The effect of cyano groups on the solubility of carbon dioxide in ionic liquids containing cyano groups in anion

The solubility of carbon dioxide (CO 2 ) was investigated using three ionic liquids containing different numbers of cyano groups in the anion, 1-hexyl-3-methylimidazolium tricyanomethanide ([c6mim][C(CN) 3 ]), 1-hexyl-3-methylimidazolium dicyanamide ([c 6 mim][N(CN) 2 ]), and 1-hexyl-3-methylimidazolium thiocyanate ([c 6 mim][SCN]). The CO 2 solubilities were determined by measuring the bubble point pressures of the CO 2 +ionic liquid mixtures at temperatures ranging from 303.15 to 373.15 K and pressure up to 105MPa. The experimental results showed that the solubilities of CO 2 in ionic liquids increased with pressure, decreased with temperature, and increased with the length of the alkyl chains in the cation. Furthermore, a higher CO 2 solubility was achieved in the ionic liquid with more cyano groups in the anion. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS), using the conventional van der Waals one fluid mixing rule and the modified Lydersen-Joback-Reid method. The average absolute deviation values of pressure (AAD-P) were 0.0658 for CO 2 +[c 6 mim][SCN], 0.0633 for CO 2 +[c 6 mim][N(CN) 2 ], and 0.0761 for CO 2 +[c 6 mim][C(CN) 3 ] system.