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-], dilution, temperature and time) on the shape of the zeolite crystal grain was investigated for MFI zeolite membranes grown on seeded supports (i.e., porous glass and alumina). The relationship between the zeolite crystal shape (i.e., tau /d ratio, M) and the synthesis variables was established. Using the empirical growth model, two sets of zeolite membranes with different crystal shapes were prepared. The first set of membranes displays different grain morphologies (,V), but has comparable thickness (tau) and grain size (d). The second set of membranes has different tau /d ratios, but with similar membrane thickness and grain morphology. Both types of membranes exhibit (1 0 1)-preferred orientation. Single gas permeation experiments demonstrate that micro-scale structural properties, such as zeolite crystal morphology can affect the separation performance of the zeolite membrane. This work represents an initial step towards the rational design of engineered zeolite membranes for separation applications. (C) 2001 Elsevier Science B.V. All rights reserved.