CN113526513B - Massive lignin-silicon dioxide composite aerogel - Google Patents
Massive lignin-silicon dioxide composite aerogel Download PDFInfo
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- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
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Abstract
The invention discloses a blocky lignin-silicon dioxide composite aerogel, which is prepared by dissolving lignin, a cross-linking agent and a chemical cross-linking catalyst in polyhydric alcohol, constructing a lignin pre-cross-linking network through chemical cross-linking to obtain a pre-cross-linking lignin liquid, then adding a silicon dioxide precursor, a silane coupling agent and deionized water, performing hydrolytic polycondensation reaction to obtain a lignin/silicon dioxide cogel network, fully contacting with an aqueous solution, performing hydrophobic self-assembly of the lignin network and in-situ mineralization of silicon dioxide gel, and drying and annealing after full reaction. The invention realizes the preparation of the uniform three-dimensional blocky lignin/silicon dioxide composite aerogel for the first time, has high porosity, high strength, hydrophobicity and self-cleaning capability, low thermal conductivity and high infrared reflection capability, and can be developed into novel light heat-insulating, heat-preserving, fireproof and noise-reducing materials.
Description
Technical Field
The invention relates to a novel material, and in particular relates to a blocky lignin-silicon dioxide composite aerogel.
Background
It is statistical that the energy consumed for building Buildings and maintaining a pleasant indoor environment accounts for more than 40% of the total global energy consumption (Apostolopoulou Kalkavoouraet, adv. mater. 2020, 2001839), while generating large amounts of greenhouse gases (Jelle, energy. building, 43(2011), 2549-. The heat insulation material can greatly reduce the heat transfer of civil and commercial buildings, thereby achieving the purpose of energy saving (Smalyukh, adv. Mater. 2020, 2001228). At present, most thermal insulation materials are derived from non-renewable petroleum-based raw materials, and will cause serious environmental problems when discarded (Zhaoet al, angelw. chem., int. ed., 2018, 57, 7580). Therefore, the search for high-performance and renewable thermal insulation materials is crucial to achieve the goals of energy saving, emission reduction and environmental protection (He et al, Small Methods, 2019, 4, 1900747). Currently, studies and reports on bio-based thermal insulation have focused on polysaccharide and protein based aerogel (foam) materials. However, the overall properties of such materials, such as thermal insulating ability, mechanical strength, and environmental resistance, are difficult to compare to petroleum-based thermal insulating materials (Zhaoet al, angelw. chem., int. ed., 2018, 57, 7580). Therefore, designing and developing bio-based aerogel materials with high strength, thermal insulation durability, and multiple functionalities would be expected to improve their competitiveness in integrated energy-saving engineering applications (e.g., energy-saving buildings) (Li et al, adv. funct. mater, 2019, 29, 1807624) and help push the early implementation of "carbon peak-to-peak" and "carbon neutralization" goals.
The silica mineralized biopolymer aerogel prepared based on the biomimetic silicification strategy generally combines the characteristics of the biopolymer and the functional characteristics of an inorganic silica material, so that the method can provide a technical platform with a wide prospect for constructing a high-performance and eco-friendly bio-based polymer aerogel (Shchippunov et al, Adv. Funct. mater. 2018, 28, 1705042; Zhang et al, Adv. Funct. mater. 2020, 30, 1910425). In recent years, research at home and abroad has mainly focused on the field of silica-mineralized (composite) aerogels of natural polysaccharide polymers, such as cellulose/silica aerogels (Zhang et al, chem. mater. 2014, 26, 2659), pectin/silica aerogels (Zhao et al, angelw. chem., int. ed. 2015, 54, 14282), and chitosan/silica aerogels (Zhu et al, ACS susteable chem. eng. 2019, 8, 71), among others. This is mainly due to the fact that the long-chain polymeric structure of polysaccharide materials is susceptible to forming a continuous three-dimensional network structure by various wet chemical methods. For example, cellulose/silica aerogels prepared by an in situ sol-gel process using siloxanes or silicates generally exhibit good mechanical flexibility and low thermal conductivity (Zhang et al, adv. funct. mater. 2019, 29, 1806407). Furthermore, the compounding of cellulose and silica also addresses to some extent the disadvantages of high hygroscopicity and biodegradability of the cellulose material itself (smallyukh et al, adv. mater. 2020, 2001228). However, due to the flexible and easily degradable molecular structure characteristics of cellulose molecules, the prepared cellulose/silica aerogel has poor dimensional stability and environmental stability, and is difficult to meet the use requirements of energy-saving engineering materials directly exposed to the outside or under extreme conditions (He et al, Small Methods, 2019, 4, 1900747). Furthermore, silica formed by in situ sol-gel processes is generally deposited in the pores of the cellulose network scaffold and makes it difficult to form good interfacial connections, thus resulting in poor mechanical properties (Pirzada et al, adv. funct. mater. 2019, 30, 1907359). Other researchers have used a cogel strategy to prepare pectin/silica (Zhao et al, angelw. chem., int. ed. 2015, 54, 14282) and chitosan/silica composite aerogel materials (Zhao et al, ACS stable chem. eng. 2016, 4, 5674). In the cogel process, the polysaccharide and silica precursor first form a homogeneous co-solution, and then a cogel is formed by chemical crosslinking or physical chelation. The method can prepare uniform silica mineralized pectin or chitosan aerogel materials, and the materials generally show excellent mechanical properties and heat insulation capability. However, the high cost of pectin and chitosan has severely hampered the large-scale application of such composite aerogels. It is noteworthy that polysaccharide/silica composite aerogels generally undergo severe shrinkage and collapse in the presence of fire due to the low carbon content of the polysaccharide, rendering them unsuitable for use as building insulation (Ma et al, adv. mater. 2020, 2003897).
