Method for preparing silicon dioxide aerogel by normal pressure drying method using rice hull ash as raw material

A technology of atmospheric drying and silicon dioxide, applied in the directions of silicon dioxide, silicon oxide, etc., can solve the problems affecting the large-scale production and application of aerogel, high equipment requirements, expensive raw material requirements, etc., and reduce production costs. , the process is simple, the effect of reducing the risk

Inactive Publication Date: 2005-09-21
TSINGHUA UNIV
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Problems solved by technology

Therefore, there are problems such as expensive raw materials, high requirements for drying equipment, complicated process, and long cycle, which lead to high cost, which directly affects the large-scale production and application of airgel.
[0008] In the applicant's previous Chinese patent (application number 03127920.1, publication number CN1449997A), the method of using the rice husk ash after the burning of agricultural waste rice husk as a silicon source to produce silicon airgel is introduced, but it still uses Supercritical drying has high requirements on equipment, so there are cost and safety problems in large-scale production

Method used

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preparation example Construction

[0021] 1) Preparation of hydrosol: Add rice husk ash to a strong alkali solution with a concentration of 0.1 to 1.0 mol / L, the ratio of the alkali solution to rice husk ash is 20 to 50:1 (L / kg), and boil at normal pressure Under the state of leaching for 5 to 120 minutes; strong alkali solution can use sodium hydroxide aqueous solution or potassium hydroxide aqueous solution.

[0022] 2) Filtration and acid treatment process: titrate and neutralize the filtrate after filtering the leaching solution with 0.1-1.0 mol / L inorganic strong acid to a pH value of 5-9, preferably 6-8, to produce silica hydrosol; Generally, hydrochloric acid or sulfuric acid can be used as the strong inorganic acid. The organosilicon compound is added to the hydrosol within 0-15 minutes of formation to form a hydrogel; the volume ratio of the added organosilicon compound to the hydrosol is 0.001-0.15, preferably 0.003-0.1. The organosilicon compound includes: orthosilicate, the chemical formula is Si(O...

Embodiment 1

[0029]10 grams of rice husk ash and 300 milliliters of 0.9mol / L NaOH solution were mixed, boiled at normal pressure for 90 minutes, and the filtrate obtained after filtering was neutralized to pH 7 with 1mol / L sulfuric acid; Add 40ml tetraethyl orthosilicate to form a hydrogel; the obtained hydrogel is aged at 20°C for 48 hours, washed 3 times with water; then soaked in ethanol for 4 hours, and then placed in 40°C air Dry in medium for 10 hours to obtain white translucent silica airgel. Its specific surface area is 499.2m 2 / g, the pore volume is 3.3cm 3 / g, the apparent density is 0.33g / cm 3 , The average pore diameter of the internal micropores is 26.5 nanometers.

Embodiment 2

[0031] 10 grams of rice husk ash and 500 milliliters of 0.1mol / L NaOH solution were mixed, boiled at normal pressure for 120 minutes, and the filtrate obtained after filtering was neutralized to a pH value of 9 with 1mol / L hydrochloric acid; Add 60ml of tetramethyl orthosilicate to the obtained hydrosol for treatment to form a hydrogel; the obtained hydrogel is aged at 23°C for 35 hours, and then washed 4 times with deionized water; then soak the hydrogel with methanol After 6 hours, it was directly placed in the air at 50°C and dried for 6 hours to obtain a white translucent silica airgel. Its specific surface area is 611.6m 2 / g, the apparent density is 0.35g / cm 3 , the pore volume is 2.5cm 3 / g, the average pore diameter of the internal micropores is 16.2 nanometers.

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Abstract

A method for dry producing the silica dioxide aerogel from rice husk ash as raw material in atmosphere pressure, belongs to the technical field of chemical industry materials producing, which comprises the following steps: leaching the rice husk ash formed by rice husk burning in the inorganic strongly basic aqueous solution and inorganic corrosive acid neutralizing basic solution to get the silica dioxide hydrosol, treating the hydrosol with organo-silicon compound to get the hydrogel, then ageing, water scrubbing, replacing the moisture in hydrogel with a organic solvent, and drying in atmosphere pressure to get the silica dioxide aerogel with the specific surface area about 400-800 m.

Description

technical field [0001] The invention belongs to the technical field of chemical material preparation, and in particular relates to a sol treatment method and a drying method in the preparation process of silica airgel. Background technique [0002] Silica airgel is a porous amorphous solid material containing a large amount of air, low density, and high porosity. Its porosity can reach 80-99.8%, and the typical pore size is in the range of 1-100nm. Silica aerogels show unique properties in many aspects such as mechanics, acoustics, thermals, optics, etc. They are obviously different from porous materials with pore structures on the order of microns and millimeters, and their fine nanostructures make the thermal conductivity of materials The efficiency is extremely low, with a large specific surface area, and the scattering of light and sound is much smaller than that of traditional porous materials. Therefore, silica aerogels have broad application prospects, and can be use...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/14
Inventor 王涛李婷
Owner TSINGHUA UNIV
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