Multiphase equilibria and critical phenomena modeling of ternary systems containing carbon dioxide + polymer + cosolvent using equations of state

by Arce-Castillo, Pedro Felipe

Abstract (Summary)
During the present decade, several experimental results on critical phenomena in phase equilibria, such as co-solvency effect, miscibility windows and two-phases LV regions in three phases LLV surfaces in ternary systems were obtained experimentally by several research groups. These phenomena are of great influence in industrial applications of near-critical and supercritical technology, since they are observed within the pressure, temperature and concentration intervals where these technological processes happen. The present thesis aimed for modeling computationally the phase equilibria (LLE, VLE, VLLE) and predict those phenomena that happen near to critical region in simple systems (CO2 + n-alkane + n-alkanol, CO2 + 2-nitrophenol + n-alkanol) and complex systems, such as polymer + CO2 + co-solvent [polypropylene (iPP) + CO2 + n-pentane; polystyrene (PS) + CO2 + cyclohexane and poly(D,L-lactide) + CO2 + dimethyl ether)] using non-cubicequations of state (EoS), with some theoretical base, as thermodynamic models. Those models were the Perturbed Chain - Statistical Associating Fluid Theory (PC-SAFT) and the Sanchez - Lacombe (SL) EoS. The results obtained in modeling of high-pressure phase equilibria of those systems were compared with those obtained by the traditional Peng- Robinson (PR) EoS. These thermodynamic models were also used in modeling the VLE and LLE of binary systems composed of common and biodegradable copolymers with solvents at low and high pressures. Each thermodynamic model has pure component parameters and one interaction parameter (in its combining rule) for each binary system. Conventional combining and van der Waals one-fluid mixing rules were used in all thermodynamic models. Pure component parameters were obtained by regression of liquid saturated vapor pressure and volume molar data for each simple component, and liquid density, pressure and temperature data for each polymer. The modeling of each binary system was made from LLE, VLE and VLLE data, obtaining one binary interaction parameter (which takes into account the interactions between two molecules). The prediction of phase behavior of ternary system was made using the binary interaction parameters of its three binary systems and the results were compared with experimental data. Optimization was made using the modified likelihood maximum method to determine the global optimum of the two types of parameters. In all the modeling of the multiphase equilibria behavior of the systems presented above, the PC-SAFT EoS had the best performance in terms of relative deviations in pressure when compared to performance of SL and PR EoS
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Martin Aznar; Martin Aznar [Orientador]; Maria Angela de Almeida Meireles; Silvana Mattedi e Silva; Marcelo Castier; Theo Guenter kieckbusch

School:Universidade Estadual de Campinas

School Location:Brazil

Source Type:Master's Thesis

Keywords:Copolimeros Critical phenomena Polymers Copolymers Liquid-liquid equilibrium Vapor-liquid High pressure Equations of state


Date of Publication:08/02/2005

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