Lignin is the most abundant natural polyphenolic material stored on earth, which has a number of attractive properties compared to polysaccharide polymers, including high molecular stiffness, excellent hydrophobicity, good thermal stability, excellent uv blocking capability, and low cost (Ragauskas et al, Science 2014, 344, 1246843). However, statistically only around 5% of lignin is effectively utilized (Jiang et al, Small 2020, 16, e 1907212). With the increasingly deepened understanding of the human society on the environmental and resource problems, the comprehensive utilization of the renewable biomass resource with strategic significance of lignin is highly regarded by governments and scientific research personnel of various countries. Compared with polysaccharide/silica aerogel materials, lignin can endow different functional characteristics and application scenes to the corresponding composite aerogel materials. It is reported in the literature that the abundant phenolic hydroxyl groups in lignin molecules not only provide coordination sites for silanol but also catalyze its condensation (Laine et al, Nature 1991, 353, 642), but the abundant phenolic and alcoholic hydroxyl groups in lignin generally cause the lignin/silane sol to rapidly undergo condensation, phase separation and co-precipitation rather than forming a uniform mixed gel network (Fang et al, j. Zhejiang Univ-SC. B2006, 7, 267), while the three-dimensional aromatic macromolecular structure of lignin generally results in weaker mechanical properties of the composite aerogel (Perez-Cantuo et al, ACS sustamable chem. eng. 2019, 7, 6959). In addition, by utilizing the amphiphilic property of lignin molecules, a micro-nano structure can be formed in situ in a composite material matrix through hydrophobic self-assembly modification, and then the enhanced bio-based nano composite material is constructed (Zhang et al, adv. funct. mater. 2019, 29, 1806912). Therefore, the efficient strategy for manufacturing the high-performance 3D blocky lignin/silicon dioxide composite aerogel is designed, so that the structure and function selectivity of the bio-based aerogel energy-saving material can be widened, and the high-value utilization process of the lignin can be promoted. At present, researches on lignin/silicon dioxide composite aerogel are only reported and are in a powder composite state, and a precedent that a 3D blocky lignin/silicon dioxide composite aerogel material is successfully constructed and applied to the field of heat preservation and insulation is not provided so far.
CN108484097A the invention belongs to the field of silica aerogel felts, and discloses a preparation method of a lignin-enhanced silica aerogel felt. Ultrasonically dispersing lignin in water to obtain a suspension; taking orthosilicate ester and ethanol, mixing uniformly, adding the suspension into the mixture, and mixing until silica sol is obtained; spreading and soaking the fibrofelt in the obtained silica sol, taking the fibrofelt out of the silica sol after complete soaking, and standing until a fibrofelt-gel composite is obtained; aging at room temperature or under heating; and (4) continuing aging and drying under the action of microwaves to obtain the lignin-enhanced silicon dioxide aerogel felt. The lignin adopted by the invention has wide sources, low cost and environmental protection, and can be uniformly dispersed in a gel network system in the process of hydrolyzing gel by dispersing the lignin in water, so that the mechanical property of the aerogel can be enhanced. In the method, the blocky silica felt is used as a main body, the lignin is used as a reinforcing filling material, the method is complex to operate, the prepared modified silica aerogel felt is poor in strength, and the application range is limited.
Disclosure of Invention
It is an object of the present invention to overcome at least one of the deficiencies of the prior art and to provide a bulk lignin-silica composite aerogel.
The technical scheme adopted by the invention is as follows:
in a first aspect of the present invention, there is provided:
the preparation method of the massive lignin-silicon dioxide composite aerogel comprises the following steps:
s1) dissolving lignin, a cross-linking agent and a chemical cross-linking catalyst in polyhydric alcohol, and constructing a lignin pre-cross-linking network through chemical cross-linking to obtain pre-cross-linking lignin liquid;
s2) adding a silicon dioxide precursor, a silane coupling agent and deionized water into the pre-crosslinked lignin liquid, and carrying out hydrolytic polycondensation reaction to obtain a lignin/silicon dioxide cogel network;
s3) fully contacting the lignin/silicon dioxide cogel network with a neutral or acidic aqueous solution, performing hydrophobic self-assembly of the lignin network and in-situ mineralization of silicon dioxide gel, drying and annealing after full reaction to obtain the massive lignin-silicon dioxide composite aerogel, wherein the aqueous solution is a solution which can not dissolve or hardly dissolve lignin.
In some examples, the mass ratio of the lignin to the crosslinking agent is 50:1 to 1:50, preferably 10:1 to 1:10, more preferably 1:3 to 3:1, and even more preferably 2: 3.
In some examples, the mass ratio of the crosslinking agent to the catalyst is 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 10:1 to 1:10, and even more preferably 30: 1.
In some examples, the mass ratio of the silica precursor to the silane coupling agent is 50:1 to 1:50, preferably 20:1 to 1:20, more preferably 10:1 to 1:10, and still more preferably 4: 1.
In some examples, the mass ratio of the deionized water to the polyol is 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 20:1 to 1:20, and even more preferably 1: 11.
In some examples, the mass concentration of the lignin in the pre-crosslinked lignin liquid is 0.1 to 50 wt%, preferably 1 to 30wt%, and more preferably 8 wt%.
In some examples, the temperature of the chemical crosslinking reaction is 10 to 150 ℃ and is not higher than the boiling point of the polyol; the reaction is preferably carried out at 50-100 ℃, and the preferable reaction time is 20-120 min.
In some examples, the hydrolytic polycondensation reaction is carried out at 10 to 150 ℃ until the mixed solution is gelled and does not flow, and preferably at 20 to 60 ℃ until the mixed solution is gelled and does not flow.
In some examples, the method of drying is selected from forced air heated drying, vacuum heated drying, freeze drying, or supercritical drying.
In some examples, the annealing method is heating annealing in air, the heating temperature is 100-200 ℃, the heating time is 0.1-12 h, and preferably 120-180 ℃ for 1-6 h.
In some examples, the polyol is selected from at least one of 1, 4-butanediol, 1, 3-butanediol, 2, 3-butanediol, diethylene glycol, triethylene glycol, ethylene glycol, glycerol, propylene glycol, polyethylene glycol, polypropylene glycol.
In some examples, the catalyst is selected from at least one of imidazole, 2-ethylimidazole, 2-methylimidazole, triethylamine, ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethylenepolyamine, dicyandiamide, NaOH, KOH, LiOH, N-dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, N ' -tetramethylalkylenediamine, N-dimethylbenzylamine, triethylenediamine, N-ethylmorpholine, N-methylmorpholine, N ' -diethylpiperazine, triethanolamine, dimethylethanolamine, pyridine, N ' -dimethylpyridine.
In some examples, the silica precursor is selected from at least one of ethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, sodium silicate, silicic acid, aluminum silicate, and magnesium silicate.
In some examples, the silane coupling agent is selected from at least one of 3- [2- (2-aminoethylamino) ethylamino ] propyl-trimethoxysilane, 3-aminopropyltrimethoxysilane, trimethoxy [3- (methylamino) propyl ] silane, N- (β -aminoethyl) - γ -aminopropyltrimethoxysilane, (3-chloropropyl) trimethoxysilane, N- [3- (trimethoxysilyl) propyl ] ethylenediamine, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxyethyltriethoxysilane, and 3-glycidoxypropyltriethoxysilane.
In some examples, the aqueous solution is at least one of deionized water, aqueous hydrochloric acid, aqueous sulfuric acid, aqueous nitric acid, aqueous phosphoric acid, and aqueous acetic acid.
In some examples, the crosslinker has the general structural formula (R) 1 ) y -R 3 -(R 2 ) x Wherein x and y are integers of 1 or more, and R 1 And R 2 Being a functional group which can react with hydroxyl groups on lignin, R 3 Is a linking group.
