Salt effect on Vapourliquid equilibrium for the binary system methanol +ethyl acetate

Abstract

In the recent time many scientists and technologists have drawn their attention towards the substitution of a solvent with a non-volatile solid salt in azeotropic distillation which alters the relative volatility. But so far, experimentally, little advancement have been made in this field. The salt effect on vapour-liquid equilibrium of the system: Methanol(1) + Ethyl Acetate(2), for constant liquid composition and under the varied concentrations of the two salts-Lithium Chloride(LiCl) and Lithium Bromide(LiBr)have been reported in this present work.
To prefigure a suitable correlation, the salt effect data obtained experimentally is analyzed. A primary estimation of salt effect on the vapour-liquid equilibrium of the binary system has been presented. Salting-in and Salting-out phenomena are also presented. Under the section of previous investigations and literature review, the history and the development of the work done in this area has been reported along with the vapour pressure measurements and VLE data for the boiling systems.
A modified othmer still, a bulb condenser, a magnetic stirrer-cum heater and a glass thermometer forms the experimental setup and refractive index method has been
used for vapour composition analysis, with the help of a digital refractometer with the prism temperature,maintained constant at 20°C i.e. nDt. Activity coefficient has been calculated using the experimental data which is further used in determining theoretical VLE data that can be further correlated with the experimental one to find thermodynamic consistency.
The effect of two inorganic salts-lithium chloride and lithium bromide on the vapor-liquid equilibria (VLE) has been investigated under the atmospheric conditions of 98.6 ± 0.03 kpa pressure. In the present study it has been found that the system forms a minimum boiling azeotrope at 0.732 mole fraction of methanol at 62.6°C. The azeotrope shifts from 0.732 to 0.629, 0,586, 0.472 and 0.471 by addition of 5%, 10%, 15% and 20% of lithium chloride by weight of methanol respectively and to 0.774, 0,706, 0.682, 0.670 by the addition of 5%, 10%, 15% and 20% lithium bromide by weight of methanol respectively. So this was concluded that by using both the salts at different concentrations e.g. 5%, 10%, 15% and 20% by weight, there was a change in relative volatility in the system and the salts were unable to eliminate the azeotrope of the system.