Development of microporous silica membranes for pervaporation by sol-gel method.

Ceramic membraneshave gained much interest for use in the pervaporation process due to their high chemical resistance and good thermal stability.Silica is one of the most attractive materials for inorganic membranes because of its good chemical stability against acid, low cost of the its precursor and its ability to be shaped into athin microporous film.Silica membranes supported on porous alumina were prepared by the sol-gel method using colloidal and polymeric sols.The effect of the sol composition on the microstructure and performance of the membranes were studied, and a strategy to improve the selectivity of the membrane was explored.From characterization of these membranes by SEM and AFM, it was found that the sol composition played a significant role in the membrane performance due to their different sizes.Data from a pervaporation measurement for the dehydration of acetic acid indicated that a multi-layer coating using sols with different compositions was effective for improving the selectivity of the membrane.The membrane pore sizes estimated from a pervaporation measurement of a pure liquid substance with known molecular diameters are reported.