Liquid–Liquid Equilibrium Measurements for the Extraction of Pyridine and Benzothiazole from n‑Alkanes Using Deep Eutectic Solvents

• Published in: Journal of chemical and engineering data 2019-11, Vol.64 (11), p.4882-4890
• Main Authors: Warrag, Samah E. E, Alli, Ruth D, Kroon, Maaike C
• Format: Article
• Language: English
• ISSN: 0021-9568; 1520-5134
• DOI: 10.1021/acs.jced.9b00413

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. Moreover, 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).