High temperature vapour-liquid equilibrium measurements with a flow apparatus


A. Cristino1, A. Palavra2 and C. Nieto de Castro1

1Departamento de Química e Bioquímica and Centro de Ciências Moleculares e Materiais, Faculdade de Ciências da Universidade de Lisboa, Portugal
2Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Portugal

Keywords: high temperature VLE measurements, flow apparatus
property: equilibrium compositions
material: water-ethanol, binary mixtures

The design of industrial processing equipment of linear alcohols, which represent an important alternative source of energy, needs accurate VLE measurements of binary mixtures involving these compounds with water at high temperatures.

A flow apparatus was built to carry out these measurements at temperatures and pressures up to 573 K and 20 MPa, respectively. A flow method was chosen to avoid the thermal degradation of alcohols at high temperatures.

The VLE equilibrium is achieved inside a high pressure cell made of 316SS with a sapphire window, sealed with gold o-rings. Inside this cell the temperature is measured using a calibrated Pt100 resistance thermometer with accuracy better than 0.1 K. The pressure was measured with two pressure transducers, operating up to 5 and 20 MPa, with accuracy better than ± 0.2% FS. Furthermore, the equilibrium compositions were determined using a new method for accurately converting vibrating tube periods of oscillation in density values developed by the authors Lampreia and Nieto de Castro (2011) using an Anton Paar vibrating tube densimeter [2], with an accuracy better than 0.1%.

VLE measurements for the system water-ethanol, were carried out to test the apparatus, for which  accurate data are available [3, 4].

References
  1. S.C.S. Rosa, C.A. Nieto de Castro, A.M.F. Palavra, Proceedings of 4th Asian Thermophysical Properties Conference, (1995), 467-470.

  2. I.M.S. Lampreia, C.A. Nieto de Castro, J. Chem. Thermodynamics, (2011), 43 537–545.

  3. V. Niesen, A.M.F. Palavra, A.J. Kidnay, V.F. Yesavage, Fluid Phase Equilibria, (1986), 31, 283-298.

  4. B. Kolbe, J. Gmehling, Fluid Phase Equilibria, (1985), 23, 213-226.

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