Silicalite, a polymorph of silica consisting of silicon-oxygen Volumetric adsorption of nitrogen and gravimetric adsorption tetrahedra which outline a three-dimensional system of interof dioxan is reported for nonporous, mesoporous, and microporous secting channels (3). Silicalite was received as precursor silicas. Adsorption on the microporous material is governed by crystals containing alkylammonium cations and hydroxyl pore volume and dimensions. Adsorption on the nonporous silica ions. The organic cations were decomposed by calcination and the mesoporous silica at up to monolayer coverages is govin air (873 K), followed by overnight stirring with 0.1 M erned by specific hydrogen bonding interactions between surface aqueous HCl, washing with water until chlorine-free, filtersilanol groups and dioxan molecules. Different silanol group distriing, and drying at ca. 373 K overnight.
butions for different silicas after standard treatment coupled with Dioxan (BDH AnalaR, ΓΊ99.5%) was purified (4) as bedifferent possible modes of adsorption casts doubt on the use of nonporous silica as a standard for the study of interactions between fore (1).
porous silicas and H-bond acceptor molecules. α§ 1996 Academic
Nitrogen adsorption on silicas at 77 K was measured volu-Press, Inc.
metrically with either a Carlo Erba Series 1800 Sorptomatic