Pebax®/TSIL blend thin film composite membranes for CO2 separation

In this study a thin film composite (TFC) membrane with a Pebax/Task-specific ionic liquid (TSIL) blend selective layer was prepared. Defect-free Pebax/TSIL layers were coated successfully on a polysulfone ultrafiltration porous support with a polydimethylsiloxane (PDMS) gutter layer. Different parameters in the membrane preparation (e.g. concentration, coating time) were investigated and optimized. The morphology of the membranes was studied by scanning electron microscopy (SEM), while the thermal properties and chemical structures of the membrane materials were investigated by thermo-gravimetric analyzer (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The CO2 separation performance of the membrane was evaluated using a mixed gas permeation test. Experimental results show that the incorporation of TSIL into the Pebax matrix can significantly increase both CO2 permeance and CO2/N-2 selectivity. With the presence of water vapor, the membrane exhibits the best CO2/N-2 selectivity at a relative humidity of around 75%, where a CO2 permeance of around 500 GPU and a CO2/N-2 selectivity of 46 were documented. A further increase in the relative humidity resulted in higher CO2 permeance but decreased CO2/N-2 selectivity. Experiments also show that CO2 permeance decreases with a CO2 partial pressure increase, which is considered a characteristic in facilitated transport membranes.