Ethanol perm‐selective B‐ZSM‐5 zeolite membranes from dilute solutions

Boron-substituted MFI (B-ZSM-5) zeolite membranes with high pervaporation (PV) performance were prepared onto seeded inexpensive macroporous α-Al2O3 supports from dilute solution and explored for the separation of ethanol/water mixtures by PV. The effects of several parameters on microstructures and PV performance of the B-ZSM-5 membranes were examined systematically, including the seed size, synthesis temperature, crystallization time, B/Si ratio, H2O/SiO2 ratio and silica source. A continuous and compact B-ZSM-5 membrane was fabricated from solution containing 1 tetraethyl orthosilicate/0.2 tetrapropylammonium hydroxide/0.06 boric acid/600 H2O at 448 K for 24 h, showing a separation factor of 55 and a flux of 2.6 kg/m2 h along with high reproducibility for a 5 wt % ethanol/water mixture at 333 K. It was demonstrated that the incorporation of boron into mobile five (MFI) structure could increase the hydrophobicity of B-ZSM-5 membrane evidenced by the improved contact angle and amount of the adsorbed ethanol, and thus enhance the PV property for ethanol/water mixtures. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2447–2458, 2016