Abstract
Experimental data of vapor–liquid equilibria (VLE) are reported for the binary systems: ethanol (1) + water (2) at 100, 1500, and 2000 kPa. The data were verified for thermodynamic consistency by using different low- and high-pressure tests. The following minimum azeotropes were found for the binary systems: x1,az = y1,az = 0.899 and T = 351.39 K at 100 kPa, x1,az = y1,az = 0.857 and T = 440.70 K at 1500 kPa, and x1,az = y1,az = 0.850 and T = 453.83 K at 2000 kPa. The quality of the azeotropic data obtained was established by considering the trend of the bibliographic azeotropic data. The phase behavior was modeled using the Peng–Robinson equation of state (EOS) with several mixing rules and the perturbed-chain statistical associating fluid theory. The experimental data were satisfactorily correlated and a qualitative agreement with these predictive models was observed.
Highlights
Greenhouse gases are produced from fossil fuel combustion, and those can be replaced by alternative fuels that generate less pollution
In estimating the costs necessary to obtain pure ethanol, the following steps should be considered: (1) a process of separation and elimination of organic matter and solid particles followed by distillation, which can be carried out by means of steam dragging; (2) rectification of the product from the previous stage with approximately 40% (w/w) in ethanol to generate a distillate with a composition close to 95% (w/w) of the alcohol; (3) recovery and recirculation of ethanol discharged by a side stream, followed by a rectification of the washed stream with approximately 5% (w/w) ethanol to take advantage of approximately 0.3% (w/w) in fusel oil from the first-stage distillate;[2,3] (4) dehydration stage that can be performed, among other different techniques, by extractive distillation[4] and azeotropic distillation.[5]
The composition of the liquid phase (x1) and vapor phase (y1) of the ethanol mole fraction for the binary system ethanol (1) + water (2) at the different pressures of this work was obtained through a calibration curve of composition versus density
Summary
Greenhouse gases are produced from fossil fuel combustion, and those can be replaced by alternative fuels (biofuels) that generate less pollution. It has long been known that the compositions of azeotropes can be modified by changing the pressure of the system.[8] it was Lewis[9] who first suggested using the pressure swing distillation in mixtures that present an azeotrope. This procedure has subsequently been suggested to separate other azeotropic mixtures,[10,11] probably, the first significant application was developed by Knapp and Doherty.[12].
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