Continuous electrochemical oxidation of biomass derived 5-(hydroxymethyl)furfural into 2,5-furandicarboxylic acid

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.