| Abstract: | Mixed matrix membranes (MMMs) of polyimide (PI) and zeolite 13X, ZSM-5 and 4A were prepared by a solution-casting procedure. The effect of zeolite loading, pore size, and hydrophilicity/hydrophobicity of zeolite on the gas separation properties of these mixed matrix membranes were studied. Experimental results indicate that permeability of He, H2, CO2, and N2 increased with zeolite loadings. Selectivity of H2/N2 shows a slight improvement for low loadings of zeolites 13X and ZSM-5 but has a decreasing trend for zeolite 4A and high loadings of zeolites 13X and ZSM-5. In addition, selectivity of H2/CO2 remains low (1–3) while selectivity of CO2/N2 is significantly improved with the incorporation of the three zeolites in the polyimide membrane. Experimental permeabilities are higher than those predicted by the Maxwell model except for H2 and N2 permeabilities of the PI-4A system which are consistent with the predicted permeabilities. The proposed modified Maxwell model is capable of predicting the permeabilities of polyimide-zeolite 4A MMMs, but fails to simulate the permeability increase induced by interface voids in the polyimide-zeolite 13X and ZSM-5 systems. |
