Preparation of aromatic polyamide membrane for alcohol dehydration by pervaporation

Two aromatic polyamide membranes were synthesized by direct polycondensation of 5-t-butyl isophthalic acid with 2,2-bis[4-(4-aminophenoxy)phenyl]hexfluoropropane, (F-aramide), and with 2,3-bis[4-(4-aminophenoxy)phenyl]propane, (H-aramide), in a solution containing triphenyl phosphite, pyridine and N-methyl-2-pyrrolidinone. The effects of feed composition, feed temperature, and the molar volume of the feed alcohol on pervaporation performance were investigated. The separation factor and the permeation rate increased with increasing ethanol concentration in the feed for both aromatic polyamide membranes. The separation factor of the H-aramide membrane was higher than that of the F-aramide for pervaporation of water:ethanol solution. For the H-aramide membrane, a separation factor of 60 and a permeation rate of 293 g m(-2)h(-1) were obtained when the concentration in the feed was 90 wt% and the feed temperature was maintained at 25 degrees C. (C) 1999 Elsevier Science Ltd. All rights reserved.