High flux MFI membranes for pervaporation

MFI membranes with a thickness of 0.5 μm prepared on a graded α-alumina support were evaluated for separation of feed mixtures of 3 wt% n-butanol/water and 10 wt% ethanol/water by pervaporation. The membranes were selective to n-butanol and ethanol. The flux observed in the present work was about 100 times higher than that previously reported for n-butanol/water separation by pervaporation and about 5 times higher than that for ethanol/water separation by pervaporation. At 60 °C, the observed n-butanol/water flux was about 4 kg m−2 h−1 and the n-butanol/water separation factor was about 10 for the best membrane. At the same temperature, the membrane displayed an ethanol/water flux of ca. 9 kg m−2 h−1 and an ethanol/water separation factor of ca. 5. A mathematical model indicated significant mass transfer resistance in the support, which reduced the flux and the selectivity of the membranes.