Liquid–Liquid Phase Equilibrium and Heat Capacity of Binary Mixture 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide + 1-Propanol

Abstract

The measurements of the liquid−liquid coexistence curve and the heat capacity for binary mixture {1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C 2 mim][NTf 2 ]) + 1-propanol} have been precisely performed. The values of the critical exponents α and β in the critical region were obtained and coincided well with the 3D-Ising ones. The complete scaling theory was applied to well represent the asymmetric behavior of the diameter of the coexistence curve, indicating an important role of the heat capacity related term in the complete scaling formulizm. A comparison of the reduced critical parameters to those predicted by the restricted primitive model clearly showed the solvophobic criticality of the studied system. ■ INTRODUCTIONBecause room temperature ionic liquids (RTILs) are characterized by high stability, high conductivity, low volatility, large heat capacity, and good dissolving ability, 1−4 they have received much attention in both fundamental studies and practical applications in recent decades. 5,6 Especially, RTILs as one kind of green solvents have replaced traditional solvents in many chemical engineering applications. Mixed RTILs/organic solvents have been used as a chemical reaction media to facilitate the separation of the products, the solvent, and the catalyst by varying the temperature or composition in the media. 7 Therefore, the detailed knowledge of liquid−liquid phase equilibrium of solutions containing RTILs is highly desired. 8 Whether the critical behavior of ionic fluids belongs to the Ising universality class was a core problem of ionic fluids criticality. 9−11 Nowadays, it is clear that the liquid−liquid phase transition of ionic solutions exhibits 3D-Ising behavior, which has been confirmed by many experimental studies and simulations by using a simple model called the restricted primitive model (RPM) for ionic fluids. 8−20 It was pointed out that, for ILs solutions with low permittivity organic solvents, the phase transition observed at ambient temperature might be driven by the Coulombic interaction, while with high permittivity solvents, the phase transition was considered to be driven by a solvophobic mechanism. 20 It was found that some IL solutions showed a crossover from the solvophobic character to the Coulombic one, and the solvophobic character of a mixture was usually accompanied by larger critical amplitudes related to the coexistence curve and the heat capacity, 14 and a special bending character of the diameter of the coexistence curve as compared to the Coulombic character.In recent years, Anisimov and co-workers 21−23 extended the complete scaling theory 24−26 to incompressible and weakly compressible liquid mixtures, which pointed out that scaling fields should be the linear mixtures of all physical fields: the chemical potential of solvent μ 1 , the difference of chemical potential between solvent and solute Δμ, the temperature T, and the pressure P. The complete scaling theory has been verified by some experiments on binary molecular liquid mixtures; ...

Effects of self-hydrogen bonding among formamide molecules on the UCST-type liquid–liquid phase separation of binary solutions with imidazolium-based ionic liquid, [Cnmim][TFSI], studied by NMR, IR, MD simulations, and SANS

“…This is the same as for other imidazolium-based IL systems at their UCST mole fraction, i.e. , [C 8 mim][TFSI]–1,4-DIO, 1 [C 2 mim][TFSI]−1-propanol 85 and [C 2 mim][TFSI]−1-butanol, 41 and [C 6 mim][TFSI]−bromobenzene. 86 By contrast, the [C 6 mim][TFSI]–FA- d 2 solution at the mole fractions far from the UCST x FA- d 2 separates upon cooling via the mean-field mechanism.…”

Analysis of thermophysical properties of binary systems containing ethyl acetate and 1-propanol or 1-butanol

“…The lines are a guide to the eye. [44], () [45], () [46], () [47], () [48], () [49], () [50], () [51], () [52], () [53], () [54], () [55], () [56], () [57], () [58], () [59], () [60], () [61], () [62], () [63], () [64], () [65], () [66], () [67], () [68], () [69], () [70], () [71], () [72], () [73], () [74], () [75], () [76], () [77], () [78], () [79], () [80], () [81], () [82], () [83], () [84], () [85], () [86], () [87], () [88], () [89], () [90], () [91], () [92]...…”

The heat capacities and critical behaviors of binary ionic solutions

“…19 Table 5 lists the critical reduced temperatures and the critical reduced densities for the binary ionic liquid solutions determined in this study and reported previously. [21][22][23][24]26,27,32,33,[39][40][41][42][43] The Monte Carlo simulation predicted the RPM values of the ionic solutions to be 0.08 and 0.05 for r c * and T c *, respectively, regardless of e r,c and s. 11 However, the experiments exhibited that the values of T c * and r c * of the ionic solutions generally increased with the e r,c of their solvents. This is attributed to the fact that the solvophobic interactions become important and visible as the coulometric force was screened.…”