Direct measurement of the heat of solution and solubility of carbon dioxide in 1-hexyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide and 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide

► Heat of solution of carbon dioxide imidazolium based ionic liquids. ► High-pressure solubility measurements of carbon dioxide in ionic liquids. ► Experimental determination of the heat of solution of gases in liquids. ► pVT determination of the solubility of gases in ionic liquids at high pressure. We report the first direct experimental determination of the enthalpies of solution of carbon dioxide in ionic liquids 1-hexyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C6mim][NTf2]) and 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]) at 313.15K and pressures up to 5MPa. The experiments are based on the detection of heat of mixing of gas with ionic liquid using a flow calorimetric technique. For both ionic liquids, gas solubilities were derived from experimental calorimetric data and were compared with solubility data obtained by a newly designed high-pressure solubility measurement apparatus. Results of enthalpies of solution were compared to enthalpies derived from Henry's law constant, available in literature. The analysis of the data reported herein confirms the consistency between the direct determination of the heats of solution and their derivation from precise enough solubility data. Also it was proven that, within the experimental uncertainty, it is possible to derive reliable solubility data from the calorimetric experiments.