The synthesis of colloidal zeolite TPA-silicalite-1

The synthesis of colloidal TPAsilicalite-1 from a clear xTPAOH-yH(2)O-TEOS precursor sol, with x=0.01-0.443 and y=20-80, has been studied at 115 degre es C. Both the starting sol and the reaction products at various times were examined by dynamic light scattering (DLS) to determine the size of the co lloidal (or sub-colloidal) particles presented. In addition, the pH of the system has been measured. The observations made with the DLS were consisten t with the literature results. In essence, uniform particles of colloidal z eolite were formed during the reaction, and their size grew linearly with r eaction time. At the same time, sub-colloidal particles smaller than 5 nm w ere also observed that persisted throughout the process. The measured pH, o n the other hand, could be satisfactorily modeled by the equilibrium theory , suggesting that an equilibrium distribution of dissolved silicates was es tablished before the reaction, and a different equilibrium was attended whe n colloidal zeolites, as well as the co-existing sub-colloidal particles, w ere observed. The number density of the colloidal particles rho was found t o depend on the 3.4 power of the silica concentration and the ratio x. (C) 1998 Elsevier Science B.V. All rights reserved.