(Liquid + liquid) equilibria for ternary mixtures of (methanol or ethanol + toluene or m-xylene + n-dodecane)
Introduction
The separation of aromatic hydrocarbons from alkanes by (liquid + liquid) extraction has been an area of active research [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. The search for suitability of new solvents, from practical and economical aspects, in (liquid + liquid) extraction is an ongoing investigation. In this line of research, the experimental measurement of (liquid + liquid) equilibria (LLE) for (furfuryl alcohol + an aromatic hydrocarbon + an alkane) [14], (N-methyl-2-pyrrolidone + an aromatic hydrocarbon + an alkane) [15], (furfural + an aromatic hydrocarbon + an alkane)[16] and (two hydrocarbons + an alcohol + water) [17] can be mentioned.
In the previous work, we reported the LLE results for the mixtures (tetramethylene sulfone or dimethyl solfoxide or ethylene carbonate + toluene or m-xylene + n-heptane or n-octane or cyclohexane) at different temperatures (298.15, 303.15 and 313.15) K and the results were correlated by the UNIQUAC and NRTL activity coefficient models. On the basis of this work, it was suggested that ethylene carbonate as a solvent was more suitable than tetramethylene sulfone or dimethyl solfoxide for extracting the aromatic hydrocarbon from alkane mixtures.
In this work, we report the LLE results for the mixtures solvent alcohol (1) + aromatic hydrocarbon (2) + alkane (3) at three temperatures 298.15 K to 313.15 K. Where the solvent is methanol or ethanol and the aromatic hydrocarbon is toluene or m-xylene and the alkane is n-dodecane.
Methanol and ethanol may be considered as the most widely used solvents in the recovery of aromatics, such as toluene and m-xylene from refinery process streams. Unfortunately, the experimental data on extraction of aromatic hydrocarbon by alcohols, such as methanol and ethanol, are scarce. Therefore, it is worthwhile to study the LLE of ternary mixtures of (methanol or ethanol + toluene or m-xylene + alkanes). The results of this study can lead to decide which alcohol methanol or ethanol has higher selectivity factor and is more suitable for solvent extraction of aromatic hydrocarbon from alkanes.
Section snippets
Experimental
Pure grade compounds, methanol, ethanol, n-dodecane, toluene, m-xylene were supplied by Merck Co. Inc., Germany. However, the purity of each compound was checked by gas chromatography, and the results confirmed the mass fraction purity was higher than 0.99.
The experimental procedure was described in the previous work [1]. Only the operating conditions of g.l.c. measurements were different which is given in table 1.
Results and discussion
The mole fractions and of constituent i, respectively, in the solvent alcohol (s) rich-phase and alkane (a) rich-phase for the studied ternary mixtures are reported in table 2. The effectiveness of extraction of the aromatic hydrocarbon (2) by the solvents (s) methanol or ethanol is given by the selectivity (S), as a measure of the ability of solvent to separate aromatic hydrocarbon from alkanes by the following equation [18]:where the (x2/x3)s is the ratio of
Conclusions
(Liquid + liquid) equilibrium data of the ternary mixtures {solvent alcohol (1) + aromatic hydrocarbon (2) + alkane (3)} were presented at different temperatures. The NRTL and UNIQUAC models were used to correlate the experimental results and to calculate the phase compositions of the studied mixtures. The selectivity and distribution coefficient of the used solvents were compared in studied ternary mixtures. In extraction of aromatics from non-aromatics the solvent with the higher selectivity and
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