Measurement of phase equilibria of supercritical ethane and paraffins

This work entails the design and development of a static variable-volume cell with the aim to measure high-pressure phase equilibria of mixtures of supercritical solvents and paraffinic hydrocarbons. The cell was used to measure the ethane–n-alkane phase equilibria and densities near the critical point of the mixture. Experimentally determined phase equilibria are reported for the binary mixtures of supercritical ethane with n-C16, n-C24 and n-C28 in the temperature range of 313–352 K. Several equations of state (EOS) were fitted to this data, and it was found that the Soave–Redlich-Kwong equation gives a reasonable representation of the measured phase equilibria but fails in the representation of the mixture densities—a known problem of cubic EOS. The use of the Patel–Teja EOS resulted in the smallest error in the liquid phase density representation.