Room temperature ionic liquid with silver salt as efficient reaction media for propylene/propane separation: Absorption equilibrium

In this study the selective absorption of propylene from their mixtures with propane by chemical complexation with silver ions in ionic liquid solutions has been performed. The solubilities of propylene and propane in the reactive medium, silver tetrafluoroborate dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate (silver salt concentration = 0.25 M), were investigated as functions of temperature and pressure. The temperature range was between 278 and 318 K for the absorption equilibrium data obtained. A simple mathematical model has been developed to describe the total propylene absorption in the reaction media under study, based in the formation of complexes with different stoichiometry, and the parameter model were obtained. It was found that gas solubilities increased with pressure and decrease with temperature of the system; this indicates that complex formation is an exothermic process and consequently the equilibrium constants will decrease with increasing temperature. Complete regeneration of the reaction media can be carried out at room temperature, 800 rpm stirrer speed and 20 mbar vacuum for 3 h. As conclusion, the recovery of the olefin (propylene) via silver complexation has been successfully carried out in ionic liquid media and, the ionic liquid containing silver ions showed higher sorption capacity for propylene than the corresponding aqueous solution. (C) 2008 Elsevier B.V. All rights reserved.