Preparation of silicalite-1 zeolite membrane by a two-stage-varying temperature synthesis for pervaporation separation of ethanol from water

A two-stage-varying temperature synthesis (TSVT) was applied to synthesize zeolite silicalite-1 membrane supported on the stainless steel tube. TSVT synthesis is carried out at low temperature, to promote nucleation, after which the temperature is rapidly increased, to promote crystal growth. The membrane with conventional one stage constant temperature method (OSCT) was also synthesized for comparison. The membrane was characterized by scanning electron microscopy (SEM) and gas permeation tests, and their pervaporation performance of ethanol from water was examined. The effect of the synthesis temperature and the crystallization time on the membrane performance was investigated. The membranes by OSCT method show low fluxes of 0.2-0.3 kg/m².h and separation factor of about 7 for ethanol over water at ethanol content of 5 wt% and 60 °C. The membranes by TSVT method gave a much higher flux and separation factor at the same operation condition. At lower second stage temperature and with low water content in the synthesis mixture, the membrane shows a high pervaporation flux of 2.8 kg/m².h with comparable separation factor of 34.3 at ethanol content of 5 wt% and 60 °C.