CN116393049A - Method for preparing high-porosity silicon-based aerogel by normal-pressure drying - Google Patents
Method for preparing high-porosity silicon-based aerogel by normal-pressure drying Download PDFInfo
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- 238000001035 drying Methods 0.000 title claims abstract description 59
- 239000004964 aerogel Substances 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 45
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 25
- 239000010703 silicon Substances 0.000 title claims abstract description 25
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 47
- 238000009830 intercalation Methods 0.000 claims abstract description 44
- 230000002687 intercalation Effects 0.000 claims abstract description 44
- 230000032683 aging Effects 0.000 claims abstract description 21
- 239000011240 wet gel Substances 0.000 claims abstract description 19
- 239000005056 polyisocyanate Substances 0.000 claims abstract description 17
- 229920001228 polyisocyanate Polymers 0.000 claims abstract description 17
- 239000002243 precursor Substances 0.000 claims abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 48
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 38
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims description 26
- 239000002904 solvent Substances 0.000 claims description 20
- -1 mcardite Chemical compound 0.000 claims description 19
- 239000004965 Silica aerogel Substances 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 17
- NIMLQBUJDJZYEJ-UHFFFAOYSA-N isophorone diisocyanate Chemical compound CC1(C)CC(N=C=O)CC(C)(CN=C=O)C1 NIMLQBUJDJZYEJ-UHFFFAOYSA-N 0.000 claims description 17
- 239000005058 Isophorone diisocyanate Substances 0.000 claims description 16
- 239000012686 silicon precursor Substances 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 15
- 229910052726 zirconium Inorganic materials 0.000 claims description 13
- 239000003607 modifier Substances 0.000 claims description 12
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- 238000006243 chemical reaction Methods 0.000 claims description 10
- 230000001105 regulatory effect Effects 0.000 claims description 10
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- 230000002209 hydrophobic effect Effects 0.000 claims description 7
- 230000004048 modification Effects 0.000 claims description 7
- 238000012986 modification Methods 0.000 claims description 7
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- 238000006482 condensation reaction Methods 0.000 claims description 6
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims description 6
- KORSJDCBLAPZEQ-UHFFFAOYSA-N dicyclohexylmethane-4,4'-diisocyanate Chemical compound C1CC(N=C=O)CCC1CC1CCC(N=C=O)CC1 KORSJDCBLAPZEQ-UHFFFAOYSA-N 0.000 claims description 6
- FUZZWVXGSFPDMH-UHFFFAOYSA-N hexanoic acid Chemical compound CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 claims description 6
- 238000006460 hydrolysis reaction Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 6
- 150000001875 compounds Chemical class 0.000 claims description 5
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- 238000000227 grinding Methods 0.000 claims description 5
- CMOAHYOGLLEOGO-UHFFFAOYSA-N oxozirconium;dihydrochloride Chemical compound Cl.Cl.[Zr]=O CMOAHYOGLLEOGO-UHFFFAOYSA-N 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052901 montmorillonite Inorganic materials 0.000 claims description 3
- FKTHNVSLHLHISI-UHFFFAOYSA-N 1,2-bis(isocyanatomethyl)benzene Chemical compound O=C=NCC1=CC=CC=C1CN=C=O FKTHNVSLHLHISI-UHFFFAOYSA-N 0.000 claims description 2
- AZYRZNIYJDKRHO-UHFFFAOYSA-N 1,3-bis(2-isocyanatopropan-2-yl)benzene Chemical compound O=C=NC(C)(C)C1=CC=CC(C(C)(C)N=C=O)=C1 AZYRZNIYJDKRHO-UHFFFAOYSA-N 0.000 claims description 2
- UPMLOUAZCHDJJD-UHFFFAOYSA-N 4,4'-Diphenylmethane Diisocyanate Chemical compound C1=CC(N=C=O)=CC=C1CC1=CC=C(N=C=O)C=C1 UPMLOUAZCHDJJD-UHFFFAOYSA-N 0.000 claims description 2
- 239000005995 Aluminium silicate Substances 0.000 claims description 2
