Influence of temperature on the liquid–liquid equilibria containing two pairs of partially miscible liquids. Water+nitromethane+1-butanol ternary system

Abstract

In order to show the influence of the temperature on the liquid–liquid equilibria and obtain an equilateral triangular prism with temperature as the vertical dimension for water+nitromethane+1-butanol ternary system, its solubilities and equilibrium data starting at 303.15 K are reported. One region of immiscibility (band type curve) is shown between 303.15 K and 340.5±0.5 K, but when the temperature increases beyond this value 2 separate binodal curves appear. Solubility data of the 2 partially miscible binary systems: water+nitromethane and water+1-butanol were also obtained. From these experimental results, both binary upper critical solution temperatures (UCST) were reported. When the temperature is decreased below the lower CST, the ternary system presents 2 binodal curves expanding toward each other until they meet with a common plait point at the lowest point on the ridge. This point (`col' or saddle point) is situated at 340.5 K±0.5 K with a ternary composition: w 1=0.61; w 2=0.22 and w 3=0.17. Tie line data were satisfactorily correlated by the method of Othmer and Tobias [D.F. Othmer, P.E. Tobias, Ind. Eng. Chem., 34 (1942) 693–696] on a mass-fraction basis, and their plait point coordinates estimated when 2 separate binodal curves were present. From experimental distribution coefficients and selectivities 1-butanol appears to be a good solvent for extraction purposes particularly when the process is carried out at room temperature.