Effect of bivalent cation inorganic salts on isobaric vapor–liquid equilibrium of methyl acetate–methanol system

• The isobaric vapor–liquid equilibrium of inorganic bivalent salts was measured for methyl acetate–methanol system.
• The bivalent cation salts (ZnNO3, CaNO3, MgNO3 and MgCl2) had greater salting out effect than univalent cation salts (LiNO3, LiCl).
• The experimental vapor–liquid equilibrium of different salts was compared and showed qualitative agreement with that calculated data using the scaled particle theory.
• The effect of anion is in the order of NO3− > Cl−.
• The effect of cation is in the order of Zn2+ > Ca2+ > Mg2+..

The salt effect of four inorganic salts, namely; zinc nitrate, calcium nitrate, magnesium nitrate and magnesium chloride on the vapor liquid equilibria of the binary methyl acetate–methanol system was investigated using a modified Othmer still at 1 atm. The salting out effect of methyl acetate was studied at different salt concentrations. For a salt concentration of 5 wt%, it was found that zinc nitrate gives better salting out effect than calcium and magnesium nitrate. Magnesium chloride also shows a salting out effect, but could not eliminate the azeotrope completely, even at higher salt concentrations. It is observed that the bivalent cation salts (ZnNO3, CaNO3, MgNO3 and MgCl2) had greater salting out effect than univalent cation salts (LiNO3,LiCl) reported earlier. Further, salting out coefficients were calculated using the scaled particle theory. The experimental vapor–liquid equilibrium data with the salts was compared with that calculated using the scaled particle theory, but only qualitative agreement was observed.