Equation of State Modeling of the Solubility of CO2/C2H6 Mixtures in 2 Cross-Linked Poly(ethylene oxide)

The solubility of gaseous mixtures of CO2 and C2H6 in cross-linked poly(ethylene oxide) (XLPEO) has been 11 modeled over a wide range of temperatures, pressures, and compositions with the Sanchez−Lacombe lattice fluid equation of 12 state (LF EoS). The model binary gas−polymer parameters have been determined from pure gas solubility data and kept 13 constant with temperature and composition. Multicomponent solubility is then calculated with no additional adjustable 14 parameters, using a fully predictive procedure. The LF EoS model describes well the mixed gas solubility behavior data over wide 15 ranges of temperature (from −20 to 35 °C), pressure (0−20 atm), and composition. The model also allows representation of the 16 solubility selectivity behavior of XLPEO at different conditions, permitting an a priori determination that ethane solubility is 17 significantly enhanced by the presence of CO2, with a consequent reduction in CO2/C2H6 solubility selectivity relative to the 18 pure gas value. In this regard, the behavior of this rubbery polymer is opposite that of many glassy systems, in which competitive 19 sorption is often dominant, and the solubility of the less soluble gas (i.e., C2H6 in this case) is decreased by the presence of CO2, 20 and the CO2 solubility selectivity is enhanced with respect to the pure gas value.