An emulsion method for producing fine, low density, high surface area silica powder from alkoxides

Abstract

Fine silica powders were prepared by the hydrolysis and condensation of an emulsion of tetraethyl orthosilicate (TEOS) droplets in a continuous water phase. No additions of alcohol, as a mutual solvent for the TEOS and water, or of strong acid or base catalysts, as required in the more conventional sol-gel methods, were used. The emulsion was produced by mechanical mixing and was stabilized against separating out of the phases by increasing the viscosity of the water with a commercial thickening agent, Texipol. The TEOS/water emulsion reacted to form into a loose particulate gel, which could be crushed to a powder after drying at 40°C. The amorphous silica powders produced had low tapping densities (approximately 0.2 g cm-3), small particle sizes (< 30 nm) and high specific surface areas (50-400 m2g-1). © 1996 Chapman & Hall.