Pervaporative recovery of n-butanol from aqueous solutions and ABE fermentation broth using thin-film silicalite-filled silicone composite membranes

The thin-film silicalite-filled silicone composite membranes were fabricated by incorporating ultrafine silicalite-1 particles, 0.1–0.2 μm, which were synthesized in our laboratory. The effects of membrane thickness and silicalite particle content on membrane properties were studied. It was found that with the increase of silicalite content in the top active layer, the selectivity for n-butanol and n-butanol flux increased, while the total flux decreased. When the silicalite-1 content was over 60%, the active layer appeared to have defects, aggregation of silicalite-1 particles, which effected the separation factor. By controlling the membrane thickness and silicalite-1 content, membranes with the total flux of 600–700 g/m2 h (n-butanol flux of 300 g/m2 h) and selectivity of 90–100 at 70°C using 10 g/l of n-butanol as feed solution were obtained. The effects of operation temperature and feed solution concentration on membrane performances were studied. The structures of the silicalite-1 particles and the composite membranes were analyzed by SEM. Separation properties for acetone n-butanol ethanol (ABE) were also investigated by using model ABE solution and ABE fermentation broth.