Fabrication of Isomorphously Substituted W-MFI Membrane with High Performance for Ethanol Separation from Water

Isomorphous substitution of heteroatoms is an effective platform for finely tuning the pore chemistry, pore structure, and surface properties of the zeolite framework as catalysts or separation membranes. A continuous and compact isomorphously substituted tungsten (W)-MFI membrane was firstly developed on coarse α-Al₂ O₃ tube dip-coated with W-MFI seeds using hydrothermal secondary growth and pretreated synthesis solution. The synthesized W-MFI membrane is found to be ethanol permselective having a pervaporation based separation factor and flux of 69 and 2.50 kg/m²  h, respectively while exhibiting the highest separation index of 170 kg/m²  h for the separation of 5 wt% ethanol-water mixture among the reported heteroatoms substituted and α-Al₂ O₃ supported tubular MFI membranes. The isomorphous substitution of W improves the hydrophobicity and also plays a significant role for the enhanced separation performance.