Detection of TPA-silicalite precursors nucleated during the room temperature aging of a clear homogeneous synthesis solution

Abstract

The transformations occurring during the aging of a clear silicalite preparation at room temperature were studied by small angle X-ray (SAXS) and neutron scattering (SANS), X-ray diffraction and IR spectroscopy. Particles with a radius of gyration of 28 Å were detected in a solution that was aged at room temperature for six months. A cylindrical form factor provided the best fit to the experimental scattering functions and so a similar particle morphology to that formed during the initial stages of the hydrothermal synthesis at 100 °C can be presumed. The IR spectrum of a freeze dried sample taken from the aged solution shows a band at 560 cm⁻¹ characteristic of the framework structure of silicalite, and a SANS contrast variation study showed that the scattering species contain the tetrapropylammonium template. The time required for the hydrothermal crystallisation of silicalite was significantly reduced by aging the silicalite preparation prior to heating to 100 °C.