Catalysis in multifunctional reactors

A multifunctional reactor is broadly defined as a multifaceted reactor system that combines a conventional reactor with any physical process to enhance the overall performance of the process to bring cost-effectiveness and/or compactness to a chemical plant. This multi-functionality can exist either on micro (catalyst) level or on macro (reactor) level [1]. There is substantial information available on several ways to achieve this task. Combining reaction with separation is one such popular approach. Here, when separation is performed in situ, several benefits like an increase in per-pass conversion and/or selectivity, energy integration, longer catalyst life, etc. are attained. When a separation process – e.g. distillation, adsorption, etc. – is to be performed simultaneously with a reaction, it imposes more restrictions on the reactor design so as to meet possible conflicting requirements that result from the reaction and separation. The existence of multiple phases as well as problems associated with heat and momentum transfer, mixing issues, etc. make the process complex, thereby attracting the attention of experts in reaction engineering, catalysis, modeling and simulation, and process design. Since catalysts are an integral part of a reactor system, many efforts have been made to manipulate its design to meet the above-mentioned challenges. A few examples are inserting special catalyst-filled envelopes into a distillation column to reduce pressure drop, manipulating the hydrophobicity of ion exchange resin in reactive chromatography for selective separation, grafting the catalyst in membrane material, etc. In this chapter, we review the recent literature on catalysts and their modified forms used in multifunctional reactors that combine reaction and separation. We restrict ourselves to the four most studied multifunctional reactors: reactive distillation, reactive stripping, membrane reactors and chromatographic reactors.