CoOOH-catalyzed anodic oxidation of 5-(hydroxymethyl)-furfural under non-alkaline conditions

• Published in: RSC sustainability 2024-07, Vol.2 (8), p.2256-2266
• Main Authors: Gey, Marten Niklas, Schröder, Uwe
• Format: Article
• Language: English
• ISSN: 2753-8125; 2753-8125
• DOI: 10.1039/d4su00050a

The oxidation of 5-(hydroxymethyl)-furfural (HMF), a platform chemical of biogenic origin, to 2,5-furandicarboxylic acid (FDCA) is a reaction of high relevance for sustainable production of polymers like polyethylene furanoate. However, a majority of the oxidation processes published to date rely on alkaline conditions, in which the instability of HMF and a resource intensive separation of FDCA are major obstacles for technological realization. In this study, we present the electrochemical oxidation of HMF in non-alkaline acetate and phosphate buffers (pH 5-7) on CoOOH modified electrodes. Current-controlled batch experiments were performed, to obtain optimal conditions with respect to the catalyst loading, current density and reaction temperature. Under optimized conditions, a FDCA yield of 94.7% in the acetate buffer (pH 5) was achieved. Through interval sampling, we were able to observe a consecutive oxidation mechanism during the optimized reaction, which mainly proceeded via the intermediate products 2,5-diformylfuran (DFF) and 5-formyl-2-furancarboxylic acid (FFCA). Furthermore, we observed that humic substances formed during the first reaction steps could also be oxidized to FDCA towards the end of the reaction. The biomass-based platform chemical HMF is electrochemically oxidized at mild pH values to 2,5-furandicarboxylic acid - a green substitute for terephthalic acid in the production of polymers like PET.