Elsevier

Fluid Phase Equilibria

Volume 231, Issue 2, 25 April 2005, Pages 163-170
Fluid Phase Equilibria

Liquid–liquid equilibria for n-alkanes (C12, C14, C17) + propylbenzene + NMP mixtures at temperatures between 298 and 328 K

https://doi.org/10.1016/j.fluid.2005.01.012Get rights and content

Abstract

Liquid–liquid equilibria for three ternary systems: dodecane, or tetradecane, or heptadecane + propylbenzene + NMP was studied over a temperature range of 298–328 K. The three systems studied exhibit type I liquid–liquid phase diagram. The effect of temperaure and n-alkane chain length upon solubility, selectivity, and distribution coefficient were investigated experimentally. The experimental results were regressed to estimate the interaction parameters between each of the three pairs of components for the UNIQUAC and the NRTL models as a function of temperature. Both models satisfactorily correlate the experimental data, however the UNIQUAC fit was slightly better than that obtained with the NRTL model. The values of distribution coefficient and selectivity were predicated from the equilibrium data.

Introduction

Ternary phase equilibrium data are essential to the proper understanding of the solvent extraction processes. The separation of aromatic and aliphatic compounds from their mixtures is an important goal in chemical operations that produce both types of compounds. On the other hand smoke point of kerosene, cetane index of diesel, and viscosity index of lubricating oil can be improved by removing aromatic hydrocarbons. N-methyl-2-pyrrolidone (NMP) is a dipolar aprotic solvent used in the well-established Arosolvan process [1] for separating aromatic hydrocarbons from petroleum fractions. A few experimental liquid–liquid equilibrium data have been published for NMP + aromatic + n-alkanes (C5–C9) and hardly any for systems containing carbon number greater than nine for the alkanes and/or aromatics [2], [3], [4], [5], [6], [7], [8], [9].

This paper is considered as a part of our project to study the liquid–liquid phase equilibria for dearomatisation of Kuwait middle distilled fraction. The purpose of this work is to study LLE of three ternary systems: system-I {dodecane (1) + propylbenzene (2) + NMP (3)}, system-II {tetradecane (1) + propylbenzene (2) + NMP (3)}, and system-III {heptadecane (1) + propylbenzene (2) + NMP (3)}. The LLE data for the studied ternary systems were measured at 298, 308, 318, and 328 K and correlated by the UNIQUAC model of Abrams and Prausnitz [10] and the NRTL model of Renon and Prausnitz [11].

Section snippets

Chemicals

The purities and refractive indices of all chemicals used in this study are presented in Table 1. The NMP and aromatic hydrocarbons were stored under 4 Å molecular sieve. The purity of the chemicals was determined by gas chromatography. All chemicals were used without further purification.

Determination of critical solution temperature (Tc)

In order to find the operating extraction temperatures, the miscibilities and critical solution temperature Tc, of the systems studied were measured. The miscibilities of binary mixtures were measured by adding

Models and predictions

Our experimental data were correlated with the UNIQUAC model of Abrams and Prausnitz [10] and the NRTL model of Renon and Prausnitz [11]. The excess Gibbs free energy of mixing gE of the NRTL model isgERT=i=13xij=1nτjiGjixjk=1nGkixkwhereτij=gijgjjRT=aijT,τji=gjigiiRT=ajiT,Gij=exp(αijτij),Gji=exp(αjiτji)where R is the gas constant, T the absolute temperature, we have set α equal to 0.2 and aij and aji are the two adjustable parameters in the model for each binary pair that we find

Experimental data

Fig. 1 presents the measured critical solution temperatures of binary mixtures: NMP + dodecane, or tetradecane, or heptadecane at different phase ratio. The equilibrium coexistence curves have a rather horizontal top and become asymmetric with increasing CH2 group of the n-alkanes. Our experimental result is in agreement with that obtained by Bittrich et al. [14].

