CN1278933C - Method for preparing silicon dioxide aerogel by normal pressure drying method using rice hull ash as raw material - Google Patents
Method for preparing silicon dioxide aerogel by normal pressure drying method using rice hull ash as raw material Download PDFInfo
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- CN1278933C CN1278933C CN 200510011378 CN200510011378A CN1278933C CN 1278933 C CN1278933 C CN 1278933C CN 200510011378 CN200510011378 CN 200510011378 CN 200510011378 A CN200510011378 A CN 200510011378A CN 1278933 C CN1278933 C CN 1278933C
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Abstract
The present invention relates to a normal pressure drying method for preparing silicon dioxide aerogel by using rice hull ash as raw material, which belongs to the technical field of chemical material preparation. In the present invention, rice hulls are combusted, and the waste material of rice hull ash is used; leaching is carried out to the waste rice hull ash by inorganic strong lye solution, inorganic strong acid neutralizes alkaline solution, and silicon dioxide hydrosol is generated; organic silicon compounds are added to the hydrosol to carry out processing, and hydrogel is generated; the hydrogel is aged and washed by water, organic solvents replace moisture in the hydrogel, normal pressure drying is carried out, and the silicon dioxide aerogel is prepared. The specific surface area is from 400 to 800 m<2>/g, the apparent density is from 0.1 to 0.5 g/cm <3>, the pore volume is from 1.0 to 4.0cm<3>/g, and the hole diameter of an internal micropore is from 1 to 80 nanometers. Compared with the traditional technology, the method can realize normal pressure drying, avoid supercritical drying equipment investment, reduce production cost and risks, and has simple technology and easy operation. The method is suitable for scale production and application.
Description
Technical field
The invention belongs to technical field of chemical material preparation, particularly method for processing sols and drying means in the aerosil preparation process.
Background technology
Aerosil is a kind of porous amorphous solid-state material that includes a large amount of air, low density, high porosity, and its porosity rate can reach 80～99.8%, and typical bore hole size is in 1～100nm scope.Aerosil is at mechanics, acoustics, calorifics, many-sides such as optics all demonstrate unique character, they obviously are different from the porous material of pore space structure in micron and millimeter magnitude, and its very thin nanostructure makes that the thermal conductivity of material is extremely low, has great specific surface area, to light, the scattering of sound is all much smaller than traditional porous material.Therefore, silica aerogel has broad application prospects, and can be used as transparent insulate material, the refrigerator lagging material, the specific acoustic resistance coupling material can also be as the super capacitor material, the new gas strainer, new catalyst or support of the catalyst etc. have broad application prospects.
Existing aerosil production method, in the domestic and international academic paper of publishing, the preparation of aerosil mostly is to do raw material with organosilicon of four alkoxyl silicones and alkyl silicate and so on or water glass, adopts supercritical fluid technology to carry out exsiccant then.In the article on being published in Applied Catalysis A:General 177 (1999) 139-148, M.Stalarski and J.Walendziewski etc., produce gel with tetraethoxy-silicane hydrolysis in ethanolic soln, then the dry aerosil that produces under super critical condition.
Be published in " Journal of Inorganic Materials ", 2001, Vol.16, in the article of No.3, Wei Jiandong, Deng Zhongsheng etc. have adopted subcritical exsiccant method to prepare aerogel.In the experiment, prepared gel is put into autoclave, add an amount of isopropylcarbinol and coating materials trimethylchlorosilane, airtight autoclave, and autoclave is heated to 240～260 ℃ from room temperature gradually, the pressure in the still finally is stabilized in 2.3～2.6Mpa.
Be published in Journal of Non-Crystalline Solids, 225 (1998), in the article of 14-18, people such as FikretKirkbir and Hideaki Murata are raw material with positive tetraethyl orthosilicate, select the 2-amylalcohol for use, octane-iso etc. can make drying pressure far below emergent pressure gel structure be caved in, but pressure still need 1.8MPa as hole liquid.
