Evaluation of Deep Eutectic Solvent for the selective extraction of toluene and quinoline at T = 308.15 K and p = 1 bar

The current work reports the selective separation of aromatic and poly aromatic hydrocarbon (PAH) with Deep Eutectic Solvents (DES). The low cost DES are based on a mixture of a hydrogen bond donor and organic salt. The organic salt namely Methyltriphenylphosphonium bromide(MTBP) along with the hydrogen bond donor (HBD) were taken in a ratio of 1:4 to synthesize potential DES. DES were then varied based on the selection of two hydrogen bond donor namely ethylene glycol(DES1) and glycerol(DES2). In order to study their effectiveness, Liquid-liquid Equilibrium experiments were performed for the removal of toluene and quinoline respectively. LLE data corresponding to the ternary systems:[DES1(1) + Toluene(2) + Heptane(3)],[DES2(1) + Toluene(2) + Heptane(3)], [DES1(1) + Quinoline(2) + Heptane(3)] and [DES2(1) + Quinoline(2) + Heptane(3)] were generated at 308.15 K and atmospheric pressure. 1H NMR analysis were then used for the quantification of both extract and raffinate phases. Distribution coefficient (β) and selectivity (S) were subsequently obtained and it was found that toluene had a poor selectivity than quinoline. The cross contamination of DES and heptane across either phases were found to be nearly zero. Further the Non-random two liquid (NRTL) and UNiversal QUAsi Chemical (UNIQUAC) thermodynamic model were used to compare the experimental tie line data. This gave an excellent fit with a root mean square deviation (RMSD) values for both models ranging from (0.28–0.31%) and (0.22–0.73%) respectively. DES1, namely Methyltriphenylphosphonium bromide + ethylene glycol was thus recommended as a potential solvent for the separation of aromatic and PAH component.