Up to now c-, h0h-, and b-oriented MFI membranes have been fabricated by secondary growth [1-7]. While c- and h0h-oriented MFI membranes were achieved by hydrothermal growth of randomly oriented MFI seeds [3-7], the b-oriented MFI membrane was fabricated after secondary growth of a b-oriented mono-layer of MFI seeds [1, 2].

We report here an extension of the process that resulted in b-oriented MFI membrane [1, 2] to fabricate thin a-oriented MFI membranes. The process includes a-oriented seed deposition and secondary growth. The characteristic shape of MFI zeolite crystal using as structure directing agent (SDA) trimer-TPA3+3I- (bis-N,N-(tripropylammoniumhexamethylene) di-N,N-propylammonium triiodide) is the b-elongated leaf-shaped crystal with Lc>Lb>La, where Li indicates crystal length along the i-axis [8, 9]. During seed deposition, the extended basal bc-plane and the small thickness along a-axis facilitate the attachment of zeolite seeds with a-out-of-plane orientation. As a result a uniform mono-layer of a-oriented seeds was formed on an á-alumina substrate. After seed deposition hydrothermal growth conditions were identified that resulted in well intergrown a-oriented MFI membranes. We will present detail microstructural characterization of these films along with permeation measurements.

1. Lai, Z., et al., Microstructural Optimization of a Zeolite Membrane for Organic Vapor Separation. Science, 2003. 300: p. 456-460.

2. Lai, Z., M. Tsapatsis, and J.P. Nicolich, Siliceous ZSM-5 Membranes by Secondary Growth of b-Oriented Seed Layers. Adv. Mater., 2004. 14(7): p. 716-729.

3. Gouzinis, A. and M. Tsapatsis, On the Preferred Orientation and Microstructural Manipulation of Molecular Sieve Films Prepared by Secondary Growth. Chem. Mater., 1998. 10: p. 2497-2504.

4. Lovallo, M.C. and M. Tsapatsis, Preferentially Oriented Submicron Silicalite Membranes. AIChE Journal, 1996. 42: p. 3020-3029.

5. Lovallo, M.C., A. Gouzinis, and M. Tsapatsis, Synthesis and Characterization of Oriented MFI Membranes Prepared by Secondary Growth. AIChe Journal, 1998. 44: p. 1903-1913.

6. Xomeritakis, G., et al., Growth, microstructure, and permeation properties of supported zeolite(MFI) films and membranes prepared by secondary growth. Chemical Engineering Science, 1999. 54: p. 3521-3531.

7. Xomeritakis, G., Z. Lai, and M. Tsapatsis, Separation of Xylene Isomer Vapors with Oriented MFI Membranes Made by Seeded Growth. Ind. Eng. Chem. Res., 2001. 40: p. 544-552.

8. Bonilla, G., Modeling, Anaylsis, and Characterization of Zeolite MFI Crystal and Membrane Growth, in Chemical Engineering. 2004, University of Massachusetts.

9. Bonilla, G., et al., Zeolite(MFI) Crystal Mophology Control Using Organic Structure-Directing Agents. Chemistry of Materials, 2004. 16(26): p. 5697-5705.