(699b) A New Method to Minimize Brittle Fracture Effects on Zeolite Membrane Performance: Demonstration In Columnar C-Oriented Zeolite Mfi Films

It is well-known that MFI type zeolites are selective for p-xylene over the other xylene isomers. There are many reports on the xylene separation performance of MFI membranes.[1-6] Among the available microstructures, 15~30 µm thick, columnar, c-oriented MFI membranes made by secondary growth of randomly oriented seed layers, are attractive for large scale industrial use, because they can be easily fabricated with high reproducibility compared to other MFI membranes made by in-situ and secondary growth methods.[7, 8] However, although single component permselectivity (or ideal selectivity) of p-xylene over o-xylene through c-oriented MFI membranes is high (up to ~ 100), the separation factor for the corresponding binary mixture is significantly lower, down to 2 ~ 4.[3] The significant reduction is attributed to the presence of non-zeolitic paths (defects) in the membranes. In particular, cracks are often generated during the synthesis, calcination or use due to the mismatch of thermal expansion behaviors of MFI films and porous supports.

We will report a new preparation method that minimizes defect formation and results in c-oriented columnar MFI membranes with unprecedented selectivities (e.g., xylene and butane isomer selectivities as high as 120 and 50, respectively). Implications in membrane manufacturing and scale up will be discussed.

References

1.Gump, C.J., et al., Industrial & Engineering Chemistry Research, 2001. 40(2), 565-577.

2.Sakai, H., T. Tomita, and T. Takahashi, Separation and Purification Technology, 2001. 25(1-3), 297-306.

3.Xomeritakis, G., Z. Lai, and M. Tsapatsis, Ind. Eng. Chem. Res., 2001. 40(2), 544-552.

4.Hedlund, J., et al., Microporous Mesoporous Mater., 2002. 52(3), 179-189.

5.Lai, Z., et al., Science (Washington, DC, U. S.), 2003. 300(5618), 456-460.

6.Yuan, W., Y.S. Lin, and W. Yang, Journal of the American Chemical Society, 2004. 126(15), 4776-4777.

7.Gouzinis, A. and M. Tsapatsis, Chem. Mater., 1998. 10(9), 2497-2504.

8.Xomeritakis, G., et al., Chem. Eng. Sci., 1999. 54(15-16), 3521-3531.