Fluid Phase Equilibria 298 (2010) 33–37 Contents lists available at ScienceDirect Fluid Phase Equilibria journal homepage: www.elsevier.com/locate/fluid “Vapor–liquid” equilibrium measurements and modeling for the cyclohexane + cyclohexanol binary system Christophe Coquelet a,b,∗ , Chien-Bin Soo a , Alain Valtz a , Dominique Richon a , Daniel Amoros c , Hubert Gayet c a MINES ParisTech, CEP/TEP – Centre Energétique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau Cedex, France b Thermodynamics Research Unit, School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, Durban, South Africa c Rhodia, Centre de Recherches et Technologies de Lyon, 85 avenue des Frères Perret, BP62, 69192 Saint-Fons Cedex, France article info Article history: Received 5 March 2010 Received in revised form 23 June 2010 Accepted 24 June 2010 Available online 1 July 2010 Keywords: “Vapor–liquid” equilibrium data Static-analytic High-pressure Cyclohexane Cyclohexanol Equation of states abstract To simulate cyclohexane oxidation reactors using a dynamic model linking kinetics, thermodynamics and hydrodynamics, the acquisition and modeling of vapor–liquid equilibria of the key components, under the process conditions, are essential. In this work, the vapor–liquid equilibria of the cyclohex- ane + cyclohexanol system were determined at temperatures 424, 444, 464 and 484 K. The measurements were carried out using an apparatus based on the “static-analytic” method, with two ROLSI TM pneu- matic capillary samplers. The generated data are successfully correlated using two equations of state, the Peng–Robinson (PR) and the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT). A compari- son of model performances reveals the former being better in data representation, while the latter has a broader applicability over larger range of temperatures. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The oxidation of cyclohexane is a significant process in the chemical industry, not only for the production of nylon inter- mediates: cyclohexanol and cyclohexanone, but also it has been the focus of catalysis research for several decades [1]. The con- ventional technology, using cobalt-based catalysts, is known to be low in efficiency, with a conversion of cyclohexane of less than 5%, and selectivities of cyclohexanol and cyclohexanone between 70% and 85% [2]. Careful control of reaction tem- perature, around 423 K, needs to be maintained to avoid the formation of byproducts [2]. Over the years, considerable research on catalysts have been carried out to balance the conversion and selectivity, without losing focus on environmental feasibil- ity. Numerous possible catalysts have been reported in open literature, but with the exception of gold [3], most processes are nevertheless carried out at 400–430 K, and separated down- stream. ∗ Corresponding author at: MINES ParisTech, CEP/TEP – Centre Energétique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau Cedex, France. Tel.: +33 1 64694962; fax: +33 1 64694968. E-mail address: christophe.coquelet@mines-paristech.fr (C. Coquelet). For unit operations and process design, experimental equi- librium data at such high temperatures are necessary. In this study, the vapor–liquid equilibrium (VLE) data for the cyclohex- ane + cyclohexanol binary system are presented at 424, 444, 464 and 484 K. Careful bibliographic studies have shown that previous experimental VLE work on the cyclohexane + cyclohexanol system were carried out predominantly at low temperatures up to 433 K [4–7]. Susarev and Lyzlova measured the ternary system cyclohex- ane + cyclohexanol + cyclohexanone at atmospheric pressure [8]. At low temperatures and pressures, the system exhibits large rela- tive volatilities, often exceeding 100 or more for cyclohexanol-rich regions. No data on liquid–liquid equilibrium have been reported for this system, while solid–liquid equilibrium has been reported for temperatures between 280 and 298 K [9]. Good VLE represen- tations of the system have been achieved in the past using the NRTL local composition model [5,6], and treating the vapor as an ideal phase [6]. In this work, we have tested modeling of our new measured data using cubic and non-cubic equation of states (EoS). The former is based on the Peng–Robinson (PR) cubic equation [10], using the Wong–Sandler (WS) mixing rule [11], and the NRTL Gibbs free energy model [12]. The latter model is the Perturbed- Chain (PC) modification of the SAFT equation [13,14], which we have enhanced for this application through an additional dipolar contribution proposed by Jog and Chapman (JC) [15] and Jog et al. [16]. 0378-3812/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2010.06.013