Be published in " Acta PhySico-Chimica Sinica ", 2003,19 (9): in 819～823 the article, Chen Longwu, Gan Lihua, people such as Hou Xiuhong by the control to the sol-gel process condition, are aided with technology such as mother liquor soaks, wears out based on two one-step hydrolysis-polycondensation method of positive tetraethyl orthosilicate (TEOS), improve the structure of gel, improve the network skeleton intensity of gel,, realized block SiO simultaneously in conjunction with means such as exchange of solvent and classification dryings
2The non-supercritical desiccating method preparation of aerogel.In the experiment, TEOS, water are mixed by a certain percentage with ethanol, adopt earlier hydrochloric acid that this mixed solution is adjusted to a certain pH value under the acidic conditions, make its abundant hydrolysis at 60 ℃ of following backflow 90min, with ammoniacal liquor it is adjusted to a certain pH value under the alkaline condition then, again uniform mixing liquid is transferred in the encloses container, at room temperature formed alcogel.Alcogel is soaked 24h with ethanol down at 60 ℃, use mother liquor immersion, the ageing 48h of the TEOS ethanolic soln of definite composition again, soak 24h with dehydrated alcohol down at 50 ℃ then, each dry 8h under 70,80,100 ℃ can obtain SiO at last
2The aerogel sample.
Comprehensive existing patented technology and bibliographical information, existing aerosil production method adopts organosilicon to do raw material more, is aided with the supercritical drying drying method simultaneously, even adopt the non-supercritical drying means also still to need higher drying pressure.Therefore, there is the expensive and drying plant requirement height of raw material, the flow process complexity, the cycle, long the grade caused the too high problem of cost, and this has directly influenced the large-scale production and the application of aerogel.
Previous Chinese patent (application number 03127920.1 the applicant, publication number CN1449997A) introduced the rice hull ash used after the burning of agricultural wastes rice husk in as the silicon source, produce the method for silica aerogel, but it still is to adopt supercritical drying, very high to equipment requirements, thus there are the cost and the safety problem of scale production.
Summary of the invention
The purpose of this invention is to provide a kind of is raw material with the rice hull ash, and constant pressure and dry prepares the method for aerosil, and this method not only raw materials cost is low, and technology is simple, and is low for equipment requirements, helps scale production.
Technical scheme of the present invention is as follows: a kind of method for preparing aerosil with the rice hull ash for the raw material constant pressure and dry, this method is raw material with the rice hull ash, through the leaching of inorganic strong alkali solution, generate silica hydrosol with basic solution in the inorganic acid, add silicoorganic compound, form hydrogel, the moisture of hydrogel in aging, washing, organic solvent replacing water gel, constant pressure and dry is prepared aerosil, and its concrete processing step is as follows:
1) rice hull ash is added in the inorganic strong alkali solution that concentration is 0.1～1.0mol/L, the ratio of its alkaline solution and rice hull ash is 20～50: 1 (L/kg), and the atmospheric boiling state leached 5～120 minutes down;
2) with the inorganic acid titration neutralization of leaching liquid filtrate filtered with 0.1～1.0mol/L, control pH value is 5～9, makes silica hydrosol; In 0～15 minute of water-sol formation,, form hydrogel to wherein adding silicoorganic compound; The silicoorganic compound that add and the volume ratio of the water-sol are 0.001～0.15; It is Si (OR) that described silicoorganic compound adopt chemical molecular formula
4Positive silicon ester, wherein R is methyl, ethyl or many carbon alkyl group; Or the employing chemical molecular formula is R
4-nSi (OR)
nAlkyl silicate, wherein R is methyl, ethyl or many carbon alkyl group, n gets 1,2 or 3;
3) with step 2) in the preparation hydrogel be to wear out under 15～60 ℃ in temperature;
4), remove foreign ion wherein with the hydrogel that obtains in the deionized water wash step 3);
5) moisture in the hydrogel that step 4) is made with organic solvent cements out;
6) hydrogel with the step 5) preparation is to carry out constant pressure and dry under 20～100 ℃ in temperature, promptly makes white translucent aerosil.
