SYNTHESIS OF ZEOLITE MEMBRANES FOR GAS SEPARATIONS

POROUS INORGANIC MEMBRANES CAN BE USED AT HIGH TEMPERATURES, AND HAVE HIGH FLUXES, MECHANICAL STRENGTH, AND CHEMICAL STABILITY. TODAY'S COMMERCIALLY AVAILABLE INORGANIC MEMBRANES HAVE LARGE PORES (>40 ), A WIDE PORE SIZE DISTRIBUTION, AND ARE IDEALLY SUITED FOR REMOVING HIGH MOLECULAR WEIGHT COMPONENTS FROM A LIQUID STREAM (ULTRAFILTRATION). HOWEVER, BECAUSE THESE MEMBRANES OPERATE ON KNUDSEN DIFFUSION, THEIR SEPARATION CO-EFFICIENTS ARE FAR TOO LOW FOR USE IN GAS SEPARATIONS. ON THE OTHER HAND, ZEOLITE MEMBRANES HAVE MUCH SMALLER PORES, AND A WELL DEFINED PORE SIZE DISTRIBUTION. SINCE THEY SEPARATE MOLECULES BY MOLECULAR SIEVING, THEY OFFER VERY HIGH SELECTIVITY. UNFORTUNATELY, WHILE THE POTENTIAL OF ZEOLITE MEMBRANES HAS LONG BEEN RECOGNIZED, THERE IS STILL NO SUITABLE PROCESSING METHOD BY WHICH EITHER DENSE FREE STANDING OR SUPPORTED MEMBRANES CAN BE MADE. RESEARCHERS ARE PREPARING ZSM-5 ZEOLITE FILM ON SIO2 AND A12O3 SUBSTRATES USING A NOVEL SYNTHETIC METHOD, AND THEN CHARACTERIZING THE CHEMICAL COMPOSITION, MORPHOLOGY, THERMAL STABILITY, AND ION-EXCHANGE ABILITY OF THE RESULTING FILMS.