(605e) Preparation of Vinyltriethoxysilane (VTES) Modified Silicalite/PDMS Hybrid Pervaporation Membranes: Membrane Characterization and Its Application in Ethanol Separation From Dilute Aqueous Solutions

To improve the affinity between silicalite and polydimethylsiloxane (PDMS), the silicalite-1 particles was modified by a novel silane coupling agent vinyltriethoxysilane (VTES) and incorporated into polydimethylsiloxane (PDMS) matrix for the preparation of silicalite/PDMS hybrid membranes. The modified silicalite-1 particles were examined by XRD, FT-IR and TGA, and the results showed that the silane coupling agent was strongly bonded to the surface of silicalite-1 particles and the modification did not influence the framework of silicalite-1 crystals. VTES enhanced the interaction of silicalite-1 particles with PDMS through chemical bonds and suppressed the formation of microvoids at polymer-silicalite interface, thus improved the thermal stability of the hybrid membrane. The effect of silicalite loading on the pervaporation performances of the hybrid membranes with dilute ethanol solutions was investigated. As compared with the unmodified hybrid membranes, the silane modified silicalite/PDMS hybrid membranes effectively improved the pervaporation selectivity at different silicalite loadings. With increasing silicalite loading, membrane selectivity increased for both unmodified and VTES modified silicalite/PDMS hybrid membranes, and a selectivity of 33 was obtained when VETS modified silicalite loadings was 67%. It was also found that with increasing silicalite loading, the total flux of both unmodified and VTES modified silicalite/PDMS hybrid membranes decreased while the ethanol flux of both hybrid membranes increased. With increasing the feed ethanol concentration at a given temperature, the total flux, ethanol flux, and ethanol concentration in permeate increased almost proportionally, while the separation factor decreased slightly and water flux decreased indistinctively at lower feed temperature and sharply at higher temperature. An increase in temperature increased the permeation fluxes. The activation energy calculated from the Arrhenius equations for both ethanol and water permeation tended to decrease with an increase in the feed ethanol concentration.