Process for preparing silicon dioxide aerogel using rice husk ash as raw material

A technology of silicon dioxide and rice husk ash, which is applied in the directions of silicon dioxide, silicon oxide, chemical instruments and methods, etc., can solve the problems such as there is no silicon dioxide aerogel, and achieves easy operation, reduced production cost, and improved technology. simple effect

Inactive Publication Date: 2003-10-22
TSINGHUA UNIV
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  • Summary
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  • Description
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Problems solved by technology

[0008] From existing patent technology and bibliographical report, do not yet have the same or similar technology of preparing silica airgel with rice husk ash as raw material with the present invention

Method used

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  • Process for preparing silicon dioxide aerogel using rice husk ash as raw material
  • Process for preparing silicon dioxide aerogel using rice husk ash as raw material

Examples

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example 1

[0031] 15 grams of rice husk ash and 500 milliliters of 0.5mol / L NaOH solution were mixed, boiled at normal pressure for 30 minutes, the filtrate obtained after filtering and washing was combined with the washing liquid, and neutralized to a pH value of 1mol / L sulfuric acid. 7; The resulting hydrogel was aged at 27 °C for 24 hours, then soaked in ethanol for 40 hours, and then placed in a high-pressure vessel with liquid CO 2 Soak for 12 hours at 20°C and 80 bar pressure; raise the temperature to 43°C within 30 minutes, and dry with supercritical carbon dioxide at 43°C and 95 bar at 0.2 kg of carbon dioxide per kg of gel per hour for 2 hours. Reduce the pressure at 43°C to normal pressure, and cool naturally to room temperature to obtain white silica airgel. Its specific surface area is 376.5m 2 / g, the apparent density is 0.332g / cm 3 , The average pore diameter of the internal micropores is 15.5 nanometers. figure 1 It is the transmission electron micrograph of the prepare...

example 2

[0033] 15 grams of rice husk ash and 400 milliliters of 0.7mol / L NaOH solution were mixed, boiled at normal pressure for 45 minutes, the filtrate obtained after filtering and washing was combined with the washing liquid, and neutralized to a pH value of 1mol / L sulfuric acid. 7.5; The resulting hydrogel was aged at 23 °C for 35 hours, then soaked in ethanol for 36 hours, and then placed in a high-pressure vessel with liquid CO 2 Soak at 18°C ​​and 90bar pressure for 20 hours; raise the temperature to 50°C within 30 minutes, dry with supercritical carbon dioxide at 50°C and 100bar at 0.6 kg of carbon dioxide per kg of gel per hour for 2 hours. Decrease the pressure to normal pressure at a temperature of 50°C, and cool naturally to room temperature to obtain a white silica airgel. Its specific surface area is 497.3m 2 / g, the apparent density is 0.232g / cm 3 , The average pore diameter of the internal micropores is 12.3 nanometers.

example 3

[0035] 25 grams of rice husk ash and 500 milliliters of 0.8mol / L NaOH solution were mixed, boiled at normal pressure for 30 minutes, the filtrate obtained after filtering and washing was combined with the washing liquid, and neutralized to a pH value of 1mol / L sulfuric acid. 6.5; The resulting hydrogel was aged at 25 °C for 30 hours, then soaked in ethanol for 48 hours, and then placed in a high-pressure vessel with liquid CO 2 Soak for 14 hours at 15°C and a pressure of 85 bar; increase the temperature to 45°C within 30 minutes and dry with supercritical carbon dioxide at 45°C and 100 bar at 0.5 kg of carbon dioxide per kg of gel per hour for 2 hours. Decrease the pressure at 45°C to normal pressure, and cool naturally to room temperature to obtain white silica airgel. Its specific surface area is 297.3m 2 / g, the apparent density is 0.532g / cm 3 , The average pore diameter of the internal micropores is 22.3 nanometers.

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Abstract

The method for preparing silicon dioxide aerogel utilizing waste material rice husk ash obtained by combusting rice husk includes the following steps: soaking the rice husk ash in organic alkaline aqueous solution, using inorganic acid to neutralize alkaline solution to produce silicon dioxide hydrosol, ageing said hydrosol, substituting water content in the hydrosol with organic solvent, then substituting organic solvent with liquid CO2, then supercritical CO2 drying so as to obtain white silicon dioxide aerogel whose specific surface area is 297.3 sq.m/g, apparent density is 0.532 g/cu.cm and internal microporous average pore size is 22.3 nano.

Description

technical field [0001] The invention belongs to the technical scope of chemical material preparation, and in particular relates to a method for preparing silicon dioxide aerogel by using rice husk ash as a raw material, which fully utilizes waste residue rice husks produced in the rice production process to turn waste into treasure. technical background [0002] Airgel is a lightweight nano-amorphous solid material containing a large amount of air, low density, and high porosity. Its slender nanoporous network makes it have very low refractive index, thermal conductivity and propagation velocity, and the characteristics of selective permeation of gas, which make airgel materials have been widely valued. [0003] Among the many aerogels, the most studied is SiO 2 airgel. Since silica airgel is a porous material with nanometers, they are obviously different from porous materials with pore structures on the order of microns and millimeters, and show unique properties in terms...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B09B3/00C01B33/14C01B33/152C01B33/157C01B33/16
Inventor 王涛唐琪
Owner TSINGHUA UNIV
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