Ilenia Rossetti
Dept. of Chemistry, University of Milan, Italy

Abstract

Flow chemistry is gaining increasing attention as a mean to achieve process intensification in the fine chemicals synthesis field. Furthermore, it can overcome heat and mass transfer limitations thanks to more efficient mixing, allowing applications characterised by insufficient yield or safety issues, when carried out in the traditional batch mode. Despite their spreading use, micro- and meso-reactors are complex systems that require some detailed modelling in order to achieve the desired process intensification effect. In this review, some examples will be provided dealing with three main modelling items. On one hand, kinetic modelling is needed in order to correctly size the reactor and to estimate its productivity with time-on-stream under different conditions. Then, fluid dynamics issues have to be carefully modelled to predict heat and mass transport properties, which are ultimately related to fluid flow inside micromixers and microreactors. All these topics will be discussed, to review the current developments in continuous microreactors modelling and design, together some examples of process simulation.

INTRODUCTION

Batch processes are the preferred choice in fine, specialty and pharmaceutical chemistry because they offer sufficient versatility and flexibility. However, they pose scale-up issues due to important heat and mass transfer limitations. Flow chemistry is increasingly addressed in the fine and pharmaceutical chemistry fields as a way to modify traditional batch processes, by transformation into continuous flow mode (1-6). Typically, this is achieved by using micro- or meso-reactors.

Continuous processes are usually designed with smaller equipment volumes, need lower maintenance and operating personnel, ultimately leading to limited costs with respect to batch analogues. Additionally, the possibility of continuous operation allows reduced wastes, better atom economy and, in general, decreased time-to-market for new products than batch processes. It has been reported that continuous flow reactors can deliver significantly higher yields, while solvent and energy wastes can be decreased up to 90% (7). Different commercial units for continuous manufacturing are already available on the market (8). A very compact system for the contin ...