Liquid−Liquid Equilibrium Measurements for the Extraction of Pyridine and Benzothiazole from n‑Alkanes Using Deep Eutectic Solvents Samah E. E. Warrag, Ruth D. Alli, and Maaike C. Kroon* Petroleum Institute, Chemical Engineering Department, Khalifa University of Science and Technology, P. O. Box 2533, Abu Dhabi, United Arab Emirates *S Supporting Information ABSTRACT: The liquid−liquid extraction of a nitrogen- containing aromatic “pyridine” and nitrogen/sulfur-containing aromatic “benzothiazole” from n-hexane and n-heptane using deep eutectic solvents (DESs) was studied in this work. A DES composed of methyltriphenylphosphonium bromide as hydrogen bond acceptor and ethylene glycol as hydrogen bond donor was selected for this separation. The main objective of this work was to assess whether the same DES can be applied for the denitrogenation “extraction of pyridine” and desulfurization “extraction of benzothiazole” of fuels. More- over, the influence of n-alkane chain length on the extraction performance was studied. First, the solubilities of the pyridine, benzothiazole, n-hexane, and n-heptane in the DES were determined at 298.2 K and 1.01 bar. Thereafter, the pseudoternary liquid−liquid equilibrium (LLE) data for the four systems {n-hexane + pyridine + DES}, {n-heptane + pyridine + DES}, {n-hexane + benzothiazole + DES}, and {n-heptane + benzothiazole + DES} were determined at a temperature of 298.2 K and a pressure of 1.01 bar. The assumption of a pseudoternary system was validated showing that none of the DES’ constituents appears in the raffinate phase. From the LLE data the distribution ratios and selectivites of pyridine and benzothiazole were calculated. Both pyridine and benzothiazole were successfully extracted from their mixtures with n-hexane and n-heptane, with pyridine showing higher selectivity than benzothiazole and almost similar distribution ratios. Finally, The LLE data were correlated with the nonrandom two-liquid model using ASPEN PLUS. The modeled results showed a strong correlation with the experimental results (relative mean standard deviation (%)) = 0.04−0.36). 1. INTRODUCTION The combustion of fuels with a high content of nitrogen and sulfur aromatics is a major source of NO x and SO x emissions that are potential pollution threats. Moreover, in view of the operational issues associated with such a high content of nitrogen and/or sulfur aromatics including gum formation, catalyst inhibition and deactivation, corrosion, storage instability, thermal instability, and metal complexation in crude oil processing, 1−3 it is invariably important to remove nitrogen and sulfur aromatics from crude oil. Nitrogen aromatic compounds in crude oils are classified as basic “derivatives of pyridine” and nonbasic “derivatives of pyrrole”, while sulfur aromatics exist as derivatives of thiophene. Catalytic hydrotreatment is the commercially established refinery process for reducing both nitrogen (hydro-denitrogenation (HDN)) and sulfur (hydro-desulfur- ization (HDS)) compounds from crude oil. This method is based on catalytically converting the nitrogen and sulfur compounds into ammonia and hydrogen sulfide, respectively, at a temperature range of 250−350 °C and pressure range of 1.5−15 MPa. 4,5 In addition to the high energy requirement of this process and the excessive hydrogen consumption, it should be noted that the method is not selective for specific nitrogen and/or sulfur impurity. Thus, it suffers from low removal efficiency for some of the nitrogen and sulfur compounds that exhibit a strong steric hindrance toward the catalytic conversion such as nitrogen and sulfur aromatics. 6 The lone pair electrons from the nitrogen/sulfur aromatics participate in the resonance stabilization of the compound making HDN/ HDS less efficient and energetically demanding. Therefore, the search for an energy efficient, low cost with high removal efficiency strategy is a compulsory task for the engineering community. Considering the alternatives for HDS, researchers have investigated many approaches including oxidative desulfuriza- tion, bio-desulfurization, adsorption, and extractive desulfuriza- Special Issue: Celebrating Our High Impact Authors Received: May 8, 2019 Accepted: July 16, 2019 Article pubs.acs.org/jced Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.jced.9b00413 J. Chem. Eng. Data XXXX, XXX, XXX−XXX Downloaded via BUFFALO STATE on July 31, 2019 at 07:45:46 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.