HIGH PRESSURE PHASE EQUILIBRIA OF SYSTEMS CARBON DIOXIDE + N-EICOSANE AND PROPANE + N-EICOSANE

S.B. RODRIGUEZ-REARTES; J.V. OLIVEIRA; M.L. CORAZZA; M. CISMONDI; M.S. ZABALOY

Complejo Vaquerías – Valle Hermoso - Córdoba – Argentina

Congreso; I REUNIÓN INTERDISCIPLINARIA DE TECNOLOGÍA Y PROCESOS QUÍMICOS (RITeQ 2008); 2008

PLAPIQUI/UNS/CONICET y UNIVERSIDAD NACIONAL DE CORDOBA

In this work we investigated the phase equilibrium behavior of the binary asymmetric systems n-eicosane (C20) + propane (C3) and n-eicosane (C20) + carbon dioxide (CO2). We used a variable-volume view cell for obtaining fluid-fluid equilibrium (FFE), solid-fluid equilibrium (SFE) and solid-fluid-fluid equilibrium (SFFE) experimental data. For the n-eicosane + propane system, we measured liquid-vapour (LV) and solid-liquid (SL) transitions at constant composition (isopleths) in the temperature range from 288.55 K to 333.45 K, and pressures up to 21.9 bar. The composition range of the isoplethic data is from 0.252 to 0.99 propane mole fraction. For the n-eicosane + carbon dioxide system, we obtained liquid-liquid (LL), SL and solid-liquid-liquid (SLL) equilibrium experimental data in the temperature range from 300.05 K to 333.15 K, and pressures up to 250 bar. The isoplethic LL and SL data correspond to the n-Eicosane mole fraction values 0.003142 and  0.004777. We modeled the phase equilibria of both systems using the Peng-Robinson equation of state for describing the fluid phases and an expression for the fugacity of pure solid n-Eicosane with parameters fit to reproduce the pure n-Eicosane melting line. We performed the phase equilibrium calculations by implementing path-following methods for tracking entire solid-fluid (SF) and solid-fluid-fluid (SFF) equilibrium curves for binary asymmetric mixtures. This made it possible to obtain complete isoplethic lines or complete three phase equilibrium lines in single runs. Although the model is relatively simple, it is able to grasp the complex observed behavior for the systems here studied.