Details
| Original language | English |
|---|---|
| Pages (from-to) | 88-96 |
| Number of pages | 9 |
| Journal | Microporous and Mesoporous Materials |
| Volume | 97 |
| Issue number | 1-3 |
| Early online date | 20 Sept 2006 |
| Publication status | Published - 29 Dec 2006 |
Abstract
The most frequently prepared molecular sieve membrane is the Al-free MFI type (silicalite 1) which shows high separation factors and a negligible intercrystalline defect permeance. By introduction of Al into the MFI lattice (ZSM-5) the hydrophilicity and the acid sites concentration increase and the adsorption properties are changed. However, for ZSM-5 membranes with increasing Al-content the intercrystalline defect transport is enhanced and, therefore, the selectivity decreases. Searching for the reasons for this behaviour, an increase of the negative surface charge (zeta-potential) of ZSM-5 crystals with enhanced Al-content is found. Since the MFI precursors in the synthesis solution are negatively charged like the growing ZSM-5 layer, it is assumed that a hindered transport and attachment of the precursors to the equally charged crystal surfaces could cause the poor intergrowth of the ZSM-5 crystals to a continuous tight membrane layer. By use of Intergrowth Supporting Substances (ISS) the crystal surface is re-charged and the crystal intergrowth is improved. Suitable ISS are small positively charged molecules, stable in the alkaline region during the synthesis at 180 °C and which can be decomposed by calcination. In this work the effect of different ISS on the permeation properties of ZSM-5 membranes with various Al-content is shown. The membranes are characterized by XRD, SEM, permporosimetry and single gas permeation.
Keywords
- Influence of ISS, Permeation properties, Si/Al-variation, Zeta-potential, ZSM-5 membranes
ASJC Scopus subject areas
- Chemistry(all)
- General Chemistry
- Materials Science(all)
- General Materials Science
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanics of Materials
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In: Microporous and Mesoporous Materials, Vol. 97, No. 1-3, 29.12.2006, p. 88-96.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Effect of crystal intergrowth supporting substances (ISS) on the permeation properties of MFI membranes with enhanced Al-content
AU - Noack, M.
AU - Kölsch, P.
AU - Dittmar, A.
AU - Stöhr, M.
AU - Georgi, G.
AU - Eckelt, R.
AU - Caro, J.
PY - 2006/12/29
Y1 - 2006/12/29
N2 - The most frequently prepared molecular sieve membrane is the Al-free MFI type (silicalite 1) which shows high separation factors and a negligible intercrystalline defect permeance. By introduction of Al into the MFI lattice (ZSM-5) the hydrophilicity and the acid sites concentration increase and the adsorption properties are changed. However, for ZSM-5 membranes with increasing Al-content the intercrystalline defect transport is enhanced and, therefore, the selectivity decreases. Searching for the reasons for this behaviour, an increase of the negative surface charge (zeta-potential) of ZSM-5 crystals with enhanced Al-content is found. Since the MFI precursors in the synthesis solution are negatively charged like the growing ZSM-5 layer, it is assumed that a hindered transport and attachment of the precursors to the equally charged crystal surfaces could cause the poor intergrowth of the ZSM-5 crystals to a continuous tight membrane layer. By use of Intergrowth Supporting Substances (ISS) the crystal surface is re-charged and the crystal intergrowth is improved. Suitable ISS are small positively charged molecules, stable in the alkaline region during the synthesis at 180 °C and which can be decomposed by calcination. In this work the effect of different ISS on the permeation properties of ZSM-5 membranes with various Al-content is shown. The membranes are characterized by XRD, SEM, permporosimetry and single gas permeation.
AB - The most frequently prepared molecular sieve membrane is the Al-free MFI type (silicalite 1) which shows high separation factors and a negligible intercrystalline defect permeance. By introduction of Al into the MFI lattice (ZSM-5) the hydrophilicity and the acid sites concentration increase and the adsorption properties are changed. However, for ZSM-5 membranes with increasing Al-content the intercrystalline defect transport is enhanced and, therefore, the selectivity decreases. Searching for the reasons for this behaviour, an increase of the negative surface charge (zeta-potential) of ZSM-5 crystals with enhanced Al-content is found. Since the MFI precursors in the synthesis solution are negatively charged like the growing ZSM-5 layer, it is assumed that a hindered transport and attachment of the precursors to the equally charged crystal surfaces could cause the poor intergrowth of the ZSM-5 crystals to a continuous tight membrane layer. By use of Intergrowth Supporting Substances (ISS) the crystal surface is re-charged and the crystal intergrowth is improved. Suitable ISS are small positively charged molecules, stable in the alkaline region during the synthesis at 180 °C and which can be decomposed by calcination. In this work the effect of different ISS on the permeation properties of ZSM-5 membranes with various Al-content is shown. The membranes are characterized by XRD, SEM, permporosimetry and single gas permeation.
KW - Influence of ISS
KW - Permeation properties
KW - Si/Al-variation
KW - Zeta-potential
KW - ZSM-5 membranes
UR - http://www.scopus.com/inward/record.url?scp=33751343443&partnerID=8YFLogxK
U2 - 10.1016/j.micromeso.2006.07.031
DO - 10.1016/j.micromeso.2006.07.031
M3 - Article
AN - SCOPUS:33751343443
VL - 97
SP - 88
EP - 96
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
SN - 1387-1811
IS - 1-3
ER -