In technical scheme of the present invention, described step 2) during with inorganic acid titration filtrate, control pH value is preferably 6～8 in; Described step 2) silicoorganic compound that add in and the volume ratio of the water-sol are preferably 0.003～0.1; Described strong base solution is inorganic hydrogen aqueous solution of sodium oxide or potassium hydroxide aqueous solution, and used inorganic acid is hydrochloric acid or sulfuric acid.Described organic solvent is low-carbon (LC) monohydroxy-alcohol or ketone.The constant pressure and dry temperature range is between 40～80 ℃ in the described step 6).
Technical program of the present invention also lies in: during with the deionized water wash gel, the volume ratio of deionized water and gel is 1～5: 1, and washing times is 1～5 time.During with the moisture in the organic solvent replacing water gel, the volume ratio of organic solvent and gel is 1～3: 1, and time swap is 1.5～4.5 hours.
The method that the present invention proposes utilizes rice hull ash as the silicon source, has realized that simultaneously drying is prepared aerosil under the condition of normal pressure.The present invention compared with prior art, have the following advantages and the high-lighting effect: 1.. replace expensive organosilicon to do raw material production nanostructure solid material aerosil with the waste material rice hull ash after the agriculture waste product rice husk burning, production cost is greatly reduced.2.. add silicoorganic compound in the water-sol and handle, can realize constant pressure and dry, avoided the input of supercritical drying equipment, reduced production cost and danger.3.. the aerogel of preparing has high-specific surface area (400～800m through the n2 absorption apparatus measurement
2/ g), high pore volume (1.0～4.0cm3/g), (0.1～0.5g/cm3), the aperture of contained micropore is nano level (pore size distribution range 1～80nm, a mean pore size 8～30nm) to low bulk density.4.. technology is simple, easy to operate, is fit to large-scale production and application.
Embodiment
The present invention for a kind of be raw material with the rice hull ash, adopt the constant pressure and dry method to prepare the method for aerosil.With the waste material rice hull ash after the rice husk burning, through in the leaching of the inorganic strong alkali aqueous solution, the inorganic acid and basic solution generate in silica hydrosol, the water-sol and add silicoorganic compound, form that hydrogel, hydrogel are aging, moisture, constant pressure and dry in the washing, organic solvent replacing water gel, prepare aerosil; Its technological process is as follows:
1) preparation of the water-sol: rice hull ash is added in the strong base solution that concentration is 0.1～1.0mol/L, and the ratio of its alkaline solution and rice hull ash is 20～50: 1 (L/kg), and the atmospheric boiling state leached 5～120 minutes down; Strong base solution can adopt aqueous sodium hydroxide solution or potassium hydroxide aqueous solution.
2) filter and the acid treatment process: is 5～9 with the leaching liquid filtrate filtered with the inorganic acid titration of the 0.1～1.0mol/L pH value that neutralizes, preferred 6～8, and make silica hydrosol: inorganic acid generally can adopt hydrochloric acid or sulfuric acid.In 0～15 minute of water-sol formation,, form hydrogel to wherein adding silicoorganic compound; The silicoorganic compound that add and the volume ratio of the water-sol are 0.001～0.15, preferred 0.003～0.1.Described silicoorganic compound comprise: positive silicon ester, chemical molecular formula is Si (OR)
4, R can be a methyl, ethyl or many carbon alkyl group, and as positive tetraethyl orthosilicate, positive quanmethyl silicate; Alkyl silicate, chemical molecular formula are R
4-nSi (OR)
n, R can be a methyl, ethyl or many carbon alkyl group, and n gets 1,2 or 3, as Trimethoxy silane, trimethylammonium silicic acid methyl esters.
3) aging: the hydrogel of preparation is worn out under 15～60 ℃ of temperature, and the time is generally at 1 minute to 48 hours.
4) washing: use the deionized water wash prepared gel, the volume ratio of deionized water and gel is generally 1～5: 1, and the time is generally at 1～12 hour.
5) organic solvent displacement: with organic solvent the moisture in the hydrogel of preparation is cemented out, the volume ratio of organic solvent and gel is generally 1～3: 1; Organic solvent is the low-carbon (LC) monohydroxy-alcohol, as methyl alcohol, and ethanol; Also can be ketone, as acetone and butanone; Time swap is generally at 1～6 hour.
