Reagents composed of organomagnesium halide are widely used to produce pharmaceuticals, flavorings and other products. Processes involving these Grignard reagents can be time-consuming, as controlled, limited addition of the chemicals is required to reduce heat generation during reactions in continuous stirred-tank reactors. Byproduct formation and final product contamination can be problematic under these conditions. Process control and product purity can now be improved with a new flow microreactor designed at Fraunhofer Institute for Microengineering and Microsystems, Germany.

The microreactor pumps the reactant through a layer of magnesium shavings, which trigger the desired reaction One of the pilot plat modules for synthesis with Grignard reagents. Source: Fraunhofer Institute for Microengineering and Microsystemsand control its progress. The double-skinned cylinder is cooled both internally and externally by a continuous flow of oil, which serves to dissipate heat and prevent byproduct formation. The entire reagent is transformed into a pure product in a matter of minutes as both reactant and product flow through the reactor with short residence times.

A four-module pilot plant has demonstrated the conversion of up to 20 liters/hour of reactant solution. A greater number of modules can be added to process larger volumes of product and realize industrial-scale production.