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

Non-equilibrium stage modeling and non-linear dynamic effects in the synthesis of TAME by reactive distillation

Tertiary-amyl methyl ether (TAME) is a potential gasoline additive that can be advantageously synthesized using the reactive distillation (RD) technology. This work emphasizes on non-linear effects in dynamic simulations of reactive distillation column. For certain configurations, dynamic simulation with equilibrium stage (EQ) model leads to sustained oscillations (limit cycles) which have been reported in our earlier work [Katariya, A. M., Moudgalya, K. M., & Mahajani, S. M. (2006). Nonlinear dynamic effects in reactive distillation for synthesis of TAME. Industrial and Engineering Chemistry Research, 45 (12), 4233–4242]. Feed condition and Damkohler number are the important parameters that influence the existence of these effects. To confirm the authenticity of the observed non-linear behaviors, a more realistic and rigorous dynamic NEQ model for a packed column is developed which uses a consistent hardware design. The steady state behavior of the NEQ model is examined by varying the number of segments and the column height. The dynamic simulation and the bifurcation study with stability analysis indicate that the parameter space, in which oscillations may be observed, is shifted in the case of NEQ model.© Elsevie

Acetalization of formaldehyde with methanol in batch and continuous reactive distillation columns

Methylal, an important raw material and a solvent, is produced by acetalization of aqueous formaldehyde with methanol. This acetalization reaction was carried out in a closed system in the presence of a cation-exchange resin Indion 130 as catalyst and was found to be equilibrium limited. In order to increase the conversion for this reaction, reactive distillation was carried. Batch reactive distillation was performed in the presence of the cation-exchange resin Indion 130 as catalyst. Continuous reactive distillation was performed in a reactive distillation column (RDC) using three different types of catalyst packing. The first type of catalyst packing was coarse size macroporous cation-exchange resin Indion 130, which was directly packed along with Raschig rings. The second type of catalyst packing was Indion 130 tied in cloth bags. The third type of catalyst packing used was a silica-supported organic catalyst. Up to 99% conversion of formaldehyde was achieved by reactive distillation. Vapor-liquid equilibrium data for the quaternary system formaldehyde-methanol-methylal-water were experimentally obtained and correlated by the UNIFAC method. On the basis of the experimental results of the single-feed continuous reactive distillation column, preliminary modeling has been performed for the calculations of the minimum reflux ratio and the number of reactive equilibrium stages in the column used for synthesis