- 239000005057 Hexamethylene diisocyanate Substances 0.000 claims description 2
- VBIIFPGSPJYLRR-UHFFFAOYSA-M Stearyltrimethylammonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCCCC[N+](C)(C)C VBIIFPGSPJYLRR-UHFFFAOYSA-M 0.000 claims description 2
- 235000012211 aluminium silicate Nutrition 0.000 claims description 2
- 229960000892 attapulgite Drugs 0.000 claims description 2
- JBIROUFYLSSYDX-UHFFFAOYSA-M benzododecinium chloride Chemical compound [Cl-].CCCCCCCCCCCC[N+](C)(C)CC1=CC=CC=C1 JBIROUFYLSSYDX-UHFFFAOYSA-M 0.000 claims description 2
- WOWHHFRSBJGXCM-UHFFFAOYSA-M cetyltrimethylammonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCC[N+](C)(C)C WOWHHFRSBJGXCM-UHFFFAOYSA-M 0.000 claims description 2
- DDXLVDQZPFLQMZ-UHFFFAOYSA-M dodecyl(trimethyl)azanium;chloride Chemical compound [Cl-].CCCCCCCCCCCC[N+](C)(C)C DDXLVDQZPFLQMZ-UHFFFAOYSA-M 0.000 claims description 2
- 230000002431 foraging effect Effects 0.000 claims description 2
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims description 2
- 229910052625 palygorskite Inorganic materials 0.000 claims description 2
- 239000002798 polar solvent Substances 0.000 claims description 2
- 150000003856 quaternary ammonium compounds Chemical group 0.000 claims description 2
- SFVFIFLLYFPGHH-UHFFFAOYSA-M stearalkonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCCCC[N+](C)(C)CC1=CC=CC=C1 SFVFIFLLYFPGHH-UHFFFAOYSA-M 0.000 claims description 2
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 abstract description 10
- 239000003054 catalyst Substances 0.000 abstract description 4
- 238000009833 condensation Methods 0.000 abstract description 2
- 230000005494 condensation Effects 0.000 abstract description 2
- 230000003301 hydrolyzing effect Effects 0.000 abstract 1
- 239000012774 insulation material Substances 0.000 abstract 1
- 239000000377 silicon dioxide Substances 0.000 description 15
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 239000000499 gel Substances 0.000 description 11
- 230000006872 improvement Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 239000012948 isocyanate Substances 0.000 description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 239000011148 porous material Substances 0.000 description 5
- 230000001965 increasing effect Effects 0.000 description 4
- 238000009413 insulation Methods 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 238000000352 supercritical drying Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000004108 freeze drying Methods 0.000 description 3
- RNYJXPUAFDFIQJ-UHFFFAOYSA-N hydron;octadecan-1-amine;chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCCCC[NH3+] RNYJXPUAFDFIQJ-UHFFFAOYSA-N 0.000 description 3
- 239000011229 interlayer Substances 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- CREMABGTGYGIQB-UHFFFAOYSA-N carbon carbon Chemical compound C.C CREMABGTGYGIQB-UHFFFAOYSA-N 0.000 description 2
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 239000011343 solid material Substances 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000010669 acid-base reaction Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001491 aromatic compounds Chemical class 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 1
- 150000002513 isocyanates Chemical class 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Silicon Compounds (AREA)
Abstract
The invention relates to the technical field of aerogel preparation, and provides a method for preparing high-porosity silicon-based aerogel by normal-pressure drying, which solves the problem of insufficient porosity of the aerogel prepared by the existing normal-pressure drying. The method comprises the following steps: (1) preparation of a modified intercalation material; (2) Preparing a modified intercalation material loaded with polyisocyanate; (3) hydrolytic condensation of aerogel precursor; and (4) ageing and drying the wet gel. The prepared aerogel has high porosity reaching 92% or more, and can be used as a heat insulation material or a catalyst carrier.
