(Liquid + liquid) equilibria of the quaternary system methanol + isooctane + cyclohexane + benzene at T = 303.15 K

doi:10.1016/j.fluid.2009.10.007

Fluid Phase Equilibria

Volume 289, Issue 1, 25 February 2010, Pages 15-19

https://doi.org/10.1016/j.fluid.2009.10.007 Get rights and content

Abstract

Tie line data of the ternary system {methanol + isooctane + cyclohexane} were obtained at T = 303.15 K. A quaternary system containing these three compounds and benzene was also studied at the same temperature, while data for {methanol + benzene + cyclohexane} and {methanol + benzene + isooctane} were taken from literature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several cyclohexane/isooctane ratios were studied. The distribution of benzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equations and compared with predictions using the UNIFAC group contribution method.

Introduction

There are increasing demands for the use of oxygenated compounds to produce lead-free gasoline. For this reason we are studying the phase equilibrium of systems containing hydrocarbons (benzene, isooctane, toluene, or cyclohexane) and oxygenated compounds (methanol, ethanol, or methyl tert-butyl ether) [1], [2], [3], [4], [5], [6].

Because of its physical and chemical properties, methanol is a good candidate for an oxygenated fuel additive. However, methanol presents partial miscibility with aliphatic hydrocarbons, but not with aromatic hydrocarbons. Therefore, it is of great importance to study systems composed by methanol and representative hydrocarbon components of gasoline, establishing the concentration ranges of hydrocarbons and methanol in which the two-phase region does not exist [7].

Having this in mind, (liquid + liquid) equilibrium (LLE) measurements of the quaternary system ${w_{1} methanol + w_{2} isooctane + w_{3} cyclohexane + w_{4} benzene}$ , named throughout the text as ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12} + w_{4} C_{6} H_{6}}$ , and one of its ternary subsystems: ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12}}$ at T = (303.15 ± 0.05) K and atmospheric pressure were performed. Data for the other two partially miscible ternary subsystems: $[{w_{1} C H_{4} O + w_{2} C_{6} H_{6} + w_{3} C_{6} H_{12}} and {w_{1} C H_{4} O + w_{2} C_{6} H_{6} + w_{3} C_{8} H_{18}}]$ were taken from previous works [1], [2], while the fourth is completely miscible $[{w_{1} C_{6} H_{12} + w_{2} C_{6} H_{6} + w_{3} C_{8} H_{18}}]$ . This particular temperature was selected because it is representative of tropical and subtropical climates.

The experimental data for the ternary system studied here were correlated with the UNIQUAC [8] and NRTL [9] models, and compared with predictions using the UNIFAC group contribution method [10].

All pairs of the UNIQUAC interaction parameters obtained from the three partially miscible ternary subsystems included in the quaternary system were averaged and, after that, they were used to predict the quaternary LLE with this model. The UNIFAC method was also used for this purpose.

To the best of our knowledge, there is no reference in the literature about of LLE either of the ternary or quaternary systems studied in this work.

Section snippets

Materials

Methanol and benzene were supplied by Merck, while cyclohexane and isooctane by Sintorgan and Anedra (Argentina), respectively. The purity of the chemicals was verified chromatographically, showing that their mass fractions were higher than 0.998. Therefore, they were used without further purification.

Methods

Before obtaining the LLE results for the quaternary system, one of its partially miscible ternary systems was studied while data for the other two were taken from the literature [1], [2]. Ternary

Results and discussion

Table 1 lists the (liquid + liquid) equilibrium data of the ternary system ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12}}$ at T = (303.15 ± 0.05) K, which is classified as type 2 by Treybal, whereas Fig. 2 shows its corresponding LLE diagram. Data predicted by the UNIFAC and correlated by the UNIQUAC and NRTL models are also shown.

Table 2 lists (liquid + liquid) equilibrium data, expressed in mass fraction, of the quaternary system ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12} + w_{4} C_{6} H_{6}}$ for each quaternary plane: P₁ = (0.7988C₆H₁₂ + 0.2012C₈H₁₈), P

Conclusions

(Liquid + liquid) equilibrium of the ternary system ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12}}$ and of the quaternary system ${w_{1} C H_{4} O + w_{2} C_{8} H_{18} + w_{3} C_{6} H_{12} + w_{4} C_{6} H_{6}}$ were investigated at T = 303.15 K, and the concentrations of both hydrocarbons and methanol beyond which only one phase is present were approximately established.

The NRTL and UNIQUAC equations fitted to the experimental data are considerably more accurate than the UNIFAC method taking into account both overall errors, F and Δm, for the ternary system.

