Preparation of NaY zeolite membranes in fluoride media and their application in dehydration of bio-alcohols

Improved NaY zeolite membranes were prepared in the presence of ammonium fluoride. The crystallization and separation performance of fluoride-derived NaY zeolite membranes were studied in comparison with fluoride-free membranes. The addition of ammonium fluoride in gel influenced the crystallization and the morphologies of NaY zeolite and zeolite layers, and effectively suppressed the formation of the impurity phase of P-type zeolite in NaY zeolite layers. The fluoride-derived NaY zeolite membranes had thinner zeolite layers and displayed both higher fluxes and separation factors for the dehydration of bio-alcohols (ethanol and butanol) than the fluoride-free membranes. The separation factors increased with the increasing kinetic diameters of alcohols for the methanol, ethanol, i-propanol and n-butanol aqueous solutions. Synthesis reproducibility of fluoride-derived membranes and membrane stability during the dehydration process were also investigated. Si-29 and F-19 MAS NMR results confirmed that fluorine anions were not included in FAU crystals. (C) 2014 Elsevier B.V. All rights reserved.