Abstract

Vapor - liquid - liquid equilibrium (VLLE) for water + MTBE + ethanol and water + MTBE 1-butanol ternary systems have been measured in a modified dynamic Guillespie type cell at the isobaric condition of 101.3 kPa and over the temperature range from 325.6 to 328.9 K for water + MTBE + ethanol mixture and from 329.5 to 355.1 K for water + MTBE + 1-butanol mixture. The quality of the measured data is thermodynamically validated by the L/W Wisniak's consistency point- point test. According to the experimental results, the liquid - liquid equilibria are Type I for water + MTBE + ethanol mixture and Type II for water + MTBE 1-butanol mixture. The VLLE for water + MTBE + ethanol mixture dis- plays heterogeneous ternary azeotrope whereas the water + MTBE 1-butanol mixture is a zeotropic ternary mixture. The experimental VLLE data for both ternary mixtures are correlated by a modified version of the nonrandom two-liquids (NRTL) activity coefficients model, which incorporates a ternary contribution. This ternary contribution reduces the global average absolute deviation from 5 % to 1.3 % for water + MTBE + ethanol mixture and from 3.1% to 1.9 % for water + MTBE 1-butanol mixture.