As explained previously pyridinium ILs achieved great success as an efficient

As explained previously pyridinium ils achieved great

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As explained previously, pyridinium ILs achieved great success as an efficient alternative for extractive desulfu- rization issues. More precisely, alkyldimethyl pyridinium- based ILs showed the best results. 14 When comparing Fig. 3 Selectivity, as a function of the thiophene mole frac- tion in the alkane-rich phase, for the ternary systems (hep- tane + thiophene + [ 1 E 3 M 5 M 2 PPy][NTf 2 ]) ( ) (heptane + thio- phene + [ 1 B 3 M 5 M 2 PPy][NTf 2 ]) ( ) and (heptane + thiophene + [ 1 H 3 M 5 MPy][NTf 2 ]) ( ) 16 at T = 298.15 K. Fig. 4 Solute distribution ratio, as a function of the thiophene mole fraction in the alkane-rich phase, for the ternary systems (heptane + thiophene + [ 1 E 3 M 5 M 2 PPy][NTf 2 ]) ( ); (heptane + thio- phene + [ 1 B 3 M 5 M 2 PPy][NTf 2 ]) ( ) and (heptane + thiophene + [ 1 H 3 M 5 MPy][NTf 2 ]) ( ) 16 at T = 298.15 K. the [ 1 E 3 M 5 M 2 PPy][NTf 2 ] and [ 1 B 3 M 5 M 2 PPy][NTf 2 ] ILs with [ 1 H 3 M 5 MPy][NTf 2 ], 16 the effect of the number of substituents can be analyzed. Solute distribution ratio and selectivity values are higher at low thiophene concentrations in the case of poly- substituted pyridinium, indicating that the capability of these pyridinium-based ILs to desulfurate increases when increasing the alkyl groups in the aromatic ring. Taking into account that practical application of desulfur- ization processes corresponds to low concentrations of sulfur- containing compounds (lowest part of triangular diagrams) and that the highest S and b values were obtained in this area, the studied ILs could be considered as an alternative for the extraction of thiophene from heptane. Although at present the ILs are more expensive than conven- tional solvents, future production of higher quantities and the 2772 | Green Chem. , 2011, 13 , 2768–2776 This journal is © The Royal Society of Chemistry 2011 Published on 18 August 2011. Downloaded by Memorial University of Newfoundland on 12/22/2018 10:10:24 PM. View Article Online
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possibility of their recovery in the process could make their use competitive. Thermodynamic correlation LLE data were correlated using the Non-Random Two Liq- uid (NRTL) thermodynamic model developed by Renon and Prausnitz. 30 Although this model was not originally developed for systems involving electrolytes, it has been successfully used to correlate the LLE data of systems involving ILs. 31 Following a common procedure, the nonrandomness param- eter in the NRTL equation, a ij , was set to different values during calculations, and the best results were achieved with a ij = 0.3. The objective function used minimizes the differences between the experimental and calculated mole fraction of the components in both phases. Correlation quality was tested calculating the root-mean- square deviation of the composition, s x , and the mean error of the solute distribution ratio, D b . These deviations were calculated as: s x x x x x ki ki ki ki i N = + = 100 2 2 1 [( ) ( ) ] I,exp I,calc II,exp II,calc 1 2 k M MN (3) D b b b b = = 100 1 2 1 M k k k k M calc (4) where M is the number of tie-lines and N the number of components in the mixture.
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