Liquid Liquid Equilibria measurements for the extraction of poly aromatic nitrogen hydrocarbons with a low cost Deep Eutectic Solvent: Experimental and theoretical insights

A low cost Deep Eutectic Solvent (DES) is used in this work to evaluate the selective extraction of poly aromatic hydrocarbons (PAH) from heptane. The DES synthesized is a combination of methyltriphenylphosphonium bromide salt and ethylene glycol as HBD at a molar ratio of 1:4. Quinoline and indoline as model PAH were then extracted from the toluene-heptane mixture at T = 35 °C. The Liquid-Liquid Equilibrium (LLE) data for the ternary system namely: DES (1) + indoline (2) + heptane (3) and quaternary systems; namely DES (1) + quinoline (2) + indoline (3) + heptane (4), DES (1) + quinoline (2) + toluene (3) + heptane (4) and DES (1) + indoline (2) + toluene (3) + heptane (4) were then measured at atmospheric pressure. The PAH concentrations in the system were varied from 5 to 70 wt% to understand the extraction efficiency of DES. The composition of the respective components in both extract and raffinate phases were measured by 1H NMR technique. It was observed that all the systems followed a type-II phase behavior where a positive slope was seen towards the PAH peak. The distribution coefficient and selectively values for PAH in extract phase were two times higher than toluene. The reliability of the measured tie line data was then correlated with the local thermodynamic models namely NRTL and UNIQUAC models which gave a root mean square deviation (RMSD) of < 1%. Further, Quantum chemical based COnductor like Screening MOdel for Real Solvents (COSMO-RS) model was also employed to predict the phase behavior of investigated systems.