Description
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to a method for preparing high-porosity silicon-based aerogel by normal pressure drying.
Background
The silica-based aerogel is a light nano solid material, and the unique nano porous three-dimensional network structure endows the silica-based aerogel with the characteristics of low density, high porosity, high specific surface area and the like, so that the silica-based aerogel has strong adsorptivity, and is greatly superior to the traditional catalyst in the aspects of activity, selectivity, service life and the like of a supported catalyst, thereby having great application value in the field of catalysis. Moreover, the silicon-based aerogel has excellent heat insulation performance, is a currently known solid material with the lowest heat conductivity, and has wide application prospect in the field of building heat preservation and heat insulation.
Silica-based aerogels are generally obtained from silicates by hydrolysis, condensation of the gel, aging, solvent substitution, drying, and the like. The common drying method comprises supercritical drying, normal pressure drying and freeze drying, and the aerogel prepared by the supercritical drying method has the advantages of minimum shrinkage, complex process, high risk, long preparation period, high requirement on equipment and the like; when the freeze drying method is adopted, the solvent is easy to change phase, so that the volume change is generated, the pore structure of the gel is damaged, and aerogel powder or particles can be obtained. Compared with supercritical drying and freeze drying, the normal pressure drying method has simple process, safe process, low requirement on equipment and continuous preparation, and therefore, the method becomes a research hot spot in recent years.
The basic principle of normal pressure drying is that wet gel samples are treated to remove solvent in nano holes at normal pressure and keep gel skeleton structures from collapsing, so that aerogel materials with excellent performance are obtained. For example, patent number CN201710172205.1 discloses a method for preparing silica aerogel at normal pressure and the prepared silica aerogel, which comprises the following steps: (1) Diluting an inorganic silicon source with water, and mixing the diluted inorganic silicon source with acid to perform an acid-base reaction to obtain silicic acid sol; (2) Performing gel forming on the silicic acid sol, and performing aging treatment on the gel after gel forming to obtain wet gel; (3) Adding a modifier base solution into wet gel until the wet gel is completely soaked, adding concentrated acid or concentrated alkali solution into the system, and carrying out surface modification treatment under a closed condition or in a device with condensing reflux equipment until the gel is completely modified from hydrophilic to hydrophobic; (4) And (3) drying the modified aerogel obtained in the step (3) to obtain the silica aerogel. The preparation method provided by the invention has the advantages of short process period, less solvent consumption and low production cost; the prepared silica aerogel product has low density and good hydrophobic property, and the heat conductivity coefficient of the silica aerogel product is extremely low, so that the silica aerogel product is very suitable for being applied to the field of heat preservation and heat insulation.
However, the conventional aerogel prepared by normal pressure drying has the following defects: when the gas replaces the solvent in the aerogel pores, the shrinkage or even collapse of the gel structure can be caused by the capillary force and the stress generated by the high specific surface energy during drying, so that the porosity of the material is far less than that of the aerogel material obtained by other methods such as supercritical drying, and the problems of large volume shrinkage and the like exist. The porosity of the aerogel largely determines whether the aerogel can be widely applied to the heat insulation field and the catalysis field, and is one of key parameters. Therefore, how to increase the porosity of the aerogel obtained by the normal pressure drying method becomes one of the important points of the study of silica-based aerogel. For example, patent number CN202010446290.8 discloses a preparation method of silica aerogel, in the preparation process of silica aerogel, a carbon-containing unsaturated double bond modifier is adopted to modify, and the obtained wet gel has carbon-carbon unsaturated double bond groups; and then placing the wet gel in a multi-mercapto aromatic compound solution to perform mercapto-alkene click chemical reaction under ultraviolet irradiation, and utilizing the characteristics of quick reaction rate and high selectivity of the mercapto-alkene click chemical reaction, forming a layer of thinner but higher-strength cross-linking aromatic compound by reacting the carbon-carbon unsaturated double bond with the multi-mercapto aromatic compound on the surface of the wet gel, so that the problem of shrinkage collapse of a silicon dioxide three-dimensional network caused by solvent volatilization can be effectively resisted when the wet gel is dried under normal pressure, and a new thought is provided for obtaining the silicon dioxide aerogel with high porosity by normal pressure drying. However, the porosity of the silica aerogel obtained by the method can only reach 49%.
