Propylene and Propane Solubility in Imidazolium, Pyridinium, and Tetralkylammonium Based Ionic Liquids Containing a Silver Salt

The gas solubility of propane and propylene in seven ionic liquids, 1-ethyl-3-methyl­imidazolium tetrafluoroborate (EMImBF₄), 1-hexyl-3-methyl­imidazolium tetrafluoroborate (HMImBF₄), 1-octyl-3-methyl­imidazolium tetrafluoroborate (OMImBF₄), 3-methyl­imidazolium nitrate (BMImNO₃), 1-butyl-3-methyl­imidazolium bis­(trifluoro­methyl­sulfonyl­imide) (BMImTf₂N), methyl­trioctyl­ammonium bis­(trifluoro­methyl­sulfonyl­imide) (MOOONTf₂N), and butyl­trimethyl­ammonium bis­(trifluoro­methyl­sulfonyl­imide) (BMMMN Tf₂N), is reported. The equilibrium isotherms of both pure gases were measured in the pure ionic liquids and in presence of a silver salt containing the same anion of the ionic liquid in a range of concentration of (0 to 0.77) mol·kg_IL^–1 at temperatures between (288 and 308) K and pressures ranging from (0 to 700) kPa. Henry’s law constant values for physical solubility as well as the characteristic parameters for chemical solubility such as chemical equilibrium constants and enthalpies of the chemical reactions between silver cations and propylene are reported. Based upon the experimental results, ionic liquids based on imidazolium cations with less and shorter alkyl substituents improve the selective separation of propylene from these mixtures. Regarding to the structure of the anion it was gathered that ionic liquids with the BF₄^– anion, combined with the AgBF₄ silver salt, provided the best results in terms of olefin capacity and selectivity. In this article we provide valuable data that evidence that the separation of propane/propylene gas mixtures by reactive absorption could represent an efficient alternative to the traditional separation process based on cryogenic distillation and serve for the new process design

Revealing the Charge Transport Mechanism in Polymerized Ionic Liquids: Insight from High Pressure Conductivity Studies

Polymerized ionic liquids (polyILs), composed mostly of organic ions covalently bonded to the polymer backbone and free counterions, are considered as ideal electrolytes for various electrochemical devices, including fuel cells, supercapacitors, and batteries. Despite large structural diversity of these systems, all of them reveal a universal but poorly understood feature: a charge transport faster than the segmental dynamics. To address this issue, we studied three novel polymer electrolyte membranes for fuel cells as well as four single-ion conductors, including highly conductive siloxane-based polyIL. Our ambient and high pressure studies revealed fundamental differences in the conducting properties of the examined systems. We demonstrate that the proposed methodology is a powerful tool to identify the charge transport mechanism in polyILs in general and thereby contribute to unraveling the microscopic nature of the decoupling phenomenon in these materials