Fluid Phase Equilibria, 58 (1990) 117-132 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 117 zyxwvutsrqponml ESTIMATION OF MULTIPLE BINARY INTERACTION PARAMETERS IN EQUATIONS OF STATE USING VLE DATA. APPLICATION TO THE TREBBLE-BISHNOI EQUATION OF STATE * P. ENGLEZOS, N. KALOGERAKIS * *, M.A. TREBBLE and P.R. BISHNOI Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive N. W., Calgary, Alb., T2N IN4 (Canada) (Received February 3,1989; accepted in final form October 31, 1989) ABSTRACT Englezos, P., Kalogerakis, N., Trebble, M.A. and Bishnoi, P.R., 1990. Estimation of multiple binary interaction parameters in equations of state using VLE data. Application to the Trebble-Bishnoi equation of state. Fluid Phase Equilibria, 58: 117-132. A systematic approach for the estimation of binary interaction parameters for equations of state is presented. A least-squares procedure which is computationally very efficient is advocated for the calculation of the binary interaction parameters. Subsequently, if the calculated phase behavior represents the experimental data without a gross bias, the statisti- cally best parameters can be obtained by maximum likelihood (ML) estimation. For these cases, the use is advocated of an implicit ML estimation procedure which is computationally significantly more efficient than the “error in variables” method. The proposed approach is particularly suitable for equations of state which have more than one interaction parameter. In such cases, the best parameter set is chosen from among several combinations of interaction parameters present in the equation of state. INTRODUCTION Equations of state (EOS) are used extensively for the calculation of high pressure equilibria and/or properties of fluid mixtures. Empirical binary interaction parameters are normally utilized in these equations to increase their correlational flexibility, particularly in non-ideal fluid systems. Re- cently, Trebble and Bishnoi (1987, 1988) proposed a cubic EOS which can * The material in this article was presented at the 4th International IUPAC Workshop, Thessaloniki, Greece, October 24-26,198s. * * Author to whom correspondence should be addressed. 037%3812/90/!§03.50 0 1990 - Elsevier Science Publishers B.V.