From Lab Procedure to Industrial Reality: Continuous Flow Diisobutylaluminum Hydride Reduction of Esters to Aldehydes

Abstract

The selective partial reduction of esters to the corresponding aldehydes has been a long-standing challenge in the field of chemistry due to rapid reaction kinetics, high exothermicity, and generation of unstable intermediates. Batch reactors, with their limited heat transfer capabilities, necessitate careful temperature control and prolonged dosing of DIBAL-H, typically at very low temperatures (−70 to −50 °C). This process, especially on a plant scale, can take several hours and often results in considerable over-reduction to the alcohol product despite the cryogenic conditions. As industries aim to increase productivity and efficiency, the transition from laboratory-scale processes to larger-scale manufacturing becomes crucial. Herein, we report a pilot-scale DIBAL-H reduction of an ester to the corresponding aldehyde with product output ranging from 0.72 to 1.2 kg/h using the benefits of continuous flow chemistry. Furthermore, we demonstrate the advantages of 3D metal printing in fabricating the flow reactor, heat exchangers, and static mixers, leading to a straightforward scale-up of this highly reactive and exothermic chemical process demanding excellent heat and mass transfer properties.