Measurement and correlation of critical properties for binary mixtures and ternary mixtures containing gasoline additives

https://doi.org/10.1016/j.jct.2014.01.025Get rights and content

Highlights

  • A high-pressure view cell was used to measure the critical properties of mixtures.

  • Three binary mixtures’ and three ternary mixtures’ critical properties were reported.

  • The experimental data of each system covered the whole mole fraction range.

  • The critical properties of the ternary mixtures were predicted with the PR–WS model.

  • Empirical equations were used to correlate the experimental results.

Abstract

The critical properties of three binary mixtures and three ternary mixtures containing gasoline additives (including methanol + 1-propanol, heptane + ethanol, heptane + 1-propanol, methanol + 1-propanol + heptane, methanol + 1-propanol + methyl tert-butyl ether (MTBE), and ethanol + heptane + MTBE) were determined by a high-pressure cell. All the critical lines of binary mixtures belong to the type I described by Scott and van Konynenburg. The system of methanol + 1-propanol showed little non-ideal behavior due to their similar molecular structures. The heptane + ethanol and heptane + 1-propanol systems showed visible non-ideal behavior for their great differences in molecular structure. The Peng–Robinson equation of state combined with the Wong–Sandler mixing rule (PR–WS) was applied to correlate the critical properties of binary mixtures. The critical points of the three ternary mixtures were predicted by the PR–WS model with the binary interaction parameters using the procedure proposed by Heidemann and Khalil. The predicted critical temperatures were in good agreement with the experimental values, while the predicted critical pressures differed from the measured values. The experimental values of binary mixtures were fitted well with the Redlich–Kister equation. The critical properties of ternary mixtures were correlated with the Cibulka’s equation, and the critical surfaces were plotted using the Cibulka’s equations.

Introduction

Supercritical fluid technology is widely used in industrial separations and chemical reaction processes, and the critical properties of the relevant pure substances and mixtures are an essential part of the technology. In addition, critical properties are important for the theoretical development of thermodynamic equations of state. But the critical properties of mixtures are scarce in the open literatures, especially for the mixtures with more than two components. Prediction is a useful way to determine the critical properties of mixtures, but the lack of experimental critical properties for mixtures with more than two components hinders the development of prediction methods. Therefore, it is urgent to report more critical properties of mixtures and develop prediction methods for estimating the critical properties of mixtures with more than two components. Some scholars have tried to predict the critical properties of ternary mixtures. For instance, Tao Liu et al. [1] predicted the critical properties of ternary mixtures by the interaction parameters obtained from binary mixtures with the hard-sphere three-parameter equation [2], [3], the Powell method [4], and the Hicks–Young method [5]. Soo [6] found that the Cibulka’s equation [7] was suitable for correlating ternary critical properties. The above methods are either complicated or correlated with the experimental data. It is necessary to find simple and accurate methods to predict the critical points of mixtures with more than two components.

In the gasoline industry, the critical properties of the additive mixtures are very scarce. Among the gasoline additives, short chain alcohols (methanol, ethanol and 1-propanol) and methyl tert-butyl ether (MTBE) are widely used for their excellent properties, such as high octane number, degradability, and low exhaust emission. In this work, we measured the critical temperatures and critical pressures of three binary mixtures (methanol + 1-propanol, heptane + ethanol, heptane + 1-propanol) and three ternary mixtures (methanol + 1-propanol + heptane, methanol + 1-propanol + MTBE, ethanol + heptane + MTBE) containing gasoline additives. Some critical properties of heptane + ethanol [6], [8] and heptane + 1-propanol [9] have been reported, but the experimental data covering the full concentration range is lack. The critical properties of the other four systems are reported for the first time. The Peng–Robinson equation of state [10] combined with the Wong–Sandler mixing rule [11], [12] (PR–WS), was used to predict the critical temperatures and critical pressures of ternary mixtures. The experimental data was also correlated with empirical equations, the Redlich–Kister equation [13] for binary mixtures, the Cibulka’s equation [7] for ternary mixtures.

Section snippets

Materials

Chemicals used in this work are listed in table 1. Their purities were all above 0.990 (mass fraction) and checked by gas chromatograph. All of the chemicals were purchased from Tianjin Guangfu Technology Development Co., Ltd. and used without further purification.

