Novel MMM using CO2 selective SSZ-16 and high-performance 6FDA-polyimide for CO2/CH4 separation

The development, characterization, and CO2/CH4 separation properties of a new mixed matrix membrane (MMM), comprises of 6FDA-DAM:DABA and small pore zeolite SSZ-16 were investigated. The MMMs were prepared with different zeolite loadings to study the filler content effects on the membrane physical and gas transport properties. Consequently, their gas separation performances were investigated at several transmembrane pressures (2, 4, 6 and 8 bar) using different binary feed gas compositions (25/75, 50/50, 75/25 vol.% of CO2/CH4) at 25 degrees C. Besides improving the membrane physical properties, SSZ-16 addition is proven to enhance the gas separation performance effectively. The MMM with 5 wt.% SSZ-16 presents an excellent filler dispersion and increased CO2 permeability by almost 2-fold while maintaining its high CO2/CH4 selectivity, with respect to the unfilled membrane (P-CO2 = 199.4 Barrer; alpha(CO2/CH4) = 35.9). Higher filler loadings show slightly lower permeability, indicating a possible polymer rigidification in the filler-polymer region. Most importantly, MMM with the highest loading presents selectivity drop by similar to 50% due to defective polymer-filler interfaces, which directly increased the CH4 permeability, concluding SSZ-16 addition is able to achieve the ideal MMM improvement only at low loadings. All the findings concerning different feed composition and transmembrane pressures are presented and discussed accordingly.