Pt NPs immobilized on core-shell magnetite microparticles: novel and highly efficient catalysts for the selective aerobic oxidation of ethanol and glycerol in water.

Three core-shell structures were prepared with pyrrole, glucose, and tetraethyl orthosilicate (TEOS), respectively, encasing magnetic Fe3O4 microparticles, through three different "green" approaches without any toxic solvents. Pt nanoparticles (NPs) were immobilized onto these supports with NaBH4 as the reducing agent. The as-prepared catalysts were characterized thoroughly by TEM, VSM, XRD, FT-IR, ICP, and XPS. As expected, the shells remarkably affected the distribution of Pt NPs and catalytic activity. Pt NPs dispersed evenly on the surface of Fe3O4@PPy and Fe3O4@C, which were much better than Fe3O4@SiO2. Most attractively, the prepared catalysts exhibited better kinetics, higher activity and stability than Pt/Fe3O4 and Pt/C for selective oxidation of ethanol to acetic acid and glycerol to glyceric acid with molecular oxygen in water. Among them, the catalyst with a shell of polypyrrole (PPy) showed the best catalytic property, affording yields of 88% and 55%, respectively. Moreover, it could be recovered facilely from the reaction mixture and recycled four times without any significant loss in activity.