Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
pubs.acs.org/jced
Measurement and Correlation of High-Pressure Densities and Atmospheric Viscosities of Ionic Liquids: 1‑Butyl-1methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide), 1‑Allyl-3methylimidazolium Bis(trifluoromethylsulfonyl)imide, 1‑Ethyl-3methylimidazolium Tetracyanoborate, and 1-Hexyl-3methylimidazolium Tetracyanoborate Yuya Hiraga,† Saki Hagiwara,‡ Yoshiyuki Sato,† and Richard L. Smith, Jr.*,†,‡ †
Research Center of Supercritical Fluid Technology, ‡Graduate School of Environmental Studies, Tohoku University, Aramaki Aza Aoba 6-6-11, Aoba-ku, Sendai 980-8579, Japan S Supporting Information *
ABSTRACT: Four ionic liquids, [bmpyr][Tf2N] (1-butyl-1methylpyrrolidinium bis(trifluoromethylsulfonyl)imide), [ a m i m ] [ T f 2 N ] (1 - a l l y l - 3- m e t h y l i m i d a z o l i u m b i s (trifluoromethylsulfonyl)imide), [emim][TCB] (1-ethyl-3methylimidazolium tetracyanoborate), and [hmim][TCB] (1hexyl-3-methylimidazolium tetracyanoborate), were studied. High-pressure densities were measured at pressures up to 200 MPa and at temperatures of 312−433 K. Densities and viscosities at atmospheric pressure were measured over a temperature range of 293 to 373 K, and average relative deviation (ARD) of correlation with Vogel−Fulcher−Tammann equation for viscosity were within 0.08%. Correlation of the density data with the Tait equation could be obtained to within 0.02% ARD. Isobaric expansivities calculated from the Tait equation were constant or decreased slightly with increasing temperature in accordance with trends commonly reported for ionic liquids. Parameters for the ε*-modified Sanchez−Lacombe equation of state are tabulated that allow correlation of the ionicliquid high-pressure densities to within an ARD of less than 0.08%.
1. INTRODUCTION
Besides gas separation systems, ionic liquids that can dissolve considerable amounts of CO2 have applications in mixed ionic liquid systems for processing biomass since they can be used to reduce the viscosity of the mixture10 or they can be used to increase the hydrogen solubility.11 In our previous work, the effect of [bmim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) was assessed against biomasssoluble ionic liquids, [bmim]Cl (1-butyl-3-methylimidazolium chloride), by measuring physical properties such as density, viscosity12 and CO2 solubility.13 Viscosity of [bmim]Cl was decreased drastically with increasing concentration of [bmim][Tf2N], and CO2 solubility in [bmim]Cl was enhanced by [bmim][Tf2N] although only a small synergistic effect was found. Therefore, [TCB] types ionic liquids are also expected to be applicable as an auxiliary solvent for biomass-soluble ionic liquids.
Ionic liquids (ILs) are being proposed as solvents for reactions and separations due to their low volatility and the ease at which their properties can be selected by changing their cation or anion constituents.1 For gas separations, ionic liquids having bulky groups, such as [Tf2N] (bis(trifluoromethylsulfonyl)imide), have been shown to have high affinity for CO2.2 Ionic liquids having [TCB] ([B(CN)4], tetracyanoborate) anion are comparable to [Tf2N]-type ionic liquids in terms of their capacity for absorbing CO2.3−9 There have been two papers that report CO2 solubilities in [hmim][TCB] (1-hexyl-3methylimidazolium tetracyanoborate)3 and [emim][TCB] (1ethyl-3-methylimidazolium tetracyanoborate).4 On the other hand, computational chemistry has been used for understanding the mechanism of high CO2 solubility of [TCB] type ionic liquids. Babarao et al.9 used classical molecular dynamics simulation to show that [emim][TCB] (1-ethyl-3-methylimidazolium tetracyanoborate) has weaker interactions between the cation and anion than [Tf2N] type ionic liquids. The cation−anion interaction was proposed as being the important characteristic that affected CO2 solubility in an ionic liquid. © XXXX American Chemical Society
Special Issue: In Honor of Cor Peters Received: August 30, 2017 Accepted: December 21, 2017
A
DOI: 10.1021/acs.jced.7b00773 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Table 1. Purities of Ionic Liquids Used in This Work and Their Pretreatment water contentf atmospheric measurements ionic liquida [bmpyr][Tf2N] [amim][Tf2N] [emim][TCB] [hmim][TCB]
CAS No. 223437-11-4 655249-87-9 742099-80-5 1240857-50-4
source Io-li-tec Kanto Chemical Merck Merck
purityb
HCd 106wHC
>0.995 c
>0.995 0.989
