Microwave synthesis of high performance FAU-type zeolite membranes: Optimization, characterization and pervaporation dehydration of alcohols

High performance FAU-type zeolite membranes were synthesized by the “in situ aging-microwave synthesis” (AM) method in a clear solution with the molar composition of 70Na2O:1Al2O3:20SiO2:2000H2O. The AM method couples in situ aging at relatively low temperature and fast crystallization under microwave heating (MH). To achieve the optimization of the synthesis parameters, the in situ aging and MH temperatures, as well as the probable ranges of the corresponding times were firstly determined by means of investigating their effects on the crystal structures and morphologies of the zeolite layers. Then the Taguchi experimental design was employed to further optimize the in situ aging and MH times of the two-stage synthesis. The as-synthesized zeolite membranes showed high pervaporation performance for the dehydration of ethanol and isopropanol aqueous solutions. Only pure water was detected in the permeate before the water content decreased to ca. 9% for water/ethanol mixtures and ca. 6% for water/isopropanol mixtures, respectively.