6) constant pressure and dry: prepared gel is carried out constant pressure and dry, and temperature is generally 20～100 ℃, and preferred 40～80 ℃, the time is generally between 1～24 hour.
Below by several specific embodiments the present invention is done the progressive explanation.
Embodiment 1
The NaOH solution of 10 gram rice hull ash and 300 milliliters of 0.9mol/L mix, and boiling is 90 minutes under normal pressure, and the filtrate that obtains after the filtration is 7 with the sulfuric acid of 1mol/L with its pH value that neutralizes; In the water-sol, add the positive tetraethyl orthosilicate of 40ml at once, form hydrogel; The hydrogel of gained wore out 48 hours at 20 ℃, washed 3 times; Use the alcohol immersion hydrogel then 4 hours, be placed on 40 ℃ of air dryings again 10 hours, promptly make white translucent aerosil.Its specific surface area is 499.2m
2/ g, pore volume are 3.3cm
3/ g, apparent density is 0.33g/cm
3, inner micropore mean pore size is 26.5 nanometers.
Embodiment 2
The NaOH solution of 10 gram rice hull ash and 500 milliliters of 0.1mol/L mix, and boiling is 120 minutes under normal pressure, and the filtrate that obtains after the filtration is 9 with the hydrochloric acid of 1mol/L with its pH value that neutralizes; In the resulting water-sol, add the positive quanmethyl silicate of 60ml after 2 minutes and handle, form hydrogel; The hydrogel of gained wore out 35 hours at 23 ℃, used deionized water wash afterwards 4 times; Soak hydrogel 6 hours with methyl alcohol then, directly be placed on 50 ℃ of air dryings 6 hours, promptly make white translucent aerosil.Its specific surface area is 611.6m
2/ g, apparent density is 0.35g/cm
3, pore volume is 2.5cm
3/ g, inner micropore mean pore size is 16.2 nanometers.
Embodiment 3
The NaOH solution of 10g rice hull ash and 200 milliliters of 1mol/L mixes, and boiling is 60 minutes under normal pressure, and the filtrate that obtains after the filtration is 5.5 with the sulfuric acid of 1mol/L with its pH value that neutralizes; In the resulting water-sol, add the 0.6ml Trimethoxy silane after 15 minutes and handle, leave standstill the formation hydrogel; The hydrogel of gained wore out 40 hours at 21 ℃, used deionized water wash afterwards 4 times; Use the alcohol immersion hydrogel then 6 hours, directly be placed on 40 ℃ of air dryings 6 hours, promptly make transparent aerosil.Its specific surface area is 748.7m
2/ g, apparent density is 0.25g/cm
3, pore volume is 1.5cm
3/ g, inner micropore mean pore size is 8.1 nanometers.
Embodiment 4
The NaOH solution of 10g rice hull ash and 200 milliliters of 1mol/L mixes, and boiling is 100 minutes under normal pressure, and the filtrate that obtains after the filtration is 5.5 with the sulfuric acid of 1mol/L with its pH value that neutralizes; In the resulting water-sol, add the 0.2ml Trimethoxy silane after 15 minutes and handle, leave standstill the formation hydrogel; The hydrogel of gained wore out 48 hours at 20 ℃, used deionized water wash afterwards 3 times; Use the alcohol immersion hydrogel then 6 hours, directly be placed on 60 ℃ of air dryings 4 hours, promptly make transparent aerosil.Its specific surface area is 731.7m
2/ g, apparent density is 0.31g/cm
3, pore volume is 1.3cm
3/ g, inner micropore mean pore size is 8.3 nanometers.
Embodiment 5
The KOH solution of 10g rice hull ash and 300 milliliters of 1mol/L mixes, and boiling is 40 minutes under normal pressure, and the filtrate that obtains after the filtration is 7 with the sulfuric acid of 1mol/L with its pH value that neutralizes; In the resulting water-sol, add the positive tetraethyl orthosilicate of 45ml after 1 minute and handle, leave standstill the formation hydrogel; The hydrogel of gained wore out 48 hours at 15 ℃, used deionized water wash afterwards 3 times; Soak hydrogel 6 hours with acetone then, directly be placed on 100 ℃ of air dryings 4 hours, promptly make translucent aerosil.Its specific surface area is 583.3m
2/ g, apparent density is 0.34g/cm
3, pore volume is 2.3cm
3/ g, inner micropore mean pore size is 14.9 nanometers.