In some examples, R 1 And R 2 Relatively independently an epoxy group, an amino group, an anhydride or a carboxyl group.
In some examples, R 3 Is polyolefin, polyether, polyA residue of an ester; or
、
、
、
、
Wherein s, p, m, n and k are integers not less than 1.
In some examples, the crosslinking agent is selected from at least one of bisphenol a diglycidyl ether, propylene glycol diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether; preferably, the number average molecular weight Mn of the crosslinking agent is 100 to 5000.
In some examples, the aqueous solution is contacted for a time period of not less than 0.1 hour, preferably 0.1 to 48 hours, preferably 5 to 10 hours.
In a second aspect of the present invention, there is provided:
the application of the lignin-silica composite aerogel of the first aspect of the invention comprises the preparation of heat insulation materials, sound insulation and noise reduction materials and flame retardant materials.
The invention has the beneficial effects that:
according to some embodiments of the invention, the preparation of uniform three-dimensional blocky lignin/silicon dioxide composite aerogel is realized for the first time, and the limitation that only powdery lignin/silicon dioxide composite aerogel can be prepared in the prior art is broken.
According to some embodiments of the invention, the preparation method is simple, the raw material modification step is not needed, and the raw material is non-toxic, renewable and environment-friendly.
In some examples of the present invention, the three-dimensional bulk lignin/silica composite aerogel has excellent mechanical stability, and the specific modulus and the specific compressive strength can be respectively as high as 376.3 kN.m/kg and 75.8 kN.m/kg.
In some embodiments of the invention, the three-dimensional bulk lignin/silica composite aerogels have high porosity (> 81%), excellent hydrophobicity (superhydrophobic), and self-cleaning ability.
In some embodiments of the present invention, the three-dimensional bulk lignin/silica composite aerogel also exhibits low thermal conductivity, unaffected by ambient humidity, high near-infrared reflectance (> 90%), and excellent fire resistance as a thermal insulation material.
Some examples of the present invention may obtain three-dimensional bulk lignin/silica composite aerogels having different three-dimensional structures by adjusting the shape of the gel reactor or by randomly mechanically cutting the sample.
Drawings
FIG. 1 is a digital photo of three-dimensional bulk lignin/silica composite aerogel prepared in different sizes and shapes;
FIG. 2 is a comparison of the states of lignin/silane sols prepared using six different solvents, respectively;
FIG. 3 shows the micro-morphology of different three-dimensional bulk lignin/silica composite aerogels;
FIG. 4 is a graph of compressive stress-strain curves for different three-dimensional bulk lignin/silica composite aerogels;
FIG. 5 is the Young's modulus of different three-dimensional bulk lignin/silica composite aerogels;
FIG. 6 shows the mesoporous pore size distribution of different three-dimensional bulk lignin/silica composite aerogels;
FIG. 7 shows water contact angles of different three-dimensional bulk lignin/silica composite aerogels;
FIG. 8 is a comparison of thermal conductivity of three-dimensional bulk lignin/silica composite aerogel (LigSi-3) and commercial phenolic foam at different relative humidities (33-94%);
FIG. 9 is a solar spectrum reflectance curve of different three-dimensional bulk lignin/silica composite aerogels;
fig. 10 is a sample back infrared imaging (b) and temperature profile (c) of three-dimensional bulk lignin/silica composite aerogel (LigSi-3) during heating on an alcohol burner flame (a) for 30 min.
Detailed Description
In a first aspect of the present invention, there is provided:
the preparation method of the massive lignin-silicon dioxide composite aerogel comprises the following steps:
dissolving lignin, a cross-linking agent and a catalyst in polyhydric alcohol, and constructing a lignin pre-crosslinking network by chemical crosslinking to obtain pre-crosslinking lignin liquid;
adding a silicon dioxide precursor, a silane coupling agent and deionized water into the pre-crosslinked lignin liquid, and carrying out hydrolytic polycondensation reaction to obtain a lignin/silicon dioxide cogel network;
fully contacting the lignin/silicon dioxide cogel network with a neutral or acidic aqueous solution, performing hydrophobic self-assembly of the lignin network and in-situ mineralization of silicon dioxide gel, drying and annealing after full reaction to obtain the massive lignin-silicon dioxide composite aerogel, wherein the aqueous solution is a solution which can not dissolve or hardly dissolve lignin.
The polyol is a good solvent of lignin, can well dissolve or disperse lignin and a lignin pre-crosslinking network, and can form rich non-covalent bond networks with lignin molecules and a silicon dioxide precursor, so that the lignin/silicon dioxide mixed sol can be effectively stabilized, and uniform massive lignin-silicon dioxide composite aerogel can be obtained. The selection of the polyol follows the principle that the lignin, the cross-linking agent and the cross-linking reaction catalyst have better dissolving capacity and the cross-linking reaction is not influenced. In some examples, the polyol is selected from at least one of 1, 4-butanediol, 1, 3-butanediol, 2, 3-butanediol, diethylene glycol, triethylene glycol, ethylene glycol, glycerol, propylene glycol, polyethylene glycol, polypropylene glycol.
By adding the cross-linking agent, the lignin macromolecules can be chemically cross-linked to form a three-dimensional network structure, so that the aerogel with stable appearance and high mechanical strength can be obtained. In some examples, the mass ratio of the lignin to the crosslinking agent is 50:1 to 1:50, preferably 10:1 to 1:10, more preferably 1:3 to 3:1, and even more preferably 2: 3. The more crosslinker is used, the denser the resulting three-dimensional crosslinked network. The mixing ratio of the lignin and the cross-linking agent can be adjusted according to specific application.
The catalyst can accelerate the crosslinking reaction more quickly and better, and is beneficial to improving the production efficiency. The corresponding kind of catalyst is selected according to the cross-linking agent used. The amount of catalyst used is adjusted based on the reaction rate and catalytic efficiency. In some examples, the mass ratio of the crosslinking agent to the catalyst is 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 10:1 to 1:10, and even more preferably 30: 1.
The silane coupling agent can better improve the compatibility of the silicon dioxide and the lignin pre-crosslinking network and improve the performance of the product. According to the concrete type of the silane coupling agent and the performance of the product, the dosage ratio of the silicon dioxide precursor and the silane coupling agent is adjusted. In some examples, the mass ratio of the silica precursor to the silane coupling agent is 50:1 to 1:50, preferably 20:1 to 1:20, more preferably 10:1 to 1:10, and still more preferably 4: 1.
Deionized water can initiate hydrolytic polycondensation, and the dosage of the deionized water can be adjusted correspondingly according to the needs of the reaction. In some examples, the mass ratio of the deionized water to the polyol is 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 20:1 to 1:20, and even more preferably 1: 11.
