Isobaric vapour–liquid equilibria for binary systems of 2-butanone with ethanol, 1-propanol, and 2-propanol at 20 and 101.3 kPa
Introduction
Traditionally, 2-butanone has been used as a solvent in paints and resin adhesives [1]. A mixture of different alcohols with this ketone that form azeotropes is a very common product. Therefore, the purification of the ketone and recovery of the alcohol for recycling are usually impracticable by distillation. The separation can be improved by adding an agent that alters the relative volatility of the components [2] (extractive distillation) or by making a simple change in pressure, provided that the azeotropic composition is sensitive to pressure [3] (pressure-swing distillation).
In the previous work VLE of the binary systems 2-butanone (1) + ethanol (2), 2-butanone (1) + 1-propanol (3), and 2-butanone (1) + 2-propanol (4) were studied at isobaric conditions. The present work was undertaken to measure the VLE data for the three systems mentioned at 20 and 101.3 kPa, with the purpose of studying the influence of the pressure on the composition of the azeotropic mixture, which is interesting in order to investigate the possibility of separation by pressure-swing distillation (PSD). This effect can be exploited to separate a binary mixture containing a minimum boiling azeotrope provided that the azeotropic mixture significantly changes composition over a moderate pressure range.
For the three binary systems, VLE data at 101.3 kPa can be found in the literature: 2-butanone + ethanol [4], [5], [6]; 2-butanone + 1-propanol [7]; 2-butanone + 2-propanol [8], [9]. No isobaric VLE data at 20 kPa are available for these three binary systems.
The experimental VLE data of the binary systems investigated were found to be thermodynamically consistent. Data reduction was carried out using the Wilson, NRTL, and UNIQUAC equations to relate activity coefficients with compositions.
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Chemicals
2-Butanone (≥99.7 mass%, assay GC) and 2-propanol (99.9 mass%, assay GC) were purchased from Aldrich Ltd., ethanol (≥99.5 mass%, analytical grade) and 1-propanol (≥99.9 mass%, assay GC) were purchased from Acros. The reagents were used without further purification after chromatography failed to show any significant impurities. The water content, determined using a Karl Fischer volumetric automatic titrator (Metrohm, 701 KF Titrino), was small in all chemicals (<0.05 mass%). Before measurements, the
Pure component vapour pressures
The pure component vapour pressure for ethanol, 1-propanol, and 2-propanol was taken from the literature [11], [12]. For 2-butanone, pure component vapour pressure was determined experimentally as a function of the temperature, using the same equipment as that for obtaining the VLE data. The pertinent results appear in Table 2. The measured vapour pressures were correlated using the Antoine equation:whose parameters Ai, Bi, and Ci are reported in Table 3 together
Conclusions
Consistent VLE data have been determined for the systems 2-butanone (1) + ethanol (2), 2-butanone (1) + 1-propanol (3), and 2-butanone (1) + 2-propanol (4) at 20 and 101.3 kPa. The Wilson, NRTL, and UNIQUAC models were capable of correlating the data for all the binary systems. Moreover, experimental data were compared to those predicted by the UNIFAC group contribution method.
The equilibrium diagrams for 2-butanone (1) + ethanol (2) and 2-butanone (1) + 2-propanol (4) show that the azeotropic composition
Acknowledgements
Financial support from the Ministerio de Ciencia y Tecnología of Spain, through project no. CTQ2007-61400/PPQ, and the FEDER European Program are gratefully acknowledged. One of the authors (E. Lladosa) has been funded by a grant from the Ministerio de Ciencia y Tecnología.
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