On defects in highly a-oriented MFI membranes
- Authors
- Kim, Eunjoo; Choi, Jungkyu; Tsapatsis, Michael
- Issue Date
- 4월-2013
- Publisher
- ELSEVIER SCIENCE BV
- Keywords
- MFI (silicalite-1) membranes; Film orientation; Secondary (seeded) growth; Xylene isomers; Butane isomers
- Citation
- MICROPOROUS AND MESOPOROUS MATERIALS, v.170, pp.1 - 8
- Indexed
- SCIE
SCOPUS
- Journal Title
- MICROPOROUS AND MESOPOROUS MATERIALS
- Volume
- 170
- Start Page
- 1
- End Page
- 8
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/103587
- DOI
- 10.1016/j.micromeso.2012.11.023
- ISSN
- 1387-1811
- Abstract
- Previously, uniformly a-oriented MFI films were synthesized via the secondary growth of an a-oriented seed layer, which was obtained by chemically depositing similar to 2 mu m thin-along-the-a-axis particles on a silica-coated alpha-Al2O3 porous disc (Choi et al., Angew. Chem. Int. Ed. 45 (2006) 1154-1158). Despite the uniformity of the a-orientation throughout the film, we found that the MFI membranes are not applicable for p-/o-xylene separation since they have significant crack and grain boundary defects. Accordingly, a-oriented MFI films were fabricated via alternative methods, motivated by the expected high separation performance that could be comparable to p-/o-xylene separations (100-400 separation factor) of a b-oriented MFI membrane. First, smaller 500 nm thin-along-the-a-axis MFI particles (small seeds) were used instead of 2 mu m thin-along-the-a-axis particles (large seeds) for seed deposition. Second, a seed layer was formed by a sonication-assisted physical deposition of the large seeds. Finally, an a-oriented seed layer comprising of the large seeds was epitaxially-grown to be the a-oriented MFI film by conducting two consecutive hydrothermal growth processes. The separation performance of the resultant MFI membranes was investigated via n-/i-butane and p-/o-xylene permeation tests. Maximum separation factors (SF) of similar to 4 and similar to 17 were achieved for p-/o-xylene and n-/i-butane isomers, respectively. These values are below the expected performance, indicating the presence of non-zeolitic pathways in a-oriented films. (C) 2012 Elsevier Inc. All rights reserved.
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