Assessing the Industrial Edge of the Lipase-Mediated Oxidation of 2,5-Diformylfuran to 2,5-Furandicarboxylic Acid: Rotating Bed Reactors, an “Acyl-Donor-Free” Oxidation Concept, and Environmental Aspects

The lipase-mediated oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA) via peracid formation is a promising alternative to valorizing furans from biorefineries. In this chemoenzymatic reaction, Candida antarcticalipase B (CALB) uses hydrogen peroxide (H₂O₂) and ethyl acetate as an acyl donor to form peracetic acid in situ, which subsequently performs the oxidation of DFF to FDCA, via the intermediate 5-formyl-2-furancarboxylic acid (FFCA). This study explores the reaction en route to its industrial application, identifying strengths and limitations. First, the origin of DFF is considered since it can proceed from biorefineries either in organic media or in aqueous solutions. The reaction is assessed in ethyl acetate with different water contents, showing that oxidations can be achieved in wet nonaqueous media. Moreover, a mixture of ethyl acetate and tert-butanol improves the FDCA yield 2-fold. Subsequently, the reaction is conducted using a rotating bed reactor (RBR), which may enable straightforward downstream processing while showing hints for future scale-up. Once H₂O₂ dosage, rotating rate, and enzyme and substrate loadings are optimized, FDCA production of up to ∼27 g/L is achieved, yet still at low DFF selectivity (∼50%). To improve the atom economy of the reaction and enhance the option of organic media recycling, which saves significant CO₂ generation during incineration, an “acyl-donor-free” concept of the lipase-mediated oxidation of DFF to FDCA is proposed, which uses catalytic amounts of FDCA to be taken by the lipase to generate per-FDCA, to oxidize DFF to form the desired product subsequently. Overall, the enzyme-mediated oxidation of DFF to FDCA may become relevant in biorefineries if improvements in the enzyme stability (against H₂O₂ and peracids), as well as in process conditions (e.g., H₂O₂ and substrate addition, downstream, etc.) are adequately tuned.