Adsorbate-Induced Expansion of Silicalite-1 Crystals

作者：Sorenson Stephanie G; Smyth Joseph R; Kocirik Milan; Zikanova Arlette; Noble Richard D; Falconer John L^*

来源：Industrial & Engineering Chemistry Research, 2008, 47(23): 9611-9616.

DOI：10.1021/ie800630g

Optical microscopy and XRD measurements show that silicalite-1 crystals expand when C(4)-C(8) alkanes and i-butane adsorb in the MFI structure at room temperature. The c-direction linear expansion was 0.20-0.45%, and was measured with XRD and optical microscopy for 200 pm crystals. n-Pentane, n-hexane, and n-heptane had the maximum linear expansion of approximately 0.54% in the b-direction, and n-hexane and n-heptane had the maximum volume expansion of 1.2%. In contrast, benzene did not cause a significant change in the unit cell Volume. The a-direction expanded least for the molecules studied except i-butane. n-Hexane expanded the silicalite-1 crystal more at 180 K than at room temperature. Crystal expansion due to n-alkane adsorption decreased the size of defects in a polycrystalline MFI membrane, and changes in the fluxes of i-octane through defects were measured by transient permeation. Loadings as low as 0.5 molecule/unit cell decreased the flux through defects at 358-473 K, but benzene had no effect. Higher loadings increased crystal expansion and decreased the defect size more. Crystal expansion was reversible.

• 出版日期2008-12-3