Fast hydrogenation: systematic development and optimisation of hydrogen reductive processes in a advanced-flow reactor

This study presents an investigation of hydrogenation reactions in a Corning Advanced-Flow Reactor glass lab scale reactor, designed to facilitate mixing in multiphasic reactions. Using ethyl cinnamate as a model substrate, systematic experiments were performed to understand the reactor potential, reaction performance, and practical operational limits using a Box-Behnken Design of Experiments approach, evaluating the effects of temperature, backpressure, and hydrogen gas flow rate. Under our tested conditions, temperature is the main statistically significant factor affecting yield. Additionally, solvent and solvent mixtures were screened with an aim to understand the minimisation of palladium deposition, with methanol–water identified as the optimal medium for reducing catalyst fouling without compromising yield. Substrate scope extension to alkenes and nitro-compounds showcased the versatility and robustness of consistently achieving near-quantitative conversions except for sterically hindered systems. These results establish the Corning Advanced-Flow Reactor as a fast, scalable, efficient, and sustainable platform for fast hydrogenation, advancing the scope of continuous-flow methodologies for chemical synthesis while addressing key challenges of catalyst blockages and process scale-up.

Impact of Flow Chemistry

The present research demonstrates the transformative impact of flow chemistry on homogeneous Pd-catalysed continuous hydrogenation overcoming traditional batch limitations. Traditional batch hydrogenation suffers from poor H₂ mass transfer, inconsistent mixing, and heat management challenges, particularly with exothermic hydrogenations prone to runaway reactions. The Corning Advanced Flow Reactor (AFR) eliminates these limitations through its microchannel design, delivering 10–100 × enhanced heat/mass transfer vs. batch systems.

The key advantages realized are:

Enhanced Safety: No headspace H₂ accumulation thereby preventing thermal runaways.

A batch equivalent would compromise safety, yield reproducibility, and commercial viability. This work establishes AFR as the scalableplatform for homogeneous hydrogenation directly translating lab discoveries into pharmaceuticals/fine chemicals manufacturing. In shortthis work would not be achievable in a batch reactor setup.