Disclosure of Invention
Therefore, in view of the above, the present invention provides a method for preparing a high-porosity silica-based aerogel by normal pressure drying, which solves the problem of insufficient porosity of the aerogel prepared by the existing normal pressure drying.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a method for preparing high-porosity silicon-based aerogel by normal pressure drying comprises the following steps:
(1) Dispersing the intercalation material into a polar solvent, dropwise adding excessive modifier at 60-80 ℃ for reaction for 6-24 h, and filtering, washing and drying after the reaction is finished to obtain a modified intercalation material;
(2) Fully grinding the modified intercalation material, adding a butyl acetate solution containing polyisocyanate, stirring and reacting for 3-24 h, and adsorbing a polyisocyanate compound between layers and on the surface of the intercalation material to obtain the modified intercalation material loaded with polyisocyanate;
(3) Dissolving a silicon precursor I and a zirconium precursor in an ethanol solvent, adding a proper amount of water, stirring and mixing uniformly, regulating the pH value to 1.0-4.0, forming a Si-O-Zr basic network after hydrolysis reaction for 20-60 min, then adding a modified intercalation material loaded with polyisocyanate, stirring for 20-60 min after ultrasonic dispersion for 2-15 min, regulating the pH value of a system to 6.0-7.0, and performing condensation reaction to form wet gel;
(4) Adding the wet gel obtained in the step (3) into an aging liquid, adding a proper amount of silicon precursor II, and heating to 45-60 ℃ for aging treatment;
after the aging is finished, the silicon-based aerogel with high porosity is obtained through hydrophobic modification, solvent replacement and normal-pressure drying. The aerogel obtained can be used as a heat insulating material or a catalyst carrier.
The further improvement is that: the intercalation material is any one of montmorillonite, bentonite, mcardite, kaolin and attapulgite, and the modifier is a quaternary ammonium compound.
The further improvement is that: the modifier is any one of dodecyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride and octadecyl dimethyl benzyl ammonium chloride.
The further improvement is that: the polyisocyanate is one or more than two of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, xylylene diisocyanate and tetramethyl m-xylylene diisocyanate which are mixed in any ratio.
The further improvement is that: the silicon precursor i is a silicon alkoxide including, but not limited to, the following: methyl orthosilicate and ethyl orthosilicate, wherein the zirconium precursor is zirconium alkoxide or zirconium oxychloride.
The further improvement is that: the adding amount of the zirconium precursor is 0.05-5% of the mass of the silicon precursor I, and the adding amount of the water is 2-6 times of the molar concentration of the silicon precursor I.
The further improvement is that: and (3) the addition amount of the modified intercalation material loaded with the polyisocyanate is 5-20% based on 100% of the total mass of the silicon precursor I, the zirconium precursor, the ethanol and the water.
The further improvement is that: the aging liquid is any one of methanol, ethanol, isopropanol and n-butanol, and the aging time is 24-72 h.
The further improvement is that: the silicon precursor II is silicon alkoxide, and the addition amount is 0.5-2% of the mass of the aging liquid. The silicon alkoxide used for the silicon precursor II may be the same as or different from the silicon precursor I.
