DETECTION OF TPA-SILICALITE PRECURSORS NUCLEATED DURING THE ROOM-TEMPERATURE AGING OF A CLEAR HOMOGENEOUS SYNTHESIS SOLUTION

The transformations occurring during the aging of a clear silicalite p reparation 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 A were detected in a solut ion that was aged at room temperature for six months. A cylindrical fo rm factor provided the best fit to the experimental scattering functio ns and so a similar particle morphology to that formed during the init ial stages of the hydrothermal synthesis at 100 degrees C can be presu med. The IR spectrum of a freeze dried sample taken from the aged solu tion shows a band at 560 cm(-1) characteristic of the framework struct ure 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 signi ficantly reduced by aging the silicalite preparation prior to heating to 100 degrees C.