Fast preparation method of silicon dioxide aerogel

Abstract

The invention provides a fast preparation method of silicon dioxide aerogel. According to the method, tetraethyl orthosilicate is used as a silicon source; low-concentration organic weak acid is added for catalyzed hydrolysis reaction; then, the condensation polymerization reaction and the hydrophobic modification of the gel are completed in one step through reasonably controlling the addition quantity of the nitrogen-containing silane, the dripping speed and the reaction time; the addition of basic catalysts is not needed; the consumption of a great number of replacement solvents in the general post hydrophobic modification method is avoided; waste liquid is not generated; the preparation period is greatly shortened; the process cost is reduced; the industrial production is easy; meanwhile, the prepared silicon dioxide aerogel product has excellent performance.

Description

technical field [0001] The invention belongs to the technical field of silica airgel preparation, and in particular relates to a rapid preparation method of silica airgel. Background technique [0002] Silica airgel has a three-dimensional network skeleton structure and low density (0.03~0.2g / cm 3 ), high porosity (85% ~ 99%), low thermal conductivity (0.01 ~ 0.03W m -1 ·K -1 ), high specific surface area (600~1200m 2 / g) and many other excellent properties, it is often used in aerospace, petroleum and petrochemical, metallurgy and other fields. [0003] Silica airgel was first prepared by Kistler in 1931 through sol-gel method and supercritical drying technology, and this method has become the most commonly used method at present. The sol-gel method usually requires two steps of acid and alkali to catalyze the hydrolysis and polycondensation of the silicon source, respectively. The acid used is generally strong organic acid such as hydrochloric acid, the alkali catalys...

AI Technical Summary

Problems solved by technology

Since the surface of the gel has hydroxyl groups after hydrolysis and polycondensation, surface alkylation is required to make it hydrophobic, so the normal pressure drying preparation process usually includes sol-gel, gel aging, solvent replacement, modification, cleaning, drying After several steps, there are many process steps and a long preparation period. The solvent replacement and modification steps need to consume a large amount of chemical reagents, and there are many waste liquids, which will have a certain impact on the environment. In addition, because the common normal pressure drying method is Heating from the outside forms a temperature gradient, often the surface is dry and the interior contains moisture, resulting in a long drying process and poor product uniformity in the large-scale production of airgel

Images