Liquid-Liquid Equilibrium of Deep Eutectic Solvent-Aromatic-Aliphatic Ternary Systems: Experimental Study with COSMO Model Predictions

Abstract

Common solvents used for aromatic extraction from aliphatics typically degrade into toxic compounds, while green alternatives perform poorly compared to the state-of-the-art solvents. Deep eutectic solvents (DES) are a novel solvent type made of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA). DES have been applied in various applications, including advanced separations. In this study, DES were studied experimentally and using the Conductor-like Screening Model (COSMO) to separate benzene from cyclohexane as model compounds for an aromatic:aliphatic system. Both equilibrium and kinetic studies were performed to determine the liquid liquid equilibrium (LLE) and mass transfer rate for the DES-based separation. Selected HBAs including tetrabutylammonium bromide (N4444Br), tetrahexylammonium bromide (N6666Br), choline chloride (ChCl), and methyltriphenylphosphonium bromide (METPB) were paired with HBDs including ethylene glycol (EG) and glycerol (Gly). COSMO was used, with adjustments to reflect DES specific interactions, to predict the liquid-liquid equilibrium (LLE). COSMO results showed that ChCl and N6666Br-based DES extracted too little benzene or too much cyclohexane, respectively, to be considered for experimental evaluation. Overall, the COSMO model predictions for LLE of EG-based DES were very accurate, with root-mean-square deviations (RMSD) below 1% for both N4444Br:EG and METPB:EG. The glycerol systems were less accurately modeled, with RMSD’s of 4% for N4444Br:Gly and 6% for METPB:Gly. The lower accuracy of glycerol system predictions fmay be due to limitations in COSMO for handling glycerol’s influence on polarizability in the DES that is not seen in EG-based DES. Mass transfer kinetics were determined experimentally for DES and the results were fit to a first order kinetics model. METPB:Gly had the highest mass transfer coefficient at 0.180 min−1, followed by N4444Br:EG at 0.143 min−1. N4444Br:Gly and METPB:EG had the lowest mass transfer coefficients at 0.096 min−1 and 0.084 min−1, respectively. It was found that mass transfer rate was not directly related to maximum benzene solubility, as N4444Br:EG and METPB:Gly had the highest and lowest benzene removal, respectively, but had similar mass transfer coefficients.

In Situ Product Recovery of β-Ionone from a Fermentation Broth: Computational Solvent Selection and Process Design of Its Extraction and Purification

“…COnductor-like Screening MOdel for Real Solvents (COSMO-RS) is a predictive quantum chemistry-based thermodynamic tool that uses only a σ-profile of the compounds as the input. , Different implementations of the COSMO-based models have been proposed, such as COSMO-SAC, Modified COSMO-SAC, COSMO-RS based electrolyte model, and different versions of COSMO-RS updated in the COSMOThermX software . COSMO-RS has been tested as a successful screening tool for several applications, i.e., for selecting organic solvents for extracting furfural and 5-hydroxymethylfurfural from water, ionic liquids for H 2 S capture, deep eutectic solvents (DES) for BTX (benzene, toluene, and xylene) extraction from aliphatics, and extracting solvents for solubilizing artemisin, among others. In fermentation processes, COSMO-RS model has been previously used for screening and solvent selection for the recovery of several classes of bioproducts such as 2-phenylethanol, , 2,3-butanediol, butanol, − 1,5-pentanediamine, succinic acid, , l -lactic acid, l -malic acid, and vanillin, using a wide range of solvents from conventional organic to tailor-made solvents such as ionic liquids or DES.…”

Advances in Deep Eutectic Solvents: New Green Solvents

“…There are two ways to separate benzene and cyclohexane mixtures: liquid-liquid extraction and extractive distillation. For the liquid-liquid extraction of benzene and cyclohexane mixtures, McGaughy and Reza [8] measured the liquid-liquid equilibrium (LLE) of benzene, cyclohexane and DESs. The selected HBAs included tetrabutylammonium bromide (N 4444 Br), tetrahexylammonium bromide (N 6666 Br), choline chloride (ChCl), and methyltriphenylphosphonium bromide (METPB), and the HBDs included ethylene glycol (EG) and glycerol (Gly).…”