Activity coefficients at infinite dilution measurements for organic solutes in the ionic liquid 1-butyl-3-methyl-imidazolium 2-(2-methoxyethoxy) ethyl sulfate using g.l.c. at T = (298.15, 303.15, and 308.15) K
Introduction
Activity coefficients at infinite dilution, (where 1 refers to the solute and 3 to the solvent), provide a useful tool for solvent selection in extractive distillation or solvent extraction processes. It is sufficient to know the separation factor at infinite dilution, of the components to be separated, in order to determine the applicability of a compound (in this work, a new ionic liquid) as a selective solvent. This work is a continuation of our investigation on ionic liquids to determine activity coefficients at infinite dilution. Our group has previously measured the for organic volatile solutes in the ionic solvents: 1-methyl-3-octyl-imidazolium chloride [1], 1-hexyl-3-methyl-imidazolium tetrafluoroborate [2], 1-hexyl-3-methyl-imidazolium hexafluorophosphate [3] and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) imide [4].
Ionic liquids (ILs) are under intense investigation, especially as replacement solvents for reaction and separations, since they exhibit negligible vapor pressure and would not, therefore, contribute to air pollution. ILs are salts that are liquid at low temperatures, which can be as low as room temperature [5].
The activity coefficients at infinite dilution, , have been determined for alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, aromatic hydrocarbons, carbon tetrachloride and methanol in the ionic liquid 1-butyl-3-methyl-imidazolium 2-(2-methoxyethoxy) ethyl sulfate, [BMIM][MDEGSO4], using gas-liquid chromatography at the temperatures T = (298.15, 303.15, and 308.15) K. The formula of anion of 1-butyl-3-methyl-imidazolium 2-(2-methoxyethoxy) ethyl sulfate is:The selectivity is the ratio of activity coefficients at infinite dilution and is given by the equation , where i and j refer to the liquids to be separated and in this work refer to hexane and benzene, respectively. The selectivity value is used to determine the potential of the ionic solvent for extractive distillation in the separation of aromatic compounds from aliphatic compounds [6].
Gas-liquid chromatography is a well-established and accurate method that is used to obtain [7], [8]. The partial molar excess enthalpies at infinite dilution values, , were also calculated from the values obtained over the temperature range.
Section snippets
Materials or chemicals
The ionic liquid ECOENG™41M, [BMIM][MDEGSO4], had a purity of >0.98 mass fraction and was supplied by Solvent Innovation. The ionic liquid was further purified by subjecting the liquid to a very low pressure of about 5 × 10−3 Pa at room temperature for approximately 30 min. This procedure removed any volatile chemicals and water from the ionic liquid. A Karl–Fischer titration method using methanol showed that the water concentration in the ionic liquid was less than 0.001 mass percent. The solutes:
Theory
The equation developed by Everett [11] and Cruickshank et al. [12]was used in this work to calculate the of solutes in the ionic liquid. The VN denotes the net retention volume of the solute, Po the outlet pressure, the mean column pressure, n3 the number of moles of solvent on the column packing, the column temperature T, the saturated vapor pressure of the solute at temperature T, B11 the second virial coefficient of pure
Results and discussion
Table 3 lists the average values for the varying amounts of solvent on the solid packing at T = (298.15, 303.15, and 308.15) K. The value for the n-alkanes, alk-1-enes, alk-1-ynes and cycloalkanes increases with an increase in carbon number. FIGURE 1, FIGURE 2, FIGURE 3 show the natural logarithm of the activity coefficients in the ionic liquid as a function of the inverse absolute temperature for four alkanes, three alkynes and three cycloalkanes, respectively. For the small temperature
Acknowledgments
The authors thank the FRD (South Africa) and KBN (Poland) for financial support for this work according to Polish–South African agreement of co-operation.
References (20)
- et al.
J. Chem. Thermodyn.
(1993) - et al.
J. Chem. Thermodyn.
(1995) - et al.
J. Chem. Thermodyn.
(2002) - et al.
J. Chem. Thermodyn.
(2003) - et al.
J. Chem. Eng. Data
(2003) - et al.
J. Chem. Eng. Data
(2003) - et al.
J. Chem. Eng. Data
(2005) Kinet. Catal.
(1996)- D. Tiegs, J. Gmehling, A. Medina, M. Soares, J. Bastos, P. Alessi, I. Kikic, Activity Coefficients at Infinte Dilution,...
- et al.
Physicochemical measurements by gas chromatography
(1979)
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