Ethanol dehydration by pervaporation using microporous silica membranes

The experimental results of the effect of the conditions of silica layer preparation, such as dip-coating velocity and calcination temperature, on the flux and selectivity of tubular silica membranes in ethanol removal by pervaporation are reported and discussed. Moreover, the influence of the physico-chemical properties of silica materials on membranes performance as a function of their preparation conditions and operation time is studied. The strong effect of silica dip-coating velocity as well as its calcination temperature on membranes performance was observed. The application of a dip-coating velocity of 1 cm s(-1) and calcination temperature of 400 degrees C let to obtain highly selective membrane with typical fluxes for ceramic membranes. Strong interactions between ethanol and silica resulted in the reduction of total flux and selectivity as function of membrane operation time. The decline in separation performance was attributed to reversible adsorption of ethanol by hydrogen bonding with hydroxyl groups on the silica surface. Pervaporation performance in ethanol dehydration (6 wt.% of water) using the synthesized silica membranes was better than that of commercially available polymeric as well as ceramic tubular membranes. The obtained values of total flux (0.417 kg m(-2) h(-1)) and selectivity (207) are one of the highest reported in the literature for ethanol dehydration.