Enhancing 5-hydroxymethylfurfural oxidation to 2,5-furan-dicarboxylic acid with Au-supported catalysts: Optimizing reaction parameters and unraveling degradation mechanism through DFT calculations

Lignocellulosic biomass holds promise for producing valuable chemicals. Among possible key reactions, the 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA) using O₂ as a final oxidant and supported Au catalysts is a promising route but that suffers from carbon balance issues. This study explores the mechanism of HMF oxidation to FDCA on a Au(111) model catalyst using computational modeling. Our results identify the main intermediate (HMFCA) and the major degradation pathways from HMF and HMFCA. Since we predict a higher degradation rate for HMF, we designed an experimental two-step approach, using a low temperature to convert fully HMF and improve the carbon balance and then raising the temperature to convert the HMFCA intermediate into FDCA. This approach was successful, reaching a high yield in FDCA (>90 %) in 8 hours while keeping the carbon balance above 97 %.