Composition of the equilibrium phases was determined by applying 1 H NMR

Composition of the equilibrium phases was determined

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Composition of the equilibrium phases was determined by applying 1 H-NMR spectroscopy. The molar fraction of each component was calculated by the integration of some selected peaks corresponding to the heptane methyl group and the pyridinium and thiophene aromatic protons. The accuracy of the method was investigated. For each study system several miscible samples were prepared by weighting with a Mettler AX-205 Delta Range balance with an uncertainty of ± 3 ¥ 10 - 4 g . Their compositions were then calculated by 1 H-NMR as described above. The upper phase error was determined by preparing miscible samples of the binary system heptane/thiophene, while the lower phase error was determined by preparing miscible samples of the ternary system, all of them at the vicinity of the tie-lines. The largest deviation between the real and calculated compositions was 0.013 for the binary system, 0.018 for the [ 1 B 3 M 5 M 2 PPy][NTf 2 ] system and 0.008 for the [ 1 E 3 M 5 M 2 PPy][NTf 2 ] system. All the experiments were performed with a 400 MHz Bruker ARX spectrometer using CDCl 3 as a solvent. Due to the small amount of IL available, the determination of several tie-lines was carried out using recovered ionic liquid. The recovery of the ionic liquid was performed under vacuum and moderate temperature, and then its purity was confirmed by 1 H NMR spectroscopy. Moreover, in order to confirm the purity of the recovered IL, the tie-lines of the binary systems were repeated using new and recovered IL. The obtained results were similar with both ILs, showing a maximum difference of ± 0.003 in mole fraction. Conclusions In this work a series of new ILs derived from pyridinium cation substituted with different alkyl chains were synthesized, and its sulfur-removal capacity were tested. The polyalkylated pyridines used as starting materials were prepared by selective metalation of 2,3,5-collidine on 2-methyl group and subsequent alkylation. With this methodology, we obtained a procedure for the selective metalation of polymethy- lated pyridines, which allows the introduction of different alkyl groups in position 2 with high yields. Liquid–liquid equilibria for the ternary systems (heptane + thiophene + [ 1 E 3 M 5 M 5 PPy][NTf 2 ]) and (heptane + thiophene + [ 1 B 3 M 5 M 2 PPy][NTf 2 ]) were determined at T = 298.15 K and at- mospheric pressure. In order to evaluate the extraction capacity of these ILs as solvents on a desulfurization process via liquid extraction, the experimental LLE compositions, selectivity and solute distribution ratio, were calculated. All studied systems present high values of selectiv- ity and solute distribution ratio, which implies that both [ 1 E 3 M 5 M 2 PPy][NTf 2 ] and [ 1 B 3 M 5 M 2 PPy][NTf 2 ], could be used as solvents for the extraction of thiophene from heptane.
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