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Method for preparing low density silica aerogel under normal pressure

A silicon dioxide, low-density technology, applied in the directions of silicon dioxide, silicon oxide, energy input, etc., can solve the problems of long production cycle, shorten the aging time of wet gel, high equipment cost, shorten the production cycle and shorten the preparation The effect of simple time and reaction conditions

Inactive Publication Date: 2013-12-11
ZHEJIANG UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Aiming at the problems and deficiencies of high equipment cost, dangerous operation, high energy consumption in the supercritical drying process, high product density and long production cycle in the normal pressure drying process, the present invention changes the silicon source and anhydrous The ratio of ethanol to water, shortening the wet gel aging time, solvent replacement time and improving the drying step operation to shorten the production cycle and reduce product density, developed a rapid preparation of low-density SiO under normal pressure conditions 2 Airgel method, which can reach as low as 49kg / m 3

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1～5

[0026] Embodiment 1~5: Different ethyl orthosilicate, water, ethanol volume ratio are compared SiO 2 Effect of Airgel Density

[0027] Take 4 mL of tetraethyl orthosilicate, take water and absolute ethanol according to different volume ratios in Table 1, mix and stir the tetraethyl orthosilicate, water and absolute ethanol evenly, add 1mol / L nitric acid to adjust the pH value to 3.5, and hydrolyze for 30 A silica sol was obtained after 1 minute. Add 1mol / L sodium hydroxide solution while stirring to adjust the pH value to 6.5, catalyze the gel for 8 minutes to obtain a wet gel, age the wet gel at room temperature for 18 hours, and then use 40mL of n-hexane for solvent replacement for 18 hours. The gel sample was immersed in 40 mL of a mixed solution of V (trimethylchlorosilane (TMCS)):V (n-hexane) at a ratio of 10:100 for hydrophobic modification for 12 hours, washed twice with 20 mL of n-hexane to remove the modified solution, and put Put it into a muffle furnace and heat i...

Embodiment 6～10

[0030] Embodiment 6~10: different acid catalysts to SiO 2 Effect of Airgel Density

[0031] According to the method of Example 1, get tetraethyl orthosilicate 4mL, V(TEOS):V(H 2 O):V(EtOH) is the mixed solution of 1:0.5:1 and stirs evenly, the difference is, after adding different acids to adjust the pH to 3.5, carry out catalytic hydrolysis, the added acid is as shown in Table 1, and then add 1mol / L potassium hydroxide solution adjusts the pH value to 6.5, catalyzes the gel for 8 minutes to obtain a wet gel, and ages the wet gel at room temperature for 18 hours, and other follow-up operations are the same as in Example 1, wherein the acid catalyst used in Example 6 is formic acid, The acid catalyst used in embodiment 7 is 1mol / L nitric acid, the acid catalyst used in embodiment 8 is benzoic acid, the acid used in embodiment 9 is 1mol / L hydrochloric acid, and the acid used in embodiment 10 is acetic acid. The results are shown in Table 2.

[0032] Table 2 Different acid ca...

Embodiment 11～13

[0035] Embodiment 11~13: different alkali catalysts to SiO 2 Effect of Airgel Density

[0036] According to the method of Example 2, get tetraethyl orthosilicate 4mL, adopt V(TEOS):V(H 2 O): V (EtOH) is a mixed solution of 1:1:3, other operations are the same as in Example 2, the difference is that after catalytic hydrolysis, different alkalis are added to adjust the pH value to 6.5, and catalytic gel is carried out, as shown in Table 3 Show, embodiment 11 is 1mol / L potassium hydroxide solution, embodiment 12 is 0.5mol / L sodium hydroxide solution, and embodiment 13 is 1mol / L ammoniacal liquor. The results are shown in Table 3.

[0037] Table 3 Different base catalysts on SiO 2 Effect of Airgel Density

[0038] Example base catalyst Density (kg / m 3 ) 11 Potassium hydroxide 51 12 sodium hydroxide 67 13 ammonia 76

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Abstract

The present invention discloses a method for preparing low density silica aerogel under normal pressure. The method comprises: mixing tetraethoxysilane, water and ethanol according to a volume ratio of 1:0.5-19:1-29, adding an acid to adjust the pH value to 3-4, carrying out catalysis hydrolysis, adding an alkali to adjust the pH value to 6-6.5, carrying out catalysis gelating for 8-10 min to obtain a wet gel, aging the wet gel for 6-36 h at a room temperature, adding n-hexane to carry out solvent replacement for 6-36 h, immersing in a trimethylchlorosilane and n-hexane mixed solution to carry out hydrophobic modification for 12-15 h, adopting a n-hexane washing solution to remove the modification solution, placing into a muffle furnace to heat to a temperature of 30-250 DEG C, drying, and finally cooling to a room temperature to obtain the silica aerogel. Test results show that the density of the SiO2 aerogel is 50-80 kg / m<3> and is significantly lower than the density of the SiO2 aerogel prepared under the normal pressure dry condition in most of the public reports.

Description

(1) Technical field [0001] The present invention relates to the preparation of silica airgel, especially relates to the preparation of low-density SiO under normal pressure drying conditions 2 Airgel method. (2) Background technology [0002] Airgel is a lightweight nanoporous amorphous solid material formed by the condensation of colloidal particles. It has a continuous network structure and has nanoscale uniformity in the microcosm. Its pore size and the entire particle are nanoscale. This kind of solid phase and pore structure with gas as the dispersion medium makes it have unique physical and chemical properties. The density has a significant impact on its physical and chemical properties. The lower the density, the higher the porosity, the larger the specific surface area, the lower the refractive index, and the lower the thermal conductivity. Airgel is widely used, and has broad application prospects in thermal insulation, industrial catalysis, aerospace, pharmaceuti...

Claims

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Application Information

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IPC IPC(8): C01B33/16
CPCY02P20/129
Inventor 尉明全张波张闯
Owner ZHEJIANG UNIV OF TECH
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