Manipulation on microstructure of MFI membranes by binary structure directing agents

The good quality pure-silica MFI zeolite membrane with hydrophobic surface was fabricated by the addition of TBABr in “TEOS-TPAOH-H 2 O” synthesis solution. The effects of TBABr on PV performance and the microstructure of MFI membranes were explored by pervaporation, single-component gas permeation, water contact angle, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS) and 13 C solid state CP MAS NMR. It was found that small amounts of TBABr could accelerate the growth and contribute to compact membranes with high bulk Si/Al ratio and good hydrophobic surface, hence resulting in better pervaporation performance. Excessive amounts of TBABr would interfere the crystallization and result in lower pervaporation performance. For example, when the TBABr/Si ratio increased to 0.01 from 0 with the TPAOH/Si ratio of 0.09, the membrane separation factor was increased from 35 to 59 with the flux of 1.85 kg m −2  h −1 for 5 wt% of ethanol/water mixtures at 60 °C.