5-Hydroxymethylfurfural (HMF) has become a benchmark chemical as it can be obtained by the processing of renewable biomass, making its downstream modification an important topic both in industry and academia. Finding catalytic processes for the selective derivatization of HMF is challenging due to its reactivity, hence mild conditions are needed. Here we report the selective oxidative esterification of HMF to methyl 5-(hydroxymethyl)furan-2-carboxylate and to dimethyl furan-2,5-dicarboxylate (FDCM) under mild conditions using oxygen (from air) as oxidant. A synergetic effect between the used catalysts, cobalt oxide over nitrogen-doped carbon, and ruthenium over carbon catalysts was observed by catalytic and electron paramagnetic resonance measurements. Kinetic analysis revealed a first order dependence on substrate for the cobalt catalyst and an apparent zero order for the ruthenium catalysts. The conversion rates were improved by the use of perfluoroether as solvent, proving that the oxygen diffusion is the limiting factor in the system.

Furanic di‐carboxylate derivatives of 5‐Hydroxymethylfurfural (HMF) are nowadays important in the polymer industry as they are used as building blocks for bio‐based polyesters. The high reactivity of HMF compels to avoid harsh synthetic conditions. Therefore, developing mild catalytic processes for its selective oxidation is a challenging task. Herein, we report the first oxidative esterification of HMF to dimethyl furan‐2,5‐dicarboxylate (FDCM) under flow conditions using oxygen as oxidant. For that purpose, a new series of nitrogen‐doped carbon‐supported bimetallic Co/Ru heterogeneous catalysts were prepared and characterized by XRD, XPS and N2 physisorption. These analyses revealed that the porosity of the materials and order of impregnation of the metals to the carbon supports lead to varying catalytic activities. Under optimized conditions the flow reactor showed a 15‐fold increase on the production of FDCM compared to batch conditions.

Ein neuer Prozess synthetisiert die Bausteine für Ethylenfuranoat. Er erlaubt, Polyethylenfuranoat zu 100 Prozent biobasiert großtechnisch zu produzieren. Es lässt sich wie Polyethylenterephthalat verwenden. Das Verfahren arbeitet katalytisch, und die Bausteine lassen sich besser verarbeiten.