Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The viscosity of mixtures of pyrrolidinium-based ionic liquids saturated with compressed CO2 was measured using a high-pressure viscometer at three different temperatures (298.15, 318.15 and 338.15 K). The high-pressure viscosity of 1-propyl-1-methyl-pyrrolidinium ([C3C1pyr]), 1-butyl-1-methyl-pyrrolidinium ([C4C1pyr]), and 1-hexyl-1-methyl- pyrrolidinium bis(trifluoromethylsulfonyl)imide ([C6C1pyr]) cations with common anion, bis(trifluoromethylsulfonyl)imide ([NTf2]), was measured up to a maximum CO2 pressure of 25 MPa. This viscosity ranged from 3.3 to 98.3 mPa.s. The viscosity of the ionic liquid/ CO2 mixture dramatically decreases with increasing of CO2 pressure up to approximately 7 MPa beyond which the viscosity decrease becomes more marginal. This is due to the vapor-liquid equilibrium (CO2 solubility) of the IL/CO2 system. The viscosity decrease at lower temperatures is more significant due to the higher CO2 solubility. The effect of alkyl chain length of the cation on the viscosity of ionic liquid/ CO2 mixture was also measured. Though the pure [CnC1pyr][NTf2] viscosity increases significantly with the increasing alkyl chain length of the cation, the viscosity of the ionic liquid/CO2 mixtures become quite similar at higher CO2 pressures (composition).