(Liquid + liquid) equilibria for ternary mixtures of (methanol or ethanol + toluene or m-xylene + n-dodecane)

https://doi.org/10.1016/j.jct.2005.04.004Get rights and content

Abstract

(Liquid + liquid) equilibrium (LLE) results for the ternary mixtures of (methanol or ethanol + toluene or m-xylene + n-dodecane) at three temperatures (298.15, 303.15 and 313.15) K are reported. The compositions of liquid phases at equilibrium were determined by g.l.c. measurements and the results were correlated with the UNIQUAC and NRTL activity coefficient models. The partition coefficients and the selectivity factor of methanol and ethanol are calculated and compared to suggest which alcohol is more suitable for extracting the aromatic hydrocarbons (toluene or m-xylene) from n-dodecane. The phase diagrams for the ternary mixtures including both the experimental and correlated tie lines are presented. From the phase diagrams and the selectivity factors it is concluded that methanol has a higher efficiency as a solvent in extraction of aromatic hydrocarbon from alkane mixtures.

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 xis and xia 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]:S=(x2/x3)s/(x2/x3)a,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

References (20)

  • K. Tamura et al.

    Fluid Phase Equilib.

    (2000)
  • D.B. Won et al.

    Fluid Phase Equilib.

    (2002)
  • H. Matsuda et al.

    Fluid Phase Equilib.

    (2004)
  • R. Rappel et al.

    Fluid Phase Equilib.

    (2002)
  • S.H. Ali et al.

    Fluid Phase Equilib.

    (2003)
  • A. Tiryaki et al.

    Fluid Phase Equilib.

    (1994)
  • M.B. Gramajo de Doz et al.

    Fluid Phase Equilib.

    (2003)
  • M. Mohsen-Nia, H. Modarress, F. Doulabi, H. Bagheri, J. Chem. Thermodyn., in...
  • G.R. Vakili-Nezhaad et al.

    J. Chem. Thermodyn.

    (2004)
  • A.A.S. Taher et al.

    Fluid Phase Equilib.

    (1996)
There are more references available in the full text version of this article.

Cited by (11)

  • Effect of linear alcohol molecular size on the self-assembly of fullerene whiskers

    2011, Materials Chemistry and Physics
    Citation Excerpt :

    This is supported by the work of Geng et al. who demonstrated that fullerene nano-wires assembled upon solvent evaporation of C60 solutions in 1,2,4-trimethylbenzene (TMB) still has solvent molecules as part of their structure and that the solvent has a novel role to play in the regulation of the molecular packing process that leads to the observed structure [29]. Thermodynamic studies addressing the interaction between linear alcohols and toluene [44–46] showed that such interaction increases as the “n” in H(CH2)nOH is decreased. Namely toluene/alcohol interaction was found to be highest for methanol, lower for ethanol, and lowest for isopropyl alcohol as reflected by their interaction parameters (a12 in the extended UNIQUAC model; −115, −84, and −46 for the methanol, ethanol, and propanol, respectively) [46].

View all citing articles on Scopus
View full text