Solubility of carbon dioxide and methane in 1-hexyl-3-methylimidazolium nitrate ionic liquid, experimental and thermodynamic modeling

Experimental data for solubility of CO2 and CH4 in 1-hexyl-3-methylimidazolium nitrate [Hmim][NO3] at temperature range of 293.15-343.15 K and pressure up to 4 MPa are reported. The solubility of CO2 is higher than that of CH4 in the entire temperature region studied. The experimental data show that the temperature has a little effect on CH4 solubility. The Henry's constant of both gas in [Hmim][NO3] are calculated and the ideal selectivity of CO2 to CH4 are reported. The ideal selectivity is increased with temperature reduction. The experimental data for CO2 solubility are compared with other types of nitrate based ionic liquids (ILs) at different temperatures and pressure. The results of this comparison reveal that the solubility of CO2 is increased with enlargement the alkyl chain length of IL cation. The experimental data are correlated with the extended Henry's law model. The virial expansion model of Pitzer is used for interpretation of the activity coefficient of the gases and the interaction parameters of the model are estimated as a function of temperature.