Assessment and modeling of the isobaric vapor-liquid-liquid equilibrium for water + cyclopentyl methyl ether + alcohol (ethanol or propan-1-ol) ternary mixtures

Abstract

The three-phase equilibria of water + cyclopentyl methyl ether (CPME) + ethanol or propan-1-ol ternary mixtures are explored from experimental determinations and theoretical modeling at a constant pressure (101.3 kPa), and over 350 K to 356 K. Experimental measurements are performed in a modified Guillespie phase equilibria dynamic cell, which includes an ultrasonic homogenizer. The reliability of the measured three-phase equilibria is validated by employing the Wisniak's L/W thermodynamic consistency test. The measured vapor-liquid-liquid equilibria (VLLE) data at 101.3 kPa are accurately predicted from the phase stability restriction coupled with the multiphase equilibrium criteria. The application of this combined approach is showcased as a thermodynamical tool to explore all possible phase equilibria regions (i.e., one-, two-, and three-phase), providing a robust representation of the multiphase equilibria. Both phase stability and the corresponding multiphase equilibria are calculated using the SAFT-VR-Mie EoS model (statistical associating fluid theory of variable range employing a Mie potential equation of state), where the association and polar nature of pure components and their binary interactions are explicitly considered.No ternary azeotropy is detected within the experimental range of stable VLLE for the water + CPME + ethanol ternary mixture, although the theoretical extrapolation of the experimental conditions using the SAFT-VR-Mie EoS suggests its existence. For the case of the water + CPME + propan-1-ol ternary mixtures, a stable VLLE with a heterogeneous ternary azeotrope is detected from the interpolation of the experimental determinations.The predicted heterogeneous ternary azeotrope supports use of the CPME as a potential entrainer candidate for dehydration of bio-alcohols (e.g., ethanol or propan-1-ol) as well as implying that the distillate products, bio-alcohols (ethanol or propan-1-ol) + CPME mixtures can be directly used as a renewable fuel without the need of additional separation stages.