WOLFRAM|DEMONSTRATIONS PROJECT

Production of Cis2-Butene and Cis2-Hexene by Cis2-Pentene Disproportionation

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composition profile
ternary diagram
temperature profile
reflux ratio
7
molar holdup
100
Consider an ideal ternary mixture composed of components cis2-butene (
A
), cis2-hexene (
B
), and cis2-pentene (
C
). This mixture is subject to an equilibrium-limited chemical reaction
2C⇌A+B
(metathesis or disproportionation of olefins: 2
×
cis2-pentene ⇌ cis2-butene + cis2-hexene) with reaction rate
r=0.5k
2
x
C
-
x
A
x
B
K
eq
, where the equilibrium constant
K
eq
=0.25
and
k=3553.6exp
-6600
RgT
, with
Rg=1.987
cal/(mol K). This mixture is fed to a reactive distillation column operating at a pressure of 3 atmospheres with 13 plates; the feed stage location is stage 5, the reactive stages go from stages 2 to 7, and the feed composition contains 100% mole
C
or pure cis2-pentene. The feed flow rate is chosen to be 100 kmol/hr. For simplicity, we assume constant molal overflow (CMO) and neglect heat effects.
This Demonstration shows three profiles: (1) the composition versus plate number for components
A
,
B
, and
C
(in red, blue, and green, respectively) with the reactive zone shown in light blue and (2) a ternary diagram with the composition of
A
versus the composition of
B
in % mole, and (3) the temperature profile in the column. In the second profile, the feed composition is shown by a magenta dot and the reactive stages 2 to 7 are displayed in blue.
The molar hold-up (in kmol) in the reactive plates is set by the user. The reboil ratio is chosen so that distillate and bottom flow rates are equal (i.e.,
s=R+1
, where
s
is the reboil ratio and
R
is the reflux ratio).
For high hold-up values (i.e., high Damköhler numbers) one recovers the equilibrium case shown by the green curve in the ternary diagram.