From Batch to Continuous Chemical Synthesis—A Toolbox Approach

A toolbox approach for the transfer of batch to continuous chemical synthesis is presented. The approach considers reaction kinetics (Type A, B, C), reacting phases (single phase, liquid–liquid, gas–liquid and liquid–solid), and the reaction network (parallel and consecutive reactions) in order to select the most appropriate reactor module (Plate, Coil, or CSTR) for continuous operation. Then, three case studies using these three fundamental reactors are presented but require special considerations. For the reaction of dimethyl-oxalate with ethylmagnesium chloride, a plug-flow multi-injection technology must be used to decrease the local heat generation and improve yield. For the nitration of salicylic acid, a Plate reactor with mixing elements favoring some back-mixing followed by a plug-flow system at elevated temperatures is used instead of a tandem mixed-flow CSTR and plug-flow Coil reactor in order to minimize the risk of thermal decomposition of intermediates with a reduced volume penalty. Finally, a ring-closing metathesis reaction is discussed for which the utilization of a CSTR allows the removal of catalyst-poisoning ethylene formed during the reaction and keeps the substrate concentration low to increase the yield above that of a batch or plug-flow system.