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The oxidation of 5-hydroxymethylfurfural (HMF) to valuable dicarboxylic acids has been investigated on magnetic-separable nanocatalysts in the search for selectivity enhancement. Cationic Ru­(4 wt %)-Fe3O4@SiO2 catalyst led to 2,5-furandicarboxylic acid (FDCA), with a selectivity of 80.6% for HMF conversion of 92%. Replacing the deposited noble metal with a transitional oneand NaOH with n-butylamine ensured further advantages, such as the increase of HMF stability and the possibility to tune the selectivity for other valuable products. Thus, under similar reaction conditions, the Fe3O4@SiO2-CoO x (10 wt % CoO x ) catalyst provided a selectivity to succinic acid (SA) of 92.7% for a HMF conversion of 78.6%, and the Fe3O4@SiO2-MnO x (10 wt % MnO x ) catalyst led to 72% selectivity to maleic acid (MAc) for HMF conversion of 5%. However, the performances in this reaction have been improved (85% selectivity to MAc for HMF conversion of 35.6%) working with a metal-free catalyst (Fe3O4@SiO2-NH2), in which the −NH2 functionalization substituted the role of the homogeneous strong base. All the investigated catalysts showed very good stability.

The one-pot production of succinic acid from glucose was investigated in pure hot water as solvent using Nb (0.02 and 0.05 moles%)-Beta zeolites obtained by a post-synthesis methodology. Structurally, they are comprised of residual framework Al-acid sites, extra-framework isolated Nb (V) and Nb2O5 pore-encapsulated clusters. The Nb-modified Beta-zeolites acted as bi-functional catalysts in which glucose is dehydrated to levulinic acid (LA) which, further, suffers an oxidation process to succinic acid (SA). After the optimization of the reaction conditions, that is, at 180 °C, 18 bar O2, and 12 h reaction time, the oxidation of glucose occurred with a selectivity to succinic acid as high as 84% for a total conversion.

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