The homogeneous nature of clear TPA-silicalite-1 precursor solutions

The polymeric silica present in clear tetrapropylammonium (TPA) silicate solutions, with the molar composition 9TPAOH:25SiO2:480H2O:100ethanol and from which discrete colloidal crystals of TPA-silicalite-1 may be synthesized, has been characterized with respect to particle size using a modified method in which the reaction rate of monomeric silica with molybdic acid was recorded. The estimated particle size of 2.8 nm obtained with this method agrees well with previous studies of the sub-colloidal fraction wherein cryo-TEM and high effect laser light scattering techniques were employed.