The further improvement is that: the normal pressure drying adopts sectional drying, and the specific conditions are as follows: firstly, heating to 56-64 ℃ and drying for 2-6 h; then heating to 75-85 ℃ and drying for 2-6 h; heating to 95-105 deg.c and drying for 2-6 hr; finally, heating to 115-130 ℃ and drying for 2-6 h.
The further improvement is that: the solvent replacement time is 12-48 h, and the replacement temperature is 20-50 ℃.
The further improvement is that: the solvent used in the solvent replacement step is a solvent having a low surface tension and a low boiling point.
By adopting the technical scheme, the invention has the beneficial effects that:
according to the invention, from a gel mechanism, the polyisocyanate compound is combined with the clay intercalation material, and the slow release of the polyisocyanate compound is achieved through the intercalation structure load, so that the enhancement of a gel skeleton and the controllable design of a micro-network structure are realized. Specifically, firstly, an intercalation material is modified, and isocyanate compounds are adsorbed between layers and on the surface of the intercalation material, so that the long-acting slow release of the isocyanate compounds is realized; then adding the modified intercalation material loaded with polyisocyanate into a silica-based sol system, slowly releasing isocyanate compounds from the intercalation material, and carrying out condensation reaction with a silica-based network to enhance the crosslinking degree of a network structure; in the heating and ageing process, the isocyanate compound is further slowly released and reacts with the residual water in the system to generate carbon dioxide and amino compound, the generated carbon dioxide can increase the porosity, and the amino compound can be complexed with silicon, so that the effects of further enhancing the network structure and improving the porosity are achieved.
By adding the zirconium-based material, a Si-O-Zr network structure can be formed, the strength of the aerogel framework is increased, and collapse in the drying process is slowed down. Furthermore, the amino compound generated by the isocyanate functional group reaction has good complexing ability for zirconium, and further enhances the Si-O-Zr network structure.
The intercalation material of the present invention, while acting as a carrier for isocyanate compounds, can also serve two additional functions: (1) Locking carbon dioxide, and preventing generated carbon dioxide gas from escaping rapidly in a sol-gel system; (2) the intercalation material acts to support the aerogel framework. The shrinkage and collapse of the structure caused by capillary force in the normal pressure drying process are effectively avoided, and the controllable construction of the silicon-based aerogel high-porosity structure under normal pressure drying is realized.
Drawings
FIG. 1 is a thermal weight loss curve of an IPDI-loaded modified bentonite intercalation material prepared in example 1 of the present invention;
FIG. 2 is a graph showing the release curves of the modified bentonite intercalation material loaded with IPDI prepared in example 1 of the present invention at different temperatures;
FIG. 3 is a schematic diagram of the reaction in step (3) of example 1 of the present invention;
FIG. 4 is a schematic diagram of the reaction in step (4) of example 1 of the present invention;
FIG. 5 is a microstructure of the silica-based aerogel prepared in example 1 of the present invention;
FIG. 6 is a microstructure of the silica-based aerogel prepared in comparative example 2.
Detailed Description
The following describes embodiments of the present invention in detail with reference to specific examples, so as to solve the technical problem by applying the technical means to the present invention, and the implementation process for achieving the technical effect can be fully understood and implemented accordingly.
Unless otherwise indicated, the technical means employed in the examples are conventional means well known to those skilled in the art, and the reagents and products employed are also commercially available. The sources of the reagents used, the trade names and the members of the list of constituents which are necessary are all indicated at the first occurrence.
