Engineering the shape of zeolite crystal grain in MFI membranes and their effects on the gas permeation properties

The effects of the synthesis parameters (i.e., [TEOS], [TPA(+)], [OH-], dil ution, temperature and time) on the shape of the zeolite crystal grain was investigated for MFI zeolite membranes grown on seeded supports (i.e., poro us glass and alumina). The relationship between the zeolite crystal shape ( i.e., tau /d ratio, M) and the synthesis variables was established. Using t he empirical growth model, two sets of zeolite membranes with different cry stal shapes were prepared. The first set of membranes displays different gr ain morphologies (,V), but has comparable thickness (tau) and grain size (d ). The second set of membranes has different tau /d ratios, but with simila r membrane thickness and grain morphology. Both types of membranes exhibit (1 0 1)-preferred orientation. Single gas permeation experiments demonstrat e that micro-scale structural properties, such as zeolite crystal morpholog y can affect the separation performance of the zeolite membrane. This work represents an initial step towards the rational design of engineered zeolit e membranes for separation applications. (C) 2001 Elsevier Science B.V. All rights reserved.