Salt effect on liquid liquid equilibrium for ternary system water +1-propanol +ethyl acetate

Abstract

Liquid/liquid extraction is a very common method used in the organic laboratory. Organic reactions often yield a number of by-products, some inorganic, some organic... Liquid/liquid extraction is often used as the initial step in the work-up of a reaction, before final purification of the product by recrystallization, distillation or sublimation. Salting-out effect can be used to improve the extraction of some solutes by modifying the solute distribution between two liquid phases. Experiments are conducted on the system Water + 1-propanol + Ethyl acetate with varying salt concentrations and varying temperatures. The basic objective of this project is to determine the best temperature range and the salt from NaCl and (NH4)2SO4 which enhances the separation or extraction of the solute by the specified solvent. The experiments were conducted and the resulting extract and raffinate phase was analyzed with the help of the gas chromatography. The plots of voltage vs time was obtained from the gas chromatography, showing the percent volume of the different components present in both the phases. For each phase a separate plot is obtained. Here we have considered two salts: NaCl and (NH4)2SO4. We have tried to show the effect of these two salts on the system at temperatures 27ºC, 32ºC and 37ºC.The solubility data are tabulated in Table 5.1 and the equilibrium data are tabulated in Table 5.2. Considering these data the solubility curves and the distribution curves were plotted. All salt containing data are reported on salt free basis. The experimental tie-line data under no salt condition were determined and presented in respective tables. It can be seen from the diagrams that the addition of the salts shifts the distribution in favour of ethyl acetate layer especially at higher salt concentrations. The presence of the salt decreases the solubility of the system increasing the heterogeneous zone. Heterogeneous area is an important characteristic. In the present system, the areas of the solubility curves are more in case of salt addition than that of without salt. At increasing salt concentrations more 1-propanol is transferred to the ethyl acetate phase. This process is usually referred to as salting out and is caused by the fact that the presence of high amounts of hydrated ions reduces the availability of the water molecules in the aqueous phase to the salvation of other solvents. Presence of salts mainly increase the concentrations of 1-propanol in organic phase and hence enlargement of the two-phase region occurred.