Effects of synthesis parameters on the zeolite membrane growth

The effects of synthesis parameters (i.e. [TEOS], [TPA(+)], [OH-], dilution and temperature) on the membrane thickness and orientation were investigat ed for MFI zeolite membranes grown onto seeded supports (i.e. porous glass and alumina). The zeolite crystals grew preferentially with its c-axis alig ned normal to the support surface. This gave the membrane a preferred orien tation of (101) at temperatures below 433 K and an orientation of (002) at higher temperatures. An empirical model for zeolite membrane growth as a fu nction of synthesis variables was derived based on the experimental data. T he model gave an adequate description of the membrane growth and provided a n excellent guide for the synthesis of zeolite membranes with engineered mi crostructure. This model was employed in preparing zeolite membranes of dif ferent thickness (tau = 2-8 mum). Helium, argon and sulfur hexaflouride wer e used as molecular probes for investigating the transport pathways through the membrane microstructure. (C) 2001 Elsevier Science B.V. All rights res erved.