Density, speed of sound, heat capacity, and related properties of 1-hexanol and 2-ethyl-1-butanol as function of temperature and pressure

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Abstract

The speeds of sound in 1-hexanol and 2-ethyl-1-butanol have been measured over the temperature range from (293.15 to 318.15) K and at pressures up to 101 MPa. The densities have been measured within the temperature range from (283.15 to 343.15 or 353.15) K under atmospheric pressure. For the measurements, a pulse-echo-overlap method and a vibrating tube densimeter have been used. Additionally, in the case of 2-ethyl-1-butanol, the isobaric heat capacities from T = (293.15 to 323.15) K at atmospheric pressure have been measured by means of a DSC calorimeter. The experimental results are then used to calculate the densities and isobaric heat capacities as a function of temperature and pressure by means of a numerical integration technique. The effects of pressure and temperature on these and the related properties are discussed. Densities are correlated by means of the Tait equation.

Highlights

► Study of the (pVT) relation obtained by acoustic method for 1-hexanol and 2-ethyl-1-butanol. ► Isobaric heat capacities of 2-ethyl-1-butanol measured by means of a DSC. ► Similarity between the behaviour of 1-hexanol and 2-ethyl-1-butanol. ► The magnitude most of the properties: 2-ethyl-1-butanol  1-hexanol. ► The temperature-pressure density data correlated by means of the Tait equation.

Introduction

The acoustic method based on accurate measurements of the speed of sound is undoubtedly a relatively simple and accurate tool of determining thermodynamic properties of compressed liquids. For this reason, such investigations were undertaken in our lab over ten years and this work is part of a continuing temperature-pressure study of associated hydroxyl liquids, above all alcohols, by means of the acoustic method. As a continuation of the investigations of alkanols (recently, the results for (1-pentanol, 2-methyl-2-butanol, and cyclopentanol) [1] as well as 2-ethyl-1-hexanol [2] have been reported), the present work is devoted to the study of the two structural alkanol isomers: 1-hexanol and 2-ethyl-1-butanol, the latter is representative of the so called 2-alkyl-1-alkanols. For both primary alkanols, the speeds of sound were measured as a function of pressure and temperature in order to provide experimental values for the calculation of the densities and isobaric heat capacities (related properties as well). The measurements were made for pressures up to 101 MPa and temperatures ranging from (293.15 to 318.15) K. As an integral part of this study, the densities for both alkanols were measured at atmospheric pressure over the temperatures ranging from (283.15 to 343.15 or 353.15) K. In the case of 2-ethyl-1-butanol, the isobaric heat capacities as a function of temperature in the temperature range from (293.15 to 323.15) K at atmospheric pressure were measured as well.

The 1-hexanol was investigated about ten years ago by one of us [3], but the applied calibration procedure was not optimal in that work. Thus, the speed of sound values deviate from the data reported in the literature. Therefore, we have decided on the re-investigation of this alcohol.

In the case of 1-hexanol, apart from our own data reported years ago [3], we have found only one data set on the speed of sound under elevated pressures [4]. In the available literature, the data on the compressed-liquid densities and related quantities are also very limited. In the case of 1-hexanol, available experimental data (up to 1994) on the compressed liquid density were critically evaluated and fitted by the Tait equation in an article by Cibulka and Ziková [5], while very recently Dávila et al. [6] reported the new density data under elevated pressures obtained by the use of a vibrating tube densimeter. In turn, the heat capacities under elevated pressures are reported by Arutyunyan [7] and Fulem et al. [8]. Arutyunyan [7] reported the heat capacity data in the pressure range from (0.1 to 60) MPa and at temperatures from (293 to 533) K while Fulem et al. [8] reported the data at pressures (2, 10, and 30) MPa and over the temperature range from (325 to 570) K. Moreover, Randzio et al. [9] calculated the heat capacity, as well as other properties, of 1-hexanol at elevated pressure from the measurements of isobaric expansivity. Noticeable is also a correlation equation between the density of primary 1-alkanol (C4 to C10) and the number of carbon atoms for pressures up to 50 MPa at T = (293.15 and 298.15) K reported by Khasanshin [10]. Khasanshin [11] proposed also a correlation equation between the speed of sound of primary 1-alkanol (C4 to C12) and the number of carbon atoms for pressures up to 100 MPa at seven temperatures in the range (303.15 to 453.15) K. Simultaneously, according to our knowledge, the speeds of sound under elevated pressures for 2-ethyl-1-butanol have not been reported yet in the available literature. No pressure-density-temperature (pρT) data are known for us in the case of 2-ethyl-1-butanol as well. Lastly, for this alkanol, also the polythermal data on the densities, the speeds of sound, and isobaric heat capacities at atmospheric pressure are limited or lacking in the available literature.

It should be noted that both alkanols are flammable (liquid and vapour), only slightly soluble in water, and have wide temperature range of the liquid phase. They are used (esterification) to produce plasticizers, pharmaceuticals, and lubricant additives. Both are also used as solvents and 1-hexanol is used as a flavouring agent.

