Controlled alcohol oxidation reactions by supported non-noble metal nanoparticles on chitin-derived N-doped carbons

A series of catalysts based on non-noble metal nanoparticles supported on chitin-derived N-doped carbons was prepared through a one-step protocol in the presence of EDTA as a ligand. Both the complexing properties of EDTA and the interaction of metal precursors with the nitrogen sites on the support surface allowed a good dispersion and a homogeneous distribution of the metal active sites. The synthesized materials were tested in the catalytic oxidation of alcohols to aldehydes and ketones. Particularly, the model reaction of oxidation of benzyl alcohol showed that iron- and even more molybdenum-based materials exhibited the best performance. At 130 °C and 20 bar, in the presence of air as an oxidant, the Mo-N/C-catalyzed reactions proceeded with excellent conversion and selectivity, both above 90%, towards the product of partial oxidation, benzaldehyde, and the catalytic performance was retained over 5 recycling runs without any loss of activity. The Mo-based system proved effective also for the conversion of some representative benzyl- and furyl-type alcohols bearing primary and secondary hydroxyl functions to the corresponding aldehydes/ketones, though the oxidation of aliphatic substrates was unsuccessful. All catalysts together with the Mo-N/C sample recovered after its use were fully characterized following a multi-technique approach involving XRD, N2-physisorption, XPS, and HRTEM-EDX analyses. Textural, morphological and chemical properties were thus compared and related to the observed trend of catalytic activity.