Liquid–Liquid, Vapor–Liquid, and Vapor–Liquid–Liquid Equilibrium Data for the Water–n-Butanol–Cyclohexane System at Atmospheric Pressure: Experimental Determination and Correlation

Abstract

The temperature and the composition of the vapor-liquid-liquid equilibrium (VLLE), and the vapor-liquid equilibrium (VLE) of a ternary mixture of water -n-butanol -cyclohexane were measured at atmospheric pressure (101.32 kPa) in a modified dynamic recirculating still. As found in the literature, the experimental data obtained reveal a ternary azeotrope at 341.86 K with a mole-fraction composition of 0.281, 0.034 and 0.685 water, n-butanol and cyclohexane, respectively. The liquid-liquid equilibrium (LLE) compositions were measured at a constant temperature of 313.15 K and compared with data in the literature collected at other temperatures.Thermodynamic consistency of all the experimental data was demonstrated. The universal * Corresponding author: vgomis@ua.es 2 quasichemical (UNIQUAC) and the non-random two-liquid (NRTL) thermodynamic models were used to correlate the VLE and LLE data while the original universal functional (UNIFAC) model was used to compare the predicted data.Keywords: Water, n-Butanol, Cyclohexane, Liquid-Liquid Equilibrium, Vapor-Liquid-Liquid Equilibrium, Experimental data. INTRODUCTIONFor 20 years, but especially since the advent of the Kyoto protocol (1997), the governments of many nations have been taking measures to reduce their greenhouse gas (GHG) emissions. These polluting emissions result from mankind's consumption of fossil fuels (such as coal or petrol) for a variety of purposes. In fact, the transport sector is widely acknowledged to be a major contributor to global warming: it accounts for around a third of all final energy consumption in the European Environment Agency member countries, and for more than a fifth of greenhouse gas emissions 1 . As a result, if countries desire to reduce their GHG emissions to meet the new regulations, substituting some of the fossil fuel burned in this sector with biofuels seems to be a viable option. In addition, the use of biofuels seems to be an alternative option to deal with the decrease in reservations of fossil fuels. Biomass can be exploited in fermentation to obtain alcohols such ethanol and butanol from this renewable source of hydrocarbons. These products have had a number of uses (medicine, chemistry) in the past; but, nowadays, they are also viewed as fuel substitutes or as additives to increase the octane number of nafta mixtures. There are further benefits to using these substances including, but not limited to, a reduced dependence 3 on other regions for fuel, improved preservation of nature and better agricultural practices. A sign of the rise in importance of biofuels is that Europe allocated 44% of its investment in energy to renewable energies and 14% to biofuels in the period [2007][2008][2009][2010][2011] 2 .In In order to acquire better knowledge about these systems' thermodynamic behavior and to study the distillation and extraction processes, accurate experimental phase equilibrium data are 4 needed. Not only is it necessary to obtain liquid-liquid equilibrium (LLE) data, but also the vapor-liquid (VLE) and, especially...

Zastosowanie symulatora ChemCAD do modelowania osuszania n-butanolu poprzez destylację heteroazeotropową

“…[13] [9] azeotropów rozpatrywanych mieszanin trójskładnikowych i ich binarnych podukładów. Niezbędne obliczenia zostały wykonane symulatorem ChemCAD.…”

“…Wybór tych substancji jest podyktowany dostępnością literaturowych danych eksperymentalnych VLLE [8][9][10][11] opracowanych przez ich autorów z myślą o osuszaniu n-butanolu. Dla trzech pierwszych układów dopasowano współczynniki równania NRTL, a w przypadku mieszaniny z n-heksanem wzięto je z pracy poprzedniej [20].…”

Multi-criteria optimization for parametrizing excess Gibbs energy models

“…These problems can be related to inconsistencies in the experimental data, but they can also result from the fact that the model cannot describe the reality perfectly. A well-known example is that the simultaneous description of vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) with G E -models often yields only poor results [3][4][5][6][7]. Also difficulties in describing both excess enthalpy and phase equilibrium data have been reported [8][9][10][11][12].…”

Liquid–Liquid Equilibrium for the Ternary Systems Water + 1-Butanol + 1-Hexanol or 1-Octanol at 303.15, 313.15, and 323.15 K

“…There are several studies using this method to extract alcohols such as ethanol, methanol, , and isobutanol with excellent performance. In order to expand the development of 1-butanol extraction units, many basic measurements about water + 1-butanol + solvents have been done on the ternary liquid–liquid equilibrium system, and relevant extractants show good extraction efficiency. − It was found that light alcohol can be extracted from the aqueous solution using a heavy alcohol . As an extension, considering that the liquid–liquid equilibrium (LLE) data of {water + 1-butanol + 1-hexanol} and {water + 1-butanol + 1-octanol} ternary systems were not given in the literature, the performances of 1-hexanol and 1-octanol to separate water and 1-butanol were investigated systematically.…”