Deep Separation of Benzene from Cyclohexane by Liquid Extraction Using Ionic Liquids as the Solvent

Abstract

Separation of benzene and cyclohexane is one of the most important and difficult processes in the petrochemical industry, especially for low benzene concentration. In this work, three ionic liquids (ILs), [Bmim][BF4], [Bpy][BF4], and [Bmim][SCN], were investigated as the solvent in the extraction of benzene from cyclohexane. The corresponding ternary liquid–liquid equilibria (LLE) were experimentally determined at T = 298.15 K and atmospheric pressure. The LLE data were correlated with the nonrandom two-liquid model, and the parameters were fitted. The separation capabilities of the ILs were evaluated in terms of the benzene distribution coefficient and solvent selectivity. The effect of the IL structure on the separation was explained based on a well-founded physical model, COSMO-RS. Finally, the extraction processes were defined, and the operation parameters were analyzed. It shows that the ILs studied are suitable solvents for the extractive separation of benzene and cyclohexane, and their separation efficiency can be generally ranked as [Bmim][BF4] > [Bpy][BF4] > [Bmim][SCN]. The extraction process for a feed with 15 mol % benzene was optimized. High product purity (cyclohexane 0.997) and high recovery efficiency (cyclohexane 96.9% and benzene 98.1%) can be reached.

Efficient removal of benzene from cyclohexane-benzene mixtures using deep eutectic solvents – COSMO-RS screening and experimental validation

“…The mathematical expressions for the interaction energies, chemical potential, and activity coefficient derived by Klamt et al can be referred to their works [27,28], and have also been summarised in our previous works [29][30][31]. COSMO-RS has been used for conducting various thermodynamic predictions and validations for critical processes such as denitrification [31,32], desulfurization [33,34] and the separation of aromatic and aliphatic mixtures [5,35,36].…”

“…One of the most challenging tasks in the chemical industry is the separation of benzene and cyclohexane. Traditional distillation is infeasible for the separation because of their close boiling points (DT b = 0.6°C at atmospheric pressure), approximately equal molecular volumes, and the binary azeotrope [3][4][5][6]. In the chemical industry, extractive distillation or azeotropic distillation is viable for the separation of benzene and cyclohexane; however, these processes are complex and consume a substantial amount of energy [1,2,6,7].…”

“…However, these solvents are typically toxic, flammable, volatile, and difficult to regenerate. In contrast to conventional solvents, ionic liquids (ILs) have been found to be promising solvents for extraction because of their high thermal stability, negligible vapor pressure, nonvolatile nature, and high solution capacity [4,5,[17][18][19]. Several ILs were studied to show good performance in extraction of benzene from cyclohexane including [ [22], and [C n Mim][PF6] (n = 4, 5, 6) [23].…”

Screening of ionic liquids for solvent-sensitive extraction –with deep desulfurization as an example

“…Comparing with the VOCs, innovative solvents ionic liquids (ILs) have several overwhelming advantages, such as negligible vapor pressure, high thermal stability, designable and tunable character, and so on (Earle and Seddon, 2000). Therefore, ILs have been regarded as potential green alternatives of organic solvents in many processes, such as extraction of metal ions and organics from aqueous solutions (Visser et al, 2001), gas separation (Zhang et al, 2012), separation of aromatic compounds from aliphatic compounds (Arce et al, 2007a(Arce et al, , 2007bMeindersma et al, 2005;Zhou et al, 2012), desulfurization and denitrogenation of fuels (Alonso et al, 2007;Anantharaj and Banerjee, 2013;Wilfred et al, 2013;Rodríguez-Cabo et al, 2013), and separation of biomolecules and drugs (Freire et al, 2010).…”

Liquid–Liquid Equilibria of Benzene + Cyclohexane + N,N-Dimethyl Acetamide + Ammonium Thiocyanate at 298.15 K and Atmospheric Pressure

“…16 Of course the choice of extractant is the key to guarantee that the extraction can be achieved. A proper extractant should have high selectivity, low volatility, and should be regenerated easily.…”