Manipulation on microstructure of MFI membranes by binary structure directing agents

Abstract The good quality pure-silica MFI zeolite membrane with hydrophobic surface was fabricated by the addition of TBABr in “TEOS-TPAOH-H2O” 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 13C 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.