The mixing ratio of the polyol and lignin can be adjusted according to the dissolving capacity of the polyol and the needs of the reaction. In some examples, the mass concentration of the lignin in the pre-crosslinked lignin liquid is 0.1 to 50 wt%, preferably 1 to 30wt%, and more preferably 8 wt%.
By adjusting the temperature of the chemical crosslinking reaction, the reaction rate can be adjusted to a certain extent. In order to obtain a suitable reaction rate, in some examples, the temperature of the chemical crosslinking reaction is 10 to 150 ℃ and is not higher than the boiling point of the polyol; preferably at 50-100 ℃.
The chemical crosslinking reaction is carried out until a lignin pre-crosslinking network is obtained, and at the end of the reaction, the lignin pre-crosslinking network still has certain fluidity and is conveniently and fully mixed with the silicon dioxide precursor. And determining the reaction time according to the progress of the reaction, wherein the preferable reaction time is 20-120 min.
In some examples, the hydrolytic polycondensation reaction is carried out at 10 to 150 ℃ until the mixed solution is gelled and does not flow, and preferably at 20 to 60 ℃ until the mixed solution is gelled and does not flow.
In some examples, the drying method is selected from conventional drying methods such as forced air heating drying, vacuum heating drying, freeze drying or supercritical drying.
In some examples, the annealing method is heating annealing in air, the heating temperature is 100-200 ℃, the heating time is 0.1-12 h, and preferably 120-180 ℃ for 1-6 h.
In some examples, the catalyst is selected from at least one of imidazole, 2-ethylimidazole, 2-methylimidazole, triethylamine, ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethylenepolyamine, dicyandiamide, NaOH, KOH, LiOH, N-dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, N ' -tetramethylalkylenediamine, N-dimethylbenzylamine, triethylenediamine, N-ethylmorpholine, N-methylmorpholine, N ' -diethylpiperazine, triethanolamine, dimethylethanolamine, pyridine, N ' -dimethylpyridine.
The lignin is used for the crosslinking reaction of hydroxyl groups, and a pre-crosslinking network can be constructed through chemical crosslinking as long as the lignin used has enough hydroxyl groups. In some examples, the structure, molecular weight, type, and source of lignin are not required, and can be various existing lignins. According to different application scenes, the required lignin can be selected. Including but not limited to alkali lignin, Kraft lignin, enzymatic lignin, organosolv lignin or lignosulphonate.
In some examples, the silica precursor is selected from at least one of ethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, sodium silicate, silicic acid, aluminum silicate, and magnesium silicate.
The silica precursor is a compound which can form a structure having a structure of-Si-O-Si-by a hydrolytic polycondensation reaction, and the kind is not particularly limited. In some examples, the silane coupling agent is selected from at least one of 3- [2- (2-aminoethylamino) ethylamino ] propyl-trimethoxysilane, 3-aminopropyltrimethoxysilane, trimethoxy [3- (methylamino) propyl ] silane, N- (β -aminoethyl) - γ -aminopropyltrimethoxysilane, (3-chloropropyl) trimethoxysilane, N- [3- (trimethoxysilyl) propyl ] ethylenediamine, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxyethyltriethoxysilane, and 3-glycidoxypropyltriethoxysilane.
In some examples, the aqueous solution is at least one of deionized water, aqueous hydrochloric acid, aqueous sulfuric acid, aqueous nitric acid, aqueous phosphoric acid, and aqueous acetic acid. The aqueous solution is a poor solvent of lignin, and the lignin/silica cogel network is fully contacted with the aqueous solution, particularly the lignin/silica cogel network is immersed in the aqueous solution, so that the hydrophobic self-assembly of the lignin network and the in-situ mineralization of the silica gel are facilitated.
In some examples, the crosslinker has the general structural formula (R) 1 ) y -R 3 -(R 2 ) x Wherein x and y are integers of 1 or more, and R 1 And R 2 Being a functional group which can react with hydroxyl groups on lignin, R 3 Is a linking group.
In some examples, R 1 And R 2 Relatively independently an epoxy group, an amino group, an anhydride or a carboxyl group.
In some examples, R 3 Is the residue of a polyolefin, polyether, polyester; or
、
、
、
、
Wherein s, p, m, n and k are integers not less than 1, preferably s, p, m, n and k are independently integers between 1 and 2000, and further integers between 1 and 500. Preferably, R 3 The molecular weight of (A) is 14-5000. R 3 The chain length of the lignin is favorable for obtaining a more flexible lignin pre-crosslinking network; on the contrary, the method is favorable for obtaining a more rigid lignin pre-crosslinking network.
In some examples, the crosslinking agent is selected from at least one of bisphenol a diglycidyl ether, propylene glycol diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether; preferably, the number average molecular weight Mn of the crosslinking agent is 100 to 5000.
In some examples, the aqueous solution is contacted for a time period of not less than 0.1 hour, preferably 0.1 to 48 hours, preferably 5 to 10 hours.
In a second aspect of the present invention, there is provided:
the application of the lignin-silica composite aerogel of the first aspect of the invention comprises the preparation of heat insulation materials, sound insulation and noise reduction materials and flame retardant materials.
The following further describes the technical solution of the present invention with reference to examples, but the embodiments of the present invention are not limited thereto.
The reagents used in the examples are commercially available without specific reference.
The room temperature in the examples is 10 to 30 ℃.
For convenience of comparison, the lignin used in the following examples was corn cob-derived enzymatic lignin (Shandong Longli Biotech Co., Ltd.) unless otherwise specified.
Example 1: preparation of three-dimensional blocky lignin/silicon dioxide composite aerogel (LigSi-1)
The lignin is enzymolysis lignin (Shandongli biological science and technology, Inc.) derived from corncob, the crosslinking agent is Propylene Glycol Diglycidyl Ether (PGDE), the solvent is 1, 4-butanediol, the catalyst is triethylamine, the silica precursor is methyltrimethoxysilane (MTMS), and the silane coupling agent is 3-Aminopropyltrimethoxysilane (APTMS).
2g of enzymatically hydrolyzed lignin was dissolved in 11 mL of 1, 4-butanediol, 3g of PGDE and 0.1g of triethylamine were then added and stirred at 60 ℃ for 1 h to form a pre-crosslinked lignin network. Adding 1g of deionized water into the solution, stirring the solution at room temperature for 1 h, sequentially adding 2g of MTMS and 0.5g of APTMS, continuing stirring the solution for 20min to promote the dissolution and hydrolysis of silane in the solution, transferring the obtained uniform sol into a polystyrene container, sealing the container, and standing the container at room temperature for 24h to complete the cogel process.
