Vapour-liquid equilibrium measurements and correlation for separating azeotropic mixture (ethyl acetate + n-heptane) by extractive distillation Kai Liu a , Tao Zhang a , Yixin Ma a , Jun Gao a , Dongmei Xu a,⇑ , Lianzheng Zhang a , Yinglong Wang b a College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China b College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China article info Article history: Received 6 January 2020 Received in revised form 31 January 2020 Accepted 5 February 2020 Available online 6 February 2020 Keywords: Vapour-liquid equilibrium Ethyl acetate n-Heptane Azeotropic mixture Extractive distillation abstract Since ethyl acetate and n-heptane can form the lowest azeotropic mixture, p-xylene and butyl butyrate were selected as extracting agents to separate the azeotrope (ethyl acetate + n-heptane) using extractive distillation. The binary isobaric vapour-liquid equilibrium (VLE) data for the binary systems (ethyl acetate + p-xylene), (ethyl acetate + butyl butyrate) and (n-heptane + butyl butyrate) were determined at 101.3 kPa using a Rose-Williams still. The measured experimental data were checked by the van Ness method and Herington test. Besides, the determined VLE data were fitted by the NRTL, UNIQUAC and Wilson thermodynamic models. The calculated root-mean-square deviation values of the tempera- ture and vapour phase mole fraction are no more than 0.19 K and 0.0053, respectively. The results showed that three thermodynamic models can be used to correlate the determined experimental data for the three binary systems. Meanwhile, the binary interaction parameters for the three thermodynamic models were optimized, which are a great help for the optimization and simulation of separating the azeotropic mixture (ethyl acetate + n-heptane). Ó 2020 Elsevier Ltd. 1. Introduction Ethyl acetate and n-heptane are useful solvents and can be used as chemical raw materials [1–4]. For the production of hexanitro- hexaazaisowurtzitane (HNIW) [5] and other chemical intermedi- ates, ethyl acetate and n-heptane are mixed as the solvent [6]. Because ethyl acetate and n-heptane can easily form the lowest azeotrope at 101.3 kPa, it is extremely difficult to separate the azeotrope formed by conventional distillation. Usually, for separat- ing azeotropic mixtures, special distillations are considered, including extractive distillation [7], azeotropic distillation [8], pressure-swing distillation [9], and salt distillation [10]. In this study, extractive distillation was applied with two extractants p- xylene and butyl butyrate to separate the azeotrope (ethyl acetate + n-heptane). For separating the azeotrope (ethyl acetate + n-heptane) by extractive distillation with the selected extracting agents, the bin- ary isobaric vapour-liquid equilibrium (VLE) data for the binary systems (ethyl acetate + p-xylene / butyl butyrate) and (n-heptane + p-xylene/butyl butyrate) are required. Until now, the binary VLE data for the azeotrope (ethyl acetate + n-heptane) have been reported in many literatures. Fernandez et al. [11] explored the binary isobaric VLE data for the azeotrope (ethyl acetate + n-heptane) at 101.3 kPa. Collinet et al. [12] reported the azeotropic data for the binary mixture (ethyl acetate + n- heptane) from low to moderate pressures. The binary isothermal experimental data of the azeotrope (ethyl acetate + n-heptane) were determined by Shealy et al. [13]. Kang and Li et al. [6] adopted N-methyl pyrrolidone (NMP) as extracting agent to sepa- rate the azeotrope (ethyl acetate + n-heptane). The isobaric VLE data for the binary systems (ethyl acetate + p-xylene) and (n- heptane + p-xylene) were determined by Carr et al. [14] and Dı ´ az et al. [15] at atmospheric pressure, respectively. However, there have been no report about the binary VLE data for the systems (ethyl acetate + butyl butyrate) and (n-heptane + butyl butyrate) at pressure of 101.3 kPa in the NIST database [16]. In this study, the binary VLE data for the mixtures (ethyl acetate + p-xylene), (ethyl acetate + butyl butyrate) and (n-heptane + butyl butyrate) were measured at 101.3 kPa. The thermodynamic consistency of the measured experimental data was checked by the van Ness method [17] and Herington test [18]. Then the determined VLE values were fitted by the NRTL [19], UNIQUAC [20] and Wilson [21] thermodynamic models. https://doi.org/10.1016/j.jct.2020.106075 0021-9614/Ó 2020 Elsevier Ltd. ⇑ Corresponding author. E-mail addresses: xudongmei@sdust.edu.cn (D. Xu). J. Chem. Thermodynamics 144 (2020) 106075 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct