Separation of a Reactive Ternary Mixture: Olefin Metathesis

Consider a ternary mixture of components , , and with relative volatilities and . The mixture is subject to an equilibrium-limited chemical reaction with reaction rate , where the equilibrium constant, . 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.

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.

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., ).

This reaction mechanism corresponds to the case of a metathesis or disproportionation of olefins (for example cis2-pentene ⇌ cis2-butene + cis2-hexene).