The gel was removed and immersed in 0.5 wt.% aqueous acetic acid for 24h, promoting in situ mineralization inside the gel and self-assembly of the lignin cross-linked network, while completing the solvent exchange step. And (3) freeze-drying the gel for 48 h (-55 ℃, 1 Pa), and then annealing at 180 ℃ for 2h to obtain the target three-dimensional blocky lignin/silicon dioxide composite aerogel, wherein the sample is recorded as LigSi-1.
The density of the sample was determined to be 0.20 g cm -3 Porosity of 80.5%, thermal conductivity of 58 mW m -1 K -1 The maximum compressive strength was 15.1 MPa, and the Young's modulus was 6.2 MPa.
Example 2: preparation of three-dimensional blocky lignin/silicon dioxide composite aerogel (LigSi-2)
The lignin is enzymolysis lignin (Shandongli biological science and technology, Inc.) derived from corncob, the crosslinking agent is Propylene Glycol Diglycidyl Ether (PGDE), the solvent is 1, 4-butanediol, the catalyst is triethylamine, the silica precursor is methyltrimethoxysilane (MTMS), and the silane coupling agent is 3-Aminopropyltrimethoxysilane (APTMS).
2g of enzymatically hydrolyzed lignin was dissolved in 19 mL of 1, 4-butanediol, 3g of PGDE and 0.1g of triethylamine were then added and stirred at 60 ℃ for 1 h to form a pre-crosslinked lignin network. Adding 1.7g of deionized water into the solution, stirring the solution at room temperature for 1 hour, sequentially adding 6g of MTMS and 1.5g of APTMS, continuing stirring the solution for 20 minutes to promote the dissolution and hydrolysis of silane in the solution, transferring the obtained uniform sol into a polystyrene container, sealing the container, and standing the container at room temperature for 24 hours to complete the cogel process.
The gel was removed and immersed in 0.5 wt.% aqueous acetic acid for 24h, promoting in situ mineralization inside the gel and self-assembly of the lignin cross-linked network, while completing the solvent exchange step. And (3) freeze-drying the gel for 48 h (-55 ℃, 1 Pa), and then annealing at 180 ℃ for 2h to obtain the target three-dimensional blocky lignin/silicon dioxide composite aerogel, wherein the sample is recorded as LigSi-2.
The density of the sample was determined to be 0.18 g cm -3 Porosity of 81.4%, thermal conductivity of 49 mW m -1 K -1 The maximum compressive strength was 16.2 MPa, and the Young's modulus was 9.7 MPa.
Example 3: preparation of three-dimensional blocky lignin/silicon dioxide composite aerogel (LigSi-3)
The lignin is enzymolysis lignin (Shandongli biological science and technology, Inc.) derived from corncob, the crosslinking agent is Propylene Glycol Diglycidyl Ether (PGDE), the solvent is 1, 4-butanediol, the catalyst is triethylamine, the silica precursor is methyltrimethoxysilane (MTMS), and the silane coupling agent is 3-Aminopropyltrimethoxysilane (APTMS).
2g of enzymatically hydrolyzed lignin was dissolved in 26 mL of 1, 4-butanediol, then 3g of PGDE and 0.1g of triethylamine were added and stirred at 60 ℃ for 1 h to form a pre-crosslinked lignin network. Adding 2.4g of deionized water into the solution, stirring the solution at room temperature for 1 hour, sequentially adding 10g of MTMS and 2.5g of APTMS, continuing stirring the solution for 20 minutes to promote the dissolution and hydrolysis of silane in the solution, transferring the obtained uniform sol into a polystyrene container, sealing the container, and standing the container at room temperature for 24 hours to complete the cogel process.
The gel was removed and immersed in 0.5 wt.% aqueous acetic acid for 24h, promoting in situ mineralization inside the gel and self-assembly of the lignin cross-linked network, while completing the solvent exchange step. Drying the gel at 103 ℃ for 12h, then annealing at 180 ℃ for 2h to obtain the target three-dimensional blocky lignin/silicon dioxide composite aerogel, and recording the sample as LigSi-3.
The density of the sample was determined to be 0.19 g cm -3 Porosity of 85.1%, and thermal conductivity of 39 mW m -1 K -1 The maximum compressive strength was 14.4 MPa, and the Young's modulus was 71.5 MPa. As shown in fig. 1, the ligasi-3 aerogel with different shapes and rules can be prepared by selecting gel containers with different shapes or by mechanical cutting.
Example 4: preparation of three-dimensional blocky lignin/silicon dioxide composite aerogel (LigSi-4)
The lignin is enzymolysis lignin (Shandongli biological science and technology, Inc.) derived from corncob, the crosslinking agent is Propylene Glycol Diglycidyl Ether (PGDE), the solvent is 1, 4-butanediol, the catalyst is triethylamine, the silica precursor is methyltrimethoxysilane (MTMS), and the silane coupling agent is 3-Aminopropyltrimethoxysilane (APTMS).
2g of enzymatically hydrolyzed lignin was dissolved in 30 mL of 1, 4-butanediol, then 3g of PGDE and 0.1g of triethylamine were added and stirred at 60 ℃ for 1 h to form a pre-crosslinked lignin network. Adding 2.7g of deionized water into the solution, stirring the solution at room temperature for 1 hour, sequentially adding 12g of MTMS and 3g of APTMS, continuing stirring the solution for 20 minutes to promote the dissolution and hydrolysis of silane in the solution, transferring the obtained uniform sol into a polystyrene container, sealing the container, and standing the container at room temperature for 24 hours to complete the cogel process.
The gel was removed and immersed in 0.5 wt.% aqueous acetic acid for 24h, promoting in situ mineralization inside the gel and self-assembly of the lignin cross-linked network, while completing the solvent exchange step. Mixing the gel with CO 2 Supercritical drying for 24h, then annealing at 180 ℃ for 2h to obtain the target three-dimensional blocky lignin/silicon dioxide composite aerogel, and recording the sample as LigSi-4.
The density of the sample was determined to be 0.23 g cm -3 Porosity of 70.6%, thermal conductivity of 44 mW m -1 K -1 The maximum compressive strength was 8.9MPa, and the Young's modulus was 59.1 MPa.
Comparative example 1: preparation of sample without addition of silica precursor and silane coupling agent (control group)
The lignin is enzymolysis lignin (Shandong Longli biological science and technology Co., Ltd.) derived from corncob, and the crosslinking agent is Propylene Glycol Diglycidyl Ether (PGDE).
2g of enzymatically hydrolyzed lignin was weighed out and dissolved in 11 mL of 1, 4-butanediol with stirring at room temperature. 1 mL of aqueous NaOH (48 wt.%) was added to the solution and stirred for 10 min. Then 17 mmol of PGDE was added and stirred at room temperature for 30 min. The homogeneous precursor solution obtained was reacted at 50 ℃ to gel. The gel was removed and solvent exchanged in 0.5 wt.% aqueous acetic acid. After three solvent exchange procedures, the wet gel was freeze dried (-55 ℃, 1 Pa) for 48 h. Finally, the dried sample was annealed at 180 ℃ for 2h to obtain a control sample.