Fig. 2 presents the measured critical solution temperature of ternary mixtures: dodecane, or tetradecane, or heptadecane + propylbenzene + 

Conclusions

An experimental investigation of equilibrium behavior of liquid–liquid, NMP + propylbenzene + dodecane, or tetradecane, or heptadecane ternary systems were carried out at temperatures of 298–328 K and at atmospheric pressure. The solubility of NMP in n-alkanes rich phase increases as the temperature increases, but it has little effect on the solubility of n-alkanes in NMP rich phase. The mutual NMP-alkanes solubility increased as the concentration of propylbenzene increases. Both the UNIQUAC and the

Acknowledgement

The authors thank the Public Authority for Applied Education and Training (PAAET-TS-01-001) for the financial support of this work.

References (14)

  • T.A. Al-Zayied et al.

    Fluid Phase Equilib.

    (1990)
  • P.O. Ferreira et al.

    Fluid Phase Equilib.

    (1984)
  • P.O. Ferreira et al.

    Fluid Phase Equilib.

    (1984)
  • S.H. Ali et al.

    Fluid Phase Equilib.

    (2003)
  • H.-J. Bittrich et al.

    Fluid Phase Equilib.

    (1996)
  • J.M. Muller et al.

    Aromatics extraction with solvent combinations

  • J.M. Nagpal et al.

    J. Chem. Technol. Biotechnol.

    (1981)
There are more references available in the full text version of this article.

Cited by (18)

  • Simulation of the deasphalting process of crude oils: Models development and extraction conditions analysis

    2022, Journal of Petroleum Science and Engineering
    Citation Excerpt :

    The first one consisted of a benchmarking between the simulated and experimental data of LLE extractions of aromatics, from mixtures of saturates and aromatics compounds. The experimental data of the LLE extractions were obtained from the literature (Al-Jimaz et al., 2005; Alkhaldi et al., 2009; Fandary et al., 2006). Table 3 lists the five systems selected for the validation, including all the compounds involved in each system, the solvent, the extraction temperatures, and the bibliographic references.

  • Liquid-liquid equilibria in the ternary systems {hexadecane+BTX aromatics+2-methoxyethanol or acetonitrile} at 298.15K

    2015, Fluid Phase Equilibria
    Citation Excerpt :

    The extraction efficiency in liquid–liquid extraction (LLE) depends on the use of a suitable solvent. A variety of organic solvents have been investigated to assess their separation properties, including sulfolane, N-methylpyrrolidone (NMP), glycole and N-formylmorpholine (NFM), 2-methoxyethanol, and acetonitrile [4–9]. However, experimental LLE data for 2-methoxyethanol and acetonitrile as a solvent mixture together with a high carbon number aliphatic compound (C12–C21) remains very limited.

  • Extraction of propylbenzene from its mixtures with heptadecane using 4-methyl-N-butylpyridinium tetrafluoroborate

    2012, Fluid Phase Equilibria
    Citation Excerpt :

    Al-Tuwaim et al. [37] reported the extraction of propylbenzene or butylbenzene from dodecane using 4-methyl-N-butylpyridinium tetrafluoroborate at different temperatures. This paper is a continuation of our study on the liquid–liquid phase equilibria for dearomatization of Kuwait middle distilled fraction [36–39]. We are interested in providing experimental LLE data containing IL.

  • Separation of propylbenzene and n-alkanes from their mixtures using 4-methyl-N-butylpyridinium tetrafluoroborate as an ionic solvent at several temperatures

    2011, Fluid Phase Equilibria
    Citation Excerpt :

    Currently, there are only a few experimental liquid–liquid equilibrium data have been published for [(mebupy)(BF4)] + aromatic + n-aliphatic (C5–C9) and hardly any for systems containing carbon number greater than nine for the aliphatic and/or aromatics [1,3,17–19]. This article is a continuation of our study on the liquid–liquid phase equilibria for dearomatization of Kuwait middle distilled fraction [20,21]. Our interest in IL is focused on providing experimental LLE data.

View all citing articles on Scopus
View full text