Solubility of CO2 in pyridinium based ionic liquids

The solubility of CO2 in six pyridinium based ionic liquids 1-butylpyridinium bis(trifluoromethylsulfonyl)imide [C4py][Tf2N], 1-octylpyridinium bis(trifluoromethylsulfonyl)imide [C8py][Tf2N], 1-decylpyridinium bis(trifluoromethylsulfonyl)imide [C10py][Tf2N], 1-dodecylpyridinium bis(trifluoromethylsulfonyl)imide [C12py][Tf2N], 1-butylpyridinium trifluoroacetate [C4py][TfAc] and 1-butylpyridinium dicyanamide [C4py][Dca] was measured at temperatures of 298.15 K, 313.15 K and 333.15 K and in the pressure range from 0.25 bar to 10 bar. The results showed that the solubility of CO2 increase with increasing pressure and decrease with increasing temperature. The solubility of CO2 in this six ionic liquids at 298.15 K was in the sequence of [C12py][Tf2N] > [C10py][Tf2N] > [C8py][Tf2N] > [C4py][Tf2N] > [C4py][TfAc] > [C4py][Dca]. The Henry's law constants, partial molar enthalpy and partial molar entropy of dissolution of CO2 gas in these ionic liquids, were also estimated. The regeneration and recyclability studies of [C4py][Tf2N] proved their thermal and physical stability for commercial applications.

► Low cost pyridinium based ionic liquids were used to study their capability for CO2 absorption. ► The effect of anion and the alkyl chain length have been discussed. ► Henry's constant, enthalpy and entropy of CO2 dissolution in the ionic liquids were estimated.