Extraction of pyridine from n-alkane mixtures using methyltriphenylphosphonium bromide-based deep eutectic solvents as extractive denitrogenation agents

摘要

In our previous work, we showed that phosphonium-based deep eutectic solvents (DESs) are good candidates for the extractive denitrogenation of oil fuels. In particular, pyridine was successfully extracted from n-hexane and n-heptane via liquid-liquid extraction. The extraction using `methyltriphenyl-phosphonium bromide and ethylene glycol' DES yielded high distribution ratios and selectivities of pyridine. In this work, two phosphonium-based DESs were prepared, the first one was a "binary DES" composed of methyltriphenylphosphonium bromide and glycerol and the second one was a "ternary DES" composed of methyltriphenylphosphonium bromide, glycerol, and ethylene glycol. One objective was to assess the extraction properties of the DESs for pyridine from n-alkanes. Another objective of this work was to study the influence of n-alkane chain length on the extraction performance. Thus, the oil models selected were n-hexane/pyridine, n-heptane/pyridine, and n-octane/pyridine. First, the prepared DESs were characterized for their water content, density, viscosity, and the degradation temperatures. Then the solubility of n-hexane, n-heptane, n-octane, and pyridine in the DESs was measured at 298.2 K and 1.01 bar. Afterward, the liquid-liquid equilibrium (LLE) data of the pseudoternary systems {n-alkane thorn pyridine thorn DES} were determined at a temperature of 298.2 K and a pressure of 1.01 bar. The consideration of a pseudo-ternary system was validated by showing that none of the DES constituents appears in the n-alkane-rich phase "the raffinate".