Example 1
A method for preparing high-porosity silicon-based aerogel by normal pressure drying is characterized by comprising the following steps: the method comprises the following steps:
(1) Adding 5g of bentonite into 100mL of ethanol, heating to 70 ℃, dropwise adding excessive octadecyl ammonium chloride to modify the bentonite, increasing the interlayer spacing of the bentonite, and filtering, washing with ethanol and drying after reacting for 8 hours to obtain modified bentonite;
(2) Taking 3g of dried modified bentonite, fully grinding, adding a butyl acetate solution containing 30wt% of isophorone diisocyanate, stirring for 6 hours, and adsorbing isophorone diisocyanate (IPDI) between layers and on the surface of the intercalation material to obtain an IPDI-loaded modified bentonite intercalation material;
referring to fig. 1, it can be seen from the thermal weight loss curve that the loading amount of the IPDI is 28%, which indicates that the IPDI is successfully adsorbed between layers and on the surface of the intercalation material;
referring to FIG. 2, by releaseThe release curve shows that the IPDI can realize slow release within 120min at normal temperature, the release rate is about 55%, and the release rate at 60 ℃ is improved to more than 70%. The slow release profile of FIG. 2 shows that at 60℃additional IPDI is released and participates in the reaction. Detection Using infrared quantification method, 1g of modified bentonite intercalation material loaded with IPDI was dispersed in 10mL of butyl acetate solution, 0.2mL of the solution was taken out with a pipette, filtered with a 0.22 μm syringe filter membrane, and mixed with 0.2g of KBr for tabletting, and measured at 2260cm -1 The peak at the position is strong.
(3) Dissolving 10mL of tetraethoxysilane and 0.5g of zirconium oxychloride in 100mL of ethanol, adding 3.25mL of water, stirring and mixing uniformly, regulating the pH value to 2.0, forming a Si-O-Zr basic network after hydrolysis reaction for 60min, then adding modified bentonite intercalation material loaded with IPDI, stirring for 20min after ultrasonic dispersion for 10min, regulating the pH value of the system to 6.5, and performing condensation reaction to form wet gel;
referring to fig. 3, bentonite is modified to form modified bentonite, isocyanate compound IPDI is adsorbed between layers and on the surface of the modified bentonite, desorption of the IPDI is promoted by ultrasonic dispersion, slow release is carried out from an intercalation material, a-NCO group in the structure reacts with a-OH group remained in the system, a Si-O-Zr network is enhanced, collapse in the drying process is slowed down, and the porosity is improved;
(4) Adding the wet gel obtained in the step (3) into an ethanol solvent, adding 0.5mL of ethyl orthosilicate, heating to 60 ℃ and aging for 48 hours;
referring to fig. 4, isophorone diisocyanate in the intercalation material is further desorbed in the process of temperature rise and aging, reacts with the residual moisture in the system, and generates carbon dioxide and amino compounds, wherein the carbon dioxide can improve the porosity, and the amino compounds can be complexed with silicon and zirconium to strengthen the Si-O-Zr network structure;
after aging is finished, adding a hydrophobic modifier for modification for 24 hours, then using an n-hexane solvent for replacement for 12 hours, wherein the replacement temperature is 40 ℃, and finally drying for 5 hours at 60 ℃, 80 ℃, 100 ℃ and 120 ℃ respectively in sequence to obtain the high-porosity silicon-based aerogel.
The silica-based aerogel obtained in this example had a density of0.187g·cm -3 Porosity of 92.9% and thermal conductivity of 0.0335 W.m -1 ·K -1 。
Example 2
A method for preparing high-porosity silicon-based aerogel by normal pressure drying comprises the following steps:
(1) Adding 5g of bentonite into 100mL of ethanol, heating to 70 ℃, dropwise adding excessive octadecyl ammonium chloride to modify the bentonite, increasing the interlayer spacing of the bentonite, and filtering, washing with ethanol and drying after reacting for 8 hours to obtain modified bentonite;
(2) Taking 3g of dried modified bentonite, fully grinding, adding a butyl acetate solution containing 30wt% of dicyclohexylmethane-4, 4 '-diisocyanate, stirring for 6h, and adsorbing dicyclohexylmethane-4, 4' -diisocyanate (HMDI) between layers and on the surface of the intercalation material to obtain an HMDI-loaded modified bentonite intercalation material;
(3) Dissolving 10mL of tetraethoxysilane and 0.5g of zirconium oxychloride in 100mL of ethanol, adding 3.25mL of water, stirring and mixing uniformly, regulating the pH value to 2.0, forming a Si-O-Zr basic network after hydrolysis reaction for 60min, then adding a modified bentonite intercalation material loaded with HMDI, stirring for 20min after ultrasonic dispersion for 10min, regulating the pH value of the system to 6.5, and performing condensation reaction to form wet gel.
(4) Adding the wet gel obtained in the step (3) into an ethanol solvent, adding 0.5mL of ethyl orthosilicate, heating to 60 ℃ and aging for 48 hours;
after aging is finished, adding a hydrophobic modifier for modification for 24 hours, then using an n-hexane solvent for replacement for 48 hours, wherein the replacement temperature is 25 ℃, and finally drying for 6 hours at 56 ℃, 75 ℃, 95 ℃ and 115 ℃ respectively in sequence to obtain the high-porosity silicon-based aerogel.
The silica-based aerogel obtained in this example had a density of 0.175 g.cm -3 Porosity is 93.4%, thermal conductivity is 0.0293 W.m -1 ·K -1 。
Example 3
A method for preparing high-porosity silicon-based aerogel by normal pressure drying comprises the following steps:
(1) Adding 5g of montmorillonite into 100mL of ethanol, heating to 60 ℃, dropwise adding excessive octadecyl ammonium chloride, modifying bentonite, increasing interlayer spacing, reacting for 24h, filtering, washing with ethanol, and drying to obtain modified montmorillonite;
(2) Taking 3g of dried modified montmorillonite, fully grinding, adding a butyl acetate solution containing 50wt% of dicyclohexylmethane-4, 4 '-diisocyanate, stirring for 6h, and adsorbing dicyclohexylmethane-4, 4' -diisocyanate (HMDI) between layers and on the surface of the intercalation material to obtain a modified montmorillonite intercalation material loaded with HMDI;
(3) Dissolving 10mL of tetraethoxysilane and 1g of zirconium oxychloride in 100mL of ethanol, adding 3.25mL of water, stirring and mixing uniformly, regulating the pH value to 2.0, forming a Si-O-Zr basic network after hydrolysis reaction for 60min, then adding a modified bentonite intercalation material loaded with HMDI, stirring for 20min after ultrasonic dispersion for 10min, regulating the pH value of the system to 6.5, and performing condensation reaction to form wet gel.
(4) Adding the wet gel obtained in the step (3) into an ethanol solvent, adding 0.5mL of ethyl orthosilicate, heating to 60 ℃ and aging for 48 hours;
after aging is finished, adding a hydrophobic modifier for modification for 24 hours, then using an n-hexane solvent for replacement for 24 hours, wherein the replacement temperature is 50 ℃, and finally drying for 3 hours at 64 ℃, 85 ℃, 106 ℃ and 130 ℃ respectively in sequence to obtain the high-porosity silicon-based aerogel.
The silica-based aerogel obtained in this example had a density of 0.176 g.cm -3 Porosity of 93.3% and thermal conductivity of 0.0304 W.m -1 ·K -1 。
Comparative example 1
The preparation of this comparative example was substantially identical to example 1, except that: omitting the step (2), and directly adding the modified bentonite obtained in the step (1) into the solution of the step (3).
The aerogel obtained in this comparative example had a density of 0.418 g.cm -3 Porosity of 84.2% and thermal conductivity of 0.0493 W.m -1 ·K -1 。
Comparative example 2
The preparation of this comparative example was substantially identical to example 1, except that: no modified bentonite intercalation material loaded with IPDI is added.
The aerogel obtained in this comparative example had a density of 0.833 g.cm -3 Porosity of 68.5%, thermal conductivity of 0.1051 W.m -1 ·K -1 。
Referring to fig. 5 and 6, it can be seen that the pore structure of the aerogel prepared in this comparative example is not obvious, which is most likely caused by the collapse of the structure during drying. The aerogel prepared in example 1 has more pore structure, which demonstrates that the modified intercalation material added with the loaded polyisocyanate is beneficial to retaining the high pore structure and improving the porosity of the aerogel.