The density of the sample was determined to be 0.26 g cm -3 Porosity of 67.5%, thermal conductivity of 101 mW m -1 K -1 The maximum compressive strength was 0.3MPa, and the Young's modulus was 1.4 MPa.
Effect of solvent on Lignin/silica composite aerogel preparation
The lignin is enzymolysis lignin (Shandongli biological science and technology, Inc.) from corncobs, the cross-linking agent is Propylene Glycol Diglycidyl Ether (PGDE), the catalyst is triethylamine, the silicon dioxide precursor is methyl trimethoxy silane (MTMS), the silane coupling agent is 3-aminopropyl trimethoxy silane (APTMS), and the solvents are five common reagents for dissolving or hydrolyzing 1, 4-Butanediol (BDO), deionized water, Ethanol (EA), acetone (CP), Tetrahydrofuran (THF) and Dioxane (DOA). 2g of enzymatically hydrolyzed lignin was dissolved in 26 mL of each of the above six solvents, 3g of PGDE and 0.1g of triethylamine were added thereto, and the mixture was stirred at 60 ℃ for 1 hour. And respectively adding 2.4g of deionized water into the solution, stirring the solution at room temperature for 1 hour, sequentially adding 10g of MTMS and 2.5g of APTMS into the solution, continuously stirring the solution for 20 minutes to promote the dissolution and hydrolysis of silane in the solution, and standing the obtained composite sol for 2 hours as shown in figure 2.
Fig. 2 comparatively shows states of the lignin/silane composite sol prepared by respectively using the above six solvents, and it can be seen from the figure that the lignin/silane composite sol prepared by respectively using 1, 4-Butanediol (BDO) as a solvent shows a uniform sol state, and the lignin/silane composite sol prepared by respectively using deionized water, Ethanol (EA), acetone (CP), Tetrahydrofuran (THF) and Dioxane (DOA) as solvents shows coprecipitation phenomena of different degrees and is difficult to form a uniform block gel. The invention adopts the polyalcohol as a unique bifunctional reagent, which not only serves as a high-efficiency solvent of lignin, but also can delay the rapid polycondensation, phase separation and coprecipitation of lignin/silicon dioxide precursor sol, and plays a role in stabilizing the lignin/silicon dioxide precursor sol, thereby ensuring the formation of uniform massive lignin/silicon dioxide cogel.
Comparison of the microscopic morphologies of different composite aerogels
The microscopic morphologies of the control group, LigSi-1, LigSi-2, LigSi-3, and LigSi-4 composite aerogel materials were observed using a field emission electron scanning microscope, respectively, and the results are shown in FIG. 3. As can be seen from the figure, the multilevel microstructure of the prepared lignin/silica composite aerogel has smaller scale as the addition amount of the silica precursor is increased. The internal microstructures of the LigSi-1 and LigSi-2 samples present hollow microsphere stacking structures, which may be caused by the emulsification of amphiphilic lignin macromolecules. When the addition amount of the silicon dioxide precursor is continuously increased, the emulsion balance is broken, and then a multi-stage and continuous micro-nano structure is formed inside the LigSi-3 sample, and the structure is different from the pearl necklace-type characteristic of the traditional brittle inorganic aerogel and shows a thicker neck connection characteristic.
Comparison of compression mechanical properties of different composite aerogels
The compression mechanical property test of the composite aerogel is carried out on a UTM-16555 mechanical testing machine (Shenzhen Sun science and technology Co., Ltd.) provided with 100N and 1000N mechanical sensors. The ratio of height to diameter was measured at a compressibility of 5 mm/min as 2: 1 cylindrical sample.
The obtained stress-strain curve is shown in fig. 4, and it can be obtained from the graph that the mechanical strength of the prepared three-dimensional bulk lignin/silica composite aerogel material tends to increase and then decrease along with the increase of the addition amount of MTMS and the coupling agent, and the strain of the material during the failure also decreases along with the increase of the addition amount of MTMS and the coupling agent.
From the linear elastic region of the compressive stress-strain curve, the corresponding young's modulus of the material can be calculated, and the result is shown in fig. 5. As can be seen from fig. 5, the young's modulus of the prepared three-dimensional bulk lignin/silica composite aerogel also shows a tendency of increasing and then decreasing with the increase of the addition amount of MTMS and the coupling agent. In the composite aerogel sample, the maximum compressive strength of the LigSi-3 can reach 14.4 MPa, the compressive modulus can reach 71.5 MPa, and the specific modulus and the specific strength respectively reach 376.3 kN.m/kg and 75.8 kN.m/kg, which are higher than most of silicon dioxide composite aerogel materials in the existing reports.
Comparing the mesoporous aperture distribution, density and porosity of different composite aerogels
Pore volume testing was performed using a Micromeritics Tristar 3000. Before the measurement the samples were degassed under high vacuum (< 0.01 mbar) at 150 ℃ for 12 h. The pore size distribution was obtained on the adsorption branch of the isotherm according to the Barrett-Joyner-Halenda (BJH) model, as shown in FIG. 6. As can be seen from fig. 6, compared to the control sample, the lignin/silica composite aerogel prepared in examples 1 to 4 has more mesopores, wherein LigSi-3 has the most abundant mesopore structure, and the pore size ranges from 30 nm to 80 nm.
The densities of the control group, the LigSi-1, the LigSi-2, the LigSi-3 and the LigSi-4 composite aerogel materials are respectively 0.26 g cm -3 、0.20 g cm -3 、0.18 g cm -3 、0.19 g cm -3 、0.23 g cm -3 It can be seen that as the addition amount of silane increases, the density of the prepared lignin/silica composite aerogel tends to decrease and then increase, wherein the densities of the ligasi-2 and ligasi-3 samples are the lowest.
The porosities of the control group, the LigSi-1, the LigSi-2, the LigSi-3 and the LigSi-4 composite aerogel materials measured by a mercury intrusion method are 67.5%, 80.5%, 81.4%, 85.1% and 70.6% respectively, and therefore, as the addition amount of silane is increased, the porosity of the prepared lignin/silicon dioxide composite aerogel presents a trend of being firstly reduced and then increased, wherein the porosity of the LigSi-3 sample is the largest.
Comparison of Water contact angles of different composite aerogels
The contact angle test was performed with a droplet shape analyzer (DSA 100, KR Ü SS, germany) with 2 μ L droplets. Fig. 7 shows surface contact angles and water drop profiles of the aerogels prepared in examples 1 to 4 and comparative example 1, from which it can be seen that the lignin/silica composite aerogel has excellent hydrophobicity compared to the control sample, and the average static water Contact Angle (CA) thereof ranges from 148 ° to 160 °, and LigSi-2, LigSi-3 and LigSi-4 all show superhydrophobic contact angle characteristics except for the sample LigSi-1.
