We prepared a clay aerogel by freeze drying an aqueous viscous suspension of a synthetic saponite (a layered clay mineral of the smectite family). The nanostructure and texture of the resulting aerogel varied with the freezing conditions. The freeze drying resulted in microporous aerogels with well-ordered (stacked) silicate layers. A fine texture was observed after freeze drying of a starting suspension at a lower concentration. Freezing in liquid propane yielded a well-defined continuous network texture. Toluene in vapor phase was oxidatively decomposed in air flow over aerogels on which platinum was deposited by an impregnation wetness method; the decomposition was probably affected by the size distribution of micropores.