ZEOLITE-FILLED PDMS MEMBRANES .2. PERVAPORATION OF HALOGENATED HYDROCARBONS

In order to study in more detail the influence of the filler on pervap oration performance, silicalite, ZSM-5, and zeolite Y were incorporate d in poly(dimethylsiloxane) (PDMS) and tested in pervaporation experim ents with binary mixtures of chlorinated hydrocarbons (Cl-HC's) in wat er. The results were compared with unfilled PDMS as a reference. The h ighest selectivities were obtained with the silicalite-filled membrane s. However, these membranes showed a decrease in permeability for volu minous components due to molecular sieving effects. In this respect, t he results with zeolite Y were rather disappointing, as its larger por e size was counteracted by its high polarity, whereas ZSM-5-filled mem branes showed intermediate selectivities. Therefore, mesoporous silica s were synthesized, silylated to assure their apolarity, and incorpora ted in PDMS. The resulting membranes showed both improved organic flux es and selectivities in comparison with all other membranes, even for voluminous organics, proving the absence of molecular sieving effects.