Comparison of thermal conductivity coefficients of different composite aerogels
The thermal conductivity coefficients of the control group, the LigSi-1, the LigSi-2, the LigSi-3 and the LigSi-4 composite aerogel materials are respectively 101 mW m by adopting a transient plane heat source method -1 K -1 、58 mW m -1 K -1 、49 mW m -1 K -1 、39 mW m -1 K -1 、44 mW m -1 K -1 It can be seen that as the addition amount of silane increases, the thermal conductivity of the prepared lignin/silica composite aerogel tends to decrease and then increase, wherein the LigSi-3 sample showsThe minimum thermal conductivity value is given.
Influence of humidity on thermal conductivity
The samples were tested in the range of 33-94% Relative Humidity (RH). The method for controlling the constant RH is as follows: RH (MgCl) in the space was controlled by placing 50 mL of different saturated salt solutions in a closed glass box 2 Saturated solution for preparing 33% RH, Mg (NO) 3 ) 2 The saturated solution is used for preparing 55 percent of RH and CuCl 2 Saturated solution for producing 65% RH, LiSO 4 The saturated solution produces 85% RH, KNO 3 Saturated solution to make 94% RH). The corresponding salt-saturated solution was placed in a sealed glass chamber (100X 60 mm) for at least 24h, maintaining an ambient temperature of 25 ℃. And then placing the sample to be tested into closed chambers with different RH for balancing for 12h, and then starting the test of the heat conductivity coefficient.
The thermal conductivity changes of LigSi-3 and commercial phenolic foams at RH of 33-94% are shown in FIG. 8. As can be seen from the graph, the change of the thermal conductivity of LigSi-3 is almost negligible with the increase of RH, and is maintained at 39-41 mW m -1 K -1 . However, the thermal conductivity of commercial phenolic foam purchased was from 38 mW m when the RH was raised from 33% to 94% -1 K -1 Sharply increased to 48 mW m -1 K -1 . On one hand, the LigSi-3 material has the super-hydrophobic characteristic and hardly absorbs water under the environment with higher relative humidity; on the other hand, the material has abundant mesoporous structure, so that water vapor in the air is difficult to enter pores inside the material. The results show that the prepared LigSi-3 aerogel material can still show stable thermal conductivity coefficient in humid air.
Comparison of solar spectrum near-infrared reflection capability of three-dimensional blocky lignin/silicon dioxide composite aerogel
And (3) performing diffuse reflection test on the prepared three-dimensional blocky lignin/silicon dioxide composite aerogel sample. Diffuse reflectance test A7 mm thick sample was tested for reflectance over the solar spectrum (0.25 μm to 2.5 μm) in the spectral wavelength range using a standard Teflon white plate as a reference, with a 0.002 μm acquisition data interval, using an ultraviolet-visible-near infrared spectrophotometer (lambda-950 with integrating sphere attachment).
FIG. 9 shows the reflectance curves of the samples for radiation in the wavelength range of 250-2500 nm. As can be seen from the graph, the LigSi-1, LigSi-2, LigSi-3 and LigSi-4 aerogel samples all exhibited strong spectral reflectances, especially reflectances at the near infrared band (780-2500 nm) of > 90%, compared to the control sample. It can be seen that the aerogel materials prepared in the embodiments 1 to 4 have excellent near infrared light reflection capability, and when the aerogel materials are used as an enclosure structure of an energy-saving building material, heat accumulation of a living space due to solar radiation can be reduced, so that the energy consumption load of an air conditioning system is reduced.
Fire resistance test of three-dimensional blocky lignin/silicon dioxide composite aerogel (LigSi-3)
To demonstrate the fire resistance of the three-dimensional bulk lignin/silica composite aerogel (ligasi-3), ligasi-3 was subjected to a fire resistance test on an alcohol lamp flame as shown in fig. 10a, and the change in surface temperature of the material with time was recorded with an infrared camera. Fig. 10b shows the condition of heating the ligasi-3 sample on the burner flame for 30min and the infrared thermal image of the back side of the sample, from which it can be seen that the ligasi-3 sample heated on the burner flame for a long time did not self-burn, but only carbonized to black in color, indicating that ligasi-3 itself has good fire resistance. It can be seen from the thermal red image that the back surface temperature is about 320 ℃ after the sample has been heated on an alcohol burner flame for 30min, which is below the destruction temperature of the inorganic cement building. Fig. 10c shows the temperature profile of the back side of the sample, from which it can be seen that the temperature of the back side of the sample reaches a maximum value at about 10 min under the heating of the alcohol burner flame, and the temperature continues to be maintained at about 320 ℃ with the time being longer, which indicates that the carbonized ligasi-3 sample still has good heat insulation performance and can block the transmission of higher temperature. Therefore, the prepared LigSi-3 material has good fire resistance, is free from ignition and pyrolysis fragmentation under the flame of an alcohol burner at 550 ℃, and maintains relatively complete macro-structural characteristics.
The foregoing is a more detailed description of the invention and is not to be taken in a limiting sense. It will be apparent to those skilled in the art that simple deductions or substitutions without departing from the spirit of the invention are within the scope of the invention.
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Claims (16)
1. The preparation method of the massive lignin-silicon dioxide composite aerogel comprises the following steps:
dissolving lignin, a cross-linking agent and a chemical cross-linking catalyst in polyhydric alcohol, and constructing a lignin pre-cross-linking network by chemical cross-linking to obtain a pre-cross-linking lignin liquid, wherein the structural general formula of the cross-linking agent is (R) 1 ) y -R 3 -(R 2 ) x Wherein x and y are integers of 1 or more, and R 1 And R 2 Being a functional group which can react with hydroxyl groups on lignin, R 3 Is a linking group, R 1 And R 2 Relatively independently an epoxy group, an amino group, an anhydride or a carboxyl group, R 3 Is the residue of a polyolefin, polyether, polyester, or
、
、
、
、
Wherein s, p, m, n and k are integers greater than or equal to 1;
adding a silicon dioxide precursor, a silane coupling agent and deionized water into the pre-crosslinked lignin liquid, and carrying out hydrolytic polycondensation reaction to obtain a lignin/silicon dioxide cogel network;
fully contacting the lignin/silicon dioxide cogel network with a neutral or acidic aqueous solution, performing hydrophobic self-assembly of the lignin network and in-situ mineralization of silicon dioxide gel, drying and annealing after full reaction to obtain the massive lignin-silicon dioxide composite aerogel, wherein the aqueous solution is a solution which can not dissolve or hardly dissolve lignin.
