The synthesis of super-hydrophilic and acid-proof Ge–ZSM-5 membranes by simultaneous incorporation of Ge and Al into a Silicalite-1 framework

A new method for synthesis of super-hydrophilic and acid-proof zeolite membranes was presented. It involved simultaneous incorporation of suitable amounts of Ge and Al into a Silicalite-1 framework. The precursor sol was prepared in an ice-water bath, and the alcohols in the precursor sol were removed at about 80 °C. It was shown that using the ice-water bath would prevent the formation of GeO2 and removing the alcohols at a relatively high temperature would lead to suitable amounts of Ge and Al in the membranes. The obtained Ge–ZSM-5 membranes were acid-proof and showed high pervaporation performance for dehydrating acetic acid and ethanol solutions. At 353 K, for feed acetic acid solutions in a concentration range of 30–98 wt%, the permeation flux of water was almost constant (about 0.57 kg/m2 h), and very little acetic acid permeated through the membrane, resulting in a very high separation factor. Similarly, for dehydration of ethanol solutions (10–98 wt%) at 343 K a water flux of approximately 2.4 kg/m2 h was obtained.