Design of Ionic Liquids for Fluorinated Gas Absorption: COSMO-RS Selection and Solubility Experiments

In recent years, the fight against climate change and them itigation of the impact offluorinated gases (F-gases) on the atmosphere is aglobal concern. Development of technologies that help to efficiently separateand recycle hydrofluorocarbons (HFCs) at the end of the refrigeration andair conditioning equipment life is a priority. The technological developmentis important to stimulate the F-gas capture, specifically difluoromethane (R-32) and 1,1,1,2-tetrafluoroethane (R-134a), due to their high global warmingpotential. In this work, the COSMO-RS method is used to analyze thesolute-solvent interactions and to determine Henry's constants of R-32 andR-134a in more than 600 ionic liquids. The three most performant ionicliquids were selected on the basis of COSMO-RS calculations, and F-gasabsorption equilibrium isotherms were measured using gravimetric and volumetric methods. Experimental results are in goodagreement with COSMO-RS predictions, with the ionic liquid tributyl(ethyl)phosphonium diethyl phosphate, [P2444][C2C2PO4],being the salt presenting the highest absorption capacities in molar and mass units compared to salts previously tested. The othertwo ionic liquids selected, trihexyltetradecylphosphonium glycinate, [P66614][C2NO2], and trihexyl(tetradecyl)phosphonium 2-cyano-pyrrole, [P66614][CNPyr], may be competitive as far as their absorption capacities are concerned. Future works will be guidedon evaluating the performance of these ionic liquids at an industrial scale by means of process simulations, in order to elucidate therole in process efficiency of other relevant absorbent properties such as viscosity, molar weight, or specific heat