Separation of Benzene-Cyclohexane Azeotropes Via Extractive Distillation Using Deep Eutectic Solvents as Entrainers

Abstract

The separation of benzene and cyclohexane azeotrope is one of the most challenging processes in the petrochemical industry. In this paper, deep eutectic solvents (DES) were used as solvents for the separation of benzene and cyclohexane. DES1 (1:2 mix of tetrabutylammonium bromide (TBAB) and levulinic acid (LA)), DES2 (1:2 mix of TBAB and ethylene glycol (EG)) and DES3 (1:2 mix of ChCl (choline chloride) and LA) were used as entrainers, and vapor-liquid equilibrium (VLE) measurements at atmospheric pressure revealed that a DES comprised of a 2:1 ratio of LA and TBAB could break this azeotrope with relative volatility (αij) up to 4.763. Correlation index suggested that the NRTL modelling approach fitted the experimental data very well. Mechanism of extractive distillation gained from FT-IR revealed that with hydrogen bonding and π–π bond interactions between levulinic acid and benzene could be responsible for the ability of this entrainer to break the azeotrope.

A Chemosensor of 1,8-Dihydroxyanthraquinone PMOs Prepared in a Ternary Deep Eutectic Solvent for the Sensitive Detection of Cu2+

“…The peak at 1106 cm –1 belongs to the −COH stretching vibration. 33 When the ternary DES is formed, blue-shifts are observed for the stretching vibration peak of −OH in ChCl and the stretching vibration and bending vibration of −NH 2 in U. At the same time, the intensity of the −OH in EG is enhanced, which indicated that they are all involved in the formation of the large number of hydrogen bonds (N–H···Cl, O–H···O, O–H···Cl, etc.)…”

Mechanism of Extractive Separation of Light Cycle Oil Using a Deep Eutectic Solvent Composed of Tetrabutylphosphonium Bromide and Levulinic Acid

“…For levulinic acid, the broad peak in the range of 3000–3500 cm –1 corresponds to the stretching vibration of hydroxyl (−OH), while the peak at 1699 cm –1 represents the stretching vibration of carbonyl (−CO) . For TBPB, the peaks at 2873–2960 cm –1 represent the methylene (−CH 2 ) and methyl (−CH 3 ) group asymmetric and symmetric stretching vibrations .…”

“…For levulinic acid, the broad peak in the range of 3000−3500 cm −1 corresponds to the stretching vibration of hydroxyl (−OH), while the peak at 1699 cm −1 represents the stretching vibration of carbonyl (−CO). 45 For TBPB, the peaks at 2873−2960 cm −1 represent the methylene (−CH 2 ) and methyl (−CH 3 ) group asymmetric and symmetric stretching vibrations. 39 After mixing levulinic acid and TBPB, their FTIR spectra clearly show that the band of the hydroxyl (−OH) group of levulinic acid narrows and shifts to a lower wavenumber (known as a red shift), with increasing the TBPB content from TBPB/LA (1:6) to TBPB/LA (1:2).…”

Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation

“…The obtained results are provided in Table 7. In the systems containing DES(TBAB:LA) (1:2) and DES(ChCl:LA) (1:2) [31], the prediction is satisfactory as the coefficient of determination is >0.99 assessed from all the three models. In the system containing DES(TBAB:LA) (1:2), the prediction is not satisfactory since the coefficient of determination is <0.99 using the three models.…”