Aspen Plus as a Tool for Process Scale-up of Externally Heat-Integrated Reactive Distillation

Since its application to the manufacture of esters in the 1920s, reactive distillation has been recognized as a valuable unit operation.  The simultaneous reaction and separation within a single piece of equipment can provide a lower capital alternative for those equilibrium reactions where the volatility of the products is substantially different.  Higher conversions can often be achieved with reactive distillation than other process alternatives.  Reactive distillation processes have been developed for both heterogeneous and homogeneous reactions – demonstrating the wide range of applicability this unit operation possesses.  There are, however, several additional considerations during the development and scale-up of such a process.  Degrees of freedom are lost when reaction and separation are combined in this manner.  In addition, several of the relationships between distillation parameters (e.g. reflux ratio and distillate purity) do not hold universally for a reactive distillation system. 

Additional degrees of freedom can be obtained through effective external heat integration and thermal management resulting in an optimum column temperature profile.  This presentation will discuss the feasibility of several heat integration and thermal management techniques through process simulation with Aspen Plus.  The potentially commercial two-column reactive distillation process for manufacturing cyclohexanol from cyclohexene via esterification and subsequent hydration will be used to illustrate the value of each technique.  Other considerations during the development and scale-up of a reactive distillation process will be discussed as well.