Elsevier

Fluid Phase Equilibria

Volume 257, Issue 2, 25 August 2007, Pages 147-150
Fluid Phase Equilibria

Measurement and correlation of liquid–liquid equilibria for acetonitrile + n-alkane systems

https://doi.org/10.1016/j.fluid.2007.01.024Get rights and content

Abstract

The reduction of sulfur content in gasoline and diesel fuel is a great environmental concern to reduce the motor vehicle emissions. Oxidative desulfurization using acetonitrile biphasic system has received much attention in recent years. The oxidative desulfurization can be oxidized the unreactive sulfur contents in the hydrodesulfurization and removed effectively. For the oxidative desulfurization process design and development, liquid–liquid equilibria (LLE) for acetonitrile biphasic systems are needed as fundamental information. In our previous work, LLE for acetonitrile + n-octane and + n-decane systems have been reported. In this work, therefore, LLE for acetonitrile + n-hexadecane system was measured. Furthermore, NRTL equation was applied to correlate the LLE for these three acetonitrile + n-alkane systems.

Introduction

The reduction of sulfur content in gasoline and diesel fuel is a great environmental concern to reduce the motor vehicle emissions. A hydrodesulfurization process has been used in many refineries, however, the new effective desulfurization processes are needed to meet the lower sulfur level regulations.

Oxidative desulfurization in acetonitrile biphasic system [1], [2], [3] has proposed in recent years. Oxidative desulfurization can oxidize the unreactive sulfur compounds in the hydrodesulfurization. The polar benzothiophenes and dibenzothiophenes, which are major sulfur containing compounds in fossil fuels, are extracted into the polar acetonitrile phase and oxidized. Oxidative desulfurization can also oxidize 4,6-dimethyldibenzothiophene effectively, which is one of the most unreactive sulfur compounds in the hydrodesulfurization [1]. In addition, oxidative desulfurization reaction can be performed at lower temperature, proposed reaction temperature is 60 °C [1], than hydrodesulfurization.

For the oxidative desulfurization process design and development, liquid–liquid equilibria (LLE) for acetonitrile biphasic systems are needed as a fundamental information. One of the examples, acetonitrile concentration in the oxidative desulfurization oil is needed to estimate the loss of acetonitrile in the oxidative desulfurization process. Furthermore, reaction and separation temperature can be adjusted based on the liquid–liquid equilibrium composition of acetonitrile + n-alkane systems.

In our previous work, LLE for acetonitrile + n-octane and + n-decane systems have been reported [4]. In this work, therefore, LLE for acetonitrile + n-hexadecane, the model for diesel fuel, system was measured with the tie-line measurement in the temperature range from 25 to 80 °C. The temperature range of the measurements was decided to cover the proposed oxidative desulfurization reaction temperature and to avoid the difficulties of sampling at higher temperature than 80 °C. Furthermore, NRTL equation [5] was applied to correlate the LLE for these acetonitrile + n-octane, + n-decane and + n-hexadecane systems to check the applicability of the model.

Section snippets

Materials

Acetonitrile (99.5%, Lot# EWH6563) was purchased from Wako Pure Chemicals Ind. Ltd. (Osaka, Japan). n-Hexadecane sample (99%, Lot# 102K3694) was purchased from Sigma–Aldrich Corporation (St. Louis, MO). All reagents were used as received.

Measurements

The tie-line measurement was used to measure the LLE of acetonitrile (1) + n-hexadecane (2) system. The experimental procedures in this work, as same as in our previous work [4], were described briefly.

The hyper glass cylinder (100 mL, Taiatsu Techno Corp.,

Correlation

LLE can be calculated by using an activity coefficient model. The equilibrium condition of component i in phase I and phase II is shown as follows:(γixi)I=(γixi)II(i=1,2)where γ is an activity coefficient and x is a mole fraction of component i. Subscripts 1 and 2 means acetonitrile and n-alkane, respectively. The simultaneous solution of Eq. (1) for all components gives equilibrium compositions.

In this work, NRTL equation [5] was used to calculate the LLE for acetonitrile (1) + n-alkane (2)

Results and discussion

The experimental LLE for acetonitrile (1) + n-hexadecane (2) system measured in this work are summarized in Table 1 and shown in Fig. 1 with the literature data for n-octane (2) [9] and n-decane (2) [9], [10] systems. The literature data [9], [10] were measured by the cloud point measurement and the other literature data [4], our previous work, were measured by the tie-line measurement, respectively. As far as we investigate, liquid–liquid equilibrium data for acetonitrile (1) + n-hexadecane (2)

Conclusions

The LLE for acetonitrile (1) + n-hexadecane (2) system were measured with the tie-line measurement. n-Hexadecane-rich phase and acetonitrile-rich phase were turn around above the temperature of 50 °C. Furthermore, the LLE for acetonitrile (1) + n-octane (2), + n-decane (2) and + n-hexadecane (2) systems were correlated with NRTL equation. The correlated results show in a good agreement with the experimental data.

    List of symbols

    g

    molar Gibbs free energy (J mol−1)

    R

    gas constant (J mol−1 K−1)

    T

    absolute temperature (K)

    x

    mole

References (10)

  • T. Furuya et al.

    Fluid Phase Equilibr.

    (2005)
  • R.M. Cuevas et al.

    Fluid Phase Equilibr.

    (1995)
  • M. Antosik et al.

    Fluid Phase Equilibr.

    (1990)
  • K. Yazu et al.

    Energy Fuels

    (2001)
  • Y. Shiraishi et al.

    Ind. Eng. Chem. Res.

    (1999)
There are more references available in the full text version of this article.

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Present address: Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, 12-1 Ichigayafunakawaramachi, Shinjuku-ku, Tokyo 162-0826, Japan.

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