Carbon dioxide/ethane mixed-gas sorption and dilation in a cross-linked poly(ethylene oxide) copolymer

Mixed-gas CO2/C2H6 sorption and dilation in a cross-linked poly(ethylene oxide) copolymer were studied at temperatures ranging from −20 to 35 °C. The polymer was prepared by photopolymerization of a solution containing 70 wt.% poly(ethylene glycol) methyl ether acrylate (PEGMEA) and 30 wt.% poly(ethylene glycol) diacrylate (PEGDA). Four different gas mixtures (10, 25, 50 and 70 mol% CO2) were considered at operating pressures up to 21 atm. At a given temperature, polymer dilation increased with pressure and CO2 content. Compared to pure-gas values, CO2 solubility was higher in the presence of ethane, an effect whose extent increased with decreasing temperature. Ethane solubility in the polymer also increased in the presence of CO2 compared to the pure-gas value at T ≥ 25 °C. However, at T ≤ 0 °C, the presence of carbon dioxide initially reduced ethane solubility. As the fugacity of CO2 in the mixture increased and the polymer dilated, ethane solubility progressively increased, eventually surpassing the pure-gas value. The multicomponent Flory–Huggins model could describe the pure- and mixed-gas data simultaneously, provided that an empirical composition dependence was included in the interaction parameters for T < 25 °C.