PERVAPORATION MEMBRANES ENDOWED WITH CATALYTIC PROPERTIES, BASED ON POLYMER BLENDS

Membranes endowed with both catalytic and separative properties were designed by using the polymer blend concept. Two polymer blend systems were studied: the poly (acrylonitrile) (PAN) -poly (styrene sulfonic acid) (PSSA) and the poly (vinyl alcohol) (PVA) -PSSA blend. From miscibility and extraction studies, it appeared that PAN-PSSA could not be employed due to polymer segregation and extraction of PSSA in the liquid mixture. In the case of PVA-PSSA, miscibility was observed at high PVA content but, whatever relative polymer concentration in the blend, PSSA extraction occurred. To circumvent this extraction problem, PVA crosslinking was carried out by heat treatment. The catalytic and separative properties of the membranes were tested with an esterification reaction mixture. Good catalytic properties were observed. A rather good selectivity was also obtained, but not sufficient for the combined process. By casting the PVA-PSSA blend onto a hydrophilic GFT membrane and by subsequently crosslinking the blend, a composite membrane with both good catalytic and separative properties was obtained.