The

Acknowledgement

Financial support from the Consejo de Investigaciones de la Universidad Nacional de Tucumán, Argentina (CIUNT, Grant 26/E418) is gratefully acknowledged.

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Cited by (4)

(Liquid–liquid) equilibria for ternary and quaternary systems of representative compounds of gasoline + methanol at 293.15 K: Experimental data and correlation
2013, Fluid Phase Equilibria
Citation Excerpt :
Higashiuchi et al. [20] reported the (liquid–liquid) equilibria for the quaternary systems (heptane + benzene + toluene + methanol), (octane + benzene + toluene + methanol), (heptane + octane + benzene + methanol), and (heptane + octane + p-xylene + methanol) at T = 298.15 K and at three different mixing ratios (P1 = 75–25, P2 = 50–50, and P3 = 25–75) of benzene and toluene for the two first systems, benzene and methanol for the third system, and p-xylene and methanol, for the last system. More recently, Gramajo de Doz et al. [21,22] reported the (liquid–liquid) equilibria for the quaternary systems (isooctane + cyclohexane + benzene + methanol) and (isooctane + methylcyclohexane + ethylbenzene + methanol); both of them measured at T = 303.15 K. To determine the tie-lines within the whole heterogeneous region of the quaternary systems, four quaternary sectional planes with several cyclohexane and isooctane, and methylcyclohexane and isooctane ratios, respectively, were studied by these authors; i.e., the sectional planes P1 = 0.7988–0.2012, P2 = 0.6066–0.3934, P3 = 0.3944–0.6056, and P4 = 0.1823–0.8177, for the first quaternary system, and the sectional planes P1 = 0.8067–0.1933, P2 = 0.5932–0.4068, P3 = 0.3912–0.6088, and P4 = 0.2009–0.7991, for the second one. Here, we report (liquid–liquid) equilibrium data for the quaternary systems (heptane + benzene + ethylbenzene + methanol) and (heptane + benzene + m-xylene + methanol), both of them measured at T = 293.15 K and at the mixing ratios of (0.5 benzene + 0.5 ethylbenzene) and (0.5 benzene + 0.5 m-xylene) to define the solubility of methanol in a gasoline model at this temperature.
(Liquid–liquid) equilibrium data for type I ternary and quaternary systems of representative compounds of gasoline and methanol as the oxygenate compound were measured at T = 293.15 K and atmospheric pressure. The experimental data were correlated with the NRTL and UNIQUAC models. The numerical procedure to calculate the (liquid–liquid) equilibria of the systems studied is based on the minimization of the system Gibbs energy along with thermodynamic stability tests, to find the most stable state of the system. Good agreement was found between experimental equilibrium data and those calculated with both thermodynamic models for all the ternary and quaternary systems studied.
(Liquid+liquid) equilibria of methanol+isooctane+methylcyclohexane+ethylbenzene quaternary system at T=303.15K
2011, Fluid Phase Equilibria
Citation Excerpt :
However, methanol presents partial miscibility with aliphatic hydrocarbons, not so with aromatic ones. Therefore, it is of great importance to study systems composed by methanol and representative hydrocarbons of gasoline, establishing the concentration ranges of hydrocarbons and methanol in which the two-phase region does not exist [7,8]. Having this in mind, (liquid + liquid) equilibrium (LLE) measurements of {w1 methanol + w2 isooctane + w3 methylcyclohexane + w4 ethylbenzene}, named throughout the text as {w1 CH4O + w2 C8H18 + w3 C7H14 + w4 C8H10}, quaternary system and its ternary subsystems: {w1 CH4O + w2 C8H10 + w3 C7H14}, {w1 CH4O + w2 C8H10 + w3 C8H18}, and {w1 CH4O + w2 C8H18 + w3 C7H14} at T = (303.15 ± 0.05 K) and atmospheric pressure were performed.
Tie line data of {methanol + isooctane + methylcyclohexane}, {methanol + ethylbenzene + methylcyclohexane}, and {methanol + ethylbenzene + isooctane} ternary systems were obtained at T = 303.15 K. A quaternary system {methanol + isooctane + methylcyclohexane + ethylbenzene} was also studied at the same temperature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several methylcyclohexane/isooctane ratios were studied. Experimental results show that the binodal surface in the solid diagram is small and that the highest ethylbenzene mass fraction values beyond which only one phase is present for the methanol-rich phase and hydrocarbon-rich one, respectively, are: 0.0783 and 0.0864 for P1, 0.0791 and 0.0906 for P2, 0.0798 and 0.0805 for P3, 0.0812 and 0.0935 for P4. So, if this quaternary system contains the correct methanol and hydrocarbons concentrations, this blend can be used as a reformulated gasoline because no phase separation should be observed. The distribution of ethylbenzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equation, and predicted with the original UNIFAC group contribution method. The equilibrium data of the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. The UNIQUAC and NRTL equations are more accurate than the UNIFAC method for the ternary systems studied here, because this last model predicts an immiscibility region larger than the experimentally observed in the methanol-rich phase. The UNIQUAC equation fitted to the experimental data is more accurate than the UNIFAC method for this quaternary system.
