Details
| Original language | English |
|---|---|
| Pages (from-to) | 329-337 |
| Number of pages | 9 |
| Journal | Microporous and Mesoporous Materials |
| Volume | 79 |
| Issue number | 1-3 |
| Early online date | 2 Feb 2005 |
| Publication status | Published - 1 Apr 2005 |
Abstract
The most frequently prepared molecular sieve membrane type is the Al-free silicalite MFI-membrane. For this membrane type high separation factors are reported for mixtures of technical importance as the xylene-isomers, hydrogen-alkanes or n/i-hydrocarbons. Other molecular sieve membranes as types LTA, ERI, FAU show small separation factors in shape selective separations, except the separation of water-solvent mixtures, which are based on hydrophilic/hydrophobic interactions rather than on molecular size exclusion. For MFI-type membranes the introduction of Al in the crystal lattice is possible in a wide range: from Si/Al ∼ 30 for the ZSM-5 type up to Si/Al ∼ ∞ for the isomorphous silicalite type. The enhancement of the Al-content in MFI-crystals of a membrane changes its hydrophilic/hydrophobic permeation properties, the stability against acids, the concentration of intercrystalline defect pores and the catalytic activity by the Brönsted centres created. In this work a systematic variation of the Si/Al-ratio was done and the membranes were characterized by single gas permeation, by permporosimetry and by mixture gas permeation. With increasing Al-content of the membrane, i.e. decreasing Si/Al-ratio, water permeance and water selectivity increase but simultaneously increasing concentrations of intercrystalline defect pores are formed. As a result of the interplay of these effects the water selectivity passes a maximum as a function of the Si/Al-ratio. The influence of Al-containing supports and of the template content of the synthesis gel on the Si/Al-ratio in both the membrane layer and in the free sediment crystals were investigated by EDX and ICP/OES. By dissolution of Al especially from γ and to a lower extent from α-alumina supports, Al-containing ZSM-5 membranes are formed from Al-free silicalite batches.
Keywords
- MFI-membrane, Permeation, Permporosimetry, Si/Al-variation
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. 79, No. 1-3, 01.04.2005, p. 329-337.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Influence of the Si/Al-ratio on the permeation properties of MFI-membranes
AU - Noack, M.
AU - Kölsch, P.
AU - Seefeld, V.
AU - Toussaint, P.
AU - Georgi, G.
AU - Caro, J.
PY - 2005/4/1
Y1 - 2005/4/1
N2 - The most frequently prepared molecular sieve membrane type is the Al-free silicalite MFI-membrane. For this membrane type high separation factors are reported for mixtures of technical importance as the xylene-isomers, hydrogen-alkanes or n/i-hydrocarbons. Other molecular sieve membranes as types LTA, ERI, FAU show small separation factors in shape selective separations, except the separation of water-solvent mixtures, which are based on hydrophilic/hydrophobic interactions rather than on molecular size exclusion. For MFI-type membranes the introduction of Al in the crystal lattice is possible in a wide range: from Si/Al ∼ 30 for the ZSM-5 type up to Si/Al ∼ ∞ for the isomorphous silicalite type. The enhancement of the Al-content in MFI-crystals of a membrane changes its hydrophilic/hydrophobic permeation properties, the stability against acids, the concentration of intercrystalline defect pores and the catalytic activity by the Brönsted centres created. In this work a systematic variation of the Si/Al-ratio was done and the membranes were characterized by single gas permeation, by permporosimetry and by mixture gas permeation. With increasing Al-content of the membrane, i.e. decreasing Si/Al-ratio, water permeance and water selectivity increase but simultaneously increasing concentrations of intercrystalline defect pores are formed. As a result of the interplay of these effects the water selectivity passes a maximum as a function of the Si/Al-ratio. The influence of Al-containing supports and of the template content of the synthesis gel on the Si/Al-ratio in both the membrane layer and in the free sediment crystals were investigated by EDX and ICP/OES. By dissolution of Al especially from γ and to a lower extent from α-alumina supports, Al-containing ZSM-5 membranes are formed from Al-free silicalite batches.
AB - The most frequently prepared molecular sieve membrane type is the Al-free silicalite MFI-membrane. For this membrane type high separation factors are reported for mixtures of technical importance as the xylene-isomers, hydrogen-alkanes or n/i-hydrocarbons. Other molecular sieve membranes as types LTA, ERI, FAU show small separation factors in shape selective separations, except the separation of water-solvent mixtures, which are based on hydrophilic/hydrophobic interactions rather than on molecular size exclusion. For MFI-type membranes the introduction of Al in the crystal lattice is possible in a wide range: from Si/Al ∼ 30 for the ZSM-5 type up to Si/Al ∼ ∞ for the isomorphous silicalite type. The enhancement of the Al-content in MFI-crystals of a membrane changes its hydrophilic/hydrophobic permeation properties, the stability against acids, the concentration of intercrystalline defect pores and the catalytic activity by the Brönsted centres created. In this work a systematic variation of the Si/Al-ratio was done and the membranes were characterized by single gas permeation, by permporosimetry and by mixture gas permeation. With increasing Al-content of the membrane, i.e. decreasing Si/Al-ratio, water permeance and water selectivity increase but simultaneously increasing concentrations of intercrystalline defect pores are formed. As a result of the interplay of these effects the water selectivity passes a maximum as a function of the Si/Al-ratio. The influence of Al-containing supports and of the template content of the synthesis gel on the Si/Al-ratio in both the membrane layer and in the free sediment crystals were investigated by EDX and ICP/OES. By dissolution of Al especially from γ and to a lower extent from α-alumina supports, Al-containing ZSM-5 membranes are formed from Al-free silicalite batches.
KW - MFI-membrane
KW - Permeation
KW - Permporosimetry
KW - Si/Al-variation
UR - http://www.scopus.com/inward/record.url?scp=14744287631&partnerID=8YFLogxK
U2 - 10.1016/j.micromeso.2005.01.004
DO - 10.1016/j.micromeso.2005.01.004
M3 - Article
AN - SCOPUS:14744287631
VL - 79
SP - 329
EP - 337
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
SN - 1387-1811
IS - 1-3
ER -