Highly selective extraction of aromatics from aliphatics using an N‐methylpyrrolidone‐based protic ionic liquid

Abstract

AbstractThe efficient and sustainable separation of aromatics from aliphatics is an ongoing challenge in chemical engineering. In this work, the protic ionic liquid N‐methylpyrrolidonium methanesulphonate ([NMP][MSA]) was used to separate toluene from n‐heptane or cyclohexane. Nuclear magnetic resonance and Fourier‐transform infrared spectroscopy were used to demonstrate the successfully synthesis of [NMP][MSA]. Density functional theory (DFT) calculations were used to confirm that the interaction of [NMP][MSA] with toluene would be stronger than those with n‐heptane and cyclohexane, with electrostatic forces and dispersion playing the primary roles and induction playing a minor role. Furthermore, independent gradient model (IGM) analysis demonstrated that van der Waals forces make a major contribution to the stability of [NMP][MSA]–toluene. For a 10 mol% toluene/n‐heptane system, the toluene distribution coefficient and selectivity were found to be 0.35 and >70, respectively, while the corresponding values were 0.40 and 27 for a 10 mol% toluene/cyclohexane system. Changing the extraction temperature seemed to have little effect on separation performance. The effects of solvent dosage, initial concentration, and extractant recycling were also investigated. Overall, our results show that [NMP][MSA] has potential for industrial use.