Disclosed herein are methods for the preparation of porous metal oxide materials, including metal oxide xerogels and metal oxide aerogels. Methods for preparing porous metal oxide materials can comprise (i) reacting a metal alkoxide with water in the presence of a catalyst system to form a partially hydrolyzed sol, (ii) contacting the partially hydrolyzed sol with a base catalyst and a non-aqueous solvent to form a precursor gel; and (iii) drying the precursor gel to form the porous metal oxide material. The catalyst system employed in step (i) comprises a combination of a weak acid and a strong acid.

A preparation method of SiO.sub.2 aerogels is for solvent replacement process during preparation of SiO.sub.2 aerogels and adopts “a manner of continuously circulation filtration” for an operation of adding solvent so that wet gel is continuously circulated and replaced (rinsing) by mass alcohol solvent and organic solvent to greatly accelerate (reducing) the time for replacement operation of wet gel solvent. At the same time, the alcohol solvent or the organic solvent passing through the reaction container separates wet gel from water content or the alcohol solution through filtration procedure. Afterward the alcohol solution and the organic solution enter the reaction container to perform solvent replacement such that fast continuously circulation filtration is performed to greatly improve the effect of replacing wet gel solvent.

Provided are a method for preparing a hydrophobic silica aerogel by the combined use of a first surface modifier and a second surface modifier, and a hydrophobic silica aerogel prepared by using the method. A hydrophobic silica aerogel having excellent physical properties and pore characteristics as well as a high degree of hydrophobicity may be prepared with high efficiency by the preparation method according to the present invention.

A preparation method of SiO.sub.2 aerogels is for solvent replacement process during preparation of SiO.sub.2 aerogels and adopts “a manner of continuously circulation filtration” for an operation of adding solvent so that wet gel is continuously circulated and replaced (rinsing) by mass alcohol solvent and organic solvent to greatly accelerate (reducing) the time for replacement operation of wet gel solvent. At the same time, the alcohol solvent or the organic solvent passing through the reaction container separates wet gel from water content or the alcohol solution through filtration procedure. Afterward the alcohol solution and the organic solution enter the reaction container to perform solvent replacement such that fast continuously circulation filtration is performed to greatly improve the effect of replacing wet gel solvent.

The present invention relates to a process for producing an aerogel material based on amorphous silica, comprising the following steps:

a) preparing a mixture comprising silica sol, alcohol, and a hydrophobizing agent activatable by acid catalysis;

b1) adding a base to the mixture formed in step a) and mixing the resulting mixture;

b2) gelation of the mixture comprising silica sol obtained in step b2), resulting in the formation of a silica gel, and optional aging of the gel;

c) adding a hydrophobization catalyst to the silica gel formed in step b2) and optionally aged, in-situ formation or controlled release of a hydrophobization catalyst, and initiation of the catalyzed hydrophobization of the silica;

d) removing the volatile constituents of the mixture formed in step c) by subcritical drying, resulting in the formation of the aerogel material, wherein at least steps b2) to d) are carried out in the same reactor.

It is an object of the invention to provide a rapid and economically viable process which is notable for efficient use of material, especially of the silylating agent, and by means of which organically modified lyo- or aerogels are obtained in a rapid and simple manner. This object is achieved by virtue of the invention providing a process for producing organically modified gels selected from lyo- and aerosols by (i) emulsifying a basic polar phase comprising water and starting materials for silicatic gels in a nonpolar phase containing a water-immiscible precursor for an active silylating agent, (ii) starting formation of gel and ageing by lowering the pH, and then (iii) starting the silylation and the exchange of solvent by lowering the pH. If the gels are aerogels, the gels provided can be used for thermal and/or acoustic insulation.

Disclosed herein are methods for the preparation of porous metal oxide materials, including metal oxide xerogels and metal oxide aerogels. Methods for preparing porous metal oxide materials can comprise (i) reacting a metal alkoxide with water in the presence of a catalyst system to form a partially hydrolyzed sol, (ii) contacting the partially hydrolyzed sol with a base catalyst and a non-aqueous solvent to form a precursor gel; and (iii) drying the precursor gel to form the porous metal oxide material. The catalyst system employed in step (i) comprises a combination of a weak acid and a strong acid.

An insulating material is used that contains a silica xerogel, and a nonwoven fabric fiber capable of generating carbon dioxide by reacting with atmospheric oxygen at a temperature of 300 C. or more. The insulating material uses oxidized acrylic as the nonwoven fabric fiber. A device uses the insulating material installed as a part of a heat insulating or a cold insulating structure, or installed between a heat-generating part and a casing.

The present invention relates to a process for producing an aerogel material based on amorphous silica, comprising the following steps: a) preparing a mixture comprising silica sol, alcohol, and a hydrophobizing agent activatable by acid catalysis; b1) adding a base to the mixture formed in step a) and mixing the resulting mixture; b2) gelation of the mixture comprising silica sol obtained in step b2), resulting in the formation of a silica gel, and optional aging of the gel; c) adding a hydrophobization catalyst to the silica gel formed in step b2) and optionally aged, in-situ formation or controlled release of a hydrophobization catalyst, and initiation of the catalyzed hydrophobization of the silica; d) removing the volatile constituents of the mixture formed in step c) by subcritical drying, resulting in the formation of the aerogel material, wherein at least steps b2) to d) are carried out in the same reactor.

A method for preparing a sol-gel derived SiO.sub.2 having a very fast bioresorption rate where a sol-gel derived SiO.sub.2 is prepared from a sol comprising water, an alkoxide or inorganic silicate and a lower alcohol using a mineral acid or a base as a catalyst and the sol is aged and dried. The method uses a pH from 1.5 to 2.5, a molar ratio of water to the alkoxide or inorganic silicate of 0.5 to 2.5, a molar ratio of alcohol to the alkoxide or inorganic silicate is 0.5; and the sol is either let to gel without induced changes of composition and without forced drying of the sol, or a change of composition is induced; and within a time of 30 minutes, from the induced change forced drying of the sol is carried out or initiated.