2. The monolithic lignin-silica composite aerogel of claim 1, wherein: the mass ratio of the lignin to the cross-linking agent is 50: 1-1: 50; and/or
The mass ratio of the cross-linking agent to the catalyst is 100: 1-1: 100; and/or
The mass ratio of the lignin to the silicon dioxide precursor is 100: 1-1: 100; and/or
The mass ratio of the silicon dioxide precursor to the silane coupling agent is 50: 1-1: 50; and/or
The mass ratio of the deionized water to the polyhydric alcohol is 100: 1-1: 100; and/or
The mass concentration of lignin in the pre-crosslinked lignin liquid is 0.1-50 wt%.
3. The monolithic lignin-silica composite aerogel of claim 2, wherein: the mass ratio of the lignin to the cross-linking agent is 10: 1-1: 10; and/or
The mass ratio of the cross-linking agent to the catalyst is 50: 1-1: 50; and/or
The mass ratio of the lignin to the silicon dioxide precursor is 50: 1-1: 50; and/or
The mass ratio of the silicon dioxide precursor to the silane coupling agent is 50: 1-1: 50; and/or
The mass ratio of the deionized water to the polyhydric alcohol is 50: 1-1: 50; and/or
The mass concentration of lignin in the pre-crosslinked lignin liquid is 1-30 wt%.
4. The monolithic lignin-silica composite aerogel of claim 3, wherein: the mass ratio of the lignin to the cross-linking agent is 1: 3-3: 1; and/or
The mass ratio of the cross-linking agent to the catalyst is 10: 1-1: 10; and/or
The mass ratio of the lignin to the silicon dioxide precursor is 10: 1-1: 10; and/or
The mass ratio of the silicon dioxide precursor to the silane coupling agent is 20: 1-1: 20; and/or
The mass ratio of the deionized water to the polyhydric alcohol is 20: 1-1: 20; and/or
The mass concentration of lignin in the pre-crosslinked lignin liquid is 8 wt%.
5. The monolithic lignin-silica composite aerogel of claim 4, wherein: the mass ratio of the lignin to the cross-linking agent is 2: 3; and/or
The mass ratio of the cross-linking agent to the catalyst is 30: 1; and/or
The mass ratio of the lignin to the silicon dioxide precursor is 1: 5; and/or
The mass ratio of the silicon dioxide precursor to the silane coupling agent is 4: 1; and/or
The mass ratio of the deionized water to the polyhydric alcohol is 1: 11; and/or
The mass concentration of lignin in the pre-crosslinked lignin liquid is 8 wt%.
6. The monolithic lignin-silica composite aerogel of claim 1, wherein: the temperature of the chemical crosslinking reaction is 10-150 ℃, and is not higher than the boiling point of the polyhydric alcohol; and/or
The hydrolytic polycondensation reaction is carried out at 10-150 ℃ until the mixed solution is gelatinized and can not flow; and/or
The drying method is selected from forced air heating drying, vacuum heating drying, freeze drying or supercritical drying; and/or
The annealing method is heating annealing in air, wherein the heating temperature is 100-200 ℃, and the heating time is 0.1-12 h.
7. The monolithic lignin-silica composite aerogel of claim 6, wherein: the temperature of the chemical crosslinking reaction is 50-100 ℃; and/or
The hydrolytic polycondensation reaction is carried out at the temperature of 20-60 ℃ until the mixed solution is gelatinized and can not flow; and/or
The annealing method is heating annealing in air, wherein the heating temperature is 120-180 ℃, and the heating time is 1-6 hours.
8. The monolithic lignin-silica composite aerogel according to claim 6 or 7, wherein: the time of the chemical crosslinking reaction is 20-120 min.
9. The monolithic lignin-silica composite aerogel of claim 1, wherein: the polyalcohol is at least one selected from 1, 4-butanediol, 1, 3-butanediol, 2, 3-butanediol, diethylene glycol, triethylene glycol, ethylene glycol, glycerol, propylene glycol, polyethylene glycol and polypropylene glycol; and/or
The catalyst is selected from at least one of imidazole, 2-ethylimidazole, 2-methylimidazole, triethylamine, ammonia water, ethylenediamine, polyethylene polyamine, dicyandiamide, NaOH, KOH, LiOH, N, N-dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, N, N, N ', N' -tetramethylalkylenediamine, N, N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N, N '-diethylpiperazine, triethanolamine, dimethylethanolamine, pyridine and N, N' -dimethylpyridine; and/or
The silicon dioxide precursor is selected from at least one of ethyl orthosilicate, methyl triethoxysilane, methyl trimethoxysilane, dimethyl diethoxy silane, dimethyl dimethoxy silane, sodium silicate, silicic acid, aluminum silicate and magnesium silicate; and/or
The silane coupling agent is selected from at least one of 3- [2- (2-aminoethylamino) ethylamino ] propyl-trimethoxysilane, 3-aminopropyltrimethoxysilane, trimethoxy [3- (methylamino) propyl ] silane, N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane, (3-chloropropyl) trimethoxysilane, N- [3- (trimethoxysilyl) propyl ] ethylenediamine, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxyethyltriethoxysilane and 3-glycidoxypropyltriethoxysilane; and/or
The aqueous solution is at least one of deionized water, hydrochloric acid aqueous solution, sulfuric acid aqueous solution, nitric acid aqueous solution, phosphoric acid aqueous solution and acetic acid aqueous solution.
10. The monolithic lignin-silica composite aerogel of claim 9, wherein: the polyethylene polyamine is at least one selected from diethylenetriamine, triethylene tetramine and triethylene diamine.
11. The monolithic lignin-silica composite aerogel of claim 1, wherein: the cross-linking agent is selected from at least one of bisphenol A diglycidyl ether, propylene glycol diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether.
12. The monolithic lignin-silica composite aerogel according to claim 1 or 11, wherein: the number average molecular weight Mn of the cross-linking agent is 100-5000.
13. The monolithic lignin-silica composite aerogel of claim 1, wherein: the contact time of the aqueous solution is not less than 0.1 h.
14. The monolithic lignin-silica composite aerogel of claim 13, wherein: the contact time of the aqueous solution is 0.1-48 h.
15. The monolithic lignin-silica composite aerogel of claim 14, wherein: the contact time of the aqueous solution is 5-10 h.
16. The application of the massive lignin-silica composite aerogel, which is as described in any one of claims 1 to 15, comprises the preparation of heat insulation materials, sound insulation and noise reduction materials and flame retardant materials.
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| CN108484097B (en) * | 2018-05-30 | 2021-09-17 | 巩义市泛锐熠辉复合材料有限公司 | Preparation method of lignin-enhanced silicon dioxide aerogel felt |
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