INTERACTION PARAMETER-ESTIMATION IN CUBIC EQUATIONS OF STATE USING BINARY PHASE-EQUILIBRIUM AND CRITICAL-POINT DATA

Two methods for the estimation of the interaction parameters in cubic equations of state by using the entire binary phase equilibrium databa se and the critical point locus, respectively, are presented. The solu tion of the optimization problem is accomplished in both methods by a Gauss-Newton-Marquardt minimization algorithm. The methods are computa tionally efficient and robust because they are based on implicit objec tive functions and hence avoid phase equilibrium or critical point cal culations during the parameter optimization. The use of the entire pha se equilibrium database and the critical locus can be a stringent test of the correlational ability of the equation of state. In the illustr ative examples, the results were obtained by using the Peng-Robinson a nd the Trebble-Bishnoi equations of state with quadratic mixing rules and temperature-independent interaction parameters.