Elsevier

Fluid Phase Equilibria

Volume 336, 25 December 2012, Pages 128-136
Fluid Phase Equilibria

Heat capacities of selected chlorohydrocarbons

https://doi.org/10.1016/j.fluid.2012.09.001Get rights and content

Abstract

Isobaric heat capacities in the liquid phase of seven selected halogenated hydrocarbons (1,1,2-trichloroethylene, (Z)- and (E)-1,2-dichloroethylene, 1,1-dichloropropane, 1,2-dichloropropane, 2,2-dichloropropane, and (trichloromethyl)benzene) were measured by using a highly sensitive Tian–Calvet calorimeter in the temperature range from 260 K to 340 K. Due to high volatility of the studied compounds the correction for sample evaporation was applied. Vapor pressure equations required for applying this correction were iteratively developed by simultaneous correlation of the literature vapor pressures and related thermal data (calorimetrically obtained vaporization enthalpies, heat capacities in the liquid and ideal-gas state). The thermodynamic properties in the ideal gaseous state were calculated using the methods of statistical thermodynamics based on fundamental vibrational frequencies and molecular structure data calculated by DFT at the B3LYP/6-311+G(2df,p) level of theory. Data on liquid heat capacities obtained in this work were merged with available literature data, critically assessed and correlated as a function of temperature.

Highlights

► Liquid heat capacities of seven chlorinated hydrocarbons were measured. ► Ideal-gas thermodynamic properties were calculated. ► Vapor pressure eqs. were developed by simultaneous correlation with heat capacities. ► Newly obtained data fill gaps in heat-capacity databases.

Introduction

Heat capacity is a basic thermophysical property, which is necessary for energy balances in chemical engineering and process control. Differences between ideal gas and liquid heat capacity can be also used for reliable extrapolation of vapor pressure down to the triple point [1]. Although there is a large database of critically evaluated liquid heat capacities [2], [3], [4] there is still significant amount of compounds (including those of large industrial and environmental importance) for which liquid heat capacity data are unreliable or not available at all [5]. To fill these gaps and to provide data for improvement of previously developed estimation method [6], liquid heat capacities for seven chlorinated hydrocarbons (1,1,2-trichloroethylene, (Z)- and (E)-1,2-dichloroethylene, 1,1-dichloropropane, 1,2-dichloropropane, 2,2-dichloropropane, and (trichloromethyl)benzene; see Table 1) in the temperature range from 260 K to 340 K were measured by Tian–Calvet calorimetry. The studied compounds except (trichloromethyl)benzene exhibit relatively high vapor pressures in the temperature range of calorimetric measurements. Literature vapor pressure data available at higher temperatures were thermodynamically extrapolated to enable evaluation of evaporation corrections. For performing the extrapolation, heat capacities of ideal gas are needed; they were calculated using the methods of statistical thermodynamics based on fundamental vibrational frequencies and molecular structure data calculated by density functional theory (DFT) at the B3LYP/6-311+G(2df,p) level of theory.

Section snippets

Simultaneous treatment of vapor pressures and related thermal data (SimCor)

Correction of measured heat capacities for sample vaporization must be evaluated when vapor pressure of sample is significant and there is vapor space above the sample. In this case the measured quantity is the heat capacity of two-phase system Ct and the saturation liquid heat capacity Csat (which is below normal boiling temperature practically indistinguishable from isobaric heat capacity Cpl) can be obtained from [4], [7]Csat=CtN+TpTsatVmlTTVNVml2pT2satwhere V is the volume of

Materials

Samples of chlorinated hydrocarbons were of commercial origin. All compounds were used as received. Their purity is summarized in Table 1. Samples were treated under dry nitrogen atmosphere during the cells filling.

Liquid heat capacity measurement

The heat capacity measurements were performed by Tian–Calvet calorimetry (μDSC IIIa, Setaram, France), where calorimetric vessel (volume 1 cm3) is surrounded by a series of thermocouples detecting heat flow from/to vessel. Heat capacity was measured by the well known three-step

Ideal-gas thermodynamic properties

Ideal gas heat capacities are required for thermodynamic extrapolation of vapor pressures to the temperature range of calorimetric determination of Cpl. The thermodynamic properties in the ideal gas state were calculated by statistical mechanics using the rigid rotor–harmonic oscillator (RRHO) approximation with correction for internal rotations. Molecular geometry optimizations and vibrational frequencies calculations were performed using the density functional theory (DFT) at the

Conclusions

The heat capacities of seven selected halogenated hydrocarbons were determined by highly sensitive Tian–Calvet calorimetry for the liquid phase (temperature range from 260 K to 340 K) and calculated by the methods of statistical thermodynamics in combination with quantum mechanics for the ideal gaseous phase (temperature range from 100 K to 1000 K). Due to relatively high vapor pressures of most samples, the liquid heat capacities were corrected for the sample vaporization. The liquid heat

Acknowledgement

This work is supported by the Ministry of Education of the Czech Republic under project ME10049 and grant MSM 604 613 7307.

References (56)

  • M. Zábranský et al.

    Fluid Phase Equilib.

    (2002)
  • M. Fulem et al.

    J. Chem. Thermodyn.

    (2006)
  • M. Fulem et al.

    Fluid Phase Equilib.

    (2011)
  • Z. Kisiel et al.

    J. Mol. Spectrosc.

    (1996)
  • Y. Nannoolal et al.

    Fluid Phase Equilib.

    (2007)
  • J.C. Van Miltenburg

    J. Chem. Thermodyn.

    (1972)
  • R. Francesconi et al.

    Chem. Eng. Sci.

    (1971)
  • V. Machát et al.

    J. Chem. Thermodyn.

    (1985)
  • V. Majer et al.

    J. Chem. Thermodyn.

    (1980)
  • R.M. Varushchenko et al.

    Fluid Phase Equilib.

    (2007)
  • K. Růžička et al.

    AIChE J.

    (1996)
  • M. Zábranský et al.

    J. Phys. Chem. Ref. Data

    (2010)
  • M. Zábranský et al.

    J. Phys. Chem. Ref. Data

    (2001)
  • M. Zábranský et al.

    Heat Capacity of Liquids. Critical Review and Recommended Values

    (1996)
  • Z. Kolská et al.

    Ind. Eng. Chem. Res.

    (2008)
  • H.J. Hoge

    J. Res. NBS

    (1946)
  • P.J. Mohr, B.N. Taylor, D.B. Newell, physics.nist.gov/constants,...
  • E.R. Cox

    J. Ind. Eng. Chem.

    (1936)
  • K. Růžička et al.

    Fluid Phase Equilib.

    (1998)
  • K. Růžička et al.

    J. Phys. Chem. Ref. Data

    (1994)
  • K. Růžička et al.

    J. Chem. Eng. Data

    (2005)
  • G.W.H. Höhne et al.

    Differential Scanning Calorimetry

    (2003)
  • M. Straka et al.

    J. Chem. Eng. Data

    (2007)
  • M. Fulem et al.

    J. Chem. Eng. Data

    (2008)
  • M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N....
  • C. Červinka et al.

    J. Chem. Eng. Data

    (2012)
  • T. Shimanouchi

    Tables of Molecular Vibrational Frequencies, NSRDS-NBS 39

    (1972)
  • M.C. Tobin

    J. Am. Chem. Soc.

    (1953)
  • View full text