(91e) Conceptual Design of Single-Feed Hybrid Multi-Product Reactive Distillation Column for Selectivity Engineering

Reactive distillation can be advantageously used for improving the selectivity of a desired product in the multi-reaction system. Process synthesis of RD systems is challenging and most of the methods developed to design these systems till now consider fully reactive columns; very few attempts have been made to accommodate hybrid configurations and complex reaction schemes. Moreover, the conceptual design methods available are  more focused  on the  feasibility of  a proposed pair  of  product  compositions  and  finding  one  design  which  satisfies  the specifications. There is a need for a more systematic methodology that able to not only assess feasibility of a proposed reactive separation task, but also to accommodate multiple configurations and provide best design alternatives based on total annualized cost as well as in terms of selectivity in case of multiple reactions.

The present work contributes in this regard and presents a new conceptual design methodology for the synthesis of single feed hybrid multiproduct reactive distillation (HMPRD) column to obtain desired selectivities in case of complex reaction systems involving single reactant (e.g. van de vusse reaction). The developed methodology is based on the boundary value method (BVM) and thus utilizes the concept of operation leaves of rectifying and stripping sections; the overlap section of which indicates the potential feasible split. A new concept of feasible stage composition region (FSCR) is introduced to check the feasible reactive stage compositions on the locus of reactive stage compositions (LRSCs). Intersections of non-reactive stage composition lines (SCLs) with the LRSCs were used in the search routine, allowing a rapid screening of feasible designs of HMPRD Columns. The approach typically generates multiple designs and allows design engineer to compare various design options in terms of energy and catalyst requirement. A technique for the distribution of catalyst loading is also provided if the catalyst loading is large for a single stage. The technique ensures that the desired selectivity remains unaffected after the distribution of catalyst loading. The applicability of the methodology is restricted to a system with single reactant (i.e. single feed configurations). The results are useful for initialising more rigorous calculations.

The methodology developed in this work facilitates a step change in conceptual design practice, offering a systematic and easy to use tool for the synthesis and design of reactive distillation columns for selectivity engineering.