2019 AIChE Annual Meeting

(230d) Effect of CO2 Pressure on the Viscosity of 1?Alkyl-1-Methylpyrrolidinium Bis(tri?uoromethylsulfonyl)Imide Ionic Liquids

Authors

Morais, A. R. C. - Presenter, University of Kansas
Baek, D. L., Idaho National Laboratory
Fox, R. V., Idaho National Laboratory
Scurto, A., University of Kansas
The effect of CO2 pressure on the viscosity of pyrrolidinium-based ionic liquids (ILs) were measured using a high-pressure viscometer at various temperatures (298.15, 318.15, and 338.15 K). The high-pressure viscosities of 1-propyl-1-methylpyrrolidinium ([C3C1Pyr]), 1-butyl-1-methylpyrrolidinium ([C4C1Pyr]), and 1-hexyl-1-methylpyrrolidinium ([C6C1Pyr]) cations with a common anion, bis(trifluoromethylsulfonyl)imide ([NTf2]), were measured up to 25 MPa of CO2 pressure. The viscosities of the IL/CO2 mixtures dramatically decrease with increasing CO2 pressure up to approximately 7 MPa, beyond which the reduction becomes marginal. This is due to the vapor−liquid equilibrium (CO2 solubility in IL) of the IL/CO2 system. The viscosity reduction is more significant at lower temperatures because of the higher CO2 solubility under those conditions. The effects of cation alkyl chain length on the viscosities of IL/CO2 mixtures were also measured. Though the pure [CnC1Pyr][NTf2] viscosities increase significantly with increasing alkyl chain length of the cation, the viscosities of the IL/CO2 mixtures are similar at higher CO2 pressures (composition).