(552e) Formation of Uniform CHA Zeolite Layers

All-silica CHA zeolites^[1] hold promise to separate CO₂ from other molecules (e.g., N₂ in the post-combustion process) through their molecular sieving. In particular, the pore size of CHA zeolites (0.370 nm × 0.417 nm)^[2] can allow only CO₂ (0.33 nm) to pass through the pore channels, while excluding the transport of larger N₂ (0.364 nm).^[3] However, conventionally synthesized near cubic Si-CHA particles have a wide size distribution (~1-20 μm).^[4-6] The wide size distribution prevents forming a close-packed layer, though the layer is critical in manufacturing zeolite films as desired in the secondary growth methodology.^[7,8]

 In an attempt to overcome this, anisotropic plate-like Si-CHA particles, discovered as the minor product along with the dominant near cubic Si-CHA particles, were adopted to make a uniform Si-CHA layer. Selected area electron diffraction and X-ray diffraction characterizations verified the CHA phase of the plate-like particles. The plate-like CHA particles could be selectively deposited on a porous the α-Al₂O₃ disc despite their lower abundance in a mixture. The uniform CHA layer was formed with a high surface coverage and the uniformity of the plate-like CHA deposits allowed a preferred out-of-plane orientation. The subsequent secondary growth of the seed layer allowed for the continuous CHA membranes. The corresponding CO₂/N₂ separation performance will be discussed in detail.

References

 [1] Camblor, M. A.; Corma, A.; Diaz-Cabanas, M. J.; Baerlocher, C. Journal of Physical Chemistry B 1998, 102, 44.

 [2] Hedin, N.; DeMartin, G. J.; Roth, W. J.; Strohmaier, K. G.; Reyes, S. C. Micropor. Mesopor. Mater. 2008, 109, 327.

 [3] Breck, D. W. Zeolite molecular sieves: strcucture, chemistry, and use; John Wiley & Sons, Inc., 1974.

 [4] Eilertsen, E. A.; Arstad, B.; Svelle, S.; Lillerud, K. P. Micropor. Mesopor. Mater. 2012, 153, 94.

 [5] Olson, D. H.; Camblor, M. A.; Villaescusa, L. A.; Kuehl, G. H. Microporous Mesoporous Mater. 2004, 67, 27.

 [6] Trzpit, M.; Rigolet, S.; Paillaud, J. L.; Marichal, C.; Soulard, M.; Patarin, J. Journal of Physical Chemistry B 2008, 112, 7257.

 [7] Jiang, H. Y.; Zhang, B. Q.; Lin, Y. S.; Li, Y. D. Chinese Science Bulletin 2004, 49, 2547.

 [8] Snyder, M. A.; Tsapatsis, M. Angew. Chem., Int. Ed. 2007, 46, 7560.