Hydrocarbon solubility, permeability, and competitive sorption effects in polymer of intrinsic microporosity (PIM-1) membranes

The sorption and permeation of pentane, hexane, and toluene through highly permeable polymer of intrinsic microporosity (PIM-1) membranes were investigated. It was established that the hydrocarbons sorbed strongly within the micro-void regions of the PIM-1 membrane. The sorption concentration was similar for the paraffins, pentane and hexane, but greater for aromatic toluene at high vapor activities. The magnitude of the hydrocarbon permeability was associated with the critical temperature of the hydrocarbon. The PIM-1 membrane displayed selectivity for the three hydrocarbons over CO2. As a consequence, the presence of the three hydrocarbons dramatically reduced the permeability of CO2 and N-2 under mixed gas-vapor conditions to 68%-95% below the dry gas value. For all three hydrocarbons the N-2 permeability was more strongly impacted than CO2 permeability, and hence the ideal CO2/N-2 selectivity of PIM-1 increased. It was determined that CO2 and N-2 solubility decreased because of hydrocarbon competitive sorption while CO2 and N-2 diffusivity also decreased because of anti-plasticization, which was due to the presence of hydrocarbon clusters within the membrane structure. There was a clear correlation between the magnitude of anti-plasticization and the critical temperature of the hydrocarbon. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 397-404