Ruthenium Supported on High-Surface-Area Zirconia as an Efficient Catalyst for the Base-Free Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

Several ZrO2‐supported ruthenium catalysts were prepared and utilized in the oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) under base‐free conditions. Full conversion of HMF and almost perfect selectivity towards FDCA (97 %) were achieved after 16 h by using pure O2 as an oxidant and water as a solvent. The catalytic tests show that the size of the Ru particles is crucial for the catalytic performance and that the utilization of high‐surface‐area ZrO2 leads to formation of very small Ru particles. Superior activity was obtained for catalysts based on ZrO2 that had been synthesized by a surface‐casting method and has high surface areas up to 256 m2 g−1. In addition to good activity and selectivity, these catalysts show also high stability and constant activity upon recycling, confirming the suitability of Ru/ZrO2 in the base‐free oxidation of HMF