TPA−Silicalite Crystallization from Homogeneous Solution: Kinetics and Mechanism of Nucleation and Growth

• DOI: 10.1021/jp971531l
• Publication Date: 2002-07-26T05:15:02Z
• Authors: Jonathan N. Watson; Lennox E. Iton; Roland I. Keir; John C. Thomas; Trevor L. Dowling; John W. White
• Keywords: Small-angle X-ray scattering; Crystal (programming language); Small-Angle Scattering

The formation and growth of tetrapropylammonium-templated crystal nuclei silicalite from a clear homogeneous solution was recorded in situ as function time at temperatures between 90 115 °C using small-angle X-ray scattering (SAXS). kinetics the nucleation process studied give an apparent activation energy 70 kJ mol-1. A neutron (SANS) contrast variation study confirms that contain tetrapropylammonium template expected stoichiometry completed crystal. Infrared spectroscopy provides evidence framework structure is present nuclei. Our SAXS SANS data both show cylindrical form factor gave best fit to measured functions for particles developed end induction period. Dynamic light measurements were used follow 100−6000 Å size domain, beyond range measurements. Scanning electron microscopy also determine morphology particle sizes sedimented crystals freeze-dried solutions. We have proposed detailed model crystallization processes wherein primary nuclei, 2 × unit cells cross section, very quickly upon heating then assemble end-to-end along c axis into 330 long crystallites during extended period, followed by aggregation polycrystalline ellipsoids length 6000 Å.