Background technology
Aerosil mutually piles up with nano SiO 2 particle the novel material surrounding and have three-dimensional porous structure.Because having low density (0.003 ~ 0.8gcm
-3), high porosity (80 ~ 99.8%), high-specific surface area (200 ~ 1000m
2g
-1), lower thermal conductivity (~ 0.02Wm
-1k
-1) etc. character make it have very wide prospect in Application Areass such as aerospace, chemical industry, energy saving building, military affairs, communication, electronics, metallurgy.
Although the research of aerogel becomes the focus that investigator pays close attention to already, really realize so far commercial scale produces and give wide popularization and application enterprise and seldom.Its major cause is the formation problems of aerogel.The preparation of aerogel adopts sol-gel method more, in wet gel drying process, existence due to liquid-gas interface creates the gel skeleton anisotropy very large capillary force and gel aperture not exclusively evenly caused and finally shows skeleton and be macroscopically subject to larger stress, cause that framework shrinkage ftractures, network structure caves in, cause the aerogel preparing gained to be usually powder or particle, be difficult to form complete block.
For preparing the bulk silicon dioxide aerogel of high-quality, generally need to adopt supercritical drying process (for example, see CN1984843A) in drying process.Because supercritical drying needs High Temperature High Pressure process, energy consumption is large, and technique is loaded down with trivial details, and the cycle is long, has certain risk, and productive rate is lower, is unfavorable for suitability for industrialized production, and high cost seriously constrains the popularization and application of aerosil.
In order to overcome this problem, many investigators attempt adopting the method for constant pressure and dry to substitute supercritical drying to prepare aerosil.Be in the Chinese patent of CN101244825A, CN102795631A take diatomite as raw material as publication number, acid catalysis molten by alkali obtains gel, exchanges and prepare aerosil at ambient pressure after organosilane surface modification through organic solvent.Publication number is, and to be raw material with rice hull ash in the Chinese patent of CN101244826A, CN102765726A obtain aerosil by sol-gel method and exchange of solvent and surface modification treatment under constant pressure and dry.Dalian University of Technology Shi Fei etc. are raw material with water glass, with trimethylchlorosilane/hexamethyldisiloxane and ethanol/trimethylchlorosilane/n-heptane solution, surface modification and exchange of solvent are carried out to silica hydrogel respectively, under constant pressure and dry, prepare aerosil.(the Jyoti L.Gurav such as J.L.Gurav, A.Venkateswara Rao, et al.J Mater Sci, 2010,45:503-510) with tetraethyl orthosilicate (TEOS) for raw material, hexamethyldisiloxane and normal hexane are respectively properties-correcting agent and prepare aerosil under exchanging solvent normal pressure.(the Sharad D.Bhagat such as S.D.Bhagat, Chang-Sup Oh, Yong-Ha Kim, et al.Microporous and Mesoporous Materials, 2007,100:350-355) and (the Bi Xu such as B.Xu, Jackie Y.Cai, et al.Microporous and Mesoporous Materials, 2012,148:145-151) and China Patent Publication No. be in CN102765725A with methyltrimethoxy silane (MTMS) for raw material, methyl alcohol prepares hydrophobic aerosil as solvent by soda acid two-step catalysis method and constant pressure and dry.Although these methods all have employed constant pressure and dry, also come with some shortcomings, show that the aerosil of preparation is based on powder, be difficult to obtain block materials; Adopt extra surface modification step and solvent exchange step, extend the production cycle, add cost; A large amount of with an organic solvent to environment.
Therefore, still need a kind of easy, low toxicity, with low cost, the method that is easy to suitability for industrialized production to prepare aerosil at present.
Summary of the invention
In the face of the problems referred to above that prior art exists, the invention provides a kind of easy, low toxicity, deficiency that with low cost, the method that is easy to suitability for industrialized production exists to the block hydrophobic silica aerogel material prepared aerosil and this method and obtain to overcome prior art.
First, the invention provides a kind of preparation method of block hydrophobic silica aerogel, said method comprising the steps of:
(1) silicon source, distilled water, tensio-active agent and basic catalyst is mixed, stir and obtain vitreosol in 5 ~ 120 minutes, wherein said silicon source is the organo-siloxane containing one or two alkyl, and the mol ratio of described silicon source, tensio-active agent, distilled water and basic catalyst is 1:(0.005 ~ 0.3): (7 ~ 45): (0.05 ~ 1.5);
(2) described vitreosol is left standstill 10 ~ 120 minutes in 10 ~ 50 DEG C;
(3) by leave standstill after vitreosol within 2 ~ 20 hours, obtain silica wet gel in 20 ~ 95 DEG C of gelation process; And
(4), after washing described silica wet gel with distilled water immersion, at 20 ~ 200 DEG C dry 1 ~ 72 hour at ambient pressure, described block hydrophobic silicon dioxide aerogel is prepared.
