Combined NMR, SAXS, and DLS Study of Concentrated Clear Solutions Used in Silicalite-1 Zeolite Synthesis

• DOI: 10.1021/cm070693j
• Publication Date: 2007-06-20T13:00:45Z
• Authors: Alexander Aerts; Lana R. A. Follens; Mohamed Haouas; Tom P. Caremans; Marc-André Delsuc; Benoit Loppinet; Jan Vermant; Bart Goderis; Francis Taulelle; Johan A. Martens; Christine E. A. K...
• Keywords: Small-angle X-ray scattering; Dispersity; Particle (ecology)

Concentrated clear solutions, as used for the preparation of Silicalite-1 zeolite, were synthesized from tetrapropylammonium hydroxide, tetraethylorthosilicate, and water. The solutions analyzed using three techniques: quantitative 29Si NMR, synchrotron small-angle X-ray scattering (SAXS), dynamic light (DLS). NMR showed coexistence silicate oligomers particles. For first time, both fractions simultaneously, providing a global, description solution microstructure. SAXS patterns, typical interacting particles, could be together with deduced particle volume fraction to estimate size. A careful analysis DLS data dynamics suspensions revealed occurrence two diffusive processes. faster process is collective diffusion. slower corresponds self-diffusion present because presence polydispersity in size, shape, and/or surface charge. coefficient provides means equivalent hydrodynamic radius. observations hence reveal complex, polydisperse mixture particles at onset zeolite formation. Implications on proposed formation mechanisms are briefly discussed.