Predictive Correlation of Phase Equilibria for CO2 + n-Alkane Binary Systems Based on Cubic Mixing Rules

MARTÍN CISMONDI; SABRINA BELÉN RODRÍGUEZ REARTES; JUAN MANUEL MILANESIO; MARCELO SANTIAGO ZABALOY

San Petersburgo

Simposio; 25th European Symposium on Applied Thermodynamics (ESAT 2011); 2011

Saint Petersburg State University, The Mendeleev Russian Chemical Society, Russian Academy of Sciences, Institute of Macromolecular Compounds

Modeling capabilities of equations of state depend strongly on the type of mixing rules implemented and procedures for the estimation of interaction parameters values. In addition, calculated densities also depend on the type of EOS, essentially on whether it is a two or threeparameter EOS, and the way pure compound parameters are obtained.Binary mixtures of CO2 with n-alkanes, from the lighter to the heavier ones, are very important forexample in CO2 based enhanced oil recovery methods (CO2 -EOR). They have been studied by an important number of authors, both experimentally and using different types of models. An  important degree of inaccuracy or scatter can be realized when comparing data from different  sources, specially for the more asymmetric systems (long chain alkanes). At the same time, modeling studies have generally achieved only partially accurate results in the correlation of phase equilibrium data in wide ranges of temperature and pressure.During the last years we have dedicated some effort and publications to explore the possibilitiesthat the flexible Cubic Mixing Rules (CMRs, Zabaloy 2008) offer for the modeling of asymmetricsystems –where quadratic mixing rules fail- and to develop parameterization procedures. In this contribution, we present results of a predictive correlation for CO2 + n-alkane binary systems in wide ranges of temperature and pressure, based on a three-parameter cubic equation of state (the RK-PR EOS, Cismondi and Mollerup 2005) coupled to CMRs.The correlation covers carbon numbers from 3 to 32. Only C1 and C2 were adjusted separately.RK-PR pure compound parameters match Tc, Pc, acentric factor and a saturated liquid density (atTr= 0.70 for alkanes and at 270K for CO2).