| Using acid pickling waste as starting material, nano-Fe3O4 crystalline materials were prepared by an alternative method of iron salt dropwised in NaOH aqueous solution, as proved by XRD, TEM, FT-IR and TG-DSC. The results showed that the Fe3O4 material was well-crystallized magnetite with an average size of about 25 nm. Effect of species and dose of dispersant, pH for precipitation of iron oxide, reaction time and temperature on morphology and size of Fe3O4 material was explored. The optimal conditions for Fe3O4 preparation were obtained: 10 mL PEG-400 as dispersant, pH = 10, reaction temperature 80 oC and time 4 h.Purity of the prepared nano-Fe3O4 was determined to be about 99.15% by ICP-MS, showing that the nano-Fe3O4 is basically single-phase magnetite. Magnetic measurement revealed the nanocrystals are stronger superparamagnetic with a saturation magnetization M(s) of 82.12 emu/g, the coercivity value H(c) of 149.20 Oe, and the remanence value M(r) of 17.09 emu/g.Catalytic performance of the prepared nano-Fe3O4 crystalline materials for selective oxidation of benzyl alcohol into benzaldehyde was evaluated under solvent-free conditions. The results exhibited that nano-Fe3O4 possessed good catalytic performance. The effect of various reaction conditions such as reaction temperature, time and dose of the catalyst etc. on the catalytic activity was discussed. The optimal reaction conditions were determined: reaction temperature 90 oC, reaction time 4 h, catalyst dose 0.2 g, molar ratio of benzyl alcohol to H2O2 1:4. Under the optimal conditions, the conversion reached at 41.24% with 83.07% selectivity to benzaldehyde. Furthermore, this catalyst material possesses stronger superparamagnetic and it could easily be separated by means of magnet. Results showed that the catalyst exhibited perfect nature of recovery and reusability. |
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