Evaluation of surface properties and pore structure of carbon on the activity of supported Ru catalysts in the aqueous-phase aerobic oxidation of HMF to FDCA

Different oxygen- and nitrogen-containing carbons were studied as supports of ruthenium catalysts for the alkaline aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to the corresponding diacid 2,5-furandicarboxylic acid FDCA. The surface properties of catalyst support (active carbon or mesoporous carbon replicated from mesostructured silica) were suggested to be a key factor deeply influencing the oxidation rates of the different steps of this reaction of ruthenium nanoparticles. The results highlight that the HMF oxidation reaction in water does not well tolerate O-functional groups, which strongly adsorb water and then block access of the substrate to the active metal sites and decrease the reaction rates. N-containing carbons were anticipated to be beneficial for the acceleration of the first step of ruthenium-alcoholate species formation. The result was the opposite, with a detrimental effect on the reaction rate when the Ru precursor was reacted with the amine-functionalized surface. (C) 2015 Elsevier B.V. All rights reserved.