Multicomponent Liquid−Liquid Equilibria Prediction for Aromatic Extraction Systems Using COSMO-RS

Abstract

A novel method based on unimolecular quantum mechanical calculations has been used to predict the multicomponent liquid-liquid equilibria (LLE). The recently developed COnductor-like Screening MOdel (COSMO), along with the most common quantum chemical package of Gaussian03 has been used in this work. COSMO-RS combines the COSMO model calculations with exact statistical thermodynamics of pairwise interacting surface segments and has been used for the evaluation of molecular interactions in liquids. COSMO-RS has been used to predict the LLE for 158 multicomponent data sets, which consist of 80 ternary, 9 quaternary, and 4 quinary systems, several of which are examined at different temperatures. The effective contact surface area (a eff ), the hydrogen-bonding coefficient (c hb ), and the cutoff surface charge density for hydrogen bonding (σ hb ) have been estimated simultaneously, using 10 ternary data sets that consist of 11 different functional groups (CH 3 , CH 2 , CH, CHdCH 2 , C-CH 3 , OH, CH 2 O, C-(CH 2 ), COO, C-Cl, CH 2 -CN) and 9 different solvents (sulfolane, dimethyl sulfoxide, N-methyl pyrrolidone, furfural, propylene carbonate, triethylene glycol, tetraethylene glycol, ethylene carbonate, dicyanobutane). Cavity radii (r i ) values up to 1.17 times greater than the Bondi radius have been used. The prediction has been initially benchmarked on the octane-toluene-sulfolane system at three temperatures: 25, 35, 45 °C, for which the root-mean-square deviations (RMSDs) are <1% for mole fraction predictions. Thereafter, the LLE has been predicted for 158 multicomponent data sets. An important aspect of our work is that, for the first time, quaternary and quinary systems have been predicted using COSMO-RS. The overall RMSD is <5% for multicomponent systems, compared to ∼1% for NRTL and UNIQUAC models and 5% for UNIFAC models.

Aromatic sulfur‐nitrogen extraction using ionic liquids: Experiments and predictions using an a priori model

“…The details of COSMO-RS are given in our previous work. [35][36][37] For the IL modeling, COSMO-RS solves the problem in either of the three steps: (a) the metafile, (b) ionpair approach, and (c) the electro neutral approach. 38 We have used metafile approach in which the ions are treated separately in the quantum chemical COSMO calculation, and the IL is described as the sum of sigma profile, area, and volume of the cation and anion.…”

Liquid–liquid equilibrium for ionic liquid systems using COSMO‐RS: Effect of cation and anion dissociation

“…COSMO parameters as used earlier, in our work on aromatic extraction of multicomponent systems, 30 have been adopted. These are given as COSMO_LL parameters in Table 2 and compared against COSMO-RS parameters of Klamt and Eckert 25 as well as against our own COS-MO_VL 29 parameters.…”

“…These are given as COSMO_LL parameters in Table 2 and compared against COSMO-RS parameters of Klamt and Eckert 25 as well as against our own COS-MO_VL 29 parameters. It needs to be emphasized that during COSMO_LL parameter estimation earlier, 30 no ionic liquid based system had been taken in the database. LLE for 32 ternary systems, based on 12 different ionic liquids that had already been reported in literature, 5-9,12-17 has been predicted.…”

“…A conformational analysis on the alkene molecule is performed similar to our previous work on multicomponent aromatic extraction systems. 30,57 To improve the prediction for systems containing alkenes, we have adopted a conformer correction in the sigma profile of alkenes. However, it should be kept in mind that there is no literature data regarding what percentage of each conformer/structure contributes to the solution.…”

“…The expressions and methodology are given in detail in our previously published work on COSMO-RS. [29][30][31] Modified versions of this model, COSMO_VL and COSMO_LL, have been used to predict the vapor-liquid equilibria (VLE), 29 LLE, 30 and infinite dilution activity coefficients (c 1 i ). 31 We will be using the COSMO_LL model for the prediction of LLE of ionic liquid based ternary systems.…”