Simple Distillation Residue Curves for a Mixture of Ethanol and Isopropanol at 750 mmHg
Simple Distillation Residue Curves for a Mixture of Ethanol and Isopropanol at 750 mmHg
The vapor-liquid equilibrium behavior of a binary mixture composed of ethanol and isopropanol at 750 mmHg can be represented by the following equation:
y=
αx
1+(α-1)x
α=1.9
The simple distillation residue curve is given by the following implicit relation:
ξ=ln(1-x)+ln
1
(α-1)
x
0
x(1-)
x
0
1-x
1-
x
0
where is the warped time, is the ethanol mole fraction in the still at , and is the initial ethanol composition in the still. Warped time is related to clock time by = dt, where and are, respectively, the vapor rate and the liquid hold-up in the still, expressed in moles per second and moles.
ξ
x(ξ)
ξ
x
0
t
dξ
V
H
V
H
Since the mixture does not have an azeotrope, the light component (i.e., ethanol) will preferentially boil off and thus we have as .
x(ξ)0
(ξ→∞)