Flow processing of microwave-assisted (heterogeneous) organic reactions

A commercially available continuous-flow reactor was adapted to run three organic reactions, e.g. two heterogeneous and one homogeneous mixture under microwave heating. The setup was operated either as a batch-loop reactor for running a biocatalyzed esterification of (R,S)-1-phenylethanol with vinyl acetate and the esterification of (S)-pyroglutamic acid with n-decanol (i.e., Laurydone process) or in a single pass for the aspirin synthesis as a homogeneous mixture. The tubular reactor has been characterized to perform a series of three equally sized, continuously operated stirred tank reactors on average. Although the (operational) costs of the microwave-heated tubular reactor are higher than conventionally heated processes in fine chemical operations, it was demonstrated that the experimental data can be used for process design. Plugging remains an important obstacle to be dealt with. However, benefits with respect to safety and scalability are expected to enable a fair compensation for the costs when implementing this novel technique.