FER MEMBRANE SYNTHESIZED BY A VAPOR-PHASE TRANSPORT METHOD - ITS STRUCTURE AND SEPARATION CHARACTERISTICS

The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was fo rmed in the pores of the alumina support, namely, a FER-alumina compos ite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporatio n tests for benzene/p-xylene mixtures were performed at 303 K. Even wh en the concentration of benzene in the feed solution was extremely sma ll (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a h igh selectivity for the benzene/p-xylene mixture suggested that the se lectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer. (C) 1997 E lsevier Science B.V.