APPLICATION OF THE PENG-ROBINSON EQUATION OF STATE TO CALCULATE INTERFACIAL-TENSIONS AND PROFILES AT VAPOR-LIQUID INTERFACES

In this work gradient theory of inhomogeneous fluids is used to describe planar interfaces. With the Helmholtz energy of the homogeneous fluid and the influence parameter of the inhomogeneous fluid, the interfacial profiles and tensions of interfaces can be predicted by gradient theory. The interfacial tension calculations, based on the Peng-Robinson equation of state and related models for the influence parameter, are presented. Laboratory as well as field studies have established that carbon dioxide is an efficient oil-displacing agent in enhanced oil recovery. Therefore special attention was given to the interfacial tension behaviour of some binary and ternary model systems, containing carbon dioxide, butane and decane. In general the predictions from the method presented in this contribution are superior in comparison with the parachor estimations.