EFFECT OF FEED COMPOSITION ON THE PERFORMANCE OF POLYMER-ZEOLITE MIXED MATRIX GAS SEPARATION MEMBRANES

An emerging membrane morphology with future potential is mixed matrix membranes composed of two interpenetrating matrices of different mater ials. In this study, mixed matrix membranes of an amorphous glassy pol ymer(polyethersulfone) and hydrophilic zeolite (4A) were prepared. An elaborate membrane preparation technique that enables incorporation of high zeolite loading into the membrane was developed. Performance of membranes was tested by using a laboratory-scale gas separation appara tus. The permeation rates of N-2, CH4, Ar, O-2, CO2, and H-2 were eval uated through a dense homogeneous PES membrane and a PES-4A mixed matr ix membrane. For the mixed matrix membrane, gas permeabilities were ei ther not changed or significantly improved. The ideal separation facto rs of economically important gas pairs were substantially increased du e to the faster permeation of H-2 and CO2 through the mixed matrix mem brane. In order to understand their interaction with each ether and wi th membrane matrices, permeabilities and selectivities of CO2/CH4, CO2 /Ar, and H-2/CH4 binaries as a function of gas composition were measur ed through a dense homogeneous PES membrane and a PES-4A mixed matrix membrane. Observed selectivity independence with respect to gas compos ition for a dense homogeneous PES membrane indicates that ternary inte ractions and factors like plasticization and gas fugacity do not affec t the gas permeation mechanism appreciably for this type of membrane. However, selectivities demonstrated a strong concentration dependency through a PES-4A mixed matrix membrane. For CO2/CH4 and CO2/Ar systems , when the CO2 concentration in the feed increased, selectivity decrea sed linearly. In the case of H-2/CH4 binaries, unlike the cases with C O2 binaries, a higher H-2 concentration in the feed caused higher sele ctivity values, The trend was also linear with H-2 concentration in th e feed. This indicates that. for mixed matrix membranes, the existence of a third component causes the gas molecules to interact with the he terogeneous membrane matrix, affecting selectivities. Selectivity depe ndency indicates the importance of gas-membrane matrix and gas-gas-mem brane matrix interactions.