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

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 (`colʹ or saddle point) is situated at 340.5 K±0.5 K with a ternary composition: w1=0.61; w2=0.22 and w3=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.