The synthesis of colloidal zeolite TPA–silicalite-1

The synthesis of colloidal TPA–silicalite-1 from a clear xTPAOH–yH₂O–TEOS precursor sol, with x=0.01–0.443 and y=20–80, has been studied at 115°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 colloidal (or sub-colloidal) particles presented. In addition, the pH of the system has been measured. The observations made with the DLS were consistent with the literature results. In essence, uniform particles of colloidal zeolite were formed during the reaction, and their size grew linearly with reaction time. At the same time, sub-colloidal particles smaller than 5 nm were also observed that persisted throughout the process. The measured pH, on the other hand, could be satisfactorily modeled by the equilibrium theory, suggesting that an equilibrium distribution of dissolved silicates was established before the reaction, and a different equilibrium was attended when colloidal zeolites, as well as the co-existing sub-colloidal particles, were observed. The number density of the colloidal particles ρ was found to depend on the 3.4 power of the silica concentration and the ratio x.