Selectivity engineering with single feed multi-side draw hybrid reactive distillation columns

• Conceptual design of multi-side draw hybrid reactive distillation columns.
• The design procedure is a combination of graphical method and simulations.
• The algorithm typically generates multiple designs of desired selectivity.
• The developed algorithm can be applied directly to multi azeotropic systems.
• Methodology is illustrated for transesterification of dimethyl carbonate with ethanol.

In multireaction systems reactive distillation (RD) not only increases the reactant conversion and purity but also proves very helpful to achieve the selectivity of the desired product. Designing a reactive distillation column for a multicomponent multireaction system is a challenging task, especially when the reactant is intermediate boiling or saddle in the residue curve map of the mixture. In the previous work (Hasan et al., 2014), we introduced simple hybrid RD column and hybrid RD column with single side draw to obtain a desired selectivity in single reactant multireaction schemes. In this work, we extend the approach further to include multi-side draw hybrid RD configuration and present, a new synthesis and design methodology. The developed algorithm is a combination of geometric method and simulation based design. We determine a surface of reactive stage compositions (SRSCs) such that if the reaction takes place at any of the compositions that belongs to SRSCs then the desired selectivity is ensured. Further, we also show that a single feed multi-side draw hybrid RD configuration is capable to give a desired selectivity in multi-reactant multireaction schemes wherein, both the reactants are saddle in the corresponding residue curve map. This is illustrated using an industrially relevant example of transesterification of dimethyl carbonate with ethanol to achieve the desired selectivity toward ethyl methyl carbonate. The results provide a good starting point for rigorous simulation. The algorithm presented here is applicable to any number of components and can be directly applied to even multi azeotropic systems as well. Though at this stage its applicability is restricted to the single feed configurations, we believe that the developed approach can be conveniently extended to multi-feed configurations with appropriate modifications.

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