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),N2 sorption,Pyridineadsorbed 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 ε-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 ε-caprolactone yield was only 3.9% and the yield of ε-caprolactone can be kept at 93.9% over MTS-W-4.0 sample after repeated use for 5 times.