Silica is one of the quite attractive membrane materials because it has characteristic features of controlled pore size and modified functional groups on the silica surface with relatively ease. However, silica shows poor hydrothermal stability. It is also well known that the hydrothermal stability of silica is improved by adding zirconia. A completely homogeneous silica-zirconia composite sols, which is prepared by the hydrolysis and condensation reactions of tetra-ethoxysilane (TEOS) and zirconium n-butoxide (ZrB) in a ethanol solvent, is need to obtain uniform and defect-free membranes. However the reaction rate of ZrB is larger than that of TEOS.
In this study, the chemical reactivity of ZrB is modified with the chelating agent acetylacetone (acac) to control a hydrolysis/condensation rate of the ZrB precursor. Porous silica-zirconia (ZrO₂: 50 mol%) membranes prepared by sol-gel techniques were used for dehydration of isopropyl alcohol/water mixtures at 75 ºC by pervaporation techniques. The membranes have the highest separation factor of 15 when silica-zirconia membrane were prepared at H+/(Si+Zr), H₂O/(Si+Zr) and acac/Zr molar ratio of 0.05 , 4 , 0.5, respectively. In addition, silica-zirconia membranes were characterized by FT-IR and FE-SEM/EDX techniques to evaluate the effect of preparation conditions such as temperature, H+/(Si+Zr), H₂O/(Si+Zr) and acac/Zr molar ratio.