Effect of water content on the equilibrium pressure of (carbon dioxide + decane and + decalin) from T= (313.15 to 333.15) K Inaura C.C. Rocha a , Rosana L. Fialho a,⇑ , José J. Marques b , Cláudio Dariva c , Fernando L.P. Pessoa d a Industrial Engineering Post Graduation Program, Federal University of Bahia, Bahia 40210-630, Brazil b Department of Chemical Engineering, Federal University of Sergipe, Sergipe 49100-000, Brazil c PEP/PBI/UNIT, NUESC/ITP, Tiradentes University, Sergipe 49032-490, Brazil d EQ/UFRJ, Federal University of Rio de Janeiro, Rio de Janeiro 21945-970, Brazil article info Article history: Received 20 February 2013 Received in revised form 7 May 2013 Accepted 10 May 2013 Available online 18 May 2013 Keywords: Phase transitions Carbon dioxide Decane Decalin Water abstract Phase behaviour of mixtures containing hydrocarbons, water and carbon dioxide are of great interest to the petroleum and related industries. However, to describe the effect of water on phase equilibria remains a challenge from theoretical and experimental point of view. Phase transitions for the {decane (C 10 H 22 ) + water + CO 2 } and {decalin (C 10 H 18 ) + water + CO 2 ) system were measured using an apparatus based on the visual synthetic method. The experimental work was carried out in a high-pressure equilib- rium cell. Using this apparatus, temperatures ranging from 313 K to 333 K and pressures up to 15 MPa can be handled. Phase transitions were mainly affected by critical points of miscibility and also by the vicinity of the CEP. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The continued interest in the use of supercritical CO 2 as at least one component of miscible displacement of hydrocarbon fluids has appeared in the petroleum industry for tertiary oil recovery since the 1980s [1]. Phase behaviour of mixtures containing hydrocar- bons, water and carbon dioxide are of great interest to petroleum and related industries due to reservoir simulation and the design of transport and separator equipment [2]. However, the effect of water on equilibrium properties remains a challenge in some industrial cases. In the literature, one can find several studies on (water + hydro- carbons) phase equilibria containing alkanes as the organic phase but little studies are found with decahydronaphthalene (decalin), as a mixture of cis- and trans- isomers. Due to the importance of decane and decalin as oil in several kinetic studies and be com- monly found in the composition of fuels [3] decane and decalin were chosen as the candidate solvents to represent normal (dec- ane) and cycloparaffins (decalin) present in petroleum. In addition, in order to do a comparison between an aliphatic and naphthenic phase behaviour, since the presence of naphthenic hydrocarbons is widely expressive in typical oils, the effect of water content on the equilibrium pressure of (C 10 H 18 + CO 2 ) was also investigated. Decane and decalin are hydrocarbons with same carbon num- ber and have almost the same molar mass. Their differences are attributed to their structures: decane has a linear chain while dec- alin is cyclical with two rings in its structure. For this reason, equi- librium phase behaviour can be quite complex and unlike. The perspective of complexity is apparent from the point of view of van Konynenburg and Scott [4]. According to their classification, the phase behaviour for the (carbon dioxide + decane) binary sys- tem is type II [5] while (carbon dioxide + decalin) exhibits type III [6]. The phase behaviour is even more extreme in the case of (decane + water) and (decalin + water) whereas there is also a significantly smaller amount of data. Apparently, these systems have not been explored from the experimental point of view. Mixtures of hydrocarbons and/or car- bon dioxide with water have received attention in the literature not only because of their practical interest but also because of the theoretical challenges presented in attempting to model such systems accurately. Both types of systems are known to form highly non-ideal mixtures due to the strong association of water. This contributes to the associated use of different types of experi- mental methods with or computational technique. The use of experimental data and thermodynamic models has been a successful in predicting the phase equilibria behaviour of fluids of interesting. However, phase equilibrium computations are usually regarded as being difficult due to lack of experimental data. Despite the fact that the literature covers a wide range of components under various temperature and pressure conditions, 0021-9614/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2013.05.015 ⇑ Corresponding author. Tel.: +55 71 32839800; fax: +55 71 32839801. E-mail addresses: rosanafialho@ufba.br, rosanalopesfialho@gmail.com (R.L. Fialho). J. Chem. Thermodynamics 65 (2013) 11–17 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct