An in situ study of crystallisation gradients during the hydrothermal/autoclave synthesis of zeolites

Abstract

Spatially-resolved energy-dispersive diffraction has been used to observe crystallisation gradients occurring during the hydrothermal/autoclave synthesis of zeolites. Two systems have been studied: membrane growth and crystallisation of zeolite 4A from bulk gels onto seeded and un-seeded α-alumina substrates, respectively. Both cases clearly show the first manifestations of crystallisation gradients during hydrothermal synthesis and these are described. The results suggest that many more such studies should be conducted to cover a range of systems and to improve synthesis methodology.