were obtained by heat curing at 120℃ for 2 hours and UV irradiation.
8. A hydrophobic cellulose aerogel, characterized in that, Prepared using the method for preparing hydrophobic cellulose aerogel as described in any one of claims 1-7.
9. An application of a hydrophobic cellulose aerogel, using the hydrophobic cellulose aerogel as described in claim 8, characterized in that, Thermal insulation layer applied to walls.