Two articles featuring Mark Shiflett and his research team and collaborators:
Article Title 1: “High-Pressure Vapor−Liquid Equilibria of 1-Alkyl-1-Methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids and CO2” Article Title 2: “Viscosity of 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Saturated with Compressed CO2”
The high-pressure vapor–liquid equilibrium for the binary systems of carbon dioxide (CO2) and a series of 1-alkyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids ([CnC1pyr][NTf2] (n = 3,4,6)) are reported at 298.15, 318.15, and 338.15 K and at pressures of up to 20 MPa. Experiments were conducted using gravimetric (IGA and XEMIS microbalances) and volumetric (high-pressure view cell) methods. The solubility of CO2 in pyrrolidinium ionic liquids increases with decreasing temperature and increasing pressure. The CO2 solubility also slightly increases with increases in alkyl chain length on the pyrrolidinium cation. The molar volume and volume expansion of CO2 + IL mixtures are also reported. The Fickian diffusion of CO2 in pyrrolidinium-based ionic liquids (∼10–10 m2·s–1) was calculated at pressures of up to 2 MPa and found to be slightly lower than the diffusivity of CO2 in an imidazolium-based ionic liquid with the [NTf2] anion.
Tugba Turnaoglu, David L. Minnick, Ana Rita C. Morais, Donna L. Baek, Robert V. Fox, Aaron M. Scurto, and Mark B. Shiflett. High-Pressure Vapor−Liquid Equilibria of 1-Alkyl-1-Methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids and CO2. Journal of Chemical & Engineering Data 2019 64 (11), 4668-4678
The viscosities of mixtures of pyrrolidinium-based ionic liquids saturated with compressed CO2 were measured using a high-pressure viscometer at three different 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 a maximum CO2 pressure of 25 MPa. These viscosities ranged from 3.3 to 98.3 mPa·s. The viscosities of the ionic liquid/CO2 mixtures dramatically decrease with increasing 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 because of the higher CO2 solubility. The effect of the alkyl chain length of the cation on the viscosity of ionic liquid/CO2 mixtures was also measured. Though the pure [CnC1Pyr][NTf2] viscosities increase significantly with increasing alkyl chain length of the cation, the viscosities of the ionic liquid/CO2 mixtures become quite similar at higher CO2 pressures (composition).
Ana Rita C. Morais, Luis M. Alaras, Donna L. Baek, Robert V. Fox, Mark B. Shiflett, and Aaron M. Scurto. Viscosity of 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Saturated with Compressed CO2. Journal of Chemical & Engineering Data, 2019, 64 (11), 4658-4667