Physical Structure of Silica Xerogel Support for Catalyst from Aged Hydrogel in Sulfuric Acid

Abstract

"Silicagel" has been usually aged in alkaline solution such as caustic ammonia, because it was considered to be an acidic substance. However, it has recently been recognized that silicagel was a kind of amphoteric substance. In this report, it was examined whether silicahydrogel could be aged in an acidic solution such as sulfuric acid solution, and what kind of xerogel were obtained from the hydrogel. Specific surface areas of the aged silica xerogel in sulfuric acid decreased to a half of that of the unaged one, while the total volume and the mean radius of micropores increased proportionally to the increase of concentration of sulfuric acid. The physical structure of silica xerogel aged in an acidic solution was shown to be ap- preciably different from that of silicagel aged in an alkaline solution.