Patent ID: 8741252

Claim:
A process for producing an aerogel, comprising: (a) placing a wet gel comprising a first solvent into a porous material treatment section of an apparatus, wherein the first solvent is alcohol, water, or a mixture thereof; (b) feeding both a supercritical second solvent and a third solvent to a high-pressure mixing section of said apparatus, wherein said supercritical second solvent is selected from the group consisting of carbon dioxide, nitrous oxide, propane, and ammonia; and, wherein said third solvent is composed of the same solvent as the first solvent; (c) mixing the third solvent and the supercritical second solvent in said high-pressure mixing section of said apparatus to form a mixed solvent; (d) discharging the mixed solvent from said high-pressure mixing section of said apparatus and feeding the mixed solvent into the porous material treatment section of said apparatus, thereby feeding the mixed solvent into the wet material, such that at least some of the first solvent in the wet gel is removed and replaced with at least some of the mixed solvent, (e) discharging the resulting solvent from said high-pressure mixing section of said apparatus, wherein said resulting solvent is a mixture of the first solvent, which has been extracted from the wet gel, and the mixed solvent; and, (f) continuously recirculating said resulting solvent into said high-pressure mixing section of said apparatus; and, (g) adding additional supercritical second solvent to said high-pressure mixing section so that the additional supercritical second solvent increases the concentration of supercritical second solvent in the continuously recirculating resulting solvent, so the mixing percentage of the second solvent continuously increases with the lapse of time during feeding.