MOLECULAR-SIEVE-MODIFIED POLYMERIC MEMBRANES FOR GAS AND VAPOR SEPARATION

CURRENT COMMERCIAL GAS SEPARATION MEMBRANES ARE MADE FROM GLASSY OR RUBBERY POLYMERS. THE TRANSPORT THROUGH THESE MEMBRANES OCCURS BY A SOLUTION-DIFFUSION MECHANISM. MOST POLYMERS SHOW A TRADE-OFF BETWEEN SELECTIVITY AND PERMEABILITY, I.E., HIGH SELECTIVITIES ARE COUPLED WITH LOW PERMEABILITIES AND VICE VERSA. RECENTLY DEVELOPED HIGHLY RIGID, GLASSY POLYMERS HAVE SHOWN DRAMATIC INCREASES OF PERMEABILITY WITHOUT SACRIFICING THE SELECTIVITY FOR THE SEPARATION OF PERMANENT GAS MIXTURES SUCH AS OXYGEN/NITROGEN, HYDROGEN/METHANE AND CARBON DIOXIDE/METHANE. HOWEVER, THE SELECTIVITIES OF CURRENT CURRENT MEMBRANE MATERIALS FOR OTHER INDUSTRIALLY IMPORTANT GAS SEPARATION APPLICATIONS-SUCH AS HYDROCARBON REMOVAL FROM NATURAL GAS, CARBON DIOXIDE SEPARATION FROM HYDROGEN-CONTAINING STREAMS, OR THE RECOVERY OF CERTAIN ORGANIC VAPORS FROM AIR-ARE INSUFFICIENT FOR A FEASIBLE MEMBRANE SEPARATION PROCESS. THE GOAL OF THIS PROJECT IS TO DEVELOP A NEW APPROACH TO IMPROVING THE SELECTIVITY OF MEMBRANES FOR THE SEPARATION OF GAS STREAMS CONTAINING CONDENSABLE GASES AND VAPORS. THE MEMBRANES CONSIST OF POLYMERS MODIFIED WITH MOLECULAR SIEVES SUCH AS ZEOLITE. RECENT EXPERIMETHYLSILOXANE OR CELLULOSE ACETATE MEMBRANES SHOW ENHANCED PERMSELECTIVITY FOR GAS SEPARATIONS. IN PHASE I, SEVERAL KINDS OF MEMBRANES ARE BEING PREPARED AND TESTED FOR APPLICATION TO GAS AND VAPOR SEPARATIONS. A SYSTEMATIC STUDY OF MOLECULAR-SIEVE-MODIFIED POLYMER MEMBRANES COULD LEAD TO NOVEL APPLICATIONS FOR MEMBRANE-BASED SEPARATIONS.