Liquid‐liquid equilibrium studies for separation of aromatics

Abstract

Liquid‐liquid equilibrium studies have been carried out on 11 solvents using two binary hydrocarbon mixtures for selective extraction of aromatics. The solvents used have been compared on the basis of selectivity, solvent capacity and tie line correlation curves. Tie line data have been determined for 18 systems. The selectivity and solvent power of solvents as obtained from limiting activity coefficient and tie line data have been compared. The selectivity and capacity of solvents have been related to their structure through an empirical parameter.

Ternary liquid–liquid equilibria for mixtures of toluene+n-heptane+an ionic liquid

“…In Fig. 3, our own experimental data and LLE data from literature [2][3][4] are shown at T = 313.2 and 348.2 K. Our experimental data and the data from Tripathi et al [2] and Rawat and Gulati [3] at 313.2 K are in good agreement with each other, but the data from De Fré and Verhoeye [4] at 348.2 K differ from our own. Both the toluene and the heptane distribution coefficients measured by De Fré are higher than our data at higher toluene concentrations and the toluene/n-heptane selectivity is lower than our data for all toluene concentrations.…”

“…This means that not much IL is lost in the raffinate phase. Due to the low solubility of n-heptane in [mmim]CH 3 SO 4 , the toluene/heptane selectivities are higher with this IL than for the Table 5 Experimental tie lines and toluene/n-heptane selectivity of the system toluene (1) + n-heptane (2) + [bmim]CH 3 Fig. 14a and b.…”

“…The binary interaction parameters for toluene + n-heptane for the ionic liquid systems were determined by regression of two data sets of the system toluene + n-heptane + [mebupy]BF 4 at T = 313.2 and 348.2 K. These parameters were then used in the determination of the interaction parameters (toluene + ionic liquid and n-heptane + ionic liquid) of the other ternary systems with ionic liquids. The binary interaction parameters for toluene + n-heptane, obtained with [mebupy]BF 4 as solvent, were not suitable for the calculation of the tie lines for the ternary system toluene + n-heptane + sulfolane, probably Table 1 Experimental tie lines and toluene/n-heptane selectivity of the system toluene (1) + n-heptane (2) + sulfolane (3) in mole fractions at p = 0.1 MPa n-Heptane-rich phase Sulfolane-rich phase Experimental selectivity because the ionic liquids are ionic and sulfolane is not. Therefore, the binary interaction parameters for the ternary mixture toluene + n-heptane + sulfolane were determined separately.…”

“…This implicates that there are no suitable separation processes available for process streams with an aromatic content below 20 wt.%. Typical solvents used are polar components such as sulfolane [2][3][4][5][6][7][8][9], N-methyl pyrrolidone (NMP) [8], N-formyl morpholine (NFM), ethylene glycols [9][10][11] or propylene carbonate [9]. Those solvents require additional distillation steps to separate the extraction solvent from both the extract and raffinate phases, and to purify the solvent, with, consequently, additional investments and energy consumption.…”

“…The solvent sulfolane is used as a comparison for this separation, because it is one of the most common solvents for extraction of aromatic hydrocarbons from mixtures of aromatic and aliphatic hydrocarbons used in industry [2][3][4][5][6][7][8][9]. LLE experiments were also carried out with sulfolane, because relevant data for the range in toluene concentrations below 20 mol% were not available.…”