Selective separation of water from aqueous alcohol solution through fluorine-containing aromatic polyamide membranes by pervaporation

For dehydrating aqueous alcohol solution by pervaporation, a fluorine-containing aromatic polyamide membrane was synthesized. The fluorine-containing polyamides were prepared by direct polycondensation of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, BAPPH, with various aromatic diacids by triphenyl phosphite and pyridine in N-methyl-2-pyrrolidinone. The novel aromatic polyamides were examined by elemental analysis, FTIR, and X-ray diffraction. The aromatic polyamides were crystalline except (A-B-2). The effects of feed composition, degree of swelling, and the molecular size of alcohols on pervaporation performances were investigated. Water molecules preferentially permeate through the aromatic polyamide membranes. A separation for water of 36 and a 383 g/m(2)h permeation rate with a 90 wt% feed ethanol concentration was obtained.