Ethanol/water mixture pervaporation performance of b-oriented silicalite-1 membranes made by gel-free secondary growth

Abstract

b-oriented silicalite-1 membranes on porous silica supports were synthesized using gel-free secondary growth. The porous silica supports were made by pressing crushed quartz fibers followed by sintering and polishing, and further modified by slip-coating three layers of Stöber silica particles (1000, 350, and 50 nm). The b-oriented seed layers were prepared by rubbing silicalite-1 particles (2 μm × 0.8 μm × 3 μm along a-, b-, and c-axis, respectively) after depositing a polymeric layer on the support. After silicalite-1 seed deposition, a final coating of spherical silica particles was applied. Well-intergrown, μm-thick, b-oriented membranes were obtained, which, after calcination, exhibited ethanol permselectivity in ethanol/water mixture pervaporation. At 60°C and for ∼5 wt % ethanol/water mixtures, the best membrane exhibited overall pervaporation separation factor of 85 (corresponding to membrane intrinsic selectivity of 7.7) and total flux of 2.1 kg/(m2·h). This performance is comparable to the best performing MFI membranes reported in the literature.