Continuous Reduction of an Ester to Aldehyde in CSTR: From Laboratory to Industrial Plant

The reduction of an ester to the corresponding aldehyde using DIBAL-H is a classic example of a reaction that is difficult to scale in batch mode. The highly exothermic nature of the reduction, combined with DIBAL-H's limited selectivity toward the ester substrate, often results in significant formation of the corresponding alcohol as an over-reduced byproduct. This paper presents the optimization and scale-up of ester reduction to aldehyde using a continuous stirred tank reactor (CSTR) technology under cryogenic conditions. Optimal reaction conditions were determined through a design of experiments (DoE) approach, employing multivariate analysis to evaluate the impact of the following key parameters: DIBAL-H equivalents, residence time, temperature. After identifying the optimal conditions to minimize the formation of over-reduced byproducts, the reaction enthalpy was experimentally measured to ensure safe and efficient operation at scale. The process was ultimately scaled successfully from the laboratory scale to multiton industrial production.