Browsing by Author "Fontolan, Emmanuele"
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- Ball milling as an effective method to prepare magnetically recoverable heterometallic catalysts for alcohol oxidationPublication . Fontolan, Emmanuele; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Kopylovich, Maximilian; Bertani, Roberta; Pombeiro, ArmandoHeterometallic double Fe2O3–CoCl2, CoCl2–V2O5, MoO3–V2O5, and triple CuO–Fe2O3–CoCl2 3d metal dispersed systems were easily prepared by ball milling at room temperature and characterized by scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energydispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). They catalyze the microwave-assisted solvent-free heterogeneous oxidation of 1-phenylethanol to acetophenone with tert-butyl hydroperoxide (t-BuOOH) as oxidant, used as a model reaction. In most of the heterometallic systems a significant improvement in the catalytic activity was observed in comparison to homometallic ones. For the tested catalytic systems and experimental conditions, the CuO–Fe2O3–CoCl2 and Fe2O3–CoCl2 systems exhibit the highest activity with maximum 78% yield and TON 39 after 1 h. The possibility of magnetic recovery of the catalysts was demonstrated for the Fe2O3–CoCl2 (3:1) system.
- Simple solvent-free preparation of dispersed composites and their application as catalysts in oxidation and hydrocarboxylation of cyclohexanePublication . Alegria, Elisabete; Fontolan, Emmanuele; Da Costa Ribeiro, Ana Paula; Kopylovich, Maximilian; Domingos, Catarina; Ferraria, Ana Maria; Bertani, Roberta; Botelho do Rego, Ana M.; Pombeiro, ArmandoA simple and clean mechanochemical synthesis at room temperature was employed to prepare CuO-Fe2O3-CoCl2 (100 nm scale), MoO3-V2O5, CuO-CoCl2, Fe2O3-CoCl2, CuO-V2O5, Cu(CH3COO)(2)-V2O5, Cu(CH3COO)(2)-MoO3 (1-100 mm scale) 3d metal based dispersed composites with different ratios of components using simple metal salts/oxides and multiwalled carbon nanotubes (CNT) or graphene oxide (GO) additives (CoCl2-CNT, CoCl2-GO). The thus prepared composite materials were characterized by Xray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). XPS analysis revealed no metal redox change upon ball milling treatment, which however promotes metal hydroxylation. The catalytic activity of the prepared composites in the heterogeneous low power microwave-assisted oxidation of cyclohexane with aq. H2O2 at 30 degrees C was notorious with yields up to 31% and selectivity up to 94% towards cyclohexanol (upon treatment with PPh3) for the CuO-CoCl2-based material. The hydro-carboxylation of cyclohexane with CO, water and K2S2O8 to produce cyclohexanecarboxylic acid bearing one more carbon atom at 60 degrees C is achieved with yields up to 17% for the reaction performed in the presence of the CuO-CoCl2 catalyst. The clean CuO-CoCl2 (1:2) catalyst preparation and the catalytic reaction (oxidation of cyclohexane) can be achieved in one-pot at low temperature, without any added organic solvent, and by using exclusively the mechanochemical energy input, with a marked 23% yield at 30 degrees C.