Vapor-Liquid Equilibrium for an Ethanol-Water Mixture

pressure in kPa

101

van Laar

Wilson

NRTL

UNIQUAC

Margules

Consider a binary mixture of ethanol and water. Vapor-liquid equilibrium (VLE) data can be computed using the modified Raoult's law:

P

y

i

=

sat

P

i

x

i

γ

i

, where

sat

P

i

is the vapor pressure,

P

is the total pressure,

x

i

and

y

i

are the liquid and vapor phase mole fractions of the light component (i.e., ethanol) when

i=1

, and finally,

γ

is the activity coefficient. You can vary the pressure

P

to any value between

50

and

200kPa

(i.e., low to moderate pressure so that the ideal gas-phase assumption holds). You can choose among five activity coefficient models (i.e., van Laar, NRTL, Wilson, Margules, or UNIQUAC). The Demonstration plots the isobaric vapor-liquid equilibrium diagram as well as the equilibrium curve. You can check that all models used to predict activity coefficients give similar results (i.e., a minimum boiling or positive azeotrope at

P=101.325kPa

).

Permanent Citation

Housam Binous, Mamdouh Al-Harthi, Brian G. Higgins

"Vapor-Liquid Equilibrium for an Ethanol-Water Mixture"
http://demonstrations.wolfram.com/VaporLiquidEquilibriumForAnEthanolWaterMixture/
Wolfram Demonstrations Project
Published: December 19, 2011