Liquid-Liquid Equilibria Data for the Quaternary System of Acetic Acid, Water, p‑Xylene, and Ethyl Acetate at 313.15 K and 101.325 kPa Gregorius Rionugroho Harvianto, † Seo Eun Kim, † Il Bong Jin, † Ki Joon Kang, ‡ and Moonyong Lee* ,† † School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea ‡ TPT Pacific Co. Ltd., Insa-Dong, Jongro-Gu, Seoul 110-290, Republic of Korea ABSTRACT: The liquid-liquid equilibria (LLE) data for the quaternary system, acetic acid, water, p-xylene, and ethyl acetate, was obtained at 313.15 K under atmospheric pressure. The composition distribution of each component on the aqueous phase and organic phase were investigated. To examine the effects of the solvent, the LLE phase diagrams at different p-xylene to ethyl acetate ratios are presented for this quaternary system. The reliability of the tie-line data of this study was also confirmed using the Othmer-Tobias and Hand equation. The distribution ratio and separation factors for the extraction of acetic acid from the aqueous solutions were obtained. Furthermore, the equilibrium data of this study was analyzed using the quasichemical activity coefficient (UNI- QUAC) and nonrandom two liquid (NRTL) models. The experimental data was correlated successfully with both the activity coefficient models that were extended with each binary interaction parameter. To determine the accuracy of each activity model, the root-mean-square deviations (RMSDs) and average absolute deviation (AAD) resulting from these models were also calculated. The RMSDs and AAD of the NRTL models were 0.0196 and 0.0213, respectively, whereas those of the UNIQUAC model were 0.0166 and 0.0114, respectively. These values showed that the UNIQUAC model is superior to the NRTL model. ■ INTRODUCTION The recovery of acetic acid from aqueous solutions is industrially and environmentally important. Acetic acid is an essential chemical raw material that is used extensively in chemical industries, such as vinyl acetate monomer production, solvent to produce terephthalic acid, acetic anhydrate synthesis, and acetate ester manufacture. 1,2 On the other hand, acetic acid is difficult to separate from water by conventional distillation because there is a tangent pinch on the pure water end in their binary vapor-liquid equilibrium (VLE) diagram under atmospheric pressure. 3-6 Consequently, the separation of acetic acid from its mixture by conventional distillation can be avoided because of its high energy consumption. 7 To identify a more effective process, the integration of extraction and distillation can be considered as a comparatively effective method because of its lower energy cost. The paramount importance of this method is to obtain an appropriate solvent that can be used as the extractant in the extraction process. Applying a suitable extractant plays a significant role in the extraction efficiency of the industrial separation process. 8,9 This paper proposes the use of p-xylene and ethyl acetate as a mixed solvent for the extraction of acetic acid from aqueous solutions. The use of p-xylene as a solvent is proposed because of its special application as the main reactant in the industrial production of terephtalic acid. In addition, ethyl acetate is used because this solvent is good for acetic acid extraction. 10,11 Several experimental studies of LLE ternary systems containing acetic acid have been published. 12-14 Furthermore, there are several papers on LLE quaternary systems containing acetic acid and water. 15-17 To extract acetic acid from water, Cehreli and Bilgin 18 examined those components combined with propionic acid and mixed solvent. Bilgin 19 further studied this by combining propionic acid with another mixed solvent. Toikka et al. 20 reported a quaternary system involving ethyl acetate and ethanol. Wang et al. 21,22 studied different solvents for the extraction of acetic acid from water. The solvents used were amyl acetate, 2-methyl ethyl acetate, 2-methyl propyl acetate, and butyl acetate. These studies covered the LLE system, including acetic acid and water with each solvent. To the best of the authors’ knowledge, there is no LLE data of quaternary systems, including the mixed solvent examined in this study. Therefore, the present study focused on the phase behavior of LLE for a quaternary system containing ethyl acetate, p-xylene, water, and acetic acid. As mentioned earlier, this study was carried out to solve real industrial problems related to acetic acid dehydration. The aim of this study was to obtain LLE data for the industrial design and process simulation of acetic acid extraction using the mixed solvent of ethyl acetate and p-xylene at 313.15 K and atmospheric pressure. The temperature of 313.15 K was chosen because the aqueous solution fed to the extractor Received: July 6, 2015 Accepted: December 8, 2015 Article pubs.acs.org/jced © XXXX American Chemical Society A DOI: 10.1021/acs.jced.5b00550 J. Chem. Eng. Data XXXX, XXX, XXX-XXX