The inventive method is carried out at ambient pressure, does not need overcritical equipment, and technique is simple, and cost is low, and security is high; And the inventive method does not need follow-up organic solvent to exchange and surface hydrophobicity modification in addition, with short production cycle, decrease environmental pollution, be convenient to carry out suitability for industrialized production.
Preferably, the mol ratio of described silicon source, tensio-active agent, distilled water and basic catalyst is 1:(0.01 ~ 0.1): (15 ~ 25): (0.1 ~ 1).
Preferably, but at least one in described silicon source methyltrimethoxy silane, dimethyldimethoxysil,ne, Union carbide A-162, dimethyldiethoxysilane, ethyl trimethoxy silane, diethyldimethoxysilane, diethyldiethoxysilane, vinyltrimethoxy silane, vinyltriethoxysilane, methylvinyldimethoxysilane, hexamethyldisiloxane, octyltri-ethoxysilane, chloropropyl triethoxysilane, METHYL TRICHLORO SILANE, dimethyldichlorosilane(DMCS), ethyl trichlorosilane and diethyl dichlorosilane.Preferred silicon source can be selected from least one in methyltrimethoxy silane, Union carbide A-162, ethyl trimethoxy silane, ethyl triethoxysilane, vinyltrimethoxy silane, vinyltriethoxysilane.
Preferably, described tensio-active agent can be at least one in Dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, palmityl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, Trimethyllaurylammonium bromide, Tetradecyl Trimethyl Ammonium Bromide, cetyl trimethylammonium bromide, Cetyltrimethylammonium bromide, polyvinyl alcohol, polyoxyethylene, carboxymethyl cellulose and polyoxyethylene glycol.
Preferably, described basic catalyst can be at least one in hexamethylenetetramine, urea and ammoniacal liquor.
Preferably, in step (2), described vitreosol is left standstill 30 ~ 80 minutes in 25 ~ 40 DEG C.
Preferably, in step (3), the temperature of described gelation process is 50 ~ 70 DEG C, and the time is 4 ~ 10 hours.
Preferably, in step (4), wash described silica wet gel 1 ~ 4 time with distilled water immersion, each soak time is 2 ~ 10 hours, and soaking temperature is 30 ~ 80 DEG C.
The block hydrophobic silica aerogel that the present invention also provides a kind of aforesaid method to prepare, the surface of wherein said block hydrophobic silica aerogel is 90 ~ 180 ° to the contact angle of water, porosity is 40 ~ 99.5%, and pore size distribution is 2 ~ 500nm, and BET specific surface area is 200 ~ 1000m
2g
-1, density is 0.01 ~ 0.95gcm
-3.
Preferably, the surface of described block hydrophobic silica aerogel is 120 ~ 180 ° to the contact angle of water, and porosity is 85 ~ 99.5%, and pore size distribution is 5 ~ 70nm, and BET specific surface area is 500 ~ 1000m
2g
-1, density is 0.1 ~ 0.3gcm
- 3.
Aerosil prepared by the present invention has good hydrophobicity and blockiness, and have vesicular structure, specific surface area is high, and density is low, can be widely used in building heat insulation, sewage disposal, petrochemical complex, support of the catalyst, the various fields such as solar energy collecting.
Embodiment
Further illustrate the present invention below in conjunction with accompanying drawing and following embodiment, should be understood that following embodiment and/or accompanying drawing are only for illustration of the present invention, and unrestricted the present invention.
The present invention introduces a kind of easy, low toxicity, method that is with low cost, that be easy to suitability for industrialized production and prepares aerosil and the obtained block hydrophobic silica aerogel of this method.
