Fluid Phase Equilibria 231 (2005) 197–210 Extension of the group contribution associating equation of state to mixtures containing phenol, aromatic acid and aromatic ether compounds S. Espinosa a , S. D´ ıaz b , T. Fornari c,∗ a Universidad del Comahue, 8300 Neuqu´ en, Argentina b PLAPIQUI - CC 717, 8000 Bah´ ıa Blanca, Argentina c ´ Area de Tecnolog´ ıa de Alimentos, Facultad de Ciencias, Universidad Aut´ onoma de Madrid, 28049 Cantoblanco, Madrid, Spain Received 24 November 2004; received in revised form 9 February 2005; accepted 11 February 2005 Abstract In this work, the Group Contribution Associating Equation of State (GCA-EoS) parameter table is extended in order to represent phase equilibrium behavior of aromatic compound mixtures, which contain the aromatic ether (ACOCH 3 ), the phenol (ACOH) and the aromatic acid (ACCOOH) groups. Pure-group parameters and interaction parameters between these groups and the paraffin (CH 3 , CH 2 ) and aromatic (ACH, AC, ACCH 3 ) groups were estimated using experimental phase equilibrium data on binary mixtures. Also, their interaction parameters with water and carbon dioxide are reported. The extended parameter table is applied to predict high-pressure phase equilibria in binary and ternary mixtures containing high value complex aromatic compounds and carbon dioxide. © 2005 Elsevier B.V. All rights reserved. Keywords: Vapor–liquid equilibria; Group contribution; Equation of state; Phenols; Aromatic acids 1. Introduction A large variety of aromatic compounds extracted from natural products have revealed great potential application in food, pharmaceutical, biochemical industries, etc. Particu- larly, many phenolic compounds comprise singular interest, because they have shown a broad range of pharmacological activities, such as antiulcer and antioxidant properties [1–3]. Separation of these compounds from their natural sources, can be achieved by high-pressure dense-gas extraction pro- cesses. Supercritical fluid extraction (SFE) using carbon dioxide has important advantages over conventional extrac- tion techniques [4,5]: the absence of both light and air during the extraction process along with the low operating temper- atures reduce the incidence of degradation reactions, while ∗ Corresponding author. Tel.: +34 91 4973583; fax: +34 91 4973579. E-mail address: tiziana.fornari@uam.es (T. Fornari). the use of CO 2 as extracting agent allows working in an en- vironmentally clean media. The key factor in SFE is the possibility to adjust the density-based solvent power by small variations in the operating conditions such as temperature, pressure and co- solvent. Knowledge of equilibrium compositions is essential for evaluating the viability of the separation processes, and hence both phase equilibria measurements [6,7] and thermodynamic models [8–10] have received considerable attention in the literature. Although many cubic-type equa- tions of state have been widely and satisfactory applied to represent phase equilibria in mixtures of complex aromatic compounds + supercritical fluids, extrapolation of these molecular models to systems for which no experimental data is available is not possible. In this sense, group contribution models offer an advantage over molecular models: a large number of compounds and mixtures can be represented with a reduced number of functional groups. 0378-3812/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2005.02.007