Separation of Small Paraffin-Olefin Mixtures With An Ionic Liquid: Thermodynamic Study Using COSMO-RS

Ionic liquids are nonvolatile solvents with desirable properties to be potential candidates for separation processes. The physicochemical properties of ILs can be tuned by different cation - anion combinations. In this paper, we use COSMO-RS to select the most promising ILs for the paraffin/olefin separation. We simulate the IL in two ways: [CA] and [C+A]. We estimate Henry’s constant of ethane, ethylene, propane, propylene, butane, butene, pentane, pentene, hexane and hexene using [C+A] COSMO model. We compared our calculations with some experiments reported in literature. The paraffin or olefin solubility in the IL is higher as increasing in the long chain of the hydrocarbon. We calculate the relative volatility and the selectivity of ethane/ethylene, propane/propylene and butane/butene. Because the [C+A] COSMO predictions overestimate the experiments, we consider the [CA] COSMO model. [CA] model deviations are smaller than those of [C+A]. Finally, from a thermodynamically point of view, we propose new promising IL for capturing ethane, propane, and butane from ethylene, propylene and butene respectively.