The technical solution used in the present invention:
(1) a certain amount of silicon source, distilled water, tensio-active agent, basic catalyst are mixed, stir 5 ~ 120min and obtain colloidal sol; Wherein silicon source is the organo-siloxane containing one or two alkyl, the mol ratio of silicon source, tensio-active agent, distilled water and basic catalyst can be 1:(0.005 ~ 0.3): (7 ~ 45): (0.05 ~ 1.5), preferred 1:(0.01 ~ 0.1): (15 ~ 25): (0.1 ~ 1);
(2) by above-mentioned colloidal sol sealing and standing, time of repose can be 10 ~ 120min, and dwell temperature can be 10 ~ 50 DEG C, and the preferred time is 30 ~ 80min, and temperature is 25 ~ 40 DEG C;
(3) by leave standstill after colloidal sol carry out gelation, gelling temperature is 20 ~ 95 DEG C, and preferred gelling temperature is 50 ~ 70 DEG C, and gelation time is 2 ~ 20h, obtains silica wet gel;
(4) the silica wet gel distilled water that step (3) obtains is carried out washing by soaking, preferably washing silica wet gel 1 ~ 4 time, each soak time 2 ~ 10h, soaking temperature 30 ~ 80 DEG C.
(5) gel that step (4) obtains is carried out seasoning or heating, drying at ambient pressure, prepare block hydrophobic silicon dioxide aerogel, drying temperature is 20 ~ 200 DEG C, and time of drying is 1 ~ 72h.
Described silicon source is methyltrimethoxy silane, dimethyldimethoxysil,ne, Union carbide A-162, dimethyldiethoxysilane, ethyl trimethoxy silane, diethyldimethoxysilane, , diethyldiethoxysilane, vinyltrimethoxy silane, vinyltriethoxysilane, methylvinyldimethoxysilane, hexamethyldisiloxane, octyltri-ethoxysilane, chloropropyl triethoxysilane, METHYL TRICHLORO SILANE, dimethyldichlorosilane(DMCS), ethyl trichlorosilane, at least one in diethyl dichlorosilane.Preferable methyl Trimethoxy silane, Union carbide A-162, ethyl trimethoxy silane, ethyl triethoxysilane, vinyltrimethoxy silane, vinyltriethoxysilane.
Described tensio-active agent can be at least one in Dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, palmityl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, Trimethyllaurylammonium bromide, Tetradecyl Trimethyl Ammonium Bromide, cetyl trimethylammonium bromide, Cetyltrimethylammonium bromide, polyvinyl alcohol, polyoxyethylene, carboxymethyl cellulose, polyoxyethylene glycol.
Described basic catalyst is the one in hexamethylenetetramine, urea, ammoniacal liquor.
Aforesaid method can obtain a kind of block hydrophobic silica aerogel, and pore size distribution is 2 ~ 500nm, is preferably 5 ~ 70nm; BET specific surface area is 200 ~ 1000m
2g
-1, be preferably 500 ~ 1000m
2g
-1; Apparent density is 0.01 ~ 0.95gcm
-3, be preferably 0.1 ~ 0.3gcm
-3, porosity is 40 ~ 99.5%, and being preferably 85 ~ 99.5%, is 90 ~ 180 ° to the contact angle of water, and be preferably 120 ~ 180 °, outward appearance is white chunks material.
Compared with prior art, advantage of the present invention is:
(1) the inventive method is carried out at ambient pressure, does not need overcritical equipment, and technique is simple, and cost is low, and security is high;
(2) the inventive method does not need follow-up organic solvent to exchange and surface hydrophobicity modification in addition, with short production cycle, decreases environmental pollution, is convenient to carry out suitability for industrialized production.
Adopt the aerosil prepared of the present invention to have good hydrophobicity and blockiness, can building heat insulation be widely used in, sewage disposal, petrochemical complex, support of the catalyst, the various fields such as solar energy collecting.
Embodiment of illustrating further is below to describe the present invention in detail.Should understand equally; following examples are only used to further illustrate the present invention; can not be interpreted as limiting the scope of the invention, some nonessential improvement that those skilled in the art's foregoing according to the present invention is made and adjustment all belong to protection scope of the present invention.The temperature that following example is concrete, time etc. are also only examples in OK range, and namely, those skilled in the art can be done in suitable scope by explanation herein and select, and do not really want the concrete numerical value being defined in Examples below.
