# Effect of Ionic Liquids on the Isobaric Vapor-Liquid Equilibrium Behavior of Acetone-Chloroform
## 3 Results and Discussion
### Modeling Results  
In 1968, [PERSON] and [PERSON] [13] proposed the NRTL model, which was suggested by most authors to correlate the data of ternary VLE containing IL [14; 15; 16]. Thus, the experimental VLE data for acetone + chloroform and acetone + chloroform + ILs systems were also correlated by the NRTL model. The binary interaction parameters in the NRTL model were regressed by minimizing the function _OF_. The correlated results are listed in Table 1. The ARD (see Equation (4)) is the average relative deviation of the experimental and predicted mole fraction of acetone in the vapor phase.  
\[OF=\sum_{1}^{n}((1-\frac{\gamma_{1}^{cal}}{\gamma_{1}^{exp}})+(1-\frac{\gamma _{2}^{cal}}{\gamma_{2}^{exp}})) \tag{3}\]  
\[ARD=\frac{1}{n}\sum_{n}\left|1-\frac{y_{1}^{cal}}{y_{1}^{exp}}\right| \tag{4}\]  
where \(n\) is the number of experimental data points.  
According to the regressed parameters of NRTL model, the mole fraction of acetone in the vapor-phase was calculated. After the VLE data were measured and calculated, the \(y-x^{\prime}\) diagrams for the ternary systems acetone + chloroform + [MMIM][DMP] and acetone + chloroform + [EMIM][DEP] are plotted in Figures 2 and 3. Meanwhile, the relative volatilities of acetone to chloroform are plotted in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**i Component** & **j Component** & \(\alpha_{\text{ij}}\) & \(\Delta\texttt{g}_{\text{ij}}\)/J mol\({}^{-1}\) & \(\Delta\texttt{g}_{\text{ij}}\)/J mol\({}^{-1}\) \\ \hline acetone & chloroform & 0.399 & \(-\)198.209 & \(-\)11.766 \\ acetone & [MMIM][DMP] & 0.217 & 1006.802 & 2707.172 \\ chloroform & [MMIM][DMP] & 0.780 & 117.775 & 10.602 \\ acetone & [EMIM][DEP] & 0.023 & 1547.298 & \(-\)725.432 \\ chloroform & [EMIM][DEP] & 0.200 & \(-\)298.873 & \(-\)407.809 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Calculated Values of Binary Parameters \(\Delta\texttt{g}_{\text{ij}}\) and \(\Delta\texttt{g}_{\text{ji}}\) in the Nonrandom Two-Liquid (NRTL) Model.  
Figure 4: Relative volatility of acetone (1) + chloroform (2) containing [MIM][DMP] or [EMIM][DEP] (3) at 101.32 kPa. x([MMIM][DMP]), %: \(\blacksquare\) 0; \(\blacklozenge\) 10; \(\blacklozenge\) 15; \(\blacklozenge\)20; x([EMIM][DEP]), %: \(\blacksquare\) 0; \(\triangle\) 10; \(\bigtriangledown\) 15; \(\bigcirc\) 20; Solid line, calculated using NRTL model.  
As shown in Figures 2-4, with the increase of the ILs content, [MMIM][DMP] and [EMIM][DEP] produced more obvious salting-out effects for acetone and the salting-out effect followed the order: 20% > 15% > 10%. Meanwhile, [EMIM][DEP] shows better separation efficiency than [MMIM][DMP] for the acetone-chloroform azeotrope by comparing the volatilities of acetone and chloroform. Because the value of \(P_{1}\)\({}^{5}\)/\(P_{2}\)\({}^{5}\) has little change from 1.198 to 1.208 in the experiments, the increase of relative volatility could be attributed to the acute change of \(\gamma_{1}\) and \(\gamma_{2}\) with the addition of ILs. The activity coefficients of acetone and chloroform based on different mole fraction of ILs are shown in Figures 5 and 6.  
It is observed that with the increased content of ILs, the values of \(\gamma_{1}\) increased and \(\gamma_{2}\) decreased over the whole range of studies. Therefore, the effect contributes to the increase in the relative volatilities and removes the azeotropic point.