The PolyActive™ thin film composite membrane (TFCM) has already been successfully applied for CO₂ separation tasks at feed pressures up to 10 bar. To investigate the applicability at higher pressures, measurements were undertaken with C₂H₄ containing gas mixtures with a composition comparable to the product stream of the oxidative coupling of methane process, as well as single gases up to a feed pressure of 30 bar. Furthermore, the permeances of the conducted gas mixture experiments were simulated. The results show a strong swelling influence of CO₂ on the used membrane depending on the CO₂ fugacity. This swelling effect leads to a pronounced decrease in selectivity. The observed membrane behavior at high pressures could not be predicted by the Free Volume Model (FVM). Two different simulations were conducted: one based on parameters calculated from single gas data measured at pressures up to 2 bar; and a second based on parameters calculated from single gas data measured at pressures from 2 to 30 bar. The two simulations differ in their prediction accuracy. However, they confirm that it is possible to predict the measured permeances in the pressure range up to an average CO₂ fugacity of 6 bar.
Keywords: CO2 separation; PolyActive™; gas permeation; oxidative coupling of methane; thin film composite membrane.