Separation of a Reactive Ternary Mixture: Olefin Metathesis
Separation of a Reactive Ternary Mixture: Olefin Metathesis
Consider a ternary mixture of components , , and with relative volatilities =4 and =0.25. The mixture is subject to an equilibrium-limited chemical reaction with reaction rate , where the equilibrium constant, =0.25. The mixture is fed to a reactive distillation column with 13 plates; the feed stage location is stage 5, the reactive stages run from 2 to 7, and the feed composition contains 100% mole . The feed flow rate is chosen as 100 kmol/hr. For simplicity, we assume constant molal overflow (CMO) and neglect heat effects.
A
B
C
α
13
α
23
2C⇌A+B
r=k-
2
x
C
x
A
x
B
K
eq
K
eq
C
This Demonstration shows two profiles: (1) the composition versus plate number for components , , and (in red, blue, and green, respectively) with the reactive zone shown in light blue and (2) a ternary diagram with the composition of versus the composition of in mole %. In the second profile, the feed composition is shown by a purple dot and reactive stages 2 to 7 are displayed in blue.
A
B
C
A
B
The Damköhler number, , is set to 200. The reboil ratio is chosen so that distillate and bottom flow rates are equal (i.e., , where is the reboil ratio and is the reflux ratio). For this very large Damköhler number, the simulation represents a situation close to reaction equilibrium (i.e., ).
Da
s=R+1
s
R
r=0
This reaction mechanism corresponds to the case of a metathesis or disproportionation of olefins (for example cis2-pentene ⇌ cis2-butene + cis2-hexene).