Abstract: A continuous electrochemical process with integrated product separation has been developed for production of 2,5-furandicarboxylic acid (FDCA) by oxidation of 5-(hydroxymethyl)furfural (HMF) in aqueous alkaline media on non-noble Ni/NiOOH foam electrodes at ambient conditions. Initially, voltammetry studies were performed in both, acid and alkaline media, on various catalyst materials: Au, Au3Pd2, Pt, PbO2, Ni/NiOOH and graphite. Preparative electrolysis was performed on Au, Au3Pd2, Pt, PbO2, Ni/NiOOH electrodes in a divided glass cell and Ni/NiOOH showed the best performance with an FDCA yield of ≈ 90% and a Faradaic efficiency of ≈ 80%. The electrolysis conditions were then optimized to industrially relevant conditions in a filter-press type flow reactor with Ni/NiOOH foam anode. HMF concentrations as high as 10 wt% were converted to FDCA at pH 12 in a buffer free 0.1 M Na2SO4 electrolyte with continuous addition of NaOH to maintain constant pH. An FDCA separation yield up to 95% was achieved via pH shift crystallization. The electrolysis and FDCA separation results were used for the design and construction of a bench-scale system where continuous FDCA production, including integrated product separation, was tested and reported in this work. This publication for the first time presents a continuous electrochemical FDCA production system with integrated product separation at industrially relevant product concentrations, 10 wt% HMF, and utilizing non-noble electrode materials.@en

The electrochemical production of valeric acid from the renewable bio-based feedstock levulinic acid has the potential to replace the oxo-process, which uses fossil-based feedstock 1-butylene. The electrochemical reduction of the ketone functionality in levulinic acid using lead or mercury cathodes has already been known for over 100 years. However, large-scale electrochemical production of valeric acid might be limited, owing to the toxicity of these materials. In this study, we identified three additional cathode materials, cadmium, indium, and zinc, which selectively and efficiently produce valeric acid. Of these materials, indium and zinc are considered more benign. More specifically, at indium there is no formation of the side product γ-valerolactone, thus resulting in the highest selectivity towards valeric acid. For the electrochemical reduction, a reaction mechanism involving the formation of an organometallic compound is proposed. Furthermore, a possible processing strategy is outlined to enable the continuous electrochemical production of valeric acid on a large scale.@en