Sn-Ti Submicrospheres with Tunable Particle Size for Cyclohexanone Baeyer-Villiger Oxidation

摘要

Sn-Ti submicrospheres with tunable particle size were successfully synthesized by adjusting the water amount over Polyvinylpyrrolidone(PVP)-assisted sol-gel method in this paper, and the effect of the submicrosphere size on the catalytic performance in the B-V oxidation of cyclohexanone by molecular oxygen was also investigated. Their physical and chemical properties were character- rized by Scanning electron microscope (SEM), X-ray diffraction (XRD), N-2 sorption, Pyridine-adsorbed IR(Py-IR), Uvioletvisible diffuse reflection spectroscopy(UV-vis), X-ray photoelectron spectra (XPS), Transmission electron microscope and Energy dispersive X-ray detector(TEM-EDX) techniques. The characterization results showed that the Sn-Ti crystal phase would be affected by the initial water amount resulting in the variation for the incorporation of tin species into the tetrahedral TiO2. The regular Sn-Ti submicrospheres with particle size about 210 +/- 5 nm and typical Lewis acidities for MTS-W-4.0 sample can be obtained when water amount was as high as 4.0 mL, and it exhibited higher catalytic performance than other catalysts where its epsilon-caprolactone yield was 97.8 . Compared to the decline range of 13.6 with the submicrospheres particle size as about 450 nm, the drop of epsilon-caprolactone yield was only 3.9 and the yield of epsilon-caprolactone can be kept at 93.9 over MTS-W-4.0 sample after repeated use for 5 times.