Influence of the Cation on the Solubility of CO2 and H2 in Ionic Liquids Based on the Bis(trifluoromethylsulfonyl)imide Anion

Experimental values for the solubility of carbon dioxide and hydrogen in three room temperature ionic liquids based on the same anion—(bistrifluoromethylsulfonyl)imide [Ntf2]—and three different cations—1-butyl-3-methylimidazolium, [C4mim], 1-ethyl-3-methylimidazolium, [C2mim] and trimethyl-butylammonium, [N4111]—are reported between 283 and 343 K and close to atmospheric pressure. Carbon dioxide, with a mole-fraction solubility of the order of 10−2, is two orders of magnitude more soluble than hydrogen. The solubility of CO2 is very similar in the three ionic liquids although slightly lower in the presence of the [C2mim] cation. In the case of H2, noticeable differences were observed with larger mole fraction solubilities in the presence of [N4111] followed by [C4mim]. All of the mole-fraction solubilities decrease with increasing temperature. From the variation of Henry’s law constants with temperature, the thermodynamic functions of solvation were calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry’s law constants from appropriate smoothing equations, is always better than ±1%.