Embodiment 1
By methyltrimethoxy silane 5.0g, cetyl trimethylammonium bromide 1.0g, distilled water 5.0g, hexamethylenetetramine 2.0g, fully be uniformly mixed 10min and obtain colloidal sol, by colloidal sol sealing and standing 120min at 25 DEG C, then at 50 DEG C, gel 10h obtains wet gel;
Distilled water immersion washing wet gel 4 times at 30 DEG C, each 2h, finally by wet gel dry 48h under the atmospheric pressure environment of 50 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.40gcm
-3, porosity 85.2%, BET specific surface area is 200m
2g
-1, the contact angle that distilled water is formed with surface is 128 °, and pore size distribution is 10 ~ 100nm.
Embodiment 2
By methyltrimethoxy silane 5.0g, cetyl trimethylammonium bromide 0.5g, distilled water 10.0g, hexamethylenetetramine 2.0g, fully be uniformly mixed 30min and obtain colloidal sol, by colloidal sol sealing and standing 60min at 35 DEG C, then at 60 DEG C, gel 5h obtains wet gel;
Distilled water immersion washing wet gel 3 times at 40 DEG C, each 2h, finally by wet gel dry 24h under the atmospheric pressure environment of 60 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.25gcm
-3, porosity 90.7%, BET specific surface area is 570m
2g
-1, the contact angle that distilled water is formed with surface is 138 °, and pore size distribution is 7 ~ 120nm.
Embodiment 3
By methyltrimethoxy silane 5.0g, cetyl trimethylammonium bromide 0.1g, distilled water 12.0g, hexamethylenetetramine 1.0g, fully be uniformly mixed 60min and obtain colloidal sol, by colloidal sol sealing and standing 30min at 40 DEG C, then at 60 DEG C, gel 6h obtains wet gel;
Distilled water immersion washing wet gel 3 times at 60 DEG C, each 2h, finally by wet gel dry 24h under the atmospheric pressure environment of 80 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.12gcm
-3, porosity 95.4%, BET specific surface area is 650m
2g
-1, the contact angle that distilled water is formed with surface is 178 °, and pore size distribution is 5 ~ 130nm.
Embodiment 4
By Union carbide A-162 5.5g, cetyl trimethylammonium bromide 1.0g, distilled water 15.0g, urea 2.0g, be fully uniformly mixed 60min and obtain colloidal sol, and by colloidal sol sealing and standing 80min at 40 DEG C, then at 50 DEG C, gel 8h obtains wet gel;
Distilled water immersion washing wet gel 4 times at 40 DEG C, each 2h, finally by wet gel dry 48h under the atmospheric pressure environment of 50 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.18gcm
-3, porosity 93.3%, BET specific surface area is 610m
2g
-1, the contact angle that distilled water is formed with surface is 165 °, and pore size distribution is 10 ~ 200nm.
Embodiment 5
By Union carbide A-162 5.5g, cetyl trimethylammonium bromide 1.0g, distilled water 15.0g, hexamethylenetetramine 1.0g, fully be uniformly mixed 120min and obtain colloidal sol, by colloidal sol sealing and standing 60min at 40 DEG C, then at 70 DEG C, gel 4h obtains wet gel;
Distilled water immersion washing wet gel 3 times at 60 DEG C, each 3h, finally by wet gel dry 10h under the atmospheric pressure environment of 150 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.33gcm
-3, porosity 87.8%, BET specific surface area is 330m
2g
-1, the contact angle that distilled water is formed with surface is 135 °, and pore size distribution is 10 ~ 150nm.
Embodiment 6
By methyltrimethoxy silane 2.5g, dimethyldimethoxysil,ne 2.0g, cetyl trimethylammonium bromide 1.0g, distilled water 10.0g, hexamethylenetetramine 2.0g, fully be uniformly mixed 120min and obtain colloidal sol, by colloidal sol sealing and standing 80min at 50 DEG C, then at 95 DEG C, gel 2h obtains wet gel;
Distilled water immersion washing wet gel 4 times at 40 DEG C, each 2h, finally by wet gel dry 48h under the atmospheric pressure environment of 50 DEG C of washing, obtains aerosil.The density of above-mentioned aerosil is 0.20gcm
-3, porosity 92.6%, BET specific surface area is 570m
2g
-1, the contact angle that distilled water is formed with surface is 158 °, and pore size distribution is 10 ~ 90nm.
Industrial applicability: aerosil prepared by the present invention is blockiness good, and porosity is high, has good hydrophobicity, preparation technology is simple, and do not need other organic solvents to carry out exchange of solvent, without the need to extra surface modification step, the cycle is short, and cost is low.The aerosil of preparation can be applicable to the fields such as building energy conservation, petrochemical complex, sewage disposal.