Accurate heat capacities measurements of imidazolium based ionic liquids


M. Rocha1, B. Schroder2, J. Coutinho2 and L. Santos1

1Centro de Investigacao em Quimica, Faculdade de Ciencias da Universidade do Porto, Portugal
2CICECO, Departamento de Química, Universidade de Aveiro, Portugal

Keywords: heat capacities, drop calorimetry
property: heat capacities
material: ionic liquids

The application of room temperature ionic liquids, RTILs, in industry requires accurate values for their physicochemical properties, such as heat capacities, vapour pressures, viscosities, etc. Heat capacities of a large number of ionic liquids have been already published in the literature.[1] However, a large fraction of the data published presents large uncertainties that, in some cases, hide some subtle irregularities in the heat capacity trend. In this work an effort was done in order to obtain highly accurate heat capacity data, at T = 298.15 K, for the imidazolium based ionic liquids using an high-precision drop heat capacity calorimeter developed by Wadsö.[2,3] The quality of the heat capacity data, is comparable, in accuracy, with the best literature data measured by adiabatic calorimetry. The results will be used to detect and understand subtle changes along the alkyl side chain length and to evaluate the effect of the cation topology in the heat capacity at 298.15 K. The additivity of the heat capacity of the imidazolium based ionic liquids will be discussed. Acknowledgements: Fundação para a Ciência e Tecnologia (FCT) and Programa Operacional Ciência e Inovação 2010 (POCI 2010) supported by the European Community Fund FEDER is acknowledge for the financial support to Project PTDC/QUI/72903/2006. B. Schröder and M. A. A. Rocha acknowledge the financial support from F.C.T. for the award of a research grant with reference SFRH/BPD/38637/2007 and SFRH/BD/60513/2009, respectively.

References
  1. Y. U. Paulechka, J. Phys. Chem. Ref. Data 39, 033108-1 - 033108-23 (2010)

  2. J. Konicek, J. Suurkuusk, I. Wadsö, Chemica Scripta 1, 217 – 220 (1971)

  3. J. Suurkuusk, I. Wadsö, J. Chem. Thermodynamics 6, 667 – 679 (1974)

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