Section snippets

Chemicals

A sample description is given in table 1. The refractive index nD (T = 298.15 K) measured with an Abbe refractometer RL3 (uncertainty ±0.0004) was 1.4157 for 1-hexanol and 1.4205 for 2-ethyl-1-butanol. The agreement with the literature data (1.4157 and 1.4205, respectively) reported by Riddick et al. [12] is excellent. In this study, the samples were always degassed in an ultrasonic cleaner just before each measurement.

Speed of sound measurements

The speeds of sound at the frequency of 2 MHz were measured under atmospheric

Speeds of sound

The experimental values of the speed of sound in 1-hexanol and 2-ethyl-1-butanol are collected in table 2 while figure 1 shows the comparison of the speed of sound (at atmospheric pressure, u0) with the literature values for 1-hexanol. As seen from figure 1, the agreement at atmospheric pressure between our results (smoothed) and the values extracted from the paper of Marks [24] (temperature dependence reported in the form of a linear equation) is satisfactory. An average absolute deviation

Calculations of densities and isobaric heat capacities at elevated pressures

As known, the acoustic method is based on the speeds of sound measured as a function of temperature and pressure. However, the density and isobaric heat capacity measured as functions of temperature at atmospheric pressure (so-called reference isobars) are an integral part of this method [43], [44], [45], [46], [47], [48]. If we assume that the acoustic wave of low frequency and amplitude is used, and no dispersive effect is present (absorption is negligible), the Newton–Laplace relation (κ = ρ−1·

Results and discussion

The values of ρ(p, T) and Cp(p, T) obtained are summarized in table S2 and S3 of the SI. Additionally, in tables S4–S7 of the SI, the isentropic compressibility κS(p, T), isobaric coefficients of thermal expansion αp(p, T), isothermal compressibility κT(p, T), and internal pressures Pint(p, T) are given.

Summary

The pressure-temperature effects on the speeds of sound, densities, and isobaric heat capacities of 1-hexanol and 2-ethyl-1-butanol are emphasized. The related thermodynamic properties are calculated. Generally, the results show an interesting similarity between the behaviour of 2-ethyl-1-butanol (primary beta-branched alkanol) and 1-hexanol (primary linear alkanol). In principle, this similarity is not surprising because these primary alkanols (structural isomers) have the same molar mass (M = 

Acknowledgments

Thanks are given for the assistance of Mariusz Rąpała and Ewa Wysocka during the measurements of the speed of sound.

References (54)

  • M.J. Dávila et al.

    J. Chem. Thermodyn.

    (2011)
  • M. Fulem et al.

    Thermochim. Acta

    (2002)
    corrigendum 389 (2002)...
  • T.S. Khasanshin

    Teplofiz. Vys. Temp.

    (1997)
  • R. Paramo et al.

    Int. J. Thermophys.

    (2003)
  • M.V. Kumaran et al.

    J. Chem. Eng. Data

    (1983)
  • S.K. Mehta et al.

    J. Solution Chem.

    (1997)
  • M.M. Piñeiro et al.

    Fluid Phase Equilib.

    (2006)
  • E. Zorębski et al.

    J. Chem. Eng. Data

    (2008)
  • F. Kermanpour et al.

    J. Mol. Liq.

    (2009)
  • F. Kimura et al.

    Fluid Phase Equlib.

    (1984)
  • G.C. Benson et al.

    J. Chem. Thermodyn.

    (1985)
  • J. Ortega

    Rev. Latinoam. Ing. Quim. Quim. Apl.

    (1986)
  • G. Benedetto et al.

    Int. J. Thermophys.

    (2005)
  • M. Zábranský et al.

    J. Phys. Chem. Ref. Data

    (2001)
  • E. Zorębski

    Mol. Quant. Acoust.

    (2007)
  • M. Dzida

    J. Chem. Eng. Data

    (2009)
  • E. Zorębski et al.

    J. Chem. Eng. Data

    (2011)
  • W. Marczak et al.

    High Temp. High Pressures

    (2000)
  • I. Sysoev et al.

    Nauchnye Trudy

    Kurski Gosudarstvenny Pedagogicheski Institut

    (1979)
  • I. Cibulka et al.

    J. Chem. Eng. Data

    (1994)
  • G.S. Arutyunyan

    Izv. Akad. Nauk. Az. SSR Ser. Fiz. Tekn. Mat. Nauk

    (1981)
  • S.L. Randzio et al.

    Fluid Phase Equilib.

    (1995)
  • T.S. Khasanshin

    Teplofiz. Vys. Temp.

    (1991)
  • J.A. Riddick et al.

    Organic Solvents

    (1986)
  • E. Zorębski, M. Zorębski, S. Ernst, Ultrasonic World Congress Proceedings, Berlin, 1995, pp....
  • A. Żak et al.

    Rev. Sci. Instrum.

    (2000)
  • M. Dzida et al.

    J. Physique IV

    (2006)
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