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Issue 38, 2014
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Microstructural optimization of MFI-type zeolite membranes for ethanol–water separation

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Abstract

High quality pure-silica MFI-type zeolite membranes are successfully prepared by simply controlling the amount of structure directing agent (SDA), i.e., tetrapropylammonium (TPA+) in the synthesis solution for seeded growth. The effects of several synthesis parameters such as alkalinity (OH/Si), TPA+ concentration (TPA+/Si), and crystallization time on the membrane pervaporation performance are investigated in detail. The synthesized MFI-type zeolite membranes are thoroughly characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, the water contact angle test, X-ray diffraction (XRD), the pervaporation test and gas permeation. The membrane microstructure is very sensitive to the TPA+/Si ratio of the synthesis solution. At a high TPA+/Si ratio (typically 0.17), parasitic twin crystals are intergrown in the zeolite layer, thus resulting in the formation of membrane defects during SDA removal treatment (calcination at 500 °C). When the membrane is prepared with a low TPA+/Si ratio (≤0.05), the appearance of twin crystals can be significantly suppressed and the synthesized dense MFI-type zeolite membranes exhibit pervaporation separation factors higher than 85 for 5 wt% ethanol–water mixtures at 60 °C. We demonstrate for the first time that controlling the SDA concentration in the precursor solution is beneficial to the elimination of membrane microstructural defects, showing a pathway to high quality MFI-type zeolite membranes.

Graphical abstract: Microstructural optimization of MFI-type zeolite membranes for ethanol–water separation

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Publication details

The article was received on 05 Jun 2014, accepted on 01 Aug 2014 and first published on 05 Aug 2014


Article type: Paper
DOI: 10.1039/C4TA02837F
Citation: J. Mater. Chem. A, 2014,2, 16093-16100
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    Microstructural optimization of MFI-type zeolite membranes for ethanol–water separation

    Y. Peng, H. Lu, Z. Wang and Y. Yan, J. Mater. Chem. A, 2014, 2, 16093
    DOI: 10.1039/C4TA02837F

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