Fabrication of High-Stability W-MFI Zeolite Membranes for Ethanol/Water Mixture Separation

Pure silica MFI (Si-MFI) zeolite membranes with desirable hydrophobicity have the potential to separate ethanol/water mixture. However, its separation performance would significantly decrease in the long-term operation due to the presence of silanol groups formed in alkaline media. In this work, silanol-free MFI zeolite membranes were prepared by the incorporation of tungsten in MFI framework. The occurrence of silanol group can be prevented by formation of W-O-Si bridges. The synthesis parameters affected the W-MFI zeolite membranes' microstructure and separation performance. For 5 wt% ethanol solution, the W-MFI zeolite mem-branes prepared at optimum condition showed stable separation performance of permeation flux as 2.81 kg m2 h1 with separation factor as 32 over 80 h at 60 degrees C. The membrane was characterized by XRD, DR UV-vis, XPS and 29Si NMR, and the results confirmed the incorporation of W and the absence of silanol groups. This research showed that W-MFI zeolite membranes are promising candidates for ethanol extraction with high stability.