Thermal stability improvement of MFI-type zeolite membranes with doped zirconia intermediate layer

Aluminum diffusion from porous alumina support at high temperatures can affect the zeolite membrane properties. In this work, yttria-stabilized zirconia (YSZ) was used as a buffer layer to improve the thermal stability of MFI-type zeolite membrane structure on porous alumina support. Membranes were prepared by the template-free secondary growth method with multiple growth steps in order to minimize intercrystalline gaps. Thermal and hydrothermal stability for MFI-type zeolite membranes were examined by observing trans-membrane average pressure, time dependency of gas permeances and phase structure change with XRD analysis. The MFI-type zeolite membrane with the YSZ intermediate layer was stable in steam at high temperatures (500 °C, partial pressure of steam: 100 kPa). XRD results for the MFI-type zeolite membranes before and after the heat treatment indicated that the YSZ intermediate layer was quite effective in preventing the diffusion of aluminum from the alumina support to zeolite layer and preventing structural change of the zeolite layer at high temperatures.