Fundamental multiparameter and association equation of state for ethanol

Abstract

The objective of this work was to develop a new fundamental equation of state for ethanol by capitalising on the equation of state by Schroeder, Penoncello and Schroeder of 2014 but with the addition of a term to account explicitly for the association effects of this fluid. Thus, three terms constituted the Helmholtz energy, i.e. the ideal gas and residual parts from the cited equation of state and the third term was the association term from the Statistical Associating Fluid Theory. By this device, the new equation of state improved on the accuracy of the equation by the cited authors and allowed to calculate the fractions of non-associated sites and monomers in good agreement with the available data. Piazza and Span in 2011 and 2013 explored, for acetic acid and methanol, respectively, this avenue of combining multiparameter equations with an association term. As ethanol is an associating fluid, it was appropriate to extend that strategy to the fluid. The calculated percentage average absolute deviations in thermodynamic properties were 0.336 for pρT, 0.815 for vapour pressures, 3.363 for saturated-liquid densities, 11.96 for saturated-vapour densities, 11.32 for isochoric heat capacities, 2.791 for isobaric heat capacities, and 0.591 for speeds of sound; for second virial coefficients the average absolute deviation was 112 cm3.mol−1. This work also included the fitting of new ancillary vapour pressure and orthobaric densities equations.