(Liquid + liquid) equilibria for mixtures of (ethylene glycol + benzene + cyclohexane) at temperatures (298.15, 308.15, and 318.15) K
2011, Journal of Chemical Thermodynamics
Citation Excerpt :
Considering the important role of a suitable non-toxic, inexpensive, and easily recoverable solvent in the extraction process operations, research into finding new solvents, in (liquid–liquid) extraction is an ongoing investigation [4]. (Liquid + liquid) equilibrium (LLE) data for a number of ternary mixtures containing solvent (such as ethylene glycol), aromatic, and aliphatic hydrocarbon (such as cyclohexane) have been published in the literature: (ethylene glycol + toluene + n-octane) at three temperatures (295.15, 301.15, and 307.15) K [4]; (cyclohexane + benzene + N-methyl formamide) and (cyclohexene + benzene + N-methyl formamide) at temperatures of (288.15, 298.15, and 308.15) K [5]; (ethylene carbonate + benzene + cyclohexane) at T = (303.15 and 313.15) K and (ethylene carbonate + BTX + cyclohexane) at T = 313.15 K [6]; (methanol + isooctane + cyclohexane) and (methanol + isooctane + cyclohexane + benzene) at T = 303.15 K [7]; (cyclohexane + benzene + sulfolane), (1-hexene + benzene + sulfolane), (hexane + benzene + sulfolane), and (heptane + toluene + sulfolane) at T = (298.15, 323.15, 348.15, and 373) K [8]; (heptanes + o-xylene + diethylene glycol) over the temperature range of (288.15 to 318.15) K [9]; ternary and quaternary systems including (cyclohexane + 1-heptene + benzene + toluene + sulfolane) at T = 298.15 K [10]; (cyclohexane + benzene + dimethylformamide + ethylene glycol) [11]; (cyclohexane + toluene + sulfolane), and (hexane + toluene + sulfolane) ternary systems [12]; (benzene + cyclohexane + N-methylimidazole, or N-ethylimidazole, or N-methylimidazolium dibutylphosphate) at T = 298.2 K and atmospheric pressure [13]; three quaternary systems (nonane + undecane + benzene + sulfolane), (nonane + undecane + toluene + sulfolane), and (nonane + undecane + m-xylene + sulfolane) at T = (298.15 and 313.15) K [14]; (heptane + N-formylmorpholine (NFM) + aromatic hydrocarbons (benzene, toluene, and xylene)) over the temperature range of (298 to 353) K [15]. In this work, experimental LLE data for ternary mixtures of (ethylene glycol + benzene + cyclohexane) were determined at temperatures (298.15, 308.15, and 318.15) K and at atmospheric pressure.
Experimental (liquid + liquid) equilibrium (LLE) data for a ternary system containing (ethylene glycol + benzene + cyclohexane) were determined at temperatures (298.15, 308.15, and 318.15) K and at atmospheric pressure. The experimental distribution coefficients and selectivity factors are presented to evaluate the efficiency of the solvent for extraction of benzene from cyclohexane. The effect of temperature in extraction of benzene from the (benzene + cyclohexane) mixture indicated that at lower temperatures the selectivity (S) is higher, but the distribution coefficient (K) is rather lower. The LLE results for the system studied were used to obtain binary interaction parameters in the UNIQUAC and NRTL models by minimizing the root mean square deviations (RMSD) between the experimental results and calculated results. Using the interaction parameters obtained, the phase equilibria in the systems were calculated and plotted. The NRTL model fits the (liquid + liquid) equilibrium data of the mixture studied slightly better. The root mean square deviations (RMSDs) obtained comparing calculated and experimental two-phase compositions are 0.92% for the NRTL model and 0.95% for the UNIQUAC model.
Comparison of Ionic Liquids to Conventional Organic Solvents for Extraction of Aromatics from Aliphatics
2016, Journal of Chemical and Engineering Data

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(Liquid + liquid) equilibria of the quaternary system methanol + isooctane + cyclohexane + benzene at T = 303.15 K

Abstract

Introduction

Section snippets

Materials

Methods

Results and discussion

Conclusions

Acknowledgement

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Fluid Phase Equilib.

J. Chem. Thermodyn.

Fluid Phase Equilib.

Sep. Sci. Technol.