Vapor-liquid equilibrium (VLE) measurements of ethanol – heptane at isothermal (363.15, 393.15 and 423.15 K) and isobaric (101.33 kPa) conditions and correlation of liquid viscosity data

Abstract

Vapor-liquid equilibria (VLE) were measured for ethanol – heptane by a modified Rose-Williams equilibrium still combined with ebulliometer at three isotherms (363.15, 393.15 and 423.15 K) and an isobar (101.33 kPa). The azeotropes were observed in VLE, and the experimental data were correlated with the Peng-Robinson-Stryjek-Vera (PRSV) equation of state. The conventional mixing rule, with kij equal to zero calculates the azeotropic pressure close to the vapor pressure of ethanol. The Adachi-Sugie (AS) mixing rule provides 0.282% average absolute relative deviation (AARD) in temperature for isobaric VLE and 1.711% AARD for isothermal VLE. Eyring theory combined with the PRSV equation enabled an average of 2.810% AARD in correlation of literature liquid viscosity data, which is sufficient for considering biofuel injector. The method will be applied to flow analysis in general process design using mixtures because viscosity can be evaluated from equation of states.

Keywords

• Vapor-liquid equilibrium
• Equation of state
• Viscosity
• Eyring theory
• Bioethanol
• Heptane