Apparatus

A high-pressure view cell was designed in our previous work [14] to determine the critical properties of mixtures. This apparatus is made of titanium material with two sapphire glass windows for visual observation. Its maximum

Experimental results

The apparatus’ reliability and the experiment procedure were checked by measuring the critical properties of pure cyclohexane, heptane, MTBE, methanol, ethanol, 1-propanol, and a binary mixture (hexane + ethanol) in the previous work [14]. The critical properties of three binary mixtures (methanol + 1-propanol, heptane + ethanol, heptane + 1-propanol) and three ternary mixtures (methanol + 1-propanol + heptane, methanol + 1-propanol + MTBE, and ethanol + heptane + MTBE) were measured over the whole range of the

Conclusions

The critical temperatures and the critical pressures of three binary mixtures (methanol + 1-propanol, heptane + ethanol, heptane + 1-propanol) and three ternary mixtures (methanol + 1-propanol + heptane, methanol + 1-propanol + MTBE, ethanol + heptane + MTBE) were measured with visual observation method by a high-pressure cell. The phase diagrams of all the binary mixtures belong to type I. Heptane + ethanol system and heptane + 1-propanol system show visible non-ideal behavior, because of the great differences

Acknowledgments

This research was supported by the Programme of Introducing Talents of Discipline to Universities (No. B060006), National Natural Science Foundation of China (No. U1162104).

References (22)

  • P. Li et al.

    Fluid Phase Equilib.

    (1991)
  • P. Li et al.

    Fluid Phase Equilib.

    (1992)
  • C.B. Soo et al.

    J. Supercrit. Fluids

    (2010)
  • A. Zawisza et al.

    J. Chem. Thermodyn.

    (1982)
  • H. Orbey et al.

    Fluid Phase Equilib.

    (1993)
  • K.W. Han et al.

    J. Chem. Thermodyn.

    (2013)
  • Th.W. de Loos et al.

    Fluid Phase Equilib.

    (1988)
  • T. Liu et al.

    J. Chem. Eng. Data

    (2001)
  • W.H. Press et al.

    Numerical Recipes-The Art of Scientific Computing

    (1986)
  • C.P. Hicks et al.

    J. Chem. Soc.

    (1977)
  • I. Cibulka

    Collect. Czech. Chem. C

    (1982)
  • Cited by (21)

    • Prediction and measurement of critical properties of gasoline surrogate fuels and biofuels

      2022, Fuel Processing Technology
      Citation Excerpt :

      Tg is the total group contribution parameters of the first–level group contribution. Using 20 sets of binary systems with Tc changing non-monotonically [32–42], we evaluated the accuracy of the four models, and the results are shown in Table 1. The most important criterion for judging is whether the non-monotonic change trend of the critical temperature is predicted, while the value of AARD is not very important.

    • Mutual diffusion coefficients of ethanol + n-heptane and diethyl carbonate + n-heptane from 288.15 K to 318.15 K

      2020, Journal of Chemical Thermodynamics
      Citation Excerpt :

      The measurement of solution property has been proved to be feasible in understanding solute-solvent interactions, and the clustering of solvent and solute molecules. For now, various thermophysical properties and thermodynamic excess properties of ethanol + n-heptane and DEC + n-heptane mixtures have been reported, such as volumetric properties, vapour-liquid equilibrium, the speed of sound, viscosity and critical properties [17–28]. However, there are no reports available on the mutual diffusion coefficient of ethanol + n-heptane and DEC + n-heptane mixtures.

    • Comparison of SAFT-VR-Mie and CP-PC-SAFT in predicting phase behavior of associating systems III. Aliphatic hydrocarbons - 1-propanol, 1-butanol and 1-pentanol

      2019, Journal of Molecular Liquids
      Citation Excerpt :

      It has been established that these data can be precisely correlated with the equation of state attached by a chemical term (EoSC) of Góral [6] comprising up to 16 adjustable parameters. In addition, several experimental studies [7–20] have demonstrated that Cubic equations of state attached by the classical and the gE-based mixing rules with fitted binary adjustable parameters can represent with varying degrees of success the high-pressure phase equilibria and critical loci of the considered systems. Besides that, Voňka et al. [21] have compared different density-dependent and -independent mixing rules with one to four binary parameters attached to a modified Redich-Kwong EoS.

    View all citing articles on Scopus
    View full text