50 years of Soave Equation of State (SRK): A source of inspiration for chemical engineers

In June 1972, Giorgio Soave published a renown scientific paper (Equilibrium constants from a modified Redlich-Kwong equation of state, Chemical Engineering Science, 27, 1197-1203), which is one of the most ever cited papers in the field of Chemical Engineering. In the 50th anniversary of this publication it seems appropriate to give a tribute to the Author, as well as quite interesting to review the revolutionary effect that his idea brought not only in chemical thermodynamics but also in the simulation, analysis and design of chemical processes. In this paper the development of the cubic Soave-Redlich-Kwong equation of state is critically summarized, and its applicability to evaluate fluid phase equilibria and chemical equilibria is discussed and explained with examples. It is also shown that the accuracy of cubic equations of state in calculating fluid phase properties mainly depends on the way their parameters are evaluated, rather than on the type of equation of state. It is concluded that still nowadays a cubic equation of state is an essential tool to deal with complex mixtures when accurate calculations are needed, provided that the required data, as well as the model limitations, are adequately considered, with just a couple of impossible-to-solve limitations. In addition, it is eventually pointed out that no more improvements to cubic equations of state are to be expected after Soave's work.