Claims (8)
1. method for preparing aerosil with the rice hull ash for the raw material constant pressure and dry is characterized in that this method carries out as follows:
1) rice hull ash is added in the inorganic strong alkali solution that concentration is 0.1～1.0mol/L, the ratio of its alkaline solution and rice hull ash is 20～50: 1 (L/kg), and the atmospheric boiling state leached 5～120 minutes down;
2) with the inorganic acid titration neutralization of leaching liquid filtrate filtered with 0.1～1.0mol/L, control pH value is 5～9, makes silica hydrosol; In 0～15 minute of water-sol formation,, form hydrogel to wherein adding silicoorganic compound; The silicoorganic compound that add and the volume ratio of the water-sol are 0.001～0.15; It is Si (OR) that described silicoorganic compound adopt chemical molecular formula
4Positive silicon ester, wherein R is methyl, ethyl; Or the employing chemical molecular formula is R
4-nSi (OR)
nAlkyl silicate, wherein R is methyl, ethyl, n gets 1,2 or 3;
3) with step 2) in the preparation hydrogel be to wear out under 15～23 ℃ in temperature;
4), remove foreign ion wherein with the hydrogel that obtains in the deionized water wash step 3);
5) moisture in the hydrogel that step 4) is made with organic solvent cements out;
6) hydrogel with the step 5) preparation is to carry out constant pressure and dry under 20～100 ℃ in temperature, promptly makes white translucent aerosil.
2. method according to claim 1 is characterized in that: when using inorganic acid titration filtrate described step 2), control pH value is 6～8.
3. method according to claim 1 is characterized in that: the silicoorganic compound that add described step 2) and the volume ratio of the water-sol are 0.003～0.1.
4. method according to claim 1 is characterized in that: described strong base solution is inorganic hydrogen aqueous solution of sodium oxide or potassium hydroxide aqueous solution, and used inorganic acid is hydrochloric acid or sulfuric acid.
5. method according to claim 1 is characterized in that: described organic solvent is methyl alcohol, ethanol or acetone.
6. method according to claim 1 is characterized in that: the constant pressure and dry temperature range is between 40～80 ℃ in the described step 6).
7. according to the described method of the arbitrary claim of claim 1～6, it is characterized in that: during with the deionized water wash gel, the volume ratio of deionized water and gel is 1～5: 1, and washing times is 1～5 time.
8. according to the described method of the arbitrary claim of claim 1～6, it is characterized in that: during moisture in the organic solvent replacing water gel, the volume ratio of organic solvent and gel is 1～3: 1, and time swap is 1.5～4.5 hours.
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102190509A (en) * | 2011-03-16 | 2011-09-21 | 吉林大学 | Method for producing silicon fertilizer from rice straws |
| CN102351507B (en) * | 2011-07-18 | 2013-04-10 | 南京工业大学 | Method for preparing fiber-reinforced SiO2 aerogel from rice husk ash as raw material |
| CN102372272A (en) * | 2011-08-15 | 2012-03-14 | 万载县辉明化工有限公司 | Preparation method of silicon dioxide for plastic film opening agent |
| CN102583403B (en) * | 2012-03-06 | 2013-09-18 | 山东理工大学 | Preparation method of super-hydrophobic nanoscale white carbon black membrane and super-hydrophobic nanoscale white carbon black powder |
| CN102602944B (en) * | 2012-03-23 | 2014-10-29 | 南通市鸣珂新型材料科技有限公司 | Method for preparing silicon dioxide aerogel by taking rice hull ash as raw material |
| CN106745005B (en) * | 2017-02-17 | 2019-05-24 | 中国神华能源股份有限公司 | A method of preparing hydrophobic silicon dioxide aerogel |
| CN116554614A (en) * | 2023-04-27 | 2023-08-08 | 安徽农业大学 | Preparation method of flame-retardant heat-insulating PVC/rice hull ash-based aerogel composite board |
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