The above description is illustrative of the embodiments using the present teachings, and is not intended to limit the scope of the present teachings to any particular modification or variation of the present teachings by those skilled in the art.
Claims (10)
1. A method for preparing high-porosity silicon-based aerogel by normal pressure drying is characterized by comprising the following steps: the method comprises the following steps:
(1) Dispersing the intercalation material into a polar solvent, dropwise adding a modifier at 60-80 ℃, wherein the addition amount of the modifier is 1.5-3 times of the mass of the intercalation material, reacting for 6-24 h, filtering, washing and drying after the reaction is finished to obtain the modified intercalation material;
(2) Fully grinding the modified intercalation material, adding a butyl acetate solution containing polyisocyanate, stirring and reacting for 3-24 h, and adsorbing a polyisocyanate compound between layers and on the surface of the intercalation material to obtain the modified intercalation material loaded with polyisocyanate;
(3) Dissolving a silicon precursor I and a zirconium precursor in an ethanol solvent, adding a proper amount of water, stirring and mixing uniformly, regulating the pH value to 1.0-4.0, forming a Si-O-Zr basic network after hydrolysis reaction for 20-60 min, then adding a modified intercalation material loaded with polyisocyanate, stirring for 20-60 min after ultrasonic dispersion for 2-15 min, regulating the pH value of a system to 6.0-7.0, and performing condensation reaction to form wet gel;
(4) Adding the wet gel obtained in the step (3) into an aging liquid, adding a proper amount of silicon precursor II, and heating to 45-60 ℃ for aging treatment; after the aging is finished, the silicon-based aerogel with high porosity is obtained through hydrophobic modification, solvent replacement and normal-pressure drying.
2. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: the intercalation material is any one of montmorillonite, bentonite, mcardite, kaolin and attapulgite, and the modifier is a quaternary ammonium compound.
3. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 2, wherein the method comprises the following steps: the modifier is any one of dodecyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride and octadecyl dimethyl benzyl ammonium chloride.
4. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: the polyisocyanate is one or more than two of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, xylylene diisocyanate and tetramethyl m-xylylene diisocyanate which are mixed in any ratio.
5. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: the silicon precursor I is silicon alkoxide, and the zirconium precursor is zirconium alkoxide or zirconium oxychloride.
6. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 5, wherein the method comprises the following steps: the adding amount of the zirconium precursor is 0.05-5% of the mass of the silicon precursor I, and the adding amount of the water is 2-6 times of the molar concentration of the silicon precursor I.
7. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: and (3) the addition amount of the modified intercalation material loaded with the polyisocyanate is 5-20% based on 100% of the total mass of the silicon precursor I, the zirconium precursor, the ethanol and the water.
8. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: the aging liquid is any one of methanol, ethanol, isopropanol and n-butanol, and the aging time is 24-72 h.
9. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: the silicon precursor II is silicon alkoxide, and the addition amount is 0.5-2% of the mass of the aging liquid.
10. The method for preparing the high-porosity silica aerogel by normal pressure drying according to claim 1, wherein the method comprises the following steps: in the step (4), the normal pressure drying adopts sectional drying, and the specific conditions are as follows: firstly, heating to 56-64 ℃ and drying for 2-6 h; then heating to 75-85 ℃ and drying for 2-6 h; heating to 95-105 deg.c and drying for 2-6 hr; finally, heating to 115-130 ℃ and drying for 2-6 h.
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| CN117942885B (en) * | 2024-03-26 | 2024-06-11 | 洛阳市浪潮消防科技股份有限公司 | Atmospheric pressure drying preparation method of aerogel with high pore volume, high specific surface area and low density |
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