Cristiano Migliorini

Continuous reactive chromatography

Abstract Reactive “simulated moving bed” chromatography (SMBR) is a continuous and counter-current operation combining chemical reaction and adsorptive separation within one single apparatus. Its application promises substantial improvements in process performance, especially for equilibrium limited reactions involving heat-sensitive products, as, for example, fine chemicals or pharmaceuticals. In this work, a general approach towards the design of a SMBR process is illustrated using the synthesis of methyl acetate, catalyzed by a sulfonated poly(styrene–divinylbenzene) resin, as a model system. Starting from a suitable mathematical representation of the experimentally determined adsorption thermodynamics and reaction kinetics, a model for a reactive chromatographic column is developed and validated. Based on an extension of this model, the SMBR process is investigated through numerical simulation, in order to identify the governing design parameters and to devise an efficient strategy towards process optimization both in terms of productivity and desorbent requirement. Finally, the feasibility of the process for the model system is proved experimentally using a SMBR unit of mini-plant scale.

Analysis of simulated moving-bed reactors

Abstract The simulated moving-bed reactor (SMBR) combines continuous countercurrent chromatographic separation with chemical reaction. This is a hybrid process, not energy-intensive and is competitive with traditional processes in which reaction and separation are carried out in different devices. The ideal application of this technology is to reactions where the once-through conversion is limited by chemical equilibrium. In this case SMBRs can achieve simultaneously the goals of complete conversion and separation of the products. Examples are esterifications, transesterifications, etherifications, acetilations, some isomerisations, hydrogenations, some enzyme reactions and others. A complete analysis of the behaviour of SMBs without chemical reaction is available. SMBR units are more complex than SMBs and more properties have to be accounted for, such as the reaction rate and the equilibrium conversion. The purpose of this work is to illustrate the behaviour and develop a design strategy for SMBRs, based on our understanding of the corresponding non-reactive units.

Design of simulated moving bed multicomponent separations: Langmuir systems

Abstract The design of the operating conditions for the separation of multicomponent mixtures using a non adsorbable eluent through simulated moving bed (SMB) technology is considered. The results obtained in the frame of Equilibrium Theory in the case of adsorption described by Langmuir models lead to the definition of explicit constraints on the operating parameters to operate the unit in the desired separation regime. In this paper this approach is extended to the new situation of the separation of a mixture of C solutes in an inert solvent, or eluent, described by the multicomponent non stoichiometric Langmuir isotherm. This represents an important problem in the field of fine chemical separations. The algorithms necessary to calculate the regions of complete separation as well as the regions where some components distribute in the extract and the raflinate, are derived. Finally, the theoretical findings are assessed through detailed simulations of different multicomponent separations in one or two SMB units.