Extraction of aromatics from petroleum naphtha reformate by solvent: UNIFAC modelling and optimization of solvent consumption Alireza Fazlali a,⇑ , Mohammad Askari-Mehrabadi a , Amir H. Mohammadi b,c,⇑ a Department of Chemical Engineering, Faculty of Engineering, Arak University, Arak, Iran b MINES ParisTech, CEP/TEP – Centre Énergétique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau, France c Thermodynamics Research Unit, School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041, South Africa article info Article history: Received 12 March 2012 Received in revised form 18 April 2012 Accepted 20 April 2012 Available online 25 April 2012 Keywords: Aromatics Ethylene carbonate (EC) 1-Cyclohexyl-2-pyrrolidone (CHP) Mixed solvent UNIFAC abstract The phase equilibria for the extraction of aromatics from a petroleum naphtha reformate using a mixed solvent of 1-cyclohexyl-2-pyrrolidone (CHP) and ethylene carbonate (EC) are investigated and modelled using the UNIFAC group contribution method. The extraction runs have been carried out at various tem- peratures and solvent compositions. Experimental results are compared favourably with those predicted from the UNIFAC method. The solvent power, processing index, solvent selectivity and capacity for aro- matic extraction from reformate are predicted successfully. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The aromatic hydrocarbon (mainly benzene, toluene, and xy- lenes (BTX)) extraction process is of great importance for the pet- rochemical industry. Design of efficient extraction processes requires an accurate model to describe the (liquid + liquid) equilib- ria between the species present, which plays a fundamental role in the achievement of high purity levels of the desired products [1,2]. Various processes have been developed for BTX extraction [3], which use different solvents like glycol-based solvent, sulfolane, N-methylpyrrolidone (NMP), etc. Mixed solvents are normally used to compromise between the desired properties of the two or more solvents. Mixing of particular solvents is essential for the practical extraction processes [4]. The 1-cyclohexyl-2-pyrrolidone (CHP) has been shown to have high capacity and low selectivity for aromatics extraction. On the other hand, ethylene carbonate (EC) was found to be a highly selective though poorly capacitive solvent. Therefore, a mixture of EC and CHP is normally used to extract the aromatics from the naphtha reformate [5]. In this work, we have measured the corresponding experimen- tal phase equilibrium data and have modelled the obtained data using the UNIFAC activity coefficient model [6]. In addition, the UNIFAC predictions for the multi-component system of reformate with the mixed solvent are compared to experimental data at var- ious temperatures, and different solvent compositions. Finally, the optimum values of solvent to feed ratios are obtained for the extraction of aromatics from naphtha reformate at the best solvent composition and various temperatures. 2. Experimental Pure grade compounds n-hexane, isooctane, cyclohexane, n- heptane, benzene, toluene, ethyl benzene, xylene, ethylene carbon- ate and 1-cyclohexyl-2-pyrrolidone were supplied by Merck. The purity of these chemicals was higher than 0.99 mass fraction. The synthetic gasoline used in extraction was prepared in the laboratory by mixing of the pure hydrocarbons listed above. Table 1 reports the compositions of this reformate (synthetic gasoline) as analyzed by gas chromatography. Three solvent compositions were investigated for a solvent-to- feed ratio of 1:1 at four temperatures 300, 310, 320 and 330 K. These compositions included 35%, 40%, and 45% 1-cyclohexyl-2- pyrrolidone in ethylene carbonate on a weight basis. The experimental setup employed for extraction process is shown in figure 1. It consisted of a 100 cm 3 cylindrical stirred glass mixer settler. The temperature was set by a thermostatic bath and 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2012.04.022 ⇑ Corresponding authors. Address: MINES ParisTech, CEP/TEP – Centre Énergé- tique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau, France. Tel.: +33 1 64 69 49 70; fax: +33 1 64 69 49 68 (A.H. Mohammadi), tel.: +98 8612625420; fax: +98 8612625421 (A. Fazlali). E-mail addresses: a-fazlali@araku.ac.ir (A. Fazlali), amir-hossein.mohammadi@ mines-paristech.fr (A.H. Mohammadi). J. Chem. Thermodynamics 53 (2012) 30–35 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct