The reaction pathways of 5-hydroxymethylfurfural conversion in a continuous flow reactor using copper catalysts

The transformation of 5-hydroxymethylfurfural is investigated using supported and bulk copper oxide catalysts. We show that the selectivity to 5-methylfuraldehyde or 2,5-diformylfuran can be controlled by the solvent and the carrier gas. The use of water as the solvent and N2 as the carrier gas led to the highest conversion and most selective pathway to 2,5-diformylfuran. Quasi in situ X-ray photoelectron spectroscopy and H2-TPR measurements revealed that H2O can re-oxidise Cu, significantly enhancing the selectivity to 5-methylfuraldehyde. Subsequent density functional theory calculations revealed more precisely the role of water in the reaction mechanism.