TY - JOUR

T1 - Preparation of MFI membranes of enlarged area with high reproducibility

AU - Noack, M.

AU - Kölsch, P.

AU - Schäfer, R.

AU - Toussaint, P.

AU - Sieber, I.

AU - Caro, J.

PY - 2001/11/15

Y1 - 2001/11/15

N2 - In the last 10 years extensive work was done in the preparation and characterization of molecular sieve membranes, especially of the types MFI, LTA and FAU. There is a remarkable progress in the synthesis of MFI membranes from the pure silica crystallization system. These silicalite-1 membranes show both separation properties by molecular size exclusion and by molecular interaction because of the hydrophobic interaction of the silica surface with permeating molecules. Silicalite-1 membranes exhibit promising permeation properties for industrially interesting mixtures as n-/ iso-alkanes or the xylene isomers. However, so far these membranes are available only with areas of 1-10 cm2, and the reproducibility of the membrane preparation is unsatisfactory. The yield of high-quality membranes is in the range of 10-30% of the preparations. In this work the membrane area was enlarged by the factor of 30, and the support shape was changed from a flat disc to a tube geometry. This was achieved by the optimization of the synthesis gel composition and the synthesis conditions. Furthermore, by changing the prepared membrane type from a mono- to a polylayer and by varying the calcination conditions, the density and size of leaks could be reduced. As a result of all these measures the yield of high-quality membranes with a minimum permselectivity of H2 to SF6 of 43 (which is five times the Knudsen factor) as a quality criterium was increased to 70% of all preparations. Special attention was given to the economy of the synthesis of MFI membranes which implies to save material, energy and time.

AB - In the last 10 years extensive work was done in the preparation and characterization of molecular sieve membranes, especially of the types MFI, LTA and FAU. There is a remarkable progress in the synthesis of MFI membranes from the pure silica crystallization system. These silicalite-1 membranes show both separation properties by molecular size exclusion and by molecular interaction because of the hydrophobic interaction of the silica surface with permeating molecules. Silicalite-1 membranes exhibit promising permeation properties for industrially interesting mixtures as n-/ iso-alkanes or the xylene isomers. However, so far these membranes are available only with areas of 1-10 cm2, and the reproducibility of the membrane preparation is unsatisfactory. The yield of high-quality membranes is in the range of 10-30% of the preparations. In this work the membrane area was enlarged by the factor of 30, and the support shape was changed from a flat disc to a tube geometry. This was achieved by the optimization of the synthesis gel composition and the synthesis conditions. Furthermore, by changing the prepared membrane type from a mono- to a polylayer and by varying the calcination conditions, the density and size of leaks could be reduced. As a result of all these measures the yield of high-quality membranes with a minimum permselectivity of H2 to SF6 of 43 (which is five times the Knudsen factor) as a quality criterium was increased to 70% of all preparations. Special attention was given to the economy of the synthesis of MFI membranes which implies to save material, energy and time.

KW - Economical formation

KW - Large area membranes

KW - MFI membranes

KW - Optimization of synthesis

KW - Reproducibility

UR - http://www.scopus.com/inward/record.url?scp=0035498022&partnerID=8YFLogxK

U2 - 10.1016/S1387-1811(01)00396-1

DO - 10.1016/S1387-1811(01)00396-1

M3 - Article

AN - SCOPUS:0035498022

VL - 49

SP - 25

EP - 37

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

SN - 1387-1811

IS - 1-3

ER -